WorldWideScience

Sample records for net isotope effect

  1. Noncovalent Hydrogen Isotope Effects

    Science.gov (United States)

    Buchachenko, A. L.; Breslavskaya, N. N.

    2018-02-01

    Zero-point energies (ZPE) and isotope effects, induced by intermolecular, noncovalent vibrations, are computed and tested by experimental data. The ZPE differences of H- and D-complexes of water with hydrogen, methane, and water molecules are about 100-300 cal/mol; they result to isotope effects IE of 1.20-1.70. Semi-ionic bonds between metal ions and water ligands in M(H2O) 6 2+ complexes are much stronger; their ZPEs are about 12-14 kcal/mol per molecule and result to IE of 1.9-2.1 at 300 K. Protonated (deuterated) water and biwater exhibit the largest ZPE differences and isotope effects; the latter are 25-28 and 12-13 for water and biwater, respectively. Noncovalent IEs contribute markedly into the experimentally measured effects and explain many anomalous and even magic properties of the effects, such as the dependence of IE on the solvents and on the presence of the third substances, enormously large isotope effects at the mild conditions, the difference between IEs measured in the reactions of individual protiated and deuterated compounds and those measured in their mixture. Noncovalent IEs are not negligible and should be taken into account to make correct and substantiated conclusions on the reaction mechanisms. The kinetic equations are derived for the total isotope effects, which include noncovalent IEs as additive factors.

  2. Isotopic effect giant resonances

    International Nuclear Information System (INIS)

    Buenerd, M.; Lebrun, D.; Martin, P.; Perrin, G.; Saintignon, P. de; Chauvin, J.; Duhamel, G.

    1981-10-01

    The systematics of the excitation energy of the giant dipole, monopole, and quadrupole resonances are shown to exhibit an isotopic effect. For a given element, the excitation energy of the transition decreases faster with the increasing neutron number than the empirical laws fitting the overall data. This effect is discussed in terms of the available models

  3. 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)

  4. Incorporation of a Cuban radiological station to the global net of isotopes in precipitations

    International Nuclear Information System (INIS)

    Dominguez L, O.; Ramos V, E.O.; Prendes A, M.; Alonso A, D.; Caveda R, C.A.

    2006-01-01

    From March, 2002 the West station of the National Net of Environmental Radiological Surveillance located in the Center of Protection and Hygiene of the Radiations, belongs to the Global Net of Isotopes in Precipitations. The obtained isotopic information of the analysis of the samples of monthly monitored precipitations (oxygen-18, deuterium and tritium) its are stored in a database, which is available through Internet. For the acceptance in the Global Net, it was necessary the incorporation to the monitoring of the station the meteorological surface variables. Also it was developed a software for the calculation of the tension of the water steam starting from the values of humidity and temperature. The obtained results in 2002 and published recently, its are inside the range of values reported for these isotopes in the Caribbean area. (Author)

  5. A non-conventional isotope separation cascade without any mixing: net cascade

    International Nuclear Information System (INIS)

    Zeng Shi; Jiang Dongjun; Ying Zhengen

    2012-01-01

    A component has different concentrations in the incoming flows at a confluent point in all existing isotope separations cascades for multi-component isotope separation and mixing is inevitable, which results in deterioration of separation performance of the separation cascade. However, realization of no-mixing at a confluent point is impossible with a conventional cascade. A non-conventional isotope separation cascade, net cascade, is found to be able to realize no mixings for all components at confluent points, and its concept is further developed here. No-mixing is fulfilled by requiring symmetrical separation of two specified key components at every stage, and the procedure of realizing no-mixing is presented in detail. Some properties of net cascade are investigated preliminarily, and the results demonstrated the no-mixing property is indeed realized. Net cascade is the only separation cascade that so far possesses the no-mixing property. (authors)

  6. 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)

  7. Aspects regarding at 13C isotope separation column control using Petri nets system

    International Nuclear Information System (INIS)

    Boca, M L; Ciortea, M E

    2015-01-01

    This paper is intended to show that Petri nets can be also applicable in the chemical industry. It used linear programming, modeling underlying Petri nets, especially discrete event systems for isotopic separation, the purpose of considering and control events in real-time through graphical representations. In this paper it is simulate the control of 13 C Isotope Separation column using Petri nets. The major problem with 13 C comes from the difficulty of obtaining it and raising its natural fraction. Carbon isotopes can be obtained using many methods, one of them being the cryogenic distillation of carbon monoxide. Some few aspects regarding operating conditions and the construction of such cryogenic plants are known today, and even less information are available as far as the separation process modeling and control are concerned. In fact, the efficient control of the carbon monoxide distillation process represents a necessity for large-scale 13 C production. Referring to a classic distillation process, some models for carbon isotope separation have been proposed, some based on mass, component and energy balance equations, some on the nonlinear wave theory or the Cohen equations. For modeling the system it was used Petri nets because in this case it is deal with discrete event systems. In use of the non-timed and with auxiliary times Petri model, the transport stream was divided into sections and these sections will be analyzed successively. Because of the complexity of the system and the large amount of calculations required it was not possible to analyze the system as a unitary whole. A first attempt to model the system as a unitary whole led to the blocking of the model during simulation, because of the large processing times. (paper)

  8. There is no temperature dependence of net biochemical fractionation of hydrogen and oxygen isotopes in tree-ring cellulose.

    Science.gov (United States)

    Roden, J S; Ehleringer, J R

    2000-01-01

    The isotopic composition of tree-ring cellulose was obtained over a two-year period from small diameter, riparian zone trees along an elevational transect in Big Cottonwood Canyon, Utah, USA to test for a possible temperature dependence of net biological fractionation during cellulose synthesis. The isotope ratios of stream water varied by only 3.6% and 0.2% in deltaD and delta18O, respectively, over an elevation change of 810m. The similarity in stream water and macroenvironment over the short (13km) transect produced nearly constant stem and leaf water deltaD and delta18O values. In addition, what few seasonal variations observed in the isotopic composition of source water and atmospheric water vapor or in leaf water evaporative enrichment were experienced equally by all sites along the elevational transect. The temperature at each site along the transect spanned a range of > or = 5 degrees C as calculated using the adiabatic lapse rate. Since the deltaD and delta18O values of stem and leaf water varied little for these trees over this elevation/temperature transect, any differences in tree-ring cellulose deltaD and delta18O values should have been associated with temperature effects on net biological fractionation. However, the slopes of the regressions of elevation versus the deltaD and delta18O values of tree-ring cellulose were not significantly different from zero indicating little or no temperature dependence of net biological fractionation. Therefore, cross-site climatic reconstruction studies using the isotope ratios of cellulose need not be concerned that temperatures during the growing season have influenced results.

  9. Isotope effects in photochemical rearrangements

    International Nuclear Information System (INIS)

    Sommer, F.

    1983-01-01

    Taking anthracene resp. 9-deuteroanthracene as the initial substance, different substitution products have been prepared. The products originating by direct photolysis have been characterized and their structure has been determined. By comparing the measured kinetic isotope effect and the quantum yield of the nondeuterated and the monodeuterated fluorenes formed it could been demonstrated that the isotope effect mainly is due to the reaction rates and the influence of the deuterium substitution upon the radiationless desactivation against that is small. (HBR) [de

  10. 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)

  11. Non-linear Isotope Effects

    DEFF Research Database (Denmark)

    Schmidt, Johan Albrecht

    ’s stratosphere is nearly mass dependent, and only a small fraction of the observed anomalous oxygen-17 excess can be attributed to N2O photolysis. In contrast, stratospheric photolysis produces a significant inverse clumped isotope effect.(ii) Stratospheric OCS photolysis significantly enrich the remaining OCS...

  12. Inferring biome-scale net primary productivity from tree-ring isotopes

    Science.gov (United States)

    Pederson, N.; Levesque, M.; Williams, A. P.; Hobi, M. L.; Smith, W. K.; Andreu-Hayles, L.

    2017-12-01

    Satellite estimates of vegetation growth (net primary productivity; NPP), tree-ring records, and forest inventories indicate that ongoing climate change and rising atmospheric CO2 concentration are altering productivity and carbon storage of forests worldwide. The impact of global change on the trends of NPP, however, remain unknown because of the lack of long-term high-resolution NPP data. For the first time, we tested if annually resolved carbon (δ13C) and oxygen (δ18O) stable isotopes from the cellulose of tree rings from trees in temperate regions could be used as a tool for inferring NPP across spatiotemporal scales. We compared satellite NPP estimates from the moderate-resolution imaging spectroradiometer sensor (MODIS, product MOD17A) and a newly developed global NPP dataset derived from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset to annually resolved tree-ring width and δ13C and δ18O records from four sites along a hydroclimatic gradient in Eastern and Central United States. We found strong correlations across large geographical regions between satellite-derived NPP and tree-ring isotopes that ranged from -0.40 to -0.91. Notably, tree-ring derived δ18O had the strongest relation to climate. The results were consistent among the studied tree species (Quercus rubra and Liriodendron tulipifera) and along the hydroclimatic conditions of our network. Our study indicates that tree-ring isotopes can potentially be used to reconstruct NPP in time and space. As such, our findings represent an important breakthrough for estimating long-term changes in vegetation productivity at the biome scale.

  13. Equilibrium deuterium isotope effect of surprising magnitude

    International Nuclear Information System (INIS)

    Goldstein, M.J.; Pressman, E.J.

    1981-01-01

    Seemingly large deuterium isotope effects are reported for the preference of deuterium for the α-chloro site to the bridgehead or to the vinyl site in samples of anti-7-chlorobicyclo[4.3.2]undecatetraene-d 1 . Studies of molecular models did not provide a basis for these large equilibrium deuterium isotope effects. The possibility is proposed that these isotope effects only appear to be large for want of comparison with isotope effects measured for molecules that might provide even greater contrasts in local force fields

  14. Isotopic tracers for net primary productivity for a terrestrial ecosystem: a case study of the Volta River basin

    International Nuclear Information System (INIS)

    Hayford, E.K.; Odamtten, G.T.; Enu-Kwesi, L.

    2006-01-01

    The coupling effect of vapour release and CO2 uptake during photosynthesis plays an important role in the carbon and hydrologic cycles. The water use efficiency (WUE) for transpiration was used in calculating the net primary productivity (NPP) for terrestrial ecosystem. Three parameters were used in calculating the water and carbon balance of the River Volta watershed. These are 1) stable isotopes of hydrogen and oxygen, 2) long-term data on precipitation and evapotranspiration, and 3) stoichiometric relations of water and carbon. Results indicate that soils in the watershed annually respire 0.199 Pg C, and that the NPP is +0.029 Pg C yr-1. This implies an annual change in CO2 to the atmosphere within the watershed. Annually, River Volta watershed receives about 380 km3 of rainfall; approximately 50 per cent of which is returned to the atmosphere through plant transpiration. Associated with annual transpiration flux is a carbon flux of 0.170 x 1015 g C yr-1 or 428 g C m-2 yr-1 from the terrestrial ecosystem. Modeled estimates of heterotrophic soil respiration exceeds slightly the estimated NPP values, implying that carbon flux to and from the Volta river watershed is close to being in balance. In other words, the watershed releases annually more carbon dioxide to the atmosphere than it takes. Apart from the terrestrial carbon flux, the balance of photosynthesis and respiration in the Volta lake was also examined. The lake was found to release carbon dioxide to the atmosphere although the magnitude of the flux is smaller than that of the terrestrial ecosystem. (au)

  15. Medium Effects in Reactions with Rare Isotopes

    International Nuclear Information System (INIS)

    Bertulani, C A; Karakoç, M

    2012-01-01

    We discuss medium effects in knockout reactions with rare isotopes of weakly-bound nuclei at intermediate energies. We show that the poorly known corrections may lead to sizable modifications of knockout cross sections and momentum dsitributions.

  16. Stable isotope methods: The effect of gut contents on isotopic ratios of zooplankton

    Science.gov (United States)

    Hill, J. M.; McQuaid, C. D.

    2011-05-01

    In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0-2.0, 2.0-4.0 and >4.0 mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations. The δ15N ratios were influenced by zooplankton size class, presumably reflecting ontogenetic changes in diet. ANOVA post hoc results and correlations in δ15N signatures among treatments suggest that gut contents may not affect overall nitrogen signatures of Euphausia spp., but that δ13C signatures may be significantly altered by their presence. Carbon interpretations however, were complicated by potential effects of variation in chitin, lipids and metabolism among tissues and the possibility of opportunistic omnivory. Consequently we advocate gut evacuation before sacrifice in euphausiids if specific tissue dissection is impractical and recommend

  17. Bibliography on vapour pressure isotope effects

    International Nuclear Information System (INIS)

    Illy, H.; Jancso, G.

    1976-03-01

    The bibliography of research on vapour pressure isotope effects from 1919 to December 1975 is presented in chronological order. Within each year the references are listed alphabetically according to the name of the first author of each work. The bibliography is followed by a Compound Index containing the names o compounds, but the type of isotopic substituation is not shown. The Author Index includes all authors of the papers. (Sz.N.Z.)

  18. Data error effects on net radiation and evapotranspiration estimation

    International Nuclear Information System (INIS)

    Llasat, M.C.; Snyder, R.L.

    1998-01-01

    The objective of this paper is to evaluate the potential error in estimating the net radiation and reference evapotranspiration resulting from errors in the measurement or estimation of weather parameters. A methodology for estimating the net radiation using hourly weather variables measured at a typical agrometeorological station (e.g., solar radiation, temperature and relative humidity) is presented. Then the error propagation analysis is made for net radiation and for reference evapotranspiration. Data from the Raimat weather station, which is located in the Catalonia region of Spain, are used to illustrate the error relationships. The results show that temperature, relative humidity and cloud cover errors have little effect on the net radiation or reference evapotranspiration. A 5°C error in estimating surface temperature leads to errors as big as 30 W m −2 at high temperature. A 4% solar radiation (R s ) error can cause a net radiation error as big as 26 W m −2 when R s ≈ 1000 W m −2 . However, the error is less when cloud cover is calculated as a function of the solar radiation. The absolute error in reference evapotranspiration (ET o ) equals the product of the net radiation error and the radiation term weighting factor [W = Δ(Δ1+γ)] in the ET o equation. Therefore, the ET o error varies between 65 and 85% of the R n error as air temperature increases from about 20° to 40°C. (author)

  19. Incorporation of a Cuban radiological station to the global net of isotopes in precipitations; Incorporacion de una estacion radiologica cubana a la red global de isotopos en precipitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez L, O.; Ramos V, E.O.; Prendes A, M.; Alonso A, D.; Caveda R, C.A. [CPHR, Calle 20 No. 4113 e/41 y 47, Playa, C.P. 11300, A.P. 6195, C.P. 10600 La Habana (Cuba)]. e-mail: orlando@cphr.edu.cu

    2006-07-01

    From March, 2002 the West station of the National Net of Environmental Radiological Surveillance located in the Center of Protection and Hygiene of the Radiations, belongs to the Global Net of Isotopes in Precipitations. The obtained isotopic information of the analysis of the samples of monthly monitored precipitations (oxygen-18, deuterium and tritium) its are stored in a database, which is available through Internet. For the acceptance in the Global Net, it was necessary the incorporation to the monitoring of the station the meteorological surface variables. Also it was developed a software for the calculation of the tension of the water steam starting from the values of humidity and temperature. The obtained results in 2002 and published recently, its are inside the range of values reported for these isotopes in the Caribbean area. (Author)

  20. Isotope effects of sulfur in chemical reactions

    International Nuclear Information System (INIS)

    Mikolajczuk, A.

    1999-01-01

    Sulfur is an important component of organic matter because it forms compounds with many elements. Due to high chemical activity of sulfur, it takes part in biological and geological processes in which isotope effects are occurring. It has been shown during last years research of isotope effects that we have take into account not only mass difference but also many other physical properties of nuclides e.g. even or odd number of neutrons in nuclei, shape and distribution of charge, turn of nuclear spin etc. The factor remains that new theoretical ideas have been formed on the base of data, being obtained in fractionation processes of heavy element isotope, particularly uranium. Now it is being well known that effects unconnected with vibration energy have also caused an effect on fractionation of considerably lighter elements like iron and magnesium. The important question is, if these effects would come to light during the separation of sulfur isotopes. Sulfur have three even isotopes M = (32, 34, 36) and one odd M 33). This problem is still open. (author)

  1. Isotope effects in pericyclic reactions, ch. 2

    International Nuclear Information System (INIS)

    Dolbier, W.R. Jr.

    1975-01-01

    A distinction is made between primary and secondary isotope effects, the primary ones being based on the relative large vibrational frequencies and ensuing large zeroprint energies for C-H vibrations whereas the secondary effects are observed in systems where the vibrational modes of the isotopically labelled site are perturbed during transformation from reactant to product. Both effects are utilised in the elucidation of mechanism in pericyclic processes. The main processes dealt with in this chapter are cycloadditions of all types and sigmatropic rearrangements

  2. Isotope effects: definitions and consequences for pharmacologic studies

    International Nuclear Information System (INIS)

    Van Langenhove, A.

    1986-01-01

    The use of stable isotope-labeled compounds for pharmacologic studies requires careful consideration of the nature of the stable isotope label (2H, 13C, 15N, 18O) and its position of incorporation in the molecule. When deuterium is used, improper positioning can lead to significant primary isotope effects. Primary isotope effects occur when the breaking of the bond to the heavy isotope is the rate-limiting step in a reaction (or metabolic transformation). A reaction will proceed slower for the molecule with the heavy isotope label because of the mass difference between the light and the heavy isotope. In addition to these primary isotope effects, smaller but nevertheless important secondary isotope effects, physicochemical isotope effects, active hydrogen/deuterium exchange, or isotope effects associated with either the enzyme-catalyzed biotransformation or the mass spectrometric ionization and fragmentation can be operative. In mechanistic studies, isotope effects are used to their advantage; however, in pharmacokinetic studies, the occurrence of isotope effects can lead to grossly misleading biologic and analytic results: the metabolism of the drug will differ when in vivo isotope effects are operative, and isotope effects occurring during the analysis procedure will obscure the true metabolic profile of the drug

  3. Carbon Stable Isotope Values in Plankton and Mussels Reflect Changes in Carbonate Chemistry Associated with Nutrient Enhanced Net Production

    Directory of Open Access Journals (Sweden)

    Autumn Oczkowski

    2018-02-01

    applied a series of mixed-effects models to observational data from Narragansett Bay and the model that included in situ δ13C and percent organic matter was the best predictor of [HCO3-]. In temperate, plankton-dominated estuaries, δ13C values in plankton and filter feeders reflect net productivity and are a valuable tool to understand the production conditions under which the base of the food chain was formed.

  4. Carbon and hydrogen isotopic effects of stomatal density in Arabidopsis thaliana

    Science.gov (United States)

    Lee, Hyejung; Feakins, Sarah J.; Sternberg, Leonel da S. L.

    2016-04-01

    Stomata are key gateways mediating carbon uptake and water loss from plants. Varied stomatal densities in fossil leaves raise the possibility that isotope effects associated with the openness of exchange may have mediated plant wax biomarker isotopic proxies for paleovegetation and paleoclimate in the geological record. Here we use Arabidopsis thaliana, a widely used model organism, to provide the first controlled tests of stomatal density on carbon and hydrogen isotopic compositions of cuticular waxes. Laboratory grown wildtype and mutants with suppressed and overexpressed stomatal densities allow us to directly test the isotope effects of stomatal densities independent of most other environmental or biological variables. Hydrogen isotope (D/H) measurements of both plant waters and plant wax n-alkanes allow us to directly constrain the isotopic effects of leaf water isotopic enrichment via transpiration and biosynthetic fractionations, which together determine the net fractionation between irrigation water and n-alkane hydrogen isotopic composition. We also measure carbon isotopic fractionations of n-alkanes and bulk leaf tissue associated with different stomatal densities. We find offsets of +15‰ for δD and -3‰ for δ13C for the overexpressed mutant compared to the suppressed mutant. Since the range of stomatal densities expressed is comparable to that found in extant plants and the Cenozoic fossil record, the results allow us to consider the magnitude of isotope effects that may be incurred by these plant adaptive responses. This study highlights the potential of genetic mutants to isolate individual isotope effects and add to our fundamental understanding of how genetics and physiology influence plant biochemicals including plant wax biomarkers.

  5. INTRAMOLECULAR ISOTOPE EFFECTS IN HYDROCARBON MASS SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, D. P.; Schachtschneider, J. H.

    1963-07-15

    Approximate calculations based on the quasi-equilibrium rate theory of the origin of mass spectra are shown to lead to an approximately correct magnitude for the intramolecular ( pi /sup -/) isotope effect on C--H bond dissociation probabilities of various deuterohydrocarbons. (auth)

  6. Combining Solvent Isotope Effects with Substrate Isotope Effects in Mechanistic Studies of Alcohol and Amine Oxidation by Enzymes*

    Science.gov (United States)

    Fitzpatrick, Paul F.

    2014-01-01

    Oxidation of alcohols and amines is catalyzed by multiple families of flavin-and pyridine nucleotide-dependent enzymes. Measurement of solvent isotope effects provides a unique mechanistic probe of the timing of the cleavage of the OH and NH bonds, necessary information for a complete description of the catalytic mechanism. The inherent ambiguities in interpretation of solvent isotope effects can be significantly decreased if isotope effects arising from isotopically labeled substrates are measured in combination with solvent isotope effects. The application of combined solvent and substrate (mainly deuterium) isotope effects to multiple enzymes is described here to illustrate the range of mechanistic insights that such an approach can provide. PMID:25448013

  7. The effect of dipolar interaction on the magnetic isotope effect

    DEFF Research Database (Denmark)

    Mojaza, Matin; Pedersen, Jørgen Boiden; Lukzen, Nikita

    2010-01-01

    A multi-channel kinetic description is used to study the magnetic isotope effect (MIE) in zero magnetic field. The maximal isotope effect is equal to the number of channels, two for the hyperfine interaction but four for the electron spin dipole–dipole interaction of the intermediate radical pair....... Quantum mechanical calculations agree with these conclusion and show that large MIE may be obtained even in the presence of a strong exchange interaction. The observed magnesium isotope effect on the rate of enzymatic synthesis of adenosine triphosphate (ATP) is approximately 3 implying that the dipolar...... interaction is responsible for the effect. Our calculations provide support for the proposed mechanism....

  8. H/D isotope effects in high temperature proton conductors

    DEFF Research Database (Denmark)

    Bonanos, Nikolaos; Huijser, A.; Poulsen, Finn Willy

    2015-01-01

    The atomic mass ratio of ca. 2 between deuterium and hydrogen is the highest for any pair of stable isotopes and results in significant and measurable H/D isotope effects in high temperature proton conductors containing these species. This paper discusses H/D isotope effects manifested in O-H/O-D...

  9. Isotope effect on confinement in DT plasmas

    International Nuclear Information System (INIS)

    Fukuyama, A.; Itoh, K.; Itoh, S.; Yagi, M.; Azumi, M.

    1994-03-01

    Isotope effect on the energy confinement time is discussed for the DT plasma. The transport theory which is based on the ballooning mode turbulence is applied. When the DT plasma is produced under the condition of β p >1, the energy confinement time of DT plasma (50% mixture) is expected to be about 1.2 times better than the D plasma with the same operation condition. (author)

  10. Study on the Effect of the Separating Unit Optimization on the Economy of Stable Isotope Separation

    Directory of Open Access Journals (Sweden)

    YANG Kun

    2015-01-01

    Full Text Available An economic criterion called as yearly net profit of single separating unit (YNPSSU was presented to evaluate the influence of structure optimization on the economy. Using YNPSSU as a criterion, economic analysis was carried out for the structure optimization of separating unit in the case of separating SiF4 to obtain the 28Si and 29Si isotope. YNPSSU was calculated and compared with that before optimization. The results showed that YNPSSU was increased by 12.3% by the structure optimization. Therefore, the structure optimization could increase the economy of the stable isotope separation effectively.

  11. Non - Adiabaticity and Novel Isotope Effect in the Doped Cuprates

    International Nuclear Information System (INIS)

    Kresin, V.; WOLF, S. A.

    1995-01-01

    This paper reports a novel isotope effect which is due to a strong non-adiabaticity that manifests itself in the dependence of the carrier concentration on the isotopic mass. The critical temperature in turn depends on the carrier concentration giving rise to a unique and non-phononic isotope shift. (author)

  12. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

    In this review we consider three classes of superconductors, namely cuprate superconductors, MgB(2) and the new Fe based superconductors. All of these three systems are layered materials and multiband compounds. Their pairing mechanisms are under discussion with the exception of MgB(2), which is widely accepted to be a 'conventional' electron-phonon interaction mediated superconductor, but extending the Bardeen-Cooper-Schrieffer (BCS) theory to account for multiband effects. Cuprates and Fe based superconductors have higher superconducting transition temperatures and more complex structures. Superconductivity is doping dependent in these material classes unlike in MgB(2) which, as a pure compound, has the highest values of T(c) and a rapid suppression of superconductivity with doping takes place. In all three material classes isotope effects have been observed, including exotic ones in the cuprates, and controversial ones in the Fe based materials. Before the area of high-temperature superconductivity, isotope effects on T(c) were the signature for phonon mediated superconductivity-even when deviations from the BCS value to smaller values were observed. Since the discovery of high T(c) materials this is no longer evident since competing mechanisms might exist and other mediating pairing interactions are discussed which are of purely electronic origin. In this work we will compare the three different material classes and especially discuss the experimentally observed isotope effects of all three systems and present a rather general analysis of them. Furthermore, we will concentrate on multiband signatures which are not generally accepted in cuprates even though they are manifest in various experiments, the evidence for those in MgB(2), and indications for them in the Fe based compounds. Mostly we will consider experimental data, but when possible also discuss theoretical models which are suited to explain the data.

  13. The effect of insecticide-treated bed net on malarial parasitaemia ...

    African Journals Online (AJOL)

    AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search ... nets sold by a social marketing project were used as the intervention group. ... Keywords: Insecticide-treated bed net, Effectiveness, Malaria control, South-South Nigeria.

  14. Use of isotope effects to elucidate enzyme mechanisms

    International Nuclear Information System (INIS)

    Cleland, W.W.

    1982-01-01

    The chemical bond breaking steps are normally not rate limiting for enzymatic reactions. However, comparison of deuterium and tritium isotope effects on the same reaction, especially when coupled with 13 C isotope effects for the same step measured with deuterated as well as unlabeled substrates, allows calculation of the intrinsic isotope effects on the bond breaking steps and thus a determination of the commitments to catalysis for the reactants. The variation in observed isotope effects as a function of reactant concentration can be used to determine kinetic mechanisms, while the pH variation of isotope effects can determine the stickiness of the reactants and which portions of the reactant mechanism are pH dependent. Finally the size of primary and secondary intrinsic isotope effects can be used to determine transition state structure

  15. Black carbon reduction will weaken the aerosol net cooling effect

    Science.gov (United States)

    Wang, Z. L.; Zhang, H.; Zhang, X. Y.

    2014-12-01

    Black carbon (BC), a distinct type of carbonaceous material formed from the incomplete combustion of fossil and biomass based fuels under certain conditions, can interact with solar radiation and clouds through its strong light-absorption ability, thereby warming the Earth's climate system. Some studies have even suggested that global warming could be slowed down in a short term by eliminating BC emission due to its short lifetime. In this study, we estimate the influence of removing some sources of BC and other co-emitted species on the aerosol radiative effect by using an aerosol-climate coupled model BCC_AGCM2.0.1_CUACE/Aero, in combination with the aerosol emissions from the Representative Concentration Pathways (RCPs) scenarios. We find that the global annual mean aerosol net cooling effect at the top of the atmosphere (TOA) will be enhanced by 0.12 W m-2 compared with present-day conditions if the BC emission is reduced exclusively to the level projected for 2100 based on the RCP2.6 scenario. This will be beneficial for the mitigation of global warming. However, the global annual mean aerosol net cooling effect at the TOA will be weakened by 1.7-2.0 W m-2 relative to present-day conditions if emissions of BC and co-emitted sulfur dioxide and organic carbon are simultaneously reduced as the most close conditions to the actual situation to the level projected for 2100 in different ways based on the RCP2.6, RCP4.5, and RCP8.5 scenarios. Because there are no effective ways to remove the BC exclusively without influencing the other co-emitted components, our results therefore indicate that a reduction in BC emission can lead to an unexpected warming on the Earth's climate system in the future.

  16. Effective utilization period of long-lasting insecticide treated nets ...

    African Journals Online (AJOL)

    The study was conducted to evaluate the bioefficacy of long-lasting insecticide treated nets (LLITNs) (PermaNet®2.0) over time and the species composition of Anopheles mosquitoes around Bahir Dar. The space spray collection method was used to determine the species composition of indoor resting Anopheles ...

  17. Net metering study of switching effects on electromechanical meters[Report prepared for the Measurement Canada Electricity Net Metering Project

    Energy Technology Data Exchange (ETDEWEB)

    Van Overberghe, L. [Measurement Canada, London, ON (Canada)

    2006-03-03

    The feasibility of introducing net metering in the electricity sector was evaluated with particular reference to a project administered by Measurement Canada and Electro-Federation Canada (MicroPower Connect) in collaboration with Natural Resources Canada. The objective of the Measurement Canada Electricity Net Metering Project is to identify and eliminate the barriers introduced by the Electricity and Gas Inspection Act regarding the introduction of net metering. The purpose was to design a device that would allow rotation reversal in a residential electromechanical single phase meter. The device should approximate any fluctuations found in a typical net metering system. A series of tests were conducted to understand the influences, on errors, of forward-to-reverse and reverse-to-forward transitions, specifically to find evidence of error migration and mechanical stress. The project was designed to find and measure the effects of forward reverse switching on an electromechanical meter resulting from a change in energy flow. Twenty metres were calibrated in the forward direction in series from light load to high load. Power factor was not adjustable. Test points were then applied in both the forward and reverse directions. The exercise yielded individual errors which were aggregated to show average found errors after 3,000 transitions. Small shifts in errors were apparent and there was no evidence to support a disk flutter theory. refs., tabs., figs.

  18. Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost-effective sampling strategy

    Science.gov (United States)

    OgéE, J.; Peylin, P.; Ciais, P.; Bariac, T.; Brunet, Y.; Berbigier, P.; Roche, C.; Richard, P.; Bardoux, G.; Bonnefond, J.-M.

    2003-06-01

    The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long-term biosphere-atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil-vegetation-atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a "perfect" simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24-hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15-20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.

  19. A model of the isotope effect of the oxide superconductor

    International Nuclear Information System (INIS)

    Zhang Liyuan.

    1989-03-01

    In this paper, a possible mechanism of producing negative correlation energy centers is proposed. Combining this electronic attractive potential with phonon mediated attractive potential between carriers the isotope effect exponent of La-Sr-Cu-O system is quantitatively explained. Generally, the isotope effect exponent is smaller than 1/2 in this mechanism. (author). 20 refs, 1 fig

  20. Secondary deuterium isotope effects in the hydrolysis of some acetals

    International Nuclear Information System (INIS)

    Paterson, R.V.

    Secondary α-deuterium kinetic isotope effects have been determined in the hydrolyses of some acetals. Benzaldehyde dimethyl acetal and 2-phenyl-1,3-dioxolan show isotope effects in agreement with an A1 mechanism. 2-Phenyl-4,4,5,5-tetramethyl-1,3-dioxolan, which has been shown to undergo hydrolysis by an A2 type mechanism, has an isotope effect in agreement with participation by water in the transition state. Hydrolysis of benzylidene norbornanediols, although complicated by isomerisation, has an isotope effect in agreement with an A2 mechanism. Kinetic isotope effects in acetals which have a neighbouring carboxyl group have also been determined. Hydrolysis of 2-carboxybenzaldehyde dimethyl acetal in aqueous and 82% w/w dioxan-water buffers has isotope effects in agreement with a large degree of carbonium ion character in the transition state. Anderson and Capon proposed nucleophilic participation in the hydrolysis of this acetal in 82% dioxan-water. The isotope effect determined in this study is not in agreement with this finding. Hydrolysis of 2-(2'-carboxyphenyl)-4,4,5,5-tetramethyl-1,3-dioxolan shows an isotope effect larger than the corresponding dioxolan without the carboxyl group in agreement with some carbonium ion character in the transition state. A new synthesis of a deuterated aldehyde is described which might be general for aldehydes which will not form benzoins readily. (author)

  1. Net Effects of Ecotourism on Threatened Species Survival.

    Directory of Open Access Journals (Sweden)

    Ralf C Buckley

    Full Text Available Many threatened species rely on ecotourism for conservation funding, but simultaneously suffer direct ecological impacts from ecotourism. For a range of IUCN-Redlisted terrestrial and marine bird and mammal species worldwide, we use population viability analyses to calculate the net effects of ecotourism on expected time to extinction, in the presence of other anthropogenic threats such as poaching, primary industries and habitat loss. Species for which these calculations are currently possible, for one or more subpopulations, include: orangutan, hoolock gibbon, golden lion tamarin, cheetah, African wild dog, New Zealand sealion, great green macaw, Egyptian vulture, and African penguin. For some but not all of these species, tourism can extend expected survival time, i.e., benefits outweigh impacts. Precise outcomes depend strongly on population parameters and starting sizes, predation, and ecotourism scale and mechanisms. Tourism does not currently overcome other major conservation threats associated with natural resource extractive industries. Similar calculations for other threatened species are currently limited by lack of basic population data.

  2. Net Effects of Ecotourism on Threatened Species Survival.

    Science.gov (United States)

    Buckley, Ralf C; Morrison, Clare; Castley, J Guy

    2016-01-01

    Many threatened species rely on ecotourism for conservation funding, but simultaneously suffer direct ecological impacts from ecotourism. For a range of IUCN-Redlisted terrestrial and marine bird and mammal species worldwide, we use population viability analyses to calculate the net effects of ecotourism on expected time to extinction, in the presence of other anthropogenic threats such as poaching, primary industries and habitat loss. Species for which these calculations are currently possible, for one or more subpopulations, include: orangutan, hoolock gibbon, golden lion tamarin, cheetah, African wild dog, New Zealand sealion, great green macaw, Egyptian vulture, and African penguin. For some but not all of these species, tourism can extend expected survival time, i.e., benefits outweigh impacts. Precise outcomes depend strongly on population parameters and starting sizes, predation, and ecotourism scale and mechanisms. Tourism does not currently overcome other major conservation threats associated with natural resource extractive industries. Similar calculations for other threatened species are currently limited by lack of basic population data.

  3. Isotope effects on the optical spectra of semiconductors

    Science.gov (United States)

    Cardona, Manuel; Thewalt, M. L. W.

    2005-10-01

    Since the end of the cold war, macroscopic amounts of separated stable isotopes of most elements have been available “off the shelf” at affordable prices. Using these materials, single crystals of many semiconductors have been grown and the dependence of their physical properties on isotopic composition has been investigated. The most conspicuous effects observed have to do with the dependence of phonon frequencies and linewidths on isotopic composition. These affect the electronic properties of solids through the mechanism of electron-phonon interaction, in particular, in the corresponding optical excitation spectra and energy gaps. This review contains a brief introduction to the history, availability, and characterization of stable isotopes, including their many applications in science and technology. It is followed by a concise discussion of the effects of isotopic composition on the vibrational spectra, including the influence of average isotopic masses and isotopic disorder on the phonons. The final sections deal with the effects of electron-phonon interaction on energy gaps, the concomitant effects on the luminescence spectra of free and bound excitons, with particular emphasis on silicon, and the effects of isotopic composition of the host material on the optical transitions between the bound states of hydrogenic impurities.

  4. Great isotope effects in compounding of sodium isotopes by macrocyclic polyether

    International Nuclear Information System (INIS)

    Knoechel, A.; Wilken, R.D.

    1978-01-01

    Isotope effects appear in the compounding of the two sodium isotopes 24 Na + and 22 Na + with macrocyclic polyethers, whose value was determined for the 13 best known polyethers. A radiometric process was used for determining the different half life periods of the nuclides used. To separate the compound and non-compound types, these were distributed between water and chloroform. The isotope ratio in the chloroform phase was compared with the output isotope ratio and the separation facfor determined from this. When using crown ethers, there was enrichment of 24 Na + by a significant amount (large crown ether) up to 3.1 +- 0.4% for 18 crown 6. The remarkably high results can be correlated by Biegeleisen's theory with other chemical conditions. There is a report on the first results of transferring these conditions to the H + /T + system. (orig.) [de

  5. Calcium hydroxide isotope effect in calcium isotope enrichment by ion exchange

    International Nuclear Information System (INIS)

    Jepson, B.E.; Shockey, G.C.

    1984-01-01

    The enrichment of calcium isotopes has been observed in ion-exchange chromatography with an aqueous phase of calcium hydroxide and a solid phase of sulfonic acid resin. The band front was exceedingly sharp as a result of the acid-base reaction occuring at the front of the band. Single-stage separation coefficients were found to be epsilon( 44 Ca/ 40 Ca) = 11 x 10 -4 and epsilon( 48 Ca/ 40 Ca) = 18 x 10 -4 . The maximum column separation factors achieved were 1.05 for calcium-44 and 1.09 for calcium-48 with the heavy isotopes enriching in the fluid phase. The calcium isotope effect between fully hydrated aqueous calcium ions and undissociated aqueous calcium hydroxide was estimated. For the calcium-44/40 isotope pair the separation coefficient was 13 x 10 -4 . 20 references, 2 figures

  6. Isotope effect in the Knight shift of potassium

    International Nuclear Information System (INIS)

    Sahm, W.; Schwenk, A.

    1975-01-01

    The Knight shifts of the potassium isotopes 39 K and 41 K were determined with high accuracy: Ksup((39)) = 0.274 35(10)% and Ksup((41)) = 0.274 93(12)%. The relative isotope effect ΔK/K = -0.210 (20)% is in agreement with the hyperfine structure anomaly 39 Δ 41 . (orig.) [de

  7. Effects of must concentration techniques on wine isotopic parameters.

    Science.gov (United States)

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

    2006-12-27

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

  8. Symmetry effects in neutron scattering from isotopically enriched Se isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Lachkar, J.; Haouat, G.; McEllistrem, M. T.; Patin, Y.; Sigaud, J.; Cocu, F.

    1975-06-01

    Differential cross sections for neutron elastic and inelastic scattering from {sup 76}Se, {sup 78}Se, {sup 80}Se and {sup 82}Se, have been measured at 8-MeV incident neutron energy and from {sup 76}Se and {sup 82}Se at 6- and 10-MeV incident energies. The differences observed in the elastic scattering cross sections are interpretable as the effects of isospin term in the scattering potentials. A full analysis of the elastic scattering data are presented.

  9. Isotope effect on the zero point energy shift upon condensation

    International Nuclear Information System (INIS)

    Kornblum, Z.C.

    1977-01-01

    The various isotope-dependent and independent atomic and molecular properties that pertain to the isotopic difference between the zero point energy (ZPE) shifts upon condensation have been derived. The theoretical development of the change of the ZPE associated with the internal molecular vibrations, due to the condensation of the gaseous molecules, has been presented on the basis of Wolfsberg's second-order perturbation treatment of the isotope-dependent London dispersion forces between liquid molecules. The isotope effect on the ZPE shift is related to the difference between the sums of the integrated intensities of the infrared absorption bands of the two gaseous isotopic molecules. Each intensity sum is expressed, in part, in terms of partial derivatives of the molecular dipole moment with respect to atomic cartesian coordinates. These derivatives are related to the isotope-independent effective charges of the atoms, which are theoretically calculated by means of a modified CNDO/2 computer program. The effective atomic charges are also calculated from available experimental infrared intensity data. The effects of isotopic substitutions of carbon-13 for carbon-12 and/or deuterium for protium, in ethylene, methane, and the fluorinated methanes, CH 3 F, CH 2 F 2 , CHF 3 , and CF 4 , on the ZPE shift upon condensation are calculated. These results compare well with the Bigeleisen B-factors, which are experimentally obtained from vapor pressure measurements of the isotopic species. Each of the following molecular properties will tend to increase the isotopic difference between the ZPE shifts upon condensation: (1) large number of highly polar bonds, (2) high molecular weight, (3) non-polar (preferably) or massive molecule, (4) non-hydrogenous molecule, and (5) closely packed liquid molecules. These properties will result in stronger dispersion forces in the liquid phase between the lighter molecules than between the isotopically heavier molecules

  10. Uranium isotopic effect studies on cation and anion exchange resins

    International Nuclear Information System (INIS)

    Sarpal, S.K.; Gupta, A.R.

    1975-01-01

    Uranium isotope effects in exchange reactions involving hexavalent and tetravalent uranium, on ion exchange resins, have been re-examined. The earlier work on uranium isotope effects in electron exchange reactions involving hexavalent and tetravalent uranium, has been critically reviewed. New experimental data on these systems in hydrochloric acid medium, has been obtained, using break-through technique on anion-exchange columns. The isotope effects in these break-through experiments have been reinterpreted in a way which is consistent with the anion exchange behaviour of the various uranium species in these systems. (author)

  11. Theory of the isotope effect in superconducting compounds

    International Nuclear Information System (INIS)

    Culetto, F.J.; Rainer, D.

    1978-05-01

    We present a theoretical analysis of the isotope effect on the superconducting transition temperature. Our method is to calculate via formal perturbation theory the response of the transition temperature to small changes of the masses of the various constituents of the compound. We discuss the relation between the isotope effect and various more fundamental parameters in strong coupling superconductors. As illustrative examples, we consider the systems Pd-H(D) alloys and the binary Chevrel phase superconductor Mo 6 Se 8 , and show that analysis of the isotope effect can yield useful information concerning interaction mechanisms in these compounds. (orig.)

  12. Biosynthetic effects on the stable carbon isotopic compositions of agal lipids: Implications for deciphering the carbon isotopic biomarker record

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schouten, S.; Klein Breteler, W.C.M.; Blokker, P.; Schogt, N.; Rijpstra, W.I.C.; Grice, K.; Baas, M.

    1998-01-01

    Thirteen species of algae covering an extensive range of classes were cultured and stable carbon isotopic compositions of their lipids were analysed in order to assess carbon isotopic fractionation effects during their biosynthesis. The fatty acids were found to have similar stable carbon isotopic

  13. Effectiveness of insecticide-treated and untreated nets to prevent malaria in India.

    Science.gov (United States)

    Van Remoortel, Hans; De Buck, Emmy; Singhal, Maneesh; Vandekerckhove, Philippe; Agarwal, Satya P

    2015-08-01

    India is the most malaria-endemic country in South-East Asia, resulting in a high socio-economic burden. Insecticide-treated or untreated nets are effective interventions to prevent malaria. As part of an Indian first-aid guideline project, we aimed to investigate the magnitude of this effect in India. We searched MEDLINE, Embase and Central to systematically review Indian studies on the effectiveness of treated or untreated vs. no nets. Parasite prevalence and annual parasite incidence served as malaria outcomes. The overall effect was investigated by performing meta-analyses and calculating the pooled risk ratios (RR) and incidence rate ratios. Of 479 articles, we finally retained 16 Indian studies. Untreated nets decreased the risk of parasite prevalence compared to no nets [RR 0.69 (95% CI; 0.55, 0.87) in high-endemic areas, RR 0.49 (95% CI; 0.28, 0.84) in low-endemic areas], as was the case but more pronounced for treated nets [RR 0.35 (95% CI; 0.26, 0.47) in high-endemic areas, risk ratio 0.16 (95% CI; 0.06, 0.44) in low-endemic areas]. Incidence rate ratios showed a similar observation: a significantly reduced rate of parasites in the blood for untreated nets vs. no nets, which was more pronounced in low-endemic areas and for those who used treated nets. The average effect of treated nets (vs. no nets) on parasite prevalence was higher in Indian studies (RR 0.16-0.35) than in non-Indian studies (data derived from a Cochrane systematic review; RR 0.58-0.87). Both treated and untreated nets have a clear protective effect against malaria in the Indian context. This effect is more pronounced there than in other countries. © 2015 John Wiley & Sons Ltd.

  14. Carbon Stable Isotope Values in Plankton and Mussels Reflect Changes in Carbonate Chemistry Associated with Nutrient Enhanced Net Production

    Science.gov (United States)

    Coastal ecosystems are inherently complex and potentially adaptive as they respond to changes in nutrient loads and climate. We documented the role that carbon stable isotope (δ13C) measurements could play in understanding that adaptation with a series of three Ecostat (i.e...

  15. Calcium isotope signature: new proxy for net change in bone volume for chronic kidney disease and diabetic rats.

    Science.gov (United States)

    Tanaka, Yu-Ki; Yajima, Nobuyuki; Higuchi, Yusuke; Yamato, Hideyuki; Hirata, Takafumi

    2017-12-01

    Herein, we measure the Ca isotope ratios ( 44 Ca/ 42 Ca and 43 Ca/ 42 Ca) in serum and bone samples collected from rats with chronic kidney disease (CKD) or diabetes mellitus (DM). For the serum samples, the isotope ratios are lower for the CKD (δ 44 Ca/ 42 Ca serum = 0.16 ± 0.11‰; 2SD, n = 6) and the DM (δ 44 Ca/ 42 Ca serum = -0.11 ± 0.25‰; 2SD, n = 7) rats than that for the control rats (δ 44 Ca/ 42 Ca serum = 0.25 ± 0.04‰; 2SD, n = 7). Bone samples from two distinct positions of 20 rats in total, namely, the center and proximal parts of the tibial diaphysis, are subject to Ca isotope analysis. The resulting δ 44 Ca/ 42 Ca values for the bone of the proximal part are about 0.3‰ lower than that for the serum samples from the same rats. The larger isotope fractionations between the serum and bone are consistent with previously reported data for vertebrate animals (e.g., Skulan and DePaolo, 1999), which suggests the preferential incorporation of lighter Ca isotopes through bone formation. For the bones from the control and CKD rats, there were no differences in the δ 44 Ca/ 42 Ca values between the positions of the bone. In contrast, the δ 44 Ca/ 42 Ca values of the bone for the DM rats were different between the positions of the bone. Due to the lower bone turnover rate for the DM rats, the δ 44 Ca/ 42 Ca for the middle of the diaphysis can reflect the Ca isotopes in the bone formed prior to the progression of DM states. Thus, the resulting δ 44 Ca/ 42 Ca values show a clear correlation with bone mineral density (BMD). This can be due to the release of isotopically lighter Ca from the bone to the serum. In the present study, our data demonstrate that the δ 44 Ca/ 42 Ca value for serum can be used as a new biomarker for evaluating changes in bone turnover rate, followed by changes in bone volume.

  16. Isotope effect in gamma-radiolysis of absorbed ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Lyapina, T G; Kotov, A G [Nauchno-Issledovatel' skij Fiziko-Khimicheskij Inst., Moscow (USSR)

    1975-07-01

    The radiolysis of NH/sub 3/ of various isotopic compounds adsorbed on silica gel or zeolite at 77degK was studied. Experimental data were treated using the kinetic equation dR/dt=GI-kIR where R=radical concentration, G=radical yield, k=radical termination constant and I=radiation dose rate. Both the values of G and R for NH/sub 3/ adsorbed on silica gel are affected by the isotopic effect of /sup 15/N, but not on zeolite. The isotopic effect is explained by the influence of protonated acidity of the silica gel surface.

  17. Isotope effect of optical activity measurements on L-α-alanine

    International Nuclear Information System (INIS)

    Darge, W.; Laczko, I.; Thiemann, W.

    1976-01-01

    If an optically active organic substance is labelled in the chirality center with another isotopic species (such as 15 N for 14 N) a pronounced variation of rotatory power is predicted. It was tried to varify this idea experimentally on L-α-alanine and found an isotope effect in ORD (optical rotatory dispersion). The magnitude of the rotation is mainly dependent on the pH of the solvent. The ratio of the optical activity alanine- 14 N/alanine- 15 N is about 1.02. It can be seen that the ratios of the molecular rotations are consistently lower than the corresponding ratios of the specific rotations. This is of course due to the fact that the molecular mass 15 M is larger than 14 M. This means tthat the mass difference is already taken into account so that the ratio of the molecular rotations could be defined as the ''net'' isotope effect in the ORDs of 15 N-substitued alanine. From the fact the ORD is different for the isotope-substitued alanine, one can reasonably assume that the absorption coefficient is also different. This leads to speculations about certain problems in the chemical evolution of the biosphere, such as the origin of optical activity. (T.G.)

  18. Kinetic isotope effect in the thermolysis of methylenecyclobutane

    International Nuclear Information System (INIS)

    Chickos, J.S.

    1979-01-01

    The intramolecular kinetic isotope effect for the thermolysis of equilibrated methylenecyclobutane-d 2 was investigated at 515 0 C as a function of pressure. A high-pressure value of k/sub H/k/sub D/ (ethylene/ethylene-d 2 ) = 0.9 was obtained at 13 cm of N 2 pressure. This value decreased to 0.86 at 70 μm total pressure. No intermolecular kinetic isotope effect was measured for the formation of ethylene from labeled and unlabeled methylenecyclobutane. The pressure and temperature dependence of the intramolecular kinetic isotope effect was used as evidence in establishing the inverse nature of the effect. The isotope effect observed was explained in terms of competing equilibrium and kinetic isotope effects in which the equilibrium isotope effects dominate. It was concluded on the bases of these results that an acyclic intermediate is involved in the fragmentation of methylenecyclobutane to ethylene and allene. The results also support the notion that deuterium prefers to accumulate at the methylene group with the greatest p character in the carbon--hydrogen bond. 1 figure, 4 tables

  19. Absence of isotope effect of diffusion in a metallic glass

    International Nuclear Information System (INIS)

    Heesemann, A.; Raetzke, K.; Faupel, F.; Hoffmann, J.; Heinemann, K.

    1995-01-01

    The isotope effect E = d ln(D)/d ln (1/√m) of Co diffusion in structurally relaxed Co 86 Zr 14 and Co 81 Zr 19 glasses has been measured by means of a radiotracer technique. Within experimental accuracy no isotope effect was detected (E < 0.04). This suggests a highly cooperative diffusion mechanism. The connection between diffusion and collective low-frequency relaxations in glasses is discussed. (orig.)

  20. The effect of netting solidity ratio and inclined angle on the hydrodynamic characteristics of knotless polyethylene netting

    Science.gov (United States)

    Tang, Hao; Hu, Fuxiang; Xu, Liuxiong; Dong, Shuchuang; Zhou, Cheng; Wang, Xuefang

    2017-10-01

    Knotless polyethylene (PE) netting has been widely used in aquaculture cages and fishing gears, especially in Japan. In this study, the hydrodynamic coefficient of six knotless PE netting panels with different solidity ratios were assessed in a flume tank under various attack angles of netting from 0° (parallel to flow) to 90° (perpendicular to flow) and current speeds from 40 cm s-1 to 130 cm s-1. It was found that the drag coefficient was related to Reynolds number, solidity ratio and attack angle of netting. The solidity ratio was positively related with drag coefficient for netting panel perpendicular to flow, whereas when setting the netting panel parallel to the flow the opposite result was obtained. For netting panels placed at an angle to the flow, the lift coefficient reached the maximum at an attack angle of 50° and then decreased as the attack angle further increased. The solidity ratio had a dual influence on drag coefficient of inclined netting panels. Compared to result in the literature, the normal drag coefficient of knotless PE netting measured in this study is larger than that of nylon netting or Dyneema netting.

  1. Effects of Net Blotch ( Pyrenophora teres ) on Malt Barley Yield and ...

    African Journals Online (AJOL)

    Barley (Hordeum vulgare L.) production is constrained by diseases such as net blotch caused by Pyrenophora teres Drechsl. The objectives of this study were to assess the effects of net blotch disease on malt barley yield and grain quality under natural infection. Four malt barley varieties (Beka, HB 120, HB 52 and Holker), ...

  2. Mass-independent isotope effects in chemical exchange reaction

    International Nuclear Information System (INIS)

    Nishizawa, Kazushige

    2000-01-01

    Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to δ 2 > which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of 53 Cr to total enrichment factor, ε 53/52 = -0.00028, for 53 Cr to 52 Cr was observed to be, ε spin = -0.0025. (author)

  3. H/D Isotope Effects in Hydrogen Bonded Systems

    Directory of Open Access Journals (Sweden)

    Aleksander Filarowski

    2013-04-01

    Full Text Available An extremely strong H/D isotope effect observed in hydrogen bonded A-H…B systems is connected with a reach diversity of the potential shape for the proton/deuteron motion. It is connected with the anharmonicity of the proton/deuteron vibrations and of the tunneling effect, particularly in cases of short bridges with low barrier for protonic and deuteronic jumping. Six extreme shapes of the proton motion are presented starting from the state without possibility of the proton transfer up to the state with a full ionization. The manifestations of the H/D isotope effect are best reflected in the infra-red absorption spectra. A most characteristic is the run of the relationship between the isotopic ratio nH/nD and position of the absorption band shown by using the example of NHN hydrogen bonds. One can distinguish a critical range of correlation when the isotopic ratio reaches the value of ca. 1 and then increases up to unusual values higher than . The critical range of the isotope effect is also visible in NQR and NMR spectra. In the critical region one observes a stepwise change of the NQR frequency reaching 1.1 MHz. In the case of NMR, the maximal isotope effect is reflected on the curve presenting the dependence of Δd (1H,2H on d (1H. This effect corresponds to the range of maximum on the correlation curve between dH and ΔpKa that is observed in various systems. There is a lack in the literature of quantitative information about the influence of isotopic substitution on the dielectric properties of hydrogen bond except the isotope effect on the ferroelectric phase transition in some hydrogen bonded crystals.

  4. Glutathione reductase: solvent equilibrium and kinetic isotope effects

    International Nuclear Information System (INIS)

    Wong, K.K.; Vanoni, M.A.; Blanchard, J.S.

    1988-01-01

    Glutathione reductase catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). The kinetic mechanism is ping-pong, and we have investigated the rate-limiting nature of proton-transfer steps in the reactions catalyzed by the spinach, yeast, and human erythrocyte glutathione reductases using a combination of alternate substrate and solvent kinetic isotope effects. With NADPH or GSSG as the variable substrate, at a fixed, saturating concentration of the other substrate, solvent kinetic isotope effects were observed on V but not V/K. Plots of Vm vs mole fraction of D 2 O (proton inventories) were linear in both cases for the yeast, spinach, and human erythrocyte enzymes. When solvent kinetic isotope effect studies were performed with DTNB instead of GSSG as an alternate substrate, a solvent kinetic isotope effect of 1.0 was observed. Solvent kinetic isotope effect measurements were also performed on the asymmetric disulfides GSSNB and GSSNP by using human erythrocyte glutathione reductase. The Km values for GSSNB and GSSNP were 70 microM and 13 microM, respectively, and V values were 62 and 57% of the one calculated for GSSG, respectively. Both of these substrates yield solvent kinetic isotope effects greater than 1.0 on both V and V/K and linear proton inventories, indicating that a single proton-transfer step is still rate limiting. These data are discussed in relationship to the chemical mechanism of GSSG reduction and the identity of the proton-transfer step whose rate is sensitive to solvent isotopic composition. Finally, the solvent equilibrium isotope effect measured with yeast glutathione reductase is 4.98, which allows us to calculate a fractionation factor for the thiol moiety of GSH of 0.456

  5. Isotope effect on the zero point energy shift upon condensation

    International Nuclear Information System (INIS)

    Kornblum, Z.C.; Ishida, T.

    1977-07-01

    The various isotope-dependent and independent atomic and molecular properties that pertain to the isotopic difference between the zero point energy (ZPE) shifts upon condensation were derived. The theoretical development of the change of the ZPE associated with the internal molecular vibrations, due to the condensation of the gaseous molecules, is presented on the basis of Wolfsberg's second-order perturbation treatment of the isotope-dependent London dispersion forces between liquid molecules. The isotope effect on the ZPE shift is related to the difference between the sums of the integrated intensities of the infrared absorption bands of the two gaseous isotopic molecules. The effective atomic charges are also calculated from available experimental infrared intensity data. The effects of isotopic substitutions of carbon-13 for carbon-12 and/or deuterium for protium, in ethylene, methane, and the fluorinated methanes, CH 3 F, CH 2 F 2 , CHF 3 , and CF 4 , on the ZPE shift upon condensation are calculated. These results compare well with the Bigeleisen B-factors, which are experimentally obtained from vapor pressure measurements of the isotopic species. Each of the following molecular properties will tend to increase the isotopic difference between the ZPE shifts upon condensation: (1) large number of highly polar bonds, (2) high molecular weight, (3) non-polar (preferably) or massive molecule, (4) non-hydrogenous molecule, and (5) closely packed liquid molecules. These properties will result in stronger dispersion forces in the liquid phase between the lighter molecules than between the isotopically heavier molecules. 36 tables, 9 figures

  6. Steric effects on the primary isotope dependence of secondary kinetic isotope effects in hydride transfer reactions in solution: caused by the isotopically different tunneling ready state conformations?

    Science.gov (United States)

    Maharjan, Binita; Raghibi Boroujeni, Mahdi; Lefton, Jonathan; White, Ormacinda R; Razzaghi, Mortezaali; Hammann, Blake A; Derakhshani-Molayousefi, Mortaza; Eilers, James E; Lu, Yun

    2015-05-27

    The observed 1° isotope effect on 2° KIEs in H-transfer reactions has recently been explained on the basis of a H-tunneling mechanism that uses the concept that the tunneling of a heavier isotope requires a shorter donor-acceptor distance (DAD) than that of a lighter isotope. The shorter DAD in D-tunneling, as compared to H-tunneling, could bring about significant spatial crowding effect that stiffens the 2° H/D vibrations, thus decreasing the 2° KIE. This leads to a new physical organic research direction that examines how structure affects the 1° isotope dependence of 2° KIEs and how this dependence provides information about the structure of the tunneling ready states (TRSs). The hypothesis is that H- and D-tunneling have TRS structures which have different DADs, and pronounced 1° isotope effect on 2° KIEs should be observed in tunneling systems that are sterically hindered. This paper investigates the hypothesis by determining the 1° isotope effect on α- and β-2° KIEs for hydride transfer reactions from various hydride donors to different carbocationic hydride acceptors in solution. The systems were designed to include the interactions of the steric groups and the targeted 2° H/D's in the TRSs. The results substantiate our hypothesis, and they are not consistent with the traditional model of H-tunneling and 1°/2° H coupled motions that has been widely used to explain the 1° isotope dependence of 2° KIEs in the enzyme-catalyzed H-transfer reactions. The behaviors of the 1° isotope dependence of 2° KIEs in solution are compared to those with alcohol dehydrogenases, and sources of the observed "puzzling" 2° KIE behaviors in these enzymes are discussed using the concept of the isotopically different TRS conformations.

  7. Bibliography on vapor pressure isotope effects

    International Nuclear Information System (INIS)

    Jancso, G.

    1980-04-01

    The first Bibliography on Vapour Pressure Isotope and covered the literature of the period from 1919 through December 1975. The present Supplement reviews the literature from January 1976 through December 1979. The bibliography is arranged in chronological order; within each year the references are listed alphabetically according to the name of the first author of each work. (author)

  8. Isotopic effects on phonon anharmonicity in layered van der Waals crystals: Isotopically pure hexagonal boron nitride

    Science.gov (United States)

    Cuscó, Ramon; Artús, Luis; Edgar, James H.; Liu, Song; Cassabois, Guillaume; Gil, Bernard

    2018-04-01

    Hexagonal boron nitride (h -BN) is a layered crystal that is attracting a great deal of attention as a promising material for nanophotonic applications. The strong optical anisotropy of this crystal is key to exploit polaritonic modes for manipulating light-matter interactions in 2D materials. h -BN has also great potential for solid-state neutron detection and neutron imaging devices, given the exceptionally high thermal neutron capture cross section of the boron-10 isotope. A good knowledge of phonons in layered crystals is essential for harnessing long-lived phonon-polariton modes for nanophotonic applications and may prove valuable for developing solid-state 10BN neutron detectors with improved device architectures and higher detection efficiencies. Although phonons in graphene and isoelectronic materials with a similar hexagonal layer structure have been studied, the effect of isotopic substitution on the phonons of such lamellar compounds has not been addressed yet. Here we present a Raman scattering study of the in-plane high-energy Raman active mode on isotopically enriched single-crystal h -BN. Phonon frequency and lifetime are measured in the 80-600-K temperature range for 10B-enriched, 11B-enriched, and natural composition high quality crystals. Their temperature dependence is explained in the light of perturbation theory calculations of the phonon self-energy. The effects of crystal anisotropy, isotopic disorder, and anharmonic phonon-decay channels are investigated in detail. The isotopic-induced changes in the phonon density of states are shown to enhance three-phonon anharmonic decay channels in 10B-enriched crystals, opening the possibility of isotope tuning of the anharmonic phonon decay processes.

  9. Inverse isotope effect in iron-based superconductor

    International Nuclear Information System (INIS)

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

    2010-01-01

    We have found that (Ba, K)Fe 2 As 2 superconductor (a transition temperature, T c ∼ 38 K) shows an inverse Iron isotope effect (α Fe = -0.18 ± 0.03, where T c ∼ M -αFe and M is the iron isotope mass), i.e. the sample containing the larger iron mass depicts higher T c . Systematic studies using three types of Fe-isotopes ( 54 Fe, natural Fe and 57 Fe) reveal a clear inverse shift on T c by measurements of temperature dependent magnetization and resistivity. The inverse isotope effect that is the first case in high-T c superconductors strongly suggests that superconducting mechanism of the iron-based system is not explained by conventional BCS theory mediated by phonons.

  10. Do evergreen and deciduous trees have different effects on net N mineralization in soil?

    Science.gov (United States)

    Mueller, Kevin E; Hobbie, Sarah E; Oleksyn, Jacek; Reich, Peter B; Eissenstat, David M

    2012-06-01

    Evergreen and deciduous plants are widely expected to have different impacts on soil nitrogen (N) availability because of differences in leaf litter chemistry and ensuing effects on net N mineralization (N(min)). We evaluated this hypothesis by compiling published data on net N(min) rates beneath co-occurring stands of evergreen and deciduous trees. The compiled data included 35 sets of co-occurring stands in temperate and boreal forests. Evergreen and deciduous stands did not have consistently divergent effects on net N(min) rates; net N(min) beneath deciduous trees was higher when comparing natural stands (19 contrasts), but equivalent to evergreens in plantations (16 contrasts). We also compared net N(min) rates beneath pairs of co-occurring genera. Most pairs of genera did not differ consistently, i.e., tree species from one genus had higher net N(min) at some sites and lower net N(min) at other sites. Moreover, several common deciduous genera (Acer, Betula, Populus) and deciduous Quercus spp. did not typically have higher net N(min) rates than common evergreen genera (Pinus, Picea). There are several reasons why tree effects on net N(min) are poorly predicted by leaf habit and phylogeny. For example, the amount of N mineralized from decomposing leaves might be less than the amount of N mineralized from organic matter pools that are less affected by leaf litter traits, such as dead roots and soil organic matter. Also, effects of plant traits and plant groups on net N(min) probably depend on site-specific factors such as stand age and soil type.

  11. Computing the net primary productivity for a savannah-dominated ecosystem using stable isotopes: a case study of the Volta River Basin

    International Nuclear Information System (INIS)

    Hayford, E.K.

    2008-01-01

    The hydrologic systems and the terrestrial ecosystem of the Volta river basin in West Africa, play important role in the carbon cycle. This is so because of the coupling of water vapour release and CO 2 uptake during photosynthesis, expressed as water use efficiency or transpiration ratio. Hydrologic and land-cover data, together with stable isotope ratio measurements of δ 18 O and δD, and data from the global network of isotopes in precipitation (GNIP) are used to determine the net primary productivity (NPP) of the Savannah-dominated ecosystem. The δ 18 O and δD values in the Volta rivers range from -4.72 to 2.37 mm -l and from -35.28 to 9.30 mm -1 SMOW, respectively. The results indicate that the vegetation is supported by 380 km 3 of rainfall, out of which 50% is returned to the atmosphere via plant transpiration. Associated with annual transpiration is the NPP of 0.170 x 10 15 gCyr -1 or 428 gCm -2 from the terrestrial ecosystem. Modelled estimates of heterotrophic soil respiration in this study slightly exceeded the NPP estimates, implying a small source of CO 2 to the atmosphere. This condition does not favour the postulated existence of a major sink of atmospheric CO 2 in the Volta basin. (au)

  12. Lithium isotope effect accompanying electrochemical intercalation of lithium into graphite

    CERN Document Server

    Yanase, S; Oi, T

    2003-01-01

    Lithium has been electrochemically intercalated from a 1:2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1 M LiClO sub 4 into graphite, and the lithium isotope fractionation accompanying the intercalation was observed. The lighter isotope was preferentially fractionated into graphite. The single-stage lithium isotope separation factor ranged from 1.007 to 1.025 at 25 C and depended little on the mole ratio of lithium to carbon of the lithium-graphite intercalation compounds (Li-GIC) formed. The separation factor increased with the relative content of lithium. This dependence seems consistent with the existence of an equilibrium isotope effect between the solvated lithium ion in the EC/MEC electrolyte solution and the lithium in graphite, and with the formation of a solid electrolyte interfaces on graphite at the early stage of intercalation. (orig.)

