Sample records for gas tracer studies

  1. Sulfur hexafluoride gas tracer studies in streams

    Microsoft Academic Search

    David E. Hibbs; J. S. Gulliver; K. L. Parkhill

    1998-01-01

    Gas tracers are useful investigative tools in the study of reaeration and the fate of volatile organic contaminants in many natural streams. They enable the direct measurement of a variety of stream parameters, including the gas exchange rates between the stream and the atmosphere, as well as the spreading rate for dissolved pollutants downstream of a discharge point or spill

  2. Sulfur hexafluoride gas tracer studies in streams

    SciTech Connect

    Hibbs, D.E.; Gulliver, J.S. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Civil Engineering; Parkhill, K.L. [Freese and Nichols, Inc., Fort Worth, TX (United States)

    1998-08-01

    Gas tracers are useful investigative tools in the study of reaeration and the fate of volatile organic contaminants in many natural streams. They enable the direct measurement of a variety of stream parameters, including the gas exchange rates between the stream and the atmosphere, as well as the spreading rate for dissolved pollutants downstream of a discharge point or spill site. The air-water mass transfer coefficients, dispersion coefficients, and mean residence times in two experimental streams and one natural stream are measured using a variation of the standard volatile tracer-dye technique. Sulfur hexafluoride (SF{sub 6}) is used as the volatile tracer and rhodamine WT is used as the conservative tracer. The low limit of quantification of SF{sub 6} makes it possible to inject SF{sub 6}-rich water into many streams and avoid complications with dosing a stream with a gaseous tracer. The experimental methods are described in detail. The SF{sub 6} measurements were extremely precise, producing smooth concentration time curves. The SF{sub 6} measurements collected in side-by-side experimental channels yielded similar values of the gas transfer coefficient.

  3. IMPLICATIONS OF RECENT NIOSH TRACER GAS STUDIES ON BLEEDER AND GOB GAS VENTILATION DESIGN

    Microsoft Academic Search

    T. P. Mucho; W. P. Diamond; F. Garcia; J. D. Byars; S. L. Cario

    The National Institute for Occupational Safety and Health (NIOSH) has been conducting research at a Pittsburgh Coalbed longwall mine to evaluate and optimize bleeder ventilation and gob gas venthole longwall methane control systems. Gas flow into these two methane control systems was investigated using a combination of Sulphur Hexafluoride (SF6) tracer gas studies and gob venthole pressure monitoring experiments. The

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

    SciTech Connect

    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 transport models needed for risk assessment.

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

    SciTech Connect

    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 for improving transport models needed for risk assessment.

  6. Modelling-tracer study for risk assessment of a proposed sour gas facility.

    PubMed

    Sakiyama, S K; Angle, R P

    1988-03-01

    As an integral part of a risk assessment of a sour gas pipeline proposed for a recreational area in the Rocky Mountain foothills, the dispersion of hydrogen sulphide was assessed using meteorological monitoring, tracer gas concentration measurement and a complex terrain diffusion model. Sulphur hexafluoride was released into the nocturnal drainage winds of two valleys in the eastern slopes of the Alberta Rockies southwest of Calgary. The resulting concentrations were measured at several points on transects at various distances from the source. The NUVAL version of the dispersion model IMPACT (Integrated Model for Plumes and Atmospherics in Complex Terrain) was site tuned using the measured concentrations and concurrent meteorological data. Relative mean absolute errors of 24-50% were obtained. The Gaussian model (PLUMES) with modified stability classes gave relative mean absolute errors of 42-64% in predicting transect maxima. Dilution rates were found to be much larger than would be experienced under similar conditions over flat terrain. PMID:24248626

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

    PubMed

    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 background concentrations to allow for increased sensitivity. PMID:25175285

  8. Overview of nitrogen-15 application as a tracer gas for material migration and retention studies in tokamaks

    NASA Astrophysics Data System (ADS)

    Petersson, P.; Rubel, M.; Possnert, G.; Brezinsek, S.; Kreter, A.; Möller, S.; Hakola, A.; Mayer, M.; Miettunen, J.; Airila, M. I.; Makkonen, T.; Neu, R.; Rohde, V.; the TEXTOR Team; ASDEX-Upgrade Team

    2014-04-01

    Experimental and analytical procedures related to the application of nitrogen-15 isotope for material migration studies have been developed and used for tracer experiments in the TEXTOR and ASDEX-Upgrade tokamaks in order to assess the retention of nitrogen in plasma-facing components made of graphite and tungsten. The surface study was performed by time-of-flight heavy ion elastic recoil detection analysis and by means of nuclear reaction analysis based on the 15N(p,??)12C process. In both tokamaks nitrogen retention has exceeded 10% of the injected gas. In ASDEX-Upgrade the largest fraction of 15N has been detected on protruding parts near the injection port, while around 4% has been found in the divertor. The ASDEX-Upgrade results have also been modeled. Helium trapping has been measured in deposits containing tungsten and nitrogen.

  9. A comparative study of the gas exchange potential between three wetland species using sulfur hexafluoride as a tracer

    Microsoft Academic Search

    N Salhani; E Stengel

    2001-01-01

    The gas-exchange potential of three wetland species (helophytes) was examined in an aquatic model vegetation facility (AMOVA) using sulfur hexafluoride (SF6) as a tracer. Three beds containing gravel and vegetated with Phragmitesaustralis, Typhalatifolia and Schoenoplectuslacustris were compared to an unvegetated gravel bed as a reference. A mass balance of SF6 emissions revealed a different seasonal emission pattern for the three

  10. Tracer gas diffusion sampling test plan

    SciTech Connect

    Rohay, V.J.

    1993-10-01

    Efforts are under way to employ active and passive vapor extraction to remove carbon tetrachloride from the soil in the 200 West Area an the Hanford Site as part of the 200 West Area Carbon Tetrachloride Expedited Response Action. In the active approach, a vacuum is applied to a well, which causes soil gas surrounding the well to be drawn up to the surface. The contaminated air is cleaned by passage through a granular activated carbon bed. There are questions concerning the radius of influence associated with application of the vacuum system and related uncertainties about the soil-gas diffusion rates with and without the vacuum system present. To address these questions, a series of tracer gas diffusion sampling tests is proposed in which an inert, nontoxic tracer gas, sulfur hexafluoride (SF{sub 6}), will be injected into a well, and the rates of SF{sub 6} diffusion through the surrounding soil horizon will be measured by sampling in nearby wells. Tracer gas tests will be conducted at sites very near the active vacuum extraction system and also at sites beyond the radius of influence of the active vacuum system. In the passive vapor extraction approach, barometric pressure fluctuations cause soil gas to be drawn to the surface through the well. At the passive sites, the effects of barometric ``pumping`` due to changes in atmospheric pressure will be investigated. Application of tracer gas testing to both the active and passive vapor extraction methods is described in the wellfield enhancement work plan (Rohay and Cameron 1993).

  11. Following Footsteps: ECD Tracer Studies.

    ERIC Educational Resources Information Center

    Smale, Jim, Editor

    2002-01-01

    This document consists of the single 2002 issue of The Bernard van Leer Foundation's "Early Childhood Matters," a periodical addressed to practitioners in the field of early childhood education and including information on projects funded by the Foundation. Articles in this issue focus on early childhood development tracer studies of former…

  12. Measuring Soil-Water Content with Gas-Phase Partitioning Tracers: Mass Transfer Limitations

    NASA Astrophysics Data System (ADS)

    Li, L.; Imhoff, P. T.

    2002-05-01

    Soil-water content is an important parameter for soil scientists, hydrologists, and engineers studying the movement of water, gas, and pollutants in the vadose zone. Traditionally, soil-water content is characterized with point measurements, which include gravimetric analysis of core samples, time domain reflectrometry, and neutron moderation. More recently, the gas-phase partitioning tracer method has been suggested as an in situ tool for obtaining soil water content over large measurement volumes. Here, two tracers move through the gas phase, one that is non-reactive and one that partitions into the bulk water. Chromatographic separation of the tracers occurs that can be related to the soil-water content in the volume traversed by the tracers. Gas-phase partitioning tracers were previously tested under controlled laboratory conditions in homogeneous porous media with reasonably homogeneous distributions of soil-water content. In natural systems, though, soil-water is often heterogeneously distributed and sometimes moving. In this study, we investigated the utility of gas-phase partitioning tracers for these conditions. Laboratory columns were constructed with homogeneous and heterogeneous distributions of sand, which resulted in homogeneous or heterogeneous distributions of soil-water after water addition. In some experiments, the water infiltrated at a steady rate. Carbon dioxide and difluoromethane were selected as bulk-water partitioning tracers, which are tracers whose predominant mechanism of retention is partitioning into water; helium was the conservative tracer. These tracers were flushed through the experimental systems, varying the tracer slug size and gas-phase velocity. Measured soil water contents where compared with known values to infer the conditions under which mass transfer limitations influence gas-phase tracer measurements.

  13. Waste tank ventilation rates measured with a tracer gas method

    SciTech Connect

    Huckaby, J.L.; Evans, J.C.; Sklarew, D.S.; Mitroshkov, A.V.

    1998-08-01

    Passive ventilation with the atmosphere is used to prevent accumulation of waste gases and vapors in the headspaces of 132 of the 177 high-level radioactive waste Tanks at the Hanford Site in Southeastern Washington State. Measurements of the passive ventilation rates are needed for the resolution of two key safety issues associated with the rates of flammable gas production and accumulation and the rates at which organic salt-nitrate salt mixtures dry out. Direct measurement of passive ventilation rates using mass flow meters is not feasible because ventilation occurs va multiple pathways to the atmosphere (i.e., via the filtered breather riser and unsealed tank risers and pits), as well as via underground connections to other tanks, junction boxes, and inactive ventilation systems. The tracer gas method discussed in this report provides a direct measurement of the rate at which gases are removed by ventilation and an indirect measurement of the ventilation rate. The tracer gas behaves as a surrogate of the waste-generated gases, but it is only diminished via ventilation, whereas the waste gases are continuously released by the waste and may be subject to depletion mechanisms other than ventilation. The fiscal year 1998 tracer studies provide new evidence that significant exchange of air occurs between tanks via the underground cascade pipes. Most of the single-shell waste tanks are connected via 7.6-cm diameter cascade pipes to one or two adjacent tanks. Tracer gas studies of the Tank U-102/U-103 system indicated that the ventilation occurring via the cascade line could be a significant fraction of the total ventilation. In this two-tank cascade, air evidently flowed from Tank U-103 to Tank U-102 for a time and then was observed to flow from Tank U-102 to Tank U-103.

  14. Preliminary Investigation of Tracer Gas Reaeration Method for Shallow Bays

    E-print Network

    Baker, Sarah H.; Holley, Edward R.

    was used with propane for the tracer gas and Rhodamine-WT, a fluorescent dye, for the "conservative" tracer. The propane was injected through porous tile diffusers, and the dye was released simultaneously. The propane acts as a model for the surface...

  15. Motorola's Exhaust Optimization Program: Tracer Gas Application for Gas Panel Enclosures 

    E-print Network

    Myart, H. R.; Camacho, R.

    2003-01-01

    Sector (SPS) fab. These obtained studies have prompted Motorola to focus on a broad range of energy conservation projects. This paper will focus on exhaust optimization through tracer gas testing. Testing has resulted in exhaust and make-up air reductions...

  16. Preliminary Investigation of Tracer Gas Reaeration Method for Shallow Bays 

    E-print Network

    Baker, Sarah H.; Holley, Edward R.

    1987-01-01

    Accurate estimates of surface exchange rates for volatile pollutants in bays are needed to allow predictions of pollutant movement and retention time. The same types of estimates can be used to calculate reaeration rates. The tracer gas technique...

  17. Ballistic Motion of a Tracer Particle Coupled to a Bose gas

    E-print Network

    Juerg Froehlich; Zhou Gang

    2013-02-06

    We study the motion of a heavy tracer particle weakly coupled to a dense interacting Bose gas exhibiting Bose-Einstein condensation. In the so-called mean-field limit, the dynamics of this system approaches one determined by nonlinear Hamiltonian evolution equations. We derive the effective dynamics of the tracer particle, which is described by a non-linear integro-differential equation with memory, and prove that if the initial speed of the tracer particle is below the speed of sound in the Bose gas the motion of the particle approaches an inertial motion at constant velocity at large times.

  18. Field measurements of tracer gas transport by barometric pumping

    SciTech Connect

    Lagus, P.L. [Lagus Applied Technology, San Diego, CA (United States); McKinnis, W.B. [Lawrence Livermore National Lab., Mercury, NV (United States); Hearst, J.R.; Burkhard, N.R.; Smith, C.F. [Lawrence Livermore National Lab., CA (United States)

    1994-07-28

    Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ``active`` tracer was driven by a large quantity of injected air; the second ``passive`` tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through {approximately}1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs.

  19. Impact of Salinity on the Air-Water Partition Coefficient of Gas Tracers

    SciTech Connect

    Zhong, Lirong; Pope, Gary A.; Evans, John C.; Cameron, Richard J.

    2005-09-01

    The use of a gas partitioning interwell tracer test (PITT) has been proposed as a standard approach to the measurement of field-scale vadose zone water saturation fractions. The accuracy of the saturation measurement is largely dependent on the determination of the air-water partitioning coefficient, K, of the tracers; however, in practice, K is also strongly influenced by the physical and chemical properties of the water. In this study, column tests were conducted to investigate the impact of salinity on tracer partitioning coefficients for two promising gas phase candidate tracers, dibromomethane and dimethylether. Sodium thiosulfate was used as a salinity surrogate. The dynamic K values of the two partitioning tracers were measured for sodium thiosulfate concentrations between 0% and 36% by weight. Methane was used as the non-partitioning tracer for all experiments. K values were found to decrease significantly with increasing sodium thiosulfate concentration. Similar correlations between K values and sodium thiosulfate concentration were found for both of the partitioning tracers tested.

  20. Estimation of Uncertainty in Tracer Gas Measurement of Air Change Rates

    PubMed Central

    Iizuka, Atsushi; Okuizumi, Yumiko; Yanagisawa, Yukio

    2010-01-01

    Simple and economical measurement of air change rates can be achieved with a passive-type tracer gas doser and sampler. However, this is made more complex by the fact many buildings are not a single fully mixed zone. This means many measurements are required to obtain information on ventilation conditions. In this study, we evaluated the uncertainty of tracer gas measurement of air change rate in n completely mixed zones. A single measurement with one tracer gas could be used to simply estimate the air change rate when n = 2. Accurate air change rates could not be obtained for n ? 2 due to a lack of information. However, the proposed method can be used to estimate an air change rate with an accuracy of <33%. Using this method, overestimation of air change rate can be avoided. The proposed estimation method will be useful in practical ventilation measurements. PMID:21318005

  1. Measuring low flows in Devonian shale gas wells with a tracer-gas flowmeter

    SciTech Connect

    Bennett, R. (Columbia Gas System Service Corp. (US)); Schettler, P.D. Jr.; Gustafson, T.D.; Gillette, I.E. (Juniata Coll., Huntingdon, PA (United States))

    1991-06-01

    In this paper a design for a downhole flowmeter that can locate and quantify gas-entry points in a well is presented. The instrument has a gas-tracer injector at its lower end and a tracer detector at its upper end. The authors determine gas flow in the well by injecting tracer gas at a precisely measured rate into the natural gas flow and measuring the concentration with the detector. The result is a wireline log that locates and quantifies natural gas sources from the decrease in measured flow as the wireline instrument passes each source. The new design has been tested against calibrated gas flows in the laboratory and in Devonian shale gas wells in the field. The new flowmeter is compared with spinner, temperature, sonic, and television logs. The instrument provides an expanded flow range compared with spinner logs and furnishes quantitative mass-flow information compared with incomplete and qualitative indications provided by temperature and sonic logs.

  2. Evaluating Gas-Phase Transport And Detection Of Noble Gas Signals From Underground Nuclear Explosions Using Chemical Tracers

    NASA Astrophysics Data System (ADS)

    Carrigan, C. R.; Hunter, S. L.; Sun, Y.; Wagoner, J. L.; Ruddle, D.; Anderson, G.; Felske, D.; Myers, K.; Zucca, J. J.; Emer, D. F.; Townsend, M.; Drellack, S.; Chipman, V.; Snelson, C. M.

    2013-12-01

    The 1993 Non-Proliferation Experiment (NPE) involved detonating 1 kiloton of chemical explosive in a subsurface cavity which also contained bottles of tracer gases (ref 1). That experiment provided an improved understanding of transport processes relevant to the detection of noble gas signals at the surface emanating from a clandestine underground nuclear explosion (UNE). As an alternative to performing large chemical detonations to simulate gas transport from UNEs, we have developed a test bed for subsurface gas transport, sampling and detection studies using a former UNE cavity. The test bed site allows for the opportunity to evaluate pathways to the surface created by the UNE as well as possible transport mechanisms including barometric pumping and cavity pressurization (ref 2). With the test bed we have monitored long-term chemical tracers as well as newly injected tracers. In order to perform high temporal resolution tracer gas monitoring, we have also developed a Subsurface Gas Smart Sampler (SGSS) which has application during an actual On Site Inspection (OSI) and is available for deployment in OSI field exercises planned for 2014. Deployment of five SGSS at the remote test bed has provided unparalleled detail concerning relationships involving tracer gas transport to the surface, barometric fluctuations and temporal variations in the natural radon concentration. We anticipate that the results of our tracer experiments will continue to support the development of improved noble gas detection technology for both OSI and International Monitoring System applications. 1. C.R. Carrigan et al., 1996, Nature, 382, p. 528. 2. Y. Sun and C.R. Carrigan, 2012, Pure Appl. Geophys., DOI 10.1007/s00024-012-0514-4.

  3. [Tracer gas evaluations of local exhaust hood performance].

    PubMed

    Ojima, Jun

    2007-09-01

    A local exhaust hood is one of the most commonly used controls for harmful contaminants in the working environment. In Japan, the performance of a hood is evaluated by hood velocity measurements, and administrative performance requirements for hoods are provided as control velocities by the Japanese Industrial Safety and Health Law. However, it is doubtful whether the control velocity would be the most suitable velocity for any industrial hood since the control velocity is not substantiated by actual measurements of the containment ability of each hood. In order to examine the suitability of the control velocity as a performance requirement, a hood performance test by the tracer gas method, using carbon dioxide (CO(2)), was conducted with an exterior type hood in a laboratory. In this study, as an index of the hood performance, capture efficiency defined as the ratio of contaminant quantity captured by the hood to the total generated contaminant quantity, was determined by measuring the CO(2) concentrations. When the assumptive capture point of the contaminant was located at a point 30 cm from the hood opening, a capture efficiency of >90% could be achieved with a suction velocity of less than the current control velocity. Without cross draft, a capture efficiency of >90% could be achieved with a suction velocity of 0.2 m/s (corresponding to 40% of the control velocity) at the capture point. Reduction of the suction velocity to 0.2 m/s caused an 80% decrease in exhaust flow rate. The effect of cross draft, set at 0.3 m/s, on the capture efficiency differed according to its direction. When the direction of the cross draft was normal to the hood centerline, the effect was not recognized and a capture efficiency of >90% could be achieved with a suction velocity of 0.2 m/s. A cross draft from a worker's back (at an angle of 45 degrees to the hood centerline) did not affect the capture efficiency, either. When the cross draft blew at an angle of 135 degrees to the hood centerline, a capture efficiency of >90% could be achieved with a suction velocity of 0.4 m/s. The reduction of suction velocity would beneficially reduce running costs of local exhaust hoods and air conditioning. Effective and economical exhaustion would be achieved if the minimum velocity obtained by the tracer gas method were to be substituted for the excessive control velocity. PMID:17938560

  4. The Shoreline Environment Atmospheric Dispersion Experiment (SEADEX): Meteorological and gas tracer data

    SciTech Connect

    Johnson, W.B.; Cantrell, B.K.; Morley, B.M.; Uthe, E.E.; Nitz, K.C.

    1987-10-01

    The SEADEX atmospheric dispersion field study was conducted during the period May 28 to June 8, 1982, in northeastern Wisconsin, the vicinity of the Kewaunee Power Plant on the western shore of Lake Michigan. The specific objectives of SEADEX were to characterize (1) the atmospheric dispersion and (2) the meteorological conditions influencing this dispersion as completely as possible during the test period. This field study included a series of controlled tracer tests utilizing state-of-the-art tracer measurement technology to determine horizontal and vertical dispersion over both land and water. Extensive meteorological measurements were obtained to thoroughly characterize the three-dimensional structure of the atmospheric boundary controlling the dispersion process. This volume presents the meteorological and gas tracer data collected during the field study. 391 figs., 32 tabs.

  5. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

    SciTech Connect

    Jung, Yoojin; Han, Byunghyun; Mostafid, M. Erfan; Chiu, Pei [Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716 (United States); Yazdani, Ramin [Yolo County Planning and Public Works Department, Division of Integrated Waste Management, Yolo County, 44090 County Rd. 28H, Woodland, CA 95776 (United States); Imhoff, Paul T., E-mail: imhoff@udel.edu [Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716 (United States)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Photoacoustic infrared spectroscopy tested for measuring tracer gas in landfills. Black-Right-Pointing-Pointer Measurement errors for tracer gases were 1-3% in landfill gas. Black-Right-Pointing-Pointer Background signals from landfill gas result in elevated limits of detection. Black-Right-Pointing-Pointer Technique is much less expensive and easier to use than GC. - Abstract: Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF{sub 6}), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.

  6. Determination of Water Saturation in Relatively Dry Porous Media Using Gas-phase Tracer Tests

    SciTech Connect

    Oostrom, Martinus; Tartakovsky, Guzel D.; Wietsma, Thomas W.; Truex, Michael J.; Dane, Jacob H.

    2011-04-15

    Soil desiccation (drying), involving water evaporation induced by dry air injection and extraction, is a potentially robust remediation process to slow migration of inorganic or radionuclide contaminants through the vadose zone. The application of gas-phase partitioning tracer tests has been proposed as a means to estimate initial water volumes and to monitor the progress of the desiccation process at pilot-test and field sites. In this paper, tracer tests have been conducted in porous medium columns with various water saturations using sulfur hexafluoride as the conservative tracer and tricholorofluoromethane and difluoromethane as the water-partitioning tracers. For porous media with minimal silt and/or organic matter fractions, tracer tests provided reasonable saturation estimates for saturations close to zero. However, for sediments with significant silt and/or organic matter fractions, tracer tests only provided satisfactory results when the water saturation was at least 0.1 - 0.2. For dryer conditions, the apparent tracer retardation increases due to air – soil sorption, which is not included in traditional retardation coefficients derived from advection-dispersion equations accounting only for air – water partitioning and water – soil sorption. Based on these results, gas-phase partitioning tracer tests may be used to determine initial water volumes in sediments, provided the initial water saturations are sufficiently large. However, tracer tests are not suitable for quantifying moisture content in desiccated sediments.

  7. Tracer study of San Vicente reservoir

    SciTech Connect

    Williams, R.T. [Water Quality Laboratory, La Mesa, CA (United States)

    1996-11-01

    The City of San Diego remains on the cutting edge of water conservation. With an unwavering commitment to maintain an adequate water supply for the future, water repurification is now being considered. The City of San Diego and San Diego Water Authority (CWA) have proposed to recycle repurified water through San Vicente Reservoir. A key component of assessing the feasibility of such a project is to calculate the retention time of repurified water in the reservoir. Working with engineering consultant team (Montgomery-Watson Engineers and Flow Science, Incorporated) two tracer studies were conducted to model the circulation and mixing of repurified water introduced into the reservoir. The goal was to determine whether repurified water recycled through San Vicente will meet the retention time criteria established by the Department of Health Services. This presentation however, will not attempt to interpret the results of the study, that aspect will be evaluated by the Flow Scientist. The objective here is to explain how the project was carried out and to focus mostly on the analytical work performed on the samples by the chemist in the City of San Diego Water Quality Laboratory.

  8. Tracer Gas as a Practical Field Diagnostic Tool for Assessing Duct System Leaks 

    E-print Network

    Cummings, J. B.

    1989-01-01

    A methodology is presented for using tracer gas testing to detect and quantify duct leakage in homes. Since air is invisible, leakage of air from duct systems often remains undetected. Smoke sticks used in conjunction with blower doors are excellent...

  9. National Biomedical Tracer Facility: Project definition study

    SciTech Connect

    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.

  10. RE-ENTRAINMENT AND DISPERSION OF EXHAUSTS FROM INDOOR RADON REDUCTION SYSTEMS: ANALYSIS OF TRACER GAS DATA

    EPA Science Inventory

    Tracer gas studies were conducted around four model houses in a wind tunnel, and around one house in the field, to quantify re-entrainment and dispersion of exhaust gases released from residential indoor radon reduction systems. Re-entrainment tests in the field suggest that acti...

  11. RE-ENTRAINMENT AND DISPERSION OF EXHAUSTS FROM INDOOR RADON REDUCTION SYSTEMS: ANALYSIS OF TRACER GAS DATA

    EPA Science Inventory

    The paper discusses two tracer gas studies, to quantify the extent to which exhaust gases from indoor radon reduction systems are re-entrained into pitched-roof houses (exposing persons indoors), and the manner in which the exhausts disperse outdoors (exposing persons outside the...

  12. Tracer Gas as a Practical Field Diagnostic Tool for Assessing Duct System Leaks

    E-print Network

    Cummings, J. B.

    1989-01-01

    TRACER GAS AS A PRACTICAL FIELD DIAGNOSTIC TOOL FOR ASSESSING DUCT SYSTEM LEAKS JAMES B. CUMMINGS Research Analyst Florida Solar Energy Center Cape Canaveral, Florida ABSTRACT A methodology is presented for using tracer gas testing to detect..., however, preclude supply leaks up to the same size as the return leaks. ~nfiltration testing both with the air handler on and off has been done by Gammage et al. (1984) (4) , Cromer and Cummings (1986) (1) , and Cummings (l988,1989) (2) , (3...

  13. Gas injection with radioactive tracer to determine reservoir continuity, East Coalinga field, California

    Microsoft Academic Search

    Tinker

    1972-01-01

    The Temblor Zone II reservoir consists of intervals of movable oil associated with intervals of high gas saturation or desaturated intervals. Natural gas injection into these desaturated intervals, using tritium and krypton as radioactive tracers has served to determine reservoir continuity. In these example cases, the desaturated intervals contained nearly all carbon dioxide gas. The injection tests also have furnished

  14. Fluorescence imaging of natural gas\\/air mixing without tracers added

    Microsoft Academic Search

    J. Kazenwadel; W. Koban; T. Kunzelmann; C. Schulz

    2001-01-01

    Odor markers present in natural gas are shown to be useful tracers for imaging of the gas\\/air mixing progress in technical burner applications. Since tetrahydrothiophene (THT) is commonly used to odor mark natural gas, it is a `natural' compound present in a wide range of technical combustion systems. The spectroscopic properties of this compound are investigated in static cell experiments

  15. Comparison of observed and predicted short-term tracer gas concentrations in the atmosphere

    SciTech Connect

    Cotter, S.J.; Miller, C.W.; Lin, W.C.T.

    1985-01-01

    The Savannah River Laboratory is in the process of conducting a series of atmospheric tracer studies. The inert gas sulfurhexafluoride is released from a height of 62 m for 15 min and concentrations in air are measured on sampling arcs up to 30 km downwind of the release point. Maximum 15 min. air concentrations from 14 of these tracer tests have been compared with the ground-level, centerline air concentration predicted with a Gaussian plume atmospheric transport model using eight different sets of atmospheric dispersion parameters. Preliminary analysis of the results from these comparisons indicates that the dispersion parameters developed at Juelich, West Germany, based on tracers released from a height of 50 m, give the best overall agreement between the predicted and observed values. The median value of the ratio of predicted to observed air concentrations for this set of parameters is 1.3, and the correlation coefficient between the log of the predictions and the log of the observations is 0.72. For the commonly used Pasquill-Gifford dispersion parameters, the values of these same statistics are 4.4 and 0.68, respectively. The Gaussian plume model is widely used to predict air concentrations resulting from short-term radionuclide release to the atmosphere. The results of comparisons such as these must be considered whenever the Gaussian model is used for such purposes. 22 references, 3 tables.

  16. Sulfur Hexaflouride Tracer Gas Evaluations on Hood Exhaust Reductions

    Microsoft Academic Search

    John A. Mosovsky

    1995-01-01

    Proposed facility energy reductions, which include exhaust fan speed and corresponding exhaust volume reductions, demand evaluations of exhaust hoods to ensure adequate containment efficiencies. Sulfur hexafluoride tracer tests were conducted on various designs of exhaust hoods in order to evaluate their performance in an exhaust-reduction mode. Performance tests were conducted on semiconductor-type wet process stations and plating tools operating in

  17. [Determination of tracer gas contents in sediment pore water of gas hydrate area by two-dimensional gas chromatography].

    PubMed

    Wang, Hu; Yang, Qunhui; Ji, Fuwu; Zhou, Huaiyang; Xue, Xiang

    2011-01-01

    A two-dimensional gas chromatographic instrument was established by the capillary flow technology (Deans Switch) and two columns (PoraPLOT Q and Molsieve 5A) and three detectors (pulsed discharge helium ionization detector, flame photometric detector and thermal conductivity detector). The instrument can be used to measure tracer gases simultaneously including hydrogen, methane, carbon dioxide and hydrogen sulfide. The detection limits of the hydrogen, methane, carbon dioxide and hydrogen sulfide were 0.51, 0.17, 82 and 0.08 micromol/mol, and the calibration curves presented good linear relationships in the range of 2-1030, 0.6-501, 120-10500 and 0.2- 49.1 micromol/mol, respectively. The relative standard deviations were less than 10% for the measurements of ten standard gases. By this method, the tracer gases in the sediment pore water of gas hydrate area in South China Sea had been detected. This method is simple, sensitive, and suitable for on-board detection. Compared with the usual methods for measuring tracer gases, the amount of a sample necessary is reduced greatly. It is useful for the survey of gas hydrate and hydrothermal resources below sea floor and for the research of dissolved gases in the ocean. PMID:21574403

  18. Estimating the gas and dye quantities for modified tracer technique measurements of stream reaeration coefficients

    USGS Publications Warehouse

    Rathbun, R.E.

    1979-01-01

    Measuring the reaeration coefficient of a stream with a modified tracer technique has been accomplished by injecting either ethylene or ethylene and propane together and a rhodamine-WT dye solution into the stream. The movement of the tracers through the stream reach after injection is described by a one-dimensional diffusion equation. The peak concentrations of the tracers at the downstream end of the reach depend on the concentrations of the tracers in the stream at the injection site, the longitudinal dispersion coefficient, the mean water velocity, the length of the reach, and the duration of the injection period. The downstream gas concentrations also depend on the gas desorption coefficients of the reach. The concentrations of the tracer gases in the stream at the injection site depend on the flow rates of the gases through the injection diffusers, the efficiency of the gas absorption process, and the stream discharge. The concentration of dye in the stream at the injection site depends on the flow rate of the dye solution, the concentration of the dye solution, and the stream discharge. Equations for estimating the gas flow rates, the quantities of the gases, the dye concentration, and the quantity of dye together with procedures for determining the variables in these equations are presented. (Woodard-USGS)

  19. Tracer Applications of Noble Gas Radionuclides in the Geosciences

    E-print Network

    Lu, Z -T; Smethie, W M; Sturchio, N C; Fischer, T P; Kennedy, B M; Purtschert, R; Severinghaus, J P; Solomon, D K; Tanhua, T; Yokochi, R

    2013-01-01

    The noble gas radionuclides, including 81Kr (half-life = 229,000 yr), 85Kr (11 yr), and 39Ar (269 yr), possess nearly ideal chemical and physical properties for studies of earth and environmental processes. Recent advances in Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, have enabled routine measurements of the radiokrypton isotopes, as well as the demonstration of the ability to measure 39Ar in environmental samples. Here we provide an overview of the ATTA technique, and a survey of recent progress made in several laboratories worldwide. We review the application of noble gas radionuclides in the geosciences and discuss how ATTA can help advance these fields, specifically determination of groundwater residence times using 81Kr, 85Kr, and 39Ar; dating old glacial ice using 81Kr; and an 39Ar survey of the main water masses of the oceans, to study circulation pathways and estimate mean residence times. Other scientific questions involving deeper circulation of fluids in the Earth's crust ...

  20. Estimation of water movement in a closed landfill based on tracer tests in gas vents and changes in leachate quality.

    PubMed

    Kim, H J; Endo, D; Sato, M; Matsuo, T; Matsuto, T

    2009-08-01

    Leachate accumulated at the Nakazono Landfill in Asahikawa, Japan due to an inadequate leachate collection and drainage system. To reduce the level of leachate in the landfill and promote the stabilization of waste, many passive gas vents were installed in addition to leachate collection vaults. This study evaluated the distribution and movement of leachate in the landfill by measuring leachate levels and conducting tracer tests in the gas vents. Water levels varied widely among gas vents and depended mainly on the vent's original ground level and depth. Leachate velocity varied greatly; it was high in the upper layers of the saturated zone in a gas vent, but this was only a superficial velocity caused by inflow from unsaturated layers. A sharp decrease in total organic carbon observed in most gas vents after installation was likely due to the effect of aerobic biodegradation in the unsaturated waste layer. This effect was limited to a small aerobic zone around the gas vent. PMID:19356917

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

    SciTech Connect

    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 estimates made.

  2. Measuring self-pollution in school buses using a tracer gas technique

    NASA Astrophysics Data System (ADS)

    Behrentz, Eduardo; Fitz, Dennis R.; Pankratz, David V.; Sabin, Lisa D.; Colome, Steven D.; Fruin, Scott A.; Winer, Arthur M.

    A potentially important, but inadequately studied, source of children's exposure to pollutants during school bus commutes is the introduction of a bus's own exhaust into the passenger compartment. We developed and applied a method to determine the amount of a bus's own exhaust penetrating into the cabin in a study of six in-use school buses over a range of routes, roadway types, fuels, and emission control technologies. A tracer gas, SF 6, was metered into the bus's exhaust system using a mass flow controller whose flow rate was logged by a data acquisition system and processed with the concurrent real-time pollutant measurement data. At the same time, the SF 6 concentration inside the bus was measured using an AeroVironment CTA-1000 continuous analyzer connected to a series of solenoids that switched the sample inlet between the front and rear of the bus cabin. To account for a baseline drift of the CTA-1000, SF 6-free air was also drawn through a line located outside at the front of the bus. Although this third sample line generally provided a reference zero value, it also showed that under certain wind conditions (i.e., wind from the rear) when the bus was stopped and was idling, significant amounts of the bus's own exhaust reached this location at the front of the bus. Self-pollution, the percentage of a bus's own exhaust that can be found inside its cabin, was a function of bus type and age, and a strong function of window position (i.e., open or closed). We estimated up to 0.3% of the air inside the cabin was from the bus's own exhaust in older buses, approximately 10 times the percentage observed for newer buses, and 25% of the black carbon concentration variance was explained by the buses' self-pollution. Analysis of the tracer gas concentrations provided a powerful tool for identifying potentially high-exposure conditions.

  3. New Tracers Identify Hydraulic Fracturing Fluids and Accidental Releases from Oil and Gas Operations

    E-print Network

    Jackson, Robert B.

    New Tracers Identify Hydraulic Fracturing Fluids and Accidental Releases from Oil and Gas fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil elemental and isotopic signatures (B/Cl, Li/Cl, 11 B, and 7 Li) useful for characterizing hydraulic

  4. Iodine as a tracer of organic material: 129 I results from gas hydrate

    E-print Network

    Fehn, Udo

    Iodine as a tracer of organic material: 129 I results from gas hydrate systems and fore arc fluids of Geochemical Exploration Oct. 2004 #12;Abstract The strong association of iodine with organic material and the presence of the cosmogenic radioisotope 129 I make the iodine isotopic system useful in tracing and dating

  5. SOME STUDIES ON THE TRACER CHEMISTRY OF POLONIUM

    Microsoft Academic Search

    K. Kimura; T. Ishimori

    1959-01-01

    BS>A summary is presented of studies on the tracer chemistry of polonium. ; The formation and composition of polonium dithizonate, polonium ; diethyldithiocarbamate, and polonium hydroxyluinolate are reported. The ; volatility of polonium compounds formed with various organic regents was ; investigated. A method for the solvent extraction of polonium with isopropyl ; ether from hydrochloric acid solutions is given.

  6. Uncertainties in gas exchange parameterization during the SAGE dual-tracer experiment

    NASA Astrophysics Data System (ADS)

    Smith, Murray J.; Ho, David T.; Law, Cliff S.; McGregor, John; Popinet, Stéphane; Schlosser, Peter

    2011-03-01

    A dual tracer experiment was carried out during the SAGE experiment using the inert tracers SF 6 and 3He, in order to determine the gas transfer velocity, k, at high wind speeds in the Southern Ocean. Wind speed/gas exchange parameterization is characterised by significant variability and we examine the major measurement uncertainties that contribute to that scatter. Correction for the airflow distortion over the research vessel, as determined by computational fluid dynamics (CFD) modelling, had the effect of increasing the calculated value of k by 30%. On the short time scales of such experiments, the spatial variability of the wind field resulted in differences between ship and satellite QuikSCAT winds, which produced significant differences in transfer velocity. With such variability between wind estimates, the comparison between gas exchange parameterizations from diverse experiments should clearly be made on the basis of the same wind product. Uncertainty in mixed layer depth of ˜10% arose from mixed layer deepening at high wind speed and limited resolution of vertical sampling. However the assumption of equal mixing of the two tracers is borne out by the experiment. Two dual tracer releases were carried out during SAGE, and showed no significant difference in transfer velocities using QuikSCAT winds, despite the differences in wind history. In the SAGE experiment, duration limitation on the development of waves was shown to be an important factor for Southern Ocean waves, despite the presence of long fetches.

  7. Subcutaneous infusion and capillary "finger stick" sampling of stable isotope tracer in metabolic studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Metabolic studies utilizing stable isotope tracer in humans have typically used intravenous tracer infusions and venous blood sampling. These studies explore subcutaneous infusion of isotope and "finger stick" capillary blood sampling to measure glucose turnover. Five subjects received simultaneous ...

  8. Determination of water saturation using gas phase partitioning tracers and time-lapse electrical conductivity measurements

    SciTech Connect

    Johnson, Timothy C.; Oostrom, Martinus; Truex, Michael J.; Thomle, Jonathan N.; Wietsma, Thomas W.

    2013-05-01

    Water saturation is an important indicator of contaminant distribution and plays a governing role in contaminant transport within the vadose zone. Understanding the water saturation distribution is critical for both remediation and contaminant flux monitoring in unsaturated environments. In this work we propose and demonstrate a method of remotely determining water saturation levels using gas phase partitioning tracers and time-lapse bulk electrical conductivity measurements. The theoretical development includes the partitioning chemistry for the tracers we demonstrate (ammonia and carbon dioxide), as well as a review of the petrophysical relationship governing how these tracers influence bulk conductivity. We also investigate methods of utilizing secondary information provided by electrical conductivity breakthrough magnitudes induced by the tracers. We test the method on clean, well characterized, intermediate-scale sand columns under controlled conditions. Results demonstrate the capability to predict partitioning coefficients and accurately monitor gas breakthrough curves along the length of the column according to the corresponding electrical conductivity response, leading to accurate water saturation estimates. This work is motivated by the need to develop effective characterization and monitoring techniques for contaminated deep vadose zone environments, and provides a proof-of-concept toward uniquely characterizing and monitoring water saturation levels at the field scale and in three-dimensions using electrical resistivity tomography.

  9. The Horsehead Nebula: a template for extragalactic high density tracers studies?

    NASA Astrophysics Data System (ADS)

    Gratier, P.; Pety, J.; Gerin, M.; Montillaud, J.; Guzman, V.; Goicoechea, J. R.

    2011-05-01

    The Horsehead Nebula, thanks to its proximity (1'' = 0.002 pc) and simple geometry is a perfect benchmark case to study the interplay between structure and chemistry in PDRs (Photon Dominated Regions). Our past studies of many tracers enabled us to obtain a clear picture of the density and temperature structure of the region. The presence of a steep density gradient (from less than 10^3 cm-3 to 10^5 cm-3 in less than 10'' = 0.02 pc) allows to probe different environments, from far-UV photon-dominated regions to shielded cold gas, in less than 50''. With the increased sensitivity available, extragalactic observations of gas tracers other than CO such as HCN, HNC, HCO^+ become more common. These observations are used in the extragalactic context to probe the density of the interstellar medium, to identify the heating mechanisms : FUV photons --- related to starburst phenomena, whose interaction with the ISM can be understood using PDR models ) or X rays --- related to AGN, using XDR models ---, and to probe star formation using specific molecular lines as tracers of embedded star forming regions. Nevertheless these observations are of low linear resolution and the details of the physics and chemistry of the interstellar medium are smeared by averaging over different environments. We will study how the understanding of these tracers in well known Galactic environments, such as the Horsehead PDR, can help the interpretation of extragalactic observations. We present high resolution multiline observations of HCN, HNC, CN and HCO^+ by the IRAM PdBI and 30m telescope instruments. We study the emission line ratios of these different molecules with the objective of comparing these high resolution observations of a well characterized Galactic region to extragalactic observations of the same tracers. Among the questions raised are : What is the importance of hyperfine anomalies in understanding the HCN and HNC observations? Can HCN be used as a tracer of star formation at subpc/pc scales? Is the HNC/HCN ratio a tracer of PDR? Are the HCO^+/HCN and HCO^+/HNC ratios good probes of density?

  10. Hanford facilities tracer study report (315 Water Treatment Facility)

    SciTech Connect

    Ambalam, T. [Kaiser Engineers Hanford Co., Richland, WA (United States)

    1995-04-14

    This report presents the results and findings of a tracer study to determine contact time for the disinfection process of 315 Water Treatment Facility that supplies sanitary water for the 300 Area. The study utilized fluoride as the tracer and contact times were determined for two flow rates. Interpolation of data and short circuiting effects are also discussed. The 315 Water Treatment Facility supplies sanitary water for the 300 Area to various process and domestic users. The Surface Water Treatment Rule (SWTR), outlined in the 1986 Safe Drinking Water Act Amendments enacted by the EPA in 1989 and regulated by the Washington State Department of Health (DOH) in Section 246-290-600 of the Washington Administrative Code (WAC), stipulates filtration and disinfection requirements for public water systems under the direct influence of surface water. The SWTR disinfection guidelines require that each treatment system achieves predetermined inactivation ratios. The inactivation by disinfection is approximated with a measure called CxT, where C is the disinfectant residual concentration and T is the effective contact time of the water with the disinfectant. The CxT calculations for the Hanford water treatment plants were derived from the total volume of the contact basin(s). In the absence of empirical data to support CxT calculations, the DOH determined that the CxT values used in the monthly reports for the water treatment plants on the Hanford site were invalid and required the performance of a tracer study at each plant. In response to that determination, a tracer study will be performed to determine the actual contact times of the facilities for the CxT calculations.

  11. Use of stable isotopically labeled tracers for studies of metabolic kinetics: An overview

    Microsoft Academic Search

    Bruce W. Patterson

    1997-01-01

    Stable isotopically labeled tracers offer a reliable and safe alternative to the use of radioactive tracers for studies of metabolic kinetics. This overview examines some of the principles and technical issues regarding mass spectrometry instrumentation, and reviews some of the approaches used in the application of stable isotopically labeled tracers to studies of protein, lipid, and carbohydrate metabolic kinetics.

  12. The Tracer Gas Method of Determining the Charging Efficiency of Two-stroke-cycle Diesel Engines

    NASA Technical Reports Server (NTRS)

    Schweitzer, P H; Deluca, Frank, Jr

    1942-01-01

    A convenient method has been developed for determining the scavenging efficiency or the charging efficiency of two-stroke-cycle engines. The method consists of introducing a suitable tracer gas into the inlet air of the running engine and measuring chemically its concentration both in the inlet and exhaust gas. Monomethylamine CH(sub 3)NH(sub 2) was found suitable for the purpose as it burns almost completely during combustion, whereas the "short-circuited" portion does not burn at all and can be determined quantitatively in the exhaust. The method was tested both on four-stroke and on two-stroke engines and is considered accurate within 1 percent.

  13. Tracer microrheology study of a hydrophobically modified comblike associative polymer.

    PubMed

    Abdala, Ahmed A; Amin, Samiul; van Zanten, John H; Khan, Saad A

    2015-04-01

    The viscoelastic properties of associative polymers are important not only for their use as rheology modifiers but also to understand their complex structure in aqueous media. In this study, the dynamics of comblike hydrophobically modified alkali swellable associative (HASE) polymers are probed using diffusing wave spectroscopy (DWS) based tracer microrheology. DWS-based tracer microrheology accurately probes the dynamics of HASE polymers, and the extracted microrheological moduli versus frequency profile obtained from this technique closely matches that obtained from rotational rheometry measurements. Quantitatively, however, the moduli extracted from DWS-based tracer microrheology measurements are slightly higher than those obtained using rotational rheometry. The creep compliance, elastic modulus, and relaxation time concentration scaling behavior exhibits a power-law dependence. The length scale associated with the elastic to glassy behavior change is obtained from the time-dependent diffusion coefficient. The Zimm-Rouse type scaling is recovered at high frequencies but shows a concentration effect switching from Zimm to more Rouse-like behavior at higher concentrations. PMID:25775221

  14. Use of tracers in materials-holdup study

    SciTech Connect

    Pillay, K.K.S.

    1983-01-01

    Holdup measurements of special nuclear materials in large processing facilities offer considerable challenges to conventional nondestructive-assay techniques. The use of judiciously chosen radioactive tracers offer a unique method of overcoming this difficulty. Three examples involving the use of /sup 46/Sc and fission products from activated uranium in large-scale experimental studies of uranium holdup are discussed. A justification for the method and its advantages along with examples of successful applications of this technique for large-sale experimental studies are presented.

  15. Analysis of alcoholic and thiocyanate type tracers in core studies and field samples

    SciTech Connect

    Gregory, S.D.; Kocsis, D.L.

    1984-09-01

    Analytical techniques have been developed and validated for the determination of alcoholic and thiocyanate tracer content. The tracer content was determined in steamflood production effluent and in low interfacial tension (LIFT) injection and production fluids. A gas chromatographic procedure was used for determining alcohol content and a complexation/colorimetric detection technique was employed for the analysis of thiocyanate tracers. The procedures have been automated to allow for maximum sample throughput and minimum operator interaction. As many as 66 samples can be analyzed automatically per day. The tracer analyses have been employed in the analysis of laboratory core samples and field production samples.

  16. A Rapid, Low-Cost Method to Determine Travel Times at Managed Aquifer Recharge Operations Using Noble Gas Tracers

    NASA Astrophysics Data System (ADS)

    Moran, J. E.; Visser, A.; Singleton, M. J.; Esser, B. K.; Halliwell, M.; Hillegonds, D. J.

    2012-12-01

    Managed aquifer recharge is a key component for the sustainable use of surface water and groundwater in the arid western U.S. When recycled water is a recharge water source, subsurface residence time, required for bacteria and virus deactivation, is best verified by application of an extrinsic tracer. Desirable tracer properties include: no real or perceived health risk, inexpensive even for a large volume of tagged water, large dynamic range, efficient introduction, convenient sampling methods, and rapid, low-cost analysis. We have developed and tested a dissolved noble gas tracer technique ideally suited for tracing large water volumes at managed aquifer recharge facilities. In an application of the method at a water district's facilities in the San Francisco Bay area, Xenon was introduced into a 106 m3 pond over a period of 7 days using a 300 m length of gas-permeable silicone tubing. Samples from the pond, near-field shallow monitoring wells, and production wells about 400 m from the recharge pond were analyzed for dissolved Xe by noble gas membrane inlet mass spectrometry (NGMIMS). The NGMIMS uses a syringe pump, gas-permeable membrane inlet, and quadrupole residual gas analyzer for measurement of noble gas concentrations. Samples are collected in VOA vials, and analysis can be carried out in real-time, with a measurement uncertainty of about 5% for Xe. Tracer first appeared in a production well 136 days after starting the tracer introduction at 0.7% (C/C0) of the peak pond xenon concentration. The cost of the tracer is about US650/106 m3 water, and the NGMIMS was assembled with parts totaling approximately US50,000, making application of the tracer method feasible for most managed aquifer recharge projects. This project is part of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program.

  17. Hourly Measurement of the Concentration and Gas-Particle Partitioning of Oxygenated Organic Tracers in Ambient Aerosol: First Results from Berkeley, CA and Rural Alabama

    NASA Astrophysics Data System (ADS)

    Isaacman, G. A.; Kreisberg, N. M.; Yee, L.; Chan, A.; Worton, D. R.; Hering, S. V.; Goldstein, A. H.

    2013-12-01

    Hourly and bi-hourly time-resolved measurements of organic tracer compounds in ambient aerosols have been successfully used to elucidate sources and formation pathways of atmospheric particulate matter. Here we extend the Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SVTAG), a custom in-situ instrument that collects, desorbs, and analyzes ambient aerosol and semi-volatile compounds with hourly time resolution, to include on-line derivatization and a second, parallel collection cell that provides simultaneous collection of both particle-phase and particle-plus-gas-phase organic compounds. By introducing a silylating agent upon desorption, SVTAG can measure highly oxygenated compounds that are not easily detected using traditional gas chromatography including most of the previously reported oxygenated tracers for biogenic and anthropogenic secondary organic aerosol. The use of a pair of matched collection cells with parallel sampling and serial analysis provides direct gas-particle partitioning information. One cell collects the total organic fraction of compounds with volatilities lower than a C13 hydrocarbon, while the other cell samples through an activated carbon denuder to selectively remove the gas-phase components. Taken together these provide a direct measurement of gas-particle partitioning to yield a check on classical absorption based partitioning theory while deviations from this theory provide constraints on other driving factors in aerosol formation chemistry, such as oligomerization, salt formation, and acidity. We present here the capabilities and utility of the dual cell SVTAG with derivatization, with chemical insights gained from initial tests on ambient Berkeley air and the first results from a rural site in Alabama obtained during the Southern Oxidant and Aerosol Study (SOAS). Tracers for varying isoprene oxidation pathways are used to explore the influence of anthropogenic emissions; concentrations of 2-methyltetrols and 2-methyl glyceric acid provide constraints on the relative importance of NOx and HO2 as the fate of the alkylperoxy (RO2) radical. Measuring these and other known biogenic tracers with hourly time resolution yields detailed diurnal variability patterns of these compounds, elucidating formation timescales and pathways. Gas-particle partitioning of these biogenic oxygenated compounds, as well as oxygenated tracers common in urban environments, are found in many cases to be well-modeled by absorptive partitioning theory. However, for many compounds, the particle-phase fraction is greatly under-predicted by simple absorption. Several commonly used biogenic secondary organic aerosol tracers that are typically considered to exist primarily in the particle phase, such as 2-methyltetrols, are shown to be 20-80% in the gas phase.

  18. Reintegration of child soldiers in Burundi: a tracer study

    PubMed Central

    2012-01-01

    Background Substantial attention and resources are aimed at the reintegration of child soldiers, yet rigorous evaluations are rare. Methods This tracer study was conducted among former child soldiers (N=452) and never-recruited peers (N=191) who participated in an economic support program in Burundi. Socio-economic outcome indicators were measured retrospectively for the period before receiving support (T1; 2005–06); immediately afterwards (T2; 2006–07); and at present (T3; 2010). Participants also rated present functional impairment and mental health indicators. Results Participants reported improvement on all indicators, especially economic opportunity and social integration. At present no difference existed between both groups on any of the outcome indicators. Socio-economic functioning was negatively related with depression- and, health complaints and positively with intervention satisfaction. Conclusion The present study demonstrates promising reintegration trajectories of former child soldiers after participating in a support program. PMID:23095403

  19. Groundwater surface water interaction study using natural isotopes tracer

    NASA Astrophysics Data System (ADS)

    Yoon, Yoon Yeol; Kim, Yong Chul; Cho, Soo Young; Lee, Kil Yong

    2015-04-01

    Tritium and stable isotopes are a component of the water molecule, they are the most conservative tracer for groundwater study. And also, radon is natural radioactive nuclide and well dissolved in groundwater. Therefore, these isotopes are used natural tracer for the study of surface water and groundwater interaction of water curtain greenhouse area. The study area used groundwater as a water curtain for warming tool of greenhouse during the winter, and is associated with issues of groundwater shortage while being subject to groundwater-river water interaction. During the winter time, these interactions were studied by using Rn-222, stable isotopes and H-3. These interaction was monitored in multi depth well and linear direction well of groundwater flow. And dam effect was also compared. Samples were collected monthly from October 2013 to April 2014. Radon and tritium were analyzed using Quantulus low background liquid scintillation counter and stable isotopes were analyzed using an IRIS (Isotope Ratio Infrared Spectroscopy ; L2120-i, Picarro). During the winter time, radon concentration was varied from 0.07 Bq/L to 8.9 Bq/L and different interaction was showed between dam. Surface water intrusion was severe at February and restored April when greenhouse warming was ended. The stable isotope results showed different trend with depth and ranged from -9.16 ‰ to -7.24 ‰ for ? 18O value, while the ?D value was ranged from -57.86 ‰ to -50.98 ‰. The groundwater age as dated by H-3 was ranged 0.23 Bq/L - 0.59 Bq/L with an average value of 0.37 Bq/L.

  20. GEOMETRIC OFFSETS ACROSS SPIRAL ARMS IN M51: NATURE OF GAS AND STAR FORMATION TRACERS

    SciTech Connect

    Louie, Melissa; Koda, Jin [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Egusa, Fumi, E-mail: melissa.louie@stonybrook.edu [Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (Japan)] [Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (Japan)

    2013-02-15

    We report measurements of geometric offsets between gas spiral arms and associated star-forming regions in the grand-design spiral galaxy M51. These offsets are a suggested measure of the star formation timescale after the compression of gas at spiral arm entry. A surprising discrepancy, by an order of magnitude, has been reported in recent offset measurements in nearby spiral galaxies. Measurements using CO and H{alpha} emission find large and ordered offsets in M51. On the contrary, small or non-ordered offsets have been found using the H I 21 cm and 24 {mu}m emissions, possible evidence against gas flow through spiral arms, and thus against the conventional density-wave theory with a stationary spiral pattern. The goal of this paper is to understand the cause of this discrepancy. We investigate potential causes by repeating those previous measurements using equivalent data, methods, and parameters. We find offsets consistent with the previous measurements and conclude that the difference of gas tracers, i.e., H I versus CO, is the primary cause. The H I emission is contaminated significantly by the gas photodissociated by recently formed stars and does not necessarily trace the compressed gas, the precursor of star formation. The H I gas and star-forming regions coincide spatially and tend to show small offsets. We find mostly positive offsets with substantial scatter between CO and H{alpha}, suggesting that gas flow through spiral arms (i.e., density wave) though the spiral pattern may not necessarily be stationary.

  1. FORMALDEHYDE AND TRACER GAS TRANSFER BETWEEN AIRSTREAMS IN ENTHALPY-TYPE AIR-TO-AIR HEAT EXCHANGERS

    SciTech Connect

    Fisk, W. J.; Pedersen, B. S.; Hekmat, D.; Chant, R. E.; Kaboli, H.

    1984-07-01

    Enthalpy exchangers are frequently employed to transfer heat and water between the supply and exhaust airstreams of mechanical ventilation systems. Concern has been expressed that some indoor-generated air pollutants, especially formaldehyde, may be transferred between airstreams by this type of heat exchanger and, thus, returned to the indoor space. This paper describes an experimental study in which the formaldehyde, tracer gas, and water vapor transfer rates in two enthalpy exchangers were measured. The first exchanger uses a crossflow core fabricated from a treated paper. The core of the second heat exchanger is a rotating heat wheel coated with lithium chloride. To reduce the transfer of gases by air leakage each core was installed in a specially fabricated case. Only 5% to 8% of the two tracer gases and 7% to 15% of the formaldehyde injected into the exhaust airstream was transferred to the supply airstream. Therefore, formaldehyde transfer between airstreams by processes other than air leakage does not seriously compromise the performance of these enthalpy exchangers. Theoretical calculations indicate, however, that the transfer of water vapor between airstreams in enthalpy exchangers can significantly diminish their ability to lower indoor formaldehyde concentrations because of the positive coupling between indoor humidity and the emission rates of formaldehyde from building materials.

  2. Hanford facilities tracer study report (315 Water Treatment Facility). Revision 1

    SciTech Connect

    Ambalam, T. [Westinghouse Hanford Co., Richland, WA (United States)

    1995-05-01

    Reported are the results and findings of a tracer study to determine contact time for the disinfection process of 315 Water Treatment Facility at 300 Area. The study utilized fluoride as the tracer and contact times were determined for two flow rates. Interpolation of data and short circuiting effects are also discussed.

  3. Radon entry rate analyses using in situ tracer gas method application.

    PubMed

    Fro?ka, A; Jílek, K

    2014-07-01

    Recently, the role of energy savings in indoor air quality deterioration has been extensively emphasised, predominantly in the context of significant air exchange rate reduction as a result of home energy retrofits. In case of refurbishment of existing buildings, the effect of energy-efficient technologies on indoor radon concentration is considerably complex and has to be carefully evaluated with respect to radon entry rate (RER) and air exchange rate alteration. For the purpose of detailed analysis of radon entry pathways, the unique infiltration experiment has been carried out using the tracer gas (N2O) method application in field conditions. Significant amount of experimental works has been done to provide an independent assessment of RER and air-exchange rate facilitating the analysis of fundamental factors influencing the indoor radon variations (e.g. indoor-outdoor pressure difference induced by wind, stack effect, heating, ventilation and operation of air-conditioning systems). PMID:24736298

  4. Carbonyl sulfide as an inverse tracer for biogenic organic carbon in gas and aerosol phases

    NASA Astrophysics Data System (ADS)

    de Gouw, J. A.; Warneke, C.; Montzka, S. A.; Holloway, J. S.; Parrish, D. D.; Fehsenfeld, F. C.; Atlas, E. L.; Weber, R. J.; Flocke, F. M.

    2009-03-01

    Carbonyl sulfide (COS) is a long-lived trace gas in the atmosphere with an oceanic source and a surface sink through the uptake by vegetation and soils. We demonstrate the use of COS as an inverse tracer for the impact of biogenic emissions on an air mass including the formation of secondary organic aerosol (SOA). Using airborne data from the summer of 2004 over the northeastern U.S., we find that air masses with reduced COS in the continental boundary layer had on average higher mixing ratios of biogenic VOCs (isoprene, monoterpenes, methanol) and their photo-oxidation products (methacrolein, methyl vinyl ketone, methyl furan and MPAN, a peroxyacyl nitrate derived from isoprene). Measurements of water-soluble organic carbon were only weakly correlated with COS, indicating that SOA formation from biogenic precursors was a small contribution to the total.

  5. Near-Road Mulltipollutant Profiles: Association between Volatile Organic Compounds and a Tracer Gas Surrogate Near a Busy Highway

    EPA Science Inventory

    This research characterizes associations between multiple pollutants in the near-road environment attributed to a roadway line source. It also examines the use of a tracer gas as a surrogate of mobile source pollutants. Air samples were collected in summa canisters along a 300 m ...

  6. Tracers of Extra-planar Gas and the Disk-Halo Connection

    NASA Astrophysics Data System (ADS)

    Dettmar, R.-J.

    2005-06-01

    Observations of diffuse ionized gas (DIG) in the halos of edge-on disk galaxies are discussed in reference to other tracers of extra-planar gas. The presence of DIG in the halo correlates well with star formation in the disk, corroborating the paradigm of a disk-halo connection with the interstellar medium driven by multiple and clustered supernovae. This is demonstrated using a survey of H+ halos with more than 70 objects. The survey allows us to establish a minimum energy release per unit area that is required to start the disk-halo mass exchange. The halo DIG is typically correlated with the presence of other gaseous phases and components of the ISM in the halo including hot X-ray gas, cosmic rays, and magnetic fields. The detection of extra-planar H II regions leads us to conclude that also molecular hydrogen must be present. From the polarization of synchrotron radio continuum maps a large scale and well ordered magnetic field in the gaseous halos can be deduced. Finally, we briefly discuss possible physical processes that lead to the formation of dusty structures in the disk-halo interface.

  7. IAEA-CN-80/66 ISOTOPE TRACERS IN GLOBAL WATER AND CLIMATE STUDIES

    E-print Network

    Edwards, Thomas W.D.

    IAEA-CN-80/66 ISOTOPE TRACERS IN GLOBAL WATER AND CLIMATE STUDIES OF THE PAST AND PRESENT T Avenue West, Waterloo ON N2L 3G1, CANADA 1 also: Isotope Hydrology Section, International Atomic Energy Agency, Wagramer Strasse 5, P.O. Box 100, A-1400 Vienna, AUSTRIA Abstract ISOTOPE TRACERS IN GLOBAL WATER

  8. Studying Star Clusters as Tracers of the LMC's Chemical Enrichment

    NASA Astrophysics Data System (ADS)

    Palma, T.; Clariá, J. J.; Geisler, D.; Ahumada, A. V.

    2015-05-01

    Based on photometric observations made with the Cerro Tololo Inter-American (CTIO) “Victor Blanco” 4-m telescope, we present the results of a study of the chemical evolution of the Large Magellanic Cloud (LMC) for the last 2.2 Gyr. As tracers of the LMC chemical enrichment, we used 39 star clusters projected on the bar, 27 on the inner disc, and 15 on the outer disc. Our sample includes 44 previously unstudied clusters. In all cases we determined the size, reddening, deprojected distance, age and metallicity. We show that the more metal-rich clusters are mainly located in the inner disc, while more metal-poor clusters are distributed throughout the entire disc. Intermediate-age clusters tend to be located at greater deprojected galactocentric distances while the youngest ones are mainly found in the inner disc. These trends are maintained when the sample is complemented with clusters observed by other authors with the same technique. These results reinforce the idea of the absence of a radial metallicity gradient in the LMC for clusters with subsolar metallicities. The resulting age-metallicity relationship appears to be independent of which LMC region is considered.

  9. Project definition study for the National Biomedical Tracer Facility

    SciTech Connect

    Roozen, K.

    1995-02-15

    The University of Alabama at Birmingham (UAB) has conducted a study of the proposed National Biomedical Tracer Facility (NBTF). In collaboration with General Atomics, RUST International, Coleman Research Corporation (CRC), IsoMed, Ernst and Young and the advisory committees, they have examined the issues relevant to the NBTF in terms of facility design, operating philosophy, and a business plan. They have utilized resources within UAB, CRC and Chem-Nuclear to develop recommendations on environmental, safety and health issues. The Institute of Medicine Panel`s Report on Isotopes for Medicine and the Life Sciences took the results of prior workshops further in developing recommendations for the mission of the NBTF. The IOM panel recommends that the NBTF accelerator have the capacity to accelerate protons to 80 MeV and a minimum of 750 microamperes of current. The panel declined to recommend a cyclotron or a linac. They emphasized a clear focus on research and development for isotope production including target design, separation chemistry and generator development. The facility needs to emphasize education and training in its mission. The facility must focus on radionuclide production for the research and clinical communities. The formation of a public-private partnership resembling the TRIUMF-Nordion model was encouraged. An advisory panel should assist with the NBTF operations and prioritization.

