Science.gov

Sample records for fluxes geochemical partitioning

  1. Flux Partitioning by Isotopic Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Wehr, R.; Munger, J. W.; Nelson, D. D.; McManus, J. B.; Zahniser, M. S.; Wofsy, S. C.; Saleska, S. R.

    2011-12-01

    Net ecosystem-atmosphere exchange of CO2 is routinely measured by eddy covariance at sites around the world, but studies of ecosystem processes are more interested in the gross photosynthetic and respiratory fluxes that comprise the net flux. The standard method of partitioning the net flux into these components has been to extrapolate nighttime respiration into daytime based on a relationship between nighttime respiration, temperature, and sometimes moisture. However, such relationships generally account for only a small portion of the variation in nighttime respiration, and the assumption that they can predict respiration throughout the day is dubious. A promising alternate method, known as isotopic flux partitioning, works by identifying the stable isotopic signatures of photosynthesis and respiration in the CO2 flux. We have used this method to partition the net flux at Harvard Forest, MA, based on eddy covariance measurements of the net 12CO2 and 13CO2 fluxes (as well as measurements of the sensible and latent heat fluxes and other meteorological variables). The CO2 isotopologues were measured at 4 Hz by an Aerodyne quantum cascade laser spectrometer with a δ13C precision of 0.4 % in 0.25 sec and 0.02 % in 100 sec. In the absence of such high-frequency, high-precision isotopic measurements, past attempts at isotopic flux partitioning have combined isotopic flask measurements with high-frequency (total) CO2 measurements to estimate the isoflux (the EC/flask approach). Others have used a conditional flask sampling approach called hyperbolic relaxed eddy accumulation (HREA). We 'sampled' our data according to each of these approaches, for comparison, and found disagreement in the calculated fluxes of ~10% for the EC/flask approach, and ~30% for HREA, at midday. To our knowledge, this is the first example of flux partitioning by isotopic eddy covariance. Wider use of this method, enabled by a new generation of laser spectrometers, promises to open a new window

  2. Partitioning Carbon Dioxide and Water Vapor Fluxes Using Correlation Analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Partitioning of eddy covariance flux measurements is routinely done to quantify the contributions of separate processes to the overall fluxes. Measurements of carbon dioxide fluxes represent the difference between gross ecosystem photosynthesis and total respiration, while measurements of water vapo...

  3. Open software tools for eddy covariance flux partitioning

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agro-ecosystem management and assessment will benefit greatly from the development of reliable techniques for partitioning evapotranspiration (ET) into evaporation (E) and transpiration (T). Among other activities, flux partitioning can aid in evaluating consumptive vs. non-consumptive agricultural...

  4. FLUXPART: An FOSS solution for Eddy covariance flux partitioning

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report on efforts to develop a FOSS solution for a particular geoscience application. Eddy covariance (EC) instruments are routinely used to measure field-scale evapotranspiration and CO2 fluxes. For many applications, it is desirable to partition the measured evapotranspiration flux into its c...

  5. Partitioning of Cd in geochemical fractions of anaerobic estuarine sediments

    NASA Astrophysics Data System (ADS)

    Rule, Joseph H.; Alden, Raymond W.

    1992-05-01

    Distribution of Cd in geochemical fractions of anaerobic estuarine sediments was determined before and after treatment of the sediments with added Cd. Portions of three sediment types (sandy, silty, and clayey) were treated with 5 and 10 mg kg -1 Cd as CdCl 2 and each type had an untreated control. Sediments were sampled at the start and at the conclusion of a 14 day laboratory bioaccumulation study. Each set was promptly extracted using a sequential technique for exchangeable, easily reducible, organic-sulphide, moderately reducible, and acid extractable phases. In the non-treated sediments, approximately 64% of the naturally occurring Cd was in the acid extractable phase with most of the balance in the organicsulphide phase (OSP). There was a similar amount of Cd in the acid extractable phase of all treatments of all sediments. For the treated sediments, the majority of the Cd was found in the OSP and ranged from 56% to 85% for all treatments and sediments. At the end of the experiment, a greater and more consistent level of Cd was present in the OSP (from 76% to 92%). These results show an initially rapid conversion of most of the added soluble Cd to the OSP with conversion of up to 92% of applied Cd to this phase within 14 days. The bulk of the OSP Cd is postulated to occur as sulphides which are an important reservoir of sediment Cd. Addition of Cd had no effect on the geochemical distribution of native Cu, Fe, Mn, Ni, Pb, or Zn.

  6. Hydrologic connectivity constrains partitioning of global terrestrial water fluxes

    NASA Astrophysics Data System (ADS)

    Good, Stephen P.; Noone, David; Bowen, Gabriel

    2015-07-01

    Continental precipitation not routed to the oceans as runoff returns to the atmosphere as evapotranspiration. Partitioning this evapotranspiration flux into interception, transpiration, soil evaporation, and surface water evaporation is difficult using traditional hydrological methods, yet critical for understanding the water cycle and linked ecological processes. We combined two large-scale flux-partitioning approaches to quantify evapotranspiration subcomponents and the hydrologic connectivity of bound, plant-available soil waters with more mobile surface waters. Globally, transpiration is 64 ± 13% (mean ± 1 standard deviation) of evapotranspiration, and 65 ± 26% of evaporation originates from soils and not surface waters. We estimate that 38 ± 28% of surface water is derived from the plant-accessed soil water pool. This limited connectivity between soil and surface waters fundamentally structures the physical and biogeochemical interactions of water transiting through catchments.

  7. Geochemical Reference Earth Model: thermal and geoneutrino fluxes

    NASA Astrophysics Data System (ADS)

    McDonough, W. F.; Huang, Y.; Chubakov, V.; Mantovani, F.; Rudnick, R. L.

    2011-12-01

    Recent results from the KamLAND geoneutrino counting experiment demonstrated that heat derived from the decay of Th and U contributes only about 40% (20±9 TW) of the Earth's total present-day power (46±3 TW) (we consider here only Th and U, since they produce the only detectable geoneutrinos). A geochemical model (e.g., mantle samples) that uses a different approach from both cosmochemical (e.g., enstatite chondrite) and geophysical (e.g., parameterized convection) approaches, and has a bulk silicate Earth (BSE) with 8.2 x 10^16 kg of U, Th/U of 3.9 and K/U of 1.4 x 10^4, with none of these heat producing elements in the metallic core, due to their pronounced chemical affinities for silicates and oxides. Geochemical, cosmochemical and geophysical models predict that the BSE has 21, 11, and 30 TW of total radiogenic heat, respectively, with the contribution from Th and U being 17, 9, 26, and TW, respectively. Consequently, the recently measured geoneutrino flux from the KamLAND is now establishing limits on acceptable compositional models for the Earth. Thus, we are at an exciting stage of discovery, where geoneutrino data will soon be able to distinguish between different models of the amount of planetary nuclear power inside the Earth, the power driving plate tectonics, the geodynamo and compositional models for accretion. We are developing a refined 3-D model of the Earth with physical and chemical inputs that are internally consistent with existing constraints (incorporating global seismological, geochemical and heat flow data); the model predicts a surface flux of geoneutrinos, along with uncertainties, which can be compared with data from the KamLAND and Borexino experiments. This 3-D model has increasing descriptive resolution towards the surface, with geological constraints being applied for the top 220 km of the Earth. This model will provide insights into the Earth's energetics and global radiogenic heat production. Starting in 2013, the Canadian, SNO

  8. GEOCHEMICAL PARTITIONING OF PB, ZN, CU, FE, AND MN ACROSS THE SEDIMENT-WATER INFERFACE IN LARGE LAKES

    EPA Science Inventory

    The early diagenetic remobilization of Mn, Fe, Zn, Cu, and Pb was evaluated by studying the geochemical partitioning of the metals among hydromorphic phases (as operationally defined by sequential-chemical extractions) in interfacial sediment (fluff) and in the sediment column, a...

  9. New Insights on Canopy Photosynthesis from novel Isotopic Flux Partitioning in a temperate forest

    NASA Astrophysics Data System (ADS)

    Saleska, Scott; Wehr, Richard; Munger, William; Zahniser, Mark; McManus, Barry; Nelson, David

    2014-05-01

    Standard approaches for partitioning net eddy fluxes of CO2 into gross primary production (GPP) and ecosystem respiration (R) typically work by extrapolating R from night to day using an empirical function fit to a week or a month of data. Such methods assume that daytime R behaves like nighttime R, and is either constant or a smoothly varying function of temperature. Isotopic partitioning is an alternative that involves no assumptions about the behavior of R or GPP (though it requires knowledge or assumptions about the isotopic fractionations occurring in and around the leaves) and which allows for the investigation of diel variations because each flux measurement is partitioned separately. A novel isotopic flux partitioning approach using the first long-term isotopic CO2 eddy flux record (measured at Harvard Forest) reveals differences in both the diel and the seasonally averaged behavior of GPP as compared to conventional partitioning. At the diel timescale, large (~10 umol m-2 s-1), rapid (~2 hours) variations in the respiratory component of measured NEE associated with subtle changes in wind direction are misattributed to GPP by conventional partitioning, leading to inconsistency in the response of GPP to photosynthetically active radiation (PAR). Isotopically partitioned GPP responds more consistently to PAR, and the seasonally averaged light response curve of isotopically partitioned GPP is more linear than that of conventionally partitioned GPP, suggesting that unsaturated (steeply inclined) leaves perform most of the canopy photosynthesis. Isotopic partitioning further suggests that conventional partitioning based on the temperature-dependent extrapolation of nighttime R overestimates GPP by 10-20%, on average, consistent with its neglect of the suppression of foliar dark respiration by sunlight. Isotopic partitioning is thus changing our interpretation of ecosystem CO2 exchange at the Harvard Forest.

  10. Impact of water use efficiency on eddy covariance flux partitioning using correlation structure analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Partitioned land surfaces fluxes (e.g. evaporation, transpiration, photosynthesis, and ecosystem respiration) are needed as input, calibration, and validation data for numerous hydrological and land surface models. However, one of the most commonly used techniques for measuring land surface fluxes,...

  11. Evaluation of carbon isotope flux partitioning theory under simplified and controlled environmental conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Separation of the photosynthetic (Fp) and respiratory (Fr) fluxes of net CO2 exchange (Fn)remains a necessary step toward understanding the biological and physical controls on carbon cycling between the soil, biomass, and atmosphere. Despite recent advancements in stable carbon isotope partitioning ...

  12. Geochemical Controls on the Partitioning and Hydrological Transport of Metals in a Human Impacted, Non-Acidic, River System

    NASA Astrophysics Data System (ADS)

    Thorslund, J.; Jarsjo, J.; Wällstedt, T.; Morth, C. M.; Lychagin, M.; Chalov, S.

    2014-12-01

    The knowledge of coupled processes controlling the spreading and fate of metals in non-acidic river systems is currently much more limited than the knowledge of metal behavior under acidic conditions (e.g., in acid mine drainage systems). Critical geochemical controls governing metal speciation may thus differ substantially between acidic and non-acidic hydrological systems. We here aim at expanding the knowledge of metals in non-acidic river systems, by considering a high pH river, influenced by mining by the largest gold mining area in the Mongolian part of the transboundary Lake Baikal drainage basin. The combined impact of geochemical and hydrological processes is investigated, to be able to understand the solubility of various heavy metals, their partitioning between particulate and dissolved phase and its impact on overall transport. We show, through site specific measurements and a geochemical modelling approach, that the combined effects of precipitation of ferrihydrite and gibbsite and associated sorption complexes of several metals can explain the high impact of suspended transport relative to total transport often seen under non-acidic conditions. Our results also identifies the phosphate mineral Hydroxyapatite as a potential key sorption site for many metals, which has both site specific and general relevance for metal partitioning under non-acidic conditions. However, an adsorption database, which is currently unavailable for hydroxyapatite, needs to be developed for appropriate sorption quantification. Furthermore, Cd, Fe, Pb and Zn were particularly sensitive to increasing DOC concentrations, which increased the solubility of these metals due to metal-organic complexation. Modeling the sensitivity to changes in geochemical parameters showed that decreasing pH and increasing DOC concentrations in downstream regions would increase the dissolution and hence the toxicity and bioavailability of many pollutants of concern in the downstream ecosystem. In

  13. WATER RESOURCES. Hydrologic connectivity constrains partitioning of global terrestrial water fluxes.

    PubMed

    Good, Stephen P; Noone, David; Bowen, Gabriel

    2015-07-10

    Continental precipitation not routed to the oceans as runoff returns to the atmosphere as evapotranspiration. Partitioning this evapotranspiration flux into interception, transpiration, soil evaporation, and surface water evaporation is difficult using traditional hydrological methods, yet critical for understanding the water cycle and linked ecological processes. We combined two large-scale flux-partitioning approaches to quantify evapotranspiration subcomponents and the hydrologic connectivity of bound, plant-available soil waters with more mobile surface waters. Globally, transpiration is 64 ± 13% (mean ± 1 standard deviation) of evapotranspiration, and 65 ± 26% of evaporation originates from soils and not surface waters. We estimate that 38 ± 28% of surface water is derived from the plant-accessed soil water pool. This limited connectivity between soil and surface waters fundamentally structures the physical and biogeochemical interactions of water transiting through catchments. PMID:26160944

  14. Dynamic Landscape Connectivity, Threshold Behavior, and Scaling Frameworks for Hydrologic and Bio-geochemical Fluxes

    NASA Astrophysics Data System (ADS)

    Foufoula, E.; Zanardo, S.; Danesh-Yazdi, M.; Zaliapin, I.; Power, M.; Dietrich, W.

    2012-12-01

    The hydrologic connectivity of landscapes (the surface fluvial and non-fluvial flowpaths and the flowpaths in the sub-surface) is temporally and spatially changing as dictated by landscape features and precipitation. Developing simple conceptual frameworks for quantifying the response of a basin (hydrologic, sedimentologic, and bio-geochemical) based on theories of network dynamics is still an open problem with slow progress. In this talk two issues will be addressed: (1) scaling of peak flows in response to space-time variable rainfall of duration smaller than the time of concentration of the basin, and (2) predictive modeling and scaling of bio-geochemical fluxes using a spatially explicit model of light and nutrient availability, streamflow, and temperature on the connected network. Data from the Walnut Gulch watershed and the Eel river at Angelo Coast Range Reserve are used for model development and testing.

  15. Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites

    NASA Astrophysics Data System (ADS)

    Wilson, Kell B.; Baldocchi, Dennis D.; Aubinet, Marc; Berbigier, Paul; Bernhofer, Christian; Dolman, Han; Falge, Eva; Field, Chris; Goldstein, Allen; Granier, Andre; Grelle, Achim; Halldor, Thorgeirsson; Hollinger, Dave; Katul, Gabriel; Law, B. E.; Lindroth, Anders; Meyers, Tilden; Moncrieff, John; Monson, Russ; Oechel, Walter; Tenhunen, John; Valentini, Riccardo; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2002-12-01

    The warm season (mid-June through late August) partitioning between sensible (H) and latent (LE) heat flux, or the Bowen ratio (β = H/LE), was investigated at 27 sites over 66 site years within the international network of eddy covariance sites (FLUXNET). Variability in β across ecosystems and climates was analyzed by quantifying general climatic and surface characteristics that control flux partitioning. The climatic control on β was quantified using the climatological resistance (Ri), which is proportional to the ratio of vapor pressure deficit (difference between saturation vapor pressure and atmospheric vapor pressure) to net radiation (large values of Ri decrease β). The control of flux partitioning by the vegetation and underlying surface was quantified by computing the surface resistance to water vapor transport (Rc, with large values tending to increase β). There was a considerable range in flux partitioning characteristics (Rc, Ri and β) among sites, but it was possible to define some general differences between vegetation types and climates. Deciduous forest sites and the agricultural site had the lowest values of Rc and β (0.25-0.50). Coniferous forests typically had a larger Rc and higher β (typically between 0.50 and 1.00 but also much larger). However, there was notable variability in Rc and Ri between coniferous site years, most notably differences between oceanic and continental climates and sites with a distinct dry summer season (Mediterranean climate). Sites with Mediterranean climates generally had the highest net radiation, Rc, Ri, and β. There was considerable variability in β between grassland site years, primarily the result of interannual differences in soil water content and Rc.

  16. Variable Quaternary chemical weathering fluxes and imbalances in marine geochemical budgets.

    PubMed

    Vance, Derek; Teagle, Damon A H; Foster, Gavin L

    2009-03-26

    Rivers are the dominant source of many elements and isotopes to the ocean. But this input from the continents is not balanced by the loss of the elements and isotopes through hydrothermal and sedimentary exchange with the oceanic crust, or by temporal changes in the marine inventory for elements that are demonstrably not in steady state. To resolve the problem of the observed imbalance in marine geochemical budgets, attention has been focused on uncertainties in the hydrothermal and sedimentary fluxes. In recent Earth history, temporally dynamic chemical weathering fluxes from the continents are an inevitable consequence of periodic glaciations. Chemical weathering rates on modern Earth are likely to remain far from equilibrium owing to the physical production of finely ground material at glacial terminations that acts as a fertile substrate for chemical weathering. Here we explore the implications of temporal changes in the riverine chemical weathering flux for oceanic geochemical budgets. We contend that the riverine flux obtained from observations of modern rivers is broadly accurate, but not representative of timescales appropriate for elements with oceanic residence longer than Quaternary glacial-interglacial cycles. We suggest that the pulse of rapid chemical weathering initiated at the last deglaciation has not yet decayed away and that weathering rates remain about two to three times the average for an entire late Quaternary glacial cycle. Taking into account the effect of the suggested non-steady-state process on the silicate weathering flux helps to reconcile the modelled marine strontium isotope budget with available data. Overall, we conclude that consideration of the temporal variability in riverine fluxes largely ameliorates long-standing problems with chemical and isotopic mass balances in the ocean. PMID:19325631

  17. Impact of water use efficiency on eddy covariance flux partitioning using correlation structure analysis

    NASA Astrophysics Data System (ADS)

    Anderson, Ray; Skaggs, Todd; Alfieri, Joseph; Kustas, William; Wang, Dong; Ayars, James

    2016-04-01

    Partitioned land surfaces fluxes (e.g. evaporation, transpiration, photosynthesis, and ecosystem respiration) are needed as input, calibration, and validation data for numerous hydrological and land surface models. However, one of the most commonly used techniques for measuring land surface fluxes, Eddy Covariance (EC), can directly measure net, combined water and carbon fluxes (evapotranspiration and net ecosystem exchange/productivity). Analysis of the correlation structure of high frequency EC time series (hereafter flux partitioning or FP) has been proposed to directly partition net EC fluxes into their constituent components using leaf-level water use efficiency (WUE) data to separate stomatal and non-stomatal transport processes. FP has significant logistical and spatial representativeness advantages over other partitioning approaches (e.g. isotopic fluxes, sap flow, microlysimeters), but the performance of the FP algorithm is reliant on the accuracy of the intercellular CO2 (ci) concentration used to parameterize WUE for each flux averaging interval. In this study, we tested several parameterizations for ci as a function of atmospheric CO2 (ca), including (1) a constant ci/ca ratio for C3 and C4 photosynthetic pathway plants, (2) species-specific ci/ca-Vapor Pressure Deficit (VPD) relationships (quadratic and linear), and (3) generalized C3 and C4 photosynthetic pathway ci/ca-VPD relationships. We tested these ci parameterizations at three agricultural EC towers from 2011-present in C4 and C3 crops (sugarcane - Saccharum officinarum L. and peach - Prunus persica), and validated again sap-flow sensors installed at the peach site. The peach results show that the species-specific parameterizations driven FP algorithm came to convergence significantly more frequently (~20% more frequently) than the constant ci/ca ratio or generic C3-VPD relationship. The FP algorithm parameterizations with a generic VPD relationship also had slightly higher transpiration (5 Wm-2

  18. Multivariate statistical analysis and partitioning of sedimentary geochemical data sets: General principles and specific MATLAB scripts

    NASA Astrophysics Data System (ADS)

    Pisias, Nicklas G.; Murray, Richard W.; Scudder, Rachel P.

    2013-10-01

    Multivariate statistical treatments of large data sets in sedimentary geochemical and other fields are rapidly becoming more popular as analytical and computational capabilities expand. Because geochemical data sets present a unique set of conditions (e.g., the closed array), application of generic off-the-shelf applications is not straightforward and can yield misleading results. We present here annotated MATLAB scripts (and specific guidelines for their use) for Q-mode factor analysis, a constrained least squares multiple linear regression technique, and a total inversion protocol, that are based on the well-known approaches taken by Dymond (1981), Leinen and Pisias (1984), Kyte et al. (1993), and their predecessors. Although these techniques have been used by investigators for the past decades, their application has been neither consistent nor transparent, as their code has remained in-house or in formats not commonly used by many of today's researchers (e.g., FORTRAN). In addition to providing the annotated scripts and instructions for use, we discuss general principles to be considered when performing multivariate statistical treatments of large geochemical data sets, provide a brief contextual history of each approach, explain their similarities and differences, and include a sample data set for the user to test their own manipulation of the scripts.

  19. Partitioning of water flux in a Sierra Nevada ponderosa pine plantation

    USGS Publications Warehouse

    Kurpius, M.R.; Panek, J.A.; Nikolov, N.T.; McKay, M.; Goldstein, Allen H.

    2003-01-01

    The weather patterns of the west side of the Sierra Nevada Mountains (cold, wet winters and hot, dry summers) strongly influence how water is partitioned between transpiration and evaporation and result in a specific strategy of water use by ponderosa pine trees (Pinus ponderosa) in this region. To investigate how year-round water fluxes were partitioned in a young ponderosa pine ecosystem in the Sierra Nevada Mountains, water fluxes were continually measured from June 2000 to May 2001 using a combination of sap flow and eddy covariance techniques (above- and below-canopy). Water fluxes were modeled at our study site using a biophysical model, FORFLUX. During summer and fall water fluxes were equally partitioned between transpiration and soil evaporation while transpiration dominated the water fluxes in winter and spring. The trees had high rates of canopy conductance and transpiration in the early morning and mid-late afternoon and a mid-day depression during the dry season. We used a diurnal centroid analysis to show that the timing of high canopy conductance and transpiration relative to high vapor pressure deficit (D) shifted with soil moisture: during periods of low soil moisture canopy conductance and transpiration peaked early in the day when D was low. Conversely, during periods of high soil moisture canopy conductance and transpiration peaked at the same time or later in the day than D. Our observations suggest a general strategy by the pine trees in which they maximize stomatal conductance, and therefore carbon fixation, throughout the day on warm sunny days with high soil moisture (i.e. warm periods in winter and late spring) and maximize stomatal conductance and carbon fixation in the morning through the dry periods. FORFLUX model estimates of evaporation and transpiration were close to measured/calculated values during the dry period, including the drought, but underestimated transpiration and overestimated evaporation during the wet period. ?? 2003

  20. The inconvenient truth about eddy covariance flux partitioning and implications for global carbon cycle estimates

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Georg; Galvagno, Marta

    2016-04-01

    Ecosystem respiration (ER) and gross primary productivity (GPP) are key carbon cycle concepts. Global estimates of ER and GPP are largely based on measurements of the net ecosystem CO2 exchange by means of the eddy covariance method from which ER and GPP are inferred using so-called flux partitioning algorithms. Using a simple two-source model of ecosystem respiration, consisting of an above-ground respiration source driven by simulated air temperature and a below-ground respiration source driven by simulated soil temperature, we demonstrate that the two most popular flux partitioning algorithms are unable to provide unbiased estimates of daytime ER (ignoring any reduction of leaf mitochondrial respiration) and thus GPP. The bias is demonstrated to be either positive or negative and to depend in a complex fashion on the driving temperature, the ratio of above- to below-ground respiration, the respective temperature sensitivities, the soil depth where the below-ground respiration source originates from (and thus phase and amplitude of soil vs. surface temperature) and day length. The insights from the modeling analysis are subject to a reality check using direct measurements of ER at a grassland where measurements of ER were conducted both during night and day using automated opaque chambers. Consistent with the modeling analysis we find that using air temperature to extrapolate from nighttime to daytime conditions overestimates daytime ER (by 20% or ca. 65 gC m-2 over a 100 day study period), while soil temperature results in an underestimation (by 4% or 12 gC m-2). We conclude with practical recommendations for eddy covariance flux partitioning in the context of the FLUXNET project.

  1. Mercury and trace metal partitioning and fluxes in suburban Southwest Ohio watersheds.

    PubMed

    Naik, Avani P; Hammerschmidt, Chad R

    2011-10-15

    Many natural watersheds are increasingly affected by changes in land use associated with suburban sprawl and such alterations may influence concentrations, partitioning, and fluxes of toxic trace metals in fluvial ecosystems. We investigated the cycling of mercury (Hg), monomethylmercury, cadmium, copper, lead, nickel, and zinc in three watersheds at the urban fringe of Dayton, Ohio, over a 13-month period. Metal concentrations were related positively to discharge in each stream, with each metal having a high affinity for suspended particles and Hg also having a noticeable association with dissolved organic carbon. Although not observed for the other metals, levels of Hg in river water varied seasonally and among streams. Yields of Hg from two of the catchments were comparable to that predicted for runoff of atmospherically deposited Hg (∼25% of wet atmospheric flux), whereas the third watershed had a significantly greater annual flux associated with greater particle-specific and filtered water Hg concentrations, presumably from a point source. Fluxes of metals other than Hg were similar among each watershed and suggestive of a ubiquitous source, which could be either atmospheric deposition or weathering. Results of this study indicate that, with the exception of Hg being increased in one watershed, processes affecting metal partitioning and loadings are similar among southwest Ohio streams and comparable to other North American rivers that are equally or less impacted by urban development. Relative differences in land use, catchment area, and presence or absence of waste water treatment facilities had little or no detectable effect on most trace metal concentrations and fluxes. This suggests that suburban encroachment on agricultural and undeveloped lands has either similarly or not substantially impacted trace metal cycling in streams at the urban fringe of Dayton and, by extension, other comparable metropolitan areas. PMID:21827962

  2. Geochemical processes and fluxes at a methane gas chimney on the Hikurangi Margin (New Zealand)

    NASA Astrophysics Data System (ADS)

    Dale, A.; Haffert, L.; Hütten, E.; Crutchley, G.; Greinert, J.; de Haas, H.; de Stigter, H.; Bialas, J.

    2012-04-01

    The initial results presented in this study focus on the pore water geochemistry of Takahe methane seep located at 1050 m water depth on the Hikurangi Margin. The main objectives are to characterize and quantify the geochemical processes occurring in the upper meters of sediment. Parasound images of the study site showed a well-defined seismic blanking zone of around 230 m in diameter that is likely generated by trapped methane gas. At the northern edge of this seismic gas chimney bubble release has been observed by using hydroacoustic methods (singlebeam and multibeam echosounders). At the seafloor the more northern part of the chimney area showed white Beggiatoa bacterial mats and in places dark sediment patches due to geochemically reduced environments. No other "seep specific" fauna as tube worms or clams as well as no massive chemoherm carbonate where found in the area. This points towards a rather young seepage history. Geochemical data measured in 8 gravity cores across the gas chimney support this notion and gas hydrate layers several cm thick were observed in several cores. Sulphate and total alkalinity concentrations varied little from seawater values in the upper 50 to 100 cm towards the southerly end of the seismic gas chimney area; a feature attributed to irrigation by escaping methane gas bubbles. At these stations, the pore fluids were highly enriched in biogenic methane. However, the dissolved methane was mostly consumed anaerobically by sulphate, resulting in steep gradients of sulphate, methane, total alkalinity and hydrogen sulphide. Geochemical gradients at reference site immediately outside the chimney area were essentially vertical, indicating very little upwards transport and dissolution of methane. The geochemical data are applied to a numerical reaction-transport model to quantify the total upward flux of methane at each station and, ultimately, for the entire gas chimney. Temperature measurements of thermistor probes attached to the barrel

  3. A procedure for partitioning bulk sediments into distinct grain-size fractions for geochemical analysis

    USGS Publications Warehouse

    Barbanti, A.; Bothner, Michael H.

    1993-01-01

    A method to separate sediments into discrete size fractions for geochemical analysis has been tested. The procedures were chosen to minimize the destruction or formation of aggregates and involved gentle sieving and settling of wet samples. Freeze-drying and sonication pretreatments, known to influence aggregates, were used for comparison. Freeze-drying was found to increase the silt/clay ratio by an average of 180 percent compared to analysis of a wet sample that had been wet sieved only. Sonication of a wet sample decreased the silt/clay ratio by 51 percent. The concentrations of metals and organic carbon in the separated fractions changed depending on the pretreatment procedures in a manner consistent with the hypothesis that aggregates consist of fine-grained organic- and metal-rich particles. The coarse silt fraction of a freeze-dried sample contained 20-44 percent higher concentrations of Zn, Cu, and organic carbon than the coarse silt fraction of the wet sample. Sonication resulted in concentrations of these analytes that were 18-33 percent lower in the coarse silt fraction than found in the wet sample. Sonication increased the concentration of lead in the clay fraction by an average of 40 percent compared to an unsonicated sample. Understanding the magnitude of change caused by different analysis protocols is an aid in designing future studies that seek to interpret the spatial distribution of contaminated sediments and their transport mechanisms. ?? 1993 Springer-Verlag.

  4. Energy balance and turbulent flux partitioning in a corn-soybean rotation in the Midwestern US

    NASA Astrophysics Data System (ADS)

    Hernandez-Ramirez, Guillermo; Hatfield, Jerry L.; Prueger, John H.; Sauer, Thomas J.

    2010-03-01

    Quantifying the energy balance above plant canopies is critical for better understanding of water balance and changes in regional weather patterns. This study examined temporal variations of energy balance terms for contrasting canopies [corn ( Zea mays L.) and soybean ( Glycine max L. Merr.)]. We monitored energy balance for 4 years using eddy-covariance systems, net radiometers, and soil heat flux plates in adjacent production fields near Ames, Iowa. On an annual basis, soybean exhibited 20% and 30% lower sensible heat flux ( H) and Bowen ratio than corn, respectively. As canopies developed, a gradual shift in turbulent fluxes occurred with decreasing H and increasing latent heat flux (LE), but with a more pronounced effect for corn. Conversely, during mid-growing season and as both canopies progressively senesced, H in general increased and LE decreased; however, soybean exhibited slightly greater LE and much lower H than corn. These temporal variations in magnitude and partitioning of turbulent fluxes translated into a pronounced energy imbalance for soybean (0.80) and an enhanced closure for corn (0.98) in August and September. These discrepancies could be directly associated with differences in momentum transport as shown by friction velocities of 0.34 and 0.28 m s-1 for corn and soybean, respectively. These results support influential roles of plant canopy on intensity and mode of surface energy exchange processes.

  5. Diel and Seasonal Behavior of Canopy Photosynthesis Revealed by Novel Isotopic Flux Partitioning in a Temperate Forest

    NASA Astrophysics Data System (ADS)

    Wehr, R. A.; Munger, J. W.; McManus, J. B.; Nelson, D. D.; Zahniser, M. S.; Saleska, S. R.

    2013-12-01

    Conventional methods for partitioning the net ecosystem-atmosphere exchange (NEE) of CO2 into gross primary production (GPP) and ecosystem respiration (R) work by extrapolating GPP or R using an empirical function fit to a week or a month of data. Accordingly, these methods do not allow investigation of short-term (e.g. diel) deviations of GPP or R from their monthly average behaviors. Moreover, these methods assume that daytime R is either constant or a smoothly varying function of temperature. Isotopic partitioning is an alternative that involves no assumptions about the behavior of R or GPP (though it requires knowledge or assumptions about the isotopic fractionations occurring in and around the leaves) and which allows for the investigation of diel variations because each flux measurement is partitioned separately. A novel isotopic flux partitioning approach using our unique long-term isotopic CO2 eddy flux record at the Harvard Forest reveals significant differences in both the diel and the seasonally averaged behavior of GPP as compared to conventional partitioning. At the diel timescale, large (~10 μmol m-2 s-1), rapid (~2 hours) variations in the respiratory component of measured NEE associated with subtle changes in wind direction (due to the breakdown of the basic EC assumption of horizontal landscape homogeneity) are misattributed to GPP by conventional partitioning, leading to inconsistency in the response of GPP to photosynthetically active radiation (PAR). Isotopically partitioned GPP responds much more consistently to PAR, and the seasonally averaged light response curve of isotopically partitioned GPP is much more linear than that of conventionally partitioned GPP (after controlling for the leaf-air water vapor gradient), suggesting that unsaturated (steeply inclined) leaves perform most of the canopy photosynthesis (Figure 1). The behavior of isotopically partitioned GPP follows largely from the observed behavior of the canopy-integrated stomatal

  6. Global observation-based diagnosis of soil moisture control on land surface flux partition

    NASA Astrophysics Data System (ADS)

    Gallego-Elvira, Belen; Taylor, Christopher M.; Harris, Phil P.; Ghent, Darren; Veal, Karen L.; Folwell, Sonja S.

    2016-04-01

    Soil moisture plays a central role in the partition of available energy at the land surface between sensible and latent heat flux to the atmosphere. As soils dry out, evapotranspiration becomes water-limited ("stressed"), and both land surface temperature (LST) and sensible heat flux rise as a result. This change in surface behaviour during dry spells directly affects critical processes in both the land and the atmosphere. Soil water deficits are often a precursor in heat waves, and they control where feedbacks on precipitation become significant. State-of-the-art global climate model (GCM) simulations for the Coupled Model Intercomparison Project Phase 5 (CMIP5) disagree on where and how strongly the surface energy budget is limited by soil moisture. Evaluation of GCM simulations at global scale is still a major challenge owing to the scarcity and uncertainty of observational datasets of land surface fluxes and soil moisture at the appropriate scale. Earth observation offers the potential to test how well GCM land schemes simulate hydrological controls on surface fluxes. In particular, satellite observations of LST provide indirect information about the surface energy partition at 1km resolution globally. Here, we present a potentially powerful methodology to evaluate soil moisture stress on surface fluxes within GCMs. Our diagnostic, Relative Warming Rate (RWR), is a measure of how rapidly the land warms relative to the overlying atmosphere during dry spells lasting at least 10 days. Under clear skies, this is a proxy for the change in sensible heat flux as soil dries out. We derived RWR from MODIS Terra and Aqua LST observations, meteorological re-analyses and satellite rainfall datasets. Globally we found that on average, the land warmed up during dry spells for 97% of the observed surface between 60S and 60N. For 73% of the area, the land warmed faster than the atmosphere (positive RWR), indicating water stressed conditions and increases in sensible heat flux

  7. Linking water and carbon fluxes in a Mediterranean oak woodland using a combined flux and ?18O partitioning approach

    NASA Astrophysics Data System (ADS)

    Dubbert, M.; Piayda, A.; Costa e Silva, F.; Correia, A.; Pereira, J. S.; Cuntz, M.; Werner, C.

    2013-12-01

    Water is one of the key factors driving ecosystem productivity, especially in water-limited ecosystems, where global climate change is expected to intensify drought and alter precipitation patterns. One such ecosystem is the ';Montado', where two vegetation layers respond differently to drought: oak trees avoid drought due to their access to deeper soil layers and ground water while herbaceous plants, surviving the summer in the form of seeds. We aimed at 1) quantifying the impact of the understory herbaceous vegetation on ecosystem carbon and water fluxes throughout the year, 2) determining the driving environmental factors for evapotranspiration (ET) and net ecosystem exchange (NEE) and 3) disentangling how ET components of the ecosystem relate to carbon dioxide exchange. We present one year data set comparing modeled and measured stable oxygen isotope signatures (δ18O) of soil evaporation, confirming that the Craig and Gordon equation leads to good agreement with measured δ18O of evaporation (Dubbert et al. 2013). Partitioning ecosystem ET and NEE into its three sources revealed a strong contribution of soil evaporation (E) and herbaceous transpiration (T) to ecosystem ET during spring and fall. In contrast, soil respiration (R) and herbaceous net carbon gain contributed to a lesser amount to ecosystem NEE during spring and fall, leading to consistently smaller water use efficiencies (WUE) of the herbaceous understory compared to the cork-oaks. Here, we demonstrate that the ability to assess ET, NEE and WUE independent of soil evaporation dynamics enables the understanding of the mechanisms of the coupling between water and carbon fluxes and their responses to drought. Dubbert, M., Cuntz, M., Piayda, A., Maguas, C., Werner, C., 2013: Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. J Hydrol. a) Oxygen isotope signatures of soil evaporation on bare soil plots calculated

  8. The use of Mediterranean shrub to flight against the land degradation. The rainfall partitioning fluxes

    NASA Astrophysics Data System (ADS)

    García-Estringana, Pablo; Nieves Alonso-Blazquez, M.; Alegre, Jesús; Cerdà, Artemi

    2014-05-01

    Desertification can be triggered by the lost of vegetation (Izzo et al., 2013). One of the impacts of the lack of vegetation is the increase in the effective rainfall and then higher soil and water losses. Vegetation can reduce the effective rainfall by interception. To recover the land that is affected by Desertification we must select plant species that will intercept the rainfall, but will not avoid the rainfall to reach the soil. This is why, studies on the plant rainfall interception are relevant to flight Land Degradation processes. Soil erosion is highly dependent on the effective rainfall (Cerdà and Lasanta, 2005; Haile and Fetene; 2012; Miao et al., 2012, Prokop and Poręba, 2012). The amount of rainfall that reaches the soil surface and can contribute to detach and transport material is determined by the interception of plants. Interception is also a key factor of the watershed hydrology (Zema et al., 2012). The importance of the rainfall partitioning fluxes is related to the climatic conditions, as climate control the plant cover and the soil properties, and then the soil losses (Cerdà, 1998). Although the shrubs has been seen as a key vegetation cover in semiarid lands to control the soil and water losses (Cerdà and Doerr, 2007) little information is available about rainfall interception in Mediterranean shrub vegetation, due to technical difficulties to measure them in such small-sized vegetation (Belmonte Serrato and Romero Diaz, 1998). The aim of this work was to assess the influence of different Mediterranean shrubs (Retama sphaerocarpa, Colutea arborescens, Dorycnium pentaphyllum, Medicago strasseri, Pistacia Lentiscus and Quercus coccifera) on rainfall partitioning fluxes (interception losses, throughfall and stemflow) in semiarid environments. The experiment was carried out under natural rainfall conditions with live specimens during two years, with automatic measurement of rainfall partitioning fluxes. In order to assess the influence of

  9. Evapotranspiration flux partitioning using an Iso-SPAC model in a temperate grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Wang, P.

    2014-12-01

    To partition evapotranspiration (ET) into soil evaporation and vegetation transpiration (T), a new numerical Iso-SPAC (coupled heat, water with isotopic tracer in Soil-Plant-Atmosphere-Continuum) model was developed and applied to a temperate-grassland ecosystem in central Japan. Several models of varying complexity have been tested with the aim of obtaining the close to true value for the isotope composition of leaf water and transpiration flux. The agreement between the model predictions and observations demonstrates that the Iso-SPAC model with a steady-state assumption for transpiration flux can reproduce seasonal variations of all the surface energy balance components,leaf and ground surface temperature as well as isotope data (canopy foliage and ET flux). This good performance was confirmed not only at diurnal timescale but also at seasonal timescale. Thus, although the non-steady-state behavior of isotope budget in a leaf and isotopic diffusion between leaf and stem or root is exactly important, the steady-state assumption is practically acceptable for seasonal timescale as a first order approximation. Sensitivity analysis both in physical flux part and isotope part suggested that T/ET is relatively insensitive to uncertainties/errors in assigned model parameters and measured input variables, which illustrated the partitioning validity. Estimated transpiration fractions using isotope composition in ET flux by Iso-SPAC model and Keeling plot are generally in good agreement, further proving validity of the both approaches. However, Keeling plot approach tended to overestimate the fraction during an early stage of glowing season and a period just after clear cutting. This overestimation is probably due to insufficient fetch and influence of transpiration from upwind forest. Consequently, Iso-SPAC model is more reliable than Keeling plot approach in most cases.The T/ET increased with grass growth, and the sharp reduction caused by clear cutting was well

  10. Partitioning water and carbon fluxes in a Mediterranean oak woodland using stable oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra; Silva, Filipe Costa e.; Pereira, Joao; Werner, Christiane

    2014-05-01

    evaporation (Dubbert et al. 2013). Moreover, we found continuously strong deviations from isotopic steady-state in plant transpiration combined with large isoforcing on the atmosphere. This implies that assuming plant transpiration to be in the steady-state can have a huge impact at least for studies that distinguish relatively short time intervals (hours, e.g. partitioning studies). Finally. partitioning ecosystem ET and NEE into its three sources revealed a strong contribution of soil evaporation (E) and herbaceous transpiration (T) to ecosystem ET during spring and fall. In contrast, soil respiration (R) and herbaceous net carbon gain contributed to a lesser amount to ecosystem NEE during spring and fall, leading to consistently smaller water use efficiencies (WUE) of the herbaceous understory compared to the cork-oaks. Craig H, Gordon, LI. 1965. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. Paper presented at the Stable Isotopes in Oceanographic Studies and Paleotemperatures, Spoleto, Italy. Dubbert M, Cuntz M, Piayda A, Maguas C, Werner C, 2013: Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. J Hydrol.

  11. Geochemical investigation of weathering processes in a forested headwater catchment: Mass-balance weathering fluxes

    USGS Publications Warehouse

    Jones, B.F.; Herman, J.S.

    2008-01-01

    Geochemical research on natural weathering has often been directed towards explanations of the chemical composition of surface water and ground water resulting from subsurface water-rock interactions. These interactions are often defined as the incongruent dissolution of primary silicates, such as feldspar, producing secondary weathering products, such as clay minerals and oxyhydroxides, and solute fluxes (Meunier and Velde, 1979). The chemical composition of the clay-mineral product is often ignored. However, in earlier investigations, the saprolitic weathering profile at the South Fork Brokenback Run (SFBR) watershed, Shenandoah National Park, Virginia, was characterized extensively in terms of its mineralogical and chemical composition (Piccoli, 1987; Pochatila et al., 2006; Jones et al., 2007) and its basic hydrology. O'Brien et al. (1997) attempted to determine the contribution of primary mineral weathering to observed stream chemistry at SFBR. Mass-balance model results, however, could provide only a rough estimate of the weathering reactions because idealized mineral compositions were utilized in the calculations. Making use of detailed information on the mineral occurrence in the regolith, the objective of the present study was to evaluate the effects of compositional variation on mineral-solute mass-balance modelling and to generate plausible quantitative weathering reactions that support both the chemical evolution of the surface water and ground water in the catchment, as well as the mineralogical evolution of the weathering profile. ?? 2008 The Mineralogical Society.

  12. Sampling Soil CO2 for Isotopic Flux Partitioning: Non Steady State Effects and Methodological Biases

    NASA Astrophysics Data System (ADS)

    Snell, H. S. K.; Robinson, D.; Midwood, A. J.

    2014-12-01

    Measurements of δ13C of soil CO2 are used to partition the surface flux into autotrophic and heterotrophic components. Models predict that the δ13CO2 of the soil efflux is perturbed by non-steady state (NSS) diffusive conditions. These could be large enough to render δ13CO2 unsuitable for accurate flux partitioning. Field studies sometimes find correlations between efflux δ13CO2 and flux or temperature, or that efflux δ13CO2 is not correlated as expected with biological drivers. We tested whether NSS effects in semi-natural soil were comparable with those predicted. We compared chamber designs and their sensitivity to changes in efflux δ13CO2. In a natural soil mesocosm, we controlled temperature to generate NSS conditions of CO2 production. We measured the δ13C of soil CO2 using in situ probes to sample the subsurface, and dynamic and forced-diffusion chambers to sample the surface efflux. Over eight hours we raised soil temperature by 4.5 OC to increase microbial respiration. Subsurface CO2 concentration doubled, surface efflux became 13C-depleted by 1 ‰ and subsurface CO2 became 13C-enriched by around 2 ‰. Opposite changes occurred when temperature was lowered and CO2 production was decreasing. Different chamber designs had inherent biases but all detected similar changes in efflux δ13CO2, which were comparable to those predicted. Measurements using dynamic chambers were more 13C-enriched than expected, probably due to advection of CO2 into the chamber. In the mesocosm soil, δ13CO2 of both efflux and subsurface was determined by physical processes of CO2 production and diffusion. Steady state conditions are unlikely to prevail in the field, so spot measurements of δ13CO2 and assumptions based on the theoretical 4.4 ‰ diffusive fractionation will not be accurate for estimating source δ13CO2. Continuous measurements could be integrated over a period suitable to reduce the influence of transient NSS conditions. It will be difficult to disentangle

  13. The role of vegetation change on surface energy partitioning: insights from a global flux monitoring network

    NASA Astrophysics Data System (ADS)

    Stoy, Paul; Juang, Jehn-Yih; Siqueira, Mario; Novick, Kim; Katul, Gabriel

    2010-05-01

    Vegetation contributes to the absorption and partitioning of energy at the Earth's surface and the surface-atmosphere flux of important greenhouse gases. Changes to vegetation alter the surface energy balance and biogeochemical fluxes. Recent publications have stressed the need to quantify both biogeochemical and biogeophysical effects of land cover change on regional and global climate using a combination of observations and models. This presentation focuses on the observational record by synthesizing surface-atmosphere radiation balance characteristics - including surface albedo and the fluxes of latent and sensible heat - across global ecosystems in the FLUXNET database. We present characteristic seasonal courses of energy balance components across globally distributed ecosystems and demonstrate the impacts of vegetation change on the surface energy balance. We then perform a perturbation analysis on the energy balance equation to quantify the effects of land cover change on surface radiometric and aerodynamic temperatures in paired eddy covariance towers across the globe. Results emphasize the importance of evapotranspiritive cooling in addition to alterations in albedo on surface temperature change. For example, in the Duke Forest experiment, increases in albedo during a shift from abandoned field to pine or hardwood forest warmed the surface by ca. 1° C on an annual basis, but enhanced evapotranspiration cooled the surface by ca. 2 to 3° C such that reforestation induced a net surface cooling. Results using a general methodology agreed with previous results (Juang et al., 2007, Geophysical Research Letters, L21408). Global modeling exercises may underemphasize the role of evaporative cooling versus that of albedo in surface energy balance studies.

  14. Simultaneous Flux Measurements of CO2, its Stable Isotope Ratios and Trace Gases Based on Eddy Accumulation Technique for Flux Partitioning

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Hirata, R.

    2007-12-01

    For the purpose of determining the CO2 uptake by terrestrial ecosystem, eddy covariance method (EC) is commonly used in the tower-flux measurements. The flux measured by this method is called 'enet ecosystem exchange (NEE)'. NEE has the meaning of difference between two component fluxes, photosynthetic uptake and respiratory release of CO2. Magnitude of both the component fluxes is far larger than NEE. Both the component fluxes have difference in response function against changes in environmental factors, such as temperature and water. Therefore it is important to evaluate the characteristics of variations in the comporent fluxes individually in the future prediction of CO2 uptake by terrestrial ecosystem. Separation of NEE into the componet fluxes is usually done by using an approximate temperature expression of respiratory flux. This approximate expression is based on the assumption that the NEE observed at nighttime equals to the respiratory flux. The photosynthetic uptake of CO2 is defined as difference between the observed NEE and 'respiration' approximated as a temperature-function. Because of its technical simplicity, this approach has provided useful information about climatology of the gross CO2 fluxes. However, the temperature expression of respiratory flux has several limitations in its application. We are now developing a flux-partitioning method using chemical tracers (e.g. stable isotopes of CO2 and carbonyl sulfide) as additional constraints. The flux partitioning using stable isotopes of CO2 is based on the imbalance of net flux of the CO2 isotopes between 'respiration' and 'photosynthesis'. On the other hand, because of this similarity in the control factors for uptake ratio, the net flux of carbonyl sulfide (COS) is regarded as a possible constraint for the functioning of variations in photosynthetic CO2 uptake by terrestrial ecosystem. Field observation of fluxes of those chemical tracers by EC method is difficult due to stringent requirements

  15. Trace element partitioning in Earth's lower mantle and implications for geochemical consequences of partial melting at the core-mantle boundary

    NASA Astrophysics Data System (ADS)

    Hirose, Kei; Shimizu, Nobumichi; van Westrenen, Wim; Fei, Yingwei

    2004-08-01

    Trace element partitioning data between CaSiO 3-perovskite (CaPv), MgSiO 3-perovskite (MgPv), calcium-aluminum silicate (CAS-phase), and coexisting melts in peridotite and mid-ocean ridge basalt (MORB) compositions were obtained at 25-27 GPa and 2400-2530 °C using multi-anvil apparatus and ion microprobe. Results clearly show that CaPv is the predominant host for large ion lithophile elements (LILE) in the lower mantle. Because of the overwhelmingly high CaPv/melt partition coefficients (>10 for many of the LILE), partial melting in the lower mantle causes strong enrichment of LILE in the CaPv-bearing solid phase residue. CaPv has the following partitioning characteristics: (1) uniformly high partition coefficients for heavy rare earth elements (HREE) (e.g. 15 for Yb), decreasing toward light REE (e.g. 7 for La), (2) systematically lower partition coefficients for high field strength elements (Nb, Zr, Ti) and Sr relative to neighboring REE, (3) high Th and U, and systematically low Pb partition coefficients. Previous high-pressure studies have shown that the stability field of CaPv above solidus temperature is much wider in basaltic composition than in peridotite, indicating that melting of subducted oceanic crust in the lower mantle could produce significant geochemical CaPv signatures. Strong enrichment in Th and U relative to Pb in CaPv would result in radiogenic Pb isotopic compositions of the CaPv-bearing solid residue. Some clinopyroxenes in plume mantle peridotite xenoliths possess trace element patterns closely resembling those of natural CaPv found in diamonds and CaPv from the present experiments, suggesting that they were inherited from the CaPv-bearing precursor. In contrast, CaPv is the first phase to disappear during partial melting of peridotite above 24 GPa, and its geochemical signature may not be observable in nature. (MgPv + CaPv) fractional crystallization from a magma ocean has previously been put forward as a mechanism for Si depletion of the

  16. Partitioning the climatic and biological controls on photosynthetic fluxes in Amazonian tropical evergreen forests

    NASA Astrophysics Data System (ADS)

    Wu, J.; Guan, K.; Albert, L.; Hayek, M.; Restrepo-Coupe, N.; Prohaska, N.; Wiedemann, K. T.; Marostica, S. F.; Stark, S. C.; Smith, M.; Silva, R. D.; Dye, D. G.; Nelson, B. W.; Huete, A. R.; Saleska, S. R.

    2014-12-01

    Understanding the mechanistic controls on tropical forests photosynthetic metabolism is a central problem of ecology and global change biology. We hypothesize two different temporal scales for the mechanisms regulating tropical photosynthesis (Gross Ecosystem Productivity, GEP): (1) at seasonal scales, leaf phenology (changing age and amount of leaves) is the primary control on GEP seasonality; (2) at the hourly scale with a constant phenological stage, climatic variables are the first order controls on GEP. In order to test this hypothesis, we partitioned the sources of GEP variation measured on eddy flux towers in central Amazon forests into biological and climatic components. The biological component (photosynthetic capacity, or PC) was defined as the monthly mean value of GEP extracted under a fixed narrow range of climate conditions, representing phenological changes associated with the amount and age of leaves. The climatic component was extracted via a path analysis of the hourly flux data, conditioned on a given monthly PC, representing the effects of fluctuating climate operating on the given PC. The main climatic variables were PAR, air-temperature, VPD, and Cloudiness Index (CI), the fraction of reduction of incident solar radiance due to clouds and aerosols relative to that expected under clear sky conditions. We found that the variability in monthly GEP arises from both seasonality of PC and that of climate, but despite the strong seasonality of climate, GEP was dominated by PC seasonality (R2=0.92). We found that the variability in hourly GEP (relative to the potential represented by monthly PC) was controlled primarily by PAR and VPD (as modified by the influence of CI). The tradeoff between the positive GEP effects of increased PAR and the negative effects of higher VPD stress indicates that tropical forests are stable in the face of modest climatic variability. For example, a significant reduction in mean cloudiness (of 0.1 CI units, corresponding

  17. Validation experiments to determine radiation partitioning of heat flux to an object in a fully turbulent fire.

    SciTech Connect

    Ricks, Allen; Blanchat, Thomas K.; Jernigan, Dann A.

    2006-06-01

    It is necessary to improve understanding and develop validation data of the heat flux incident to an object located within the fire plume for the validation of SIERRA/ FUEGO/SYRINX fire and SIERRA/CALORE. One key aspect of the validation data sets is the determination of the relative contribution of the radiative and convective heat fluxes. To meet this objective, a cylindrical calorimeter with sufficient instrumentation to measure total and radiative heat flux had been designed and fabricated. This calorimeter will be tested both in the controlled radiative environment of the Penlight facility and in a fire environment in the FLAME/Radiant Heat (FRH) facility. Validation experiments are specifically designed for direct comparison with the computational predictions. Making meaningful comparisons between the computational and experimental results requires careful characterization and control of the experimental features or parameters used as inputs into the computational model. Validation experiments must be designed to capture the essential physical phenomena, including all relevant initial and boundary conditions. A significant question of interest to modeling heat flux incident to an object in or near a fire is the contribution of the radiation and convection modes of heat transfer. The series of experiments documented in this test plan is designed to provide data on the radiation partitioning, defined as the fraction of the total heat flux that is due to radiation.

  18. Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Luo, Wensui; Spalding, Brian Patrick; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-01-01

    Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.

  19. PARTITIONING OF WATER FLUX IN A SIERRA NEVADA PONDEROSA PINE PLANTATION. (R826601)

    EPA Science Inventory

    The weather patterns of the west side of the Sierra Nevada Mountains (cold, wet winters and hot, dry summers) strongly influence how water is partitioned between transpiration and evaporation and result in a specific strategy of water use by ponderosa pine trees (Pinus pond...

  20. Episodic particle flux in the deep Sargasso Sea: an organic geochemical assessment

    NASA Astrophysics Data System (ADS)

    Conte, Maureen H.; Weber, J. C.; Ralph, Nathan

    1998-11-01

    Since 1978, the Oceanic Flux Program (OFP) time-series sediment trap study has continuously measured particle fluxes in the deep Sargasso Sea (31°50'N, 64°10'W). One feature of this 19+ year record has been the episodic occurrence of large, short-lived flux maxima that are not associated with the annual spring bloom. These maxima generally occur during the Dec.-Jan. period, but not necessarily every year. They have also occurred in other seasons. In January 1996, OFP traps located at 3200 and 3400 m depths intercepted a major flux "event" in which there was an abrupt, threefold increase in mass flux at both depths. Mass flux measured at 3200 m during the event (87 mg m -2 d -1) was the highest recorded since biweekly resolved sampling was begun in 1989. Organic biomarker analyses of material collected prior to, and during, this high flux event determined that there was an abrupt change in material composition associated with the sudden flux increase. Prior to the event, cholesterol, a single bacteriaderived C 27 hopanone (22,29,30-tris norhopan-21-one), and saturated and odd/branched fatty acids predominated: these compounds indicated that the sedimenting material was extensively degraded. During the event, organic material was greatly enriched in C 26-C 29 phytosterols, haptophyte algae-derived C 37-C 39 alkenones, labile polyunsaturated acids, degradation products such as steroidal ketones, and also in bacteria-derived compounds such as C 27-C 34 hopanoids and β and ω-1 hydroxy acids. These compounds indicated the organic fraction contained a large amount of relatively fresh phytoplankton-derived debris and tracers of bacterial biomass and metabolism, which suggested that the sinking material was undergoing active bacterial decomposition. Thus, the flux "event" appears to have resulted from a shortlived bloom in the overlying surface waters which, for reasons not currently apparent, was inefficiently remineralized in the upper ocean and rapidly settled to

  1. The geochemical continuous monitoring network of Vulcano Island (Italy): Long-time variations of SO2 and CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Inguaggiato, Salvatore; Vita, Fabio; Calderone, Lorenzo; Sollami, Aldo

    2015-04-01

    Vulcano Island, located in the Aeolian Archipelago, is an active volcano that has been in state of solphataric activity, since the last eruption (1888-1890). At present, the main exhalative activity is in the northern part of the island, it is revealed by a wide fumaroles field, on the active edifice of "La Fossa" crater, (100°C <450°C). As part of the volcanic monitoring programs, the extensive parameters have a determining role in the evaluation of the mass-output involved. For this reason, in the last years the Vulcano continuous monitoring network was implemented with equipments to measure the fluxes of SO2 "plume" and CO2 soil emitted from the summit crater. In particular, in the 2007 a station to measure the soil CO2 degassing (VCS) was installed in the summit area outside of the fumarolic field. Moreover, inside of the NOVAC project program, an UV-scanning DOAS was installed in the Palizzi area to measure the total SO2 flux emitted from the entire degassing crater area. Here we present the long time variations recorded in the 2007-2014 period. The CO2 soil degassing showed an average flux of 1600 ± 250 g m-2 d-1 representing the background value during "normal" solphataric activity at the permanent station. In the investigated period anomalous values up to 16,000 g m-2 d-1 was recorded in the last months of 2009. The SO2 "plume" degassing showed an average flux of 12 t d-1 with an anomalous degassing process also recorded at the end of 2009 with values up to 100 t d-1. Moreover, a slight increasing trend of SO2 fluxes was recorded in the last years. In the monitoring of active volcanoes, the recorded contemporaneous variations of independent geochemical parameters highlights the importance of the extensive parameters, able to provide information about deeper changes driving the solphataric activity.

  2. Influence of gas-particle partitioning on ammonia and nitric acid fluxes above a deciduous forest in the Midwestern USA

    NASA Astrophysics Data System (ADS)

    Hansen, K.; Sørensen, L. L.; Hornsby, K. E.; Boegh, E.; Pryor, S. C.

    2013-12-01

    Quantifying the atmosphere-biosphere exchange of reactive nitrogen gasses (including ammonia (NH3) and nitric acid (HNO3)) is crucial to assessing the impact of anthropogenic activities on natural and semi-natural ecosystems. However, measuring the deposition of reactive nitrogen is challenging due to bi-directionality of the flux, and the dynamics of the chemical gas/aerosol equilibrium of NH3 and HNO3 (or other atmospheric acids) with aerosol-phase ammonium (NH4+) and nitrate (NO3-). NH3 and HNO3 are both very reactive and typically exhibit higher deposition velocities than aerosol NH4+. Therefore, the phase partitioning between gas and aerosol phases can have a significant effect on local budgets and atmospheric transport distances (Nemitz et al., Atmos. Chem. Phys., 2004). In this study, fluxes of NH3, HNO3 and carbon dioxide (CO2) along with size-resolved N-aerosol concentrations are measured above the deciduous forest, Morgan Monroe State Forest (MMSF) in south-central Indiana (39°53'N, 86°25'W) during a field campaign. Two relaxed eddy accumulation (REA) systems are used to measure fluxes and concentrations of NH3 and HNO3 at 44 m. The NH3 REA system operates based on wet effluent diffusion denuders with detection by florescence and half-hourly flux measurements are calculated. HNO3 REA system is based on gas capture on sodium chloride (NaCl) coated denuders with subsequent analysis by ion-chromatography, and the resulting fluxes have a resolution of 3-4 hours. CO2 fluxes are measured by eddy covariance using a closed-path Licor LI-7500, while two MSP MOUDI-110 impactors are used to measure the 24-hourly average inorganic and 48 hourly averaged organic ion concentrations in 11 size bins, respectively, just above the canopy level (28 m). The results of this field campaign are used to quantify the fluxes of NH3, HNO3, CO2 to/from the forest during the transition towards senescence, and to investigate process-level controls (e.g. the role of phase

  3. SEDIMENT GEOCHEMICAL MODEL

    EPA Science Inventory

    Until recently, sediment geochemical models (diagenetic models) have been only able to explain sedimentary flux and concentration profiles for a few simplified geochemical cycles (e.g., nitrogen, carbon and sulfur). However with advances in numerical methods, increased accuracy ...

  4. Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States

    NASA Astrophysics Data System (ADS)

    Lawrence, Corey R.; Painter, T. H.; Landry, C. C.; Neff, J. C.

    2010-09-01

    Dust deposition in the Rocky Mountains may be an important biogeochemical flux from upwind ecosystems. Seasonal (winter/spring) dust mass fluxes to the San Juan Mountains during the period from 2004 to 2008 ranged from 5 to 10 g m-2, with individual deposition events reaching as high as 2 g m-2. Dust deposited in the San Juan Mountains was primarily composed of silt- and clay-sized particles, indicating a regional source area. The concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations, whereas trace element concentrations were often enriched. In particular, dust collected from the San Juan Mountain snowpack was characterized by enrichments of heavy metals including As, Cu, Cd, Mo, Pb, and Zn. The mineral composition of dust partially explained dust geochemistry; however, based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic-, and not the mineral-, fraction of dust. Our observations show that the dust-derived fluxes of several nutrients and trace metals are substantial and, because many elements are deposited in a mobile form, could be important controls of vegetation, soil, or surface water chemistry. The flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the Rocky Mountains.

  5. Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments

    SciTech Connect

    Zhang, Fan; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2008-01-01

    This study investigated sorption of uranium and technetium onto aluminum and iron hydroxides during titration of a contaminated groundwater using both Na hydroxide and carbonate as titrants. The contaminated groundwater has a low pH of 3.8 and high concentrations of NO3-, SO42-, Al, Ca, Mg, Mn, trace metals such as Ni and Co, and radionuclides such as U and Tc. During titration, most Al and Fe were precipitated out at pH above ~4.5. U as well as Tc was found to be removed from aqueous phase at pH below ~5.5, but to some extent released at higher pH values. An earlier geochemical equilibrium reaction path model that considered aqueous complexation and precipitation/dissolution reactions predicted mineral precipitation and adequately described concentration variations of Al, Fe and some other metal cations, but failed to predict sulfate, U and Tc concentrations during titration. Previous studies have shown that Fe- and Al-oxyhydroxides strongly sorb dissolved sulfate, U and Tc species. Therefore, an anion exchange model was developed for the sorption of sulfate, U and Tc onto Al and Fe hydroxides. With the additional consideration of the anion exchange reactions, concentration profiles of sulfate, U and Tc were more accurately predicted. Results of this study indicate that consideration of complex reactions such as sorption/desorption on mixed mineral phases, in addition to hydrolysis and precipitation, could improve the prediction of various contaminants during pre- and post-groundwater treatment practices.

  6. New geochemical models of core formation in the Moon from metal-silicate partitioning of 15 siderophile elements

    NASA Astrophysics Data System (ADS)

    Steenstra, E. S.; Rai, N.; Knibbe, J. S.; Lin, Y. H.; van Westrenen, W.

    2016-05-01

    We re-examine the conditions at which core formation in the Moon may have occurred by linking the observed lunar mantle depletions of 15 siderophile elements, including volatile siderophile elements (VSE) to predictive equations derived from a database compilation of metal-silicate partition coefficients obtained at lunar-relevant pressure-temperature-oxygen fugacity (P- T- fO2) conditions. Our results suggest that at mantle temperatures between the solidus and liquidus the depletions for all elements considered can be satisfied, but only if the Moon was essentially fully molten at the time of core formation while assuming a S-rich (>8 wt%) core comprising 2.5 wt% of the mass of the Moon. However, we observe that at temperatures exceeding the mantle liquidus, with increasing temperature the core S content required to satisfy the element depletions is reduced. As a S-poor core is likely from recent lunar mantle estimates of S abundance, this suggests much higher temperatures during lunar core formation than previously proposed. We conclude that the VSE depletions in the lunar mantle can be solely explained by core formation depletion, suggesting that no significant devolatilization has occurred in later periods of lunar evolution. This is in agreement with the discovery of significant amounts of other volatiles in the lunar interior, but hard to reconcile with current lunar formation models.

  7. Vegetation controls on surface heat flux partitioning, and land-atmosphere coupling

    NASA Astrophysics Data System (ADS)

    Williams, Ian N.; Torn, Margaret S.

    2015-11-01

    We provide observational evidence that land-atmosphere coupling is underestimated by a conventional metric defined by the correlation between soil moisture and surface evaporative fraction (latent heat flux normalized by the sum of sensible and latent heat flux). Land-atmosphere coupling is 3 times stronger when using leaf area index as a correlate of evaporative fraction instead of soil moisture, in the Southern Great Plains. The role of vegetation was confirmed using adjacent flux measurement sites having identical atmospheric forcing but different vegetation phenology. Transpiration makes the relationship between evaporative fraction and soil moisture nonlinear and gives the appearance of weak coupling when using linear soil moisture metrics. Regions of substantial coupling extend to semiarid and humid continental climates across the United States, in terms of correlations between vegetation metrics and evaporative fraction. The hydrological cycle is more tightly constrained by the land surface than previously inferred from soil moisture.

  8. Estimation of carbon dioxide flux and source partitioning over Beijing, China.

    PubMed

    Song, Tao; Wang, Yuesi; Sun, Yang

    2013-12-01

    The magnitude and partitioning of carbon dioxide emission from the urban area in Beijing, China was estimated based on a statistical approach. Results showed that the urban surface is a net source of CO2 to atmosphere. The main sources of CO2 are vehicles, which accounted for 75.5% and 38.9% of CO2 emission in summer and winter, respectively. At midday in summer, the CO2 uptake of -0.034 mg/(m2 x sec) indicated that vegetation is an important sink of CO2 in summer. Comparison between the annual emission rates of CO2 from the statistical approach and that directly measured by the eddy covariance technique implies that a bottom-up emission approach is a viable means to estimate CO2 emission in an urban area. PMID:24649674

  9. Anthropogenic rare earth element fluxes into floodplains: Coupling between geochemical monitoring and hydrodynamic sediment transport modelling

    NASA Astrophysics Data System (ADS)

    Hissler, Christophe; Hostache, Renaud; Iffly, Jean François; Pfister, Laurent; Stille, Peter

    2015-09-01

    As all rare earth elements (REEs) have an increasingly important role in high tech industries, they are now recognized as emergent pollutants in river systems impacted by anthropogenic activity. Over the past 20 years, significant anthropogenic contributions were reported for Gd, La and Sm, and we may expect that REE contamination in rivers is to further increase in a near future. Despite the work done to assess the environmental impact of REE pollutions in larger river systems, we are still lacking information on the dynamics of these anthropogenic compounds in relation to hydrological changes. Here, we observed for the first time particulate Ce originating from local industrial activities in Luxembourg and we quantified the anthropogenic contribution to the REE fluxes at the river basin scale during a single flood event.

  10. Comparing three methods of NEE-flux partitioning from the same grassland ecosystem: the 13C, 18O isotope approach and using simulated Ecosystem respiration

    NASA Astrophysics Data System (ADS)

    Siegwolf, R.; Bantelmann, E.; Saurer, M.; Eugster, W.; Buchmann, N.

    2007-12-01

    As a change in the global climate occurs with increasing temperatures, the Carbon exchange processes of terrestrial ecosystems will change as well. However, it is difficult to quantify the degree to what ecosystem respiration will change relative to the CO2 uptake by photosynthesis. To estimate the carbon sequestration potential of terrestrial vegetation cover it is essential to know both fluxes: ecosystem respiration and the carbon uptake by the vegetation cover. Therefore the net ecosystem exchange of CO2 (NEE) was measured with the eddy covariance method and separated into assimilation and respiration flux. We applied three different approaches, 1) the conventional method, applying the nighttime relationship between soil temperature and NEE for calculating the respiration flux during the day, 2) the use of stable carbon and 3) oxygen isotopes. We compared the results of the three partitioning exercises for a temperate grassland ecosystem in the pre-Alps of Switzerland for four days in June 2004. The assimilation flux derived with the conventional NEE partitioning approach, was best represented at low PAR and low temperatures, in the morning between 5 and 9 am. With increasing temperature and PAR the assimilation for the whole canopy was underestimated. For partitioning NEE via 18O approach, correlations of temperature and radiation with assimilation and respiration flux were significantly higher for the partitioning approach with 18O than for the 13C NEE partitioning. A sensitivity analysis showed the importance of an accurate determination of the equilibrium term θ between CO2 and leaf water δ18O for the NEE partitioning with 18O. For using 13C to partition NEE, the correct magnitude of the 13C fractionation and for the respiration term is essential. The analysis of the data showed that for low light and low morning temperatures the conventional method delivers reasonably good results. When the temperatures exceeded 21°C the isotope approach provided the

  11. Evaluating the influence of plant-specific physiological parameterizations on the partitioning of land surface energy fluxes

    NASA Astrophysics Data System (ADS)

    Sulis, Mauro; Langensiepen, Matthias; Shrestha, Prabhakar; Schickling, Anke; Simmer, Clemens; Kollet, Stefan

    2015-04-01

    Vegetation has a significant influence on the partitioning of radiative forcing, the spatial and temporal variability of soil water and soil temperature. Therefore plant physiological properties play a key role in mediating and amplifying interactions and feedback mechanisms in the soil-vegetation-atmosphere continuum. Because of the direct impact on latent heat fluxes, these properties may also influence weather generating processes, such as the evolution of the atmospheric boundary layer (ABL). In land surface models, plant physiological properties are usually obtained from literature synthesis by unifying several plant/crop species in predefined vegetation classes. In this work, crop-specific physiological characteristics, retrieved from detailed field measurements, are included in the bio-physical parameterization of the Community Land Model (CLM), which is a component of the Terrestrial Systems Modeling Platform (TerrSysMP). The measured set of parameters for two typical European mid-latitudinal crops (sugar beet and winter wheat) is validated using eddy covariance measurements (sensible heat and latent heat) over multiple years from three measurement sites located in the North Rhine-Westphalia region, Germany. We found clear improvements of CLM simulations, when using the crop-specific physiological characteristics of the plants instead of the generic crop type when compared to the measurements. In particular, the increase of latent heat fluxes in conjunction with decreased sensible heat fluxes as simulated by the two new crop-specific parameter sets leads to an improved quantification of the diurnal energy partitioning. These findings are cross-validated using estimates of gross primary production extracted from net ecosystem exchange measurements. This independent analysis reveals that the better agreement between observed and simulated latent heat using the plant-specific physiological properties largely stems from an improved simulation of the

  12. Carbon Flux Partitioning in an Old-Growth Forest: Study of Seasonal and Interannual Variation

    NASA Astrophysics Data System (ADS)

    Paw U, K.; Falk, M.