  13. Clumped isotope effects during OH and Cl oxidation of methane

    DEFF Research Database (Denmark)

    Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan Albrecht

    2017-01-01

    A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produ......A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH...... effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE...... reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane...

  14. Effect of gamma radiation on chlorophylls contents, net photosynthesis and respiration of chlorella pyrenoidosa

    International Nuclear Information System (INIS)

    Fernandez Gonzalez, J.; Martin Moreno, C.

    1983-01-01

    The effect of five doses of gamma radiation: 10, 100, 500, 1000 and 5000 Gy on chlorophylls content, net photosynthesis and respiration of chlorella pyrenoidosa has been studied. A decrease in chlorophylls levels is produced after irradiation at 500, 1000 and 5000 Gy, being, at first 'b' chlorophyll affected to a greater extent than 'a' chlorophyll. Net photosynthesis and respiration decline throughout the time of the observations after irradiation, this depressing effect being much more remarkable for the first one. Net photosynthesis inhibition levels of about 30% have got only five hours post irradiation at a dose of 5000 Gy. (author)

  15. Concentration effect on inter-mineral equilibrium isotope fractionation: insights from Mg and Ca isotopic systems

    Science.gov (United States)

    Huang, F.; Wang, W.; Zhou, C.; Kang, J.; Wu, Z.

    2017-12-01

    Many naturally occurring minerals, such as carbonate, garnet, pyroxene, and feldspar, are solid solutions with large variations in chemical compositions. Such variations may affect mineral structures and modify the chemical bonding environment around atoms, which further impacts the equilibrium isotope fractionation factors among minerals. Here we investigated the effects of Mg content on equilibrium Mg and Ca isotope fractionation among carbonates and Ca content on equilibrium Ca isotope fractionation between orthopyroxene (opx) and clinopyroxene (cpx) using first-principles calculations. Our results show that the average Mg-O bond length increases with decreasing Mg/(Mg+Ca) in calcite when it is greater than 1/48[1] and the average Ca-O bond length significantly decreases with decreasing Ca/(Ca+Mg+Fe) in opx when it ranges from 2/16 to 1/48[2]. Equilibrium isotope fractionation is mainly controlled by bond strengths, which could be measured by bond lengths. Thus, 103lnα26Mg/24Mg between dolomite and calcite dramatically increases with decreasing Mg/(Mg+Ca) in calcite [1] and it reaches a constant value when it is lower than 1/48. 103lnα44Ca/40Ca between opx and cpx significantly increases with decreasing Ca content in opx when Ca/(Ca+Mg+Fe) ranges from 2/16 to 1/48 [2]. If Ca/(Ca+Mg+Fe) is below 1/48, 103lnα44Ca/40Ca is not sensitive to Ca content. Based on our results, we conclude that the concentration effect on equilibrium isotope fractionation could be significant within a certain range of chemical composition of minerals, which should be a ubiquitous phenomenon in solid solution systems. [1] Wang, W., Qin, T., Zhou, C., Huang, S., Wu, Z., Huang, F., 2017. GCA 208, 185-197. [2] Feng, C., Qin, T., Huang, S., Wu, Z., Huang, F., 2014. GCA 143, 132-142.

  16. Pollution and Climate Effects on Tree-Ring Nitrogen Isotopes

    Science.gov (United States)

    Savard, M. M.; Bégin, C.; Marion, J.; Smirnoff, A.

    2009-04-01

    Georgian Bay reflect deposition of NOx emissions from cars and coal-power plants, with higher proportions from coal burning in Georgian Bay (Savard et al., 2009b). This interpretation is conceivable because recent monitoring indicates that coal-power plant NOx emissions play an important role in the annual N budget in Ontario, but they are negligible on the Quebec side. CONCLUSION Interpretations of long tree-ring N isotopic series in terms of effects generated by airborne N-species have been previously advocated. Here we further propose that the contrasted isotopic trends obtained for wood samples from two regions reflect different regional anthropogenic N deposition combined with variations of climatic conditions. This research suggests that nitrogen tree-ring series may record both regional climatic conditions and anthropogenic perturbations of the N cycle. REFERENCES Savard, M.M., Bégin,C., Marion, J., Aznar, J.-C., Smirnoff, A., 2009a. Changes of Air Quality in an urban region as inferred from tree-ring width and stable isotopes. Chapter 9 in "Relating Atmospheric Source Apportionment to Vegetation Effects: Establishing Cause Effect Relationships" (A. Legge ed.). Elsevier, Amsterdam; doi: 10.1016/S1474-8177(08)00209x. Savard, M.M., Bégin, C., Smirnoff, A., Marion, J., Rioux-Paquette, E., 2009b. Tree-ring nitrogen isotopes reflect climatic effects and anthropogenic NOx emissions. Env. Sci. Tech (doi: 10.1021/es802437k).

  17. Mass independent isotope effects and their observations in nature

    International Nuclear Information System (INIS)

    Thiemens, M.H.

    2002-01-01

    In 1983, Thiemens and Heidenreich reported the first chemically produced mass independent isotope effect. A significant feature of the fractionation was that it identically produced the isotopic relation observed in the calcium-aluminum inclusions in the Allende meteorite. This δ 17 O=δ 18 O composition had previously been thought to represent a nucleosynthetic component as no chemical process was capable of producing a mass independent isotopic composition. It now appears nearly certain that the meteoritic oxygen isotopic anomalies were produced by chemical, rather than nuclear, processes. Since oxygen is the major element in stony planets this represents a major event in the formation of the solar system. In a recent review (Thiemens, 1999), it has been shown that mass independent isotopic compositions are pervasive in the Earth's atmosphere. Molecules which have been demonstrated to possess mass independent isotopic compositions include: O 2 , O 3 , CO 2 , CO, and N 2 O. In each case, the specific nature of the mass independent isotopic composition has provided details of their atmospheric chemistry that could not have been obtained by any other measurement technique. Most recently, solid materials have been observed to possess mass independent isotopic composition. In this paper, these observations are briefly discussed. These solid reservoirs include: 1) carbonates and sulphates from Mars, 2) terrestrial aerosol sulphate, 3) sulphides and sulphates from the Earth, ranging in time from 3.8 to 2.2 billion years before present, 4) sulphates from the Namibian desert and 5) the Antartic Dry Valleys. The information obtained from these measurements is extraordinarily wide ranging, extending from understanding the history of Martian atmosphereregolith interaction to the evolution of the oxygen in the Earth's earliest atmosphere. As was the case for gas phase species, this information and insight could not have been obtained by any other measurement technique

  18. Transport hysteresis and hydrogen isotope effect on confinement

    Science.gov (United States)

    Itoh, S.-I.; Itoh, K.

    2018-03-01

    A Gedankenexperiment on hydrogen isotope effect is developed, using the transport model with transport hysteresis. The transport model with hysteresis is applied to case where the modulational electron cyclotron heating is imposed near the mid-radius of the toroidal plasmas. The perturbation propagates either outward or inward, being associated with the clockwise (CW) hysteresis or counter-clockwise (CCW) hysteresis, respectively. The hydrogen isotope effects on the CW and CCW hysteresis are investigated. The local component of turbulence-driven transport is assumed to be the gyro-Bohm diffusion. While the effect of hydrogen mass number is screened in the response of CW hysteresis, it is amplified in CCW hysteresis. This result motivates the experimental studies to compare CW and CCW cases in order to obtain further insight into the physics of hydrogen isotope effects.

  19. Isotope and mixture effects on neoclassical transport in the pedestal

    Science.gov (United States)

    Pusztai, Istvan; Buller, Stefan; Omotani, John T.; Newton, Sarah L.

    2017-10-01

    The isotope mass scaling of the energy confinement time in tokamak plasmas differs from gyro-Bohm estimates, with implications for the extrapolation from current experiments to D-T reactors. Differences in mass scaling in L-mode and various H-mode regimes suggest that the isotope effect may originate from the pedestal. In the pedestal, sharp gradients render local diffusive estimates invalid, and global effects due to orbit-width scale profile variations have to be taken into account. We calculate neoclassical cross-field fluxes from a radially global drift-kinetic equation using the PERFECT code, to study isotope composition effects in density pedestals. The relative reduction to the peak heat flux due to global effects as a function of the density scale length is found to saturate at an isotope-dependent value that is larger for heavier ions. We also consider D-T and H-D mixtures with a focus on isotope separation. The ability to reproduce the mixture results via single-species simulations with artificial ``DT'' and ``HD'' species has been considered. These computationally convenient single ion simulations give a good estimate of the total ion heat flux in corresponding mixtures. Funding received from the International Career Grant of Vetenskapsradet (VR) (330-2014-6313) with Marie Sklodowska Curie Actions, Cofund, Project INCA 600398, and Framework Grant for Strategic Energy Research of VR (2014-5392).

  20. The effect of net foreign assets on saving rate

    Directory of Open Access Journals (Sweden)

    Ben David Nissim

    2014-01-01

    Full Text Available Observing empirical data we find that many countries try to delay the decision of increasing saving rate in order to avoid a decrease of the living standards. However the delay leads a deterioration of countries financial stability. We present a simple theoretical model that connects between countries' saving rate and their net foreign assets. Using cross section data set of 135 countries in 2010 we estimated the econometric relation between saving rate in 2010 as dependent variable and two explanatory variables: the current account in 2010 and the aggregated current account during 1980-2010. Our findings show that industrial countries in a bad financial state tend to decrease their saving rate as external debt is larger causing to deterioration in external debt while countries with good financial state tend to increase their saving rate and the tendency increase as financial state becomes better. Only in countries with a very large external debt saving rate tends to grow. The results point that gross foreign debt will keep increasing and will worsen world financial state causing increased risk of getting into a world crisis.

  1. Anharmonic phonons and the isotope effect in superconductivity

    International Nuclear Information System (INIS)

    Crespi, V.H.; Cohen, M.L.; Penn, D.R.

    1991-01-01

    Anharmonic interionic potentials are examined in an Einstein model to study the unusual isotope-effect exponents for the high-T c oxides. The mass dependences of the electron-phonon coupling constant λ and the average phonon frequency √ left-angle ω 2 right-angle are computed from weighted sums over the oscillator levels. The isotope-effect exponent is depressed below 1/2 by either a double-well potential or a potential with positive quadratic and quartic parts. Numerical solutions of Schroedinger's equation for double-well potentials produce λ's in the range 1.5--4 for a material with a vanishing isotope-effect parameter α. However, low phonon frequencies limit T c to roughly 15 K. A negative quartic perturbation to a harmonic well can increase α above 1/2. In the extreme-strong-coupling limit, α is 1/2, regardless of anharmonicity

  2. Effect of net surface charge on particle sizing and material recognition by using phase Doppler anemometry

    International Nuclear Information System (INIS)

    Zhou Jun; Xie Li

    2011-01-01

    By taking net surface charge into consideration, the scattering field of particles illuminated by dual laser beams of phase Doppler anemometry (PDA) is computed based on Mie's theory, and the effect of net surface charge on the phase-diameter relationship and the phase ratio is studied. It is found that the phase-diameter relationship and the relationship between the phase ratio and the refractive index of charged particles could be significantly different from those of uncharged particles, which would lead to errors in particle sizing and the measurement of refractive indices. A method of recognizing charged particles and determining the value of their surface conductivity, which is related to net surface charge, is proposed by utilizing the effect of net surface charge on the measurement of refractive indices using PDA.

  3. Effect of net surface charge on particle sizing and material recognition by using phase Doppler anemometry

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Jun; Xie Li

    2011-01-20

    By taking net surface charge into consideration, the scattering field of particles illuminated by dual laser beams of phase Doppler anemometry (PDA) is computed based on Mie's theory, and the effect of net surface charge on the phase-diameter relationship and the phase ratio is studied. It is found that the phase-diameter relationship and the relationship between the phase ratio and the refractive index of charged particles could be significantly different from those of uncharged particles, which would lead to errors in particle sizing and the measurement of refractive indices. A method of recognizing charged particles and determining the value of their surface conductivity, which is related to net surface charge, is proposed by utilizing the effect of net surface charge on the measurement of refractive indices using PDA.

  4. Kinetic isotope effects and aliphatic diazo-compounds

    International Nuclear Information System (INIS)

    Albery, W.J.; Conway, C.W.; Hall, J.A.

    1976-01-01

    Results are reported for the variation of the rate of decomposition of ethyl diazomalonate (EDM) and diazomalonate anions with pH and for the deuterium solvent isotope effect for EDM. The shape of the pH profile is explained by successive protonations of the anions. Ethyl diazoacetate is observed as an intermediate in the decomposition of EDM. The degree of proton transfer in the EDM transition state is deduced from the solvent isotope effect and the results together with those for other aliphatic diazo-compounds are discussed in terms of the Marcus theory. (author)

  5. Shifts in rotifer life history in response to stable isotope enrichment: testing theories of isotope effects on organismal growth

    Science.gov (United States)

    2017-01-01

    In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic isotope effects in vivo. Here, I demonstrate profound changes in life histories of the rotifer Brachionus plicatilis fed 15N-enriched algae (0.4–5.0 at%); i.e. at the enrichment levels commonly used in ecological studies. These findings support theoretically predicted effects of heavy isotope enrichment on growth, metabolism and ageing in biological systems and underline the importance of accounting for such effects when using stable isotope labelling in experimental studies. PMID:28405367

  6. 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.)

  7. The net effects of the Project NetWork return-to-work case management experiment on participant earnings, benefit receipt, and other outcomes.

    Science.gov (United States)

    Kornfeld, R; Rupp, K

    2000-01-01

    The Social Security Administration (SSA) initiated Project NetWork in 1991 to test case management as a means of promoting employment among persons with disabilities. The demonstration, which targeted Social Security Disability Insurance (DI) beneficiaries and Supplemental Security Income (SSI) applicants and recipients, offered intensive outreach, work-incentive waivers, and case management/referral services. Participation in Project NetWork was voluntary. Volunteers were randomly assigned to the "treatment" group or the "control" group. Those assigned to the treatment group met individually with a case or referral manager who arranged for rehabilitation and employment services, helped clients develop an individual employment plan, and provided direct employment counseling services. Volunteers assigned to the control group could not receive services from Project NetWork but remained eligible for any employment assistance already available in their communities. For both treatment and control groups, the demonstration waived specific DI and SSI program rules considered to be work disincentives. The experimental impact study thus measures the incremental effects of case and referral management services. The eight demonstration sites were successful in implementing the experimental design roughly as planned. Project NetWork staff were able to recruit large numbers of participants and to provide rehabilitation and employment services on a substantial scale. Most of the sites easily reached their enrollment targets and were able to attract volunteers with demographic characteristics similar to those of the entire SSI and DI caseload and a broad range of moderate and severe disabilities. However, by many measures, volunteers were generally more "work-ready" than project eligible in the demonstration areas who did not volunteer to receive NetWork services. Project NetWork case management increased average annual earnings by $220 per year over the first 2 years following

  8. Chlorine isotope effects from isotope ratio mass spectrometry suggest intramolecular C-Cl bond competition in trichloroethene (TCE) reductive dehalogenation.

    Science.gov (United States)

    Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

    2014-05-20

    Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms.

  9. Chlorine Isotope Effects from Isotope Ratio Mass Spectrometry Suggest Intramolecular C-Cl Bond Competition in Trichloroethene (TCE Reductive Dehalogenation

    Directory of Open Access Journals (Sweden)

    Stefan Cretnik

    2014-05-01

    Full Text Available Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (biochemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE dehalogenation was investigated. Selective biotransformation reactions (i of tetrachloroethene (PCE to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii of TCE to cis-1,2-dichloroethene (cis-DCE in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were −19.0‰ ± 0.9‰ (PCE and −12.2‰ ± 1.0‰ (TCE (95% confidence intervals. Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (−5.0‰ ± 0.1‰ and TCE (−3.6‰ ± 0.2‰. In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by −16.3‰ ± 1.4‰ (standard error than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of −2.4‰ ± 0.3‰ and the product chloride an isotope effect of −6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals. A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect. These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition. This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I or single electron transfer as reductive dehalogenation mechanisms.

  10. Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition

    International Nuclear Information System (INIS)

    Zielinski, M.; Zielinska, A.; Papiernik-Zielinska, H.; McKenzie, J.A.; Bernasconi, S.; Paul, H.

    1998-01-01

    Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition above and below its melting temperature have been studied and compared with the primary (PKIE) and secondary kinetic isotope effects (SKIE) of 13 C and 18 O, respectively, in the decarboxylation of other heterocyclic acids. The temperature dependence of the secondary oxygen-18 isotope effects is negative in the total 221-255 deg C temperature interval investigated initially. The 13 C KIE measured above melting point of N.A. (temperature interval 235-270 deg C) are located in the range 1.007-1.009. Below melting point of nicotinic acid the 13 C KIE are larger and reveal the negative temperature dependence ( 13 C KIE decreases with decreasing the reaction temperature from 1.013/at 230 deg C to 1.0114/at 221 deg C). A discussion of the above isotopic results is presented. (author)

  11. Secondary isotope effects on alpha-cleavage reactions

    International Nuclear Information System (INIS)

    Ingemann, S.; Hammerum, S.

    1980-01-01

    Kinetic deuterium isotope effects on mass spectral reactions have in several instances been utilized to provide structural information and to answer mechanistic questions. Typically, the influence of the deuterium label on the rate of one of a number of competing reactions has been studied. Secondary isotope effects have usually been assumed to be relatively insignificant in comparison with the observed kinetic effects, even though various workers have shown that secondary isotope effects may indeed exert a considerable influence on the rates of competing simple cleavages. Recent studies have provided quantitative data to show that the mere presence of deuterium atoms up to six bonds away may influence the rate of a simple cleavage reaction. In relation to an investigation of rearrangements accompanying simple cleavage reactions, a semi-quantitative measure was needed of the variation of the secondary isotope effect with the number of bonds between the deuterium label and the point of rupture. The influence has therefore been examined of the presence of remote deuterium atoms on a typical simple cleavage reaction, the α-cleavage of aliphatic amines. As a model compound, N-methyldipentylamine was chosen, systematically labelled with deuterium. (author)

  12. Deuterium secondary isotope kinetic effects in imine formation reactions

    International Nuclear Information System (INIS)

    Amaral, L. do; Rossi, M.H.

    1986-01-01

    The kinetic α-deuterium isotope effects, K D /K H , for reaction mechanisms is studied. The reaction of pH function to m-bromobenzaldehyde, semicarbazide nucleophile, methoxy-amine and hydroxylamine are analysed. (M.J.C.) [pt

  13. Magic numbers and isotopic effect of ion clusters

    International Nuclear Information System (INIS)

    Wang Guanghou

    1989-04-01

    The magic numbers and isotopic effect as well as stable configurations in relation to the charge state of the clusters are discussed. Ionic (atomic) clusters are small atomic aggregates, a physical state between gas and solid states, and have many interesting properties, some of them are more or less similar to those in nuclei

  14. In situ autumn ozone fumigation of mature Norway spruce - Effects on net photosynthesis

    DEFF Research Database (Denmark)

    Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2002-01-01

    concentration. The experiment was conducted during 70 days during the autumn. Our system could not detect any ozone effects on dark respiration, but eventually effects on dark respiration could be masked in signal noise. An inhibition of daily net photosynthesis in ozone treated shoots was apparent......, and it is was found that a mean increase in ozone concentration of 10 nl l(-1) reduced net photosynthesis with 7.4 %. This effect should be related to a pre-exposure during the season of AOT40 12.5 mul l(-1) h....

  15. Transient competitive complexation in biological kinetic isotope fractionation explains nonsteady isotopic effects: Theory and application to denitrification in soils

    Science.gov (United States)

    Maggi, Federico; Riley, William J.

    2009-12-01

    The theoretical formulation of biological kinetic isotope fractionation often assumes first-order or Michaelis-Menten kinetics, the latter solved under the quasi-steady state assumption. Both formulations lead to a constant isotope fractionation factor, therefore they may return incorrect estimations of isotopic effects and misleading interpretations of isotopic signatures when fractionation is not a steady process. We have analyzed the isotopic signature of denitrification in biogeochemical soil systems by Menyailo and Hungate (2006) in which high and variable 15N-N2O enrichment during N2O production and inverse isotope fractionation during N2O consumption could not be explained with first-order kinetics and the Rayleigh equation, or with Michaelis-Menten kinetics. When Michaelis-Menten kinetics were coupled to Monod kinetics to describe biomass and enzyme dynamics, and the quasi-steady state assumption was relaxed, transient Michaelis-Menten-Monod kinetics accurately reproduced the observed concentrations, and variable and inverse isotope fractionations. These results imply a substantial revision in modeling isotopic effects, suggesting that steady state kinetics such as first-order, Rayleigh, and classic Michaelis-Menten kinetics should be superseded by transient kinetics in conjunction with biomass and enzyme dynamics.

  16. Isotope effects accompanying evaporation of water from leaky containers.

    Science.gov (United States)

    Rozanski, Kazimierz; Chmura, Lukasz

    2008-03-01

    Laboratory experiments aimed at quantifying isotope effects associated with partial evaporation of water from leaky containers have been performed under three different settings: (i) evaporation into dry atmosphere, performed in a dynamic mode, (ii) evaporation into dry atmosphere, performed in a static mode, and (iii) evaporation into free laboratory atmosphere. The results demonstrate that evaporative enrichment of water stored in leaky containers can be properly described in the framework of the Craig-Gordon evaporation model. The key parameter controlling the degree of isotope enrichment is the remaining fraction of water in the leaking containers. Other factors such as temperature, relative humidity, or extent of kinetic fractionation play only minor roles. Satisfactory agreement between observed and predicted isotope enrichments for both (18)O and (2)H in experiments for the case of evaporation into dry atmosphere could be obtained only when molecular diffusivity ratios of isotope water molecules as suggested recently by Cappa et al. [J. Geophys. Res., 108, 4525-4535, (2003).] were adopted. However, the observed and modelled isotope enrichments for (2)H and (18)O could be reconciled also for the ratios of molecular diffusivities obtained by Merlivat [J. Chem. Phys., 69, 2864-2871 (1978).], if non-negligible transport resistance in the viscous liquid sub-layer adjacent to the evaporating surface is considered. The evaporation experiments revealed that the loss of mass of water stored in leaky containers in the order of 1%, will lead to an increase of the heavy isotope content in this water by ca. 0.35 and 1.1 per thousand, for delta (18)O and delta (2)H, respectively.

  17. Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

    Science.gov (United States)

    Sutcliffe, James; Colborn, Kathryn L

    2015-05-13

    Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect

  18. Optimum measuring net for correcting mineralizing heterogeneity effect in XRF sampling

    International Nuclear Information System (INIS)

    Zhou Sichun; Zhao Youqing; Zhang Yuhuan

    2000-01-01

    The mineralizing heterogeneity effect in XRF sampling was investigated with theory of mathematical statistics. A method called 'Optimum measuring Net' has been developed. The theoretical estimation and experimental results show that the mineralizing heterogeneity effect can be cut down to the minimum with the method

  19. Entomological determinants of insecticide-treated bed net effectiveness in Western Myanmar

    NARCIS (Netherlands)

    Smithuis, Frank M.; Kyaw, Moe Kyaw; Phe, U. Ohn; van der Broek, Ingrid; Katterman, Nina; Rogers, Colin; Almeida, Patrick; Kager, Piet A.; Stepniewska, Kasia; Lubell, Yoel; Simpson, Julie A.; White, Nicholas J.

    2013-01-01

    In a large cluster randomized control trial of insecticide-treated bed nets (ITN) in Western Myanmar the malaria protective effect of ITN was found to be highly variable and, in aggregate, the effect was not statistically significant. A coincident entomological investigation measured malaria vector

  20. Tritium conductivity and isotope effect in proton-conducting perovskites

    International Nuclear Information System (INIS)

    Mukundan, R.; Brosha, E.L.; Birdsell, S.A.; Costello, A.L.; Garzon, F.H.; Willms, R.S.

    1999-01-01

    The tritium ion conductivities of SrZr 0.9 Yb 0.1 O 2.95 and BaCe 0.9 Yb 0.1 O 2.95 have been measured by ac impedance analysis. The high tritium conductivity of these perovskites could potentially lead to their application as an electrochemical membrane for the recovery of tritium from tritiated gas streams. The conductivities of these perovskites, along with SrCe 0.95 Yb 0.05 O 2.975 , were also measured in hydrogen- and deuterium-containing atmospheres to illustrate the isotope effect. For the strontium zirconate and barium cerate samples, the impedance plot consists of two clearly resolved arcs, a bulk and a grain boundary arc, in the temperature range 50--350 C. However, for the strontium cerate sample, the clear resolution of the bulk conductivity was not possible and only the total conductivity was measurable. Thus, the isotope effect was clearly established only for the strontium zirconate and barium cerate samples. The decrease in bulk conductivity with increasing isotope mass was found to be a result of an increase in the activation energy for conduction accompanied by a decrease in the pre-exponential factor. Since the concentration of the mobile species (H+, D+, or T+) should remain relatively constant at T < 350 C, this increase in activation energy is directly attributable to the increased activation energy for the isotope mobility

  1. Modification of the isotope effect due to pair breaking

    International Nuclear Information System (INIS)

    Carbotte, J.P.; Greeson, M.; Perez-Gonzalez, A.

    1991-01-01

    We have calculated the effect of pair breaking on the isotope-effect coefficient (β) of a superconductor. We find that, as the pair-breaking scattering rate is increased, β also increases in absolute value. Values of β much larger than the canonical value of 1/2 can easily be achieved even in models where the electron-phonon interaction contributes only a very small amount to the value of the intrinsic critical temperature

  2. The effect of the 'no net loss' of habitat guiding principle on Manitoba Hydro's Conawapa project

    International Nuclear Information System (INIS)

    Dick, C.J.

    1992-04-01

    The potential effect of the 'no net loss' principle on Manitoba Hydro's Conawapa hydroelectric project is assessed, including an examination of the process by which the no net loss principle will likely be implemented at the site, based on a review of past applications of the policy. The no net loss principle was developed by the federal Department of Fisheries of Oceans (DFO) as part of their 1986 Policy for the Management of Fish Habitats. The overall objective of the policy is to achieve a net gain of the productive capacity of fish habitats in Canada. Application of the policy to specific developments is based upon maintaining the productive capacity of fish habitats as well as the needs of users groups. The policy has not yet been applied to an inland hydroelectric project. Achieving no net losses may be difficult in regard to large projects such as a hydro dam, however a review of past applications of the policy reveal a number of concepts that have been employed by the DFO when applying the no net loss principle. These concepts were applied to the Conawapa project to make recommendations to achieve no net loss if the project is developed. Mitigation and compensation measures must be developed for both brook trout and lake sturgeon habitat, and should include a combination of habitat enhancement and increased protection and compliance. Measures should also be developed for other species such as lake cisco and lake whitefish, both of which may be a food source for beluga whales. The Conawapa forebay may be given consideration as compensation for lost habitat. 81 refs., 11 figs., 2 tabs

  3. Storm Effects on Net Ecosystem Productivity in Boreal Forests

    Science.gov (United States)

    Vestin, Patrik; Grelle, Achim; Lagergren, Fredrik; Hellström, Margareta; Langvall, Ola; Lindroth, Anders

    2010-05-01

    Regional carbon budgets are to some extent determined by disturbance in ecosystems. Disturbance is believed to be partly responsible for the large inter-annual variability of the terrestrial carbon balance. When neglecting anthropogenic disturbance, forest fires have been considered the most important kind of disturbance. However, also insect outbreaks and wind-throw may be major factors in regional carbon budgets. The effects of wind-throw on CO2 fluxes in boreal forests are not well known due to lack of data. Principally, the reduced carbon sequestration capacity, increased substrate availability and severe soil perturbation following wind-throw are expected to result in increased CO2 fluxes from the forest to the atmosphere. In January 2005, the storm Gudrun hit Sweden, which resulted in approx. 66 × 106m3storm-felled stem wood distributed over an area of approx. 272 000 ha. Eddy covariance flux measurements started at storm-felled areas in Asa and Toftaholm in central Sweden during summer 2005. Data from the first months suggests increased CO2 fluxes by a factor of 2.5-10, as compared to normal silviculture (clear-cutting). An important question is how long such enhanced CO2 fluxes persist. The BIOME-BGC model will be calibrated against measured CO2 fluxes from both sites for 2005 through 2009. Modeled data will be used to fill gaps in the data sets and annual carbon balances will be calculated. Data from Asa and Toftaholm will be presented at the conference.

  4. Isotope effects in photo dissociation of ozone with visible light

    Science.gov (United States)

    Früchtl, Marion; Janssen, Christof; Röckmann, Thomas

    2014-05-01

    Ozone (O3) plays a key role for many chemical oxidation processes in the Earth's atmosphere. In these chemical reactions, ozone can transfer oxygen to other trace gases. This is particularly interesting, since O3 has a very peculiar isotope composition. Following the mass dependent fractionation equation δ17O = 0.52 * δ18O, most fractionation processes depend directly on mass. However, O3 shows an offset to the mass dependent fractionation line. Processes, which show such anomalies, are termed mass independent fractionations (MIF). A very well studied example for a chemical reaction that leads to mass independent fractionation is the O3 formation reaction. To what degree O3 destruction reactions need to be considered in order to understand the isotope composition of atmospheric O3 is still not fully understood and an open question within scientific community. We set up new experiments to investigate the isotope effect resulting from photo dissociation of O3 in the Chappuis band (R1). Initial O3 is produced by an electric discharge. After photolysis O3 is collected in a cold trap at the triple point temperature of nitrogen (63K). O3 is then converted to O2 in order to measure the oxygen isotopes of O3 using isotope ratio mass spectrometry. To isolate O3 photo dissociation (R1) from O3 decomposition (R2) and secondary O3 formation (R3), we use varying amounts of carbon monoxide (CO) as O atom quencher (R4). In this way we suppress the O + O3 reaction (R3) and determine the isotope fractionation in R1 and R2 separately. We present first results on the isotope effects in O3 photo dissociation with visible light in the presence of different bath gases. Results are interpreted based on chemical kinetics modeling. (R1) O3 + hυ → O (3P) + O2 (R2) O3 + O (3P) → 2 O2 (R3) O + O2 + M → O3 + M (R4) O (3P) + CO + M → CO2 + M

  5. Marginal-Fermi-liquid theory and the isotope effect

    International Nuclear Information System (INIS)

    Nicol, E.J.; Carbotte, J.P.

    1991-01-01

    In the marginal-Fermi-liquid model, the coupling between two electrons is via charge (attractive) and spin (repulsive) fluctuations, and so it does not exhibit an isotope effect. To include this effect, an additional phonon contribution must be introduced. Using the case of YBa 2 Cu 3 O 7 , for illustrative purposes, with a total isotope effect coefficient of β tot congruent 0.05 at a T c of 90 K, we find that the implied electron-phonon mass renormalization is very small for coupling to high-energy phonons but increases rapidly with decreasing phonon frequency or an increasing amount of spin fluctuations. Finally, we examine how β increases with decreasing T c when charge fluctuations are reduced or spin fluctuations augmented

  6. Field-emission from parabolic tips: Current distributions, the net current, and effective emission area

    Science.gov (United States)

    Biswas, Debabrata

    2018-04-01

    Field emission from nano-structured emitters primarily takes place from the tips. Using recent results on the variation of the enhancement factor around the apex [Biswas et al., Ultramicroscopy 185, 1-4 (2018)], analytical expressions for the surface distribution of net emitted electrons, as well as the total and normal energy distributions are derived in terms of the apex radius Ra and the local electric field at the apex Ea. Formulae for the net emitted current and effective emission area in terms of these quantities are also obtained.

  7. Net Gain

    International Development Research Centre (IDRC) Digital Library (Canada)

    Describing the effect of tax incentives for import, production, and sale of nets and insecticides; and ..... So far, China is the only country where a system for the routine treatment of ...... 1993), and the trials in Ecuador and Peru (Kroeger et al.

  8. Estimating climate change effects on net primary production of rangelands in the United States

    Science.gov (United States)

    Matthew C. Reeves; Adam L. Moreno; Karen E. Bagne; Steven W. Running

    2014-01-01

    The potential effects of climate change on net primary productivity (NPP) of U.S. rangelands were evaluated using estimated climate regimes from the A1B, A2 and B2 global change scenarios imposed on the biogeochemical cycling model, Biome-BGC from 2001 to 2100. Temperature, precipitation, vapor pressure deficit, day length, solar radiation, CO2 enrichment and nitrogen...

  9. Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

    International Nuclear Information System (INIS)

    Zielinski, M.; Czarnota, G.; Papiernik-Zielinska, H.; Kasprzyk, G.; Gumolka, L.; Staedter, W.

    1993-01-01

    The 13 C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphoric acids (PA) and by 85% H 3 PO 4 has been studied in the temperature interval of 60-150 deg C. The values of the 13 C (1) isotope effects in the decarbonylation of lactic acid in 100% H 3 PO 4 , in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C (1)- OH bond is broken in the rate-controlling step of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90-130 deg C the experimental 13 C fractionation factors determined in concentrated PA approach quite closely the 13 C fractionation corresponding to C (2)- C (1) bond scission. The 13 C (1) kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110-150 deg C coincide with the 13 C isotope effects calculated assuming that the frequency corresponding to the C (1) -OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H 3 PO 4 has been suggested. A possible secondary 18 O and a primary 18 O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too. (author) 21 refs.; 3 tabs

  10. Isotope effects in ion-exchange equilibria in aqueous and mixed solvent systems

    International Nuclear Information System (INIS)

    Gupta, A.R.

    1979-01-01

    Isotope effects in ion-exchange equilibria in aqueous and mixed solvents are analyzed in terms of the general features of ion-exchange equilibria and of isotope effects in chemical equilibria. The special role of solvent fractionation effects in ion-exchange equilibria in mixed solvents is pointed out. The various situations arising in isotope fractionation in ion exchange in mixed solvents due to solvent fractionation effects are theoretically discussed. The experimental data on lithium isotope effects in ion-exchange equilibria in mixed solvents are shown to conform to the above situations. The limitations of ion-exchange equilibria in mixed solvents for isotope fractionation are pointed out. 3 tables

  11. Aerodynamic effects in isotope separation by gaseous diffusion

    International Nuclear Information System (INIS)

    Bert, L.A.; Prosperetti, A.; Fiocchi, R.

    1978-01-01

    The turbulent flow of an isotopic mixture in a porous-walled pipe is considered in the presence of suction through the wall. A simple model is formulated for the evaluation of aerodynamic effects on the separation efficiency. The predictions of the model are found to compare very favourably with experiment. In the limit of small suction velocities, results obtained by other investigators for diffusion in a turbulent steam are recovered. (author)

  12. Cost and cost effectiveness of long-lasting insecticide-treated bed nets - a model-based analysis

    Directory of Open Access Journals (Sweden)

    Pulkki-Brännström Anni-Maria

    2012-04-01

    Full Text Available Abstract Background The World Health Organization recommends that national malaria programmes universally distribute long-lasting insecticide-treated bed nets (LLINs. LLINs provide effective insecticide protection for at least three years while conventional nets must be retreated every 6-12 months. LLINs may also promise longer physical durability (lifespan, but at a higher unit price. No prospective data currently available is sufficient to calculate the comparative cost effectiveness of different net types. We thus constructed a model to explore the cost effectiveness of LLINs, asking how a longer lifespan affects the relative cost effectiveness of nets, and if, when and why LLINs might be preferred to conventional insecticide-treated nets. An innovation of our model is that we also considered the replenishment need i.e. loss of nets over time. Methods We modelled the choice of net over a 10-year period to facilitate the comparison of nets with different lifespan (and/or price and replenishment need over time. Our base case represents a large-scale programme which achieves high coverage and usage throughout the population by distributing either LLINs or conventional nets through existing health services, and retreats a large proportion of conventional nets regularly at low cost. We identified the determinants of bed net programme cost effectiveness and parameter values for usage rate, delivery and retreatment cost from the literature. One-way sensitivity analysis was conducted to explicitly compare the differential effect of changing parameters such as price, lifespan, usage and replenishment need. Results If conventional and long-lasting bed nets have the same physical lifespan (3 years, LLINs are more cost effective unless they are priced at more than USD 1.5 above the price of conventional nets. Because a longer lifespan brings delivery cost savings, each one year increase in lifespan can be accompanied by a USD 1 or more increase in price

  13. Vapour pressure isotope effects in liquid hydrogen chloride

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, J.N.C.; Calado, J.C.G. (Instituto Superior Tecnico, Lisbon (Portugal)); Jancso, Gabor (Hungarian Academy of Sciences, Budapest (Hungary). Central Research Inst. for Physics)

    1992-08-10

    The difference between the vapour pressures of HCl and DCl has been measured over the temperature range 170-203 K by a differential manometric technique in a precision cryostat. In this range the vapour pressure of HCl is higher than that of DCl by 3.2% at 170 K, decreasing to 0.9% at 200 K. The reduced partition function ratios f[sub l]/f[sub g] derived from the vapour pressure data can be described by the equation ln(f[sub l]/f[sub g]) = (3914.57[+-]10)/T[sup 2] - (17.730[+-]0.055)/T. The experimentally observed H-D vapour pressure isotope effect, together with the values on the [sup 35]Cl-[sup 37]Cl isotope effect available in the literature, is interpreted in the light of the statistical theory of isotope effects in condensed systems by using spectroscopic data of the vapour and liquid phases. The results indicate that the rotation in liquid hydrogen chloride is hindered. Temperature-dependent force constants for the hindered translational and rotational motions were invoked in order to obtain better agreement between the model calculation and experiment. (author).

  14. Perceptions on the effect of small electric fans on comfort inside bed nets in southern Ghana: a qualitative study.

    Science.gov (United States)

    Jaeger, Mulako S; Briët, Olivier J T; Keating, Joseph; Ahorlu, Collins K; Yukich, Joshua O; Oppong, Samuel; Nardini, Peter; Pfeiffer, Constanze

    2016-12-01

    Long-lasting insecticidal nets (LLINs) are known to be highly effective in reducing malaria transmission, morbidity and mortality. However, among those owning an LLIN, use rates are often suboptimal. A reported barrier to bed net use is discomfort due to heat. This qualitative study was part of a larger evaluation conducted in communities without electricity in rural Ghana to assess whether 0.8 W solar powered net fans can increase net use. Twenty-three key informant interviews with household heads in the study communities in Shai-Osudoku District, southern Ghana, were conducted from July to August 2015. The purpose of the interviews was to obtain insight into perceptions of participants about the net fan system in relation to LLIN use. While all study participants reported using LLINs, with mosquito nuisance prevention as the prime motivation, heat was also mentioned as a key barrier to net use. Respondents appreciated the net fans because they improved comfort inside bed nets. The LED light on the fan stand became the main source of light at night and positively influenced the perception of the intervention as a whole. The general acceptance of the net fan system by the study participants highlights the potential of the intervention to improve comfort inside mosquito nets. This, therefore, has a potential to increase bed net use in areas with low access to electricity.

  15. Effect of Interband Interaction on Isotope Effect Coefficient of Mg B2 Superconductors

    International Nuclear Information System (INIS)

    Udomsamuthirun, P.; Kumvongsa, C.; Burakorn, A.; Changkanarth, P.; Maneeratanakul, S.

    2005-10-01

    In this research, the exact formula of Tc s equation and the isotope effect coefficient of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of interband interaction .In each band ,our model consist of two paring interactions : the electron-phonon interaction and non-electron-phonon interaction . According to the numerical calculation, we find that the isotope effect coefficient of MgB 2 , α=3 . 0 with T c 40 K can be found in the weak coupling regime and interband interaction of electron-phonon show more effect on isotope effect coefficient than interband interaction of non-phonon-electron

  16. Isotopic modeling of the sub-cloud evaporation effect in precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Salamalikis, V., E-mail: vsalamalik@upatras.gr [Laboratory of Atmospheric Physics, Department of Physics, University of Patras, GR 26500 Patras (Greece); Argiriou, A.A. [Laboratory of Atmospheric Physics, Department of Physics, University of Patras, GR 26500 Patras (Greece); Dotsika, E. [Stable Isotope Unit, Institute of Nanoscience and Nanotechnology, National Center of Scientific Research ‘Demokritos’, Ag. Paraskevi Attikis, 15310 Athens (Greece)

    2016-02-15

    In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a ‘heat capacity’ model providing high correlation coefficients for both isotopes (R{sup 2} > 80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH = 95%) sub-cloud evaporation is negligible and the

  17. Isotopic modeling of the sub-cloud evaporation effect in precipitation

    International Nuclear Information System (INIS)

    Salamalikis, V.; Argiriou, A.A.; Dotsika, E.

    2016-01-01

    In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a ‘heat capacity’ model providing high correlation coefficients for both isotopes (R"2 > 80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH = 95%) sub-cloud evaporation is negligible and the

  18. Carbon-13 isotope effects on 199Hg nuclear shielding

    International Nuclear Information System (INIS)

    Sebald, Angelika; Wrackmeyer, Bernd

    1985-01-01

    Secondary 13 C/ 12 C isotope effects on 199 Hg nuclear shielding (Δdeltasup(i)( 199 Hg)) are of interest because of the unusual shift to high frequency which has been observed for a few alkyl mercury compounds. Continuing interest in the NMR parameters of mercury compounds prompted a search for the values Δdeltasup(i)( 199 Hg) in a greater variety of organomercurials. This should help to find out about the range of Δdeltasup(i)( 199 Hg) and to obtain a firmer basis for the discussion of the high-frequency shifts. The data and experimental conditions are given for chemical shifts delta 199 Hg, coupling constants sup(n)J( 199 Hg 13 C) and 13 C/ 12 C isotope shifts Δdeltasup(i)( 199 Hg) of fourteen 199 Hg organomercury compounds. The results are discussed. (author)

  19. System effectiveness of a targeted free mass distribution of long lasting insecticidal nets in Zanzibar, Tanzania

    Directory of Open Access Journals (Sweden)

    Abass Ali K

    2010-06-01

    Full Text Available Abstract Background Insecticide-treated nets (ITN and long-lasting insecticidal treated nets (LLIN are important means of malaria prevention. Although there is consensus regarding their importance, there is uncertainty as to which delivery strategies are optimal for dispensing these life saving interventions. A targeted mass distribution of free LLINs to children under five and pregnant women was implemented in Zanzibar between August 2005 and January 2006. The outcomes of this distribution among children under five were evaluated, four to nine months after implementation. Methods Two cross-sectional surveys were conducted in May 2006 in two districts of Zanzibar: Micheweni (MI on Pemba Island and North A (NA on Unguja Island. Household interviews were conducted with 509 caretakers of under-five children, who were surveyed for socio-economic status, the net distribution process, perceptions and use of bed nets. Each step in the distribution process was assessed in all children one to five years of age for unconditional and conditional proportion of success. System effectiveness (the accumulated proportion of success and equity effectiveness were calculated, and predictors for LLIN use were identified. Results The overall proportion of children under five sleeping under any type of treated net was 83.7% (318/380 in MI and 91.8% (357/389 in NA. The LLIN usage was 56.8% (216/380 in MI and 86.9% (338/389 in NA. Overall system effectiveness was 49% in MI and 87% in NA, and equity was found in the distribution scale-up in NA. In both districts, the predicting factor of a child sleeping under an LLIN was caretakers thinking that LLINs are better than conventional nets (OR = 2.8, p = 0.005 in MI and 2.5, p = 0.041 in NA, in addition to receiving an LLIN (OR = 4.9, p Conclusions Targeted free mass distribution of LLINs can result in high and equitable bed net coverage among children under five. However, in order to sustain high effective coverage, there

  20. Selected bibliography on deuterium isotope effects and heavy water

    International Nuclear Information System (INIS)

    Dave, S.M.; Donde, M.M.

    1983-01-01

    In recent years, there has been a great deal of interest in using deuterium and heavy water not only in nuclear industry but also in various fields of basic as well as applied research in physics, chemistry and biology. As a result, the literature is being enriched with a large number of research papers and technical reports published each year. Thus, to enable the scientists to have an easy reference to these works, an endeavour has been made in this selected bibliography, to enlist the publications related to these fields. Since the interest is concerned mainly with heavy water production processes, deuterium isotope effects etc., several aspects (e.g. nuclear) of deuterium have not been covered here. The material in this bibliography which cites 2388 references has been classified under six broad headings, viz. (1) Production of heavy water, (2) Study of deuterium isotope effects, (3) Analysis and Properties of heavy water, (4) Laser Separation of deuterium, (5) Isotopic exchange reactions, and (6) Miscellaneous. The sources of information used for this compilation are chemical abstracts, nuclear science abstracts, INIS Atomindex and also some scattered search through journals and reports available in the B.A.R.C. library. However, in spite of sincere attempts for a wide coverage, no claim is being made towards the exhaustiveness of this bibliography. (author)

  1. Kinetic isotope effects and how to describe them

    Directory of Open Access Journals (Sweden)

    Konstantin Karandashev

    2017-11-01

    Full Text Available We review several methods for computing kinetic isotope effects in chemical reactions including semiclassical and quantum instanton theory. These methods describe both the quantization of vibrational modes as well as tunneling and are applied to the ⋅H + H2 and ⋅H + CH4 reactions. The absolute rate constants computed with the semiclassical instanton method both using on-the-fly electronic structure calculations and fitted potential-energy surfaces are also compared directly with exact quantum dynamics results. The error inherent in the instanton approximation is found to be relatively small and similar in magnitude to that introduced by using fitted surfaces. The kinetic isotope effect computed by the quantum instanton is even more accurate, and although it is computationally more expensive, the efficiency can be improved by path-integral acceleration techniques. We also test a simple approach for designing potential-energy surfaces for the example of proton transfer in malonaldehyde. The tunneling splittings are computed, and although they are found to deviate from experimental results, the ratio of the splitting to that of an isotopically substituted form is in much better agreement. We discuss the strengths and limitations of the potential-energy surface and based on our findings suggest ways in which it can be improved.

  2. Effect of decreasing dietary phosphorus supply on net recycling of inorganic phosphate in lactating dairy cows.

    Science.gov (United States)

    Puggaard, L; Kristensen, N B; Sehested, J

    2011-03-01

    Five ruminally cannulated lactating Holstein cows, fitted with permanent indwelling catheters in the mesenteric vein, hepatic vein, portal vein, and an artery were used to study intestinal absorption and net recycling of inorganic phosphate (P(i)) to the gastrointestinal tract. Treatments were low P (LP; 2.4 g of P/kg of DM) and high P (HP; 3.4 g of P/kg of DM). The dietary total P (tP) concentrations were obtained by replacing 0.50% calcium carbonate in the LP diet with 0.50% monocalcium phosphate in the HP diet. Diets were fed for 14 d and cows were sampled on d 14 in each period. Cows were fed restrictively, resulting in equal dry matter intakes as well as milk, fat, and protein yields between treatments. Net P(i) recycling (primarily salivary) was estimated as the difference between net portal plasma flux (net absorption of P(i)) and apparently digested tP (feed - fecal tP difference). Phosphorus intake, apparently digested tP, and fecal tP excretion decreased with LP. An effect of decreased tP intake on net portal plasma flux of P(i) could not be detected. However, despite numerically minute net fluxes across the liver, the net splanchnic flux of P(i) was less in LP compared with that in HP. Though arterial plasma P(i) concentration decreased, net P(i) recycling was not decreased when tP intake was decreased, and recycling of P(i) was maintained at the expense of deposition of P(i) in bones. Data are not consistent with salivary P(i) secretion being the primary regulator of P(i) homeostasis at low tP intakes. On the contrary, maintaining salivary P(i) recycling at low tP intakes indicates that rumen function was prioritized at the expense of bone P reserves. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  3. Magnetic field and magnetic isotope effects on photochemical reactions

    International Nuclear Information System (INIS)

    Wakasa, Masanobu

    1999-01-01

    By at present exact experiments and the theoretical analysis, it was clear that the magnetic field less than 2 T affected a radical pair reaction and biradical reaction. The radical pair life and the dissipative radical yield showed the magnetic field effects on chemical reactions. The radical pair mechanism and the triplet mechanism were known as the mechanism of magnetic field effects. The radical pair mechanism consists of four mechanisms such as the homogeneous hyperfine interaction (HFC), the delta-g mechanism, the relaxation mechanism and the level cross mechanism. In order to observe the magnetic effects of the radical pair mechanism, two conditions need, namely, the recombination rate of singlet radical pair > the dissipation rate and the spin exchange rate > the dissipation rate. A nanosecond laser photo-decomposition equipment can observe the magnetic field effects. The inversion phenomena of magnetic field effect, isolation of the relaxation mechanism and the delta-g mechanism, the magnetic field effect of heavy metal radical reaction, the magnetic field effect in homogeneous solvent, saturation of delta-g mechanism are explained. The succeeded examples of isotope concentration by the magnetic isotope effect are 17 O, 19 Si, 33 S, 73 Ge and 235 U. (S.Y.)

  4. Salt effects on isotope partitioning and their geochemical implications: An overview

    International Nuclear Information System (INIS)

    Horita, J.; Cole, D.R.; Fortier, S.M.

    1996-01-01

    Essential to the use of stable isotopes as natural tracers and geothermometers is the knowledge of equilibrium isotope partitioning between different phases and species, which is usually a function of temperature only. The one exception known to date is oxygen and hydrogen isotope fractionation between liquid water and other phases (steam, gases, minerals), which changes upon the addition of salts to water, i.e., the isotope salt salt effect. Our knowledge of this effect, the difference between activity and composition (a-X) of isotopic water molecules in salt solutions, is very limited and controversial, especially at elevated temperatures. For the last several years, we have been conducting a detailed, systematic experimental study at Oak Ridge National Laboratory to determine the isotope salt effects from room temperature to elevated temperatures (currently to 500 degree C). From this effort, a simple, coherent picture of the isotope salt effect is emerging, that differs markedly from the complex results reported in the literature. In this communication, we present an overview on the isotope salt effect, obtained chiefly from our study. Observed isotope salt effects in salt solutions are significant even at elevated temperatures. The importance and implications of the isotope salt effect for isotopic studies of brine-dominated systems are also discussed in general terms

  5. The net effect of alternative allocation ratios on recruitment time and trial cost.

    Science.gov (United States)

    Vozdolska, Ralitza; Sano, Mary; Aisen, Paul; Edland, Steven D

    2009-04-01

    Increasing the proportion of subjects allocated to the experimental treatment in controlled clinical trials is often advocated as a method of increasing recruitment rates and improving the performance of trials. The presumption is that the higher likelihood of randomization to the experimental treatment will be perceived by potential study enrollees as an added benefit of participation and will increase recruitment rates and speed the completion of trials. However, studies with alternative allocation ratios require a larger sample size to maintain statistical power, which may result in a net increase in time required to complete recruitment and a net increase in total trial cost. To describe the potential net effect of alternative allocation ratios on recruitment time and trial cost. Models of recruitment time and trial cost were developed and used to compare trials with 1:1 allocation to trials with alternative allocation ratios under a range of per subject costs, per day costs, and enrollment rates. In regard to time required to complete recruitment, alternative allocation ratios are net beneficial if the recruitment rate improves by more than about 4% for trials with a 1.5:1 allocation ratio and 12% for trials with a 2:1 allocation ratio. More substantial improvements in recruitment rate, 13 and 47% respectively for scenarios we considered, are required for alternative allocation to be net beneficial in terms of tangible monetary cost. The cost models were developed expressly for trials comparing proportions or means across treatment groups. Using alternative allocation ratio designs to improve recruitment may or may not be time and cost-effective. Using alternative allocation for this purpose should only be considered for trial contexts where there is both clear evidence that the alternative design does improve recruitment rates and the attained time or cost efficiency justifies the added study subject burden implied by a larger sample size.

  6. Isotope enrichment effect of gaseous mixtures in standing sound vibration

    International Nuclear Information System (INIS)

    Knesebeck, R.L.

    1984-01-01

    When standing acoustic waves are excited in a tube containing a mixture of two gases, a partial zonal fractioning of the components arises as consequence of mass transport by diffusion, driven by the thermal and pressure gradients which are associeted with the standing waves. This effect is present in each zone corresponding to a quarter wavelength, with the heavier component becoming enriched at the nodes fo the standing waves and deplected at the crests. The magnitude of the enrichment in one of the components of a binary gas mixture is given by Δω=ap 2 /lambda [b + (1-bω)] 2 . Where ω is the mass concentration of the component in the mixture, a and b are parameters which are related to molecular proprieties of the gases, p is the relative pressure amplitude of the standing wave and lambda is its wavelength. For a natural mixture of uranium hexafluorate, with 0.715% of the uranium isotope 340 an enrichment of about 2 x 10 -6 % in the concentration of this isotope is theorecticaly attainable per stage consisting of a quarter wavelenght, when a standing acoustical wave of relative pressure amplitude of 0,2 and wavelenght of 20 cm is used. Since standing acoustical waves are easely excited in gas columns, an isotope enrichment plant made of a cascade of tubes in which standing waves are excited, is presumably feasible with relatively low investment and operation costs. (Author) [pt

  7. Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

    International Nuclear Information System (INIS)

    Ivlev, A.A.; Kaloshin, A.G.; Koroleva, M.Ya.

    1982-01-01

    The analysis of the carbon isotope distribution in carbohydrates and amino acids of some photosynthesizing organisms revealed the close relationship between distribution and the pathways of biosynthesis of the molecules. This relationship is explained on the basis of the previously proposed mechanism of carbon isotope fractionation in a cell, in which the chief part is played by kinetic isotope effects in the pyruvate decarboxylation reaction progressively increased in the conjugated processes of gluconeogenesis. Isotope differences of C 2 and C 3 fragments arising in decarboxylation of pyruvate, as well as isotope differences of biogenic acceptor and environmental CO 2 appearing in assimilation are the main reasons of the observed intramolecular isotopic heterogeneity of biomolecules. The heterogeneity is preserved in metabolites owing to an incomplete mixing of carbon atoms in biochemical reactions. The probable existence of two pools of carbohydrates in photosynthesizing organisms different in isotopic composition is predicted. Two types of intramolecular isotope distribution in amino acids are shown. (author)

  8. On the Effect of Planetary Stable Isotope Compositions on Growth and Survival of Terrestrial Organisms.

    Directory of Open Access Journals (Sweden)

    Xueshu Xie

    Full Text Available Isotopic compositions of reactants affect the rates of chemical and biochemical reactions. Usually it is assumed that heavy stable isotope enrichment leads to progressively slower reactions. Yet the effect of stable isotopes may be nonlinear, as exemplified by the "isotopic resonance" phenomenon. Since the isotopic compositions of other planets of Solar system, including Mars and Venus, are markedly different from terrestrial (e.g., deuterium content is ≈5 and ≈100 times higher, respectively, it is far from certain that terrestrial life will thrive in these isotopic conditions. Here we found that Martian deuterium content negatively affected survival of shrimp in semi-closed biosphere on a year-long time scale. Moreover, the bacterium Escherichia coli grows slower at Martian isotopic compositions and even slower at Venus's compositions. Thus, the biological impact of varying stable isotope compositions needs to be taken into account when planning interplanetary missions.

  9. Factors shaping effective utilization of health information technology in urban safety-net clinics.

    Science.gov (United States)

    George, Sheba; Garth, Belinda; Fish, Allison; Baker, Richard

    2013-09-01

    Urban safety-net clinics are considered prime targets for the adoption of health information technology innovations; however, little is known about their utilization in such safety-net settings. Current scholarship provides limited guidance on the implementation of health information technology into safety-net settings as it typically assumes that adopting institutions have sufficient basic resources. This study addresses this gap by exploring the unique challenges urban resource-poor safety-net clinics must consider when adopting and utilizing health information technology. In-depth interviews (N = 15) were used with key stakeholders (clinic chief executive officers, medical directors, nursing directors, chief financial officers, and information technology directors) from staff at four clinics to explore (a) nonhealth information technology-related clinic needs, (b) how health information technology may provide solutions, and (c) perceptions of and experiences with health information technology. Participants identified several challenges, some of which appear amenable to health information technology solutions. Also identified were requirements for effective utilization of health information technology including physical infrastructural improvements, funding for equipment/training, creation of user groups to share health information technology knowledge/experiences, and specially tailored electronic billing guidelines. We found that despite the potential benefit that can be derived from health information technologies, the unplanned and uninformed introduction of these tools into these settings might actually create more problems than are solved. From these data, we were able to identify a set of factors that should be considered when integrating health information technology into the existing workflows of low-resourced urban safety-net clinics in order to maximize their utilization and enhance the quality of health care in such settings.

  10. Effect of gamma radiation on chlorophylls content, net photosynthesis and respiration of Chlorella pyrenoidosa

    International Nuclear Information System (INIS)

    Martin Moreno, C.; Fernandez Gonzalez, J.

    1983-01-01

    The effect of five doses of gamma radiation: 10, 100, 500, 1000 and 5000 Gy on chlorophylls content, net photosynthesis and respiration of Chlorella pyrenoidosa has been studied. A decrease in chlorophylls levels is produced after irradiation at 500, 1000 and 5000 Gy, being, at first b chlorophyll affected to a greater extent than a chlorophyll. Net photosynthesis and respiration decline throughout the time of the observation after irradiation, this depressing effect being much more remarkable for the first one. Met photosynthesis inhibition levels of about 30% are got only five hours post irradiation at a dose of 5000 Gy. Radio estimation by low doses, although obtained in some cases for tho 10 Gy dose, has not been statistically confirmed. (Author) 23 refs

  11. Effect of network topology on the evolutionary ultimatum game based on the net-profit decision

    Science.gov (United States)

    Ye, Shun-Qiang; Wang, Lu; Jones, Michael C.; Ye, Ye; Wang, Meng; Xie, Neng-Gang

    2016-04-01

    The ubiquity of altruist behavior amongst humans has long been a significant puzzle in the social sciences. Ultimatum game has proved to be a useful tool for explaining altruistic behavior among selfish individuals. In an ultimatum game where alternating roles exist, we suppose that players make their decisions based on the net profit of their own. In this paper, we specify a player's strategy with two parameters: offer level α ∈ [ 0,1) and net profit acceptance level β ∈ [ - 1,1). By Monte Carlo simulation, we analyze separately the effect of the size of the neighborhood, the small-world property and the heterogeneity of the degree distributions of the networks. Results show that compared with results observed for homogeneous networks, heterogeneous networks lead to more rational outcomes. Moreover, network structure has no effect on the evolution of kindness level, so moderate kindness is adaptable to any social groups and organizations.

  12. Influence of 15N enrichment on the net isotopic fractionation factor during the reduction of nitrate to nitrous oxide in soil

    DEFF Research Database (Denmark)

    Mathieu, O.; Levegue, J.; Henault, C.

    2007-01-01

    Nitrous oxide, a greenhouse gas, is mainly emitted from soils during the denitrification process. Nitrogen stable-isotope investigations can help to characterise the N(2)O source and N(2)O production mechanisms. The stable-isotope approach is increasingly used with (15)N natural abundance...

  13. The costs and effects of a nationwide insecticide-treated net programme: the case of Malawi

    Directory of Open Access Journals (Sweden)

    Ortiz Juan

    2005-05-01

    Full Text Available Abstract Background Insecticide-treated nets (ITNs are a proven intervention to reduce the burden of malaria, yet there remains a debate as to the best method of ensuring they are universally utilized. This study is a cost-effectiveness analysis of an intervention in Malawi that started in 1998, in Blantyre district, before expanding nationwide. Over the 5-year period, 1.5 million ITNs were sold. Methods The costs were calculated retrospectively through analysis of expenditure data. Costs and effects were measured as cost per treated-net year (cost/TNY and cost per net distributed. Results The mean cost/TNY was calculated at $4.41, and the mean cost/ITN distributed at $2.63. It also shows evidence of economies of scale, with the cost/TNY falling from $7.69 in year one (72,196 ITN to $3.44 in year five (720,577 ITN. Cost/ITN distributed dropped from $5.04 to $1.92. Conclusion Combining targeting and social marketing has the potential of being both cost-effective and capable of achieving high levels of coverage, and it is possible that increasing returns to scale can be achieved.

  14. Computational Replication of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Solution Hydride-Transfer Reactions: Supporting the Isotopically Different Tunneling Ready State Conformations.

    Science.gov (United States)

    Derakhshani-Molayousefi, Mortaza; Kashefolgheta, Sadra; Eilers, James E; Lu, Yun

    2016-06-30

    We recently reported a study of the steric effect on the 1° isotope dependence of 2° KIEs for several hydride-transfer reactions in solution (J. Am. Chem. Soc. 2015, 137, 6653). The unusual 2° KIEs decrease as the 1° isotope changes from H to D, and more in the sterically hindered systems. These were explained in terms of a more crowded tunneling ready state (TRS) conformation in D-tunneling, which has a shorter donor-acceptor distance (DAD) than in H-tunneling. To examine the isotopic DAD difference explanation, in this paper, following an activated motion-assisted H-tunneling model that requires a shorter DAD in a heavier isotope transfer process, we computed the 2° KIEs at various H/D positions at different DADs (2.9 Å to 3.5 Å) for the hydride-transfer reactions from 2-propanol to the xanthylium and thioxanthylium ions (Xn(+) and TXn(+)) and their 9-phenyl substituted derivatives (Ph(T)Xn(+)). The calculated 2° KIEs match the experiments and the calculated DAD effect on the 2° KIEs fits the observed 1° isotope effect on the 2° KIEs. These support the motion-assisted H-tunneling model and the isotopically different TRS conformations. Furthermore, it was found that the TRS of the sterically hindered Ph(T)Xn(+) system does not possess a longer DAD than that of the (T)Xn(+) system. This predicts a no larger 1° KIE in the former system than in the latter. The observed 1° KIE order is, however, contrary to the prediction. This implicates the stronger DAD-compression vibrations coupled to the bulky Ph(T)Xn(+) reaction coordinate.

  15. Monopole Effect on Isotopes in Sn and Pb Regions

    Directory of Open Access Journals (Sweden)

    M. KHITER

    2016-11-01

    Full Text Available Abstract. When going toward in description of neutron-rich nuclei, the monopole field plays a determining role in the properties of the quasiparticle states and their interactions. Detailed theoretical in shell model calculations of the characteristics of the neutron-rich isotopes in 132Sn and 208Pb regions are performed using the monopole hamiltonien effect. Some modification mentioned in literatures of effectives interactions are introduced for evaluated the effective single-particle energies. Their effect show a successful and consistent description of excitation energies spectra of these nuclei.Keywords:Nuclear Structure, Monopole Hamiltonian, Odd-Odd Nuclei,Three body Effects, Similarity, 21.60.Cs; 27.60. +j; 21.30.Fe

  16. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps......, to location-based social networks and games, such as Foursquare and facebook. Warns of the threats these technologies, such as data surveillance, present to our sense of privacy, while also outlining the opportunities for pro-social developments. Provides a theory of the web in the context of the history...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  17. Correcting Detector Efficiency Effects in Event-by-Event Net-Proton Fluctuations

    CERN Document Server

    Peters, Michael

    2016-01-01

    Measurements of fluctuations of conserved quantities give valuable information on the susceptibilities of the nuclear matter produced in a heavy-ion collision, and could in principle be used to distinguish QGP from hadronic matter. However, measurements of the cumulants of conserved-quantity distributions are affected by the detector efficiency, which must be accounted for in order to ensure accuracy. Following the development of a toy model that simulates detector efficiency effects on net-proton number, various correction methods, including those developed by A. Bzdak and V. Koch, were implemented and tested in a wide range of conditions. We find that the first four cumulants of net-proton-number distribution can be accurately reproduced by the Koch-Bzdak corrections with reasonable input statistics. Various methods of correcting for $p_T$ dependence of detector efficiency are also explored.

  18. Managing soil organic carbon in agriculture: the net effect on greenhouse gas emissions

    International Nuclear Information System (INIS)

    Marland, Gregg; West, Tristram O.; Schlamadinger, Bernhard; Canella, Lorenza

    2003-01-01

    A change in agricultural practice can increase carbon sequestration in agricultural soils. To know the net effect on greenhouse gas emissions to the atmosphere, however, we consider associated changes in CO 2 emissions resulting from the consumption of fossil fuels, emissions of other greenhouse gases and effects on land productivity and crop yield. We also consider how these factors will evolve over time. A change from conventional tillage to no-till agriculture, based on data for average practice in the U.S.; will result in net carbon sequestration in the soil that averages 337 kg C/ha/yr for the initial 20 yr with a decline to near zero in the following 20 yr, and continuing savings in CO 2 emissions because of reduced use of fossil fuels. The long-term results, considering all factors, can generally be expected to show decreased net greenhouse gas emissions. The quantitative details, however, depend on the site-specific impact of the conversion from conventional to no-till agriculture on agricultural yield and N 2 O emissions from nitrogen fertilizer

  19. 2D net shape weaving for cost effective manufacture of textile reinforced composites

    Science.gov (United States)

    Vo, D. M. P.; Kern, M.; Hoffmann, G.; Cherif, C.

    2017-10-01

    Despite significant weight and performance advantages over metal parts, the today’s demand for fibre-reinforced polymer composites (FRPC) has been limited mainly by their large manufacturing cost. The combination of dry textile preforms and low-cost consolidation processes such as resin transfer molding (RTM) has been appointed as a promising approach to low-cost FRPC manufacture. At the current state of the art, tooling and impregnation technology is well understood whereas preform fabrication technology has not been developed effectively. This paper presents an advanced 2D net shape weaving technology developed with the aim to establish a more cost effective system for the manufacture of dry textile preforms for FRPC. 2D net shape weaving is developed based on open reed weave (ORW) technology and enables the manufacture of 2D contoured woven fabrics with firm edge, so that oversize cutting and hand trimming after molding are no longer required. The introduction of 2D net shape woven fabrics helps to reduce material waste, cycle time and preform manufacturing cost significantly. Furthermore, higher grade of automation in preform fabrication can be achieved.

