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1

Tracer gas technique developed to study diffusive leakages of air pollutants from petrochemical complexes.  

National Technical Information Service (NTIS)

A tracer gas technique has been developed by NILU to study emission rates and diffusion of gases in industrial building complexes. This paper describes the technique and outlines the design and requirements for simulations and gives several examples of fi...

B. Sivertsen

1995-01-01

2

Multiple-tracer gas analyzer  

SciTech Connect

A multi-gas tracer system has been designed, built, and used on an explosively fractured oil shale rubble bed. This paper deals exclusively with the hardware, software, and overall operation of the tracer system. This system is a field portable, self-contained unit, which utilizes a mass spectrometer for gas analysis. The unit has a 20 channel sample port capability and is controlled by a desk top computer. The system is configured to provide a dynamic sensitivity range of up to six orders of magnitude. A roots blower is manifolded to the unit to provide continuous flow in all sample lines. The continuous flow process allows representative samples as well as decreasing the time between each measurement. Typical multiplex cycle time to evaluate four unique gases is approximately 12 seconds.

Uhl, J.E.

1982-01-01

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

2006-05-06

4

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

5

Dow shale site tracer gas pressurization study. Final report. Appendix: energy from in situ processing of Antrim oil shale  

Microsoft Academic Search

A series of tracer gas pressurization experiments were undertaken at the Dow shale site at Peck, Michigan. The study was conducted to evaluate flow communication between boreholes open to both the Antrim and False Antrim layers of the retort volume, determine permeability and porosity distributions within the retort volume, and to assess qualitatively the uniformity of the fracturing or rubblization

E. W. Peterson; P. L. Lagus

1977-01-01

6

A pilot study of the behavior of gas- and particle-phase ETS tracers in residences  

SciTech Connect

Our previous study of environmental tobacco smoke (ETS) in a three-room environmental chamber showed that smoking history significantly influenced inter-room ETS transport, particularly of gas-phase nicotine. We conducted a three-home pilot study where smoking was limited to one room. Single-smoker residences were monitored during five one-week periods while the smoker participated in a smoking cessation program. Nicotine traced ETS particles were detected reliably in the smoking rooms (SRs) and unreliably in the non-smoking rooms (NSRs). On average, the ventilation- and volume-normalized smoking rate, 0.1 Cigarette-h{sup -1} m{sup -3}, added about 17 and 4 {micro}g m{sup -3} of ETS particles into the SR and NSR, while average nicotine concentration increases were 2 and 0.06 {micro}g m{sup -3}, respectively. Thus, nicotine tracers may underestimate ETS particle exposure in a NSR (e.g., a child's bedroom) by a factor of 2 to 8. In other words, ETS exposure predicted from nicotine concentrations could be almost an order of magnitude lower than actual exposure.

Apte, Michael; Gundel, Lara; Dod, Raymond; Chang, Gee-Min; Sextro, Richard

2002-02-01

7

A laboratory study of tracer tomography  

NASA Astrophysics Data System (ADS)

A tracer tomographic laboratory study was performed with consolidated fractured rock in three-dimensional space. The investigated fractured sandstone sample was characterized by significant matrix permeability. The laboratory transport experiments were conducted using gas-flow and gas-tracer transport techniques that enable the generation of various flow-field patterns via adjustable boundary conditions within a short experimental time period. In total, 72 gas-tracer (helium) tests were performed by systematically changing the injection and monitoring configuration after each test. For the inversion of the tracer breakthrough curves an inversion scheme was applied, based on the transformation of the governing transport equation into a form of the eikonal equation. The reliability of the inversion results was assessed with singular value decomposition of the trajectory density matrix. The applied inversion technique allowed for the three-dimensional reconstruction of the interstitial velocity with a high resolution. The three-dimensional interstitial velocity distribution shows clearly that the transport is dominated by the matrix while the fractures show no apparent influence on the transport responses.

Brauchler, R.; Böhm, G.; Leven, C.; Dietrich, P.; Sauter, M.

2013-09-01

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 for...

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 48-...

R. C. Doeffinger

1976-01-01

10

Effect of room air recirculation delay on the decay rate of tracer gas concentration  

SciTech Connect

Tracer gas measurements are commonly used to estimate the fresh air exchange rate in a room or building. Published tracer decay methods account for fresh air supply, infiltration, and leaks in ductwork. However, the time delay associated with a ventilation system recirculating tracer back to the room also affects the decay rate. We present an analytical study of tracer gas decay in a well-mixed, mechanically-ventilated room with recirculation. The analysis shows that failing to account for delays can lead to under- or over-estimates of the fresh air supply, depending on whether the decay rate calculation includes the duct volume.

Kristoffersen, A.R.; Gadgil, A.J.; Lorenzetti, D.M.

2004-05-01

11

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

Microsoft Academic Search

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 depth; barometric pressure, rainfall, and wind speed were monitored at the soil surface. Linear and multiple regression analysis under natural environmental conditions are influenced by soil moisture content,

C. Chen; D. M. Thomas

1994-01-01

12

RADIOACTIVE TRACERS IN HYDROLOGIC STUDIES  

Microsoft Academic Search

Experiments were carried out in lakes and reservoirs in Massachusetts to ; determine eddy diffusion coefficients. The average eddy diffusion coefficient ; divided by the radius of the eddy was found to be 0.09 ft\\/sec. Experiments to ; determine the average velocity of streams and the dilution in streams by use of ; radioactive tracers were then performed. The diffusion

1958-01-01

13

Contaminated vadose zone characterization using partitioning gas tracers  

Microsoft Academic Search

This paper describes laboratory research conducted to investigate the performance of partitioning tracers for the detection of nonaqueous-phase liquids (NAPLs) in vadose zones. Once evaluated, the tracers may be used for volume estimation of NAPLs and remediation performance assessment of vadose zones. These laboratory studies used glass chromatography columns packed with: (1) Ottawa sand; and then (2) in a separate

G. Allen Whitley Jr; Daene C. McKinney; Gary A. Pope; Bruce A. Rouse; Neil E. Deeds

1999-01-01

14

Dissolved gas and isotopic tracers of denitrification  

SciTech Connect

We present results from field studies in California (USA) where tritium-helium age dating is used in conjunction with major gases (N{sub 2}, O{sub 2}, CH{sub 4}, CO{sub 2}), noble gases (He, Ne, Ar, Kr, Xe), and stable isotopes ({sup 15}N/{sup 14}N, {sup 18}O/{sup 16}O) in order to document nitrate loading and denitrification associated with confined animal agricultural operations and septic systems. Preliminary results show that in-field extraction of the full suite of dissolved gases will be possible using a new Gas Extraction System under development to augment the current Noble Gas Mass Spectrometry and Membrane Inlet Mass Spectrometry techniques. Ascribing observed groundwater nitrate levels to specific current and past land use practices is often complicated by uncertainty in groundwater age and the degree and locus of dentrification. Groundwater age dating at dairy field sites using the {sup 3}H-{sup 3}He method indicates that the highest nitrate concentrations (150-260 mg/L-NO3) occur in waters with apparent ages of <5 yrs, whereas older waters contain excess N{sub 2} from saturated zone denitrification [1]. At a residential septic system site in Livermore, CA, waters with young apparent ages (<1 yr) proximal to leach line drainage have lower nitrate concentrations and elevated nitrate {delta}{sup 15}N and {delta}{sup 18}O values consistent with denitrification, but little evidence for excess N{sub 2}, indicating that denitrification is occurring in the unsaturated zone. Degassing of groundwater can complicate efforts to calculate travel times [2] and to quantify denitrification. Degassed groundwater underlying dairy operations is formed by two distinct mechanisms: (1) recharge of manure lagoon water affected by biogenic gas ebullition [3] and (2) saturated zone denitrification producing N{sub 2} gas above solubility in groundwater. Gas loss due to both mechanisms is evident in the concentrations of noble gases and major gases in dairy groundwater samples.

Singleton, M J; Moran, J E; Esser, B K; McNab, W W; Carle, S F; Cey, B D

2008-02-28

15

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

16

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

17

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

18

Greenhouse Ventilation Rate: Theory and Measurement with Tracer Gas Techniques  

Microsoft Academic Search

Leakage and ventilation rates were measured in a four span glasshouse at Silsoe Research Institute. Two tracer gas techniques were used, a decay rate method with different positions of the leeward ventilator (0, 10 and 20% of the maximum opening) and a continuous injection method with the leeward ventilators open 10%. The influences of wind speed, wind direction and temperature

F. J. Baptista; B. J. Bailey; J. M. Randall; J. F. Meneses

1999-01-01

19

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

SciTech Connect

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

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

2005-09-01

20

Estimation of Uncertainty in Tracer Gas Measurement of Air Change Rates  

PubMed Central

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

Iizuka, Atsushi; Okuizumi, Yumiko; Yanagisawa, Yukio

2010-01-01

21

Estimation of uncertainty in tracer gas measurement of air change rates.  

PubMed

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

Iizuka, Atsushi; Okuizumi, Yumiko; Yanagisawa, Yukio

2010-12-16

22

In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers  

Microsoft Academic Search

Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the

Philip D. Nightingale; Gill Malin; Cliff S. Law; Andrew J. Watson; Peter S. Liss; Malcolm I. Liddicoat; Jacqueline Boutin; Robert C. Upstill-Goddard

2000-01-01

23

[Tracer gas evaluations of local exhaust hood performance].  

PubMed

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

Ojima, Jun

2007-09-01

24

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

Microsoft Academic Search

Soil-water content is an important parameter for soil scientists, hydrologists, and engineers studying the movement of water, gas, and pollutants in the vadose zone. Traditionally, soil-water content is characterized with point measurements, which include gravimetric analysis of core samples, time domain reflectrometry, and neutron moderation. More recently, the gas-phase partitioning tracer method has been suggested as an in situ tool

L. Li; P. T. Imhoff

2002-01-01

25

Simultaneous Use of Tracers for Ocean Circulation Studies.  

National Technical Information Service (NTIS)

A method for the simultaneous use of tracers for oceanic circulation studies is developed. To permit the inclusion of tracers that are subject to biochemical transformation a simple model for photosynthesis, bacterial decomposition and chemical dissolutio...

B. Bolin A. Bjoerkstroem K. Holmen B. Moore

1982-01-01

26

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

27

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.

1992-01-01

28

Dissolved gas tracers in groundwater: Simplified injection, sampling, and analysis  

NASA Astrophysics Data System (ADS)

Simplified injection, sampling, and analytical procedures using dissolved gases as groundwater tracers are presented for use in saturated conditions at both the laboratory and field scales. The injection of gases into the groundwater is accomplished by allowing the gas to diffuse through semipermeable tubing, minimizing the formation of bubbles that could modify the hydraulic properties around the well. We have simplified the collection of dissolved gases by developing a passive in situ headspace sampler the employs a semipermeable membrane and copper tubing equipped with a schrader valve. The headspace within the sampler equilibrates with the dissolved gases in the groundwater in around 24 hours, and no groundwater is collected, which is of great advantage for use in contaminated sites. The design parameters and the time to equilibrium of the headspace sampler can be adjusted for investigation requirements using the analytical equation presented. The analysis of the gases for tracer content is performed by using a common gas chromatograph fitted with a thermal conductivity detector. Examples of the use of these methods at both the laboratory and field scales are presented.

Sanford, William E.; Shropshire, Robin G.; Solomon, D. Kip

29

Gas tracer transport in a heterogeneous fracture in two-phase flow conditions. Experimental and modeling results  

NASA Astrophysics Data System (ADS)

Large amounts of gas can result from anaerobic corrosion of metals and from chemical and biological degradation of organic substances in underground repositories for radioactive waste. Gas generation may lead to the formation of a buoyant gas phase bubble (i.e. zone with increased gas saturation surrounded by water) and to the migration of radioactive gaseous species. In this situation, gaseous species migration is controlled by (1) advection, dispersion and diffusion within the gas bubble, and (2) dissolution in the water surrounding the gas bubble and diffusion of the dissolved species away from the interface. A number of gas tracer tests were performed in the framework of the GAs Migration (GAM) project to study the role played by dissolution/diffusion phenomena in gas transport. Tracers were selected to display a large range of solubility and diffusion coefficients, which should have led to significant chromatographic separation in the breakthrough curves (BTCs) of the tracers. However, measured BTCs displayed much smaller chromatographic separation than expected. These curves were interpreted using (1) a numerical model of multiphase flow and tracer transport in the fracture plane and diffusion into the immobile water, and (2) a simple two box model. Results showed that dissolution/diffusion into immobile water regions played a small role, and tailing appears to have been largely controlled by diffusion into dead gas volumes, such as boreholes.

Jódar, Jorge; Medina, Agustín; Carrera, Jesús

2011-11-01

30

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

Microsoft Academic Search

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

J. P. Rydock; B. K. Lamb

1994-01-01

31

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

32

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

33

Application of the gas tracer method for measuring oxygen transfer rates in subsurface flow constructed wetlands.  

PubMed

The oxygen transfer rate (OTR) has a significant impact on the design, optimal operation and modelling of constructed wetlands treating wastewater. Oxygen consumption is very fast in wetlands and the OTR cannot be determined using an oxygen mass balance. This problem is circumvented in this study by applying the gas tracer method. Experiments were conducted in an unplanted gravel bed (dimensions L x W x d 125 x 50 x 35 cm filled with a 30-cm layer of 10-11-mm gravel) and a planted horizontal subsurface flow constructed wetland (HSSFCW) (L x W x d 110 x 70 x 38 cm filled with a 30-cm layer of 3.5-mm gravel with Phragmites australis). Tap water saturated with propane as gas tracer (pure or commercial cooking gas, depending on the test) was used. The mass transfer ratio between oxygen and commercial propane gas was quite constant and averaged R = 1.03, which is slightly lower than the value of R = 1.39 that is usually reported for pure propane. The OTR ranged from 0.31 to 5.04 g O(2) m(-2) d(-1) in the unplanted gravel bed and from 0.3 to 3.2 g O(2) m(-2) d(-1) in the HSSFCW, depending on the hydraulic retention time (HRT). The results of this study suggest that the OTR in HSSFCW is very low for the oxygen demand of standard wastewater and the OTR calculations based on mass balances and theoretical stoichiometric considerations overestimate OTR values by a factor that ranges from 10 to 100. The gas tracer method is a promising tool for determining OTR in constructed wetlands, with commercial gas proving to be a viable low-cost alternative for determining OTR. PMID:20542312

Tyroller, Lina; Rousseau, Diederik P L; Santa, Santa; García, Joan

2010-05-25

34

In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers  

NASA Astrophysics Data System (ADS)

Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the volatile tracers and allows three estimations of the transfer velocity for the same time period. The first estimation of the power dependence of gas transfer on molecular diffusivity in the marine environment is reported. This allows the impact of bubbles on estimates of the transfer velocity derived from changes in the helium/sulphur hexafluoride ratio to be assessed. Data from earlier dual tracer experiments are reinterpreted, and findings suggest that results from all dual tracer experiments are mutually consistent. The complete data set is used to test published parameterizations of gas transfer with wind speed. A gas ex- change relationship that shows a dependence on wind speed intermediate between those ofLiss and Merlivat [1986] and Wanninkhof [1992] is found to be optimal. The dual tracer data are shown to be reasonably consistent with global estimates of gas exchange based on the uptake of natural and bomb-derived radiocarbon. The degree of scatter in the data when plotted against wind speed suggests that parameters not scaling with wind speed are also influencing gas exchange rates.

Nightingale, Philip D.; Malin, Gill; Law, Cliff S.; Watson, Andrew J.; Liss, Peter S.; Liddicoat, Malcolm I.; Boutin, Jacqueline; Upstill-Goddard, Robert C.

