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1

Neutrally buoyant tracer in gas cleaning equipment: a case study  

NASA Astrophysics Data System (ADS)

A generic problem when studying the gas flow in gas cleaning equipment is that any conventional tracer, whether solid particles or liquid droplets, is separated out in accordance with the purpose of the equipment. This makes it impossible, for instance, to visualize the core of the vortex in centrifugal gas cleaning equipment. This paper explores the use of a neutrally buoyant tracer. The tracer is soap bubbles filled with helium. The smaller density of the helium relative to the surrounding air is precisely compensated by the mass of the bubble film to create a neutrally buoyant tracer. The method is used to study the flow in a swirl-tube gas-solid separator, highlighting flow features that cannot be shown with, for instance, LDA. Results are shown as controlled exposure time photographs, where pathlines of the tracer show the flow pattern. The results are further clarified by high-time-resolution pressure measurements at the walls. The work shows that the vortex core can be directly visualized using this technique. The vortex core is observed to, under some conditions, bend to—and spin around—the wall of the separator. Under other conditions, the vortex core coincides with the separator axis, and extends to the bottom of the hopper under the swirl tube. Also the flow in the downstream tubing is studied. The possibilities for obtaining quantitative data for the gas velocity field are discussed, and a promising method for doing this is identified.

Peng, Weiming; Hoffmann, Alex C.; Dries, Huub W. A.; Regelink, Michiel; Foo, Kee-Khoon

2005-12-01

2

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

SciTech Connect

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.

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

2006-05-06

3

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

SciTech Connect

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.

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

2006-05-06

4

ANALYSIS OF ESTUARINE TRACER-GAS TRANSPORT AND DESORPTION.  

USGS Publications Warehouse

The riverine tracer-gas technique provides a direct, reach-averaged measure of gas exchange, is fairly simple to implement, and is widely accepted for determining reaeration-rate coefficients in rivers. The method, however, is not directly applicable to flows having vertical density gradients. Consequently, studies were undertaken to develop and evaluate methods for obtaining surface-exchange coefficients from estuarine tracer-gas data. Reasonable estimates of the desorption coefficient (within 50 percent of the correct value) were obtained when an analytical solution of the transport equation was compared with data from a numerically simulated continuous release of tracer gas.

Bales, Jerad, D.; Holley, Edward, R.

1987-01-01

5

Novel Tracer Method To Measure Isotopic Labeled Gas-Phase Nitrous Acid (HO(15)NO) in Biogeochemical Studies.  

PubMed

Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ?60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the (15)N relative exceedance, ?((15)N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ?((15)N) = 0.2-0.5, the relative standard deviation of ?((15)N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO(15)NO emissions from soil in a dynamic chamber with and without spiking (15)N labeled urea. The identification of HO(15)NO from soil with (15)N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2(-) as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2(-) in the hydrosphere. PMID:24954648

Wu, Dianming; Kampf, Christopher J; Pöschl, Ulrich; Oswald, Robert; Cui, Junfang; Ermel, Michael; Hu, Chunsheng; Trebs, Ivonne; Sörgel, Matthias

2014-07-15

6

Natural and artificial nobel gas hydrologic tracers  

SciTech Connect

Noble gas isotopes provide opportunities for ground water tracing. Both naturally occurring tracers and artificially injected tracers can be used. The equilibration of water with the earth`s atmosphere records the temperature and atmospheric pressure during ground water recharge. This temperature/pressure record can be used to distinguish cold recharge from warmer recharge with a resolution of 1-2 C temperature and 500m in altitude. The radioactive decay of U and Th produce large concentrations of 4He in old ground water and this 4He signature can be useful in tracing the small addition of old water (>10,000 yr.) to young water (<100 yr.). The decay of 3H present either form nuclear testing or cosmic ray interactions leads to detectable amounts of 3He in young ground water (<50 yr.). By measuring both 3H and 3He, the mean age of the 3H in the water can be calculated. In addition to these natural tracers, isotopically enriched noble gas isotopes are readily available at low cost and can be used an non-hazardous water tracers. This inert, persistent, and harmless tracing technique can used in many situations at a cost of about one dollar per million gallons of water traced.

Hudson, G.B.

1994-06-01

7

Measuring Low Flows in Devonian Shale Gas Wells With a Tracer-Gas Flowmeter  

Microsoft Academic Search

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

Richmond Bennett; Paul Schettler Jr.; Todd Gustafson; Illona Gillette

1991-01-01

8

Air Change Measurements Using a Tracer Gas Technique.  

National Technical Information Service (NTIS)

The air change rate in a single story office building was measured using a tracer gas technique. The air change rate was determined by the rate of decay method using sulfur hexafluoride as the tracer gas. A total of eight tests were conducted within a 48-...

R. C. Doeffinger

1976-01-01

9

Air Change Measurements Using a Tracer Gas Technique.  

National Technical Information Service (NTIS)

The air change rate in a single story office building was measured using a tracer gas technique. The air change rate was determined by the rate of decay method using sulfur hexafluoride as the tracer gas. A total of eight tests were conducted within a for...

R. C. Doeffinger

1976-01-01

10

Effective Dynamics of a Tracer Particle Interacting with an Ideal Bose Gas  

NASA Astrophysics Data System (ADS)

We study a system consisting of a heavy quantum particle, called the tracer particle, coupled to an ideal gas of light Bose particles, the ratio of masses of the tracer particle and a gas particle being proportional to the gas density. All particles have non-relativistic kinematics. The tracer particle is driven by an external potential and couples to the gas particles through a pair potential. We compare the quantum dynamics of this system to an effective dynamics given by a Newtonian equation of motion for the tracer particle coupled to a classical wave equation for the Bose gas. We quantify the closeness of these two dynamics as the mean-field limit is approached (gas density ). Our estimates allow us to interchange the thermodynamic with the mean-field limit.

Deckert, Dirk-André; Fröhlich, Jürg; Pickl, Peter; Pizzo, Alessandro

2014-06-01

11

Flowmetering of natural gas pipelines by tracer gas pulse injection  

NASA Astrophysics Data System (ADS)

We investigate the tracer gas pulse injection method for flowmetering of natural gas pipelines. The principle of the measurement consists of detecting the passage of the pulse at two locations along the pipeline, from which the time of passage is calculated. The measurement accuracy depends on how the pulse form evolves due to turbulent diffusion and convective distortion in the pipe, as well as due to the influence of bends. We discuss these factors to evaluate the applicability of the method to pipelines of kilometer distances. We also perform a three-dimensional numerical analysis to understand the spatial pulse dispersion, and numerical analysis shows that the influence of pipe bends was not significant. Both experimental and theoretical results indicate the existence of axial diffusion coefficients, even in pipelines with bends. These results enable us to predict the evolution of the pulse concentration profile. Finally, we demonstrate acceptable precision for practical flowmetering applications in actual utility pipelines.

Takeuchi, Tomoaki; Murai, Yuichi

2010-01-01

12

Comparison of single- and two-bubble class gas–liquid recirculation models — application to pilot-plant radioactive tracer studies during methanol synthesis  

Microsoft Academic Search

Radioactive gas tracer measurements conducted during liquid-phase methanol synthesis from syngas in a pilot-scale slurry bubble column at the alternate fuels development unit (AFDU), La Porte have been compared with simulations from two mechanistic reactor models — single-bubble class model (SBCM) and two-bubble class model (TBCM). The model parameters are estimated from an independent sub-model gas and liquid recirculation, and

Puneet Gupta; Muthanna H. Al-Dahhan; Milorad P. Dudukovic; Bernard A. Toseland

2001-01-01

13

Comparison of modelled and measured tracer gas concentrations during the Across North America Tracer Experiment (ANATEX)  

SciTech Connect

The 24-hour surface concentrations of several perfluorocarbon tracer gases measured during the 1987 Across North America Tracer Experiment (ANATEX) provided a unique continental-scale data set with which to evaluate long-range transport and diffusion models. One such model, a multilayer Lagrangian model, was evaluated in the ANATEX Model Evaluation Study (AMES) by comparing distributions and time series of calculated and measured tracer concentrations at bands of sampling sites nearly equidistant from one of the two tracer release sites and by computing spatial differences in the concentration-weighted centroids of 20, 24-hour tracer footprints or composite plumes. The results for this model indicated that it overemphasized the effects of the stronger upper-level winds. In spite of the bias in transport speed, the distributions of the calculated and measured concentrations were quite similar.

Clark, T.L.; Cohn, R.D.; Seilkop, S.K.; Draxler, R.R.; Heffter, J.L.

1989-01-01

14

Comparison of modelled and measured tracer gas concentrations during the Across North America Tracer Experiment (ANATEX)  

Microsoft Academic Search

The 24-hour surface concentrations of several perfluorocarbon tracer gases measured during the 1987 Across North America Tracer Experiment (ANATEX) provided a unique continental-scale data set with which to evaluate long-range transport and diffusion models. One such model, a multilayer Lagrangian model, was evaluated in the ANATEX Model Evaluation Study (AMES) by comparing distributions and time series of calculated and measured

T. L. Clark; R. D. Cohn; S. K. Seilkop; R. R. Draxler; J. L. Heffter

1989-01-01

15

Partitioning Gas Tracer Technology for Measuring Water in Landfills  

NASA Astrophysics Data System (ADS)

Unstable landfills can result in significant environmental contamination and can become a risk to public health. To reduce this risk, water may be added to landfills to ensure that enough moisture exists for biodegradation of organic wastes. In this case risks associated with future breaks in the landfill cap are significantly reduced because organic material is degraded more rapidly. To modify moisture conditions and enhance biodegradation, leachate is typically collected from the bottom of the landfill and then recirculated near the top. It is difficult, though, to know how much leachate to add and where to add it to achieve uniform moisture conditions. This situation is exacerbated by the heterogeneous nature of landfill materials, which is known to cause short circuiting of infiltrating water, a process that has been virtually impossible to measure or model. Accurate methods for measuring the amount of water in landfills would be valuable aids for implementing leachate recirculation systems. Current methods for measuring water are inadequate, though, since they provide point measurements and are frequently affected by heterogeneity of the solid waste composition and solid waste compaction. The value of point measurements is significantly reduced in systems where water flows preferentially, such as in landfills. Here, spatially integrated measurements might be of greater value. In this research we are evaluating a promising technology, the partitioning gas tracer test, to measure the water saturation within landfills, the amount of free water in solid waste divided by the volume of the voids. The partitioning gas tracer test was recently developed by researchers working in the vadose zone. In this methodology two gas tracers are injected into a landfill. One tracer is non-reactive with landfill materials, while the second partitions into and out of free water trapped within the pore space of the solid waste. Chromatographic separation of the tracers occurs between the point of tracer injection and tracer extraction because the partitioning tracer is retarded due to water in the landfill. The degree of tracer retardation can be used to determine the average water saturation between the injection and extraction points. This partitioning gas tracer test yields a large-scale estimate of the water saturation, is not affected by solid waste compaction or heterogeneity in the composition of the solid waste, and has been successfully tested in a recent field experiment in soils. We report the results from a series of laboratory experiments designed to evaluate this technology with various trash mixtures. Experimental conditions were selected to mimic the range of moisture conditions that may exist within municipal landfills. The influence of leachate composition and temperature on gas tracer partitioning were also evaluated. In our trash mixtures, the partitioning gas tracer test determined volumetric water contents that were within 12% of actual values. We discuss these data in detail and describe environmental conditions (e.g., temperature variations) that may affect the utility of the partitioning gas tracer test.

Briening, M. L.; Jakubowitch, A.; Imhoff, P. T.; Chiu, P. C.; Tittlebaum, M. E.

2002-12-01

16

Improved accuracy and precision of gas chromatography\\/mass spectrometry measurements for metabolic tracers  

Microsoft Academic Search

The use of stable-isotope tracer methodology to study substrate metabolic kinetics requires accurate measurement of the tracer to tracee ratio (TTR), often by gas chromatography\\/mass spectrometry (GC\\/MS). Many approaches for measurement of the TTR by GC\\/MS do not use standards of known isotopic enrichment to control for variability in instrument response. In addition, most GC\\/MS applications exhibit some degree of

Bruce W. Patterson; Guohong Zhao; Samuel Klein

1998-01-01

17

Double tracer gas process for locating conduit leaks  

SciTech Connect

This apparatus generally relates to the art of detecting leaks in fluid-flow systems, and more particularly to a double tracer gas process for detecting leakages in underground conduit-type piping systems. The double tracer process of the work comprises the insertion of a tracer gas consisting of the mixture or combination of methane and argon in the protective conduit in an access point such as a man hole. Methane is a lighter-than-air hydrocarbon, and it will rise to the surface and vent to the atmosphere. It is easily detected with portable flame ionization equipment. Flame ionization detectors detect only hydrocarbons in small amounts; very small leaks may be detected. Argon is heavier than air and can be detected with suitable instruments, such as a gas-a-phon. A test hole is bored into the ground over the conduit-type piping system under test, and samples of the subsurface atmosphere in the test hole are drawn into the gas-a-phon by a suitable hose. If argon is present in the subsurface atmosphere in the test hole in the area of the conduit, a reading is noted on the instrument. 3 claims.

Heim, P.M.

1980-02-26

18

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

SciTech Connect

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.

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

19

Estimating fracture spacing from natural tracers in shale-gas production  

NASA Astrophysics Data System (ADS)

Resource appraisal and long-term recovery potential of shale gas relies on the characteristics of the fracture networks created within the formation. Both well testing and analysis of micro-seismic data can provide information on fracture characteristics, but approaches that directly utilize observations of gas transport through the fractures are not well-developed. We examine transport of natural tracers and analyze the breakthrough curves (BTC's) of these tracers with a multi-rate mass transfer (MMT) model to elucidate fracture characteristics. The focus here is on numerical simulation studies to determine constraints on the ability to accurately estimate fracture network characteristics as a function of the diffusion coefficients of the natural tracers, the number and timing of observations, the flow rates from the well, and the noise in the observations. Traditional tracer testing approaches for dual-porosity systems analyze the BTC of an injected tracer to obtain fracture spacing considering a single spacing value. An alternative model is the MMT model where diffusive mass transfer occurs simultaneously over a range of matrix block sizes defined by a statistical distribution (e.g., log-normal, gamma, or power-law). The goal of the estimation is defining the parameters of the fracture spacing distribution. The MMT model has not yet been applied to analysis of natural in situ natural tracers. Natural tracers are omnipresent in the subsurface, potentially obviating the needed for introduced tracers, and could be used to improve upon fracture characteristics estimated from pressure transient and decline curve production analysis. Results of this study provide guidance for data collection and analysis of natural tracers in fractured shale formations. Parameter estimation on simulated BTC's will provide guidance on the necessary timing of BTC sampling in field experiments. The MMT model can result in non-unique or nonphysical parameter estimates. We address this with Bayesian estimation approaches that can define uncertainty in estimated parameters as a posterior probability distribution. We will also use Bayesian estimation to examine model identifiability (e.g., selecting between parametric distributions of fracture spacing) from various BTC's. Application of the MMT model to natural tracers and hydraulic fractures in shale will require extension of the model to account for partitioning of the tracers between multiple phases and different mass transfer behavior in mixed gas-liquid (e.g., oil or groundwater rich) systems. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Bauer, S. J.; McKenna, S. A.; Heath, J. E.; Gardner, P.

2012-12-01

20

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

NASA Astrophysics Data System (ADS)

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.

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

21

Assessment of Dispersing Tracer Gas with Ventilation Air Stream to Detect Mine Fires.  

National Technical Information Service (NTIS)

A remote heat-activiated stench gas-tracer gas mine alarm system was developed to reduce the time between fire detection and personnel notification. The stench gas-tracer gas system contains ethyl mercaptan for personnel warning and a fluorocarbon for tra...

M. D. Marshall

1983-01-01

22

Analysis of volatile phase transport in soils using natural radon gas as a tracer  

SciTech Connect

We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

Chen, C.; Thomas, D.M.

1992-12-31

23

Comparison of Modelled and Measured Tracer Gas Concentrations during the Across North America Tracer Experiment (ANATEX),  

National Technical Information Service (NTIS)

The 24-hour surface concentrations of several perfluorocarbon tracer gases measured during the 1987 Across North America Tracer Experiment (ANATEX) provided a unique continental-scale data set with which to evaluate long-range transport and diffusion mode...

T. L. Clark R. D. Cohn S. K. Seilkop R. R. Draxler J. L. Heffter

1989-01-01

24

Stable and radioactive tracers in Ru biokinetic studies  

Microsoft Academic Search

The feasibility of ruthenium metabolism studies by stable tracer administration, with a methodology based on proton nuclear activation, is presented. In order to test that the amount of stable tracer administered does not perturb significantly the mechanism investigated, a series of comparative experiments with administration of both radioactive and stable tracers has been performed on animals. As the most critical

M. C. Cantone; D. De Bartolo; A. Giussani; N. Molho; L. Pirola; G. Gambarini; Ch. Hansen; P. Roth; E. Werner

1994-01-01

25

Applications of transient tracers to hydrological and oceanographic studies  

Microsoft Academic Search

During the past decades, transient tracers have been applied to a variety of problems in oceanography and hydrology. Most of these studies deal with the determination of pathways, formation rates, and mean residence times of certain water masses. Here, the basic common principles of transient tracer applications in oceanography and hydrology are described. Selected examples of tracer applications in oceanography

P. Schlosser; W. M. Smethie

2001-01-01

26

Gastric activity studies using a magnetic tracer.  

PubMed

A magnetic pulse generator has been set up in order to study gastric activity. Two coils 1.05 m in diameter, arranged in a Helmholtz configuration, were used. The system generated magnetic field pulses higher than 15 mT, of duration 17.3+/-1.2 ms. Measurements were performed in 11 male volunteers, with average age 29.3+/-6.4 years and body mass index 26.0+/-4.8 kg m(-2). Magnetite (Fe3O4) particles with diameters from 75 to 125 microm were used as magnetic tracers, which were mixed in 250 ml of yogurt in concentrations from 2 to 5 g. Signals were registered by using a high speed 3 axis fluxgate digital magnetometer and processed to determine the relaxation of the magnetic tracers by fitting a first-order exponential function to the data, a mean relaxation constant K = 116+/-40 s(-1) was obtained. Also, an average gastric peristaltic frequency was measured; a value of 3.2+/-0.3 cpm was determined. PMID:15535190

Cordova-Fraga, T; Bernal-Alvarado, J J; Gutierrez-Juarez, G; Sosa, M; Vargas-Luna, M

2004-10-01

27

COMPARISON OF MODELLED AND MEASURED TRACER GAS CONCENTRATIONS DURING THE ACROSS NORTH AMERICA TRACER EXPERIMENT (ANATEX)  

EPA Science Inventory

The 24-hour surface concentrations of several perfluorocarbon tracer gases measured during the 1987 Across North America Tracer Experiment (ANATEX) provided a unique continental-scale data set with which to evaluate long-range transport and diffusion models. One such model, a mul...

28

Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland  

NASA Astrophysics Data System (ADS)

Compacted snow (firn) preserves a continuous record of atmospheric composition up to a century back in time. Firn air transport modeling is essential for interpretation of firn gas records. Each site needs to be characterised individually through a tuning procedure, in which the effective diffusivity at each depth is adjusted to optimise the agreement between modeled and measured mixing ratios of a selected reference gas (usually CO2). We present the characterisation of the NEEM site, Northern Greenland (77.45° N 51.06° W), where an ensemble of ten reference tracers is used to constrain the diffusivity reconstruction. By analysing uncertainties in both data and the reference gas atmospheric histories, we can objectively assign weights to each of the gases used for the model tuning, and define a root mean square criterion that is minimised in the tuning. Each tracer constrains the firn profile differently through its unique atmospheric history and free air diffusivity, making our multiple-tracer characterisation method a clear improvement over the commonly used single-tracer tuning. Six firn air transport models are tuned to the NEEM site; all models successfully reproduce the data within a 1? Gaussian distribution. The modern day ?age, i.e. the difference between gas age and ice age, is calculated to be 182 ± 8 yr. We find evidence that diffusivity does not vanish completely in the firn lock-in zone, as is commonly assumed. We further present the first intercomparison study of firn air models, where we introduce diagnostic scenarios designed to probe specific aspects of the model physics. Our results show that there are major differences in the way the models handle advective transport. Furthermore diffusive fractionation of isotopes in the firn is poorly constrained by the models, which has consequences for attempts to reconstruct the isotopic composition of trace gases back in time using firn air and ice core records.

Buizert, C.; Martinerie, P.; Petrenko, V. V.; Severinghaus, J. P.; Trudinger, C. M.; Witrant, E.; Rosen, J. L.; Orsi, A. J.; Rubino, M.; Etheridge, D. M.; Steele, L. P.; Hogan, C.; Laube, J. C.; Sturges, W. T.; Levchenko, V. A.; Smith, A. M.; Levin, I.; Conway, T. J.; Dlugokencky, E. J.; Lang, P. M.; Kawamura, K.; Jenk, T. M.; White, J. W. C.; Sowers, T.; Schwander, J.; Blunier, T.

2011-05-01

29

A continuous fast-response dual-tracer analyzer for halogenated atmospheric tracer studies  

SciTech Connect

An apparatus for the simultaneous measurement of two tracers, sulfur hexafluoride (SF6) and a perfluorocarbon compound, is introduced. The new instrument is a modification of a commercially available fast-response, continuous analyzer for single halogenated atmospheric tracer studies. A two-channel flow system was implemented consisting of an alumina cartridge in one channel and a glass beads cartridge of equal flow resistance in the second channel. The alumina passes only sulfur hexafluoride, while the glass beads pass both SF6 and the perfluoroarbon tracer. The SF6 is quantified directly from the electron capture detector (ECD) signal in the alumina channel, and the perfluorocarbon concentration is obtained from the difference of the ECD responses in the two channels. The dual-tracer analyzer is field portable for mobile operations or fixed-location monitoring, has a response time of 1.2 s, and has limits of detection of about 15 pptv for SF6 and 10 pptv for perfluoro-methylcyclohexane, which was the principal perfluorocarbon tracer used in this study. The present instrument configuration, which requires periodic purging of the adsorbent trap, can obtain continuous measurements for a 10-15-min segment in every half hour of operation. Dual-tracer data from a field demonstration test are presented.

Rydock, J.P.; Lamb, B.K. [Washington State Univ., Pullman, WA (United States)] [Washington State Univ., Pullman, WA (United States)

1994-10-01

30

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

SciTech Connect

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.

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

31

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

PubMed

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(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. PMID:21996285

Jung, Yoojin; Han, Byunghyun; Mostafid, M Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T

2012-02-01

32

Generation of ethylene tracer by noncatalytic pyrolysis of natural gas at elevated pressure  

USGS Publications Warehouse

There is a critical need within the pipeline gas industry for an inexpensive and reliable technology to generate an identification tag or tracer that can be added to pipeline gas to identify gas that may escape and improve the deliverability and management of gas in underground storage fields. Ethylene is an ideal tracer, because it does not exist naturally in the pipeline gas, and because its physical properties are similar to the pipeline gas components. A pyrolysis process, known as the Tragen process, has been developed to continuously convert the ???2%-4% ethane component present in pipeline gas into ethylene at common pipeline pressures of 800 psi. In our studies of the Tragen process, pyrolysis without steam addition achieved a maximum ethylene yield of 28%-35% at a temperature range of 700-775 ??C, corresponding to an ethylene concentration of 4600-5800 ppm in the product gas. Coke deposition was determined to occur at a significant rate in the pyrolysis reactor without steam addition. The ?? 13C isotopic analysis of gas components showed a ?? 13C value of ethylene similar to ethane in the pipeline gas, indicating that most of the ethylene was generated from decomposition of the ethane in the raw gas. However, ?? 13C isotopic analysis of the deposited coke showed that coke was primarily produced from methane, rather than from ethane or other heavier hydrocarbons. No coke deposition was observed with the addition of steam at concentrations of > 20% by volume. The dilution with steam also improved the ethylene yield. ?? 2005 American Chemical Society.

Lu, Y.; Chen, S.; Rostam-Abadi, M.; Ruch, R.; Coleman, D.; Benson, L. J.

2005-01-01

33

Multiple Isotopic Tracers for Study of Coastal Hydrological Processes  

Microsoft Academic Search

This study focused on the combined use of radon and radium isotopes as tracers of near-shore geophysical processes including submarine groundwater discharge (SGD), water exchange rates, and atmospheric evasion. Methods were developed for easier measurement of long-lived radium isotopes in natural waters and for continuous radon surveying over larger areas in the coastal zone. These tracer techniques were used to

Henrieta Dulaiova

2005-01-01

34

National Biomedical Tracer Facility: Project definition study  

SciTech Connect

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.

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

1995-05-31

35

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

SciTech Connect

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.

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

2011-04-15

36

Nitrous oxide as a tracer gas in the ASHRAE 110-1995 Standard.  

PubMed

ANSI/ASHRAE Standard 110 provides a quantitative method for testing the performance of laboratory fume hoods. Through release of a known quantity (4.0 Lpm) of a tracer gas, and subsequent monitoring of the tracer gas concentration in the "breathing zone" of a mannequin positioned in front of the hood, this method allows for evaluation of laboratory hood performance. Standard 110 specifies sulfur hexafluoride (SF6) as the tracer gas; however, suitable alternatives are allowed. Through three series of performance tests, this analysis serves to investigate the use of nitrous oxide (N2O) as an alternate tracer gas for hood performance testing. Single gas tests were performed according to ASHRAE Standard 110-1995 with each tracer gas individually. These tests showed identical results using an acceptance criterion of AU 0.1 with the sash half open, nominal 18 inches (0.46m) high, and the face velocity at a nominal 60 fpm (0.3 m/s). Most data collected in these single gas tests, for both tracer gases, were below the minimum detection limit, thus two dual gas tests were developed for simultaneous sampling of both tracer gases. Dual gas dual ejector tests were performed with both tracer gases released simultaneously through two ejectors, and the concentration measured with two detectors using a common sampling probe. Dual gas single ejector tests were performed with both tracer gases released though a single ejector, and the concentration measured in the same manner as the dual gas dual ejector tests. The dual gas dual ejector tests showed excellent correlation, with R typically greater than 0.9. Variance was observed in the resulting regression line for each hood, likely due to non-symmetry between the two challenges caused by variables beyond the control of the investigators. Dual gas single ejector tests resulted in exceptional correlation, with R>0.99 typically for the consolidated data, with a slope of 1.0. These data indicate equivalent results for ASHRAE 110 performance testing using either SF6 or N2O, indicating N2O as an applicable alternate tracer gas. PMID:24283334

Burke, Martin; Wong, Larry; Gonzales, Ben A; Knutson, Gerhard

2014-01-01

37

Rapid measurements and mapping of tracer gas concentrations in a large indoor space  

NASA Astrophysics Data System (ADS)

Rapid mapping of gas concentrations in air benefits studies of atmospheric phenomena ranging from pollutant dispersion to surface layer meteorology. Here we demonstrate a technique that combines multiple-open-path tunable-diode-laser spectroscopy and computed tomography to map tracer gas concentrations with approximately 0.5 m spatial and 7 s temporal resolution. Releasing CH 4 as a tracer gas in a large (7 m×9 m×11 m high) ventilated chamber, we measured path-integrated CH 4 concentrations over a planar array of 28 "long" (2-10 m) optical paths, recording a complete sequence of measurements every 7 s during the course of hour-long experiments. Maps of CH 4 concentration were reconstructed from the long path data using a computed tomography algorithm that employed simulated annealing to search for a best fit solution. The reconstructed maps were compared with simultaneous measurements from 28 "short" (0.5 m) optical paths located in the same measurement plane. On average, the reconstructed maps capture ˜74% of the variance in the short path measurements. The accuracy of the reconstructed maps is limited, in large part, by the number of optical paths and the time required for the measurement. Straightforward enhancements to the instrumentation will allow rapid mapping of three-dimensional gas concentrations in indoor and outdoor air, with sub-second temporal resolution.

Fischer, Marc L.; Price, Phillip N.; Thatcher, Tracy L.; Schwalbe, Carrie A.; Craig, Mathias J.; Wood, Emily E.; Sextro, Richard G.; Gadgil, Ashok J.

38

Quantification of cholesterol tracers by gas chromatography--negative ion chemical ionization mass spectrometry.  

PubMed

Because of its high sensitivity, gas chromatography negative ion chemical ionization mass spectrometry (GC-NCI-MS) is a potentially valuable analytical tool for the study of cholesterol metabolism. Of several derivatives prepared for potential use in tracer studies pentafluorobenzoyl cholesterol was selected because it formed rapidly at ambient temperature and was stable for long periods, could be detected at a level of 1 fmol, and yielded a mass spectrum in which the molecular ion was the principal component. Hexadeuterated cholesterol tracer ([26,26,26,27,27,27-2H6]cholesterol) could be detected in dilutions up to 2700 in unlabeled cholesterol by selected ion monitoring with a coefficient of variation averaging 3.2%. In seven normal subjects tracer cholesterol was infused intravenously and plasma cholesterol enrichment was determined after 4 h. The measured rapidly miscible cholesterol pool was 391.0 +/- 38.6 mg cholesterol/kg. Negative ion mass spectrometry of pentafluorobenzyol cholesterol will facilitate analysis of both small amounts of natural cholesterol and labeled cholesterol in applications where sensitivity is critical. PMID:8946736

Ostlund, R E; Hsu, F F; Bosner, M S; Stenson, W F; Hachey, D L

1996-11-01

39

Gas- and particulate-phase specific tracer and toxic organic compounds in environmental tobacco smoke.  

PubMed

Cigarette smoke constituents are worthy of concern and characterized as carcinogens. Different experiment conditions may affect the environmental tobacco smoke (ETS) constituents. A study was undertaken in a 75.5-m3 spare office to evaluate ETS constituents in a real environment. Thirty-four volatile organic compounds (VOCs) including three ETS tracers: nicotine, 2,5-dimethylfuran and 3-ethenylpyridine (3-EP), 19 carbonyl compounds, 54 semi-volatile compounds (24 polycyclic aromatic hydrocarbons (PAHs) and 30 alkanes) as well as CO and total particulate matter (TPM) from 15 leading commercial brands were determined. ETS constituents did not increase with increasing cigarette tar. ETS tracers nicotine and 3-EP were affected greatly due to more sorption and surface reactions in real world compared to other studies conducted in chamber, which resulted in 2-5 times lower. Benzene, toluene, ethylbenzene, xylenes, acrolein, 2-butanone and the high molecular weight compounds exhibited little affect. Pearson correlation analyses show that gas-phase and particulate-phase ETS tracers did not show significant correlation, but within each homologue many of compounds correlated significantly. Indole and cholesta-3,5-diene were also detected in ETS. These results may be useful in efforts to better understand the health effect of ETS exposure and source apportionment. PMID:15975627

Bi, Xinhui; Sheng, Guoying; Feng, Yanli; Fu, Jiamo; Xie, Juexin

2005-12-01

40

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...

41

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...

42

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

SciTech Connect

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.

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

1985-01-01

43

National Biomedical Tracer Facility. Project definition study  

Microsoft Academic Search

We request a $25 million government-guaranteed, interest-free loan to be repaid over a 30-year period for construction and initial operations of a cyclotron-based National Biomedical Tracer Facility (NBTF) in North Central Texas. The NBTF will be co-located with a linear accelerator-based commercial radioisotope production facility, funded by the private sector at approximately $28 million. In addition, research radioisotope production by

1995-01-01

44

Estimation of road traffic emission factors from a long term tracer study  

NASA Astrophysics Data System (ADS)

Road traffic emissions, one of the largest source categories in megacity inventories, are highly uncertain. It is essential to develop methodologies to reduce these uncertainties to manage air quality more effectively. In this paper, we propose a methodology to estimate road traffic emission factors (EFs) from a tracer experiment and from roadside pollutants measurements. We emitted continuously during about 300 non-consecutive hours a passive tracer from a finite line source placed on one site of an urban street. At the same time, we measured continuously the resulting tracer concentrations at the other side of the street with a portable on-line gas chromatograph. We used n-propane contained in commercial liquid petroleum gas (LPG) as a passive tracer. Propane offers several advantages to traditional tracers (SF6, N2O, CFCs): low price, easily available, non-reactive, negligible global warming potential, and easy to detect with commercial on-line gas chromatographs. The tracer experiment was carried out from January to March 2007 in a busy street of Ho Chi Minh City (Vietnam). Traffic volume, weather information and pollutant concentrations were also measured at the measurement site. We used the results of the tracer experiment to calculate the dilution factors and afterwards we used these dilution factors, the traffic counts and the pollutant concentrations to estimate the EFs. The proposed method assumes that the finite emission line represents the emission produced by traffic in the full area of the street and therefore there is an error associated to this assumption. We use the Computational Fluids Dynamics (CFD) model MISKAM to calculate this error and to correct the HCMC EFs. EFs for 15 volatile organic compounds (VOCs) and NO are reported here. A comparison with available studies reveals that most of the EFs estimated here are within the range of EFs reported in other studies.

Belalcazar, Luis Carlos; Fuhrer, Oliver; Ho, Minh Dung; Zarate, Erika; Clappier, Alain

2009-12-01

45

Development of atmospheric tracer methods to measure methane emissions from natural gas facilities and urban areas  

Microsoft Academic Search

A new, integrated methodology to locate and measure methane emissions from natural gas systems has been developed. Atmospheric methane sources are identified by elevated ambient CHâ concentrations meaured with a mobile laser-based methane analyzer. The total methane emission rate from a source is obtained by simulating the source with a sulfur hexafluoride (SFâ) tracer gas release and by measuring methane

Brian Lamb; E. Allwine; R. Siverson; H. Westberg; J. B. McManus; C. B. Kolb; J. H. Shorter; B. Mosher; D. Blaha; R. C. Harris; Robert Lott; Hal Westburg; Pat Zimmerman

1995-01-01

46

Use of tracer gas technique for industrial exhaust hood efficiency evaluation--where to sample?  

PubMed

A tracer gas technique using sulfur hexafluoride (SF6) was developed for the evaluation of industrial exhaust hood efficiency. In addition to other parameters, accuracy of this method depends on proper location of the sampling probe. The sampling probe should be located in the duct at a minimum distance from the investigated hood where the SF6 is dispersed uniformly across the duct cross section. To determine the minimum sampling distance, the SF6 dispersion in the duct in fully developed turbulent flow was studied at four duct configurations frequently found in industry: straight duct, straight duct-side branch, straight duct-one elbow, and straight duct-two elbows combinations. Based on the established SF6 dispersion factor, the minimum sampling distances were determined as follows: for straight duct, at least 50 duct diameters; for straight duct-side branch combination, at least 25 duct diameters; for straight duct-one elbow combination, 7 duct diameters; and for straight duct-two elbow combination, 4 duct diameters. Sampling at (or beyond) these distances minimizes the error caused by the non-homogeneous dispersion of SF6 in the duct and contributes to the accuracy of the tracer gas technique. PMID:3717012

Hampl, V; Niemelä, R; Shulman, S; Bartley, D L

1986-05-01

47

National Biomedical Tracer Facility. Project definition study  

SciTech Connect

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

Schafer, R.

1995-02-14

48

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

PubMed

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

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

2011-01-01

49

Prospective Payment System Evaluation Studies-Selection of Tracers in Studies of PPS and Service Utilization.  

National Technical Information Service (NTIS)

The report shows an attempt to establish rational criteria for the selection of tracer diagnoses for studies in health services research, and to develop an algorithm for the selection of optimal tracers under different experimental conditions.

C. Sennett

1988-01-01

50

Application of a Tracer Gas Challenge with a Human Subject to Investigate Factors Affecting the Performance of Laboratory Fume Hoods  

Microsoft Academic Search

The results of a “user” tracer gas test were applied to investigate the effects of various parameters on hood containment ability and to evaluate accepted methods to classify hood performance. This user tracer gas test was performed with a human subject standing in front of the hood. Based on the data collected, face velocity, its variability, and cross drafts are

Brent A. Altemose; Michael R. Flynn; Jay Sprankle

1998-01-01

51

TRACER STUDY OF SEDIMENT-WATER INTERACTIONS IN ESTUARIES  

EPA Science Inventory

Rates of sediment bioturbation and advective exchange of water across the sediment-water interface in Narragansett Bay, Rhode Island were studied by radioactive tracer experiments. The 'biological pumping rate' of water across the interface (.7 + or - .3 cc/sq cm day) was calcula...

52

Project definition study for the National Biomedical Tracer Facility  

Microsoft Academic Search

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

Roozen

1995-01-01

53

Sediment tracers in water erosion studies: Current approaches and challenges  

NASA Astrophysics Data System (ADS)

The quest for alternative methods of soil losses assessment, due to water erosion to complement and enhance existing methods has directed attention to the use of tracing approaches because of the additional information they provide, such as sediment source identification, tracking of sediment movement across the landscape at various temporal and spatial scales and soil erosion rates. For these reasons, the utility and robustness of sediment tracing approaches using a wide range of substances and soil properties have been evaluated in numerous studies. A comprehensive literature review on tracing approaches used in water erosion studies was carried out in June 2011 using the Web of Science database and as search terms in the title or as keywords: "erosion AND tracer" OR "sediment AND tracer" OR "sediment AND tracking". The search excluded reviews and tillage and/or wind erosion studies. Only studies that used tracers to make a determination of water erosion or sedimentation rates, or in some cases relative erosion contribution, were considered in this study, and were further refined by manually checking that the articles corresponded to experiments involving sediment studies using tracers, as defined within the context of this review. Five distinct groups of tracing approaches were identified: fallout radionuclides, rare earth elements, soil magnetism and magnetic substances, other tracers, and sediment fingerprinting techniques. This abstract presents a synthesis of the current approaches of each of the tracing techniques identified in assessing soil erosion and sediment redistribution and a summary with the commonalities and differences between the approaches and identifying research gaps and future trends.

Guzmán, Gema; Quinton, John N.; Nearing, Mark A.; Mabit, Lionel; Giráldez, Juan V.; Gómez, José A.

2013-04-01

54

Radon as a natural tracer for gas transport within uranium waste rock piles.  

PubMed

Acid mine drainage (AMD) has been identified as the main cause for outflow of acid water and radioactive/non-radioactive contaminants. AMD encompasses pyrites oxidation when water and oxygen are available. AMD was identified in uranium waste rock piles (WRPs) of Indústrias Nucleares do Brasil-Caldas facility (Brazilian uranium mine), resulting in high costs for water treatment. AMD reduction is the main challenge, and scientific investigation has been conducted to understand oxygen and water transportation within WRPs, where (222)Rn is used as natural tracer for oxygen transportation. The study consists of soil radon gas mapping in the top layer of WRP4 using active soil gas pumping, radon adsorption in active charcoal and (222)Rn determination using high-resolution gamma-ray spectrometry. A sampling network of 71 points was built where samples were collected at a depth of 40 cm. Soil radon gas concentration ranged from 33.7 to 1484.2 kBq m(-3) with mean concentration of 320.7±263.3 kBq m(-3). PMID:24729565

Silva, N C; Chagas, E G L; Abreu, C B; Dias, D C S; Lopez, D; Guerreiro, E T Z; Alberti, H L C; Braz, M L; Branco, O; Fleming, P

2014-07-01

55

Evaluation of Partitioning Gas Tracer Tests for Measuring Water in Landfills  

NASA Astrophysics Data System (ADS)

Methane is an important greenhouse gas, and landfills are the largest anthropogenic source in many developed countries. Bioreactor landfills have been proposed as one means of abating greenhouse gas emissions from landfills. Here, the decomposition of organic wastes is enhanced by the controlled addition of water or leachate to maintain optimal conditions for waste decomposition. Greenhouse gas abatement is accomplished by sequestration of photosynthetically derived carbon in wastes, CO2 offsets from energy use of waste derived gas, and mitigation of methane emission from the wastes. An important issue in the operation of bioreactor landfills is knowing how much water to add and where to add it. Accurate methods for measuring the amount of water in landfills would be valuable aids for implementing leachate recirculation systems. Current methods for measuring water are inadequate, though, since they provide point measurements and are frequently affected by heterogeneity of the solid waste composition and solid waste compaction. The value of point measurements is significantly reduced in systems where water flows preferentially, such as in landfills. Here, spatially integrated measurements might be of greater value. We are evaluating a promising technology, the partitioning gas tracer test, to measure the water saturation within landfills, the amount of free water in solid waste divided by the volume of the voids. The partitioning gas tracer test was recently developed by researchers working in the vadose zone. We report the results from laboratory and field tests designed to evaluate the partitioning gas tracer test within an anaerobic landfill operated by the Delaware Solid Waste Authority. Vertical wells were installed within the landfill to inject and extract tracer gases. Gas flow and tracer gas movement in the solid waste were controlled by the landfill's existing gas collection system, which included vertical wells installed throughout the landfill through which a vacuum was applied. The results from this test are reported along with an overview of a similar test planned for the bioreactor landfill cells operated by the Yolo County Department of Planning and Public Works.

Imhoff, P. T.; Han, B.; Jafarpour, Y.; Gallagher, V. N.; Chiu, P. C.; Fluman, D. A.; Vasuki, N. C.; Yazdani, R.; Augenstein, D.; Cohen, K. K.

2003-12-01

56

Assessment of steady-state propane-gas tracer method for determining reaeration coefficients, Chenango River, New York  

USGS Publications Warehouse

A test was conducted in a meandering 9.6-km reach of the Chenango River, New York, to assess the feasibility of a two-dimensional steady-state propane-gas tracer method as a means of estimating in situ reaeration coefficients. It is concluded that the method, which combines an instantaneous release of dye tracer with a long duration release of propane gas tracer, is very feasible for determining gas-desorption coefficients and wind effects in a wide river. However, the method does not appear to be ready for immediate operational applications. (USGS)

Yotsukura, Nobuhiro; Steadfast, D. A.; Jirka, G. H.