  20. An improved null model for assessing the net effects of multiple stressors on communities.

    Science.gov (United States)

    Thompson, Patrick L; MacLennan, Megan M; Vinebrooke, Rolf D

    2018-01-01

    Ecological stressors (i.e., environmental factors outside their normal range of variation) can mediate each other through their interactions, leading to unexpected combined effects on communities. Determining whether the net effect of stressors is ecologically surprising requires comparing their cumulative impact to a null model that represents the linear combination of their individual effects (i.e., an additive expectation). However, we show that standard additive and multiplicative null models that base their predictions on the effects of single stressors on community properties (e.g., species richness or biomass) do not provide this linear expectation, leading to incorrect interpretations of antagonistic and synergistic responses by communities. We present an alternative, the compositional null model, which instead bases its predictions on the effects of stressors on individual species, and then aggregates them to the community level. Simulations demonstrate the improved ability of the compositional null model to accurately provide a linear expectation of the net effect of stressors. We simulate the response of communities to paired stressors that affect species in a purely additive fashion and compare the relative abilities of the compositional null model and two standard community property null models (additive and multiplicative) to predict these linear changes in species richness and community biomass across different combinations (both positive, negative, or opposite) and intensities of stressors. The compositional model predicts the linear effects of multiple stressors under almost all scenarios, allowing for proper classification of net effects, whereas the standard null models do not. Our findings suggest that current estimates of the prevalence of ecological surprises on communities based on community property null models are unreliable, and should be improved by integrating the responses of individual species to the community level as does our

  1. 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

  2. Costs and effects of the Tanzanian national voucher scheme for insecticide-treated nets

    Directory of Open Access Journals (Sweden)

    Hanson Kara

    2008-02-01

    Full Text Available Abstract Background The cost-effectiveness of insecticide-treated nets (ITNs in reducing morbidity and mortality is well established. International focus has now moved on to how best to scale up coverage and what financing mechanisms might be used to achieve this. The approach in Tanzania has been to deliver a targeted subsidy for those most vulnerable to the effects of malaria while at the same time providing support to the development of the commercial ITN distribution system. In October 2004, with funds from the Global Fund to Fight AIDS Tuberculosis and Malaria, the government launched the Tanzania National Voucher Scheme (TNVS, a nationwide discounted voucher scheme for ITNs for pregnant women and their infants. This paper analyses the costs and effects of the scheme and compares it with other approaches to distribution. Methods Economic costs were estimated using the ingredients approach whereby all resources required in the delivery of the intervention (including the user contribution are quantified and valued. Effects were measured in terms of number of vouchers used (and therefore nets delivered and treated nets years. Estimates were also made for the cost per malaria case and death averted. Results and Conclusion The total financial cost of the programme represents around 5% of the Ministry of Health's total budget. The average economic cost of delivering an ITN using the voucher scheme, including the user contribution, was $7.57. The cost-effectiveness results are within the benchmarks set by other malaria prevention studies. The Government of Tanzania's approach to scaling up ITNs uses both the public and private sectors in order to achieve and sustain the level of coverage required to meet the Abuja targets. The results presented here suggest that the TNVS is a cost-effective strategy for delivering subsidized ITNs to targeted vulnerable groups.

  3. Quantum tunneling observed without its characteristic large kinetic isotope effects.

    Science.gov (United States)

    Hama, Tetsuya; Ueta, Hirokazu; Kouchi, Akira; Watanabe, Naoki

    2015-06-16

    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle's ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1-1.5) despite the large intrinsic H/D KIE of tunneling (≳ 100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system.

  4. Charge exchange effect on laser isotope separation of atomic uranium

    International Nuclear Information System (INIS)

    Niki, Hideaki; Izawa, Yasukazu; Otani, Hiroyasu; Yamanaka, Chiyoe

    1982-01-01

    Uranium isotope separating experiment was performed using the two-step photoionization technique with dye laser and nitrogen laser by heating uranium metal with electron beam and producing atomic beam using generated vapour. The experimental results are described after explaining the two-step photoionization by laser, experimental apparatus, the selection of exciting wavelength and others. Enrichment factor depends largely on the spectrum purity of dye laser which is the exciting source. A large enrichment factor of 48.3 times was obtained for spectrum width 0.03A. To put the uranium isotope separation with laser into practice, the increase of uranium atomic density is considered to be necessary for improving the yield. Experimental investigation was first carried out on the charge exchange effect that seems most likely to affect the decrease of enrichment factor, and the charge exchange cross-section was determined. The charge exchange cross-section depends on the relative kinetic energy between ions and atoms. The experimental result showed that the cross-section was about 5 x 10 -13 cm 2 at 1 eV and 10 -13 cm 2 at 90 eV. These values are roughly ten times as great as those calculated in Lawrence Livermore Laboratory, and it is expected that they become the greatest factor for giving the upper limit of uranium atomic density in a process of practical application. (Wakatsuki, Y.)

  5. Introduction to chemistry and applications in nature of mass independent isotope effects special feature.

    Science.gov (United States)

    Thiemens, Mark H

    2013-10-29

    Stable isotope ratio variations are regulated by physical and chemical laws. These rules depend on a relation with mass differences between isotopes. New classes of isotope variation effects that deviate from mass dependent laws, termed mass independent isotope effects, were discovered in 1983 and have a wide range of applications in basic chemistry and nature. In this special edition, new applications of these effects to physical chemistry, solar system origin models, terrestrial atmospheric and biogenic evolution, polar paleo climatology, snowball earth geology, and present day atmospheric sciences are presented.

  6. Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Kamounah, Fadhil S.; Gryko, Daniel T.

    2013-01-01

    Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be nega...

  7. Ionic conductivity in aqueous solutions: deuterium isotope effect

    International Nuclear Information System (INIS)

    Samanta, Alok; Ghosh, Swapan K.

    1997-01-01

    A simple theoretical investigation of the calculation of ionic conductivity in aqueous solution is presented. The dipolar hard sphere model for the solvent which has been successful elsewhere has been employed here and it has been possible to reproduce the experimental results quite accurately for both water and heavy water using only two parameters. In a more detailed theoretical approach one should employ better models for water with proper account of its vibrations, liberations and also hydrogen bonding. It is also of interest to study the temperature effect and the concentration dependence of the conductivity. The time-dependent friction can also be calculated from the present formalism and be used for the study of isotope effect in proton transfer reactions or other aspects of chemical dynamics

  8. Determining and addressing obstacles to the effective use of long-lasting insecticide-impregnated nets in rural Tanzania

    Directory of Open Access Journals (Sweden)

    Benziger Peter W

    2009-12-01

    Full Text Available Abstract Background The objective of this project was to achieve high, sustainable levels of net coverage in a village in rural Tanzania by combining free distribution of long-lasting insecticide-impregnated nets (LLINs with community-tailored education. In Tanzania, malaria is the leading cause of morbidity and mortality. Although malaria bed nets have a well-established role in reducing disease burden, few rural households have access to nets, and effective use depends on personal practices and attitudes. Methods Five practices and attitudes inconsistent with effective LLIN use were identified from household interviews (n = 10. A randomized survey of villagers (n = 132 verified local prevalence of these practices and attitudes. Community leaders held an educational session for two members of every household addressing these practice and attitudes, demonstrating proper LLIN use, and emphasizing behaviour modification. Attendees received one or two LLINs per household. Surveys distributed three weeks (n = 104 and 15 months (n = 104 post-intervention assessed corrected practices and attitudes. Project efficacy was defined by correction of baseline practices and attitudes as well as high rates of reported daily net use, with statistical significance determined by chi-square test. Results Baseline interviews and surveys revealed incorrect practices and attitudes regarding 1 use of nets in dry season, 2 need to retreat LLINs, 3 children napping under nets, 4 need to repair nets, and 5 net procurement as a priority, with 53- 88.6% incorrect responses (11.4-47% correct responses. A three-week follow-up demonstrated 83-95% correct responses. Fifteen-month follow-up showed statistically significant (p Conclusions Results suggest that addressing community-specific practices and attitudes prior to LLIN distribution promotes consistent and correct use, and helps change attitudes towards bed nets as a preventative health measure. Future LLIN distributions

  9. The isotope altitude effect reflected in groundwater: a case study from Slovenia.

    Science.gov (United States)

    Mezga, Kim; Urbanc, Janko; Cerar, Sonja

    2014-01-01

    This paper presents the stable isotope data of oxygen (δ(18)O) and hydrogen (δ(2)H) in groundwater from 83 sampling locations in Slovenia and their interpretation. The isotopic composition of water was monitored over 3 years (2009-2011), and each location was sampled twice. New findings on the isotopic composition of sampled groundwater are presented, and the data are also compared to past studies regarding the isotopic composition of precipitation, surface water, and groundwater in Slovenia. This study comprises: (1) the general characteristics of the isotopic composition of oxygen and hydrogen in groundwater in Slovenia, (2) the spatial distribution of oxygen isotope composition (δ(18)O) and d-excess in groundwater, (3) the groundwater isotope altitude effect, (4) the correlation between groundwater d-excess and the recharge area altitude of the sampling location, (5) the relation between hydrogen and oxygen isotopes in groundwater in comparison to the global precipitation isotope data, (6) the groundwater isotope effect of distance from the sea, and (7) the estimated relation between the mean temperature of recharge area and δ(18)O in groundwater.

  10. Computational study of substrate isotope effect probes of transition state structure for acetylcholinesterase catalysis

    International Nuclear Information System (INIS)

    Sikorski, R.S.; Malany, S.; Seravalli, J.; Quinn, D.M.

    2002-01-01

    Secondary isotope effects for carbonyl addition reactions of methyl thioacetate, acetone and acetaldehyde have been calculated by ab initio quantum mechanical methods in an effect to interpret measured β-deuterium isotope effects on acetylcholinesterase-catalysed hydrolysis of acetylthiocholine. The calculated β-deuterium isotope effect for equilibrium addition of methanol to methyl thioacetate is D3 K eq = 0.965, and the corresponding effect for addition of methoxide ion to methyl thioacetate wherein three waters are hydrogen bonded to the carbonyl oxyanion is D3 K eq = 1.086. Neither of these calculated isotope effects is an inverse as the experimental β-deuterium isotope effect for acetylcholinesterase-catalysed hydrolysis of acetylthiocholine, D3 K eq = 0.90±0.03. Structural comparisons show that the water-solvated methoxide adduct of methyl thioacetate is more expanded than is the natural methanol addition adduct, and suggest that the degree of which the isotope effect is inverse (i.e. less than) is inversely correlated to the degree of expansion of the adduct. A similar correlation of α-deuterium and β-deuterium secondary isotope effects with the degree of expansion of the adducts is found for equilibrium additions of methanol and methoxide ion to acetylaldehyde. These computational results suggest that the markedly inverse β-deuterium isotope effect for the acetylcholinesterase reaction arises from enzymatic compression of the transition state. (author)

  11. Isotopic shifts in chemical exchange systems. 1. Large isotope effects in the complexation of Na+ isotopes by macrocyclic polyethers

    International Nuclear Information System (INIS)

    Knoechel, A.; Wilken, R.D.

    1981-01-01

    The complexation of 24 Na + and 22 Na + by 18 of the most widely used macrocyclic polyethers (crown ethers and monocyclic and bicyclic aminopolyethers) has been investigated in view of possible equilibrium isotope shifts. Solvated salts and polyether complexes were distributed differently into two phases and isotope ratios determined in both phases. Chloroform/water systems were shown to be particularly suitable to the investigations allowing favorable distribution for Na + and 13 of the 18 polyethers employed. With crown ethers 24 Na + enrichment varied from nonsignficant values (for large crown ethers) up to 3.1 +- 0.4% (18-crown-6). In the case of bicyclic aminopolyethers, ligands with cages of optimum size to accommodate Na + showed 24 Na + enrichment between O (nonsignificant) (2.2/sub B/2./sub B/) and 5.2 +- 1.8% (2.2.1). In contrast, for 2.2.2. and its derivatives, being too large for Na + , 22 Na + enrichment varying from O (nonsignificant) (2.2.2.p) up to 5.4 +- 0.5% (2.2.2.) has been observed. These values are remarkably high. They are explained by different bonding in solvate structure and polyether complex by using the theoretical approach of Bigeleisen

  12. Simulation of distribution nets for natural gas, in stationary state considering the compressible effects

    International Nuclear Information System (INIS)

    Valbuena C, Javier

    1997-01-01

    The general method is presented to calculate the losses of pressure in a RTD starting from the geometry of the net (diameter and longitude), of the real behavior of the gas, of the ruggedness of the pipe and of the flow, considering the compressibility of the fluid so much as the influence of the compressible effects. The simulation method is derived of the principles of conservation of mass and energy for a gas that follows a reversible poly tropic process of stable state and stable flow - stationary regime

  13. Isotope effect on superconductivity and Raman phonons of Pyrochlore Cd2Re2O7

    Science.gov (United States)

    Razavi, F. S.; Hajialamdari, M.; Reedyk, M.; Kremer, R. K.

    2018-06-01

    Cd2Re2O7 is the only α-Pyrochlore exhibiting superconductivity with a transition temperature (Tc) of ∼ 1 K. In this study, we present the effect of oxygen isotope (18O) as well as combined 18O and cadmium isotope (116Cd) substitution on the superconductivity and Raman scattering spectrum of Cd2Re2O7. The change of Tc and the energy gap Δ(T) are reported using various techniques including point contact spectroscopy. The shift in Raman phonon frequencies upon isotope substitution will be compared with measurement of the isotope effect on the superconducting transition temperature.

  14. Effects of Climate Change and Shifts in Forest Composition on Forest Net Primary Production

    Institute of Scientific and Technical Information of China (English)

    Jyh-Min Chiang; Louts R. Iverson; Anantha Prasad; Kim J. Brown

    2008-01-01

    Forests are dynamic in both structure and species composition, and these dynamics are strongly Influenced by climate.However, the net effects of future tree species composition on net primary production (NPP) are not well understood. The objective of this work was to model the potential range shifts of tree species (DISTRIB Model) and predict their impacts on NPP (PnET-Ⅱ Model) that will be associated with alterations in species composition. We selected four 200 × 200 km areas In Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-Ⅱ model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m2 per year. The effects of potential species redistributions on NPP were moderate (-12% to +8%) compared with the influence of future climatic changes (-60% to +25%). The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.

  15. Isotope Effect on the Thermal Conductivity of Graphene

    Directory of Open Access Journals (Sweden)

    Hengji Zhang

    2010-01-01

    Full Text Available The thermal conductivity (TC of isolated graphene with different concentrations of isotope (C13 is studied with equilibrium molecular dynamics method at 300 K. In the limit of pure C12 or C13 graphene, TC of graphene in zigzag and armchair directions are ~630 W/mK and ~1000W/mK, respectively. We find that the TC of graphene can be maximally reduced by ~80%, in both armchair and zigzag directions, when a random distribution of C12 and C13 is assumed at different doping concentrations. Therefore, our simulation results suggest an effective way to tune the TC of graphene without changing its atomic and electronic structure, thus yielding a promising application for nanoelectronics and thermoelectricity of graphene-based nano device.

  16. Petri Nets

    Indian Academy of Sciences (India)

    In a computer system, for example, typical discrete events ... This project brought out a series of influential reports on Petri net theory in the mid and late ... Technology became a leading centre for Petri net research and from then on, Petri nets ...

  17. Mechanism of the flame ionization detector. II. Isotope effects and heteroatom effects

    DEFF Research Database (Denmark)

    Holm, Torkil

    1997-01-01

    The relative molar flame ionization detecton (FID) response (RMR) for a hydrocarbon does not change when deuterium is substituted for hydrogen. The exception is methane for which an inverse deuterium effect of 3..5% is observed for tetradeuteriomethane. [13C]Methane shows an inverse isotope effect...... of 2%. The reason for the small or non-existent isotope effects is that H/2H exchange takes place in the pre-combustion hydrogenolysis in the flame. This was shown by taking samples from the lower part of the flame by means of a fused silica capillary probe. By the same technique the hydrogenolytic...

  18. NMR spectroscopic determination of an equilibrium isotope effect on the hydration of cobalt(II)

    International Nuclear Information System (INIS)

    Evilia, R.F.; Saunders, M.

    1985-01-01

    A recently reported NMR method for the measurement of deuterium equilibrium isotope effects is applied to the hydration of the paramagnetic cobalt(II) ion. An isotope effect of about 1.3% is measured. A substantial difference between the intrinsic shift of H 2 O and D 2 O when coordinated to cobalt is also measured

  19. Electrochemical H-D isotope effect at metal-perovskite proton conductor interfaces

    DEFF Research Database (Denmark)

    Kek, D.; Bonanos, N.

    1999-01-01

    The H-D isotope effect on the electrode kinetics of a metal-proton conductor interface has been investigated. The current-voltage behaviour depends on the nature of the electrode (Ni, Ag), the atmosphere (H(2), D(2)), the partial pressures of the gases, and the temperature. The isotope effect was...

  20. Effect of density of state on isotope effect exponent of two-band superconductors

    International Nuclear Information System (INIS)

    Udomsamuthirun, P.; Kumvongsa, C.; Burakorn, A.; Changkanarth, P.; Yoksan, S.

    2005-01-01

    The exact formula of T c 's equation and the isotope effect exponent of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of two kinds of density of state: constant and van Hove singularity. The paring interaction in each band consisted of two parts: the electron-phonon interaction and non-electron-phonon interaction are included in our model. We find that the interband interaction of electron-phonon show more effect on isotope exponent than the intraband interaction and the isotope effect exponent with constant density of state can fit to experimental data, MgB 2 and high-T c superconductor, better than van Hove singularity density of state

  1. Attributable effects from information and outreach programs: Net to gross, NEBs, and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, David Juri; Skumatz, Lisa A. [Skumatz Economic Research Associates, Inc. (SERA) (United States)

    2007-07-01

    Education, outreach, advertising, and training programs provide particular difficulties in evaluation, as they focus on modifying behaviors and purchases rather than directly installing measures. This paper summarizes the results of a literature review of more than 80 studies evaluating strengths and weaknesses of evaluation work on outreach and education programs. Then, the paper presents the results of several applications of advanced evaluation techniques that are being applied to outreach, education, and training programs. This paper provides the results from detailed net-to-gross (NTG) and non-energy benefits (NEB) evaluations of outreach, training, and education programs, including:A training and education geared toward commercial architects and engineers; Two similar programs geared toward residential builders and remodelers; Residential appliance-related education and outreach programs (Energy Star); and An information-based university program.We provide information from detailed evaluations of the share of energy savings and attributable effects that are due to the program's efforts (net-to-gross ratio), and the non-energy benefits (NEBs) recognized by participants. These results augment the usual evaluation studies, and provide insights that can guide informational, outreach, and training programs to maximize their effectiveness. The attribution and NEB results provide a fuller picture of the benefits from the program, support more sophisticated benefit-cost analysis, provide direction for maximizing program 'bang for the buck', and help support program decision-making and marketing.

  2. Higher order net-proton number cumulants dependence on the centrality definition and other spurious effects

    Science.gov (United States)

    Sombun, S.; Steinheimer, J.; Herold, C.; Limphirat, A.; Yan, Y.; Bleicher, M.

    2018-02-01

    We study the dependence of the normalized moments of the net-proton multiplicity distributions on the definition of centrality in relativistic nuclear collisions at a beam energy of \\sqrt{{s}{NN}}=7.7 {GeV}. Using the ultra relativistic quantum molecular dynamics model as event generator we find that the centrality definition has a large effect on the extracted cumulant ratios. Furthermore we find that the finite efficiency for the determination of the centrality introduces an additional systematic uncertainty. Finally, we quantitatively investigate the effects of event-pile up and other possible spurious effects which may change the measured proton number. We find that pile-up alone is not sufficient to describe the data and show that a random double counting of events, adding significantly to the measured proton number, affects mainly the higher order cumulants in most central collisions.

  3. Isotope effect and deuterium excess parameter revolution in ice and snow melt

    International Nuclear Information System (INIS)

    Yin Guan; Ni Shijun; Fan Xiao; Wu Hao

    2003-01-01

    The change of water isotope composition actually is a integrated reaction depending on the change of environment. The ice and snow melt of different seasons in high mountain can obviously influence the change of isotope composition and deuterium excess parameter of surface flow and shallow groundwater. To know the isotopic fractionation caused by this special natural background, explore its forming and evolvement, is unusually important for estimating, the relationship between the environment, climate and water resources in an area. Taking the example of isotope composition of surface flow and shallow groundwater in Daocheng, Sichuan, this paper mainly introduced the changing law of isotope composition and deuterium excess parameter of surface flow and hot-spring on conditions of ice and snow melt with different seasons in high mountain; emphatically discussed the isotope effect and deuterium excess parameter revolution in the process of ice and snow melting and its reason. (authors)

  4. Land Use Effects on Net Greenhouse Gas Fluxes in the US Great Plains: Historical Trends and Model Projections

    Science.gov (United States)

    Del Grosso, S. J.; Parton, W. J.; Ojima, D. S.; Mosier, A. R.; Mosier, A. R.; Paustian, K.; Peterson, G. A.

    2001-12-01

    We present maps showing regional patterns of land use change and soil C levels in the US Great Plains during the 20th century and time series of net greenhouse gas fluxes associated with different land uses. Net greenhouse gas fluxes were calculated by accounting for soil CO2 fluxes, the CO2 equivalents of N2O emissions and CH4 uptake, and the CO2 costs of N fertilizer production. Both historical and modern agriculture in this region have been net sources of greenhouse gases. The primary reason for this, prior to 1950, is that agriculture mined soil C and resulted in net CO2 emissions. When chemical N fertilizer became widely used in the 1950's agricultural soils began to sequester CO2-C but these soils were still net greenhouse gas sources if the effects of increased N2O emissions and decreased CH4 uptake are included. The sensitivity of net greenhouse gas fluxes to conventional and alternative land uses was explored using the DAYCENT ecosystem model. Model projections suggest that conversion to no-till, reduction of the fallow period, and use of nitrification inhibitors can significantly decrease net greenhouse gas emissions in dryland and irrigated systems, while maintaining or increasing crop yields.

  5. Silver diffusion and isotope effect in silver rubidium iodide

    International Nuclear Information System (INIS)

    Arzigian, J.S.

    1980-01-01

    The diffusion coefficient of silver in RbAg 4 I 5 was measured in both superionic phases using radiotracer Ag-110m and serial sectioning with a low temperature sectioning apparatus. The activation energies for diffusion in alpha-RbAg 4 I 5 and beta-RbAg 4 I 5 , respectively, are 0.11 +- 0.01 eV and 0.20 +- 0.04 eV. An isotope effect for diffusion was also measured in both superionic phases. Ag-105 and Ag-110m radioisotopes were used with gamma spectroscopy and energy discrimination. The effect is small, with no significant temperature variation, with the value at 333 0 K being 0.12 +- 0.01. The second-order phase transition at 208 0 K has a small effect, if any, on the magnitude of the effect. The data suggest that a highly cooperative transport mechanism is responsible for the unusually high values of both the conductivity and diffusion coefficient. Although it is not possible to deduce the particular mechanism involved, theories inolving ionic polarons, or cooperative motion, such as crowdions or solitons, seem consistent with the observed results

  6. Effects of ozone on growth, net photosynthesis and yield of two African varieties of Vigna unguiculata.

    Science.gov (United States)

    Tetteh, Rashied; Yamaguchi, Masahiro; Wada, Yoshiharu; Funada, Ryo; Izuta, Takeshi

    2015-01-01

    To assess the effects of O(3)on growth, net photosynthesis and yield of two African varieties of cowpea(Vigna unguiculata L.), Blackeye and Asontem were exposed as potted plants to air that was either filtered to remove O(3) (FA), non-filtered air (NF), non-filtered with added O3 of approximately 50 nL L(-1) (ppb) from 11:00 to 16:00 (NF + O(3)) for 88 days in open-top chambers. The mean O(3) concentration (11:00-16:00) during the exposure period had a range from 16 ppb in the FA treatment to 118 ppb in the NF + O(3) treatment. Net photosynthetic rate and leaf area per plant were significantly reduced by exposure to O(3), reducing the growth of both varieties. Exposure to O(3) significantly reduced the 100-seed weight and number of seeds per pod. As a result, cowpea yield was significantly reduced by long-term exposure to O(3), with no difference in sensitivity between the varieties.

  7. Effect of varying frontal systems on stable oxygen and carbon isotopic compositions of modern planktic foraminifera of Southern Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, M.; Mohan, R.; Meloth, T.; Naik, S.S.; Sudhakar, M.

    , sediment cores and other physi- cal oceanographic parameters were collected. Here, we present the isotopic results obtained from planktic foraminifera from the plankton net samples and sur- face sediments. We find that, in this region too, plank- tic... characteristics in the Indian sector of the Southern Ocean. The δ 18 O value of planktic foraminifera is mainly governed by SST fluctuations: the samples be- come isotopically heavier polewards. Further, the plank- tic foraminifera appear to secrete...

  8. The effect of nitrogen fertilization and irradiation on barley susceptibility to net blotch disease

    International Nuclear Information System (INIS)

    Arabi, M.I.E.; Al-safadi, B.; Charbaji, T.

    2000-11-01

    Isolates of Drechslera teres f. sp. teres that cause net blotch symptoms on barley were collected from fields in different regions of Syria. there virulence spectra were determined using 11 barley cultivars. Cultivars exhibited a continuos range of response from very susceptible to moderately resistant. Isolate Raqa 13 had the highest mean virulence, then Halap 2, whereas ICARDA 3 was the lowest virulent. The effect of three concentrations (1000, 1500, 2000 ppm) of nitrogen (Urea 45%) fertilizer, and two doses of gamma ray (10 and 20 Gy), on susceptibility to infection by Drechslera teres were studied. Two barley cultivars (Thibaut and Furia) were used in this study. Results showed that 1000 ppm (N) and 15 Gy dose treatment had a positive effect on decreasing the susceptibility. (author)

  9. Determination of the variation of mercury isotope concentration based on spectral-phase effects

    International Nuclear Information System (INIS)

    Ganeev, A.A.; Man', D.D.; Turkin, Yu.I.

    1988-01-01

    A method of isotopic atomic-absorption analysis, based on spectral-phase effects in which there is no need to use several sources of radiation with pure isotopes of the analyte element, was developed. The method made it possible to simplify the analysis and to determine the variation of the concentration of mercury isotopes from one deposit to another with an accuracy several times higher that of traditional methods of spectral isotopic analysis. The method was tested on mercury 198 and mercury 202. The isotopic analyzer is diagramed and described. The mechanism of spectral-phase effects was determined by the difference in effective photon lifetimes, corresponding to different components of the hyperfine structure of the resonance line of mercury at 254 nm

  10. The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

    Directory of Open Access Journals (Sweden)

    M. Alkhatib

    2012-05-01

    Full Text Available The nitrogen (N stable isotopic composition of pore water nitrate and total dissolved N (TDN was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. N isotope effects on the water column associated with the benthic exchange of nitrate (εapp and TDN (εsed during benthic nitrification-denitrification coupling were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+. We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net fixed N loss was barely expressed at the scale of sediment-water exchange, with ϵapp values <3‰. The strongest under-expression (i.e. lowest εapp of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate εapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of εsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly elevate εsed above εapp. Calculated εsed values were within the range of 4.6 ± 2

  11. Biological isotopy. Introduction to the isotopic effects and to their applications in biology

    International Nuclear Information System (INIS)

    Tcherkez, G.

    2010-01-01

    Since their discovery in the beginning of the 20. century, the study of stable isotopes has considerably developed. This domain, which remained limited in its applications until the 1990's, has become particularly important thereafter thanks to its practical applications and in particular to its economical impacts. Many techniques used in fraud control, in drugs use control, in selection of high-yield plants etc are based on isotopic abundance measurements. This reference book gives a synthesis of our actual knowledge on the use of stable isotopes and of isotope fractionation in biology. It presents the basic notions of isotopic biochemistry and explains the origin of the isotopic effects. The application principles of these effects to metabolism, to organisms physiology, to environmental biology etc are explained and detailed using examples and exercises. The first chapters present the basic knowledge which defines, from a mathematical point-of-view, the isotopic effects of chemical reactions or of physical processes taking place in biology. The measurements principle of natural isotopes abundance is then synthesised. Finally, all these notions are applied at different scales: enzymes, physiology, metabolism, environment, ecosystems and fraud crackdown. (J.S.)

  12. Isotope effect of impurity diffusion of cadmium in silver

    International Nuclear Information System (INIS)

    Rockosch, H.J.; Herzig, C.

    1984-01-01

    The isotope effect of impurity diffusion of cadmium in silver single crystals was measured with the radioisotopes 115 Cd/ 109 Cd by gamma spectrometry. As a mean value E = 0.37 at T = 1060 K was obtained. The correlation factor f /SUB Cd/ = 0.41 is in disagreement with previous results of other investigators due to their unfavourable experimental approach. The present value of f /SUB Cd/ , however, is consistent with those of In and Sn in Ag. A comparison with the corresponding correlation factors in the copper solvent reveals a distinct influence of lattice perturbations because of the different atomic volumes of the solvents. Since the size effect is neglected in the electrostatic diffusion model, the agreement with this model is only qualitative. The frequency ratios for vacancy jumps were calculated. The free binding enthalpy of the vacancy-impurity complex was estimated to be Δg /SUB Cd/ = -0.064 eV. This value is smaller than those for In and Sn in Ag and complies with the relative diffusivities of these impurities in Ag

  13. Distance-dependent shifts in net effects by an unpalatable nettle on a palatable plant species

    Science.gov (United States)

    Suzuki, Satoshi N.; Suzuki, Ryo O.

    2011-07-01

    We examined whether the relative importance of facilitation and competition effects by an unpalatable perennial ( Urtica thunbergiana) on a palatable annual ( Persicaria longiseta) change with the spatial distance between them in a long-term deer-grazing habitat. Survivorship, growth, size, and fecundity of Persicaria were recorded at 1-2-month intervals during growing seasons in 2 successive years and were compared among individuals located in different positions relative to the canopy of Urtica: at the centre, internal edge, external edge, and far from the canopy. Survivorship of Persicaria was significantly higher at the centre of the Urtica canopy than outside the canopy early in the growing season in both years. No significant differences in Persicaria growth were observed among the four positions in most periods, except in one when growth was significantly higher at the centre, internal, and external edges of the canopy compared to outside the canopy. We found spatial shifts in the net effects of Urtica on Persicaria fecundity, from positive effects under the canopy centre to negative effects under the external edge of the canopy in the first year, and from negative effects under the centre to positive effects under the external edge in the second year. These results demonstrate that the relative importance of positive and negative effects of Urtica on Persicaria vary temporally within and among years and spatially around a single Urtica plant. Spatiotemporal variation in plant interactions may be attributable to annual and seasonal variation in vegetation productivity and grazing pressure.

  14. Effect of interband interaction on isotope effect exponent of MgB2 ...

    Indian Academy of Sciences (India)

    The interband interaction of the electron–phonon interaction shows more effect on the isotope exponent than on the non-phonon interaction. Acknowledgement. The authors would like to thank Thailand Research Fund for financial support and the University of the Thai Chamber of Commerce for partial financial support and.

  15. Proteolytic Remodeling of Perineuronal Nets: Effects on Synaptic Plasticity and Neuronal Population Dynamics

    Directory of Open Access Journals (Sweden)

    P. Lorenzo Bozzelli

    2018-01-01

    Full Text Available The perineuronal net (PNN represents a lattice-like structure that is prominently expressed along the soma and proximal dendrites of parvalbumin- (PV- positive interneurons in varied brain regions including the cortex and hippocampus. It is thus apposed to sites at which PV neurons receive synaptic input. Emerging evidence suggests that changes in PNN integrity may affect glutamatergic input to PV interneurons, a population that is critical for the expression of synchronous neuronal population discharges that occur with gamma oscillations and sharp-wave ripples. The present review is focused on the composition of PNNs, posttranslation modulation of PNN components by sulfation and proteolysis, PNN alterations in disease, and potential effects of PNN remodeling on neuronal plasticity at the single-cell and population level.

  16. Electromagnetic effects on the NET first wall caused by a plasma disruption event

    International Nuclear Information System (INIS)

    Crutzen, Y.R.; Biggio, M.; Farfaletti-Casali, F.

    1987-01-01

    During the event of a major plasma disruption, the structural components of the NET fusion reactor, such as the First Wall (FW), are subjected to strong electromagnetic transients arising from the interaction of the induced eddy currents with the large magnetic field which confines and equilibrates the plasma ring. Finite element structural analyses (static, vibration, transient dynamic) have been performed to examine stresses, deformations and reactions, generated by the electromagnetic loads, in the modular blanket-enveloping box outboard FW segment. Considering the last three engineering design variations of the outboard FW module, an improvement is obtained for the new Double Null FW configuration because of the drastic reduction of electromagnetic effects and induced stresses, mainly due to increased segmentation of the internal components

  17. Management effects on net ecosystem carbon and GHG budgets at European crop sites

    DEFF Research Database (Denmark)

    Ceschia, Eric; Bêziat, P; Dejoux, J.F.

    2010-01-01

    The greenhouse gas budgets of 15 European crop sites covering a large climatic gradient and corresponding to 41 site-years were estimated. The sites included a wide range of management practices (organic and/or mineral fertilisation, tillage or ploughing, with or without straw removal....... The variability of the different terms and their relative contributions to the net ecosystem carbon budget (NECB) were analysed for all site-years, and the effect of management on NECB was assessed. To account for greenhouse gas (GHG) fluxes that were not directly measured on site, we estimated the emissions...... caused by field operations (EFO) for each site using emission factors from the literature. The EFO were added to the NECB to calculate the total GHG budget (GHGB) for a range of cropping systems and management regimes. N2O emissions were calculated following the IPCC (2007) guidelines, and CH4 emissions...

  18. Isotope effects in lithium hydride and lithium deuteride crystals by molecular dynamics simulations.

    Science.gov (United States)

    Dammak, Hichem; Antoshchenkova, Ekaterina; Hayoun, Marc; Finocchi, Fabio

    2012-10-31

    Molecular dynamics (MD) simulations have been carried out to study isotope effects in lithium hydride and lithium deuteride crystals. Quantum effects on nuclear motion have been included through a quantum thermal bath (QTB). The interatomic forces were described either within the density functional theory (DFT) in the generalized gradient approximation (GGA) or by the phenomenological approach using the shell model. For both models, the isotopic shift in the lattice parameter can be successfully predicted by QTB-MD simulations. The slope of the experimental isotopic shift in pressure is satisfactorily reproduced by QTB-MD within DFT-GGA, in contrast to both density functional perturbation theory and QTB-MD with the shell model. We have analyzed the reasons for these discrepancies through the vibrational densities of states and the isotopic shifts in bulk modulus. The results illustrate the importance of anharmonic contributions to vibrations and to the isotopic pressure shift between LiH and LiD.

  19. Thermal Conductivity of Nanotubes: Effects of Chirality and Isotope Impurity

    OpenAIRE

    Gang, Zhang; Li, Baowen

    2005-01-01

    We study the dependence of thermal conductivity of single walled nanotubes (SWNT) on chirality and isotope impurity by nonequilibrium molecular dynamics method with accurate potentials. It is found that, contrary to electronic conductivity, the thermal conductivity is insensitive to the chirality. The isotope impurity, however, can reduce the thermal conductivity up to 60% and change the temperature dependence behavior. We also study the dependence of thermal conductivity on tube length for t...

  20. Hydrogen isotope effect through Pd in hydrogen transport pipe

    International Nuclear Information System (INIS)

    Tamaki, Masayoshi

    1992-01-01

    This investigation concerns hydrogen system with hydrogen transport pipes for transportation, purification, isotope separation and storage of hydrogen and its isotopes. A principle of the hydrogen transport pipe (heat pipe having hydrogen transport function) was proposed. It is comprised of the heat pipe and palladium alloy tubes as inlet, outlet, and the separation membrane of hydrogen. The operation was as follows: (1) gas was introduced into the heat pipe through the membrane in the evaporator; (2) the introduced gas was transported toward the condenser by the vapor flow; (3) the transported gas was swept and compressed to the end of the condenser by the vapor pressure; and (4) the compressed gas was exhausted from the heat pipe through the membrane in the condenser. The characteristics of the hydrogen transport pipe were examined for various working conditions. Basic performance concerning transportation, evacuation and compression was experimentally verified. Isotopic dihydrogen gases (H 2 and D 2 ) were used as feed gas for examining the intrinsic performance of the isotope separation by the hydrogen transport pipe. A simulated experiment for hydrogen isotope separation was carried out using a hydrogen-helium gas mixture. The hydrogen transport pipe has a potential for isotope separation and purification of hydrogen, deuterium and tritium in fusion reactor technology. (author)

  1. Matrix effects in laser ablation molecular isotopic spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Staci, E-mail: staci.brown@cepast.famu.edu [Department of Physics, Florida A and M University, 2077 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); Ford, Alan, E-mail: alan.ford@alakaidefense.com [Alakai Defense Systems, 197 Replacement Ave, Suite 102, Fort Leonard Wood, MO 65473 (United States); Akpovo, Charlemagne C., E-mail: charlemagne.akpovo@cepast.famu.edu [Department of Physics, Florida A and M University, 2077 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); Martinez, Jorge, E-mail: jmartinez@cepast.famu.edu [Department of Physics, Florida A and M University, 2077 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States); Johnson, Lewis, E-mail: lewis@cepast.famu.edu [Department of Physics, Florida A and M University, 2077 E. Paul Dirac Drive, Tallahassee, FL 32310 (United States)

    2014-11-01

    Recently, it has been shown that laser-induced breakdown spectroscopy (LIBS) can be used for the detection of isotopes of elements via isotopic shifts in diatomic species in a technique known as laser ablation molecular isotopic spectrometry (LAMIS). While LAMIS works quite well for isotopic analysis of pure compounds under optimal conditions, it is desirable for it to be applicable for a variety of compounds and matrices. However, the LIBS plasma emission associated with LAMIS depends on several parameters, including the applied electric field of the laser pulse, the physical properties of the material being investigated, and the presence of additional elements other than the element of interest. In this paper, we address some of the pitfalls arising from these dependencies when using LAMIS for the determination of the relative isotopic abundance of boron-containing materials with varying chemical matrices. - Highlights: • LAMIS usually determines isotopic composition of boron compounds within 3 percent. • LaBO{sub 3} and some boron-containing mixtures yield inaccurate LAMIS results. • Higher laser energy reduces variability but does not remedy poor LAMIS outcomes.

  2. Investigation of the feeding effect on the 13C/12C isotope ratio of the hormones in bovine urine using gas chromatography/combustion isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Balizs, Gabor; Jainz, Annett; Horvatovich, Peter

    2005-01-01

    The effect of the feeding on the 13C/12C isotope ratio of four endogenous steroid hormones testosterone (T), epi-testosterone (epi-T), dehydroepiandrosterone (DHEA) and etiocholanolone (ETIO) in bovine urine was investigated. An analytical method to determine the accurate isotope ratio was developed

  3. Green roof adoption in atlanta, georgia: the effects of building characteristics and subsidies on net private, public, and social benefits.

    Science.gov (United States)

    Mullen, Jeffrey D; Lamsal, Madhur; Colson, Greg

    2013-10-01

    This research draws on and expands previous studies that have quantified the costs and benefits associated with conventional roofs versus green roofs. Using parameters from those studies to define alternative scenarios, we estimate from a private, public, and social perspective the costs and benefits of installing and maintaining an extensive green roof in Atlanta, GA. Results indicate net private benefits are a decreasing function of roof size and vary considerably across scenarios. In contrast, net public benefits are highly stable across scenarios, ranging from $32.49 to $32.90 m(-2). In addition, we evaluate two alternative subsidy regimes: (i) a general subsidy provided to every building that adopts a green roof and (ii) a targeted subsidy provided only to buildings for which net private benefits are negative but net public benefits are positive. In 6 of the 12 general subsidy scenarios the optimal public policy is not to offer a subsidy; in 5 scenarios the optimal subsidy rate is between $20 and $27 m(-2); and in 1 scenario the optimal rate is $5 m(-2). The optimal rate with a targeted subsidy is between $20 and $27 m(-2) in 11 scenarios and no subsidy is optimal in the twelfth. In most scenarios, a significant portion of net public benefits are generated by buildings for which net private benefits are positive. This suggests a policy focused on information dissemination and technical assistance may be more cost-effective than direct subsidy payments.

  4. COST-EFFECTIVE APPROACH TO ESTIMATE UNREPORTED DATA: REBUILDING HISTORY OF LIFT-NET FISHING IN KWANDANG WATERS

    Directory of Open Access Journals (Sweden)

    Andhika Prima Prasetyo

    2014-12-01

    Full Text Available This paper aims to develop cost-effective approach regarding the estimation unreported annual catch data of lift-net fishery using Google Earth imagery. Lift net fishery is one of the main fishing activities of coastal community in Kwandang Bay, it has been faced problem of uncertain fisheries status due to limited recorded data. Combination of a Monte Carlo procedure was applied by involving couple of assumptions on parameters such as estimate growth rate of the total number of lift-net per years (10%, day at sea per unit per month (21 days and operated lift-net per month (50% and 80%. The results showed that 101 units of lift-nets were found around Kwandang waters based on Google Earth imagery recorded in October, 7th 2010, and this were used as a benchmark of calculation. This prediction was 28 units higher than official data from North Gorontalo District of Marine Affairs and Fisheries Services (DKP Gorontalo Utara. Compared with capture fisheries statistics issued by Kwandang CFP, the estimated lift-net catches based on two-scenarios represent additional catches of 46 % and 86 %. These results suggested and could be used as a correction index to improve the reliability of Kwandang District officially reported fisheries statistics as a baseline to develop a local common fisheries policy.

  5. Intramolecular kinetic isotope effect in gas-phase proton-transfer reactions

    International Nuclear Information System (INIS)

    Wellman, K.M.; Victoriano, M.E.; Isolani, P.C.; Riveros, J.M.

    1979-01-01

    The k/sub H//k/sub D/ isotope effects were determined by ICR for the reaction of substituted toluenes with several alkoxides. The results showed a definite trend for k/sub H//k/sub D/ starting as a normal isotope effect for appreciably exothermic reaction (> 3 kcal mol -1 ) and proceeding smoothly toward an inverse isotope effect as the reaction approached thermoneutrality or becomes endothermic. These observations were explained by a reaction which involved a double minima potential with a central energy barrier

  6. Transient competitive complexation in biological kinetic isotope fractionation explains non-steady isotopic effects: Theory and application to denitrification in soils

    Energy Technology Data Exchange (ETDEWEB)

    Maggi, F.M.; Riley, W.J.

    2009-06-01

    The theoretical formulation of biological kinetic reactions in isotopic applications often assume first-order or Michaelis-Menten-Monod kinetics under the quasi-steady-state assumption to simplify the system kinetics. However, isotopic e ects have the same order of magnitude as the potential error introduced by these simpli cations. Both formulations lead to a constant fractionation factor which may yield incorrect estimations of the isotopic effect and a misleading interpretation of the isotopic signature of a reaction. We have analyzed the isotopic signature of denitri cation in biogeochemical soil systems by Menyailo and Hungate [2006], where high {sup 15}N{sub 2}O enrichment during N{sub 2}O production and inverse isotope fractionation during N{sub 2}O consumption could not be explained with first-order kinetics and the Rayleigh equation, or with the quasi-steady-state Michaelis-Menten-Monod kinetics. When the quasi-steady-state assumption was relaxed, transient Michaelis-Menten-Monod kinetics accurately reproduced the observations and aided in interpretation of experimental isotopic signatures. These results may imply a substantial revision in using the Rayleigh equation for interpretation of isotopic signatures and in modeling biological kinetic isotope fractionation with first-order kinetics or quasi-steady-state Michaelis-Menten-Monod kinetics.

  7. Effect Of Substrates On The Fractionation Of Hydrogen Isotopes During Lipid-Biosynthesis By Haloarcula marismortui

    Science.gov (United States)

    Dirghangi, S. S.; Pagani, M.

    2010-12-01

    Lipids form an important class of proxies for paleoclimatological research, and hydrogen isotope ratios of lipids are being increasingly used for understanding changes in the hydrological system. Proper understanding of hydrogen isotope fractionation during lipid biosynthesis is therefore important and attention has been directed toward understanding the magnitude of hydrogen isotope fractionation that occurs during lipid biosynthesis in various organisms. Hydrogen isotope ratios of lipids depend on the hydrogen isotopic composition of the ambient water, hydrogen isotopic composition of NADPH used during biosynthesis, growth conditions, pathways of lipid biosynthesis, and substrates in the case of heterotrophic organisms. Recently it has been observed that NADPH contributes a significant part of the hydrogen in fatty acids synthesized by bacteria during heterotrophic growth (Zhang et al, 2009). As NADPH is formed by reduction of NADP+ during metabolism of substrates, different metabolic pathways form NADPH with different D/H ratios, which in turn results in variation in D/H ratios of lipids (Zhang et al, 2009). Therefore, substrates play a significant role in hydrogen isotopic compositions of lipids. For this study, we are investigating the effects of substrates on hydrogen isotope fractionation during biosynthesis of isoprenoidal lipids by heterotrophically growing halophilic archaea. Haloarcula marismortui is a halophilic archaea which synthesizes Archaeol (a diether lipid) and other isoprenoidal lipids. We have grown Haloarcula marismortui in pure cultures on three different substrates and are in the process of evaluating isotopic variability of Archaeol and other lipids associated with substrate and the D/H composition of ambient water. Our results will be helpful for a better understanding of hydrogen isotope fractionations during lipid synthesis by archaea. Also, halophilic archaea are the only source of archaeol in hypersaline environments. Therefore, our

  8. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  9. The effect of deltamethrin-treated net fencing around cattle enclosures on outdoor-biting mosquitoes in Kumasi, Ghana.

    Directory of Open Access Journals (Sweden)

    Marta Ferreira Maia

    Full Text Available Classic vector control strategies target mosquitoes indoors as the main transmitters of malaria are indoor-biting and -resting mosquitoes. However, the intensive use of insecticide-treated bed-nets (ITNs and indoor residual spraying have put selective pressure on mosquitoes to adapt in order to obtain human blood meals. Thus, early-evening and outdoor vector activity is becoming an increasing concern. This study assessed the effect of a deltamethrin-treated net (100 mg/m(2 attached to a one-meter high fence around outdoor cattle enclosures on the number of mosquitoes landing on humans. Mosquitoes were collected from four cattle enclosures: Pen A - with cattle and no net; B - with cattle and protected by an untreated net; C - with cattle and protected by a deltamethrin-treated net; D - no cattle and no net. A total of 3217 culicines and 1017 anophelines were collected, of which 388 were Anopheles gambiae and 629 An. ziemanni. In the absence of cattle nearly 3 times more An. gambiae (p<0.0001 landed on humans. The deltamethrin-treated net significantly reduced (nearly three-fold, p<0.0001 culicine landings inside enclosures. The sporozoite rate of the zoophilic An. ziemanni, known to be a secondary malaria vector, was as high as that of the most competent vector An. gambiae; raising the potential of zoophilic species as secondary malaria vectors. After deployment of the ITNs a deltamethrin persistence of 9 months was observed despite exposure to African weather conditions. The outdoor use of ITNs resulted in a significant reduction of host-seeking culicines inside enclosures. Further studies investigating the effectiveness and spatial repellence of ITNs around other outdoor sites, such as bars and cooking areas, as well as their direct effect on vector-borne disease transmission are needed to evaluate its potential as an appropriate outdoor vector control tool for rural Africa.

  10. Effects of topography on simulated net primary productivity at landscape scale.

    Science.gov (United States)

    Chen, X F; Chen, J M; An, S Q; Ju, W M

    2007-11-01

    Local topography significantly affects spatial variations of climatic variables and soil water movement in complex terrain. Therefore, the distribution and productivity of ecosystems are closely linked to topography. Using a coupled terrestrial carbon and hydrological model (BEPS-TerrainLab model), the topographic effects on the net primary productivity (NPP) are analyzed through four modelling experiments for a 5700 km(2) area in Baohe River basin, Shaanxi Province, northwest of China. The model was able to capture 81% of the variability in NPP estimated from tree rings, with a mean relative error of 3.1%. The average NPP in 2003 for the study area was 741 gCm(-2)yr(-1) from a model run including topographic effects on the distributions of climate variables and lateral flow of ground water. Topography has considerable effect on NPP, which peaks near 1350 m above the sea level. An elevation increase of 100 m above this level reduces the average annual NPP by about 25 gCm(-2). The terrain aspect gives rise to a NPP change of 5% for forests located below 1900 m as a result of its influence on incident solar radiation. For the whole study area, a simulation totally excluding topographic effects on the distributions of climatic variables and ground water movement overestimated the average NPP by 5%.

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

    International Nuclear Information System (INIS)

    Hines, V.; Johnston, M.

    1989-01-01

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

  12. Carbon isotope effects in carbohydrates and amino acids of photosynthesizing organisms

    Energy Technology Data Exchange (ETDEWEB)

    Ivlev, A.A.; Kaloshin, A.G.; Koroleva, M.Ya. (Ministerstvo Geologii SSR, Moscow)

    1982-02-10

    The analysis of the carbon isotope distribution in carbohydrates and amino acids of some photosynthesizing organisms revealed the close relationship between distribution and the pathways of biosynthesis of the molecules. This relationship is explained on the basis of the previously proposed mechanism of carbon isotope fractionation in a cell, in which the chief part is played by kinetic isotope effects in the pyruvate decarboxylation reaction progressively increased in the conjugated processes of gluconeogenesis. Isotope differences of C/sub 2/ and C/sub 3/ fragments arising in decarboxylation of pyruvate, as well as isotope differences of biogenic acceptor and environmental CO/sub 2/ appearing in assimilation are the main reasons of the observed intramolecular isotopic heterogeneity of biomolecules. The heterogeneity is preserved in metabolites owing to an incomplete mixing of carbon atoms in biochemical reactions. The probable existence of two pools of carbohydrates in photosynthesizing organisms different in isotopic composition is predicted. Two types of intramolecular isotope distribution in amino acids are shown.

  13. Effect of the magnetic isotope of magnesium, 25Mg, on post-radiation recovery of Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Grodzinskij, D.M.; Evstyukhina, T.A.; Kol'tover, V.K.; Korolev, V.G.; Kutlakhmedov, Yu.A.; Grodzinskij, D.M.; Evstyukhina, T.A.; Kol'tover, V.K.; Korolev, V.G.; Kutlakhmedov, Yu.A.; Grodzinskij, D.M.; Evstyukhina, T.A.; Kol'tover, V.K.; Korolev, V.G.; Kutlakhmedov, Yu.A.

    2011-01-01

    Among three stable magnesium isotopes, 24 Mg, 25 Mg, and 26 Mg with natural abundance 79, 10, and 11%, only 25 Mg has the nuclear spin (I=5/2) and, therefore, the nuclear magnetic moment. Two other isotopes are spinless (I=0) and, hence, have no magnetic moment. We have revealed that magnetic isotope 25 Mg, by comparison to nonmagnetic isotope 24 Mg, essentially stimulates the recovery process in the yeast cells, Saccharomyces cerevisiae, after UV irradiation. Thus, we have first documented the magnetic isotope effect in radiation biology. This finding opens up the way to the development of novel radio-protectors based on the stable magnetic isotopes.

  14. Community-wide effects of permethrin-treated bed nets on child mortality and malaria morbidity in western Kenya

    NARCIS (Netherlands)

    Hawley, William A.; Phillips-Howard, Penelope A.; ter Kuile, Feiko O.; Terlouw, Dianne J.; Vulule, John M.; Ombok, Maurice; Nahlen, Bernard L.; Gimnig, John E.; Kariuki, Simon K.; Kolczak, Margarette S.; Hightower, Allen W.

    2003-01-01

    Spatial analyses of the effect of insecticide (permethrin)-treated bed nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on

  15. Studies of isotopic effects in the excited electronic states of molecular systems

    International Nuclear Information System (INIS)

    1982-01-01

    Rare gas halogen (RGH) lasers serve as convenient tools for a range of photophysical processes which exhibit isotope effects. This document summarizes progress in the production of molecular systems in their electronic excited states with the aid of RGH lasers, and the various isotopic effects one can study under these conditions. We conclude that the basic physical mechanisms involved in the isotopically sensitive characteristics of excited molecular electronic states are sufficiently selective to be useful in both the detection and separation of many atomic materials

  16. D/H isotope effects in π-complexes of deuterated hexamethylbenzenes with the nitrosonium cation

    International Nuclear Information System (INIS)

    Borodkin, G.I.; Elanov, I.R.; Shakirov, M.M.; Shubin, V.G.

    1993-01-01

    The isotope effects of deuterium, manifested in the 13 C NMR spectra of complexes of deuterated hexamethylbenzenes C 6 (CD 3 ) n ·(CH 3 ) 6-n with the nitrosonium cation, have been studied. The small values observed for the isotopic perturbation are evidence of π-bonding of the NO + group to the hexamethylbenzene molecule. The applicability of an additive scheme of calculation of isotope effects for the ring carbon atoms of the complexes, based on the increment of replacement of the CH 3 group by CD 3 in hexamethylbenzene, has been demonstrated

  17. Secondary partitioning isotope effects on solvolytic ion pair intermediates

    International Nuclear Information System (INIS)

    Abbey, K.J.

    1976-01-01

    The thermal decomposition of N-benzhydryl N-nitrosobenzamide (BNB) has been shown to produce an ion pair which either forms ester or reacts with the solvent. In ethanol, the fraction of ester produced, R, was much smaller than R values obtained from solvolysis or from the diphenyldiazomethane (DDM)-benzoic acid reaction, which was suggested to yield the same ion pair as solvolysis. This difference led to the conclusion that the ionic species for the nitrosamide decomposition is a nitrogen-separated ion pair. This study was initiated on the assumption that BNB led to solvolytic ion pairs, but that both the intimate and solvent-separated ion pairs were produced directly from the nitrosamide. The use of α-tritiated BNB for the study of partitioning isotope effects (PIE's) in this system led to activity ratios much lower than expected from other reported work. Results of studies of ''special'' salt effect were not consistent for all situations, but the results do suggest that the assumption that BNB leads to solvolytic ion pairs is probably valid. The investigation of the more stable p-methoxybenzhydryl benzoate system proved to be highly productive. The ester fraction produced, R, responded dramatically to the addition of common-ion as well as ''special'' salts. The functional relationship of R on salt concentration could be explained in terms of Winstein's solvolytic scheme where the intimate ion pair, the solvent-separated ion pair, and the dissociated ion were important. Tritium-labelled compounds were used for PIE studies on 3 different compounds, and three different methods of reaction are proposed

  18. Heavy-atom isotope effects on binding of reactants to lactate dehydrogenase and pyruvate kinase

    International Nuclear Information System (INIS)

    Gawlita, E.

    1993-04-01

    18 O and 13 C kinetic isotope effects have been measured on the reaction of pyruvate kinase with phospho-enol-pyruvate and ADP using a remote label technique. The magnitude of both investigated isotope effects showed a dependence on the concentration of ADP. However, while the carbon effect was simply 'washed out' to unity at high ATP concentration, the oxygen effect becomes inverse and reached 0.9928 at the highest used concentration of ADP. Such a result testifies that the assumption of the negligible effect of isotopic substitution on enzyme-substrate associations remains correct only for carbon effects. An equilibrium 18 O isotope effect on association of oxalate with lactate dehydrogenase in the presence of NADHP has been evaluated by both experimental and theoretical means. Experimental methods, which involved equilibrium dialysis and gas chromatographic/mass spectrometric measurement of isotopic ration, yielded an inverse value of 0.9840. Semiempirical methods involved vibrational analysis of oxalate in two different environments. The comparison of calculated values with the experimentally determined isotope effect indicated that the AM 1 Hamiltonian proved superior to its PM 3 counterpart in this modelling. 160 refs, 8 figs, 18 tabs

  19. Limits on the expression of enzyme-mediated solvent isotope effects

    International Nuclear Information System (INIS)

    Northrop, D.B.

    1981-01-01

    Steady-state analysis of primary solvent isotope effects on enzyme-catalyzed reactions, mediated by solvent-shielded di- or triprotic groups on the enzyme, yields equations describing the upper limit of intramolecular isotopic discrimation. For diprotic groups [P/sub H]/[P/sub D/] = 3k/sub H//k/sub D/ + 3), and for triprotic groups [P/sub H/]/[P/sub D/] = [7(k/sub H//k/sub D/ 2 = 10k/sub H/k/sub D/ + 1]/[(k/sub H//k/sub D/) 2 + 10k/sub H//k/sub D/ + 7]. Given a normal intrinsic isotope effect of k/sub H//k/sub D/ = 7, maximal isotopic discrimation in 50:50 H 2 O:D 2 O is therefore 2.2 and 3.3, respectively, versus 1.0 for a monoprotic group. Intermediate values of isotope discrimination may be interpreted with respect to distinguishing enzyme-mediated catalytic mechanisms from those of direct transfer between solvent and substrate, and to identifying mediating groups, by comparisons of isotopic discrimination at high and low concentrations of substrates and by reference to intrinsic and intermolecular isotope effects

  20. Solvent-dependent deuterium isotope effects in the 15N NMR spectra of an ammonium ion

    International Nuclear Information System (INIS)

    Wielogorska, E.; Jackowski, K.

    2000-01-01

    Deuterium isotope effects on 15 N NMR chemical shifts and spin-spin coupling constants have been investigated for the 15 N enriched ammonium chloride (conc. 15 NH 4 + ion has been observed in water, methanol, ethanol and dimethylsulfoxide, while the 15 ND 4 + has been monitored in the analogous deuterated liquids. It is shown that the isotope effect in nitrogen chemical shifts ( 1 Δ 15 N( 2/1 H)), significantly different in various solvents, changes from -1.392 ppm in dimethylsulfoxide to -0.071 ppm in ethanol. The 1 J(N,H) and 1 J(N,D) coupling constants have been measured for acidic solutions under conditions of slow proton (or deuterium) exchange. The reduced coupling constants have been estimated to present isotope effects in the spin-spin coupling constants. The latter isotope effects are fairly small. (author)

  1. Isotope effects in the equilibrium and non-equilibrium vaporization of tritiated water and ice

    International Nuclear Information System (INIS)

    Baumgaertner, F.; Kim, M.-A.

    1990-01-01

    The vaporization isotope effect of the HTO/H 2 O system has been measured at various temperatures and pressures under equilibrium as well as non-equilibrium conditions. The isotope effect values measured in equilibrium sublimation or distillation are in good agreement with the theoretical values based on the harmonic oscillator model. In non-equilibrium vaporization at low temperatures ( 0 C), the isotope effect decreases rapidly with decreasing system pressure and becomes negligible when the system pressure is lowered more than one tenth of the equilibrium vapor pressure. At higher temperatures, the isotope effect decreases very slowly with decreasing system pressure. Discussion is extended for the application of the present results to the study of biological enrichment of tritium. (author)

  2. 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.)

  3. Magnetic sheath effect on the gross and net erosion rates due to impurities

    Science.gov (United States)

    Mellet, N.; Pégourié, B.; Martin, C.; Gunn, J. P.; Bufferand, H.; Roubin, P.

    2016-02-01

    Simulations of impurity trajectories in deuterium plasmas in the vicinity of the surface are performed by taking into account the magnetic sheath in conditions relevant for ITER and WEST. We show that the magnetic sheath has a strong effect on the average impact angle of impurities in divertor conditions and that it can lead to an increase of ≈ 60% at the gross erosion maximum for neon (Ne+4) compared to the case when only the cyclotron motion is considered. The evaluation of the net erosion has been undertaken by retaining local redeposition of tungsten (W). We investigate how it is affected by the sheath magnetic potential profile. The largest effect is however observed when an energy distribution is considered. In this case the number of particles that manage to exit the sheath is larger as it is dominated by the more energetic particles. The comparison with other work is also discussed. The application to a scenario of the WEST project is finally performed, which exhibits a moderate, however non negligible, erosion of the plasma facing components.

  4. Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects

    CERN Document Server

    Rumolo, Giovanni; Zimmermann, Frank; ECLOUD'12

    2013-01-01

    This report contains the Proceedings of the Joint INFN-Frascati, INFN-Pisa, CERN-LER and EuCARD-AccNet Mini-Workshop on Electron-Cloud Effects, “ECLOUD12”, held at La Biodola, Isola d’Elba, from 5 to 9 June 2012. The ECLOUD12 workshop reviewed many recent electron-cloud (EC) observations at existing storage rings, EC predictions for future accelerators, electron-cloud studies at DAFNE, EC mitigation by clearing electrodes and graphite/carbon coatings, modeling of incoherent EC effects, self-consistent simulations, synergies with other communities like the Valencia Space Consortium and the European Space Agency. ECLOUD12 discussed new EC observations at existing machines including LHC, CesrTA, PETRA-3, J-PARC, and FNAL MI; latest experimental efforts to characterize the EC – including EC diagnostics, experimental techniques, mitigation techniques such as coating and conditioning, advanced chemical and physical analyses of various vacuum-chamber surfaces, beam instabilities and emittance growth –; the...

  5. Proceedings of Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects

    International Nuclear Information System (INIS)

    Cimino, R; Rumolo, Giovanni; Zimmermann, Frank

    2013-01-01

    This report contains the Proceedings of the Joint INFN-Frascati, INFN-Pisa, CERN-LER and EuCARD-AccNet Mini-Workshop on Electron-Cloud Effects, “ECLOUD12”, held at La Biodola, Isola d’Elba, from 5 to 9 June 2012. The ECLOUD12 workshop reviewed many recent electron-cloud (EC) observations at existing storage rings, EC predictions for future accelerators, electron-cloud studies at DAFNE, EC mitigation by clearing electrodes and graphite/carbon coatings, modeling of incoherent EC effects, self-consistent simulations, synergies with other communities like the Valencia Space Consortium and the European Space Agency. ECLOUD12 discussed new EC observations at existing machines including LHC, CesrTA, PETRA-3, J-PARC, and FNAL MI; latest experimental efforts to characterize the EC – including EC diagnostics, experimental techniques, mitigation techniques such as coating and conditioning, advanced chemical and physical analyses of various vacuum-chamber surfaces, beam instabilities and emittance growth –; the status of EC physics models and (new, more versatile and additional) simulation codes and their comparison with recently acquired experimental data; and the mitigation requirements and potential performance limitations imposed by the EC on upgraded and future machines, including HL-LHC, FAIR, ILC, Project-X, SuperB and SuperKEKB. A dedicated session addressed problems related to RF breakdown and multipacting for space applications. A number of open questions and future R&D needs were identified

  6. Effects of inorganic anions on carbon isotope fractionation during Fenton-like degradation of trichloroethene

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yunde [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China); Laboratory of Basin Hydrology and Wetland Eco-restoration, China University of Geosciences, Wuhan 430074 (China); Zhou, Aiguo, E-mail: aiguozhou@cug.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China); Gan, Yiqun; Li, Xiaoqian [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); School of Environmental Studies, China University of Geosciences, Wuhan 430074 (China)

    2016-05-05

    Highlights: • The effect of inorganic anions on carbon isotope fractionation was evaluated. • The enrichment factors was independent concentration of NO{sub 3}{sup −}, or SO{sub 4}{sup 2−}. • Cl{sup −} significantly influenced the carbon isotope fractionation. - Abstract: Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (ε value). A comparison of ε values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the ε values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the ε values (ranging from −6.3 ± 0.8 to 10 ± 1.3‰) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate ε values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes.

  7. Effects of inorganic anions on carbon isotope fractionation during Fenton-like degradation of trichloroethene

    International Nuclear Information System (INIS)

    Liu, Yunde; Zhou, Aiguo; Gan, Yiqun; Li, Xiaoqian

    2016-01-01

    Highlights: • The effect of inorganic anions on carbon isotope fractionation was evaluated. • The enrichment factors was independent concentration of NO_3"−, or SO_4"2"−. • Cl"− significantly influenced the carbon isotope fractionation. - Abstract: Understanding the magnitude and variability in isotope fractionation with respect to specific processes is crucial to the application of stable isotopic analysis as a tool to infer and quantify transformation processes. The variability of carbon isotope fractionation during Fenton-like degradation of trichloroethene (TCE) in the presence of different inorganic ions (nitrate, sulfate, and chloride), was investigated to evaluate the potential effects of inorganic anions on carbon isotope enrichment factor (ε value). A comparison of ε values obtained in deionized water, nitrate solution, and sulfate solution demonstrated that the ε values were identical and not affected by the presence of nitrate and sulfate. In the presence of chloride, however, the ε values (ranging from −6.3 ± 0.8 to 10 ± 1.3‰) were variable and depended on the chloride concentration, indicating that chloride could significantly affect carbon isotope fractionation during Fenton-like degradation of TCE. Thus, caution should be exercised in selecting appropriate ε values for the field application of stable isotope analysis, as various chloride concentrations may be present due to naturally present or introduced with pH adjustment and iron salts during Fenton-like remediation. Furthermore, the effects of chloride on carbon isotope fractionation may be able to provide new insights about reaction mechanisms of Fenton-like processes.