  10. Application of multitracer technology to petroleum reservoir studies. [Perfluorocarbon tracer technology

    SciTech Connect

    Senum, G.I.

    1992-09-01

    The objectives of this research program are to: Improve the assessment of the character of petroleum reservoirs using tracer technology for the monitoring and improvement of EOR techniques, specifically, (a) to apply the presently available multitracer perfluorocarbon tracer (PFI) technology to the study of petroleum reservoirs in characterizing reservoir bulk subsurface flow transport and dispersion rates; and (b) to demonstrate that PFTs with differing physical properties will interact with differing rates of adsorption and dispersion within such reservoirs, from which may be inferred difference in the character and/or extent of petroleum in those reservoirs. Develop additional tracers, and tracer injection, sampling and analyses methodologies for use in petroleum reservoir characterization experiments. Develop a data base of petroleum transport and dispersion properties from tracer experiments for use by modellers for developing, validating and extending petroleum reservoirs models used for characterizing petroleum reservoirs. Technical progress is discussed according to the three ongoing field experiments at the Naval Petroleum Reserve in California (NPRC).

  11. Analysis techniques for tracer studies of oxidation. M. S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Basu, S. N.

    1984-01-01

    Analysis techniques to obtain quantitative diffusion data from tracer concentration profiles were developed. Mass balance ideas were applied to determine the mechanism of oxide growth and to separate the fraction of inward and outward growth of oxide scales. The process of inward oxygen diffusion with exchange was theoretically modelled and the effect of lattice diffusivity, grain boundary diffusivity and grain size on the tracer concentration profile was studied. The development of the tracer concentration profile in a growing oxide scale was simulated. The double oxidation technique was applied to a FeCrAl-Zr alloy using 0-18 as a tracer. SIMS was used to obtain the tracer concentration profile. The formation of lacey oxide on the alloy was discussed. Careful consideration was given to the quality of data required to obtain quantitative information.

  12. 13N as a tracer for studying glutamate metabolism

    PubMed Central

    Cooper, Arthur J. L.

    2010-01-01

    This mini-review summarizes studies my associates and I carried out that are relevant to the topic of the present volume [i.e. glutamate dehydrogenase (GDH)] using radioactive 13N (t½ 9.96 min) as a biological tracer. These studies revealed the previously unrecognized rapidity with which nitrogen is exchanged among certain metabolites in vivo. For example, our work demonstrated that a) the t½ for conversion of portal vein ammonia to urea in the rat liver is ~10–11 sec, despite the need for five enzyme-catalyzed steps and two mitochondrial transport steps, b) the residence time for ammonia in the blood of anesthetized rats is ?7–8 sec, c) the t½ for incorporation of blood-borne ammonia into glutamine in the normal rat brain is <3 sec, and d) equilibration between glutamate and aspartate nitrogen in rat liver is extremely rapid (seconds), a reflection of the fact that the components of the hepatic aspartate aminotransferase reaction are in thermodynamic equilibrium. Our work emphasizes the importance of the GDH reaction in rat liver as a conduit for dissimilating or assimilating ammonia as needed. In contrast, our work shows that the GDH reaction in rat brain appears to operate mostly in the direction of ammonia production (dissimilation). The importance of the GDH reaction as an endogenous source of ammonia in the brain and the relation of GDH to the brain glutamine cycle is discussed. Finally, our work integrates with the increasing use of positron emission tomography (PET) and nuclear magnetic resonance (NMR) to study brain ammonia uptake and brain glutamine, respectively, in normal individuals and in patients with liver disease or other diseases associated with hyperammonemia. PMID:21108979

  13. TRACER DISPERSION STUDIES FOR HYDRAULIC CHARACTERIZATION OF PIPES

    EPA Science Inventory

    A series of experiments were conducted at the U. S. Environmental Protection Agency (EPA) Test & Evaluation (T&E) Facility in Cincinnati, Ohio, to quantify longitudinal dispersion of a sodium fluoride tracer in polyvinyl chloride (PVC) pipe and ductile iron pipe under laminar, tr...

  14. Sediment tracers in water erosion studies: Current approaches and challenges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The interest in the use of sediment tracers as a complementary tool to traditional water soil erosion or deposition measurements or assessment has increased due to the additional information they may provide such as sediment source identification and tracking of sediment movement over the landscape ...

  15. Optimization of Sampling Positions for Measuring Ventilation Rates in Naturally Ventilated Buildings Using Tracer Gas

    PubMed Central

    Shen, Xiong; Zong, Chao; Zhang, Guoqiang

    2012-01-01

    Finding out the optimal sampling positions for measurement of ventilation rates in a naturally ventilated building using tracer gas is a challenge. Affected by the wind and the opening status, the representative positions inside the building may change dynamically at any time. An optimization procedure using the Response Surface Methodology (RSM) was conducted. In this method, the concentration field inside the building was estimated by a three-order RSM polynomial model. The experimental sampling positions to develop the model were chosen from the cross-section area of a pitched-roof building. The Optimal Design method which can decrease the bias of the model was adopted to select these sampling positions. Experiments with a scale model building were conducted in a wind tunnel to achieve observed values of those positions. Finally, the models in different cases of opening states and wind conditions were established and the optimum sampling position was obtained with a desirability level up to 92% inside the model building. The optimization was further confirmed by another round of experiments.

  16. Apparatus for measuring and displaying leakage rates in a tracer gas leakage detector

    SciTech Connect

    Morel, J.; Tallon, J.

    1985-04-16

    A tracer gas leakage detector mainly comprises a primary vacuum pump which is selectably connectable to a unit to be tested for leakage, an inlet valve also connectable to the unit to be tested and communicating with a measurement cell capable of being evacuated by a primary pump and a secondary pump. The inlet valve includes a motor-controlled valve member to enable the aperture through the inlet valve to be servo-controlled to the inlet pressure of the measurement cell, and conversion means providing an electrical signal representative of the aperture. The apparatus for measuring and displaying the leakage flow rate is connected to receive the aperture size representing electrical signal and includes a display system for displaying, as a function of the aperture size representing electrical signal, a valid sub-range of n decades of possible valid measurements taken from a total measuring range of N decades for the apparatus as a whole, thereby warning users that any indicated leakage flow rate values outside the valid sub-range are spurious. The N decades may be marked on a band (22) which is movable relative to a window (24). A pointer (25) is also movable relative to the window. A reading is valid if the pointer lies in the window.

  17. Source apportionment of wintertime gas-phase and particle-phase air pollutants using organic compounds as tracers

    Microsoft Academic Search

    James J. Schauer; Glen R. Cass

    2000-01-01

    Two chemical mass balance receptor models are developed which can determine the source contributions to atmospheric pollutant concentrations using organic compounds as tracers. The first model uses particle-phase organic compounds to apportion the primary source contribution to atmospheric fine particulate organic carbon concentrations and fine particle mass concentrations. The second receptor model simultaneously uses both volatile gas-phase hydrocarbon and particle-phase

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

    SciTech Connect

    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.

  19. Measurements of waste tank passive ventilation rates using tracer gases

    SciTech Connect

    Huckaby, J.L.; Olsen, K.B.; Sklarew, D.S.; Evans, J.C.; Remund, K.M.

    1997-09-01

    This report presents the results of ventilation rate studies of eight passively ventilated high-level radioactive waste tanks using tracer gases. Head space ventilation rates were determined for Tanks A-101, AX-102, AX-103, BY-105, C-107, S-102, U-103, and U-105 using sulfur hexafluoride (SF{sub 6}) and/or helium (He) as tracer gases. Passive ventilation rates are needed for the resolution of several key safety issues. These safety issues are associated with the rates of flammable gas production and ventilation, the rates at which organic salt-nitrate salt mixtures dry out, and the estimation of organic solvent waste surface areas. This tracer gas study involves injecting a tracer gas into the tank headspace and measuring its concentration at different times to establish the rate at which the tracer is removed by ventilation. Tracer gas injection and sample collection were performed by SGN Eurisys Service Corporation and/or Lockheed Martin Hanford Corporation, Characterization Project Operations. Headspace samples were analyzed for He and SF{sub 6} by Pacific Northwest National Laboratory (PNNL). The tracer gas method was first demonstrated on Tank S-102. Tests were conducted on Tank S-102 to verify that the tracer gas was uniformly distributed throughout the tank headspace before baseline samples were collected, and that mixing was sufficiently vigorous to maintain an approximately uniform distribution of tracer gas in the headspace during the course of the study. Headspace samples, collected from a location about 4 in away from the injection point and 15, 30, and 60 minutes after the injection of He and SF{sub 6}, indicated that both tracer gases were rapidly mixed. The samples were found to have the same concentration of tracer gases after 1 hour as after 24 hours, suggesting that mixing of the tracer gas was essentially complete within 1 hour.

  20. Using biofuel tracers to study alternative combustion regimes

    NASA Astrophysics Data System (ADS)

    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 CO 2 emissions are countered with higher nitrogen oxides (NO x) 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 NO x formation. Altering the combustion regime to burn at temperatures below the NO x 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 NO x 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.

  1. Multiple tracer study in Horonobe, northern Hokkaido, Japan: 1. Residence time estimation based on multiple environmental tracers and lumped parameter models

    NASA Astrophysics Data System (ADS)

    Kashiwaya, Koki; Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Mizuno, Takashi

    2014-11-01

    A multiple tracer study was conducted in the coastal plain of Horonobe, northern Hokkaido, Japan. To accomplish reliable estimates of groundwater residence time, multiple tracer approach, employing both gaseous and nongaseous environmental tracers, and lumped parameter models (LPMs) were applied in combination. Environmental tracers including 3H, 3H/3He, 36Cl, and SF6 were analyzed and compared with values estimated from LPMs to select the most appropriate tracer and models to describe groundwater flow regime in the study area. Time series of 36Cl/Cl input in the study area were reconstructed and used in the LPMs. From comparison of the analyzed and modeled results, an index of 3H/3He was selected as the most appropriate for investigation of the study area. The relationship between the 3H/3He index and 36Cl/Cl indicated reliability of the 3H/3He index, but 36Cl/Cl values of the samples were lower than the models. This discrepancy was caused by underestimation of Cl- concentration of recharging water in the calculation of 36Cl/Cl input. SF6 mixing ratios of the samples were slightly higher than the models and it suggested involvement of terrigenic SF6. Three well groups, northern Shimonuma wells (NSW), southern Shimonuma wells (SSW), and Hamasato wells (HW), were respectively consistent with exponential piston flow model (EPM), binary mixing model (BMM), and exponential mixing model (EMM). Relational expressions between the 3H/3He index and mean residence time or mixing fraction of young groundwater (assumed to contain no tritiogenic 3He) with old groundwater (all 3H decayed to tritiogenic 3He) were obtained based on the models. The mean residence time determined from the 3H/3He index and the expressions were 19-78 years for NSW and 1-648 years for HW. The mixing fraction of young groundwater was less than 10% at all SSW. Nongaseous tracers, including 36Cl are not influenced by factors specific for gaseous tracers, such as excess air and degassing. Analyses of multiple tracers, including both gaseous and nongaseous tracers, and comparison using LPMs were effective to show plausibility of the estimated residence time, and they contributed to understanding of groundwater flow regime in the study area.

  2. PET Tracers To Study Clinically Relevant Hepatic Transporters.

    PubMed

    Testa, Andrea; Zanda, Matteo; Elmore, Charles S; Sharma, Pradeep

    2015-07-01

    Transporter proteins expressed on the cell membranes of hepatocytes are directly involved in the hepatic clearance, mediating the transport of drugs and metabolites through the hepatocyte, from the bloodstream into the bile. Reduction of hepatic transporter activity (due to chemical inhibition, genetic polymorphism, or low expression) can increase systemic or liver exposure to potentially toxic compounds, causing adverse effects. Many clinically used drugs have been associated with inhibition of hepatic transporters in vitro, suggesting the potential involvement of liver transporters in drug-drug interactions (DDIs). Recently, radiolabeled hepatic transporter substrates have been successfully employed in positron emission tomography (PET) imaging to demonstrate inhibition of clinically relevant hepatic transporters. The present article briefly describes the clinical relevance of hepatic transporters followed by a review of the application of PET imaging for the determination of pharmacokinetic parameters useful to describe the transporter activity and the design, accessibility, and preclinical and clinical applications of available radiotracers. Finally, based on the analysis of the strengths and limitations of the available tracers, some criteria for the development of novel PET probes for hepatic transporters and new potential applications are suggested. PMID:26034841

  3. The Horsehead Nebula: a template for extragalactic high density tracers studies?

    Microsoft Academic Search

    P. Gratier; J. Pety; M. Gerin; J. Montillaud; V. Guzman; J. R. Goicoechea

    2011-01-01

    The Horsehead Nebula, thanks to its proximity (1'' = 0.002 pc) and simple geometry is a perfect benchmark case to study the interplay between structure and chemistry in PDRs (Photon Dominated Regions). Our past studies of many tracers enabled us to obtain a clear picture of the density and temperature structure of the region. The presence of a steep density

  4. Effect of tidal phase on solute flushing from a strait: SF6 tracer study in the East River, New York

    NASA Astrophysics Data System (ADS)

    Caplow, T.; Schlosser, P.; Ho, D. T.

    2003-12-01

    Flow in the East River, a 25 km tidal strait connecting Long Island Sound with New York Harbor, is driven by a tidal phase lag between the two ends of the strait. The direction and rate of solutes transported in the strait, including natural materials as well as anthropogenic contaminants, has important implications for the environmental management of Long Island Sound and other fragile local ecosystems. Sulfur hexafluoride (SF6) is a successful deliberate tracer for rivers, estuaries, and coastal areas. It is non-reactive, inexpensive, and offers an extremely low detection limit. High-resolution transport studies of complex coastal and estuarine areas up to 100 km2, and lasting up to two weeks, have recently been achieved using a boat-mounted SF6 measurement system with a sampling interval of 1 min and a detection limit of 1 x 10-14 mol L-1. In June 2003, two injections of 6.2 mol sulfur hexafluoride (SF6) were made 8 days apart in the East River to study residual circulation and rates of solute dissipation at different states of the tide. Both injections were made at the same location, but the first injection occurred at the slack before flood (northward flow), and the second injection occurred at the slack before ebb (southward flow). Tidally synchronized surveys of the SF6 tracer patch were made by boat for 7 days following the flood injection and for 5 days following the ebb injection. For the flood and ebb injections, respectively, mean displacement of the center of tracer mass within the East River, a proxy for residual circulation, was northward at 0.31 +/- 0.35 and 1.5 +/- 1.0 km day-1, mean fractional tracer loss due to tidal flushing was 0.32 +/- 0.06 day-1 and 0.52 +/- 0.10 day-1, and mean residence time was 2.6 +/- 0.4 days and 1.3 +/- 0.6 days. These tracer loss rates include a small correction for air-water gas exchange, which was estimated by a combination of previously established relationships between gas transfer velocity and wind speeds, river flow velocities, and rain rates. Residual circulation appeared to have little impact on tracer fate, while the state of the tide at the time of injection had a large impact. Tracer injected on the ebb tide dissipated more rapidly, indicating a large differential between the mixing power at the two ends of the strait. (In the case of the East River, New York Harbor offered more rapid mixing than Long Island Sound). These results suggest that tidal phasing of contaminant discharges in a strait of this kind (where the tidal excursion is comparable to the length of the strait) has the potential to reduce ecological impacts, by increasing flushing rates and directing a greater fraction of solutes away from ecologically sensitive areas.

  5. Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice

    E-print Network

    Eicken, Hajo

    Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice H. Eicken) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater

  6. USING CONTINUOUS MONITORS FOR CONDUCTING TRACER STUDIES IN WATER DISTRIBUTION SYSTEMS

    EPA Science Inventory

    The use of online monitors for conducting a distribution system tracer study is proving to be an essential tool to accurately understand the flow dynamics in a distribution system. In a series of field testing sponsored by U. S. Environmental Protection Agency (EPA) and Greater ...

  7. Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.

    PubMed

    Zhao, Yunliang; Kreisberg, Nathan M; Worton, David R; Isaacman, Gabriel; Weber, Robin J; Liu, Shang; Day, Douglas A; Russell, Lynn M; Markovic, Milos Z; VandenBoer, Trevor C; Murphy, Jennifer G; Hering, Susanne V; Goldstein, Allen H

    2013-04-16

    In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA. PMID:23448102

  8. Numerical Simulations and Tracer Studies as a Tool to Support Water Circulation Modeling in Breeding Reservoirs

    NASA Astrophysics Data System (ADS)

    Zima, Piotr

    2014-12-01

    The article presents a proposal of a method for computer-aided design and analysis of breeding reservoirs in zoos and aquariums. The method applied involves the use of computer simulations of water circulation in breeding pools. A mathematical model of a pool was developed, and a tracer study was carried out. A simplified model of two-dimensional flow in the form of a biharmonic equation for the stream function (converted into components of the velocity vector) was adopted to describe the flow field. This equation, supplemented by appropriate boundary conditions, was solved numerically by the finite difference method. Next, a tracer migration equation was solved, which was a two-dimensional advection-dispersion equation describing the unsteady transport of a non-active, permanent solute. In order to obtain a proper solution, a tracer study (with rhodamine WT as a tracer) was conducted in situ. The results of these measurements were compared with numerical solutions obtained. The results of numerical simulations made it possible to reconstruct water circulation in the breading pool and to identify still water zones, where water circulation was impeded.

  9. Passive tracers and active dynamics a model study of hydrography and circulation in the northern North Atlantic

    E-print Network

    Passive tracers and active dynamics ­ a model study of hydrography and circulation in the northern Terms 1635 Oceans; 4532 General circulation; 4536 Hydrography and Tracers 4215 Climate and interannual the variability in current strength, because hydrography and circulation generally respond to the same atmospheric

  10. Biotinylated dextran amine and biocytin hydrochloride are useful tracers for the study of retinal projections in the frog

    Microsoft Academic Search

    F. Scalia; S. M. Galoyan; S. Eisner; E. Harris; W. Su

    1997-01-01

    Anatomical study of the topographic organization of retinal projections requires a tracer capable of resolving fine morphological detail and permitting analysis of the projection from either the whole retina or selected areas. To obtain a permanent record of the experiments and to have access to ultrastructural data, it is preferable for the tracer to be compatible with both brightfield microscopy

  11. An SF6 Tracer Study of the Flow Dynamics in the Stockton Deep Water Ship Channel: Implications

    E-print Network

    Ho, David

    An SF6 Tracer Study of the Flow Dynamics in the Stockton Deep Water Ship Channel: Implications6) tracer release experi- ment was conducted in the Stockton Deep Water Ship Channel (DWSC concentrations maintained a steady state value of 4 mg l-1 . These values are below water quality objectives

  12. Inductively coupled plasma mass spectrometry for stable isotope metabolic tracer studies of living systems

    SciTech Connect

    Luong, E.

    1999-05-10

    This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 {+-} 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by this method is 10.2 {+-} 0.4 ng/g, while the certified value is 11.5 {+-} 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 {+-} 0.1 ng/g. The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry (GC-combustion-IRMS). Trytophan, myoglobin, and {beta}-cyclodextrin are chosen for the study, initial observation of spectral interference of {sup 13}C{sup +} with {sup 12}C{sup 1}H{sup +} comes from the incomplete dissociation of myoglobin and/or {beta}-cyclodextrin.

  13. Sample site selection for tracer studies applying a unidirectional circulatory approach

    SciTech Connect

    Layman, D.K.; Wolfe, R.R.

    1987-08-01

    The optimal arterial or venous sites for infusion and sampling during isotopic tracer studies have not been established. This study determined the relationship of plasma and tissue enrichment (E) when isotopes were infused in an artery and sampled from a vein (av mode) or infused in a vein and sampled from an artery (va mode). Adult dogs were given primed constant infusions of (3-/sup 13/C)lactate, (1-/sup 13/C)leucine, and /sup 14/C-labeled bicarbonate. Simultaneous samples were drawn from the vena cava, aortic arch, and breath. Tissue samples were removed from skeletal muscle, liver, kidney, and gut. Breath samples were analyzed for /sup 14/CO/sub 2/ by liquid scintillation counting and plasma isotopic enrichments of (/sup 13/C)lactate, (/sup 13/C)leucine, and alpha-(/sup 13/C)ketoisocaproate (KIC) were determined by gas chromatography-mass spectrometry. By using the va mode, the plasma E for lactate and leucine were 30-40% above tissue E. The av mode provided an accurate reflection of tissue E for lactate, which equilibrates rapidly with tissues, and a reasonable estimate for leucine, which exchanges more slowly. The isotopic enrichment of plasma KIC more directly reflected tissue leucine E than did plasma leucine E, and KIC enrichment was insensitive to sampling site. We also evaluated theoretically a circulatory model that predicts venous isotopic enrichments when the va mode is used. We conclude that the av mode is optimal but that the problems arising from use of the va mode can be overcome by use of a metabolic product (i.e., KIC) or by calculation of venous specific activity with our circulatory mode.

  14. A Study Plan for Determining Recharge Rates at the Hanford Site Using Environmental Tracers

    SciTech Connect

    Murphy,, E. M.; Szecsody,, J. E.; Phillips,, S. J.

    1991-02-01

    This report presents a study plan tor estimating recharge at the Hanford Site using environmental tracers. Past operations at the Hanford Site have led to both soil and groundwater contamination, and recharge is one of the primary mechanisms for transporting contaminants through the vadose zone and into the groundwater. The prediction of contaminant movement or transport is one aspect of performance assessment and an important step in the remedial investigation/feasibility study (RI/FS) process. In the past, recharge has been characterized by collecting lysimeter data. Although lysimeters can generate important and reliable data, their limitations include 1) fixed location, 2) fixed sediment contents, 3) edge effects, 4) low rates, and 5) relatively short duration of measurement. These limitations impact the ability to characterize the spatial distribution of recharge at the Hanford Site, and thus the ability to predict contaminant movement in the vadose zone. An alternative to using fixed lysimeters for determining recharge rates in the vadose zone is to use environmental tracers. Tracers that have been used to study water movement in the vadose zone include total chloride, {sup 36}CI, {sup 3}H, and {sup 2}H/{sup 18}O. Atmospheric levels of {sup 36}CI and {sup 3}H increased during nuclear bomb testing in the Pacific, and the resulting "bomb pulse" or peak concentration can be measured in the soil profile. Locally, past operations at the Hanford Site have resu~ed in the atmospheric release of numerous chemical and isotopic tracers, including nitrate, {sup 129}I, and {sup 99}Tc. The radionuclides, in particular, reached a well-defined atmospheric peak in 1945. Atmospheric releases of {sup 129}I and {sup 99}Tc were greatly reduced by mid-1946, but nitrogen oxides continued to be released from the uranium separations facilities. As a result, the nitrate concentrations probably peaked in the mid-1950s, when the greatest number of separations facilities were operating. Seven study sites on the Hanford Site have been selected, in two primary soil types that are believed to represent the extremes in recharge, the Quincy sand and the Warden silt loam. An additional background study site upwind of the Hanford facilities has been chosen at the Yakima Firing Center. Study sites at Hanford were chosen close to micrometeorology stations on downwind transects from the operational facilities. Initial testing will be done on sites that lack perennial vegetation. Six tracer techniques (total chlortde, {sup 36}Cl, {sup 3}H, nitrate, {sup 129}I, and {sup 99}Tc) will be tested on at least one site in the Quincy sand, one site in the Warden si~ loam, and the background site, to determine which combination of tracers wortks best for a given soil type. In subsequent years, additional sites will be investigated to determine the effect of vegetation on recharge estimates and on the performance of individual tracers. The use of environmental tracers is perhaps the only cost-effective method for estimating the spatial vartability of recharge at a site as large as Hanford. The tracer techniques used at Hanford have wide applicability at other and sites operated by the U.S. Department of Energy as well as at low-level radioactive waste disposal sites.

  15. Characterization of crushed tuff for the evaluation of the fate of tracers in transport studies in the unsaturated zone

    SciTech Connect

    Polzer, W.L.; Fuentes, H.R.; Raymond, R.; Bish, D.L.; Gladney, E.S.; Lopez, E.A.

    1987-03-01

    Results of field-scale (caisson) transport studies under unsaturated moisture and steady and nonsteady flow conditions indicate variability and a lack of conservation of mass in solute transport. The tuff materials used in that study were analyzed for the presence of tracers and of freshly precipitated material to help explain the variability and lack of conservation of mass. Selected tuff samples were characterized by neutron activation analysis for tracer identification, by x-ray diffraction for mineral identification, by petrographic analysis for identification of freshly precipitated material, and by x-ray fluorescence analysis for identification of major and trace elements. The results of these analyses indicate no obvious presence of freshly precipitated material that would retard tracer movement. The presence of the nonsorbing tracers (bromide and iodide) suggest the retention of these tracers in immobile water. The presence of the nonsorbing tracers (bromide and iodide) suggest the retention of these tracers in immobile water. The presence of sorbing and nonsorbing tracers on the tuff at some locations (even cesium at the 415-cm depth) and not at others suggests variability in transport. 15 refs., 14 figs., 9 tabs.

  16. Nitrate turnover in a peat soil under drained and rewetted conditions: results from a [(15)N]nitrate-bromide double-tracer study.

    PubMed

    Russow, Rolf; Tauchnitz, Nadine; Spott, Oliver; Mothes, Sibylle; Bernsdorf, Sabine; Meissner, Ralph

    2013-01-01

    Under natural conditions, peatlands are generally nitrate-limited. However, recent concerns about an additional N input into peatlands by atmospheric N deposition have highlighted the risk of an increased denitrification activity and hence the likelihood of a rise of emissions of the greenhouse gas nitrous oxide. Therefore, the aim of the present study was to investigate the turnover of added nitrate in a drained and a rewetted peatland using a [(15)N]nitrate-bromide double-tracer method. The double-tracer method allows a separation between physical effects (dilution, dispersion and dislocation) and microbial and chemical nitrate transformation by comparing with the conservative Br(-) tracer. In the drained peat site, low NO3(-) consumption rates have been observed. In contrast, NO3(-) consumption at the rewetted peat site rises rapidly to about 100% within 4 days after tracer application. Concomitantly, the (15)N abundances of nitrite and ammonium in soil water increased and lead to the conclusion that, besides commonly known NO3(-) reduction to nitrite (i.e. denitrification), a dissimilatory nitrate reduction to ammonium has simultaneously taken place. The present study reveals that increasing NO3(-) inputs into rewetted peatlands via atmospheric deposition results in a rapid NO3(-) consumption, which could lead to an increase in N2O emissions into the atmosphere. PMID:24313368

  17. Tracer Study of the Botswana Library School Graduates.

    ERIC Educational Resources Information Center

    Aina, L. O.; Moahi, K.

    1999-01-01

    Describes the results of a survey of graduates of the Department of Library and Information Studies, University of Botswana that was conducted to determine their characteristics, the relevance of their training to their present jobs, and their perceptions of the curriculum. A copy of the questionnaire used is appended. (Author/LRW)

  18. Hydrogen behavior near surface regions in Mo and W studied by tritium tracer technique

    NASA Astrophysics Data System (ADS)

    Hoshihira, Takamitsu; Otsuka, Teppei; Wakabayashi, Ryusuke; Tanabe, Tetsuo

    2011-10-01

    Tritium tracer techniques are applied to observe behavior of hydrogen (tritium (T)) in near surface regions of Mo and W loaded by gaseous absorption (GAS) and a glow discharge (GDC). GDC produces blisters on both Mo and W surfaces and Tritium Auto-RadioGraph (TARG) showed the thickness of blister skins is larger than the escaping depth of T ?-electrons, around 1 ?m. For GAS specimens, T evolution is likely controlled by diffusion giving diffusion coefficients of, D=1.5×10-7exp-{41 kJ/mol}/{RT} m s D=4.3×10-9exp-{38 kJ/mol}/{RT} m s at 273-323 K. GDC specimens show much smaller diffusion coefficients with higher activation energies and T release continues very long, suggesting T release from blisters.

  19. Stable water isotopes as tracers in studies of lacustrine groundwater discharge

    NASA Astrophysics Data System (ADS)

    Lewandowski, Jörg; Pöschke, Franziska; Meinikmann, Karin; Rudnick, Sebastian; Périllon, Cécile; Elmarami, Hatem; Massmann, Gudrun; Stumpp, Christine

    2015-04-01

    Different tracers are used in ecohydrology to study transport processes across groundwater-surface water interfaces. The stable water isotopes oxygen-18 and deuterium as parts of the water molecule are close to perfect tracers since their behavior in aquifers is quite conservative. Isotopic signatures of groundwater and surface water differ due to the impact of evaporation on lake water. Stable isotope measurements are nowadays orders of magnitude cheaper, faster, and easier due to the recent development of cavity ring-down spectroscopy. Based on that analytical progress, we suggest a much broader use and highlight a number of promising ecohydrological applications in studies of lacustrine groundwater discharge. For example, they might be used to clearly distinguish between in- and exfiltration zones of lakes, to identify temporal fluctuations of in- and exfiltration, but also to identify sampling artifacts due to short circuits during sampling with lakebed piezometers.

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

    SciTech Connect

    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.

  1. DNA tracers with information capacity and high detection sensitivity tested in groundwater studies

    NASA Astrophysics Data System (ADS)

    Sabir, I. H.; Torgersen, Jacob; Haldorsen, Sylvi; Aleström, Peter

    1999-06-01

    In order to investigate the usefulness of unique synthetic DNA tracers in groundwater, a field experiment was conducted in Norway. DNA tracers and a sodium-chloride tracer were injected into an aquifer. The transport of DNA molecules was interpreted by comparing with the plume of chloride ions under forced-gradient steady-state flow conditions. Spatial concentration moments described the migration of conservative tracers. Mobility and migration of DNA in groundwater demonstrate that DNA tracers can be detected by using the polymerase chain reaction (PCR) and DNA sequence analysis. The results indicate that DNA tracers can be valuable tools as tracers in groundwater investigations.

  2. A reliability and usability study of TRACEr-RAV: the technique for the retrospective analysis of cognitive errors--for rail, Australian version.

    PubMed

    Baysari, Melissa T; Caponecchia, Carlo; McIntosh, Andrew S

    2011-11-01

    The aim of this study was to compare the usability and reliability of two human error identification tools: TRACEr-Rail (developed by the Rail Safety and Standards Board in the UK) and TRACEr-RAV (an Australian specific version of the tool). Following an attempt to modify TRACEr-Rail to more appropriately suit the Australian rail context, it was predicted that TRACEr-RAV would be rated as more usable and be applied more consistently by Australian users than TRACEr-Rail. In Experiment 1, twenty-five rail employees used either TRACEr-Rail or TRACEr-RAV1 to extract and classify errors from six Australian rail incident reports. In Experiment 2, eleven university students used both TRACEr-Rail and TRACEr-RAV2 to extract and classify errors from three incident summaries. The results revealed that although modification of TRACEr-Rail to become TRACEr-RAV1 and TRACEr-RAV2 did not result in improved inter-rater reliability, modification resulted in improved ratings of usability in Experiment 2. Most participants in Experiment 2 preferred TRACEr-RAV2 to TRACEr-Rail. The poor inter-rater reliability observed was most likely the result of inadequate training, limited practice in using the tools, and insufficient human factors knowledge. PMID:21354553

  3. Dissolved noble gas and isotopic tracers reveal vulnerability of groundwater in a small, high-elevation catchment to predicted climate changes

    Microsoft Academic Search

    Michael J. Singleton; Jean E. Moran

    2010-01-01

    Noble gas concentrations and multiple isotopic tracers in groundwater and stream water at a small, high-elevation catchment of the Sierra Nevada Mountains constrain recharge conditions and subsurface residence times of different groundwater components. We identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water with elevated radiogenic 4He that has experienced longer

  4. Use of a simple model for studying oceanic tracer distributions and the global carbon cycle

    Microsoft Academic Search

    U. Siegenthaler; F. Joos

    1992-01-01

    The paper studies, based on work of Shaffer and Sarmiento (1992), a model for simulating the transport of CO2 and tracers in the ocean (HILDA, for High-Latitude Exchange\\/Interior Diffusion-Advection Model) that combines features of box models and of the box-diffusion model. Different ways of calibration are compared, and it is found that, in order to reproduce the distributions of natural

  5. National Biomedical Tracer Facility (NBTF). Project definition study: Phase I

    SciTech Connect

    Lagunas-Solar, M.C.

    1995-02-15

    This report describes a five-year plan for the construction and commissioning of a reliable and versatile NBTF facility for the production of high-quality, high-yield radioisotopes for research, biomedical, and industrial applications. The report is organized in nine sections providing, in consecutive order, responses to the nine questions posed by the U.S. Department of Energy in its solicitation for the NBTF Project Definition Study. In order to preserve direct correspondence (e.g., Sec. 3 = 3rd item), this Introduction is numbered {open_quotes}0.{close_quotes} Accelerator and facility designs are covered in Section 1 (Accelerator Design) and Section 2 (Facility Design). Preliminary estimates of capital costs are detailed in Section 3 (Design and Construction Costs). Full licensing requirements, including federal, state, and local ordinances, are discussed in Section 4 (Permits). A plan for the management of hazardous materials to be generated by NBTF is presented in Section 5 (Waste Management). An evaluation of NBTF`s economic viability and its potential market impact is detailed in Section 6(Business Plan), and is complemented by the plans in Section 7 (Operating Plan) and Section 8 (Radioisotope Plan). Finally, a plan for NBTF`s research, education, and outreach programs is presented in Section 9 (Research and Education Programs).

  6. Field studies of streamflow generation using natural and injected tracers on Bickford and Walker Branch Watersheds

    SciTech Connect

    Genereux, D.; Hemond, H. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Civil Engineering; Mulholland, P. [Oak Ridge National Lab., TN (United States)

    1992-05-01

    Field studies of streamflow generation were undertaken on two forested watersheds, the West Road subcatchment of Bickford Watershed in central Massachusetts and the West Fork of Walker Branch Watershed in eastern Tennessee. A major component of the research was development of a two-stage methodology for the use of naturally-occurring {sup 222}Rn as a tracer. The first of the two stages was solving a mass-balance equation for {sup 222}Rn around a stream reach of interest in order to calculate Rn{sub q}, the {sup 222}Rn content of the lateral inflow to the reach; a conservative tracer (chloride) and a volatile tracer (propane) were injected into the study stream to account for lateral inflow to, and volatilization from, the study reach. The second stage involved quantitative comparison of Rn{sub q} to the measured {sup 222}Rn concentrations of different subsurface waters in order to assess how important these waters were in contributing lateral inflow to the stream reach.

  7. Flow optimization study of a batch microfluidics PET tracer synthesizing device

    PubMed Central

    Elizarov, Arkadij M.; Meinhart, Carl; van Dam, R. Michael; Huang, Jiang; Daridon, Antoine; Heath, James R.; Kolb, Hartmuth C.

    2010-01-01

    We present numerical modeling and experimental studies of flow optimization inside a batch microfluidic micro-reactor used for synthesis of human-scale doses of Positron Emission Tomography (PET) tracers. Novel techniques are used for mixing within, and eluting liquid out of, the coin-shaped reaction chamber. Numerical solutions of the general incompressible Navier Stokes equations along with time-dependent elution scalar field equation for the three dimensional coin-shaped geometry were obtained and validated using fluorescence imaging analysis techniques. Utilizing the approach presented in this work, we were able to identify optimized geometrical and operational conditions for the micro-reactor in the absence of radioactive material commonly used in PET related tracer production platforms as well as evaluate the designed and fabricated micro-reactor using numerical and experimental validations. PMID:21072595

  8. STRATEGIES FOR QUANTIFYING PET IMAGING DATA FROM TRACER STUDIES OF BRAIN RECEPTORS AND ENZYMES.

    SciTech Connect

    Logan, J.

    2001-04-02

    A description of some of the methods used in neuroreceptor imaging to distinguish changes in receptor availability has been presented in this chapter. It is necessary to look beyond regional uptake of the tracer since uptake generally is affected by factors other than the number of receptors for which the tracer has affinity. An exception is the infusion method producing an equilibrium state. The techniques vary in complexity some requiring arterial blood measurements of unmetabolized tracer and multiple time uptake data. Others require only a few plasma and uptake measurements and those based on a reference region require no plasma measurements. We have outlined some of the limitations of the different methods. Laruelle (1999) has pointed out that test/retest studies to which various methods can be applied are crucial in determining the optimal method for a particular study. The choice of method will also depend upon the application. In a clinical setting, methods not involving arterial blood sampling are generally preferred. In the future techniques for externally measuring arterial plasma radioactivity with only a few blood samples for metabolite correction will extend the modeling options of clinical PET. Also since parametric images can provide information beyond that of ROI analysis, improved techniques for generating such images will be important, particularly for ligands requiring more than a one-compartment model. Techniques such as the wavelet transform proposed by Turkheimer et al. (2000) may prove to be important in reducing noise and improving quantitation.

  9. Overview of SIMS-Based Experimental Studies of Tracer Diffusion in Solids and Application to Mg Self-Diffusion

    SciTech Connect

    Kulkarni, Nagraj S [ORNL; Warmack, Robert J Bruce [ORNL; Radhakrishnan, Balasubramaniam [ORNL; HunterJr., Jerry [Virginia Polytechnic Institute and State University; Sohn, Yong Ho [University of Central Florida; Coffey, Kevin [University of Central Florida; Murch, Prof. Graeme [University of Newcastle, NSW, Australia; Belova, Irina [University of Newcastle, NSW, Australia

    2014-01-01

    Tracer diffusivities provide the most fundamental information on diffusion in materials and are the foundation of robust diffusion databases. Compared to traditional radiotracer techniques that utilize radioactive isotopes, the secondary ion mass spectrometry (SIMS) based thin-film technique for tracer diffusion is based on the use of enriched stable isotopes that can be accurately profiled using SIMS. Experimental procedures & techniques that are utilized for the measurement of tracer diffusion coefficients are presented for pure magnesium, which presents some unique challenges due to the ease of oxidation. The development of a modified Shewmon-Rhines diffusion capsule for annealing Mg and an ultra-high vacuum (UHV) system for sputter deposition of Mg isotopes are discussed. Optimized conditions for accurate SIMS depth profiling in polycrystalline Mg are provided. An automated procedure for the correction of heat-up and cool-down times during tracer diffusion annealing is discussed. The non-linear fitting of a SIMS depth profile data using the thin film Gaussian solution to obtain the tracer diffusivity along with the background tracer concentration and tracer film thickness is discussed. An Arrhenius fit of the Mg self-diffusion data obtained using the low-temperature SIMS measurements from this study and the high-temperature radiotracer measurements of Shewmon and Rhines (1954) was found to be a good representation of both types of diffusion data that cover a broad range of temperatures between 250 - 627 C (523 900 K).

  10. Biotinylated dextran amine and biocytin hydrochloride are useful tracers for the study of retinal projections in the frog.

    PubMed

    Scalia, F; Galoyan, S M; Eisner, S; Harris, E; Su, W

    1997-10-01

    Anatomical study of the topographic organization of retinal projections requires a tracer capable of resolving fine morphological detail and permitting analysis of the projection from either the whole retina or selected areas. To obtain a permanent record of the experiments and to have access to ultrastructural data, it is preferable for the tracer to be compatible with both brightfield microscopy and electron microscopy. Biotinylated dextran amine and biocytin hydrochloride, as employed in the present experiments, meet these needs exceptionally well for anterograde tracing studies on the frog visual system. Both tracers labeled axons and terminal arbors more prominently than comparable material studied by the widely used methods of anterograde fiber-filling with horseradish peroxidase or cobalt. When used to trace the projections from small sectors of retina, the finest unmyelinated fibers in layers A, C and E of the frog optic tectum and their synaptic boutons were made readily visible by the new tracers. PMID:9350968

  11. Wind tunnel experiment of tracer gas diffusion within unstable boundary layer over coastal region

    Microsoft Academic Search

    K Sada

    2002-01-01

    A wind tunnel experiment was carried out to simulate stack gas diffusion within an unstable atmospheric boundary layer over a coastal region. The wind tunnel floor, 4m leeward of the entrance of the test section, was heated to 90°C over a length of 6m in the streamwise direction, and wind tunnel experiments were performed under the flat plate condition with

  12. Primary productivity, new productivity, and their relation to carbon flux during two Southern Ocean Gas Exchange tracer experiments

    NASA Astrophysics Data System (ADS)

    Lance, Veronica P.; Strutton, Peter G.; Vaillancourt, Robert D.; Hargreaves, Bruce R.; Zhang, Jia-Zhong; Marra, John

    2012-04-01

    Biological uptake rates of inorganic carbon and nitrate were measured during two sequential tracer release gas exchange experiments, together known as the Southern Ocean Gas Exchange Experiment (SO GasEx) in the southwest Atlantic sector of the Southern Ocean Antarctic Zone (51°N, 38°W). Primary productivity estimated from 14C incubations ranged from 26.7 to 47.2 mmol C m-2 d-1 in the first experiment (Patch 1) and 13.7 to 39.4 mmol C m-2 d-1 in the second experiment (Patch 2). Nitrate-based productivity estimated from 15NO3 incubations ranged from 5.8 to 13.1 mmol C m-2 d-1 in Patch 1 and 1.9 to 7.1 mmol C m-2 d-1 in Patch 2. The average ratio of nitrate-based productivity to primary productivity (approximating the f ratio) was 0.24 in Patch 1 and 0.15 in Patch 2. Chlorophyll concentrations for both patches were less than 1 mg m-3. Photochemical efficiency (Fv/Fm) was low (˜0.3) in Patch 1 and moderate (˜0.45) in Patch 2. Si(OH)4 concentrations were potentially limiting (<1 mmol m-3 for Patch 1 and ˜3 mmol m-3 for Patch 2), while NH4+ concentrations were elevated (˜1 mmol m-3 for Patch 1 and ˜2.2 mmol m-3 for Patch 2) compared with typical open ocean Antarctic Zone water. We hypothesize that Patch 1 productivity was regulated by the availability of Si(OH)4, while Patch 2 productivity was regulated by grazers. Primary production and nitrate-based production (as a proxy for C export) determined here provide components for a mixed layer carbon budget from which the air-sea flux of CO2 will be quantified.

  13. Tracer Gas Transport under Mixed Convection Conditions in anExperimental Atrium: Comparison Between Experiments and CFDPredictions

    SciTech Connect

    Jayaraman, Buvaneswari; Finlayson, Elizabeth U.; Sohn, MichaelD.; Thatcher, Tracy L.; Price, Phillip N.; Wood, Emily E.; Sextro,Richard G.; Gadgil, Ashok J.

    2006-01-01

    We compare computational fluid dynamics (CFD) predictions using a steady-state Reynolds Averaged Navier-Stokes (RANS) model with experimental data on airflow and pollutant dispersion under mixed-convection conditions in a 7 x 9 x 11m high experimental facility. The Rayleigh number, based on height, was O(10{sup 11}) and the atrium was mechanically ventilated. We released tracer gas in the atrium and measured the spatial distribution of concentrations; we then modeled the experiment using four different levels of modeling detail. The four computational models differ in the choice of temperature boundary conditions and the choice of turbulence model. Predictions from a low-Reynolds-number k-{var_epsilon} model with detailed boundary conditions agreed well with the data using three different model-measurement comparison metrics. Results from the same model with a single temperature prescribed for each wall also agreed well with the data. Predictions of a standard k-{var_epsilon} model were about the same as those of an isothermal model; neither performed well. Implications of the results for practical applications are discussed.

  14. DEVELOPMENT OF STATIC METHOD FOR THE MEASUREMENT OF PARTITION COEFFICIENTS BETWEEN NAPL AND COMMON GAS TRACER COMPOUNDS

    EPA Science Inventory

    Many volatile compounds are being used for field scale partitioning tracer experiments. The design and analysis of these partitioning tracer tests require knowledge of these compounds' nonaqueous phase (NAPL) to air partition coefficient and many of these are not readily availabl...

  15. Evaluation of a Eulerian and Lagrangian air quality model using perfluorocarbon tracers released in Texas for the BRAVO haze study

    NASA Astrophysics Data System (ADS)

    Schichtel, Bret A.; Barna, Michael G.; Gebhart, Kristi A.; Malm, William C.

    The Big Bend Regional Aerosol and Visibility Observational (BRAVO) study was designed to determine the sources of haze at Big Bend National Park, Texas, using a combination of source and receptor models. BRAVO included an intensive monitoring campaign from July to October 1999 that included the release of perfluorocarbon tracers from four locations at distances 230-750 km from Big Bend and measured at 24 sites. The tracer measurements near Big Bend were used to evaluate the dispersion mechanisms in the REMSAD Eulerian model and the CAPITA Monte Carlo (CMC) Lagrangian model used in BRAVO. Both models used 36 km MM5 wind fields as input. The CMC model also used a combination of routinely available 80 and 190 km wind fields from the National Weather Service's National Centers for Environmental Prediction (NCEP) as input. A model's performance is limited by inherent uncertainties due to errors in the tracer concentrations and a model's inability to simulate sub-resolution variability. A range in the inherent uncertainty was estimated by comparing tracer data at nearby monitoring sites. It was found that the REMSAD and CMC models, using the MM5 wind field, produced performance statistics generally within this inherent uncertainty. The CMC simulation using the NCEP wind fields could reproduce the timing of tracer impacts at Big Bend, but not the concentration values, due to a systematic underestimation. It appears that the underestimation was partly due to excessive vertical dilution from high mixing depths. The model simulations were more sensitive to the input wind fields than the models' different dispersion mechanisms. Comparisons of REMSAD to CMC tracer simulations using the MM5 wind fields had correlations between 0.75 and 0.82, depending on the tracer, but the tracer simulations using the two wind fields in the CMC model had correlations between 0.37 and 0.5.

  16. Using tracer technique to study the flow behavior of surfactant foam.

    PubMed

    Tsai, Yih-Jin; Chou, Feng-Chih; Cheng, Shin-Jen

    2009-07-30

    Surfactant foam was used to remove absorbed hydrocarbons from soils. The nature and extent of the foam pathway decide the efficiency of this technology. The characteristics and behavior of foam flow are difficult to visually observe. In this study, laboratory sandbox experiments were performed to estimate the flow behavior of surfactant foam and thus elucidate the properties and flow behavior of surfactant foam. To quantitatively determine the distribution of foam and evaluate accurately the flow field of foam in the soil, this study designed a special technique, applying micro-scale iron powder as a tracer. The foam generated with 4% (w/v) mixed solution of Span 60 and sodium dodecyl sulfate (SDS) showed an excellent stability and quality, which made it particularly apt for this study. The results indicated that the foam flows through the zone above the clay planes and also flows through the zone between the clay planes. The heterogeneous sand does not inhibit the invasion of foam flow. Moreover, the results of tracer tests and photographs of the foam distributions in sandbox were identical in the behavior of foam flow. This knowledge is valuable for providing insight into the foam remediation of contaminated soil. PMID:19157697

  17. Noble gas tracers of mantle processes beneath the Galápagos archipelago (Invited)

    NASA Astrophysics Data System (ADS)

    Kurz, M. D.; Harpp, K. S.; Geist, D.; Fornari, D. J.; Curtice, J.; Lott, D. E.; Jenkins, W. J.

    2010-12-01

    Recent measurements in dredged glassy basalts from the western and northern submarine edges of the Galápagos archipelago (R/V Revelle/Drift04 and R/V Melville/MV1007 expeditions, respectively) allow a new examination of the spatial distribution of the noble gas isotopic compositions. The large dynamic range in helium isotopic compositions (6.5 to 30 times atmosphere (Ra)) coupled with the spatial distribution of recent submarine and subaerial volcanism provides a unique picture of mantle dynamics. The highest 3He/4He in the Galápagos are found in basalts from Fernandina volcano at the western edge of the archipelago, which also has the most unradiogenic neon isotopic compositions, suggesting that Fernandina lies above the hotspot center. The high helium isotopic signal drops off asymmetrically to the north and south of Fernandina, with higher 3He/4He ratios found to the South, ranging from 10 to 20 Ra near Cerro Azul, Sierra Negra, and Floreana. To the north of Fernandina, 3He/4He ratios decrease rapidly, reaching values close to MORB at Volcan Ecuador (9.8 to 11.4 Ra), Volcan Wolf (8.1 to 9.2 Ra), and Roca Redonda (7.6 to 9.5 Ra). Preliminary data suggests that He, Ne, and Ar isotopes are correlated in basalts from the western edge of the Galápagos. Using neon isotope data to correct 40Ar/36Ar for atmospheric influence shows that 3He/4He is negatively correlated with (extrapolated) 40Ar/36Ar, and strongly suggests that the noble gas variations relate to mantle source, which has important implications for deep earth noble gas budgets. New data from seamounts in the area between the Galápagos Spreading Center (GSC) and the main archipelago reveal relatively small hotspot helium contributions. The region between the GSC and Isla Pinta is characterized by 3He/4He close to MORB (7.3 to 7.7 Ra). The only evidence of hotspot helium contributions is observed at the southernmost end of the Wolf Darwin Lineament (9.3 Ra) and at the shoal between Genovesa and Marchena (9.5 Ra), which are separated by low values near Isla Pinta (6.5 to 6.9 Ra). This remarkable spatial variability in 3He/4He relates to heterogeneities within the upwelling hotspot, coupled with mantle melting at various depths, as the upwelling material advects to the northeast. The most striking result is the lack of (large) helium anomalies near the GSC, in contrast with other non-volatile geochemical indicators of hotspot influence, indicating that helium is extremely incompatible and is efficiently removed during the initial stages of hotspot upwelling.

  18. Sulfur Hexafluoride Tracer Dispersion within Cherry Orchard

    E-print Network

    Collins, Gary S.

    Sulfur Hexafluoride Tracer Dispersion within Cherry Orchard Zeyuan Chen, S. Edburg, and B. Lamb the correspondence between tracer gas concentration and atmospheric stability. Within the Tukey Cherry Orchard, we

  19. SF6 Tracer Release Study: A Contaminant Fate Study in Newtown Creek

    NASA Astrophysics Data System (ADS)

    Schmieder, P. J.; Ho, D. T.; Peter, S.; Simpson, H. J.; Flores, S.; Dugan, W. A.

    2004-12-01

    Newtown Creek is a 5.5km creek that discharges into the East River, a 25km strait connecting Long Island Sound to the north and the New York Harbor to the south. Surface runoff dominates the freshwater input into the creek, for natural tributaries no longer exist. The areas directly adjacent to the creek are highly industrialized, and New York City's largest Water Pollution Control Plant (WPCP) discharges directly into creek. In August 2004, we injected sulfur hexafluoride (SF6) into Newtown creek to study the fate of oil seeping into the creek from an underground oil spill and the fate of nutrient rich effluent from the WPCP. We monitored SF6 in Newtown Creek, the East River, and the Upper Bay of New York Harbor for 7 consecutive days following the injection in order to investigate the spreading patterns and transport mechanics of waters exiting the creek, and to determine the ultimate fate of the contaminants/solutes originating in Newtown Creek. Dissolved oxygen (DO) measurements were collected simultaneously with SF6 measurements. A strong DO gradient exists in the creek, where waters in the upper reaches are anoxic. We use SF6 data to calculate mean residence times for Newtown Creek waters. SF6 was detected above background concentrations approximately 15km to the south of the creek at the Verrazano Bridge only 1 day after the tracer injection. By combining the movements of the SF6 distribution, the position of the oxygen gradient, and the residence time of Newtown Creek water, we can determine a lower boundary for oxygen consumption rates.

  20. Human biokinetic data and a new compartmental model of zirconium--a tracer study with enriched stable isotopes.

    PubMed

    Greiter, Matthias B; Giussani, Augusto; Höllriegl, Vera; Li, Wei Bo; Oeh, Uwe

    2011-09-01

    Biokinetic models describing the uptake, distribution and excretion of trace elements are an essential tool in nutrition, toxicology, or internal dosimetry of radionuclides. Zirconium, especially its radioisotope (95)Zr, is relevant to radiation protection due to its production in uranium fission and neutron activation of nuclear fuel cladding material. We present a comprehensive set of human data from a tracer study with stable isotopes of zirconium. The data are used to refine a biokinetic model of zirconium. Six female and seven male healthy adult volunteers participated in the study. It includes 16 complete double tracer investigations with oral ingestion and intravenous injection, and seven supplemental investigations. Tracer concentrations were measured in blood plasma and urine collected up to 100 d after tracer administration. The four data sets (two chemical tracer forms in plasma and urine) each encompass 105-240 measured concentration values above detection limits. Total fractional absorption of ingested zirconium was found to be 0.001 for zirconium in citrate-buffered drinking solution and 0.007 for zirconium oxalate solution. Biokinetic models were developed based on the linear first-order kinetic compartmental model approach used by the International Commission on Radiological Protection (ICRP). The main differences of the optimized systemic model of zirconium to the current ICRP model are (1) recycling into the transfer compartment made necessary by the observed tracer clearance from plasma, (2) different parameters related to fractional absorption for each form of the ingested tracer, and (3) a physiologically based excretion pathway to urine. The study considerably expands the knowledge on the biokinetics of zirconium, which was until now dominated by data from animal studies. The proposed systemic model improves the existing ICRP model, yet is based on the same principles and fits well into the ICRP radiation protection approach. PMID:21724239

  1. URCHIN: Reverse ray tracer

    NASA Astrophysics Data System (ADS)

    Altay, Gabriel; Theuns, Tom

    2014-12-01

    URCHIN is a Smoothed Particle Hydrodynamics (SPH) reverse ray tracer (i.e. from particles to sources). It calculates the amount of shielding from a uniform background that each particle experiences. Preservation of the adaptive density field resolution present in many gas dynamics codes and uniform sampling of gas resolution elements with rays are two of the benefits of URCHIN; it also offers preservation of Galilean invariance, high spectral resolution, and preservation of the standard uniform UV background in optically thin gas.

  2. Alma observations of nearby luminous infrared galaxies with various agn energetic contributions using dense gas tracers

    SciTech Connect

    Imanishi, Masatoshi [Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Nakanishi, Kouichiro, E-mail: masa.imanishi@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2014-07-01

    We present the results of our ALMA Cycle 0 observations, using HCN/HCO{sup +}/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO{sup +} J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO{sup +} J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO{sup +} J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

  3. ALMA Observations of Nearby Luminous Infrared Galaxies with Various AGN Energetic Contributions Using Dense Gas Tracers

    NASA Astrophysics Data System (ADS)

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2014-07-01

    We present the results of our ALMA Cycle 0 observations, using HCN/HCO+/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO+ J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO+ J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO+ J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

  4. Dual tracer autoradiographic study with thallium-201 and radioiodinated fatty acid in cardiomyopathic hamsters

    SciTech Connect

    Kurata, C.; Kobayashi, A.; Yamazaki, N.

    1989-01-01

    To investigate the usefulness of myocardial scintigraphy with radioiodinated 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in cardiomyopathy, quantitative dual tracer autoradiographic study with /sup 201/Tl and (/sup 125/I)BMIPP was performed in 27 cardiomyopathic Bio 14.6 Syrian hamsters and eight normal hamsters. Furthermore, 16 Bio 14.6 Syrian hamsters aged 21 days were divided into verapamil-treated (during 70 days) and control groups (respectively, n = 8), and autoradiography with /sup 201/Tl and (/sup 125/I)BMIPP was performed. Quantitative autoradiography demonstrated an uncoupling of /sup 201/Tl and (/sup 125/I)BMIPP distributions and a regional heterogeneity of (/sup 125/I)BMIPP distribution in cardiomyopathic hamsters aged more than 2 mo, while normal hamsters showed only mild heterogeneity of (/sup 125/I)BMIPP distribution without an uncoupling of tracers. Age-matched comparison between normal and cardiomyopathic hamsters (5-8 mo old) demonstrated that a difference between their (/sup 125/I)BMIPP distributions are more marked than that between their /sup 201/Tl distributions. Furthermore, (/sup 125/I)BMIPP visualized effects of verapamil on cardiomyopathy more distinctly than did /sup 201/Tl. In conclusion, myocardial imaging with (/sup 123/I)BMIPP could be useful for investigating cardiomyopathy and evaluating the efficacy of therapeutic intervention in patients with cardiomyopathy.

  5. Effects of solute breakthrough curve tail truncation on residence time estimates: A synthesis of solute tracer injection studies

    NASA Astrophysics Data System (ADS)

    Drummond, J. D.; Covino, T. P.; Aubeneau, A. F.; Leong, D.; Patil, S.; Schumer, R.; Packman, A. I.

    2012-09-01

    Hydrologic transport and retention strongly affect biogeochemical processes that are critical to stream ecosystems. Tracer injection studies are often used to characterize solute transport and retention in stream reaches, but the range of processes accurately resolved with this approach is not clear. Solute residence time distributions depend on both in-stream mixing and exchange with the hyporheic zone and the larger groundwater system. Observed in-stream breakthrough curves have most commonly been modeled with in-stream advection-dispersion plus an exponential residence time distribution, but process-based models suggest that hyporheic exchange is a fractal process, and that hyporheic residence time distributions are more appropriately characterized by power law tailing. We synthesized results from a variety of tracer-injection studies to investigate the information content of tracer breakthrough curves. We found that breakthrough curve tails are often not well characterized in stream tracer experiments. The two main reasons for this are: 1) experimental truncation of breakthrough curves, which occurs when sampling ends before all tracer mass reaches the sampling location, and 2) sensitivity truncation of breakthrough curves, when tracer concentrations in the tail are too low to be detected reliably above background levels. Tail truncation reduces observed mass recovery and obscures assessment of breakthrough curve tailing and solute residence time. Failure to consider tail truncation leads to underestimation of hyporheic exchange and solute retention and to corresponding overestimation of hyporheic biogeochemical transformation rates. Based on these findings, we propose criteria for improved design of in-stream tracer injection experiments to improve assessment of solute tailing behavior.

  6. Measuring self-pollution in school buses using a tracer gas technique

    Microsoft Academic Search

    Eduardo Behrentz; Dennis R Fitz; David V Pankratz; Lisa D Sabin; Steven D Colome; Scott A Fruin; Arthur M Winer

    2004-01-01

    A potentially important, but inadequately studied, source of children's exposure to pollutants during school bus commutes is the introduction of a bus's own exhaust into the passenger compartment. We developed and applied a method to determine the amount of a bus's own exhaust penetrating into the cabin in a study of six in-use school buses over a range of routes,

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

    SciTech Connect

    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.

  8. 13C-tracer and gas chromatography-mass spectrometry analyses reveal metabolic flux distribution in the oleaginous microalga Chlorella protothecoides.

    PubMed

    Xiong, Wei; Liu, Lixia; Wu, Chao; Yang, Chen; Wu, Qingyu

    2010-10-01

    The green alga Chlorella protothecoides has received considerable attention because it accumulates neutral triacylglycerols, commonly regarded as an ideal feedstock for biodiesel production. In order to gain a better understanding of its metabolism, tracer experiments with [U-(13)C]/[1-(13)C]glucose were performed with heterotrophic growth of C. protothecoides for identifying the metabolic network topology and estimating intracellular fluxes. Gas chromatography-mass spectrometry analysis tracked the labeling patterns of protein-bound amino acids, revealing a metabolic network consisting of the glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle with inactive glyoxylate shunt. Evidence of phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and malic enzyme activity was also obtained. It was demonstrated that the relative activity of the pentose phosphate pathway to glycolysis under nitrogen-limited environment increased, reflecting excess NADPH requirements for lipid biosynthesis. Although the growth rate and cellular oil content were significantly altered in response to nitrogen limitation, global flux distribution of C. protothecoides remained stable, exhibiting the rigidity of central carbon metabolism. In conclusion, quantitative knowledge on the metabolic flux distribution of oleaginous alga obtained in this study may be of value in designing strategies for metabolic engineering of desirable bioproducts. PMID:20720172

  9. 13C-Tracer and Gas Chromatography-Mass Spectrometry Analyses Reveal Metabolic Flux Distribution in the Oleaginous Microalga Chlorella protothecoides1[C][W][OA

    PubMed Central

    Xiong, Wei; Liu, Lixia; Wu, Chao; Yang, Chen; Wu, Qingyu

    2010-01-01

    The green alga Chlorella protothecoides has received considerable attention because it accumulates neutral triacylglycerols, commonly regarded as an ideal feedstock for biodiesel production. In order to gain a better understanding of its metabolism, tracer experiments with [U-13C]/[1-13C]glucose were performed with heterotrophic growth of C. protothecoides for identifying the metabolic network topology and estimating intracellular fluxes. Gas chromatography-mass spectrometry analysis tracked the labeling patterns of protein-bound amino acids, revealing a metabolic network consisting of the glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle with inactive glyoxylate shunt. Evidence of phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and malic enzyme activity was also obtained. It was demonstrated that the relative activity of the pentose phosphate pathway to glycolysis under nitrogen-limited environment increased, reflecting excess NADPH requirements for lipid biosynthesis. Although the growth rate and cellular oil content were significantly altered in response to nitrogen limitation, global flux distribution of C. protothecoides remained stable, exhibiting the rigidity of central carbon metabolism. In conclusion, quantitative knowledge on the metabolic flux distribution of oleaginous alga obtained in this study may be of value in designing strategies for metabolic engineering of desirable bioproducts. PMID:20720172

  10. Accounting for Dispersion and time-dependent Input Signals during Gas Tracer Tests and their Effect on the Estimation of Reaeration, Respiration and Photosynthesis in Streams

    NASA Astrophysics Data System (ADS)

    Knapp, Julia; Osenbrück, Karsten; Olaf, Cirpka

    2015-04-01

    The variation of dissolved oxygen (DO) in streams, are caused by a number of processes, of which respiration and primary production are considered to be the most important ones (Odum, 1956; Staehr et al., 2012). Measuring respiration and photosynthesis rates in streams based on recorded time series of DO requires good knowledge on the reaeration fluxes at the given locations. For this, gas tracer tests can be conducted, and reaeration coefficients determined from the observed decrease in gas concentration along the stretch (Genereux and Hemond, 1990): ( ) --1- -cup- k2 = t2 - t1 ln Rcdown (1) with the gas concentrations measured at an upstream location, cup[ML-3], and a downstream location, cdown. t1[T] andt2 [T] denote the measurement times at the two locations and R [-] represents the recovery rate which can also be obtained from conservative tracer data. The typical procedure for analysis, however, contains a number of assumptions, as it neglects dispersion and does not take into account possible fluctuations of the input signal. We derive the influence of these aspects mathematically and illustrate them on the basis of field data obtained from a propane gas tracer test. For this, we compare the reaeration coefficients obtained from approaches with dispersion and/or a time-dependent input signals to the standard approach. Travel times and travel time distributions between the different measurement stations are obtained from a simultaneously performed conservative tracer test with fluorescein. In order to show the carry-over effect to metabolic rates, we furthermore estimate respiration and photosynthesis rates from the calculated reaeration coefficients and measured oxygen data. This way, we are able to show that neglecting dispersion significantly underestimates reaeration, and the impact of the time-dependent input concentration cannot be disregarded either. When estimated reaeration rates are used to calculate respiration and photosynthesis from measured oxygen data, these effects carry over, leading to higher respiration rates for higher reaeration. References: Genereux, D. P., & Hemond, H. F. (1990). Naturally-Occurring Rn-222 as a Tracer for Streamflow Generation - Steady-State Methodology and Field Example. Water Resources Research, 26(12), 3065-3075. doi: Doi 10.1029/Wr026i012p03065 Odum, H. T. (1956). Primary production in flowing waters. Limnol. Oceanogr, 1(2), 102-117. Staehr, P. A., Testa, J. M., Kemp, W. M., Cole, J. J., Sand-Jensen, K., & Smith, S. V. (2012). The metabolism of aquatic ecosystems: history, applications, and future challenges. Aquatic Sciences, 74(1), 15-29. doi: DOI 10.1007/s00027-011-0199-2

  11. Long-range (CAPTEX (Cross-APpalachian Tracer EXperiment)) and complex terrain (ASCOT (Atmospheric Studies of COmplex Terrain)) perfluorocarbon tracer studies

    SciTech Connect

    Jeffter, J.L.; Yamada, T.; Dietz, R.N.

