WorldWideScience

Sample records for surfzone tracer dispersion

  1. Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

    OpenAIRE

    Clark, David B.; Feddersen, Falk; Omand, Melissa M.; Guza, R.T.

    2009-01-01

    Decisions about recreational beach closures would be enhanced if better estimates of surfzone contaminant transport and dilution were available. In situ methods for measuring fluorescent Rhodamine WT dye tracer in the surfzone are presented, increasing the temporal and spatial resolution over previous surfzone techniques. Bubbles and sand suspended by breaking waves in the surfzone interfere with in situ optical fluorometer dye measurements, increasing the lower bound for dye detection (≈ 1 p...

  2. Tracer Dispersion in a Multi-compartment Structure

    CERN Document Server

    Skvortsov, A; Gamble, G; Roberts, M; Ilaya, O; Pitaliadda, D

    2012-01-01

    An experimental study of the tracer dispersion in a complex structure is presented. A point source of tracer (dyed salt) was placed inside a multi-compartment structure embedded in water tank. This experimental setting corresponds to a hazardous tracer release inside the engineering structure (building, ship, aircarft etc). A system of conductivity sensors was deployed to monitor the propagation of a tracer plume in the structure, including tracer trapping inside some compartments and its release to the outside environment through the external openings. The experimental data is processed by employing the ideas of scaling and self-similarity of underlying transport processes. The established and validated scaling laws provide a rigorous way to up-scale the results of laboratory modeling to real operational scenarios and can be used as an important step in the development of risk-assessment models for the first responders to hazardous releases. Keywords: hazardous plume, tracer dispersion, diffusion and advecti...

  3. Studies of Tracer Dispersion and Fluid Flow in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Rage, T.

    1996-12-31

    This doctoral thesis explores the connection between the topology of a porous medium and its macroscopic transport properties and is based on computerized simulation. In porous media, both diffusion and convection contribute to the dispersion of a tracer and their combined effect is emphasized. The governing equations are solved numerically, using finite differences and Monte Carlo technique. The influence of finite Reynolds number on the outcome of echo-experiments is discussed. Comparing experiments and simulations it is found that nonlinear inertial forces lead to a visible deformation of a returned tracer at surprisingly small Reynolds numbers. In a study of tracer dispersion and fluid flow in periodic arrays of discs it is demonstrated that the mechanisms of mechanical dispersion in periodic media and in natural (non-periodic) porous media are essentially different. Measurements of the percolation probability distribution of a sandstone sample is presented. Local porosity theory predicts that this simple geometric function of a porous medium is of dominant importance for its macroscopic transport properties. It is demonstrated that many aspects of transport through fractures can be studied by using simple but realistic models and readily available computer resources. An example may be the transport of hydrocarbon fluids from the source rock to a reservoir. 165 refs., 44 figs., 1 table

  4. Influence of Dispersion on Transport of Tracer through Unsaturated Porous Media

    Directory of Open Access Journals (Sweden)

    T Bunsri

    2008-01-01

    Full Text Available The dispersion phenomenon has resulted from the various water flow magnitude and direction in porous media. The dissolved tracer tends to spread due to dispersion and then travel time of tracer through the porous media increases. In unsaturated porous media, dispersion coefficient varies with non-linear Darcy’s velocity and the water content. These effects observed in both of the laboratory scale sand and soil columns (20 cm. The unsaturated infiltration column and tracer tests have been used to interpret the relationships between Darcy’s velocity and the water content together with the dispersion coefficient. However, the dispersivity coefficient cannot be measured directly, it has to determine from advection-dispersion equation (ADE, which can be used to model the tracer transport in unsaturated porous media. The model was used to describe the non-linear functions of water contents and dispersivities for both porous media. The simulations have been verified that the dispersion of tracer through soil is higher than sand column and also travel time of tracer through soil is longer than sand column. Even though, soil has very low degree of pore velocity, the high dispersivity is observed in the simulations. The water content and tracer concentration profiles reveal that the increase of dispersivity induces the increase of flow path distance and the decrease of pore velocity. The maximum dispersivity was observed when the water content of porous media is relatively low; this leads the maximum of spreading of tracer.

  5. Tracer dispersion in a percolation network with spatial correlations

    Science.gov (United States)

    Makse; Andrade; Eugene Stanley H

    2000-01-01

    We analyze the transport properties of a neutral tracer in a carrier fluid flowing through percolationlike porous media with spatial correlations. We model convection in the mass transport process using the velocity field obtained by the numerical solution of the Navier-Stokes and continuity equations in the pore space. We find that the resulting statistical properties of the tracer show a transition from a subdiffusion regime at low Peclet number to an enhanced diffusion regime at high Peclet number.

  6. Estimation of longitudinal and transverse dispersivities in the Twin Lake natural gradient tracer tests

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Seiji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Moltyaner, G.L.

    1998-06-01

    The field scale tracer tests were carried out with a non-reactive tracer of {sup 131}I at Twin Lake on the Chalk River Laboratory (CRL) site in Atomic Energy of Canada Limited (AECL). The natural gradient dispersion test such as the Twin Lake tracer test is very few and useful for evaluating mass transport parameters and testing groundwater flow and transport models. In this report, mass transport parameters, velocity, longitudinal and transverse dispersivities, were estimated from the Twin Lake 40 m tracer tests. This estimation was performed to provide dispersion data for 3-D transport modelling in the Lake 233 site scale (600 m in east-west direction and 1400 m in north-south direction). Two different methods were applied to the measured breakthrough curves of {sup 131}I in order to evaluate velocity and longitudinal dispersivity. The first method is the fitting procedure of the 1-D advection-dispersion solution, and the second one is the temporal moments analysis. The effect of applying these methods to field data on transport parameters was discussed in this study. The vertical profiles of {sup 131}I were used in the estimation of transverse dispersivity by fitting the 3-D advection-dispersion solution. This report refereed to the effect of variable velocity on the estimated dispersivities. The correlation between magnitude of both dispersivities and the travel distance up to 40 m was also investigated. (author)

  7. Measurements of Contaminant Dispersion in ventilated Rooms by a Passive Tracer Gas Technique

    DEFF Research Database (Denmark)

    Heiselberg, Per; Bergsøe, Niels Christian

    During recent years the interest in the passive tracer gas technique has grown rapidly. The method has mainly been used in the field for measurements of air infiltration rates in buildings. This paper describes measurements of the contaminant dispersion in a ventilated room using a passive tracer...... gas technique and the results are compared with the results from a conventional method. Vertical profiles of concentration in the middle of the room have been measured at different ventilation air flow rates and different locations of the tracer gas source. The results showed good correspondence...... between the methods within an accuracy of ± 10- 15% in large parts of the room. In regions close to the tracer gas sources the differences were larger. The results gave at the same time recommendations for the use of the passive tracer gas technique for measurements of the air infiltration rates...

  8. High shear dispersion of tracers in polyolefins for improving their detection

    Directory of Open Access Journals (Sweden)

    Valérie Massardier

    2015-10-01

    Full Text Available Abstract An efficient recycling of end-of-life products is of crucial interest from an economical and ecological point of view. However, the near infrared spectroscopy often used for the optic sorting processes is limited because of the absorption of carbon black present in black plastics and as it only sorts as a function of chemical formulas. The tracing technology developed in this study is based on the dispersion of lanthanide complexes particles into polymers to give them a code that can be related to their formulation and viscosity that are important parameters for their re-processing. As the success of this technology is conditioned by achieving a fine dispersion of the tracer particles, we also focus on accomplishing a fine dispersion of tracer particles by using a high shear process. Processing under high shear rate (N= 800 rpm has proved to play a determining role in dispersing finely and homogenously tracer particles within PP matrix. Thanks to the good quality of dispersion, the detection of three tracers at a level of 0.1 wt% has been successfully achieved, even in black matrices for an acquisition time of 10 ms.

  9. Urban Dispersion Program MSG05 Field Study: Summary of Tracer and Meteorological Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2006-08-09

    The Urban Dispersion Program is a multi-year project, funded by the U.S. Department of Homeland Security, to better understand the flow and dispersion of airborne contaminants through and around the deep street canyons of New York City. The first tracer and meteorological field study was a limited study conducted during March 2005 near the Madison Square Garden in midtown Manhattan. Six safe, inert, gaseous perfluorocarbon tracers were released simultaneously at five street-level locations during two experimental days. In addition to collecting tracer data, meteorological data were also collected. Brookhaven National Laboratory conducted the bulk of the tracer and meteorological field efforts with Pacific Northwest National Laboratory and Stevens Institute of Technology assisting by measuring the vertical profile of winds. The Environmental Protection Agency worked with Brookhaven National Laboratory in accomplishing the personal exposure component of the study. This report presents some results from this analysis. In general, different release locations showed vastly different plume footprints for tracer materials, and the situation was made very complex with upwind and/or crosswind transport of tracer near street-level for the different release locations. Overall wind speeds and directions upwind and over the city were generally constant throughout each of the two experimental periods.

  10. Field studies of transport and dispersion of atmospheric tracers in nocturnal drainage flows

    Energy Technology Data Exchange (ETDEWEB)

    Gudiksen, P.H.; Ferber, G.J.; Fowler, M.M.; Eberhard, W.L.; Fosberg, M.A.; Knuth, W.R.

    1984-01-01

    A series of tracer experiments were carried out as part of the Atmospheric Studies in Complex Terrain (ASCOT) program to evaluate pollutant transport and dispersion characteristics of nocturnal drainage flows within a valley in northern California. The results indicate that the degree of interaction of the drainage flows with the larger scale regional flows are strongly dependent on how well the shallow drainage flows are shielded by the surrounding topography from the external environment. For the valley under study, the drainage flows from about mid-slope elevations and below were generally decoupled from the externally generated flows; as evidenced by the similarity of the surface tracer distribution produced during widely varying regional flow conditions. However, tracers released immediately above the drainage flows near the ridge top did reveal considerable mixing between the transition layer flows and the underlying surface drainage flows. Likewise, the transport and dispersion of the tracers at elevated heights within the valley basin were extremely dependent on the influences of the regional scale flows on the valley circulation. The dispersion rates associated with the transition layer flows were dependent on topographic constraints but were appreciably higher than those reported for homogeneous flat terrain situations.

  11. Uncertainty Quantification of Tracer Dispersion with the PMVP Model under Realistic Conditions

    Science.gov (United States)

    Meyer, D. W.; Duenser, S.

    2015-12-01

    The polar Markovian velocity process (PVMP) model provides a computationally efficient method to propagate input uncertainty stemming from unknown permeability fields to output flow and transport statistics [Meyer and Tchelepi, WRR, 2010; Meyer, Jenny, and Tchelepi, WRR, 2010; Meyer et al., WRR, 2013]. Compared with classical Monte Carlo (MC) sampling, the PMVP model provides predictions of tracer concentration statistics at computing times that are three orders of magnitude smaller. Consequently, the PMVP model is as well significantly faster than accelerated sampling techniques such as multi-level MC or polynomial chaos expansions. In this work, we further evaluate the PMVP model performance by applying the model for tracer dispersion predictions in a setup derived from the well-known MADE field experiment [Boggs et al., WRR, 1992]. We perform detailed model validations against reference MC simulations and conclude that the model provides overall accurate dispersion predictions under realistic conditions.

  12. Influence of the disorder on tracer dispersion in a flow channel

    CERN Document Server

    Charette, V J; Chertcoff, R; Auradou, H; Hulin, J P; Ippolito, I; Charette, Victor Javier; Evangelista, Elisa; Chertcoff, Ricardo; Auradou, Harold; Hulin, Jean-Pierre; Ippolito, Irene

    2006-01-01

    Tracer dispersion is studied experimentally in periodic or disordered arrays of beads in a capillary tube. Dispersion is measured from light absorption variations near the outlet following a steplike injection of dye at the inlet. Visualizations using dye and pure glycerol are also performed in similar geometries. Taylor dispersion is dominant both in an empty tube and for a periodic array of beads: the dispersivity $l\\_d$ increases with the P\\'eclet number $Pe$ respectively as $Pe$ and $Pe^{0.82}$ and is larger by a factor of 8 in the second case. In a disordered packing of smaller beads (1/3 of the tube diameter) geometrical dispersion associated to the disorder of the flow field is dominant with a constant value of $l\\_d$ reached at high P\\'eclet numbers. The minimum dispersivity is slightly higher than in homogeneous nonconsolidated packings of small grains, likely due heterogeneities resulting from wall effects. In a disordered packing with the same beads as in the periodic configuration, $l\\_d$ is up to...

  13. Endospores of thermophilic bacteria as tracers of microbial dispersal by ocean currents.

    Science.gov (United States)

    Müller, Albert Leopold; de Rezende, Júlia Rosa; Hubert, Casey R J; Kjeldsen, Kasper Urup; Lagkouvardos, Ilias; Berry, David; Jørgensen, Bo Barker; Loy, Alexander

    2014-06-01

    Microbial biogeography is influenced by the combined effects of passive dispersal and environmental selection, but the contribution of either factor can be difficult to discern. As thermophilic bacteria cannot grow in the cold seabed, their inactive spores are not subject to environmental selection. We therefore conducted a global experimental survey using thermophilic endospores that are passively deposited by sedimentation to the cold seafloor as tracers to study the effect of dispersal by ocean currents on the biogeography of marine microorganisms. Our analysis of 81 different marine sediments from around the world identified 146 species-level 16S rRNA phylotypes of endospore-forming, thermophilic Firmicutes. Phylotypes showed various patterns of spatial distribution in the world oceans and were dispersal-limited to different degrees. Co-occurrence of several phylotypes in locations separated by great distances (west of Svalbard, the Baltic Sea and the Gulf of California) demonstrated a widespread but not ubiquitous distribution. In contrast, Arctic regions with water masses that are relatively isolated from global ocean circulation (Baffin Bay and east of Svalbard) were characterized by low phylotype richness and different compositions of phylotypes. The observed distribution pattern of thermophilic endospores in marine sediments suggests that the impact of passive dispersal on marine microbial biogeography is controlled by the connectivity of local water masses to ocean circulation.

  14. Evaluation of the ERP dispersion model using Darlington tracer-study data. Report No. 90-200-K

    Energy Technology Data Exchange (ETDEWEB)

    Wright, S.C.

    1990-01-01

    In this study, site-boundary atmospheric dilution factors calculated by the atmospheric dispersion model used in the ERP (Emergency Response Planning) computer code were compared to data collected during the Darlington tracer study. The purpose of this comparison was to obtain estimates of model uncertainty under a variety of conditions. This report provides background on ERP, the ERP dispersion model and the Darlington tracer study. Model evaluation techniques are discussed briefly, and the results of the comparison of model calculations with the field data are presented and reviewed.

  15. Quantification of methane emissions from 15 Danish landfills using the mobile tracer dispersion method

    Energy Technology Data Exchange (ETDEWEB)

    Mønster, Jacob [Department of Environmental Engineering, Technical University of Denmark, Miljøvej – Building 113, DK-2800 Lyngby (Denmark); Samuelsson, Jerker, E-mail: jerker.samuelsson@fluxsense.se [Chalmers University of Technology/FluxSense AB, SE-41296 Göteborg (Sweden); Kjeldsen, Peter [Department of Environmental Engineering, Technical University of Denmark, Miljøvej – Building 113, DK-2800 Lyngby (Denmark); Scheutz, Charlotte, E-mail: chas@env.dtu.dk [Department of Environmental Engineering, Technical University of Denmark, Miljøvej – Building 113, DK-2800 Lyngby (Denmark)

    2015-01-15

    Highlights: • Quantification of whole landfill site methane emission at 15 landfills. • Multiple on-site source identification and quantification. • Quantified methane emission from shredder waste and composting. • Large difference between measured and reported methane emissions. - Abstract: Whole-site methane emissions from 15 Danish landfills were assessed using a mobile tracer dispersion method with either Fourier transform infrared spectroscopy (FTIR), using nitrous oxide as a tracer gas, or cavity ring-down spectrometry (CRDS), using acetylene as a tracer gas. The landfills were chosen to represent the different stages of the lifetime of a landfill, including open, active, and closed covered landfills, as well as those with and without gas extraction for utilisation or flaring. Measurements also included landfills with biocover for oxidizing any fugitive methane. Methane emission rates ranged from 2.6 to 60.8 kg h{sup −1}, corresponding to 0.7–13.2 g m{sup −2} d{sup −1}, with the largest emission rates per area coming from landfills with malfunctioning gas extraction systems installed, and the smallest emission rates from landfills closed decades ago and landfills with an engineered biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41–81%. Landfills where shredder waste was deposited showed significant methane emissions, with the largest emission from newly deposited shredder waste. The average methane emission from the landfills was 154 tons y{sup −1}. This average was obtained from a few measurement campaigns conducted at each of the 15 landfills and extrapolating to annual emissions requires more measurements. Assuming that these landfills are representative of the average Danish landfill, the total emission from Danish landfills were calculated at 20,600 tons y{sup −1}, which is significantly lower than the 33,300 tons y{sup −1} estimated for the national greenhouse gas inventory for

  16. Lagrangian Particle Dispersion Model Intercomparison and Evaluation Utilizing Measurements from Controlled Tracer Release Experiments

    Science.gov (United States)

    Hegarty, J. D.; Draxler, R.; Stein, A. F.; Brioude, J.; Eluszkiewicz, J.; Mountain, M.; Nehrkorn, T.; Andrews, A. E.

    2012-12-01

    The accuracy of greenhouse gas (GHG) fluxes estimated using inverse methods is highly dependent on the fidelity of the atmospheric transport model employed. Lagrangian particle dispersion models (LPDMs) driven by customized meteorological output from mesoscale models have emerged as a powerful tool in inverse GHG estimates at policy-relevant regional and urban scales, for several reasons: 1) Mesoscale meteorology can be available at higher resolution than in most global models, and therefore has the potential to be more realistic, 2) the Lagrangian approach minimizes numerical diffusion present in Eulerian models and is thus better able to represent transport in the near-field of measurement locations, and 3) the Lagrangian approach offers an efficient way to compute the grid-scale adjoint of the transport model ("footprints") by running transport backwards in time. Motivated by these considerations, we intercompare three widely used LPDMs (HYSPLIT, STILT, and FLEXPART) driven by identical meteorological input from the Weather Research and Forecasting (WRF) model against measurements from the controlled tracer release experiments (ready-testbed.arl.noaa.gov/HYSPLIT_datem.php). Our analysis includes statistical assessments of each LPDM in terms of its ability to simulate the observed tracer concentrations, reversibility, and sensitivity to the WRF configuration, particularly with regard to the simulation of the planetary boundary layer.

  17. Skyscraper rooftop tracer concentration observations in Manhattan and comparisons with urban dispersion models

    Science.gov (United States)

    Hanna, Steven; Chang, Joseph

    2015-04-01

    This paper focuses on the observed and model-predicted rooftop concentrations on very tall buildings at distances less than a few hundred meters downwind of near-surface releases in built-up urban centers. These results are important when public health must be protected in populated urban areas with deliberate or accidental releases of toxic chemicals, or with significant traffic emissions. Observations of tracer concentrations taken at seven samplers on skyscraper rooftops (113 m SCIPUFF model. There is a general tendency towards an underprediction of the rooftop concentrations and a slightly smaller underprediction of the surface concentrations. The median ratio of rooftop to surface concentrations is underpredicted by most of the meteorology-urban module options, with much scatter for all options. These results underline the need to better parameterize the dispersion of plumes in the street canyons and recirculating eddies around tall buildings.

  18. Iterative ensemble Kalman filter for atmospheric dispersion in nuclear accidents: An application to Kincaid tracer experiment.

    Science.gov (United States)

    Zhang, X L; Su, G F; Chen, J G; Raskob, W; Yuan, H Y; Huang, Q Y

    2015-10-30

    Information about atmospheric dispersion of radionuclides is vitally important for planning effective countermeasures during nuclear accidents. Results of dispersion models have high spatial and temporal resolutions, but they are not accurate enough due to the uncertain source term and the errors in meteorological data. Environmental measurements are more reliable, but they are scarce and unable to give forecasts. In this study, our newly proposed iterative ensemble Kalman filter (EnKF) data assimilation scheme is used to combine model results and environmental measurements. The system is thoroughly validated against the observations in the Kincaid tracer experiment. The initial first-guess emissions are assumed to be six magnitudes underestimated. The iterative EnKF system rapidly corrects the errors in the emission rate and wind data, thereby significantly improving the model results (>80% reduction of the normalized mean square error, r=0.71). Sensitivity tests are conducted to investigate the influence of meteorological parameters. The results indicate that the system is sensitive to boundary layer height. When the heights from the numerical weather prediction model are used, only 62.5% of reconstructed emission rates are within a factor two of the actual emissions. This increases to 87.5% when the heights derived from the on-site observations are used.

  19. Local study of pollutants dispersion by a real time tracer method; Etude locale de la dispersion de polluants par une methode de tracage en temps reel

    Energy Technology Data Exchange (ETDEWEB)

    Faivre-Pierret, R.X.; Sestier-Carlin, R.; Berne, P.

    1992-12-31

    It is possible to use a Gaussian mathematical model of atmospheric dispersion for calculating atmospheric transfer coefficient (ATC) in long range model, but for proximity models, an experimental model using a tracer technic has to take in account ground effects and natural or artificial obstacles. SF{sub 6} tracer method gives the true plume ground trace in real time. The measured ATC shows a larger ground trace, lower concentration in the axis, and a displacement of the maximum concentration with regard to wind axis in comparison with the calculated ATC. (A.B.). 14 refs., 4 figs., 1 tab.

  20. Iterative ensemble Kalman filter for atmospheric dispersion in nuclear accidents: An application to Kincaid tracer experiment

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.L.; Su, G.F.; Chen, J.G. [Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Raskob, W. [Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology, Karlsruhe, D-76021 (Germany); Yuan, H.Y., E-mail: hy-yuan@outlook.com [Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Huang, Q.Y. [Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

    2015-10-30

    Highlights: • We integrate the iterative EnKF method into the POLYPHEMUS platform. • We thoroughly evaluate the data assimilation system against the Kincaid dataset. • The data assimilation system substantially improves the model predictions. • More than 60% of the retrieved emissions are within a factor two of actual values. • The results reveal that the boundary layer height is the key influential factor. - Abstract: Information about atmospheric dispersion of radionuclides is vitally important for planning effective countermeasures during nuclear accidents. Results of dispersion models have high spatial and temporal resolutions, but they are not accurate enough due to the uncertain source term and the errors in meteorological data. Environmental measurements are more reliable, but they are scarce and unable to give forecasts. In this study, our newly proposed iterative ensemble Kalman filter (EnKF) data assimilation scheme is used to combine model results and environmental measurements. The system is thoroughly validated against the observations in the Kincaid tracer experiment. The initial first-guess emissions are assumed to be six magnitudes underestimated. The iterative EnKF system rapidly corrects the errors in the emission rate and wind data, thereby significantly improving the model results (>80% reduction of the normalized mean square error, r = 0.71). Sensitivity tests are conducted to investigate the influence of meteorological parameters. The results indicate that the system is sensitive to boundary layer height. When the heights from the numerical weather prediction model are used, only 62.5% of reconstructed emission rates are within a factor two of the actual emissions. This increases to 87.5% when the heights derived from the on-site observations are used.

  1. Surfzone monitoring using rotary wing unmanned aerial vehicles

    NARCIS (Netherlands)

    Brouwer, R.L.; De Schipper, M.A.; Rynne, P.F.; Graham, F.J.; Reniers, A.J.H.M.; Macmahan, J.H.

    2015-01-01

    This study investigates the potential of rotary wing unmanned aerial vehicles (UAVs) to monitor the surfzone. This paper shows that these UAVs are extremely flexible surveying platforms that can gather nearcontinuous moderate spatial resolution and high temporal resolution imagery from a fixed posit

  2. Surfzone monitoring using rotary wing unmanned aerial vehicles

    NARCIS (Netherlands)

    Brouwer, R.L.; De Schipper, M.A.; Rynne, P.F.; Graham, F.J.; Reniers, A.J.H.M.; Macmahan, J.H.

    2015-01-01

    This study investigates the potential of rotary wing unmanned aerial vehicles (UAVs) to monitor the surfzone. This paper shows that these UAVs are extremely flexible surveying platforms that can gather nearcontinuous moderate spatial resolution and high temporal resolution imagery from a fixed

  3. Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

    Energy Technology Data Exchange (ETDEWEB)

    Hensel, F.; Rohde, U.

    1998-10-01

    The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H{sub 2}O{sub 2}. Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J{sub gas}{approx}5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j{sub gas} and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H{sub 2}O{sub 2} disintegration and low gas superficial velocities. (orig.)

  4. Greenhouse gas emission quantification from wastewater treatment plants, using a tracer gas dispersion method

    DEFF Research Database (Denmark)

    Delre, Antonio; Mønster, Jacob; Scheutz, Charlotte

    2017-01-01

    Plant-integrated methane (CH4) and nitrous oxide (N2O) emission quantifications were performed at five Scandinavian wastewater treatment plants, using a ground-based remote sensing approach that combines a controlled release of tracer gas from the plant with downwind concentration measurements. C...

  5. Tracer gas experiment to verify the dispersion from a tall stack

    Energy Technology Data Exchange (ETDEWEB)

    Sivertsen, B. [Norwegian Inst. for Air Research, Kjeller (Norway); Irwin, J.S. [National Oceanic and Atmospheric Administration, Research Triangle Park, NC (United States)

    1996-12-31

    At the request of the Ministerios de Obras Publicas y Urbanismo (MOPU) in Madrid, the Norwegian Institute for Air Research (NILU) planned and carried out a comprehensive field experiment at the Andorra (Teruel) power plant in Spain. All together, eleven releases of sulfur hexafluoride (SF6) tracer were carried out at the 1,200 MW electric coal fired power plant. The tracer was emitted into the atmosphere from the 343 m high stack, stack exit diameter of 9 m. The stack gas emission characteristics were nearly constant during the period having an exit temperature of 175.1 C (1.9), exit velocity of 35.5 m/s (0.14) and sulfur dioxide (SO{sub 2}) emission rate of 46.1 {times} 10{sup 3} kg/hr (5.15 {times} 10{sup 3}); standard deviations are listed in parentheses. Samples were taken at the surface along sampling arcs located approximately 8, 23, 43 and 75 km downwind. The releases were undertaken during typical late spring daytime conditions. The synoptic weather conditions were dominated by a large high pressure system on the Atlantic, west of Spain. Fronts were passing the area from the north and a low pressure system was developing over central Europe (Germany). Winds at the surface were generally brisk from the northwest at 7 to 12 m/s.

  6. The relation between velocity dispersion and mass in simulated clusters of galaxies: dependence on the tracer and the baryonic physics

    CERN Document Server

    Munari, Emiliano; Borgani, Stefano; Murante, Giuseppe; Fabjan, Dunja

    2013-01-01

    [Abridged] We present an analysis of the relation between the masses of cluster- and group-sized halos, extracted from $\\Lambda$CDM cosmological N-body and hydrodynamic simulations, and their velocity dispersions, at different redshifts from $z=2$ to $z=0$. The main aim of this analysis is to understand how the implementation of baryonic physics in simulations affects such relation, i.e. to what extent the use of the velocity dispersion as a proxy for cluster mass determination is hampered by the imperfect knowledge of the baryonic physics. In our analysis we use several sets of simulations with different physics implemented. Velocity dispersions are determined using three different tracers, DM particles, subhalos, and galaxies. We confirm that DM particles trace a relation that is fully consistent with the theoretical expectations based on the virial theorem and with previous results presented in the literature. On the other hand, subhalos and galaxies trace steeper relations, and with larger values of the n...

  7. A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part 2: Gas Tracer Dispersion

    Science.gov (United States)

    Nelson, Matthew A.; Brown, Michael J.; Halverson, Scot A.; Bieringer, Paul E.; Annunzio, Andrew; Bieberbach, George; Meech, Scott

    2016-12-01

    The Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The first method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model's Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.

  8. Stellar mass versus velocity dispersion as tracer of the lensing signal around bulge-dominated galaxies

    CERN Document Server

    van Uitert, Edo; Franx, Marijn; Gilbank, David G; Gladders, Michael D; Yee, H K C

    2012-01-01

    We present the results of a weak gravitational lensing analysis to determine whether the stellar mass or the velocity dispersion is more closely related to the amplitude of the lensing signal around galaxies - and hence to the projected distribution of dark matter. The lensing signal on scales smaller than the virial radius corresponds most closely to the lensing velocity dispersion in the case of a singular isothermal profile, but is on larger scales also sensitive to the clustering of the haloes. We select over 4000 lens galaxies at a redshift z<0.2 with concentrated (or bulge-dominated) surface brightness profiles from the ~300 square degree overlap between the Red-sequence Cluster Survey 2 (RCS2) and the data release 7 (DR7) of the Sloan Digital Sky Survey (SDSS). We consider both the spectroscopic velocity dispersion and a model velocity dispersion (a combination of the stellar mass, the size and the Sersic index of a galaxy). Comparing the model and spectroscopic velocity dispersion we find that they...

  9. Anisotropy of tracer dispersion in rough model fractures with sheared walls

    CERN Document Server

    Boschan, Alejandro; Ippolito, Irene; Chertcoff, Ricardo; Hulin, Jean-Pierre

    2008-01-01

    Dispersion experiments are compared for two transparent model fractures with identical complementary rough walls but with a relative shear displacement $\\vec{\\delta}$ parallel ($\\vec{\\delta}\\parallel \\vec{U}$) or perpendicular ($\\vec{\\delta} \\perp \\vec{U}$) to the flow velocity $\\vec{U}$. The structure of the mixing front is characterized by mapping the local normalized local transit time $\\bar t(x,y)$ and dispersivity $\\alpha(x,y)$. For $\\vec{\\delta} \\perp \\vec{U}$, displacement fronts display large fingers: their geometry and the distribution of $\\bar t(x,y)U/x$ are well reproduced by assuming parallel channels of hydraulic conductance deduced from the aperture field. For $\\vec{\\delta} \\parallel \\vec{U}$, the front is flatter and $\\alpha(x,y)$ displays a narrow distribution and a Taylor-like variation with $Pe$.

  10. Atmospheric Transport Modeling with 3D Lagrangian Dispersion Codes Compared with SF6 Tracer Experiments at Regional Scale

    Directory of Open Access Journals (Sweden)

    François Van Dorpe

    2007-01-01

    Full Text Available The results of four gas tracer experiments of atmospheric dispersion on a regional scale are used for the benchmarking of two atmospheric dispersion modeling codes, MINERVE-SPRAY (CEA, and NOSTRADAMUS (IBRAE. The main topic of this comparison is to estimate the Lagrangian code capability to predict the radionuclide atmospheric transfer on a large field, in the case of risk assessment of nuclear power plant for example. For the four experiments, the results of calculations show a rather good agreement between the two codes, and the order of magnitude of the concentrations measured on the soil is predicted. Simulation is best for sampling points located ten kilometers from the source, while we note a divergence for more distant points results (difference in concentrations by a factor 2 to 5. This divergence may be explained by the fact that, for these four experiments, only one weather station (near the point source was used on a field of 10 000 km2, generating the simulation of a uniform wind field throughout the calculation domain.

  11. Surfzone currents at Candolim and Miramar beaches of Goa, India: measurements and comparisons

    Digital Repository Service at National Institute of Oceanography (India)

    Yadhunath, E.M.; JayaKumar, S.; Jishad, M.; Gowthaman, R.; Rajasekaran, C.; Pednekar, P.S.

    Measurements in the surfzone current are often carried out using Acoustic Doppler Velocimeters, Electromagnetic current meters, as well as visual observations based on floats A simple approach is used to install an Aanderaa current meter in water...

  12. Tracer gas dispersion in ducts-study of a new compact device using arrays of sonic micro jets

    Energy Technology Data Exchange (ETDEWEB)

    Silva, A.R. [Instituto Nacional de Engenharia e Tecnologia Industrial (INETI), Lisboa (Portugal); Afonso, C.F. [Faculdade de Engenharia, Universidade do Porto Departmento de Mecanica e Gestao Industrial, Porto (Portugal)

    2004-07-01

    One of the most feasible ways to measure duct airflows is by tracer gas techniques, especially for complex situations when the duct lengths are short as well as their access, which makes extremely difficult or impossible other methods to be implemented. One problem associated with the implementation of tracer gas technique when the ducts lengths are short is due to the impossibility of achieving complete mixing of the tracer with airflow and its sampling. In this work, the development of a new device for the injection of tracer gas in ducts is discussed as well as a new tracer-sampling device. The developed injection device has a compact tubular shape, with magnetic fixation to be easy to apply in duct walls. An array of sonic micro jets in counter current direction, with the possibility of angular movement according to its main axle ensures a complete mixing of the tracer in very short distances. The tracer-sampling device, with a very effective integration function, feeds the sampling system for analysis. Both devices were tested in a wind tunnel of approximately 21 m total length. The tests distances between injection and integration device considered were: X/Dh = 22; X/Dh = 4; X/Dh 2; and X/Dh = 1. For very short distances of X/Dh = 2 and X/Dh = 1, semi-empirical expressions were needed. A good reproducibility of airflow rate values was obtained. These preliminary tests showed that the practical implementation of tracer gas techniques in HVAC systems for measuring airflow rates with a very short mixing distance is possible with the devices developed. (author)

  13. Quantfication of longitudinal dispersion by upscaling Brownian motion of tracer displacement in a 3D pore-scale network model

    NARCIS (Netherlands)

    Acharya, R.C.; Dijke, van M.I.J.; Sorbie, K.S.; Zee, van der S.E.A.T.M.; Leijnse, A.

    2007-01-01

    We present a 3D network model with particle tracking to upscale 3D Brownian motion of non-reactive tracer particles subjected to a velocity field in the network bonds, representing both local diffusion and convection. At the intersections of the bonds (nodes) various jump conditions are implemented.

  14. Surfzone wave characteristics during flood tide on the central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    JayaKumar, S.; Jishad, M.; Yadhunath, E.M.; Rajasekaran, C.; Gowthaman, R.; Pednekar, P.S.; Luis, R.; Mehra, P.

    waves by wave method show that surfzone wave-height increased with time during a flood tide and the mean wave period decreased with time up to mid tide and then increased during the rest of the measurement period at Keri and Miramar beaches. At Candolim...

  15. Atmospheric dispersion of an elevated release in a rural environment: Comparison between field SF 6 tracer measurements and computations of Briggs and ADMS models

    Science.gov (United States)

    Connan, O.; Leroy, C.; Derkx, F.; Maro, D.; Hébert, D.; Roupsard, P.; Rozet, M.

    2011-12-01

    The French Institute for Radiological Protection and Nuclear Safety (IRSN), in collaboration with VEOLIA (French environmental services company), conducted experimental campaigns to study atmospheric dispersion around an Energy Recycling Unit (EUR). The objectives were to study dispersion for an elevated release in a rural environment and to compare results with those of models. The atmospheric dispersion was studied by SF 6 tracer injection into a 40 m high stack. Maximum values of experimental Atmospheric Transfer Coefficients (ATC max) and horizontal dispersion standard deviations ( σh) were compared to predictions from a first generation Briggs gaussian model as well as results from the latest generation ADMS 4.1 gaussian model. In neutral atmospheric conditions, the Briggs and ADMS models are in good agreement with experimental data in terms of ATC and σh. In unstable condition, for σh, both ADMS and Briggs models slightly overestimate the data for winter and summer conditions. In unstable conditions, ADMS and Briggs models overestimated ATC max. The statistical evaluation of the models versus experimental data shows neither models ever meets all of the criteria for good performance. However, statistical evaluation indicates that the ADMS model is more suitable for neutral condition, and that the Briggs model is more reliable for summer unstable conditions.

  16. Experimental and numerical investigation of the internal kinetics of a surf-zone plunging breaker

    DEFF Research Database (Denmark)

    Emarat, Narumon; Forehand, David I.M.; Christensen, Erik Damgaard

    2012-01-01

    Over the last couple of decades both the qualitative and quantitative understanding of breaking waves in the surf zone have greatly increased. This is due to the advances in experimental and numerical techniques. However, few comparisons between these two different investigative techniques...... for surfzone breaking waves have been reported. In this study, a comparison is made between the experimental and numerical investigation of the internal kinematics of a surf-zone plunging breaker. The full-field velocity measuring technique known as Particle Image Velocimetry (PIV) is used in the experiments....... In the hybrid numerical scheme, the main model solves the Navier–Stokes equations using a Finite Volume method and the free-surface is simulated using a Volume of Fluid (VOF) method. An important feature of this work is that, unlike in most other comparisons between numerical and experimental results, the exact...

  17. Design and analysis of tracer tests to determine effective porosity and dispersivity in fractured sedimentary rocks, Newark Basin, New Jersey

    Energy Technology Data Exchange (ETDEWEB)

    Carleton, G.B.; Welty, C.; Buxton, H.T.

    1999-11-01

    Investigations of the transport and fate of contaminants in fractured-rock aquifers require knowledge of aquifer hydraulic and transport characteristics to improve prediction of the rate and direction of movement of contaminated ground water. This report describes an approach to estimating hydraulic and transport properties in fractured-rock aquifers; demonstrates the approach at a sedimentary fractured-rock site in the Newark Basin, N.J.; and provides values for hydraulic and transport properties at the site. The approach has three components: (1) characterization of the hydrogeologic framework of ground-water flow within the rock-fracture network, (2) estimation of the distribution of hydraulic properties (hydraulic conductivity and storage coefficient) within that framework, and (3) estimation of transport properties (effective porosity and dispersivity). The approach includes alternatives with increasingly complex data-collection and analysis techniques.

  18. Design and analysis of tracer tests to determine effective porosity and dispersivity in fractured sedimentary rocks, Newark Basin, New Jersey

    Energy Technology Data Exchange (ETDEWEB)

    Carleton, G.B.; Welty, C.; Buxton, H.T.

    1999-01-01

    Investigations of the transport and fate of contaminants in fractured-rock aquifers require knowledge of aquifer hydraulic and transport characteristics to improve prediction of the rate and direction of movement of contaminated ground water. This report describes an approach to estimating hydraulic and transport properties in fractured-rock aquifers; demonstrates the approach at a sedimentary fractured-rock site in the Newark Basin, N.J.; and provides values for hydraulic and transport properties at the site. The approach has three components: (1) characterization of the hydrogeologic framework of ground-water flow within the rock-fracture network, (2) estimation of the distribution of hydraulic properties (hydraulic conductivity and storage coefficient) within that framework, and (3) estimation of transport properties (effective porosity and dispersivity). The approach includes alternatives with increasingly complex data-collection and analysis techniques.

  19. Biased swimming cells do not disperse in pipes as tracers: a population model based on microscale behaviour

    CERN Document Server

    Bearon, R N; Croze, O A

    2012-01-01

    There is much current interest in modelling suspensions of algae and other micro-organisms for biotechnological exploitation, and many bioreactors are of tubular design. Using generalized Taylor dispersion theory, we develop a population-level swimming-advection-diffusion model for suspensions of micro-organisms in a vertical pipe flow. In particular, a combination of gravitational and viscous torques acting on individual cells can affect their swimming behaviour, which is termed gyrotaxis. This typically leads to local cell drift and diffusion in a suspension of cells. In a flow in a pipe, small amounts of radial drift across streamlines can have a major impact on the effective axial drift and diffusion of the cells. We present a Galerkin method to calculate the local mean swimming velocity and diffusion tensor based on local shear for arbitrary flow rates. This method is validated with asymptotic results obtained in the limits of weak and strong shear. We solve the resultant swimming-advection-diffusion equ...

  20. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  1. Journal: Efficient Hydrologic Tracer-Test Design for Tracer ...

    Science.gov (United States)

    Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection-dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relatipnships that descrive solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for descri

  2. Chemical Tracer Methods: Chapter 7

    Science.gov (United States)

    Healy, Richard W.

    2017-01-01

    Tracers have a wide variety of uses in hydrologic studies: providing quantitative or qualitative estimates of recharge, identifying sources of recharge, providing information on velocities and travel times of water movement, assessing the importance of preferential flow paths, providing information on hydrodynamic dispersion, and providing data for calibration of water flow and solute-transport models (Walker, 1998; Cook and Herczeg, 2000; Scanlon et al., 2002b). Tracers generally are ions, isotopes, or gases that move with water and that can be detected in the atmosphere, in surface waters, and in the subsurface. Heat also is transported by water; therefore, temperatures can be used to trace water movement. This chapter focuses on the use of chemical and isotopic tracers in the subsurface to estimate recharge. Tracer use in surface-water studies to determine groundwater discharge to streams is addressed in Chapter 4; the use of temperature as a tracer is described in Chapter 8.Following the nomenclature of Scanlon et al. (2002b), tracers are grouped into three categories: natural environmental tracers, historical tracers, and applied tracers. Natural environmental tracers are those that are transported to or created within the atmosphere under natural processes; these tracers are carried to the Earth’s surface as wet or dry atmospheric deposition. The most commonly used natural environmental tracer is chloride (Cl) (Allison and Hughes, 1978). Ocean water, through the process of evaporation, is the primary source of atmospheric Cl. Other tracers in this category include chlorine-36 (36Cl) and tritium (3H); these two isotopes are produced naturally in the Earth’s atmosphere; however, there are additional anthropogenic sources of them.

  3. Environmental Tracers

    Directory of Open Access Journals (Sweden)

    Trevor Elliot

    2014-10-01

    Full Text Available Environmental tracers continue to provide an important tool for understanding the source, flow and mixing dynamics of water resource systems through their imprint on the system or their sensitivity to alteration within it. However, 60 years or so after the first isotopic tracer studies were applied to hydrology, the use of isotopes and other environmental tracers are still not routinely necessarily applied in hydrogeological and water resources investigations where appropriate. There is therefore a continuing need to promote their use for developing sustainable management policies for the protection of water resources and the aquatic environment. This Special Issue focuses on the robustness or fitness-for-purpose of the application and use of environmental tracers in addressing problems and opportunities scientifically, to promote their wider use and to address substantive issues of vulnerability, sustainability, and uncertainty in (groundwater resources systems and their management.

  4. Simultaneous Observations of Beach and Surf-Zone Topography from a sUAS

    Science.gov (United States)

    Slocum, R. K.; Brodie, K. L.; Spore, N.

    2016-02-01

    Beaches and surf-zones can vary rapidly in time and space, necessitating frequent, spatially extensive observations for up-to-date knowledge on their current condition. Traditional surveying methods are expensive, can be dangerous in large wave conditions, and can lack sufficient spatial density. Existing remote sensing technologies have focused on both active sensing (airborne lidar, X-band radar) or passive sensing (electro-optical or infrared imagery) to either directly measure elevations of the beach and seafloor or exploit the optical signal of refracting and breaking waves in the surf-zone. These methods, however, can be prohibitively expensive for widespread, high temporal frequency use, or lack the spatial coverage required to quantify a large stretch of beach. UAS offer an affordable and accessible alternative, but existing COTS UAS sensor suites are not optimized for generation of bathymetry and topography at the same time. Here, we present a new approach using an inexpensive, custom multi-camera sensor designed with a wide field of view for integration on either a fixed wing of multirotor UAS platform. We introduce a processing methodology and workflow to generate a topographic pointcloud and rectified imagery of the water surface using structure from motion algorithms. The topographic pointcloud data is processed to generate a DSM of the beach and extract morphologic parameters (beach slope, dune toe, etc). Rectified imagery of the water surface is used to quantify sandbar location as well as perform a celerity based bathymetric inversion. Accuracy of this methodology is calculated by comparing processed data to lidar pointclouds, as well as photo identifiable targets on the beach and jetted into the surf zone. Funded by the USACE Military Engineering POD:A&U Program and Coastal Field Data Collection Program.

  5. Exotic tracers for atmospheric studies

    Energy Technology Data Exchange (ETDEWEB)

    Lovelock, J.E. (Brazzos Ltd., Launceston (UK)); Ferber, G.J. (National Oceanic and Atmospheric Administration, Silver Spring, MD (USA). Air Resources Lab.)

    1982-01-01

    Tracer materials can be injected into the atmosphere to study transport and dispersion processes and to validate air pollution model calculations. Tracers should be inert, non-toxic and harmless to the environment. Tracers for long-range experiments, where dilution is very great, must be measurable at extremely low concentrations, well below the parts per trillion level. Compounds suitable for long-range tracer work are rare and efforts should be made to reserve them for meteorological studies, barring them from commercial uses which would increase atmospheric background concentrations. The use of these exotic tracers, including certain perfluorocarbons and isotopically labelled methanes, should be coordinated within the meteorological community to minimize interferences and maximise research benefits.

  6. Exotic tracers for atmospheric studies

    Science.gov (United States)

    Lovelock, James E.; Ferber, Gilbert J.

    Tracer materials can be injected into the atmosphere to study transport and dispersion processes and to validate air pollution model calculations. Tracers should be inert, non-toxic and harmless to the environment. Tracers for long-range experiments, where dilution is very great, must be measurable at extremely low concentrations, well below the parts per trillion level. Compounds suitable for long-range tracer work are rare and efforts should be made to reserve them for meteorological studies, barring them from commercial uses which would increase atmospheric background concentrations. The use of these exotic tracers, including certain perfluorocarbons and isotopically labelled methanes, should be coordinated within the meteorological community to minimize interferences and maximize research benefits.

  7. Fast hydrodynamic model for medium- and long-term dispersion in seawater in the English Channel and southern North Sea, qualitative and quantitative validation by radionuclide tracers

    Science.gov (United States)

    du Bois, P. Bailly; Dumas, F.

    The database for medium- and long-term model validation using 125Sb released by the La Hague reprocessing plant includes 1400 measurements performed between 1987 and 1994 in the English Channel and the North Sea and data for each release since 1982. Antimony-125 has a conservative behaviour in water masses over a period of several years. These data can be used qualitatively and quantitatively to compare the measured concentrations with the calculated ones and quantities of tracers. Tritium measurements are also available for model calibration. A two-dimensional hydrodynamic model has been developed to allow repetitive long-term simulations. This model uses a database of residual tidal currents calculated using the Lagrangian barycentric method [Salomon, J.C., Guéguéniat, P., Orbi, A., Baron, Y., 1988. A Lagrangian model for long-term tidally induced transport and mixing. Verification by artificial radionuclide concentrations. In: Guary, J.C., Guéguéniat, P., Pentreath, R.J. (Eds.), Radionuclides: A Tool for Oceanography, Cherbourg 1-5 June, 1987. Elsevier Applied Science Publishers, London, New York, pp. 384-394]. The area covered by the model includes the English Channel, the southern North Sea and the Irish Sea with a mesh size of 1 km. The main adjustment parameters of this model are the sources of wind data used and the calculation method for evaluating wind stress at the sea surface. With these parameters, the fluxes of radionuclides and water masses in the English Channel and the North Sea were balanced for the whole period of field measurements (1987-1994). The correlation factor between individual measurements in seawater and calculation results is 0.88 with an average error of ±54%, the error attributable to the measurement process being 15% on average. The mean flux through the Dover Strait is 126,000 m 3 s -1, close from the one obtained from previous studies [Salomon, J.C., Breton, M., Guéguéniat, P. 1993. Computed residual flow through the Dover

  8. Using a Gas-Phase Tracer Test to Characterize the Impact of Landfill Gas Generation on Advective-Dispersive Transport of VOCs in the Vadose Zone.

    Science.gov (United States)

    Monger, Gregg R; Duncan, Candice Morrison; Brusseau, Mark L

    2014-12-01

    A gas-phase tracer test (GTT) was conducted at a landfill in Tucson, AZ, to help elucidate the impact of landfill gas generation on the transport and fate of chlorinated aliphatic volatile organic contaminants (VOCs). Sulfur hexafluoride (SF6) was used as the non-reactive gas tracer. Gas samples were collected from a multiport monitoring well located 15.2 m from the injection well, and analyzed for SF6, CH4, CO2, and VOCs. The travel times determined for SF6 from the tracer test are approximately two to ten times smaller than estimated travel times that incorporate transport by only gas-phase diffusion. In addition, significant concentrations of CH4 and CO2 were measured, indicating production of landfill gas. Based on these results, it is hypothesized that the enhanced rates of transport observed for SF6 are caused by advective transport associated with landfill gas generation. The rates of transport varied vertically, which is attributed to multiple factors including spatial variability of water content, refuse mass, refuse permeability, and gas generation.

  9. Analysis of tracer and thermal transients during reinjection

    Energy Technology Data Exchange (ETDEWEB)

    Kocabas, I.

    1989-10-01

    This work studied tracer and thermal transients during reinjection in geothermal reserviors and developed a new technique which combines the results from interwell tracer tests and thermal injection-backflow tests to estimate the thermal breakthrough times. Tracer tests are essential to determine the degree of connectivity between the injection wells and the producing wells. To analyze the tracer return profiles quantitatively, we employed three mathematical models namely, the convection-dispersion (CD) model, matrix diffusion (MD) model, and the Avodnin (AD) model, which were developed to study tracer and heat transport in a single vertical fracture. We considered three types of tracer tests namely, interwell tracer tests without recirculation, interwell tracer tests with recirculation, and injection-backflow tracer tests. To estimate the model parameters, we used a nonlinear regression program to match tracer return profiles to the solutions.

  10. Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion under Varying Atmospheric Stability Conditions

    Science.gov (United States)

    A roadway toxics dispersion study was conducted by the Field Research Division (FRD) of NOAA at the Idaho National Laboratory (INL) near Idaho Falls, ID to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmosph...

  11. Prediction and assimilation of surf-zone processes using a Bayesian network: Part I: Forward models

    Science.gov (United States)

    Plant, Nathaniel G.; Holland, K. Todd

    2011-01-01

    Prediction of coastal processes, including waves, currents, and sediment transport, can be obtained from a variety of detailed geophysical-process models with many simulations showing significant skill. This capability supports a wide range of research and applied efforts that can benefit from accurate numerical predictions. However, the predictions are only as accurate as the data used to drive the models and, given the large temporal and spatial variability of the surf zone, inaccuracies in data are unavoidable such that useful predictions require corresponding estimates of uncertainty. We demonstrate how a Bayesian-network model can be used to provide accurate predictions of wave-height evolution in the surf zone given very sparse and/or inaccurate boundary-condition data. The approach is based on a formal treatment of a data-assimilation problem that takes advantage of significant reduction of the dimensionality of the model system. We demonstrate that predictions of a detailed geophysical model of the wave evolution are reproduced accurately using a Bayesian approach. In this surf-zone application, forward prediction skill was 83%, and uncertainties in the model inputs were accurately transferred to uncertainty in output variables. We also demonstrate that if modeling uncertainties were not conveyed to the Bayesian network (i.e., perfect data or model were assumed), then overly optimistic prediction uncertainties were computed. More consistent predictions and uncertainties were obtained by including model-parameter errors as a source of input uncertainty. Improved predictions (skill of 90%) were achieved because the Bayesian network simultaneously estimated optimal parameters while predicting wave heights.

  12. Spatial and temporal variations of diurnal ichthyofauna on surf-zone of São Francisco do Itabapoana beaches, Rio de Janeiro State, Brazil

    Directory of Open Access Journals (Sweden)

    Gomes Marcelo Paes

    2003-01-01

    Full Text Available Spatial and temporal variations of diurnal ichthyofauna and the environmental variables influences on its distribution were studied at the surf-zone of three beaches of São Francisco do Itabapoana, northern coast of Rio de Janeiro, Brazil. From August/1999 to August/2000, three beach seine hauls were made monthly, and environmental variables were recorded. A total number of 4,562 fishes (74,155g were sampled at the three beaches, where estuarine-dependent species prevailed (44%, followed by marine (31%, estuarine (19% and freshwater species (3%. Species richness, number of individuals and wet weight were significantly higher at Gargaú, followed by Manguinhos and Barra do Itabapoana, respectively. Canonical Correspondence Analysis highlighted influences of the rivers flushing, salinity and plant abundance on the diurnal ichthyofauna distribution and dynamics of São Francisco do Itabapoana surf-zone.

  13. The design and implementation of a semi-autonomous surf-zone robot using advanced sensors and a common robot operating system

    OpenAIRE

    Hickle, Jason.; Halle, Steven

    2011-01-01

    Approved for public release; distribution is unlimited. A semi-autonomous vehicle, MONTe, was designed, modeled and tested for deployment and operation in a surf-zone coastal environment. The MONTe platform was designed to use unique land based locomotion that incorporates wheel-legs(WhegsTM) and a tail. Semi-autonomy was realized with data from onboard sensors and implemented through open source Robot Operating System (ROS), hosted on an Ubuntu Linux based processor. Communications vi...

  14. Packet Tracer network simulator

    CERN Document Server

    Jesin, A

    2014-01-01

    A practical, fast-paced guide that gives you all the information you need to successfully create networks and simulate them using Packet Tracer.Packet Tracer Network Simulator is aimed at students, instructors, and network administrators who wish to use this simulator to learn how to perform networking instead of investing in expensive, specialized hardware. This book assumes that you have a good amount of Cisco networking knowledge, and it will focus more on Packet Tracer rather than networking.

  15. Structural aspects of the surf-zone fish assemblage at King's Beach, Algoa Bay, South Africa: Long-term fluctuations

    Science.gov (United States)

    Lasiak, Theresa A.

    1984-04-01

    Regular collections of fish were obtained from the surf-zone at King's Beach, Algoa Bay. A total of 3970 fish, representing 50 species was caught with a coarse net and 16 857 fish, representing 37 species, were caught with a fine net. Predominant species were the blacktail, Diplodus sargus; the sand steenbras, Lithognathus mormyrus; the mullet, Liza richardsoni; the gorrie, Pomadasys olivaceum; the white stumpnose, Rhabdosargus globiceps; the sandshark, Rhinobatos annulatus; and the streepie, Sarpa salpa. No seasonal trends were discernible in the overall abundance or species diversity. The species composition of the dominant component of the fish assemblage varied considerably. This indicated instability in the community structure and cast doubts on the applicability of a classic community concept and the use of diversity indices. Neither classification nor correspondence analysis were of any use in identifying a characteristic species component. Multiple regression analysis indicated that short-term variations in wind conditions might be a primary determinant of fluctuations in abundance. The lack of seasonality in the community parameters may reflect the fact that short-term variability masks seasonal perturbations.

  16. Geologic flow characterization using tracer techniques

    Energy Technology Data Exchange (ETDEWEB)

    Klett, R. D.; Tyner, C. E.; Hertel, Jr., E. S.

    1981-04-01

    A new tracer flow-test system has been developed for in situ characterization of geologic formations. This report describes two sets of test equipment: one portable and one for testing in deep formations. Equations are derived for in situ detector calibration, raw data reduction, and flow logging. Data analysis techniques are presented for computing porosity and permeability in unconfined isotropic media, and porosity, permeability and fracture characteristics in media with confined or unconfined two-dimensional flow. The effects of tracer pulse spreading due to divergence, dispersion, and porous formations are also included.

  17. CityFlux perfluorocarbon tracer experiments

    Science.gov (United States)

    Petersson, F. K.; Martin, D.; White, I. R.; Henshaw, S. J.; Nickless, G.; Longley, I.; Percival, C. J.; Gallagher, M.; Shallcross, D. E.

    2010-07-01

    In June 2006, two perfluorocarbon tracer experiments were conducted in central Manchester UK as part of the CityFlux campaign. The main aim was to investigate vertical dispersion in an urban area during convective conditions, but dispersion mechanisms within the street network were also studied. Paired receptors were used in most cases where one receptor was located at ground level and one at roof level. One receptor was located on the roof of Portland Tower which is an 80 m high building in central Manchester. Source receptor distances in the two experiments varied between 120 and 600 m. The results reveal that maximum concentration was sometimes found at roof level rather than at ground level implying the effectiveness of convective forces on dispersion. The degree of vertical dispersion was found to be dependent on source receptor distance as well as on building height in proximity to the release site. Evidence of flow channelling in a street canyon was also found. Both a Gaussian profile and a street network model were applied and the results show that the urban topography may lead to highly effective flow channelling which therefore may be a very important dispersion mechanism should the right meteorological conditions prevail. The experimental results from this campaign have also been compared with a simple urban dispersion model that was developed during the DAPPLE framework and show good agreement with this. The results presented here are some of the first published regarding vertical dispersion. More tracer experiments are needed in order to further characterise vertical concentration profiles and their dependence on, for instance, atmospheric stability. The impact of urban topography on pollutant dispersion is important to focus on in future tracer experiments in order to improve performance of models as well as for our understanding of the relationship between air quality and public health.

  18. CityFlux perfluorocarbon tracer experiments

    Directory of Open Access Journals (Sweden)

    F. K. Petersson

    2010-01-01

    Full Text Available In June 2006, two perfluorocarbon tracer experiments were conducted in central Manchester UK as part of the CityFlux campaign. The main aim was to investigate vertical dispersion in an urban area during convective conditions, but dispersion mechanisms within the street network were also studied. Paired receptors were used in most cases where one receptor was located at ground level and one at roof level. One receptor was located on the roof of Portland Tower which is an 80 m high building in central Manchester. Source receptor distances in the two experiments varied between 120 and 600 m.

    The results reveal that maximum concentration was sometimes found at roof level rather than at ground level implying the effectiveness of convective forces on dispersion. The degree of vertical dispersion was found to be dependent on source receptor distance as well as on building height in proximity to the release site.

    Evidence of flow channelling in a street canyon was also found. Both a Gaussian profile and a street network model were applied and the results show that the urban topography may lead to highly effective flow channelling which therefore may be a very important dispersion mechanism should the right meteorological conditions prevail.

    The experimental results from this campaign have also been compared with a simple urban dispersion model that was developed during the DAPPLE framework and show good agreement with this.

    The results presented here are some of the first published regarding vertical dispersion. More tracer experiments are needed in order to further characterise vertical concentration profiles and their dependence on, for instance, atmospheric stability. The impact of urban topography on pollutant dispersion is important to focus on in future tracer experiments in order to improve performance of models as well as for our understanding of the relationship between air quality and public health.

  19. CityFlux perfluorocarbon tracer experiments

    Directory of Open Access Journals (Sweden)

    F. K. Petersson

    2010-07-01

    Full Text Available In June 2006, two perfluorocarbon tracer experiments were conducted in central Manchester UK as part of the CityFlux campaign. The main aim was to investigate vertical dispersion in an urban area during convective conditions, but dispersion mechanisms within the street network were also studied. Paired receptors were used in most cases where one receptor was located at ground level and one at roof level. One receptor was located on the roof of Portland Tower which is an 80 m high building in central Manchester. Source receptor distances in the two experiments varied between 120 and 600 m.

    The results reveal that maximum concentration was sometimes found at roof level rather than at ground level implying the effectiveness of convective forces on dispersion. The degree of vertical dispersion was found to be dependent on source receptor distance as well as on building height in proximity to the release site.

    Evidence of flow channelling in a street canyon was also found. Both a Gaussian profile and a street network model were applied and the results show that the urban topography may lead to highly effective flow channelling which therefore may be a very important dispersion mechanism should the right meteorological conditions prevail.

    The experimental results from this campaign have also been compared with a simple urban dispersion model that was developed during the DAPPLE framework and show good agreement with this.

    The results presented here are some of the first published regarding vertical dispersion. More tracer experiments are needed in order to further characterise vertical concentration profiles and their dependence on, for instance, atmospheric stability. The impact of urban topography on pollutant dispersion is important to focus on in future tracer experiments in order to improve performance of models as well as for our understanding of the relationship between air quality and public health.

  20. Tracer attenuation in groundwater

    Science.gov (United States)

    Cvetkovic, Vladimir

    2011-12-01

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e., irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  1. Observations and modeling of a tidal inlet dye tracer plume

    Science.gov (United States)

    Feddersen, Falk; Olabarrieta, Maitane; Guza, R. T.; Winters, D.; Raubenheimer, Britt; Elgar, Steve

    2016-10-01

    A 9 km long tracer plume was created by continuously releasing Rhodamine WT dye for 2.2 h during ebb tide within the southern edge of the main tidal channel at New River Inlet, NC on 7 May 2012, with highly obliquely incident waves and alongshore winds. Over 6 h from release, COAWST (coupled ROMS and SWAN, including wave, wind, and tidal forcing) modeled dye compares well with (aerial hyperspectral and in situ) observed dye concentration. Dye first was transported rapidly seaward along the main channel and partially advected across the ebb-tidal shoal until reaching the offshore edge of the shoal. Dye did not eject offshore in an ebb-tidal jet because the obliquely incident breaking waves retarded the inlet-mouth ebb-tidal flow and forced currents along the ebb shoal. The dye plume largely was confined to <4 m depth. Dye was then transported downcoast in the narrow (few 100 m wide) surfzone of the beach bordering the inlet at 0.3 m s-1 driven by wave breaking. Over 6 h, the dye plume is not significantly affected by buoyancy. Observed dye mass balances close indicating all released dye is accounted for. Modeled and observed dye behaviors are qualitatively similar. The model simulates well the evolution of the dye center of mass, lateral spreading, surface area, and maximum concentration, as well as regional ("inlet" and "ocean") dye mass balances. This indicates that the model represents well the dynamics of the ebb-tidal dye plume. Details of the dye transport pathways across the ebb shoal are modeled poorly perhaps owing to low-resolution and smoothed model bathymetry. Wave forcing effects have a large impact on the dye transport.

  2. Application of neutron activation tracer sediment technique on environmental science

    Institute of Scientific and Technical Information of China (English)

    YinYi; ZhongWei-Ni; 等

    1997-01-01

    Field and laboratory inverstigations were carried out to study the transport and dispersion law of polluted sediments near wastewater outlet using neutron activation tracer technique.The direction of transport and dispersion of polluted sediments,dispersion amount in different directions,sedimentary region of polluted sediment and evaluation of polluted risk are given.This provided a new test method for the study of environmental science and added a new forecasted content for the evaluation of environmental influence.

  3. Rates of Gravel Dispersion

    Science.gov (United States)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  4. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum...... BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground Sources. Turbulence measurements LIP to 3-5 times the building height Lire needed for direct use in dispersion Calculations....

  5. Tracer injection techniques in flowing surface water

    Science.gov (United States)

    Wörman, A.

    2009-04-01

    Residence time distributions for flowing water and reactive matter are commonly used integrated properties of the transport process for determining technical issues of water resource management and in eco-hydrological science. Two general issues for tracer techniques are that the concentration-vs-time relation following a tracer injection (the breakthrough curve) gives unique transport information in different parts of the curve and separation of hydromechanical and reactive mechanisms often require simultaneous tracer injections. This presentation discusses evaluation methods for simultaneous tracer injections based on examples of tracer experiments in small rivers, streams and wetlands. Tritiated water is used as a practically inert substance to reflect the actual hydrodynamics, but other involved tracers are Cr(III)-51, P-32 and N-15. Hydromechanical, in-stream dispersion is reflected as a symmetrical spreading of the spatial concentration distribution. This requires that the transport distance over water depth is larger than about five times the flow Peclet number. Transversal retention of both inert and reactive solutes is reflected in terms of the tail of the breakthrough curve. Especially, reactive solutes can have a substantial magnification of the tailing behaviour depending on reaction rates or partitioning coefficients. To accurately discriminate between the effects of reactions and hydromechanical mixing its is relevant to use simultaneous injections of inert and reactive tracers with a sequential or integrated evaluation procedure. As an example, the slope of the P-32 tailing is consistently smaller than that of a simultaneous tritium injection in Ekeby wetland, Eskilstuna. The same applies to N-15 injected in the same experiment, but nitrogen is affected also by a systematic loss due to denitrification. Uptake in stream-bed sediments can be caused by a pumping effect arising when a variable pressure field is created on the stream bottom due to bed

  6. Distribution and sources of surfzone bacteria at Huntington Beach before and after disinfection on an ocean outfall - A frequency-domain analysis

    Science.gov (United States)

    Noble, M.A.; Xu, J. P.; Robertson, G.L.; Rosenfeld, L.K.