    2003-12-01

    We investigate the decompostion of eddy flux measurements of net ecosystem exchange (NEE) into gross primary productivity (GPP), ecosystem respiration (Reco) and the temporal dynamics of component fluxes for 4 « years of data from long-term measurements of carbon fluxes above and within Old-growth Forest at the Wind River Canopy Crane AMERIFLUX site. Trees at the site are up to 500 years old and 65 meters tall. The forest structure at the site is complex for a temperate conifer stand with seven gymnosperm and two angiosperm tree species in the 2.3 ha crane circle, large standing biomass and large amounts of woody debris on the forest floor. Soil respiration is a major contributor to the carbon budget at the site with roughly 75% of total respiration on average. The annual estimates of net ecosystem exchange (NEE) of carbon range from a strong sink (2.1 tC/ha per year) to a source (-0.5 tC/ha per year). Summers are usually warm and dry (1998, 2001) but relatively wet and cool ones have been observed (1999). Precipitation levels throughout the observation period varied from 1600 to 2600 mm with the latter close to the 25-year average. The main period of maximum carbon uptake is limited to the months March through May when ecosystem respiration and water stress are low. Stand-level light response functions show optima for low temperatures and diffuse light conditions. Reco also shows a clear seasonal pattern but lags significantly behind NEE with a maximum in late summer and has a range of 13 - 16 tC/ha per year. GPP shows a similar lag against NEE but is relatively invariant on an annual basis (16 tC/ha).

  13. Stand-level patterns of carbon fluxes and partitioning in a Eucalyptus grandis plantation across a gradient of productivity, in Sao Paulo State, Brazil.

    PubMed

    Campoe, Otávio C; Stape, José Luiz; Laclau, Jean-Paul; Marsden, Claire; Nouvellon, Yann

    2012-06-01

    Wood production represents a large but variable fraction of gross primary production (GPP) in highly productive Eucalyptus plantations. Assessing patterns of carbon (C) partitioning (C flux as a fraction of GPP) between above- and belowground components is essential to understand mechanisms driving the C budget of these plantations. Better knowledge of fluxes and partitioning to woody and non-woody tissues in response to site characteristics and resource availability could provide opportunities to increase forest productivity. Our study aimed at investigating how C allocation varied within one apparently homogeneous 90 ha stand of Eucalyptus grandis (W. Hill ex Maiden) in Southeastern Brazil. We assessed annual above-ground net primary production (ANPP: stem, leaf, and branch production) and total belowground C flux (TBCF: the sum of root production and respiration and mycorrhizal production and respiration), GPP (computed as the sum of ANPP, TBCF and estimated aboveground respiration) on 12 plots representing the gradient of productivity found within the stand. The spatial heterogeneity of topography and associated soil attributes across the stand likely explained this fertility gradient. Component fluxes of GPP and C partitioning were found to vary among plots. Stem NPP ranged from 554 g C m(-2) year(-1) on the plot with lowest GPP to 923 g C m(-2) year(-1) on the plot with highest GPP. Total belowground carbon flux ranged from 497 to 1235 g C m(-2) year(-1) and showed no relationship with ANPP or GPP. Carbon partitioning to stem NPP increased from 0.19 to 0.23, showing a positive trend of increase with GPP (R(2) = 0.29, P = 0.07). Variations in stem wood production across the gradient of productivity observed at our experimental site were a result of the variability in C partitioning to different forest system components. PMID:22543478

  14. Geochemical Fluxes Associated With a Long-range Dust Cloud From the Gobi Desert Region, Central Asia.

    NASA Astrophysics Data System (ADS)

    Zdanowicz, C. M.; Hall, G. E.; Vaive, J. E.

    2003-12-01

    In early April, 2001, an exceptionally intense series of dust storms originated in the Gobi desert region of southern Mongolia and northern China. The dust cloud generated during these storms was tracked by satellite over the North Pacific Ocean and was detected all across North America. Instrumented floats deployed in the subarctic western Pacific Ocean revealed a near-doubling of the carbon biomass in the mixed layer over the 2-week period following the passage of the dust cloud, illustrating the impact of the dust on biological productivity in the surface Ocean (Bishop et al. 2002, Nature vol. 298). During its passage over northwestern America ca April 13, 2001, the Gobi dust plume deposited a widespread, distinctive layer of yellowish-red dust-laden snow, up to 5-cm thick, in the icefields of the St-Elias mountains, Yukon Territory. The dust fallout was probably enhanced by snowfall scavenging associated with orographic uplift of the moist Pacific air mass over the high mountain range (max elevation 5959 m). Samples of dust-laden snow were collected from a series of sites on the Mount Logan massif (60 N, 140 W), during a glaciological research expedition. The samples, collected between elevations of 2400 and 5340 m, contained as much as 80 ppm (mass) of dust. The dust particles were analyzed in the laboratories of the Geological Survey of Canada to characterize their physical attributes (e.g., grain size distribution) as well as their bulk mineralogical and geochemical composition. The concentrations of over 60 major, minor and trace elements were determined using ICP-MS an ICP-ES, including some important nutrients and biolimiting to biointermediate elements such as P, Si, Ba and Ca. Using these measurements, we calculated first-order estimates of the depositional fluxes for various geochemical elements associated with the Gobi dust fallout. Such detailed compositional data on far-traveled dust clouds are rarely available. We hope our findings presented here

  15. Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Cuntz, Matthias; Piayda, Arndt; Maguás, Cristina; Werner, Christiane

    2013-07-01

    Stable oxygen isotopes of water provide a valuable tracer for water movements within ecosystems and are used to estimate the contribution of transpiration to total ecosystem evapotranspiration (ft). We tested the Craig and Gordon equation against continuous field measurements of isotopic composition of evaporation and assessed the impact for partitioning evapotranspiration. Therefore, evaporation (E) and its isotopic signature (δ18OE) on bare soil plots, as well as evapotranspiration (ET) and its corresponding isotopic composition of (δ18OET) of an herbaceous layer was measured with a cavity ring-down spectrometer connected to a soil chamber on a field site in central Portugal. We quantified the variation in δ18OE arising from uncertainties in the determination of environmental input variables to the Craig and Gordon equation: the isotope signature (δ18Oe) and the temperature at the evaporating site (Te), and the kinetic fractionation factor (αk). We could hence quantify ft based on measured δ18OET, modeled δ18OE from observed soil water isotopic composition at the evaporating site (δ18Oe), and modeled δ18O of transpiration (δ18OT) from observed total soil water isotopic composition. Our results demonstrate that predicting δ18OE using the Craig and Gordon equation leads to good agreement with measured δ18OE given that the temperature and 18O isotope profiles of the soil are thoroughly characterized. However, modeled δ18OE is highly sensitive to changes in Te and δ18Oe as well as αk. This markedly affected the partition results of transpiration and evaporation from the total ET flux: The fraction of transpiration (ft) varied strongly using different formulations for αk and assuming steady or non-steady state transpiration. These findings provide a first comparison of laser-based and modeled isotopic compositions of evaporation based on the Craig and Gordon equation under field conditions. This is of special interest for studies using stable isotopes

  16. Gas geochemical survey of long dormant Ciomadul volcano (South Harghita Mts., Romania): constraints on the flux and origin of fluids

    NASA Astrophysics Data System (ADS)

    Kis, Boglárka-Mercedesz; Ionescu, Artur; Harangi, Szabolcs; Palcsu, László; Etiope, Giuseppe; Baciu, Cǎlin

    2016-04-01

    The Ciomadul, located in the South Harghita Mountains (Eastern Carpathians, Romania) is the youngest volcano built by the Neogene volcanism in the Carpathian-Pannonian Region. The volcanic activity was characterized by an initial extrusive lava dome building period from about 200 ka to 100 ka followed by a more explosive eruption stage from 57 to 32 ka. Although the volcano seems to be inactive, several features (e.g. geophysical anomalies in the crust; fast remobilization of near solidus long lasting crystal mush prior to the past eruptions) suggest that melt-bearing magmatic body could still exist beneath the Ciomadul. This is supported by the abundance of dry gas emanations (CO2, CH4, H2S), CO2 rich mineral water springs and bubbling pools. The long-term observation of seemingly inactive, dormant volcanoes has become important in the past years (Ontake volcano-Japan, Colli Albani volcano-Italy). Gas-geochemical survey and monitoring (noble gases, isotopic composition of carbon species, flux measurements) of such volcanoes is an adequate tool in detecting changes in their volcanic plumbing system. Starting from 2015 we commenced a gas-monitoring study to constrain the origin of fluids at Ciomadul by measuring the flux of two gas-species and collecting the gas-phase from several mofettes and mineral water springs. A total of 46 sites have been surveyed, including 29 gas emanations (mofettes and bubbling pools), 3 drilled wells, 11 springs and 3 surface water sites. We provide the first complex CO2 and CH4 flux measurements in the area considering mofettes and bubbling pools. The CO2 flux values range between 10 and 264 kg/day while the CH4 flux has a range between 125 and 4723 g/day. Estimates of total CO2 and CH4 output into the atmosphere are ~229 and ~1.3 t/year, respectively. These values are consistent with other geothermal systems in Europe. The chemical composition of samples indicate CO2 content of up to 96.77%, CH4 content up to 1.42% and He content up to

  17. Partitioning CO2 Fluxes in Transitional Bioenergy CROPS:EFFECT of Land Use Change

    NASA Astrophysics Data System (ADS)

    Zenone, T.; Chen, J.; Hamilton, S. K.; Robertson, G. P.

    2010-12-01

    The demand for alternatives to petroleum is increasing the production of bioenergy. Undisturbed ecosystems in different part of the globe were converted to bioenergy cultivations. In this study we examined the effect of land conversion on C Pools and fluxes using the Eddy Covariance (EC) technique in seven sites in southwestern Michigan undergoing such conversions. Of the seven sites, four had been managed for the Conservation Reserve Program (CRP) during the last 20 years to maintain them as grasslands. The other three were cultivated in a corn/soybean rotation. The effects of land use change were studied during 2009 when six of the fields (three CRP and three crop fields) were converted to soybean cultivation, with the 7th site remained as a grassland reference. Daytime estimates of ecosystem respiration (Reco) were obtained from the night NEE-temperature relationship. An Arrhenius-type model was used to describe the temperature dependence of Reco. The Gross Primary Productivity (GPP) was then obtained by subtracting Reco from NEE. Soil CO2 fluxes (SRR) were measured in all sites with a portable EGM-4 infrared gas analyzer (PP-Systems, UK). SRR, soil temperature, and soil moisture were analyzed using a two-way ANOVA with repeated measures analyses on one factor. SRR was modeled using a nonlinear regression function to describe SRR as dependant on soil temperature and soil moisture, expressed as soil water content relative to the soil water content at field capacity (RSWC). Standard errors of nonlinear regression parameters were estimated by a bootstrapping algorithm. During winter the agricultural sites were essentially carbon (C) neutral while the grasslands were C sources, with average emissions of 15 g C m-2 month-1. The annual NEP at sites converted from CRP to soybeans had a net emission of 156 (± 25) - 128 (± 27) g C m-2 year-1. The sites previously cultivated as corn/soybean rotation was a net C uptake, with NEP ranging from -91 (± 26) to -57 (± 21) g

  18. Variability in surface energy flux partitioning during Washita '92: Resulting effects on Penman-Monteith and Priestley-Taylor parameters

    USGS Publications Warehouse

    Kustas, W.P.; Stannard, D.I.; Allwine, K.J.

    1996-01-01

    During the Washita '92 field experiment, the local surface energy balance was evaluated at four locations in the USDA-ARS Little Washita River Watershed near Chickasha, OK, using the Bowen ratio-energy balance (BREB) approach. For any given day, differences in the partitioning of the available energy appeared to be mostly a function of the type of vegetation at the site, while the actual magnitude of the fluxes was mostly affected by cloud cover. The soil surface was initially wet, and gradually dried during the field experiment. However, there was not a corresponding decrease in the evaporative fraction, which would have indicated a decreasing contribution of soil evaporation to the total latent heat flux. Ground weather data indicated a large shift in the direction and magnitude of the surface winds, and a significant increase in air temperature and vapor pressure deficit. During this period, the evaporative fraction actually increased at two of the four sites. The response of the different sites to the changing near- surface atmospheric conditions was studied in more detail by evaluating the canopy resistance (r(c)) to evaporation using the Penman-Monteith equation and the Priestley-Taylor parameter (??). Midday averages of r(c) and (??) tended to decrease (increase) with increasing vapor pressure deficit for two of the sites while such a trend was not evident for the other two sites. Estimates of stomatal resistances indicated that significant plant physiological differences existed between the sites containing weedy vegetation versus the grasses at the pasture/rangeland sites. Even though soil moisture conditions were relatively wet, ?? was less than 1 at all sites and there was no trend in ?? as a function of surface soil moisture conditions. These findings suggest that vegetation types in mixed agricultural/rangeland ecosystems can have significantly different responses to similar atmospheric forcing conditions.

  19. Surface Energy Exchange in a Tropical Montane Cloud Forest Environment: Flux Partitioning, and Seasonal and Land Cover-Related Variations

    NASA Astrophysics Data System (ADS)

    Holwerda, F.; Alvarado-Barrientos, M. S.; González-Martínez, T.

    2015-12-01

    Relationships between seasonal climate, land cover and surface energy exchange in tropical montane cloud forest (TMCF) environments are poorly understood. Yet, understanding these linkages is essential to evaluating the impacts of land use and climate change on the functioning of these unique ecosystems. In central Veracruz, Mexico, TMCF occurs between 1100 and 2500 m asl. The canopy of this forest consists of a mix of deciduous and broadleaved-evergreen tree species, the former of which shed their leaves for a short period during the dry season. The aim of this study was to quantify the surface energy balance, and seasonal variations therein, for TMCF, as well as for shaded coffee (CO) and sugarcane (SU), two important land uses that have replaced TMCF at lower elevations. Sensible (H) and latent heat (LE) fluxes were measured using eddy covariance and sap flow methods. Other measurements included: micrometeorological variables, soil heat flux, soil moisture and vegetation characteristics. Partitioning of available energy (A) into H and LE showed important seasonal changes as well as differences among land covers. During the wet-season month of July, average midday Bowen ratios for sunny days were lowest and least variable among land covers: 0.5 in TMCF and SU versus 0.7 in CO. However, because of higher A, along with lower Bowen ratio with respect to CO, LE over TMCF was ca. 20% higher compared to CO and SU. During the late dry-season months of March and April, average midday Bowen ratios for sunny days were generally much higher and more variable among land covers. The higher Bowen ratios indicated a reduction of LE under the drier conditions prevailing (low soil moisture and high VPD), something rarely observed in TMCFs. Moreover, because some trees were still partially leafless in March, LE over TMCF was about half that over CO and SU, suggesting an important effect of phenology on energy exchange of this TMCF. Observed differences between seasons and land

  20. Spatial distribution of seafloor bio-geological and geochemical processes as proxies of fluid flux regime and evolution of a carbonate/hydrates mound, northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Macelloni, Leonardo; Brunner, Charlotte A.; Caruso, Simona; Lutken, Carol B.; D'Emidio, Marco; Lapham, Laura L.

    2013-04-01

    Woolsey Mound, a carbonate/hydrate complex of cold seeps, vents, and seafloor pockmarks in Mississippi Canyon Block 118, is the site of the Gulf of Mexico Hydrates Research Consortium's (GOMHRC) multi-sensor, multi-disciplinary, permanent seafloor observatory. In preparation for installing the observatory, the site has been studied through geophysical, biological, geological, and geochemical surveys. By integrating high-resolution, swath bathymetry, acoustic imagery, seafloor video, and shallow geological samples in a morpho-bio-geological model, we have identified a complex mound structure consisting of three main crater complexes: southeast, northwest, and southwest. Each crater complex is associated with a distinct fault. The crater complexes exhibit differences in morphology, bathymetric relief, exposed hydrates, fluid venting, sediment accumulation rates, sediment diagenesis, and biological community patterns. Spatial distribution of these attributes suggests that the complexes represent three different fluid flux regimes: the southeast complex seems to be an extinct or quiescent vent; the northwest complex exhibits young, vigorous activity; and the southwest complex is a mature, fully open vent. Geochemical evidence from pore-water gradients corroborates this model suggesting that upward fluid flux waxes and wanes over time and that microbial activity is sensitive to such change. Sulfate and methane concentrations show that microbial activity is patchy in distribution and is typically higher within the northwest and southwest complexes, but is diminished significantly over the southeast complex. Biological community composition corroborates the presence of distinct conditions at the three crater complexes. The fact that three different fluid flux regimes coexist within a single mound complex confirms the dynamic nature of the plumbing system that discharges gases into bottom water. Furthermore, the spatial distribution of bio-geological processes appears to

  1. Using an input manipulation experiment to partition greenhouse gas fluxes from a commercial Miscanthus plantation in the UK

    NASA Astrophysics Data System (ADS)

    Robertson, Andy; Davies, Christian; Smith, Pete; McNamara, Niall

    2014-05-01

    Miscanthus is a lignocellulosic C4 crop that can be grown for a number of practical end-uses but recently interest has increased in its viability as a bioenergy crop; both providing a renewable source of energy and helping to limit climate change by reducing carbon (C) emissions associated with energy generation. Recent studies have shown that Miscanthus plantations may increase stocks of soil organic carbon (SOC) however there is still considerable uncertainty surrounding estimates of net C exchange and the best management practices to achieve the best greenhouse gas (GHG) mitigation potential. Using an input manipulation experiment, we monitored emissions of N2O, CH4 and CO2 from living Miscanthus roots, aboveground plant litter and soil individually to quantify and partition these emissions and better understand the influence of abiotic factors on SOC and GHG dynamics under Miscanthus. In January 2009 twenty-five 2 m2 plots were set up in a three-year old 11 hectare commercial Miscanthus plantation in Lincolnshire, UK; with five replicates of five treatments. These treatments varied plant input (roots or senesced aboveground plant litter) to the soil by way of controlled exclusion techniques. The delta 13C value of soil C and CO2 emitted from each treatment was measured monthly between March 2009 and March 2013. Measurements of CH4 and N2O emissions were also taken at the soil surface from each treatment. Miscanthus-derived emissions were determined using the isotopic discrimination between C4 plant matter and C3 soil, and the treatments were compared to assess their effects on C inputs and outputs to the soil. Both CH4 and N2O emissions were below detection limits, mainly due to a lack of fertiliser additions and limited disturbance of the agricultural site. However, results for CO2 emissions indicate a strong seasonal variation; litter decomposition forms a large portion of the CO2 emissions in winter and spring whereas root respiration dominates the summer

  2. Spatial and temporal geochemical trends in the hydrothermal system of Yellowstone National Park: Inferences from river solute fluxes

    USGS Publications Warehouse

    Hurwitz, S.; Lowenstern, J. B.; Heasler, H.

    2007-01-01

    We present and analyze a chemical dataset that includes the concentrations and fluxes of HCO3-, SO42-, Cl-, and F- in the major rivers draining Yellowstone National Park (YNP) for the 2002-2004 water years (1 October 2001 - 30 September 2004). The total (molar) flux in all rivers decreases in the following order, HCO3- > Cl- > SO42- > F-, but each river is characterized by a distinct chemical composition, implying large-scale spatial heterogeneity in the inputs of the various solutes. The data also display non-uniform temporal trends; whereas solute concentrations and fluxes are nearly constant during base-flow conditions, concentrations decrease, solute fluxes increase, and HCO3-/Cl-, and SO42-/Cl- increase during the late-spring high-flow period. HCO3-/SO42- decreases with increasing discharge in the Madison and Falls Rivers, but increases with discharge in the Yellowstone and Snake Rivers. The non-linear relations between solute concentrations and river discharge and the change in anion ratios associated with spring runoff are explained by mixing between two components: (1) a component that is discharged during base-flow conditions and (2) a component associated with snow-melt runoff characterized by higher HCO3-/Cl- and SO42-/Cl-. The fraction of the second component is greater in the Yellowstone and Snake Rivers, which host lakes in their drainage basins and where a large fraction of the solute flux follows thaw of ice cover in the spring months. Although the total river HCO3- flux is larger than the flux of other solutes (HCO3-/Cl- ??? 3), the CO2 equivalent flux is only ??? 1% of the estimated emission of magmatic CO2 soil emissions from Yellowstone. No anomalous solute flux in response to perturbations in the hydrothermal system was observed, possibly because gage locations are too distant from areas of disturbance, or because of the relatively low sampling frequency. In order to detect changes in river hydrothermal solute fluxes, sampling at higher

  3. Evidence for Niche Partitioning Revealed by the Distribution of Sulfur Oxidation Genes Collected from Areas of a Terrestrial Sulfidic Spring with Differing Geochemical Conditions

    PubMed Central

    Engel, Annette Summers

    2013-01-01

    The diversity and phylogenetic significance of bacterial genes in the environment has been well studied, but comparatively little attention has been devoted to understanding the functional significance of different variations of the same metabolic gene that occur in the same environment. We analyzed the geographic distribution of 16S rRNA pyrosequences and soxB genes along a geochemical gradient in a terrestrial sulfidic spring to identify how different taxonomic variations of the soxB gene were naturally distributed within the spring outflow channel and to identify possible evidence for altered SoxB enzyme function in nature. Distinct compositional differences between bacteria that utilize their SoxB enzyme in the Paracoccus sulfide oxidation pathway (e.g., Bradyrhizobium, Paracoccus, and Rhodovulum) and bacteria that utilize their SoxB enzyme in the branched pathway (e.g., Chlorobium, Thiothrix, Thiobacillus, Halothiobacillus, and Thiomonas) were identified. Different variations of the soxB genes were present at different locations within the spring outflow channel in a manner that significantly corresponded to geochemical conditions. The distribution of the different soxB gene sequence variations suggests that the enzymes encoded by these genes are functionally different and could be optimized to specific geochemical conditions that define niche space for bacteria capable of oxidizing reduced sulfur compounds. PMID:23220955

  4. Interactions of Cd and Cu in anaerobic estuarine sediments. 2: Bioavailability, body burdens and respiration effects as related to geochemical partitioning

    SciTech Connect

    Rule, J.H.; Alden, R.W. III

    1996-04-01

    The relationship between Cd and Cu distribution in sediment geochemical fractions and their bioavailability was studied. A fine-sandy textured estuarine sediment was treated with all combinations of 0, 2.5, and 5 mg/kg Cd and 0, 12, and 25 mg/kg Cu using the chloride salts of each metal. Grass shrimp (Palaemonetes pugio), blue mussel (Mytilus edulis), and hard clam (Mercenaria mercenaria) were exposed to the treated sediments in aquaria with 20 ppt artificial seawater for 14 d. Sediments were sequentially extracted before and after organism exposure to determine the exchangeable, easily reducible, organic-sulfide, moderately reducible, and acid extractable phases. Low mortalities were observed for all organism types and none were attributable to any of the treatments. The Cd and Cu concentrations in the easily reducible and organic-sulfide phases were found to be significantly related to the bioavailability of these metals. The most highly significant relationship was established between Cd in the easily reducible phase and body burden of Cd in the blue mussel. Notable interactions were found between Cd and Cu in some of the geochemical phases, body burdens, and respiration rates. Metal uptake, respiration, and interactions were highly dependent on the test species. A significant correlation was found between increased body burden and depressed respiration for Cd but not for Cu. Multiple regression models are used to describe these relationships. It appears that the interactive responses in the organisms are driven primarily by the sediment geochemical effects and mediated by individual organism processes. These results underscore the necessity of multicomponent (multielement) studies in assessing the fate and effects of toxic elements in the environment.

  5. Environment and phenology: CO2 net ecosystem exchange and CO2 flux partitioning at an acid and oligotrophic mire system in northern Sweden

    NASA Astrophysics Data System (ADS)

    Gažovič, Michal; Peichl, Matthias; Vermeij, Ilse; Limpens, Juul; Nilsson, Mats. B.

    2015-04-01

    Static chamber and environmental measurements in combination with vegetation indices (i.e. vascular green area (VGA) and the greenness chromatic color index (gcc) derived from digital camera images) were used to investigate effects of environment and phenology on the CO2 net ecosystem exchange (NEE) and CO2 flux partitioning at the Degerö Stormyr site in northern Sweden (64°11' 23.565" N, 19°33' 55.291 E) during two environmentally different years. Our measurement design included a control plot, a moss plot (where vascular plants were removed by clipping) and four heterotrophic respiration (RH) collars (where all green moss and vascular plant biomass were removed) to partition between soil heterotrophic and plant autotrophic (moss and vascular plants) respiration (RA), as well as between moss and vascular plant gross primary production (GPP). Environmental conditions, especially the shallow snow cover, peat soil frost and cold spring in 2014 caused delayed onset of spring green up, reduced soil respiration flux and reduced GPP of vascular plants. Soil temperature measured in 26 cm depth started to rise from spring temperatures of ~ 0.6 °C in 2013 and 0.15 °C in 2014 about 20 days earlier in 2013 compared to 2014. With earlier onset of the growing season and higher soil temperatures in 2013, heterotrophic soil respiration was higher in year 2013 than in year 2014. In 2013, RH dominated the total ecosystem respiration in all months but June and August. On contrary, autotrophic respiration dominated ecosystem respiration in all months of 2014. In both years, vascular plants and mosses were more or less equally contributing to autotrophic respiration. We measured higher GPP in year 2013 compared to year 2014. Also VGA and gcc were higher in spring and throughout the rest of 2013 compared to 2014. The onset of VGA was delayed by ~ 10 days in 2014. In general, total GPP was dominated by GPP of vascular plants in both years, although moss GPP had substantial

  6. Genome-scale modeling of light-driven reductant partitioning and carbon fluxes in diazotrophic unicellular cyanobacterium Cyanothece sp. ATCC 51142

    SciTech Connect

    Vu, Trang; Stolyar, Sergey; Pinchuk, Grigoriy E.; Hill, Eric A.; Kucek, Leo A.; Brown, Roslyn N.; Lipton, Mary S.; Osterman, Andrei L.; Fredrickson, Jim K.; Konopka, Allan; Beliaev, Alex S.; Reed, Jennifer L.

    2012-04-05

    Genome-scale metabolic models have proven useful for answering fundamental questions about metabolic capabilities of a variety of microorganisms, as well as informing their metabolic engineering. However, only a few models are available for oxygenic photosynthetic microorganisms, particularly in cyanobacteria in which photosynthetic and respiratory electron transport chains (ETC) share components. We addressed the complexity of cyanobacterial ETC by developing a genome-scale model for the diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142. The resulting metabolic reconstruction, iCce806, consists of 806 genes associated with 667 metabolic reactions and includes a detailed representation of the ETC and a biomass equation based on experimental measurements. Both computational and experimental approaches were used to investigate light-driven metabolism in Cyanothece sp. ATCC 51142, with a particular focus on reductant production and partitioning within the ETC. The simulation results suggest that growth and metabolic flux distributions are substantially impacted by the relative amounts of light going into the individual photosystems. When photosystem II flux is high, terminal oxidases of respiratory electron transport are predicted to be an important mechanism for removing excess electrons. When photosystem I flux is high cyclic electron transport becomes important. Model predictions of growth rates were in good quantitative agreement with measured growth rates, and predictions of reaction usage were qualitatively consistent with protein and mRNA expression data, when these latter datasets were used to constrain the model.

  7. Genome-Scale Modeling of Light-Driven Reductant Partitioning and Carbon Fluxes in Diazotrophic Unicellular Cyanobacterium Cyanothece sp. ATCC 51142

    SciTech Connect

    Vu, Trang; Stolyar, Sergey; Pinchuk, Grigoriy E.; Hill, Eric A.; Kucek, Leo A.; Brown, Roslyn N.; Lipton, Mary S.; Osterman, Andrei L.; Fredrickson, Jim K.; Konopka, Allan; Beliaev, Alex S.; Reed, Jennifer L.

    2012-04-05

    Genome-scale metabolic models have proven useful for answering fundamental questions about metabolic capabilities of a variety of microorganisms, as well as informing their metabolic engineering. However, only a few models are available for oxygenic photosynthetic microorganisms, particularly in cyanobacteria in which photosynthetic and respiratory electron transport chains (ETC) share components. We addressed the complexity of cyanobacterial ETC by developing a genome-scale model for the diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142. The resulting metabolic reconstruction, iCce806, consists of 806 genes associated with 667 metabolic reactions and includes a detailed representation of the ETC and a biomass equation based on experimental measurements. Both computational and experimental approaches were used to investigate light-driven metabolism in Cyanothece sp. ATCC 51142, with a particular focus on reductant production and partitioning within the ETC. The simulation results suggest that growth and metabolic flux distributions are substantially impacted by the relative amounts of light going into the individual photosystems. When photosystem II flux is high, terminal oxidases of respiratory electron transport are predicted to be an important mechanism for removing excess electrons. When photosystem I flux is high cyclic electron transport becomes important. Model predictions of growth rates were in good quantitative agreement with measured growth rates, and predictions of reaction usage were ualitatively consistent with protein and mRNA expression data, when these latter datasets were used to constrain the model.

  8. Solid phase evolution in the Biosphere 2 hillslope experiment as predicted by modeling of hydrologic and geochemical fluxes

    SciTech Connect

    Dontsova, K.; Steefel, C.I.; Desilets, S.; Thompson, A.; Chorover, J.

    2009-07-15

    A reactive transport geochemical modeling study was conducted to help predict the mineral transformations occurring over a ten year time-scale that are expected to impact soil hydraulic properties in the Biosphere 2 (B2) synthetic hillslope experiment. The modeling sought to predict the rate and extent of weathering of a granular basalt (selected for hillslope construction) as a function of climatic drivers, and to assess the feedback effects of such weathering processes on the hydraulic properties of the hillslope. Flow vectors were imported from HYDRUS into a reactive transport code, CrunchFlow2007, which was then used to model mineral weathering coupled to reactive solute transport. Associated particle size evolution was translated into changes in saturated hydraulic conductivity using Rosetta software. We found that flow characteristics, including velocity and saturation, strongly influenced the predicted extent of incongruent mineral weathering and neo-phase precipitation on the hillslope. Results were also highly sensitive to specific surface areas of the soil media, consistent with surface reaction controls on dissolution. Effects of fluid flow on weathering resulted in significant differences in the prediction of soil particle size distributions, which should feedback to alter hillslope hydraulic conductivities.

  9. Composition of pore and spring waters from Baby Bare: global implications of geochemical fluxes from a ridge flank hydrothermal system

    NASA Astrophysics Data System (ADS)

    Wheat, C. Geoffrey; Mottl, Michael J.

    2000-02-01

    by compilations of data from other ridge-flank sites, which show a systematic relationship between inferred basement water composition and temperature. We use the Baby Bare spring waters along with constraints from the riverine flux of Mg to estimate upper limits on the global fluxes of 14 elements at warm ridge-flank sites such as Baby Bare. Maximum calculated fluxes of Mg, Ca, sulfate, B, and K may equal or exceed 25% of the riverine flux, and such sites may represent the missing, high K/Rb sink required for the K budget. Additional fluxes from/to the crust on ridge flanks are expected from cool (<20-25°C) hydrothermal sites.

  10. Stable oxygen isotope and flux partitioning demonstrates understory of an oak savanna contributes up to half of ecosystem carbon and water exchange

    PubMed Central

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra C.; Costa e Silva, Filipe; Pereira, Joao S.; Werner, Christiane

    2014-01-01

    Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxes between the soil and vegetation components is crucial to gain mechanistic understanding of vegetation effects on carbon and water cycling. However, the possible impact of herbaceous vegetation in savanna type ecosystems is often overlooked. Therefore, we aimed at quantifying understory vegetation effects on the water balance and productivity of a Mediterranean oak savanna. ET and net ecosystem CO2 exchange (NEE) were partitioned based on flux and stable oxygen isotope measurements and also rain infiltration was estimated. The understory vegetation contributed importantly to total ecosystem ET and GPP with a maximum of 43 and 51%, respectively. It reached water-use efficiencies (WUE; ratio of carbon gain by water loss) similar to cork-oak trees. The understory vegetation inhibited soil evaporation (E) and, although E was large during wet periods, it did not diminish WUE during water-limited times. The understory strongly increased soil water infiltration, specifically following major rain events. At the same time, the understory itself was vulnerable to drought, which led to an earlier senescence of the understory growing under trees as compared to open areas, due to competition for water. Thus, beneficial understory effects are dominant and contribute to the resilience of this ecosystem. At the same time the vulnerability of the understory to drought suggests that future climate change scenarios for the Mediterranean basin threaten understory development. This in turn will very likely diminish beneficial understory effects like infiltration and ground water recharge and therefore ecosystem resilience to drought. PMID

  11. Composition of pore and spring waters from Baby Bare: Global implications of geochemical fluxes from a ridge flank hydrothermal system

    SciTech Connect

    Wheat, C.G.; Mottl, M.J.

    2000-02-01

    Warm hydrothermal springs were discovered on Baby Bare, which is an isolated basement outcrop on 3.5 Ma-old crust on the eastern flank of the Juan de Fuca Ridge. The authors have sampled these spring waters from a manned submersible, along with associated sediment pore waters from 48 gravity and piston cores. Systematic variations in the chemical composition of these waters indicate that hydrothermal reactions in basement at moderate temperatures remove Na, K, Li, Rb, Mg, TCO{sub 2}, alkalinity, and phosphate from the circulating seawater and leach Ca, Sr, Si, B, and Mn from the oceanic crust; and that reactions with the turbidite sediment surrounding Baby Bare remove Na, Li, Mg, Ca, Sr, and sulfate from the pore water while producing ammonium and Si and both producing and consuming phosphate, nitrate, alkalinity, Mn, and Fe. K, Rb, and B are relatively unreactive in the sediment column. The composition of altered seawater in basement at Baby Bare is similar to the inferred composition of 58 C formation water from crust nearly twice as old (5.9 Ma) on the southern flank of the Costa Rica Rift. The Baby Bare fluids also exhibit the same directions of net elemental transfer between basalt and seawater as solutions produced in laboratory experiments at a similar temperature, and complement compositional changes form seawater observed in seafloor basalts altered at cool to moderate temperatures. The common parameter among the two ridge flanks and experiments is temperature, suggesting that the residence time of seawater in the two ridge-flank sites is sufficiently long for the solutions to equilibrate with altered basalt. The authors use the Baby Bare spring water to estimate upper limits on the global fluxes of 14 elements at warm ridge-flank sites such as Baby Bare. Maximum calculated fluxes of Mg, Ca, sulfate, B, and K may equal or exceed 25% of the riverine flux, and such sites may represent the missing, high K/Rb sink required for the K budget.

  12. GPP/RE Partitioning of Long-term Network Flux Data as a Tool for Estimating Ecosystem-scale Ecophysiological Parameters of Grasslands and Croplands

    NASA Astrophysics Data System (ADS)

    Gilmanov, T. G.; Wylie, B. K.; Gu, Y.; Howard, D. M.; Zhang, L.

    2013-12-01

    The physiologically based model of canopy CO2 exchange by Thornly and Johnson (2000) modified to incorporate vapor pressure deficit (VPD) limitation of photosynthesis is a robust tool for partitioning tower network net CO2 exchange data into gross photosynthesis (GPP) and ecosystem respiration (RE) (Gilmanov et al. 2013a, b). In addition to 30-min and daily photosynthesis and respiration values, the procedure generates daily estimates and uncertainties of essential ecosystem-scale parameters such as apparent quantum yield ALPHA, photosynthetic capacity AMAX, convexity of light response THETA, gross ecological light-use efficiency LUE, daytime ecosystem respiration rate RDAY, and nighttime ecosystem respiration rate RNIGHT. These ecosystem-scale parameters are highly demanded by the modeling community and open opportunities for comparison with the rich data of leaf-level estimates of corresponding parameters available from physiological studies of previous decades. Based on the data for 70+ site-years of flux tower measurements at the non-forest sites of the Ameriflux network and the non-affiliated sites, we present results of the comparative analysis and multi-site synthesis of the magnitudes, uncertainties, patterns of seasonal and yearly dynamics, and spatiotemporal distribution of these parameters for grasslands and croplands of the conterminous United States (CONUS). Combining this site-level parameter data set with the rich spatiotemporal data sets of a remotely sensed vegetation index, weather and climate conditions, and site biophysical and geophysical features (phenology, photosynthetically active radiation, and soil water holding capacity) using methods of multivariate analysis (e.g., Cubist regression tree) offers new opportunities for predictive modeling and scaling-up of ecosystem-scale parameters of carbon cycling in grassland and agricultural ecosystems of CONUS (Zhang et al. 2011; Gu et al. 2012). REFERENCES Gilmanov TG, Baker JM, Bernacchi CJ

  13. Environmental release and mass flux partitioning of PCDD/Fs during normal and transient operation of full scale waste to energy plants.

    PubMed

    Grosso, Mario; Cernuschi, Stefano; Giugliano, Michele; Lonati, Giovanni; Rigamonti, Lucia

    2007-04-01

    The paper reports on global release and mass partitioning in the flux of residues of PCDD/Fs, evaluated with dedicated field campaigns at a municipal solid waste incineration plant during normal and transient operation. Results are compared with those obtained in other installations equipped with furnaces, energy recovery options and flue gas treatment technologies representative of most of the European incineration plants currently in operation. Levels of the pollutants of interest were determined in all the solid, liquid and gaseous residues produced by every single facility, and the results analysed in terms of the effects arising from the fed waste and the configuration of the plant. PCDD/Fs total release between 1.5 and 45 microg I-TEQ per ton of burned waste was evaluated, with lower values resulting from the adoption of catalytic conversion process for flue gas treatment. Most of the mass flux emitted is associated with solid residues deriving from activated carbon PCCD/F dry removal options, with significant contributions also from fly ash produced by particulate removal devices located immediately downstream the boiler and from scrubber blowdowns treatment sludge. During transient operating conditions the dioxin total release may increase by 50% with comparison to steady-state functioning. PMID:17222439

  14. Geochemical Analyses of Surface and Shallow Gas Flux and Composition Over a Proposed Carbon Sequestration Site in Eastern Kentucky

    SciTech Connect

    Thomas Parris; Michael Solis; Kathryn Takacs

    2009-12-31

    Using soil gas chemistry to detect leakage from underground reservoirs (i.e. microseepage) requires that the natural range of soil gas flux and chemistry be fully characterized. To meet this need, soil gas flux (CO{sub 2}, CH{sub 4}) and the bulk (CO{sub 2}, CH{sub 4}) and isotopic chemistry ({delta}{sup 13}C-CO2) of shallow soil gases (<1 m, 3.3 ft) were measured at 25 locations distributed among two active oil and gas fields, an active strip mine, and a relatively undisturbed research forest in eastern Kentucky. The measurements apportion the biologic, atmospheric, and geologic influences on soil gas composition under varying degrees of human surface disturbance. The measurements also highlight potential challenges in using soil gas chemistry as a monitoring tool where the surface cover consists of reclaimed mine land or is underlain by shallow coals. For example, enrichment of ({delta}{sup 13}C-CO2) and high CH{sub 4} concentrations in soils have been historically used as indicators of microseepage, but in the reclaimed mine lands similar soil chemistry characteristics likely result from dissolution of carbonate cement in siliciclastic clasts having {delta}{sup 13}C values close to 0{per_thousand} and degassing of coal fragments. The gases accumulate in the reclaimed mine land soils because intense compaction reduces soil permeability, thereby impeding equilibration with the atmosphere. Consequently, the reclaimed mine lands provide a false microseepage anomaly. Further potential challenges arise from low permeability zones associated with compacted soils in reclaimed mine lands and shallow coals in undisturbed areas that might impede upward gas migration. To investigate the effect of these materials on gas migration and composition, four 10 m (33 ft) deep monitoring wells were drilled in reclaimed mine material and in undisturbed soils with and without coals. The wells, configured with sampling zones at discrete intervals, show the persistence of some of the

  15. The 2014 Effusive eruption of Stromboli Volcano: The observed geochemical variations of soil CO2 fluxes and PCO2 in the thermal waters.

    NASA Astrophysics Data System (ADS)

    Inguaggiato, Salvatore; Vita, Fabio; Mazot, Agnes; Jacome Paz, Marianna Patricia; Cangemi, Marianna; Sollami, Aldo

    2016-04-01

    The Stromboli volcano, the more active of the Aeolian Archipelago, is characterized by an open conduct degassing system with a continuous explosive activity every 20-30'. In the recent years, effusive activities occurred in 1985, 2002-2003, 2007 and in 2014 while paroxysmal events have taken place only on 5th April 2003 and 15th March 2007. The geochemical monitoring program has been carried out through routine thermal well sampling (COA well) and continuous soil CO2 flux measurements on the summit of the volcano (STR02). The long time series of CO2 fluxes acquired in 1999-2008 period led to the identification of three classes of degassing Low (< 4000 g m‑2 d‑1), Normal (4000-10,000 g m‑2 d‑1) and High (> 10,000 g m‑2 d‑1). The data of soil CO2 fluxes in the 2010-2012 period showed a sustained degassing with daily average values almost always higher than the 10,000 g m‑2 d‑1. During the end 2012-begin 2013 a new trend in increase of soil CO2 flux was recorded with fluxes up to 20,000 g m‑2 d‑1. It is very interesting to note that the COA well showed an increase of the dissolved CO2 concentration from 60 to 200 cc/l STP recorded from the end of the eruption 2007 to mid-2010. Then, after a slight decrease in dissolved CO2 concentration of around 90 cc/l STP (December 2010), there was a new trend in growth, up to values of about 160 cc/l STP (April 2013). This continuous growth trend of the partial pressure of CO2 in the thermal aquifer, corroborates abnormal soil CO2 fluxes recorded at the summit of the volcano, supporting the hypothesis of a continuous process of pressurization of the volcanic system. On 7 August a new fracture opened at 650 m a.s.l., and lava moved down along the Sciara del Fuoco, reaching the sea; concurrently, persistent explosive activity ceased. On 28 October the lava flow abruptly decreased, until 13-17 November, when the effusion ceased. Six soil CO2 campaign to estimate the total output discharged from the summit area of

  16. Rising Mean Annual Temperature Increases Carbon Flux and Alters Partitioning, but Does Not Change Ecosystem Carbon Storage in Hawaiian Tropical Montane Wet Forest

    NASA Astrophysics Data System (ADS)

    Litton, C. M.; Giardina, C. P.; Selmants, P.

    2014-12-01

    Terrestrial ecosystem carbon (C) storage exceeds that in the atmosphere by a factor of four, and represents a dynamic balance among C input, allocation, and loss. This balance is likely being altered by climate change, but the response of terrestrial C cycling to warming remains poorly quantified, particularly in tropical forests which play a disproportionately large role in the global C cycle. Over the past five years, we have quantified above- and belowground C pools and fluxes in nine permanent plots spanning a 5.2°C mean annual temperature (MAT) gradient (13-18.2°C) in Hawaiian tropical montane wet forest. This elevation gradient is unique in that substrate type and age, soil type, soil water balance, canopy vegetation, and disturbance history are constant, allowing us to isolate the impact of long-term, whole ecosystem warming on C input, allocation, loss and storage. Across the gradient, soil respiration, litterfall, litter decomposition, total belowground C flux, aboveground net primary productivity, and estimates of gross primary production (GPP) all increase linearly and positively with MAT. Carbon partitioning is dynamic, shifting from below- to aboveground with warming, likely in response to a warming-induced increase in the cycling and availability of soil nutrients. In contrast to observed patterns in C flux, live biomass C, soil C, and total ecosystem C pools remained remarkably constant with MAT. There was also no difference in soil bacterial taxon richness, phylogenetic diversity, or community composition with MAT. Taken together these results indicate that in tropical montane wet forests, increased temperatures in the absence of water limitation or disturbance will accelerate C cycling, will not alter ecosystem C storage, and will shift the products of photosynthesis from below- to aboveground. These results agree with an increasing number of studies, and collectively provide a unique insight into anticipated warming-induced changes in tropical

  17. The Gas Transfer through Polar Sea ice experiment: Insights into the rates and pathways that determine geochemical fluxes

    NASA Astrophysics Data System (ADS)

    Lovely, A.; Loose, B.; Schlosser, P.; McGillis, W.; Zappa, C.; Perovich, D.; Brown, S.; Morell, T.; Hsueh, D.; Friedrich, R.

    2015-12-01

    Sea ice is a defining feature of the polar marine environment. It is a critical domain for marine biota and it regulates ocean-atmosphere exchange, including the exchange of greenhouse gases such as CO2 and CH4. In this study, we determined the rates and pathways that govern gas transport through a mixed sea ice cover. N2O, SF6, 3He, 4He, and Ne were used as gas tracers of the exchange processes that take place at the ice-water and air-water interfaces in a laboratory sea ice experiment. Observation of the changes in gas concentrations during freezing revealed that He is indeed more soluble in ice than in water; Ne is less soluble in ice, and the larger gases (N2O and SF6) are mostly excluded during the freezing process. Model estimates of gas diffusion through ice were calibrated using measurements of bulk gas content in ice cores, yielding gas transfer velocity through ice (kice) of ˜5 × 10-4 m d-1. In comparison, the effective air-sea gas transfer velocities (keff) ranged up to 0.33 m d-1 providing further evidence that very little mixed-layer ventilation takes place via gas diffusion through columnar sea ice. However, this ventilation is distinct from air-ice gas fluxes driven by sea ice biogeochemistry. The magnitude of keff showed a clear increasing trend with wind speed and current velocity beneath the ice, as well as the combination of the two. This result indicates that gas transfer cannot be uniquely predicted by wind speed alone in the presence of sea ice.

  18. Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes in a Mediterranean oak savannah to partition evapotranspiration

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Matthias, Cuntz; Arndt, Piayda; Christane, Werner

    2013-04-01

    Stable oxygen isotopes of water provide a valuable tracer for water movements within ecosystems and are used to estimate the contribution of transpiration to total ecosystem evapotranspiration (ft). We tested the Craig and Gordon equation against continuous field measurements of isotopic composition of evaporation and assessed the impact for partitioning evapotranspiration. Therefore, evaporation (E) and its isotopic signature (δ18OE) on bare soil plots, as well as evapotranspiration (ET) and its corresponding isotopic composition of (δ18OET) of an herbaceous understory layer was measured with a cavity ring-down spectrometer connected to a soil chamber on a field site in central Portugal. We quantified the variation in δ18OE arising from uncertainties in the determination of environmental input variables to the Craig and Gordon equation: the isotope signature at the evaporating site (δ18Oe), the temperature at the evaporating site (Te), and the kinetic fractionation factor (αk). We could hence quantify ft based on measured δ18OET, modeled δ18OE from observed soil water isotopic composition at the evaporating site (δ18Oe), and modeled δ18O of transpiration (δ18OT) from observed total soil water isotopic composition. Our results demonstrate that predicting δ18OE using the Craig and Gordon equation leads to good agreement with measured δ18OE given that the temperature and isotope profiles of the soil are thoroughly characterized. However, modeled δ18OE is highly sensitive to changes in Te and δ18Oe as well as αk. This markedly affected the partition results of transpiration and evaporation from the total ET flux: The fraction of transpiration (ft) varied strongly using different formulations for αk and assuming steady or non-steady state transpiration. These findings provide a first comparison of laser-based and modeled isotopic compositions of evaporation based on the Craig and Gordon equation under field conditions. This is of special interest for

  19. Partition search

    SciTech Connect

    Ginsberg, M.L.

    1996-12-31

    We introduce a new form of game search called partition search that incorporates dependency analysis, allowing substantial reductions in the portion of the tree that needs to be expanded. Both theoretical results and experimental data are presented. For the game of bridge, partition search provides approximately as much of an improvement over existing methods as {alpha}-{beta} pruning provides over minimax.

  20. Across- and along-arc geochemical variations of lava chemistry in the Sangihe arc: Various fluid and melt slab fluxes in response to slab temperature

    NASA Astrophysics Data System (ADS)

    Hanyu, Takeshi; Gill, James; Tatsumi, Yoshiyuki; Kimura, Jun-Ichi; Sato, Keiko; Chang, Qing; Senda, Ryoko; Miyazaki, Takashi; Hirahara, Yuka; Takahashi, Toshiro; Zulkarnain, Iskandar

    2012-10-01

    The Sangihe arc, northern Indonesia, is an oceanic arc that is the western half of the only active arc-arc collision on Earth. To elucidate magma genesis and slab thermal structure in such a setting, we have obtained new geochemical data for lavas from the entire Sangihe arc. In the southern arc, the volcanic front lavas are enriched in fluid-mobile elements, while the rear arc lavas are more enriched in melt-mobile elements. The proportion of sediment versus altered oceanic crust in the slab component is only ˜20% but still larger in Sangihe than other arcs in the western Pacific such as Izu, suggesting more subduction of the thick sediments in the narrowing Molucca Sea. The slab component changes in character across the arc from low-temperature fluid, through high-temperature fluid, to partial melt during progressive subduction. The geochemical systematics, the estimated mass fraction of the slab component, and the inferred stability of accessory rutile, zircon, and phengite in the slab are all similar between the southern Sangihe and Izu arcs, indicating that the thermal structure of the slab is not affected by impending collision. In contrast, lavas from the dormant northern Sangihe arc show geochemical characteristics similar to the Quaternary rear arc rather than the Quaternary volcanic front lavas in the southern arc. This may be related to advanced collision in the northern arc that could have slowed the subduction rate and heated the slab in the Pliocene followed by cessation of volcanic activity in the Quaternary.

  1. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  2. Spatial variation in fluid flow and geochemical fluxes across the sediment-seawater interface at the Carlos Ribeiro mud volcano (Gulf of Cadiz)

    NASA Astrophysics Data System (ADS)

    Vanneste, Heleen; Kelly-Gerreyn, Boris A.; Connelly, Douglas P.; James, Rachael H.; Haeckel, Matthias; Fisher, Rebecca E.; Heeschen, Katja; Mills, Rachel A.

    2011-02-01

    Submarine mud volcanism is an important pathway for transfer of deep-sourced fluids enriched in hydrocarbons and other elements into the ocean. Numerous mud volcanoes (MVs) have been discovered along oceanic plate margins, and integrated elemental fluxes are potentially significant for oceanic chemical budgets. Here, we present the first detailed study of the spatial variation in fluid and chemical fluxes at the Carlos Ribeiro MV in the Gulf of Cadiz. To this end, we combine analyses of the chemical composition of pore fluids with a 1-D transport-reaction model to quantify fluid fluxes, and fluxes of boron, lithium and methane, across the sediment-seawater interface. The pore fluids are significantly depleted in chloride, but enriched in lithium, boron and hydrocarbons, relative to seawater. Pore water profiles of sulphate, hydrogen sulphide and total alkalinity indicate that anaerobic oxidation of methane occurs at 34-180 cm depth below seafloor. Clay mineral dehydration, and in particular the transformation of smectite to illite, produces pore fluids that are depleted in chloride and potassium. Profiles of boron, lithium and potassium are closely related, which suggests that lithium and boron are released from the sediments during this transformation. Pore fluids are expelled into the water column by advection; fluid flow velocities are 4 cm yr -1 at the apex of the MV but they rapidly decrease to 0.4 cm yr -1 at the periphery. The associated fluxes of boron, lithium and methane vary between 7-301, 0.5-6 and 0-806 mmol m -2 yr -1, respectively. We demonstrate that fluxes of Li and B due to mud volcanism may be important on a global scale, however, release of methane into the overlying water column is suppressed by microbial methanotrophy.

  3. Partitioning the Controls on Carbon Flux Between Light Absorption and Light Use Efficiency: Insights From High Spatial and Temporal Resolution Remote Sensing.

    NASA Astrophysics Data System (ADS)

    Sims, D. A.; Kwon, H.; Luo, H.; Oechel, W.; Gamon, J.

    2001-12-01

    Comparisons between eddy covariance measurements of CO2 flux and remotely sensed spectral reflectance are often limited by mis-matches in temporal and spatial scales. Eddy flux measurements are made continuously through time whereas satellite sensors typically measure only once per day or less and many days may be lost because of cloud cover. In addition, satellite sensors such as MODIS have pixel sizes as large as a whole eddy flux footprint, making precise spatial correlation difficult. In order to better match the temporal and spatial scales of remote sensing measurements to those of eddy flux, we installed automated systems (optical sampling instruments on a tram system) within eddy covariance tower footprints at Sky Oaks field station near San Diego, CA. This system measured hyperspectral (narrow-band) reflectance over a 100 m transect throughout diurnal and seasonal cycles. These data were used to explore the controls on carbon flux and to develop models for scaling eddy flux measurements to the surrounding region. Fractional absorbed radiation (estimated from NDVI) varied dramatically over the diurnal cycle but was relatively constant across seasons in this evergreen shrub dominated system. By contrast, seasonal carbon flux varied more closely with optical signals of light-use efficiency. Consequently, large seasonal changes in carbon flux were primarily a function of light-use efficiency rather than light absorption. These data suggest that models based solely on light absorption by vegetation may miss large fluctuations in carbon exchange resulting from downregulation of photosynthesis. Although this ecosystem may be an extreme case, there are many evergreen ecosystems in which photosynthetic downregulation could play a large role. Application of this optical measuring system at other FLUXNET sites would greatly increase our understanding of the role of photosynthetic downregulation in global carbon cycles.

  4. Assessing the Accuracy and Precision of Inorganic Geochemical Data Produced through Flux Fusion and Acid Digestions: Multiple (60+) Comprehensive Analyses of BHVO-2 and the Development of Improved "Accepted" Values

    NASA Astrophysics Data System (ADS)

    Ireland, T. J.; Scudder, R.; Dunlea, A. G.; Anderson, C. H.; Murray, R. W.

    2014-12-01

    The use of geological standard reference materials (SRMs) to assess both the accuracy and the reproducibility of geochemical data is a vital consideration in determining the major and trace element abundances of geologic, oceanographic, and environmental samples. Calibration curves commonly are generated that are predicated on accurate analyses of these SRMs. As a means to verify the robustness of these calibration curves, a SRM can also be run as an unknown item (i.e., not included as a data point in the calibration). The experimentally derived composition of the SRM can thus be compared to the certified (or otherwise accepted) value. This comparison gives a direct measure of the accuracy of the method used. Similarly, if the same SRM is analyzed as an unknown over multiple analytical sessions, the external reproducibility of the method can be evaluated. Two common bulk digestion methods used in geochemical analysis are flux fusion and acid digestion. The flux fusion technique is excellent at ensuring complete digestion of a variety of sample types, is quick, and does not involve much use of hazardous acids. However, this technique is hampered by a high amount of total dissolved solids and may be accompanied by an increased analytical blank for certain trace elements. On the other hand, acid digestion (using a cocktail of concentrated nitric, hydrochloric and hydrofluoric acids) provides an exceptionally clean digestion with very low analytical blanks. However, this technique results in a loss of Si from the system and may compromise results for a few other elements (e.g., Ge). Our lab uses flux fusion for the determination of major elements and a few key trace elements by ICP-ES, while acid digestion is used for Ti and trace element analyses by ICP-MS. Here we present major and trace element data for BHVO-2, a frequently used SRM derived from a Hawaiian basalt, gathered over a period of over two years (30+ analyses by each technique). We show that both digestion

  5. Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope

    NASA Astrophysics Data System (ADS)

    Wiaux, F.; Vanclooster, M.; Van Oost, K.

    2015-08-01

    In this study we aim to elucidate the role of physical conditions and gas transfer mechanism along soil profiles in the decomposition and storage of soil organic carbon (OC) in subsoil layers. We use a qualitative approach showing the temporal evolution and the vertical profile description of CO2 fluxes and abiotic variables. We assessed soil CO2 fluxes throughout two contrasted soil profiles (i.e. summit and footslope positions) along a hillslope in the central loess belt of Belgium. We measured the time series of soil temperature, soil moisture and CO2 concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO2 flux at different depths using Fick's diffusion law and horizon specific diffusivity coefficients. The calculated fluxes allowed assessing the contribution of different soil layers to surface CO2 fluxes. We constrained the soil gas diffusivity coefficients using direct observations of soil surface CO2 fluxes from chamber-based measurements and obtained a good prediction power of soil surface CO2 fluxes with an R2 of 92 %. We observed that the temporal evolution of soil CO2 emissions at the summit position is mainly controlled by temperature. In contrast, at the footslope, we found that long periods of CO2 accumulation in the subsoil alternates with short peaks of important CO2 release. This was related to the high water filled pore space that limits the transfer of CO2 along the soil profile at this slope position. Furthermore, the results show that approximately 90 to 95 % of the surface CO2 fluxes originate from the first 10 cm of the soil profile at the footslope. This indicates that soil OC in this depositional context can be stabilized at depth, i.e. below 10 cm. This study highlights the need to consider soil physical properties and their dynamics when assessing and modeling soil CO2 emissions. Finally, changes in the physical environment of depositional soils (e.g. longer dry periods) may affect the

  6. Partitioning soil CO2 fluxes by tree-girdling in a Mediterranean (Pinus pinaster) ecosystem reveals a different response of autotrophic and heterotrophic components to environmental variables and photosynthesis under drought conditions

    NASA Astrophysics Data System (ADS)

    Matteucci, M.; Cescatti, A.; Gruening, C.; Ballarin, I. G.; Guenther, S.; Magnani, F.; Nali, C.; Lorenzini, G.

    2012-04-01

    The response of ecosystems to environmental factors, such as temperature and rainfall, is crucial to understand the impact of climate change on the terrestrial C cycle. Forest soil respiration represents the main pathway by which photosynthetically assimilated C is released to atmosphere; its intensity depends not only on soil environmental conditions, but also on the availability of organic substrates respired by roots and microorganisms. Several techniques have been applied to partition the autotrophic and heterotrophic components of soil respiration in boreal and temperate forests; there is a general lack of information, on the contrary, on the dynamics of soil CO2 efflux in Mediterranean ecosystems. The IPCC A1B scenario highlighted the importance of the Mediterranean area since it is expected to experience a temperature increase (from 2.2 °C to 5.1 °C) and a rainfall reduction ranging from -4 to -27% on annual basis. We used the tree-girdling technique together with periodic chamber-based measurements to study the partitioning of total soil respiration (Rs) into its autotrophic (Ra) and heterotrophic (Rh) components in a 60-year old forest in Central Italy (San Rossore) dominated by Pinus pinaster. This technique has been extensively used to block the flux of photosynthates from leaves to roots, thus stopping the autotrophic root respiration in the soil. We found that two weeks after the treatment soil respiration in the girdled plots decreased by 29% and remained stable over the period of analysis, suggesting that Rh dominates total soil respiration. The anomalous low rainfall regimen of May to October 2011 (102 mm cumulated rain) associated with average air temperatures (with a mean value of 19,6 °C over the period) gave us the opportunity to investigate the decoupled response of soil respiration to water and temperature. Time series analysis performed under this severe drought conditions showed overall low values of soil respiration with three clear

  7. Geochemical and petrological observations of gas transport at arc volcanoes

    NASA Astrophysics Data System (ADS)

    Edmonds, M.; Herd, R. A.; Humphreys, M.; Aiuppa, A.; Giudice, G.; Guida, R.; Moretti, R.; Christopher, T. E.; Rawson, H.

    2010-12-01

    Understanding the abundance and composition of vapour in magma chambers and the mechanisms of vapour transport in volcanic systems is of immense importance. Exsolved vapour in a magma storage area affects eruption style and duration, and influences ground deformation and other geophysical manifestations owing to its compressibility. Ultimately, we wish to understand how much pre-eruptive exsolved vapour exists and what role mafic magma supply at depth plays in supplying it. Soufriere Hills Volcano, Montserrat, has become an exceptionally well-monitored volcanic system and there is now an abundance of detailed geochemical and petrological information regarding magma degassing and gas transport processes. The eruption provides a unique opportunity to study the effects of open system mafic magma injection, mingling and degassing, which is occurring on the same time scale as eruption. We examine the geochemical and petrological evidence for magma mingling, degassing and gas fluxing at Soufriere Hills Volcano. We use measurements of gas flux and composition, using DOAS and a multigas sensor. We examine petrological and textural evidence for mafic magma supplying volatiles to the system, including evidence from phenocryst zoning and composition. We show that the mafic magma supplies volatiles as well as heat to the overlying resident andesite. Due to the strong partitioning of sulphur into a vapour phase at depth under oxidising conditions, the sulphur dissolved in the intruding mafic magma becomes segregated into vapour, along with carbon dioxide and water. The vapour is transported to the surface during both eruptive and non-eruptive periods, implying either that significant permeability exists within the system, or that magma convection operates. There is some evidence for gas fluxing, which suggests that gas may be transported through the magma. We draw comparisons with other recent studies of volatile transport in arc systems to show that some observations may be

  8. Geochemical characteristics and fluxes of organic carbon in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), China.

    PubMed

    Zhang, Shurong; Lu, X X; Sun, Huiguo; Han, Jingtai; Higgitt, David Laurence

    2009-01-01

    This study aims to investigate the state of the riverine organic carbon in the Luodingjiang River under human impacts, such as reforestation, construction of reservoirs and in-stream damming. Seasonal and spatial characteristics of total suspended sediment (TSS), dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as C/N ratios and the stable carbon isotopic signatures of POC (delta(13)C(POC)) were examined based on a one-year study (2005) in the basin-wide scale. More frequent sampling was conducted in the outlet of the river basin at Guanliang hydrological station. DOC and POC concentrations showed flush effects with increasing water discharge and sediment load in the basin-wide scale. Atomic C/N ratio of POC had a positive relationship with TSS in the outlet of the basin, indicating the reduced aquatic sources and enhanced terrestrial sources during the high flood season. However, the similar relationship was not observed in the basin-wide scale mainly due to the spatial distributions of soil organic carbon and TSS. delta(13)C(POC) showed obvious seasonal variations with enriched values in the period with high TSS concentration, reflecting the increased contribution from C(4) plants with enhanced soil erosion. The specific flux of the total organic carbon (2.30 t km(-)(2) year(-1)) was smaller than the global average level. The ratio of DOC to POC was 1.17, which is higher than most rivers under Asian monsoon climate regime. The organic carbon flux was estimated to decline with decreasing sediment load as a result of reforestation, reservoir construction and in-stream damming, which demonstrates the impacts of human disturbances on the global carbon cycle. PMID:19004473

  9. Distribution, partitioning and fluxes of dissolved and particulate organic C, N and P in the eastern North Pacific and Southern Oceans

    NASA Astrophysics Data System (ADS)

    Loh, Ai Ning; Bauer, James E.

    2000-12-01

    applied to estimate the contributions of dissolved and suspended particulate organic C, N and P fluxes from the upper mixed layer into the permanent thermocline. Estimated vertical DOM fluxes were 28-63% of the total organic matter fluxes; POM susp and POM sink fluxes were 8-20 and 28-52% of the total.

  10. Carbon pools and fluxes in a Tibetan alpine Kobresia pygmaea pasture partitioned by coupled eddy-covariance measurements and ¹³CO₂ pulse labeling.

    PubMed

    Ingrisch, Johannes; Biermann, Tobias; Seeber, Elke; Leipold, Thomas; Li, Maoshan; Ma, Yaoming; Xu, Xingliang; Miehe, Georg; Guggenberger, Georg; Foken, Thomas; Kuzyakov, Yakov

    2015-02-01

    The Tibetan highlands host the largest alpine grassland ecosystems worldwide, bearing soils that store substantial stocks of carbon (C) that are very sensitive to land use changes. This study focuses on the cycling of photoassimilated C within a Kobresia pygmaea pasture, the dominating ecosystems on the Tibetan highlands. We investigated short-term effects of grazing cessation and the role of the characteristic Kobresia root turf on C fluxes and belowground C turnover. By combining eddy-covariance measurements with (13)CO₂ pulse labeling we applied a powerful new approach to measure absolute fluxes of assimilates within and between various pools of the plant-soil-atmosphere system. The roots and soil each store roughly 50% of the overall C in the system (76 Mg C ha(-1)), with only a minor contribution from shoots, which is also expressed in the root:shoot ratio of 90. During June and July the pasture acted as a weak C sink with a strong uptake of approximately 2 g C m(-2) d(-1) in the first half of July. The root turf was the main compartment for the turnover of photoassimilates, with a subset of highly dynamic roots (mean residence time 20 days), and plays a key role for the C cycling and C storage in this ecosystem. The short-term grazing cessation only affected aboveground biomass but not ecosystem scale C exchange or assimilate allocation into roots and soil. PMID:25461119

  11. Flux of carbonate melt from deeply subducted pelitic sediments: Geophysical and geochemical implications for the source of Central American volcanic arc

    NASA Astrophysics Data System (ADS)

    Tsuno, Kyusei; Dasgupta, Rajdeep; Danielson, Lisa; Righter, Kevin

    2012-08-01

    We determined the fluid-present and fluid-absent near-solidus melting of an Al-poor carbonated pelite at 3-7 GPa, to constrain the possible influence of sediment melt in subduction zones. Hydrous silicate melt is produced at the solidi at 3-4 GPa whereas Na-K-rich carbonatite is produced at the solidi at ≥5 GPa for both starting compositions. At ≥5 GPa and 1050°C, immiscible carbonate and silicate melts appear with carbonate melt forming isolated pockets embedded in silicate melt. Application of our data to Nicaraguan slab suggests that sediment melting may not occur at sub-arc depth (˜170 km) but carbonatite production can occur atop slab or by diapiric rise of carbonated-silicate mélange zone to the mantle wedge at ˜200-250 km depth. Flux of carbonatite to shallower arc-source can explain the geochemistry of Nicaraguan primary magma (low SiO2 and high CaO, Ba/La). Comparison of carbonate-silicate melt immiscibility field with mantle wedge thermal structure suggests that carbonatite might temporally be trapped in viscous silicate melt, and contribute to seismic low-velocity zone at deep mantle wedge of Nicaragua.

  12. The Oxygen quantum yield in diverse algae and cyanobacteria is controlled by partitioning of flux between linear and cyclic electron flow within photosystem II.

    PubMed

    Ananyev, Gennady; Gates, Colin; Dismukes, G Charles

    2016-09-01

    We have measured flash-induced oxygen quantum yields (O2-QYs) and primary charge separation (Chl variable fluorescence yield, Fv/Fm) in vivo among phylogenetically diverse microalgae and cyanobacteria. Higher O2-QYs can be attained in cells by releasing constraints on charge transfer at the Photosystem II (PSII) acceptor side by adding membrane-permeable benzoquinone (BQ) derivatives that oxidize plastosemiquinone QB(-) and QBH2. This method allows uncoupling PSII turnover from its natural regulation in living cells, without artifacts of isolating PSII complexes. This approach reveals different extents of regulation across species, controlled at the QB(-) acceptor site. Arthrospira maxima is confirmed as the most efficient PSII-WOC (water oxidizing complex) and exhibits the least regulation of flux. Thermosynechococcus elongatus exhibits an O2-QY of 30%, suggesting strong downregulation. WOC cycle simulations with the most accurate model (VZAD) show that a light-driven backward transition (net addition of an electron to the WOC, distinct from recombination) occurs in up to 25% of native PSIIs in the S2 and S3 states, while adding BQ prevents backward transitions and increases the lifetime of S2 and S3 by 10-fold. Backward transitions occur in PSIIs that have plastosemiquinone radicals in the QB site and are postulated to be physiologically regulated pathways for storing light energy as proton gradient through direct PSII-cyclic electron flow (PSII-CEF). PSII-CEF is independent of classical PSI/cyt-b6f-CEF and provides an alternative proton translocation pathway for energy conversion. PSII-CEF enables variable fluxes between linear and cyclic electron pathways, thus accommodating species-dependent needs for redox and ion-gradient energy sources powered by a single photosystem. PMID:27117512

  13. Experimental investigations of water fluxes within the soil-vegetation-atmosphere system: Stable isotope mass-balance approach to partition evaporation and transpiration

    NASA Astrophysics Data System (ADS)

    Wenninger, Jochen; Beza, Desta Tadesse; Uhlenbrook, Stefan

    Irrigated agriculture is the largest user of freshwater worldwide and the scale of irrigated agriculture can be so large that it can have dramatic effects on the water cycle and even alter regional climates. Therefore, it is vital to improve the water use efficiency of irrigated lands in order to address the sustainable use of water resources, the growing need for agricultural products, and the health of ecosystems. Environmental isotopes have unique attributes that make them particularly suitable for tracing hydrological pathways and quantifying hydrological fluxes within the soil-vegetation-atmosphere system. The stable isotopic composition of soil water is mainly controlled by precipitation or irrigation inputs and evaporative losses. Because transpiration does not fractionate soil water isotopes, it is possible to estimate the relative proportions of evaporation and transpiration using isotopic mass balance calculations. In this study experimental investigations, combining classical hydrometric measurements, tracer hydrological methods and a soil water model were applied to laboratory lysimeters to study the transpiration processes of Teff ( Eragrostis tea (Zucc.) Trotter). Teff is an annual bunch cereal and an important aliment in Ethiopia and Eritrea and it is also gaining popularity in other countries. To determine the soil water contents, sensors using a capacitance/frequency domain technology were installed at different depths and soil water samples for the isotope analysis were taken using pore water samplers. Water contents in different depths and water fluxes, such as percolation and evaporation were modeled using the HYDRUS-1D software package. By using an isotope mass balance model the total evaporation and the fractions between soil evaporation and transpiration could be determined. The water losses which were estimated using the isotope mass-balance approach are in good agreement with the measured values using classical hydrometric measurements. The

  14. Global geochemical problems

    NASA Technical Reports Server (NTRS)

    Harriss, R. C.