    1986-01-01

    Perfluorocarbon tracer (PFT) technology, consisting of tracers, samplers, and analytical equipment, has been deployed in numerous meteorological experiments for the verification of long-range and complex terrain transport and dispersion models. The CAPTEX (Cross-APpalachain Tracer EXperiment) ''83 was conducted from mid-September through October 1983, in which seven 3-h tracer releases (5 from Dayton, Ohio, and 2 from Sudbury, Ontario) were made of a single PFT. Ground sampling occurred at 80 sites in the northeastern US and southeastern Canada at distances of 300 to 1100 km from the release sites, with a total of 3000 samples collected. Seven aircraft gathered 1600 crosswind and vertical spiral samples at distance of 200 to 900 km from the release sites. Peak ground concentrations of over 30 times background and peak aircraft values of over 150 times background were measured at the most distant sites; some typical results are shown. The branching atmospheric trajectory (BAT) long-range transport was described. The model-calculated maximum ground level PFT concentrations were compared with the measured concentration isopleths as well as through the use of scatter diagrams of concentrations, spatial errors, and frequency of space- and time-averaged concentrations. The average spatial error found for each of the 7 releases ranged from 1.3/sup 0/ to 1.7/sup 0/ lat. The crosswind standard deviations of aircraft traverses at 600 to 800 km downwind varied from 12 to 20 km which corresponded to 1.0/sup 0/ to 1.6/sup 0/ lat., indicating that the model was accurate to within one standard deviation of the real-time tracer profiles. On average, for the 7 runs, 50% of the model-calculated concentrations were within a factor of 20 of the observations, indicating that, in general, 1/sup 0/ lat. shifts can easily cause order-of-magnitude changes in observed concentrations.

  12. Tracer diffusion in colloidal gels

    E-print Network

    Sujin Babu; Jean Christophe Gimel; Taco Nicolai

    2007-05-09

    Computer simulations were done of the mean square displacement (MSD) of tracer particles in colloidal gels formed by diffusion or reaction limited aggregation of hard spheres. The diffusion coefficient was found to be determined by the volume fraction accessible to the spherical tracers ($\\phi_a$) independent of the gel structure or the tracer size. In all cases, critical slowing down was observed at $\\phi_a\\approx 0.03$ and was characterized by the same scaling laws reported earlier for tracer diffusion in a Lorentz gas. Strong heterogeneity of the MSD was observed at small $\\phi_a$ and was related to the size distribution of pores.

  13. Sensory innervation of the suprarenal gland in the albino rat: a fluorescent tract tracer study.

    PubMed

    Sangari, S K; Khatri, K; Sengupta, P

    1998-01-01

    The afferent innervation of the suprarenal gland was studied by using a fluorescent tract tracer in the adult albino rat. The left suprarenal gland was injected slowly with 5 microl of 2% aqueous suspension of Fast blue. After a survival period of 4-5 days, the dorsal root ganglia were dissected out and 15-microm-thick plastic (JB 4) sections were examined under the fluorescent microscope. The labelled neurons were seen from the third thoracic to second lumbar dorsal root ganglia, ipsilateral to the site of injection with maximum concentration from T6 to T11. These primary sensory neurons were round to oval in shape, varied from 7 microm to 40 microm in size, and were distributed randomly in the dorsal root ganglia. The labelling of the primary sensory neurons in the dorsal root ganglia confirms the presence of sensory nerve endings in the suprarenal gland that may be responsible for the vascular distension and hormonal release. PMID:9445094

  14. Estimation algorithms for dynamic tracer studies using positron-emission tomography.

    PubMed

    Ollinger, J M

    1987-01-01

    Algorithms are developed for estimating statistics for use by parameter estimation algorithms in dynamic tracer studies utilizing positron-emission tomography and requiring high temporal resolution. Two types of statistics are considered. One can be used with the expectation-maximization algorithm to compute maximum likelihood parameter estimates, and the other computes a histogram of activity levels versus time for use with weighted least squares parameter estimation algorithms. An estimator of the variance of this histogram is also given. Variants for use with both time-of-flight and projection data collected at high frame rates are presented. The algorithms account for the effects of attenuation, randoms, detector efficiency, and nonuniform sampling. PMID:18230437

  15. Novel method for analyzing transient response data obtained in isotopic tracer studies of CO hydrogenation

    SciTech Connect

    De Pontes, M.; Yokomizo, G.H.; Bell, A.T.

    1987-03-01

    A method is described for analyzing transient response data obtained in isotopic tracer studies of CO hydrogenation. Methane is assumed to be produced by the independent hydrogenation of various pools of carbon present on the catalyst surface, but no assumptions are made about the number of such pools nor the homogeneity of their reactivity. Application of the method to data for Ru and Ni catalysts reveals bimodal spectra of first-order rate coefficients. The peaks in these spectra are assigned to specific forms of adsorbed carbon. It is also shown that the ability to resolve different carbon forms and the heterogeneity in the reactivity of these forms is closely linked to the noise in the experimentally observed transients. 24 references.

  16. Double retrograde tracer study of the thalamostriatal projections to the cat caudate nucleus.

    PubMed

    de las Heras, S; Mengual, E; Giménez-Amaya, J M

    1999-05-01

    The distribution of thalamostriatal neurons projecting to the cat caudate nucleus was examined by retrograde fluorescent tracers. Thus, Fast Blue and Diamidino Yellow were concomitantly injected in different rostrocaudal, dorsoventral, or mediolateral sectors of the caudate nucleus. The main findings of this study are as follows: (1) few double-labeled cells were found after two injections in different sectors of the caudate nucleus; (2) double-labeled neurons were more abundant after adjacent injections and they were mainly located in the caudal intralaminar nuclei, in the rhomboid nucleus and in the dorsal mediodorsal nucleus; and (3) there were variations in the spatial organization of the thalamostriatal neurons projecting to various sectors of the caudate nucleus in the different thalamic nuclei known to project to this part of the striatum. PMID:10231128

  17. The use of stable tracers to study intestinal calcium absorption. The Italian Society of Osteoporosis.

    PubMed

    1995-09-01

    This paper represents the final document released by the Italian Society of Osteoporosis (S.I.OP.), on the occasion of its fifth annual meeting held in Padova, Italy (November 30-December 3, 1993). The S.I.OP. has in fact planned to periodically organize a conference on still-debated, controversial issues. After an exhaustive discussion of the various aspects of the problem by qualified experts in the field, a solution will be proposed by the members of the Society. The problems related to the use of radioactive tracers to study intestinal calcium absorption and the possible ways to over-come them were the issues discussed last year, by four panelists (R. P. Heaney, C. Gennari, G. Mioni, and S. Minisola) coordinated by G. F. Mazzuoli. PMID:8541147

  18. Experimental and numerical study of heavy gas dispersion in a ventilated room.

    PubMed

    Ricciardi, Laurent; Prévost, Corinne; Bouilloux, Laurent; Sestier-Carlin, Roger

    2008-04-01

    In order to better evaluate the consequences of an accidental release of heavy gas, such as uranium hexafluoride (UF(6)), in some installations in the nuclear fuel cycle, an experimental and numerical study was conducted by IRSN on heavy gas dispersion in a ventilated room. This study was based on about 20 injection configurations of a large quantity of a heavy tracer gas, sulphur hexafluoride (SF(6)), inside two ventilated rooms of different sizes. Stratification of the tracer gas was detected in all the configurations studied, even at low concentrations. Numerical simulations performed with the multidimensional CFX code enabled the stratification and the concentration levels reached in the rooms to be predicted overall, and the higher the air flow rate, the more satisfactory the comparison between simulation and experiment. PMID:17804157

  19. An experimental tracer study of the role of macropores in infiltration in grassland soils

    NASA Astrophysics Data System (ADS)

    Weiler, Markus; Naef, Felix

    2003-02-01

    Water flow in macropores is an important mechanism of infiltration in natural soils and, as such, is crucial for the prediction of runoff generation. The major flow processes controlling macropore flow are the initiation of macropore flow (water supply into macropores) and the water transfer from the macropores into the surrounding soil matrix (interaction). The water movement during infiltration and the resulting flow paths were studied with combined sprinkling and dye tracer experiments under different rainfall intensities and initial soil moisture conditions. The dye tracer was continuously applied with the sprinkling water on 1 m2 plots. After the sprinkling, horizontal and vertical soil sections were prepared for surveying dye patterns, which showed the cumulated flow pathways in the soils. These experiments were carried out on four hillslope sites covered with grassland, where earthworms mainly built the macropore system. The evaluation of the flow processes in the soil was based on classified dye patterns and measurements of water content and matric potential. The results illustrate how flow in earthworm channels influences general hydrological flow processes during extreme rainfall events. Macropore flow was initiated from the soil surface or from a saturated or partially saturated soil layer. Transfer of water from the macropores into the soil matrix was mainly influenced by the soil properties and soil water content. The permeability of the underlying bedrock in combination with this transfer of water controlled the drainage of the macropores. Finally, major effects of macropore flow processes on the hydrological response were extracted. Infiltration excess overland flow was reduced if water bypassed the less permeable layer through macropores, saturation excess overland flow was less affected by macropores, and subsurface flow was activated very rapidly because the infiltrated water bypassed the soil matrix. This study highlights the most important processes that have to be considered in order to understand better and to model infiltration in natural soils in the future.

  20. Quantifying the contribution of grape hexoses to wine volatiles by high-precision [U¹³C]-glucose tracer studies.

    PubMed

    Nisbet, Mark A; Tobias, Herbert J; Brenna, J Thomas; Sacks, Gavin L; Mansfield, Anna Katharine

    2014-07-16

    Many fermentation volatiles important to wine aroma potentially arise from yeast metabolism of hexose sugars, but assessing the relative importance of these pathways is challenging due to high endogenous hexose substrate concentrations. To overcome this problem, gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) was used to measure high-precision (13)C/(12)C isotope ratios of volatiles in wines produced from juices spiked with tracer levels (0.01-1 APE) of uniformly labeled [U-(13)C]-glucose. The contribution of hexose to individual volatiles was determined from the degree of (13)C enrichment. As expected, straight-chain fatty acids and their corresponding ethyl esters were derived almost exclusively from hexoses. Most fusel alcohols and their acetate esters were also majority hexose-derived, indicating the importance of anabolic pathways for their formation. Only two compounds were not derived primarily from hexoses (hexanol and isobutyric acid). This approach can be extended to other food systems or substrates for studying precursor-product relationships. PMID:24960193

  1. The feasibility of ethyl iodide as an atmospheric tracer 

    E-print Network

    Everett, Joe Vincent

    1976-01-01

    tracer by Argonne National Lab (Sc57, Co65). The gas was released from a cylinder and collected using evacuated flasks. A modified version of a commercial halogen leak detector or gas-chromagraph was used to analyze the Freon. Concentrations of 0. 1... studies around nuclear power plants are concerned with the movement of the radioactive gases, why not use the particular gas as a tracer. Some- times this will not work due to the problems of collection; however, in the case of ' I this method works...

  2. Predictive value of tracer studies for /sup 131/I treatment in hyperthyroid cats

    SciTech Connect

    Broome, M.R.; Turrel, J.M.; Hays, M.T.

    1988-02-01

    In 76 cats with hyperthyroidism, peak thyroidal radioiodine (/sup 131/I) uptakes and effective half-lives were determined after administration of tracer and therapeutic activities of /sup 131/I. In 6 additional hyperthyroid cats, only peak thyroidal uptakes after administration of tracer and therapeutic activities of /sup 131/I were determined. Good correlation was found between peak thyroidal uptakes of tracer and therapeutic /sup 131/I; however, only fair correlation was observed between effective half-lives. In 79% of the cats, the effective half-life for therapeutic /sup 131/I was longer than that for tracer /sup 131/I. After administration of therapeutic activity of /sup 131/I, monoexponential and biphasic decay curves were observed in 51 and 16 cats, respectively. Using therapeutic kinetic data, radiation doses to the thyroid gland were calculated retrospectively on the basis of 2 methods for determining the activity of /sup 131/I administered: (1) actual administration of tracer-compensated activity and (2) hypothetic administration of uniform activity (3 mCi). Because of the good predictive ability of tracer kinetic data for the therapeutic kinetic data, the tracer-compensated radiation doses came significantly (P = 0.008) closer to the therapeutic goal than did the uniform-activity doses. In addition, the use of tracer kinetic information reduced the extent of the tendency for consistently high uniform-activity doses. A manual method for acquiring tracer kinetic data was developed and was an acceptable alternative to computerized techniques. Adoption of this method gives individuals and institutions with limited finances the opportunity to characterize the iodine kinetics in cats before proceeding with administration of therapeutic activities of /sup 131/I.

  3. The Experience of Receiving and Then Losing a Scholarship: A Tracer Study of Secondary School Scholarship Recipients in Uganda

    ERIC Educational Resources Information Center

    Watson, Cathy; Chapman, David W.; Okurut, Charles Opolot

    2014-01-01

    This study reports findings of a tracer that investigated differences in the profile and subsequent experiences of scholarship recipients in Uganda who were able to complete the lower secondary school cycle (O level) without interruption (N = 174) and those that dropped out before completing their O-level cycle (N = 51), thereby losing their…

  4. AIRBORNE LIDAR MONITORING OF FLUORESCENT DYE PARTICLES AS A TRACER TO CHARACTERIZE TRANSPORT AND DISPERSION: A FEASIBILITY STUDY

    EPA Science Inventory

    The feasibility of using airborne lidar to observe the three-dimensional distribution of fluorescent dye particle (FDP) tracers in long-range atmospheric transport and dispersion studies has been successfully demonstrated in field experiments conducted in the North East U.S. duri...

  5. Boron and lithium isotopes as groundwater tracers: a study at the Fresh Kills Landfill, Staten Island, New York, USA

    Microsoft Academic Search

    James F Hogan; Joel D Blum

    2003-01-01

    A study was conducted at the Fresh Kills landfill, Staten Island, New York to investigate the use of B and Li isotopes as tracers of mixing and flow in the groundwater environment. Four end-member waters are present at the Fresh Kills: freshwater, seawater, a geochemically distinct transitional groundwater (that occurs in the zone of mixing between seawater and freshwater) and

  6. Human biokinetic data and a new compartmental model of zirconium — A tracer study with enriched stable isotopes

    Microsoft Academic Search

    Matthias B. Greiter; Augusto Giussani; Vera Höllriegl; Wei Bo Li; Uwe Oeh

    2011-01-01

    Biokinetic models describing the uptake, distribution and excretion of trace elements are an essential tool in nutrition, toxicology, or internal dosimetry of radionuclides. Zirconium, especially its radioisotope 95Zr, is relevant to radiation protection due to its production in uranium fission and neutron activation of nuclear fuel cladding material. We present a comprehensive set of human data from a tracer study

  7. A Study on Physiological Parameter Estimation Accuracy for Tracer Kinetic Modeling with Posttron Emission Tomography (PET)

    Microsoft Academic Search

    Xinmin Wang; Dagan Feng

    1992-01-01

    Tracer kinetic modeling with Positron Emission Tomography requires measurements of the time-activity curves in both plasma (PTAC) and tissue to estimate physiological parameters. Ideally, this PTAC should be the tracer local capillary plasma time-activity curve (CPTAC). However, due to the inaccessibility of direct measurement of CPTAC, the arterial plasma time-activity curve (APTAC) is usually used to replace CPTAC. The range

  8. A comparison of selected organic tracers for quantitative scalar imaging in the gas phase via laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Faust, Stephan; Goschütz, Martin; Kaiser, Sebastian A.; Dreier, Thomas; Schulz, Christof

    2014-10-01

    This paper compares three of the tracers most commonly used for laser-induced fluorescence in gaseous flows, toluene, naphthalene, and acetone. Additionally, anisole (methoxybenzene, CH3OC6H5) is included in the comparison. Each tracer is employed to image the scalar field in the same nonreacting transient impinging turbulent jet. The jet fluid is seeded with tracer vapor in a bubbler, excitation is at 266 nm, and both air and nitrogen are used as bath gases. Measured signals are compared to theoretical predictions based on fluorescence quantum yield, absorption cross-section, and vapor pressure. We find that anisole shows the highest total signal intensity of all investigated species, while naphthalene features the highest signal per molecule. Acetone has the advantage of being insensitive to quenching by oxygen and that its fluorescence is partly at visible wavelengths. In addition to this volatility-limited scenario at room temperature, we also compare the expected relative signals for elevated temperatures and for a hypothetical case in which the amount of admissible tracer seeding is limited.

  9. Zinc isotope ratio imaging of rat brain thin sections from stable isotope tracer studies by LA-MC-ICP-MS.

    PubMed

    Urgast, Dagmar S; Hill, Sarah; Kwun, In-Sook; Beattie, John H; Goenaga-Infante, Heidi; Feldmann, Jörg

    2012-10-01

    Zinc stable isotope tracers (??Zn and ??Zn) were injected into rats at two different time points to investigate the feasibility of using tracers to study zinc kinetics at the microscale within distinct tissue features. Laser ablation coupled to multi-collector ICP-MS was used to analyse average isotope ratios in liver thin sections and to generate bio-images showing zinc isotope ratio distribution in brain thin sections. Average isotope ratios of all samples from treated animals were found to be statistically different (P < 0.05) from samples from untreated control animals. Furthermore, differing isotope ratios in physiological features of the brain, namely hippocampus, amygdala, cortex and hypothalamus, were identified. This indicates that these regions differ in their zinc metabolism kinetics. While cortex and hypothalamus contain more tracer two days after injection than 14 days after injection, the opposite is true for hippocampus and amygdala. This study showed that stable isotope tracer experiments can be combined with laser ablation MC-ICP-MS to measure trace element kinetics in tissues at a microscale level. PMID:22907676

  10. Myelinated nerve fibres and the fate of lanthanum tracer: an in vivo study.

    PubMed

    Mackenzie, M L; Shorer, Z; Ghabriel, M N; Allt, G

    1984-01-01

    The permeability of the marginal tight junctional system of myelin was tested in the rat employing the electron-dense tracer lanthanum nitrate. Lanthanum was either included in the fixative used for vascular perfusion (at a concentration of 20 mM) or was microinjected in vivo into the sural or tibial nerve (5, 10 and 20 mM). After 5-60 minutes, the microinjected nerves were fixed either by immersion or vascular perfusion. Lanthanum tracer was present in the intraperiod line gap of myelin, irrespective of the mode of application of the tracer, the method of fixation or the time of exposure to lanthanum. However, the tracer was present more extensively when included in the fixative compared with in vivo microinjection. Internodally, lanthanum was usually restricted to the inner, or more commonly, the outer lamellae of larger fibres, while all lamellae were usually penetrated by tracer in smaller fibres. Paranodally, compact myelin was more extensively penetrated. The periaxonal space (between axon and Schwann cell) was readily accessible to tracer. It is concluded that the marginal tight junctional system of myelin is apparently of the 'leaky' type and is permeable to ions. The findings have implications for the electrophysiology and pathophysiology of the myelinated nerve fibre. PMID:6368509

  11. Innovative techniques for the description of reservoir heterogeneity using tracers. Second technical annual progress report, October 1991--September 1992

    SciTech Connect

    Pope, G.A.; Sepehrnoori, K.

    1992-12-31

    This second annual report on innovative uses of tracers for reservoir characterization contains four sections each describing a novel use of oilfield tracers. The first section describes and illustrates the use of a new single-well tracer test to estimate wettability. This test consists of the injection of brine containing tracers followed by oil containing tracers, a shut-in period to allow some of the tracers to react, and then production of the tracers. The inclusion of the oil injection slug with tracers is unique to this test, and this is what makes the test work. We adapted our chemical simulator, UTCHEM, to enable us to study this tracer method and made an extensive simulation study to evaluate the effects of wettability based upon characteristic curves for relative permeability and capillary pressure for differing wetting states typical of oil reservoirs. The second section of this report describes a new method for analyzing interwell tracer data based upon a type-curve approach. Theoretical frequency response functions were used to build type curves of ``transfer function`` and ``phase spectrum`` that have dimensionless heterogeneity index as a parameter to characterize a stochastic permeability field. We illustrate this method by analyzing field tracer data. The third section of this report describes a new theory for interpreting interwell tracer data in terms of channeling and dispersive behavior for reservoirs. Once again, a stochastic approach to reservoir description is taken. The fourth section of this report describes our simulation of perfluorocarbon gas tracers. This new tracer technology developed at Brookhaven National Laboratory is being tested at the Elk Hills Naval Petroleum Reserve No. 1 in California. We report preliminary simulations made of these tracers in one of the oil reservoirs under evaluation with these tracers in this field. Our compostional simulator (UTCOMP) was used for this simulation study.

  12. Diatoms as a tracer of hydrological connectivity: the Oak Creek case study (Oregon, USA)

    NASA Astrophysics Data System (ADS)

    Antonelli, Marta; Martínez-Carreras, Nuria; Frentress, Jay; Pfister, Laurent

    2015-04-01

    The vast heterogeneity and complexity of rainfall-runoff transformation processes expresses itself in a multitude of water sources and flowpaths - ultimately resulting in the well-known intricacy of hydrological connectivity. Pioneering work of Pfister et al. (2009) conducted in the Weierbach catchment (0.45 km2, NW Luxembourg, semi-oceanic climate) demonstrated the potential for diatoms (unicellular, eukaryotic algae) to be used as a tracer of hydrological connectivity. Diatoms originating from terrestrial habitats had been shown to be systematically flushed from the riparian areas into the stream during storm events. Here, we present a study conducted in the Oak Creek(0.17 km2, Oregon, Mediterranean climate), characterised by a large riparian area. Our first working hypothesis (H1) stipulates that diatoms are an ubiquitous tracer of fast hydrological flowpaths. The second hypothesis (H2) states that the riparian area is the major reservoir of terrestrial diatoms that contributes to the flushing process during rainfall events. A winter rainfall-runoff event was monitored in March 2012. Diatom samples were collected from soil, moss, epipelon and streamwater in order to characterise the communities along the hillslope-riparian-stream (HRS) continuum. Diatoms in each sample were also assigned to different wetness categories (according to Van Dam et al., 1994). The catchment was instrumented with an ISCO automatic streamwater sampler and the samples were analysed for conductivity, 18O, 2H, chemical elements and presence/abundance of diatoms belonging to different wetness categories. Our results show that the percentage of diatom species originating from habitats located outside of the stream evolves along the rising and falling limbs of the hydrograph. This observation confirms the event-related flushing of diatoms from terrestrial habitats to the stream and, consequently, the potential for diatoms to be used for the detection of hydrological connectivity in the hillslope-riparian-stream continuum (H1). Moreover, almost no strictly terrestrial diatoms were found in the stream during the event, indicating the majority of the diatoms (identified as aerophytic) being exported from the riparian area (H2).

  13. Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

    USGS Publications Warehouse

    Templer, P.H.; Mack, M.C.; Chapin, F. S., III; Christenson, L.M.; Compton, J.E.; Crook, H.D.; Currie, W.S.; Curtis, C.J.; Dail, D.B.; D'Antonio, C. M.; Emmett, B.A.; Epstein, H.E.; Goodale, C.L.; Gundersen, P.; Hobbie, S.E.; Holland, K.; Hooper, D.U.; Hungate, B.A.; Lamontagne, S.; Nadelhoffer, K.J.; Osenberg, C.W.; Perakis, S.S.; Schleppi, P.; Schimel, J.; Schmidt, I.K.; Sommerkorn, M.; Spoelstra, J.; Tietema, A.; Wessel, W.W.; Zak, D.R.

    2012-01-01

    Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3–18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C: N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N·ha-1·yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

  14. A CFD study of gas-solid jet in a CFB riser flow

    SciTech Connect

    Li, Tingwen; Guenther, Chris

    2012-03-01

    Three-dimensional high-resolution numerical simulations of a gas–solid jet in a high-density riser flow were conducted. The impact of gas–solid injection on the riser flow hydrodynamics was investigated with respect to voidage, tracer mass fractions, and solids velocity distribution. The behaviors of a gas–solid jet in the riser crossflow were studied through the unsteady numerical simulations. Substantial separation of the jetting gas and solids in the riser crossflow was observed. Mixing of the injected gas and solids with the riser flow was investigated and backmixing of gas and solids was evaluated. In the current numerical study, both the overall hydrodynamics of riser flow and the characteristics of gas–solid jet were reasonably predicted compared with the experimental measurements made at NETL.

  15. An Analytical Solution for Slug-Tracer Tests in FracturedReservoirs

    SciTech Connect

    Shan, Chao; Pruess, Karsten

    2005-03-02

    The transport of chemicals or heat in fractured reservoirs is strongly affected by the fracture-matrix interfacial area. In a vapor-dominated geothermal reservoir, this area can be estimated by inert gas tracer tests, where gas diffusion between the fracture and matrix causes the tracer breakthrough curve (BTC) to have a long tail determined by the interfacial area. For water-saturated conditions, recent studies suggest that sorbing solute tracers can also generate strong tails in BTCs that may allow a determination of the fracture-matrix interfacial area. To theoretically explore such a useful phenomenon, this paper develops an analytical solution for BTCs in slug-tracer tests in a water-saturated fractured reservoir. The solution shows that increased sorption should have the same effect on BTCs as an increase of the diffusion coefficient. The solution is useful for understanding transport mechanisms, verifying numerical codes, and for identifying appropriate chemicals as tracers for the characterization of fractured reservoirs.

  16. SEDIMENT REWORKING AND TRANSPORT IN EASTERN LAKE SUPERIOR: IN SITU RARE EARTH ELEMENT TRACER STUDIES

    EPA Science Inventory

    A rare earth element (REE) tracer pellet was deployed at the floor of the Ile Parisienne basin of eastern Lake Superior to measure representative sediment reworking and transport processes in the benthic boundary layer of the prnfundal Great Lakes. Samarium oxide, a high neutron-...

  17. Observation and modeling of catchment-scale solute transport in the hydrologic response: A tracer study

    Microsoft Academic Search

    G. Botter; F. Peratoner; M. Putti; A. Zuliani; R. Zonta; A. Rinaldo; M. Marani

    2008-01-01

    The coherent description of water flow and solute transport within heterogeneous hydrologic media (e.g., hillslopes or entire catchments) in response to external rainfall forcings represents a challenge in hydrological modeling. In this paper the mechanisms determining the mobilization and transport of solutes in soils through the paths of runoff formation are investigated by means of a tracer experiment conducted within

  18. 40K-40Ca systematics as a Tracer of Silicate Weathering: A Himalayan case study

    NASA Astrophysics Data System (ADS)

    Davenport, Jesse; Caro, Guillaume; France-Lanord, Christian

    2015-04-01

    This study investigates the use of the 40K-40Ca system as a tracer to better quantify the contributions of silicate and carbonate lithologies in the dissolved load of major Himalayan rivers. Previous work using Sr isotopes as a proxy for silicate weathering has been complicated by the redistribution of radiogenic 87Sr between silicate and carbonate lithologies, particularly in the Lesser Himalaya, where dolomites exhibit 87Sr/86Sr ratios as high as 0.85. The 40Ca signature of carbonates, on the other hand, appears to be remarkably resistant to metamorphism and dolomitization [1]. It was therefore anticipated that the 40K-40Ca system could circumvent issues associated with such secondary events, and yield more robust constraints on the relative contribution of silicate vs. carbonate lithologies in dissolved river loads. The main difficulty in applying the 40K-40Ca decay scheme as a tracer lies in the analytical precision required to measure small variations (~1 É?-unit) on the large 40Ca isotope (96.9%). This difficulty can now be overcome using the Finnigan Triton TIMS, which allows measurements of the 40Ca/44Ca ratio with external precision of 0.35 É?-unit in multidynamic mode. Using this method, we generated high-precision 40Ca data on carbonates/dolomites, bedload sediments, dissolved load, and clay samples originating from and representing the main litho-tectonic units of the Himalaya. Our results show that metamorphosed dolomites from the Lesser Himalaya (LH) exhibit no radiogenic 40Ca excess despite highly variable 87Sr/86Sr signatures (0.73-0.85). Thus, all Himalayan carbonates appear to be characterized by a homogeneous É?40Ca=0. In contrast, silicate material is radiogenic, with É?40Ca averaging +1 in the Tethyan Sedimentary Series (TSS), +1.6 in the High Himalaya crystalline (HHC) and +4 É?-units in the LH. Results obtained from a series of 35 Himalayan rivers (including the Brahmaputra, Ganga and its main tributaries) show that É?40Ca in the dissolved load is significantly influenced by silicate weathering, with É?40Ca ranging from +0.1 in rivers draining carbonate dominated catchments to +1.6 É?-units in rivers draining predominantly gneissic catchments of the High Himalaya. No simple relation exists between 87Sr and 40Ca systematics, which likely reflects the decoupling of Rb-Sr and K-Ca systems in LH dolomites. In contrast, 40Ca signatures correlate well with proxies of carbonate weathering such as Ca/Na or Mg/Na ratios. Overall, our results indicate that the 40Ca signature of Himalayan rivers primarily reflects the lithological nature of their erosional source, and highlight the significant contribution of HHC gneisses to the dissolved calcium budget of the Ganga and Brahmaputra. [1] Caro et al. (2010) EPSL 296, 124-132

  19. Exploring Hydrofluorocarbons as Groundwater Age Tracers (Invited)

    NASA Astrophysics Data System (ADS)

    Haase, K. B.; Busenberg, E.; Plummer, L. N.; Casile, G.; Sanford, W. E.

    2013-12-01

    Groundwater dating tracers are an essential tool for analyzing hydrologic conditions in groundwater systems. Commonly used tracers for dating post-1940's groundwater include sulfur hexafluoride (SF6), chlorofluorocarbons (CFCs), 3H-3He, and other isotopic tracers (85Kr, ?2H and ?18O isotopes, etc.). Each tracer carries a corresponding set of advantages and limitations imposed by field, analytical, and interpretive methods. Increasing the number available tracers is appealing, particularly if they possess inert chemical properties and unique temporal emission histories from other tracers. Atmospherically derived halogenated trace gases continue to hold untapped potential for new tracers, as they are generally inert and their emission histories are well documented. SF5CF3, and CFC-13 were previously shown to have application as dating tracers, though their low mixing ratios and low solubility require large amounts of water to be degassed for their quantification. Two related groups of compounds, hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are hypothesized to be potential age tracers, having similar mixing ratios to the CFCs and relatively high solubility. However, these compounds yield gas chromatography electron capture detector (GC-ECD) responses that are 10-2 -10-5 less than CFC-12, making purge and trap or field stripping GC-ECD approaches impractical. Therefore, in order to use dissolved HCFCs and HFCs as age tracers, different approaches are needed. To solve this problem, we developed an analytical method that uses an atomic emission detector (GC-AED) in place of an ECD to detect fluorinated compounds. In contrast to the ECD, the AED is a universally sensitive, highly linear, elementally specific detector. The new GC-AED system is being used to measure chlorodifluoromethane (HCFC-22), 1,1,1,2-tetrafluoroethane (HFC-134a), and other fluorinated compounds in one liter water samples to study their potential as age dating tracers. HCFC-22 is a refrigerant introduced in the 1940's, with atmospheric mixing ratios increasing through the 1990s to the present value of ?230 pptv. HFC-134a is typically is used as a chlorine-free replacement for CFC-12, finding use in air-condition systems and as an inert aerosol blowing agent, with a mixing ratio that has increased from <1 in 1994 to ?75 pptv at present (2013). Their unique atmospheric histories and chemistry compared to CFCs makes these compounds interesting age tracer candidates, particularly in situations where multiple tracers enhance interpretive value. For instance, inclusion in lumped parameter mixing models and in situations where SF6 or the CFCs are present in elevated concentrations from non-atmospheric sources such that they cannot be used for dating purposes. Analysis of standards, air equilibrated water, and blanks suggests the GC-AED system is capable of detecting concentrations ?200 fM (HCFC-22) and ?100 fM (HFC-134a), corresponding to piston flow ages of 54 and 18 yr, respectively, with a typical uncertainty of ?1 yr. Preliminary comparisons with CFC and SF6 analyses show general agreement between the techniques (within a few years), and ongoing intercomparison studies will be discussed.

  20. Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2HH2O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

    USGS Publications Warehouse

    Révész, Kinga M.; Lollar, Barbara Sherwood; Kirshtein, Julie D.; Tiedeman, Claire R.; Imbrigiotta, Thomas E.; Goode, Daniel J.; Shapiro, Allen M.; Voytek, Mary A.; Lancombe, Pierre J.; Busenberg, Eurybiades

    2014-01-01

    An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in 2H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the ?13C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the ?2H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H2 gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE + VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average 13C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the BA was intensive only in wells where an amendment was distributed during injection, it is necessary to adequately distribute the amendments throughout the fractured rock to achieve substantial bioremediation. The slowdown in BA effect after a year is due to some extend to the decrease abundant of appropriate microbes, but more likely the decreased concentration of electron donor.

  1. Tracer and hydrometric study of preferential flow in large undisturbed soil cores from the Georgia Piedmont, USA

    USGS Publications Warehouse

    McIntosh, Janice; McDonnell, Jeffrey J.; Peters, Norman E.

    1999-01-01

    We studied the temporal patterns of tracer throughput in the outflow of large (30 cm diameter by 38 cm long) undisturbed cores from the Panola Mountain Research Watershed, Georgia. Tracer breakthrough was affected by soil structure and rainfall intensity. Two rainfall intensities (20 and 40 mm hr-1) for separate Cl- and Br- amended solutions were applied to two cores (one extracted from a hillslope soil and one extracted from a residual clay soil on the ridge). For both low and high rainfall intensity experiments, preferential flow occurred in the clay core, but not in the hillslope core. The preferential flow is attributed to well-developed interpedal macrochannels that are commonly found in structured clay soils, characteristic of the ridge site. However, each rainfall intensity exceeded the matrix infiltration capacity at the top of the hillslope core, but did not exceed the matrix infiltration capacity at the middle and bottom of the hillslope core and at all levels in the clay core. Localized zones of saturation created when rainfall intensity exceeds the matrix infiltration capacity may cause water and tracer to overflow from the matrix into macrochannels, where preferential flow occurs to depth in otherwise unsaturated soil. Copyright © 1999 John Wiley & Sons, Ltd.

  2. Isotopic tracer techniques for studying the bioavailability and bioefficacy of dietary carotenoids, particularly beta-carotene, in humans: a review.

    PubMed

    van Lieshout, Machteld; West, Clive E; van Breemen, Richard B

    2003-01-01

    Vitamin A deficiency is a serious health problem in many developing countries. Provitamin A carotenoids in fruit and vegetables are the major source of vitamin A for a large proportion of the world's population. However, the contribution of plant foods is substantial only when both the consumption and provitamin A content of such food is high and, at the same time, the bioefficacy of the provitamin A is high. With respect to provitamin A carotenoids, the term bioefficacy is defined as the product of the fraction of the ingested amount that is absorbed (bioavailability) and the fraction of that which is converted to retinol in the body (bioconversion). Isotopic tracer techniques can meet the need for accurate and precise estimates of the bioavailability, bioconversion, and bioefficacy of dietary carotenoids in humans. Use of such techniques will enable proper evaluation of food-based approaches to eliminating vitamin A deficiency. In addition, the putative antioxidant capacities of carotenoids can be better understood if their bioavailability is known. Here, we discuss how tracer techniques can be applied to obtain reliable and representative data. A step-by-step discussion of aspects related to these techniques is provided, including study design, choice of isotopic tracers, dosing regimen, collection of samples, chemical analysis of samples, and data analysis. PMID:12499318

  3. 3, 24372471, 2006 Chalk tracer test

    E-print Network

    Paris-Sud XI, Université de

    HESSD 3, 2437­2471, 2006 Chalk tracer test study S. A. Mathias et al. Title Page Abstract study of two chalk tracer tests S. A. Mathias1 , A. P. Butler1 , T. C. Atkinson 2,3 , S. Kachi3 (simon.mathias@imperial.ac.uk) 2437 #12;HESSD 3, 2437­2471, 2006 Chalk tracer test study S. A. Mathias et

  4. Warm gas TVC design study

    NASA Technical Reports Server (NTRS)

    Moorhead, S. B., Jr.

    1973-01-01

    A warm gas thrust vector control system was studied to optimize the injection geometry for a specific engine configuration, and an injection valve was designed capable of meeting the base line requirements. To optimize injection geometry, studies were made to determine the performance effects of varying injection location, angle, port size, and port configuration. Having minimized the injection flow rate required, a warm gas valve was designed to handle the required flow. A direct drive hydraulic servovalve capable of operating with highly contaminated hydraulic fluid was designed. The valve is sized to flow 15 gpm at 3000 psia and the direct drive feature is capable of applying a spool force of 200 pounds. The baseline requirements are the development of 6 deg of thrust vector control utilizing 2000 F (total temperature) gas for 180 seconds on a 1.37 million pound thrust engine burning LOX and RP-1 at a chamber pressure of 250 psia with a 155 inch long conical nozzle having a 68 inch diameter throat and a 153 inch diameter exit.

  5. Development of a rapid and accurate method for determining partition coefficients of chemical tracers between oils and brines (for single well tracer tests). Final report

    SciTech Connect

    Carlisle, C.T.; Kapoor, S.

    1982-12-01

    The objective of this work was as follows: (a) To develop a rapid and accurate method for determining chemical tracer partition coefficients (K-Values). (b) To study how common reservoir parameters (brine salinity, temperature, crude oil characteristics, gas-to-oil ratio and chemical tracer concentration) effect chemical tracer partition coefficients. We have developed a high pressure (up to 5000 psig), high temperature (up to 220/sup 0/F) system for rapidly and accurately determining chemical tracer partition coefficients for an oil/brine system. Reservoir brine is circulated in a closed system of known volume. This system is comprised of an equilibrium cell in which a known volume of oil is held stationary and a brine circulating loop. Known aliquots of chemical tracer are added to the system and the concentration of the chemical tracer in the brine phase is analyzed via gas chromatograph. A tracer mass balance is used to determine the concentration of the chemical tracer in the oil phase and hence, the partition coefficient is determined. Ethyl acetate partition coefficients were studied over a wide range of ethyl acetate concentrations, reservoir temperatures and brine salinities for a highly naphthenic crude oil. Some experiments were also conducted to determine the effect of gas-to-oil ratio and crude oil type on the partition coefficients. In general, the ethyl acetate partition coefficients increased with an increase in temperature, ethyl acetate concentration and brine salinity while a slight decrease was observed for an increase in the gas-to-oil ratio. We have correlated the experimentally determined ethyl acetate partition coefficients with the ethyl acetate concentrate, temperature, brine salinity and the gas-to-oil ratio. This correlation can predict K-Values to within +- 10%. 5 figures, 3 tables.

  6. AIR INFILTRATION MEASUREMENTS USING TRACER GASES: A LITERATURE REVIEW

    EPA Science Inventory

    The report gives results of a literature review of air filtration measurements using tracer gases, including sulfur hexafluoride, hydrogen, carbon monoxide, carbon dioxide, nitrous oxide, and radioactive argon and krypton. Sulfur hexafluoride is the commonest tracer gas of choice...

  7. DENSE GAS TRACERS IN PERSEUS: RELATING THE N{sub 2}H{sup +}, NH{sub 3}, AND DUST CONTINUUM PROPERTIES OF PRE- AND PROTOSTELLAR CORES

    SciTech Connect

    Johnstone, Doug; Kirk, Helen [National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Rosolowsky, Erik [University of British Columbia Okanagan, Kelowna, BC V1V 1V7 (Canada); Tafalla, Mario, E-mail: doug.johnstone@nrc-cnrc.gc.c [Observatorio Astronomico Nacional (IGN), Alfonso XII 3, E-28014 Madrid (Spain)

    2010-03-10

    We investigate 35 prestellar cores and 36 protostellar cores in the Perseus molecular cloud. We find a very tight correlation between the physical parameters describing the N{sub 2}H{sup +} and NH{sub 3} gas. Both the velocity centroids and the line widths of N{sub 2}H{sup +} and NH{sub 3} correlate much better than either species correlates with CO, as expected if the nitrogen-bearing species are probing primarily the dense core gas where the CO has been depleted. We also find a tight correlation in the inferred abundance ratio between N{sub 2}H{sup +} and para-NH{sub 3} across all cores, with N(p-NH{sub 3})/N(N{sub 2}H{sup +}) = 22 +- 10. We find a mild correlation between NH{sub 3} (and N{sub 2}H{sup +}) column density and the (sub)millimeter dust continuum derived H{sub 2} column density for prestellar cores, N(p-NH{sub 3})/N(H{sub 2}) {approx}10{sup -8}, but do not find a fixed ratio for protostellar cores. The observations suggest that in the Perseus molecular cloud the formation and destruction mechanisms for the two nitrogen-bearing species are similar, regardless of the physical conditions in the dense core gas. While the equivalence of N{sub 2}H{sup +} and NH{sub 3} as powerful tracers of dense gas is validated, the lack of correspondence between these species and the (sub)millimeter dust continuum observations for protostellar cores is disconcerting and presently unexplained.

  8. Study of sediment movement in an irrigated maize-cotton system combining rainfall simulations, sediment tracers and soil erosion models

    NASA Astrophysics Data System (ADS)

    Guzmán, Gema; Laguna, Ana; Cañasveras, Juan Carlos; Boulal, Hakim; Barrón, Vidal; Gómez-Macpherson, Helena; Giráldez, Juan Vicente; Gómez, José Alfonso

    2015-05-01

    Although soil erosion is one of the main threats to agriculture sustainability in many areas of the world, its processes are difficult to measure and still need a better characterization. The use of iron oxides as sediment tracers, combined with erosion and mixing models opens up a pathway for improving the knowledge of the erosion and redistribution of soil, determining sediment sources and sinks. In this study, magnetite and a multivariate mixing model were used in rainfall simulations at the micro-plot scale to determine the source of the sediment at different stages of a furrow-ridge system both with (+T) and without (-T) wheel tracks. At a plot scale, magnetite, hematite and goethite combined with two soil erosion models based on the kinematic wave approach were used in a sprinkler irrigation test to study trends in sediment transport and tracer dynamics along furrow lengths under a wide range of scenarios. In the absence of any stubble cover, sediment contribution from the ridges was larger than the furrow bed one, almost 90%, while an opposite trend was observed with stubble, with a smaller contribution from the ridge (32%) than that of the bed, at the micro-plot trials. Furthermore, at a plot scale, the tracer concentration analysis showed an exponentially decreasing trend with the downstream distance both for sediment detachment along furrows and soil source contribution from tagged segments. The parameters of the distributed model KINEROS2 have been estimated using the PEST Model to obtain a more accurate evaluation. Afterwards, this model was used to simulate a broad range of common scenarios of topography and rainfall from commercial farms in southern Spain. Higher slopes had a significant influence on sediment yields while long furrow distances allowed a more efficient water use. For the control of runoff, and therefore soil loss, an equilibrium between irrigation design (intensity, duration, water pattern) and hydric needs of the crops should be defined in order to establish a sustainable management strategy.

  9. Performance evaluation of AERMOD, CALPUFF, and legacy air dispersion models using the Winter Validation Tracer Study dataset

    NASA Astrophysics Data System (ADS)

    Rood, Arthur S.

    2014-06-01

    The performance of the steady-state air dispersion models AERMOD and Industrial Source Complex 2 (ISC2), and Lagrangian puff models CALPUFF and RATCHET were evaluated using the Winter Validation Tracer Study dataset. The Winter Validation Tracer Study was performed in February 1991 at the former Rocky Flats Environmental Technology Site near Denver, Colorado. Twelve, 11-h tests were conducted where a conservative tracer was released and measured hourly at 140 samplers in concentric rings 8 km and 16 km from the release point. Performance objectives were unpaired maximum one- and nine-hour average concentration, location of plume maximum, plume impact area, arc-integrated concentration, unpaired nine-hour average concentration, and paired ensemble means. Performance objectives were aimed at addressing regulatory compliance, and dose reconstruction assessment questions. The objective of regulatory compliance is not to underestimate maximum concentrations whereas for dose reconstruction, the objective is an unbiased estimate of concentration in space and time. Performance measures included the fractional bias, normalized mean square error, geometric mean, geometric mean variance, correlation coefficient, and fraction of observations within a factor of two. The Lagrangian puff models tended to exhibit the smallest variance, highest correlation, and highest number of predictions within a factor of two compared to the steady-state models at both the 8-km and 16-km distance. Maximum one- and nine-hour average concentrations were less likely to be under-predicted by the steady-state models compared to the Lagrangian puff models. The characteristic of the steady-state models not to under-predict maximum concentrations make them well suited for regulatory compliance demonstration, whereas the Lagrangian puff models are better suited for dose reconstruction and long range transport.

  10. Sediment reworking and transport in eastern lake superior: In-situ rare-earth element tracer studies

    SciTech Connect

    Krezoski, J.R.

    1989-01-01

    Considerable attention has been focused on understanding modes and rates of post-depositional sediment reworking in the Great Lakes with the result that virtually all theoretical models describing particle dynamics or reconstructing the history of pollutant input in the lakes include surficial sediment reworking terms. A rare earth element (REE) tracer pellet was deployed at the floor of the Ile Parisienne basin of eastern Lake Superior to measure representative sediment reworking and transport processes in the benthic boundary layer of the profundal Great Lakes. Samarium oxide, a high neutron-capture cross-section REE, was added at a concentration 30,000 greater than found naturally in the lake sediments. After 23 days the study site was reoccupied and eleven submersible-taken punch cores were collected from within and around the labeled area. Verticle core sections were then examined by instrumental neutron activation analysis. These results demonstrate the utility of in-situ tracer studies at profundal depths and suggest that longer-term studies will permit accurate measurement of post-depositional redistribution processes at the sediment-water interface of freshwater and marine environments.

  11. Oxygen tracer diffusion in single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Cawley, James D.; Halloran, John W.; Cooper, Alfred R.

    1991-01-01

    Oxygen tracer diffusion coefficients are determined in single-crystal alumina samples with differing dopant levels using the gas-exchange technique. The diffusion direction is parallel to the c-axis and the ambient PO2 is 1 atm (100,000 Pa) for all experiments except a single run with a low PO2, approximately 10 to the -15th atm (10 to the -10th Pa) produced by a CO/CO2 mixture. The diffusion is insensitive to both impurities and ambient PO2. The insensitivities are discussed in terms of point-defect clustering. Prior tracer studies are compared and discussed.

  12. Fluorescent particle tracers for surface hydrology: development of a sensing station for field studies

    NASA Astrophysics Data System (ADS)

    Capocci, I.; Mocio, G.; Insogna, F.; Tauro, F.; Petroselli, A.; Rapiti, R.; Cipollari, G.; Grimaldi, S.; Porfiri, M.

    2012-04-01

    This work focuses on the development and testing of a sensing station for the detection and tracking of a new class of fluorescent particle tracers for surface hydrology. This tracing methodology is based on the release of microspheres that fluoresce at labeled wavelengths in natural streams. The particles are detected as they transit below a sensing station that comprises a light source and a digital camera. Video feed from the station is then processed to obtain direct flow measurements and stream reach travel times. This novel tracing technology is a low-cost measurement system that can be implemented on a variety of real-world settings, spanning from small scale streams to few centimeters rills in natural hillslopes. In particular, the use of insoluble buoyant particles limits the tracer dispersion from adhesion to natural substrates and thus minimizes the amount of tracing material for experimental measurements. Further, particle enhanced fluorescence allows for non-intrusively detecting the tracer without deploying probes and samplers in the water. The performance of the sensing station is assessed by conducting a large array of experiments under different flow and acquisition conditions. More specifically, experiments are performed for multiple flow velocities, camera acquisition frequencies, light sources, and distances of the sensing station from the flow surface. Particles are deployed in a custom built artificial water channel of adjustable slope to simulate varying flow conditions. A high definition bullet camera is used to detect particles that fluoresce either in green or red and two optical filters, corresponding to the emission wavelengths of the particles, are incorporated in the sensing station. In this implementation, green emission is elicited by using Ultra Violet lights, while white light drives the red emission. Experimental results confirm the versatility and the effectiveness of the proposed methodology. Both particle types are found to be easily detected in a wide range of flow conditions. This evidence favors the use of red particles whose controlled fluorescent emission does not require costly Ultra Violet lamps and is rather based on commonly available light sources. Therefore, at a limited cost, powerful white lights can be used in the system and allow for increased fields of view.

  13. The potential of silica encapsulated DNA magnetite microparticles (SiDNAMag) for multi-tracer studies in subsurface hydrology

    NASA Astrophysics Data System (ADS)

    Willem Foppen, Jan; Bogaard, Thom; van Osnabrugge, Bart; Puddu, Michela; Grass, Robert

    2015-04-01

    With tracer experiments, knowledge on solute transport, travel times, flow pathways, source areas, and linkages between infiltration and exfiltration zones in subsurface hydrological studies can be obtained. To overcome the well-known limitations of artificial tracers, we report here the development and application of an inexpensive method to produce large quantities of environmentally friendly 150-200 nm microparticles composed of a magnetite core to which small fragments of synthetic 80 nt ssDNA were adsorbed, which were then covered by a layer of inert silica (acronym: SiDNAMag). The main advantages of using DNA are the theoretically unlimited amount of different DNA tracers and the low DNA detection limit using the quantitative polymerase chain reaction (qPCR); the main advantage of the silica layer is to prevent DNA decay, while the magnetite core facilitates magnetic separation, recovery and up-concentration. In 10 cm columns of saturated quartz sand, we first injected NaCl, a conservative salt tracer, and measured the breakthrough. Then, we injected SiDNAMag suspended in water of known composition, harvested the SiDNAMag in column effluent samples, and measured the DNA concentration via qPCR after dissolving the SiDNAMag. The results indicated that the timing of the rising limb of the DNA breakthrough curve, the plateau phase and the falling limb were identical to the NaCl breakthrough curve. However, the relative maximum DNA concentration reached during the plateau phase was around 0.3, indicating that around 70% of the SiDNAMag mass was retained in the column. From these results we inferred that SiDNAMag was not retarded and therefore not subject to equilibrium sorption. Instead, first order irreversible kinetic attachment appeared to be the dominant retention mechanism. Based on our results, we speculate that, despite significant retention, due to the low DNA detection limit and the possibility of magnetic up-concentration, the use of SiDNAMag is a very promising technique to determine complex flow patterns, travel times, and flow pathways in many different subsurface hydrological applications.

  14. PET Radiopharmaceuticals for Imaging Integrin Expression: Tracers in Clinical Studies and Recent Developments

    PubMed Central

    Maschauer, Simone

    2014-01-01

    Noninvasive determination of integrin expression has become an interesting approach in nuclear medicine. Since the discovery of the first 18F-labeled cyclic RGD peptide as radiotracer for imaging integrin ?v?3 expression in vivo, there have been carried out enormous efforts to develop RGD peptides for PET imaging. Moreover, in recent years, additional integrins, including ?5?1 and ?v?6, came into the focus of pharmaceutical radiochemistry. This review will discuss the tracers already evaluated in clinical trials and summarize the preliminary outcome. It will also give an overview on recent developments to further optimize the first-generation compounds such as [18F]Galacto-RGD. This includes recently developed 18F-labeling strategies and also new approaches in 68Ga-complex chemistry. Furthermore, the approaches to develop radiopharmaceuticals targeting integrin ?5?1 and ?v?6 will be summarized and discussed. PMID:25013808

  15. Halon-1301, a new Groundwater Age Tracer

    NASA Astrophysics Data System (ADS)

    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 concentration of Halon-1301, which indicates absence of local anthropogenic or geologic sources (contamination), despite some samples showing CFC contamination. We found agreement of 71% of mean age estimates with ages inferred from tritium and SF6 within +/- 2 years, for samples where direct age comparison could be made. The remaining sites showed reduced concentrations of Halon-1301 along with reduced concentrations of CFCs. The reasons for this need to be further assessed, but are likely caused by sorption or degradation of Halon-1301. Further Halon-1301 studies are planned covering various hydrogeologic situations, land use practises, and redox conditions to evaluate the potential of Halon-1301 as groundwater tracer, and to elucidate the causes for reduced Halon-1301 concentrations. Acknowledgements Greater Wellington Regional Council, especially S. Tidswell, is thanked for support and organisation of the sampling of the groundwater wells. This study is part of a PhD supported by GNS Science as part of the Smart Aquifer Characterization program funded by the New Zealand Ministry for Science and Innovation (http://www.smart-project.info/). References Beyer, M., van der Raaij, R., Morgenstern, U., Jackson, B. (2014) Potential groundwater age tracer found: Halon-1301 (CF3Br), as previously identified as CFC-13 (CF3Cl), Water Resources Research. Busenberg, E. and Plummer, L.N. (2008) Dating groundwater with trifluoromethyl sulfurpentafluoride (SF5CF3), sulfurhexafluoride (SF6), CF3Cl (CFC-13) & CF2CL2 (CFC-12), Water Resources Research 44

  16. Dispersion of passive tracer in the atmospheric convective boundary layer with wind shears: a review of laboratory and numerical model studies

    Microsoft Academic Search

    E. Fedorovich

    2004-01-01

    Summary Paper reviews recent laboratory and numerical model studies of passive gaseous tracer dispersion in the atmospheric convective boundary layer (CBL) with surface and elevated wind shears. Atmospheric measurement data used for validation of these two model techniques are briefly discussed as well. A historical overview is given of laboratory studies of dispersion in the atmospheric CBL. Model studies of

  17. Investigation of helical flow by using tracer technique

    NASA Astrophysics Data System (ADS)

    Alt?nsoy, N.; Tu?rul, A. B.; Bayta?, F.; Baydo?an, N.; Karatepe, N.; Hac?yakupo?lu, S.; Büyük, B.

    2013-05-01

    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.

  18. Tracer studies and hydraulic behaviour of planted and un-planted vertical-flow constructed wetlands.

    PubMed

    Cota, R S; von Sperling, M; Penido, R C S

    2011-01-01

    The aim of this research was to assess the hydraulic behaviour of three intermittently-fed vertical flow wetland units operated in parallel, designed for the treatment of raw wastewater generated in the city of Belo Horizonte, Brazil. The system was designed to serve 100 PE (-1 m2/PE). The first filter was planted with cattail (Typha latifolia), the second with Tifton-85 (Cynodon spp.) and the third was maintained without plants (control unit). NaCl tracer tests were conducted to determine the residence time distribution. The tests were done with water when the system was unused (clean media) and also after an 11-month operation period with wastewater (used media), using two different dosing regimes (lower and higher frequency). Results showed a strong tendency towards the hydraulic completely mixed regime. A great dispersion in the units and the presence of short circuiting and dead zones were observed. The unsaturated condition in a large volume of the filter, even during the draining stage, was confirmed for the three units. The dosing regime, the resting period duration, the age of the filter and the presence of plants were found to influence the hydraulic processes in the units. PMID:22214051

  19. SEAPORT LIQUID NATURAL GAS STUDY

    SciTech Connect

    COOK,Z.

    1999-02-01

    The Seaport Liquid Natural Gas Study has attempted to evaluate the potential for using LNG in a variety of heavy-duty vehicle and equipment applications at the Ports of Los Angeles and Oakland. Specifically, this analysis has focused on the handling and transport of containerized cargo to, from and within these two facilities. In terms of containerized cargo throughput, Los Angeles and Oakland are the second and sixth busiest ports in the US, respectively, and together handle nearly 4.5 million TEUs per year. At present, the landside handling and transportation of containerized cargo is heavily dependent on diesel-powered, heavy-duty vehicles and equipment, the utilization of which contributes significantly to the overall emissions impact of port-related activities. Emissions from diesel units have been the subject of increasing scrutiny and regulatory action, particularly in California. In the past two years alone, particulate matter from diesel exhaust has been listed as a toxic air contaminant by CAM, and major lawsuits have been filed against several of California's largest supermarket chains, alleging violation of Proposition 65 statutes in connection with diesel emissions from their distribution facilities. CARE3 has also indicated that it may take further regulatory action relating to the TAC listing. In spite of these developments and the very large diesel emissions associated with port operations, there has been little AFV penetration in these applications. Nearly all port operators interviewed by CALSTART expressed an awareness of the issues surrounding diesel use; however, none appeared to be taking proactive steps to address them. Furthermore, while a less controversial issue than emissions, the dominance of diesel fuel use in heavy-duty vehicles contributes to a continued reliance on imported fuels. The increasing concern regarding diesel use, and the concurrent lack of alternative fuel use and vigorous emissions reduction activity at the Ports provide both the backdrop and the impetus for this study.

  20. VOXEL-LEVEL MAPPING OF TRACER KINETICS IN PET STUDIES: A STATISTICAL APPROACH EMPHASIZING TISSUE LIFE TABLES1

    PubMed Central

    O’Sullivan, Finbarr; Muzi, Mark; Mankoff, David A.; Eary, Janet F.; Spence, Alexander M.; Krohn, Kenneth A.

    2014-01-01

    Most radiotracers used in dynamic positron emission tomography (PET) scanning act in a linear time-invariant fashion so that the measured time-course data are a convolution between the time course of the tracer in the arterial supply and the local tissue impulse response, known as the tissue residue function. In statistical terms the residue is a life table for the transit time of injected radiotracer atoms. The residue provides a description of the tracer kinetic information measurable by a dynamic PET scan. Decomposition of the residue function allows separation of rapid vascular kinetics from slower blood-tissue exchanges and tissue retention. For voxel-level analysis, we propose that residues be modeled by mixtures of nonparametrically derived basis residues obtained by segmentation of the full data volume. Spatial and temporal aspects of diagnostics associated with voxel-level model fitting are emphasized. Illustrative examples, some involving cancer imaging studies, are presented. Data from cerebral PET scanning with 18F fluoro-deoxyglucose (FDG) and 15O water (H2O) in normal subjects is used to evaluate the approach. Cross-validation is used to make regional comparisons between residues estimated using adaptive mixture models with more conventional compartmental modeling techniques. Simulations studies are used to theoretically examine mean square error performance and to explore the benefit of voxel-level analysis when the primary interest is a statistical summary of regional kinetics. The work highlights the contribution that multivariate analysis tools and life-table concepts can make in the recovery of local metabolic information from dynamic PET studies, particularly ones in which the assumptions of compartmental-like models, with residues that are sums of exponentials, might not be certain. PMID:25392718

  1. Three-dimensional tracer model study of atmospheric CO2 - Response to seasonal exchanges with the terrestrial biosphere

    Microsoft Academic Search

    I. Fung; K. Prentice; E. Matthews; J. Lerner; G. Russell

    1983-01-01

    A three-dimensional tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere. The tracer model uses winds generated by a global general circulation model to advect and convect CO2; no explicit diffusion coefficients are employed. A biospheric exchange function constructed from a map of net primary productivity, and

  2. A pilot study of the feasibility of long-term human bone balance during perimenopause using a 41Ca tracer

    NASA Astrophysics Data System (ADS)

    Hui, S. K.; Prior, J.; Gelbart, Z.; Johnson, R. R.; Lentle, B. C.; Paul, M.

    2007-06-01

    The mechanisms governing calcium fluxes during bone remodeling processes in perimenopausal women are poorly known. Despite higher, albeit erratic, estradiol levels in perimenopause, spine bone loss is greater than during the first five years past the final menstrual flow when estradiol becomes low. Understanding changes during this dynamic transition are important to prevent fragility fractures in midlife and older women. The exploration of long-lived 41Ca (T1/2 = 1.04 × 105 yrs) tracer measurements using accelerator mass spectrometry (AMS) leads to the possibility of monitoring bone remodeling balance. With this new technology, we explored a pilot long-term feasibility study of bone health by measuring the 41Ca trace element in urine for six years from premenopausal to later perimenopausal phases in one midlife woman. We measured bone mineral density in parallel.

  3. Study of Formation Mechanisms of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Sheng; Wu, Cheng-Yueh; Hsieh, Bieng-Zih

    2015-04-01

    Gas hydrates, which had been found in subsurface geological environments of deep-sea sediments and permafrost regions, are solid crystalline compounds of gas molecules and water. The estimated energy resources of hydrates are at least twice of that of the conventional fossil fuel in the world. Gas hydrates have a great opportunity to become a dominating future energy. In the past years, many laboratory experiments had been conducted to study chemical and thermodynamic characteristics of gas hydrates in order to investigate the formation and dissociation mechanisms of hydrates. However, it is difficult to observe the formation and dissociation of hydrates in a porous media from a physical experiment directly. The purpose of this study was to model the dynamic formation mechanisms of gas hydrate in porous media by reservoir simulation. Two models were designed for this study: 1) a closed-system static model with separated gas and water zones; this model was a hydrate equilibrium model to investigate the behavior of the formation of hydrates near the initial gas-water contact; and 2) an open-system dynamic model with a continuous bottom-up gas flow; this model simulated the behavior of gas migration and studied the formation of hydrates from flowed gas and static formation water in porous media. A phase behavior module was developed in this study for reservoir simulator to model the pressure-volume-temperature (PVT) behavior of hydrates. The thermodynamic equilibriums and chemical reactions were coupled with the phase behavior module to have functions modelling the formation and dissociation of hydrates from/to water and gas. The simulation models used in this study were validated from the code-comparison project proposed by the NETL. According to the modelling results of the closed-system static model, we found that predominated location for the formation of hydrates was below the gas-water contact (or at the top of water zone). The maximum hydrate saturation observed was located just below the gas-water contact. The open-system dynamic model showed that the hydrates were basically uniformly distributed in a homogeneous porous media at a constant gas migration rate. However, if the gas migration rate was extremely low, the hydrates will tend to concentrate at the bottom of water zone (i.e. at the first contact of the water and the flowed gas) and finally blocked the vertical flow of gas. The models we designed can be scaled up to a field scale, and the research findings from this study can be contributed to the dispersion analysis of an in-situ hydrate reservoir.