    2006-01-01

    Fecal indicator bacteria (FIB) were measured approximately 5 days a week in ankle-depth water at 19 surfzone stations along Huntington Beach and Newport Beach, California, from 1998 to the end of 2003. These sampling periods span the time before and after treated sewage effluent, discharged into the coastal ocean from the local outfall, was disinfected. Bacterial samples were also taken in the vicinity of the outfall during the pre- and post-disinfection periods. Our analysis of the results from both data sets suggest that land-based sources, rather than the local outfall, were the source of the FIB responsible for the frequent closures and postings of local beaches in the summers of 2001 and 2002. Because the annual cycle is the dominant frequency in the fecal and total coliform data sets at most sampling stations, we infer that sources associated with local runoff were responsible for the majority of coliform contamination along wide stretches of the beach. The dominant fortnightly cycle in enterococci at many surfzone sampling stations suggests that the source for these relatively frequent bacteria contamination events in summer is related to the wetting and draining of the land due to the large tidal excursions found during spring tides. Along the most frequently closed section of the beach at stations 3N-15N, the fortnightly cycle is dominant in all FIBs. The strikingly different spatial and spectral patterns found in coliform and in enterococci suggest the presence of different sources, at least for large sections of beach. The presence of a relatively large enterococci fortnightly cycle along the beaches near Newport Harbor indicates that contamination sources similar to those found off Huntington Beach are present, though not at high enough levels to close the Newport beaches. ?? 2006 Elsevier Ltd. All rights reserved.

  7. Transport and Dispersion Model Predictions of Elevated Source Tracer Experiments in the Copenhagen Area: Comparisons of Hazard Prediction and Assessment Capability (HPAC) and National Atmospheric Release Advisory Center (NARAC) Emergency Response Model Predictions

    Science.gov (United States)

    2006-07-01

    before the sampling arcs for these elevated releases. Based on this study, we recommend that the HPAC/ SCIPUFF developer reexamine the algorithm and...Integrated Puff Model ( SCIPUFF ) • Lagrangian model that uses Gaussian puff method; turbulent dispersion parameterization is based on second-order closure...error # 99 in the .log file from the SCIPUFF Weather Input Model (SWIM)]. We speculate that the cause of this error is the absence of any co-located

  8. Interpretation of Water Tracer Simulation in the H-1 Segment of the Gullfaks Field

    Energy Technology Data Exchange (ETDEWEB)

    Moid, Farrukh

    2000-07-01

    This thesis describes the water tracer simulation in the H-1 segment of the Gullfaks field. Three passive water tracer slugs were injected from the two producing wells during water flooding, pressure maintenance and reservoir monitoring program in the Gullfaks field. The same program is considered in this thesis. Computer Modelling Group's (CMG) simulator STARS is used for the general reservoir simulation and a separate module for tracer flow (ITRC-SIM) which is incorporated in the STARS and developed at Institute For Energy (IFE) is used for the tracer simulation. Water cut and tracer concentration data are used in history matching of the field. History matching is performed by changing the transmissibility and permeability of different layers; also the effect of changing saturations near the well bore on history matching is examined. It is noted that water cut is sensitive to transmissibility of the layers and the saturation around the well bore. Tracers are found to be moving in the most permeable layers. The corresponding history matching of water and tracer production shows a severe loss of first tracer injected because of imbibition process. Water phase velocity and areal communication between different wells are determined. Advance numerical features of tracer module ITRC-SIM such as flux limiting scheme and grid refinement scheme are evaluated and are found to be an important tool for reducing the numerical smearing. The effects of dispersion and diffusion on tracer response curve are also evaluated. Dispersion makes the tracer concentration curve smeared. Simulation results of water cut and tracer concentration show a good history match for this reservoir. The improved simulation model and the tracer module for this reservoir can be used for the prediction of future performance of the reservoir and interpretation of the tracer behaviour in the reservoir. (author)

  9. Tracer tomography (in) rocks!

    Science.gov (United States)

    Somogyvári, Márk; Jalali, Mohammadreza; Jimenez Parras, Santos; Bayer, Peter

    2016-04-01

    Physical behavior of fractured aquifers is rigorously controlled by the presence of interconnected conductive fractures, as they represent the main pathways for flow and transport. Ideally, they are simulated as a discrete fracture network (DFN) in a model to capture the role of fracture system geometry, i.e. fracture length, height, and width (aperture/transmissivity). Such network may be constrained by prior geological information or direct data resources such as field mapping, borehole logging and geophysics. With the many geometric features, however, calibration of a DFN to measured data is challenging. This is especially the case when spatial properties of a fracture network need to be calibrated to flow and transport data. One way to increase the insight in a fractured rock is by combining the information from multiple field tests. In this study, a tomographic configuration that combines multiple tracer tests is suggested. These tests are conducted from a borehole with different injection levels that act as sources. In a downgradient borehole, the tracer is recorded at different levels or receivers, in order to maximize insight in the spatial heterogeneity of the rock. As tracer here we chose heat, and temperature breakthrough curves are recorded. The recorded tracer data is inverted using a novel stochastic trans-dimensional Markov Chain Monte Carlo procedure. An initial DFN solution is generated and sequentially modified given available geological information, such as expected fracture density, orientation, length distribution, spacing and persistency. During this sequential modification, the DFN evolves in a trans-dimensional inversion space through adding and/or deleting fracture segments. This stochastic inversion algorithm requires a large number of thousands of model runs to converge, and thus using a fast and robust forward model is essential to keep the calculation efficient. To reach this goal, an upwind coupled finite difference method is employed

  10. Development of radioisotope tracer technology

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Joon Ha; Lee, Myun Joo; Jung, Sung Hee; Park, Soon Chul; Lim, Dong Soon; Kim, Jae Ho; Lee, Jae Choon; Lee, Doo Sung; Cho, Yong Suk; Shin, Sung Kuan

    2000-04-01

    The purpose of this study is to develop the radioisotope tracer technology, which can be used in solving industrial and environmental problems and to build a strong tracer group to support the local industries. In relation to the tracer technology in 1999, experiments to estimate the efficiencies of a sludge digester of a waste water treatment plant and a submerged biological reactor of a dye industry were conducted. As a result, the tracer technology for optimization of facilities related to wastewater treatment has been developed and is believed to contribute to improve their operation efficiency. The quantification of the experimental result was attempted to improve the confidence of tracer technology by ECRIN program which basically uses the MCNP simulation principle. Using thin layer activation technique, wear of tappet shim was estimated. Thin layer surface of a tappet shim was irradiated by proton beam and the correlation between the measured activity loss and the amount of wear was established. The equipment was developed to adjust the energy of proton which collides with the surface of tappet. The tracer project team has participated into the tracer test for estimating the efficiency of RFCC system in SK cooperation. From the experiment the tracer team has obtained the primary elements to be considered for judging the efficiency of RFCC unit. By developing the tracer techniques to test huge industrial units like RFCC, the tracer team will be able to support the local industries that require technical services to solve any urgent trouble. (author)

  11. Quantifying solute transport processes: are chemically "conservative" tracers electrically conservative?

    Science.gov (United States)

    Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.

    2012-01-01

    The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.

  12. Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, June 1--December 31, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Stetzenbach, K.J.

    1990-12-31

    Ground water tracers are solutes dissolved in or carried by ground water to delineate flow pathways. Tracers provide information on direction and speed of water movement and that of contaminants that might be conveyed by the water. Tracers can also be used to measure effective porosity, hydraulic conductivity, dispersivity and solute distribution coefficients. For most applications tracers should be conservative, that is, move at the same rate as the water and not sorb to aquifer materials. Tracers must have a number of properties to be functional. Regardless of the desired properties, the chemical and physical behavior of a tracer in ground water and the porous medium under study must be understood. Good estimates of tracer behavior can be obtained from laboratory studies. Studies in this proposal will address tracer properties with analytical method development, static sorption and degradation studies and column transport studies, Mutagenicity tests will be performed on promising candidates. The tracers that will be used for these experiments are fluorinated organic acids and other organic compounds that have the chemical and biological stability necessary to be effective in the Yucca Mountain environment. Special emphasis will be placed on compounds that fluoresce or have very large ultraviolet absorption coefficients for very high analytical sensitivity.

  13. Radon as geological tracer

    Energy Technology Data Exchange (ETDEWEB)

    Lacerda, T.; Anjos, R.M. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Fisica; Valladares, D.L.; Rizzotto, M.; Velasco, H.; Ayub, J. Juri [Universidad Nacional de San Luis (Argentina). Inst. de Matematica Aplicada San Luis (IMASL); Silva, A.A.R. da; Yoshimura, E.M. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica

    2012-07-01

    Full text: This work presents measurements of {sup 222}Rn levels performed in La Carolina gold mine and Los Condores tungsten mine at the province of San Luis, Argentina, today used for tourist visitation, and can evaluate the potential use of such radioactive noble gas as tracer or marker for geological processes in underground environments. By concentrations of {sup 40}K, {sup 232}Th and {sup 23}'8U were also measured in the walls of tunnels were determined the rocks mineral composition, what indicated that the mines have the same composition. In this sense, we used nuclear trace plastic detectors CR-39, gamma spectrometry of rock samples and Geiger-Muller (GM) monitors The patterns of radon gas transportation processes revealed that La Carolina could be interpreted through a model based on a radioactive gas confined into a single entrance tube, with constant cross section and air velocity. Los Condores, which has a second main entrance, could be interpreted through a model based on a radioactive gas confined into a two entrance tube, allowing a chimney effect for air circulation. The results showed the high potential of using {sup 222}Rn as a geological tracer. In what concerns the occupational hazard, in summer (time of more intense tourist activity in the mine) La Carolina presented a mean concentration of the radioactive noble gas that exceeds in four times the action level of 1,5 kBq m{sup -3} recommended by the International Commission of Radiological Protection (ICRP). The chimney effect shows the low mean concentration of radon in Los Condores. (author)

  14. Effects of crude oil on water and tracer movement in the unsaturated and saturated zones

    Science.gov (United States)

    Delin, Geoffrey N.; Herkelrath, William N.

    2017-05-01

    A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the periphery of the oil. Preferential flow resulted in reduced tracer interaction with the soil, adsorption, and dispersion and faster tracer movement in the oily zone than expected. Tracers were freely transported through the oily zone to the water table. Recharge calculations support the idea that the oil does not substantially affect recharge in the oily zone. This is an important result indicating that previous model-based assumptions of decreased recharge beneath the oil were incorrect. Results have important implications for modeling the fate and transport of dissolved contaminants at hydrocarbon spill sites.

  15. Compilation and analyses of results from cross-hole tracer tests with conservative tracers

    Energy Technology Data Exchange (ETDEWEB)

    Hjerne, Calle; Nordqvist, Rune; Harrstroem, Johan (Geosigma AB (Sweden))

    2010-09-15

    diffusivity was found. However, indications of a relationship between mass balance aperture and apparent storativity from hydraulic interference tests as well as between mean residence time and pressure response time were found. This may indicate that there exists an indirect relationship between mass balance aperture and hydraulic diffusivity. Estimates of dispersivity in terms of Peclet numbers (Pe) from the tracer tests were also viewed in the report. However, no clear relationship between Pe and transmissivity or travel distance was found

  16. Investigation of helical flow by using tracer technique

    Directory of Open Access Journals (Sweden)

    Hacıyakupoğlu S.

    2013-05-01

    Full Text Available The flow through coiled tubes is, in practice, important for pipe systems, heat exchangers, chemical reactors, mixers of different gas components, etc., and is physically interesting because of the peculiar characteristics caused by the centrifugal force. Therefore, it is not so easy to observe flow parameters in the helical pipe experimentally. Tracer techniques are being increasingly used to determine characteristics such as volume flow rate, residence time, dispersion and mixing process in industry. In this study, the flow in the helical pipe was obtained in the laboratory and investigated by using the tracer technique. The experimental system including the helical pipe was set up in the laboratory. In the experiments methylene-blue (C16H17N3S has been used as the tracer. The experiments were successfully performed with different flow rates and their results were evaluated with the flow parameters.

  17. Proceedings of the atmospheric tracers and tracer application workshop

    Energy Technology Data Exchange (ETDEWEB)

    Barr, S.; Gedayloo, T. (comps.)

    1979-12-01

    In addition to presentations by participating members a general discussion was held in order to summarize and outline the goals and objectives of the workshop. A number of new low level background tracers such as heavy methanes, perfluorocarbons, multiply labeled isotopes such as /sup 13/C/sup 18/O/sub 2/, helium 3, in addition to sample collection techniques and analytical methods for various tracers were discussed. This report is a summary of discussions and papers presented at this workshop.

  18. Assessing preferential flow by simultaneously injecting nanoparticle and chemical tracers

    KAUST Repository

    Subramanian, S. K.

    2013-01-01

    The exact manner in which preferential (e.g., much faster than average) flow occurs in the subsurface through small fractures or permeable connected pathways of other kinds is important to many processes but is difficult to determine, because most chemical tracers diffuse quickly enough from small flow channels that they appear to move more uniformly through the rock than they actually do. We show how preferential flow can be assessed by injecting 2 to 5 nm carbon particles (C-Dots) and an inert KBr chemical tracer at different flow rates into a permeable core channel that is surrounded by a less permeable matrix in laboratory apparatus of three different designs. When the KBr tracer has a long enough transit through the system to diffuse into the matrix, but the C-Dot tracer does not, the C-Dot tracer arrives first and the KBr tracer later, and the separation measures the degree of preferential flow. Tracer sequestration in the matrix can be estimated with a Peclet number, and this is useful for experiment design. A model is used to determine the best fitting core and matrix dispersion parameters and refine estimates of the core and matrix porosities. Almost the same parameter values explain all experiments. The methods demonstrated in the laboratory can be applied to field tests. If nanoparticles can be designed that do not stick while flowing through the subsurface, the methods presented here could be used to determine the degree of fracture control in natural environments, and this capability would have very wide ranging value and applicability.

  19. Natural organic compounds as tracers for biomass combustion in aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Simoneit, B.R.T. [Brookhaven National Lab., Upton, NY (United States)]|[Oregon State Univ., Corvallis, OR (United States). Coll. of Oceanic and Atmospheric Sciences; Abas, M.R. bin [Brookhaven National Lab., Upton, NY (United States)]|[Univ. of Malaya, Kuala Lumpur (Malaysia); Cass, G.R. [Brookhaven National Lab., Upton, NY (United States)]|[California Inst. of Tech., Pasadena, CA (United States). Environmental Engineering Science Dept.; Rogge, W.F. [Brookhaven National Lab., Upton, NY (United States)]|[Florida International Univ., University Park, FL (United States). Dept. of Civil and Environmental Engineering; Mazurek, M.A. [Brookhaven National Lab., Upton, NY (United States); Standley, L.J. [Academy of Natural Sciences, Avondale, PA (United States). Stroud Water Research Center; Hildemann, L.M. [Stanford Univ., CA (United States). Dept. of Civil Engineering

    1995-08-01

    Biomass combustion is an important primary source of carbonaceous particles in the global atmosphere. Although various molecular markers have already been proposed for this process, additional specific organic tracers need to be characterized. The injection of natural product organic tracers to smoke occurs primarily by direct volatilization/steam stripping and by thermal alteration based on combustion temperature. The degree of alteration increases as the burn temperature rises and the moisture content of the fuel decreases. Although the molecular composition of organic matter in smoke particles is highly variable, the molecular structures of the tracers are generally source specific. The homologous compound series and biomarkers present in smoke particles are derived directly from plant wax, gum and resin by volatilization and secondarily from pyrolysis of biopolymers, wax, gum and resin. The complexity of the organic components of smoke aerosol is illustrated with examples from controlled burns of temperate and tropical biomass fuels. Burning of biomass from temperate regions (i.e., conifers) yields characteristic tracers from diterpenoids as well as phenolics and other oxygenated species, which are recognizable in urban airsheds. The major organic components of smoke particles from tropical biomass are straight-chain, aliphatic and oxygenated compounds and triterpenoids. The precursor-to-product approach of organic geochemistry can be applied successfully to provide tracers for studying smoke plume chemistry and dispersion.

  20. TracerLPM (Version 1): An Excel® workbook for interpreting groundwater age distributions from environmental tracer data

    Science.gov (United States)

    Jurgens, Bryant C.; Böhlke, J.K.; Eberts, Sandra M.

    2012-01-01

    TracerLPM is an interactive Excel® (2007 or later) workbook program for evaluating groundwater age distributions from environmental tracer data by using lumped parameter models (LPMs). Lumped parameter models are mathematical models of transport based on simplified aquifer geometry and flow configurations that account for effects of hydrodynamic dispersion or mixing within the aquifer, well bore, or discharge area. Five primary LPMs are included in the workbook: piston-flow model (PFM), exponential mixing model (EMM), exponential piston-flow model (EPM), partial exponential model (PEM), and dispersion model (DM). Binary mixing models (BMM) can be created by combining primary LPMs in various combinations. Travel time through the unsaturated zone can be included as an additional parameter. TracerLPM also allows users to enter age distributions determined from other methods, such as particle tracking results from numerical groundwater-flow models or from other LPMs not included in this program. Tracers of both young groundwater (anthropogenic atmospheric gases and isotopic substances indicating post-1940s recharge) and much older groundwater (carbon-14 and helium-4) can be interpreted simultaneously so that estimates of the groundwater age distribution for samples with a wide range of ages can be constrained. TracerLPM is organized to permit a comprehensive interpretive approach consisting of hydrogeologic conceptualization, visual examination of data and models, and best-fit parameter estimation. Groundwater age distributions can be evaluated by comparing measured and modeled tracer concentrations in two ways: (1) multiple tracers analyzed simultaneously can be evaluated against each other for concordance with modeled concentrations (tracer-tracer application) or (2) tracer time-series data can be evaluated for concordance with modeled trends (tracer-time application). Groundwater-age estimates can also be obtained for samples with a single tracer measurement at one

  1. Driven tracers in narrow channels

    Science.gov (United States)

    Cividini, J.; Mukamel, D.; Posch, H. A.

    2017-01-01

    Steady-state properties of a driven tracer moving in a narrow two-dimensional (2D) channel of quiescent medium are studied. The tracer drives the system out of equilibrium, perturbs the density and pressure fields, and gives the bath particles a nonzero average velocity, creating a current in the channel. Three models in which the confining effect of the channel is probed are analyzed and compared in this study: the first is the simple symmetric exclusion process (SSEP), for which the stationary density profile and the pressure on the walls in the frame of the tracer are computed. We show that the tracer acts like a dipolar source in an average velocity field. The spatial structure of this 2D strip is then simplified to a one-dimensional (1D) SSEP, in which exchanges of position between the tracer and the bath particles are allowed. Using a combination of mean-field theory and exact solution in the limit where no exchange is allowed gives good predictions of the velocity of the tracer and the density field. Finally, we show that results obtained for the 1D SSEP with exchanges also apply to a gas of overdamped hard disks in a narrow channel. The correspondence between the parameters of the SSEP and of the gas of hard disks is systematic and follows from simple intuitive arguments. Our analytical results are checked numerically.

  2. Preliminary assessment of surf-zone and estuarine line-fish species of the Dwesa-Cwebe Marine Protected Area, Eastern Cape, South Africa

    Directory of Open Access Journals (Sweden)

    Jan A. Venter

    2012-09-01

    Full Text Available A preliminary assessment of surf-zone and estuarine line fish was carried out in the DwesaCwebe Marine Protected Area (MPA, on the Wild Coast, South Africa. The purpose was to provide baseline data on inshore line-fish stocks in the MPA. A total of 28 species was recorded, of which 53% have a conservation status reflecting some concern and 43% are endemic to southern Africa. This highlights the value of the MPA for protection of important line-fish species. Within the MPA, localised differences were detected in species diversity, size frequency and catch per unit effort between unexploited and illegally exploited areas. These differences were more prominent in slow growing, long-lived species. It thus appears that illegal exploitation is negatively affecting fish populations within the MPA, which counteract and potentially could eliminate the benefits of fish protection typically associated with no-take MPAs. These results highlight the need for improved law enforcement and better communication with neighbouring communities to increase awareness. It is further recommended that the current no-take status of the MPA should be maintained. In addition, baseline fisheries information was collected on certain fish species that could be used to inform future conservation management of the MPA.Conservation implications: The Dwesa-Cwebe Marine Protected Area is unique and important for the conservation of key surf zone and estuarine fish species. However there is a significant risk to the fish populations due to illegal exploitation. Key interventions should include enhanced law enforcement but, more important, the creation of alternative livelihoods and long term sustainable benefits to local communities.

  3. Tracer Diffusion in a Soft Glassy Material

    Science.gov (United States)

    Petit, Laure; Barentin, Catherine; Colombani, Jean; Ybert, Christophe; Barrat, Jean-Louis; Bocquet, Lydéric

    2008-07-01

    We have carried out Fluorescence Recovery After Photobleaching measurements of the diffusion of tracers of various sizes in a colloidal glass (a Laponite suspension). We have shown that the diffusion is only dependent on the ratio of the tracer size and the distance between Laponite disks. This suggests that the tracer diffusion hindrance in the glass stems from the hydrodynamical interactions between the tracer and the Laponite network, the physico-chemical Laponite-tracer interaction playing a negligible role.

  4. Impact of meteorological inflow uncertainty on tracer transport and source estimation in urban atmospheres

    Science.gov (United States)

    Lucas, Donald D.; Gowardhan, Akshay; Cameron-Smith, Philip; Baskett, Ronald L.

    2016-10-01

    A computational Bayesian inverse technique is used to quantify the effects of meteorological inflow uncertainty on tracer transport and source estimation in a complex urban environment. We estimate a probability distribution of meteorological inflow by comparing wind observations to Monte Carlo simulations from the Aeolus model. Aeolus is a computational fluid dynamics model that simulates atmospheric and tracer flow around buildings and structures at meter-scale resolution. Uncertainty in the inflow is propagated through forward and backward Lagrangian dispersion calculations to determine the impact on tracer transport and the ability to estimate the release location of an unknown source. Our uncertainty methods are compared against measurements from an intensive observation period during the Joint Urban 2003 tracer release experiment conducted in Oklahoma City. The best estimate of the inflow at 50 m above ground for the selected period has a wind speed and direction of 4.6-2.5+2.0 m s-1 and 158.0-23+16 , where the uncertainty is a 95% confidence range. The wind speed values prescribed in previous studies differ from our best estimate by two or more standard deviations. Inflow probabilities are also used to weight backward dispersion plumes and produce a spatial map of likely tracer release locations. For the Oklahoma City case, this map pinpoints the location of the known release to within 20 m. By evaluating the dispersion patterns associated with other likely release locations, we further show that inflow uncertainty can explain the differences between simulated and measured tracer concentrations.

  5. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...

  6. A method to estimate dispersion in sampling catheters and to calculate dispersion-free blood time-activity curves

    OpenAIRE

    Munk, Ole Lajord; Keiding, Susanne; Bass, Ludvik

    2008-01-01

    The authors developed a transmission-dispersion model to estimate dispersion in blood sampling systems and to calculate dispersion-free input functions needed for kinetic analysis. Transport of molecules through catheters was considered in two parts: a central part with convective transmission of molecules and a stagnant layer that molecules may enter and leave. The authors measured dispersion caused by automatic and manual blood sampling using three PET tracers that distribute differently in...

  7. Tracer Flux Balance at an Urban Canyon Intersection

    Science.gov (United States)

    Carpentieri, Matteo; Robins, Alan G.

    2010-05-01

    Despite their importance for pollutant dispersion in urban areas, the special features of dispersion at street intersections are rarely taken into account by operational air quality models. Several previous studies have demonstrated the complex flow patterns that occur at street intersections, even with simple geometry. This study presents results from wind-tunnel experiments on a reduced scale model of a complex but realistic urban intersection, located in central London. Tracer concentration measurements were used to derive three-dimensional maps of the concentration field within the intersection. In combination with a previous study (Carpentieri et al., Boundary-Layer Meteorol 133:277-296, 2009) where the velocity field was measured in the same model, a methodology for the calculation of the mean tracer flux balance at the intersection was developed and applied. The calculation highlighted several limitations of current state-of-the-art canyon dispersion models, arising mainly from the complex geometry of the intersection. Despite its limitations, the proposed methodology could be further developed in order to derive, assess and implement street intersection dispersion models for complex urban areas.

  8. Tracer Modeling with the Hybrid Coordinates Ocean Model (hycom)

    Science.gov (United States)

    Garraffo, Z. D.; Kim, H.; Li, B.; Mehra, A.; Rivin, I.; Spindler, T.; Tolman, H. L.

    2012-12-01

    A series of tracer simulations have been started at NCEP/NWS aiming to a variety of applications, from dispersion of contaminants in estimations motivated by the Japanese nuclear accident near Fukushima, to nutrient estimations. The tracer capabilities of HYCOM are used, in regional domains, nested to daily nowcast/forecast fields from 1/12 HYCOM (RTOFS-Global) model output. A Fukushima Cs-137 simulation is now run in operational mode (RTOFS_ET). The simulation was initialized at the time of the Fukushima nuclear accident, and includes atmospheric deposition of Cs-137 and coastal discharge from a high resolution coastal model (ROMS done at NOAA/NOS). Almost all tracer moved offshore before the end of the first year after the accident. The tracer initially deposited in the Pacific ocean through the atmosphere slowly moves eastward and to deeper waters following the 3D ocean circulation. A series of simulations were started for nutrient estimations in the Gulf Stream and Mid Atlantic Bight region. Initially the capabilities implemented in HYCOM are used. The work aims to monitoring nutrients in the chosen region. Work is done in collaboration with Victoria Coles of U. Maryland.

  9. Streamwise decrease of the 'unsteady' virtual velocity of gravel tracers

    Science.gov (United States)

    Klösch, Mario; Gmeiner, Philipp; Habersack, Helmut

    2017-04-01

    Gravel tracers are usually inserted and transported on top of the riverbed, before they disperse vertically and laterally due to periods of intense bedload, the passage of bed forms, lateral channel migration and storage on bars. Buried grains have a lower probability of entrainment, resulting in a reduction of overall mobility, and, on average, in a deceleration of the particles with distance downstream. As a consequence, the results derived from tracer experiments and their significance for gravel transport may depend on the time scale of the investigation period, complicating the comparison of results from different experiments. We developed a regression method, which establishes a direct link between the transport velocity and the unsteady flow variables to yield an 'unsteady' virtual velocity, while considering the tracer slowdown with distance downstream in the regression. For that purpose, the two parameters of a linear excess shear velocity formula (the critical shear velocity u*c and coefficient a) were defined as functions of the travelled distance since the tracer's insertion. Application to published RFID tracer data from the Mameyes River, Puerto Rico, showed that during the investigation period the critical shear velocity u*c of tracers representing the median bed particle diameter (0.11 m) increased from 0.36 m s-1 to 0.44 m s-1, while the coefficient a decreased from the dimensionless value of 4.22 to 3.53, suggesting a reduction of the unsteady virtual velocity at the highest shear velocity in the investigation period from 0.40 m s-1 to 0.08 m s-1. Consideration of the tracer slowdown improved the root mean square error of the calculated mean displacements of the median bed particle diameter from 8.82 m to 0.34 m. As in previous work these results suggest the need of considering the history of transport when deriving travel distances and travel velocities, depending on the aim of the tracer study. The introduced method now allows estimating the

  10. Polyethyleneimine as tracer for electron microscopy

    NARCIS (Netherlands)

    Schurer, Jacob Willem

    1980-01-01

    In this thesis the development of a tracer particle for use in electron microscopy is described. Attempts were made to use this tracer particle in immuno-electron microscopy and to trace negatively charged tissue components. ... Zie: Summary

  11. A Water Mass Tracer Detected in Aerosols Demonstrates Ocean-Atmosphere Mass Transfer and Links Sea Spray Aerosol to Source Waters

    Science.gov (United States)

    Pendergraft, M.; Grimes, D. J.; Giddings, S. N.; Feddersen, F.; Prather, K. A.; Santander, M.; Lee, C.; Beall, C.

    2016-12-01

    During September and October of 2015 the Cross Surfzone/Inner-shelf Dye Exchange (CSIDE) project released rhodamine WT dye to study nearshore water movement and exchange offshore along a Southern California sandy beach. We utilized this opportunity to investigate ocean-atmosphere mass transfer via sea spray aerosol and linkage to source waters. Aerosol-concentrating sampling equipment was deployed at beachside and inland locations during three dye releases. Concentrated aerosol samples were analyzed for dye content using fluorescence spectroscopy. Here we present the ocean and atmosphere conditions associated with the presence and absence of dye in aerosol samples. Dye was identified in aerosol samples collected 0.1-0.3 km from the shoreline for 6 hs during the first and third dye releases of the CSIDE project. During these releases the dye persisted in the waters upwind of the sampling equipment. Dye was not detected in aerosol samples collected during the second release during which dye was moved away from waters upwind of the sampling equipment. Recovery of a chemical tracer in sea spray aerosol allows direct linkage to a known source area in the ocean that is independent of, but supported by, wind data. Our observations demonstrate: a tight ocean-atmosphere spatial coupling; a short residence time of coastal marine constituents before transfer to the atmosphere; that the ocean is both a sink for and a source of atmospheric and terrestrial material; and that human inputs to the ocean can return to us in sea spray aerosol.

  12. Turbulent dispersion in cloud-topped boundary layers

    NARCIS (Netherlands)

    Verzijlbergh, R.A.; Jonker, H.J.J.; Heus, T.; Vilà-Guerau de Arellano, J.

    2009-01-01

    Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary

  13. Characterization of fractured reservoirs using tracer and flow-rate data

    Science.gov (United States)

    Juliusson, Egill; Horne, Roland N.

    2013-05-01

    This article introduces a robust method for characterizing fractured reservoirs using tracer and flow-rate data. The flow-rate data are used to infer the interwell connectivity matrix, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find a function called the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods was developed to estimate the tracer kernels in situations where data are collected at variable flow rate or variable-injected concentration conditions. This characterization method was developed to describe enhanced geothermal systems, although it works well in general for characterizing incompressible flow in fractured reservoirs (e.g., geothermal, carbon sequestration, radioactive waste and waterfloods of oil fields) where transverse dispersivity can be considered negligible and production takes place at constant bottomhole pressure conditions. The inferred metrics can be used to sketch informative field maps and predict tracer breakthrough curves at variable flow-rate conditions.

  14. Tracer-tracer relations as a tool for research on polar ozone loss

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Rolf

    2010-07-01

    The report includes the following chapters: (1) Introduction: ozone in the atmosphere, anthropogenic influence on the ozone layer, polar stratospheric ozone loss; (2) Tracer-tracer relations in the stratosphere: tracer-tracer relations as a tool in atmospheric research; impact of cosmic-ray-induced heterogeneous chemistry on polar ozone; (3) quantifying polar ozone loss from ozone-tracer relations: principles of tracer-tracer correlation techniques; reference ozone-tracer relations in the early polar vortex; impact of mixing on ozone-tracer relations in the polar vortex; impact of mesospheric intrusions on ozone-tracer relations in the stratospheric polar vortex calculation of chemical ozone loss in the arctic in March 2003 based on ILAS-II measurements; (4) epilogue.

  15. Simulation of soluble waste transport and buildup in surface waters using tracers

    Science.gov (United States)

    Kilpatrick, F.A.

    1993-01-01

    Soluble tracers can be used to simulate the transport and dispersion of soluble wastes that might have been introduced or are planned for introduction into surface waters. Measured tracer-response curves produced from the injection of a known quantity of soluble tracer can be used in conjunction with the superposition principle to simulate potential waste buildup in streams, lakes, and estuaries. Such information is particularly valuable to environmental and water-resource planners in determining the effects of proposed waste discharges. The theory, techniques, analysis, and presentation of results of tracer-waste simulation tests in rivers, lakes, and estuaries are described. This manual builds on other manuals dealing with dye tracing by emphasizing the expanded use of data from time-of-travel studies.

  16. Tracer diffusion inside fibrinogen layers

    Science.gov (United States)

    Cieśla, Michał; Gudowska-Nowak, Ewa; Sagués, Francesc; Sokolov, Igor M.

    2014-01-01

    We investigate the obstructed motion of tracer (test) particles in crowded environments by carrying simulations of two-dimensional Gaussian random walk in model fibrinogen monolayers of different orientational ordering. The fibrinogen molecules are significantly anisotropic and therefore they can form structures where orientational ordering, similar to the one observed in nematic liquid crystals, appears. The work focuses on the dependence between level of the orientational order (degree of environmental crowding) of fibrinogen molecules inside a layer and non-Fickian character of the diffusion process of spherical tracer particles moving within the domain. It is shown that in general particles motion is subdiffusive and strongly anisotropic, and its characteristic features significantly change with the orientational order parameter, concentration of fibrinogens, and radius of a diffusing probe.

  17. Tracer diffusion inside fibrinogen layers

    CERN Document Server

    Cieśla, Michał; Sagués, Francesc; Sokolov, Igor M

    2013-01-01

    We investigate the motion of tracer (test) particles in crowded environments by carrying simulations of two-dimensional Gaussian random walk in model fibrinogen monolayers of different orientational ordering. The fibrinogen molecules are significantly anisotropic and therefore they can form structures where orientational ordering, similar to the one observed in nematic liquid crystals, appears. The work focuses on the dependence between level of the orientational order (degree of environmental crowding) of fibrinogen molecules inside a layer and non-Fickian character of the diffusion process of spherical tracer particles moving within the domain. It is shown that in general particles motion is subdiffusive and strongly anisotropic, and its characteristic features significantly change with the orientational order parameter, concentration of fibrinogens and radius of a diffusing probe.

  18. Sulfadimethoxine transport in soil columns in relation to sorbable and non-sorbable tracers.

    Science.gov (United States)

    Park, Jong Yol; Huwe, Bernd

    2016-06-01

    In this study, miscible displacement experiment and batch sorption experiments were performed with sulfadimethoxine, dye tracer, Brilliant Blue FCF (BB) and a conservative tracer (bromide) to depict, analyse and interpret transport paths of sulfadimethoxine in undisturbed and disturbed soil columns. Batch sorption experiment revealed that sorption potential increased in the order: Brilliant Blue FCF > sulfadimethoxine > bromide. The horizontal spatial patterns of sulfadimethoxine and the tracers were analysed in each depth, and selective samples were taken in horizontal cross-section. Non-adsorbable and conservative tracer, bromide spread more widely into longitudinal and horizontal direction than sulfadimethoxine and Brilliant Blue FCF, since adsorption reduced transversal dispersion of the sulfadimethoxine and dye. In non-stained area, residual concentrations of sulfadimethoxine were relatively lower than in stained areas. Therefore, Brilliant Blue FCF distribution can be used to approximate sulfadimethoxine movement in soil. However, presence of preferential flow networks found in undisturbed soil cores can enhance mobility of sulfadimethoxine and the tracers, due to faster flow velocities and non-equilibrium adsorption. Our findings showed that other dye tracers may also be applicable to identify transport pathways of various organic contaminants, of which physico-chemical properties are similar to those of the dye tracers. Preferential flow should be considered for drinking water managements and transport modelling, since this allows faster pollutants transport from their sources, and create critical consequences for groundwater quality and solute transport modelling.

  19. Analysis of Injection-Backflow Tracer Tests in Fractured Geothermal Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Kocabas, I.; Horne, R.N.

    1987-01-20

    Tracer tests have been an important technique for determining the flow and reservoir characteristics in various rock matrix systems. While the interwell tracer tests are aimed at the characterization of the regions between the wells, single-well injection-backflow tracer tests may be useful tools of preliminary evaluation, before implementing long term interwell tracer tests. This work is concerned with the quantitative evaluation of the tracer return profiles obtained from single well injection-backflow tracer tests. First, two mathematical models of tracer transport through fractures, have been reviewed. These two models are based on two different principles: Taylor Dispersion along the fracture and simultaneous diffusion in and out of the adjacent matrix. Then the governing equations for the transport during the injection-backflow tests have been solved. Finally the results were applied to field data obtained from Raft River and East Mesa geothermal fields. In order to determine the values of the parameters of the models that define the transport mechanisms through fractures a non-linear optimization technique was employed. 26 refs., 10 figs.

  20. Atmospheric monitoring of a perfluorocarbon tracer at the 2009 ZERT Center experiment

    Science.gov (United States)

    Pekney, Natalie; Wells, Arthur; Rodney Diehl, J.; McNeil, Matthew; Lesko, Natalie; Armstrong, James; Ference, Robert

    2012-02-01

    Field experiments at Montana State University are conducted for the U.S. Department of Energy as part of the Zero Emissions Research and Technology Center (ZERT) to test and verify monitoring techniques for carbon capture and storage (CCS). A controlled release of CO 2 with an added perfluorocarbon tracer was conducted in July 2009 in a multi-laboratory study of atmospheric transport and detection technologies. Tracer plume dispersion was measured with various meteorological conditions using a tethered balloon system with Multi-Tube Remote Samplers (MTRS) at elevations of 10 m, 20 m, and 40 m above ground level (AGL), as well as a ground-based portable tower with monitors containing sorbent material to collect the tracer at 1 m, 2 m, 3 m, and 4 m AGL. Researchers designed a horizontal grid of sampling locations centered at the tracer plume source, with the tower positioned at 10 m and 30 m in both upwind and downwind directions, and the MTRS spaced at 50 m and 90 m downwind and 90 m upwind. Tracer was consistently detected at elevated concentrations at downwind sampling locations. With very few exceptions, higher tracer concentrations correlated with lower elevations. Researchers observed no statistical difference between sampling at 50 m and 90 m downwind at the same elevation. The US EPA AERMOD model applied using site-specific information predicted transport and dispersion of the tracer. Model results are compared to experimental data from the 2009 ZERT experiment. Successful characterization of the tracer plume simulated by the ZERT experiment is considered a step toward demonstrating the feasibility of remote sampling with unmanned aerial systems (UAS's) at future sequestration sites.

  1. A parameter identifiability study of two chalk tracer tests

    Directory of Open Access Journals (Sweden)

    S. A. Mathias

    2006-08-01

    Full Text Available As with most fractured rock formations, Chalk is highly heterogeneous. Therefore, meaningful estimates of model parameters must be obtained at a scale comparable with the process of concern. These are frequently obtained by calibrating an appropriate model to observed concentration-time data from radially convergent tracer tests (RCTT. Arguably, an appropriate model should consider radially convergent dispersion (RCD and Fickian matrix diffusion. Such a model requires the estimation of at least four parameters. A question arises as to whether or not this level of model complexity is supported by the information contained within the calibration data. Generally modellers have not answered this question due to the calibration techniques employed. A dual-porosity model with RCD was calibrated to two tracer test datasets from different UK Chalk aquifers. A multivariate sensitivity analysis, which assumed only a priori upper and lower bounds for each model parameter, was undertaken. Rather than looking at measures of uncertainty, the shape of the multivariate objective function surface was used to determine whether a parameter was identifiable. Non-identifiable parameters were then removed and the procedure was repeated until all remaining parameters were identifiable.

    It was found that the single fracture model (SFM (which ignores mechanical dispersion obtained the best mass recovery, excellent model performance and best parameter identifiability in both the tests studied. However, there was no objective evidence suggesting that mechanical dispersion was negligible. Moreover, the SFM (with just two parameters was found to be good at approximating the Single Fracture Dispersion Model SFDM (with three parameters when different, and potentially erroneous parameters, were used. Overall, this study emphasises the importance of adequate temporal sampling of breakthrough curve data prior to peak concentrations, to ensure adequate characterisation of

  2. Turbulent flux and the diffusion of passive tracers in electrostatic turbulence

    DEFF Research Database (Denmark)

    Basu, R.; Jessen, T.; Naulin, V.

    2003-01-01

    is in good agreement with the one derived from the turbulent ExB-flux by using Fick's law. Employing the Lagrangian conservation of the "Potential Vorticity'' in the Hasegawa-Wakatani equations, the analytical support for this result is obtained. The transport estimated by passive tracer dispersion...

  3. Velocity dispersion around ellipticals in MOND

    CERN Document Server

    Tiret, O; Angus, G W; Famaey, B; Zhao, H S

    2007-01-01

    We investigate how different models that have been proposed for solving the dark matter problem can fit the velocity dispersion observed around elliptical galaxies, on either a small scale (~ 20kpc) with stellar tracers, such as planetary nebulae, or large scale (~ 200kpc) with satellite galaxies as tracers. Predictions of Newtonian gravity, either containing pure baryonic matter, or embedded in massive cold dark matter (CDM) haloes, are compared with predictions of the modified gravity of MOND. The standard CDM model has problems on a small scale, and the Newtonian pure baryonic model has difficulties on a large scale, while a fit with MOND is possible on both scales.

  4. Radon-222 and beryllium-7 as natural tracer; Radon-222 und Beryllium-7 als natuerliche Tracer

    Energy Technology Data Exchange (ETDEWEB)

    Frank, G.; Steinkopff, T. [Deutscher Wetterdienst, Offenbach (Germany). Radioaktivitaetsueberwachung; Salvamoser, J. [Institut fuer Angewandte Isotopen-, Gas- und Umweltuntersuchungen (IGU), Woerthsee (Germany)

    2016-07-01

    The Global Atmosphere Watch Program (GAW) is intended to analyse worldwide the influence of anthropogenic emissions to the atmosphere. Data are continuously transferred to the ''World Data Centre for Green House Gases'' of the WMO. For the study of atmospheric transports the natural radionuclides Rn-222, Be-7, Pb-210, Pb- 214 and Bi-214 are continuously measured at the Umweltforschungsstation Schneefernerhaus (2650 m) and at the Zugspitze (2962 m) by the Deutscher Wetterdienst (DWD, German Weather Service). The measurements support the classification of atmospheric transport, atmospheric dilution and dispersion models of gaseous and aerosol bond micro pollutants. Results are carried out in combination with meteorological data. It is shown the optimization and effect of a new sampling site for the measurement of Rn-222 activity at the Zugspitze. Results of Rn-222 and Be-7 concentrations are shown in relation to horizontal and vertical dispersion of air masses. The origin of natural Rn-222 and Be-7 are known, therefore both nuclides are well suited for the research of atmospheric transport. Rn-222 is an ideal tracer, because there is no influence by atmospheric processes (chemical processes, wash out effects).

  5. Tracer tests in geothermal resource management

    Directory of Open Access Journals (Sweden)

    Axelsson G.

    2013-05-01

    Full Text Available Geothermal reinjection involves injecting energy-depleted fluid back into geothermal systems, providing an effective mode of waste-water disposal as well as supplementary fluid recharge. Cooling of production boreholes is one of the main disadvantages associated with reinjection, however. Tracer testing is an important tool for reinjection studies because tracer tests actually have a predictive power since tracer transport is orders of magnitude faster than cold-front advancement around reinjection boreholes. A simple and efficient method of tracer test interpretation, assuming specific flow channels connecting reinjection and production boreholes, is available. It simulates tracer return profiles and estimates properties of the flow channels, which are consequently used for predicting the production borehole cooling. Numerous examples are available worldwide on the successful application of tracer tests in geothermal management, many involving the application of this interpretation technique. Tracer tests are also used for general subsurface hydrological studies in geothermal systems and for flow rate measurements in two-phase geothermal pipelines. The tracers most commonly used in geothermal applications are fluorescent dyes, chemical substances and radioactive isotopes. New temperature-resistant tracers have also been introduced and high-tech tracers are being considered.

  6. An investigation of radial tracer flow in naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Jetzabeth, Ramirez-Sabag; Fernando, Samaniego V.; Jesus, Rivera R.; Fernando Rodriguez

    1991-01-01

    This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile region where longitudinal dispersion and convection take place and a stagnant region where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared to those previously presented in literature by Moench and Ogata, Tang et al., Chen et al., and Hsieh et al. The solution is numerically inverted by means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., for short times) was carried out. The influence of various dimensionless parameters that enter into the solution was investigated. A discussion of results obtained through the Crump and Stehfest algorithm is presented, concluding that the Crump method provides more reliable tracer concentrations.

  7. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  8. Turbulent pair dispersion as a continuous-time random walk

    CERN Document Server

    Thalabard, Simon; Bec, Jeremie

    2014-01-01

    The phenomenology of turbulent relative dispersion is revisited. A heuristic scenario is proposed, in which pairs of tracers undergo a succession of independent ballistic separations during time intervals whose lengths fluctuate. This approach suggests that the logarithm of the distance between tracers self-averages and performs a continuous-time random walk. This leads to specific predictions for the probability distribution of separations, that differ from those obtained using scale-dependent eddy-diffusivity models (e.g. in the framework of Richardson's approach). Such predictions are tested against high-resolution simulations and shed new lights on the explosive separation between tracers.

  9. Tracer tests in geothermal resource management

    OpenAIRE

    Axelsson G.

    2013-01-01

    Geothermal reinjection involves injecting energy-depleted fluid back into geothermal systems, providing an effective mode of waste-water disposal as well as supplementary fluid recharge. Cooling of production boreholes is one of the main disadvantages associated with reinjection, however. Tracer testing is an important tool for reinjection studies because tracer tests actually have a predictive power since tracer transport is orders of magnitude faster than cold-front advancement around reinj...

  10. Tracer SWIW tests in propped and un-propped fractures: parameter sensitivity issues, revisited

    Science.gov (United States)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2017-04-01

    Single-well injection-withdrawal (SWIW) or 'push-then-pull' tracer methods appear attractive for a number of reasons: less uncertainty on design and dimensioning, and lower tracer quantities required than for inter-well tests; stronger tracer signals, enabling easier and cheaper metering, and shorter metering duration required, reaching higher tracer mass recovery than in inter-well tests; last not least: no need for a second well. However, SWIW tracer signal inversion faces a major issue: the 'push-then-pull' design weakens the correlation between tracer residence times and georeservoir transport parameters, inducing insensitivity or ambiguity of tracer signal inversion w. r. to some of those georeservoir parameters that are supposed to be the target of tracer tests par excellence: pore velocity, transport-effective porosity, fracture or fissure aperture and spacing or density (where applicable), fluid/solid or fluid/fluid phase interface density. Hydraulic methods cannot measure the transport-effective values of such parameters, because pressure signals correlate neither with fluid motion, nor with material fluxes through (fluid-rock, or fluid-fluid) phase interfaces. The notorious ambiguity impeding parameter inversion from SWIW test signals has nourished several 'modeling attitudes': (i) regard dispersion as the key process encompassing whatever superposition of underlying transport phenomena, and seek a statistical description of flow-path collectives enabling to characterize dispersion independently of any other transport parameter, as proposed by Gouze et al. (2008), with Hansen et al. (2016) offering a comprehensive analysis of the various ways dispersion model assumptions interfere with parameter inversion from SWIW tests; (ii) regard diffusion as the key process, and seek for a large-time, asymptotically advection-independent regime in the measured tracer signals (Haggerty et al. 2001), enabling a dispersion-independent characterization of multiple

  11. Tracer-Test Planning Using the Efficient Hydrologic Tracer-Test Design (Ehtd) Program (2003)

    Science.gov (United States)

    Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test ...

  12. Bed load tracer mobility in a mixed bedrock/alluvial channel

    Science.gov (United States)

    Ferguson, R. I.; Sharma, B. P.; Hodge, R. A.; Hardy, R. J.; Warburton, J.

    2017-04-01

    The presence of bare or partially covered rock in an otherwise alluvial river implies a downstream change in transport capacity relative to supply. Field investigations of this change and what causes it are lacking. We used two sets of magnet-tagged tracer clasts to investigate bed load transport during the same sequence of floods in fully alluvial, bare rock, and partial-cover reaches of an upland stream. High-flow shear stresses in different reaches were calculated by using stage loggers. Tracers seeded in the upstream alluvial channel moved more slowly than elsewhere until the frontrunners reached bare rock and sped up. Tracers seeded on bare rock moved rapidly off it and accumulated just upstream from, and later in, a partial-cover zone with many boulders. The backwater effect of the boulder-rich zone is significant in reducing tracer mobility. Tracer movement over full or partial sediment cover was size selective but dispersion over bare rock was not. Along-channel changes in tracer mobility are interpreted in terms of measured differences in shear stress and estimated differences in threshold stress.

  13. Diagnosing Ocean Tracer Transport from Sellafield and Dounreay by Equivalent Diffusion and Age

    Institute of Scientific and Technical Information of China (English)

    Steinar ORRE; Yongqi GAO; Helge DRANGE; Eric DELEERSNIJDER

    2008-01-01

    simple approach for estimating the equivalent diffusion for diagnosing tracer transport is proposed.Two difierent expressions are derived;one iS based directly on an analytical solution of the two-dimensionaladvection-diffnsion equation.the other uses the variance of the tracer distribution.To illustrate some featuresof the equivalent diffusion and possible applications thereof,idealized releases of passive tracers from thenuclear ruel reprocessing plants at Sellafield in the Irish Sea and Dounrea.v on the northern coast of Scotlandhave been simulated with a regionalisopycnic co-ordinate Ocean General Circulation Model.Both continuousand pulse releases are considered;the former being representative of the actual historical discharges from thereprocessing plants,the latter resembling an accidental scenario.Age tracers are included to calculate themean time elapsed since the tracers left their source regions.It iS found that in the Nordic Seas the age oftracers from Dounreay is approximately 2 years younger than the age from Sellafield.Although tracers fromboth sources eventually end up along the same transport routes,signifcant qualitative differences regardingthe dispersion properties are found.It is argued that one single parameter,the equivalent horizontal diffusion,which iS estimated to be in the range of 20-56 m2 s-1 from Sellafield and 170-485 m2 s-1 from Dounreay,determines these difierences.

  14. "Dispersion modeling approaches for near road | Science ...

    Science.gov (United States)

    Roadway design and roadside barriers can have significant effects on the dispersion of traffic-generated pollutants, especially in the near-road environment. Dispersion models that can accurately simulate these effects are needed to fully assess these impacts for a variety of applications. For example, such models can be useful for evaluating the mitigation potential of roadside barriers in reducing near-road exposures and their associated adverse health effects. Two databases, a tracer field study and a wind tunnel study, provide measurements used in the development and/or validation of algorithms to simulate dispersion in the presence of noise barriers. The tracer field study was performed in Idaho Falls, ID, USA with a 6-m noise barrier and a finite line source in a variety of atmospheric conditions. The second study was performed in the meteorological wind tunnel at the US EPA and simulated line sources at different distances from a model noise barrier to capture the effect on emissions from individual lanes of traffic. In both cases, velocity and concentration measurements characterized the effect of the barrier on dispersion.This paper presents comparisons with the two datasets of the barrier algorithms implemented in two different dispersion models: US EPA’s R-LINE (a research dispersion modelling tool under development by the US EPA’s Office of Research and Development) and CERC’s ADMS model (ADMS-Urban). In R-LINE the physical features reveal

  15. Tracers for Characterizing Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Karen Wright; George Redden; Carl D. Palmer; Harry Rollins; Mark Stone; Mason Harrup; Laurence C. Hull

    2010-02-01

    Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates; however, tracers that undergo temperature-dependent changes can provide more detailed information about the thermal profile along the flow path through the reservoir. To be effectively applied, the thermal reaction rates of such temperature sensitive traces must be well characterized for the range of conditions that exist in geothermal systems. Reactive tracers proposed in the literature include benzoic and carboxylic acids (Adams) and organic esters and amides (Robinson et al.); however, the practical temperature range over which these tracers can be applied (100-275°C) is somewhat limited. Further, for organic esters and amides, little is known about their sorption to the reservoir matrix and how such reactions impact data interpretation. Another approach involves tracers where the reference condition is internal to the tracer itself. Two examples are: 1) racemization of polymeric amino acids, and 2) mineral thermoluminescence. In these cases internal ratios of states are measured rather than extents of degradation and mass loss. Racemization of poly-L-lactic acid (for example) is temperature sensitive and therefore can be used as a temperature-recording tracer depending on the rates of racemization and stability of the amino acids. Heat-induced quenching of thermoluminescence of pre-irradiated LiF can also be used. To protect the tracers from alterations (extraneous reactions, dissolution) in geothermal environments we are encapsulating the tracers in core-shell colloidal structures that will subsequently be tested for their ability to be transported and to protect the

  16. Tracers for Characterizing Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Karen Wright; George Redden; Carl D. Palmer; Harry Rollins; Mark Stone; Mason Harrup; Laurence C. Hull

    2010-02-01

    Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates; however, tracers that undergo temperature-dependent changes can provide more detailed information about the thermal profile along the flow path through the reservoir. To be effectively applied, the thermal reaction rates of such temperature sensitive traces must be well characterized for the range of conditions that exist in geothermal systems. Reactive tracers proposed in the literature include benzoic and carboxylic acids (Adams) and organic esters and amides (Robinson et al.); however, the practical temperature range over which these tracers can be applied (100-275°C) is somewhat limited. Further, for organic esters and amides, little is known about their sorption to the reservoir matrix and how such reactions impact data interpretation. Another approach involves tracers where the reference condition is internal to the tracer itself. Two examples are: 1) racemization of polymeric amino acids, and 2) mineral thermoluminescence. In these cases internal ratios of states are measured rather than extents of degradation and mass loss. Racemization of poly-L-lactic acid (for example) is temperature sensitive and therefore can be used as a temperature-recording tracer depending on the rates of racemization and stability of the amino acids. Heat-induced quenching of thermoluminescence of pre-irradiated LiF can also be used. To protect the tracers from alterations (extraneous reactions, dissolution) in geothermal environments we are encapsulating the tracers in core-shell colloidal structures that will subsequently be tested for their ability to be transported and to protect the

  17. On superdiffusive behavior of a passive tracer in a random flow

    Science.gov (United States)

    Komorowski, Tomasz; Nieznaj, Ernest

    2008-12-01

    In this note we consider a passive tracer model describing particle dispersion in a turbulent flow. The trajectory of the particle is given by the solution of an ordinary differential equation ẋ(t)=F(x(t)), x(0)=x, where F(x) is a divergence-free, random vector field that is spatially homogeneous and isotropic. We show that trajectories of the tracer display superdiffusive behavior when the random velocity F(x) decorrelates, at large distances, but does it not rapidly but rather at some moderate rate. The main tools used in the proofs are variational principles and Tauberian-type theorems.

  18. Effect on tracer concentrations of ABL depth models in complex terrain

    Energy Technology Data Exchange (ETDEWEB)

    Galmarini, S.; Salin, P. [Joint Research Center Ispra (Italy); Anfossi, D.; Trini-Castelli, S. [CNR-ICGF, Turin (Italy); Schayes, G. [Univ. Louvain-la-Neuve, Louvain (Belgium)

    1997-10-01

    In the present preliminary study we use different ABL (atmospheric boundary layer) depth formulations to study atmospheric dispersion in complex-terrain conditions. The flow in an Alpine valley during the tracer experiment TRANSALP is simulated by means of a mesoscale model and a tracer dispersion is reproduced using a Lagrangian particle model. The ABL dept enters as key parameter in particle model turbulent-dispersion formulation. The preliminary results reveal that the ABL depth parameter can influence the dispersion process but that in the case of a dispersion in a valley-daytime flow the results depend much more strongly on the model horizontal and vertical resolution. A relatively coarse horizontal resolution implies a considerable smoothing of the topography that largely affects the dispersion characteristics. The vertical resolution does not allow on to resolve with sufficient details the rapid and large variation of the flow characteristic as the terrain feature vary. Two of the methods used to determine the ABL depth depend strongly on the resolution. The method that instead depends only on surface parameters like heat flux and surface based stability allowed us to obtain results to be considered satisfactory for what concerns the dispersion process, quite consistent with the flow model results, less numeric dependent and more physically sound. (LN)

  19. Single-well "push-pull" partitioning tracer test for NAPL detection in the subsurface.

    Science.gov (United States)

    Istok, Jonathan D; Field, Jennifer A; Schroth, Martin H; Davis, Brian M; Dwarakanath, Varadarajan

    2002-06-15

    Previous environmental applications of partitioning tracer tests to detect and quantify nonaqueous phase liquid (NAPL) contamination in the subsurface have been limited to well-to-well tests. However, theory and numerical modeling suggests that single-well injection-extraction ("push-pull") partitioning tracer tests can also potentially detect and quantify NAPL contamination. In this type of test, retardation factors for injected partitioning tracers are estimated from the increase in apparent dispersion observed in extraction-phase breakthrough curves in the presence of NAPL. A series of laboratory push-pull tests was conducted in physical aquifer models (PAMs) packed with natural aquifer sediment prepared with and without the presence of trichloroethene (TCE) NAPL. Field tests were conducted in an aquifer contaminated with petroleum hydrocarbon NAPL. Injected test solutions contained a suite of partitioning and conservative (nonpartitioning) alcohol tracers. Laboratory push-pull partitioning tracer tests were able to detect and quantify sorption of partitioning tracers to aquifer sediment (in the absence of NAPL) and to detect NAPL when it was present. NAPL saturations computed from estimated retardation factors bracketed those computed from known volumes of emplaced NAPL in the sediment pack. However, numerical modeling with assumed homogeneous NAPL distribution and linear equilibrium partitioning of tracers between aqueous and NAPL phases was unable to reproduce all features of observed breakthrough curves. Excavation of the sediment pack after all tests indicated that a portion of the emplaced NAPL had sunk to the bottom of the PAM invalidating the modeling assumption of homogeneous NAPL distribution. Moreover, the apparent dispersion in extraction-phase breakthrough curves decreased when the injection-extraction pumping rate was decreased, suggesting that mass transfer limitations existed during laboratory tests. Field push-pull partitioning tracer tests were

  20. Identification of transport processes in Southern Indian fractured crystalline rock using forced-gradient tracer experiments

    Science.gov (United States)

    Guihéneuf, Nicolas; Bour, Olivier; Boisson, Alexandre; Le Borgne, Tanguy; Becker, Matthew R.; Nigon, Benoit; Wajiduddin, Mohammed; Ahmed, Shakeel; Maréchal, Jean-Christophe

    2015-04-01

    from the borehole that leads to mass exchange between flow paths and thus increase dispersion of tracer.

  1. Anomalous Dispersion in a Sand Bed River

    Science.gov (United States)

    Bradley, D. N.; Tucker, G. E.; Benson, D. M.

    2009-04-01

    There has been a recent surge of interest in non-local, heavy-tailed models of sediment transport and dispersion that are governed by fractional order differential equations. These models have a firm mathematical foundation and have been successfully applied in a variety of transport systems, but their use in geomorphology has been minimal because the data required to validate the models is difficult to acquire. We use data from a nearly 50-year-old tracer experiment to test a fluvial bed load transport model with a two unique features. First, the model uses a heavy-tailed particle velocity distribution with a divergent second moment to reproduce the anomalously high fraction of tracer mass observed in the downstream tail of the spatial distribution. Second, the model partitions mass into a detectable mobile phase and an undetectable, immobile phase. This two-phase transport model predicts two other features observed in the data: a decrease in the amount of detected tracer mass over the course of the experiment and the high initial velocity of the tracer plume. Because our model uses a heavy-tailed velocity distribution with a divergent second moment it is non-local and non-Fickian and able to reproduce aspects of the data that a local, Fickian model cannot. The model's successful prediction of the observed concentration profiles provides some of the first evidence of anomalous dispersion of bed load in a natural river.

  2. The Accurate Particle Tracer Code

    CERN Document Server

    Wang, Yulei; Qin, Hong; Yu, Zhi

    2016-01-01

    The Accurate Particle Tracer (APT) code is designed for large-scale particle simulations on dynamical systems. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and non-linear problems. Under the well-designed integrated and modularized framework, APT serves as a universal platform for researchers from different fields, such as plasma physics, accelerator physics, space science, fusion energy research, computational mathematics, software engineering, and high-performance computation. The APT code consists of seven main modules, including the I/O module, the initialization module, the particle pusher module, the parallelization module, the field configuration module, the external force-field module, and the extendible module. The I/O module, supported by Lua and Hdf5 projects, provides a user-friendly interface for both numerical simulation and data analysis. A series of new geometric numerical methods...

  3. Bacteriophages as surface and ground water tracers

    Directory of Open Access Journals (Sweden)

    P. Rossi

    1998-01-01

    Full Text Available Bacteriophages are increasingly used as tracers for quantitative analysis in both hydrology and hydrogeology. The biological particles are neither toxic nor pathogenic for other living organisms as they penetrate only a specific bacterial host. They have many advantages over classical fluorescent tracers and offer the additional possibility of multi-point injection for tracer tests. Several years of research make them suitable for quantitative transport analysis and flow boundary delineation in both surface and ground waters, including karst, fractured and porous media aquifers. This article presents the effective application of bacteriophages based on their use in differing Swiss hydrological environments and compares their behaviour to conventional coloured dye or salt-type tracers. In surface water and karst aquifers, bacteriophages travel at about the same speed as the typically referenced fluorescent tracers (uranine, sulphurhodamine G extra. In aquifers of interstitial porosity, however, they appear to migrate more rapidly than fluorescent tracers, albeit with a significant reduction in their numbers within the porous media. This faster travel time implies that a modified rationale is needed for defining some ground water protection area boundaries. Further developments of other bacteriophages and their documentation as tracer methods should result in an accurate and efficient tracer tool that will be a proven alternative to conventional fluorescent dyes.

  4. Bacteriophages as surface and ground water tracers

    Science.gov (United States)

    Rossi, P.; Dörfliger, N.; Kennedy, K.; Müller, I.; Aragno, M.

    Bacteriophages are increasingly used as tracers for quantitative analysis in both hydrology and hydrogeology. The biological particles are neither toxic nor pathogenic for other living organisms as they penetrate only a specific bacterial host. They have many advantages over classical fluorescent tracers and offer the additional possibility of multi-point injection for tracer tests. Several years of research make them suitable for quantitative transport analysis and flow boundary delineation in both surface and ground waters, including karst, fractured and porous media aquifers. This article presents the effective application of bacteriophages based on their use in differing Swiss hydrological environments and compares their behaviour to conventional coloured dye or salt-type tracers. In surface water and karst aquifers, bacteriophages travel at about the same speed as the typically referenced fluorescent tracers (uranine, sulphurhodamine G extra). In aquifers of interstitial porosity, however, they appear to migrate more rapidly than fluorescent tracers, albeit with a significant reduction in their numbers within the porous media. This faster travel time implies that a modified rationale is needed for defining some ground water protection area boundaries. Further developments of other bacteriophages and their documentation as tracer methods should result in an accurate and efficient tracer tool that will be a proven alternative to conventional fluorescent dyes.

  5. The Copenhagen tracer experiments: Reporting of measurements

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Lyck, E.

    2002-01-01

    buoyancy from a tower at a height of 115 meters and then collected 2-3 meters above ground-level at positions in up to three crosswind arcs of tracer sampling units, positioned 2-6 km from the point of release. Three consecutive 20 min averaged tracer concentrations were measured, allowing for a total...

  6. Effect of tracer buoyancy on tracer experiments conducted in fractured crystalline bedrock

    Science.gov (United States)

    Becker, Matthew W.