    1980-01-01

    Application of remote sensing techniques to the solution of geochemical problems is considered with emphasis on the 'carbon-cycle'. The problem of carbon dioxide sinks and the areal extent of coral reefs are treated. In order to assess the problems cited it is suggested that remote sensing techniques be utilized to: (1)monitor globally the carbonate and bicarbonate concentrations in surface waters of the world ocean; (2)monitor the freshwater and oceanic biomass and associated dissolved organic carbon; (3) inventory the coral reef areas and types and the associated oceanographic climatic conditions; and (4)measure the heavy metal fluxes from forested and vegetated areas, from volcanos, from different types of crustal rocks, from soils, and from sea surfaces.

  15. Connections between groundwater flow and transpiration partitioning.

    PubMed

    Maxwell, Reed M; Condon, Laura E

    2016-07-22

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes. PMID:27463671

  16. Connections between groundwater flow and transpiration partitioning

    NASA Astrophysics Data System (ADS)

    Maxwell, Reed M.; Condon, Laura E.

    2016-07-01

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes.

  17. Computer modeling of pesticide fate at the hillslope scale. Influence of vegetated filter strips on surface runoff pesticides transfer and partitioning between surface and subsurface fluxes

    NASA Astrophysics Data System (ADS)

    Djabelkhir, K.; Carluer, N.; Lauvernet, C.

    2012-04-01

    inside and between lanscape elements, with an adapted level of complexity. This led us to Catchment Modelling Framework (CMF), which fills these criteria. On top of that, structure of this model makes it possible to integrate buffer zones and pesticides behaviour simulation ; more, it needs data which are available on our study site. This hillslope model will be tested on the Morcille site, in the Beaujolais area (France) which is one of the sites monitored by the non point source pollution team of Irstea in Lyon, and for data on surface and subsurface fluxes is available.

  18. Tissue partitioning of micro-essential metals in the vent bivalve Bathymodiolus azoricus and associated organisms (endosymbiont bacteria and a parasite polychaete) from geochemically distinct vents of the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Kádár, Enikõ; Costa, Valentina; Santos, Ricardo S.; Powell, Jonathan J.

    2006-07-01

    Hydrothermal communities are built on highly specialised organisms possessing effective adaptation mechanisms to tolerate elevated levels of toxic heavy metals typical of these extreme habitats. Bioavailability and tissue compartmentalisation of micro-essential metals (Cu, Zn, and Fe) were investigated in the bivalve Bathymodiolus azoricus from three geochemically distinct hydrothermal vents (Rainbow, Lucky Strike, Menez Gwen). Additionally , in order to make inferences on the effect of biological interactions on the metal uptake, the bivalves' endosymbiont bacteria and commensal parasite Branchipolynoe seepensis were analysed for metal bioaccumulation. Micro-essential metal concentrations in byssus threads exceeded many-fold concentrations in the gill and digestive gland, which in turn were consistently one order of magnitude above levels measured in the mantle. In spite of its high metal concentrations, the byssus is unlikely to be an active bioaccumulator. Its high surface to mass ratio and its binding sites for metals suggest a reversible adsorption of micro-essential metals in the vent mussel. Inter-site comparison showed highest Fe concentrations in tissues of mussels from the Rainbow site, whereas Zn and Cu in all tissues were highest in mussels from the Lucky Strike site, reflecting metal concentrations in the water surrounding macro-invertebrates at these vent sites. The omnipresence of the commensal parasite polychaete in gills of B. azoricus from the Lucky Strike vent field, unlike the other sites, is suggested to be an adaptation to the typically elevated Fe concentrations in the water column near mussel beds. Unprecedented Fe concentrations measured in the digestive gland of mussels from the Rainbow site (4000 μg g - 1 , three times higher than levels in bivalves from polluted sites) call for further post-capture ecotoxicological investigations of potentially novel Fe-handling strategies. We provide the first information on the bioaccumulation

  19. Continental-pelagic carbonate partitioning and the global carbonate-silicate cycle

    NASA Technical Reports Server (NTRS)

    Caldeira, K.; Rampino, M. R. (Principal Investigator)

    1991-01-01

    A carbonate-silicate geochemical cycle model is developed and used to explore dynamic and climatic consequences of constraints on shallow-water carbonate burial and possible carbon loss to the mantle associated with sea-floor subduction. The model partitions carbonate deposition between shallow-water and deep-water environments and includes carbon fluxes between the mantle and lithosphere. When total lithospheric carbonate mass is constant, there are two stable steady states, one in which the carbonate burial flux is mostly continental and another in which it is mostly pelagic. The continental steady state is characterized by a low metamorphic CO2 flux to the atmosphere and predominantly shallow-water carbonate burial. The pelagic steady state is characterized by a high metamorphic CO2 flux and predominantly deep-water carbonate burial. For reasonable parameter values, when total lithospheric carbonate mass is allowed to vary, the model oscillates between predominantly continental and predominantly pelagic modes. Model results suggest that carbonate deposition patterns established during the Cenozoic may be pushing the Earth system from the continental to the pelagic mode on a time scale of 10(8) yr, with a possible consequent order-of-magnitude increase in the metamorphic CO2 flux to the atmosphere.

  20. Geochemical data synthesis and analysis

    NASA Technical Reports Server (NTRS)

    Philpotts, J. A.

    1979-01-01

    Data obtained at the Goddard Flight Center were collected for the purpose of completing analyses started at Goddard in order to maximize the scientific yield of the geochemistry program which was terminated in 1977. The major analytical task undertaken was to complete Gd analyses on a large number of samples already analyzed by mass spectrometry for other rare earth element abundances at Goddard. Gd values are important for pinning down the central part of the geochemically significant rare earth abundance pattern and are especially useful in the high precision definition of the utilitarian Eu anomaly. Isotope-dilution Gd abundances were obtained for 39 samples. The data are for 27 partition-coefficient samples, six Apollo 15 and 16 breccia samples, four terrestrial impactities, and associated rock standards.

  1. VARIATIONS IN THE SPECTRAL PROPERTIES OF FRESHWATER AND ESTUARINE CDOM CAUSED BY PARTITIONING ONTO RIVER AND ESTUARINE SEDIMENTS

    EPA Science Inventory

    The optical properties and geochemical cycling of chromophoric dissolved organic matter (CDOM) are altered by its sorption to freshwater and estuarine sediments. Measured partition coefficients (Kp) of Satilla River (Georgia) and Cape Fear River estuary (North Carolina) CDOM ran...

  2. UNDERSTANDING VARIATION IN PARTITION COEFFICIENT KD, VALUES, VOLUME III: AMERICIUM, ARSENIC, CURIUM, IODINE, NEPTUNIUM, RADIUM, AND TECHNETIUM

    EPA Science Inventory

    This report describes the conceptualization, measurement, and use of the partition (or distribution) coefficient, Kd, parameter, and the geochemical aqueous solution and sorbent properties that are most important in controlling adsorption/retardation behavior of selected contamin...

  3. Pan-arctic river fluxes of polychlorinated biphenyls.

    PubMed

    Carrizo, Daniel; Gustafsson, Örjan

    2011-10-01

    Observations of polychlorinated biphenyls (PCB) concentrations in fluvial surface sediments near the mouths of the six Great Arctic Rivers (GARs; Ob, Yenisey, Lena, Indigirka, Kolyma, and Mackenzie) were combined with annual dissolved organic carbon (DOC) and particulate organic carbon (POC) loadings and hydraulic discharge to estimate the pan-Arctic river flux of PCBs. The highest total-phase fluxes of ∑(13)PCB were found for the Ob River, with 184 kg/yr and the smallest for the Indigirka River with 3.9 kg/yr. Consistent with a continent-scale trend among the Eurasian GARs of increasing POC concentrations eastward, which is extending to the North American Mackenzie River, a general shift in the estimated PCB partitioning from dissolved to particle-associated flux was found toward the east. Pentachlorinated and hexachlorinated PCBs constituted the majority (>70%) of the total PCB fluxes in the Eurasian Rivers. In contrast, trichlorinated and tetrachlorinated congeners were the most abundant in the Mackenzie (≈ 75%). The total ∑(13)PCB fluxes from the pan-Arctic rivers are here estimated to be ∼0.4 tonne/yr. This is geochemically consistent with the inventory of total PCBs in the Polar Mixed Layer of the entire Arctic Ocean (0.39 tonne) and about a factor 2 less than two new estimates of the PCB settling export to Arctic subsurface waters. Hence, the yearly Great Arctic River PCB fluxes only represent 0.001% of the historical PCB emission into the global environment. To our knowledge, this is the first estimate of circum-Arctic river flux of any organic pollutant based on a comprehensive investigation of the pollutants in several rivers and it contributes toward a more complete understanding of large-scale contaminant cycling in the Arctic. PMID:21863827

  4. Continuous partition lattice

    PubMed Central

    Björner, Anders

    1987-01-01

    A continuous analogue to the partition lattices is presented. This is the metric completion of the direct limit of a system of embeddings of the finite partition lattices. The construction is analogous to von Neumann's construction of a continuous geometry over a field F from the finite-dimensional projective geometries over F. PMID:16593874

  5. Serpentinization-assisted deformation processes and characterization of hydrothermal fluxes at mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Genc, Gence

    Seafloor hydrothermal systems play a significantly important role in Earth’s energy and geochemical budgets and support the existence and development of complex biological ecosystems by providing nutrient and energy to microbial and macrafaunal ecosystems through geochemical fluxes. Heat output and fluid flow are key parameters which characterize hydrothermal systems at oceanic spreading centers by constraining models of hydrothermal circulation. Although integrated measurements of heat flux in plumes are critically important as well, quantification of heat flux at discrete sources (vent orifices versus patches of seafloor shimmering diffuse flow) from direct measurements is particularly essential for examining the partitioning of heat flow into focused and diffuse components of venting and determining geochemical fluxes from these two modes of flow. Hydrothermal heat output also constrains the permeability of young oceanic crust and thickness of the conductive boundary layer that separates magmatic heat source from overlying hydrothermal circulation. This dissertation will be fundamentally focused on three main inter-connected topics: (1) the design and development of direct high- or low-temperature heat flow measuring devices for hydrothermal systems, (2) the collection of new heat output results on four cruises between 2008 and 2010 at several distinct hydrothermal sites along mid-ocean ridges (MORs) to estimate total heat output from individual vent structures such as Dante, Hulk or the whole vent field (e.g., Main Endeavour Vent Field (MEF)), the partitioning between focused and diffuse hydrothermal venting in MEF, and determination of initial estimates of geochemical flux from diffuse hydrothermal fluids which may be influenced by the activity in subsurface biosphere and finally (3) the deformation and uplift associated with serpentinization at MORs and subduction zones. Despite extensive efforts spent for the last couple of decades on heat flow measurement

  6. A New Round of Global Geochemical Mapping: Opportunity and Challenge to China

    NASA Astrophysics Data System (ADS)

    Cheng, Hangxin; Yang, Zhongfang; Xi, Xiaohuan; Zhao, Chuandong; Xie, Xuejin

    Since the projects of "International Geochemical Mapping (IGCP259)" and "Global Geochemical Baseline (IGCP360)" were met with approval by UNESCO in 1988, decisive contributions of working out the methodological guidance and the technical standard of global geochemical mapping have been made by China and Europe. Though demonstrations have been made by China and Europe through carrying out the projects of "Environmental Geochemical Monitoring Network and Dynamic Geochemical Mapping (EGMON)" and "FOREG geochemical baseline mapping", respectively, the expectation of acquiring a general picture of global geochemistry in 10 years has not yet been realized. Geochemists from China and Norway are now deliberating, through International Association of Hydrological Sciences/International Commission on Continental Erosion (IAHS/ICCE), about a major international cooperative project on "Global Geochemical Mapping and Sediment-Bound Flux of Major World Rivers", on carrying out a new round global geochemical mapping, and planning to start working first on the Arctic region under the project of the Year of Polar (IPY317). The practical plan for the global geochemical mapping is based on the "Draft of Sampling Plan of Floodplain Sediments" for the global geochemical mapping suggested by China and the "Draft of Sampling Plan of Overbank Sediments in Deltas" suggested by Norway, thereby further strengthening the advantages of Chinese methodology in geochemical mapping. After analyzing the opportunities and challenges to China, this article suggests that the competent authorities of science and technology should take the initiative of supporting the new round global geochemical mapping.

  7. Fuzzy Partition Models for Fitting a Set of Partitions.

    ERIC Educational Resources Information Center

    Gordon, A. D.; Vichi, M.

    2001-01-01

    Describes methods for fitting a fuzzy consensus partition to a set of partitions of the same set of objects. Describes and illustrates three models defining median partitions and compares these methods to an alternative approach to obtaining a consensus fuzzy partition. Discusses interesting differences in the results. (SLD)

  8. Partitioning and parallel radiosity

    NASA Astrophysics Data System (ADS)

    Merzouk, S.; Winkler, C.; Paul, J. C.

    1996-03-01

    This paper proposes a theoretical framework, based on domain subdivision for parallel radiosity. Moreover, three various implementation approaches, taking advantage of partitioning algorithms and global shared memory architecture, are presented.

  9. Equilibration timescale of atmospheric secondary organic aerosol partitioning

    NASA Astrophysics Data System (ADS)

    Shiraiwa, Manabu; Seinfeld, John H.

    2012-12-01

    Secondary organic aerosol (SOA) formed from partitioning of oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs) accounts for a substantial portion of atmospheric particulate matter. In describing SOA formation, it is generally assumed that VOC oxidation products rapidly adopt gas-aerosol equilibrium. Here we estimate the equilibration timescale, τeq, of SOA gas-particle partitioning using a state-of-the-art kinetic flux model. τeq is found to be of order seconds to minutes for partitioning of relatively high volatility organic compounds into liquid particles, thereby adhering to equilibrium gas-particle partitioning. However, τeq increases to hours or days for organic aerosol associated with semi-solid particles, low volatility, large particle size, and low mass loadings. Instantaneous equilibrium partitioning may lead to substantial overestimation of particle mass concentration and underestimation of gas-phase concentration.

  10. Isotope-based evapotranspiration partition in semi-arid environments

    NASA Astrophysics Data System (ADS)

    Wang, Lixin; Parkes, Stephen; McCabe, Matthew; Azcurra, Cecilia; Wang, Jin; Graham, Peter

    2013-04-01

    Evapotranspiration (ET) partitioning is important for quantifying the water budget and understanding vegetation control on water cycles in various ecosystems. With the development of spectroscopy-based techniques for in-situ isotope measurements, the use of stable isotope based ET partition is rising rapidly. The sub-daily scale ET partition, however, is still rarely seen in the literature. In this study, we conducted an intensive field campaign measuring ET partition using laser-based isotope and chamber techniques in a pasture system between May and June 2012 in eastern Australia. Six soil collars were used, three of which had natural vegetation and the other three were bare soil collars where vegetation was artificially removed. The vegetated and bare soil collars were used to determine the isotopic composition of ET and evaporation, respectively. The isotopic composition of the transpiration flux was determined using a Licor leaf chamber for grasses inside the vegetated collars. The diurnal patterns in dET, dE and dT are observed. In the morning, they are depleted and became more enriched and level off during mid-day. Overall the total ET flux is dominated by evaporation, though transpiration contributions are relatively higher between 10am and 12pm. D-excess is a conservative tracer of ET components and may not be useful in ET partition. This study demonstrated the use of chamber-based measurements for direct partitioning of ET at sub-daily scale and showed a rarely observed diurnal pattern of ET partition.

  11. Partitioning Breaks Communities

    NASA Astrophysics Data System (ADS)

    Reid, Fergal; McDaid, Aaron; Hurley, Neil

    Considering a clique as a conservative definition of community structure, we examine how graph partitioning algorithms interact with cliques. Many popular community-finding algorithms partition the entire graph into non-overlapping communities. We show that on a wide range of empirical networks, from different domains, significant numbers of cliques are split across the separate partitions produced by these algorithms. We then examine the largest connected component of the subgraph formed by retaining only edges in cliques, and apply partitioning strategies that explicitly minimise the number of cliques split. We further examine several modern overlapping community finding algorithms, in terms of the interaction between cliques and the communities they find, and in terms of the global overlap of the sets of communities they find. We conclude that, due to the connectedness of many networks, any community finding algorithm that produces partitions must fail to find at least some significant structures. Moreover, contrary to traditional intuition, in some empirical networks, strong ties and cliques frequently do cross community boundaries; much community structure is fundamentally overlapping and unpartitionable in nature.

  12. Geochemical modeling: a review

    SciTech Connect

    Jenne, E.A.

    1981-06-01

    Two general families of geochemical models presently exist. The ion speciation-solubility group of geochemical models contain submodels to first calculate a distribution of aqueous species and to secondly test the hypothesis that the water is near equilibrium with particular solid phases. These models may or may not calculate the adsorption of dissolved constituents and simulate the dissolution and precipitation (mass transfer) of solid phases. Another family of geochemical models, the reaction path models, simulates the stepwise precipitation of solid phases as a result of reacting specified amounts of water and rock. Reaction path models first perform an aqueous speciation of the dissolved constituents of the water, test solubility hypotheses, then perform the reaction path modeling. Certain improvements in the present versions of these models would enhance their value and usefulness to applications in nuclear-waste isolation, etc. Mass-transfer calculations of limited extent are certainly within the capabilities of state-of-the-art models. However, the reaction path models require an expansion of their thermodynamic data bases and systematic validation before they are generally accepted.

  13. Partition density functional theory

    NASA Astrophysics Data System (ADS)

    Nafziger, Jonathan

    Partition density functional theory (PDFT) is a method for dividing a molecular electronic structure calculation into fragment calculations. The molecular density and energy corresponding to Kohn Sham density-functional theory (KS-DFT) may be exactly recovered from these fragments. Each fragment acts as an isolated system except for the influence of a global one-body 'partition' potential which deforms the fragment densities. In this work, the developments of PDFT are put into the context of other fragment-based density functional methods. We developed three numerical implementations of PDFT: One within the NWChem computational chemistry package using basis sets, and the other two developed from scratch using real-space grids. It is shown that all three of these programs can exactly reproduce a KS-DFT calculation via fragment calculations. The first of our in-house codes handles non-interacting electrons in arbitrary one-dimensional potentials with any number of fragments. This code is used to explore how the exact partition potential changes for different partitionings of the same system and also to study features which determine which systems yield non-integer PDFT occupations and which systems are locked into integer PDFT occupations. The second in-house code, CADMium, performs real-space calculations of diatomic molecules. Features of the exact partition potential are studied for a variety of cases and an analytical formula determining singularities in the partition potential is derived. We introduce an approximation for the non-additive kinetic energy and show how this quantity can be computed exactly. Finally a PDFT functional is developed to address the issues of static correlation and delocalization errors in approximations within DFT. The functional is applied to the dissociation of H2 + and H2.

  14. FNAS phase partitions

    NASA Technical Reports Server (NTRS)

    Vanalstine, James M.

    1993-01-01

    Project NAS8-36955 D.O. #100 initially involved the following tasks: (1) evaluation of various coatings' ability to control wall wetting and surface zeta potential expression; (2) testing various methods to mix and control the demixing of phase systems; and (3) videomicroscopic investigation of cell partition. Three complementary areas were identified for modification and extension of the original contract. They were: (1) identification of new supports for column cell partition; (2) electrokinetic detection of protein adsorption; and (3) emulsion studies related to bioseparations.

  15. Cumulants of partitions

    NASA Astrophysics Data System (ADS)

    Weiss, Christoph; Block, Martin; Holthaus, Martin; Schmieder, Gerald

    2003-02-01

    We utilize the formal equivalence between the number-partitioning problem and a harmonically trapped ideal Bose gas within the microcanonical ensemble for characterizing the probability distribution which governs the number of addends occurring in an unrestricted partition of a natural number n. By deriving accurate asymptotic formulae for its coefficients of skewness and excess, it is shown that this distribution remains non-Gaussian even when n is made arbitrarily large. Both skewness and excess vary substantially before settling to their constant-limiting values for n > 1010.

  16. Mechanisms and Geochemical Models of Core Formation

    NASA Astrophysics Data System (ADS)

    David Rubie; Seth Andrew Jacobson

    2016-03-01

    The formation of the Earth's core is a consequence of planetary accretion and processes in the Earth's interior. The mechanical process of planetary differentiation is likely to occur in large, if not global, magma oceans created by the collisions of planetary embryos. Metal-silicate segregation in magma oceans occurs rapidly and efficiently unlike grain scale percolation according to laboratory experiments and calculations. Geochemical models of the core formation process as planetary accretion proceeds are becoming increasingly realistic. Single stage and continuous core formation models have evolved into multi-stage models that are couple to the output of dynamical models of the giant impact phase of planet formation. The models that are most successful in matching the chemical composition of the Earth's mantle, based on experimentally-derived element partition coefficients, show that the temperature and pressure of metal-silicate equilibration must increase as a function of time and mass accreted and so must the oxygen fugacity of the equilibrating material. The latter can occur if silicon partitions into the core and through the late delivery of oxidized material. Coupled dynamical accretion and multi-stage core formation models predict the evolving mantle and core compositions of all the terrestrial planets simultaneously and also place strong constraints on the bulk compositions and oxidation states of primitive bodies in the protoplanetary disk.

  17. Geochemical Evidence for a Terrestrial Magma Ocean

    NASA Technical Reports Server (NTRS)

    Agee, Carl B.

    1999-01-01

    The aftermath of phase separation and crystal-liquid fractionation in a magma ocean should leave a planet geochemically differentiated. Subsequent convective and other mixing processes may operate over time to obscure geochemical evidence of magma ocean differentiation. On the other hand, core formation is probably the most permanent, irreversible part of planetary differentiation. Hence the geochemical traces of core separation should be the most distinct remnants left behind in the mantle and crust, In the case of the Earth, core formation apparently coincided with a magma ocean that extended to a depth of approximately 1000 km. Evidence for this is found in high pressure element partitioning behavior of Ni and Co between liquid silicate and liquid iron alloy, and with the Ni-Co ratio and the abundance of Ni and Co in the Earth's upper mantle. A terrestrial magma ocean with a depth of 1000 km will solidify from the bottom up and first crystallize in the perovskite stability field. The largest effect of perovskite fractionation on major element distribution is to decrease the Si-Mg ratio in the silicate liquid and increase the Si-Mg ratio in the crystalline cumulate. Therefore, if a magma ocean with perovskite fractionation existed, then one could expect to observe an upper mantle with a lower than chondritic Si-Mg ratio. This is indeed observed in modern upper mantle peridotites. Although more experimental work is needed to fully understand the high-pressure behavior of trace element partitioning, it is likely that Hf is more compatible than Lu in perovskite-silicate liquid pairs. Thus, perovskite fractionation produces a molten mantle with a higher than chondritic Lu-Hf ratio. Arndt and Blichert-Toft measured Hf isotope compositions of Barberton komatiites that seem to require a source region with a long-lived, high Lu-Hf ratio. It is plausible that that these Barberton komatiites were generated within the majorite stability field by remelting a perovskite

  18. New Aperture Partitioning Element

    NASA Astrophysics Data System (ADS)

    Griffin, S.; Calef, B.; Williams, S.

    Postprocessing in an optical system can be aided by adding an optical element to partition the pupil into a number of segments. When imaging through the atmosphere, the recorded data are blurred by temperature-induced variations in the index of refraction along the line of sight. Using speckle imaging techniques developed in the astronomy community, this blurring can be corrected to some degree. The effectiveness of these techniques is diminished by redundant baselines in the pupil. Partitioning the pupil reduces the degree of baseline redundancy, and therefore improves the quality of images that can be obtained from the system. It is possible to implement the described approach on an optical system with a segmented primary mirror, but not very practical. This is because most optical systems do not have segmented primary mirrors, and those that do have relatively low bandwidth positioning of segments due to their large mass and inertia. It is much more practical to position an active aperture partitioning element at an aft optics pupil of the optical system. This paper describes the design, implementation and testing of a new aperture partitioning element that is completely reflective and reconfigurable. The device uses four independent, annular segments that can be positioned with a high degree of accuracy without impacting optical wavefront of each segment. This mirror has been produced and is currently deployed and working on the 3.6 m telescope.

  19. ARSENIC SOLID-PHASE PARTITIONING IN REDUCING SEDIMENTS OF CONTAMINATED WETLAND

    EPA Science Inventory

    The geochemical partitioning of arsenic in organic-rich sediments from a contaminated wetland is examined using X-ray absorption spectroscopy and selective chemical extraction procedures, and evaluated in context to the anoxic diagenesis of iron and sulfur. The interaction betwe...

  20. Geochemical surveys in the Lusi mud eruption

    NASA Astrophysics Data System (ADS)

    Sciarra, Alessandra; Mazzini, Adriano; Etiope, Giuseppe; Inguaggiato, Salvatore; Hussein, Alwi; Hadi J., Soffian

    2016-04-01

    The Lusi mud eruption started in May 2006 following to a 6.3 M earthquake striking the Java Island. In the framework of the Lusi Lab project (ERC grant n° 308126) we carried out geochemical surveys in the Sidoarjo district (Eastern Java Island, Indonesia) to investigate the gas bearing properties of the Watukosek fault system that crosses the Lusi mud eruption area. Soil gas (222Rn, CO2, CH4) concentration and flux measurements were performed 1) along two detailed profiles (~ 1km long), trending almost W-E direction, and 2) inside the Lusi embankment (about 7 km2) built to contain the erupted mud. Higher gas concentrations and fluxes were detected at the intersection with the Watukosek fault and the antithetic fault system. These zones characterized by the association of higher soil gas values constitute preferential migration pathways for fluids towards surface. The fractures release mainly CO2 (with peaks up to 400 g/m2day) and display higher temperatures (up to 41°C). The main shear zones are populated by numerous seeps that expel mostly CH4. Flux measurements in the seeping pools reveal that φCO2 is an order of magnitude higher than that measured in the fractures, and two orders of magnitude higher for φCH4. An additional geochemical profile was completed perpendicularly to the Watukosek fault escarpement (W-E direction) at the foots of the Penanngungang volcano. Results reveal CO2 and CH4 flux values significantly lower than those measured in the embankment, however an increase of radon and flux measurements is observed approaching the foots of the escarpment. These measurements are complemented with a database of ~350 CH4 and CO2 flux measurements and some soil gas concentrations (He, H2, CO2, CH4 and C2H6) and their isotopic analyses (δ13C-CH4, δD-CH4 and δ13C-CO2). Results show that the whole area is characterized by diffused gas release through seeps, fractures, microfractures and soil degassing. The collected results shed light on the origin of the

  1. Environmental Status and geochemical assessment Sediments of Lake Skadar, Montenegro.

    PubMed

    Kastratović, Vlatko; Jaćimović, Željko; Bigović, Miljan; Đurović, Dijana; Krivokapić, Slađana

    2016-08-01

    The environmental mobility and geochemical partitioning of ten metals were examined in sediments collected from the six locations around Lake Skadar in Montenegro. A three-step sequential extraction procedure was used to determine the distribution of the metals in various substrates of lacustrine sediments, and the concentrations were measured in the liquid extract by ICP-OES. The largest portion of the total amount of cadmium, strontium and manganese can be found in sediment bound to the hydrated iron and manganese oxides; cobalt, lead, copper and nickel in the oxidizable fraction and the highest portion of chromium, vanadium and zinc are in the residual fraction. The most mobilized and potentially mobile metals are strontium, cadmium and cobalt while the most immobilized metals are chromium, vanadium and zinc. Based on geochemical parameters, an assessment of sediment contamination by the investigated metals was performed and the results showed potential risks ranging from "no risk" to "low risk" to the environment. PMID:27384227

  2. The Geochemical Earth Reference Model (GERM)

    SciTech Connect

    Staudigel, H.; Albarede, F.; Shaw, H.; McDonough, B.; White, W.

    1996-12-01

    The Geochemical Earth Reference Model (GERM) initiative is a grass- roots effort with the goal of establishing a community consensus on a chemical characterization of the Earth, its major reservoirs, and the fluxes between them. Long term goal of GERM is a chemical reservoir characterization analogous to the geophysical effort of the Preliminary Reference Earth Model (PREM). Chemical fluxes between reservoirs are included into GERM to illuminate the long-term chemical evolution of the Earth and to characterize the Earth as a dynamic chemical system. In turn, these fluxes control geological processes and influence hydrosphere-atmosphere-climate dynamics. While these long-term goals are clearly the focus of GERM, the process of establishing GERM itself is just as important as its ultimate goal. The GERM initiative is developed in an open community discussion on the World Wide Web (GERM home page is at http://www-ep.es.llnl. gov/germ/germ-home.html) that is mediated by a series of editors with responsibilities for distinct reservoirs and fluxes. Beginning with the original workshop in Lyons (March 1996) GERM is continued to be developed on the Internet, punctuated by workshops and special sessions at professional meetings. It is planned to complete the first model by mid-1997, followed by a call for papers for a February 1998 GERM conference in La Jolla, California.

  3. Petrogenetic modeling of Hawaiian tholeiitic basalts - A geochemical approach

    NASA Technical Reports Server (NTRS)

    Budahn, J. R.; Schmitt, R. A.

    1985-01-01

    The abundances of 29 elements in 33 samples of tholeiitic basalts from five volcanoes in Hawaii are determined by neutron-activation analysis; the results are presented in tables and graphs with the data of Murali et al. (1977) for a sixth volcano and characterized in detail; and geochemical partial-melting models are constructed to explain the origin of these basalts. The models proposed are based on olivine crystallization from three distinct source compositions (determined from the REE and Sc partitioning) and correspond to the volcano groups Mauna Kea, Kohala, and Kilauea; Mauna Loa and Lanai; and Koolau.

  4. Geochemical Speciation Mass Transfer

    SciTech Connect

    1985-12-01

    PHREEQC is designed to model geochemical reactions. Based on an ion association aqueous model, PHREEQC can calculate pH, redox potential, and mass transfer as a function of reaction progress. It can be used to describe geochemical processes for both far-field and near-field performance assessment and to evaluate data acquisition needs and test data. It can also calculate the composition of solutions in equilibrium with multiple phases. The data base, including elements, aqueous species, and mineral phases, is independent of the program and is completely user-definable. PHREEQC requires thermodynamic data for each solid, gaseous, or dissolved chemical species being modeled. The two data bases, PREPHR and DEQPAK7, supplied with PHREEQC are for testing purposes only and should not be applied to real problems without first being carefully examined. The conceptual model embodied in PHREEQC is the ion-association model of Pearson and Noronha. In this model a set of mass action equations are established for each ion pair (and controlling solid phases when making mass transfer calculations) along with a set of mass balance equations for each element considered. These sets of equations are coupled using activity coefficient values for each aqueous species and solved using a continued fraction approach for the mass balances combined with a modified Newton-Raphson technique for all other equations. The activity coefficient expressions in PHREEQC include the extended Debye-Huckel, WATEQ Debye-Huckel, and Davies equations from the original United States Geological Survey version of the program. The auxiliary preprocessor program PHTL, which is derived from EQTL, converts EQ3/6 thermodynamic data to PHREEQC format so that the two programs can be compared. PHREEQC can be used to determine solubility limits on the radionuclides present in the waste form. These solubility constraints may be input to the WAPPA leach model.

  5. Geochemical Speciation Mass Transfer

    Energy Science and Technology Software Center (ESTSC)

    1985-12-01

    PHREEQC is designed to model geochemical reactions. Based on an ion association aqueous model, PHREEQC can calculate pH, redox potential, and mass transfer as a function of reaction progress. It can be used to describe geochemical processes for both far-field and near-field performance assessment and to evaluate data acquisition needs and test data. It can also calculate the composition of solutions in equilibrium with multiple phases. The data base, including elements, aqueous species, and mineralmore » phases, is independent of the program and is completely user-definable. PHREEQC requires thermodynamic data for each solid, gaseous, or dissolved chemical species being modeled. The two data bases, PREPHR and DEQPAK7, supplied with PHREEQC are for testing purposes only and should not be applied to real problems without first being carefully examined. The conceptual model embodied in PHREEQC is the ion-association model of Pearson and Noronha. In this model a set of mass action equations are established for each ion pair (and controlling solid phases when making mass transfer calculations) along with a set of mass balance equations for each element considered. These sets of equations are coupled using activity coefficient values for each aqueous species and solved using a continued fraction approach for the mass balances combined with a modified Newton-Raphson technique for all other equations. The activity coefficient expressions in PHREEQC include the extended Debye-Huckel, WATEQ Debye-Huckel, and Davies equations from the original United States Geological Survey version of the program. The auxiliary preprocessor program PHTL, which is derived from EQTL, converts EQ3/6 thermodynamic data to PHREEQC format so that the two programs can be compared. PHREEQC can be used to determine solubility limits on the radionuclides present in the waste form. These solubility constraints may be input to the WAPPA leach model.« less

  6. Disentangling event-scale hydrologic flow partitioning in mountains of the Korean Peninsula under extreme precipitation

    NASA Astrophysics Data System (ADS)

    Shope, Christopher L.

    2016-07-01

    Mountainous headwaters include a variety of spatial landscape units; however, the flow contribution from different hydrologic components is complex and often unclear. In addition to complex landscape controls, temporal meteorological drivers play an important role in the distribution between surface runoff and subsurface storage changes. This spatiotemporal variability in partitioning can influence catchment-wide flow accumulation and nutrient and sediment loading. We use a multi-year, multi-method analysis of stable isotopes, geochemical indicators, and discharge distributed throughout the Haean catchment in South Korea to identify temporal variability in hydrologic flow partitioning from surface runoff, springs, shallow interflow, and groundwater under monsoonal conditions. By combining a weighted, multi-method discharge approach, high frequency, synoptic, catchment-wide isotopic and geochemical sampling, and baseflow analysis, we characterize watershed-scale spatiotemporal hydrologic flow partitioning. Meteorological drivers are spatially variable throughout the catchment and temporally between individual events. Baseflow contributions in the high elevation, forested areas are up to 50%, while the majority of the catchment is approximately 20%. Our study builds on previously reported seasonality of isotopic signatures by quantifying trends in distributed event-based partitioning of isotopic tracers. We demonstrate that high frequency flow partitioning can accurately be determined in mountainous topography with high precipitation and that there is a need for multiple method characterizations. Our results further show the benefit of spatially distributed synoptic sampling for process understanding of hydrologic partitioning throughout the watersheds.

  7. Environmental Applications of Geochemical Modeling

    NASA Astrophysics Data System (ADS)

    Zhu, Chen; Anderson, Greg

    2002-05-01

    This book discusses the application of geochemical models to environmental practice and studies, through the use of numerous case studies of real-world environmental problems, such as acid mine drainage, pit lake chemistry, nuclear waste disposal, and landfill leachates. In each example the authors clearly define the environmental threat in question; explain how geochemical modeling may help solve the problem posed; and advise the reader how to prepare input files for geochemical modeling codes and interpret the results in terms of meeting regulatory requirements.

  8. Problems with the process partitioning theory of stratocumulus entrainment

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    Three different approaches to partitioning were proposed. Ball (1960), Lilly (1968), and Deardorff et al. (1969, 1974) considered the sign of the net buoyancy flux at each level. If the net flux is positive, it is counted as TKE producing; otherwise, it is counted as TKE consuming. This approach can be called Eulerian partitioning. The second approach can be called process partitioning. It is assumed that the various processes acting in concert each produce and consume the same energy as if they acted independently (Manins and Turner, 1978). The total rates of TKE production and consumption are obtained by summing the effects of all the forcing processes. The third approach is Lagrangian partitioning. Each air parcel is considered as either producing or consuming TKE, according to the sign of the product of its density and vertical velocity anomalies. Stage and Businger (1981a,b) have applied process partitioning to the cloud topped mixed layer. One of the most important processes influencing entrainment into such a layer is cloud top radiative cooling. The production and consumption due to entrainment and radiative cooling are thus closely related. Model results are sensitive to the choice of formulation.

  9. Chemical amplification based on fluid partitioning

    DOEpatents

    Anderson, Brian L.; Colston, Jr., Billy W.; Elkin, Chris

    2006-05-09

    A system for nucleic acid amplification of a sample comprises partitioning the sample into partitioned sections and performing PCR on the partitioned sections of the sample. Another embodiment of the invention provides a system for nucleic acid amplification and detection of a sample comprising partitioning the sample into partitioned sections, performing PCR on the partitioned sections of the sample, and detecting and analyzing the partitioned sections of the sample.

  10. Estuarine removal of glacial iron and implications for iron fluxes to the ocean

    NASA Astrophysics Data System (ADS)

    Schroth, Andrew W.; Crusius, John; Hoyer, Ian; Campbell, Robert

    2014-06-01

    While recent work demonstrates that glacial meltwater provides a substantial and relatively labile flux of the micronutrient iron to oceans, the role of high-latitude estuary environments as a potential sink of glacial iron is unknown. Here we present the first quantitative description of iron removal in a meltwater-dominated estuary. We find that 85% of "dissolved" Fe is removed in the low-salinity region of the estuary along with 41% of "total dissolvable" iron associated with glacial flour. We couple these findings with hydrologic and geochemical data from Gulf of Alaska (GoA) glacierized catchments to calculate meltwater-derived fluxes of size and species partitioned Fe to the GoA. Iron flux data indicate that labile iron in the glacial flour and associated Fe minerals dominate the meltwater contribution to the Fe budget of the GoA. As such, GoA nutrient cycles and related ecosystems could be strongly influenced by continued ice loss in its watershed.

  11. Leaf area controls on energy partitioning of a temperate mountain grassland

    PubMed Central

    Hammerle, A.; Haslwanter, A.; Tappeiner, U.; Cernusca, A.; Wohlfahrt, G.

    2013-01-01

    Using a six year data set of eddy covariance flux measurements of sensible and latent heat, soil heat flux, net radiation, above-ground phytomass and meteorological driving forces energy partitioning was investigated at a temperate mountain grassland managed as a hay meadow in the Stubai Valley (Austria). The main findings of the study were: (i) Energy partitioning was dominated by latent heat, followed by sensible heat and the soil heat flux; (ii) When compared to standard environmental forcings, the amount of green plant matter, which due to three cuts varied considerably during the vegetation period, explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) There were little, if any, indications of water stress effects on energy partitioning, despite reductions in soil water availability in combination with high evaporative demand, e.g. during the summer drought of 2003. PMID:24348583

  12. Characterizing the Influence of Flow Regime and Landcover on the Geochemical Nature and Magnitude of Riverine Phosphorus and Trace Metal Loads

    NASA Astrophysics Data System (ADS)

    Rosenberg, B.; Schroth, A. W.

    2014-12-01

    Within aquatic systems, phosphorus (P) is a common limiting nutrient present in low bioavailable concentrations. Colloidal and particulate phases of the trace metals manganese (Mn) and iron (Fe) are common scavengers of phosphate in the freshwater environment, and the distribution and stability of such phases is thought to influence the bioavailability of P. The partitioning and flux of P and TM in rivers can be driven by the geochemical source of these constituents, as well as the hydrologic/biogeochemical pathways active within the watershed, both of which vary based on hydrologic condition and landcover. This study investigates how different landcovers (suburban, agricultural, forested, glacial) contribute to P and TM flux and partitioning during high-flow events (snowmelt, glacial melt, storms). High-resolution water and suspended sediment sampling was conducted during snowmelt in Vermont, as well as during summer storms and baseflow conditions. In Alaska, samples were collected during baseflow, glacial melt, and storm events to provide additional data from other landcovers and hydrologic systems. Initial analyses suggest that the size fraction, loading, and relative lability of water and suspended sediment pools of TM and P are strongly influenced by both land cover and seasonality/hydrology. Samples collected during snowmelt in VT show high concentrations of dissolved and potentially bioavailable particulate P at the start of melt that decrease over time. Coupled with high discharge events, a substantial load of labile P is delivered during this particular high flow period. As snowmelt transitions to baseflow conditions, with intermittent storms the character of the suspended sediment changes drastically, with lower total concentrations of P and TM as well as a lower proportion of extractable P (bound to easily reduced oxyhydroxides) to total sediment P. This study highlights that the snowmelt period is not only important from an overall all load standpoint

  13. Geochemical Arrays at Woolsey Mound Seafloor Observatory

    NASA Astrophysics Data System (ADS)

    Sleeper, K.; Wilson, R. M.; Chanton, J.; Lapham, L.; Farr, N.; Camilli, R.; Martens, C. S.; Pontbriand, C.

    2011-12-01

    A suite of geochemical monitoring arrays has been developed for the Woolsey Mound Seafloor Observatory in the northern Gulf of Mexico to evaluate the oceanographic and tectonic forcing factors on the formation and stability of gas hydrates. These arrays are designed to collect sustained, time-series data of chemical concentrations, gradients and fluxes from the subsurface to the seafloor and into the near bottom water column. A Pore Fluid Array provides time-series measurements of methane, sulfate and salinity in subsurface pore waters to evaluate microbial activity, hydrate formation and/or hydrate dissociation. A Chimney Sampler Array collects in situ chemical and physical readings at the benthic boundary. The array is designed around a vertical cylinder with a known volume and washout rate for measuring chemical gradients and flux at the seafloor. The Benthic Boundary Layer Array extends into the water column with a package of sensors in a node close to the seafloor and a similar node 20 m above the seafloor to evaluate upward, downward and transversely advecting fluids. The three arrays can be used in concert to evaluate a release of methane by the dissociation of gas hydrates: the Pore Fluid Array identifies the breakdown of gas hydrates in the subsurface, the Chimney Array determines the rate of flux at the seafloor and the Benthic Boundary Layer Array evaluates the fate of the release in the water column. Combining the data from the geochemical arrays with output from the geophysical arrays provides key information to evaluate the specific and relative importance of tectonic and oceanographic triggers for hydrate dissociation. New probes and deployment platforms have been developed for the installation and maintenance of the arrays and new systems are in place and under development for the recovery of the data. Generally, the complete array or its components have to be recovered to download the data. However, this summer 2011, a new optic modem system was

  14. An in situ approach to study trace element partitioning in the laser heated diamond anvil cell

    SciTech Connect

    Petitgirard, S.; Mezouar, M.; Borchert, M.; Appel, K.; Liermann, H.-P.; Andrault, D.

    2012-01-15

    Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample melting based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth.

  15. An in situ approach to study trace element partitioning in the laser heated diamond anvil cell.

    PubMed

    Petitgirard, S; Borchert, M; Andrault, D; Appel, K; Mezouar, M; Liermann, H-P

    2012-01-01

    Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample melting based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth. PMID:22299967

  16. Land surface energy partitioning revisited: A novel approach based on single depth soil measurement

    NASA Astrophysics Data System (ADS)

    Yang, Jiachuan; Wang, Zhi-Hua

    2014-12-01

    The partitioning of solar energy into sensible, latent, and ground heat fluxes over the land surface is responsible for changes of state variables in the soil-atmosphere system. Recent research enables the reconstruction of the land surface temperature and ground heat flux using Green's function approach, as well as the estimate of the distribution of available energy into latent and sensible heat fluxes based on linear stability analysis. Combining the Green's function approach and linear stability analysis, we propose a new physically based numerical procedure to estimate the land surface energy partitioning in this paper. The new method is capable of predicting all surface energy budgets using a single depth soil measurement; the model reliability is evaluated with comparisons to flux tower measurements. The results of this study deepen our insight into the implicit link between surface energy partition and subsurface soil dynamics and how the link can be employed to related research areas.

  17. Traceds: An Experimental Trace Element Partitioning Database

    NASA Astrophysics Data System (ADS)

    Nielsen, R. L.; Ghiorso, M. S.

    2014-12-01

    The goal of this project, which is part of the EARTHCHEM initiative, is to compile the existing experimental trace element partitioning data, and to develop a transparent, accessible resource for the community. The primary goal of experimental trace element partitioning studies is to create a database that can be used to develop models of how trace elements behave in natural geochemical systems. The range of approaches as to how this is accomplished and how the data are reported differs dramatically from one system to another and one investigator to another. This provides serious challenges to the creation of a coherent database - and suggests the need for a standard format for data presentation and reporting. The driving force for this compilation is to provide community access to the complete database for trace element experiments. Our new effort includes all the published analytical results from experimental determinations. In compiling the data, we have set a minimum standard for the data to be included. The threshold criteria include: Experimental conditions (temperature, pressure, device, container, time, etc.) Major element composition of the phases Trace element analyses of the phases Data sources that did not report these minimum components were not included. The rationale for not including such data is that the degree of equilibration is unknown, and more important, no rigorous approach to modeling the behavior of trace elements is possible without a knowledge of the actual concentrations or the temperature and pressure of formation. The data are stored using a schema derived from that of the Library of Experimental Phase Relations (LEPR), modified to account for additional metadata, and restructured to permit multiple analytical entries for various element/technique/standard combinations. Our ultimate goal is to produce a database together with a flexible user interface that will be useful for experimentalists to set up their work and to build

  18. Quantum field theory of partitions

    SciTech Connect

    Bender, C.M.; Brody, D.C.; Meister, B.K.

    1999-07-01

    Given a sequence of numbers {l_brace}a{sub n}{r_brace}, it is always possible to find a set of Feynman rules that reproduce that sequence. For the special case of the partitions of the integers, the appropriate Feynman rules give rise to graphs that represent the partitions in a clear pictorial fashion. These Feynman rules can be used to generate the Bell numbers B(n) and the Stirling numbers S(n,k) that are associated with the partitions of the integers. {copyright} {ital 1999 American Institute of Physics.}

  19. Probabilistic framework for network partition

    NASA Astrophysics Data System (ADS)

    Li, Tiejun; Liu, Jian; E, Weinan

    2009-08-01

    Given a large and complex network, we would like to find the partition of this network into a small number of clusters. This question has been addressed in many different ways. In a previous paper, we proposed a deterministic framework for an optimal partition of a network as well as the associated algorithms. In this paper, we extend this framework to a probabilistic setting, in which each node has a certain probability of belonging to a certain cluster. Two classes of numerical algorithms for such a probabilistic network partition are presented and tested. Application to three representative examples is discussed.

  20. Partitioning ecosystems for sustainability.

    PubMed

    Murray, Martyn G

    2016-03-01

    Decline in the abundance of renewable natural resources (RNRs) coupled with increasing demands of an expanding human population will greatly intensify competition for Earth's natural resources during this century, yet curiously, analytical approaches to the management of productive ecosystems (ecological theory of wildlife harvesting, tragedy of the commons, green economics, and bioeconomics) give only peripheral attention to the driving influence of competition on resource exploitation. Here, I apply resource competition theory (RCT) to the exploitation of RNRs and derive four general policies in support of their sustainable and equitable use: (1) regulate resource extraction technology to avoid damage to the resource base; (2) increase efficiency of resource use and reduce waste at every step in the resource supply chain and distribution network; (3) partition ecosystems with the harvesting niche as the basic organizing principle for sustainable management of natural resources by multiple users; and (4) increase negative feedback between consumer and resource to bring about long-term sustainable use. A simple policy framework demonstrates how RCT integrates with other elements of sustainability science to better manage productive ecosystems. Several problem areas of RNR management are discussed in the light of RCT, including tragedy of the commons, overharvesting, resource collapse, bycatch, single species quotas, and simplification of ecosystems. PMID:27209800

  1. Graph Partitioning and Sequencing Software

    Energy Science and Technology Software Center (ESTSC)

    1995-09-19

    Graph partitioning is a fundemental problem in many scientific contexts. CHACO2.0 is a software package designed to partition and sequence graphs. CHACO2.0 allows for recursive application of several methods for finding small edge separators in weighted graphs. These methods include inertial, spectral, Kernighan Lin and multilevel methods in addition to several simpler strategies. Each of these approaches can be used to partition the graph into two, four, or eight pieces at each level of recursion.more » In addition, the Kernighan Lin method can be used to improve partitions generated by any of the other algorithms. CHACO2.0 can also be used to address various graph sequencing problems, with applications to scientific computing, database design, gene sequencing and other problems.« less

  2. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    NASA Astrophysics Data System (ADS)

    Perry, F. V.; Crowe, B. M.

    Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.

  3. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    SciTech Connect

    Perry, F.V.; Crowe, B.M.

    1991-12-31

    Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.

  4. New geochemical insights into volcanic degassing.

    PubMed

    Edmonds, Marie

    2008-12-28

    Magma degassing plays a fundamental role in controlling the style of volcanic eruptions. Whether a volcanic eruption is explosive, or effusive, is of crucial importance to approximately 500 million people living in the shadow of hazardous volcanoes worldwide. Studies of how gases exsolve and separate from magma prior to and during eruptions have been given new impetus by the emergence of more accurate and automated methods to measure volatile species both as volcanic gases and dissolved in the glasses of erupted products. The composition of volcanic gases is dependent on a number of factors, the most important being magma composition and the depth of gas-melt segregation prior to eruption; this latter parameter has proved difficult to constrain in the past, yet is arguably the most critical for controlling eruptive style. Spectroscopic techniques operating in the infrared have proved to be of great value in measuring the composition of gases at high temporal resolution. Such methods, when used in tandem with microanalytical geochemical investigations of erupted products, are leading to better constraints on the depth at which gases are generated and separated from magma. A number of recent studies have focused on transitions between explosive and effusive activity and have led to a better understanding of gas-melt segregation at basaltic volcanoes. Other studies have focused on degassing during intermediate and silicic eruptions. Important new results include the recognition of fluxing by deep-derived gases, which buffer the amount of dissolved volatiles in the melt at shallow depths, and the observation of gas flow up permeable conduit wall shear zones, which may be the primary mechanism for gas loss at the cusp of the most explosive and unpredictable volcanic eruptions. In this paper, I review current and future directions in the field of geochemical studies of volcanic degassing processes and illustrate how the new insights are beginning to change the way in

  5. Evaporative partitioning in a unified land model

    NASA Astrophysics Data System (ADS)

    Livneh, B.; Lettenmaier, D. P.; Restrepo, P. J.

    2009-12-01

    Accurate partitioning of precipitation into evapotranspiration and runoff, and more generally estimation of the surface water balance, is crucial both for hydrologic forecasting and numerical weather and climate prediction. One important aspect of this issue is the partitioning of evapotranspiration into soil evaporation, canopy evaporation, and plant transpiration, which in turn has implications for other terms in the surface water balance. In the first part of the study, we tested several well known land surface models in multi-year simulations over the continental U.S. Among the models, which included the Variable Infiltration Capacity (VIC) model, the Community Land Model (CLM), the Noah Land Surface Model (Noah LSM), and the NASA Catchment model, there were substantial variations in the partitioning. These results motivated a more detailed evaluation, using data for two catchments that were a part of the second phase of the Distributed Model Intercomparison Project (DMIP-2), the East Fork Carson River Basin and the Illinois River Basin. In this portion of the study, we evaluated a unified land model (ULM) which is a merger of the NWS Sacramento Soil Moisture Accounting model (SAC-SMA), which is used operationally for flood and seasonal streamflow prediction, and the Noah LSM, which is the land scheme used in NOAA’s suite of weather and climate prediction models. Our overall objective is to leverage the operational strengths of each model, specifically to improve streamflow prediction and soil moisture states within the Noah LSM framework, and to add a vegetation component to the SAC-SMA model. Partitioning of evapotranspiration into its three components is a key part of the ULM performance, and controls our ability to use calibrated SAC-SMA parameters within the ULM framework. In our evaluations at the DMIP-2 sites, we examined sensitivities of soil moisture and evaporative components in ULM to changes in vegetation cover, root zone depth, canopy

  6. Partitioning of Organic Contaminants and Tracer Compounds in a CO2-Brine System at High Salinities

    NASA Astrophysics Data System (ADS)

    Thomas, B.; Kharaka, Y. K.; Rosenbauer, R. J.; Janesko, D.; Trutna, J.

    2011-12-01

    Nonionic chemical species including gases and organic compounds partition between the fluid CO2 phase and the aqueous phase in geologic carbon sequestration systems. The injection and migration of CO2 in geologic carbon sequestration systems covers a wide range of pressure and temperature, so it is important to understand the partitioning of these compounds at various P-T conditions and salinities. Geochemical data is particularly lacking for the partitioning of organic contaminant compounds and tracer compounds between highly saline brines and CO2. Most groundwater is relatively low in organic contaminants; however, groundwater associated with hydrocarbon migration pathways, enhanced oil recovery (EOR), and hydrocarbon storage or extraction can contain high concentrations of known organic contaminants. CO2 injection in these systems may therefore be more likely to result in partitioning of contaminants into the CO2 phase that could, upon migration, represent an important risk to groundwater resources. We present the experimental apparatus and determination of partition coefficients between brine and CO2 for a suite of compounds including benzene, toluene, ethylbenzene, xylene (BTEX), and low molecular weight polynuclear aromatic hydrocarbons (PAHs). In addition, partition coefficients are determined for the important gas phase tracer compounds: SF6 and Krypton covering a P-T envelope consistent with CO2 injection and plume migration to the near surface.

  7. Partition behaviour of alkylphenols in crude oil/brine systems under subsurface conditions

    NASA Astrophysics Data System (ADS)

    Bennett, B.; Larter, S. R.

    1997-10-01

    Partition of organic solutes between oils and water in the subsurface is an important geochemical process occurring during petroleum migration and reservoiring, during water washing, and during petroleum production. Currently no data exists on the quantitative aspects of the partition process at subsurface conditions for solutes such as phenols and aromatic hydrocarbons which are major components of both oils and waters. We have constructed an equilibration device for oils and waters based on flow injection analysis principles to measure partition coefficients of alkylphenols in crude oil/brine systems under reservoir conditions. Concentrations of C 0C 2 alkylphenols in waters and solid phase extracts of crude oils produced in the device were determined by reverse phase high performance liquid chromatography with electrochemical detection (RP-HPLC-ED), partition coefficients being measured as a function of pressure (25-340 bar), temperature (25-150°C), and water salinity (0-100,000 mg/L sodium chloride) for a variety of oils. Partition coefficients for all compounds decreased with increasing temperature, increased with water salinity and crude oil bulk NSO content, and showed little change with varying pressure. These laboratory measurements, determined under conditions close to those typically encountered in petroleum reservoirs, suggest temperature, water salinity, and crude oil bulk NSO content will have important influence on oil-water partition processes in the subsurface during migration and water washing.

  8. Beyond simple linear mixing models: process-based isotope partitioning of ecological processes.

    PubMed

    Ogle, Kiona; Tucker, Colin; Cable, Jessica M

    2014-01-01

    Stable isotopes are valuable tools for partitioning the components contributing to ecological processes of interest, such as animal diets and trophic interactions, plant resource use, ecosystem gas fluxes, streamflow, and many more. Stable isotope data are often analyzed with simple linear mixing (SLM) models to partition the contributions of different sources, but SLM models cannot incorporate a mechanistic understanding of the underlying processes and do not accommodate additional data associated with these processes (e.g., environmental covariates, flux data, gut contents). Thus, SLM models lack predictive ability. We describe a process-based mixing (PBM) model approach for integrating stable isotopes, other data sources, and process models to partition different sources or process components. This is accomplished via a hierarchical Bayesian framework that quantifies multiple sources of uncertainty and enables the incorporation of process models and prior information to help constrain the source-specific proportional contributions, thereby potentially avoiding identifiability issues that plague SLM models applied to "too many" sources. We discuss the application of the PBM model framework to three diverse examples: temporal and spatial partitioning of streamflow, estimation of plant rooting profiles and water uptake profiles (or water sources) with extension to partitioning soil and ecosystem CO2 fluxes, and reconstructing animal diets. These examples illustrate the advantages of the PBM modeling approach, which facilitates incorporation of ecological theory and diverse sources of information into the mixing model framework, thus enabling one to partition key process components across time and space. PMID:24640543

  9. Partitioning of Nanoparticles into Organic Phases and Model Cells

    SciTech Connect

    Posner, J.D.; Westerhoff, P.; Hou, W-C.

    2011-08-25

    dissolved substances" or "more like colloids" as the division between behaviors of macromolecules versus colloids remains ill-defined. Below we detail our work on two broadly defined objectives: (i) Partitioning of ENP into octanol, lipid bilayer, and water, and (ii) disruption of lipid bilayers by ENPs. We have found that the partitioning of NP reaches pseudo-equilibrium distributions between water and organic phases. The equilibrium partitioning most strongly depends on the particle surface charge, which leads us to the conclusion that electrostatic interactions are critical to understanding the fate of NP in the environment. We also show that the kinetic rate at which particle partition is a function of their size (small particles partition faster by number) as can be predicted from simple DLVO models. We have found that particle number density is the most effective dosimetry to present our results and provide quantitative comparison across experiments and experimental platforms. Cumulatively, our work shows that lipid bilayers are a more effective organic phase than octanol because of the definable surface area and ease of interpretation of the results. Our early comparison of NP partitioning between water and lipids suggest that this measurement can be predictive of bioaccumulation in aquatic organisms. We have shown that nanoparticle disrupt lipid bilayer membranes and detail how NP-bilayer interaction leads to the malfunction of lipid bilayers in regulating the fluxes of ionic charges and molecules. Our results show that the disruption of the lipid membranes is similar to that of toxin melittin, except single particles can disrupt a bilayer. We show that only a single particle is required to disrupt a 150 nm DOPC liposome. The equilibrium leakage of membranes is a function of the particle number density and particle surface charge, consistent with results from our partitioning experiments. Our disruption experiments with varying surface functionality show that

  10. Tracer Partitioning in Two-Phase Flow

    NASA Astrophysics Data System (ADS)

    Sathaye, K.; Hesse, M. A.

    2012-12-01

    The concentration distributions of geochemical tracers in a subsurface reservoir can be used as an indication of the reservoir flow paths and constituent fluid origin. In this case, we are motivated by the origin of marked geochemical gradients in the Bravo Dome natural CO2 reservoir in northeastern New Mexico. This reservoir contains 99% CO2 with various trace noble gas components and overlies the formation brine in a sloping aquifer. It is thought that magmatic CO2 entered the reservoir, and displaced the brine. This displacement created gradients in the concentrations of the noble gases. Two models to explain noble gas partitioning in two-phase flow are presented here. The first model assumes that the noble gases act as tracers and uses a first order non-linear partial differential equation to compute the volume fraction of each phase along the displament path. A one-way coupled partial differential equation determines the tracer concentration, which has no effect on the overall flow or phase saturations. The second model treats each noble gas as a regular component resulting in a three-component, two-phase system. As the noble gas injection concentration goes to zero, we see the three-component system behave like the one-way coupled system of the first model. Both the analytical and numerical solutions are presented for these models. For the process of a gas displacing a liquid, we see that a noble gas tracer with greater preference for the gas phase, such as Helium, will move more quickly along the flowpath than a heavier tracer that will more easily enter the liquid phase, such as Argon. When we include partial miscibility of both the major and trace components, these differences in speed are shown in a bank of the tracer at the saturation front. In the three component model, the noble gas bank has finite width and concentration. In the limit where the noble gas is treated as a tracer, the width of the bank is zero and the concentration increases linearly

  11. Geochemical cycles of atmospheric gases

    NASA Technical Reports Server (NTRS)

    Walker, J. C. G.; Drever, J. I.

    1988-01-01

    The processes that control the atmosphere and atmospheric changes are reviewed. The geochemical cycles of water vapor, nitrogen, carbon dioxide, oxygen, and minor atmospheric constituents are examined. Changes in atmospheric chemistry with time are discussed using evidence from the rock record and analysis of the present atmosphere. The role of biological evolution in the history of the atmosphere and projected changes in the future atmosphere are considered.

  12. New Instrumentation for Phase Partitioning

    NASA Technical Reports Server (NTRS)

    Harris, J. M.

    1985-01-01

    Cells and molecules can be purified by partitioning between the two immiscible liquid phases formed by aqueous solutions of poly/ethylene glycol and dextran. Such purification can be more selective, higher yielding, and less destructive to sensitive biological materials than other available techniques. Earth's gravitational field is a hindering factor as it causes sedimentation of particles to be purified and shear-induced particle randomization. The present proposal is directed toward developing new instrumentation for performing phase partitioning both on Earth and in microgravity.

  13. Geochemical characterization of seaplane lagoon sediments, Alameda Naval Air Station

    SciTech Connect

    Bono, A; Carroll, S; Esser, B; Luther, G W; O'Day, P; Randall, S

    1999-08-16

    Our objective in the characterization of sediments from Seaplane Lagoon at the Alameda Naval Air Station (NAS) was to determine the geochemical interactions that control the partitioning of cadmium, chromium, cobalt, copper, lead, mercury, nickel, and zinc between the sediments and the porewaters. Our approach was to collect several cores at the east outfall location of the Seaplane Lagoon. We determined the porewater chemistry by (1) making in situ micro-electrode measurements, (2) extracting porewaters, and (3) modeling geochemical reactions. We determined the sediment chemistry by measuring (1) elemental abundance, (2) mineralogy, and (3) trace-element speciation. This information should help the US Navy determine the long-term hazard of the sediments if they are left in place and the short-term hazard if they are dredged. We did not fully examine the geochemistry of sediments from the West Beach Landfill Wetlands site, because these sediments were distinct from the Seaplane Lagoon sediments. Our initial motivation for studying the Landfill Wetlands site was to determine the trace-element geochemistry in Seaplane Lagoon sediments that had been dredged and then disposed in the Landfill Wetlands. Unfortunately, the location of these dredged sediments is unknown. The cores we sampled were not from the Seaplane Lagoon.

  14. Rectilinear partitioning of irregular data parallel computations

    NASA Technical Reports Server (NTRS)

    Nicol, David M.

    1991-01-01

    New mapping algorithms for domain oriented data-parallel computations, where the workload is distributed irregularly throughout the domain, but exhibits localized communication patterns are described. Researchers consider the problem of partitioning the domain for parallel processing in such a way that the workload on the most heavily loaded processor is minimized, subject to the constraint that the partition be perfectly rectilinear. Rectilinear partitions are useful on architectures that have a fast local mesh network. Discussed here is an improved algorithm for finding the optimal partitioning in one dimension, new algorithms for partitioning in two dimensions, and optimal partitioning in three dimensions. The application of these algorithms to real problems are discussed.

  15. A review of the recent geochemical evolution of Piton de la Fournaise volcano (1927-2010)

    USGS Publications Warehouse

    Pietruszka, Aaron J.; Vlastélic, Ivan

    2015-01-01

    Between 1927 and 2010, more than one hundred eruptions of Piton de la Fournaise produced ~1 km3 of lava, and the volcano’s summit collapsed twice (in 1931 and 2007). These lavas display, respectively, 20 and 65 % of the Sr–Nd and the Pb isotope ranges reported for La Réunion volcanoes over their known eruptive record (3.8 Ma). Variations in major and trace element concentrations and Sr–Pb isotopes do not define a temporal trend at the scale of the century, but display systematic short-term cyclic fluctuations. The positive correlation between 87Sr/86Sr and ratios of trace elements that are more versus less incompatible during partial melting of the mantle (e.g., Nd/Sm, La/Sm) probably results from the sampling of small-scale heterogeneities within the plume source. Changes in the degree of melting and/or crystallization are debated, but these appear ultimately linked to source properties. Lead isotopes do not co-vary with Sr isotopes, in part because of the partitioning of Pb into dense metallic phases that are preferentially sampled during high-flux eruptions. Taken together, Sr–Nd–Pb–Os–Th isotopes do not support contamination of magma with genetically unrelated components, such as the underlying Indian oceanic crust, mantle lithosphere, seawater, or seawater-altered lavas. Yet, in some rare cases (e.g. the 1998 Hudson eruption), the compositional patterns suggest that the parental magma assimilated older volcanic products within the edifice, such as crystal cumulates and/or interstitial differentiated melts. The geochemical fluctuations over the 1927–2010 time period constrain the residence time of magma in the shallow reservoir to 10–30 years and its size to 0.1–0.3 km3. The magma residence time during the course of the long-lived 1998 eruption is estimated to be an order of magnitude shorter, but the reservoir was probably of similar size. Instead, the shorter magma residence for the 1998 eruption was probably due to a higher magma

  16. Monomial Crystals and Partition Crystals

    NASA Astrophysics Data System (ADS)

    Tingley, Peter

    2010-04-01

    Recently Fayers introduced a large family of combinatorial realizations of the fundamental crystal B(Λ0) for ^sln, where the vertices are indexed by certain partitions. He showed that special cases of this construction agree with the Misra-Miwa realization and with Berg's ladder crystal. Here we show that another special case is naturally isomorphic to a realization using Nakajima's monomial crystal.

  17. Set covering, partition and packing

    SciTech Connect

    Hulme, B.L.; Baca, L.S.

    1984-03-01

    Set covering problems are known to be solvable by Boolean algebraic methods. This report shows that set partition and set packing problems can be solved by the same algebraic methods because these problems can be converted into covering problems. Many applications are possible including security patrol assignment which is used as an example.

  18. METAL PARTITIONING IN COMBUSTION PROCESSES

    EPA Science Inventory

    This article summarizes ongoing research efforts at the National Risk Management Research Laboratory of the U.S. Environmental Protection Agency examining [high temperature] metal behavior within combustion environments. The partitioning of non-volatile (Cr and Ni), semi-volatil...

  19. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    SciTech Connect

    Perry, F.V.; Crowe, B.M.

    1992-11-01

    This paper reports that petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers at Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crustal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells is considered remote.

  20. Some trees with partition dimension three

    NASA Astrophysics Data System (ADS)

    Fredlina, Ketut Queena; Baskoro, Edy Tri

    2016-02-01

    The concept of partition dimension of a graph was introduced by Chartrand, E. Salehi and P. Zhang (1998) [2]. Let G(V, E) be a connected graph. For S ⊆ V (G) and v ∈ V (G), define the distance d(v, S) from v to S is min{d(v, x)|x ∈ S}. Let Π be an ordered partition of V (G) and Π = {S1, S2, ..., Sk }. The representation r(v|Π) of vertex v with respect to Π is (d(v, S1), d(v, S2), ..., d(v, Sk)). If the representations of all vertices are distinct, then the partition Π is called a resolving partition of G. The partition dimension of G is the minimum k such that G has a resolving partition with k partition classes. In this paper, we characterize some classes of trees with partition dimension three, namely olive trees, weeds, and centipedes.

  1. Terminology for trace-element partitioning

    SciTech Connect

    Beattie, P. ); Drake, M. ); Jones, J.; McKay, G. ); Leeman, W. ); Longhi, J. ); Nielsen, R. ); Palme, H. ); Shaw, D. ); Takahashi, E. ); Watson, B. )

    1993-04-01

    A self-consistent terminology for partitioning data is presented. Ratios of the concentration of a component in two phases are termed partition coefficients and given the symbol D. Ratios of partition coefficients are termed exchange coefficients and given the symbol K[sub D]. The prefix bulk implies that these coefficients are weighted according to the proportions of coexisting phases. Bulk partition and bulk exchange coefficients are denoted by [bar D] and [ovr K[sub D

  2. Shale to Regolith Evolution: The Controls on Catchment Solute Fluxes

    NASA Astrophysics Data System (ADS)

    Sullivan, Pamela; Goddéris, Yves; Shi, Yuning; Singha, Kamini; Clarke, Brian; Schott, Jacques; Duff, Chritopher; Brantley, Susan

    2014-05-01

    Understanding the factors that control the formation of regolith and the evolution of pore space within regolith as it is moves upward to the surface is of global importance. Unfortunately, both access and high costs have been prohibitive in gathering information about the bedrock-regolith boundary. Recognizing the need for data at depth, the Critical Zone Observatory (CZO) network initiated the "Drill the Ridge" project. The goal of this project is to investigate fresh bedrock at each CZO and then to perform an array of downhole geophysical survey and geochemical analyses to understand regolith formation. In response to this call, several ridgetop boreholes were drilled at the Susquehanna Shale Hills CZO in 2012 and 2013. Here we present the optical televiewer and gamma logs of these boreholes, along with downcore bulk geochemical analysis to shed light on the geochemical and lithological controls on the evolution of the watershed. Observations of catchment hydrology are also being used with estimates of hydrologic parameters to quantify near-surface geologic evolution and geochemical fluxes associated with weathering at depth. To quantify the contribution of weathering fluxes from the mobile regolith, we then link the meteorological forcing from the North American Land Data Assimilation System (NLDAS-2), the fully-coupled land-surface Penn State Integrated Hydrologic Model (Flux-PIHM), and the geochemical box model WITCH. With this cascade of models, solute fluxes for the CZO are being simulated. At depth, the bulk geochemical analysis of ridgetop sediments indicates that pyrite had the deepest depletion front, which was concurrent with the regional water table position. Hydrologic data together with detailed borehole and bulk soil/rock geochemical analysis elucidated an eastern to western progression in lithology across the SSHCZO catchment controls fracture distribution and thus groundwater flow. Where shale and mudstone underlie the eastern portion of

  3. Evapotranspiration partition at sub-daily scale using laser and chamber techniques

    NASA Astrophysics Data System (ADS)

    Wang, L.; Parkes, S. D.; McCabe, M. F.; Azcurra, C.; Wang, J.

    2012-12-01

    Evapotranspiration (ET) partitioning is important for quantifying the water budget and understanding vegetation control on water cycles in various ecosystems. With the development of spectroscopy-based techniques for in-situ isotope measurements, the use of stable isotope based ET partition is rising rapidly. The sub-daily scale ET partition, however, is still rarely seen in the literature. In this study, we conducted an intensive field campaign measuring ET partition using laser-based isotope and chamber techniques in a pasture system between May and June 2012 in eastern Australia. Six soil collars were used, three of which had natural vegetation and the other three were bare soil collars where vegetation was artificially removed. The vegetated and bare soil collars were used to determine the isotopic composition of ET and evaporation, respectively. The isotopic composition of the transpiration flux was determined using a Licor leaf chamber for grasses inside the vegetated collars. The diurnal patterns in isotopic compositions were observed. In the morning, the isotopic compositions were depleted. The isotopic composition of ET became more enriched and leveled off during midday. Similar patterns were found for the isotopic composition of evaporation. Overall the total ET flux over the campaign was dominated by evaporation, though transpiration contributions were high between 10am and 12pm. This study demonstrated the use of chamber-based measurements for direct partitioning of ET at sub-daily scale and showed a rarely observed diurnal pattern of ET partition.