  4. Study of the olivocochlear neurons using two different tracers, fast blue and cholera toxin, in hypothyroid rats.

    PubMed

    Cantos, R; López, D E; Sala, M L; Rueda, J

    2000-04-01

    Congenital hypothyroidism results in deafness that is caused by changes in the auditory receptor, including scanty development of the outer hair cells and a lack of synaptogenesis between these cells and the efferent system. although the afferent population is present. The normal efferent innervation of the cochlea originates in the superior olivary complex, arising from efferent neurons belonging to the lateral or to the medial olivocochlear system. In the rat, the former is constituted by neurons located in the lateral superior olivary nucleus, that project to the inner hair cells, while the later originates in the ventral nuclei of the trapezoid body and project to the outer hair cells. The aim of this work is to study the localization, number and morphology of the olivochochlear neurons in congenital hypothyroid animals by means of the injections of the retrograde tracers, either fast blue or cholera toxin, in the cochlea. The mean total number of labeled olivocochlear neurons after injection of fast blue in hypothyroid animals was 1,016, and in control ones was 1,027. Using cholera toxin, the mean total number of labeled olivocochlear neurons was slightly lower: 863 in hypothyroid animals versus 910 in control ones. Although both tracers showed no significant differences between groups, when the somatic area of the labeled olivocochlear neurons is considered, the size of all of the three different population of cells (lateral olivocochlear neurons, medial olivocochlear neurons and shell neurons) was significantly lower in the hypothyroid rats. This is the first study of the olivocochlear neurons in hypothyroid animals. The conclusion from this work is that in hypothyroid rats the labeled olivocochlear neurons are significantly smaller but that there is not any modification in the localization and number of the labeled olivocochlear neurons, suggesting that thyroid hormones are necessary for the neuronal growth. However, most of the medial olivocochlear neurons do not make contact with their target, so their maintenance suggests that the axons are in contact with other structures of the cochlea. PMID:10794166

  5. Olfacto-retinalis pathway in Austrolebias charrua fishes: a neuronal tracer study.

    PubMed

    Rosillo, J C; Olivera-Bravo, S; Casanova, G; García-Verdugo, J M; Fernández, A S

    2013-12-01

    The olfacto-retinal centrifugal system, a constant component of the central nervous system that appears to exist in all vertebrate groups, is part of the terminal nerve (TN) complex. TN allows the integration of different sensory modalities, and its anatomic variability may have functional and evolutionary significance. We propose that the olfacto-retinal branch of TN is an important anatomical link that allows the functional interaction between olfactory and visual systems in Austrolebias. By injecting three different neuronal tracers (biocytin, horseradish peroxidase, and 1,1'-dioctadecyl-3,3,3',3'tetramethyl-indocarbocyanine perchlorate (DiI)) in the left eye of Austrolebias charrua fishes, we identified the olfacto-retinal branch of TN and related neuronal somas that were differentiable by location, shape, and size. The olfacto-retinal TN branch is composed of numerous thin axons that run ventrally along the olfactory bulb (OB) and telencephalic lobes, and appears to originate from a group of many small monopolar neurons located in the rostral portion of both the ipsi- and contralateral OB (referred to as region 1). Labeled cells were found in two other regions: bipolar and multipolar neurons in the transition between the OB and telencephalic lobes (region 2) and two other groups in the preoptic/pretectal area (region 3). In this last region, the most rostral group is constituted by monopolar pear-shaped neurons and may belong to the septo-preoptic TN complex. The second group, putatively located in the pretectal region, is formed by pseudounipolar neurons and coincides with a conserved vertebrate nucleus of the centrifugal retinal system not involved in the TN complex. The found that connections between the olfactory and visual systems via the olfacto-retinal TN branch suggest an early interaction between these sensory modalities, and contribute to the identification of their currently unknown circuital organization. PMID:24012745

  6. Analysis of tracer and thermal transients during reinjection

    SciTech Connect

    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.

  7. Comparative study of tracer diffusion of HTO, 22Na + and 36Cl - in compacted kaolinite, illite and montmorillonite

    NASA Astrophysics Data System (ADS)

    Glaus, Martin A.; Frick, Sabrina; Rossé, Roger; Loon, Luc R. Van

    2010-04-01

    The through-diffusion of HTO, 22Na + and 36Cl - in kaolinite, homo-ionic Na-illite and homo-ionic Na-montmorillonite was measured at a high degree of compaction as a function of the salt concentration in the 'external solution', i.e. in the solution in contact with the clay sample. The clays were chosen for this study because of their differences in the number and nature of ion exchange sites leading to different proportions of interlayer-, inter-particle and free pore water. It was found that the diffusive mass transfer of Na + in Na-montmorillonite and Na-illite increased with decreasing external salt concentration, while the opposite trend was observed for the diffusion of Cl -. These trends are more pronounced in the case of Na-montmorillonite than in Na-illite, while almost no salt effect was observed for kaolinite. Similarly no salt effect was observed for the diffusion of HTO through all of the clays tested. These observations are in agreement with a conceptual model where it is assumed that cations diffuse preferentially in the interlayer or diffuse double-layer porosity, while anions are almost completely excluded from these regions. In the case of Na + diffusion, the salt effects can be explained by an influence on the concentration gradient of diffusing cations, while in the case of Cl - the external salt concentration has an effect on the accessible porosity. Effective diffusion coefficients of Cl - fulfil the same relationship to porosity as those of the uncharged HTO, when using accessible porosities for such a comparison. Furthermore it is shown that pore diffusion coefficients for the three tracers are fairly well correlated with the respective diffusion coefficients in bulk water, if the effective diffusion coefficients for Na + are derived from calculated tracer concentration gradients in the interlayer or diffuse double-layer porosities.

  8. Carbon Dioxide Induced Ocean Climatic Change and Tracer Experiment with AN Atmosphere-Ocean General Circulation Model

    Microsoft Academic Search

    Xingjian Jiang

    1991-01-01

    The principal objective of this study is to determine whether or not the penetration of a passive tracer is analogous to the penetration of a greenhouse-gas-induced heating. The Atmosphere-Ocean General Circulation Model (A-O GCM) has been used to study CO_2 -induced climate change and the penetration of passive tracers into the world ocean. The present climate and a 2 x

  9. Carbon dioxide induced ocean climatic change and tracer experiment with an atmosphere-ocean general circulation model

    Microsoft Academic Search

    Xingjian Jiang; Xingjian

    1991-01-01

    The principal objective of this study is to determine whether or not the penetration of a passive tracer is analogous to the penetration of a greenhouse-gas-induced heating. The Atmosphere Ocean General Circulation Model (A-O GCM) has been used to study CO2-induced climate change and the penetration of passive tracers into the world ocean. The present climate and a 2 x

  10. The Reanalysis for Stratospheric Trace-gas Studies

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Li, Shuhua

    2002-01-01

    In order to re-examine trace gas transport in the middle atmosphere for the period May 1991 until April 1995, a "reanalysis" is being performed using an up-to-date version of the DAO's "GEOS" assimilation system. The Reanalysis for Stratospheric Trace-gas Studies (ReSTS) is intended to provide state-of-the-art estimates of the atmosphere during a period when the Upper Atmospheric Research Satellite provided a high density of trace-gas observations, and when the aerosol loading from the eruption of Mount Pinatubo contaminated the lower stratosphere, at the same time performing a natural tracer transport experiment. This study will present the first results from ReSTS, focussing on the improvements over the meteorological analyses produced by the then-operational GEOS-1 data assimilation system; emphasis will be placed on the improved representations of physical processes between GEOS-1 and the current GEOS-4 systems, highlighting the transport properties of the datasets. Alongside the production of a comprehensive atmospheric dataset, important components of ReSTS include performing sensitivity studies to the formulation of the assimilation system (including the representation of physical processes in the GCM, such as feedbacks between ozone/aerosols and meteorology) and to the inclusion of additional data types (including limb-sounding temperature data alongside the TOVS observations). Impacts of some of these factors on the analyzed meteorology and transport will be discussed. Of particular interest are attempts to determine the relative importance of various steps in the assimilation process to the quality of the final analyses.

  11. The effect of wind and currents on gas exchange in an estuarine system

    NASA Technical Reports Server (NTRS)

    Broecker, W. S.; Ledwell, J. R.; Bopp, R.

    1987-01-01

    The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF6, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF6, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF6 and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

  12. GREEN RIVER AIR QUALITY MODEL DEVELOPMENT: METEOROGICAL AND TRACER DATA-FIELD STUDY IN BRUSH VALLEY, COLORADO, JULY-AUGUST, 1982

    EPA Science Inventory

    Special meteorological and atmospheric tracer studies were conducted during a three-week period in July and August of 1982 in the Brush Creek Valley of northwestern Colorado. The experiments were conducted by the U.S. Department of Energy's Pacific Northwest Laboratory (PNL) as p...

  13. Gas-cooled fast breeder reactor studies

    Microsoft Academic Search

    J. B. Dee; P. Fortescue; J. A. Larrimore

    1973-01-01

    Recent design and assessment work performed on gas-cooled fast breeder ; reactors by Gulf General Atomic is outlined. A description is glven of the 300 ; MW(e) gas-cooled fast breeder reactor demonstration plant design, and safety ; aspects of the plant are discussed, including potential flow blockage and coolant ; depressurization accidents. In addition preliminary studies of larger GCFR ;

  14. An Analysis of Whole Body Tracer Kinetics in Dynamic PET Studies With Application to Image-Based Blood Input Function Extraction

    PubMed Central

    Huang, Jian; O’Sullivan, Finbarr

    2014-01-01

    In a positron emission tomography (PET) study, the local uptake of the tracer is dependent on vascular delivery and retention. For dynamic studies the measured uptake time-course information can be best interpreted when knowledge of the time-course of tracer in the blood is available. This is certainly true for the most established tracers such as 18F-Fluorodeoxyglucose (FDG) and 15O-Water (H2O). Since direct sampling of blood as part of PET studies is increasingly impractical, there is ongoing interest in image-extraction of blood time-course information. But analysis of PET-measured blood pool signals is complicated because they will typically involve a combination of arterial, venous and tissue information. Thus, a careful appreciation of these components is needed to interpret the available data. To facilitate this process, we propose a novel Markov chain model for representation of the circulation of a tracer atom in the body. The model represents both arterial and venous time-course patterns. Under reasonable conditions equilibration of tracer activity in arterial and venous blood is achieved by the end of the PET study—consistent with empirical measurement. Statistical inference for Markov model parameters is a challenge. A penalized nonlinear least squares process, incorporating a generalized cross-validation score, is proposed. Random effects analysis is used to adaptively specify the structure of the penalty function based on historical samples of directly measured blood data. A collection of arterially sampled data from PET studies with FDG and H2O is used to illustrate the methodology. These data analyses are highly supportive of the overall modeling approach. An adaptation of the model to the problem of extraction of arterial blood signals from imaging data is also developed and promising preliminary results for cerebral and thoracic imaging studies with FDG and H2O are obtained. PMID:24770914

  15. A study on the effect of inlet turbulence on gas mixing for single point aerosol sampling 

    E-print Network

    Mohan, Anand

    2001-01-01

    The efficiency of certain mixing elements in achieving conditions suited for single point sampling is evaluated. Experimental measurements of velocity and tracer gas concentration are taken to determine the same. Readings are taken under conditions...

  16. Effects of solute breakthrough curve tail truncation on residence time estimates: A synthesis of solute tracer injection studies

    E-print Network

    Covino, Tim

    appropriately characterized by power law tailing. We synthesized results from a variety of tracer residence time. Failure to consider tail truncation leads to underestimation of hyporheic exchange and solute retention and to corresponding overestimation of hyporheic biogeochemical transformation rates

  17. Fate of nitrogen in riparian forest soils and trees: an 15N tracer study simulating salmon decay.

    PubMed

    Drake, Deanne C; Naiman, I Robert J; Bechtold, J Scott

    2006-05-01

    We introduced an 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon N and, ultimately, mechanisms regulating potential links between salmon abundance and tree growth. The 15N tracer simulated deposition of 7.25 kg of salmon (fresh) to four 50-m2 plots. We added NH4+ (the initial product of salmon carcass decay) and other important nutrients provided by carcasses (P, S, K, Mg, Ca) to soils in late October 2003, coincident with local salmon spawning. We followed the 15N tracer through soil and tree pools for one year. Biological uptake of the 15N tracer occurred quickly: 64% of the 15N tracer was bound in soil microbiota within 14 days, and roots of the dominant riparian tree, western red cedar (Thuja plicata), began to take up 15N tracer within seven days. Root uptake continued through the winter. The 15N tracer content of soil organic matter reached a maximum of approximately 52%, five weeks after the application, and a relative equilibrium of approximately 40% within five months. Six months after the addition, in spring 2004, at least 37% of the 15N tracer was found in tree tissues: approximately 23% in foliage, approximately 11% in roots, and approximately 3% in stems. Within the stems, xylem and phloem sap contained approximately 96% of the tracer N, and approximately 4% was in structural xylem N. After one year, at least 28% of the 15N tracer was still found in trees, and loss from the plots was only approximately 20%. The large portion of tracer N taken up in the fall and reallocated to leaves and stems the following spring provides mechanistic evidence for a one-year-lagged tree-growth response to salmon nutrients. Salmon nutrients have been deposited in the Kennedy Creek system each fall for centuries, but the system shows no evidence of nutrient saturation. Rates of N uptake and retention are a function of site history and disturbance and also may be the result of a legacy effect, in which annual salmon nutrient addition may lead to increased efficiency of nutrient uptake and use. PMID:16761604

  18. Impurity transport studies by means of tracer-encapsulated solid pellet injection in neutral beam heated plasmas on LHD

    Microsoft Academic Search

    N. Tamura; S. Sudo; K. V. Khlopenkov; S. Kato; V. Yu Sergeev; S. Muto; K. Sato; H. Funaba; K. Tanaka; T. Tokuzawa; I. Yamada; K. Narihara; Y. Nakamura; K. Kawahata; N. Ohyabu; O. Motojima; LHD experimental groups

    2003-01-01

    The quantitative properties of impurity transport in large helical device (LHD) plasmas heated by neutral beam injection have been investigated by means of tracer-encapsulated solid pellet (TESPEL) injection. In the case of a titanium (Ti) tracer, the behaviour of the emission lines from the highly ionized Ti impurity, Ti Kalpha(EHe-like~4.7 keV) and Ti XIX (lambda = 16.959 nm), has been

  19. Analysis of the Summer 2004 ozone budget over the United States using Intercontinental Transport Experiment Ozonesonde Network Study (IONS) observations and Model of Ozone and Related Tracers (MOZART4) simulations

    Microsoft Academic Search

    G. G. Pfister; L. K. Emmons; P. G. Hess; J.-F. Lamarque; A. M. Thompson; J. E. Yorks

    2008-01-01

    The origin of ozone over the summertime contiguous United States during summer 2004 was examined using the Intercontinental Transport Experiment (INTEX-A) Ozonesonde Network Study (IONS-04) over North America. We estimate the budget using the global chemistry transport Model of Ozone and Related Tracers version 4 (MOZART-4) with synthetic tracers that keep track of the ozone produced from selected NOx sources

  20. Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted.

    PubMed

    Dorich, C D; Varner, R K; Pereira, A B D; Martineau, R; Soder, K J; Brito, A F

    2015-04-01

    The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176±34d in milk, 40.7±6.1kg of milk yield, and 685±49kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458g/d (standard error of the mean=18g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination=0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination=0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or outdoors is warranted to further assess the GQS and SF6 methodologies. PMID:25660738

  1. Determination of traveltimes in the lower San Joaquin River basin, California, from dye-tracer studies during 1994-1995

    USGS Publications Warehouse

    Kratzer, Charles R.; Biagtan, Rhoda N.

    1997-01-01

    Dye-tracer studies were done in the lower San Joaquin River Basin in February 1994, June 1994, and February 1995. Dye releases were made in the Merced River (February 1994), Salt Slough (June 1994), Tuolumne River (February 1995), and Dry Creek (February 1995). The traveltimes determined in the studies aided the interpretation of pesticide data collected during storm sampling and guided sample collection during a Lagrangian pesticide study. All three studies used rhodamine WT 20-percent dye solution, which was released as a slug in midstream. The mean traveltime determined in the dye studies were compared to estimates based on regression equations of mean stream velocity as a function of streamflow. Dye recovery, the ratio of the calculated dye load at downstream sites to the initial amount of dye released, was determined for the 1994 studies and a dye-dosage formula was evaluated for all studies. In the February 1994 study, mean traveltime from the Merced River at River Road to the San Joaquin River near Vernalis (46.8 river miles) was 38.5 hours, and to the Delta-Mendota Canal at Tracy pumps (84.3 river miles) was 90.4 hours. In the June 1994 study, mean traveltime from Salt Slough at Highway 165 to Vernalis (64.0 river miles) was 80.1 hours. In the February 1995 study, the mean traveltime from the Tuolumne River at Roberts Ferry to Vernalis (51.5 river miles) was 35.8 hours. For the 1994 studies, the regression equations provided suitable estimates of travel-time, with ratios of estimated traveltime to mean dye traveltime of 0.94 to 1.08. However, for the 1995 dye studies, the equations considerably underestimated traveltime, with ratios of 0.49 to 0.73.In the February 1994 study, 70 percent of the dye released was recovered at Vernalis and 35percent was recovered at the Delta-Mendota Canal at Tracy pumps. In the June 1994 study, recovery was 61 percent at Patterson, 43 percent just upstream of the Tuolumne River confluence, and 37 percent at Vernalis. The dye-dosage formula overestimated the dye required for a given downstream concentration for the 1994 studies by ratios of 1.07 to 2.12. The ratios for the February 1995 studies were 0.67 to 0.95 for the Tuolumne River and 1.21 for Dry Creek. In all studies, the estimates improved with length of dye study.

  2. DNA Based Hydrological Tracers

    NASA Astrophysics Data System (ADS)

    Sharma, A. N.; Buchanan, B. P.; Luo, D.; Walter, M. T.

    2011-12-01

    In order to answer questions that involve multiple and potentially interacting hydrological flowpaths, multiple tracers with identical transport properties that can nonetheless be distinguished from each other are required. We are developing such an engineered tracer system that allows a large number of individual tracers to be simultaneously distinguished from one another. This new tracer is composed of polylactic acid (PLA) microspheres into which short strands of synthetic DNA and paramagnetic iron oxide nanoparticles are incorporated. The synthetic DNA serves as the "label" or "tag" in our tracers that allow us to distinguish one tracer from another. Paramagnetic iron oxide nanoparticles are included in the tracer to facilitate magnetic concentration of the tracers in water samples. The eventual goal of this project is to develop technologies for identifying and characterizing different flowpaths at field and watershed scales by using multiple sets of polymer microspheres, each coded with unique DNA sequences, of which there are essentially limitless combinations, i.e., many flowpaths can be uniquely coded. The potential advantages of this strategy compared to conventional tracers are the elimination of background interferences, the ability to segregate superimposed flowpaths through the design of strictly unique DNA tags and the biodegradability of the tracers. This presentation highlights recent advances, new challenges, and potential applications for this tracer technology.

  3. A tracer experiment study to evaluate the CALPUFF real time application in a near-field complex terrain setting

    NASA Astrophysics Data System (ADS)

    cui, Huiling; Yao, Rentai; Xu, Xiangjun; Xin, Cuntian; Yang, jinming

    2011-12-01

    CALPUFF is an atmospheric source-receptor model recommended by the US Environmental Protection Agency (EPA) for use on a case-by-case basis in complex terrain and wind condition. As the bulk of validation of CALPUFF has focused on long-range or short-range but long-term dispersion, we can not gauge the reliability of the model for predicting the short-term emission in near-field especially complex terrain, and sometimes this situation is important for emergency emission. To validate the CALPUFF's application in such condition, we carried out a tracer experiment in a near-field complex terrain setting and used CALPUFF atmospheric dispersion model to simulate the tracer experiment in real condition. From the centroid trajectory comparison of predictions and measures, we can see that the model can correctly predict the centroid trajectory and shape of tracer cloud, and the results also indicate that sufficient observed weather data only can develop a good wind field for near-field. From the concentration comparison in each arc, we can see the model underestimate horizontal extent of tracer puff and can not reflect the irregular characters showed in measurements. The result of global analysis is FOEX of -25.91%, FA2 of 27.06%, FA5 of 61.41%. The simulations shows that the CALPUFF can simulate the position and direction of tracer cloud in near-field complex terrain but underestimate over measurements especially in peak concentrations.

  4. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonium (NH4 +) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4 + movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring...

  5. Isotope Tracers as Tools for Identifying Water Sources in Developing Regions: Case of Study in Southern Ecuador

    NASA Astrophysics Data System (ADS)

    Mosquera, G.; Lazo, P.; Crespo, P.; Célleri, R.

    2014-12-01

    Páramo ecosystems are widely recognized for their high water regulation capacity and as the main source of runoff generation in the Andean region. Understanding the hydrological functioning of the fragile wet Andean páramo ecosystems is critical in the mountainous regions of South America given their high susceptibility to global and local stressors such as land use change and climate change and variability . Despite this, most of the basins in the Andean mountain range are still ungauged, resulting in a currently hindered hydrologic analysis of the water sources contributing to runoff generation in the high-elevation páramo ecosystems. To improve this situation and provide a baseline for future tracer-based hydrologic studies, the isotopic signature of water samples collected within the Zhurucay River experimental basin (7.53 km2) was analyzed. The study area is located in the southern Ecuador and stretches over an altitudinal range of 3200 and 3900 m a.s.l. Water samples in rainfall, streamflow, and soils were collected between May 2011 and May 2013. Streamflow hydrometric and isotopic information within the study site was collected using a nested monitoring system. The main soils in the study site are the Andosols mainly located in the steep slopes, and the Histosols (Andean páramo wetlands) predominantly located at the bottom of the valley. Results reveal that the Andosols drain the infiltrated rainfall water to the Histosols. The Histosols on their turn feed creeks and small rivers. Pre-event water stored in the Histosols is the primary source of runoff generation throughout the year. Defining the water sources contributing to runoff generation is the first step towards the establishment of scientifically-based programs of management and conservation of water resources in the Andean region; and the monitoring of isotopic information has proven useful to improve the understanding of the ecosystem's hydrologic behavior.

  6. Evaluation of Tracer Diffusion in Layered System Using X-Ray CT

    Microsoft Academic Search

    A. F. Alajmi; A. Grader; S. F. Alkafeef

    2009-01-01

    Characterizing and understanding the porous media network structure are essential for maintaining and enhancing oil and gas recovery. The pore system controls the fluid transport processes, described by the permeability and diffusion. This work studies vertical diffusion of tracer solution (sodium iodine, NaI) in a 60 cm long and 5 cm diameter layered Berea Sandstone sample that was partially fractured

  7. NOAA EPA Near-Roadway Sound Barrier Atmospheric Tracer Study 2008

    EPA Science Inventory

    A roadway toxics dispersion study was conducted at the Idaho National Laboratory to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The key finding was that reduced concentrations were me...

  8. AIRBORNE LIDAR TRACKING OF FLUORESCENT TRACERS FOR ATMOSPHERIC TRANSPORT AND DIFFUSION STUDIES

    EPA Science Inventory

    Development and validation of transport models for the study of regional acid deposition require improved observations of pollutant transport and dispersion processes. Current methods for tracking air-parcel is limited to constant density surfaces using tetroons or by gaseous tra...

  9. A TRACER STUDY OF THE TRANSPORT OF CHROMIUM IN FLUORIDE FUEL SYSTEMS

    Microsoft Academic Search

    R. B. Price; D. N. Sunderman; M. Pobereskin; G. D. Calkin

    1957-01-01

    An experimental study was made of the mass transport of chromium in poly-; thermal Inconel-fluoride fuel systems. The transport of chromium was followed by ; toe technique of adding radioactive Cr⁵¹ to the system as either CrFâ; , in the salt or as elemental chromium in the solid phase. The rates of ; diffusion of chromium in Inconel at 600,

  10. Fundamental study on gas monitoring in CELSS

    NASA Technical Reports Server (NTRS)

    Nishi, I.; Tateishi, T.; Tomizawa, G.; Nitta, K.; Oguchi, M.

    1987-01-01

    A mass spectrometer and computer system was developed for conducting a fundamental study on gas monitoring in a Controlled Ecological Life Support System. Respiration and metabolism of the hamster and photosynthesis of the Spirulina were measured in a combination system consisting of a hamster chamber and a Spirulina cultivator. They are connected through a membrane gas exchanger. Some technical problems were examined. In the mass spectrometric gas monitoring, a simultaneous multisample measurement was developed by employing a rotating exchange valve. Long term precise measurement was obtained by employing an automatic calibration system. The membrane gas sampling probe proved to be useful for long term measurement. The cultivation rate of the Spirulina was effectively changed by controlling CO2 and light supply. The experimental results are helpful for improving the hamster-spirulina system.

  11. Fundamental study on gas monitoring in celss

    NASA Astrophysics Data System (ADS)

    Nishi, I.; Tateishi, T.; Tomizawa, G.; Nitta, K.; Oguchi, M.

    A mass spectrometer and computer system was developed for conducting a fundamental study on gas monitoring in CELSS. Respiration and metabolism of the hamster and photosynthesis of the Spirulina were measured in a combination system consisting of a hamster chamber and a Spirulina cultivator. They are connected through a membrane gas exchanger. Some technical problems were examined. In the mass spectrometric gas monitoring, a simultaneous multi-sample measurement was developed by employing a rotating exchange valve. Long term precise measurement was obtained by employing an automatic calibration system. The membrane gas sampling probe proved to be useful for long term measurement. The cultivation rate of the Spirulina was effectively changed by controlling CO2 and light supply. The experimental results are helpful for improving the hamster-spirulina system.

  12. A Lagrangian SF 6 tracer study of an anticyclonic eddy in the North Atlantic: patch evolution, vertical mixing and nutrient supply to the mixed layer

    Microsoft Academic Search

    C. S. Law; A. P. Martin; M. I. Liddicoat; A. J. Watson; K. J. Richards; E. M. S. Woodward

    2001-01-01

    Biological and biogeochemical change in the surface mixed layer of an anticyclonic eddy at 60°N in the North Atlantic were monitored within a Lagrangian time-series study using the tracer sulphur hexafluoride (SF6). Four ARGOS buoys initially released at the patch centre remained closely associated with the SF6 patch over a 10-day period, with the near-circular eddy streamlines contributing to the

  13. The Effect of Small Tumor Volumes upon Intra-tumoral Tracer Uptake Heterogeneity Studies

    PubMed Central

    Brooks, Frank J.; Grigsby, Perry W.

    2014-01-01

    The number of studies in the literature involving quantification of the metabolic heterogeneity seen in 18F-fluorodeoxyglucose position emission tomography (FDG-PET) images has increased sharply over recent years. We hypothesize that inclusion of very small regions-of-interest as unique data points will have deleterious effects upon these studies. Methods Using a combination of probability theory and clinical FDG-PET data, we numerically calculate the curve describing the probability a given tumor volume is large enough to adequately sample the underlying tumor biology assayed via a Siemens Biograph 40 True Point Tomograph hybrid PET/CT scanner at a planar resolution of 4 mm and trans-axial resolution of 4 mm (64 mm3 voxel size). We then employ a computer simulation to isolate the effects of tumor volume upon the image local entropy. Results We computed the underlying global intensity distribution for 70 cervical cancer tumors ranging from 5 to 310 cm3) which were ensemble averaged over the same intensity scale. From this distribution, we determined that about 700 total voxels (45 cm3) are required to give 95% certainty that the global intensity distribution has been sampled adequately enough such that common statistical comparisons of individual tumor intensity distributions can be made canonically. We demonstrate that one previously suggested measure of heterogeneity is dependent on tumor volume. Furthermore, that heterogeneity measure is about 5 times more sensitive to volume changes for volumes below the proposed minimum than for those above it. Conclusion We find that inclusion of tumor volumes below 45 cm3 can profoundly bias comparisons of intra-tumoral uptake heterogeneity metrics derived from the current generation of whole-body FDG-PET scanner data. PMID:24263086

  14. Magnetofossils as tracers of oxygenation change: a case study from the stratified Pettaquamscutt River Estuary

    NASA Astrophysics Data System (ADS)

    Chen, A. P.; Berounsky, V. M.; Chan, M. K.; Moskowitz, B. M.; Andrade Lima, E.; Kopp, R. E.; Cady, C.; Weiss, B. P.; Hesse, P. P.

    2013-12-01

    Magnetotactic bacteria (MB) are motile organisms commonly found around the oxic-anoxic-interface (OAI) in sediments and stratified water columns. Magnetite and greigite crystals synthesized by MB intracellularly, termed magnetosomes, can be preserved in sediments as magnetofossils. Changes in OAI thickness (due to changes in temperature, clathrate dissociation & methane oxidation, organic carbon supply/oxidation, or sedimentation rate) would produce proportional changes in MB population and sedimentary magnetofossil concentration. While potentially useful as an oxygenation proxy, magnetofossil quantification techniques and variables controlling their preservation in sediments need to be better understood. Most prior work focused on cultured magnetite-MB and sediment mixtures while studies of greigite-MB (found just below the OAI in the sulfidic hypolimnion) is lacking because axenic cultures do not exist. To address these issues, we study wild magnetite- and greigite-MB from the seasonally stratified Pettaquamscutt River Estuary Upper Basin (RI, USA) as a function of water depth, d. Transmission electron microscope imaging of 21 MB (377 magnetosomes) revealed a complexity in wild MB not found in cultures. From d=3.9 m-7.0 m, live-cell assays confirmed the presence of multiple MB morphotypes, both north- (majority) and south-seeking (minority), and a few magnetic protists. Based on a previous microscopy study just 1.4 km south of Upper Basin (Bazylinski et al., 1995), magnetite-MB are expected for d<5.0 m, mix magnetite- and greigite-MB for 5.0 m6.0 m. Coercivity distributions for all depths are characterized by a small variance, reflecting uniformity in magnetosome size. Interestingly, despite changing from dominant magnetite to greigite-MB with increasing depth, the median coercivity remained largely unchanged. Median coercivity is therefore not diagnostic of magnetosome mineralogy. We also report ferromagnetic resonance spectroscopy (FMR) results. The first derivative of the absorption spectra for d<5.6 m typically present multiple low-field maxima, which is consistent with observations from magnetite-MB cultures. In contrast, only one maximum in the spectra was observed for 6.0 m

  15. Isotope Tracer Studies of Diffusion in Sillicates and of Geological Transport Processes Using Actinide Elements

    SciTech Connect

    Wasserburg, Gerald J

    2008-07-31

    The objectives were directed toward understanding the transport of chemical species in nature, with particular emphasis on aqueous transport in solution, in colloids, and on particles. Major improvements in measuring ultra-low concentrations of rare elements were achieved. We focused on two areas of studies: (1) Field, laboratory, and theoretical studies of the transport and deposition of U, Th isotopes and their daughter products in natural systems; and (2) Study of calcium isotope fractionation effects in marine carbonates and in carbonates precipitated in the laboratory, under controlled temperature, pH, and rates of precipitation. A major study of isotopic fractionation of Ca during calcite growth from solution has been completed and published. It was found that the isotopic shifts widely reported in the literature and attributed to biological processes are in fact due to a small equilibrium fractionation factor that is suppressed by supersaturation of the solution. These effects were demonstrated in the laboratory and with consideration of the solution conditions in natural systems, where [Ca{sup 2+}] >> [CO{sub 3}{sup 2-}] + [HCO{sub 3}{sup -}]. The controlling rate is not the diffusion of Ca, as was earlier proposed, but rather the rate of supply of [CO{sub 3}{sup 2-}] ions to the interface. This now opens the issues of isotopic fractionation of many elements to a more physical-chemical approach. The isotopic composition of Ca {Delta}({sup 44}Ca/{sup 40}Ca) in calcite crystals has been determined relative to that in the parent solutions by TIMS using a double spike. Solutions were exposed to an atmosphere of NH{sub 3} and CO{sub 2}, provided by the decomposition of (NH4)2CO3. Alkalinity, pH, and concentrations of CO{sub 3}{sup 2-}, HCO{sub 3}{sup -}, and CO{sub 2} in solution were determined. The procedures permitted us to determine {Delta}({sup 44}Ca/{sup 40}Ca) over a range of pH conditions, with the associated ranges of alkalinity. Two solutions with greatly different Ca concentrations were used, but, in all cases, the condition [Ca] >> [CO{sub 3}{sup 2-}] was met. A wide range in {Delta}({sup 44}Ca/{sup 40}Ca) was found for the calcite crystals, extending from 0.04 {+-} 0.13 to -1.34 {+-} 0.15 {per_thousand}, generally anticorrelating with the amount of Ca removed from the solution. The results show that {Delta}({sup 44}Ca/{sup 40}Ca) is a linear function of the saturation state of the solution with respect to calcite ({Omega}). The two parameters are very well correlated over a wide range in {Omega} for each solution with a given [Ca]. Solutions, which were vigorously stirred, showed a much smaller range in {Delta}({sup 44}Ca/{sup 40}Ca) and gave values of -0.42 {+-} 0.14 {per_thousand}, with the largest effect at low {Omega}. It is concluded that the diffusive flow of CO{sub 3}{sup 2-} into the immediate neighborhood of the crystal-solution interface is the rate-controlling mechanism and that diffusive transport of Ca{sup 2+} is not a significant factor. The data are simply explained by the assumptions that: (a) the immediate interface of the crystal and the solution is at equilibrium with {Delta}({sup 44}Ca/{sup 40}Ca) {approx} -1.5 {+-} 0.25 {per_thousand}, and (b) diffusive inflow of CO{sub 3}{sup 2-} causes supersaturation, thus precipitating Ca from the regions, exterior to the narrow zone of equilibrium. We consider this model to be a plausible explanation of the available data reported in the literature. The well-resolved but small and regular isotope fractionation shifts in Ca are thus not related to the diffusion of very large hydrated Ca complexes, but rather due to the ready availability of Ca in the general neighborhood of the crystal solution interface. The largest isotopic shift which occurs is a small equilibrium effect which is then subdued by supersaturation precipitation for solutions where [Ca{sup 2+}] >> [CO{sub 3}{sup 2-}] + [HCO{sub 3}{sup -}]. It is shown that there is a clear temperature dependence of the net isotopic shifts, which is simply due to changes in {Omega}

  16. Tracer study of batch sedimentation. [Resin beads - 45 and 62. mu. m in diameter

    SciTech Connect

    Bigot, P.C.; Lee, A.H.

    1982-04-01

    The initial particle-concentration profile in batch settling tests was assessed and determined to be uniform. Two sets of data for batch-settling tests using cobalt-57-traced ion-exchange resin beads (45 and 62 ..mu..m in diameter) were compared with existing theories and models. A single suspended-solids zone was observed in agreement with the predictions of Dixon; the Richardson-Zaki correlation predicted the settling velocity as a function of void fraction to within 5%. Studies with a bimodal particle-size distribution of equal fraction of 45- and 62-..mu..m particles showed that the larger particles settled at the same velocity as in a single-particle-size distribution but that the smaller ones settled slower than for a single-particle-size distribution at a given void fraction. The ratio of the settling velocity of the smaller particles in a bimodal-particle-size distribution u/sub b/ to the settling velocity of these particles in a single particle-size distribution u/sub s/ was correlated by raising to the (3.78 +- 0.47) power the effective void fraction of the resulting upper settling zone containing only the smaller particles.

  17. The fate of cyanobacterial blooms in vegetated and unvegetated sediments of a shallow eutrophic lake: A stable isotope tracer study

    Microsoft Academic Search

    Kuanyi Li; Zhengwen Liu; Binhe Gu

    2010-01-01

    An experiment using nitrogen stable isotope tracer (15N) was conducted to track the fate of nitrogen derived from cyanobacterial blooms and the effectiveness with which the seasonal blooms are retained by vegetated and unvegetated sediment in a large shallow eutrophic lake (Lake Taihu, China). 15N enriched Microcystis was injected into both unvegetated sediment and sediment occupied by common reed (Phragmites

  18. Biological tracer method

    DOEpatents

    Strong-Gunderson, Janet M. (Ten Mile, TN); Palumbo, Anthony V. (Oak Ridge, TN)

    1998-01-01

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer.

  19. Biological tracer method

    DOEpatents

    Strong-Gunderson, J.M.; Palumbo, A.V.

    1998-09-15

    The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer. 2 figs.

  20. Nitrate retention and removal in Mediterranean streams with contrasting land uses: a 15N tracer study

    NASA Astrophysics Data System (ADS)

    von Schiller, D.; Martí, E.; Riera, J. L.

    2008-08-01

    We used 15N-labelled nitrate (NO-3) additions to investigate nitrogen (N) cycling at the whole-reach scale in three Mediterranean streams subjected to contrasting land uses (i.e. forested, urban and agricultural). Our aim was to examine: i) the magnitude and relative importance of NO-3 retention (i.e. assimilatory uptake), and removal, (i.e. denitrification), ii) the relative contribution of the different primary uptake compartments to NO-3 retention, and iii) the regeneration, transformation and export pathways of the retained N. The concentration of NO-3 increased and that of dissolved oxygen (DO) decreased from the forested to the agricultural stream, with intermediate values in the urban stream. Standing stocks of primary uptake compartments were similar among streams and dominated by detritus compartments (i.e. fine and coarse benthic organic matter). In agreement, metabolism was net heterotrophic in all streams, although the degree of heterotrophy increased from the forested to the agricultural stream. The NO-3 uptake length decreased along this gradient, whereas the NO-3 mass-transfer velocity and the areal NO-3 uptake rate were highest in the urban stream. Denitrification was not detectable in the forested stream, but accounted for 9% and 68% of total NO-3 uptake in the urban and the agricultural stream, respectively. The relative contribution of detritus compartments to NO-3 assimilatory uptake was highest in the forested and lowest in the agricultural stream. In all streams, the retained N was rapidly transferred to higher trophic levels and regenerated back to the water column. Due to a strong coupling between regeneration and nitrification, most retained N was exported from the experimental reaches in the form of NO-3. This study evidences fast N cycling in Mediterranean streams. Moreover, results indicate that permanent NO-3 removal via denitrification may be enhanced over temporary NO-3 retention via assimilatory uptake in heterotrophic human-altered streams characterized by high NO-3 and low DO concentrations.

  1. Lanthanum tracer and freeze-fracture studies suggest that compartmentalisation of early bone matrix may be related to initial mineralisation.

    PubMed Central

    Soares, A M; Arana-Chavez, V E; Reid, A R; Katchburian, E

    1992-01-01

    In adult bone the calcified matrix and enclosed osteocytes are separated from the extracellular space by a continuous layer of bone lining cells. It thus appears that bone matrix is compartmentalised and, as such, may constitute a 'milieu intérieur' which is different from the general extracellular space. Since adult bone matrix is compartmentalised and matrix vesicles also form a microcompartment, it is conceivable that compartmentalisation, in early osteogenesis, may be a requirement for the initial events of the mineralisation process. We have therefore conducted an ultrastructural, tracer, and freeze-fracture study to determine the stage in which bone matrix becomes compartmentalised and also to find out whether there are tight junctions between osteoblasts. The results show that in early nonmineralised stages and in incipient mineralisation, lanthanum penetrates all intercellular spaces and the newly forming bone matrix which is rich in matrix vesicles and collagen. With the progression of mineralisation, when all matrix vesicles appear mineralised and calcification is 'spreading' to the surrounding matrix, lanthanum is restricted to intercellular spaces and conspicuous macular tight junctions are present between osteoblasts. We suggest that matrix vesicles act as microcompartments for calcification when the early bone matrix is in continuity with the surrounding extracellular space. In later stages, when lanthanum fails to penetrate the matrix, matrix vesicles may no longer be necessary because the bone matrix itself is compartmentalised, thus allowing for localised changes in composition that might favour mineral deposition. Images Figs 1-4 Fig. 5 Fig. 6-8 Fig. 9-11 Fig. 12 Figs. 13-15 Fig. 16 Fig. 17 Fig. 18 Figs. 19-20 PMID:1295872

  2. Laminar segregation of GABAergic neurons in the avian nucleus isthmi pars magnocellularis: a retrograde tracer and comparative study.

    PubMed

    Faunes, Macarena; Fernández, Sara; Gutiérrez-Ibáñez, Cristián; Iwaniuk, Andrew N; Wylie, Douglas R; Mpodozis, Jorge; Karten, Harvey J; Marín, Gonzalo

    2013-06-01

    The isthmic complex is part of a visual midbrain circuit thought to be involved in stimulus selection and spatial attention. In birds, this circuit is composed of the nuclei isthmi pars magnocellularis (Imc), pars parvocellularis (Ipc), and pars semilunaris (SLu), all of them reciprocally connected to the ipsilateral optic tectum (TeO). The Imc conveys heterotopic inhibition to the TeO, Ipc, and SLu via widespread ?-aminobutyric acid (GABA)ergic axons that allow global competitive interactions among simultaneous sensory inputs. Anatomical studies in the chick have described a cytoarchitectonically uniform Imc nucleus containing two intermingled cell types: one projecting to the Ipc and SLu and the other to the TeO. Here we report that in passerine species, the Imc is segregated into an internal division displaying larger, sparsely distributed cells, and an external division displaying smaller, more densely packed cells. In vivo and in vitro injections of neural tracers in the TeO and the Ipc of the zebra finch demonstrated that neurons from the external and internal subdivisions project to the Ipc and the TeO, respectively, indicating that each Imc subdivision contains one of the two cell types hodologically defined in the chick. In an extensive survey across avian orders, we found that, in addition to passerines, only species of Piciformes and Rallidae exhibited a segregated Imc, whereas all other groups exhibited a uniform Imc. These results offer a comparative basis to investigate the functional role played by each Imc neural type in the competitive interactions mediated by this nucleus. PMID:23124899

  3. Effect of wind and currents on gas exchange in an estuarine system. Final technical report, 1 August 1986-31 July 1987

    SciTech Connect

    Broecker, W.S.; Ledwell, J.R.; Bopp, R.

    1987-11-01

    The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF/sub 6/, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF/sub 6/, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF/sub 6/ and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

  4. High temperature gas-cooled reactor: gas turbine application study

    SciTech Connect

    Not Available

    1980-12-01

    The high-temperature capability of the High-Temperature Gas-Cooled Reactor (HTGR) is a distinguishing characteristic which has long been recognized as significant both within the US and within foreign nuclear energy programs. This high-temperature capability of the HTGR concept leads to increased efficiency in conventional applications and, in addition, makes possible a number of unique applications in both electrical generation and industrial process heat. In particular, coupling the HTGR nuclear heat source to the Brayton (gas turbine) Cycle offers significant potential benefits to operating utilities. This HTGR-GT Application Study documents the effort to evaluate the appropriateness of the HTGR-GT as an HTGR Lead Project. The scope of this effort included evaluation of the HTGR-GT technology, evaluation of potential HTGR-GT markets, assessment of the economics of commercial HTGR-GT plants, and evaluation of the program and expenditures necessary to establish HTGR-GT technology through the completion of the Lead Project.

  5. Solvent Extraction Behavior of Astatine and Radioiodine at Tracer Concentrations

    Microsoft Academic Search

    M. S. Sultana; A. Toyoshima; A. Mito; N. Takahashi; H. Baba; H. Watarai

    2000-01-01

    The solvent extraction behavior of radioioine and astatine has been investigated under various conditions in order to compare the extraction behavior of astatine with radioiodine at tracer concentration. In this study, basic tracer solutions of astatine and radioiodine were extracted into the CS2 solution under various conditions. Astatine existed as a pure species in the tracer solution and formed cationic

  6. Experimental morphology of insect olfaction: tracer studies, X-ray microanalysis, autoradiography, and immunocytochemistry with silkmoth antennae.

    PubMed

    Steinbrecht, R A

    1992-09-01

    The general morphology and methodological peculiarities of insect sensilla are briefly reviewed. The stimulus conducting pore-tubule systems of pheromone-sensitive sensilla of the silkmoths Bombyx mori and Antheraea polyphemus are described. Lipophilic tracers readily enter the hair lumen, while hydrophilic tracers do so only after prolonged extraction with lipid solvents and/or pronase. X-ray microanalysis demonstrates a high potassium content of the sensillum lymph; calcium was only found in the haemolymph above detection limit. Auxiliary cells rapidly take up radioactive leucine administered via the haemolymph. Antibodies against pheromone-binding protein of Antheraea polyphemus label the sensillum lymph of sensilla trichodea, but not of sensilla basiconica in A. polyphemus as well as in B. mori. The cytoplasm of auxiliary cells of the sensilla trichodea is also labelled. The results are discussed in context with present hypotheses on the role of sensillum lymph in stimulus transport and inactivation. PMID:1392064

  7. Feasibility study of silver iodide smoke as an atmospheric dispersion tracer for Rocky Flats Plant site, July 1983December 1984

    Microsoft Academic Search

    Langer

    1986-01-01

    At Rocky Flats Plant, we developed a technique that employs the release of silver iodide (AgI) smoke as a very economical tracer for air dispersion around the Plant. In an emergency, the AgI smoke would trace a contaminant plume over long distances, in real time, to guide emergency response. To test this technique, we experimented with first releasing AgI smoke

  8. Development of Kinetic Interface Sensitive Tracers (KIS-Tracer) for Supercritical Carbon Dioxide Injections into Deep Saline Aquifers

    NASA Astrophysics Data System (ADS)

    Schaffer, M.; Maier, F.; Licha, T.; Sauter, M.

    2012-04-01

    The storage of captured CO2 into geological formations is recently one of the most promising technologies to mitigate anthropogenic greenhouse gas emissions into the earth's atmosphere. Deep saline aquifers are considered as the most potential sequestration sites of CO2 due to their huge storage capacities of several thousand Gt. Ongoing research deals mainly with the investigation of relevant physico-chemical processes, the fate of CO2 and the risk assessment during and after supercritical CO2 (scCO2) injections. The occurring processes at the interface between injected scCO2 and formation brine play a major role to evaluate the fate and behavior of scCO2 in the reservoir. This is because the interface represents a reactive zone where numerous physico-chemical processes like dissolution of scCO2 in water as well as dissolution and precipitation of minerals take place. In most cases it is desired to maximize the interface size to increase the storage efficiency. Therefore, knowledge on interface size and dynamics would allow the observation of plume spreading and the detection of mixing or fingering effects. In order to gain this information innovative tracers are necessary which are able to quantify the temporal and spatial development of scCO2/water interfaces. As a result, it may be possible to assess the storage efficiency and to optimize subsequent injections. Up to now, such time-dependent tracers for reservoir studies are not available and limited to equilibrium tracers (known as partitioning and interfacial tracers, respectively). Therefore, novel reactive tracers (KIS-Tracers) are developed to overcome this gap. The idea is to find suitable molecules which allow the implementation of a defined chemical reaction at the interface. Due to the known kinetic constants the change of interface size can be characterized over time. The new tracer is injected together with the supercritical CO2 (scCO2) into a deep saline aquifer. Afterwards, the tracer adsorbs at the interface and undergoes hydrolysis in contact with water. As a consequence, two water soluble reaction products are formed and can be measured in the water phase over time. Here, the reaction kinetics is the rate-limiting step for the phase transfer and strongly dependents on reservoir properties, such as temperature and pH. Such tracer molecules must have the following properties: i) low polarity (high log KOW) to ensure high scCO2 solubility and to minimize distribution into the water phase; (ii) at least one highly water soluble reaction product, which does not do partitioning back into the scCO2 phase; (iii) low detection limit. On the basis of naphthalenesulfonic acid, an established geothermal tracer, different molecules with the desired properties were synthesized and tested in the laboratory. For studying the occurring processes at the interface under atmospheric pressure conditions the scCO2 was replaced with a non-polar organic solvent. The experiments were conducted in a static batch system with constant interfacial area as well as in a dynamic system with changing interface size. In parallel, a macroscopic model which couples mass transfer and reaction kinetics is developed to interpret the data. In conclusion, experiments indicate that the integration of hydrolysis kinetics is possible and even one of the reaction products may be used as additional partitioning tracer, i.e. for measuring the residual saturation.

  9. Freeze-fracture study of the epidermal cells of a teleost with particular reference to intercellular junctions and permeability to tracer.

    PubMed

    Ferri, S; Sesso, A

    1979-01-01

    The plasmatic membranes, the intercellular junctions and the intercellular spaces of the epidermis of the fish Pimelodus maculatus were studied by freeze-fracture and by lanthanum methods. The observations has confirmed the presence of desmosomes. Gap junctions were not found and the tight junctions can be seen very rarely, arranged to form small discrete maculae. The finger-print pattern due to the microridges of the apical plasma membrane of the superficial cells was studied by direct replicas. The tracer penetrates all the intercellular epidermal spaces but failed to penetrate the dermis, suggesting the presence of a barrier at the dermo-epidermal level. PMID:574691

  10. The SPECT tracer [ 123 I]ADAM binds selectively to serotonin transporters: a double-blind, placebo-controlled study in healthy young men

    Microsoft Academic Search

    Elsmarieke van de Giessen; Jan Booij

    2010-01-01

    Purpose  The tracer 123I-2-([2-({dimethylamino}methyl)phenyl]thio)-5-iodophenylamine ([123I]ADAM) has been developed to image serotonin transporters (SERTs) with SPECT. Preclinical studies have shown that [123I]ADAM binds selectively to SERTs. Moreover, initial human studies have shown that [123I]ADAM binding could be blocked by selective serotonin reuptake inhibitors (SSRIs). However, in humans it has not been proven\\u000a that [123I]ADAM binds selectively to SERTs.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  We examined the in

  11. Selection of Actinide Chemical Analogues for WIPP Tests: Potential Nonradioactive Sorbing and Nonsorbing Tracers for Study of Ion Transport in the Environment

    SciTech Connect

    Dale Spall; Robert Villarreal

    1998-08-01

    Chemical characteristics of the actinides (Th, U, Np, Pu, Am) have been studied relative to nonradioactive chemical elements that have similar characteristics in an attempt to identify a group of actinide chemical analogues that are nonradioactive. In general, the chemistries of the actinides, especially U, Np, Pu, and Am, are very complex and attempts to identify a single chemical analogue for each oxidation state were not successful. However, the rationale for selecting a group of chemical analogues that would mimic the actinides as a group is provided. The categorization of possible chemical analogues (tracers) with similar chemical properties was based on the following criteria. Categorization was studied according.

  12. Use of geochemical and isotope tracers to assess groundwater dependency of a terrestrial ecosystem: case study from southern Poland

    NASA Astrophysics Data System (ADS)

    Zurek, Anna J.; Witczak, Stanislaw; Kania, Jaroslaw; Rozanski, Kazimierz; Dulinski, Marek; Wachniew, Przemyslaw

    2015-04-01

    The presented study was aimed at better understanding of the functioning of groundwater dependent terrestrial ecosystem (GDTE) located in the south of Poland. The studied GDTE consists of a valuable forest stand (Niepolomice Forest) and associated wetland (Wielkie Bloto fen). It relies not only on shallow, unconfined aquifer but indirectly also on groundwater originating from the deeper confined aquifer, underlying the Quaternary cover and separated from it by an aquitard of variable thickness. The main objective of the study was to evaluate the contribution of groundwater to the water balance of the studied GDTE and thereby assess the potential risk to this system associated with intense exploitation of the deeper aquifer. The Wielkie B?oto fen area and the adjacent parts of Niepolomice Forest are drained by the Dluga Woda stream with 8.2 km2 of gauged catchment area. Hydrometric measurements, carried out on the Dluga Woda stream over two-year period (August 2011 - August 2013) were supplemented by chemical and isotope analyses of stream water, monitored on monthly basis. Physico-chemical parameters of the stream water (SEC, pH, Na content, Na/Cl molar ratio) and isotope tracers (deuterium, oxygen-18 and tritium) were used to quantify the expected contribution of groundwater seepage from the deeper aquifer to the water balance of the Dluga Woda catchment. The mean transit time of water through the catchment, derived from temporal variations of ?18O and tritium content in the Dluga Woda stream, was in the order of three months. This fast component of the total discharge of Dluga Woda stream is associated surface runoff and groundwater flow paths through the Quaternary cover. The slow component devoid of tritium and probably originated from the deeper Neogene aquifer is equal to approximately 30% of the total discharge. The relationships between the physico-chemical parameters of the stream water and the flow rate of Dluga Woda clearly indicate that the monitored parameters approach distinct values characteristic for groundwater in the deeper aquifer for the lowest discharge rates of the stream. These low flow rates are also accompanied by low tritium contents in the stream water. This collective evidence strongly suggest that discharge of Dluga Woda stream at low stands carries significant contribution of groundwater seeping from Neogene aquifer in the area of Wielkie Bloto fen. Modelling of long-term impact on the regional groundwater flow field of groundwater abstraction by the nearby cluster of water-supply wells suggests that temporal disappearance of stream flow during summer months may occur, with potentially severe consequences for the status of the studied GDTE. Acknowledgements. The study was supported by the GENESIS project funded by the European Commission 7FP (project contract 226536) and by statutory funds of the AGH University of Science and Technology (projects no. 11.11.220.01 and 11.11.140.026). References: Zurek A.J., Witczak S., Dulinski M., Wachniew P., Rozanski K., Kania J., Postawa A., Karczewski J., and Moscicki W.J.: Quantification of anthropogenic impact on groundwater dependent terrestrial ecosystem using geochemical and isotope tools combined with 3D flow and transport modeling, Hydrol. Earth Syst. Sci. Discuss., 11, 9671-9713, 2014

  13. Dual-tracer background subtraction approach for fluorescent molecular tomography

    PubMed Central

    Holt, Robert W.; El-Ghussein, Fadi; Davis, Scott C.; Samkoe, Kimberley S.; Gunn, Jason R.; Leblond, Frederic; Pogue, Brian W.

    2013-01-01

    Abstract. Diffuse fluorescence tomography requires high contrast-to-background ratios to accurately reconstruct inclusions of interest. This is a problem when imaging the uptake of fluorescently labeled molecularly targeted tracers in tissue, which can result in high levels of heterogeneously distributed background uptake. We present a dual-tracer background subtraction approach, wherein signal from the uptake of an untargeted tracer is subtracted from targeted tracer signal prior to image reconstruction, resulting in maps of targeted tracer binding. The approach is demonstrated in simulations, a phantom study, and in a mouse glioma imaging study, demonstrating substantial improvement over conventional and homogenous background subtraction image reconstruction approaches. PMID:23292612

  14. A study of a radon gas scrubber

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoyi; Guiseppe, Vincente E.; Mei, Dongming

    2012-03-01

    Radon gas and its progeny are critical sources of background for low background experimental devices. The required reduction of radon levels in the air of the experimental area can typically be achieved with a radon scrubbing system. For testing purposes, a single column system has been built at USD to study the radon-adsorption properties of activated charcoal under different conditions. In this paper, we will demonstrate the working principle and test results.

  15. Single-well tracer test sensitivity w. r. to hydrofrac and matrix parameters (case study for the Horstberg site in the N-German Sedimentary Basin)

    NASA Astrophysics Data System (ADS)

    Ghergut, I.; Behrens, H.; Holzbecher, E.; Jung, R.; Sauter, M.; Tischner, T.

    2012-04-01

    At the geothermal pilot site Horstberg in the N-German Sedimentary Basin, a complex field experiment program was conducted (2003-2007) by the Federal Institute for Geosciences and Natural Resources (BGR) together with the Leibniz Institute for Applied Geosciences (GGA), aimed at evaluating the performance of innovative technologies for heat extraction, for direct use, from a single geothermal well[1],[2]. The envisaged single-well operation schemes comprised inter-layer circulation through a large-area hydrofrac (whose successful creation could thus be demonstrated), and single-screen 'huff-puff' in suitable (stimulated) layers, seated in sandstone-claystone formations in 3-4 km depth, with temperatures exceeding 160 ° C. Relying on Horstberg tracer-test data, we analyze heat and solute tracer transport in three characteristic hydraulic settings: (A) single-screen, multi-layer push-pull, with spiking and sampling at lower well-screen in low-permeability sandstone layer ('Detfurth'), from which hydrofrac propagation (through several adjacent layers) was initiated; (B) single-screen, single-layer push-pull, with spiking and sampling at upper well-screen within a more permeable sandstone layer ('Solling'); (C) inter-layer vertical push through above-mentioned hydrofrac, with spiking at well-screen of A, and sampling at well-screen of B. Owing to drill-hole deviation, the hydraulically-induced frac will, in its vertical propagation, reach the upper sandstone layer in a certain horizontal distance X from the upper well-screen, whose value turns out to be the major controlling parameter for the system's thermal lifetime under operation scheme C (values of X below ~8 m leading to premature thermal breakthrough, with the minimum-target rate of fluid turnover; however, the injection pressure required for maintaining the target outflow rate will also increase with X, which renders scheme C uneconomical, or technically-infeasible, when X exceeds ~15 m). Tracer signals in C are, as well, sensitive w. r. to X, but the effects of increasing X, upon tracer signals, are largely indistinguishable from those of increasing Solling porosity. Further numerical simulations of heat and solute tracer transport in above-named test settings reveal significant disparities between parameter sensitivities attainable in the same kind of test (A, B) conducted at different layers, as well as between solute concentration and temperature signal sensitivities w. r. to transport parameters in one and the same test (C). Why? - Test A features fracture flow, and dual-continuum transport, whereas test B features single-continuum flow and transport (within the host rock, with negligible losses to the hydrofrac). Flow is rapid in test A (being fracture-dominated), but slow in test B (being confined to the host rock). In test C, fluid first flows through the hydrofrac mainly, next it 'must' flow through the upper sandstone; heat transport is dominated by matrix diffusion across the hydrofrac (along which it thus experiences strong retardation), whereas solute transport is dominated by matrix micro-fissure and intra-particle diffusion within the upper sandstone (where it experiences strong retardation). We examine the implications of these findings upon the inversion of transport-effective hydrofrac parameters from measured tracer signals, and upon the tracer-based predictability of the system's thermal lifetime under different operation schemes. [1]http://www.geothermal-energy.org/pdf/IGAstandard/SGW/2005/jung.pdf [2]http://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/2272.pdf Acknowledgement: This study is funded by MWK Niedersachsen (Lower-Saxony's Science and Culture Ministry) and by Baker Hughes (Celle) within task units 'G6' and 'G7' of the Collaborative Research Project 'gebo' (Geothermal Energy and High-Performance Drilling).

  16. Tracer attenuation in groundwater

    NASA Astrophysics Data System (ADS)

    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.

  17. Gas Gun Studies of Interface Wear Effects

    NASA Astrophysics Data System (ADS)

    Jackson, Tyler; Kennedy, Greg; Thadhani, Naresh

    2011-06-01

    The characteristics of interface wear were studied by performing gas gun experiments at velocities up to 1 km/s. The approach involved developing coefficients of constitutive strength models for Al 6061 and OFHC-Cu, then using those to design die geometry for interface wear gas gun experiments. Taylor rod-on-anvil impact experiments were performed to obtain coefficients of the Johnson-Cook constitutive strength model by correlating experimentally obtained deformed states of impacted samples with those predicted using ANSYS AUTODYN hydrocode. Simulations were used with validated strength models to design geometry involving acceleration of Al rods through a copper concentric cylindrical angular extrusion die. Experiments were conducted using 7.62 mm and 80 mm diameter gas guns. Differences in the microstructure of the interface layer and microhardness values illustrate that stress-strain conditions produced during acceleration of Al through the hollow concentric copper die, at velocities less than 800 m/s, result in formation of a layer via solid state alloying due to severe plastic deformation, while higher velocities produce an interface layer consisting of melted and re-solidified aluminum.

  18. Tracer tomography: design concepts and field experiments using heat as a tracer.

    PubMed

    Doro, Kennedy O; Cirpka, Olaf A; Leven, Carsten

    2015-04-01

    Numerical and laboratory studies have provided evidence that combining hydraulic tomography with tomographic tracer tests could improve the estimation of hydraulic conductivity compared with using hydraulic data alone. Field demonstrations, however, have been lacking so far, which we attribute to experimental difficulties. In this study, we present a conceptual design and experimental applications of tracer tomography at the field scale using heat as a tracer. In our experimental design, we improve active heat tracer testing by minimizing possible effects of heat losses, buoyancy, viscosity, and changing boundary conditions. We also utilize a cost-effective approach of measuring temperature changes in situ at high resolution. We apply the presented method to the 8?m thick heterogeneous, sandy gravel, alluvial aquifer at the Lauswiesen Hydrogeological Research Site in Tübingen, Germany. Results of our tomographic heat-tracer experiments are in line with earlier work on characterizing the aquifer at the test site. We demonstrate from the experimental perspective that tracer tomography is applicable and suitable at the field scale using heat as a tracer. The experimental results also demonstrate the potential of heat-tracer tomography as a cost-effective means for characterizing aquifer heterogeneity. PMID:25393211

  19. 20 CFR 718.105 - Arterial blood-gas studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Arterial blood-gas studies. 718.105 Section 718.105...Development of Medical Evidence § 718.105 Arterial blood-gas studies. (a) Blood-gas studies are performed to detect an...

  20. 20 CFR 718.105 - Arterial blood-gas studies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Arterial blood-gas studies. 718.105 Section 718.105...Development of Medical Evidence § 718.105 Arterial blood-gas studies. (a) Blood-gas studies are performed to detect an...

  1. A Study of a Radon Gas Scrubber

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoyi; Schmitz, Andrew; Guiseppe, Vincente; Mei, Dongming

    2011-04-01

    Radon gas and its progeny are critical source of background for low background experimental devices. The required reduction of radon levels in air of the experimental area can typically be achieved with a radon scrubbing system. Various designs and techniques are commonly adopted in building a radon scrubber. For testing purpose, a single column system has been built at USD to study the radon-adsorption properties of activated charcoal. In this paper, we will demonstrate the working principle and test results. This work is supported by the NSF Grant PHY-0758120.

  2. Tracer mixing at fracture intersections

    SciTech Connect

    Li, Guomin

    2001-02-10

    Discrete network models are one of the approaches used to simulate a dissolved contaminant, which is usually represented as a tracer in modeling studies, in fractured rocks. The discrete models include large numbers of individual fractures within the network structure, with flow and transport described on the scale of an individual fracture. Numerical simulations for the mixing characteristics and transfer probabilities of a tracer through a fracture intersection are performed for this study. A random-walk, particle-tracking model is applied to simulate tracer transport in fracture intersections by moving particles through space using individual advective and diffusive steps. The simulation results are compared with existing numerical and analytical solutions for a continuous intersection over a wide range of Peclet numbers. This study attempts to characterize the relative concentration at the outflow branches for a continuous intersection with different flow fields. The simulation results demonstrate that the mixing characteristics at the fracture intersections are a function not only of the Peclet number but also of the flow field pattern.

  3. Tracer studies to characterize the effects of roadside noise barriers on near-road pollutant dispersion under varying atmospheric stability conditions

    NASA Astrophysics Data System (ADS)

    Finn, Dennis; Clawson, Kirk L.; Carter, Roger G.; Rich, Jason D.; Eckman, Richard M.; Perry, Steven G.; Isakov, Vlad; Heist, David K.