  8. Petri Nets

    Indian Academy of Sciences (India)

    GENERAL I ARTICLE ... In Part 1 of this two-part article, we have seen im- ..... mable logic controller and VLSI arrays, office automation systems, workflow management systems, ... complex discrete event and real-time systems; and Petri nets.

  9. Controls of Net Ecosystem Exchange at an Old Field, a Pine Plantation, and a Hardwood Forest under Identical Climatic and Edaphic Conditions-Isotopic Studies

    Energy Technology Data Exchange (ETDEWEB)

    Chanton, J. P.; Mortazavi, B.

    2004-11-04

    During the past year we have submitted two manuscripts. 1. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions (in Press). Oecologia 2. Mortazavi, B. and J. P. Chanton. Use of Keeling plots for determining sources of dissolved organic carbon in nearshore and open ocean systems (Published in Limnology and Oceanography (2004) Vol 49 pages 102-108). 3. Mortazavi, B., J. L. Prater, and J. P. Chanton (2004). A field-based method for simultaneous measurements of the 18O and 13C of soil CO2 efflux. Biogeosciences Vol 1:1-16 Most recent products delivered: Mortazavi, B. and J. P. Chanton. Abiotic and biotic controls on the 13C of respired CO2 in the southeastern US forest mosaics and a new technique for measuring the of soil CO2 efflux. Joint Biosphere Stable Isotope Network (US) and Stable Isotopes in Biosphere Atmosphere Exchange (EU) 2004 Meeting, Interlaken, Switzerland, March 31-April 4, 2004. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions. American Geophysical Union Fall Meeting, San Francisco, USA, December 8-12, 2003. Prater, J., Mortazavi, B. and J. P. Chanton. Measurement of discrimination against 13C during photosynthesis and quantification of the short-term variability of 13C over a diurnal cycle. American Geophysical Union Fall Meeting, San Francisco, USA, December 8-12, 2003.

  10. Effects of Channel Geometry and Coolant Fluid on Thermoelectric Net Power

    DEFF Research Database (Denmark)

    Rezaniakolaei, Alireza; Rosendahl, Lasse; Sørensen, Kim

    2014-01-01

    Channel geometry has a strong influence on the heat transfer coefficient and cooling energy input in a heat sink. The net power output in a thermoelectric generator (TEG) can be defined as power generation minus the required cooling energy in TEG. This study aims to evaluate the net power generat......, and the maximum net power output occurs at smaller Reynolds number when the channel hydraulic diameter reduces....... generation in TEG for different size of hydraulic diameter of plate-fin heat sink and over a wide range of Reynolds number. The particular focus of this study is to find optimal Reynolds number in each considered channel hydraulic diameter and to explore optimal channel hydraulic diameter for maximum TEG net...

  11. Isotope effects in interstellar molecules by chemical hyperfine interaction

    International Nuclear Information System (INIS)

    Haberkorn, R.; Michel-Beyerle, M.E.

    1977-01-01

    If free radicals recombine on grain surfaces, not only the different masses of isotopes but also their differing nuclear spin moments (e.g. 12 C/ 13 C, 14 N/ 15 N, 17 O/ 18 O) may imply variations in the recombination probability due to hyperfine interaction. This mechanism has not been accounted for so far. (orig.) [de

  12. Solvent isotope effect on the fluorescence of azoalkanes

    International Nuclear Information System (INIS)

    Mirbach, M.J.; Mirbach, M.F.; Cherry, W.R.; Turro, N.J.; Engel, P.

    1977-01-01

    A study of fluorescence quantum yields and fluorescence lifetimes of two cyclic azoalkanes reveal a striking dependence of phisub(F) and tausub(F) on solvent and on isotopic substitution (OH → OD). A mechanism involving specific deactivation of the fluorescent state from a hydrogen bonded complex is proposed to rationalize the data. (orig./HK) [de

  13. Radioactive isotope and isomer separation with using light induced drift effect

    International Nuclear Information System (INIS)

    Hradecny, C.; Slovak, J.; Tethal, T.; Ermolaev, I.M.; Shalagin, A.M.

    1991-01-01

    The isotope separation with using light induced drift (LID) is discussed. The basic theoretical characteristics of the method are deduced: separation simultaneously with an arbitrary high enrichment and without significant losses; separation productivity up to 100 μg/h. These characteristics are sufficient and very convenient for separation of expensive radioactive isotopes and isomers which are applied in medicine and science. The first experimental separation of the radioactive isotopes ( 22,24 Na) by using the LID effect is reported. 13 refs.; 5 figs

  14. Climate dependence of the CO2 fertilization effect on terrestrial net primary production

    International Nuclear Information System (INIS)

    Alexandrov, G.A.; Yamagata, Y.; Oikawa, T.

    2003-01-01

    The quantitative formulation of the fertilization effect of CO 2 enrichment on net primary production (NPP) introduced by Keeling and Bacastow in 1970s (known as Keeling's formula) has been recognized as a summary of experimental data and has been used in various assessments of the industrial impact on atmospheric chemistry. Nevertheless, the magnitude of the formula's key coefficient, the so-called growth factor, has remained open to question. Some of the global carbon cycle modelers avoid this question by tuning growth factor and choosing the value that fits the observed course of atmospheric CO 2 changes. However, for mapping terrestrial sinks induced by the CO 2 fertilization effect one needs a geographical pattern of the growth factor rather than its globally averaged value. The earlier approach to this problem involved formulating the climate dependence of the growth factor and the derivation of its global pattern from climatic variables (whose geographical distribution is known). We use a process-based model (TsuBiMo) for this purpose and derive the values of growth factor for major biomes for comparison our approach with the earlier studies. Contrary to the earlier prevailing opinion, TsuBiMo predicts that these values decrease with mean annual temperature (excluding biomes of limited water supply). We attribute this result to the effect of light limitation caused by mutual shading inside a canopy, which was considered earlier as unimportant, and conclude that current hypotheses about CO 2 fertilization effect (and thus projections of the related carbon sink) are very sensitive to the choice of driving forces taken into account

  15. Mass balance and isotope effects during nitrogen transport through septic tank systems with packed-bed (sand) filters

    Science.gov (United States)

    Hinkle, S.R.; Böhlke, J.K.; Fisher, L.H.

    2008-01-01

    Septic tank systems are an important source of NO3- to many aquifers, yet characterization of N mass balance and isotope systematics following septic tank effluent discharge into unsaturated sediments has received limited attention. In this study, samples of septic tank effluent before and after transport through single-pass packed-bed filters (sand filters) were evaluated to elucidate mass balance and isotope effects associated with septic tank effluent discharge to unsaturated sediments. Chemical and isotopic data from five newly installed pairs and ten established pairs of septic tanks and packed-bed filters serving single homes in Oregon indicate that aqueous solute concentrations are affected by variations in recharge (precipitation, evapotranspiration), NH4+ sorption (primarily in immature systems), nitrification, and gaseous N loss via NH3 volatilization and(or) N2 or N2O release during nitrification/denitrification. Substantial NH4+ sorption capacity was also observed in laboratory columns with synthetic effluent. Septic tank effluent ??15N-NH4+ values were almost constant and averaged + 4.9??? ?? 0.4??? (1 ??). In contrast, ??15N values of NO3- leaving mature packed-bed filters were variable (+ 0.8 to + 14.4???) and averaged + 7.2??? ?? 2.6???. Net N loss in the two networks of packed-bed filters was indicated by average 10-30% decreases in Cl--normalized N concentrations and 2-3??? increases in ??15N, consistent with fractionation accompanying gaseous N losses and corroborating established links between septic tank effluent and NO3- in a local, shallow aquifer. Values of ??18O-NO3- leaving mature packed-bed filters ranged from - 10.2 to - 2.3??? (mean - 6.4??? ?? 1.8???), and were intermediate between a 2/3 H2O-O + 1/3 O2-O conceptualization and a 100% H2O-O conceptualization of ??18O-NO3- generation during nitrification.

  16. Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

    Directory of Open Access Journals (Sweden)

    T. S. David

    2007-09-01

    Full Text Available Droughts reduce gross primary production (GPP and ecosystem respiration (Reco, contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean, droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003–2006 the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE between −861 and −399 g C m−2 year−1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between −140 and −28 g C m−2 year−1 and in the grassland between −190 and +49 g C m−2 year−1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD, as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September of 2004–2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004–2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE. The grassland was a net source of carbon dioxide (+49 g C m−2 year−1. In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation

  17. Aim High or Go Low? Pricing Strategies and Enrollment Effects when the Net Price Elasticity Varies with Need and Ability

    Science.gov (United States)

    Curs, Bradley R.; Singell, Larry D., Jr.

    2010-01-01

    Detailed data on individual applicants to a large public university are used to demonstrate that net price responsiveness decreases with need and ability. Enrollment effects are simulated and show a movement towards a high tuition/high aid (low tuition/low aid) policy significantly lowers (raises) tuition revenue with a modest increase (decrease)…

  18. Effect of permethrin-treated bed nets on the spatial distribution of malaria vectors in western Kenya

    NARCIS (Netherlands)

    Gimnig, John E.; Kolczak, Margarette S.; Hightower, Allen W.; Vulule, John M.; Schoute, Erik; Kamau, Luna; Phillips-Howard, Penelope A.; ter Kuile, Feiko O.; Nahlen, Bernard L.; Hawley, William A.

    2003-01-01

    The effect of insecticide (permethrin)-treated bed nets (ITNs) on the spatial distribution of malaria vectors in neighboring villages lacking ITNs was studied during a randomized controlled trial of ITNs in western Kenya. There was a trend of decreased abundance of Anopheles gambiae with decreasing

  19. Heating Has No Effect on the Net Protein Utilisation from Egg Whites in Rats

    Directory of Open Access Journals (Sweden)

    Ryosuke Matsuoka

    2017-01-01

    Full Text Available Egg whites (EW are a good source of protein; however, they are typically heated prior to consumption. Therefore, we investigated the effects of different heating conditions on the protein utilisation rate of EW. Male Sprague-Dawley rats (n=36, 198±1 g were divided into six groups and fed American Institute of Nutrition-76 chow containing unheated EW, soft-boiled EW, boiled EW, milk whey protein, soybean protein, or no protein over a 10-day period using pair-feeding. Urine and faeces were sampled daily beginning on day 5 to measure nitrogen content and the net protein utilisation (NPU rate. The soybean protein group had a significantly lower level of food intake and was thus excluded from subsequent analyses. The NPU value was similar among the unheated, soft-boiled, and boiled EW groups (97.5±0.4, 96.5±0.1, and 96.5±0.7, resp.. The EW group values were significantly higher than the whey group values (90.5±1.0. These results show that EW serve as a good source of protein, irrespective of heating.

  20. Effect of 1-methylcyclopropene on shelf life, visual quality and nutritional quality of netted melon.

    Science.gov (United States)

    Shi, Y; Wang, B L; Shui, D J; Cao, L L; Wang, C; Yang, T; Wang, X Y; Ye, H X

    2015-04-01

    The effects of 1-methylcyclopropene (1-MCP) on shelf life, fruit visual quality and nutritional quality were investigated. Netted melons were treated with air (control) and 0.6 µl l(-1) 1-MCP at 25 ℃ for 24 h, and then stored at 25 ℃ or 10 ℃ for 10 days. 1-MCP significantly extended the shelf life, inhibited weight loss and delayed firmness decline of melon fruits. Ethylene production was also inhibited and respiration rate was declined. 1-MCP retarded 1-aminocyclopropane-1-carboxylic acid (ACC) increases and inhibited ACC synthase and ACC oxidase activity. Moreover, 1-MCP treatment reduced the decrease in total soluble solids and titratable acidity, as well as the decrease of the content of sugars (sucrose, fructose and glucose). These results indicated that 1-MCP treatment is a good method to extend melon shelf life and maintain fruit quality, and the combination of 1-MCP and low temperature storage resulted in more acceptable fruit quality. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  1. Modeling the effects of integrating larval habitat source reduction and insecticide treated nets for malaria control.

    Directory of Open Access Journals (Sweden)

    Laith Yakob

    Full Text Available Integrated vector management for malaria control has received a lot of recent interest. Attacking multiple points in the transmission cycle is hoped to act synergistically and improve upon current single-tool interventions based on the use of insecticide-treated bed nets (ITNs. In the present study, we theoretically examined the application of larval habitat source reduction with ITNs in reducing malaria transmission. We selected this type of environmental management to complement ITNs because of a potential secondary mode of action that both control strategies share. In addition to increasing vector mortality, ITNs reduce the rate at which female mosquitoes locate human hosts for blood feeding, thereby extending their gonotrophic cycle. Similarly, while reducing adult vector emergence and abundance, source reduction of larval habitats may prolong the cycle duration by extending delays in locating oviposition sites. We found, however, that source reduction of larval habitats only operates through this secondary mode of action when habitat density is below a critical threshold. Hence, we illustrate how this strategy becomes increasingly effective when larval habitats are limited. We also demonstrate that habitat source reduction is better suited to human populations of higher density and in the presence of insecticide resistance or when the insecticidal properties of ITNs are depleted.

  2. The relative effectiveness of managed care penetration and the healthcare safety net in reducing avoidable hospitalizations.

    Science.gov (United States)

    Pracht, Etienne E; Orban, Barbara L; Comins, Meg M; Large, John T; Asin-Oostburg, Virginia

    2011-01-01

    Avoidable hospitalizations represent a key indicator for access to, and the quality of, primary care. Therefore, understanding their behavior is essential in terms of management of healthcare resources and costs. This analysis examines the affect of 2 healthcare strategies on the rate of avoidable hospitalization, managed care and the healthcare safety net. The avoidable hospitalizations definition developed by Weissman et al. (1992) was used to identify relevant inpatient episodes. A 2-stage simultaneous equations multivariate regression model with instrumental variables was used to estimate the relative influence of HMO penetration and the composition of local hospital markets on the rate of avoidable hospitalizations. Control variables in the model include healthcare supply and demand, demographic, socioeconomic, and health status characteristics. Increased market presence of public hospitals significantly reduced avoidable hospitalizations. HMO penetration did not influence the rate of avoidable hospitalizations. The results suggest that public investments in healthcare facilities and infrastructure are more effective in reducing avoidable hospitalizations. © 2011 National Association for Healthcare Quality.

  3. Temperature and Pressure Depences on the Isotopic Fractionation Effect in the Thermal Decomposition of Ozone

    Directory of Open Access Journals (Sweden)

    Su-Ju Kim

    1997-12-01

    Full Text Available To understand the mass-independent isotopic fractionation effects, thermal decomposition of ozone was performed. Initial oxygen gas was converted to ozone completely. Then, the ozone was decomposed to oxygen at various temperatures(30~150C. Isotopic compositions of product oxygen and residual ozone were measured using a stable isotope mass spectrometer. The experimental results were compared with the studies which were peformed at the similar conditions. From the raw experimental data, the functions of the instantaneous fractionation factors were calculated by the least square fit. The results clearly showed the temperature dependence. They also showed the pressure dependence and the surface effect. This study may play an important role in the study of ozone decomposition mechanism. It can be applied to explain the mass-independent isotopic pattern found in stratospheric ozone and in meteorites.

  4. Evaluation of the effects of repeated hand washing, sunlight, smoke and dirt on the persistence of deltamethrin on insecticide-treated nets.

    Science.gov (United States)

    Kayedi, M H; Lines, J D; Haghdoost, A A; Vatandoost, M H; Rassi, Y; Khamisabady, K

    2008-08-01

    Field studies were carried out in Iran to evaluate the effect of various factors (washing, sun, smoke, dust and dirt) on the residual insecticidal activity of PermaNet (a brand of long-lasting insecticidal net), and on nets conventionally treated with deltamethrin (K-O Tab), using bioassay tests. Thirty-two nets were washed five or 15 times, and eight nets were not washed at all. Nets were washed vigorously in cold tap water (17 degrees C, pH 8.9) with a detergent. Hand rubbing continued for 3min. After washing, some nets were exposed to dense smoke from a dung-hay fire for 3min and were also left exposed to the dusty wind between washes. One group of nets was exposed to the sunlight for the full 3-d interval between washes; another was exposed to sunlight for just 3h after each wash; two other groups were kept in the shade. There was a significantly greater loss of activity in nets exposed to the sun throughout the 3-d interval between washes: that is, for a total of 15 to 45 d. However, short sunlight exposure (maximum 3h between washes) during drying did not have any effect. We did not find any significant effect of exposure to dirt, dust and smoke after washing. It is concluded that the effect of sun is much smaller than that of washing, and that drying nets for a few hours in the sun is not harmful.

  5. 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

  6. [Effects of reduced solar radiation on winter wheat flag leaf net photosynthetic rate].

    Science.gov (United States)

    Zheng, You-Fei; Ni, Yan-Li; Mai, Bo-Ru; Wu, Rong-Jun; Feng, Yan; Sun, Jian; Li, Jian; Xu, Jing-Xin

    2011-06-01

    Taking winter wheat Triticum aestivum L. (cv. Yangmai 13) as test material, a field experiment was conducted in Nanjing City to study the effects of simulated reduced solar radiation on the diurnal variation of winter wheat flag leaf photosynthetic rate and the main affecting factors. Five treatments were installed, i. e., 15% (T15), 20% (T20) , 40% (T40), 60% (T60), and 100% (CK) of total incident solar radiation. Reduced solar irradiance increased the chlorophyll and lutein contents significantly, but decreased the net photosynthetic rate (Pn). Under different solar irradiance, the diurnal variation of Pn had greater difference, and the daily maximum Pn was in the order of CK > T60 > T40 > T 20 > T15. In CK, the Pn exhibited a double peak diurnal curve; while in the other four treatments, the Pn showed a single peak curve, and the peak was lagged behind that of CK. Correlation analysis showed that reduced solar irradiance was the main factor affecting the diurnal variation of Pn, but the physiological parameters also played important roles in determining the diurnal variation of Pn. In treatments T60 and T40, the photosynthesis active radiation (PAR), leaf temperature (T1) , stomatal conductance (Gs) , and transpiration rate (Tr) were significantly positively correlated with Pn, suggesting their positive effects on Pn. The intercellular CO2 concentration (Ci) and stomatal limitation (Ls) had significant negative correlations with Pn in treatments T60 and T40 but significant positive correlations with Pn in treatments T20 and T15, implying that the Ci and Ls had negative (or positive) effects on Pn when the solar irradiance was higher (or lower) than 40% of incident solar irradiance.

  7. Radiation risk of tissue late effects, a net consequence of probabilities of various cellular responses

    International Nuclear Information System (INIS)

    Feinendegen, L.E.

    1991-01-01

    Late effects from the exposure to low doses of ionizing radiation are hardly or not at all observed in man mainly due to the low values of risk coefficients that preclude statistical analyses of data from populations that are exposed to doses less than 0.2 Gy. In order to arrive at an assessment of potential risk from radiation exposure in the low dose range, the microdosimetry approach is essential. In the low dose range, ionizing radiation generates particle tracks, mainly electrons, which are distributed rather heterogeneously within the exposed tissue. Taking the individual cell as the elemental unit of life, observations and calculations of cellular responses to being hit by energy depositions events from low LET type are analysed. It emerges that besides the probability of a hit cell to sustain a detrimental effect with the consequense of malignant transformation there are probabilities of various adaptive responses that equipp the hit cell with a benefit. On the one hand, an improvement of cellular radical detoxification was observed in mouse bone marrow cells; another adaptive response pertaining to improved DNA repair, was reported for human lymphocytes. The improved radical detoxification in mouse bone marrow cells lasts for a period of 5-10 hours and improved DNA repair in human lymphocytes was seen for some 60 hours following acute irradiation. It is speculated that improved radical detoxification and improved DNA repair may reduce the probability of spontaneous carcinogenesis. Thus it is proposed to weigh the probability of detriment for a hit cell within a multicellular system against the probability of benefit through adaptive responses in other hit cells in the same system per radiation exposure. In doing this, the net effect of low doses of low LET radiation in tissue with individual cells being hit by energy deposition events could be zero or even beneficial. (orig./MG)

  8. Mechanistic investigations of the hydrolysis of amides, oxoesters and thioesters via kinetic isotope effects and positional isotope exchange.

    Science.gov (United States)

    Robins, Lori I; Fogle, Emily J; Marlier, John F

    2015-11-01

    The hydrolysis of amides, oxoesters and thioesters is an important reaction in both organic chemistry and biochemistry. Kinetic isotope effects (KIEs) are one of the most important physical organic methods for determining the most likely transition state structure and rate-determining step of these reaction mechanisms. This method induces a very small change in reaction rates, which, in turn, results in a minimum disturbance of the natural mechanism. KIE studies were carried out on both the non-enzymatic and the enzyme-catalyzed reactions in an effort to compare both types of mechanisms. In these studies the amides and esters of formic acid were chosen because this molecular structure allowed development of methodology to determine heavy-atom solvent (nucleophile) KIEs. This type of isotope effect is difficult to measure, but is rich in mechanistic information. Results of these investigations point to transition states with varying degrees of tetrahedral character that fit a classical stepwise mechanism. This article is part of a special issue entitled: Enzyme Transition States from Theory and Experiment. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Isotopic incorporation and the effects of fasting and dietary lipid content on isotopic discrimination in large carnivorous mammals

    Science.gov (United States)

    Rode, Karyn D.; Stricker, Craig A.; Erlenbach, Joy; Robbins, Charles T.; Cherry, Seth; Newsome, Seth D.; Cutting, Amy; Jensen, Shannon; Stenhouse, Gordon; Brooks, Matt; Hash, Amy; Nicassio, Nicole

    2016-01-01

    There has been considerable emphasis on understanding isotopic discrimination for diet estimation in omnivores. However, discrimination may differ for carnivores, particularly species that consume lipid-rich diets. Here, we examined the potential implications of several factors when using stable isotopes to estimate the diets of bears, which can consume lipid-rich diets and, alternatively, fast for weeks to months. We conducted feeding trials with captive brown bears (Ursus arctos) and polar bears (Ursus maritimus). As dietary lipid content increased to ∼90%, we observed increasing differences between blood plasma and diets that had not been lipid extracted (∆13Ctissue-bulk diet) and slightly decreasing differences between plasma δ13C and lipid-extracted diet. Plasma Δ15Ntissue-bulk diet increased with increasing protein content for the four polar bears in this study and data for other mammals from previous studies that were fed purely carnivorous diets. Four adult and four yearling brown bears that fasted 120 d had plasma δ15N values that changed by <±2‰. Fasting bears exhibited no trend in plasma δ13C. Isotopic incorporation in red blood cells and whole blood was ≥6 mo in subadult and adult bears, which is considerably longer than previously measured in younger and smaller black bears (Ursus americanus). Our results suggest that short-term fasting in carnivores has minimal effects on δ13C and δ15N discrimination between predators and their prey but that dietary lipid content is an important factor directly affecting δ13C discrimination and indirectly affecting δ15N discrimination via the inverse relationship with dietary protein content.

  10. Normal coordinate treatment of liquid water and calculation of vapor pressure isotope effects

    International Nuclear Information System (INIS)

    Gellai, B.; Van Hook, W.A.

    1983-01-01

    A vibrational analysis of liquid water is reported, assuming a completely hydrogen-bonded network with continuously varying strengths of the hydrogen bonds. Frequency distribution calculations are made for intramolecular stretching and bending modes and for the intramolecular frequency region. The calculated distributions are compared with the experimental spectroscopic ones. As another test, vapor pressure isotope effects are calculated from the theoretical distributions for some isotopic water molecules. Results are compared with those of other authors obtained from a mixture model. (author)

  11. Effectiveness of different pre-treatments in recovering pre-burial isotopic ratios of charred plants.

    Science.gov (United States)

    Brinkkemper, O; Braadbaart, F; van Os, B; van Hoesel, A; van Brussel, A A N; Fernandes, R

    2018-02-15

    Isotopic analysis of archaeological charred plant remains offers useful archaeological information. However, adequate sample pre-treatment protocols may be necessary to provide a contamination-free isotopic signal while limiting sample loss and achieving a high throughput. Under these constraints, research was undertaken to compare the performance of different pre-treatment protocols. Charred archaeological plant material was selected for isotopic analysis (δ 13 C and δ 15 N values) by isotope ratio mass spectrometry from a variety of plant species, time periods and soil conditions. Preservation conditions and the effectiveness of cleaning protocols were assessed through Fourier transform infrared spectroscopy and X-ray fluorescence (XRF) spectrometry. An acid-base-acid protocol, successfully employed in radiocarbon dating, was used to define a contamination-free isotopic reference. Acid-base-acid isotopic measurements were compared with those obtained from untreated material and an acid-only protocol. The isotopic signals of untreated material and the acid-only protocol typically did not differ more than 1‰ from those of the acid-base-acid reference. There were no significant isotopic offsets between acid-base-acid and acid-only or untreated samples. Sample losses in the acid-base-acid protocol were on average 50 ± 17% (maximum = 98.4%). Elemental XRF measurements showed promising results in the detection of more contaminated samples albeit with a high rate of false positives. For the large range of preservation conditions described in the study, untreated charred plant samples, water cleaned of sediments, provide reliable stable isotope ratios of carbon and nitrogen. The use of pre-treatments may be necessary under different preservation conditions or more conservative measurement uncertainties should be reported. Copyright © 2017 John Wiley & Sons, Ltd.

  12. Net profit flow per country from 1980 to 2009: The long-term effects of foreign direct investment

    Science.gov (United States)

    2017-01-01

    Aim of the paper The paper aims at describing and explaining net profit flows per country for the period 1980–2009. Net profit flows result from Foreign Direct Investment (FDI) stock and profit repatriation: inward stock creating a profit outflow and outward FDI stock a profit inflow. Profit flows, especially ‘normal’ ones are not commonly researched. Theoretical background According to world-system theory, countries are part of a system characterised by a core, semi-periphery and periphery, as shown by network analyses of trade relations. Network analyses based on ownership relations of TransNational Corporations (TNCs) show that the top 50 firms that control about 40% of the world economy are almost exclusively located in core countries. So, we may expect a hierarchy in net profit flows with core countries on top and the periphery at the bottom. FDI outflows from the core countries especially rose in the 1990s, so we may expect that the difference has grown in time. Data and results A dataset on 'net profit flow' per country is developed. There are diverging developments in net profit flows since the 1980s, as expected: ever more positive for core countries, negative and ever lower for semi-peripheral and peripheral countries, in particular from the 1990s onwards. A fixed effects quantile regression using publicly available data confirms the prediction that peripheral countries share a unique characteristic: their outward investments do not have a positive influence on net profit flow as is the case with semi-peripheral and core countries. The most probable explanation is that peripheral outward investments are indirectly owned by firms located in core and semi-peripheral countries, so all peripheral profit inflows end up in those countries. PMID:28654644

  13. Net profit flow per country from 1980 to 2009: The long-term effects of foreign direct investment.

    Science.gov (United States)

    Akkermans, Dirk H M

    2017-01-01

    The paper aims at describing and explaining net profit flows per country for the period 1980-2009. Net profit flows result from Foreign Direct Investment (FDI) stock and profit repatriation: inward stock creating a profit outflow and outward FDI stock a profit inflow. Profit flows, especially 'normal' ones are not commonly researched. According to world-system theory, countries are part of a system characterised by a core, semi-periphery and periphery, as shown by network analyses of trade relations. Network analyses based on ownership relations of TransNational Corporations (TNCs) show that the top 50 firms that control about 40% of the world economy are almost exclusively located in core countries. So, we may expect a hierarchy in net profit flows with core countries on top and the periphery at the bottom. FDI outflows from the core countries especially rose in the 1990s, so we may expect that the difference has grown in time. A dataset on 'net profit flow' per country is developed. There are diverging developments in net profit flows since the 1980s, as expected: ever more positive for core countries, negative and ever lower for semi-peripheral and peripheral countries, in particular from the 1990s onwards. A fixed effects quantile regression using publicly available data confirms the prediction that peripheral countries share a unique characteristic: their outward investments do not have a positive influence on net profit flow as is the case with semi-peripheral and core countries. The most probable explanation is that peripheral outward investments are indirectly owned by firms located in core and semi-peripheral countries, so all peripheral profit inflows end up in those countries.

  14. The effective management of medical isotope production in research reactors

    International Nuclear Information System (INIS)

    Drummond, D.T.

    1993-01-01

    During the 50-yr history of the use of radioisotopes for medical applications, research reactors have played a pivotal role in the production of many if not most of the key products. The marriage between research reactors and production operations is subject to significant challenges on two fronts. The medical applications of the radioisotope products impose some unique constraints and requirements on the production process. In addition, the mandates and priorities of a research reactor are not always congruent with the demands of a production environment. This paper briefly reviews the historical development of medical isotope production, identifies the unique challenges facing this endeavor, and discusses the management of the relationship between the isotope producer and the research reactor operator. Finally, the key elements of a successful relationship are identified

  15. Investigating the effects of abyssal peridotite alteration on Si, Mg and Zn isotopes

    Science.gov (United States)

    Savage, P. S.; Wimpenny, J.; Harvey, J.; Yin, Q.; Moynier, F.

    2013-12-01

    Around 1/3 of Earth's divergent ridge system is now classified as "slow" spreading [1], exposing ultramafic rocks (abyssal peridotites) at the seafloor. Such material is often highly altered by serpentinisation and steatisation (talc formation). It is crucial to understand such processes in order to access the original composition of the mantle, and to quantify any impact on ocean composition. Here we examine the effect of both serpentinisation and steatisation on Si, Mg and Zn isotopes. Hydrothermal alteration and seafloor weathering are both sources of oceanic Si [2] and weathering of abyssal peridotites is a source of oceanic Mg [3]; hence isotopic fractionation as a result of seafloor alteration could affect oceanic Si and Mg isotope composition. Zinc isotopes can provide complimentary information; the magnitude and direction of fractionation is highly dependent on complexing ligand [4] and can provide compositional information on the fluids driving metasomatism. For this study, two cores from the well-characterised abyssal peridotites recovered on ODP Leg 209 were examined [5]. Hole 1274a peridotites exhibit variable serpentinisation at ~200°C, whereas samples from Hole 1268a have been comprehensively serpentinised and then subsequently steatised to talc facies at ~350°C, by a low Mg/Si, low pH fluid. The Si, Mg and Zn isotope compositions of 1274a samples are extremely homogeneous, identical to that of pristine mantle rocks (BSE) i.e., serpentinisation at this locality was predominantly isochemical [5]. In contrast, samples from 1268a show greater isotopic variability. In all samples, Mg is enriched in the heavier isotopes relative to BSE, consistent with formation of isotopically heavy secondary phases [6]. For Si, serpentinised samples are slightly enriched in the lighter isotopes compared to BSE, again consistent with the behaviour of Si during formation of secondary phases [7]. Within the steatised samples, some exhibit enrichments in the lighter Si

  16. ICP-MS as the method of the determination of gallium, indium and thallium isotope ratios in the studies of isotope effects in the chromatography systems

    International Nuclear Information System (INIS)

    Herdzik, I.

    2006-01-01

    The procedure of the determination of gallium, indium and thallium isotope ratios and its application to the studies of the isotope effects in chromatography systems by the ICP-MS method (inductively coupled plasma-mass spectrometry) are presented. It was shown that it is possible to determine the isotope ratios of gallium ( 69/71 Ga), indium ( 113/115 In) and thallium ( 203/205 Tl) with the relative standard deviation 0.03-0.07%. Such precision appeared to be sufficient to calculate the unit separation factors in the column chromatographic processes. (author) [pl

  17. Lithium isotope effect in the extraction systems of polyethers: effect of salt concentration

    International Nuclear Information System (INIS)

    Fang Shengqiang; Fu Lian

    1991-01-01

    Separation factors of lithium isotopes at 20 deg C were determined in the extraction systems of B15C5-CHCl 3 /LiBr-H 2 O. The initial concentration of LiBr was controlled in the extent of more than 2 mol/l. It may be established that the increase of LiBr concentration causes a remarkable increase of the separation factor. The essence of this effect due to the change in salt concentration was discussed in connection with examination of relevant phenomena in literature. It can be concluded that the relationship between α and Cm, the concentration of lithium salt, is dependent on K Q and K P express respectively, lithium isotope exchange equilibrium constants between Li-crownether complex and hydrated lithium ion for lithium concentration less than 1-2 mol/l, and between lithium salt ion pair and hydrated lithium ion for lithium concentration more than 2 mol/l in aqueous phase

  18. Effects of Recent Regional Soil Moisture Variability on Global Net Ecosystem CO2 Exchange

    Science.gov (United States)

    Jones, L. A.; Madani, N.; Kimball, J. S.; Reichle, R. H.; Colliander, A.

    2017-12-01

    Soil moisture exerts a major regional control on the inter-annual variability of the global land sink for atmospheric CO2. In semi-arid regions, annual biomass production is closely coupled to variability in soil moisture availability, while in cold-season-affected regions, summer drought offsets the effects of advancing spring phenology. Availability of satellite solar-induced fluorescence (SIF) observations and improvements in atmospheric inversions has led to unprecedented ability to monitor atmospheric sink strength. However, discrepancies still exist between such top-down estimates as atmospheric inversion and bottom-up process and satellite driven models, indicating that relative strength, mechanisms, and interaction of driving factors remain poorly understood. We use soil moisture fields informed by Soil Moisture Active Passive Mission (SMAP) observations to compare recent (2015-2017) and historic (2000-2014) variability in net ecosystem land-atmosphere CO2 exchange (NEE). The operational SMAP Level 4 Carbon (L4C) product relates ground-based flux tower measurements to other bottom-up and global top-down estimates to underlying soil moisture and other driving conditions using data-assimilation-based SMAP Level 4 Soil Moisture (L4SM). Droughts in coastal Brazil, South Africa, Eastern Africa, and an anomalous wet period in Eastern Australia were observed by L4C. A seasonal seesaw pattern of below-normal sink strength at high latitudes relative to slightly above-normal sink strength for mid-latitudes was also observed. Whereas SMAP-based soil moisture is relatively informative for short-term temporal variability, soil moisture biases that vary in space and with season constrain the ability of the L4C estimates to accurately resolve NEE. Such biases might be caused by irrigation and plant-accessible ground-water. Nevertheless, SMAP L4C daily NEE estimates connect top-down estimates to variability of effective driving factors for accurate estimates of regional

  19. Sumoylation of the net inhibitory domain (NID) is stimulated by PIAS1 and has a negative effect on the transcriptional activity of Net.

    Science.gov (United States)

    Wasylyk, Christine; Criqui-Filipe, Paola; Wasylyk, Bohdan

    2005-01-27

    Net (Elk-3, Sap-2, Erp) and the related ternary complex factors Elk-1 and Sap-1 are effectors of multiple signalling pathways at the transcriptional level and play a key role in the dynamic regulation of gene expression. Net is distinct from Elk-1 and Sap-1, in that it is a strong repressor of transcription that is converted to an activator by the Ras/Erk signalling pathway. Two autonomous repression domains of Net, the NID and the CID, mediate repression. We have previously shown that the co-repressor CtBP is implicated in repression by the CID. In this report we show that repression by the NID involves a different pathway, sumoylation by Ubc9 and PIAS1. PIAS1 interacts with the NID in the two-hybrid assay and in vitro. Ubc9 and PIAS1 stimulate sumoylation in vivo of lysine 162 in the NID. Sumoylation of lysine 162 increases repression by Net and decreases the positive activity of Net. These results increase our understanding of how one of the ternary complex factors regulates transcription, and contribute to the understanding of how different domains of a transcription factor participate in the complexity of regulation of gene expression.

  20. Effect of decreasing dietary phosphorus supply on net recycling of inorganic phosphate in lactating dairy cows

    DEFF Research Database (Denmark)

    Puggaard, Liselotte; Kristensen, Niels Bastian; Sehested, Jens Jakob

    2011-01-01

    (LP; 2.4 g of P/kg of DM) and high P (HP; 3.4 g of P/kg of DM). The dietary total P (tP) concentrations were obtained by replacing 0.50% calcium carbonate in the LP diet with 0.50% monocalcium phosphate in the HP diet. Diets were fed for 14 d and cows were sampled on d 14 in each period. Cows were fed...... restrictively, resulting in equal dry matter intakes as well as milk, fat, and protein yields between treatments. Net Pi recycling (primarily salivary) was estimated as the difference between net portal plasma flux (net absorption of Pi) and apparently digested tP (feed – fecal tP difference). Phosphorus intake...

  1. Effects of Educational Intervention on Long-Lasting Insecticidal Nets Use in a Malarious Area, Southeast Iran

    Directory of Open Access Journals (Sweden)

    Abdol Hossein Madani

    2012-04-01

    Full Text Available Long-lasting insecticidal nets (LLINs have been advocated as an effective tool against malaria transmission. However, success of this community based intervention largely depends on the knowledge and practice regarding malaria and its prevention. According to the national strategy plan on evaluation of LLINs (Olyset nets, this study was conducted to determine the perceptions and practices about malaria and to improve use of LLINs in Bashagard district, one of the important foci of malaria in southeast Iran. The study area comprised 14 villages that were randomized in two clusters and designated as LLINs and untreated nets. Each of households in both clusters received two bed nets by the free distribution and delivery. After one month quantitative data collection method was used to collect information regarding the objectives of the study. On the basis of this information, an educational program was carried out in both areas to increase motivation for use of bed nets. Community knowledge and practice regarding malaria and LLIN use assessed pre- and post-educational program. The data were analyzed using SPSS ver.16 software. At baseline, 77.5% of respondents in intervention and 69.4 % in control area mentioned mosquito bite as the cause of malaria, this awareness increased significantly in intervention (90.3% and control areas (87.9%, following the educational program. A significant increase also was seen in the proportion of households who used LLINs the previous night (92.5% compared with untreated nets (87.1%. Educational status was an important predictor of LLINs use. Regular use of LLIN was considerably higher than the targeted coverage (80% which recommended by World Heaths Organization. About 81.1% and 85.3% of respondents from LLIN and control areas reported that mosquito nuisance and subsequent malaria transmission were the main determinants of bed net use. These findings highlight a need for educational intervention in implementation of

  2. RESTful NET

    CERN Document Server

    Flanders, Jon

    2008-01-01

    RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa

  3. Improved netting

    International Nuclear Information System (INIS)

    Bramley, A.; Clabburn, R.J.T.

    1976-01-01

    A method is described for producing netting composed of longitudinal and transverse threads of irradiation cross linked thermoplastic material, the threads being joined together at their crossings by moulded masses of cross linked thermoplastic material. The thread may be formed of polyethylene filaments, subjected to a radiation dose of 15 to 25 MR. The moulding can be conducted at 245 0 to 260 0 C or higher. The product is claimed to be an improved quality of netting, with bonds of increased strength between crossing threads. (U.K.)

  4. Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

    Science.gov (United States)

    Luk, Louis Y P; Ruiz-Pernía, J Javier; Adesina, Aduragbemi S; Loveridge, E Joel; Tuñón, Iñaki; Moliner, Vincent; Allemann, Rudolf K

    2015-07-27

    Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N-terminal segment containing heavy isotopes ((2) H, (13) C, (15) N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C-terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N-terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C-terminal segment. QM/MM studies support the idea that dynamic effects on catalysis mostly originate from the C-terminal segment. The use of isotope hybrids provides insights into the microscopic mechanism of dynamic coupling, which is difficult to obtain with other studies, and helps define the dynamic networks of intramolecular interactions central to enzyme catalysis. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  5. Radioactive Emissions from Fission-Based Medical Isotope Production and Their Effect on Global Nuclear Explosion Detection

    International Nuclear Information System (INIS)

    Bowyer, T.; Saey, P.

    2015-01-01

    The use of medical isotopes, such as Tc-99m, is widespread with over 30 million procedures being performed every year, but the fission-based production of isotopes used for medical procedures causes emissions into the environment. This paper will show that gaseous radioactive isotopes of xenon, such as Xe-133, are released in high quantities, because they have a high fission cross section and they are difficult to scrub from the processes used to produce the medical isotopes due to their largely unreactive nature. Unfortunately, the reasons that large amounts of radioactive xenon isotopes are emitted from isotope production are the same as those that make these isotopes the most useful isotopes for the detection of underground nuclear explosions. Relatively recently, the nuclear explosion monitoring community has established a provisional monitoring network for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) that includes radioactive xenon monitoring as a major component. This community has discovered that emissions from medical isotope production present a more serious problem to nuclear explosion monitoring than thought when the network was first conceived. To address the growing problem, a group of scientists in both the monitoring and the isotope production communities have come together to attempt to find scientific and pragmatic ways to address the emissions problems, recognizing that medical isotope production should not be adversely affected, while monitoring for nuclear explosions should remain effective as isotope production grows, changes, and spreads globally. (author)

  6. Isotope effects in the evaporation of water: a status report of the Craig-Gordon model.

    Science.gov (United States)

    Horita, Juske; Rozanski, Kazimierz; Cohen, Shabtai

    2008-03-01

    The Craig-Gordon model (C-G model) [H. Craig, L.I. Gordon. Deuterium and oxygen 18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperatures, E. Tongiorgi (Ed.), pp. 9-130, Laboratorio di Geologia Nucleare, Pisa (1965).] has been synonymous with the isotope effects associated with the evaporation of water from surface waters, soils, and vegetations, which in turn constitutes a critical component of the global water cycle. On the occasion of the four decades of its successful applications to isotope geochemistry and hydrology, an attempt is made to: (a) examine its physical background within the framework of modern evaporation models, (b) evaluate our current knowledge of the environmental parameters of the C-G model, and (c) comment on a general strategy for the use of these parameters in field applications. Despite its simplistic representation of evaporation processes at the water-air interface, the C-G model appears to be adequate to provide the isotopic composition of the evaporation flux. This is largely due to its nature for representing isotopic compositions (a ratio of two fluxes of different isotopic water molecules) under the same environmental conditions. Among many environmental parameters that are included in the C-G model, accurate description and calculations are still problematic of the kinetic isotope effects that occur in a diffusion-dominated thin layer of air next to the water-air interface. In field applications, it is of importance to accurately evaluate several environmental parameters, particularly the relative humidity and isotopic compositions of the 'free-atmosphere', for a system under investigation over a given time-scale of interest (e.g., hourly to daily to seasonally). With a growing interest in the studies of water cycles of different spatial and temporal scales, including paleoclimate and water resource studies, the importance and utility of the C-G model is also likely to

  7. Isotope effect study of κ-(BEDT-TTF)2Cu(NCS)2: Labeling in the anion

    International Nuclear Information System (INIS)

    Kini, A.M.; Wang, H.H.; Schlueter, J.A.

    1995-01-01

    Since the initial discovery of organic superconductivity in 1979, a large number of organic superconductors have now been synthesized. However, the mechanism of electron-pairing in these novel superconductors has remained largely unresolved. Isotope effect studies constitute an important experimental tool for the investigation of whether or not the electron-pairing mechanism in organic superconductors is phonon-mediated, as in conventional superconductors. Recent isotope effect studies in the authors' laboratory, involving seven different isotopically labeled BEDT-TTF (or ET) derivatives, have demonstrated the following: (1) intramolecular phonon modes involving C double-bond C and Csingle bondS stretching vibrations in the ET donor molecule are not the dominant mediators of electron-pairing, and (2) in κ-(ET) 2 Cu(NCS) 2 , there exist two competing isotope effects--a normal mass effect, i.e., lowering of T c upon isotopic labeling, when the ET molecular mass is increased by concurrent 13 C and 34 S labeling, in addition to an inverse isotope effect upon deuterium labeling in ET. It is of great interest to investigate if there is an isotope effect when the charge-compensating anions, which are also located within the non-conducting layer in the superconducting cation-radical salts, are isotopically labeled. The existence of an isotope effect when the anions are labeled would be indicative of electron-pairing with the mediation of vibrational frequencies associated with the anions. In this paper, the authors present the results of the first isotope effect study in which isotopic labeling in the anion portion of κ-(ET) 2 Cu(NCS) 2 is carried out. The authors find no isotope effect when the carbon and nitrogen atoms of the thiocyanate groups in the anion are replaced with 13 C and 15 N isotopes

  8. Cl and C isotope analysis to assess the effectiveness of chlorinated ethene degradation by zero-valent iron: Evidence from dual element and product isotope values

    International Nuclear Information System (INIS)

    Audí-Miró, Carme; Cretnik, Stefan; Otero, Neus; Palau, Jordi; Shouakar-Stash, Orfan; Soler, Albert

    2013-01-01

    Highlights: ► TCE and cis-DCE Cl isotope fractionation was investigated for the first time with ZVI. ► A C–Cl bond is broken in the rate-limiting step during ethylene ZVI dechlorination. ► Dual C/Cl isotope plot is a promising tool to discriminate abiotic degradation. ► Product-related carbon isotopic fractionation gives evidence of abiotic degradation. ► Hydrogenolysis and β-dichloroelimination pathways occur simultaneously. - Abstract: This study investigated C and, for the first time, Cl isotope fractionation of trichloroethene (TCE) and cis-dichloroethene (cis-DCE) during reductive dechlorination by cast zero-valent iron (ZVI). Hydrogenolysis and β-dichloroelimination pathways occurred as parallel reactions, with ethene and ethane deriving from the β-dichloroelimination pathway. Carbon isotope fractionation of TCE and cis-DCE was consistent for different batches of Fe studied. Transformation of TCE and cis-DCE showed Cl isotopic enrichment factors (ε Cl ) of −2.6‰ ± 0.1‰ (TCE) and −6.2‰ ± 0.8‰ (cis-DCE), with Apparent Kinetic Isotope Effects (AKIE Cl ) for Cl of 1.008 ± 0.001 (TCE) and 1.013 ± 0.002 (cis-DCE). This indicates that a C–Cl bond breakage is rate-determining in TCE and cis-DCE transformation by ZVI. Two approaches were investigated to evaluate if isotope fractionation analysis can distinguish the effectiveness of transformation by ZVI as opposed to natural biodegradation. (i) Dual isotope plots. This study reports the first dual (C, Cl) element isotope plots for TCE and cis-DCE degradation by ZVI. The pattern for cis-DCE differs markedly from that reported for biodegradation of the same compound by KB-1, a commercially available Dehalococcoides-containing culture. The different trends suggest an expedient approach to distinguish abiotic and biotic transformation, but this needs to be confirmed in future studies. (ii) Product-related isotope fractionation. Carbon isotope ratios of the hydrogenolysis product cis

  9. A novel methodology to investigate isotopic biosignatures

    Science.gov (United States)

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

    2012-04-01

    An enduring goal of trace metal isotopic studies of Earth History is to find isotopic 'fingerprints' of life or of life's individual physiochemical processes. Generally, such signatures are sought by relating an isotopic effect observed in controlled laboratory conditions or a well-characterized environment to a more complex system or the geological record. However, such an approach is ultimately limited because life exerts numerous isotopic fractionations on any one element so it is hard to dissect the resultant net fractionation into its individual components. Further, different organisms, often with the same apparent cellular function, can express different isotopic fractionation factors. We have used a novel method to investigate the isotopic fractionation associated with a single physiological process-enzyme specific isotopic fractionation. We selected Cd isotopes since only one biological use of Cd is known, CdCA (a Cd/Zn carbonic anhydrase from the coastal diatom T. Weissflogii). Thus, our investigation can also inform the long standing mystery as to why this generally toxic element appears to have a nutrient-like dissolved isotopic and concentration profile in the oceans. We used the pET-15b plasmid to insert the CdCA gene into the E. coli genome. There is no known biochemical function for Cd in E. coli, making it an ideal vector for studying distinct physiological processes within a single organism. The uptake of Cd and associated isotopic fractionation was determined for both normal cells and those expressing CdCA. It was found that whole cells always exhibited a preference for the light isotopes of Cd, regardless of the expression of CdCA; adsorption of Cd to cell surfaces was not seen to cause isotopic fractionation. However, the cleaning procedure employed exerted a strong control on the observed isotopic composition of cells. Using existing protein purification techniques, we measured the Cd isotopic composition of different subcellular fractions of E

  10. Ab initio calculations of the Fe(II) and Fe(III) isotopic effects in citrates, nicotianamine, and phytosiderophore, and new Fe isotopic measurements in higher plants

    Science.gov (United States)

    Moynier, Frédéric; Fujii, Toshiyuki; Wang, Kun; Foriel, Julien

    2013-05-01

    Iron is one of the most abundant transition metal in higher plants and variations in its isotopic compositions can be used to trace its utilization. In order to better understand the effect of plant-induced isotopic fractionation on the global Fe cycling, we have estimated by quantum chemical calculations the magnitude of the isotopic fractionation between different Fe species relevant to the transport and storage of Fe in higher plants: Fe(II)-citrate, Fe(III)-citrate, Fe(II)-nicotianamine, and Fe(III)-phytosiderophore. The ab initio calculations show firstly, that Fe(II)-nicotianamine is ˜3‰ (56Fe/54Fe) isotopically lighter than Fe(III)-phytosiderophore; secondly, even in the absence of redox changes of Fe, change in the speciation alone can create up to ˜1.5‰ isotopic fractionation. For example, Fe(III)-phytosiderophore is up to 1.5‰ heavier than Fe(III)-citrate2 and Fe(II)-nicotianamine is up to 1‰ heavier than Fe(II)-citrate. In addition, in order to better understand the Fe isotopic fractionation between different plant components, we have analyzed the iron isotopic composition of different organs (roots, seeds, germinated seeds, leaves and stems) from six species of higher plants: the dicot lentil (Lens culinaris), and the graminaceous monocots Virginia wild rye (Elymus virginicus), Johnsongrass (Sorghum halepense), Kentucky bluegrass (Poa pratensis), river oat (Uniola latifolia), and Indian goosegrass (Eleusine indica). The calculations may explain that the roots of strategy-II plants (Fe(III)-phytosiderophore) are isotopically heavier (by about 1‰ for the δ56Fe) than the upper parts of the plants (Fe transported as Fe(III)-citrate in the xylem or Fe(II)-nicotianamine in the phloem). In addition, we suggest that the isotopic variations observed between younger and older leaves could be explained by mixing of Fe received from the xylem and the phloem.

  11. Effect of insecticide-treated bed nets on house-entry by malaria mosquitoes: The flight response recorded in a semi-field study in Kenya.

    Science.gov (United States)

    Spitzen, Jeroen; Koelewijn, Teun; Mukabana, W Richard; Takken, Willem

    2017-08-01

    Insecticide-treated nets are currently a major tool to reduce malaria transmission. Their level of repellency affects contact of the mosquito with the net, but may also influence the mosquito's entry into the house. The response of host-seeking malaria mosquitoes approaching the eave of an experimental house was recorded within a large screen house. We compared entry- and exit rates in relation to the presence in the house of different insecticide-treated bed nets (ITNs) with an untreated net. Mosquitoes were lured towards the house by dispensing a synthetic host-odour blend from within the net in the house. Complementary WHO bioassays revealed that the treated nets caused high knock-down- and mortality responses to the Anopheles gambiae sensu stricto strain tested. The proportion of mosquitoes that came into view of the cameras and subsequently entered the house did not differ between treated nets and the untreated net. Treated nets did not affect proportions of mosquitoes that exited the house and departed from view around the eave. However, the percentage of house-leaving and re-entering mosquitoes when an insecticide- treated net was present, was lower than in the presence of an untreated net. Our results indicated that there was no spatial repellent effect from pyrethroid-treated nets that influences house-entry at eave level. It is argued that the toxic effect of treated bed nets resulted in a reduced number of mosquitoes re-entering the house, which could thereby affect malaria transmission in neighbouring, unprotected houses. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  12. Petri Nets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52 ... Author Affiliations. Y Narahari1. Department of Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.

  13. Aspartate beta-decarboxylase from Alcaligenes faecalis: carbon-13 kinetic isotope effect and deuterium exchange experiments

    International Nuclear Information System (INIS)

    Rosenberg, R.M.; O'Leary, M.H.

    1985-01-01

    The authors have measured the 13 C kinetic isotope effect at pH 4.0, 5.0, 6.0, and 6.5 and in D 2 O at pH 5.0 and the rate of D-H exchange of the alpha and beta protons of aspartic acid in D 2 O at pH 5.0 for the reaction catalyzed by the enzyme aspartate beta-decarboxylase from Alcaligenes faecalis. The 13 C kinetic isotope effect, with a value of 1.0099 +/- 0.0002 at pH 5.0, is less than the intrinsic isotope effect for the decarboxylation step, indicating that the decarboxylation step is not entirely rate limiting. The authors have been able to estimate probable values of the relative free energies of the transition states of the enzymatic reaction up to and including the decarboxylation step from the 13 C kinetic isotope effect and the rate of D-H exchange of alpha-H. The pH dependence of the kinetic isotope effect reflects the pKa of the pyridine nitrogen of the coenzyme pyridoxal 5'-phosphate but not that of the imine nitrogen. A mechanism is proposed for the exchange of aspartate beta-H that is consistent with the stereochemistry suggested earlier

  14. Effects of precipitation changes on aboveground net primary production and soil respiration in a switchgrass field

    Science.gov (United States)

    This study attempted to test whether switchgrass aboveground net primary production (ANPP) responds to precipitation (PPT) changes in a double asymmetry pattern as framed by Knapp et al. (2016), and whether it is held true for other ecosystem processes such as soil respiration (SR). Data were colle...

  15. The stable isotope amount effect: New insights from NEXRAD echo tops, Luquillo Mountains, Puerto Rico

    Science.gov (United States)

    Scholl, Martha A.; Shanley, James B.; Zegarra, Jan Paul; Coplen, Tyler B.

    2009-01-01

    The stable isotope amount effect has often been invoked to explain patterns of isotopic composition of rainfall in the tropics. This paper describes a new approach, correlating the isotopic composition of precipitation with cloud height and atmospheric temperature using NEXRAD radar echo tops, which are a measure of the maximum altitude of rainfall within the clouds. The seasonal differences in echo top altitudes and their corresponding temperatures are correlated with the isotopic composition of rainfall. These results offer another factor to consider in interpretation of the seasonal variation in isotopic composition of tropical rainfall, which has previously been linked to amount or rainout effects and not to temperature effects. Rain and cloud water isotope collectors in the Luquillo Mountains in northeastern Puerto Rico were sampled monthly for three years and precipitation was analyzed for δ18O and δ2H. Precipitation enriched in 18O and 2H occurred during the winter dry season (approximately December–May) and was associated with a weather pattern of trade wind showers and frontal systems. During the summer rainy season (approximately June–November), precipitation was depleted in 18O and 2H and originated in low pressure systems and convection associated with waves embedded in the prevailing easterly airflow. Rain substantially depleted in 18O and 2H compared to the aforementioned weather patterns occurred during large low pressure systems. Weather analysis showed that 29% of rain input to the Luquillo Mountains was trade wind orographic rainfall, and 30% of rainfall could be attributed to easterly waves and low pressure systems. Isotopic signatures associated with these major climate patterns can be used to determine their influence on streamflow and groundwater recharge and to monitor possible effects of climate change on regional water resources.

  16. Dew water effects on leaf water using a stable isotope approach

    Science.gov (United States)

    Kim, K.; Lee, X.

    2009-12-01

    The presence of dew is a common meteorological phenomenon in field conditions and takes into account for significant portion of hydrologic processes in terrestrial ecosystems. The isotope composition of leaf water plays an important role in the isotopic water and carbon fluxes between terrestrial plants and the atmosphere. However, the consequence of dew formation in the plant-atmosphere relations has been ignored in many studies. The objective of this study is to improve our understanding of environmental and biological controls on the leaf water in equilibrium with dew water through laboratory experiments. Five species of plants (soybean, corn, sorghum, wheat, cotton) were grown hydroponically with water of a known isotopic content in a greenhouse. On the day of the experiment, they were first moved to ambient environment in full sunlight for at least 6 hr and then into a dark container inside the lab for up to 48 hr in which water vapor isotope ratios, temperature, and humidity were controlled. This arrangement created a step change in the forcing on the plant isotopic exchange. Leaves were sampled prior to the transfer to the dark container and 6 more times every 4 - 12 hr over the experiment. Humidity inside the container was saturated to mimic dew events in field conditions. Water from the leaf samples was extracted by a vacuum line and was analyzed for both δD and δ18O. The dataset will allow us to evaluate leaf water isotopic theories by exploring the transitions of the isotopic ratio of leaf water in response to the step change. Specifically, we are interested in whether the stomatal opening is an effective pathway for gaseous exchange in total darkness and how the transitional behaviors of the isotopic ratio of leaf water differ between the C3 and C4 photosynthesis pathways.

  17. Alternate substrates and isotope effects as a probe of the malic enzyme reaction

    International Nuclear Information System (INIS)

    Gavva, S.R.

    1988-01-01

    Dissociation constants for alternative dinucleotide substrates and competitive inhibitors suggest that the dinucleotide binding site of the Ascaris suum NAD-malic enzyme is hydrophobic in the vicinity of the nicotinamide ring. Changes in the divalent metal ion activator from Mg 2+ to Mn 2+ or Cd 2+ results in a decrease in the dinucleotide affinity and an increase in the affinity for malate. Primary deuterium and 13 C isotope effects obtained with the different metal ions suggest either a change in the transition state structure for the hydride transfer or decarboxylation steps or both. Deuterium isotope effects are finite whether reactants are maintained at saturating or limiting concentrations with all the metal ions and dinucleotide substrates used. For the native enzyme, primary deuterium isotope effects increase with a concomitant decrease in the 13 C effects when NAD is replaced by an alternate dinucleotide substrate different in redox potential

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

    International Nuclear Information System (INIS)

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

    1991-01-01

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

  19. Kinetic isotope effects in reaction of ferment oxidation of tritium-labelled D-galactosamine

    International Nuclear Information System (INIS)

    Akulov, G.P.; Korsakova, N.A.

    1992-01-01

    Primary, secondary and intramolecular kinetic isotopic effects in reaction of ferment oxidation of D-galactosamine labelled by tritium in position 6, were measured. When comparing values of the effects with previously obtained results for similar reaction D-[6- 3 H]galactose, it was ascertained that the presence of aminogroup in galactopyranosyl mainly affects kinetics of substrate-ferment complex formation stage. The possibility to use kinetic isotope effects for increase in molar activity of D-galactosamine, labelled by tritium in position 6, is shown

  20. Gamma-radiation and isotopic effect on the critical behavior in triglycine selenate crystals

    Science.gov (United States)

    Kassem, M. E.; Hamed, A. E.; Abulnasr, L.; Abboudy, S.

    1994-11-01

    Isotopic effects in pure and γ-irradiated triglycine selenate crystals were investigated using the specific heat ( Cp) technique. The obtained results showed an interesting dependence of the critical behavior of Cp on the deuterium content. With increasing content of deuterium, the character of the phase transition changed from a second order (γ-type) to a first order transition. After γ-irradiation, the behavior of Cp around the phase transition region was essentially affected. The transition temperature, Tc, decreased and Δ Cp depressed, and the transition became broad. It was noted that the effect of γ-irradiation is opposite to the isotopic effect.

  1. Gamma-radiation and isotopic effect on the critical behavior in triglycine selenate crystals

    International Nuclear Information System (INIS)

    Kassem, M.E.; Hamed, A.E.; Abulnasr, L.; Abboudy, S.

    1994-01-01

    Isotopic effects in pure and γ-irradiated triglycine selenate crystals were investigated using the specific heat (C p ) technique. The obtained results showed an interesting dependence of the critical behavior of C p on the deuterium content. With increasing content of deuterium, the character of the phase transition changed from a second order (λ-type) to a first order transition. After γ-irradiation, the behavior of C p around the phase transition region was essentially affected. The transition temperature, T c , decreased and ΔC p depressed, and the transition became broad. It was noted that the effect of γ-irradiation is opposite to the isotopic effect. (author)

  2. Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

    Science.gov (United States)

    Chen, J. M.; Chen, X.; Ju, W.

    2013-07-01

    Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE) in NPP modelled at the 1 km resolution is reduced from 14.8 g C m-2 yr-1 to 4.8 g C m-2 yr-1 in comparison with NPP modelled at 30 m resolution, where the mean NPP is 668 g C m-2 yr-1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI) and elevation have small and additive effects on improving the spatial scaling

  3. Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

    Directory of Open Access Journals (Sweden)

    J. M. Chen

    2013-07-01

    Full Text Available Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE in NPP modelled at the 1 km resolution is reduced from 14.8 g C m−2 yr−1 to 4.8 g C m−2 yr−1 in comparison with NPP modelled at 30 m resolution, where the mean NPP is 668 g C m−2 yr−1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI and elevation have small and additive effects on improving

  4. Effect of operating methods of wind turbine generator system on net power extraction under wind velocity fluctuations in fields

    Energy Technology Data Exchange (ETDEWEB)

    Wakui, Tetsuya; Yamaguchi, Kazuya; Hashizume, Takumi [Waseda Univ., Advanced Research Inst. for Science and Engineering, Tokyo (Japan); Outa, Eisuke [Waseda Univ., Mechanical Engineering Dept., Tokyo (Japan); Tanzawa, Yoshiaki [Nippon Inst. of Technology, Mechanical Engineering Dept., Saitama (Japan)

    1999-01-01

    The effect of how a wind turbine generator system is operated is discussed from the viewpoint of net power extraction with wind velocity fluctuation in relation to the scale and the dynamic behaviour of the system. On a wind turbine generator system consisting of a Darrieus-Savonius hybrid wind turbine, a load generator and a battery, we took up two operating methods: constant tip speed ratio operation for a stand-alone system (Scheme 1) and synchronous operation by connecting a grid (Scheme 2). With our simulation model, using the result of the net extracting power, we clarified that Scheme 1 is more effective than Scheme 2 for small-scale systems. Furthermore, in Scheme 1, the appropriate rated power output of the system under each wind condition can be confirmed. (Author)

  5. Some measurements of H/D polarizability isotope effects using differential refractometry

    Energy Technology Data Exchange (ETDEWEB)

    Foster Smith, M; Van Hook, W A [Tennessee Univ., Knoxville (USA). Dept. of Chemistry

    1989-05-01

    Refractive index differences between the H and D isomers of some common molecules in the liquid phase were measured between 404.7 and 690.0 nm. The data are combined with information on molar volume isotope effects to yield values for H/D isotope effects on the static polarizability, the vibrational contribution to the static and frequency dependent parts of the polarizability, and the H/D isotope effect on the second moment of the electronic charge distribution. The present results suffice to demonstrate the practicability of this technique to measure the components of the polarizability listed above. However for accurate resolution of the vibrational and second moment contributions, refractive index data of still greater precision will be required. (orig.).

  6. Some measurements of H/D polarizability isotope effects using differential refractometry

    International Nuclear Information System (INIS)

    Foster Smith, M.; Van Hook, W.A.

    1989-01-01

    Refractive index differences between the H and D isomers of some common molecules in the liquid phase were measured between 404.7 and 690.0 nm. The data are combined with information on molar volume isotope effects to yield values for H/D isotope effects on the static polarizability, the vibrational contribution to the static and frequency dependent parts of the polarizability, and the H/D isotope effect on the second moment of the electronic charge distribution. The present results suffice to demonstrate the practicability of this technique to measure the components of the polarizability listed above. However for accurate resolution of the vibrational and second moment contributions, refractive index data of still greater precision will be required. (orig.)

  7. Nitrogen and Oxygen Isotope Effects of Ammonia Oxidation by Thermophilic Thaumarchaeota from a Geothermal Water Stream.

    Science.gov (United States)

    Nishizawa, Manabu; Sakai, Sanae; Konno, Uta; Nakahara, Nozomi; Takaki, Yoshihiro; Saito, Yumi; Imachi, Hiroyuki; Tasumi, Eiji; Makabe, Akiko; Koba, Keisuke; Takai, Ken

    2016-08-01

    Ammonia oxidation regulates the balance of reduced and oxidized nitrogen pools in nature. Although ammonia-oxidizing archaea have been recently recognized to often outnumber ammonia-oxidizing bacteria in various environments, the contribution of ammonia-oxidizing archaea is still uncertain due to difficulties in the in situ quantification of ammonia oxidation activity. Nitrogen and oxygen isotope ratios of nitrite (δ(15)NNO2- and δ(18)ONO2-, respectively) are geochemical tracers for evaluating the sources and the in situ rate of nitrite turnover determined from the activities of nitrification and denitrification; however, the isotope ratios of nitrite from archaeal ammonia oxidation have been characterized only for a few marine species. We first report the isotope effects of ammonia oxidation at 70°C by thermophilic Thaumarchaeota populations composed almost entirely of "Candidatus Nitrosocaldus." The nitrogen isotope effect of ammonia oxidation varied with ambient pH (25‰ to 32‰) and strongly suggests the oxidation of ammonia, not ammonium. The δ(18)O value of nitrite produced from ammonia oxidation varied with the δ(18)O value of water in the medium but was lower than the isotopic equilibrium value in water. Because experiments have shown that the half-life of abiotic oxygen isotope exchange between nitrite and water is longer than 33 h at 70°C and pH ≥6.6, the rate of ammonia oxidation by thermophilic Thaumarchaeota could be estimated using δ(18)ONO2- in geothermal environments, where the biological nitrite turnover is likely faster than 33 h. This study extended the range of application of nitrite isotopes as a geochemical clock of the ammonia oxidation activity to high-temperature environments. Because ammonia oxidation is generally the rate-limiting step in nitrification that regulates the balance of reduced and oxidized nitrogen pools in nature, it is important to understand the biological and environmental factors underlying the regulation of

  8. A multielement isotopic study of refractory FUN and F CAIs: Mass-dependent and mass-independent isotope effects

    Science.gov (United States)

    Kööp, Levke; Nakashima, Daisuke; Heck, Philipp R.; Kita, Noriko T.; Tenner, Travis J.; Krot, Alexander N.; Nagashima, Kazuhide; Park, Changkun; Davis, Andrew M.