2000-03-01

35

Hanford facilities tracer study report (315 Water Treatment Facility)  

Microsoft Academic Search

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

Ambalam

1995-01-01

36

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

37

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

NASA Astrophysics Data System (ADS)

Air was sampled from the porous firn layer at the NEEM site in Northern Greenland. We use an ensemble of ten reference tracers of known atmospheric history to characterise the transport properties of the site. 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 depth-diffusivity reconstruction. We define an objective root mean square criterion that is minimised in the model tuning procedure. 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. A comparison between two replicate boreholes drilled 64 m apart shows differences in measured mixing ratio profiles that exceed the experimental error. We find evidence that diffusivity does not vanish completely in the lock-in zone, as is commonly assumed. The ice age- gas age difference (?age) at the firn-ice transition is calculated to be 182+3-9 yr. 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.

2012-05-01

38

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...

39

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...

40

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

Microsoft Academic Search

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

Tinker

1972-01-01

41

Verification of subsurface barrier integrity using perfluorocarbon gas tracers  

Microsoft Academic Search

Use of perfluorocarbon (PFT) gaseous tracers shows promise as an excellent means of demonstrating subsurface barrier integrity. The PFT technology has been applied at Brookhaven National Laboratory to evaluate the colloidal silica (CS) barrier installed during the summer of 1997. This program involved two separate experimental phases. In the first phase, PFTs were injected into the native soil for a

T. M. SULLIVAN; B. GIBBS; G. SENUM; M. SCHWARTZ; T. HOPKINGS; J. HEISER

1998-01-01

42

The NPE gas tracer test and the development of on-site inspection techniques  

SciTech Connect

Tracer gases emplaced in or near the detonation cavity of the 1-kiloton NonProliferation Event required 1.5 and 13.5 months for sulfur hexaflouride and helium-3, respectively, to reach the surface of Rainier Mesa from an emplacement depth of 400 meters. The sites that first produced tracer gases are those located in known faults and fractures. Numerical modeling suggests that transport to the surface is accomplished within this time frame through atmospheric pumping along high permeability pathways such as fractures. The difference in travel time between the two tracers is due to differences in gas diffusivity and can also be explained by our numerical modeling.

Carrigan, C.; Heinle, R.; Zucca, J.J.

1995-04-13

43

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

44

[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

45

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

USGS Publications Warehouse

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

Rathbun, R. E.

1979-01-01

46

The effect of bubble-mediated gas transfer on purposeful dual-gaseous tracer experiments  

Microsoft Academic Search

For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the

William E. Asher; Rik Wanninkhof

1998-01-01

47

The application of radioactive tracers to oil reservoir waterflood studies  

SciTech Connect

Radioactive tracers are now commonly used to monitor the progress of water injection in oil reservoir secondary recovery schemes. The injection water is labelled with a ''water following'' tracer (such as /sup 3/H/sub 2/O, H/sup 14/CO/sup -//sub 3/), and the produced water from the wells of interest is then sampled and analysed to determine the time to initial breakthrough and the subsequent tracer concentration profile. This may be compared with computer model predictions based on geological and operational data, and provide the reservoir engineer with a greater understanding of the reservoir structure and performance. This paper discusses the factors involved in the selection of tracers, including their chemical form, and deals with the logistics of transporting and using radioactive materials offshore. Counting techniques are described for the measurement of low levels of beta(..beta..) and gamma(..gamma..) -emitting isotopes, and computer models are presented for use in planning tracer studies and in interpreting the results. Some field results are compared with these model predictions, indicating the application to reservoir engineering decisions.

Wheeler, V.J.; Parsons, T.V.; Conchie, S.J.; Durham, B.

1985-01-01

48

Adaptation of the perfluorocarbon tracer technology for aqueous-phase studies in subsurface applications  

Microsoft Academic Search

The perfluorocarbon tracer (PFT) technology as developed by the Tracer Technology Center at Brookhaven National Laboratory can be easily adapted for use as in aqueous-phase tracer studies in subsurface hydrological applications. The advantages of the PFT technology in this application is that it is a multi-tracer technology, up to 5 or 6 PFTs may be used in an experiment, the

G. I. Senum; R. W. Goodrich; R. Wilson; R. N. Dietz

1990-01-01

49

Evaluation of SF6 as a Tracer Gas for Determining Smoke Movement in Shipboard Fires.  

National Technical Information Service (NTIS)

This test program evaluated the application of using Sulfur Hexafluoride(SF6) as a tracer gas for determining smoke movement in ships. The testing was carried out on board the U.S. Coast Guard research vessel ALBERT E. WATTS. The test area consisted of a ...

D. E. Beene H. E. Schultz

1986-01-01

50

STATISTICAL DATA ANALYSIS METHOD FOR MULTIZONAL AIRFLOW MEASUREMENT USING MULTIPLE KINDS OF PERFLUOROCARBON TRACER GAS  

Microsoft Academic Search

Conventional multiple types of perfluorocarbon tracers use the number of gases equal to the number of zones (n). The possible n×n+n airflows are solved from the mass balance of the gas and the airflow balance. However, some airflows may not occur because of the actual interzonal geometry, and the introduction of unnecessary, unknown parameters can impair the accuracy of the

Hiroyasu OKUYAMA; Yoshinori ONISHI; Shin-ichi TANABE; Seiichi KASHIHARA

51

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

Microsoft Academic Search

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

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

2011-01-01

52

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

53

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

SciTech Connect

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 CH{sub 4} 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 (SF{sub 6}) tracer gas release and by measuring methane and tracer concentrations along downwind sampling paths using mobile, real-time analyzers. Combustion sources of methane are distinguished from noncombustion sources by concurrent ambient carbon dioxide measurements. Three variations on the tracer ratio method are described for application to (1) small underground vaults, (2) above-ground natural gas facilities, and (3) diffuse methane emissions from an entire town. Results from controlled releases and from replicate tests demonstrate that the tracer ratio approach can yield total emission rates to within approximately {+-}15%. The estimated accuracy of emission estimates for urban areas with a variety of diffuse emissions is {+-}50%. 21 refs., 5 figs., 6 tabs.

Lamb, B.K.; Allwine, E.; Siverson, R.; Westberg, H. [Washington State Univ., Pullman, WA (United States); McManus, J.B.; Kolb, C.B.; Shorter, J.H. [Aerodyne Research, Inc., Billerica, MA (United States); Mosher, B.; Blaha, D.; Harris, R.C. [Univ. of New Hampshire, Durham, NH (United States)] [and others

1995-06-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

55

Tracer study of proximity and recirculation effects on exposure risk in an airliner cabin.  

PubMed

There is continuing concern about whether and to what extent airliner cabins represent an increased risk of transmission of airborne infectious disease. The purpose of this study was to examine through a simple experiment the relative importance of close proximity and partial recirculation of cabin air on the potential risk of disease transmission. Results are presented from measurements of instantaneous point source dispersion in a cabin on a commercial airline flight. A small amount of tracer gas was released as a puff in the passenger cabin of a wide body jet at cruise altitude. Tracer gas samples were taken manually in the period immediately after the release by two technicians sitting 2 m and 30 m forward of the release point in the cabin. The maximum tracer concentration observed at the 2 m sampling point occurred at 5 s after the release and was a factor of 500 greater than the maximum observed at the 30 m sampling point, which occurred 6.5 min after the release. The integrated tracer exposure at the 2 m location was approximately a factor of 30 greater than at the 30 m location. Assuming risk of transmission is proportional to dose, then the results support the hypotheses that infectious diseases are transmitted primarily between people sitting in close proximity to each other in an aircraft cabin and that partial recirculation of ventilation air in the cabin has a negligible impact on occupants' risk of exposure. PMID:14960054

Rydock, James P

2004-02-01

56

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

57

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

58

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

59

Gas-phase Partitioning Tracer Tests to Quantify Water Content in Relatively Dry and Desiccated Porous Media  

Microsoft Academic Search

Soil desiccation is a potentially robust remediation process to slow migration of inorganic or radionuclide contaminants through the unsaturated 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 field sites. Tracer tests have been conducted in porous medium columns with

M. Truex; M. Oostrom; G. D. Tartakovsky; T. W. Wietsma

2010-01-01

60

Tracer Studies on F-Actin Fluctuations  

NASA Astrophysics Data System (ADS)

We present a study on the fluctuations of semiflexible actin filaments using fluorescence videomicroscopy, focusing on the end-to-end fluctuations of single filaments. In order to specifically measure the position of the polymer's ends, we developed a novel noninvasive method that consists of annealing short end tags to the filaments. This allows us to probe polymer fluctuations to a very high accuracy. We compared the distribution of the end-to-end distance with recent theoretical results, and found excellent agreement. We also studied the dynamics of the mean-square end-to-end distance ?R2(t) and orientation of the ends, ??2(t), finding power laws t3/4 and t1/4, respectively. Scaling behavior for ?R2(t) is observed over several decades in relaxation time in agreement with theoretical results.

Le Goff, Loïc; Hallatschek, Oskar; Frey, Erwin; Amblard, François

2002-12-01

61

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

SciTech Connect

An experimental study is described in which 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

62

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

63

Application of tracer techniques to studies on autoxidation reactions  

Microsoft Academic Search

Summary  The tracers containing deuterium, carbon isotopes, and heavy oxygen that may be applied to the studies on autoxidation reactions\\u000a are described. The autoxidation of the deuterated compounds formed by replacing hydrogen atoms on the double bond has given\\u000a concrete experimental evidence for the following phenomena of autoxidation reaction: a) initial attack of oxygen at the double\\u000a bond and the inherent

N. A. Khan

1953-01-01

64

Study of stomach motility using the relaxation of magnetic tracers  

NASA Astrophysics Data System (ADS)

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.

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

1999-07-01

65

THE APPLICATION OF RADIOACTIVE TRACERS TO OIL RESERVOIR WATERFLOOD STUDIES  

Microsoft Academic Search

Radioactive tracers are now commonly used to monitor the progress of water injection in oil reservoir secondary recovery schemes. The injection water is labelled with a ''water following'' tracer (such as ³HâO, H¹⁴CO⁻â), and the produced water from the wells of interest is then sampled and analysed to determine the time to initial breakthrough and the subsequent tracer concentration profile.

V. J. Wheeler; T. V. Parsons; S. J. Conchie; B. Durham

1985-01-01

66

Coupling a Knudsen reactor with the short lived radioactive tracer 13N for atmospheric chemistry studies  

NASA Astrophysics Data System (ADS)

A Knudsen cell flow reactor was coupled to an online gas phase source of the short-lived radioactive tracer 13N to study the adsorption of nitrogen oxides on ice at temperatures relevant for the upper troposphere. This novel approach has several benefits over the conventional coupling of a Knudsen cell with a mass spectrometer. Experiments at lower partial pressures close to atmospheric conditions are possible. The uptake to the substrate is a direct observable of the experiment. Operation of the experiment in continuous or pulse mode allows to retrieve steady state uptake kinetics and more details of adsorption and desorption kinetics.

Schreiber, S.; Kerbrat, M.; Huthwelker, T.; Birrer, M.; Ammann, M.

2013-03-01

67

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

68

A pore network model study of the fluid-fluid interfacial areas measured by dynamic-interface tracer depletion and miscible displacement water phase advective tracer methods  

NASA Astrophysics Data System (ADS)

Fluid-fluid interfacial areas in porous media are of considerable interest due to the impact they have on a wide range of practical applications involving mass transfer between phases, as well as for their importance in understanding unsaturated and multiphase flow behaviors in porous media. Tracer methods provide a low-cost experimental approach for determining interfacial areas in porous media. Although a number of different tracer methods have been developed, uncertainty remains as to exactly what areas they measure. The work presented here uses pore network model simulations to study the behavior of tracers during simulated tracer measurements for two different specific water-phase tracer methods: the dynamic-interface tracer depletion method and the miscible displacement tracer method. The hypothesis driving this work was that different tracer methods likely measure different areas as a result of the very different ways tracers are used. Experimental data sets for six different porous media were used to validate the model and provide comparison with model-simulated tracer-based area measurements. Results of the work suggest that areas measured using the dynamic-interface tracer depletion method closely match total fluid-fluid interfacial areas, as long as the extent of tracer depletion during the method is relatively small. However, areas measured with the miscible displacement method likely fall somewhere between capillary and total fluid-fluid areas. Calculations conducted with realistic diffusion coefficients and film thicknesses indicate that diffusion and head-driven flow in films are insufficient to allow significant tracer access to film area, suggesting the potential importance of other mechanisms. Calculations conducted as a part of the work suggest that Leverett estimates of maximum area formed during drainage may be closer to total areas than previously reported.

Kibbey, Tohren C. G.; Chen, Lixia

2012-10-01

69

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

70

Studies of impurity migration in TEXTOR by local tracer injection  

NASA Astrophysics Data System (ADS)

Tracer experiments have been carried out by injection 13C marked methane through test limiters exposed to the scrape-off-layer in TEXTOR. The influence of impact energy and flux on depositing 13C species has been studied. One experiment has been performed with biased test limiter (-300 V) in order to increase energy of positively charged ions and the other one with 10 times reduced 13CH4 injection rate compared to previously used injection rate. Biasing of the test limiter increases the resulting 13C deposition by a factor of ˜6 - post-mortem analysis yields a 13C deposition efficiency of ˜1.7% compared to ˜0.3% without biasing. Reducing the injection rate increases 13C deposition efficiency to ˜0.7%, which is more than two times larger compared to experiments with previously used injection rate. ERO modelling shows that enhanced re-erosion of redeposits is still necessary to reproduce measured 13C deposition efficiencies.

TEXTOR Team Kirschner, A.; Wienhold, P.; Borodin, D.; Björkas, C.; Van Hoey, O.; Matveev, D.; Brezinsek, S.; Kreter, A.; Laengner, M.; Ohya, K.; Philipps, V.; Pospieszczyk, A.; Samm, U.; Schweer, B.

2013-07-01

71

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

SciTech Connect

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

Stetzenbach, K.J.

1990-12-31

72

A parameter identifiability study of two chalk tracer tests  

NASA Astrophysics Data System (ADS)

As with most fractured rock formations, Chalk is highly heterogeneous. Therefore, meaningful estimates of model parameters must be obtained at a scale comparable with the process of concern. These are frequently obtained by calibrating an appropriate model to observed concentration-time data from radially convergent tracer tests (RCTT). Arguably, an appropriate model should consider radially convergent dispersion (RCD) and Fickian matrix diffusion. Such a model requires the estimation of at least four parameters. A question arises as to whether or not this level of model complexity is supported by the information contained within the calibration data. Generally modellers have not answered this question due to the calibration techniques employed. A dual-porosity model with RCD was calibrated to two tracer test datasets from different UK Chalk aquifers. A multivariate sensitivity analysis, which assumed only a priori upper and lower bounds for each model parameter, was undertaken. Rather than looking at measures of uncertainty, the shape of the multivariate objective function surface was used to determine whether a parameter was identifiable. Non-identifiable parameters were then removed and the procedure was repeated until all remaining parameters were identifiable. It was found that the single fracture model (SFM) (which ignores mechanical dispersion) obtained the best mass recovery, excellent model performance and best parameter identifiability in both the tests studied. However, there was no objective evidence suggesting that mechanical dispersion was negligible. Moreover, the SFM (with just two parameters) was found to be good at approximating the Single Fracture Dispersion Model SFDM (with three parameters) when different, and potentially erroneous parameters, were used. Overall, this study emphasises the importance of adequate temporal sampling of breakthrough curve data prior to peak concentrations, to ensure adequate characterisation of mechanical dispersion processes, and continued monitoring afterwards, to ensure adequate characterisation of fracture spacing (where possible), when parameterising dual-porosity solute transport models.

Mathias, S. A.; Butler, A. P.; Atkinson, T. C.; Kachi, S.; Ward, R. S.

2006-08-01

73

Studies of Tracer Dispersion and Fluid Flow in Porous Media.  

National Technical Information Service (NTIS)

This doctoral thesis explores the connection between the topology of a porous medium and its macroscopic transport properties and is based on computerized simulation. In porous media, both diffusion and convection contribute to the dispersion of a tracer ...