    2010-01-01

    A roadway toxics dispersion study was conducted at the Idaho National Laboratory (INL) to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The homogeneous fetch of the INL, controlled emission source, lack of other manmade or natural flow obstructions, and absence of vehicle-generated turbulence reduced the ambiguities in interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF 6) from two 54 m long line sources, one for an experiment with a 90 m long noise barrier and one for a control experiment without a barrier. Simultaneous near-surface tracer concentration measurements were made with bag samplers on identical sampling grids downwind from the line sources. An array of six 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of higher concentrations and the absolute magnitudes of the concentrations both increased as atmospheric stability increased; (2) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same relative locations on the control experiment at all atmospheric stabilities; (3) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (4) the barrier tended to trap high concentrations near the "roadway" (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.

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

    NASA Astrophysics Data System (ADS)

    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 correlation between (early) tracer signals and (later) thermal breakthrough can be re-established. Thus, thermosensitive tracers are indispensable for predicting thermal breakthrough, in such geothermal reservoirs whose 'hydrogeological personality' is given by a finite set of fractures, with flow occurring both across and along the fractures. In terms of the 'gebo benchmark-model' typology investigated by Hördt et al. (2011) [http://eposters.agu.org/abstracts/models-of-geothermal-reservoirs-as-a-basis-for-interdisciplinary-cooperation/] , such systems combine flow and transport patterns of the 'petrothermal' type and of the so-called 'deep-aquifer' type: across the fractures, heat is travelling faster than conservative-solute tracers; along the fractures, conservative-solute tracers experience much less retardation by transversal exchange (matrix diffusion), than heat; fluid (and tracer) flow is not limited to the fractures; matrix flow yields essential contribution to prolonging the fluid (and tracer) residence time. Thermal lifetime results from the opposite effects of fracture aperture as an: advection-related parameter: fluid travel time increases with increasing fracture aperture advection-unrelated parameter: fracture - matrix exchange rate increases with decreasing fracture aperture, which accelerates transport across the fracture, but retards transport along the fracture. In conservative-solute tracer signals, all these fracture aperture effects on tracer transport are masked by the very long residence time associated with the matrix flow component. Thermosensitive tracers are able to 'magnify' the visibility of fracture aperture effects against matrix flow effects. Acknowledgment: This study benefits from thermosensitive-tracer research conducted within the projects Smart Tracers and LOGRO, funded by the German Ministry for Environment, Nature Conservation and Nuclear Safety (BMU, 0327579 and 0325111B) and by Energie Baden-Württemberg (EnBW).

  5. Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

    USGS Publications Warehouse

    Shapiro, Stephanie D.; Plummer, L. Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.; Runkle, Donna L.

    2012-01-01

    Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N2, O2, Ar, CH4, and CO2) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N2-Ar-based) where available. The N2-Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N2-Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages compiled in this report are provided as a consistent means of reporting the tracer data. The tracer-based piston-flow ages may provide an initial interpretation of age in cases in which mixing is minimal and may aid in developing a basic conceptualization of groundwater age in an aquifer. These interpretations are based on the assumption that tracer transport is by advection only and that no mixing occurs. In addition, it is assumed that other uncertainties are minimized, including tracer degradation, sorption, contamination, or fractionation, and that terrigenic (natural) sources of tracers, and spatially variable atmospheric tracer concentrations are constrained.

  6. A Study of the Mechanism of Corrosion of Some Ferritic Steels in High Pressure Carbon Dioxide with the Aid of Oxygen18 as a Tracer II. High Silicon Mild Steel

    Microsoft Academic Search

    C. Gleave; J. M. Calvert; D. G. Lees; P. C. Rowlands

    1982-01-01

    The oxidation mechanisms of a high-silicon mild steel (a fully killed steel) in high pressure (4.1 MPa) CO_2 at 773 K have been investigated with the aid of 18O as a tracer. In the protective region of oxidation oxide formation occurred at the oxide-gas interface, within the scale and possibly also at the oxide-metal interface. The oxide growth within the

  7. OH as a Tracer for Molecular Gas in the Galaxy: Line Ratios and Signatures of non-LTE Findings in the ISM

    NASA Astrophysics Data System (ADS)

    Engelke, Philip; Allen, Ronald J.; Hogg, David E.

    2015-01-01

    While carrying out a blind survey of OH emission in a quiescent region towards the outer galaxy near l = 105 degrees, b = 1 degree using the Green Bank Telescope, we analyzed the ratios of the line strengths and identified several non-LTE emission sources in addition to the majority that were in LTE. The fact that the majority of OH features were in LTE ratios suggests that in general, OH can be a useful tracer for components of the molecular ISM that may not be traced by CO. However, the several non-LTE OH features observed demonstrate that such a blind survey can also be put to other uses. One of the non-LTE features was identified as a known OH-IR star, which we found could be easily identified with 1665 and 1667 MHz spectra alone, even though OH-IR stars are most prominent in 1612 MHz. We also identified several 1720 MHz masers features in the local ISM, which were found at adjacent positions in the sky along an arc shape. These masers are likely to be tracing a C-shock propagating through the local ISM, covering several survey positions.

  8. Use of radioactive tracers in the evaluation of penile hemodynamics: history, methodology and measurements

    Microsoft Academic Search

    LS Zuckier

    1997-01-01

    Radionuclide tracer techniques are intimately associated with some of the early ground-breaking investigations in erectile dysfunction and have evolved along with the field. At the present time, the various investigations can be grouped into four categories: labeled blood-pool; tracer washout; tracer washin and combined blood-pool\\/tracer and tracer washout examinations. Blood pool studies are most useful in assessing the integrity of

  9. Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence

    E-print Network

    Schmidt, Matthias

    Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence Angela Busse; accepted 7 November 2007; published online 13 December 2007 Magnetohydrodynamic MHD turbulence is studied

  10. Isotopic Tracer Study of Hydraulic Transfer Between Native Woody Shrubs and Associated Annual Crops Under Dry Conditions in the Sahel

    NASA Astrophysics Data System (ADS)

    Bogie, Nathaniel; Bayala, Roger; Diedhiou, Ibrahima; Fogel, Marilyn; Dick, Richard; Ghezzehei, Teamrat A.

    2015-04-01

    Erratic precipitation at the beginning and end of the rainy season combined with short drought periods during the cropping season pose a major challenge for rain-fed agriculture and food security in the Sahel. Research has shown that intercropping annual crops with native evergreen woody shrubs in Senegal can greatly increase crop productivity. Hydraulic redistribution (HR), or the diurnal rewetting of dry soil by the pathway of the root system that extends into wetter soil has been found in many plants and climates worldwide. The HR pathway could be a factor in Senegal where water provided by shrubs aids crop growth during dry periods but this has not been confirmed. Therefore, the objective was to determine the ability of shrubs to provide water to millet plants using the deuterium tracer. Penisetum glaucum (Pearl Millet) was grown in association with the native woody shrub Guiera senegalensis under drip irrigation until 68 days after sowing, followed by a with holding of water during late flowering and early grain-filling stage. Within 10 days the soils in the stressed plots became extremely dry with water potentials ranging from -0.5 Mpa to -3.0 Mpa at 20cm depth. Twenty days after the initiation of water stress, vials of isotopically enriched deuterium tracer was sealed around cut roots of three separate shrubs at a depth of 1.0 m followed by sampling of aboveground tissue from injection shrubs and closely growing crop plants over a period of five days. Using cryogenic vacuum distillation, plant water samples were extracted from plant tissue. With lab work completed on two replications, a highly enriched deuterium signal was observed in the tissue water of the shrub beginning twelve hours after the injection. In the same replication thirty-six hours after the beginning of injection, a highly enriched pulse of deuterium in the crop growing directly adjacent to the injection shrub was observed. In a concurrent injection to a nearby shrub under much drier conditions, slight pulses of enrichment were found in the shrub and crop, though with much lower magnitudes. Although this was a simulated drought experiment, we were able to recreate conditions similar to those experienced at this site under rain-fed conditions, where the presence of drought is a constant threat at the beginning and the end of the season. These findings support the hypothesis that there is transfer of hydraulically lifted water from native woody shrubs to annual food crops in the region.

  11. Sedimentation, bioturbation, and sedimentary fabric evolution on a modern mesotidal mudflat: A multi-tracer study of processes, rates, and scales

    NASA Astrophysics Data System (ADS)

    Bentley, Samuel J.; Swales, Andrew; Pyenson, Benjamin; Dawe, Justin

    2014-03-01

    A study of muddy tidal-flat sedimentation and bioturbation was undertaken in the Waitetuna Arm of Raglan Harbor, New Zealand, to evaluate the physical and biological processes that control cycling of sediment between the intertidal seabed and sediment-water interface, and also the formation of tidal flat sedimentary fabric and fine-scale stratigraphy. Cores were collected along an intertidal transect, and analyzed for sedimentary fabric, 210Pb and 7Be radiochemical distributions, and grain size. At the same locations, a new approach for time-series core-X-radiography study was undertaken (spanning 191 days), using magnetite-rich sand as a tracer for sedimentation and bioturbation processes in shallow tidal flat sediments. Sedimentary fabric consists of a shallow stratified layer overlying a deeper zone of intensely bioturbated shelly mud. Bioadvection mixes the deeper zone and contributes fine sediment to the surface stratified layer, via biodeposition. Physical resuspension and deposition of surface muds by wave and tidal flow are also likely contributors to formation of the surficial stratified layer, but physical stratification is not observed below this depth. The deliberate tracer study allowed calculation of bioadvection rates that control strata formation, and can be used to model diagenetic processes. Results suggest that the upper ˜15 cm of seabed can be fully mixed over timescales <1.75 y. Such mixing will erase pre-existing sedimentary fabric and transport buried sediment and chemical compounds back to the tidal-flat surface. Shallow biodiffusion also exists, but produces much slower and shallower mass transport. Best fits for 210Pb profiles using a diagenetic bioadvection/sedimentation model and independently measured tiered bioadvection rates suggest that sediment accumulation rates (SARs) on the tidal flat are ˜0.25 cm/y, near the low end of contemporary New Zealand muddy intertidal SARs. Frequent deposition and erosion of the surface layer demonstrates that long-term sediment accumulation captures only a small fraction of sediment deposited at any one time. Model results also suggest that our magnetite tracer method may slightly underestimate short-term shallow mixing rates (demonstrated by 7Be profiles), and slightly overestimate longer-term, deeper bioturbation rates (demonstrated by 210Pb profiles).

  12. DETECTION OF HIGH MOLECULAR WEIGHT ORGANIC TRACERS IN VEGETATION SMOKE SAMPLES BY HIGH-TEMPERATURE GAS CHROMATOGRAPHY-MASS SPECTROMETRY. (R823990)

    EPA Science Inventory

    High-temperature high-resolution gas chromatography (HTGC) is an established technique for the separation of complex mixtures of high molecular weight (HMW) compounds which do not elute when analyzed on conventional GC columns. The combination of this technique wit...

  13. GAS COOLED, MOLTEN SALT HEAT EXCHANGER--DESIGN STUDY

    Microsoft Academic Search

    MacPherson

    1958-01-01

    BS> One of the major problems in the economic evaluation of the ; application of forced circulation, gas cooling to high temperature, molten salt ; power reactor systems is the definition of the required heat transfer equipment, ; its size and operating cost. A design study of the saltto-gas heat exchangers ; for such a gas-cooled system has recently been

  14. Polarization Optimization for Laser Polarized Noble Gas MR Studies

    Microsoft Academic Search

    K. P. Coulter; M. S. Rosen; R. C. Welsh; S. D. Swanson; T. E. Chupp

    1996-01-01

    The efficacy of laser polarized noble gas Magnetic Resonance (MR) imaging and spectroscopy depends critically on the ability to produce large magnetizations of the gases used. While signal size is directly related to both the polarization and concentration of the gas, sufficient volumes of gas can also allow studies to be done which examine the time dependence of the biological

  15. Ionized Gas in Damped Lyman-alpha Systems and Its Effects on Elemental Abundance Studies

    E-print Network

    J. Christopher Howk; Kenneth R. Sembach

    1999-07-29

    Recent high-resolution observations of metal absorption lines in high-redshift damped Ly-alpha systems have shown that Al III, a tracer of moderately-ionized gas, very often has a velocity structure indistinguishable from that of low-ionization gas. Regions of ionized and neutral hydrogen in these systems are likely cospatial. The higher-ionization Si IV and C IV absorption shows a much weaker or non-existent correlation with the low ionization material, implying that the regions traced by Al III are photoionized by a soft (stellar) spectrum, by a hard (power law) spectrum with a very low ionization parameter, or a combination of both. We discuss the ionization of the damped Ly-alpha systems and use photoionization equilibrium models to make quantitative estimates of its effects on abundance studies in these systems. We show that ionization effects may be large enough to account for the observed dispersion in absolute metal abundances in damped Ly-alpha systems, causing systematically higher abundances in lower column density systems. The observed Si^+/Fe^+ and Zn^+/Cr^+ ratios may systematically overestimate the intrinsic Si/Fe and Zn/Cr ratios, respectively, if ionized gas is present in these systems, thereby mimicking the effects of alpha-element enrichment or dust depletion.

  16. Studies of a Dual Noble Gas Maser

    Microsoft Academic Search

    R. E. Stoner; D. Bear; E. R. Oteiza; R. L. Walsworth; M. A. Rosenberry; T. E. Chupp

    1996-01-01

    The dual noble gas maser (DNGM) supports the simultaneous, active maser oscillation of co-habitating ensembles of ^129Xe and ^3He gas operating on their nuclear spin-1\\/2 Zeeman transitions. Population inversions for the ^129Xe and ^3He masers are created by spin-exchange collisions between the noble gas atoms and laser-optically-pumped rubidium vapor. We will describe ongoing development of a second-generation DNGM at the

  17. Tracers in vascular casting resins enhance backscattering brightness.

    PubMed

    Schraufnagel, Dean E; Ganesan, Dhanalakshmi P

    2002-01-01

    Studying cast microvasculature with scanning electron microscopy has expanded our knowledge of many circulations, but need arises to determine the blood source of vascular beds that are supplied by two circulations. One way to do this is to mark the casting resin by adding a tracer compound that can be detected in the scanning electron microscope. A potential method of distinguishing different substances is to detect the backscattered electrons that are emitted from the tracer if the tracer is a heavier element, because heavier elements backscatter more electrons. To explore different tracers, we tested lead, titanium, iron, osmium, and uranium as solutions of different polarity and powders. The tracers were added to 1 ml of methyl methacrylate in log concentrations. Shrinkage, hardness, cast quality, and change in brightness from the tracer were compared with multivariate analysis at scanning electron microscopic working distances of 15 and 39 mm on carbon-coated and uncoated specimens. Several concentrations caused sedimentation of the tracer and prevented the resin from solidifying. Tetraethyl lead shortened the hardening time: uranyl acetate and osmium tetroxide prolonged it. Most tracers decreased shrinkage. When lead citrate and Reynolds solutions were removed, the brightness correlated with increasing atomic number, concentration of the tracer, and mean atomic number of the specimen (p <0.0001). The substances that increased contrast most were tetraethyl lead and uranium. Backscattering electron detection can distinguish methacrylate casts that have small amounts of heavier elements added to them, but an optimal tracer has not yet been established. PMID:12074492

  18. Results from air-injection and tracer testing in the upper Tiva Canyon, Bow Ridge Fault, and upper Paintbrush contact alcoves of the Exploratory Studies Facility, August 1994 through July 1996, Yucca Mountain, Nevada

    USGS Publications Warehouse

    LeCain, Gary D.

    1998-01-01

    Air-injection and tracer testing were conducted in the upper Tiva Canyon, Bow Ridge Fault, and upper Paintbrush contact alcoves in the Exploratory Studies Facility at Yucca Mountain, Nevada, from August 1994 to July 1991. The study was conducted by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy.

  19. Synthesis and Evaluation of 15-(4-(2-[18F]Fluoroethoxy)phenyl)pentadecanoic Acid: a Potential PET Tracer for Studying Myocardial Fatty Acid Metabolism

    PubMed Central

    Tu, Zhude; Li, Shihong; Sharp, Terry L.; Herrero, Pilar; Dence, Carmen S.; Gropler, Robert J.; Mach, Robert H.

    2010-01-01

    15-(4-(2-[18F]fluoroethoxy)phenyl)pentadecanoic acid ([18F]7) was synthesized as a PET probe for assessing myocardial fatty acid metabolism. The radiosynthesis of [18F]7 was accomplished using a two step reaction, starting with the corresponding tosylate ester, methyl 15-(4-(2-(tosyloxy)ethoxy)phenyl)pentadecanoate (5) and gave the radiolabeled fatty acid, [18F]7 in a radiolabeling yield of 55 – 60% and a specific activity of > 2,000 Ci/mmol (decay corrected to EOB). The biological evaluation of [18F]7 in rats displayed high uptake in heart (1.94%.ID/g at 5 min), which was higher than the uptake (%ID/g) in blood, lung, muscle, pancreas and brain. MicroPET studies of [18F]7 in Sprague-Dawley rats demonstrated excellent images of the myocardium when compared with [11C]palmitate images in the same animal. Moreover, the tracer kinetics of [18F]7 paralleled those seen with [11C]palmitate, with an early peak followed by biphasic washout. When compared to [11C]palmitate, [18F]7 exhibited a slower early clearance (0.17 ± 0.01 vs. 0.30 ± 0.02, P < 0.0001) and a significantly higher late clearance (0.0030 ± 0.0005 vs. 0.0006 ± 0.00013, P < 0.01). These initial studies suggest that [18F]7 could be a potentially useful clinical PET tracer to assess abnormal myocardial fatty acid metabolism. PMID:21070001

  20. Neurotoxicity after intracarotid 1,3-bis(2-chloroethyl)-1-nitrosourea administration in the rat: Hemodynamic changes studied by double-tracer autoradiography

    SciTech Connect

    Nagahiro, S.; Yamamoto, Y.L.; Diksic, M.; Mitsuka, S.; Sugimoto, S.; Feindel, W. (Cone Laboratory for Neurosurgical Research, Montreal Neurological Institute, Quebec (Canada))

    1991-07-01

    Changes in blood-brain (BBB) permeability and local cerebral blood flow after intracarotid administration of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) were examined quantitatively in rats with double-tracer autoradiography using (14C)alpha-amino-isobutyric acid and (18F)fluoroantipyrine. Forty-eight female Wistar rats were divided into four groups. The control group (Group 1) received 1 ml of 5% dextrose. The other three groups received three different doses of BCNU dissolved in 5% dextrose: Group 2 rats received 1 mg, Group 3 3 mg, and Group 4 10 mg. The tracer study was performed on Day 1 or Days 4 to 12 after intracarotid administration of BCNU. In 11 rats in Group 2, there were no changes of BBB permeability. Transient BBB permeability changes were seen in the striatum or hippocampus in 3 of the 5 rats (60%) in Group 3 within 24 hours. In 8 of 9 rats (89%) in the same group, late BBB permeability changes were observed in the hypothalamus with or without histological changes. BBB permeability changes were seen in all rats of Group 4. Focal increase of local cerebral blood flow on the infused side compared with the non-infused side of the brain was observed, although not at a significant level, in 5 of 25 rats examined with (18F)fluoroantipyrine. The results of BBB permeability and histological examinations and study of heterogenous distribution by (18F)fluorodeoxyglucose indicated that the ipsilateral subcortical structures such as the hypothalamus, amygdala, internal capsule, and caudate putamen have the highest incidence of neurotoxicity, which are closely related to histopathological damage seen in human BCNU leucoencephalopathy.

  1. Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Willis, Ron J.

    1992-01-01

    Past research and applications have demonstrated the advantages and usefulness of lidar detection of a single fluorescent tracer to track air motions. Earlier researchers performed an analytical study that showed good potential for lidar discrimination and tracking of two or three different fluorescent tracers at the same time. The present paper summarizes the multiple fluorescent tracer method, discusses its expected advantages and problems, and describes our field test of this new technique.

  2. An analytical solution for slug tracer tests in fractured reservoirs

    Microsoft Academic Search

    Chao Shan; Karsten Pruess

    2005-01-01

    The transport of chemicals or heat in fractured reservoirs is strongly affected by the fracture-matrix interfacial area. Under unsaturated conditions, such as in vapor-dominated geothermal reservoirs, this area can be estimated from inert gas tracer tests that produce a characteristic tail in tracer breakthrough curves (BTCs). For water-saturated conditions, molecular diffusion is orders of magnitude smaller, and tails in BTCs

  3. NEXT GENERATION GAS TURBINE (NGGT) SYSTEMS STUDY

    SciTech Connect

    Unknown

    2001-12-05

    Building upon the 1999 AD Little Study, an expanded market analysis was performed by GE Power Systems in 2001 to quantify the potential demand for an NGGT product. This analysis concluded that improvements to the US energy situation might be best served in the near/mid term (2002-2009) by a ''Technology-Focused'' program rather than a specific ''Product-Focused'' program. Within this new program focus, GEPS performed a parametric screening study of options in the three broad candidate categories of gas turbines: aero-derivative, heavy duty, and a potential hybrid combining components of the other two categories. GEPS's goal was to determine the best candidate systems that could achieve the DOE PRDA expectations and GEPS's internal design criteria in the period specified for initial product introduction, circa 2005. Performance feasibility studies were conducted on candidate systems selected in the screening task, and critical technology areas were identified where further development would be required to meet the program goals. DOE PRDA operating parameters were found to be achievable by 2005 through evolutionary technology. As a result, the study was re-directed toward technology enhancements for interim product introductions and advanced/revolutionary technology for potential NGGT product configurations. Candidate technologies were identified, both evolutionary and revolutionary, with a potential for possible development products via growth step improvements. Benefits were analyzed from two perspectives: (1) What would be the attributes of the top candidate system assuming the relevant technologies were developed and available for an NGGT market opportunity in 2009/2010; and (2) What would be the expected level of public benefit, assuming relevant technologies were incorporated into existing new and current field products as they became available. Candidate systems incorporating these technologies were assessed as to how they could serve multiple applications, both in terms of incorporation of technology into current products, as well as to an NGGT product. In summary, potential program costs are shown for development of the candidate systems along with the importance of future DOE enabling participation. Three main conclusions have been established via this study: (1) Rapid recent changes within the power generation regulatory environment and the resulting ''bubble'' of gas turbine orders has altered the timing and relative significance associated with the conclusions of the ADL study upon which the original DOE NGGT solicitation was based. (2) Assuming that the relevant technologies were developed and available for an NGGT market opportunity circa 2010, the top candidate system that meets or exceeds the DOE PRDA requirements was determined to be a hybrid aero-derivative/heavy duty concept. (3) An investment by DOE of approximately $23MM/year to develop NGGT technologies near/mid term for validation and migration into a reasonable fraction of the installed base of GE F-class products could be leveraged into $1.2B Public Benefit, with greatest benefits resulting from RAM improvements. In addition to the monetary Public Benefit, there is also significant benefit in terms of reduced energy consumption, and reduced power plant land usage.

  4. Use of environmental tracers to study the chemical evolution of shallow ground water in a karst area of northern Florida

    SciTech Connect

    Katz, B.G. (Geological Survey, Tallahassee, FL (United States)); Plummer, L.N.; Busenberg, E. (Geological Survey, Reston, VA (United States))

    1993-03-01

    The pathways of shallow ground-water flow in poorly confined aquifer systems of northern FL are influenced by inflow to and outflow from numerous sinkhole lakes that are characteristic of the Sand Hills karst region. Ground-water samples were collected immediately upgradient and downgradient from Lake Barco at depths of 1.6--29 m below the water table from observation wells completed in the surficial aquifer system, the intermediate confining unit (icu), and the Upper Floridan aquifer. Samples were also collected of rainfall, lake water, and ground water at a depth of 4.1 m beneath the lake bottom. The environmental tracers tritium and chlorofluorocarbons were used to estimate mean residence times of water and rates of chemical mass transfer along flow paths. Water samples collected from wells upgradient of the lake were oxic and had CFC-model recharge dates between 1971 and 1986. The content of delta H-2 and delta O-18 of water from the two aquifer systems and the icu was nearly identical to the isotopic composition of rainfall. Changes in the chemical composition of the ground water with depth were simulated by reacting rainfall with minerals and dissolved gases that exist in the hydrogeologic units. Ground-water samples collected from sites beneath and downgradient of the lake were anoxic, with measured concentrations of hydrogen sulfide and methane ranging from 0.02--0.58 mg/l and 0.30--6.1 mg/l, respectively. CFC-model recharge dates ranged from 1956 to 1983. The data indicated that ground water downgradient of the lake is being recharged by leakage of lake water. The chemical composition of ground water is influenced by the movement of lake water through reducing, organic-rich sediments accumulated at the bottom. Along the downgradient flow paths, the water chemistry evolves from the composition of lake water and is modified by subsequent reactions including reduction of sulfate and ferric iron, methanogenesis, and dissolution and precipitation of minerals.

  5. Ultraviolet studies of the interstellar gas

    NASA Technical Reports Server (NTRS)

    Spitzer, L., Jr.; Jenkins, E. B.

    1975-01-01

    Sounding-rocket and satellite UV observations of interstellar gas clouds are reviewed with major attention given to Copernicus observations of interstellar absorption lines. Analysis of typical absorption-line data is outlined, and observations are reviewed for atomic hydrogen as well as interstellar H2, HD, and CO molecules. Investigations of atomic abundances in H I regions are summarized, measurements of atomic deuterium abundances in the interstellar gas are examined, and the properties of ionized interstellar gas are described. Theoretical analyses of the physical state of the interstellar gas are summarized with respect to ionization by energetic radiation, cool H I clouds, and the intercloud medium. The data obtained thus far are shown to indicate mean temperatures of about 80 K, particle densities between 10 and 1000 per cu cm, and a depletion of heavy elements that becomes greatly enhanced with increasing condensation temperature for those H I regions with strong H2 lines.

  6. HST/COS detection of a Ne VIII absorber towards PG 1407+265: An unambiguous tracer of collisionally ionized hot gas?

    E-print Network

    Hussain, Tanvir; Narayanan, Anand; Srianand, Raghunathan; Wakker, Bart P; Charlton, Jane C; Pathak, Amit

    2014-01-01

    We report the detection of Ne VIII in a z_abs = 0.59961 absorber towards the QSO PG 1407+265 (z_em = 0.94). Besides Ne VIII, absorption from HI Lyman series lines (HI 1025 - 915), several other low (C II, N II, O II, and S II), intermediate (C III, N III, N IV, O III, S IV, and S V) and high (S VI, O VI, and Ne VIII) ionization metal lines are detected. Disparity in the absorption line kinematics between different ions implies that the absorbing gas comprises of multiple ionization phases. The low and the intermediate ions (except S V) trace a compact (~ 410 pc), metal-rich (Z ~ Z_sun) and over-dense (log n_H ~ -2.6) photoionized region that sustained star-formation for a prolonged period. The high ions, Ne VIII and O VI, can be explained as arising in a low density (-5.3 Z_sun) and diffuse (~ 180 kpc) photoionized gas. The S V, S VI and C IV (detected in the FOS spectrum) require an intermediate photoionization phase with -4.2 < log n_H < -3.5. Alternatively, a pure collisional ionization model, as us...

  7. Evaluation of C-14 as a natural tracer for injected fluids at theAidlin sector of The Geysers geothermal system through modeling ofmineral-water-gas Reactions

    SciTech Connect

    Dobson, Patrick; Sonnenthal, Eric; Lewicki, Jennifer; Kennedy, Mack

    2006-06-01

    A reactive-transport model for 14C was developed to test its applicability to the Aidlin geothermal system. Using TOUGHREACT, we developed a 1-D grid to evaluate the effects of water injection and subsequent water-rock-gas interaction on the compositions of the produced fluids. A dual-permeability model of the fracture-matrix system was used to describe reaction-transport processes in which the permeability of the fractures is many orders of magnitude higher than that of the rock matrix. The geochemical system included the principal minerals (K-feldspar, plagioclase, calcite, silica polymorphs) of the metagraywackes that comprise the geothermal reservoir rocks. Initial simulation results predict that the gas-phase CO2 in the reservoir will become more enriched in 14C as air-equilibrated injectate water (with a modern carbon signature) is incorporated into the system, and that these changes will precede accompanying decreases in reservoir temperature. The effects of injection on 14C in the rock matrix will be lessened somewhat because of the dissolution of matrix calcite with ''dead'' carbon.

  8. Tracer for circulation determinations

    SciTech Connect

    Moore, H.; Santos, S.; Wysong, R. D.

    1985-03-19

    An improved tracer particle is described comprising an ion exchange core having a polymer coating thereon, the coated ion exchange core having a reaction site capable of reacting with a compound containing an oxirane group, said coated ion exchange core having been treated with a compound containing an oxirane group to react with said coated ion exchange core causing an increase in mass of the tracer particle. Preferably, the ion exchange core is labelled with a radionuclide. These particles have improved characteristics including improved stability against leaching and improved handling properties. Such particles are useful in circulatory determinations involving the injection of the particles as a suspension in a physiologically acceptable carrier or medium into the circulatory system of animals.

  9. Isotopes and Tracers

    NSDL National Science Digital Library

    Thomas Meixner

    This assignment offers students several problems that help them understand the basic of mixing models and their use in understanding the controls on water quality in the environment. The purpose of the assignment is to help students integrate across the various topics in environmental chemistry in the context of flow and transport. Students will hopefully learn how reactive and non-reactive tracers can be used in conjunction to fully understand a chemical system.

  10. An integrated study of nutrient leaching and greenhouse gas emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrient leaching and greenhouse gas emission are two of the primary environmental impacts of crop production. These processes have been studied at great length separately, but few integrated studies of leaching and greenhouse gas emission have been conducted. We measured nutrient leaching and green...

  11. Analysis of multicomopnent groundwater flow in karst aquifer by CFC, tritium, tracer test and modelling, case study at Skaistkalnes vicinity, Latvia

    NASA Astrophysics Data System (ADS)

    Bikshe, Janis; Babre, Alise; Delina, Aija; Popovs, Konrads

    2014-05-01

    Groundwater in karst environments tends to have difficulties to distinguish multiple flows if several sources of water are present. Skaistkalne vicinity faces with such situation where old groundwater, fresh groundwater and inflow from river Iecava occurs. Attempts were made to distinguish groundwater residence time of multiple components of water applying CFC and tritium dating techniques supplied by tracer test and numerical model of study area. Study area covers territory between two rivers Iecava and Memele with water level difference of 7 meters and horizontal distance of 2.2 kilometres between both. Study area consists of karst affected Devonian gypsum and carbonaceous rocks covered by Quaternary low to high permeable deposits. Confined groundwater at depth of 10-25 meters where analysed by CFC's and tritium. At this depth groundwater exhibits anoxic reducing environment that has caused degradation of CFC's at similar degree in all samples. Taking it into account, mean residence time based on CFC piston flow model is 22 - 42 years and 28 - 34 years based on binary mixing model. Tritium results show signs of incensement of groundwater residence time towards discharge area. CFC combined with tritium proved increased vertical velocity in middle part between the rivers likely caused by hydrogeological window in Quaternary deposits created by karst processes. Numerical model (Delina et al. 2012) was applied and calculations yielded groundwater flow velocity rate at 0.3 - 1 m/day in area between the rivers. Investigation of CFC data resulted in possible groundwater flow rate of at a minimum of 0.2 m/day although it's not applicable to all sampled wells due to specific hydrogeological conditions. Tracer test was made between the rivers in order to distinguish main water flow paths and flow velocity. Results showed that very high permeable conduits connect rivers and karst lakes with velocity rates of 800 - 1300 m/day. Complex investigation leads to conclude that three different sources of groundwater occur characterized by different flow velocity, recharge age and chemical composition. Although CFC's has been degraded, it is possible to use the results to distinguish groundwater different components and even to estimate groundwater flow velocity because of near located recharge and discharge areas. Tritium results doesn't show considerable variations along flow path with 6 TU in average confirming conclusions based on CFC's. Tracer test approve very high groundwater velocity zones in study area that supposedly doesn't mix with groundwater in matrix. References Delina A., Babre A., Popovs K., Sennikovs J., Grinberga B. 2012. Effects of karst processes on surface water and groundwater hydrology at Skaistkalne vicinity, Latvia. - Hydrology Research, 43(4), IWA Publishing, pp. 445-459, doi:10.2166/nh.2012.123. This study is supported by ERAF project Nr. 1013/00542DP/2.1.1.1.0/13/APIA/VIAA/007

  12. Study the gas sensing properties of boron nitride nanosheets

    SciTech Connect

    Sajjad, Muhammad; Feng, Peter, E-mail: p.feng@upr.edu

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized boron nitride nanosheets (BNNSs) on silicon substrate. • We analyzed gas sensing properties of BNNSs-based gas-sensor device. • CH{sub 4} gas is used to measure gas-sensing properties of the device. • Quick response and recovery time of the device is recorded. • BNNSs showed excellent sensitivity to the working gas. - Abstract: In the present communication, we report on the synthesis of boron nitride nanosheets (BNNSs) and study of their gas sensing properties. BNNSs are synthesized by irradiating pyrolytic hexagonal boron nitride (h-BN) target using CO{sub 2} laser pulses. High resolution transmission electron microscopic measurements (HRTEM) revealed 2-dientional honeycomb crystal lattice structure of BNNSs. HRTEM, electron diffraction, XRD and Raman scattering measurements clearly identified h-BN. Gas sensing properties of synthesized BNNSs were analyzed with prototype gas sensor using methane as working gas. A systematic response curve of the sensor is recorded in each cycle of gas “in” and “out”; suggesting excellent sensitivity and high performance of BNNSs-based gas-sensor.

  13. Gas release and conductivity modification studies

    NASA Technical Reports Server (NTRS)

    Linson, L. M.; Baxter, D. C.

    1979-01-01

    The behavior of gas clouds produced by releases from orbital velocity in either a point release or venting mode is described by the modification of snowplow equations valid in an intermediate altitude regime. Quantitative estimates are produced for the time dependence of the radius of the cloud, the average internal energy, the translational velocity, and the distance traveled. The dependence of these quantities on the assumed density profile, the internal energy of the gas, and the ratio of specific heats is examined. The new feature is the inclusion of the effect of the large orbital velocity. The resulting gas cloud models are used to calculate the characteristics of the field line integrated Pedersen conductivity enhancements that would be produced by the release of barium thermite at orbital velocity in either the point release or venting modes as a function of release altitude and chemical payload weight.

  14. Parametric Study of Gas Turbine Film-Cooling

    E-print Network

    Liu, Kevin

    2012-10-19

    In this study, the film-cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions. The study consisted of three parts: 1) turbine blade span film...

  15. MINERAL BIOAVAILABILITY AND METABOLISM DETERMINED BY USING STABLE ISOTOPE TRACERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Definitive data on mineral bioavailability in humans and animals can be obtained by using isotopic tracers. The use of stable isotope tracers to study important issues in mineral nutrition has expanded rapidly in the past two decades, particularly in humans. Stable isotopes have a number of advanta...

  16. The impacts of tracer selection and corrections for organic matter and particle size on the results of quantitative sediment fingerprinting. A case study from the Nene basin, UK.

    NASA Astrophysics Data System (ADS)

    Pulley, Simon; Ian, Foster; Paula, Antunes

    2014-05-01

    In recent years, sediment fingerprinting methodologies have gained widespread adoption when tracing sediment provenance in geomorphological research. A wide variety of tracers have been employed in the published literature, with corrections for particle size and organic matter applied when the researcher judged them necessary. This paper aims to explore the errors associated with tracer use by a comparison of fingerprinting results obtained using fallout and lithogenic radionuclides, geochemical, and mineral magnetic tracers in a range of environments located in the Nene basin, UK. Specifically, fingerprinting was undertaken on lake, reservoir and floodplain sediment cores, on actively transported suspended sediment and on overbank and channel bed sediment deposits. Tracer groups were investigated both alone and in combination to determine the differences between their sediment provenance predictions and potential causes of these differences. Additionally, simple organic and particle size corrections were applied to determine if they improve the agreement between the tracer group predictions. Key results showed that when fingerprinting contributions from channel banks to actively transported or recently deposited sediments the tracer group predictions varied by 24% on average. These differences could not be clearly attributed to changes in the sediment during erosion or transport. Instead, the most likely cause of differences was the pre-existing spatial variability in tracer concentrations within sediment sources, combined with highly localised erosion. This resulted in the collected sediment source samples not being representative of the actual sediment sources. Average differences in provenance predictions between the different tracer groups in lake, reservoir and floodplain sediment cores were lowest in the reservoir core at 19% and highest in some floodplain cores, with differences in predictions in excess of 50%. In these latter samples organic enrichment of the sediment, selective transport of fine particles and post-depositional chemical changes to the sediment were determined to be the likely cause of the differences. It was determined that organic and particle size corrections made the differences between tracer groups larger in most cases, although differences between tracer group predictions were reduced in two of the four floodplain cores.

  17. Polarization optimization for laser polarized noble gas MR studies

    SciTech Connect

    Coulter, K.P.; Rosen, M.S.; Welsh, R.C.; Swanson, S.D.; Chupp, T.E. [Univ. of Michigan, Ann Arbor, MI (United States)

    1996-05-01

    The efficacy of laser polarized noble gas Magnetic Resonance (MR) imaging and spectroscopy depends critically on the ability to produce large magnetizations of the gases used. While signal size is directly related to both the polarization and concentration of the gas, sufficient volumes of gas can also allow studies to be done which examine the time dependence of the biological uptake of polarized noble gas. The authors have undertaken MR imaging and spectroscopy studies with Xe and He. These studies have concentrated on the use of high power laser diode arrays (LDAs) as the most practical means to produce large magnetizations. They discuss the technique and optimization of polarized noble gas production for these medical imaging and spectroscopy experiments.

  18. Gas jet study in microgravity environment

    Microsoft Academic Search

    Vitor Botelho; J. A. do Aido Pais; R. Rocha

    2006-01-01

    In this article we report on the variations of behaviour, shape, size and density profile of a CO2 gas jet near the laminar\\u000a regime, during the transition from macro (1.8G) to microgravity (0G) experienced on board a A300 ZERO-G Airbus performing\\u000a parabolic flights, using a Mach-Zehnder interferometer and Schlieren imaging techniques. Both optical techniques used have\\u000a been successful in visualizing

  19. The random walk of tracers through river catchments

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-08-01

    River catchments play critical roles in regional economies and in the global economy. In addition, rivers carry large volumes of nutrients, pollutants, and several other forms of tracers into the ocean. An intricate system of pathways and channels, both on the surface and in the subsurface of catchments, allows rivers to carry large volumes of tracers. However, scientists do not yet fully understand how pollutants and other tracers travel through the intricate web of channels in the catchment areas of rivers. In a new study, Cvetkovic et al show that the travel path of tracers through channels can be modeled as a random walk, which is mathematically similar to the path an animal would trace when foraging. Previous studies have applied the random walk approach to understand the behavior of fluids flowing through aquifers and soils but not to model the transport mechanism of tracers that travel passively with water flowing through catchments.

  20. Helium as a Dynamical Tracer in the Thermosphere

    NASA Astrophysics Data System (ADS)

    Thayer, J. P.; Liu, X.; Wang, W.; Burns, A. G.

    2014-12-01

    Helium has been a missing constituent in current thermosphere general circulation models. Although typically a minor gas relative to the more abundant major gasses, its unique properties of being chemically inert and light make it an excellent tracer of thermosphere dynamics. Studying helium can help simplify understanding of transport effects. This understanding can then be projected to other gasses whose overall structure and behavior are complex but, by contrasting with helium, can be evaluated for its transport dependencies. The dynamical influences on composition impact estimates of thermosphere mass density, where helium during solar minima can have a direct contribution, as well as ionosphere electron density. Furthermore, helium estimates in the upper thermosphere during solar minima have not been observed since the 1976 minimum. Indirect estimates of helium in the upper thermosphere during the recent extreme solar minimum indicates winter-time helium concentrations exceeded NRL-MSISE00 estimates by 30%-70% during periods of quiet geomagnetic activity. For times of active geomagnetic conditions, helium concentrations near ~450 km altitude are estimated to decrease while oxygen concentrations increase. An investigation of the altitude structure in thermosphere mass density storm-time perturbations reveal the important effects of composition change with maximum perturbation occurring near the He/O transition region and a much weaker maximum occurring near the O/N2 transition region. However, evaluating helium behavior and its role as a dynamical tracer is not straightforward and model development is necessary to adequately establish the connection to specific dynamical processes. Fortunately recent efforts have led to the implementation of helium modules in the NCAR TIEGCM and TIME-GCM. In this invited talk, the simulated helium behavior and structure will be shown to reproduce observations (such as the wintertime helium bulge and storm-time response) and its utility as a dynamical tracer of thermosphere dynamics will be elucidated.

  1. Quantification of methane and nitrous oxide emissions from various waste treatment facilities by tracer dilution method

    NASA Astrophysics Data System (ADS)

    Mønster, Jacob; Rella, Chris; Jacobson, Gloria; Kjeldsen, Peter; Scheutz, Charlotte

    2013-04-01

    Urban activities generate solid and liquid waste, and the handling and aftercare of the waste results in the emission of various compounds into the surrounding environment. Some of these compounds are emitted as gasses into the atmosphere, including methane and nitrous oxide. Methane and nitrous oxide are strong greenhouse gases and are considered to have 25 and 298 times the greenhouse gas potential of carbon dioxide on a hundred years term (Solomon et al. 2007). Global observations of both gasses have shown increasing concentrations that significantly contribute to the greenhouse gas effect. Methane and nitrous oxide are emitted from both natural and anthropogenic sources and inventories of source specific fugitive emissions from the anthropogenic sources of methane and nitrous oxide of are often estimated on the basis of modeling and mass balance. Though these methods are well-developed, actual measurements for quantification of the emissions is a very useful tool for verifying the modeling and mass balance as well as for validation initiatives done for lowering the emissions of methane and nitrous oxide. One approach to performing such measurements is the tracer dilution method (Galle et al. 2001, Scheutz et al. 2011), where the exact location of the source is located and a tracer gas is released at this source location at a known flow. The ratio of downwind concentrations of the tracer gas and the methane and nitrous oxide gives the emissions rates of the greenhouse gases. This tracer dilution method can be performed using both stationary and mobile measurements and in both cases, real-time measurements of both tracer and quantified gas are required, placing high demands on the analytical detection method. To perform the methane and nitrous oxide measurements, two robust instruments capable of real-time measurements were used, based on cavity ring-down spectroscopy and operating in the near-infrared spectral region. One instrument measured the methane and tracer gas concentrations while another measured the nitrous oxide concentration. We present the performance of these instruments at different waste treatment facilities (waste water treatment plants, composting facilities, sludge mineralization beds, anaerobic digesters and landfills) in Denmark, and discuss the strengths and limitations of the method of the method for quantifying methane and nitrous oxide emissions from the different sources. Furthermore, we have measured the methane emissions from 10 landfills with emission rates ranging from 5 to 135 kg/h depending on the age, state, content and aftercare of the landfill. In addition, we have studied 3 waste water treatment plants, and found nitrous oxide emission of 200 to 700 g/h from the aeration tanks and a total methane emission ranging from 2 to 15 kg/h, with the primary emission coming from the sludge treatment. References Galle, B., Samuelsson, J., Svensson, B.H., and Börjesson, G. (2001). Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy. Environmental Science & Technology 35 (1), 21-25 Scheutz, C., Samuelsson, J., Fredenslund, A. M., and Kjeldsen, P. (2011). Quantification of multiple methane emission sources at landfills using a double tracer technique. Waste Management, 31(5), 1009-17 Solomon, S., D. Qin, M. Manning, R.B. Alley, T. Berntsen, N.L. Bindoff, Z. Chen, A. Chidthaisong, J.M. Gregory, G.C. Hegerl, M. Heimann, B. Hewitson, B.J. Hoskins, F. Joos, J. Jouzel, V. Kattsov, U. Lohmann, T.Matsuno, M. Molina, N. Nicholls, J.Overpeck, G. Raga, V. Ramaswamy, J. Ren, M. Rusticucci, R. Somerville, T.F. Stocker, P. Whetton, R.A.Wood and D. Wratt, 2007: Technical Summary. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

  2. Assimilation of observations of radiation level into an atmospheric transport model: A case study with the particle filter and the ETEX tracer dataset

    NASA Astrophysics Data System (ADS)

    Hiemstra, Paul H.; Karssenberg, Derek; van Dijk, Arjan

    2011-11-01

    Atmospheric transport models and observations from monitoring networks are commonly used aids for forecasting spatial distribution of contamination in case of a radiological incident. In this study, we assessed the particle filter data-assimilation technique as a tool for ensemble forecasting the spread of radioactivity. We used measurements from the ETEX-1 tracer experiment and model results from the NPK-Puff atmospheric dispersion model. We showed that assimilation of observations improves the ensemble forecast compared to runs without data assimilation. The improvement is most prominent for nowcasting: the mean squared error was reduced by a factor of 7. For forecasting, the improvement of the mean squared error resulting from assimilation of observations was found to dissipate within a few hours. We ranked absolute model values and observations and calculated the mean squared error of the ranked values. This measure of the correctness of the pattern of high and low values showed an improvement for forecasting up to 48 h. We conclude that the particle filter is an effective tool in better modeling the spread of radioactivity following a release.

  3. Impacts of Wood Additions on Dissolved and Particulate Nutrient Retention in an Agriculturally Impacted Stream: A Multi-Tracer Injection Study at Whatawhata, New Zealand

    NASA Astrophysics Data System (ADS)

    Drummond, J. D.; Wright-Stow, A.; Nagels, J.; Quinn, J.; Franklin, P.; Packman, A. I.

    2014-12-01

    Wood is a key component in forested streams, playing an important ecological and physical role in creating step-pool profiles, enhancing habitat heterogeneity, retaining organic matter, and changing water velocity. Wood additions can increase surface water-groundwater exchange, increasing in-stream residence times by slowing water velocities and providing high depositional areas for fine particles (i.e. particulate nutrients C, N, P). Thus, wood additions may create biogeochemical hotspots in streams that allow greater potential for local nutrient cycling and processing. The objectives of this research were to determine if added wood enhances in-stream heterogeneity, results in more complex flow paths, increases natural retention of further organic matter and changes geomorphic characteristics of the stream reach. We conducted a conservative solute and fluorescent fine particle tracer injection study in an agriculturally impacted stream with emplaced wood additions to estimate in-stream retention times in the Whatawhata catchment, North Island of New Zealand. Although similar solute peak concentrations were observed at the different in-stream sampling sites, increased retention was observed near to the wood. Both fine particle deposition and retention time was increased near the emplaced log. Fine particles were also analyzed in situ in sediment and biofilms on cobbles throughout the stream reach following the injection. A direct positive correlation was observed between cobble biofilm biomass and particle accumulation within this retention area. In general, the addition of wood to these agriculturally impacted streams enhanced hydraulic complexity and increased the retention of solute and fine particles.

  4. Upscaling particle transport in discrete fracture networks: 2. Reactive tracers

    NASA Astrophysics Data System (ADS)

    Frampton, A.; Cvetkovic, V.

    2007-10-01

    We study sorbing tracer transport through discrete fracture networks using a stochastic Lagrangian framework, combined with the methodology for upscaling particle breakthrough curves developed in the first part of this article series. Results indicate that this procedure can accurately predict expected normalized tracer discharge for an upscaled distance of 1 order of magnitude in terms of transport scale, which for our simulations is about 2 orders of magnitude greater than the mean fracture segment scale. Specifically, we show the importance of retaining the correlation between the water residence time ? and the hydrodynamic control of retention ? in order to make accurate tracer discharge predictions. Also, we show that the extreme tails of ? and ? distributions have essentially no impact on tracer discharge. These results are illustrated using the unlimited diffusion model, and for two hypothetical tracers with properties designed to capture the behavior of many commonly occurring natural radionuclides.

  5. Experimental and theoretical studies of gas consumption in the gas carburizing process

    Microsoft Academic Search

    Lars Sproge; John Ågren

    1988-01-01

    In this work, the gas carburizing process is studied theoretically and experimentally. In particular, the possibility of lowering\\u000a the gas consumption is investigated.\\u000a \\u000a A mathematical model which accounts for the carbon diffusion in the steel, the surface reactions on the steel, and the change\\u000a in the furnace atmosphere composition caused by the carburizing reactions is developed. Two experimental series are

  6. A study of water driven oil encroachment into gas caps 

    E-print Network

    Ritch, Harlan J

    1958-01-01

    A STUDY OF WATER DRIVEN OIL ENCROACHMENT INTO GAS CAPS LIBRARY A S I COLLEGE OF TEXAS A Thesis By HARLAN J. RITCH ~ ~ ~ Submitted to the Graduate School oi' the Agricultural and Mechanical College of Texas in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE May, 1958 Major Subject: Petroleum Engineering A STUDY OF WATER DRIVEN OIL ENCROACHMENT INTO GAS CAPS A Thesis By HARLAN J. RITCH Approved as to style and content by: hairxnan of Coxnxnittee) (Head...

  7. Complex brain circuits studied via simultaneous and permanent detection of three transported neuroanatomical tracers in the same histological section

    Microsoft Academic Search

    J. L Lanciego; F. G Wouterlood; E Erro; J Arribas; N Gonzalo; X Urra; S Cervantes; J. M Giménez-Amaya

    2000-01-01

    Experimental neuroanatomical tracing methods lie at the basis of the study of the nervous system. When the scientific question is relatively straightforward, it may be sufficient to derive satisfactory answers from experiments in which a single neuroanatomical tracing method is applied. In various scientific paradigms however, for instance when the degree of convergence of two different projections on a particular

  8. Thalamic reticular input to the rat visual thalamus: a single fiber study using biocytin as an anterograde tracer

    Microsoft Academic Search

    Didier Pinault; Jacques Bourassa

    1995-01-01

    This study describes the axonal projections of single thalamic reticular (TR) neurons within the visual thalamus in rats. Experiments were performed under urethane anesthesia and reticular cells were labeled by extracellular or juxtacellular microiontophoretic applications of biocytin. The axonal arborizations of 19 TR cells projecting to the dorsal lateral geniculate nucleus (DLG) or to the lateral dorsal\\/lateral posterior complex (LD\\/LP)

  9. Corticothalamic projections from the primary visual cortex in rats: a single fiber study using biocytin as an anterograde tracer

    Microsoft Academic Search

    J. Bourassa

    1995-01-01

    This study investigates the pattern of axonal projections of single corticothalamic neurons from the rat primary visual cortex. Microiontophoretic injections of biocytin were made in cortical laminae V and VI to label small pools of corticothalamic cells and their intrathalamic axonal projections. After a survival period of 48 h, the animals were perfused and the tissue was processed for biocytin

  10. North American Natural Gas Markets: Selected technical studies. Volume 3

    SciTech Connect

    Huntington, H.G.; Schuler, G.E. [eds.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  11. North American Natural Gas Markets: Selected technical studies

    SciTech Connect

    Huntington, H.G.; Schuler, G.E. (eds.)

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  12. The use of radon as tracer in environmental sciences

    NASA Astrophysics Data System (ADS)

    Quindos Poncela, Luis; Sainz Fernandez, Carlos; Fuente Merino, Ismael; Gutierrez Villanueva, Jose; Gonzalez Diez, Alberto

    2013-08-01

    Radon can be used as a naturally occurring tracer for environmental processes. By means of grab-sampling or continuous monitoring of radon concentration, it is possible to assess several types of dynamic phenomena in air and water. We present a review of the use of radon and its progeny at the University of Cantabria. Radon can be an atmospheric dynamics indicator related with air mass interchange near land-sea discontinuities as well as for the study of vertical variations of air parameters (average values of different types of stability: 131-580 Bq m-3). Concerning indoor gas, we present some results obtained at Altamira Cave (Spain): from 222 to 6549 Bq m-3 (Hall) and from 999 to 6697 Bq m-3 (Paintings Room). Finally, variations of radon concentration in soil (0.3 to 9.1 kBq m-3) and underground water (values up to 500 Bq l-1) provide relevant information about different geophysical phenomena.

  13. A Preliminary Study of the Draining Lymph Node Basin in Advanced Lower Rectal Cancer Using a Radioactive Tracer

    Microsoft Academic Search

    Kimihiko Funahashi; Junichi Koike; Morio Shimada; Kosuke Okamoto; Tomohiko Goto; Tatsuo Teramoto

    2006-01-01

    \\u000a Purpose  This study was designed to examine the draining lymph node basin at highest risk of metastasis in lower rectal cancer using\\u000a 99 mTc-tin colloid.\\u000a \\u000a \\u000a \\u000a Methods  In 43 patients, the area with highest hot nodes density was defined as the draining lymph node basin using a gamma probe.\\u000a Metastatic states of all removed lymph nodes were examined histologically.\\u000a \\u000a \\u000a \\u000a Results  A total of 203 hot

  14. Diffusion NMR Methods Applied to Xenon Gas for Materials Study

    E-print Network

    R. W. Mair; M. S. Rosen; R. Wang; D. G. Cory; R. L. Walsworth

    2002-11-09

    We report initial NMR studies of i) xenon gas diffusion in model heterogeneous porous media, and ii) continuous flow laser-polarized xenon gas. Both areas utilize the Pulsed Gradient Spin Echo techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients - a brief overview of this area is provided in the introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t), (an indicator of mean squared displacement) to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. The Pade approximation is used to interpolate D(t) data between the short and long time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20 - 200 mm/s). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm/s due to the high diffusivity of gases compared to liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data: namely, flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack.

  15. Feasibility study of full-reactor gas core demonstration test

    NASA Technical Reports Server (NTRS)

    Kunze, J. F.; Lofthouse, J. H.; Shaffer, C. J.; Macbeth, P. J.

    1973-01-01

    Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved.

  16. Combined Radio and Dye-tracer Study To Determine The Persistence and Efficiency of Preferential Flow Paths In Untilled Agricultural Soils

    Microsoft Academic Search

    R. Penfield; T. Centofanti; A. Albrecht; E. Frossard; H. Flühler

    2002-01-01

    To investigate the persistence and transport efficiency of flow paths in structured soils, two radiotracer experiments have been performed in unsaturated, untilled agricultural loams (eutric cambisol above glacial moraine). In both experiments, four radioactive tracers (54Mn, 57Co, 65Zn, and 134Cs) and a Brilliant Blue dye solution were applied prior to excavation and sampling, and radionuclides were consistently found to be

  17. Study of the hydrodynamic behaviour of the batch and continuous torus reactor in laminar and turbulent flow regimes by means of tracer methods

    Microsoft Academic Search

    H Benkhelifa; J Legrand; P Legentilhomme; A Montillet

    2000-01-01

    In this work, the flow modelling of a toroidal reactor in batch or continuous operating modes is obtained by the experimental determination of the tracer concentration evolution in batch mode and the residence time distribution in continuous configuration, for mixing Reynolds numbers between 15 and 8×104 with water and glucose solutions. The comparison of the mean circulation times measured at

  18. Integrating Source Apportionment Tracers into a Bottom-up Inventory of Methane Emissions in the Barnett Shale Hydraulic Fracturing Region.

    PubMed

    Townsend-Small, Amy; Marrero, Josette E; Lyon, David R; Simpson, Isobel J; Meinardi, Simone; Blake, Donald R

    2015-07-01

    A growing dependence on natural gas for energy may exacerbate emissions of the greenhouse gas methane (CH4). Identifying fingerprints of these emissions is critical to our understanding of potential impacts. Here, we compare stable isotopic and alkane ratio tracers of natural gas, agricultural, and urban CH4 sources in the Barnett Shale hydraulic fracturing region near Fort Worth, Texas. Thermogenic and biogenic sources were compositionally distinct, and emissions from oil wells were enriched in alkanes and isotopically depleted relative to natural gas wells. Emissions from natural gas production varied in ?(13)C and alkane ratio composition, with ?D-CH4 representing the most consistent tracer of natural gas sources. We integrated our data into a bottom-up inventory of CH4 for the region, resulting in an inventory of ethane (C2H6) sources for comparison to top-down estimates of CH4 and C2H6 emissions. Methane emissions in the Barnett are a complex mixture of urban, agricultural, and fossil fuel sources, which makes source apportionment challenging. For example, spatial heterogeneity in gas composition and high C2H6/CH4 ratios in emissions from conventional oil production add uncertainty to top-down models of source apportionment. Future top-down studies may benefit from the addition of ?D-CH4 to distinguish thermogenic and biogenic sources. PMID:26148556

  19. Small Gas Turbine Combustor Primary Zone Study

    NASA Technical Reports Server (NTRS)

    Sullivan, R. E.; Young, E. R.; Miles, G. A.; Williams, J. R.

    1983-01-01

    A development process is described which consists of design, fabrication, and preliminary test evaluations of three approaches to internal aerodynamic primary zone flow patterns: (1) conventional double vortex swirl stabilization; (2) reverse flow swirl stabilization; and (3) large single vortex flow system. Each concept incorporates special design features aimed at extending the performance capability of the small engine combustor. Since inherent geometry of these combustors result in small combustion zone height and high surface area to volume ratio, design features focus on internal aerodynamics, fuel placement, and advanced cooling. The combustors are evaluated on a full scale annular combustor rig. A correlation of the primary zone performance with the overall performance is accomplished using three intrusion type gas sampling probes located at the exit of the primary zone section. Empirical and numerical methods are used for designing and predicting the performance of the three combustor concepts and their subsequent modifications. The calibration of analytical procedures with actual test results permits an updating of the analytical design techniques applicable to small reverse flow annular combustors.

  20. Technique for elevated release of sulfur hexafluoride tracer

    SciTech Connect

    Whiteman, C.D.; Glover, D.W.

    1983-08-01

    Study of the dispersion of atmospheric pollutants has benefited greatly in the past from the use of artificial tracers. The study described in this paper used tethered balloons which carry one end of a hose aloft, through which a gaseous tracer can be dispensed. From the field tests it was concluded that the tandem balloon system is useful in atmospheric tracer experiments where a single balloon has insufficient lift to provide a release at the desired elevation. The SF/sub 6/ release system proved to be portable, easy to use, and suitable for simulating continuous elevated pollutant releases. 3 figures. (DP)

  1. EQUILIBRIUM FLUCTUATIONS FOR A DRIVEN TRACER PARTICLE DYNAMICS

    E-print Network

    EQUILIBRIUM FLUCTUATIONS FOR A DRIVEN TRACER PARTICLE DYNAMICS Cl' audio Landim, S' ergio B rescaled position p fflX(ffl \\Gamma2 t) of the tagged particle converges, as ffl ! 0, to the finite of as a caricature model of the microscopic dynam­ ics of particles of a gas or fluid and has originated in attempts

  2. Gas jet disruption mitigation studies on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Granetz, R.; Whyte, D. G.; Izzo, V. A.; Biewer, T.; Reinke, M. L.; Terry, J.; Bader, A.; Bakhtiari, M.; Jernigan, T.; Wurden, G.

    2006-12-01

    Damaging effects of disruptions are a major concern for Alcator C-Mod, ITER and future tokamak reactors. High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the operational requirements of fast response time and reliability, while still being benign to subsequent discharges. Disruption mitigation experiments using an optimized gas jet injection system are being carried out on Alcator C-Mod to study the physics of gas jet penetration into high pressure plasmas, as well as the ability of the gas jet impurities to convert plasma energy into radiation on timescales consistent with C-Mod's fast quench times, and to reduce halo currents given C-Mod's high-current density. The dependence of impurity penetration and effectiveness on noble gas species (He, Ne, Ar, Kr) is also being studied. It is found that the high-pressure neutral gas jet does not penetrate deeply into the C-Mod plasma, and yet prompt core thermal quenches are observed on all gas jet shots. 3D MHD modelling of the disruption physics with NIMROD shows that edge cooling of the plasma triggers fast growing tearing modes which rapidly produce a stochastic region in the core of the plasma and loss of thermal energy. This may explain the apparent effectiveness of the gas jet in C-Mod despite its limited penetration. The higher-Z gases (Ne, Ar, Kr) also proved effective at reducing halo currents and decreasing thermal deposition to the divertor surfaces. In addition, noble gas jet injection proved to be benign for plasma operation with C-Mod's metal (Mo) wall, actually improving the reliability of the startup in the following discharge.

  3. NMR studies of laser-polarized xenon gas flow

    Microsoft Academic Search

    R. W. Mair; R. Wang; M. S. Rosen; R. L. Walsworth; D. Candela

    2003-01-01

    NMR techniques that are commonly used to measure diffusion can also be used to measure fluid velocity and\\/or acceleration. In recent years, laser-polarized noble gas NMR has developed into a powerful tool for spin density and diffusion imaging; however few attempts have been made to study gas flow by NMR. We report initial NMR velocity measurements of continuously flowing laser-polarized

  4. Studies related to the deep earth gas: Final report

    SciTech Connect

    Gold, T.; Patnaik, P.; Soter, S.

    1990-01-01

    Studies were conducted on the origin of natural gas and petroleum and on the role of natural gas in a number of natural phenomena. Laboratory investigations and theoretical findings give strong support to the existence of abiogenic methane deep in the Earth's mantle and lower crust and show that methane at high temperatures and pressures may be in equilibrium with a great range of hydrocarbons, some of which are important constituents or building blocks of petroleum. A list of publications is included.

  5. Krypton and sulfur hexafluoride as non-aqueous phase liquid partitioning tracers in the saturated zone

    NASA Astrophysics Data System (ADS)

    Montague, T. E.; Elliot, T. E.

    2003-04-01

    The contamination of land and groundwater by Non-Aqueous Phase Liquids (NAPLs) is a common problem in industrialised countries. Tools to characterise the extent of aquifer contamination are important in aiding remediation strategies. This preliminary research aims to employ Kr and SF6 as applied bulk partitioning tracers for the detection and quantification of NAPL volumes in the saturated zone of subsurface environments. These gases potentially are inert, non-toxic, environmentally friendly and cost -effective tools for assessing NAPL contamination in the subsurface. A protocol is developed for giving reliable dissolved gas concentration data that can give NAPL-water partition coefficients for these gases by simple mass balance. One Dimensional (1-D) column tests are presented to illustrate the effectiveness of these gases as NAPL partitioning tracers, using dissolved bromide as a comparative conservative tracer. Resultant Break Through Curves (BTCs) are analysed by method of moments and the NAPL volume estimation based on the tracer data compared with known NAPL addition to the columns. Retardation of these tracers compared to the conservative Br tracer is clear evidence that these gases can be effectively employed as bulk partitioning tracers in the saturated zone and are a useful tool for estimating NAPL saturation. Proposals for the use of dissolved Kr and SF6 gases as novel tracers potentially for other non aqueous phases (e.g. organic matter) in the saturated zone in conjunction with other intelligent tracers (e.g. interfacial tracers) are also discussed.

  6. Water budgets of Italian and Dutch gravel pit lakes: a study using a fen as a natural evaporation pan, stable isotopes and conservative tracer modeling.