1984-01-01

57

Hanford facilities tracer study report (315 Water Treatment Facility)  

SciTech Connect

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.

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

1995-04-14

58

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, July 1, 1991--December 31, 1991  

SciTech Connect

Studies continued on organic tracers for use as hydrologic tracers as part of the Yucca Mountain Site Characterization project. Tracers studied include benzoic acids, cinnamic acids, and salicylic acids. The main focus of the work performed during the time period from 07/01/91 to 12/31/91 has been the continuation of (1) LC-MS optimization for tracer identification, (2) batch sorption and degradation studies, (3) neoprene tubing evaluation studies, and (4) soil column evaluation of tracer compounds. All of these areas of research (except perhaps the neoprene tubing evaluation) are ongoing and will continue throughout the coming year.

Dombrowski, T.; Stetzenbach, K.

1991-12-31

59

A first study of SF 6 as a transient tracer in the Southern Ocean  

Microsoft Academic Search

Halogenated transient tracers such as the chlorofluorocarbons CFC-11, CFC-12 and CFC-113 are commonly used in oceanographic studies. These compounds enter the ocean via the atmosphere and their transient atmospheric concentrations make them valuable as oceanic tracers. The trends of rapidly rising atmospheric concentrations of these tracers are however broken, and the oceanic signal becomes increasingly more difficult to decipher. There

Toste Tanhua; K. Anders Olsson; Elisabet Fogelqvist

2004-01-01

60

A Study of Tracer Distribution Parameter Estimation from Sparse Samples  

Microsoft Academic Search

How do design parameters such as the spacing of sampling stations affect the quality of information obtained from atmospheric dispersion experiments? In large-scale experiments such as the Cross-Appalachian Tracer Experiment (CAPTEX) and the Across North America Tracer Experiment (ANATEX), the average crosswind spacing between surface sampling stations may be of the same order as, or greater than, the tracer cloud

J. Z. Holland

1991-01-01

61

Use of tracers in materials-holdup study  

SciTech Connect

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.

Pillay, K.K.S.

1983-01-01

62

Geometric Offsets across Spiral Arms in M51: Nature of Gas and Star Formation Tracers  

NASA Astrophysics Data System (ADS)

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? 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 ?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?, suggesting that gas flow through spiral arms (i.e., density wave) though the spiral pattern may not necessarily be stationary.

Louie, Melissa; Koda, Jin; Egusa, Fumi

2013-02-01

63

Study of stomach motility using the relaxation of magnetic tracers.  

PubMed

Magnetic tracers can be observed in the interior of the human body to give information about their quantity, position and state of order. With the aim of detecting and studying the degree of disorder of these tracers after they have been previously magnetized inside the stomach, a system composed of magnetization coils and magnetic detectors was developed. Helmholtz coils of diameter 84 cm were used to magnetize the sample and the remanent magnetization (RM) was detected with two first-order gradiometric fluxgate arrays each with a 15 cm base line, sensitivity of 0.5 nT and common mode rejection (CMR) of at least 10. The system allows simultaneous measurement in the anterior and posterior projections of the stomach. Measurements of the time evolution of the RM were performed in vitro and in normal subjects after the ingestion of a test meal labelled with magnetic particles. The data were fitted with an exponential curve and the relaxation time tau was obtained. Initial studies were performed to ascertain the action of a drug that is known to affect the gastric motility, showing that the decay of the remanent magnetization was indeed due to stomach contractions. PMID:10442706

Carneiro, A A; Baffa, O; Oliveira, R B

1999-07-01

64

In-situ characterization of soil-water content using gas-phase partitioning tracer tests: field-scale evaluation.  

PubMed

Field-scale tests were performed to evaluate the effectiveness of the gas-phase partitioning tracer method for in-situ measurement of soil-water content. The tracer tests were conducted before and after a controlled infiltration event to evaluate performance at two water contents. Nonpartitioning (sulfur hexafluoride) and water-partitioning (difluoromethane) tracers were injected into the test zone, and their effluent breakthrough curves were analyzed using the method of moments to calculate retardation factors for difluoromethane. Soil-water contents estimated using the tracer data were compared to soil-water contents obtained independently using gravimetric core analysis, neutron scattering, and bore-hole ground penetrating radar. For the test conducted under drier soil conditions, the soil-water content estimated from the tracer test was identical to the independently measured values of 8.6% (equivalent to water saturation of 23%). For the test conducted under wetter soil conditions, the tracer test derived soil-water content was 81% of the independently measured values of 12.2% (equivalent to water saturation of 32%). The reduced efficacy at the higher soil-water content may reflectthe impact of advective and/ or diffusive mass transfer constraints on gas-phase transport. The results presented herein indicate that the partitioning tracer method is an effective technique to measure soil-water content at the field scale, especially for sites with moderate to low soil-water contents. PMID:12901662

Keller, Jason M; Brusseau, Mark L

2003-07-15

65

Vertical Tracer Concentration Profiles Measured During the Joint Urban 2003 Dispersion Study  

SciTech Connect

An atmospheric tracer dispersion study known as Joint Urban 2003 was conducted in Oklahoma City, Oklahoma during the summer of 2003. As part of this field program, vertical concentration profiles were measured at approximately 1 km from downtown tracer gas release locations. These profiles indicated that the urban landscape was very effective in mixing the plume vertically. The height of the plume centerline (as determined by the maximum concentration over the depth of the measurements) for any specific 30 min period varied over the 65 m measurement range. Most of the variations in tracer concentration observed in the profile time series were related to changes in wind direction as opposed to changes in turbulence. As a simple analysis tool for emergency response, maximum normalized concentration curves were developed with 5-minute averaged measurements. These curves give the maximum concentration (normalized by the release rate) that would be observed as a function of downwind distance in an urban area. The 5-min data resulted in greater concentrations than predicted with a simple Gaussian plume model. However, the curve compared well with results from a computational fluid dynamics simulation. This dispersion dataset is a valuable asset not only for refining air quality models, but also for developing new tools for emergency response personnel in the event of a toxic release.

Flaherty, Julia E.; Lamb, Brian K.; Allwine, K Jerry; Allwine, Eugene J.

2007-12-01

66

Atmospheric noble gases as tracers of biogenic gas dynamics in a shallow unconfined aquifer  

NASA Astrophysics Data System (ADS)

Atmospheric noble gases (NGs) were used to investigate biogenic gas dynamics in a shallow unconfined aquifer impacted by a crude oil spill, near Bemidji, MN. Concentrations of 3,4He, 20,22Ne, 36,40Ar, Kr, and Xe were determined for gas- and aqueous-phase samples collected from the vadose and saturated zones, respectively. Systematic elemental fractionation of Ne, Ar, Kr, and Xe with respect to air was observed in both of these hydrogeologic zones. Within the vadose zone, relative ratios of Ne and Ar to Kr and Xe revealed distinct process-related trends when compared to corresponding ratios for air. The degree of NG deviation from atmospheric concentrations generally increased with greater atomic mass (i.e., ?Xe > ?Kr > ?Ar > ?Ne), indicating that Kr and Xe are the most sensitive NG tracers in the vadose zone. Reactive transport modeling of the gas data confirms that elemental fractionation can be explained by mass-dependent variations in diffusive fluxes of NGs opposite to a total pressure gradient established between different biogeochemical process zones. Depletion of atmospheric NGs was also observed within a methanogenic zone of petroleum hydrocarbon degradation located below the water table. Solubility normalized NG abundances followed the order Xe > Kr > Ar > Ne, which is indicative of dissolved NG partitioning into the gas phase in response to bubble formation and possibly ebullition. Observed elemental NG ratios of Ne/Kr, Ne/Xe, Ar/Xe, and Kr/Xe and a modeling analysis provide strong evidence that CH4 generation below the water table caused gas exsolution and possibly ebullition and carbon transfer from groundwater to the vadose zone. These results suggest that noble gases provide sensitive tracers in biologically active unconfined aquifers and can assist in identifying carbon cycling and transfer within the vadose zone, the capillary fringe, and below the water table.

Jones, Katherine L.; Lindsay, Matthew B. J.; Kipfer, Rolf; Mayer, K. Ulrich

2014-03-01

67

Tracer Study of Vertical Exchange by Cumulus Clouds.  

NASA Astrophysics Data System (ADS)

This paper examines the exchange of material by convective cloud processes between the mixed layer and the overlying free troposphere. It describes results of a field experiment that was conducted in Lexington, Kentucky, during the period from 20 July to 24 August 1983 to study the processes associated with the vertical transport of acidic pollutants by nonprecipitating cumulus convection. An aircraft released SF6 tracer either within or above the mixed layer, and it was sampled by another aircraft at various levels within or above the mixed layer in the active cumulus convective cloud zone, as well as on the ground. The results show that mixed layer pollutants are vented above the entrainment zone of its boundary layer into the overlying cloud layer by fields of active cumulus and that such active clouds may force cloud layer air downward into the mixed layer.

Ching, J. K. S.; Alkezweeny, A. J.

1986-11-01

68

Gas and particulate-phase specific tracer and toxic organic compounds in environmental tobacco smoke  

Microsoft Academic Search

Cigarette smoke constituents are worthy of concern and characterized as carcinogens. Different experiment conditions may affect the environmental tobacco smoke (ETS) constituents. A study was undertaken in a 75.5-m3 spare office to evaluate ETS constituents in a real environment. Thirty-four volatile organic compounds (VOCs) including three ETS tracers: nicotine, 2,5-dimethylfuran and 3-ethenylpyridine (3-EP), 19 carbonyl compounds, 54 semi-volatile compounds (24

Xinhui Bi; Guoying Sheng; Yanli Feng; Jiamo Fu; Juexin Xie

2005-01-01

69

Effect of release rate of the SF(6) tracer on methane emission estimates based on ruminal and breath gas samples.  

PubMed

The release rate (RR) of sulphur hexafluoride (SF(6)) gas from permeation tube in the rumen appears to be positively related with methane (CH(4)) emissions calculated using the SF(6) tracer technique. Gas samples of breath and ruminal headspace were collected simultaneously in order to evaluate the hypothesis that transactions of SF(6) in the rumen are the source for this relationship. Six non-lactating dairy cows fitted with rumen cannulae were subdivided into two groups and randomly assigned to a two-period crossover design to permeation tubes with low RR (LRR = 1.577 mg/day) or two-times higher RR (HRR = 3.147 mg/day) RR. The cows were fed limited amounts of maize silage (80% ad libitum) split into two meals (40% at 0800 h and 60% at 1600 h). Each period consisted of 3-day gas sampling. Immediately before the morning feed and then each hour over 8 h, ruminal gas samples (50 ml) were withdrawn through the cannula fitted with stoppers to prevent opening. Simultaneously, 8-h integrated breath gas samples were collected over the same period. Ratios of concentration of CH(4)/SF(6), CO(2)/SF(6) and CO(2)/CH(4) and emission estimates of CH(4) and CO(2) were calculated for each sample source using the SF(6) tracer technique principles. The LRR treatment yielded higher (P < 0.001) ruminal CH(4)/SF(6) (by 1.79 times) and CO(2)/SF(6) (by 1.90 times) ratios than the HRR treatment; however, these differences were lower than the 2.0 times difference expected from the RR between the LRR and HRR. Consequently, the LRR treatment was associated with lower (P < 0.01) ruminal emissions of CH(4) over the 8-h collection period than with the HRR treatment (+11%), a difference also confirmed by the breath samples (+11%). RR treatments did not differ (P = 0.53) in ruminal or breath CO(2) emissions; however, our results confirm that the SF(6) tracer seems inappropriate for CO(2) emissions estimation in ruminants. Irrespective of the RR treatment, breath samples yielded 8% to 9% higher CH(4) emission estimates than the ruminal samples (P = 0.01). The relationship between rumen and breath sources for CH(4) emissions was better for LRR than for HRR treatment, suggesting that tracer performance decreases with the highest RR of SF(6) tested in our study (3.1 mg/day). A hypothesis is discussed with regard to the mechanism responsible for the relationship between RR and CH(4) emission estimates. The use of permeation tubes with small range in RR is recommended in animal experiments to decrease variability in CH(4) emission estimates using the SF(6) tracer technique. PMID:22436232

Martin, C; Koolaard, J; Rochette, Y; Clark, H; Jouany, J P; Pinares-Patiño, C S

2012-03-01

70

Is HCN a True Tracer of Dense Molecular Gas in Luminous and Ultraluminous Infrared Galaxies?  

NASA Astrophysics Data System (ADS)

We present the results of the first HCO+ survey probing the dense molecular gas content of a sample of 16 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). Previous work, based on HCN (1-0) observations, had shown that LIRGs and ULIRGs possess a significantly higher fraction of dense molecular gas compared to normal galaxies. While the picture issued from HCO+ partly confirms this result, we have discovered an intriguing correlation between the HCN (1-0)/HCO+ (1-0) luminosity ratio and the IR luminosity of the galaxy (LIR). This trend casts doubts on the use of HCN as an unbiased quantitative tracer of the dense molecular gas content in LIRGs and ULIRGs. A plausible scenario explaining the observed trend implies that X-rays coming from an embedded active galactic nucleus may play a dominant role in the chemistry of molecular gas at LIR>=1012 Lsolar. We discuss the implications of this result for the understanding of LIRGs, ULIRGs, and high-redshift gas-rich galaxies.

Graciá-Carpio, J.; García-Burillo, S.; Planesas, P.; Colina, L.

2006-04-01

71

Studying Thermohaline Circulation in the Ocean by Means of Transient Tracer Data  

Microsoft Academic Search

\\u000a Transient tracers include primarily certain chlorofluorocarbons (CFCs), tritium, tritiugenic 3He, and bomb 14C, the oceanic distributions of which allow investigation of thermohaline circulation of the ocean and of interior-ocean mixing.\\u000a Features of the tracers and their distributions are outlined, and examples are given of oceanographic studies employing tracer\\u000a data. Spreading of surface waters into the interior ocean and pathways of

Wolfgang Roether

72

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

SciTech Connect

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.

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

73

Retention of Tracer Gas from Instantaneous Releases of SF6 in an Urban Environment  

SciTech Connect

Data from a series of instantaneous releases of SF6 tracer during the Joint Urban 2003 study in Oklahoma City have been analyzed to determine characteristic retention times for puffs in an urban environment. Results from nine real-time tracer detectors with a time response of 0.5 seconds were used in the analysis. Distances from the source ranged from less than 200 m to over 1 km. For each individual intensive operating period (IOP), the detector locations were adjusted so that, given the expected wind directions during the releases, the detectors would lie generally downwind of the release point. As a result, building characteristics upwind of the detectors varied from one IOP to the next. Animations of the tracer concentrations show clear evidence of channeling along street canyons approximately parallel to the prevailing wind directions, trapping in street canyons perpendicular to the flow, and other complex circulation patterns. Retention times for individual puffs ranged from a few minutes to over 20 minutes, with a strong mode in the distribution around 11 minutes. There was surprisingly little correlation with wind speed or direction. Comparisons with simple puff models are presented.

Doran, J. C.; Allwine, K Jerry; Clawson, Kirk L.; Carter, Roger G.

2006-01-01

74

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

SciTech Connect

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.

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

1995-05-01

75

An Assessment of steady-state propane-gas tracer method for reaeration coefficients, Cowaselon Creek, New York  

USGS Publications Warehouse

Three tests were conducted in a straight 5.2-km reach of the Cowaselon Creek, Canastota, New York, in order to assess feasibility of the steady-state propane-gas tracer method as a means of estimating in situ reaeration coefficients. It is concluded that the steady-state method, which combines as instantaneous injection of dye tracer with a long-duration injection of propane tracer, is an operationally feasible field technique and provides a very reliable means of determining the propane desorption coefficient in steady-channel flow. The effect of wind shear on propane desorption coefficients was not detected in any tests, apparently due to the sheltering effect of high banks. The reaeration coefficient is estimated by applying a conversion factor determined from laboratory experiments to the gas desorption coefficient. (USGS)

Yotsukura, N.; Stedfast, D. A.; Draper, R. E.; Brutsaert, W. H.

1983-01-01

76

Measuring seasonal variations of moisture in a landfill with the partitioning gas tracer test.  

PubMed

Seven pilot-scale partitioning gas tracer tests (PGTTs) were conducted to assess the accuracy and reproducibility of this method for measuring water in municipal solid waste landfills. Tests were conducted in the same location over a 12-month period, and measured moisture conditions ranged from possible dry waste to refuse with a moisture content of 24.7%. The final moisture content of 24.7% was in reasonable agreement with gravimetric measurements of excavated refuse, where the moisture content was 26.5+/-6.0 CI%. Laboratory tests were used to assess the utility of the PGTT for measuring water in small pores, water sorbed to solid surfaces, and the influence of dry waste on PGTTs. These experiments indicated that when refuse surfaces are not completely solvated with water, PGTTs may produce misleading results (negative estimates) of water saturation and moisture content. PMID:16458495

Han, Byunghyun; Jafarpour, Behnam; Gallagher, Victoria N; Imhoff, Paul T; Chiu, Pei C; Fluman, Daniel A

2006-01-01

77

Measuring seasonal variations of moisture in a landfill with the partitioning gas tracer test  

SciTech Connect

Seven pilot-scale partitioning gas tracer tests (PGTTs) were conducted to assess the accuracy and reproducibility of this method for measuring water in municipal solid waste landfills. Tests were conducted in the same location over a 12-month period, and measured moisture conditions ranged from possible dry waste to refuse with a moisture content of 24.7%. The final moisture content of 24.7% was in reasonable agreement with gravimetric measurements of excavated refuse, where the moisture content was 26.5 {+-} 6.0CI%. Laboratory tests were used to assess the utility of the PGTT for measuring water in small pores, water sorbed to solid surfaces, and the influence of dry waste on PGTTs. These experiments indicated that when refuse surfaces are not completely solvated with water, PGTTs may produce misleading results (negative estimates) of water saturation and moisture content.

Han, Byunghyun [Department of Civil and Environmental Engineering, University of Delaware, 301 DuPont Hall, Newark, DE 19716 (United States); Jafarpour, Behnam [Department of Civil and Environmental Engineering, University of Delaware, 301 DuPont Hall, Newark, DE 19716 (United States); Gallagher, Victoria N. [Department of Civil and Environmental Engineering, University of Delaware, 301 DuPont Hall, Newark, DE 19716 (United States); Imhoff, Paul T. [Department of Civil and Environmental Engineering, University of Delaware, 301 DuPont Hall, Newark, DE 19716 (United States)]. E-mail: imhoff@udel.edu; Chiu, Pei C. [Department of Civil and Environmental Engineering, University of Delaware, 301 DuPont Hall, Newark, DE 19716 (United States); Fluman, Daniel A. [Delaware Solid Waste Authority, 1128 S. Bradford St. Dover, DE 19903-0455 (United States)

2006-07-01

78

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

PubMed

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

Fro?ka, A; Jílek, K

2014-07-01

79

Fructose metabolism in humans - what isotopic tracer studies tell us  

PubMed Central

Fructose consumption and its implications on public health are currently under study. This work reviewed the metabolic fate of dietary fructose based on isotope tracer studies in humans. The mean oxidation rate of dietary fructose was 45.0%?±?10.7 (mean?±?SD) in non-exercising subjects within 3–6?hours and 45.8%?±?7.3 in exercising subjects within 2–3?hours. When fructose was ingested together with glucose, the mean oxidation rate of the mixed sugars increased to 66.0%?±?8.2 in exercising subjects. The mean conversion rate from fructose to glucose was 41%?±?10.5 (mean?±?SD) in 3–6?hours after ingestion. The conversion amount from fructose to glycogen remains to be further clarified. A small percentage of ingested fructose (<1%) appears to be directly converted to plasma TG. However, hyperlipidemic effects of larger amounts of fructose consumption are observed in studies using infused labeled acetate to quantify longer term de novo lipogenesis. While the mechanisms for the hyperlipidemic effect remain controversial, energy source shifting and lipid sparing may play a role in the effect, in addition to de novo lipogenesis. Finally, approximately a quarter of ingested fructose can be converted into lactate within a few of hours. The reviewed data provides a profile of how dietary fructose is utilized in humans.

2012-01-01

80

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

NASA Astrophysics Data System (ADS)

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.

Dettmar, R.-J.

2005-06-01

81

Application of a tracer gas challenge with a human subject to investigate factors affecting the performance of laboratory fume hoods.  

PubMed

The results of a "user" tracer gas test were applied to investigate the effects of various parameters on hood containment ability and to evaluate accepted methods to classify hood performance. This user tracer gas test was performed with a human subject standing in front of the hood. Based on the data collected, face velocity, its variability, and cross drafts are important in determining hood leakage. Results indicate that the temporal variability of face velocity may deserve as much consideration as its spatial variability, a parameter more traditionally recognized as being important. The data collected indicate that hoods with horizontally sliding sash doors perform better with the doors positioned to provide a center opening rather than when all of the doors are pushed to one side. The observed smoke patterns suggest that this trend is caused by the location and instability of vortices formed along the perimeter edge when all doors are pushed to one side. The results of manikin tracer gas tests and the user tracer gas test are inconsistent, suggesting that more research is needed to determine how best to evaluate whether a hood protects its users. PMID:9858975

Altemose, B A; Flynn, M R; Sprankle, J

1998-05-01

82

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 ...

83

Study of stability zone influences and tracer patterns from the 1987 ANATEX (Across North America Tracer Experiment) experiment  

Microsoft Academic Search

In this paper, we will show preliminary results which appear to connect much of the hit and miss behavior of the surface tracer samples to large scale stability zones 100 to 1000 km wide. With these wintertime stability effects in mind, we have done the best we can to characterize the observed overall tracer patterns as well as individual tracer

William M. Porch; Frank A. Gifford; Donald E. Hoard

1988-01-01

84

Project definition study for the National Biomedical Tracer Facility  

SciTech Connect

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.

Roozen, K.

1995-02-15

85

Assessing the containment efficiency of a microbiological safety cabinet during the simultaneous generation of a nanoaerosol and a tracer gas.  

PubMed

The intention of this article is to compare the containment performance of a Type II microbiological safety cabinet (MSC) confronted with the simultaneous generation of a saline nanoparticle aerosol and a tracer gas (SF(6)). The back dissemination coefficient, defined as the ratio of the pollutant concentration measured outside the enclosure to the pollutant flow rate emitted inside the enclosure, is calculated in order to quantify the level of protection of each airborne contaminant tested for three enclosure operating configurations: an initial configuration (without perturbations), a configuration exposing a dummy in front of the enclosure (simulation of an operator), and a configuration employing the movement of a plate in front of the enclosure (simulation of human movement). Based on the results of this study, we observed that nanoparticulate and gaseous behaviours are strongly correlated, thus showing the predominance of air-driven transport over particle-specific behaviour. The average level of protection afforded by the MSC was found systematically slightly higher for the nanoaerosol than for the gas in the studied configurations (emission properties of the source, operating conditions, and measurement protocols). This improved protection efficiency, however, cannot be considered as a warrant of protection for operators since operating condition and ventilation parameters are still more influential on the containment than the pollutant nature (i.e. nanoaerosol or gas). PMID:23123312

Cesard, V; Belut, E; Prevost, C; Taniere, A; Rimbert, N

2013-04-01

86

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

NASA Technical Reports Server (NTRS)

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.

Basu, S. N.

1984-01-01

87

Carbon monoxide emission as a precise tracer of molecular gas in the Andromeda galaxy  

NASA Astrophysics Data System (ADS)

Stars are known to form in clouds of cold molecular hydrogen, which are relatively poorly understood despite being one of the main components of the interstellar medium. The problem is that H2 is invisible in the cold interstellar medium, so its distribution and motion must be inferred from observations of minor constituents of the clouds, such as carbon monoxide and dust. Most of our present knowledge comes from observations of CO emission, but there is much debate on whether this is an effective tracer of H2: it might miss a large fraction of the molecular gas. It is difficult to address this question on the basis of observations within the Milky Way alone, whose edge-on orientation makes it hard to discern the distant cloud structures. We have therefore surveyed the CO emission of the molecular clouds of M31 (the Andromeda galaxy), the nearest spiral galaxy to the Milky Way, and investigated the extent to which it follows the extinction of starlight by dust. We find a remarkably tight association between the CO emission and the dust, from which we conclude that CO does indeed trace all of the molecular gas.

Neininger, N.; Guélin, M.; Ungerechts, H.; Lucas, R.; Wielebinski, R.

1998-10-01

88

Across North America Tracer Experiment (ANATEX). Model Evaluation Study.  

National Technical Information Service (NTIS)

Three perfluorocarbon tracer gases were released at 2.5-day or 5.0-day intervals from two sites in central North America and sampled for 24-hr periods at 77 surface sites. The source-receptor distances ranged from less than 30 km to 3,000 km. The data wer...

T. L. Clark R. D. Cohn

1990-01-01

89

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...

90

Gas Flow Measurements by 3D Particle Tracking Velocimetry Using Coloured Tracer Particles  

Microsoft Academic Search

This work describes an original approach for 3D Particle Tracking Velocimetry (3D PTV), applicable also for gaseous flows\\u000a and based on tracer particles of different colours. On the images acquired by several cameras, tracer particles are handled\\u000a by colour recognition and 3D localisation. Then, the PTV tracking algorithm rebuilds the trajectories of the tracer particles\\u000a using a criterion of Minimum Acceleration. Theoretical

Dominique Tarlet; Christian Bendicks; Christoph Roloff; Róbert Bordás; Bernd Wunderlich; Bernd Michaelis; Dominique Thévenin

91

Green River air quality model development: meteorological and tracer data, July/August 1982 field study in Brush Valley, Colorado  

SciTech Connect

Meteorological and atmospheric tracer studies were conducted during a 3-week period in July and August of 1982 in the Brush Creek Valley of northwestern Colorado. The objective of the field experiments was to obtain data to evaluate a model, called VALMET, developed at PNL to predict dispersion of air pollutants released from an elevated stack located within a deep mountain valley in the post-sunrise temperature inversion breakup period. Three tracer experiments were conducted in the valley during the 2-week period. In these experiments, sulfur hexafluoride (SF/sub 6/) was released from a height of approximately 100 m, beginning before sunrise and continuing until the nocturnal down-valley winds reversed several hours after sunrise. Dispersion of the sulfur hexafluoride after release was evaluated by measuring SF/sub 6/ concentrations in ambient air samples taken from sampling devices operated within the valley up to about 8 km down valley from the source. An instrumented research aircraft was also used to measure concentrations in and above the valley. Tracer samples were collected using a network of radio-controlled bag sampling stations, two manually operated gas chromatographs, a continuous SF/sub 6/ monitor, and a vertical SF/sub 6/ profiler. In addition, basic meteorological data were collected during the tracer experiments. Frequent profiles of vertical wind and temperature structure were obtained with tethered balloons operated at the release site and at a site 7.7 km down the valley from the release site. 10 references, 63 figures, 50 tables.

Whiteman, C.D.; Lee, R.N.; Orgill, M.M.; Zak, B.D.

1984-06-01

92

Compartmental Modeling and Dosimetry of in Vivo Metabolic Studies of Leucine and Three Secretory Proteins in Humans Using Radioactive Tracers  

Microsoft Academic Search

Physical and mathematical models provide a systematic means of looking at biological systems. Radioactive tracer kinetic studies open a unique window to study complex tracee systems such as protein metabolism in humans. This research deals with compartmental modeling of tracer kinetic data on leucine and apolipoprotein metabolism obtained using an endogenous tritiated leucine tracer administered as a bolus, and application

Vaidehi Venkatakrishnan

1995-01-01

93

THE NEW YORK CITY URBAN DISPERSION PROGRAM MARCH 2005 FIELD STUDY: TRACER METHODS AND RESULTS.  

SciTech Connect

The Urban Dispersion Program March 2005 Field Study tracer releases, sampling, and analytical methods are described in detail. There were two days where tracer releases and sampling were conducted. A total of 16.0 g of six tracers were released during the first test day or Intensive Observation Period (IOP) 1 and 15.7 g during IOP 2. Three types of sampling instruments were used in this study. Sequential air samplers, or SAS, collected six-minute samples, while Brookhaven atmospheric tracer samplers (BATS) and personal air samplers (PAS) collected thirty-minute samples. There were a total of 1300 samples resulting from the two IOPs. Confidence limits in the sampling and analysis method were 20% as determined from 100 duplicate samples. The sample recovery rate was 84%. The integrally averaged 6-minute samples were compared to the 30-minute samples. The agreement was found to be good in most cases. The validity of using a background tracer to calculate sample volumes was examined and also found to have a confidence level of 20%. Methods for improving sampling and analysis are discussed. The data described in this report are available as Excel files. An additional Excel file of quality assured tracer data for use in model validation efforts is also available. The file consists of extensively quality assured BATS tracer data with background concentrations subtracted.

WATSON, T.B.; HEISER, J.; KALB, P.; DIETZ, R.N.; WILKE, R.; WIESER, R.; VIGNATO, G.

2005-10-01

94

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, January 1, 1995--March 31, 1995  

SciTech Connect

Fluorinated organic acids were utilized in a test study as hydrologic tracers for the Yucca Mountain Project. Fluorinated acids included cinnamic acid; benzoic acid, and toluic acid. Results are discussed pertaining to retention time, elution time, and stability.

Stetzenbach, K.; Farnham, I.

1995-05-01

95

Study plan for determining recharge rates at the Hanford Site using environmental tracers.  

National Technical Information Service (NTIS)

This report presents a study plan for 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 transport...

E. M. Murphy J. E. Szercsody

1991-01-01

96

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization study. [Quarterly] progress report, April 1, 1995--June 3, 1995  

SciTech Connect

The focus for this quarter has been on completing the laboratory studies in preparation for the C-Well tracer tests. These studies include measuring the solubilities for each of the fluorinated benzoic acids as well as determining the stabilities of these compounds through both batch and column testing. A batch test for four pyridone compounds was also initiated. The Tracer QA procedures were approved by the YM USGS on May 24, 1995. The batch testing was repeated using these procedures.

Stetzenbach, K.; Farnham, I.

1995-08-01

97

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study; Progress report, January 1, 1991--June 30, 1991  

SciTech Connect

Studies continue on the use of organic acids as tracers in hydrology studies of Yucca Mountain. Work performed during this time period has been concentrated in three main areas: the familiarization with, and optimization of, the LC-MS hardware and data system; the initial development of soil column test procedures, which are used for evaluation of both the columns themselves and the tracer compounds; and continuation of the batch sorption and degradation studies for the potential tracers. All three of these tasks will continue, as the addition of new tracer compounds, analytical information, and equipment will necessitate further evaluation of existing methods and procedures. Also included in this report is the final report on an information system.

Stetzenbach, K.J.

1991-12-31

98

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

SciTech Connect

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.

Morel, J.; Tallon, J.

1985-04-16

99

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

Microsoft Academic Search

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

James J. Schauer; Glen R. Cass

2000-01-01

100

Glass mixing theory and tracer study results from the SF-10 run  

SciTech Connect

A general, partial differential equation governing glass mixing in the Slurry Fed Ceramic Melter (SFCM) was derived and a solution obtained based upon certain simplifying assumptions. Tracer studies were then conducted in the SFCM during the SF-10 run to test the theory and characterize glass mixing in this melter. Analysis of the tracer data shows that glass mixing in the SFCM can be explained by use of a model of two, well-mixed tanks in series.

Bowman, B.W.; Routt, K.R.

1988-08-01

101

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

USGS Publications Warehouse

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 of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

Bohlke, J. K.; Smith, R. L.; Miller, D. N.

2006-01-01

102

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

SciTech Connect

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.

Allwine, K Jerry; Flaherty, Julia E.

2006-08-09

103

A Study of Tracer Distribution Parameter Estimation from Sparse Samples.  

NASA Astrophysics Data System (ADS)

How do design parameters such as the spacing of sampling stations affect the quality of information obtained from atmospheric dispersion experiments? In large-scale experiments such as the Cross-Appalachian Tracer Experiment (CAPTEX) and the Across North America Tracer Experiment (ANATEX), the average crosswind spacing between surface sampling stations may be of the same order as, or greater than, the tracer cloud width parameter y. For such sparse samplings, investigated are the errors in estimating five parameters of the crosswind distribution of tracer dosage or concentration: the crosswind integrated dosage (M); the centroid coordinate (); the lateral dispersion parameter (y); the skewness (S); and the kurtosis (K). These are examined as functions of the ratio of y to , the nonuniformity of station spacing, and the location of relative to the nearest sampling station. Tracer experiments are simulated with the Gaussian distribution model, as well as a non-Gaussian model consisting of the sum of two Gaussian distributions with different means and variances. It is found that increasingly sparse sampling produces an increasing negative bias in estimates of y and positive bias in K, as well as increasing root-mean-square errors of all the parameters. Root-mean-square errors also increase with increasing range of skewness and kurtosis of mixed populations of non-Gaussian distributions and with increasing range of random spacings of stations.To examine the feasibility of inferring errors in the five distribution parameters from field experiments, large sets of simulated trials are performed in which selected `observables' as well as the distribution parameter errors are computed. Sets of trials differ with respect to the range of non-Gaussian distribution parameters, the range of random variation of station spacing, and the range of average sampling station density. For each set of trials conditional means and variances of the errors in estimates of the five distribution parameters are computed as functions of simulated observable parameters representing apparent sampling grid density, displacement of nearest station relative to apparent centroid, and central grid interval anomaly relative to average spacing. These functions contain a large fraction of the error variance for y, S, and K, but a relatively small fraction for M and .Errors estimated from such sets of simulations, given observable predictors from eight CAPTEX cases with very sparse crosswind sampling in a narrow (100 km) crosswind strip, are compared with errors estimated from the observations by using more dense samplings, obtained from a wider (300 km) annular strip, as `truth.' Errors in y, S, and K, predicted by the conditional means from the simulated trials, correlated well with those estimated from the CAPTEX data but errors in M and did not. The Gaussian and non-Gaussian distribution sets differ little in their ability to predict conditional bias errors, but the residual rms errors estimated from comparison with CAPTEX data are grossly underestimated by the Gaussian model and appear to be better predicted using appropriate non-Gaussian models.The results suggest that traditional analysis of data from a sampling array such as that employed in CAPTEX may systematically underestimate the lateral dispersion by more than 30%, and overestimate the kurtosis by more than a factor of 3. The observed distributions appear to have systematically large kurtosis compared to the Gaussian.

Holland, J. Z.

1991-01-01

104

Using Biofuel Tracers to Study Alternative Combustion Regimes  

SciTech Connect

Interest in the use of alternative fuels and combustion regimes 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{sub 2} emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions, and higher noise. Noise and PM have traditionally been the obstacles toward consumer acceptance of Diesel passenger cars in North America, while NOx (a key component in photochemical smog) has been more of an engineering challenge. Diesels are lean burning (combustion with excess oxygen) and reducing NOx to N2 in an oxygen rich environment is difficult. Adding oxygenated compounds to the fuel helps reduce PM emissions, but relying on fuel alone to reduce PM is unrealistic. Keeping peak combustion temperature below 1700 K prevents NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous Charge Compression Ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to validate combustion modeling.

Mack, J H; Flowers, D L; Buchholz, B A; Dibble, R W

2006-02-14

105

Formaldehyde and tracer gas transfer between airstreams in enthalpy-type air-to-air heat exchangers  

NASA Astrophysics Data System (ADS)

The formaldehyde, tracer gas, and water vapor transfer rates in two enthalpy exchangers were measured. The first exchanger uses a cross flow 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.

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

1984-07-01

106

Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO sub 2 catalysts  

SciTech Connect

Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

Krishna, K.R.

1992-01-01

107

Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO{sub 2} catalysts  

SciTech Connect

Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involved in chain growth. Isotopic tracers are used in conjunction with transient-response techniques in this study of Fischer-Tropsch synthesis over Ru/TiO{sub 2} catalysts. Experiments are conducted at a total pressure of 1 atmosphere, reaction temperatures of 453--498 K and D{sub 2}/CO (or H{sub 2}/CO) ratios of 2--5. Synthesis products are analyzed by gas chromatography or isotope-ratio gas chromatography-mass spectrometry. Rate constants for chain initiation, propagation and termination are evaluated under steady-state reaction conditions by using transients in isotopic composition. The activation energy for chain termination is much higher than that for propagation, accounting for the observed decrease in the chain growth parameter are also estimated. Coverages by reaction intermediates are also estimated. When small amounts of {sup 12}C-labelled ethylene are added to {sup 13}CO/H{sub 2} synthesis gas, ethylene acts as the sole chain initiator. Ethylene-derived carbon also accounts for 45% of the C{sub 1} monomer pool. 102 refs., 29 figs., 11 tabs.

Krishna, K.R.

1992-01-01

108

Ubiquitous argonium (ArH+) in the diffuse interstellar medium: A molecular tracer of almost purely atomic gas  

NASA Astrophysics Data System (ADS)

Aims: We describe the assignment of a previously unidentified interstellar absorption line to ArH+ and discuss its relevance in the context of hydride absorption in diffuse gas with a low H2 fraction. The confidence of the assignment to ArH+ is discussed, and the column densities are determined toward several lines of sight. The results are then discussed in the framework of chemical models, with the aim of explaining the observed column densities. Methods: We fitted the spectral lines with multiple velocity components, and determined column densities from the line-to-continuum ratio. The column densities of ArH+ were compared to those of other species, tracing interstellar medium (ISM) components with different H2 abundances. We constructed chemical models that take UV radiation and cosmic ray ionization into account. Results: Thanks to the detection of two isotopologues, 36ArH+ and 38ArH+, we are confident about the carrier assignment to ArH+. NeH+ is not detected with a limit of [NeH+]/[ArH+] ? 0.1. The derived column densities agree well with the predictions of chemical models. ArH+ is a unique tracer of gas with a fractional H2 abundance of 10-4 - 10-3 and shows little correlation to H2O+, which traces gas with a fractional H2 abundance of ?0.1. Conclusions: A careful analysis of variations in the ArH+, OH+, H2O+, and HF column densities promises to be a faithful tracer of the distribution of the H2 fractional abundance by providing unique information on a poorly known phase in the cycle of interstellar matter and on its transition from atomic diffuse gas to dense molecular gas traced by CO emission. Abundances of these species put strong observational constraints upon magnetohydrodynamical (MHD)simulations of the interstellar medium, and potentially could evolve into a tool characterizing the ISM. Paradoxically, the ArH+ molecule is a better tracer of almost purely atomic hydrogen gas than Hi itself, since Hi can also be present in gas with a significant molecular content, but ArH+ singles out gas that is >99.9% atomic.

Schilke, P.; Neufeld, D. A.; Müller, H. S. P.; Comito, C.; Bergin, E. A.; Lis, D. C.; Gerin, M.; Black, J. H.; Wolfire, M.; Indriolo, N.; Pearson, J. C.; Menten, K. M.; Winkel, B.; Sánchez-Monge, Á.; Möller, T.; Godard, B.; Falgarone, E.

2014-06-01

109

An evaluation of the estimation of road traffic emission factors from tracer studies  

NASA Astrophysics Data System (ADS)

Road traffic emission factors (EFs) are one of the main sources of uncertainties in emission inventories; it is necessary to develop methods to reduce these uncertainties to manage air quality more efficiently. Recently an alternative method has been proposed to estimate the EFs. In that work the emission factors were estimated from a long term tracer study developed in Ho Chi Minh City (HCMC) Vietnam. A passive tracer was continuously emitted from a finite line source placed in one side of an urban street canyon. Simultaneously, the resulting tracer concentrations were monitored at the other side of the street. The results of this experiment were used to calculate the dispersion factors and afterwards, these dispersion factors were used to estimate the EFs. In this paper we use the Computational Fluids Dynamics (CFD) model WinMISKAM to critically evaluate the proposed methodology. In a first step, we use the results of the tracer study to validate the CFD model. Results show that the model is able to simulate quite well the tracer dispersion in most of the cases. The model is then used to evaluate the effect of varying the source configuration and to correct the EFs. A comparison with available studies shows that the corrected EFs are within the range of the EFs reported in other studies. Finally, the CFD model is used to find a source configuration that better represents the vehicle emissions and that may be used in future studies to estimate the EFs more accurately. Results show that a 200 m line placed in the center of the street would represent very well the vehicle emissions. This work shows that it is possible to accurately estimate the EFs from tracer studies.

Belalcazar, Luis Carlos; Clappier, Alain; Blond, Nadège; Flassak, Thomas; Eichhorn, Joachim

2010-10-01

110

Study of stability zone influences and tracer patterns from the 1987 ANATEX (Across North America Tracer Experiment) experiment  

NASA Astrophysics Data System (ADS)

In this paper, we will show preliminary results which appear to connect much of the hit and miss behavior of the surface tracer samples to large scale stability zones 100 to 1000 km wide. With these wintertime stability effects in mind, we have done the best we can to characterize the observed overall tracer patterns as well as individual tracer releases. This type of survey information is important to numerical model development. Diagnostic models often have difficulty reproducing surface plume concentrations where transport over stable layers have occurred. Prognostic models can, in theory, model effects of strong stable layers. However, these models would have great difficulty predicting large scale stable regions such as those observed during ANATEX. Also, though these models have ways of budging in synoptic wind fields, temperature observations are presently ignored. This is because if both wind and temperature observations are forced too strongly into the model, conflicting results may be produced.

Porch, William M.; Gifford, Frank A.; Hoard, Donald E.

111

Study of stability zone influences and tracer patterns from the 1987 ANATEX (Across North America Tracer Experiment) experiment  

SciTech Connect

In this paper, we will show preliminary results which appear to connect much of the hit and miss behavior of the surface tracer samples to large scale stability zones 100 to 1000 km wide. With these wintertime stability effects in mind, we have done the best we can to characterize the observed overall tracer patterns as well as individual tracer releases. This type of survey information is important to numerical model development. Diagnostic models often have difficulty reproducing surface plume concentrations where transport over stable layers have occurred. Prognostic models can, in theory, model effects of strong stable layers. However, these models would have great difficulty predicting large scale stable regions such as those observed during ANATEX. Also, though these models have ways of budging in synoptic wind fields, temperature observations are presently ignored. This is because if both wind and temperature observations are forced too strongly into the model, conflicting results may be produced. 12 refs., 5 figs.