    2003-02-01

    Tracer buoyancy has been shown to influence breakthrough from two-well tracer experiments conducted in porous media. Two-well tracer experiments are presented from fractured crystalline bedrock, in which the specific gravity of the tracer injectate varied from 1.0002 to 1.0133. Under the forced hydraulic conditions imposed, no difference in breakthrough was noted for the three experiments. These results show that even relatively dense tracer injectate solutions may have an insignificant effect on breakthrough when imposed gradients are sufficiently large.

  7. The Art of Tomographic Tracer Tests

    Science.gov (United States)

    Cirpka, O. A.; Leven, C.; Doro, K. O.; Sanchez-Leon, E. E.

    2015-12-01

    In tracer tomography several tracer tests are performed within an aquifer and breakthrough curves are observed at multiple observation points. In the analysis, hydraulic conductivity is estimated as spatially variable, 3-D field subject to some smoothness constraint. Coupled flow and transport models using this conductivity fields are requested to meet observed tracer data. The approach can be combined with hydraulic tomography.We have performed hydraulic-tomography and tracer-tomography tests using heat and fluorescein as tracers at a field site close to Tübingen, Germany. The aquifer consists of 8-9m alluvials sands and gravels overlain by 1-2m alluvial fines. The hydraulic setup consists of a forced flow field between an injection/extraction well couple, embedded in the forced flow field of another well couple. By turning injection to extraction wells, and vice versa, two different flow fields were considered. Injection wells were separated into several sections by packers, and water was injected into each section proportional to its transmissivity. The water injected into one of the sections contained the tracer. Multi-level observation wells were equiped with thermometers (for heat-tracer tests), on-line fluoremeters (for teh dye tracers), and pressure transducers. Processing of the breakthrough curves included data cleaning, non-parametric deconvolution, and calculation of temperal moments of the estimated transfer functions.The joint inversion of hydraulic-head measurements and temporal moments of heat-tracer transfer functions was done by the quasi-linear geostatistical approach on a computing cluster. As alternative, we directly invert the time series (without temporal moments) by Ensemble-Kalman filtering.The high diffusion coefficient of temperature diminishes the penetration of the heat-tracer into the aquifer, which can partially be compensated by reverting the flow field and repeating the tracer tests. In tests with fluorscent tracers the signal

  8. Unsaturated water flow and tracer transport modeling with Alliances

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, Alina, E-mail: alina.constantin@nuclear.ro [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania); Genty, Alain, E-mail: alain.genty@cea.fr [CEA Saclay, DM2S/SFME/LSE, Gif-sur-Yvette 91191 cedex (France); Diaconu, Daniela; Bucur, Crina [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania)

    2013-12-15

    Highlights: • Simulation of water flow and solute transport at Saligny site, Romania was done. • Computation was based on the available experimental data with Alliances platform. • Very good results were obtained for the saturation profile in steady state. • Close fit to experimental data for saturation profile at 3 m in transient state. • Large dispersivity coefficients were fitted to match tracer experiment. - Abstract: Understanding water flow and solute transport in porous media is of central importance in predicting the radionuclide fate in the geological environment, a topic of interest for the performance and safety assessment studies for nuclear waste disposal. However, it is not easy to predict transport properties in real systems because they are geologically heterogeneous from the pore scale upwards. This paper addresses the simulation of water flow and solute transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on the current available experimental data for this zone and was performed within Alliances, a software platform initially jointly developed by French organizations CEA, ANDRA and EDF. The output of the model developed was compared with the measured values in terms of saturation profile of the soil for water movement, in both steady and transient state. Very good results were obtained for the saturation profile in steady state and a close fit of the simulation over experimental data for the water saturation profile at a depth of 3 m in transient state. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, a tracer test was launched on site and dispersivity coefficients of the solute were fitted in order to match the experimental concentration determined on samples from different locations of the site. Results much close to the experiment were obtained for a longitudinal

  9. Dispersion Modeling.

    Science.gov (United States)

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  10. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  11. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  12. Longitudinal dispersion in natural channels: 3. An aggregated dead zone model applied to the River Severn, U.K.

    Science.gov (United States)

    Davis, P. M.; Atkinson, T. C.

    An Aggregated Dead Zone (ADZ) model is presented for longitudinal dispersion of tracer in river channels, in which the channel cross-section is divided into two parallel regions: the bulk flow and dead zone storage. Tracer particles in the bulk flow are assumed to obey plug-flow advection at the discharge velocity U without any mixing effects. The dispersive properties of the model are completely embodied in the residence time for tracer storage in the dead zone. The model provides an excellent description and prediction of empirical concentration-time distributions, for times t ADZ model is a potentially useful tool for practical prediction of dispersion in natural channels.

  13. Comparison of Heat and Bromide as Ground Water Tracers Near Streams

    Science.gov (United States)

    Constantz, J.; Cox, M.H.; Su, G.W.

    2003-01-01

    Heat and bromide were compared as tracers for examining stream/ground water exchanges along the middle reaches of the Santa Clara River, California, during a 10-hour surface water sodium bromide injection test. Three cross sections that comprise six shallow (sodium bromide injection test. Vertical, one-dimensional simulations of bromide concentrations in the sediments yielded a good match to the observed bromide concentrations, without adjustment of any model parameters except solute dispersivities. This indicates that, for the spatial and temporal scales examined on the Santa Clara River, the use of heat and bromide as tracers provide comparable information with respect to apparent hydraulic conductivities and fluxes for sediments near streams. In other settings, caution should be used due to differences in the nature of conservative (bromide) versus nonconservative (heat) tracers, particularly when preferential flowpaths are present.

  14. Estimation of Fluorescent Dye Amount in Tracer Dye Test

    Science.gov (United States)

    Pekkan, Emrah; Balkan, Erman; Balkan, Emir

    2015-04-01

    Karstic groundwater is more influenced by human than the groundwater that disperse in pores. On the other hand karstic groundwater resources, in addition to providing agricultural needs, livestock breeding, drinking and domestic water in most of the months of the year, they also supply drinking water to the wild life at high altitudes. Therefore sustainability and hydrogeological investigation of karstic resources is critical. Tracing techniques are widely used in hydrologic and hydrogeologic studies to determine water storage, flow rate, direction and protection area of groundwater resources. Karanfil Mountain (2800 m), located in Adana, Turkey, is one of the karstic recharge areas of the natural springs spread around its periphery. During explorations of the caves of Karanfil mountain, a 600 m deep cave was found by the Turkish and Polish cavers. At the bottom of the cave there is an underground river with a flow rate of approximately 0.5 m3/s during August 2014. The main spring is located 8 km far from the cave's entrance and its mean flow rate changes between 3.4 m3/s and 0.21 m3/s in March and September respectively according to a flowrate observation station of Directorate of Water Works of Turkey. As such frequent storms, snowmelt and normal seasonal variations in rainfall have a significant and rapid effect on the volume of this main spring resource. The objective of our research is to determine and estimate dye amount before its application on the field inspired from the previously literature on the subject. This estimation is intended to provide a preliminary application of a tracer test of a karstic system. In this study dye injection, inlet point will be an underground river located inside the cave and the observation station will be the spring that is approximately 8 km far from the cave entrance. On the other hand there is 600 meter elevation difference between cave entrance and outlet spring. In this test Rodamin-WT will be used as tracer and the

  15. Laboratory experiments on dispersive transport across interfaces: The role of flow direction

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, B.; Cortis, A.; Dror, I.; Scher, H.

    2009-04-01

    We present experimental evidence of asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials. Breakthrough curves are measured for tracer pulses that migrate in a steady state flow field through a column that contains adjacent segments of coarse and fine porous media. The breakthrough curves show significant differences in behavior, with tracers migrating from fine medium to coarse medium arriving significantly faster than those from coarse medium to fine medium. As the flow rate increases, the differences between the breakthrough curves diminish. We argue that this behavior indicates the occurrence of significant, time-dependent tracer accumulation in the resident concentration profile across the heterogeneity interface. Conventional modeling using the advection-dispersion equation is demonstrated to be unable to capture this asymmetric behavior. However, tracer accumulation at the interface has been observed in particle-tracking simulations, which may be related to the asymmetry in the observed breakthrough curves.

  16. Using Tracer Technology to Characterize Contaminated Pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Maresca, Joseph, W., Jr., Ph.D.; Bratton, Wesley, L., Ph.D., P.E.; Dickerson, Wilhelmina; Hales, Rochelle

    2005-12-30

    The Pipeline Characterization Using Tracers (PCUT) technique uses conservative and partitioning, reactive or other interactive tracers to remotely determine the amount of contaminant within a run of piping or ductwork. The PCUT system was motivated by a method that has been successfully used to characterize subsurface soil contaminants and is similar in operation to that of a gas chromatography column. By injecting a ?slug? of both conservative and partitioning tracers at one end (or section) of the piping and measuring the time history of the concentration of the tracers at the other end (or another section) of the pipe, the presence, location, and amount of contaminant within the pipe or duct can be determined. The tracers are transported along the pipe or duct by a gas flow field, typically air or nitrogen, which has a velocity that is slow enough so that the partitioning tracer has time to interact with the contaminant before the tracer slug completely passes over the contaminate region. PCUT not only identifies the presence of contamination, it also can locate the contamination along the pipeline and quantify the amount of residual. PCUT can be used in support of deactivation and decommissioning (D&D) of piping and ducts that may have been contaminated with hazardous chemicals such as chlorinated solvents, petroleum products, radioactive materials, or heavy metals, such as mercury.

  17. Tracer design for magnetic particle imaging (invited).

    Science.gov (United States)

    Ferguson, R Matthew; Khandhar, Amit P; Krishnan, Kannan M

    2012-04-01

    Magnetic particle imaging (MPI) uses safe iron oxide nanoparticle tracers to offer fundamentally new capabilities for medical imaging, in applications as vascular imaging and ultra-sensitive cancer therapeutics. MPI is perhaps the first medical imaging platform to intrinsically exploit nanoscale material properties. MPI tracers contain magnetic nanoparticles whose tunable, size-dependent magnetic properties can be optimized by selecting a particular particle size and narrow size-distribution. In this paper we present experimental MPI measurements acquired using a homemade MPI magnetometer: a zero-dimensional MPI imaging system designed to characterize tracer performance by measuring the derivative of the time-varying tracer magnetization, M'(H(t)), at a driving frequency of 25 kHz. We show that MPI performance is optimized by selecting phase-pure magnetite tracers of a particular size and narrow size distribution; in this work, tracers with 20 nm median diameter, log-normal distribution shape parameter, σ(v), equal to 0.26, and hydrodynamic diameter equal to 30 nm showed the best performance. Furthermore, these optimized MPI tracers show 4 × greater signal intensity (measured at the third harmonic) and 20% better spatial resolution compared with commercial nanoparticles developed for MRI.

  18. Saline tracer visualized with three-dimensional electrical resistivity tomography: Field-scale spatial moment analysis

    Science.gov (United States)

    Singha, Kamini; Gorelick, Steven M.

    2005-01-01

    Cross-well electrical resistivity tomography (ERT) was used to monitor the migration of a saline tracer in a two-well pumping-injection experiment conducted at the Massachusetts Military Reservation in Cape Cod, Massachusetts. After injecting 2200 mg/L of sodium chloride for 9 hours, ERT data sets were collected from four wells every 6 hours for 20 days. More than 180,000 resistance measurements were collected during the tracer test. Each ERT data set was inverted to produce a sequence of 3-D snapshot maps that track the plume. In addition to the ERT experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values. Using modified moment analysis of the electrical conductivity tomograms, the mass, center of mass, and spatial variance of the imaged tracer plume were estimated. Although the tomograms provide valuable insights into field-scale tracer migration behavior and aquifer heterogeneity, standard tomographic inversion and application of Archie's law to convert electrical conductivities to solute concentration results in underestimation of tracer mass. Such underestimation is attributed to (1) reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and (2) spatial smoothing (regularization) from tomographic inversion. The center of mass estimated from the ERT inversions coincided with that given by migration of the tracer plume using 3-D advective-dispersion simulation. The 3-D plumes seen using ERT exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well.

  19. A Preliminary Study on the Measurement of Sediment Concentration in Hill-Slope Runoff with an Electrolyte Tracer

    Directory of Open Access Journals (Sweden)

    Xiaonan Shi Fan Zhang

    2012-01-01

    Full Text Available Sediment concentration in hill-slope runoff is an important index for soil erosion. Developing a reliable and portable measuring system of sediment concentration is a core issue for soil and water conservation study, especially for the Tibetan Plateau under unfavorable climate and terrain conditions for field investigation. Challenges include uneven distribution of sediment across a runoff section as well as difficulty in detecting a wide range of particle sizes. An electrolyte tracer, with the advantage of uniform distribution and its widely used electric-conductivity sensor, can avoid the problems of direct measurement of sediment. A new measurement method of sediment concentration in runoff with an electrolyte tracer is proposed based on a premise that sediment concentration is closely correlated with hydrodynamic dispersion coefficient of solute in runoff. In this study, an experiment system of hill-slope runoff with an electrolyte tracer and sediments is first designed. Second, two model parameters in the advective-dispersive equation of solute transport, flow velocity and diffusion coefficient, are inversely estimated by calibrating the observed concentrations of an electrolyte tracer. And third, the relationship between sediment concentrations and hydrodynamic dispersion coefficients are defined through specified regression. As a result, a measurement system of sediment concentration in hill-slope runoff with an electrolyte tracer is primarily established by integrating the relationship of variables, experiment system, and model theory.

  20. Compartmental modeling and tracer kinetics

    CERN Document Server

    Anderson, David H

    1983-01-01

    This monograph is concerned with mathematical aspects of compartmental an­ alysis. In particular, linear models are closely analyzed since they are fully justifiable as an investigative tool in tracer experiments. The objective of the monograph is to bring the reader up to date on some of the current mathematical prob­ lems of interest in compartmental analysis. This is accomplished by reviewing mathematical developments in the literature, especially over the last 10-15 years, and by presenting some new thoughts and directions for future mathematical research. These notes started as a series of lectures that I gave while visiting with the Division of Applied ~1athematics, Brown University, 1979, and have developed in­ to this collection of articles aimed at the reader with a beginning graduate level background in mathematics. The text can be used as a self-paced reading course. With this in mind, exercises have been appropriately placed throughout the notes. As an aid in reading the material, the e~d of a ...

  1. Boundary integral method application in the transportation modeling of radioactive tracers in porous ways; Aplicacao do metodo da integral de contorno na modelagem do transporte de tracadores radioativos em meios porosos

    Energy Technology Data Exchange (ETDEWEB)

    Ferroni, Jose Geraldo

    1996-03-01

    This work describes a method for estimating the effluent concentrations of radioactive tracers in production wells, considering well to well injection tests and piston-like displacements of fluids in the reservoir. The model for tracer transportation takes into account effects of convection and hydrodynamic dispersion. (author)

  2. Tracer concentration profiles measured in central London as part of the REPARTEE campaign

    Science.gov (United States)

    Martin, D.; Petersson, K. F.; White, I. R.; Henshaw, S. J.; Nickless, G.; Lovelock, A.; Barlow, J. F.; Dunbar, T.; Wood, C. R.; Shallcross, D. E.

    2011-01-01

    There have been relatively few tracer experiments carried out that have looked at vertical plume spread in urban areas. In this paper we present results from two tracer (cyclic perfluorocarbon) experiments carried out in 2006 and 2007 in central London centred on the BT Tower as part of the REPARTEE (Regent's Park and Tower Environmental Experiment) campaign. The height of the tower gives a unique opportunity to study vertical dispersion profiles and transport times in central London. Vertical gradients are contrasted with the relevant Pasquill stability classes. Estimation of lateral advection and vertical mixing times are made and compared with previous measurements. Data are then compared with a simple operational dispersion model and contrasted with data taken in central London as part of the DAPPLE campaign. This correlates dosage with non-dimensionalised distance from source. Such analyses illustrate the feasibility of the use of these empirical correlations over these prescribed distances in central London.

  3. Tracer concentration profiles measured in central London as part of the REPARTEE campaign

    Directory of Open Access Journals (Sweden)

    D. Martin

    2011-01-01

    Full Text Available There have been relatively few tracer experiments carried out that have looked at vertical plume spread in urban areas. In this paper we present results from two tracer (cyclic perfluorocarbon experiments carried out in 2006 and 2007 in central London centred on the BT Tower as part of the REPARTEE (Regent's Park and Tower Environmental Experiment campaign. The height of the tower gives a unique opportunity to study vertical dispersion profiles and transport times in central London. Vertical gradients are contrasted with the relevant Pasquill stability classes. Estimation of lateral advection and vertical mixing times are made and compared with previous measurements. Data are then compared with a simple operational dispersion model and contrasted with data taken in central London as part of the DAPPLE campaign. This correlates dosage with non-dimensionalised distance from source. Such analyses illustrate the feasibility of the use of these empirical correlations over these prescribed distances in central London.

  4. Joint DOE/NRC field study of tracer migration in the unsaturated zone

    Energy Technology Data Exchange (ETDEWEB)

    Nyhan, J.; Polzer, W.; Essington, E.; Cokal, E.; Lane, L.; Lopez, E.; Stallings, E.; Walker, R.

    1986-03-01

    The results of a joint DOE/NRC field experiment to evaluate leaching and transport of solutes in a sandy silt backfill used for shallow land burial operations at Los Alamos are presented for steady-state and unsteady-state flow conditions. The migration of iodide, bromide, and lithium through the backfill material is studied as functions of depth and time and they are compared with one another. The bromide and iodide tracer data are used to estimate the diffusion coefficient, the tortuosity factor, and dispersivity. These values are used to calculate effective dispersion coefficients for subsequent analyses of the retardation factor and the distribution coefficient for lithium using least squares procedures. The results of the tracer migration study are discussed relative to challenges facing the waste management community, and chemical transport modeling opportunities are presented for a modeling workshop to be held in FY86.

  5. Effects of waves on water dispersion in a semi-enclosed estuarine bay

    Science.gov (United States)

    Delpey, M. T.; Ardhuin, F.; Otheguy, P.

    2012-04-01

    The bay of Saint Jean de Luz - Ciboure is a touristic destination located in the south west of France on the Basque coast. This small bay is 1.5km wide for 1km long. It is semi-enclosed by breakwaters, so that the area is mostly protected from waves except in its eastern part, where wave breaking is regularly observed over a shallow rock shelf. In the rest of the area the currents are generally weak. The bay receives fresh water inflows from two rivers. During intense raining events, the rivers can introduce pollutants in the bay. The input of pollutants combined with the low level dynamic of the area can affect the water quality for several days. To study such a phenomenon, mechanisms of water dispersion in the bay are investigated. The present paper focuses on the effects of waves on bay dynamics. Several field experiments were conducted in the area, combining wave and current measurements from a set of ADCP and ADV, lagrangian difter experiments in the surfzone, salinity and temperature profile measurements. An analysis of this set of various data is provided. It reveals that the bay combines remarkable density stratification due to fresh water inflows and occasionally intense wave-induced currents in the surfzone. These currents have a strong influence on river plume dynamics when the sea state is energetic. Moreover, modifications of hydrodynamics in the bay passes are found to be remarkably correlated with sea state evolutions. This result suggests a significant impact of waves on the bay flushing. To further analyse these phenomena, a three dimensional numerical model of bay hydrodynamics is developed. The model aims at reproducing fresh water inflows combined with wind-, tide- and wave-induced currents and mixing. The model of the bay is implemented using the code MOHID , which has been modified to allow the three dimensional representation of wave-current interactions proposed by Ardhuin et al. [2008b] . The circulation is forced by the wave field modelled

  6. Tracers discrimination of sediment provenience in rural catchment through EDXRF

    Energy Technology Data Exchange (ETDEWEB)

    Melquiades, Fabio L. [Universidade Estadual do Centro Oeste (UNICENTRO), Guarapuava, PR (Brazil). Dept. de Fisica; Thomaz, Edivaldo L. [Universidade Estadual do Centro Oeste (UNICENTRO), Guarapuava, PR (Brazil). Dept. de Geografia

    2010-07-01

    Full text: Sediment dynamics understanding in a drainage system is fundamental for soil and water conservation at hydro graphic basins. This work aim was to discriminate sediment provenance tracers in rural basin. Sediment samples from different points in the headwater (road, forest, riverbank, river sediment deposit) were collected. Energy Dispersive X-ray Fluorescence (EDXRF) was the analytical technique applied, which was efficient to detect the chemical composition of the sediments. The samples were dried for 48h at 50 deg C, ground and sieved for granulometry 1mm. In natura samples (3 g) were placed in cells covered with mylar film for irradiation. Titanium, Mn, Fe, Cu, Zn, Y and Zr were identified. It was concluded that the elements, when analyzed individually or paired, do not allow a clear environment distinction except for yttrium (Y) that indicates distinct characteristics between the riverbank materials related to the other environments. However, the cluster analysis provided discrimination between the different sources of sediment. Also, it was verified that the recent deposited sediment in the river channel displays greater similarity with the materials of the road than with the riverbank. It is probable that the roads has been the mainly sediment source in the studied headwater. The methodology is innovative for tracer determination in soil and erosion quantification. (author)

  7. Tracer monitoring of enhanced oil recovery projects

    Directory of Open Access Journals (Sweden)

    Kleven R.

    2013-05-01

    Full Text Available In enhanced oil recovery (EOR, chemicals are injected into the oil reservoir, either to increase macroscopic sweep efficiency, or to reduce remaining oil saturation in swept zones. Tracers can be used to identify reservoirs that are specifically suited for EOR operations. Injection of a selection of partitioning tracers, combined with frequent sample analysis of produced fluids, provides information suited for estimation of residual oil saturation. Tracers can also be used to evaluate and optimize the application of EOR chemicals in the reservoir. Suitable tracers will follow the EOR chemicals and assist in evaluation of retention, degradation or trapping. In addition to field applications, tracers also have a large potential as a tool to perform mechanistic studies of EOR chemicals in laboratory experiments. By labelling EOR chemicals with radioactive isotopes of elements such as H, C and S, detailed studies of transport mechanisms can be carried out. Co-injection of labelled compounds in dynamic flooding experiments in porous media will give information about retention or separation of the unique compounds constituting the chemical formulation. Separation of such compounds may be detrimental to obtaining the EOR effect expected. The paper gives new information of specific methods, and discusses current status for use of tracers in EOR operations.

  8. A comparison of SLAM and SCIPUFF using SEADEX tracer data

    Energy Technology Data Exchange (ETDEWEB)

    Atchison, M.K.

    1999-07-01

    The transport and diffusion models SCIPUFF (Second-order Closure Integrated Puff) and SLAM (Short-range Layered Atmospheric Model) were compared against each other using the land-sea breeze tracer data set SEADEX (The Shoreline Environment Atmospheric Dispersion Experiment). Predicted concentrations from both of these models were compared to observed concentrations at distances up to 15 km from a source for two of nine SEADEX releases. Emphasis was placed on a comparison of model output produced using various types of weather data (surface and upper-air). For the SEADEX release 1, SLAM was better at predicting the peak concentrations while SCIPUFF did a better job of predicting the overall plume widths. For SEADEX release 6, both SCIPUFF and SLAM performed similarly. However, SLAM moved the plume too fast compared to SCIPUFF and the actual observed plume location.

  9. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  10. CH as a Molecular Gas Tracer and C-shock Tracer Across a Molecular Cloud Boundary in Taurus

    Science.gov (United States)

    Xu, Duo; Li, Di

    2016-12-01

    We present new observations of all three ground-state transitions of the methylidyne (CH) radical and all four ground-state transitions of the hydroxyl (OH) radical toward a sharp boundary region of the Taurus molecular cloud. These data were analyzed in conjunction with existing CO and dust images. The derived CH abundance is consistent with previous observations of translucent clouds (0.8 ≤ A v ≤ 2.1 mag). The X(CH)-factor is nearly a constant (1.0 ± 0.06) × 1022 cm-2 K-1 km-1 s in this extinction range, with less dispersion than that of the more widely used molecular tracers CO and OH. CH turns out be a better tracer of total column density in such an intermediate extinction range than CO or OH. Compared with previous observations, CH is overabundant below 1 mag extinction. Such an overabundance of CH is consistent with the presence of a C-shock. CH has two kinematic components, one of which shifts from 5.3 to 6 km s-1, while the other stays at 6.8 km s-1 when moving from outside toward inside of the cloud. These velocity behaviors exactly match previous OH observation. The shifting of the two kinematic components indicates colliding streams or gas flow at the boundary region, which could be the cause of the C-shock.

  11. Using RFID and accelerometer-embedded tracers to measure probabilities of bed load transport, step lengths, and rest times in a mountain stream

    Science.gov (United States)

    Olinde, Lindsay; Johnson, Joel P. L.

    2015-09-01

    We present new measurements of bed load tracer transport in a mountain stream over several snowmelt seasons. Cumulative displacements were measured using passive tracers, which consisted of gravel and cobbles embedded with radio frequency identification tags. The timing of bed load motion during 11 transporting events was quantified with active tracers, i.e., accelerometer-embedded cobbles. Probabilities of cobble transport increased with discharge above a threshold, and exhibited slight to moderate hysteresis during snowmelt hydrographs. Dividing cumulative displacements by the number of movements recorded by each active tracer constrained average step lengths. Average step lengths increased with discharge, and distributions of average step lengths and cumulative displacements were thin tailed. Distributions of rest times followed heavy-tailed power law scaling. Rest time scaling varied somewhat with discharge and with the degree to which tracers were incorporated into the streambed. The combination of thin-tailed displacement distributions and heavy-tailed rest time distributions predict superdiffusive dispersion.

  12. Evaluation of leakage from fume hoods using tracer gas, tracer nanoparticles and nanopowder handling test methodologies.

    Science.gov (United States)

    Dunn, Kevin H; Tsai, Candace Su-Jung; Woskie, Susan R; Bennett, James S; Garcia, Alberto; Ellenbecker, Michael J

    2014-01-01

    The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the hood opening. These containment tests were conducted across a range of hood face velocities (60, 80, and 100 ft/min) and with the room ventilation system turned off and on. For the tracer gas and tracer nanoparticle tests, leakage was much more prominent on the left side of the hood (closest to the room supply air diffuser) although some leakage was noted on the right side and in the BZ sample locations. During the tracer gas and tracer nanoparticle tests, leakage was primarily noted when the room air conditioner was on for both the low and medium hood exhaust airflows. When the room air conditioner was turned off, the static tracer gas tests showed good containment across most test conditions. The tracer gas and nanoparticle test results were well correlated showing hood leakage under the same conditions and at the same sample locations. The impact of a room air conditioner was demonstrated with containment being adversely impacted during the use of room air ventilation. The tracer nanoparticle approach is a simple method requiring minimal setup and instrumentation. However, the method requires the reduction in

  13. Journal: A Review of Some Tracer-Test Design Equations for Tracer-Mass Estimation and Sample Collection Frequency

    Science.gov (United States)

    Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estima...

  14. Journal: A Review of Some Tracer-Test Design Equations for Tracer-Mass Estimation and Sample Collection Frequency

    Science.gov (United States)

    Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estima...

  15. Tracer-based prediction of thermal reservoir lifetime: scope, limitations, and the role of thermosensitive tracers

    Science.gov (United States)

    Ghergut, I.; Behrens, H.; Karmakar, S.; Licha, T.; Nottebohm, M.; Sauter, M.

    2012-04-01

    Thermal-lifetime prediction is a traditional endeavour of inter-well tracer tests conducted in geothermal reservoirs. Early tracer test signals (detectable within the first few years of operation) are expected to correlate with late-time production temperature evolutions ('thermal breakthrough', supposed to not occur before some decades of operation) of a geothermal reservoir. Whenever a geothermal reservoir can be described as a single-fracture system, its thermal lifetime will, ideally, be determined by two parameters (say, fracture aperture and porosity), whose inversion from conservative-tracer test signals is straightforward and non-ambiguous (provided that the tracer tests, and their interpretation, are performed in accordance to the rules of the art). However, as soon as only 'few more' fractures are considered, this clear-cut correlation is broken. A given geothermal reservoir can simultaneously feature a single-fracture behaviour, in terms of heat transport, and a multiple-fracture behaviour, in terms of solute tracer transport (or vice-versa), whose effective values of fracture apertures, spacings, and porosities are essentially uncorrelated between heat and solute tracers. Solute transport parameters derived from conservative-tracer tests will no longer characterize the heat transport processes (and thus temperature evolutions) taking place in the same reservoir. Parameters determining its thermal lifetime will remain 'invisible' to conservative tracers in inter-well tests. We demonstrate this issue at the example of a five-fracture system, representing a deep-geothermal reservoir, with well-doublet placement inducing fluid flow 'obliquely' to the fractures. Thermal breakthrough in this system is found to strongly depend on fracture apertures, whereas conservative-solute tracer signals from inter-well tests in the same system do not show a clear-cut correlation with fracture apertures. Only by using thermosensitive substances as tracers, a reliable

  16. Testing and comparison of four ionic tracers to measure stream flow loss by multiple tracer injection

    Science.gov (United States)

    Zellweger, G.W.

    1994-01-01

    An injectate containing lithium, sodium, chloride and bromide was added continuously at five sites along a 507 m study reach of St Kevin Gulch, Lake County, Colorado to determine which sections of the stream were losing water to the stream bed and to ascertain how well the four tracers performed. The acidity of the stream (pH 3.6) made it possible for lithium and sodium, which are normally absorbed by ion exchange with stream bed sediment, to be used as conservative tracers. Net flow losses as low as 0.81 s-1, or 8% of flow, were calculated between measuring sites. By comparing the results of simultaneous injection it was determined whether subsections of the study reach were influent or effluent. Evaluation of tracer concentrations along 116 m of stream indicated that all four tracers behaved conservatively. Discharges measured by Parshall flumes were 4-18% greater than discharges measured by tracer dilution. -from Author

  17. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... positions close to the boundaries. Different rules have been suggested in the literature with justifications based on simulation studies. Herein the relevant stochastic differential equation model is formulated in a particular way. The formulation is based on the marginal transformation of the position...... dependent particle velocity into a position independent Gaussian velocity. Boundary conditions are obtained from Itos rule of stochastic differentiation. The model directly point at a canonical rule of reflection for the approximating random walk with finite time step. This reflection rule is different from...

  18. TRACER - TRACING AND CONTROL OF ENGINEERING REQUIREMENTS

    Science.gov (United States)

    Turner, P. R.

    1994-01-01

    TRACER (Tracing and Control of Engineering Requirements) is a database/word processing system created to document and maintain the order of both requirements and descriptive material associated with an engineering project. A set of hierarchical documents are normally generated for a project whereby the requirements of the higher level documents levy requirements on the same level or lower level documents. Traditionally, the requirements are handled almost entirely by manual paper methods. The problem with a typical paper system, however, is that requirements written and changed continuously in different areas lead to misunderstandings and noncompliance. The purpose of TRACER is to automate the capture, tracing, reviewing, and managing of requirements for an engineering project. The engineering project still requires communications, negotiations, interactions, and iterations among people and organizations, but TRACER promotes succinct and precise identification and treatment of real requirements separate from the descriptive prose in a document. TRACER permits the documentation of an engineering project's requirements and progress in a logical, controllable, traceable manner. TRACER's attributes include the presentation of current requirements and status from any linked computer terminal and the ability to differentiate headers and descriptive material from the requirements. Related requirements can be linked and traced. The program also enables portions of documents to be printed, individual approval and release of requirements, and the tracing of requirements down into the equipment specification. Requirement "links" can be made "pending" and invisible to others until the pending link is made "binding". Individuals affected by linked requirements can be notified of significant changes with acknowledgement of the changes required. An unlimited number of documents can be created for a project and an ASCII import feature permits existing documents to be incorporated

  19. TRACER - TRACING AND CONTROL OF ENGINEERING REQUIREMENTS

    Science.gov (United States)

    Turner, P. R.

    1994-01-01

    TRACER (Tracing and Control of Engineering Requirements) is a database/word processing system created to document and maintain the order of both requirements and descriptive material associated with an engineering project. A set of hierarchical documents are normally generated for a project whereby the requirements of the higher level documents levy requirements on the same level or lower level documents. Traditionally, the requirements are handled almost entirely by manual paper methods. The problem with a typical paper system, however, is that requirements written and changed continuously in different areas lead to misunderstandings and noncompliance. The purpose of TRACER is to automate the capture, tracing, reviewing, and managing of requirements for an engineering project. The engineering project still requires communications, negotiations, interactions, and iterations among people and organizations, but TRACER promotes succinct and precise identification and treatment of real requirements separate from the descriptive prose in a document. TRACER permits the documentation of an engineering project's requirements and progress in a logical, controllable, traceable manner. TRACER's attributes include the presentation of current requirements and status from any linked computer terminal and the ability to differentiate headers and descriptive material from the requirements. Related requirements can be linked and traced. The program also enables portions of documents to be printed, individual approval and release of requirements, and the tracing of requirements down into the equipment specification. Requirement "links" can be made "pending" and invisible to others until the pending link is made "binding". Individuals affected by linked requirements can be notified of significant changes with acknowledgement of the changes required. An unlimited number of documents can be created for a project and an ASCII import feature permits existing documents to be incorporated

  20. Comparison of denitrification activity measurements in groundwater using cores and natural-gradient tracer tests

    Science.gov (United States)

    Smith, R.L.; Garabedian, S.P.; Brooks, M.H.

    1996-01-01

    The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In this study, we measured in situ rates of denitrification in a nitrate- contaminated aquifer using small-scale, natural-gradient tracer tests and compared the results with rates obtained from laboratory incubations with aquifer core material. Activity was measured using the acetylene block technique. For the tracer tests, co-injection of acetylene and bromide into the aquifer produced a 30 ??M increase in nitrous oxide after 10 m of transport (23-30 days). An advection-dispersion transport model was modified to include an acetylene-dependent nitrous oxide production term and used to simulate the tracer breakthrough curves. The model required a 4-day lag period and a relatively low sensitivity to acetylene to match the narrow nitrous oxide breakthrough curves. Estimates of in situ denitrification rates were 0.60 and 1.51 nmol of N2O produced cm-3 aquifer day-1 for two successive tests. Aquifer core material collected from the tracer test site and incubated as mixed slurries in flasks and as intact cores yielded rates that were 1.2-26 times higher than the tracer test rate estimates. Results with the coring-dependent techniques were variable and subject to the small- scale heterogeneity within the aquifer, while the tracer tests integrated the heterogeneity along a flow path, giving a rate estimate that is more applicable to transport at the scale of the aquifer.

  1. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    Energy Technology Data Exchange (ETDEWEB)

    B.M. Freifeild

    2001-10-18

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  2. Tracer diffusion in active suspensions

    Science.gov (United States)

    Burkholder, Eric W.; Brady, John F.

    2017-05-01

    We study the diffusion of a Brownian probe particle of size R in a dilute dispersion of active Brownian particles of size a , characteristic swim speed U0, reorientation time τR, and mechanical energy ksTs=ζaU02τR/6 , where ζa is the Stokes drag coefficient of a swimmer. The probe has a thermal diffusivity DP=kBT /ζP , where kBT is the thermal energy of the solvent and ζP is the Stokes drag coefficient for the probe. When the swimmers are inactive, collisions between the probe and the swimmers sterically hinder the probe's diffusive motion. In competition with this steric hindrance is an enhancement driven by the activity of the swimmers. The strength of swimming relative to thermal diffusion is set by Pes=U0a /DP . The active contribution to the diffusivity scales as Pes2 for weak swimming and Pes for strong swimming, but the transition between these two regimes is nonmonotonic. When fluctuations in the probe motion decay on the time scale τR, the active diffusivity scales as ksTs/ζP : the probe moves as if it were immersed in a solvent with energy ksTs rather than kBT .

  3. Tracer transport modeling with the Alliances platform in the presence of evapotranspiration

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, A.; Diaconu, D.; Bucur, C. [Institute for Nuclear Research, Pitesti (Romania); Genty, A. [CEA Saclay, Gif-sur-Yvette (France)

    2013-11-15

    The knowledge and understanding of water flow and solute transport in the unsaturated zone is becoming increasingly important especially in mitigation of groundwater pollution. Fate of radionuclide in the geological environment is a topic to address in performance and safety assessment studies for nuclear waste disposal and may be modeled considering flow and transport in porous media. However, often, due to the heterogeneity and anisotropy of the real systems, the computer simulations may be difficult to render the real behavior. This paper addresses the simulation of a tracer transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on experimental data and was performed with the Alliances platform, a numerical tool developed by French organizations CEA, ANDRA and EDF. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, the dispersivity coefficients of iodine were investigated in order to match the experimental concentration determined on samples from different locations of the site. A close fit of the simulation over experimental data for the water saturation profile at a depth of 0.5 m in transient state was targeted by taking into account evapotranspiration in order to obtain a realistic estimation of the water infiltration in the porous media. Dispersivity coefficients obtained from the simulation of the tracer transport are in good order of magnitude for the unsaturated area and allow to have a good preview of the tracer plume. However, further investigations are recommended on new samples in order to validate the migration of the tracer plume as expected. (orig.)

  4. Sediment routing through channel confluences: RFID tracer experiments from a gravel-bed river headwaters

    Science.gov (United States)

    Imhoff, K.; Wilcox, A. C.

    2014-12-01

    Tributary confluences may significantly impact large-scale patterns of sediment transport because of their role in connecting individual streams in a network. These unique locations feature complex flow structures and geomorphic features, and may represent ecological hotspots. Sediment transport across confluences is poorly understood, however. We present research on coarse sediment transport and dispersion through confluences using sediment tracers in the East Fork Bitterroot River, Montana, USA. We tagged a range of gravel (>40 mm) and cobble particles with Radio Frequency Identification (RFID) tags and painted smaller (10-40 mm) gravels, and then we traced them through confluences in a montane river's headwaters. We measured the effects of confluences on dispersion, path length, and depositional location and compare properties of sediment routing with a non-confluence control reach. We also measured topographic change through repeat bed surveys and combined topography, hydraulics, and tracer measurements to calculate basal shear and critical Shields stresses for different grain sizes. Field observations suggest that tagged particles in confluences routed along flanks of scour holes in confluences, with sediment depositing further downstream along bank-lateral bars than within the channel thalweg. Travel distances of RFID-tagged particles ranged up to 35 meters from original seeding points, with initial recovery rates of RFID-tagged tracers ranging between 84-89%. In both confluence and control reaches only partial mobility was observed within the entire tracer population, suggesting a hiding effect imposed by the roughness of the bed. Particles seeded in the channel thalweg experienced further travel distances than those seeded towards the banks and on bars. Differences in dispersion between confluence and control reaches are implied by field observation. This study quantified patterns of sediment routing within confluences and provided insight to the importance

  5. Enhanced Oil Recovery: Aqueous Flow Tracer Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Joseph Rovani; John Schabron

    2009-02-01

    A low detection limit analytical method was developed to measure a suite of benzoic acid and fluorinated benzoic acid compounds intended for use as tracers for enhanced oil recovery operations. Although the new high performance liquid chromatography separation successfully measured the tracers in an aqueous matrix at low part per billion levels, the low detection limits could not be achieved in oil field water due to interference problems with the hydrocarbon-saturated water using the system's UV detector. Commercial instrument vendors were contacted in an effort to determine if mass spectrometry could be used as an alternate detection technique. The results of their work demonstrate that low part per billion analysis of the tracer compounds in oil field water could be achieved using ultra performance liquid chromatography mass spectrometry.

  6. Dispersed Indeterminacy

    CERN Document Server

    Fayngold, Moses

    2013-01-01

    A state of a single particle can be represented by a quantum blob in the corresponding phase space, or a patch (granule) in its 2-D subspace. Its area is frequently stated to be no less than, implying that such a granule is an indivisible quantum of the 2-D phase space. But this is generally not true, as is evident, for instance, from representation of some states in the basis of innately discrete observables like angular momentum. Here we consider some dispersed states involving the evanescent waves different from that in the total internal reflection. Such states are represented by a set of separated granules with individual areas, but with the total indeterminacy . An idealized model has a discrete Wigner function and is described by a superposition of eigenstates with eigenvalues and forming an infinite periodic array of dots on the phase plane. The question about the total indeterminacy in such state is discussed. We argue that the eigenstates corresponding to the considered EW cannot be singled out by a...

  7. Transformationally decoupling clustering and tracer bias

    CERN Document Server

    Neyrinck, Mark C

    2014-01-01

    Gaussianizing transformations are used statistically in many non-cosmological fields, but in cosmology, we are only starting to apply them. Here I explain a strategy of analyzing the 1-point function (PDF) of a spatial field, together with the 'essential' clustering statistics of the Gaussianized field, which are invariant to a local transformation. In cosmology, if the tracer sampling is sufficient, this achieves two important goals. First, it can greatly multiply the Fisher information, which is negligible on nonlinear scales in the usual $\\delta$ statistics. Second, it decouples clustering statistics from a local bias description for tracers such as galaxies.

  8. A review of methods for modelling environmental tracers in groundwater: Advantages of tracer concentration simulation

    Science.gov (United States)

    Turnadge, Chris; Smerdon, Brian D.

    2014-11-01

    Mathematical models of varying complexity have been developed since the 1960s to interpret environmental tracer concentrations in groundwater flow systems. This review examines published studies of model-based environmental tracer interpretation, the progress of different modelling approaches, and also considers the value of modelling tracer concentrations directly rather than estimations of groundwater age. Based on citation metrics generated using the Web of Science and Google Scholar reference databases, the most highly utilised interpretation approaches are lumped parameter models (421 citations), followed closely by direct age models (220 citations). A third approach is the use of mixing cell models (99 citations). Although lumped parameter models are conceptually simple and require limited data, they are unsuitable for characterising the internal dynamics of a hydrogeological system and/or under conditions where large scale anthropogenic stresses occur within a groundwater basin. Groundwater age modelling, and in particular, the simulation of environmental tracer transport that explicitly accounts for the accumulation and decay of tracer mass, has proven to be highly beneficial in constraining numerical models. Recent improvements in computing power have made numerical simulation of tracer transport feasible. We argue that, unlike directly simulated ages, the results of tracer mass transport simulation can be compared directly to observations, without needing to correct for apparent age bias or other confounding factors.

  9. A spreadsheet program for two-well tracer test data analysis.

    Science.gov (United States)

    Tang, Guoping; Watson, David B; Parker, Jack C; Brooks, Scott C

    2012-01-01

    Two-well tracer tests are often conducted to investigate subsurface solute transport in the field. Analyzing breakthrough curves in extraction and monitoring wells using numerical methods is nontrivial due to highly nonuniform flow conditions. We extended approximate analytical solutions for the advection-dispersion equation for an injection-extraction well doublet in a homogeneous confined aquifer under steady-state flow conditions for equal injection and extraction rates with no transverse dispersion and negligible ambient flow, and implemented the solutions in Microsoft Excel using Visual Basic for Application (VBA). Functions were implemented to calculate concentrations in extraction and monitoring wells at any location due to a step or pulse injection. Type curves for a step injection were compared with those calculated by numerically integrating the solution for a pulse injection. The results from the two approaches are similar when the dispersivity is small. As the dispersivity increases, the latter was found to be more accurate but requires more computing time. The code was verified by comparing the results with published-type curves and applied to analyze data from the literature. The method can be used as a first approximation for two-well tracer test design and data analysis, and to check accuracy of numerical solutions. The code and example files are publicly available.

  10. Accuracy of travel time distribution (TTD) models as affected by TTD complexity, observation errors, and model and tracer selection

    Science.gov (United States)

    Green, Christopher T.; Zhang, Yong; Jurgens, Bryant C.; Starn, J. Jeffrey; Landon, Matthew K.

    2014-01-01

    Analytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic datasets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for one public-supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer (NO3−) concentrations. Analytical models included a new, scale-dependent dispersivity model (SDM) for two-dimensional transport from the watertable to a well, and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for NO3− and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.

  11. Natural products and altered derivatives as tracers for biomass combustion in aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Simoneit, B.R.T. [Oregon State Univ., Corvallis, OR (United States); Radzi bin Abas, M. [Univ. of Malaya, Kuala Lumpur (Malaysia); Cass, G.R. [California Institute of Technology, Pasadena, CA (United States)] [and others

    1995-12-01

    Biomass combustion is an important primary source of carbonaceous particles in the global atmosphere. Various molecular markers have been proposed for this process but additional specific tracers are needed. The injection of natural product organic compounds into smoke occurs primarily by direct volatilization/steam stripping and by pyrolysis. Although the composition of organic matter in smoke particles is highly variable, the molecular structures of the tracers are generally source specific. Homologous compounds and biomarkers present in smoke are derived directly from plant wax, gum and resin by volatilization and secondarily from pyrolysis of biopolymers (e.g., lignin, cutin, suberin), wax, gum and resin. The component complexity is illustrated with examples from controlled bums of temperate and tropical biomass fuels. Conifer smoke contains characteristic tracers from diterpenoids as well as phenolics and other oxygenated species. These are recognizable in urban airsheds. The major organic components of smoke from tropical biomass are straight-chain, aliphatic and oxygenated compounds and triterpenoids. Several compounds are potential key indicators for combustion of such biomass. The precursor to product approach of organic geochemistry can be applied successfully to provide molecular tracers for studying smoke plume chemistry and dispersion.

  12. Analysis of tracer responses in the BULLION Forced-Gradient Experiment at Pahute Mesa, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Paul W. Reimus; Marc J. Haga

    1999-10-01

    This report presents an analysis of the tracer data from the BULLION forced-gradient experiment (FGE) conducted on Pahute Mesa at the Nevada Test Site from June 2, 1997 through August 28, 1997, for the Underground Test Area (UGTA) Program. It also serves to document the polystyrene microsphere data from the FGE. The FGE involved the injection of solute and colloid tracers into wells ER-20-6 No. 1 and ER-20-6 No. 2 while ER-20-6 No. 3 was pumped at approximately 116 gallons per minute (gpm). The experimental configuration and test design are described briefly in this report; more details are provided elsewhere (IT, 1996, 1997, 1998). The tracer responses in the various wells yielded valuable information about transport processes such as longitudinal dispersion, matrix diffusion and colloid transport in the hydrogeologic system in the vicinity of the BULLION nuclear test cavity. Parameter values describing these processes are derived from the semi-analytical model interpretations presented in this report. A companion report (IT, 1998) presents more detailed numerical modeling interpretations of the solute tracer responses.

  13. Blood tracer kinetics in the arterial tree.

    Directory of Open Access Journals (Sweden)

    Elias Kellner

    Full Text Available Evaluation of blood supply of different organs relies on labeling blood with a suitable tracer. The tracer kinetics is linear: Tracer concentration at an observation site is a linear response to an input somewhere upstream the arterial flow. The corresponding impulse response functions are currently treated empirically without incorporating the relation to the vascular morphology of an organ. In this work we address this relation for the first time. We demonstrate that the form of the response function in the entire arterial tree is reduced to that of individual vessel segments under approximation of good blood mixing at vessel bifurcations. The resulting expression simplifies significantly when the geometric scaling of the vascular tree is taken into account. This suggests a new way to access the vascular morphology in vivo using experimentally determined response functions. However, it is an ill-posed inverse problem as demonstrated by an example using measured arterial spin labeling in large brain arteries. We further analyze transport in individual vessel segments and demonstrate that experimentally accessible tracer concentration in vessel segments depends on the measurement principle. Explicit expressions for the response functions are obtained for the major middle part of the arterial tree in which the blood flow in individual vessel segments can be treated as laminar. When applied to the analysis of regional cerebral blood flow measurements for which the necessary arterial input is evaluated in the carotid arteries, present theory predicts about 20% underestimation, which is in agreement with recent experimental data.

  14. Blood tracer kinetics in the arterial tree.

    Science.gov (United States)

    Kellner, Elias; Gall, Peter; Günther, Matthias; Reisert, Marco; Mader, Irina; Fleysher, Roman; Kiselev, Valerij G

    2014-01-01

    Evaluation of blood supply of different organs relies on labeling blood with a suitable tracer. The tracer kinetics is linear: Tracer concentration at an observation site is a linear response to an input somewhere upstream the arterial flow. The corresponding impulse response functions are currently treated empirically without incorporating the relation to the vascular morphology of an organ. In this work we address this relation for the first time. We demonstrate that the form of the response function in the entire arterial tree is reduced to that of individual vessel segments under approximation of good blood mixing at vessel bifurcations. The resulting expression simplifies significantly when the geometric scaling of the vascular tree is taken into account. This suggests a new way to access the vascular morphology in vivo using experimentally determined response functions. However, it is an ill-posed inverse problem as demonstrated by an example using measured arterial spin labeling in large brain arteries. We further analyze transport in individual vessel segments and demonstrate that experimentally accessible tracer concentration in vessel segments depends on the measurement principle. Explicit expressions for the response functions are obtained for the major middle part of the arterial tree in which the blood flow in individual vessel segments can be treated as laminar. When applied to the analysis of regional cerebral blood flow measurements for which the necessary arterial input is evaluated in the carotid arteries, present theory predicts about 20% underestimation, which is in agreement with recent experimental data.

  15. Fractal tracer distributions in turbulent field theories

    DEFF Research Database (Denmark)

    Hansen, J. Lundbek; Bohr, Tomas

    1998-01-01

    We study the motion of passive tracers in a two-dimensional turbulent velocity field generated by the Kuramoto-Sivashinsky equation. By varying the direction of the velocity-vector with respect to the field-gradient we can continuously vary the two Lyapunov exponents for the particle motion and t...

  16. Suitability of tracers; Eignung von Tracern

    Energy Technology Data Exchange (ETDEWEB)

    Klotz, D. [GSF - Forschungszentrum fuer Umwelt und Gesundheit GmbH, Neuherberg (Germany). Inst. fuer Hydrologie

    1999-02-01

    Hydrological tracer techniques are a means of making statements on the direction and speed of underground water. One of the simpler tasks is to find out whether there is hydrological communication between two given points. This requires a determination of the direction of flow, which places less exacting demands on the properties of the tracer than does the task of determining the flow velocity of underground water. Tracer methods can serve to infer from flow velocity the distance (flow) velocity, which is defined as the ratio between the distance between two points located in flow direction and the actual time it takes water to flow from one to the other. [Deutsch] Mit Hilfe der hydrologischen Markierungstechniken koennen Aussagen ueber die Richtung und die Geschwindigkeit von Bewegungen des unterirdischen Wassers gemacht werden. Der einfachere Fall liegt vor, wenn festgestellt werden soll, ob zwischen zwei Punkten eine hydrologische Verbindung besteht. Bei dieser Fliessrichtungsbestimmung sind die Forderungen an die Eigenschaften der einzusetzenden Tracer geringer als bei der Bestimmung der Geschwindigkeit des unterirdischen Wassers. Von den Geschwindigkeiten des unterirdischen Wassers ist die Abstands-(Fliess)geschwindigkeit, die definiert ist durch das Verhaeltnis aus dem Abstand und der wahren Fliesszeit zwischen zwei in Bewegungsrichtung gelegenen Punkten, durch Tracermethoden zu bestimmen. (orig.)

  17. Using neural networks to describe tracer correlations

    Directory of Open Access Journals (Sweden)

    D. J. Lary

    2004-01-01

    Full Text Available Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and methane volume mixing ratio (v.m.r.. In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH4-N2O correlation with a correlation coefficient between simulated and training values of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE which has continuously observed CH4  (but not N2O from 1991 till the present. The neural network Fortran code used is available for download.

  18. Travel-time-based thermal tracer tomography

    Science.gov (United States)

    Somogyvári, Márk; Bayer, Peter; Brauchler, Ralf

    2016-05-01

    Active thermal tracer testing is a technique to get information about the flow and transport properties of an aquifer. In this paper we propose an innovative methodology using active thermal tracers in a tomographic setup to reconstruct cross-well hydraulic conductivity profiles. This is facilitated by assuming that the propagation of the injected thermal tracer is mainly controlled by advection. To reduce the effects of density and viscosity changes and thermal diffusion, early-time diagnostics are used and specific travel times of the tracer breakthrough curves are extracted. These travel times are inverted with an eikonal solver using the staggered grid method to reduce constraints from the pre-defined grid geometry and to improve the resolution. Finally, non-reliable pixels are removed from the derived hydraulic conductivity tomograms. The method is applied to successfully reconstruct cross-well profiles as well as a 3-D block of a high-resolution fluvio-aeolian aquifer analog data set. Sensitivity analysis reveals a negligible role of the injection temperature, but more attention has to be drawn to other technical parameters such as the injection rate. This is investigated in more detail through model-based testing using diverse hydraulic and thermal conditions in order to delineate the feasible range of applications for the new tomographic approach.

  19. Nanoparticle tracers in calcium carbonate porous media

    KAUST Repository

    Li, Yan Vivian

    2014-07-15

    Tracers are perhaps the most direct way of diagnosing subsurface fluid flow pathways for ground water decontamination and for natural gas and oil production. Nanoparticle tracers could be particularly effective because they do not diffuse away from the fractures or channels where flow occurs and thus take much less time to travel between two points. In combination with a chemical tracer they can measure the degree of flow concentration. A prerequisite for tracer applications is that the particles are not retained in the porous media as the result of aggregation or sticking to mineral surfaces. By screening eight nanoparticles (3-100 nm in diameter) for retention when passed through calcium carbonate packed laboratory columns in artificial oil field brine solutions of variable ionic strength we show that the nanoparticles with the least retention are 3 nm in diameter, nearly uncharged, and decorated with highly hydrophilic polymeric ligands. The details of these column experiments and the tri-modal distribution of zeta potential of the calcite sand particles in the brine used in our tests suggests that parts of the calcite surface have positive zeta potential and the retention of negatively charged nanoparticles occurs at these sites. Only neutral nanoparticles are immune to at least some retention. © 2014 Springer Science+Business Media.

  20. Halon-1301, a new Groundwater Age Tracer

    Science.gov (United States)

    Beyer, Monique; van der Raaij, Rob; Morgenstern, Uwe; Jackson, Bethanna

    2015-04-01

    Groundwater dating is an important tool to assess groundwater resources in regards to direction and time scale of groundwater flow and recharge and to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However ambiguous age interpretations are often faced, due to a limited set of available tracers and limitations of each tracer method when applied alone. There is a need for additional, complementary groundwater age tracers. We recently discovered that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate [Beyer et al, 2014]. Halon-1301 can be determined along with SF6, SF5CF3 and CFC-12 in groundwater using a gas chromatography setup with attached electron capture detector developed by Busenberg and Plummer [2008]. Halon-1301 has not been assessed in groundwater. This study assesses the behaviour of Halon-1301 in water and its suitability as a groundwater age tracer. We determined Halon-1301 in 17 groundwater and various modern (river) waters sites located in 3 different groundwater systems in the Wellington Region, New Zealand. These waters have been previously dated with tritium, CFC-12, CFC-11 and SF6 with mean residence times ranging from 0.5 to over 100 years. The waters range from oxic to anoxic and some show evidence of CFC contamination or degradation. This allows us to assess the different properties affecting the suitability of Halon-1301 as groundwater age tracer, such as its conservativeness in water and local contamination potential. The samples are analysed for Halon-1301 and SF6simultaneously, which allows identification of issues commonly faced when using gaseous tracers such as contamination with modern air during sampling. Overall we found in the assessed groundwater samples Halon-1301 is a feasible new groundwater tracer. No sample indicated significantly elevated

  1. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  2. Laplace transform in tracer kinetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hauser, Eliete B., E-mail: eliete@pucrs.br [Instituto do Cerebro (InsCer/FAMAT/PUC-RS), Porto Alegre, RS, (Brazil). Faculdade de Matematica

    2013-07-01

    The main objective this paper is to quantify the pharmacokinetic processes: absorption, distribution and elimination of radiopharmaceutical(tracer), using Laplace transform method. When the drug is administered intravenously absorption is complete and is available in the bloodstream to be distributed throughout the whole body in all tissues and fluids, and to be eliminated. Mathematical modeling seeks to describe the processes of distribution and elimination through compartments, where distinct pools of tracer (spatial location or chemical state) are assigned to different compartments. A compartment model is described by a system of differential equations, where each equation represents the sum of all the transfer rates to and from a specific compartment. In this work a two-tissue irreversible compartment model is used for description of tracer, [{sup 18}F]2-fluor-2deoxy-D-glucose. In order to determine the parameters of the model, it is necessary to have information about the tracer delivery in the form of an input function representing the time-course of tracer concentration in arterial blood or plasma. We estimate the arterial input function in two stages and apply the Levenberg-Marquardt Method to solve nonlinear regressions. The transport of FDG across de arterial blood is very fast in the first ten minutes and then decreases slowly. We use de Heaviside function to represent this situation and this is the main contribution of this study. We apply the Laplace transform and the analytical solution for two-tissue irreversible compartment model is obtained. The only approach is to determinate de arterial input function. (author)

  3. An inexpensive field fluorometer for hydrogeological tracer tests with three tracers and turbidity measurement

    OpenAIRE

    Schnegg, Pierre-André

    2005-01-01

    The Geomagnetism Group of the University of Neuchâtel has recently designed a flow-through field fluorometer with added spectral capabilities for hydrological tracer tests. This instrument is equipped with four optical axes allowing water sample illumination with four independent light sources at different wavelenghs covering the full spectrum from UV to red. As many as three conveniently selected (dye) tracers can be simultaneously measured and separeted from a cocktail. Careful turbidity me...

  4. EVALUATION OF LEAKAGE FROM FUME HOODS USING TRACER GAS, TRACER NANOPARTICLES AND NANOPOWDER HANDLING TEST METHODOLOGIES

    OpenAIRE

    Dunn, Kevin H.; Tsai, Candace Su-Jung; Woskie, Susan R.; Bennett, James S.; Garcia, Alberto; Ellenbecker, Michael J.

    2014-01-01

    The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tr...

  5. Tracking different freshwater plumes at the Bay of Biscay scale by using a dissolved radioactive tracer: tritium (HTO)

    Science.gov (United States)

    Oms, Pierre-Emmanuel; Bailly du Bois, Pascal; Dumas, Franck; Lazure, Pascal; Morillon, Mehdi; Solier, Luc; Voiseux, Claire; Le Corre, Cédric; Maire, Donovan

    2017-04-01

    New measurements of a radioactive tracer (tritium) on the whole continental shelf of the Bay of Biscay during several oceanographic campaigns between 2008 and 2016 allow comparison with results of the plume dispersion from the regional circulation model, MARS3D (Lazure and Dumas, 2008). Seaward dispersion of freshwater in the Bay of Biscay is highly variable in time and depends on many processes like tide, wind, freshwater runoff or water mass stratification. Until now salinity was a useful tracer to describe dispersion of freshwater, but the complexity to account for these different sources require an additional conservative tracer. Tritium (3H) is a radionuclide tracer released as HTO in the Bay of Biscay by nuclear power plant through two French rivers, Loire and Gironde. Tritium inflow from Loire and Gironde are well known thanks to plants operator data and an effort of daily measurements. Indeed an automated and daily integrated sampling system is deployed in the Loire River and the Gironde Estuary. These plumes are clearly detectable over the continental shelf despite very low tritium concentrations (0.05 - 0.5 Bq/L, 0.5 - 5 TU). In order to determine such low tritium concentrations in the Bay of Biscay, we use a mass spectrometer to measure the 3He (gas) produced by radioactive disintegration of tritium after 3He ingrowth (1 - 6 months). The aim of this work is to describes and quantify the dispersion processes occurring in the continental shelf according to seasons. Thanks to assessments of the model dispersion compared to in-situ measurements, quantification of the residential time of freshwater in the continental shelf as well as quantification of their transfer from continental shelf to abyssal plain is possible. The 3H/S ratio will allow an estimation of respective inputs from Loire and Gironde in the bay.

  6. Tracer concentration profiles measured in central London as part of the REPARTEE campaign

    Directory of Open Access Journals (Sweden)

    D. E. Shallcross

    2009-11-01

    Full Text Available There have been relatively few tracer experiments carried out that have looked at vertical plume spread in urban areas. In this paper we present results from cyclic perfluorocarbon tracer experiments carried out in 2006 and 2007 in central London centred on the BT Tower as part of the REPARTEE (Regent's Park and Tower Environmental Experiment campaign. The height of the tower gives a unique opportunity to study dispersion over a large vertical gradient. These gradients are then compared with classical Gaussian profiles of the relevant stability classes over a range of distances as well as interpretation of data with reference to both anemometry and LIDAR measurements made. Data are then compared with an operational model and contrasted with data taken in central London as part of the DAPPLE campaign looking at dosage compared with non-dimensionalised distance from source. Such analysis illustrates the feasibility of the use of these empirical correlations over these prescribed distances in central London.

  7. Virtual velocity of tracers in a gravel-bed river using size-based competence duration

    Science.gov (United States)

    Milan, David J.

    2013-09-01

    Virtual velocity (Vi) of river gravels is commonly used to determine sediment transport rates and gravel dispersion dynamics. Virtual velocity is calculated from tracer gravel step-length data as the distance travelled divided by the duration of competence. However, no allowance is usually made for differences in competence duration according to grain size. In this investigation, Vi of gravel tracer clasts for the River Rede, Northumberland, UK, is calculated using a method that takes into consideration an approximation of size-based competence duration. Although scaled transport distance data compared favourably to past studies, it was the comparatively smaller clasts that tended to have lower Vi in comparison to coarser clasts, because of their longer competence duration, contrasting with previously published research. The key findings of the study serve as proof of concept and should be adopted in future studies that focus upon Vi estimation.

  8. PET tracers for somatostatin receptor imaging of neuroendocrine tumors

    DEFF Research Database (Denmark)

    Johnbeck, Camilla Bardram; Knigge, Ulrich; Kjær, Andreas

    2014-01-01

    Neuroendocrine tumors have shown rising incidence mainly due to higher clinical awareness and better diagnostic tools over the last 30 years. Functional imaging of neuroendocrine tumors with PET tracers is an evolving field that is continuously refining the affinity of new tracers in the search...... these PET tracers further....

  9. Natural tracer profiles across argillaceous formations

    Energy Technology Data Exchange (ETDEWEB)

    Mazurek, Martin, E-mail: mazurek@geo.unibe.ch [Rock-Water Interaction, Institute of Geological Sciences, University of Bern (Switzerland); Alt-Epping, Peter [Rock-Water Interaction, Institute of Geological Sciences, University of Bern (Switzerland); Bath, Adrian [Intellisci, Willoughby on the Wolds, Loughborough LE12 6SZ (United Kingdom); Gimmi, Thomas [Rock-Water Interaction, Institute of Geological Sciences, University of Bern (Switzerland)] [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Niklaus Waber, H. [Rock-Water Interaction, Institute of Geological Sciences, University of Bern (Switzerland); Buschaert, Stephane [Andra, Parc de la Croix Blanche, 92298 Chatenay-Malabry Cedex (France); Canniere, Pierre De; Craen, Mieke De [SCK-CEN, 2400 Mol (Belgium); Gautschi, Andreas [Nagra, 5430 Wettingen (Switzerland); Savoye, Sebastien [IRSN, 92262 Fontenay-aux-Roses Cedex (France); Vinsot, Agnes [Andra, Parc de la Croix Blanche, 92298 Chatenay-Malabry Cedex (France); Wemaere, Isabelle [SCK-CEN, 2400 Mol (Belgium); Wouters, Laurent [Ondraf/Niras, 1210 Brussels (Belgium)

    2011-07-15

    Highlights: > Solute transport processes in clay and shale formations at nine sites are examined. > Conservative pore-water tracers (e.g. Cl{sup -}, {delta}{sup 18}O, {delta}{sup 2}H, He) show regular profiles. > These indicate the dominance of diffusive transport over times of 10{sup 5}-10{sup 6} years. > The contribution of vertical advection to transport is limited or negligible. > Modelled evolution times are in line with independent palaeo-hydrogeological data. - Abstract: Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl{sup -}, Br{sup -}), water isotopes ({delta}{sup 18}O, {delta}{sup 2}H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in . Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the

  10. Using conversions of chemically reacting tracers for numerical determination of temperature profiles in flowing systems and temperature histories in batch systems

    Energy Technology Data Exchange (ETDEWEB)

    Brown, L.F.; Chemburkar, R.M.; Robinson, B.A.; Travis, B.J.