    2018-01-01

    Calcium-aluminum-rich inclusions (CAIs) are the oldest dated objects that formed inside the Solar System. Among these are rare, enigmatic objects with large mass-dependent fractionation effects (F CAIs), which sometimes also have large nucleosynthetic anomalies and a low initial abundance of the short-lived radionuclide 26Al (FUN CAIs). We have studied seven refractory hibonite-rich CAIs and one grossite-rich CAI from the Murchison (CM2) meteorite for their oxygen, calcium, and titanium isotopic compositions. The 26Al-26Mg system was also studied in seven of these CAIs. We found mass-dependent heavy isotope enrichment in all measured elements, but never simultaneously in the same CAI. The data are hard to reconcile with a single-stage melt evaporation origin and may require reintroduction or reequilibration for magnesium, oxygen and titanium after evaporation for some of the studied CAIs. The initial 26Al/27Al ratios inferred from model isochrons span a range from <1 × 10-6 to canonical (∼5 × 10-5). The CAIs show a mutual exclusivity relationship between inferred incorporation of live 26Al and the presence of resolvable anomalies in 48Ca and 50Ti. Furthermore, a relationship exists between 26Al incorporation and Δ17O in the hibonite-rich CAIs (i.e., 26Al-free CAIs have resolved variations in Δ17O, while CAIs with resolved 26Mg excesses have Δ17O values close to -23‰). Only the grossite-rich CAI has a relatively enhanced Δ17O value (∼-17‰) in spite of a near-canonical 26Al/27Al. We interpret these data as indicating that fractionated hibonite-rich CAIs formed over an extended time period and sampled multiple stages in the isotopic evolution of the solar nebula, including: (1) an 26Al-poor nebula with large positive and negative anomalies in 48Ca and 50Ti and variable Δ17O; (2) a stage of 26Al-admixture, during which anomalies in 48Ca and 50Ti had been largely diluted and a Δ17O value of ∼-23‰ had been achieved in the CAI formation region; and (3

  9. Effectiveness and equity of the Tanzania National Voucher Scheme for mosquito nets over 10 years of implementation.

    Science.gov (United States)

    Kramer, Karen; Mandike, Renata; Nathan, Rose; Mohamed, Ally; Lynch, Matthew; Brown, Nick; Mnzava, Ally; Rimisho, Wilhelmina; Lengeler, Christian

    2017-06-15

    The Tanzania National Voucher Scheme (TNVS) was a public private partnership managed by the Ministry of Health that provided pregnant women and infants with highly subsidized (long-lasting) insecticide-treated nets between 2004 and 2014. It was implemented in the context of the National Insecticide Treated Nets (NATNETS) Programme and was the main keep up strategy for vulnerable populations. The programme design was adjusted considerably over time to incorporate new evidence, shifting public health policies, and changing donor priorities. Three TNVS models can be distinguished: (1) the fixed discount; (2) the fixed top-up; (3) the hybrid voucher model. The changes improved equity and effectiveness, but also had a profound effect on how the programme was managed and implemented. The TNVS reached the majority of beneficiaries with vouchers, and significantly increased household ownership and use of LLINs. While two mass distribution campaigns implemented between 2009 and 2011 achieved universal coverage and equity, the TNVS ensured continuous protection of the vulnerable populations before, during and after the campaigns. The TNVS stimulated and maintained a large national retail network which managed the LLIN supply chain. The effectiveness of the TNVS was a function of several interdependent factors, including the supply chain of vouchers through the public health system; the supply chain of nets in the commercial sector; the demand for nets from voucher recipients; management and risk mitigation measures; and the influence of global and donor objectives. The TNVS was a highly innovative and globally influential programme, which stimulated the thinking around effectively and equitably distributing ITNs, and contributed directly to the evolution of global policy. It was a fundamental component of the NATNETS programme which protected a malaria-vulnerable population for over a decade.

  10. Cytochrome P-450 dependent ethanol oxidation. Kinetic isotope effects and absence of stereoselectivity

    International Nuclear Information System (INIS)

    Ekstroem, G.; Norsten, C.; Cronholm, T.; Ingelman-Sundberg, M.

    1987-01-01

    Deuterium isotope effects [/sup D/(V/K)] and stereoselectivity of ethanol oxidation in cytochrome P-450 containing systems and in the xanthine-xanthine oxidase system were compared with those of yeast alcohol dehydrogenase. The isotope effects were determined by using both a noncompetitive method, including incubation of unlabeled of [1,1- 2 H 2 ] ethanol at various concentrations, and a competitive method, where 1:1 mixtures of [1- 13 C]- and [ 2 H 6 ] ethanol or [2,2,2- 2 H 3 ]- and [1,1- 2 H 2 ] ethanol were incubated and the acetaldehyde formed was analyzed by gas chromatography/mass spectrometry. The /sup D/(V/K) isotope effects of the cytochrome P-450 dependent ethanol oxidation were about 4 with liver microsomes from imidazole-, phenobarbital- or acetone-treated rabbits or with microsomes from acetone- or ethanol-treated rats. Similar isotope effects were reached with reconstituted membranes containing the rabbit ethanol-inducible cytochrome P-450 (LMeb), whereas control rat microsomes and membranes containing rabbit phenobarbital-inducible P-450 LM 2 oxidized the alcohol with /sup D/(V/K) of about 2.8 and 1.8, respectively. Addition of Fe/sup III/EDTA either to microsomes from phenobarbital-treated rabbits or to membranes containing P-450 LMeb significantly lowered the isotope effect. Incubations of all cytochrome P-450 containing systems of the xanthine-xanthine oxidase systems with (1R)- and (1S)-[1- 2 H] ethanol, revealed, taking the isotope effects into account, that 44-66% of the ethanol oxidized had lost the 1-pro-R hydrogen. The data indicate that cytochrome P-450 dependent ethanol oxidation is not stereospecific and that cleavage of the C 1 -H bond appears to be a rate-determining step in the catalysis by the ethanol-inducible form of P-450. The contribution of hydroxyl radicals in ethanol oxidation by the various enzymic systems is discussed

  11. Evaluation of runaway-electron effects on plasma-facing components for NET

    Science.gov (United States)

    Bolt, H.; Calén, H.

    1991-03-01

    Runaway electrons which are generated during disruptions can cause serious damage to plasma facing components in a next generation device like NET. A study was performed to quantify the response of NET plasma facing components to runaway-electron impact. For the determination of the energy deposition in the component materials Monte Carlo computations were performed. Since the subsurface metal structures can be strongly heated under runaway-electron impact from the computed results damage threshold values for the thermal excursions were derived. These damage thresholds are strongly dependent on the materials selection and the component design. For a carbonmolybdenum divertor with 10 and 20 mm carbon armour thickness and 1 degree electron incidence the damage thresholds are 100 MJ/m 2 and 220 MJ/m 2. The thresholds for a carbon-copper divertor under the same conditions are about 50% lower. On the first wall damage is anticipated for energy depositions above 180 MJ/m 2.

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

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  13. Deuterium isotope effect on the intramolecular electron transfer in Pseudomonas aeruginosa azurin

    DEFF Research Database (Denmark)

    Farver, O.; Zhang, Jingdong; Chi, Qijin

    2001-01-01

    rather than negative. Isotope effects are, however, also inherent in the nuclear reorganization Gibbs free energy and in the tunneling factor for the electron transfer process. A slightly larger thermal protein expansion in H2O than in D2O (0.001 nm K-1) is sufficient both to account for the activation......Intramolecular electron transfer in azurin in water and deuterium oxide has been studied over a broad temperature range. The kinetic deuterium isotope effect, k(H)/k(D), is smaller than unity (0.7 at 298 K), primarily caused by the different activation entropies in water (-56.5 J K-1 mol(-1...

  14. 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.)

  15. Effects of trace element concentration on enzyme controlled stable isotope fractionation during aerobic biodegradation of toluene.

    Science.gov (United States)

    Mancini, Silvia A; Hirschorn, Sarah K; Elsner, Martin; Lacrampe-Couloume, Georges; Sleep, Brent E; Edwards, Elizabeth A; Lollar, Barbara Sherwood

    2006-12-15

    The effects of iron concentration on carbon and hydrogen isotopic fractionation during aerobic biodegradation of toluene by Pseudomonas putida mt-2 were investigated using a low iron medium and two different high iron media. Mean carbon enrichment factors (epsilonc) determined using a Rayleigh isotopic model were smaller in culture grown under high iron conditions (epsilonc = -1.7+/-0.1%) compared to low iron conditions (epsilonc = -2.5+/-0.3%). Mean hydrogen enrichment factors (epsilonH) were also significantly smaller for culture grown under high iron conditions (epsilonH = -77 +/-4%) versus low iron conditions (EpsilonH = -159+/-11%). A mechanistic model for enzyme kinetics was used to relate differences in the magnitude of isotopic fractionation for low iron versus high iron cultures to the efficiency of the enzymatic transformation. The increase of carbon and hydrogen enrichment factors at low iron concentrations suggests a slower enzyme-catalyzed substrate conversion step (k2) relative to the enzyme-substrate binding step (k-l) at low iron concentration. While the observed differences were subtle and, hence, do not significantly impact the ability to use stable isotope analysis in the field, these results demonstrated that resolvable differences in carbon and hydrogen isotopic fractionation were related to low and high iron conditions. This novel result highlights the need to further investigate the effects of other trace elements known to be key components of biodegradative enzymes.

  16. Correlation of the vapor pressure isotope effect with molecular force fields in the liquid state

    International Nuclear Information System (INIS)

    Pollin, J.S.; Ishida, T.

    1976-07-01

    The present work is concerned with the development and application of a new model for condensed phase interactions with which the vapor pressure isotope effect (vpie) may be related to molecular forces and structure. The model considers the condensed phase as being represented by a cluster of regularly arranged molecules consisting of a central molecule and a variable number of molecules in the first coordination shell. The methods of normal coordinate analysis are used to determine the modes of vibration of the condensed phase cluster from which, in turn, the isotopic reduced partition function can be calculated. Using the medium cluster model, the observed vpie for a series of methane isotopes has been successfully reproduced with better agreement with experiment than has been possible using the simple cell model. We conclude, however, that insofar as the medium cluster model provides a reasonable picture of the liquid state, the vpie is not sufficiently sensitive to molecular orientation to permit an experimental determination of intermolecular configuration in the condensed phase through measurement of isotopic pressure ratios. The virtual independence of vapor pressure isotope effects on molecular orientation at large cluster sizes is a demonstration of the general acceptability of the cell model assumptions for vpie calculations

  17. Dynamical barrier and isotope effects in the simplest substitution reaction via Walden inversion mechanism

    Science.gov (United States)

    Zhao, Zhiqiang; Zhang, Zhaojun; Liu, Shu; Zhang, Dong H.

    2017-02-01

    Reactions occurring at a carbon atom through the Walden inversion mechanism are one of the most important and useful classes of reactions in chemistry. Here we report an accurate theoretical study of the simplest reaction of that type: the H+CH4 substitution reaction and its isotope analogues. It is found that the reaction threshold versus collision energy is considerably higher than the barrier height. The reaction exhibits a strong normal secondary isotope effect on the cross-sections measured above the reaction threshold, and a small but reverse secondary kinetic isotope effect at room temperature. Detailed analysis reveals that the reaction proceeds along a path with a higher barrier height instead of the minimum-energy path because the umbrella angle of the non-reacting methyl group cannot change synchronously with the other reaction coordinates during the reaction due to insufficient energy transfer from the translational motion to the umbrella mode.

  18. Isotopic effects in the neon fixed point: uncertainty of the calibration data correction

    Science.gov (United States)

    Steur, Peter P. M.; Pavese, Franco; Fellmuth, Bernd; Hermier, Yves; Hill, Kenneth D.; Seog Kim, Jin; Lipinski, Leszek; Nagao, Keisuke; Nakano, Tohru; Peruzzi, Andrea; Sparasci, Fernando; Szmyrka-Grzebyk, Anna; Tamura, Osamu; Tew, Weston L.; Valkiers, Staf; van Geel, Jan

    2015-02-01

    The neon triple point is one of the defining fixed points of the International Temperature Scale of 1990 (ITS-90). Although recognizing that natural neon is a mixture of isotopes, the ITS-90 definition only states that the neon should be of ‘natural isotopic composition’, without any further requirements. A preliminary study in 2005 indicated that most of the observed variability in the realized neon triple point temperatures within a range of about 0.5 mK can be attributed to the variability in isotopic composition among different samples of ‘natural’ neon. Based on the results of an International Project (EUROMET Project No. 770), the Consultative Committee for Thermometry decided to improve the realization of the neon fixed point by assigning the ITS-90 temperature value 24.5561 K to neon with the isotopic composition recommended by IUPAC, accompanied by a quadratic equation to take the deviations from the reference composition into account. In this paper, the uncertainties of the equation are discussed and an uncertainty budget is presented. The resulting standard uncertainty due to the isotopic effect (k = 1) after correction of the calibration data is reduced to (4 to 40) μK when using neon of ‘natural’ isotopic composition or to 30 μK when using 20Ne. For comparison, an uncertainty component of 0.15 mK should be included in the uncertainty budget for the neon triple point if the isotopic composition is unknown, i.e. whenever the correction cannot be applied.

  19. Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

    Science.gov (United States)

    Green, Christopher T.; Böhlke, John Karl; Bekins, Barbara A.; Phillips, Steven P.

    2010-01-01

    Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O2 reduction rate, denitrification rate, O2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample‐based estimates of “apparent” parameters with “true“ (intrinsic) values. For this aquifer, non‐Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O2threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport.

  20. A Distinct Magnetic Isotope Effect Measured in Atmospheric Mercury in Epiphytes

    Science.gov (United States)

    Ghosh, S.; Odom, A. L.

    2007-12-01

    Due to the importance of Mercury as an environmental contaminant, mercury cycling in the atmosphere has been extensively studied. However, there still remain uncertainties in the relative amounts of natural and anthropogenic emissions, atmospheric deposition rates as well as the spatial variation of atmospheric mercury. Part of a study to determine the isotopic composition of mercury deposited from the atmosphere has involved the use of epiphytes as monitors. The greatest advantage of such natural monitors is that a widespread, high-density network is possible at low cost. One of the disadvantages at present is that these monitors likely contain different mercury species (for example both gaseous, elemental mercury trapped by adsorption and Hg (II) by wet deposition). The project began with the understanding that biochemical reactions involving metallothioneins within the epiphytes might have produced an isotopic effect. One such regional network was composed of samples of Tillandsia usenoides (common name: Spanish moss) collected along the eastern Coastal Plain of the U.S. from northern Florida to North Carolina. The isotopic composition of a sample is expressed as permil deviations from a standard. The deviations are defined as δAHg = \\left(\\frac{Rsample}{Rstd}-1 \\right)1000 ‰ , where A represents the atomic mass number. R=\\frac{AHg}{202Hg} were measured for the isotopes 198Hg, 199Hg, 200Hg, 201Hg, 202Hg and 204Hg relative to the mercury standard SRM NIST 3133, by a standard-sample bracketing technique. For all samples, the delta values of the even-N plotted against atomic mass numbers define a linear curve. For the odd-N isotopes, δ199Hg and δ201Hg deviate from this mass-dependent fractionation (MDF) relationship and indicate a mass-independent fractionation (MIF) effect and a negative anomaly, i.e. a depletion in 199Hg and 201Hg relative to the even-N isotopes. These deviations are expressed as Δ199Hg = δ199Hgtotal - δ199HgMDF. A Δ201Hg/Δ199Hg

  1. Effects of arbuscular mycorrhizal fungi on gas exchange and stable isotope ratio of δ13C, δ15N of leymus chinensis plant

    International Nuclear Information System (INIS)

    Shi Weiqi; Wang Guoan; Li Xiaolin

    2008-01-01

    Leymus chinensis, one of dominant species in Inner Mongolia grassland, was selected to evaluate the effects of arbuscular mycorrhizal fungi (AMF) on plant gas change parameters and stable isotope ratio in pot culture. The plant was inoculated with two mycorrhizal fungi, Glomus intraradices and Glomus claroidum, and the uninoculated plant was used as the control check. On the 45th , 60th , 75th days after sowing, gas exchange parameters and stable isotope ratio were measured. The results showed that AM infection promoted phosphoms content, stomatal conductance and photosynthetic rate of Leymus chinensis, reduced host δ 15 N, however, it did not influence host intrinsic water using efficiency and δ 13 C. It was the growth time that significantly affected the gas exchange and stable isotope ratio of δ 13 C and δ 15 N. And the interaction of inoculation and growth time also influenced on the net photosynthetic rate, δ 13 C and δ 15 N of the host. Stomatal conductance and photosynthetic rate were always changed the same direction by arbuscular mycorrhizal fungi causing no significant difference between mycorrhizal and non-mycorrhizal plant. AMF absorbed nitrogen and accumulated δ 15 N, thus, it transformed less 15 N into the host, and as a result, the mycorrhizal plant had lower δ 15 N. Therefore, the results gave a new way and reference to know of the grass balance of carbon gain and water cost and the nitrogen cycle in grassland. (authors)

  2. Methyl-coenzyme M reductase from methanogenic archaea: isotope effects on label exchange and ethane formation with the homologous substrate ethyl-coenzyme M.

    Science.gov (United States)

    Scheller, Silvan; Goenrich, Meike; Thauer, Rudolf K; Jaun, Bernhard

    2013-10-09

    Ethyl-coenzyme M (CH3CH2-S-CH2CH2-SO3(-), Et-S-CoM) serves as a homologous substrate for the enzyme methyl-coenzyme M reductase (MCR) resulting in the product ethane instead of methane. The catalytic reaction proceeds via an intermediate that already contains all six C-H bonds of the product. Because product release occurs after a second, rate-limiting step, many cycles of intermediate formation and reconversion to substrate occur before a substantial amount of ethane is released. In deuterated buffer, the intermediate becomes labeled, and C-H activation in the back reaction rapidly leads to labeled Et-S-CoM, which enables intermediate formation to be detected. Here, we present a comprehensive analysis of this pre-equilibrium. (2)H- and (13)C-labeled isotopologues of Et-S-CoM were used as the substrates, and the time course of each isotopologue was followed by NMR spectroscopy. A kinetic simulation including kinetic isotope effects allowed determination of the primary and α- and β-secondary isotope effects for intermediate formation and for the C-H/C-D bond activation in the ethane-containing intermediate. The values obtained are in accordance with those found for the native substrate Me-S-CoM (see preceding publication, Scheller, S.; Goenrich, M.; Thauer, R. K.; Jaun, B. J. Am. Chem. Soc. 2013, 135, DOI: 10.1021/ja406485z) and thus imply the same catalytic mechanism for both substrates. The experiment by Floss and co-workers, demonstrating a net inversion of configuration to chiral ethane with CH3CDT-S-CoM as the substrate, is compatible with the observed rapid isotope exchange if the isotope effects measured here are taken into account.

  3. Horizontal ichthyoplankton tow-net system with unobstructed net opening

    Science.gov (United States)

    Nester, Robert T.

    1987-01-01

    The larval fish sampler described here consists of a modified bridle, frame, and net system with an obstruction-free net opening and is small enough for use on boats 10 m or less in length. The tow net features a square net frame attached to a 0.5-m-diameter cylinder-on-cone plankton net with a bridle designed to eliminate all obstructions forward of the net opening, significantly reducing currents and vibrations in the water directly preceding the net. This system was effective in collecting larvae representing more than 25 species of fish at sampling depths ranging from surface to 10 m and could easily be used at greater depths.

  4. Net Community and Gross Photosynthetic Production Rates in the Eastern Tropical South Pacific, as Determined from O2/AR Ratios and Triple Oxygen Isotopic Composition of Dissolved O2

    Science.gov (United States)

    Prokopenko, M. G.; Yeung, L. Y.; Berelson, W.; Fleming, J.; Rollins, N.; Young, E. D.; Haskell, W. Z.; Hammond, D. E.; Capone, D. G.

    2010-12-01

    This study assesses the rates of ocean carbon production and its fate with respect to recycling or export in the Eastern Tropical South Pacific (ETSP). ETSP has been previously identified as a region where N2 fixation and denitrification may be spatially coupled; this is also a region of localized CO2 outgassing. Using an Equilibrated Inlet Mass Spectrometer (EIMS) system, we obtained continuous measurements of the biological O2 supersaturation in the mixed layer along the ship track encompassing a region bounded by 10-20° S and 80-100° W in January - March, 2010. Vertical profiles were also taken at selected stations and analyzed for dissolved O2/Ar ratios on EIMS and triple oxygen isotope composition (17O excess) on a multi-collector IRMS (Isotope Ratio Mass Spectrometer) at UCLA. Gas exchange rates were estimated using two approaches: the Rn-222 deficit method and the wind parameterization method, which utilized wind speeds extracted from ASCAT satellite database. Oxygen Net Community Production (O-NCP) rates calculated based on biological O2 supersaturation ranged from slightly negative to ~ 0.3 - 15 mmol/m2d, with higher rates along the northern part of the transect. Oxygen Gross Community Production (O-GPP) rates calculated from 17O excess were between 50 ± 20 and 200 ± 40 mmol/m2d, with higher rates observed along the northern cruise transect as well. Notably, the NCP/GPP ratios along the northern transect were higher by the factor of 2 to 3 than their southern counterparts. The O2/Ar-based NCP rates were comparable to POC flux measured with floating traps deployed at the southern stations, but exceeded by a factor of 5-10 the trap POC fluxes obtained at the northern stations. A one-dimensional box model has been constructed to quantify the magnitude of oxygen primary production below the mixed layer. The results of this work will be integrated with measurements of 15-N2 uptake that are in progress, to constrain the potential contribution of N2 fixation

  5. Isotopic and spin-nuclear effects in solid hydrogens (Review Article)

    Science.gov (United States)

    Freiman, Yuri A.; Crespo, Yanier

    2017-12-01

    The multiple isotopic family of hydrogens (H2, HD, D2, HT, DT, T2) due to large differences in the de Boer quantum parameter and inertia moments displays a diversity of pronounced quantum isotopic solid-state effects. The homonuclear members of this family (H2, D2, T2) due to the permutation symmetry are subjects of the constraints of quantum mechanics which link the possible rotational states of these molecules to their total nuclear spin giving rise to the existence of two spin-nuclear modifications, ortho- and parahydrogens, possessing substantially different properties. Consequently, hydrogen solids present an unique opportunity for studying both isotope and spin-nuclear effects. The rotational spectra of heteronuclear hydrogens (HD, HT, DT) are free from limitations imposed by the permutation symmetry. As a result, the ground state of these species in solid state is virtually degenerate. The most dramatic consequence of this fact is an effect similar to the Pomeranchuk effect in 3He which in the case of the solid heteronuclear hydrogens manifests itself as the reentrant broken symmetry phase transitions. In this review article we discuss thermodynamic and kinetic effects pertaining to different isotopic and spin-nuclear species, as well as problems that still remain to be solved.

  6. Beyond pure offsetting: Assessing options to generate Net-Mitigation-Effects in carbon market mechanisms

    International Nuclear Information System (INIS)

    Warnecke, Carsten; Wartmann, Sina; Höhne, Niklas; Blok, Kornelis

    2014-01-01

    The current project-based carbon market mechanisms such as the Clean Development Mechanism (CDM) and the Joint Implementation (JI) do not have a direct impact on global greenhouse gas emission levels, because they only replace or offset emissions. Nor do they contribute to host country's national greenhouse gas emission reduction targets. Contributions to net emission reductions in host countries is likely to become mandatory in new mechanisms under development such as in the framework for various approaches, a new market-based mechanism and even in a reformed JI. This research analysed the question if approaches for carbon market-based mechanisms exist that allow the generation of net emission reductions in host countries while keeping project initiation attractive. We present a criteria-based assessment method and apply it for four generic options in existing mechanisms and derive implications for future mechanism frameworks. We identified the application of “discounts” on the amount of avoided emissions for the issuance of carbon credits and “standardisation below business as usual” as most promising options over “limiting the crediting period” and “over-conservativeness”. We propose to apply these options differentiated over project types based on internal rate of return to ensure cost-efficiency and attractiveness. - Highlights: • Options for net emission reductions of market-based mechanisms are assessed. • Research combines past and current views for project and sector-based mechanisms. • Implementation ensures initiation of mitigation activities is not discouraged. • Important insights for methodological design of new market-based mechanisms. • Profitability-based approach for project-based mechanisms suggested

  7. Memory Effects Study of Measuring Radioactive Xenon Isotopes With β-γ Coincidence Method

    International Nuclear Information System (INIS)

    Jia Huaimao; Wang Shilian; Wang Jun; Li Qi; Zhao Yungang; Fan Yuanqing; Zhang Xinjun

    2010-01-01

    The β-γ coincidence technique is a kind of the key important method to detect radioactive xenon isotopes for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). This paper describes noble gases memory effects of β-γ coincidence detector. Xenon memory effects were measured and its influence on detector's minimum detectable activity (MDA) was evaluated. The methods of reducing xenon memory effects were studied. In conclusion, aluminium coated plastic scintillator and YAP scintillator can remarkably decrease xenon memory effects. (authors)

  8. Effect of Different Carbon Substrates on Nitrate Stable Isotope Fractionation During Microbial Denitrification

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian

    2012-01-01

    -labeled water and 18O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed......In batch experiments, we studied the isotope fractionation in N and O of dissolved nitrate during dentrification. Denitrifying strains Thauera aromatica and “Aromatoleum aromaticum strain EbN1” were grown under strictly anaerobic conditions with acetate, benzoate, and toluene as carbon sources. 18O...... of nitrate transport across the cell wall compared to the kinetics of the intracellular nitrate reduction step of microbial denitrification....

  9. Effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions.

    Science.gov (United States)

    Zhang, Zhiyuan; Zhang, Renduo; Cescatti, Alessandro; Wohlfahrt, Georg; Buchmann, Nina; Zhu, Juan; Chen, Guanhong; Moyano, Fernando; Pumpanen, Jukka; Hirano, Takashi; Takagi, Kentaro; Merbold, Lutz

    2017-06-08

    The net ecosystem CO 2 exchange is the result of the imbalance between the assimilation process (gross primary production, GPP) and ecosystem respiration (RE). The aim of this study was to investigate temperature sensitivities of these processes and the effect of climate warming on the annual terrestrial net ecosystem CO 2 exchange globally in the boreal and temperate regions. A database of 403 site-years of ecosystem flux data at 101 sites in the world was collected and analyzed. Temperature sensitivities of rates of RE and GPP were quantified with Q 10 , defined as the increase of RE (or GPP) rates with a temperature rise of 10 °C. Results showed that on the annual time scale, the intrinsic temperature sensitivity of GPP (Q 10sG ) was higher than or equivalent to the intrinsic temperature sensitivity of RE (Q 10sR ). Q 10sG was negatively correlated to the mean annual temperature (MAT), whereas Q 10sR was independent of MAT. The analysis of the current temperature sensitivities and net ecosystem production suggested that temperature rise might enhance the CO 2 sink of terrestrial ecosystems both in the boreal and temperate regions. In addition, ecosystems in these regions with different plant functional types should sequester more CO 2 with climate warming.

  10. Kinetic isotope effect studies of the S-adenosylmethionine synthetase reaction

    International Nuclear Information System (INIS)

    Markham, G.D.; Parkin, D.W.; Schramm, V.L.

    1986-01-01

    S-adenosylmethionine (AdoMet) synthetase catalyzes a unique substitution reaction at the 5' carbon of MgATP. Kinetic isotope effect (V/K) measurements have been used to investigate the mechanism of AdoMet synthetase from E. coli. Changes in 3 H/ 14 C ratios when AdoMet is formed from a mixture of either ([5'- 14 C]ATP and [5'- 12 C,1'- 3 H]ATP) or ([5'- 3 H]ATP and [5'- 1 H,1'- 14 C]ATP) were examined. The effects of varying the concentrations of the co-substrate methionine and the monovalent cation activator K + were investigated. Substitution of 14 C for 12 C at the 5' position of ATP yields a primary V/K kinetic isotope effect ( 12 C/ 14 C) of 1.128 +/- 0.004 at low K + and methionine concentrations. The observed isotope effect diminishes slightly to 1.107 +/- 0.003 when both K + and methionine are present at saturating concentrations, suggesting that MgATP has only a low commitment to catalysis from at conditions near Vmax. No secondary V/K 3 H isotope effect from [5'- 3 H]ATP was detected ( 1 H/ 3 H) = 0.997 +/- 0.003. The magnitude of the primary 14 C isotope effect and the small secondary 3 H effect demonstrate that AdoMet synthesis occurs with a S/sub N/ 2 transition state which is symmetric with respect to the sulfur nucleophile and the departing tripolyphosphate group

  11. The effect of small solar powered 'Bͻkͻͻ' net fans on mosquito net use: results from a randomized controlled cross-over trial in southern Ghana.

    Science.gov (United States)

    Briët, Olivier J T; Yukich, Joshua O; Pfeiffer, Constanze; Miller, William; Jaeger, Mulako S; Khanna, Nitin; Oppong, Samuel; Nardini, Peter; Ahorlu, Collins K; Keating, Joseph

    2017-01-03

    Long-lasting insecticidal nets (LLINs) are ineffective malaria transmission prevention tools if they are unused. Discomfort due to heat is the most commonly reported reason for not using nets, but this problem is largely unaddressed. With increasing rural electrification and the dropping price of solar power, fans could improve comfort inside nets and be affordable to populations in malaria endemic areas. Here, results are presented from a pilot randomized controlled cross-over study testing the effect of fans on LLIN use. Eighty-three households from two rural communities in Greater Accra, Ghana, randomized into three groups, participated in a 10-month cross-over trial. After a screening survey to identify eligible households, all households received new LLINs. Bͻkͻͻ net fan systems (one fan per member) were given to households in Group 1 and water filters were given to households in Group 2. At mid-point, Group 1 and 2 crossed over interventions. Households in Group 1 and 2 participated in fortnightly surveys on households' practices related to nets, fans and water filters, while households in Group 3 were surveyed only at screening, mid-point and study end. Entomological and weather data were collected throughout the study. Analysis took both 'per protocol' (PP) and 'intention to treat' (ITT) approaches. The mid- and end-point survey data from Group 1 and 2 were analysed using Firth logistic regressions. Fortnightly survey data from all groups were analysed using logistic regressions with random effects. Provision of fans to households appeared to increase net use in this study. Although the increase in net use explained by fans was not significant in the primary analyses (ITT odds ratio 3.24, p > 0.01; PP odds ratio = 1.17, p > 0.01), it was significant in secondary PP analysis (odds ratio = 1.95, p Fan use was 90-100% depending on the fortnightly visit. This pilot study could not provide definitive evidence that fans increase net use. A larger

  12. Effect of Calcium Oxide Microstructure on the Diffusion of Isotopes

    CERN Document Server

    Fernandes Ramos, João Pedro; Stora, T

    2012-01-01

    Calcium oxide (CaO) powder targets have been successfully used at CERN-ISOLDE to produce neutron deficient exotic argon and carbon isotopes under proton irradiation at high temperatures (>1000°C). These targets outperform the other related targets for the production of the same beams. However, they presented either slow release rates (yields) from the beginning or a rapid decrease over time. This problem was believed to come from the target microstructure degradation, justifying the material investigation. In order to do so, the synthesis, reactivity in ambient air and sintering kinetics of CaO were studied, through surface area determination by N2 adsorption, X-ray diffraction for crystalline phase identification and crystallite size determination, and scanning and transmission electron microscopy to investigate the microstructure. The synthesis studies revealed that a nanometric material is obtained from the decarbonation of CaCO3 in vacuum at temperatures higher than 550°C, which is very reactive in air....

  13. Carbon-13 kinetic isotope effects in the decarbonylations of lactic acid containing 13C at the natural abundance level

    International Nuclear Information System (INIS)

    Zielinski, M.; Czarnota, G.; Papiernik-Zielinska, H.

    1992-01-01

    The 13 C kinetic isotope fractionation in the decarbonylation of lactic acid of natural isotopic composition by sulfuric acid has been studied in the temperature range of 20-80 deg C. The 13 C (1) isotope separation in the decarbonylation of lactic acid by concentrated sulfuric acid depends strongly on the temperature above 40 deg C. Below this temperature the 13 C isotope effect in the decarbonylation of lactic acid by concentrated sulfuric acid is normal similarly as has been found in the decarbonylation of lactic [1- 14 C] acid. The experimental values of k (12C) /k (13C) ratios of isotopic rate constants for 12 C and 13 C are close to, but slightly higher than theoretical 13 C-kinetic isotope effects calculated (neglecting tunneling) under the asumption that the C (1) -OH bond is broken in the rate-controlling step of the dehydration reaction. Dilution of concentrated sulfuric acid with water up to 1.4 molar (H 2 O)/(H 2 SO 4 ) ratio caused the increase of the 13 C isotope fractionation from 1.0273 found in concentrated sulfuric acid at 80.5 deg C to 1.0536±0.0008 (at 80.6 deg C). A discussion of the abnormally high temperature dependence of 14 C and 13 C isotope fractionation in this reaction and the discussion of the problem of relative 14 C/ 13 C kinetic isotope effects is given. (author) 18 refs.; 2 tabs

  14. Effect of netting direction and number of meshes around on size selection in the codend for Baltic cod (Gadus morhua)

    DEFF Research Database (Denmark)

    Wienbeck, Harald; Herrmann, Bent; Moderhak, Waldemar

    2011-01-01

    We investigated experimentally the effect that turning the netting direction 90° (T90) and halving the number of meshes around in the circumference in a diamond mesh codend had on size selection of Baltic cod. The results generally agreed with predictions of a previous simulation-based study. Both...... modifications had a significant positive effect on the size selection of cod. The best selection results were obtained for a codend in which both factors were applied together. For that codend, very little between-haul variation in cod size selection was detected, especially compared to the reference codend...

  15. Anomalous H/D isotope effect on 35Cl NQR frequencies and H/D isotope effect on 1H MAS NMR spectra in pyrrolidinium p-chlorobenzoate

    International Nuclear Information System (INIS)

    Nakano, Ryo; Honda, Hisashi; Nakata, Eiichi; Takamizawa, Satoshi; Noro, Sumiko; Kimura, Taiki; Kyo, Shin-shin; Ishimaru, Shin'ichi; Miyake, Ryosuke

    2010-01-01

    An anomalous isotope effect was observed in the 35 Cl NQR frequency of pyrrolidinium p-chlorobenzoate (C 4 H 8 NH 2 + ·ClC 6 H 4 COO - ) by deuterium substitution of hydrogen atoms which form two kinds of N-H...O type hydrogen bonds. Large negative frequency shifts of the 35 Cl resonance lines, reaching 309 kHz at 77 K and 267 kHz at 293 K, were obtained upon deuteration, although the Cl atom in the molecule formed no hydrogen bonds in the crystal. 1 H MAS NMR lines showed significant changes by the deuterium substitution, while in contrast, small shifts of 13 C CP/MAS NMR signals were obtained. Our measurements of 1 H NMR spin-lattice relaxation times (T 1 ) suggested that the H/D isotope shifts detected from the 35 Cl NQR frequencies and 1 H NMR spectra are due to structural changes rather than molecular dynamics. Single-crystal X-ray diffraction measurements showed two remarkable H/D isotope differences in the molecular arrangements, (1) the N-H length along the crystallographic a axis became 1 pm shorter, and (2) the dihedral angle between benzene and the pyrrolidine ring changed by 1.1(2)deg upon deuteration. Using density functional theory estimations, the anomalous 35 Cl NQR frequency shifts and 1 H MAS NMR line-shape changes could be explained by the dihedral angle change rather than the N-H length difference. (author)

  16. 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)

  17. Kinetic secondary deuterium isotope effect in addition of nucleophile to m-bromobenzaldehyde

    International Nuclear Information System (INIS)

    Amaral, L. do; Rossi, M.H.

    1985-01-01

    The kinetic secondary deuterium isotope effects, KD/KH for hydrated proton catalyzed addition of semicarbazide, methoxyamine and hydroxylamine to m-bromobenzaldehyde is studied. The nature of the nucleophile, addition of the carbonyl group and the chemical reactions are evaluated. (M.J.C.) [pt

  18. Studies on the magnetic after-effect of hydrogen isotopes in hexagonal crystals

    International Nuclear Information System (INIS)

    Herbst, G.

    1979-01-01

    The behaviour of hydrogen isotopes in hexagonal gadolinium, in intermetallic compounds of the RECo 5 type (RE = rare earth metal), and in cobalt alloys with small concentrations of alloyed impurity atoms was studied using the magnetic after-effect method in the temperature range between 4.2 K and 300 K. (orig./WBU) [de

  19. Synthesis of seven deuteromethyl-caffeine analogues observation of deuterium isotope effects on CMR analysis

    Energy Technology Data Exchange (ETDEWEB)

    Falconnet, J.B.; Brazier, J.L.; Desage, M.

    1986-03-01

    The synthesis of all 7 N-trideuteromethyl isotopomers of caffeine by reaction of trideuteromethyl iodide (C/sup 2/H/sub 3/I) with the appropriate xanthine molecules is described. The use of proton, deuterium and carbon-13-NMR as a first step in purity assessment revealed /sup 13/C-NMR deuterium isotope effects on the resonance of perdeuteromethyl carbons.

  20. Kinetic isotope effect in the reaction of dehydration of fructose into 5-hydroxymethylfurfural

    International Nuclear Information System (INIS)

    Grin', S.A.; Tsimbaliev, S.R.; Gel'fand, S.Yu.

    1993-01-01

    Kinetic isotopic effect in the reaction of fructose dehydration into 5- hydroxymethylfurfural was determined. The results suggest hydrogen participation in the limiting stage of the process. The assumption that proton addition to 4, 5, 6 -trihydroxy - 2- on - hexal is the limiting stage is made

  1. A new cascade method for studying isotope effect in chemical exchange system without valance change

    International Nuclear Information System (INIS)

    Wen Xiaoning; Luo Wenzong

    1987-01-01

    A new cascade method for studying isotope effect in chemical exchange system without valance change is developed and described. This method is simple to use and consumes less extractant as compared with the commonly used Woodward method. It is also convenient for unstable systems

  2. Kinetic mechanism and isotope effects of Pseudomonas cepacia 3-hydroxybenzoate-t-hydroxylase

    International Nuclear Information System (INIS)

    Wang, L.H.; Yu, Y.; Hamzah, R.Y.; Tu, S.C.

    1986-01-01

    The kinetic mechanism of Pseudomonas cepacia 3-hydroxybenzoate-6-hydroxylase has been delineated. Double reciprocal plots of initial rate versus m-hydroxybenzoate concentration at a constant level of oxygen and several fixed concentrations of NADH yielded a set of converging lines. Similar reciprocal plots of velocity versus NADH concentration at a constant oxygen level and several fixed m-hydroxybenzoate concentrations also showed converging lines. In contrast, double reciprocal plots of initial rate versus NADH concentration at a fixed m-hydroxybenzoate level and several oxygen concentrations showed a series of parallel lines. Parallel lines were also obtained from double reciprocal plots of initial rate versus m-hydroxybenzoate concentration at a fixed NADH level and varying oxygen concentrations. These results suggest a sequential binding of m-hydroxybenzoate and NADH by the hydroxylase. The enzyme-bound FAD is reduced and NAD is released. The reduced enzyme subsequently reacts with oxygen leading to the formation of other products. This hydroxylase exhibited a primary isotope effect of /sup D/V = 3.5 for (4R)-[4- 2 H] NADH but no isotope effect was observed with (4S)-[4- 2 H]NADH. An isotope effect of /sup T/V/K = 5.0 was also observed using (4R)-[4- 3 H]NADH. This tritium isotope effect was apparently independent of m-hydroxybenzoate concentration

  3. Stable isotope enrichment in laboratory ant colonies: effects of colony age, metamorphosis, diet, and fat storage

    Science.gov (United States)

    Ecologists use stable isotopes to infer diets and trophic levels of animals in food webs, yet some assumptions underlying these inferences have not been thoroughly tested. We used laboratory-reared colonies of Solenopsis invicta Buren (Formicidae: Solenopsidini) to test the effects of metamorphosis,...

  4. Calcium isotope effects in ion exchange electromigration and calcium isotope analysis by thermo-ionization mass spectrometry

    International Nuclear Information System (INIS)

    Fujii, Y.; Hoshi, J.; Iwamoto, H.; Okamoto, M.; Kakihana, H.

    1985-01-01

    Calcium ions were made to electromigrate along a cation exchange membrane. The abundance ratios of the calcium isotopes (Ca-40, 42, 43, 44, 48) in the migrated bands were measured by thermo-ionization mass spectrometry. The lighter isotopes were enriched in the front part of the migrated band. The increments in the isotope abundance ratios were found to be proportional to the mass difference of the isotopes. The observed epsilon-values per unit mass difference (epsilon/ΔM) were 1.26 x 10 -4 (at 20 0 C), 1.85 x 10 -4 (at 25 0 C) and 2.4 x 10 -4 (at 40 0 C). The mass spectrometry was improved by using a low temperature for the evaporation of CaI 2 . (orig.)

  5. Isotope puzzle in sputtering

    International Nuclear Information System (INIS)

    Zheng Liping

    1998-01-01

    Mechanisms affecting multicomponent material sputtering are complex. Isotope sputtering is the simplest in the multicomponent materials sputtering. Although only mass effect plays a dominant role in the isotope sputtering, there is still an isotope puzzle in sputtering by ion bombardment. The major arguments are as follows: (1) At the zero fluence, is the isotope enrichment ejection-angle-independent or ejection-angle-dependent? (2) Is the isotope angular effect the primary or the secondary sputter effect? (3) How to understand the action of momentum asymmetry in collision cascade on the isotope sputtering?

  6. Effect of a dual-task net-step exercise on cognitive and gait function in older adults.

    Science.gov (United States)

    Kitazawa, Kazutoshi; Showa, Satoko; Hiraoka, Akira; Fushiki, Yasuhiro; Sakauchi, Humio; Mori, Mitsuru

    2015-01-01

    Participation in generally recommended aerobics or strength exercises may be challenging for older adults. Therefore, it is necessary to consider the types and levels of physical activities suited for them to improve their cognitive and gait function and adherence to exercise programs. This has prompted efforts to identify exercises that require less physical strength and frequency of performance, while still offering cognitive and health benefits. Here, we aimed to assess the effect of a novel dual-task net-step exercise (NSE) performed once a week for 8 consecutive weeks on improvements in cognitive performance and gait function in an older population. In this pretest/posttest experimental case control study, 60 healthy older adults (mean age 76.4 years) were recruited from community-dwelling people and separated randomly into 2 groups: a dual-task NSE group and a control group. The NSE group was asked to walk across a net without stepping on the ropes or being caught in the net. Two computer panel-type cognitive functional assessments, the Touch-M and Touch Panel-Type Dementia Assessment Scale, were administered at baseline and after 8 weeks of intervention to determine the effects of NSE. Improvements in gait function were also evaluated using Timed Up and Go test scores. Mixed-effect models with repeated measures (group × time) (analysis of variance, F test) were used to test the effects of NSE. Adjustments were made for covariates including age and sex (analysis of covariance). The NSE group showed significant improvement in cognitive performance (6.8% change; total Touch-M score 5.4 points; P = .04) and gait performance (11.5% change; Timed Up and Go time -0.98 second; P cognitive and gait performance in healthy older adults. Our results indicate that NSE offers an option for a large segment of the older population who need an easier way to maintain their cognitive health and gait function.

  7. An unusual isotope effect in a high-transition-temperature superconductor

    International Nuclear Information System (INIS)

    Gweon, G.-H.; Sasagawa, T.; Zhou, S.Y.; Graf, J.; Takagi, H.; Lee, D.-H.; Lanzara, A.

    2004-01-01

    In conventional superconductors, the electron pairing that allows superconductivity is caused by exchange of virtual phonons, which are quanta of lattice vibration. For high-transition-temperature (high-Tc) superconductors, it is far from clear that phonons are involved in the pairing at all. For example, the negligible change in Tc of optimally doped Bi2Sr2CaCu2O8 (Bi2212) upon oxygen isotope substitution (16O to 18O leads to Tc decreasing from 92 to 91 K) has often been taken to mean that phonons play an insignificant role in this material. Here we provide a detailed comparison of the electron dynamics of Bi2212 samples containing different oxygen isotopes, using angle-resolved photoemission spectroscopy. Our data show definite and strong isotope effects. Surprisingly, the effects mainly appear in broad high-energy humps, commonly referred to as ''incoherent peaks''. As a function of temperature and electron momentum, the magnitude of the isotope effect closely correlates with the superconducting gap--that is, the pair binding energy. We suggest that these results can be explained in a dynamic spin-Peierls picture, where the singlet pairing of electrons and the electron-lattice coupling mutually enhance each other

  8. Isotope effects in the non enzymic glycation of hemoglobin catalyzed by DPG

    International Nuclear Information System (INIS)

    Gil, Herminia; Uzcategui, Jorge

    1993-01-01

    The paradigmatic reaction of glucose with hemoglobin (Hb A o ) has been studied and is known to occur most rapidly at the N-terminal valine of the β-subunit. An initial, rapid imine formation is succeeded by slower Amadori rearrangement. Non enzymic glycation of Hb A o was studied in vitro in buffer Tris 10 mM in H 2 O and D 2 O, pH 7.3, pD 7.8 at 37 deg C at a fixed concentration of 2,3 diphosphoglycerate (DPG). The reaction exhibits identical rates in protium and deuterium oxides. When D-glucose-2-h is compared with D-glucose-2-d, the kinetic isotope effect for the DPG-dependent rate is 2.1 ± 0.3, while the DPG-independent rate constant shows no isotope effect (1.1 ± 0.1). The absence of a rate in isotopic water solvents shows that proton donation for solvent, lyons or DPG does not limit the rate. The substrate isotope effect of around 2 for the DPG kinetic term indicates that the proton abstraction step of the Amadori rearrangement by DPG is wholly or partially rate-limiting for this reaction. (author)

  9. Isotope effects in the non enzymic glycation of hemoglobin catalyzed by DPG

    Energy Technology Data Exchange (ETDEWEB)

    Gil, Herminia; Uzcategui, Jorge [Universidad de Los Andes, Merida (Venezuela). Dept. de Quimica

    1993-12-31

    The paradigmatic reaction of glucose with hemoglobin (Hb A{sub o}) has been studied and is known to occur most rapidly at the N-terminal valine of the {beta}-subunit. An initial, rapid imine formation is succeeded by slower Amadori rearrangement. Non enzymic glycation of Hb A{sub o} was studied in vitro in buffer Tris 10 mM in H{sub 2} O and D{sub 2} O, pH 7.3, pD 7.8 at 37 deg C at a fixed concentration of 2,3 diphosphoglycerate (DPG). The reaction exhibits identical rates in protium and deuterium oxides. When D-glucose-2-h is compared with D-glucose-2-d, the kinetic isotope effect for the DPG-dependent rate is 2.1 {+-} 0.3, while the DPG-independent rate constant shows no isotope effect (1.1 {+-} 0.1). The absence of a rate in isotopic water solvents shows that proton donation for solvent, lyons or DPG does not limit the rate. The substrate isotope effect of around 2 for the DPG kinetic term indicates that the proton abstraction step of the Amadori rearrangement by DPG is wholly or partially rate-limiting for this reaction. (author) 23 refs., 4 figs.

  10. Interactive Effects of CO2 Concentration and Water Regime on Stable Isotope Signatures, Nitrogen Assimilation and Growth in Sweet Pepper

    Directory of Open Access Journals (Sweden)

    María D. Serret

    2018-01-01

    Full Text Available Sweet pepper is among the most widely cultivated horticultural crops in the Mediterranean basin, being frequently grown hydroponically under cover in combination with CO2 fertilization and water conditions ranging from optimal to suboptimal. The aim of this study is to develop a simple model, based on the analysis of plant stable isotopes in their natural abundance, gas exchange traits and N concentration, to assess sweet pepper growth. Plants were grown in a growth chamber for near 6 weeks. Two [CO2] (400 and 800 μmol mol−1, three water regimes (control and mild and moderate water stress and four genotypes were assayed. For each combination of genotype, [CO2] and water regime five plants were evaluated. Water stress applied caused significant decreases in water potential, net assimilation, stomatal conductance, intercellular to atmospheric [CO2], and significant increases in water use efficiency, leaf chlorophyll content and carbon isotope composition, while the relative water content, the osmotic potential and the content of anthocyanins did change not under stress compared to control conditions support this statement. Nevertheless, water regime affects plant growth via nitrogen assimilation, which is associated with the transpiration stream, particularly at high [CO2], while the lower N concentration caused by rising [CO2] is not associated with stomatal closure. The stable isotope composition of carbon, oxygen, and nitrogen (δ13C, δ18O, and δ15N in plant matter are affected not only by water regime but also by rising [CO2]. Thus, δ18O increased probably as response to decreases in transpiration, while the increase in δ15N may reflect not only a lower stomatal conductance but a higher nitrogen demand in leaves or shifts in nitrogen metabolism associated with decreases in photorespiration. The way that δ13C explains differences in plant growth across water regimes within a given [CO2], seems to be mediated through its direct

  11. Deuterium isotope effects on toluene metabolism. Product release as a rate-limiting step in cytochrome P-450 catalysis

    International Nuclear Information System (INIS)

    Ling, K.H.; Hanzlik, R.P.

    1989-01-01

    Liver microsomes from phenobarbital-induced rats oxidize toluene to a mixture of benzyl alcohol plus o-, m- and p-cresol (ca. 69:31). Stepwise deuteration of the methyl group causes stepwise decreases in the yield of benzyl alcohol relative to cresols (ca. 24:76 for toluene-d3). For benzyl alcohol formation from toluene-d3 DV = 1.92 and D(V/K) = 3.53. Surprisingly, however, stepwise deuteration induces stepwise increases in total oxidation, giving rise to an inverse isotope effect overall (DV = 0.67 for toluene-d3). Throughout the series (i.e. d0, d1, d2, d3) the ratios of cresol isomers remain constant. These results are interpreted in terms of product release for benzyl alcohol being slower than release of cresols (or their epoxide precursors), and slow enough to be partially rate-limiting in turnover. Thus metabolic switching to cresol formation causes a net acceleration of turnover

  12. Excitation functions and isotopic effects in (n, p) reactions for stable nickel isotopes from reaction threshold to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Lalremruata, B. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: marema@physics.unipune.ernet.in; Ganesan, S. [Reactor Physics Design Division, BARC, Mumbai 58 (India); Bhoraskar, V.N. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: vnb@physics.unipune.ernet; Dhole, S.D. [Department of Physics, University of Pune, Ganeshkhind, Pune-411007, Maharashtra (India)], E-mail: sanjay@physics.unipune.ernet.in

    2009-05-01

    The excitation function for (n, p) reactions from reaction threshold to 20 MeV on five nickel isotopes viz; {sup 58}Ni, {sup 60}Ni, {sup 61}Ni, {sup 62}Ni and {sup 64}Ni were calculated using Talys-1.0 nuclear model code involving the fixed set of global parameters. A good agreement between the calculated and measured data is obtained with minimum effort on parameter fitting and only one free parameter called 'Shell damping factor'. This is of importance to the validation of nuclear model approaches with increased predictive power. The systematic decrease in (n, p) cross-sections with increasing neutron number in reactions induced by neutrons on isotopes of nickel is explained in terms of the proton separation energy and the pre-equilibrium model. The compound nucleus and pre-equilibrium reaction mechanism as well as the isotopic effects were also studied.

  13. Effect on phloridzin on net rate of liquid absorption from the pleural space of rabbits.

    Science.gov (United States)

    Zocchi, L; Agostoni, E; Raffaini, A

    1996-11-01

    Previous indirect findings have suggested the occurrence of solute-coupled liquid absorption from the pleural space, consistent with Na(+)-K(+)-ATPase on the interstitial side plus a Na(+)-H+ and CI(-)-HCO3- double exchange on the luminal side of the pleural mesothelium. To assess whether Na(+)-glucose cotransport also operates on the luminal side, the relationship between net rate of liquid absorption from the right pleural space (Jnet) and volume of liquid injected into this space (0.5, 1 or 2 ml) was determined in anaesthetized rabbits during hydrothoraces with phloridzin (10(-3)M) or with phloridzin plus 4-acetamido-4'-isothiocyanatostilbene-2, 2'-disulphonic acid (SITS; 1.5 x 10(-4)M). The relationship obtained during hydrothoraces with phloridzin was displaced downwards by 0.09 ml h-1 relative to that in control hydrothoraces (P pleural mesothelium, operating simultaneously with the double exchange also under physiological conditions.

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

    Energy Technology Data Exchange (ETDEWEB)

    Berhanu, Tesfaye A.; Erbland, Joseph; Savarino, Joël [Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, F-38041 Grenoble (France); Univ. Grenoble Alpes, LGGE, F-38041 Grenoble (France); Meusinger, Carl; Johnson, Matthew S. [Copenhagen Center for Atmospheric Research (CCAR), Department of Chemistry, University of Copenhagen, Copenhagen (Denmark); Jost, Rémy [Laboratoire de Interdisciplinaire de Physique (LIPHY) Univ. de Grenoble, Grenoble (France); Bhattacharya, S. K. [Research Center for Environmental Changes, Academia Sinica, Nangang, Taipei 115, Taiwan (China)

    2014-06-28

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

  15. Preliminary Failure Modes, Effects and Criticality Analysis (FMECA) of the conceptual Brayton Isotope Power System (BIPS) Flight System

    International Nuclear Information System (INIS)

    Miller, L.G.

    1976-01-01

    A failure modes, effects and criticality analysis (FMECA) was made of the Brayton Isotope Power System Flight System (BIPS-FS) as presently conceived. The components analyzed include: Mini-BRU; Heat Source Assembly (HSA); Mini-Brayton Recuperator (MBR); Space Radiator; Ducts and Bellows, Insulation System; Controls; and Isotope Heat Source (IHS)

  16. Using Beads and Divided Containers to Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom

    Science.gov (United States)

    Campbell, Dean J.; Brewer, Emily R.; Martinez, Keri A.; Fitzjarrald, Tamara J.

    2017-01-01

    The purpose of this laboratory experiment is to study fundamental concepts of kinetics and equilibria and the isotope effects associated with both of these concepts. The concepts of isotopes in introductory and general chemistry courses are typically used within the contexts of atomic weights and radioactivity. Kinetic and equilibrium isotope…

  17. Solvent effects and secondary isotope effects for probing diradical character in the thermal decarboxylation of β-peroxylactones

    International Nuclear Information System (INIS)

    Adam, W.; Cueto, O.; Guedes, L.N.; Rodriguez, L.O.

    1978-01-01

    The lack of solvent effects in the activation parameters and product distribution and the lack of secondary deuterium isotope effects at the α-carbon and β-alkyl migrant substantiates that the thermal decarboxylation of β-peroxy lactones proceeds via a 1,5-diradical

  18. Large effect of irradiance on hydrogen isotope fractionation of alkenones in Emiliania huxleyi

    Science.gov (United States)

    van der Meer, Marcel T. J.; Benthien, Albert; French, Katherine L.; Epping, Eric; Zondervan, Ingrid; Reichart, Gert-Jan; Bijma, Jelle; Sinninghe Damsté, Jaap S.; Schouten, Stefan

    2015-07-01

    The hydrogen isotopic (δD) composition of long-chain alkenones produced by certain haptophyte algae has been suggested as a potential proxy for reconstructing paleo sea surface salinity. However, environmental parameters other than salinity may also affect the δD of alkenones. We investigated the impact of the level of irradiance on hydrogen isotopic fractionation of alkenones versus growth water by cultivating two strains of the cosmopolitan haptophyte Emiliania huxleyi at different light intensities. The hydrogen isotope fractionation decreased by approximately 40‰ when irradiance was increased from 15 to 200 μmol photons m-2 s-1 above which it was relatively constant. The response is likely a direct effect of photosystem I and II activity as the relationship of the fractionation factor α versus light intensity can be described by an Eilers-Peeters photosynthesis model. This irradiance effect is in agreement with published δD data of alkenones derived from suspended particulate matter collected from different depths in the photic zone of the Gulf of California and the eastern tropical North Pacific. However, haptophyte algae tend to bloom at relatively high light intensities (>500 μmol photons m-2 s-1) occurring at the sea surface, at which hydrogen isotope fractionation is relatively constant and not affected by changes in light intensity. Alkenones accumulating in the sediment are likely mostly derived from these surface water haptophyte blooms, when the largest amount of biomass is produced. Therefore, the observed irradiance effect is unlikely to affect the applicability of the hydrogen isotopic composition of sedimentary long chain alkenones as a proxy for paleosalinity.

  19. Solvent isotope effects upon the thermodynamics of some transition-metal redox couples in aqueous media

    International Nuclear Information System (INIS)

    Weaver, M.J.; Nettles, S.M.

    1980-01-01

    The effects of substituting D 2 O for H 2 O as solvent upon the formal potentials of a number of transition-metal redox couples containing aquo, ammine, and simple chelating ligands have been investigated with the intention of evaluating the importance of specific solvation factors in the thermodynamics of such couples. The solvent liquid junction formed between H 2 O and D 2 O was shown to have a negligible effect on the measured formal potentials. Substantial solvent isotope effects were observed for a number of these systems, particularly for couples containing aquo ligands. The effects of separately deuterating the ligands and the surrounding solvent were investigated for some ammine couples. Possible origins of the solvent isotope effects are discussed in terms of changes in metal-ligand and ligand-solvent interactions. It is tentatively concluded that the latter influence provides the predominant contribution to the observed effects for aquo couples arising from increases in the extent of hydrogen bonding between the aquo ligands and surrounding solvent when D 2 O replaces H 2 O. The implications of these results in unraveling the solvent isotope effects upon the kinetics of simple redox reactions are also considered

  20. Effect of light on N2 fixation and net nitrogen release of Trichodesmium in a field study

    Science.gov (United States)

    Lu, Yangyang; Wen, Zuozhu; Shi, Dalin; Chen, Mingming; Zhang, Yao; Bonnet, Sophie; Li, Yuhang; Tian, Jiwei; Kao, Shuh-Ji

    2018-01-01

    Dinitrogen fixation (NF) by marine cyanobacteria is an important pathway to replenish the oceanic bioavailable nitrogen inventory. Light is the key to modulating NF; however, field studies investigating the light response curve (NF-I curve) of NF rate and the effect of light on diazotroph-derived nitrogen (DDN) net release are relatively sparse in the literature, hampering prediction using models. A dissolution method was applied using uncontaminated 15N2 gas to examine how the light changes may influence the NF intensity and DDN net release in the oligotrophic ocean. Experiments were conducted at stations with diazotrophs dominated by filamentous cyanobacterium Trichodesmium spp. in the western Pacific and the South China Sea. The effect of light on carbon fixation (CF) was measured in parallel using the 13C tracer method specifically for a station characterized by Trichodesmium bloom. Both NF-I and CF-I curves showed a Ik (light saturation coefficient) range of 193 to 315 µE m-2 s-1, with light saturation at around 400 µE m-2 s-1. The proportion of DDN net release ranged from ˜ 6 to ˜ 50 %, suggesting an increasing trend as the light intensity decreased. At the Trichodesmium bloom station, we found that the CF / NF ratio was light-dependent and the ratio started to increase as light was lower than the carbon compensation point of 200 µE m-2 s-1. Under low-light stress, Trichodesmium physiologically preferred to allocate more energy for CF to alleviate the intensive carbon consumption by respiration; thus, there is a metabolism tradeoff between CF and NF pathways. Results showed that short-term ( energy associated with the variation in light intensity would be helpful for prediction of the global biogeochemical cycle of N by models involving Trichodesmium blooms.

  1. Health impact and cost-effectiveness of a private sector bed net distribution: experimental evidence from Zambia.

    Science.gov (United States)

    Sedlmayr, Richard; Fink, Günther; Miller, John M; Earle, Duncan; Steketee, Richard W

    2013-03-18

    Relatively few programmes have attempted to actively engage the private sector in national malaria control efforts. This paper evaluates the health impact of a large-scale distribution of insecticide-treated nets (ITNs) conducted in partnership with a Zambian agribusiness, and its cost-effectiveness from the perspective of the National Malaria Control Programme (NMCP). The study was designed as a cluster-randomized controlled trial. A list of 81,597 cotton farmers was obtained from Dunavant, a contract farming company in Zambia's cotton sector, in December 2010. 39,963 (49%) were randomly selected to obtain one ITN each. Follow-up interviews were conducted with 438 farmers in the treatment and 458 farmers in the control group in June and July 2011. Treatment and control households were compared with respect to bed net ownership, bed net usage, self-reported fever, and self-reported confirmed malaria. Cost data was collected throughout the programme. The distribution effectively reached target beneficiaries, with approximately 95% of households in the treatment group reporting that they had received an ITN through the programme. The average increase in the fraction of household members sleeping under an ITN the night prior to the interview was 14.6 percentage points (p-value US$ per ITN to Zambia's NMCP. The results illustrate that existing private sector networks can efficiently control malaria in remote rural regions. The intra-household allocation of ITNs distributed through this channel was comparable to that of ITNs received from other sources, and the health impact remained substantial.

  2. SkyNet: Modular nuclear reaction network library

    Science.gov (United States)

    Lippuner, Jonas; Roberts, Luke F.

    2017-10-01

    The general-purpose nuclear reaction network SkyNet evolves the abundances of nuclear species under the influence of nuclear reactions. SkyNet can be used to compute the nucleosynthesis evolution in all astrophysical scenarios where nucleosynthesis occurs. Any list of isotopes can be evolved and SkyNet supports various different types of nuclear reactions. SkyNet is modular, permitting new or existing physics, such as nuclear reactions or equations of state, to be easily added or modified.

  3. Dose formation and hematologic effects with prolonged internal exposure of rats by isotope 131I

    International Nuclear Information System (INIS)

    Sova, O.A.; Drozd, Yi.P.

    2013-01-01

    Processes in single dose formation and long-term domestic revenue 131 I in rats was investigated. Original method of estimating absorbed doses in hemacyte for macro-dosemeters indicators was proposed. Dose factors for hemacyte and the dynamics of the blood-forming organs doses for prolonged two cases of prolonged exposure was calculated. Hematologic effects were studied for two variants of entry of the isotope. Peculiarities of doses formation and identified hematological effects are discussed

  4. Isotope effect on the zero point energy shift upon condensation. I. Formulation and application to ethylene, methane, and fluoromethanes

    International Nuclear Information System (INIS)

    Kornblum, Z.C.; Ishida, T.