Porch, W.M.; Gifford, F.A.; Hoard, D.E.

1988-01-01

112

Deposition of Contaminated Sediments in Boston Harbor Studied Using Fluorescent Dye and Particle Tracers  

NASA Astrophysics Data System (ADS)

The residence time of water and suspended particles in Fort Point Channel, a sub-region of Boston Harbor containing a major combined sewer overflow and highly contaminated sediment, was determined during three field surveys by measuring the disappearance of fluorescent tracers from the water column. Flushing by advective movement was quantified using Rhodamine WT dye, a dissolved tracer which has negligible interaction with suspended sediment. The fate of suspended particles was inferred from measured concentrations of fluorescent pigment particles which were initially well mixed with Rhodamine dye and which have a size range and settling velocity comparable to the sewage particles of interest. Dye and particle concentrations were measured by fluorescent spectroscopy of water samples obtained throughout the channel over a week following tracer introduction. Dye measurements indicate that channel water is replaced on a scale of 1-2·7 days, depending on tidal amplitude and phase during tracer release, and the magnitude of freshwater inflow. Ratios of normalized particle concentration to dye concentration suggest effective deposition velocities of 1·5-3·3 m day -1; this is an order of magnitude faster than observed in laboratory settling columns suggesting that removal of suspended tracer particles from Fort Point Channel during our surveys may have been the result of scavenging by a bottom ' fluff ' layer. This finding is consistent with our previous observation of particle deposition in Salem Sound, Massachusetts, U.S.A. and in controlled laboratory studies of particle aggregation at the sediment-water interface.

Adams, E. E.; Stolzenbach, K. D.; Lee, J.-J.; Caroli, J.; Funk, D.

1998-03-01

113

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site Characterization Study. Progress report, July 1, 1994--September 30, 1994  

SciTech Connect

The work performed during this quarter consists of the continuation of the batch studies for the fluorinated benzoic acids and the evaluation of LC/MS for the analysis of these potential tracers. Column studies for these compounds have also been initiated.

Stetzenbach, K.

1994-12-01

114

Measuring the emission rate of an aerosol source placed in a ventilated room using a tracer gas: influence of particle wall deposition.  

PubMed

A method to measure the emission rate of an airborne pollutant source using a tracer gas was tested in the case of an aerosol source. The influence of particle deposition on the walls of a test room of 72 m3 was studied. The deposition rate of an aerosol of MgCl2 was determined by means of two methods: one based on measuring the aerosol concentration decay inside the ventilated room, the other based on calculation of the material mass balance. The concentration decay was monitored by optical counting and the aerosol mass concentration determined by means of sampling on a filter and analysis of the mass deposited by atomic absorption spectrometry. Four series of measurements were carried out. The curve giving the deposition rate according to the particle aerodynamic diameter (d(ae)) was established and shows deposition rates higher than those predicted using the model of Corner. The decay method gives the best results. The study carried out has shown that the phenomenon of deposition has little effect on the measurement of the aerosol source emission rate using a tracer gas for particles of aerodynamic diameter < 5 microm (underestimation < 25%). For particles of a greater diameter, wall deposition is an extremely limiting factor for the method, the influence of which can, however, be limited by using a test booth of small volume and keeping the sampling duration as short as possible. PMID:12176722

Bémer, D; Lecler, M T; Régnier, R; Hecht, G; Gerber, J M

2002-04-01

115

Tracer studies of anodic films formed on aluminium in malonic and oxalic acids  

NASA Astrophysics Data System (ADS)

Using a tungsten-containing layer, incorporated into sputtering-deposited aluminium, as a tracer, the growth of porous anodic films in malonic and oxalic acid electrolytes has been investigated using transmission electron microscopy, Rutherford backscattering spectroscopy and nuclear reaction analysis. Comparisons were also made with films formed in phosphoric acid electrolyte, which have been studied previously. The findings reveal a distortion of the tracer layer within the barrier region of the porous films, evident as a lagging of the tracer beneath the pores relative to that in the adjacent cell wall region. Further, the films are significantly thicker than the layer of metal consumed during anodizing and display smooth-sided pores. The anodizing behaviours are consistent with a major role for field-assisted flow of film material within the barrier layer in the development of the pores.

Garcia-Vergara, S. J.; Skeldon, P.; Thompson, G. E.; Habakaki, H.

2007-12-01

116

Study of Stability Zone Influences and Tracer Patterns from the 1987 ANATEX (Across North America Tracer Experiment) Experiment.  

National Technical Information Service (NTIS)

In this paper, we will show preliminary results which appear to connect much of the hit and miss behavior of the surface tracer samples to large scale stability zones 100 to 1000 km wide. With these wintertime stability effects in mind, we have done the b...

W. M. Porch F. A. Gifford D. E. Hoard

1988-01-01

117

Simultaneous measurement of gas hold-up and mass transfer coefficient by tracer dynamic technique in “Emulsair” reactor with an emulsion-venturi distributor  

Microsoft Academic Search

Hydrodynamics and gas–liquid mass transfer have been investigated in an “Emulsair” reactor with cocurrent downflow of gas and liquid. This consists of a cylindrical tank with conical bottom topped by an emulsion-venturi as the gas–liquid distributor in which the gas is self-aspired by action of the kinetic energy of the liquid recirculation. An original tracer dynamic technique using the CO2–N2\\/water

B. Gourich; M. Belhaj Soulami; A. Zoulalian; M. Ziyad

2005-01-01

118

Terrestrial inert gases - Isotope tracer studies and clues to primordial components in the mantle  

NASA Astrophysics Data System (ADS)

The use of He-3/He-4 measurements for characterizing terrestrial materials and tracing natural-system processes is surveyed. Terrestrial He is classified according to its He-3/He-4 ratio, expressed as R/R-A where R-A is the He-3/He-4 ratio of atmospheric He, 1.4 x 10 to the -6th; radiogenic He typical of continental rocks has R/R-A of 0.01-0.1, while mantle He, typical of midoceanic ridge basalts (MORB) and other geothermal environments and attributed to gas entrapment during the earth's formation, has R/R-A of 5-30. Determinations of R/R-A for MORB and for samples from hot spots, from Tristan da Cunha, and from subduction zones are compared with Sr, Nd, Ar, Ne, and Xe data and shown to support a two-layer (depleted/fertile) model of the mantle, with mixing processes accounting for tectonic variations in R/R-A. The use of He-3 as a tracer for mapping ocean circulation patterns, studying ridge-crest tectonic and hydrothermal processes, and geothermal and hydrologic prospecting is described.

Lupton, J. E.

119

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain site characterization study. Progress report, October 1, 1994--December 31, 1994  

SciTech Connect

The bromide anion has been used extensively as a tracer for mapping the flow of groundwater. It has proven to be both a safe and reliable groundwater tracer. The goal in this study is to find several tracing compounds with characteristics similar to the bromide anion to be used in multiple well tracing tests. Four groups of fluorinated organic acids were selected as candidates for groundwater tracers. These groups include fluorinated benzoic acids (FBA), fluorinated salicylic acids (FSA), fluorinated toluic acids (FTA), and fluorinated cinnamic acids (FCA). These compounds have been shown to move readily with the flow of water and do not adsorb to soil. They are also non-toxic. In this study, the retention of the fluorinated organic acids on to a soil column is compared to that of the bromide ion. The time required for the elution of each analyte from the soil column is measured using a UV-Vis detector. The soils consist of the light, medium, and dark tuffs used in the batch study. The work performed during this quarter consists of the continuation of the batch studies for the fluorinated benzoic acids and column studies for several potential tracer compounds.

Stetzenbach, K.; Farnham, I.

1994-12-31

120

/sup 15/N tracer kinetic studies on the validity of various /sup 15/N tracer substances for determining whole-body protein parameters in very small preterm infants  

SciTech Connect

Reliable /sup 15/N tracer substances for tracer kinetic determination of whole-body protein parameters in very small preterm infants are still a matter of intensive research, especially after some doubts have been raised about the validity of (/sup 15/N)glycine, a commonly used /sup 15/N tracer. Protein turnover, synthesis, breakdown, and further protein metabolism data were determined by a paired comparison in four preterm infants. Their post-conceptual age was 32.2 +/- 0.8 weeks, and their body weight was 1670 +/- 181 g. Tracer substances applied in this study were a (/sup 15/N)amino acid mixture (Ia) and (/sup 15/N)glycine (Ib). In a second group of three infants with a post conceptual age of /sup 15/N-labeled 32.0 +/- 1.0 weeks and a body weight of 1,907 +/- 137 g, yeast protein hydrolysate (II) was used as a tracer substance. A three-pool model was employed for the analysis of the data. This model takes into account renal and fecal /sup 15/N losses after a single /sup 15/N pulse. Protein turnovers were as follows: 11.9 +/- 3.1 g kg-1 d-1 (Ia), 16.2 +/- 2.5 g kg-1 d-1 (Ib), and 10.8 +/- 3.0 g kg-1 d-1 (II). We were able to demonstrate an overestimation of the protein turnover when Ib was used. There was an expected correspondence in the results obtained from Ia and II. The /sup 15/N-labeled yeast protein hydrolysate is a relatively cheap tracer that allows reliable determination of whole-body protein parameters in very small preterm infants.

Plath, C.; Heine, W.; Wutzke, K.D.; Krienke, L.; Toewe, J.M.; Massute, G.; Windischmann, C.

1987-05-01

121

In vitro study of PET tumor tracers at normal and elevated media glucose levels  

SciTech Connect

FDG uptake in tumors is decreased by hyperglycemia. Little is known about the effect of hyperglycemia on non-FDG PET tracer uptake in tumors. This study was designed to determine if PET tumor tracers are affected by chronic exposure of tumor cells to high media glucose levels. Human ovarian adenocarcinoma (HTB77IP3) cells normally grown at 100 mg/dl of glucose were grown in media with 100 or 300 mg/dl of glucose. At 20, 26 and 38 days after initial culture (6-7 days after subculture), uptakes of 3H-labeled FDG, Thymidine (Thy), Methionine (Met) and Leucine (Leu) into the cells (n=4) were determined at the same glucose level as growth media. Tracer uptake per 1 million cells was measured after a 60 min uptake period. Presented are percentage of tracer uptake of cells grown at 300 mg/dl of glucose relative to uptake of cells grown at 100 mg/dl of glucose (mean {plus_minus} SD of 20, 26, and 38 days culture). Paired t-tests were used to compare tracer uptake of cells grown and assayed at both glucose levels. P values <0.05 were considered significant. FDG uptake of cells grown and assayed at 300 mg/dl of glucose was significantly decreased, compared with uptake of cells grown and assayed at 100 mg/dl of glucose. By contrast, uptake of Thy, Met and Leu were not different between cells grown and assayed at 100 or 300 mg/dl of glucose. These results indicate that tumor uptake of Thy, Met and Leu do not depend on media glucose level and suggest that these tracers labeled with C-11 are suitable for hyperglycemic patients, in whom tumor FDG uptake is expected to be impaired.

Torizuka, T.; Clavo, A.C.; Wahl, R.L. [Univ. of Michigan, Ann Arbor, MI (United States)

1996-05-01

122

Long-Range (CAPTEX (Cross-APpalachian Tracer EXperiment)) and Complex Terrain (ASCOT (Atmospheric Studies of COmplex Terrain)) Perfluorocarbon Tracer Studies.  

National Technical Information Service (NTIS)

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...

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

1986-01-01

123

Using noble gas tracers to estimate residual CO2 saturation in the field: results from the CO2CRC Otway residual saturation and dissolution test  

NASA Astrophysics Data System (ADS)

Residual CO2 saturation is a critically important parameter in CO2 storage as it can have a large impact on the available secure storage volume and post-injection CO2 migration. A suite of single-well tests to measure residual trapping was conducted at the Otway test site in Victoria, Australia during 2011. One or more of these tests could be conducted at a prospective CO2 storage site before large-scale injection. The test involved injection of 150 tonnes of pure carbon dioxide followed by 454 tonnes of CO2-saturated formation water to drive the carbon dioxide to residual saturation. This work presents a brief overview of the full test sequence, followed by the analysis and interpretation of the tests using noble gas tracers. Prior to CO2 injection krypton (Kr) and xenon (Xe) tracers were injected and back-produced to characterise the aquifer under single-phase conditions. After CO2 had been driven to residual the two tracers were injected and produced again. The noble gases act as non-partitioning aqueous-phase tracers in the undisturbed aquifer and as partitioning tracers in the presence of residual CO2. To estimate residual saturation from the tracer test data a one-dimensional radial model of the near-well region is used. In the model there are only two independent parameters: the apparent dispersivity of each tracer and the residual CO2 saturation. Independent analysis of the Kr and Xe tracer production curves gives the same estimate of residual saturation to within the accuracy of the method. Furthermore the residual from the noble gas tracer tests is consistent with other measurements in the sequence of tests.

LaForce, T.; Ennis-King, J.; Paterson, L.

2013-12-01

124

Tracer studies of radionuclide migration in fractured rock at a scale of 1 meter  

Microsoft Academic Search

The Large Block Tracer Test is a series of experiments to study the migration of radionuclides through fractures in rock at the scale of one meter. The separate effects to be considered are sorption onto minerals within the rock matrix; diffusion of radionuclide species through the rock matrix, diffusion and hydrodynamic dispersion within the fracture; and the effect of heterogeneity

R. S. Rundberg; B. Travis; T. T. Vandergraaf; D. J. Drew

1995-01-01

125

Uncertainties in Air Exchange using Continuous-Injection, Long-Term Sampling Tracer-Gas Methods  

SciTech Connect

The PerFluorocarbon Tracer (PFT) method is a low-cost approach commonly used for measuring air exchange in buildings using tracer gases. It is a specific application of the more general Continuous-Injection, Long-Term Sampling (CILTS) method. The technique is widely used but there has been little work on understanding the uncertainties (both precision and bias) associated with its use, particularly given that it is typically deployed by untrained or lightly trained people to minimize experimental costs. In this article we will conduct a first-principles error analysis to estimate the uncertainties and then compare that analysis to CILTS measurements that were over-sampled, through the use of multiple tracers and emitter and sampler distribution patterns, in three houses. We find that the CILTS method can have an overall uncertainty of 10-15percent in ideal circumstances, but that even in highly controlled field experiments done by trained experimenters expected uncertainties are about 20percent. In addition, there are many field conditions (such as open windows) where CILTS is not likely to provide any quantitative data. Even avoiding the worst situations of assumption violations CILTS should be considered as having a something like a ?factor of two? uncertainty for the broad field trials that it is typically used in. We provide guidance on how to deploy CILTS and design the experiment to minimize uncertainties.

Sherman, Max H.; Walker, Iain S.; Lunden, Melissa M.

2013-12-01

126

Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research  

NASA Astrophysics Data System (ADS)

During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer studies is critically discussed, where special emphasis is set on evaluating different data processing strategies on the example of enriched stable Sr isotopes.1 The analytical key parameters such as blank (Kr, Sr and Rb), variation of the natural Sr isotopic composition in the sample, mass bias, interferences (Rb) and total combined uncertainty are considered. A full metrological protocol for data processing using IPD is presented based on data gained during two transgenerational marking studies of fish, where the transfer of a Sr isotope double spike (84Sr and 86Sr) from female spawners of common carp (Cyprinus carpio L.) and brown trout (Salmo trutta f.f.)2 to the centre of the otoliths of their offspring was studied by (LA)-MC-ICP-MS. 1J. Irrgeher, A. Zitek, M. Cervicek and T. Prohaska, J. Anal. At. Spectrom., 2014, 29, 193-200. 2A. Zitek, J. Irrgeher, M. Kletzl, T. Weismann and T. Prohaska, Fish. Manage. Ecol., 2013, 20, 654-361.

Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

2014-05-01

127

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

NASA Astrophysics Data System (ADS)

Within the deep-geothermal research project at GroßSchönebeck in the NE German Basin, targeting volcanic rocks (Lower Rotliegend) and siliciclastics (Upper Rotliegend) in the Lower Permian by means of a well doublet with several screening intervals between 3815 and 4247 m b.s.l., several artificial fractures with different geometric and hydraulic characteristics were created at each well, aiming to increase reservoir performance [1], [2]. It could not be told a priori which of the various fracturing treatments was to prove as most promising in terms of future reservoir productivity. At the intended-production well (GS-4), one large-area waterfrac was created in the low-permeability volcanic rocks, and two gel-proppant fractures in selected sandstone layers. Each fracturing treatment was accompanied by the injection of a water-dissolved tracer slug, followed by a defined volume of tracer-free ('chaser') fluid [3]. Each frac received a different species of a sulfonated aromatic acid salt, as a conservative water tracer. During subsequent backflow tests (either gas-based lifting, or production by means of a downhole submersible pump), each frac can contribute a certain (more or less constant) amount to the measured total discharge (also depending on whether and when each frac 'starts' contributing, and which effective aperture and area it actually 'manifests' during the process). Since these individual-frac discharge amounts cannot be measured directly, it was endeavoured to indirectly determine ('resolve') them from tracer signals as detectable in the overall backflow discharge. Therefore, we need to examine how these tracer signals depend on local discharge values and on local hydrogeologic parameters (matrix porosity, permeability distribution; frac transmissivity, thickness, effective area and aperture), and to what extent hydrogeological uncertainty will impede the inversion of local discharge values. To this end, a parameter sensitivity study was conducted on a simplified flow and tracer transport model (using FEOW and assuming Darcian flow within the matrix, Hagen-Poiseuille flow within the waterfrac, and either D or H-P flow within the gel-proppant fracs), whose main findings are: (1) late tracer signals are almost independent on matrix porosity, permeability distribution, frac area (length), thickness and effective aperture, while being highly sensitive to local discharge values; 'late' means a backflow or production volume at least fivefold the injected chaser volume; (2a) early tracer signals (concentration 'peak' intervals) may exhibit slight 'acceleration' and 'damping' with increasing matrix porosity or increasing frac aperture (a 'paradoxical' behaviour which is not really surprising for single-well 'push-then-backflow' tests, actually owing to flow-field dispersion[4]), and (2b) a non-monotonous response to varying frac area, being almost insensitive to frac area as long as the linear-flow regime prevails against the radial-flow regime (effects of the latter only becoming visible at very low frac areas); (2c) the effects of these various factors on early-time tracer signals are not unambiguously discernible from each other, and this ambiguity would persist even if frac-resolved (in-situ) discharge metering were feasible. For each of the three fracs (k=1,2,3), a 'type-curve' set Ck(Q,t) (parametrized by discharge values Q) can be generated. Since every frac received a different tracer, tracer signals measured within the overall backflow will differ from individual-frac type-curves by mere dilution (no 'superposition'). Type-curve dilution by factor Qk/Qtotal can be compared to measured tracer concentrations in the total discharge, ck(ti), (i = 1, ..., no. of tracer samplings). From a formal point of view, the unknown discharge values Qk can be determined as the solution of a linear optimization task subject to the constraint Q1 + Q2 + Q3 = Qtotal (the latter being a measured value). It is recommendable to perform 'optimization' manually, rather than by resorting to automated solutions provided by some linea

Ghergut, Julia; Behrens, Horst; Sauter, Martin

2014-05-01

128

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

PubMed

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

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

129

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

Microsoft Academic Search

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

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

1999-01-01

130

Experimental design for estimating parameters of rate-limited mass transfer: Analysis of stream tracer studies  

USGS Publications Warehouse

Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow moving. We present a methodology for (1) evaluating and comparing alternative stream tracer experiment designs and (2) identifying those combinations of stream transport properties that pose limitations to parameter estimation and therefore a challenge to tracer test design. The methodology uses the concept of global parameter uncertainty analysis, which couples solute transport simulation with parameter uncertainty analysis in a Monte Carlo framework. Two general conclusions resulted from this work. First, the solute injection and sampling strategy has an important effect on the reliability of transport parameter estimates. We found that constant injection with sampling through concentration rise, plateau, and fall provided considerably more reliable parameter estimates than a pulse injection across the spectrum of transport scenarios likely encountered in high-gradient streams. Second, for a given tracer test design, the uncertainties in mass transfer and storage-zone parameter estimates are strongly dependent on the experimental Damkohler number, DaI, which is a dimensionless combination of the rates of exchange between the stream and storage zones, the stream-water velocity, and the stream reach length of the experiment. Parameter uncertainties are lowest at DaI values on the order of 1.0. When DaI values are much less than 1.0 (owing to high velocity, long exchange timescale, and/or short reach length), parameter uncertainties are high because only a small amount of tracer interacts with storage zones in the reach. For the opposite conditions (DaI >> 1.0), solute exchange rates are fast relative to stream-water velocity and all solute is exchanged with the storage zone over the experimental reach. As DaI increases, tracer dispersion caused by hyporheic exchange eventually reaches an equilibrium condition and storage-zone exchange parameters become essentially nonidentifiable.

Wagner, B. J.; Harvey, J. W.

1997-01-01

131

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

SciTech Connect

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.

Luong, E.

1999-05-10

132

Sample site selection for tracer studies applying a unidirectional circulatory approach  

SciTech Connect

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.

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

1987-08-01

133

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

SciTech Connect

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.

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

1991-02-01

134

TRACER STUDY OF VERTICAL EXCHANGE BY CUMULUS CLOUDS  

EPA Science Inventory

The exchange of material by convective cloud processes between the mixed layer and the overlying free troposphere is examined. The paper describes results of a field experiment that was conducted in Lexington, Kentucky during the period from July 20 to August 24, 1983 to study th...

135

Modeling of meteorology, tracer transport and chemistry for the Uintah Basin Winter Ozone Studies 2012 and 2013  

NASA Astrophysics Data System (ADS)

The Uintah Basin Winter Ozone Studies (UBWOS) field campaigns took place during winter of 2012 and 2013 in the Uintah Basin, Utah. The studies were aimed at characterizing meteorology, emissions of atmospheric constituents and air chemistry in a region abundant with oil and gas production, with associated emissions of various volatile organic compounds (VOCs) and NOx. High ozone pollution events were observed throughout the Uintah Basin during the winter of 2013, but not during the winter of 2012. A clear understanding of the processes leading to high ozone events is still lacking. We present here high spatiotemporal resolution simulations of meteorology, tracer transport and gas chemistry over the basin during January-February, 2012 and 2013 using the WRF/Chem regional photochemical model. Correctly characterizing the meteorology poses unique challenges due to complex terrain, cold-pool conditions, and shallow inversion layers observed during the winter of 2013. We discuss the approach taken to adequately simulate the meteorology over the basin and present evaluations of the modeled meteorology using surface, lidar and tethersonde measurements. Initial simulations use a passive tracer within the model as a surrogate for CH4 released from oil and gas wells. These tracer transport simulations show that concentrations of inert, emitted species near the surface in 2013 were 4-8 times higher than 2012 due to much shallower boundary layers and reduced winds in 2013. This is supported by in-situ measurements of CH4 made at the Horse Pool surface station during the field campaigns. Full photochemical simulations are forced by VOC and NOx emissions that are determined in a top-down approach, using observed emission ratios of VOC and NOx relative to CH4, along with available information of active wells, compressors, and processing plants. We focus on differences in meteorology, temperature, and radiation between the two winters in determining ozone concentrations in the basin. The model is then used diagnostically to assess first-order sensitivities of basin-wide ozone to NOx or VOC emissions, and how they depend on the environmental differences between the winters of 2012 and 2013.

Ahmadov, R.; McKeen, S. A.; Angevine, W. M.; Frost, G. J.; Roberts, J. M.; De Gouw, J. A.; Warneke, C.; Peischl, J.; Brown, S. S.; Edwards, P. M.; Wild, R. J.; Pichugina, Y. L.; Banta, R. M.; Brewer, A.; Senff, C. J.; Langford, A. O.; Petron, G.; Karion, A.; Sweeney, C.; Schnell, R. C.; Johnson, B.; Zamora, R. J.; Helmig, D.; Park, J.; Evans, J.; Stephens, C. R.; Olson, J. B.; Trainer, M.

2013-12-01

136

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

SciTech Connect

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.

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

1986-03-01

137

Radon as a tracer of biogenic gas equilibration and transport from methane-saturated sediments  

NASA Technical Reports Server (NTRS)

Data on Rn-222 activity in methane-rich gas bubbles from anoxic coastal sediments of Cape Lookout Bight, North Carolina, were used to determine gas equilibration with pore waters and the rates of ebullitive stripping and transport of gases to overlying waters and the atmosphere. Results showed that, during summer months, the bubble ebullition process strips and transports 1.9-4.8 percent/day of the standing crop of radon (and, by inference, other gases equilibrated with gas bubbles) in surface sediments of Cape Lookout Bight to the troposphere. Thus, the ebullitive mode of gas transport represents an effective mechanism for delivering reduced biogenic gases directly to the atmosphere.

Martens, Christopher S.; Chanton, Jeffrey P.

1989-01-01

138

Silicic-acid uptake in diatoms studied with [ 68 Ge]germanic acid as tracer  

Microsoft Academic Search

Uptake of silicic acid in the diatoms Navicula pelliculosa and Nitzschia alba was studied, using the natural isotope, 28Si, or a radioisotope, 31Si. The rate of uptake of silicic acid was also determined by using [68Ge]germanic acid as a tracer of silicic acid. At a given silicicacid concentration in the growth medium, the fractions of [68Ge]germanic acid taken up followed

Farooq Azam

1974-01-01

139

A diffusion wake model for tracer ultrastructure permeability studies in microvessels  

Microsoft Academic Search

developed a time-dependent diffu- sion model for analyzing the concentration profiles of low- molecular-weight tracers in the interendothelial clefts of the capillary wall that takes into account the three-dimensional time-dependent filling of the surrounding tissue space. The model provides a connecting link between two methods to investigate transvascular exchange: electron-microscopic ex- periments to study the time-dependent wake formed by low-

B. M. FU; F. E. CURRY; S. WEINBAUM

1995-01-01

140

Airborne Lidar tracking of fluorescent tracers for atmospheric transport and diffusion studies  

Microsoft Academic Search

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 tracers requiring the use of in-situ aircraft. The feasibility of using an airborne lidar system to observe atmospheric transport and dispersion of fluorescent-dye

Edward E. Uthe; William Viezee; Bruce M. Morley; Jason K. S. Ching

1985-01-01

141

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

PubMed

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

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

2013-01-01

142

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

SciTech Connect

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.

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

143

Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes.  

PubMed

Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers. PMID:21644136

Keiser, Teresa; Höllriegl, Vera; Giussani, Augusto; Oeh, Uwe

2011-06-01

144

Distribution of chromophoric dissolved organic matter in the North Atlantic: Implications for biogeochemistry and tracer studies  

NASA Astrophysics Data System (ADS)

Chromophoric dissolved organic material (CDOM), the colored fraction of the dissolved organic material (DOM) pool, is a highly dynamic property found throughout the open ocean. Most CDOM found away from continental margins is of open ocean origin and is not derived from riverine input or coastal runoff. CDOM is an optical property; hence, its concentration can be easily detected over large spatial scales using (for example) satellite-borne sensors. Net CDOM production is related to heterotrophic bacterial cycling processes while its losses are due to photobleaching. Vertical distributions of CDOM and in particular its surface signature are therefore regulated by vertical mixing processes in conjunction with these basic CDOM cycling processes. These properties make CDOM a potential ocean circulation tracer whose surface expression can be constrained globally by ocean color data. We are participating in selected CO2/CLIVAR Repeat Hydrography program cruises in order to collect an unprecedented baseline ocean CDOM dataset, to evaluate biological and dynamic processes controlling CDOM, and to evaluate the use of CDOM as an ocean tracer. Initial results from the North Atlantic A16N, A20, and A22 sections show that CDOM abundance (evaluated as optical absorption coefficient) tracks major oceanographic features such as the subtropical mode water and Gulf Stream recirculation. CDOM also has a slight inverse relationship with overall dissolved organic carbon (DOC) concentration. CDOM abundances also appear to correlate to distributions of transient and conserved tracers. These results are consistent with our findings concerning CDOM cycling from our ongoing study at the Bermuda Atlantic Time-series Study (BATS) station, and encourage further application of CDOM to tracer problems.

Nelson, N. B.; Siegel, D. A.; Carlson, C. A.; Klamberg, J.; Goldberg, S. J.; Swan, C.

2004-12-01

145

Tracer Interaction Effects During Partitioning Tracer Tests for NAPL Detection  

NASA Astrophysics Data System (ADS)

Partitioning tracer tests have been used in laboratory and field investigations to quantify the amount of nonaqueous phase liquid (NAPL) within porous media. In these tests multiple chemical tracers are typically injected into flowing groundwater: conservative tracers react minimally with the NAPL, while non-conservative tracers partition into the NAPL and exhibit retarded transport. The mean travel times of the conservative and partitioning tracers can be used to estimate the NAPL saturation in the swept zone. When multiple tracers are injected in the system, the tracers themselves change the chemical composition of the NAPL, which may affect partitioning behavior. Although co-tracer interactions have been considered by others, there are no reports of such effects during actual partitioning tracer tests. In this study tracer partitioning was examined in static batch systems and dynamic column experiments using 2,3-dimethyl-2-butanol and 1-hexanol as partitioning tracers and trichloroethylene as the NAPL. Co-tracer effects resulted in nonlinear partitioning of 2,3-dimethyl-2-butanol in batch tests, which increased with increasing tracer concentrations. The UNIFAC model was used to predict tracer activities in the NAPL, and the resulting predictions of tracer partitioning matched the data trends. Column experiments were conducted with these same tracers, and nonlinear tracer partitioning associated with co-tracer effects resulted in underestimation of NAPL mass in some systems. If linear partitioning were assumed, a priori analysis suggested that nonlinear partitioning would result in an overestimation of NAPL saturation. We discuss these observations and suggest guidelines for avoiding co-tracer effects during partitioning tracer tests.

Imhoff, P. T.; Pirestani, K.; Jafarpour, Y.; Spivey, K. M.

2002-05-01

146

Optimal design of sampling schedules for studying glucose kinetics with tracers  

SciTech Connect

Minimum size sampling schedules for estimating glucose kinetic parameters from an impulsive (bolus) tracer injection in normal humans and rats are presented. Glucose kinetics are described by a two-compartment linear model, and reference values of the parameters are estimated from a data base with many samples. The optimal sampling schedule (OSS) is determined in each individual by using a D-optimal criterion and consists of four samples. A population optimal sampling schedule (POSS) applicable to all the individuals of a given population is then determined, and its reliability and efficiency in recovering kinetic parameters (e.g., rate constants, plasma clearance rate, and mean residence time) is assessed. The influence of model and measurement error on OSS is discussed. Moreover, the adoption of an enhanced POSS (EPOSS, 8 samples) is shown to improve accuracy and precision of parameter estimates in a predictable manner. Finally some suggestions are given for obtaining more information from turnover studies using a constant infusion of tracer, with or without a priming pulse of tracer.

Cobelli, C.; Ruggeri, A. (Universita di Padova, Padua (Italy))

1989-09-01

147

Hydrogasification Gas Processing Studies.  

National Technical Information Service (NTIS)

Three methods of separating hydrogen from methane and carbon monoxide were evaluated: use of a moving bed of activated carbon (hypersorption), use of cryogenics, and use of an ''absorbing oil'' to absorb the methane. The feed gas stream studied was the ma...

1978-01-01

148

Cold-flow studies for the H-Coal reactor. Part II. Gas-mixing model  

Microsoft Academic Search

The gas mixing in a three-phase fluidized bed was studied in a cold flow reactor model. Experiments were conducted using nitrogen, kerosene, and extrudates of hydrodesulfurization catalyst. Utilizing Argon-41 as a tracer, the residence time distribution was studied. Based on these measurements, it was found that addition of coal fines significantly affected the gas flow inside the reactor. It was

I. A. Vasalos; D. N. Rundell; E. M. Bild; M. H. Peters

1980-01-01

149

Isotopic analysis and multi tracer tests to study groundwater circulation in a landslide in Southern Alps  

NASA Astrophysics Data System (ADS)

Understanding groundwater circulation in landslides is often necessary to assess their dynamics and forecast movements. Fontana landslide is placed in Canton Ticino, its main body is constituted by gneiss, that is covered by moraine and other deposits related to the mass movements like debris flows and, rock fall. Gneiss that originally has low hydraulic conductivity increases their aquifer properties due to weathering and fracture presence. In fact several springs are present in across the landslide some of them having discharge up to 1 m3 S-1. To study groundwater circulation in the landslide body, a multi tracer test was designed and water samples taken. 3 tracers (Naphtionate, Sulphorhodamine B and Uranine) were injected underground. Injection mass was calculated by using EHTD (EPA, 2003), 2 field fluorimeters were placed in springs considered to be the main water discharge of the system for continuous monitoring. Other springs with smaller discharge scattered along the landslide body were monitored by using charcoal bags. Water samples also were taken for chemical and stable isotopes analysis. The tracers' presence was also monitored in the river crossing the area collecting surface flow from snowmelt and springs. Even if the landslide has a small area, isotopic composition of water from springs shows clear differences. All samples plot close to the local meteoric water line, and an altitude effect is visible. Chemical composition is relatively uniform however some differences can also be seen. Concerning tracers the only that arrived at monitored points was uranine, and it was detected in the charcoal bags. Considering tracer concentration in ppm, in the charcoal and travel times to restitution points was possible to have conceptual model for groundwater flow across the landslide. Circulation is rapid and recharge controlled by snowmelt in spring and precipitation in late spring to autumn. Snow accumulates at the top of the landslide where an elongated topographic basin is present filled by blocks infiltrates and feed the springs located at lower altitude but close to the basin. Those springs not originally considered for discharge monitoring, are draining the water from the basin and could be better correlated to landslide movement, respect to other springs with similar discharge rates but farther from the concentrated infiltration area represented by the topographic basin.

Pera, Sebastian; Marzocchi, Roberto; Bronzini, Simona

2014-05-01

150

Experimental and model transport and diffusion studies in complex terrain with emphasis on tracer studies  

SciTech Connect

The U.S. Department of Energy (DOE) Atmospheric Studies in Complex Terrain (ASCOT) program began in the fall of 1978 as a multiple DOE and other Federal Laboratory program devoted to developing a better physical understanding of atmospheric boundary layer flows in areas of complex terrain. The first technical challenge undertaken by the program was an investigation of atmospheric boundary layer phenomena associated with the development, continuation and breakup of nocturnal drainage wind flows. This paper discusses the general objectives the program has addressed during the past several years and focuses on results from a major field experiment conducted in 1980 in The Geysers area of northern California. Specifically, results from measurements of simultaneous tracer releases are compared to calculations from a mass-consistent wind field model coupled to a particle-in-cell transport and diffusion model. Results of these comparisons show that model calculations agree with measurements within a factor of 5 approximately 50 percent of the time. Part of the difficulty faced by the models in these comparison studies is associated with large variabilities between measurements made by samplers located one or two ..delta..x apart when compared to the resolution of the models. Space and time averaging improves the comparisons considerably, although the design of the field experiment did not allow the determination of optimum spacial and temporal averages. 14 references, 9 figures, 2 tables.

Dickerson, M.H.; Foster, K.T.; Gudiksen, P.H.

1984-02-01

151

The effects of breaking waves on dual-tracer gas exchange experiments  

SciTech Connect

Quantification of air-sea gas fluxes is important in understanding the global ocean carbon cycle, determining the effect of biologically produced gases on remote marine tropospheric aerosol production, and measuring the atmospheric lifetimes of trace gases. Direct measurement of the flux, F, of a sparingly soluble gas through the air-sea interface is extremely difficult in general, and F is often calculated as F = k{sub L}{delta}C where k{sub L} is the transfer velocity of the gas and AC is its air-sea concentration difference. In the absence of bubbles, k{sub L} is a function of the near-surface aqueous-phase turbulence and the molecular diffusivity of the gas. Although direct measurement of {delta}C is relatively simple, oceanic measurements of k{sub L} are problematical. Because of this, k{sub L} is usually estimated from empirical parameterizations for k{sub L} in terms of wind speed, U. The linear relation between F and k{sub L} at a constant {delta}C implies that the accuracy of the parameterization of k{sub L} in terms of U is critical in calculating F. This is especially true when U is large, since experiments in wind tunnels, lakes, and the ocean suggest that k{sub L} increases quadratically with U (Wanninkhof, 1992). With the exact functional form of the relation between U and k{sub L} not definitively known at present, estimation of k{sub L} at high U could be inaccurate. This problem could be resolved with further oceanic measurements of k{sub L} at high U. However, increases in U are also associated with increases in the frequency of wave breaking. Whitecaps are known to generate bubble plumes, and these bubbles could have a significant effect on the measurement of k{sub L}.

Asher, W. [Pacific Northwest Lab., Sequim, WA (United States); Wanninkhof, R. [National Oceanic and Atomospheric Administration/Atlantic Oceanographic and Meterological Lab., Miami, FL (United States)

1995-07-01

152

Multiple tracer studies of bone uptake of /sup 99m/Tc-MDP and /sup 85/Sr  

SciTech Connect

Multiple tracer outflow dilution studies were performed on the normal canine tibia. In all cases /sup 125/I-labeled albumin was used as a vascular tracer. In one series of experiments /sup 99m/Tc-labeled methylene diphosphonate and (/sup 14/C)sucrose were used as test tracers, and in a second series /sup 85/Sr and /sup 22/Na were used. A bolus of three tracers was injected into the tibial nutrient artery, and fractional concentrations appearing in the ipsilateral femoral vein were measured for a period of 5 min. A distributed model, containing parameters for capillary and bone permeability and apparent volumes of distribution of interstitial fluid, was fitted to these data. It was found that there was no discrimination between movement of /sup 85/Sr or /sup 22/Na from interstitial fluid space into bone. Transcapillary exchange does not appear to be a significant barrier to exchange between blood and bone surfaces.

McCarthy, I.D.; Hughes, S.P.

1989-05-01

153

A rapid method for the measurement of sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), and Halon 1211 (CF2ClBr) in hydrologic tracer studies  

USGS Publications Warehouse

A rapid headspace method for the simultaneous laboratory determination of intentionally introduced hydrologic tracers, sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), Halon 1211 (CF2ClBr), and other halocarbons in water and gases is described. The high sensitivity of the procedure allows for introduction of minimal tracer mass (a few grams) into hydrologic systems with a large dynamic range of analytical detection (dilutions to 1:108). Analysis times by gas chromatography with electron capture detector are less than 1 min for SF6; about 2 min for SF6 and SF5CF3; and 4 min for SF6, SF5CF3, and Halon 1211. Many samples can be rapidly collected, preserved in stoppered septum bottles, and analyzed at a later time in the laboratory. Examples are provided showing the effectiveness of the gas tracer test studies in varied hydrogeological settings.

Busenberg, Eurybiades; Plummer, L. Niel

2010-01-01

154

A rapid method for the measurement of sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), and Halon 1211 (CF2ClBr) in hydrologic tracer studies  

NASA Astrophysics Data System (ADS)

A rapid headspace method for the simultaneous laboratory determination of intentionally introduced hydrologic tracers, sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), Halon 1211 (CF2ClBr), and other halocarbons in water and gases is described. The high sensitivity of the procedure allows for introduction of minimal tracer mass (a few grams) into hydrologic systems with a large dynamic range of analytical detection (dilutions to 1:108). Analysis times by gas chromatography with electron capture detector are less than 1 min for SF6; about 2 min for SF6 and SF5CF3; and 4 min for SF6, SF5CF3, and Halon 1211. Many samples can be rapidly collected, preserved in stoppered septum bottles, and analyzed at a later time in the laboratory. Examples are provided showing the effectiveness of the gas tracer test studies in varied hydrogeological settings.

Busenberg, Eurybiades; Plummer, L. Niel

2010-11-01

155

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

NASA Astrophysics Data System (ADS)

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 flow paths, and (3) upwelling of deep fluids that have "magmatic" helium and carbon isotope signatures. Results from our study illuminate two important aspects of the hydrological system that will have a direct impact on how this system responds to climate change: (1) recharge to the alluvial aquifer occurs primarily on the lower slopes of the catchment and is therefore sensitive to changes in snowline elevation and (2) deep groundwater in the western part of the aquifer is very young and provides very little buffering capacity. Although apparent groundwater ages indicate residence times range from less than a year to several decades, the water that recharges seasonally dominates the alluvial aquifer. Noble gas recharge temperatures are close to mean annual air temperature, and are 5°-11° higher than would be expected for direct influx of snowmelt. Excess air concentrations, indicating entrapment of air bubbles during recharge, are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over vegetated areas on the lower slopes, as indicated by ?13C-dissolved inorganic carbon values that are consistent with incorporation of CO2 from soil respiration.

Singleton, Michael J.; Moran, Jean E.

2010-12-01

156

Detection of high molecular weight organic tracers in vegetation smoke samples by high-temperature gas chromatography-mass spectrometry  

SciTech Connect

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 with mass spectrometry is not so common and application to aerosols is novel. The HTGC and HTGC-MS analyses of smoke samples taken by particle filtration from combustion of different species of plants provided the characterization of various classes of HMW compounds reported to occur for the first time in emissions from biomass burning. Among these components are a series of wax esters with up to 58 carbon numbers, aliphatic hydrocarbons, triglycerides, long chain methyl ketones, alkanols and a series of triterpenyl fatty acid esters which have been characterized as novel natural products. Long chain fatty acids with more than 32 carbon numbers are not present in the smoke samples analyzed. The HMW compounds in smoke samples from the burning of plants from Amazonia indicate the input of directly volatilized natural products in the original plants during their combustion. However, the major organic compounds extracted from smoke consist of a series of lower molecular weight polar components, which are not natural products but the result of the thermal breakdown of cellulose and lignin. In contrast, the HMW natural products may be suitable tracers for specific sources of vegetation combustion because they are emitted as particles without thermal alternation in the smoke and can thus be related directly to the original plant material.