    1996-04-01

    This report presents the mathematical bases for measuring internal temperatures within batch and flowing systems using chemically reacting tracers. This approach can obtain temperature profiles of plug-flow systems and temperature histories within batch systems. The differential equations for reactant conversion can be converted into Fredholm integral equations of the first kind. The experimental variable is the tracer-reaction activation energy. When more than one tracer is used, the reactions must have different activation energies to gain information. In systems with temperature extrema, multiple solutions for the temperature profiles or histories can exist, When a single parameter in the temperature distribution is needed, a single-tracer test may furnish this information. For multi-reaction tracer tests, three Fredholm equations are developed. Effects of tracer-reaction activation energy, number of tracers used, and error in the data are evaluated. The methods can determine temperature histories and profiles for many existing systems, and can be a basis for analysis of the more complicated dispersed-flow systems. An alternative to using the Fredholm-equation approach is the use of an assumed temperature- distribution function and incorporation of this function into the basic integral equation describing tracer behavior. The function contains adjustable parameters which are optimized to give the temperature distribution. The iterative Fredholm equation method is tested to see what is required to discriminate between two models of the temperature behavior of Hot Dry Rock (HDR) geothermal reservoirs. Experimentally, ester and amide hydrolyses are valid HDR tracer reactions for measuring temperatures in the range 75-100{degrees}C. Hydrolyses of bromobenzene derivatives are valid HDR tracer reactions for measuring temperatures in the range 150-275{degrees}C.

  11. A field test of tracer transport and organic contaminant elution in a stratified aquifer at the Rocky Mountain Arsenal (Denver, Colorado, U.S.A.)

    Science.gov (United States)

    Thorbjarnarson, Kathryn W.; Mackay, Douglas M.

    1997-01-01

    A tracer-elution experiment was conducted in a 9-m-thick alluvial sand aquifer at the Rocky Mountain Arsenal, Denver, Colorado, within an extensive 1,1,1-trichloroethene and trichloroethene plume. The forced-gradient flow field was controlled by an injection well and an extraction well separated by 8.4 m and aligned in the direction of the natural-gradient flow. Upon extraction, the contaminant-laden water was treated by air stripping and reinjected into the injection well. Iodide tracer was added to the injection flow during the initial 27.5 h of the experiment. Tracer transport and organic contaminant elution were monitored by four 0.15-m-screened drive points and a fully penetrating monitoring well. Relative permeabilities, dispersivities and retardation factors were estimated from tracer breakthrough and contaminant elution curves by the moment method and by curve-fitting with an advection-dispersion model. Tracer transport through the four strata sampled by the drive points indicated a permeability variation of three orders of magnitude. Contaminant elution was not observed in the lowest-permeability stratum monitored during the experiment. In all monitored strata, contaminant elution was controlled primarily by permeability effects on water flow and exhibited minimal retardation or desorption effects. The fully penetrating monitoring well exhibited a tracer response primarily from the more permeable strata with the addition of tracer from the less permeable strata producing an increased breakthrough spreading. This increased spreading or dispersion was reflected in a higher longitudinal dispersivity estimate (1.2 m assuming a homogeneous aquifer) than dispersivity estimates from the drive-point sampler tracer curves (ranging from 5 to 21 cm). Contaminant elution curves from the fully penetrating monitoring well exhibited an initial response primarily from the more permeable strata (rapid elution of contaminants) and provided no insight into the elution

  12. Tracer Diffusion Mechanism in Amorphous Solids

    Directory of Open Access Journals (Sweden)

    P. K. Hung

    2011-01-01

    Full Text Available Tracer diffusion in amorphous solid is studied by mean of nB-bubble statistic. The nB-bubble is defined as a group of atoms around a spherical void and large bubble that represents a structural defect which could be eliminated under thermal annealing. It was found that amorphous alloys such as CoxB100−x (x=90, 81.5 and 70 and Fe80P20 suffer from a large number of vacancy bubbles which function like diffusion vehicle. The concentration of vacancy bubble weakly depends on temperature, but essentially on the relaxation degree of considered sample. The diffusion coefficient estimated for proposed mechanism via vacancy bubbles is in a reasonable agreement with experiment for actual amorphous alloys. The relaxation effect for tracer diffusion in amorphous alloys is interpreted by the elimination of vacancy bubbles under thermal annealing.

  13. The medical applications of radioactive tracers

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, J.G.

    1947-12-31

    This report provides a broad yet in depth overview of the use of radioactive materials as tracers in medicine and biology for the period of 1935--1947. Particular attention is paid to is of radio-sodium, radio-iodine, radio-iron, radio-phosphorus, radio-strontium, and fission products. The main thrust of this paper is human rather than animal work and focuses in work that has been published.

  14. Molecules as tracers of galaxy evolution

    DEFF Research Database (Denmark)

    Costagliola, F.; Aalto, S.; I. Rodriguez, M.;

    2011-01-01

    We investigate the molecular gas properties of a sample of 23 galaxies in order to find and test chemical signatures of galaxy evolution and to compare them to IR evolutionary tracers. Observation at 3 mm wavelengths were obtained with the EMIR broadband receiver, mounted on the IRAM 30 m telesco...... detect the molecule in its vibrationally excited state.We find low HNC/HCN line ratios (...

  15. Insight from simulations of single-well injection-withdrawal tracer tests on simple and complex fractures

    Energy Technology Data Exchange (ETDEWEB)

    Tsang, C.-F.; Doughty, C.

    2009-08-06

    The single-well injection withdrawal (SWIW) test, a tracer test utilizing only one well, is proposed as a useful contribution to site characterization of fractured rock, as well as providing parameters relevant to tracer diffusion and sorption. The usual conceptual model of flow and solute transport through fractured rock with low matrix permeability involves solute advection and dispersion through a fracture network coupled with diffusion and sorption into the surrounding rock matrix. Unlike two-well tracer tests, results of SWIW tests are ideally independent of advective heterogeneity, channeling and flow dimension, and, instead, focus on diffusive and sorptive characteristics of tracer (solute) transport. Thus, they can be used specifically to study such characteristics and evaluate the diffusive parameters associated with tracer transport through fractured media. We conduct simulations of SWIW tests on simple and complex fracture models, the latter being defined as having two subfractures with altered rock blocks in between and gouge material in their apertures. Using parameters from the Aspo site in Sweden, we calculate and study SWIW tracer breakthrough curves (BTCs) from a test involving four days of injection and then withdrawal. By examining the peak concentration C{sub pk} of the SWIW BTCs for a variety of parameters, we confirm that C{sub pk} is largely insensitive to the fracture advective flow properties, in particular to permeability heterogeneity over the fracture plane or to subdividing the flow into two subfractures in the third dimension orthogonal to the fracture plane. The peak arrival time t{sub pk} is not a function of fracture or rock properties, but is controlled by the time schedule of the SWIW test. The study shows that the SWIW test is useful for the study of tracer diffusion-sorption processes, including the effect of the so-called flow-wetted surface (FWS) of the fracture. Calculations with schematic models with different FWS values are

  16. Comparison of rhodomine-WT and sodium chloride tracer transport in a 4th order arctic river

    Science.gov (United States)

    Smull, E. M.; Wlostowski, A. N.; Gooseff, M. N.; Bowden, W. B.; Wollheim, W. M.

    2012-12-01

    Conservative tracers are useful for tracking a parcel of water through a river reach and understanding tracer transport phenomena (i.e. advection, dispersion, and transient storage). Rhodomine- WT (RWT) and sodium chloride (NaCl) are two popular stream tracers. NaCl is considered to be conservative and relatively inexpensive, yet it cannot be detected at very low concentrations. On the other hand, RWT can be detected at very low concentrations (conservative tracer additions in large rivers. Differences in RWT behavior at various flow conditions indicate limitations for its use as a conservative tracer at lower discharges on a given reach. At higher discharges, RWT provides the benefit of a broader data set without considerable effects from sorption-desorption processes. Figure 1: NaCl and RWT BTC tails (tpk - t99) under two contrasting discharge conditions. A more defined difference in tail shape is present at 500 l/s compared to 1400 l/s. Also, the window of detection is longer for RWT compared to NaCl under both flow conditions.

  17. Very Massive Tracers and Higher Derivative Biases

    CERN Document Server

    Fujita, Tomohiro; Senatore, Leonardo; Vlah, Zvonimir; Angulo, Raul

    2016-01-01

    Most of the upcoming cosmological information will come from analyzing the clustering of the Large Scale Structures (LSS) of the universe through LSS or CMB observations. It is therefore essential to be able to understand their behavior with exquisite precision. The Effective Field Theory of Large Scale Structures (EFTofLSS) provides a consistent framework to make predictions for LSS observables in the mildly non-linear regime. In this paper we focus on biased tracers. We argue that in calculations at a given order in the dark matter perturbations, highly biased tracers will underperform because of their larger higher derivative biases. A natural prediction of the EFTofLSS is therefore that by simply adding higher derivative biases, all tracers should perform comparably well. We implement this prediction for the halo-halo and the halo-matter power spectra at one loop, and the halo-halo-halo, halo-halo-matter, and halo-matter-matter bispectra at tree-level, and compare with simulations. We find good agreement ...

  18. Tracer technology modeling the flow of fluids

    CERN Document Server

    Levenspiel, Octave

    2012-01-01

    A vessel’s behavior as a heat exchanger, absorber, reactor, or other process unit is dependent upon how fluid flows through the vessel.  In early engineering, the designer would assume either plug flow or mixed flow of the fluid through the vessel.  However, these assumptions were oftentimes inaccurate, sometimes being off by a volume factor of 100 or more.  The result of this unreliable figure produced ineffective products in multiple reaction systems.   Written by a pioneering researcher in the field of chemical engineering, the tracer method was introduced to provide more accurate flow data.  First, the tracer method measured the actual flow of fluid through a vessel.  Second, it developed a suitable model to represent the flow in question.  Such models are used to follow the flow of fluid in chemical reactors and other process units, like in rivers and streams, or solid and porous structures.  In medicine, the tracer method is used to study the flow of chemicals—harmful  and harmless—in the...

  19. Kubo formulas for dispersion in heterogeneous periodic nonequilibrium systems

    Science.gov (United States)

    Guérin, T.; Dean, D. S.

    2015-12-01

    We consider the dispersion properties of tracer particles moving in nonequilibrium heterogeneous periodic media. The tracer motion is described by a Fokker-Planck equation with arbitrary spatially periodic (but constant in time) local diffusion tensors and drifts, eventually with the presence of obstacles. We derive a Kubo-like formula for the time-dependent effective diffusion tensor valid in any dimension. From this general formula, we derive expressions for the late time effective diffusion tensor and drift in these systems. In addition, we find an explicit formula for the late finite-time corrections to these transport coefficients. In one dimension, we give a closed analytical formula for the transport coefficients. The formulas derived here are very general and provide a straightforward method to compute the dispersion properties in arbitrary nonequilibrium periodic advection-diffusion systems.

  20. Wastewater effluent dispersal in Southern California Bays

    KAUST Repository

    Uchiyama, Yusuke

    2014-03-01

    The dispersal and dilution of urban wastewater effluents from offshore, subsurface outfalls is simulated with a comprehensive circulation model with downscaling in nested grid configurations for San Pedro and Santa Monica Bays in Southern California during Fall of 2006. The circulation is comprised of mean persistent currents, mesoscale and submesoscale eddies, and tides. Effluent volume inflow rates at Huntington Beach and Hyperion are specified, and both their present outfall locations and alternative nearshore diversion sites are assessed. The effluent tracer concentration fields are highly intermittent mainly due to eddy currents, and their probability distribution functions have long tails of high concentration. The dilution rate is controlled by submesoscale stirring and straining in tracer filaments. The dominant dispersal pattern is alongshore in both directions, approximately along isobaths, over distances of more than 10. km before dilution takes over. The current outfall locations mostly keep the effluent below the surface and away from the shore, as intended, but the nearshore diversions do not. © 2014 Elsevier Ltd.

  1. Quantifying Methane Fluxes Simply and Accurately: The Tracer Dilution Method

    Science.gov (United States)

    Rella, Christopher; Crosson, Eric; Green, Roger; Hater, Gary; Dayton, Dave; Lafleur, Rick; Merrill, Ray; Tan, Sze; Thoma, Eben

    2010-05-01

    Methane is an important atmospheric constituent with a wide variety of sources, both natural and anthropogenic, including wetlands and other water bodies, permafrost, farms, landfills, and areas with significant petrochemical exploration, drilling, transport, or processing, or refining occurs. Despite its importance to the carbon cycle, its significant impact as a greenhouse gas, and its ubiquity in modern life as a source of energy, its sources and sinks in marine and terrestrial ecosystems are only poorly understood. This is largely because high quality, quantitative measurements of methane fluxes in these different environments have not been available, due both to the lack of robust field-deployable instrumentation as well as to the fact that most significant sources of methane extend over large areas (from 10's to 1,000,000's of square meters) and are heterogeneous emitters - i.e., the methane is not emitted evenly over the area in question. Quantifying the total methane emissions from such sources becomes a tremendous challenge, compounded by the fact that atmospheric transport from emission point to detection point can be highly variable. In this presentation we describe a robust, accurate, and easy-to-deploy technique called the tracer dilution method, in which a known gas (such as acetylene, nitrous oxide, or sulfur hexafluoride) is released in the same vicinity of the methane emissions. Measurements of methane and the tracer gas are then made downwind of the release point, in the so-called far-field, where the area of methane emissions cannot be distinguished from a point source (i.e., the two gas plumes are well-mixed). In this regime, the methane emissions are given by the ratio of the two measured concentrations, multiplied by the known tracer emission rate. The challenges associated with atmospheric variability and heterogeneous methane emissions are handled automatically by the transport and dispersion of the tracer. We present detailed methane flux

  2. Hanford atmospheric dispersion data: 1960 through June 1967

    Energy Technology Data Exchange (ETDEWEB)

    Nickola, P.W.; Ramsdell, J.V.; Glantz, C.S.; Kerns, R.E.

    1983-11-01

    This volume presents dispersion and supporting meteorological data from experiments conducted over relatively flat terrain at Hanford, Washington from January 1960 through June 1967. The nature of the experiments, the sampling grids, and the tracer techniques used are described in the narrative portion of the document. Appendices contain the time-integrated concentrations for samplers within the plumes, summaries of the concentration distributions across the plumes, and wind and temperature profile data for each release period. 18 references, 7 figures, 3 tables.

  3. Early Student Support for Process Studies of Surface Freshwater Dispersal

    Science.gov (United States)

    2016-06-24

    light field is varied to decay exponentially with depth. The spectra of tracer variance are computed for different growth rates and related to the...To) 06/24/2016 FINAL 12/01 /2012-03/31 /2016 4. TITLE AND SUBTITLE sa. CONTRACT NUMBER Early Student Support for Process Studies of Surface...ONRREPORT Early Student Support Process Studies of Surface Freshwater Dispersal June 24, 2016 Amala Mahadevan Woods Hole Oceanographic Institution

  4. Asian Tracer Experiment and Atmospheric Modeling (TEAM) Project: Draft Field Work Plan for the Asian Long-Range Tracer Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2007-08-01

    This report provides an experimental plan for a proposed Asian long-range tracer study as part of the international Tracer Experiment and Atmospheric Modeling (TEAM) Project. The TEAM partners are China, Japan, South Korea and the United States. Optimal times of year to conduct the study, meteorological measurements needed, proposed tracer release locations, proposed tracer sampling locations and the proposed durations of tracer releases and subsequent sampling are given. Also given are the activities necessary to prepare for the study and the schedule for completing the preparation activities leading to conducting the actual field operations. This report is intended to provide the TEAM members with the information necessary for planning and conducting the Asian long-range tracer study. The experimental plan is proposed, at this time, to describe the efforts necessary to conduct the Asian long-range tracer study, and the plan will undoubtedly be revised and refined as the planning goes forward over the next year.

  5. Enhanced diffusion of tracer particles in dilute bacterial suspensions.

    Science.gov (United States)

    Morozov, Alexander; Marenduzzo, Davide

    2014-04-28

    Swimming bacteria create long-range velocity fields that stir a large volume of fluid and move around passive particles dispersed in the fluid. Recent experiments and simulations have shown that long-time mean-squared displacement of passive particles in a bath of swimming bacteria exhibits diffusive behaviour with an effective diffusion coefficient significantly larger than its thermal counterpart. A comprehensive theoretical prediction of this effective diffusion coefficient and the understanding of the enhancement mechanism remain a challenge. Here, we adapt the kinetic theory by Lin et al., J. Fluid Mech., 2011, 669, 167 developed for 'squirmers' to the bacterial case to quantitatively predict enhanced diffusivity of tracer particles in dilute two- and three-dimensional suspensions of swimming bacteria. We demonstrate that the effective diffusion coefficient is a product of the bacterial number density, their swimming speed, a geometric factor characterising the velocity field created by a single bacterium, and a numerical factor. We show that the numerical factor is, in fact, a rather strong function of the system parameters, most notably the run length of the bacteria, and that these dependencies have to be taken into account to quantitatively predict the enhanced diffusivity. We perform molecular-dynamics-type simulations to confirm the conclusions of the kinetic theory. Our results are in good agreement with the values of enhanced diffusivity measured in recent two- and three-dimensional experiments.

  6. Transport and Dispersion of Nanoparticles in Periodic Nanopost Arrays

    KAUST Repository

    He, Kai

    2014-05-27

    Nanoparticles transported through highly confined porous media exhibit faster breakthrough than small molecule tracers. Despite important technological applications in advanced materials, human health, energy, and environment, the microscale mechanisms leading to early breakthrough have not been identified. Here, we measure dispersion of nanoparticles at the single-particle scale in regular arrays of nanoposts and show that for highly confined flows of dilute suspensions of nanoparticles the longitudinal and transverse velocities exhibit distinct scaling behaviors. The distributions of transverse particle velocities become narrower and more non-Gaussian when the particles are strongly confined. As a result, the transverse dispersion of highly confined nanoparticles at low Péclet numbers is significantly less important than longitudinal dispersion, leading to early breakthrough. This finding suggests a fundamental mechanism by which to control dispersion and thereby improve efficacy of nanoparticles applied for advanced polymer nanocomposites, drug delivery, hydrocarbon production, and environmental remediation. © 2014 American Chemical Society.

  7. Longitudinal dispersion in natural channels: 3. An aggregated dead zone model applied to the River Severn, U.K.

    Directory of Open Access Journals (Sweden)

    P. M. Davis

    2000-01-01

    Full Text Available An Aggregated Dead Zone (ADZ model is presented for longitudinal dispersion of tracer in river channels, in which the channel cross-section is divided into two parallel regions: the bulk flow and dead zone storage. Tracer particles in the bulk flow are assumed to obey plug-flow advection at the discharge velocity U without any mixing effects. The dispersive properties of the model are completely embodied in the residence time for tracer storage in the dead zone. The model provides an excellent description and prediction of empirical concentration-time distributions, for times t Its physical realism is demonstrated by using it to describe the evolution of a tracer cloud in the River Severn, U.K., and by comparing it with a more complex model which incorporates the additional effects of shear flow dispersion within the bulk flow. The ADZ model is a potentially useful tool for practical prediction of dispersion in natural channels. Keywords: Channels; dispersion; dead zones; tracers; River Severn

  8. Acceptance criteria for urban dispersion model evaluation

    Science.gov (United States)

    Hanna, Steven; Chang, Joseph

    2012-05-01

    The authors suggested acceptance criteria for rural dispersion models' performance measures in this journal in 2004. The current paper suggests modified values of acceptance criteria for urban applications and tests them with tracer data from four urban field experiments. For the arc-maximum concentrations, the fractional bias should have a magnitude 0.3. For all data paired in space, for which a threshold concentration must always be defined, the normalized absolute difference should be SCIPUFF dispersion model with the urban canopy option and the urban dispersion model (UDM) option. In each set of evaluations, three or four likely options are tested for meteorological inputs (e.g., a local building top wind speed, the closest National Weather Service airport observations, or outputs from numerical weather prediction models). It is found that, due to large natural variability in the urban data, there is not a large difference between the performance measures for the two model options and the three or four meteorological input options. The more detailed UDM and the state-of-the-art numerical weather models do provide a slight improvement over the other options. The proposed urban dispersion model acceptance criteria are satisfied at over half of the field experiments.

  9. Direct inversion of circulation and mixing from tracer measurements - Part 1: Method

    Science.gov (United States)

    von Clarmann, Thomas; Grabowski, Udo

    2016-11-01

    From a series of zonal mean global stratospheric tracer measurements sampled in altitude vs. latitude, circulation and mixing patterns are inferred by the inverse solution of the continuity equation. As a first step, the continuity equation is written as a tendency equation, which is numerically integrated over time to predict a later atmospheric state, i.e., mixing ratio and air density. The integration is formally performed by the multiplication of the initially measured atmospheric state vector by a linear prediction operator. Further, the derivative of the predicted atmospheric state with respect to the wind vector components and mixing coefficients is used to find the most likely wind vector components and mixing coefficients which minimize the residual between the predicted atmospheric state and the later measurement of the atmospheric state. Unless multiple tracers are used, this inversion problem is under-determined, and dispersive behavior of the prediction further destabilizes the inversion. Both these problems are addressed by regularization. For this purpose, a first-order smoothness constraint has been chosen. The usefulness of this method is demonstrated by application to various tracer measurements recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This method aims at a diagnosis of the Brewer-Dobson circulation without involving the concept of the mean age of stratospheric air, and related problems like the stratospheric tape recorder, or intrusions of mesospheric air into the stratosphere.

  10. Strontium and bromide as tracers in X-ray microanalysis of biological tissue

    Energy Technology Data Exchange (ETDEWEB)

    Wroblewski, J.; Sagstroem, S.M.; Mulders, H.; Roomans, G.M. (Karolinska Institutet, Stockholm (Sweden))

    1989-09-01

    Since energy dispersive X-ray microanalysis cannot distinguish between isotopes of the same element, alternative methods have to be used to get information similar to that obtained in experiments with radioactive tracers. In the present study, strontium was used as a tracer for calcium, and bromide as a tracer for chloride. Rats were injected with strontium chloride in vivo, and the uptake of strontium in the acinar cells of the submandibular gland was studied. Eventually a Sr/Ca ratio of 0.3 was reached. In some animals, secretion of mucus had been elicited by stimulation with isoproterenol 4 h prior to injection of strontium chloride. Exchange of calcium for strontium was enhanced by prior injection with isoproterenol. In a second experiment, rats were injected with sodium bromide, and the uptake of bromide by the submandibular acinar cells was followed in time, both in pilocarpine-stimulated and unstimulated glands. Under the experimental conditions, bromide was rapidly taken up by the cells, and the cellular Br/Cl ratio was close to that found in serum. Submandibular glands take up Br somewhat faster than other tissues (liver, heart muscle, skeletal muscle). The uptake of Br in pancreatic acinar cells was studied in vitro. These experiments showed a 1:1 ratio (molar) exchange of Cl for Br.

  11. Semianalytical Solutions of Radioactive or Reactive Tracer Transport in Layered Fractured Media

    Energy Technology Data Exchange (ETDEWEB)

    G.J. Moridis; G. S. Bodvarsson

    2001-10-01

    In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. {sup 239}Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species.

  12. MOTION OF TRACER PARTICLES IN A CENTRIFUGAL PUMP AND ITS TRACKING CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    LI Ya-lin; YUAN Shou-qi; TANG Yue; YUAN Jian-ping

    2012-01-01

    The Basset-Boussinesq-Oseen (BBO) equation can be used for most flows to trace the motion of a particle,but in a centrifugal pump,among the forces that act on the particles,one should also include those due to the impeller rotation,as additional effects.This paper firstly reviews various approximations of the BBO equation for the motion of dispersion particles in a viscous fluid.Then based on the motion equation for particles in low Reynolds number centrifugal pumps,a formula for calculating the tracking characteristics of tracer particles is deduced through the Fourier integral transformation.After that the deviations of the particle motion from the fluid motion,as predicted by the various approximations,are discussed and compared.At last,with an emphasis on the Particle Image Velocimetry (PIV) results,the tracking characteristics of particles are estimated.Also,advantages and disadvantages of different tracer particles are discussed and suitable tracer particles for application in PIV studies for flow fields in centrifugal pumps are suggested.

  13. Semianalytical solutions of radioactive or reactive tracer transport in layered fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Moridis, G.J.; Bodvarsson, G.S.

    2001-10-10

    In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of {sup 3}H, {sup 237}Np and {sup 239}Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. {sup 239}Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species.

  14. Detection of tracer materials in the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, A.; Lovelock, J.E.

    1981-12-08

    As oxygen is an electron absorber it is desirable, when monitoring an atmospheric flow for the presence of tracer materials capable of detection in an electron capture detector, to remove the oxygen from the flow to the detector. The invention introduces a hydrogen supply directly into the atmospheric flow to allow the hydrogen to combine catalytically with the oxygen content of the flow to form water or water vapor. The thus formed water or water vapor is extracted from the flow proceeding to the detector. The reaction can occur within a palladium or palladium alloy conduit forming a part of the flow path to the detector.

  15. Developement of radioisotope tracer technique; development of verification method for hydraulic model using radioisotope tracer techniques in the municipal wastewater treatment plants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C. W.; Kim, S. H.; Kim, J. W.; Yun, J. S.; Wo, S. B. [Pusan National University, Pusan (Korea)

    2001-04-01

    This study focuses on the development of the computational fluid dynamics that can be used in secondary clarifier in wastewater treatment plants. This model could describe the internal flow characteristics and predicted similar results as the isotopic tracer experiment. Therefore, it was demonstrated that the isotopic tracer method was a powerful tool as a hydrodynamic model to understand the internal hydraulics. Generally the secondary clarifier can be improved by special design, changing coagulation characteristics by addition of coagulation chemicals and well management by experienced operator. Because of expensive coagulation chemicals and limited availability of experienced operator, the improvement of the design is feasible way to upgrade the secondary clarifier. Though it is very complex and difficult to model the fluid dynamics, CFD model can describe correctly density flow, short circuiting, turbulent dispersion and settling characteristics. There are few trust worthy methods for verifying the hydrodynamic model. Also, it is very difficult to prove the flow by experiment in secondary sedimentation tank because of the disturbing the flow by the experimental equipment. However, the isotope tracer experiment is known as a useful tool for the study of the hydraulic characteristics and floc movement in the sedimentation tank because the isotope tracer does not disturb the internal flow and provide the data quickly through the on-line system. Therefore, the computed fluid dynamic model was developed to make the isotope tracer experiment available as a model verifying method. Predicted results in model simulation were made the same pattern as the experiment on-line data with the time. These results were compared each other. Also, the model explained the detail flow pattern of the area without the monitoring in the sedimentation tank and visualized the internal flow and concentration distribution with time using the graphic software. Because of the complicated

  16. Developement of radioisotope tracer technique; development of verification method for hydraulic model using radioisotope tracer techniques in the municipal wastewater treatment plants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C. W.; Kim, S. H.; Kim, J. W.; Yun, J. S.; Wo, S. B. [Pusan National University, Pusan (Korea)

    2001-04-01

    This study focuses on the development of the computational fluid dynamics that can be used in secondary clarifier in wastewater treatment plants. This model could describe the internal flow characteristics and predicted similar results as the isotopic tracer experiment. Therefore, it was demonstrated that the isotopic tracer method was a powerful tool as a hydrodynamic model to understand the internal hydraulics. Generally the secondary clarifier can be improved by special design, changing coagulation characteristics by addition of coagulation chemicals and well management by experienced operator. Because of expensive coagulation chemicals and limited availability of experienced operator, the improvement of the design is feasible way to upgrade the secondary clarifier. Though it is very complex and difficult to model the fluid dynamics, CFD model can describe correctly density flow, short circuiting, turbulent dispersion and settling characteristics. There are few trust worthy methods for verifying the hydrodynamic model. Also, it is very difficult to prove the flow by experiment in secondary sedimentation tank because of the disturbing the flow by the experimental equipment. However, the isotope tracer experiment is known as a useful tool for the study of the hydraulic characteristics and floc movement in the sedimentation tank because the isotope tracer does not disturb the internal flow and provide the data quickly through the on-line system. Therefore, the computed fluid dynamic model was developed to make the isotope tracer experiment available as a model verifying method. Predicted results in model simulation were made the same pattern as the experiment on-line data with the time. These results were compared each other. Also, the model explained the detail flow pattern of the area without the monitoring in the sedimentation tank and visualized the internal flow and concentration distribution with time using the graphic software. Because of the complicated

  17. Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space.

    Science.gov (United States)

    Masui, Kiyoshi Wesley; Sigurdson, Kris

    2015-09-18

    We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

  18. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  19. Determination of Transport Parameters in Unsaturated Zone by Tracer Experiment in the Porous Aquifer located at Ljubljana, Slovenia

    Science.gov (United States)

    Vidmar, S.; Cencur Curk, B.

    2009-04-01

    The gravel sandy aquifer of Ljubljansko polje is the source of drinking water for nearly 300.000 inhabitants of the Ljubljana city and vicinity. There are two main waterworks: Kleče and Hrastje. The plain area of Ljubljansko polje is a tectonic sink and consists of river sediments that can reach in thickness more than 100 m in the deepest part. The bedrock is the impermeable permocarbonic clayey shale, mudstones and sandstones. The hydraulic conductivity of Ljubljansko polje sediments is very good, from 10-2 m/s in the central part to 3.7•10-3 m/s on the borders of the plain. The average groundwater level is 20 m below surface. A numerical groundwater flow model was established for the wider area of the Ljubljansko polje aquifer. The fore mentioned model was not calibrated on solute transport parameters but only on water levels and this lead to unreliability in the transport model and its predictions of pollution scenarios. The transport model needs to calculate reliable scenarios of pollution dispersion, which can only be achieved with the application of real transport parameters. Human activities in the area of the Hrastje waterworks of Ljubljana threaten to degrade groundwater quality. For this reason several tracer experiments were carried out in the past. Despite a great risk, the experiments were performed on the catchment area of the Hrastje waterworks, inside the second water protection zone. During the experiments the water from Hrastje waterworks was still in use for drinking water supply. The tracer experiments were carried out in order to determine the solute transport parameters such as advection, dispersion and sorption. The research proved that the tracers could be used safely on sensitive area and that the researchers are capable and qualified to carry it out with a highest level of security. Since none of the past tracer experiments, carried out in the same area, gave us any detailed information on pollutant spreading in unsaturated zone a new

  20. Dispersion y dinamica poblacional

    Science.gov (United States)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  1. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and redu

  2. Perfluorocarbon Gas Tracer Studies to Support Risk Assessment Modeling of Critical Infrastructure Subjected to Terrorist Attacks

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, Terry M.; Heiser, John H.; Watson, Tom; Allwine, K Jerry; Flaherty, Julia E.

    2006-05-06

    Development of real-time predictive modeling to identify the dispersion and/or source(s) of airborne weapons of mass destruction including chemical, biological, radiological, and nuclear material in urban environments is needed to improve response to potential releases of these materials via either terrorist or accidental means. These models will also prove useful in defining airborne pollution dispersion in urban environments for pollution management/abatement programs. Predicting gas flow in an urban setting on a scale of less than a few kilometers is a complicated and challenging task due to the irregular flow paths that occur along streets and alleys and around buildings of different sizes and shapes, i.e., “urban canyons”. In addition, air exchange between the outside and buildings and subway areas further complicate the situation. Transport models that are used to predict dispersion of WMD/CBRN materials or to back track the source of the release require high-density data and need defensible parameterizations of urban processes. Errors in the data or any of the parameter inputs or assumptions will lead to misidentification of the airborne spread or source release location(s). The need for these models to provide output in a real-time fashion if they are to be useful for emergency response provides another challenge. To improve the ability of New York City’s (NYC's) emergency management teams and first response personnel to protect the public during releases of hazardous materials, the New York City Urban Dispersion Program (UDP) has been initiated. This is a four year research program being conducted from 2004 through 2007. This paper will discuss ground level and subway Perfluorocarbon tracer (PFT) release studies conducted in New York City. The studies released multiple tracers to study ground level and vertical transport of contaminants. This paper will discuss the results from these tests and how these results can be used for improving

  3. Stream Tracer Integrity: Comparative Analyses of Rhodamine-WT and Sodium Chloride through Transient Storage Modeling

    Science.gov (United States)

    Smull, E. M.; Wlostowski, A. N.; Gooseff, M. N.; Bowden, W. B.; Wollheim, W. M.

    2013-12-01

    Solute transport in natural channels describes the transport of water and dissolved matter through a river reach of interest. Conservative tracers allow us to label a parcel of stream water, such that we can track its movement downstream through space and time. A transient storage model (TSM) can be fit to the breakthrough curve (BTC) following a stream tracer experiment, as a way to quantify advection, dispersion, and transient storage processes. Arctic streams and rivers, in particular, are continuously underlain by permafrost, which provides for a simplified surface water-groundwater exchange. Sodium chloride (NaCl) and Rhodamine-WT (RWT) are widely used tracers, and differences between the two in conservative behavior and detection limits have been noted in small-scale field and laboratory studies. This study seeks to further this understanding by applying the OTIS model to NaCl and RWT BTC data from a field study on the Kuparuk River, Alaska, at varying flow rates. There are two main questions to be answered: 1) Do differences in NaCl and RWT manifest in OTIS parameter values? 2) Are the OTIS model results reliable for NaCl, RWT, or both? Fieldwork was performed in the summer of 2012 on the Kuparuk River, and modeling was performed using a modified OTIS framework, which provided for parameter optimization and further global sensitivity analyses. The results of this study will contribute to the greater body of literature surrounding Arctic stream hydrology, and it will assist in methodology for future tracer field studies. Additionally, the modeling work will provide an analysis for OTIS parameter identifiability, and assess stream tracer integrity (i.e. how well the BTC data represents the system) and its relation to TSM performance (i.e. how well the TSM can find a unique fit to the BTC data). The quantitative tools used can be applied to other solute transport studies, to better understand potential deviations in model outcome due to stream tracer choice and

  4. Performance Testing of Tracer Gas and Tracer Aerosol Detectors for use in Radionuclide NESHAP Compliance Testing

    Energy Technology Data Exchange (ETDEWEB)

    Fuehne, David Patrick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lattin, Rebecca Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-28

    The Rad-NESHAP program, part of the Air Quality Compliance team of LANL’s Compliance Programs group (EPC-CP), and the Radiation Instrumentation & Calibration team, part of the Radiation Protection Services group (RP-SVS), frequently partner on issues relating to characterizing air flow streams. This memo documents the most recent example of this partnership, involving performance testing of sulfur hexafluoride detectors for use in stack gas mixing tests. Additionally, members of the Rad-NESHAP program performed a functional trending test on a pair of optical particle counters, comparing results from a non-calibrated instrument to a calibrated instrument. Prior to commissioning a new stack sampling system, the ANSI Standard for stack sampling requires that the stack sample location must meet several criteria, including uniformity of tracer gas and aerosol mixing in the air stream. For these mix tests, tracer media (sulfur hexafluoride gas or liquid oil aerosol particles) are injected into the stack air stream and the resulting air concentrations are measured across the plane of the stack at the proposed sampling location. The coefficient of variation of these media concentrations must be under 20% when evaluated over the central 2/3 area of the stack or duct. The instruments which measure these air concentrations must be tested prior to the stack tests in order to ensure their linear response to varying air concentrations of either tracer gas or tracer aerosol. The instruments used in tracer gas and aerosol mix testing cannot be calibrated by the LANL Standards and Calibration Laboratory, so they would normally be sent off-site for factory calibration by the vendor. Operational requirements can prevent formal factory calibration of some instruments after they have been used in hazardous settings, e.g., within a radiological facility with potential airborne contamination. The performance tests described in this document are intended to demonstrate the reliable

  5. How to chase a tracer - combining conventional salt tracer testing and direct push electrical conductivity profiling for enhanced aquifer characterization

    Science.gov (United States)

    Vienken, Thomas; Huber, Emanuel; Kreck, Manuel; Huggenberger, Peter; Dietrich, Peter

    2017-01-01

    Tracer testing is a well-established technique in hydrogeological site characterization. However, certain a priori knowledge of the hydraulic regime is required beforehand to avoid test failure, e.g. miss of tracer. In this study, we propose a novel tracer test concept for the hydraulic characterization of shallow unconsolidated sedimentary deposits when only scarce a priori information on the hydraulic regime is available. Therefore, we combine conventional salt tracer testing with direct push vertical high resolution electrical conductivity logging. The proposed tracer test concept was successfully tested on coarse, braided river deposits of the Tagliamento River, Italy. With limited a priori information available two tracer tests were performed in three days to reliably determine ground water flow direction and velocity allowing on-site decision-making to adaptively install observation wells for reliable breakthrough curve measurements. Furthermore, direct push vertical electrical profiling provided essential information about the plume characteristics with outstanding measurement resolution and efficiency.

  6. Flow Data for Solute Transport Modeling from Tracer Experiments in a Stream Not Continuously Gaining Water

    Science.gov (United States)

    Bencala, K. E.; Kimball, B. A.; Gooseff, M. N.

    2007-12-01

    In-stream tracer experiments are a well-established method for determining flow data to be incorporated in solute transport modeling. For a gaining stream, this method is implemented to provide spatial flow data at scales of minutes and tens of meters without physical disturbance to the flow of water, the streambed, or biota. Of importance for solute transport modeling, solute inflow loading along the stream can be estimated with this spatial data. The tracer information can also be interpreted to characterize hyporheic exchange time-scales for a stream with hyporheic exchange flowpaths (HEFs) that are short relative to the distance over which the stream gains water. The interpretation of tracer data becomes uncertain for a stream that is not gaining water continuously over intended study reach. We demonstrate, with straight-forward mass-balances, uncertainties for solute loading which arise in the analysis of streams locally losing water while predominantly gaining water (and solutes) over a larger scale. With field data from Mineral Creek (Silverton, Colorado) we illustrate the further uncertainty distinguishing HEFs from (locally) losing segments of the stream. Comparison of bromide tracer with ambient sulfate concentrations suggests that subsurface inflows and outflows, concurrent with likely HEFs, occur in a hydrogeochemical setting of multiple, dispersed and mixed, sources of water along a 64 m sub-reach of the predominately gaining, but locally losing, stream. To compute stream-reach mass-balances (the simplest of water quality models) there is a need to quantitatively define the character and source of contaminants entering streams from ground-water pathways, as well as the potential for changes in water chemistry and contaminant concentrations along flow paths crossing the sediment-water interface. Identification of inflow solute mass requires quantifying water gain, loss, and hyporheic exchange in addition to concentration.

  7. Sorption and transformation of the reactive tracers resazurin and resorufin in natural river sediments

    Science.gov (United States)

    Lemke, D.; González-Pinzón, R.; Liao, Z.; Wöhling, T.; Osenbrück, K.; Haggerty, R.; Cirpka, O. A.

    2014-08-01

    Resazurin (Raz) and its reaction product resorufin (Rru) have increasingly been used as reactive tracers to quantify metabolic activity and hyporheic exchange in streams. Previous work has indicated that these compounds undergo sorption in stream sediments. We present laboratory experiments on Raz and Rru transport, sorption, and transformation, consisting of 4 column and 72 batch tests using 2 sediments with different physicochemical properties under neutral (pH = 7) and alkaline (pH = 9) conditions. The study aimed at identifying the key processes of reactive transport of Raz and Rru in streambed sediments and the experimental setup best suited for their determination. Data from column experiments were simulated by a travel-time-based model accounting for physical transport, equilibrium and kinetic sorption, and three first-order reactions. We derived the travel-time distributions directly from the breakthrough curve (BTC) of the conservative tracer, fluorescein, rather than from fitting an advective-dispersive transport model, and inferred from those distributions the transfer functions of Raz and Rru, which provided conclusive approximations of the measured BTCs. The most likely reactive transport parameters and their uncertainty were determined by a Markov chain-Monte Carlo approach. Sorption isotherms of both compounds were obtained from batch experiments. We found that kinetic sorption dominates sorption of both Raz and Rru, with characteristic timescales of sorption in the order of 12 to 298 min. Linear sorption models for both Raz and Rru appeared adequate for concentrations that are typically applied in field tracer tests. The proposed two-site sorption model helps to interpret transient tracer tests using the Raz-Rru system.

  8. A joint velocity-concentration PDF method for tracer flow in heterogeneous porous media

    Science.gov (United States)

    Meyer, Daniel W.; Jenny, Patrick; Tchelepi, Hamdi A.

    2010-12-01

    The probability density function (PDF) of the local concentration of a contaminant, or tracer, is an important component of risk assessment in applications that involve flow in heterogeneous subsurface formations. In this paper, a novel joint velocity-concentration PDF method for tracer flow in highly heterogeneous porous media is introduced. The PDF formalism accounts for advective transport, pore-scale dispersion (PSD), and molecular diffusion. Low-order approximations (LOAs), which are usually obtained using a perturbation expansion, typically lead to Gaussian one-point velocity PDFs. Moreover, LOAs provide reasonable approximations for small log conductivity variances (i.e., σY2 Caroni and Fiorotto (2005) for saturated transport in velocity fields, which are stationary in space and time, for domains with σY2 = 0.05, 1, and 2 and Péclet numbers ranging from 100 to 10,000. PSD is modeled using constant anisotropic dispersion coefficients in both the reference MC computations and our PDF method.

  9. Modeling tracer transport in randomly heterogeneous porous media by nonlocal moment equations: Anomalous transport

    Science.gov (United States)

    Morales-Casique, E.; Lezama-Campos, J. L.; Guadagnini, A.; Neuman, S. P.

    2013-05-01

    Modeling tracer transport in geologic porous media suffers from the corrupt characterization of the spatial distribution of hydrogeologic properties of the system and the incomplete knowledge of processes governing transport at multiple scales. Representations of transport dynamics based on a Fickian model of the kind considered in the advection-dispersion equation (ADE) fail to capture (a) the temporal variation associated with the rate of spreading of a tracer, and (b) the distribution of early and late arrival times which are often observed in field and/or laboratory scenarios and are considered as the signature of anomalous transport. Elsewhere we have presented exact stochastic moment equations to model tracer transport in randomly heterogeneous aquifers. We have also developed a closure scheme which enables one to provide numerical solutions of such moment equations at different orders of approximations. The resulting (ensemble) average and variance of concentration fields were found to display a good agreement against Monte Carlo - based simulation results for mildly heterogeneous (or well-conditioned strongly heterogeneous) media. Here we explore the ability of the moment equations approach to describe the distribution of early arrival times and late time tailing effects which can be observed in Monte-Carlo based breakthrough curves (BTCs) of the (ensemble) mean concentration. We show that BTCs of mean resident concentration calculated at a fixed space location through higher-order approximations of moment equations display long tailing features of the kind which is typically associated with anomalous transport behavior and are not represented by an ADE model with constant dispersive parameter, such as the zero-order approximation.

  10. Medium-Range Dispersion Experiments Downwind from a Shoreline in Near Neutral Conditions

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Lyck, E.

    1980-01-01

    Five atmospheric dispersion experiments, all assigned Pasquill stability class D, were performed at Risø National Laboratory. The tracer sulphurhexafluoride was released at a height of 60 m from the Risø meteorological tower, situated on a peninsula in the Roskilde Fjord, Denmark, and was sampled...

  11. On the linearity of tracer bias around voids

    Science.gov (United States)

    Pollina, Giorgia; Hamaus, Nico; Dolag, Klaus; Weller, Jochen; Baldi, Marco; Moscardini, Lauro

    2017-07-01

    The large-scale structure of the Universe can be observed only via luminous tracers of the dark matter. However, the clustering statistics of tracers are biased and depend on various properties, such as their host-halo mass and assembly history. On very large scales, this tracer bias results in a constant offset in the clustering amplitude, known as linear bias. Towards smaller non-linear scales, this is no longer the case and tracer bias becomes a complicated function of scale and time. We focus on tracer bias centred on cosmic voids, i.e. depressions of the density field that spatially dominate the Universe. We consider three types of tracers: galaxies, galaxy clusters and active galactic nuclei, extracted from the hydrodynamical simulation Magneticum Pathfinder. In contrast to common clustering statistics that focus on auto-correlations of tracers, we find that void-tracer cross-correlations are successfully described by a linear bias relation. The tracer-density profile of voids can thus be related to their matter-density profile by a single number. We show that it coincides with the linear tracer bias extracted from the large-scale auto-correlation function and expectations from theory, if sufficiently large voids are considered. For smaller voids we observe a shift towards higher values. This has important consequences on cosmological parameter inference, as the problem of unknown tracer bias is alleviated up to a constant number. The smallest scales in existing data sets become accessible to simpler models, providing numerous modes of the density field that have been disregarded so far, but may help to further reduce statistical errors in constraining cosmology.

  12. Effects of vertical shear in modelling horizontal oceanic dispersion

    Science.gov (United States)

    Lanotte, A. S.; Corrado, R.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

    2016-02-01

    The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ˜ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

  13. Design of a perfluorocarbon tracer based monitoring network to support monitoring verification and accounting of sequestered CO2

    Science.gov (United States)

    Watson, T.; Sullivan, T.

    2013-05-01

    The levels of CO2 in the atmosphere have been growing since the beginning of the industrial revolution. The current level is 391 ppm. If there are no efforts to mitigate CO2 emissions, the levels will rise to 750 ppm by 2100. Geologic carbon sequestration is one strategy that may be used to begin to reduce emissions. Sequestration will not be effective unless reservoir leak rates are significantly less than 1%. There must be rigorous monitoring protocols in place to ensure sequestration projects meet regulatory and environmental goals. Monitoring for CO2 leakage directly is difficult because of the large background levels and variability of CO2 in the atmosphere. Using tracers to tag the sequestered CO2 can mitigate some of the difficulties of direct measurement but a tracer monitoring network and the levels of tagging need to be carefully designed. Simple diffusion and dispersion models are used to predict the surface and atmospheric concentrations that would be seen by a network monitoring a sequestration site. Levels of tracer necessary to detect leaks from 0.01 to 1% are presented and suggestions for effective monitoring and protection of global tracer utility are presented.

  14. Design of a perfluorocarbon tracer based monitoring network to support monitoring verification and accounting of sequestered CO2

    Directory of Open Access Journals (Sweden)

    Sullivan T.

    2013-05-01

    Full Text Available The levels of CO2 in the atmosphere have been growing since the beginning of the industrial revolution. The current level is 391 ppm. If there are no efforts to mitigate CO2 emissions, the levels will rise to 750 ppm by 2100. Geologic carbon sequestration is one strategy that may be used to begin to reduce emissions. Sequestration will not be effective unless reservoir leak rates are significantly less than 1%. There must be rigorous monitoring protocols in place to ensure sequestration projects meet regulatory and environmental goals. Monitoring for CO2 leakage directly is difficult because of the large background levels and variability of CO2 in the atmosphere. Using tracers to tag the sequestered CO2 can mitigate some of the difficulties of direct measurement but a tracer monitoring network and the levels of tagging need to be carefully designed. Simple diffusion and dispersion models are used to predict the surface and atmospheric concentrations that would be seen by a network monitoring a sequestration site. Levels of tracer necessary to detect leaks from 0.01 to 1% are presented and suggestions for effective monitoring and protection of global tracer utility are presented.

  15. Dating of shallow groundwater--Comparison of the transient tracers 3H/3He chlorofluorocarbons and 85Kr

    Science.gov (United States)

    Ekwurzel, Brenda; Schlosser, Peter; Smethie, William M.; Plummer, L. Niel; Busenberg, Eurybiades; Michel, Robert L.; Weppernig, Ralf; Stute, Martin

    1994-01-01

    This paper describes a direct comparison of apparent ages derived from 3H/3He, chlorofluorocarbons (CCl3F and CCl2F2), and 85Kr measurements in shallow groundwater. Wells chosen for this study are completed in the unconfined surficial aquifers in late Cenozoic Atlantic Coastal Plain sediments of the Delmarva Peninsula, on the east coast of the United States. Most of the apparent tracer ages agree within 2 years of each other for recharge dates between 1965 and 1990. Discrepancies in apparent tracer ages usually can be explained by hydrological processes such as mixing in a discharge area. Recharge rate calculations based on apparent tracer age gradients at multilevel well locations agree with previous recharge estimates. High recharge rates on the Delmarva Peninsula result in nearly complete dissolved-gas confinement in the groundwater. The remarkable agreement between the different tracer ages indicates negligible mixing of waters of different ages, insignificant dispersion, minimal gas loss to the atmosphere, and insignificant sorption-desorption processes at this location.

  16. Resting Study of Tracer Experiment on Catalytic Wet Oxidation Reactor under Micro-gravity and Earth Gravity Conditions

    Institute of Scientific and Technical Information of China (English)

    YANG Ji; JIA Jin-ping

    2005-01-01

    The International Space Station(ISS) employs catalytic wet oxidation carried out in a Volatile Reactor Assembly (VRA) for water recycling. Previous earth gravity experiments show that the VRA is very effective at removing polar,low molecular weight organics. To compare the reactor performance under micro-gravity and Earth gravity conditions,a tracer study was performed on a space shuttle in 1999 by using 0. 2% potassium carbonate as the chemical tracer.In this paper, the experimental data were analyzed and it is indicated that the reactor can be considered as a plug flow one under both micro-gravity and earth gravity experimental conditions. It has also been proved that dispersion is not important in the VRA reactor under the experimental conditions. Tracer retardation was observed in the experiments and it is most likely caused by catalyst adsorption. It is concluded that the following reasons may also have influence on the retardation of mean residence time: (1) the liquid can be held by appurtenances, which will retard the mean residence time; (2) the pores can hold the tracer, which can also retard the mean residence time.

  17. Quantification of methane emissions from 15 Danish landfills using the mobile tracer dispersion method

    DEFF Research Database (Denmark)

    Mønster, Jacob; Samuelsson, Jerker; Kjeldsen, Peter

    2015-01-01

    biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41-81%. Landfills where shredder waste was deposited showed significant methane emissions, with the largest emission from newly deposited shredder waste. The average methane emission from the landfills...

  18. Transport and Dispersion of Dye-tracer and Drifters at a Tidal Inlet

    Science.gov (United States)

    2015-01-09

    Oceanography lOD/SIO/UCSD 0209 9500 Gilman Drive La Jolla CA 92093-0209 8. PERFORMING ORGANIZATION REPORT NUMBER N00014-13-1-0126 9. SPONSORING...dangerous substances, and predicting where optical . The project objective, to measure mixing and transport in a small tidal inlet, was achieved in...Falk Feddersen Scripps Institutions of Oceanography lOD/SIO/UCSD 0209, 9500 Oilman Drive, La Jolla CA 92093-0209 858.534.4345, 858.534.0300 (FAX

  19. Using natural isotopes as tracers of Saharan dust dispersion: a case study in the Azores - Portugal

    Directory of Open Access Journals (Sweden)

    Charles Holmes

    2005-06-01

    Full Text Available After mineral aerosol transport from Sahara Desert, through the North Atlantic, analysis on beryllium 7 and lead 210 were carried out on Azorean aerosol samples. Knowing about the isotope activity of beryllium 7 and lead 210 on aerosol, will permit to study stratospheric intrusions and others physical characteristics of the North Atlantic atmospheric transport. Based on beryllium 7/lead 210 ratios it is possible to differentiate insular and marine aerosol from continental aerosol.

  20. Star clusters as tracers of galaxy evolution

    CERN Document Server

    Konstantopoulos, Iraklis S

    2009-01-01

    Star clusters represent the most common 'mode' of star formation. They are found in all types of environments, cascading down from galaxy groups and merging pairs through starbursts to normal galaxies and dwarves and even isolated regions in extragalactic space. As they maintain a link to the overall star formation in a system, they can be used as tracers of the star formation history of environments located at distances prohibitive to the study of individual stars. This makes them ideally suited to the study of mergers and interactions in galaxy pairs and groups. In this work we present observations of the star cluster populations in the local starburst galaxy M82, post-interaction spiral NGC 6872, the "Antennae" merging pair and two compact groups, "Stephan's Quintet" and HCG 7. In each case, we extract information on the clusters and their hosts using mainly HST photometry and Gemini spectroscopy.

  1. Elemental tracers for Chinese source dust

    Institute of Scientific and Technical Information of China (English)

    张小曳; 张光宇; 朱光华; 张德二; 安芷生; 陈拓; 黄湘萍

    1996-01-01

    The mass-particle size distributions of 10 dust-carrying elements in aerosol particles were determined tor 12 sites in desert regions of northern China. The desert dust is proved to he of origin of eolian loess deposited on the Loess Plateau. Their transport to the loess was mainly attributable to the non-dust storm processes under the interglacial climate condition. The impact ot" dust storm on the accumulation of the loess increased in the glacial stage. On the basis of the signatures of 4 dust elements (Al. Fe, Mg and Sc). Chinese dust is believed to have 3 major desert sources (northwestern deserts, northern high dust deserts and northern low dust deserts). With a chemical element balance model, an elemental tracer system is established to proportion the export of China-source dust.

  2. Tracer studies of nitrogen assimilation in yeast.

    Science.gov (United States)

    ABRAMS, R; HAMMARSTEN, E

    1949-01-01

    By using N(15) as a tracer the assimilation of ammonia by the yeast, Torulopsis utilis, has been studied. It has been shown that: 1. There was no measurable incorporation of N in the protein or polynucleotide purine of carbon-starved yeast. 2. When ammonia is added to nitrogen-starved yeast there is a long lag period before division begins during which the yeast rapidly synthesizes protein, this process being accompanied by a turnover of polynucleotide purine. There was no significant dilution of the N(15)H(4) (+) of the medium by ordinary NH(4) (+). 3. When yeast containing N(15) is allowed to divide and grow in ordinary ammonia, the total amount of N(15) in the yeast remains constant. The dicarboxylic amino acids are most diluted, while arginine and nucleic acid guanine are not diluted at all.

  3. National Biomedical Tracer Facility. Project definition study

    Energy Technology Data Exchange (ETDEWEB)

    Schafer, R.

    1995-02-14

    We request a $25 million government-guaranteed, interest-free loan to be repaid over a 30-year period for construction and initial operations of a cyclotron-based National Biomedical Tracer Facility (NBTF) in North Central Texas. The NBTF will be co-located with a linear accelerator-based commercial radioisotope production facility, funded by the private sector at approximately $28 million. In addition, research radioisotope production by the NBTF will be coordinated through an association with an existing U.S. nuclear reactor center that will produce research and commercial radioisotopes through neutron reactions. The combined facilities will provide the full range of technology for radioisotope production and research: fast neutrons, thermal neutrons, and particle beams (H{sup -}, H{sup +}, and D{sup +}). The proposed NBTF facility includes an 80 MeV, 1 mA H{sup -} cyclotron that will produce proton-induced (neutron deficient) research isotopes.

  4. Urban Pollutant Transport and Infiltration into Buildings Using Perfluorocarbon Tracers

    Science.gov (United States)

    Matthews, James C.; Bacak, Asan; Khan, M. Anwar H.; Wright, Matthew D.; Priestley, Michael; Martin, Damien; Percival, Carl J.; Shallcross, Dudley E.

    2017-01-01

    People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO2 tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants. PMID:28230812

  5. Urban Pollutant Transport and Infiltration into Buildings Using Perfluorocarbon Tracers.

    Science.gov (United States)

    Matthews, James C; Bacak, Asan; Khan, M Anwar H; Wright, Matthew D; Priestley, Michael; Martin, Damien; Percival, Carl J; Shallcross, Dudley E

    2017-02-21

    People spend the majority of their time indoors and therefore the quality of indoor air is worthy of investigation; indoor air quality is affected by indoor sources of pollutants and from pollutants entering buildings from outdoors. In this study, unique perfluorocarbon tracers were released in five experiments at a 100 m and ~2 km distance from a large university building in Manchester, UK and tracer was also released inside the building to measure the amount of outdoor material penetrating into buildings and the flow of material within the building itself. Air samples of the tracer were taken in several rooms within the building, and a CO₂ tracer was used within the building to estimate air-exchange rates. Air-exchange rates were found to vary between 0.57 and 10.90 per hour. Indoor perfluorocarbon tracer concentrations were paired to outdoor tracer concentrations, and in-out ratios were found to vary between 0.01 and 3.6. The largest room with the lowest air-exchange rate exhibited elevated tracer concentrations for over 60 min after the release had finished, but generally had the lowest concentrations, the room with the highest ventilation rates had the highest concentration over 30 min, but the peak decayed more rapidly. Tracer concentrations indoors compared to outdoors imply that pollutants remain within buildings after they have cleared outside, which must be considered when evaluating human exposure to outdoor pollutants.

  6. On the linearity of tracer bias around voids

    CERN Document Server

    Pollina, Giorgia; Dolag, Klaus; Weller, Jochen; Baldi, Marco; Moscardini, Lauro

    2016-01-01

    The large-scale structure of the universe can only be observed directly via luminous tracers of the underlying distribution of dark matter. However, the clustering statistics of tracers are biased and depend on various properties of the tracers themselves, such as their host-halo mass and formation and assembly history. On very large scales, where density fluctuations are within the linear regime, this tracer bias results in a constant offset in the clustering amplitude, which is known as linear bias. Towards smaller non-linear scales, this is no longer the case and tracer bias becomes a complicated function of scale and time. We focus on tracer bias centered on cosmic voids, depressions of the density field that spatially dominate the universe. We consider three different types of tracers: galaxies, galaxy clusters and AGNs, extracted from the hydrodynamical simulation suite Magneticum Pathfinder. In contrast to common clustering statistics that focus on the auto-correlation of tracers, we find that void-tra...

  7. Toxicity of fluorescent tracers and their degradation byproducts

    Directory of Open Access Journals (Sweden)

    Philippe Gombert

    2017-01-01

    Full Text Available Tracer tests are frequently used to delineate catchment area of water supply springs in karstic zones. In the karstic chalk of Normandy, the main tracers used are fluorescent: uranine, sulforhodamine B, naphtionate, and Tinopal®. In this area, a statistical analysis shows that less than half of the injected tracers joins the monitored restitution points and enters the drinking water system where they undergo chlorination. Most of the injected tracers is absorbed in the rock matrix or is thrown out of the aquifer via karstic springs: then it can join superficial waters where it is degraded due to the sun and air action. The paper presents firstly the laboratory degradation of a first batch of fluorescent tracers in contact with chlorine, in order to simulate their passage through a water treatment system for human consumption. A second batch of the same tracers is subjected to agents of natural degradation: ultraviolet illumination, sunlight and air sparging. Most tracers is degraded, and toxicity and ecotoxicity tests (on rats, daphniae and algae are performed on degradation byproducts. These tests do not show any acute toxicity but a low to moderate ecotoxicity. In conclusion, the most used fluorescent tracers of the Normandy karstic chalk and their artificial and natural degradation byproducts do not exhibit significant toxicity to humans and the aquatic environment, at the concentrations generally noted at the restitution points.

  8. Surfzone dynamics of the Konkan coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Anand, N.M.; Nayak, B.U.

    The Konkan Coast has the distinct morphological features than the rest of the Indian Coast. Field studies on beach variation, littoral environmental observation and longshore sediment transport were carried out for a period of one year, between...

  9. Surf-zone Underwater Robotic Demonstration Platform

    Science.gov (United States)

    2014-01-01

    dynamically advantageous shape for a robotic system. To address locomotive factors ARA completed a research and technical study based on an Archimedes ...effective hull shape. To study mobility and traction a propulsion system based on an Archimedes screw drive was used. A drive design based on an... Archimedes screw was chosen because of its ability to operate in various mediums with varying flow rates. A test bed was designed and assembled in order to

  10. Turbulent dispersion in cloud-topped boundary layers

    Science.gov (United States)

    Verzijlbergh, R. A.; Jonker, H. J. J.; Heus, T.; Vilöguerau de Arellano, J.

    2009-02-01

    Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary layer (for reference), 2) a "smoke" cloud boundary layer in which the turbulence is driven by radiative cooling, 3) a stratocumulus topped boundary layer and 4) a shallow cumulus topped boundary layer. We show that the dispersion characteristics of the smoke cloud boundary layer as well as the stratocumulus situation can be well understood by borrowing concepts from previous studies of dispersion in the dry convective boundary layer. A general result is that the presence of clouds enhances mixing and dispersion - a notion that is not always reflected well in traditional parameterization models, in which clouds usually suppress dispersion by diminishing solar irradiance. The dispersion characteristics of a cumulus cloud layer turn out to be markedly different from the other three cases and the results can not be explained by only considering the well-known top-hat velocity distribution. To understand the surprising characteristics in the shallow cumulus layer, this case has been examined in more detail by 1) determining the velocity distribution conditioned on the distance to the nearest cloud and 2) accounting for the wavelike behaviour associated with the stratified dry environment.

  11. General Motors sulfate dispersion experiment: experimental procedures and results

    Energy Technology Data Exchange (ETDEWEB)

    Cadle, S.H.; Chock, D.P.; Monson, P.R.; Heuss, J.M.

    1977-01-01

    A massive experiment was conducted at the General Motors Proving Ground to measure the dispersion of sulfates generated by catalyst equipped vehicles. 352 cars equipped with catalysts and air pumps were driven on a 10 kilometer test track to provide a simulated freeway situation with a traffic density of 5462 cars/hour. Experiments were conducted on 17 days in October 1975, providing sixty-six 30 min data sets. On most days, the experiment was carried out early in the morning in order to run under the most adverse meteorological conditions available. Samples of airborne sulfate and a gas tracer, sulfur hexafluoride, as well as extensive meteorological data were collected simultaneously at 20 sampling points under a wide variety of meteorological conditions. The maximum measured increase in sulfate from each 30 min data set was generally found next to the roadway at the lowest level and varied from 3 to 15 ..mu..g/m/sup 3/. This increase in sulfate over background fell off rapidly with height and distance. Sulfate increases in vehicles (2 hr averages) ranged from 0 to 20 ..mu..g/m/sup 3/, and averaged 4 ..mu..g/m/sup 3/. Within experimental uncertainty, the sulfate aerosol and the gas tracer were found to disperse in the same manner. The tracer data have also been used to calculate the sulfate emission rate of the vehicles.