  4. Energy Partition From Various Climate Conditions And Land Use Types

    NASA Astrophysics Data System (ADS)

    Cheng, Chi-Han; Hsu2, Pang-Chi

    2015-04-01

    Investigating how energy partitions and what factors control energy exchange is critical for better understanding the hydrological cycle, boundary layer dynamics, and land -atmosphere coupling. Climate and land use conditions are the two main factors to control energy partitation. However, previous studies discussed energy partition and factors that controlled Bowen ratio (i.e., ratio of sensible heat flux to latent heat flux) in limited land use types and climate conditions. To provide a more comprehensive analysis over various climate and vegetation types, in this study, we studied eleven different land use types in the eight different climate zones within the United State. The results found out that the Mediterranean climate zone with dry summer season, dry arid (desert) climate zone, and the higher latitude area with severe winter would had higher Bowen ratio, lower precipitation and net radiation. In contrast, the humid climate zones had the lower Bowen ratio, higher net radiation and precipitation. Moreover, the higher Bowen ratio usually happened in the winter or early spring seasons. Regarding land conditions, it is found that soil moistures are the key factor to control Bowen ratio in the drier climate areas. Hence, the grassland and closed shrublands sites have higher Bowen ratio than deciduous broadleaf forests and evergreen needle-leaf forests sites' because of shallower root systems that lack access to the full storage of water in the vadose zone. However, in the humid areas, land use factors, such as stomatal resistance and leaf area, would play an important role in changing latent heat and sensible heat. Based on the tight relationships between Bowen ratio and conditions of climate and land use, we suggest that Bowen ratio could be a useful tool for understanding the potential feedbacks of changes in climate and land use to energy partition and exchange.

  5. The geochemical composition of the terrestrial surface (without soils) and comparison with the upper continental crust

    NASA Astrophysics Data System (ADS)

    Hartmann, Jens; Dürr, Hans H.; Moosdorf, Nils; Meybeck, Michel; Kempe, Stephan

    2012-01-01

    The terrestrial surface, the "skin of the earth", is an important interface for global (geochemical) material fluxes between major reservoirs of the Earth system: continental and oceanic crust, ocean and atmosphere. Because of a lack in knowledge of the geochemical composition of the terrestrial surface, it is not well understood how the geochemical evolution of the Earth's crust is impacted by its properties. Therefore, here a first estimate of the geochemical composition of the terrestrial surface is provided, which can be used for further analysis. The geochemical average compositions of distinct lithological classes are calculated based on a literature review and applied to a global lithological map. Comparison with the bulk composition of the upper continental crust shows that the geochemical composition of the terrestrial surface (below the soil horizons) is significantly different from the assumed average of the upper continental crust. Specifically, the elements Ca, S, C, Cl and Mg are enriched at the terrestrial surface, while Na is depleted (and probably K). Analysis of these results provide further evidence that chemical weathering, chemical alteration of minerals in marine settings, biogeochemical processes (e.g. sulphate reduction in sediments and biomineralization) and evaporite deposition are important for the geochemical composition of the terrestrial surface on geological time scales. The movement of significant amounts of carbonate to the terrestrial surface is identified as the major process for observed Ca-differences. Because abrupt and significant changes of the carbonate abundance on the terrestrial surface are likely influencing CO2-consumption rates by chemical weathering on geological time scales and thus the carbon cycle, refined, spatially resolved analysis is suggested. This should include the recognition of the geochemical composition of the shelf areas, now being below sea level.

  6. TAPIR--Finnish national geochemical baseline database.

    PubMed

    Jarva, Jaana; Tarvainen, Timo; Reinikainen, Jussi; Eklund, Mikael

    2010-09-15

    In Finland, a Government Decree on the Assessment of Soil Contamination and Remediation Needs has generated a need for reliable and readily accessible data on geochemical baseline concentrations in Finnish soils. According to the Decree, baseline concentrations, referring both to the natural geological background concentrations and the diffuse anthropogenic input of substances, shall be taken into account in the soil contamination assessment process. This baseline information is provided in a national geochemical baseline database, TAPIR, that is publicly available via the Internet. Geochemical provinces with elevated baseline concentrations were delineated to provide regional geochemical baseline values. The nationwide geochemical datasets were used to divide Finland into geochemical provinces. Several metals (Co, Cr, Cu, Ni, V, and Zn) showed anomalous concentrations in seven regions that were defined as metal provinces. Arsenic did not follow a similar distribution to any other elements, and four arsenic provinces were separately determined. Nationwide geochemical datasets were not available for some other important elements such as Cd and Pb. Although these elements are included in the TAPIR system, their distribution does not necessarily follow the ones pre-defined for metal and arsenic provinces. Regional geochemical baseline values, presented as upper limit of geochemical variation within the region, can be used as trigger values to assess potential soil contamination. Baseline values have also been used to determine upper and lower guideline values that must be taken into account as a tool in basic risk assessment. If regional geochemical baseline values are available, the national guideline values prescribed in the Decree based on ecological risks can be modified accordingly. The national geochemical baseline database provides scientifically sound, easily accessible and generally accepted information on the baseline values, and it can be used in various

  7. Growth rate controlled barium partitioning in calcite and aragonite

    NASA Astrophysics Data System (ADS)

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2016-04-01

    The barium (Ba) content and the Ba/Ca molar ratios in biogenic and abiotic carbonates have been widely used from the scientific community as a geochemical proxy especially in marine and early diagenetic settings. The Ba content of carbonate minerals has been earlier associated to changes in oceanic circulation that may have been caused by upwelling, changes in weathering regimes and river-runoff as well as melt water discharge. The physicochemical controls of Ba ion incorporation in the two most abundant CaCO3 polymorphs found in Earth's surface environments, i.e. calcite and aragonite, have adequately been studied only for calcite. These earlier studies (i.e. [1]) suggest that at increasing growth rate, Ba partitioning in calcite is increasing as well. In contrast, to date the effect of growth rate on the partitioning of Ba in aragonite remains questionable, despite the fact that this mineral phase is the predominant carbonate-forming polymorph in shallow marine environments. To shed light on the mechanisms controlling Ba ion uptake in carbonates in this study we performed steady-state Ba co-precipitation experiments with calcite and aragonite at 25°C. The obtained results for the partitioning of Ba in calcite are in good agreement with those reported earlier by [1], whereas those for aragonite indicate a reduction of Ba partitioning at elevated aragonite growth rates, with the partitioning coefficient value between solid and fluid to be approaching the unity. This finding is good agreement with the formation of a solid solution in the aragonite-witherite system, owing to the isostructural crystallography of the two mineral phases. Moreover, our data set provides new insights that are required for reconstructing the evolution of the Ba content of pristine marine versus diagenetically altered carbonate minerals commonly occurring in marine subfloor settings, as the thermodynamically less stable aragonite will transform to calcite enriched in Ba, whilst affecting

  8. Light Elements in the Core: Constraints from Gallium Partitioning

    NASA Astrophysics Data System (ADS)

    Blanchard, I.; Badro, J.; Siebert, J.; Ryerson, F. J.

    2014-12-01

    The formation of Earth's core has left a compositional imprint on the mantle, depleting and fractionating most of its siderophile (iron-loving) elements. Gallium is a moderately siderophile, hence it should be strongly depleted in the mantle. However, gallium concentration in the mantle matches that of lithophile (silicate-loving) elements having the same volatility. That is to say that either gallium behaves as a lithophile element during core formation, or a large influx of gallium was brought to the Earth after the core had formed. Geochemical evidence does not support the latter hypothesis, as it would require all other lithophile elements with similar volatility to be enriched in the mantle, or for late accretion to be composed of anomalously gallium-rich objects. In order to mitigate this issue, experimental studies have tried to understand how gallium behaves during core segregation by gauging the effects of pressure, temperature and oxygen fugacity on the partitioning of gallium between metal and silicate. None of these parameters provided the first-order change required to match the observation. We investigated the influence of core composition on gallium partitioning. The core in known to contain light-elements (oxygen, silicon sulfur and carbon), and those can change the activity of gallium in the metal, and strongly affect the behavior of gallium during core formation. We performed a series of metal-silicate partitioning experiments (2 GPa, 1673-2073 K) in a piston-cylinder press. We varied the light-element composition of the metal and observed that Si and O have a very strong influence on the activity of gallium, making it more lithophile. We then modeled terrestrial accretion as a continuous process and tested different accretion histories; we can reproduce the mantle concentration of gallium if the core segregates in a deep magma ocean (>40 GPa) and contains large amounts of silicon or oxygen.

  9. Proceedings of the workshop on geochemical modeling

    SciTech Connect

    Not Available

    1986-01-01

    The following collection of papers was presented at a workshop on geochemical modeling that was sponsored by the Office of Civilian Radioactive Waste Management Program at the Lawrence Livermore National Laboratory (LLNL). The LLNL Waste Management Program sponsored this conference based on their belief that geochemical modeling is particularly important to the radioactive waste disposal project because of the need to predict the consequences of long-term water-rock interactions at the proposed repository site. The papers included in this volume represent a subset of the papers presented at the Fallen Leaf Lake Conference and cover a broad spectrum of detail and breadth in a subject that reflects the diverse research interests of the conference participants. These papers provide an insightful look into the current status of geochemical modeling and illustrate how various geochemical modeling codes have been applied to problems of geochemical interest. The emphasis of these papers includes traditional geochemical modeling studies of individual geochemical systems, the mathematical and theoretical development and refinement of new modeling capabilities, and enhancements of data bases on which the computations are based. The papers in this proceedings volume have been organized into the following four areas: Geochemical Model Development, Hydrothermal and Geothermal Systems, Sedimentary and Low Temperature Environments, and Data Base Development. The participants of this symposium and a complete list of the talks presented are listed in the appendices.

  10. A generalized flux function for three-dimensional magnetic reconnection

    SciTech Connect

    Yeates, A. R.; Hornig, G.

    2011-10-15

    The definition and measurement of magnetic reconnection in three-dimensional magnetic fields with multiple reconnection sites is a challenging problem, particularly in fields lacking null points. We propose a generalization of the familiar two-dimensional concept of a magnetic flux function to the case of a three-dimensional field connecting two planar boundaries. In this initial analysis, we require the normal magnetic field to have the same distribution on both boundaries. Using hyperbolic fixed points of the field line mapping, and their global stable and unstable manifolds, we define a unique flux partition of the magnetic field. This partition is more complicated than the corresponding (well-known) construction in a two-dimensional field, owing to the possibility of heteroclinic points and chaotic magnetic regions. Nevertheless, we show how the partition reconnection rate is readily measured with the generalized flux function. We relate our partition reconnection rate to the common definition of three-dimensional reconnection in terms of integrated parallel electric field. An analytical example demonstrates the theory and shows how the flux partition responds to an isolated reconnection event.

  11. Kinetic partitioning mechanism of HDV ribozyme folding

    NASA Astrophysics Data System (ADS)

    Chen, Jiawen; Gong, Sha; Wang, Yujie; Zhang, Wenbing

    2014-01-01

    RNA folding kinetics is directly tied to RNA biological functions. We introduce here a new approach for predicting the folding kinetics of RNA secondary structure with pseudoknots. This approach is based on our previous established helix-based method for predicting the folding kinetics of RNA secondary structure. In this approach, the transition rates for an elementary step: (1) formation, (2) disruption of a helix stem, and (3) helix formation with concomitant partial melting of an incompatible helix, are calculated with the free energy landscape. The folding kinetics of the Hepatitis delta virus (HDV) ribozyme and the mutated sequences are studied with this method. The folding pathways are identified by recursive searching the states with high net flux-in(out) population starting from the native state. The theory results are in good agreement with that of the experiments. The results indicate that the bi-phasic folding kinetics for the wt HDV sequence is ascribed to the kinetic partitioning mechanism: Part of the population will quickly fold to the native state along the fast pathway, while another part of the population will fold along the slow pathway, in which the population is trapped in a non-native state. Single mutation not only changes the folding rate but also the folding pathway.

  12. Kinetic partitioning mechanism of HDV ribozyme folding

    SciTech Connect

    Chen, Jiawen; Gong, Sha; Wang, Yujie; Zhang, Wenbing

    2014-01-14

    RNA folding kinetics is directly tied to RNA biological functions. We introduce here a new approach for predicting the folding kinetics of RNA secondary structure with pseudoknots. This approach is based on our previous established helix-based method for predicting the folding kinetics of RNA secondary structure. In this approach, the transition rates for an elementary step: (1) formation, (2) disruption of a helix stem, and (3) helix formation with concomitant partial melting of an incompatible helix, are calculated with the free energy landscape. The folding kinetics of the Hepatitis delta virus (HDV) ribozyme and the mutated sequences are studied with this method. The folding pathways are identified by recursive searching the states with high net flux-in(out) population starting from the native state. The theory results are in good agreement with that of the experiments. The results indicate that the bi-phasic folding kinetics for the wt HDV sequence is ascribed to the kinetic partitioning mechanism: Part of the population will quickly fold to the native state along the fast pathway, while another part of the population will fold along the slow pathway, in which the population is trapped in a non-native state. Single mutation not only changes the folding rate but also the folding pathway.

  13. Geochemical challenge to earthquake prediction.

    PubMed Central

    Wakita, H

    1996-01-01

    The current status of geochemical and groundwater observations for earthquake prediction in Japan is described. The development of the observations is discussed in relation to the progress of the earthquake prediction program in Japan. Three major findings obtained from our recent studies are outlined. (i) Long-term radon observation data over 18 years at the SKE (Suikoen) well indicate that the anomalous radon change before the 1978 Izu-Oshima-kinkai earthquake can with high probability be attributed to precursory changes. (ii) It is proposed that certain sensitive wells exist which have the potential to detect precursory changes. (iii) The appearance and nonappearance of coseismic radon drops at the KSM (Kashima) well reflect changes in the regional stress state of an observation area. In addition, some preliminary results of chemical changes of groundwater prior to the 1995 Kobe (Hyogo-ken nanbu) earthquake are presented. PMID:11607665

  14. PHREEQC. Geochemical Speciation Mass Transfer

    SciTech Connect

    Parkhurst, D.L.

    1995-01-01

    PHREEQC is designed to model geochemical reactions. Based on an ion association aqueous model, PHREEQC can calculate pH, redox potential, and mass transfer as a function of reaction progress. It can be used to describe geochemical processes for both far-field and near-field performance assessment and to evaluate data acquisition needs and test data. It can also calculate the composition of solutions in equilibrium with multiple phases. The data base, including elements, aqueous species, and mineral phases, is independent of the program and is completely user-definable. PHREEQC requires thermodynamic data for each solid, gaseous, or dissolved chemical species being modeled. The two data bases, PREPHR and DEQPAK7, supplied with PHREEQC are for testing purposes only and should not be applied to real problems without first being carefully examined. The conceptual model embodied in PHREEQC is the ion-association model of Pearson and Noronha. In this model a set of mass action equations are established for each ion pair (and controlling solid phases when making mass transfer calculations) along with a set of mass balance equations for each element considered. These sets of equations are coupled using activity coefficient values for each aqueous species and solved using a continued fraction approach for the mass balances combined with a modified Newton-Raphson technique for all other equations. The activity coefficient expressions in PHREEQC include the extended Debye-Huckel, WATEQ Debye-Huckel, and Davies equations from the original United States Geological Survey version of the program. The auxiliary preprocessor program PHTL, which is derived from EQTL, converts EQ3/6 thermodynamic data to PHREEQC format so that the two programs can be compared. PHREEQC can be used to determine solubility limits on the radionuclides present in the waste form. These solubility constraints may be input to the WAPPA leach model.

  15. Control of sulfur partitioning between primary and secondary metabolism.

    PubMed

    Mugford, Sarah G; Lee, Bok-Rye; Koprivova, Anna; Matthewman, Colette; Kopriva, Stanislav

    2011-01-01

    Sulfur is an essential nutrient for all organisms. Plants take up most sulfur as inorganic sulfate, reduce it and incorporate it into cysteine during primary sulfate assimilation. However, some of the sulfate is partitioned into the secondary metabolism to synthesize a variety of sulfated compounds. The two pathways of sulfate utilization branch after activation of sulfate to adenosine 5'-phosphosulfate (APS). Recently we showed that the enzyme APS kinase limits the availability of activated sulfate for the synthesis of sulfated secondary compounds in Arabidopsis. To further dissect the control of sulfur partitioning between the primary and secondary metabolism, we analysed plants in which activities of enzymes that use APS as a substrate were increased or reduced. Reduction in APS kinase activity led to reduced levels of glucosinolates as a major class of sulfated secondary metabolites and an increased concentration of thiols, products of primary reduction. However, over-expression of this gene does not affect the levels of glucosinolates. Over-expression of APS reductase had no effect on glucosinolate levels but did increase thiol levels, but neither glucosinolate nor thiol levels were affected in mutants lacking the APR2 isoform of this enzyme. Measuring the flux through sulfate assimilation using [(35) S]sulfate confirmed the larger flow of sulfur to primary assimilation when APS kinase activity was reduced. Thus, at least in Arabidopsis, the interplay between APS reductase and APS kinase is important for sulfur partitioning between the primary and secondary metabolism. PMID:21175893

  16. About Thinning Invariant Partition Structures

    NASA Astrophysics Data System (ADS)

    Starr, Shannon; Vermesi, Brigitta; Wei, Ang

    2012-08-01

    Bernoulli- p thinning has been well-studied for point processes. Here we consider three other cases: (1) sequences ( X 1, X 2,…); (2) gaps of such sequences ( X n+1- X 1) n∈ℕ; (3) partition structures. For the first case we characterize the distributions which are simultaneously invariant under Bernoulli- p thinning for all p∈(0,1]. Based on this, we make conjectures for the latter two cases, and provide a potential approach for proof. We explain the relation to spin glasses, which is complementary to important previous work of Aizenman and Ruzmaikina, Arguin, and Shkolnikov.

  17. On some trees having partition dimension four

    NASA Astrophysics Data System (ADS)

    Ida Bagus Kade Puja Arimbawa, K.; Baskoro, Edy Tri

    2016-02-01

    In 1998, G. Chartrand, E. Salehi and P. Zhang introduced the notion of partition dimension of a graph. Since then, the study of this graph parameter has received much attention. A number of results have been obtained to know the values of partition dimensions of various classes of graphs. However, for some particular classes of graphs, finding of their partition dimensions is still not completely solved, for instances a class of general tree. In this paper, we study the properties of trees having partition dimension 4. In particular, we show that, for olive trees O(n), its partition dimension is equal to 4 if and only if 8 ≤ n ≤ 17. We also characterize all centipede trees having partition dimension 4.

  18. Metal-Silicate Partitioning of Tungsten from 10 to 50 GPa

    NASA Technical Reports Server (NTRS)

    Shofner, G. A.; Campbell, A. J.; Danielson, L.; Rahman, Z.; Righter, K.

    2014-01-01

    Geochemical models of core formation are commonly based on core and mantle abundances of siderophile elements that partitioned between silicate and metal in a magma ocean in the early Earth. Tungsten is a moderately siderophile element that may provide constraints on the pressure, temperature, composition, and oxygen fugacity conditions, and on the timing of core formation in the Earth. Previous experimental studies suggest that pressure exerts little to no influence over W metal-silicate partitioning up to 24 GPa, and indicate that the stronger influences are temperature, composition, and oxygen fugacity. However, core formation models based in part on W, predict metal-silicate equilibration pressures outside the available experimental pressure range, requiring extrapolation of parameterized models. Therefore, higher pressure experimental data on W were needed to constrain this important parameter.

  19. Concentration and partitioning of metals in intertidal biofilms: implications for metal bioavailability to shorebirds.

    PubMed

    McCormick, Jodine; St Clair, C Toby; Bendell, L I

    2014-03-01

    We compared zinc, copper and cadmium concentrations and the operationally defined geochemical partitioning of the three metals in sediments enriched with biofilm versus sediments without obvious biofilm present (reference) sampled from five locations within the Fraser River Delta, British Columbia, Canada. Two-way ANOVA's with site and biofilm (enriched or reference) as the two factors were applied to determine if metal concentrations or the partitioning of the metal was dependent on the two factors. Sediment enriched in biofilm contained greater amounts of aqua regia extracted zinc and copper and tended to have greater amounts of reducible cadmium as compared to reference sediments. By contrast, reference sediments had greater concentrations of easily reducible copper suggesting differences in speciation between the two sediment types. Greater concentrations of reducible cadmium within biofilm may provide a route of contaminant exposure to shorebirds whose diet is dependent on biofilm. PMID:24381098

  20. Chemical amplification based on fluid partitioning in an immiscible liquid

    DOEpatents

    Anderson, Brian L.; Colston, Bill W.; Elkin, Christopher J.

    2010-09-28

    A system for nucleic acid amplification of a sample comprises partitioning the sample into partitioned sections and performing PCR on the partitioned sections of the sample. Another embodiment of the invention provides a system for nucleic acid amplification and detection of a sample comprising partitioning the sample into partitioned sections, performing PCR on the partitioned sections of the sample, and detecting and analyzing the partitioned sections of the sample.

  1. Groundwater sources and geochemical processes in a crystalline fault aquifer

    NASA Astrophysics Data System (ADS)

    Roques, Clément; Aquilina, Luc; Bour, Olivier; Maréchal, Jean-Christophe; Dewandel, Benoît; Pauwels, Hélène; Labasque, Thierry; Vergnaud-Ayraud, Virginie; Hochreutener, Rebecca

    2014-11-01

    The origin of water flowing in faults and fractures at great depth is poorly known in crystalline media. This paper describes a field study designed to characterize the geochemical compartmentalization of a deep aquifer system constituted by a graben structure where a permeable fault zone was identified. Analyses of the major chemical elements, trace elements, dissolved gases and stable water isotopes reveal the origin of dissolved components for each permeable domain and provide information on various water sources involved during different seasonal regimes. The geochemical response induced by performing a pumping test in the fault-zone is examined, in order to quantify mixing processes and contribution of different permeable domains to the flow. Reactive processes enhanced by the pumped fluxes are also identified and discussed. The fault zone presents different geochemical responses related to changes in hydraulic regime. They are interpreted as different water sources related to various permeable structures within the aquifer. During the low water regime, results suggest mixing of recent water with a clear contribution of older water of inter-glacial origin (recharge temperature around 7 °C), suggesting the involvement of water trapped in a local low-permeability matrix domain or the contribution of large scale circulation loops. During the high water level period, due to inversion of the hydraulic gradient between the major permeable fault zone and its surrounding domains, modern water predominantly flows down to the deep bedrock and ensures recharge at a local scale within the graben. Pumping in a permeable fault zone induces hydraulic connections with storage-reservoirs. The overlaid regolith domain ensures part of the flow rate for long term pumping (around 20% in the present case). During late-time pumping, orthogonal fluxes coming from the fractured domains surrounding the major fault zone are dominant. Storage in the connected fracture network within the

  2. Displaying multimedia environmental partitioning by triangular diagrams

    SciTech Connect

    Lee, S.C.; Mackay, D.

    1995-11-01

    It is suggested that equilateral triangular diagrams are a useful method of depicting the equilibrium partitioning of organic chemicals among the three primary environmental media of the atmosphere, the hydrosphere, and the organosphere (natural organic matter and biotic lipids and waxes). The technique is useful for grouping chemicals into classes according to their partitioning tendencies, for depicting the incremental effects of substituents such as alkyl groups and chlorine, and for showing how partitioning changes in response to changes in temperature.

  3. Parameters of photosynthetic energy partitioning.

    PubMed

    Lazár, Dušan

    2015-03-01

    Almost every laboratory dealing with plant physiology, photosynthesis research, remote sensing, and plant phenotyping possesses a fluorometer to measure a kind of chlorophyll (Chl) fluorescence induction (FLI). When the slow Chl FLI is measured with addition of saturating pulses and far-red illumination, the so-called quenching analysis followed by the so-called relaxation analysis in darkness can be realized. These measurements then serve for evaluation of the so-called energy partitioning, that is, calculation of quantum yields of photochemical and of different types of non-photochemical processes. Several theories have been suggested for photosynthetic energy partitioning. The current work aims to summarize all the existing theories, namely their equations for the quantum yields, their meaning and their assumptions. In the framework of these theories it is also found here that the well-known NPQ parameter ( [Formula: see text] ; Bilger and Björkman, 1990) equals the ratio of the quantum yield of regulatory light-induced non-photochemical quenching to the quantum yield of constitutive non-regulatory non-photochemical quenching (ΦNPQ/Φf,D). A similar relationship is also found here for the PQ parameter (ΦP/Φf,D). PMID:25569797

  4. Mass partitioning effects in diffusion transport.

    PubMed

    Kojic, Milos; Milosevic, Miljan; Wu, Suhong; Blanco, Elvin; Ferrari, Mauro; Ziemys, Arturas

    2015-08-28

    Frequent mass exchange takes place in a heterogeneous environment among several phases, where mass partitioning may occur at the interface of phases. Analytical and computational methods for diffusion do not usually incorporate molecule partitioning masking the true picture of mass transport. Here we present a computational finite element methodology to calculate diffusion mass transport with a partitioning phenomenon included and the analysis of the effects of partitioning. Our numerical results showed that partitioning controls equilibrated mass distribution as expected from analytical solutions. The experimental validation of mass release from drug-loaded nanoparticles showed that partitioning might even dominate in some cases with respect to diffusion itself. The analysis of diffusion kinetics in the parameter space of partitioning and diffusivity showed that partitioning is an extremely important parameter in systems, where mass diffusivity is fast and that the concentration of nanoparticles can control payload retention inside nanoparticles. The computational and experimental results suggest that partitioning and physiochemical properties of phases play an important, if not crucial, role in diffusion transport and should be included in the studies of mass transport processes. PMID:26204522

  5. Partitioning Autotrophic and Heterotrophic Respiration at Howland Forest

    NASA Astrophysics Data System (ADS)

    Carbone, M. S.; Hollinger, D. Y.; Davidson, E. A.; Hughes, H.; Savage, K. E.

    2014-12-01

    Terrestrial ecosystem respiration is the combined flux of CO2 to the atmosphere from above- and below-ground, plant (autotrophic) and microbial (heterotrophic) sources. Flux measurements alone (e.g., from eddy covariance towers or soil chambers) cannot distinguish the contributions from these sources, which may change seasonally and respond differently to temperature and moisture. The development of improved process-based models that can predict how plants and microbes respond to changing environmental conditions (on seasonal, interannual, or decadal timescales) requires data from field experiments to distinguish among these respiration sources. We tested the viability of partitioning of soil and ecosystem respiration into autotrophic and heterotrophic components with different approaches at the Howland Forest in central Maine, USA. These include an experimental manipulation using the classic root trenching approach, combined with continuous measurements of d13CO2 as well as targeted ∆14CO2 measurements. For the isotopic measurements, we used a two-end member isotope mass balance approach to determine the fraction of soil respiration from autotrophic and heterotrophic sources. Results from these approaches will be compared, and together used in a model-data fusion context to better constrain the partitioning of ecosystem respiration in the ecosystem model, FöBAAR.

  6. Metal-silicate partitioning of Ni and Co in a deep magma ocean

    NASA Astrophysics Data System (ADS)

    Siebert, Julien; Badro, James; Antonangeli, Daniele; Ryerson, Frederick J.

    2012-03-01

    The pattern of siderophile (iron-loving) element abundance in the silicate portion of the Earth is a consequence of metal separation during core formation. The apparent excess of nickel and cobalt in mantle-derived rocks has been attributed to metal-silicate equilibration in a deep terrestrial magma ocean. Based on the extrapolation of phase equilibria and metal-silicate partitioning results obtained at lower pressure (P) and temperature (T), previous estimates of the P-T of equilibration are all greater than 25 GPa and 3000 K. Using the laser-heated diamond anvil cell, we have extended metal-silicate partitioning measurements for Ni and Co to 75 GPa and 4400 K, exceeding the liquidus temperatures for both metal and silicate (basalt or peridotite) and, therefore, achieving thermodynamic conditions directly comparable to those of the magma ocean. The metal-silicate partition coefficients of nickel and cobalt decrease with increasing pressure and reach the values required to yield present mantle concentrations at ~ 50 GPa. At these conditions, silicon and oxygen concentrations measured in the metallic liquid allow to solve the seismically constrained core density deficit. Above 60 GPa, the partition coefficients become too low, resulting in an overabundance of Ni and Co in the silicate mantle. Our data therefore support the paradigm of core formation in a deep mama ocean, providing an upper bound for the depth at which Earth's core may have formed, and explaining the main geophysical (density) and geochemical (excess siderophile elements) observables.

  7. Temporal dynamics of carbon partitioning and rhizodeposition in wheat.

    PubMed

    Dilkes, Nigel B; Jones, David L; Farrar, John

    2004-02-01

    The temporal dynamics of partitioning and rhizodeposition of recent photosynthate in wheat (Triticum aestivum) roots were quantified in situ in solution culture. After a 30-min pulse of (14)CO(2) to a single intact leaf, (14)C activities of individual carbon fluxes in the root, including exudation, respiration, and root content, were measured continuously over the next 20 h concurrently with (14)C efflux from the leaf. Immediately after the end of the (14)CO(2) pulse, (14)C activity was detected in the root, the hydroponic solution, and in root respiration. The rate of (14)C exudation from the root was maximal after 2 to 3 h, and declined to one-third of maximum after a further 5 h. Completion of the rapid phase of (14)C efflux from the leaf coincided with peak (14)C exudation rate. Thus, exudation flux is much more rapidly and dynamically coupled to current photosynthesis than has been appreciated. Careful cross-calibration of (14)C counting methods allowed a dynamic (14)C budget to be constructed for the root. Cumulative (14)C exudation after 20 h was around 3% of (14)C fixed in photosynthesis. Partitioning of photosynthate between shoot and root was manipulated by partial defoliation before applying the (14)CO(2) pulse to the remaining intact leaf. Although the rate of photosynthesis was largely unaffected by partial defoliation, the proportion of new photosynthate subsequently partitioned to and exuded from the root was substantially reduced. This clearly indicates that exudation depends more on the rate of carbon import into the root than on the rate of photosynthesis. PMID:14764904

  8. Evapotranspiration partitioning in a semi-arid African savanna using stable isotopes of water vapor

    NASA Astrophysics Data System (ADS)

    Soderberg, K.; Good, S. P.; O'Connor, M.; King, E. G.; Caylor, K. K.

    2012-04-01

    Evapotranspiration (ET) represents a major flux of water out of semi-arid ecosystems. Thus, understanding ET dynamics is central to the study of African savanna health and productivity. At our study site in central Kenya (Mpala Research Centre), we have been using stable isotopes of water vapor to partition ET into its constituent parts of plant transpiration (T) and soil evaporation (E). This effort includes continuous measurement (1 Hz) of δ2H and δ18O in water vapor using a portable water vapor isotope analyzer mounted on a 22.5 m eddy covariance flux tower. The flux tower has been collecting data since early 2010. The isotopic end-member of δET is calculated using a Keeling Plot approach, whereas δT and δE are measured directly via a leaf chamber and tubing buried in the soil, respectively. Here we report on a two recent sets of measurements for partitioning ET in the Kenya Long-term Exclosure Experiment (KLEE) and a nearby grassland. We combine leaf level measurements of photosynthesis and water use with canopy-scale isotope measurements for ET partitioning. In the KLEE experiment we compare ET partitioning in a 4 ha plot that has only seen cattle grazing for the past 15 years with an adjacent plot that has undergone grazing by both cattle and wild herbivores (antelope, elephants, giraffe). These results are compared with a detailed study of ET in an artificially watered grassland.

  9. Geochemical Modeling Of Aqueous Systems

    Energy Science and Technology Software Center (ESTSC)

    1995-09-07

    EQ3/6 is a software package for geochemical modeling of aqueous systems. This description pertains to version 7.2b. It addresses aqueous speciation, thermodynamic equilibrium, disequilibrium, and chemical kinetics. The major components of the package are EQ3NR, a speciation-solubility code, and EQ6 a reaction path code. EQ3NR is useful for analyzing groundwater chemistry data, calculating solubility limits, and determining whether certain reactions are in states of equilibrium or disequilibrium. It also initializes EQ6 calculations. EQ6 models themore » consequences of reacting an aqueous solution with a specified set of reactants (e.g., minerals or waste forms). It can also model fluid mixing and the effects of changes in temperature. Each of five supporting data files contain both standard state and activity coefficient-related data. Three support the use of the Davies or B-dot equations for the activity coefficients; the other two support the use of Pitzer''s equations. The temperature range of the thermodynamic data on the data files varies from 25 degrees C only to 0-300 degrees C.« less

  10. Collected radiochemical and geochemical procedures

    SciTech Connect

    Kleinberg, J

    1990-05-01

    This revision of LA-1721, 4th Ed., Collected Radiochemical Procedures, reflects the activities of two groups in the Isotope and Nuclear Chemistry Division of the Los Alamos National Laboratory: INC-11, Nuclear and radiochemistry; and INC-7, Isotope Geochemistry. The procedures fall into five categories: I. Separation of Radionuclides from Uranium, Fission-Product Solutions, and Nuclear Debris; II. Separation of Products from Irradiated Targets; III. Preparation of Samples for Mass Spectrometric Analysis; IV. Dissolution Procedures; and V. Geochemical Procedures. With one exception, the first category of procedures is ordered by the positions of the elements in the Periodic Table, with separate parts on the Representative Elements (the A groups); the d-Transition Elements (the B groups and the Transition Triads); and the Lanthanides (Rare Earths) and Actinides (the 4f- and 5f-Transition Elements). The members of Group IIIB-- scandium, yttrium, and lanthanum--are included with the lanthanides, elements they resemble closely in chemistry and with which they occur in nature. The procedures dealing with the isolation of products from irradiated targets are arranged by target element.

  11. Geochemical methods of prospecting for hydrocarbons

    SciTech Connect

    Duchscherer, W. Jr.

    1980-12-01

    Because the commonly used reflection-seismograph exploration technique misses many marginal low-relief structural prospects and regardless of its electronic computer sophistication, overlooks almost all stratigraphic traps, the hydrocarbon exploration industry should take a look at geochemical prospecting methods, which detect geochemical anomalies in the near-surface soils by measuring the thermal dissociation of the soil carbonates that are found overlying hydrocarbon accumulations. To promote understanding of such prospecting techniques, Geochemical Surveys reviews the methods used, the soil-alteration patterns, the lateral and vertical migration of hydrocarbon gases, the halo phenomenon (a ring or annual anomaly), the geochemical modification of sediments, and the data-interpretation and exploration procedures involved in a carbonate ..delta.. C analysis, which measures the residual, stable, cumulative effect of hydrocarbon migration.

  12. The geochemical transformation of soils by agriculture and its dependence on soil erosion: An application of the geochemical mass balance approach.

    PubMed

    Yoo, Kyungsoo; Fisher, Beth; Ji, Junling; Aufdenkampe, Anthony; Klaminder, Jonatan

    2015-07-15

    Agricultural activities alter elemental budgets of soils and thus their long-term geochemical development and suitability for food production. This study examined the utility of a geochemical mass balance approach that has been frequently used for understanding geochemical aspect of soil formation, but has not previously been applied to agricultural settings. Protected forest served as a reference to quantify the cumulative fluxes of Ca, P, K, and Pb at a nearby tilled crop land. This comparison was made at two sites with contrasting erosional environments: relatively flat Coastal Plain in Delaware vs. hilly Piedmont in Pennsylvania. Mass balance calculations suggested that liming not only replenished the Ca lost prior to agricultural practice but also added substantial surplus at both sites. At the relatively slowly eroding Coastal Plain site, the agricultural soil exhibited enrichment of P and less depletion of K, while both elements were depleted in the forest soil. At the rapidly eroding Piedmont site, erosion inhibited P enrichment. In similar, agricultural Pb contamination appeared to have resulted in Pb enrichment in the relatively slowly eroding Coastal Plain agricultural soil, while not in the rapidly eroding Piedmont soils. We conclude that agricultural practices transform soils into a new geochemical state where current levels of Ca, P, and Pb exceed those provided by the local soil minerals, but such impacts are significantly offset by soil erosion. PMID:25847176

  13. The National Geochemical Survey; database and documentation

    USGS Publications Warehouse

    U.S. Geological Survey

    2004-01-01

    The USGS, in collaboration with other federal and state government agencies, industry, and academia, is conducting the National Geochemical Survey (NGS) to produce a body of geochemical data for the United States based primarily on stream sediments, analyzed using a consistent set of methods. These data will compose a complete, national-scale geochemical coverage of the US, and will enable construction of geochemical maps, refine estimates of baseline concentrations of chemical elements in the sampled media, and provide context for a wide variety of studies in the geological and environmental sciences. The goal of the NGS is to analyze at least one stream-sediment sample in every 289 km2 area by a single set of analytical methods across the entire nation, with other solid sample media substituted where necessary. The NGS incorporates geochemical data from a variety of sources, including existing analyses in USGS databases, reanalyses of samples in USGS archives, and analyses of newly collected samples. At the present time, the NGS includes data covering ~71% of the land area of the US, including samples in all 50 states. This version of the online report provides complete access to NGS data, describes the history of the project, the methodology used, and presents preliminary geochemical maps for all analyzed elements. Future editions of this and other related reports will include the results of analysis of variance studies, as well as interpretive products related to the NGS data.

  14. Geochemical characteristics of crustal anatexis during the formation of migmatite at the Southern Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Zeng, Lingsen; Saleeby, Jason B.; Ducea, Mihai

    2005-11-01

    We provide data on the geochemical and isotopic consequences of nonmodal partial melting of a thick Jurassic pelite unit at mid-crustal levels that produced a migmatite complex in conjunction with the intrusion of part of the southern Sierra Nevada batholith at ca. 100 Ma. Field relations suggest that this pelitic migmatite formed and then abruptly solidified prior to substantial mobilization and escape of its melt products. Hence, this area yields insights into potential mid-crustal level contributions of crustal components into Cordilleran-type batholiths. Major and trace-element analyses in addition to field and petrographic data demonstrate that leucosomes are products of partial melting of the pelitic protolith host. Compared with the metapelites, leucosomes have higher Sr and lower Sm concentrations and lower Rb/Sr ratios. The initial 87Sr/86Sr ratios of leucosomes range from 0.7124 to 0.7247, similar to those of the metapelite protoliths (0.7125-0.7221). However, the leucosomes have a much wider range of initial ɛNd values, which range from -6.0 to -11.0, as compared to -8.7 to -11.3 for the metapelites. Sr and Nd isotopic compositions of the leucosomes, migmatites, and metapelites suggest disequilibrium partial melting of the metapelite protolith. Based on their Sr, Nd, and other trace-element characteristics, two groups of leucosomes have been identified. Group A leucosomes have relatively high Rb, Pb, Ba, and K2O contents, Rb/Sr ratios (0.15fluxed melting of quartz + feldspar assemblage with minor involvement of muscovite. Breakdown of quartz and plagioclase with minor contributions from muscovite resulted in low Rb/Sr ratios characterizing both group A and

  15. Assimilate partitioning during reproductive growth

    SciTech Connect

    Finazzo, S.F.; Davenport, T.L.

    1987-04-01

    Leaves having various phyllotactic relationships to fruitlets were labeled for 1 hour with 10/sub r/Ci of /sup 14/CO/sub 2/. Fruitlets were also labeled. Fruitlets did fix /sup 14/CO/sub 2/. Translocation of radioactivity from the peel into the fruit occurred slowly and to a limited extent. No evidence of translocation out of the fruitlets was observed. Assimilate partitioning in avocado was strongly influenced by phyllotaxy. If a fruit and the labeled leaf had the same phyllotaxy then greater than 95% of the radiolabel was present in this fruit. When the fruit did not have the same phyllotaxy as the labeled leaf, the radiolabel distribution was skewed with 70% of the label going to a single adjacent position. Avocado fruitlets exhibit uniform labeling throughout a particular tissue. In avocado, assimilates preferentially move from leaves to fruits with the same phyllotaxy.

  16. Building Ecology and Partition Design. Technical Bulletin.

    ERIC Educational Resources Information Center

    Maryland State Dept. of Education, Baltimore.

    This bulletin is intended as a resource for school system facility planners and architects who design schools. Ways in which decision makers can incorporate environmental concerns in the design of school buildings are detailed. Focus is on the design of interior partition systems. Partition systems in schools serve several purposes; they define…

  17. A Partitioning Technique for Defining Instructional Groups.

    ERIC Educational Resources Information Center

    Baker, Frank B.; Hubert, Lawrence J.

    1979-01-01

    A technique is presented for partitioning N students into K groups of fixed sizes using a given measure of proximity for all student pairs. The measure of proximity is typically calculated from a set of variables and constitutes the data needed for a criterion of partition "fit." (Author)

  18. Geochemical processes at mineral surfaces

    SciTech Connect

    Davis, J.A.; Hayes, K.F.

    1986-01-01

    This volume includes 32 papers which were presented at a symposium on geochemical processes at mineral-water interfaces in 1985 and which bring to bear on this area a very wide range of expertise. The discontinuities in properties which occur at the mineral-water interface have profound effects on the movement of naturally occurring ions. Weathering and precipitation processes control the concentrations and speciation of ions in natural waters and the movements of these within the hydrosphere; both classes of processes take place at mineral-water interfaces. After an introductory overview, the book is divided into seven major sections, each dealing with one of the aspects of the processes occurring at the mineral-water interface. Five papers deal with the physical properties of the mineral-water interface; these represent a well-balanced mix of experimental and theoretical (mathematical modeling) work. Adsorption phenomena are dealt with in another five papers; these are largely experimental in character. Ion-exchange processes are discussed in four papers, one of which addresses the use of relaxation methods to study ion exchange kinetics at the microscopic level. Spectroscopic techniques (including electron-spin resonance and Moessbauer spectroscopy) are utilized in four papers. Chemical reactions, mainly redox processes, at mineral-water interfaces are treated in four papers, one of which deals with non-biological organic reactions. Solid-solution formation and equilibria are the subjects of another set of four articles, and the last group of papers deals with the processes involved in precipitation and dissolution, including weathering.

  19. Geochemical Origin of Biological Molecules

    NASA Astrophysics Data System (ADS)

    Bassez, Marie-Paule

    2013-04-01

    A model for the geochemical origin of biological molecules is presented. Rocks such as peridotites and basalts, which contain ferromagnesian minerals, evolve in the presence of water. Their hydrolysis is an exothermic reaction which generates heat and a release of H2 and of minerals with modified structures. The hydrogen reacts with the CO2 embedded inside the rock or with the CO2 of the environment to form CO in an hydrothermal process. With the N2 of the environment, and with an activation source arising from cosmic radiation, ferromagnesian rocks might evolve towards the abiotic formation of biological molecules, such as peptide like macromolecules which produce amino acids after acid hydrolysis. The reactions concerned are described. The production of hydrothermal CO is discussed in geological sites containing ferromagnesian silicate minerals and the low intensity of the Earth's magnetic field during Paleoarchaean Era is also discussed. It is concluded that excitation sources arising from cosmic radiation were much more abundant during Paleoarchaean Era and that macromolecular structures of biological relevance might consequently form during Archaean Eon, as a product of the chemical evolution of the rocks and of their mineral contents. This synthesis of abiotically formed biological molecules is consecutively discussed for meteorites and other planets such as Mars. This model for the geochemical origin of biological molecules has first been proposed in 2008 in the context of reactions involving catalysers such as kaolinite [Bassez 2008a] and then presented in conferences and articles [Bassez 2008b, 2009, 2012; Bassez et al. 2009a to 2012b]. BASSEZ M.P. 2008a Synthèse prébiotique dans les conditions hydrothermales, CNRIUT'08, Lyon 29-30/05/2008, Conf. and open access article:http://liris.cnrs.fr/~cnriut08/actes/ 29 mai 11h-12h40. BASSEZ M.P. 2008b Prebiotic synthesis under hydrothermal conditions, ISSOL'08, P2-6, Firenze-Italy, 24-29/08/2008. Poster at the

  20. Purification of biomaterials by phase partitioning

    NASA Technical Reports Server (NTRS)

    Harris, J. M.

    1984-01-01

    A technique which is particularly suited to microgravity environments and which is potentially more powerful than electrophoresis is phase partitioning. Phase partitioning is purification by partitioning between the two immiscible aqueous layers formed by solution of the polymers poly(ethylene glycol) and dextran in water. This technique proved to be very useful for separations in one-g but is limited for cells because the cells are more dense than the phase solutions thus tend to sediment to the bottom of the container before reaching equilibrium with the preferred phase. There are three phases to work in this area: synthesis of new polymers for affinity phase partitioning; development of automated apparatus for ground-based separations; and design of apparatus for performing simple phase partitioning space experiments, including examination of mechanisms for separating phases in the absence of gravity.

  1. Bicriterion methods for partitioning dissimilarity matrices.

    PubMed

    Brusco, Michael J; Cradit, J Dennis

    2005-11-01

    Partitioning indices associated with the within-cluster sums of pairwise dissimilarities often exhibit a systematic bias towards clusters of a particular size, whereas minimization of the partition diameter (i.e. the maximum dissimilarity element across all pairs of objects within the same cluster) does not typically have this problem. However, when the partition-diameter criterion is used, there is often a myriad of alternative optimal solutions that can vary significantly with respect to their substantive interpretation. We propose a bicriterion partitioning approach that considers both diameter and within-cluster sums in the optimization problem and facilitates selection from among the alternative optima. We developed several MATLAB-based exchange algorithms that rapidly provide excellent solutions to bicriterion partitioning problems. These algorithms were evaluated using synthetic data sets, as well as an empirical dissimilarity matrix. PMID:16293203

  2. Cell partition in two phase polymer systems

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.

    1979-01-01

    Aqueous phase-separated polymer solutions can be used as support media for the partition of biological macromolecules, organelles and cells. Cell separations using the technique have proven to be extremely sensitive to cell surface properties but application of the systems are limited to cells or aggregates which do not significantly while the phases are settling. Partition in zero g in principle removes this limitation but an external driving force must be applied to induce the phases to separate since their density difference disappears. We have recently shown that an applied electric field can supply the necessary driving force. We are proposing to utilize the NASA FES to study field-driven phase separation and cell partition on the ground and in zero g to help define the separation/partition process, with the ultimate goal being to develop partition as a zero g cell separation technique.

  3. Modeling energy and mass fluxes from prairie canopies

    NASA Technical Reports Server (NTRS)

    Norman, John M.

    1992-01-01

    The main emphasis of this research project is on partitioning of mass and energy fluxes between vegetation and soil at the FIFE site, preparation of data from the FIFE Information System for an international thermal data set comparison, and studying the relation between surface temperatures observed from satellites and in situ measurements of surface temperature.

  4. Upscaling and downscaling of land surface fluxes with surface temperature

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land surface temperature (LST) is a key surface boundary condition that is significantly correlated to surface flux partitioning between latent and sensible heat. The spatial and temporal variation in LST is driven by radiation, wind, vegetation cover and roughness as well as soil moisture status ...

  5. Dense Subgraph Partition of Positive Hypergraphs.

    PubMed

    Liu, Hairong; Latecki, Longin Jan; Yan, Shuicheng

    2015-03-01

    In this paper, we present a novel partition framework, called dense subgraph partition (DSP), to automatically, precisely and efficiently decompose a positive hypergraph into dense subgraphs. A positive hypergraph is a graph or hypergraph whose edges, except self-loops, have positive weights. We first define the concepts of core subgraph, conditional core subgraph, and disjoint partition of a conditional core subgraph, then define DSP based on them. The result of DSP is an ordered list of dense subgraphs with decreasing densities, which uncovers all underlying clusters, as well as outliers. A divide-and-conquer algorithm, called min-partition evolution, is proposed to efficiently compute the partition. DSP has many appealing properties. First, it is a nonparametric partition and it reveals all meaningful clusters in a bottom-up way. Second, it has an exact and efficient solution, called min-partition evolution algorithm. The min-partition evolution algorithm is a divide-and-conquer algorithm, thus time-efficient and memory-friendly, and suitable for parallel processing. Third, it is a unified partition framework for a broad range of graphs and hypergraphs. We also establish its relationship with the densest k-subgraph problem (DkS), an NP-hard but fundamental problem in graph theory, and prove that DSP gives precise solutions to DkS for all kin a graph-dependent set, called critical k-set. To our best knowledge, this is a strong result which has not been reported before. Moreover, as our experimental results show, for sparse graphs, especially web graphs, the size of critical k-set is close to the number of vertices in the graph. We test the proposed partition framework on various tasks, and the experimental results clearly illustrate its advantages. PMID:26353260

  6. Field-Scale Partitioning of Ecosystem Respiration Components Suggests Carbon Stabilization in a Bioenergy Grass Ecosystem

    NASA Astrophysics Data System (ADS)

    Black, C. K.; Miller, J. N.; Masters, M. D.; Bernacchi, C.; DeLucia, E. H.

    2014-12-01

    Annually-harvested agroecosystems have the potential to be net carbon sinks only if their root systems allocate sufficient carbon belowground and if this carbon is then retained as stable soil organic matter. Soil respiration measurements are the most common approach to evaluate the stability of soil carbon at experimental time scales, but valid inferences require the partitioning of soil respiration into root-derived (current-year C) and heterotrophic (older C) components. This partitioning is challenging at the field scale because roots and soil are intricately mixed and physical separation in impossible without disturbing the fluxes to be measured. To partition soil flux and estimate the C sink potential of bioenergy crops, we used the carbon isotope difference between C3 and C4 plant species to quantify respiration from roots of three C4 grasses (maize, Miscanthus, and switchgrass) grown in a site with a mixed cropping history where respiration from the breakdown of old soil carbon has a mixed C3-C4 signature. We used a Keeling plot approach to partition fluxes both at the soil surface using soil chambers and from the whole field using continuous flow sampling of air within and above the canopy. Although soil respiration rates from perennial grasses were higher than those from maize, the isotopic signature of respired carbon indicated that the fraction of soil CO2 flux attributable to current-year vegetation was 1.5 (switchgrass) to 2 (Miscanthus) times greater in perennials than that from maize, indicating that soil CO2 flux came mostly from roots and turnover of soil organic matter was reduced in the perennial crops. This reduction in soil heterotrophic respiration, combined with the much greater quantities of C allocated belowground by perennial grasses compared to maize, suggests that perennial grasses grown as bioenergy crops may be able to provide an additional climate benefit by acting as carbon sinks in addition to reducing fossil fuel consumption.

  7. The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates

    NASA Astrophysics Data System (ADS)

    Atchley, Adam L.; Navarre-Sitchler, Alexis K.; Maxwell, Reed M.

    2014-09-01

    The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb2 +) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb2 + concentrations within the plume. Dissimilarities between ensemble Pb2 + concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb2 + concentrations are the same for all three

  8. The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates.

    PubMed

    Atchley, Adam L; Navarre-Sitchler, Alexis K; Maxwell, Reed M

    2014-09-01

    The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb(2+)) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb(2+) concentrations within the plume. Dissimilarities between ensemble Pb(2+) concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb(2+) concentrations are the same for all

  9. Selecting optimal partitioning schemes for phylogenomic datasets

    PubMed Central

    2014-01-01

    Background Partitioning involves estimating independent models of molecular evolution for different subsets of sites in a sequence alignment, and has been shown to improve phylogenetic inference. Current methods for estimating best-fit partitioning schemes, however, are only computationally feasible with datasets of fewer than 100 loci. This is a problem because datasets with thousands of loci are increasingly common in phylogenetics. Methods We develop two novel methods for estimating best-fit partitioning schemes on large phylogenomic datasets: strict and relaxed hierarchical clustering. These methods use information from the underlying data to cluster together similar subsets of sites in an alignment, and build on clustering approaches that have been proposed elsewhere. Results We compare the performance of our methods to each other, and to existing methods for selecting partitioning schemes. We demonstrate that while strict hierarchical clustering has the best computational efficiency on very large datasets, relaxed hierarchical clustering provides scalable efficiency and returns dramatically better partitioning schemes as assessed by common criteria such as AICc and BIC scores. Conclusions These two methods provide the best current approaches to inferring partitioning schemes for very large datasets. We provide free open-source implementations of the methods in the PartitionFinder software. We hope that the use of these methods will help to improve the inferences made from large phylogenomic datasets. PMID:24742000

  10. Accretion and core formation: constraints from metal-silicate partitioning.

    PubMed

    Wood, Bernard J

    2008-11-28

    Experimental metal-silicate partitioning data for Ni, Co, V, Cr, Nb, Mn, Si and W were used to investigate the geochemical consequences of a range of models for accretion and core formation on Earth. The starting assumptions were chondritic ratios of refractory elements in the Earth and the segregation of metal at the bottom of a magma ocean, which deepened as the planet grew and which had, at its base, a temperature close to the liquidus of the silicate. The models examined were as follows. (i) Continuous segregation from a mantle which is chemically homogeneous and which has a fixed oxidation state, corresponding to 6.26 per cent oxidized Fe. Although Ni, Co and W partitioning is consistent with chondritic ratios, the current V content of the silicate Earth cannot be reconciled with core segregation under these conditions of fixed oxidation state. (ii) Continuous segregation from a mantle which is chemically homogeneous but in which the Earth became more oxidized as it grew. In this case, the Ni, Co, W, V, Cr and Nb contents of core and mantle are easily matched to those calculated from the chondritic ratios of refractory elements. The magma ocean is calculated to maintain a thickness approximately 35 per cent of the depth to the core-mantle boundary in the accreting Earth, yielding a maximum pressure of 44GPa. This model yields a Si content of the core of 5.7 per cent, in good agreement with cosmochemical estimates and with recent isotopic data. (iii) Continuous segregation from a mantle which is not homogeneous and in which the core equilibrates with a restricted volume of mantle at the base of the magma ocean. This is found to increase depth of the magma ocean by approximately 50 per cent. All of the other elements (except Mn) have partitioning consistent with chondritic abundances in the Earth, provided the Earth became, as before, progressively oxidized during accretion. (iv) Continuous segregation of metal from a crystal-melt mush. In this case, pressures

  11. Partitioning of Si and platinum group elements between liquid and solid Fe-Si alloys

    NASA Astrophysics Data System (ADS)

    Morard, G.; Siebert, J.; Badro, J.

    2014-05-01

    Crystallization of the Earth's inner core fractionates major and minor elements between the solid and liquid metal, leaving physical and geochemical imprints on the Earth's core. For example, the density jump observed at the Inner Core Boundary (ICB) is related to the preferential partitioning of lighter elements in the liquid outer core. The fractionation of Os, Re and Pt between liquid and solid during inner core crystallization has been invoked as a process that explains the observed Os isotopic signature of mantle plume-derived lavas (Brandon et al., 1998; Brandon and Walker, 2005) in terms of core-mantle interaction. In this article we measured partitioning of Si, Os, Re and Pt between liquid and solid metal. Isobaric (2 GPa) experiments were conducted in a piston-cylinder press at temperatures between 1250 °C and 1600 °C in which an imposed thermal gradient through the sample provided solid-liquid coexistence in the Fe-Si system. We determined the narrow melting loop in the Fe-Si system using Si partitioning values and showed that order-disorder transition in the Fe-Si solid phases can have a large effect on Si partitioning. We also found constant partition coefficients (DOs, DPt, DRe) between liquid and solid metal, for Si concentrations ranging from 2 to 12 wt%. The compact structure of Fe-Si liquid alloys is compatible with incorporation of Si and platinum group elements (PGEs) elements precluding solid-liquid fractionation. Such phase diagram properties are relevant for other light elements such as S and C at high pressure and is not consistent with inter-elemental fractionation of PGEs during metal crystallization at Earth's inner core conditions. We therefore propose that the peculiar Os isotopic signature observed in plume-derived lavas is more likely explained by mantle source heterogeneity (Meibom et al., 2002; Baker and Krogh Jensen, 2004; Luguet et al., 2008).

  12. Partitioning of regular computation on multiprocessor systems

    NASA Technical Reports Server (NTRS)

    Lee, Fung Fung

    1988-01-01

    Problem partitioning of regular computation over two dimensional meshes on multiprocessor systems is examined. The regular computation model considered involves repetitive evaluation of values at each mesh point with local communication. The computational workload and the communication pattern are the same at each mesh point. The regular computation model arises in numerical solutions of partial differential equations and simulations of cellular automata. Given a communication pattern, a systematic way to generate a family of partitions is presented. The influence of various partitioning schemes on performance is compared on the basis of computation to communication ratio.

  13. Convex Regression with Interpretable Sharp Partitions

    PubMed Central

    Petersen, Ashley; Simon, Noah; Witten, Daniela

    2016-01-01

    We consider the problem of predicting an outcome variable on the basis of a small number of covariates, using an interpretable yet non-additive model. We propose convex regression with interpretable sharp partitions (CRISP) for this task. CRISP partitions the covariate space into blocks in a data-adaptive way, and fits a mean model within each block. Unlike other partitioning methods, CRISP is fit using a non-greedy approach by solving a convex optimization problem, resulting in low-variance fits. We explore the properties of CRISP, and evaluate its performance in a simulation study and on a housing price data set.

  14. Quantum Dilogarithms and Partition q-Series

    NASA Astrophysics Data System (ADS)

    Kato, Akishi; Terashima, Yuji

    2015-08-01

    In our previous work (Kato and Terashima, Commun Math Phys. arXiv:1403.6569, 2014), we introduced the partition q-series for mutation loop γ—a loop in exchange quiver. In this paper, we show that for a certain class of mutation sequences, called reddening sequences, the graded version of partition q-series essentially coincides with the ordered product of quantum dilogarithm associated with each mutation; the partition q-series provides a state-sum description of combinatorial Donaldson-Thomas invariants introduced by Keller.

  15. How pervasive is the Hirshfeld partitioning?

    SciTech Connect

    Heidar-Zadeh, Farnaz; Ayers, Paul W.

    2015-01-28

    One can partition the molecular density into its atomic contributions by minimizing the divergence of the atom-in-molecule densities from their corresponding reference pro-atomic densities, subject to the constraint that the sum of the atom-in-molecule densities is the total molecular density. We expose conditions on the divergence measure that are necessary, and sufficient, to recover the popular Hirshfeld partitioning. Specifically, among all local measures of the divergence between two probability distribution functions, the Hirshfeld partitioning is obtained only for f-divergences.

  16. Partitioning technique for open systems

    NASA Astrophysics Data System (ADS)

    Brändas, Erkki J.

    2010-11-01

    The focus of the present contribution is essentially confined to three research areas carried out during the author's turns as visiting (assistant, associate and full) professor at the University of Florida's Quantum Theory Project, QTP. The first two topics relate to perturbation theory and spectral theory for self-adjoint operators in Hilbert space. The third subject concerns analytic extensions to non-self-adjoint problems, where particular consequences of the occurrence of continuous energy spectra are measured. In these studies general partitioning methods serve as general cover for perturbation-, variational- and general matrix theory. In addition we follow up associated inferences for the time dependent problem as well as recent results and conclusions of a rather general yet surprising character. Although the author spent most of his times at QTP during visits in the 1970s and 1980s, collaborations with department members and shorter stays continued through later decades. Nevertheless the impact must be somewhat fragmentary, yet it is hoped that the present account is sufficiently self-contained to be realistic and constructive.

  17. Lipid partitioning during cardiac stress.

    PubMed

    Kolwicz, Stephen C

    2016-10-01

    It is well documented that fatty acids serve as the primary fuel substrate for the contracting myocardium. However, extensive research has identified significant changes in the myocardial oxidation of fatty acids during acute or chronic cardiac stress. As a result, the redistribution or partitioning of fatty acids due to metabolic derangements could have biological implications. Fatty acids can be stored as triacylglycerols, serve as critical components for biosynthesis of phospholipid membranes, and form the potent signaling molecules, diacylglycerol and ceramides. Therefore, the contribution of lipid metabolism to health and disease is more intricate than a balance of uptake and oxidation. In this review, the available data regarding alterations that occur in endogenous cardiac lipid pathways during the pathological stressors of ischemia-reperfusion and pathological hypertrophy/heart failure are highlighted. In addition, changes in endogenous lipids observed in exercise training models are presented for comparison. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk. PMID:27040509

  18. HPAM: Hirshfeld Partitioned Atomic Multipoles

    PubMed Central

    Elking, Dennis M.; Perera, Lalith; Pedersen, Lee G.

    2011-01-01

    An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank lmax on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from lmax = 0 (atomic charges) to lmax = 4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank lmax are shown to exactly reproduce ab initio molecular multipole moments of rank L for L ≤ lmax. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only (lmax = 0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used. PMID:22140274

  19. REE Partitioning in Lunar Minerals

    NASA Technical Reports Server (NTRS)

    Rapp, J. F.; Lapen, T. J.; Draper, D. S.

    2015-01-01

    Rare earth elements (REE) are an extremely useful tool in modeling lunar magmatic processes. Here we present the first experimentally derived plagioclase/melt partition coefficients in lunar compositions covering the entire suite of REE. Positive europium anomalies are ubiquitous in the plagioclase-rich rocks of the lunar highlands, and complementary negative Eu anomalies are found in most lunar basalts. These features are taken as evidence of a large-scale differentiation event, with crystallization of a global-scale lunar magma ocean (LMO) resulting in a plagioclase flotation crust and a mafic lunar interior from which mare basalts were subsequently derived. However, the extent of the Eu anomaly in lunar rocks is variable. Fagan and Neal [1] reported highly anorthitic plagioclase grains in lunar impact melt rock 60635,19 that displayed negative Eu anomalies as well as the more usual positive anomalies. Indeed some grains in the sample are reported to display both positive and negative anomalies. Judging from cathodoluminescence images, these anomalies do not appear to be associated with crystal overgrowths or zones.

  20. Energy partitioning schemes: a dilemma.

    PubMed

    Mayer, I

    2007-01-01

    Two closely related energy partitioning schemes, in which the total energy is presented as a sum of atomic and diatomic contributions by using the "atomic decomposition of identity", are compared on the example of N,N-dimethylformamide, a simple but chemically rich molecule. Both schemes account for different intramolecular interactions, for instance they identify the weak C-H...O intramolecular interactions, but give completely different numbers. (The energy decomposition scheme based on the virial theorem is also considered.) The comparison of the two schemes resulted in a dilemma which is especially striking when these schemes are applied for molecules distorted from their equilibrium structures: one either gets numbers which are "on the chemical scale" and have quite appealing values at the equilibrium molecular geometries, but exhibiting a counter-intuitive distance dependence (the two-center energy components increase in absolute value with the increase of the interatomic distances)--or numbers with too large absolute values but "correct" distance behaviour. The problem is connected with the quick decay of the diatomic kinetic energy components. PMID:17328441

  1. Broad climatological variation of surface energy balance partitioning across land and ocean predicted from the maximum power limit

    NASA Astrophysics Data System (ADS)

    Dhara, Chirag; Renner, Maik; Kleidon, Axel

    2016-07-01

    Longwave radiation and turbulent heat fluxes are the mechanisms by which the Earth's surface transfers heat into the atmosphere, thus affecting the surface temperature. However, the energy partitioning between the radiative and turbulent components is poorly constrained by energy and mass balances alone. We use a simple energy balance model with the thermodynamic limit of maximum power as an additional constraint to determine this partitioning. Despite discrepancies over tropical oceans, we find that the broad variation of heat fluxes and surface temperatures in the ERA-Interim reanalyzed observations can be recovered from this approach. The estimates depend considerably on the formulation of longwave radiative transfer, and a spatially uniform offset is related to the assumed cold temperature sink at which the heat engine operates. Our results suggest that the steady state surface energy partitioning may reflect the maximum power constraint.

  2. New geochemical investigations in Platanares and Azacualpa geothermal sites (Honduras)

    NASA Astrophysics Data System (ADS)

    Barberi, Franco; Carapezza, Maria Luisa; Cioni, Roberto; Lelli, Matteo; Menichini, Matia; Ranaldi, Massimo; Ricci, Tullio; Tarchini, Luca

    2013-05-01

    Platanares and Azacualpa geothermal sites of Honduras are located in an inner part of the Caribbean Plate far from the active volcanic front of Central America. Here geology indicates that there are not the conditions for the occurrence of shallow magmatic heat sources for high-enthalpy geothermal resources. Geothermal perspectives are related to the possibility of a deep circulation of meteoric water along faults and the storage of the heated fluid in fractured permeable reservoirs. Geochemical geothermometers indicate a temperature for the deeper part of the geothermal reservoir close to 200 °C for Platanares and of 150-170 °C for Azacualpa. Calcite scaling, with subordinate silica deposition has to be expected in both sites. CO2 soil flux investigations have been carried out in both areas and reveal the presence of positive anomalies likely corresponding to the presence at depth of fractured degassing geothermal reservoirs. Compared with the geothermal areas of Central Italy whose reservoirs are hosted in carbonate rocks, e.g. Latera (Chiodini et al., 2007), the CO2 soil flux measured in Honduras is significantly lower (mean of 17 g/m2day at Platanares and of 163 g/m2day at Azacualpa) probably because of the dominant silicate nature of the deep reservoirs.

  3. Combined thermodynamic-geochemical modeling in metamorphic geology: Boron as tracer of fluid-rock interaction

    NASA Astrophysics Data System (ADS)

    Konrad-Schmolke, Matthias; Halama, Ralf

    2014-11-01

    Quantitative geochemical modeling is today applied in a variety of geological environments from the petrogenesis of igneous rocks to radioactive waste disposal. In addition, the development of thermodynamic databases and computer programs to calculate equilibrium phase diagrams has greatly advanced our ability to model geodynamic processes. Combined with experimental data on elemental partitioning and isotopic fractionation, thermodynamic forward modeling unfolds enormous capacities that are far from exhausted. In metamorphic petrology the combination of thermodynamic and trace element forward modeling can be used to study and to quantify processes at spatial scales from μm to km. The thermodynamic forward models utilize Gibbs energy minimization to quantify mineralogical changes along a reaction path of a chemically open fluid/rock system. These results are combined with mass balanced trace element calculations to determine the trace element distribution between rock and melt/fluid during the metamorphic evolution. Thus, effects of mineral reactions, fluid-rock interaction and element transport in metamorphic rocks on the trace element and isotopic composition of minerals, rocks and percolating fluids or melts can be predicted. Here we illustrate the capacities of combined thermodynamic-geochemical modeling based on two examples relevant to mass transfer during metamorphism. The first example focuses on fluid-rock interaction in and around a blueschist-facies shear zone in felsic gneisses, where fluid-induced mineral reactions and their effects on boron (B) concentrations and isotopic compositions in white mica are modeled. In the second example, fluid release from a subducted slab, the associated transport of B as well as variations in B concentrations and isotopic compositions in liberated fluids and residual rocks are modeled. We compare the modeled results of both examples to geochemical data of natural minerals and rocks and demonstrate that the combination

  4. Reducing variance in batch partitioning measurements

    SciTech Connect

    Mariner, Paul E.

    2010-08-11

    The partitioning experiment is commonly performed with little or no attention to reducing measurement variance. Batch test procedures such as those used to measure K{sub d} values (e.g., ASTM D 4646 and EPA402 -R-99-004A) do not explain how to evaluate measurement uncertainty nor how to minimize measurement variance. In fact, ASTM D 4646 prescribes a sorbent:water ratio that prevents variance minimization. Consequently, the variance of a set of partitioning measurements can be extreme and even absurd. Such data sets, which are commonplace, hamper probabilistic modeling efforts. An error-savvy design requires adjustment of the solution:sorbent ratio so that approximately half of the sorbate partitions to the sorbent. Results of Monte Carlo simulations indicate that this simple step can markedly improve the precision and statistical characterization of partitioning uncertainty.

  5. Cell Partition in Two Polymer Aqueous Phases

    NASA Technical Reports Server (NTRS)

    Harris, J. M.

    1985-01-01

    Partition of biological cells in two phase aqueous polymer systems is recognized as a powerful separation technique which is limited by gravity. The synthesis of new, selective polymer ligand conjugates to be used in affinity partition separations is of interest. The two most commonly used polymers in two phase partitioning are dextran and polyethylene glycol. A thorough review of the chemistry of these polymers was begun, particularly in the area of protein attachment. Preliminary studies indicate the importance in affinity partitioning of minimizing gravity induced randomizing forces in the phase separation process. The PEG-protein conjugates that were prepared appear to be ideally suited for achieving high quality purifications in a microgravity environment. An interesting spin-off of this synthetic work was the observation of catalytic activity for certain of our polymer derivatives.

  6. Metal pollution in a contaminated bay: relationship between metal geochemical fractionation in sediments and accumulation in a polychaete.

    PubMed

    Fan, Wenhong; Xu, Zhizhen; Wang, Wen-Xiong

    2014-08-01

    Jinzhou Bay in Northern China has been seriously contaminated with metals due to the impacts of smelting activities. In this study, we investigated the relationship between metal accumulation in a deposit-feeding polychaete Neanthes japonica and metal concentration and geochemical fractionation (Cd, Cu, Pb, Zn and Ni) in sediments of Jinzhou Bay. Compared with the historical data, metals in the more mobile geochemical fraction (exchangeable and carbonate fractions) were gradually partitioned into the more stable fraction (Fe-Mn oxides) over time. Metal concentration and geochemical fractionation in sediment significantly affected metal bioavailability and accumulation in polychaetes, except for Ni. Metal accumulation in polychaetes was significantly influenced by Fe or Mn content, and to a lesser degree by organic matter. Prediction of metal bioaccumulation in polychaetes was greatly improved by normalizing metal concentrations to Mn content in sediment. The geochemical fractionation of metals in sediments including the exchangeable, organic matter and Fe-Mn oxides were important in controlling the sediment metal bioavailability to polychaetes. PMID:24811945

  7. Parallel partitioning strategies for the adaptive solution of conservation laws

    SciTech Connect

    Devine, K.D.; Flaherty, J.E.; Loy, R.M.