Elias, V.O.; Simoneit, B.R.T. (Oregon State Univ., Corvallis, OR (United States)); Pereira, A.S.; Cardoso, J.N. (Univ. Federal do Rio de Janeiro (Brazil)); Cabral, J.A. (Inst. de Pesquisas da Amazonia, Amazonas (Brazil))

1999-07-15

157

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

PubMed

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

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

2009-07-30

158

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

159

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

NASA Astrophysics Data System (ADS)

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.

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

2004-12-01

160

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-J lines of dense gas tracers  

Microsoft Academic Search

Context: Single-dish observations of molecular tracers have suggested that both star formation and an AGN can drive the gas chemistry of the central ~kpc of active galaxies. The irradiation by UV photons from an starburst or by X-rays from an AGN is expected to produce different signatures in molecular chemistry, which existing data on low-J lines cannot distinguish, as they

J. P. Pérez-Beaupuits; M. Spaans; S. Aalto; S. García-Burillo; A. Fuente; A. Usero

2009-01-01

161

Universal model for accurate calculation of tracer diffusion coefficients in gas, liquid and supercritical systems.  

PubMed

In this work it is presented a new model for accurate calculation of binary diffusivities (D12) of solutes infinitely diluted in gas, liquid and supercritical solvents. It is based on a Lennard-Jones (LJ) model, and contains two parameters: the molecular diameter of the solvent and a diffusion activation energy. The model is universal since it is applicable to polar, weakly polar, and non-polar solutes and/or solvents, over wide ranges of temperature and density. Its validation was accomplished with the largest database ever compiled, namely 487 systems with 8293 points totally, covering polar (180 systems/2335 points) and non-polar or weakly polar (307 systems/5958 points) mixtures, for which the average errors were 2.65% and 2.97%, respectively. With regard to the physical states of the systems, the average deviations achieved were 1.56% for gaseous (73 systems/1036 points), 2.90% for supercritical (173 systems/4398 points), and 2.92% for liquid (241 systems/2859 points). Furthermore, the model exhibited excellent prediction ability. Ten expressions from the literature were adopted for comparison, but provided worse results or were not applicable to polar systems. A spreadsheet for D12 calculation is provided online for users in Supplementary Data. PMID:23601290

Lito, Patrícia F; Magalhães, Ana L; Gomes, José R B; Silva, Carlos M

2013-05-17

162

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

NASA Astrophysics Data System (ADS)

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.

Imanishi, Masatoshi; Nakanishi, Kouichiro

2014-07-01

163

Proton nuclear activation in stable tracer technique for ruthenium metabolism studies  

NASA Astrophysics Data System (ADS)

A methodology is presented, based on proton nuclear activation (PNA), for the contemporary determination of two stable isotopes of ruthenium in biological samples. This technique can be successfully applied in studying the biokinetics of oligoelements, avoiding radiation hazards. On the basis of the possible proton-induced nuclear reactions and the decay characteristics of radioactive products, (p, n) reactions on 99Ru and 101Ru resulted to be the most convenient. The minimum detectable quantities resulted to be 15 and 3 ng/ml of plasma respectively. Ru fractional intestinal absorption in an experimental animal was determined, as a feasibility test for applications to humans. Following double tracer technique, one male rabbit was orally given 1 mg of 99Ru and was injected 78 ?g of 101Ru. Eleven blood samples were drawn within 300 min after administration. Concentrations in plasma samples of intravenously and orally given Ru tracers are reported, as a function of time after administration. Fractional intestinal absorption was determined from concentrations of both isotopes, using the convolution integral technique. A Ru intestinal absorption of (5.5 ± 0.8)% within 300 min from the oral administration was obtained. The results show the effectiveness of this methodology and its applicability for future investigations in humans.

Cantone, M. C.; de Bartolo, D.; Gambarini, G.; Giussani, A.; Ottolenghi, A.; Pirola, L.; Hansen, Ch.; Roth, P.; Werner, E.

1994-12-01

164

Tracer Recovery and Mixing from Two Geothermal Injection-Backflow Studies  

Microsoft Academic Search

Injection-backflow tracer testing on a single well is not a commonly used procedure for geothermal reservoir evaluation, and, consequently, there is little published information on the character or interpretation of tracer recovery curves. Two field experiments were conducted to develop chemical tracer procedures for use with injection-backflow testing, one on the fracture-permeability Raft River reservoir and the other on the

R. M. Capuano; M. C. Adams; P. M. Wright

1983-01-01

165

The use of a 18 O tracer and Rutherford backscattering spectrometry to study the oxidation mechanism of NiAl  

Microsoft Academic Search

The oxidation mechanism of NiAl was investigated in the temperature range between 1170 K and 1420 K. Oxidation was performed by alternating exposure of the samples to natural oxygen and oxygen gas enriched with 18O. The 18O tracer was profiled by using the reaction with 800 keV protons, 18O(p,?)15N. Rutherford Backscattering Spectrometry of 2 MeV 4He+ was used to check

E. W. A. Young; J. H. W. De Wit

1985-01-01

166

Investigation of Contaminant Transport and Dispersion in New York Harbor by a High Resolution SF6 Tracer Study  

NASA Astrophysics Data System (ADS)

Sulfur hexafluoride (SF6) has been used successfully as a deliberate tracer for rivers, estuaries, and coastal areas, due to its inert nature, non-toxicity, and extremely low detection limit. An automated, high-resolution SF6 measurement system mounted on a boat was recently developed for several projects on the Hudson River. The system has a sampling interval of two minutes and a detection limit of 1 x 10-14 mol L-1. Real-time data visualization enables revisions of sampling strategy during the experiment. A single injection has allowed observation of advection rates, dispersion processes, and air-water gas exchange for up to two weeks, and longer experiments are possible. This equipment, with minor modifications, was applied to New York Harbor in July 2002. New York Harbor is one of the busiest seaports in the United States, processing nearly \\100 billion in cargo each year. Most of the shipping facilities are located in Newark Bay (approximately 15 km^{2}) or in two adjacent channels: the Kill van Kull (6 km long) and the Arthur Kill (20 km long). Newark Bay, which is mostly saline, is fed by the Hackensack and Passaic Rivers, both of which flow through heavily industrialized areas. Ultimately, these waters drain through the Kills to Raritan Bay and the Atlantic Ocean. Due to a combination of point sources, runoff, wastewater treatment plants, and emissions from the shipping industry, Newark Bay and the Kills receive a large volume and variety of contaminants, including petroleum, heavy metals, PCBs, and dioxins. In addition, much of the area is subject to ongoing and extensive navigational dredging, causing widespread re-suspension of previously deposited contaminants. A small quantity (ca. 2 mols) of SF_{6}$ was injected into northern Newark Bay to investigate the spreading of water throughout the Bay, the Kills, and the tidal portions of the Passaic and Hackensack Rivers. The tracer was successfully monitored across most of this area for 12 consecutive days. Most measurements were taken at a depth of 1 m, with deeper profiles at certain locations. Numerous CTD casts were made to examine the halocline and thermocline at different points. The study period coincided with relatively dry and calm conditions. The data suggest rapid initial dispersion, both laterally and vertically, driven by the tides. However, flushing of the area as a whole was slow during the study period. After two weeks, the tracer persisted throughout Newark Bay, the Kills, and the lower reaches of the rivers. Bulk seaward advection was weak, although a considerable quantity of tracer found its way out of the Kills due to tidal action, whereupon it was heavily diluted in Raritan Bay or Upper New York Bay. Overall, the study enables prediction of available response time for certain contamination events, while also providing critical validation data for computational fluid dynamics models of this area.

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

2002-12-01

167

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

SciTech Connect

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.

Wright, S.C.

1990-01-01

168

Controls on Hyporheic Nitrate Removal: Assessing Transport and Substrate Limitations with 15N Tracer Studies (Invited)  

NASA Astrophysics Data System (ADS)

We examined transport time and substrate controls on hyporheic (HZ) nitrification and denitrification in an upland agricultural stream with a series of 15N tracer studies - whole-stream and in situ well-to-well steady-state 15NO3- and conservative tracer (Cl-) addition experiments. For the whole-stream experiment, we measured relevant solute, 15N isotope, and hydraulic transport conditions of the reach and along HZ flowpaths of an instrumented gravel bar. HZ exchange was observed across the entire gravel bar with flowpath lengths up to 4.2m and corresponding median residence times greater than 28.5h. The HZ transitioned from a net nitrification environment at its head (small residence times, <6.9h) to a net denitrification environment at its tail (large residence times, 6.9-28.5h). HZ denitrification was confirmed as 15N2 was produced across the entire gravel bar. Production of 15N2 across all observed flowpaths and residence times indicated that denitrification microsites are present even where net nitrification occurred. At large residence times, the rate of denitrification decreased despite persistent anoxic conditions, indicating substrate (NO3- and carbon) limitations. Consequently, we conducted in situ 15NO3-, conservative tracers (Cl- and Br), and acetate injection experiments to determine how the availability of labile dissolved organic carbon (DOC) as acetate influences microbial denitrification in the HZ, especially along anoxic flowpaths with large residence times. The acetate addition to the HZ stimulated significant increases in 15N2 production by factors of 2.7 to 26.1 in all receiving wells, and significant decreases of NO3- and DOC aromaticity in the wells most hydrologically connected to the injection. Further, 100% of acetate was retained in the HZ, a portion of which is due to biological consumption. These studies demonstrate that: 1. the HZ is an active nitrogen sink in this study system, 2. the distinction between net nitrification and denitrification in the HZ is a function of residence time and exhibits threshold behavior, and 3. microbial denitrification in anaerobic portions of the HZ can be limited by labile DOC supply.

Zarnetske, J. P.; Haggerty, R.; Wondzell, S. M.; Baker, M. A.

2010-12-01

169

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, July 1, 1995--September 30, 1995.  

National Technical Information Service (NTIS)

Laboratory work on tracers to be used for C-Well tracer tests is complete. Solubilities for fluorinated benzoic acids in J13 water were determined and the stability of these compounds to both degradation and sorption on ground tuff measured in batch and c...

K. Stetzenbach I. Farnham

1995-01-01

170

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, July 1, 1995September 30, 1995  

Microsoft Academic Search

Laboratory work on tracers to be used for C-Well tracer tests is complete. Solubilities for fluorinated benzoic acids in J13 water were determined and the stability of these compounds to both degradation and sorption on ground tuff measured in batch and column tests.

K. Stetzenbach; I. Farnham

1995-01-01

171

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study. Progress report, July 1, 1995--September 30, 1995  

SciTech Connect

Laboratory work on tracers to be used for C-Well tracer tests is complete. Solubilities for fluorinated benzoic acids in J13 water were determined and the stability of these compounds to both degradation and sorption on ground tuff measured in batch and column tests.

Stetzenbach, K.; Farnham, I. [Nevada Univ., Las Vegas, NV (United States). Harry Reid Center for Environmental Studies

1995-12-01

172

A tracer study of ventilation in the Japan/East Sea  

NASA Astrophysics Data System (ADS)

During the Circulation Research in East Asian Marginal Seas (CREAMS) summer cruises in 1999, a suite of samples was collected for tracer analysis. Oxygen isotopes combined with tritium-helium ventilation timescales and noble gas measurements give unique insights into the ventilation of water masses in the Japan/East Sea (JES). In particular, noble gases and oxygen isotopes are indicators of brine rejection, which may assist in explaining the recent changes observed in the ventilation of the JES. Oxygen isotope data presented here indicate that both thermally driven convection and brine rejection have played significant roles in deep-water formation but that brine rejection is unlikely to be a significant contributor at the moment. A 6-box ventilation model of the JES, calibrated with tritium and helium-3 measurements, performed better when a significant decrease of dense-water formation rates in the mid-1960s was incorporated. However, the model calculations suggest that Japan Sea Intermediate Water formation is still occurring. Subduction of sea-ice melt water may be a significant ventilation mechanism for this water mass, based on an argon saturation minimum at the recently ventilated salinity minimum in the northwestern sector of the JES. The salinity and oxygen isotope budgets imply a potential bottom-water formation rate of 3.97±0.89×10 12 m 3 yr -1 due to brine rejection, which could account for a time averaged fraction of between 25% and 35% of the ventilation of subsurface water formation in the JES.

Postlethwaite, C. F.; Rohling, E. J.; Jenkins, W. J.; Walker, C. F.

2005-06-01

173

Reaeration coefficients of six streams in New York; a comparison of results obtained by a hydrocarbon-gas tracer method with those obtained by radioactive tracers and predictive equations  

USGS Publications Warehouse

Stream-reaeration measurements were made in selected reaches on six streams in New York State from 1978 to 1981 with hydrocarbon-gas and dye tracers. The sites were Canadaigua Outlet near Canadaigua, Oswego River at Fulton, Hudson River at Fort Miller, Cayadutta Creek near Johnstown, Chenango River near Morrisville, and Payne Brook near Hamilton. The reaches represent a wide range of discharge, water-surface slope, velocity, and streambed composition. Flows ranged from less than 2 cu ft/sq on the Chenango River to 4,100 cu ft/sq on the Hudson River, and water-surface slope within the reaches ranged from less than 1 foot/mile on the Hudson and Oswego Rivers to more than 50 ft/mi on Cayadutta Creek. The corresponding stream-reaeration coefficients ranged from 0.77 units/day for one reach on Canadaigua Outlet to 52 units/day on Cayadutta Creek. The reaeration coefficients for Canadaigua Outlet compared well with those obtained on the same reach 10 years earlier by radioactive tracers. Comparison of measured reaeration coefficients with those calculated from 10 predictive equations based on stream-channel characteristics yielded mean errors that range from 51% to 103%. No single equation gave reliable accuracy for all stream reaches. (USGS)

Stedfast, D. A.; Draper, R. E.

1986-01-01

174

On the characteristics of the wet deposition process using radon as a tracer gas.  

PubMed

A quantitatively characterised atmospheric process can provide important information on a variety of atmospheric models and help one to understand the deposition process in the atmosphere. In this study, the total activity concentrations of (214)Pb and (214)Bi and the activity ratios of (214)Bi/(214)Pb in collected rain samples were measured by two-inch well-type NaI(Tl) detectors. Observed precipitations were classified by the origins of their air mass (continental/maritime) and their meteorological conditions (cold/warm front, high/low pressure). The result shows that (1) when the air mass passed over the continent of Asia 5 d prior to the precipitation, the activity concentration of radon decay products in the rainwater tended to be higher than when the air mass passed over from the Pacific Ocean; (2) higher activity concentrations were more frequently observed in precipitations accompanied with a cold front than warm/stationary front; (3) in general, the activity ratios of (214)Bi/(214)Pb decrease with increase in rain intensity. PMID:24714112

Liu, Heng; Daisuke, Kondo; Motokiyo, Matsuda; Hirao, Shigekazu; Moriizumi, Jun; Yamazawa, Hiromi

2014-07-01

175

Rocky Flats 1990--91 winter validation tracer study: Volume 1  

SciTech Connect

During the winter of 1990--91, North American Weather Consultants (NAWC) and its subcontractor, ABB Environmental Services (ABBES), conducted a Winter Validation Study (WVS) for EG&G Rocky Flats involving 12 separate tracer experiments conducted between February 3 and February 19, 1991. Six experiments were conducted during nighttime hours and four experiments were conducted during daytime hours. In addition, there was one day/night and one night/day transitional experiment conducted. The primary purpose of the WVS was to gather data to further the approval process for the Terrain Responsive Atmospheric Code (TRAC). TRAC is an atmospheric dispersion model developed and operated at the Department of Energy`s (DOE`s) Rocky Flats Plant (RFP) north of Denver, Colorado. A secondary objective was to gather data that will serve to validate the TRAC model physics.

Brown, K.J. [North American Weather Consultants, Salt Lake City, UT (United States)

1991-10-01

176

THE ULTRASTRUCTURAL BASIS OF CAPILLARY PERMEABILITY STUDIED WITH PEROXIDASE AS A TRACER  

PubMed Central

The transendothelial passage of horseradish peroxidase, injected intravenously into mice, was studied at the ultrastructural level in capillaries of cardiac and skeletal muscle. Peroxidase appeared to permeate endothelial intercellular clefts and cell junctions. Abnormal peroxidase-induced vascular leakage was excluded. Neutral lanthanum tracer gave similar results. The endothelial cell junctions were considered to be maculae occludentes, with gaps of about 40 A in width between the maculae, rather than zonulae occludentes. Some observations in favor of concurrent vesicular transport of peroxidase were also made. It is concluded that the endothelial cell junctions are most likely to be the morphological equivalent of the small pore system proposed by physiologists for the passage of small, lipid-insoluble molecules across the endothelium.

Karnovsky, Morris J.

1967-01-01

177

Hydrological Tracer Studies at a DOE IFRC Site in Rifle, Colorado  

NASA Astrophysics Data System (ADS)

Research activities at the Department of Energy Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, have demonstrated that uranium can successfully be removed from groundwater through stimulation of indigenous metal-reducing bacteria, such as members of the Geobacteraceae. While such removal strategies may be effective over short timescales, the large inventory of uranium sorbed to aquifer sediments contributes to a diffuse and widespread contaminant plume at the Rifle site, leading to persistent uranium contamination of groundwater. Complicating the long-term plume behavior are seasonal changes in aquifer properties (e.g. fluctuating water levels, variations in dissolved oxygen and organic carbon, etc.) that accompany snowmelt and elevated river stage in the Colorado River. As the impact of such changes on contaminant behavior at Rifle is poorly understood, development of novel methods, such as isotopic techniques, is warranted to better constrain aquifer flow properties and resolve surface water-groundwater interactions that may influence long-term uranium mobility. In addition to floodplain scale (ca. 10 hectare) studies of uranium mobility, ongoing research at Rifle is investigating coupled approaches to desorb and reductively immobilize pools of sorbed and aqueous uranium. Performed as part of the “Super 8” field experiment (2010), a variety of conservative and non-conservative chemical compounds were injected into the Rifle aquifer to assess transport properties and quantify rates of reductive immobilization of uranium under different alkalinity conditions. Conservative tracers included sodium bromide (20mM), deuterium (500‰), and O-18 (25‰), whereas reactive amendments included sodium bicarbonate (50mM) and sodium acetate (6mM); the latter two were designed to enhance desorption of uranium from sediments and stimulate the activity of uranium-reducing microorganisms, respectively. The need to introduce the reactive amendments at different times and locations necessitated the use of distinct conservative tracers to delineate the spatial distribution of the injected plumes within the aquifer as a function time. Here we report on the field measurements of groundwater stable isotopes and bromide concentrations during the injection experiments. The data indicate differences in groundwater transport pathways as a function of injection and highlight the value of using multiple conservation tracers to resolve overlapping injection source terms.

Gupta, M.; Williams, K. H.; Berman, E. S.; Conrad, M. E.

2010-12-01

178

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

PubMed

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

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

2010-10-01

179

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

NASA Astrophysics Data System (ADS)

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.

Weiler, Markus; Naef, Felix

2003-02-01

180

Studying coupled hydrological and micro-biological processes by means of tracer injections and mathematical models  

NASA Astrophysics Data System (ADS)

To throw light on coupled hydrological, chemical and microbiological processes in treatment wetlands, this study uses both radioactive water and reactive tracers. A tracer mixture consisting of tritiated water, P-32 in the form of PO4- and N-15 in the form of N2O was injected to the 2.6 hectare large Ekeby wetland, Sweden. From the breakthrough curves of tritium, the mean residence time of water in pond 1 can be estimated to be about 3 to 3.5 days. The total injected activity of phosphorus was 17.98 GBq and about 13.73 GBq was recovered at the outlet during the investigation period ending 10 days and 16 hours after the start of the injection. This implies that 24% of the phosphate solution was removed in the November - December period in which the experiment was performed. The total injected amount of N-15 was 42.1 grams and 29.6 grams was retained at the effluent. This means that 30% of the nitrogen was either retained in the wetland or removed due to denitrification. An analysis of regular monitoring data shows that the annual removal rate in the entire wetland (each flow line passes two ponds in series) is about 50% for total phosphorus and 25% for total nitrogen. Probably, the most important mechanism for this removal is adsorption onto particulate matter and deposition. Analyses of vegetation material indicate that a certain (minor) fraction was adsorbed to submersed and emerging macrophytes, like Elodera Canadensis, Thypa sp. (Cattail) and Glyceria sp. (Manna grass). A 2D mathematical model for both water flow and solute transport could explain the N-transport through the wetland. The model accounts for the rate-limited exchange with bed sediments and denitrification in the water and bed sediment. Independent batch tests indicate a particularly high microbiological activity in the bed sediments. The rate-limited exchange with the bed limits also the denitrification capacity of the wetland.

Worman, A.; Kjellin, J. P.; Lindahl, A.; Johansson, H.

2005-05-01

181

Trends of radionuclide sorption by estuarine sediments. Experimental studies using 133Ba as a tracer.  

PubMed

Sediments play an important (but still poorly understood) role in the dispersion and final fate of radionuclides and other hazardous materials in aquatic systems. Adopting an experimental point of view, the present work deals with the transfer of a radioactive tracer from water to sediments. Sediments and waters were sampled in the Odiel and Tinto estuaries (South-West Spain) with anthropogenic-enhanced 226Ra concentrations. 133Ba was used as a tracer since it is a gamma emitter and a good analogue of the environmental behaviour of 226Ra. Laboratory experiments have been carried out to quantify the uptake kinetics of 133Ba by sediments in aqueous suspensions and by sediment cores under a water column at rest. Depth distributions of 133Ba in sediments have been studied with different contact times and using sediment samples with different grain sizes. The results reveal an important and fast uptake by suspended sediments (up to 40% in 10 min with a 20 g l(-1) suspension) and sediment cores (up to 70% in a few minutes). The kinetics of the uptake by suspended sediments could be reasonably described by a model of two parallel and reversible reactions followed by a weakly-reversible reaction. The total uptake and the rate of reaction decreased with the increment of grain size. Furthermore, uptake following diffusion through the interstitial water was hardly detectable beyond 1 cm depth. For the case with more experimental results, the depth distribution could be reasonably described by the analytical solution based on the use of an effective diffusion coefficient (4.2 x 10(-12) m2 s(-1)) and the measured intrinsic distribution coefficient (kd = 63 +/- 6 l kg(-1)). PMID:14967515

Barros, H; Laissaoui, A; Abril, J M

2004-02-01

182

Quantifying the contribution of grape hexoses to wine volatiles by high-precision [u(13)c]-glucose tracer studies.  

PubMed

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

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

2014-07-16

183

A fluorescence correlation spectroscopy study of macromolecular tracer diffusion in polymer solutions.  

PubMed

We discuss the manner in which the dynamics of tracer polystyrene chains varies with the concentration of matrix polystyrene chains dissolved in toluene. Using fluorescence correlation spectroscopy and theory, it is shown that the cooperative diffusion coefficient of the matrix polystyrene chains can be measured by fluorescence correlation spectroscopy in the semidilute entangled concentration regime. In addition the self-diffusion coefficient of the tracer polystyrene chains can be detected for arbitrary concentrations. The measured cooperative diffusion coefficient is independent of the molecular weight of the tracer polystyrene chains because it is a characteristic feature of the transient entanglement network. PMID:21406777

Zettl, Ute; Ballauff, Matthias; Harnau, Ludger

2010-11-23

184

The Voices of Their Childhood: Families and Early Years' Practitioners Developing Emancipatory Methodologies through a Tracer Study  

ERIC Educational Resources Information Center

The Pen Green Tracer Study questions the difference we may or may not have made to children's lives. An initial cohort of young people, now aged between 11-20, revisited their nursery in 2010. Their stories prompted discussion on parental involvement and advocacy within the education system, key worker attachment, and children's sense of self. Our…

Whalley, Margy; Arnold, Cath; Lawrence, Penny; Peerless, Sally

2012-01-01

185

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

186

Validation studies of iodine-123-iodoamphetamine as a cerebral blood flow tracer using emission tomography.  

PubMed

We studied the radioisotope iodine-123-iodoamphetamine ([123I]IMP) and its performance in single-photon emission computed tomographic (SPECT) studies of cerebral blood flow (CBF). In seven normal volunteers, IMP/SPECT CBF measurements were calculated using a two-compartment model and were compared with the results of CBF measurements utilizing (O15)-H2O and positron emission tomography (PET). Calculated mean PET CBF was 57.6 ml/100 g/min while the SPECT CBF value was 47.3 ml/100 g/min. The response of IMP/SPECT CBF to alterations in arterial PaCO2 was studied in hypo-, eu- and hypercarbic subjects. SPECT CBF values showed a reactivity of 1.03 ml/100 g/min per mmHg PaCO2 change. These results show that the IMP/SPECT CBF technique may be used for quantitative imaging of CBF in man. They provide further support for IMP as a CBF tracer. PMID:2384805

Greenberg, J H; Kushner, M; Rango, M; Alavi, A; Reivich, M

1990-08-01

187

Quantifying uncertainties in tracer-based hydrograph separations: a case study for two-, three- and five-component hydrograph separations in a mountainous catchment  

Microsoft Academic Search

The hydrograph separation technique using natural tracers, in which different runoff components are quantified according to their chemical signature, is a widely used method for investigating runoff generation processes at the catchment scale. The first objective of this study is to demonstrate a modified methodology for separating three and five runoff components using 18O and dissolved silica as tracers. The

Stefan Uhlenbrook; Simon Hoeg

2003-01-01

188

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

USGS Publications Warehouse

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.

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

189

Intermediate-Scale Tests of the Gas-Phase Partitioning Tracer Method for Measuring Soil-Water Content  

Microsoft Academic Search

which retards its movement with respect to that of the nonpartitioning volumetric soil-water content of 0.06. Following an infiltration tracer. This retardation is a function of the soil-water content. The volumetric soil-water contents estimated from comparative moment event to increase the soil-water content to 0.15, two more analysis of the measured breakthrough curves were compared with experiments (3 and 4)

T. D. Carlson; M. S. Costanza-Robinson; J. Keller; P. J. Wierenga; M. L. Brusseau

2003-01-01

190

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain site characterization study. Final report  

SciTech Connect

Extensive tracer testing is expected to take place at the C-well complex in the Nevada Test Site as part of the Yucca Mountain Site Characterization Project. The C-well complex consists of one pumping well, C3, and two injection wells, C1 and C2 into which tracer will be introduced. The goal of this research was to provide USGS with numerous tracers to completed these tests. Several classes of fluorinated organic acids have been evaluated. These include numerous isomers of fluorinated benzoic acids, cinnamic acids, and salicylic acids. Also several derivatives of 2-hydroxy nicotinic acid (pyridone) have been tested. The stability of these compounds was determined using batch and column tests. Ames testing (mutagenicity/carcinogenicity) was conducted on the fluorinated benzoic acids and a literature review of toxicity of the fluorobenzoates and three perfluoro aliphatic acids was prepared. Solubilities were measured and method development work was performed to optimize the detection of these compounds. A Quality Assurance (QA) Program was developed under existing DOE and USGS guidelines. The program includes QA procedures and technical standard operating procedures. A tracer test, using sodium iodide, was performed at the C-well complex. HRC chemists performed analyses on site, to provide real time data for the USGS hydrologists and in the laboratories at UNLV. Over 2,500 analyses were performed. This report provides the results of the laboratory experiments and literature reviews used to evaluate the potential tracers and reports on the results of the iodide C-well tracer test.

Stetzenbach, K.; Farnham, I.

1996-06-01

191

Identification and characterization of conservative organic tracers for use as hydrologic tracers for the Yucca Mountain Site characterization study; Progress report, April 1, 1993--June 30, 1993  

SciTech Connect

This report is in two parts one for the fluorinated benzoic acids and one for the fluorinated aliphatic acids. The assumptions made in the report regarding the amount of tracer that will be used, dilution of the tracer during the test and the length of exposure (if any) to individuals drinking the water were made by the authors. These assumptions must really come from the USGS hydrologists in charge of the c-well tracer testing program. Accurate estimates of dilution of the tracer during the test are also important because of solubility limitations of some of the tracers. Three of the difluorobenzoic acids have relatively low solubilities and may not be usable if the dilution estimates are large. The toxicologist that reviewed the document agreed with our conclusion that the fluorinated benzoic and toluic acids do not represent a health hazard if used under the conditions as outlined in the report. We are currently testing 15 of these compounds, and if even if three difluorobenzoic acids cannot be used because of solubility limitations we will still have 12 tracers. The toxicologist felt that the aliphatic fluorinated acids potentially present more of a health risk than the aromatic. This assessment was based on the fact of a known allergic response to halothane anesthetic. This risk, although minimal, is known and he felt that was enough reason to recommend against their use. The authors feel that the toxicologists interpretation of this risk was overly conservative, however, we will not go against his recommendation at this time for the following reasons. First, without the aliphatic compounds we still have 12 to 15 fluorinated aromatic acids which, should be enough for the c-well tests. Second, to get a permit to use aliphatic compounds would undoubtedly require a hearing which could be quite lengthy.

Dombrowski, T.; Stetzenbach, K.

1993-08-01

192

The use of air as a natural tracer infractured hydrothermal systems, Los Azufres, Mexico, case study  

SciTech Connect

Injection of atmospheric air mixed with cold water has been occurring since 1982 at the Los Azufres geothermal field. Several chemical and thermodynamical evidences show that air injection into this fractured hydrothermal system could be considered as a long term natural tracer test. Nitrogen and Argon separated from the air mixture migrate, under the action of the induced injection-extraction gradient, from reinjection sectors to production zones following preferential paths closely related to high permeability conduits. A coarse numerical estimation of the average permeability tensor existing at Tejamaniles, the southern sector, explains the unsuccessful recovery of the artificial tracer tests performed in past years: the anisotropic nature of the fractured volcanic rock would demand considerably quantities of tracer in order to be detected at the producing wells, especially when fluid extraction was low. At the same time concentrations of calcium, cesium, chloride, potassium, rubidium and sodium, are increasing in the liquid produced by the oldest wells of this field's sector.

Mario Cesar Sudrez Arriaga; Hector Gutierrez Puente, Josefina Moreno Ochoa

1991-01-01

193

Tracer airflow measurement system (TRAMS)  

DOEpatents

A method and apparatus for measuring fluid flow in a duct is disclosed. The invention uses a novel high velocity tracer injector system, an optional insertable folding mixing fan for homogenizing the tracer within the duct bulk fluid flow, and a perforated hose sampling system. A preferred embodiment uses CO.sub.2 as a tracer gas for measuring air flow in commercial and/or residential ducts. In extant commercial buildings, ducts not readily accessible by hanging ceilings may be drilled with readily plugged small diameter holes to allow for injection, optional mixing where desired using a novel insertable foldable mixing fan, and sampling hose.

Wang, Duo (Albany, CA)

2007-04-24

194

Comparison of [11C]cocaine binding at tracer and pharmacological doses of baboon brain: A PET study  

SciTech Connect

In vitro studies have shown that cocaine (C) binds to both high and low affinity sites on the dopamine transporter (DAT). We have previously characterized the binding of tracer doses of [{sup 11}C]cocaine (C*)to a high affinity site on the DAT. To assess if in vivo C also binds to low affinity sites we used PET to compare binding of tracer doses (17.8{plus_minus}12.2 {mu}g C) of C* to pharmacological doses (8 mg of C coadministered with C*). Sixteen paired studies were done to assess test/retest variability, specific versus non specific binding and to characterize binding profile. Dynamic scans were started immediately after injection of C* (5-8 mCi) for 50 min on the CTI-931 (6 x 6 x 6.5 mm FWHM). Time activity curves for tissue concentration and for unchanged tracer in plasma were used to calculate the transport constant between plasma and tissue (K1) and to obtain the distribution volume (DV). The ratio of the DV in striatum (ST) to that in cerebellum (CB) (which corresponds to Bmax/Kd-1) was used as model parameter. Peak brain uptake of C* was significantly higher for tracer than for pharmacological doses (0.041 versus 0.033 % dose/cc), as were the values for K1 (1.07{plus_minus}0.21 versus 0.68{plus_minus}0.26 (t=3.0 p<0.01)). Repeated measures were reproducible for tracer ({plus_minus}2%) and pharmacological doses of C* ({plus_minus}4%). Tracer dose C* showed highest binding and slowest clearance in ST which was reduced by C (0.5-2.0 mg/kg iv, -25 to -30%) and by drugs that inhibit DAT (2mg/kg nomifensine - 21%, 0.5 mg/kg methylphenidate -12%) and was increased by serotonin transporter inhibitors (5HT-Ti) (2 mg/kg citalopram +11%, 0.5 mg/kg fluoxetine +6%) and not changed by NE transporter inhibitors (0.5 mg/kg desipramine or 2 mg/kg tomoxetine). The increase with (5HT-Ti) may reflect neurotransmitter interactions or changes in bioavailability. At pharmacological doses C* showed homogeneous distribution and was not changed by C nor by any of the above drugs.

Volkow, N.D.; Fowler, J.S.; Logan, J. [Brookhaven National Lab., Upton, NY (United States)] [and others

1994-05-01

195

Seawater Corrosion Studies of Emissively-Coated Haynes 25: Radioactive Tracer Techniques.  

National Technical Information Service (NTIS)

Corrosion rates of uncoated, half- and completely-emissively-coated Haynes 25 have been measured in seawater by use of radioactive tracer techniques. The corrosion rates observed for the (1) uncoated and (2) half- and completely-coated specimens were nomi...

D. A. Kubose H. A. Goya M. G. Lai H. I. Cordova

1967-01-01

196

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-...

197

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

National Technical Information Service (NTIS)

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 a...

J. E. Flaherty K. J. Allwin

2006-01-01

198

Electrogenic Cl ? absorption by Amphiuma small intestine: Dependence on serosal Na + from tracer and Cl ? microelectrode studies  

Microsoft Academic Search

Summary The Na+ requirement for active, electrogenic Cl? absorption byAmphiuma small intestine was studied by tracer techniques and double-barreled Cl?-sensitive microelectrodes. Addition of Cl? to a Cl?-free medium bathingin vitro intestinal segments produced a saturable (Km=5.4mm) increase in shortcircuit current (Isc) which was inhibitable by 1mm SITS. The selectivity sequence for the anion-evoked current was Cl?=Br?>SCN?>NO3?>F?=I?. Current evoked by Cl?

John F. White; Dorothy Ellingsen; Kevin Burnup

1984-01-01

199

Utilizing Mass Measurements in Tracer Studies - A Systematic Approach to Efficient Modeling  

PubMed Central

Tracer enrichment data are fitted by multicompartmental models to estimate rate constants and fluxes or transport rates. In apolipoprotein turnover studies, mass measurements are also available, e.g., apolipoprotein B (apoB) levels in VLDL, IDL and LDL, and are often essential to calculate some of the rate constants. The usual method to use mass measurements is to estimate pool masses along with rate constants. A systematic alternative approach is developed to use flux balances around pools to express some rate constants in terms of the other rate constants and the measured masses. The resulting reduction in the number of parameters to be estimated makes the modeling more efficient. In models that would be unidentifiable without mass measurements, the usual approach and the proposed approach yield identical results. In a simple two-pool model, the number of unknown parameters is reduced from four to two. In a published 5-pool model for apoB kinetics with three mass measurements, the number of parameters is reduced from 12 to 9. With m mass measurements, the number of responses to be fitted and the number of parameters to be estimated are each reduced by m, a simplification by 1/4 to 1/3 in a typical pool model. Besides a proportionate reduction in computational effort, there is a further benefit since the dimensionality of the problem is also decreased significantly, which means ease of convergence and a smaller likelihood of suboptimal solutions. While our approach is conceptually straightforward, the dependencies get considerably more complex with increasing model size. To generate dependency definitions automatically, a web-accessible program is available at http://biomath.info/poolfit/constraints.

Ramakrishnan, Rajasekhar; Ramakrishnan, Janak D.

2008-01-01

200

Exploring Hydrofluorocarbons as Groundwater Age Tracers (Invited)  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

201

Observations of isotopic heterogeneities toward embedded cores and binary systems: potential tracers of varying chemical evolutionary pathways in protostellar gas  

NASA Astrophysics Data System (ADS)

Detailed observations of protostellar gas have enabled the study of isotopic anomalies and peculiarities related to solar system chemical evolution, including the discrepancy in 12C/13C between the solar system and local ISM, and the oxygen isotope anomaly observed in meteorites. Further, comparing targets differing in mass, morphology, parent cloud and galactocentric radius offers an expanded view into the protostellar evolutionary process across a range of potential protoplanetary systems. Using the near-infrared CO rovibrational bands obtained with VLT-CRIRES at very high resolution (R ~ 95,000), we derived precise column densities of observable CO isotopologues (12C16O, 13C16O, 12C18O and 12C17O) toward 13 lines-of-site, representing 7 local star-forming clouds. Sources ranged from low-mass embedded cores, protostellar disks, foreground clouds, including 3 binary systems. We found significant heterogeneity in 12CO/13CO abundance ratios (~ 85 to 165) as compared to the solar system and local ISM, which may be in part due to the interplay between the CO ice and gas reservoirs as most strongly evidenced in our cold-gas sources. The finding of more similar values in 12CO/13CO toward the binary systems DoAr24E (Ophiuchus), EC 90 (Serpens), and potentially for VV CrA (Corona Australis), suggests that these data could be tracing homogeneities in chemical evolutionary pathways in binary gas reservoirs (spanning a radius of a few hundred AU) as compared to embedded cores separated in either the same parent cloud or between star-forming clouds. Heterogeneities in oxygen isotope ratios are found toward several objects in the same star-forming cloud (Ophiuchus) and between objects in 5 different clouds, with a potential correlation with evolutionary stage. Using Keck-NIRSPEC (R ~ 25,000), we have recently expanded these observations of protostellar carbon and oxygen reservoirs to include high mass, high luminosity protostars at varying locations toward the Galactic plane.

Smith, Rachel L.; Pontoppidan, Klaus M.; Blake, Geoffrey A.; Boogert, A. C. Adwin; Lockwood, Alexandra C.

2013-07-01

202

Reworked calcareous nannofossils as ocean dynamic tracers: The Guadiana shelf case study (SW Iberia)  

NASA Astrophysics Data System (ADS)

For most micropalaeontological studies the presence of reworked specimens is usually considered as a disturbing factor where palaeoenvironmental or biostratigraphic interpretations are to be made. However, reworking of microfossils such as calcareous nannofossils can be used as an additional parameter in routine micropalaeontological work, providing useful information on erosion-transport processes acting on silty-clay sized particles deriving from areas surrounding the sedimentary basin under study. Most of the reworked calcareous nannofossils found in the Guadiana estuary water column (September 2001), adjacent shelf surface sediments, and a slope section of the Gulf of Cadiz were mainly of Upper Cretaceous age (Campanian to Maastrichtian), being dominated by Biscutum spp., Cribrosphaerella ehrenbergii, Prediscosphaera cretacea and Watznaueria barnesae. Since there are no Upper Cretaceous outcrops in the Guadiana's hydrographic basin or southern Portugal, the source of this material must be located elsewhere. Matrix breccias from mud volcanoes discovered in deeper water southern Portuguese and western Moroccan margins of the Gulf of Cadiz during the TTR-10 cruise in July/August 2000, as well as silty-clay sediments from its slopes, revealed similar calcareous nannofossil assemblages as those found on the Algarve continental shelf and inside the Guadiana's estuary. This may indicate that most of the reworked nannofossils have their origin in deepwater areas of the Gulf of Cadiz. The good preservation of most of the reworked Cretaceous nannofossils suggest that, shortly after resuspension, swift transport occurred from the source area to the coastal region of the Guadiana's river mouth, implicating a northward change in the deep Mediterranean water direction within the Gulf of Cadiz, which reaches the upper southwest Iberia slope. The Mediterranean Outflow is, therefore, the major mechanism accountable for transporting Upper Cretaceous material to the southwest Iberian margin and the Atlantic inflow, together with longitudinal coastal currents, is the probable responsible for carrying and spreading eastward these reworked silty-clay sized particles over the Portuguese and Spanish continental shelf. This case study is a clear example of the potential importance of calcareous nannofossils as ocean dynamic tracers for particles within the silty-clay fraction.

Ferreira, J.; Cachão, M.; González, R.

2008-08-01

203

Study of solid and liquid behavior in large copper flotation cells (130 m2) using radioactive tracers  

NASA Astrophysics Data System (ADS)

The behavior of the solid and liquid phases, in large flotation cells, was characterized by means of the radioactive tracer technique. The use of radioactive tracers enabled the identification of the Residence Time Distribution, of floatable and non-floatable solid, from continuous (on-line) measuring at the output streams of the flotation cells. For this study, the proper radioactive tracers were selected and applied in order to characterize the different phases; i.e. for liquid phase Br-82 as Ammonium Bromide, for floatable solid recovered in the concentrate Cu-64, and for non-floatable solid in three particle size classes (coarse: >150 ?m, intermediate: <150 ?m and >45 ?m, and fine: <45 ?m), Na-24. The experimental results confirmed the strong effect of particle size on the Residence Time Distribution, and mean residence time of solids in larger flotation cells, and consequently in flotation hydrodynamics. From a hydrodynamic point of view, the experimental data confirmed that a single mechanical flotation cells, of large size, can deviate significantly from perfect mixing. The experimental work was developed in a 130 m3 industrial flotation cell of the rougher circuit at El Teniente Division, Codelco-Chile.

Díaz, F.; Jiménez, O.; Yianatos, J.; Contreras, F.

2013-05-01

204

Across North America Tracer Experiment (ANATEX). Model evaluation study. Final report  

Microsoft Academic Search

Three perfluorocarbon tracer gases were released at 2.5-day or 5.0-day intervals from two sites in central North America and sampled for 24-hr periods at 77 surface sites. The source-receptor distances ranged from less than 30 km to 3,000 km. The data were used to evaluate the long-range transport and diffusion simulations of acid deposition models and to establish a range

T. L. Clark; R. D. Cohn

1990-01-01

205

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean  

USGS Publications Warehouse

Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and atmospheric transport.