  12. Aespoe Hard Rock Laboratory. Final report of the first stage of the tracer retention understanding experiments

    Energy Technology Data Exchange (ETDEWEB)

    Winberg, A. [Conterra AB, Uppsala (Sweden); Andersson, Peter [Geosigma AB, Uppsala (Sweden); Hermanson, Jan [Golder Grundteknik, Solna (Sweden); Byegaard, Johan [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Nuclear Chemistry; Cvetkovic, V. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Water Resources Engineering; Birgersson, Lars [Kemakta Konsult AB, Stockholm (Sweden)

    2000-03-15

    from its surrounding. The near proximity of the experimental array to the tunnel (10-15 m) implies a strong gradient (approximately 10%) in the structure, which has to be overcome and controlled during the experiments. A methodology for characterising fracture pore space using resin injection, excavation using large diameter coring and subsequent analysis with photo-microscopic and image analysis techniques was developed and tested at a separate site. The results show that epoxy resin can be injected over several hours, and that the estimated areal spread is in the order of square metres. The mean apertures of the two investigated samples were 239 and 266 microns, respectively. Assessment of spatial correlation show practical ranges in the order of a few millimetres. Performed tracer tests with conservative tracers in Feature A show that the feature is connected between its interpreted intercepts in the array. The parameters evaluated from the conservative tests; flow porosity, dispersivity and fracture conductivity are similar, indicating a relative homogeneity. Previous work has identified cationic tracers, featured by sorption through ion exchange, as the most suitable tracers for sorbing tracer experiments at ambient Aespoe conditions. Laboratory experiments on generic Aespoe material and site-specific material included batch sorption experiments on various size fractions of the geological material, and through diffusion experiments on core samples of variable length on a centimetre length scale. The sorbtivity was found to be strongly affected by the biotite content and the sorption was also found to increase with contact time. The sorbtivity was found to follow the relative order; {sup 22}Na{sup +} < {sup 47}Ca{sup 2+} {approx_equal} {sup 85}Sr{sup 2+} << {sup 86}Rb{sup +} {approx_equal} {sup 133}Ba{sup 2+} The field tracer tests, using essentially the same cocktail of sorbing tracers as in the laboratory, were found to show the same relative sorbtivity as seen

  13. Characterization of an alluvial aquifer with thermal tracer tomography

    Science.gov (United States)

    Somogyvári, Márk; Bayer, Peter

    2017-04-01

    In the summer of 2015, a series of thermal tracer tests was performed at the Widen field site in northeast Switzerland. At this site numerous hydraulic, tracer, geophysical and hydrogeophysical field tests have been conducted in the past to investigate a shallow alluvial aquifer. The goals of the campaign in 2015 were to design a cost-effective thermal tracer tomography setup and to validate the concept of travel time-based thermal tracer tomography under field conditions. Thermal tracer tomography uses repeated thermal tracer injections with different injection depths and distributed temperature measurements to map the hydraulic conductivity distribution of a heterogeneous aquifer. The tracer application was designed with minimal experimental time and cost. Water was heated in inflatable swimming pools using direct sunlight of the warm summer days, and it was injected as low temperature pulses in a well. Because of the small amount of injected heat, no long recovery times were required between the repeated heat tracer injections and every test started from natural thermal conditions. At Widen, four thermal tracer tests were performed during a period of three days. Temperatures were measured in one downgradient well using a distributed temperature measurement system installed at seven depth points. Totally 12 temperature breakthrough curves were collected. Travel time based tomographic inversion assumes that thermal transport is dominated by advection and the travel time of the thermal tracer can be related to the hydraulic conductivities of the aquifer. This assumption is valid in many shallow porous aquifers where the groundwater flow is fast. In our application, the travel time problem was treated by a tomographic solver, analogous to seismic tomography, to derive the hydraulic conductivity distribution. At the test site, a two-dimensional cross-well hydraulic conductivity profile was reconstructed with the travel time based inversion. The reconstructed profile

  14. Dispersion management with metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  15. Vowel dispersion in Truku

    OpenAIRE

    Chiang, Wen-yu; Chiang, Fang-mei

    2013-01-01

    This study investigates the dispersion of vowel space in Truku, an endangered Austronesian language in Taiwan. Adaptive Dispersion (Liljencrants and Lindblom, 1972; Lindblom, 1986, 1990) proposes that the distinctive sounds of a language tend to be positioned in phonetic space in a way that maximizes perceptual contrast. For example, languages with large vowel inventories tend to expand the overall acoustic vowel space. Adaptive Dispersion predicts that the distance between the point vowels w...

  16. Methods and systems using encapsulated tracers and chemicals for reservoir interrogation and manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Jeffery; Aines, Roger D; Duoss, Eric B; Spadaccini, Christopher M

    2014-11-04

    An apparatus, method, and system of reservoir interrogation. A tracer is encapsulating in a receptacle. The receptacle containing the tracer is injected into the reservoir. The tracer is analyzed for reservoir interrogation.

  17. System identification by experimental data processing, application to turbulent transport of a tracer in pipe flow

    Energy Technology Data Exchange (ETDEWEB)

    Burgos, Manuel [Universidad Catolica del Uruguay, Montevideo (Uruguay). Facultad de Ingenieria y Tecnologias]. E-mail: mburgos@ucu.edu.uy; Getto, Daniel; Berne, Philippe [Commissariat a l' Energie Atomique, C.E.A. Grenoble, Cedex 9 (France). Section d' Application des Traceurs]. E-mail: daniel.getto@cea.fr; philippe.berne@cea.fr

    2005-07-01

    System identification is the first, and probably the most important step in detecting abnormal behavior, control system design or performance improving. Data analysis is performed for studying the plant behavior, sensitivity of operation procedures and several other goals. In all these cases, the observed data is the convolution of an input function, and the system's impulse response. Practical discrete time convolutions may be performed multiplying a matrix built from the impulse response by the input vector, but for deconvolution it is necessary to invert the matrix which is singular in a causal system. Another method for deconvolution is by means of Fourier Transforms. Actual readings are usually corrupted by noise and, besides, their transform shows high low frequencies components and high frequency ones mainly due to additive noise. Subjective decisions as cut-off frequency should be taken as well. This paper proposes a deconvolution method based on parameters fitting of suitable models, where they exist, and estimation of values where analytical forms are not available. It is based on the global, non linear fitting of them, with a maximum likelihood criteria. An application of the method is shown using data from two fluid flow experiments. The experimental test rigs basically consist in a long section of straight pipe in which fluid is flowing. A pulse of tracer is injected at the entrance and detected at various locations along the pipe. An attempt of deconvolution of signals from successive probes using a classical model describing the flow of tracer as a plug moving with the average fluid velocity, plus some axial dispersion. The parameters are for instance the velocity of the plug and a dispersion coefficient. After parameter fitting, the model is found to reproduce the experimental data well. The flow rates deduced from the adjusted travel times are in very good agreement with the actual values. In addition, the flow dispersion coefficient is

  18. A review of biomarker compounds as source indicators and tracers for air pollution

    Energy Technology Data Exchange (ETDEWEB)

    Simoneit, B.R.T. [Oregon State Univ., Corvallis, OR (United States). Environmental and Petroleum Geochemistry Group

    1999-07-01

    . Although the molecular composition of organic matter in smoke particles is highly variable, the molecular tracers are generally still source specific. Retene has been utilized as a tracer for conifer smoke in urban aerosols, but is not always detectable. Dehydroabietic acid is generally more concentrated in the atmosphere from the same emission sources. Degradation products from biopolymers (e.g., levoglucosan from cellulose) are also excellent tracers. An overview of the biomarker compositions of biomass smoke types is presented here. Defining additional tracers of thermally-altered and directly-emitted natural products in smoke aids the assessment of the organic matter type and input from biomass combustion to aerosols. The precursor to product approach of compound characterization by organic geochemistry can be applied successfully to provide tracers for studying the chemistry and dispersion of ambient aerosols and smoke plumes. (orig.)

  19. A Model of Dispersion in Pollutant Transport; Un modelo de dispersion en el transporte de contaminantes

    Energy Technology Data Exchange (ETDEWEB)

    Maron Dominguez, David Ernesto [Instituto Superior Politecnico Jose A. Echeverrria (Cuba)

    2002-09-01

    A numeric model is show for the solution of the inverse problem in pollutant transport. Quadratic and cubic elements were used in the discretization by the MEF of the equation of the dispersion. The algorithms of the inverse model are verified and compared with analytic solutions reported in the literature. The application of the model to the calibration of the parameters of a wetland used a s a filter in the treatment of wastewater is shown. The wetland was created in the laboratory and measurements of sodium fluorescein concentrations of a test were used as tracer. The dispersion coefficient, the retardation coefficient, the degradation coefficient, and the parameter of weight of the discretization in time were gauged. The results shown prove the good approximation of the dispersion coefficient obtained with a value estimated by another method. The graphs of the adjustments obtained are also shown. [Spanish] Se muestra un modelo numerico para la resolucion del problema inverso en el transporte de contaminantes. Se emplearon elementos cuadraticos y cubicos en la discretizacion por el metodo de los elementos finitos de la ecuacion de la ecuacion de la dispersion. Se verifican y se comparan los algoritmos del modelo inverso con una solucion analitica reportada en la literatura. Se muestra la aplicacion del modelo a la calibracion de los parametros de un humedal utilizado como filtro en el tratamiento de agua residuales. El humedal se construyo en el laboratorio y se utilizaron mediciones de concentraciones de fluoresceina sodica de una prueba de trazado. Se calibraron el coeficiente de dispersion, el coeficiente de retardo, el coeficiente de degradacion y el parametro de peso de la discretizacion en el tiempo. Se muestran los resultados obtenidos, comprobandose la buena aproximacion del coeficiente de dispersion con un valor estimado por otro metodo. Se muestran las graficas de los ajustes que se lograron.

  20. Transport study in unsaturated porous media by tracer experiment in a dichromatic X-ray experimental device

    Directory of Open Access Journals (Sweden)

    Néel M.C.

    2013-05-01

    Full Text Available Estimating contaminant migration in the context of waste disposal and/or environmental remediation of polluted soils requires a complete understanding of the underlying transport processes. In unsaturated porous media, water content is one of the most determining parameters to describe solute migration because it impacts directly on solute pore velocity. However, numerous studies are satisfied with only a global or a partial spatial distribution of water content within the studied porous media. Therefore, distribution of water content in porous media must be precisely achieved to optimize transport processes modeling. Tracer experiments with downward flow were performed on the BEETI experimental device equipped with a sand column. Water content and concentration profiles of tracer (KI were measured along the column during experiment. The relative dispersion of water content, calculated along the column, gives an idea of influence of this parameter on transport properties. A relationship between pore velocity, Darcy flow velocity and water content is proposed.

  1. Transport study in unsaturated porous media by tracer experiment in a dichromatic X-ray experimental device

    Science.gov (United States)

    Latrille, C.; Néel, M. C.

    2013-05-01

    Estimating contaminant migration in the context of waste disposal and/or environmental remediation of polluted soils requires a complete understanding of the underlying transport processes. In unsaturated porous media, water content is one of the most determining parameters to describe solute migration because it impacts directly on solute pore velocity. However, numerous studies are satisfied with only a global or a partial spatial distribution of water content within the studied porous media. Therefore, distribution of water content in porous media must be precisely achieved to optimize transport processes modeling. Tracer experiments with downward flow were performed on the BEETI experimental device equipped with a sand column. Water content and concentration profiles of tracer (KI) were measured along the column during experiment. The relative dispersion of water content, calculated along the column, gives an idea of influence of this parameter on transport properties. A relationship between pore velocity, Darcy flow velocity and water content is proposed.

  2. Geometry and violent events in turbulent pair dispersion

    CERN Document Server

    Bitane, Rehab; Bec, Jeremie

    2012-01-01

    The statistics of Lagrangian pair dispersion in a homogeneous isotropic flow is investigated by means of direct numerical simulations. The focus is on deviations from Richardson eddy-diffusivity model and in particular on the strong fluctuations experienced by tracers. Evidence is obtained that the distribution of distances attains an almost self-similar regime characterized by a very weak intermittency. The timescale of convergence to this behavior is found to be given by the kinetic energy dissipation time measured at the scale of the initial separation. Conversely the velocity differences between tracers are displaying a strongly anomalous behavior whose scaling properties are very close to that of Lagrangian structure functions. These violent fluctuations are interpreted geometrically and are shown to be responsible for a long-term memory of the initial separation. Despite this strong intermittency, it is found that the mixed moment defined by the ratio between the cube of the longitudinal velocity differ...

  3. Seed dispersal in fens

    Science.gov (United States)

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  4. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  5. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  6. Quantifying heterogeneous transport of a tracer and a degradable contaminant in the field, with snowmelt and irrigation

    Directory of Open Access Journals (Sweden)

    D. Schotanus

    2012-08-01

    Full Text Available To examine the persistence of preferential flow paths in a field soil, and to compare the leaching of a degradable contaminant with the leaching of a tracer, two field experiments were performed using a multi-compartment sampler (MCS. The first experiment was carried out during the snowmelt period in early spring, characterized by high infiltration fluxes from snowmelt. The second experiment was carried out in early summer with irrigation to mimic homogeneous rainfall. During the second experiment, the soil was warmer and degradation of the degradable contaminant was observed. For both experiments, the highest tracer concentrations were found in the same area of the sampler, but the leached tracer masses of the individual locations were not highly correlated. Thus, the preferential flow paths were stable between the two experiments. With a lower infiltration rate, in the second experiment, more isolated peaks in the drainage and the leached masses were found than in the first experiment. Therefore, it is concluded that the soil heterogeneity is mainly caused by local differences in the soil hydraulic properties, and not by macropores. With higher infiltration rates, the high and low leaching cells were more clustered. The leached masses of the degradable contaminant were lower than the leached masses of the tracer, but the masses were highly correlated. The first-order degradation rate and the dispersivity were fitted with CXTFIT; the first-order degradation rate was 0.02 d−1, and the dispersivity varied between 1.9 and 7.1 cm. The persistence of the flow paths during the experiments suggests soil heterogeneity as the driver for heterogeneous flow and solute transport in this soil. At the MCS scale, heterogeneous snowmelt did not seem to have much influence on the flow and solute paths.

  7. Quantification of tracer plume transport parameters in 2D saturated porous media by cross-borehole ERT imaging

    Science.gov (United States)

    Lekmine, G.; Auradou, H.; Pessel, M.; Rayner, J. L.

    2017-04-01

    Cross-borehole ERT imaging was tested to quantify the average velocity and transport parameters of tracer plumes in saturated porous media. Seven tracer tests were performed at different flow rates and monitored by either a vertical or horizontal dipole-dipole ERT sequence. These sequences were tested to reconstruct the shape and temporally follow the spread of the tracer plumes through a background regularization procedure. Data sets were inverted with the same inversion parameters and 2D model sections of resistivity ratios were converted to tracer concentrations. Both array types provided an accurate estimation of the average pore velocity vz. The total mass Mtot recovered was always overestimated by the horizontal dipole-dipole and underestimated by the vertical dipole-dipole. The vertical dipole-dipole was however reliable to quantify the longitudinal dispersivity λz, while the horizontal dipole-dipole returned better estimation for the transverse component λx. λ and Mtot were mainly influenced by the 2D distribution of the cumulated electrical sensitivity and the Shadow Effects induced by the third dimension. The size reduction of the edge of the plume was also related to the inability of the inversion process to reconstruct sharp resistivity contrasts at the interface. Smoothing was counterbalanced by a non-realistic rise of the ERT concentrations around the centre of mass returning overpredicted total masses. A sensitivity analysis on the cementation factor m and the porosity ϕ demonstrated that a change in one of these parameters by 8% involved non negligible variations by 30 and 40% of the dispersion coefficients and mass recovery.

  8. Perfect Dispersive Medium

    CERN Document Server

    Gupta, Shulabh

    2015-01-01

    Dispersion is at the heart of all ultrafast real-time signal processing systems across the entire electromagnetic spectrum ranging from radio-frequencies to optics. However, following Kramer-Kronig relations, these signal processing systems have been plagued with the parasitic amplitude distortions due to frequency dependent, and non-flat amplitude transmission of naturally dispersive media. This issue puts a serious limitation on the applicability and performance of these signal processing systems. To solve the above mentioned issue, a perfect dispersive medium is proposed in this work, which artificially violates the Kramer-Kronig relations, while satisfying all causality requirements. The proposed dispersive metamaterial is based on loss-gain metasurface pairs and exhibit a perfectly flat transmission response along with arbitrary dispersion in a broad bandwidth, thereby solving a seemingly unavoidable issue in all ultrafast signal processing systems. Such a metamaterial is further shown using sub-waveleng...

  9. Evolution of dispersal distance.

    Science.gov (United States)

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  10. Tracer diffusivity and effective temperature in bacterial suspensions

    CERN Document Server

    Patteson, Alison E; Purohit, Prashant K; Arratia, Paulo E

    2015-01-01

    The dynamics of tracer particles in \\textit{E. coli} suspensions are experimentally investigated as a function of particle size and bacteria concentration. We find that tracer diffusivity is enhanced due to particle-bacteria interactions and varies non-monotonically with particle size, exhibiting a peak at sizes comparable to the bacterial length. The time scale characterizing the transition from ballistic to diffusive regime increases monotonically with \\textit{E. coli} concentration and particle size. Diffusivity measurements are then used to estimate suspension effective temperature, which varies nonlinearly with tracer size, suggesting that measures of activity are probe size dependent.

  11. Radionuclide Tracers for Myocardial Perfusion Imaging and Blood Flow Quantification.

    Science.gov (United States)

    deKemp, Robert A; Renaud, Jennifer M; Klein, Ran; Beanlands, Rob S B

    2016-02-01

    Myocardial perfusion imaging is performed most commonly using Tc-99m-sestamibi or tetrofosmin SPECT as well as Rb-82-rubidium or N-13-ammonia PET. Diseased-to-normal tissue contrast is determined by the tracer retention fraction, which decreases nonlinearly with flow. Reduced tissue perfusion results in reduced tracer retention, but the severity of perfusion defects is typically underestimated by 20% to 40%. Compared to SPECT, retention of the PET tracers is more linearly related to flow, and therefore, the perfusion defects are measured more accurately using N-13-ammonia or Rb-82.

  12. Laboratory Testing of Magnetic Tracers for Soil Erosion Measurement*1

    Institute of Scientific and Technical Information of China (English)

    HU Guo-Qing; DONG Yuan-Jie; WANG Hui; QIU Xian-Kui; WANG Yan-Hua

    2011-01-01

    Soil erosion, which includes soil detachment, transport, and deposition, is one of the important dynamic land surface processes. The magnetic tracer method is a useful method for studying soil erosion processes. In this study, five types of magnetic tracers were made with fine soil, fly ash, cement, bentonite, and magnetic powder (reduced iron powder) using the method of disk granulation. The tracers were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow experiments to simulate the interrill and rill components of soil erosion, in order to select one or more tracers which could be used to study detachment and deposition by the erosive forces of raindrops and surface flow of water on a slope. The results showed that the five types of magnetic tracers with high magnetic susceptibility and a wide range of sizes had a range of 0.99-1.29 gcm-s in bulk density. In the interrill and rill experiments, the tracers FC1 and FC2 which consisted of fly ash and cement at ratios of 1:1 and 2:1, respectively, were transported in phase with soil particles since the magnetic susceptibility of sediment approximated that of the soil which was uneroded and the slopes of the regression equations between the detachment of sediment and magnetic tracers FC1 and FC2 were very close to the expected value of 20, which was the original soil/tracer ratio. The detachment and deposition on slopes could be accurately reflected by the magnetic susceptibility differences. The change in magnetic susceptibility depended on whether deposition or detachment occurred. However, the tracer FS which consisted of fine soil and the tracers FB1 and FB2 which consisted of fly ash and bentonite at ratios of 1:1 and 2:1, respectively, were all unsuitable for soil erosion study since there was no consistent relationship between sediment and tracer detachment for increasing amounts of runoff. Therefore, the tracers FC1 and FC2 could be used to study soil erosion by water.

  13. Small Molecule PET Tracers in Drug Discovery.

    Science.gov (United States)

    Donnelly, David J

    2017-09-01

    The process of discovering and developing a new pharmaceutical is a long, difficult, and risky process that requires numerous resources. Molecular imaging techniques such as PET have recently become a useful tool for making decisions along a drug candidate's development timeline. PET is a translational, noninvasive imaging technique that provides quantitative information about a potential drug candidate and its target at the molecular level. Using this technique provides decisional information to ensure that the right drug candidate is being chosen, for the right target, at the right dose within the right patient population. This review will focus on small molecule PET tracers and how they are used within the drug discovery process. PET provides key information about a drug candidate's pharmacokinetic and pharmacodynamic properties in both preclinical and clinical studies. PET is being used in all phases of the drug discovery and development process, and the goal of these studies are to accelerate the process in which drugs are developed. Copyright © 2017. Published by Elsevier Inc.

  14. National Biomedical Tracer Facility: Project definition study

    Energy Technology Data Exchange (ETDEWEB)

    Heaton, R.; Peterson, E. [Los Alamos National Lab., NM (United States); Smith, P. [Smith (P.A.) Concepts and Designs (United States)

    1995-05-31

    The Los Alamos National Laboratory is an ideal institution and New Mexico is an ideal location for siting the National Biomedical Tracer Facility (NBTF). The essence of the Los Alamos proposal is the development of two complementary irradiation facilities that combined with our existing radiochemical processing hot cell facilities and waste handling and disposal facilities provide a low cost alternative to other proposals that seek to satisfy the objectives of the NBTF. We propose the construction of a 30 MeV cyclotron facility at the site of the radiochemical facilities, and the construction of a 100 MeV target station at LAMPF to satisfy the requirements and objectives of the NBTF. We do not require any modifications to our existing radiochemical processing hot cell facilities or our waste treatment and disposal facilities to accomplish the objectives of the NBTF. The total capital cost for the facility defined by the project definition study is $15.2 M. This cost estimate includes $9.9 M for the cyclotron and associated facility, $2.0 M for the 100 MeV target station at LAMPF, and $3.3 M for design.

  15. TRACER STUDY OF RTU GRADUATES: AN ANALYSIS

    Directory of Open Access Journals (Sweden)

    Thelma L. Ramirez

    2014-01-01

    Full Text Available This paper aimed to determine if the field of specialization in the different colleges of RTU graduates and their academic-acquired skills and competencies are related to their present occupations. A modified Graduate Tracer Study (GTS instrument was utilized to gather the quantitative data. Out of 500 questionnaires administered, there were 250 graduates returned answered questionnaires representing the three Colleges: Education, Arts and Sciences, Business and Entrepreneurial Technology. A face to face interview was also conducted in order to support the gathered data. The SPSS was used to generate results from the acquired quantitative data using the frequency counts, percentage and the Chi-square goodness of fit test. The findings revealed that the graduates claimed that their knowledge, academic-acquired skills and competencies contributed greatly in their job performance. The Chi-square goodness of fit proved that there is a significant relationship between the graduates’ fields of specialization and their occupations after graduation. Likewise, the academic-acquired skills and competencies of the graduates are relevant to their chosen occupations. The results further proved that RTU produces marketable and appropriately trained graduates with the majority landing in course-related jobs within a short period after graduation. The study also indicates that the RTU graduates possess the skills and competencies necessary to succeed in this competitive world. However eexpansion of tie-ups with private business entities is made to at least maintain the high employability level of the graduates.

  16. Gaseous versus Stellar Velocity Dispersion in Emission-Line Galaxies

    Institute of Scientific and Technical Information of China (English)

    Xiao-Yan Chen; Cai-Na Hao; Jing Wang

    2008-01-01

    We compare the ionized gas velocity dispersion σgas with the stellar velocity dis-persion σ* in star-forming galaxies, composite galaxies, Low Ionization Nuclear Emission-line Regions (LINERs) and Seyfert 2s, compiled from a cross-identification of Sloan Digital Sky Survey Fourth Data Release (SDSS DR4) and Point Source Catalogue Redshift Survey (PSCz). We measure σgas from the FWHMs of emission lines (Hα, [NII]λλ6548, 6583 and [SII] λλ6716, 6731). A significant correlation between the gas and stellar velocity dispersion exists, despite substantial scatter. The mean value of the gas to stellar velocity dispersion ratio is close to unity. This suggests that gas velocity dispersion can substitute for the stellar veloc-ity dispersion as a tracer of the gravitational potential well for all the four types of galaxies,but the involved uncertainties are different from type to type. We also studied σgas/σ* as a function of the redshift and the axial ratio to test the effects of aperture and galaxy inclina-tion, and found that both effects are weak. Finally we checked the trend of σgas/σ* with the infrared luminosity and found no significant correlation.

  17. Tracing river gravels: Insights into dispersion from a long-term field experiment

    Science.gov (United States)

    Haschenburger, J. K.

    2013-10-01

    Sediment dispersion is a fundamental component of the sediment transfer process in gravel-bed rivers. Modeling this process requires an understanding of the collective movement of mixed-size clasts. This study explores the temporal evolution of gravel dispersion to underscore the importance of field observation in informing modeling efforts. Magnetically tagged gravels deployed in Carnation Creek have been monitored repeatedly over 17 years. Four metrics used to describe the extent of dispersion document that the overall shape in the spatial distribution of grain location changes over time. The general trends mask the complexity of the dispersion process, expressed by channel sections where tracers are concentrated regardless of grain size. The distribution of total grain displacement responsible for dispersion evolves as tracers become well mixed. Results demonstrate that observations from the field are crucial to the understanding and modeling of sediment dispersion because they provide key insights into the dispersion process that must be known a priori for mathematical modeling and similar observations cannot be collected using laboratory flumes.

  18. On the methods for determining the transverse dispersion coefficient in river mixing

    Science.gov (United States)

    Baek, Kyong Oh; Seo, Il Won

    2016-04-01

    In this study, the strengths and weaknesses of existing methods for determining the dispersion coefficient in the two-dimensional river mixing model were assessed based on hydraulic and tracer data sets acquired from experiments conducted on either laboratory channels or natural rivers. From the results of this study, it can be concluded that, when the longitudinal dispersion coefficient as well as the transverse dispersion coefficients must be determined in the transient concentration situation, the two-dimensional routing procedures, 2D RP and 2D STRP, can be employed to calculate dispersion coefficients among the observation methods. For the steady concentration situation, the STRP can be applied to calculate the transverse dispersion coefficient. When the tracer data are not available, either theoretical or empirical equations by the estimation method can be used to calculate the dispersion coefficient using the geometric and hydraulic data sets. Application of the theoretical and empirical equations to the laboratory channel showed that equations by Baek and Seo [[3], 2011] predicted reasonable values while equations by Fischer [23] and Boxwall and Guymer (2003) overestimated by factors of ten to one hundred. Among existing empirical equations, those by Jeon et al. [28] and Baek and Seo [6] gave the agreeable values of the transverse dispersion coefficient for most cases of natural rivers. Further, the theoretical equation by Baek and Seo [5] has the potential to be broadly applied to both laboratory and natural channels.

  19. Axial Dispersion in Segmented Gas-Liquid Flow: Effects of the Channel Curvature

    Science.gov (United States)

    Muradoglu, Metin

    2009-11-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows have been studied computationally in a two-dimensional setting using a front-tracking/finite-volume method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion and dispersion increases with channel curvature. It is known that there is no dispersion in straight channels since a lubricating thin liquid layer persists on the wall. However this lubricating liquid layer is periodically broken in the curved channel case leading to enhanced axial dispersion. It is found that the dispersion increases as the Peclet number (Pe) decreases both in straight and curved channels. Difference between the straight and curved channel decreases continuously as the Peclet number decreases and virtually disappears at low Peclet numbers, i.e., Pestudy. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe->∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  20. A Systematic Method For Tracer Test Analysis: An Example Using Beowawe Tracer Data

    Energy Technology Data Exchange (ETDEWEB)

    G. Michael Shook

    2005-01-01

    Quantitative analysis of tracer data using moment analysis requires a strict adherence to a set of rules which include data normalization, correction for thermal decay, deconvolution, extrapolation, and integration. If done correctly, the method yields specific information on swept pore volume, flow geometry and fluid velocity, and an understanding of the nature of reservoir boundaries. All calculations required for the interpretation can be done in a spreadsheet. The steps required for moment analysis are reviewed in this paper. Data taken from the literature is used in an example calculation.

  1. Measuring gene flow from two birdsfoot trefoil (Lotus corniculatus) field trials using transgenes as tracer markers.

    Science.gov (United States)

    De Marchis, F; Bellucci, M; Arcioni, S

    2003-06-01

    Genetic engineering is becoming a useful tool in the improvement of plants but concern has been expressed about the potential environmental risks of releasing genetically modified (GM) organisms into the environment. Attention has focused on pollen dispersal as a major issue in the risk assessment of transgenic crop plants. In this study, pollen-mediated dispersal of transgenes via cross-fertilization was examined. Plants of Lotus corniculatus L. transformed with either the Escherichia coli asparagine synthetase gene asnA or the beta-glucuronidase gene uidA, were used as the pollen donor. Nontransgenic plants belonging to the species L. corniculatus L., L. tenuis Waldst. and Kit. ex Willd, and L. pedunculatus Cav., were utilized as recipients. Two experimental fields were established in two areas of central Italy. Plants carrying the uidA gene were partially sterile, therefore only the asnA gene was used as a tracer marker. No transgene flow between L. corniculatus transformants and the nontransgenic L. tenuis and L. pedunculatus plants was detected. As regards nontransgenic L. corniculatus plants, in one location flow of asnA transgene was detected up to 18 m from the 1.8 m2 donor plot. In the other location, pollen dispersal occurred up to 120 m from the 14 m2 pollinating plot.

  2. Determination of the Tracer Diffusion Coefficient of Soft Polystyrene Nanoparticles using Neutron Reflectivity

    Science.gov (United States)

    Imel, Adam; Miller, Brad; Holley, Wade; Baskaran, Durairaj; Mays, Jimmy; Dadmun, Mark

    2015-03-01

    The diffusion properties of nanoparticles in polymer nanocomposites are largely unknown and depend intimately on the dispersion of the nanoparticles. We examine the diffusion of soft, organic nanoparticles, which disperse in a polymer matrix due to the interpenetration of polymer chains and particles and the reduction in the depletion of entropy in the system. The impact of the presence of soft nanoparticles on the diffusion coefficient of polystyrene chains has recently been determined with neutron reflectivity. This was completed by monitoring the interdiffusion of deuterated and protonated polystyrene nanocomposite bilayers with and without the soft nanoparticles dispersed throughout both layers and extracting the diffusion coefficient from the one-dimensional solution to Fick's second law of diffusion. In this work, we extend this method to bilayer systems with only the soft nanoparticles as one of the layers and a linear deuterated polystyrene as an adjacent layer. The development of this method allows us to determine the tracer diffusion coefficient of the soft polystyrene nanoparticles for the first time by analyzing the mutual diffusion coefficient from Fick's second law and the fast and slow modes theories for diffusion.

  3. Heat Transfer Characterization Using Heat and Solute Tracer Tests in a Shallow Alluvial Aquifer

    Science.gov (United States)

    Dassargues, A.

    2013-12-01

    Very low enthalpy geothermal systems are increasingly considered for heating or cooling using groundwater energy combined with heat pumps. The design and the impact of shallow geothermal systems are often assessed in a semi-empirical way. It is accepted by most of the private partners but not by environmental authorities deploring a lack of rigorous evaluation of the mid- to long-term impact on groundwater. In view of a more rigorous methodology, heat and dye tracers are used for estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The experimental field site, is equipped with 21 piezometers drilled in alluvial deposits composed of a loam layer overlying a sand and gravel layer constituting the alluvial aquifer. The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring evolution of groundwater temperature and tracer concentration in 3 control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. On the field: view from the injection well in direction of the pumping well through the three monitoring panels Temperature monitoring in the pumping well and in the piezometers of the three panels: heat transfer is faster in the lower part of the aquifer (blue curves) than in the upper part (red curves). Breakthrough curves are also more dispersed in the upper part with longer tailings.

  4. West Twin Creek Alaska Subsurface Bromide Tracer Experiment, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data was produced as part of a subsurface tracer experiment performed on a boreal hillslope in July, 2015. The data is separated into three files: 'Well...

  5. Microfluidics for Synthesis of Peptide-Based PET Tracers

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2013-01-01

    Full Text Available Positron emission tomography (PET is a powerful noninvasive tool for acquisition of the physiological parameters in human and animals with the help of PET tracers. Among all the PET tracers, radiolabeled peptides have been widely explored for cancer-related receptor imaging due to their high affinity and specificity to receptors. But radiochemistry procedures for production of peptide-based PET tracers are usually complex, which makes large-scale clinical studies relatively challenging. New radiolabeling technologies which could simplify synthesis and purification procedures, are extremely needed. Over the last decade, microfluidics and lab-on-a-chip (LOC technology have boomed as powerful tools in the field of organic chemistry, which potentially provide significant help to the PET chemistry. In this minireview, microfluidic radiolabeling technology is described and its application for synthesis of peptide-based PET tracers is summarized and discussed.

  6. Chlorine isotopes potential as geo-chemical tracers

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Pradhan, U.K.; Banerjee, R.

    The potential of chlorine isotopes as tracers of geo-chemical processes of earth and the oceans is highlighted based on systematic studies carried out in understanding the chlorine isotope fractionation mechanism, its constancy in seawater and its...

  7. Tracking thermal fronts with temperature-sensitive, chemically reactive tracers

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, B.A.; Birdsell, S.A.

    1987-01-01

    Los Alamos is developing tracer techniques using reactive chemicals to track thermal fronts in fractured geothermal reservoirs. If a nonadsorbing tracer flowing from the injection to production well chemically reacts, its reaction rate will be a strong function of temperature. Thus the extent of chemical reaction will be greatest early in the lifetime of the system, and less as the thermal front progresses from the injection to production well. Early laboratory experiments identified tracers with chemical kinetics suitable for reservoirs in the temperature range of 75 to 100/sup 0/C. Recent kinetics studies have focused on the kinetics of hydrolysis of derivatives of bromobenzene. This class of reactions can be used in reservoirs ranging in temperature from 150 to 275/sup 0/C, which is of greater interest to the geothermal industry. Future studies will include laboratory adsorption experiments to identify possibly unwanted adsorption on granite, development of sensitive analytical techniques, and a field demonstration of the reactive tracer concept.

  8. A theoretical framework of tracer methods for marine sediment dynamics

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new theoretical framework of tracer methods is proposed in the present contribution, on the basis of mass conservation. This model is applicable for both artificial and natural tracers. It can be used to calculate the spatial distribution patterns of sediment transport rate, thus providing independent information and verification for the results derived from empirical formulae. For the procedures of the calculation, first, the tracer concentration and topographic maps of two times are obtained. Then, the spatial and temporal changes in the concentration and seabed elevation are calculated, and the boundary conditions required are determined by field observations (such as flow and bedform migration measurements). Finally, based upon eqs. (1) and (13), the transport rate is calculated and expressed as a function of the position over the study area. Further, appropriate modifications to the model may allow the tracer to have different densities and grain size distributions from the bulk sediment.

  9. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  10. Assessment of Halon-1301 as a groundwater age tracer

    OpenAIRE

    M. Beyer; R. van der Raaij; U. Morgenstern; Jackson, B.(Department of Physics, University of Pennsylvania, Philadelphia, PA, United States)

    2015-01-01

    Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and timescale of groundwater flow and recharge, contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their individual restricted applicat...

  11. Assessment of Halon-1301 as a groundwater age tracer

    OpenAIRE

    M. Beyer; R. van der Raaij; U. Morgenstern; Jackson, B.(Department of Physics, University of Pennsylvania, Philadelphia, PA, United States)

    2015-01-01

    Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and time scale of groundwater flow and recharge, to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their in...

  12. Mobility of Metal Tracers in Unsaturated Tuffs of Busted Butte

    Science.gov (United States)

    Groffman, A. R.

    2001-12-01

    A complex tracer mixture was injected continuously for over two years into a 10 m x 10 m x 7 m block of unsaturated tuff as part of the Busted Butte unsaturated-zone tracer test at Yucca Mountain. The test was designed to measure tracer transport within the Topopah Springs and Calico Hills tuffs, units that occur between the potential high-level nuclear waste repository at Yucca Mountain and the water table below. The mixture included nonreactive (Br, I, and fluorinated benzoic acids (FBAs)) and reactive tracers (Li, Ce, Sm, Ni, Co, and Mn). Bromide, I, FBAs, and Li were detected during the test on absorbent pads emplaced in a series of solute collection boreholes located beneath the injectors but the more strongly sorbing metals did not reach the collection boreholes during this period. To determine the distribution and mobility of these metals, tracer constituents were extracted from tuff samples collected during overcoring and mineback of the test block. Tracers were extracted from the tuff samples by leaching with a 5% nitric acid solution for metals and a bicarbonate-carbonate buffer for anions. Results from the overcore sample suite show that metals have migrated through the tuff in the region adjacent to and immediately below the tracer injectors. Consistent with laboratory sorption measurements and observed breakthrough in the collection boreholes, rock analyses showed that Li is the most mobile of the metals. Co and Ni behave similarly, traveling tens of cm from the injection sites, while Sm and Ce moved far less, possibly due to precipitation reactions in addition to sorption. Determination of Mn transport is complicated by high background concentrations in the tuff; additional background samples are currently being evaluated. As expected, our rock analyses show that the nonreactive tracers Br and FBAs have moved beyond the overcore region, corroborating results from collection boreholes.

  13. A Really Good Hammer: Quantification of Mass Transfer Using Perfluorocarbon Tracers (475th Brookhaven Lecture)

    Energy Technology Data Exchange (ETDEWEB)

    Watson, Tom [BNL Environmental Sciences, Tracer Technology Group

    2012-02-15

    Brookhaven Lab’s perfluorocarbon tracer (PFT) technology can be viewed as a hammer looking for nails. But, according to Tom Watson, leader of the Lab’s Tracer Technology Group in the Environmental Research and Technology Division (ERTD), “It’s a really good hammer!” The colorless, odorless and safe gases have a number of research uses, from modeling how airborne contaminants might move through urban canyons to help first responders plan their response to potential terrorist attacks and accidents to locating leaks in underground gas pipes. Their extremely low background level — detectable at one part per quadrillion — allows their transport to be easily tracked. Lab researchers used PFTs during the 2005 Urban Dispersion Program field studies in New York City, gathering data to help improve models of how a gas or chemical release might move around Manhattan’s tall buildings and canyons. Closer to home, scientists also used PFTs to make ventilation measurements in Bldg. 400 on the Lab site to provide data to test air flow models used in determining the effects of passive and active air exchange on the levels of indoor and outdoor air pollution, and to determine the effects of an accidental or intentional release of hazardous substances in or around buildings.

  14. A cubic matrix-fracture geometry model for radial tracer flow in naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Jetzabeth Ramirez-Sabag; Fernando Samaniego V.

    1992-01-01

    This study presents a general solution for the radial flow of tracers in naturally fractured reservoirs, with cubic blocks matrix-fracture geometry. Continuous and finite step injection of chemical and radioactive tracers are considered. The reservoir is treated as being composed of two regions: a mobile where dispersion and convection take place and a stagnant where only diffusion and adsorption are allowed. Radioactive decay is considered in both regions. The model of this study is thoroughly compared under proper simplified conditions to those previously presented in the literature. The coupled matrix to fracture solution in the Laplace space is numerically inverted by means of the Crump algorithm. A detailed validation of the model with respect to solutions previously presented and/or simplified physical conditions solutions (i.e., homogeneous case) or limit solutions (i.e., naturally fractured nearly homogeneous) was carried out. The influence of the three of the main dimensionless parameters that enter into the solution was carefully investigated. A comparison of results for three different naturally fractured systems, vertical fractures (linear flow), horizontal fractures (radial flow) and the cubic geometry model of this study, is presented.

  15. Small Molecule PET Tracers for Transporter Imaging.

    Science.gov (United States)

    Kilbourn, Michael R

    2017-09-01

    As the field of PET has expanded and an ever-increasing number and variety of compounds have been radiolabeled as potential in vivo tracers of biochemistry, transporters have become important primary targets or facilitators of radiotracer uptake and distribution. A transporter can be the primary target through the development of a specific high-affinity radioligand: examples are the multiple high-affinity radioligands for the neuronal membrane neurotransmitter or vesicular transporters, used to image nerve terminals in the brain. The goal of a radiotracer might be to study the function of a transporter through the use of a radiolabeled substrate, such as the application of 3-O-[(11)C]methyl]glucose to measure rates of glucose transport through the blood-brain barrier. In many cases, transporters are required for radiotracer distributions, but the targeted biochemistries might be unrelated: an example is the use of 2-deoxy-2-[(18)F]FDG for imaging glucose metabolism, where initial passage of the radiotracer through cell membranes requires the action of specific glucose transporters. Finally, there are transporters such as p-glycoprotein that function to extrude small molecules from tissues, and can effectively work against successful uptake of radiotracers. The diversity of structures and functions of transporters, their importance in human health and disease, and their role in therapeutic drug disposition suggest that in vivo imaging of transporter location and function will continue to be a point of emphasis in PET radiopharmaceutical development. In this review, the variety of transporters and their importance for in vivo PET radiotracer development and application are discussed. Transporters have thus joined the other major protein targets such as G-protein coupled receptors, ligand-gated ion channels, enzymes, and aggregated proteins as of high interest for understanding human health and disease. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Determination of stream reaeration coefficients by use of tracers

    Science.gov (United States)

    Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.

    1989-01-01

    Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed whereby a radioactive tracer gas was injected into a stream-the principle being that the tracer gas would be desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. This manual describes the slug-injection and constant-rate-injection methods of measuring gas-tracer desorption. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, on methods of injection, sampling, and analysis, and on techniques for computing desorption and reaeration coefficients.

  17. Fourier analysis of multi-tracer cosmological surveys

    CERN Document Server

    Abramo, L Raul; Loureiro, Arthur

    2015-01-01

    We present optimal quadratic estimators for the Fourier analysis of cosmological surveys that detect several different types of tracers of large-scale structure. Our estimators can be used to simultaneously fit the matter power spectrum and the biases of the tracers - as well as redshift-space distortions (RSDs), non-Gaussianities (NGs), or any other effects that are manifested through differences between the clusterings of distinct species of tracers. Our estimators reduce to the one by Feldman, Kaiser & Peacock (ApJ 1994, FKP) in the case of a survey consisting of a single species of tracer. We show that the multi-tracer estimators are unbiased, and that their covariance is given by the inverse of the multi-tracer Fisher matrix (Abramo, MNRAS 2013; Abramo & Leonard, MNRAS 2013). When the biases, RSDs and NGs are fixed to their fiducial values, and one is only interested in measuring the underlying power spectrum, our estimators are projected into the estimator found by Percival, Verde & Peacock ...

  18. Energy spectra and passive tracer cascades in turbulent flows

    CERN Document Server

    Jolly, Michael

    2016-01-01

    We study the influence of the energy spectrum on the extent of the cascade range of a passive tracer in turbulent flows. The interesting cases are when there are two different spectra over the potential range of the tracer cascade (in 2D when the tracer forcing is in the inverse energy cascade range, and in 3D when the Schmidt number Sc is large). The extent of the tracer cascade range is then limited by the width of the range for the shallower of the two energy spectra. Nevertheless, we show that in dimension $d=2,3$ the tracer cascade range extends (up to a logarithm) to $\\kappa_{d\\text{D}}^{p}$, where $\\kappa_{d\\text{D}}$ is the wavenumber beyond which diffusion should dominate and $p$ is arbitrarily close to 1, provided Sc is larger than a certain power (depending on $p$) of the Grashof number. We also derive estimates which suggest that in 2D, for Sc${}\\sim1$ a wide tracer cascade can coexist with a significant inverse energy cascade at Grashof numbers large enough to produce a turbulent flow.

  19. Dispersion forces in methane

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Coulon, P.; Luyckx, R.

    1977-01-01

    The coefficients of the R-6 and R-7 terms in the series representation of the dispersion interaction between two methane molecules and between methane and helium, neon and argon are calculated by a variation method.

  20. HYDROGEL TRACER BEADS: THE DEVELOPMENT, MODIFICATION, AND TESTING OF AN INNOVATIVE TRACER FOR BETTER UNDERSTANDING LNAPL TRANSPORT IN KARST AQUIFERS

    Energy Technology Data Exchange (ETDEWEB)

    Amanda Laskoskie, Harry M. Edenborn, and Dorothy J. Vesper

    2012-01-01

    The goal of this specific research task is to develop proxy tracers that mimic contaminant movement to better understand and predict contaminant fate and transport in karst aquifers. Hydrogel tracer beads are transported as a separate phase than water and can used as a proxy tracer to mimic the transport of non-aqueous phase liquids (NAPL). They can be constructed with different densities, sizes & chemical attributes. This poster describes the creation and optimization of the beads and the field testing of buoyant beads, including sampling, tracer analysis, and quantitative analysis. The buoyant beads are transported ahead of the dissolved solutes, suggesting that light NAPL (LNAPL) transport in karst may occur faster than predicted from traditional tracing techniques. The hydrogel beads were successful in illustrating this enhanced transport.

  1. On the use of flow-storage repartitions derived from artificial tracer tests for geothermal reservoir characterization in the Malm-Molasse basin: a theoretical study

    Science.gov (United States)

    Dewi, Dina Silvia; Osaigbovo Enomayo, Augustine; Mohsin, Rizwan; Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

    2016-04-01

    Flow-storage repartition (FSR) analysis (Shook 2003) is a versatile tool for characterizing subsurface flow and transport systems. FSR can be derived from measured signals of inter-well tracer tests, if certain requirements are met - basically, the same as required for equivalence between fluid residence time distribution (RTD) and a measured inter-well tracer signal (pre-processed and de-convolved if necessary). Nominally, a FSR is derived from a RTD as a trajectory in normalized {1st, 0th}-order statistical moment space; more intuitively, as a parametric plot of 0th-order against 1st-order statistical moments of RTD truncated at time t, with t as a parameter running from the first tracer input to the latest available tracer sampling; 0th-order moments being normalized by the total tracer recovery, and 1st-order moments by the mean RT. Fracture-dominated systems plot in the upper left (high F , low S) region of FSR diagrams; a homogeneous single-continuum with no dispersion (infinite Peclet number) displays a straight line from {F ,S}={0,0} to {F ,S}={1,1}. This analysis tool appears particularly attractive for characterizing markedly-heterogeneous, porous-fissured-fractured (partly karstified) formations like those targeted by geothermal exploration in the Malm-Molasse basin in Southern Germany, and especially for quantifying flow and transport contributions from contrasting facies types ('reef' versus 'bedded'). However, tracer tests conducted in such systems with inter-well distances of some hundreds of metres (as required by economic considerations on geothermal reservoir sizing) face the problem of very long residence times - and thus the need to deal with incomplete (truncated) signals. For the geothermal well triplet at the Sauerlach site near Munich, tracer peak arrival times exceeding 2 years have been predicted, and signal tails decreasing by less than 50% over >10 years, which puts great uncertainty on the (extrapolation-based) normalizing factors

  2. Fickian dispersion is anomalous

    Science.gov (United States)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  3. Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams.

    Science.gov (United States)

    Knapp, Julia L A; Osenbrück, Karsten; Cirpka, Olaf A

    2015-10-15

    Estimating respiration and photosynthesis rates in streams usually requires good knowledge of reaeration at the given locations. For this purpose, gas-tracer tests can be conducted, and reaeration rate coefficients are determined from the decrease in gas concentration along the river stretch. The typical procedure for analysis of such tests is based on simplifying assumptions, as it neglects dispersion altogether and does not consider possible fluctuations and trends in the input signal. We mathematically derive the influence of these non-idealities on estimated reaeration rates and how they are propagated onto the evaluation of aerobic respiration and photosynthesis rates from oxygen monitoring. We apply the approach to field data obtained from a gas-tracer test using propane in a second-order stream in Southwest Germany. We calculate the reaeration rate coefficients accounting for dispersion as well as trends and uncertainty in the input signals and compare them to the standard approach. We show that neglecting dispersion significantly underestimates reaeration, and results between sections cannot be compared if trends in the input signal of the gas tracer are disregarded. Using time series of dissolved oxygen and the various estimates of reaeration, we infer respiration and photosynthesis rates for the same stream section, demonstrating that the bias and uncertainty of reaeration using the different approaches significantly affects the calculation of metabolic rates.

  4. Gyrotactic swimmer dispersion in pipe flow: experimental challenge of competing models

    CERN Document Server

    Croze, O A; Bees, M A

    2016-01-01

    Suspensions of microswimmers are a rich source of fascinating new fluid mechanics. Recently we predicted the nonclassical pipe flow dispersion of gyrotactic microalgae, whose orientation is biased by gravity and flow shear. Analytical theory predicts that these active swimmers disperse in a markedly distinct manner from passive tracers (Taylor dispersion). Dispersing swimmers display nonzero drift and effective diffusivity that is non-monotonic with Peclet number. Such predictions agree with numerical simulations, but hitherto have not been tested experimentally. Here, we extend the theory to realistically describe suspensions of negatively buoyant bi-flagellate algae and obtain new predictions for the model species Dunaliella salina, parametrised using tracking video microscopy. We then present a new experimental method to measure gyrotactic dispersion using fluorescently stained D. salina and provide a preliminary comparison with predictions of a nonzero drift above the mean flow. Finally, we propose furthe...

  5. Atmospheric dispersion of argon-41 from anuclear research reactor: measurement and modeling of plume geometry and gamma radiation field

    DEFF Research Database (Denmark)

    Lauritzen, Bent; Astrup, Poul; Drews, Martin

    2003-01-01

    An atmospheric dispersion experiment was conducted using a visible tracer along with the routine release of argon-41 from the BR1 research reactor in Mol, Belgium. Simultaneous measurements of plume geometry and radiation fields for argon-41 decay were performed as well as measurements of the argon...

  6. Atmospheric dispersion of argon-41 from anuclear research reactor: measurement and modeling of plume geometry and gamma radiation field

    DEFF Research Database (Denmark)

    Lauritzen, Bent; Astrup, Poul; Drews, Martin

    2003-01-01

    An atmospheric dispersion experiment was conducted using a visible tracer along with the routine release of argon-41 from the BR1 research reactor in Mol, Belgium. Simultaneous measurements of plume geometry and radiation fields for argon-41 decay were performed as well as measurements of the argon...

  7. Sistem Pre Kompilasi Data Tracer Studi Online Ditjen Belmawa Ristekdikti (Studi Kasus: Politeknik Harapan Bersama

    Directory of Open Access Journals (Sweden)

    Very Kurnia Bakti

    2017-01-01

    Full Text Available Tracer studi merupakan salah satu upaya yang diharapkan dapat menyediakan informasi untuk mengevaluasi hasil pendidikan di Politeknik Harapan Bersama dari kuisioner yang diberikan kepada alumni. Kegiatan tracer studi ini sudah dilaksanakan secara online, namun masih terdapat kendala pada bagian sistem yang digunakan saat ini, hal tersebut menyebabkan Politeknik Harapan Bersama tidak dapat melaporkan / mengunggah hasil tracer studi kepada Ditjen Belmawa Ristekdikti, dimana form kuisioner dan data export tracer studi yang dihasilkan berbeda dengan kebutuhan seperti yang tercantum pada surat edaran No. 313/B/SE/2016 tentang pelaksanaan tracer studi di tingkat perguruan tinggi. Mengingat pentingnya tracer studi sebagai umpan balik bagi Politeknik Harapan Bersama, maka perlu solusi untuk mengatasi kekurangan sistem ini. Dengan merubah sistem yang ada dengan sistem tracer studi yang baru merupakan solusi yang tepat dalam permasalahan ini. Sistem tracer studi yang baru mampu menghasilkan data tracer studi alumni dan pengisian form kuisioner sesuai dengan standar Ditjen Belmawa Ristekdikti yang dapat diunggah sistem tracer studi ristekdikti.

  8. PERFLUOROCARBON GAS TRACER STUDIES TO SUPPORT RISK ASSESSMENT MODELING OF CRITICAL INFRASTRUCTURE SUBJECTED TO TERRORIST ATTACKS.

    Energy Technology Data Exchange (ETDEWEB)

    SULLIVAN, T.M.; HEISER, J.; WATSON, T.; ALLWINE, K.J.; FLAHERTY, J.E.

    2006-05-06

    Development of real-time predictive modeling to identify the dispersion and/or source(s) of airborne weapons of mass destruction including chemical, biological, radiological, and nuclear material in urban environments is needed to improve response to potential releases of these materials via either terrorist or accidental means. These models will also prove useful in defining airborne pollution dispersion in urban environments for pollution management/abatement programs. Predicting gas flow in an urban setting on a scale of less than a few kilometers is a complicated and challenging task due to the irregular flow paths that occur along streets and alleys and around buildings of different sizes and shapes, i.e., ''urban canyons''. In addition, air exchange between the outside and buildings and subway areas further complicate the situation. Transport models that are used to predict dispersion of WMD/CBRN materials or to back track the source of the release require high-density data and need defensible parameterizations of urban processes. Errors in the data or any of the parameter inputs or assumptions will lead to misidentification of the airborne spread or source release location(s). The need for these models to provide output in a real-time fashion if they are to be useful for emergency response provides another challenge. To improve the ability of New York City's (NYC's) emergency management teams and first response personnel to protect the public during releases of hazardous materials, the New York City Urban Dispersion Program (UDP) has been initiated. This is a four year research program being conducted from 2004 through 2007. This paper will discuss ground level and subway Perfluorocarbon tracer (PFT) release studies conducted in New York City. The studies released multiple tracers to study ground level and vertical transport of contaminants. This paper will discuss the results from these tests and how these results can be used

  9. Study on Radioecology and Tracer of Iodine-129

    Energy Technology Data Exchange (ETDEWEB)

    Xiaolin, Hou [Riso National Laboratory, NUK, DK, Roskilde (Denmark)

    2004-07-01

    Iodine-129 (15.7 Ma) is a naturally occurring radioisotope of iodine. The ratio of {sup 129}I/{sup 127}I was estimated to be {approx} 10{sup -12} in the ocean and 10{sup -11} in the territorial environment in pre-nuclear era, releases from nuclear weapon tests have increased this ratio to {approx} 10{sup -10}. However, a large amount of iodine-129 was released from various nuclear facilities, and the greatest releases of {sup 129}I are from two European reprocessing plants, especially in recent years. By 1998, 2600 Kg and 220 Kg {sup 129}I have been discharged to the marine environment and atmosphere from La Hague (France) and Sellafield reprocessing plants, respectively. This amount is tens times larger than the total {sup 129}I inventory in the pre-nuclear ocean and weapon test releases. Although there is no significant radiation risk for the human health at present level of {sup 129}I, the continuously increasing production and release of {sup 129}I make the accumulation of {sup 129}I in the environment, immigration, cycle and long term radioecological risk should be give more attention due to its long half-life, high accumulation in human thyroid and high mobility. Iodine is a conservative element in the ocean, the large amount of iodine-129 discharged to the marine system can therefore be used as a oceanographic tracer to study the physical dispersion, mixing and circulative processes of water mass in the ocean. In Riso national laboratory, a radiochemical neutron activation analysis method was developed, using this method the radioecology and tracer of iodine-129 was studied. Some representative works are presented below. (1) Evaluation of radiation exposure of humans to iodine-129. The human and animal thyroids collected from different places, such as Tianjin in China, Gemol in Belarus, Ribe in Denmark, human urine in Denmark, seafood in China were analysed for iodine-129 concentration and {sup 129}I/{sup 127}I ratio, the exposure level were compared with

  10. Copper Ion as a New Leakage Tracer

    Directory of Open Access Journals (Sweden)

    Modaresi J.

    2013-12-01

    Full Text Available Statement of Problem: Most failures of root canal treatments are caused by bacteria. Studies showed that the most common cause of endodontic failures were the incomplete obturation of the root canal and the lack of adequate apical seal. Some in-vitro methods are used to estimate sealing quality, generally by measuring microleakage that allows the tracer agent to penetrate the filled canal.Purpose: Conventional methods of evaluating the seal of endodontically treated teeth are complicated and have some drawbacks. We used copper ion diffusion method to assess the leakage and the results were compared to dye penetration method.Materials and Method: The crowns of 21 extracted teeth were cut off at the CEJ level. After preparing the canals, the teeth were placed in tubes containing saline. They were divided randomly into 15 experimental cases; 3 positive and 3 negative controls. Positive controls were filled by single cone without sealer while the experimental and the negative control groups were filled by lateral technique. The coronal portion of gutta was removed and 9mm was left. The external surface of each tooth was coated with nail polish. Two millimeters of apical portion was immersed into 9ml of distilled water and 0.3ml of CuSO4 solution was injected into the coronal portion. After 2 days, copper sulfate was measured by an atomic absorption spectrophotometer. The teeth were then immersed in 2% methylene blue for 24 hours, sectioned and the extent of dye penetration was measured by a stereomicroscope.Results: The maximum and minimum recorded copper ion concentrations for the experimental group were 18.37 and 2.87ppm respectively. The maximum and minimum recorded dye penetrations for the experimental group were 8.5 and 3.5mm respectively. The statistical analysis, adopting paired samples test, showed poor correlation between average recorded results of two methods.Conclusion: Based on our results, there was no significant correlation between

  11. Quantifying signal dispersion in a hybrid ice core melting system.

    Science.gov (United States)

    Breton, Daniel J; Koffman, Bess G; Kurbatov, Andrei V; Kreutz, Karl J; Hamilton, Gordon S

    2012-11-06

    We describe a microcontroller-based ice core melting and data logging system allowing simultaneous depth coregistration of a continuous flow analysis (CFA) system (for microparticle and conductivity measurement) and a discrete sample analysis system (for geochemistry and microparticles), both supplied from the same melted ice core section. This hybrid melting system employs an ice parcel tracking algorithm which calculates real-time sample transport through all portions of the meltwater handling system, enabling accurate (1 mm) depth coregistration of all measurements. Signal dispersion is analyzed using residence time theory, experimental results of tracer injection tests and antiparallel melting of replicate cores to rigorously quantify the signal dispersion in our system. Our dispersion-limited resolution is 1.0 cm in ice and ~2 cm in firn. We experimentally observe the peak lead phenomenon, where signal dispersion causes the measured CFA peak associated with a given event to be depth assigned ~1 cm shallower than the true event depth. Dispersion effects on resolution and signal depth assignment are discussed in detail. Our results have implications for comparisons of chemistry and physical properties data recorded using multiple instruments and for deconvolution methods of enhancing CFA depth resolution.

  12. Laboratory investigation of longitudinal dispersion in anisotropic porous media

    Science.gov (United States)

    Silliman, S.E.; Konikow, L.F.; Voss, C.I.

    1987-01-01

    In this study, laboratory experiments were used to investigate mechanisms that may cause anisotropy in the dispersion coefficient and to investigate the relation between anisotropy in hydraulic conductivity and anisotropy in longitudinal dispersion. Measurements of sodium chloride concentration (used as a tracer) were made at 105 in situ sampling locations in a new type of sand box designed to allow flow in either of two perpendicular directions. Two types of hydraulic anisotropy were examined. The first consisted of structured zones of increased hydraulic conductivity within a lower-conductivity medium. The second type involved low-conductivity platelike inclusions within a homogeneous, isotropic medium. The plates were aligned such that the tortuosity was increased only in one principal direction of permeability. Results using two examples of the first type of media showed that the apparent longitudinal dispersivities for flow parallel to the high-conductivity direction were greater than those perpendicular to this direction. Two examples of the second type of media produced smaller apparent longitudinal dispersivities for flow parallel to the high-conductivity direction. The results suggest that the mechanisms causing dispersive anisotropy can be related, conceptually, to the factors causing hydraulic anisotropy.

  13. Testing fundamentals: The chemical state of geochemical tracers in biominerals.

    Science.gov (United States)

    Branson, O.; Redfern, S. A. T.; Read, E.; Elderfield, H.

    2015-12-01

    The use of many carbonate-derived geochemical proxies is underpinned by the assumption that tracer elements are incorporated 'ideally' as impurities the mineral lattice, following relatively straightforward kinetic and thermodynamic drives. This allows comparison to inorganic precipitation experiments, and provides a systematic starting point from which to translate geochemical tracers to environmental records. Biomineral carbonates are a prominent source of geochemical proxy material, and are far from an ideal inorganic system. They are structurally and compositionally heterogeneous mineral-organic composites, produced in tightly controlled biological environments, possibly via non-classical crystal growth mechanisms. Biominerals offer numerous opportunities for tracers to be incorporated in a 'non-ideal' state. For instance, tracers could be hosted within the organic component of the structure, in interstitial micro-domains of a separate mineral phase, or in localized high-impurity clusters. If a proxy element is hosted in a non-ideal state, our understanding of its incorporation and preservation is flawed, and the theoretical basis behind the proxies derived from it must be reevaluated. Thus far, the assumption of ideal tracer incorporation has remained largely untested, owing to the spatial resolution and sensitivity limits of available techniques. Developments in high-resolution, high-sensitivity X-ray spectroscopy at Scanning Transmission X-Ray Microscopes (STXMs) have allowed us to measure trace element coordination in foraminiferal calcite, at length-scales relevant to biomineralisation processes and tracer incorporation. This instrument has allowed us to test the fundamental assumptions behind several geochemical proxy elements. We present a summary of four STXM studies, assessing the chemical state and distribution of Mg (Branson et al, 2014), B (Branson et al, 2015), S and Na (unpub.), and highlight the implications of these data for the use of these

  14. Multiple Tracer Tests in Porous Media During Clogging

    Science.gov (United States)

    Englert, A.; Banning, A.; Siegmund, J.; Freye, S.; Goekpinar, T.

    2015-12-01

    Transport processes are known to be governed by the physical and chemical heterogeneity of the subsurface. Clogging processes can alter this heterogeneity as function of time and thus can modify transport. To understand transport under clogging conditions and to unravel the potential of multiple tracer tests to characterize such transport process we perform column and sandbox experiments. Our recently developed column and sandbox experiments are used to perform multiple tracer tests during clogging. In a first set of experiments, a cubic cell of 0.1 m x 0.1 m x 0.1 m is used to experimentally estimate flow and transport characteristics of an unconsolidated sediment through Darcy and tracer experiments. The water streaming through the experiment is amended with ammonium sulfate permanently. Salt tracers are added to the streaming water repeatedly, to be detected at micro electrodes at the inflow and the outflow of the cubic cell. Through repeated syringe injections of a barium chloride solution into the center of the cubic cell clogging processes are forced to occur around the mixing zone of the injected and streaming water by precipitation of barium sulfate. In a second set of experiments, a sandbox model including a sediment body of 0.3 m x 0.3 m x 0.1 m is used. Tracer, streaming, and injection water chemistry is kept similar to the cubic cell experiments. However, tracer breakthrough is now detected at nine positions within the experiment and at the inflow and the outflow of the sandbox model. Injection of barium chloride solution is now at two locations around the center of the sandbox model. Flow and transport characteristics of the sediment body are estimated based on Darcy and tracer experiments, which are performed repeatedly. Combined analysis of local and ensemble breakthrough curves and integrated numerical modeling will be used to understand effective and local flow and transport in a in a porous medium during clogging.

  15. A thalium-doped sodium iodide well counter for radioactive tracer applications with naturally-abundant 40K

    Science.gov (United States)

    Parker, Andrew J.; Boxall, Colin; Joyce, Malcolm J.; Schotanus, Paul

    2013-09-01

    The use of a thallium-doped sodium-iodide well-type scintillation detector for the assay of the low-activity radioisotope 40K, in open-source potassium chloride aqueous solutions, is described. The hazards, safety concerns and radiowaste generation associated with using open-source radioactive isotopes can present significant difficulties, the use of hot cells and escalated costs in radioanalytical laboratory research. A solution to this is the use of low-hazard alternatives that mimic the migration and dispersion characteristics of notable fission products (in this case 137Cs). The use of NaI(Tl) as a detection medium for naturally-abundant levels of 40K in a range of media is widespread, but the use of 40K as a radioactive tracer has not been reported. The use of such low-activity sources is often complicated by the ability to detect them efficiently. In this paper a scintillator detector designed to detect the naturally-abundant 40K present in potassium chloride in tracer applications is described. Examples of the use of potassium chloride as a tracer are given in the context of ion exchange and electrochemical migration studies, and comparisons in performance are drawn from literature with hyper pure germanium semiconductor detectors, which are more commonly utilised detectors in high-resolution counting applications.