T. Rage

1996-01-01

74

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

75

Moisture balance and tracer gas technique for ventilation rates measurement and greenhouse gases and ammonia emissions quantification in naturally ventilated buildings  

Microsoft Academic Search

Experiments were performed to study the ventilation rates in a naturally ventilated animal building through four summer seasons and three winter seasons. The ventilation rates were determined using moisture (H2O) balance, tracer gas technique (TGT) and CO2-balance. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH3, CH4, CO2 and N2O), temperature and relative

M. Samer; C. Ammon; C. Loebsin; M. Fiedler; W. Berg; P. Sanftleben; R. Brunsch

76

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

77

Near-road multipollutant profiles: Associations between volatile organic compounds and a tracer gas surrogate near a busy highway  

Microsoft Academic Search

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 transect normal to a highway in Raleigh, North Carolina for five sampling periods spanning four days.

Timothy M. Barzyk; Anna Ciesielski; Richard C. Shores; Eben D. Thoma; Robert L. Seila; Vlad Isakov; Richard W. Baldauf

2012-01-01

78

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

Microsoft Academic Search

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

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

1984-01-01

79

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 ...

80

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

Microsoft Academic Search

The objectives of this research program are to: Improve the assessment of the character of petroleum reservoirs using tracer technology for the monitoring and improvement of EOR techniques, specifically, (a) to apply the presently available multitracer perfluorocarbon tracer (PFI) technology to the study of petroleum reservoirs in characterizing reservoir bulk subsurface flow transport and dispersion rates; and (b) to demonstrate

Senum

1992-01-01

81

Simultaneous Analyses and Applications of Multiple Fluorobenzoate and Halide Tracers in Hydrologic Studies  

SciTech Connect

An analytical method that employs ion chromatography has been developed to more fully exploit the use of fluorobenzoic acids (FBAs) and halides as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g., nitrate and sulfate). The usefulness of this ion chromatographic (IC) analytical method is demonstrated in both field and laboratory tracer experiments. Field experiments in unsaturated tuff featuring fractures or a fault show that this efficient and cost-effective method helps achieve the objectives of tracer studies that use multiple FBAs and/or diffusivity tracers (simultaneous use of one or more FBA and halide). The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the United States--mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need--reveal several insights about tracer transport behavior: (1) Bromide and FBAs are not always transported conservatively. (2) The delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy. (3) Any use of iodine as a hydrologic tracer should take into account the different sorption behaviors of iodide and iodate and the possible conversion of iodine's initial chemical form. (4) The transport behavior of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments.

Hu, Q; Moran, J E

2004-01-22

82

Deuterium used as artificial tracer in column studies under saturated water flow conditions  

NASA Astrophysics Data System (ADS)

In contrast to numerous investigations using deuterium as an environmental tracer, hydrological investigations with deuterium-labelled water are rather rare. Currently applications in groundwater studies are restricted due to increasing costs of spiking large water quantities but an application as intelligent tracer might be of advantage especially in combination with other tracers and under distinct environmental conditions. Therefore deuterium was applied as artificial tracer in column experiments that are well proved as a tool to characterise tracer behaviour in recent studies. Deuterium was tested in comparison to the more familiar conservative tracer fluorescein. Varying experimental conditions, e.g. column length (0.5, 1.0, 1.5 m), initial tracer concentration (0.01, 0.02, 0.2 mg) and flow velocity (1.5 to 6.0 m/d) were used to investigate tracer behaviour under saturated water flow conditions. Deuterium was analysed using an H/Device with chrome reduction connected to an isotope ratio mass spectrometer and expressed in relative concentrations [per mill V-SMOW]. Theoretical tracer breakthrough curves were calculated using a one dimensional dispersion model. The results indicate higher mean transport velocities and smaller dispersion for deuterium in all experiments. Due to different molecule properties that also determine the interaction of soil substrate and tracer, deuterium indicates a more conservative transport behaviour. Deuterium is non-toxic, completely soluble, chemically and biologically stable and not subject to light-influenced decay. Furthermore, it shows promise for investigations of water flow in the unsaturated zone, and of interactions of water in soil-plant-atmosphere systems. A further discussion of problems, together with possibilities for applying deuterium as an artificial tracer, will be presented.

Koeniger, P.; Geiges, M.; Leibundgut, Ch.

2003-04-01

83

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

84

13N as a tracer for studying glutamate metabolism  

PubMed Central

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

Cooper, Arthur J. L.

2010-01-01

85

Tracer Particles for Application to PIV Studies of Liquid Helium  

Microsoft Academic Search

Material selection and methods for introduction of tracer particles into liquid helium are reviewed for application in particle image velocimetry experiments. The combination of low temperature environment and low-density fluid place unique requirements on particle selection. Options discussed include a variety of commercially available solid particles of different size and density as well as solid particles generated by freezing liquids

T. Zhang; D. Celik; S. W. Van Sciver

2004-01-01

86

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

87

ACROSS NORTH AMERICA TRACER EXPERIMENT (ANATEX) MODEL EVALUATION STUDY  

EPA Science Inventory

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-h periods at 77 surface sites. he source-receptor distances ranged from less than 30 km to 3,000 km. he data were used to evaluate the long-...

88

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...

89

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

90

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

91

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.  

National Technical Information Service (NTIS)

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 st...

K. Stetzenbach I. Farnham

1995-01-01

92

Determination of gas-phase nitric acid using a tracer technique  

Microsoft Academic Search

A tracer technique has been developed in this laboratory which allows the measurement of aqueous-phase oxidation of SO2 in clouds. We are now extending this technique to the chemistry of nitrogen species in clouds. Using a conservative tracer such as selenium we can determine the fraction of cloudwater nitrate that is the result of aerosol scavenging. At remote sites this

C. D Judd; L Husain

2000-01-01

93

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

94

Air pollution tracer studies in the lower atmosphere. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the use of tracers to study lower atmospheric air pollution movements. Citations discuss project descriptions and results, techniques, and tracer materials. Tracer movement from nuclear power plants, industrial stacks, and urban areas is discussed. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1997-05-01

95

Reducing Ambiguity in Isotopic Studies Using a Multi-tracer Approach  

Microsoft Academic Search

Naturally-occurring radiogenic and stable isotope tracers are commonly used in studies of water-rock interaction to provide both process and water\\/solute source information. Several isotope tracers have been proposed as diagnostic process indicators, and have been used for that purpose without a full understanding of important factors controlling their behavior such as isotope distributions and fractionation mechanisms. Experience shows that these

T. D. Bullen; A. F. White; C. W. Childs

2001-01-01

96

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

97

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

98

Measurements of waste tank passive ventilation rates using tracer gases  

SciTech Connect

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

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

1997-09-01

99

Uncertainties associated with the estimation of mass balances and gaussian parameters from atmospheric tracer studies  

SciTech Connect

Data resulting from two atmospheric tracer experiments in the land-sea breeze winds in Los Angeles, CA are used to compare the observed and released amounts of tracer (a mass balance). The mass balance calculation indicated that essentially all of the tracer transported to sea during the land breeze was transpoted back across the shore during the subsequent sea breeze. A methodology for calculating a mass balance and the associated uncertainties is presented. The experimental and calculation procedures presented allowed mass balance estimates with less uncertainty than is present in individual measurements of concentration or mixing height. Similarly, a methodology for calculating dispersion parameters for the gaussian plume model from tracer data is discussed and applied to the results of two atmospheric tracer studies conducted during the afternoon sea breeze in the Santa Barbara Channel of California. The method presented involves the integral definitions of the statistical quantities. By considering only tracer concentrations greater than 10% of the maximum concentration, and by considering sufficiently many data points, the uncertainty associated with the parameter estimation was again less than the relative uncertainties in any individual data point. These studies were primarily designed to relate the uncertainties in estimates of mass balances and in estimations of gaussian parameters to the uncertainties inherent within field data.

Sackinger, P.A.; Reible, D.D.; Shair, F.H.

1982-07-01

100

Air intake contamination by building exhausts: tracer gas investigation of atmospheric dispersion models in the urban environment.  

PubMed

The establishment of a safe distance between sources of pollution and air intakes is based on a complex exercise that should take into account several wind, physical, and topographical factors. To estimate the maximum concentrations of the pollutants as a function of the distance from the emission source, some heating, ventilation, and air conditioning (HVAC) system designers use the atmospheric dispersion models suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Two of these models, the Halitsky and Wilson-Chui-Lamb models, have been developed and evaluated mainly with laboratory data. There have been relatively few evaluations with full-scale field data. The objective of this study, carried out on a building in downtown Montreal, Quebec, Canada, was to compare the measured concentrations of a tracer gas emitted by an exhaust stack with those predicted by these models. The results indicate that the Halitsky model gives lower than actual dilution, while the Wilson-Chui-Lamb model generally gives acceptable estimates, with occasional over-estimations of the dilution. PMID:15143790

Lazure, Louis; Saathoff, Pat; Stathopoulos, Ted

2002-02-01

101

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

SciTech Connect

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 organic compounds as tracers to determine source contributions to non-methane organic gases in the atmosphere. Both models are applied to data collected in California's San Joaquin Valley during two severe wintertime air pollution episodes. Source contributions to fine particle air quality are calculated for two urban sites, Fresno and Bakersfield, and one background site, Kern Wildlife Refuge. Primary particle emissions from hardwood combustion, softwood combustion, diesel engines, meat cooking, and gasoline-powered motor vehicles contribute on average 79% of the airborne fine particle organic compound mass at the urban sites during both episodes with smaller but still measurable contributions from fine particle road dust and natural gas combustion aerosol. Anthropogenic primary particle sources contribute less than 10% of the fine particle mass concentration at the background site. The combined gas-phase and particle-phase organic compound receptor model shows that gasoline-powered motor vehicle exhaust and gasoline vapors are the largest contributors to nonmethane organic gases concentrations followed by natural gas leakage. Smaller but statistically significant contributions to organic vapors from wood combustion, meat cooking, and diesel exhaust also are quantified.

Schauer, J.J.; Cass, G.R.

2000-05-01

102

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

103

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

104

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

105

Engineering task plan for determining breathing rates in singleshell tanks using tracer gas  

SciTech Connect

The testing of single shell tanks to determine breathing rates. Inert tracer gases helium, and sulfur hexafluoride will be injected into the tanks AX-103, BY-105, C-107 and U-103. Periodic samples will be taken over a three month interval to determine actual headspace breathing rates.

Andersen, J.A.

1997-04-02

106

Comparison of the perfluorocarbon and tracer gas decay methods for assessing infiltration rates in residents  

Microsoft Academic Search

The passive perfluorocarbon tracer (PFT) technique for determining air infiltration rates into homes and buildings was evaluated in an environmental chamber. The impact of sampler orientation at a constant ventilation rate and a constant temperature, of variable ventilation rate at a constant temperature, and of variable temperature at a constant ventilation rate were evaluated. The average relative standard deviation of

L. Schaap; B. P. Leaderer; S. Renes; H. Verstraelen; T. Tosun; R. N. Dietz

1985-01-01

107

Airborne Lidar Tracking of Fluorescent Tracers for Atmospheric Transport and Diffusion Studies.  

NASA Astrophysics Data System (ADS)

Development and validation of transport models for the study of regional acid deposition require improved observations of pollutant transport and dispersion processes. No suitable method for air-parcel tracking along nonconstant density surfaces is available. The feasibility of using an airborne lidar system to observe atmospheric transport and dispersion of fluorescent-dye-particle (FDP) tracers was demonstrated for various meteorological conditions and FDP-release scenarios in the general area of the Cross-Appalachian Tracer Experiment (CAPTEX) during October 1983. This paper presents some of the results obtained on six case studies, each of which illustrates a unique application of the technique.

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

1985-10-01

108

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

109

Perturbative path-integral study of active- and passive-tracer diffusion in fluctuating fields  

NASA Astrophysics Data System (ADS)

We study the effective diffusion constant of a Brownian particle linearly coupled to a thermally fluctuating scalar field. We use a path-integral method to compute the effective diffusion coefficient perturbatively to lowest order in the coupling constant. This method can be applied to cases where the field is affected by the particle (an active tracer) and cases where the tracer is passive. Our results are applicable to a wide range of physical problems, from a protein diffusing in a membrane to the dispersion of a passive tracer in a random potential. In the case of passive diffusion in a scalar field, we show that the coupling to the field can, in some cases, speed up the diffusion corresponding to a form of stochastic resonance. Our results on passive diffusion are also confirmed via a perturbative calculation of the probability density function of the particle in a Fokker-Planck formulation of the problem. Numerical simulations on simplified systems corroborate our results.

Démery, Vincent; Dean, David S.

2011-07-01

110

Dye Tracer Study at the Saginaw Bay, Michigan, Confined Disposal Facility.  

National Technical Information Service (NTIS)

A dye tracer study was performed in August 1987 at the Saginaw Bay, Michigan, dredged material confined disposal facility (CDF). The purpose of the study was to locate the points or areas of outflow or seepage through prepared limestone dikes of the CDF u...

B. M. McEnroe P. R. Schroeder

1988-01-01

111

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

112

A new double-tracer gas single-breath washout to assess early cystic fibrosis lung disease.  

PubMed

In cystic fibrosis (CF), tests for ventilation inhomogeneity are sensitive but not established for clinical routine. We assessed feasibility of a new double-tracer gas single-breath washout (SBW) in school-aged children with CF and control subjects, and compared SBW between groups and with multiple-breath nitrogen washout (MBNW). Three SBW and MBNW were performed in 118 children (66 with CF) using a side-stream ultrasonic flowmeter setup. The double-tracer gas containing 5% sulfur hexafluoride and 26.3% helium was applied during one tidal breath. Outcomes were SBW phase III slope (SIII(DTG)), MBNW-derived lung clearance index (LCI), and indices of acinar (S(acin)) and conductive (S(cond)) ventilation inhomogeneity. SBW took significantly less time to perform than MBNW. SBW and MBNW were feasible in 109 (92.4%) and 98 (83.0%) children, respectively. SIII(DTG) differed between children with CF and controls, mean±sd was -456.7±492.8 and -88.4±129.1 mg·mol·L(-1), respectively. Abnormal SIII(DTG) was present in 36 (59%) children with CF. SIII(DTG) was associated with LCI (r= -0.58) and S(acin) (r= -0.58), but not with S(cond). In CF, steeply sloping SIII(DTG) potentially reflects ventilation inhomogeneity near the acinus entrance. This tidal SBW is a promising test to assess ventilation inhomogeneity in an easy and fast way. PMID:22599360

Singer, Florian; Stern, Georgette; Thamrin, Cindy; Abbas, Chiara; Casaulta, Carmen; Frey, Urs; Latzin, Philipp

2012-05-17

113

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

Microsoft Academic Search

Perfluorocarbon tracer (PFT) technology, consisting of tracers, samplers, and analytical equipment, has been deployed in numerous meteorological experiments for the verification of long-range and complex terrain transport and dispersion models. The CAPTEX (Cross-APpalachain Tracer EXperiment) ''83 was conducted from mid-September through October 1983, in which seven 3-h tracer releases (5 from Dayton, Ohio, and 2 from Sudbury, Ontario) were made

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

1986-01-01

114

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

Microsoft Academic Search

(1) At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H2 18 O, 7Be,

H. Eicken; H. R. Krouse; D. Kadko; D. K. Perovich

2000-01-01

115

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

Microsoft Academic Search

At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H218O, 7Be, and release of

H. Eicken; H. R. Krouse; D. Kadko; D. K. Perovich

2002-01-01

116

Results of Chemical Analyses for Alcove 8/Niche 3 Tracer Studies.  

National Technical Information Service (NTIS)

This is the final report detailing the analyses performed under ORD-FY04-011 'Chemical Analyses for Alcove 8/Niche 3 Tracer Studies.' This work was performed under The University and Community College System of Nevada (UCCSN) and the Department of Energy ...