    1995-12-31

    We describe and examine the performance of adaptive methods for Solving hyperbolic systems of conservation laws on massively parallel computers. The differential system is approximated by a discontinuous Galerkin finite element method with a hierarchical Legendre piecewise polynomial basis for the spatial discretization. Fluxes at element boundaries are computed by solving an approximate Riemann problem; a projection limiter is applied to keep the average solution monotone; time discretization is performed by Runge-Kutta integration; and a p-refinement-based error estimate is used as an enrichment indicator. Adaptive order (p-) and mesh (h-) refinement algorithms are presented and demonstrated. Using an element-based dynamic load balancing algorithm called tiling and adaptive p-refinement, parallel efficiencies of over 60% are achieved on a 1024-processor nCUBE/2 hypercube. We also demonstrate a fast, tree-based parallel partitioning strategy for three-dimensional octree-structured meshes. This method produces partition quality comparable to recursive spectral bisection at a greatly reduced cost.

  8. Partitioned Exhaled Nitric Oxide to Non-Invasively Assess Asthma

    PubMed Central

    Puckett, James L.; George, Steven C.

    2008-01-01

    Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperresponsiveness. Chronic repetitive bouts of acute inflammation lead to airway wall remodeling and possibly the sequelae of fixed airflow obstruction. Nitric oxide (NO) is a reactive molecule synthesized by NO synthases (NOS). NOS are expressed by cells within the airway wall and functionally, two NOS isoforms exist: constitutive and inducible. In asthma, the inducible isoform is over expressed, leading to increased production of NO, which diffuses into the airway lumen, where it can be detected in the exhaled breath. The exhaled NO signal can be partitioned into airway and alveolar components by measuring exhaled NO at multiple flows and applying mathematical models of pulmonary NO dynamics. The airway NO flux and alveolar NO concentration can be elevated in adults and children with asthma and have been correlated with markers of airway inflammation and airflow obstruction in cross-sectional studies. Longitudinal studies which specifically address the clinical potential of partitioning exhaled NO for diagnosis, managing therapy, and predicting exacerbation are needed. PMID:18718562

  9. Deriving the Hirshfeld partitioning using distance metrics

    SciTech Connect

    Heidar-Zadeh, Farnaz; Ayers, Paul W.; Bultinck, Patrick

    2014-09-07

    The atoms in molecules associated with the Hirshfeld partitioning minimize the generalized Hellinger-Bhattacharya distance to the reference pro-atom densities. Moreover, the reference pro-atoms can be chosen by minimizing the distance between the pro-molecule density and the true molecular density. This provides an alternative to both the heuristic “stockholder” and the mathematical information-theoretic interpretations of the Hirshfeld partitioning. These results extend to any member of the family of f-divergences.

  10. Isorropia Partitioning and Load Balancing Package

    Energy Science and Technology Software Center (ESTSC)

    2006-09-01

    Isorropia is a partitioning and load balancing package which interfaces with the Zoltan library. Isorropia can accept input objects such as matrices and matrix-graphs, and repartition/redistribute them into a better data distribution on parallel computers. Isorropia is primarily an interface package, utilizing graph and hypergraph partitioning algorithms that are in the Zoltan library which is a third-party library to Tilinos.

  11. Deriving the Hirshfeld partitioning using distance metrics

    NASA Astrophysics Data System (ADS)

    Heidar-Zadeh, Farnaz; Ayers, Paul W.; Bultinck, Patrick

    2014-09-01

    The atoms in molecules associated with the Hirshfeld partitioning minimize the generalized Hellinger-Bhattacharya distance to the reference pro-atom densities. Moreover, the reference pro-atoms can be chosen by minimizing the distance between the pro-molecule density and the true molecular density. This provides an alternative to both the heuristic "stockholder" and the mathematical information-theoretic interpretations of the Hirshfeld partitioning. These results extend to any member of the family of f-divergences.

  12. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  13. A rheostat mechanism governs the bifurcation of carbon flux in mycobacteria.

    PubMed

    Murima, Paul; Zimmermann, Michael; Chopra, Tarun; Pojer, Florence; Fonti, Giulia; Dal Peraro, Matteo; Alonso, Sylvie; Sauer, Uwe; Pethe, Kevin; McKinney, John D

    2016-01-01

    Fatty acid metabolism is an important feature of the pathogenicity of Mycobacterium tuberculosis during infection. Consumption of fatty acids requires regulation of carbon flux bifurcation between the oxidative TCA cycle and the glyoxylate shunt. In Escherichia coli, flux bifurcation is regulated by phosphorylation-mediated inhibition of isocitrate dehydrogenase (ICD), a paradigmatic example of post-translational mechanisms governing metabolic fluxes. Here, we demonstrate that, in contrast to E. coli, carbon flux bifurcation in mycobacteria is regulated not by phosphorylation but through metabolic cross-activation of ICD by glyoxylate, which is produced by the glyoxylate shunt enzyme isocitrate lyase (ICL). This regulatory circuit maintains stable partitioning of fluxes, thus ensuring a balance between anaplerosis, energy production, and precursor biosynthesis. The rheostat-like mechanism of metabolite-mediated control of flux partitioning demonstrates the importance of allosteric regulation during metabolic steady-state. The sensitivity of this regulatory mechanism to perturbations presents a potentially attractive target for chemotherapy. PMID:27555519

  14. A rheostat mechanism governs the bifurcation of carbon flux in mycobacteria

    PubMed Central

    Murima, Paul; Zimmermann, Michael; Chopra, Tarun; Pojer, Florence; Fonti, Giulia; Dal Peraro, Matteo; Alonso, Sylvie; Sauer, Uwe; Pethe, Kevin; McKinney, John D.

    2016-01-01

    Fatty acid metabolism is an important feature of the pathogenicity of Mycobacterium tuberculosis during infection. Consumption of fatty acids requires regulation of carbon flux bifurcation between the oxidative TCA cycle and the glyoxylate shunt. In Escherichia coli, flux bifurcation is regulated by phosphorylation-mediated inhibition of isocitrate dehydrogenase (ICD), a paradigmatic example of post-translational mechanisms governing metabolic fluxes. Here, we demonstrate that, in contrast to E. coli, carbon flux bifurcation in mycobacteria is regulated not by phosphorylation but through metabolic cross-activation of ICD by glyoxylate, which is produced by the glyoxylate shunt enzyme isocitrate lyase (ICL). This regulatory circuit maintains stable partitioning of fluxes, thus ensuring a balance between anaplerosis, energy production, and precursor biosynthesis. The rheostat-like mechanism of metabolite-mediated control of flux partitioning demonstrates the importance of allosteric regulation during metabolic steady-state. The sensitivity of this regulatory mechanism to perturbations presents a potentially attractive target for chemotherapy. PMID:27555519

  15. The evaporative fraction as a measure of surface energy partitioning

    SciTech Connect

    Nichols, W.E. ); Cuenca, R.H. )

    1990-01-01

    The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program's SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

  16. Laboratory simulation of organic geochemical processes.

    NASA Technical Reports Server (NTRS)

    Eglinton, G.

    1972-01-01

    Discussion of laboratory simulations that are important to organic geochemistry in that they provide direct evidence relating to geochemical cycles involving carbon. Reviewed processes and experiments include reactions occurring in the geosphere, particularly, short-term diagenesis of biolipids and organochlorine pesticides in estuarine muds, as well as maturation of organic matter in ancient sediments.

  17. Geochemical Reaction Mechanism Discovery from Molecular Simulation

    DOE PAGESBeta

    Stack, Andrew G.; Kent, Paul R. C.

    2014-11-10

    Methods to explore reactions using computer simulation are becoming increasingly quantitative, versatile, and robust. In this review, a rationale for how molecular simulation can help build better geochemical kinetics models is first given. We summarize some common methods that geochemists use to simulate reaction mechanisms, specifically classical molecular dynamics and quantum chemical methods and discuss their strengths and weaknesses. Useful tools such as umbrella sampling and metadynamics that enable one to explore reactions are discussed. Several case studies wherein geochemists have used these tools to understand reaction mechanisms are presented, including water exchange and sorption on aqueous species and mineralmore » surfaces, surface charging, crystal growth and dissolution, and electron transfer. The impact that molecular simulation has had on our understanding of geochemical reactivity are highlighted in each case. In the future, it is anticipated that molecular simulation of geochemical reaction mechanisms will become more commonplace as a tool to validate and interpret experimental data, and provide a check on the plausibility of geochemical kinetic models.« less

  18. Geochemical Reaction Mechanism Discovery from Molecular Simulation

    SciTech Connect

    Stack, Andrew G.; Kent, Paul R. C.

    2014-11-10

    Methods to explore reactions using computer simulation are becoming increasingly quantitative, versatile, and robust. In this review, a rationale for how molecular simulation can help build better geochemical kinetics models is first given. We summarize some common methods that geochemists use to simulate reaction mechanisms, specifically classical molecular dynamics and quantum chemical methods and discuss their strengths and weaknesses. Useful tools such as umbrella sampling and metadynamics that enable one to explore reactions are discussed. Several case studies wherein geochemists have used these tools to understand reaction mechanisms are presented, including water exchange and sorption on aqueous species and mineral surfaces, surface charging, crystal growth and dissolution, and electron transfer. The impact that molecular simulation has had on our understanding of geochemical reactivity are highlighted in each case. In the future, it is anticipated that molecular simulation of geochemical reaction mechanisms will become more commonplace as a tool to validate and interpret experimental data, and provide a check on the plausibility of geochemical kinetic models.

  19. Software Partitioning Schemes for Advanced Simulation Computer Systems. Final Report.

    ERIC Educational Resources Information Center

    Clymer, S. J.

    Conducted to design software partitioning techniques for use by the Air Force to partition a large flight simulator program for optimal execution on alternative configurations, this study resulted in a mathematical model which defines characteristics for an optimal partition, and a manually demonstrated partitioning algorithm design which…

  20. Gliding Box method applied to trace element distribution of a geochemical data set

    NASA Astrophysics Data System (ADS)

    Paz González, Antonio; Vidal Vázquez, Eva; Rosario García Moreno, M.; Paz Ferreiro, Jorge; Saa Requejo, Antonio; María Tarquis, Ana

    2010-05-01

    The application of fractal theory to process geochemical prospecting data can provide useful information for evaluating mineralization potential. A geochemical survey was carried out in the west area of Coruña province (NW Spain). Major elements and trace elements were determined by standard analytical techniques. It is well known that there are specific elements or arrays of elements, which are associated with specific types of mineralization. Arsenic has been used to evaluate the metallogenetic importance of the studied zone. Moreover, as can be considered as a pathfinder of Au, as these two elements are genetically associated. The main objective of this study was to use multifractal analysis to characterize the distribution of three trace elements, namely Au, As, and Sb. Concerning the local geology, the study area comprises predominantly acid rocks, mainly alkaline and calcalkaline granites, gneiss and migmatites. The most significant structural feature of this zone is the presence of a mylonitic band, with an approximate NE-SW orientation. The data set used in this study comprises 323 samples collected, with standard geochemical criteria, preferentially in the B horizon of the soil. Occasionally where this horizon was not present, samples were collected from the C horizon. Samples were taken in a rectilinear grid. The sampling lines were perpendicular to the NE-SW tectonic structures. Frequency distributions of the studied elements departed from normal. Coefficients of variation ranked as follows: Sb < As < Au. Significant correlation coefficients between Au, Sb, and As were found, even if these were low. The so-called ‘gliding box' algorithm (GB) proposed originally for lacunarity analysis has been extended to multifractal modelling and provides an alternative to the ‘box-counting' method for implementing multifractal analysis. The partitioning method applied in GB algorithm constructs samples by gliding a box of certain size (a) over the grid map in all

  1. A combined geochemical and hydrological approach for understanding macronutrient sources

    NASA Astrophysics Data System (ADS)

    Lapworth, Dan J.; Gooddy, Daren C.; Kent, Flo; Heaton, Tim H. E.; Cole, Steven J.; Allen, Debbie

    2013-09-01

    This study employed complementary geochemical techniques and distributed hydrological modelling to investigate multiple sources of catchment macronutrients and characterise their changes in contrasting storm and baseflow conditions. This approach was demonstrated for the Beult catchment in the county of Kent (England), a designated Site of Special Scientific Interest (SSSI) indentified as failing to meet water quality standards for key nutrients under the Water Framework Directive. Significant changes in nutrient stoichiometry and bioavailability are observed for surface waters under contrasting flow regimes. Soluble reactive phosphorus (SRP) concentrations are approximately twice as high during baseflow compared to high flow, while the inverse is true for particulate, colloidal and dissolved hydrolysable phosphorus, dissolved organic carbon and nitrate. Nitrogen (N):phosphorus (P) ratios are lower during baseflow for most surface waters impacted by diffuse sources of pollution. Fluorescence indices of dissolved organic matter (DOM) show that waste water inputs may be locally important sources of more complex low molecular weight DOM, particularly during baseflow. Nitrate N and O isotope signatures, combined with other dissolved chemical tracers, confirm the dominance of wastewater N inputs at sites downsteam of sewerage treatment works during baseflow, with a shift towards the soil N pool in surface waters across the catchment during high flow. Distributed hydrological modelling using the Grid-to-Grid model reveal areas with the greatest runoff also export higher N and P concentrations, and hence deliver a greater flux of macronutrients, while forested areas with low nutrient concentrations reduce runoff and nutrient fluxes. During periods of high runoff, nested sampling indicates that nutrient fluxes scale with catchment area. This combined approach enables a more thorough assessment of the macronutrient sources and dynamics, better informing management options

  2. The geochemical geometry of mantle plumes

    NASA Astrophysics Data System (ADS)

    Jackson, Matthew

    2015-04-01

    Lavas erupted at oceanic hotspot volcanoes exhibit tremendous isotopic variability, which indicates that the mantle sources of the hotspots are highly heterogeneous geochemically. A key question is how the surface expression of hotspot lavas relates to the spatial distribution of the geochemical components within upwelling mantle plumes. Significant progress has been made in recent years relating the geographic distribution of geochemical heterogeneities in hotspot lavas to parallel volcanic lineaments that define the traces of oceanic hotspot tracks. For example, a well known geographic separation of parallel volcanic lineaments at Hawaii - the Loa and Kea trends - are also isotopically resolved. In addition to the Hawaiian example, clear patterns relating the geographic distribution of geochemical components along hotspot tracks are emerging from a suite of global hotspots, and these patterns suggest that geochemical heterogeneities are highly organized within upwelling mantle plume conduits. At the Samoan hotspot, the Pb-isotopic compositions measured in lavas reveal several geochemical groups, and each group corresponds to a different geographic lineament of volcanoes. Each group has a geochemical signature that relates to each of the canonical low 3He/4He mantle endmembers: EMII (enriched mantle 2), EMI (enriched mantle 1), HIMU (high U/Pb) and DM (depleted mantle). In Pb-isotopic space, the four geochemical groups each form an array that trends toward a common component (thus forming an "X-shape" in Pb-isotopic space). The region of isotope space where the 4 Pb-isotopic array intersect is defined by the highest 3He/4He (up to 34 Ra, or ratio to atmosphere) in the Samoan hotspot. In Pb-isotopic space, 3He/4He decreases monotonically along each of the Pb-isotopic groups away from the common region of convergence. In order to quantify the relationship between He and Pb isotopes, 3He/4He is plotted versus distance from the common component in Pb-isotopic space

  3. Alaska Geochemical Database (AGDB)-Geochemical data for rock, sediment, soil, mineral, and concentrate sample media

    USGS Publications Warehouse

    Granitto, Matthew; Bailey, Elizabeth A.; Schmidt, Jeanine M.; Shew, Nora B.; Gamble, Bruce M.; Labay, Keith A.

    2011-01-01

    The Alaska Geochemical Database (AGDB) was created and designed to compile and integrate geochemical data from Alaska in order to facilitate geologic mapping, petrologic studies, mineral resource assessments, definition of geochemical baseline values and statistics, environmental impact assessments, and studies in medical geology. This Microsoft Access database serves as a data archive in support of present and future Alaskan geologic and geochemical projects, and contains data tables describing historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 85 laboratory and field analytical methods on 264,095 rock, sediment, soil, mineral and heavy-mineral concentrate samples. Most samples were collected by U.S. Geological Survey (USGS) personnel and analyzed in USGS laboratories or, under contracts, in commercial analytical laboratories. These data represent analyses of samples collected as part of various USGS programs and projects from 1962 to 2009. In addition, mineralogical data from 18,138 nonmagnetic heavy mineral concentrate samples are included in this database. The AGDB includes historical geochemical data originally archived in the USGS Rock Analysis Storage System (RASS) database, used from the mid-1960s through the late 1980s and the USGS PLUTO database used from the mid-1970s through the mid-1990s. All of these data are currently maintained in the Oracle-based National Geochemical Database (NGDB). Retrievals from the NGDB were used to generate most of the AGDB data set. These data were checked for accuracy regarding sample location, sample media type, and analytical methods used. This arduous process of reviewing, verifying and, where necessary, editing all USGS geochemical data resulted in a significantly improved Alaska geochemical dataset. USGS data that were not previously in the NGDB because the data predate the earliest USGS geochemical databases, or were once excluded for programmatic reasons

  4. Hydrological and geochemical consequences of river regulation - hyporheic perspective

    NASA Astrophysics Data System (ADS)

    Siergieiev, Dmytro; Lundberg, Angela; Widerlund, Anders

    2014-05-01

    River-aquifer interfaces, essential for ecosystem functioning in terms of nutrient exchange and biological habitat, appear greatly threatened worldwide. Although river regulation is a vast pressure on river-aquifer interaction, influencing entire watersheds, knowledge about hyporheic exchange in regulated rivers is rather limited. In this study, we combine two decades of research on hydrological and geochemical impacts of hydropower regulation on river water and hyporheic zone in two large boreal rivers, unregulated Kalix River and regulated Lule River. Altered river discharge, with reduced spring peaks, daily summer fluctuations and elevated winter base flow severely modified Lule River water geochemistry and thus the transport of solutes to the Bothnian Bay (Baltic Sea). Further, these river modifications changed the river-aquifer exchange on both daily and seasonal scale, which resulted in deteriorated hyporheic conditions with reduced riverbed hydraulic conductivity (formation of a clogging layer) reflected in a declined hyporheic flux. Altered hydrological regime of the hyporheic zone created quasi-stagnant conditions beneath the river-aquifer interface and promoted the formation of geochemically suboxic environment. Taken that hyporheic water is a mixture of river water and groundwater, mixing models for the regulated site demonstrate a considerable addition of Fe, Mn, Al, NH4 and removal of dissolved oxygen and nitrate, which suggests the hyporheic zone in the Lule River to be a source of solutes. This contradicts the observations from the hyporheic zone in the unregulated river, with opposite behaviour functioning as a barrier. These results suggest that the hyporheic zone function is dependent on the river discharge and the state of the river-aquifer connectivity. Improved knowledge about the latter on a watershed scale will substantially increase our understanding about the status and potential pressures of riverine ecosystems and assist management and

  5. Geochemical Monitoring In Campi Flegrei From 1970 To 2000.

    NASA Astrophysics Data System (ADS)

    Avino, R.; Caliro, S.; Chiodini, G.; del Gaudio, C.; di Matteo, V.; Pece, R.; Russo, M.

    At the present, the activity of Campi Flegrei caldera is characterized by strong fumarolic emissions at Solfatara and minor emissions at Baia and Mofete. Two bradyseismic crises, centred at Pozzuoli, interested the caldera in recent times: in 1969-1972 (maximum uplift of 1.7 m) and in 1982-1984 when the area was affected by a maximum uplift of 1.8 m and by several thousands earthquakes. More recently, three minor sudden ground uplifts and seismic swarms were recorded in 1989-90, in 1994 and in 2000. In the late `70s started a systemat ic work of geochemical surveillance based on the monitoring of the fumarolic fluids of Solfatara. In addition, in 1983 was added the monitoring of radon concentration, temperature and pH in the waters of three wells (Damiani, Costagliola and Tortorelli). Measures at Tortorelli were interrupted in 1993, because of technical problems, while Damiani and Costagliola are still monitored. The variations of radon, temperature and pH monitored in the three wells and compositional changes in Solfatara fumaroles show a clear correlation with the different phases of the bradyseismic crisis. Concurrent changes of physical and chemical parameters were recorded during 1989, 1994-1996 and 2000. The most complete set of geochemical data, which also includes measurements of the diffuse degassing at Solfatara, regards the last crisis. The soil uplift was accompanied by a significant increase of diffuse CO2 fluxes, increments in temperature and pressures of the hydrothermal system, estimated by gas-indicators, and by a marked increase of the radon content in the waters. The data suggest that variations of fluid pressure within the hydrothermal system are one of the main causes of ground deformation episodes at Campi Flegrei.

  6. Geobiochemistry: Placing Biochemistry in Its Geochemical Context

    NASA Astrophysics Data System (ADS)

    Shock, E.; Boyer, G. M.; Canovas, P. A., III; Prasad, A.; Dick, J. M.

    2014-12-01

    Goals of geobiochemistry include simultaneously evaluating the relative stabilities of microbial cells and minerals, and predicting how the composition of biomolecules can change in response to the progress of geochemical reactions. Recent developments in theoretical geochemistry make it possible to predict standard thermodynamic properties of proteins, nucleotides, lipids, and many metabolites including the constituents of the citric acid cycle, at all temperatures and pressures where life is known to occur, and beyond. Combining these predictions with constraints from geochemical data makes it possible to assess the relative stabilities of biomolecules. Resulting independent predictions of the environmental occurrence of homologous proteins and lipid side-chains can be compared with observations from metagenomic and metalipidomic data to quantify geochemical driving forces that shape the composition of biomolecules. In addition, the energetic costs of generating biomolecules from within a diverse range of habitable environments can be evaluated in terms of prevailing geochemical variables. Comparisons of geochemical bioenergetic calculations across habitats leads to the generalization that the availability of H2 determines the cost of autotrophic biosynthesis relative to the aquatic environment external to microbial cells, and that pH, temperature, pressure, and availability of C, N, P, and S are typically secondary. Increasingly reduced conditions, which are determined by reactions of water with mineral surfaces and mineral assemblages, allow many biosynthetic reactions to shift from costing energy to releasing energy. Protein and lipid synthesis, as well as the reverse citric acid cycle, become energy-releasing processes under these conditions. The resulting energy balances that determine habitability contrast dramatically with assumptions derived from oxic surface conditions, such as those where human biochemistry operates.

  7. Geochemical patterns in proximal and distal Toba glass

    NASA Astrophysics Data System (ADS)

    Gatti, E.; Achyuthan, H.; Villa, I. M.; Gibbard, P. L.; Oppenheimer, C.

    2012-12-01

    The geochemical components of the Youngest Toba Tuff (YTT) are a direct characteristic of the ashfall that can elucidate magmatic processes and depositional mechanisms of the YTT ultra-distal deposits. We synthesises all readily available geochemical data on glass compositions of the YTT. The dataset includes 69 analyses from the literature and three new analyses, and it reveals considerable variability on in glass composition. The data are used to infer the origins of these geochemical differences in terms of compositional zonation of the magma reservoir, post-depositional alteration, and methodological biases. Magma chamber zonation is found to be the major control on chemical differences in the YTT glass: FeO/TiO2 ratios vary by a factor of ten, reflecting the evolution of the eruption. Post-depositional leaching and weathering is responsible for up to 50% of the differences in mobile element abundances. Na2O/Ka2O and SiO2/Al2O3 ratios are significantly lower in marine depositional sites compared with terrestrial sites. Exceptions to this are ash from the pelagic environment of the Central Indian Ocean Basin (CIOB), whose Na2O/Ka2O ratio is 20% higher than that of other marine sites, and samples from the shallow deltaic and hemipelagic areas of the South China Sea (SCS) and the Arabian Sea, whose SiO2/Al2O3 ratios are similar to those found for terrestrial distal sites. We suggest the water depth in the CIOB and the large flux of terrigenous sediment sourced from the Pearl and Indus Rivers are responsible for the diagenetic differences. Inter-laboratory comparisons indicate that methodological biases are small. The principal findings are: (i) The YTT glass geochemistry at a given site strongly reflects the stage of the eruption (ii) Post-depositional glass alteration is controlled by the depositional environment, i.e., hemipelagic deltaic marine basin, versus pelagic deep ocean basin, versus terrestrial basin, and (iii) All the samples show a minor 'laboratory

  8. Geochemical and Geomechanical Effects on Wellbore Cement Fractures

    DOE PAGESBeta

    Um, Wooyong; Jung, Hun Bok; Kabilan, Senthil; Fernandez, Carlos A.; Brown, Christopher F.

    2014-12-31

    Experimental studies were conducted using batch reactors, X-ray microtomograpy (XMT), and computational fluid dynamics (CFD) simulation to determine changes in cement fracture surfaces, fluid flow pathways, and permeability with geochemical and geomechanical processes. Composite Portland cement-basalt caprock core with artificial fractures was prepared and reacted with CO2-saturated groundwater at 50°C and 10 MPa for 3 to 3.5 months under static conditions to understand the geochemical and geomechanical effects on the integrity of wellbores containing defects. Cement-basalt interface samples were subjected to mechanical stress at 2.7 MPa before the CO2 reaction. XMT provided three-dimensional (3-D) visualization of the opening and interconnectionmore » of cement fractures due to mechanical stress. After the CO2 reaction, XMT images revealed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along fractures located at the cement-basalt interface. The permeability calculated based on CFD simulation was in agreement with the experimentally measured permeability. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated groundwater under static conditions, whereas fractures along the cement-caprock interface are still likely to remain vulnerable to the leakage of CO2. CFD simulation for the flow of different fluids (CO2-saturated brine and supercritical CO2) using a pressure difference of 20 kPa and 200 kPa along ~2 cm-long cement fractures showed that a pressure gradient increase resulted in an increase of CO2 fluids flux by a factor of only ~3-9 because the friction of CO2 fluids on cement fracture surfaces increased with higher flow rate as well. At the same pressure gradient, the simulated flow rate was higher for supercritical CO2 than CO2-saturated brine by a factor of only ~2-3, because the viscosity of supercritical CO2 is

  9. Geochemical and Geomechanical Effects on Wellbore Cement Fractures

    SciTech Connect

    Um, Wooyong; Jung, Hun Bok; Kabilan, Senthil; Fernandez, Carlos A.; Brown, Christopher F.

    2014-12-31

    Experimental studies were conducted using batch reactors, X-ray microtomograpy (XMT), and computational fluid dynamics (CFD) simulation to determine changes in cement fracture surfaces, fluid flow pathways, and permeability with geochemical and geomechanical processes. Composite Portland cement-basalt caprock core with artificial fractures was prepared and reacted with CO2-saturated groundwater at 50°C and 10 MPa for 3 to 3.5 months under static conditions to understand the geochemical and geomechanical effects on the integrity of wellbores containing defects. Cement-basalt interface samples were subjected to mechanical stress at 2.7 MPa before the CO2 reaction. XMT provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. After the CO2 reaction, XMT images revealed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along fractures located at the cement-basalt interface. The permeability calculated based on CFD simulation was in agreement with the experimentally measured permeability. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated groundwater under static conditions, whereas fractures along the cement-caprock interface are still likely to remain vulnerable to the leakage of CO2. CFD simulation for the flow of different fluids (CO2-saturated brine and supercritical CO2) using a pressure difference of 20 kPa and 200 kPa along ~2 cm-long cement fractures showed that a pressure gradient increase resulted in an increase of CO2 fluids flux by a factor of only ~3-9 because the friction of CO2 fluids on cement fracture surfaces increased with higher flow rate as well. At the same pressure gradient, the simulated flow rate was higher for supercritical CO2 than CO2-saturated brine by a factor of only ~2-3, because the viscosity of supercritical CO2 is much

  10. Partitioned time discretization for atmosphere-ocean interaction

    NASA Astrophysics Data System (ADS)

    Connors, Jeffrey M.

    Numerical algorithms are proposed, analyzed and tested for improved efficiency and reliability of the dynamic core of climate codes. The commonly used rigid lid hypothesis is assumed, which allows instantaneous response of the interface to changes in mass. Additionally, moisture transport is ignored, resulting in a static interface. A central algorithmic feature is the numerical decoupling of the atmosphere and ocean calculations by a semi-implicit treatment of the interface data, i.e. partitioned time stepping. Algorithms are developed for simplified continuum models retaining the key mathematical structure of the atmosphere-ocean equations. The work begins by studying linear parameterization of momentum ux in terms of wind shear, coupling the equations. Partitioned variants of backward-Euler are developed allowing large time steps. Higher order accuracy is achieved by deferred correction. Adaptations are developed for nonlinear coupling. Most notably an application of geometric averaging is used to retain unconditional stability. This algorithm is extended to allow different size time steps for the subcalculations. Full numerical analyses are performed and computational experiments are provided. Next, heat convection is added including a nonlinear parameterization of heat flux in terms of wind shear and temperature. A partitioned algorithm is developed for the atmosphere and ocean coupled velocity-temperature system that retains unconditional stability. Furthermore, uncertainty quantification is performed in this case due to the importance of reliably calculating heat transport phenomena in climate modeling. Noise is introduced in two coupling parameters with an important role in stability. Numerical tests investigate the variance in temperature, velocity and average surface temperature. Partitioned methods are highly efficient for linearly coupled 2 fluid problems. Extensions of these methods for nonlinear coupling where the interface data is processed properly

  11. The Partition Intervalometer: A Programmable Underwater Timer for Marking Accumulated Sediment Profiles Collected in Anderson Sediment Traps: Development, Operation, Testing Procedures, and Field Results

    USGS Publications Warehouse

    Rendigs, Richard R.; Anderson, Roger Y.; Xu, Jingping; Davis, Raymond E.; Bergeron, Emile M.

    2009-01-01

    This manual illustrates the development of a programmable instrument designed to deploy a series of wafer-shaped discs (partitions) into the collection tube of a sediment trap in various aquatic environments. These hydrodynamically shaped discs are deployed at discrete time intervals from the Intervalometer and provide markers that delineate time intervals within the sediments that accumulate in the collection tube. The timer and mechanical system are lodged in an air-filled, water-tight pressure housing that is vertically hung within the confines of a cone-shaped sediment trap. The instrumentation has been operationally pressure tested to an equivalent water depth of approximately 1 km. Flaws discovered during extensive laboratory and pressure testing resulted in the implementation of several mechanical modifications (such as a redesign of the rotor and the discs) that improved the operation of the rotor assembly as well as the release of discs through the end cap. These results also identified a preferred azimuth placement of the rotor disc relative to the drop hole of the end cap. In the initial field trial, five sediment traps and coupled Intervalometers were attached to moored arrays and deployed at two sites off the coast of Southern California for approximately 8 months. Each of the instruments released 18 discs at the programmed 10 day intervals, except one unit, which experienced a malfunction after approximately 4 months. Most of the discs oriented in a near-horizontal position upon the surface of the sediment in the collection tubes. Sampling of the sediments for geochemical analyses was improved by these clearly defined markers, which indicated the changes in the flux and nature of sediments accumulated during the deployment period of each sediment trap.

  12. Estimating terrestrial uranium and thorium by antineutrino flux measurements

    PubMed Central

    Dye, Stephen T.; Guillian, Eugene H.

    2008-01-01

    Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This article describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle by using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a midcontinental and a midoceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understanding of the deep interior of the Earth. PMID:18172211

  13. Magnetic-flux pump

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  14. The partitioning of copper among selected phases of geologic media of two porphyry copper districts, Puerto Rico

    USGS Publications Warehouse

    Learned, R.E.; Chao, T.T.; Sanzolone, R.F.

    1981-01-01

    In experiments designed to determine the manner in which copper is partitioned among selected phases that constitute geologic media, we have applied the five-step sequential extraction procedure of Chao and Theobald to the analysis of drill core, soils, and stream sediments of the Rio Vivi and Rio Tanama porphyry copper districts of Puerto Rico. The extraction procedure affords a convenient means of determining the trace-metal content of the following fractions: (1) Mn oxides and "reactive" Fe oxides; (2) "amorphous" Fe oxides; (3) "crystalline" Fe oxides; (4) sulfides and magnetite; and (5) silicates. An additional extraction between steps (1) and (2) was performed to determine organic-related copper in stream sediments. The experimental results indicate that apportionment of copper among phases constituting geologic media is a function of geochemical environment. Distinctive partitioning patterns were derived from the analysis of drill core from each of three geochemical zones: (a) the supergene zone of oxidation; (b) the supergene zone of enrichment; and (c) the hypogene zone; and similarly, from the analysis of; (d) soils on a weakly leached capping; (e) soils on a strongly leached capping; and (f) active stream sediment. The experimental results also show that geochemical contrasts (anomaly-to-background ratios) vary widely among the five fractions of each sampling medium investigated, and that at least one fraction of each medium provides substantially stronger contrast than does the bulk medium. Fraction (1) provides optimal contrast for stream sediments of the district; fraction (2) provides optimal contrast for soils on a weakly leached capping; fraction (3) provides optimal contrast for soils on a strongly leached capping. Selective extraction procedures appear to have important applications to the orientation and interpretive stages of geochemical exploration. Further investigation and testing of a similar nature are recommended. ?? 1981.

  15. Fluid(s)/Melt Partitioning of COHSCl Volatiles and Associated Controls on Volcanic Degassing (Invited)

    NASA Astrophysics Data System (ADS)

    Webster, J. D.

    2013-12-01

    Magmas are variably enriched in the four primary volatile components H2O, CO2, S, and Cl. Current understanding of how these volatiles dissolve in and exsolve from silicate melts is limited by insufficient experimental data and resulting constraints on models bearing on volatile solubilities in geochemically complex (C-, H-, S-, and Cl-bearing) melts and coexisting fluids. Moreover, eruptive magmas involve a wide range of melt compositions, yet to be investigated systematically. These limitations restrict accurate interpretation of processes of magma evolution and degassing and make it difficult to reconcile compositions of volcanic gases at surface with those of magmatic fluids at depth. Recent experimental research on geochemically complex fluids at 25-800 MPa has begun to elucidate solubilities of C, H, S, and Cl in silicate melts and coexisting vapor with or without a saline liquid phase. Expressed as partition coefficients between Cl- and S-bearing aqueous or aqueous-carbonic fluid(s) and coexisting silicate melt, results show that although pressure exerts a fundamental control on the partitioning of these volatiles (Lesne et al., 2011; Witham et al., 2012), the compositions of C-, H-, S-, and Cl-bearing fluids also influence volatile partitioning. For some P-T-X conditions, the effects can be quite strong. The CO2 partition coefficient, for example, increasingly favors the fluid as S is added to haplogranitic melt at oxygen fugacities below ca. NNO-0.3. New research on rhyolitic and phonolitic melts at 200 MPa demonstrates that S partitioning between fluid(s) and melt does not vary with the CO2 content of the system even with as much as 60 mole % CO2 in the fluid(s). Thus the dilution effect of adding of CO2 reduces the S concentrations dissolved in the fluid(s) and in melt to a similar extent. Likewise, experiments on andesitic melt of Teague et al. (2008) show a strong solubility of S in CO2-enriched aqueous vapors from 200-800 MPa. Typically, the most CO2

  16. A geomorphic-geochemical framework for quantifying the cycling of sediment-associated contaminants in fluvial systems

    NASA Astrophysics Data System (ADS)

    Byrne, Patrick; Lopez-Tarazon, Jose; Williams, Richard

    2016-04-01

    Recent high-profile contamination events linked to extreme floods have underlined the persistent environmental risk posed by legacy metals stored in fluvial systems worldwide. While we understand that the fate of sediment-associated metals is largely determined by the dynamics of the fluvial transport system, we still lack a process-based understanding of the spatial and temporal mechanisms that affect the physical and geochemical transfer of metals through catchments. This interdisciplinary project will exploit advances in geomorphic and geochemical analyses to develop a methodological approach and conceptual framework to answer key questions related to the dynamics and timescales of metal cycling in fluvial systems. The approach will be tested in two reaches of the mining-impacted Afon Twymyn, Wales. The main objectives are: (i) quantify the physical transport of sediment and metals over a range of river flows and model sediment pathways; (ii) establish the geochemical mobility and speciation of sediment-associated metals and how this is modified through the sediment pathways. To achieve these objectives a geomorphic-geochemical combined methodology will be applied. It includes: (i) Aerial imagery that will be acquired from UAV surveys pre- and post-high flows and transformed into high-resolution DEMs using Structure-from-Motion; (ii) suspended sediment flux will be estimated indirectly by field calibration with a logging turbidimeter; (iii) 2D hydraulic and sediment transport model (Delft3D) will be used to quantify the transport of sediment and associated metals and to map the source, pathway and sink of contaminated sediment; (iv) soil and sediment samples (including suspended sediment) will be collected pre- and post-high flows for geochemical (concentration, speciation) and mineralogical (XRD, SEM) analyses; (v) finally, a geochemical model (Geochemists Workbench) will be developed to generate hypotheses that explain observed geochemical change as a function

  17. The influence of organic carbon flux on benthic foraminiferal proxies

    NASA Astrophysics Data System (ADS)

    Corliss, B. H.; Sun, X.; Brown, C. W.; Showers, W. J.

    2005-12-01

    During the last 30 years, deep-sea benthic foraminifera have been widely used in reconstructing environmental conditions in the deep sea. Initial suggestions of faunal-water mass associations were never substantiated and, instead, organic carbon flux was identified as a primary influence on species and assemblage patterns. Organic carbon flux also impacts the chemistry of deep water masses and is reflected in the stable isotopic and trace element composition of a number of deep-sea taxa. The timing of delivery of organic carbon can also have an affect on foraminiferal chemistry. Carbon-13 data of Holocene Epistominella exigua from the North Atlantic show a 0.9 per mil change over 60 degrees of latitude that can be correlated to seasonality of productivity, based on a comparison of SeaWIFS satellite imagery. Seasonality and mean annual primary productivity do not affect the carbon-13 of Planulina wuellerstorfi in the North Atlantic, although P. wuellerstorfi exhibits significant variability. Our results suggest that the carbon-13 of E. exigua in conjunction with P. wuellerstorfi can be used to reconstruct seasonality of primary productivity. These findings raise the possibility that other geochemical proxies influenced by particle flux from the surface may be affected by periodic flux events that create phytodetritus layers and change the chemistry of the microhabitats occupied by some benthic foraminiferal species. Existing studies suggest that organic carbon flux and seasonality of flux influence both faunal and geochemical signals from benthic foraminiferal. These relationships can be used to reconstruct primary productivity and seasonality, in addition to deep-water circulation, and illustrate the importance of incorporating ecological information in the interpretation of geochemical data from deep sea taxa.

  18. Multi-A Graph Patrolling and Partitioning

    NASA Astrophysics Data System (ADS)

    Elor, Y.; Bruckstein, A. M.

    2012-12-01

    We introduce a novel multi agent patrolling algorithm inspired by the behavior of gas filled balloons. Very low capability ant-like agents are considered with the task of patrolling an unknown area modeled as a graph. While executing the proposed algorithm, the agents dynamically partition the graph between them using simple local interactions, every agent assuming the responsibility for patrolling his subgraph. Balanced graph partition is an emergent behavior due to the local interactions between the agents in the swarm. Extensive simulations on various graphs (environments) showed that the average time to reach a balanced partition is linear with the graph size. The simulations yielded a convincing argument for conjecturing that if the graph being patrolled contains a balanced partition, the agents will find it. However, we could not prove this. Nevertheless, we have proved that if a balanced partition is reached, the maximum time lag between two successive visits to any vertex using the proposed strategy is at most twice the optimal so the patrol quality is at least half the optimal. In case of weighted graphs the patrol quality is at least (1)/(2){lmin}/{lmax} of the optimal where lmax (lmin) is the longest (shortest) edge in the graph.

  19. Metal-silicate partitioning during core formation on super-Earths

    NASA Astrophysics Data System (ADS)

    Schaefer, L. K.; Jacobsen, S. B.; Petaev, M. I.; Sasselov, D. D.; Remo, J. L.

    2015-12-01

    Separation of the Earth into a rocky mantle and metallic Fe core is a problem long studied in the planetary science community (e.g. [1]). The timing of core formation influences the abundances of the siderophile elements found in the Earth's mantle, and the mechanism of core formation influences the degree of chemical equilibration between the rocky mantle and the core at the time of metal separation. However, limited work has been done on formation of metallic cores and its effects on mantle chemistry in rocky planets larger than the Earth. Super-Earths, exoplanets with masses up to ~ 5 Earth masses and radii up to ~1.6-1.7 Earth radii, have significantly larger internal pressures and consequently higher internal temperatures than the Earth, therefore conclusions from Earth-centric studies of core formation may be erroneous. Partitioning coefficients for many of the relevant elements (e.g. Fe, Ni, Si, O, etc.) are available in the literature, but only to relatively low pressures. The relevant pressures for super-Earths are significantly larger. However, data on Fe-O-Ni-Si partitioning at pressures (200-500 GPa) and temperatures relevant to super-Earths have been measured by laser-induced shocks with the ZBL laser at Sandia National Laboratory with a method described in [2]. We will present a model which integrates this data with lower pressure partition coefficients from the literature (e.g. [3],[4],[5]), with special emphasis on Fe and O, to describe partitioning behavior at high pressures and discuss its implications for core size and composition on rocky super-Earths. [1] Ringwood, A.E. (1977) Geochem. J. 11, 111-135. [2] Remo, J.L., Petaev, M.I., Jacobsen, S. B. (2008) LPSC abstract, 1420. [3] Frost, D.J. et al. (2010) JGR, B02202. [4] Kombayashi, T. (2014) JGR, 4164-4177. [5] Rubie, D.C. et al. (2011) EPSL, 301, 31-42. [5

  20. Partitioning of Pb, Cd, and Cu in natural and disturbed salt marshes of eastern San Francisco Bay

    SciTech Connect

    Alai, M.; Fegan, N. . Dept. of Geological Sciences)

    1993-04-01

    Sediment from different marsh systems along eastern San Francisco Bay was analyzed to determine how metals are partitioned in different environments influenced by human activity. Human influences in the marshes may have altered the geochemical processes controlling the metal partitioning. The three marsh systems analyzed include a natural marsh (San Francisco Wildlife Refuge), a natural marsh influenced by landfill leachate (Triangle Marsh), and a disturbed marsh constructed of artificial fill (Hayward Landing). The trace metal concentrations were compared in: easily exchangeable, weakly acid soluble, reducible, and oxidizable fractions representing the sediment phases of: clays, carbonates, Mn or Fe oxyhydroxides, and sulfides or organic material, respectively. The sediment fractions were analyzed for Pb, Cd, and Cu. In all three marshes, the pattern of metal partitioning with depth is similar; however, there are some inconsistencies. The Pb, Cd, and Cu in the reducible fraction typically decrease with depth while the metals in the oxidizable fraction generally increase or remain approximately constant with depth. This data suggests that the partitioning of metals in all three environments is initially controlled by sorption of metals onto Mn or Fe oxyhydroxides at the surface and shifts to organic or sulfides as the sediments is buried and the environment becomes more reducing.

  1. Partitioning of evaporation into transpiration, soil evaporation and interception: a comparison between isotope measurements and a HYDRUS-1D model

    NASA Astrophysics Data System (ADS)

    Sutanto, S. J.; Wenninger, J.; Coenders-Gerrits, A. M. J.; Uhlenbrook, S.

    2012-08-01

    Knowledge of the water fluxes within the soil-vegetation-atmosphere system is crucial to improve water use efficiency in irrigated land. Many studies have tried to quantify these fluxes, but they encountered difficulties in quantifying the relative contribution of evaporation and transpiration. In this study, we compared three different methods to estimate evaporation fluxes during simulated summer conditions in a grass-covered lysimeter in the laboratory. Only two of these methods can be used to partition total evaporation into transpiration, soil evaporation and interception. A water balance calculation (whereby rainfall, soil moisture and percolation were measured) was used for comparison as a benchmark. A HYDRUS-1D model and isotope measurements were used for the partitioning of total evaporation. The isotope mass balance method partitions total evaporation of 3.4 mm d-1 into 0.4 mm d-1 for soil evaporation, 0.3 mm d-1 for interception and 2.6 mm d-1 for transpiration, while the HYDRUS-1D partitions total evaporation of 3.7 mm d-1 into 1 mm d-1 for soil evaporation, 0.3 mm d-1 for interception and 2.3 mm d-1 for transpiration. From the comparison, we concluded that the isotope mass balance is better for low temporal resolution analysis than the HYDRUS-1D. On the other hand, HYDRUS-1D is better for high temporal resolution analysis than the isotope mass balance.

  2. New parallel SOR method by domain partitioning

    SciTech Connect

    Xie, D.; Adams, L.

    1999-07-01

    In this paper the authors propose and analyze a new parallel SOR method, the PSOR method, formulated by using domain partitioning and interprocessor data communication techniques. They prove that the PSOR method has the same asymptotic rate of convergence as the Red/Black (R/B) SOR method for the five-point stencil on both strip and block partitions, and as the four-color (R/B/G/O) SOR method for the nine-point stencil on strip partitions. They also demonstrate the parallel performance of the PSOR method on four different MIMD multiprocessors (a KSR1, an Intel Delta, a Paragon, and an IBM SP2). Finally, they compare the parallel performance of PSOR, R/B SOR, and R/B/G/O SOR. Numerical results on the Paragon indicate that PSOR is more efficient than R/B SOR and R/B/G/O SOR in both computation and interprocessor data communication.

  3. Fourier transform spectrometer controller for partitioned architectures

    NASA Astrophysics Data System (ADS)

    Tamas-Selicean, D.; Keymeulen, D.; Berisford, D.; Carlson, R.; Hand, K.; Pop, P.; Wadsworth, W.; Levy, R.

    The current trend in spacecraft computing is to integrate applications of different criticality levels on the same platform using no separation. This approach increases the complexity of the development, verification and integration processes, with an impact on the whole system life cycle. Researchers at ESA and NASA advocated for the use of partitioned architecture to reduce this complexity. Partitioned architectures rely on platform mechanisms to provide robust temporal and spatial separation between applications. Such architectures have been successfully implemented in several industries, such as avionics and automotive. In this paper we investigate the challenges of developing and the benefits of integrating a scientific instrument, namely a Fourier Transform Spectrometer, in such a partitioned architecture.

  4. Parallel algorithms for dynamically partitioning unstructured grids

    SciTech Connect

    Diniz, P.; Plimpton, S.; Hendrickson, B.; Leland, R.

    1994-10-01

    Grid partitioning is the method of choice for decomposing a wide variety of computational problems into naturally parallel pieces. In problems where computational load on the grid or the grid itself changes as the simulation progresses, the ability to repartition dynamically and in parallel is attractive for achieving higher performance. We describe three algorithms suitable for parallel dynamic load-balancing which attempt to partition unstructured grids so that computational load is balanced and communication is minimized. The execution time of algorithms and the quality of the partitions they generate are compared to results from serial partitioners for two large grids. The integration of the algorithms into a parallel particle simulation is also briefly discussed.

  5. Some comments on molecular partition functions

    SciTech Connect

    Sharp, C.M.

    1987-03-01

    In models of cool stellar atmospheres where molecules are important, molecular spectroscopic data can be used to calculate partition functions, from which equilibrium constants hence abundances can be obtained. In this report, it is shown that simple analytic approximations can be used to calculate very easily the partition functions of diatomic molecules, and comparisons are made for the two particularly important astrophysical molecules, H/sub 2/ and CO, with other work where the partition functions are calculated by explicitly summing over a very large number of energy levels. It is found that these analytic approximations give excellent agreement with more detailed calculations and are certainly adequate for many purposes. This method is very convenient, as only a few spectroscopic constants are needed, and the analytic formulae are very easily evaluated.

  6. the Geochemical Structure of the Hawaiian Plume

    NASA Astrophysics Data System (ADS)

    Huang, S.; Frey, F. A.

    2005-12-01

    The spatial arrangement of modern Hawaiian volcanoes forms two offset trends, the Kea and Loa trends. Lavas from these two volcanic trends have important geochemical differences; e.g., Loa and Kea trend lavas form different trends in 87Sr/86Sr and 208Pb*/206Pb* vs 3He/4He plots (e.g., Kurz et al., 1995; Lassiter et al., 1996). Abouchami et al. (2005) noted that, compared with Kea trend lavas, Loa trend lavas have relatively higher 208Pb/204Pb at a given 206Pb/204Pb, i.e., Loa trend lavas have higher 208Pb*/206Pb*. Kea and Loa trend lavas also form different trends in plots of 208Pb*/206Pb* vs Hf, Sr and Nd isotopic ratios. An important observation is that in these isotopic ratio plots, Loihi lavas are located at the intersections of the near-linear Loa and Kea trends; implying that the Loihi component (high 3He/4He) is a common source component for Loa and Kea trend volcanoes. The other ends of the Loa and Kea trends are defined by Koolau and Mauna Kea lavas, and are designated as the Koolau and Kea components. Loa trend lavas sample the Koolau and Loihi components, and the Kea trend lavas sample the Kea and Loihi components. The Loa-Kea geochemical differences have been inferred to reflect source characteristics. Consequently, different models for the structure of the Hawaiian plume have been proposed, for example, a concentrically zoned plume (Lassiter et al., 1996) and a bilaterally asymmetric plume (Abouchami et al., 2005). Based on the temporal variations of geochemical compositions of shield lavas from several Hawaiian shields, such as Mauna Kea, Koolau and Haleakala, as well as melt inclusion study, Kurz et al. (2004) and Ren et al. (2005) proposed that although the plume is grossly zoned, there are Kea- and Loa-type sources present throughout the plume. In this study, we propose that Loa and Kea volcanoes sample a common, geochemically heterogeneous mantle plume source which contains the Koolau, Kea and Loihi components. These geochemical heterogeneities

  7. Seeking a geochemical identifier for authigenic carbonate

    PubMed Central

    Zhao, Ming-Yu; Zheng, Yong-Fei; Zhao, Yan-Yan

    2016-01-01

    Authigenic carbonate was recently invoked as a third major global carbon sink in addition to primary marine carbonate and organic carbon. Distinguishing the two carbonate sinks is fundamental to our understanding of Earth's carbon cycle and its role in regulating the evolution of atmospheric oxygen. Here, using microscale geochemical measurements of carbonates in Early Triassic strata, we show that the growth of authigenic carbonate follows a different trajectory from primary marine carbonate in a cross-plot of uranium concentration and carbon isotope composition. Thus, a combination of the two geochemical variables is able to distinguish between the two carbonate sinks. The temporal distribution of authigenic carbonates in the Early Triassic strata suggests that the increase in the extent of carbonate authigenesis acted as a negative feedback to the elevated atmospheric CO2 concentration. PMID:26947562

  8. Seeking a geochemical identifier for authigenic carbonate

    NASA Astrophysics Data System (ADS)

    Zhao, Ming-Yu; Zheng, Yong-Fei; Zhao, Yan-Yan

    2016-03-01

    Authigenic carbonate was recently invoked as a third major global carbon sink in addition to primary marine carbonate and organic carbon. Distinguishing the two carbonate sinks is fundamental to our understanding of Earth's carbon cycle and its role in regulating the evolution of atmospheric oxygen. Here, using microscale geochemical measurements of carbonates in Early Triassic strata, we show that the growth of authigenic carbonate follows a different trajectory from primary marine carbonate in a cross-plot of uranium concentration and carbon isotope composition. Thus, a combination of the two geochemical variables is able to distinguish between the two carbonate sinks. The temporal distribution of authigenic carbonates in the Early Triassic strata suggests that the increase in the extent of carbonate authigenesis acted as a negative feedback to the elevated atmospheric CO2 concentration.

  9. Seeking a geochemical identifier for authigenic carbonate.

    PubMed

    Zhao, Ming-Yu; Zheng, Yong-Fei; Zhao, Yan-Yan

    2016-01-01

    Authigenic carbonate was recently invoked as a third major global carbon sink in addition to primary marine carbonate and organic carbon. Distinguishing the two carbonate sinks is fundamental to our understanding of Earth's carbon cycle and its role in regulating the evolution of atmospheric oxygen. Here, using microscale geochemical measurements of carbonates in Early Triassic strata, we show that the growth of authigenic carbonate follows a different trajectory from primary marine carbonate in a cross-plot of uranium concentration and carbon isotope composition. Thus, a combination of the two geochemical variables is able to distinguish between the two carbonate sinks. The temporal distribution of authigenic carbonates in the Early Triassic strata suggests that the increase in the extent of carbonate authigenesis acted as a negative feedback to the elevated atmospheric CO2 concentration. PMID:26947562

  10. Geochemical dynamics in selected Yellowstone hydrothermal features

    NASA Astrophysics Data System (ADS)

    Druschel, G.; Kamyshny, A.; Findlay, A.; Nuzzio, D.

    2010-12-01

    Yellowstone National Park has a wide diversity of thermal features, and includes springs with a range of pH conditions that significantly impact sulfur speciation. We have utilized a combination of voltammetric and spectroscopic techniques to characterize the intermediate sulfur chemistry of Cinder Pool, Evening Primrose, Ojo Caliente, Frying Pan, Azure, and Dragon thermal springs. These measurements additionally have demonstrated the geochemical dynamics inherent in these systems; significant variability in chemical speciation occur in many of these thermal features due to changes in gas supply rates, fluid discharge rates, and thermal differences that occur on second time scales. The dynamics of the geochemical settings shown may significantly impact how microorganisms interact with the sulfur forms in these systems.

  11. Nitrogen Partitioning Between Reduced Silicate Melts and Metallic Iron Alloys

    NASA Astrophysics Data System (ADS)

    Armstrong, L. S.; Falksen, E.; Von Der Handt, A.; Hirschmann, M. M.

    2014-12-01

    Solubility and partitioning of elements during early planetary history is critical in understanding element concentrations and distribution in the terrestrial planets. Nitrogen is the most depleted element in the bulk silicate Earth relative to CI chondrites [1], which may be explained by its high pressure behavior under reduced conditions relevant to planetary accretion and differentiation. Under oxidized conditions N dissolves in silicate melts as N2, but as fO2 decreases N-H species become the dominant form of dissolved N and the solubility increases [2-7]. DNmetal/melt (the N partition coefficient between metal and melt) is affected by pressure, fO2, fH2, and metal composition [3-5] but with less than 20 published experiments over a wide pressure range, these dependencies have been poorly constrained. Here we present new N-bearing experiments on graphite-saturated silicate melts in equilibrium with Fe-rich metallic melts. Experiments were performed at 1.2 GPa and 1400 ˚C in a piston cylinder apparatus, with N added as Si3N4, FexN, and urea [(NH2)2CO] to basaltic starting compositions. Glassy and metallic run products were gold coated and analyzed by EMPA. Detection limits and standard errors in N concentrations were improved (e.g. better than 1% for > 0.4 wt% N) relative to previous studies [2-5] by fitting non-linear backgrounds to wavelength-scans on standards and unknowns. Preliminary experiments with fO2 of IW-2 to IW-4 produced glasses with a maximum of 0.6 wt% N and metals with a maximum of 1.1 wt% N. DNmetal/melt are comparable to values at a similar pressure determined in the LH-DAC [5]. Further experiments will explore the effects of fO2 and H content on DN and N solubility. References: [1] Halliday (2013) GCA 105, 146-171. [2] Libourel et al. (2003) GCA 67, 4123-4135. [3] Kadik et al. (2011) Geochem. Int. 49, 429-438. [4] Kadik et al. (2013) PEPI 214, 14-24. [5] Roskosz et al. (2013) GCA 121, 15-28. [6] Stanley et al. (2014) GCA 129, 54-76. [7

  12. Synthesizing Earth's geochemical data for hydrogeochemical analysis

    NASA Astrophysics Data System (ADS)

    Brantley, S. L.; Kubicki, J.; Miller, D.; Richter, D.; Giles, L.; Mitra, P.

    2007-12-01

    For over 200 years, geochemical, microbiological, and chemical data have been collected to describe the evolution of the surface earth. Many of these measurements are data showing variations in time or in space. To forward predict hydrologic response to changing tectonic, climatic, or anthropogenic forcings requires synthesis of these data and utilization in hydrogeochemical models. Increasingly, scientists are attempting to synthesize such data in order to make predictions for new regions or for future time periods. However, to make such complex geochemical data accessible requires development of sophisticated cyberinfrastructures that both invite uploading as well as usage of data. Two such cyberinfrastructure (CI) initiatives are currently developing, one to invite and promote the use of environmental kinetics data (laboratory time course data) through ChemxSeer, and the other to invite and promote the use of spatially indexed geochemical data for the Earth's Critical Zone through CZEN.org. The vision of these CI initiatives is to provide cyber-enhanced portals that encourage domain scientists to upload their data before publication (in private cyberspace), and to make these data eventually publicly accessible (after an embargo period). If the CI can be made to provide services to the domain specialist - e.g. to provide data analysis services or data comparison services - we envision that scientists will upload data. In addition, the CI can promote the use and comparison of datasets across disciplines. For example, the CI can facilitate the use of spatially indexed geochemical data by scientists more accustomed to dealing with time-course data for hydrologic flow, and can provide user-friendly interfaces with CI established to facilitate the use of hydrologic data. Examples of the usage of synthesized data to predict soil development over the last 13ky and its effects on active hydrological flow boundaries in surficial systems will be discussed for i) a N

  13. Geochemical patterns in the soils of Cyprus.

    PubMed

    Cohen, David R; Rutherford, Neil F; Morisseau, Eleni; Zissimos, Andreas M

    2012-03-15

    The soil geochemical atlas of Cyprus is a recent addition to the series of national to continental-scale geochemical mapping programmes implemented over the last two decades for environmental and resource applications. The study has been conducted at the high sampling density of 1 site per 1km(2), with multi-element and multi-method analysis performed on samples of top soil (0-25cm) and sub soil (50-75cm) from a grid of over 5350 sites across a major portion of Cyprus. Major and most trace elements display sharp concentration changes across the main geological boundaries but a high degree of spatial continuity and consistency of values within those boundaries. Some elements display one to two orders of magnitude difference in median concentrations between the soils developed over ultramafic or mafic units and those developed over sedimentary rocks or alluvial units. The ratio of aqua regia-extractable to total metal contents provides an indication of the general mineralogical host for a number of trace elements. The majority of soils are near-neutral to alkaline with the small proportion of areas with soil pH<5 largely restricted to the major Cu deposits. There is strong correlation between top soil and sub soil geochemical values. Where the concentrations of some elements (including Pb, Hg and Sn) are indicative of contamination, the values are typically higher in the top soil samples in these areas. Variations in the concentration of elements with strong redox controls on mobility are linked to changes in sedimentary environment between deep and shallow marine conditions. Some element patterns can be related to the effects of urbanisation and sulphide mining operations; however the dominant control on soil geochemistry is the parent geology and regolith forming processes. The atlas demonstrates the effectiveness of high-density sampling in mapping local to regional-scale features of the geochemical landscape. PMID:22330424

  14. Summary report on geochemical barrier special study

    SciTech Connect

    Not Available

    1988-12-01

    Long-term management of uranium mill tailings must provide assurance that soluble contaminants will not migrate beyond the Point of Compliance. Conventional management alternatives provide containment through the use of physical barriers which are designed to prevent migration of water through the tailings pile. An alternative is to geochemically modify the tailings to immobilize the contaminants. This investigation examined three potential geochemical modifiers to determine their ability to immobilize inorganic groundwater contaminants found in uranium mill tailings. These modifiers were hydrated lime (Ca(OH){sub 2}), limestone (CaCO{sub 3}), and a sphaegnum peat moss. This investigation focused on both the geochemical interactions between the tailings and the modifiers, and the effects the modifiers had on the physical strength of the tailings. The geochemical investigations began with characterization of the tailings by X-ray diffraction and scanning electron microscopy. This was followed by batch leaching experiments in which various concentrations of each modifier were added to tailings in shaker flasks and allowed to come to equilibrium. Finally, column experiments were conducted to simulate flow through a tailings pile. The results show that all of the modifiers were at least moderately effective at immobilizing most of the groundwater contaminants of concern at uranium mill tailings sites. Hydrated lime was able to achieve 90 percent concentration reduction of arsenic, cadmium, selenium, uranium, and sulfate when added at a two percent concentration. Limestone was somewhat less effective and peat removed greater than 90 percent of arsenic, lead, uranium, and sulfate at a one percent concentration. The column tests showed that kinetic and/or mass transfer limitations are important and that sufficient time must be allowed for the immobilization reactions to occur.

  15. DNA Partitioning in Confining Nanofluidic Slits

    NASA Astrophysics Data System (ADS)

    Greenier, Madeline; Levy, Stephen

    We measure the partitioning of double stranded DNA molecules in moderately and strongly confining nanofluidic slit-like structures. Using fluorescent microscopy, the free energy penalty of confinement is inferred by comparing the concentration of DNA molecules in adjoining slits of different depths. These depths range in size from several persistence lengths to the DNA molecule's radius of gyration. The partition coefficient is determined as a function of the slit depth, DNA contour length, and DNA topology. We compare our results to theory and Monte Carlo simulations that predict the loss of free energy for ideal and semiflexible excluded volume polymers confined between parallel plates.

  16. Partition signed social networks via clustering dynamics

    NASA Astrophysics Data System (ADS)

    Wu, Jianshe; Zhang, Long; Li, Yong; Jiao, Yang

    2016-02-01

    Inspired by the dynamics phenomenon occurred in social networks, the WJJLGS model is modified to imitate the clustering dynamics of signed social networks. Analyses show that the clustering dynamics of the model can be applied to partition signed social networks. Traditionally, blockmodel is applied to partition signed networks. In this paper, a detailed dynamics-based algorithm for signed social networks (DBAS) is presented. Simulations on several typical real-world and illustrative networks that have been analyzed by the blockmodel verify the correctness of the proposed algorithm. The efficiency of the algorithm is verified on large scale synthetic networks.

  17. Partitioning SAT Instances for Distributed Solving

    NASA Astrophysics Data System (ADS)

    Hyvärinen, Antti E. J.; Junttila, Tommi; Niemelä, Ilkka

    In this paper we study the problem of solving hard propositional satisfiability problem (SAT) instances in a computing grid or cloud, where run times and communication between parallel running computations are limited.We study analytically an approach where the instance is partitioned iteratively into a tree of subproblems and each node in the tree is solved in parallel.We present new methods for constructing partitions which combine clause learning and lookahead. The methods are incorporated into the iterative approach and its performance is demonstrated with an extensive comparison against the best sequential solvers in the SAT competition 2009 as well as against two efficient parallel solvers.

  18. Partitioning of light lithophile elements during basalt eruptions on Earth and application to Martian shergottites

    NASA Astrophysics Data System (ADS)

    Edmonds, Marie

    2015-02-01

    An enigmatic record of light lithophile element (LLE) zoning in pyroxenes in basaltic shergottite meteorites, whereby LLE concentrations decrease dramatically from the cores to the rims, has been interpreted as being due to partitioning of LLE into a hydrous vapor during magma ascent to the surface on Mars. These trends are used as evidence that Martian basaltic melts are water-rich (McSween et al., 2001). Lithium and boron are light lithophile elements (LLE) that partition into volcanic minerals and into vapor from silicate melts, making them potential tracers of degassing processes during magma ascent to the surface of Earth and of other planets. While LLE degassing behavior is relatively well understood for silica-rich melts, where water and LLE concentrations are relatively high, very little data exists for LLE abundance, heterogeneity and degassing in basaltic melts. The lack of data hampers interpretation of the trends in the shergottite meteorites. Through a geochemical study of LLE, volatile and trace elements in olivine-hosted melt inclusions from Kilauea Volcano, Hawaii, it can be demonstrated that lithium behaves similarly to the light to middle rare Earth elements during melting, magma mixing and fractionation. Considerable heterogeneity in lithium and boron is inherited from mantle-derived primary melts, which is dominant over the fractionation and degassing signal. Lithium and boron are only very weakly volatile in basaltic melt erupted from Kilauea Volcano, with vapor-melt partition coefficients <0.1. Degassing of LLE is further inhibited at high temperatures. Pyroxene and associated melt inclusion LLE concentrations from a range of volcanoes are used to quantify lithium pyroxene-melt partition coefficients, which correlate negatively with melt H2O content, ranging from 0.13 at low water contents to <0.08 at H2O contents >4 wt%. The observed terrestrial LLE partitioning behavior is extrapolated to Martian primitive melts through modeling. The zoning

  19. Geochemical evolution of a fractured zone in the cap rock of an underground carbon storage site

    NASA Astrophysics Data System (ADS)

    Vialle, S.; Druhan, J. L.; Maher, K.

    2013-12-01

    Assessment and management of environmental risks associated with underground storage of CO2 in geological systems is essential for the commercial deployment of this technology. A major risk is leakage of the CO2 from its storage reservoir, through wellbores, and along faults and fractures in the cap rock. The geochemical reactions likely to take place as CO2 leaks through a damage zone and their impact on cap rock integrity still need to be better understood and quantified. Should CO2 leakage occur, geochemical reactions would govern the environmental impact on shallow groundwater aquifers and could provide an indication of the leak prior to surface-based monitoring techniques. We used the reactive transport code TOUGH2/TOUGHREACT to model a leakage scenario through a fractured cap rock. Since geochemical reactions will strongly depend upon the local hydrodynamics of the CO2 leak, the first step of the study is to provide an appropriate physical representation of fluid flow through the system. Typically, for a low porosity rock formation, a fault/damaged zone system is composed of a core of low permeability and a damage zone with second-order fractures whose density decreases with distance from the fault core. Permeability is thus increased along the fault plane and laterally decreases down to the permeability value of the undamaged cap rock. Appropriate scaling relationships (e.g., and analytical expression of for permeability as a function of fracture aperture and fracture density), effective physical parameters as well as constitutive relationships are carefully chosen to model the fractured system, treated as an equivalent porous medium. The cap rock is initially saturated with brine (salinity of 0.15 in mass fraction) and due to overpressure in the lower storage reservoir, CO2 migrates through the damage zone. Geochemical reactions involve both salt precipitation due to the partitioning of H2O and CO2 between liquid and gas phases as well as well reactions

  20. Application of the two-source energy balance model to partition evapotranspiration in an arid wine vineyard

    NASA Astrophysics Data System (ADS)

    Kool, Dilia; Kustas, William P.; Agam, Nurit

    2016-04-01

    The partitioning of evapotranspiration (ET) into transpiration (T), a productive water use, and soil water evaporation (E), which is generally considered a water loss, is highly relevant to agriculture in the light of increasing desertification and water scarcity. This task is challenged by the complexity of soil and plant interactions, coupled with changes in atmospheric and soil water content conditions. Many of the processes controlling water/energy exchange are not adequately modeled. The two-source energy balance model (TSEB) was evaluated and adapted for independent E and T estimations in an isolated drip-irrigated wine vineyard in the arid Negev desert. The TSEB model estimates ET by computing vegetation and soil energy fluxes using remotely sensed composite surface temperature, local weather data (solar radiation, air temperature and humidity, and wind speed), and vegetation metrics (row spacing, canopy height and width, and leaf area). The soil and vegetation energy fluxes are computed numerically using a system of temperature gradient and resistance equations; where soil and canopy temperatures are derived from the composite surface temperature. For estimation of ET, the TSEB model has been shown to perform well for various agricultural crops under a wide range of environmental conditions, but validation of T and E fluxes is limited to one study in a well-watered cotton crop. Extending the TSEB approach to water-limited vineyards demands careful consideration regarding how the complex canopy structure of vineyards will influence the accuracy of the partitioning between E and T. Data for evaluation of the TSEB model were collected over a season (bud break till harvest). Composite, canopy, and soil surface temperatures were measured using infrared thermometers. The composite vegetation and soil surface energy fluxes were assessed using independent measurements of net radiation, and soil, sensible and latent heat flux. The below canopy energy balance was

  1. Spatial and temporal variations in percolation fluxes in a tropical Andosol influenced by banana cropping patterns

    NASA Astrophysics Data System (ADS)

    Cattan, P.; Voltz, M.; Cabidoche, Y.-M.; Lacas, J.-G.; Sansoulet, J.

    2007-03-01

    SummarySpatial variability in percolation fluxes was studied in field plots cropped with banana plants, which induce very heterogeneous rainfall partitioning at the soil surface, with high subsequent infiltration in Andosols. Percolation fluxes were measured for just over a year at 1-7 day intervals in eight wick (WL) and gravity lysimeters (GL) that had been buried in the soil at a depth of 60 cm. The results revealed that WL captured unsaturated fluxes while GL only functioned after ponding occurred. The percolation flux measurements were highly biased with both systems, i.e. overpercolation with WL and underpercolation with GL. Percolation fluxes seemed, however, to be mainly unsaturated in the soil types studied. High percolation flux variability was noted on a plot scale, which could be explained by the vegetation structure: total percolation flux (WL) was 2.1-fold higher under banana plants; saturated percolation flux (GL) was 7-fold higher under banana plants and almost absent between banana plants. Eighty-eight per cent of the total variance in percolation flux could be explained by the rainfall intensity under the banana canopy, calculated while taking the rainfall partitioning by the vegetation and the initial water status into account. The number of lysimeters required for assessing percolation flux in a field plot can be reduced by taking the spatial patterns of the flux boundary conditions into account.

  2. The Surface Heat Flux as a Function of Ground Cover for Climate Models

    NASA Technical Reports Server (NTRS)

    Vukovich, Fred M.; Wayland, Robert; Toll, David

    1997-01-01

    Surface heat fluxes were examined as a function of surface properties and meteorological conditions in a 100 km x 100 km grid square at 1-km spatial resolution centered at the location of the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE), the Forest Ecosystem Dynamics site in central Maine, and a semiarid rangeland site around Walnut Gulch, Arizona. This investigation treats the surface heat flux variability within a GCM grid box to provide insight into methods for treating that variability in climate models. The heat fluxes were calculated using NOAA AVHRR and available meteorological data. The average heat fluxes that were estimated using the various area ground-cover representations were compared with the ensemble average heat fluxes for the entire area, which were assumed to be the best representation of the heat fluxes for the areas. Average beat fluxes were estimated for the entire 100 km x 100 km area based on a single ground-cover representation, and the mean error for the area sensible heat flux was about 10% and for the area latent heat flux, 21%. The estimation error was reduced, and in some cases significantly reduced, when the area heat fluxes were estimated by partitioning the area according to significant ground cover. The most significant effect of the partitioning was on the latent heat flux estimates.