    NASA Astrophysics Data System (ADS)

    Nella Mollema, Pauline; Antonellini, Marco

    2015-04-01

    Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form where the gravel pits are below the water table and fill with groundwater. Their presence changes the drainage patterns, water- and hydrochemical budgets of a watershed. We have studied the water budget of two gravel pit lakes systems using stable H and O isotopes of water as well as conservative tracer (Cl) modeling. The Dutch gravel pit lakes are a fluvial fresh water system of 70 lakes along the Meuse River and the Italian gravel pit lakes are a brackish system along the Adriatic coast. Surface water evaporation from the gravel pit lakes is larger than the actual evapotranspiration of the grass land and forests that were replaced. The ratio of evaporation to total flow into the Dutch lakes was determined by using a Fen as a natural evaporation pan: the isotope content of the Tuspeel Fen, filled with rain water and sampled in a dry and warm summer period (August 2012), is representative for the limiting isotopic enrichment under local hydro meteorological conditions. The Local Evaporation line (LEL) was determined ?2 H = 4.20 ? 18O - 14.10 (R² = 0.99) and the ratio of total inflow to evaporation for three gravel pit lakes were calculated to be 22.6 for the De Lange Vlieter lake used for drinking water production, 11.3 for the Boschmolen Lake and 8.9 for the Anna's Beemd lake showing that groundwater flow is much larger than evaporation. The Italian gravel pit lakes are characterized by high salinity (TDS = 4.6-12.3 g L-1). Stable isotope data show that these latter gravel pit lakes are fed by groundwater, which is a mix between fresh Apennine River water and brackish (Holocene) Adriatic Sea water. The local evaporation line is determined: ?2H = 5.02 ?18O - 10.49. The ratio of total inflow to evaporation is 5. Conservative tracer modeling indicates that the chloride concentration in the Italian gravel pit lakes stabilizes after a short period of rapid increase, because water leaving the lake via groundwater flow, driven by the drainage system, removes part of the Cl that accumulates in the lake due to evapo-concentration. Under climate change, rising sea levels and continuing land subsidence as well as increasing precipitation would increase the need for drainage which would enhance groundwater flow through the lake. The resulting steady-state Cl concentration of the lakes could become less than the current Cl concentration. This effect would be larger than increasing evapo- concentration. Both gravel pit lake systems have a large flux of groundwater into and out of the lakes driven by evaporation and (artificial) drainage with important consequences for the water- and hydrochemical budgets of the whole watershed and in particular on freshwater quantity and groundwater salinity.

  7. A study on transient and steady state sensor data for identification of individual gas concentrations in their gas mixtures

    Microsoft Academic Search

    Ali Gulbag; Fevzullah Temurtas

    2007-01-01

    In this study, a comparative study was performed for the quantitative identification of individual gas concentrations (trichloroethylene and acetone) in their gas mixtures using transient and steady state sensor responses. For this purpose, three neural network (NN) structures were used. The quartz crystal microbalance (QCM) type sensors were selected as gas sensors. One of the neural networks was used for

  8. Biological conversion of synthesis gas. Topical report: Bioreactor studies

    SciTech Connect

    Basu, R.; Klasson, K.T.; Clausen, E.C.; Gaddy, J.L.

    1993-09-01

    The purpose of the proposed research is to develop a technically and economically feasible process for biologically producing H{sub 2} from synthesis gas while, at the same time, removing harmful sulfur gas compounds. Six major tasks are being studied: culture development, where the best cultures are selected and conditions optimized for simultaneous hydrogen production and sulfur gas removal; mass transfer and kinetic studies in which equations necessary for process design are developed; bioreactor design studies, where the cultures chosen in Task 1 are utilized in continuous reaction vessels to demonstrate process feasibility and define operating conditions; evaluation of biological synthesis gas conversion under limiting conditions in preparation for industrial demonstration studies; process scale-up where laboratory data are scaled to larger-size units in preparation for process demonstration in a pilot-scale unit; and economic evaluation, where process simulations are used to project process economics and identify high cost areas during sensitivity analyses. The purpose of this report is to present results from bioreactor studies involving H{sub 2} production by water gas shift and H{sub 2}S removal to produce elemental sulfur. Many of the results for H{sub 2} production by Rhodospirillum rubrum have been presented during earlier contracts. Thus, this report concentrates mainly on H{sub 2}S conversion to elemental sulfur by R. rubrum.

  9. Test plan for determining breathing rates in single shell tanksusing tracer gases. Revision 1

    SciTech Connect

    Andersen, J.A.

    1997-06-20

    This test plan specifies the requirements and conditions for the injection of tracer gas (Helium (He)) into single shell tanks to determine breathing rates using periodic sampling. The eight tanks which have been selected at the time this Test Plan was developed are A-101, AX-102, AX-103, BY-105, C-107, U-103 (U-103 is counted twice, once during the winter months and once during the summer), and U-105. Other tanks to be sampled will be assigned by Pacific Northwest National Laboratory (PNNL) at a later date in the study process as resources allow, the document shall be revised as required. The sampling of headspace for each of these tanks shall be performed using available risers or the Standard Hydrogen Monitoring System (SHMS) cabinet as available. The tank farm vapor cognizant engineer shall assign the injection and sample testing point for each tank and document the point in the field work package. SUMMA TMI canisters, equipped in-line with dual particulate air filters and two silica gel sorbent traps will be used to collect the gas samples. The purpose of dual particulate air filters is to ensure no radioactive particulates are transferred to the SUMMA TMI canisters. The silica gel sorbent traps will effectively eliminate any tritiated water vapor that may be present in the sample gas stream. PNNL shall supply the tracer gases injection system and shall perform the analysis on the headspace samples. TWRS Characterization project shall inject the tracer gas and perform the sampling. Refer to Engineering Task Plan HNF-SD-TWR-ETP-002 for a detailed description of the responsibilities for this task.

  10. Tracer transport by the diabatic circulation deduced from satellite observations

    NASA Technical Reports Server (NTRS)

    Solomon, S.; Kiehl, J. T.; Garcia, R. R.; Grose, W.

    1986-01-01

    Nimbus-7 sensor data were used to track the diabatic circulation in the stratosphere to study the advective transport of CH4 and N2O as tracer species. Advective transport by the mean circulation was found to be a function of the temperature field and associated deviations from radiative equilibrium. A photochemical model was applied to account for the disappearance of the tracer species from the stratosphere. Comparisons between the SAMS data and modeling on the basis of the chemical loss rates of the tracers and the LIMS circulation data showed that the model predictions underestimated the resident abundances, although the global distributions and circulations exhibited a good match.

  11. Isotopic tracers for water and solute movement in desert soils

    SciTech Connect

    Phillips, F.M. [New Mexico Inst. of Mining and Technology, Socorro (United States)

    1993-06-01

    Most soil-physics investigations focus on agricultural soils and as a result the physics of soil-water processes in desert soils are comparatively poorly understood. Long-term tracer experiments provide valuable information. Among the most useful environmental tracers, from atmospheric nuclear weapons testing, are tritium and chlorine-36. Conclusions of studies of these tracers include the following: thermal vapor diffusions is important in water movement in desert soils; upward refluxing of the liquid phase during the summer separates volatile from non-volatile components; net infiltration rates over 30 years are a few millimeters or less in all soils investigated. 4 refs. 2 figs.

  12. Crystallographic studies of gas sorption in metal–organic frameworks

    PubMed Central

    Carrington, Elliot J.; Vitórica-Yrezábal, Iñigo J.; Brammer, Lee

    2014-01-01

    Metal–organic frameworks (MOFs) are a class of porous crystalline materials of modular design. One of the primary applications of these materials is in the adsorption and separation of gases, with potential benefits to the energy, transport and medical sectors. In situ crystallography of MOFs under gas atmospheres has enabled the behaviour of the frameworks under gas loading to be investigated and has established the precise location of adsorbed gas molecules in a significant number of MOFs. This article reviews progress in such crystallographic studies, which has taken place over the past decade, but has its origins in earlier studies of zeolites, clathrates etc. The review considers studies by single-crystal or powder diffraction using either X-rays or neutrons. Features of MOFs that strongly affect gas sorption behaviour are discussed in the context of in situ crystallographic studies, specifically framework flexibility, and the presence of (organic) functional groups and unsaturated (open) metal sites within pores that can form specific interactions with gas molecules. PMID:24892587

  13. Off-gassing induced tracer release from molten basalt pools

    SciTech Connect

    Cronenberg, A.W. [Engineering Science and Analysis, Albuquerque, NM (United States); Callow, R.A. [EG and G Idaho, Inc., Idaho Falls, ID (United States)

    1994-01-01

    Two in situ vitrification (ISV) field tests were conducted at the Idaho National Engineering Laboratory (INEL) during the summer of 1990 to assess ISV suitability for long-term stabilization of buried waste that contains transuranic and other radionuclide contaminants. The ISV process uses electrical resistance heating to melt buried waste and soil in place, which upon cooldown and resolidification fixes the waste into a vitrified (glass-like) form. In these two ISV field tests, small quantities of rare-earth oxides (tracers DY{sub 2}O{sub 3}, Yb{sub 2}O{sub 3}, and Tb{sub 4}O{sub 7}) were placed in the test pits to simulate the presence of plutonium oxides and assess plutonium retention/release behavior. The analysis presented in this report indicates that dissolution of tracer oxides into basaltic melts can be expected with subsequent tracer molecular or microparticle carry-off by escaping gas bubbles, which is similar to adsorptive bubble separation and ion flotation processes employed in the chemical industry to separate dilute heavy species from liquids under gas sparging conditions. Gaseous bubble escape from the melt surface and associated aerosolization is believed to be responsible for small quantities of tracer ejection from the melt surface to the cover hood and off-gas collection system. Methods of controlling off-gassing during ISV would be expected to improve the overall retention of such heavy oxide contaminants during melting/vitrification of buried waste.

  14. Non-universal tracer diffusion in crowded media of non-inert obstacles.

    PubMed

    Ghosh, Surya K; Cherstvy, Andrey G; Metzler, Ralf

    2015-01-21

    We study the diffusion of a tracer particle, which moves in continuum space between a lattice of excluded volume, immobile non-inert obstacles. In particular, we analyse how the strength of the tracer-obstacle interactions and the volume occupancy of the crowders alter the diffusive motion of the tracer. From the details of partitioning of the tracer diffusion modes between trapping states when bound to obstacles and bulk diffusion, we examine the degree of localisation of the tracer in the lattice of crowders. We study the properties of the tracer diffusion in terms of the ensemble and time averaged mean squared displacements, the trapping time distributions, the amplitude variation of the time averaged mean squared displacements, and the non-Gaussianity parameter of the diffusing tracer. We conclude that tracer-obstacle adsorption and binding triggers a transient anomalous diffusion. From a very narrow spread of recorded individual time averaged trajectories we exclude continuous type random walk processes as the underlying physical model of the tracer diffusion in our system. For moderate tracer-crowder attraction the motion is found to be fully ergodic, while at stronger attraction strength a transient disparity between ensemble and time averaged mean squared displacements occurs. We also put our results into perspective with findings from experimental single-particle tracking and simulations of the diffusion of tagged tracers in dense crowded suspensions. Our results have implications for the diffusion, transport, and spreading of chemical components in highly crowded environments inside living cells and other structured liquids. PMID:25474476

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

    SciTech Connect

    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.

  16. Development of Standardized Mobile Tracer Correlation Approach for Large Area Emission Measurements (DRAFT UNDER EPA REVIEW)

    NASA Astrophysics Data System (ADS)

    Foster-wittig, T. A.; Thoma, E.; Green, R.; Hater, G.; Swan, N.; Chanton, J.

    2013-12-01

    Improved understanding of air emissions from large area sources such as landfills, waste water ponds, open-source processing, and agricultural operations is a topic of increasing environmental importance. In many cases, the size of the area source, coupled with spatial-heterogeneity, make direct (on-site) emission assessment difficult; methane emissions, from landfills for example, can be particularly complex [Thoma et al, 2009]. Recently, whole-facility (remote) measurement approaches based on tracer correlation have been utilized [Scheutz et al, 2011]. The approach uses a mobile platform to simultaneously measure a metered-release of a conservative gas (the tracer) along with the target compound (methane in the case of landfills). The known-rate tracer release provides a measure of atmospheric dispersion at the downwind observing location allowing the area source emission to be determined by a ratio calculation [Green et al, 2010]. Although powerful in concept, the approach has been somewhat limited to research applications due to the complexities and cost of the high-sensitivity measurement equipment required to quantify the part-per billion levels of tracer and target gas at kilometer-scale distances. The advent of compact, robust, and easy to use near-infrared optical measurement systems (such as cavity ring down spectroscopy) allow the tracer correlation approach to be investigated for wider use. Over the last several years, Waste Management Inc., the U.S. EPA, and collaborators have conducted method evaluation activities to determine the viability of a standardized approach through execution of a large number of field measurement trials at U.S. landfills. As opposed to previous studies [Scheutz et al, 2011] conducted at night (optimal plume transport conditions), the current work evaluated realistic use-scenarios; these scenarios include execution by non-scientist personnel, daylight operation, and full range of atmospheric condition (all plume transport conditions). The trials tested a novel tracer gas (acetylene), chosen for its performance and cost characteristics. This presentation will summarize method development activities for the field test trials (107 test days, with repeat measurements at 14 separate landfill sites). In addition to a brief description of the measurement technology, the method performance will be described, and primary data quality indicators and use conditions will be explored. Because measurements were taken under daylight and a variety of atmospheric conditions, the range of distance and wind conditions allows us to make conclusions about the strengths and limitations of the method. This enables us to show when and where it is possible to make a quality measurement using this technique and therefore develop a standardized method for large area emission measurements. Green, R. et al (2010). 'Methane Emission Measured at Two California Landfills by OTM-10 and an Acetylene Tracer Method.' Global Waste Management Symposium. San Antonio, Texas. Scheutz, C. et al. (2011). 'Quantification of multiple methane emission sources at landfills using a double tracer technique." Waste Management 31(5): 1009-1017. Thoma, E., et al (2009). 'Development of EPA OTM 10 for landfill applications." Journal of Environmental Engineering 136(8): 769-776.

  17. Cost study justifies internal coating on 48-in. gas line

    Microsoft Academic Search

    R. G. Worthingham; B. Asante; G. A. Carmichael; T. Dunsmore

    1994-01-01

    A study of the effectiveness of internal coatings in enhancing the flow efficiency of high-pressure gas pipelines has led NOVA Corp. of Alberta, Calgary, to coat internally 95 miles of 48-in. pipe during 1994--95. The study's objective was to obtain data for realistic pipeline simulations for evaluating the economics of coating used to enhance flow efficiency. The study measured the

  18. Tracer assisted characterization of deep fractured-porous reservoirs

    Microsoft Academic Search

    I. Ghergut; M. Sauter; H. Behrens; M. Lodemann; C. I. McDermott

    2006-01-01

    Heat and solute tracer tests can provide additional information on transport properties such as fluid velocities and fluid-rock contact surface areas as well as assist in the quantification of changes in these properties following hydraulic stimulation experiments. These characteristics cannot be provided by the analysis of hydraulic tests. A multi-tracer technique is illustrated for two case studies: (i) a long-term,

  19. PET tracers in musculoskeletal disease beyond FDG.

    PubMed

    Wieder, Hinrich A; Pomykala, Kelsey L; Benz, Matthias R; Buck, Andreas K; Herrmann, Ken

    2014-04-01

    Musculoskeletal tumors comprise a multitude of tumor entities with different grades of malignancy, biological behavior, and therapeutic options. Positron emission tomography (PET) using the glucose analog [18F]fluorodeoxyglucose (FDG) is an established imaging modality for detection and staging of cancer, despite some shortcomings. Numerous studies have evaluated the role of PET imaging musculoskeletal tumors beyond FDG. The use of more specific novel PET radiopharmaceuticals such as the proliferation marker [18F]fluorodeoxythymidine (FLT), the bone-imaging agent [18F]sodium fluoride, amino acid tracers ([11C]methionine, [18F]fluoroethyltyrosine), or biomarkers of neoangiogenesis ([18F]galacto-RGD) can potentially provide insights into the biology of musculoskeletal tumors with focus on tumor grading, treatment monitoring, posttherapy assessment, and estimation of individual prognosis. In this article, we review the potential role of these alternative PET tracers in musculoskeletal disorders with emphasis on oncologic applications. PMID:24715445

  20. A feasibility study of a hypersonic real-gas facility

    NASA Technical Reports Server (NTRS)

    Gully, J. H.; Driga, M. D.; Weldon, W. F.

    1987-01-01

    A four month feasibility study of a hypersonic real-gas free flight test facility for NASA Langley Research Center (LARC) was performed. The feasibility of using a high-energy electromagnetic launcher (EML) to accelerate complex models (lifting and nonlifting) in the hypersonic, real-gas facility was examined. Issues addressed include: design and performance of the accelerator; design and performance of the power supply; design and operation of the sabot and payload during acceleration and separation; effects of high current, magnetic fields, temperature, and stress on the sabot and payload; and survivability of payload instrumentation during acceleration, flight, and soft catch.

  1. Setup optimization toward accurate ageing studies of gas filled detectors

    NASA Astrophysics Data System (ADS)

    Abuhoza, A.; Schmidt, H. R.; Biswas, S.; Frankenfeld, U.; Hehner, J.; Schmidt, C. J.

    2013-08-01

    An infrastructure has been set up at the GSI detector laboratory to study the influence of construction materials on the ageing properties of gas filled detectors, such as multi-wire proportional chamber (MWPC), gas electron multiplier (GEM). Optimization of an ageing setup was performed by observing the variation of the normalized gain obtained using two identical MWPCs. An accuracy in the relative gain measurement below 1% has been achieved by monitoring environmental conditions and by systematic improvements of the measuring equipment. Ageing test of fiberglass G11 has been performed.

  2. AFB/open cycle gas turbine conceptual design study

    NASA Technical Reports Server (NTRS)

    Dickinson, T. W.; Tashjian, R.

    1983-01-01

    Applications of coal fired atmospheric fluidized bed gas turbine systems in industrial cogeneration are identified. Based on site-specific conceptual designs, the potential benefits of the AFB/gas turbine system were compared with an atmospheric fluidized design steam boiler/steam turbine system. The application of these cogeneration systems at four industrial plant sites is reviewed. A performance and benefit analysis was made along with a study of the representativeness of the sites both in regard to their own industry and compared to industry as a whole. A site was selected for the conceptual design, which included detailed site definition, AFB/gas turbine and AFB/steam turbine cogeneration system designs, detailed cost estimates, and comparative performance and benefit analysis. Market and benefit analyses identified the potential market penetration for the cogeneration technologies and quantified the potential benefits.

  3. Experimental study on engine gas-path component fault monitoring using exhaust gas electrostatic signal

    NASA Astrophysics Data System (ADS)

    Sun, Jianzhong; Zuo, Hongfu; Liu, Pengpeng; Wen, Zhenhua

    2013-12-01

    This paper presents the recent development in engine gas-path components health monitoring using electrostatic sensors in combination with signal-processing techniques. Two ground-based engine electrostatic monitoring experiments are reported and the exhaust gas electrostatic monitoring signal-based fault-detection method is proposed. It is found that the water washing, oil leakage and combustor linear cracking result in an increase in the activity level of the electrostatic monitoring signal, which can be detected by the electrostatic monitoring system. For on-line health monitoring of the gas-path components, a baseline model-based fault-detection method is proposed and the multivariate state estimation technique is used to establish the baseline model for the electrostatic monitoring signal. The method is applied to a data set from a turbo-shaft engine electrostatic monitoring experiment. The results of the case study show that the system with the developed method is capable of detecting the gas-path component fault in an on-line fashion.

  4. Dyes as tracers for vadose zone hydrology

    NASA Astrophysics Data System (ADS)

    Flury, Markus; Wai, Nu Nu

    2003-03-01

    Dyes are important tracers to investigate subsurface water movement. For more than a century, dye tracers have provided clues about the hydrological cycle as well as flow and transport processes in the subsurface. Groundwater contamination often originates in the vadose zone. Agrochemicals applied to the soil surface, toxic compounds accidentally spilled by human activities, and contaminants released from waste repositories leach through the vadose zone and can ultimately pollute groundwater resources. Dyes are an important tool to assess flow pathways of such contaminants. This review compiles information on dyes used as hydrological tracers, with particular emphasis on vadose zone hydrology. We summarize briefly different human-applied tracers, including nondye tracers. We then provide a historical sketch of the use of dyes as tracers and describe newer developments in visualization and quantification of tracer experiments. Relevant chemical properties of dyes used as tracers are discussed and illustrated with dye intermediates and selected dye tracers. The types of dyes used as tracers in subsurface hydrology are summarized, and recommendations are made regarding the use of dye tracers. The review concludes with a toxicological assessment of dyes used as hydrological tracers. Many different dyes have been proposed as tracers for water movement in the subsurface. All of these compounds, however, are to some degree retarded by the subsurface medium. Nevertheless, dyes are useful tracers to visualize flow pathways.

  5. Electrical studies for an industrial gas turbine cogeneration facility

    SciTech Connect

    Doughty, R.L.; Kalkstein, E.W. (Du Pont de Nemours (E.I.) and Co., Newark, DE (USA). Engineering Dept. Parsons (Ralph M.) Co., Pasadena, CA (USA)); Willoughby, R.D. (Thomas A. Edison Technical Center, Cooper Power System, 11131 Adams Road, Frankville, WI (US))

    1989-07-01

    Electrical studies are required to assure the proper integration of a gas-turbine cogeneration facility into an existing industrial-plant electrical system and the connected utility grid. Details of such a study effort are presented, including boundary-limit definition for the system model, individual component modeling, load-flow and short-circuit studies, stability studies, and simulation of on-line isolation from the electric utility during system undervoltage or underfrequency conditions. The impact of the studies on the design process and plant system reliability is discussed.

  6. Evaluation of PM 10 emission rates from paved and unpaved roads using tracer techniques

    NASA Astrophysics Data System (ADS)

    Claiborn, Candis; Mitra, Arundhati; Adams, Glenn; Bamesberger, Lee; Allwine, Gene; Kantamaneni, Ravi; Lamb, Brian; Westberg, Hal

    Spokane, WA, is a nonattainment area for airborne particulate matter smaller than 10?m (PM 10), so that a detailed emission inventory for PM 10 is needed to evaluate various control strategies. It is thought that emissions from paved and unpaved roads in Spokane contribute three-fourths of the anthropogenic PM 10 (neglecting wind-blown dust from agricultural areas). A study was conducted in the summer and fall of 1992 and again in the spring and summer of 1994 to measure PM 10 emission rates from paved and unpaved roads in Eastern Washington state using a novel tracer technique. A known amount of an inert tracer (SF 6) was released and concentrations of PM 10 and SF 6 downwind of the road, along with meteorological parameters and traffic volume, were measured. The results of the tracer experiments showed that within experimental uncertainties the PM 10 and the tracer gas disperse in the same manner, suggesting that the use of a tracer in a line source to simulate roadway PM 10 emissions can provide a tool for improving the existing emission inventories from roads. The emission factors obtained from two unpaved road experiments (136 g per vehicle per kilometer traveled, or g VKT -1, and 336 g VKT -1) were similar in magnitude to those predicted using currently accepted empirical algorithms. The factors determined from six paved road experiments were approximately 80% higher than that predicted using current formulae (6.7 ± 3.7 g VKT -1 compared to 3.7 g VKT -1) for two-lane roads with daily traffic less than 10,000 vehicles. For major highways (4 + lanes and traffic in excess of 10,000 vehicles per day) the emission factors obtained from the tracer experiments were, on average, 44% lower than those predicted using standard formulae (1.0 ± 0.5 g VKT -1 compared to 1.8 g VKT -1). The calculated emission factors for paved roads exhibited a wide range of variability, suggesting that in order to quantify PM 10 emission rates from paved roads, more investigation is warranted.

  7. Diffusion NMR methods applied to xenon gas for materials study.

    PubMed

    Mair, R W; Rosen, M S; Wang, R; Cory, D G; Walsworth, R L

    2002-12-01

    We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. PMID:12807139

  8. Macro and micro scale interactions between cohesive sediment tracers and natural mud.

    NASA Astrophysics Data System (ADS)

    Spencer, Kate; Manning, Andrew; Droppo, Ian; Leppard, Gary; Benson, Thomas

    2010-05-01

    Understanding the dispersion patterns of fine, cohesive sediment (< 63 micron) is fundamental to the sustainable management of aquatic environments. In order to develop sediment transport models and predict sediment dispersion, accurate field techniques for the measurement of sediment transport are required. Although this is relatively simple for the sand sized fraction, measuring transport pathways for cohesive sediment is more problematic. Cohesive sediment tracers developed for this purpose include synthetic tracer particles (e.g. polymers) and labelled natural clays (e.g. Mahler et al. 1998, Yin et al. 1999, Krezoski 1985; Spencer et al. 2007) and a fundamental assumption is that the tracer has the same physical properties as natural sediment. For the cohesive fraction this means that the tracer must be incorporated into and transported via floc aggregates (Black et al. 2006). A few studies have examined the physical behaviour of cohesive tracers (e.g. Manning et al. in press) but most are limited to the examination of gross settling characteristics (e.g. Louisse et al. 1986) rather than floc formation and behaviour. This work focuses on a labelled natural clay; a Ho-montmorillonite (see Spencer et al. 2007). The aims of this work were to examine the physical characteristics, internal structure and settling dynamics of the tracer and to determine whether the tracer flocculated and interacted with natural estuarine muds at both macro- and microscales. To our knowledge, this is the first study to present data examining the flocculation characteristics and structure of cohesive sediment tracers and their interaction with natural sediment. Macroscale floc characteristics such as floc size and settling velocity measurements were obtained using the LabSFLOC - Laboratory Spectral Flocculation Characteristics - instrument. Floc density, porosity, dry mass, and mass settling flux were then calculated. Floc internal microstructure (1-2 nm) and elemental floc composition were observed using TEM (transmission electron microscopy) and EDS (energy dispersive spectroscopy). The tracer formed macroflocs (i.e. flocs > 160 micron important for sediment deposition) that could not be distinguished statistically in terms of size and settling velocity from natural mud, although the tracer microflocs (< 160 micron and important building blocks for floc growth) were statistically smaller and settled more slowly. Due to the absence of organic matter tracer flocs were spheroidal in shape compared to elongate ‘stringer' natural mud flocs. The interaction of the tracer and natural mud was examined by observing the physical and dynamic floc characteristics of tracer and natural mud mixtures. The microflocs decreased linearly in floc size and sphericity with increasing tracer content suggesting interaction between tracer and natural mud. However, individual microflocs (< 20 micron using TEM) containing both tracer and natural mud were not observed suggesting that this interaction is not on a particle to particle basis, rather macroflocs are comprised of discrete microflocs of pure tracer or pure natural mud. Macroflocs comprising both tracer and natural mud mixtures were larger and settled faster than either the pure tracer or pure natural mud flocs. We hypothesise that this is due to irregular packing of the differently shaped natural mud and tracer flocs. Therefore, the tracer flocculates and has key characteristics which can not be distinguished from natural cohesive mud. The tracer interacts with natural mud, but because of floc shape the transport characteristics of mixed flocs differ from natural mud. Therefore, although this tracer meets some requirements of tracer technology and is superior to synthetic tracer particles in terms of matching the physical characteristics of cohesive mud, the mixed tracer and natural mud flocs have different settling behaviour. This has implications for the use of cohesive tracers to understand natural mud transport.

  9. Noisy Lagrangian Tracers for Filtering Random Rotating Compressible Flows

    NASA Astrophysics Data System (ADS)

    Chen, Nan; Majda, Andrew J.; Tong, Xin T.

    2015-06-01

    The recovery of a random turbulent velocity field using Lagrangian tracers that move with the fluid flow is a practically important problem. This paper studies the filtering skill of -noisy Lagrangian tracers in recovering random rotating compressible flows that are a linear combination of random incompressible geostrophically balanced (GB) flow and random rotating compressible gravity waves. The idealized random fields are defined through forced damped random amplitudes of Fourier eigenmodes of the rotating shallow-water equations with the rotation rate measured by the Rossby number . In many realistic geophysical flows, there is fast rotation so satisfies and the random rotating shallow-water equations become a slow-fast system where often the primary practical objective is the recovery of the GB component from the Lagrangian tracer observations. Unfortunately, the -noisy Lagrangian tracer observations are highly nonlinear and mix the slow GB modes and the fast gravity modes. Despite this inherent nonlinearity, it is shown here that there are closed analytical formulas for the optimal filter for recovering these random rotating compressible flows for any involving Ricatti equations with random coefficients. The performance of the optimal filter is compared and contrasted through mathematical theorems and concise numerical experiments with the performance of the optimal filter for the incompressible GB random flow with -noisy Lagrangian tracers involving only the GB part of the flow. In addition, a sub-optimal filter is defined for recovering the GB flow alone through observing the -noisy random compressible Lagrangian trajectories, so the effect of the gravity wave dynamics is unresolved but effects the tracer observations. Rigorous theorems proved below through suitable stochastic fast-wave averaging techniques and explicit formulas rigorously demonstrate that all these filters have comparable skill in recovering the slow GB flow in the limit for any bounded time interval. Concise numerical experiments confirm the mathematical theory and elucidate various new features of filter performance as the Rossby number , the number of tracers and the tracer noise variance change.

  10. Comparison of three magnetic nanoparticle tracers for sentinel lymph node biopsy in an in vivo porcine model

    PubMed Central

    Pouw, Joost J; Ahmed, Muneer; Anninga, Bauke; Schuurman, Kimberley; Pinder, Sarah E; Van Hemelrijck, Mieke; Pankhurst, Quentin A; Douek, Michael; ten Haken, Bennie

    2015-01-01

    Introduction Breast cancer staging with sentinel lymph node biopsy relies on the use of radioisotopes, which limits the availability of the procedure worldwide. The use of a magnetic nanoparticle tracer and a handheld magnetometer provides a radiation-free alternative, which was recently evaluated in two clinical trials. The hydrodynamic particle size of the used magnetic tracer differs substantially from the radioisotope tracer and could therefore benefit from optimization. The aim of this study was to assess the performance of three different-sized magnetic nanoparticle tracers for sentinel lymph node biopsy within an in vivo porcine model. Materials and methods Sentinel lymph node biopsy was performed within a validated porcine model using three magnetic nanoparticle tracers, approved for use in humans (ferumoxytol, with hydrodynamic diameter dH =32 nm; Sienna+®, dH =59 nm; and ferumoxide, dH =111 nm), and a handheld magnetometer. Magnetometer counts (transcutaneous and ex vivo), iron quantification (vibrating sample magnetometry), and histopathological assessments were performed on all ex vivo nodes. Results Transcutaneous “hotspots” were present in 12/12 cases within 30 minutes of injection for the 59 nm tracer, compared to 7/12 for the 32 nm tracer and 8/12 for the 111 nm tracer, at the same time point. Ex vivo magnetometer counts were significantly greater for the 59 nm tracer than for the other tracers. Significantly more nodes per basin were excised for the 32 nm tracer compared to other tracers, indicating poor retention of the 32 nm tracer. Using the 59 nm tracer resulted in a significantly higher iron accumulation compared to the 32 nm tracer. Conclusion The 59 nm tracer demonstrated rapid lymphatic uptake, retention in the first nodes reached, and accumulation in high concentration, making it the most suitable tracer for intraoperative sentinel lymph node localization. PMID:25709445

  11. Experimental Study of High-Z Gas Buffers in Gas-Filled ICF Engines

    SciTech Connect

    Rhodes, M A; Kane, J; Loosmore, G; DeMuth, J; Latkowski, J

    2010-12-03

    ICF power plants, such as the LIFE scheme at LLNL, may employ a high-Z, target-chamber gas-fill to moderate the first-wall heat-pulse due to x-rays and energetic ions released during target detonation. To reduce the uncertainties of cooling and beam/target propagation through such gas-filled chambers, we present a pulsed plasma source producing 2-5 eV plasma comprised of high-Z gases. We use a 5-kJ, 100-ns theta discharge for high peak plasma-heating-power, an electrode-less discharge for minimizing impurities, and unobstructed axial access for diagnostics and beam (and/or target) propagation studies. We will report on the plasma source requirements, design process, and the system design.

  12. Tracer Lamination in the Stratosphere: A Global Climatology

    NASA Technical Reports Server (NTRS)

    Appenzeller, Christof; Holton, James R.

    1997-01-01

    Vertical soundings of stratospheric ozone often exhibit laminated tracer structures characterized by strong vertical tracer gradients. The change in time of these gradients is used to define a tracer lamination rate. It is shown that this quantity can be calculated by the cross product of the horizontal temperature and horizontal tracer gradients. A climatology based on UARS satellite-borne ozone data and on ozone-like pseudotracer data is presented. Three stratospheric regions with high lamination rates were found: the part of the stratospheric overworld which is influenced by the polar vortex, the part of the lowermost stratosphere which is influenced by the tropopause and a third region in the subtropical lower stratosphere mainly characterized with strong vertical shear. High lamination rates in the stratospheric overworld were absent during summer, whereas in the lowermost stratosphere high lamination rates were found year-round. This is consistent with the occurrence and seasonal variation of the horizontal tracer gradient and vertical shear necessary for tilting the tracer surfaces. During winter, high lamination rates associated with the stratospheric polar vortex are present down to approximately 100 hPa. Several features of the derived climatology are roughly consistent with earlier balloon-borne studies. The patterns in the southern and northern hemisphere are comparable, but details differ as anticipated from a less disturbed and more symmetric southern polar vortex.

  13. Hydrogeological processes in a fluviokarstic area inferred from the analysis of natural hydrogeochemical tracers. The case study of eastern Serranía de Ronda (S Spain)

    NASA Astrophysics Data System (ADS)

    Barberá, J. A.; Andreo, B.

    2015-04-01

    In riverine karst areas, surface water interacts with the groundwater flowing through carbonate aquifers. Understanding the interference of water fluxes in this type of environments is essential to effectively manage the groundwater resources, particularly in areas where karst aquifers comprise the main source of drinking water. In this research, the interaction between surface water and groundwater in the Turón river valley (eastern Serranía de Ronda, S Spain) and the functioning of Sierra Blanquilla karst aquifer have been characterised by means of hydrodynamic monitoring and the combined use of physical-chemical parameters and natural hydrogeochemical tracers. The results show connected/gaining streams in the river stretches close to the permanent springs, while in the surroundings of the overflow springs the river reaches behave as gaining (high flow) and as perched/losing (low flow). Soil natural tracers permit tracing runoff arising from the upper part of the hydrological watershed via river, which interacts with the groundwater drained in the main discharge area of the aquifer. Furthermore, the analysis of hydrogeochemical data and chemographs demonstrate that Sierra Blanquilla aquifer behaves as a typical conduit flow system in which the unsaturated zone predominantly participates during high flow periods, while the saturated zone is more active in low flow, when the groundwater inputs maintain the Turón river discharge. The more detailed understanding of how the hydrogeochemical characteristics of groundwater vary over time and space has direct consequences on karst spring protection and in the environmental preservation of groundwater-ecodependent systems.

  14. Radium uptake during barite recrystallization at 23 ± 2 °C as a function of solution composition: An experimental 133Ba and 226Ra tracer study

    NASA Astrophysics Data System (ADS)

    Curti, E.; Fujiwara, K.; Iijima, K.; Tits, J.; Cuesta, C.; Kitamura, A.; Glaus, M. A.; Müller, W.

    2010-06-01

    High-purity synthetic barite powder was added to pure water or aqueous solutions of soluble salts (BaCl 2, Na 2SO 4, NaCl and NaHCO 3) at 23 ± 2 °C and atmospheric pressure. After a short pre-equilibration time (4 h) the suspensions were spiked either with 133Ba or 226Ra and reacted under constant agitation during 120-406 days. The pH values ranged from 4 to 8 and solid to liquid (S/L) ratios varied from 0.01 to 5 g/l. The uptake of the radiotracers by barite was monitored through repeated sampling of the aqueous solutions and radiometric analysis. For both 133Ba and 226Ra, our data consistently showed a continuous, slow decrease of radioactivity in the aqueous phase. Mass balance calculations indicated that the removal of 133Ba activity from aqueous solution cannot be explained by surface adsorption only, as it largely exceeded the 100% monolayer coverage limit. This result was a strong argument in favor of recrystallization (driven by a dissolution-precipitation mechanism) as the main uptake mechanism. Because complete isotopic equilibration between aqueous solution and barite was approached or even reached in some experiments, we concluded that during the reaction all or substantial fractions of the initial solid had been replaced by newly formed barite. The 133Ba data could be successfully fitted assuming constant recrystallization rates and homogeneous distribution of the tracer into the newly formed barite. An alternative model based on partial equilibrium of 133Ba with the mineral surface (without internal isotopic equilibration of the solid) could not reproduce the measured activity data, unless multistage recrystallization kinetics was assumed. Calculated recrystallization rates in the salt solutions ranged from 2.8 × 10 -11 to 1.9 × 10 -10 mol m -2 s -1 (2.4-16 ?mol m -2 d -1), with no specific trend related to solution composition. For the suspensions prepared in pure water, significantly higher rates (˜5.7 × 10 -10 mol m -2 s -1 or ˜49 ?mol m -2 d -1) were determined. Radium uptake by barite was determined by monitoring the decrease of 226Ra activity in the aqueous solution with alpha spectrometry, after filtration of the suspensions and sintering. The evaluation of the Ra uptake experiments, in conjunction with the recrystallization data, consistently indicated formation of non-ideal solid solutions, with moderately high Margules parameters ( WAB = 3720-6200 J/mol, a0 = 1.5-2.5). These parameters are significantly larger than an estimated value from the literature ( WAB = 1240 J/mol, a0 = 0.5). In conclusion, our results confirm that radium forms solid solutions with barite at fast kinetic rates and in complete thermodynamic equilibrium with the aqueous solutions. Moreover, this study provides quantitative thermodynamic data that can be used for the calculation of radium concentration limits in environmentally relevant systems, such as radioactive waste repositories and uranium mill tailings.

  15. Investigation of Carbon Distribution with 14 C as Tracer for Carbon Dioxide (CO 2 ) Sequestration through NH 4 HCO 3 Production

    Microsoft Academic Search

    Zhongxian Cheng; Youhua Ma; Xin Li; Wei-Ping Pan; Zhiming Zhang

    2007-01-01

    This work studies carbon fate using 14C tracer technique in ecosystems when synthesized fertilizer is applied. The concept of aqueous ammonia solution scrubbing CO2 from flue gas is used in the fertilizer synthesis. Products after the capture are ammonium bicarbonate (ABC, NH4HCO3) or long-term effect ammonium bicarbonate (LEABC, NH4HCO3), an economic source of nitrogen fertilizer. The fertilizer (ABC or LEABC)

  16. Selected examples of gas-phase ion chemistry studies.

    PubMed

    Nibbering, Nico M M

    2013-01-01

    Gas-phase ion chemistry is an area in mass spectrometry that has received much research interest since the mid fifties of the last century. Although the focus of mass spectrometric research has shifted the last twenty years largely to life science studies, including proteomics, genomics and metabolomics, there are still several groups in the world active in gas-phase ion chemistry of both positive and negative ions, either unimolecularly and/or bimolecularly. In this tutorial lecture the formation and determination of tautomeric ion structures and intra-ionic catalyzed tautomerization in the gas phase will be discussed. In addition, an example of formation of different tautomeric structures in protic and aprotic solvents under electrospray ionization conditions will be given, as established by gas-phase infrared multiphoton dissociation spectroscopy. This will be followed by presenting an example of time-resolved MS/MS which enables to identify the structure of an ion, generated at a particular molecular ion lifetime. At the end of the lecture the power of ion mobility will be shown in elucidating the mechanism of epimerization of bis-Tröger bases having chiral nitrogen centers. PMID:24349921

  17. Melanin-concentrating hormone and neuropeptide EI projections from the lateral hypothalamic area and zona incerta to the medial septal nucleus and spinal cord: a study using multiple neuronal tracers.

    PubMed

    Bittencourt, J C; Elias, C F

    1998-09-14

    The projection pathways of neurons containing melanin-concentrating hormone (MCH) and neuropeptide EI (NEI), two peptides colocalized in the lateral hypothalamic area (LHA) of the rat, were mapped using the retrogradely transported fluorescent dyes, true blue (TB) and diamidino yellow (DY). TB and DY were injected into the medial septum/diagonal band complex (MS/DBC) and the thoracic level of the spinal cord (SpCd), respectively. Brains from rats receiving only one or both tracer injections were immunohistochemically stained for MCH in the spinal cord and NEI in the forebrain. In the MS/DBC, NEI-immunoreactive (-ir) fibers are concentrated in the MS and in the vertical and horizontal limbs of the DBC. In the SpCd, MCH-ir fibers are concentrated primarily in lamina X. Of the diencephalic NEI-ir neurons, 37.15% project to the MS/DBC and reside in the rostromedial zona incerta (ZIm), in the LHAt and LHAp, and in the perifornical region. Of the diencephalic MCH-ir neurons, 20.2% project to the SpCd and reside in the LHAt and LHAp. In addition, 2. 2% of the MCH-ir cells and 8.7% of the NEI-ir cells in the hypothalamus were labeled with both retrograde tracers and thus project to both the MS/DBC and SpCd. These dual projection neurons are located mainly in the LHAt and LHAp. Anterograde injections of the tracer Phaseolus vulgaris leucoagglutinin into the LHAt and ZIm corroborated our findings in the retrograde studies. Potential autonomic and behavioral roles of the NEI and MCH systems in the MS/DBC and the SpCd are discussed. PMID:9733903

  18. TRACING MOLECULAR GAS MASS IN EXTREME EXTRAGALACTIC ENVIRONMENTS: AN OBSERVATIONAL STUDY

    SciTech Connect

    Zhu Ming [Joint Astronomy Centre/National Research Council Canada, 660 N. A'ohoku Place, University Park, Hilo, HI 96720 (United States); Papadopoulos, Padeli P. [Argelander Instituet fuer Astronomie, Auf dem Huegel 71, 53121 Bonn (Germany); Xilouris, Emmanuel M. [Institute of Astronomy and Astrophysics, National Observatory of Athens, P. Penteli, 15236 Athens (Greece); Kuno, Nario [Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1305 (Japan); Lisenfeld, Ute, E-mail: m.zhu@jach.hawaii.ed, E-mail: padeli@astro.uni-bonn.d, E-mail: xilouris@astro.noa.g, E-mail: kuno@nro.nao.ac.j, E-mail: ute@ugr.e [Departamento de fisica Teorica y del Cosmos, Universidad de Granada (Spain)

    2009-12-01

    We present a new observational study of the {sup 12}CO(1-0) line emission as an H{sub 2} gas mass tracer under extreme conditions in extragalactic environments. Our approach is to study the full neutral interstellar medium (H{sub 2}, H I, and dust) of two galaxies whose bulk interstellar medium (ISM) resides in environments that mark (and bracket) the excitation extremes of the ISM conditions found in infrared luminous galaxies, the starburst NGC 3310, and the quiescent spiral NGC 157. Our study maintains a robust statistical notion of the so-called X = N(H{sub 2})/I {sub CO} factor (i.e., a large ensemble of clouds is involved) while exploring its dependence on the very different average ISM conditions prevailing within these two systems. These are constrained by fully sampled {sup 12}CO(3-2) and {sup 12}CO(1-0) observations, at a matched beam resolution of half-power beam width approx15'', obtained with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii) and the 45 m telescope of the Nobeyama Radio Observatory in Japan, combined with sensitive 850 mum and 450 mum dust emission and H I interferometric images which allow a complete view of all the neutral ISM components. Complementary {sup 12}CO(2-1) observations were obtained with the JCMT toward the center of the two galaxies. We found an X factor varying by a factor of 5 within the spiral galaxy NGC 157 and about two times lower than the Galactic value in NGC 3310. In addition, the dust emission spectrum in NGC 3310 shows a pronounced submillimeter 'excess'. We tried to fit this excess by a cold dust component but very low temperatures were required (T {sub C} approx 5-11 K) with a correspondingly low gas-to-dust mass ratio of approx5-43. We furthermore show that it is not possible to maintain the large quantities of dust required at these low temperatures in this starburst galaxy. Instead, we conclude that the dust properties need to be different from Galactic dust in order to fit the submillimeter 'excess'. We show that the dust spectral energy distribution can be fitted by an enhanced abundance of very small grains and discuss different alternatives.

  19. Numerical studies of hypersonic binary gas-mixture flows near a sphere

    E-print Network

    Riabov, Vladimir V.

    Numerical studies of hypersonic binary gas-mixture flows near a sphere V.V. Riabov 1 Diffusive] to study the flow. In the present study, diffusive effects in hypersonic flows of binary gas-mixtures near

  20. 2009 Arctic Mars Analogue Svalbard Expedition (AMASE) Evolved Gas Studies

    Microsoft Academic Search

    P. R. Mahaffy; A. McAdam; J. Eigenbrode; A. Steele

    2009-01-01

    The Arctic Mars Analogue Svalbard Expedition (AMASE) continued its multi-year campaign in August 2009 to study selected sedimentary and igneous environments in this geological diverse archipelago using a variety of measurement techniques and protocols that are candidates for future Mars missions. The X-ray diffraction mineralogical and evolved gas analysis (EGA) employed during the AMASE-2009 campaign closely mimicked similar experiments that

  1. A radio study of gas loss processes in nearby galaxies

    Microsoft Academic Search

    Ananda Hota

    2007-01-01

    The work in this thesis involves detailed multi-frequency radio continuum (from 325 MHz to 15 GHz) and HI spectroscopic studies of a few representative nearby galaxies which are experiencing gas-loss from their disks due to different physical processes. These processes are starburst-driven galactic wind or superwind outflow (NGC1482, NGC6764), active galactic nucleus (AGN)-driven nuclear outflow (NGC6764, NGC4438), ram pressure stripping

  2. Theoretical and experimental studies of optically pumped molecular gas lasers

    Microsoft Academic Search

    Amarin Ratanavis

    2010-01-01

    Optically pumped molecular gas lasers based on vibrational-rotational transitions in the infrared spectral region were studied experimentally and theoretically. A model was developed to predict the performance of such lasers and explore their potentials for energy and power scaling. This rate equation model was applied to explore the performance of a second-overtone (pulsed) and a first-overtone (CW) pumped HBr laser.

  3. Ab initio study of CNT NO 2 gas sensor

    Microsoft Academic Search

    Shu Peng; Kyeongjae Cho; Pengfei Qi; Hongjie Dai

    2004-01-01

    NO2 gas adsorption, diffusion, and reaction on a single walled carbon nanotube (SWNT) surface are studied using ab initio simulations. The small diffusion barriers of NO2 on SWNT surface suggest that NO2 molecules can produce NO and NO3 through chemical reactions. From the estimation of diffusion barriers and binding energies of NO2, NO, and NO3 on a SWNT surface, we

  4. Study of real-time visualization of gas\\/odor flow image using gas sensor array

    Microsoft Academic Search

    H Ishida; T Yamanaka; N Kushida; T Nakamoto; T Moriizumi

    2000-01-01

    A new method to find a gas\\/odor source is proposed. A portable homogeneous gas sensor array is used to visualize the flow of a target gas. The direction of a gas source is estimated using a real-time image processing algorithm, and the source is located by following the estimated direction. The design of the sensor array has been performed using

  5. Tracer interrelationships in the stratosphere

    Microsoft Academic Search

    R. Alan Plumb

    2007-01-01

    Relationships between long-lived stratospheric tracers, manifested in similar spatial structures on scales ranging from a few to several thousand kilometers, are displayed most strikingly if the mixing ratio of one is plotted against another, when the data collapse onto remarkably compact curves. Distinct curves form in the polar vortex, the midlatitude “surf zones”, and the tropics. Theory predicts such relationships

  6. A simulation study on gas-to-liquid (natural gas to Fischer–Tropsch synthetic fuel) process optimization

    Microsoft Academic Search

    Yong Heon Kim; Ki-Won Jun; Hyunku Joo; Chonghun Han; In Kyu Song

    2009-01-01

    A simulation study on gas-to-liquid (natural gas to Fischer–Tropsch synthetic fuel) process was carried out in order to find optimum reaction conditions for maximum production of synthetic fuel. Optimum operating condition for GTL (gas-to-liquid) process was determined by changing reaction variable such as temperature. During the simulation, overall synthetic process was assumed to proceed under steady-state conditions. It was also

  7. Chelated Indium Activable Tracers for Geothermal Reservoirs

    E-print Network

    Stanford University

    SGP-TR-99 Chelated Indium Activable Tracers for Geothermal Reservoirs Constantinos V. Indium was se1ecti:d to be the most promising activable tracer. The thermal stability of indium tracer of the soluble indium concentration was made as a f'unction of time by neutron activation analysis. From the data

  8. Tracer Tests in flooded underground mines

    Microsoft Academic Search

    Ch. Wolkersdorfer

    Tracer tests are a common means to investigate the hydrogeological conditions in the hydro- sphere. Nevertheless, only few successful tracer tests in flooded underground mines have been described. In two flooded German underground mines tracer tests with club moss spores (Lycopodium clavatum) and mi- crospheres had been conducted by the use of the LydiA technique. Both times, effective velocities between

  9. Hydraulic fracture diagnosis using chemical tracers

    SciTech Connect

    Gardien, C.J.; Pope, G.A.; Hill, A.D. [Univ. of Texas, Austin, TX (United States)

    1996-12-31

    In this paper, the use of a single-well tracer test for hydraulic fracture diagnosis is explored. Existing methods for hydraulic fracture diagnosis (e.g. well logging and pressure transient testing) often do not provide accurate or unique solutions, so improved methods are needed. The principle behind the use of tracers for hydraulic fracture diagnosis is the dominance of the fracture on the flow field in a hydraulically fractured reservoir and the strong influence of fracture parameters on the flow field. This will be reflected in the tracer response curves of a single-well tracer test in a fractured well, making the tracer test diagnostic of the fracture and its parameters. Several kinds of tracers (conservative, sorbing, reactive and partitioning) have been tested for their diagnostic value by numerical modeling. The major factors of influence on the tracer response have been identified. These factors are combined in a ratio, the tracer influence ratio, which can be used for the estimation of the product of fracture length and fracture height. The tracer behavior is dispersion dominated, which implies that the tracer dispersivity must be known for the tracer test interpretation, or it could be estimated from another tracer test in the same well or another well in the formation. Extensive sensitivity analyses have indicated that the tracer test is only mildly sensitive to a large number of variables which is beneficial for the purpose of hydraulic fracture diagnosis. A conservative tracer appears to be the best candidate for hydraulic fracture diagnosis using a single-well test since it has the largest diagnostic value when the tracer test is optimized.

  10. The Postshock Chemical Lifetimes of Outflow Tracers and a Possible New Mechanism to Produce Water Ice Mantles

    NASA Technical Reports Server (NTRS)

    Bergin, Edwin A.; Melnick, Gary J.; Neufeld, David A.

    1998-01-01

    We have used a coupled time-dependent chemical and dynamical model to investigate the lifetime of the chemical legacy in the wake of C-type shocks. We concentrate this study on the chemistry of H2O and O2, two molecules which are predicted to have abundances that are significantly affected in shock-heated gas. Two models are presented: (1) a three-stage model of preshock, shocked, and postshock gas; and (2) a Monte Carlo cloud simulation where we explore the effects of stochastic shock activity on molecular gas over a cloud lifetime. For both models we separately examine the pure gas-phase chemistry as well as the chemistry including the interactions of molecules with grain surfaces. In agreement with previous studies, we find that shock velocities in excess of 10 km/s are required to convert all of the oxygen not locked in CO into H2O before the gas has an opportunity to cool. For pure gas phase models the lifetime of the high water abundances, or "H2O legacy," in the postshock gas is approximately (4-7) x 10(exp 5) yr, independent of the gas density. A density dependence for the lifetime of H2O is found in gas-grain models as the water molecules deplete onto grains at the depletion timescale. Through the Monte Carlo cloud simulation we demonstrate that the time-average abundance of H2O, the weighted average of the amount of time gas spends in preshock, shock, and postshock stages, is a sensitive function of the frequency of shocks. Thus we predict that the abundance of H2O, and to a lesser extent O2, can be used to trace the history of shock activity in molecular gas. We use previous large-scale surveys of molecular outflows to constrain the frequency of 10 km/s shocks in regions with varying star formation properties and discuss the observations required to test these results. We discuss the postshock lifetimes for other possible outflow tracers (e.g., SiO and CH3OH) and show that the differences between the lifetimes for various tracers can produce potentially observable chemical variations between younger and older outflows. For gas-grain models we find that the abundance of water-ice on grain surfaces can be quite large and is comparable to that observed in molecular clouds. This offers a possible alternative method to create water mantles without resorting to grain surface chemistry: gas heating and chemical modification due to a C-type shock and subsequent depletion of the gas-phase species onto grain mantles.

  11. Study of the vapor-gas front of a variable conductance thermosyphon using advanced optical techniques 

    E-print Network

    Doerksen, Glenn Robert

    1993-01-01

    The influence of noncondensable gases on the operation of a thermosyphon was studied experimentally. The operating characteristics were studied while varying the power input, gas quantity, and gas type. The results were compared with existing...

  12. Fractal tracer distributions in turbulent field theories

    E-print Network

    Jonas Lundbek Hansen; Tomas Bohr

    1997-09-09

    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 thereby find a regime in which the particle distribution is a strange attractor. We compare the Lyapunov dimension to the information dimension of actual particle distributions and show that there is good agreement with the Kaplan-Yorke conjecture. Similar phenomena have been observed experimentally.

  13. Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer

    SciTech Connect

    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.

  14. Analysing the capabilities and limitations of tracer tests in stream-aquifer systems

    USGS Publications Warehouse

    Wagner, B.J.; Harvey, J.W.

    2001-01-01

    The goal of this study was to identify the limitations that apply when we couple conservative-tracer injection with reactive solute sampling to identify the transport and reaction processes active in a stream. Our methodology applies Monte Carlo uncertainty analysis to assess the ability of the tracer approach to identify the governing transport and reaction processes for a wide range of stream-solute transport and reaction scenarios likely to be encountered in high-gradient streams. Our analyses identified dimensionless factors that define the capabilities and limitations of the tracer approach. These factors provide a framework for comparing and contrasting alternative tracer test designs.

  15. A Tracer Interaction Method for Nonlinear Pharmacokinetics Analysis: Application to Evaluation of Nonlinear Elimination

    Microsoft Academic Search

    P. Veng-Pedersen; J. A. Widness; J. Wang; R. L. Schmidt

    1997-01-01

    A drug tracer is most commonly applied to get information about the pharmacokinetics (PK) of a drug that is not confounded by an endogenously produced drug or an unknown drug input. An equally important use of tracers that has not been fully recognized is their use in the study of nonlinear PK behavior. In the present study a system analysis

  16. 28 CFR Appendix B to Part 79 - Blood-Gas Study Tables

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2 2010-07-01 2010-07-01 false Blood-Gas Study Tables B Appendix B to Part 79... Pt. 79, App. B Appendix B to Part 79—Blood-Gas Study Tables For arterial blood-gas studies performed at test locations...

  17. 28 CFR Appendix B to Part 79 - Blood-Gas Study Tables

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2 2013-07-01 2013-07-01 false Blood-Gas Study Tables B Appendix B to Part 79... Pt. 79, App. B Appendix B to Part 79—Blood-Gas Study Tables For arterial blood-gas studies performed at test locations...

  18. 28 CFR Appendix B to Part 79 - Blood-Gas Study Tables

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2 2014-07-01 2014-07-01 false Blood-Gas Study Tables B Appendix B to Part 79... Pt. 79, App. B Appendix B to Part 79—Blood-Gas Study Tables For arterial blood-gas studies performed at test locations...

  19. 28 CFR Appendix B to Part 79 - Blood-Gas Study Tables

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2 2012-07-01 2012-07-01 false Blood-Gas Study Tables B Appendix B to Part 79... Pt. 79, App. B Appendix B to Part 79—Blood-Gas Study Tables For arterial blood-gas studies performed at test locations...

  20. 28 CFR Appendix B to Part 79 - Blood-Gas Study Tables

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2 2011-07-01 2011-07-01 false Blood-Gas Study Tables B Appendix B to Part 79... Pt. 79, App. B Appendix B to Part 79—Blood-Gas Study Tables For arterial blood-gas studies performed at test locations...

  1. Tracer diffusion inside fibrinogen layers

    NASA Astrophysics Data System (ADS)

    Cie?la, Micha?; 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.

  2. Neurotransmitters in the Gas Phase: La-Mb Studies

    NASA Astrophysics Data System (ADS)

    Cabezas, C.; Mata, S.; López, J. C.; Alonso, J. L.

    2011-06-01

    LA-MB-FTMW spectroscopy combines laser ablation with Fourier transform microwave spectroscopy in supersonic jets overcoming the problems of thermal decomposition associated with conventional heating methods. We present here the results on LA-MB-FTMW studies of some neurotransmitters. Six conformers of dopamine, four of adrenaline, five of noradrenaline and three conformers of serotonin have been characterized in the gas phase. The rotational and nuclear quadrupole coupling constants extracted from the analysis of the rotational spectrum are directly compared with those predicted by ab initio methods to achieve the conclusive identification of different conformers and the experimental characterization of the intramolecular forces at play which control conformational preferences.

  3. Numerical studies of gas composition differentiation during gas hydrate formation: An application to the IODP site 1327

    NASA Astrophysics Data System (ADS)

    Yuncheng, C.; Chen, D.

    2014-12-01

    Structure I methane hydrate is the most common type found in nature. Structure I gas hydrate has two types of cages that gas molecules may be hosted. Because the larger cavities filled with ethane would be more stable than those filled by methane (Sloan and Koh, 2008), the larger cavities preferentially enclose ethane during the formation of gas hydrate, which results gas composition differentiation during gas hydrate formation. Based on the principle of gas composition differentiation, we establish a numerical model for the gas composition differentiation between methane and ethane during gas hydrate accumulation and applied the model to IODP site 1327. The simulation shows that the gas composition differentiation only occurs at the interval where gas hydrate presents. The lowest methane/ethane (C1/C2) point indicates the bottom of hydrate zone, and the composition differentiation produces the upward increase of C1/C2 within the gas hydrate zone. The C1/C2 reaches the largest value at the top occurrence of gas hydrate and keeps relative stable above the top occurrence of gas hydrate. The top and bottom occurrence of gas hydrate indicated by the inflection points of the C1/C2 profile are similar to those indicated by the negative anomalies of measured chloride concentrations (Riedel et al., 2006). By comparing with the measured C1/C2, the differentiation coefficient (kh=Xe,h/Xe,w, Xe,h is C1/C2 of the formed gas hydrate, Xe,w [mol/kg] is the concentration of ethane in water ) is calculated to 70 kg/mol. The top occurrence of gas hydrate indicated by the C1/C2 profile also confines the water flux to be 0.4kg/m2-year, similar to that confined by the chloride profile. To best fit the measured C1/C2 profile, the methane flux is calculated to 0.04mol/m2-year. Therefore, the C1/C2 profile could be used to obtain the gas hydrate accumulation information. Acknowledgments:This study was supported by Chinese National Science Foundation (grant 41303044, 91228206 ) ReferencesRiedel M, Collett T S, Malone, M J, et al. (2006), Proceedings of the Integrated Ocean Drilling, Volume 311. Sloan D E, Koh C A. (2008), Clathrate Hydrates of Natural Gases. Third edition. CRC Press, New York,USA

  4. Progress in isotope tracer hydrology in Canada

    NASA Astrophysics Data System (ADS)

    Gibson, J. J.; Edwards, T. W. D.; Birks, S. J.; St Amour, N. A.; Buhay, W. M.; McEachern, P.; Wolfe, B. B.; Peters, D. L.

    2005-01-01

    An overview of current research in isotope hydrology, focusing on recent Canadian contributions, is discussed under the headings: precipitation networks, hydrograph separation and groundwater studies, river basin hydrology, lake and catchment water balance, and isotope palaeohydrology from lake sediment records. Tracer-based techniques, relying primarily on the naturally occurring environmental isotopes, have been integrated into a range of hydrological and biogeochemical research programmes, as they effectively complement physical and chemical techniques. A significant geographic focus of Canadian isotope hydrology research has been on the Mackenzie River basin, forming contributions to programmes such as the Global Energy and Water Cycle Experiment. Canadian research has also directly supported international efforts such as the International Atomic Energy Agency's (IAEA) Global Network for Isotopes in Precipitation and IAEAs Coordinated Research Project on Large River Basins. One significant trend in Canadian research is toward sustained long-term monitoring of precipitation and river discharge to enable better characterization of spatial and temporal variability in isotope signatures and their underlying causes. One fundamental conclusion drawn from previous studies in Canada is that combined use of 18O and 2H enables the distinction of precipitation variability from evaporation effects, which offers significant advantages over use of the individual tracers alone. The study of hydrological controls on water chemistry is one emerging research trend that stems from the unique ability to integrate isotope sampling within both water quality and water quantity surveys. Copyright

  5. Upscaling particle transport in discrete fracture networks: 1. Nonreactive tracers

    NASA Astrophysics Data System (ADS)

    Frampton, A.; Cvetkovic, V.

    2007-10-01

    We study tracer transport through discrete fracture networks and develop a methodology for upscaling particle breakthrough curves on the basis of fracture segment data. Our prime interest is to model the early arrival and peak of tracer breakthrough curves, i.e., to capture the bulk of the tracer mass arrival. This study is based on two-dimensional discrete fracture network simulations, combined with a truncated one-sided stable distribution as a model for upscaling particle transitions. Results indicate that this model can accurately capture the bulk mass and peak of the breakthrough distributions for an upscaled distance of at least 1 order of magnitude in terms of transport scale, which for our simulations is about 2 orders of magnitude greater than the mean fracture segment scale. We also introduce an accurate mapping algorithm for transforming Eulerian into Lagrangian flow statistics, without a priori knowledge of network connectivity.

  6. A high-performance hysteresis loop tracer

    NASA Astrophysics Data System (ADS)

    Kulik, Tadeusz; Savage, Howard T.; Hernando, Antonio

    1993-05-01

    A high-performance and inexpensive hysteresis loop tracer has been developed to measure quasistatic (0.02 Hz or less) hysteresis loops of soft ferromagnetic materials. It was applied very successfully to measure straight pieces of amorphous and nanocrystalline ribbons and amorphous wires. Especially high-magnetic-field resolution is required when nanocrystalline ferromagnets and amorphous wires are measured. Nanocrystalline materials exhibit very low coercivity (Hc=0.1-0.5 A/m). The error of Hc measurement using this tracer does not exceed 0.05 A/m even though the amorphous wires have very small cross section (0.008 mm2). The examples of hysteresis loops measured at low (50 A/m) and high magnetic field (14 kA/m) are presented. The apparatus consists of an IBM-compatible computer equipped with 12 bit analog-to-digital and digital-to-analog converters, bipolar power supply, fluxmeter, solenoid and a pickup coil connected to a compensation coil. This equipment is free of 50 Hz noise, a significant problem in the performance of low-frequency loop tracers. The software was developed to enable measurement and immediate display of the M-H hysteresis loop. Previous loops also can be displayed and printed. Calibration of the setup is also possible. In the case of straight samples the measurements are followed by calculation of demagnetization factor Nd(calc.) using the ellipsoidal approximation of the sample shape. It was found that the experimental value of Nd is 30%-40% of the calculated value Nd(calc.) for the ribbons studied. Higher values of Nd correspond to the thicker ribbons where better agreement was obtained.