J. Daniels

2006-01-01

117

Holographic relaxation spectroscopic study on the structure of gelatin gel doped with fluorescein as a tracer  

Microsoft Academic Search

The structures of gelatin gels have been studied by holographic relaxation spectroscopy (HRS) with fluorescein as a doped tracer. An HRS spectrum with double peaks has been observed. It has been experimentally proven that this “anomalous” HRS spectrum is related to the structures of the gelatin gels. It is shown that two kinds of gel networks are formed when a

Chi Wu; W. Schrof; D. Lilge; E. Luddecke; D. Horn

1991-01-01

118

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

2013-03-27

119

Validation studies of tracer tests in a fracture zone at the Finnsjön research area  

NASA Astrophysics Data System (ADS)

Tracer experiments were performed in a fracture zone, extending several hundred metres, in crystalline rock in Sweden. This paper describes modellings of tracer experiments (radially converging and dipole test) and their numerical results. We have applied a variable aperture channeling model to both tracer tests and evaluated steady-state channel flows in the fracture zone. Solute transport in the channel flows was simulated by a particle-tracking technique considering matrix diffusion. Calculated breakthrough curves and pressures were compared with experimental ones. The calculated breakthrough curve obtained by an equivalen porous medium model was also compared with data from the dipole experiment. Our models seem to explain the experimental results well, but some important assumptions are necessary for calibration of the breakthrough curves. Further experimental data related to the assumptions and geostatistics would be needed for the full validation of the flow and transport model. Study shows that the mean apertures of fractures calibrated with the tracer tests increase with increasing flow rates.

Kimura, Hideo; Munakata, Masahiro

120

Study of alternative tracer tests in characterizing transport in fractured rocks  

SciTech Connect

Flow and transport calculations are carried out by numerical simulation for different tracer designs: single-well radially diverging/converging (huff-puff), single well radially converging, and two-well injection-withdrawal (doublet) in a 2D fracture zone. The fractured rocks are conceptualized as a dual-continuum: the well-connected fractures forming a heterogeneous continuum for advective transport, and the less permeable matrix forming a second continuum for tracer diffusion. Results show that the huff-puff design is a good diagnostic test for matrix diffusion. The two-well doublet design averages over a large volume and corrects for the extreme sensitivity to spatial heterogeneities of the single well converging test, but requires prior knowledge of presence or absence of matrix diffusion to give reliable estimate of transport parameters. Results of this study demonstrate that using a suite of different tracer designs is important to reduce the uncertainty in association with solving the inverse problem of tracer test interpretation to characterize transport in fracture rocks. 10 refs., 4 figs., 1 tab.

Tsang, Y.W. [Univ. of California, Berkeley, CA (United States)

1995-06-01

121

Quantification of metal loading in French Gulch, Summit County, Colorado, using a tracer-injection study, July 1996. Final report  

SciTech Connect

The objective of this report is to present a description of the complex hydrology of the French Gulch site using the tracer-injection study and the synoptic sampling. In particular, the tracer injection allows for evaluation of the effect of the hydrology on the fate and transport of the metals in French Gulch.

Kimball, B.A.; Runkel, R.L.; Gerner, L.J.

1999-10-01

122

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

123

Using Tracer Experiments To Study Phosphorus Transfer From Soil To Overland Flow  

NASA Astrophysics Data System (ADS)

Diffuse phosphorus (P) losses from agricultural land contribute to the eutrophication of surface water bodies in Switzerland. Grassland soils in areas of high animal stock densities are often prone to high P losses due to over-fertilization and a strong accumu- lation of P in the topsoil. In order to understand the effects of management practices and remediation measures on P transfer into runoff water at a small scale it is impor- tant to localize the sources of this phosphorus within the soil profile and to describe the water flows within the topsoil­overland flow system. We are studying the effects of remediation measures on P availability in the soil and on P concentrations in overland flow in a field experiment. We are using tracer exper- iments to examine the mixing behavior of water applied with a sprinkling device onto the soil surface with pre-event soil water and to trace the contribution of those two water sources to overland flow. Two plots were pre-irrigated with a solution of KBr in order to label the soil solu- tion. After a few days of equilibration, two fluorescent dyes were applied to different areas of the plots at a constant rate of 40 mm h-1. Surface runoff was analyzed for tracer concentrations. Small soil monoliths (0.35 * 0.25 *0.20 m3) were excavated and the tracer distribution within the blocks was mapped using a digital camera, optical filters, and tracer specific excitation light source. This tracing technique allowed for independent mapping of the distribution of two simultaneously applied tracers. The experiments demonstrated heterogenous infiltration of the dyes, negligible lat- eral translocation of the dyes within the soil, minimal transfer of the pre-applied Br- into overland flow, early breakthrough of the dye tracers in overland flow which was independent of the tracers sorption properties and a recovery of the dyes that corre- sponded to the runoff ratio. In all, the experiments indicate a very restricted interac- tion between surface applied sprinkling water recovered in overland flow with the soil. However, dissolved reactive P concentrations (DRP) in overland flow from the same plots were high (0.5­1.5 mg DRP L-1). These findings indicate that fast desorption processes within a thin topsoil layer with high P availability, rather than outflow of P-enriched pre-event soil solution control P concentrations in overland flow.

Vollmer, T.; Stamm, C.; Schaerer, M.; Sinaj, S.; Frossard, E.; Fluehler, H.

124

Evaluation of Partitioning Gas Tracer Tests for Measuring Water in Landfills  

Microsoft Academic Search

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

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

2003-01-01

125

Determination of gas-phase nitric acid using a tracer technique  

NASA Astrophysics Data System (ADS)

A tracer technique has been developed in this laboratory which allows the measurement of aqueous-phase oxidation of SO 2 in clouds. We are now extending this technique to the chemistry of nitrogen species in clouds. Using a conservative tracer such as selenium we can determine the fraction of cloudwater nitrate that is the result of aerosol scavenging. At remote sites this allows the calculation of the nitric acid mixing ratio in the precloud air from measurements made during a cloud event. We have used this technique to determine the pre-cloud nitric acid partial pressure at Whiteface Mountain (WFM) for three cloud events. The calculated concentrations for an event on 2 August 1997 agree with measurements made at a second site below cloud level using filterpacks. Nitric acid concentrations for cloud events during July 1995, yielded values of <0.1-10.0 ppbv. At highly polluted sites closer to NO x sources the technique may provide a method of determining if there is any aqueous-phase oxidation of N(III) occurring.

Judd, C. D.; Husain, L.

126

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

127

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

SciTech Connect

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

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

1987-03-01

128

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...

129

TRACER STUDIES OF TRANSPORT AND TRANSFORMATION IN CUMULI  

EPA Science Inventory

The results from a study of the transport and transformation of pollutants are reported. irborne measurements near Champaign, llinois and Milwaukee, Wisconsin were made during the summers of 1990 and 1992. easurements of the aerosol size distribution, wind, turbulence, cloud micr...

130

A tracer study in an Alaskan gravel beach and its implications on the persistence of the Exxon Valdez oil.  

PubMed

Despite great efforts including bioremediation, the 1989 Exxon Valdez oil spills persist in many gravel beaches in Prince William Sound, Alaska, USA. To explore this mystery, a lithium tracer study was conducted along two transects on one of these beaches. The tracer injections and transports were successfully simulated using the 2-dimensional numerical model MARUN. The tracer stayed much longer in the oil-persisting, right transect (facing landwand) than in the clean, left transect. If the tracer is approximately regarded as oils, oils in the upper layer would have more opportunities to enter the lower layer in the right transect than in the left one. This may qualitatively explain the oil persistence within the right transect. When the tracer is regarded as nutrients, the long stay of nutrients within the right transect implies that the oil persistence along the right transect was not due to the lack of nutrients during the bioremediation. PMID:21492883

Li, Hailong; Boufadel, Michel C

2011-04-14

131

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

132

Isotopic Tracer and Kinetic Studies of Oxidative Dehydrogenation Pathways on Vanadium Oxide Catalysts  

Microsoft Academic Search

Kinetic analysis and isotopic tracer studies were used to identify elementary steps and their reversibility in the oxidative dehydrogenation of propane on VOx\\/ZrO2 catalysts with VOx surface densities between 1.6 and 6 VOx\\/nm2. Competitive reactions of C3H6 and CH313CH2CH3 showed that CO forms via secondary combustion of propene intermediates. CO2 formed via this reaction and also via the direct combustion

Kaidong Chen; Andrei Khodakov; Jun Yang; Alexis T. Bell; Enrique Iglesia

1999-01-01

133

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

Microsoft Academic Search

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

U. Siegenthaler; F. Joos

1992-01-01

134

Field Studies of Streamflow Generation Using Natural and Injected Tracers on Bickford and Walker Branch Watersheds  

Microsoft Academic Search

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 ²²²Rn as a tracer. The first of the two stages was

Genereux

1992-01-01

135

A comparison of three radionuclide myocardial perfusion tracers in clinical practice: the ROBUST study  

Microsoft Academic Search

There are no large studies available to guide the selection of thallium (Tl), methoxyisobutylisonitrile (MIBI) or tetrofosmin (Tf) for myocardial perfusion imaging. Our objective was to compare the technical and clinical performance of the three in routine clinical practice. We randomised 2,560 patients to receive Tl, MIBI or Tf. A 1-day stress\\/rest protocol was used for MIBI and Tf. Tracer

Akhil Kapur; Katherine A. Latus; Glyn Davies; Rhanju T. Dhawan; Sian Eastick; Peter H. Jarritt; George Roussakis; Melanie C. Young; Constantinos Anagnostopoulos; Jimmy Bomanji; Durval C. Costa; Dudley J. Pennell; Elizabeth M. Prvulovich; Peter J. Ell; Richard S. Underwood

2002-01-01

136

Studies on the influence of the structural modifications in the tracer on the immunoassay of progesterone.  

PubMed

The main objective of the present study was to examine the influence of different bridges in radioiodinated tracers on the assay performance of progesterone using antibodies. Three homologous and two heterologous immunoassay systems for the measurement of progesterone in human serum are described. Using an antiserum raised against progesterone-11alpha-hemisuccinate-bovine serum albumin (BSA), assays with homologous radioligands, namely progesterone-11alpha-hemisuccinate-125I-tyrosine methyl ester (TME) and progesterone-11alpha-hemisuccinate-125I-histamine, heterologous bridge radioligand, namely progesterone-11alpha-hemiphthalate-125I-TME, and a heterologous site radioligand namely progesterone-3-(O-carboxymethyl) oxime (CMO)-125I-histamine were optimized. A homologous assay system, using antiserum raised against progesterone-3-carboxymethyl oxime-BSA and progesterone-3-CMO-125I-histamine as the radioligand was also optimized to develop a radio-immunoassay (RIA) for serum progesterone. Amongst the two homologous radioligands, viz., progesterone-11alpha-hemisuccinate-125I-histamine and the corresponding TME conjugate tracer, the former yielded a standard curve with a higher slope (-0.6) as compared to the latter (-0.5). The heterologous bridge system with progesterone-11alpha-hemiphthalate-125I-TME resulted in a more sensitive assay (slope of -0.8) than the homologous tracers, whilst the heterologous site radioligand, viz., progesterone-3-CMO-125I-histamine gave the most sensitive assay (slope of -1.2). The homologous assay with antiserum against progesterone-3-CMO-BSA and progesterone-3-CMO-125I-histamine tracer gave a standard curve having a slope of -0.97. The two antibodies developed against progesterone, viz., progesterone-11alpha-hemisuccinate-BSA and progesterone-3-CMO-BSA were characterized for their titre, sensitivity, and specificity. Considering the slope, sensitivity, cross-reactivity, and the quality of tracer, the assay system using antiserum against progesterone-11alpha-hemisuccinate-BSA and progesterone-3-CMO-125I-histamine was found to be suitable for the development of RIA for serum progesterone. The bridges used in an immunogen for production of antibodies, as well as in the preparation of tracer, have a great influence on the assay characteristics. PMID:16711253

Karir, Tarveen; Samuel, Grace; Kothari, Kanchan; Sivaprasad, N; Venkatesh, Meera

2006-01-01

137

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

138

Flow optimization study of a batch microfluidics PET tracer synthesizing device  

PubMed Central

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

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

2010-01-01

139

Stationary and time-dependent indoor tracer-gas concentration profiles measured by OP-FTIR remote sensing and SBFM-computed tomography  

Microsoft Academic Search

Measurement of gas concentrations in indoor air using optical remote sensing (ORS) and computed tomography (CT) has been suggested but not thoroughly investigated. We present experiments in which one time-varying and 11 different steady-state tracer-gas concentration profiles were generated in a ventilated chamber and sampled in a horizontal plane by an open-path Fourier transform infrared (OP-FTIR) spectrometer for subsequent CT

A. C. Drescher; D. Y. Park; M. G. Yost; A. J. Gadgil; S. P. Levine; W. W. Nazaroff

1997-01-01

140

Monte Carlo studies on the response of the TRACER cosmic ray detector  

NASA Astrophysics Data System (ADS)

TRACER (Transition Radiation Array for Cosmic Energetic Radiation) is a large area balloon-borne detector for the determination of the energy spectra of heavy cosmic ray nuclei (8<=Z <=26) in the energy range from ˜500 MeV/nucleon up to ˜10 TeV/nucleon. The key component of TRACER is an array of 1600 single wire proportional tubes. The tube array provides the trajectory of the particle and also the Lorentz factor from the measurement of specific ionization loss (dE/dx) and transition radiation. The trajectory reconstruction procedure is complex and Monte Carlo studies are essential for the development of the algorithm. A full Monte Carlo simulation has been developed for TRACER using GEANT4. In addition to track reconstruction the simulation investigates important instrument characteristics such as geometric aperture, intrinsic resolution, ?-ray contribution to the signals, calibration of energy measurements, deconvolution of energy spectra and determination of particle fluxes. We shall describe in detail the Monte Carlo studies and compare them to data obtained during a long duration balloon flight in 2003.

Hoeppner, Christian

2005-04-01

141

Optimizing sequential dual tracer P.E.T. studies using a combined 2D\\/3D imaging protocol  

Microsoft Academic Search

We have investigated a combined 2D\\/3D protocol for minimizing contamination in dual tracer P.E.T. studies in which the tracers are administered on a timescale that is short compared to the half-lives. We have performed a series of phantom studies on an Advance and a Discovery ST (GE Healthcare Technologies), using a torso phantom with cardiac insert (Data Spectrum Corporation) to

John W. Wilson; Timothy G. Turkington; James G. Colsher; Salvador Borges-Neto; Robert E. Reiman; R. E. Coleman

2004-01-01

142

Hydrophilic and lipophilic radiopharmaceuticals as tracers in pharmaceutical development: In vitro - In vivo studies  

PubMed Central

Background Scintigraphic studies have been performed to assess the release, both in vitro and in vivo, of radiotracers from tablet formulations. Four different tracers with differing physicochemical characteristics have been evaluated to assess their suitability as models for drug delivery. Methods In-vitro disintegration and dissolution studies have been performed at pH 1, 4 and 7. In-vivo studies have been performed by scintigraphic imaging in healthy volunteers. Two hydrophilic tracers, (99mTc-DTPA) and (99mTc-MDP), and two lipophilic tracers, (99mTc-ECD) and (99mTc-MIBI), were used as drug models. Results Dissolution and disintegration profiles, differed depending on the drug model chosen. In vitro dissolution velocity constants indicated a probable retention of the radiotracer in the formulation. In vivo disintegration velocity constants showed important variability for each radiopharmaceutical. Pearson statistical test showed no correlation between in vitro drug release, and in vivo behaviour, for 99mTc-DTPA, 99mTc-ECD and 99mTc-MIBI. High correlation coefficients were found for 99mTc-MDP not only for in vitro dissolution and disintegration studies but also for in vivo scintigraphic studies. Conclusion Scintigraphic studies have made a significant contribution to the development of drug delivery systems. It is essential, however, to choose the appropriate radiotracers as models of drug behaviour. This study has demonstrated significant differences in release patterns, depending on the model chosen. It is likely that each formulation would require the development of a specific model, rather than being able to use a generic drug model on the basis of its physicochemical characteristics.