  16. Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors.

    Science.gov (United States)

    Croze, Ottavio A; Sardina, Gaetano; Ahmed, Mansoor; Bees, Martin A; Brandt, Luca

    2013-04-06

    Shear flow significantly affects the transport of swimming algae in suspension. For example, viscous and gravitational torques bias bottom-heavy cells to swim towards regions of downwelling fluid (gyrotaxis). It is necessary to understand how such biases affect algal dispersion in natural and industrial flows, especially in view of growing interest in algal photobioreactors. Motivated by this, we here study the dispersion of gyrotactic algae in laminar and turbulent channel flows using direct numerical simulation (DNS) and a previously published analytical swimming dispersion theory. Time-resolved dispersion measures are evaluated as functions of the Péclet and Reynolds numbers in upwelling and downwelling flows. For laminar flows, DNS results are compared with theory using competing descriptions of biased swimming cells in shear flow. Excellent agreement is found for predictions that employ generalized Taylor dispersion. The results highlight peculiarities of gyrotactic swimmer dispersion relative to passive tracers. In laminar downwelling flow the cell distribution drifts in excess of the mean flow, increasing in magnitude with Péclet number. The cell effective axial diffusivity increases and decreases with Péclet number (for tracers it merely increases). In turbulent flows, gyrotactic effects are weaker, but discernable and manifested as non-zero drift. These results should have a significant impact on photobioreactor design.

  17. Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors

    Science.gov (United States)

    Croze, Ottavio A.; Sardina, Gaetano; Ahmed, Mansoor; Bees, Martin A.; Brandt, Luca

    2013-01-01

    Shear flow significantly affects the transport of swimming algae in suspension. For example, viscous and gravitational torques bias bottom-heavy cells to swim towards regions of downwelling fluid (gyrotaxis). It is necessary to understand how such biases affect algal dispersion in natural and industrial flows, especially in view of growing interest in algal photobioreactors. Motivated by this, we here study the dispersion of gyrotactic algae in laminar and turbulent channel flows using direct numerical simulation (DNS) and a previously published analytical swimming dispersion theory. Time-resolved dispersion measures are evaluated as functions of the Péclet and Reynolds numbers in upwelling and downwelling flows. For laminar flows, DNS results are compared with theory using competing descriptions of biased swimming cells in shear flow. Excellent agreement is found for predictions that employ generalized Taylor dispersion. The results highlight peculiarities of gyrotactic swimmer dispersion relative to passive tracers. In laminar downwelling flow the cell distribution drifts in excess of the mean flow, increasing in magnitude with Péclet number. The cell effective axial diffusivity increases and decreases with Péclet number (for tracers it merely increases). In turbulent flows, gyrotactic effects are weaker, but discernable and manifested as non-zero drift. These results should have a significant impact on photobioreactor design. PMID:23407572

  18. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    KAUST Repository

    Li, Yan Vivian

    2016-03-02

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl2, and MgCl2) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl2 and MgCl2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl2 and MgCl2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.

  19. Influence of lithology on tracer movement in the vadose zone of the Calcaire de Beauce aquifer (France).

    Science.gov (United States)

    Viel, Emélie; Coquet, Yves; Dedewanou, Myriam; Binet, Stéphane

    2016-04-01

    The "Calcaire de Beauce" aquifer is contaminated by nitrate and pesticides mostly coming from agricultural activities. In this region the saturated part of the aquifer is relatively well known compared to the unsaturated (vadose) zone. This unsaturated zone can extend to more than 20 m in depth, and may play a significant role in the retention and/or release of pollutants or in the rate of nitrate transfer to wells. In order to improve knowledge on the dispersion of contaminants in the vadose zone, a tracer experiment took place at the Lycée de la Saussaye near Chartres. A pit, 4 meter in width, 1.60 meter deep and 1 meter large was excavated in a Beauce limestone, giving access to the vadose zone. The surface organic soil layer (40 cm) was excavated. Thirty Liters of brilliant blue (FCF) at a concentration of 6 g/L have been applied to the surface at a rate of 0.14 L/h/m² with automatic sprinklers during 66 h. The pit has then cut successively in four vertical profiles at 0, 33, 66, 100 cm from the edge. A RGB-photo and a lithological description was taken for each vertical profile. Image processing (ratio red canal /green canal) was applied to picture the plume of brilliant blue (BB). Areas filled with BB were converted into polygons using ArcGIS and compared with the lithological description. The proportion of tracer filled area at a given depth was used to evaluate the dispersion of the tracer with depth. The lithology present within the 4 profiles was very heterogeneous from fine ocher limestone to clay. Some profils are structured with tilt around 120° to the right in the (x,z) plane. Dye maps showed irregular plume dispersion with fast flows. A "fingered" front of BB was observed and was oriented according a tilt of 110-120° in the (x,z) plane. This distribution appears to be controlled by the lithology, with tracer moving around the low permeable lithologies. Fast flow distribution and lithological observation showed the same tilt, indicating a link

  20. Tracer-based quantification of individual frac discharge in single-well multiple-frac backflow: sensitivity study

    Science.gov (United States)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2014-05-01

    a simplified flow and tracer transport model (using FEOW and assuming Darcian flow within the matrix, Hagen-Poiseuille flow within the waterfrac, and either D or H-P flow within the gel-proppant fracs), whose main findings are: (1) late tracer signals are almost independent on matrix porosity, permeability distribution, frac area (length), thickness and effective aperture, while being highly sensitive to local discharge values; 'late' means a backflow or production volume at least fivefold the injected chaser volume; (2a) early tracer signals (concentration 'peak' intervals) may exhibit slight 'acceleration' and 'damping' with increasing matrix porosity or increasing frac aperture (a 'paradoxical' behaviour which is not really surprising for single-well 'push-then-backflow' tests, actually owing to flow-field dispersion[4]), and (2b) a non-monotonous response to varying frac area, being almost insensitive to frac area as long as the linear-flow regime prevails against the radial-flow regime (effects of the latter only becoming visible at very low frac areas); (2c) the effects of these various factors on early-time tracer signals are not unambiguously discernible from each other, and this ambiguity would persist even if frac-resolved (in-situ) discharge metering were feasible. For each of the three fracs (k=1,2,3), a 'type-curve' set Ck(Q,t) (parametrized by discharge values Q) can be generated. Since every frac received a different tracer, tracer signals measured within the overall backflow will differ from individual-frac type-curves by mere dilution (no 'superposition'). Type-curve dilution by factor Qk/Qtotal can be compared to measured tracer concentrations in the total discharge, ck(ti), (i = 1, ..., no. of tracer samplings). From a formal point of view, the unknown discharge values Qk can be determined as the solution of a linear optimization task subject to the constraint Q1 + Q2 + Q3 = Qtotal (the latter being a measured value). It is recommendable to

  1. Development of radioisotope tracer technology and nucleonic control system

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Joon Ha; Lee, Myun Joo; Jung, Sung Hee and others

    1999-04-01

    The purpose of this study is to develop the radioisotope tracer technology, which can be used in solving industrial and environmental problems and basic technology of nuclear control systems that are widely used for automation of industrial plants, and to build a strong tracer group to support the local industries. In relation to the tracer technology, the data acquisition system, the column scanning equipment and the detection pig for a leakage test have been developed. In order to use in analyzing data of tracer experiments, a computer program for the analysis of residence time distribution has been created as well. These results were utilized in developing the tracer technologies, such as the column scanning, the flow measurement using the dilution method, the simultaneous monitoring rotational movement of piston rings and the optimization of a waste water treatment facility, and the technologies were successfully demonstrated in the local industrial. The stripper of RFCC reactor has been examined to find an unwanted structure in it by imminent request from the industry. Related to the development of nucleonic control system, the state of art report on the technology has been written and an equipment for the analysis of asphalt content has been developed. (author)

  2. Passive Tracer Dynamics in 4 Point-Vortex Flow

    CERN Document Server

    Laforgia, A; Kuznetsov, L V; Zaslavsky, G M

    2000-01-01

    The advection of passive tracers in a system of 4 identical point vortices is studied when the motion of the vortices is chaotic. The phenomenon of vortex-pairing has been observed and statistics of the pairing time is computed. The distribution exhibits a power-law tail with exponent (\\sim 3.6), implying finite average pairing time. Tracer motion is studied for a chosen initial condition of the vortex system. Accessible phase space is investigated. The size of the cores around the vortices is well approximated by the minimum inter-vortex distance and stickiness to these cores is observed. We investigate the origin of stickiness which we link to the phenomenon of vortex pairing and jumps of tracers between cores. Motion within the core is considered and fluctuations are shown to scale with tracer-vortex distance (r) as (r^{6}). No outward or inward diffusion of tracers are observed. This investigation allows the separation of the accessible phase space in four distinct regions, each with its own specific prop...

  3. Coping with power dispersion?

    DEFF Research Database (Denmark)

    2014-01-01

    The last decades have witnessed a significant shift in policy competences away from central governments in Europe. The reallocation of competences spans over three dimensions: upwards; sideways; and downwards. This collection takes the dispersion of powers as a starting point and seeks to assess...... how the actors involved cope with the new configurations. In this introduction, we discuss the conceptualization of power dispersion and highlight the ways in which the contributions add to this research agenda. We then outline some general conclusions and end by indicating future avenues of research...

  4. Theoretical model of intravascular paramagnetic tracers effect on tissue relaxation

    DEFF Research Database (Denmark)

    Kjølby, Birgitte Fuglsang; Østergaard, Leif; Kiselev, Valerij G

    2006-01-01

    that the relaxivity of intravascular contrast agents depends significantly on the host tissue. This agrees with experimental data by Johnson et al. (Magn Reson Med 2000;44:909). In particular, the present results suggest a several-fold increase in the relaxivity of Gd-based contrast agents in brain tissue compared...... with bulk blood. The enhancement of relaxation in tissue is due to the contrast in magnetic susceptibility between blood vessels and parenchyma induced by the presence of paramagnetic tracer. Beyond the perfusion measurements, the results can be applied to quantitation of functional MRI and to vessel size......The concentration of MRI tracers cannot be measured directly by MRI and is commonly evaluated indirectly using their relaxation effect. This study develops a comprehensive theoretical model to describe the transverse relaxation in perfused tissue caused by intravascular tracers. The model takes...

  5. Preparation of intravenous cholesterol tracer using current good manufacturing practices.

    Science.gov (United States)

    Lin, Xiaobo; Ma, Lina; Racette, Susan B; Swaney, William P; Ostlund, Richard E

    2015-12-01

    Studies of human reverse cholesterol transport require intravenous infusion of cholesterol tracers. Because insoluble lipids may pose risk and because it is desirable to have consistent doses of defined composition available over many months, we investigated the manufacture of cholesterol tracer under current good manufacturing practice (CGMP) conditions appropriate for phase 1 investigation. Cholesterol tracer was prepared by sterile admixture of unlabeled cholesterol or cholesterol-d7 in ethanol with 20% Intralipid(®). The resulting material was filtered through a 1.2 micron particulate filter, stored at 4°C, and tested at time 0, 1.5, 3, 6, and 9 months for sterility, pyrogenicity, autoxidation, and particle size and aggregation. The limiting factor for stability was a rise in thiobarbituric acid-reacting substances of 9.6-fold over 9 months (P postproduction. CGMP manufacturing methods can be achieved in the academic setting and need to be considered for critical components of future metabolic studies.

  6. Dynamics and mechanics of bed-load tracer particles

    Directory of Open Access Journals (Sweden)

    C. B. Phillips

    2014-12-01

    Full Text Available Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

  7. How well do different tracers constrain the firn diffusivity profile?

    Directory of Open Access Journals (Sweden)

    C. M. Trudinger

    2013-02-01

    Full Text Available Firn air transport models are used to interpret measurements of the composition of air in firn and bubbles trapped in ice in order to reconstruct past atmospheric composition. The diffusivity profile in the firn is usually calibrated by comparing modelled and measured concentrations for tracers with known atmospheric history. However, in most cases this is an under-determined inverse problem, often with multiple solutions giving an adequate fit to the data (this is known as equifinality. Here we describe a method to estimate the firn diffusivity profile that allows multiple solutions to be identified, in order to quantify the uncertainty in diffusivity due to equifinality. We then look at how well different combinations of tracers constrain the firn diffusivity profile. Tracers with rapid atmospheric variations like CH3CCl3, HFCs and 14CO2 are most useful for constraining molecular diffusivity, while &delta:15N2 is useful for constraining parameters related to convective mixing near the surface. When errors in the observations are small and Gaussian, three carefully selected tracers are able to constrain the molecular diffusivity profile well with minimal equifinality. However, with realistic data errors or additional processes to constrain, there is benefit to including as many tracers as possible to reduce the uncertainties. We calculate CO2 age distributions and their spectral widths with uncertainties for five firn sites (NEEM, DE08-2, DSSW20K, South Pole 1995 and South Pole 2001 with quite different characteristics and tracers available for calibration. We recommend moving away from the use of a firn model with one calibrated parameter set to infer atmospheric histories, and instead suggest using multiple parameter sets, preferably with multiple representations of uncertain processes, to assist in quantification of the uncertainties.

  8. How well do different tracers constrain the firn diffusivity profile?

    Directory of Open Access Journals (Sweden)

    C. M. Trudinger

    2012-07-01

    Full Text Available Firn air transport models are used to interpret measurements of the composition of air in firn and bubbles trapped in ice in order to reconstruct past atmospheric composition. The diffusivity profile in the firn is usually calibrated by comparing modelled and measured concentrations for tracers with known atmospheric history. However, in some cases this is an under-determined inverse problem, often with multiple solutions giving an adequate fit to the data (this is known as equifinality. Here we describe a method to estimate the firn diffusivity profile that allows multiple solutions to be identified, in order to quantify the uncertainty in diffusivity due to equifinality. We then look at how well different combinations of tracers constrain the firn diffusivity profile. Tracers with rapid atmospheric variations like CH3CCl3, HFCs and 14CO2 are most useful for constraining molecular diffusivity, while δ15N2 is useful for constraining parameters related to convective mixing near the surface. When errors in the observations are small and Gaussian, three carefully selected tracers are able to constrain the molecular diffusivity profile well with minimal equifinality. However, with realistic data errors or additional processes to constrain, there is benefit to including as many tracers as possible to reduce the uncertainties. We calculate CO2 age distributions and their spectral widths with uncertainties for five firn sites (NEEM, DE08-2, DSSW20K, South Pole 1995 and South Pole 2001 with quite different characteristics and tracers available for calibration. We recommend moving away from the use of a single firn model with one calibrated parameter set to infer atmospheric histories, and instead suggest using multiple parameter sets, preferably with multiple representations of uncertain processes, to allow quantification of the uncertainties.

  9. Gas phase dispersion in compost as a function of different water contents and air flow rates

    Science.gov (United States)

    Sharma, Prabhakar; Poulsen, Tjalfe G.

    2009-07-01

    Gas phase dispersion in a natural porous medium (yard waste compost) was investigated as a function of gas flow velocity and compost volumetric water content using oxygen and nitrogen as tracer gases. The compost was chosen because it has a very wide water content range and because it represents a wide range of porous media, including soils and biofilter media. Column breakthrough curves for oxygen and nitrogen were measured at relatively low pore gas velocities, corresponding to those observed in for instance soil vapor extraction systems or biofilters for air cleaning at biogas plants or composting facilities. Total gas mechanical dispersion-molecular diffusion coefficients were fitted from the breakthrough curves using a one-dimensional numerical solution to the advection-dispersion equation and used to determine gas dispersivities at different volumetric gas contents. The results showed that gas mechanical dispersion dominated over molecular diffusion with mechanical dispersion for all water contents and pore gas velocities investigated. Importance of mechanical dispersion increased with increasing pore gas velocity and compost water content. The results further showed that gas dispersivity was relatively constant at high values of compost gas-filled porosity but increased with decreasing gas-filled porosity at lower values of gas-filled porosity. Results finally showed that measurement uncertainty in gas dispersivity is generally highest at low values of pore gas velocity.

  10. Performance of a dispersion model to estimate methane loss from cattle in pens.

    Science.gov (United States)

    McGinn, S M; Beauchemin, K A; Flesch, T K; Coates, T

    2009-01-01

    Accurate measurements of enteric methane (CH(4)) emissions from cattle (Bos taurus) are necessary to improve emission coefficients used in national emissions inventories, and to evaluate mitigation strategies. Our study was conducted to evaluate a novel approach that allowed near continuous CH(4) measurement from beef cattle confined in pens. The backward Lagrangian Stochastic (bLS) dispersion technique was used in conjunction with global position system (GPS) information from individual animals, to evaluate CH(4) emissions from pens of cattle. The dispersion technique was compared to estimates of CH(4) production using the SF(6) tracer technique. Sixty growing beef cattle were fed a diet containing 60% barley silage (dry matter basis) supplemented with either barley (Hordeum vulgare L.) grain or corn (Zea mays L.) distillers dried grains. The results show that daily CH(4) emissions were about 7% lower for the dispersion technique than for the tracer technique (185 vs. 199 g CH(4) animal(-1) d(-1)). The precision of the dispersion technique, relative to the SF(6) tracer technique, expressed by the Pearson coefficient was 0.76; the relative accuracy given by the concordance coefficient was 0.69. The bLS dispersion technique was able to detect differences (P emissions ranging from 161 to 279 g CH(4) animal(-1) d(-1). Configuring the cattle as point sources resulted in more accurate CH(4) emissions than assuming a uniform area release from the pen surface. The results indicate that the bLS dispersion technique using cattle as point sources can be used to accurately measure enteric CH(4) from cattle and to evaluate the impact of dietary mitigation strategies.

  11. Rebuilding sources of linear tracers after atmospheric concentration measurements

    Directory of Open Access Journals (Sweden)

    J.-P. Issartel

    2003-01-01

    Full Text Available The identification of widespread sources of passive tracers out of atmospheric concentration measurements has become an important challenge of modern meteorology. The paper proposes some mathematical tracks to address the reconstruction of the complex space-time geometry of the sources of linear tracers. The methods are based upon the use of retroplumes. The inverse problem is addressed in a deterministic non statistical frame. The information obtained by local measurements is spread by introducing the concept of illumination. The constraint that the source is non negative is also addressed. The experimental source ETEX1 is rebuilt in order to evaluate an impulse response of the algorithms.

  12. Preliminary assessment of halogenated alkanes as vapor-phase tracers

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

    1991-01-01

    New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

  13. Observation of individual tracer atoms in an ultracold dilute gas

    CERN Document Server

    Hohmann, Michael; Lausch, Tobias; Mayer, Daniel; Schmidt, Felix; Lutz, Eric; Widera, Artur

    2016-01-01

    Understanding the motion of a tracer particle in a rarefied gas is of fundamental and practical importance. We report the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the nonequilibrium relaxation of the initial nonthermal state and detect the effect of single collisions which has eluded observation so far. We show that after few collisions, the measured spatial distribution of the light tracer atoms is correctly described by a generalized Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers.

  14. Tracer Cycles and Water Ages in Heterogeneous Catchments and Aquifers

    Science.gov (United States)

    Kirchner, J. W.; Jasechko, S.

    2015-12-01

    Estimates of catchment mean transit times are often based on seasonal cycles of stable isotope tracers in precipitation and streamflow. In many cases these transit time estimates are derived directly from sine-wave fitting to the observed seasonal isotope cycles. Broadly similar results are also obtained from time-domain convolutions or explicit tracer modeling, because here too the dominant tracer signal that these techniques seek to match is the seasonal isotopic cycle. Here I use simple benchmark tests to show that estimates of mean transit times based on seasonal tracer cycles will typically be wrong by several hundred percent, when applied to catchments with realistic degrees of spatial heterogeneity. This aggregation bias arises from the strong nonlinearity in the relationship between tracer cycle amplitude and mean travel time. A similar bias arises in estimates of mean transit times in nonstationary catchments. Since typical real-world catchments are both spatially heterogeneous and nonstationary, this analysis poses a fundamental challenge to tracer-based estimates of mean transit times. I propose an alternative storage metric, the fraction of "young water" in streamflow, defined as the fraction of runoff with transit times of less than roughly 0.2 years. I show that young water fractions are virtually free of aggregation bias; that is, they can be accurately estimated from tracer cycles in highly heterogeneous mixtures of subcatchments with strongly contrasting transit time distributions. They can also be reliably estimated in strongly nonstationary catchments. Young water fractions can be estimated separately for individual flow regimes, allowing direct determination of how shifts in hydraulic regime alter the fraction of water reaching the stream by fast flowpaths. One can also estimate the chemical composition of idealized "young water" and "old water" end-members, using relationships between young water fractions and solute concentrations across

  15. North Atlantic ventilation using chlorofluorocarbons and idealised-tracer simulations

    Directory of Open Access Journals (Sweden)

    Yan-Chun He

    2012-10-01

    Full Text Available The simulated chlorofluorocarbon CFC-11 and 29 geographically defined CFC-11 tracers, as well as 29 geographically defined idealised tracers, are used to quantify the regional contribution to the ventilation of the North Atlantic Ocean in a global version of the Miami Isopycnal Coordinate Ocean Model (MICOM driven by the daily NCEP/NCAR forcing. Age tracers attached to 29 idealised tracers are also used to estimate the timescales for the water masses’ transports. Our results show that the simulated overturning circulation matches the available observed data for both intensity and variability, and the simulated distribution of CFC-11 concentration in the subtropical North Atlantic Ocean is in good agreement with the observations, particularly above 800 m in depth. We found that the sandwich-like distribution of CFC-11 concentration in the subtropical North Atlantic in both the observations and simulations is mainly caused by subduction from the western and eastern subpolar North Atlantic, but the contribution of the former (56.0% is almost four times larger than that of the latter (15.7%. We demonstrated that the ocean dynamics, instead of the source function, determine the annual and inter-annual variability in both dynamically active tracer (such as water temperature and salinity and passive tracer (such as CFC-11 and idealised tracer concentrations in the deep North Atlantic. The ‘apparent age’ distribution shows that the surface water in the western subpolar North Atlantic takes about 12 yr to reach the Nordic Seas and takes 20 yr from the Nordic Seas to the subtropical deep North Atlantic. The transit-time derived by ‘optimum time lag’ approach shows a 9.3–13.6 yr lag for the signals propagating from the western subpolar North Atlantic to the subtropical North Atlantic, which is generally consistent with that of about 10 yr derived from the ‘apparent age’. The study suggests that geographically defined tracers can be used as

  16. Gas-solute dispersivity ratio in granular porous media as related to particle size distribution and particle shape

    DEFF Research Database (Denmark)

    Pugliese, Lorenzo; Poulsen, Tjalfe; Straface, Salvatore

    2013-01-01

    data. This paper evaluates the possibility for estimating solute dispersion based on gas dispersion measurements. Breakthrough measurements were carried out at different fluid velocities (covering the same range in Reynolds number), using O2 and NaCl as gas and solute tracers, respectively. Three...... different, granular porous materials were used: (1) crushed granite (very angular particles), (2) gravel (particles of intermediate roundness) and (3) Leca® (almost spherical particles). For each material, 21 different particle size fractions were used. Gas and solute dispersion coefficients were determined...

  17. Experiments to Evaluate and Implement Passive Tracer Gas Methods to Measure Ventilation Rates in Homes

    Energy Technology Data Exchange (ETDEWEB)

    Lunden, Melissa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Faulkner, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Heredia, Elizabeth [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Cohn, Sebastian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Dickerhoff, Darryl [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Noris, Federico [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Logue, Jennifer [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Hotchi, Toshifumi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Singer, Brett [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sherman, Max H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-10-01

    This report documents experiments performed in three homes to assess the methodology used to determine air exchange rates using passive tracer techniques. The experiments used four different tracer gases emitted simultaneously but implemented with different spatial coverage in the home. Two different tracer gas sampling methods were used. The results characterize the factors of the execution and analysis of the passive tracer technique that affect the uncertainty in the calculated air exchange rates. These factors include uncertainties in tracer gas emission rates, differences in measured concentrations for different tracer gases, temporal and spatial variability of the concentrations, the comparison between different gas sampling methods, and the effect of different ventilation conditions.

  18. Axial dispersion in segmented gas-liquid flow: Effects of alternating channel curvature

    Science.gov (United States)

    Muradoglu, Metin

    2010-12-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows are studied computationally in a two-dimensional setting using a finite-volume/front-tracking method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion. The lubricating thin liquid layer that persists on the wall of a straight channel is periodically broken in the serpentine channel leading to enhanced axial dispersion. It is also found that the axial dispersion is always larger in the serpentine channel than that in the straight channel but the effects of channel curvature are more pronounced at high Peclet numbers, i.e., Pe>104. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe→∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  19. Flow and dispersion in anisotropic porous media: a Lattice-Boltzmann study

    CERN Document Server

    Maggiolo, Dario; Guarnieri, Massimo

    2016-01-01

    Given their capability of spreading active chemical species and collecting electricity, porous media made of carbon fibers are extensively used as diffusion layers in energy storage systems, such as redox flow batteries. In spite of this, the dispersion dynamics of species inside porous media is still not well understood and often lends itself to different interpretations. Actually, the microscopic design of efficient porous media which can potentially and effectively improve the performances of flow batteries, is a still open challenge. The present study aims to investigate the effect of fibrous media micro-structure on dispersion, in particular the effect of fiber orientation on drag and dispersion dynamics. Several Lattice-Boltzmann simulations of {flows through} differently-oriented fibrous media coupled with Lagrangian simulations of particle tracers have been performed. Results show that orienting fibers preferentially along the streamwise direction minimizes the drag and maximizes the dispersion, which...

  20. Anomalous dispersion of Lagrangian particles in local regions of turbulent flows revealed by convex hull analysis

    CERN Document Server

    Pratt, J; Mueller, W -C; Chapman, S C; Watkins, N W

    2014-01-01

    Local regions of anomalous particle dispersion, and intermittent events that occur in turbulent flows can greatly influence the global statistical description of the flow. These local behaviors can be identified and analyzed by comparing the growth of neighboring convex hulls of Lagrangian tracer particles. Although in our simulations of homogeneous turbulence the convex hulls generally grow in size, after the Lagrangian particles that define the convex hulls begin to disperse, our analysis reveals short periods when the convex hulls of the Lagrangian particles shrink, evidence that particles are not dispersing simply. Shrinkage can be associated with anisotropic flows, since it occurs most frequently in the presence of a mean magnetic field or thermal convection. We compare dispersion between a wide range of statistically homogeneous and stationary turbulent flows ranging from homogeneous isotropic Navier-Stokes turbulence over different configurations of magnetohydrodynamic turbulence and Boussinesq convect...

  1. PARTRACK - A particle tracking algorithm for transport and dispersion of solutes in a sparsely fractured rock

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Urban [Computer-aided Fluid Engineering AB, Norrkoeping (Sweden)

    2001-04-01

    A particle tracking algorithm, PARTRACK, that simulates transport and dispersion in a sparsely fractured rock is described. The main novel feature of the algorithm is the introduction of multiple particle states. It is demonstrated that the introduction of this feature allows for the simultaneous simulation of Taylor dispersion, sorption and matrix diffusion. A number of test cases are used to verify and demonstrate the features of PARTRACK. It is shown that PARTRACK can simulate the following processes, believed to be important for the problem addressed: the split up of a tracer cloud at a fracture intersection, channeling in a fracture plane, Taylor dispersion and matrix diffusion and sorption. From the results of the test cases, it is concluded that PARTRACK is an adequate framework for simulation of transport and dispersion of a solute in a sparsely fractured rock.

  2. The effect of unresolved binaries on globular cluster proper-motion dispersion profiles

    CERN Document Server

    Bianchini, P; van de Ven, G; Schinnerer, E; Bellini, A; van der Marel, R P; Watkins, L L; Anderson, J

    2016-01-01

    High-precision kinematic studies of globular clusters require an accurate knowledge of all possible sources of contamination. Amongst other sources, binary stars can introduce systematic biases in the kinematics. Using a set of Monte Carlo cluster simulations with different concentrations and binary fractions, we investigate the effect of unresolved binaries on proper-motion dispersion profiles, treating the simulations like HST proper-motion samples. Since globular clusters evolve towards a state of partial energy equipartition, more massive stars lose energy and decrease their velocity dispersion. As a consequence, on average, binaries have a lower velocity dispersion, since they are more massive kinematic tracers. We show that, in the case of clusters with high binary fraction (initial binary fraction of 50%) and high concentration (i.e., closer to energy equipartition), unresolved binaries introduce a color-dependent bias in the velocity dispersion of main-sequence stars of the order of 0.1-0.3 km s$^{-1}...

  3. Dispersion of Particles on Fluid-Liquid Interfaces

    Science.gov (United States)

    Dalal, B.; Gurupatham, S.; Hossain, M.; Fischer, I.; Singh, P.; Joseph, D.

    2011-11-01

    This talk is concerned with the dispersion of particles on the fluid-liquid interface. In our previous studies we have shown that when small particles, e.g., flour, pollen, etc., come in contact with an air-liquid interface, they disperse in a manner that appears explosive. This is due to the fact that the capillary force pulls particles into the interface causing them to accelerate to a relatively-large velocity. The motion of particles in the direction normal to the interface is inertia dominated, and so they oscillate vertically about the equilibrium position before coming to a stop under viscous drag. This causes a radially-outward lateral flow on the interface that causes nearby particles to move away. In experiments the strength of the lateral flow was measured using tracer particles that were placed on the interface for this purpose. The dispersion on a liquid-liquid interface was relatively weaker than on an air-liquid interface, and occurred over a longer period of time. This partly was a consequence of the fact that particles became separated while sedimenting through the upper liquid and reached the interface over a time interval that lasted for several seconds. The rate of dispersion depended on the size of particles, the particle and liquids densities, the viscosities of the liquids involved, and the contact angle.

  4. TRAC, a collaborative computer tool for tracer-test interpretation

    Science.gov (United States)

    Gutierrez, A.; Klinka, T.; Thiéry, D.; Buscarlet, E.; Binet, S.; Jozja, N.; Défarge, C.; Leclerc, B.; Fécamp, C.; Ahumada, Y.; Elsass, J.

    2013-05-01

    Artificial tracer tests are widely used by consulting engineers for demonstrating water circulation, proving the existence of leakage, or estimating groundwater velocity. However, the interpretation of such tests is often very basic, with the result that decision makers and professionals commonly face unreliable results through hasty and empirical interpretation. There is thus an increasing need for a reliable interpretation tool, compatible with the latest operating systems and available in several languages. BRGM, the French Geological Survey, has developed a project together with hydrogeologists from various other organizations to build software assembling several analytical solutions in order to comply with various field contexts. This computer program, called TRAC, is very light and simple, allowing the user to add his own analytical solution if the formula is not yet included. It aims at collaborative improvement by sharing the tool and the solutions. TRAC can be used for interpreting data recovered from a tracer test as well as for simulating the transport of a tracer in the saturated zone (for the time being). Calibration of a site operation is based on considering the hydrodynamic and hydrodispersive features of groundwater flow as well as the amount, nature and injection mode of the artificial tracer. The software is available in French, English and Spanish, and the latest version can be downloaded from the web site http://trac.brgm.fr">http://trac.brgm.fr.

  5. Correlative microscopy of densely labeled projection neurons using neural tracers.

    Science.gov (United States)

    Oberti, Daniele; Kirschmann, Moritz A; Hahnloser, Richard H R

    2010-01-01

    Three-dimensional morphological information about neural microcircuits is of high interest in neuroscience, but acquiring this information remains challenging. A promising new correlative technique for brain imaging is array tomography (Micheva and Smith, 2007), in which series of ultrathin brain sections are treated with fluorescent antibodies against neurotransmitters and synaptic proteins. Treated sections are repeatedly imaged in the fluorescence light microscope (FLM) and then in the electron microscope (EM). We explore a similar correlative imaging technique in which we differentially label distinct populations of projection neurons, the key routers of electrical signals in the brain. In songbirds, projection neurons can easily be labeled using neural tracers, because the vocal control areas are segregated into separate nuclei. We inject tracers into areas afferent and efferent to the main premotor area for vocal production, HVC, to retrogradely and anterogradely label different classes of projection neurons. We optimize tissue preparation protocols to achieve high fluorescence contrast in the FLM and good ultrastructure in the EM (using osmium tetroxide). Although tracer fluorescence is lost during EM preparation, we localize the tracer molecules after fixation and embedding by using fluorescent antibodies against them. We detect signals mainly in somata and dendrites, allowing us to classify synapses within a single ultrathin section as belonging to a particular type of projection neuron. The use of our method will be to provide statistical information about connectivity among different neuron classes, and to elucidate how signals in the brain are processed and routed among different areas.

  6. Correlative microscopy of densely labeled projection neurons using neural tracers

    Directory of Open Access Journals (Sweden)

    Daniele Oberti

    2010-06-01

    Full Text Available Three-dimensional morphological information about neural microcircuits is of high interest in neuroscience, but acquiring this information remains challenging. A promising new correlative technique for brain imaging is array tomography (Micheva and Smith, 2007, in which series of ultrathin brain sections are treated with fluorescent antibodies against neurotransmitters and synaptic proteins. Treated sections are repeatedly imaged in the fluorescence light microscope (FLM and then in the electron microscope (EM. We explore a similar correlative imaging technique in which we differentially label distinct populations of projection neurons, the key routers of electrical signals in the brain. In songbirds, projection neurons can easily be labeled using neural tracers, because the vocal control areas are segregated into separate nuclei. We inject tracers into areas afferent and efferent to the main premotor area for vocal production, HVC, to retrogradely and anterogradely label different classes of projection neurons. We optimize tissue preparation protocols to achieve high fluorescence contrast in the FLM and good ultrastructure in the EM (using osmium tetroxide. Although tracer fluorescence is lost during EM preparation, we localize the tracer molecules after fixation and embedding by using fluorescent antibodies against them. We detect signals mainly in somata and dendrites, allowing us to classify synapses within a single ultrathin section as belonging to a particular type of projection neuron. The use of our method will be to provide statistical information about connectivity among different neuron classes, and to elucidate how signals in the brain are processed and routed among different areas.

  7. Tracer Studies In A Laboratory Beach Subjected To Waves

    Science.gov (United States)

    This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present...

  8. Microfluidics: A Groundbreaking Technology for PET Tracer Production?

    Directory of Open Access Journals (Sweden)

    Björn Wängler

    2013-07-01

    Full Text Available Application of microfluidics to Positron Emission Tomography (PET tracer synthesis has attracted increasing interest within the last decade. The technical advantages of microfluidics, in particular the high surface to volume ratio and resulting fast thermal heating and cooling rates of reagents can lead to reduced reaction times, increased synthesis yields and reduced by-products. In addition automated reaction optimization, reduced consumption of expensive reagents and a path towards a reduced system footprint have been successfully demonstrated. The processing of radioactivity levels required for routine production, use of microfluidic-produced PET tracer doses in preclinical and clinical imaging as well as feasibility studies on autoradiolytic decomposition have all given promising results. However, the number of microfluidic synthesizers utilized for commercial routine production of PET tracers is very limited. This study reviews the state of the art in microfluidic PET tracer synthesis, highlighting critical design aspects, strengths, weaknesses and presenting several characteristics of the diverse PET market space which are thought to have a significant impact on research, development and engineering of microfluidic devices in this field. Furthermore, the topics of batch- and single-dose production, cyclotron to quality control integration as well as centralized versus de-centralized market distribution models are addressed.

  9. Tracer Studies In A Laboratory Beach Subjected To Waves

    Science.gov (United States)

    This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present...

  10. 76 FR 71610 - Market Test of First-Class Tracer

    Science.gov (United States)

    2011-11-18

    ... research and development costs incurred in connection with new product development. Id. Statutory authority... product, First- Class Tracer. This document describes the proposed test, addresses procedural aspects of... a market test beginning on or about December 7, 2011, of an experimental market dominant...

  11. Granulation of Pyrotechnic Tracer Composition R284T

    Science.gov (United States)

    1988-03-01

    Properties of Materials used in Pyrotechnic Compositions (1963). Engineering Design Handbook - Military Pyrotechnic Series Part 3. AMPC 706-187. 4...Ml Cartridge AMPC 706-185 APPLICATION: Main Tracer Charge TM9-1910 Ellern STORAGE: NATO DoD McIntyre Hazards Class (Q/D 1.1 7 Cabbaje & Ewing

  12. Carbon monoxide : A quantitative tracer for fossil fuel CO2?

    NARCIS (Netherlands)

    Gamnitzer, Ulrike; Karstens, Ute; Kromer, Bernd; Neubert, Rolf E. M.; Meijer, Harro A. J.; Schroeder, Hartwig; Levin, Ingeborg

    2006-01-01

    Carbon monoxide (CO), carbon dioxide (CO2), and radiocarbon ((CO2)-C-14) measurements have been made in Heidelberg from 2001 to 2004 in order to determine the regional fossil fuel CO2 component and to investigate the application of CO as a quantitative tracer for fossil fuel CO2 (CO2(foss)). The obs

  13. Diagnostic Implications of the Reactivity of Fluorescence Tracers

    Energy Technology Data Exchange (ETDEWEB)

    Sick, V; Westbrook, C

    2008-07-14

    Measurements of fuel concentration distributions with planar laser induced fluorescence of tracer molecules that are added to a base fuel are commonly used in combustion research and development. It usually is assumed that the tracer concentration follows the parent fuel concentration if physical properties such as those determining evaporation are matched. As an example to address this general issue a computational study of combustion of biacetyl/iso-octane mixtures was performed to investigate how well the concentration of biacetyl represents the concentration of iso-octane. For premixed mixture conditions with flame propagation the spatial concentration profiles of the two species in the flame front are separated by 110 {micro}m at 1 bar and by 11 {micro}m at 10 bar. For practical applications this spatial separation is insignificantly small. However, for conditions that mimic ignition and combustion in diesel and HCCI-like operation the differences in tracer and fuel concentration can be significant, exceeding hundreds of percent. At low initial temperature biacetyl was found to be more stable whereas at higher temperature (>1000K) iso-octane is more stable. Similar findings were obtained for a multi-component fuel comprised of iso-octane, n-heptane, methylcyclohexane, and toluene. It may be assumed that similar differences can exist for other tracer/fuel combinations. Caution has therefore to be applied when interpreting PLIF measurements in homogeneous reaction conditions such as in HCCI engine studies.

  14. Unit vent airflow measurements using a tracer gas technique

    Energy Technology Data Exchange (ETDEWEB)

    Adams, D.G. [Union Electric Company, Fulton, MO (United States); Lagus, P.L. [Lagus Applied Technology, Inc., San Diego, CA (United States); Fleming, K.M. [NCS Corp., Columbus, OH (United States)

    1997-08-01

    An alternative method for assessing flowrates that does not depend on point measurements of air flow velocity is the constant tracer injection technique. In this method one injects a tracer gas at a constant rate into a duct and measures the resulting concentration downstream of the injection point. A simple equation derived from the conservation of mass allows calculation of the flowrate at the point of injection. Flowrate data obtained using both a pitot tube and a flow measuring station were compared with tracer gas flowrate measurements in the unit vent duct at the Callaway Nuclear Station during late 1995 and early 1996. These data are presented and discussed with an eye toward obtaining precise flowrate data for release rate calculations. The advantages and disadvantages of the technique are also described. In those test situations for which many flowrate combinations are required, or in large area ducts, a tracer flowrate determination requires fewer man-hours than does a conventional traverse-based technique and does not require knowledge of the duct area. 6 refs., 10 figs., 6 tabs.

  15. Bridging the gaps in 18F PET tracer development

    Science.gov (United States)

    Campbell, Michael G.; Mercier, Joel; Genicot, Christophe; Gouverneur, Véronique; Hooker, Jacob M.; Ritter, Tobias

    2017-01-01

    As compared to the drug discovery process, the development of new 18F PET tracers lacks a well-established pipeline that advances compounds from academic research to candidacy for (pre)clinical imaging. In order to bridge the gaps between methodological advances and clinical success, we must rethink the development process from training to implementation.

  16. Uptake and transport of positron-emitting tracer in plants

    Energy Technology Data Exchange (ETDEWEB)

    Kume, Tamikazu; Matsuhashi, Shinpei; Shimazu, Masamitsu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment] [and others

    1997-03-01

    The transport of a positron-emitting isotope introduced into a plant was dynamically followed by a special observation apparatus called `Positron-Emitting Tracer Imaging System`. In the system, annihilation {gamma}-rays from the positron emitter are detected with two planer detectors (5 x 6 cm square). The water containing ca. 5 MBq/ml of {sup 18}F was fed to the cut stem of soybean for 2 min and then the images of tracer activity were recorded for 30 - 50 min. When the midrib of a leaf near the petiole was cut just before measurement, the activity in the injured leaf was decreased but detected even at the apex. This result suggests that the damaged leaf recovered the uptake of water through the lamina. Maximum tracer activities in leaves of unirradiated plant were observed within 10 min, whereas those of irradiated plant at 100 Gy were observed after over 25 min. The final activity of irradiated plant after 30 min was lower than that of unirradiated plant. In case of beans, there was a difference in the absorption behavior of the {sup 18}F-labeled water between unirradiated and irradiated samples. These results show that the system is effective to observe the uptake and transportation of water containing positron emitting tracer for the study of damage and recovery functions of plants. (author)

  17. Spatially Dispersed Employee Recovery

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders; Torfadóttir, Embla

    2014-01-01

    Employee recovery addresses either employee well-being or management's practices in aiding employees in recovering themselves following a service failure. This paper surveys the cabin crew at a small, European, low-cost carrier and investigates employees' perceptions of management practices to aid...... personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector......, who have a work place away from a fixed or central location and have minimal management contact. Results suggest that the support employees receive from management, such as recognition, information sharing, training, and strategic awareness are all important for spatially dispersed front...

  18. Assessment of Halon-1301 as a groundwater age tracer

    Science.gov (United States)

    Beyer, M.; van der Raaij, R.; Morgenstern, U.; Jackson, B.

    2015-06-01

    Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and timescale of groundwater flow and recharge, contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their individual restricted application ranges. For more robust groundwater dating multiple tracers need to be applied complementarily (or other characterisation methods need to be used to complement tracer information). It is important that additional, groundwater age tracers are found to ensure robust groundwater dating in future. We have recently suggested that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate, but its behaviour in water and suitability as a groundwater age tracer had not yet been assessed in detail. In this study, we determined Halon-1301 and inferred age information in 17 New Zealand groundwater samples and various modern (river) water samples. The samples were simultaneously analysed for Halon-1301 and SF6, which allowed for identification of issues such as contamination of the water with modern air during sampling. All analysed groundwater sites had also been previously dated with tritium, CFC-12, CFC-11 and SF6, and exhibited mean residence times ranging from modern (close to 0 years) to over 100 years. The investigated groundwater samples ranged from oxic to highly anoxic. All samples with available CFC data were degraded and/or contaminated in one or both of CFC-11 and CFC-12. This allowed us to make a first attempt of assessing the conservativeness of Halon-1301 in water, in terms of presence of local sources and its sensitivity towards degradation, which could affect the suitability of Halon-1301 as groundwater age tracer. Overall we found Halon-1301

  19. Synthesis and characterization of environmentally friendly fluorescent particle tracers

    Science.gov (United States)

    Tauro, Flavia; Porfiri, Maurizio; Rapiti, Emiliano; Grimaldi, Salvatore

    2013-04-01

    Tracers are widely used in experimental fluid mechanics and hydrology to investigate complex flows and water cycle processes. Commonly used tracers include dyes, artificial tracers, naturally occurring isotopes and chemicals, microorganisms, and DNA-based systems. Tracers should be characterized by low detection limits and high accuracy in following water paths and flow structures. For natural studies, tracers are also expected to be nontoxic and with low sorption affinity to natural substrates to minimize losses in the environment. In this context, while isotopes are completely natural, their use in field studies is limited by their ubiquity and, therefore, by the high uncertainty in data processing methodologies. Further, the use of dyes and artificial tracers can be hampered by extremely low detection limits due to dilution in natural streams and microorganisms, while DNA-based system may require physical sampling and time-consuming functionalization and detection procedures. In this work, we present the synthesis and characterization of fluorescent beads incorporating an eco-compatible fluorophore for environmental and laboratory applications. The particles are synthesized from natural beeswax through an inexpensive thermal procedure and can be engineered to present variable densities and diameters. A thorough characterization of their surface morphology at the nanoscale, crystal structure and size, chemical composition, and dye incorporation into the beeswax matrix is described by using a wide array of microscopy techniques. In addition, the particle fluorescence response is studied by performing excitation and emission scans on melted beeswax bead samples. The feasibility of using the synthesized particles in environmental settings is assessed through the design of ad-hoc weathering agent experiments where the beads are exposed to high energy radiation and hot water. Further, a proof of concept test is described to understand the particles' potential as a

  20. Light dispersion in space

    Science.gov (United States)

    Barbosa, L. C.

    2015-09-01

    Considering an idea of F. Arago in 1853 regarding light dispersion through the light ether in the interstellar space, this paper presents a new idea on an alternative interpretation of the cosmological red shift of the galaxies in the universe. The model is based on an analogy with the temporal material dispersion that occurs with light in the optical fiber core. Since intergalactic space is transparent, according to the model, this phenomenon is related to the gravitational potential existing in the whole space. Thus, it is possible to find a new interpretation to Hubble's constant. In space, light undergoes a dispersion process in its path, which is interpreted by a red shift equation of the type Δz = HL, since H = (d2n/dλ2 Δv Δλ), where H means the Hubble constant, n is the refractive index of the intergalactic space, Δλ is the spectral width of the extragalactic source, and Δv is the variation of the speed of light caused by the gravitational potential. We observe that this "constant" is governed by three new parameters. Light traveling the intergalactic space undergoes red shift due to this mechanism, while light amplitude decreases with time, and the wavelength always increases, thus producing the same type of behavior given by Hubble's Law. It can be demonstrated that the dark matter phenomenon is produced by the apparent speed of light of the stars on the periphery of the galaxies, without the existence of dark energy. Based on this new idea, the model of the universe is static, lacking expansion. Other phenomena may be interpreted based on this new model of the universe. We have what we call temporal gravitational dispersion of light in space produced by the variations of the speed of light, due to the presence of the gravitational potential in the whole space.

  1. Disabling Radiological Dispersal Terror

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M

    2002-11-08

    Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.

  2. Estimation of mechanical dispersion and dispersivity in a soil-gas system by column experiments and the dusty gas model.

    Science.gov (United States)

    Hibi, Yoshihiko; Kanou, Yuki; Ohira, Yuki

    2012-04-01

    In a previous study, column experiments were carried out with Toyoura sand (permeability 2.05×10(-11)m(2)) and Toyoura sand mixed with bentonite (permeability 9.96×10(-13)m(2)) to obtain the molecular diffusion coefficient, the Knudsen diffusion coefficient, the tortuosity for the molecular diffusion coefficient, and the mechanical dispersion coefficient of soil-gas systems. In this study, we conducted column experiments with field soil (permeability 2.0×10(-13)m(2)) and showed that the above parameters can be obtained for both less-permeable and more-permeable soils by using the proposed method for obtaining the parameters and performing column experiments. We then estimated dispersivity from the mechanical dispersion coefficients obtained by the column experiments. We found that the dispersivity depended on the mole fraction of the tracer gas and could be represented by a quadratic equation. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Analysis of single-hole and cross-hole tracer tests conducted at the Nye County early warning drilling program well complex, Nye County, Nevada

    Science.gov (United States)

    Umari, A.; Earle, J.D.; Fahy, M.F.

    2006-01-01

    As part of the effort to understand the flow and transport characteristics downgradient from the proposed high-level radioactive waste geologic repository at Yucca Mountain, Nevada, single- and cross-hole tracer tests were conducted from December 2004 through October 2005 in boreholes at the Nye County 22 well complex. The results were analyzed for transport properties using both numerical and analytical solutions of the governing advection dispersion equation. Preliminary results indicate effective flow porosity values ranging from 1.0 ?? 10-2 for an individual flow path to 2.0 ?? 10 -1 for composite flow paths, longitudinal dispersivity ranging from 0.3 to 3 m, and a transverse horizontal dispersivity of 0.03 m. Individual flow paths identified from the cross-hole testing indicate some solute diffusion into the stagnant portion of the alluvial aquifer.

  4. The determination of mass of metabolites with tracers

    Energy Technology Data Exchange (ETDEWEB)

    Katz, J. (Cedars-Sinai Medical Center, Los Angeles, CA (USA))

    1989-08-01

    Application of tracers in vivo for the determination of replacement and mass of bloodborne compounds at steady state is discussed. Theory and methods to determine mass with tracers (total amount of compound-tracee-within the body) for compartmental and noncompartmental systems are presented, and their limitations examined. Methods to derive mass from the specific activity curves after bolus injection or infusion of tracer are described using graphic procedures or by equations using the parameters of exponential curves. The relationship between assumed models and the interpretation of tracer data is examined. The determination of both replacement (appearance, which equals utilization at steady state) and mass of most compounds present in both extracellular and intracellular fluids (such as lactate and amino acids) requires the application of the A-V mode for tracer administration and sampling of blood. Recycling of carbon affects the determination of mass with {sup 14}C. Estimates of true mass are provided with tritium-labeled compounds, even when tritium loss is by exchange with protons or through futile cycling. Estimates of the amount (body mass) of lactate, alanine, glutamate, and proline obtained with tritium-labeled compounds are presented. Most of these masses are intracellular. The concentration of lactate in tissues equals or is greater, and that of amino acids much greater than that in plasma. Hence, the so-called distribution space for these compounds, calculated conventionally by dividing mass by plasma concentration, would appear to be equal to or greater than the body water of lactate, and several liters per kilogram for amino acids.

  5. Dynamics of ellipsoidal tracers in swimming algal suspensions

    Science.gov (United States)

    Yang, Ou; Peng, Yi; Liu, Zhengyang; Tang, Chao; Xu, Xinliang; Cheng, Xiang

    2016-10-01

    Enhanced diffusion of passive tracers immersed in active fluids is a universal feature of active fluids and has been extensively studied in recent years. Similar to microrheology for equilibrium complex fluids, the unusual enhanced particle dynamics reveal intrinsic properties of active fluids. Nevertheless, previous studies have shown that the translational dynamics of spherical tracers are qualitatively similar, independent of whether active particles are pushers or pullers—the two fundamental classes of active fluids. Is it possible to distinguish pushers from pullers by simply imaging the dynamics of passive tracers? Here, we investigated the diffusion of isolated ellipsoids in algal C. reinhardtii suspensions—a model for puller-type active fluids. In combination with our previous results on pusher-type E. coli suspensions [Peng et al., Phys. Rev. Lett. 116, 068303 (2016), 10.1103/PhysRevLett.116.068303], we showed that the dynamics of asymmetric tracers show a profound difference in pushers and pullers due to their rotational degree of freedom. Although the laboratory-frame translation and rotation of ellipsoids are enhanced in both pushers and pullers, similar to spherical tracers, the anisotropic diffusion in the body frame of ellipsoids shows opposite trends in the two classes of active fluids. An ellipsoid diffuses fastest along its major axis when immersed in pullers, whereas it diffuses slowest along the major axis in pushers. This striking difference can be qualitatively explained using a simple hydrodynamic model. In addition, our study on algal suspensions reveals that the influence of the near-field advection of algal swimming flows on the translation and rotation of ellipsoids shows different ranges and strengths. Our work provides not only new insights into universal organizing principles of active fluids, but also a convenient tool for detecting the class of active particles.

  6. A Lagrangian particle method with remeshing for tracer transport on the sphere

    Science.gov (United States)

    Bosler, Peter A.; Kent, James; Krasny, Robert; Jablonowski, Christiane

    2017-07-01

    A Lagrangian particle method (called LPM) based on the flow map is presented for tracer transport on the sphere. The particles carry tracer values and are located at the centers and vertices of triangular Lagrangian panels. Remeshing is applied to control particle disorder and two schemes are compared, one using direct tracer interpolation and another using inverse flow map interpolation with sampling of the initial tracer density. Test cases include a moving-vortices flow and reversing-deformational flow with both zero and nonzero divergence, as well as smooth and discontinuous tracers. We examine the accuracy of the computed tracer density and tracer integral, and preservation of nonlinear correlation in a pair of tracers. We compare results obtained using LPM and the Lin-Rood finite-volume scheme. An adaptive particle/panel refinement scheme is demonstrated.

  7. Feasibility of large scale deliberate tracer release experiments in or below the oceanic thermocline

    Energy Technology Data Exchange (ETDEWEB)

    Shepherd, J.G.; Broecker, W.S.

    1981-02-01

    The relative importance of lateral and vertical mixing in the interior of the oceans cannot be reliably determined from conventional oceanographic measurements, nor from observations of fallout radionuclides. It is suggested that the problem could be most effectively studied by an experiment in which a large quantity of a suitable tracer was deliberately released in deep water, and its subsequent dispersion was followed for at least one year. The feasibility of such an experiment is examined. It is concluded that it is indeed feasible, and that helium-3 would be the most suitable tracer, with tritium as a possible alternative. About 30 g f Helium-3 would be needed for each release. Such a quantity may be dissoled in about 1 m/sup 3/ of water at pressures greater than 500 dbar, is easily available, and would cost about $100K. Concentrations would have fallen to unmeasurable levels by the time the patch had spread sufficiently to interfere with measurements of natural or radiogenic helium-3. The patch would need to be marked with dusters of neutrally buoyant floats in order that its movement may be followed. It is estimated that it would be around 1000 km across after one year, and anything from a few meters to a few hundred meters thick. Vertically integrating samples would probably be most suitable, used in conjunction with ship-board helium-3 mass spectrometer. Methods of dissolving the helium in situ, and making the release with minimum disturbance are also proposed. The cost would be several million dollars, spread over several years.

  8. Dispersion in deep polar firn driven by synoptic-scale surface pressure variability

    Science.gov (United States)

    Buizert, Christo; Severinghaus, Jeffrey P.

    2016-09-01

    Commonly, three mechanisms of firn air transport are distinguished: molecular diffusion, advection, and near-surface convective mixing. Here we identify and describe a fourth mechanism, namely dispersion driven by synoptic-scale surface pressure variability (or barometric pumping). We use published gas chromatography experiments on firn samples to derive the along-flow dispersivity of firn, and combine this dispersivity with a dynamical air pressure propagation model forced by surface air pressure time series to estimate the magnitude of dispersive mixing in the firn. We show that dispersion dominates mixing within the firn lock-in zone. Trace gas concentrations measured in firn air samples from various polar sites confirm that dispersive mixing occurs. Including dispersive mixing in a firn air transport model suggests that our theoretical estimates have the correct order of magnitude, yet may overestimate the true dispersion. We further show that strong barometric pumping, such as at the Law Dome site, may reduce the gravitational enrichment of δ15N-N2 and other tracers below gravitational equilibrium, questioning the traditional definition of the lock-in depth as the depth where δ15N enrichment ceases. Last, we propose that 86Kr excess may act as a proxy for past synoptic activity (or paleo-storminess) at the site.

  9. Quantitative myocardial perfusion magnetic resonance imaging: the impact of pulsatile flow on contrast agent bolus dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Graafen, Dirk; Hamer, Julia; Weber, Stefan; Schreiber, Laura M, E-mail: graafen@uni-mainz.de [Section of Medical Physics, Department of Radiology, Johannes Gutenberg University Medical Center, Mainz (Germany)

    2011-08-21

    Myocardial blood flow (MBF) can be quantified using T{sub 1}-weighted first-pass magnetic resonance imaging (MRI) in combination with a tracer-kinetic model, like MMID4. This procedure requires the knowledge of an arterial input function which is usually estimated from the left ventricle (LV). Dispersion of the contrast agent bolus may occur between the LV and the tissue of interest. The aim of this study was to investigate the dispersion under conditions of physiological pulsatile blood flow, and to simulate its effect on MBF quantification. The dispersion was simulated in coronary arteries using a computational fluid dynamics (CFD) approach. Simulations were accomplished on straight vessels with stenosis of different degrees and shapes. The results show that dispersion is more pronounced under resting conditions than during hyperemia. Stenosis leads to a reduction of dispersion. In consequence, dispersion results in a systematic MBF underestimation between -0.4% and -9.3%. The relative MBF error depends not only on the dispersion but also on the actual MBF itself. Since MBF under rest is more underestimated than under stress, myocardial perfusion reserve is overestimated between 0.1% and 4.5%. Considering other sources of errors in myocardial perfusion MRI, systematic errors of MBF by bolus dispersion are relatively small.

  10. Hydraulic Conductivity Estimate via Tracer Test and Ensemble Kalman Filter Data Assimilation: Theoretical and Numerical Fundamentals

    Science.gov (United States)

    Crestani, E.; Camporese, M.; Salandin, P.

    2011-12-01

    Hydraulic properties of natural aquifers, such as porosity, hydraulic conductivity, and storativity, exhibit an erratic spatial variability at different scales that is difficult to recognize without expensive in situ sampling campaigns, laboratory analyses, and, when available, spatially distributed pumping tests. Nevertheless, the importance of the heterogeneous structure of natural formations on solute transport is well recognized, being the non-Fickian evolution of contaminant plumes and the relevant dispersive phenomena controlled by the variability of the hydraulic conductivity K at the local scale. Tracer test analyses have been widely adopted to identify the complex distribution of in situ hydraulic properties. In particular, the use of geophysical methods like the borehole Electrical Resistivity Tomography (ERT) have been in rapid increase, due to their potential to accurately describe the spatio-temporal evolution of the injected solute. Under the assumptions that the solute spreads as a passive tracer and with high values of the Peclet number, the plume evolution is controlled by the porosity and the spatial distribution of hydraulic conductivity. Combining the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique, the purpose of this study is to infer the spatial distribution of K at the local scale from a sequence of time-lapse concentration imaging. The capabilities of the proposed approach are investigated simulating various assimilation experiments via synthetic tracer tests in a three-dimensional finite domain reproducing a heterogeneous aquifer. In a first scenario, all the available concentration measurements are assimilated and the entire hydraulic conductivity field is updated, while in the remaining scenarios the K values are updated only in a limited number of nodes by assimilating the concentrations in these same nodes, the hydraulic conductivity in the rest of the domain being the result of a

  11. Numerical Analysis of a Short-Term Tracer Experiment in Fractured Sandstone

    Directory of Open Access Journals (Sweden)

    Tai-Sheng Liou

    2007-01-01

    Full Text Available A short-term, pulse injection tracer experiment conducted in fractured quartzitic sandstone at Kukuan, Taiwan was analyzed. Tracer transport at the test site was dominated by advection but a specific attenuation mechanism leading to breakthrough curve (BTC tailing also seemed to exist. Matrix diffusion was hypothesized as the transport mechanism that results in the tailing. This hypothesis was proved by comparing the field BTC with numerical simulation results obtained by the general-purpose flow/transport simulator, TOUGH2, based on a single-fracture conceptual model. Due to the lack of accuracy of estimating the interporosity flux by the conventional double porosity model (DPM, TOUGH2 was incorporated with the multiple interacting continua (MINC scheme to simulate the transient characteristics of the interporosity flux. In MINC, rock matrix is discretized as a series of continua according to the perpendicular distance from the fracture that adjoins the matrix. The closer the rock matrix is to the fracture, the finer the rock matrix is discretized. This concept is fundamentally different from DPM in that rock matrix is no longer treated as a single continuum. Simulation results by TOUGH2-MINC have successfully reproduced the observed BTC tailing even under the dominating advection effect. Sensitivity studies showed that TOUGH2-MINC is sensitive to parameters including fracture aperture (2b, matrix porosity (nm and effective molecular diffusion coefficient in matrix (Dm. If 2b, nm , Dm , are respectively 200 _?¿m, 2%, 10-11 m2 s -1, and if hydrodynamic dispersion coefficient (D is 1.69 ¡__n10-6 m2 s -1, TOUGH2-MINC result can well fit the field BTC. Furthermore, the importance of matrix diffusion was verified by fitting the field BTC with analytical solutions that either neglect matrix diffusion or consider the mass exchange between mobile and immobile zones within the fracture as the attenuation transport mechanism. It was found that the BTC

  12. Characterizing storm water dispersion and dilution from small coastal streams

    Science.gov (United States)

    Romero, Leonel; Siegel, David A.; McWilliams, James C.; Uchiyama, Yusuke; Jones, Charles

    2016-06-01

    Characterizing the dispersion and dilution of storm water from small coastal creeks is important for understanding the importance of land-derived subsidies to nearby ecosystems and the management of anthropogenic pollutants. In Southern California, creek runoff is episodic, intense, and short-lived while the plumes are buoyant, all of which make the field sampling of freshwater plumes challenging. Numerical modeling offers a viable way to characterize these systems. The dilution and dispersion of freshwater from two creeks that discharge into the Santa Barbara Channel, California is investigated using Regional Ocean Modeling System (ROMS) simulations with a horizontal resolution of 100 m. Tight coupling is found among precipitation, hydrologic discharge, wind forcing, and submesoscale flow structures which all contribute to plume evolution. During flooding, plumes are narrow and attached to the coast, due to downwelling/onshore wind forcing and intense vorticity filaments lying parallel to the shelf. As the storm passes, the winds typically shift to offshore/upwelling favorable conditions and the plume is advected offshore which enhances its dilution. Plumes reach the bottom nearshore while they form thin layers a few meters thick offshore. Dilution field of passive tracers released with the runoff is strongly anisotropic with stronger cross-shelf gradients than along-shelf. Dispersion analysis of statistical moments of the passive tracer distribution results in scale-dependent diffusivities consistent with the particle-pair analysis of Romero et al. Model validation, the roles of submesoscale processes, and wind forcing on plume evolution and application to ecological issues and marine resource management are discussed.

  13. The Fischa-Dagnitz spring, Southern Vienna Basin: a multi tracer time series study re-assessing earlier conceptual assumptions.

    Science.gov (United States)

    Suckow, Axel; Gerber, Christoph; Kralik, Martin; Sültenfuss, Jürgen; Purtschert, Roland

    2013-04-01

    The gravel aquifer of the Southern Vienna Basin is a very important backup drinking water resource for the city of Vienna. A discharge location, the Fischa-Dagnitz spring in the Southern Vienna Basin, Austria, was re-investigated in 2011, five years after the gas exchange tracer test published in (Stolp et al., 2010), and sampled for stable isotopes 18O/2H, tritium, 3He, SF6 and 85Kr (Gerber et al., 2012). Additionally, new tritium time series data (Davis et al., 1967), previously not considered in Stolp et al. (2010), were included. These show a higher and earlier tritium peak of >300 TU in 1965 in the discharge of the Fischa-Dagnitz spring as compared to 221 TU in 1972 considered in Stolp et al. (2010). The new 3He, SF6 and 85Kr gas tracer data from 2011 confirm the earlier finding for 3He of Stolp et al. (2010) and indicate a more recent equilibration with the atmosphere than the water bound tracers 18O, 2H and tritium. A new modelling attempt using the Lumpy code (Suckow, 2012) confirmed the discrepancy between the tritium data and the gaseous tracers 3He, SF6 and 85Kr. No steady-state combination of local recharge (represented by an exponential model) and Schwarza river infiltration flowing through the gravel aquifer (represented by a parallel dispersion model) can equally well explain both the tritium time series and the gas tracer results. A revised conceptual model proposes that a pinching of the aquifer at unconformities in the gravel body or a fault zone known in the gravel body forces groundwater along the flow path closer to the surface and exposes it to the atmosphere. This would tend to reset the "dating" clock for the gaseous tracers 3He, SF6 and 85Kr, which can equilibrate quickly with the atmosphere, but not for tritium, which marks the transport behaviour of the water itself. These findings are of importance also for other multi-tracer assessments of groundwater movement in phreatic aquifer systems. References: Davis, G.H., Payne, B.R., Dincer, T

  14. Numerical simulation of a natural gradient tracer experiment for the natural attenuation study: flow and physical transport.