Kumar, A.; Abouchami, W.; Galer, S. J. G.; Garrison, V. H.; Williams, E.; Andreae, M. O.

2014-01-01

206

Preliminary Results from a Gas Tracer Injection Experiment in the Upper Oceanic Crust on the Eastern Flank of the Juan de Fuca Ridge  

NASA Astrophysics Data System (ADS)

We present the first results from a gas tracer injection experiment in the ocean crust on the eastern flank of the Juan de Fuca Ridge, in an area of vigorous hydrothermal circulation. A mixture of tracers was injected in Hole 1362B in 2010, during IODP Expedition 327, as part of a 24-hour pumping experiment. Fluid samples were subsequently collected from this hole and three additional holes (1026B, 1362A, and 1301A), located 300 to 500 m away. The array of holes is located on 3.5 M.y. old seafloor, and oriented N20°E, subparallel to the Endeavor Segment of Juan de Fuca Ridge, 100 km to the west. Sulfur hexafluoride (SF6) was injected at a concentration of 0.0192 mol/min, with fluid pumping rate of 6.7 L/s for 20.2 h, resulting in a mean concentration of 47.6 ?M and 23.3 mol of SF6 being added to crustal fluids. Borehole fluid samples were collected in copper coils using osmotic pumps attached to the wellheads of several long-term, subseafloor observatories (CORKs). These samples were recovered from the seafloor using a remotely-operated vehicle in 2011 and 2013. Analyses of SF6 concentrations in samples recovered in 2011 indicate the first arrival of SF6 in Hole 1301A, 550 m south of the injection Hole 1362B, ~265 days after injection. This suggests that the most rapid lateral transport of gas (at the leading edge of the plume) occurred at ~2 m/day. Samples recovered in 2013 should provide a more complete breakthrough curve, allowing assessment of the mean lateral transport rate. Additional insights will come from analysis of metal salts and particle tracers injected contemporaneously with the SF6, the cross-hole pressure response to injection and a two-year fluid discharge experiment. Additional wellhead samples will be collected in Summer 2014, as will downhole osmosamplers deployed in perforated casing within the upper ocean crust in Holes 1362A and 1362B.

Neira, N. M.; Clark, J. F.; Fisher, A. T.; Wheat, C. G.

2013-12-01

207

Textural characterization of media composed of compacted pieces of cardboard and polyethylene using a gas tracer method.  

PubMed

The aim of this work is the experimental determination of effective transport properties of porous media consisting of compacted pieces of cardboard and polyethylene (PE). The proposed method itself is more general and can be applied to many different materials and contexts. Three major transport properties were determined: porosity, tortuosity factor and permeability. Three parameters characterizing the media were varied over a wide range: the bulk density, the size of the elements entering the mix, and the proportion of cardboard and PE in the mix. The properties were measured by means of a specially designed experimental device based on miscible gas tracing. The porosity and tortuosity factor were simultaneously determined by parametric identification, based on the experimental sample output response to an inlet gas concentration step change compared to the results of a direct numerical model. Permeability was calculated in the standard way from the measurement of the pressure drop across the sample. The reproducibility of the measurements was very good. It was found that changing the material density of the medium significantly affects all three structural properties. When the bulk density is varied between 300 and 900 kg m(-3), the tortuosity factor varies in a range as large as 18-8 and the permeability decreases by a ratio of 2-3. The tortuosity factor shows unusual variation, characterized by a decrease when density is increased above 500 kg m(-3). The size of the elements does not significantly affect the structural properties of the medium in the range of parameters studied. PMID:18947990

Kacem, M; Salvador, S; Quintard, M

2009-02-01

208

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

SciTech Connect

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.

Li, Tingwen; Guenther, Chris

2012-03-01

209

Radioisotope tracer studies in the NASA Skylab ethothermic brazing experiment M-552  

NASA Technical Reports Server (NTRS)

The first use of radioisotope tracer for mapping flow patterns during brazing of metal components in a space environment (near-zero gravity) proved successful. A nickel ferrule was brazed to a nickel tube with Lithobraze BT (71.8% Ag, 28% Cu, 0.2% Li) which contained a trace amount of radioactive Ag-110. Mapping of the flow of the braze alloy in the annulus formed between the tube and the concentric ferrule was determined by counting the radiation intensity as a function of position in the braze joint. Significant information concerning the thermal history of the braze was determined.

Braski, D. N.; Adair, H. L.; Kobisk, E. H.

1974-01-01

210

Viral Tracer Studies Indicate Contamination of Marine Waters by Sewage Disposal Practices in Key Largo, Florida  

PubMed Central

Domestic wastewater disposal practices in the Florida Keys are primarily limited to on-site disposal systems such as septic tanks, injection wells, and illegal cesspits. Poorly treated sewage is thus released into the highly porous subsurface Key Largo limestone matrix. To investigate the fate and transport of sewage in the subsurface environment and the potential for contamination of marine surface waters, we employed bacteriophages as tracers in a domestic septic system and a simulated injection well in Key Largo, Florida. Transport of bacteriophage (Phi)HSIC-1 from the septic tank to adjacent surface canal waters and outstanding marine waters occurred in as little as 11 and 23 h, respectively. Transport of the Salmonella phage PRD1 from the simulated injection well to a canal adjacent to the injection site occurred in 11.2 h. Estimated rates of migration of viral tracers ranged from 0.57 to 24.2 m/h, over 500-fold greater than flow rates measured previously by subsurface flow meters in similar environments. These results suggest that current on-site disposal practices can lead to contamination of the subsurface and surface marine waters in the Keys.

Paul, J. H.; Rose, J. B.; Brown, J.; Shinn, E. A.; Miller, S.; Farrah, S. R.

1995-01-01

211

Across North America Tracer Experiment (ANATEX). Model evaluation study. Final report  

SciTech Connect

Three perfluorocarbon tracer gases were released at 2.5-day or 5.0-day intervals from two sites in central North America and sampled for 24-hr periods at 77 surface sites. The source-receptor distances ranged from less than 30 km to 3,000 km. The data were used to evaluate the long-range transport and diffusion simulations of acid deposition models and to establish a range of uncertainty for various model genres. The performances of three single-layer Lagrangian, six multiple-layer Lagrangian, and two multiple-layer Eulerian models were assessed using quantifiable measures based on comparisons of ensemble mean concentrations and plume widths as well as trajectory errors expressed as a function of transport time. In general, the multiple-layer Lagrangian models performed best in simulating the transport of the tracers, while the Eulerian models performed best in simulating the ensemble concentration frequency distributions. After 0.5 day of transport, trajectory errors ranged from 100 km to 400 km; after 2.5 days, the errors ranged from 300 km to 800 km. Beyond 2.5 days, errors from four Lagrangian models plateaued, while errors for the other models continued to increase, peaking at nearly 1,100 km after 3.5 days.

Clark, T.L.; Cohn, R.D.

1990-06-01

212

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

NASA Astrophysics Data System (ADS)

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.

Rood, Arthur S.

2014-06-01

213

Groundwater age structure and palaeo hydrogeology over a 500 kyr time scale revealed from Krypton 81and a multiple tracer study: Great Artesian Basin  

NASA Astrophysics Data System (ADS)

We report on the most comprehensive set of krypton -81 data to be analysed so far. Our study site is on the western margin of the Great Artesian Basin (GAB). The study area is focused on the western margin of the GAB between the Finke River system in the Northern Territory and the iconic Dalhousie springs in South Australia. This represents the direction of groundwater flow from recharge to discharge through the Dalhousie spring complex. Because of its vast size and the potential for large regional flow systems to occur, the GAB has been considered an ideal basin to test emerging groundwater dating techniques such as Cl-36 and He-4. However both of these techniques are subjected to large degrees of uncertainty, as they require a detailed understanding of different sources and sinks of these two isotopes. Contrasting this Kr-81 is considered to be an ideal tracer as it contains only one source, the atmosphere with no or at most minimal sub surface production. For the first time we have provided a comprehensive suite of analyse not only of Cl-36, He-4, C-14, Ar-39, stable isotopes of the water molecule and noble gases but also, Kr-85 and Kr-81. Our results indicate a spectrum of 'groundwater ages' ranging from modern as indicated by thermonuclear C-14 and Ar-39 up to hundreds of thousands of years as indicated by Kr-81, Cl-36 and He-4. The data set indicates a wide range of stable isotopes of the water molecule as well as variability in noble gas recharge temperatures that suggest that not only has this region been subjected to changes in climate in the recharge zone but also testaments to a changes in the dominate direction of rainfall indicated by a change in recharge mechanism at the beginning of the Holocene. As suggested previously this groundwater flow transect may represent an ideal 'type section' for testing new and emerging environmental tracers in hydrogeology.

Love, A. J.; Purtschert, R.; Jiang, W.; Lu, Z.; Tosaki, Y.; Fulton, S.; Wohling, D.; Shand, P.; Broder, L.; Aeschbach, W.; Rousseau=Gueutin, P.

2013-12-01

214

Numerical simulation of a natural gradient tracer experiment for the natural attenuation study: flow and physical transport.  

PubMed

Results are presented for numerical simulations of ground water flow and physical transport associated with a natural gradient tracer experiment conducted within a heterogeneous alluvial aquifer of the Natural Attenuation Study (NATS) site near Columbus, Mississippi. A principal goal of NATS is to evaluate biogeochemical models that predict the rate and extent of natural biodegradation under field conditions. This paper describes the initial phase in the model evaluation process, i.e., calibration of flow and physical transport models that simulate conservative bromide tracer plume evolution during NATS. An initial large-scale flow model (LSM) is developed encompassing the experimental site and surrounding region. This model is subsequently scaled down in telescopic fashion to an intermediate-scale ground water flow model (ISM) covering the tracer-monitoring network, followed by a small-scale transport model (SSM) focused on the small region of hydrocarbon plume migration observed during NATS. The LSM uses inferred depositional features of the site in conjunction with hydraulic conductivity (K) data from aquifer tests and borehole flowmeter tests to establish large-scale K and flow field trends in and around the experimental site. The subsequent ISM incorporates specified flux boundary conditions and large-scale K trends obtained from the calibrated LSM, while preserving small-scale K structure based on some 4000 flowmeter data for solute transport modeling. The configuration of the ISM-predicted potentiometric surface approximates that of the observed surface within a root mean squared error of 0.15 m. The SSM is based on the dual-domain mass-transfer approach. Despite the well-recognized difficulties in modeling solute transport in extremely heterogeneous media as found at the NATS site, the dual-domain model adequately reproduced the observed bromide concentration distributions. Differences in observed and predicted bromide concentration distributions are attributed to aquifer heterogeneity at the decimeter (dm) and smaller scales. The calibrated transport parameters for the SSM (i.e., 1:7 for the ratio of mobile-to-total porosity; 2.5 x 10(-3) day-1 for the mass-transfer coefficient; 1 m for longitudinal dispersivity; and 0.1 m for transverse dispersivity) are consistent with separate numerical simulations of two earlier tracer experiments at the site. The multiscale modeling approach adopted in this study permits the incorporation of both large-scale geologic features important for flow simulation and small-scale heterogeneities critical for transport simulation. In addition, the dual-domain transport model provides a foundation for multispecies reactive transport modeling studies of natural attenuation of hydrocarbons during NATS. PMID:11447854

Julian, H E; Boggs, J M; Zheng, C; Feehley, C E

2001-01-01

215

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

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.

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

216

Petroleum characterization by perfluorocarbon tracers  

SciTech Connect

Perfluorocarbon tracers (PFTs), a class of six compounds, were used to help characterize the Shallow Oil Zone (SOZ) reservoir at the Naval Petroleum Reserve in California (NPRC) at Elk Hills. The SOZ reservoir is undergoing a pilot gas injection program to assess the technical feasibility and economic viability of injecting gas into the SOZ for improved oil recovery. PFTs were utilized in the pilot gas injection to qualitatively assess the extent of the pilot gas injection so as to determine the degree of gas containment within the SOZ reservoir.

Senum, G.I.; Fajer, R.W. (Brookhaven National Lab., Upton, NY (United States)); Harris, B.R. Jr. (USDOE Naval Petroleum Reserves in California, Tupman, CA (United States)); DeRose, W.E. (Bechtel Petroleum Operations, Inc., Tupman, CA (United States)); Ottaviani, W.L. (Chevron U.S.A., Inc., Bakersfield, CA (United States))

1992-02-01

217

OTEC gas-desorption studies  

SciTech Connect

OTEC gas desorption studies were initiated with the goal of mitigating these effects and were carried out in four areas: (1) vacuum deaeration in a packed column, (2) deaeration in a barometric water intake system, (3) noncondensibles disposal through hydraulic air compression, and (4) OTEC deaeration subsystems' analysis. Laboratory experiments to date have completed the vacuum deaeration test of three different kinds of packings, barometric intake deaeration experiments, and a series of hydraulic air compression tests. Preliminary analyses based on the experimental data have shown that, as compared to the previous baseline study, reduction both in deaerator cost and pumping power can be realized with a combination of barometric intake and packed column deaeration. The design and operation of the gas desorption test loop, experimental and computer simulation results obtained, and an analysis of OTEC deaeration subsystem design based on the test results and their implication on OTEC open-cycle power systems are presented.

Chen, F.C.; Golshani, A.

1981-01-01

218

High-precision isotope ratio mass spectrometry and stable isotope precursors for tracer studies in cell culture.  

PubMed

The use of stable isotope-labeled tracers is demonstrated in an in vitro system with analysis by high-precision isotope ratio mass spectrometry (IRMS), using n-3 long-chain polyunsaturated fatty acid (LCP) biosynthesis from [U-(13)C]18:3n-3 (18:3n-3*) in Y79 human retinoblastoma cells as a model system. The cells were cultured as a suspension in RPMI 1640 medium supplemented with 15% fetal calf serum at 37 degrees C with 5% CO(2) in air. They were harvested by sedimentation and cell lipids were extracted to determine the presence of 18:3n-3* metabolites using gas chromatography-combustion (GCC)-IRMS. As the dose of 18:3n-3* was systematically increased from treatment to treatment, the atom percent excess and the amounts of biosynthesized LCP* increased, while the percentage dose in each n-3 LCP* remained constant. Cultures incubated with 0.5 micromol (10 microM) of albumin-bound 18:3n-3, composed of 18:3n-3* diluted 1/60 or 1/100 with natural abundance 18:3n-3, yielded products with enrichments about 1.5 at.% excess (delta(13)C(PDB) < 1500 per thousand), which is optimal for high-precision measurements. Kinetics in Y79 cells incubated with 18:3n-3* showed that n-3 LCP* incorporation increased over time; 18:3n-3*, 20:5n-3*, 22:5n-3*, and 22:6n-3* were detected at all time points with the 1/60 dilution. These data document experimental parameters for optimal stable isotope use and IRMS detection for in vitro tracer methodology. PMID:11078586

Huang, M C; Muddana, S; Horowitz, E N; McCormick, C C; Infante, J P; Brenna, J T

2000-12-01

219

Atmospheric and soil-gas monitoring for surface leakage at the San Juan Basin CO{sub 2} pilot test site at Pump Canyon New Mexico, using perfluorocarbon tracers, CO{sub 2} soil-gas flux and soil-gas hydrocarbons  

SciTech Connect

Near-surface monitoring and subsurface characterization activities were undertaken in collaboration with the Southwest Regional Carbon Sequestration Partnership on their San Juan Basin coal-bed methane pilot test site near Navajo City, New Mexico. Nearly 18,407 short tons (1.670 × 107 kg) of CO{sub 2} were injected into 3 seams of the Fruitland coal between July 2008 and April 2009. Between September 18 and October 30, 2008, two additions of approximately 20 L each of perfluorocarbon (PFC) tracers were mixed with the CO{sub 2} at the injection wellhead. PFC tracers in soil-gas and in the atmosphere were monitored over a period of 2 years using a rectangular array of permanent installations. Additional monitors were placed near existing well bores and at other locations of potential leakage identified during the pre-injection site survey. Monitoring was conducted using sorbent containing tubes to collect any released PFC tracer from soil-gas or the atmosphere. Near-surface monitoring activities also included CO{sub 2} surface flux and carbon isotopes, soil-gas hydrocarbon levels, and electrical conductivity in the soil. The value of the PFC tracers was demonstrated when a significant leakage event was detected near an offset production well. Subsurface characterization activities, including 3D seismic interpretation and attribute analysis, were conducted to evaluate reservoir integrity and the potential that leakage of injected CO{sub 2} might occur. Leakage from the injection reservoir was not detected. PFC tracers made breakthroughs at 2 of 3 offset wells which were not otherwise directly observable in produced gases containing 20–30% CO{sub 2}. These results have aided reservoir geophysical and simulation investigations to track the underground movement of CO{sub 2}. 3D seismic analysis provided a possible interpretation for the order of appearance of tracers at production wells.

Wells, Arthur W.; Diehl, J. Rodney; Strazisar, Brian R.; Wilson, Thomas; H Stanko, Dennis C.

2012-05-01

220

A comparison of 13C nuclear magnetic resonance and 14C tracer studies of hepatic metabolism.  

PubMed

The gluconeogenic pathway from 13C-labeled substrates, each of which contained the 14C-labeled counterpart at a tracer level, has been followed in isolated rat liver cells and in isolated perfused mouse liver. The gluconeogenic flux from glycerol, the synthesis of glycogen, the stimulation of glycogenolysis by glucagon, the recycling of triacylglycerol, and an increase in pentose cycle activity under the influence of phenazine methosulfate were all observed directly in the 13C NMR spectra of perfused liver or isolated hepatocytes. The relative concentrations of 13C label at specific carbons measured by the NMR spectra under these conditions agreed closely with 14C isotopic distributions measured in extracts of the same doubly labeled samples for specific activities of greater than or equal to 3%. The label distributions measured by both methods were the same to within the experimental errors, which ranged from +/- 2% to +/- 7% in these experiments. PMID:7009612

Cohen, S M; Rognstad, R; Shulman, R G; Katz, J

1981-04-10

221

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

PubMed Central

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.

Maschauer, Simone

2014-01-01

222

Oxygen tracer diffusion in single-crystal alumina  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

223

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

SciTech Connect

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 particles, then tracking them up to 50 km from the Plant by vehicle and aircraft under various typical weather conditions. Able to detect single AgI particles as small as 0.01 ..mu..m in real time, a portable cloud chamber operated on either a pickup truck or a small aircraft. For both procedures, a simple smoke generator operating unattended produced up to 1 x 10/sup 15/ particles/g of AgI. Ground tracking of the smoke (1) showed the influence on dispersion by the midday shift from downslope to upslope flow during stable conditions and (2) provided an interesting case study of a nearby thunderstorm as a transient effect. Aerial tracking during eight flights covered a wide range of meteorological conditions. Convective flow often lofted the smoke completely off the ground before it left the Plant boundary. During inversion conditions, the tracer remained within 100 m of the ground.

Langer, G.

1986-09-22

224

Studies of skeletal tracer kinetics IV. Optimum time delay for Tc-99m(Sn) methylene disphosphonate bone imaging  

SciTech Connect

The kinetics of the skeletal tracer Tc-99m(Sn)methylene diphosphonate (Tc-MDP) were studied in four older patients without significant bony disease by means of compartmental analysis. Solution of the model was obtained by digital computer techniques. Tracer concentrations for target and background areas (to reflect bone and soft-tissue regions) as time functions were generated for three different imaging criteria: counting rate, a figure of merit, and contrast. The figure of merit reached a maximum early in the second hour after dose administration, but contrast was found to attain a plateau at 6 h. Either of these criteria is in accord with recommendations in the literature for otpimal imaging delay time with Tc-MDP. Bone biopsy in one patient was in good agreement with the model's prediction. Compartmental analysis provides an objective method for determining the optimal imaging delay time, depending on the criterion chosen. The method can be used for any radiopharmaceutical if the compartmental model is known and can be solved.

Makler, P.T. Jr.; Charkes, N.D.

1980-07-01

225

Transient tracers in the ocean (TTO) program: the North Atlantic study, 1981: the Tropical Atlantic study, 1983  

Microsoft Academic Search

The two parts of this major geochemical and physical oceanographic expedition took place on the research vessel Knorr of the Woods Hole Oceanographic Institution. The expeditions were designed to observe the passage of man-made geochemical tracers into the interior of the ocean. A systematic survey revealed the penetration into the thermocline and deep ocean of the products of man's military\\/industrial

Peter G. Brewer; Jorge L. Sarmiento; William M. Smethie

1985-01-01

226

The use of tracer gases to determine dust dispersion patterns and ventilation parameters in a mineral processing plant.  

PubMed

A study was conducted in a fluorspar milling plant to assess the effectiveness of tracer gases as a reliable supplement to conventional air-monitoring and ventilation measurements. In the course of this study, a tracer gas was used as a surrogate substance to analyze the direction and the rate of spread of contaminants from various potential dust production points in the plant. Time-weighted average and continuous mineral dust concentrations were measured in several areas of the plant; these results were compared and correlated with steady-state tracer gas concentrations in the mill. Time-weighted average dust concentrations varied between 0.18 and 0.57 mg/m3 for total dust and 0.04 and 0.20 mg/m3 for quartz respirable dust, depending on the location. Correlation of these values with steady-state tracer gas concentrations yielded linear relationships with correlation coefficients (R2) of 0.95 and 0.87, respectively, for total and quartz dust. Results from this study, therefore, indicate that tracer gases may help model the spread of airborne respirable dust from point sources. These tracer gas releases also allowed the simultaneous quantitative determination of air residence times and contaminant clearance times from the building. Hence, tracer gases will help industrial hygienists obtain useful data with respect to building ventilation. PMID:1605111

Grenier, M G; Hardcastle, S G; Kunchur, G; Butler, K

1992-06-01

227

Tracer dating and ocean ventilation  

SciTech Connect

The interpretation of transient tracer observations depends on difficult to obtain information on the evolution in time of the tracer boundary conditions and interior distributions. Recent studies have attempted to circumvent this problem by making use of a derived quantity, age, based on the simultaneous distribution of two complementary tracers, such as tritium and its daughter, helium 3. The age is defined with reference to the surface such that the boundary condition takes on a constant value of zero. The authors use a two-dimensional model to explore the circumstances under which such a combination of conservation equations for two complementary tracers can lead to a cancellation of the time derivative terms. An interesting aspect of this approach is that mixing can serve as a source or sink of tracer based age. The authors define an idealized ventilation age tracer that is conservative with respect to mixing, and they explore how its behavior compares with that of the tracer-based ages over a range of advective and diffusive parameters.

Thiele, G.; Sarmiento, J.L. (Princeton Univ., NJ (United States))

1990-06-15

228

Injected Helium: A New Hydrological Tracer.  

National Technical Information Service (NTIS)

Five types of experiments were conducted to investigate dissolved helium gas as an injected water tracer, both in the subsurface water and open water: instrument development, sand column, soil columns, groundwater in basalt aquifer, and open water in tank...

S. K. Gupta L. S. Lau P. S. Moravcik A. E. Kadi

1990-01-01

229

A tracer study of the Arctic Ocean's liquid freshwater export variability  

NASA Astrophysics Data System (ADS)

We present an analysis of the variability of the liquid Arctic freshwater (FW) export, using a simulation from the Community Climate System Model Version 3 (CCSM3) that includes passive tracers for FW from different sources. It is shown that the FW exported through the western Canadian Arctic Archipelago (CAA) comes mainly from the Pacific and from North American runoff. The variability of the FW export from both of these sources is generally in phase, due to the strong influence of variations of the velocity anomaly on the CAA FW export variability. The velocity anomaly in the CAA is in turn mainly governed by variations in the large-scale atmospheric circulation (i.e., the Arctic Oscillation). In Fram Strait, the FW export is mainly composed of Eurasian runoff and FW of Pacific origin. The variability of the Fram Strait FW export is governed both by changes in the velocity and in the FW concentration, and the variability of the FW concentration from the two largest sources is not in phase. The Eurasian runoff export through Fram Strait depends strongly on the release of FW from the Eurasian shelf, which occurs during years with an anticyclonic circulation anomaly (negative Vorticity index) and takes 3 years to reach Fram Strait after leaving the shelf. In contrast, the variability of the Pacific FW export through Fram Strait is mainly controlled by changes in the Pacific FW storage in the Beaufort Gyre, with an increased export during years with a cyclonic circulation anomaly (positive Vorticity index).

Jahn, Alexandra; Tremblay, L. Bruno; Newton, Robert; Holland, Marika M.; Mysak, Lawrence A.; Dmitrenko, Igor A.

2010-07-01

230

Atom exchange between aqueous Fe(II) and goethite: an Fe isotope tracer study.  

PubMed

The reaction of aqueous Fe(II) with Fe(III) oxides is a complex process, comprising sorption, electron transfer, and in some cases, reductive dissolution and transformation to secondary minerals. To better understand the dynamics of these reactions, we measured the extent and rate of Fe isotope exchange between aqueous Fe(II) and goethite using a 57Fe isotope tracer approach. We observed near-complete exchange of Fe atoms between the aqueous phase and goethite nanorods over a 30-day time period. Despite direct isotopic evidence for extensive mixing between the aqueous and goethite Fe, no phase transformation was observed, nor did the size or shape of the goethite rods change appreciably. High-resolution transmission electron microscopy images, however, appear to indicate that some recrystallization of the goethite particles may have occurred. Near-complete exchange of Fe between aqueous Fe(II) and goethite, coupled with negligible change in the goethite mineralogy and morphology, suggests a mechanism of coupled growth (via sorption and electron transfer) and dissolution at separate crystallographic goethite sites. We propose that sorption and dissolution sites are linked via conduction through the bulk crystal, as was recently demonstrated for hematite. Extensive mixing between aqueous Fe(II) and goethite, a relatively stable iron oxide, has significant implications for heavy metal sequestration and release (e.g., arsenic and uranium), as well as reduction of soil and groundwater contaminants. PMID:19320165

Handler, Robert M; Beard, Brian L; Johnson, Clark M; Scherer, Michelle M

2009-02-15

231

Automatic alignment of renal DCE-MRI image series for improvement of quantitative tracer kinetic studies  

NASA Astrophysics Data System (ADS)

Tracer kinetic modeling with dynamic contrast enhanced MRI (DCE-MRI) and the quantification of the kinetic parameters are active fields of research which have the potential to improve the measurement of renal function. However, the strong coronal motion of the kidney in the time series inhibits an accurate assessment of the kinetic parameters. Automatic motion correction is challenging due to the large movement of the kidney and the strong intensity changes caused by the injected bolus. In this work, we improve the quantification results by a template matching motion correction method using a gradient-based similarity measure. Thus, a tedious manual motion correction is replaced by an automatic procedure. The only remaining user interaction is reduced to a selection of a reference slice and a coarse manual segmentation of the kidney in this slice. These steps do not present an overhead to the interaction needed for the assessment of the kinetic parameters. In order to achieve reliable and fast results, we constrain the degrees of freedom for the correction method as far as possible. Furthermore, we compare our method to deformable registration using the same similarity measure. In all our tests, the presented template matching correction was superior to the deformable approach in terms of reliability, leading to more accurate parameter quantification. The evaluation on 10 patient data series with 180-230 images each demonstrate that the quantitative analysis by a two-compartment model can be improved by our method.

Zikic, Darko; Sourbron, Steven; Feng, Xinxing; Michaely, Henrik J.; Khamene, Ali; Navab, Nassir

2008-04-01

232

Rapid dual-tracer PTSM+ATSM PET imaging of tumour blood flow and hypoxia: a simulation study  

NASA Astrophysics Data System (ADS)

Blood flow and hypoxia are interrelated aspects of physiology that affect cancer treatment and response. Cu-PTSM and Cu-ATSM are related PET tracers for blood flow and hypoxia, and the ability to rapidly image both tracers in a single scan would bring several advantages over conventional single-tracer techniques. Using dynamic imaging with staggered injections, overlapping signals for multiple PET tracers may be recovered utilizing information from kinetics and radioactive decay. In this work, rapid dual-tracer PTSM+ATSM PET was simulated and tested as a function of injection delay, order and relative dose for several copper isotopes, and the results were compared relative to separate single-tracer data. Time-activity curves representing a broad range of tumour blood flow and hypoxia levels were simulated, and parallel dual-tracer compartment modelling was used to recover the signals for each tracer. The main results were tested further using a torso phantom simulation of PET tumour imaging. Using scans as short as 30 minutes, the dual-tracer method provided measures of blood flow and hypoxia similar to single-tracer imaging. The best performance was obtained by injecting PTSM first and using a somewhat higher dose for ATSM. Comparable results for different copper isotopes suggest that tracer kinetics with staggered injections play a more important role than radioactive decay in the signal separation process. Rapid PTSM+ATSM PET has excellent potential for characterizing both tumour blood flow and hypoxia in a single, fast scan, provided that technological hurdles related to algorithm development and routine use can be overcome.

Rust, T. C.; Kadrmas, D. J.

2006-01-01

233

Application of Stable Isotope Tracers to Studies of Zooplankton Feeding, using the Rotifer Brachionus calyciflorus as an Example  

Microsoft Academic Search

We present a protocol and calculation methods for the determination of zooplankton ingestion and assimilation rates with stable isotope tracers. These methods have been developed from experiments with the rotifer Brachionus calyciflorus that had been fed 13C-labelled Scenedesmus obliquus. Stable isotope tracers offer the same advantages as radioisotopes. These include the possibility for direct and accurate quantification of ingestion and

Antonie M. Verschoor; Harry Boonstra; Thijs Meijer

2005-01-01

234

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

Microsoft Academic Search

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

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

1983-01-01

235

Determination of stream reaeration coefficients by use of tracers  

USGS Publications Warehouse

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

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

1987-01-01

236

Preferential flow in heterogeneous forest-reclaimed lignitic mine soil I. Cell-lysimeter and multiple-tracer study  

NASA Astrophysics Data System (ADS)

Flow and transport processes in forest-reclaimed lignitic mine soils are required to quantify water and element budgets, which are important for long-term predictions of restored ecosystem stability and development of mining area water quality. Soil water pressure head and solute concentration measurements using tensiometers and suction cups showed strong spatial heterogeneity possibly indicating preferential flow effects. Properties and spatial structures of the mostly sandy mine soils and transport processes, however, have not sufficiently been known for detailed assessments. The objective of this study was to quantitatively analyse flow paths and measure amount and spatial distribtion of leaching. Water and element fluxes were studied at a reclaimed mine spoil site, which was afforested in 1982 with Pinus nigra. At a 3.3 m2 plot, the total percolating water was collected in 110 cm soil depth by 45 squared suction cells of 27 cm edge length each. A multi-tracer solution containing deuterium, bromide, and terbuthylazine was applied evenly at the plot surface and imposed to natural infiltration. Leaching was measured for a period of about 2 years. One third of the cells never delivered any drainage water while few cells had large drainage rates which in one case even exceeded local infiltration rates. About 71 % of the drainage was through 9 % of the area. The spatial distribution of the leached bromide tracer did not always correspond with that of drainage. Relative concentrations of bromide and deuterium were similar. Terbuthylazine was observed only sporadically during the first drainage period and at relatively small concentrations just above the analytical detection limit. Leaching patterns of the sorptive herbicide indicate only relatively small nonequilibrium-type preferential flow. Sediment structures, water repellent regions, and tree root distributions seem to be important for funneling and flow path formation.

Hangen, E.; Gerke, H. H.; Schaaf, W.; Hüttl, R. F.

2003-04-01

237

Developing a method to track oil and gas produced water discharges in estuarine systems using salinity as a conservative tracer.  

PubMed

Produced water is a high salinity by-product resulting from oil and gas production. Disposal methods include surface water discharge from a point source. The current field method used for fate and effect determinations in open water estuarine systems involves extending a compass oriented transect (COT) from the point source discharge--a method designed for a uniform offshore environment that might be inappropriate for the hydrologic and geomorphologic complexities found in estuarine systems. Research was conducted in a canal and a small, semi-enclosed bay to observe effluent behaviour and to determine if salinity could be used to track the effluent. A salinity/conductivity/temperature (SCT) probe measured water properties within 1 cm of the sediment surface and identified a thin, bottom salinity plume that would have gone undetected by conventional instruments. The plume flowed across the sediment surface and towards greater depths. Plume-affected sampling stations exhibited higher levels of sediment contaminant indicators (SCIs) and indicated that station location could affect impact conclusions. PMID:11763224

Woodall, D W; Gambrell, R P; Rabalais, N N; Delaune, R D

2001-11-01

238

Microanalytical isotope ratio measurements and elemental mapping using laser ablation ICP-MS for tissue thin sections: zinc tracer studies in rats.  

PubMed

The kinetics of zinc absorption, metabolism and excretion is extensively studied by nutritionists. Stable isotopes of zinc can be used to identify body zinc compartments that have different turnover kinetics. Since the compartments might belong to physiological subsections of different organs, there is a need for microsampling analysis to determine isotope ratios of the trace element zinc in tissue samples. Here, we study the feasibility to use laser ablation coupled to quadrupole ICP-MS for the determination of zinc tracers given to rats at different time points with the aim to generate isotope ratio bioimages of heart tissue. A double tracer ((70)Zn and (67)Zn) experiment with rats was designed to label the exchangeable zinc pool as well as the stable zinc pool. The isotope ratios determined by laser ablation ICP-MS were evaluated by additional measurements of tissue digests. Accumulated tracers which made up more than 0.1% of total zinc could be identified in the tissues of the treated rats. It was established that at least 50 measurements from the microsampling were necessary to distinguish between controls and a tracer treated rat resulting in reduced resolution of the bioimage. With the parameters used, features in the tissue thin sections of at least 250 ?m(2) in size are necessary to detect the incorporation of a tracer. When different time points have to be measured, higher precisions are required and therefore a larger area needs to be ablated (1 mm(2)). Using the bioimages and pool measurements from one physiological feature, it was possible to show that the aorta cell walls incorporate the zinc tracer at the different time points. PMID:22006243

Urgast, Dagmar S; Ou, Ou; Gordon, Margaret-Jane; Raab, Andrea; Nixon, Graeme F; Kwun, In-Sook; Beattie, John H; Feldmann, Jörg

2012-01-01

239

Tracer tests in geothermal resource management  

NASA Astrophysics Data System (ADS)

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

Axelsson, G.

2013-05-01

240

Study of Weathering Velocity of Rocks with Uranium as a Natural Tracer. Application to Two Drainage Basins of the North-East of Brazil.  

National Technical Information Service (NTIS)

A study on rock weathering rate, i.e. rock-soil interface formation, was performed by measuring the elements dissolved in river waters. These elements are used as natural tracers. This work has been carried out in the drainage basin of Preto and Salgado R...

L. M. da Costa Pinto Moreira Nordemann

1977-01-01

241

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...

242

Sentinel lymph node mapping of breast cancer: a case-control study of methylene blue tracer compared to isosulfan blue.  

PubMed

Isosulfan blue has been traditionally used as a tracer to map the lymphatic system during identification of the sentinel lymph node. However, allergic reactions may be life threatening. We compared the efficacy of methylene blue dye as a tracer for sentinel lymph node biopsy to isosulfan blue dye. In an analysis of 164 cases, there was no clinical or statistically significant difference in the success rate of sentinel node biopsy (P = 0.22), the number of blue sentinel nodes harvested (P = 0.46), the concordance with radioactive sentinel nodes (P = 0.92), or the incidence of metastases (P = 0.87) when methylene blue tracer was compared to isosulfan blue. No adverse reaction to either blue dye was observed. In conclusion, intraparenchymal injection of methylene blue dye is a reliable tracer for the lymphatic system and nodal identification during sentinel node mapping for breast cancer. It is safe, inexpensive, and readily available. PMID:15529840

Eldrageely, Kamal; Vargas, M Perla; Khalkhali, Iraj; Venegas, Rose; Burla, Melissa; Gonzalez, Katherine D; Vargas, Hernan I

2004-10-01

243

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

PubMed

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 (18)F-Fluorodeoxyglucose (FDG) and (15)O-Water (H 2O). 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 H 2 O 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 H 2 O are obtained. PMID:24770914

Huang, Jian; O'Sullivan, Finbarr

2014-05-01

244

In-situ characterizations of dense non-aqueous phase liquids using partitioning tracers. Annual progress report, September 15, 1996--September 14, 1997  

SciTech Connect

'This paper describes laboratory research conducted to investigate the use of partitioning tracers for the detection, volume estimation, and remediation performance assessment of vadose zones contaminated by nonaqueous phase liquids (NAPLs). These laboratory studies used Ottawa sand and field soil packed columns. The columns were saturated, then reduced to residual saturations of water and NAPL, creating a three phase system of air, water, and NAPL. Conservative and partitioning gas tracers were injected into the column and their elutions were analyzed. The method of moments was used to estimate partition coefficients between the air and NAPL phases for each of the tracers. The partition coefficients and retardation factors are used to select appropriate tracers for NAPL detection and volume estimation in the field. This research identified several perfluorocarbon tracers suitable for use in the field and demonstrated the feasibility of using partitioning tracers as a tool for NAPL detection and volume estimation in the vadose zone.'

Pope, G.A.; McKinney, D.C. [Univ. of Texas, Austin, TX (US); Gupta, A.D. [Texas A and M Univ., College Station, TX (US); Jackson, R.E.; Jin, M. [Duke Engineering Services, Inc., Austin, TX (US)

1998-01-23

245

Plant uptake of cations under nutrient limitation: An environmental tracer study using Ca/Sr and K/Rb ratios  

NASA Astrophysics Data System (ADS)

Vascular plant growth builds soils and ecosystem nutrient capital by sequestering and partitioning atmospheric CO2 into organic matter and continental runoff and driving terrestrial water and energy balances. Plant root-system functions, e.g. nutrient mobilization and uptake, are altered by environmental stress. However, the stress-response relationships are poorly understood. Chemical tracers have potential for assessing contributions of nutrients from various nutrient pools. Our objective is to quantitatively study how varying degrees of nutrient limitation (and corresponding needs to extract base cations from mineral sources) influence Ca and K uptake functions in a plant-root-mineral system. We are studying plant-driven mineral weathering in column experiments with red pine (Pinus resinosa) seedlings. The columns contain quartz sand amended with anorthite and biotite that constitute the sole mineral sources of Ca and K. These minerals also contain known amounts of Sr and Rb, which exhibit chemical behavior similar to Ca and K, respectively. The solution source of Ca and K was varied by adding 0% (no dissolved Ca and K), 10%, 30%, or 100% of a full strength Ca and K nutrient solution through irrigation water in which both Sr and Rb concentrations were negligible. Selected columns were destructively sampled at 3, 6 and 9 months to harvest biomass and measure plant uptake of cations. We used Ca/Sr and K/Rb ratio results to estimate the contributions of Ca and K from mineral and solution sources. For the 0% nutrient treatment, the Ca/Sr and K/Rb ratios in total biomass at 3 months, compared with those in the mineral phases, suggested preferential uptake of Ca and K over Sr and Rb, respectively, and allowed us to determine uptake discrimination factors for both cations. The K/Rb ratios in total biomass increased with greater K availability in the solution source, as expected, but Ca/Sr ratios did not show any dependence on Ca availability in the solution source. Using a tracer mass balance model, we computed the fraction of K from the mineral source in the total biomass, which decreased with longer growth time and more K supply from the solution source. For Ca, the model results suggested that the mineral was the major source of Ca in the plants throughout the experiment. Comparison of results for above- and below-ground biomass showed significantly higher Ca/Sr and K/Rb ratios above ground, indicating strong fractionation of Ca and K during transport within the tree. Our results highlight the potential importance of species-specific and temporal variations in cation uptake that may require consideration as we work to understand water and nutrient cycles in aggrading forest ecosystems.

Shi, Z.; Keller, C. K.; Stacks, D.; Grant, M.; Harsh, J. B.; Letourneau, M.; Gill, R. A.; Balogh-Brunstad, Z.; Thomashow, L.; Dohnalkova, A.

2012-12-01

246

Human ketone body production and utilization studied using tracer techniques: Regulation by free fatty acids, insulin, catecholamines, and thyroid hormones  

SciTech Connect

Ketone body concentrations fluctuate markedly during physiological and pathological conditions. Tracer techniques have been developed in recent years to study production, utilization, and the metabolic clearance rate of ketone bodies. This review describes data on the roles of insulin, catecholamines, and thyroid hormones in the regulation of ketone body kinetics. The data indicate that insulin lowers ketone body concentrations by three independent mechanisms: first, it inhibits lipolysis, and thus lowers free fatty acid availability for ketogenesis; second, it restrains ketone body production within the liver; third, it enhances peripheral ketone body utilization. To assess these effects in humans in vivo, experimental models were developed to study insulin effects with controlled concentrations of free fatty acids, insulin, glucagon, and ketone bodies. Presently available data also support an important role of catecholamines in increasing ketone body concentrations. Evidence was presented that norepinephrine increases ketogenesis not only by stimulating lipolysis, and thus releasing free fatty acids, but also by increasing intrahepatic ketogenesis. Thyroid hormone availability was associated with lipolysis and ketogenesis. Ketone body concentrations after an overnight fast were only modestly elevated in hyperthyroidism resulting from increased peripheral ketone body clearance. There was a significant correlation between serum triiodothyronine levels and the ketone body metabolic clearance rate. Thus, ketone body homeostasis in human subjects resulted from the interaction of hormones such as insulin, catecholamines, and thyroid hormones regulating lipolysis, intrahepatic ketogenesis, and peripheral ketone body utilization. 58 references.

Keller, U.; Lustenberger, M.; Mueller-Brand, J.G.; Gerber, P.P.; Stauffacher, W.