Teran, Mariella; Savio, Eduardo; Paolino, Andrea; Frier, Malcolm

2005-01-01

143

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

Microsoft Academic Search

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

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

2011-01-01

144

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

145

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

SciTech Connect

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

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

2006-01-01

146

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

147

Hydrocarbon precombusting catalyst survey and optimization for perfluorocarbon tracer analysis in subsurface tracer applications  

Microsoft Academic Search

The extension of the perfluorocarbon tracer (PFT) technology, as developed for atmospheric dispersion and transport studies to petroleum reservoir characterization studies, required the development of a more robust catalyst to remove analysis interferents caused by the adsorption of 5 liter hydrocarbon reservoir gas samples containing PFT onto carbonaceous adsorbent samplers. Two approaches were studied: (1) replacement of the present internal

G. I. Senum; E. A. Cote; T. W. DOttavio; R. N. Dietz

1989-01-01

148

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

PubMed

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

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

2011-07-02

149

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

2013-03-27

150

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

SciTech Connect

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

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

1989-01-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

152

Laboratory characterization of non-aqueous phase liquid\\/tracer interaction in support of a vadose zone partitioning interwell tracer test  

Microsoft Academic Search

Contaminant characterization is important for successful remediation of non-aqueous phase liquids (NAPLs) in the unsaturated zone. A partitioning interwell tracer test (PITT) can provide a good estimate of average subsurface NAPL saturations. Screening experiments were completed in the laboratory to evaluate several gas tracers for a PITT study to be completed in the vadose zone at Kirtland Air Force Base

Neil E. Deeds; Daene C. McKinney; Gary A. Pope

2000-01-01

153

Dye tracer study at the Saginaw Bay, Michigan, confined disposal facility. Final report  

SciTech Connect

A dye tracer study was performed in August 1987 at the Saginaw Bay, Michigan, dredged material confined disposal facility (CDF). The purpose of the study was to locate the points or areas of outflow or seepage through prepared limestone dikes of the CDF under a variety of wind conditions. The study was conducted to determine whether significant quantities of contaminants were escaping from the site in the seepage through the dikes. The fluorescent dye Rhodamine WT was added to the water in the CDF and allowed to disperse by wind currents. Water samples were collected every 50 ft (15 m) inside and out- side the dikes, and the dye concentrations were measured. Using a mass balance technique, the relative outflow for each 50-ft reach of dike was estimated. Higher seepage rates were determined to exist along the shoreward dike in the deep east side of the south cell of the CDF under all wind conditions.

Schroeder, P.R.; McEnroe, B.M.

1988-12-01

154

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

155

Tracer simulation study of potential solute movement in Port Royal Sound, South Carolina  

USGS Publications Warehouse

A tracer study was conducted in Port Royal Sound to simulate the movement and ultimate pattern of concentration of a solute continuously injected into the flow. A total of 750 pounds of Rhodamine WT dye was injected by boat during a period of 24.8 hours in a line across the Colleton River. During the following 43 days, samples of water were taken at selected points in the sound, and the concentration of dye in the samples was determined by fluorometric analysis. The data obtained in the field study were used with theoretical models to compute the ultimate pattern of concentration of nonconservative and conservative solutes for a hypothetical continuous injection at the site on the Colleton River.

Kilpatrick, F. A.; Cummings, T. Ray

1972-01-01

156

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

157

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

158

Case History of Radioactive Tracers and Techniques in Fairway Field  

Microsoft Academic Search

Radioactive tracers have been useful in tracing the movement of injected gas in the Fairway alternate gas-water miscible recovery project. The configuration of the gas displacement fronts and variations in sweep patterns with changing reservoir pressure gradients, as well as the source of breakthrough in producing wells, can be inferred from tracers detected in produced gas samples. Radioactive tracer measurements

Tom Calhoun II; Gary Hurford

1970-01-01

159

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

PubMed Central

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

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

2010-01-01

160

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

161

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

SciTech Connect

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

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

1988-02-01

162

Environmental tracers  

NASA Astrophysics Data System (ADS)

Several naturally occurring tracers of water in natural systems (for example, stable isotopes of oxygen and hydrogen) are being widely used to determine the flow paths that water takes through a catchment. These chart the course of water from when it lands on the soil surface as rain or snow until it flows out of the catchment as streamflow. Tracing of hydrological flow paths, in conjunction with geochemical studies of how water interacts with rocks and soils, has led to new understanding of the hydrochemistry of upland forested catchments. Although a large fraction of precipitation that reaches the forest floor infiltrates into the very permeable soils, studies have disproved the once-prevalent notion that water slowly percolates through soils and rocks. Instead, preferred flow paths along old root channels, dessication cracks, and other heterogeneities in the soils transmit water and solute rapidly both vertically and downslope. This rapid movement profoundly affects the chemical reactions in the soils, influencing, for example, how “acid rain” affects the chemical composition of soil and stream water. Major findings from recent work are that downslope transport occurs along preferred paths in the shallow, normally unsaturated portions of the soil; and that riparian areas (wetlands immediately adjacent to the stream channel) play an extraordinarily important role in catchment hydrochemistry.

Hornberger, George

163

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

Microsoft Academic Search

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

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

1984-01-01

164

Field experiments on the study of bed-load transport using tracer technologies in Haiphong Harbour Area  

Microsoft Academic Search

In the last decade, the sedimentation rate in Haiphong access channel became a serious problem. But experimental data were not enough for interpreting the main causes and evaluating the flux of sediments flocked into the access channel. The first and second experiments on the study of bed-load transport using tracer technologies have been carried out in the navigation channel area.

P. N. Chuong; P. D. Hien; P. S. Hai

1994-01-01

165

Education, Employment and Earnings of Secondary School and University Leavers in Tanzania: Evidence from a Tracer Study  

Microsoft Academic Search

This study uses a tracer survey of secondary school completers in Tanzania to analyse the impact of educational qualifications on labour market earnings. We show that the rates of return to the highest educational qualifications for wage employees are not negligible and, at the margin, provide an investment incentive. However, we find little evidence of human capital effects in the

Samer Al-Samarrai; Barry Reilly

2008-01-01

166

Methodology of studies on chemical processes in water runoff from rock and shallow soil cover using radioactive tracers  

Microsoft Academic Search

Studies of flow patterns and chemical processes in water runoff from small plots (natural ‘fields’ with an area of about 5 m2) have been carried out. Simulated rain containing radioactive tracers, i.e. T (as HTO), Ca (45Ca2+), S (35SO

J. B. Dahl; C. Qvenild; O. Tollan; N. Christophersen; H. M. Seip

1979-01-01

167

A STABLE ISOTOPE TRACER STUDY OF NITROGEN UPTAKE AND TRANSFORMATION IN AN OLD-GROWTH FOREST STREAM  

Microsoft Academic Search

The understanding of nitrogen dynamics in streams of temperate forest bi- omes historically has been constrained by a combination of anthropogenic disturbances and technical limitations. We report here on a study in an undisturbed stream in Oregon, USA, using a stable isotopic tracer to quantify uptake, transformation, and retention of nitrogen. We added 15NH4Cl for six weeks to Mack Creek,

Linda R. Ashkenas; Sherri L. Johnson; Stan V. Gregory; Jennifer L. Tank; Wilfred M. Wollheim

2004-01-01

168

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

Microsoft Academic Search

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

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

2011-01-01

169

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

Microsoft Academic Search

The Big Bend Regional Aerosol and Visibility Observational (BRAVO) study was designed to determine the sources of haze at Big Bend National Park, Texas, using a combination of source and receptor models. BRAVO included an intensive monitoring campaign from July to October 1999 that included the release of perfluorocarbon tracers from four locations at distances 230–750km from Big Bend and

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

2005-01-01

170

The Numerical Simulation of a Tracer-Release Field Project to Study Motion within the Nocturnal Boundary Layer  

Microsoft Academic Search

The Savannah River National Laboratory (SRNL), Brookhaven National Laboratory (BNL), the University of Georgia (UGA), and the National Oceanic and Atmospheric Administration (NOAA) conducted a regional tracer experiment to study the nocturnal behavior of CO2 in the vicinity of an instrumented tall tower during two nights on May 11th and 12th, 2009. The experiment consisted of a release of five

D. W. Werth; M. Y. Leclerc; R. Buckley; M. Parker; R. Kurzeja; H. F. Duarte; G. Zhang; D. Durden

2009-01-01

171

A comparative uptake study of multiplexed PET tracers in mice with turpentine-induced inflammation.  

PubMed

The potential value of multiplexed positron emission tomography (PET) tracers in mice with turpentine-induced inflammation was evaluated and compared with 2-[¹?F]fluoro-2-deoxy-D-glucose ([¹?F]FDG) for glucose metabolism imaging. These PET tracers included [¹?F]fluoromethylcholine ([¹?F]FCH) for choline metabolism imaging, (S-[¹¹C]methyl)-D-cysteine ([¹¹C]DMCYS) for amino acid metabolism imaging, [¹¹C]bis(zinc(II)-dipicolylamine) ([¹¹C]DPA-Zn²?) for apoptosis imaging, 2-(4-N-[¹¹C]-methylaminophenyl)-6-hydroxybenzothiazole ([¹¹C]PIB) for ? amyloid binding imaging, and [¹?F]fluoride (¹?F?) for bone metabolism imaging. In mice with turpentine-induced inflammation mice, the biodistribution of all the tracers mentioned above at 5, 15, 30, 45, and 60 min postinjection was determined. Also, the time-course curves of the tracer uptake ratios for inflammatory thigh muscle (IM) to normal uninflammatory thigh muscle (NM), IM to blood (BL), IM to brain (BR), and IM to liver (LI) were acquired, respectively. Moreover, PET imaging with the tracers within 60 min postinjection on a clinical PET/CT scanner was also conducted. [¹?F]FDG and ¹?F? showed relatively higher uptake ratios for IM to NM, IM to BL, IM to BR, and IM to LI than [¹?F]FCH, [¹¹C]DPA-Zn²?, [¹¹C]DMCYS and [¹¹C]PIB, which were highly consistent with the results delineated in PET images. The results demonstrate that ¹?F? seems to be a potential PET tracer for inflammation imaging. [¹?F]FCH and [¹¹C]DMCYS, with lower accumulation in inflammatory tissue than [¹?F]FDG, are not good PET tracers for inflammation imaging. As a promising inflammatory tracer, the chemical structure of [¹¹C]DPA-Zn²? needs to be further optimized. PMID:23183886

Huang, Tingting; Wang, Hongliang; Tang, Ganghua; Liang, Xiang; Nie, Dahong; Yi, Chang; Wu, Kening

2012-11-26

172

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

PubMed

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

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

2012-08-20

173

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

SciTech Connect

We studied the radioisotope iodine-123-iodoamphetamine (({sup 123}I)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)-H{sub 2}O 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 PaCO{sub 2} was studied in hypo-, eu- and hypercarbic subjects. SPECT CBF values showed a reactivity of 1.03 ml/100 g/min per mmHg PaCO{sub 2} 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.

Greenberg, J.H.; Kushner, M.; Rango, M.; Alavi, A.; Reivich, M. (Univ. of Pennsylvania, Philadelphia (USA))

1990-08-01

174

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

SciTech Connect

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

Pope, G.A.; Sepehrnoori, K.

1992-12-31

175

[The use of magnetic tracers in hemodynamics. A proposed model study].  

PubMed

Velocity of blood flow is critical in specific clinical situations. Available non invasive blood velocimeters gives only qualitative informations; quantitative estimates can be obtained invasively. We investigated the possibility of estimating the velocity of fluids using magnetic tracer. A model for the laminar blood flow inside a vessel was developed. A biomagnetometer was used to measure the fluid tracer velocity. The experimental setup was designed to mimic blood flow. A PVC tube simulated the vessel. The tube was connected to a bottle of normal saline. The tracer injection took place 25 cm distal to the saline bottle. The system was calibrated to a constant flow velocity of about 1 cm/s. A paramagnetic fluid (Magnevist, Schering, Berlin) was adopted as a tracer. In each session an amount of 2 cm3 was injected into the tube within 5 seconds. The recording equipment consisted of a second order gradiometer (baseline 7 cm, pick-up coil diameter 1.5 cm) coupled to a rfSQUID magnetometer. The recording bandwidth was dc-3 Hz, the sampling rate 32 Hz with 12 bit digitalization. The biomagnetic system was positioned immediately above the tube 55 cm away from the injection site. The total recording time for each session was 240 seconds. The injection of the tracer took place 60 seconds after the beginning of the data acquisition. Five measuring sessions in the earth magnetic field were performed at first and showed a low signal-to-noise ratio.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8290136

Basile, M; Massari, R; Del Gratta, C; Romani, G L

1993-09-15

176

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

PubMed

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 (< 1 week after 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 x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition. PMID:22928411

Templer, P H; Mack, M C; Chapin, F S; 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

2012-08-01

177

Statistical data analysis method for multi-zonal airflow measurement using multiple kinds of perfluorocarbon tracer gas  

Microsoft Academic Search

Conventional multi-zonal ventilation measurement methods by multiple types of perfluorocarbon tracers use a number of different gases equal to the number of zones (n). The possible n×n+n airflows are estimated from the mass balance of the gases and the airflow balance. However, some airflows may not occur because of inter-zonal geometry, and the introduction of unnecessary, unknown parameters can impair

Hiroyasu Okuyama; Yoshinori Onishi; Shin-ichi Tanabe; Seiichi Kashihara

2009-01-01

178

A study of positrons from Soviet nuclear powered satellites as tracers for magnetospheric research  

SciTech Connect

Two Soviet satellites carrying nuclear reactors operated in circular 790 km orbits (65{degree} inclination) in 1987 and 1988. Positrons generated in the satellites' surfaces by the intense reactor gamma radiation escaped and were trapped for periods of minutes to hours in the geomagnetic field. These positrons have been observed on many occasions by gamma ray sensors on the SMM satellite (in 500 km orbit) which identify the positrons by the 511 keV gamma rays created when they annihilate in the satellite surface. The SMM detector provides a time resolution of 64 milliseconds. It has recorded positron rise-times of less than 0.5 second (corresponding to about 1 positron gyroradius) on many occasions as it encounters the low-L edge of positrons injected by the Soviet satellites as far as half-way around the earth. We are studying the potential of these sharply defined positron shells as magnetospheric tracers and as a means for examining particle diffusion and loss processes. 3 refs., 5 figs.

Hones, E.W. Jr. (Mission Research Corp., Los Alamos, NM (USA))

1990-01-01

179

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

180

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

181

Potential soluble, reactive, adsorptive and particulate tracers for source-receptor experiments in MATEX  

Microsoft Academic Search

A survey of potential non-conservative tracers for use in source-receptor studies in acid deposition is presented. Classes of tracers considered were water soluble tracers, chemically reactive tracers, adsorptive tracers and particulate tracers. A criterion used for the selection of compounds for nonconservative tracers is that they be as reasonably compatible in the analytical detection system used for the conservative perfluorocarbon

G. I. Senum; R. N. Dietz

1985-01-01

182

Collisional decoherence of a tracer particle moving in one dimension  

SciTech Connect

We study decoherence of the external degree of freedom of a tracer particle moving in a one-dimensional dilute Boltzmann gas. We find that phase averaging is the dominant decoherence effect, rather than information exchange between tracer and gas particles. While a coherent superposition of two wave packets with different mean positions quickly turns into a mixed state, it is demonstrated that such superpositions of different momenta are robust to phase averaging, until the two wave packets acquire a different position due to the different velocity of each wave packet.

Kamleitner, Ingo [Institut fuer Theory der Kondensierten Materie, Karlsruher Institut fuer Technologie, D-76128 Karlsruhe (Germany) and Centre for Quantum Computer Technology, Physics Department, Macquarie University, Sydney, New South Wales 2109 (Australia)

2010-11-15

183

An Analytical Solution for Slug-Tracer Tests in FracturedReservoirs  

SciTech Connect

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

Shan, Chao; Pruess, Karsten

2005-03-02

184

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

185

Petroleum characterization by perfluorocarbon tracers  

Microsoft Academic Search

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

G. I. Senum; R. W. Fajer; B. R. Jr. Harris; W. E. DeRose; W. L. Ottaviani

1992-01-01

186

Development of a membrane-assisted fluidized bed reactor - 1 - Gas phase back-mixing and bubble-to-emulsion phase mass transfer using tracer injection and ultrasound experiments  

Microsoft Academic Search

A small laboratory-scale membrane-assisted fluidized bed reactor (MAFBR) was constructed in order to experimentally demonstrate the benefits of this reactor concept, especially the enhanced bubble-to-emulsion phase mass transfer and the reduced overall axial gas phase back-mixing, due to the presence of the membranes and permeation of gas through the membranes. With steady-state tracer gas injection experiments, it was demonstrated that

S. A. R. K. Deshmukh; J. A. Laverman; A. H. G. Cents; Sint Annaland van M; J. A. M. Kuipers

2005-01-01

187

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

Microsoft Academic Search

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

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

2010-01-01

188

Simultaneous Analyses and Applications of Multiple Fluorobenzoate and Halide Tracers in Hydrologic Studies  

Microsoft Academic Search

An analytical method that employs ion chromatography has been developed to more fully exploit the use of fluorobenzoic acids (FBAs) and halides as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g., nitrate and sulfate).