    1978-01-01

    A method of evaluating the isotope effect (IE) on the zero point energy (ZPE) shift upon condensation due to the London dispersion forces in the liquid has been formulated. It is expressed to the first order, as a product of an isotope-independent liquid factor and a factor of isotopic differences in gas-phase properties. The theory has been tested by calculating the effective atomic charges for carbon and hydrogen in ethylene, according to the CNDO/2 molecular orbital algorithm, and it correctly predicts the magnitude of the IE on the ZPE shift and the first-order sum rules involving the isotopic ethylenes. However, it fails to explain the difference in vapor pressures of isotopic isomers. The theory has also been applied to the D/H and to the 13 C/ 12 C isotope effects in methane and fluoromethanes. The results obtained from the CNDO/2 calculations have been compared with the experimental values of the total infrared absorption intensities and of the IE on the ZPE shift of isotopic methanes. Based on these calculations, the molecular properties that enhance the stronger dispersion forces in the liquid phase between the lighter molecules than between the isotopically heavier molecules, and hence favor a large IE on the ZPE shift, have been deduced

  5. Flood effects on efflux and net production of nitrous oxide in river floodplain soils

    Science.gov (United States)

    Riaz, Muhammad; Bruderer, Christian; Niklaus, Pascal A.; Luster, Jörg

    2016-04-01

    Floodplain soils are often rich in nutrients and exhibit high spatial heterogeneity in terms of geomorphology, soil environmental conditions and substrate availability for processes involved in carbon and nutrient cycling. In addition, fluctuating water tables lead to temporally changing redox conditions. In such systems, there are ideal conditions for the occurrence of hot spots and moments of nitrous oxide emissions, a potent greenhouse gas. The factors that govern the spatial heterogeneity and dynamics of N2O formation in floodplain soils and the surface efflux of this gas are not fully understood. A particular issue is the contribution of N2O formation in the subsoil to surface efflux. We studied this question in the floodplain of a restored section of the Thur river (NE Switzerland) which is characterized by a flashy flow regime. As a consequence, the floodplain soils are unsaturated most of the time. We showed earlier that saturation during flood pulses leads to short phases of generally anoxic conditions followed by a drying phase with anoxic conditions within aggregates and oxic conditions in larger soil pores. The latter conditions are conducive for spatially closely-coupled nitrification-denitrification and related hot moments of nitrous oxide formation. In a floodplain zone characterized by about one meter of young, sandy sediments, that are mostly covered by the tall grass Phalaris arundinacea, we measured at several time points before and after a small flood event N2O surface efflux with the closed-chamber method, and assessed N2O concentrations in the soil air at four different depths using gas-permeable tubings. In addition, we calculated the N2O diffusivity in the soil from Radon diffusivity. The latter was estimated in-situ from the recovery of Radon concentration in the gas-permeable tubings after purging with ambient air. All these data were then used to calculate net N2O production rates at different soil depths with the gradient method. In

  6. Isotope exchange reactions on ceramic breeder materials and their effect on tritium inventory

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, M; Baba, A [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Kawamura, Y; Nishi, M

    1998-03-01

    Though lithium ceramic materials such as Li{sub 2}O, LiAlO{sub 2}, Li{sub 2}ZrO{sub 3}, Li{sub 2}TiO{sub 3} and Li{sub 4}SiO{sub 4} are considered as breeding materials in the blanket of a D-T fusion reactor, the release behavior of the bred tritium in these solid breeder materials has not been fully understood. The isotope exchange reaction rate between hydrogen isotopes in the purge gas and tritium on the surface of breeding materials have not been quantified yet, although helium gas with hydrogen or deuterium is planned to be used as the blanket purge gas in the recent blanket designs. The mass transfer coefficient representing the isotope exchange reaction between H{sub 2} and D{sub 2}O or that between D{sub 2} and H{sub 2}O in the ceramic breeding materials bed is experimentally obtained in this study. Effects of isotope exchange reactions on the tritium inventory in the bleeding blanket is discussed based on data obtained in this study where effects of diffusion of tritium in the grain, absorption of water in the bulk of grain, and adsorption of water on the surface of grain, together with two types of isotope exchange reactions are considered. The way to estimate the tritium inventory in a Li{sub 2}ZrO{sub 3} blanket used in this study shows a good agreement with data obtained in such in-situ experiments as MOZART, EXOTIC-5, 6 and TRINE experiments. (author)

  7. First-principles theory of anharmonicity and the inverse isotope effect in superconducting palladium-hydride compounds.

    Science.gov (United States)

    Errea, Ion; Calandra, Matteo; Mauri, Francesco

    2013-10-25

    Palladium hydrides display the largest isotope effect anomaly known in the literature. Replacement of hydrogen with the heavier isotopes leads to higher superconducting temperatures, a behavior inconsistent with harmonic theory. Solving the self-consistent harmonic approximation by a stochastic approach, we obtain the anharmonic free energy, the thermal expansion, and the superconducting properties fully ab initio. We find that the phonon spectra are strongly renormalized by anharmonicity far beyond the perturbative regime. Superconductivity is phonon mediated, but the harmonic approximation largely overestimates the superconducting critical temperatures. We explain the inverse isotope effect, obtaining a -0.38 value for the isotope coefficient in good agreement with experiments, hydrogen anharmonicity being mainly responsible for the isotope anomaly.

  8. Tungsten isotopic compositions of iron meteorites: Chronological constraints vs. cosmogenic effects

    Science.gov (United States)

    Markowski, A.; Quitté, G.; Halliday, A. N.; Kleine, T.

    2006-02-01

    High-precision W isotopic compositions are presented for 35 iron meteorites from 7 magmatic groups (IC, IIAB, IID, IIIAB, IIIF, IVA, and IVB) and 3 non-magmatic groups (IAB, IIICD, and IIE). Small but resolvable isotopic variations are present both within and between iron meteorite groups. Variations in the 182W/ 184W ratio reflect either time intervals of metal-silicate differentiation, or result from the burnout of W isotopes caused by a prolonged exposure to galactic cosmic rays. Calculated apparent time spans for some groups of magmatic iron meteorites correspond to 8.5 ± 2.1 My (IID), 5.1 ± 2.3 My (IIAB), and 5.3 ± 1.3 My (IVB). These time intervals are significantly longer than those predicated from models of planetesimal accretion. It is shown that cosmogenic effects can account for a large part of the W isotopic variation. No simple relationship exists with exposure ages, compromising any reliable method of correction. After allowance for maximum possible cosmogenic effects, it is found that there is no evidence that any of the magmatic iron meteorites studied here have initial W isotopic compositions that differ from those of Allende CAIs [ ɛ182W = - 3.47 ± 0.20; [T. Kleine, K. Mezger, H. Palme, E. Scherer and C. Münker, Early core formation in asteroids and late accretion of chondrite parent bodies: evidence from 182Hf- 182W in CAIs, metal-rich chondrites and iron meteorites, Geochim. Cosmochim. Acta (in press)]. Cosmogenic corrections cannot yet be made with sufficient accuracy to obtain highly precise ages for iron meteorites. Some of the corrected ages nevertheless require extremely early metal-silicate segregation no later than 1 My after formation of CAIs. Therefore, magmatic iron meteorites appear to provide the best examples yet identified of material derived from the first planetesimals that grew by runaway growth, as modelled in dynamic simulations. Non-magmatic iron meteorites have a more radiogenic W isotopic composition than magmatic

  9. Isotope and fast ions turbulence suppression effects: Consequences for high-β ITER plasmas

    Science.gov (United States)

    Garcia, J.; Görler, T.; Jenko, F.

    2018-05-01

    The impact of isotope effects and fast ions on microturbulence is analyzed by means of non-linear gyrokinetic simulations for an ITER hybrid scenario at high beta obtained from previous integrated modelling simulations with simplified assumptions. Simulations show that ITER might work very close to threshold, and in these conditions, significant turbulence suppression is found from DD to DT plasmas. Electromagnetic effects are shown to play an important role in the onset of this isotope effect. Additionally, even external ExB flow shear, which is expected to be low in ITER, has a stronger impact on DT than on DD. The fast ions generated by fusion reactions can additionally reduce turbulence even more although the impact in ITER seems weaker than in present-day tokamaks.

  10. Gamma-radiation and isotopic effect on the critical behavior in triglycine selenate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kassem, M.E.; Hamed, A.E.; Abulnasr, L.; Abboudy, S. [Alexandria Univ. (Egypt). Dept. of Physics

    1994-11-01

    Isotopic effects in pure and {gamma}-irradiated triglycine selenate crystals were investigated using the specific heat (C{sub p}) technique. The obtained results showed an interesting dependence of the critical behavior of C{sub p} on the deuterium content. With increasing content of deuterium, the character of the phase transition changed from a second order ({lambda}-type) to a first order transition. After {gamma}-irradiation, the behavior of C{sub p} around the phase transition region was essentially affected. The transition temperature, T{sub c}, decreased and {Delta}C{sub p} depressed, and the transition became broad. It was noted that the effect of {gamma}-irradiation is opposite to the isotopic effect. (author).

  11. The effects of Earth's magnetic field on 3-inch diameter photomultipliers used in KM3NeT neutrino telescope

    Directory of Open Access Journals (Sweden)

    Giordano V.

    2016-01-01

    Full Text Available The KM3NeT neutrino telescope will be the largest underwater neutrino telescope and will be located in the abyss of the Mediterranean Sea. In neutrino telescopes the key element of the detector is the optical module and for KM3NeT it consists of 31 PMTs stored inside a transparent pressure-resistant glass sphere of 17-inch that serves as mechanical protection while ensuring good light transmission. Since the PMTs installed into an underwater neutrino telescope can change their orientation because of movements of the detector structure due to sea currents, the influence of Earth's magnetic field has been investigated. Magnetic shielding by means of a mu-metal cage is used to reduce magnetic effects and to make the response of the PMT sufficiently orientation independent. In order to quantify the effect on magnetic field, we compared measurements on variation of gain, transit time spread and detection efficiency for a 3-inch PMT in shielded and unshielded condition at 3 PMT inclinations. Data shows that variations are sufficiently low especially for timing properties.

  12. Net air emissions from electric vehicles: the effect of carbon price and charging strategies.

    Science.gov (United States)

    Peterson, Scott B; Whitacre, J F; Apt, Jay

    2011-03-01

    Plug-in hybrid electric vehicles (PHEVs) may become part of the transportation fleet on time scales of a decade or two. We calculate the electric grid load increase and emissions due to vehicle battery charging in PJM and NYISO with the current generation mix, the current mix with a $50/tonne CO(2) price, and this case but with existing coal generators retrofitted with 80% CO(2) capture. We also examine all new generation being natural gas or wind+gas. PHEV fleet percentages between 0.4 and 50% are examined. Vehicles with small (4 kWh) and large (16 kWh) batteries are modeled with driving patterns from the National Household Transportation Survey. Three charging strategies and three scenarios for future electric generation are considered. When compared to 2020 CAFE standards, net CO(2) emissions in New York are reduced by switching from gasoline to electricity; coal-heavy PJM shows somewhat smaller benefits unless coal units are fitted with CCS or replaced with lower CO(2) generation. NO(X) is reduced in both RTOs, but there is upward pressure on SO(2) emissions or allowance prices under a cap.

  13. Remote Laboratory NetLab for Effective Teaching of 1st Year Engineering Students

    Directory of Open Access Journals (Sweden)

    Z. Nedic

    2007-08-01

    Full Text Available Practical skills are important attributes of every engineering graduate. The Internet has provided tertiary education with the opportunity to develop innovative learning environments. The teaching and learning of practical skills has gained a new dimension with the emergence of remote laboratories. The rapidly growing number of remote laboratories (RL worldwide is the evidence that the educational community has recognized their potential to develop into a creative, flexible, engaging, and student-cantered learning environment. Even a brief review of the existing RLs shows a large diversity in their structure, design and implementation. However, not many researchers disclose how their RLs are integrated within their curricula. Therefore, an important question still remains to be answered: how to optimize the design of RLs and their integration in a course curriculum for the best learning outcomes? This problem is particularly important when RLs are used in teaching 1st year students who have limited technical knowledge and practical experience in using real equipment. In this paper we would like to share our experiences with NetLab, an RL developed at the University of South Australia (UniSA for teaching 1st year engineering students and make recommendations for improvements in teaching practices based on it.

  14. Effects of climate warming on net primary productivity in China during 1961-2010.

    Science.gov (United States)

    Gu, Fengxue; Zhang, Yuandong; Huang, Mei; Tao, Bo; Guo, Rui; Yan, Changrong

    2017-09-01

    The response of ecosystems to different magnitudes of climate warming and corresponding precipitation changes during the last few decades may provide an important reference for predicting the magnitude and trajectory of net primary productivity (NPP) in the future. In this study, a process-based ecosystem model, Carbon Exchange between Vegetation, Soil and Atmosphere (CEVSA), was used to investigate the response of NPP to warming at both national and subregional scales during 1961-2010. The results suggest that a 1.3°C increase in temperature stimulated the positive changing trend in NPP at national scale during the past 50 years. Regardless of the magnitude of temperature increase, warming enhanced the increase in NPP; however, the positive trend of NPP decreased when warming exceeded 2°C. The largest increase in NPP was found in regions where temperature increased by 1-2°C, and this rate of increase also contributed the most to the total increase in NPP in China's terrestrial ecosystems. Decreasing precipitation depressed the positive trend in NPP that was stimulated by warming. In northern China, warming depressed the increasing trend of NPP and warming that was accompanied by decreasing precipitation led to negative changing trends in NPP in large parts of northern China, especially when warming exceeded 2°C. However, warming stimulated the increase in NPP until warming was greater than 2°C, and decreased precipitation helped to increase the NPP in southern China.

  15. The Isotopologue Record of Repeat Vital Effect Offenders: Tracking (Dis)equilibrium Effects in Sea Urchins and Nannofossil Using Clumped Isotopes

    Science.gov (United States)

    John, C. M.; Davies, A.; Drury, A. J.

    2016-12-01

    Vital effects vary between species and affect various isotopic systems in unequal proportion. The magnitude of the response of different isotopic systems might thus be key in understanding biologically-mediated disequilibrium, especially in groups that show a tendency to be "repeat offenders" with regards to vital effects. Here we present carbon, oxygen, and clumped isotope data from echinoderm calcite and nannofossil ooze, both of which exhibit strong vital effects in bulk isotopes. Our study is the first to investigate the clumped isotope (dis)equilibrium of echinoids. Results from two echinoids, three marine gastropods and a bivalve mollusk from modern beach deposits of Bali, Indonesia, highlight a significant offset in clumped isotopes of a regular echinoid test from expected values, interpreted as evidence of a similar "vital effect" as observed in surface corals. This is in contrast to the test of an irregular "sand dollar" echinoid, with clumped isotope values within error of expected sea surface temperature. Furthermore, data on the inter-skeletal variability in the clumped isotopic composition of two regular echinoid species shows that the spines of the echinoids are in equilibrium with seawater with respect to clumped isotopes, but the test is not. For the nannofossil material, no clumped isotope vital effects are observed, consistent with previously published studies but at odds with strong vital effects in carbon and oxygen isotopes, often correlated with cell-size. In addition, we reveal that the <63 micron fraction of deep-sea ooze could constitute useful material for clumped isotope studies. An intriguing result of our study is that vital effects are mostly absent in clumped isotopes, even in phylums known for important isotopic effects. It remains to be explained why some parts of the echinoids show clear vital effects, notably enrichment in clumped isotopes of urchin tests. Mechanisms that could explain this include pH effects during calcification

  16. The economic effect of electricity net-metering with solar PV: Consequences for network cost recovery, cross subsidies and policy objectives

    International Nuclear Information System (INIS)

    Eid, Cherrelle; Reneses Guillén, Javier; Frías Marín, Pablo; Hakvoort, Rudi

    2014-01-01

    Net-metering is commonly known as a practice by which owners of distributed generation (DG) units may offset their electricity consumption from the grid with local generation. The increasing number of prosumers (consumers that both produce and consume electricity) with solar photovoltaic (PV) generation combined with net-metering results in reduced incomes for many network utilities worldwide. Consequently, this pushes utilities to increase charges per kW h in order to recover costs. For non-PV owners, this could result into inequality issues due to the fact that also non-PV owners have to pay higher chargers for their electricity consumed to make up for netted costs of PV-owners. In order to provide insight in those inequality issues caused by net-metering, this study presents the effects on cross-subsidies, cost recovery and policy objectives evolving from different applied netmetering and tariff designs for a residential consumer. Eventually this paper provides recommendations regarding tariffs and metering that will result in more explicit incentives for PV, instead of the current implicit incentives which are present to PV owners due to net-metering. - Highlights: • Network users are frequently charged by energy charging and fixed charging. • Net-metering with energy charging causes potential problems for DSO cost recovery. • Increasing rolling credit timeframes amplify net-metering impacts on cost recovery. • Observed capacity charging can incentivize local storage and self-consumption. • PV owners should receive direct incentives in order to avoid cross subsidization

  17. Experimental investigation of nitrogen isotopic effects associated with ammonia degassing at 0-70 °C

    Science.gov (United States)

    Deng, Yuying; Li, Yingzhou; Li, Long

    2018-04-01

    Ammonia degassing is a common process in natural alkaline waters and in the atmosphere. To quantitatively assess the nitrogen cycle in these systems, the essential parameter of nitrogen isotope fractionation factors associated with ammonia degassing is required, but still not constrained yet. In this study, we carried out laboratory experiments to examine the nitrogen isotope behavior during ammonia degassing in alkaline conditions. The experiments started with ammonium sulfate solution with excess sodium hydroxide. The reaction can be described as: NH4+ + OH- (excess) → NH3·nH2O → NH3 (g)↑. Two sets of experiments, one with ammonia degassing under static conditions and the other with ammonia degassing by bubbling of N2 gas, were carried out at 2, 21, 50, and 70 °C. The results indicate that kinetic isotopic effects are dominated during efficient degassing of ammonia in the bubbling experiments, which yielded kinetic nitrogen isotope fractionation factors αNH3(g)-NH3(aq) of 0.9898 at 2 °C, 0.9918 at 21 °C, 0.9935 at 50 °C and 0.9948 at 70 °C. These values show a good relationship with temperature as 103lnαNH3(g)-NH3(aq) = 14.6 - 6.8 × 1000/T. In contrast, isotopic effects during less efficient degassing of ammonia in the static experiments are more complicated. The results do not match either kinetic isotope fractionation or equilibrium isotope fractionation but sit between these two. The most likely cause is that back dissolution of the degassed ammonia occurred in these experiments and consequently shifted kinetic isotope fractionation toward equilibrium isotope fractionation. Our experimental results highlight complicated isotopic effects may occur in natural environments, and need to be fully considered in the interpretation of field data.

  18. The Effect of a Short-term Glucose Deprivation on Neuron Net Functioning of Hippocampus Primary Culture on a Multi-electrode Matrix

    OpenAIRE

    Vedunova M.V.; Korotchenko S.A.; Balashova A.N.; Isakova A.O.; Khaspekov L.G.; Kazantsev V.B.; Mukhina I.V.

    2011-01-01

    There has been studied the effect of a short-term glucose deprivation on neuron net functioning of hippocampus primary culture developing within 32 days on a multi-electrode matrix MED64 (Alpha MED Sciences Company, Japan) in an early and remote periods after deprivation. A short-term glucose deprivation (20 min) has been shown to result in the increase of electrobiological activity of neuron net of hippocampus primary culture, with the cascade of metabolic reactions being activated leading t...

  19. Selecting HVAC Systems to Achieve Comfortable and Cost-effective Residential Net-Zero Energy Buildings.

    Science.gov (United States)

    Wu, Wei; Skye, Harrison M; Domanski, Piotr A

    2018-02-15

    HVAC is responsible for the largest share of energy use in residential buildings and plays an important role in broader implementation of net-zero energy building (NZEB). This study investigated the energy, comfort and economic performance of commercially-available HVAC technologies for a residential NZEB. An experimentally-validated model was used to evaluate ventilation, dehumidification, and heat pump options for the NZEB in the mixed-humid climate zone. Ventilation options were compared to mechanical ventilation without recovery; a heat recovery ventilator (HRV) and energy recovery ventilator (ERV) respectively reduced the HVAC energy by 13.5 % and 17.4 % and reduced the building energy by 7.5 % and 9.7 %. There was no significant difference in thermal comfort between the ventilation options. Dehumidification options were compared to an air-source heat pump (ASHP) with a separate dehumidifier; the ASHP with dedicated dehumidification reduced the HVAC energy by 7.3 % and the building energy by 3.9 %. The ASHP-only option (without dedicated dehumidification) reduced the initial investment but provided the worst comfort due to high humidity levels. Finally, ground-source heat pump (GSHP) alternatives were compared to the ASHP; the GSHP with two and three boreholes reduced the HVAC energy by 26.0 % and 29.2 % and the building energy by 13.1 % and 14.7 %. The economics of each HVAC configuration was analyzed using installation cost data and two electricity price structures. The GSHPs with the ERV and dedicated dehumidification provided the highest energy savings and good comfort, but were the most expensive. The ASHP with dedicated dehumidification and the ERV (or HRV) provided reasonable payback periods.

  20. Effects of UVB radiation on net community production in the upper global ocean

    KAUST Repository

    Garcia-Corral, Lara S.

    2016-08-31

    Aim Erosion of the stratospheric ozone layer together with oligotrophication of the subtropical ocean is leading to enhanced exposure to ultraviolet B (UVB) radiation in ocean surface waters. The impact of increased exposure to UVB on planktonic primary producers and heterotrophs is uncertain. Here we test the null hypothesis that net community production (NCP) of plankton communities in surface waters of the tropical and subtropical ocean is not affected by ambient UVB radiation and extend this test to the global ocean, including the polar oceans and the Mediterranean Sea using previous results. Location We conducted experiments with 131 surface communities sampled during a circumnavigation cruise along the tropical and subtropical ocean and combined these results with 89 previous reports encompassing the Atlantic, Pacific, Arctic and Southern Oceans and the Mediterranean Sea. Methods The use of quartz (transparent to UVB radiation) and borosilicate glass materials (opaque to most UVB) for incubations allowed us to compare NCP between communities where UVB is excluded and those receiving natural UVB radiation. Results We found that NCP varies when exposed to natural UVB radiation compared to those where UVB was removed. NCP of autotrophic communities tended to decrease under natural UVB radiation, whereas the NCP of heterotrophic communities tended to increase. However, these variations showed the opposite trend under higher levels of UVB radiation. Main conclusions Our results suggest that earlier estimates of NCP for surface communities, which were hitherto derived using materials blocking UVB radiation were biased, with the direction and magnitude of this bias depending on the metabolic status of the communities and the underwater penetration of UVB radiation.

  1. Effects of low concentrations of sulfur dioxide on net photosynthesis and dark respiration of Vicia faba

    Energy Technology Data Exchange (ETDEWEB)

    Black, V J; Unsworth, M H

    1979-01-01

    Rates of net photosynthesis, P/sub N/, and dark respiration of Vicia faba plants were measured in the laboratory in clean air and in air containing up to 175 parts 10/sup -9/ (500 ..mu..g m/sup -3/) SO/sub 2/. At all SO/sub 2/ concentrations exceeding 35 parts 10/sup -9/, P/sub N/ was inhibited compared with clean air. At light saturation, the magnitude of inhibition depended on SO/sub 2/ concentration but at low irradiances the inhibition was independent of concentration. Dark respiration rates increased substantially, independent of concentration. When exposures continued for up to 3 days, P/sub N/ returned to clean air values about 1 h after fumigation ceased: dark respiration recovered after one photoperiod. There were no visible injuries. Reviewing possible mechanisms responsible for the inhibition of P/sub N/, it is suggested that SO/sub 2/ competes with CO/sub 2/ for binding sites in RuBP carboxylase. Analysis of resistance analogues demonstrates that SO/sub 2/ altered both stomatal and internal (residual) resistances. A model of crop photosynthesis shows the implications of the observed responses for the growth of field crops in which plants are assumed to respond like laboratory plants. Photosynthesis of the crop would be less sensitive than that of individual plants to SO/sub 2/ concentration. Daily dry matter accumulation of hypothetical polluted crops would be substantially less than clean air values but would vary relatively little with SO/sub 2/ concentration. It is concluded that physiological bases exist to account for observed reductions in growth of plants at very low SO/sub 2/ concentrations, and that thresholds for plant responses to SO/sub 2/ require reassessment. 30 references, 5 figures, 1 table.

  2. Study of isotope effects in the hydrogen transport of an 8% CrWVTa martensitic steel

    International Nuclear Information System (INIS)

    Esteban, G.A.; Sedano, L.A.; Perujo, A.; Douglas, K.

    2001-01-01

    A time-dependent gas-phase isovolumetric desorption technique has been used to assess the isotope effects in the diffusive transport parameters of hydrogen in an 8% CrWVTa reduced activation martensitic steel in the temperature range of 423-892 K and driving pressures from 4 x 10 4 - 1 x 10 5 Pa. The experiments have been run with both protium and deuterium obtaining their respective transport parameters, diffusivity (D), Sieverts' constant (K S ), permeability (Φ), trap site density (η t ) and the trapping activation energy (E t ). Isotope effects on steel are analysed and compared with α-iron. A new way to derive more accurate tritium transport parameters is proposed. (orig.)

  3. Isotope Effects in the Reactions of Chloroform Isotopologues with Cl, OH and OD

    DEFF Research Database (Denmark)

    Nilsson, Elna Johanna Kristina; Johnson, Matthew Stanley; Nielsen, Claus J.

    2009-01-01

    The kinetic isotope effects in the reactions of CHCl3, CDCl3, and 13CHCl3 with Cl, OH, and OD radicals have been determined in relative rate experiments at 298 ( 1 K and atmospheric pressure monitored by long path FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral.......002, kCHCl3+OD/kCDCl3+OD ) 3.95 ( 0.03, and kCHCl3+OD/k13CHCl3+OD ) 1.032 ( 0.004. Larger isotope effects in the OH reactions than in the Cl reactions are opposite to the trends for CH4 and CH3Cl reported in the literature. The origin of these differences was investigated using electronic structure...

  4. A study on the isotope effects in the reduction of carbon dioxide by zinc

    International Nuclear Information System (INIS)

    Senegacnik, M.

    1957-06-01

    We have determined the isotope effects which occur in the reduction of carbon dioxide by zinc. It has been shown that in the case of irreversible surface reactions, Bernstein's equation which permits the calculation of the fractionation factor is still valid. These experimental factors are in good agreement with those obtained by calculating the partition functions of the adsorbed activated complexes. In the reaction mechanism used, the model of the activated complex corresponds to the dissociation of one of the carbon oxygen bonds CO 2 → CO + O. Perturbations arising from the slight reversibility of the reaction Zn + CO 2 ↔ ZnO + CO on the isotope effects on the carbon and oxygen atoms have also been calculated. (author) [fr

  5. Mechanism of Nitrogenase H 2 Formation by Metal-Hydride Protonation Probed by Mediated Electrocatalysis and H/D Isotope Effects

    Energy Technology Data Exchange (ETDEWEB)

    Khadka, Nimesh [Department of Chemistry; Milton, Ross D. [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States; Shaw, Sudipta [Department of Chemistry; Lukoyanov, Dmitriy [Department; Dean, Dennis R. [Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States; Minteer, Shelley D. [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States; Raugei, Simone [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Hoffman, Brian M. [Department; Seefeldt, Lance C. [Department of Chemistry

    2017-09-15

    Nitrogenase catalyzes the reduction of dinitrogen (N2) to ammonia (NH3) with obligatory reduction of protons (H+) to dihydrogen (H2) through a mechanism involving reductive elimination of two [Fe-H-Fe] bridging hydrides at its active site FeMo-cofactor. The overall rate-limiting step is associated with ATP-driven electron delivery from Fe protein, precluding isotope effect measurements on substrate reduction steps. Here, we use mediated bioelectrocatalysis to drive electron delivery to MoFe protein without Fe protein and ATP hydrolysis, thereby eliminating the normal rate-limiting step. The ratio of catalytic current in mixtures of H2O and D2O, the proton inventory, changes linearly with the D2O/H2O ratio, revealing that a single H/D is involved in the rate limiting step. Kinetic models, along with measurements that vary the electron/proton delivery rate and use different substrates, reveal that the rate-limiting step under these conditions is the H2 formation reaction. Altering the chemical environment around the active site FeMo-cofactor in the MoFe protein either by substituting nearby amino acids or transferring the isolated FeMo-cofactor into a different peptide matrix, changes the net isotope effect, but the proton inventory plot remains linear, consistent with an unchanging rate-limiting step. Density functional theory predicts a transition state for H2 formation where the proton from S-H+ moves to the hydride in Fe-H-, predicting the number and magnitude of the observed H/D isotope effect. This study not only reveals the mechanism of H2 formation, but also illustrates a strategy for mechanistic study that can be applied to other enzymes and to biomimetic complexes.

  6. Effect of sodium channel blocker, pilsicainide hydrochloride, on net inward current of atrial myocytes in thyroid hormone toxicosis rats.

    Science.gov (United States)

    Yamakawa, Munesada; Sunagawa, Masanori; Shimabukuro, Michio; Higa, Namio; Takasu, Nobuyuki; Kosugi, Tadayoshi

    2005-07-01

    To investigate effect of pilsicainide hydrochloride (pilsicainide) on electrocardiogram (ECG) signals and action potentials (APs) of atrial myocytes, levo-thyroxine (T4, 500 microg/kg body weight) was daily injected into peritoneal cavity of Sprague-Dawley rats for 14 days. T4-treatment significantly shortened RR interval, P wave, and QRS complex durations on ECG. Although pilsicainide did not affect the heart rate, P wave and corrected QT interval (QTc) was increased in T4-treated rats. AP recordings revealed that AP durations at 20%, 50%, and 90% repolarization were significantly shortened and maximal rate of rise (Max dV/dt) was significantly increased in T4-treated rat atrial cells. Pilsicainide significantly decreased AP amplitude (APA) and Max dV/dt in both control and T4-treated rat atrial cells. Concentration-inhibition study demonstrated that pilsicainide significantly inhibited net inward current of T4-treated rats at lower concentration (IC50 of 29.2 microg/mL) than that of control rats (133 microg/mL). In conclusion, pilsicainide could decrease the conduction velocity in T4-treated rat atrium by decreasing the Max dV/dt and net inward current, which could be a possible treatment of thyrotoxicosis-induced arrhythmia.

  7. Effect of Shock-Induced Cavitation Bubble Collapse on the damage in the Simulated Perineuronal Net of the Brain.

    Science.gov (United States)

    Wu, Yuan-Ting; Adnan, Ashfaq

    2017-07-13

    The purpose of this study is to conduct modeling and simulation to understand the effect of shock-induced mechanical loading, in the form of cavitation bubble collapse, on damage to the brain's perineuronal nets (PNNs). It is known that high-energy implosion due to cavitation collapse is responsible for corrosion or surface damage in many mechanical devices. In this case, cavitation refers to the bubble created by pressure drop. The presence of a similar damage mechanism in biophysical systems has long being suspected but not well-explored. In this paper, we use reactive molecular dynamics (MD) to simulate the scenario of a shock wave induced cavitation collapse within the perineuronal net (PNN), which is the near-neuron domain of a brain's extracellular matrix (ECM). Our model is focused on the damage in hyaluronan (HA), which is the main structural component of PNN. We have investigated the roles of cavitation bubble location, shockwave intensity and the size of a cavitation bubble on the structural evolution of PNN. Simulation results show that the localized supersonic water hammer created by an asymmetrical bubble collapse may break the hyaluronan. As such, the current study advances current knowledge and understanding of the connection between PNN damage and neurodegenerative disorders.

  8. Evidence for H2/D2 isotope effects on Fischer-Tropsch synthesis over supported ruthenium catalysts

    International Nuclear Information System (INIS)

    Kellner, C.S.; Bell, A.T.

    1981-01-01

    The effects of using D 2 rather than H 2 during Fischer-Tropsch synthesis were investigated using alumina- and silica-supported Ru catalysts. For the alumina-supported catalysts, the rate of CD 4 formation was 1.4 to 1.6 times faster than the formation of CH 4 . A noticeable isotope effect was also observed for higher molecular weight products. The magnitude of the isotope effects observed using the silica-supported catalyst was much smaller than that found using the alumina-supported catalysts. The formation of olefins relative to paraffins was found to be higher when H 2 rather than D 2 was used, independent of the catalyst support. The observed isotope effects are explained in terms of a mechanism for CO hydrogenation and are shown to arise from a complex combination of the kinetic and equilibrium isotope effects associated with elementary processes occurring on the catalyst surface

  9. Concerted and stepwise mechanisms in cycloaddition reactions: potential surfaces and isotope effects

    International Nuclear Information System (INIS)

    Houk, K.N.; Yi Li; Storer, Joey; Raimondi, Laura; Beno, Brett

    1994-01-01

    CASSCF/6-31G * calculations have been performed on concerted and stepwise Diels-Alder reactions of butadiene with ethene, the dimerization of butadiene, and the dimerization of cyclobutadiene. The relative energies of concerted and stepwise mechanisms are compared, and the factors influencing these ''energies of concert'' are discussed. The comparison of calculated isotope effects to experimental data provides support for theoretical results. (Author)

  10. pH-Free Measurement of Relative Acidities, Including Isotope Effects.

    Science.gov (United States)

    Perrin, Charles L

    2017-01-01

    A powerful pH-free multicomponent NMR titration method can measure relative acidities, even of closely related compounds, with excellent accuracy. The history of the method is presented, along with details of its implementation and a comparison with earlier NMR titrations using a pH electrode. Many of its areas of applicability are described, especially equilibrium isotope effects. The advantages of the method, some practical considerations, and potential pitfalls are considered. © 2017 Elsevier Inc. All rights reserved.

  11. Kinetic tritium isotopic effects in the position 2 for 5'-hydroxy-L-tryptophane

    International Nuclear Information System (INIS)

    Boroda, E.; Kanska, M.

    2006-01-01

    Tryptophanase converts 5'-hydroxy-L-tryptophane to pyrogronic acid and ammonia, however there are known conditions for the reversed reaction. Mechanism of the processes are not known till now. Kinetic isotopic effect (KIE) permits finding the rate determining stage in the multistage process. In presented communication, 5'-hydroxy-[2- 3 H]-L-tryptophane was synthesized and the KIE in the room temperature determined for different reaction stages

  12. Relative rate study of the kinetic isotope effect in the 13CH3D + Cl reaction

    DEFF Research Database (Denmark)

    Joelsson, Lars Magnus Torvald; Forecast, Roslyn; Schmidt, Johan Albrecht

    2014-01-01

    The 13CH3D/12CH4kinetic isotope effect, α13CH3D, of CH4 + Cl is determined for the first time, using the relative rate technique and Fourier transform infrared (FTIR) spectroscopy. α13CH3D is found to be 1.60 ± 0.04. In addition, a quantum chemistry/transition state theory model with tunneling...

  13. Kinetic Isotope Effects (KIE) and Density Functional Theory (DFT): A Match Made in Heaven?

    DEFF Research Database (Denmark)

    Christensen, Niels Johan; Fristrup, Peter

    2015-01-01

    Determination of experimental kinetic isotope effects (KIE) is one of the most useful tools for the exploration of reaction mechanisms in organometallic chemistry. The approach has been further strengthened during the last decade with advances in modern computational chemistry. This allows for th...... reaction). The approach is highlighted by using recent examples from both stoichiometric and catalytic reactions, homogeneous and heterogeneous catalysis, and enzyme catalysis to illustrate the expected accuracy and utility of this approach....

  14. Environmental effects on the stable carbon and oxygen isotopic ...

    African Journals Online (AJOL)

    USER

    2010-08-16

    Aug 16, 2010 ... which may be influenced by the river run-off due to heavy rainfall. The coral skeleton was ... including cloud cover (Weber and Woodhead, 1972;. Muscatine et al. ..... The effect of colony topography on climate signals in coral ...

  15. Isotope effects on chemical shifts in tautomeric systems with double proton transfer. Citronin

    International Nuclear Information System (INIS)

    Hansen, P.E.; Langgard, M.; Bolvig, S.

    1998-01-01

    Primary and secondary deuterium isotope effects on 1 H and 13 C chemical shifts are measured in citrinin, a tautomeric compound with an unusual doubly intramolecularly hydrogen bonded structure. The isotope effects are to a large extent dominated by equilibrium contributions and deuteration leads to more of the deuterated enol forms rather than the deuterated acid form. 1 H 13 C and 17 O nuclear shieldings are calculated using density functional ab initio methods. A very good correlation between calculated nuclear shieldings and experimental 1 H and 13 C chemical shifts is obtained. The tautomeric equilibrium can be analyzed based on the isotope effects on B-6 and C-8 carbons and shows an increase in the o-quinone form on lowering the temperature. Furthermore, upon deuteration the largest equilibrium shift is found for deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration is increasing at lower temperature. (author)

  16. Deuterium kinetic isotope effects in the 1,4-dimethylenecyclohexane boat cope rearrangement

    International Nuclear Information System (INIS)

    Gajewski, J.J.; Jimenez, J.L.

    1986-01-01

    In order to examine the extent of bond making in the boat-like 3,3-sigmatropic shift transition states, trans-2,3-dimethyl-1,4-dimethylenecyclohexane (T) and its exomethylene tetradeuteria derivative (TXD) were prepared. The 3,3-shift of TXD at 305 0 C results in interconversion of starting material, 5,5,6,6-tetradeuterio-trans-2,3-dimethyl-1,4-dimethylene-cyclohexane (TND), and 2,2,3,3-tetradeuterio-anti-1,4-diethylidenecyclohexane (AD). A kinetic analysis of the first-order rate equations for the three-component system in both protio and deuterio species by numerical integration of the data and simplex minimization of the rate constants with symmetry and the assumption of no equilibrium or kinetic isotope effect on the TND-AD reaction gives a bond making kinetic isotope effect of 1/1.04 (0.04). The equilibrium isotope effects observed are 1/1.16 (0.04) so that the extent of bond formation in this boat-like bicyclo[2.2.2]octyl transition state is roughly 25%, a value to be compared with ca. 67% in chair-like acyclic 3,3-shift transition states. This rules out significant intervention of a bicyclo[2.2.2]octane-1,4-diyl intermediate or transition state. 30 references, 6 figures, 4 tables

  17. Solvent and solute isotope effects in the aqueous solution of gases. Progress report, July 1, 1978-October 31, 1979

    International Nuclear Information System (INIS)

    Benson, B.B.; Krause, D. Jr.

    1979-10-01

    After developing a 3 He/ 4 He dual beam collection system for the mass spectrometer, the isotopic fractionation factor was determined for helium dissolved in H 2 O, D 2 O, seawater and ethanol. In all solvents the temperature dependence of the fractionation is different from that for a simple isotope vapor pressure effect. Addition of salt to H 2 O increases the fractionation, and the relative salting-out coefficient changes with temperature. A double isotopic effect occurs - the fractionations in D 2 O and H 2 O differ. In ethanol the fractionation is 25% less than in H 2 O

  18. Effect of untreated bed nets on blood-fed Phlebotomus argentipes in kala-azar endemic foci in Nepal and India.

    Science.gov (United States)

    Picado, Albert; Kumar, Vijay; Das, Murari; Burniston, Ian; Roy, Lalita; Suman, Rijal; Dinesh, Diwakar; Coosemans, Marc; Sundar, Shyam; Shreekant, Kesari; Boelaert, Marleen; Davies, Clive; Cameron, Mary

    2009-12-01

    Observational studies in the Indian subcontinent have shown that untreated nets may be protective against visceral leishmaniasis (VL). In this study, we evaluated the effect of untreated nets on the blood feeding rates of Phlebotomus argentipes as well as the human blood index (HBI) in VL endemic villages in India and Nepal. The study had a 'before and after intervention' design in 58 households in six clusters. The use of untreated nets reduced the blood feeding rate by 85% (95% CI 76.5-91.1%) and the HBI by 42.2% (95% CI 11.1-62.5%). These results provide circumstantial evidence that untreated nets may provide some degree of personal protection against sand fly bites.

  19. 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

  20. Kinetic α-deuterium isotope effect as a probe of transition state structure and reaction mechanism in nucleoside hydrolysis

    International Nuclear Information System (INIS)

    Stein, R.L.

    1978-01-01

    Theoretical equilibrium α-deuterium isotope effects were calculated for systems modeling nucleoside and glycoside hydrolyses using a computer program (Burton, G.W., Sims, L.B., Wilson, J.C., and Fry, A.J., J. Amer. Chem. Soc., 99, 3374(1977)) which computes isotope effects directly from the expression of Biegeleisen and Mayer (Biegeleisen, J. and Mayer, M.G., J. Chem. Phys., 17, 675(1949)). For nucleoside hydrolysis proceeding through an oxocarbonium ion intermediate, KH/KD = 1.21 to 1.25; while for nucleoside hydrolysis proceeding through an oxocarbonium ion intermediate KH/KD = 1.15 to 1.19. The models used in the calculations were generated systematically and involved a minimum of subjectivity in the selection of molecular parameters. The isotope effects calculated formed the basis for the interpretation of experimental kinetic α-deuterium isotope effects for nucleoside and glycoside hydrolysis

  1. Communication: Isotopic effects on tunneling motions in the water trimer

    International Nuclear Information System (INIS)

    Videla, Pablo E.; Rossky, Peter J.; Laria, D.

    2016-01-01

    We present results of ring polymer molecular dynamics simulations that shed light on the effects of nuclear quantum fluctuations on tunneling motions in cyclic [H 2 O] 3 and [D 2 O] 3 , at the representative temperature of T = 75 K. In particular, we focus attention on free energies associated with two key isomerization processes: The first one corresponds to flipping transitions of dangling OH bonds, between up and down positions with respect to the O–O–O plane of the cluster; the second involves the interchange between connecting and dangling hydrogen bond character of the H-atoms in a tagged water molecule. Zero point energy and tunneling effects lead to sensible reductions of the free energy barriers. Due to the lighter nature of the H nuclei, these modifications are more marked in [H 2 O] 3 than in [D 2 O] 3 . Estimates of the characteristic time scales describing the flipping transitions are consistent with those predicted based on standard transition-state-approximation arguments

  2. Communication: Isotopic effects on tunneling motions in the water trimer

    Energy Technology Data Exchange (ETDEWEB)

    Videla, Pablo E. [Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires (Argentina); Rossky, Peter J. [Department of Chemistry, Rice University, Houston, Texas 77251-1892 (United States); Laria, D., E-mail: dhlaria@cnea.gov.ar [Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires (Argentina); Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires (Argentina)

    2016-02-14

    We present results of ring polymer molecular dynamics simulations that shed light on the effects of nuclear quantum fluctuations on tunneling motions in cyclic [H{sub 2}O]{sub 3} and [D{sub 2}O]{sub 3}, at the representative temperature of T = 75 K. In particular, we focus attention on free energies associated with two key isomerization processes: The first one corresponds to flipping transitions of dangling OH bonds, between up and down positions with respect to the O–O–O plane of the cluster; the second involves the interchange between connecting and dangling hydrogen bond character of the H-atoms in a tagged water molecule. Zero point energy and tunneling effects lead to sensible reductions of the free energy barriers. Due to the lighter nature of the H nuclei, these modifications are more marked in [H{sub 2}O]{sub 3} than in [D{sub 2}O]{sub 3}. Estimates of the characteristic time scales describing the flipping transitions are consistent with those predicted based on standard transition-state-approximation arguments.

  3. A three-dimensional numerical investigation of trapezoid baffles effect on non-isothermal reactant transport and cell net power in a PEMFC

    International Nuclear Information System (INIS)

    Perng, Shiang-Wuu; Wu, Horng-Wen

    2015-01-01

    Highlights: • We study how angle and height of trapezoid baffle affect PEMFC net power. • The jet-type, trapping, and blockage effects augment non-isothermal transport in flow channel. • Greater angles and heights of trapezoid baffles provide more reactant to the catalyst layer. • Baffles of 1.5 mm and 90° fully block flow channel to show bad heat transfer and large pressure drop. • Maximum enhancement of cell net power is 90% with baffles of 60° angle and 1.125 mm height. - Abstract: The present study performed a three-dimensional numerical simulation to observe how trapezoid baffles affect non-isothermal reactant transports and cell net power in the proton exchange membrane fuel cell (PEMFC) by the SIMPLE-C method. The geometric parameters of trapezoid baffles installed in the gas channel employed in this study include the angle and height with the same gas diffusion and catalyst layers to realize the cell net power considering the effect of liquid water formation on the fluid flow field. The cell net power is adopted to evaluate the real enhancement of cell performance due to the additional pumping power induced by the pressure loss through the PEMFC. The results illustrated that compared with traditional gas channel without baffles, the novel gas channel with trapezoid baffles, whose angle is 60° and height is 1.125 mm, enhances the cell net power best by approximately 90% among all trapezoid baffle designs

  4. Moderating factors of immediate, gross, and net cross-brand effects of price promotions

    NARCIS (Netherlands)

    C. Horváth (Csilla); D. Fok (Dennis)

    2013-01-01

    textabstractThis article examines cross-price promotional effects in a dynamic context. Among other things, we investigate whether previously established findings hold when consumer and competitive dynamics are taken into account. Five main influential effects (asymmetric price effect, neighborhood

  5. On the Isotopic Altitude Effect of Precipitation in the Northern Adriatic (Croatia)

    Energy Technology Data Exchange (ETDEWEB)

    Roller-Lutz, Z.; Mance, D.; Hunjak, T., E-mail: Roller@medri.hr [Stable Isotope Laboratory, Medical Faculty, University of Rijeka, Rijeka (Croatia); Lutz, H. O. [Stable Isotope Laboratory, Medical Faculty, University of Rijeka, Rijeka (Croatia); Physics Faculty, Bielefeld University, Bielefeld (Germany)

    2013-07-15

    The upper (northern) Adriatic is very rich in precipitation. This input into the water system and its stable isotope composition is a basic factor, knowledge of which is required for proper use and management of water resources. The geomorphology of the region (e.g., mountains of 1400 m next to the sea) can cause specific local conditions. The isotopic composition of precipitation has been measured in various locations at different altitudes. For {delta}{sup 18}O this 'altitude effect' is found to lie around -0.2 per mille /100 m; its exact value depends on the specific location and the season. The {delta}{sup 2}H values and the d-excess vary correspondingly. (author)

  6. Sensitized charge carrier injection into organic crystals studied by isotope effects in weak magnetic fields

    International Nuclear Information System (INIS)

    Bube, W.; Michel-Beyerle, M.E.; Haberkorn, R.; Steffens, E.

    1977-01-01

    The magnetic field (H approximately 50 Oe) dependence of the rhodamine sensitized triplet exciton density in anthracene crystals is influenced by isotopic substitution. This confirms the hyperfine interaction as mechanism explaining the change of the spin multiplicity in the initially formed singlet state of the radical pair. The isotope effect occurs in the sensitizing dye ( 14 N/ 15 N) rather than at the molecular site of the injected charge within the crystal. This can be understood in terms of the high hopping frequency of the charge carriers as compared to the time constant of the hyperfine induced singlet-triplet transition. Since the dye molecules adsorb in an oriented fashion, the angular dependence of the magnetic field modulation of the triplet exciton density can be interpreted without assuming any additional interactions. (Auth.)

  7. Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

    Science.gov (United States)

    Elkins, Madeline H.; Williams, Holly L.; Neumark, Daniel M.

    2016-05-01

    The excited state relaxation dynamics of the solvated electron in H2O and D2O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H2O and 102 ± 8 fs in D2O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

  8. Isotopic spin effect in three-pion Bose-Einstein correlations

    International Nuclear Information System (INIS)

    Suzuki, N.

    1998-01-01

    Bose-Einstein (BE) correlations of identical particles in multiple production processes are extensively studied last years because they give an information on the space-time region of interaction. The basic effect is analogous to Hanbury-Brown - Twiss (HBT) interferometry in optics and suggests statistical production of the particles (mainly π mesons). The possible presence of coherent pionic component (for example, in the case of disoriented chiral condensate formation) modifies the HBT effect. On the other hand, the pions (contrary to photons) are subject to isotopic spin (and electric charge) conservation and so they can not be emitted independently. While the corresponding change of the statistical part is not essential for large multiplicities, the coherent part changes substantially when isotopic spin conservation is taken into account. BE correlations of the pions in the presence of both statistical and coherent components are reconsidered taking into account isotopic spin conservation in the coherent part. That will result in appearance of additional contribution to pionic correlation function. (author)

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

    Science.gov (United States)

    Wang, Dunyou; Kwak, Dochan (Technical Monitor)

    2002-01-01

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

  10. The effect of aromatization on the isotopic compositions of hydrocarbons during early diagenesis

    Science.gov (United States)

    Freeman, K. H.; Boreham, C. J.; Summons, R. E.; Hayes, J. M.

    1994-01-01

    Polycyclic aromatic hydrocarbons with varying degrees of aromatization were isolated from the Eocene Messel Shale (Rheingraben, Germany). The high abundances of these compounds and their structural resemblances to cyclic triterpenoid lipids are consistent with derivation from microbial rather than thermal processes. Compounds structurally related to oleanane contain from five to nine double bonds; those within a series of aromatized hopanoids contain from three to nine. All are products of diagenetic reactions that remove hydrogen or methyl groups, and, in several cases, break carbon-carbon bonds to open rings. Aromatized products are on average depleted in 13C relative to possible precursors by l.2% (range: l.5% enrichment to 4% depletion, n = 9). The dependence of 13C content on the number of double bonds is not, however, statistically significant and it must be concluded that there is no strong evidence for isotopic fractionation accompanying diagenetic aromatization. Isotopic differences between series (structures related to ursane, des-A-ursane, des-A-lupane, des-A-arborane, and possibly, des-A-gammacerane are present) are much greater, indicating that 13C contents are controlled primarily by source effects. Fractionations due to chromatographic isotope effects during HPLC ranged from 0.1 to 2.8%.

  11. Effect of complexing reagents on the ionization constant of boric acid and its relation to isotopic exchange separation factor

    International Nuclear Information System (INIS)

    Sharma, B.K.; Subramanian, R.; Mathur, P.K.

    1991-01-01

    The effect of change in concentration of complexing reagents having two or more hydroxyl groups, viz., ethylene glycol, propylene glycol, dextrose and mannitol on the ionization constant of boric acid has been studied by pH-metric titration method. The effect of increase in ionization constant of boric acid on isotopic exchange separation factor for the separation of isotopes of boron by ion exchange chromatography has been studied by the batch method. (author). 9 refs

  12. Diffusion related isotopic fractionation effects with one-dimensional advective–dispersive transport

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Bruce S. [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Lollar, Barbara Sherwood [Earth Sciences Department, University of Toronto, 22 Russell Street, Toronto, ON M5S 3B1 (Canada); Passeport, Elodie [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada); Chemical Engineering and Applied Chemistry Department, University of Toronto, 200 College Street, Toronto, ON M5S 3E5 (Canada); Sleep, Brent E., E-mail: sleep@ecf.utoronto.ca [Civil Engineering Department, University of Toronto, 35 St George Street, Toronto, ON M5S 1A4 (Canada)

    2016-04-15

    Aqueous phase diffusion-related isotope fractionation (DRIF) for carbon isotopes was investigated for common groundwater contaminants in systems in which transport could be considered to be one-dimensional. This paper focuses not only on theoretically observable DRIF effects in these systems but introduces the important concept of constraining “observable” DRIF based on constraints imposed by the scale of measurements in the field, and on standard limits of detection and analytical uncertainty. Specifically, constraints for the detection of DRIF were determined in terms of the diffusive fractionation factor, the initial concentration of contaminants (C{sub 0}), the method detection limit (MDL) for isotopic analysis, the transport time, and the ratio of the longitudinal mechanical dispersion coefficient to effective molecular diffusion coefficient (D{sub mech}/D{sub eff}). The results allow a determination of field conditions under which DRIF may be an important factor in the use of stable carbon isotope measurements for evaluation of contaminant transport and transformation for one-dimensional advective–dispersive transport. This study demonstrates that for diffusion-dominated transport of BTEX, MTBE, and chlorinated ethenes, DRIF effects are only detectable for the smaller molar mass compounds such as vinyl chloride for C{sub 0}/MDL ratios of 50 or higher. Much larger C{sub 0}/MDL ratios, corresponding to higher source concentrations or lower detection limits, are necessary for DRIF to be detectable for the higher molar mass compounds. The distance over which DRIF is observable for VC is small (less than 1 m) for a relatively young diffusive plume (< 100 years), and DRIF will not easily be detected by using the conventional sampling approach with “typical” well spacing (at least several meters). With contaminant transport by advection, mechanical dispersion, and molecular diffusion this study suggests that in field sites where D{sub mech}/D{sub eff} is

  13. Diffusion related isotopic fractionation effects with one-dimensional advective–dispersive transport

    International Nuclear Information System (INIS)

    Xu, Bruce S.; Lollar, Barbara Sherwood; Passeport, Elodie; Sleep, Brent E.

    2016-01-01

    Aqueous phase diffusion-related isotope fractionation (DRIF) for carbon isotopes was investigated for common groundwater contaminants in systems in which transport could be considered to be one-dimensional. This paper focuses not only on theoretically observable DRIF effects in these systems but introduces the important concept of constraining “observable” DRIF based on constraints imposed by the scale of measurements in the field, and on standard limits of detection and analytical uncertainty. Specifically, constraints for the detection of DRIF were determined in terms of the diffusive fractionation factor, the initial concentration of contaminants (C_0), the method detection limit (MDL) for isotopic analysis, the transport time, and the ratio of the longitudinal mechanical dispersion coefficient to effective molecular diffusion coefficient (D_m_e_c_h/D_e_f_f). The results allow a determination of field conditions under which DRIF may be an important factor in the use of stable carbon isotope measurements for evaluation of contaminant transport and transformation for one-dimensional advective–dispersive transport. This study demonstrates that for diffusion-dominated transport of BTEX, MTBE, and chlorinated ethenes, DRIF effects are only detectable for the smaller molar mass compounds such as vinyl chloride for C_0/MDL ratios of 50 or higher. Much larger C_0/MDL ratios, corresponding to higher source concentrations or lower detection limits, are necessary for DRIF to be detectable for the higher molar mass compounds. The distance over which DRIF is observable for VC is small (less than 1 m) for a relatively young diffusive plume (< 100 years), and DRIF will not easily be detected by using the conventional sampling approach with “typical” well spacing (at least several meters). With contaminant transport by advection, mechanical dispersion, and molecular diffusion this study suggests that in field sites where D_m_e_c_h/D_e_f_f is larger than 10, DRIF

  14. Lattice Boltzmann Simulation of Kinetic Isotope Effect During Snow Crystal Formation

    Science.gov (United States)

    Lu, G.; Depaolo, D. J.; Kang, Q.; Zhang, D.

    2007-12-01

    and allows us to scale the numerical calculations to atmospheric conditions. Our calculations confirm that the crystal/vapor isotopic fractionation approaches the equilibrium value, and the crystals are compact (circular in 2D) as the saturation factor approaches unity (S= 1.0). However, few natural crystals form under such conditions. At higher oversaturation (e.g. S = 1.2), dendritic crystals of millimeter size develop on timescales appropriate to cloud processes, and kinetic effects control isotopic fractionation. Fractionation factors for dendritic crystals are similar to those predicted by the spherical diffusion model, but the model also gives estimates of crystal heterogeneity. Dendritic crystals are constrained to be relatively large, with dimension much greater than about 20D/k. The most difficult aspect of the modeling is to account for the large density difference between air and ice, which requires us to use a fictitious higher density for the vapor-oversaturated air and scale the crystal growth time accordingly. An approach using a larger scale simulation and the domain decomposition method can provide a vapor flux for a nested smaller scale calculation. The results clarify the controls on crystal growth, and the relationships between saturation state, growth rate, crystal morphology and isotopic fractionation.

  15. Costs and effects of two public sector delivery channels for long-lasting insecticidal nets in Uganda

    Directory of Open Access Journals (Sweden)

    Strachan Daniel

    2010-04-01

    Full Text Available Abstract Background In Uganda, long-lasting insecticidal nets (LLIN have been predominantly delivered through two public sector channels: targeted campaigns or routine antenatal care (ANC services. Their combination in a mixed-model strategy is being advocated to quickly increase LLIN coverage and maintain it over time, but there is little evidence on the efficiency of each system. This study evaluated the two delivery channels regarding LLIN retention and use, and estimated the associated costs, to contribute towards the evidence-base on LLIN delivery channels in Uganda. Methods Household surveys were conducted 5-7 months after LLIN distribution, combining questionnaires with visual verification of LLIN presence. Focus groups and interviews were conducted to further investigate determinants of LLIN retention and use. Campaign distribution was evaluated in Jinja and Adjumani while ANC distribution was evaluated only in the latter district. Costs were calculated from the provider perspective through retrospective analysis of expenditure data, and effects were estimated as cost per LLIN delivered and cost per treated-net-year (TNY. These effects were calculated for the total number of LLINs delivered and for those retained and used. Results After 5-7 months, over 90% of LLINs were still owned by recipients, and between 74% (Jinja and 99% (ANC Adjumani were being used. Costing results showed that delivery was cheapest for the campaign in Jinja and highest for the ANC channel, with economic delivery cost per net retained and used of USD 1.10 and USD 2.31, respectively. Financial delivery costs for the two channels were similar in the same location, USD 1.04 for campaign or USD 1.07 for ANC delivery in Adjumani, but differed between locations (USD 0.67 for campaign delivery in Jinja. Economic cost for ANC distribution were considerably higher (USD 2.27 compared to campaign costs (USD 1.23 in Adjumani. Conclusions Targeted campaigns and routine ANC

  16. Costs and effects of two public sector delivery channels for long-lasting insecticidal nets in Uganda.

    Science.gov (United States)

    Kolaczinski, Jan H; Kolaczinski, Kate; Kyabayinze, Daniel; Strachan, Daniel; Temperley, Matilda; Wijayanandana, Nayantara; Kilian, Albert

    2010-04-20

    In Uganda, long-lasting insecticidal nets (LLIN) have been predominantly delivered through two public sector channels: targeted campaigns or routine antenatal care (ANC) services. Their combination in a mixed-model strategy is being advocated to quickly increase LLIN coverage and maintain it over time, but there is little evidence on the efficiency of each system. This study evaluated the two delivery channels regarding LLIN retention and use, and estimated the associated costs, to contribute towards the evidence-base on LLIN delivery channels in Uganda. Household surveys were conducted 5-7 months after LLIN distribution, combining questionnaires with visual verification of LLIN presence. Focus groups and interviews were conducted to further investigate determinants of LLIN retention and use. Campaign distribution was evaluated in Jinja and Adjumani while ANC distribution was evaluated only in the latter district. Costs were calculated from the provider perspective through retrospective analysis of expenditure data, and effects were estimated as cost per LLIN delivered and cost per treated-net-year (TNY). These effects were calculated for the total number of LLINs delivered and for those retained and used. After 5-7 months, over 90% of LLINs were still owned by recipients, and between 74% (Jinja) and 99% (ANC Adjumani) were being used. Costing results showed that delivery was cheapest for the campaign in Jinja and highest for the ANC channel, with economic delivery cost per net retained and used of USD 1.10 and USD 2.31, respectively. Financial delivery costs for the two channels were similar in the same location, USD 1.04 for campaign or USD 1.07 for ANC delivery in Adjumani, but differed between locations (USD 0.67 for campaign delivery in Jinja). Economic cost for ANC distribution were considerably higher (USD 2.27) compared to campaign costs (USD 1.23) in Adjumani. Targeted campaigns and routine ANC services can both achieve high LLIN retention and use among

  17. Evaluating cleansing effects on trace elements and stable isotope values in feathers of oiled birds.

    Science.gov (United States)

    Valladares, Sonia; Moreno, Roćio; Jover, Lluis; Sanpera, Carola

    2010-01-01

    Feathers of seabirds are widely used as a nondestructive tissue for pollution monitoring of trace elements, as well as convenient samples for trophic ecology studies by means of stable isotope analysis (SIA). Nevertheless, feathers can be occasionally impregnated with oil from deliberate ship discharges and from massive oil spill accidents. The feather structure makes them effective traps for particles and are subject to external contamination. It is unknown to what extent the oil adhered to feathers can change trace element concentrations or stable isotope signatures. This study has two primary objectives: (1) to assess if there are differences between trace element concentrations and stable isotope signatures of oiled and clean feathers, and (2) to determine if the cleansing of oiled feathers using commonly applied techniques such as sodium hydroxide (NaOH) washes in combination with an organic solvent (hexane) is more effective than using NaOH alone. In order to do this, we analysed trace elements (Se, Hg, Pb, Cu and Zn) and stable isotopes (delta(13)C and delta(15)N) of individual feathers of yellow-legged gulls (Larus michahellis) which were affected by the 2002 Prestige oil spill in Galicia (NW Spain). Two sets of feathers were analysed, one group were oil-free (Control group) and the other had oil adhered to its surface (Oiled group). We expected to find differences between control and oiled feathers when cleaning exclusively with NaOH and no differences when using hexane. Our results did not show significant differences between Control and Oiled groups as a consequence of the cleansing method used. Unexpectedly, the additional cleansing with hexane resulted in decreasing selenium concentrations and increasing zinc and delta(15)N values in all groups of feathers.

  18. Effect of drink carbohydrate content on postexercise gastric emptying, rehydration, and the calculation of net fluid balance.

    Science.gov (United States)

    Clayton, David J; Evans, Gethin H; James, Lewis J

    2014-02-01

    The purpose of this study was to examine the gastric emptying and rehydration effects of hypotonic and hypertonic glucose-electrolyte drinks after exercise-induced dehydration. Eight healthy males lost ~1.8% body mass by intermittent cycling and rehydrated (150% of body mass loss) with a hypotonic 2% (2% trial) or a hypertonic 10% (10% trial) glucose-electrolyte drink over 60 min. Blood and urine samples were taken at preexercise, postexercise, and 60, 120, 180, and 240 min postexercise. Gastric and test drink volume were determined 15, 30, 45, 60, 90, and 120 min postexercise. At the end of the gastric sampling period 0.3% (2% trial) and 42.1% (10% trial; p rehydration drink might be mediated by a slower rate of gastric emptying, but the slow gastric emptying of such solutions makes rehydration efficiency difficult to determine in the hours immediately after drinking, compromising the calculation of net fluid balance.

  19. 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

  20. Effect of amino acids on the precipitation kinetics and Ca isotopic composition of gypsum

    Science.gov (United States)

    Harouaka, Khadouja; Kubicki, James D.; Fantle, Matthew S.

    2017-12-01

    Stirred gypsum (CaSO4 · 2H2O) precipitation experiments (initial Ωgypsum = 2.4 ± 0.14, duration ≈ 1.0-1.5 h) were conducted in the presence of the amino acids glycine (190 μM), L-alanine (190 μM), D- and L-arginine (45 μM), and L-tyrosine (200 μM) to investigate the effect of simple organic compounds on both the precipitation kinetics and Ca isotopic composition of gypsum. Relative to abiotic controls, glycine, tyrosine, and alanine inhibited precipitation rates by ∼22%, 27%, and 29%, respectively, while L- and D-arginine accelerated crystal growth by ∼8% and 48%, respectively. With the exception of tyrosine, amino acid induced inhibition resulted in fractionation factors (αs-f) associated with precipitation that were no more than 0.3‰ lower than amino acid-free controls. In contrast, the tyrosine and D- and L-arginine experiments had αs-f values associated with precipitation that were similar to the controls. Our experimental results indicate that Ca isotopic fractionation associated with gypsum precipitation is impacted by growth inhibition in the presence of amino acids. Specifically, we propose that the surface-specific binding of amino acids to gypsum can change the equilibrium fractionation factor of the bulk mineral. We investigate the hypothesis that amino acids can influence the growth of gypsum at specific crystal faces via adsorption and that different faces have distinct fractionation factors (αface-fluid). Accordingly, preferential sorption of amino acids at particular faces changes the relative, face-specific mass fluxes of Ca during growth, which influences the bulk isotopic composition of the mineral. Density functional theory (DFT) calculations suggest that the energetic favorability of glycine sorption onto gypsum crystal faces occurs in the order: (1 1 0) > (0 1 0) > (1 2 0) > (0 1 1), while glycine sorption onto the (-1 1 1) face was found to be energetically unfavorable. Face-specific fractionation factors constrained by

  1. Magnetic isotope effect and theory of atomic orbital hybridization to predict a mechanism of chemical exchange reactions.

    Science.gov (United States)

    Epov, Vladimir N

    2011-08-07

    A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions. This journal is © the Owner Societies 2011

  2. Measurement of the isotope effect of the diffusion of silver and gold in gold and of silver in silver-gold alloys

    International Nuclear Information System (INIS)

    Wolter, D.

    1974-01-01

    The silver isotopes Ag 105 and Agsup(110m) and the gold isotopes Au 195 and Au 199 were used for isotope effect measurements. The isotope effect of the gold self-diffusion was measured on four monocrystals samples at about 850 0 C, that of silver in gold monocrystals at five different temperatures between 731 0 C and 1050 0 C. Furthermore, the isotope effect for silver at 904 0 C was measured on seven silver-gold alloys of varying silver concentration. The correlation factor was determined from the measurements. (HPOE/LH) [de

  3. Middle-School Understanding of the Greenhouse Effect using a NetLogo Computer Model

    Science.gov (United States)

    Schultz, L.; Koons, P. O.; Schauffler, M.

    2009-12-01

    We investigated the effectiveness of a freely available agent based, modeling program as a learning tool for seventh and eighth grade students to explore the greenhouse effect without added curriculum. The investigation was conducted at two Maine middle-schools with 136 seventh-grade students and 11 eighth-grade students in eight classes. Students were given a pre-test that consisted of a concept map, a free-response question, and multiple-choice questions about how the greenhouse effect influences the Earth's temperature. The computer model simulates the greenhouse effect and allows students to manipulate atmospheric and surface conditions to observe the effects on the Earth’s temperature. Students explored the Greenhouse Effect model for approximately twenty minutes with only two focus questions for guidance. After the exploration period, students were given a post-test that was identical to the pre-test. Parametric post-test analysis of the assessments indicated middle-school students gained in their understanding about how the greenhouse effect influences the Earth's temperature after exploring the computer model for approximately twenty minutes. The magnitude of the changes in pre- and post-test concept map and free-response scores were small (average free-response post-test score of 7.0) compared to an expert's score (48), indicating that students understood only a few of the system relationships. While students gained in their understanding about the greenhouse effect, there was evidence that students held onto their misconceptions that (1) carbon dioxide in the atmosphere deteriorates the ozone layer, (2) the greenhouse effect is a result of humans burning fossil fuels, and (3) infrared and visible light have similar behaviors with greenhouse gases. We recommend using the Greenhouse Effect computer model with guided inquiry to focus students’ investigations on the system relationships in the model.

  4. Deuterium isotope effects during formation of phenols by hepatic monoxygenases. Evidence for an alternative to the arene oxide pathway

    International Nuclear Information System (INIS)

    Tomaszewski, J.E.; Jerina, D.M.; Daly, J.W.