1989-05-01

247

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

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

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

2008-01-01

248

A vibrational spectroscopic sup 18 O tracer study of pyrite oxidation  

SciTech Connect

Pyrite was oxidized under {sup 18}O{sub 2} gas in H{sub 2}{sup 16}O solutions, with and without added ferric ion, and the sulfate produced was analysed by vibrational spectroscopy to determine the relative amounts of sulfate isotopomers (S{sup 16}O{sub n}{sup 18}O{sub 4{minus}n}{sup 2{minus}}) formed. At 70C and pH 1, with no added Fe{sup 3+}, the majority of the sulfate formed was that which derived all four oxygen atoms from water (i.e., S{sup 16}O{sub 4}{sup 2{minus}}), but significant amounts of two other isotopomers, S{sup 16}O{sub 3}{sup 18}O{sup 2{minus}} and S{sup 16}O{sub 2}{sup 18}O{sub 2}{sup 2{minus}}, which derive one or two oxygen atoms from molecular oxygen were observed. When Fe{sup 3+} was added at the start under identical conditions, no S{sup 16}O{sub 2}{sup 18}O{sub 2}{sup 2{minus}} was observed. The major isotopomer formed was still S{sup 16}O{sub 4}{sup 2{minus}}, with S{sup 16}O{sub 3}{sup 18}O{sup 2{minus}} present as a minor product. Experiments which were performed at initial pH 7 yielded similar results, as did others performed at 20C, although the amounts of the minor isotopomers fromed vary with temperature. All of the results were confirmed by performing identical experiments with the source of the oxygen isotopes reversed, that is, by oxidixing pyrite under air in H{sub 2}{sup 18}O solutions and obtaining the same products in isotopic reverse.

Reedy, B.J.; Beattie, J.K. (Univ. of Sydney (Australia)); Lowson, R.T. (Australian Nuclear Science and Technology Organisation, Sutherland (Australia))

1991-06-01

249

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

250

Experimental study in a rotating channel on the similarity law of tracer concentration distribution in the turbulent Ekman boundary layer  

NASA Astrophysics Data System (ADS)

Concentration disrribution of airborne pollutants released into the atmosphere by large and elevated industrial sources or extended urban areas generally depends on the dynamical and thermal structure of the whole depth of the atmospheric planetary boundary layer (PBL). In order to be able to get meaningful predictions of pollutant dispersion from simple dispersion formulae using surface parameters as input data (like the Gaussian one), it is necessary to establish some reliable relationships between these surface parameters and the whole PBL's vertical structure. This paper presents the results of laboratory experiments in rotating hydraulic channel, aimed at investigating the influence of the Earth rotation on the dispersion of tracers which spread in a near-neutral Ekman turbulent PBL and at expressing the change of u and v components of mean wind with height in terms of rotation and turbulence scales typical of the atmospheric PBL. The results provide some evidence that in a near-neutral PBL the profiles of dilution ratio, adimensionalized by means of friction velocity u ? = ? overlineu'w' and Coriolis parameter f = 2? sin? , as a function of an adimensional height zf/? u?, where ? is the von Karman constant, can be described by a universal function for a given Rossby number of the flow. This result confirms the theoretical expectation put forth by Wippermann and Yordanov in their study on the prediction of concentration patterns in a rotating turbulent PBL.

Alessio, S.; Briatore, L.; Ferrero, E.; Longhetto, A.; Giraud, C.; Morra, O.

251

Effects of trichloroacetic acid on the nitrogen metabolism of Pinus sylvestris--a 13C/15N tracer study.  

PubMed

Trichloroacetic acid (TCA) can be found in various environmental compartments like air, rain and plants all over the world. It is assumed that TCA is an atmospheric degradation product of volatile chloroorganic hydrocarbons. The herbicide effect of TCA in higher concentrations is well known, but not much is known about the phytotoxic effects in environmentally relevant concentrations. It can be shown in this study by using the 13C/15N stable isotope tracer technique that [13C]TCA is taken up by roots of two-year-old seedlings of Pinus sylvestris L. and transported into the needles. At the same time the effect of the substance on nitrogen metabolism can be analyzed by measuring the incorporation of 15NO3- into different nitrogen fractions of the plant. The more [13C]TCA incorporation, the higher the synthesis of 15N labelled amino acids and proteins is. These effects on the nitrogen metabolism are probably based on the activation of stress- and detoxification metabolism. It has to be assumed that there is an influence on N metabolism of Pinus sylvestris caused by the deposition of environmentally relevant TCA concentrations. PMID:11827283

Hafner, Christoph; Jung, Klaus; Schüürmann, Gerrit

2002-01-01

252

Technical note: Can the sulfur hexafluoride tracer gas technique be used to accurately measure enteric methane production from ruminally cannulated cattle?  

PubMed

An experiment was conducted to determine whether using ruminally cannulated cattle affects the estimate of enteric methane (CH(4)) emissions when using the sulfur hexafluoride (SF(6)) tracer technique with samples taken from a head canister. Eleven beef cattle were surgically fitted with several types of ruminal cannula (2C, 3C, 3C+washer, 9C; Bar Diamond, Parma, ID). The 2C and 3C models (outer and inner flanges with opposite curvature) had medium to high leakage, whereas the 9C models (outer and inner flanges with the same curvature) provided minimum to moderate leakage of gas. A total of 48 cow-day measurements were conducted. For each animal, a permeation tube containing sulfur hexafluoride (SF(6)) was placed in the rumen, and a sample of air from around the nose and mouth was drawn through tubing into an evacuated canister (head canister). A second sample of air was collected from outside the rumen near the cannula into another canister (cannula canister). Background concentrations were also monitored. The methane (CH(4)) emission was estimated from the daily CH(4) and SF(6) concentrations in the head canister (uncorrected). The permeation SF(6) release rate was then partitioned based on the proportion of the SF(6) concentration measured in the head vs. the cannula canister. The CH(4) emissions at each site were calculated using the two release rates and the two CH(4):SF(6) concentration ratios. The head and cannula emissions were summed to obtain the total emission (corrected). The difference (corrected - uncorrected) in CH4 emission was attributed to the differences in CH(4):SF(6) ratio at the 2 exit locations. The proportions of CH(4) and SF(6) recovered at the head were greater (P < 0.001) for the 9C cannulas (64% and 66%) compared with the other cannulas, which were similar (P > 0.05; 2C, 6% and 4%; 3C, 17% and 15%; 3C+washer, 19% and 14%). Uncorrected CH(4) emissions were ± 10% of corrected emissions for 53% of the cow-day measurements. Only when more than 80% of the SF(6) escaped via the rumen did the difference between the uncorrected and corrected CH(4) emissions exceed 20%. We concluded that using cannulated cattle introduces more variability into the SF(6) technique used with a head canister, a technique that is already highly variable. Thus, use of cannulated animals is not recommended when using the SF(6) technique with head canister. However, if cannulated cattle are used, the cannulas need to be tight-fitting to minimize leakage, and large animal numbers are needed to overcome the additional variability. PMID:22408084

Beauchemin, K A; Coates, T; Farr, B; McGinn, S M

2012-08-01

253

Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements  

SciTech Connect

The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; [sup 238]U-[sup 230]Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

Wasserburg, G.J.

1992-01-01

254

Application of stable isotope tracers in the study of exercise metabolism in children: a primer.  

PubMed

Exercise metabolism in children has traditionally been assessed using the respiratory exchange ratio (RER) to determine the contributions of fat and carbohydrate to the exercise energy demands. Although easily measured, RER measurements have limitations. Other methods to assess metabolism such as the obtainment of a muscle biopsy and the use of nuclear magnetic resonance spectroscopy carry ethical and feasibility concerns, respectively, which limit their use in studies involving children. Stable isotopes, used routinely in studies involving adults, can also be applied in studies involving children in an ethical and feasible manner. Two common stable isotopes used in metabolic studies involving children include carbon-13 (13C) and nitrogen-15 (15N). 13C-glucose can be used to study carbohydrate metabolism and 15N-glycine can be used to assess protein metabolism. This article reviews the use of 13C-glucose and 15N-glycine to study exercise metabolism in children, considers some of the associated ethical aspects, explains the general methodology involved in administering these isotopes and the resources required, and describes studies involving children utilizing these methods. Finally, suggestions for future research are provided to encourage further use of these techniques. PMID:24662114

Mahon, Anthony D; Timmons, Brian W

2014-02-01

255

The Reanalysis for Stratospheric Trace-gas Studies  

NASA Technical Reports Server (NTRS)

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.

Pawson, Steven; Li, Shuhua

2002-01-01

256

Diverse mechanisms of growth inhibition by luteolin, resveratrol, and quercetin in MIA PaCa-2 cells: a comparative glucose tracer study with the fatty acid synthase inhibitor C75  

PubMed Central

The rationale of this dose matching/dose escalating study was to compare a panel of flavonoids—luteolin, resveratrol, and quercetin—against the metabolite flux-controlling properties of a synthetic targeted fatty acid synthase inhibitor drug C75 on multiple macromolecule synthesis pathways in pancreatic tumor cells using [1,2-13C2]-d-glucose as the single precursor metabolic tracer. MIA PaCa-2 pancreatic adenocarcinoma cells were cultured for 48 h in the presence of 0.1% DMSO (control), or 50 or 100 ?M of each test compound, while intracellular glycogen, RNA ribose, palmitate and cholesterol as well as extra cellular 13CO2, lactate and glutamate production patterns were measured using gas chromatography/mass spectrometry (GC/MS) and stable isotope-based dynamic metabolic profiling (SiDMAP). The use of 50% [1,2-13C2]-d-glucose as tracer resulted in an average of 24 excess 13CO2 molecules for each 1,000 CO2 molecule in the culture media, which was decreased by 29 and 33% (P < 0.01) with 100 ?M C75 and luteolin treatments, respectively. Extracellular tracer glucose-derived 13C-labeled lactate fractions (?m) were between 45.52 and 47.49% in all cultures with a molar ratio of 2.47% M + 1/?m lactate produced indirectly by direct oxidation of glucose in the pentose cycle in control cultures; treatment with 100 ?M C75 and luteolin decreased this figure to 1.80 and 1.67%. The tracer glucose-derived 13C labeled fraction (?m) of ribonucleotide ribose was 34.73% in controls, which was decreased to 20.58 and 8.45% with C75, 16.15 and 6.86% with luteolin, 27.66 and 19.25% with resveratrol, and 30.09 and 25.67% with quercetin, respectively. Luteolin effectively decreased nucleotide precursor synthesis pentose cycle flux primarily via the oxidative branch, where we observed a 41.74% flux (M + 1/?m) in control cells, in comparison with only a 37.19%, 32.74%, or a 26.57%, 25.47% M + 1/?m flux (P < 0.001) after 50 or 100 ?M C75 or luteolin treatment. Intracellular de novo fatty acid palmitate (C16:0) synthesis was severely and equally blocked by C75 and luteolin treatments indicated by the 5.49% (control), 2.29 or 2.47% (C75) and 2.21 or 2.73% (luteolin) tracer glucose-derived 13C-labeled fractions, respectively. On the other hand there was a significant 192 and 159% (P < 0.001), and a 103 and 117% (P < 0.01) increase in tracer glucose-derived cholesterol after C75 or luteolin treatment. Only resveratrol and quercetin at 100 ?M inhibited tracer glucose-derived glycogen labeling (?m) and turnover by 34.8 and 23.8%, respectively. The flavonoid luteolin possesses equal efficacy to inhibit fatty acid palmitate de novo synthesis as well as nucleotide RNA ribose turnover via the oxidative branch of the pentose cycle in comparison with the targeted fatty acid synthase inhibitor synthetic compound C75. Luteolin is also effective in stringently controlling glucose entry and anaplerosis in the TCA cycle, while it promotes less glucose flux towards cholesterol synthesis than that of C75. In contrast, quercetin and resveratrol inhibit glycogen synthesis and turnover as their underlying mechanism of controlling tumor cell proliferation. Therefore the flavonoid luteolin controls fatty and nucleic acid syntheses as well as energy production with pharmacological strength, which can be explored as a non-toxic natural treatment modality for pancreatic cancer.

Li, Luyi; Chen, Monica; Lagunero, F. Tracy; Go, Vay Liang W.; Boros, Laszlo G.

2011-01-01

257

Contribution to the Study of the Behavior of Tetravalent Technetium at Tracer Amounts in Aqueous Media.  

National Technical Information Service (NTIS)

The behavior of /sup 99m/Tc was studied first in perchloric media. Reduction of TcO sub 4- by BH sub 4- at pH 7 in perchloric medium leads to Tc(IV) as a radiocolloid (20 percent) and soluble TcO sub 2 (50 percent). Acidification of the medium oxidizes th...

J. Y. Guennec

1976-01-01

258

Contribution of isoprene to chemical budgets: A model tracer study with the NCAR CTM MOZART4  

Microsoft Academic Search

We present a study of the sensitivity of isoprene emission calculations in a global chemistry transport model (CTM) to input land cover characteristics and analyze the impacts of changes in isoprene on the tropospheric budgets of atmospheric key species. The CTM Model for Ozone and Related Chemical Species, version 4 (MOZART-4) includes the online calculation of isoprene emissions based on

G. G. Pfister; L. K. Emmons; P. G. Hess; J.-F. Lamarque; J. J. Orlando; S. Walters; A. Guenther; P. I. Palmer; P. J. Lawrence

2008-01-01

259

Proton nuclear activation in stable tracer technique for ruthenium metabolism studies  

Microsoft Academic Search

A methodology is presented, based on proton nuclear activation (PNA), for the contemporary determination of two stable isotopes of ruthenium in biological samples. This technique can be successfully applied in studying the biokinetics of oligoelements, avoiding radiation hazards. On the basis of the possible proton-induced nuclear reactions and the decay characteristics of radioactive products, (p, n) reactions on 99Ru and

M. C. Cantone; D. de Bartolo; G. Gambarini; A. Giussani; A. Ottolenghi; L. Pirola; Ch. Hansen; P. Roth; E. Werner

1994-01-01

260

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

Microsoft Academic Search

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,

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

1957-01-01

261

Biotinylated dextran amine as an anterograde tracer for single- and double-labeling studies.  

PubMed

Fluorescent dextran amines have recently been reported to be useful for anterograde pathway tracing. However, fluorescent markers are not always ideal for detailed mapping studies. We therefore evaluated the efficacy of a biotinylated dextran amine (BDA) for anterograde labeling in several different preparations. BDA was visualized with an avidin-biotinylated HRP (ABC) procedure followed by a standard or metal-enhanced diaminobenzidine (DAB) reaction. After iontophoretic injections of BDA into neocortex-like telencephalic regions in pigeons or into visual or somatosensory cortex in rats, there was excellent and abundant labeling of axons and terminals in forebrain, midbrain and hindbrain target areas with 1-week survival times. Large pressure injections of BDA into the avian telencephalon were also found to result in extensive anterograde labeling. We then carried out a series of studies using 2-color DAB double-labeling to determine effective approaches for combining BDA labeling with other labeling methods. Using an isolated embryonic chick spinal cord-hindlimb preparation, we combined BDA labeling with another anterograde labeling method to differentially label two sets of projections. In these studies, sensory neuron and motoneuron projections into the limb from the same segmental level, or motoneuron projections into the limb from two separate segments were differentially labeled by using HRP (visualized first with a blue/black metal-DAB reaction) and BDA (visualized second with a brown DAB reaction). In other double-labeling studies, we combined BDA labeling of axons and terminals with immunohistochemical labeling of neurons. In these experiments, telencephalic neurons in pigeons or rats were labeled immunohistochemically for parvalbumin or substance P (using a brown DAB reaction) and BDA-labeled axons were labeled blue/black (using a metal-intensified DAB reaction). Double-labeling was successful regardless of whether the entire immunohistochemical labeling procedure preceded or followed the BDA labeling procedure. Together, these studies show that BDA is effective for anterograde pathway tracing and can be used in double-label studies with other labeling methods. PMID:1381034

Veenman, C L; Reiner, A; Honig, M G

1992-03-01

262

Preservation and incubation time-induced bias in tracer-aided grazing studies on meiofauna  

Microsoft Academic Search

A recent review suggests that meiofauna are important grazers of microphytobenthic primary production as well as of bacterial\\u000a secondary production. The potential importance of meiofauna grazers may nevertheless have systematically been underestimated,\\u000a since label leakage from chemically preserved animals has hitherto not been accounted for. Furthermore, a majority of studies\\u000a have used relatively long incubation times and assumed, rather than

T. Moens; L. Verbeeck; M. Vincx

1999-01-01

263

Immunosensors for pollutants working in organic media. Study of performances of different tracers with luminescent detection  

Microsoft Academic Search

A comparative study of enzymatic and non-enzymatic labels combined with luminescence detection, developed for immunosensing of pesticide residues (carbaryl, 1-naphthol, irgarol 1051) in organic media, is presented. Peroxidase and alkaline phosphatase enzymes with fluorogenic (3-p-hydroxyphenylpropanoic acid) and luminogenic (AMPPD derivative) substrates, respectively, were assessed as enzymatic markers. As an alternative, terbium(III) chelate, with time-resolved fluorescence detection, was evaluated as a

M. A. González-Martínez; J. Penalva; J. C. Rodríguez-Urbis; E. Brunet; A. Maquieira; R. Puchades

2006-01-01

264

The preparation of soft gelatin capsules for a radioactive tracer study.  

PubMed

Clinical doses are developed for the oral coadministration of radiolabeled and nonlabeled forms of a poorly soluble investigational compound: OPC-41061. The release rates of the labeled and nonlabeled forms are equated and matched to the release rate of the polymer spray-dried form of the drug in the proposed market product. The study involves the physicochemical characterization of the powders using thermal analysis and dissolution testing, development and extemporaneous manufacture of liquid-filled soft gelatin capsules, and dissolution and stability testing of the final dosage form. Thermal analysis indicated that the labeled powder was amorphous and that the nonlabeled powder, which had been jet-milled, was crystalline. Dissolution testing of the jet-milled and spray-dried powders indicated that the former was released at a significantly slower rate. A liquid formulation containing 25% dimethyl acetamide and 75% polyethylene glycol 400 (PEG 400) solubilized the desired dose of 60 mg and exhibited a drug profile that was similar to the spray-dried formulation. The final formulation was a soft gelatin capsule containing 60 mg of drug, including 100 microCi radioactivity, dissolved in 0.8 ml of a 25% dimethyl acetamide/75% PEG 400 solution. The formulation was chemically and physically stable for a period greater than the duration of the study. PMID:10578504

Tesconi, M S; Bramer, S L; Yalkowsky, S H

1999-01-01

265

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

SciTech Connect

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.

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

1982-04-01

266

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

SciTech Connect

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}

Wasserburg, Gerald J

2008-07-31

267

Analysis of tracer and thermal transients during reinjection.  

National Technical Information Service (NTIS)

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 time...

I. Kocabas

1989-01-01

268

Direct hypothalamic innervation of the trigeminal motor nucleus: a retrograde tracer study.  

PubMed

It is currently thought that the hypothalamus influences motor output through connections with premotor structures which in turn project to motor nuclei. However, hypocretinergic/orexinergic projections to different motor pools have recently been demonstrated. The present study was undertaken to examine whether hypocretinergic/orexinergic neurons are the only source of projections from the hypothalamus to the trigeminal motor nucleus in the guinea-pig. Cholera toxin subunit b was injected into the trigeminal motor nucleus in order to retrogradely label premotor neurons. Two anatomically separated populations of labeled neurons were observed in the hypothalamus: one group was distributed along the dorsal zone of the lateral hypothalamic area, the lateral portion of the dorsomedial hypothalamic nucleus and the perifornical nucleus; the other was located within the periventricular portion of the dorsomedial hypothalamic nucleus. Numerous cholera toxin subunit b+ neurons in both populations displayed glutamate-like immunoreactivity. In addition, premotor neurons containing hypocretin/orexin were distributed throughout the lateral dorsomedial hypothalamic nucleus, perifornical nucleus and lateral hypothalamic area. Other premotor neurons were immunostained for melanin concentrating hormone; these cells, which were located within the lateral hypothalamic area and the perifornical nucleus, were intermingled with glutamatergic and hypocretinergic/orexinergic neurons. Nitrergic premotor neurons were located only in the periventricular zone of the dorsomedial hypothalamic nucleus. None of the hypothalamic premotor neurons were GABAergic, cholinergic or monoaminergic. The existence of diverse neurotransmitter systems projecting from the hypothalamus to the trigeminal motor pool indicates that this diencephalic structure may influence the numerous functions that are subserved by the trigeminal motor system. PMID:16226839

McGregor, R; Damián, A; Fabbiani, G; Torterolo, P; Pose, I; Chase, M; Morales, F R

2005-01-01

269

Long-Term Tracer Study at Los Alamos, New Mexico. Part II: Evaluation and Comparison of Several Methods to Determine Dispersion Coefficients  

Microsoft Academic Search

A long-term tracer study was conducted to evaluate dispersion in complex terrain in support of air quality and emergency response initiatives. An array of monitors continuously measured external radiation levels at different directions and distances from a 30-m-high radionuclide emission source. The monitors were located at distances ranging from 550 to 2800 m downwind of the release stack. Winds were

Brent M. Bowen

1994-01-01

270

Application of stable isotopes in environmental tracer studies – Measurement of monomethylmercury (CH3Hg+) by isotope dilution ICP-MS and detection of species transformation  

Microsoft Academic Search

The monovalent cation monomethylmercury (CH3Hg+) was determined in certified reference materials by isotope dilution GC\\/ICP-MS and good agreement between measured and certified\\u000a values has been found. The use of enriched stable isotopes with subsequent detection by ICP-MS is a powerful tracer technique\\u000a to study dynamic environmental processes. For the first time, it was possible to monitor opposite processes like Hg2+

H. Hintelmann; R. D. Evans

1997-01-01

271

Use of the enriched stable isotope Cr50 as a tracer to study the metabolism of chromium (III) in normal and diabetic rats  

Microsoft Academic Search

The activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer to study the metabolism of chromium(III) [CR(III)] intragastrically administered in normal and diabetic\\u000a rats. The comparison of absorption, distribution, and excretion in organs and tissues of the two groups do not show much alteration,\\u000a but some differences exist indeed. The contents of51Cr radioactivity of the diabetic rats

Weiyue Feng; Wenjun Ding; Qinfang Qian; Zhifang Chai

1998-01-01

272

Enhanced flue gas conditioning study  

SciTech Connect

Many electrostatic precipitators (ESPS) do not achieve acceptable particulate removal efficiencies because of high-resistivity ash. One method to improve ESP performance is to employ chemical conditioning agents to reduce fly ash resistivity. Widely used agents include sulfur trioxide (SO[sub 3]) and ammonia, which are sometimes used simultaneously. For some fly ashes, that have a low affinity for SO[sub 3], conditioning with SO[sub 3] alone is not adequate to reduce resistivity without excessive amounts of SO[sub 3] exiting the stack. In such cases, the use of ammonia in addition to SO[sub 3] may reduce the amount of required SO[sub 3] and prevent the emission of excess SO[sub 3] out of the stack. The general objective of the work was to test enhanced flue gas conditioning methods to improve the performance of ESPS. Specific objectives were to (1) verify the relationship between the required SO[sub 3] injection rates to maintain the desired fly ash resistivity and temperature for four coals, (2) verify that dual conditioning with both ammonia and SO[sub 3] promotes SO[sub 3] utilization and allows for resistivity modification with moderate SO[sub 3] injection rates, and (3) verify the effectiveness and practicality of an enhanced flue gas conditioning (EFGC) method. The EFGC method is a proprietary development of Wahlco, Inc.

Miller, S.J.; Laudal, D.L.

1991-11-01

273

NPS Gas Gun for Planar Impact Studies  

NASA Astrophysics Data System (ADS)

The Naval Postgraduate School (NPS) commissioned a Gas Gun for shock wave studies on 9^th October 2009, by performing the first experiment. The Gas Gun is the key element of NPS Shock Wave Research Program within the Physics Department, where well-characterized planar impacts are essential for obtaining high quality data, to characterize a solid material. This first experiment was very successful, and returned key data on the quality of the impact conditions created. The Gas Gun is designed by SANDIA NATIONAL LABORATORIES, and the NPS spent twelve months fabricating the components of the Gas Gun and six months assembling the Gas Gun. Three inch projectile are launched at velocities up to 0.5 km/s, creating high pressure and temperature states that can be used to characterize the fundamental response of relevant materials to dynamic loading. The projectile is launched from a `wrap around' gas breech where helium gas is pressurized to relatively low pressure. This gas is used to accelerate the projectile down a 3m barrel. Upon impact, the speed of the projectile and the flatness of the impact is measured, via a stepped circular pin array circuit. The next stage of development for the Gas Gun is to integrate a Velocity Interferometer System for Any Reflector (VISAR). The VISAR sees all the waves that flow through the target plate as a result of the impact. This is a key diagnostic for determining material properties under dynamic loading conditions.

Cheong Ho, Chien; Hixson, Robert

2009-11-01

274

Lamellar organization of pontocerebellar neuronal populations. A multi-tracer and 3-D computer reconstruction study in the cat.  

PubMed

This study deals with the three-dimensional arrangement of populations of pontocerebellar cell bodies projecting to the parafloccular complex. The fluorescent tracers rhodamine B isothiocyanate, fluoro-gold and fast blue were injected in either adjacent or separated cerebellar folia. A set of coordinates (x, y, z) was assigned to each retrogradely labelled cell and the total distribution reconstructed and displayed on a graphics workstation. At a large scale, we found that the majority of the cells of each labelled population (all projecting to the same folium) were confined to a lamella-shaped tissue volume. Each lamella extended from medial to lateral, and accordingly followed the curving of the pontine grey around the corticospinal and corticobulbar fibre tracts. At a smaller scale, i.e. within each lamellar subspace, the neurons belonging to one labelled population were distributed in aggregates of various shapes. To enable further analysis of the shapes of the intralaminar aggregates, we developed a computer program for unfolding of the lamellae, based on cubic B-spline approximation. The flattened reconstructions were three-dimensional polygonal windows, circumscribing the large majority of the labelled cell swarm (usually 70-80% of the total number of labelled cells in one population). The present findings, taken together with previous data on a gradual, rather than disjunctive, shift of pontocerebellar neuronal position in relation to a gradual shift of target region (Bjaalie et al., Anat. Rec.,231, 510-523, 1991), suggest that the cerebropontocerebellar system may be organized according to a set of fairly simple topographic rules. PMID:7513239

Nikundiwe, A M; Bjaalie, J G; Brodal, P

1994-02-01

275

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

PubMed

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

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

2013-06-01

276

Stream velocity and dispersion characteristics determined by dye-tracer studies on selected stream reaches in the Willamette River basin, Oregon  

USGS Publications Warehouse

Dye-tracer analyses were done in the Willamette River and nine tributaries of the Willamette River during low to medium stream-discharge conditions, from April 1992 to July 1993, to determine velocity and dispersion. These analyses helped answer questions regarding time of arrival, peak concentra- tions, and persistence of constituents dissolved in the flow for various stream discharges. The time of travel of the peak and leading and trailing edge of the dye cloud was determined for each stream segment studied, and was related to discharge at an index location for each stream. An equation was developed, based on the dye-tracer measurements, to estimate the velocity of the peak of a solute cloud for unmeasured streams. The results of the dye-tracer study on the Willamette River from river mile 161.2 to river mile 138.3 were compared with results from a previous study of the same river reach, and the results indicated that the velocity regime in the low and medium flow range has not changed since 1968. To identify the dispersion characteristics of a conservative solute in each stream segment, a relation was developed between the elapsed time from injection to the peak concentration measured at each sampling location. A general equation was developed to estimate the unit-peak concentration for a given elapsed time after a solute was introduced to the stream.

Lee, K. K.

1995-01-01

277

Next Generation Gas Turbine (NGGT) Systems Study.  

National Technical Information Service (NTIS)

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 co...

2001-01-01

278

Evaluation of the Emission Rate from a Gaseous Source: Development of a Method Using a Helium Tracer  

Microsoft Academic Search

A tracer gas (helium) has been used to determine the emission rate of a gaseous pollutant source of acetone. The method principle consists of measuring the pollutant concentration in the vicinity of the source and the pollutant transfer coefficient determined with the tracer gas. The ratio of the pollutant concentration by the tracer gas transfer coefficient gives the pollutant emission

D. Bémer; J. M. Dessagne; G. Aubertin

1999-01-01

279

Evaluating the accretion of meteoritic debris and interplanetary dust particles in the GPC-3 sediment core using noble gas and mineralogical tracers  

NASA Astrophysics Data System (ADS)

Extraterrestrial (ET) noble gases (helium and neon) in 35 sediment samples from Central Pacific core LL-44 GPC-3 demonstrate the variable flux of interplanetary dust particles (IDPs) and major meteorite impacts over the past 70 Ma (21-72 Ma). Spinel mineralogical and chemical compositions clearly distinguish major impact events from the continuous flux of IDPs, including the well-established Cretaceous/Tertiary (K/T) and late Eocene (E/O) impact boundaries. No spinel grains with chemical or mineralogical evidence of a distinctly ET origin were found in an extensive survey of 'background' samples (i.e. non E/O or K/T boundary) suggesting that either the carrier grains for ET noble gas occur within the Fe-Ti oxide mineral fraction observed in this study (found to include ilmenite and ulvospinel) or are too small for identification by SEM. The presence of ilmenite and ulvospinel suggest lunar regolith is a potential source for ET noble gas-rich particles. Noble gas analysis on both the EMF (extractable magnetic fraction) and the Bulk minus EMF (Bulk - EMF) show that the He and Ne compositions are consistent with partially degassed noble gas signatures of zero-age magnetic grains (Z-MAG) and stratospheric interplanetary dust particles (IDPs). Conclusive evidence for a 'planetary' (Ne-A) noble gas signature is found only in the bulk sediments at the K/T boundary, although all GPC-3 K/T fractions (Bulk, EMF, and HF Digestion) plot along a mixing line between planetary (Ne-A) and solar wind (SW). Spinels from major impact boundaries (K/T; E/O) exhibit dendritic texture and elevated [Ni], consistent with previous reports. In contrast to the otherwise consistent [3He] signal from IDPs, the [3He] at the known impact boundaries (K/T and E/O) actually decreases. These anomalously low [3He] are accompanied by significantly elevated [Ne] and significantly lower (3He/20Ne)solar ratios (˜10× lower) produced by both preferentially degassing of He relative to Ne at times of increased flux of larger ET material. Degassed ("degassed-He/enriched-Ne profile") noble gas characteristics occur in two sample intervals that do not correspond to any known impact events (47 and 71 Ma), explained by an influx of larger particles. SEM analysis of the 47 Ma sample shows spinels with dendritic textures, but without distinctive markers of large meteorite impacts (e.g. elevated Ni). Particle size increases and degassed signatures may be caused by major bolides, micrometeorites, comet showers; or simply a flux of larger IDPs, potentially with a different source.

Darrah, Thomas H.; Poreda, Robert J.

2012-05-01

280

Tracer Partitioning in Two-Phase Flow  

NASA Astrophysics Data System (ADS)

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

Sathaye, K.; Hesse, M. A.

2012-12-01

281

Investigation of Contaminant Transport and Dispersion in New York Harbor by a High Resolution SF6 Tracer Study  

Microsoft Academic Search

Sulfur hexafluoride (SF6) has been used successfully as a deliberate tracer for rivers, estuaries, and coastal areas, due to its inert nature, non-toxicity, and extremely low detection limit. An automated, high-resolution SF6 measurement system mounted on a boat was recently developed for several projects on the Hudson River. The system has a sampling interval of two minutes and a detection

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

2002-01-01

282

Water vapor recycling induced by the MJO convection: Application of water isotope tracers to the study of tropical convection  

NASA Astrophysics Data System (ADS)

Here, we newly introduce water isotope tracers to understand tropical convection system, which has been a major challenging subject in meteorology, and consider what new findings they can provide us. Water has several naturally occurring isotopes (H216O, HDO, H218O etc.), and in the atmosphere, the behavior of isotopic ratio of them in the atmosphere is intimately linked to the transportation of atmospheric water due to significant vertical profile that isotopic ratio progressively decrease with altitude and cloud physics due to the fractionation, which occurs during phase change in the cloud. For example, because heavy isotopes are enriched in the condensation phase, vapor in the cloud is more depleted in heavy isotopes as amount of precipitation increase. In this study, using newly obtained observational data from satellite (TES/AURA) and MISMO campaign program carried out in the tropical Indian Ocean in 2006, we examine the relationship between the isotopic composition of water and convective processes, and then identify the key process governing the isotopic behavior in the tropics using single column model including the Arakawa-Schubert cumulus parameterization. New findings of this study are that 1) minimum isotope peaks in the intrapersonal isotopic variation almost overlap with the active convection period includes the MJO. 2) During the active convection, eastward-propagating precipitation system was observed frequently, and by repeatedly passing of rainfall systems, isotopic composition of water in the lower atmosphere has gradually decreased. This isotopic shift from inactive to active convection period is well reproduced by the model. Model result suggests that in active convection period, due to successive convective circulation, water vapor in the atmosphere is well mixed. Because isotopic composition of atmospheric water gradually decreases toward high altitude, active vertical circulation results in lower isotopic composition in the lower atmosphere. That means isotopic composition in the lower atmosphere can be considered as the indicator of the intensity of downdraft and subsidence. The strong negative peak of isotopic composition associated with MJO reflects high contribution of downdraft and subsidence.

Kurita, N.; Noone, D. C.; Yamada, H.; Yoneyama, K.

2009-12-01

283

NEXT GENERATION GAS TURBINE SYSTEMS STUDY  

SciTech Connect

Under sponsorship of the U.S. Department of Energy's National Energy Technology Laboratory, Siemens Westinghouse Power Corporation has conducted a study of Next Generation Gas Turbine Systems that embraces the goals of the DOE's High Efficiency Engines and Turbines and Vision 21 programs. The Siemens Westinghouse Next Generation Gas Turbine (NGGT) Systems program was a 24-month study looking at the feasibility of a NGGT for the emerging deregulated distributed generation market. Initial efforts focused on a modular gas turbine using an innovative blend of proven technologies from the Siemens Westinghouse W501 series of gas turbines and new enabling technologies to serve a wide variety of applications. The flexibility to serve both 50-Hz and 60-Hz applications, use a wide range of fuels and be configured for peaking, intermediate and base load duty cycles was the ultimate goal. As the study progressed the emphasis shifted from a flexible gas turbine system of a specific size to a broader gas turbine technology focus. This shift in direction allowed for greater placement of technology among both the existing fleet and new engine designs, regardless of size, and will ultimately provide for greater public benefit. This report describes the study efforts and provides the resultant conclusions and recommendations for future technology development in collaboration with the DOE.

Benjamin C. Wiant; Ihor S. Diakunchak; Dennis A. Horazak; Harry T. Morehead

2003-03-01

284

Northern gas fields and NGH technology. A feasibility study to develop natural gas hydrate technology for the international gas markets.  

National Technical Information Service (NTIS)

Two natural gas fields have been studied for three different technological solutions using two different economic theories. The aim was to examine whether a new technology for transporting natural gas, Natural Gas Hydrates (NGH), can compete with the exis...

T. R. Ramsland E. F. Loy S. Doesen

1997-01-01

285

Achievements and opportunities from ESF Research Networking Programme: Natural molecular structures as drivers and tracers of terrestrial C fluxes, and COST Action 639: Greenhouse gas budget of soils under changing climate and land use  

NASA Astrophysics Data System (ADS)

One of the activities of the European Science Foundation (ESF, www.esf.org) is developing European scale Research Networking Programmes (RNPs). RNPs lay the foundation for nationally funded research groups to address major scientific and research infrastructure issues, in order to advance the frontiers of existing science. MOLTER (www.esf.org/molter or www.molter.no) is such an RNP. MOLTER stands for "Natural molecular structures as drivers and tracers of terrestrial C fluxes" aims at stimulating the use of isotopic and organic chemistry to study carbon stabilization and biogeochemistry in terrestrial ecosystems and soils in particular. The understanding of the formation, stabilization and decomposition of complex organic compounds in the environment is currently being revolutionized by advanced techniques in identification, quantification, and origin tracing of functional groups and individual molecules. MOLTER focuses on five major research themes: - Molecular composition and turnover time of soil organic matter; - Plant molecular structures as drivers of C stabilisation in soils; - Fire transformations of plant and soil molecular structures - Molecular markers in soils; - Dissolved organic molecules in soils: origin, functionality and transport. These research themes are covered via the following activities: - Organisation of international conferences; - Organisation of specific topical workshops; - Organisation of summer schools for PhD students; - Short- and long-term exchange grants for scientists. MOLTER is supported by research funding or performing agencies from Austria, Belgium, France, Germany, the Netherlands, Norway, Romania, Spain, Sweden, Switzerland and the United Kingdom. The ESF is also the implementing agency of COST (European Cooperation in Science and Technology, www.cost.esf.org), one of the longest-running European instruments supporting cooperation among scientists and researchers across Europe. COST Action 639 "Greenhouse gas budget of soils under changing climate and land use" (BurnOut) (www.cost.esf.org/domains_actions/essem/Actions/changing_climate or bfw.ac.at/rz/bfwcms.web?dok=5906) BurnOut aims at improving the management of greenhouse gas emissions from European soils under different regimes of ecosystem disturbances and land-use change. This will allow the identification of soil and site conditions (hot spots) that are vulnerable to greenhouse gas emissions. The specific objectives are: - Identification of hot spots of greenhouse gas emissions from soils; - Identification of soil and site conditions that are vulnerable to GHG emissions; - Development of an advanced greenhouse gas reporting concept across different of land forms, land use and land use changes; - Communication of policy relevant GHG reporting concepts; Burnout covers the following activities: - Organisation of specific topical workshops; - Short-term scientific visits for scientists. Participating countries in BurnOut are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, Germany, Greece, Hungary, Ireland, Israel, Italy, Lithuania, Netherlands, Norway, Portugal, Romania, Slovak Republic, Slovenia, Spain, Spain, Sweden, Switzerland, Turkey, United Kingdom, Russian Federation, and Bosnia Herzegovina. During this oral presentation, possible lines of cooperation, opportunities and recent achievements will be exemplified and the audience will be invited to contribute their views on these initiatives.

Boeckx, P.; Rasse, D.; Jandl, R.

2009-04-01

286

Gaseous tracer technique for estimating air-water interfacial areas and interface mobility  

SciTech Connect

A series of gaseous miscible displacement experiments were conducted to estimate specific air-water interfacial areas (a{sub i}) and water contents in an unsaturated sand column. A straight-chain hydrocarbon (h-decane) was used as the gaseous interfacial tracer and methylene chloride and chloroform were used as the water-partitioning gaseous tracers. A gas chromatographic technique was employed for the tracer experiments conducted at room temperature using nitrogen as the mobile phase and water as the immobile liquid. Tracer experiments covered a water saturation (S{sub w}) range of 1.5 to 56%. The largest a{sub i} value, measured at the lowest S{sub w} (1.5%), was somewhat smaller than the solid surface area as determined using the nitrogen-sorption technique. As S{sub w} increased, a{sub i} values decreased exponentially to {approximately}80 cm{sup 2} cm{sup {minus}3} at S{sub w} of 56%. Within a limited S{sub w} range (0.29 < S{sub w} < 0.55), where both aqueous and gaseous interfacial tracer data were measured, the a{sub i} values measured using a gaseous tracer (n-decane) were 2 to 3 times larger than those measured in a previous study using an aqueous interfacial tracer (sodium dodecylbenzene sulfonate [SDBS]). The velocity of the air-water interface was estimated to be between 23 and 36% of the bulk pore-water velocity. The water contents measured using water-partitioning tracers were within {+-}5% of those based on gravimetric measurements.

Kim, H.; Suresh, P.; Rao, C.; Annable, M.D.

1999-12-01

287

Tracer attenuation in groundwater  

NASA Astrophysics Data System (ADS)

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.

Cvetkovic, Vladimir

2011-12-01

288

Fundamental study on gas monitoring in CELSS  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

289

Fundamental study on gas monitoring in celss  

NASA Astrophysics Data System (ADS)

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.

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

290

Dual-tracer background subtraction approach for fluorescent molecular tomography  

PubMed Central

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.

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

2013-01-01

291

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

SciTech Connect

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.

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

1987-11-01

292

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

SciTech Connect

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

Allwine, K Jerry; Flaherty, Julia E.

2007-08-01

293

Perfluorocarbons as Hydrological Tracers.  

National Technical Information Service (NTIS)

The feasibility of using perfluorocarbons in a highly sensitive and environmentally safe water tracer scheme was examined. It was found possible to disperse the perfluorocarbon into an aqueous medium by formation of a stable microemulsion or through the u...

S. L. Kerrin

1981-01-01

294

New physical Lagrangian tracer  

SciTech Connect

A physical Lagrangian tracer will be operational and available for use within the near future. The tracer is an adjustable buoyancy constant volume balloon with an onboard microprocessor to serve an appropriate array of sensors, and to control buoyancy. Tracking and data reporting is to be accomplished via the ARGOS satellite-borne data system, yielding both a local and a world-wide capability. 5 references, 1 figure.

Zak, B.D.

1984-01-01

295

Synthesis, characterization, and monkey PET studies of [¹?F]MK-1312, a PET tracer for quantification of mGluR1 receptor occupancy by MK-5435.  