Q Hu; J E Moran

2004-01-01

189

Simultaneous analyses and applications of multiple fluorobenzoate and halide tracers in hydrologic studies  

Microsoft Academic Search

An analytical method that employs ion chromatography has been developed to exploit the use of fluorobenzoic acids (FBAs) and halides more fully as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g. nitrate and sulphate).

Qinhong Hu; Jean E. Moran

2005-01-01

190

Study of Particle Movement in Conical Fluidized Beds Using the Tracer Method.  

National Technical Information Service (NTIS)

In the work reported here, a method is described which enables the path and speed of the particles during fluidization to be measured using a tracer particle technique. Using statistical methods, it is then possible to determine the path-time diagram, the...

H. J. Penkalla E. Gyarmati H. Nickel

1976-01-01

191

Relationship between glucose volume of distribution and the extracellular space: a multiple tracer study  

Microsoft Academic Search

Although the use of radioisotopes in the investigation of glucose metabolism dates back more than 50 years, several relevant quantitative aspects have not been definitively determined. These include the volume of distribution (Vd) of glucose and recycling of glucose radioisotopes from liver glycogen. These problems are further complicated by methodological issues such as the following: (1) glucose tracers have different

Andrea Mari; Peter Thomas Zafian; Joana Achanfuo-Yeboah; Raul Cesar Camacho

2011-01-01

192

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

SciTech Connect

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 found that gas bubbles tend to flow upward in the center of the reactor, with a downward flow of gas bubbles near the walls.

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

1980-01-01

193

The fate of dissolved dimethylsulfoniopropionate (DMSP) in seawater: tracer studies using 35S-DMSP  

NASA Astrophysics Data System (ADS)

The algal osmolyte dimethylsulfoniopropionate (DMSP) is distributed globally in the marine euphotic zone, where it represents a major form of reduced sulfur. Previous investigations of DMSP cycling have focused mainly on its degradation to the volatile sulfur species dimethylsulfide (DMS) and little is known about the other possible fates of the sulfur. In this study 35S-DMSP was used to trace the biogeochemical fate of sulfur in the natural pool of dissolved DMSP in seawater. Dissolved 35S-DMSP added to seawater was degraded within hours, with the 35S partitioning into three major, relatively stable, operational pools: particulates, dissolved non-volatile degradation products (DNVS), and volatiles. The mean values for partitioning of DMSP obtained from 20 different seawater incubations were (in terms of sulfur): particulates (33%; range 6-85%;); DNVS (46%; range 21-74%); and volatiles (9%; range 2-21%). Oceanic water samples had lower incorporation of DMSP-S into particulates and higher incorporation into DNVS as compared with coastal-shelf samples. Transient accumulation of untransformed 35S-DMSP in bacteria accounted for some of the particulate 35S, but most of the cell-associated DMSP was rapidly transformed and the sulfur incorporated into relatively stable macromolecules. 35S-labeled DNVS accumulated steadily during DMSP metabolism and approximately half of this pool was confirmed to be sulfate, implying that oxidation of DMSP-sulfur takes place on time scales of minutes to hours. Volatile products were produced rapidly from 35S-DMSP, but most were consumed within 1-3 h. Experiments showed that methanethiol (MeSH) was the major volatile compound produced from tracer DMSP, with longer-lived DMS formed in lower amounts. Tracer additions of 35S-MeSH to seawater resulted in incorporation of sulfur into cellular macromolecules and DNVS, suggesting MeSH was an intermediate in the conversion of DMSP into these pools. Experiments with 35S-DMS revealed that turnover of DMS was much slower than for DMSP or MeSH, and the retention of the DMS-sulfur in particles was only a minor fraction of the total amount metabolized. The majority of the 35S-DMS was transformed into DNVS including sulfate. Temperature and DMSP concentration significantly affected the partitioning of sulfur during DMSP degradation, with lower temperatures and higher substrate concentrations causing a shift from particulate into volatile and non-volatile dissolved products. Our work demonstrates that natural turnover of dissolved DMSP results in minor net production of sulfur gases, and substantial production of previously unrecognized products (particulate and dissolved non-volatile sulfur). The main fates of DMSP are tied to assimilation and oxidation of the reduced sulfur by microorganisms, both of which may act as important controls on the production of climatically active DMS.

Kiene, Ronald P.; Linn, Laura J.

2000-08-01

194

OTEC gas desorption studies  

NASA Astrophysics Data System (ADS)

Experiments on deaeration in packed columns and barometric intake systems, and with hydraulic air compression for open-cycle OTEC systems are reported. A gas desorption test loop consisting of water storage tanks, a vacuum system, a liquid recirculating system, an air supply, a column test section, and two barometric leg test sections was used to perform the tests. The aerated water was directed through columns filled with either ceramic Raschig rings or plastic pall rings, and the system vacuum pressure, which drives the deaeration process, was found to be dependent on water velocity and intake pipe height. The addition of a barometric intake pipe increased the deaeration effect 10%, and further tests were run with lengths of PVC pipe as potential means for noncondensibles disposal through hydraulic air compression. Using the kinetic energy from the effluent flow to condense steam in the noncondensible stream improved the system efficiency.

Chen, F. C.; Golshani, A.

1982-02-01

195

Airflow in ducts: Measurement by perfluorocarbon (PFT) tracer  

Microsoft Academic Search

This paper describes the development of a tracer-gas system for measuring airflow in ducts, The fast-response system is capable of sampling different types of gases including a perfluorocarbon tracer (PFT) which was used for this siudy. The PFT, which is a liquid at room temperature, was injected into the duct using a thermostatically controlled heating block Tracer gas samples were

K. W. Cheong; S. B. Riffat

1994-01-01

196

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

197

Coupling of groundwater and surface water at Lake Willersinnweiher: Groundwater modeling and tracer studies  

Microsoft Academic Search

.  Coupling between groundwater and surface water at Lake Willersinnweiher, a gravel pit lake in the Upper Rhine Graben without\\u000a any surface in- or outflow, was investigated using both a groundwater model and the tracers 18O and SF6. Based on groundwater modeling, recharge and discharge areas around the lake as well as the residence time of the lake water\\u000a were determined

Ute Wollschläger; Johann Ilmberger; Margot Isenbeck-Schröter; Andreas M. Kreuzer; Christoph von Rohden; Kurt Roth; Wolfgang Schäfer

2007-01-01

198

TRACER: a resource to study the regulatory architecture of the mouse genome  

PubMed Central

Background Mammalian genes are regulated through the action of multiple regulatory elements, often distributed across large regions. The mechanisms that control the integration of these diverse inputs into specific gene expression patterns are still poorly understood. New approaches enabling the dissection of these mechanisms in vivo are needed. Results Here, we describe TRACER (http://tracerdatabase.embl.de), a resource that centralizes information from a large on-going functional exploration of the mouse genome with different transposon-associated regulatory sensors. Hundreds of insertions have been mapped to specific genomic positions, and their corresponding regulatory potential has been documented by analysis of the expression of the reporter sensor gene in mouse embryos. The data can be easily accessed and provides information on the regulatory activities present in a large number of genomic regions, notably in gene-poor intervals that have been associated with human diseases. Conclusions TRACER data enables comparisons with the expression pattern of neighbouring genes, activity of surrounding regulatory elements or with other genomic features, revealing the underlying regulatory architecture of these loci. TRACER mouse lines can also be requested for in vivo transposition and chromosomal engineering, to analyse further regions of interest.

2013-01-01

199

In-Situ Study of Denitrification in the Elk Valley Aquifer: Second Tracer Test  

NASA Astrophysics Data System (ADS)

The purpose of the second tracer test performed in the Elk Valley Aquifer in-situ mesocosms was to monitor aquifer geochemistry under further nitrate loading. The hypotheses being tested were: 1) Sulfide would continue to serve as the dominant electron donor for denitrification, and 2) geochemical conditions would indicate that organic carbon is also an important electron donor. Comparing the data set of the second tracer test to that of the first tracer test, the following conclusions are apparent: 1) Denitrification rates in the second test were about half those of the first test. 2) Denitrification by sulfide decreased from up to 61% for the first test to a maximum of 48% in the second test. 3) Nitrogen isotope fractionation suggests a more electron-donor deficient environment in the second test than in the first. Geochemical modeling using PHREEQC-2 was used to provide insights on the importance of organic carbon as an electron donor for denitrification. The model simulations employ mineral equilibria, cation exchange, dilution, and oxidation-reduction reactions to describe changes in major water quality parameters. Model results support our hypothesis that organic carbon is also an important electron donor for denitrification in the Elk Valley Aquifer.

Skubinna, P. A.; Korom, S. F.

2001-05-01

200

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

NASA Astrophysics Data System (ADS)

At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H218O, 7Be, and release of fluorescent dyes), complemented by in situ sea-ice permeability measurements. It was shown that the balance between meltwater supply at the surface (averaging between 3.5 and 10.5 mm d-1) and ice permeability (between <10-11 and >10-9 m2) determines the retention and pooling of meltwater, which in turn controls ice albedo. We found that the seasonal evolution of first-year and multiyear ice permeability and surface morphology determine four distinct stages of melt. At the start of the ablation season (stage 1), ponding is widespread and lateral melt flow dominates. Several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones. Significant formation of underwater ice, composed between <30 and >50% of meteoric water, formed at these drainage sites. Complete removal of snow cover, increase in ice permeability, and reductions in hydraulic gradients driving fluid flow mark stage 2, concurrent with a reduction in pond coverage and albedo. During stage 3, maximum permeabilities were measured, with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first-year and thin multiyear ice. Enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration, concurrent with increases in pond salinities and 7Be. Advective heat flows of several tens of watts per square meter were derived, promoting widening of ponds and increases in pond coverage. Stage 4 corresponds to freeze-up. Roughly 40% of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under-ice ponds (with a total net retention of 15%). Based on this work, areas of improvement for fully prognostic simulations of ice albedo are identified, calling for parameterizations of sea-ice permeability and the integration of ice topography and refined ablation schemes into atmosphere-ice-ocean models.

Eicken, H.; Krouse, H. R.; Kadko, D.; Perovich, D. K.

2002-10-01

201

Subsurface barrier integrity verification using perfluorocarbon tracers  

Microsoft Academic Search

Subsurface barriers are an extremely promising remediation option to many waste management problems. Gas phase tracers include perfluorocarbon tracers (PFT`s) and chlorofluorocarbon tracers (CFC`s). Both have been applied for leak detection in subsurface systems. The focus of this report is to describe the barrier verification tests conducted using PFT`s and analysis of the data from the tests. PFT verification tests

T. M. Sullivan; J. Heiser; L. Milian; G. Senum

1996-01-01

202

The Numerical Simulation of a Tracer-Release Field Project to Study Motion within the Nocturnal Boundary Layer  

NASA Astrophysics Data System (ADS)

The Savannah River National Laboratory (SRNL), Brookhaven National Laboratory (BNL), the University of Georgia (UGA), and the National Oceanic and Atmospheric Administration (NOAA) conducted a regional tracer experiment to study the nocturnal behavior of CO2 in the vicinity of an instrumented tall tower during two nights on May 11th and 12th, 2009. The experiment consisted of a release of five perfluorocarbon tracer (PFTs) compounds in twelve unique locations in Aiken County, South Carolina. Intensive meteorological measurements including in-situ turbulence were made in conjunction with the release and sampling of the PFTs. A 300m tower was also used to collect data from higher levels, allowing us to determine the extent to which the tracer was mixed vertically. Lagrangian plume simulations performed during the experiment demonstrated transport over distances of >8 km, and correlated well with in situ sampling. The area was characterized by heavy vegetation cover, and carbon dioxide concentrations were also monitored in an effort to determine how respiration and advection affect CO2 levels in the stable layer. Tracer release locations were carefully selected via a fine-scale mesoscale modeling study of similar nights. The purpose of these experiments was to provide data that will be used to increase the understanding of the terrestrial carbon budget, especially with respect to nocturnal boundary layer (NBL) phenomena such as low level jets and breaking gravity waves. Using these data, a simulation of the motion of the tracer within the boundary layer was developed using the Regional Atmospheric Modeling System (RAMS) mesoscale model coupled to a tracer model. The RAMS model was also coupled to the Simple Biosphere (SiB) vegetation model, which allowed for the simulation of the release of carbon dioxide into the NBL. The simulation results are used to validate the NBL hypothesis of CO2 monitoring, by which the release of CO2 can be correlated with the accumulation of CO2 in the boundary layer beneath a stable ‘lid’, which impedes vertical mixing. This is done with both the tracer, in which the release rate is known and no advection occurs, and for CO2, in which the release rate is not known and for which advection of CO2 must be accounted. The high resolution of the simulation allows us to resolve the small-scale motions within the NBL, which are important to nocturnal transport. Flux data from the tall tower were studied to learn more about the eddy transport, and also to detect the occurrence of transport ‘events’ in which the CO2 and H2O values experience a sudden increase. A wavelet analysis is also applied, and reveals the existence of eddy activity dominated by eddies of diameter 90-240m.

Werth, D. W.; Leclerc, M. Y.; Buckley, R.; Parker, M.; Kurzeja, R.; Duarte, H. F.; Zhang, G.; Durden, D.

2009-12-01

203

Rio Vista gas leak study: Belleaire Gas Field, California  

Microsoft Academic Search

The Rio Vista gas leak study evaluated methods for remotely sensing gas leaks from buried pipelines and developed methods to elucidate methane transport and microbial oxidation in soils. Remote-sensing methods were evaluated by singing gas leaks along an abandoned Pacific Gas and Electric (PG E) gas field collection line in northern California and applying surface-based and airborne remote-sensing techniques in

Wilkey

1992-01-01

204

Diffusion of oxygen tracer into deuterium-gas-baked IrO{sub x}/Pb(Zr,TiO{sub 3})Pt capacitors and Pb(Zr,Ti)O{sub 3}Pt films  

SciTech Connect

Deuterium gas (D{sub 2}) ambient heat treatment of ferroelectric Pb(Zr,Ti)O{sub 3} (PZT) thin-film capacitors with a top electrode of iridium oxide and a bottom electrode of platinum showed significant polarization loss when baked at 200 deg. C at a pressure of 5 Torr. The D{sub 2} gas treatment of the capacitors partially reduced the iridium oxide (IrO{sub x}, where x is 1tracer ({sup 18}O{sub 2}) gases which recovered the ferroelectric properties and the D concentration in the PZT decreased to the detection level of 10{sup 17} at./cm{sup 3}. The oxygen tracer concentration was highest in the IrO{sub x} film and much lower in the PZT. Comparison of the oxygen tracer SIMS profiles of the PZT annealed in tracer oxygen or preannealed in oxygen followed by oxygen tracer annealing showed little difference in the calculated PZT oxygen tracer diffusion coefficient of 5x10{sup -15} cm{sup 2}/s. If the PZT was reduced by the D{sub 2} gas, an increase in the oxygen diffusion coefficient would be expected as has been proposed in the literature, but this was not observed experimentally. These results indicate that the loss of polarization in the PZT capacitor is primarily due to the inhibition of ferroelectric domain switching by possible formation of [OD{sup -}].