  3. Controls on OIB and MORB Geochemical Variabilty

    NASA Astrophysics Data System (ADS)

    Shorttle, O.; Maclennan, J.

    2014-12-01

    The geochemical variability preserved in Ocean Island and Mid-ocean ridge basalt (MORB) is a key tracer of the magmatic storage and transport processes they experience during their ascent through the mantle and crust. The effect of these processes is to collapse the huge diversity of melt compositions predicted to form during polybaric fractional melting of a lithologically heterogeneous mantle, into the narrow range we see expressed in most ocean island and mid-ocean ridge settings. Magma mixing can therefore be seen as contaminating the variance structure of primitive mantle melts, akin to the way in which wall-rock assimilation contaminates melts by chemical addition. The key observation from the melt inclusion and whole-rock records from ocean islands such as Iceland, is that as crystallisation proceeds mixing in magma chambers progressively reduces geochemical variability, until by ~5wt% MgO almost all primary chemical diversity has been lost. These chemical systematics allow us to extend the observations made at ocean islands to make predictions about how mixing processes should operate in MORB generally and the key factors controlling mixing efficiency: melt flow out of the mantle, crustal thickness, magma supply rate, and by extension spreading rate, and mantle potential temperature. However, with its low sampling density, the global MORB database does not easily allow testing of these hypotheses. We have developed a novel geospatial statistical analysis to bridge the gap between observations made on a small scale - at single ocean islands and ridge segments - to the entire global dataset of MORB chemistry. By analysing the geochemical variance in MORB over a range of bandwidths we have captured the ~200km lengthscale at which the simple relationships between geochemical variability and MgO appear. Our results demonstrate that on short lengthscales mantle chemical structure and magmatic processes operate coherently in destruction of geochemical variability

  4. Ranking Geochemical Energy Availability in Hydrothermal Ecosystems

    NASA Astrophysics Data System (ADS)

    Holland, M. E.; Shock, E. L.; Meyer-Dombard, D.; Amend, J. P.

    2004-12-01

    The energy available to hyperthermophilic microorganisms in hot springs can be theoretically estimated using thermodynamic calculations based on geochemical measurements. The relative abundance of different geochemical energy sources (the "ranking" of these reactions) in particular hot springs may provide one explanation for the differences in hot spring microbial communities and also facilitate the culture of ecologically-relevant microorganisms. Geochemical sampling of seven Yellowstone National Park hot springs was repeated five times from 1999 to 2004 with the intent to compare the geochemistry and geochemical energy available to microorganisms. These seven hot springs were located in three separate regions of Yellowstone National Park: three hot springs, including Obsidian Pool, were sampled in the Mud Volcano area; two in the Sylvan Springs area (Gibbon Meadows); and one each in Imperial Meadows and Sentinel Meadows (Lower Geyser Basin). The hot springs were 75 to 93° C (with one 65° C exception) and spanned the bulk of the pH range at Yellowstone (pH 1.8 to 7.6). Geochemical measurements made on hot springs included redox-active species containing C, N, O, H, S, and Fe; these species were measured by field spectrophotometry and ion chromatography of fluid samples and gas chromatographic analysis of gas samples. From these measurements chemical affinities were calculated for 179 inorganic reactions which encompass the suite of autotrophic energy sources potentially available in each pool. Composite affinities for each reaction were compiled for each of the seven primary pools. The composite for each pool was assembled from repeat measurements from the primary pool as well as nearby pools with similar geochemistry. Calculations show that over half of these inorganic reactions could provide enough energy for a microorganism to survive, based on the threshold value of energy required by {it E. coli} (20 kJ per mole of electron pairs). Some microorganisms

  5. A theory for optimal heat transfer in a partitioned convection cell

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Bao, Yun; She, Zhen-Su

    2015-11-01

    We report a theory explaining recent observation of significant enhancement of heat transfer in a partitioned Rayleigh-Bénard convection (RBC), where vertical adiabatic boards are inserted into the enclosure with narrow channel left open between partition boards and the cooling/heating plates. An enhancement of heat transfer of up to 2.7 times is observed compared to normal RBC cell without partitions. It is found that laminar wall jet is formed in the narrow horizontal channel, which makes the thermal boundary layer thinner. Two asymptotic trends, a channel flow and a boundary layer, describe the motions of the jets in the horizontal channel, and the competition between them gives rise to an optimized state for the global heat transfer, with an optimal width of the sub-cell W/H =0.038-0.083 for Γ = 1, and an optimal spacing of the horizontal channel b/H =0.011 for Γ = 5. The former (channel) yields a heat flux linearly proportional to b for small b, whereas the latter (boundary layer) follows -2/3-law for large b. We suggest that the partitioned RBC provides a vehicle for heat enhancement with a wide range of industrial applications. This work was supported by National Nature Science Fund of China under Grant No. 11372362.

  6. Influence of carbon partitioning kinetics on final Austenite fraction during quenching and partitioning

    SciTech Connect

    Clarke, Amy J; Speer, John G; Matlock, David K; Rizzo, F C; Edmonds, David V; Santofimia, Maria J

    2009-01-01

    The quenching and partitioning (Q&P) process is a two-stage heat-treatment procedure proposed for producing steel microstructures that contain carbon-enriched retained austenite. In Q&P processing, austenite stabilization is accomplished by carbon partitioning from supersaturated martensite. A quench temperature selection methodology was developed to predict an optimum process quench temperature; extension of this methodology to include carbon partitioning kinetics is developed here. Final austenite fraction is less sensitive to quench temperature than previously predicted, in agreement with experimental results.

  7. Energy partitioning and environmental influence factors in different vegetation types in the GEWEX Asian Monsoon Experiment

    NASA Astrophysics Data System (ADS)

    Liu, Fengshan; Tao, Fulu; Li, Shenggong; Zhang, Shuai; Xiao, Dengpan; Wang, Meng

    2014-12-01

    Environmental influences upon energy balance in areas of different vegetation types (i.e., forest at Kog-Ma in Thailand and at Yakutsk in Russia, grassland at Amdo in Chinese Tibet and at Arvaikheer in Mongolia, and mixed farmland at Tak in Thailand) in the GEWEX Asian Monsoon Experiment were investigated. The sites we investigated are geographically and climatologically different; and consequently had quite large variations in temperature ( T), water vapor pressure deficit (VPD), soil moisture (SM), and precipitation (PPT). During May-October, the net radiation flux ( R n) (in W·m-2) was 406.21 at Tak, 365.57 at Kog-Ma, 390.97 at Amdo, 316.65 at Arvaikheer, and 287.10 at Yakutsk. During the growing period, the R n partitioned into latent heat flux ( λE/ R n) was greater than that partitioned into sensible heat flux ( H/ R n) at Tak and at Kog-Ma. In contrast, λE/ R n was lower than H/ R n at Arvaikheer, H/ R n was less than λE/ R n between DOY 149 and DOY 270 at Amdo, and between DOY 165 and DOY 235 at Yakutsk. The R n partitioned into ground heat flux was generally less than 0.15. The short-wave albedo was 0.12, 0.18, and 0.20 at the forest, mixed land, and grass sites, respectively. At an hourly scale, energy partitions had no correlation with environmental factors, based on average summer halfhourly values. At a seasonal scale energy partitions were linearly correlated (usually p<0.05) with T, VPD, and SM. The λE/ R n increased with increases in SM, T, and VPD at forest areas. At mixed farmlands, λE/ R n generally had positive correlations with SM, T, and VPD, but was restrained at extremely high values of VPD and T. At grasslands, λE/ R n was enhanced with increases of SM and T, but was decreased with VPD.

  8. Models of geochemical systems from mixture theory: diffusion

    SciTech Connect

    Kirwan, A.D. Jr; Kump, L.R.

    1987-05-01

    The problem of diffusion of a geochemical component in a natural environment is investigated from the standpoint of mixture theory. The approach here differs from previous diffusion studies in that both the conservation of mass and momentum for the component is considered. This approach avoids parameterizing the diffusive flux in the mass equation by Fick's law. It is shown that when the momentum equation is included with the mass equation, the linear approximation for the space-time distribution of a solute in a binary system is the telegraph equation, well known from electrodynamics. This contrasts with the diffusion equation, which relies on introducing the Fick's law assumption into the conservation of mass equation for the solute. Solutions for both the diffusion and telegraph equation models are obtained and compared for the case of migration of a minor component into the sea bed when the sediment-water interface concentration is a prescribed function of time. Although the stationary, steady state solutions of the telegraph and diffusion equations are identical, the former has a transient solution in which fluctuations propagate at finite speed. The Fickian assumption, in contrast, requires an infinite speed of propagation.

  9. Partitioning and lipophilicity in quantitative structure-activity relationships.

    PubMed Central

    Dearden, J C

    1985-01-01

    The history of the relationship of biological activity to partition coefficient and related properties is briefly reviewed. The dominance of partition coefficient in quantitation of structure-activity relationships is emphasized, although the importance of other factors is also demonstrated. Various mathematical models of in vivo transport and binding are discussed; most of these involve partitioning as the primary mechanism of transport. The models describe observed quantitative structure-activity relationships (QSARs) well on the whole, confirming that partitioning is of key importance in in vivo behavior of a xenobiotic. The partition coefficient is shown to correlate with numerous other parameters representing bulk, such as molecular weight, volume and surface area, parachor and calculated indices such as molecular connectivity; this is especially so for apolar molecules, because for polar molecules lipophilicity factors into both bulk and polar or hydrogen bonding components. The relationship of partition coefficient to chromatographic parameters is discussed, and it is shown that such parameters, which are often readily obtainable experimentally, can successfully supplant partition coefficient in QSARs. The relationship of aqueous solubility with partition coefficient is examined in detail. Correlations are observed, even with solid compounds, and these can be used to predict solubility. The additive/constitutive nature of partition coefficient is discussed extensively, as are the available schemes for the calculation of partition coefficient. Finally the use of partition coefficient to provide structural information is considered. It is shown that partition coefficient can be a valuable structural tool, especially if the enthalpy and entropy of partitioning are available. PMID:3905374

  10. PARTITIONING OF METALS IN ROTARY KILN INCINERATION

    EPA Science Inventory

    This research project investigated the fate of trace metals in rotary kiln incineration with venturi- and packed tower-scrubber particulate- and acid gas-control. est plan was developed, using a factorial experimental design, to study the partitioning of metals among kiln ash, sc...

  11. Lipid metabolism and nutrient partitioning strategies.

    PubMed

    Morris, A M; Calsbeek, D J; Eckel, R H

    2004-10-01

    The increasing prevalence of overweight and obesity worldwide is daunting and requires prompt attention by the affected, health care profession, government and the pharmaceutical industry. Because overweight/obesity are defined as an excess of adipose tissue mass, all approaches in prevention and treatment must consider redirecting lipid storage in adipose tissue to oxidative metabolism. Lipid partitioning is a complex process that involves interaction between fat and other macronutrients, particularly carbohydrate. In an isocaloric environment, when fat is stored carbohydrate is oxidized and vice versa. Processes that influence fat partitioning in a manner in which weight is maintained must be modified by changes in organ-specific fat transport and metabolism. When therapy is considered, however, changes in lipid partitioning alone will be ineffective unless a negative energy balance is also achieved, i.e. energy expenditure exceeds energy intake. The intent of this review is to focus on molecules including hormones, enzymes, cytokines, membrane transport proteins, and transcription factors directly involved in fat trafficking and partitioning that could be potential drug targets. Some examples of favorably altering body composition by systemic and/or tissue specific modification of these molecules have already been provided with gene knockout and/or transgenic approaches in mice. The translation of this science to humans remains a challenging task. PMID:15544448

  12. Hydrologic transport and partitioning of phosphorus fractions

    NASA Astrophysics Data System (ADS)

    Berretta, C.; Sansalone, J.

    2011-06-01

    SummaryPhosphorus (P) in rainfall-runoff partitions between dissolved and particulate matter (PM) bound phases. This study investigates the transport and partitioning of P to PM fractions in runoff from a landscaped and biogenically-loaded carpark in Gainesville, FL (GNV). Additionally, partitioning and concentration results are compared to a similarly-sized concrete-paved source area of a similar rainfall depth frequency distribution in Baton Rouge, LA (BTR), where in contrast vehicular traffic represents the main source of pollutants. Results illustrate that concentrations of P fractions (dissolved, suspended, settleable and sediment) for GNV are one to two orders of magnitude higher than BTR. Despite these differences the dissolved fraction ( f d) and partitioning coefficient ( K d) distributions are similar, illustrating that P is predominantly bound to PM fractions. Examining PM size fractions, specific capacity for P (PSC) indicates that the P concentration order is suspended > settleable > sediment for GNV, similarly to BTR. For GNV the dominant PM mass fraction is sediment (>75 μm), while the mass of P is distributed predominantly between sediment and suspended (<25 μm) fractions since these PM mass fractions dominated the settleable one. With respect to transport of PM and P fractions the predominance of events for both areas is mass-limited first-flush, although each fraction illustrated unique washoff parameters. However, while transport is predominantly mass-limited, the transport of each PM and P fraction is influenced by separate hydrologic parameters.

  13. Set Partitions and the Multiplication Principle

    ERIC Educational Resources Information Center

    Lockwood, Elise; Caughman, John S., IV

    2016-01-01

    To further understand student thinking in the context of combinatorial enumeration, we examine student work on a problem involving set partitions. In this context, we note some key features of the multiplication principle that were often not attended to by students. We also share a productive way of thinking that emerged for several students who…

  14. UNCERTAINTY IN SOURCE PARTITIONING USING STABLE ISOTOPES

    EPA Science Inventory

    Stable isotope analyses are often used to quantify the contribution of multiple sources to a mixture, such as proportions of food sources in an animal's diet, C3 vs. C4 plant inputs to soil organic carbon, etc. Linear mixing models can be used to partition two sources with a sin...

  15. A review of approaches for evapotranspiration partitioning

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Partitioning of evapotranspiration (ET) into evaporation from the soil surface (E) and transpiration (T) is challenging but important in order to assess biomass production and the allocation of increasingly scarce water resources. Generally T is the desired component with the water being used to enh...

  16. Measure-theoretic sensitivity via finite partitions

    NASA Astrophysics Data System (ADS)

    Li, Jian

    2016-07-01

    For every positive integer n≥slant 2 , we introduce the concept of measure-theoretic n-sensitivity for measure-theoretic dynamical systems via finite measurable partitions, and show that an ergodic system is measure-theoretically n-sensitive but not (n  +  1)-sensitive if and only if its maximal pattern entropy is log n .

  17. hydrogen partitioning between postperovskite and bridgmanite

    NASA Astrophysics Data System (ADS)

    Townsend, J. P.; Jacobsen, S. D.; Bina, C. R.; Tsuchiya, J.

    2015-12-01

    We present new results from first-principles calculations of phonon spectra of lower mantle phases of MgSiO3 bridgmanite (brg) and postperovskite (ppv) including hydrous defects, and alumino-hydrous defects. We compute the partition coefficient of hydrogen between ppv and brg for hydrous and alumino-hydrous compositions at D" pressures and temperatures from first-principles lattice dynamics simulations and free energy calculations computed under the quasiharmonic approximation. We find that for aluminum free hydrous conditions the hydrogen partition coefficient between ppv and brg ranges from 0.2-0.8 within D". However, in the presence of aluminum the aluminum-hydrogen partition coefficient between ppv and brg is approximately 1.5. In general for a given pressure, lower temperature increases the partitioning of hydrogen into ppv for the aluminous models, but not for the aluminum free models. Because aluminum is is expected to occur in both natural slab and mantle compositions this suggests aluminous-hydrous ppv may be a host for water in D".

  18. Mapping Pesticide Partition Coefficients By Electromagnetic Induction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A potential method for reducing pesticide leaching is to base application rates on the leaching potential of a specific chemical and soil combination. However, leaching is determined in part by the partitioning of the chemical between the soil and soil solution, which varies across a field. Standard...

  19. Creep-fatigue analysis by Strainrange Partitioning

    NASA Technical Reports Server (NTRS)

    Manson, S. S.; Halford, G. R.; Hirschbere, M. H.

    1973-01-01

    Strainrange Partitioning provides unifying framework for characterizing high-temperature, low-cycle, creep-fatigue properties of metals and alloys. Method offers distinct advantage to designers of immediately providing reliable upper and lower bounds on cyclic life for any type of inelastic strain cycle that may be encountered in service.

  20. Uranium and rare earth partitioning in Synroc

    SciTech Connect

    Smith, K.L.; Lumpkin, G.R.; Blackford, M.G.

    1993-12-31

    Improved AEM techniques were used to investigate three Synrocs containing 10 wt% simulated HLW and a fourth sample with {approximately}18 wt% simulated HLW. One of the 10 wt% loaded Synrocs also contained an addition of 1.0 wt% Na{sub 2}O and another contained an addition of 2.0 wt% Fe{sub 2}O{sub 3}. This work is part of a larger study initiated with the objective of determining if the bulk composition of Synroc affects the partitioning of elements between individual phases. Results from the four samples in this study show that, as expected, elemental partitioning is mainly controlled by the ionic radius criterion, with smaller Y, Gd, and U ions having a preference for zirconolite and the larger Ce and Nd ions favouring perovskite. Additions of Na and Fe lead to the formation of CAT and loveringite at the expense of rutile or Magneli phases, but only have minor effects on partitioning coefficients. Partitioning coefficients, D{sup Z/P}, for REE, Y, and U in the four Synrocs are the same (within experimental error).

  1. Partition function of interacting calorons ensemble

    NASA Astrophysics Data System (ADS)

    Deldar, S.; Kiamari, M.

    2016-01-01

    We present a method for computing the partition function of a caloron ensemble taking into account the interaction of calorons. We focus on caloron-Dirac string interaction and show that the metric that Diakonov and Petrov offered, works well in the limit where this interaction occurs. We suggest computing the correlation function of two polyakov loops by applying Ewald's method.

  2. A comparison of trenched plot techniques for partitioning soil respiration

    SciTech Connect

    Bond-Lamberty, Benjamin; Bronson, Dustin; Bladyka, Emma; Gower, Stith T.

    2011-07-16

    Partitioning the soil surface CO{sub 2} flux (R{sub S}) flux is an important step in understanding ecosystem-level carbon cycling, given that R{sub S} is poorly constrained and its source components may have different responses to climate change. Trenched plots are a classic method of separating the R{sub S} source fluxes, but labor-intensive and may cause considerable disturbance to the soil environment. This study tested if various methods of plant suppression in trenched plots affected R{sub S} fluxes, quantified the R{sub S} response to soil temperature and moisture changes, and estimated the heterotrophic contribution to R{sub S}. It was performed in a boreal black spruce (Picea mariana) plantation, using a complete randomized design, during the 2007 growing season (May-November). Trenched plots had significantly lower R{sub S} than control plots, with differences appearing {approx}100 days after trenching; spatial variability doubled after trenching but then declined throughout the experiment. Most trenching treatments had significantly lower (by {approx}0.5 {mu}mol m{sup -2} s{sup -1}) R{sub S} than the controls, and there was no significant difference in R{sub S} among the various trenching treatments. Soil temperature at 2 cm explained more R{sub S} variability than did 10-cm temperature or soil moisture. Temperature sensitivity (Q10) declined in the control plots from {approx}2.6 (at 5 C) to {approx}1.6 (at 15 C); trenched plots values were higher, from 3.1 at 5 C to 1.9 at 15 C. We estimated R{sub S} for the study period to be 241 {+-} 40 g C m{sup -2}, with roots contributing 64% of R{sub S} after accounting for fine root decay, and 293 g C m{sup -2} for the entire year. These findings suggest that laborious hand weeding of vegetation may be usefully replaced by other methods, easing future studies of this large and poorly-understood carbon flux.

  3. A geochemical atlas of South Carolina--an example using data from the National Geochemical Survey

    USGS Publications Warehouse

    Sutphin, David M.

    2005-01-01

    National Geochemical Survey data from stream-sediment and soil samples, which have been analyzed using consistent methods, were used to create maps, graphs, and tables that were assembled in a consistent atlas format that characterizes the distribution of major and trace chemical elements in South Carolina. Distribution patterns of the elements in South Carolina may assist mineral exploration, agriculture, waste-disposal-siting issues, health, environmental, and other studies. This atlas is an example of how data from the National Geochemical Survey may be used to identify general or regional patterns of elemental occurrences and to provide a snapshot of element concentration in smaller areas.

  4. Geochemical anomalies in the bottom waters of the Tadjoura rift zone, Gulf of Aden

    SciTech Connect

    Demina, L.L.; Tambiev, S.B.

    1987-04-01

    The study of geochemical fields and geochemical anomalies is a necessary part of exploration for ore deposits on the ocean floor. Geochemical processes related to hydrothermal activity occurring at the boundary between different media are of special interest. About 10 years ago, concentrations of suspended iron 20 times greater than those in the overlying waters were found in the bottom waters of the Mid-Atlantic Rift near 26/sup 0/N. A number of reports then appeared, showing that in other rift zones as well, the bottom/water interface is characterized by elevated concentrations of iron, manganese, zinc, copper, nickel, and other elements. Thus the present writers were persuaded that the minor elements in bottom waters can serve as indicators of hydrothermal flux to the ocean floor. In carrying out investigations of this kind, one must study the distribution of the metals not only in the bottom waters, but through the entire depth of the sea, so that anomalies can be detected and localized against the level of the background concentrations. In addition, to obtain information on the sources of the metals, one must determine not just the total contents, but also distinguish the metals in solution and in suspension. Results are discussed. The observations clarify the relations between dissolved and suspended forms of metals in weakly mineralized waters above oceanic rifts. 13 references, 5 figures, 5 tables.

  5. Fluxes of Ultrafine Particles Over and In a Deciduous Forest

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.

    2013-12-01

    Given the importance of forests to land surface cover and particle removal (due to the very high deposition velocities and well-developed turbulence) there is a specific need to understand removal to, and in, forests. Fluxes of size-resolved and total particle number fluxes over (at 46 m) and in (at 7 m) a deciduous forest over a 14 month period are presented based on data from two Gill 3-D WindMaster Pro sonic anemometers, an Ultrafine Condensation Particle Counter (UCPC) operated at 10 Hz and a Fast Mobility Particle Sizer (FMPS) operated at 1 Hz. Size-resolved particle profiles during the same period are measured using a separate FMPS scanning at three measurement heights across the canopy (top, middle and bottom). Three methods are being applied to derive the total number and size-resolved fluxes from the UCPC and FMPS respectively; eddy covariance, inertial dissipation and the co-spectral approach. The results are integrated with fluxes of sensible heat, momentum and carbon dioxide derived using a Licor LI-7200. Results for the total number flux concentrations and the size-resolved concentrations derived using the three different approaches applied to the above canopy sampling level show a high degree of accord, but that the eddy-covariance fluxes are generally of smaller magnitude than those derived using the spectral methods. In keeping with prior research our results show a considerable number of fluxes are characterized by upward fluxes. Further our results show distinctly different flux diurnal profiles for the nucleation versus Aitken mode particles indicating some differential control on fluxes of particles of different sizes (including a role for aerosol dynamics). This presentation will provide details regarding the experimental approach, flux and gradient estimation methodologies, diagnose the size dependence of the fluxes, and compare and contrast the canopy and ground partitioning of the particle fluxes during leaf-on and leaf-off periods.

  6. Temporal and Spatial Heterogeneities of Surface Fluxes in an Urban Environment

    NASA Astrophysics Data System (ADS)

    Yeung, J. K.; Smith, J. A.; Baeck, M. L.; Bou-Zeid, E.; Ramamurthy, P.

    2011-12-01

    In this study, we examine the regional climatology of the water cycle in urban environments through analyses of the surface energy balance. Analyses center on long-term observations (2007 - 2011) and land-surface model simulations of latent and sensible heat flux for the Princeton University campus. Model analyses are based on the Noah Land Surface Model (LSM), which is widely used for problems involving coupled land-atmospheric interactions. The research site is characterized by a mixture of grassland, trees, and urban surfaces. Partitioning of net radiation between latent and sensible heat flux plays an important role in determining the regional rainfall climatology. This research is motivated by the following question: How does temporal variability of soil moisture and vegetation state affect the partitioning of net radiation between latent and sensible heat flux in a heterogeneous urban environment? We use turbulent-flux measurements at a 5-minute time scale from an eddy covariance station, as well as measurements of the surface radiation balance (upwelling and downwelling longwave and shortwave), meteorological variables, CO2 concentration, soil moisture, and precipitation. Additionally, a water vapor-CO2 (q-c) flux similarity method developed by Scanlon and Kustas (2010) was implemented to partition the measured latent heat flux at the eddy covariance station into bare soil evaporation and transpiration components; results from this partitioning are used to examine the Noah land-surface model formulation. We show that: 1.) soil moisture plays an important role in the surface energy balance, even for this heterogeneous urban environment, 2.) the Noah LSM does a poor job of capturing soil moisture variability, due largely to inadequate representation of vertical structure of urban soils, 3.) seasonal variation of vegetation state is important for the surface energy balance, and 4.) the bare-soil evaporation simulated by the Noah LSM exhibits a positive

  7. Partitioning of residual D-limonene cleaner vapor among organic materials in weapons

    SciTech Connect

    LeMay, J.D.

    1993-03-01

    D-limonene is a replacement solvent selected by Sandia and Allied-Signal to clean solder flux from electronics assemblies in firesets and programmers. D-limonene is much slower drying than the solvents it has replaced and this has raised concerns that residual quantities of the cleaner could be trapped in the electronics assemblies and eventually carried into warhead assemblies. This paper describes a study designed to evaluate how vapors from residual d-limonene cleaner would be partitioned among typical organic materials in a Livermore device. The goal was to identify possible compatibility problems arising from the use of d-limonene and, in particular, any interactions it may have with energetic materials. To predict the partitioning behavior of d-limonene, a simple model was developed and its predictions are compared to the experimental findings.

  8. Optimising query execution time in LHCb Bookkeeping System using partition pruning and Partition-Wise joins

    NASA Astrophysics Data System (ADS)

    Mathe, Zoltan; Charpentier, Philippe

    2014-06-01

    The LHCb experiment produces a huge amount of data which has associated metadata such as run number, data taking condition (detector status when the data was taken), simulation condition, etc. The data are stored in files, replicated on the Computing Grid around the world. The LHCb Bookkeeping System provides methods for retrieving datasets based on their metadata. The metadata is stored in a hybrid database model, which is a mixture of Relational and Hierarchical database models and is based on the Oracle Relational Database Management System (RDBMS). The database access has to be reliable and fast. In order to achieve a high timing performance, the tables are partitioned and the queries are executed in parallel. When we store large amounts of data the partition pruning is essential for database performance, because it reduces the amount of data retrieved from the disk and optimises the resource utilisation. This research presented here is focusing on the extended composite partitioning strategy such as range-hash partition, partition pruning and usage of the Partition-Wise joins. The system has to serve thousands of queries per minute, the performance and capability of the system is measured when the above performance optimization techniques are used.

  9. Meteoric 10Be as a tool to investigate human induced soil fluxes: a conceptual model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; De Vente, Joris; Boix-Fayos, Carolina; Minella, Jean; Baken, Stijn; Smolders, Erik

    2014-05-01

    The use of meteoric 10Be as a tool to understand long term landscape behavior is becoming increasingly popular. Due its high residence time, meteoric 10Be allows in principle to investigate in situ erosion rates over time scales exceeding the period studied with classical approaches such as 137Cs. The use of meteoric 10Be strongly contributes to the traditional interpretation of sedimentary archives which cannot be unequivocally coupled to sediment production and could provide biased information over longer time scales (Sadler, 1981). So far, meteoric 10Be has successfully been used in geochemical fingerprinting of sediments, to date soil profiles, to assess soil residence times and to quantify downslope soil fluxes using accumulated 10Be inventories along a hill slope. However, less attention is given to the potential use of the tracer to directly asses human induced changes in soil fluxes through deforestation, cultivation and reforestation. A good understanding of the processes governing the distribution of meteoric 10Be both within the soil profile and at landscape scale is essential before meteoric 10Be can be successfully applied to assess human impact. We developed a spatially explicit 2D-model (Be2D) in order to gain insight in meteoric 10Be movement along a hillslope that is subject to human disturbance. Be2D integrates both horizontal soil fluxes and vertical meteoric 10Be movement throughout the soil prolife. Horizontal soil fluxes are predicted using (i) well studied geomorphical laws for natural erosion and soil formation as well as (ii) human accelerated water and tillage erosion. Vertical movement of meteoric 10Be throughout the soil profile is implemented by inserting depth dependent retardation calculated using experimentally determined partition coefficients (Kd). The model was applied to different environments such as (i) the Belgian loess belt, characterized by aeolian deposits enriched in inherited meteoric 10Be, (ii) highly degraded and stony

  10. Advective excess Ba transport as shown from sediment and trap geochemical signatures

    SciTech Connect

    Fagel, N.; Andre, L.; Dehairs, F.

    1999-08-01

    The authors report the results of a geochemical study of sediment and trap material. Major and trace elements (Zr, Ba, rare earth elements, and Th) were analyzed on bulk sedimentary material collected along the NE Atlantic margin. The aim is to test the widespread use of Ba-barite as a proxy for paleoproductivity in a continental margin area. This environment is of great interest because atmospheric-oceanic exchanges are important. In sediments, the geochemical signatures remain close to an upper crust reference, with flat shale-normalized rare earth elements patterns and constant elementary ratios. The calculated biogenic fraction of Ba or excess Ba (20--45%) remains lower than the excess Ba record in trap material (80--99%). The evolution of the geochemical signature along the margin reflects variable dilution of a detrital Post Archean Australian Shale-like component by a biogenic carbonaceous seawater-derived component. The trap material displays a wide range of variation in its trace element content (e.g., Ba {approximately}150--3,000 ppm, Zr {approximately}2--100 ppm), except for the abyssal site, which is characterized by constant signature. In the two other sites, all of the trace element contents increase with water depth and present pronounced seasonal changes at each sampled water depth. The amount of excess Ba also increases in the deepest traps, and its evolution throughout the year mimics the change of the other analyzed trace elements. In contrast, its relationships with particulate organic carbon are not obvious. In terms of fluxes, two periods of enhanced excess Ba fluxes are observed: (1) excess Ba flux increases with the detrital-like elements like Th especially during winter, and (2) excess Ba flux is enhanced without any change for the other trace elements during spring. To explain the first case, a supply through lateral advection is proposed. Such transient input of significant excess Ba flux will have a great impact on the yearly averaged

  11. 33. Elevation of Doors / Typical Cement Toilet Partitions / ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    33. Elevation of Doors / Typical Cement Toilet Partitions / Typical Cement Shower Bath Partitions / Typical Marble Shower Bath Partitions / Dispensary Cupboard Supply Room Cupboard Similar / Section / Kitchen Cupboard and Sink / Screened Porch Cupboard (drawing 10) - Whittier State School, Hospital & Receiving Building, 11850 East Whittier Boulevard, Whittier, Los Angeles County, CA

  12. 47 CFR 27.904 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1670-1675 MHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  13. 47 CFR 95.823 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. (a) Eligibility. Parties seeking Commission approval of geographic partitioning or spectrum disaggregation of 218-219 MHz Service system licenses shall request...

  14. 47 CFR 27.805 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1.4 GHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  15. 47 CFR 27.904 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1670-1675 MHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  16. 47 CFR 90.911 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.911 Partitioned licenses and disaggregated spectrum. (a) Eligibility...) that constitute the partitioned area. (2) Disaggregation. Spectrum may be disaggregated in any...

  17. 47 CFR 27.904 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1670-1675 MHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  18. 47 CFR 90.911 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.911 Partitioned licenses and disaggregated spectrum. (a) Eligibility...) that constitute the partitioned area. (2) Disaggregation. Spectrum may be disaggregated in any...

  19. 47 CFR 95.823 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. (a) Eligibility. Parties seeking Commission approval of geographic partitioning or spectrum disaggregation of 218-219 MHz Service system licenses shall request...

  20. 47 CFR 90.911 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.911 Partitioned licenses and disaggregated spectrum. (a) Eligibility...) that constitute the partitioned area. (2) Disaggregation. Spectrum may be disaggregated in any...

  1. 47 CFR 90.813 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.813 Partitioned licenses and disaggregated spectrum. (a) Eligibility.... Spectrum may be disaggregated in any amount. (3) Combined partitioning and disaggregation. The...

  2. 47 CFR 90.911 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.911 Partitioned licenses and disaggregated spectrum. (a) Eligibility...) that constitute the partitioned area. (2) Disaggregation. Spectrum may be disaggregated in any...

  3. 47 CFR 90.813 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.813 Partitioned licenses and disaggregated spectrum. (a) Eligibility.... Spectrum may be disaggregated in any amount. (3) Combined partitioning and disaggregation. The...

  4. 47 CFR 90.813 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.813 Partitioned licenses and disaggregated spectrum. (a) Eligibility.... Spectrum may be disaggregated in any amount. (3) Combined partitioning and disaggregation. The...

  5. 47 CFR 27.805 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1.4 GHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  6. 47 CFR 95.823 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. (a) Eligibility. Parties seeking Commission approval of geographic partitioning or spectrum disaggregation of 218-219 MHz Service system licenses shall request...

  7. 47 CFR 95.823 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. (a) Eligibility. Parties seeking Commission approval of geographic partitioning or spectrum disaggregation of 218-219 MHz Service system licenses shall request...

  8. 47 CFR 90.813 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.813 Partitioned licenses and disaggregated spectrum. (a) Eligibility.... Spectrum may be disaggregated in any amount. (3) Combined partitioning and disaggregation. The...

  9. 47 CFR 90.813 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.813 Partitioned licenses and disaggregated spectrum. (a) Eligibility.... Spectrum may be disaggregated in any amount. (3) Combined partitioning and disaggregation. The...

  10. 47 CFR 27.805 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1.4 GHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  11. 47 CFR 90.911 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Partitioned licenses and disaggregated spectrum... Specialized Mobile Radio Service § 90.911 Partitioned licenses and disaggregated spectrum. (a) Eligibility...) that constitute the partitioned area. (2) Disaggregation. Spectrum may be disaggregated in any...

  12. 47 CFR 95.823 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. (a) Eligibility. Parties seeking Commission approval of geographic partitioning or spectrum disaggregation of 218-219 MHz Service system licenses shall request...

  13. 47 CFR 27.904 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Geographic partitioning and spectrum... partitioning and spectrum disaggregation. An entity that acquires a portion of a 1670-1675 MHz band licensee's geographic area or spectrum subject to a geographic partitioning or spectrum disaggregation agreement...

  14. A Geochemical Speciation Program Based on PHREEQE

    Energy Science and Technology Software Center (ESTSC)

    1992-02-18

    HARPHRQ is a program based on the code PHREEQE and is designed to model geochemical reactions. Like PHREEQE, it can calculate the pH, redox potential and mass transfer as a function of reaction progress and the composition of solution in equilibrium with multiple phases. In addition, HARPHRQ includes options to allow the composition of a solution at a fixed pH to be calculated and to automatically add or remove mineral phases as they become saturatedmore » or exhausted. A separate module can also be interfaced to give a choice of sorption models including the triple-layer model.« less

  15. DNA-based methods of geochemical prospecting

    DOEpatents

    Ashby, Matthew

    2011-12-06

    The present invention relates to methods for performing surveys of the genetic diversity of a population. The invention also relates to methods for performing genetic analyses of a population. The invention further relates to methods for the creation of databases comprising the survey information and the databases created by these methods. The invention also relates to methods for analyzing the information to correlate the presence of nucleic acid markers with desired parameters in a sample. These methods have application in the fields of geochemical exploration, agriculture, bioremediation, environmental analysis, clinical microbiology, forensic science and medicine.

  16. The geochemical significance of contaminant assemblages

    SciTech Connect

    Hites, R.A.

    1996-12-31

    Molecular markers are groups of compounds that come from specific sources. Following the dispersion and reactions of these compounds in the environment can frequently help us understand biotic and abiotic geochemical processes. This talk will focus on collections of anthropogenic compounds as they move through the earth`s atmosphere. We will present two examples: (a) We have used the concentrations of mixtures of twenty-two highly chlorinated pesticides in tree bark to understand the global dispersion of these compounds and to distinguish the {open_quotes}global distillation effect{close_quotes} from local sources.

  17. Characterizing In Situ Uranium and Groundwater Flux

    NASA Astrophysics Data System (ADS)

    Cho, J.; Newman, M. A.; Stucker, V.; Peacock, A.; Ranville, J.; Cabaniss, S.; Hatfield, K.; Annable, M. D.; Klammler, H.; Perminova, I. V.

    2010-12-01

    The goal of this project is to develop a new sensor that incorporates the field-tested concepts of the passive flux meter to provide direct in situ measures of uranium and groundwater fluxes. The sensor uses two sorbents and resident tracers to measure uranium flux and specific discharge directly; but, sensor principles and design should also apply to fluxes of other radionuclides. Flux measurements will assist with obtaining field-scale quantification of subsurface processes affecting uranium transport (e.g., advection) and transformation (e.g., uranium attenuation) and further advance conceptual and computational models for field scale simulations. Project efforts will expand our current understanding of how field-scale spatial variations in uranium fluxes and those for salient electron donor/acceptors, and groundwater are coupled to spatial variations in measured microbial biomass/community composition, effective field-scale uranium mass balances, attenuation, and stability. The new sensor uses an anion exchange resin to measure uranium fluxes and activated carbon with resident tracers to measure water fluxes. Several anion-exchange resins including Dowex 21K and 21K XLT, Purolite A500, and Lewatit S6328 were tested as sorbents for capturing uranium on the sensor and Lewatit S6328 was determined to be the most effective over the widest pH range. Four branched alcohols proved useful as resident tracers for measuring groundwater flows using activated carbon for both laboratory and field conditions. The flux sensor was redesigned to prevent the discharge of tracers to the environment, and the new design was tested in laboratory box aquifers and the field. Geochemical modeling of equilibrium speciation using Visual Minteq and an up-to-date thermodynamic data base suggested Ca-tricarbonato-uranyl complexes predominate under field conditions, while calculated uranyl ion activities were sensitive to changes in pH, dissolved inorganic carbon (DIC) and alkaline earth

  18. The flux of oxygen within tissues.

    PubMed

    McCabe, Michael G P; Maguire, David J; Bourgain, Renaat

    2003-01-01

    Diffusive flux of oxygen through tissues which are essentially connective and have few cells, display reduced diffusion coefficients when compared to that through an equivalent lamina of water. In general even significant reductions can be explained in terms of the exclusions imposed on small molecular weight diffusates by the large hydrodynamic domains of the connective tissue components. An alternative way of explaining this large exclusion is to point to the very large microscopic viscosities which large interacting polymers impose upon the solvent (water). By contrast, the diffusive flux of oxygen through tissues composed of contiguously packed and actively respiring cells, shows an increased diffusive flux for oxygen when compared to that through an equivalent water lamina. This increase can be explained in terms of the substantial solubility of oxygen within the membrane phase of the cells. This high oxygen partition coefficient into cell lipids has several consequences. Firstly oxygen diffusion will be directed and two dimensional rather than random and three dimensional. Secondly this diffusion will be directed towards the oxygen-consuming sites which are located at lipid surfaces. Thirdly the aqueous oxygen partial pressure will be kept low (since re-supply is constrained while consumption is continuous). This low aqueous environment permits all of the cell soluble redox systems to be maintained efficiently at low metabolic cost, as well as minimising the risk of unscheduled oxidations. Viewed from this perspective, the high value found for oxygen partition coefficient into the erythrocyte membrane suggests that evolution of membrane structure and components may have been driven in part by the selective advantages of high oxygen solubility. PMID:15174633

  19. Partitioning of strontium-90 among aqueous and mineral species in a contaminated aquifer

    SciTech Connect

    Jackson, R.E.; Inch, K.J.

    1983-04-01

    The geochemical partitioning of a toxic metal contaminant, /sup 90/Sr, during its migration through a shallow sand aquifer is discussed. Adsorption of /sup 90/Sr from the contaminated groundwaters (pH approx. 6, I approx.0.001) causes it to have a migration velocity of only 3% of that of transporting ground water. Five microscopically identified adsorbents were isolated in the aquifer sediments and showed the following affinity sequence for /sup 90/Sr: vermiculite > feldspar > biotite > muscovite > quartz. While 4a80% of the adsorbed /sup 90/Sr is exchangeable with 0.1 M SrCl/sub 2/, the residual adsorbed /sup 90/Sr is strongly correlated with extractable Fe, Al, and Mn, suggesting specific adsorption by these metal oxides. An equilibrium adsorption model was used to determine the partitioning of /sup 90/Sr between adsorbents and between solid and solution phases. Over 90% of all /sup 90/SR in the aquifer is adsorbed. Approximately 90% of all adsorbed /sup 90/SR is equally divided between vermiculite and feldspar minerals.

  20. Energy balance and non-turbulent fluxes

    NASA Astrophysics Data System (ADS)

    Moderow, Uta; Feigenwinter, Christian; Bernhofer, Christian

    2010-05-01

    Often, the sum of the turbulent fluxes of sensible heat and latent heat from eddy covariance (EC) measurements does not match the available energy (sum of net radiation, ground heat flux and storage changes). This is referred to as energy balance closure gap. The reported imbalances vary between 0% and 50% (Laubach 1996). In various publications, it has been shown that the uncertainty of the available energy itself does not explain the gap (Vogt et al. 1996; Moderow et al. 2009). Among other reasons, the underestimation is attributed to an underestimation of turbulent fluxes and undetected non-turbulent transport processes, i.e. advection (e.g. Foken et al. 2006). The imbalance is typically larger during nighttime than during daytime as the EC method fails to capture non-turbulent transports that can be significant during night (e.g. Aubinet 2008). Results for the budget of CO2 showed that including non-turbulent fluxes can change the budgets considerably. Hence, it is interesting to see how the budget of energy is changed. Here, the consequences of including advective fluxes of sensible heat and latent heat in the energy balance are explored with focus on nighttime conditions. Non-turbulent fluxes will be inspected critically regarding their plausibility. Following Bernhofer et al. (2003), a ratio similar to Bowen's ratio of the turbulent fluxes are defined for the non-turbulent fluxes and compared to each other. This might have implications for the partitioning of the available energy into sensible heat and latent heat. Data of the ADVEX-campaigns (Feigenwinter et al. 2008) of three different sites across Europe are used and selected periods are inspected. References Aubinet M (2008) Eddy covariance CO2-flux measurements in nocturnal conditions: An analysis of the problem. Ecol Appl 18: 1368-1378 Bernhofer C, Grünwald T, Schwiebus A, Vogt R (2003) Exploring the consequences of non-zero energy balance closure for total surface flux. In: Bernhofer C (ed

  1. Microbiological and Geochemical Characterization of the Deep Subsurface Environment: Kumano Mud Volcano, Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Case, D. H.; Ijiri, A.; Morono, Y.; Orphan, V. J.; Inagaki, F.

    2013-12-01

    Submarine mud volcanoes play an important environmental role by delivering deep-sourced fluids, elements, and hydrocarbons to the seafloor. These fluxes in turn support chemosynthetic benthic communities. However, due to difficulty in accessing the deep biosphere most mud volcano samples only represent the top one to several meters below seafloor (mbsf) obtainable by remotely operated vehicle (ROV) or gravity cores. Thus, the geochemical and microbiological conditions, as well as vertical homogeneity, deep within mud volcanoes remains poorly constrained. In 2012, using the deep-sea drilling vessel Chikyu, we drilled one of the most active submarine mud volcanoes in the Kumano forearc basin of the Nankai Trough, off the Kii Peninsula of Japan (33°67.581'N, 136°56.8085'E: 1,986.7 m in water depth). Cores were obtained down to 200 mbsf. Cell counts indicate the presence of microorganisms at relatively low abundance (less than 105 cells/cm3) throughout the cored depth. Molecular analyses reveal vertical heterogeneity in the microbial community composition, including specific depth horizons harboring putative methanogenic and methanotrophic phylotypes at >100 mbsf. Geochemical profiles indicate the potential for microbial activity and rate measurements with radiotracers revealed active homoacetogenesis rates that were 2-3 orders of magnitude higher than rates of homo- and acetoclastic methanogenesis. To assess active autotrophic, methanotrophic and heterotrophic populations, 13C- and 15N-amendment experiments with sediment samples collected from 15 and 115 mbsf were established and single cell stable isotope analyses with nanoSIMS are in progress. Our samples and analyses represent a unique observation of a subseafloor setting different from previously explored stratified sediments on continental margins and will allow further understanding of how submarine mud volcanoes contribute to geochemical and microbiological fluxes into the surface biosphere.

  2. Investigating sulfur partitioning between nominally volatile-free minerals and silicate melts

    NASA Astrophysics Data System (ADS)

    Marzoli, A.; Callegaro, S.; Baker, D. R.; Geraki, K.; Maneta, V.

    2015-12-01

    Despite the key role played by volatile species in magmatic systems, it is still challenging to quantify their concentrations in ancient melts. We suggested a quantitative approach for estimating S contents in basaltic melts (Callegaro et al., 2014), based on direct measurement of S on clinopyroxene and calculation of its concentration in the melt through an experimentally determined partition coefficient (KD). We further investigated the partitioning of sulfur between silicate melts and nominally volatile-free minerals (olivine, orthopyroxene, clinopyroxene, and plagioclase), as well as between melt and amphibole. Partitioning experiments were performed with basaltic, andesitic and dacitic bulk compositions, at hydrous and anhydrous conditions, and at high and low oxygen fugacities (fO2), where sulfur in the melt is dominantly present as an S6+ or S2- species, respectively (Wilke et al., 2011). Sulfur concentrations in melts were measured by electron microprobe and in crystals by synchrotron X-ray fluorescence. At low fO2 the average crystal/liquid KDs for sulfur vary from 0.0004 (at a maximum) for olivine, to 0.003 (another maximum) for orthopyroxene, to 0.03 for clinopyroxene, and to 0.07 for plagioclase. The KDs correlate positively with the cation-oxygen bond lengths in the crystals. At high fO2 the KDs drop to approximately one-third of those observed at low fO2. These observations suggest that S2- replaces oxygen in the crystal structure. Water has no measureable influence on the crystal/melt partitioning of sulfur. Clinopyroxene/melt KDs are correlated with the Mg/(Mg+Fe) ratio of the crystal, but appear insensitive to the IVAl in the structure. Plagioclase/melt S partitioning appears unaffected by anorthite content and iron concentration in the crystal. These new KDs allow the determination of sulfur concentration in the igneous melts co-existing with these crystals and provide insights into the volatile concentrations of ancient magmas and their possible

  3. STRATIFIED COMPOSITION EFFECTS ON PLANETARY NEUTRON FLUX

    SciTech Connect

    O. GASNAULT; ET AL

    2001-01-01

    All the bodies of the solar system that are directly irradiated by the galactic cosmic rays, emit enough neutrons to allow a measurement from space. These leakage neutron fluxes are indexes of the surface composition, depending on the energy of the neutrons [1]. Recent work propose geochemical interpretations of these fluxes: the thermal energy range is sensitive to iron, titanium, rare earth elements and thorium [2, 3], the epithermal energy range is sensitive to hydrogen, samarium and gadolinium [2] and the fast energy range is representative of the average soil atomic mass [4]. Nevertheless these studies make the hypothesis of a composition uniform within the footprint of the spectrometer and independent of depth. We show in this abstract that a stratified composition could change significantly the flux intensity and complicate the interpretation of the measurements. The neutron leakage flux is a competition between production effects (sensitive at high energy) and diffusion-capture effects (mostly sensitive at low energy). On one hand, it happens to be that the elements which produce the higher number of neutrons in typical lunar compositions are iron and titanium, which have also large cross section of absorption with the neutrons. On the other hand, the maximum of neutron intensity does not occur at the surface but at about 180 g cm{sup {minus}2} in depth. Therefore, if we have an iron- and/or titanium-rich soil (important production of neutrons) with a top layer having less iron and/or titanium (i.e. more transparent to the neutrons), we can expect an enhancement of the flux compared to a uniform composition.

  4. Geochemical controls on groundwater chemistry in shales

    SciTech Connect

    Von Damm, K.L.

    1989-01-01

    The chemistry of groundwaters is one of the most important parameters in determining the mobility of species within a rock formation. A three pronged approach was used to determine the composition of, and geochemical controls, on groundwaters specifically within shale formations: (1) available data were collected from the literature, the US Geological Survey WATSTORE data base, and field sampling, (2) the geochemical modeling code EQ3/6 was used to simulate interaction of various shales and groundwaters, and (3) several types of shale were reacted with synthetic groundwaters in the laboratory. The comparison of model results to field and laboratory data provide a means of validating the models, as well as a means of deconvoluting complex field interactions. Results suggest that groundwaters in shales have a wide range in composition and are primarily of the Na-Cl-HCO/sub 3/- type. The constancy of the Na:Cl (molar) ratio at 1:1 and the Ca:Mg ratio from 3:1 to 1:1 suggests the importance of halite and carbonates in controlling groundwater compositions. In agreement with the reaction path modeling, most of the groundwaters are neutral to slightly alkaline at low temperatures. Model and experimental results suggest that reaction (1) at elevated temperatures, or (2) in the presence of oxygen will lead to more acidic conditions. Some acetate was found to be produced in the experiments; depending on the constraints applied, large amounts of acetate were produced in the model results. 13 refs., 1 tab.

  5. Forensic Analysis using Geological and Geochemical Techniques

    NASA Astrophysics Data System (ADS)

    Hoogewerff, J.

    2009-04-01

    Due to the globalisation of legal (and illegal) trade there is an increasing demand for techniques which can verify the geographical origin and transfer routes of many legal and illegal commodities and products. Although geological techniques have been used in forensic investigations since the emergence of forensics as a science in the late eighteen hundreds, the last decade has seen a marked increase in geo-scientists initiating concept studies using the latest analytical techniques, including studying natural abundance isotope variations, micro analysis with laser ablation ICPMS and geochemical mapping. Most of the concept studies have shown a good potential but uptake by the law enforcement and legal community has been limited due to concerns about the admissibility of the new methods. As an introduction to the UGU2009 session "Forensic Provenancing using Geological and Geochemical Techniques" I will give an overview of the state of the art of forensic geology and the issues that concern the admissibility of geological forensic evidence. I will use examples from the NITECRIME and FIRMS networks, the EU TRACE project and other projects and literature to illustrate the important issues at hand.

  6. Archean crust-mantle geochemical differentiation

    NASA Technical Reports Server (NTRS)

    Tilton, G. R.

    1983-01-01

    Isotope measurements on carbonatite complexes and komatiites can provide information on the geochemical character and geochemical evolution of the mantle, including the sub-continental mantle. Measurements on young samples establish the validity of the method. These are based on Sr, Nd and Pb data from the Tertiary-Mesozoic Gorgona komatiite and Sr and Pb data from the Cretaceous Oka carbonatite complex. In both cases the data describe a LIL element-depleted source similar to that observed presently in MORB. Carbonatite data have been used to study the mantle beneath the Superior Province of the Canadian Shield one billion years (1 AE) ago. The framework for this investigation was established by Bell et al., who showed that large areas of the province appear to be underlain by LIL element-depleted mantle (Sr-85/Sr-86=0.7028) at 1 AE ago. Additionally Bell et al. found four complexes to have higher initial Sr ratios (Sr-87/Sr-86=0.7038), which they correlated with less depleted (bulk earth?) mantle sources, or possibly crustal contamination. Pb isotope relationships in four of the complexes have been studied by Bell et al.

  7. Is formamide a geochemically plausible prebiotic solvent?

    PubMed

    Bada, Jeffrey L; Chalmers, John H; Cleaves, H James

    2016-07-27

    From a geochemical perspective, significant amounts of pure formamide (HCONH2) would have likely been rare on the early Earth. There may have been mixed formamide-water solutions, but even in the presence of catalyst, solutions with >20 weight% water in formamide would not have produced significant amounts of prebiotic compounds. It might be feasible to produce relatively pure formamide by a rare occurrence of freezing formamide/water mixtures at temperatures lower than formamide's freezing point (2.55 °C) but greater than the freezing point of water. Because of the high density of formamide ice it would have sunk and accumulated at the bottom of the solution. If the remaining water froze on the surface of this ice, and was then removed by a sublimation-ablation process, a small amount of pure formamide ice might have been produced. In addition a recent report suggested that ∼85 weight% formamide could be prepared by a geochemical type of fractional distillation process, offering another possible route for prebiotic formamide production. PMID:27253848

  8. Bipartite graph partitioning and data clustering

    SciTech Connect

    Zha, Hongyuan; He, Xiaofeng; Ding, Chris; Gu, Ming; Simon, Horst D.

    2001-05-07

    Many data types arising from data mining applications can be modeled as bipartite graphs, examples include terms and documents in a text corpus, customers and purchasing items in market basket analysis and reviewers and movies in a movie recommender system. In this paper, the authors propose a new data clustering method based on partitioning the underlying biopartite graph. The partition is constructed by minimizing a normalized sum of edge weights between unmatched pairs of vertices of the bipartite graph. They show that an approximate solution to the minimization problem can be obtained by computing a partial singular value decomposition (SVD) of the associated edge weight matrix of the bipartite graph. They point out the connection of their clustering algorithm to correspondence analysis used in multivariate analysis. They also briefly discuss the issue of assigning data objects to multiple clusters. In the experimental results, they apply their clustering algorithm to the problem of document clustering to illustrate its effectiveness and efficiency.

  9. Partition coefficients of three new anticonvulsants.

    PubMed

    Hernandez-Gallegos, Z; Lehmann, P A

    1990-11-01

    The partition coefficients of three homologous anticonvulsant phenylalkylamides [racemic alpha-hydroxy-alpha-ethyl-alpha-phenylacetamide (HEPA); beta-hydroxy-beta-ethyl-beta-phenylpropionamide (HEPP); and gamma-hydroxy-gamma-ethyl-gamma-phenylbutyramide (HEPB)] were determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The system was calibrated with a series of simple amines and amides, using their published log P values. The log kw values (methanol:water, extrapolated to 100% water) were 1.260 for HEPA, 1.670 for HEPP, and 1.852 for HEPB. From these results, the partition coefficients (log P) were calculated by regression as 1.20, 1.83, and 2.11, respectively. The log P values were essentially equal to those calculated by the Leo-Hansch fragmental method. Since the potency of the three anticonvulsants is approximately the same in a variety of tests, no dependence on lipophilicity could be established. PMID:2292764

  10. Number Partitioning via Quantum Adiabatic Computation

    NASA Technical Reports Server (NTRS)

    Smelyanskiy, Vadim N.; Toussaint, Udo; Clancy, Daniel (Technical Monitor)

    2002-01-01

    We study both analytically and numerically the complexity of the adiabatic quantum evolution algorithm applied to random instances of combinatorial optimization problems. We use as an example the NP-complete set partition problem and obtain an asymptotic expression for the minimal gap separating the ground and exited states of a system during the execution of the algorithm. We show that for computationally hard problem instances the size of the minimal gap scales exponentially with the problem size. This result is in qualitative agreement with the direct numerical simulation of the algorithm for small instances of the set partition problem. We describe the statistical properties of the optimization problem that are responsible for the exponential behavior of the algorithm.

  11. Analysis of fractals with combined partition

    NASA Astrophysics Data System (ADS)

    Dedovich, T. G.; Tokarev, M. V.

    2016-03-01

    The space—time properties in the general theory of relativity, as well as the discreteness and non-Archimedean property of space in the quantum theory of gravitation, are discussed. It is emphasized that the properties of bodies in non-Archimedean spaces coincide with the properties of the field of P-adic numbers and fractals. It is suggested that parton showers, used for describing interactions between particles and nuclei at high energies, have a fractal structure. A mechanism of fractal formation with combined partition is considered. The modified SePaC method is offered for the analysis of such fractals. The BC, PaC, and SePaC methods for determining a fractal dimension and other fractal characteristics (numbers of levels and values of a base of forming a fractal) are considered. It is found that the SePaC method has advantages for the analysis of fractals with combined partition.

  12. Rotational partition functions for linear molecules

    NASA Astrophysics Data System (ADS)

    McDowell, Robin S.

    1988-01-01

    An accurate closed-form expression for the rotational partition function of linear polyatomic molecules in 1Sigma electronic states is derived, including the effect of nuclear spin (significant at very low temperatures) and of quartic and sextic centrifugal distortion terms (significant at moderate and high temperatures). The proper first-order quantum correction to the classical rigid-rotator partition function is shown to yield Qr = about 1/beta exp beta/3, where beta is defined as hcB / kT and B is the rotational constant in per cm; for beta of 0.2 or greater additional power-series terms in beta are necessary. Comparison between the results of this treatment and exact summations are made for HCN and C2H2 at temperatures from 2 to 5000 K, including separate evaluation of the conributions of nuclear spin and centrifugal distortion.

  13. Mantle Mineral/Silicate Melt Partitioning

    NASA Astrophysics Data System (ADS)

    McFarlane, E. A.; Drake, M. J.

    1992-07-01

    Introduction: The partitioning of elements among mantle phases and silicate melts is of interest in unraveling the early thermal history of the Earth. It has been proposed that the elevated Mg/Si ratio of the upper mantle of the Earth is a consequence of the flotation of olivine into the upper mantle (Agee and Walker, 1988). Agee and Walker (1988) have generated a model via mass balance by assuming average mineral compositions to generate upper mantle peridotite. This model determines that upper mantle peridotite could result from the addition of 32.7% olivine and 0.9% majorite garnet into the upper mantle, and subtraction of 27.6% perovskite from the upper mantle (Agee and Walker, 1988). The present contribution uses experimental data to examine the consequences of such multiple phase fractionations enabling an independent evaluation of the above mentioned model. Here we use Mg-perovskite/melt partition coefficients from both a synthetic and a natural system (KLB-1) obtained from this laboratory. Also used are partition coefficient values for majorite garnet/melt, beta spinel/melt and olivine/melt partitioning (McFarlane et al., 1991b; McFarlane et al., 1992). Multiple phase fractionations are examined using the equilibrium crystallization equation and partition coefficient values. The mineral proportions determined by Agee and Walker (1988) are converted into weight fractions and used to compute a bulk partition coefficient value. Discussion: There has been a significant debate concerning whether measured values of trace element partition coefficients permit large-scale fractionation of liquidus phases from an early terrestrial magma ocean (Kato et al., 1988a,b; Walker and Agee, 1989; Drake, 1989; Drake et al., 1991; McFarlane et al., 1990, 1991). It should be noted that it is unclear which, if any, numerical values of partition coefficients are appropriate for examining this question, and certainly the assumptions for the current model must be more fully

  14. Grid-based partitioning for comparing attractors

    NASA Astrophysics Data System (ADS)

    Carroll, T. L.; Byers, J. M.

    2016-04-01

    Stationary dynamical systems have invariant measures (or densities) that are characteristic of the particular dynamical system. We develop a method to characterize this density by partitioning the attractor into the smallest regions in phase space that contain information about the structure of the attractor. To accomplish this, we develop a statistic that tells us if we get more information about our data by dividing a set of data points into partitions rather than just lumping all the points together. We use this method to show that not only can we detect small changes in an attractor from a circuit experiment, but we can also distinguish between a large set of numerically generated chaotic attractors designed by Sprott. These comparisons are not limited to chaotic attractors—they should work for signals from any finite-dimensional dynamical system.

  15. A geochemical atlas of North Carolina, USA

    USGS Publications Warehouse

    Reid, J.C.

    1993-01-01

    A geochemical atlas of North Carolina, U.S.A., was prepared using National Uranium Resource Evaluation (NURE) stream-sediment data. Before termination of the NURE program, sampling of nearly the entire state (48,666 square miles of land area) was completed and geochemical analyses were obtained. The NURE data are applicable to mineral exploration, agriculture, waste disposal siting issues, health, and environmental studies. Applications in state government include resource surveys to assist mineral exploration by identifying geochemical anomalies and areas of mineralization. Agriculture seeks to identify areas with favorable (or unfavorable) conditions for plant growth, disease, and crop productivity. Trace elements such as cobalt, copper, chromium, iron, manganese, zinc, and molybdenum must be present within narrow ranges in soils for optimum growth and productivity. Trace elements as a contributing factor to disease are of concern to health professionals. Industry can use pH and conductivity data for water samples to site facilities which require specific water quality. The North Carolina NURE database consists of stream-sediment samples, groundwater samples, and stream-water analyses. The statewide database consists of 6,744 stream-sediment sites, 5,778 groundwater sample sites, and 295 stream-water sites. Neutron activation analyses were provided for U, Br, Cl, F, Mn, Na, Al, V, Dy in groundwater and stream water, and for U, Th, Hf, Ce, Fe, Mn, Na, Sc, Ti, V, Al, Dy, Eu, La, Sm, Yb, and Lu in stream sediments. Supplemental analyses by other techniques were reported on U (extractable), Ag, As, Ba, Be, Ca, Co, Cr, Cu, K, Li, Mg, Mo, Nb, Ni, P, Pb, Se, Sn, Sr, W, Y, and Zn for 4,619 stream-sediment samples. A small subset of 334 stream samples was analyzed for gold. The goal of the atlas was to make available the statewide NURE data with minimal interpretation to enable prospective users to modify and manipulate the data for their end use. The atlas provides only

  16. Partition algebraic design of asynchronous sequential circuits

    NASA Technical Reports Server (NTRS)

    Maki, Gary K.; Chen, Kristen Q.; Gopalakrishnan, Suresh K.

    1993-01-01

    Tracey's Theorem has long been recognized as essential in generating state assignments for asynchronous sequential circuits. This paper shows that partitioning variables derived from Tracey's Theorem also has a significant impact in generating the design equations. Moreover, this theorem is important to the fundamental understanding of asynchronous sequential operation. The results of this work simplify asynchronous logic design. Moreover, detection of safe circuits is made easier.

  17. Metal partitioning and toxicity in sewage sludge

    SciTech Connect

    Carlson-Ekvall, C.E.A.; Morrison, G.M.

    1995-12-31

    Over 20 years of research has failed to provide an unequivocal correlation between chemically extracted metals in sewage sludge applied to agricultural soil and either metal toxicity to soil organisms or crop uptake. Partitioning of metals between phases and species can provide a better estimation of mobility and potential bioavailability. Partition coefficients, K{sub D} for Cd, Cu, Pb and Zn in a sludge/water solution were determined considering the sludge/water solution as a three-phase system (particulate, colloidal and electrochemically available) over a range of pH values, ionic strengths, contact times and sludge/water ratios and compared with the KD values for sludge/water solution as a two-phase system (aqueous phase and particulate phase). Partitioning results were interpreted in terms of metal mobility from sludge to colloids and in terms of potential bioavailability from colloids to electrochemically available. The results show that both mobility and potential bioavailability are high for Zn, while Cu partitions into the mobile colloidal phase which is relatively non-bioavailable. Lead is almost completely bound to the solid phase, and is neither mobile nor bioavailable. A comparison between K, values and toxicity shows that Zn in sludge is more toxic than can be accounted for in the aqueous phase, which can be due to synergistic effects between sludge organics and Zn. Copper demonstrates clear synergism which can be attributed to the formation of lipid-soluble Cu complexes with known sludge components such as LAS, caffeine, myristic acid and nonylphenol.

  18. Pure Partition Functions of Multiple SLEs

    NASA Astrophysics Data System (ADS)

    Kytölä, Kalle; Peltola, Eveliina

    2016-08-01

    Multiple Schramm-Loewner Evolutions (SLE) are conformally invariant random processes of several curves, whose construction by growth processes relies on partition functions—Möbius covariant solutions to a system of second order partial differential equations. In this article, we use a quantum group technique to construct a distinguished basis of solutions, which conjecturally correspond to the extremal points of the convex set of probability measures of multiple SLEs.

  19. GPS/INS integration by functional partitioning

    NASA Astrophysics Data System (ADS)

    Diesel, John W.

    It is shown that a GPS/INS system integrated by functional partitioning can satisfy all of the RTCA navigation requirements and goals. This is accomplished by accurately calibrating the INS using GPS after the inertial instruments are thermally stabilized and by exploiting the very slow subsequent error growth in the INS information. In this way, autonomous integrity monitoring can be achieved using only existing or presently planned systems.

  20. Pure Partition Functions of Multiple SLEs

    NASA Astrophysics Data System (ADS)

    Kytölä, Kalle; Peltola, Eveliina

    2016-05-01

    Multiple Schramm-Loewner Evolutions (SLE) are conformally invariant random processes of several curves, whose construction by growth processes relies on partition functions—Möbius covariant solutions to a system of second order partial differential equations. In this article, we use a quantum group technique to construct a distinguished basis of solutions, which conjecturally correspond to the extremal points of the convex set of probability measures of multiple SLEs.

  1. Partitioning networks into communities by message passing.

    PubMed

    Lai, Darong; Nardini, Christine; Lu, Hongtao

    2011-01-01

    Community structures are found to exist ubiquitously in a number of systems conveniently represented as complex networks. Partitioning networks into communities is thus important and crucial to both capture and simplify these systems' complexity. The prevalent and standard approach to meet this goal is related to the maximization of a quality function, modularity, which measures the goodness of a partition of a network into communities. However, it has recently been found that modularity maximization suffers from a resolution limit, which prevents its effectiveness and range of applications. Even when neglecting the resolution limit, methods designed for detecting communities in undirected networks cannot always be easily extended, and even less directly applied, to directed networks (for which specifically designed community detection methods are very limited). Furthermore, real-world networks are frequently found to possess hierarchical structure and the problem of revealing such type of structure is far from being addressed. In this paper, we propose a scheme that partitions networks into communities by electing community leaders via message passing between nodes. Using random walk on networks, this scheme derives an effective similarity measure between nodes, which is closely related to community memberships of nodes. Importantly, this approach can be applied to a very broad range of networks types. In fact, the successful validation of the proposed scheme on real and synthetic networks shows that this approach can effectively (i) address the problem of resolution limit and (ii) find communities in both directed and undirected networks within a unified framework, including revealing multiple levels of robust community partitions. PMID:21405752

  2. Scheduling and process migration in partitioned multiprocessors

    SciTech Connect

    Gait, J. )

    1990-03-01

    A partitioned multiprocessor (PM) has a shared global bus and nonshared local memories. This paper studies a process scheduler, called the two-tier scheduler (TTS), for a PM. In a PM local scheduling amortizes the cost of loading processes in local memory. Global scheduling migrates processes to balance load. A tunable time quantum is adjusted so the average process completes execution on the processor on which it is first scheduled, and only relatively long lived processes are rescheduled globally.

  3. Phase partitioning in space and on earth

    NASA Technical Reports Server (NTRS)

    Van Alstine, James M.; Karr, Laurel J.; Snyder, Robert S.; Matsos, Helen C.; Curreri, Peter A.; Harris, J. Milton; Bamberger, Stephan B.; Boyce, John; Brooks, Donald E.

    1987-01-01

    The influence of gravity on the efficiency and quality of the impressive separations achievable by bioparticle partitioning is investigated by demixing polymer phase systems in microgravity. The study involves the neutral polymers dextran and polyethylene glycol, which form a two-phase system in aqueous solution at low concentrations. It is found that demixing in low-gravity occurs primarily by coalescence, whereas on earth the demixing occurs because of density differences between the phases.

  4. Environment Partitioning and Reactivity of Polybrominated Diphenylethers

    NASA Technical Reports Server (NTRS)

    Hua, Inez; Iraci, Laura T.; Jafvert, Chad; Bezares-Cruz, Juan

    2004-01-01

    Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants. Annual global demand for these compounds was over 67,000 metric tons in 2001. PBDEs have recently been extensively investigated as environmental contaminants because they have been detected in air, sediment, and tissue samples from urban and remote areas. Important issues include quantifying PBDE partitioning in various environmental compartments, and elucidating transformation pathways. The partitioning of PBDE congeners to aerosols was estimated for 16 sites in the United States, Canada, and Mexico. The aerosol particles were PM2.5, the total suspended particle (TSP) concentration varied between 3.0 - 55.4 micro g/cubic meter, and the organic fraction ranged from 11 - 41%; these data are published values for each site. It is estimated that the largest fraction of each PBDE associated with the aerosol particles occurs in Mexico City, and the smallest fraction in Colorado Plateau. Although the organic fraction in Mexico City is about 60% of that observed in the Colorado Plateau, the TSP is larger by a factor of about 18.5, and it is the difference in TSP that strongly influences the fraction of particle-bound PBDE in this case. PBDE partitioning to PM2.5 particles also varies seasonally because of temperature variations. For the less brominated congeners the percentage that is particle-bound is relatively low, regardless of air temperature. In contrast, the heavier congeners exhibit a significant temperature dependence: as the temperature decreases (fall, winter) the percentage of PBDE that is particle-bound increases. The partitioning calculations complement experimental data indicating that decabromodiphenyl ether (DBDE) dissolved in hexane transforms very rapidly when irradiated with solar light. DBDE is the most highly brominated PBDE congener (10 bromine atoms) and occurs in the commercial formulation which is subject to the largest global demand.