  7. Study of ternary-component bismuth molybdate catalysts by /sup 18/O/sub 2/ tracer in the oxidation of propylene to acrolein

    SciTech Connect

    Ueda, W.; Moro-oka, Y.; Ikawa, T.

    1981-08-01

    Participation of lattice oxide ions of ternary-component bismuth molybdate catalysts M-Bi-Mo-O (M = Ni, Co, Mg, Mn, Ca, Sr, Ba, and Pb) was investigated using the /sup 18/O/sub 2/ tracer in the selective oxidation of propylene to acrolein. The participation of the lattice oxide ions in the oxidation is prominent on every catalyst but the extent of the participation varies significantly depending on the structure of the catalyst. Only lattice oxide ions in the bismuth molybdate phase are incorporated into the oxidized products on the catalysts (M = Ni, Co, Mg, and Mn) where M have smaller ionic radius than Bi/sup 3 +/; catalyst particles are composed of a shell of bismuth molybdates and a core of MMoO/sub 4/. On the other hand, whole oxide ions in the active particles are involved in the oxidation on catalysts having a scheelite-type structure (M = Ca, Sr, Ba, and Pb) where M has a comparable ionic radius to Bi/sup 3 +/.

  8. Steady-state single cell model simulations of photoacclimation in a vertically mixed layer: implications for biological tracer studies and primary productivity

    NASA Astrophysics Data System (ADS)

    Dusenberry, J. A.

    2000-03-01

    A numerical single-cell photoacclimation-diffusion model was constructed and used to develop criteria regarding the use of individual phytoplankton cells as tracers for vertical mixing and to illustrate how rates of vertical mixing might affect phytoplankton physiology. Both first-order and logistic representations of photoacclimation kinetics were used. Steady state was assumed for simplicity and to provide a starting point for further investigations. The modeled variance and higher moments (within a phytoplankton population) of a generic photoacclimative parameter all show trends, which are diagnostic of mixing rates and/or boundary effects. This allowed the establishment of criteria by which frequency distributions of phytoplankton physiological properties (e.g., cell fluorescence) might be used as indicators of vertical mixing. The same model can be used to predict the effects of vertical mixing on phytoplankton productivity and growth. Application of the model to both photosynthesis and carbon to chlorophyll ratios suggested that a combination of vertical mixing and hysteresis (as represented in the logistic model of photoacclimation) in acclimation kinetics can enhance specific growth rates of phytoplankton. This enhanced growth occurred as a result of mixing-induced variation in carbon to chlorophyll ratios and is in contrast to chlorophyll-specific productivity, which was maximal at low mixing rates. Differential rates of photoacclimation to upward vs. downward shifts in irradiance, may enable phytoplankton cells to better survive in a turbulent environment.

  9. A study of the sources and sinks of methane and methyl chloroform using a global three-dimensional Lagrangian tropospheric tracer transport model

    NASA Technical Reports Server (NTRS)

    Taylor, John A.; Brasseur, G. P.; Zimmerman, P. R.; Cicerone, R. J.

    1991-01-01

    Sources and sinks of methane and methyl chloroform are investigated using a global three-dimensional Lagrangian tropospheric tracer transport model with parameterized hydroxyl and temperature fields. Using the hydroxyl radical field calibrated to the methyl chloroform observations, the globally averaged release of methane and its spatial and temporal distribution were investigated. Two source function models of the spatial and temporal distribution of the flux of methane to the atmosphere were developed. The first model was based on the assumption that methane is emitted as a proportion of net primary productivity (NPP). The second model identified source regions for methane from rice paddies, wetlands, enteric fermentation, termites, and biomass burning based on high-resolution land use data. The most significant difference between the two models were predictions of methane fluxes over China and South East Asia, the location of most of the world's rice paddies, indicating that either the assumption that a uniform fraction of NPP is converted to methane is not valid for rice paddies, or that NPP is underestimated for rice paddies, or that present methane emission estimates from rice paddies are too high.

  10. Hydrodynamic tracer diffusion in suspensions of swimming bacteria

    NASA Astrophysics Data System (ADS)

    Kasyap, T. V.; Koch, Donald L.; Wu, Mingming

    2014-08-01

    We present theoretical predictions, simulations, and experimental measurements of the diffusion of passive, Brownian tracer particles in the bulk of three-dimensional suspensions of swimming bacteria performing run-tumble random walks. In the theory, we derive an explicit expression for the "hydrodynamic" tracer diffusivity that results from the fluid disturbances created by a slender-body model of bacteria by ensemble averaging the mass conservation equation of the tracer over the space of tracer-bacterium interactions which are assumed to be binary. The theory assumes that the orientations of the bacterium before and after a tumble are uncorrelated and the fluid velocity disturbance created by the bacterium is small compared to its swimming speed. The dependence of the non-dimensional hydrodynamic diffusivity widetilde{D_h} obtained by scaling the dimensional hydrodynamic diffusivity by nL3UsL on the persistence in bacterial swimming and the Brownian diffusivity of the tracer are studied in detail through two nondimensional parameters—a Peclet number Pe = UsL/D which is the ratio of the time scale of bacterial swimming to the tracer diffusion time scale and a non-dimensional persistence time ?* = Us?/L obtained by scaling the dimensional bacterial persistence time by the time that a bacterium takes to swim over a distance equal to its length. Here, n, Us, ?, and L are the concentration, swimming speed, tumbling time, and the overall length of the bacteria, respectively, and D is the Brownian diffusivity of the tracer. widetilde{D_h} is found to be a monotonically increasing function of ?* and a non-monotonic function of Pe with a Pe1/2 scaling in the Pe ? 1 limit, an intermediate peak and a constant value in the Pe ? 1 limit for the typical case of wild-type bacteria with ?* = O(1). In the simulation study we compute the bacterial contribution to the tracer diffusivity from explicit numerical simulations of binary tracer-bacterium interactions to examine the validity of the weak disturbance assumption made in the theory, and to investigate the effects of correlations in the pre- and post-tumble bacterium orientations and the excluded volume (steric) interactions between the bacterium and the tracer. It is found that the weak disturbance assumption does not have a statistically significant effect on widetilde{D_h} and correlations among pre- and post-tumble bacterium orientations and bacterium-tracer excluded volume interactions are found to enhance the tracer diffusivity by modest but statistically significant factors. Finally, we measure the effective diffusion coefficient of 1.01 ?m diameter colloidal tracer particles in the bulk of a suspension of wild-type E. Coli cells and compare the experimental measurements with the predictions made by the theory and simulations.

  11. Lateral stirring of large-scale tracer fields by altimetry

    NASA Astrophysics Data System (ADS)

    Dencausse, Guillaume; Morrow, Rosemary; Rogé, Marine; Fleury, Sara

    2014-01-01

    Ocean surface fronts and filaments have a strong impact on the global ocean circulation and biogeochemistry. Surface Lagrangian advection with time-evolving altimetric geostrophic velocities can be used to simulate the submesoscale front and filament structures in large-scale tracer fields. We study this technique in the Southern Ocean region south of Tasmania, a domain marked by strong meso- to submesoscale features such as the fronts of the Antarctic Circumpolar Current (ACC). Starting with large-scale surface tracer fields that we stir with altimetric velocities, we determine `advected' fields which compare well with high-resolution in situ or satellite tracer data. We find that fine scales are best represented in a statistical sense after an optimal advection time of ˜2 weeks, with enhanced signatures of the ACC fronts and better spectral energy. The technique works best in moderate to high EKE regions where lateral advection dominates. This technique may be used to infer the distribution of unresolved small scales in any physical or biogeochemical surface tracer that is dominated by lateral advection. Submesoscale dynamics also impact the subsurface of the ocean, and the Lagrangian advection at depth shows promising results. Finally, we show that climatological tracer fields computed from the advected large-scale fields display improved fine-scale mean features, such as the ACC fronts, which can be useful in the context of ocean modelling.

  12. A statistical study of H i gas in nearby narrow-line AGN-hosting galaxies

    SciTech Connect

    Zhu, Yi-Nan; Wu, Hong, E-mail: zyn@bao.ac.cn, E-mail: hwu@bao.ac.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2015-01-01

    As a quenching mechanism, active galactic nucleus (AGN) feedback could suppress on going star formation in host galaxies. On the basis of a sample of galaxies selected from the Arecibo Legacy Fast ALFA (ALFALFA) H i survey, the dependence of the H i mass (M{sub H} {sub i}), stellar mass (M{sub *}), and H i-to-stellar mass ratio (M{sub H} {sub i}/M{sub *}) on various tracers of AGN activity are presented and analyzed in this paper. Almost all the AGN hostings in this sample are gas-rich galaxies, and there is not any evidence to indicate that the AGN activity could increase or decrease either M{sub H} {sub i} or M{sub H} {sub i}/M{sub *}. The position of the cold neutral gas cannot be fixed accurately based only on available H i data, due to the large beam size of ALFALFA survey. In addition, even though AGN hostings are more easily detected by an H i survey compared with absorption line galaxies, these two types of galaxies show similar star formation history. If an AGN hosting would ultimately evolve into an old red galaxy with low cold gas, then when and how the gas has been exhausted must be solved by future hypotheses and observations.

  13. Pharmaceuticals as Groundwater Tracers - Applications and Limitations

    NASA Astrophysics Data System (ADS)

    Scheytt, T. J.; Mersmann, P.; Heberer, T.

    2003-12-01

    Pharmaceutically active substances and metabolites are found at concentrations up to the microgram/L-level in groundwater samples from the Berlin (Germany) area and from several other places world wide. Among the compounds detected in groundwater are clofibric acid, propyphenazone, diclofenac, ibuprofen, and carbamazepine. Clofibric acid, the active metabolite of clofibrate and etofibrate (blood lipid regulators) is detected in groundwater at maximum concentrations of 7300 ng/L. Among the most important input paths of drugs are excretion and disposal into the sewage system. Groundwater contamination is likely to be due to leaky sewage systems, influent streams, bank filtration, and irrigation with effluent water from sewage treatment plants. There are no known natural sources of the above mentioned pharmaceuticals. The use of pharmaceuticals as tracers may include: (a) Quantification of infiltration from underground septic tanks (b) Detection of leaky sewage systems / leaky sewage pipes (c) Estimation of the effectiveness of sewage treatment plants (d) Identification of transport pathways of other organic compounds (e) Quantification of surface water / groundwater interaction (f) Characterization of the biodegradation potential. The use of pharmaceuticals as tracers is limited by variations in input. These variations depend on the amount of drugs prescribed and used in the study area, the social structure of the community, the amount of hospital discharge, and temporal concentration variations. Furthermore, the analysis of trace amounts of pharmaceuticals is sophisticated and expensive and may therefore limit the applicability of pharmaceuticals as tracers. Finally, the transport and degradation behavior of pharmaceuticals is not fully understood. Preliminary experiments in the laboratory were conducted using sediment material and groundwater from the Berlin area to evaluate the transport and sorption behavior of selected drugs. Results of the column experiments show that clofibric acid exhibits no degradation and almost no retardation (Rf = 1.1) whereas ibuprofen is biodegraded (> 90 %) under aerobic conditions. Carbamazepine shows no degradation in the soil column experiments but significant retardation under the prevailing conditions. We conclude that clofibric acid will show the transport behavior of a conservative tracer, whereas ibuprofen may be used to characterize the biodegradation potential in the aerobic zone.

  14. Simulating tracer transport in variably saturated soils and shallow groundwater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to develop a realistic model to simulate the complex processes of flow and tracer transport in variably saturated soils and to compare simulation results with the detailed monitoring observations. The USDA-ARS OPE3 field site was selected for the case study due to ava...

  15. Natural and synthetic gas hydrates studied by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Savy, Jean-Philippe; Bigalke, Nikolaus; Aloisi, Giovanni; Kossel, Elke; Pansegrau, Moritz; Haeckel, Matthias

    2010-05-01

    Over the past decade, the interest in using CH4-hydrates as an energy resource and CO2-hydrates as a storage option for anthropogenic CO2 has grown in the scientific community as well as in the oil and gas industry. Among all the techniques used to characterize gas hydrates, the non-destructive, non-invasive Raman spectroscopy provides significant insights into the structure and composition of hydrates. In this study, we compare gas hydrates synthetically produced in the laboratory with natural hydrate samples collected from marine sediments. CO2 and CH4 gas hydrates were investigated with a high-resolution Raman microscope at in-situ p-T conditions. A water-filled glass capillary (inner diameter: 1.7 mm) was placed in a stainless steel cell, which was sealed, cooled down to 3.6 ° C and pressurized to 60 bar with liquid CO2. Video images taken after 1 h revealed droplets (~10 ?m in diameter) trapped in the ice-like solid. The two Fermi dyads of CO2 in the liquid and hydrate phase at 1274 & 1381 cm1 and 1280 & 1384 cm-1, respectively, confirm the presence of liquid CO2 droplets trapped in a CO2-hydrate matrix. Equivalent experiments were conducted with CH4 gas at 1 ° C and 90 bar. The nucleation of CH4-hydrate was followed in the Raman spectral region of the C-H stretching mode. At the early stage of the nucleation, the peak at 2915 cm-1 (CH4 in small cages) was stronger than the one at 2904 cm-1 (CH4 in large cages) indicating that methane starts to populate the small 512 cages of the s-I hydrate structure first and then, as nucleation continues, the large cages are stabilized leading to a quickly growing peak at 2904 cm-1 until a final peak intensity ratio of 3.7 is established. In contrast to other studies, intermediate stabilization of the s-II structure was not observed. Video images confirmed the absence of gas inclusions. The hydrate density, 1.1 & 0.9 for CO2-hydrate and CH4-hydrate respectively, compared to the one of water may explain the formation of inclusions during the crystallization of hydrates. Finally, we investigated a natural CH4 hydrate sample collected from Hikurangi Margin, New Zealand. Areal mapping of the sample revealed a constant peak area ratio of 3.7 between large and small cages, identical to our synthetic CH4-hydrate. We also used the relative Raman signal intensities between CH4 and H2O to quantify the spatial variation in cage occupancy and methane concentration in the natural hydrate sample. Compared to synthetic CH4-hydrate, the natural sample shows an inhomogeneous overall distribution of methane content.

  16. How many tracers do we need for end member mixing analysis (EMMA)? A sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Barthold, Frauke K.; Tyralla, Christoph; Schneider, Katrin; Vaché, Kellie B.; Frede, Hans-Georg; Breuer, Lutz

    2011-08-01

    End member mixing analysis (EMMA) is a commonly applied method to identify and quantify the dominant runoff producing sources of water. It employs tracers to determine the dimensionality of the hydrologic system. Many EMMA studies have been conducted using two to six tracers, with some of the main tracers being Ca, Na, Cl-, water isotopes, and alkalinity. Few studies use larger tracer sets including minor trace elements such as Li, Rb, Sr, and Ba. None of the studies has addressed the question of the tracer set size and composition, despite the fact that these determine which and how many end members (EM) will be identified. We examine how tracer set size and composition affects the conceptual model that results from an EMMA. We developed an automatic procedure that conducts EMMA while iteratively changing tracer set size and composition. We used a set of 14 tracers and 9 EMs. The validity of the resulting conceptual models was investigated under the aspects of dimensionality, EM combinations, and contributions to stream water. From the 16,369 possibilities, 23 delivered plausible results. The resulting conceptual models are highly sensitive to the tracer set size and composition. The moderate reproducibility of EM contributions indicates a still missing EM. It also emphasizes that the major elements are not always the most useful tracers and that larger tracer sets have an enhanced capacity to avoid false conclusions about catchment functioning. The presented approach produces results that may not be apparent from the traditional approach and it is a first step to add the idea of statistical significance to the EMMA approach.

  17. ARE RADON GAS MEASUREMENTS ADEQUATE FOR EPIDEMIOLOGICAL STUDIES AND CASE CONTROL

    E-print Network

    Yu, K.N.

    ARE RADON GAS MEASUREMENTS ADEQUATE FOR EPIDEMIOLOGICAL STUDIES AND CASE CONTROL STUDIES OF RADON 2004 The lung dose derived from radon is not attributed to the radon gas itself, but instead to its of the radon risk, the excess number of cancers are related to the radon gas exposure, and not to the radon

  18. Acceleration of passive tracers in compressible turbulent flow.

    PubMed

    Yang, Yantao; Wang, Jianchun; Shi, Yipeng; Xiao, Zuoli; He, X T; Chen, Shiyi

    2013-02-01

    In compressible turbulence at high Reynolds and Mach numbers, shocklets emerge as a new type of flow structure in addition to intense vortices as in incompressible turbulence. Using numerical simulation of compressible homogeneous isotropic turbulence, we conduct a Lagrangian study to explore the effects of shocklets on the dynamics of passive tracers. We show that shocklets cause very strong intermittency and short correlation time of tracer acceleration. The probability density function of acceleration magnitude exhibits a -2.5 power-law scaling in the high compression region. Through a heuristic model, we demonstrate that this scaling is directly related to the statistical behavior of strong negative velocity divergence, i.e., the local compression. Tracers experience intense acceleration near shocklets, and most of them are decelerated, usually with large curvatures in their trajectories. PMID:23432253

  19. Acceleration of Passive Tracers in Compressible Turbulent Flow

    NASA Astrophysics Data System (ADS)

    Yang, Yantao; Wang, Jianchun; Shi, Yipeng; Xiao, Zuoli; He, X. T.; Chen, Shiyi

    2013-02-01

    In compressible turbulence at high Reynolds and Mach numbers, shocklets emerge as a new type of flow structure in addition to intense vortices as in incompressible turbulence. Using numerical simulation of compressible homogeneous isotropic turbulence, we conduct a Lagrangian study to explore the effects of shocklets on the dynamics of passive tracers. We show that shocklets cause very strong intermittency and short correlation time of tracer acceleration. The probability density function of acceleration magnitude exhibits a -2.5 power-law scaling in the high compression region. Through a heuristic model, we demonstrate that this scaling is directly related to the statistical behavior of strong negative velocity divergence, i.e., the local compression. Tracers experience intense acceleration near shocklets, and most of them are decelerated, usually with large curvatures in their trajectories.

  20. Study of gas flow dynamics in porous and granular media with laser-polarized ¹²?Xe NMR

    E-print Network

    Wang, Ruopeng, 1972-

    2005-01-01

    This thesis presents Nuclear Magnetic Resonance (NMR) studies of gas flow dynamics in porous and granular media by using laser-polarized ¹²?Xe . Two different physical processes, the gas transport in porous rock cores and ...

  1. Using tracers to understand the hydrology of an abandoned underground coal mine

    SciTech Connect

    Canty, G.A.; Everett, J.W. [Univ. of Oklahoma, Norman, OK (United States). Dept. of Civil Engineering and Environmental Science

    1998-12-31

    Flooded underground mines pose a difficult problem for remediation efforts requiring hydrologic information. Mine environments are hydraulically complicated due to sinuous travel paths and variable hydraulic gradients. For an acidic mine remediation project, conducted by the University of Oklahoma in conjunction with the Oklahoma Conservation Commission, a tracer study was undertaken to identify basic hydrologic properties of a flooded coal mine. The study was conducted to investigate the possibility of in-situ remediation of acidic mine water with the use of alkaline coal combustion by-products. Information on the rate of flow and ``connectiveness`` of injection wells with the discharge point was needed to develop a treatment strategy. Fluorescent dyes are not typically used in mine tracer studies because of the low pH values associated with certain mines and a tendency to adsorb ferric iron precipitates. However, Rhodamine WT was used in one tracer test because it can be detected at low concentrations. Due to poor recovery, a second tracer test was undertaken using a more conservative tracer-chloride. Each tracer produced similar travel time results. Findings from this study suggest that Rhodamine WT can be used under slightly acidic conditions, with mixed results. The more conservative tracer provided somewhat better results, but recovery was still poor. Use of these tracers has provided some valuable information with regard to mine hydrology, but additional questions have been raised.

  2. Rapid and simple determination of delivery after iontophoretic and pressure injections of radiolabeled tracer substances.

    PubMed

    Imai, H; Steindler, D A; Kitai, S T

    1983-04-01

    A fluorographic method is described using X-ray film analysis for the determination of delivery of radiolabeled tracer substances both in Agar plates and in tissue sections. This method is most useful in neuroanatomical autoradiographic studies for providing rapid identification of delivery, placement, and extent of an injection site after iontophoresis or pressure injections of radiolabeled axonal tracer substances. PMID:6688104

  3. Performance study using natural gas, hydrogen-supplemented natural gas and hydrogen in AVL research engine

    Microsoft Academic Search

    F. Duebel; K. Schmillen; B. Nagalingam

    1983-01-01

    Performance tests with natural gas, hydrogen-supplemented CH4, and H2-fueled configurations of the AVL research engine are reported. A comparison is made of the properties of H2 and natural gas, noting that natural gas benefits such as heating value, higher ignition energy, and narrow ignition limits are at least partially offset by H2 wide ignition limits which allow elimination of throttling,

  4. Study of Mixed Collisionality Gas Flow in the VASIMR Thruster

    Microsoft Academic Search

    Oleg Batishchev; Kim Molvig

    2000-01-01

    The degree of gas ionization in the VASIMR plasma thruster [1] is about one percent. This allows separating of the gas propellant flow from the plasma dynamics. The Knudsen number of the hydrogen (deuterium) or helium gas flow in a system of pipes of varying diameter falls into the .2-5 range. This indicates that the kinetic approach is required. First

  5. Metastable noble gas apparatus for laser photoionisation studies

    Microsoft Academic Search

    J. P. Czechanski; B. H. Houston; R. B. Kay

    1989-01-01

    Metastable noble gas atoms are produced by crossing a low-energy electron sheet beam with a jet of gas injected by an automotive fuel injector. A laser beam is directed at right angles through the wide dimension of the electron beam, and the gas jet is directed at a small (19 degrees ) angle to the laser beam. An electric field

  6. AVO studies of gas sands via physical modeling

    SciTech Connect

    Tadepalli, S.V.; Sekharan, K.K.; Ebrom, D.A. [Univ. of Houston, TX (United States)

    1994-12-31

    A physical modeling experiment was conducted over a simple model consisting of three layers. The three layers were epoxy, Foamglas, and epoxy. The materials of these layers correspond to shale, gas sand and shale in the real earth. A trench was drilled in this model and the ground roll was successfully attenuated prior to seismic data acquisition over this model. Transducer directivity corrections were made based on empirically derived least square function. An elastic synthetic based on wave equation and an acoustic synthetic based on ray tracing were computed over this model. Elastic, and acoustic AVO modeling data corresponding to the top interface (epoxy and Foamglas) were compared to the AVO data of the physical model. The results show a consistent decrease of amplitude versus offset at this interface. This amplitude decrease with offset is due to the anomalous density contrast between epoxy and Foamglas material. This experiment demonstrates that the physical modeling can be used to simulate gas sand reservoirs in the actual field AVO studies.

  7. Conceptual design study of an improved automotive gas turbine powertrain

    NASA Technical Reports Server (NTRS)

    Wagner, C. E. (editor); Pampreen, R. C. (editor)

    1979-01-01

    Automotive gas turbine concepts with significant technological advantages over the spark ignition (SI) engine were assessed. Possible design concepts were rated with respect to fuel economy and near-term application. A program plan which outlines the development of the improved gas turbine (IGT) concept that best met the goals and objectives of the study identifies the research and development work needed to meet the goal of entering a production engineering phase by 1983. The fuel economy goal is to show at least a 20% improvement over a conventional 1976 SI engine/vehicle system. On the basis of achieving the fuel economy goal, of overall suitability to mechanical design, and of automotive mass production cost, the powertrain selected was a single-shaft engine with a radial turbine and a continuously variable transmission (CVT). Design turbine inlet temperature was 1150 C. Reflecting near-term technology, the turbine rotor would be made of an advanced superalloy, and the transmission would be a hydromechanical CVT. With successful progress in long-lead R&D in ceramic technology and the belt-drive CVT, the turbine inlet temperature would be 1350 C to achieve near-maximum fuel economy.

  8. Study of gel materials as radioactive 222Rn gas detectors.

    PubMed

    Espinosa, G; Golzarri, J I; Rickards, J; Gammage, R B

    2006-01-01

    Commercial hair gel material (polyvinyl pyrolydone triethanolamine carbopol in water) and bacteriological agar (phycocolloid extracted from a group of red-purple algae, usually Gelidium sp.) have been studied as radioactive radon gas detectors. The detection method is based on the diffusion of the radioactive gas in the gel material, and the subsequent measurement of trapped products of the natural decay of radon by gamma spectrometry. From the several radon daughters with gamma radiation emission (214Pb, 214Bi, 214Po, 210Pb, 210Po), two elements, 214Pb (0.352 MeV) and 214Bi (0.609 MeV), were chosen for the analysis in this work; in order to determine the best sensitivity, corrections were made for the short half-life of the analysed isotopes. For the gamma spectrometry analysis, a hyperpure germanium solid state detector was used, associated with a PC multichannel analyser card with Maestro and Microsoft Excel software. The results show the viability of the method: a linear response in a wide radon concentration range (450-10,000 Bq m(-3)), reproducibility of data, easy handling and low cost of the gel material. This detection methodology opens new possibilities for measurements of radon and other radioactive gases. PMID:16709716

  9. Numerical simulations of the spread of floating passive tracer released at the Old Harry prospect

    NASA Astrophysics Data System (ADS)

    Bourgault, Daniel; Cyr, Frédéric; Dumont, Dany; Carter, Angela

    2014-05-01

    The Gulf of St Lawrence is under immediate pressure for oil and gas exploration, particularly at the Old Harry prospect. A synthesis of the regulatory process that has taken place over the last few years indicates that important societal decisions soon to be made by various ministries and environmental groups are going to be based on numerous disagreements between the private sector and government agencies. The review also shows that the regulatory process has taken place with a complete lack of independent oceanographic research. Yet, the Gulf of St Lawrence is a complex environment that has never been specifically studied for oil and gas exploitation. Motivated by this knowledge gap, preliminary numerical experiments are carried out where the spreading of a passive floating tracer released at Old Harry is examined. Results indicate that the tracer released at Old Harry may follow preferentially two main paths. The first path is northward along the French Shore of Newfoundland, and the second path is along the main axis of the Laurentian Channel. The most probable coastlines to be touched by water flowing through Old Harry are Cape Breton and the southern portion of the French Shore, especially Cape Anguille and the Port au Port Peninsula. The Magdalen Islands are less susceptible to being affected than those regions but the probability is not negligible. These preliminary results provide guidance for future more in-depth and complete multidisciplinary studies from which informed decision-making scenarios could eventually be made regarding the exploration and development of oil and gas at the Old Harry prospect in particular and, more generally, in the Gulf of St Lawrence.

  10. Primordial black holes as biased tracers

    NASA Astrophysics Data System (ADS)

    Tada, Yuichiro; Yokoyama, Shuichiro

    2015-06-01

    Primordial black holes (PBHs) are theoretical black holes which can be formed during the radiation dominant era through the gravitational collapse of radiational overdensities. It has been well known that in the context of the structure formation in our Universe such collapsed objects, e.g., halos/galaxies, could be considered as bias tracers of underlying matter fluctuations and the halo/galaxy bias has been studied well. Applying such a biased tracer picture to PBHs, we investigate the large scale clustering of PBHs and obtain an almost mass-independent constraint to the scenario that the dark matter (DM) consists of PBHs. We focus on the case where the statistics of the primordial curvature perturbations is almost Gaussian, but with small local-type non-Gaussianity. If PBHs account for the DM abundance, such a large scale clustering of PBHs behaves as nothing but the matter isocurvature perturbation which is strictly constrained by the observations of cosmic microwave backgrounds (CMBs). From this constraint, we show that, in the case where a certain single field causes both CMB temperature perturbations and PBH formation, the PBH-DM scenario is excluded even with quite small local-type non-Gaussianity, |fNL|˜O (0.01 ).

  11. Evaluation of saline tracer performance during electrical conductivity groundwater monitoring.

    PubMed

    Mastrocicco, Micòl; Prommer, Henning; Pasti, Luisa; Palpacelli, Stefano; Colombani, Nicolò

    2011-04-25

    Saline solutions are the most commonly used hydrological tracers, because they can be easily and economically monitored by in situ instrumentation such as electrical conductivity (EC) loggers in wells or by geoelectrical measurements. Unfortunately, these low-cost techniques only provide information on the total concentration of ions in solution, i.e., they cannot resolve the ionic composition of the aqueous solution. This limitation can introduce a bias in the estimation of aquifer parameters where sorption phenomena between saline tracers and sediments become relevant. In general, only selected anions such as Cl(-) and Br(-) are recognised to be transported unretarded and they are referred to as conservative tracers or mobile anions. However, cations within the saline tracer may interact with the soil matrix through a range of processes such as ion exchange, surface complexation and via physical mass-transfer phenomena. Heterogeneous reactions with minerals or mineral surfaces may not be negligible where aquifers are composed of fine alluvial sediments. The focus of the present study was to examine and to quantify the bias between the aquifer parameters estimated during model-based interpretation of experimental data of EC measurements of saline tracer relative to the aquifer parameters found by specific measurements (i.e. via ionic chromatography, IC) of truly conservative species. To accomplish this, column displacement experiments with alluvial aquifer materials collected from the Po lowlands (Italy) were performed under water saturated conditions. The behaviour of six selected, commonly used saline tracers (i.e., LiCl, KCl, and NaCl; LiBr, KBr, and NaBr) was studied and the data analysed by inverse modelling. The results demonstrate that the use of EC as a tracer can lead to an erroneous parameterisation of the investigated porous media, if the reactions between solute and matrix are neglected. In general, errors were significant except for KCl and KBr, which is due to the weak interaction between dissolved K(+) and the sediment material. The study shows that laboratory scale pre-investigations can help with tracer selection and to optimise the concentration range targeted for in situ multilevel monitoring by unspecific geoelectrical instrumentation. PMID:21324545

  12. Quantifying Mountain Front Recharge Using Isotopic Tracers

    NASA Astrophysics Data System (ADS)

    Wahi, A. K.; Ekwurzel, B.; Hogan, J. F.; Eastoe, C. J.; Baillie, M. N.

    2005-05-01

    To improve our conceptual and quantitative understanding of mountain-front/mountain-block recharge (MFR) associated with the Huachuca Mountains of the Upper San Pedro River Basin in Arizona, we employed a suite of geochemical measurements including isotopic tracers and noble gases. MFR is frequently the dominant source of recharge to alluvial basins in the semiarid Basin and Range province. It consists of mountain runoff that infiltrates at the mountain front (mountain-front recharge), and percolation through the mountain bedrock that reaches the basin via the movement of deep groundwater (mountain-block recharge). The rate of MFR can be estimated from a water balance, a Darcy's law analysis, or inverse modeling of groundwater processes. Despite the large volume of research on water resources in the basin and the critical importance of MFR to the water budget, the best estimates of MFR obtained using these methods may have errors as large as 100%. We find that geochemical tracers address mechanistic questions regarding recharge seasonality, location, and rates as well as addressing groundwater flowpaths and residence times. The gradient of stable isotopes of hydrogen and oxygen in groundwater with elevation mirrors that of regional precipitation, providing a constraint on the location and seasonality of recharge. Stable isotopic signatures indicate that MFR is dominated by winter precipitation but has 1/3 or more contribution from monsoon precipitation. Detectable tritium and 14C values greater than 100 pMC for springs, shallow groundwater in mountain canyons, and from wells along the mountain front indicate decade-scale residence times. Away from the mountain front 14C values rapidly decrease, reaching 12.3±0.2 pMC near the river. This suggests total basin residence times greater than 10,000 years, consistent with past measurements. Ongoing analysis of noble gas concentrations will provide an indication of recharge conditions. The solubility of noble gases in water depends on temperature and pressure; thus, noble gas concentrations provide a means to distinguish water samples recharged at different elevations.

  13. Gas

    MedlinePLUS

    ... and pain in the belly—especially after a big meal. Foods that can cause gas Some people naturally produce ... your stomach or throw up . Your breasts are big and sore . The area around your nipples gets darker. You crave certain foods. Or you really dislike certain foods. You feel ...

  14. TRACER-TEST PLANNING USING THE EFFICIENT HYDROLOGIC TRACER-TEST DESIGN (EHTD) PROGRAM 2003

    EPA Science Inventory

    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 ...

  15. TRACER-TEST PLANNING USING THE EFFICIENT HYDROLOGIC TRACER-TEST DESIGN (EHTD) PROGRAM 2005

    EPA Science Inventory

    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 ...

  16. Impact Studies Using a One Stage Light Gas Gun

    E-print Network

    Jorge Carmona; Mike Cook; Jimmy Schmoke; Katie Harper; Jerry Reay; Lorin Matthews; Truell Hyde

    2004-01-29

    The Center for Astrophysics,Space Physics, and Engineering Research (CASPER) has completed construction and calibration of a Light Gas Gun (LGG), which is used for low velocity impact studies. At geosynchronous orbit, space debris can impact commercial satellites at velocities of 500 m/s [1] reducing their useful lifetime. Additionally, there is an ever-increasing population of abandoned nonoperational satellites and related debris in these orbits [2]. Therefore, it is important to clearly understand the physics behind how such collisions can cause structural damage. This is most easily determined by measuring the damage incurred on representative material exposed to test collisions in the laboratory. Data collected in this manner will not only help illuminate the shock physics involved but can also aid in providing methods for designing advanced shielding for satellites.

  17. Gas recombination device design and cost study. Final report

    SciTech Connect

    Not Available

    1980-07-01

    Under a contract with Argonne National Laboratory, VARTA Batterie AG. conducted a design and cost study of hydrogen-oxygen recombination devices (HORD) for use with utility load-leveling lead-acid cells. Design specifications for the devices, through extensive calculation of the heat-flow conditions of the unit, were developed. Catalyst and condenser surface areas were specified. The exact dimensions can, however, be adjusted to the cell dimension and the space available above the cell. Design specifications were also developed for additional components required to ensure proper function of the recombination device, including metal hydride compound decomposer, aerosol retainer, and gas storage component. Costs for HORD were estimated to range from $4 to $10/kWh cell capacity for the production of a large number of units (greater than or equal to 10,000 units). The cost is a function of cell size and positive grid design. 21 figures, 2 tables.

  18. Heat and solute tracers: how do they compare in heterogeneous aquifers?

    PubMed

    Irvine, Dylan J; Simmons, Craig T; Werner, Adrian D; Graf, Thomas

    2015-04-01

    A comparison of groundwater velocity in heterogeneous aquifers estimated from hydraulic methods, heat and solute tracers was made using numerical simulations. Aquifer heterogeneity was described by geostatistical properties of the Borden, Cape Cod, North Bay, and MADE aquifers. Both heat and solute tracers displayed little systematic under- or over-estimation in velocity relative to a hydraulic control. The worst cases were under-estimates of 6.63% for solute and 2.13% for the heat tracer. Both under- and over-estimation of velocity from the heat tracer relative to the solute tracer occurred. Differences between the estimates from the tracer methods increased as the mean velocity decreased, owing to differences in rates of molecular diffusion and thermal conduction. The variance in estimated velocity using all methods increased as the variance in log-hydraulic conductivity (K) and correlation length scales increased. The variance in velocity for each scenario was remarkably small when compared to ?2 ln(K) for all methods tested. The largest variability identified was for the solute tracer where 95% of velocity estimates ranged by a factor of 19 in simulations where 95% of the K values varied by almost four orders of magnitude. For the same K-fields, this range was a factor of 11 for the heat tracer. The variance in estimated velocity was always lowest when using heat as a tracer. The study results suggest that a solute tracer will provide more understanding about the variance in velocity caused by aquifer heterogeneity and a heat tracer provides a better approximation of the mean velocity. PMID:24359493

  19. Correlated random walk in lattices: Tracer diffusion at general concentration

    Microsoft Academic Search

    R. A. Tahir-Kheli; R. J. Elliott

    1983-01-01

    A problem of considerable physical interest, wherein a tracer of arbitrary species diffuses against a dynamic background of double occupancy avoiding classical particles of concentration x hopping on regular lattices, is studied. The theory is exact to the leading order in vacancy concentration, v=1-x, and to two leading orders in x. Moreover, in the intermediate concentration, it incorporates all the

  20. Difluoromethane as partitioning tracer to estimate vadose water saturations

    Microsoft Academic Search

    Neil E. Deeds; Daene C. McKinney; Gary A. Pope; G. Allen Whitley Jr

    1999-01-01

    Water saturation in the vadose zone is an important parameter for many nonaqueous phase liquid (NAPL) remediation technologies, Conventional soil boring analyses may not provide accurate average water saturation data. Previous studies have shown that a partitioning interwell tracer test (PITT) can provide an accurate estimate of average subsurface NAPL saturations. The PITT is proposed as a suitable technology for

  1. Desert dust aerosol age characterized by massage tracking of tracers

    E-print Network

    Zender, Charles

    . Introduction [2] Atmospheric aerosols have large impacts on climate, biogeochemistry and human health. Aerosol solu- bility is a crucial factor in atmospheric delivery of bio- available ocean nutrients to sizeresolved dust aerosol tracers to study the age of dust that remains in the atmosphere and the age of dust

  2. Feasibility of perfluorocarbon tracers (PFTs) in atmospheric source-receptor experiments

    SciTech Connect

    Dietz, R.N.; Senum, G.I.

    1984-03-01

    A brief description of the perfluorocarbon tracer (PFT) system, which includes the tracers and the release equipment, the air samplers and the analyzers, is presented along with details on the research needs to provide a viable system for MATEX-scenario experiments. The present family of 2 viable PFTs needs to be increased to 5 to 6. Given the present precision of the analysis system, a one year long tracer experiment consisting of 4 hour releases every 60 hours from 5 different sites would require nearly 150 metric tons of PFTs at a cost of $15,000,000. Shortcomings in the programmable sampler include the pump, the sampling sequence control flexibility, data storage and retrieval, and the lack of remote communication capability; sampler adsorbent studies are also needed. The analytical system, including the catalyst processing bed, the chromatography column resolution, and the linearity of the detector, is in need of significant improvement. A higher resolution analysis system could significantly reduce analysis time but, more importantly, reduce tracer requirements more than 10-fold, for a cost savings potential of more than $13,000,000. A model is presented to demonstrate the feasibility of tracer material balances. Assessment of earlier long-range tracer experiments indicates the need for possibly 400 ground sampling sites requiring $8 to $14 million worth of samplers for a one-year tracer experiment. As many as six aircraft would be needed to conduct airborne model validation and material balance studies for each tracer plume.

  3. Measurement of LNAPL flow using single-well tracer dilution techniques.

    PubMed

    Sale, Tom; Taylor, Geoffrey Ryan; Iltis, Gabriel; Lyverse, Mark

    2007-01-01

    This paper describes the use of single-well tracer dilution techniques to resolve the rate of light nonaqueous phase liquid (LNAPL) flow through wells and the adjacent geologic formation. Laboratory studies are presented in which a fluorescing tracer is added to LNAPL in wells. An in-well mixer keeps the tracer well mixed in the LNAPL. Tracer concentrations in LNAPL are measured through time using a fiber optic cable and a spectrometer. Results indicate that the rate of tracer depletion is proportional to the rate of LNAPL flow through the well and the adjacent formation. Tracer dilution methods are demonstrated for vertically averaged LNAPL Darcy velocities of 0.00048 to 0.11 m/d and LNAPL thicknesses of 9 to 24 cm. Over the range of conditions studied, results agree closely with steady-state LNAPL flow rates imposed by pumping. A key parameter for estimating LNAPL flow rates in the formation is the flow convergence factor alpha. Measured convergence factors for 0.030-inch wire wrap, 0.030-inch-slotted polyvinyl chloride (PVC), and 0.010-inch-slotted PVC are 1.7, 0.91, and 0.79, respectively. In addition, methods for using tracer dilution data to determine formation transmissivity to LNAPL are presented. Results suggest that single-well tracer dilution techniques are a viable approach for measuring in situ LNAPL flow and formation transmissivity to LNAPL. PMID:17760583

  4. Fluorescent particle tracers for surface hydrology

    NASA Astrophysics Data System (ADS)

    Tauro, F.; Grimaldi, S.; Rapiti, E.; Porfiri, M.

    2012-12-01

    Accurate estimates of flow velocity in natural environments are essential for the understanding of runoff and overland flow formation, rill development, erosion, and infiltration and evaporation mechanisms. Tracing technologies are generally considered valuable tools to estimate flow velocity in small watershed streams and shallow water flows. In this framework, a novel tracing methodology based on the deployment and observation of enhanced fluorescence particles for surface flow measurements is proposed. This approach aims at mitigating practical limitations of traditional techniques for monitoring stream and overland flows. Specifically, the insolubility of the particles minimizes tracer adhesion to natural substrates and, therefore, is expected to reduce the requisite quantity of tracing material as compared to liquid dyes. Further, the enhanced visibility of the fluorescent particles allows for non-intrusively detecting the tracer through imaging techniques without deploying bulky probes and samplers in the water. These features along with the use of basic and resilient equipment provide grounding for applying the proposed methodology in ephemeral micro-channels, high-sediment load flows, and heavy floods. The feasibility of the methodology is studied by conducting characterization analysis in laboratory settings and proof-of-concept experiments in natural environments. In addition, image analysis techniques are developed to automatically and noninvasively detect and trace the trajectory of the particles on surface flows. Experiments are performed in a natural mountainous river to assess the performance of the particles in stream flow settings, where high velocity regimes, presence of foam, and light reflections pose serious challenges to bead detection. Particles are used to conduct flow measurements at a stream cross-section and travel time experiments in stream reaches of up to 30 m. Bead diameters of a few millimeters are selected to compensate for high flow rates. Experimental results demonstrate that the fluorescent particles can be used to reliably trace high velocity streams in adverse illumination conditions and in the presence of foam and reflections on the water surface. Furthermore, flow velocities and travel times calculated through an array of commonly used tracers are consistent with results obtained through the proposed methodology and demonstrate a higher reliability of the fluorescent particles versus traditional tracers that are affected by dispersions and turbulence. Additional proof-of-concept experiments are conducted on a semi-natural hillslope plot under high turbidity loads and soil and rain drops interaction. Ad-hoc experiments with particles of varying diameters ranging from 75 to 1180 ?m are performed to assess the visibility and detectability of the particle tracers in these severe environmental conditions and their feasibility in estimating overland flow velocities. Videos of beads' transit are processed through both supervised and unsupervised techniques to obtain average surface velocities of water flowing on the hill. Experimental results have demonstrated the feasibility of using the particles for environmental applications and have led to the identification of optimal diameters, namely, 1000-1180 ?m, for flow measurements in the described hillslope plot.

  5. The Tertiary FAWAG Process on Gas and Water Invaded Zones: An Experimental Study

    Microsoft Academic Search

    A. Gandomkar; R. Kharrat

    2012-01-01

    In this research, experimental investigations of foam-assisted water alternating gas and water alternating gas processes in carbonate cores are studied in order to estimate the increases in the oil recovery in the gas and water invaded zones. Core flooding experiments were performed for low-temperature fractured carbonate cores, chosen from one of the Iranian carbonate oil reservoirs, under tertiary recovery conditions.

  6. Parametric and discharge studies of three-color gas-mix ion lasers

    Microsoft Academic Search

    Samir A. Ahmed; William M. Keeffe

    1974-01-01

    The relationship between gas concentration and laser power output is examined for mixed noble gas ion lasers. Specifically, a parametric study was carried out on argon-krypton lasers with cw three-color power outputs of over 3 W, balanced to give white light as defined by CIE illuminant C. It is found that provided total gas density is maintained constant, argon and

  7. System study of an MHD\\/gas turbine combined-cycle baseload power plant

    Microsoft Academic Search

    Annen

    1982-01-01

    The MHD\\/gas turbine combined-cycle system has been designed specifically for applications where the availability of cooling water is very limited. The base case systems which were studied consisted of an MHD plant with a gas turbine bottoming plant, and required no cooling water. The gas turbine plant uses only air as its working fluid and receives its energy input from

  8. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    E-print Network

    Walsworth, Ronald L.

    Applications of controlled-flow laser-polarized xenon gas to porous and granular media study R. W of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting

  9. Study Guide 2010 for Full-Time Students Master of Oil and Gas Engineering

    E-print Network

    Tobar, Michael

    Study Guide 2010 for Full-Time Students Master of Oil and Gas Engineering Graduate Diploma in Oil Oil & Gas Economics PETR8503 Reservoir Engineering Possible Options (example only) CIVL4130 Offshore freedom to choose units from the available options listed in the Master of Oil and Gas Engineering Table

  10. Study Guide 2012 for Full-Time Students Master of Oil and Gas Engineering

    E-print Network

    Tobar, Michael

    Study Guide 2012 for Full-Time Students Master of Oil and Gas Engineering Graduate Diploma in Oil Oil & Gas Economics PETR8503 Reservoir Engineering Possible Options (example only) PETR8510 Petroleum freedom to choose units from the available options listed in the Master of Oil and Gas Engineering Table

  11. Balloon tracer for atmospheric pollutants

    SciTech Connect

    Lichfield, E.W.; Ivey, M.D.; Zak, B.D.; Church, H.W.

    1985-01-01

    An operational prototype of the Balloon Tracer was developed and described. This prototype was designed to be capable of meeting all of the desired specifications for the Balloon Tracer. Its buoyancy adjustment subsystem is shown. Three Gilian instrument pumps operating in parallel provide a flow of about 12 litres per minute, depending upon backpressure. The miniature Klippard mechanical valves are actuated by a servo mechanism which only requires power when the state of the valves is being changed. The balloon itself for the operational prototype is just under 3 meters in diameter. A block diagram of the operational prototype payload measures ambient pressure, temperature, and humidity obtained from AIR which outputs its data in ASCII format. The vertical anemometer, which has a measured starting speed of under 2 cm/s, makes use of a Gill styrofoam propeller and a Spaulding Instruments rotation sendor. The command decoder is built around a chip developed originally for remote control television tuners. The command receiver operating on 13.8035 MHz was developed and built by Hock Engineering. The Argos transmitter is a Telonics platform transmitter terminal. The heart of the control system is an Intel 8052AH BASIC microcomputer with both random access and read only memory.

  12. Gas generation results and venting study for transuranic waste drums

    SciTech Connect

    Kazanjian, A.R.; Arnold, P.M.; Simmons, W.C.; D'Amico, E.L.

    1985-09-23

    Sixteen waste drums, containing six categories of plutonium-contaminated waste, were monitored for venting and gas generation for six months. The venting devices tested appeared adequate to relieve pressure and prevent hydrogen accumulation. Most of the gas generation, primarily H2 and CO2, was due to radiolytic decomposition of the hydrogenous wastes. Comparison of the gas yields with those obtained previously in laboratory tests showed very reasonable agreement with few exceptions.

  13. Tracers of Past Ocean Circulation

    NASA Astrophysics Data System (ADS)

    Lynch-Stieglitz, J.

    2003-12-01

    Information about how the ocean circulated during the past is useful in understanding changes in ocean and atmospheric chemistry, changes in the fluxes of heat and freshwater between the ocean and atmosphere, and changes in global wind patterns. The circulation of surface waters in the ocean leaves an imprint on sea surface temperature, and is also inextricably linked to the patterns of oceanic productivity. Much valuable information about past ocean circulation has been inferred from reconstructions of surface ocean temperature and productivity, which are covered in separate chapters. Here the focus is on the geochemical tracers that are used to infer the flow patterns and mixing of subsurface water masses.Several decades ago it was realized that chemistry of the shells of benthic foraminifera (carbon isotope and Cd/Ca ratios) carried an imprint of the nutrient content of deep-water masses (Shackleton, 1977; Broecker, 1982; Boyle, 1981). This led rapidly to the recognition that the water masses in the Atlantic Ocean were arrayed differently during the last glacial maximum than they are today, and the hypothesis that the glacial arrangement reflected a diminished contribution of low-nutrient North Atlantic deep water (NADW) ( Curry and Lohmann, 1982; Boyle and Keigwin, 1982). More detailed spatial reconstructions indicated a shallow nutrient-depleted water mass overlying a more nutrient-rich water mass in the glacial Atlantic. These findings spurred advances not only in geochemistry but in oceanography and climatology, as workers in these fields attempted to simulate the inferred glacial circulation patterns and assess the vulnerability of the modern ocean circulation to changes such as observed for the last ice age.While the nutrient distributions in the glacial Atlantic Ocean were consistent with a diminished flow of NADW, they also could have reflected an increase in inflow from the South Atlantic and/or a shallower yet undiminished deep-water mass. Clearly, tracers capable of giving information on deep-water flow rate, rather than nutrient content alone, were needed. Differences between surface water (measured on planktonic foraminifera) and deep-water (measured on coexisting benthic foraminifera) radiocarbon concentrations provided the first rate constraint (Broecker et al., 1988; Shackleton et al., 1988). Reduced amounts of protactinium relative to the more particle-reactive thorium in the glacial Atlantic suggested that deep water was exported from the Atlantic during glacial times ( Yu et al., 1996). More recently, density gradients in upper waters have been used to infer changes in the upper ocean return flow that compensates the deep-water export ( Lynch-Stieglitz et al., 1999b).Many of these tracers of paleo-ocean flow have been applied to all of the ocean basins, and have been extended in time throughout the Neogene. Despite this progress, a consistent picture of the circulation of the ocean during even the last ice age has yet to emerge. While circulation tracers suggest a rearrangement of water masses in the Atlantic, there is still considerable disagreement about the water masses and circulation in the rest of the World Ocean. Some of this arises from still insufficient data coverage, but some is the result of conflicting information from the various deep circulation tracers. In this chapter, we examine in more detail the methods used to reconstruct past ocean circulation, which will illuminate the source of some of this conflicting information.

  14. Combining natural and man-made DNA tracers to advance understanding of hydrologic flow pathway evolution

    NASA Astrophysics Data System (ADS)

    Dahlke, H. E.; Walter, M. T.; Lyon, S. W.; Rosqvist, G. N.

    2014-12-01

    Identifying and characterizing the sources, pathways and residence times of water and associated constituents is critical to developing improved understanding of watershed-stream connections and hydrological/ecological/biogeochemical models. To date the most robust information is obtained from integrated studies that combine natural tracers (e.g. isotopes, geochemical tracers) with controlled chemical tracer (e.g., bromide, dyes) or colloidal tracer (e.g., carboxilated microspheres, tagged clay particles, microorganisms) applications. In the presented study we explore how understanding of sources and flow pathways of water derived from natural tracer studies can be improved and expanded in space and time by simultaneously introducing man-made, synthetic DNA-based microtracers. The microtracer used were composed of polylactic acid (PLA) microspheres into which short strands of synthetic DNA and paramagnetic iron oxide nanoparticles are incorporated. Tracer experiments using both natural tracers and the DNA-based microtracers were conducted in the sub-arctic, glacierized Tarfala (21.7 km2) catchment in northern Sweden. Isotopic hydrograph separations revealed that even though storm runoff was dominated by pre-event water the event water (i.e. rainfall) contributions to streamflow increased throughout the summer season as glacial snow cover decreased. This suggests that glaciers are a major source of the rainwater fraction in streamflow. Simultaneous injections of ten unique DNA-based microtracers confirmed this hypothesis and revealed that the transit time of water traveling from the glacier surface to the stream decreased fourfold over the summer season leading to instantaneous rainwater contributions during storm events. These results highlight that integrating simultaneous tracer injections (injecting tracers at multiple places at one time) with traditional tracer methods (sampling multiple times at one place) rather than using either approach in isolation can provide new insights into the source, timing and mixing of water moving through hydrologic systems.

  15. Evaluating the Representation of Transport Processes in Climate Models using Idealised Radioactive Tracers

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Stevenson, David; Wild, Oliver

    2015-04-01

    The mean age of air is now widely adopted as a diagnostic to compare stratospheric transport in climate models. This can be constrained using observed values of long-lived chemical tracers, and is often derived in models using a passive tracer with infinite lifetime by measuring the elapsed time since last contact with the source region. This method can be extended to derive a tropospheric mean age, which has been used to compare tropospheric transport between models. However, it is difficult to validate this using observations due the limited number of measurements and the complexity of tropospheric transport and chemistry, as a large number of processes with different timescales contribute to the observed tracer values. We probe tropospheric transport in models using radioactive tracers with lifetimes spanning from minutes to years, matching the timescales of relevant transport processes. We derive a tracer transport spectrum similar to that in oceanic studies using the maximum-entropy method from mixing ratios of these idealised radioactive tracers emitted at the surface. Diagnostics calculated from the transport spectrum are used to estimate the relative contributions of tracers with different timescales to the final tracer mixing ratio. Such a transport spectrum can also be constructed using observations of chemical species with different lifetimes. We compare model results from FRSGC/UCI chemistry-transport model and the UK Met-Office Unified Model/UKCA and evaluate the differences in terms of model representation of various processes.

  16. Slew-rate dependence of tracer magnetization response in magnetic particle imaging

    SciTech Connect

    Shah, Saqlain A.; Krishnan, K. M., E-mail: kannanmk@uw.edu [Materials Science and Engineering, University of Washington, Seattle, Washington 98195 (United States); Ferguson, R. M. [LodeSpin Labs, P.O. Box 95632, Seattle, Washington 98145 (United States)

    2014-10-28

    Magnetic Particle Imaging (MPI) is a new biomedical imaging technique that produces real-time, high-resolution tomographic images of superparamagnetic iron oxide nanoparticle tracers. Currently, 25?kHz and 20?mT/?{sub 0} excitation fields are common in MPI, but lower field amplitudes may be necessary for patient safety in future designs. Here, we address fundamental questions about MPI tracer magnetization dynamics and predict tracer performance in future scanners that employ new combinations of excitation field amplitude (H{sub o}) and frequency (?). Using an optimized, monodisperse MPI tracer, we studied how several combinations of drive field frequencies and amplitudes affect the tracer's response, using Magnetic Particle Spectrometry and AC hysteresis, for drive field conditions at 15.5, 26, and 40.2?kHz, with field amplitudes ranging from 7 to 52?mT/?{sub 0}. For both fluid and immobilized nanoparticle samples, we determined that magnetic response was dominated by Néel reversal. Furthermore, we observed that the peak slew-rate (?H{sub o}) determined the tracer magnetic response. Smaller amplitudes provided correspondingly smaller field of view, sometimes resulting in excitation of minor hysteresis loops. Changing the drive field conditions but keeping the peak slew-rate constant kept the tracer response almost the same. Higher peak slew-rates led to reduced maximum signal intensity and greater coercivity in the tracer response. Our experimental results were in reasonable agreement with Stoner-Wohlfarth model based theories.

  17. Use of sulfur hexafluoride and perfluorocarbon tracers in plutonium storage containers for leak detection

    SciTech Connect

    Kung, J.K. [Univ. of Texas, Austin, TX (United States)] [Univ. of Texas, Austin, TX (United States)

    1998-05-01

    This study involves an investigation of the feasibility of a tracer-based leak detection system for long-term interim plutonium storage. In particular, a protocol has been developed based on the use of inert tracers with varying concentrations in order to {open_quotes}fingerprint{close_quotes} or {open_quotes}tag{close_quotes} specific containers. A particular combination of tracers at specific ratios could be injected into the free volume of each container, allowing for the detection of leaks as well as determination of the location of leaking containers. Based on plutonium storage considerations, sulfur hexafluoride and four perfluorocarbon tracers were selected and should allow a wide range of viable fingerprinting combinations. A {open_quotes}high-low{close_quotes} protocol which uses two distinct chromatographic peak areas or concentration levels, is recommended. Combinations of air exchange rates, detection durations, and detectability limits are examined in order to predict minimum tracer concentrations required for injection in storage containers.

  18. Natural gas leak dispersion studies using an infrared gas-imaging system

    NASA Astrophysics Data System (ADS)

    McRae, Thomas G.; Altpeter, L. L. T.

    1995-02-01

    The Gas Research Institute (GRI) has been investigating improved methods for the detection of gas leaks, particularly from buried pipes. Detection of natural gas leaks by infrared remote sensing, using topographical targets, can provide a significantly improved method for gas leak surveys, where the remote sensing system is capable of scanning large areas for leaks. For any candidate remote sensing system, the performance goal of greatest interest is the detection limit (DL), which should be as low as possible. A method is described by means of which a realistic DL may be estimated before the start of any proposed R & D project. A key feature of this method is the ability to challenge candidate remote sensing systems with a realistic 3-D model of small turbulent plumes from ground level gas leaks. To obtain these 3-D models, a novel electro-optical technique was developed in which real-time infrared optical density distributions and fluctuations of gas leak plumes from controlled releases of methane were captured as video images. These optical density plume images may be used with the infrared beam geometry of the candidate remote sensing system to achieve realistic estimates of the DL.

  19. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    Flexible Metal-Organic frameworks that exhibit a gate-opening (GO) adsorption mechanism have potential for gas separations and gas storage. The GO phenomenon occurs when molecular gates in the structure expand/contract in response to the activation/de-activation of a system variable e.g. temperature, pressure or gas. Sharp discontinuities in the isotherm leading to S-shapes and large adsorption-desorption hysteresis are typical of this phenomenon. This study investigates the kinetics and thermodynamics of the GO behavior by combining adsorption measurements and analytical modeling of adsorption kinetics and capacity as a function of adsorbate, GO pressure, and temperature. Basic understanding of GO mechanism will help harness GO-MOF's as adsorbents for gas separations and storage. Experiments were performed on two precharacterized MOFs with verified GO behavior. These are (1) Zn2(bpdc)2(bpee), which expands from a relative amorphous to crystalline structure and (2) Cu[(dhbc) 2(4,4f-bpy)]H2O, a mutually interdigitated 2-D structure (bpdc = biphenyldicarboxylate, bpee = 1,2]bipyridylethene; DMF = N,N-dimethyl formamide, dhbc= 2,5-dihydroxybenzoic acid, bpy=bipyridine). Both sub- and super-critical adsorption data were collected using three adsorption units: a standard low-pressure volumetric adsorption unit, a commercial high-pressure gravimetric analyzer and a custom-built high-pressure differential volumetric unit. Collected laboratory data were combined with published adsorption rate and isotherm data for analysis to broaden the range of data collection. The accuracy of the high-pressure differential unit was improved by over 300-fold by changing analytical methods of processing data to establish a reliable null correction. A pronounced effect of the allowed experimental time was found at cryogenic temperatures on (1). Tightening the stability criteria used by the adsorption equipment to determine equilibration increased the experimental time from the order of minutes to >60 hours, and this in turn, led to a ˜300 fold increase in capacity, convergence of capacities at similar reduced temperatures (critical temperature being the reducing parameter), discontinuities in the isotherms, lowering of gate-opening pressures, changes in the isotherm shapes as well as width of hysteresis loops. Although an experimental time effect was also seen for H2 adsorption at 77K, H2 showed no discontinuity in the adsorption isotherm, adsorption-desorption hysteresis was much less pronounced, and equilibration required significantly less time. The significant difference in rates of adsorption by different gases was attributed to an activated configurational diffusion regime in which the diffusing species moves through a corrugated surface potential when the diameter of the adsorbate approaches that of the pore. A concentration-dependent diffusion model coupled with insufficient equilibration time provides an alternate explanation to describe the stepwise adsorption behavior in GO-MOFs and the changes in capacities. A sigmoid shape of adsorption rate data at cryogenic temperatures is atypical of simple Fickian diffusion, suggesting a more complex mechanistic explanation is required to explain adsorption kinetics to GO-MOFs. Extending the unreacted shrinking core model from the field of catalyst deactivation suggests that relaxation will be much faster relative to diffusion when temperature is increased even by just 10K. From a thermodynamic perspective, adsorption isotherms on (2) demonstrate universality when pressure and temperature are scaled/reduced according to those at critical conditions. At similar reduced conditions, isotherms of gases on (2) converged and both capacity and pressure points of discontinuities showed a predictive behavior. Discrete levels of capacities were found which decrease in temperature. Existence of a universal parameter of heat of gate-opening is calculated and the heats of adsorption and structural expansion are shown to be separable. This adsorption universality suggests a means to predict adsorption ca

  20. A Cross-Hole, Multi-Year Tracer Injection Experiment in the Volcanic Ocean Crust

    NASA Astrophysics Data System (ADS)

    Fisher, A. T.; Neira, N. M.; Wheat, C. G.; Clark, J. F.; Becker, K.; Hsieh, C. C.; Rappe, M. S.

    2014-12-01

    We present preliminary results from the first cross-hole tracer injection experiment in the volcanic ocean crust. The test site is on 3.5 to 3.6 M.y. old seafloor on the eastern flank of the Juan de Fuca Ridge. Six borehole subseafloor observatories (CORKs) were installed during three scientific ocean drilling expeditions, five arrayed along a 1 km profile aligned with the strike of underlying abyssal hills (Holes 1026B, 1301A/B, and 1362A/B), and one offset 2.4 km to the east (1027C). Before installing the sixth CORK in Hole 1362B, in 2010, we injected a mixture of tracers (dissolved gas, metal salts, particles) during 24 hours into the upper ocean crust. Seafloor samplers connected CORKs, sampling from different locations in the crust, were recovered during servicing expeditions in 2011 and 2013; downhole samplers that contain records from the full four years following tracer injection will be recovered in Summer 2014. Analyses of dissolved gas tracers collected with wellhead samplers through 2013 suggest that the dominant flow direction in upper basement is south to north, as inferred from regional thermal data and the chemistry of geochemical (pore fluid and borehole) samples. The apparent tracer flow rate in upper basement is on the order of meters/day, but calculations are complicated by an incomplete CORK seal in Hole 1301A, which resulted in discharge from this system that also "pulled" water and tracer to the south. Samples were collected from the tracer injection borehole, Hole 1362B, and a sampling site 200 m to the north, Hole 1362A, beginning one year after tracer injection, after opening a large-diameter ball valve on the wellhead of Hole 1362B to initiate a long-term free flow experiment. Analyses of these samples suggest that much of the tracer injected in 2010 remained close to Hole 1362B rather than being advected and dispersed into the formation. It also appears that much of the tracer transport to Hole 1362A occurred within one or more relatively thin/isolated zones, because tracer concentrations remain relatively high and there is a long tail of gradually decreasing values during the last two years of sampling. This interpretation is consistent with the highly layered and laterally continuous volcanic stratigraphy observed in basement boreholes drilled at Sites 1301 and 1362.

  1. Continuous Temperature and Water-Level Data Collected for a Heat Tracer Study on a Selected Reach of Tri-State Canal, Western Nebraska, 2007

    USGS Publications Warehouse

    Hobza, Christopher M.