Cross, J.S.; Kurihara, K.; Haneda, H. [Fujitsu Limited and Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi 243-0197 (Japan); National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan)

2005-11-01

205

Application of tracer packet technique to the study of the bio-sorption of heavy and toxic metal radionuclides by algae  

Microsoft Academic Search

The bio-sorption of heavy and toxic radionuclides by three genera of algae from different taxonomic groups was studied employing the recently developed 'Tracer Packet' technique. The tracer packet of heavy and toxic metals' contained 197Hg, 198,199,200,201Tl, 199,200,201Pb, 204Bi and 204,205Po radionuclides in carrier-free state and was produced by irradiating a gold metal foil with medium energy 7Li and 12C beams

D. Nayak; S. Lahiri; A. Mukhopadhyay; R. Pal

2003-01-01

206

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

207

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

208

Stationary and time-dependent indoor tracer-gas concentration profiles measured by OP-FTIR remote sensing and SBFM-computed tomography  

NASA Astrophysics Data System (ADS)

Measurement of gas concentrations in indoor air using optical remote sensing (ORS) and computed tomography (CT) has been suggested but not thoroughly investigated. We present experiments in which one time-varying and 11 different steady-state tracer-gas concentration profiles were generated in a ventilated chamber and sampled in a horizontal plane by an open-path Fourier transform infrared (OP-FTIR) spectrometer for subsequent CT inversion. CT reconstructions were performed using the recently developed smooth basis function minimization (SBFM) technique. The CT reconstructions were compared with simultaneously gathered point-sample concentration measurements. Agreement between the two sampling methods was qualitatively very good, with concentration profiles generated by both methods showing the same features of peak location and shape. Quantitative agreement was generally good to within 50%. We discuss the sources of discrepancy and suggest directions for future research, especially with regard to monitoring time-dependent processes. With further refinements in the SBFM algorithm and improvements in optical remote sensing hardware, this technique promises to yield rapid and accurate measurements of the spatial distribution of gases in indoor environments.

Drescher, A. C.; Park, D. Y.; Yost, M. G.; Gadgil, A. J.; Levine, S. P.; Nazaroff, W. W.

209

Using dissolved noble gas and isotopic tracers to evaluate the vulnerability of groundwater resources in a small, high elevation catchment to predicted climate changes  

SciTech Connect

We use noble gas concentrations and multiple isotopic tracers in groundwater and stream water in a small high elevation catchment to provide a snapshot of temperature, altitude, and physical processes at the time of recharge; and to determine subsurface residence times of different groundwater components. They identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water from bedrock aquifers that have elevated radiogenic {sup 4}He, and (3) upwelling of deep fluids that have 'mantle' helium and hydrothermal carbon isotope signatures. Although a bimodal distribution in apparent groundwater age indicates that groundwater storage times range from less than a year to several decades, water that recharges seasonally is the largest likely contributor to stream baseflow. Under climate change scnearios with earlier snowmelt, the groundwater that moves through the alluvial aquifer seasonally will be depleted earlier, providing less baseflow and possible extreme low flows in the creek during summer and fall. Dissolved noble gas measurements indciate recharge temperatures are 5 to 11 degrees higher than would be expected for direct influx of snowmelt, and that excess air concentrations are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over diffuse vegetated areas, as indicated by {delta}{sup 13}C-DIC values that are consistent with incorporation of CO{sub 2} from soil respiration. Recharge temperatures are close to or slightly higher than mean annual air temperature, and are consistent with recharge during May and June, when snowpack melting occurs.

Singleton, M J; Moran, J E

2009-10-02

210

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

NASA Astrophysics Data System (ADS)

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 do not trace gas at high temperature and density. Depending on the angular scale of a galaxy, the observed low-J lines can be dominated by the emission coming from the starburst ring rather than from the central region. Aims: With the incorporation of high-J molecular lines, we aim to constrain the physical conditions of the dense gas in the central region of the Seyfert 2 galaxy NGC 1068 and to determine signatures of the AGN or the starburst contribution. Methods: We used the James Clerk Maxwell Telescope to observe the J = 4-3 transition of HCN, HNC, and HCO^+, as well as the CN NJ = 25/2-13/2 and NJ = 35/2-25/2, in NGC 1068. We estimate the excitation conditions of HCN, HNC, and CN, based on the line intensity ratios and radiative transfer models. We discuss the results in the context of models of irradiation of the molecular gas by UV light and X-rays. Results: A first-order estimate leads to starburst contribution factors of 0.58 and 0.56 for the CN and HCN J=1-0 lines, respectively. We find that the bulk emission of HCN, HNC, CN, and the high-J HCO+ emerge from dense gas (n(H2) ? 105 cm-3). However, the low-J HCO+ lines (dominating the HCO+ column density) trace less dense (n(H2) < 105 cm-3) and colder (TK ? 20 K) gas, whereas the high-J HCO+ emerges from warmer (> 30 K) gas than the other molecules. We also find that the HNC/HCN and CN/HCN line intensity ratios decrease with increasing rotational quantum number J. Conclusions: The HCO+ J = 4-3 line intensity, compared with the lower transition lines and with the HCN J = 4-3 line, support the influence of a local XDR environment. The estimated N(CN)/N(HCN) ~ 1-4 column density ratios are indicative of an XDR/AGN environment with a possible contribution of grain-surface chemistry induced by X-rays or shocks. Appendices are only available in electronic form at http://www.aanda.org

Pérez-Beaupuits, J. P.; Spaans, M.; van der Tak, F. F. S.; Aalto, S.; García-Burillo, S.; Fuente, A.; Usero, A.

2009-08-01

211

Dark matter in the Milky Way. II. The HI gas distribution as a tracer of the gravitational potential  

Microsoft Academic Search

Context: Gas within a galaxy is forced to establish pressure balance against gravitational forces. The shape of an unperturbed gaseous disk can be used to constrain dark matter models. Aims: We derive the 3D HI volume density distribution for the Milky Way out to a galactocentric radius of 40 kpc and a height of 20 kpc to constrain the Galactic

P. M. W. Kalberla; L. Dedes; J. Kerp; U. Haud

2007-01-01

212

Simulation and interpretation of inter-well tracer tests  

NASA Astrophysics Data System (ADS)

In inter-well tracer tests (IWTT), chemical compounds or radioactive isotopes are used to label injection water and gas to establish well connections and fluid patterns in petroleum reservoirs. Tracer simulation is an invaluable tool to ease the interpretation of IWTT results and is also required for assisted history matching application of tracer data. In this paper we present a new simulation technique to analyse and interpret tracer results. Laboratory results are used to establish and test formulations of the tracer conservation equations, and the technique is used to provide simulated tracer responses that are compared with observed tracer data from an extensive tracer program. The implemented tracer simulation methodology use a fast post-processing of previously simulated reservoir simulation runs. This provides a fast, flexible and powerful method for analysing gas tracer behaviour in reservoirs. We show that simulation time for tracers can be reduced by factor 100 compared to solving the tracer flow equations simultaneously with the reservoir fluid flow equations. The post-processing technique, combined with a flexible built-in local tracer-grid refinement is exploited to reduce numerical smearing, particularly severe for narrow tracer pulses.

Huseby, Olaf; Sagen, Jan; Viig, Sissel; Dugstad, Øyvind

2013-05-01

213

An in vivo study with an MRI tracer method reveals the biophysical properties of interstitial fluid in the rat brain.  

PubMed

The nature of brain interstitial fluid (ISF) has long been a subject of controversy. Most of the previous studies on brain ISF were carried out in vitro. In the present study, a novel method was developed to characterize ISF in the living rat brain by magnetic resonance (MR) imaging using gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) as a tracer. Sprague Dawley rats (n=8) were subjected to MR scanning before and after the introduction of Gd-DTPA into the caudate nucleus. A one-way drainage of brain ISF was demonstrated on the dynamic MR images. According to the traditional diffusion model, the diffusion and clearance rate constants of the tracer within brain extracellular space (ECS) were derived as (3.38+-1.07)×10(-4) mm(2) s(-1) and (7.60±4.18)×10(-5) s(-1). Both diffusion and bulk flow contributed to the drainage of ISF from the caudate nucleus, which demonstrated an ISF-cerebrospinal fluid confluence in the subarachnoid space at the lateral and ventral surface of the brain cortex at 3 h after the injection. By using this newly developed method, the brain ECS and ISF can be quantitatively measured simultaneously in the living brain, which will enhance the understanding of ISF and improve the efficiency of drug therapy via the brain interstitium. PMID:23015126

Han, HongBin; Li, Kai; Yan, JunHao; Zhu, Kai; Fu, Yu

2012-09-27

214

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

215

Tracer Transport in Fractured Rocks.  

National Technical Information Service (NTIS)

Recent interest in the safety of toxic waste underground disposal and nuclear waste geologic repositories has motivated many studies of tracer transport in fractured media. Fractures occur in most geologic formations and introduce a high degree of heterog...

C. F. Tsang Y. W. Tsang F. V. Hale

1988-01-01

216

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

217

Depth-resolved water column spectral absorption of sunlight by phytoplankon during the Southern Ocean Gas Exchange (SOGasEx) Lagrangian tracer experiments  

NASA Astrophysics Data System (ADS)

Optical measurements made during gas exchange tracer experiments in the Southern Ocean, Atlantic sector near 51°S, 38°W from March-April 2008 (SOGasEx) were used to develop daily integrated depth- resolved PAR absorbed by phytoplankton. Particulate and phytoplankton pigment spectral absorption coefficients (ap and aph), and methanol-extracted chlorophyll-a concentrations (chl-a) from discrete samples within and below the upper mixed layer (40 stations) were combined with data from optical casts where chlorophyll-a and cdom fluorescence and PAR scalar irradiance were measured (11 stations), PAR Kd was measured from a buoy free of ship shadow for 0-5m (11 stations), and Wetlabs AC-9 whole water absorption coefficients to 150m were measured (14 stations, with 3 in common with fluorescence data) to estimate depth-resolved values for both total spectral absorption and spectral PAR irradiance. By combining depth-adjusted spectral absorption of phytoplankton pigments (aph) with depth-adjusted PAR spectral irradiance we estimated depth-resolved daily PAR irradiance absorbed by photosynthetic pigments. These data can be compared with time-integrated primary production measurements conducted on deck where solar exposure or lamp exposure was modified to simulate a range of depths. Such a synthesis should improve our estimates of depth-integrated daily primary production, and ultimately contribute to refining estimates of carbon export rates to be incorporated into a carbon budget and CO2 air-sea flux models for the SOGasEx experiments.

Hargreaves, B. R.

2008-12-01

218

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

219

Diapycnal flow through the Georges Bank Tidal Front: A Dye Tracer Study  

NASA Astrophysics Data System (ADS)

A fluorescent dye tracer, Fluorescein, injected into the bottom mixed layer at the seaward edge of the tidal front on Georges Bank has provided the first quantitative measurement of an on-bank diapycnal Lagrangian flow through the front. From the warming of the dye patch, 2.5 × 10-6 °C/s and 7.8 × 10-6 °C/s on the south flank and northeast peak respectively, as it passed through the frontal temperature gradient we infer an on-bank flow of 1.9 cm/s on the south flank and 3.2 cm/s on the northeast peak. The heat flux required for this warming is predominantly due to vertical mixing within the tidal front. These observations further demonstrate the utility of direct Lagrangian measurements and provide quantitative estimates of the cross-frontal exchange on Georges Bank, the focus of the U.S GLOBEC Northwest Atlantic/Georges Bank Phase III program.

Houghton, Robert W.; Ho, Cheng

220

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

221

Participation of periolivary neurons in the auditory brainstem circuitry. A Golgi, tracer and degeneration study.  

PubMed

Neurons in the periolivary areas of cat were described using Golgi methods and HRP labeling, and spineless neurons with distant projecting axons and spinous with local ramifying axons were distinguished. Spineless neurons fell into two classes, fusiform and multipolar cells characterised by the large number of terminals of various size, shape, vesicle content and membrane attachment articulating with them and both were identified as projection cells by retrograde tracer. They were, however, distinguished by the shape and orientation of their perikarya, the number, direction, branching pattern and composition of the presynaptic complement of their dendrites and their numerical occurrence and distribution among the periolivary areas. Spinous neurons had multipolar somata, wavy spinous dendrites spherically displayed and local, profusely ramifying axon arbor. Their somata and dendrites had few synaptic contacts with afferents, their axonal terminals escaped degeneration and since they failed to get labelled retrogradely from external sources they were considered as local interneurons. Based on morphological criteria and experimental results four types of axons were described. The large terminals with asymmetric membrane contacts and round vesicles took origin from the cochlear nuclei, and terminals of symmetrical membrane specialisation with pleomorphic vesicle content were traced from the inferior colliculus. Small profiles containing ovoid vesicles were considered as terminals of interneurons and the few, with round vesicles as local axoncollaterals. PMID:9123992

Kiss, A; Majorossy, K

1996-01-01

222

Rio Vista gas leak study: Belleaire Gas Field, California  

SciTech Connect

The Rio Vista gas leak study evaluated methods for remotely sensing gas leaks from buried pipelines and developed methods to elucidate methane transport and microbial oxidation in soils. Remote-sensing methods were evaluated by singing gas leaks along an abandoned Pacific Gas and Electric (PG E) gas field collection line in northern California and applying surface-based and airborne remote-sensing techniques in the field, including thermal imaging, laser imaging, and multispectral imagery. The remote-sensing techniques exhibited limitations in range and in their ability to correlate with ground truth data. To elucidate methane transport and microbial oxidation in soils, a study of a controlled leak permitted field testing of methods so that such processes could be monitored and evaluated. Monitoring and evaluation techniques included (1) field measurement of soil-gas concentrations, temperatures, and pressures; (2) laboratory measurement of soil physical/chemical properties and activity of methane-oxidizing microorganisms by means of field samples; and (3) development of a preliminary numerical analysis technique for combined soil-gas transport/methane oxidation. Soil-gas concentrations at various depths responded rapidly to the high rate of gas leakage. The number of methane-oxidizing microorganisms in site soils rapidly increased when the gas leak was initiated and decreased after the leak was terminated. The preliminary field, laboratory, and numerical analysis techniques tested for this study of a controlled gas leak could be successfully applied to future studies of gas leaks. Because soil-gas movement is rapid and temporally variable, the use of several complementary techniques that permit generalization of site-specific results is favored.

Wilkey, P.L. (Argonne National Lab., IL (United States))

1992-08-01

223

Modeling and interpretation of two-phase flow and tracer studies from a subbituminous coal seam in the San Juan basin of New Mexico  

SciTech Connect

Field and modeling studies were performed to characterize two-phase flow within the natural cleat structure of an upper Cretaceous subbituminous coal seam. A two borehole pattern with open completion was used in a study of dewatering and tracer residence time distribution. Air was pumped into a five meter thick seam located about 170 meters below the surface. Krypton 85 was used as the airborne tracer. Air inflow and air and water production rates and tracer arrival times were monitored. The field tests were simulated with a two-phase, three component, porous flow code. Results showed that the air inflow and air and water outflow rates and breakthrough times could not be modeled assuming a uniform darcy-type permeability. The use of a pressure dependent permeability did provide, however, a much better match with the field data.

Nuttall, H.E.; Travis, B.J.

1980-01-01

224

The Transient Tracers in the Ocean (TTO) program: The North Atlantic Study, 1981; The Tropical Atlantic Study, 1983  

NASA Astrophysics Data System (ADS)

The scientific papers here collected result from the Transient Tracers in the Ocean (TTO) program. The two parts of this major geochemical and physical oceanographie expedition took place in the North Atlantic Ocean in 1981 and in the Tropical Atlantic in 1983 on the research vessel Knorr of the Woods Hole Oceanographie Institution. The expeditions, sponsored by the National Science Foundation and the U.S. Department of Energy (North Atlantic only), were designed to observe the passage of man-made geochemical tracers into the interior of the ocean. The foundations for such an experiment were laid in the 1972-1978 GEOSECS program. Here, for the first time, a systematic survey revealed the penetration into the thermocline and deep ocean of the products of man's military/industrial activities, principally tritium and carbon-14 resulting from atmospheric testing of nuclear weapons, which terminated with the nuclear test ban treaty in 1962.

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

1985-01-01

225

Strontium, a tracer to study the transport of calcium in mineralizing tissues by electron probe microanalysis.  