    1975-01-01

    The in vivo and in vitro metabolisms of normal and deuterated aromatic substrates have been investigated in rats. Significant isotope effects (k/ sub H//k/sub D/ equals 1.3-1.75) were associated with in vivo formation of meta-hydroxylated metabolites from 1:1 mixtures of normal and perdeuterio-(arylring) nitrobenzene, methyl phenyl sulfide, and methyl phenyl sulfone. Since isotope effects of this magnitude are incompatible with arene oxides as intermediates in the formation of phenols, the results provide evidence that multiple pathways are responsible for the formation of phenols in mammals. Significant isotope effects were not associated with the formation of the other phenolic isomers of nitrobenzene, methyl phenyl sulfone, or methyl phenyl sulfide or with the formation of phenolic products from anisole, bromobenzene, chlorobenzene, fluorobenzene, benzonitrile, naphthalene, zoxazolamine, acetanilide, biphenyl, diphenylhydantoin, benzene, o- and p-xylene, toluene, and mesitylene. Significant isotope effects might not be observable with the latter substrates if the kinetic parameters for oxidation of substrate change or if the arene oxide pathway greatly predominates. Furthermore, extensive in vivo metabolism of any substrate would make isotope effects unobservable by the procedure employed, namely the analysis of isotope content in metabolites formed from 1:1 mixtures of normal and deuterated substrates. (U.S.)

  5. Covariance of oxygen and hydrogen isotopic composition in plant water: Species effects

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, L.W.; DeNiro, M.J. (Univ. of California, Los Angeles (United States))

    1989-12-01

    Leaf water becomes enriched in the heavy isotopes of oxygen and hydrogen during evapotranspiration. The magnitude of the enrichment has been shown to be influenced by temperature and humidity, but the effects of species-specific factors on leaf water enrichment of D and {sup 18}O have not been studied for different plants growing together. To learn whether leaf water enrichment patterns and processes for D and {sup 18}O are different for individual species growing under the same environmental conditions the authors tested the proposal that leaf waters in plants with crassulacean acid metabolism (CAM) show high sloped (m in the leaf water equation {delta}D = m {delta}{sup 18}O + b) than in C{sub 3} plants. They determined the relationships between the stable hydrogen ({delta}D) and oxygen ({delta}{sup 18}O) isotope ratios of leaf waters collected during the diurnal cycle of evapotranspiration for Yucca schidigera, Ephedra aspera, Agave deserti, Prunus ilicifolia, Yucca whipplei, Heteromeles arbutifolia, Dyckia fosteriana, Simmondsia chinensis, and Encelia farinosa growing at two sites in southern California. The findings indicate that m in the aforementioned equation is related to the overall residence time for water in the leaf and proportions of water subjected to repeated evapotranspiration enrichments of heavy isotopes.

  6. Impurity effects of hydrogen isotope retention on boronized wall in LHD

    International Nuclear Information System (INIS)

    Oya, Yasuhisa; Okuno, Kenji; Ashikawa, Naoko; Nishimura, Kiyohiko; Sagara, Akio

    2010-11-01

    The impurity effect on hydrogen isotopes retention in the boron film deposited in LHD was evaluated by means of XPS and TDS. It was found that the impurity concentrations in boron film were increased after H-H main plasma exposure in LHD. The ratio of hydrogen retention trapped by impurity to total hydrogen retention during H-H main plasma exposure was reached to 70%, although that of deuterium retention by impurity in D 2 + implanted LHD-boron film was about 35%. In addition, the dynamic chemical sputtering of hydrogen isotopes with impurity as the form of water and / or hydrocarbons was occurred by energetic hydrogen isotopes irradiation. It was expected that the enhancement of impurity concentration during plasma exposure in LHD would induce the dynamic formation of volatile molecules and their re-emission to plasma. These facts would prevent stable plasma operation in LHD, concluding that the dynamic impurity behavior in boron film during plasma exposure is one of key issues for the steady-state plasma operation in LHD. (author)

  7. The effect of natural weathering on the chemical and isotopic composition of biotites

    International Nuclear Information System (INIS)

    Clauer, N.; Bonnot-Courtois, C.

    1982-01-01

    The effect of progressive natural weathering on the isotopic (Rb-Sr, K-Ar, deltaD, delta 18 O) and chemical (REE, H 2 O + ) compositions of biotite has been studied on a suite of migmatitic biotites from the Chad Republic. During the early stages of weathering the Rb-Sr system is strongly affected, the hydrogen and oxygen isotope compositions change markedly, the minerals are depleted in light REE, the water content increases by a factor of two, and the K-Ar system is relatively little disturbed. During intensive weathering the K-Ar system is more strongly disturbed than the Rb-Sr system. Most of the isotopic and chemical modifications take place under nonequilibrium conditions and occur before newly formed kaolinite and/or smectite can be detected. These observations suggest that (a) 'protominerals' may form within the biotite structure during the initial period of weathering, and (b) only when chemical equilibrium is approached in the weathering profile are new minerals able to form. (author)

  8. Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals

    Science.gov (United States)

    Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

    2014-07-01

    In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit δ18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The δ18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured δ18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured δ18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the δ18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral

  9. Covariance of oxygen and hydrogen isotopic compositions in plant water: species effects

    International Nuclear Information System (INIS)

    Cooper, L.W.; DeNiro, M.J.

    1989-01-01

    Leaf water becomes enriched in the heavy isotopes of oxygen and hydrogen during evapotranspiration. The magnitude of the enrichment has been shown to be influenced by temperature and humidity, but the effects of species—specific factors on leaf water enrichment of D and 18 O have not been studied for different plants growing together. Accordingly, to learn whether leaf water enrichment patterns and processes for D and 18 O are different for individual species growing under the same environmental conditions we tested the proposal that leaf waters in plants with crassulacean acid metabolism (CAM) show higher slopes (m in the leaf water equation °D = m ° 18 O + b) than in C 3 plants. We determined the relationships between the stable hydrogen (°D) and oxygen (° 18 O) isotope ratios of leaf waters collected during the diurnal cycle of evapotranspiration for Yucca schidigera, Ephedra aspera, Agave deserti, Prunus ilicifolia, Yucca whipplei, Heteromeles arbutifolia, Dyckia fosteriana, Simmondsia chinensis, and Encelia farinosa growing at two sites in southern California. Slopes (m in the above leaf water equation) ranged from 1.50 to 3.21, compared to °8 for meteoric water, but differences in slope could not be attributed to carboxylation pathway (CAM vs. C 3 ) nor climate (coastal California vs. Sonoran Desert). Higher slopes were correlated with greater overall ranges of leaf water enrichment of D and 18 O. Water in plants with higher slopes also differed most from unaltered meteoric water. Leaf water isotope ratios in plants with lower slopes were better correlated with temperature and humidity. The findings indicate that m in the aforementioned equation is related to the overall residence time for water in the leaf and proportions of water subjected to repeated evapotranspiration enrichments of heavy isotopes

  10. Vinyl ether hydrolysis. VII. Isotope effects on catalysis by aqueous hydrofluoric acid

    International Nuclear Information System (INIS)

    Kresge, A.J.; Chen, H.J.; Chiang, Y.

    1977-01-01

    Comparison of rates of hydrolysis of three vinyl ethers catalyzed by HF in H 2 O and DF in D 2 O at 25 0 C gives primary isotope effects in the range k/sub H//k/sub D/ = 3.3 to 3.5. The unexpectedly small size of these effects may be attributed to strong, ω = 1325 to 1450 cm -1 , hydrogenic bending vibrations in the proton transfer transition states of these reactions along with the lack of compensatory bending vibrations in the diatomic proton donor

  11. Secondary isotope effects and tunneling in elimination reaction of quaternary ammonium salts

    International Nuclear Information System (INIS)

    Lin, S.

    1993-01-01

    In order to gain more experimental evidence of the tunneling effect on the non-transferred isotopically-substituted hydrogen in the rate determining step and to investigate in more detail concerning the variable nature of the E2 transition state, tritium tracer-labeled β- and/or α-phenyl substituted ethyltrimethylammonium ions in the elimination reaction and their 2,2-d 2 analogues were studied. The three different substrates are 2-(p-trifluoromethylphenyl)ethyltrimethylammonium bromide (I), 1-phenylethyltrimethylammonium bromide (II) and 1-phenyl- 2-p-chlorophenylethyltrimethylammonium bromide (III). The reactions were found to proceed via a concerted E2 process. The proton is more than one-half transferred to the base at the transition state, especially for case I and III. There is more C beta -H and less C alpha -N bond rupture at the transition state when an electron-withdrawing group is introduced on the β-phenyl ring, i.e., more carbonion character in the transition state. The secondary tritium isotope effects were measured and they were found larger than the maximum value. (1.17) for rehybridization. It was found that these values were strongly temperature dependent. They increase as the temperature goes down. The Arrenhius pre-exponential factors were below unity and the exponential factor to convert the isotope effect of D/T to H/T were much greater than predicted for zero-point energy effects alone (3.26). Tunneling turns to be the only plausible explanation. By reviewing this evidence, one may conclude that the contribution of tunneling is indeed a common occurrence in proton transfer processes. For elimination of compound I, the tunneling effect is greatest while it is less for the other two, which are about the same, but the nature of their transition states is quite different. The variable nature of the transition states for the three eliminations are discussed in terms of the More O'Ferral-Jencks diagram

  12. Contribution of the net charge to the regulatory effects of amino acids and epsilon-poly(L-lysine) on the gelatinization behavior of potato starch granules.

    Science.gov (United States)

    Ito, Azusa; Hattori, Makoto; Yoshida, Tadashi; Takahashi, Koji

    2006-01-01

    The effects of lysine (Lys), monosodium glutamate (GluNa), glycine, alanine and epsilon-poly(L-lysine) (PL) with different degrees of polymerization on the gelatinization behavior of potato starch granules were investigated by DSC, viscosity and swelling measurements, microscopic observation, and measurement of the retained amino acid amount to clarify the contribution of the net charge to their regulatory effects on the gelatinization behavior. The amino acids and PL each contributed to an increase in the gelatinization temperature, and a decrease in the peak viscosity and swelling. These effects strongly depended on the absolute value of their net charge. The disappearance of a negative or positive net charge by adjusting the pH value weakened the contribution. The swelling index and size of the potato starch granules changed according to replacement of the swelling medium. The amino acids and PL were easily retained by the swollen potato starch granules according to replacement of the outer solution of the starch granules.

  13. Simultaneous reductions in emissions of black carbon and co-emitted species will weaken the aerosol net cooling effect

    Science.gov (United States)

    Wang, Z. L.; Zhang, H.; Zhang, X. Y.

    2015-04-01

    Black carbon (BC), a distinct type of carbonaceous material formed from the incomplete combustion of fossil and biomass based fuels under certain conditions, can interact with solar radiation and clouds through its strong light-absorption ability, thereby warming the Earth's climate system. Some studies have even suggested that global warming could be slowed down in the short term by eliminating BC emission due to its short lifetime. In this study, we estimate the influence of removing some sources of BC and other co-emitted species on the aerosol radiative effect by using an aerosol-climate atmosphere-only model BCC_AGCM2.0.1_CUACE/Aero with prescribed sea surface temperature and sea ice cover, in combination with the aerosol emissions from the Representative Concentration Pathways (RCPs) scenarios. We find that the global annual mean aerosol net cooling effect at the top of the atmosphere (TOA) will be enhanced by 0.12 W m-2 compared with recent past year 2000 levels if the emissions of only BC are reduced to the level projected for 2100 based on the RCP2.6 scenario. This will be beneficial~for the mitigation of global warming. However, both aerosol negative direct and indirect radiative effects are weakened when BC and its co-emitted species (sulfur dioxide and organic carbon) are simultaneously reduced. Relative to year 2000 levels, the global annual mean aerosol net cooling effect at the TOA will be weakened by 1.7-2.0 W m-2 if the emissions of all these aerosols are decreased to the levels projected for 2100 in different ways based on the RCP2.6, RCP4.5, and RCP8.5 scenarios. Because there are no effective ways to remove the BC exclusively without influencing the other co-emitted components, our results therefore indicate that a reduction in BC emission can lead to an unexpected warming on the Earth's climate system in the future.

  14. It's like night and day: Diel net-effects on Cercopagidae densities in the Laurentian Great Lakes

    Science.gov (United States)

    Armenio, Patricia M.; Bunnell, David B.; Adams, Jean V.; Watson, Nicole M.; Woelmer, Whitney

    2017-01-01

    In the Laurentian Great Lakes, zooplankters are often sampled using standard ≤153 μm mesh nets without regard to the time of day they are collected. We sampled Cercopagidae during 2013–2014 in northern Lake Huron during day, dusk, and night using two different nets (a 0.5 m wide 153 μm mesh “standard” net and a 0.75 m wide 285 μm mesh “Bythotrephes” net) to determine if there were any differences in their sampled densities. Bythotrephes densities with the standard net were approximately 2.07-fold greater when captured at night than during the day. No time of day bias occurred with the Bythotrephes net. Nighttime Bythotrephes densities did not differ between the two net types. Cercopagis densities did not vary with net type or the time of day in this study, but future work should revisit this result given our low sample size and the low occurrence of Cercopagis in Lake Huron. To reduce bias and calculate accurate density estimates, Cercopagidae should be sampled at night if using a standard net or any time of day with the Bythotrephes net. Given the large impact of invasive predatory cladocerans Bythotrephes longimanus and Cercopagis pengoi on food webs since their invasion in the Laurentian Great Lakes in the 1980s, proper estimation of their densities is essential.

  15. Net effects of gasoline price changes on transit ridership in U.S. urban areas.

    Science.gov (United States)

    2014-12-01

    Using panel data of transit ridership and gasoline prices for ten selected U.S. urbanized areas over the time period of 2002 to 2011, : this study analyzes the effect of gasoline prices on ridership of the four main transit modesbus, light rail, h...

  16. Effect of use of insecticide treated nets on birth outcomes among ...

    African Journals Online (AJOL)

    The major impact of malaria during pregnancy in these regions is caused by persistent or recurrent, predominantly low-grade, sometimes sub-patent, parasitaemia. In Nigeria, malaria has severe negative effects on maternal health and birth outcomes, resulting in maternal anaemia, a high incidence of miscarriages and low ...

  17. Rotational effects of polymeric fluids on shape of filaments in melt extruded net structures

    CSIR Research Space (South Africa)

    Rawal, A

    2006-01-01

    Full Text Available -circular geometries on their peripheries and the filaments are produced when the slots in disk and annulus are offset from each other. The effect of die rotation on the shape of filament is investigated by analysing the polymer flow inside the complex die slots...

  18. Communication for the Workplace: An Integrated Language Approach. Second Edition. Job Skills. Net Effect Series.

    Science.gov (United States)

    Ettinger, Blanche; Perfetto, Edda

    Using a developmental, hands-on approach, this text/workbook helps students master the basic English skills that are essential to write effective business correspondence, to recognize language errors, and to develop decision-making and problem-solving skills. Its step-by-step focus and industry-specific format encourages students to review,…

  19. Tidal effects on net ecosystem exchange of carbon in an estuarine wetland

    Science.gov (United States)

    H. Guo; A. Noormets; B. Zhao; J. Chen; G. Sun; Y. Gu; B. Li; J. Chen

    2009-01-01

    One year of continuous data from two eddy-flux towers established along an elevation gradient incoastal Shanghai was analyzed to evaluate the tidal effect on carbon flux (Fc) over an estuarine wetland.The measured wavelet spectra and cospectra of Fc and other environmental factors demonstrated thatthe...

  20. Net effects of nitrogen fertilization on the nutritive value and digestibility of oat forages

    Science.gov (United States)

    Applications of soil amendments containing N are part of routine forage management strategies for grasses, with a primary goal of increasing forage yield. However, the effects of N fertilization on forage nutritive value, estimates of energy density, and in-vitro DM or NDF disappearance often have b...

  1. Effect of insecticide treated nets fence in protect- ing cattle against ...

    African Journals Online (AJOL)

    . Negl. Trop. Dis., 5(10), e1343. Byford, R.L., Craig, M.E., and Crosby, B.L. 1982. A Review of on Ectoparasites and. Their Cattle Production' Effect. J. Anim. Sci., 70, 597– 602. Catangui, M.A., Campbell, J.B., Thomas, G.D., Boxler, D.J. 1993.

  2. Topographical effects of climate dataset and their impacts on the estimation of regional net primary productivity

    Science.gov (United States)

    Sun, L. Qing; Feng, Feng X.

    2014-11-01

    In this study, we first built and compared two different climate datasets for Wuling mountainous area in 2010, one of which considered topographical effects during the ANUSPLIN interpolation was referred as terrain-based climate dataset, while the other one did not was called ordinary climate dataset. Then, we quantified the topographical effects of climatic inputs on NPP estimation by inputting two different climate datasets to the same ecosystem model, the Boreal Ecosystem Productivity Simulator (BEPS), to evaluate the importance of considering relief when estimating NPP. Finally, we found the primary contributing variables to the topographical effects through a series of experiments given an overall accuracy of the model output for NPP. The results showed that: (1) The terrain-based climate dataset presented more reliable topographic information and had closer agreements with the station dataset than the ordinary climate dataset at successive time series of 365 days in terms of the daily mean values. (2) On average, ordinary climate dataset underestimated NPP by 12.5% compared with terrain-based climate dataset over the whole study area. (3) The primary climate variables contributing to the topographical effects of climatic inputs for Wuling mountainous area were temperatures, which suggest that it is necessary to correct temperature differences for estimating NPP accurately in such a complex terrain.

  3. Properties of porous netted materials

    International Nuclear Information System (INIS)

    Daragan, V.D.; Drozdov, B.G.; Kotov, A.Yu.; Mel'nikov, G.N.; Pustogarov, A.V.

    1987-01-01

    Hydraulic and strength characteristics, efficient heat conduction and inner heat exchange coefficient are experimentally studied for porous netted materials on the base of the brass nets as dependent on porosity, cell size and method of net laying. Results of the studies are presented. It is shown that due to anisotropy of the material properties the hydraulic resistance in the direction parallel to the nets plane is 1.3-1.6 times higher than in the perpendicular one. Values of the effective heat conduction in the direction perpendicular to the nets plane at Π>0.45 agree with the data from literature, at Π<0.45 a deviation from the calculated values is marked in the direction of the heat conduction decrease

  4. Study of the matrix specific mass discrimination effects during inductively coupled plasma mass spectrometry isotope ratio measurements

    International Nuclear Information System (INIS)

    Vassileva, E.; Quetel, Ch.R.

    2004-01-01

    Sample matrix related effects on mass discrimination during inductively coupled plasma mass spectrometry (ICP-MS) isotope ratio measurements have only been rarely reported. However, they can lead to errors larger than the uncertainty claimed on the ratio results when not properly taken into account or corrected for. These matrix specific affects were experienced during an Isotope Dilution Mass Spectrometry (IDMS) campaign we carried out for the certification of the Cd amount content in some food digest samples (7% acidity and salts content around 450μg g -1 ). Dilution was not possible for Cd only present at the low ng g -1 level. Up to 1% difference was observed on Cd isotope ratio results between measurements performed directly or after matrix separation. This was a significant difference considering that less than 1.5% relative combined uncertainty was eventually estimated for these IDMS measurements. Similar results could be obtained either way after the implementation of necessary corrections. The direct measurement approach associated to a correction for mass discrimination effects using the food digest sample itself (and the IUPAC table values as reference for the natural Cd isotopic composition) was preferred as it was the easiest. Consequently, the impact of matrix effects on mass discrimination during isotope ratio measurements with two types of ICP- MS (quadrupole and magnetic sector instruments) was studied for 4 elements (Li, Cu, Cd and Tl). Samples of varying salinity (up to 0.25%) and acidity (up to 7%) characteristics were prepared using isotopic certified reference materials of these elements. The long term and short-term stability, respectively reproducibility and repeatability, of the results, as well as the evolution of the difference to certified ratio values were monitored. As expected the 13 investigated isotopic ratios were all sensitive to variations in salt and acid concentrations. Our experiments also showed that simultaneous variation

  5. Dual temperature effects on oxygen isotopic ratio of shallow-water coral skeleton: Consequences on seasonal and interannual records

    Science.gov (United States)

    Juillet-Leclerc, A.; Reynaud, S.

    2009-04-01

    Oxygen isotopic ratio from coral skeleton is regarded for a long time as promising climate archives at seasonal scale. Although in isotopic disequilibrium relative to seawater, it is supposed to obey to the isotope thermometer. Indeed, coral oxygen isotopic records are strongly temperature dependent, but d18O-temperature calibrations derived from different corals are highly variable. The isotope thermometer assumption does not take into account vital effects due to biogenic origin of the mineral. Corals are animals living in symbiosis with algae (zooxanthellae). Interactions between symbiont photosynthesis and coral skeleton carbonation have been abundantly observed but they remain poorly understood and the effects of photosynthesis on coral growth and skeleton oxygen ratio are ignored. Coral cultured under two light conditions enabled to relate metabolic parameters and oxygen isotopic variability with photosynthetic activity. By examining responses provided by each colony they revealed that photosynthesis significantly affected d18O, by an opposite sense compared with the sole temperature influence. Since temperature and light changes are associated during seasonal variations, this complicates the interpretation of seasonal record. Additionally, this complexity is amplified because photosynthetic activity is also directly impacted by temperature variability. Thus, the annual isotopic amplitude due to the "physical" temperature influence is partly compensated through photosynthesis. Similar opposite effect is also shown by extension rate of the cultured colonies. First, we will examine and quantify consequences of photosynthesis on growth rate and oxygen isotopic signature, from cultured corals. Second, we will consider the consequences of this vital effect on data series, at seasonal and interannual time scales.

  6. The Effect of Phytase on the Oxygen Isotope Composition of Phosphate

    Science.gov (United States)

    von Sperber, C.; Tamburini, F.; Bernasconi, S. M.; Frossard, E.

    2013-12-01

    Plants and microorganisms under phosphorus (P) stress release extracellular phosphatases as a strategy to acquire inorganic phosphate (Pi) (1-2). These enzymes catalyze the hydrolysis of phosphoesters leading to a release of Pi. The enzymatic hydrolysis leads, via a nucleophilic attack, to the incorporation of one oxygen atom from the water into the newly formed Pi molecule. During the incorporation, an isotopic fractionation occurs, which might be used to identify the origin of Pi in the environment (3-6). While the effect of phosphomonoesterases and phosphodiesterases on the oxygen isotope composition of phosphate has been examined, there are, so far, no studies dealing with the effect of phytases (4-6). Phytases catalyze the hydrolysis of myo-inositol-hexakis-phosphate (IP6), which is an important component of organic P in many ecosystems (7). Enzymatic assays with phytase from wheat germ and Aspergillus niger were prepared under sterile and temperature controlled conditions in order to determine the effect of phytases on the oxygen isotope composition of phosphate, which has been liberated from IP6 via enzymatic hydrolysis. Assays with phytase from wheat germ lead to a turnover of the substrate close to 100%, while assays with phytase from Aspergillus niger lead to a turnover of the substrate close to 80%. In the case of the assays with phytase from wheat germ, our results indicate that one sixth of the total 24 oxygen which are associated to the phosphates in IP6 are exchanged with oxygen from water. From this we conclude that the incorporation of one oxygen atom from water occurs only at four phosphate molecules of IP6, while two phosphate molecules do not experience an incorporation of oxygen. This suggests that during the enzymatic hydrolysis, four P-O bonds and two C-O bonds are broken. Provided that, the isotopic fractionation can be calculated with an isotopic mass balance resulting in -8.4‰ (×3.6 SD). This is a value very similar to those reported

  7. Net benefits: assessing the effectiveness of clinical networks in Australia through qualitative methods

    Directory of Open Access Journals (Sweden)

    Cunningham Frances C

    2012-11-01

    Full Text Available Abstract Background In the 21st century, government and industry are supplementing hierarchical, bureaucratic forms of organization with network forms, compatible with principles of devolved governance and decentralization of services. Clinical networks are employed as a key health policy approach to engage clinicians in improving patient care in Australia. With significant investment in such networks in Australia and internationally, it is important to assess their effectiveness and sustainability as implementation mechanisms. Methods In two purposively selected, musculoskeletal clinical networks, members and stakeholders were interviewed to ascertain their perceptions regarding key factors relating to network effectiveness and sustainability. We adopted a three-level approach to evaluating network effectiveness: at the community, network, and member levels, across the network lifecycle. Results Both networks studied are advisory networks displaying characteristics of the ‘enclave’ type of non-hierarchical network. They are hybrids of the mandated and natural network forms. In the short term, at member level, both networks were striving to create connectivity and collaboration of members. Over the short to medium term, at network level, both networks applied multi-disciplinary engagement in successfully developing models of care as key outputs, and disseminating information to stakeholders. In the long term, at both community and network levels, stakeholders would measure effectiveness by the broader statewide influence of the network in changing and improving practice. At community level, in the long term, stakeholders acknowledged both networks had raised the profile, and provided a ‘voice’ for musculoskeletal conditions, evidencing some progress with implementation of the network mission while pursuing additional implementation strategies. Conclusions This research sheds light on stakeholders’ perceptions of assessing clinical

  8. Net benefits: assessing the effectiveness of clinical networks in Australia through qualitative methods.

    Science.gov (United States)

    Cunningham, Frances C; Ranmuthugala, Geetha; Westbrook, Johanna I; Braithwaite, Jeffrey

    2012-11-02

    In the 21st century, government and industry are supplementing hierarchical, bureaucratic forms of organization with network forms, compatible with principles of devolved governance and decentralization of services. Clinical networks are employed as a key health policy approach to engage clinicians in improving patient care in Australia. With significant investment in such networks in Australia and internationally, it is important to assess their effectiveness and sustainability as implementation mechanisms. In two purposively selected, musculoskeletal clinical networks, members and stakeholders were interviewed to ascertain their perceptions regarding key factors relating to network effectiveness and sustainability. We adopted a three-level approach to evaluating network effectiveness: at the community, network, and member levels, across the network lifecycle. Both networks studied are advisory networks displaying characteristics of the 'enclave' type of non-hierarchical network. They are hybrids of the mandated and natural network forms. In the short term, at member level, both networks were striving to create connectivity and collaboration of members. Over the short to medium term, at network level, both networks applied multi-disciplinary engagement in successfully developing models of care as key outputs, and disseminating information to stakeholders. In the long term, at both community and network levels, stakeholders would measure effectiveness by the broader statewide influence of the network in changing and improving practice. At community level, in the long term, stakeholders acknowledged both networks had raised the profile, and provided a 'voice' for musculoskeletal conditions, evidencing some progress with implementation of the network mission while pursuing additional implementation strategies. This research sheds light on stakeholders' perceptions of assessing clinical network effectiveness at community, network, and member levels during the network

  9. Intra-event isotope and raindrop size data of tropical rain reveal effects concealed by event averaged data

    Science.gov (United States)

    Managave, S. R.; Jani, R. A.; Narayana Rao, T.; Sunilkumar, K.; Satheeshkumar, S.; Ramesh, R.

    2016-08-01

    Evaporation of rain is known to contribute water vapor, a potent greenhouse gas, to the atmosphere. Stable oxygen and hydrogen isotopic compositions (δ18O and, δD, respectively) of precipitation, usually measured/presented as values integrated over rain events or monthly mean values, are important tools for detecting evaporation effects. The slope ~8 of the linear relationship between such time-averaged values of δD and δ18O (called the meteoric water line) is widely accepted as a proof of condensation under isotopic equilibrium and absence of evaporation of rain during atmospheric fall. Here, through a simultaneous investigation of the isotopic and drop size distributions of seventeen rain events sampled on an intra-event scale at Gadanki (13.5°N, 79.2°E), southern India, we demonstrate that the evaporation effects, not evident in the time-averaged data, are significantly manifested in the sub-samples of individual rain events. We detect this through (1) slopes significantly less than 8 for the δD-δ18O relation on intra-event scale and (2) significant positive correlations between deuterium excess ( d-excess = δD - 8*δ18O; lower values in rain indicate evaporation) and the mass-weighted mean diameter of the raindrops ( D m ). An estimated ~44 % of rain is influenced by evaporation. This study also reveals a signature of isotopic equilibration of rain with the cloud base vapor, the processes important for modeling isotopic composition of precipitation. d-excess values of rain are modified by the post-condensation processes and the present approach offers a way to identify the d-excess values least affected by such processes. Isotope-enabled global circulation models could be improved by incorporating intra-event isotopic data and raindrop size dependent isotopic effects.

  10. Effects of Net Metering on the Use of Small-Scale Wind Systems in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Forsyth, T. L.; Pedden, M.; Gagliano, T.

    2002-11-01

    Factors such as technological advancements, steadily decreasing costs, consumer demand, and state and federal policies are combining to make wind energy the world's fastest growing energy source. State and federal policies are facilitating the growth of the domestic, large-scale wind power market; however, small-scale wind projects (those with a capacity of less than 100 kilowatts[kW]) still face challenges in many states. Net metering, also referred to as net billing, is one particular policy that states are implementing to encourage the use of small renewable energy systems. Net metering allows individual, grid-tied customers who generate electricity using a small renewable energy system to receive credit from their utility for any excess power they generate beyond what they consume. Under most state rules, residential, commercial, and industrial customers are eligible for net metering; however, some states restrict eligibility to particular customer classes. This paper illustrates how net metering programs in certain states vary considerably in terms of how customers are credited for excess power they generate; the type and size of eligible technologies and whether the utility; the state, or some other entity administers the program. This paper focuses on10 particular states where net metering policies are in place. It analyzes how the different versions of these programs affect the use of small-scale wind technologies and whether some versions are more favorable to this technology than others. The choice of citizens in some states to net meter with photovoltaics is also examined.

  11. Kinetic isotope effect studies on milk xanthine oxidase and on chicken liver xanthine dehydrogenase

    International Nuclear Information System (INIS)

    D'Ardenne, S.C.; Edmondson, D.E.

    1990-01-01

    The effect of isotopic substitution of the 8-H of xanthine (with 2 H and 3 H) on the rate of oxidation by bovine xanthine oxidase and by chicken xanthine dehydrogenase has been measured. V/K isotope effects were determined from competition experiments. No difference in H/T (V/K) values was observed between xanthine oxidase and xanthine dehydrogenase. Xanthine dehydrogenase exhibited a larger T/D (V/K) value than that observed for xanthine oxidase. Observed H/T (V/K) values for either enzyme are less than those H/T (V/K) values calculated with D/T (V/K) data. These discrepancies are suggested to arise from the presence of a rate-limiting step(s) prior to the irreversible C-H bond cleavage step in the mechanistic pathways of both enzymes. These kinetic complexities preclude examination of whether tunneling contributes to the reaction coordinate for the H-transfer step in each enzyme. No observable exchange of tritium with solvent is observed during the anaerobic incubation of [8- 3 H]xanthine with either enzyme, which suggests the reverse commitment to catalysis (C r ) is essentially zero. With the assumption of adherence to reduced mass relationships, the intrinsic deuterium isotope effect ( D k) for xanthine oxidation is calculated. By the use of these values and steady-state kinetic data, the minimal rate for the hydrogen-transfer step is calculated to be ∼75-fold faster than k cat for xanthine oxidase and ∼10-fold faster than k cat for xanthine dehydrogenase. Values calculated for each enzyme were found to be identical within experimental uncertainty

  12. Effect of photo-selective nettings on post-harvest quality and bioactive compounds in selected tomato cultivars.

    Science.gov (United States)

    Selahle, Maphoko Kamogelo; Sivakumar, Dharini; Soundy, Puffy

    2014-08-01

    Photo-selective coloured netting is referred to as a 'new agro-technological' concept adopted to manipulate light quality changes that can induce favourable responses in plants. Tomato (Solanum lycopersicum L.) cultivars AlvaV, Irit and SCX 248 grown under the black net (commercial net, 25% shading) showed higher weight loss, loss of firmness, ascorbic acid content and decline in the ratio of soluble solids content/titrable acidity during post-harvest storage (low-temperature storage at 10°C and 90% relative humidity for 21 days followed by market shelf conditions at 25°C for 2 days). During post-harvest storage, lycopene, β-carotene, total phenolic content and antioxidant scavenging activity were higher in cvs AlfaV and Irit grown under the black or pearl nets. However, the β-carotene, total phenolic content and antioxidant scavenging activity were higher in SCX 248 grown under the red net during post-harvest storage. Cultivar AlfaV grown under the red and pearl nets had a higher number of odour active aroma compounds during post-harvest storage. Panellists preferred cv. AlfaV grown under the pearl nets after storage based on taste, overall appearance and firm textured fruits. Pearl photo-selective nets retained the overall fruit quality and bioactive components in cvs AlfaV and Irit during post-harvest storage. Red photo-selective nets, however, showed greater influence on retention of overall fruit quality and bioactive compounds in cv. SCX 248 during post-harvest storage. © 2013 Society of Chemical Industry.

  13. 13C Kinetic isotopic effect of polymerization on monomers with multiple bond

    International Nuclear Information System (INIS)

    Berman, E.L.; Polyakov, V.B.; Makovetskij, K.L.; Golenko, T.G.; Galimov, Eh.M.; AN SSSR, Moscow. Inst. Organicheskoj Khimii; AN SSSR, Moscow. Inst. Geokhimii i Analiticheskoj Khimii)

    1988-01-01

    13 C kinetic isotopic effect (KIE) of anionic and radical polymerization and metathesis reaction of monomers with multiple bonds are studied and correlation between the found KIE values of polymerization and the structure of transition state is established. 13 C KIE of polymerization reactions are investigated using monomers with natural content of the isotope. Polymerization was carried out using high-vacuum equipment: radical polymerization of methyl acrylate (MA) and vinyl acetate in benzene solution under the effect of benzoyl peroxide (60 deg C); anionic polymerization of MA, initiated by potassium butyl cellosolvolate, was realized in mass at 25 deg C; cyclopentene metathesis reaction was conducted in benzene under the effect of initiating system WCl 6 - (C 3 H 5 ) 2 Si(CH 3 ) 2 at -30 deg C; phenylacetylene polymers were prepared by polymerization in benzene solution at 20 deg C under the effect of WCl 6 . It is ascertained that 13 C KIE of radical and anionic polymerization of olefins and cycloolefin metathesis constitutes 2.0 -2.4%. Polymerization of compound with ternary bond is accompanied by a lower value of 13 C KIE (<1%), which is explained by double bond of reacting bond in transition state

  14. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1987-01-01

    The author describes a Petri net model, called coloured Petri nets (CP-nets), by means of which it is possible to describe large systems without having to cope with unnecessary details. The author introduces CP-nets and provide a first impression of their modeling power and the suitability...

  15. Learning Visual Basic NET

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Learning Visual Basic .NET is a complete introduction to VB.NET and object-oriented programming. By using hundreds of examples, this book demonstrates how to develop various kinds of applications--including those that work with databases--and web services. Learning Visual Basic .NET will help you build a solid foundation in .NET.

  16. Isotope effect in the diffusion of hydrogen and deuterium in polymers

    Energy Technology Data Exchange (ETDEWEB)

    Toi, K.; Takeuchi, K.; Tokuda, T.

    1980-02-01

    Temperature dependences of diffusion and permeation coefficients of hydrogen and deuterium in glassy and rubbery polymer films have been measured. The size of the free volume element in rubbery polymers has been calculated according to the theory of Frisch and Rogers for the quantum isotope effect, but the free volume is too large for precise calculation below the glass-transition temperature. The cooperative movement of segments is also discussed using the ratio of preexponential factors for diffusion mechanisms above and below the glass-transition temperature.

  17. Isotope effect with energy-dependent density of states and impurities

    International Nuclear Information System (INIS)

    Williams, P.J.; Carbotte, J.P.

    1992-01-01

    We have calculated the total isotope coefficient β in a model where there is energy-dependent structure in the electronic density of states. We model the structure with a simple Lorentzian. In our calculation, doping has the effect of shifting the Fermi level and broadening the structure in the density of states. We have treated the dopants both as normal and as magnetic impurities. The asymmetry observed in the experimental data is found in our results. However, the complete range of values observed is difficult to reproduce. We question also whether the shifts in Fermi level required in such models are reasonable

  18. Oxygen isotope effect on 55Mn nuclear magnetic shielding in permanganate

    International Nuclear Information System (INIS)

    Haase, A.R.; Lutz, O.; Mueller, M.; Nolle, A.

    1976-01-01

    By Fourier transform NMR spectroscopy the 55 Mn resonance lines of the different permanganate species 55 Mn 16 Osub(4-n) 18 Osub(n) - (n=0,1,2,3,4) have been resolved in aqueous solutions of potassium permanganate. An isotope effect on the Larmor frequency of 55 Mn of (0.599 +- 0.015)ppm to lower frequency was found for the substition of an 16 O atom by an 18 O atom in the permanganate ion. An oxygen exchange rate in the permanganate-water system is given. (orig.) [de

  19. Isotopic effects in the muon transfer from pmu and dmu to heavier atoms.

    Science.gov (United States)

    Dupays, Arnaud

    2004-07-23

    The results of accurate hyperspherical calculations of the muon-transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen, and neon are reported. Very good agreement with measured rates is obtained and, for the three systems, the isotopic effect is perfectly reproduced. The transfer rate is higher for deuterium in the cases of nitrogen and neon due to constructive interferences between two transfer paths. The lower transfer rate for deuterium in the case of oxygen results from a large resonant contribution. Copyright 2004 The American Physical Society

  20. Effects of winter temperature and summer drought on net ecosystem exchange of CO2 in a temperate peatland

    Science.gov (United States)

    Helfter, Carole; Campbell, Claire; Dinsmore, Kerry; Drewer, Julia; Coyle, Mhairi; Anderson, Margaret; Skiba, Ute; Nemitz, Eiko; Billett, Michael; Sutton, Mark

    2014-05-01

    Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide (CO2); their ability to sequester C is a natural feedback mechanism controlled by climatic variables such as precipitation, temperature, length of growing season and period of snow cover. In the UK it has been predicted that peatlands could become a net source of carbon in response to climate change with climate models predicting a rise in global temperature of ca. 3oC between 1961-1990 and 2100. Land-atmosphere exchange of CO2in peatlands exhibits marked seasonal and inter-annual variations, which have significant short- and long-term effects on carbon sink strength. Net ecosystem exchange (NEE) of CO2 has been measured continuously by eddy-covariance (EC) at Auchencorth Moss (55° 47'32 N, 3° 14'35 W, 267 m a.s.l.), a temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from 5 m and the site has a mean annual precipitation of 1155 mm. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species (Sphagnum spp. and Polytrichum spp.). The EC system consists of a LiCOR 7000 closed-path infrared gas analyser for the simultaneous measurement of CO2 and water vapour and of a Gill Windmaster Pro ultrasonic anemometer. Over the 10 year period, the site was a consistent yet variable sink of CO2 ranging from -34.1 to -135.9 g CO2-C m-2 yr-1 (mean of -69.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing seasons and mean winter air temperature explained 93% of the variability in summertime sink strength, indicating a phenological memory-effect. Plant development and productivity were stunted by colder winters causing a net reduction in the annual carbon sink strength of this peatland where autotrophic processes are thought to be

  1. The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Fradera, J., E-mail: jfradera@ubu.es; Cuesta-López, S., E-mail: scuesta@ubu.es

    2013-12-15

    The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety. Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAM® CFD tool for 0D–3D simulations. Results for a 0D case show the impact of a He dispersed phase of nano bubbles on hydrogen isotopes inventory at different temperatures as well as the inventory evolution during a He nucleation event. In addition, 1D and 2D axisymmetric cases are exposed showing the effect of a He dispersed gas phase on hydrogen isotope permeation through a lithium lead eutectic alloy and the effect of vortical structures on hydrogen isotope transport at a backward facing step. Exposed results give a valuable insight on current nuclear technology regarding the importance of controlling hydrogen isotope transport and its interactions with nucleation event through gas absorption processes.

  2. Effect of propolis ethanol extract on myostatin gene expression and muscle morphometry of Nile tilapia in net cages.

    Science.gov (United States)

    Buck, E L; Mizubuti, I Y; Alfieri, A A; Otonel, R A A; Buck, L Y; Souza, F P; Prado-Calixto, O P; Poveda-Parra, A R; Alexandre Filho, L; Lopera-Barrero, N M

    2017-03-16

    Propolis can be used as growth enhancer due to its antimicrobial, antioxidant, and immune-stimulant properties, but its effects on morphometry and muscle gene expression are largely unknown. The present study evaluates the influence of propolis on muscle morphometry and myostatin gene expression in Nile tilapia (Oreochromis niloticus) bred in net cages. Reversed males (GIFT strain) with an initial weight of 170 ± 25 g were distributed in a (2 x 4) factorial scheme, with two diets (DPRO, commercial diet with 4% propolis ethanol extract and DCON, commercial diet without propolis, control) and four assessment periods (0, 35, 70, and 105 experimental days). Muscles were evaluated at each assessment period. Histomorphometric analysis classified the fiber diameters into four groups: 50 μm. RT-qPCR was performed to assess myostatin gene expression. Fibers 30 µm (30-50 and > 50 µm) at 70 days were 25.39% and 40.07% for DPRO and DCON, respectively. There was greater myostatin gene expression at 105 days, averaging 1.93 and 1.89 for DCON and DPRO, respectively, with no significant difference in any of the analyzed periods. Propolis ethanol extract did not affect the diameter of muscle fibers or the gene expression of myostatin. Future studies should describe the mechanisms of natural products' effects on muscle growth and development since these factors are highly relevant for fish production performance.

  3. Effects of system net charge and electrostatic truncation on all-atom constant pH molecular dynamics †

    Science.gov (United States)

    Chen, Wei; Shen, Jana K.

    2014-01-01

    Constant pH molecular dynamics offers a means to rigorously study the effects of solution pH on dynamical processes. Here we address two critical questions arising from the most recent developments of the all-atom continuous constant pH molecular dynamics (CpHMD) method: 1) What is the effect of spatial electrostatic truncation on the sampling of protonation states? 2) Is the enforcement of electrical neutrality necessary for constant pH simulations? We first examined how the generalized reaction field and force shifting schemes modify the electrostatic forces on the titration coordinates. Free energy simulations of model compounds were then carried out to delineate the errors in the deprotonation free energy and salt-bridge stability due to electrostatic truncation and system net charge. Finally, CpHMD titration of a mini-protein HP36 was used to understand the manifestation of the two types of errors in the calculated pK a values. The major finding is that enforcing charge neutrality under all pH conditions and at all time via co-titrating ions significantly improves the accuracy of protonation-state sampling. We suggest that such finding is also relevant for simulations with particle-mesh Ewald, considering the known artifacts due to charge-compensating background plasma. PMID:25142416

  4. Effects of system net charge and electrostatic truncation on all-atom constant pH molecular dynamics.

    Science.gov (United States)

    Chen, Wei; Shen, Jana K

    2014-10-15

    Constant pH molecular dynamics offers a means to rigorously study the effects of solution pH on dynamical processes. Here, we address two critical questions arising from the most recent developments of the all-atom continuous constant pH molecular dynamics (CpHMD) method: (1) What is the effect of spatial electrostatic truncation on the sampling of protonation states? (2) Is the enforcement of electrical neutrality necessary for constant pH simulations? We first examined how the generalized reaction field and force-shifting schemes modify the electrostatic forces on the titration coordinates. Free energy simulations of model compounds were then carried out to delineate the errors in the deprotonation free energy and salt-bridge stability due to electrostatic truncation and system net charge. Finally, CpHMD titration of a mini-protein HP36 was used to understand the manifestation of the two types of errors in the calculated pK(a) values. The major finding is that enforcing charge neutrality under all pH conditions and at all time via cotitrating ions significantly improves the accuracy of protonation-state sampling. We suggest that such finding is also relevant for simulations with particle mesh Ewald, considering the known artifacts due to charge-compensating background plasma. Copyright © 2014 Wiley Periodicals, Inc.

  5. Disentangling effects of growth and nutritional status on seabird stable isotope ratios

    Science.gov (United States)

    Sears, J.; Hatch, Shyla A.; O'Brien, D. M.

    2009-01-01

    A growing number of studies suggest that an individual's physiology affects its carbon and nitrogen stable isotope signatures, obscuring a signal often assumed to be only a reflection of diet and foraging location. We examined effects of growth and moderate food restriction on red blood cell (RBC) and feather ??15N and ??13C in rhinoceros auklet chicks (Cerorhinca monocerata), a piscivorous seabird. Chicks were reared in captivity and fed either control (75 g/day; n = 7) or ~40% restricted (40 g/day; n = 6) amounts of high quality forage fish. We quantified effects of growth on isotopic fractionation by comparing ??15N and ??13C in control chicks to those of captive, non-growing subadult auklets (n = 11) fed the same diet. To estimate natural levels of isotopic variation, we also collected blood from a random sample of free-living rhinoceros auklet adults and chicks in the Gulf of Alaska (n = 15 for each), as well as adult feather samples (n = 13). In the captive experiment, moderate food restriction caused significant depletion in ??15N of both RBCs and feathers in treatment chicks compared to control chicks. Growth also induced depletion in RBC ??15N, with chicks exhibiting lower ??15N when they were growing the fastest. As growth slowed, ??15N increased, resulting in an overall pattern of enrichment over the course of the nestling period. Combined effects of growth and restriction depleted ??15N in chick RBCs by 0.92???. We propose that increased nitrogen-use efficiency is responsible for 15N depletion in both growing and food-restricted chicks. ??15N values in RBCs of free-ranging auklets fell within a range of only 1.03???, while feather ??15N varied widely. Together, our captive and field results suggest that both growth and moderate food restriction can affect stable isotope ratios in an ecologically meaningful way in RBCs although not feathers due to greater natural variability in this tissue. ?? 2008 Springer-Verlag.

  6. The oxygen isotope effect on the in-plane penetration depth in cuprate superconductors

    International Nuclear Information System (INIS)

    Khasanov, R; Shengelaya, A; Morenzoni, E; Conder, K; Savic, I M; Keller, H

    2004-01-01

    Muon spin rotation (μSR) studies of the oxygen isotope ( 16 O/ 18 O) effect (OIE) on the in-plane magnetic field penetration depth λ ab in cuprate high-temperature superconductors (HTS) are presented. First, the doping dependence of the OIE on the transition temperature T c in various HTS is briefly discussed. It is observed that different cuprate families show similar doping dependences of the OIE on T c . Then, bulk μSR, low-energy μSR, and magnetization studies of the total and site-selective OIE on λ ab are described in some detail. A substantial OIE on λ ab was observed in various cuprate families at all doping levels, suggesting that cuprate HTS are non-adiabatic superconductors. The experiments clearly demonstrate that the total OIE on T c and λ ab arise from the oxygen sites within the superconducting CuO 2 planes, demonstrating that the phonon modes involving the movement of planar oxygen are dominantly coupled to the supercarriers. Finally, it is shown that the OIE on T c and λ ab exhibit a relation that appears to be generic for different families of cuprate HTS. The observation of these unusual isotope effects implies that lattice effects play an essential role in cuprate HTS and have to be considered in any realistic model of high-temperature superconductivity

  7. The oxygen isotope effect on the in-plane penetration depth in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Khasanov, R [Physik-Institut der Universitaet Zuerich, CH-8057 Zurich (Switzerland); Shengelaya, A [Physik-Institut der Universitaet Zuerich, CH-8057 Zurich (Switzerland); Morenzoni, E [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Conder, K [Laboratory for Neutron Scattering, ETH Zuerich and PSI Villigen, CH-5232 Villigen PSI (Switzerland); Savic, I M [Faculty of Physics, University of Belgrade, 11001 Belgrade (Serbia and Montenegro); Keller, H [Physik-Institut der Universitaet Zuerich, CH-8057 Zurich (Switzerland)

    2004-10-13

    Muon spin rotation ({mu}SR) studies of the oxygen isotope ({sup 16}O/{sup 18}O) effect (OIE) on the in-plane magnetic field penetration depth {lambda}{sub ab} in cuprate high-temperature superconductors (HTS) are presented. First, the doping dependence of the OIE on the transition temperature T{sub c} in various HTS is briefly discussed. It is observed that different cuprate families show similar doping dependences of the OIE on T{sub c}. Then, bulk {mu}SR, low-energy {mu}SR, and magnetization studies of the total and site-selective OIE on {lambda}{sub ab} are described in some detail. A substantial OIE on {lambda}{sub ab} was observed in various cuprate families at all doping levels, suggesting that cuprate HTS are non-adiabatic superconductors. The experiments clearly demonstrate that the total OIE on T{sub c} and {lambda}{sub ab} arise from the oxygen sites within the superconducting CuO{sub 2} planes, demonstrating that the phonon modes involving the movement of planar oxygen are dominantly coupled to the supercarriers. Finally, it is shown that the OIE on T{sub c} and {lambda}{sub ab} exhibit a relation that appears to be generic for different families of cuprate HTS. The observation of these unusual isotope effects implies that lattice effects play an essential role in cuprate HTS and have to be considered in any realistic model of high-temperature superconductivity.

  8. The effect of irradiance on long-term skeletal growth and net photosynthesis in Galaxea fascicularis under four light conditions.

    NARCIS (Netherlands)

    Schutter, M.; Velthoven, van B.; Janse, M.; Osinga, R.; Janssen, M.G.J.; Wijffels, R.H.; Verreth, J.A.J.

    2008-01-01

    The relation between irradiance, skeletal growth and net photosynthesis was studied for the scleractinian coral Galaxea fascicularis to provide experimental evidence for mediation of light-enhanced calcification through photosynthesis. The hypothesis was tested that skeletal growth and

  9. Comparison of the effects of two bongo net mesh sizes on the estimation of abundance and size of Engraulidae eggs

    Directory of Open Access Journals (Sweden)

    Jana Menegassi del Favero

    2015-06-01

    Full Text Available Abstract Studies of ichthyoplankton retention by nets of different mesh sizes are important because they help in choosing a sampler when planning collection and the establishment of correction factors. These factors make it possible to compare studies performed with nets of different mesh sizes. In most studies of mesh retention of fish eggs, the taxonomic identification is done at the family level, resulting in the loss of detailed information. We separated Engraulidae eggs, obtained with 0.333 mm and 0.505 mm mesh bongo nets at 172 oceanographic stations in the southeastern Brazilian Bight, into four groups based on their morphometric characteristics. The difference in the abundance of eggs caught by the two nets was not significant for those groups with highest volume, types A and B, but in type C (Engraulis anchoita, the most eccentric, and in type D, of the smallest volume, the difference was significant. However, no significant difference was observed in the egg size sampled with each net for E. anchoita and type D, which exhibited higher abundance in the 0.333 mm mesh net and minor axis varying from 0.45-0.71 mm, smaller than the 0.505 mm mesh aperture and the mesh diagonal.

  10. Isotope effects in mass-spectrometry; Les effets isotopiques en spectrometrie de masse

    Energy Technology Data Exchange (ETDEWEB)

    Leicknam, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires. Departement de physico-chimie, service des isotopes stables, section de spectrometrie de masse

    1967-05-01

    In the first part, a review is made of the work concerning the influence of isotopic substitution on the stabilities of ionised molecules and the bond-breaking probabilities; metastable transitions are also affected by this substitution. A model based on the Franck-Condon principle accounts for the experimentally observed isotopic effects for diatomic molecules; to a certain extent it is possible to generalise the calculation for the case of isotopic molecules of carbon dioxide gas. For deuterated polyatomic molecules there exist a {pi} effect making it possible to compare the relative stabilities of the X-H and X-D bonds, and a {gamma} effect which characterizes the different behaviours of the X-H bond in a normal molecule and in its partially deuterated homologue. Usually there is a very marked {pi} effect (e.g. the C-D bonds are more difficult to break than the homologous C-H bonds) and a {gamma} effect, the partial deuteration of a molecule leading in general to an increase in the probability of breakage of a given bond. An interpretation of {pi} and {gamma} effects based on Rosenstock near-equilibrium theory accounts for the observed phenomena, qualitatively at least, in the case of propane and acetylene. In the second part are gathered together results concerning isotopic effects produced during the formation of rearranged ions. The existence of cyclic transition ions has made it possible for Mc Lafferty to explain the existence of these ions in the mass spectrum; isotopic substitution leads to a modification of the rearrangement mechanism, the bonding forces being no longer the same. (author) [French] Dans une premiere partie, on rassemble les travaux concernant l'influence de la substitution isotopique sur les stabilites des molecules ionisees et les probabilites de rupture des liaisons; les transitions metastables sont egalement modifiees par cette substitution. Un modele base sur le principe de Franck-Condon rend compte des effets isotopiques

  11. Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico.

    Science.gov (United States)

    Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

    2013-12-01

    [1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings ( δ 18 O tr ). Interannual variation in δ 18 O tr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ 13 C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ 18 O tr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18 O-depleted rain in the region and seem to have affected the δ 18 O tr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ 18 O tr of M . acantholoba can be used as a proxy for source water δ 18 O and that interannual variation in δ 18 O prec is caused by a regional amount effect. This contrasts with δ 18 O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in

  12. [Effects of drip irrigation with plastic mulching on the net primary productivity, soil heterotrophic respiration, and net CO2 exchange flux of cotton field ecosystem in Xinjiang, Northwest China].

    Science.gov (United States)

    Li, Zhi-Guo; Zhang, Run-Hua; Lai, Dong-Mei; Yan, Zheng-Yue; Jiang, Li; Tian, Chang-Yan

    2012-04-01

    In April-October, 2009, a field experiment was conducted to study the effects of drip irrigation with plastic mulching (MD) on the net primary productivity (NPP), soil heterotrophic respiration (Rh) , and net CO2 exchange flux (NEF(CO2)) of cotton field ecosystem in Xinjiang, taking the traditional flood irrigation with no mulching (NF) as the control. With the increasing time, the NPP, Rh, and NEF(CO2) in treatments MD and NF all presented a trend of increasing first and decreased then. As compared with NF, MD increased the aboveground and belowground biomass and the NPP of cotton, and decreased the Rh. Over the whole growth period, the Rh in treatment MD (214 g C x m(-2)) was smaller than that in treatment NF (317 g C x m(-2)), but the NEF(CO2) in treatment MD (1030 g C x m(-2)) was higher than that in treatment NF (649 g C x m(-2)). Treatment MD could fix the atmospheric CO2 approximately 479 g C x m(-2) higher than treatment NF. Drip irrigation with plastic mulching could promote crop productivity while decreasing soil CO2 emission, being an important agricultural measure for the carbon sequestration and emission reduction of cropland ecosystems in arid area.

  13. Laser separation of uranium isotopes

    International Nuclear Information System (INIS)

    Porter, J.T.

    1981-01-01

    Method and apparatus for separating uranium isotopes are claimed. The method comprises the steps of irradiating a uranyl source material at a wavelength selective to a desired isotope and at an effective temperature for isotope spectral line splitting below about 77 deg.K., further irradiating the source material within the fluorescent lifetime of the source material to selectively photochemically reduce the excited isotopic species, and chemically separating the reduced isotope species from the remaining uranyl salt compound

  14. Synergistic effect of embryo vaccination with Eimeria profilin and Clostridium perfringens NetB proteins on inducing protective immunity against necrotic enteritis in broiler chickens

    Science.gov (United States)

    The effects of embryo vaccination with Eimeria profilin plus Clostridium perfringens NetB toxin proteins in combination with the Montanide IMS-OVO adjuvant on the chicken immune response to necrotic enteritis were investigated using an E. maxima/C. perfringens co-infection model. Eighteen-day-old br...

  15. 26 CFR 1.996-8 - Effect of carryback of capital loss or net operating loss to prior DISC taxable year.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 10 2010-04-01 2010-04-01 false Effect of carryback of capital loss or net operating loss to prior DISC taxable year. 1.996-8 Section 1.996-8 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES Domestic International Sales...

  16. Effect of baking and fermentation on the stable carbon and nitrogen isotope ratios of grain-based food.

    Science.gov (United States)

    Bostic, Joshua N; Palafox, Sherilyn J; Rottmueller, Marina E; Jahren, A Hope

    2015-05-30

    Isotope ratio mass spectrometry (IRMS) is used extensively to reconstruct general attributes of prehistoric and modern diets in both humans and animals. In order to apply these methods to the accurate determination of specific intakes of foods/nutrients of interest, the isotopic signature of individually consumed foods must be constrained. For example, 86% of the calories consumed in the USA are derived from processed and prepared foods, but the relationship between the stable isotope composition of raw ingredients and the resulting products has not been characterized. To examine the effect of common cooking techniques on the stable isotope composition of grain-based food items, we prepared yeast buns and sugar cookies from standardized recipes and measured bulk δ(13) C and δ(15) N values of samples collected throughout a 75 min fermentation process (buns) and before and after baking at 190°C (buns and cookies). Simple isotope mixing models were used to determine if the isotopic signatures of 13 multi-ingredient foods could be estimated from the isotopic signatures of their constituent raw ingredients. No variations in δ(13) C or δ(15) N values were detected between pre- and post-baked yeast buns (pre: -24.78‰/2.61‰, post: -24.75‰/2.74‰), beet-sugar cookies (pre: -24.48‰/3.84‰, post: -24.47‰/3.57‰), and cane-sugar cookies (pre: -19.07‰/2.97‰, post: -19.02‰/3.21‰), or throughout a 75 min fermentation process in yeast buns. Using isotopic mass balance equations, the δ(13) C/δ(15) N values of multi-ingredient foods were estimated from the isotopic composition of constituent raw ingredients to within 0.14 ± 0.13‰/0.24 ± 0.17‰ for gravimetrically measured recipes and 0.40 ± 0.38‰/0.58 ± 0.53‰ for volumetrically measured recipes. Two common food preparation techniques, baking and fermentation, do not substantially affect the carbon or nitrogen isotopic signature of grain-based foods. Mass-balance equations can be used to

  17. Effect of adrenaline and alpha-agonists on net rate of liquid absorption from the pleural space of rabbits.

    Science.gov (United States)

    Zocchi, L; Raffaini, A; Agostoni, E

    1997-05-01

    Indirect evidence supporting a solute-coupled liquid absorption from the pleural space of rabbits has recently been provided; moreover, the beta 2-adrenoceptor agonist terbutaline has been found to increase this absorption. In this study the effect of adrenaline and alpha-adrenoceptor agonists on net rate of liquid absorption (Jnet) from albumin Ringer hydrothoraces of various sizes has been determined in anaesthetized rabbits. In hydrothoraces with adrenaline (5 x 10(-6) M) the relationship between Jnet and volume of liquid injected was displaced upwards by 0.09 ml h-1 relative to that in control hydrothoraces (P liquid absorption, since beta-agonists inhibit lymphatic activity while, at relatively high concentrations, they may increase active transport. Conversely, the strong stimulation of lymphatic alpha-receptors that should occur with adrenaline after beta-blockade may fail to increase lymphatic drainage, because it has been shown that the increase in contraction frequency of lymphatics may be balanced by the decrease in their stroke volume. Arterial blood pressure during the hydrothoraces with adrenaline was unchanged. In hydrothoraces with the alpha 2-agonist clonidine (5 x 10(-6) M; a less potent agent than adrenaline) the slope of the relationship between Jnet and volume injected increased by 26% (P liquid load. In hydrothoraces with the alpha 1-agonist phenylephrine (5 x 10(-6) or 10(-7) M) Jnet was simlar to control values.

  18. Effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on pH, net oxygen production, and respiration by algae

    Science.gov (United States)

    Scholefield, Ronald J.; Fredricks, Kim T.; Slaght, Karen S.; Seelye, James G.

    1999-01-01

    The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used in the United States and Canada for more than 35 years to control larval sea lampreys (Petromyzon marinus) in tributaries of the Great Lakes. Occasionally, during stream treatments with TFM, nontarget-fish mortality reaches unacceptable levels. These losses could be due to the presence of sensitive fish species, excess TFM, or a combination of factors that influence the toxicity of TFM, such as delays in daily stream reaeration by algae resulting in extended periods of low pH and low dissolved oxygen (DO). We determined the effects of a broad range of TFM concentrations on net DO production and respiration by two species of algae, in two culture media (high alkalinity and low alkalinity). The pH and DO in cultures of Chlorella pyrenoidosa and Selenastrum capricornutum were recorded at time zero and again after a 9-h exposure to TFM under either lighted or dark conditions. Algal cultures exposed to TFM concentrations typical of those used to control sea lampreys in streams showed only small changes in pH (<0.1) and small reductions in DO (about 8% in lighted conditions and 11% in dark conditions). Changes in pH and DO of this magnitude probably do not change the efficacy of TFM or cause nontarget fish mortality if algae are the predominant photosynthetic organisms in the stream.

  19. Isotopic effect on the quantum tunneling of the magnetization of molecular nanomagnets

    International Nuclear Information System (INIS)

    Sessoli, Roberta; Caneschi, Andrea; Gatteschi, Dante; Sorace, Lorenzo; Cornia, Andrea; Wernsdorfer, Wolfgang

    2001-01-01

    The molecular cluster [Fe 8 (tacn) 6 O 2 (OH) 12 ]Br 8 ·9H 2 O, Fe 8 , characterized by S=10, with biaxial magnetic anisotropy is an ideal system to investigate quantum effects in the dynamics of the magnetization. Resonant quantum tunneling gives rise to stepped hysteresis cycles and below 0.35 K pure quantum tunneling of the magnetization has been observed. The role of hyperfine fields in promoting the tunneling as a source of dynamic broadening of the states involved in the tunnel transition is investigated by preparing and characterizing two isotopically enriched samples using 57 Fe and 2 H. The relaxation rate in the tunneling regime is proportional to the hyperfine field generated by the nuclei. Also, the intrinsic linewidth of the tunneling resonance scales with the hyperfine field as confirmed by calculations of the super (or transfer) and direct hyperfine interactions. Preliminary results on a novel cluster of formula [Fe 4 (OCH 3 ) 6 (dpm) 6 ], Fe 4 , suited for a more dramatic isotope effect on the tunneling rate are also reported

  20. Isotopic effect on the quantum tunneling of the magnetization of molecular nanomagnets

    Energy Technology Data Exchange (ETDEWEB)

    Sessoli, Roberta E-mail: sessoli@chim1.unifi.it; Caneschi, Andrea; Gatteschi, Dante; Sorace, Lorenzo; Cornia, Andrea; Wernsdorfer, Wolfgang

    2001-05-01

    The molecular cluster [Fe{sub 8}(tacn){sub 6}O{sub 2}(OH){sub 12}]Br{sub 8}{center_dot}9H{sub 2}O, Fe{sub 8}, characterized by S=10, with biaxial magnetic anisotropy is an ideal system to investigate quantum effects in the dynamics of the magnetization. Resonant quantum tunneling gives rise to stepped hysteresis cycles and below 0.35 K pure quantum tunneling of the magnetization has been observed. The role of hyperfine fields in promoting the tunneling as a source of dynamic broadening of the states involved in the tunnel transition is investigated by preparing and characterizing two isotopically enriched samples using {sup 57}Fe and {sup 2}H. The relaxation rate in the tunneling regime is proportional to the hyperfine field generated by the nuclei. Also, the intrinsic linewidth of the tunneling resonance scales with the hyperfine field as confirmed by calculations of the super (or transfer) and direct hyperfine interactions. Preliminary results on a novel cluster of formula [Fe{sub 4}(OCH{sub 3}){sub 6}(dpm){sub 6}], Fe{sub 4}, suited for a more dramatic isotope effect on the tunneling rate are also reported.

  1. Trace element and isotopic effects arising from magma migration beneath mid-ocean ridges

    International Nuclear Information System (INIS)

    Kenyon, P.M.

    1990-01-01

    The trace element concentrations and isotopic ratios in the magma erupted on mid-ocean ridges may differ from those in the source material due to physical effects such as porous flow dispersion, exchange of trace elements between the fluid and solid phases during magma migration, and convective mixing in magma chambers. These differences are in addition to those produced by better known processes such as fractional crystallization and partial melting. The effects of the three former processes are described. It is predicted that magma typically reaches the sub-ridge magma chambers with a spatial heterogeneity only slightly reduced from that of the source material, but with a subdued variation in time. Convective mixing then further reduces the spatial heterogeneity. Application of the results for convective mixing to a recent Fourier analysis of 87 Sr/ 86 Sr variations along the Mid-Atlantic Ridge suggests that the falloff in amplitude of variation observed with decreasing wavelength in the Mid-Atlantic Ridge data cannot be explained by convective mixing in magma chambers. Instead, it is postulated that this falloff is due to the mechanics of the production and/or the solid-state convective mixing of chemical and isotopic heterogeneities in the solid mantle. (orig.)

  2. Isotopic study of the effect of Tarbela reservoir on the groundwater system in the downstream areas

    International Nuclear Information System (INIS)

    Sajjad, M.I.; Tasneem, M.A.; Hussain, S.D.; Khan, I.H.; Ali, M.; Latif, Z.

    1994-04-01

    Isotopic studies were carried out on the right side of river Indus, downstream of Tarbela dam to study the effect of Tarbela Reservoir on the groundwater system. The main objectives of the study were to determine the hydraulic connection, if any, between the Tarbela Lake and the groundwater appearing in the ponds near Gadon Amazai, see the effect of Tarbela dam on the groundwater system in the downstream areas, compute the relative contribution of different recharge sources towards groundwater system and to estimate residence time of groundwater in the area. Isotopic data reveals that the ponds near Gadoon Amazai area are being recharged by local rains and there is no contribution of Tarbela lake. The area around Gadoon Amazai, Topi and Kalabat is solely recharged by local rains while the area around Swabi, Zaida and Lahor has mixed recharge with major contribution from local canal system. Tritium data suggests that the residence time of groundwater in the study area varies from a few years to 30 years. Te groundwater in the area has low dissolved salt contents and is, generally, of good quality. (author) 19 figs

  3. Kinetic α secondary deuterium isotope effects for O-ethyl S-phenyl benzaldehyde acetal hydrolysis

    International Nuclear Information System (INIS)

    Ferraz, J.P.; Cordes, E.H.