  5. Nickel partitioning in biogenic and abiogenic ferrihydrite: The influence of silica and implications for ancient environments

    NASA Astrophysics Data System (ADS)

    Eickhoff, Merle; Obst, Martin; Schröder, Christian; Hitchcock, Adam P.; Tyliszczak, Tolek; Martinez, Raul E.; Robbins, Leslie J.; Konhauser, Kurt O.; Kappler, Andreas

    2014-09-01

    Fe(III) (oxyhydr)oxides are ubiquitous in modern soils and sediments, and their large surface area leads to scavenging of trace elements. Experimental trace element partitioning between Fe(III) (oxyhydr)oxides and aqueous solutions have been used to elucidate the geochemical composition of the Precambrian oceans based on the trace element concentrations in Precambrian banded iron formations (BIFs). However, previous partitioning experiments did not consider the potential influence of microbially-derived organic material, even though it is widely believed that bacterial phytoplankton was involved in Fe(II) oxidation and the deposition of BIF primary minerals. Therefore, the present study focuses on sorption of Ni to, and co-precipitation of Ni with, both biogenic ferrihydrite precipitated by the freshwater photoferrotroph Rhodobacter ferrooxidans SW2 and the marine photoferrotroph Rhodovulum iodosum, as well as chemically synthesized ferrihydrite. We considered the influence of cellular organic material, medium composition and the availability of dissolved silica. Our results show a preferential association of Ni with ferrihydrite, and not with the microbial cells or extracellular organic substances. We found that the addition of silica (2 mM) did not influence Ni partitioning but led to the encrustation of some cells with ferrihydrite and amorphous silica. The two- to threefold lower Ni/Fe ratio in biogenic as compared to abiogenic ferrihydrite is probably due to a competition between Ni and organic matter for sorption sites on the mineral surface. Additionally, the competition of ions present at high concentrations in marine medium for sorption sites led to decreased Ni sorption or co-precipitation. Based on our data we conclude that, if the Fe(III) minerals deposited in BIFs were - at least to some extent - biological, then the Ni concentrations in the early ocean would have been higher than previously suggested. This study shows the importance of considering the

  6. Airborne phthalate partitioning to cotton clothing

    NASA Astrophysics Data System (ADS)

    Morrison, Glenn; Li, Hongwan; Mishra, Santosh; Buechlein, Melissa

    2015-08-01

    Accumulation on indoor surfaces and fabrics can increase dermal uptake and non-dietary ingestion of semi-volatile organic compounds. To better understand the potential for dermal uptake of phthalates from clothing, we measured the mass accumulation on cotton fabrics of two phthalate esters commonly identified in indoor air: diethylphthalate (DEP) and di-n-butyl phthalate (DnBP). In 10-day chamber experiments, we observed strong air-to-cloth partitioning of these phthalates to shirts and jean material. Area-normalized partition coefficients ranged from 209 to 411 (μg/m2)/(μg/m3) for DEP and 2850 to 6580 (μg/m2)/(μg/m3) for DnBP. Clothing volume-normalized partition coefficients averaged 2.6 × 105 (μg/m3)/(μg/m3) for DEP and 3.9 × 106 (μg/m3)/(μg/m3) for DnBP. At equilibrium, we estimate that a typical set of cotton clothing can sorb DnBP from the equivalent of >10,000 m3 of indoor air, thereby substantially decreasing external mass-transfer barriers to dermal uptake. Further, we estimate that a significant fraction of a child's body burden of DnBP may come from mouthing fabric material that has been equilibrated with indoor air.

  7. Diversity partitioning during the Cambrian radiation.

    PubMed

    Na, Lin; Kiessling, Wolfgang

    2015-04-14

    The fossil record offers unique insights into the environmental and geographic partitioning of biodiversity during global diversifications. We explored biodiversity patterns during the Cambrian radiation, the most dramatic radiation in Earth history. We assessed how the overall increase in global diversity was partitioned between within-community (alpha) and between-community (beta) components and how beta diversity was partitioned among environments and geographic regions. Changes in gamma diversity in the Cambrian were chiefly driven by changes in beta diversity. The combined trajectories of alpha and beta diversity during the initial diversification suggest low competition and high predation within communities. Beta diversity has similar trajectories both among environments and geographic regions, but turnover between adjacent paleocontinents was probably the main driver of diversification. Our study elucidates that global biodiversity during the Cambrian radiation was driven by niche contraction at local scales and vicariance at continental scales. The latter supports previous arguments for the importance of plate tectonics in the Cambrian radiation, namely the breakup of Pannotia. PMID:25825755

  8. Biogeography of time partitioning in mammals

    PubMed Central

    Bennie, Jonathan J.; Duffy, James P.; Inger, Richard; Gaston, Kevin J.

    2014-01-01

    Many animals regulate their activity over a 24-h sleep–wake cycle, concentrating their peak periods of activity to coincide with the hours of daylight, darkness, or twilight, or using different periods of light and darkness in more complex ways. These behavioral differences, which are in themselves functional traits, are associated with suites of physiological and morphological adaptations with implications for the ecological roles of species. The biogeography of diel time partitioning is, however, poorly understood. Here, we document basic biogeographic patterns of time partitioning by mammals and ecologically relevant large-scale patterns of natural variation in “illuminated activity time” constrained by temperature, and we determine how well the first of these are predicted by the second. Although the majority of mammals are nocturnal, the distributions of diurnal and crepuscular species richness are strongly associated with the availability of biologically useful daylight and twilight, respectively. Cathemerality is associated with relatively long hours of daylight and twilight in the northern Holarctic region, whereas the proportion of nocturnal species is highest in arid regions and lowest at extreme high altitudes. Although thermal constraints on activity have been identified as key to the distributions of organisms, constraints due to functional adaptation to the light environment are less well studied. Global patterns in diversity are constrained by the availability of the temporal niche; disruption of these constraints by the spread of artificial lighting and anthropogenic climate change, and the potential effects on time partitioning, are likely to be critical influences on species’ future distributions. PMID:25225371

  9. Diversity partitioning during the Cambrian radiation

    PubMed Central

    Na, Lin; Kiessling, Wolfgang

    2015-01-01

    The fossil record offers unique insights into the environmental and geographic partitioning of biodiversity during global diversifications. We explored biodiversity patterns during the Cambrian radiation, the most dramatic radiation in Earth history. We assessed how the overall increase in global diversity was partitioned between within-community (alpha) and between-community (beta) components and how beta diversity was partitioned among environments and geographic regions. Changes in gamma diversity in the Cambrian were chiefly driven by changes in beta diversity. The combined trajectories of alpha and beta diversity during the initial diversification suggest low competition and high predation within communities. Beta diversity has similar trajectories both among environments and geographic regions, but turnover between adjacent paleocontinents was probably the main driver of diversification. Our study elucidates that global biodiversity during the Cambrian radiation was driven by niche contraction at local scales and vicariance at continental scales. The latter supports previous arguments for the importance of plate tectonics in the Cambrian radiation, namely the breakup of Pannotia. PMID:25825755

  10. On bottleneck partitioning k-ary n-cubes

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Mao, Weizhen

    1994-01-01

    Graph partitioning is a topic of extensive interest, with applications to parallel processing. In this context graph nodes typically represent computation, and edges represent communication. One seeks to distribute the workload by partitioning the graph so that every processor has approximately the same workload, and the communication cost (measured as a function of edges exposed by the partition) is minimized. Measures of partition quality vary; in this paper we consider a processor's cost to be the sum of its computation and communication costs, and consider the cost of a partition to be the bottleneck, or maximal processor cost induced by the partition. For a general graph the problem of finding an optimal partitioning is intractable. In this paper we restrict our attention to the class of k-art n-cube graphs with uniformly weighted nodes. Given mild restrictions on the node weight and number of processors, we identify partitions yielding the smallest bottleneck. We also demonstrate by example that some restrictions are necessary for the partitions we identify to be optimal. In particular, there exist cases where partitions that evenly partition nodes need not be optimal.

  11. Initial Melting and wall-rock flux-melting of a wet multi-component mantle and its implications for the formation of MORB

    NASA Astrophysics Data System (ADS)

    Morgan, J. P.; Hasenclever, J.

    2013-12-01

    We explore several simple scenarios for wet melting of a heterogeneous multi- component mantle. In our melting formulation the mantle is viewed as a mixture consisting of a heterogeneously depleted peridotite matrix with embedded veins of fertile peridotite and/or geochemically enriched pyroxenite. These lithological units differ in their mineral composition but are assumed to have diffusively equilibrated both their water/hydrogen content and temperature over the hundreds of millions to billions of years prior to entering a melting region. During the melting process, however, only thermal but not chemical (water) equilibrium is assumed between the lithologies, which is a reasonable assumption for veins with thicknesses on the order of few tens to few hundreds of meters, a thermal diffusivity of 10^-6 m^2/s and a diffusivity of hydrogen of less than 3*10^-9 m^2/s. The thermodynamic formulation of the multi-component melting process, during which all components have to share thermal energy, is based on Phipps Morgan (2001). The wet melting parameterization by Katz et al. (2003) has been included in the thermodynamic formulation by modifying its solidus-depletion-dependence and treating water partitioning during melting as partitioning of a trace element with a D-value like that of Ce. Usually, fractional melting with a small trapped melt fraction is assumed. We will mostly discuss results from 1-D model calculations, which represent the idealized decompression of a multi-component mantle rising underneath a mid-ocean ridge. Melt-migration is assumed to occur as vertical ascent within each column. We have also extended the formulation to examine the effects of rising melts on 'flux-melting' the wall-rock through which they migrate. We are still testing to see if this mechanism can be the reason why ridge melts almost always have major element chemistries in equilibrium with a peridotitic mantle, while the incompatible trace elements in EMORB reflect the influence of

  12. Polymers as Reference Partitioning Phase: Polymer Calibration for an Analytically Operational Approach To Quantify Multimedia Phase Partitioning.

    PubMed

    Gilbert, Dorothea; Witt, Gesine; Smedes, Foppe; Mayer, Philipp

    2016-06-01

    Polymers are increasingly applied for the enrichment of hydrophobic organic chemicals (HOCs) from various types of samples and media in many analytical partitioning-based measuring techniques. We propose using polymers as a reference partitioning phase and introduce polymer-polymer partitioning as the basis for a deeper insight into partitioning differences of HOCs between polymers, calibrating analytical methods, and consistency checking of existing and calculation of new partition coefficients. Polymer-polymer partition coefficients were determined for polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs) by equilibrating 13 silicones, including polydimethylsiloxane (PDMS) and low-density polyethylene (LDPE) in methanol-water solutions. Methanol as cosolvent ensured that all polymers reached equilibrium while its effect on the polymers' properties did not significantly affect silicone-silicone partition coefficients. However, we noticed minor cosolvent effects on determined polymer-polymer partition coefficients. Polymer-polymer partition coefficients near unity confirmed identical absorption capacities of several PDMS materials, whereas larger deviations from unity were indicated within the group of silicones and between silicones and LDPE. Uncertainty in polymer volume due to imprecise coating thickness or the presence of fillers was identified as the source of error for partition coefficients. New polymer-based (LDPE-lipid, PDMS-air) and multimedia partition coefficients (lipid-water, air-water) were calculated by applying the new concept of a polymer as reference partitioning phase and by using polymer-polymer partition coefficients as conversion factors. The present study encourages the use of polymer-polymer partition coefficients, recognizing that polymers can serve as a linking third phase for a quantitative understanding of equilibrium partitioning of HOCs between any two phases. PMID:27115830

  13. Constraints on core formation in Vesta from metal-silicate partitioning of siderophile elements

    NASA Astrophysics Data System (ADS)

    Steenstra, E. S.; Knibbe, J. S.; Rai, N.; van Westrenen, W.

    2016-03-01

    It is now widely accepted that the asteroid 4-Vesta has an Fe-rich metallic core, but the composition of the core and the conditions prevailing during core-mantle differentiation are poorly constrained. In light of new constraints on Vesta's geophysical and geochemical properties obtained by the DAWN mission, we have re-examined the conditions at which core-mantle differentiation in Vesta may have occurred by linking the estimated mantle depletions of siderophile elements P, Co, Ni, Cu, Ga, Ge, Mo and W in the vestan mantle to newly derived predictive equations for core-mantle partitioning of these elements. We extend the number of elements previously considered in geochemical modeling of vestan core formation and use published metal-silicate partitioning data obtained at low pressures to characterize the dependence of metal/silicate partition coefficients (D) on pressure, temperature, oxygen fugacity and composition of the silicate and metallic melt. In our modeling we implement newly derived mantle depletions of P, Co, Ni and Ga through analysis of published HED meteorite analyses and assess two contrasting bulk compositional models for Vesta. Modeling results using Monte Carlo simulations constrain vestan core formation to have occurred at mildly reducing conditions of approximately 2 log units below the iron-wüstite (IW) buffer (ΔIW = -2.05 ± 0.20) if the two most likely bulk compositions (binary mixtures of H + CM or H + CV chondritic meteorites) are considered, assuming a temperature range between 1725 and 1850 K and a sulfur-free pure Fe core. If the core is assumed to be sulfur-rich (15 wt.% S) as predicted by the latter bulk compositional models, observed depletions for all eight siderophile elements can be simultaneously satisfied at ΔIW = -2.35 ± 0.10 and 1725-1850 K for the H + CV bulk composition and ΔIW = -2.30 ± 0.15 and 1725-1850 K for the H + CM bulk composition. More reducing conditions are not consistent with the observed siderophile

  14. Return flux experiment

    NASA Technical Reports Server (NTRS)

    Tveekrem, June L.

    1992-01-01

    All spacecraft emit molecules via outgassing, thruster plumes, vents, etc. The return flux is the portion of those molecules that scatter from the ambient atmosphere and return to the spacecraft. Return flux allows critical spacecraft surfaces to become contaminated even when there is no direct line of sight between the contamination source and the critical surface. Data from the Long Duration Exposure Facility (LDEF) show that contamination of LDEF surfaces could not have come entirely from direct flux. The data suggest significant return flux. Several computer models have been developed to simulate return flux, but the predictions have never been verified in orbit. Large uncertainties in predictions lead to overly conservative spacecraft designs. The purpose of the REturn FLux EXperiment (REFLEX) is to fly a controlled experiment that can be directly compared with predictions from several models.

  15. Safety-Critical Partitioned Software Architecture: A Partitioned Software Architecture for Robotic

    NASA Technical Reports Server (NTRS)

    Horvath, Greg; Chung, Seung H.; Cilloniz-Bicchi, Ferner

    2011-01-01

    The flight software on virtually every mission currently managed by JPL has several major flaws that make it vulnerable to potentially fatal software defects. Many of these problems can be addressed by recently developed partitioned operating systems (OS). JPL has avoided adopting a partitioned operating system on its flight missions, primarily because doing so would require significant changes in flight software design, and the risks associated with changes of that magnitude cannot be accepted by an active flight project. The choice of a partitioned OS can have a dramatic effect on the overall system and software architecture, allowing for realization of benefits far beyond the concerns typically associated with the choice of OS. Specifically, we believe that a partitioned operating system, when coupled with an appropriate architecture, can provide a strong infrastructure for developing systems for which reusability, modifiability, testability, and reliability are essential qualities. By adopting a partitioned OS, projects can gain benefits throughout the entire development lifecycle, from requirements and design, all the way to implementation, testing, and operations.

  16. Effect of lamp type and temperature on development, carbon partitioning and yield of soybean

    NASA Astrophysics Data System (ADS)

    Dougher, T. A. O.; Bugbee, B.

    1997-01-01

    Soybeans grown in controlled environments are commonly taller than field-grown plants. In controlled environments, including liquid hydroponics, height of the dwarf cultivar ``Hoyt'' was reduced from 46 to 33 cm when plants were grown under metal halide lamps compared to high pressure sodium lamps at the same photosynthetic photon flux. Metal halide lamps reduced total biomass 14% but did not significantly reduce seed yield. Neither increasing temperature nor altering the difference between day/night temperature affected plant height. Increasing temperature from 21 to 27 degC increased yield 32%. High temperature significantly increased carbon partitioning to stems and increased harvest index.

  17. Sea-air partitioning of mercury in the equatorial Pacific Ocean

    SciTech Connect

    Kim, J.P.; Fitzgerald, W.F.

    1986-03-07

    The partitioning of gaseous mercury between the atmosphere and surface waters was determined in the equatorial Pacific Ocean. The highest concentrations of dissolved gaseous mercury occurred in cooler, nutrient-rich waters that characterize equatorial upwelling and increased biological productivity at the sea surface. The surface waters were supersaturated with respect to elemental mercury; a significant flux of elemental mercury to the atmosphere is predicted for the equatorial Pacific. When normalized to primary production on a global basis, the ocean effluxes of mercury may rival anthropogenic emissions of mercury to the atmosphere. 23 references, 2 figures.

  18. Paleoproterozoic Kimozero kimberlite (Karelian Craton): Geological setting and geochemical typing

    NASA Astrophysics Data System (ADS)

    Kargin, A. V.; Babarina, I. I.; Bogatikov, O. A.; Yutkina, E. V.; Kondrashov, I. A.

    2015-11-01

    Geological and structural mapping of Paleoproterozoic Kimozero kimberlite with account for lithological facies and geochemical specialization provides evidence for the multiphase structure of the kimberlite pipe, which underwent fragmentation as a result of shear-faulting deformations. Two geochemical types of kimberlite (magnesium and carbonate) are distinguished.

  19. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  20. Aspects of flux compactification

    NASA Astrophysics Data System (ADS)

    Liu, Tao

    In this thesis, we study three main aspects of flux compactifications: (1) classify supergravity solutions from flux compactification; (2) construct flux-deformed geometry and 4D low-energy theory to describe these flux vacua; and (3) study 4D particle phenomenology and cosmology of flux vacua. In the first part, we review G-structure, the basic tool to study supersymmetric flux solutions, and some typical solutions obtained in heterotic, type IIA and type IIB string theories. Then we present a comprehensive classification of supersymmetric vacua of M-theory compactification on 7D manifolds with general four-form fluxes. We analyze the cases where the resulting four-dimensional vacua have N = 1, 2, 3, 4 supersymmetry and the internal space allows for SU(2)-, SU(3)- or G 2-structures. In particular, we find for N = 2 supersymmetry, that the external space-time is Minkowski and the base manifold of the internal space is conformally Kahler for SU(2) structures, while for SU(3) structures the internal space has to be Einstein-Sasaki and no internal fluxes are allowed. Moreover, we provide a new vacuum with N = 1 supersymmetry and SU(3) structure, where all fluxes are non-zero and the first order differential equations are solved. In the second part, we simply review the methods used to construct one subclass of fluxed-deformed geometry or the so-called "twisted manifold", and the associated 4D effective theory describing these flux vacua. Then by employing (generalized) Scherk-Schwarz reduction, we construct the geometric twisting for Calabi-Yau manifolds of Voisin-Borcea type (K 3 x T2)/ Z2 and study the superpotential in a type IIA orientifold based on this geometry. The twists modify the direct product by fibering the K 3 over T2 while preserving the Z2 involution. As an important application, the Voisin-Borcea class contains T6/( Z2 x Z2 ), the usual setting for intersecting D6 brane model building. Past work in this context considered only those twists inherited

  1. The evaporative fraction as a measure of surface energy partitioning

    SciTech Connect

    Nichols, W.E.; Cuenca, R.H.

    1990-12-31

    The evaporative fraction is a ratio that expresses the proportion of turbulent flux energy over land surfaces devoted to evaporation and transpiration (evapotranspiration). It has been used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on mid-day remote sensing measurements. The HAPEX-MOBILHY program`s SAMER system provided surface energy balance data over a range of agricultural crops and soil types. The databases from this large-scale field experiment was analyzed for the purpose of studying the behavior and daylight stability of the evaporative fraction in both ideal and general meteorological conditions. Strong linear relations were found to exist between the mid-day evaporative fraction and the daylight mean evaporative fraction. Statistical tests however rejected the hypothesis that the two quantities were equal. The relations between the evaporative fraction and the surface soil moisture as well as soil moisture in the complete vegetation root zone were also explored.

  2. Ammonia Partitioning into the Condensed Phase in Winter Time Conditions

    NASA Astrophysics Data System (ADS)

    Green, J. R.; Bililign, S.; Fiddler, M. N.; Leen, J. B.; Holloway, J. S.; Fibiger, D. L.; McDuffie, E. E.; Thornton, J. A.; Brown, S. S.

    2015-12-01

    Secondary aerosol (SOA) formation has been linked to health problems and environmental damage in regions impacted by the emission of gaseous NH3 and SO2. SOA formation, (NH4)2SO4 and NH4NO3, in the presence of NO NO2, is favored under high relative humidity and low temperature and low temperature conditions. In the East and Mid Atlantic regions of the United States humidity is low in wintertime. Utilizing ambient concentration data of gaseous NO, NO2, SO2 and NH3 collected aboard a survey aircraft we examined the partitioning of gaseous NH3 towards aerosol products. The calculated mixing ratio of gaseous SO2/NH3 correlated with relative humidity will give an indication of the potential SOA formation when the mixing ratio of other reactants is small in the region of interest. The data obtained originates from a series of night and day survey flights on a C-130 aircraft that occurred from February 3 to March 13, 2015 over the Eastern coastal region of the United States extending from New York to Florida. NOx was obtained from the Airborne Ring-down Nitrogen Oxide Laser Detector (ARNOLD) instrument (NOAA) and Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) (UC Berkley). SO2 measurements were done using the TECO 43C SO2 analyzer and for NH3 measurements the an Ammonia Analyzer - Trace (NH3) (Los Gatos Research). Estimates of aerosol dry deposition fluxes are presented.

  3. Use of partial dissolution techniques in geochemical exploration

    USGS Publications Warehouse

    Chao, T.T.

    1984-01-01

    Application of partial dissolution techniques to geochemical exploration has advanced from an early empirical approach to an approach based on sound geochemical principles. This advance assures a prominent future position for the use of these techniques in geochemical exploration for concealed mineral deposits. Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as "nonselective" extraction and as "selective" extraction in terms of the relative specificity of the extraction. The choice of dissolution techniques for use in geochemical exploration is dictated by the geology of the area, the type and degree of weathering, and the expected chemical forms of the ore and of the pathfinding elements. Case histories have illustrated many instances where partial dissolution techniques exhibit advantages over conventional methods of chemical analysis used in geochemical exploration. ?? 1984.

  4. High dimensional data clustering by partitioning the hypergraphs using dense subgraph partition

    NASA Astrophysics Data System (ADS)

    Sun, Xili; Tian, Shoucai; Lu, Yonggang

    2015-12-01

    Due to the curse of dimensionality, traditional clustering methods usually fail to produce meaningful results for the high dimensional data. Hypergraph partition is believed to be a promising method for dealing with this challenge. In this paper, we first construct a graph G from the data by defining an adjacency relationship between the data points using Shared Reverse k Nearest Neighbors (SRNN). Then a hypergraph is created from the graph G by defining the hyperedges to be all the maximal cliques in the graph G. After the hypergraph is produced, a powerful hypergraph partitioning method called dense subgraph partition (DSP) combined with the k-medoids method is used to produce the final clustering results. The proposed method is evaluated on several real high-dimensional datasets, and the experimental results show that the proposed method can improve the clustering results of the high dimensional data compared with applying k-medoids method directly on the original data.

  5. Trace element partitioning between ilmenite and anhydrous silicate melt: shedding light on the formation of lunar mare basalts

    NASA Astrophysics Data System (ADS)

    van Kan Parker, M.; Mason, P. R.; van Westrenen, W.

    2009-12-01

    Ilmenite (FeTiO3) is the main titanium-bearing, oxide mineral on the Moon. In contrast to its relatively minor role in terrestrial magmatic processes, it played a crucial role in the late stages of lunar magma ocean (LMO) crystallisation and in subsequent mare basalt formation. Quantifying its major and trace element incorporation behaviour at different conditions during partial melting and crystallisation processes is essential to constrain lunar interior evolution models. Trace element partitioning between ilmenite and silicate melt is poorly studied. Trace element partitioning between equilibrium phases depends on pressure, temperature, composition and oxygen fugacity. However, currently available ilmenite-melt partitioning data do not systematically consider these parameters. As a result, no predictive model explaining the large variations in partition coefficients seen in the literature is available. We performed systematic high-pressure, high-temperature ilmenite-melt partitioning experiments in the CaO-FeO-MgO-Al2O3-TiO2-SiO2 (CFMATS) system. Starting materials were doped with a wide range of trace elements (LILE, REE, HFSE and transition metals). Experiments were carried out at atmospheric pressure in platinum capsules, and at high pressure in an end-loaded piston cylinder at the VU University using graphite-lined Pt capsules. Major and trace element compositions of experimental charges were determined using a JEOL Electron Microprobe (VU University) and laser ablation ICP-MS (Utrecht University), respectively. Our results show that transition metals are generally compatible at pressures between 1.1 and 1.7 GPa and 1580 ± 10 K, with Cr having the highest partition coefficient (D ~ 6), followed by V (D ~ 3.5). Mn and Co have D values near 1. The HFSE are moderately incompatible at elevated pressures, with partition coefficients of 0.11-0.54. The REE are all incompatible, with HREE D values of 0.06 ± 0.03, and LILE D values are all <0.004. No clear pressure

  6. SULFUR DIOXIDE FLUX INTO LEAVES OF 'GERANIUM CAROLINIANUM' L.: EVIDENCE FOR A NONSTOMATAL OR RESIDUAL RESISTANCE

    EPA Science Inventory

    The concurrent exchange of SO2 and H2O vapor between the atmosphere and foliage of Geranium carolinanum was investigated using a whole-plant gas exchange chamber. Total leaf flux of SO2 was partitioned into leaf surface and internal fractions. The emission rate of SO2-induced H2S...

  7. Productivity and carbon dioxide exchange of the leguminous crops: Estimates from flux tower measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net CO2 exchange data on legume crops at 17 flux tower sites in North America and 3 sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration using a light-response function method, resulting in new estimates of ecosystem-scale ec...

  8. Video Meteor Fluxes

    NASA Technical Reports Server (NTRS)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    The flux of meteoroids, or number of meteoroids per unit area per unit time, is critical for calibrating models of meteoroid stream formation and for estimating the hazard to spacecraft from shower and sporadic meteors. Although observations of meteors in the millimetre to centimetre size range are common, flux measurements (particularly for sporadic meteors, which make up the majority of meteoroid flux) are less so. It is necessary to know the collecting area and collection time for a given set of observations, and to correct for observing biases and the sensitivity of the system. Previous measurements of sporadic fluxes are summarized in Figure 1; the values are given as a total number of meteoroids striking the earth in one year to a given limiting mass. The Gr n et al. (1985) flux model is included in the figure for reference. Fluxes for sporadic meteoroids impacting the Earth have been calculated for objects in the centimeter size range using Super-Schmidt observations (Hawkins & Upton, 1958); this study used about 300 meteors, and used only the physical area of overlap of the cameras at 90 km to calculate the flux, corrected for angular speed of meteors, since a large angular speed reduces the maximum brightness of the meteor on the film, and radiant elevation, which takes into account the geometric reduction in flux when the meteors are not perpendicular to the horizontal. They bring up corrections for both partial trails (which tends to increase the collecting area) and incomplete overlap at heights other than 90 km (which tends to decrease it) as effects that will affect the flux, but estimated that the two effects cancelled one another. Halliday et al. (1984) calculated the flux of meteorite-dropping fireballs with fragment masses greater than 50 g, over the physical area of sky accessible to the MORP fireball cameras, counting only observations in clear weather. In the micron size range, LDEF measurements of small craters on spacecraft have been used to

  9. A geochemical basis for endomyocardial fibrosis.

    PubMed

    Valiathan, M S; Kartha, C C; Panday, V K; Dang, H S; Sunta, C M

    1986-09-01

    In a search for geochemical factors that could play a role in the pathogenesis of tropical endomyocardial fibrosis, endomyocardial tissue samples obtained from patients at necropsy or operation were analysed for major elements present in laterite and monazite, which are important soil constituents of Kerala State of India. Atomic absorption spectrophotometry was used for detecting iron, silicon, aluminium, zinc, magnesium, calcium, sodium, potassium, and manganese and neutron activation analysis for thorium. Compared with control samples from victims of fatal accidents, an excess of thorium, sodium, and calcium and a deficiency of magnesium were present in samples from patients. It has been shown earlier that the staple diets of people in Kerala have high concentrations of thorium, and these data show that thorium can become concentrated in cardiac tissues. It is speculated that thorium excess in conjunction with magnesium deficiency may play a role in the causation of tropical endomyocardial fibrosis. PMID:3791358

  10. Geochemical exploration for uranium in playas.

    USGS Publications Warehouse

    Leach, D.L.; Puchlik, K.P.; Glanzman, R.K.

    1980-01-01

    Although playa sediments at spring discharge areas contain as much as 58 ppm U, evaporation and mobilization processes were found to limit their potential as resources of U. Other metals, however, such as Zn, W, and Au may have a geochemical signature in the playas. There are certain conditions that would make some playas more favorable for the accumulation of U: 1) the presence of precursor carbonate-rich saline lakes; 2) nearby U-rich source rocks; 3) restricted groundwater discharge into the playa; 4) localized precipitation mechanisms or phases in the playa;5) large drainage basins and adequate precipitation; and 6) stability of a hydrologically closed basin for a long period of time.- from Authors

  11. A brief history of partitions of numbers, partition functions and their modern applications

    NASA Astrophysics Data System (ADS)

    Debnath, Lokenath

    2016-04-01

    'Number rules the universe.' The Pythagoras 'If you wish to forsee the future of mathematics our course is to study the history and present conditions of the science.' Henri Poincaré 'The primary source (Urqell) of all mathematics are integers.' Hermann Minkowski This paper is written to commemorate the centennial anniversary of the Mathematical Association of America. It deals with a short history of different kinds of natural numbers including triangular, square, pentagonal, hexagonal and k-gonal numbers, and their simple properties and their geometrical representations. Included are Euclid's and Pythagorean's main contributions to elementary number theory with the main contents of the Euclid Elements of the 13-volume masterpiece of mathematical work. This is followed by Euler's new discovery of the additive number theory based on partitions of numbers. Special attention is given to many examples, Euler's theorems on partitions of numbers with geometrical representations of Ferrers' graphs, Young's diagrams, Lagrange's four-square theorem and the celebrated Waring problem. Included are Euler's generating functions for the partitions of numbers, Euler's pentagonal number theorem, Gauss' triangular and square number theorems and the Jacobi triple product identity. Applications of the theory of partitions of numbers to different statistics such as the Bose- Einstein, Fermi- Dirac, Gentile, and Maxwell- Boltzmann statistics are briefly discussed. Special attention is given to pedagogical information through historical approach to number theory so that students and teachers at the school, college and university levels can become familiar with the basic concepts of partitions of numbers, partition functions and their modern applications, and can pursue advanced study and research in analytical and computational number theory.

  12. The geochemical atlas of Italian soils

    NASA Astrophysics Data System (ADS)

    De Vivo, Benedetto; Cicchella, Domenico; Albanese, Stefano; Dinelli, Enrico; Giaccio, Lucia; Lima, Annamaria; Valera, Paolo

    2014-05-01

    The geochemical Atlas of Italian agricultural and grazing land soils was carried out as part of GEMAS project whose objective was to characterize soils of rural areas of the whole Europe. Soil samples were collected at an average sampling density of 1 site per 2500 km2. Two different sample types were collected: (1) 121 agricultural soils (Ap) on regularly ploughed land to a depth of 20 cm and (2) 121 grazing land soils (Gr) (land under permanent grass cover) to a depth of 10 cm. All soil samples were air dried, sieved to <2 mm, homogenised and finally split into 10 sub-samples. Both sample types (Ap and Gr) were analysed at the BGR for a suite of 41 elements by WD-XRFS. The same samples were also analysed after AR and MMI extractions by a combination of ICP-AES and ICP-MS for 53 elements. In addition, other parameters were determined: pH, TOC, total carbon and total sulphur, LOI, CEC, Sr-isotopes, Pb-isotopes, MIR-spectra. By means of a GIS software, georeferenced data of the Italian territory were used to produce the geochemical maps of all the analysed elements for both agricultural and grazing land soils. Specifically, for each element and sampling media a map reporting interpolated data and graduated dots was produced; univariate statistics and graphs were also associated to each map. The Atlas also contain: 5 maps for regional variability of factor scores of elemental associations resulting from R-mode factor analysis and 15 baseline and land use maps for some selected elements (As, Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sn, Tl, V, Zn) following the Italian intervention criteria.

  13. Code System to Model Aqueous Geochemical Equilibria.

    Energy Science and Technology Software Center (ESTSC)

    2001-08-23

    Version: 00 MINTEQ is a geochemical program to model aqueous solutions and the interactions of aqueous solutions with hypothesized assemblages of solid phases. It was developed for the Environmental Protection Agency to perform the calculations necessary to simulate the contact of waste solutions with heterogeneous sediments or the interaction of ground water with solidified wastes. MINTEQ can calculate ion speciation/solubility, adsorption, oxidation-reduction, gas phase equilibria, and precipitation/dissolution ofsolid phases. MINTEQ can accept a finite massmore » for any solid considered for dissolution and will dissolve the specified solid phase only until its initial mass is exhausted. This ability enables MINTEQ to model flow-through systems. In these systems the masses of solid phases that precipitate at earlier pore volumes can be dissolved at later pore volumes according to thermodynamic constraints imposed by the solution composition and solid phases present. The ability to model these systems permits evaluation of the geochemistry of dissolved traced metals, such as low-level waste in shallow land burial sites. MINTEQ was designed to solve geochemical equilibria for systems composed of one kilogram of water, various amounts of material dissolved in solution, and any solid materials that are present. Systems modeled using MINTEQ can exchange energy and material (open systems) or just energy (closed systems) with the surrounding environment. Each system is composed of a number of phases. Every phase is a region with distinct composition and physically definable boundaries. All of the material in the aqueous solution forms one phase. The gas phase is composed of any gaseous material present, and each compositionally and structurally distinct solid forms a separate phase.« less

  14. Geochemical characteristics of Cretaceous carbonatites from Angola

    NASA Astrophysics Data System (ADS)

    Alberti, A.; Castorina, F.; Censi, P.; Comin-Chiaramonti, P.; Gomes, C. B.

    1999-12-01

    The Early Cretaceous (138-130 Ma) carbonatites and associated alkaline rocks of Angola belong to the Paraná-Angola-Etendeka Province and occur as ring complexes and other central-type intrusions along northeast trending tectonic lineaments, parallel to the trend of coeval Namibian alkaline complexes. Most of the Angolan carbonatite-alkaline bodies are located along the apical part of the Moçamedes Arch, a structure representing the African counterpart of the Ponta Grossa Arch in southern Brazil, where several alkaline-carbonatite complexes were also emplaced in the Early Cretaceous. Geochemical and isotopic (C, 0, Sr and Nd) characteristics determined for five carbonatitic occurrences indicate that: (1) the overall geochemical composition, including the OC isotopes, is within the range of the Early and Late Cretaceous Brazilian occurrences from the Paraná Basin; (2) the La versus {La}/{Yb} relationships are consistent with the exsolution of CO i2-rich melts from trachyphonolitic magmas; and (3) the {143Nd}/{144Nd} and {87Sr}/{86Sr} initial ratios are similar to the initial isotopic ratios (129 Ma) of alkaline complexes in northwest Namibia. In contrast, the Lupongola carbonatites have a distinctly different {143Nd}/{144Nd} initial ratio, suggesting a different source. The Angolan carbonatites have SrNd isotopic compositions ranging from bulk earth to time-integrated depleted sources. Since those from eastern Paraguay (at the western fringe of the Paraná-Angola-Etendeka Province) and Brazil appear to be related to mantle-derived melts with time-integrated enriched or B.E. isotopic characteristics, it is concluded that the carbonatites of the Paraná-Angola-Etendeka Province have compositionally distinct mantle sources. Such mantle heterogeneity is attributed to 'metasomatic processes', which would have occurred at ca 0.6-0.7 Ga (Angola, northwest Namibia and Brazil) and ca 1.8 Ga (eastern Paraguay), as suggested by Nd-model ages.

  15. Resolving Magnetic Flux Patches at the Surface of the Core

    NASA Technical Reports Server (NTRS)

    OBrien, Michael S.

    1996-01-01

    The geomagnetic field at a given epoch can be used to partition the surface of the liquid outer core into a finite number of contiguous regions in which the radial component of the magnetic flux density, B (sub r), is of one sign. These flux patches are instrumental in providing detail to surface fluid flows inferred from the changing geomagnetic field and in evaluating the validity of the frozen-flux approximation on which such inferences rely. Most of the flux patches in models of the modem field are small and enclose little flux compared to the total unsigned flux emanating from the core. To demonstrate that such patches are not required to explain the most spatially complete and accurate data presently available, those from the Magsat mission, I have constructed a smooth core field model that fits the Magsat data but does not possess small flux patches. I conclude that our present knowledge of the geomagnetic field does not allow us to resolve these features reliably at the core-mantle boundary; thus we possess less information about core flow than previously believed.

  16. A Partitioning Algorithm for Block-Diagonal Matrices With Overlap

    SciTech Connect

    Guy Antoine Atenekeng Kahou; Laura Grigori; Masha Sosonkina

    2008-02-02

    We present a graph partitioning algorithm that aims at partitioning a sparse matrix into a block-diagonal form, such that any two consecutive blocks overlap. We denote this form of the matrix as the overlapped block-diagonal matrix. The partitioned matrix is suitable for applying the explicit formulation of Multiplicative Schwarz preconditioner (EFMS) described in [3]. The graph partitioning algorithm partitions the graph of the input matrix into K partitions, such that every partition {Omega}{sub i} has at most two neighbors {Omega}{sub i-1} and {Omega}{sub i+1}. First, an ordering algorithm, such as the reverse Cuthill-McKee algorithm, that reduces the matrix profile is performed. An initial overlapped block-diagonal partition is obtained from the profile of the matrix. An iterative strategy is then used to further refine the partitioning by allowing nodes to be transferred between neighboring partitions. Experiments are performed on matrices arising from real-world applications to show the feasibility and usefulness of this approach.

  17. LCLS Spectral Flux Viewer

    Energy Science and Technology Software Center (ESTSC)

    2005-10-25

    This application (FluxViewer) is a tool for displaying spectral flux data for the Linac Coherent Light Source (LCLS). This tool allows the user to view sliced spatial and energy distributions of the photons selected for specific energies and positions transverse to the beam axis.

  18. Global Fluorine Flux Associated with Submarine Hydrothermal Fluids

    NASA Astrophysics Data System (ADS)

    Kagoshima, T.; Sano, Y.

    2015-12-01

    We estimated a fluorine flux associated with hydrothermal fluid emission at mid-ocean ridges (MOR) based on vent fluid chemistry and MORB vesicle compositions. Multiplication of fluorine concentrations in submarine hydrothermal fluids and the vent fluid flux at MOR may give us an estimate of fluorine flux at MOR. A worldwide vent chemistry research [1] suggested that submarine vent fluids are depleted in fluorine (<0.74 ppm F) relative to seawater (1.29 ppm F). The global flux of submarine hydrothermal fluids of (8.0+/-2.1)x1015 g/y was calculated using a numerical Bayesian inversion procedure to explain the relationship between compositions of high-temperature hydrothermal fluids and altered sheeted dikes, which enables us to estimate fluorine flux to be less than (3.1+/-0.8)x108 mol/y. This value is almost comparable with fluorine flux of (7.1+/-2.8)x108 mol/y estimated using F/3He ratios in MORB vesicles and the known 3He flux at MOR [3]. This flux calculation is based on preferentially degassed components from the magma as a form of MORB vesicle, thus may be related to fluorine flux associated with hydrothermal fluid emission. However, this flux should be overestimated because seawater incursion was not considered for the calculation. The average of the two different fluxes was calculated to be (5.1+/-2.0)x108 mol/y, which may be the maximum value of fluorine flux associated with hydrothermal fluid emission at MOR. It should be noted that this flux is much lower than the one estimated using the F/CO2 ratio in the MORB source and the known CO2 flux from the mantle [4] because the most of fluorine resides in the melt and should not be released immediately after formation of oceanic crust. Comparing MOR and arc fluxes, the global cycle of fluorine will be discussed in the presentation. [1] German & Von Damm (2006) Treatise On Geochemistry 6 (eds Holland & Turekian) 181-222 (Elsevier, London). [2] Coogan & Dosso (2012) EPSL 323-324, 92-101. [3] Kagoshima et al

  19. Rainfall partitioning by vegetation under Mediterranean conditions. A review of studies in Europe

    NASA Astrophysics Data System (ADS)

    Llorens, Pilar; Domingo, Francisco

    2007-03-01

    SummaryRainfall partitioning by vegetation plays an important role affecting the water balance at local and catchment scale due to the control that vegetation canopies exert by modifying both evaporation and the redistribution of incident rainfall. The parameters associated with this process can be found in the literature but this task is not always easy. In this context, this paper presents an exhaustive review of experimental studies dealing with rainfall interception in the Mediterranean area of Europe in the last 30 years, with information on 29 different species (89% referred to tree stands and 11% to shrubs or bushes) from 83 sites in 63 research areas found in 90 papers on studies performed in France, Greece, Italy, Portugal and Spain. The revision includes articles in international journals and books (37%), local journals (27%), Ph.D. dissertations, Master's theses and technical documents (27%) and proceedings (10%) until 2004. The studies are representative of a wide range of rainfall, temperatures and potential evapotranspiration. The lack of a standard protocol to measure bulk rainfall, throughfall and stemflow in interception studies makes it difficult to merge information in this type of review. Nevertheless, this review presents a detailed classification of the information compiled according to research focus, climate and vegetation characteristics, rainfall partitioning flux measurement methods and the quality of the information, giving rise to an important database of rainfall partitioning studies in the European Mediterranean area.

  20. Partitioning of Evapotranspiration Using a Stable Water Isotope Technique in a High Temperature Agricultural Production System

    NASA Astrophysics Data System (ADS)

    Lu, X.; Liang, L.; Wang, L.; Jenerette, D.; Grantz, D. A.

    2015-12-01

    Agricultural production in the hot and arid low desert systems of southern California relies heavily on irrigation. A better understanding of how much and to what extent the irrigation water is transpired by crops relative to being lost through evaporation will contribute to better management of increasingly limited agricultural water resources. In this study, we examined the evapotranspiration (ET) partitioning over a field of forage sorghum (S. bicolor) during a growing season with several irrigation cycles. In several field campaigns we used continuous measurements of near-surface variations in the stable isotopic composition of water vapor (δ2H). We employed custom built transparent chambers coupled with a laser-based isotope analyzer and used Keeling plot and mass balance methods for surface flux partitioning. The preliminary results show that δT is more enriched than δE in the early growing season, and becomes less enriched than δE later in the season as canopy cover increases. There is an increase in the contribution of transpiration to ET as (1) leaf area index increases, and (2) as soil surface moisture declines. These results are consistent with theory, and extend these measurements to an environment that experiences extreme soil surface temperatures. The data further support the use of chamber based methods with stable isotopic analysis for characterization of ET partitioning in challenging field environments.

  1. Knowledge base rule partitioning design for CLIPS

    NASA Technical Reports Server (NTRS)

    Mainardi, Joseph D.; Szatkowski, G. P.

    1990-01-01

    This describes a knowledge base (KB) partitioning approach to solve the problem of real-time performance using the CLIPS AI shell when containing large numbers of rules and facts. This work is funded under the joint USAF/NASA Advanced Launch System (ALS) Program as applied research in expert systems to perform vehicle checkout for real-time controller and diagnostic monitoring tasks. The Expert System advanced development project (ADP-2302) main objective is to provide robust systems responding to new data frames of 0.1 to 1.0 second intervals. The intelligent system control must be performed within the specified real-time window, in order to meet the demands of the given application. Partitioning the KB reduces the complexity of the inferencing Rete net at any given time. This reduced complexity improves performance but without undo impacts during load and unload cycles. The second objective is to produce highly reliable intelligent systems. This requires simple and automated approaches to the KB verification & validation task. Partitioning the KB reduces rule interaction complexity overall. Reduced interaction simplifies the V&V testing necessary by focusing attention only on individual areas of interest. Many systems require a robustness that involves a large number of rules, most of which are mutually exclusive under different phases or conditions. The ideal solution is to control the knowledge base by loading rules that directly apply for that condition, while stripping out all rules and facts that are not used during that cycle. The practical approach is to cluster rules and facts into associated 'blocks'. A simple approach has been designed to control the addition and deletion of 'blocks' of rules and facts, while allowing real-time operations to run freely. Timing tests for real-time performance for specific machines under R/T operating systems have not been completed but are planned as part of the analysis process to validate the design.

  2. Boron, beryllium, and lithium, partitioning in olivine

    SciTech Connect

    Neroda, Elizabeth

    1996-05-01

    A one atmosphere experimental study was performed to determine the mineral/melt partition coefficients for B, Be, and Li in forsteritic olivine. Two compositions were chosen along the 1350{degrees}C isotherm, 1b (Fo{sub 17.3} Ab{sub 82.7} An{sub 0} by weight) and 8c (Fo{sub 30} Ab{sub 23.3} An{sub 47.8}, by weight) were then combined in equal amounts to form a composition was doped with 25ppm Li, B, Yb, Nb, Zr, Sr, and Hf, 50ppm Sm, and 100ppm Be, Nd, Ce, and Rb. Electron and ion microprobe analyses showed that the olivine crystals and surrounding glasses were homogeneous with respect to major and trace elements. Partition coefficients calculated from these analyses are as follows: 1b: D{sub B} = 4.41 ({+-} 2.3) E-03, D{sub Be} = 2.86 ({+-} 0.45) E-03, D{sub Li} = 1.54 ({+-} 0.21) E-01, 50/50: D{sub B} = 2.86 ({+-} 0.5) E-03, D{sub Be} = 2.07 ({+-} 0.09) E-03, D{sub Li} = 1.51 ({+-} 0.18) E-01, 8c: D{sub B} = 6.05 ({+-} 1.5) E-03, D{sub Be} = 1.81 ({+-} 0.03) E-03, D{sub Li} = 1.31 ({+-} 0.09) E-01. The results of this study will combined with similar data for other minerals as part of a larger study to understand the partitioning behavior of B, Be, and Li in melting of the upper mantle at subduction zones.

  3. Entanglement concentration of three-partite states

    SciTech Connect

    Groisman, Berry; Linden, Noah; Popescu, Sandu

    2005-12-15

    We investigate the concentration of multiparty entanglement by focusing on a simple family of three-partite pure states, superpositions of Greenberger-Horne-Zeilinger states and singlets. Despite the simplicity of the states, we show that they cannot be reversibly concentrated by the standard entanglement concentration procedure, to which they seem ideally suited. Our results cast doubt on the idea that for each N there might be a finite set of N-party states into which any pure state can be reversibly transformed. We further relate our results to the concept of locking of entanglement of formation.

  4. The minimal length and quantum partition functions

    NASA Astrophysics Data System (ADS)

    Abbasiyan-Motlaq, M.; Pedram, P.

    2014-08-01

    We study the thermodynamics of various physical systems in the framework of the generalized uncertainty principle that implies a minimal length uncertainty proportional to the Planck length. We present a general scheme to analytically calculate the quantum partition function of the physical systems to first order of the deformation parameter based on the behavior of the modified energy spectrum and compare our results with the classical approach. Also, we find the modified internal energy and heat capacity of the systems for the anti-Snyder framework.

  5. Spatially-partitioned many-body vortices

    NASA Astrophysics Data System (ADS)

    Klaiman, S.; Alon, O. E.

    2016-02-01

    A vortex in Bose-Einstein condensates is a localized object which looks much like a tiny tornado storm. It is well described by mean-field theory. In the present work we go beyond the current paradigm and introduce many-body vortices. These are made of spatially- partitioned clouds, carry definite total angular momentum, and are fragmented rather than condensed objects which can only be described beyond mean-field theory. A phase diagram based on a mean-field model assists in predicting the parameters where many-body vortices occur. Implications are briefly discussed.

  6. Partitioning technique for discrete quantum systems

    SciTech Connect

    Jin, L.; Song, Z.

    2011-06-15

    We develop the partitioning technique for quantum discrete systems. The graph consists of several subgraphs: a central graph and several branch graphs, with each branch graph being rooted by an individual node on the central one. We show that the effective Hamiltonian on the central graph can be constructed by adding additional potentials on the branch-root nodes, which generates the same result as does the the original Hamiltonian on the entire graph. Exactly solvable models are presented to demonstrate the main points of this paper.

  7. Light period regulation of carbohydrate partitioning

    NASA Technical Reports Server (NTRS)

    Janes, Harry W.

    1994-01-01

    We have shown that the photosynthetic period is important in regulating carbon partitioning. Even when the same amount of carbon is fixed over a 24h period considerably more is translocated out of the leaf under the longer photosynthetic period. This is extremely important when parts of the plant other than the leaves are to be sold. It is also important to notice the amount of carbon respired in the short photosynthetic period. The light period effect on carbohydrate fixation, dark respiration, and translocation is shown in this report.

  8. Tracing the allocation of water in rainfed rice ecosystem by partitioning evapotranspiration of rainfed rice (Oryza Sativa L.)

    NASA Astrophysics Data System (ADS)

    Nay-Htoon, Bhone; Dubbert, Maren; Wei, Xue; Cuntz, Matthias; Ko, Jonghan; Tenhunen, John; Werner, Christiane

    2015-04-01

    To understand productive and unproductive water use of crop production, partitioning evapotranspiration (ET ) into evaporation (E) and transpiration (T ) is important. Water movements within the eco-hydrologic cycle of agroecosystems can be traced by stable oxygen isotopes of water (δ18O) and plant transpiration and soil evaporation can also be estimated by tracing the δ18O. We quantified the contribution of transpiration to total ecosystem evapotranspiration of rainfed rice field by a stable oxygen isotope approach and FAO 56 dual crop modelling approach. Our study aims to provide quantification of ecosystem water cycle of rainfed rice by partitioning productive and unproductive water use since productivity and water use of rice which is a highly water demanding agroecosystem, is under intense research. Crop season total evapotranspiration fluxes from rainfed rice was mainly dominated by transpiration (T to ET contribution (T /ET ) = 65%) and domination of transpiration over evaporation fluxes was noted since early vegetative stage (Leaf Area Index = 0.8 m2 m-2) until harvesting. T /ET of rainfed rice fluctuated with changes in soil water content (SWC) and the highest T /ET was found at SWC of 0.34 m3 m-3, during seedling stage. Our results demonstrate that partitioning ET by FAO 56 dual crop model is in a good agreement with δ18O isotope based ET partitioning results. Using monthly mean values of leaf resistance and vegetation index derived crop coefficients instead of original fixed parameters of the FAO 56 dual crop model resulted better agreement with δ18O isotope based ET partitioning.

  9. Modular properties of full 5D SYM partition function

    NASA Astrophysics Data System (ADS)

    Qiu, Jian; Tizzano, Luigi; Winding, Jacob; Zabzine, Maxim

    2016-03-01

    We study properties of the full partition function for the U(1) 5D N = {2}^{ast } gauge theory with adjoint hypermultiplet of mass M . This theory is ultimately related to abelian 6D (2,0) theory. We construct the full non-perturbative partition function on toric Sasaki-Einstein manifolds by gluing flat copies of the Nekrasov partition function and we express the full partition function in terms of the generalized double elliptic gamma function G 2 C associated with a certain moment map cone C. The answer exhibits a curious SL(4 , ℤ) modular property. Finally, we propose a set of rules to construct the partition function that resembles the calculation of 5d supersymmetric partition function with the insert ion of defects of various co-dimensions.

  10. A Robustness Testing Campaign for IMA-SP Partitioning Kernels

    NASA Astrophysics Data System (ADS)

    Grixti, Stephen; Lopez Trecastro, Jorge; Sammut, Nicholas; Zammit-Mangion, David

    2015-09-01

    With time and space partitioned architectures becoming increasingly appealing to the European space sector, the dependability of partitioning kernel technology is a key factor to its applicability in European Space Agency projects. This paper explores the potential of the data type fault model, which injects faults through the Application Program Interface, in partitioning kernel robustness testing. This fault injection methodology has been tailored to investigate its relevance in uncovering vulnerabilities within partitioning kernels and potentially contributing towards fault removal campaigns within this domain. This is demonstrated through a robustness testing case study of the XtratuM partitioning kernel for SPARC LEON3 processors. The robustness campaign exposed a number of vulnerabilities in XtratuM, exhibiting the potential benefits of using such a methodology for the robustness assessment of partitioning kernels.

  11. How drought severity constrains GPP and its partitioning among carbon pools in a Quercus ilex coppice?

    NASA Astrophysics Data System (ADS)

    Rambal, S.; Lempereur, M.; Limousin, J. M.; Martin-StPaul, N. K.; Ourcival, J. M.; Rodríguez-Calcerrada, J.

    2014-06-01

    The partitioning of photosynthates toward biomass compartments has a crucial role in the carbon sink function of forests. Few studies have examined how carbon is allocated toward plant compartments in drought prone forests. We analyzed the fate of GPP in relation to yearly water deficit in an old evergreen Mediterranean Quercus ilex coppice severely affected by water limitations. Gross and net carbon fluxes between the ecosystem and the atmosphere were measured with an eddy-covariance flux tower running continuously since 2001. Discrete measurements of litterfall, stem growth and fAPAR allowed us to derive annual productions of leaves, wood, flowers and acorns and an isometric relationship between stem and belowground biomass has been used to estimate perennial belowground growth. By combining eddy-covariance fluxes with annual productions we managed to close a C budget and derive values of autotrophic and heterotrophic respirations, NPP and carbon use efficiency (CUE, the ratio between NPP and GPP). Average values of yearly NEP, GPP and Reco were 282, 1259 and 977 g C m-2. The corresponding ANPP components were 142.5, 26.4 and 69.6 g C m-2 for leaves, reproductive effort (flowers and fruits) and stems. Gross and net carbon exchange between the ecosystem and the atmosphere were affected by annual water deficit. Partitioning to the different plant compartments was also impacted by drought, with a hierarchy of responses going from the most affected, the stem growth, to the least affected, the leaf production. The average CUE was 0.40, which is well in the range for Mediterranean-type forest ecosystems. CUE tended to decrease more slightly in response to drought than GPP and NPP, probably due to drought-acclimation of autotrophic respiration. Overall, our results provide a baseline for modeling the inter-annual variations of carbon fluxes and allocation in this widespread Mediterranean ecosystem and highlight the value of maintaining continuous experimental

  12. Method for chemical amplification based on fluid partitioning in an immiscible liquid

    DOEpatents

    Anderson, Brian L.; Colston, Bill W.; Elkin, Christopher J.

    2015-06-02

    A system for nucleic acid amplification of a sample comprises partitioning the sample into partitioned sections and performing PCR on the partitioned sections of the sample. Another embodiment of the invention provides a system for nucleic acid amplification and detection of a sample comprising partitioning the sample into partitioned sections, performing PCR on the partitioned sections of the sample, and detecting and analyzing the partitioned sections of the sample.

  13. Apparatus for chemical amplification based on fluid partitioning in an immiscible liquid

    DOEpatents

    Anderson, Brian L.; Colston, Bill W.; Elkin, Christopher J.

    2012-05-08

    A system for nucleic acid amplification of a sample comprises partitioning the sample into partitioned sections and performing PCR on the partitioned sections of the sample. Another embodiment of the invention provides a system for nucleic acid amplification and detection of a sample comprising partitioning the sample into partitioned sections, performing PCR on the partitioned sections of the sample, and detecting and analyzing the partitioned sections of the sample.

  14. TAP - Tools for Adaptive Partitioning v. 0.99 Beta

    Energy Science and Technology Software Center (ESTSC)

    2008-11-19

    TAP is a set of tools which are essential for conducting research on adaptive partitioners. The basic premise is that a single partitioner may not be a good choice for adaptive mesh simulations; rather one must match a partitioner (obtained from a partitioning package like Zoltan, ParMetis etc) with the mesh being partitioned. TAP provides the tools that can judge the suitability of a partitioning algorithm to a given mesh.

  15. Flux vector splitting and approximate Newton methods. [for solution of steady Euler equations

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.; Pulliam, T. H.

    1983-01-01

    In the present investigation, the basic approach is employed to view an iterative scheme as Newton's method or as a modified Newton's method. Attention is given to various modified Newton methods which can arise from differencing schemes for the Euler equations. Flux vector splitting is considered as the basic spatial differencing technique. This technique is based on the partition of a flux vector into groups which have certain properties. The Euler equations fluxes can be split into two groups, the first group having a flux Jacobian with all positive eigenvalues, and the second group having a flux Jacobian with all negative eigenvalues. Flux vector splitting based on a velocity-sound speed split is considered along with the use of numerical techniques to analyze nonlinear systems, and the steady Euler equations for quasi-one-dimensional flow in a nozzle. Results are given for steady flows with shocks.

  16. A Push-Pull Test to Measure Volatilization Fluxes of Organic Pollutants without Flux Chambers

    NASA Astrophysics Data System (ADS)

    Reid, M. C.; Jaffe, P. R.

    2011-12-01

    Volatilization of organic contaminants is a potentially significant removal mechanism from wetlands, but field measurements are scarce and the physiochemical controls on volatilization from wetland soils remain poorly understood. It has been established that volatilization rates of certain pollutants are enhanced by vegetation and are strongly correlated with evapotranspiration (ET). These observations rely on flux chambers measurements, which are characterized by significant uncertainty due the chamber's effects on the meteorological variables around the plant and consequent impact on the biophysical processes governing ET and plant uptake of soil contaminants. Here we present data from a mesocosm study using a modified single-well push-pull test to measure in-situ volatilization rates from inundated soils vegetated with the wetland macrophytes Scirpus acutus and Typha latifolia, as well as from unplanted soil. This new method uses a test solution containing the volatile tracers sulfur hexafluoride (SF6), helium (He), and dichlorodifluoromethane (CFC-12) to estimate first-order volatilization rates and examine the relationship between physiochemical properties and volatilization rates. The test also yields an estimate for the volume of subsurface gas bubbles, which is used to derive a retardation factor for the effect of interphase partitioning on the estimation of kinetic parameters. We evaluate models to partition observed fluxes into different pathways for plant-mediated volatilization: transpirational uptake and consequent volatilization, and gas-phase diffusion through porous root aerenchyma. Those models are then used to scale tracer-derived volatilization fluxes to priority organic pollutants including benzene, trichloroethylene, and vinyl chloride. We also discuss the implementation of this method at field scales to estimate volatilization as a component of phytoremediation applications.

  17. Directed flux motor

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2011-01-01

    A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

  18. Heat Flux Sensor

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A heat flux microsensor developed under a NASP Small Business Innovation Research (SBIR) has a wide range of potential commercial applications. Vatell Corporation originally designed microsensors for use in very high temperatures. The company then used the technology to develop heat flux sensors to measure the rate of heat energy flowing in and out of a surface as well as readings on the surface temperature. Additional major advantages include response to heat flux in less than 10 microseconds and the ability to withstand temperatures up to 1,200 degrees centigrade. Commercial applications are used in high speed aerodynamics, supersonic combustion, blade cooling, and mass flow measurements, etc.

  19. Strainrange partitioning: A total strain range version

    NASA Technical Reports Server (NTRS)

    Halford, G. R.; Saltsman, J. F.

    1983-01-01

    Procedures are presented for expressing the Strainrange Partitioning (SRP) method for creep fatigue life prediction in terms of total strain range. Inelastic and elastic strain-range - life relations are summed to give total strain-range - life relations. The life components due to inelastic strains are dealt with using conventional SRP procedures while the life components due to elastic strains are expressed as families of time-dependent terms for each type of SRP cycle. Cyclic constitutive material behavior plays an important role in establishing the elastic strain-range - life relations as well as the partitioning of the inelastic strains. To apply the approach, however, it is not necessary to have to determine the magnitude of the inelastic strain range. The total strain SRP approach is evaluated and verified using two nickel base superalloys, AF2-1DA and Rene 95. Excellent agreement is demonstrated between observed and predicted cyclic lifetimes with 70 to 80 percent of the predicted lives falling within factors of two of the observed lives. The total strain-range SRP approach should be of considerable practical value to designers who are faced with creep-fatigue problems for which the inelastic strains cannot be calculated with sufficient accuracy to make reliable life predictions by the conventional inelastic strain range SRP approach.

  20. Gait Partitioning Methods: A Systematic Review.

    PubMed

    Taborri, Juri; Palermo, Eduardo; Rossi, Stefano; Cappa, Paolo

    2016-01-01

    In the last years, gait phase partitioning has come to be a challenging research topic due to its impact on several applications related to gait technologies. A variety of sensors can be used to feed algorithms for gait phase partitioning, mainly classifiable as wearable or non-wearable. Among wearable sensors, footswitches or foot pressure insoles are generally considered as the gold standard; however, to overcome some inherent limitations of the former, inertial measurement units have become popular in recent decades. Valuable results have been achieved also though electromyography, electroneurography, and ultrasonic sensors. Non-wearable sensors, such as opto-electronic systems along with force platforms, remain the most accurate system to perform gait analysis in an indoor environment. In the present paper we identify, select, and categorize the available methodologies for gait phase detection, analyzing advantages and disadvantages of each solution. Finally, we comparatively examine the obtainable gait phase granularities, the usable computational methodologies and the optimal sensor placements on the targeted body segments. PMID:26751449

  1. Inversion of hematocrit partition at microfluidic bifurcations.

    PubMed

    Shen, Zaiyi; Coupier, Gwennou; Kaoui, Badr; Polack, Benoît; Harting, Jens; Misbah, Chaouqi; Podgorski, Thomas

    2016-05-01

    Partitioning of red blood cells (RBCs) at the level of bifurcations in the microcirculatory system affects many physiological functions yet it remains poorly understood. We address this problem by using T-shaped microfluidic bifurcations as a model. Our computer simulations and in vitro experiments reveal that the hematocrit (ϕ0) partition depends strongly on RBC deformability, as long as ϕ0<20% (within the normal range in microcirculation), and can even lead to complete deprivation of RBCs in a child branch. Furthermore, we discover a deviation from the Zweifach-Fung effect which states that the child branch with lower flow rate recruits less RBCs than the higher flow rate child branch. At small enough ϕ0, we get the inverse scenario, and the hematocrit in the lower flow rate child branch is even higher than in the parent vessel. We explain this result by an intricate up-stream RBC organization and we highlight the extreme dependence of RBC transport on geometrical and cell mechanical properties. These parameters can lead to unexpected behaviors with consequences on the microcirculatory function and oxygen delivery in healthy and pathological conditions. PMID:26744089

  2. New parallel SOR method by domain partitioning

    SciTech Connect

    Xie, Dexuan

    1996-12-31

    In this paper, we propose and analyze a new parallel SOR method, the PSOR method, formulated by using domain partitioning together with an interprocessor data-communication technique. For the 5-point approximation to the Poisson equation on a square, we show that the ordering of the PSOR based on the strip partition leads to a consistently ordered matrix, and hence the PSOR and the SOR using the row-wise ordering have the same convergence rate. However, in general, the ordering used in PSOR may not be {open_quote}consistently ordered{close_quotes}. So, there is a need to analyze the convergence of PSOR directly. In this paper, we present a PSOR theory, and show that the PSOR method can have the same asymptotic rate of convergence as the corresponding sequential SOR method for a wide class of linear systems in which the matrix is {open_quotes}consistently ordered{close_quotes}. Finally, we demonstrate the parallel performance of the PSOR method on four different message passing multiprocessors (a KSR1, the Intel Delta, an Intel Paragon and an IBM SP2), along with a comparison with the point Red-Black and four-color SOR methods.

  3. Approximate algorithms for partitioning and assignment problems

    NASA Technical Reports Server (NTRS)

    Iqbal, M. A.

    1986-01-01

    The problem of optimally assigning the modules of a parallel/pipelined program over the processors of a multiple computer system under certain restrictions on the interconnection structure of the program as well as the multiple computer system was considered. For a variety of such programs it is possible to find linear time if a partition of the program exists in which the load on any processor is within a certain bound. This method, when combined with a binary search over a finite range, provides an approximate solution to the partitioning problem. The specific problems considered were: a chain structured parallel program over a chain-like computer system, multiple chain-like programs over a host-satellite system, and a tree structured parallel program over a host-satellite system. For a problem with m modules and n processors, the complexity of the algorithm is no worse than O(mnlog(W sub T/epsilon)), where W sub T is the cost of assigning all modules to one processor and epsilon the desired accuracy.

  4. Unsupervised image categorization by hypergraph partition.

    PubMed

    Huang, Yuchi; Liu, Qingshan; Lv, Fengjun; Gong, Yihong; Metaxas, Dimitris N

    2011-06-01

    We present a framework for unsupervised image categorization in which images containing specific objects are taken as vertices in a hypergraph and the task of image clustering is formulated as the problem of hypergraph partition. First, a novel method is proposed to select the region of interest (ROI) of each image, and then hyperedges are constructed based on shape and appearance features extracted from the ROIs. Each vertex (image) and its k-nearest neighbors (based on shape or appearance descriptors) form two kinds of hyperedges. The weight of a hyperedge is computed as the sum of the pairwise affinities within the hyperedge. Through all of the hyperedges, not only the local grouping relationships among the images are described, but also the merits of the shape and appearance characteristics are integrated together to enhance the clustering performance. Finally, a generalized spectral clustering technique is used to solve the hypergraph partition problem. We compare the proposed method to several methods and its effectiveness is demonstrated by extensive experiments on three image databases. PMID:21282850

  5. Ferrous iron partitioning in the lower mantle

    NASA Astrophysics Data System (ADS)

    Muir, Joshua M. R.; Brodholt, John P.

    2016-08-01

    We used density functional theory (DFT) to examine the partitioning of ferrous iron between periclase and bridgmanite under lower mantle conditions. To study the effects of the three major variables - pressure, temperature and concentration - these have been varied from 0 to 150 GPa, from 1000 to 4000 K and from 0 to 100% total iron content. We find that increasing temperature increases KD, increasing iron concentration decreases KD, while pressure can both increase and decrease KD. We find that KD decreases slowly from about 0.32 to 0.06 with depth under lower mantle conditions. We also find that KD increases sharply to 0.15 in the very lowermost mantle due to the strong temperature increases near the CMB. Spin transitions have a large effect on the activity of ferropericlase which causes KD to vary with pressure in a peak-like fashion. Despite the apparently large changes in KD through the mantle, this actually results in relatively small changes in total iron content in the two phases, with XFefp ranging from about 0.20 to 0.35, before decreasing again to about 0.28 at the CMB, and XFebd has a pretty constant value of about 0.04-0.07 throughout the lower mantle. For the very high Fe concentrations suggested for ULVZs, Fe partitions very strongly into ferropericlase.

  6. Partitioning of on-demand electron pairs

    NASA Astrophysics Data System (ADS)

    Ubbelohde, Niels; Hohls, Frank; Kashcheyevs, Vyacheslavs; Wagner, Timo; Fricke, Lukas; Kästner, Bernd; Pierz, Klaus; Schumacher, Hans W.; Haug, Rolf J.

    2015-01-01

    The on-demand generation and separation of entangled photon pairs are key components of quantum information processing in quantum optics. In an electronic analogue, the decomposition of electron pairs represents an essential building block for using the quantum state of ballistic electrons in electron quantum optics. The scattering of electrons has been used to probe the particle statistics of stochastic sources in Hanbury Brown and Twiss experiments and the recent advent of on-demand sources further offers the possibility to achieve indistinguishability between multiple sources in Hong-Ou-Mandel experiments. Cooper pairs impinging stochastically at a mesoscopic beamsplitter have been successfully partitioned, as verified by measuring the coincidence of arrival. Here, we demonstrate the splitting of electron pairs generated on demand. Coincidence correlation measurements allow the reconstruction of the full counting statistics, revealing regimes of statistically independent, distinguishable or correlated partitioning, and have been envisioned as a source of information on the quantum state of the electron pair. The high pair-splitting fidelity opens a path to future on-demand generation of spin-entangled electron pairs from a suitably prepared two-electron quantum-dot ground state.

  7. Determining Peptide Partitioning Properties via Computer Simulation

    PubMed Central

    Ulmschneider, Jakob P.; Ulmschneider, Martin B.

    2010-01-01

    The transfer of polypeptide segments into lipid bilayers to form transmembrane helices represents the crucial first step in cellular membrane protein folding and assembly. This process is driven by complex and poorly understood atomic interactions of peptides with the lipid bilayer environment. The lack of suitable experimental techniques that can resolve these processes both at atomic resolution and nanosecond timescales has spurred the development of computational techniques. In this review, we summarize the significant progress achieved in the last few years in elucidating the partitioning of peptides into lipid bilayer membranes using atomic detail molecular dynamics simulations. Indeed, partitioning simulations can now provide a wealth of structural and dynamic information. Furthermore, we show that peptide-induced bilayer distortions, insertion pathways, transfer free energies, and kinetic insertion barriers are now accurate enough to complement experiments. Further advances in simulation methods and force field parameter accuracy promise to turn molecular dynamics simulations into a powerful tool for investigating a wide range of membrane active peptide phenomena. PMID:21107546

  8. Gait Partitioning Methods: A Systematic Review

    PubMed Central

    Taborri, Juri; Palermo, Eduardo; Rossi, Stefano; Cappa, Paolo

    2016-01-01

    In the last years, gait phase partitioning has come to be a challenging research topic due to its impact on several applications related to gait technologies. A variety of sensors can be used to feed algorithms for gait phase partitioning, mainly classifiable as wearable or non-wearable. Among wearable sensors, footswitches or foot pressure insoles are generally considered as the gold standard; however, to overcome some inherent limitations of the former, inertial measurement units have become popular in recent decades. Valuable results have been achieved also though electromyography, electroneurography, and ultrasonic sensors. Non-wearable sensors, such as opto-electronic systems along with force platforms, remain the most accurate system to perform gait analysis in an indoor environment. In the present paper we identify, select, and categorize the available methodologies for gait phase detection, analyzing advantages and disadvantages of each solution. Finally, we comparatively examine the obtainable gait phase granularities, the usable computational methodologies and the optimal sensor placements on the targeted body segments. PMID:26751449

  9. Life prediction modeling based on strainrange partitioning

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.