    Science.gov (United States)

    Julian, H E; Boggs, J M; Zheng, C; Feehley, C E

    2001-01-01

    attributed to aquifer heterogeneity at the decimeter (dm) and smaller scales. The calibrated transport parameters for the SSM (i.e., 1:7 for the ratio of mobile-to-total porosity; 2.5 x 10(-3) day-1 for the mass-transfer coefficient; 1 m for longitudinal dispersivity; and 0.1 m for transverse dispersivity) are consistent with separate numerical simulations of two earlier tracer experiments at the site. The multiscale modeling approach adopted in this study permits the incorporation of both large-scale geologic features important for flow simulation and small-scale heterogeneities critical for transport simulation. In addition, the dual-domain transport model provides a foundation for multispecies reactive transport modeling studies of natural attenuation of hydrocarbons during NATS.

  15. Nozzle for electric dispersion reactor

    Science.gov (United States)

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1995-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  16. Computational Fluid Dynamics Simulations of Contrast Agent Bolus Dispersion in a Coronary Bifurcation: Impact on MRI-Based Quantification of Myocardial Perfusion

    OpenAIRE

    Regine Schmidt; Dirk Graafen; Stefan Weber; Schreiber, Laura M.

    2013-01-01

    Contrast-enhanced first-pass magnetic resonance imaging (MRI) in combination with a tracer kinetic model, for example, MMID4, can be used to determine myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Typically, the arterial input function (AIF) required for this methodology is estimated from the left ventricle (LV). Dispersion of the contrast agent bolus might occur between the LV and the myocardial tissue. Negligence of bolus dispersion could cause an error in MBF determin...

  17. Well ER-6-1 Tracer Test Analysis: Yucca Flat, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

    Energy Technology Data Exchange (ETDEWEB)

    Greg Ruskauff

    2006-09-01

    The ER-6-1 multiple-well aquifer test-tracer test (MWAT-TT) investigated groundwater flow and transport processes relevant to the transport of radionuclides from sources on the Nevada Test Site (NTS) through the lower carbonate aquifer (LCA) hydrostratigraphic unit (HSU). The LCA, which is present beneath much of the NTS, is the principal aquifer for much of southern Nevada. This aquifer consists mostly of limestone and dolomite, and is pervasively fractured. Groundwater flow in this aquifer is primarily in the fractures, and the hydraulic properties are primarily related to fracture frequency and fracture characteristics (e.g., mineral coatings, aperture, connectivity). The objective of the multiple-well aquifer test (MWAT) was to determine flow and hydraulic characteristics for the LCA in Yucca Flat. The data were used to derive representative flow model and parameter values for the LCA. The items of specific interest are: Hydraulic conductivity; Storage parameters; Dual-porosity behavior; and Fracture flow characteristics. The objective of the tracer transport experiment was to evaluate the transport properties and processes of the LCA and to derive representative transport parameter values for the LCA. The properties of specific interest are: Effective porosity; Matrix diffusion; Longitudinal dispersivity; Adsorption characteristics; and Colloid transport characteristics. These properties substantially control the rate of transport of contaminants in the groundwater system and concentration distributions. To best support modeling at the scale of the corrective action unit (CAU), these properties must be investigated at the field scale. The processes represented by these parameters are affected by in-situ factors that are either difficult to investigate at the laboratory scale or operate at a much larger scale than can be reproduced in the laboratory. Measurements at the field scale provide a better understanding of the effective average parameter values. The

  18. Ensemble-based simultaneous emission estimates and improved forecast of radioactive pollution from nuclear power plant accidents: application to ETEX tracer experiment.

    Science.gov (United States)

    Zhang, X L; Li, Q B; Su, G F; Yuan, M Q

    2015-04-01

    The accidental release of radioactive materials from nuclear power plant leads to radioactive pollution. We apply an augmented ensemble Kalman filter (EnKF) with a chemical transport model to jointly estimate the emissions of Perfluoromethylcyclohexane (PMCH), a tracer substitute for radionuclides, from a point source during the European Tracer Experiment, and to improve the forecast of its dispersion downwind. We perturb wind fields to account for meteorological uncertainties. We expand the state vector of PMCH concentrations through continuously adding an a priori emission rate for each succeeding assimilation cycle. We adopt a time-correlated red noise to simulate the temporal emission fluctuation. The improved EnKF system rapidly updates (and reduces) the excessively large initial first-guess emissions, thereby significantly improves subsequent forecasts (r = 0.83, p 80% average reduction of the normalized mean square error).

  19. Validity condition of separating dispersion of PCFs into material dispersion and geometrical dispersion

    Institute of Scientific and Technical Information of China (English)

    Wei Wang; Lantian Hou; Zhaolun Liu; Guiyao Zhou

    2009-01-01

    When using normalized dispersion method for the dispersion design of photonic crystal fibers(PCFs),it is vital that the group velocity dispersion of PCF can be seen as the sum of geometrical dispersion and material dispersion.However,the error induced by this way of calculation will deteriorate the final results.Taking 5 ps/(km·nm)and 5% as absolute error and relative error limits,respectively,the structure parameter boundaries of PCFs about when separating total dispersion into geometrical and material components is valid are provided for wavelength shorter than 1700 nm.By using these two criteria together,it is adequate to evaluate the simulatcd dispersion of PCFs when normalized dispersion method is employed.

  20. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    OpenAIRE

    Mandeep Singh; S.K. Raghuwanshi

    2013-01-01

    This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when disper...

  1. Developing a dispersant spraying capability

    Energy Technology Data Exchange (ETDEWEB)

    Gill, S.D.

    1979-01-01

    In developing a national dispersant spraying capability, the Canadian Coast Guard (CCG) has undertaken a modification program to enable the conventional offshore spraying gear to be mounted on almost any vessel of convenience. Smaller, more versatile inshore spraying vessels and pumps have been designed and built. With the popularization of concentrated dispersants, the inshore pumping equipment can be used aboard hovercraft for special application situations. A program of acquiring mobile dispersant storage tanks has been undertaken with auxiliary equipment that will facilitate the shipment of dispersants in bulk by air freight. Work also has commenced on extending the dispersant application program to include the CCG fleet of helicopters.

  2. Analysis of Conservative Tracer Tests in the Bullfrog, Tram, and Prow Pass Tuffs, 1996 to 1998, Yucca Mountain, Nye County, Nevada

    Science.gov (United States)

    Umari, Amjad; Fahy, Michael F.; Earle, John D.; Tucci, Patrick

    2008-01-01

    To evaluate the potential for transport of radionuclides in ground water from the proposed high-level nuclear-waste repository at Yucca Mountain, Nevada, conservative (nonsorbing) tracer tests were conducted among three boreholes, known as the C-hole Complex, and values for transport (or flow) porosity, storage (or matrix) porosity, longitudinal dispersivity, and the extent of matrix diffusion were obtained. The C-holes are completed in a sequence of Miocene tuffaceous rock, consisting of nonwelded to densely welded ash-flow tuff with intervals of ash-fall tuff and volcaniclastic rocks, covered by Quaternary alluvium. The lower part of the tuffaceous-rock sequence includes the Prow Pass, Bullfrog, and Tram Tuffs of the Crater Flat Group. The rocks are pervaded by tectonic and cooling fractures. Paleozoic limestone and dolomite underlie the tuffaceous rocks. Four radially convergent and one partially recirculating conservative (nonsorbing) tracer tests were conducted at the C-hole Complex from 1996 to 1998 to establish values for flow porosity, storage porosity, longitudinal dispersivity, and extent of matrix diffusion in the Bullfrog and Tram Tuffs and the Prow Pass Tuff. Tracer tests included (1) injection of iodide into the combined Bullfrog-Tram interval; (2) injection of 2,6 difluorobenzoic acid into the Lower Bullfrog interval; (3) injection of 3-carbamoyl-2-pyridone into the Lower Bullfrog interval; and (4) injection of iodide and 2,4,5 trifluorobenzoic acid, followed by 2,3,4,5 tetrafluorobenzoic acid, into the Prow Pass Tuff. All tracer tests were analyzed by the Moench single- and dual-porosity analytical solutions to the advection-dispersion equation or by superposition of these solutions. Nonlinear regression techniques were used to corroborate tracer solution results, to obtain optimal parameter values from the solutions, and to quantify parameter uncertainty resulting from analyzing two of the three radially convergent conservative tracer tests

  3. Assessment of Halon-1301 as a groundwater age tracer

    Directory of Open Access Journals (Sweden)

    M. Beyer

    2015-01-01

    Full Text Available Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and time scale of groundwater flow and recharge, to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their individual restricted application ranges. For more robust groundwater dating multiple tracers need to be applied complementarily and it is vital that additional, groundwater age tracers are found to ensure robust groundwater dating in future. We recently suggested that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate, but its behaviour in water and suitability as a groundwater age tracer had not yet been assessed in detail. In this study, we determine Halon-1301 and infer age information in 17 New Zealand groundwaters and various modern (river water samples. The samples are simultaneously analysed for Halon-1301 and SF6, which allows identification of issues such as contamination of the water with modern air during sampling. Water at all analysed groundwater sites have also been previously dated with tritium, CFC-12, CFC-11 and SF6, and exhibit mean residence times ranging from modern (close to 0 years to over 100 years. The investigated groundwater ranged from oxic to highly anoxic, and some showed evidence of CFC contamination or degradation. This allowed us to make a first attempt of assessing the conservativeness of Halon-1301 in water, in terms of presence of local sources and its sensitivity towards degradation etc., which could affect the suitability of Halon-1301 as groundwater age tracer. Overall we found Halon-1301 reliably inferred the mean residence time of groundwater recharged between 1980 and 2014. Where direct age comparison

  4. Effects of pore-scale dispersion, degree of heterogeneity, sampling size, and source volume on the concentration moments of conservative solutes in heterogeneous formations

    Science.gov (United States)

    Daniele Tonina; Alberto Bellin

    2008-01-01

    Pore-scale dispersion (PSD), aquifer heterogeneity, sampling volume, and source size influence solute concentrations of conservative tracers transported in heterogeneous porous formations. In this work, we developed a new set of analytical solutions for the concentration ensemble mean, variance, and coefficient of variation (CV), which consider the effects of all these...

  5. Experimental and modelling investigations of tracer transport in variably saturated agricultural soil of Thailand: Column study

    Directory of Open Access Journals (Sweden)

    Tulaya Masipan

    2016-03-01

    Full Text Available Tracer (Bromide movement through the unsaturated agricultural soil was investigated in soil columns. Two tracer column experiments, with a diameter of 7 cm and a depth of 25 cm, were vertically homogeneous packed with sandy loam and then carried out to investigate bromide (Br− transport under different water contents (at steady flow condition. One soil column (Column 1 represents the unsaturated agricultural soil in dry season (with water content ranging from 0.23 to 0.26 and the other (Column 2 represents the soil in wet season (water content from 0.24 to 0.35. Bromide samples were periodically collected by vacuum tubes inserted at 6.25 cm equally spaced intervals (e.g., 6.25, 12.5, 18.75 and 25 cm along the length of the column and the effluent collected at the end of the column. The observed breakthrough curves (BTCs of bromide in both columns represented a relative smooth and sigmodal curves at different distances (sampling ports. Dispersivity (α, cm for sandy loam at different locations was numerically estimated by curve fitting the experimental data with HYDRUS-1D. The α can be well described by the convection–dispersion equation and these values derived from Column 1 (ranging from 0.37 to 0.98 cm are more than those from Column 2 (0.25–0.59. Moreover, the α in both columns increases with the travel distance due to the scale-dependent effect. Furthermore, the α values were plotted on a log–log scale against travel distances and they yield empirical power law relationships with an excellent correlation (α = 0.102 (L0.697, R2 = 0.999 and α = 0.086 (L0.579, R2 = 0.963 for Column 1 and 2, respectively.

  6. Dispersion Interactions in Water Clusters.

    Science.gov (United States)

    Guidez, Emilie B; Gordon, Mark S

    2017-05-18

    The importance of dispersion forces in water clusters is examined using the effective fragment potential (EFP) method. Since the original EFP1 water potential does not include dispersion, a dispersion correction to the EFP1 potential (EFP1-D) was derived and implemented. The addition of dispersion to the EFP1 potential yields improved geometries for water clusters that contain 2-6 molecules. The importance of the odd E7 contribution to the dispersion energy is investigated. The E7 dispersion term is repulsive for all of the water clusters studied here and can have a magnitude that is as large as half of the E6 value. The E7 term therefore contributes to larger intermolecular distances for the optimized geometries. Inclusion of many-body effects and/or higher order terms may be necessary to further improve dispersion energies and optimized geometries.

  7. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  8. Final Report for the Joint Urban 2003 Atmospheric Dispersion Study in Oklahoma City: Lawrence Livermore National Laboratory participation

    Energy Technology Data Exchange (ETDEWEB)

    Leach, M J

    2005-10-12

    The Joint Urban 2003 (JU2003) field study was designed to collect meteorological and tracer data resolving atmospheric dispersion at scales-of-motion ranging from flows in and around a single city block, in and around several blocks in the downtown Central Business District (CBD), and into the suburban Oklahoma City area a few km from the CBD. Indoor tracer and flow measurements within four downtown study buildings were also made in conjunction with detailed outdoor measurements investigating the outdoor-indoor exchange rates and mechanisms. The movement of tracer within the study buildings was also studied. The data from the field experiment is being used to evaluate models that are being developed for predicting dispersion of contaminants in urban areas. These models may be fast-response models based on semi-empirical algorithms that are used in real-time emergencies, or highly sophisticated computational fluid dynamics models that resolve individual building faces and crevices. The data from the field experiment, together with the models, can then be used to develop other advanced tools that are especially valuable in the efforts to thwart terrorists. These include tools for finding location and characteristics of a contaminant source; tools that can be used for real-time response or for forensic investigation. The tools will make use of monitoring networks for biological agents that are being established in several sensitive cities throughout the nation. This major urban study was conducted beginning June 28 and ending July 31, 2003. It included several integrated scientific components necessary to describe and understand the physical processes governing dispersion within and surrounding an urban area and into and within building environments. The components included characterizing: (1) the urban boundary layer and the development of the urban boundary layer within the atmospheric boundary layer, (2) the flows within and downwind of the tall-building core, (3

  9. Quantum optical rotatory dispersion

    Science.gov (United States)

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-01-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements. PMID:27713928

  10. A monitoring system of radioactive tracers in hydroponic solution for research on plant physiology

    Energy Technology Data Exchange (ETDEWEB)

    Suzui, N.; Kawachi, N.; Ishioka, N.; Fujimaki, S. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Takasaki, Gunma 370-1292 (Japan); Yamaguchi, M. [Takasaki Advanced Radiation Research Institute, Atomic Energy Agency, Takasaki, Gunma 370-1292 (Japan)

    2009-07-01

    The mechanism of nutrient uptake in plants has received considerable attention in the field of plant science. Here we describe the development of a new monitoring system of radioactive tracers in hydroponic solution, which enables the noninvasive measurement of radioactive tracer uptake by an intact plant. In addition, we incorporated a weighing instrument into this system in order to simultaneously monitor water uptake by the same plant. For an evaluation of this monitoring system, we conducted a tracer experiment with a rice plant and a positron-emitting radioactive tracer, and successfully obtained continuous data for the amounts of radioactive tracer and water taken up by the intact plant over 36 h. (authors)

  11. Application of enriched stable isotopes as tracers in biological systems

    DEFF Research Database (Denmark)

    Stürup, Stefan; Hansen, Helle Rüsz; Gammelgaard, Bente

    2008-01-01

    The application of enriched stable isotopes of minerals and trace elements as tracers in biological systems is a rapidly growing research field that benefits from the many new developments in inorganic mass spectrometric instrumentation, primarily within inductively coupled plasma mass spectrometry...... (ICP-MS) instrumentation, such as reaction/collision cell ICP-MS and multicollector ICP-MS with improved isotope ratio measurement and interference removal capabilities. Adaptation and refinement of radioisotope tracer experiment methodologies for enriched stable isotope experiments......, and the development of new methodologies coupled with more advanced compartmental and mathematical models for the distribution of elements in living organisms has enabled a broader use of enriched stable isotope experiments in the biological sciences. This review discusses the current and future uses of enriched...

  12. In-situ fracture mapping using geotomography and brine tracers

    Energy Technology Data Exchange (ETDEWEB)

    Deadrick, F.J.; Ramirez, A.L.; Lytle, R.J.

    1981-01-01

    The Lawrence Livermore National Laboratory is currently assessing the capabilities of high resolution geophysical methods to characterize geologic sites for the disposal of high level nuclear waste. A successful experiment has recently been performed in which salt water tracers and high frequency electromagnetic waves were utilized to map rock mass fracture zones in-situ. Multiple cross-borehole EM transmissions were used to generate a tomographic image of the fractured rock region between two boreholes. The tomographs obtained correlate well with conventional wireline geophysical logs which can be used to infer the location of fractured zones in the rock mass. This indirect data suggests that the geotomography and brine tracer technique may have merit in mapping fractured zones between boreholes.

  13. FormTracer - A Mathematica Tracing Package Using FORM

    CERN Document Server

    Cyrol, Anton K; Strodthoff, Nils

    2016-01-01

    We present FormTracer, a high-performance, general purpose, easy-to-use Mathematica tracing package which uses FORM. It supports arbitrary space and spinor dimensions as well as an arbitrary number of simple compact Lie groups. While keeping the usability of the Mathematica interface, it relies on the efficiency of FORM. An additional performance gain is achieved by a decomposition algorithm that avoids redundant traces in the product tensors spaces. FormTracer supports a wide range of syntaxes which endows it with a high flexibility. Mathematica notebooks that automatically install the package and guide the user through performing standard traces in space-time, spinor and gauge-group spaces are provided.

  14. A historical perspective on radioisotopic tracers in metabolism and biochemistry.

    Science.gov (United States)

    Lappin, Graham

    2015-01-01

    Radioisotopes are used routinely in the modern laboratory to trace and quantify a myriad of biochemical processes. The technique has a captivating history peppered with groundbreaking science and with more than its share of Nobel Prizes. The discovery of radioactivity at the end of the 19th century paved the way to understanding atomic structure and quickly led to the use of radioisotopes to trace the fate of molecules as they flowed through complex organic life. The 1940s saw the first radiotracer studies using homemade instrumentation and analytical techniques such as paper chromatography. This article follows the history of radioisotopic tracers from meager beginnings, through to the most recent applications. The author hopes that those researchers involved in radioisotopic tracer studies today will pause to remember the origins of the technique and those who pioneered this fascinating science.

  15. A Galaxy-Halo Model for Multiple Cosmological Tracers

    CERN Document Server

    Bull, Philip

    2016-01-01

    The information extracted from large galaxy surveys with the likes of DES, DESI, Euclid, LSST, SKA, and WFIRST will be greatly enhanced if the resultant galaxy catalogues can be cross-correlated with one another. Predicting the nature of the information gain, and developing the tools to realise it, depends on establishing a consistent model of how the galaxies detected by each survey trace the same underlying matter distribution. Existing analytic methods, such as halo occupation distribution (HOD) modelling, are not well-suited for this task, and can suffer from ambiguities and tuning issues when applied to multiple tracers. We construct a simple alternative that provides a common model for the connection between galaxies and dark matter halos across a wide range of wavelengths (and thus tracer populations). This is based on a chain of parametrised statistical distributions that model the connection between (a) halo mass and bulk physical properties of galaxies, such as star-formation rate; and (b) those sam...

  16. ARAC results from phase II of the European tracer experiment

    Energy Technology Data Exchange (ETDEWEB)

    Pace, J.C.; Nasstrom, J.S.

    1997-07-01

    A comparison is provided of the results of calculations by the Atmospheric Release Advisory Capability (ARAC) during two phases of the European Tracer Experiment (ETEX). In phase I of ETEX, participants generated predictions in real time of the concentration of inert tracer gases released from a site in Western France. Each participating group based their predictions on the meteorological data they had available. In phase II, all participants were required to recalculate predictions based on the same meteorological data, which was generated and supplied by the European Centre for Medium- Range Weather Forecasts (ECMWF). ARAC used ECMWF data and also made additional changes to its model configuration,, with the result that ARAC`s accuracy during phase II was much better than for phase I. Experiments described in this paper examine the effect of each of these changes, and show that each change contributed to the improvement.

  17. Artificial sweeteners as potential tracers of municipal landfill leachate.

    Science.gov (United States)

    Roy, James W; Van Stempvoort, Dale R; Bickerton, Greg

    2014-01-01

    Artificial sweeteners are gaining acceptance as tracers of human wastewater in the environment. The 3 artificial sweeteners analyzed in this study were detected in leachate or leachate-impacted groundwater at levels comparable to those of untreated wastewater at 14 of 15 municipal landfill sites tested, including several closed for >50 years. Saccharin was the dominant sweetener in old (pre-1990) landfills, while newer landfills were dominated by saccharin and acesulfame (introduced 2 decades ago; dominant in wastewater). Cyclamate was also detected, but less frequently. A case study at one site illustrates the use of artificial sweeteners to identify a landfill-impacted groundwater plume discharging to a stream. The study results suggest that artificial sweeteners can be useful tracers for current and legacy landfill contamination, with relative abundances of the sweeteners potentially providing diagnostic ability to distinguish different landfills or landfill cells, including crude age-dating, and to distinguish landfill and wastewater sources.

  18. Tracer Methods for Characterizing Fracture Creation in Engineered Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Rose, Peter [Energy & Geoscience Institute at the University of Utah, Salt Lake City, UT (United States); Harris, Joel [Univ. of Utah, Salt Lake City, UT (United States)

    2014-05-08

    The aim of this proposal is to develop, through novel high-temperature-tracing approaches, three technologies for characterizing fracture creation within Engineered Geothermal Systems (EGS). The objective of a first task is to identify, develop and demonstrate adsorbing tracers for characterizing interwell reservoir-rock surface areas and fracture spacing. The objective of a second task is to develop and demonstrate a methodology for measuring fracture surface areas adjacent to single wells. The objective of a third task is to design, fabricate and test an instrument that makes use of tracers for measuring fluid flow between newly created fractures and wellbores. In one method of deployment, it will be used to identify qualitatively which fractures were activated during a hydraulic stimulation experiment. In a second method of deployment, it will serve to measure quantitatively the rate of fluid flowing from one or more activated fracture during a production test following a hydraulic stimulation.

  19. Evaluation of anthropogenic secondary organic aerosol tracers from aromatic hydrocarbons

    Science.gov (United States)

    Al-Naiema, Ibrahim M.; Stone, Elizabeth A.

    2017-02-01

    Products of secondary organic aerosol (SOA) from aromatic volatile organic compounds (VOCs) - 2,3-dihydroxy-4-oxopentanoic acid, dicarboxylic acids, nitromonoaromatics, and furandiones - were evaluated for their potential to serve as anthropogenic SOA tracers with respect to their (1) ambient concentrations and detectability in PM2.5 in Iowa City, IA, USA; (2) gas-particle partitioning behaviour; and (3) source specificity by way of correlations with primary and secondary source tracers and literature review. A widely used tracer for toluene-derived SOA, 2,3-dihydroxy-4-oxopentanoic acid was only detected in the particle phase (Fp = 1) at low but consistently measurable ambient concentrations (averaging 0.3 ng m-3). Four aromatic dicarboxylic acids were detected at relatively higher concentrations (9.1-34.5 ng m-3), of which phthalic acid was the most abundant. Phthalic acid had a low particle-phase fraction (Fp = 0.26) likely due to quantitation interferences from phthalic anhydride, while 4-methylphthalic acid was predominantly in the particle phase (Fp = 0.82). Phthalic acid and 4-methylphthalic acid were both highly correlated with 2,3-dihydroxy-4-oxopentanoic acid (rs = 0.73, p = 0.003; rs = 0.80, p hydrocarbons; however the substantial partitioning toward the gas phase (Fp ≤ 0.16) and their water sensitivity limit their application as tracers. The outcome of this study is the demonstration that 2,3-dihydroxy-4-oxopentanoic acid, phthalic acid, 4-methylphthalic acid, and 4-hydroxy-3-nitrobenzyl alcohol are good candidates for tracing SOA from aromatic VOCs.

  20. nTRACER/COBRA-TF Coupling and Initial Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jaejin; Joo, Han Gyu [Seoul National University, Seoul (Korea, Republic of); Perin, Yann; Velkov, Kiril [GRS, Garching (Germany)

    2015-05-15

    The nTRACER direct whole core calculation code being developed at Seoul National University (SNU) has an internal T/H module to determine the temperature and density fields in the reactor. However, this module is based on a quite simplified model and considers only axial flow. The weakness of not-considering radial flow was overcome by coupling the MATRA (Multichannel Analysis for steady-state and Transient in Rod Array) code with nTRACER. MATRA can generate more realistic and detailed T/H field information for nTRACER, but it is a legacy code and does not have an efficient parallel computing capability. On the contrary, the COBRA-TF (Coolant-Boiling in Rod Arrays Two Fluids, CTF) subchannel code, which was developed for the T/H analysis of Light Water Reactor (LWR) vessels, has a good parallel computing capability based on the Message Passing Interface (MPI). The initial assessment of the coupled code demonstrates that more realistic coolant temperatures are obtainable by using CTF. The change in pin power distribution is noted with the realistic flow distribution even though the change is insignificant. The calculation utilizing the boron tracking model of CTF is noticeable. It makes possible for nTRACER to handle nonuniform boron distributions which can be encountered during some transients. Since further validation of the coupling is necessary, the coupling capabilities will be extended to transient applications where non-uniform distributions of inlet parameters such as boron concentration but also coolant temperature can occur.

  1. Design and Fabrication of a Prototype Tracer Surveillance Tester

    Science.gov (United States)

    1983-06-01

    problem with reproducibility and reliability at low spin rates. (6) The existing light sensor assembly and optico - electronic conditioning circuitry...is quite useful to redesign the light sensor assembly/ optico -electronic circuitry so as to obtain quantitative information on the actual intensity...pressurization/depressurization characteristics 31 of the combustion chamber 8a Oscilloscope trace of tracer RPM and light sensor output for 32 30,000

  2. A tracer bolus method for investigating glutamine kinetics in humans.

    Directory of Open Access Journals (Sweden)

    Maiko Mori

    Full Text Available Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control, 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control, and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control. In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide.

  3. PET and SPET tracers for mapping the cardiac nervous system

    Energy Technology Data Exchange (ETDEWEB)

    Langer, Oliver; Halldin, Christer [Department of Clinical Neuroscience, Psychiatry Section, Karolinska Institute, Karolinska Hospital, 17176 Stockholm (Sweden)

    2002-03-01

    The human cardiac nervous system consists of a sympathetic and a parasympathetic branch with (-)-norepinephrine and acetylcholine as the respective endogenous neurotransmitters. Dysfunction of the cardiac nervous system is implicated in various types of cardiac disease, such as heart failure, myocardial infarction and diabetic autonomic neuropathy. In vivo assessment of the distribution and function of cardiac sympathetic and parasympathetic neurones with positron emission tomography (PET) and single-photon emission tomography (SPET) can be achieved by means of a number of carbon-11-, fluorine-18-, bromine-76- and iodine-123-labelled tracer molecules. Available tracers for mapping sympathetic neurones can be divided into radiolabelled catecholamines, such as 6-[{sup 18}F]fluorodopamine, (-)-6-[{sup 18}F]fluoronorepinephrine and (-)-[{sup 11}C]epinephrine, and radiolabelled catecholamine analogues, such as [{sup 123}I]meta-iodobenzylguanidine, [{sup 11}C]meta-hydroxyephedrine, [{sup 18}F]fluorometaraminol, [{sup 11}C]phenylephrine and meta-[{sup 76}Br]bromobenzylguanidine. Resistance to metabolism by monoamine oxidase and catechol-O-methyl transferase simplifies the myocardial kinetics of the second group. Both groups of compounds are excellent agents for an overall assessment of sympathetic innervation. Biomathematical modelling of tracer kinetics is complicated by the complexity of the steps governing neuronal uptake, retention and release of these agents as well as by their high neuronal affinity, which leads to partial flow dependence of uptake. Mapping of cardiac parasympathetic neurones is limited by a low density and focal distribution pattern of these neurones in myocardium. Available tracers are derivatives of vesamicol, a molecule that binds to a receptor associated with the vesicular acetylcholine transporter. Compounds like (-)-[{sup 18}F]fluoroethoxybenzovesamicol display a high degree of non-specific binding in myocardium which restricts their utility

  4. Thermal tracer tomography: from numerical simulation to field implementation

    Science.gov (United States)

    Somogyvári, Márk; Brauchler, Ralf; Bayer, Peter

    2016-04-01

    Choosing heat for subsurface investigations is attractive because changes in temperature can be easily measured, and natural variations are typically slower than the timescale of the experiments. The tomographical setup expands the applicability of such tests to reconstruct the spatial distribution of hydraulic aquifer properties. A new inversion methodology is presented for thermal tracer tomography, using tracer travel times to invert the hydraulic conductivity distribution of the aquifer. If we can assume that heat transport is driven by advection, the travel time of the thermal tracer can be related to the hydraulic parameters of the aquifer. With this assumption other thermal effects such as thermal diffusion or density driven flow appear as noise in the results. To reduce these effects the early time diagnostics of the recorded breakthrough curves are used, focusing on the fastest transport routes between the sources and receivers. The inverse problem of the experiment thus can be formulated as a classical travel time problem, and it can be solved using standard eikonal solver algorithms known from seismic or hydraulic tomography. The method is demonstrated with a high resolution 3-D aquifer analog dataset. The generated 3-D reconstruction reveals the potential of the method, especially in finding the preferential flow paths within the aquifer. Aside from this, the developed method is computationally efficient and can provide results in a fragment of the time required for full-physics model calibration. The method is also tested under field conditions. Four heat tracer injections were performed during a three day field campaign at the Widen field site in northeast Switzerland. Pulse signals were used and the temperature evolution was measured downstream using a distributed measurement system. The preliminary results of the tomographic inversion correspond well with the findings of earlier studies from the field site imaging the same geological features as

  5. Bromide as a tracer for studying water movement and nitrate displacement in soils: comparison with stable isotope tracers; Bromid als Tracer zur Untersuchung der Wasserbewegung und der Nitratverlagerung in Boeden: Vergleich mit stabilisotopen Tracern

    Energy Technology Data Exchange (ETDEWEB)

    Russow, R.; Knappe, S. [UFZ - Umweltforschungszentrum Leipzig-Halle GmbH, Bad Lauchstaedt (Germany). Sektion Bodenforschung

    1999-02-01

    Tracers are an ideal means of studying water movement and associated nitrate displacement. Often bromide is preferred as a tracer because it is considered a representative tracer for water and because, being a conservative tracer (i.e. not involved in chemical and biological soil processes), it can be used for studying anion transport in soils. Moreover, it is less expensive and easier to measure than the stable isotopes deuterium and {sup 15}N. Its great advantage over radioactive tracers (e.g. tritium), which outweighs their extreme sensitivity and ease of measurement and which it has in common with stable isotopes, is that it does not require radiation protection measures. However, there are also constraints on the use of bromide as a tracer in soil/water/plant systems. Our own studies on different soils using D{sub 2}O, bromide and [{sup 15}N]-nitrate in lysimeters suggest that the above assumptions on bromide tracers need not always be valid under conditions as they prevail in biologically active soils. As the present paper shows, these studies permit a good assessment of the possibilities and limits to these tracers. [Deutsch] Fuer die Untersuchung der Wasserbewegung sowie der daran gekoppelten Nitrat-Verlagerung ist der Einsatz von Tracern das Mittel der Wahl. Dabei wird Bromid als Tracer haeufig bevorzugt, da es allgemein als ein repraesentativer Tracer fuer Wasser und als konservativer Tracer (nicht involviert in chemische und biologische Bodenprozesse) zur Untersuchung des Anionentransportes in Boeden angesehen wird und es gegenueber den stabilen Isotopen Deuterium und {sup 15}N billiger und einfacher zu bestimmen ist. Gegenueber den radioaktiven Tracern (z.B. Tritium), die zwar sehr empfindlich und einfach messbar sind, besteht der grosse Vorteil, dass, wie bei den stabilen Isotopen, keine Strahlenschutzmassnahmen ergriffen werden muessen. Es gibt jedoch auch einschraenkende Hinweise fuer die Verwendung von Bromid als Tracer im System Boden

  6. Numerical evaluation of the PERTH (PERiodic Tracer Hierarchy) method for estimating time-variable travel time distribution in variably saturated soils

    Science.gov (United States)

    Kim, M.; Harman, C. J.

    2013-12-01

    -tracking model. HYDRUS-1D was used to solve Richards' equation and the advection-dispersion equation for ideal tracers introduced at different points during an irrigation event in a ';virtual experiment', and the PERTH method was used to extract the time-variable transit time distribution. The 1D particle-tracking model was developed to simulate particle trajectories using the Fokker-Plank-Ito scheme based on the saturation and water flux fields estimated by HYDRUS-1D. The results of the particle-tracking model estimate the ';true' travel time distribution and allow us to validate the result of PERTH. The result reveals that the PERTH method well approximates the simulated time-variable travel time distribution on plot scale. Also, the key assumption of PERTH method was supported in this case. In addition, this research further suggests an optimal way to configure the tracer hierarchy of PERTH in complex flow experiments. The numerical analysis of this study demonstrates that the PERTH method may be a useful method for obtaining experimental observations of time-variable travel time distributions in well-controlled environments where periodic forcing conditions can be set.

  7. Application of separable parameter space techniques to multi-tracer PET compartment modeling

    Science.gov (United States)

    Zhang, Jeff L.; Morey, A. Michael; Kadrmas, Dan J.

    2016-02-01

    Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg-Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models.

  8. Radioisotope tracer study in a sludge hygienization research irradiator (SHRI).

    Science.gov (United States)

    Pant, H J; Thýn, J; Zitný, R; Bhatt, B C

    2001-01-01

    A radioisotope tracer study has been carried out in a batch type sludge hygienization research irradiator with flow from top to bottom, the objective being to measure flow rate, circulation and mixing times and to investigate the hydrodynamic behaviour of the irradiator for identifying the cause(s) of malfunction. A stimulus-response technique with NH4(82)Br as a tracer was used to measure the above parameters. Experiments were carried out at three different flow rates, i.e 1.0, 0.64 and 0.33 m3/min. Three combined models based on a set of differential equations are proposed and used to simulate the measured tracer concentration curves. The obtained parameters were used to estimate dead volume and analyse hydrodynamic behaviour of the irradiator. The nonlinear regression problem of model parameter estimation was solved using the Marquardt-Levenberg method. The measured flow rate was found to be in good agreement with the values shown by the flow meter. The circulation times were found to be half of the mixing times. A simple approach for estimation of dose based on a known vertical dose-rate profile inside the irradiator is presented. About one-fourth of the volume of the irradiator was found to be dead at lower flow rates and this decreased with increase in flow rate. At higher flow rates, a semi stagnant volume was found with slow exchange of flow between the active and dead volumes.

  9. Radioisotope tracer study in a sludge hygienization research irradiator (SHRI)

    Energy Technology Data Exchange (ETDEWEB)

    Pant, H.J. E-mail: hjpant@aspsara.barc.ernet.in; Thyn, J.; Zitny, R.; Bhatt, B.C

    2001-01-15

    A radioisotope tracer study has been carried out in a batch type sludge hygienization research irradiator with flow from top to bottom, the objective being to measure flow rate, circulation and mixing times and to investigate the hydrodynamic behaviour of the irradiator for identifying the cause(s) of malfunction. A stimulus-response technique with NH{sup 82}{sub 4}Br as a tracer was used to measure the above parameters. Experiments were carried out at three different flow rates, i.e 1.0, 0.64 and 0.33 m{sup 3}/min. Three combined models based on a set of differential equations are proposed and used to simulate the measured tracer concentration curves. The obtained parameters were used to estimate dead volume and analyse hydrodynamic behaviour of the irradiator. The nonlinear regression problem of model parameter estimation was solved using the Marquardt-Levenberg method. The measured flow rate was found to be in good agreement with the values shown by the flow meter. The circulation times were found to be half of the mixing times. A simple approach for estimation of dose based on a known vertical dose-rate profile inside the irradiator is presented. About one-fourth of the volume of the irradiator was found to be dead at lower flow rates and this decreased with increase in flow rate. At higher flow rates, a semi stagnant volume was found with slow exchange of flow between the active and dead volumes.

  10. Using atmospheric tracers to reduce uncertainty in groundwater recharge areas.

    Science.gov (United States)

    Starn, J Jeffrey; Bagtzoglou, Amvrossios C; Robbins, Gary A

    2010-01-01

    A Monte Carlo-based approach to assess uncertainty in recharge areas shows that incorporation of atmospheric tracer observations (in this case, tritium concentration) and prior information on model parameters leads to more precise predictions of recharge areas. Variance-covariance matrices, from model calibration and calculation of sensitivities, were used to generate parameter sets that account for parameter correlation and uncertainty. Constraining parameter sets to those that met acceptance criteria, which included a standard error criterion, did not appear to bias model results. Although the addition of atmospheric tracer observations and prior information produced similar changes in the extent of predicted recharge areas, prior information had the effect of increasing probabilities within the recharge area to a greater extent than atmospheric tracer observations. Uncertainty in the recharge area propagates into predictions that directly affect water quality, such as land cover in the recharge area associated with a well and the residence time associated with the well. Assessments of well vulnerability that depend on these factors should include an assessment of model parameter uncertainty. A formal simulation of parameter uncertainty can be used to delineate probabilistic recharge areas, and the results can be expressed in ways that can be useful to water-resource managers. Although no one model is the correct model, the results of multiple models can be evaluated in terms of the decision being made and the probability of a given outcome from each model.

  11. Radon as tracer to identify discharge sections at Juatuba basin

    Energy Technology Data Exchange (ETDEWEB)

    Chagas, Claudio Jose; Ferreira, Vinicius Verna Magalhaes; Fonseca, Raquel Luisa Mageste; Rocha, Zildete; Moreira, Rubens Martins; Lemos, Nayron Cosme; Menezes, Angela de Barros Correia, E-mail: vvmf@cdtn.br, E-mail: rlmf@cdtn.br, E-mail: cjc@cdtn.br, E-mail: rochaz@cdtn.br, E-mail: rubens@cdtn.br, E-mail: menezes@cdtn.br, E-mail: lemosnc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Santos, Talita Oliveira, E-mail: talitaolsantos@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Escola de Engenharia. Departamento de Engenharia Nuclear. Programa de Pos-Graduacao em Ciencias e Tecnicas Nucleares

    2015-07-01

    The use of natural tracers in hydrological studies is a very useful tool, being applied in several studies. One of these tracers is the radon, {sup 222}Rn, noble gas derived from natural sources, been found in all underground waters, as a product of radioactive decay of the {sup 226}Ra. This gas can be found in the air, water, rocks or soil. In this paper, the {sup 222}Rn detection in surface water was used as tracer in order to identify aquifer discharge sections in surface water at the Fundao stream, which belongs to the Juatuba river basin, through the second semester of 2014 and the first semester of 2015, in three sampling campaigns. The {sup 222}Rn measurements at Fundao stream were carried out using the equipment RAD 7. The results showed that {sup 222}Rn is present in some sections of the water course suggesting that there is a connection between groundwater and surface water. It also justifies the variation in the water level in the stream, recorded by a fluviometric station. (author)

  12. A galaxy-halo model for multiple cosmological tracers

    Science.gov (United States)

    Bull, Philip

    2017-10-01

    The information extracted from large galaxy surveys with the likes of DES, DESI, Euclid, LSST, SKA, and WFIRST will be greatly enhanced if the resultant galaxy catalogues can be cross-correlated with one another. Predicting the nature of the information gain, and developing the tools to realize it, depends on establishing a consistent model of how the galaxies detected by each survey trace the same underlying matter distribution. Existing analytic methods, such as halo occupation distribution modelling, are not well suited for this task, and can suffer from ambiguities and tuning issues when applied to multiple tracers. In this paper, we take the first step towards constructing an alternative that provides a common model for the connection between galaxies and dark matter haloes across a wide range of wavelengths (and thus tracer populations). This is based on a chain of parametrized statistical distributions that model the connection between (i) halo mass and bulk physical properties of galaxies, such as star formation rate; and (ii) those same physical properties and a variety of emission processes. The result is a flexible parametric model that allows analytic halo model calculations of one-point functions to be carried out for multiple tracers, as well as providing semi realistic galaxy properties for fast mock catalogue generation.

  13. Consistency Problem with Tracer Advection in the Atmospheric Model GAMIL

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai; WAN Hui; WANG Bin; ZHANG Meigen

    2008-01-01

    The radon transport test,which is a widely used test case for atmospheric transport models,is carried out to evaluate the tracer advection schemes in the Grid-Point Atmospheric Model of IAP-LASG (GAMIL).TWO of the three available schemes in the model are found to be associated with significant biases in the polar regions and in the upper part of the atmosphere,which implies potentially large errors in the simulation of ozone-like tracers.Theoretical analyses show that inconsistency exists between the advection schemes and the discrete continuity equation in the dynamical core of GAMIL and consequently leads to spurious sources and sinks in the tracer transport equation.The impact of this type of inconsistency is demonstrated by idealized tests and identified as the cause of the aforementioned biases.Other potential effects of this inconsistency are also discussed.Results of this study provide some hints for choosing suitable advection schemes in the GAMIL model.At least for the polar-region-concentrated atmospheric components and the closely correlated chemical species,the Flux-Form Semi-Lagrangian advection scheme produces more reasonable simulations of the large-scale transport processes without significantly increasing the computational expense.

  14. Metal stable isotope signatures as tracers in environmental geochemistry.

    Science.gov (United States)

    Wiederhold, Jan G

    2015-03-03

    The biogeochemical cycling of metals in natural systems is often accompanied by stable isotope fractionation which can now be measured due to recent analytical advances. In consequence, a new research field has emerged over the last two decades, complementing the traditional stable isotope systems (H, C, O, N, S) with many more elements across the periodic table (Li, B, Mg, Si, Cl, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Ge, Se, Br, Sr, Mo, Ag, Cd, Sn, Sb, Te, Ba, W, Pt, Hg, Tl, U) which are being explored and potentially applicable as novel geochemical tracers. This review presents the application of metal stable isotopes as source and process tracers in environmental studies, in particular by using mixing and Rayleigh model approaches. The most important concepts of mass-dependent and mass-independent metal stable isotope fractionation are introduced, and the extent of natural isotopic variations for different elements is compared. A particular focus lies on a discussion of processes (redox transformations, complexation, sorption, precipitation, dissolution, evaporation, diffusion, biological cycling) which are able to induce metal stable isotope fractionation in environmental systems. Additionally, the usefulness and limitations of metal stable isotope signatures as tracers in environmental geochemistry are discussed and future perspectives presented.

  15. Methane emission quantification from landfills using a double tracer approach

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Samuelsson, J.; Fredenslund, Anders Michael

    2007-01-01

    in the October respectively February measurement. The CH4 emission from the compost area was 0.5 kg CH4 h-1, whereas the carbon dioxide (CO2) flux and nitrous oxide (N2O) was quantified to be in the order of 332 kg CO2 h-1 and 0.06 kg N2O h-1 respectively. The sludge pit located west of the compost material......A tracer method was successfully used for quantification of the whole methane (CH4) emission from Fakse landfill. By using two different tracers the emission from different sections of the landfill could be quantified. Furthermore, is was possible to determine the emissions from local on site...... sources; a composting facility and a sewage sludge storage unit by scaling the tracer method down. Two field campaigns were performed; during October 11-12, 2006 and February 19-20, 2007. At both field campaigns an overall leak search showed that the CH4 emission from the old landfill section...

  16. Lattice-Boltzmann Simulations of Microswimmer-Tracer Interactions

    CERN Document Server

    de Graaf, Joost

    2016-01-01

    Hydrodynamic interactions in systems comprised of self-propelled particles, such as swimming microorganisms, and passive tracers have a significant impact on the tracer dynamics compared to the equivalent "dry" sample. However, such interactions are often difficult to take into account in simulations due to their computational cost. Here, we perform a systematic investigation of swimmer-tracer interaction using an efficient force/counter-force based lattice-Boltzmann (LB) algorithm [J. de Graaf~\\textit{et al.}, J. Chem. Phys.~\\textbf{144}, 134106 (2016)], in order to validate its applicability to study large-scale microswimmer suspensions. We show that the LB algorithm reproduces far-field theoretical results well, both in a system with periodic boundary conditions and in a spherical cavity with no-slip walls, for which we derive expressions here. The LB algorithm has an inherent near-field renormalization of the flow field, due to the force interpolation between the swimmers and the lattice. This strongly pe...

  17. Application of transition metal isotope tracers in global change research

    Institute of Scientific and Technical Information of China (English)

    SONG Jinming; Thomas F. Pedersen

    2005-01-01

    High-precision isotope composition determinations using multicollector, magnetic-sector inductively coupled plasma mass spectrometry (MC-ICPMS) have recently revealed that some transition metal isotopes such as those of Mo, Fe, Cu, Zn etc. can be used as biogeochemical tracers in global change research.The Mo isotope system may be useful in paleoredox investigations indicating that δ 97/95Mo in seawater may co-vary with changes in the relative proportions of anoxic and oxic sedimentation in the ocean, and that this variation may be recorded in δ 97/95Mo of anoxic sediments. The Mo continental flux into the oceans and the global Mo isotope budget can be estimated fromδ 97/95MO values. The Fe isotope composition in seawater is an important issue because Fe plays a controlling role in biological productivity in the oceans and its abundance in seawater may have substantial effect on climate changes. Iron isotope fractionations could result from bio- and abio-processes and have about 0.1% variation (δ 56/54Fe), so Fe isotopes considered alone cannot be used to distinguish the products of abiotic and biotic Fe processing in geological records. Cu and Zn isotopes are also used as biogeochemical tracers, but the researches are relatively less. This review mainly focuses on the methods for preparation, purification and determination of new isotope tracer samples, and on isotope applications in marine environmental changes.

  18. Cosmological constraints from multiple tracers in spectroscopic surveys

    CERN Document Server

    Alarcon, Alex; Gaztañaga, Enrique

    2016-01-01

    We use the Fisher matrix formalism to study the expansion and growth history of the Universe using galaxy clustering with 2D angular cross-correlation tomography in spectroscopic or high resolution photometric redshift surveys. The radial information is contained in the cross correlations between narrow redshift bins. We show how multiple tracers with redshift space distortions cancel sample variance and arbitrarily improve the constraints on the dark energy equation of state $\\omega(z)$ and the growth parameter $\\gamma$ in the noiseless limit. The improvement for multiple tracers quickly increases with the bias difference between the tracers, up to a factor $\\sim4$ in $\\text{FoM}_{\\gamma\\omega}$. We model a magnitude limited survey with realistic density and bias using a conditional luminosity function, finding a factor 1.3-9.0 improvement in $\\text{FoM}_{\\gamma\\omega}$ -- depending on global density -- with a split in a halo mass proxy. Partly overlapping redshift bins improve the constraints in multiple tr...

  19. Dispersion Rates of Gravel Sizes in a Natural Channel

    Science.gov (United States)

    Haschenburger, J. K.

    2011-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. Few studies are available to inform on the streamwise rate of gravel dispersion in natural channels, especially over a longer time scale. This research uses a gravel tracing program to quantify both the mean and maximum rates of different size fractions over 17 flood seasons. Empirical observations were collected in Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. An average of 15 ± 5 floods per year facilitates frequent streambed activity and relatively high bed material transport rates, typically under partial sediment transport conditions. About 2000 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1991 and 1992. Streamwise dispersion rates were quantified for the eight size fractions as virtual velocities based on 11 tracer recoveries completed between 1991 and 2008. Maximum velocities were calculated using the 10 largest values for each fraction. During the study period 258 floods capable of moving bedload occurred, with two exceeding the estimated bankfull discharge. The hydrological forcing driving the dispersion process was quantified by expended flow energy. Fractional virtual velocities as a function of flow energy are fairly well described by power functions. In absolute terms, finer gravels have higher rates of dispersion than coarser gravels as expected. A slowdown in mean velocities over time occurs more quickly with finer gravels; function exponents range from -0.2 to -0.5. Maximum velocities adjusted more quickly than mean values, with function exponents spanning from -0.4 to -0.8. These grain size differences contribute to the streamwise sorting of bed material.

  20. Dynamical mass modeling of dispersion-supported dwarf galaxies

    Science.gov (United States)

    Wolf, Joseph

    The currently favored cold dark matter cosmology (LCDM) has had much success in reproducing the large scale structure of the universe. However, on smaller scales there are some possible discrepancies when attempting to match galactic observations with properties of halos in dissipationless LCDM simulations. One advantageous method to test small scale simulations with observations is through dynamical mass modeling of nearby dwarf spheroidal galaxies (dSphs). The stellar tracers of dSphs are dispersion-supported, which poses a significant challenge in accurately deriving mass profiles. Unlike rotationally-supported galaxies, the dynamics of which can be well-approximated by one-dimensional physics, modeling dispersion-supported systems given only line-of-sight data results in a well-known degeneracy between the mass profile and the velocity dispersion anisotropy. The core of this dissertation is rooted in a new advancement which we have discovered: the range of solutions allowed by the mass-anisotropy degeneracy varies as a function of radius, with a considerable minimal near the deprojected half-light radius of almost all observed dispersion-supported galaxies. This finding allows for a wide range of applications in galaxy formation scenarios to be explored in an attempt to address, amongst other hypotheses, whether the LCDM framework needs to be modified in order to reproduce observations on the small scale. This thesis is comprised of both the derivation of this finding, and its applicability to all dispersion-supported systems, ranging from dwarfs galaxies consisting of a few hundred stars to systems of 'intracluster light', containing over a trillion stars. Rarely does one have the privilege of working with systems that span such a large range in luminosity (or any intrinsic property) in a short graduate career. Although the large applicability of this scale-free finding allows for discussion in many subfields, this thesis will mainly focus on one topic: dwarf

  1. Entropically induced asymmetric passage times of charged tracers across corrugated channels

    Energy Technology Data Exchange (ETDEWEB)

    Malgaretti, Paolo, E-mail: malgaretti@is.mpg.de [Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart (Germany); IV Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart (Germany); Department de Fisica Fonamental, Universitat de Barcelona, Barcelona (Spain); Pagonabarraga, Ignacio; Miguel Rubi, J. [Department de Fisica Fonamental, Universitat de Barcelona, Barcelona (Spain)

    2016-01-21

    We analyze the diffusion of charged and neutral tracers suspended in an electrolyte embedded in a channel of varying cross section. Making use of systematic approximations, the diffusion equation governing the motion of tracers is mapped into an effective 1D equation describing the dynamics along the longitudinal axis of the channel where its varying-section is encoded as an effective entropic potential. This simplified approach allows us to characterize tracer diffusion under generic confinement by measuring their mean first passage time (MFPT). In particular, we show that the interplay between geometrical confinement and electrostatic interactions strongly affect the MFTP of tracers across corrugated channels hence leading to alternative means to control tracers translocation across charged pores. Finally, our results show that the MFPTs of a charged tracer in opposite directions along an asymmetric channel may differ We expect our results to be relevant for biological as well synthetic devices whose dynamics is controlled by the detection of diluted tracers.

  2. Entropically induced asymmetric passage times of charged tracers across corrugated channels.

    Science.gov (United States)

    Malgaretti, Paolo; Pagonabarraga, Ignacio; Rubi, J Miguel

    2016-01-21

    We analyze the diffusion of charged and neutral tracers suspended in an electrolyte embedded in a channel of varying cross section. Making use of systematic approximations, the diffusion equation governing the motion of tracers is mapped into an effective 1D equation describing the dynamics along the longitudinal axis of the channel where its varying-section is encoded as an effective entropic potential. This simplified approach allows us to characterize tracer diffusion under generic confinement by measuring their mean first passage time (MFPT). In particular, we show that the interplay between geometrical confinement and electrostatic interactions strongly affect the MFTP of tracers across corrugated channels hence leading to alternative means to control tracers translocation across charged pores. Finally, our results show that the MFPTs of a charged tracer in opposite directions along an asymmetric channel may differ We expect our results to be relevant for biological as well synthetic devices whose dynamics is controlled by the detection of diluted tracers.

  3. In-Situ Characterization of Dense Non-Aqueous Phase Liquids Using Partitioning Tracers

    Energy Technology Data Exchange (ETDEWEB)

    Gary A. Pope; Daene C. McKinney; Akhil Datta Gupta; Richard E. Jackson; Minquan Jin

    2000-03-20

    Majors advances have been made during the past three years in our research on interwell partitioning tracers tests (PITTs). These advances include (1) progress on the inverse problem of how to estimate the three-dimensional distribution of NAPL in aquifers from the tracer data, (2) the first ever partitioning tracer experiments in dual porosity media, (3) the first modeling of partitioning tracers in dual porosity media (4) experiments with complex NAPLs such as coal tar, (5) the development of an accurate and simple method to predict partition coefficients using the equivalent alkane carbon number approach, (6) partitioning tracer experiments in large model aquifers with permeability layers, (7) the first ever analysis of partitioning tracer data to estimate the change in composition of a NAPL before and after remediation (8) the first ever analysis of partitioning tracer data after a field demonstration of surfactant foam to remediate NAPL and (9) experiments at elevated temperatures .

  4. Determining the dispersion characteristics of rivers from the frequency response of the system

    Science.gov (United States)

    Lambertz, Peter; Palancar, MaríA. C.; Aragón, José M.; Gil, Roberto

    2006-09-01

    A new method of determining the parameters of an aggregated dead zone model (ADZ) to predict longitudinal dispersion in rivers is presented. The method is based on the frequency response analysis (FRA) of observed field tests, which consist of tracer injections (input) and measurement of tracer in downstream sampling points (output) located downstream from the injection point. The ADZ is a combination of plug and completely mixed flow compartments. The ADZ parameters (number of compartments, mean residence time, and delay time) are evaluated by means of Bode plots that give the system order (number of compartments), gain, time constant (mean residence time of each compartment) and delay time. The FRA-ADZ method was checked with tracer data runs in two Spanish rivers, the Tagus and the Ebro rivers. The experimental tracer concentration versus time distributions were compared with the ADZ predicted curves, which were calculated using parameters obtained from the FRA method, and with curves predicted by several classical models. The residence time of several reaches within the two studied rivers was predicted by the FRA-ADZ method with a relative error lower than 10%. The method is generally applicable to ideal and nonideal inputs and is particularly well suited to arbitrary-shaped initial source concentration distributions.

  5. Anomalous transport in disordered fracture networks: Spatial Markov model for dispersion with variable injection modes

    Science.gov (United States)

    Kang, Peter K.; Dentz, Marco; Le Borgne, Tanguy; Lee, Seunghak; Juanes, Ruben

    2017-08-01

    We investigate tracer transport on random discrete fracture networks that are characterized by the statistics of the fracture geometry and hydraulic conductivity. While it is well known that tracer transport through fractured media can be anomalous and particle injection modes can have major impact on dispersion, the incorporation of injection modes into effective transport modeling has remained an open issue. The fundamental reason behind this challenge is that-even if the Eulerian fluid velocity is steady-the Lagrangian velocity distribution experienced by tracer particles evolves with time from its initial distribution, which is dictated by the injection mode, to a stationary velocity distribution. We quantify this evolution by a Markov model for particle velocities that are equidistantly sampled along trajectories. This stochastic approach allows for the systematic incorporation of the initial velocity distribution and quantifies the interplay between velocity distribution and spatial and temporal correlation. The proposed spatial Markov model is characterized by the initial velocity distribution, which is determined by the particle injection mode, the stationary Lagrangian velocity distribution, which is derived from the Eulerian velocity distribution, and the spatial velocity correlation length, which is related to the characteristic fracture length. This effective model leads to a time-domain random walk for the evolution of particle positions and velocities, whose joint distribution follows a Boltzmann equation. Finally, we demonstrate that the proposed model can successfully predict anomalous transport through discrete fracture networks with different levels of heterogeneity and arbitrary tracer injection modes.

  6. Multiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory

    Science.gov (United States)

    Scudeler, Carlotta; Pangle, Luke; Pasetto, Damiano; Niu, Guo-Yue; Volkmann, Till; Paniconi, Claudio; Putti, Mario; Troch, Peter

    2016-10-01

    This paper explores the challenges of model parameterization and process representation when simulating multiple hydrologic responses from a highly controlled unsaturated flow and transport experiment with a physically based model. The experiment, conducted at the Landscape Evolution Observatory (LEO), involved alternate injections of water and deuterium-enriched water into an initially very dry hillslope. The multivariate observations included point measures of water content and tracer concentration in the soil, total storage within the hillslope, and integrated fluxes of water and tracer through the seepage face. The simulations were performed with a three-dimensional finite element model that solves the Richards and advection-dispersion equations. Integrated flow, integrated transport, distributed flow, and distributed transport responses were successively analyzed, with parameterization choices at each step supported by standard model performance metrics. In the first steps of our analysis, where seepage face flow, water storage, and average concentration at the seepage face were the target responses, an adequate match between measured and simulated variables was obtained using a simple parameterization consistent with that from a prior flow-only experiment at LEO. When passing to the distributed responses, it was necessary to introduce complexity to additional soil hydraulic parameters to obtain an adequate match for the point-scale flow response. This also improved the match against point measures of tracer concentration, although model performance here was considerably poorer. This suggests that still greater complexity is needed in the model parameterization, or that there may be gaps in process representation for simulating solute transport phenomena in very dry soils.

  7. GA-based dynamical correction of dispersion coefficients in Lagrangian puff model

    Institute of Scientific and Technical Information of China (English)

    马元巍; 王德忠; 吉志龙

    2015-01-01

    In atmospheric dispersion models of nuclear accident, the dispersion coefficients were usually obtained by tracer experiment, which are constant in different atmospheric stability classifications. In fact, the atmospheric wind field is complex and unstable. The dispersion coefficients change even in the same atmospheric stability, hence the great errors brought in. According to the regulation, the air concentration of nuclides around nuclear power plant should be monitored during an accident. The monitoring data can be used to correct dispersion coefficients dynamically. The error can be minimized by correcting the coefficients. This reverse problem is nonlinear and sensitive to initial value. The property of searching the optimal solution of Genetic Algorithm (GA) is suitable for complex high-dimensional situation. In this paper, coupling with Lagrange dispersion model, GA is used to estimate the coefficients. The simulation results show that GA scheme performs well when the error is big. When the correcting process is used in the experiment data, the GA-estimated results are numerical instable. The success rate of estimation is 5%lower than the one without correction. Taking into account the continuity of the dispersion coefficient, Savitzky-Golay filter is used to smooth the estimated parameters. The success rate of estimation increases to 75.86%. This method can improve the accuracy of atmospheric dispersion simulation.

  8. QT dispersion and P wave dispersion in patients with fibromyalgia.

    Science.gov (United States)

    Yolbaş, Servet; Yıldırım, Ahmet; Düzenci, Deccane; Karakaya, Bülent; Dağlı, Mustafa Necati; Koca, Süleyman Serdar

    2016-12-01

    Fibromyalgia (FM) is a chronic disease characterized by widespread pain. Somatic complaints associated with the cardiovascular system, such as chest pain and palpitations, are frequently seen in FM patients. P and QT dispersions are simple and inexpensive measurements reflecting the regional heterogeneity of atrial and ventricular repolarization, respectively. QT dispersion can cause serious ventricular arrhythmias. The aim of the present study was to evaluate QT dispersion and P wave dispersion in patients with FM. The study involved 48 FM patients who fulfilled the established criteria and 32 healthy controls (HC). A standard 12-lead electrocardiogram was performed on all participants. QT dispersion was defined as the difference between the longest and the shortest QT intervals. Similarly, the differences between the shortest and longest P waves were defined as P wave dispersion. The QT dispersion and corrected QT dispersion were shorter in the FM group compared with the HC group (pdispersion value, there was no significant difference between the FM and HC groups (p=0.088). Longer QT and P wave dispersions are not problems in patients with FM. Therefore, it may be concluded that fibromyalgia does not include an increased risk of atrial and/or ventricular arrhythmias.

  9. Quantifying inflow uncertainties in RANS simulations of urban pollutant dispersion

    Science.gov (United States)

    García-Sánchez, C.; Van Tendeloo, G.; Gorlé, C.

    2017-07-01

    Numerical simulations of flow and pollutant dispersion in urban environments have the potential to support design and policy decisions that could reduce the population's exposure to air pollution. Reynolds-averaged Navier-Stokes simulations are a common modeling technique for urban flow and dispersion, but several sources of uncertainty in the simulations can affect the accuracy of the results. The present study proposes a method to quantify the uncertainty related to variability in the inflow boundary conditions. The method is applied to predict flow and pollutant dispersion in downtown Oklahoma City and the results are compared to field measurements available from the Joint Urban 2003 measurement campaign. Three uncertain parameters that define the inflow profiles for velocity, turbulence kinetic energy and turbulence dissipation are defined: the velocity magnitude and direction, and the terrain roughness length. The uncertain parameter space is defined based on the available measurement data, and a non-intrusive propagation approach that employs 729 simulations is used to quantify the uncertainty in the simulation output. A variance based sensitivity analysis is performed to identify the most influential uncertain parameters, and it is shown that the predicted tracer concentrations are influenced by all three uncertain variables. Subsequently, we specify different probability distributions for the uncertain inflow variables based on the available measurement data and calculate the corresponding means and 95% confidence intervals for comparison with the field measurements at 35 locations in downtown Oklahoma City.

  10. Quantification of dispersed phase concentration using light sheet imaging methods

    Science.gov (United States)

    Knowles, Philip L.; Kiger, Ken T.

    2012-03-01

    With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of spurious "cross-talk," an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more if a single-point measure of the sheet width is used.

  11. SMED - Sulphur MEditerranean Dispersion

    Science.gov (United States)

    Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

    2016-04-01

    Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model

  12. Simulation of radionuclide dispersion in the Pacific Ocean from Mururoa Atoll

    Energy Technology Data Exchange (ETDEWEB)

    Lazar, A. [Laboratoire d' Oceanographie Dynamique et de Climatologie, Unite Mixte de Recherche CNRS-ORSTOM-UPMC, Universite Pierre et Marie Curie, Paris (France); Rancher, J. [CEA/DAM/DSR/DTDS/SARI, BP 12, 91680 Bruyeres-le-Chatel (France)

    1999-04-01

    A series of numerical simulations was carried out to evaluate, on a Tropical South Pacific scale, the consequences over 10 yr of radionuclide releases to the ocean from French Polynesian nuclear test sites. Tracer advection and diffusion terms were computed based on a dispersion model using ocean dynamics and turbulent mixing coefficients derived from an Ocean General Circulation Model on the basis of a yearly climatological average. Preliminary experiments demonstrated sensitivity of the results to injection depth and type. Two instant unit releases were then carried out at the model characteristic depths of 5 and 364 m: maximum concentrations decrease by factors of more than 10{sup 4} and 10{sup 3}, respectively, over 10 yr. Temporal evolution tables for concentrations are given and can be applied to any given quantity of tracer introduced from Mururoa atoll into the Pacific Ocean. Taken as a whole, our results present, from qualitative and quantitative viewpoints, different dispersion scenarios as a function of release characteristics. Finally, a comparison with the surface release study by Ribbe and Tomczak (1990) shows that, while the order of magnitude of tracer concentrations is comparable, the direction of propagation is significantly different. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  13. Thermal convection and species dispersion in tilted tubes embedded in rocks

    Science.gov (United States)

    Sánchez, F.; Medina, A.; Higuera, F. J.