    1979-01-01

    The rate of hydrolysis of O-ethyl S-phenyl benzaldehyde acetal at 25 0 C in 20% dioxane--80% water is independent of pH over the range pH6-12; k/sub obsd/ = 1.9 x 10 -7 s -1 . Under more acidic conditions, the rate increases linearly with the activity of the hydrated proton; k 2 = 2.95 x 10 -2 M -1 s -1 . The kinetic α secondary deuterium isotope effect for acid-catalyzed hydrolysis of O-ethyl S-phenyl benzaldehyde acetal, measured at 25 0 C in 20% aqueous dioxane containing 0.05 M HCl, is k/sub H//k/sub D/ = 1.038 +- 0.008, a value consistent with a transition state in which the C--S bond is stretched rather little. In contrast, the corresponding isotope effect for the pH-independent hydrolysis of this substrate, measured at 42.5 0 C in 20% dioxane, is 1.13 +- 0.02, a value consistent with complete C--S bond cleavage in the transition state and rate-determining diffusion apart of the ion-pair formed as the initial intermediate, in accord with the suggestion of Jensen and Jencks. 1 figure, 4 tables

  4. 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.)

  5. Solvent isotope effects on tautomerization equilibria of papain and model thiolamines

    International Nuclear Information System (INIS)

    Creighton, D.J.; Schamp, D.J.

    1980-01-01

    The state of ionization of the active site sulfhydryl group of papain at the pH-optimum of activity (pH approximately 6.5) remains a controversial issue. An alternative approach to the problem is reported here which utilizes the difference between the isotopic fractionation factor of the S-H bond (phi approximately equal to 0.4) and the N-H bond (phi = 0.97). In principle, the tautomerization equilibrium should be subject to an inverse solvent deuterium isotope effect in which the non-ionised form is more stable relative to the ionised form in D 2 O compared to H 2 O (K(H 2 O)/K(D 2 O) = phisub(SH)/phisub(MH) approximately equal to 0.4). This priniciple has been successfully tested on the tautomerization equilibria of cysteine and β-mercaptoethylamine from spectrophotometric titrations. To the extent that these simple thiolamines model the spectral properties of the tautomeric species envisioned in the active site of papain, the tautomerization equilibrium constant for papain is estimated (K(H 2 O) approximately equal to 2) from a comparison of the effect of solvent D 2 O on the mercaptide ion spectra of the thiolamines and the mercaptide ion-like difference absorption spectrum of papain. (Auth.)

  6. Antiproton-nucleus interaction and nuclear E2 resonance effect in molybdenum and neodymium isotopes

    International Nuclear Information System (INIS)

    Kanert, W.

    1986-01-01

    Antiprotonix X-radiation from 92 Mo, 94 Mo, 95 Mo, 98 Mo, 100 Mo and 146 Nd, 148 Nd was measured with Ge detectors at the LEAR (CERN). The nuclear E2 resonance effect (configuration mixing by dynamic electric quadrupole interaction) was for the first time observed in antiprotonic atoms. It effects in 94 Mo, 95 Mo, and 98 Mo a mixing of the atomic levels (7,6) and (5,4). From the resulting weakening of the antiprotonic X-ray line (7→6) in comparison with the nonresonant isotope 92 Mo information on the effects of the strong interaction in the (5,4) level was obtained which is in Mo not directly observable. The absorption widths by strong interactions in the level (6,5) resulted for 92 Mo, 94 Mo, 95 Mo, and 98 Mo to 1.4±0.3 keV, 2.3±0.9 keV, 1.9±0.4 keV, and 2.3±0.7 keV, the energy shifts by strong interactions to 0.46±0.08 keV, 0.64±0.22 keV, 0.74±0.12 keV, and 0.55±0.16 keV. In the nonresonant isotope 92 Mo the absorption width of the level (7,6) to 19.5±1.2 eV. A fit of the effective scattering length to the data for 92 Mo resulted anti a = (0.25+3.05i) fm. In 100 Mo the predicted case of strong coupling could be experimentally established by the nearly complete extinction of the line (8→7) and the broadening of the line (9→8). In 148 Nd the nuclear E2 resonance effect effects a mixing of the levels (9,8) and (8,6) and by this a reduction of the line (9→8) in comparison to 146 Nd. For this isotope information on the effects of the strong interaction could be extracted separately for the fine structure components. (orig.) [de

  7. Mixing rules for and effects of other hydrogen isotopes and of isotopic swamping on tritium recovery and loss to biosphere from fusion reactors

    International Nuclear Information System (INIS)

    Pendergrass, J.H.

    1978-01-01

    Efficient recovery of bred and unburnt tritium from fusion reactors, and control of its migration within reactors and of its escape into the biosphere are essential for self-sufficient fuel cycles and for public, plant personnel, and environmental protection. Tritium in fusion reactors will be mixed with unburnt deuterium and protium introduced by (n,p) reactions and diffusion into coolant loops from steam cycles. Rational design for tritium recovery and escape prevention must acknowledge this fact. Consequences of isotopic admixture are explored, mixing rules for projected fusion reactor dilute-solution conditions are developed, and a rule of thumb regarding their effects on tritium recovery methods is formulated

  8. Deflection of atomic beams with isotope separation by optical resonance radiation using stimulated emission and the ac stark effect

    International Nuclear Information System (INIS)

    Bjorkholm, J.E.; Liao, P.F.H.

    1977-01-01

    Improved atomic beam deflection and improved isotope separation, even in vapors, is proposed by substituting the A.C. Stark effect for the baseband chirp of the pushing beam in the prior proposal by I. Nebenzahl et al., Applied Physics Letters, Vol. 25, page 327 (September 1974). The efficiency inherent in re-using the photons as in the Nebenzahl et al proposal is retained; but the external frequency chirpers are avoided. The entire process is performed by two pulses of monochromatic coherent light, thereby avoiding the complication of amplifying frequency-modulated light pulses. The A.C. Stark effect is provided by the second beam of coherent monochromatic light, which is sufficiently intense to chirp the energy levels of the atoms or isotopes of the atomic beam or vapor. Although, in general, the A.C. Stark effect will alter the isotope shift somewhat, it is not eliminated. In fact, the appropriate choice of frequencies of the pushing and chirping beams may even relax the requirements with respect to the isotope absorption line shift for effective separation. That is, it may make the isotope absorption lines more easily resolvable

  9. Investigations on the heterogenous catalytic hydrogenation using isotope effect and gamma- and neutron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kudlacek, R; Cabicar, J [Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Katedra Jaderne Chemie

    1976-01-01

    The kinetic and solvent isotope effects during the maleic acid heterogeneous catalytic hydrogenation and deuteration in light and heavy water have been studied. Also the effect of the gamma and neutron irradiation on the Ni-ZnO catalysts (with various ratios of components) on the reaction kinetics and mechanism has been measured, as well as the effect of pH on the adsorption behaviour of maleic acid and the temperature dependence of the reaction rate. Existence of different adsorption centers for hydrogen and maleic acid could be deduced from these experiments. A reaction mechanism based on the two-dimensional diffusion of components in the surface is proposed. The catalyst is formed from Ni and ZnO-microspheres. Hydrogen is bound to nickel and maleic acid is adsorbed on the ZnO-microspheres. The reaction takes place on the boundary layers of these microspheres.

  10. Quantification and isotopic analysis of intracellular sulfur metabolites in the dissimilatory sulfate reduction pathway

    Science.gov (United States)

    Sim, Min Sub; Paris, Guillaume; Adkins, Jess F.; Orphan, Victoria J.; Sessions, Alex L.

    2017-06-01

    Microbial sulfate reduction exhibits a normal isotope effect, leaving unreacted sulfate enriched in 34S and producing sulfide that is depleted in 34S. However, the magnitude of sulfur isotope fractionation is quite variable. The resulting changes in sulfur isotope abundance have been used to trace microbial sulfate reduction in modern and ancient ecosystems, but the intracellular mechanism(s) underlying the wide range of fractionations remains unclear. Here we report the concentrations and isotopic ratios of sulfur metabolites in the dissimilatory sulfate reduction pathway of Desulfovibrio alaskensis. Intracellular sulfate and APS levels change depending on the growth phase, peaking at the end of exponential phase, while sulfite accumulates in the cell during stationary phase. During exponential growth, intracellular sulfate and APS are strongly enriched in 34S. The fractionation between internal and external sulfate is up to 49‰, while at the same time that between external sulfate and sulfide is just a few permil. We interpret this pattern to indicate that enzymatic fractionations remain large but the net fractionation between sulfate and sulfide is muted by the closed-system limitation of intracellular sulfate. This 'reservoir effect' diminishes upon cessation of exponential phase growth, allowing the expression of larger net sulfur isotope fractionations. Thus, the relative rates of sulfate exchange across the membrane versus intracellular sulfate reduction should govern the overall (net) fractionation that is expressed. A strong reservoir effect due to vigorous sulfate reduction might be responsible for the well-established inverse correlation between sulfur isotope fractionation and the cell-specific rate of sulfate reduction, while at the same time intraspecies differences in sulfate uptake and/or exchange rates could account for the significant scatter in this relationship. Our approach, together with ongoing investigations of the kinetic isotope

  11. Groundwater Inputs to Rivers: Hydrological, Biogeochemical and Ecological Effects Inferred by Environmental Isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Stellato, L. [Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE), Seconda Universita degli Studi di Napoli, Caserta (Italy); Newman, B. D. [Isotope Hydrology Section, International Atomic Energy Agency, Vienna (Austria)

    2013-05-15

    In an effort to improve river management, numerous studies over the past two decades have supported the concept that river water and groundwater need to be considered together, as part of a hydrologic continuum. In particular, studies of the interface between surface water and groundwater (the hyporheic zone) have seen the tight collaboration of catchment hydrologists and stream ecologists in order to elucidate processes affecting stream functioning. Groundwater and surface waters interact at different spatial and temporal scales depending on system hydrology and geomorphology, which in turn influence nutrient cycling and in-stream ecology in relation to climatic, geologic, biotic and anthropogenic factors. In this paper, groundwater inputs to rivers are explored from two different and complementary perspectives: the hydrogeological, describing the generally acknowledged mechanisms of streamflow generation and the main factors controlling stream-aquifer interactions, and the ecologic, describing the processes occurring at the hyporheical and the riparian zones and their possible effects on stream functioning and on nutrient cycling, also taking into consideration the impact of human activities. Groundwater inflows to rivers can be important controls on hot moment/hot spot type biogeochemical behaviors. A description of the common methods used to assess these processes is provided emphasizing tracer methods (including physical, chemical and isotopic). In particular, naturally occurring isotopes are useful tools to identify stream discharge components, biogeochemical processes involved in nutrient cycling (such as N and P dynamics), nutrient sources and transport to rivers, and subsurface storage zones and residence times of hyporheic water. Several studies which have employed isotope techniques to clarify the processes occurring when groundwater enters the river,are reported in this chapter, with a view to highlighting both the advantages and limitations of these

  12. Isotope effect studies of chicken liver NADP malic enzyme: role of the metal ion and viscosity dependence

    International Nuclear Information System (INIS)

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

    1988-01-01

    The role of the metal ion in the oxidative decarboxylation of malate by chicken liver NADP malic enzyme and details of the reaction mechanism have been investigated by 13 C isotope effects. With saturating NADP and the indicated metal ion at a total concentration 10-fold higher than its K/sub m/, the following primary 13 C kinetic isotope effects at C 4 of malate [ 13 (VK/sub mal/)] were observed at pH 8.0: Mg 2+ , 1.0336; Mn 2+ , 1.0365; Cd 2+ , 1.0366; Zn 2+ , 1.0337; Co 2+ , 1.0283; Ni 2+ , 1.025. Knowing the partitioning of the intermediate oxalacetate between decarboxylation to pyuvate and reduction to malate allows calculation of the intrinsic carbon isotope effect for decarboxylation to pyuvate and reduction to malate allows calculation of the intrinsic carbon isotope effect for decarboxylation. For Mg 2+ as activator, this was 1.049 with NADP and 1.046 with 3-acetylpyridine adenine dinucleotide phosphate, although the intrinsic primary deuterium isotope effects on dehydrogenation were 5.6 and 4.2, and the partition ratios of the oxalacetate intermediate for decarboxylation as opposed to hydride transfer were 0.11 and 3.96. It was not possible to calculate reasonable intrinsic carbon isotope effects with the other metal ions by use of the partitioning ratio of oxalacetate because of decarboxylation by another mechanism. The variation of 13 (VK/sub mal/) with pH was used to dissect the total forward and external components. When the authors attempted to use the variation of 13 (VK/sub mal/) with solution viscosity to determine the internal and external commitments, incorrect values were obtained because of a specific effect of the viscosogen in decreasing the K/sub m/ for malate, so that VK/sub mal/ actually increased with viscosity instead of decreasing, as theory predicts

  13. Cost-effective sampling of 137Cs-derived net soil redistribution: part 1 – estimating the spatial mean across scales of variation

    International Nuclear Information System (INIS)

    Li, Y.; Chappell, A.; Nyamdavaa, B.; Yu, H.; Davaasuren, D.; Zoljargal, K.

    2015-01-01

    The 137 Cs technique for estimating net time-integrated soil redistribution is valuable for understanding the factors controlling soil redistribution by all processes. The literature on this technique is dominated by studies of individual fields and describes its typically time-consuming nature. We contend that the community making these studies has inappropriately assumed that many 137 Cs measurements are required and hence estimates of net soil redistribution can only be made at the field scale. Here, we support future studies of 137 Cs-derived net soil redistribution to apply their often limited resources across scales of variation (field, catchment, region etc.) without compromising the quality of the estimates at any scale. We describe a hybrid, design-based and model-based, stratified random sampling design with composites to estimate the sampling variance and a cost model for fieldwork and laboratory measurements. Geostatistical mapping of net (1954–2012) soil redistribution as a case study on the Chinese Loess Plateau is compared with estimates for several other sampling designs popular in the literature. We demonstrate the cost-effectiveness of the hybrid design for spatial estimation of net soil redistribution. To demonstrate the limitations of current sampling approaches to cut across scales of variation, we extrapolate our estimate of net soil redistribution across the region, show that for the same resources, estimates from many fields could have been provided and would elucidate the cause of differences within and between regional estimates. We recommend that future studies evaluate carefully the sampling design to consider the opportunity to investigate 137 Cs-derived net soil redistribution across scales of variation. - Highlights: • The 137 Cs technique estimates net time-integrated soil redistribution by all processes. • It is time-consuming and dominated by studies of individual fields. • We use limited resources to estimate soil

  14. Deduction of kinetic mechanism in multisubstrate enzyme reactions from tritium isotope effects. Application to dopamine beta-hydroxylase

    International Nuclear Information System (INIS)

    Klinman, J.P.; Humphries, H.; Voet, J.G.

    1980-01-01

    Primary tritium isotope effects have been measured for the hydroxylation of [2-3H] dopamine catalyzed by dopamine beta-hydroxylase. Experimental values vary from 8.8 +/- 1.4 at 0.02 mM oxygen to 4.1 +/- 0.6 at 1.0 mM oxygen. It is shown that the observed dependence of the isotope effect on oxygen concentration provides unequivocal evidence for a kinetically significant dissociation of both dopamine and oxygen from enzyme, ternary complex. This approach, which is applicable to any multisubstrate enzyme characterized by detectable kinetic isotope effects, provides an alternate to classical methods for the elucidation of kinetic order in enzyme-catalyzed reactions

  15. Molybdenum isotope variations in calc-alkaline lavas from the Banda arc, Indonesia: Assessing the effect of crystal fractionation in creating isotopically heavy continental crust

    NARCIS (Netherlands)

    Wille, Martin; Nebel, Oliver; Pettke, Thomas; Vroon, Pieter Z.; König, Stephan; Schoenberg, Ronny

    2018-01-01

    Recent studies report a large Mo isotope variability of up to 1‰ (expressed in δ98/95MoNIST3134) in convergent margin lavas. These isotopic variations have been associated with subduction zone processes and ultimately may account for heavy and variable isotope signatures in evolved continental

  16. Isotope effect in the carbonyl sulfide reaction with O(3P)

    DEFF Research Database (Denmark)

    Hattori, Shohei; Schmidt, Johan Albrecht; Mahler, Denise W.

    2012-01-01

    The sulfur kinetic isotope effect (KIE) in the reaction of carbonyl sulfide (OCS) with O((3)P) was studied in relative rate experiments at 298 ± 2 K and 955 ± 10 mbar. The reaction was carried out in a photochemical reactor using long path FTIR detection, and data were analyzed using a nonlinear...... least-squares spectral fitting procedure with line parameters from the HITRAN database. The ratio of the rate of the reaction of OC(34)S relative to OC(32)S was found to be 0.9783 ± 0.0062 ((34)e = (-21.7 ± 6.2)‰). The KIE was also calculated using quantum chemistry and classical transition state theory......; at 300 K, the isotopic fractionation was found to be (34)e = -14.8‰. The OCS sink reaction with O((3)P) cannot explain the large fractionation in (34)S, over +73‰, indicated by remote sensing data. In addition, (34)e in OCS photolysis and OH oxidation are not larger than 10‰, indicating that...

  17. Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Elkins, Madeline H.; Williams, Holly L. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Neumark, Daniel M., E-mail: dneumark@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2016-05-14

    The excited state relaxation dynamics of the solvated electron in H{sub 2}O and D{sub 2}O are investigated using time-resolved photoelectron spectroscopy in a liquid microjet. The data show that the initial excited state decays on a time scale of 75 ± 12 fs in H{sub 2}O and 102 ± 8 fs in D{sub 2}O, followed by slower relaxation on time scales of 400 ± 70 fs and 390 ± 70 fs that are isotopically invariant within the precision of our measurements. Based on the time evolution of the transient signals, the faster and slower time constants are assigned to p → s internal conversion (IC) of the hydrated electron and relaxation on the ground electronic state, respectively. This assignment is consistent with the non-adiabatic mechanism for relaxation of the hydrated electron and yields an isotope effect of 1.4 ± 0.2 for IC of the hydrated electron.

  18. Lithium isotope effects in chemical exchange with (2,2,1) cryptand

    International Nuclear Information System (INIS)

    Jepson, B.E.; Cairns, G.A.

    1979-01-01

    Equilibrium single-stage separation factors were determined for three lithium - (2,2,1) cryptand two-phase chemical exchange systems. The equilibrated phases consisted of an aqueous solution of a lithium salt and a chloroform solution of lithium cryptate salt complex. Lithium-6 concentrated in the organic phase in all cases, and the lithium isotope exchange rate with (2,2,1) cryptand was rapid. The separation factors were α = 1.026 +- 0.006 (LiBr exchange), α = 1.035 +- 0.003 (LiTFA), and α = 1.041 +- 0.006 (LiTFA + HTFA), where TFA represents trifluoroacetate. These values were compared with separation factors of other lithium chemical exchange systems. This work has shown that separation factors are influenced by the choice of chemical species and parameters. It has also demonstrated that significant lithium isotope effects can be obtained without a valence change of the metal exchanging between the aquo and cryptate complexes

  19. Pre-steady state transients in the Drosophila alcohol dehydrogenase catalyzed reaction: isotope effects and stereospecificity

    International Nuclear Information System (INIS)

    Place, A.R.; Eccleston, J.F.

    1987-01-01

    The alcohol dehydrogenase (ADH) isolated from Drosophila is unique among alcohol metabolizing enzymes by not requiring metals for catalysis, by showing 4-pro-S (B-sided) hydride transfer stereospecificity, and by possessing a greater catalytic turnover rate for secondary alcohols than for primary alcohols. They have extended their studies on the kinetic mechanism for this enzyme by examining the pre-steady state transients of ternary complex interconversion using stopped-flow fluorescence methods. When enzyme and a 30-fold molar excess of NADH is mixed with excess acetadehyde, methyl ethyl ketone (MEK), or cyclohexanone a rapid (> 100 s -1 ) transient is observe before the steady-state. The rates are insensitive to isotope substitution. With the substrate MEK, the rate and amplitude suggests a single turnover of the enzyme. Similar pre-steady state transients are observed when enzyme and a 50-fold molar excess of NAD + is mixed with ethanol, 2-propanol, and cyclohexanol. The rates show a hyperbolic concentration dependence and a deuterium isotope effect. With d 6 -deuteroethanol the transient no longer occurs in the pre-steady state. When the optical isomers of secondary alcohols are used as substrates, transients are observed only in the R-(-) isomers for all chain lengths. With 2-S(+)-heptanol and 2-S(+)-octanol no transients occur

  20. Isotope effect in heavy/light water suspensions of optically active gold nanoparticles

    Science.gov (United States)

    Kutsenko, V. Y.; Artykulnyi, O. P.; Petrenko, V. I.; Avdeev, M. V.; Marchenko, O. A.; Bulavin, L. A.; Snegir, S. V.

    2018-04-01

    Aqueous suspensions of optically active gold nanoparticles coated with trisodium citrate were synthesized in light (H2O) water and mixture of light and heavy (H2O/D2O) water using the modified Turkevich protocol. The objective of the paper was to verify sensitivity of neutron scattering methods (in particular, neutron reflectometry) to the potential isotope H/D substitution in the stabilizing organic shell around particles in colloidal solutions. First, the isotope effect was studied with respect to the changes in the structural properties of metal particles (size, shape, crystalline morphology) in solutions by electron microscopy including high-resolution transmission electron microscopy from dried systems. The structural factors determining the variation in the adsorption spectra in addition to the change in the optical properties of surrounding medium were discussed. Then, neutron reflectometry was applied to the layered nanoparticles anchored on a silicon wafer via 3-aminopropyltriethoxysilane molecules to reveal the presence of deuterated water molecules in the shell presumably formed by citrate molecules around the metallic core.

  1. Shell and isotopic effects in neutron interaction with nuclei. [Optical model and nucleus asymmetry correlations

    Energy Technology Data Exchange (ETDEWEB)

    Pasechnik, M V

    1978-01-01

    Major results of investigations into the shell structure of deformed nuclei with the number of neutrons of approximately 100, as well as new isotopic effects in the inelastic scattering of fast neutrons with nuclei are reported. The experiments conducted at the WWR-M research reactor have shown a substantial dependence of the nuclear excited energy-level density on the mass number and the number of neutrons. The fact resulted in a conclusion that the deformed nuclei possess filled shells, that was an incentive to revise the whole nuclear shell concept. In particular it was established that the property of magicity rests not only on the sphericity of nuclei but it may be also observed in strongly deformed nuclei. The isotope-spin dependence of the nuclear potential was studied at the AG-5 pulse electrostatic generator. The parameters of the potential were determined by comparing the experimental data on inelastic scattering and polarization of fast neutrons by nuclei from /sup 48/Ti to /sup 209/Bi with the calculations in terms of the optical model. Simple correlations were established between the optical potential and the nucleus asymmetry parameter ..cap alpha..=N-Z/A in wide ranges of mass numbers and neutron energy.

  2. Alpha heating and isotopic mass effects in JET plasmas with sawteeth

    Energy Technology Data Exchange (ETDEWEB)

    Budny, R. V. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Team, JET [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK

    2016-02-09

    The alpha heating experiment in the Joint European Torus (JET) 1997 DTE1 campaign is re-examined. Several effects correlated with tritium content and thermal hydrogenic isotopic mass < A> weaken the conclusion that alpha heating was clearly observed. These effects delayed the occurrence of significant sawtooth crashes allowing the electron and ion temperatures T e and T i to achieve higher values. Under otherwise equal circumstances T e and T i were typically higher for discharges with higher < A >, and significant scaling of T i, T e, and total stored energy with < A > were observed. The higher T i led to increased ion–electron heating rates with magnitudes comparable to those computed for alpha electron heating. Rates of other heating/loss processes also had comparable magnitudes. Simulations of T e assuming the observed scaling of T i are qualitatively consistent with the measured profiles, without invoking alpha heating

  3. Thermodynamic isotope effects of D2 and T2 reaction with uranium

    International Nuclear Information System (INIS)

    Huang Gang; Long Xinggui; Liang Jianhua; Yang Benfu; Liu Wenke

    2010-01-01

    The p-c-T curves of deuterium and tritium absorption by uranium and p-t curves of desorption were measured. The balance pressure of absorption and desorption on different temperatures were got and then the thermodynamic parameters were determined according to the Van't Hoff equation. It shows that the balance pressure of deuterium absorption is lower than that of tritium absorption on the same temperature and atom ratio. It has the same phenomena for desorption but there are obvious hysteresis effect for reversible process of absorption and desorption. There are a little thermodynamic isotope effects when deuterium and tritium absorption and desorption by uranium estimating from enthalpy and entropy values. (authors)

  4. Master Robotic Net

    Directory of Open Access Journals (Sweden)

    Vladimir Lipunov

    2010-01-01

    Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

  5. alfa-Deuterium kinetic isotope effects in reactions of methyllithium. Is better aggregation the cause of lower reactivity?

    DEFF Research Database (Denmark)

    Holm, Torkil

    1996-01-01

    The value of kH/kD for alfa deuterium kinetic isotope effects for the reaction of methyllithium and methylmagnesium iodid with a series of substrates are consistently ca. 10-15 % higher for the lithium reagent. This may indicate a pre-equilibrium......The value of kH/kD for alfa deuterium kinetic isotope effects for the reaction of methyllithium and methylmagnesium iodid with a series of substrates are consistently ca. 10-15 % higher for the lithium reagent. This may indicate a pre-equilibrium...

  6. Isotope effects in the diffusion of hydrogen and deuterium in ferromagnetic binary alloys of the Cu3Au type

    International Nuclear Information System (INIS)

    Hirscher, M.; Maier, C.U.; Schwendemann, B.; Kronmueller, H.

    1989-01-01

    The diffusion behaviour of hydrogen and deuterium at low temperatures was investigated in ordered and disordered alloys of Ni 3 Fe, Ni 3 Mn, and Fe 3 Pt by means of magnetic after-effect (MAE) measurements. After hydrogen charging all specimens show characteristic MAE relaxation spectra, which can be described taking into account the different octahedral positions of the hydrogen atoms in the Cu 3 Au structure. The observed isotope effect can qualitatively be explained by a thermally activated tunnelling process of the hydrogen isotopes. (orig.)

  7. Mass-dependent and non-mass-dependent isotope effects in ozone photolysis: Resolving theory and experiments

    International Nuclear Information System (INIS)

    Cole, Amanda S.; Boering, Kristie A.

    2006-01-01

    In addition to the anomalous 17 O and 18 O isotope effects in the three-body ozone formation reaction O+O 2 +M, isotope effects in the destruction of ozone by photolysis may also play a role in determining the isotopic composition of ozone and other trace gases in the atmosphere. While previous experiments on ozone photolysis at 254 nm were interpreted as evidence for preferential loss of light ozone that is anomalous (or 'non-mass-dependent'), recent semiempirical theoretical calculations predicted a preferential loss of heavy ozone at that wavelength that is mass dependent. Through photochemical modeling results presented here, we resolve this apparent contradiction between experiment and theory. Specifically, we show that the formation of ozone during the UV photolysis experiments is not negligible, as had been assumed, and that the well-known non-mass-dependent isotope effects in ozone formation can account for the non-mass-dependent enrichment of the heavy isotopologs of ozone observed in the experiment. Thus, no unusual non-mass-dependent fractionation in ozone photolysis must be invoked to explain the experimental results. Furthermore, we show that theoretical predictions of a mass-dependent preferential loss of the heavy isotopologs of ozone during UV photolysis are not inconsistent with the experimental data, particularly if mass-dependent isotope effects in the chemical loss reactions of ozone during the photolysis experiments or experimental artifacts enrich the remaining ozone in 17 O and 18 O. Before the calculated fractionation factors can be quantitatively evaluated, however, further investigation of possible mass-dependent isotope effects in the reactions of ozone with O( 1 D), O( 3 P), O 2 ( 1 Δ), and O 2 ( 1 Σ) is needed through experiments we suggest here

  8. Possibilities and scope of the double isotope effect method in the elucidation of mechanisms of enzyme catalyzed reactions

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, H L; Medina, R [Technische Univ. Muenchen, Freising (Germany, F.R.). Lehrstuhl fuer Allgemeine Chemie und Biochemie

    1991-01-01

    Kinetic isotope effects on enzyme catalyzed reactions are indicative for the first irreversible in a sequence of individual steps. Hints on the relative velocities of other steps can only be obtained from the partitioning factor R and its dependence on external reaction conditions. In general, the experimental data needed are obtained from isotope abundance measurements in a defined position of the substrate or product as a function of turnover. This method does not reveal events dealing with neighbour atoms or preceding the main isotope sensitive step. In the method presented here, the analytical measurement is extended to the second atom involved in a bond fission of formation (Double Isotope Effect Method). It is shown that the additional results obtained support the identification of the main isotopically sensitive step and its relative contribution to the overall reaction rate, the identification of other kinetically significant steps and the differentiation between stepwise and concerted reaction mechanisms. The method and its advantages are demonstrated on reactions comprising C-N-bond splitting (urease and arginase reaction), C-C-bound fission (reactions catalyzed by pyruvate-dehydrogenase, pyruvate-formiate-lyase and lactate-oxidase), C-O-bound formation (ribulose-bisphosphate-oxygenase reaction), and N-O-bond fission (nitrate- and nitrite-reductase reactions). (orig.).

  9. Planning of nets

    International Nuclear Information System (INIS)

    Carberry, M

    1996-01-01

    The paper is about the planning of nets in areas of low density like it is the case of the rural areas. The author includes economic and technological aspects, planning of nets, demands and management among others

  10. Annotating Coloured Petri Nets

    DEFF Research Database (Denmark)

    Lindstrøm, Bo; Wells, Lisa Marie

    2002-01-01

    Coloured Petri nets (CP-nets) can be used for several fundamentally different purposes like functional analysis, performance analysis, and visualisation. To be able to use the corresponding tool extensions and libraries it is sometimes necessary to include extra auxiliary information in the CP......-net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... of the same basic CP-net. One solution to this problem is that the auxiliary information is not integrated into colour sets and arc inscriptions of a CP-net, but is kept separately. This makes it easy to disable this auxiliary information if a CP-net is to be used for another purpose. This paper proposes...

  11. The effect of warming on grassland evapotranspiration partitioning using laser-based isotope monitoring techniques

    KAUST Repository

    Wang, Lixin; Niu, Shuli; Good, Stephen P.; Soderberg, Keir; McCabe, Matthew; Sherry, Rebecca A.; Luo, Yiqi; Zhou, Xuhui; Xia, Jianyang; Caylor, Kelly K.

    2013-01-01

    The proportion of transpiration (T) in total evapotranspiration (ET) is an important parameter that provides insight into the degree of biological influence on the hydrological cycles. Studies addressing the effects of climatic warming on the ecosystem total water balance are scarce, and measured warming effects on the T/ET ratio in field experiments have not been seen in the literature. In this study, we quantified T/ET ratios under ambient and warming treatments in a grassland ecosystem using a stable isotope approach. The measurements were made at a long-term grassland warming site in Oklahoma during the May-June peak growing season of 2011. Chamber-based methods were used to estimate the δ2H isotopic composition of evaporation (δE), transpiration (δT) and the aggregated evapotranspiration (δET). A modified commercial conifer leaf chamber was used for δT, a modified commercial soil chamber was used for δE and a custom built chamber was used for δET. The δE, δET and δT were quantified using both the Keeling plot approach and a mass balance method, with the Craig-Gordon model approach also used to calculate δE. Multiple methods demonstrated no significant difference between control and warming plots for both δET and δT. Though the chamber-based estimates and the Craig-Gordon results diverged by about 12‰, all methods showed that δE was more depleted in the warming plots. This decrease in δE indicates that the evaporation flux as a percentage of total water flux necessarily decreased for δET to remain constant, which was confirmed by field observations. The T/ET ratio in the control treatment was 0.65 or 0.77 and the ratio found in the warming treatment was 0.83 or 0.86, based on the chamber method and the Craig-Gordon approach. Sensitivity analysis of the Craig-Gordon model demonstrates that the warming-induced decrease in soil liquid water isotopic composition is the major factor responsible for the observed δE depletion and the temperature

  12. The effect of warming on grassland evapotranspiration partitioning using laser-based isotope monitoring techniques

    KAUST Repository

    Wang, Lixin

    2013-06-01

    The proportion of transpiration (T) in total evapotranspiration (ET) is an important parameter that provides insight into the degree of biological influence on the hydrological cycles. Studies addressing the effects of climatic warming on the ecosystem total water balance are scarce, and measured warming effects on the T/ET ratio in field experiments have not been seen in the literature. In this study, we quantified T/ET ratios under ambient and warming treatments in a grassland ecosystem using a stable isotope approach. The measurements were made at a long-term grassland warming site in Oklahoma during the May-June peak growing season of 2011. Chamber-based methods were used to estimate the δ2H isotopic composition of evaporation (δE), transpiration (δT) and the aggregated evapotranspiration (δET). A modified commercial conifer leaf chamber was used for δT, a modified commercial soil chamber was used for δE and a custom built chamber was used for δET. The δE, δET and δT were quantified using both the Keeling plot approach and a mass balance method, with the Craig-Gordon model approach also used to calculate δE. Multiple methods demonstrated no significant difference between control and warming plots for both δET and δT. Though the chamber-based estimates and the Craig-Gordon results diverged by about 12‰, all methods showed that δE was more depleted in the warming plots. This decrease in δE indicates that the evaporation flux as a percentage of total water flux necessarily decreased for δET to remain constant, which was confirmed by field observations. The T/ET ratio in the control treatment was 0.65 or 0.77 and the ratio found in the warming treatment was 0.83 or 0.86, based on the chamber method and the Craig-Gordon approach. Sensitivity analysis of the Craig-Gordon model demonstrates that the warming-induced decrease in soil liquid water isotopic composition is the major factor responsible for the observed δE depletion and the temperature

  13. Effects of sulfur dioxide on net CO/sub 2/ assimilation in the lichen Evernia mesomorpha Nyl

    Energy Technology Data Exchange (ETDEWEB)

    Huebert, D B; L' Hirondelle, S J; Addison, P A

    1985-01-01

    Physiologically active thalli of the lichen Evernia mesomorpha Nyl. were very sensitive to short-term fumigations with low concentrations of gaseous sulfur dioxide. Net CO/sub 2/ assimilation rate (NAR) was significantly reduced after exposure to 0.085 ..mu..l l/sup -1/ (250 ..mu..g m/sup -3/) SO/sub 2/ for 1 h or more, and the reduction increased with increasing concentration. Duration of exposure had no significant effect on NAR, indicating the importance of rate of SO/sub 2/ uptake rather than the total amount absorbed. Respiration was significantly reduced after 4 h or more of exposure to 0.265 ..mu..l l/sup -1/ (639 ..mu..g m/sup -3/) SO/sub 2/ or higher. Recovery of NAR after fumigation was dependent on both SO/sub 2/ concentration and duration of fumigation, and on the time allowed for recovery. Virtually complete recovery occurred within 24 h after episodes with up to 0.355 ..mu..l l/sup -1/ (856 ..mu..g m/sup -3/) SO/sub 2/ for 1 h and 0.085 ..mu..l l/sup -1/ SO/sub 2/ for 4 h. Above these levels, recovery was incomplete or nonexistent after 24 h in clean air. The level of sensitivity found can be attributed to the environmental conditions during fumigation, which prevented thallus desiccation and inactivity. Based on this study, neither the concept of dose (concentration x time) nor that of threshold levels of SO/sub 2/ fumigations are supported. Peak exposures to SO/sub 2/ for short periods may be of primary importance in determining the survival of lichens in industrial areas.

  14. Direct and indirect effects of climatic variations on the interannual variability in net ecosystem exchange across terrestrial ecosystems

    Directory of Open Access Journals (Sweden)

    Junjiong Shao

    2016-08-01

    Full Text Available Climatic variables not only directly affect the interannual variability (IAV in net ecosystem exchange of CO2 (NEE but also indirectly drive it by changing the physiological parameters. Identifying these direct and indirect paths can reveal the underlying mechanisms of carbon (C dynamics. In this study, we applied a path analysis using flux data from 65 sites to quantify the direct and indirect climatic effects on IAV in NEE and to evaluate the potential relationships among the climatic variables and physiological parameters that represent physiology and phenology of ecosystems. We found that the maximum photosynthetic rate was the most important factor for the IAV in gross primary productivity (GPP, which was mainly induced by the variation in vapour pressure deficit. For ecosystem respiration (RE, the most important drivers were GPP and the reference respiratory rate. The biome type regulated the direct and indirect paths, with distinctive differences between forests and non-forests, evergreen needleleaf forests and deciduous broadleaf forests, and between grasslands and croplands. Different paths were also found among wet, moist and dry ecosystems. However, the climatic variables can only partly explain the IAV in physiological parameters, suggesting that the latter may also result from other biotic and disturbance factors. In addition, the climatic variables related to NEE were not necessarily the same as those related to GPP and RE, indicating the emerging difficulty encountered when studying the IAV in NEE. Overall, our results highlight the contribution of certain physiological parameters to the IAV in C fluxes and the importance of biome type and multi-year water conditions, which should receive more attention in future experimental and modelling research.

  15. Isotope separation of 22Na and 24Na with using light induced drift effect

    International Nuclear Information System (INIS)

    Hradecny, C.; Tethal, T.; Ermolaev, I.M.; Zemlyanoj, S.G.; Zuzaan, P.

    1993-01-01

    The LIDIS (Light Drift Isotope Separation) separator without a gas flow is discussed. It is shown, that atomization degree of the separated isotopes limited real separation coefficient. The better buffer gas purification allowed to increase the experimental separation factor of 22 Na and 24 Na isotopes up to 25. The new experimental set up allow to increase the separation efficiency up to 50%. 12 refs.; 5 figs

  16. Estimation of the specific mass effect in the isotope shifts of energy levels in the optical spectrum of Ba I and Ba II

    International Nuclear Information System (INIS)

    Pendrill, L.R.

    1984-01-01

    A graphical method for separating mass and volume effects from purely optical isotope shift data is presented and compared with King's ''bunching'' method. Recent experimental data on isotope shifts for a wide range of spectral lines in the naturally abundant isotopes of Ba I and Ba II are analysed. Some agreement is found with muonic X-ray data concerning the nuclear size for the isotopes 136, 137 and 138, but there is disagreement (over 20%) for the other isotopes. The level isotope shifts are further parameterised in terms of a linear model, and the specific mass effect is decomposed into sums of one-electron and two-electron shift parameters with respect to the inert-gas like ground state of Ba III. (orig.)

  17. Applying the net-benefit framework for analyzing and presenting cost-effectiveness analysis of a maternal and newborn health intervention.

    Directory of Open Access Journals (Sweden)

    Sennen Hounton

    Full Text Available BACKGROUND: Coverage of maternal and newborn health (MNH interventions is often influenced by important determinants and decision makers are often concerned with equity issues. The net-benefit framework developed and applied alongside clinical trials and in pharmacoeconomics offers the potential for exploring how cost-effectiveness of MNH interventions varies at the margin by important covariates as well as for handling uncertainties around the ICER estimate. AIM: We applied the net-benefit framework to analyze cost-effectiveness of the Skilled Care Initiative and assessed relative advantages over a standard computation of incremental cost effectiveness ratios. METHODS: Household and facility surveys were carried out from January to July 2006 in Ouargaye district (where the Skilled Care Initiative was implemented and Diapaga (comparison site district in Burkina Faso. Pregnancy-related and perinatal mortality were retrospectively assessed and data were collected on place of delivery, education, asset ownership, place, and distance to health facilities, costs borne by households for institutional delivery, and cost of standard provision of maternal care. Descriptive and regression analyses were performed. RESULTS: There was a 30% increase in institutional births in the intervention district compared to 10% increase in comparison district, and a significant reduction of perinatal mortality rates (OR 0.75, CI 0.70-0.80 in intervention district. The incremental cost for achieving one additional institutional delivery in Ouargaye district compared to Diapaga district was estimated to be 170 international dollars and varied significantly by covariates. However, the joint probability distribution (net-benefit framework of the effectiveness measure (institutional delivery, the cost data and covariates indicated distance to health facilities as the single most important determinant of the cost-effectiveness analysis with implications for policy making

  18. [Effects of plastic film mulching and nitrogen application rate on net global warming potential in semiarid rain-fed maize cropland].

    Science.gov (United States)

    Liu, Jian Can; Wang, Ze Lin; Yue, Shan Chao; Li, Shi Qing

    2018-04-01

    A one-year field experiment was conducted to evaluate the effects of plastic film mulching (FM) and nitrogen application rates applied to rain-fed maize fields on net global warming potential (Net GWP) and greenhouse gas intensity (GHGI) at the Changwu Agricultural and Ecological Experimental Station. Both GWP and GHGI were affected by the plastic film mulching and nitrogen application rate. Under the FM treatment, maize yield ranged from 1643 to 16699 kg·hm -2 , the net GWP (CO 2 -eq) ranged from 595 to 4376 kg·hm -2 ·a -1 , and the GHGI (CO 2 -eq) ranged from 213 to 358 kg·t -1 . The grain yield of maize, net GWP and GHGI for the UM (no mulching) treatment were 956 to 8821 kg·hm -2 , 342 to 4004 kg·hm -2 ·a -1 and 204 to 520 kg·t -1 , respectively. The results suggested that plastic film mulching could simultaneously improve grain yield and decrease GHGI in rain-fed cropland along with nitrogen fertilizer of 250 kg·hm -2 .

  19. The Effect of Mass Media Campaign on the Use of Insecticide-Treated Bed Nets among Pregnant Women in Nigeria

    Directory of Open Access Journals (Sweden)

    A. Ankomah

    2014-01-01

    Full Text Available Background. Malaria during pregnancy is a major public health problem in Nigeria especially in malaria-endemic areas. It increases the risk of low birth weight and child/maternal morbidity/mortality. This paper addresses the impact of radio campaigns on the use of insecticide-treated bed nets among pregnant women in Nigeria. Methods. A total of 2,348 pregnant women were interviewed during the survey across 21 of Nigeria’s 36 states. Respondents were selected through a multistage sampling technique. Analysis was based on multivariate logistic regression. Results. Respondents who knew that sleeping under ITN prevents malaria were 3.2 times more likely to sleep under net (OR: 3.15; 95% CI: 2.28 to 4.33; P<0.0001. Those who listened to radio are also about 1.6 times more likely to use ITN (OR: 1.56; 95% CI: 1.07 to 2.28; P=0.020, while respondents who had heard of a specific sponsored radio campaign on ITN are 1.53 times more likely to use a bed net (P=0.019. Conclusion. Pregnant women who listened to mass media campaigns were more likely to adopt strategies to protect themselves from malaria. Therefore, behavior change communication messages that are aimed at promoting net use and antenatal attendance are necessary in combating malaria.

  20. Competition H(D) kinetic isotope effects in the autoxidation of hydrocarbons.

    Science.gov (United States)

    Muchalski, Hubert; Levonyak, Alexander J; Xu, Libin; Ingold, Keith U; Porter, Ned A

    2015-01-14

    Hydrogen atom transfer is central to many important radical chain sequences. We report here a method for determination of both the primary and secondary isotope effects for symmetrical substrates by the use of NMR. Intramolecular competition reactions were carried out on substrates having an increasing number of deuterium atoms at symmetry-related sites. Products that arise from peroxyl radical abstraction at each position of the various substrates reflect the competition rates for H(D) abstraction. The primary KIE for autoxidation of tetralin was determined to be 15.9 ± 1.4, a value that exceeds the maximum predicted by differences in H(D) zero-point energies (∼7) and strongly suggests that H atom abstraction by the peroxyl radical occurs with substantial quantum mechanical tunneling.

  1. Isotope and Electric Field Effects in Dissociative Recombination of D3+

    International Nuclear Information System (INIS)

    Larsson, M.; Rosen, S.; Danared, H.; Larson, A.; Le Padellec, A.; Semaniak, J.; Stroemholm, C.; Peterson, J.R.

    1997-01-01

    The cross section for dissociative recombination of vibrationally cold D 3 + has been measured at the ion storage ring CRYRING. The rate constant at 300K, α=2.7x10 -8 cm 3 s -1 , is a factor of 4.3 smaller than the corresponding value for H 3 + measured earlier in CRYRING. An electric field of 30V/cm was introduced in the electron-ion interaction region. This had no measurable effect on the dissociative recombination cross section. This suggests that the cross sections measured in storage rings for H 3 + and its isotopic variants can be directly compared with theoretical results once such results become available. copyright 1997 The American Physical Society

  2. Isotope substitution effects on preferred conformations of some hydrocarbon radical cations

    International Nuclear Information System (INIS)

    Lunell, S.; Eriksson, L.A.

    1992-01-01

    The stability of different conformational isomers of partially deuterated radical cations of ethane, butane, and cyclopropane is studied at the HF/6-31G** and MP2/6-31G** levels. It is shown that the superposition patterns of spectra corresponding to different isomers, observed in ESR spectroscopy, are accurately reproduced by Boltzmann statistics based on differences in vibrational zero-point energies (ZPE), provided that the temperature is high enough to overcome existing barriers toward internal pseudorotation in the cations. For the ethane and butane cations, the most stable conformations are, as expected, those which are deuterated in the short CH bonds, while this is found not to be the case for the cyclopropane cation. The latter result is explained by shifts in the low-frequency bending modes, which counteract the anticipated isotope effect on the C H stretching modes

  3. The short range effective interaction and the spectra of calcium isotopes in (f-p) space

    International Nuclear Information System (INIS)

    Qing-ying, Z.; Shen-wu, L.; Jian-xin, W.

    1986-01-01

    In this work, the authors use a new type of extremely short range interaction, the double delta interaction (DDI) to calculate the low-lying spectra of calcium isotopes /sup 41/Ca through /sup 48/Ca. The configuration space (f-p) includes configurations ( f/sub 7/2//sup n/ ) and ( f/sub 7/2//sup n-1/2p/sub 3/2/). The calculated energies are compared with experimental data for 75 levels. For comparison, they also use usual modified surface delta interaction (MSDI) to calculate the same spectra aforementioned. It is clear that the results calculated with DDI are better than with MSDI. Therefore, in the short-range effective interaction the addition of body delta force to the modified surface delta force may improve the agreement with experiment. The authors believe that the conclusion will not be changed if one enlarges the shell model space

  4. Anomalous H/D isotope effect on 35Cl NQR frequencies in piperidinium p-chlorobenzoate

    International Nuclear Information System (INIS)

    Nakano, Ryo; Honda, Hisashi; Kimura, Taiki; Nakata, Eiichi; Takamizawa, Satoshi; Noro, Sumiko; Ishimaru, Shin'ichi

    2008-01-01

    Anomalous isotope effects were detected in the 35 Cl nuclear quadrupole resonance (NQR) frequency of piperidinium p-chlrobenzoate (C 5 H 10 NH. ClC 6 H 4 COOH) by deuteration of hydrogen atoms. The atoms were determined to form two kinds of N-H...O type H-bonds in the crystal structure. Large frequency shifts of the 35 Cl resonance lines reaching 288 kHz at 77 K and 278 kHz at room temperature were caused upon deuteration, in spite of the fact that the Cl atoms in the molecule do not form hydrogen bonds in the crystal. Results of single crystal X-ray diffraction measurements and density-functional-theorem calculations suggest that a dihedral-angle change of 1.8 o between benzene and the piperidine ring contributes to 35 Cl NQR anomalous frequency shifts.

  5. Catalytic recruitment in the inactivation of acetylcholinesterase by soman: temperature dependence of the solvent isotope effect

    International Nuclear Information System (INIS)

    Kovach, I.M.; Huber, J.H.A.; Schowen, R.L.

    1988-01-01

    3,3-Dimethyl-2-butyl methylphosphonofluoridate (soman) recruits at least 60-70% of the catalytic power of acetylcholinesterase during phosphonylation of the active-site serine, as compared with the acetylation by acetylcholine. The solvent isotope effect is 1.34 +/- 0.11 and is temperature independent within experimental error between 5 and 45 0 C. This observation is quite similar to what has been found for the reactions of aryl acetates and anilides. Average activation parameters for the same temperature range are ΔH* = 7.3 +/- 0.6 kcal/mol and ΔS* = -4 +/- 2 eu (H 2 O) and ΔH* = 7.1 +/- 0.4 kcal/mol and ΔS* = -6 +/- 1 eu (D 2 O). A rate-limiting process with 50% contribution of an induced-fit conformational change is supported by the data

  6. The role of symmetry in the mass independent isotope effect in ozone

    Science.gov (United States)

    Michalski, Greg; Bhattacharya, S. K.

    2009-01-01

    Understanding the internal distribution of “anomalous” isotope enrichments has important implications for validating theoretical postulates on the origin of these enrichments in molecules such as ozone and for understanding the transfer of these enrichments to other compounds in the atmosphere via mass transfer. Here, we present an approach, using the reaction NO2− + O3, for assessing the internal distribution of the Δ17O anomaly and the δ18O enrichment in ozone produced by electric discharge. The Δ17O results strongly support the symmetry mechanism for generating mass independent fractionations, and the δ18O results are consistent with published data. Positional Δ17O and δ18O enrichments in ozone can now be more effectively used in photochemical models that use mass balance oxygen atom transfer mechanisms to infer atmospheric oxidation chemistry. PMID:19307571

  7. 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.

  8. Variability in mesophyll conductance between barley genotypes, and effects on transpiration efficiency and carbon isotope discrimination.

    Science.gov (United States)

    Barbour, Margaret M; Warren, Charles R; Farquhar, Graham D; Forrester, Guy; Brown, Hamish

    2010-07-01

    Leaf internal, or mesophyll, conductance to CO(2) (g(m)) is a significant and variable limitation of photosynthesis that also affects leaf transpiration efficiency (TE). Genotypic variation in g(m) and the effect of g(m) on TE were assessed in six barley genotypes (four Hordeum vulgare and two H. bulbosum). Significant variation in g(m) was found between genotypes, and was correlated with photosynthetic rate. The genotype with the highest g(m) also had the highest TE and the lowest carbon isotope discrimination as recorded in leaf tissue (Delta(p)). These results suggest g(m) has unexplored potential to provide TE improvement within crop breeding programmes.

  9. Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts

    International Nuclear Information System (INIS)

    Mori, T.; Masuda, H.; Imai, H.; Miyamoto, A.; Baba, S.; Murakami, Y.

    1982-01-01

    Kinetics and hydrogen-deuterium isotope effects in the methanation of adsorbed CO molecules on a Ni/SiO 2 catalyst were precisely measured by using pulse surface reaction rate analysis (PSRA). When a CO pulse was injected into flowing hydrogen, it was immediately adsorbed on the catalyst and gradually hydrogenated to CH 4 and H 2 O. The amounts of CH 4 and H 2 O produced by the hydrogenation of the adsorbed CO were determined up to various times, and it was found that CH 4 and H 2 O were produced at the same rate. When O 2 instead of CO was injected, H 2 O was immediately produced. From these results, the rate-determining step of the reaction was found to be C-O bond dissociation of an adsorbed CO molecule or a partially hydrogenated CO species. By PSRA, the rate constant for the C-O bond dissocition process per adsorbed CO molecule (k/sub H/) was determined at various temperatures, and the Arrhenius parameters of the rate constant were obtained. The rate constant in flowing deuterium (k/sub D/) was also determined. it was found that k/sub D/ is considerably larger than k/sub H/, indicating an inverse isotope effect. The average value of k/sub H//k/sub D/ was 0.75. From these results, it was concluded that adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but it is partially hydrogenated before C-O bond dissociation under the conditions of the PSRA experiment. 8 figures

  10. Calculations of kinetic isotope effects in the syn-eliminations of (2-phenylethyl)dimethylamine oxides

    International Nuclear Information System (INIS)

    Shafiei-Kermani, H.R.

    1987-01-01

    Transition state theory (TST) calculations of kinetic isotope effects (KIE) for the syn-elimination of (2-phenylethyl)dimethylamine oxides have been carried out for a series of transition state (TS) models encompassing both E1-like and E1cB-like regions of the E2 mechanistic spectrum. A large number of different reaction coordinates were explored for both unsolvated and for coordination of solvent dimethylsulfoxide in the cyclic transition state models. The models of reaction for both solvated and unsolvated models of proton transfer are presented. A simplified method for easier initial screening of reaction coordinate contributions is developed, discussed, and found to produce accurate approximations to the full model KIE values. Both unsolvated and solvated models show E1-like E2 mechanism and the calculated values from both models are in extremely good agreement with experimentally measured KIE. Both models were used to investigate para-substituted derivatives (Z = CL, OCH 3 ) of the parent compound (Z = H). The transition states are related by a shift in structure parallel to the central E2 diagonal of an O'Ferrall-Jencks-Fry reaction diagram, as predicted by Thornton, indicating that in the absence of other factors, the extent to which negative charge is accumulated at C/sub β/ in the transition state is a function primarily of the leaving group. All of the structural parameters such as bond distances and bond angles were related to independent bond orders. Beta-deuterium isotope effects produced by both solvated and nonsolvated models are temperature dependent

  11. The effects of the 'key' molar mass on the design of a cascade handling a multi-isotopic mixture

    International Nuclear Information System (INIS)

    Raichura, R.C.; Al-Janabi, M.A.M.

    1991-01-01

    The parameters required for describing the characteristics of separating units and cascades handling a multi-isotope mixture are first reviewed from previous work and then expressed in terms of a newly defined parameter called the 'Key' molar mass. The effects of the latter on the operating and economic parameters of a gas centrifuge cascade handling a multi-isotopic mixture are studied. Only cascades of the 'primitive' type, i.e. those in which the feed of a stage is made up of the light and heavy fractions of neighbouring stages, are considered. The costs incurred in obtaining outputs with specified concentrations are then discussed. (author)

  12. Numerical simulation of bellows effect on flow and separation of uranium isotopes in a supercritical gas centrifuge

    International Nuclear Information System (INIS)

    Borisevich, V.D.; Morozov, O.E.; Godisov, O.N.

    2000-01-01

    Numerical solving of the Navier-Stokes and convection-diffusion equations by the finite difference technique has been applied to study the influence of bellows on the flow and separation of uranium isotopes in a single supercritical gas centrifuge. Dependence of the separative power of a gas centrifuge on geometric parameters and position of a bellows on a rotor wall as well as the effect of scoop drag and feed flow on isotope separation in a gas centrifuge with a bellows have been obtained in computing experiments. It was demonstrated that increase of the separative power with increase of the gas centrifuge length is less considerable than predicted by the Dirac's law

  13. Density functional theory calculations of H/D isotope effects on polymer electrolyte membrane fuel cell operations

    Energy Technology Data Exchange (ETDEWEB)

    Yanase, Satoshi; Oi, Takao [Sophia Univ., Tokyo (Japan). Faculty of Science and Technology

    2015-10-01

    To elucidate hydrogen isotope effects observed between fuel and exhaust hydrogen gases during polymer electrolyte membrane fuel cell operations, H-to-D reduced partition function ratios (RPFRs) for the hydrogen species in the Pt catalyst phase of the anode and the electrolyte membrane phase of the fuel cell were evaluated by density functional theory calculations on model species of the two phases. The evaluation yielded 3.2365 as the value of the equilibrium constant of the hydrogen isotope exchange reaction between the two phases at 39 C, which was close to the experimentally estimated value of 3.46-3.99 at the same temperature. It was indicated that H{sup +} ions on the Pt catalyst surface of the anode and H species in the electrolyte membrane phase were isotopically in equilibrium with one another during fuel cell operations.

  14. The effect of fusion-relevant helium levels on the mechanical properties of isotopically tailored ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hankin, G.L. [Loughborough Univ. (United Kingdom); Hamilton, M.L.; Gelles, D.S. [Pacific Northwest National Lab., Richland, WA (United States)] [and others

    1997-04-01

    The yield and maximum strengths of an irradiated series of isotopically tailored ferritic alloys were evaluated using the shear punch test. The composition of three of the alloys was Fe-12Cr-1.5Ni. Different balances of nickel isotopes were used in each alloy in order to produce different helium levels. A fourth alloy, which contained no nickel, was also irradiated. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys, and as expected, the strength of the alloys decreased with increasing irradiation temperature. Helium itself, up to 75 appm over 7 dpa appears to have little effect on the mechanical properties of the alloys.

  15. Influence of Three-square-well Interaction Potential on Isotope Effect Coefficient of High-TC Superconductors

    International Nuclear Information System (INIS)

    Udomsamuthirun, P.; Dokkaemklang, S.; Kumvongsa, C.; Maneeratanakul, S.

    2005-10-01

    In this research, the exact formula of the isotope effect coefficient of s wave and d-wave superconductor in weak-coupling limit are derived by using a three square- well interaction potential that pairing interaction consists of 3 parts : an attractive electron-phonon interaction, an attractive non-electron-phonon interaction , and a repulsive Coulomb interaction . op ac , w w and c w is the characteristic energy cutoff of the Debye phonon , non-phonon ,and Coulomb respectively and 2 / 1 ac M- a w , and c op , w w do not depend on isotope mass(M). We find that, in all case of consideration, the isotope coefficient converges to 0.5 at lower value of Coulomb coupling constant and larger values of phonon and non-phonon coupling constant

  16. Effects of land use and fine-scale environmental heterogeneity on net ecosystem production over a temperate coniferous forest landscape

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David P.; Guzy, Michael; Lefsky, Michael A.; Tuyl, Steve van; Sun, Osbert; Law, Beverly E. [Oregon State Univ. Corvallis, OR (United States). Dept. of Forest Science; Daly, Chris [Oregon State Univ., Corvallis, OR (United States). Dept. of Geosciences

    2003-04-01

    In temperate coniferous forests, spatial variation in net ecosystem production (NEP) is often associated with variation in stand age and heterogeneity in environmental factors such as soil depth. However, coarse spatial resolution analyses used to evaluate the terrestrial contribution to global NEP do not generally incorporate these effects. In this study, a fine-scale (25 m grid) analysis of NEP over a 164-km{sup 2} area of productive coniferous forests in the Pacific Northwest region of the United States was made to evaluate the effects of including fine scale information in landscape-scale NEP assessments. The Enhanced Thematic Mapper (ETM+) sensor resolved five cover classes in the study area and further differentiated between young, mature and old-growth conifer stands. ETM+ was also used to map current leaf area index (LAI) based on an empirical relationship of observed LAI to spectral vegetation indices. A daily time step climatology, based on 18 years of meteorological observations, was distributed (1 km resolution) over the mountainous terrain of the study area using the DAYMET model. Estimates of carbon pools and flux associated with soil, litter, coarse woody debris and live trees were then generated by running a carbon cycle model (Biome-BGC) to a state that reflected the current successional status and LAI of each grid cell, as indicated by the remote sensing observations. Estimated annual NEP for 1997 over the complete study area averaged 230 g C m{sup 2}, with most of the area acting as a carbon sink. The area-wide NEP is strongly positive because of reduced harvesting in the last decade and the recovery of areas harvested between 1940 and 1990. The average value was greater than would be indicated if the entire area was assumed to be a mature conifer stand, as in a coarse-scale analysis. The mean NEP varied interannually by over a factor of two. This variation was 38% less than the interannual variation for a single point. The integration of process

  17. Effects of land use and fine-scale environmental heterogeneity on net ecosystem production over a temperate coniferous forest landscape

    International Nuclear Information System (INIS)

    Turner, David P.; Guzy, Michael; Lefsky, Michael A.; Tuyl, Steve van; Sun, Osbert; Law, Beverly E.; Daly, Chris

    2003-01-01

    In temperate coniferous forests, spatial variation in net ecosystem production (NEP) is often associated with variation in stand age and heterogeneity in environmental factors such as soil depth. However, coarse spatial resolution analyses used to evaluate the terrestrial contribution to global NEP do not generally incorporate these effects. In this study, a fine-scale (25 m grid) analysis of NEP over a 164-km 2 area of productive coniferous forests in the Pacific Northwest region of the United States was made to evaluate the effects of including fine scale information in landscape-scale NEP assessments. The Enhanced Thematic Mapper (ETM+) sensor resolved five cover classes in the study area and further differentiated between young, mature and old-growth conifer stands. ETM+ was also used to map current leaf area index (LAI) based on an empirical relationship of observed LAI to spectral vegetation indices. A daily time step climatology, based on 18 years of meteorological observations, was distributed (1 km resolution) over the mountainous terrain of the study area using the DAYMET model. Estimates of carbon pools and flux associated with soil, litter, coarse woody debris and live trees were then generated by running a carbon cycle model (Biome-BGC) to a state that reflected the current successional status and LAI of each grid cell, as indicated by the remote sensing observations. Estimated annual NEP for 1997 over the complete study area averaged 230 g C m 2 , with most of the area acting as a carbon sink. The area-wide NEP is strongly positive because of reduced harvesting in the last decade and the recovery of areas harvested between 1940 and 1990. The average value was greater than would be indicated if the entire area was assumed to be a mature conifer stand, as in a coarse-scale analysis. The mean NEP varied interannually by over a factor of two. This variation was 38% less than the interannual variation for a single point. The integration of process models

  18. Isotopes in oxidation reactions

    International Nuclear Information System (INIS)

    Stewart, R.

    1976-01-01

    The use of isotopes in the study of organic oxidation mechanisms is discussed. The help provided by tracer studies to demonstrate the two-equivalent path - hydride transfer, is illustrated by the examples of carbonium oxidants and the Wacker reaction. The role of kinetic isotope effects in the study of the scission of carbon-hydrogen bonds is illustrated by hydride abstraction, hydrogen atom abstraction, proton abstraction and quantum mechanical tunnelling. Isotopic studies on the oxidation of alcohols, carbonyl compounds, amines and hydrocarbons are discussed. The role of isotopes in the study of biochemical oxidation is illustrated with a discussion on nicotinamide and flavin coenzymes. (B.R.H.)

  19. The use of mediation analysis to assess the effects of a behaviour change communication strategy on bed net ideation and household universal coverage in Tanzania.

    Science.gov (United States)

    Ricotta, Emily E; Boulay, Marc; Ainslie, Robert; Babalola, Stella; Fotheringham, Megan; Koenker, Hannah; Lynch, Matthew

    2015-01-21

    SBCC campaigns are designed to act on cognitive, social and emotional factors at the individual or community level. The combination of these factors, referred to as 'ideation', play a role in determining behaviour by reinforcing and confirming decisions about a particular health topic. This study introduces ideation theory and mediation analysis as a way to evaluate the impact of a malaria SBCC campaign in Tanzania, to determine whether exposure to a communication programme influenced universal coverage through mediating ideational variables. A household survey in three districts where community change agents (CCAs) were active was conducted to collect information on ITN use, number of ITNs in the household, and perceptions about ITN use and ownership. Variables relating to attitudes and beliefs were combined to make 'net ideation'. Using an ideational framework, a mediation analysis was conducted to see the impact exposure to a CCA only, mass media and community (M & C) messaging only, or exposure to both, had on household universal coverage, through the mediating variable net ideation. All three levels of exposure (CCA, M & C messaging, or exposure to both) were significantly associated with increased net ideation (CCA: 0.283, 95% CI: 0.136-0.429, p-value: mediation analysis is an applicable new tool to assess SBCC campaigns. Ideation as a mediator of the effects of communication exposure on household universal coverage has implications for designing SBCC to support both mass and continuous distribution efforts, since both heavily rely on consumer participation to obtain and maintain ITNs. Such systems can be strengthened by SBCC programming, generating demand through improving social norms about net ownership and use, perceived benefits of nets, and other behavioural constructs.

  20. Investigation of the enzymatic mechanism of yeast orotidine-5'-monophosphate decarboxylase using 13C kinetic isotope effects

    International Nuclear Information System (INIS)

    Smiley, J.A.; Bell, J.B.; Jones, M.E.; Paneth, P.; O'Leary, M.H.

    1991-01-01

    Orotidine-5'-monophosphate decarboxylase (ODCase) from Saccharomyces cerevisiae displays an observed 13 C kinetic isotope effect of 1.0247 ± 0.0008 at 25 C, pH 6.8. The observed isotope effect is sensitive to changes in the reaction medium, such as pH, temperature, or glycerol content. The value of 1.0494 ± 0.0006 measured at pH 4.0, 25 C, is not altered significantly by temperature or glycerol, and thus the intrinsic isotope effect for the reaction is apparently being observed under these conditions and decarboxylation is almost entirely rate-determining. These data require a catalytic mechanism with freely reversible binding and one in which a very limited contribution to the overall rate is made by chemical steps preceding decarboxylation; the zwitterion mechanism of Beak and Siegel, which involves only protonation of the pyrimidine ring, is such a mechanism. With use of an intrinsic isotope effect of 1.05, a partitioning factor of less than unity is calculated for ODCase at pH 6.0, 25 C. A quantitative kinetic analysis using this result excludes the possibility of an enzymatic mechanism involving covalent attachment of an enzyme nucleophile to C-5 of the pyrimidine ring. These data fit a kinetic model in which an enzyme proton necessary for catalysis is titrated at high pH, thus providing evidence for the catalytic mechanism of Beak and Siegal