    1988-01-01

    Strainrange partitioning (SRP) is an integrated low-cycle-fatigue life predicting system. It was created specifically for calculating cyclic crack initiation life under severe high-temperature fatigue conditions. The key feature of the SRP system is its recognition of the interacting mechanisms of cyclic inelastic deformation that govern cyclic life at high temperatures. The SRP system bridges the gap between the mechanistic level of understanding that breeds new and better materials and the phenomenological level wherein workable engineering life prediction methods are in great demand. The system was recently expanded to address engineering fatigue problems in the low-strain, long-life, nominally elastic regime. This breakthrough, along with other advances in material behavior and testing technology, has permitted the system to also encompass low-strain thermomechanical loading conditions. Other important refinements of the originally proposed method include procedures for dealing with life-reducing effects of multiaxial loading, ratcheting, mean stresses, nonrepetitive (cumulative loading) loading, and environmental and long-time exposure. Procedure were also developed for partitioning creep and plastic strain and for estimating strainrange versus life relations from tensile and creep rupture properties. Each of the important engineering features of the SRP system are discussed and examples shown of how they help toward predicting high-temperature fatigue life under practical, although complex, loading conditions.

  10. Geochemical assessment of iron and vanadium relationships in oxic soil environments

    SciTech Connect

    Aide, M.

    2005-07-01

    Geochemical assessment has become a cost-effective and highly accurate tool for estimating metal contamination, especially in those cases where the level of contamination is not considered severe. Difficulties frequently arise in attempting to discriminate between pristine metal concentrations and low-level environmental impacts. As all example, vanadium contamination is frequently associated with coal and petroleum by-products; however air and water contamination pathways are also possible. The purpose of this investigation was to characterize the V and Fe concentration relationship among a wide variety of soil types and to formulate an estimate of the pristine V concentrations in these soils. If a linear relationship may be established between Fe and V then geochemical analysis of impacted soils may discriminate between V as a natural background component and anthropogenic V Forty-six moderately well-drained to well-drained soil profiles having cambic, argillic or calcic soil horizons were characterized,for Fe and V using an aqua-regia digestion to determine if these soils exhibited a one-to-one correspondence between V and Fe. Such a correspondence was authenticated for the majority of these soils and may be used to discriminate between natural and anthropogenic V The presence of argillic, calcic or fragipan horizons did not reduce the one-to-one correspondence between V and Fe, suggesting that these soil processes did not selectively partition either V or Fe. The method needs to be further evaluated for soils having anoxic soil conditions, lithologic discontinuities and other specific pedogenic processes.

  11. Combining Hydrologic and Geochemical Methods to Quantify Sources and Volumetric Contributions of Baseflow

    NASA Astrophysics Data System (ADS)

    Shope, C. L.; Stolp, B.; Marston, T.; Miller, M. P.; Heilweil, V. M.; Susong, D.

    2013-12-01

    A cohesive definition and robust understanding of stream baseflow remains elusive, particularly at broad temporal and spatial scales in snowmelt dominated watersheds. In these types of settings, baseflow is quantified (or estimated) using a number of approaches including hydrograph separation based on gaged streamflow, watershed and groundwater modeling, and chemical transport partitioning. In western US seasonal snowmelt-dominated watersheds, runoff is the primary contributor to streamflow. However, many separation methods incorporate the seasonal snowmelt runoff generation as baseflow. The question remains whether this baseflow is an artifact of the algorithm used or an accurate assessment of the groundwater flow processes that are altered during snowmelt induced recharge. We used a combination of hydrologic and geochemical hydrograph separation methods to estimate the spatial discretization and volumetric contribution of baseflow and spring discharge in a northern Utah watershed. Results of the various separation techniques were evaluated from continuous streamflow records, discrete stream discharge measurements, and geochemical indicators of in-stream conditions. Results suggested that the majority of baseflow inputs to the watershed are constrained to the catchment headwaters. The comparison identifies strengths and weaknesses in both the separation methods and data collection choices used to elucidate baseflow separation. The benefit of this study is that it offers general suggestions for baseflow separation, a first-order assessment of data-collection that will increase confidence in baseflow estimates and points to potential methods for scaling up to regional estimates. We further compare the results from the baseflow separation in Utah to multiple baseflow estimation results from the Tomorrow River in Wisconsin.

  12. Geochemical processes between steel projectiles and silica-rich targets in hypervelocity impact experiments

    NASA Astrophysics Data System (ADS)

    Ebert, Matthias; Hecht, Lutz; Deutsch, Alexander; Kenkmann, Thomas; Wirth, Richard; Berndt, Jasper

    2014-05-01

    The possibility of fractionation processes between projectile and target matter is critical with regard to the classification of the impactor type from geochemical analysis of impactites from natural craters. Here we present results of five hypervelocity MEMIN impact experiments (Poelchau et al., 2013) using the Cr-V-Co-Mo-W-rich steel D290-1 as projectile and two different silica-rich lithologies (Seeberger sandstone and Taunus quartzite) as target materials. Our study is focused on geochemical target-projectile interaction occurring in highly shocked and projectile-rich ejecta fragments. In all of the investigated impact experiments, whether sandstone or quartzite targets, the ejecta fragments show (i) shock-metamorphic features e.g., planar-deformation features (PDF) and the formation of silica glasses, (ii) partially melting of projectile and target, and (iii) significant mechanical and chemical mixing of the target rock with projectile material. The silica-rich target melts are strongly enriched in the "projectile tracer elements" Cr, V, and Fe, but have just minor enrichments of Co, W, and Mo. Inter-element ratios of these tracer elements within the contaminated target melts differ strongly from the original ratios in the steel. The fractionation results from differences in the reactivity of the respective elements with oxygen during interaction of the metal melt with silicate melt. Our results indicate that the principles of projectile-target interaction and associated fractionation do not depend on impact energies (at least for the selected experimental conditions) and water-saturation of the target. Partitioning of projectile tracer elements into the silicate target melt is much more enhanced in experiments with a non-porous quartzite target compared with the porous sandstone target. This is mainly the result of higher impact pressures, consequently higher temperatures and longer reaction times at high temperatures in the experiments with quartzite as

  13. Investigation of the geochemical evolution of groundwater under agricultural land: A case study in northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Ledesma-Ruiz, Rogelio; Pastén-Zapata, Ernesto; Parra, Roberto; Harter, Thomas; Mahlknecht, Jürgen

    2015-02-01

    Zona Citrícola is an important area for Mexico due to its citriculture activity. Situated in a sub-humid to humid climate adjacent to the Sierra Madre Oriental, this valley hosts an aquifer system that represents sequences of shales, marls, conglomerates, and alluvial deposits. Groundwater flows from mountainous recharge areas to the basin-fill deposits and provides base flows to supply drinking water to the adjacent metropolitan area of Monterrey. Recent studies examining the groundwater quality of the study area urge the mitigation of groundwater pollution. The objective of this study was to characterize the physical and chemical properties of the groundwater and to assess the processes controlling the groundwater's chemistry. Correlation was used to identify associations among various geochemical constituents. Factor analysis was applied to identify the water's chemical characteristics that were responsible for generating most of the variability within the dataset. Hierarchical cluster analysis was employed in combination with a post-hoc analysis of variance to partition the water samples into hydrochemical water groups: recharge waters (Ca-HCO3), transition zone waters (Ca-HCO3-SO4 to Ca-SO4-HCO3) and discharge waters (Ca-SO4). Inverse geochemical models of these groups were developed and constrained using PHREEQC to elucidate the chemical reactions controlling the water's chemistry between an initial (recharge) and final water. The primary reactions contributing to salinity were the following: (1) water-rock interactions, including the weathering of evaporitic rocks and dedolomitization; (2) dissolution of soil gas carbon dioxide; and (3) input from animal/human wastewater and manure in combination with by denitrification processes. Contributions from silicate weathering to salinity ranged from less important to insignificant. The findings suggest that it may not be cost-effective to regulate manure application to mitigate groundwater pollution.

  14. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Tackley, P. J.; Xie, S.

    2001-12-01

    The thermal and chemical evolution of Earth's mantle and plates are inextricably coupled by the plate tectonic - mantle convective system. Convection causes chemical differentiation, recycling and mixing, while chemical variations affect the convection through physical properties such as density and viscosity which depend on composition. It is now possible to construct numerical mantle convection models that track the thermo-chemical evolution of major and minor elements, and which can be used to test prospective models and hypotheses regarding Earth's chemical and thermal evolution. Model thermal and chemical structures can be compared to results from seismic tomography, while geochemical signatures (e.g., trace element ratios) can be compared to geochemical observations. The presented, two-dimensional model combines a simplified 2-component major element model with tracking of the most important trace elements, using a tracer method. Melting is self-consistently treated using a solidus, with melt placed on the surface as crust. Partitioning of trace elements occurs between melt and residue. Decaying heat-producing elements and secular cooling of the mantle and core provide the driving heat sources. Pseudo-plastic yielding of the lithosphere gives a first-order approximation of plate tectonics, and also allows planets with a rigid lid or intermittent plate tectonics to be modeled simply by increasing the yield strength. Preliminary models with an initially homogeneous mantle show that regions with a HIMU-like signature can be generated by crustal recycling, and regions with high 3He/4He ratios can be generated by residuum recycling. Outgassing of Argon is within the observed range. Models with initially layered mantles will also be investigated. In future it will be important to include a more realistic bulk compositional model that allows continental crust as well as oceanic crust to form, and to extend the model to three dimensions since toroidal flow may alter

  15. Synthesis of benthic flux components in the Patos Lagoon coastal zone, Rio Grande do Sul, Brazil

    NASA Astrophysics Data System (ADS)

    King, J. N.

    2012-12-01

    The primary objective of this work is to synthesize components of benthic flux in the Patos Lagoon coastal zone, Rio Grande do Sul, Brazil. Specifically, the component of benthic discharge flux forced by the terrestrial hydraulic gradient is 0.8 m3 d-1; components of benthic discharge and recharge flux associated with the groundwater tidal prism are both 2.1 m3 d-1; components of benthic discharge and recharge flux forced by surface-gravity wave setup are both 6.3 m3 d-1; the component of benthic discharge flux that transports radium-228 is 350 m3 d-1; and components of benthic discharge and recharge flux forced by surface-gravity waves propagating over a porous medium are both 1400 m3 d-1. (All models are normalized per meter shoreline.) Benthic flux is a function of components forced by individual mechanisms and nonlinear interactions that exist between components. Constructive and destructive interference may enhance or diminish the contribution of benthic flux components. It may not be possible to model benthic flux by summing component magnitudes. Geochemical tracer techniques may not accurately model benthic discharge flux or submarine groundwater discharge (SGD). A conceptual model provides a framework on which to quantitatively characterize benthic discharge flux and SGD with a multifaceted approach.

  16. The Extraterrestrial Mass Flux on the Early Earth

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Arnold, G. L.; Mojzsis, S. J.; Zahnle, K. J.

    1999-01-01

    We have measured iridium and platinum in ancient metasediments to obtain the first direct constraints on the extraterrestrial mass flux at the Earth's surface before 3.8 Gyr (the Hadean era). The craters of the Moon record an intense "late heavy bombardment" (LHB) beginning as early as 4.15 Gyr, and terminating ca.3.85 +/- 0.05 Gyr. Recent geochemical studies of metasediments and other supracrustal rocks from Akilia Island, in southern West Greenland, appear to extend both the record of marine sedimentation and the record of metabolically-sophisticated life to > 3.8 Gyr. Additional information is contained in the original extended abstract.

  17. A partitioning strategy for nonuniform problems on multiprocessors

    NASA Technical Reports Server (NTRS)

    Berger, M. J.; Bokhari, S.

    1985-01-01

    The partitioning of a problem on a domain with unequal work estimates in different subddomains is considered in a way that balances the work load across multiple processors. Such a problem arises for example in solving partial differential equations using an adaptive method that places extra grid points in certain subregions of the domain. A binary decomposition of the domain is used to partition it into rectangles requiring equal computational effort. The communication costs of mapping this partitioning onto different microprocessors: a mesh-connected array, a tree machine and a hypercube is then studied. The communication cost expressions can be used to determine the optimal depth of the above partitioning.

  18. Diffusive isothermal partitioning in a layered medium with geologic applications

    NASA Technical Reports Server (NTRS)

    Hopper, R. W.; Uhlmann, D. R.

    1976-01-01

    The diffusive isothermal partitioning of solute in a layered two-phase material has been analyzed to help elucidate the phenomenon of solute partitioning in multiphase lunar and terrestrial materials and to estimate the cooling history of samples. After reviewing the physical chemistry of partitioning and the case of an infinite one-dimensional diffusion couple, we solve in analytic form the case of a finite one-dimensional couple. The solution can be used to estimate cooling histories or to interpret laboratory experiments on partitioning. A sample calculation is included.

  19. A Framework for Parallel Nonlinear Optimization by Partitioning Localized Constraints

    SciTech Connect

    Xu, You; Chen, Yixin

    2008-06-28

    We present a novel parallel framework for solving large-scale continuous nonlinear optimization problems based on constraint partitioning. The framework distributes constraints and variables to parallel processors and uses an existing solver to handle the partitioned subproblems. In contrast to most previous decomposition methods that require either separability or convexity of constraints, our approach is based on a new constraint partitioning theory and can handle nonconvex problems with inseparable global constraints. We also propose a hypergraph partitioning method to recognize the problem structure. Experimental results show that the proposed parallel algorithm can efficiently solve some difficult test cases.

  20. Molecular partitioning based on the kinetic energy density

    NASA Astrophysics Data System (ADS)

    Noorizadeh, Siamak

    2016-05-01

    Molecular partitioning based on the kinetic energy density is performed to a number of chemical species, which show non-nuclear attractors (NNA) in their gradient maps of the electron density. It is found that NNAs are removed using this molecular partitioning and although the virial theorem is not valid for all of the basins obtained in the being used AIM, all of the atoms obtained using the new approach obey this theorem. A comparison is also made between some atomic topological parameters which are obtained from the new partitioning approach and those calculated based on the electron density partitioning.

  1. Deep eutectic solvents in countercurrent and centrifugal partition chromatography.

    PubMed

    Roehrer, Simon; Bezold, Franziska; García, Eva Marra; Minceva, Mirjana

    2016-02-19

    Deep eutectic solvents (DESs) were evaluated as solvents in centrifugal partition chromatography, a liquid-liquid chromatography separation technology. To this end, the partition coefficients of ten natural compounds of different hydrophobicity were determined in non-aqueous biphasic systems containing DES. The influence of the composition of DESs and the presence of water in the biphasic system on the partition coefficient were also examined. In addition, several process relevant physical properties of the biphasic system, such as the density and viscosity of the phases, were measured. A mixture of three to four hydrophobic compounds was successfully separated in a centrifugal partition extractor using a heptane/ethanol/DES biphasic system. PMID:26810802

  2. The leaching behaviour and geochemical fractionation of trace elements in hydraulically disposed weathered coal fly ash.

    PubMed

    Nyale, Sammy M; Eze, Chuks P; Akinyeye, Richard O; Gitari, Wilson M; Akinyemi, Segun A; Fatoba, Olanrewaju O; Petrik, Leslie F

    2014-01-01

    A five-step sequential extraction (SE) procedure was used to investigate the leaching behaviour and geochemical partitioning of the trace elements As, Zn, Pb, Ni, Mo, Cr and Cu in a 20-year-old fly ash (FA) dump. The weathered FA, which was hydraulically co-disposed with salt laden brine in slurry form (FA: brine ratio of 1:5), was analyzed and compared with fresh FA. The weathered FA samples were collected from three cores, drilled at a coal-fired power station in the Republic of South Africa while the fresh FA sample was collected from the hoppers in the ash collection system at the power station. The FA samples were sequentially leached using: ultrapure water; ammonium acetate buffer solution (pH 7); ammonium acetate buffer solution (pH 5); hydroxylamine hydrochloride in nitric acid (pH 2) and finally the residues were digested using a combination of HClO4: HF: HNO3 acids. Digestion of as received (unleached) FA samples was also done using a combination of HClO4: HF: HNO3 acids in order to determine the total metal content. The trace element analysis was done using ICP-OES (Varian 710-ES). The SE procedure revealed that the trace elements present in the fresh FA and the weathered FA samples obtained from the three cores could leach upon exposure to different environmental conditions. The trace elements showed continuous partitioning between five geochemical phases i.e., water soluble fraction, exchangeable fraction, carbonate fraction, Fe and Mn fraction and residual fraction. Although the highest concentration of the trace elements (ranging 65.51%-86.34%) was contained in the residual fraction, a considerable amount of each trace element (ranging 4.42%-27.43%) was released from the labile phases (water soluble, exchangeable and carbonate fractions), indicating that the trace species readily leach from the dumped FA under environmental conditions thus pose a danger to the receiving environment and to groundwater. PMID:24171424

  3. Quantifying the effects of tidal amplitude on river delta network flow partitioning

    NASA Astrophysics Data System (ADS)

    Hiatt, M. R.; Sendrowski, A.; Passalacqua, P.

    2014-12-01

    Deltas are generally classified as river-, tide-, or wave-dominated systems, but the influences of all environmental forces cannot be ignored when fully addressing the dynamics of the system. For example, in river-dominated deltas, river flow from the feeder channel acts as the primary driver of dynamics within the system by delivering water, sediment, and nutrients through the distributary channels, but tides and waves may affect their allocation within the network. There has been work on the asymmetry of environmental fluxes at bifurcations, but relatively few studies exist on the water partitioning at the network scale. Understanding the network and environmental effects on the flux of water, sediment, and nutrients would benefit delta restoration projects and management practices. In this study, we investigate the allocation of water flow among the five major distributary channels at Wax Lake Delta (WLD), a micro-tidal river-dominated delta in coastal Louisiana, and the effects of tidal amplitude on distributary channel discharges. We collect and compare discharge results from acoustic Doppler current profiler (ADCP) velocity transects between spring and neap tide and between falling and rising tide. The results show that discharges increased from spring to neap tide and from rising to falling tide. We investigate the spatial gradients of tidal influence within the network and validate hydraulic geometry relations for tidally influenced channels. Our results give insight into the control of network structure on flow partitioning and show the degree of tidal influence on channel flow in the river-dominated WLD.

  4. Isotopic air sampling in a tallgrass prairie to partition net ecosystem CO2 exchange

    NASA Astrophysics Data System (ADS)

    Lai, Chun-Ta; Schauer, Andrew J.; Owensby, Clenton; Ham, Jay M.; Ehleringer, James R.

    2003-09-01

    Stable isotope ratios of various ecosystem components and net ecosystem exchange (NEE) CO2 fluxes were measured in a C3-C4 mixture tallgrass prairie near Manhattan, Kansas. The July 2002 study period was chosen because of contrasting soil moisture contents, which allowed us to address the effects of drought on photosynthetic CO2 uptake and isotopic discrimination. Significantly higher NEE fluxes were observed for both daytime uptake and nighttime respiration during well-watered conditions when compared to a drought period. Given these differences, we investigated two carbon-flux partitioning questions: (1) What proportions of NEE were contributed by C3 versus C4 species? (2) What proportions of NEE fluxes resulted from canopy assimilation versus ecosystem respiration? To evaluate these questions, air samples were collected every 2 hours during daytime for 3 consecutive days at the same height as the eddy covariance system. These air samples were analyzed for both carbon isotope ratios and CO2 concentrations to establish an empirical relationship for isoflux calculations. An automated air sampling system was used to collect nighttime air samples to estimate the carbon isotope ratios of ecosystem respiration (δR) at weekly intervals for the entire growing season. Models of C3 and C4 photosynthesis were employed to estimate bulk canopy intercellular CO2 concentration in order to calculate photosynthetic discrimination against 13C. Our isotope/NEE results showed that for this grassland, C4 vegetation contributed ˜80% of the NEE fluxes during the drought period and later ˜100% of the NEE fluxes in response to an impulse of intense precipitation. For the entire growing season, the C4 contribution ranged from ˜68% early in the spring to nearly 100% in the late summer. Using an isotopic approach, the calculated partitioned respiratory fluxes were slightly greater than chamber-measured estimates during midday under well-watered conditions. In addition, time series

  5. Partition Coefficients at High Pressure and Temperature

    NASA Astrophysics Data System (ADS)

    Righter, K.; Drake, M. J.

    2003-12-01

    Differentiation of terrestrial planets includes separation of a metallic core and possible later fractionation of mineral phases within either a solid or molten mantle (Figure 1). Lithophile and siderophile elements can be used to understand these two different physical processes, and ascertain whether they operated in the early Earth. The distribution of elements in planets can be understood by measuring the partition coefficient, D (ratio of concentrations of an element in different phases (minerals, metals, or melts)). (14K)Figure 1. Schematic cross-section through the Earth, showing: (a) an early magma ocean stage and (b) a later cool and differentiated stage. The siderophile elements (iron-loving) encompass over 30 elements and are defined as those elements for which D(metal/silicate)>1, and are useful for deciphering the details of core formation. This group of elements is commonly broken up into several subclasses, including the slightly siderophile elements (1104). Because these three groups encompass a wide range of partition coefficient values, they can be very useful in trying to determine the conditions under which metal may have equilibrated with the mantle (or a magma ocean). Because metal and silicate may equilibrate by several different mechanisms, such as at the base of a deep magma ocean, or as metal droplets descend through a molten mantle, partition coefficients can potentially shed light on which mechanism may be most important, thus linking the physics and chemistry of core formation. In this chapter, we summarize metal/silicate partitioning of siderophile elements and show how they may be used to understand planetary core formation.Once a planet is differentiated into core and mantle, a mantle will cool during convection, and can start in either a molten or solid state, depending upon the initial thermal conditions. If hot enough, minerals will

  6. Predictive Radiological Background Distributions from Geochemical Data

    NASA Astrophysics Data System (ADS)

    Haber, D.; Burnley, P. C.; Marsac, K.; Malchow, R.

    2014-12-01

    Gamma ray surveys are an important tool for both national security interests as well as industry in determininglocations of both anthropogenic radiological sources and natural occurrences of radiologic material. The purpose ofthis project is to predict the radiologic exposure rate of geologic materials by creating a model using publishedgeochemical data, geologic data, GIS software, and freely available remote sensing data sets. If K, U, and Thabundance values are known for a given geologic unit, the expected radiation exposure rate can be calculated. Oneof the primary challenges surrounding this project is that alluvial units are classified by age rather than rock type. Itis therefore important to determine sediment sources and estimate their relative contribution to alluvial units.ASTER data from the Terra satellite can differentiate between surface mineralogies and can aid us in calculating therelative percentage of sediment from each source and by extension the geochemical concentrations of challengingsurfaces such as alluvium. An additional problem is that U and Th do not directly contribute to the measuredradiation exposure rate. Instead, daughter isotopes of these radioelements emit detectable gamma rays and may nothave reached equilibrium in younger surfaces. U can take up to 1.5 Ma to come to equilibrium with its daughterisotopes while Th takes only about 40 years. Further modeling with software such as Monte Carlo N-ParticleTransport from Los Alamos National Laboratory, will help us correct for this disequilibrium in our models. Once the predicted exposure rate is calculated for a geologic unit, it can then be assigned to a geographic area basedon geologic and geomorphic trends. This prediction will be subtracted from data collected through aerial surveys,effectively ignoring geology, and allowing areas of interest to be narrowed down considerably. The study areasinclude the alluvium on the west shore of Lake Mohave and Government Wash north of Lake Mead

  7. Geochemical heterogeneities within the Crozet hotspot

    NASA Astrophysics Data System (ADS)

    Breton, Thomas; Nauret, François; Pichat, Sylvain; Moine, Bertrand; Moreira, Manuel; Rose-Koga, Estelle F.; Auclair, Delphine; Bosq, Chantal; Wavrant, Laurène-Marie

    2013-08-01

    The Crozet Plateau is a 54 Ma-old volcanic plateau that supports five islands characterized by recent volcanic manifestations that are the surface expression of a deep-mantle plume. Due to their remote location and difficult access, the Crozet Islands are poorly sampled. Both the petrological descriptions and geochemical data are scarce. Thus, the sources of the Crozet plume are still under debate. Similarly, the interactions between the Southwest Indian Ridge (SWIR) and the Crozet plume remain questioned. Here, we present a new set of isotopes (Pb, Sr, Nd and He), major and trace elements data on basalts from three islands of the Crozet Archipelago: Penguins, East, and Possession Islands. Our main purpose is to characterize the sources of the Crozet plume and to test its influence at regional scale. Two groups of lavas can be distinguished based on the isotopic data: East and Possession lavas, and Penguins lavas. Principal component analyses on our high-precision Pb isotopes data and literature data show that two mantle sources can explain most of the geochemical variability measured in Crozet lavas. A third minor contribution is however needed to fully explain the data. The entire set of isotopic compositions (Pb, Sr, Nd and He) can be explained by a mixing between three mantle sources: (1) a FOZO (Focus Zone) component, with 206Pb/204Pb higher than 19.5 and high 207Pb/204Pb, 208Pb/204Pb 87Sr/86Sr, 143Nd/144Nd and R/Ra (R/Ra=(He3/He4)sample/(He3/He4)atmosphere) ratios, that is mainly sampled Penguins lavas, (2) a component called “East-Possession” that is mostly sampled by the East-Possession lava group and which presents Pb, Sr and Nd isotope signatures similar to those of the Reunion-Mauritius Islands, and (3) a third minor contribution of the local Depleted MORB Mantle (DMM). The new He isotopes data on the Crozet plume allow us to propose that Crozet plume material is present in the segment of the Southwest Indian Ridge located between the Indomed (ITF

  8. Partitioning planning studies: Preliminary evaluation of metal and radionuclide partitioning the high-temperature thermal treatment systems

    SciTech Connect

    Liekhus, K.; Grandy, J.; Chambers, A.

    1997-03-01

    A preliminary study of toxic metals and radionuclide partitioning during high-temperature processing of mixed waste has been conducted during Fiscal Year 1996 within the Environmental Management Technology Evaluation Project. The study included: (a) identification of relevant partitioning mechanisms that cause feed material to be distributed between the solid, molten, and gas phases within a thermal treatment system; (b) evaluations of existing test data from applicable demonstration test programs as a means to identify and understand elemental and species partitioning; and, (c) evaluation of theoretical or empirical partitioning models for use in predicting elemental or species partitioning in a thermal treatment system. This preliminary study was conducted to identify the need for and the viability of developing the tools capable of describing and predicting toxic metals and radionuclide partitioning in the most applicable mixed waste thermal treatment processes. This document presents the results and recommendations resulting from this study that may serve as an impetus for developing and implementing these predictive tools.

  9. Partitioning evapotranspiration based on the concept of underlying water use efficiency

    NASA Astrophysics Data System (ADS)

    Zhou, Sha; Yu, Bofu; Zhang, Yao; Huang, Yuefei; Wang, Guangqian

    2016-02-01

    Evapotranspiration (ET) is dominated by transpiration (T) in the terrestrial water cycle. However, continuous measurement of transpiration is still difficult, and the effect of vegetation on ET partitioning is unclear. The concept of underlying water use efficiency (uWUE) was used to develop a new method for ET partitioning by assuming that the maximum, or the potential uWUE is related to T while the averaged or apparent uWUE is related to ET. T/ET was thus estimated as the ratio of the apparent over the potential uWUE using half-hourly flux data from 17 AmeriFlux sites. The estimated potential uWUE was shown to be essentially constant for 14 of the 17 sites, and was broadly consistent with the uWUE evaluated at the leaf scale. The annual T/ET was the highest for croplands, i.e., 0.69 for corn and 0.62 for soybean, followed by grasslands (0.60) and evergreen needle leaf forests (0.56), and was the lowest for deciduous broadleaf forests (0.52). The enhanced vegetation index (EVI) was shown to be significantly correlated with T/ET and could explain about 75% of the variation in T/ET among the 71 site-years. The coefficients of determination between EVI and T/ET were 0.84 and 0.82 for corn and soybean, respectively, and 0.77 for deciduous broadleaf forests and grasslands, but only 0.37 for evergreen needle leaf forests. This ET partitioning method is sound in principle and simple to apply in practice, and would enhance the value and role of global FLUXNET in estimating T/ET variations and monitoring ecosystem dynamics.

  10. Acid soldering flux poisoning

    MedlinePlus

    The harmful substances in soldering fluxes are called hydrocarbons. They include: Ammonium chloride Rosin Hydrochloric acid Zinc ... Lee DC. Hydrocarbons. In: Marx JA, Hockberger RS, Walls RM, et ... Rosen's Emergency Medicine: Concepts and Clinical Practice . 8th ...

  11. Cryogenic flux-concentrator

    NASA Technical Reports Server (NTRS)

    Bailey, B. M.; Brechna, H.; Hill, D. A.

    1969-01-01

    Flux concentrator has high primary to secondary coupling efficiency enabling it to produce high magnetic fields. The device provides versatility in pulse duration, magnetic field strengths and power sources.

  12. Constraining geochemistry and biological primary productivity in hydrothermal systems via in situ mass spectrometric geochemical mapping

    NASA Astrophysics Data System (ADS)

    Vidoudez, Charles; Marcon, Yann; Bach, Wolfgang; Lebris, Nadine; Dubilier, Nicole; Girguis, Peter

    2014-05-01

    Hydrothermal vent ecosystems are biological hot spots, supported by chemoautotrophic primary productivity and achieving densities comparable to rainforests. Nevertheless, our understanding of the geochemical factors that govern the distribution of animals and microbes within vents is limited. It is well known that vent endemic organisms are found in specific vent "microenvironments", and that these microenvironments are distributed -coarsely speaking- in predictable patterns within a vent field. However, the relative differences in activity among these faunal patches, and their role in influencing geochemical flux remains largely unknown due to historical limitations in our ability to sample and quantify geochemical constituents with fine spatial resolution. In particular, the distribution of biologically important volatiles around vent fields is poorly constrained, as is the degree to which their distribution influences the destiny and distribution of organisms. To characterize the relationship between the distribution of volatiles, chemosynthetic microbes, and chemosynthetic symbioses, we generated detailed geo-referenced maps of methane, hydrogen sulfide, carbon dioxide and oxygen (four of the key volatiles that are both vent- and seawater derived) using an in situ mass spectrometer (ISMS). We characterized these concentrations in over 130 spots across three vent sites associated with the mid-Atlantic ridge in the Menez Gwen vent field. We quantified gases in sites ranging from hot fluids to mussel beds, and found notable relationships between the distribution and consumption of hydrogen sulfide and methane and the animal and microbial communities. Finally, we also developed a metabolic energy "map", which enables us to constrain both the potential energy that is available to these communities as well as the extent to which it is being used, and places constraints on the extent of primary production that can be supported by the realized use of these volatiles.

  13. Geochemical heterogeneities in magma beneath Mount Etna recorded by 2001-2006 melt inclusions

    NASA Astrophysics Data System (ADS)

    Schiavi, Federica; Rosciglione, Alberto; Kitagawa, Hiroshi; Kobayashi, Katsura; Nakamura, Eizo; Nuccio, Pasquale Mario; Ottolini, Luisa; Paonita, Antonio; Vannucci, Riccardo

    2015-07-01

    We present a geochemical study on olivine and clinopyroxene-hosted melt inclusions (MIs) from 2001 to 2006 Etna basaltic lavas and pyroclastites. Three MI suites are distinguished on the basis of trace element fingerprinting. Type-1 MIs (from 2001 Upper South and 2002 Northeast vents) share their trace element signature with low-K lavas erupted before 1971. Critical trace element ratios (e.g., K/La, Ba/Nb), along with Pb isotope data of Type-1 MIs provide evidence for a heterogeneous mantle source resulting from mixing of three end-members with geochemical and isotopic characteristics of EM2, DMM, and HIMU components. Type-1 MIs composition does not support involvement of subduction-related components. Type-2 (from 2001 Lower and 2002 South vents) and Type-3 (2004 eruption) MIs reveal "ghost plagioclase signatures," namely lower concentrations in strongly incompatible elements, and positive Sr, Ba, and Eu anomalies. Both Type-1 and Type-2 MIs occur in 2006 olivines, which highlight the occurrence of mixing between Type-1 and Type-2 end-members. Type-2/Type-3 MIs testify to en route processes (plagioclase assimilation and volatile fluxing) peculiar for "deep dike fed" eruptions. The latter are strongly controlled by tectonics or flank instability that occasionally promote upraise of undegassed, more radiogenic primitive magma, which may interact with plagioclase-rich crystal mush/cumulates before erupting. Type-2/Type-3 MIs approach the less radiogenic Pb isotopic composition of plagioclase from prehistoric lavas, thus suggesting geochemical overprinting of present-day melts by older products released from distinct mantle sources. Our study emphasizes that MIs microanalysis offers new insights on both source characteristics and en route processes, allowing to a link between melt composition and magma dynamics.

  14. Venus: Geochemical conclusions from the Magellan data

    NASA Astrophysics Data System (ADS)

    Wood, J. A.

    1992-12-01

    Though the Magellan mission was not designed to collect geochemical or petrological information, it has done so nonetheless. Since the time of the Pioneer Venus mission it has been known that high-altitude (greater than 2.5-5 km) mountainous areas on Venus exhibit anomalously low radiothermal emissivity (e less than 0.6). Magellan has greatly refined and extended these observations. The low emissivity requires surface material in the uplands to have a mineralogical composition that gives it a high bulk dielectric constant, greater than 20. The dielectric constant of dry terrestrial volcanic rocks seldom exceeds 7. The high-dielectric character of high-altitude surface material cannot be a primary property of the local volcanic rock, because there is no reason why rock having the required special mineralogy would erupt only at high altitudes. Therefore it is a secondary property; the primary Venus rock has reacted with the atmosphere to form a mineralogically different surface layer, and the secondary minerals formed are controlled by the ambient temperature, which decreases with altitude on Venus. A further investigation of venusian mineralogy is presented.

  15. Geochemical and isotopic water results, Barrow, Alaska, 2012-2013

    DOE Data Explorer

    Heikoop, Jeff; Wilson, Cathy; Newman, Brent

    2012-07-18

    Data include a large suite of analytes (geochemical and isotopic) for samples collected in Barrow, Alaska (2012-2013). Sample types are indicated, and include soil pore waters, drainage waters, snowmelt, precipitation, and permafrost samples.

  16. Toxicity of major geochemical ions to freshwater species

    EPA Science Inventory

    Extensive testing regarding the toxicity of major geochemical ions to Ceriodaphnia dubia, Hyalella azteca, and Pimephales promelas will be presented. For C. dubia, tests of single salts and binary mixtures in various dilution waters demonstrated multiple mechanisms of toxicity an...

  17. Preliminary geochemical/geophysical model of Yucca Mountain

    SciTech Connect

    Greenwade, L.E.; Cederberg, G.A.

    1987-12-31

    A comprehensive geochemical/geophysical model incorporates the current and relevant stratigraphic, petrologic, hydrogeologic, geochemical, and material data associated with a candidate repository at Yucca Mountain, Nevada. A geochemical/geophysical model will provide support and confidence to the Systems Performance calculations, determine whether the data collected as part of the site characterization provide the information needed by the design and performance assessment task, and provide the most accurate and referenced foundation on which to base the radionuclide transport calculations. In this report, the known repository data are compiled and unknown parameter values are estimated based on the available data. It is concluded that more data are needed before the geochemical/geophysical model of Yucca Mountain can be regarded as satisfactory and suitable base for multidimensional predicative flow and transport simulations. Recommendations for future studies concerning site characterization and data acquisition are presented. 36 refs., 1 fig., 2 tabs.

  18. Man as an object of geochemical and geophysical influences

    NASA Astrophysics Data System (ADS)

    Stoilova, Irina

    There are an increasing number of papers in the last years that evidence of a correlation between geochemical and geophysical factors and human health parameters and human behaviour. The basic factors that could affect human health and behaviour are: the geochemical composition of the geographical environment; the tectonic processes; the geomagnetic field variations (GMV), the climatic changes and the changes of the solar activity as well as the fact that all of them could influence mutually each other. The subject of this paper is the theoretical basis of the geochemical and geophysical influences on human health. The biological mechanisms according to which the geomagnetic field influences the psychological and behavioural reactions of people are not highlighted or identified yet. We present some of the existing suggestions and theories trying to explain these mechanisms. The studies performed in this area and the obtained results will be very useful in developing measures to protect man from the harmful influence of geochemical and geophysical factors.

  19. GEOCHEM-EZ: a chemical speciation program with greater power and flexibility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    GEOCHEM –EZ is a multi-functional chemical speciation program, which was designed to replace the existing GEOCHEM-PC, a program that can only be used on DOS consoles. Chemical speciation programs, such as GEOCHEM (Sposito and Mattigod, 1980) and GEOCHEM-PC (Parker et al., 1995), have been excellent ...

  20. Geochemical variations during the 2012 Emilia seismic sequence

    NASA Astrophysics Data System (ADS)

    Sciarra, Alessandra; Cantucci, Barbara; Galli, Gianfranco; Cinti, Daniele; Pizzino, Luca

    2015-04-01

    Several geochemical surveys (soil gas and shallow water) were performed in the Modena province (Massa Finalese, Finale Emilia, Medolla and S. Felice sul Panaro), during 2006-2014 period. In May-June 2012, a seismic sequence (main shocks of ML 5.9 and 5.8) was occurred closely to the investigated area. In this area 300 CO2 and CH4 fluxes measurements, 150 soil gas concentrations (He, H2, CO2, CH4 and C2H6), 30 shallow waters and their isotopic analyses (δ13C- CH4, δD- CH4 and δ13C- CO2) were performed in April-May 2006, October and December 2008, repeated in May and September 2012, June 2013 and July 2014 afterwards the 2012 Emilia seismic sequences. Chemical composition of soil gas are dominated by CH4 in the southern part by CO2 in the northern part. Very anomalous fluxes and concentrations are recorded in spot areas; elsewhere CO2 and CH4 values are very low, within the typical range of vegetative and of organic exhalation of the cultivated soil. After the seismic sequence the CH4 and CO2 fluxes are increased of one order of magnitude in the spotty areas, whereas in the surrounding area the values are within the background. On the contrary, CH4 concentration decrease (40%v/v in the 2012 surveys) and CO2 concentration increase until to 12.7%v/v (2013 survey). Isotopic gas analysis were carried out only on samples with anomalous values. Pre-seismic data hint a thermogenic origin of CH4 probably linked to leakage from a deep source in the Medolla area. Conversely, 2012/2013 isotopic data indicate a typical biogenic origin (i.e. microbial hydrocarbon production) of the CH4, as recognized elsewhere in the Po Plain and surroundings. The δ13C-CO2 value suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived) probably related to anaerobic oxidation of heavy hydrocarbons. Water samples, collected from domestic, industrial and hydrocarbons exploration wells, allowed us to recognize different families of waters. Waters are meteoric in origin and

  1. Geochemical characterization of the Nirano Mud Volcano Field

    NASA Astrophysics Data System (ADS)

    Sciarra, Alessandra; Cantucci, Barbara; Ricci, Tullio; Conventi, Marzia

    2016-04-01

    Mud volcanoes, among fluid venting structures, are the most important phenomena related to natural seepage from the Earth's surface. The occurrence of mud volcanoes is controlled by several factors, such as tectonic activity and continuous hydrocarbon accumulation in a reservoir. Mud volcanoes in Italy occur along the external compressive margin of the Apennine chain. These mud volcanoes are usually small and unspectacular, when compared to other world examples. They rarely exhibit the periodic explosions, which is often related to important seismic activity. The Nirano Mud Volcano Field (NMVF) is located in the western sector of the Modena Apennine margin (Italy), which belongs to the Northern Apennines. The NMVF occurs over the crest of a thrust anticline associated with the main Pede-Apennine thrust and represents a good example of an onshore relationship between a mud volcano caldera structure and active thrust deformation, even if the fluid pathways are still not well understood at depth. The mud volcanoes are distributed along an area of about 10 ha, inside of the wider Natural Reserve, and are situated at the bottom of a wide sub-circular depression. The NMVF is currently formed by four main vents composed of a number of individual active cones (or gryphons) defining structural alignments trending ENE-WSW. A geochemical soil gas survey of 230 CO2 and CH4 fluxes and 150 CO2, CH4, Rn, He, H2 concentration measurements has been carried out inside the NMVF. Moreover, the fluid emissions from 4 active cones located in different sectors of NMVF have been sampled for chemical and isotopical analysis of water and free gas. The distribution of pathfinder elements as 222Rn, He e H2 has been studied in order to identify potential faults and/or fractures related to preferential migration pathways and the possible interactions between reservoir and surface. Soil gas data highlight two zones characterized by higher values, localized in the WSW and ENE of the NMVF area. In

  2. Constraining Habitable Environments on Mars by Quantifying Available Geochemical Energy

    NASA Astrophysics Data System (ADS)

    Tierney, L. L.; Jakosky, B. M.

    2009-12-01

    The search for life on Mars includes the availability of liquid water, access to biogenic elements and an energy source. In the past, when water was more abundant on Mars, a source of energy may have been the limiting factor for potential life. Energy, either from photosynthesis or chemosynthesis, is required in order to drive metabolism. Potential martian organisms most likely took advantage of chemosynthetic reactions at and below the surface. Terrestrial chemolithoautotrophs, for example, thrive off of chemical disequilibrium that exists in many environments and use inorganic redox (reduction-oxidation) reactions to drive metabolism and create cellular biomass. The chemical disequilibrium of six different martian environments were modeled in this study and analyzed incorporating a range of water and rock compositions, water:rock mass ratios, atmospheric fugacities, pH, and temperatures. All of these models can be applied to specific sites on Mars including environments similar to Meridiani Planum and Gusev Crater. Both a mass transfer geochemical model of groundwater-basalt interaction and a mixing model of groundwater-hydrothermal fluid interaction were used to estimate hypothetical martian fluid compositions that results from mixing over the entire reaction path. By determining the overall Gibbs free energy yields for redox reactions in the H-O-C-S-Fe-Mn system, the amount of geochemical energy that was available for potential chemolithoautotrophic microorganisms was quantified and the amount of biomass that could have been sustained was estimated. The quantity of biomass that can be formed and supported within a system depends on energy availability, thus sites that have higher levels and fluxes of energy have greater potential to support life. Results show that iron- and sulfur-oxidation reactions would have been the most favorable redox reactions in aqueous systems where groundwater and rock interacted at or near the surface. These types of reactions could

  3. Isotopic partitioning of net ecosystem CO2 exchange reveals the importance of methane oxidation in a boreal peatland

    NASA Astrophysics Data System (ADS)

    Hasselquist, Niles; Peichl, Matthias; Öquist, Mats; Crill, Patrick; Nilsson, Mats

    2016-04-01

    Partitioning net ecosystem CO2 exchange (NEE) into its different flux components is crucial as it provides a mechanistic framework to better assess how the terrestrial carbon cycle may respond to projected environmental change. This is especially important for northern boreal peatlands, which store approximately one-quarter of the world's soil carbon and yet at the same time are projected to experience some of the greatest environmental changes in the future. Using an experimental setup with automated chambers for measuring NEE (transparent chambers), ecosystem respiration (Reco; opaque chambers) and heterotrophic respiration (Rh; opaque chambers on vegetation-free trenched plots) in combination with continuous measurements of δ13C using near-infrared, diode-laser-based cavity-ring down spectroscopy (Picarro G1101-i analyzer), we partitioned NEE of CO2 into gross primary productivity (GPP), ecosystem respiration (Reco), heterotrophic respiration (Rh) and autotrophic respiration (Ra) using two different approaches (i.e., chamber- and isotope-based methods) in a boreal peatland in northern Sweden (Degerö). Given that δ13C was continuously measured in each chamber, we were also able to further partition Rh into soil organic matter (SOM) mineralization by saprotrophic microbes and the oxidation of methane (CH4) by methanotrophic bacteria. During the ten day measurement period (in late July 2014), the average daily NEE flux at the mire was -0.6 g C m-2 d-1. Overall, the two partitioning approaches yielded similar estimates for the different NEE component fluxes. Average daily fluxes of Rh and Ra were similar in magnitude, yet these two flux components showed contrasting diurnal responses: Ra was greatest during the day whereas there was little diurnal variation in Rh. In general, average 13C signature of CO2 efflux from the Rh chambers (-41.1 ± 0.6 ‰) was between the 13C signature of SOM (-25.8 ± 0.6 ‰) and CH4 in pore water (-69.0 ± 0.8 ‰). Assuming that

  4. Interspecific resource partitioning in sympatric ursids

    USGS Publications Warehouse

    Belant, J.L.; Kielland, K.; Follmann, E.H.; Adams, L.G.

    2006-01-01

    The fundamental niche of a species is rarely if ever realized because the presence of other species restricts it to a narrower range of ecological conditions. The effects of this narrower range of conditions define how resources are partitioned. Resource partitioning has been inferred but not demonstrated previously for sympatric ursids. We estimated assimilated diet in relation to body condition (body fat and lean and total body mass) and reproduction for sympatric brown bears (Ursus arctos) and American black bears (U. americanus) in southcentral Alaska, 1998-2000. Based on isotopic analysis of blood and keratin in claws, salmon (Oncorhynchus spp.) predominated in brown bear diets (>53% annually) whereas black bears assimilated 0-25% salmon annually. Black bears did not exploit salmon during a year with below average spawning numbers, probably because brown bears deterred black bear access to salmon. Proportion of salmon in assimilated diet was consistent across years for brown bears and represented the major portion of their diet. Body size of brown bears in the study area approached mean body size of several coastal brown bear populations, demonstrating the importance of salmon availability to body condition. Black bears occurred at a comparable density (mass:mass), but body condition varied and was related directly to the amount of salmon assimilated in their diet. Both species gained most lean body mass during spring and all body fat during summer when salmon were present. Improved body condition (i.e., increased percentage body fat) from salmon consumption reduced catabolism of lean body mass during hibernation, resulting in better body condition the following spring. Further, black bear reproduction was directly related to body condition; reproductive rates were reduced when body condition was lower. High body fat content across years for brown bears was reflected in consistently high reproductive levels. We suggest that the fundamental niche of black bears

  5. Interspecific resource partitioning in sympatric ursids.

    PubMed

    Belant, Jerrold L; Kielland, Knut; Follmann, Erich H; Adams, Layne G

    2006-12-01

    The fundamental niche of a species is rarely if ever realized because the presence of other species restricts it to a narrower range of ecological conditions. The effects of this narrower range of conditions define how resources are partitioned. Resource partitioning has been inferred but not demonstrated previously for sympatric ursids. We estimated assimilated diet in relation to body condition (body fat and lean and total body mass) and reproduction for sympatric brown bears (Ursus arctos) and American black bears (U. americanus) in south-central Alaska, 1998-2000. Based on isotopic analysis of blood and keratin in claws, salmon (Oncorhynchus spp.) predominated in brown bear diets (> 53% annually) whereas black bears assimilated 0-25% salmon annually. Black bears did not exploit salmon during a year with below average spawning numbers, probably because brown bears deterred black bear access to salmon. Proportion of salmon in assimilated diet was consistent across years for brown bears and represented the major portion of their diet. Body size of brown bears in the study area approached mean body size of several coastal brown bear populations, demonstrating the importance of salmon availability to body condition. Black bears occurred at a comparable density (mass:mass), but body condition varied and was related directly to the amount of salmon assimilated in their diet. Both species gained most lean body mass during spring and all body fat during summer when salmon were present. Improved body condition (i.e., increased percentage body fat) from salmon consumption reduced catabolism of lean body mass during hibernation, resulting in better body condition the following spring. Further, black bear reproduction was directly related to body condition; reproductive rates were reduced when body condition was lower. High body fat content across years for brown bears was reflected in consistently high reproductive levels. We suggest that the fundamental niche of black

  6. Comparison of mathematical methods of geochemical data processing

    NASA Astrophysics Data System (ADS)

    Marfin, A.; Lychagin, D. V.; Shapovalov, A.; Alfyorova, E. A.

    2015-09-01

    We have analyzed the data on concentration of geochemical elements within the 3- DV regional geochemical field. We have determined the fractal dimension index of spider diagrams and found the fractal nature of the distribution of chemical elements along the profile. We have compared these data with the results of the correlation analysis and hierarchical clustering methods. The agreement between the grouping of the elements according to the values of fractal dimension and the results of statistical analysis method was considered satisfactory.

  7. Understanding the Hydrological Controls on the Water Chemistry at the Watershed Scale Using an Integrated Hydro-Thermo-Geochemical Model PIHM-RT

    NASA Astrophysics Data System (ADS)

    Bao, C.; Li, L.; Shi, Y.; Qiao, C.; Sullivan, P. L.; Brantley, S. L.; Duffy, C.

    2013-12-01

    Hydrological and geochemical processes are intricately coupled at the watershed scale. Despite recent advances, modeling the complex hydro-thermo-geochemical interactions at the watershed scale has been challenging. Many efforts have been put forward to solve the well-known puzzles such as the 'double paradox ' raised by Kirchner either mechanistically or through simplified numerical modeling. However, a major gap remains in explicitly modeling and integrating these processes at the watershed scale. This work presents an integrated approach to understanding and quantifying the hydrologic controls on water chemistry at the watershed scale. A fully coupled finite volume hydro -thermo-geochemical model, PIHM-RT (Penn State Integrated Hydrologic Model -Reactive Transport) has been developed based on the land surface hydrologic model, Flux-PIHM. Flux-PIHM is capable of simulating the terrestrial water cycle and the surface energy balance (SEB) to reproduce the spatially distributed observations of water, temperature, and saturation . Adding the reactive transport module enables explicit modeling of the evolving water chemistry, which is controlled by hydrologic processes and geochemical reactions. The reactions include mineral dissolution, precipitation and ion exchange. PIHM-RT utilizes an a priori database EQ3EQ6 that is widely used for geochemical thermodynamics and kinetics. The RT module utilizes an operator splitting scheme described in Zysset et al. (1994), to solve for the advection-dispersion-reaction equation (ADR). The advection dispersion equation was solved using the Euler forward method and the reaction process was solved implicitly. In addition, because the reaction and transport processes differ significantly between the unsaturated and saturated zones, we implemented a volume explicit mass conservation law to account for the variable depth of groundwater and the mixing process involved at the boundary between the saturated and unsaturated zone. The use

  8. Three-phase partitioning of hydrolyzed levan.

    PubMed

    Coimbra, Cynthia Gisele de Oliveira; Lopes, Carlos Edison; Calazans, Glícia Maria Torres

    2010-06-01

    During the fructose and polymerization to synthesize levan, smaller fructooligosaccharide (FOS) molecules are produced. FOS can also be obtained by levan hydrolysis. Three-phase partitioning (TPP) is a separation technique that has been used for polysaccharide precipitation and gathers t-butanol and ammonium sulphate to exclude the polymer from the aqueous solution. In this work TPP was tested to separate levan and FOS from aqueous solution. The FOS used was obtained from Zymomonas mobilis levan acid hydrolysis and fractionation with ethanol. The yield of low TPP fractions was higher than those obtained from the native levan. The F-90 exhibited a higher yield than other fractions. However, when applying the TPP technique to lightest fraction not precipitated by ethanol at 90% (F>90), the intermediate phase was not possible to be visualize. These results have potential application because they show that by using the levan TPP separation it is possible to separate low-molecular weight sugar. PMID:20163956

  9. Hypergraph Partitioning for Automatic Memory Hierarchy Management

    SciTech Connect

    Krishnamoorthy, Sriram; Catalyurek, Umit; Nieplocha, Jarek; Rountev, Atanas; Sadayappan, Ponnuswamy

    2007-11-15

    The paper presents present a mechanism for automatic management of the memory hierarchy, including secondary storage, in the context of a global address space parallel programming framework. The programmer specifies the parallelism and locality in the computation. The scheduling of the computation into stages, together with the movement of the associated data between secondary storage and global memory, and between global memory and local memory, is automatically managed by the framework. A novel formulation of hypergraph partitioning is used to model the optimization problem of minimizing disk I/O by improving locality of access. Experimental evaluation of the proposed approach using a sub-computation from the quantum chemistry domain shows a reduction in the disk I/O cost by upto a factor of 11, and a reduction in turnaround time by upto 97%, as compared to alternatives used in state-of-the-art quantum chemistry codes.

  10. Exometabolite niche partitioning among sympatric soil bacteria

    DOE PAGESBeta

    Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Hummel, Eric; Da Rocha, Ulisses Nunes; Chakraborty, Romy; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; et al

    2015-09-22

    Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13-26% of available metabolites,more » with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. In conclusion, these results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity.« less

  11. Metal separations using aqueous biphasic partitioning systems

    SciTech Connect

    Chaiko, D.J.; Zaslavsky, B.; Rollins, A.N.; Vojta, Y.; Gartelmann, J.; Mego, W.

    1996-05-01

    Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that the authors have studied are generated by combining an aqueous salt solution with an aqueous polymer solution. They have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. They have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this report they review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.

  12. Multicore Software Architectures on Virtualized Partitioned Systems

    NASA Astrophysics Data System (ADS)

    Carrascosa, E.; Masmano, M.; Balbastre, P.; Crespo, A.; Galizzi, J.

    2014-08-01

    Embedded system design is evolving in terms of complexity towards the use of multiprocessor architectures, increasing performance and reducing costs while presenting a low impact on critical design aspects. However, the use of multi-core technologies entails an increment in the level of indeterminism that is not acceptable for safety critical applications where predictability is crucial. This paper focuses on analysing the factors related to indeterminism on multicore systems and the methods to attenuate their impact, providing a series of guidelines aimed to obtain on-board software qualification. Time and space partitioning (TSP) is presented as a suitable mean to handle indeterminism, while XtratuM, an open source TSP hyper-visor designed to comply with safety critical real-time requirements, has been selected to adopt a practical approach to the subject.

  13. Energy Partition and Variability of Earthquakes

    NASA Astrophysics Data System (ADS)

    Kanamori, H.

    2003-12-01

    During an earthquake the potential energy (strain energy + gravitational energy + rotational energy) is released, and the released potential energy (Δ W) is partitioned into radiated energy (ER), fracture energy (EG), and thermal energy (E H). How Δ W is partitioned into these energies controls the behavior of an earthquake. The merit of the slip-weakening concept is that only ER and EG control the dynamics, and EH can be treated separately to discuss the thermal characteristics of an earthquake. In general, if EG/E_R is small, the event is ``brittle", if EG /ER is large, the event is ``quasi static" or, in more common terms, ``slow earthquakes" or ``creep". If EH is very large, the event may well be called a thermal runaway rather than an earthquake. The difference in energy partition has important implications for the rupture initiation, evolution and excitation of long-period ground motions from very large earthquakes. We review the current state of knowledge on this problem in light of seismological observations and the basic physics of fracture. With seismological methods, we can measure only ER and the lower-bound of Δ W, Δ W0, and estimation of other energies involves many assumptions. ER: Although ER can be directly measured from the radiated waves, its determination is difficult because a large fraction of energy radiated at the source is attenuated during propagation. With the commonly used teleseismic and regional methods, only for events with MW>7 and MW>4, respectively, we can directly measure more than 10% of the total radiated energy. The rest must be estimated after correction for attenuation. Thus, large uncertainties are involved, especially for small earthquakes. Δ W0: To estimate Δ W0, estimation of the source dimension is required. Again, only for large earthquakes, the source dimension can be estimated reliably. With the source dimension, the static stress drop, Δ σ S, and Δ W0, can be estimated. EG: Seismologically, EG is the energy

  14. Recursive Partitioning Method on Competing Risk Outcomes

    PubMed Central

    Xu, Wei; Che, Jiahua; Kong, Qin

    2016-01-01

    In some cancer clinical studies, researchers have interests to explore the risk factors associated with competing risk outcomes such as recurrence-free survival. We develop a novel recursive partitioning framework on competing risk data for both prognostic and predictive model constructions. We define specific splitting rules, pruning algorithm, and final tree selection algorithm for the competing risk tree models. This methodology is quite flexible that it can corporate both semiparametric method using Cox proportional hazards model and parametric competing risk model. Both prognostic and predictive tree models are developed to adjust for potential confounding factors. Extensive simulations show that our methods have well-controlled type I error and robust power performance. Finally, we apply both Cox proportional hazards model and flexible parametric model for prognostic tree development on a retrospective clinical study on oropharyngeal cancer patients. PMID:27486300

  15. Exometabolite niche partitioning among sympatric soil bacteria

    SciTech Connect

    Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Hummel, Eric; Da Rocha, Ulisses Nunes; Chakraborty, Romy; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R.

    2015-09-22

    Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13-26% of available metabolites, with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. In conclusion, these results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity.

  16. Advanced Aqueous Separation Systems for Actinide Partitioning

    SciTech Connect

    Nash, Kenneth L.; Clark, Sue; Meier, G Patrick; Alexandratos, Spiro; Paine, Robert; Hancock, Robert; Ensor, Dale

    2012-03-21

    One of the most challenging aspects of advanced processing of spent nuclear fuel is the need to isolate transuranium elements from fission product lanthanides. This project expanded the scope of earlier investigations of americium (Am) partitioning from the lanthanides with the synthesis of new separations materials and a centralized focus on radiochemical characterization of the separation systems that could be developed based on these new materials. The primary objective of this program was to explore alternative materials for actinide separations and to link the design of new reagents for actinide separations to characterizations based on actinide chemistry. In the predominant trivalent oxidation state, the chemistry of lanthanides overlaps substantially with that of the trivalent actinides and their mutual separation is quite challenging.

  17. Partitioned-Interval Quantum Optical Communications Receiver

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.

    2013-01-01

    The proposed quantum receiver in this innovation partitions each binary signal interval into two unequal segments: a short "pre-measurement" segment in the beginning of the symbol interval used to make an initial guess with better probability than 50/50 guessing, and a much longer segment used to make the high-sensitivity signal detection via field-cancellation and photon-counting detection. It was found that by assigning as little as 10% of the total signal energy to the pre-measurement segment, the initial 50/50 guess can be improved to about 70/30, using the best available measurements such as classical coherent or "optimized Kennedy" detection.

  18. Partitional Classification: A Complement to Phylogeny

    PubMed Central

    Salomon, Marc; Dassy, Bruno

    2016-01-01

    The tree of life is currently an active object of research, though next to vertical gene transmission non vertical gene transfers proved to play a significant role in the evolutionary process. To overcome this difficulty, trees of life are now constructed from genes hypothesized vital, on the assumption that these are all transmitted vertically. This view has been challenged. As a frame for this discussion, we developed a partitional taxonomical system clustering taxa at a high taxonomical rank. Our analysis (1) selects RNase P RNA sequences of bacterial, archaeal, and eucaryal genera from genetic databases, (2) submits the sequences, aligned, to k-medoid analysis to obtain clusters, (3) establishes the correspondence between clusters and taxa, (4) constructs from the taxa a new type of taxon, the genetic community (GC), and (5) classifies the GCs: Archaea–Eukaryotes contrastingly different from the six others, all bacterial. The GCs would be the broadest frame to carry out the phylogenies. PMID:27346943

  19. Exometabolite niche partitioning among sympatric soil bacteria.

    PubMed

    Baran, Richard; Brodie, Eoin L; Mayberry-Lewis, Jazmine; Hummel, Eric; Da Rocha, Ulisses Nunes; Chakraborty, Romy; Bowen, Benjamin P; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R

    2015-01-01

    Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13-26% of available metabolites, with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. These results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity. PMID:26392107

  20. Exometabolite niche partitioning among sympatric soil bacteria

    PubMed Central

    Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Hummel, Eric; Da Rocha, Ulisses Nunes; Chakraborty, Romy; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R.

    2015-01-01

    Soils are arguably the most microbially diverse ecosystems. Physicochemical properties have been associated with the maintenance of this diversity. Yet, the role of microbial substrate specialization is largely unexplored since substrate utilization studies have focused on simple substrates, not the complex mixtures representative of the soil environment. Here we examine the exometabolite composition of desert biological soil crusts (biocrusts) and the substrate preferences of seven biocrust isolates. The biocrust's main primary producer releases a diverse array of metabolites, and isolates of physically associated taxa use unique subsets of the complex metabolite pool. Individual isolates use only 13−26% of available metabolites, with only 2 out of 470 used by all and 40% not used by any. An extension of this approach to a mesophilic soil environment also reveals high levels of microbial substrate specialization. These results suggest that exometabolite niche partitioning may be an important factor in the maintenance of microbial diversity. PMID:26392107

  1. Environmental Controls of Microbial Resource Partitioning in Soils

    NASA Astrophysics Data System (ADS)

    Kandeler, Ellen; Poll, Christian; Kramer, Susanne; Mueller, Karolin; Marhan, Sven

    2015-04-01

    The mineralization and flow of plant-derived carbon in soils is relevant to global carbon cycling. Current models of organismic carbon fluxes in soil assume that separate bacterial and fungal energy channels exist in soil. Recent studies disentangle the herbivore and detritivore pathways of microbial resource use, identify the key players contributing to these two different pathways, and determine to what extent microbial substrate use is affected by environmental controls. To follow the kinetics of litter and root decomposition and to quantify the contribution of key players, it is necessary to use isotopic approaches like PLFA-SIP and ergosterol-SIP. It was shown that bacteria and sugar consuming fungi initiated litter decomposition in an incubation experiment during the first two weeks, whereas higher fungi started to grow after the depletion of low molecular weight substrates. Analyses of PLFA-SIP revealed, for example, that fungi assimilated C directly from the litter, whereas bacteria took up substrates in the soil and therefore depended more on external transport processes than fungi. In addition, we will present data from a field experiment showing the incorporation of root and shoot litter C into organic and microbial C pools under field conditions over a period of two years. Similar amounts of C derived from the two resources differing in substrate quality and amount were incorporated into microbial C and ergosterol pools over time, indicating the importance of root-derived C for the soil food web. High incorporation of maize C (up to 76%) into ergosterol suggests fast and high assimilation of maize C into fungal biomass. Nevertheless, there is still a debate whether bacteria, archaea and fungi start feeding on new substrates at the same time or if their activity occurs at different successional stages. This presentation gives a summery of current knowledge on microbial resource partitioning under lab and field conditions.

  2. Quantitative framework for preferential flow initiation and partitioning

    USGS Publications Warehouse

    Nimmo, John R.

    2016-01-01

    A model for preferential flow in macropores is based on the short-range spatial distribution of soil matrix infiltrability. It uses elementary areas at two different scales. One is the traditional representative elementary area (REA), which includes a sufficient heterogeneity to typify larger areas, as for measuring field-scale infiltrability. The other, called an elementary matrix area (EMA), is smaller, but large enough to represent the local infiltrability of soil matrix material, between macropores. When water is applied to the land surface, each EMA absorbs water up to the rate of its matrix infiltrability. Excess water flows into a macropore, becoming preferential flow. The land surface then can be represented by a mesoscale (EMA-scale) distribution of matrix infiltrabilities. Total preferential flow at a given depth is the sum of contributions from all EMAs. Applying the model, one case study with multi-year field measurements of both preferential and diffuse fluxes at a specific depth was used to obtain parameter values by inverse calculation. The results quantify the preferential–diffuse partition of flow from individual storms that differed in rainfall amount, intensity, antecedent soil water, and other factors. Another case study provided measured values of matrix infiltrability to estimate parameter values for comparison and illustrative predictions. These examples give a self-consistent picture from the combination of parameter values, directions of sensitivities, and magnitudes of differences caused by different variables. One major practical use of this model is to calculate the dependence of preferential flow on climate-related factors, such as varying soil wetness and rainfall intensity.

  3. Carbon partitioning to the terpenoid biosynthetic pathway enables heterologous β-phellandrene production in Escherichia coli cultures.

    PubMed

    Formighieri, Cinzia; Melis, Anastasios

    2014-12-01

    Escherichia coli was used as a microbial system for the heterologous synthesis of β-phellandrene, a monoterpene of plant origin with several potential commercial applications. Expression of Lavandula angustifolia β-phellandrene synthase (PHLS), alone or in combination with Picea abies geranyl-diphosphate synthase in E. coli, resulted in no β-phellandrene accumulation, in sharp contrast to observations with PHLS-transformed cyanobacteria. Lack of β-phellandrene biosynthesis in E. coli was attributed to the limited endogenous carbon partitioning through the native 2-C-methylerythritol-4-phosphate (MEP) pathway. Heterologous co-expression of the mevalonic acid pathway, enhancing cellular carbon partitioning and flux toward the universal isoprenoid precursors, isopentenyl-diphosphate and dimethylallyl-diphosphate, was required to confer β-phellandrene production. Differences in endogenous carbon flux toward the synthesis of isoprenoids between photosynthetic (Synechocystis) and non-photosynthetic bacteria (E. coli) are discussed in terms of differences in the regulation of carbon partitioning through the MEP biosynthetic pathway in the two systems. PMID:25116411

  4. The CORSAGE Programme: Continuous Orbital Remote Sensing of Archipelagic Geochemical Effects

    NASA Technical Reports Server (NTRS)

    Acker, J. G.; Brown, C. W.; Hine, A. C.

    1997-01-01

    Current and pending oceanographic remote sensing technology allows the conceptualization of a programme designed to investigate ocean island interactions that could induce short-term nearshore fluxes of particulate organic carbon and biogenic calcium carbonate from pelagic island archipelagoes. These events will influence the geochemistry of adjacent waters, particularly the marine carbon system. Justification and design are provided for a study that would combine oceanographic satellite remote sensing (visible and infrared radiometry, altimetry and scatterometry) with shore-based facilities. A programme incorporating the methodology outlined here would seek to identify the mechanisms that cause such events, assess their geochemical significance, and provide both analytical and predictive capabilities for observations on greater temporal and spatial scales.

  5. REE and Strontium Partition Coefficients for Nakhla Pyroxenes

    NASA Technical Reports Server (NTRS)

    Oe, K.; McKay, G.; Le, L.

    2001-01-01

    We present new partition coefficients for REE and Sr determined using a synthetic melt that crystallizes pyroxenes very similar in composition to Nakhla pyroxene cores. We believe these are the most appropriate partition coefficients to use in studying Nakhla Additional information is contained in the original extended abstract..

  6. The Emergence of DP in the Partitive Structure

    ERIC Educational Resources Information Center

    Stickney, Helen

    2009-01-01

    This dissertation is a first look at English-speaking children's acquisition of the syntax of the partitive. It presents four experiments that contrast three types of structures and examines how they interact with adjectival modification: the partitive, the pseudopartitive and complex nouns with prepositional adjuncts. The experimentation…

  7. High-temperature asymptotics of supersymmetric partition functions

    NASA Astrophysics Data System (ADS)

    Ardehali, Arash Arabi

    2016-07-01

    We study the supersymmetric partition function of 4d supersymmetric gauge theories with a U(1) R-symmetry on Euclidean S 3 × S β 1 , with S 3 the unit-radius squashed three-sphere, and β the circumference of the circle. For superconformal theories, this partition function coincides (up to a Casimir energy factor) with the 4d superconformal index.

  8. Knowledge Partitioning in Categorization: Constraints on Exemplar Models

    ERIC Educational Resources Information Center

    Yang, Lee-Xieng; Lewandowsky, Stephan

    2004-01-01

    The authors present 2 experiments that establish the presence of knowledge partitioning in perceptual categorization. Many participants learned to rely on a context cue, which did not predict category membership but identified partial boundaries, to gate independent partial categorization strategies. When participants partitioned their knowledge,…

  9. 47 CFR 101.1111 - Partitioning and disaggregation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Partitioning and disaggregation. 101.1111 Section 101.1111 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Competitive Bidding Procedures for LMDS § 101.1111 Partitioning...

  10. 47 CFR 101.1111 - Partitioning and disaggregation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Partitioning and disaggregation. 101.1111 Section 101.1111 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Competitive Bidding Procedures for LMDS § 101.1111 Partitioning...

  11. 47 CFR 27.15 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Geographic partitioning and spectrum disaggregation. 27.15 Section 27.15 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Applications and Licenses § 27.15 Geographic partitioning and spectrum disaggregation....

  12. Simple partitions of a hyperbolic plane of positive curvature

    SciTech Connect

    Romakina, Lyudmila N

    2012-09-30

    We construct special monohedral isotropic partitions with symmetries of the hyperbolic plane H of positive curvature with a simple 4-contour as a cell. An analogue of mosaic in these partitions called a tiling is introduced. Also we consider some fractal tilings. The existence of band tilings in each homological series with code (m, n) is proved. Bibliography: 14 titles.

  13. 47 CFR 101.1415 - Partitioning and disaggregation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Partitioning and disaggregation. 101.1415 Section 101.1415 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Multichannel Video Distribution and Data Service Rules for the 12.2-12.7 GHz Band § 101.1415 Partitioning...

  14. 47 CFR 101.1415 - Partitioning and disaggregation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Partitioning and disaggregation. 101.1415 Section 101.1415 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Multichannel Video Distribution and Data Service Rules for the 12.2-12.7 GHz Band § 101.1415 Partitioning...

  15. PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND WASTE

    EPA Science Inventory

    This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition ...

  16. 47 CFR 22.948 - Partitioning and Disaggregation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... partition or disaggregate their spectrum to other qualified entities. (2) Partitioning. During the five year... obtaining disaggregated spectrum may only use such spectrum in that portion of the cellular market encompassed by the original licensee's CGSA and may not use such spectrum to provide service to...

  17. 47 CFR 90.365 - Partitioned licenses and disaggregated spectrum.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Partitioned licenses and disaggregated spectrum... § 90.365 Partitioned licenses and disaggregated spectrum. (a) Eligibility. (1) Party seeking approval... disaggregate their licensed spectrum at any time following the grant of their licenses. Multilateration...

  18. 47 CFR 101.1323 - Spectrum aggregation, disaggregation, and partitioning.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Spectrum aggregation, disaggregation, and... Requirements § 101.1323 Spectrum aggregation, disaggregation, and partitioning. (a) Eligibility. (1) Parties... aggregate spectrum in any MAS bands, but may not disaggregate their licensed spectrum or partition...

  19. 47 CFR 101.1323 - Spectrum aggregation, disaggregation, and partitioning.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Spectrum aggregation, disaggregation, and... Requirements § 101.1323 Spectrum aggregation, disaggregation, and partitioning. (a) Eligibility. (1) Parties... aggregate spectrum in any MAS bands, but may not disaggregate their licensed spectrum or partition...

  20. 47 CFR 27.15 - Geographic partitioning and spectrum disaggregation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Geographic partitioning and spectrum... Geographic partitioning and spectrum disaggregation. Link to an amendment published at 79 FR 48537, Aug. 15... licensed spectrum at any time following the grant of their licenses. (b) Technical...