PubMed

Two moderately lipophilic, high affinity ligands for metabotropic glutamate receptor subtype 1 (mGluR1) were radiolabeled with a positron-emitting radioisotope and evaluated in rhesus monkey as potential PET tracers. Both ligands were radiolabeled with fluorine-18 via nucleophilic displacement of the corresponding 2-chloropyridine precursor with [¹?F]potassium fluoride. [¹?F]MK-1312 was found to have a suitable signal for quantification of mGluR1 receptors in nonhuman primates and was more thoroughly characterized. In vitro autoradiographic studies with [¹?F]MK-1312 in rhesus monkey and human brain tissue slices revealed an uptake distribution consistent with the known distribution of mGluR1, with the highest uptake in the cerebellum, moderate uptake in the hippocampus, thalamus, and cortical regions, and lowest uptake in the caudate and putamen. In vitro saturation binding studies in rhesus monkey and human cerebellum homogenates confirmed that [¹?F]MK-1312 binds to a single site with a B(max) /K(d) ratio of 132 and 98, respectively. PET studies in rhesus monkey with [¹?F]MK-1312 showed high brain uptake and a regional distribution consistent with in vitro autoradiography results. Blockade of [¹?F]MK-1312 uptake with mGluR1 allosteric antagonist MK-5435 dose-dependently reduced tracer uptake in all regions of gray matter to a similarly low level of tracer uptake. This revealed a large specific signal useful for determination of mGluR1 receptor occupancy in rhesus monkey. Taken together, these results are promising for clinical PET studies with [¹?F]MK-1312 to determine mGluR1 occupancy of MK-5435. PMID:20524178

Hostetler, Eric D; Eng, Waisi; Joshi, Aniket D; Sanabria-Bohórquez, Sandra; Kawamoto, Hiroshi; Ito, Satoru; O'Malley, Stacey; Krause, Stephen; Ryan, Christine; Patel, Shil; Williams, Mangay; Riffel, Kerry; Suzuki, Gentaroh; Ozaki, Satoshi; Ohta, Hisashi; Cook, Jacquelynn; Burns, H Donald; Hargreaves, Richard

2011-02-01

296

A stream tracer technique employing ionic tracers and specific conductance data  

Microsoft Academic Search

The stream tracer technique and transient storage models (TSMs) have become common tools in stream solute and hyporheic exchange studies. The expense and logistics associated with water sample collection and analysis often results in limited temporal resolution of stream tracer breakthrough curves (BTCs). Samples are often collected without a priori or real-time knowledge of BTC information, which can result in

B. L. McGlynn; M. N. Gooseff

2004-01-01

297

Gas geochemistry studies at the gas hydrate occurrence in the permafrost environment of Mallik (NWT, Canada)  

NASA Astrophysics Data System (ADS)

We present real-time mud gas monitoring data as well as results of noble gas and isotope investigations from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. Mud gas monitoring (extraction of gas dissolved in the drill mud followed by real-time analysis) revealed more or less complete gas depth profiles of Mallik 4L-38 and Mallik 5L-38 wells for N_2, O_2, Ar, He, CO_2, H_2, CH_4, C_2H_6, C_3H_8, C_4H10, and 222Rn; both wells are approx. 1150 m deep. Based on the molecular and and isotopic composition, hydrocarbons occurring at shallow depth (down to ˜400 m) are mostly of microbial origin. Below 400 m, the gas wetness parameter (CH_4/(C_2H_6 + C_3H_8)) and isotopes indicate mixing with thermogenic gas. Gas accumulation at the base of permafrost (˜650 m) as well as ?13C and helium isotopic data implies that the permafrost inhibits gas flux from below. Gas hydrate occurrence at Mallik is known in a depth between ˜890 m and 1100 m. The upper section of the hydrate bearing zone (890 m--920 m) consists predominantly of methane bearing gas hydrates. Between 920 m and 1050 m, concentration of C_2H_6, C_3H_8, and C_4H10 increases due to the occurrence of organic rich sediment layers. Below that interval, the gas composition is similar to the upper section of the hydrate zone. At the base of the hydrate bearing zone (˜1100 m), elevated helium and methane concentrations and their isotopic composition leads to the assumption that gas hydrates act as a barrier for gas migration from below. In mud gas samples from the hydrate zone, the concentrations of all noble gases are lower than in air. Using Ne as a tracer for air contamination, the air-normalized abundances of Ar, Ke and Xe in those samples increase with their mass. Non-atmospheric elemental ratios of the heavier noble gases are most possible the result of elemental fractionation during hydrate formation.

Wiersberg, T.; Erzinger, J.; Zimmer, M.; Schicks, J.; Dahms, E.; Mallik Working Group

2003-04-01

298

Characterization of organic compounds and molecular tracers from biomass burning smoke in South China I: Broad-leaf trees and shrubs  

Microsoft Academic Search

Biomass burning smoke constituents are worthy of concern due to its influence on climate and human health. The organic constituents and distributions of molecular tracers emitted from burning smoke of six natural vegetations including monsoon evergreen broad-leaf trees and shrubs in South China were determined in this study. The gas and particle samples were collected and analyzed by gas chromatography–mass

Zhenzhen Wang; Xinhui Bi; Guoying Sheng; Jiamo Fu

2009-01-01

299

High temperature gas-cooled reactor: gas turbine application study  

SciTech Connect

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.

Not Available

1980-12-01

300

Dating of young groundwater using tritium and gaseous tracers (SF6, SF5CF3, CFC-12, H-1301): case study from southern Poland  

NASA Astrophysics Data System (ADS)

Groundwater is an important source of potable water in many countries. While it covers ca. 50% of the global drinking water needs, in Europe this share is even higher, reaching approximately 70%. Nowadays, this strategic resource is at risk due to anthropogenic pollutants of various nature entering shallow aquifers. Proper management of groundwater resources requires thorough understanding of groundwater dynamics on time scales characteristic for the history of pollutant input to groundwater. The bomb-tritium has been used for several decades now as a tracer of choice to detect recent recharge and to quantify groundwater residence times on time scales extending from several years to several decades. The lumped-parameter modeling was the most often employed approach in this context. Since nowadays atmospheric concentrations of tritium are approaching natural levels in most parts of the world, the usage of this tracer has become more problematic. Therefore, there is a growing interest in alternative indicators of groundwater age in shallow aquifers. Anthropogenic trace gases present in the atmosphere, such as freons (CFC-11, CFC-12, CFC-113) and sulfur hexafluoride (SF6), have been applied in numerous case studies as substitutes of tritium. Here we present the results of a comprehensive study aimed at quantifying mean residence time of groundwater in the recharge area of porous sandy aquifer system located in the southern Poland. The principal economic role of the aquifer, consisting of two water-bearing strata, is to provide potable water for public and private users. The yield of the aquifer is insufficient to meet all the needs and, as a consequence, licensing conflicts arise between water supply companies and industry on the amount of water available for safe exploitation. To quantify residence time distribution (RTD) functions of water parcels arriving at the production wells located in the recharge area of the aquifer, tritium along with several gaseous tracers was employed. Apart of well-established tracers such as SF6 and CFC-12, also other trace gases present in the atmosphere (SF5CF3 and H-1301) were tested as age indicators of young groundwater. Time series of tracer concentrations in the sampled boreholes were interpreted with the aid of lumped-parameter models. In parallel, the arrival times of tracers to the selected wells were calculated with the aid of 3D flow and transport model available for the studied groundwater system and compared with the RTD functions obtained from lumped-parameter modeling. Acknowledgements. Partial financial support of this work through GENESIS project (http:/www.thegenesisproject.eu) funded by the European Commission 7FP contract 226536 and through the funds from the Polish Ministry of Science and High Education (projects Nr. N N525 362637 and 11.11.220.01) is kindly acknowledged.

Rozanski, Kazimierz; Bartyzel, Jakub; Dulinski, Marek; Kuc, Tadeusz; Sliwka, Ireneusz; Mochalski, Pawel; Kania, Jaroslaw; Witczak, Stanislaw

2013-04-01

301

Qualitative and quantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and sucrose caramels by gas-liquid chromatography-mass spectrometry. Di-D-fructose dianhydrides as tracers of caramel authenticity.  

PubMed

The monosaccharide (D-fructose, D-glucose, anhydrosugars), disaccharide (glucobioses) and pseudodisaccharide (di-D-fructose dianhydrides) content of D-fructose, D-glucose and sucrose caramels has been determined by gas-liquid chromatography-mass spectrometry (GLC-MS) of their trimethylsilyl (TMS) or TMS-oxime derivatives. The chromatographic profiles revealed significant differences in the disaccharide/pseudodisaccharide distribution depending on the caramel source: a D-fructose caramel contains prominent proportions of di-D-fructose dianhydrides, a D-glucose caramel mainly D-glucobioses, and a sucrose caramel similar proportions of both disaccharide/pseudodisaccharide series. It is noteworthy that di-D-fructose dianhydrides are found in all three types of caramels and might then be used as specific tracers of the authenticity of caramel, i.e., a product resulting from the controlled heat treatment of food-grade carbohydrates for use as food additives. PMID:10399331

Ratsimba, V; García Fernández, J M; Defaye, J; Nigay, H; Voilley, A

1999-06-01

302

Tracer mixing at fracture intersections  

SciTech Connect

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.

Li, Guomin

2001-02-10

303

a Meteorological Tracer Technique Using Uranine Dye  

Microsoft Academic Search

A water-soluble fluorescent-dye aerosol has been used successfully as a meteorological tracer. Because of simple instrumental analysis of field samples and great sensitivity, the technique offers large savings in the cost of tracer studies. The aerosol consists of 2- to 10-micron particles of uranine, generated by pneumatic atomization of a solution. The analysis is based on the fluorescence of a

Elmer Robinson; J. A. MacLeod; C. E. Lapple

1959-01-01

304

CO, NOx and 13CO2 as tracers for fossil fuel CO2: results from a pilot study in Paris during winter 2010  

NASA Astrophysics Data System (ADS)

Measurements of the mole fraction of the CO2 and its isotopes were performed in Paris during the MEGAPOLI winter campaign (January-February 2010). Radiocarbon (14CO2) measurements were used to identify the relative contributions of 77% CO2 from fossil fuel consumption (CO2ff from liquid and gas combustion) and 23% from biospheric CO2 (CO2 from the use of biofuels and from human and plant respiration: CO2bio). These percentages correspond to average mole fractions of 26.4 ppm and 8.2 ppm for CO2ff and CO2bio, respectively. The 13CO2 analysis indicated that gas and liquid fuel contributed 70% and 30%, respectively, of the CO2 emission from fossil fuel use. Continuous measurements of CO and NOx and the ratios CO/CO2ff and NOx/CO2ff derived from radiocarbon measurements during four days make it possible to estimate the fossil fuel CO2 contribution over the entire campaign. The ratios CO/CO2ff and NOx/CO2ff are functions of air mass origin and exhibited daily ranges of 7.9 to 14.5 ppb ppm-1 and 1.1 to 4.3 ppb ppm-1, respectively. These ratios are consistent with different emission inventories given the uncertainties of the different approaches. By using both tracers to derive the fossil fuel CO2, we observed similar diurnal cycles with two maxima during rush hour traffic.

Lopez, M.; Schmidt, M.; Delmotte, M.; Colomb, A.; Gros, V.; Janssen, C.; Lehman, S. J.; Mondelain, D.; Perrussel, O.; Ramonet, M.; Xueref-Remy, I.; Bousquet, P.

2013-08-01

305

Comparison of /sup 13/C nuclear magnetic resonance and /sup 14/C tracer studies of hepatic metabolism. [Rats and mice  

SciTech Connect

The gluconeogenic pathway from /sup 13/C-labeled substrates, each of which contained the /sup 14/C-labeled counterpart at a tracer level, has been followed in isolated rat liver cells and in isolated perfused mouse liver. The gluconeogenic flux from glycerol, the synthesis of glycogen, the synthesis of glycogen, the stimulation of glycogenolysis by glucagon, the recycling of triacylglycerol, and an increase in pentose cycle activity under the influence of phenazine methosulfate were all observed directly in the /sup 13/C NMR spectra of perfused liver or isolated hepatocytes. The relative concentrations of /sup 13/C label at specific carbons measured by the NMR spectra under these conditions agreed closely with /sup 14/C isotopic distributions measured in extracts of the same doubly labeled samples for specific activities of greater than or equal to 3%. The label distributions measured by both methods were the same to within the experimental errors, which ranged from +-2% to +-7% in these experiments.

Cohen, S.M. (Merck Inst. for Therapeutic Research, Rathway, NJ); Rognstad, R.; Shulman, R.G.; Katz, J.

1981-04-10

306

Hydrochemistry and boron isotopes as natural tracers in the study of groundwaters from North Chianan Plain, Taiwan.  

PubMed

In this paper, hydrochemistry and boron isotopes are successfully applied to elucidate hydrogeological processes by the use of natural tracers. The hydrochemical analysis identifies four end-members in the hydrochemical evolution of groundwater from the North Chianan plain groundwater district. A few groundwater contain extraordinary chlorine concentrations of up to 48,000 mg l(-1). However, the hydrochemistry of groundwater only reveals that high saline water is a dominant factor in groundwater hydrochemistry. It is thought that these groundwater experienced precipitation of carbonates during seawater evaporation that did not involve the precipitation of gypsum. Boron isotopes are very efficient tracers in determining the source of salinisation. The boron isotopes reveal the results of mixing of evaporated seawater and water-sediment interaction. In general, the boron isotope ratio of the groundwater is controlled by a two-end-member mixing system, which is composed of evaporated seawater (isotopically heavy) and fresh surface water (isotopically light). Due to a long lagoonal period in the coastal plain, the groundwaters in the downstream area generally have high Cl/B ratios and relatively heavy boron isotope ratios while those in the upstream area are composed of low Cl/B and light boron isotopes. However, there is not a resolvable mixing trend between the Cl/B ratio and the isotopic composition of boron. It is probably obscured by a highly variable boron isotope ratio in fresh surface water and through fractionation associated with water-rock interaction. Both factors would decrease the boron isotope ratio but one effect cannot be distinguished from the other. PMID:23998391

Lu, Hsueh-Yu

2014-01-01

307

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2010 CFR

...blood-gas studies. (a) Blood-gas studies are performed to detect...impairment in the process of alveolar gas exchange. This defect will...primarily as a fall in arterial oxygen tension either at rest or during exercise. No blood-gas study shall be performed if...

2010-04-01

308

Experimental study on gas permeability of mudstones  

NASA Astrophysics Data System (ADS)

The paper presents the results of gas permeability measurements of mudstones from MHM (Meuse/Haute-Marne) site by the help of measurement facilities in GIG laboratory. The transient pulse technique was used, which can measure very low permeabilities (up to 10 -22 m 2). Cylindrical 40 mm diameter and about 40 mm length samples come from different distances with respect to the wall of the main access shaft of the MHM URL. The relationship between the permeability and the state of stress is studied and the problem of gas transfer in the saturated sample is analyzed. The relationship between the rupture of sample and the permeability will be also discussed. Experimental (and numerical) results show that the Callovo-Oxfordian stratum of MHM has very low gas permeabilities (?2 × 10 -21 m 2). The disturbance linked to the excavation of shafts is not significant. Results show that the interstice gradient of gas pressure can induce pore water displacement. Furthermore, it was found that the permeability does not change very much even if a rupture occurs in tests with a confining pressure (11 MPa) equivalent to the lithological pressure at the depth of about 467 m.

Billiotte, Joël; Yang, Diansen; Su, Kun

309

Determination of stream reaeration coefficients by use of tracers  

USGS Publications Warehouse

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

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

1989-01-01

310

A study of a radon gas scrubber  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

311

A Study of a Radon Gas Scrubber  

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

312

The Reanalysis for Stratospheric Trace Gas Studies  

NASA Technical Reports Server (NTRS)

The "Reanalysis for Stratospheric Trace Gas Studies" (ReSTS) project intends to provide a state-of-the-art meteorological dataset for use in chemistry-transport models (CTMs). The initial focus is on the period from May 1991 until April 1995, which encompasses the initial few years of observations from NASA's Upper Atmosphere Research Satellite (UARS) as well as the abrupt increase and slow decay of volcanic aerosol loading from Mount Pinatubo. The reanalysis is being performed using NASA's operational "GEOS-4" data assimilation system. The results presented in this paper will begin with an overview of the meteorology of the ReSTS period, validating the ReSTS data against independent analyses, followed by an evaluation of the system statistics (the "Observation minus Forecast" for different input data types). Some sensitivities to the assumptions made in the assimilation process will be presented, including aspects of the forecast model and the statistical model used in the observation-forecast merging. Aspects of trace-gas transport will be discussed, focussing on the on-line water vapor distribution (which is a quasi-inert trace gas in the stratosphere), off-line transport studies of ozone and selected long-lived species, as well as assimilated ozone. The results will be discussed in the context of transport studies and our ability to use reanalyzed datasets to examine long-term variations in the meteorology and composition of the middle atmosphere.

Pawson, Steven

2003-01-01

313

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

Microsoft Academic Search

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

LS Zuckier

1997-01-01

314

Inorganic Tracer Use - Lake Fryxell  

NSF Publications Database

Title : Inorganic Tracer Use - Lake Fryxell Type : Antarctic EAM NSF Org: OD / OPP Date : June 27 ... Action Memorandum (Inorganic Tracer Use at Lake Fryxell) To: Files (S.7 - Environment) Manager ...

315

Novel and non-traditional use of stable isotope tracers to study metal bioavailability from natural particles  

USGS Publications Warehouse

We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails (Lymnaea stagnalis) to synthetic water spiked with Cu that was 99.4% 65Cu to increase the relative abundance of 65Cu in the snail’s tissues from 32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing Fe–Al particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used 63Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes.

Croteau, Marie-Noele; Cain, Daniel J.; Fuller, Christopher C.

2013-01-01

316

Analysis of tracer and thermal transients during reinjection  

SciTech Connect

This work studied tracer and thermal transients during reinjection in geothermal reservoirs 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, they employed three mathematical models namely, the convection-dispersion (CD) model, matrix diffusion (MD) model, and the Avdonin (AD) model, which were developed to study tracer and heat transport in a single vertical fracture. The authors 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 non-linear regression program to match tracer return profiles to the solutions. We matched the appropriate solutions to the three sets of data obtained from the interwell tracer tests without recirculation at Wairakei, New Zealand. All model matches had small residuals but differed considerably in capturing the distinctive features such as peak time and tailing of the profiles. We developed new solutions to the mathematical models to interpret the return profiles from interwell tracer tests with recirculation. They also developed solutions to the CD and MD models to interpret the return profiles of injection-backflow tracer tests. Finally they suggested thermal injection-backflow tests as a means to estimate the thermal transport parameters. The solution to the MD model can be used for interpreting thermal injection-backflow tests.

Kocabas, I.

1990-01-01

317

Solar/Gas Systems Impact Analysis Study.  

National Technical Information Service (NTIS)

The impacts of solar/gas technologies on gas consumers and on gas utilities was measured separately and compared against the impacts of competing gas and electric systems in four climatic regions of the U.S. A methodology was developed for measuring the b...

E. F. Hahn B. Preble C. P. Neill J. C. Loose T. E. Poe

1984-01-01

318

Past leaded gasoline emissions as a nonpoint source tracer in riparian systems: A study of river inputs to San Francisco Bay  

USGS Publications Warehouse

Variations in the isotopic composition of lead in 1995-1998 river waters flowing into San Francisco Bay trace the washout of lead deposited in the drainage basin from leaded gasoline combustion. At the confluence of the Sacramento and San Joaquin rivers where they enter the Bay, the isotopic compositions of lead in the waters define a linear trend away from the measured historical compositions of leaded gas in California. The river waters are shifted away from leaded gasoline values and toward an isotopic composition similar to Sierra Nevadan inputs which became the predominant source of sedimentation in San Francisco Bay following the onset of hydraulic gold mining in 1853. Using lead isotopic compositions of hydraulic mine sediments and average leaded gasoline as mixing end members, we calculate that more than 50% of the lead in the present river water originated from leaded gasoline combustion. The strong adsorption of lead (log K(d) > 7.4) to particulates appears to limit the flushing of gasoline lead from the drainage basin, and the removal of that lead from the system may have reached an asymptotic limit. Consequently, gasoline lead isotopes should prove to be a useful nonpoint source tracer of the environmental distribution of particle- reactive anthropogenic metals in freshwater systems.

Dunlap, C. E.; Bouse, R.; Flegal, A. R.

2000-01-01

319

Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J = 4 ? 3, HCO+ J = 4 ? 3, and CS J = 7 ? 6  

NASA Astrophysics Data System (ADS)

We report HCN J = 4 ? 3, HCO+ J = 4 ? 3, and CS J = 7 ? 6 observations in 20 nearby star-forming galaxies with the Atacama Pathfinder EXperiment 12 m telescope. Combined with four HCN, three HCO+, and four CS detections from the literature, we probe the empirical link between the luminosity of molecular gas (L^{\\prime }_gas) and that of infrared emission (L IR), up to the highest gas densities (~106 cm-3) that have been probed so far. For nearby galaxies with large radii, we measure the IR luminosity within the submillimeter beam size (14''-18'') to match the molecular emission. We find linear slopes for L^{\\prime }_{CS\\, J=7{--}6}-L IR and L^{\\prime }_{HCN\\, J=4{--}3}-L IR, and a slightly super-linear slope for L^{\\prime }_{HCO^+\\, J=4{--}3}-L IR. The correlation of L^{\\prime }_{CS\\, J=7{--}6}-L IR even extends over eight orders of luminosity magnitude down to Galactic dense cores, with a fit of log(L IR) =1.00(± 0.01) ×log(L^{\\prime }_{CS\\, J=7{--}6}) + 4.03(± 0.04). Such linear correlations appear to hold for all densities >104 cm-3, and indicate that star formation rate is not related to the free-fall timescale for dense molecular gas.

Zhang, Zhi-Yu; Gao, Yu; Henkel, Christian; Zhao, Yinghe; Wang, Junzhi; Menten, Karl M.; Güsten, Rolf

2014-04-01

320

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...

321

Tight gas sands study breaks down drilling and completion costs  

Microsoft Academic Search

Given the high cost to drill and complete tight gas sand wells, advances in drilling and completion technology that result in even modest cost savings to the producer have the potential to generate tremendous savings for the natural gas industry. The Gas Research Institute sponsored a study to evaluate drilling and completion costs in selected tight gas sands. The objective

B. Brunsman; B. Saunders

1994-01-01

322

Evaluating short-term changes in recreational water quality during a hydrograph event using a combination of microbial tracers, environmental microbiology, microbial source tracking and hydrological techniques: a case study in Southwest Wales, UK.  

PubMed

Quantitative assessment of multiple sources to short-term variations in recreational water quality, as indexed by faecal indicator organism (FIO) concentrations, is becoming increasingly important with adoption of modern water quality standards and catchment-based water quality management requirements (e.g. the EU Water Framework Directive, Article 11 'Programmes of Measures' and the US Clean Water Act, 'Total Maximum Daily Loads'). This paper describes a study combining microbial tracers, intensive FIO measurement, open channel hydrology and molecular microbial source tracking (MST) to enhance understanding of recreational water quality at Amroth in southwest Wales, UK. Microbial tracers were released from four stream inputs during a moderate hydrograph event. Tracers from two local streams impacted simultaneously with a period of maximum FIO concentrations at the near-shore compliance monitoring site. Connection between these inputs and this site were rapid (9-33 min). Water quality impairment from a more remote stream input followed, 12.85 h after tracer release, sustaining FIO concentrations above desired compliance levels. MST analysis showed dominance of ruminant Bacteroidales genetic markers, associated with agricultural pollution. This integration of tracers and MST offers additional information on the movement and individual sources causing water quality impairment. PMID:20630556

Wyer, Mark D; Kay, David; Watkins, John; Davies, Cheryl; Kay, Chris; Thomas, Rod; Porter, Jonathan; Stapleton, Carl M; Moore, Heather

2010-09-01

323

Noble gases as natural tracers of water circulation in the Paris Basin: 2. Calibration of a groundwater flow model using noble gas isotope data  

NASA Astrophysics Data System (ADS)

Using the rare gas concentrations in the aquifers of the Paris Basin (see part 1 of this series), a numerical model of a two-dimensional cross section of the entire Paris Basin was built to simulate groundwater flow and the transport of 3He, 4He, and 40Ar isotopes. The model included seven aquifers separated by seven aquitards in a steady state flow regime. Transport of the gases is by advection, diffusion, and dispersion in steady or transient states. The 4He transport was simulated first and made it possible to calibrate both the crustal flux of this isotope and the average permeability of each aquifer, which were then favorably compared with measured values. These values present a high variability from aquifer to aquifer, between 8.5 × 10-7 and 3.5 × 10-4 m s-1. The water velocities and average residence times were also estimated. Average turnover times for the different aquifers are highly variable, ranging from 8700 years for the shallowest one (Ypresian) to 30 Myr for the deepest one (Trias). The calibrated model was also able to correctly represent the distribution of 3He and 40Ar in the basin. Diffusion proved to be an important mechanism for vertical transfer through the aquitards of the helium isotopes, as opposed to 40Ar, which is transported mainly by advection. On the basis of the (4He/40Ar) radiogenic ratio a constant value of 10-l1 m s-1 was attributed to the permeability of all the aquitards. A sensitivity study showed that the permeability of the aquitards situated in the lower part of the basin (Lias and aquitards in the Triassic and Dogger) could not be higher than 10-11 m s-1 given the observed distribution of the radiogenic 4He/40Ar ratio, but a lower limit could not be defined. The crustal fluxes of 3He, 4He, and 40Ar in the basin were estimated at 4.33 × 10-13 mol m-2 yr-1, 4. × 10-6 mol m-2 yr-1 and 2.52 × 10-7 mol m-2 yr-1, respectively. The simulation of the 3He and 4He transport showed that theR/Ra ratio (value of the measured R = 3He/4He ratio normalized to the atmospheric ratio Ra) entering at the base of the Trias from the bedrock remained constant while crossing the basin except in the zones close to the recharge areas where it is influenced by the atmospheric component. This constancy is due to the low radiogenic/nucleogenic production rate of these isotopes inside the basin, as compared to the crustal flux.

Castro, Maria Clara; Goblet, Patrick; Ledoux, Emmanuel; Violette, Sophie; de Marsily, Ghislain

1998-10-01

324

Lidar tracking of multiple fluorescent tracers: Method and field test  

NASA Technical Reports Server (NTRS)

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.

Eberhard, Wynn L.; Willis, Ron J.

1992-01-01

325

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

SciTech Connect

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.

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

326

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

PubMed Central

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.

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

2010-01-01

327

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-J lines of dense gas tracers (Erratum)  

Microsoft Academic Search

With the incorporation of high-J molecular lines, we aim to constrain the\\u000aphysical conditions of the dense gas in the central region of the Seyfert 2\\u000agalaxy NGC 1068 and to determine signatures of the AGN or the starburst\\u000acontribution.\\u000a We used the James Clerk Maxwell Telescope to observe the J=4-3 transition of\\u000aHCN, HNC, and HCO+, as well as

J. P. Pérez-Beaupuits; M. Spaans; S. Aalto; S. García-Burillo; A. Fuente; A. Usero

2009-01-01

328

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

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.

LeCain, Gary D.

1998-01-01

329

Cancer Tracer Synthesis Resources  

Cancer.gov

The Cancer Imaging Program has been creating Investigational New Drug Applications (IND) for imaging agents in order to engage in multi-center clinical trials of these materials. A subset of the documents filed is being made available to the research community to implement routine synthesis of tracers at their own facilities and to assist investigators with the filing of their own INDs. The first of these document sets is for F-18 fluorothymidine (FLT).

330

N2O As A Tracer Of Antarctic Atmospheric Flows  

NASA Technical Reports Server (NTRS)

Report discusses use of natural N2O as tracer gas in effort to determine large-scale lower stratospheric air flows during 1987 Airborne Antarctic Ozone Experiment. Data essential to understanding motions of air into and out of southern polar vortex and "ozone hole". N2O chosen as tracer because it has purely tropospheric sources, has troposheric lifetime greater than 20 years, and has long chemical lifetime in lower stratosphere.

Loewenstein, M.; Podolske, J. R.; Chan, K. R.; Strahan, S. E.

1992-01-01

331

A personal exposure study employing scripted activities and paths in conjunction with atmospheric releases of perfluorocarbon tracers in Manhattan, New York  

PubMed Central

A personal exposure study was conducted in New York City as part of the Urban Dispersion Program (UDP). It examined the contact of individuals with four harmless perflourocarbon tracers (PFT) released in Midtown Manhattan with approval by city agencies at separate locations, during two types of experiments, completed during each release period. Two continuous 1 h release periods separated by a 1.5 h ventilation time were completed on 3 October 2005. Stationary site and personal exposure measurements were taken during each period, and the first half hour after the release ended. Two types of scripted exposure activities are reported: Outdoor Source Scale, and Outdoor Neighborhood Scale; requiring 1- and 10-min duration samples, respectively. The results showed that exposures were influenced by the surface winds, the urban terrain, and the movements of people and vehicles typical in urban centers. The source scale exposure data indicated that local conditions significantly affected the distribution of each tracer, and consequently the exposures. The highest PFT exposures resulted from interaction of the scripted activities with local surface conditions. The range measured for 1- min exposures were large with measured values exceeding 5000 ppqv (parts per quadrillion by volume). The neighborhood scale measurements quantified exposures at distances up to seven blocks away from the release points. Generally, but not always, the PFT levels returned quickly to zero indicating that after cessation of the emissions the concentrations decrease rapidly, and reduce the intensity of local exposures. The near source and neighborhood personal exposure route results provided information to establish a baseline for determining how a release could affect both the general public and emergency responders, and evaluate the adequacy of re-entry or exit strategies from a local area. Finally, the data also show that local characteristics can produce “hot spots”.

LIOY, PAUL J; VALLERO, DANIEL; FOLEY, GARY; GEORGOPOULOS, PANOS; HEISER, JOHN; WATSON, TOM; REYNOLDS, MICHAEL; DALOIA, JAMES; TONG, SAI; ISUKAPALLI, SASTRY

2014-01-01

332

Particle and tracer diffusion in complex liquids  

NASA Astrophysics Data System (ADS)

The diffusion of fluorescent tracers can be studied using fluorescence correlation spectroscopy (FCS). This powerful method offers the possibility to monitor very small tracers at low concentrations, down to single molecules. Furthermore it possesses a sub-femtoliter detection volume that can be precisely positioned in a heterogeneous environment to probe the local dynamics. Despite its great potential and high versatility in addressing the diffusion and transport properties in complex systems, FCS has been predominantly applied in molecular and cell biology. Here we present some applications that are more relevant for material and soft matter science. First, we study the diffusion of single tracers with molecular sizes in undiluted polymer systems. Next, the diffusion of small molecules and semiconductor nanoparticles (quantum dots) in silica inverse opals is studied and correlated to the size and morphology of the inverse opals. Finally, we show how FCS can be used to measure the diffusion coefficient of nanoparticles at water-oil interfaces.

Koynov, Kaloian; Butt, Hans-Jürgen

2013-02-01

333

Tight Gas Sands Log Interpretation: Problem Study.  

National Technical Information Service (NTIS)

A large undeveloped natural gas resource exists in low-permeability (tight) sandstone reservoirs. Difficulties in reservoir characterization and estimation of production potential in tight gas sands have hindered the development of this resource. Interpre...

C. L. Biddison E. R. Monson G. C. Kukal K. E. Simons R. E. Hill

1983-01-01

334

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

A reactive-transport model for 14C was developed to test itsapplicability to the Aidlin geothermal system. Using TOUGHREACT, wedeveloped a 1-D grid to evaluate the effects of water injection andsubsequent water-rock-gas interaction on the compositions of the producedfluids. A dual-permeability model of the fracture-matrix system was usedto describe reaction-transport processes in which the permeability of thefractures is many orders of magnitude higher than that of the rockmatrix. The geochemical system included the principal minerals(K-feldspar, plagioclase, calcite, silica polymorphs) of themetagraywackes that comprise the geothermal reservoir rocks. Initialsimulation results predict that the gas-phase CO2 in the reservoir willbecome more enriched in 14C as air-equilibrated injectate water (with amodern carbon signature) is incorporated into the system, and that thesechanges will precede accompanying decreases in reservoir temperature. Theeffects of injection on 14C in the rock matrix will be lessened somewhatbecause of the dissolution of matrix calcite with "dead"carbon.

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

2006-06-01

335

PAC Probes as Diffusion Tracers in Solids  

NASA Astrophysics Data System (ADS)

Perturbed angular correlation (PAC) probe atoms have been used as tracers to study diffusion in solids. The method works for diffusion on a sublattice for which the point symmetry is noncubic and the electric field gradient (EFG) at the probe nucleus reorients in each jump. Such motion leads to relaxation of the nuclear quadrupole interaction. Precise values of the tracer jump frequency have been obtained from fits of measured PAC perturbation functions. Results obtained to date are reviewed for Cd tracer atoms in rare-earth indides such as LaIn3 that have the L12 crystal structure, for which each jump on the In-sublattice reorients the EFG by 90°. New results are presented for LaSn3 and prospects for future studies are outlined.

Collins, Gary S.; Favrot, AuréLie; Kang, Li; Nieuwenhuis, Egbert Rein; Solodovnikov, Denys; Wang, Jipeng; Zacate, Matthew O.

2004-12-01

336

Study ranks oil, gas industry technology needs  

SciTech Connect

A survey of majors, other integrated oil and gas companies, independents, and service companies identified a wide variety of new and improved technologies that the oil and gas industry will need to continue to effectively and efficiently find, produce, and process oil and gas reserves. The survey is included in the National Petroleum Council`s July 19, 1995, draft report Research, Development, and Demonstration Needs of the Oil and Gas Industry. NPC identified 250 technologies in the following 11 areas: exploration, development, drilling and completion, production, deepwater offshore, Arctic region activities, oil processing refining, gas processing, gas gathering, gas storage, and environmental and regulatory. This article summarizes the results of the survey and describes the respondents. Four articles that follow describe the 250 technologies addressed in the survey in more detail.

Moritis, G.

1995-10-30

337

A ROLE FOR ALTIMETER RADARS IN GAS EXCHANGE STUDIES  

Microsoft Academic Search

Accurate estimates of air-sea transfer rates of radiatively active gases are needed for studies of regional and global gas cycling and for climate change studies. However, estimates using traditional wind speed - gas transfer velocity parameterizations vary by a factor of 2- 3, contributing significantly to error budgets in global modeling of gas exchange and the carbon cycle. A decade

Nelson M. Frew; David M. Glover; Scott J. McCue

338

Atmospheric trace gas studies in Antarctica  

SciTech Connect

This paper overviews trace gas studies that were carried out in Antarctica, with an emphasis on those by the Washingon State University Laboratory for Atmospheric Research. The results of trend analysis revealed that, although the atmospheric concentrations of F-11, F-12, CH3CCl3, and other halocarbons are still increasing, their rate of increase has slowed from the increasing rates observed in the 1970s. Vertical concentration profiles in Antarctica are shown to be dependent upon the seasonal variations in circulation patterns associated with the final warming and breakup of the polar vortex. It is shown that the stratospheric-tropospheric air exchange over Antarctica is influenced primarily by the following factors: (1) general circulation patterns with subsidence over the polar regions, (2) stratospheric air injection in the vicinity of jet streams and injection from tropopause folding upstream of troughs, and (3) mountain waves of sufficient magnitude to displace air parcels across the tropopause. 120 references.

Cronn, D.R.; Schilling, K.J.

1988-08-01

339

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)

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

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

2014-05-01

340

On the Interpretation of tracer experiments  

SciTech Connect

Recently, two new developments appeared in the literature on modelling flow and transport in heterogeneous systems. The first one is the use of two different concentration variables namely, the resident and flux concentrations, in tracer studies. The second one involves representing the heterogeneity by means of a frequency disribution function for immobile phase size. Based on these developments, this work involves a classification of the solutions of transport equation in heterogeneous systems. It also demonstrates interpretation of tracer experiments in such systems. Distinguishing between the resident and flux concentration variables prevents the inconsistencies between theoretical solutions and actual conditions of experiments and hence, allows correct interpretation of tracer return profiles. Representing heterogeneities by means of frequency distribution functions allows representing matrix blocks of various sizes likely to exist in a fractured reservoir.

Kocabas, Ibrahim; Horne, Roland N.; Brigham, William E.

1994-01-20

341

Geologic studies of deep natural gas resources  

USGS Publications Warehouse

In 1995, the USGS estimated a mean resource of 114 trillion cubic feet of undiscovered technically recoverable natural gas in plays deeper than 15,000 feet/4,572 meters in onshore regions of the United States. This volume summarizes major conclusions of ongoing work. Chapters A and B address the areal extent of drilling and distribution of deep basins in the U.S. Chapter C summarizes distribution of deep sedimentary basins and potential for deep gas in the former Soviet Union. Chapters D and E are geochemical papers addressing source-rock issues and deep gas generation. Chapter F develops a probabilistic method for subdividing gas resources into depth slices, and chapter G analyzes the relative uncertainty of estimates of deep gas in plays in the Gulf Coast Region. Chapter H evaluates the mechanism of hydrogenation of deep, high-rank spent kerogen by water, with subsequent generation of methane-rich HC gas.

edited by Dyman, T. S.; Kuuskraa, V. A.

2001-01-01

342

Gas purification studies at IGISOL-4  

NASA Astrophysics Data System (ADS)

A new gas purification system has been constructed at the upgraded IGISOL facility, Jyväskylä, to meet the need for ultra-high purity helium and argon buffer gas used in the ion guide technique. The purification of helium using liquid nitrogen-cooled cold traps is investigated and compared with unpurified gas using mass spectra obtained at the focal plane of the separator. Neon, an impurity intrinsic to the in-house recycled helium, was seen to have high sensitivity to the impurity level of the gas which is expected to reach sub-parts-per-billion level.

Pohjalainen, I.; Moore, I. D.; Eronen, T.; Jokinen, A.; Penttilä, H.; Rinta-Antila, S.

2014-06-01

343

CAESIUM137 AS A SOIL EROSION TRACER: A REVIEW  

Microsoft Academic Search

Abstract: Abstract: Abstract: Abstract: This paper describes a method of soil erosion and soil movement measurements using 137Cs as a tracer. This technique has been used successfully employed for more than 30 years. Caesium-137 is a valuable tracer to study soil erosion. Its chemical and biological move- ment in soil is limited. Practically all redeposition of caesium-137 in soil after

GRZEGORZ J. PORÊBA

2006-01-01

344

Tracer experiments in Eastern Devonian shale  

SciTech Connect

For the purpose of characterizing the properties of the Eastern Devonian gas shale, a seven-day tracer experiment was carried out in August of 1981 by the Los Alamos National Laboratory as part of the DOE's Offset-Well Test. Two wells had been drilled in a Columbia Gas Company field in southeastern Ohio, each with a downhole separation of approximately 120 feet from an existing production well. The isoceles triangle formed by the three wells had an apex angle of approximately 110 degrees. About 56,000 SCF of nitrogen were injected into a producing zone located at a depth of 3300 feet in one of the wells. Gas was then produced from the various wells at different rates and pressures for the duration of the test. Both pressure and gas composition in the three wells were monitored throughout the test.

Cook, T.L.; Brown, L.F.; Meadows, W.R.

1982-01-01

345

VAPOR-PHASE TRANSPORT OF TRICHLOROETHENE IN AN INTERMEDIATE-SCALE VADOSE-ZONE SYSTEM: RETENTION PROCESSES AND TRACER-BASED PREDICTION  

PubMed Central

Gas-phase miscible-displacement experiments were conducted using a large weighing lysimeter to evaluate retention processes for volatile organic compounds (VOCs) in water-unsaturated (vadoze-zone) systems, and to test the utility of gas-phase tracers for predicting VOC retardation. Trichloroethene (TCE) served as a model VOC, while trichlorofluoromethane (CFM) and heptane were used as partitioning tracers to independently characterize retention by water and the air-water interface, respectively. Retardation factors for TCE ranged between 1.9 and 3.5, depending on water content. The results indicate that dissolution into the bulk water was the primary retention mechanism for TCE under all conditions studied, contributing approximately two thirds of the total measured retention. Accumulation at the air-water interface comprised a significant fraction of the observed retention for all experiments, with an average contribution of approximately 24%. Sorption to the solid phase contributed approximately 10% to retention. Water contents and air-water interfacial areas estimated based on the CFM and heptane tracer data, respectively, were similar to independently measured values. Retardation factors for TCE predicted using the partitioning-tracer data were in reasonable agreement with the measured values. These results suggest that gas-phase tracer tests hold promise for characterizing the retention and transport of VOCs in the vadose-zone.

Costanza-Robinson, Molly S.; Carlson, Tyson D.; Brusseau, Mark L.

2013-01-01

346

Radium Isotopes as Tracers of Coastal Circulation Pathways in the Mid- Atlantic Bight.  

National Technical Information Service (NTIS)

Pathways of exchange between the shelf and slope in the Mid-Atlantic Bight were investigated using radiochemical tracer and hydrographic measurements. The four naturally occuring radium isotopes were used as coastal water mass tracers. The final study inc...

L. L. Rasmussen

2003-01-01

347

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

National Technical Information Service (NTIS)

This report provides an experimental plan for a proposed Asian long-range tracer study as part of the international Tracer Experiment and Atmospheric Modeling (TEAM) Project. The TEAM partners are China, Japan, South Korea and the United States. Optimal t...

J. E. Flaherty K. J. Allwine

2007-01-01

348

A stream tracer technique employing ionic tracers and specific conductance data applied to the Maimai catchment, New Zealand  

Microsoft Academic Search

The stream tracer technique and transient storage models (TSMs) have become common tools in stream solute and hyporheic exchange studies. The expense and logistics associated with water sample collection and analysis often results in limited temporal resolution of stream tracer breakthrough curves (BTCs). Samples are often collected without ap riorior real-time knowledge of BTC information, which can result in poor

Michael N. Gooseff; Brian L. McGlynn

2005-01-01

349

A stream tracer technique employing ionic tracers and specific conductance data applied to the Maimai catchment, New Zealand  

Microsoft Academic Search

The stream tracer technique and transient storage models (TSMs) have become common tools in stream solute and hyporheic exchange studies. The expense and logistics associated with water sample collection and analysis often results in limited temporal resolution of stream tracer breakthrough curves (BTCs). Samples are often collected without a priori or real-time knowledge of BTC information, which can result in

Michael N. Gooseff; Brian L. McGlynn

2005-01-01

350

Assessment of loading history of compartments in the knee using bone SPECT/CT: a study combining alignment and 99mTc-HDP tracer uptake/distribution patterns.  