    2004-11-01

    This work is intended for getting a better knowledge about the role that fractures play in the transport of passive substances in the geophysical context (diagenesis and dispersion of contaminants are phenomena tight related). The thermal convection and the transport of an ideal tracer in a single, tilted, small aspect ratio tube embedded in an impermeable rock were studied. The fluid-filled tube and the tube filled with a saturated porous medium were analyzed. The impervious rock is affected by a constant vertical temperature gradient and its thermal conductivity is large respect to that of the flow zone. Closed-form analytical solutions, restricted to small Rayleigh numbers, were obtained for the temperature in the solid and for velocity and temperature within the flow zones. Experiments for the fluid-filled tube showed good agreement. The temperature distribution in the solid was measured by an infrared camera and by the PIV technique the convective velocity field was estimated. Theoretical velocity fields were included in a numerical analysis of dispersion of an ideal tracer which was initially on a small area located on the tube's wall. How far the tracer travels through the tube and the rate it enters to the system were found to be strongly affected by the convective flows.

  14. Amplified Dispersive Optical Tomography

    CERN Document Server

    Goda, Keisuke; Jalali, Bahram

    2008-01-01

    Optical coherence tomography (OCT) has proven to be a powerful technique for studying tissue morphology in ophthalmology, cardiology, and endomicroscopy. Its performance is limited by the fundamental trade-off between the imaging sensitivity and acquisition speed -- a predicament common in virtually all imaging systems. In this paper, we circumvent this limit by using distributed Raman post-amplification of the reflection from the sample. We combine the amplification with simultaneously performed dispersive Fourier transformation, a process that maps the optical spectrum into an easily measured time-domain waveform. The Raman amplification enables measurement of weak signals which are otherwise buried in noise. It extends the depth range without sacrificing the acquisition speed or causing damage to the sample. As proof of concept, single-shot imaging with 15 dB improvement in sensitivity at an axial scan rate of 36.6 MHz is demonstrated.

  15. Natural dispersion revisited.

    Science.gov (United States)

    Johansen, Øistein; Reed, Mark; Bodsberg, Nils Rune

    2015-04-15

    This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper.

  16. A comparison of resting images from two myocardial perfusion tracers

    Energy Technology Data Exchange (ETDEWEB)

    Anagnostopoulos, C. [Royal Brompton Hospital, London (United Kingdom); Laney, R. [Royal Brompton Hospital, London (United Kingdom); Pennell, D. [National Heart and Lung Inst., London (United Kingdom); Proukakis, H. [University of Athens Medical School (Greece); Underwood, R. [National Heart and Lung Inst., London (United Kingdom)

    1995-09-01

    We have compared stress-redistribution and delayed rest thallium-201 with rest technetium-99m methoxyisobutylisonitrile (MIBI) tomograms in order to compare the tracers for the assessment of myocardial viability and to validate a rapid protocol combining the two tracers. We studied 30 consecutive patients with known or suspected coronary artery disease [group 1: 16 with normal left ventricular function, mean left ventricular ejection fraction (LVEF) 55%, SD 6%; group 2: 14 with abnormal function, mean LVEF 28%, SD 8%]. {sup 201}Tl was injected during infusion of adenosine followed by acquisition of conventional stress and redistribution tomograms. On a separate day, {sup 201}Tl was injected at rest with imaging 4 h later. {sup 99m}Tc-MIBI was then given at rest and imaging was performed. Three images were compared: redistribution {sup 201}Tl, rest {sup 201}Tl, and rest {sup 99m}Tc-MIBI. Tracer activity was classified visually and quantitatively in nine segments and segments with>50% activity were defined as containing clinically significant viable myocardium. Mean global tracer uptake as a percentage of maximum was similar in group 1 (rest {sup 201}Tl 69%{+-}12%, redistribution {sup 201}Tl 69%{+-}15%, rest {sup 99m}Tc-MIBI 70%{+-}13%), but in group 2 mean tracer uptake was significantly greater in the rest {sup 201}Tl images (59%{+-}16%) than in redistribution {sup 201}Tl images (53%{+-}17%) or rest {sup 99m}Tc-MIBI images (53%{+-}19%). Overall agreement for regional uptake score was excellent ({kappa} from 0.79 to 0.84), although there were a significant number of segments with less uptake shown by redistribution {sup 201}Tl and by rest {sup 99m}Tc-MIBI than by rest {sup 201}Tl in group 2. The number of segments with significant viable myocardium in group 1 was very similar between the three images but in group 2 rest {sup 201}Tl identified significantly more segments as viable than the other images. (orig./MG) (orig.). With 1 fig., 7 tabs.

  17. Inter-comparison of Aermod and ISC3 modeling results to the Alaska tracer field experiment

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    AERMOD is an advanced plume model that incorporates updated treatments of the boundary layer theory, understanding of turbulence and dispersion, and includes handling of terrain interactions as well as the PRIME downwash algorithm. It was reported that the US EPA approved AERMOD for short-range dispersion modeling. It was the high time that AERMOD would replace ISC3. ISC3 is a traditional Gaussian plume model regarded as the regulatory model of US EPA with the capacity of building downwash similar to that of AERMOD. In this paper, the authors describe the advantages of AERMOD over the regulatory model of ISC3 by comparing their predicted ground level concentrations (GLC) along downwind distance to the Alaska tracer field data. The field experiment features buoyant release of effluent at elevated height over a flat terrain and local flows influenced by building downwash. Three measures to compare the observed and simulated concentration data, such as linear regression, quantile-quantile (QQ) and residual box are utilized. To sum up, AERMOD shows significantly better space-time correlation and probability distribution than the ISC3, which frequently overestimates the GLC for effluent released with significant plume rise under stable atmospheric conditions. The performance of AERMOD is greatly enhanced by introducing the state-of-the-art knowledge of boundary layer meteorology as well as the turbulence parameterization method. In particular, AERMOD takes into account the meander effect on coherent plume in stable condition with current state-of-the-art Planetary Boundary Layer (PBL) parameterizations, while ISC3 is not capable of producing such important effect. Generally speaking, 1.17 is the overall predicted-to-observed ratio for short-term averages using AERMOD. 1.94 is the overall predicted-to-observed ratio for short-term averages using ISC3.

  18. River infiltration to a subtropical alluvial aquifer inferred using multiple environmental tracers

    Science.gov (United States)

    Lamontagne, S.; Taylor, A. R.; Batlle-Aguilar, J.; Suckow, A.; Cook, P. G.; Smith, S. D.; Morgenstern, U.; Stewart, M. K.

    2015-06-01

    Chloride (Cl-), stable isotope ratios of water (δ18O and δ2H), sulfur hexafluoride (SF6), tritium (3H), carbon-14 (14C), noble gases (4He, Ne, and Ar), and hydrometry were used to characterize groundwater-surface water interactions, in particular infiltration rates, for the Lower Namoi River (New South Wales, Australia). The study period (four sampling campaigns between November 2009 and November 2011) represented the end of a decade-long drought followed by several high-flow events. The hydrometry showed that the river was generally losing to the alluvium, except when storm-derived floodwaves in the river channel generated bank recharge—discharge cycles. Using 3H/14C-derived estimates of groundwater mean residence time along the transect, infiltration rates ranged from 0.6 to 5 m yr-1. However, when using the peak transition age (a more realistic estimate of travel time in highly dispersive environments), the range in infiltration rate was larger (4-270 m yr-1). Both river water (highest δ2H, δ18O, SF6, 3H, and 14C) and an older groundwater source (lowest δ2H, δ18O, SF6, 3H, 14C, and highest 4He) were found in the riparian zone. This old groundwater end-member may represent leakage from an underlying confined aquifer (Great Artesian Basin). Environmental tracers may be used to estimate infiltration rates in this riparian environment but the presence of multiple sources of water and a high dispersion induced by frequent variations in the water table complicates their interpretation.

  19. The Dispersion and Burial of Well-Mixed Gravels

    Science.gov (United States)

    Haschenburger, J. K.

    2012-12-01

    Over the last two decades, results from numerous tracing experiments have shed light on grain kinematics in gravel-bed channels, including the distance of grain displacement and the depth of vertical mixing. However, most of these studies report results for relatively short temporal and spatial scales, when the behavior of tagged gravels may not reflect the overall streambed dynamics. The purpose of this talk is to highlight the grain kinematics of well-mixed gravels. Field observations come from a tracing experiment operated for nearly 20 years in Carnation Creek, which is located on the west coast of Vancouver Island, Canada. The small gravel-bed river with pool-riffle-bar morphology and large woody debris experiences an average of 15 ± 5 floods per year, which facilitates frequent streambed activity and relatively high bed material transport rates typically under partial sediment transport conditions. The magnetically tagged gravels, which range in size from 16 to 180 mm, have been recovered more than 10 times over the study period. Evaluation of the spatial distribution of tagged gravels over time documents the complex evolution of streamwise dispersion. Once tracers are well mixed vertically, the displacement of mobile gravels is only partly influenced by the tracer starting position in the bed morphology and its depth of burial before a given flooding period.

  20. Acoustic Rectification in Dispersive Media

    Science.gov (United States)

    Cantrell, John H.

    2008-01-01

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  1. Hydrodispersive characterization of a sandy porous medium by tracer tests carried out in laboratory on undisturbed soil samples

    Science.gov (United States)

    Ferrante, Aldo Pedro; Fallico, Carmine; Rios, Ana C.; Fernanda Rivera, Maria; Santillan, Patricio; Salazar, Mario

    2013-04-01

    The contamination of large areas and correspondent aquifers often imposes to implement some recovery operations which are generally complex and very expensive. Anyway, these interventions necessarily require the preventive characterization of the aquifers to be reclaimed and in particular the knowledge of the relevant hydrodispersive parameters. The determination of these parameters requires the implementation tracer tests for the specific site (Sauty JP, 1978). To reduce cost and time that such test requires tracer tests on undisturbed soil samples, representative of the whole aquifer, can be performed. These laboratory tests are much less expensive and require less time, but the results are certainly less reliable than those obtained by field tests for several reasons, including the particular scale of investigation. In any case the hydrodispersive parameters values, obtained by tests carried out in laboratory, can provide useful information on the considered aquifer, allowing to carry out initial verifications on the transmission and propagation of the pollutants in the aquifer considered. For this purpose, tracer tests with inlet of short time were carried out in the Soil Physics Laboratory of the Department of Soil Protection (University of Calabria), on a series of sandy soil samples with six different lengths, repeating each test with three different water flow velocities (5 m/d; 10 m/s and 15 m/d) (J. Feyen et al., 1998). The lengths of the samples taken into account are respectively 15 cm, 24 cm, 30 cm, 45 cm, 60 cm and 75 cm, while the solution used for each test was made of 100 ml of water and NaCl with a concentration of this substance corresponding to 10 g/L. For the porous medium taken into consideration a particle size analysis was carried out, resulting primarily made of sand, with total porosity equal to 0.33. Each soil sample was placed in a flow cell in which was inlet the tracer from the bottom upwards, measuring by a conductivimeter the

  2. Minnesota 1973 atmospheric boundary layer experiment: Micrometeorological and tracer data archive. Set 1 (revision 2) documentation report

    Science.gov (United States)

    Woodruff, R. K.; Droppo, J. G.; Glantz, C. S.

    1987-03-01

    An archive for micrometeorological and tracer dispersion data was developed by Battelle, Pacific Northwest Labs. for the U.S. Environmental Protection Agency. The archive was designed to make the results of extensive field tests readily accessible to EPA for model testing, development, and verification efforts. Documentation was provided for one of the archived data sets, The Minnesota 1973 Boundary Layer Experiment. The aim of the effort was to archive invaluable data sets in a timely fashion before the necessary supporting information about the data becomes lost forever. The entries are as follows: data set fact summary, a narrative description of experimental and data, special information, references, a description of archive data files, contacts (names, addresses, and phone numbers) and standard experiment summary table. Revision 2 includes previously unpublished rawinsonde profile data.

  3. Seed dispersal of desert annuals.

    Science.gov (United States)

    Venable, D Lawrence; Flores-Martinez, Arturo; Muller-Landau, Helene C; Barron-Gafford, Greg; Becerra, Judith X

    2008-08-01

    We quantified seed dispersal in a guild of Sonoran Desert winter desert annuals at a protected natural field site in Tucson, Arizona, USA. Seed production was suppressed under shrub canopies, in the open areas between shrubs, or both by applying an herbicide prior to seed set in large, randomly assigned removal plots (10-30 m diameter). Seedlings were censused along transects crossing the reproductive suppression borders shortly after germination. Dispersal kernels were estimated for Pectocarya recurvata and Schismus barbatus from the change in seedling densities with distance from these borders via inverse modeling. Estimated dispersal distances were short, with most seeds traveling less than a meter. The adhesive seeds of P. recurvata went farther than the small S. barbatus seeds, which have no obvious dispersal adaptation. Seeds dispersed farther downslope than upslope and farther when dispersing into open areas than when dispersing into shrubs. Dispersal distances were short relative to the pattern of spatial heterogeneity created by the shrub and open space mosaic. This suggests that dispersal could contribute to local population buildup, possibly facilitating species coexistence. Overall, these results support the hypothesis that escape in time via delayed germination is likely to be more important for desert annuals than escape in space.

  4. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  5. MULTISPECIES REACTIVE TRACER TEST IN A SAND AND GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS: PART 2: TRANSPORT OF CHROMIUM (VI) AND LEAD-, COPPER-, AND ZINC-EDTA TRACERS

    Science.gov (United States)

    This report discusses the transport of a group of reactive tracers over the course of a large-scale, natural gradient tracer test conducted at the USGS Cape Cod Toxic Substances Hydrology Research site, near Falmouth, Massachusetts. The overall objectives of the experiment were ...

  6. Overview of the Full-scale Radiological Dispersal Device Field Trials.

    Science.gov (United States)

    Green, Anna Rae; Erhardt, Lorne; Lebel, Luke; Duke, M John M; Jones, Trevor; White, Dan; Quayle, Debora

    2016-05-01

    In 2012, Defence Research and Development Canada, in partnership with a number of other Canadian and International organizations, led a series of three field trials designed to simulate a Radiological Dispersal Device (RDD). These trials, known as the Full-Scale RDD (FSRDD) Field Trials, involved the explosive dispersal of a short-lived radioactive tracer ((140)La, t1/2 = 40.293 h). The FSRDD Field Trials required a significant effort in their planning, preparation, and execution to ensure that they were carried out in a safe, efficient manner and that the scientific goals of the trials were met. The discussion presented here details the planning and execution of the trials, outlines the relevant radiation safety aspects, provides a summary of the source term and atmospheric conditions for the three dispersal events, and provides an overview of the measurements that were made to track the plumes and deposition patterns.

  7. Quantifying Reaeration Rates in Alpine Streams Using Deliberate Gas Tracer Experiments

    Directory of Open Access Journals (Sweden)

    Andrew Benson

    2014-04-01

    Full Text Available Gas exchange across the air-water interface is a critical process that maintains adequate dissolved oxygen (DO in the water column to support life. Oxygen reaeration rates can be accurately measured using deliberate gas tracers, like sulfur hexafluoride (SF6 or xenon (Xe. Two continuous release experiments were conducted in different creeks in the Sierra Nevada of California: Sagehen Creek in September, 2009, using SF6 and Martis Creek in August, 2012, using both SF6 and Xe. Measuring gas loss along the creek, which was approximated with the one-dimensional advection-dispersion equation, allows for the estimation of the SF6 or Xe reaeration coefficient (KSF6, KXe, which is converted to DO reaeration (KDO or K2 using Schmidt numbers. Mean KSF6 for upper and lower Sagehen and Martis Creeks were, respectively, 34 day−1, 37 day−1 and 33 day−1, with corresponding KDOs of 61 day−1, 66 day−1 and 47 day−1. In Martis Creek, KXe was slightly higher (21% than KSF6, but the calculated KDO from SF6 agreed with the calculated KDO from Xe within about 15%; this difference may be due to bubble-enhanced gas transfer. Established empirical equations of KDO using stream characteristics did a poor job predicting KDO for both creeks.

  8. Development of micromarkers with various photoluminescence colors as tracers for shadowing pursuits.

    Science.gov (United States)

    Kurata, Shoji; Hirano, Haruo; Nagai, Masatoshi

    2008-02-01

    Micromarkers with five photoluminescence colors were developed as tracers for shadowing pursuits. The markers are colorless powders with particle diameters of several tens to several hundreds of micrometers, prepared using a cryogenic sample crusher. They were visualized using red, green, yellow, magenta or cyan photoluminescence under ultraviolet light at approximately 365 nm. The markers were composed of photoluminescent compounds dispersed in polyvinyl butyral. The photoluminescent compounds in the polyvinyl butyral were stable under ambient conditions for more than one year after application. The compounds with the red, green, yellow, magenta and cyan photoluminescence contained a europium (Eu(3+)) complex, a terbium (Tb(3+)) complex, a mixture of Tb(3+) and Eu(3+) complexes, a mixture of Eu(3+) complex and o-coumaric acid, and a mixture of Tb(3+) complex and 7-hydroxycoumarin along with a few drops of a sodium bicarbonate aqueous solution, respectively. Neodymium (Nd(3+)) and ytterbium (Yb(3+)) complexes with photoluminescence in the near-IR wavelength region can also be added to these visible photoluminescent compounds as secret markers for discrimination. The markers were non-destructively identified using a microscopic FT-IR spectrometer and a microscopic spectrometer equipped with a fluorescence detector.

  9. Comparison of AERMOD to EIAA with Respect to the Latest Tracer Field Data

    Institute of Scientific and Technical Information of China (English)

    Duo-Xing Yang; Ka-Hing Yau; Shi-Bei Li; Xiao-Hong Zhao; Jesse Thé

    2005-01-01

    The USEPA proposed AERMOD for short-range dispersion modeling and simultaneous deletion of ISC. In contrast, the regulatory model of China is a traditional Gaussian plume model similar to ISC. This paper demonstrates the advantage of AERMOD over the regulatory model of China by comparing their predicted ground level concentrations (GLC) along downwind distance to the Alaska tracer field data. The field experiment features buoyant release of effluent at elevated height over flat terrain and local flows influenced by building downwash. AERMOD shows significantly better space-time correlation and probability distribution than the China regulatory model, which frequently underestimates the GLC for effluent released with significant plume rise in stable atmospheric conditions. The performance of AERMOD is greatly enhanced by incorporating the state-of-the-art knowledge of boundary layer meteorology. In particular, AERMOD employs similarity theory in replacement of the discrete Pasquill-Gilford stability class; PDF modeling of asymmetric vertical diffusion of convective plumes; partial plume penetration across mixing height ceiling; and the PRIMEmodel for building downwash.

  10. Urban Dispersion Program Overview and MID05 Field Study Summary

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2007-07-31

    The Urban Dispersion Program (UDP) was a 4-year project (2004–2007) funded by the U.S. Department of Homeland Security with additional support from the Defense Threat Reduction Agency. The U.S. Environmental Protection Agency (EPA) also contributed to UDP through funding a human-exposure component of the New York City (NYC) field studies in addition to supporting an EPA scientist in conducting modeling studies of NYC. The primary goal of UDP was to improve the scientific understanding of the flow and diffusion of airborne contaminants through and around the deep street canyons of NYC. The overall UDP project manager and lead scientist was Dr. Jerry Allwine of Pacific Northwest National Laboratory. UDP had several accomplishments that included conducting two tracer and meteorological field studies in Midtown Manhattan.

  11. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    Directory of Open Access Journals (Sweden)

    Mandeep Singh

    2013-03-01

    Full Text Available This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when dispersion term up to fifth order are added. We have used the two cascaded Mach-Zehnder Modulators for our proposed model and tried to show the dispersion effect with the help of modulation depth factor of MZM, which have been not discussed earlier.

  12. Development of Models to Simulate Tracer Tests for Characterization of Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Mark D.; Reimus, Paul; Vermeul, Vincent R.; Rose, Peter; Dean, Cynthia A.; Watson, Tom B.; Newell, D.; Leecaster, Kevin; Brauser, Eric

    2013-05-01

    A recent report found that power and heat produced from enhanced (or engineered) geothermal systems (EGSs) could have a major impact on the U.S energy production capability while having a minimal impact on the environment. EGS resources differ from high-grade hydrothermal resources in that they lack sufficient temperature distribution, permeability/porosity, fluid saturation, or recharge of reservoir fluids. Therefore, quantitative characterization of temperature distributions and the surface area available for heat transfer in EGS is necessary for the design and commercial development of the geothermal energy of a potential EGS site. The goal of this project is to provide integrated tracer and tracer interpretation tools to facilitate this characterization. This project was initially focused on tracer development with the application of perfluorinated tracer (PFT) compounds, non-reactive tracers used in numerous applications from atmospheric transport to underground leak detection, to geothermal systems, and evaluation of encapsulated PFTs that would release tracers at targeted reservoir temperatures. After the 2011 midyear review and subsequent discussions with the U.S. Department of Energy Geothermal Technology Program (GTP), emphasis was shifted to interpretive tool development, testing, and validation. Subsurface modeling capabilities are an important component of this project for both the design of suitable tracers and the interpretation of data from in situ tracer tests, be they single- or multi-well tests. The purpose of this report is to describe the results of the tracer and model development for simulating and conducting tracer tests for characterizing EGS parameters.

  13. Journal: A Review of Some Tracer-Test Design Equations for ...

    Science.gov (United States)

    Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers' experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-

  14. Technical Note: Coupling of chemical processes with the Modular Earth Submodel System (MESSy submodel TRACER

    Directory of Open Access Journals (Sweden)

    P. Jöckel

    2007-11-01

    Full Text Available The implementation of processes related to chemistry into Earth System Models and their coupling within such systems requires the consistent description of the chemical species involved. We provide a tool (written in Fortran95 to structure and manage information about constituents, herein after referred to as tracers, namely the Modular Earth Submodel System (MESSy generic (i.e., infrastructure submodel TRACER. With TRACER it is possible to define a multitude of tracer sets, depending on the spatio-temporal representation (i.e., the grid structure of the model. The required information about a specific chemical species is split into the static meta-information about the characteristics of the species, and its (generally in time and space variable abundance in the corresponding representation. TRACER moreover includes two submodels. One is TRACER_FAMILY, an implementation of the tracer family concept. It distinguishes between two types: type-1 families are usually applied to handle strongly related tracers (e.g., fast equilibrating species for a specific process (e.g., advection. In contrast to this, type-2 families are applied for tagging techniques, in which specific species are artificially decomposed and associated with additional information, in order to conserve the linear relationship between the family and its members. The second submodel is TRACER_PDEF, which corrects and budgets numerical negative overshoots that arise in many process implementations due to the numerical limitations (limited precision, rounding errors. The submodel therefore guarantees the positive definiteness of the tracers and stabilises the integration scheme. As a by-product, it further provides a global tracer mass diagnostic. Last but not least, we present the submodel PTRAC for the definition of prognostic tracers via a Fortran95 namelist. TRACER with its submodels and PTRAC can readily be applied to a variety of models without further requirements. The code and

  15. A tracer-based inversion method for diagnosing eddy-induced diffusivity and advection

    Science.gov (United States)

    Bachman, S. D.; Fox-Kemper, B.; Bryan, F. O.

    2015-02-01

    A diagnosis method is presented which inverts a set of tracer flux statistics into an eddy-induced transport intended to apply for all tracers. The underlying assumption is that a linear flux-gradient relationship describes eddy-induced tracer transport, but a full tensor coefficient is assumed rather than a scalar coefficient which allows for down-gradient and skew transports. Thus, Lagrangian advection and anisotropic diffusion not necessarily aligned with the tracer gradient can be diagnosed. In this method, multiple passive tracers are initialized in an eddy-resolving flow simulation. Their spatially-averaged gradients form a matrix, where the gradient of each tracer is assumed to satisfy an identical flux-gradient relationship. The resulting linear system, which is overdetermined when using more than three tracers, is then solved to obtain an eddy transport tensor R which describes the eddy advection (antisymmetric part of R) and potentially anisotropic diffusion (symmetric part of R) in terms of coarse-grained variables. The mathematical basis for this inversion method is presented here, along with practical guidelines for its implementation. We present recommendations for initialization of the passive tracers, maintaining the required misalignment of the tracer gradients, correcting for nonconservative effects, and quantifying the error in the diagnosed transport tensor. A method is proposed to find unique, tracer-independent, distinct rotational and divergent Lagrangian transport operators, but the results indicate that these operators are not meaningfully relatable to tracer-independent eddy advection or diffusion. With the optimal method of diagnosis, the diagnosed transport tensor is capable of predicting the fluxes of other tracers that are withheld from the diagnosis, including even active tracers such as buoyancy, such that relative errors of 14% or less are found.

  16. Determination of Groundwater Velocity and Dispersion Parameters by Borehole Wall Multielectrode Geoelectrics

    Science.gov (United States)

    Kessels, W.; Wuttke, M. W.

    2007-05-01

    A single well technique to determine groundwater flow values and transport parameters is presented. Multielectrode arrays are placed at the filtered casing depth by an inflatable packer or are installed on the borehole wall behind the casing.Tracer water with a higher or lower specific electrical conductivity (salinity) which is injected between the electrodes. This tracer plume then moves into the natural groundwater flow field. The observation of this movement by geoelectric logging enables the determination of the groundwater velocity and salinity. The transport parameters "effective porosity" and "dispersion length" can also be derived. The geoelectric logging uses n borehole electrodes and two grounding electrodes. Thus, either n independent two point measurements or n*(n-1)/2 pole-to-pole measurements can be conducted to obtain a full set of geoelectric measurements. This set is used to derive all electrode combinations by applying the law of superposition and reciprocity. The tracer distribution around the borehole during and after injection depends on the hydraulic and transport parameters of the aquifer and the filter sand. The transport parameter "porosity" plus the total injected tracer volume determines the tracer distribution around the borehole. The transport parameter "dispersivity" determines the abruptness of the tracer front. The method was tested by undertaking measurements in a lab aquifer filled with sand. The results are discussed and the limitations of the method are shown. Multielectrode installations behind casing were tested in situ in the two scientific boreholes CAT-LUD-1 and CAT- LUD-1A drilled in the northern part of Germany. A multielectrode packer system was designed, built and tested in these boreholes. The results are compared with colloid observations in the borehole and hydraulic triangulation in surrounded observation wells. Here, the interpretation of these in situ measurements is mainly restricted to two point geoelectric

  17. The NET effect of dispersants

    NARCIS (Netherlands)

    Marieke Zeinstra-Helfrich; Wierd Koops; Albertinka J. Murk

    2015-01-01

    Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and

  18. Fermion dispersion in axion medium

    OpenAIRE

    Mikheev, N. V.; Narynskaya, E. N.

    2008-01-01

    The interaction of a fermion with the dense axion medium is investigated for the purpose of finding an axion medium effect on the fermion dispersion. It is shown that axion medium influence on the fermion dispersion under astrophysical conditions is negligible small if the correct Lagrangian of the axion-fermion interaction is used.

  19. Large deviations in Taylor dispersion

    Science.gov (United States)

    Kahlen, Marcel; Engel, Andreas; Van den Broeck, Christian

    2017-01-01

    We establish a link between the phenomenon of Taylor dispersion and the theory of empirical distributions. Using this connection, we derive, upon applying the theory of large deviations, an alternative and much more precise description of the long-time regime for Taylor dispersion.

  20. Pigment dispersion syndrome

    Directory of Open Access Journals (Sweden)

    C.S. Sandhya

    2013-10-01

    Full Text Available We report of the rare occurrence of pigment dispersion syndrome (PDS with posterior subcapsular cataract in both eyes in a young male patient. The patient presented with complaints of progressive decrease in vision of one year duration. The patient also had high myopia with mild iridodonesis, phacodonesis and anterior insertion of zonules. Classical signs of PDS like Krukenberg's spindle on the posterior corneal surface were evident on slit lamp examination; transillumination defects in the iris could not be elicited by retroillumination as the iris was heavily pigmented. Gonioscopy revealed heavy and uniform pigmentation of trabecular meshwork. Evidence of a characteristic iris configuration on optical coherence tomography (OCT, namely, posterior bowing of iris in the mid periphery suggested the diagnosis of PDS. This case highlights the importance of OCT in identifying the iris configuration characteristically seen in PDS even in the absence of transillumination defects in the iris and reiterates the need to look for subtle signs like phacodonesis which are important when surgical intervention is planned.

  1. Dispersion in unit disks

    CERN Document Server

    Dumitrescu, Adrian

    2009-01-01

    We present two new approximation algorithms with (improved) constant ratios for selecting $n$ points in $n$ unit disks such that the minimum pairwise distance among the points is maximized. (I) A very simple $O(n \\log{n})$-time algorithm with ratio 0.5110 for disjoint unit disks. In combination with an algorithm of Cabello \\cite{Ca07}, it yields a $O(n^2)$-time algorithm with ratio of 0.4487 for dispersion in $n$ not necessarily disjoint unit disks. (II) A more sophisticated LP-based algorithm with ratio 0.6495 for disjoint unit disks that uses a linear number of variables and constraints, and runs in polynomial time. The algorithm introduces a novel technique which combines linear programming and projections for approximating distances. The previous best approximation ratio for disjoint unit disks was 1/2. Our results give a partial answer to an open question raised by Cabello \\cite{Ca07}, who asked whether 1/2 could be improved.

  2. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the

  3. POISSON project - I - Emission lines as accretion tracers in Young Stellar Objects: results from observations of Chamaleon I and II sources

    CERN Document Server

    Antoniucci, S; Nisini, B; Giannini, T; Lorenzetti, D; Eisloeffel, J; Bacciotti, F; Cabrit, S; Garatti, A Caratti o; Dougados, C; Ray, T

    2011-01-01

    We present the results of the analysis of LR optical-NIR spectra (0.6-2.4 um) of a sample 47 YSOs in the ChaI and II star-forming clouds. These data are part of the POISSON project (Protostellar Optical-Infrared Spectral Survey on NTT). The aim is to determine the accretion luminosity (Lacc) and mass accretion rate (Macc) of the sources through the analysis of the detected emission features. We also aim at verifying the reliability and consistency of the existing empirical relationships connecting emission line luminosity and Lacc. We employ five tracers (OI-6300A, Ha, CaII-8542A, Pab, and Brg) to derive the accretion luminosity. The tracers provide Lacc values showing different scatters when plotted as a function of L*. The Brg seems the most reliable, since it gives the minimum Lacc dispersion over the entire range of L*, whereas the other tracers provide much more scattered Lacc values, not expected for the homogeneous sample we are observing. The comparison between Lacc(Brg) and Lacc obtained from the oth...

  4. Can fog contribute to the nutrition of Chamaecyparis obtusa var. formosana? Uptake of a fog solute tracer into foliage and transport to roots.

    Science.gov (United States)

    Lai, I-Ling; Schroeder, Walter H; Wu, Jiunn-Tzong; Kuo-Huang, Ling-Long; Mohl, Carola; Chou, Chang-Hung

    2007-07-01

    Yellow cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl. var. formosana (Hayata) Rehder) is the predominant tree species of Taiwan's nutrient-poor, mountain fog forests. Little is known about the potential contribution of solute uptake from fog to the overall nutrition of these trees. Shoots of yellow cypress seedlings were misted with artificial fog containing the tracer rubidium (Rb) in laboratory and field experiments to determine if there is solute uptake from the fog. After misting shoots for six weeks, substantial amounts of tracer were detected in unexposed roots by inductively coupled plasma mass spectroscopy bulk analysis. Possible routes of entry were examined by element imaging with energy dispersive X-ray analysis. Direct uptake of the tracer into leaves across the cuticle and epidermis was small, excluding this as the major uptake path. Accumulations of Rb were found on leaf surfaces along the edges of the leaves. The almost daily changes in fog coverage and air humidity may enhance the accumulation of fog solutes at leaf edges. Accumulation of Rb was also found in narrow clefts between opposite leaves and between the outermost and underlying alternating stacked leaves. The clefts provide a direct passage from the leaf surface to the space beneath the imbricate leaves and the underlying alternate leaves, possibly facilitating solute uptake from fog, which in turn may contribute to the nutrition of yellow cypress.

  5. A new aquifer assessment tool using reactive tracers

    Science.gov (United States)

    McKnight, D.; Smalley, A. L.; Banwart, S. A.; Lerner, D. N.; Thomson, N. R.; Thornton, S. F.; Wilson, R. D.

    2003-04-01

    A major obstacle to making informed decisions about trigger levels for restoration and choosing remediation options is that current Site Investigation (SI) practice fails to make optimal use of available SI techniques resulting in poor value for money in conceptual site models. Often it is simply too expensive to obtain the type of site data required to build the case for natural attenuation, even though this restoration option may be relatively cheaper than a pump-and-treat system. In particular, aquifer property measurement techniques for groundwater transport and reactions are too costly and this results in over-reliance on literature values or model assumptions. This results in overly uncertain predictions of in situ performance and therefore unnecessarily cautious risk assessment and costly remediation strategies. Therefore, cost-effective SI tools that have the capability of producing high quality characterisation data are required. The dipole flow test which circulates groundwater between isolated injection (source) and extraction (sink) chambers within a single borehole has been used successfully by others to delineate heterogeneous hydraulic properties in both highly permeable and fractured rock aquifers. We propose to extend this approach by adding a suite of reactive tracers into a dipole flow field to assess the geochemical properties and biodegradation potential of aquifers. If successful this will provide a method to ascertain site-specific parameters for use in appropriate reactive transport models. The initial phase of this project involves the construction of a laboratory-scale physical model of a dipole probe to investigate the utility of the dipole flow and reactive tracer test (DFRTT) as an aquifer assessment tool. This phase will also serve as the developmental stage between mathematical theory and a host of planned field trials. The development of the laboratory-scale DFRTT including initial scoping calculations, numerical simulation results

  6. Anthropogenic contaminants as tracers in an urbanizing karst aquifer

    Science.gov (United States)

    Mahler, Barbara; Massei, Nicolas

    2007-04-01

    Karst aquifers are uniquely vulnerable to contamination. In the Barton Springs segment of the karstic Edwards aquifer (Texas, U.S.A.), urban contaminants such as pesticides and volatile organic compounds frequently are detected in spring base flow. To determine whether contaminant concentrations change in response to storms, and if they therefore might act as tracers of focused recharge, samples were collected from Barton Springs at closely spaced intervals following three storms. Two herbicides (atrazine and simazine), two insecticides (carbaryl and diazinon), and a solvent (tetrachloroethene) described breakthrough curves over a 1-week period following one or more storms. The breakthrough curves were decomposed into two to five log-normal subcurves, which were interpreted as representing pulses of contaminants moving through the aquifer. Each subcurve could be used in the same way as an artificial tracer to determine travel time to and recovery at the spring. The contaminants have several advantages over artificial tracers: they represent the actual compounds of interest, they are injected essentially simultaneously at several points, and they are injected under those conditions when transport is of the most interest, i.e., following storms. The response of storm discharge, specific conductance, and contaminant loading at the spring depended on initial aquifer flow conditions, which varied from very low (spring discharge of 0.48 m 3/s) to high (spring discharge of 2.7 m 3/s): concentrations and recovery were the highest when initial aquifer flow conditions were low. This behavior provides information about aquifer structure and the influence of aquifer flow condition on transport properties.

  7. Small-molecule PET Tracers for Imaging Proteinopathies.

    Science.gov (United States)

    Mathis, Chester A; Lopresti, Brian J; Ikonomovic, Milos D; Klunk, William E

    2017-09-01

    In this chapter, we provide a review of the challenges and advances in developing successful PET imaging agents for 3 major types of aggregated amyloid proteins: amyloid-beta (Aβ), tau, and alpha-synuclein (α-syn). These 3 amyloids are involved in the pathogenesis of a variety of neurodegenerative diseases, referred to as proteinopathies or proteopathies, that include Alzheimer disease, Lewy body dementias, multiple system atrophy, and frontotemporal dementias, among others. In the Introduction section, we briefly discuss the history of amyloid in neurodegenerative diseases and describe why progress in developing effective imaging agents has been hampered by the failure of crystallography to provide definitive ligand-protein interactions for rational radioligand design efforts. Instead, the field has relied on largely serendipitous, trial-and-error methods to achieve useful and specific PET amyloid imaging tracers for Aβ, tau, and α-syn deposits. Because many of the proteopathies involve more than 1 amyloid protein, it is important to develop selective PET tracers for the different amyloids to help assess the relative contribution of each to total amyloid burden. We use Pittsburgh compound B to illustrate some of the critical steps in developing a potent and selective Aβ PET imaging agent. Other selective Aβ and tau PET imaging compounds have followed similar pathways in their developmental processes. Success for selective α-syn PET imaging agents has not been realized yet, but work is ongoing in multiple laboratories throughout the world. In the tau sections, we provide background regarding 3-repeat (3R) and 4-repeat (4R) tau proteins and how they can affect the binding of tau radioligands in different tauopathies. We review the ongoing efforts to assess the properties of tau ligands, which are useful in 3R, 4R, or combined 3R-4R tauopathies. Finally, we describe in the α-syn sections recent attempts to develop selective tracers to image

  8. Air Flow and Dispersion Section

    Energy Technology Data Exchange (ETDEWEB)

    Slinn, W. G.N.; Nicola, P. W.; Powell, D. C.; Davis, W. E.

    1976-03-01

    There are eight papers in this section. Some of the fundamentals of atmospheric dispersion of pollutants are examined with theoretical analyses as well as detailed experimental investigations. Emphasis has been placed on analyzing and summarizing previous experimental dispersion data with more realistic and fundamentally sound approaches to plume behavior. The goal is to finalize improved short-range dispersion models from existing data, removing inconsistencies and inadequacies in presently applied assessment models. Dispersion and transport efforts in the future should aim toward evaluating plume behavior on meso and regional scales. The complex features of flow and dispersion through storms, and in the vicinity of significant terrain characteristics influencing local to regional circulations must receive future emphasis. (auth)

  9. Rebuilding sources of linear tracers after atmospheric concentration concentration

    Directory of Open Access Journals (Sweden)

    J.-P. Issartel

    2003-06-01

    Full Text Available The identification of widespread sources of passive tracers out of atmospheric concentration measurements has become an important challenge of modern meteorology. The paper proposes some mathematical tracks to address this reconstruction of the complex space-time geometry of the sources. The methods are based upon the use of retroplumes. The inverse problem is addressed in a deterministic non statistical frame. The information obtained by local measurements is spread by introducing the concept of illumination. The constraint that the source to be rebuilt is non negative is also addressed. The experimental source ETEX1 is rebuilt in order to evaluate an impulse response of the algorithms.

  10. Flexible tools for interpreting tracer measurements and recent applications

    Science.gov (United States)

    Gusyev, M.; Stewart, M.

    2012-04-01

    Steady increase of groundwater abstraction and nitrate concentrations in groundwater due to agricultural and industrial practices is a major concern for groundwater availability and deterioration of groundwater quality in New Zealand. Studies on groundwater in the Waimea Plains (for example) have shown effects of nitrate input from both diffuse and point sources since 1940. Groundwaters in gravel aquifers under Christchurch have also been studied since 1970 to characterise their flowpaths and recharge sources. In these and other cases, the mixing of waters from different recharge sources following different flow paths can be determined with the use of various tracers and the future course of nitrate concentration in the groundwaters predicted. The input of radionuclides to hydrological systems from nuclear weapons testing in the 1950s and 60s revealed that outflows from such systems often comprise mixtures of water with very wide ranges of ages. Many authors have described methods of deconvolving such outputs with the use of lumped parameter models (LPMs). LPMs are evaluated using specialized software or Excel spreadsheets to compute simulations to measurements of system outputs and therefore estimate parameters of the age distribution. Excel allows easy modification of the code to enable application to individual hydrological features and for a variety of isotopes and chemicals. For the New Zealand studies, Excel spreadsheets with coded Visual Basic functions are used to deduce age distributions based on stable isotope, SF6, CFCs, 3H and 14C data (in order of ages). In particular, 3H is becoming increasingly useful as an age tracer due to the decrease of ambiguity from nuclear testing provided that the measurements can be made with high accuracy (Stewart et al., 2012).These age distributions allow us to derive the input histories of chemicals (e.g. nitrate) and the groundwater recharge sources. In addition, recent developments in modelling groundwater flow and

  11. Environmental radionuclides tracers and timers of terrestrial processes

    CERN Document Server

    Froehlich, Klaus

    2009-01-01

    The book presents a state-of-the-art summary of knowledge on the use of radionuclides to study processes and systems in the continental part of the Earth's environment. It is conceived as a companion to the two volumes of this series, which deal with isotopes as tracers in the marine environment (Livingston, Marine Radioactivity) and with the radioecology of natural and man-made terrestrial systems (Shaw, Radioactivity in Terrestrial Ecosystems). Although the book focuses on natural and anthropogenic radionuclides (radioactive isotopes), it also refers to stable environmental isotopes, which i

  12. Quality assurance and quantitative error analysis by tracer techniques

    Energy Technology Data Exchange (ETDEWEB)

    Schuetze, N.; Hermann, U.

    1983-12-01

    The locations, types and sources of casting defects have been tested by tracer techniques. Certain sites of moulds were labelled using /sup 199/Au, /sup 24/Na sodium carbonate solution, and technetium solution produced in the technetium generator on a /sup 99/Mo//sup 99/Tc elution column. Evaluations were made by means of activity measurements and autoradiography. The locations and causes of casting defects can be determined by error analysis. The surface defects of castings resulting from the moulding materials and from the blacking can be detected by technetium, the subsurface defects are located by gold.

  13. Geotropic tracers in turbulent flows: a proxy for fluid acceleration

    CERN Document Server

    Boffetta, Guido; De Lillo, Filippo; Santamaria, Francesco

    2013-01-01

    We investigate the statistics of orientation of small, neutrally buoyant, spherical tracers whose center of mass is displaced from the geometrical center. If appropriate-sized particles are considered, a linear relation can be derived between the horizontal components of the orientation vector and the same components of acceleration. Direct numerical simulations are carried out, showing that such relation can be used to reconstruct the statistics of acceleration fluctuations up to the order of the gravitational acceleration. Based on such results, we suggest a novel method for the local experimental measurement of accelerations in turbulent flows.

  14. The characterization of petroleum contamination in heterogenous media using partitioning tracer method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, E.; Rhee, S.; Park, J. [Seoul National Univ. (Korea, Republic of). Dept. of Civil and Environmental Engineering

    2009-07-01

    A partitioning tracer method for characterizing petroleum contamination in heterogenous media was discussed. The average saturation level of nonaqueous phase liquids (NAPLs) was calculated by comparing the transport of the partitioning tracers to a conservative tracer. The NAPL saturation level represented a continuous value throughout the contaminated site. Experiments were conducted in a 2-D sandbox divided into 4 parts using different-sized sands. Soils were contaminated with a mixture of kerosene and diesel. Partitioning tracer tests were conducted both before and after contamination. A partitioning batch test was conducted to determine the partition coefficient (K) of the tracer between the NAPL and water. Breakthrough curves were obtained, and a retardation factor (R) was calculated. Results of the study showed that the calculated NAPL saturation was in good agreement with determined values. It was concluded that the partitioning tracer test is an accurate method of locating and quantifying NAPLs.

  15. A Fundamental Approach to the Simulation of Flow and Dispersion in Fractured Media

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.D.

    1983-12-15

    Fracture systems may be generalized in terms of number and orientation of sets of parallel fractures and the distribution of length, width, thickness and separation. Borehole measurements may be used to particularize these parameters for a specific site. Global flow and dispersion in an aquifer occur in the interconnected fractures and may be related to specific fracture elements. A fluid dynamics code named SALE has been used to solve the Navier-Stokes equations for laminar flow in these elemental geometries. A marker particle calculation has been added to characterize longitudinal dispersion due to the velocity profile across the fracture and lateral dispersion due to flow disturbances at junctions. Local flow and dispersion in the matrix occur in the finer fracture structure and are evaluated using porous media approaches. These results or models are integrated in a 2D isothermal reservoir simulator named FRACSL. Discrete fractures are superimposed on the edges or diagnoals of rectangular grid elements. Water may flow from node to node through the matrix or through the fracture. The heads are found by iterating for the distribution which conserves the appropriate local mass. Marker particles are used to monitor the tracer dispersion due to motion in the fractures, in the matrix and between the two. Results are given showing flow and dispersion in an orthogonal junction and in a sample fractured reservoir.

  16. Sonde for Downhole Measurement of Water Turbidity and Dye Tracer Concentration

    OpenAIRE

    Schnegg, Pierre-André; Bossy, F.

    2005-01-01

    A new flow-through field fluorometer sonde has been designed for use in downhole tracer tests in 2’’ boreholes. The instrument is capable of determining the partial concentration of two dye tracers present simultaneously in the water. In addition, turbidity can be measured if the water is free of tracers. Although the sonde is aimed at boreholed hydrological investigations, it can also be used in surface waters.

  17. Final Progress Report for Project Entitled: Quantum Dot Tracers for Use in Engineered Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Rose, Peter [Univ. of Utah, Salt Lake City, UT (United States); Bartl, Michael [Univ. of Utah, Salt Lake City, UT (United States); Reimus, Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Williams, Mark [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mella, Mike [Univ. of Utah, Salt Lake City, UT (United States)

    2015-09-12

    The objective of this project was to develop and demonstrate a new class of tracers that offer great promise for use in characterizing fracture networks in EGS reservoirs. From laboratory synthesis and testing through numerical modeling and field demonstrations, we have demonstrated the amazing versatility and applicability of quantum dot tracers. This report summarizes the results of four years of research into the design, synthesis, and characterization of semiconductor nanocrystals (quantum dots) for use as geothermal tracers.

  18. Fractured-rock hydrogeophysics with electrically conductive and neutrally buoyant tracers

    Science.gov (United States)

    Shakas, A.; Linde, N.; Baron, L.; Le Borgne, T.; Bour, O.; Lavenant, N.; Gerard, M. F.

    2016-12-01

    Artificial tracer tests help to characterize and understand the dynamics of groundwater systems. This remains a challenging task, especially when dealing with highly heterogeneous formations in which flow can be very localized and the interpretation of tracer breakthrough curves may be ambiguous. As a complement to tracer tests, ground-penetrating radar (GPR) and electrical resistivity tomography can map the space-time migration of electrically conductive tracers. In hydrogeophysics, the most common tracer is dissolved table salt in water. However, conventional salt tracers lead to density effects that are often ignored. Even less than 1% density variations can have a dramatic effect on transport behavior and affect tracer tests in complex ways. Such effects have been demonstrated in our previous experiments that used single-hole GPR to monitor saline push-pull tests in fractured granite. It is possible to model density effects, but this leads to computational complexity and field dynamics that are not necessarily representative of the natural responses of the system. To minimize density effects, we performed a new set of push-pull tests using a neutrally buoyant and electrically conductive tracer at the same test site located close to Ploemeur, France. This novel tracer consists of a mixture of salt (NaCl), water and pure ethanol. Ethanol has a density of 789 g/L at 20° C and is used to counter-act the salt-induced density increase. Our GPR time-lapse images and tracer breakthrough data indicate a largely reversible transport process that confirms the neutral buoyancy of the tracer. Ethanol is biodegradable and does not pose significant environmental issues. Furthermore, calibration of the neutral-buoyant mixture is straightforward to perform in the field using Archimedes principle. Based on these results, we argue that neutrally buoyant ethanol-salt-water mixtures are ideal for a wide variety of hydrogeophysical tracer tests in porous or fractured media.

  19. Dispersive suspended microextraction.

    Science.gov (United States)

    Yang, Zhong-Hua; Liu, Yu; Lu, Yue-Le; Wu, Tong; Zhou, Zhi-Qiang; Liu, Dong-Hui

    2011-11-14

    A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases' separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1 μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0 μL p-xylene was selected as extraction solvent, extraction speed was 1200 rpm, extraction time was 30 s, the restoration speed was 800 rpm, the restoration time was 8 min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05 μg L(-1). The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1-100.0 μg L(-1). Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices.

  20. Development of vertical dispersion coefficients for rolling terrain environments. [Mathematical models

    Energy Technology Data Exchange (ETDEWEB)

    Sherer, D.L.; Minott, D.H.; Hilst, G.R.

    1977-01-01

    The Gaussian plume dispersion model is used to calculate expected concentrations of radioactive material downwind from point or line sources, including planned nuclear power stations. The standard Pasquill-Gifford dispersion coefficients (sigma/sub ..gamma../, sigma/sub Z/) normally used with the Gaussian model have been developed primarily for flat, smooth terrain. For terrains that are not flat and smooth, other dispersion coefficients which account for the dispersive effects of terrain-induced mechanical turbulence are needed. It is ERDA's objective to specify reliable dispersion coefficients that will represent a broader range of topographic conditions than was intended for the standard Pasquill-Gifford coefficients. The U. S. Army has carried out a program with similar objectives, but most of the information generated has had little visibility beyond the Department of Defense. During the first phase of this ERDA project, release of the Army data was arranged, and in this second phase of work, data from Army tracer-dispersion tests have been used to develop coefficients for dispersion over rural, rolling terrain. In order to derive vertical dispersion coefficients characteristic of rural, rolling terrain from the Army data, the meandering plume hypothesis has been applied. The meandering plume hypothesis holds that total dispersion (sigma/sub ZT/) is comprised of two components; the first component, sigma/sub ZI/, is the diffusion of a plume segment (puff) about its own center; the other component (sigma/sub ZM/) is the meander of individual puff trajectories about the centerline of the time-averaged plume.

  1. THE MADISON SQUARE GARDEN DISPERSION STUDY (MSG05) METEOROLOGICAL DATA DESCRIPTION.

    Energy Technology Data Exchange (ETDEWEB)

    REYNOLDS, R.M.

    2006-10-01

    MSG05 was a study of atmospheric transport and dispersion in the deep urban canyons of Midtown New York City, in the area of Madison Square Garden. This downtown area is considered to be a prime target for terrorist activities, and has one of the largest commuter populations in the world. Little is known about air flow and hazardous gas dispersion in such scenarios, since previous urban field experiments have focused on small to medium sized cities with much smaller street canyons. On March 10 and 14, 2005, a series of Perfluorocarbon Tracer (PFT) tracers were released and tracked with about 30 sampling stations at radial distances of about 0.2 and 0.4 km, with vertical profiles near a 250 m tall building (One Penn Plaza). Meteorological stations collected wind data in the MSG vicinity, at street level and rooftop level. MSG05 is expected to provide useful information on rapid vertical dispersion will assist in planning for more extensive studies. This data release is being made available to a restricted group of key scientists who have worked on the project. Part of the QA program involves feedback from scientists and modelers who are working on this study. This document describes the meteorological component of the project. The file organization and metadata are detailed so that a researcher can work with the data sets.

  2. Effect of room air recirculation delay on the decay rate of tracer gas concentration

    Energy Technology Data Exchange (ETDEWEB)

    Kristoffersen, A.R.; Gadgil, A.J.; Lorenzetti, D.M.

    2004-05-01

    Tracer gas measurements are commonly used to estimate the fresh air exchange rate in a room or building. Published tracer decay methods account for fresh air supply, infiltration, and leaks in ductwork. However, the time delay associated with a ventilation system recirculating tracer back to the room also affects the decay rate. We present an analytical study of tracer gas decay in a well-mixed, mechanically-ventilated room with recirculation. The analysis shows that failing to account for delays can lead to under- or over-estimates of the fresh air supply, depending on whether the decay rate calculation includes the duct volume.

  3. Tracer transport in fractured crystalline rock: Evidence of nondiffusive breakthrough tailing

    Science.gov (United States)

    Becker, M.W.; Shapiro, A.M.

    2000-01-01

    Extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media. This behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels, along fracture walls, or within the bulk matrix. We present a field example where tracer breakthrough tailing apparently results from nondiffusive transport. Tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme. Deuterated water, bromide, and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity. The late time behavior of the normalized breakthrough curves were consistent for all tracers, even when the pumping rate was changed. The lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes. This finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock.

  4. Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, S.P.H.T. [Lawrence Livermore National Lab., CA (United States); King, J.C. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Vieira, N.E. [National Inst. of Child Health and Human Development, Bethesda, MD (United States); Woodhouse, L.R. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Yergey, A.L. [National Inst. of Child Health and Human Development, Bethesda, MD (United States)

    1996-08-01

    Accelerator mass spectrometry is so sensitive to small quantities of {sup 41}Ca that it might be used as a tracer in the study of human calcium kinetics to generate unique kinds of data. In contrast with the use of other Ca isotopic tracers, {sup 41}Ca tracer can be so administered that the tracer movements between the various body pools achieve a quasi steady state. Resorbing bone may thus be directly measured. We have tested such a protocol against a conventional stable isotope experiment with good agreement.

  5. Low-cost, High Flexibility I-V Curve Tracer for Photovoltaic Modules

    DEFF Research Database (Denmark)

    Ibirriaga, Julen Joseba Maestro; Pena, Xabier Miquelez de Mendiluce; Opritescu, Adrian

    2010-01-01

    This work presents the design, construction and test of an in-door low cost, high flexibility I-V curve tracer for photovoltaic modules. The tracer is connected to a Xenon lamp based flashing solar simulator. The designed tracer is able to deal with the very fast changing irradiation conditions...... and its control software offers the flexibility to automatically adapt to the different irradiation conditions set by the flashing solar simulator. Simulation and experimental tests have been carried out, in order to verify the behaviour and performance of the designed I-V curve tracer....

  6. Estimation of migration characteristics of a nonsorbing tracer through an artificial rock fracture

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, B. H.; Park, J. K.; Han, P. S. [KAERI, Taejon (Korea, Republic of)

    1998-10-01

    Experiment on the transport of a nonsorbing tracer in an artificial rock fracture was carried out. The scale of an artificial rock was 50x20x5cm. The migration field was assumed as a two dimensional system. Eosine, a kind of an organic dye, was used as a nonsorbing tracer. This tracer was injected as a pulse function in a point source and point withdraw system. Volumetric flow rate was 0.5ml/min. The migration plume of the tracer was captured by a digital camera and compared with a result from transport modeling.

  7. The use of synthetic colloids in tracer transport experiments in saturated rock fractures

    Energy Technology Data Exchange (ETDEWEB)

    Reimus, Paul William [Univ. of California, Berkeley, CA (United States)

    1995-08-01

    Studies of groundwater flow and contaminant transport in saturated, fractured geologic media are of great interest to researchers studying the potential long-term storage of hazardous wastes in or near such media. A popular technique for conducting such studies is to introduce tracers having different chemical and physical properties into a system and then observe the tracers at one or more downstream locations, inferring flow and transport mechanisms from the breakthrough characteristics of the different tracers. Many tracer studies have been conducted in saturated, fractured media to help develop and/or refine models capable of predicting contaminant transport over large scales in such media.

  8. AN INTEGRATED APPROACH TO CHARACTERIZING BYPASSED OIL IN HETEROGENEOUS AND FRACTURED RESERVOIRS USING PARTITIONING TRACERS

    Energy Technology Data Exchange (ETDEWEB)

    Akhil Datta-Gupta

    2003-08-01

    We explore the use of efficient streamline-based simulation approaches for modeling partitioning interwell tracer tests in hydrocarbon reservoirs. Specifically, we utilize the unique features of streamline models to develop an efficient approach for interpretation and history matching of field tracer response. A critical aspect here is the underdetermined and highly ill-posed nature of the associated inverse problems. We have adopted an integrated approach whereby we combine data from multiple sources to minimize the uncertainty and non-uniqueness in the interpreted results. For partitioning interwell tracer tests, these are primarily the distribution of reservoir permeability and oil saturation distribution. A novel approach to multiscale data integration using Markov Random Fields (MRF) has been developed to integrate static data sources from the reservoir such as core, well log and 3-D seismic data. We have also explored the use of a finite difference reservoir simulator, UTCHEM, for field-scale design and optimization of partitioning interwell tracer tests. The finite-difference model allows us to include detailed physics associated with reactive tracer transport, particularly those related with transverse and cross-streamline mechanisms. We have investigated the potential use of downhole tracer samplers and also the use of natural tracers for the design of partitioning tracer tests. Finally, the behavior of partitioning tracer tests in fractured reservoirs is investigated using a dual-porosity finite-difference model.

  9. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing

    2016-12-08

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  10. Accurate blood flow measurements: are artificial tracers necessary?

    Science.gov (United States)

    Poelma, Christian; Kloosterman, Astrid; Hierck, Beerend P; Westerweel, Jerry

    2012-01-01

    Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case), as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements). These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

  11. Using biofuel tracers to study alternative combustion regimes

    Science.gov (United States)

    Mack, J. H.; Flowers, D. L.; Buchholz, B. A.; Dibble, R. W.

    2007-06-01

    Interest in the use of alternative fuels and engines is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO2 emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions and higher noise. Adding oxygenated compounds to the fuel helps reduce PM emissions. However, relying on fuel alone to reduce PM is unrealistic due to economic constraints and difficult due to the emerging PM standards. Keeping peak combustion temperature below 1700 K inhibits NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous charge compression ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to improve our combustion modeling.

  12. Titan's post-equinox circulation revealed using chemical tracers

    Science.gov (United States)

    Teanby, N. A.; Irwin, P. G. J.; Nixon, C. A.; de Kok, R.; Vinatier, S.; Coustenis, A.; Calcutt, S. B.

    2012-04-01

    Titan’s atmosphere harbors a vast array of minor chemical compounds produced by its active photochemical cycle - including many hydrocarbon and nitrile species. These species have a wide range of lifetimes and can be used as chemical tracers of atmospheric motion on a variety of time scales (Teanby et al 2008). Therefore, by measuring how the abundances of these species vary during Cassini’s mission so far, it is possible to probe changes in Titan’s general circulation. Here we use eight years of Cassini Composite InfraRed Spectrometer (CIRS) data to study how the atmospheric circulation behaves during the equinox and post-equinox periods. As northern winter progressed to northern spring, significant changes in the distribution of trace gases were observed. These include an increase in trace gas abundance at the north pole and northward migration of the vortex boundary. The implications of the observed changed will be discussed - including a possible interpretation of the recent changes as a weakening of the north polar vortex accompanied by a reduction in cross-vortex mixing. References: Teanby, N. A., et al. (2008) "Titan's winter polar vortex structure revealed by chemical tracers". JGR-Planets, Vol. 113, E12003. Figure showing the observed variations in temperature and composition from the mission so far.

  13. Acupuncture meridians demythified. A study using the radioactive tracer method

    Energy Technology Data Exchange (ETDEWEB)

    Simon, J.; Esquerre, J.P.; Guiraud, R.; Guiraud, G.; Lazorthes, Y.

    1988-07-01

    Radioactive trajectories can be visualized by injecting a radioactive tracer, technetium 99 m, at the site of acupuncture points. To determine the exact nature of these trajectories we performed several experiments on healthy volunteers, and our results may be summarized as follows. The target organs of technetium 99 m, and notably the thyroid gland, were always visualized. The circulating radioactivity, visible on scintiscans and confirmed by venous blood counts, was not negligible. The radioactive trajectories we observed were often divided at their starting point and did not extend along the whole length of the acupuncture meridians they might have made visible. The radioactive trajectories disappeared after venous blockade to reappear when the blockade was lifted. Finally, the radioactive trajectories obtained were very similar after injection at the acupuncture point and at a control point. These findings indicate a lymphatic and venous drainage of the radioactive tracer at the site of injection followed by transportation through the veins, rather than visualization of acupuncture meridians as suggested by some authors.

  14. Inversion of Hydrological Tracer Test Data Using TomogrpahicConstraints

    Energy Technology Data Exchange (ETDEWEB)

    Linde, Niklas; Finsterle, Stefan; Hubbard, Susan

    2004-11-11

    A reasonable description of the hydraulic conductivity structure is a prerequisite for modeling contaminant transport. However, formulations of hydrogeological inverse problems utilizing hydrogeological data only often fail to reliably resolve features at a resolution required for accurately predicting transport. Incorporation of geophysical data into the inverse problem offers the potential to increase this resolution. In this study, we invert hydrological tracer test data using the shape and relative magnitude variations derived from geophysical tomographic data to regionalize a hydrogeological inverse problem in order to estimate the hydraulic conductivity structure. Our approach does not require that the petrophysical relationship be known a-priori, but that it is linear and stationary within each geophysical anomaly. However, tomograms are imperfect models of geophysical properties and geophysical properties are not necessarily strongly linked to hydraulic conductivity. Therefore, we focus on synthetic examples where the correlation between radar velocity and hydraulic conductivity, as well as the geophysical data acquisition errors, are varied in order to assess what aspects of the hydraulic conductivity structure we can expect to resolve under different conditions. The results indicate that regularization of the tracer inversion procedure using geophysical data improves estimates of hydraulic conductivity. We find that even under conditions of corrupted geophysical data, we can accurately estimate the effective hydraulic conductivity and areas of high and low hydraulic conductivity. However, given imperfect geophysical data, our results suggest that we cannot expect accurate estimates of the variability of the hydraulic conductivity structure.

  15. Isotopologues of dense gas tracers in NGC 1068

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Junzhi; Qiu, Jianjie [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030, Shanghai (China); Zhang, Zhi-Yu [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Shi, Yong [School of Astronomy and Space Science, Nanjing University, Nanjing, 210093 (China); Zhang, Jiangshui [Center For Astrophysics, GuangZhou University, 510006, GuangZhou (China); Fang, Min, E-mail: jzwang@shao.ac.cn [ESO, Karl Schwarzschild Strasse 2, D-85748 Garching bei Munich (Germany)

    2014-11-20

    We present observations of isotopic lines of dense gas tracers toward the nuclear region of nearby Seyfert 2 galaxy NGC 1068 with the IRAM 30 m telescope and the Atacama Pathfinder Experiment (APEX) 12 m telescope. We detected four isotopic lines (H{sup 13}CN 1-0, H{sup 13}CO{sup +} 1-0, HN{sup 13}C 1-0, and HC{sup 18}O{sup +} 1-0) at the 3 mm band with the IRAM 30 m telescope and obtained upper limits of other lines. We calculated optical depths of dense gas tracers with the detected isotopic lines of HCN 1-0, HCO{sup +} 1-0, and HNC 1-0. We find that the {sup 14}N/{sup 15}N abundance ratio is greater than 420 if we adopt the upper limit of HC{sup 15}N(1-0) emission. Combining this with fluxes of 1-0 lines from IRAM 30 m observations and the upper limit of 3-2 lines from APEX 12 m observations, we also estimated the excitation condition of molecular gas in the nuclear region of NGC 1068, which is less dense than that in the extreme starburst regions of galaxies.

  16. Accurate blood flow measurements: are artificial tracers necessary?

    Directory of Open Access Journals (Sweden)

    Christian Poelma

    Full Text Available Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case, as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (appro