    2008-01-01

    The water supply in parts of the North Platte River Basin in the Nebraska Panhandle has been designated as fully appropriated or over appropriated by the Nebraska Department of Natural Resources. Recent legislation (LB 962) requires the North Platte Natural Resources District and the Nebraska Department of Natural Resources to develop an Integrated Management Plan to balance ground- and surface-water supply and demand within the North Platte Natural Resources District. For a ground-water-flow model to accurately simulate existing or future ground-water and surface-water conditions, accurate estimates of specific input variables such as streambed conductance or canal-seepage rates are required. As of 2008, the values input into ground-water models were estimated on the basis of interpreted lithology from test holes and geophysical surveys. Often, contrasts of several orders of magnitude exist for streambed conductance among the various sediment textures present locally, and thin, near-surface layers of fine sediment can clog the streambed, substantially reducing conductance. To accurately quantify the rates of leakage from irrigation canals and estimate ground-water recharge, the U.S. Geological Survey, in cooperation with the North Platte Natural Resources District, collected continuous temperature and water-level data to use heat as a tracer for a selected reach of Tri-State Canal west of Scottsbluff, Nebraska. Continuous records of subsurface temperature, ground-water level, canal stage, and water temperature, and sediment core data are presented in this report. Subsurface temperature was monitored at four vertical sensor arrays of thermocouples installed at various depths beneath the canal bed from March through September 2007. Canal stage and water temperature were measured from June to September 2007. Ground-water level was recorded continuously in an observation well drilled near the subsurface temperature monitoring site. These data sets were collected for use as inputs for a computer model to estimate the vertical hydraulic conductivity. Before the initiation of flow, diurnal variations in subsurface temperature occurred because of daytime heating and nighttime cooling of bed sediment. Flow in Tri-State Canal was first detected on June 16 at the monitoring site as a disruption in the temperature signal in the shallowest thermocouple in all four vertical sensor arrays. This disruption in the temperature pattern occurred in deeper thermocouples at slightly later times during the rapid infiltration of canal water. The ground-water level began to rise approximately 23 hours after flow was first detected at the monitoring site. Canal stage rose for 7 days until the maximum flow capacity of the canal was approached on June 23, 2007. Measured water temperatures ranged from 18 to 25 degrees Celsius (C) while the canal was flowing near maximum capacity. Small diurnal variations of 1.0 to 1.5 degrees C in water temperature were recorded during this time. Measured ground-water levels rose constantly during the entire irrigation season until levels peaked on September 3, 2007, 3 days after diversions to Tri-State Canal ceased.

  2. Evaluating oil, gas ventures in W. Siberia: Feasibility studies

    SciTech Connect

    Krug, J.A. (Questa Engineering Corp., Golden, CO (United States)); Connelly, W. (Pangea International Inc., Golden, CO (United States))

    1993-02-08

    This article discusses the methodology and calculations used in performing the economic evaluations for a typical western Siberia oil project venture. The discussion of taxes, funds, depreciation, and costs assumes the venture is a stock company and that economics are calculated on a project basis. Most ventures available to western companies are delineated oil fields that are not yet developed or producing. The authors focus on this type of property. The required elements for an economic evaluation include original-oil-in-place (OOIP) and recoverable reserves; development plan and associated production forecast; and capital requirements and operating costs. The level of evaluation-i.e., screening, preliminary feasibility study, Technical Efficiency of Organization (TEO), or full feasibility study-determines the detail needed for each of these elements. Several economic analyses of a venture should be made to evaluate the sensitivity of alternative development plans, joint venture deal terms, capital requirements, operating costs, product prices, and taxation variables. The first three parts of this five part series dealt with (1) log and core data, (2) reservoir description and (3) flow tests and reservoir performance, and provided a technical foundation for the evaluation of oil and gas ventures in western Siberia.

  3. Microfluidics: a groundbreaking technology for PET tracer production?

    PubMed

    Rensch, Christian; Jackson, Alexander; Lindner, Simon; Salvamoser, Ruben; Samper, Victor; Riese, Stefan; Bartenstein, Peter; Wängler, Carmen; Wängler, Björn

    2013-01-01

    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. PMID:23884128

  4. Diagnostic Implications of the Reactivity of Fluorescence Tracers

    SciTech Connect

    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.

  5. Retention of chemical tracers in geothermal reservoirs

    SciTech Connect

    Horne, R.N.; Breitenbach, K.A.; Fossum, M.P.

    1982-01-01

    The advantages and disadvantages of chemical tracers for use in geothermal reservoir monitoring are examined. Tracers are used to determine the magnitude of connectivity between injection and production wells in order to estimate the likelihood of premature fluid breakthrough. Even though chemical tracers are generally less environmentally sensitive than radioactive materials, quantities injected need to be much larger to be distinguishable by chemical analysis. As a result, a non-equilibrium concentration of tracer material is injected into the reservoir, and the tracer is susceptible to retention within the reservoir by ion exchange, diffusion into the solids or immobile reservoir fluid, adsorption or dissolution. These various reactions lead to changes in the tracer concentration as the traced fluid flows through the reservoir, and therefore reduce the capability of the experiment to distinguish concentration changes due to purely mechanical effects. Experimental observations reported here show that substantial fractions of KI tracer were retained under reservoir conditions, even though it appears that the retained material was subsequently released into more dilute fluid. The result is an apparent storage and release mechanism that will distort the later response of a tracer breakthrough.

  6. USING TRACERS TO DESCRIBE NAPL HETEROGENEITY

    EPA Science Inventory

    Tracers are frequently used to estimate both the average travel time for water flow through the tracer swept volume and NAPL saturation. The same data can be used to develop a statistical distribution describing the hydraulic conductivity in the sept volume and a possible distri...

  7. Bacteriophages as surface and ground water tracers

    NASA Astrophysics Data System (ADS)

    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.

  8. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    Microsoft Academic Search

    R. W. Maira; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth

    We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear

  9. Study of Gas Adsorption on Biphasic Nanostructured Surfaces

    NASA Astrophysics Data System (ADS)

    Nader, Rami; Hamieh, Tayssir; Villieras, Frédéric; Angelina. Razafitianamaharav; Toufaily, Joumana; Mcheik, Ali S.; Thomas, Fabien

    This work has carried out on grafted nanoparticles oxide silica to determine the possible existence of “nanoeffect”. The textural properties and heterogeneity of surface of the samples were studied at the interface solid-gas. The Geometric properties were discussed in terms of the surface area while the energy properties were discussed in terms of the reactive sites of the surface.In the framework of this study, firstly, the sample was used in the non-grafted state and then in the grafted state using a hydrophilic molecule and a hydrophobic molecule. Several techniques have been used: Infrared spectroscopy, X ray diffraction, the point by point volumetric technique, which enable us to study the interactions between the adsorbate and the solid surface. Finally we have determined the size and electro thermal mobility using zestasizer (Nano ZS). The results obtained show that there are two types of groups silanols and siloxanes on the silica OX5 giving a composite hydrophilic-hydrophobic. This character causes a singular behavior in adsorptive material, the presence of hydrophilic groups, strongly polarized, and is detected by infrared spectroscopy. These groups cause significant differences depending on the polarizability of the probe molecules, and the adsorption of argon shows no heterogeneity of the surface, while nitrogen is adsorbed on the polar sites at low relative pressure, While the volumetric continues to adsorption of argon and nitrogen on combustion silica to obtain and to highlight sites of high energy and polar surface sites. The combustion silica which has been used as adsorbent in this study has an amorphous surface, virtually free of impurities indicates that the sample is not micro porous and grafting of the molecules makes a decrease in high energy sites or to a relative increase in surface low energy.

  10. Dual signature tracer: A new tool for soil management and research.

    NASA Astrophysics Data System (ADS)

    Poleykett, Jack; Quinton, John; Armstrong, Alona; Maher, Barbara; Black, Kevin

    2015-04-01

    The significant detrimental effects that occur, both on and off site due to the transport of soil are well documented. Now more than ever, it is vital to understand the pathways, processes and fate of transported sediments, to underpin environmental strategy and develop robust forecast models. Researchers have employed a broad range of materials and techniques to trace the movement of soil through space and time. However, three primary challenges still remain: 1) to develop a tracer that has the same or similar hydraulic characteristics as soil: 2) to develop a tracer able to replicate the broad and variable particle size distribution of soils; and: 3) to develop a tracing methodology that increases the volume, and quality of data collected from the field. This study approaches these challenges using a unique 'dual signature' tracer comprising natural mineral material directly coated with a fluorescent dye pigment and loaded during coating with a naturally occurring magnetic mineral oxide creating a tracer with both fluorescent properties and para-magnetic character. An assessment of the effectiveness of the tracer as a tracer of soil was conducted at the soil box and plot scale under controlled rainfall conditions, to: 1) examine the behaviour of the tracer, and: 2) to assess the efficiency of the different tools available to monitor the tracer post- deployment. At the plot scale, a unique site specific tracer was developed to match the hydraulic characteristics (particle size distribution and specific gravity), of the native soil enabling the source-sink relationship, transport pathways and transport rate through the environment to be investigated. Spatial mapping of the tracer distribution within each plot was also conducted using photography and Ultra Violet (UV) illumination. The results of this study provide the basis for the development of a unique soil tracing methodology, which can be applied to investigate soil transport processes, at a range of scales in a variety of settings. Keywords: soil, processes, erosion, tracing, fluorescent, magnetic

  11. A Study of Hybrid Insulation Composition Joint using Gas and Solid Insulator for Gas Insulated Power Equipment

    NASA Astrophysics Data System (ADS)

    Shinkai, Hiroyuki; Goshima, Hisashi; Yashima, Masafumi

    SF6 is used as the main insulation gas for gas-insulated switchgear (GIS), but it has recently become a gas that must be restricted because of its greenhouse effect. To date, we have studied the insulation characteristics of compressed N2 and CO2 as a possible alternative for SF6. We have reported that N2 or CO2 must be pressurized up to 2.0MPa when it is used as a substitute for SF6 of 0.5MPa. Therefore, we have proposed a hybrid insulation composition that uses the gas and solid insulators. Because the central conductor of GIS is the covered by solid insulator in this composition, the high-pressure gas of 2.0MPa is not needed. However, the joint of the solid insulator becomes the weak point for discharge development. In this paper, we describe the effective configuration for the improvement of withstand voltage on the basis of the experiment. As a result, the most effective connector was made of resin without an implanted electrode and the configuration was the case without the solid-solid interface between the solid insulator of the central conductor and the resin connector. In this experiment, the improvement of the breakdown electric field of the hybrid composition was 44% or more compared with the case of only gas insulation (conventional method). In addition, a further improvement can be expected by optimizing the insulation creepage distance and configuration.

  12. Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

    NASA Technical Reports Server (NTRS)

    Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

    1986-01-01

    The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

  13. Matching tracer selection to georeservoir typology - A note on geothermal reservoir classification

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Licha, Tobias; Sauter, Martin

    2013-04-01

    Thermal-lifetime prediction is a traditional endeavor 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 drop (so-called '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, 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 just few more fractures are considered, this clear-cut correlation is broken. A given geothermal reservoir can simultaneously exhibit a single-fracture behavior, in terms of heat transport, and a multiple-fracture behavior, 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. Non-conservative tracers, in particular sorptive and thermo-sensitive compounds, can be used to overcome this gap between heat and tracer transport. However, significant differences exist, w. r. to tracer functionality, between different geothermal systems: (I) hot natural aquifers (with predominantly 'porous media' character), (II) aquifer-based EGS, (III) petrothermally-based EGS, (IV) naturally-fractured systems. Conservative tracers are indispensable to characterizing any of (I) - (IV), but their residence time distribution (with mean residence time MRT) correlates differently with thermal lifetime: the more pronounced the petrothermal character (with effective aperture w), the more the quadratic term (proportional to Dth*MRT2/w2) will prevail within thermal lifetime. It therefore turns out that thermo-sensitive tracers are less useful (roughly speaking) in petrothermal, than in aquifer-based reservoirs; whereas sorptive tracers prove more useful in petrothermally-dominated, than in aquifer-based reservoirs. Acknowledgement: This study was conducted within task unit G6 of the project gebo ('Geothermal Energy and High-Performance Drilling'), funded by the Lower-Saxonian Ministry of Science and Culture and by Baker Hughes (Celle), Germany.

  14. Techno-socio-economic study of bio-gas plants

    SciTech Connect

    Not Available

    1981-01-01

    This study covers technological, social and economic aspects of the biogas program in Chitawan, Nepal. Many interesting facts are revealed which may be useful for future planning of Nepalese biogas programs. Concerning the social aspects, only big farmers (having more than 4 bighas of land and more than 10 domestic animals) were found to have biogas plants. No farmer who had a biogas plant was illiterate. As for the technical aspects of the total gas ovens used in the area, 66% were of BTI design. Most of the ovens were of 0.45-m/sup 3/ capacity. The life of BTI ovens was found to be shorter than the life of ovens of other companies. BTI ovens are not useful when farmers have to use a big pot for cooking. All farmers of the area were found to be convinced of the utility of the biogas plant. With regard to the economic aspects of using biogas plants, farmers were able to save 53% of the total expenditure which they had been spending for fuel. Wood consumption was reduced to 50% by using biogas. The internal rate of return of a 2.8-m/sup 3/ biogas plant was found to be 14% assuming that the plant would last for 20 years. Most of the farmers in the area did not have biogas plants. The main reason given was that there were not enough capital and cattle to begin such an operation.

  15. Development of an airborne perfluorocyclocarbon tracer system and its first application for Lagrangian experiments

    NASA Astrophysics Data System (ADS)

    Ren, Y.; Schlager, H.; Lichtenstern, M.; Baumann, R.

    2013-12-01

    A perfluorocyclocarbon (PFC) tracer system (PERTRAS) has been developed, specifically designed for Lagrangian aircraft experiment. With PERTRAS air masses of interest can be tagged with a PFC compound and followed over a time period of up to three days to investigate the transport and mixing of air masses, photochemical transformations of trace gases, and microphysical processes in aerosol layers and clouds. It consists of three main parts: tracer release unit (RU), adsorption tube sampler (ATS) and tracer analytical system. The RU and ATS can be deployed from aircraft, ships and ground sites. The sample tubes are analyzed in the laboratory using a thermal desorber/gas chromatography/mass spectrometry (TD/GC/MS) system. The first deployment of PERTRAS was made in the framework of a Lagrangian experiment during the field campaign of the EU SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project in November, 2011. The tracer PMCP (perfluoromethylcyclopetane) was released from the deck of the research vessel Sonne. Based on the forecasts of the tracer dispersion using the HYSPLIT model, samples were collected by ATS on board DLR research aircraft Falcon. Enhanced PMCP concentrations above ambient PMCP background values were detected during three intersects of the tracer plume. In general, good agreement was found between the measurement and the HYSPLIT model results demonstrating the capability and feasibility of PERTRAS to support Lagrangian transport and dispersion experiments. We present the experimental technique of PERTRAS, the first application during SHIVA, and plans for future aircraft experiments using PERTRAS.

  16. A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Mcclure, John C.; Hou, Haihui Ron

    1994-01-01

    A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.

  17. Evaluating the reliability of the stream tracer approach to characterize stream-subsurface water exchange

    USGS Publications Warehouse

    Harvey, J.W.; Wagner, B.J.; Bencala, K.E.

    1996-01-01

    Stream water was locally recharged into shallow groundwater flow paths that returned to the stream (hyporheic exchange) in St. Kevin Gulch, a Rocky Mountain stream in Colorado contaminated by acid mine drainage. Two approaches were used to characterize hyporheic exchange: sub- reach-scale measurement of hydraulic heads and hydraulic conductivity to compute streambed fluxes (hydrometric approach) and reachscale modeling of in- stream solute tracer injections to determine characteristic length and timescales of exchange with storage zones (stream tracer approach). Subsurface data were the standard of comparison used to evaluate the reliability of the stream tracer approach to characterize hyporheic exchange. The reach-averaged hyporheic exchange flux (1.5 mL s-1 m-1), determined by hydrometric methods, was largest when stream base flow was low (10 L s-1); hyporheic exchange persisted when base flow was 10- fold higher, decreasing by approximately 30%. Reliability of the stream tracer approach to detect hyporheic exchange was assessed using first- order uncertainty analysis that considered model parameter sensitivity. The stream tracer approach did not reliably characterize hyporheic exchange at high base flow: the model was apparently more sensitive to exchange with surface water storage zones than with the hyporheic zone. At low base flow the stream tracer approach reliably characterized exchange between the stream and gravel streambed (timescale of hours) but was relatively insensitive to slower exchange with deeper alluvium (timescale of tens of hours) that was detected by subsurface measurements. The stream tracer approach was therefore not equally sensitive to all timescales of hyporheic exchange. We conclude that while the stream tracer approach is an efficient means to characterize surface-subsurface exchange, future studies will need to more routinely consider decreasing sensitivities of tracer methods at higher base flow and a potential bias toward characterizing only a fast component of hyporheic exchange. Stream tracer models with multiple rate constants to consider both fast exchange with streambed gravel and slower exchange with deeper alluvium appear to be warranted.

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

    NASA Astrophysics Data System (ADS)

    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 reliably inferred the mean residence time of groundwater recharged between 1980 and 2014. Where direct age comparison could be made 71% of mean age estimates for the studied groundwater sites were in agreement with ages inferred from tritium and SF6 (within an uncertainty of 1 standard deviation). The remaining (anoxic) sites showed reduced concentrations of Halon-1301 along with even further reduced concentrations of CFCs. The reason(s) for this need to be further assessed, but are likely to be caused by sorption or degradation of the compounds. Despite some groundwater samples showing evidence of contamination from industrial or agricultural sources (inferred by elevated CFC concentrations), no sample showed a significantly elevated concentration of Halon-1301, which suggests no local anthropogenic or geologic sources of Halon-1301 contamination.

  19. Twin Lake Tracer Tests: Setting, methodology, and hydraulic conductivity distribution

    NASA Astrophysics Data System (ADS)

    Killey, R. W. D.; Moltyaner, G. L.

    1988-10-01

    Following evaluation of three potential sites, a fluvial sand aquifer with high (0.7-1.6 m d-1) linear average groundwater flow velocities was instrumented with a fully penetrating injection well and 82 monitoring installations over a 40-m flow path length. Two natural gradient tracer migration experiments have employed pulse injections of a nonreactive radioisotope (131I) in a study of hydraulic conductivity structure and dispersive characteristics of the flow system. The use of a gamma-emitting radionuclide in these experiments allowed measurement of tracer distribution by scanning fully penetrating boreholes with a scintillation detector. This technique provided many advantages in data collection over conventional tracers, including unprecedented resolution of the vertical distribution of tracer, measurements without pumping and the attendant concerns for flow system perturbation, and minimal manpower for sample analysis. Tracer breakthroughs at monitors along the axis of flow revealed the presence of heterogeneities in aquifer hydraulic conductivity at two scales. Over the 40-m path length, six regions with hydraulic conductivities substantially different from adjacent strata were identified. Thicknesses of these regions varied from 0.2 to more than 3 m; their lateral extents (in the direction of groundwater flow) ranged from 15 m to more than 40 m. Smaller strata, with an average thickness of 0.34 m and lengths of less than 10 m, were detected within all six of the hydraulic conductivity regions, but there was no evidence of increases in local dispersivity with increased transport distance as a result of these variations. The six hydraulic conductivity regions do, however, have measurable effects on whole-aquifer dispersion. Stratification characteristics of the tested aquifer, believed to have been deposited in a sandy braided river, are consistent with those observed in similar modern environments. Estimation of the magnitude and spatial structure of hydraulic conductivity variations in aquifers of concern would be greatly aided by studies of the stratification characteristics in well-exposed modern or lithified sedimentary analogues.

  20. A study of natural gas extraction in Marcellus shale

    E-print Network

    Boswell, Zachary (Zachary Karol)

    2011-01-01

    With the dramatic increases in crude oil prices there has been a need to find reliable energy substitutions. One substitution that has been used in the United States is natural gas. However, with the increased use of natural ...

  1. A Study of Strategies for Oil and Gas Auctions 

    E-print Network

    Nordt, David Paul

    2010-10-12

    Oil and gas auctions help transact billions of dollars in property sales in the US each year. Value is lost by participants with ineffective strategies. Federal lease auctions have been investigated from public data, but ...

  2. Experimental Characterization and Molecular Study of Natural Gas Mixtures 

    E-print Network

    Cristancho Blanco, Diego Edison

    2011-08-08

    Natural Gas (NG) plays an important role in the energy demand in the United States and throughout the world. Its characteristics as a clean, versatile and a sustainable source of energy makes it an important alternative ...

  3. Wind tunnel studies of gas dispersion from ground level source

    NASA Astrophysics Data System (ADS)

    Michálek, Petr; Zacho, David

    2015-05-01

    Measurements of gas dispersion from ground source were performed in a boundary layer wind tunnel in VZLU Prague. The measurements include non-buoyant gas dispersion behind a ground level source on a flat plane, on a simple rectangular building model and behind a model hill and rectangular barrier. These measurements will serve for verification of a new gas dispersion software being developed in VZLU. The dispersion model is intended for use by firemen and ambulance services in the case of an accident for immediate estimation of the area with dangerous gas concentration. The dispersion model will use precalculated results for chosen areas in the Czech Republic with industrial plants and residential building in the neighborhood. The size of contaminated area will be estimated using actual meteorological situation, i.e. wind speed and direction etc. and precalculated data of flow and dispersion in the chosen location.

  4. Study of a cumulative gas phenomenon in plasma focus discharge

    Microsoft Academic Search

    H. M. Soliman; T. M. Allam; S. T. Abd El-Latif

    2009-01-01

    A cumulative phenomenon of nitrogen gas at a pressure of 3.3 torr in a 1.2 kJ coaxial plasma focus discharge device was investigated experimentally. Variations of nitrogen gas density in the axial phase along the inter-electrode region were estimated experimentally from the plasma current sheath (PCS) dynamics in terms of its velocity, acceleration as well as axial magnetic force data. An inclination

  5. Computational study of gas quenching on carburizing hypoid ring gear

    Microsoft Academic Search

    T. Sugimoto; M. Qin; Y. Watanabe

    2006-01-01

    Due to its pure convective heat transfer, flexible process parameters, and clean nontoxic quenching medium, gas quenching\\u000a has become a solution to traditional quench distortion and growing environmental problems. To further improve the productivity\\u000a of gas quenching, the present quench pressure and flow velocity have been increased to five or more times greater than those\\u000a common 10 to 20 years

  6. Studies on a micro combustor for gas turbine engines

    Microsoft Academic Search

    X. C. Shan; Z. F. Wang; Y. F. Jin; M. Wu; J. Hua; C. K. Wong; R. Maeda

    2005-01-01

    The design, fabrication and characterization of a silicon-based micro combustor for gas turbine engines are reported in this paper. The micro combustor consists of seven-layer microstructures fabricated from silicon wafers, and it adopts a novel fuel-air recirculation channel for extending gas flow path. Numerical simulations based on computational fluid dynamics (CFD) demonstrate a guideline for selecting parameters during combustor operation

  7. Remaining life assessment (RLA) of gas based units — case studies

    Microsoft Academic Search

    C. R. Prasad; Kulvir Singh

    2010-01-01

    Gas based power plants, particularly the hot gas path components, are subjected to very harsh and rigorous environments. Many\\u000a time dependent degradation mechanisms such as creep, fatigue, erosion, corrosion, electro mechanical fretting and embrittlement\\u000a act in combination. The plants are, therefore, designed for a finite life. In order to avoid premature failures, margins of\\u000a safety are provided and a number

  8. Gas transport and free volume study in polyethylene based epoxy membranes

    NASA Astrophysics Data System (ADS)

    Patil, Pushkar N.; Checchetto, R.; Ferragut, R.; Aghion, S.; Miotello, A.; Brusa, R. S.

    2015-06-01

    The mechanism of gas diffusivity in amine modified epoxy membranes is studied in the frame of free volume properties. Epoxy membranes with two different crosslinking densities and composite with Graphene nanoplatelets were prepared by solvent casting method. The free volume parameters measured by Positron Annihilation Spectroscopy (PAS) show inverse correlation with crosslinking density of the samples. The gas permeability and diffusivity for CO2 have been studied by gas permeation measurements. The study reveals that the gas permeability and diffusivity change significantly as a function of crosslinking density, free volumes and structural relaxations of the molecular chains.

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

    PubMed

    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, ?(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. PMID:22434939

  10. Tracer design for magnetic particle imaging (invited)

    NASA Astrophysics Data System (ADS)

    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, ?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.

  11. Cardiac PET perfusion tracers: current status and future directions.

    PubMed

    Maddahi, Jamshid; Packard, René R S

    2014-09-01

    PET myocardial perfusion imaging (MPI) is increasingly being used for noninvasive detection and evaluation of coronary artery disease. However, the widespread use of PET MPI has been limited by the shortcomings of the current PET perfusion tracers. The availability of these tracers is limited by the need for an onsite ((15)O water and (13)N ammonia) or nearby ((13)N ammonia) cyclotron or commitment to costly generators ((82)Rb). Owing to the short half-lives, such as 76 seconds for (82)Rb, 2.06 minutes for (15)O water, and 9.96 minutes for (13)N ammonia, their use in conjunction with treadmill exercise stress testing is either not possible ((82)Rb and (15)O water) or not practical ((13)N ammonia). Furthermore, the long positron range of (82)Rb makes image resolution suboptimal and its low myocardial extraction limits its defect resolution. In recent years, development of an (18)F-labeled PET perfusion tracer has gathered considerable interest. The longer half-life of (18)F (109 minutes) would make the tracer available as a unit dose from regional cyclotrons and allow use in conjunction with treadmill exercise testing. Furthermore, the short positron range of (18)F would result in better image resolution. Flurpiridaz F 18 is by far the most thoroughly studied in animal models and is the only (18)F-based PET MPI radiotracer currently undergoing clinical evaluation. Preclinical and clinical experience with Flurpiridaz F 18 demonstrated a high myocardial extraction fraction, high image and defect resolution, high myocardial uptake, slow myocardial clearance, and high myocardial-to-background contrast that was stable over time-important properties of an ideal PET MPI radiotracer. Preclinical data from other (18)F-labeled myocardial perfusion tracers are encouraging. PMID:25234078

  12. Predicted fate of tritium residuum from groundwater tracer experiments in the Amargosa Desert, southern Nevada

    SciTech Connect

    Brikowski, T.

    1993-07-01

    Analytic solutions are used in this study to evaluate potential groundwater transport of tritium used in goundwater tracer tests southwest of the Nevada Test Site. Possible transport from this site is of interest because initial radionuclide concentrations were high and the site is close to goundwater discharge points (12 km). Anecdotal evidence indicates that 90 percent of these tracers were removed by pumping at the completion of the tests; this study examines the probable transport of the tracers with and without the removal. Classical dispersive transport analytic solutions are used, treating the tracer test as a point slug injection. Input parameters for the solutions were measured at the site, and consideration of parameter uncertainty is incorporated in the results. With removal of the tracer, the maximum expected region with above-Safe Drinking Water Act (40 CFR 121) concentrations of tritium extends 5 km from the injection point, and does not reach any sites of public access. Detectable tritium from the tests is likely to have reached the Ash Meadows fault zone, but flow along the fault probably diluted the tracer to below detection limits before arrival at springs along the fault. Arrival at the springs would have occurred 20 to 25 years after the tests. Without removal of the tracer, the solutions indicate that tritium concentrations just above Safe Drinking Water Act standards would have reached the Ash Meadows fault zone. In this case, detectable tritium might have been found in Devil`s Hole or Longstreet Spring, the nearest points of possible public exposure.

  13. Computational study of porous materials for gas separations

    NASA Astrophysics Data System (ADS)

    Lin, Li-Chiang

    Nanoporous materials such as zeolites, zeolitic imidazolate frameworks (ZIFs), and metal-organic frameworks (MOFs) are used as sorbents or membranes for gas separations such as carbon dioxide capture, methane capture, paraffin/olefin separations, etc. The total number of nanoporous materials is large; by changing the chemical composition and/or the structural topologies we can envision an infinite number of possible materials. In practice one can synthesize and fully characterize only a small subset of these materials. Hence, computational study can play an important role by utilizing various techniques in molecular simulations as well as quantum chemical calculations to accelerate the search for optimal materials for various energy-related separations. Accordingly, several large-scale computational screenings of over one hundred thousand materials have been performed to find the best materials for carbon capture, methane capture, and ethane/ethene separation. These large-scale screenings identified a number of promising materials for different applications. Moreover, the analysis of these screening studies yielded insights into those molecular characteristics of a material that contribute to an optimal performance for a given application. These insights provided useful guidelines for future structural design and synthesis. For instance, one of the screening studies indicated that some zeolite structures can potentially reduce the energy penalty imposed on a coal-fired power plant by as much as 35% compared to the near-term MEA technology for carbon capture application. These optimal structures have topologies with a maximized density of pockets and they capture and release CO2 molecules with an optimal energy. These screening studies also pointed to some systems, for which conventional force fields were unable to make sufficiently reliable predictions of the adsorption isotherms of different gasses, e.g., CO2 in MOFs with open-metal sites. For these systems, we developed a systematic, transferable, and efficient methodology to generate force fields by using high-level quantum chemical calculations for accurate predictions of properties. The method was first applied to study the adsorption of CO2 and N2 in Mg-MOF-74, an open-metal site MOF. Two different approaches were developed: one approach based on MP2 calculations on a representative cluster and a second approach based on DFT calculations on a fully periodic MOF. Both approaches gave significantly better predictions of the experimental adsorption isotherms compared to conventional force fields. In addition, we extended the DFT approach to study water adsorption in these materials. Moreover, instead of deriving detailed force fields, we have also proposed an alternative method to efficiently correct initial trial force fields with little information obtained from quantum chemical calculations. Finally, we studied the dynamics of CO2 in Mg-MOF-74 using molecular simulations. This study addressed the dynamic behaviors of CO 2 adsorbed in Mg-MOF-74, and provided an alternative explanation to the experimentally measured chemical shifts of 13C labeled CO2 adsorbed in a powder Mg-MOF-74 sample. Our results further illustrated that subtle changes in the topology of frameworks greatly influence CO2 dynamics.

  14. Radon monitoring in gas turbine and thermal power station; A comparative study

    Microsoft Academic Search

    K. Kant; S. K. Chakarvarti

    Background: In this study, measurement of indoor radon and its progeny levels was carried out in Gas Turbine Power Station in Haryana (India), where natural gas is used as fuel. For comparison, the results of a study carried out in thermal power plant in Haryana are also presented. Radon being a ubiquitous air pollutant has global impact and its monitoring

  15. PILOT FIELD STUDIES OF FGD WASTE DISPOSAL AT LOUISVILLE GAS AND ELECTRIC

    EPA Science Inventory

    The report gives results of pilot field studies of flue gas desulfurization (FGD) waste disposal at Louisville Gas and Electric Co. The studies showed that properly prepared landfill from FGD sludge/fly ash mixtures can prevent trace element contamination of underlying groundwate...

  16. The drivers of greenhouse gas emissions: What do we learn from local case studies?

    Microsoft Academic Search

    David P. Angel; Samuel Attoh; David Kromm; Jennifer Dehart; Rachel Slocum; Stephen White

    1998-01-01

    What can local case studies contribute to our understanding of the processes underlying the growth in greenhouse gas emissions? Since much abatement and mitigation are local in character, it is important that policy makers identify the mix of local, national and international processes that contribute to changes in greenhouse gas emissions. Drawing upon the results of case studies in Kansas,

  17. Feasibility Studies on Commercialized Fast Breeder Reactor System (2) Gas Cooled High Temperature FBR

    Microsoft Academic Search

    Yoshihiro Kiso; Jun Kobayashi; Masanori Kid; Masashi Nomura; Masakazu Ichimiya

    Japan Nuclear Cycle Development Institute (JNC) and Electric Utilities have been conducting Feasibility Studies on Commercialized FBR Systems since July 1999 under the cooperation Agreement. In that studies the preliminary concepts of various types of fast breeder reactors such as sodium cooled, heavy metal cooled and gas cooled reactors etc. have been designed and evaluated. For the gas cooled reactors,

  18. Strontium isotopes as tracers of ecosystem processes: theory and methods

    Microsoft Academic Search

    Rosemary C. Capo; Brian W. Stewart; Oliver A. Chadwick

    1998-01-01

    The strontium (Sr) isotope method can be a powerful tool in studies of chemical weathering and soil genesis, cation provenance and mobility, and the chronostratigraphic correlation of marine sediments. It is a sensitive geochemical tracer, applicable to large-scale ecosystem studies as well as to centimeter-scaled examination of cation mobility within a soil profile. The 87Sr\\/86Sr ratios of natural materials reflect

  19. Three-Dimensional Bayesian Geostatistical Aquifer Characterization at the Hanford 300 Area using Tracer Test Data

    SciTech Connect

    Chen, Xingyuan; Murakami, Haruko; Hahn, Melanie S.; Hammond, Glenn E.; Rockhold, Mark L.; Zachara, John M.; Rubin, Yoram

    2012-06-01

    Tracer testing under natural or forced gradient flow holds the potential to provide useful information for characterizing subsurface properties, through monitoring, modeling and interpretation of the tracer plume migration in an aquifer. Non-reactive tracer experiments were conducted at the Hanford 300 Area, along with constant-rate injection tests and electromagnetic borehole flowmeter (EBF) profiling. A Bayesian data assimilation technique, the method of anchored distributions (MAD) [Rubin et al., 2010], was applied to assimilate the experimental tracer test data with the other types of data and to infer the three-dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of the Hanford formation. In this study, the Bayesian prior information on the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using the constant-rate injection tests and the EBF data. The posterior distribution of the conductivity field was obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells. MAD was implemented with the massively-parallel three-dimensional flow and transport code PFLOTRAN to cope with the highly transient flow boundary conditions at the site and to meet the computational demands of MAD. A synthetic study proved that the proposed method could effectively invert tracer test data to capture the essential spatial heterogeneity of the three-dimensional hydraulic conductivity field. Application of MAD to actual field data shows that the hydrogeological model, when conditioned on the tracer test data, can reproduce the tracer transport behavior better than the field characterized without the tracer test data. This study successfully demonstrates that MAD can sequentially assimilate multi-scale multi-type field data through a consistent Bayesian framework.

  20. Onboard Inert Gas Generation System/Onboard Oxygen Gas Generation System (OBIGGS/OBOGS) Study. Part 2; Gas Separation Technology--State of the Art

    NASA Technical Reports Server (NTRS)

    Reynolds, Thomas L.; Eklund, Thor I.; Haack, Gregory A.

    2001-01-01

    This purpose of this contract study task was to investigate the State of the Art in Gas Separation Technologies utilized for separating air into both nitrogen and oxygen gases for potential applications on commercial aircraft. The intended applications included: nitrogen gas for fuel tank inerting, cargo compartment fire protection, and emergency oxygen for passenger and crew use in the event of loss of cabin pressure. The approach was to investigate three principle methods of gas separation: Hollow Fiber Membrane (HFM), Ceramic Membrane (CM), and liquefaction: Total Atmospheric Liquefaction of Oxygen and Nitrogen (TALON). Additional data on the performance of molecular sieve pressure swing adsorption (PSA) systems was also collected and discussed. Performance comparisons of these technologies are contained in the body of the report.

  1. Dust-to-gas ratio, $X_{\\rm CO}$ factor and CO-dark gas in the Galactic anticentre: an observational study

    E-print Network

    Chen, B -Q; Yuan, H -B; Huang, Y; Xiang, M -S

    2015-01-01

    We investigate the correlation between extinction and H~{\\sc i} and CO emission at intermediate and high Galactic latitudes ($|b|>10\\degr$) within the footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic anticentre (XSTPS-GAC) on small and large scales. In Paper I (Chen et al. 2014), we present a three-dimensional dust extinction map within the footprint of XSTPS-GAC, covering a sky area of over 6,000\\,deg$^2$ at a spatial angular resolution of 6\\,arcmin. In the current work, the map is combined with data from gas tracers, including H~{\\sc i} data from the Galactic Arecibo L-band Feed Array H~{\\sc i} survey and CO data from the Planck mission, to constrain the values of dust-to-gas ratio $DGR=A_V/N({\\rm H})$ and CO-to-$\\rm H_2$ conversion factor $X_{\\rm CO}=N({\\rm H_2})/W_{\\rm CO}$ for the entire GAC footprint excluding the Galactic plane, as well as for selected star-forming regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse gas in the northern Galactic hemis...

  2. The Challenges of Change: A Tracer Study of San Preschool Children in Botswana. Early Childhood Development: Practice and Reflections. Following Footsteps.

    ERIC Educational Resources Information Center

    le Roux, Willemien

    This report details findings of a study undertaken during 1993-1995 in the Ghanzi District of Botswana to ascertain the progress of the San children in primary school, comparing children who attended preschool to those who did not. The report also describes the Bokamoso Preschool Programme, started in 1986. Data for the study were collected…

  3. Conceptual design study of an Improved Gas Turbine (IGT) powertrain

    NASA Technical Reports Server (NTRS)

    Johnson, R. A.

    1979-01-01

    Design concepts for an improved automotive gas turbine powertrain are discussed. Twenty percent fuel economy improvement (over 1976), competitive costs (initial and life cycle), high reliability/life, low emissions, and noise/safety compliance were among the factors considered. The powertrain selected consists of a two shaft gas turbine engine with variable geometry aerodynamic components and a single disk rotating regenerator. The regenerator disk, gasifier turbine rotor, and several hot section flowpath parts are ceramic. The powertrain utilizes a conventional automatic transmission. The closest competitor was a single shaft turbine engine matched to a continuously variable transmission (CVT). Both candidate powertrain systems were found to be similar in many respects; however, the CVT represented a significant increase in development cost, technical risk, and production start-up costs over the conventional automatic transmission. Installation of the gas turbine powertrain was investigated for a transverse mounted, front wheel drive vehicle.

  4. Modern approaches to studying gas adsorption in nanoporous carbons

    SciTech Connect

    Morris, James R [ORNL; Contescu, Cristian I [ORNL; Chisholm, Matthew F [ORNL; Cooper, Valentino R [ORNL; Guo, Junjie [University of Tennessee, Knoxville (UTK); He, Lilin [ORNL; Ihm, Yungok [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Mamontov, Eugene [ORNL; Melnichenko, Yuri B [ORNL; Olsen, Raina J [ORNL; Pennycook, Stephen J [ORNL; Stone, Matthew B [ORNL; Zhang, Hongxin [ORNL; Gallego, Nidia C [ORNL

    2013-01-01

    Conventional approaches to understanding gas adsorption capacity of nanoporous carbons have emphasized the relationship with the effective surface area, but more recent work has demonstrated the importance of local structures and pore-size-dependent adsorption. We present some recent developments that provide new insights into local structures in nanoporous carbon and their effect on gas adsorption and uptake characteristics. Experiments and theory show that appropriately tuned pores can strongly enhance local adsorption, and that pore sizes can be used to tune adsorption characteristics. In the case of H2 adsorbed on nanostructured carbon, quasielastic and inelastic neutron scattering probes demonstrate novel quantum effects in the motion of adsorbed molecules.

  5. Systematic study of Optical Feshbach Resonances in an ideal gas

    E-print Network

    S. Blatt; T. L. Nicholson; B. J. Bloom; J. R. Williams; J. W. Thomsen; P. S. Julienne; J. Ye

    2011-06-06

    Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the Optical Feshbach Resonance (OFR) effect in an ultracold gas of bosonic $^{88}$Sr. A systematic measurement of three resonances allows precise determinations of the OFR strength and scaling law, in agreement with coupled-channels theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. OFR could be used to control atomic interactions with high spatial and temporal resolution.

  6. Tracers for monitoring the activity of sodium/glucose cotransporters in health and disease

    DOEpatents

    Wright, Ernest M; Barrio, Jorge R; Hirayama, Bruce A; Kepe, Vladimir

    2014-09-30

    Radiolabeled tracers for sodium/glucose cotransporters (SGLTs), their synthesis, and their use are provided. The tracers are methyl or ethyl pyranosides having an equatorial hydroxyl group at carbon-2 and a C 1 preferred conformation, radiolabeled with .sup.18F, .sup.123I, or .sup.124I, or free hexoses radiolabeled with .sup.18F, .sup.123I, or .sup.124. Also provided are in vivo and in vitro techniques for using these and other tracers as analytical and diagnostic tools to study glucose transport, in health and disease, and to evaluate therapeutic interventions.

  7. Estimates of tracer-based piston-flow ages of groundwater from selected sites-National Water-Quality Assessment Program, 1992-2005

    USGS Publications Warehouse

    Hinkle, Stephen R.; Shapiro, Stephanie D.; Plummer, L. Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.

    2011-01-01

    This report documents selected age data interpreted from measured concentrations of environmental tracers in groundwater from 1,399 National Water-Quality Assessment (NAWQA) Program groundwater sites across the United States. The tracers of interest were chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis primarily were from wells representing two types of NAWQA groundwater studies - Land-Use Studies (shallow wells, usually monitoring wells, in recharge areas under dominant land-use settings) and Major-Aquifer Studies (wells, usually domestic supply wells, in principal aquifers and representing the shallow, used resource). Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) associated with Land-Use Studies also were included. Tracer samples were collected between 1992 and 2005, although two networks sampled from 2006 to 2007 were included because of network-specific needs. Tracer data from other NAWQA Program components (Flow System Studies, which are assessments of processes and trends along groundwater flow paths, and various topical studies) were not compiled herein. Tracer data from NAWQA Land-Use Studies and Major-Aquifer Studies that previously had been interpreted and published are compiled herein (as piston-flow ages), but have not been reinterpreted. Tracer data that previously had not been interpreted and published are evaluated using documented methods and compiled with aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), estimates of tracer-based piston-flow ages, and selected ancillary data, such as redox indicators, well construction, and major dissolved gases (N2, O2, Ar, CH4, and CO2). Tracer-based piston-flow ages documented in this report are simplistic representations of the tracer data. Tracer-based piston-flow ages are a convenient means of conceptualizing groundwater age. However, the piston-flow model is based on the potentially limiting assumptions that tracer transport is advective and that no mixing occurs. Additional uncertainties can arise from tracer degradation, sorption, contamination, or fractionation; terrigenic (natural) sources of tracers; spatially variable atmospheric tracer concentrations; and incomplete understanding of mechanisms of recharge or of the conditions under which atmospheric tracers were partitioned to recharge. The effects of some of these uncertainties are considered herein. For example, degradation, contamination, or fractionation often can be identified or inferred. However, detailed analysis of the effects of such uncertainties on the tracer-based piston-flow ages is constrained by sparse data and an absence of complementary lines of evidence, such as detailed solute transport simulations. Thus, the tracer-based piston-flow ages compiled in this report represent only an initial interpretation of the tracer data.

  8. Computing experiments for study of cadmium isotope separation by gas centrifuges

    NASA Astrophysics Data System (ADS)

    Aisen, E. M.; Borisevich, V. D.; Potapov, D. V.; Rudnev, A. I.; Sulaberidze, G. A.; Tikhomirov, A. V.

    The basic regularities for enrichment of the 116Cd isotope in the form of cadmium dimethyl in a single gas centrifuge and a square cascade of gas centrifuges have been studied by means of numerical simulation techniques. In these computing experiments it has been found the influence of a loss of the process gas due to its partial decomposition to enrichment of the desired isotope.

  9. Air Resources Laboratory Atmospheric Tracer Technology

    E-print Network

    sits in an automobile or aircraft passenger seat and attaches with standard seat belts. Time Integrated that measures tracer concentrations every second. The analyzer is easily carried on a seat of a vehicle. Photo

  10. Use of reactive tracers to determine ambient OH radical concentrations: application within the indoor environment.

    PubMed

    White, Iain R; Martin, Damien; Muñoz, M Paz; Petersson, Fredrik K; Henshaw, Stephen J; Nickless, Graham; Lloyd-Jones, Guy C; Clemitshaw, Kevin C; Shallcross, Dudley E

    2010-08-15

    The hydroxyl radical (OH) plays a key role in determining indoor air quality. However, its highly reactive nature and low concentration indoors impede direct analysis. This paper describes the techniques used to indirectly quantify indoor OH, including the development of a new method based on the instantaneous release of chemical tracers into the air. This method was used to detect ambient OH in two indoor seminar rooms following tracer detection by gas chromatography-mass spectrometry (GCMS). The results from these tests add to the small number of experiments that have measured indoor OH which are discussed with regard to future directions within air quality research. PMID:20704225

  11. Status and integration of studies of gas generation in Hanford wastes

    SciTech Connect

    Pederson, L.R.; Bryan, S.A.

    1996-10-01

    The purpose of this report is to review recent progress in determining the mechanism, kinetics, and stoichiometry of gas generation in Hanford waste tanks. Information has been gathered from the results of (1) laboratory studies with simulated wastes; (2) laboratory studies with actual waste core samples (Tanks SY-101 and SY-103); (3) studies of thermal and radiolytic reactions in the gas phase; (4) gas solubility evaluations; and (5) in-tank gas composition data. The results of laboratory studies using simulated wastes, which were aimed at determining chemical mechanisms responsible for gas generation, are summarized in Section 2. Emphasized are findings from work performed at the Georgia Institute of Technology (GIT), which was conducted under subcontract to Pacific Northwest National Laboratory (PNNL) and completed in FY 1996. Thermally activated pathways for the decomposition of hydroxyethylethylene-diaminetriacetic acid (HEDTA, trisodium salt) in simulated wastes were established by this work, among other accomplishments.

  12. Study on Exploring for Oil, Gas Using Hyperion data

    NASA Astrophysics Data System (ADS)

    Xu, D.-Q.; Ni, G.-Q.; Jiang, L.-L.; Ge, S.-L.

    Reflectance spectra in the visible and near-infrared wavelengths provide a rapid and inexpensive means for determining the mineralogy of samples and obtaining information on chemical composition Hydrocarbon microseepage theory setup a cause-and-effect relation between oil and gas reservoirs and some special surface alterations Therefore we can explore for oil gas by determining reflectance spectra of surface alterations This determination can be fulfilled by means of field work and hyperspectral remote sensing Our cooperative R D project which is sponsored by China National Petroleum Corporation CNPC and committing itself to exploration of oil gas in Qinghai area of China using NASA experimental Hyperion hyperspectral satellite documents a macroscopical feature of reflectance spectra of typical observation points in gas fields and then proposes a method in order to provide surface distribution information e g classification of alterations based on the reflectance spectra determined from the field and remote sensing and obtain anomaly zones of the special alterations This method mainly includes preprocessing of Hyperion images to improve the poor SNR Signal Noise Ratio of them principal component analysis PCA based on wavelet transform to reduce dimensionality and techniques providing surface distribution information using both absorption-band parameters such as the position depth width and asymmetry of the spectra and similarity of the entire shape between two spectra Finally several anomaly zones of alterations are obtained which are

  13. Study of a zirconium getter for purification of xenon gas

    E-print Network

    Dobi, A; Hall, C; Kaufman, L; Langford, T; Slutsky, S; Yen, Y R

    2010-01-01

    Oxygen, nitrogen and methane purification efficiencies for a common zirconium getter are measured in 1050 Torr of xenon gas. Starting with impurity concentrations near 10^{-6} g/g, the outlet impurity level is found to be less than 120*10^{-12} g/g for O2 and less than 950*10^{-12} g/g for N2. For methane we find residual contamination of the purified gas at concentrations varying over three orders of magnitude, depending on the purifier temperature and the gas flow rate. A slight reduction in the purifier's methane efficiency is observed after 13 mg of this impurity has been absorbed, which we attribute to partial exhaustion of the purifier's capacity for this species. We also find that the purifier's ability to absorb N2 and methane can be extinguished long before any decrease in O2 performance is observed, and slower flow rates should be employed for xenon purification due to the cooling effect that the heavy gas has on the getter.

  14. Experimental studies of rare gas clusters in strong laser fields

    Microsoft Academic Search

    David Ashot Khatchatrian

    1997-01-01

    In this thesis we propose a method of probing homogeneous and heterogeneous rare gas cluster properties by investigation of the kinetic energy release of the fragment ions from completely disintegrating clusters under a long ionization potential. Argon, having essentially no isotopes, is an ideal element for kinetic energy measurements. Nanosecond scale KrF* eximer laser is used. The stability of the

  15. Energy Economizer for Low Temperature Stack Gas: A Case Study 

    E-print Network

    Tipton, J. A.

    1979-01-01

    , the burner air supply is preheated by passing through the heat exchanger. Sensitive design problems that had to be resolved were: Overall cost-effectiveness; below dew point cooling of stack gas causing acid corrosion; and selection of an effective heat...

  16. Species-specific isotope tracers to study the accumulation and biotransformation of mixtures of inorganic and methyl mercury by the microalga Chlamydomonas reinhardtii.

    PubMed

    Bravo, Andrea Garcia; Le Faucheur, Séverine; Monperrus, Mathilde; Amouroux, David; Slaveykova, Vera I

    2014-09-01

    The present study demonstrates that species-specific isotope tracing is an useful tool to precisely measure Hg accumulation and transformations capabilities of living organisms at concentrations naturally encountered in the environment. To that end, a phytoplanktonic green alga Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae) was exposed to mixtures of (199)-isotopically enriched inorganic mercury ((199)IHg) and of (201)-isotopically enriched monomethylmercury ((201)CH3Hg) at a concentration range between less than 1 pM to 4 nM. Additionally, one exposure concentration of both mercury species was also studied separately to evaluate possible interactive effects. No difference in the intracellular contents was observed for algae exposed to (199)IHg and (201)CH3Hg alone or in their mixture, suggesting similar accumulation capacity for both species at the studied concentrations. Demethylation of (201)CH3Hg was observed at the highest exposure concentrations, whereas no methylation was detected. PMID:24932531

  17. Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

    E-print Network

    R. W. Mair; R. Wang; M. S. Rosen; D. Candela; D. G. Cory; R. L. Walsworth

    2002-11-09

    We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting from a wide distribution of velocities in the flow field. The maximum velocity experienced in the flow can be calculated from this minimum, and is seen to agree with the information from the complete velocity spectrum, or motion propagator, as well as previously published images. The susceptibility of gas flows to parameters such as gas mixture content, and hence viscosity, are observed in experiments aimed at identifying clear structural features from echo attenuation plots of gas flow in porous media. Gas-phase NMR scattering, or position correlation flow-diffraction, previously clearly seen in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack is not so clear in experiments using a different gas mixture. A propagator analysis shows most gas in the sample remains close to static, while a small portion moves through a presumably near-unimpeded path at high velocities.

  18. Development of improved technologies and techniques for reducing base gas requirements in underground gas storage facilities: Simulation study of hanson field gas storage reservoir. Final report, May 1989-November 1989

    SciTech Connect

    Modine, A.D.

    1989-11-01

    Base gas requirements in the U.S. amount to a few trillion cubic feet. The Gas Research Institute has proposed a gas storage operating plan whereby an inert gas or a low BTU gas could be injected to replace part of the hydrocarbon gas. A reservoir simulator has been developed, enhanced and tested to solve gas-water reservoir problems where the gas may be treated as a two-component miscible mixture. The previously developed reservoir simulator was further enhanced to include a local grid refinement option, which allows the engineer to study a portion of the field in more detail compared to the rest of the field. The simulator was tested for correctness and completeness. A simulation study was conducted for the Hanson Field Gas Storage Reservoir using two models with different layering. The reservoir history matching was duplicated and several prediction cases were run to study the effectiveness of the replacement of base gas with an inert gas. The results show that replacement of a portion of the hydrocarbon base gas with an inert gas can be an attractive alternative for the gas storage industry.

  19. Study of Multi-scale Transport Phenomena in Tight Gas and Shale Gas Reservoir Systems 

    E-print Network

    Freeman, Craig Matthew

    2013-11-25

    will then be validated against core analyses and experiments, and surface flowing gas composition data. Finally the numerical model will be used to generate a model-based analysis technique with the aim of reducing uncertainty in reservoir characteristics. 1... are not analogous to those of coal (Schettler and Parmely 1991). The Langmuir model was based on the theory described above. In its application to desorption in shales and coal, it has been treated as semi-empirically, where the two values of the parameters...

  20. Study of Multi-scale Transport Phenomena in Tight Gas and Shale Gas Reservoir Systems

    E-print Network

    Freeman, Craig Matthew

    2013-11-25

    will then be validated against core analyses and experiments, and surface flowing gas composition data. Finally the numerical model will be used to generate a model-based analysis technique with the aim of reducing uncertainty in reservoir characteristics. 1... are not analogous to those of coal (Schettler and Parmely 1991). The Langmuir model was based on the theory described above. In its application to desorption in shales and coal, it has been treated as semi-empirically, where the two values of the parameters...

  1. Dispersion of tracer particles in a compressible flow

    E-print Network

    John R. Cressman; Walter I. Goldburg; Joerg Schumacher

    2004-02-19

    The turbulent diffusion of Lagrangian tracer particles has been studied in a flow on the surface of a large tank of water and in computer simulations. The effect of flow compressibility is captured in images of particle fields. The velocity field of floating particles has a divergence, whose probability density function shows exponential tails. Also studied is the motion of pairs and triplets of particles. The mean square separation is fitted to the scaling form ~ t^alpha, and in contrast with the Richardson-Kolmogorov prediction, an extended range with a reduced scaling exponent of alpha=1.65 pm 0.1 is found. Clustering is also manifest in strongly deformed triangles spanned within triplets of tracers.

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

    NASA Astrophysics Data System (ADS)

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

    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 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 could be made 71% of mean age estimates for the studied groundwater sites were in agreement with ages inferred from tritium and SF6 (within ± 2 years). The remaining (anoxic) sites showed reduced concentrations of Halon-1301 along with even further reduced concentrations of CFCs. The reason(s) for this need to be further assessed, but are likely to be caused by sorption or degradation of the compounds. Despite some groundwater samples showing evidence of contamination from industrial or agricultural sources via elevated CFC concentrations, no sample indicated significantly elevated concentration of Halon-1301, which may indicate a lack of local anthropogenic or geologic sources of Halon-1301 contamination.

  3. Imaging Ferromagnetic Tracers with a Magnetoresistive Sensors Array

    Microsoft Academic Search

    Juan A. Leyva; Antonio A. O. Carneiro; Lui´s O. Murta; O. Baffa

    2006-01-01

    The aim of this work was to study the feasibility to obtain images from a distribution of ferromagnetic tracers using a magnetoresistive multichannel sensor array (MRA). A magnetic imaging system formed by a linear array composed of 12 magnetoresistive sensors (Honeywell HMC 1001) was constructed covering a scanning area of (16×18) cm2. The signal was pre-processed for off-set correction and

  4. A REVIEW OF SOME TRACER-TEST DESIGN EQUATIONS FOR TRACER-MASS ESTIMATION AND SAMPLE COLLECTION FREQUENCY

    EPA Science Inventory

    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...

  5. Radiological design study of First Optics Enclosure against secondary gas bremsstrahlung for the Canadian Light Source

    Microsoft Academic Search

    J. Asai; H. Hirayama

    2004-01-01

    The design study of the First Optics Enclosure (FOE) against radiation due to secondary gas bremsstrahlung is performed for the beamlines at the Canadian Light Source. The back wall, side walls and roof of the FOE are made of lead. Placed in the FOE are a thin copper metal as a source of secondary gas bremsstrahlung and a tungsten beam

  6. Emission factor estimation in regional air quality studies of residential natural gas fuel interchangeability

    E-print Network

    Dabdub, Donald

    Emission factor estimation in regional air quality studies of residential natural gas fuel for natural gas burner emissions data. The method is built to compensate for the typically small sample size. The method integrates multiple measures of quantified goodness of fit. The method provides a means

  7. A Laboratory Study of the Schmidt Number Dependency of Air-Water Gas

    E-print Network

    Jaehne, Bernd

    A Laboratory Study of the Schmidt Number Dependency of Air-Water Gas Transfer Kerstin Richter1 measurements in two different wind-wave facilities. Key Words: Schmidt number exponent, transfer velocity. Gas Transfer at Water Surfaces, Kyoto, May 17-21, 2010 copyright Kyoto University Press, 2011 #12

  8. A study of Stark effects of Rydberg p states of noble gas atoms

    Microsoft Academic Search

    T. Jiang; M. D. Bowden; E. Wagenaars; E. Stoffels; G. M. W. Kroesen

    2006-01-01

    We have studied the Stark effect for Rydberg p states of noble gas atoms using laser optogalvanic spectroscopy. The measurements were performed in the sheath region of noble gas glow discharges. Laser excitation from metastable states to np states was monitored by optogalvanic spectroscopy. Clear Stark shifts were observed and the experimental results were compared with a theoretical calculation based

  9. Fuel economy screening study of advanced automotive gas turbine engines

    NASA Technical Reports Server (NTRS)

    Klann, J. L.

    1980-01-01

    Fuel economy potentials were calculated and compared among ten turbomachinery configurations. All gas turbine engines were evaluated with a continuously variable transmission in a 1978 compact car. A reference fuel economy was calculated for the car with its conventional spark ignition piston engine and three speed automatic transmission. Two promising engine/transmission combinations, using gasoline, had 55 to 60 percent gains over the reference fuel economy. Fuel economy sensitivities to engine design parameter changes were also calculated for these two combinations.

  10. Gas exchange strategy in the Nile crocodile: a morphometric study

    Microsoft Academic Search

    S. F. Perry

    1990-01-01

    The respiratory surface area (SAR) per kilogram body mass (MB), the harmonic mean thickness of the air-blood barrier (thtR) in the gas exchange tissue, and the anatomical diffusion factor (ADF=SAR\\/thtR per MB) were calculated for four juvenile Nile crocodiles. The ADF of three small specimens (mean MB=3.59 kg) was 625 cm2·µm-1·kg-1. The values varied considerably among individuals and were similar

  11. Model-based observer: a gas turbine engine case study

    Microsoft Academic Search

    Oliver F. Qi; P. J. Gawthrop; N. R. L. Maccallum

    1992-01-01

    A model-based control approach to synthesizing a nonlinear controller for a single-spool gas turbine engine is described. Since the main control variable, engine thrust, cannot be directly measured, a model-based observer is considered to provide online estimation of the thrust for feedback control. Both proportional and proportional-integral (PI) observers have been used in the model-based observer design. The latter is

  12. Fuel economy screening study of advanced automotive gas turbine engines

    Microsoft Academic Search

    Klann

    1980-01-01

    Fuel-economy potentials were calculated and compared among 10 turbomachinery configurations. All gas-turbine engines were evaluated with a continuously variable transmission in a 1978 compact car. A reference fuel economy was calculated for the car with its conventional spark-ignition piston engine and three-speed automatic transmission. The best free-turbine engine was also evaluated with the conventional transmission. Two promising engine\\/transmission combinations, using

  13. The use of stable isotopes to study ecosystem gas exchange

    Microsoft Academic Search

    D. Yakir; L. da S. L. Sternberg

    2000-01-01

    Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem research is increasing.\\u000a In this review we introduce and discuss the relevant details underlying the use of carbon and oxygen isotopic compositions\\u000a in ecosystem gas exchange research. The current use and potential developments of stable isotope measurements together with\\u000a concentration and flux measurements of CO2

  14. Crosswell seismic studies in Gas Hydrate-bearing sediments

    Microsoft Academic Search

    K. Bauer; R. G. Pratt; M. H. Weber; Ch. Haberland; T. Ryberg; B. E. Medioli; S. Shimizu

    2004-01-01

    Crosswell seismic experiments were carried out using two, 1160 m observation wells (Mallik 3L- 38 and 4L-38), each located 42.5 m from the central, 1188 m production research well (5L-38). These provide images of a gas hydrate interval between 900 and 1100 m depth, and portions of the surrounding sedimentary sequences. A baseline survey was conducted to provide the background

  15. Study of gas-electric making of bottle glass

    Microsoft Academic Search

    K. A. Pchelyakov; V. P. Sokolova; G. A. Lesnova; V. Z. Ostapenko; V. A. Gaivoronskii; V. A. Pakhomov

    1975-01-01

    bottle-making machines R-7 have been installed with the furnace. One of the means of raising the specific productivity of tank furnaces is the high-temperature glassmaking. However, increasing the temperature of the flame space to 1580~176 by gas burning would have necessitated considerable constructional changes in different furnace elements and substitution of a large portion of the upper refractory lining of

  16. Circulating bed absorption for flue gas desulfurization: A fundamental study

    SciTech Connect

    Neathery, J.K.; Schaefer, J.; Stencel, J. [Univ. of Kentucky, Lexington, KY (United States); Burnett, T.; Norwood, V.

    1994-12-31

    The Tennessee Valley Authority (TVA) has been interested in the circulating bed absorption (CBA) technology for the control of sulfur dioxide (SO{sub 2}) emissions from coal-fired power plants. This technology incorporates a semi-dry, lime-based flue gas desulfurization (FGD) process that offers some potentially significant advantages over conventional spray dryer and wet scrubbing FGD systems. In a project co-funded by the TVA and the Center for Applied Energy Research (CAER), a pilot-scale fluid bed reactor was modified to simulate a generic CBA process. The objective of the CAER test program was to evaluate the influence of basic operating parameters such as calcium-to-sulfur ratio (Ca/S), inlet flue gas temperature, flyash loading, fuel chloride, gas residence time and approach to saturation temperature on the overall sulfur capture and sorbent utilization in the CBA process. The overall sulfur capture varied between 45 and 99.5% depending on the specific test conditions. An increased fuel chloride level enhanced the sulfur capture in the system. Fly ash also enhanced sulfur capture and was postulated to assist in CBA reactor particle agglomeration. The reactor SO{sub 2} capture efficiency decreased with increasing inlet SO{sub 2} concentration and a constant Ca/S ratio.

  17. Sensitivity analysis of tracer transport in variably saturated soils at USDA-ARS OPE3 field site

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to assess the effects of uncertainties in hydrologic and geochemical parameters on the results of simulations of the tracer transport in variably saturated soils at the USDA-ARS OPE3 field site. A tracer experiment with a pulse of KCL solution applied to an irrigatio...

  18. Electron-dense tracer evidence for a blood—brain barrier in the cuttlefish Sepia officinalis

    Microsoft Academic Search

    N. J. Abbott; M. Bundgaard

    1992-01-01

    Summary Electron-dense tracers were used to study the permeability of the blood—brain interface in a cephalopod mollusc, the cuttlefishSepia officinalis. Gel filtration established that horseradish peroxidase is a suitable tracer forin vivo injection, but microperoxidase is not, being subject to binding by plasma proteins. Perfusion-fixed brain vertical and optic lobes showed no endogenous peroxidatic activity. Horseradish peroxidase was injected intravenously,

  19. Seiche-induced resuspension in Lake Kinneret: A fluorescent tracer experiment

    Microsoft Academic Search

    B. Shteinman; W. Eckert; S. Kaganowsky; T. Zohary

    1997-01-01

    In warm-monomictic Lake Kinneret, wind-induced internal waves with amplitudes of up to 10 meters are common during April –\\u000a October. This study was aimed to follow the horizontal and vertical transport of resuspended particles due to internal wave\\u000a activity using fluorescently-dyed sediment particles (lake sediments and lyophilized algal cells) as tracers. Color-coded\\u000a (5 colors) tracers were deployed along a transact

  20. Analytical solutions of tracer transport in fractured rock associated with precipitation-dissolution reactions

    Microsoft Academic Search

    Hui-Hai Liu; Sumit Mukhopadhyay; Nicolas Spycher; Burton M. Kennedy

    2011-01-01

    Precipitation-dissolution reactions are important for a number of applications such as isotopic tracer transport in the subsurface.\\u000a Analytical solutions have been developed for tracer transport in both single-fracture and multiple-fracture systems associated\\u000a with these reactions under transient and steady-state transport conditions. These solutions also take into account advective\\u000a transport in fractures and molecular diffusion in the rock matrix. For studying