PubMed

This study investigates if the mechanical/anatomical alignment influences the intensity values as well as the distribution pattern of SPECT/CT tracer uptake. Eighty-five knees (mean age 48 ± 16) undergoing 99mTc-HDP-SPECT/CT due to pain were prospectively included. SPECT/CTs were analyzed using a previously validated localization method. The maximum intensities in each femoral, tibial, and patellar joint compartment (medial, lateral, central, superior, and inferior) were noted using a color-coded grading scale (0-10). The Kellgren-Lawrence osteoarthritis score (KL) was assessed on standardized radiographs. Long leg radiographs were used to assess the mechanical/anatomical leg alignment, which was classified as varus, valgus, or neutral. The alignment and KL was correlated with the intensity of tracer uptake in each area of interest (p < 0.05). The intensity of SPECT/CT tracer uptake in the medial and lateral knee compartment significantly correlated with varus or valgus alignment of the knee. A higher degree of osteoarthritis was significantly related to higher tracer uptake in the corresponding joint compartments. SPECT/CT reflects the specific loading pattern of the knee with regard to its alignment. It is also related to the degree of osteoarthritis. Hence, SPECT/CT should be considered for follow-up of patients after realignment treatments, osteotomies, deloader devices, or insoles. PMID:22886713

Hirschmann, Michael T; Schön, Stephan; Afifi, Faik K; Amsler, Felix; Rasch, Helmut; Friederich, Niklaus F; Arnold, Markus P

2013-02-01

351

Experimental Study of Gas Hydrate Dynamics  

NASA Astrophysics Data System (ADS)

Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine and Petroleum Geology 2010, 27, (6), 1157-1165.

Fandino, O.; Ruffine, L.

2011-12-01

352

Experimental studies of selective acid gas removal: Absorption of hydrogen sulfide and carbon dioxide into aqueous methyldiethanolamine using packed columns  

SciTech Connect

The use of aqueous methyldiethanolamine (MDEA) for selective removal of hydrogen sulfide from acid gas streams has been studied in a 2 inch column packed with 1/4 inch ceramic Intalox saddles. The column was operated in a counter-current, steady state fashion. The feed gas composition varied between 1 and 5 mole % hydrogen sulfide and between 0 and 50 mole % carbon dioxide. In order to assist the development of packed column absorption models, the rate at which pure carbon dioxide absorbs into 2 M MDEA was measured as a function of pressure, liquid flow rate and packed bed length. The importance of end effects was carefully evaluated. In addition, draining and tracer methods were used to estimate the amount of static holdup present in the column. Using classical draining methods, as much as 50 % of the total holdup was found to be static. However, according to the step decrease in tracer method, less than 5 % of the total holdup was static. Since the step decrease in tracer method measures the amount of static holdup present in the bed under irrigated conditions, it seems likely that the draining method provides an unrealistic estimate of static holdup. Thus, although the notion of static holdup may be useful as a means of correlating mass transfer coefficients, the data indicate that very little static holdup exists in the column under irrigated conditions. Hence, in the absence of a mechanistically sound model, the choice of whether to use static holdup or dispersion as a means of accounting for deviations from plug flow in the liquid phase should be made on the basis of computational convenience.

Schubert, C.N.

1988-01-01

353

Dispersion of charged tracers in charged porous media  

NASA Astrophysics Data System (ADS)

We report a lattice-Boltzmann scheme to compute the dispersion of charged tracers in charged porous media under the combined effect of advection, diffusion and electro-migration. To this end, we extend the moment propagation approach, introduced to study the dispersion of neutral tracers (Lowe C. and Frenkel D., Phys. Rev. Lett., 77 (1996) 4552), to include the effect of electrostatic forces. This method allows us to compute the velocity autocorrelation function of the charged tracers with high accuracy. The algorithm is validated studying the dispersion coefficient in the case of electro-osmotic flow in a slit without added salt. We find excellent agreement between the numerical and analytical results. This method also provides the full time dependence of the diffusion coefficient, including for charged tracers. We illustrate on the slit case how D(t), which is measured by NMR to probe the geometry of porous media, reflects how the porosity explored by tracers depends on their charge.

Rotenberg, B.; Pagonabarraga, I.; Frenkel, D.

2008-08-01

354

NEXT GENERATION GAS TURBINE (NGGT) SYSTEMS STUDY  

SciTech Connect

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.

Unknown

2001-12-05

355

Theoretical Studies of Gas Phase Bioanions  

NASA Astrophysics Data System (ADS)

Theoretical studies provide insight into anionic states formed by some peptides and nucleic acid bases. A coexistence of conventional valence states and dipole-bound states will be demonstrated for some nucleic acid bases. It will be shown that the instability of zwitterion forms of amino acids in the gas phase relative to their canonical tautomers could be suppressed by attaching an excess electron. As demonstrated for zwitterions of glycine, betaine, and arginine, the solvation by an excess electron provides an extra stabilization by 6-8 kcal/mol relative to the corresponding canonical structures. Simple chemical reactions induced by electron attachment will be discussed. First, we will show that the tautomerization between zwitterionic and canonical forms of isolated amino acids is facilitated by excess electron attachment. For arginine, for example, the anionic tautomers are quasidegenerate in their electronic energies, and the reaction barrier is significantly lowered in comparison with the neutral species. Second, an intermolecular proton transfer induced by electron attachment in the uracil-glycine complex will be discussed. The theoretical results will be compared with the state-of-the-art experimental data from photoelectron spectroscopy and Rydberg electron transfer experiments.

Gutowski, Maciej

2002-03-01

356

Simple light gas guns for hypervelocity studies  

SciTech Connect

Two-stage light guns are used extensively in hypervelocity research. The applications of this technology include impact studies and special materials development. Oak Ridge National Laboratory (ORNL) has developed two-stage guns that accelerate small projectiles (4-mm nominal diameter) to velocities of up to {approx}5 km/s. These guns are relatively small and simple (thus, easy to operate), allowing a significant number of test shots to be carried out and data accumulated in a short time. Materials that have been used for projectiles include plastics, frozen isotopes of hydrogen, and lithium hydride. One gun has been used to demonstrate repetitive operation at a rate of 0.7 Hz; and, with a few design improvements, it appears capable of performing at firing frequencies of 1--2 Hz. A schematic of ORNL two-stage device is shown below. Unlike most such devices, no rupture disks are used. Instead, a fast valve (high-flow type) initiates the acceleration process in the first stage. Projectiles can be loaded into the gun breech via the slide mechanism; this action has been automated which allows repetitive firing. Alternatively, the device is equipped with pipe gun'' apparatus in which gas can be frozen in situ in the gun barrel to form the projectile. This equipment operates with high reliability and is well suited for small-scale testing at high velocity. 17 refs., 6 figs., 2 tabs.

Combs, S.K.; Haselton, H.H.; Milora, S.L.

1990-01-01

357

Multiphase, multicomponent parameter estimation for liquid and vapor fluxes in deep arid systems using hydrologic data and natural environmental tracers  

USGS Publications Warehouse

Multiphase, multicomponent numerical models of long-term unsaturated-zone liquid and vapor movement were created for a thick alluvial basin at the Nevada Test Site to predict present-day liquid and vapor fluxes. The numerical models are based on recently developed conceptual models of unsaturated-zone moisture movement in thick alluvium that explain present-day water potential and tracer profiles in terms of major climate and vegetation transitions that have occurred during the past 10 000 yr or more. The numerical models were calibrated using borehole hydrologic and environmental tracer data available from a low-level radioactive waste management site located in a former nuclear weapons testing area. The environmental tracer data used in the model calibration includes tracers that migrate in both the liquid and vapor phases (??D, ??18O) and tracers that migrate solely as dissolved solutes (Cl), thus enabling the estimation of some gas-phase as well as liquid-phase transport parameters. Parameter uncertainties and correlations identified during model calibration were used to generate parameter combinations for a set of Monte Carlo simulations to more fully characterize the uncertainty in liquid and vapor fluxes. The calculated background liquid and vapor fluxes decrease as the estimated time since the transition to the present-day arid climate increases. However, on the whole, the estimated fluxes display relatively little variability because correlations among parameters tend to create parameter sets for which changes in some parameters offset the effects of others in the set. Independent estimates on the timing since the climate transition established from packrat midden data were essential for constraining the model calibration results. The study demonstrates the utility of environmental tracer data in developing numerical models of liquid- and gas-phase moisture movement and the importance of considering parameter correlations when using Monte Carlo analysis to characterize the uncertainty in moisture fluxes. ?? Soil Science Society of America.

Kwicklis, E. M.; Wolfsberg, A. V.; Stauffer, P. H.; Walvoord, M. A.; Sully, M. J.

2006-01-01

358

Use of rubidium, manganese, and zinc as tracers to measure intestinal permeability by PIXE analysis: basal study in an experimental enteritis model.  

PubMed

Intestinal permeability has been suggested to be closely linked with the etiology or activity of Crohn's disease. However, current methods for measurement of intestinal permeability are too laborious for routine examination, as they require urine collection and/or use of radioisotopes. The present study was performed to develop a more convenient and safer method for assessing intestinal permeability using blood samples rather than urine. Rats with indomethacin-induced enteritis were orally administered Rb, Mn, and Zn as tracers. Intestinal permeability was determined by assaying the levels of Rb, Mn, and Zn in blood samples by particle-induced X-ray emission (PIXE). The distributions of Rb, Mn, and Zn in the small intestine after administration were analyzed by micro-PIXE. The conventional PIXE analysis showed that the levels of Rb and Zn in the blood in the enteritis group were correlated with the grade of enteritis. The micro-PIXE analysis showed that Rb, Mn, and Zn were translocated into the wall of the proximal small intestine 5 min after administration, and this effect was more conspicuous in the enteritis group than in controls. Analysis of blood or small intestine tissue samples using the PIXE allows determination of both intestinal permeability and the route of permeation. PMID:15051898

Nakao, Keitaro; Suzuki, Yasuo; Imaseki, Hitoshi; Joshima, Hisamasa; Tamanoi, Itsuro; Saito, Yasushi

2004-04-01

359

Fluid dynamic studies on scattering aerosol and its generation for application as tracer particles in supersonic flow measurements utilizing laser Doppler velocimeter  

NASA Technical Reports Server (NTRS)

An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited oscillatory fluid velocity field and by comparing the ratio of particle velocity amplitude to the fluid velocity amplitude as a function of particle size and the frequency of oscillation. Particle velocity was measured by using a differential laser Doppler velocimeter. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. It is indicated that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

Mazumder, M. K.; Hoyle, B. D.; Kirsch, K. J.

1974-01-01

360

The fate of motoneurons in the spinal cord after peripheral nerve repair: a quantitative study using the neural tracer horseradish peroxidase.  

PubMed

This study assessed the changes that occurred in the spinal motoneuron pool after the repair of a specific peripheral nerve by means of several clinically appropriate surgical techniques: nerve graft, muscle graft, and epineurial suture. The motoneuron pool relating to a single muscle was assessed at 50, 100, 200, and 300 days after repair via retrograde axonal transport of the neural tracer horseradish peroxidase. The results indicate that although a small portion of the motoneuron population dies following peripheral nerve surgery, this is not a significant number. The majority of the anterior horn cells appear to have the ability to both survive nerve transection and form new functional connections with the regenerated nerve after repair. The degree of cell loss is influenced by the nature of the injury and the method of repair implemented. Injuries involving neurotmesis result in the loss of a greater proportion of the cell population than less severe injuries involving axonotmesis. A greater proportion of the motoneuron population is preserved when the severed nerve has been repaired using a direct epineurial suture than when repair is achieved by means of a graft. The two methods of grafting produced comparable results, although the muscle graft tended to result in the preservation of a greater number of cells than the nerve graft, making it an acceptable alternative method for the surgical repair of short gaps in peripheral nerves. PMID:7897525

Gilmour, J A; Myles, L M; Glasby, M A

1995-04-01

361

Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements. Progress report  

SciTech Connect

The following are reported: high abundance sensitivity mass spectrometer for U-Th studies; {sup 238}U-{sup 230}Th disequilibrium in recent lavas from Iceland; water-rock interaction from U-Th studies; resonance ionization mass spectrometry of Os and Ti isotopes; and self-diffusion of Mg.

Wasserburg, G.J.

1992-12-31

362

Inhalation pharmacokinetics based on gas uptake studies  

Microsoft Academic Search

An improved pharmacokinetic model is described for inhalation of volatile xenobiotics from a closed gas phase system. This model is based on steady-state kinetics and covers metabolic elimination processes of either first-order, zero-order, or Michaelis-Menten characteristics. It is emphasized that the distribution of a volatile compound between gas phase and organism under steady-state conditions may be much different from a

J. G. Filser; H. M. Bolt

1981-01-01

363

Evaluation of Spatial Straightness Error using LaserTRACER  

NASA Astrophysics Data System (ADS)

In order to improve the evaluation precision of spatial straightness error, new measurement setup using 4 LaserTRACERs were built at National Institute of Metrology (NIM). The LaserTRACER is a length measurement device with sub-micron accuracy. In principle, the LaserTRACER is a traceable interferometer. Experiment was implemented on a granite rail with air-suspending slider to test the spatial straightness of the rail. In the experiment, the retroreflector was mounted on slider and moves alone the rail after the spatial frame of axes was built. Using 4 LaserTRACERs, the spatial coordinates can be calculated by Multilateration algorithm. The optimal arrangement of LaserTRACERs is studied by simulation and experiment. The mathematical model based on GBT11336-2004 was built, and Least squares method is used in the spatial line fitting. The measurement principle and results were verified by comparison with SpatialAnalyzer and Metrolog XG.

He, Mingzhao; Ye, Xiaoyou; Li, Jianshuang; Gan, Xiaochuan

2013-01-01

364

Using predictive uncertainty analysis to optimise tracer test design and data acquisition  

NASA Astrophysics Data System (ADS)

Tracer injection tests are regularly-used tools to identify and characterise flow and transport mechanisms in aquifers. Examples of practical applications are manifold and include, among others, managed aquifer recharge schemes, aquifer thermal energy storage systems and, increasingly important, the disposal of produced water from oil and shale gas wells. The hydrogeological and geochemical data collected during the injection tests are often employed to assess the potential impacts of injection on receptors such as drinking water wells and regularly serve as a basis for the development of conceptual and numerical models that underpin the prediction of potential impacts. As all field tracer injection tests impose substantial logistical and financial efforts, it is crucial to develop a solid a-priori understanding of the value of the various monitoring data to select monitoring strategies which provide the greatest return on investment. In this study, we demonstrate the ability of linear predictive uncertainty analysis (i.e. “data worth analysis”) to quantify the usefulness of different tracer types (bromide, temperature, methane and chloride as examples) and head measurements in the context of a field-scale aquifer injection trial of coal seam gas (CSG) co-produced water. Data worth was evaluated in terms of tracer type, in terms of tracer test design (e.g., injection rate, duration of test and the applied measurement frequency) and monitoring disposition to increase the reliability of injection impact assessments. This was followed by an uncertainty targeted Pareto analysis, which allowed the interdependencies of cost and predictive reliability for alternative monitoring campaigns to be compared directly. For the evaluated injection test, the data worth analysis assessed bromide as superior to head data and all other tracers during early sampling times. However, with time, chloride became a more suitable tracer to constrain simulations of physical transport processes, followed by methane. Temperature data was assessed as the least informative of the solute tracers. However, taking costs of data acquisition into account, it could be shown that temperature data when used in conjunction with other tracers was a valuable and cost-effective marker species due to temperatures low cost to worth ratio. In contrast, the high costs of acquisition of methane data compared to its muted worth, highlighted methanes unfavourable return on investment. Areas of optimal monitoring bore position as well as optimal numbers of bores for the investigated injection site were also established. The proposed tracer test optimisation is done through the application of common use groundwater flow and transport models in conjunction with publicly available tools for predictive uncertainty analysis to provide modelers and practitioners with a powerful yet efficient and cost effective tool which is generally applicable and easily transferrable from the present study to many applications beyond the case study of injection of treated CSG produced water.

Wallis, Ilka; Moore, Catherine; Post, Vincent; Wolf, Leif; Martens, Evelien; Prommer, Henning

2014-07-01

365

Gas absorption studies in microporous hollow fiber membrane modules  

Microsoft Academic Search

A comprehensive experimental investigation of gas-liquid absorption in a shell-and-tube type microporous hydrophobic hollow fiber device in a parallel flow configuration was carried out. Two modes of countercurrent gas-liquid contacting were studied, the wetted mode (absorbent liquid filled pores) and the nonwetted mode (gas-filled pores). The absorbent flowed through the fiber bore in most of the experiments. The systems studied

Sujatha Karoor; Kamalesh K. Sirkar

1993-01-01

366

Radioactive tracer studies of soil and litter arthropod food chains. Progress report, November 1, 1975October 31, 1976. [¹³Cs, Sr  

Microsoft Academic Search

Progress is described in radioisotope measurement of nutrient element flow in soil-litter arthropod food chains. Two models of accumulation (Goldstein-Elwood, Reichle-Crossley) were tested experimentally and found to yield equivalent predictions of ¹³Cs and Sr movement through arthropod populations. Radioisotope retention studies were used to compare trophic strategies of soil tipulids from arctic tundra and temperate forest. Arctic tipulids were found

Crossley; D. A. Jr

1976-01-01

367

A prospective randomised study comparing oral 13C-bicarbonate tracer technique versus indirect calorimetry for measurement of energy expenditure in adults  

PubMed Central

Background and Aims Accurate assessment of energy expenditure (EE) is important in guiding nutritional therapy but current methods are unsatisfactory. This study compared the oral 13C-bicarbonate tracer (BT) technique using the IRIS® system (Wagner, Germany) against indirect calorimetry (IC, ventilated-hood) to measure CO2 output (VCO2) and thus estimate EE. Methods Ten overnight-fasted healthy male volunteers were randomised to studies at rest or mild exercise in a crossover manner. During each study BT-IRIS® and IC were used simultaneously to measure VCO2 and thus EE. Participants ingested a drink labelled with 50mg 13C-bicarbonate and breath samples were collected every 5 min for 180 min and analysed using IRIS®. Bland-Altman plots were used to assess agreement between the two techniques in measurements of VCO2 (L/day) and estimates of EE (kJ/day). Results Mean ± SE age and BMI of participants were 21.1 ± 1.1 yrs and 23.6 ± 0.6 kg/m2. Both at rest and exercise, there was small bias but overall poor agreement between the two techniques as evident by the wide 95% limits of agreement in measurements of VCO2 and EE: rest VCO2 (bias 1.4, SD 93, 95% limits of agreement ?180 to 183), rest EE (?8.3, 1830, ?3595 to 3578), exercise VCO2 (49.3, 66.1, ?80.4 to 178.9) and exercise EE (1083, 1944, ?2727 to 4893). Furthermore, there was also evidence of systematic error in these measurements. Conclusion Prior to clinical application, further optimisation of the BT-IRIS® system should be undertaken, given the poor agreement with IC in measuring VCO2 and estimating EE.

Awad, Sherif; Cui, Helen; Wright, Jeff W; Jackson, Sarah; Macdonald, Ian A; Lobo, Dileep N

2014-01-01

368

Gas release and conductivity modification studies  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

369

Magnetic properties as tracers for source-to-sink dispersal of sediments: A case study in the Taiwan Strait  

NASA Astrophysics Data System (ADS)

Different lithologies between Taiwan and southeastern China lead to diverse mineralogical composition for weathering products derived from the two shores of the Taiwan Strait. Pyrrhotite and magnetite are respectively the dominant magnetic minerals associated with fluvial sediments from western Taiwan and southeastern China. While magnetite commonly co-exists with pyrrhotite in sediments sourced from Taiwan, pyrrhotite has not been found in sediments sourced from mainland China. Associated with such a distinction are vast differences in magnetic properties, including magnetic susceptibility (?), SIRM, HIRM and the S-ratio, which can be used to study the provenances of sediments in the Taiwan Strait and adjoining marginal seas. Based on any two of these parameters, the magnetic characteristics of much of the Taiwan Strait sediment can be explained using a two-endmember mixing model. Source-to-sink dispersal of sediments in the Taiwan Strait can then be traced from the distribution of these parameters. The results not only corroborate an earlier study based on radionuclides and particle size distribution ( Huh et al., 2011) but reveal more diagnostic details. Besides spatial distribution based on a large number (216) of surface sediments, we also analyzed temporal variation of magnetic properties in six well-dated cores collected at key sites along the sediment source-to-sink pathways. From profiles of these parameters in cores from the middle of the northern Taiwan Strait, it is calculated that sediment supply from Taiwan has increased substantially in the past five decades, which may very well be related to accelerated land use and increased frequency of intense rainfalls in Taiwan during the same period. The approach described in this work may be extended to other source-to-sink systems around the world and through time, especially the mountainous islands fringing the Pacific and Indian Oceans in southeastern Asia. As with Taiwan, these islands have high denudation rates and pyrrhotite is in all likelihood a mineral characteristic of their metamorphic terrains.

Horng, Chorng-Shern; Huh, Chih-An

2011-09-01

370

Single-scan dual-tracer FLT+FDG PET tumor characterization  

PubMed Central

Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from the multi-tracer PET signal. The ability to rapidly and reliably image both 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) would provide complementary measures of tumor metabolism and proliferative activity, with important applications in guiding oncologic treatment decisions and assessing response. However, this tracer combination presents one of the most challenging dual-tracer signal-separation problems—both tracers have the same radioactive half-life, and the injection delay is short relative to the half-life and tracer kinetics. This work investigates techniques for single-scan dual-tracer FLT+FDG PET tumor imaging, characterizing the performance of recovering static and dynamic imaging measures for each tracer from dual-tracer datasets. Simulation studies were performed to characterize dual-tracer signal-separation performance for imaging protocols with both injection orders and injection delays of 10–60 min. Better performance was observed when FLT was administered first, and longer delays before administration of FDG provided more robust signal-separation and recovery of the single-tracer imaging measures. An injection delay of 30 min led to good recovery (R > 0.96) of static image values (e.g. SUV), Knet, and K1 as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k2, k3) was less robust, indicating that information regarding these parameters was harder to recover in the presence of statistical noise and dual-tracer effects. Performance of the dual-tracer FLT(0 min)+FDG(32 min) technique was further evaluated using PET/CT imaging studies in five patients with primary brain tumors where the data from separate scans of each tracer were combined to synthesize dual-tracer scans with known single-tracer components; results demonstrated similar dual-tracer signal recovery performance. We conclude that rapid dual-tracer FLT+FDG tumor imaging is feasible and can provide quantitative tumor imaging measures comparable to those from conventional separate-scan imaging.

Kadrmas, Dan J; Rust, Thomas C; Hoffman, John M

2013-01-01

371

{Use of isotopic tracers for the study of the interaction of surface water and groundwater in a karst environment.}  

NASA Astrophysics Data System (ADS)

Domenico Guida1, Michele Guida2, Albina Cuomo1, Davide Guadagnuolo2, Antonia Longobardi1, Vincenzo Siervo3 1 Dipartimento di Ingegneria Civile dell'Università di Salerno 2 Dipartimento di Fisica dell'Università di Salerno 3 C.U.G. RI., Salerno Groundwater and surface water resources management represents a present key issue, both in the hydrogeological and the hydrological fields. An integrated approach, accounting for hydrogeological, hydrological, geochemical and biological features can be a valuable tool, being fundamental in karstic landscape because of the great system variability and because of the frequently complex anthropic interaction. In this study we focus on a particular case study, the Bussento river basin, located in the Campania region, Southern Italy, which is well known to hydrogeology and geomorphology scientists for its karstic features, as summit highland with dolines and poljes, lowland with blind valleys, disappearing streams into sinkholes and cave systems. The catchment groundwater circulation is very complex and frequently groundwater inflows from the outside of the hydrological watershed and groundwater outflows toward surrounding drainage systems occur. We aim at propose a validation of a conceptual hydro-geological model (Guida D. et al., 1980; Iaccarino G., et al., 1986; e Guida D. et al.,1988, Guida D. et al., 2005) and to this purpose a measurements campaign, of about one year, has been undertaken along the Bussento for the acquisition of data about the Rn222 concentration in the waters, using a Rad7 water probe and a Rad7H2O (Durridge Inc., South Australia). Besides radon concentration, more chemical and physical variables have been measured, such as pH, water temperature, dissolved oxygen, atmospheric pressure, water conductivity, water resistivity. The preliminary results enable us to consider this as an useful methodology for the localization of the contributions of the groundwaters, diffused along the riverbed, and for their proportional assessment compared with the superficial back return flow. This program will allow at the end of the investigation to have an innovative methodology for the separation of quick, delayed, return flows from the base-flow, due to groundwater contributions as a function of groundwater recharge and hydrological and geomorphological river bed dynamics.

Cuomo, A.

2009-04-01

372

Beryllium-7 as a tracer to study mechanisms and rates of metal scavenging from lake surface waters  

SciTech Connect

The removal of Be-7 from lake surface waters (Lake Lugano, Switzerland/Italy) was studied from September 1995 to May 1996. During this period the atmospheric input and sedimentary flux of Be-7, as well as concentrations of dissolved (< 10 kD), colloidal (10 kD-1{micro}m), and particulate (> 1 {micro}m) Be-7 in the epilimnion were measured. The separation of dissolved, colloidal, and particulate fractions of Be-7 was carried out using continuous flow centrifugation (CFC) and tangential flow filtration (TFF) techniques. Lacustrine colloids were shown to be much more efficient sorbents for Be-7 than the suspended particles. Particle concentrations C{sub p} ranged from 0.5 to 2 mg/L. The ratio of colloid (> 10 kD) to particle concentration C{sub c}/C{sub p} was close to 0.09 during winter months when detrital inputs are dominant, but was higher (0.16) in summer and in spring after an algal bloom. The Be-7 data were used to estimate coagulation rates of colloids. The highest coagulation rates along with the lowest K{sub c} were found after an algal bloom in spring.

Steinmann, P.; Billen, T.; Loizeau, J.L.; Dominik, J. [Univ. de Geneve, Versoix (Switzerland)] [Univ. de Geneve, Versoix (Switzerland)

1999-06-01

373

EPA GAS PHASE CHEMISTRY CHAMBER STUDIES  

EPA Science Inventory

Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

374

Numerical study of a helicon gas discharge  

Microsoft Academic Search

Plasma sources based on the helicon gas discharge are widely used in industry [1] due to their high efficiency. We investigate performance of a particular helicon plasma sources designed for the VASIMR [2] plasma thruster. Specifically we are interested in the VX-10 configuration [3] operating with hydrogen or helium plasmas. Firstly, we use our zero-dimensional model to characterize plasma condition

Oleg Batishchev; Kim Molvig

2001-01-01

375

Systematic study of broadband terahertz gas sensor  

Microsoft Academic Search

Broadband terahertz wave detection through field-induced second harmonic generation was systematically investigated using selected gases. The dependences of the detected second harmonic intensity on probe pulse energy, bias field strength, gas pressure, and third order nonlinear susceptibility are systematically investigated with xenon, nitrogen, SF6, and alkanes. Experiment results reveal that the detected second harmonic intensity quadratically depends on the third

Xiaofei Lu; Nicholas Karpowicz; Yunqing Chen; X.-C. Zhang

2008-01-01

376

/sup 18/F-2-deoxy-2-fluoro-D-glucose as a tracer in the positron emission tomographic study of senile dementia  

SciTech Connect

Using /sup 18/F-2-deoxy-2-fluoro-D-glucose as a tracer, the authors obtained positron emission tomographic scans of 11 patients with senile dementia and 6 age-matched controls. The rate of glucose metabolism was significantly lower in the patients with senile dementia and significantly correlated with the degree of cognitive impairment.

Farkas, T.; Ferris, S.H.; Wolf, A.P.; De Leon, M.J.; Christman, D.R.; Reisberg, B.; Alavi, A.; Fowler, J.S.; George, A.E.; Reivich, M.

1982-03-01

377

Study of the Effectiveness and Application of Environmental Tritium as a Ground Water Tracer in a Semi-Arid Region in Botswana.  

National Technical Information Service (NTIS)

This report describes a long-term investigation of ground water with environmental tritium in a semi-arid area in the southern Hemisphere. The objectives of the investigation were to evaluate the effectiveness of tritium as a tracer at very low levels and...

B. T. Verhagen J. P. F. Sellschop C. M. H. Jennings

1974-01-01

378

Lead isotope composition of tree rings as bio-geochemical tracers of heavy metal pollution: a reconnaissance study from Firenze, Italy  

Microsoft Academic Search

Pb isotope composition of tree rings (Celtis Australis) and urban aerosols have been determined to assess whether arboreal species can be used as bio-geochemical tracers of the evolution of heavy metal pollution to the environment. Particular care was paid to setting up a high quality analytical technique to work with arboreal species with low Pb content. The Pb isotope composition

Simone Tommasini; Gareth R Davies; Tim Elliott

2000-01-01

379

Stable isotope tracers of water vapor sources in the Atacama Desert, Northern Chile: a pilot study on the Chajnantor Plateau  

NASA Astrophysics Data System (ADS)

Subtropical deserts form in response to the interaction of large-scale processes, including atmospheric circulation and oceanic currents, with local features like topography. The degree to which each of these factors controls desert formation and the anticipated impacts of variations in each as climate changes, however, are poorly understood. Stable isotope compositions of water vapor in desert air can help to distinguish between moisture sources and processes that control aridity. The Atacama Desert, located in northern Chile between latitudes 23S and 27S, provides a natural laboratory in which to test the degree to which water vapor isotopologues enable the distinction between processes that control humidity, including the Hadley Circulation, the cold Humboldt Current off the coast of Chile, and the orographic effect of the Andes, in this subtropical desert. Water vapor isotopologues and concentrations were measured in real time using a cavity-ringdown spectrometer deployed on the Chajnantor Plateau over a three-week period from mid-July early August 2010. The elevation of the Plateau, 5000 m amsl (~550 hPa), places it above the boundary layer, allowing the evaluation of the Rayleigh fractionation model from the coast inland. Values reported by the instrument were verified with air samples taken at the coast and the Plateau, which were analyzed on an MAT-252 mass spectrometer. Water vapor concentrations and ?D values varied spatially and temporally. Water vapor concentrations on the Plateau ranged from 200 to 3664 ppmv with a mean value of 536 ppmv. In contrast, water vapor concentrations at the coast were approximately 10000 ppmv, and at Yungay, 60 km inland, water vapor concentrations ranged from 1300 to 2000 ppmv from morning to evening. ?D values on the Plateau ranged from -526‰ to -100‰ with a mean value of 290‰ with enriched values correlated to periods with higher water vapor concentrations. There are no strong diurnal variations in water vapor concentrations and corresponding ?D values on the Plateau, however, water vapor concentrations generally increase after sunrise and reach their maxima in the evening. Temperatures on the Plateau were consistently around 0 degrees C during the pilot study with dewpoint temperatures around -20 degrees C and specific humidity ranging from 0.20 to 2.0 g/kg. Within this range of specific humidity, the Rayleigh fractionation model predicts ?D values between -570‰ and -300‰. Preliminary results from this pilot study show that ?D values are more enriched than predicted by a Rayleigh fractionation curve for water originating at the ocean and moving inland to an elevation of 5000 m. Instead, ?D for water vapor on the Chajnantor Plateau falls along a mixing curve between upper- and lower-troposphere sources. Long term monitoring is necessary to understand the complex interplay between atmospheric and oceanic processes combined with topography responsible for the both water vapor concentrations and ?D values observed on the Chajnantor Plateau.

Samuels, K. E.; Galewsky, J.; Sharp, Z. D.; Rella, C.; Ward, D.

2010-12-01

380

The use of radon as tracer in environmental sciences  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

381

Constraining the age distribution of highly mixed groundwater using 39Ar: A multiple environmental tracer (3H/3He, 85Kr, 39Ar, and 14C) study in the semiconfined Fontainebleau Sands Aquifer (France)  

NASA Astrophysics Data System (ADS)

A multitracer (3H/3He, 85Kr, 39Ar, and 14C) approach is used to investigate the age structure of groundwater in the semiconfined Fontainebleau Sands Aquifer that is located in the shallower part of the Paris Basin (France). The hydrogeological situation, which is characterized by spatially extended recharge, large screen intervals, and possible leakage from deeper aquifers, led us to expect a wide range of residence times and pronounced mixing of different water components. Consequently, a large set of tracers with corresponding dating ranges was adopted. Commonly used tracers for young groundwater (3H, 3He, and 85Kr) can identify only those components with ages below 50 years. This approach is reliable if a large fraction of the water recharge occurs within this period. However, if a considerable fraction is older than 50 years, a tracer that covers intermediate age ranges below 1000 years is needed. We examine the use of 39Ar, a noble gas radioisotope with a half-life of 269 years, to constrain the age distribution of groundwater in this timescale range. Recharge rate, depth of water table, and the age structure of the groundwater are estimated by inverse modeling. The obtained recharge rates of 100-150 mm/yr are comparable to estimations using hydrograph data. Best agreement between the modeled and measured tracer concentrations was achieved for a thickness of the unsaturated soil zone of 30-40 m, coinciding well with the observed thicknesses of the unsaturated zone in the area. Transport times of water and gas from the soil surface to the water table range between 10 and 40 and 1 and 6 years, respectively. Reconstructed concentrations of 85Kr and 3H at the water table were used for saturated flow modeling. The exponential box model was found to reproduce the field data best. Conceptionally, this finding agrees well with the spatially extended recharge and large screened intervals in the project area. Best fits between model and field results were obtained for mean residence times of 1-129 years. The 39Ar measurements as well as the box model approach indicate the presence of older waters (3H and 85Kr free). Using 39Ar to date this old component resulted in residence times of the old water components on the order of about 100-400 years. The 14C measurements provide additional evidence for the correctness of the proposed age structure.

Corcho Alvarado, J. A.; Purtschert, R.; Barbecot, F.; Chabault, C.; Rueedi, J.; Schneider, V.; Aeschbach-Hertig, W.; Kipfer, R.; Loosli, H. H.

2007-03-01

382

High temperature heat exchanger studies for applications to gas turbines  

NASA Astrophysics Data System (ADS)

Growing demand for environmentally friendly aero gas-turbine engines with lower emissions and improved specific fuel consumption can be met by incorporating heat exchangers into gas turbines. Relevant researches in such areas as the design of a heat exchanger matrix, materials selection, manufacturing technology, and optimization by a variety of researchers have been reviewed in this paper. Based on results reported in previous studies, potential heat exchanger designs for an aero gas turbine recuperator, intercooler, and cooling-air cooler are suggested.

Min, June Kee; Jeong, Ji Hwan; Ha, Man Yeong; Kim, Kui Soon

2009-12-01

383

Direct contribution of nitrogen deposition to nitrous oxide emissions in a temperate beech and spruce forest - a 15N tracer study  

NASA Astrophysics Data System (ADS)

The impact of atmospheric nitrogen (N) deposition on nitrous oxide (N2O) emissions in forest ecosystems is still unclear. Our study assessed the direct contribution of N deposition to N2O emissions in temperate forests exposed to chronic high N depositions using a 15N labelling technique. In a Norway spruce stand (Picea abies) and in a beech stand (Fagus sylvatica) at the Solling, Germany, we used a low concentrated 15N-labelled ammonium-nitrate solution to simulate N deposition. Nitrous oxide fluxes and 15N isotope abundances in N2O were measured using the closed chamber method combined with 15N isotope analyses. Emissions of N2O were higher in the beech stand (2.6 ± 0.6 kg N ha-1 yr-1) than in the spruce stand (0.3 ± 0.1 kg N ha-1 yr-1). We observed a direct effect of N input on 15N-N2O emissions, which lasted for less than three weeks and was mainly caused by denitrification. No further increase in 15N enrichment of N2O occurred during a one-year experiment, which was probably due to immobilisation of deposited N. The annual emission factor for N2O from deposited N was 0.1% for the spruce stand and 0.6% for the beech stand. Standard methods used in the literature applied to the same stands grossly overestimated emission factors with values of up to 25%. Only 6-13% of the total N2O emissions were derived from direct N depositions. Whether the remaining emissions resulted from accumulated anthropogenic N depositions or native soil N, could not be distinguished with the applied methods. The 15N tracer technique is a useful tool, which may improve estimates of the current contribution of N deposition to N2O emissions.

Eickenscheidt, N.; Brumme, R.; Veldkamp, E.

2011-03-01

384

Simple Spreadsheet Models For Interpretation Of Fractured Media Tracer Tests  

EPA Science Inventory

An analysis of a gas-phase partitioning tracer test conducted through fractured media is discussed within this paper. The analysis employed matching eight simple mathematical models to the experimental data to determine transport parameters. All of the models tested; two porous...

385

USE OF PERFLUOROCARBON TRACER (PFT) TECHNOLOGY FOR SUBSURFACE BARRIER INTEGRITY VERIFICATION AT THE WALDO TEST SITE.  

SciTech Connect

Testing of perfluorocarbon gas tracers (PFT) on a subsurface barrier with known flaws was conducted at the Waldo Test Site operated by Science and Engineering Associates, Inc (SEA). The tests involved the use of five unique PFTs with a different tracer injected along the interior of each wall of the barrier. A fifth tracer was injected exterior to the barrier to examine the validity of diffusion controlled transport of the PFTs. The PFTs were injected for three days at a nominal flow rate of 15 cm{sup 3}/min and concentrations in the range of a few hundred ppm. Approximately 65 liters of air laced with tracer was injected for each tracer. The tracers were able to accurately detect the presence of the engineered flaws. Two flaws were detected on the north and east walls, and one flaw was detected on the south and west walls. In addition, one non-engineered flaw at the seam between the north and east walls was also detected. The use of multiple tracers provided independent confirmation of the flaws and permitted a distinction between tracers arriving at a monitoring port after being released from a nearby flaw and non-engineered flaws. The PFTs detected the smallest flaw, 0.5 inches in diameter. Visual inspection of the data showed excellent agreement with the known flaw locations and the relative size of the flaws was accurately estimated. Simultaneous with the PFT tests, SEA conducted tests with another gas tracer sulfur hexafluoride (SF{sub 6}).

SULLIVAN,T.

1999-06-01

386

Numerical study of a helicon gas discharge  

NASA Astrophysics Data System (ADS)

Plasma sources based on the helicon gas discharge are widely used in industry [1] due to their high efficiency. We investigate performance of a particular helicon plasma sources designed for the VASIMR [2] plasma thruster. Specifically we are interested in the VX-10 configuration [3] operating with hydrogen or helium plasmas. Firstly, we use our zero-dimensional model to characterize plasma condition and composition [4]. Next we couple it to one-dimensional hybrid model [5] for a rarified gas flow in the system feeding pipe - quartz tube of the helicon. We perform numerical analysis of plasma source operation in different regimes. Results are compared and used to explain experimental data [3]. Finally, we'll discuss more detailed fully kinetic models for the gas and plasma species evolution in the helicon discharge with parameters typical to that of the VASIMR plasma thruster. [1] M.A. Lieberman and A.J.Lihtenberg, , 'Principles of plasma discharges and materials processing', Wiley, NY, 1994; [2] F.Chang-Diaz et al, Bull. APS 45 (7) 129, 2000; [3] J. Squire et al., Bull. APS 45 (7) 130, 2000; [4] O.Batishchev and Kim Molvig, AIAA technical paper 2000-3754, 2000; [5] O.Batishchev and Kim Molvig, AIAA technical paper 2001-0963, 2001.

Batishchev, Oleg; Molvig, Kim

2001-06-01

387

Assessment of a Geothermal Doublet in the Malm Aquifer Using a Push-Pull Tracer Test  

NASA Astrophysics Data System (ADS)

Geothermal exploration of the Malm aquifer in Bavaria is highly successful. Data about the long-term operation, however, is still scarce, although detailed knowledge about the processes occurring in the aquifer is a key requirement to run geothermal facilities efficiently and economically. While there usually is a constant flow of data from the production well (temperatures, hydraulic data, hydrochemical conditions, gas composition) not even the temperatures in the immediate surrounding of the reinjection well are accessible or known. In 2011 the geothermal facility in Pullach was extended with a third geothermal well reaching into the Malm aquifer which is now used as a reinjection well. The former reinjection well was converted to a production well after 5 years of operation. This setting offers a unique opportunity to study the processes in the vicinity of a reinjection well and provides the data base to describe the hydraulic, thermal and hydrochemical performance of the reservoir. The viscosity of the reinjected cold water is increasing by 60% compared to the production well, thus one would expect an increase of the reinjection pressure as the cold water plume spreads around the reinjection well. Measurements, however, show a significant decrease of the reinjection pressure, suggesting processes in the aquifer which positively change the hydraulic properties and overcompensate the viscosity effects. Hydrochemical data and modeling indicate that a dissolution of the matrix along the flow pathways is responsible for the decreasing reinjection pressures. The change of the flow direction from reinjection to production was used to conduct a push-pull tracer test. Here, a series of fluorescent dye pulses was added to the reinjected water before the former reinjection well was shut down (push phase). These tracers included a conservative tracer (Fluorescein), surface-sensitive tracers (Eosin/Sulforhodamin B), and a NAPL-sensitive tracer (Na-Naphthionate). After changing to production mode in October 2012 the pull phase was started. The different behavior of the tracers within the reservoir delivers data about dispersion, sorption properties, matrix interaction and the regional flux. First tracer breakthrough curves point to a significant heterogeneity of the flow pathways and that regional flow is not negligible.

Lafogler, Mark; Somogyi, Gabriella; Nießner, Reinhard; Baumann, Thomas

2013-04-01