PubMed

In growth plate cartilage the mineralization starts extracellularly in the lower hypertrophic zone. The mineral formed is the calcium phosphate apatite. Enough calcium and phosphate must be available at the mineralization front as well as in regions with proceeding mineralization. There must be a transport of Ca (and phosphate) to these sites. Electron probe X-ray microanalysis is a well established method to analyze element concentrations in small volumes, but it cannot discriminate isotopes. Strontium is similar to Ca in its chemical and biological behaviour and is therefore a suitable tracer to investigate the transport of Ca. Small amounts of Sr (0.1 g per kg body weight) were administered intraperitoneally to young rats. After definite intervals of time ranging from 10 to 120 min, 2-4 rats were killed. On freeze dried cryosections the Sr/Ca ratio of the serum and of the intra- and extracellular space of the growth plate were measured. The Sr/Ca ratio reaches its maximum after about 10 min in the serum and after 20 min in the extracellular space of growth plate cartilage. The intracellular Sr/Ca ratio shows large variations because of the low intracellular Ca and Sr concentration, and is lower than the extracellular ratio for times shorter than 30 min. No significant differences were found between the different cell zones of the unmineralized growth plate cartilage. The results demonstrate that the transport of Ca to the growth plate cartilage is relatively fast and that in growth plate cartilage, Ca is transported extracellularly, not intracellularly. PMID:8316791

Krefting, E R; Frentzel, K; Tessarek, J; Höhling, H J

1993-03-01

226

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

PubMed

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

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

2013-09-03

227

Analysis of tracer and thermal transients during reinjection  

SciTech Connect

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

Kocabas, I.

1989-10-01

228

Tracer transport in fractured rocks  

SciTech Connect

Recent interest in the safety of toxic waste underground disposal and nuclear waste geologic repositories has motivated many studies of tracer transport in fractured media. Fractures occur in most geologic formations and introduce a high degree of heterogeneity. Within each fracture, the aperture is not constant in value but strongly varying. Thus for such media, tracer tends to flow through preferred flowpaths or channels within the fractures. Along each of these channels, the aperture is also strongly varying. A detailed analysis is carried out on a 2D single fracture with variable apertures and the flow through channels is demonstrated. The channels defined this way are not rigidly set pathways for tracer transport, but are the preferred flow paths in the sense of stream-tubes in the potential theory. It is shown that such variable-aperture channels can be characterized by an aperture probability distribution function, and not by the exact deterministic geometric locations. We also demonstrate that the 2D tracer transport in a fracture can be calculated by a model of a system of 1D channels characterized by this distribution function only. Due to the channeling character of tracer transport in fractured rock, random point measurements of tracer breakthrough curves may give results with a wide spread in value due to statistical fluctuations. The present paper suggests that such a wide spread can probably be greatly reduced by making line/areal (or multiple) measurements covering a few spatial correlation lengths. 13 refs., 11 figs., 1 tab.

Tsang, C.F.; Tsang, Y.W.; Hale, F.V.

1988-07-01

229

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

230

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

Microsoft Academic Search

Researchers from Brookhaven National Laboratory (BNL) tested perfluorocarbon (PFT) gas tracers on a subsurface barrier with known flaws at the Waldo test facility [operated by Science and Engineering Associates, Inc (SEA)]. The tests involved the use of five unique PFT tracers with a different tracer injected along the interior of each wall of the barrier. A fifth tracer was injected

T. SULLIVAN; J. HEISER; G. SENUM; L. MILLIAN

2000-01-01

231

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

Microsoft Academic Search

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

Paul J Lioy; Daniel Vallero; Gary Foley; Panos Georgopoulos; John Heiser; Tom Watson; Michael Reynolds; James Daloia; Sai Tong; Sastry Isukapalli

2007-01-01

232

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

Microsoft Academic Search

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

Xingjian Jiang

1991-01-01

233

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

Microsoft Academic Search

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

Xingjian Jiang; Xingjian

1991-01-01

234

Using Tracer Technology to Characterize Contaminated Pipelines  

SciTech Connect

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

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

2005-12-30

235

DNA Based Hydrological Tracers  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

236

Gobar Gas Plant - A Study.  

National Technical Information Service (NTIS)

The Gobar Gas Plant has drawn the attention of the government and the people in the context of the countrywide scarcity of fuel and manure. The gas plants of the Sevapuri block, Varanasi, U.P., have been taken into consideration for the purposes of the st...

K. K. Mukherjee

1974-01-01

237

A tracer study of the Floridan aquifer in southeastern Georgia: Implications for groundwater flow and paleoclimate  

NASA Astrophysics Data System (ADS)

Distributions of stable isotopes of water, radiocarbon, noble gases, and chloride (Cl) in groundwater from the Upper Floridan aquifer in southeastern Georgia suggest that down gradient of the Gulf Trough this aquifer contains waters representative of both regional and local groundwater flow systems. In this area, locally recharged waters tend to remain near the top of the aquifer and do not mix substantially with the regional groundwater flow system. Noble gas temperatures suggest that this region of Georgia was 4.0+/-0.6°C cooler during the last glacial period (LGP). Similar temperature changes have been reported for southern Texas and northern New Mexico, suggesting that the southern United States cooled uniformly during the LGP. Stable isotopes of water became enriched down gradient from the recharge area. These enrichments which have been observed before appear to result from local influx of shallow groundwater into the regional aquifer system rather than representing a climate change signal. An inland gradient of the stable isotope composition (0.60+/-0.14‰/100km in ?18O) was found in young (Holocene) water. After correcting for the change in the stable isotope composition of the ocean during the LGP, water that was recharged during the LGP was found to be slightly depleted in stable isotopes relative to modern recharge (??18O=0.6+/-0.4‰). Assuming the modern inland gradient, the change in ?18O is consistent with a shift in the coastline, which was caused by the lower sea level during the LGP.

Clark, Jordan F.; Stute, Martin; Schlosser, Peter; Drenkard, Stefan; Bonani, Georges

238

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

239

Study of Gas Solid Flow Characteristics in Cyclone Inlet Ducts of A300Mwe CFB Boiler  

NASA Astrophysics Data System (ADS)

Gas solid flow characteristics in cyclone's inlet duct of a 300MW CFB boiler were studied in a cold circulating fluidized bed (CFB) experimental setup according to a 410t/h CFB boiler with a scale of 10?1. Tracer particles were adopted in the experiment and their motion trajectories in the two kinds of cyclone's inlet ducts were photographed by a high-speed camera. By analyzing the motion trajectories of tracer particles, acceleration performance of particle phases in the two inlet ducts was obtained. Results indicate that the acceleration performance of particles in the long inlet duct is better than that in the short inlet duct, but the pressure drop of the long inlet duct is higher. Meanwhile, under the same operating conditions, both the separation efficiency and the pressure drop of the cyclone are higher when the cyclone is connected with the long inlet duct. Figs 11, Tabs 4 and refs 10.

Tang, J. Y.; Lu, X. F.; Lai, J.; Liu, H. Z.

240

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

National Technical Information Service (NTIS)

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 pote...

J. Heiser J. E. Flaherty K. J. Allwine T. Watson T. M. Sullivan

2006-01-01

241

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

Microsoft Academic Search

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

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

2006-01-01

242

SEAPORT LIQUID NATURAL GAS STUDY  

SciTech Connect

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

COOK,Z.

1999-02-01

243

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

244

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

245

Characterization of two-phase flow regimes in horizontal tubes using 81mKr tracer experiments.  

PubMed

The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones. In this case, the tracer experiments are more difficult to perform. In order to check for the capabilities of tracer experiments to be used for the flow mal-distribution diagnosis in the case of multi-phase heat exchangers, we present here a preliminary study on the simplest possible system: two-phase flows in a horizontal tube. (81m)Kr is used as gas tracer and properly collimated NaI (TI) crystal scintillators as detectors. The specific shape of the tracer response allows two-phase flow regimes to be characterized. Signal analysis allows the estimation of the gas phase real average velocity and consequently of the liquid phase real average velocity as well as of the volumetric void fraction. These results are compared successfully to those obtained with liquid phase tracer experiments previously presented by Oriol et al. 2007. Characterization of the two-phase flow regimes and liquid dispersion in horizontal and vertical tubes using coloured tracer and no intrusive optical detector. Chem. Eng. Sci. 63(1), 24-34, as well as to those given by correlations from literature. PMID:18487056

Oriol, Jean; Leclerc, Jean Pierre; Berne, Philippe; Gousseau, Georges; Jallut, Christian; Tochon, Patrice; Clement, Patrice

2008-04-12

246

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

USGS Publications Warehouse

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

Kratzer, Charles R.; Biagtan, Rhoda N.

1997-01-01

247

Field Characterization of Reservoir Flow Paths Using Miscible and Immiscible Tracer Tests  

NASA Astrophysics Data System (ADS)

Injection of supercritical CO2 into deep, brine-filled reservoirs may be used to slow the effect that greenhouse gas emissions have on global warming. During injection, the large contrast in fluid densities and viscosities causes immiscible displacement of the brine by CO2, resulting in a two-phase system. We performed a series of tracer tests during the Frio CO2 sequestration pilot program to study immiscible and miscible fluid displacement through the Frio sandstone, a deep saline reservoir located beneath the Gulf Coast Region of Texas. A two-well tracer test was initially performed to evaluate miscible fluid displacement in the single-phase, brine-filled reservoir. A dipole flow field was first established by pumping brine from a well penetrating the reservoir and then injecting it back into the same formation using a second well. A tracer, added to the injected water and monitored at the pumping well, allowed us to evaluate interwell travel times and tracer-breakthrough curves. These results are compared to CO2 travel times and gas-tracer-breakthrough curves obtained from immiscible displacement of brine by CO2, collected during a subsequent single-well CO2 flood (radial divergence test). CO2 breakthrough was faster than model predictions, and sweep efficiencies were relatively small, suggesting that gas movement occurred along preferential pathways. Estimates of formation dispersivity, porosity-thickness products and brine saturation provide further insight into the nature of these pathways.

Trautz, R. C.; Freifeld, B. M.; Doughty, C.; Benson, S. M.; Phelps, T. J.; McCallum, S. D.

2005-12-01

248

STUDY OF CATALYST FLOW IN FLUID CATALYTIC CRACKING BY MEANS OF RADIOACTIVE TRACERS  

Microsoft Academic Search

A method is given for preparing a Co⁶°-labeled silicaalumina fluid ; cracking catalyst for catalyst flow studies and for control of fluid catalyst ; cracking equipment. ln the method, a water solution of cobait nitrate containing ; Co⁶° is mixed with the catalyst, and the impregnated catalyst is heated to ; decompose the nitrate. Equipment for injecting the catalyst into

J. J. Mitchell; A. J. Jr. Kinsella

1962-01-01

249

Study of the cocrystallization of nikel ion with magnesium ammonium sulfate using 63 Ni tracer  

Microsoft Academic Search

The cocrystallization of nickel ammonium sulfate with magnesium ammonium sulfate has been studied at low concentrations of\\u000a the nickel salt, using radiotracer63Ni. The applicability of the equations developed byBerthelot andNernst, Doerner andHoskins, andAbu Elamayem is discussed. It is concluded that only the logarithmic equation of Doerner-Hoskins holds good for this picromerite system.\\u000a This reveals that during crystallization the crystals that

D. S. Mahadevappa; A. S. A. Murthy

1972-01-01

250

Stable isotope and fatty acid tracers in energy and nutrient studies of jellyfish: a review  

Microsoft Academic Search

Studies of the trophic ecology of gelatinous zooplankton have predominantly employed gut content analyses and grazing experiments.\\u000a These approaches record only what is consumed rather than what is assimilated by the jellyfish, only provide evidence of recent\\u000a feeding, and unless digestion rates of different prey are known, may provide biased estimates of the relative importance of\\u000a different prey to jellyfish

K. A. Pitt; R. M. Connolly; T. Meziane

251

Stable isotope and fatty acid tracers in energy and nutrient studies of jellyfish: a review  

Microsoft Academic Search

Studies of the trophic ecology of gelatinous zooplankton have predominantly employed gut content analyses and grazing experiments.\\u000a These approaches record only what is consumed rather than what is assimilated by the jellyfish, only provide evidence of recent\\u000a feeding, and unless digestion rates of different prey are known, may provide biased estimates of the relative importance of\\u000a different prey to jellyfish

K. A. Pitt; R. M. Connolly; T. Meziane

2009-01-01

252

Potential Threats from a Likely Nuclear Power Plant Accident: a Climatological Trajectory Analysis and Tracer Study  

Microsoft Academic Search

The legacy of Chernobyl is not the only nuclear accident likely to confront Turkish territory, which is not far from other\\u000a insecure power plants, especially the Metsamor. The main purpose of this study was to examine the possible impacts to Turkish\\u000a territory of a hypothetical accident at the Metsamor Nuclear Plant. The research was performed based on two different methodologies:

Tayfun Kindap; Ufuk Utku Turuncoglu; Shu-Hua Chen; Alper Unal; Mehmet Karaca

2009-01-01

253

Applications of a total dissolved gas pressure probe in ground water studies.  

PubMed

Measurements of dissolved gases have numerous applications in ground water hydrology, and it is now possible to measure the total dissolved gas pressure in situ using a probe. Dissolved gas pressure is measured by submerging a headspace volume with a gas-permeable membrane, allowing dissolved gases in the water to equilibrate with gases in the headspace, then measuring the pressure in the headspace with a pressure transducer. Total dissolved gas pressure (TGP) probes have many potential uses in ground water studies employing dissolved gases, including: (1) determining approximate excess air levels, which may provide information about the time and location of recharge; (2) screening wells for air contamination, which can compromise the accuracy of dissolved gas tracer techniques: (3) detecting a trapped gas phase, which can significantly reduce hydraulic conductivity and impede the transport of dissolved solutes and gases; (4) enabling the use of gas-filled passive diffusion samplers for determining accurate dissolved gas concentrations; and (5) determining relative concentrations of CH4 and CO2 when they are known to be highly abundant. Although TGP probes designed for surface water have been available for several years, TGP probes suitable for ground water applications have only recently become available. Herein we present what are, to our knowledge, the first reported ground water dissolved gas data collected using a TGP probe. We also explain the basic operating principles of these probes and discuss the potential applications listed. PMID:12873007

Manning, Andrew H; Solomon, D Kip; Sheldon, Amy L

254

Isotope Tracers in Catchment Hydrology  

NASA Astrophysics Data System (ADS)

The drainage basin has been a fundamental unit of study in hydrology and geomorphology throughout the modern era of these Earth sciences. The basin, or catchment, is a convenient unit because it typically is well defined topographically, can be studied as a series of nested units of increasing size, and is an open system for which inputs and outputs of mass and energy can be defined and measured. Small catchments have been the “outdoor laboratories” for hydrologists interested in rainfall-runoff relationships, for geochemists interested in the export of weathering products from the landscape, and for ecosystem ecologists interested in biogeochemical cycling.Research studies on small catchments have evolved from a strong focus on strictly input-output relationships (a “black-box” approach) to a focus on understanding flow paths, residence times, and biological and chemical reactions within the catchment. Tracers are essential tools for such work. In catchment studies, tracers that move with the water but do not interact with biota, soils, and rocks are sought so that water itself can be followed. Other tracers are used to follow selected biogeochemical reactions. A multitude of stable and radioactive isotopes has been used as tracers in catchment studies.

Hornberger, George M.

255

Brainstem Reticular Nuclei that Project to the Thalamus in Rats: A Retrograde Tracer Study; pp. 1–22  

Microsoft Academic Search

The precise nuclear origins of projections from the brainstem reticular formation to the thalamus were identified in rats using two retrograde tracing substances: wheat germ agglutinin-horseradish peroxidase conjugate, and Fluoro-Gold. Injections of these tracers were made into a variety of thalamic nuclei, including the intralaminar nuclei (most of these also involved the lateral part of the mediodorsal nucleus), the central

D. B. Newman; C. Y. Ginsberg

1994-01-01

256

Geophysical Methods, Tracer Leakage, and Flow Modeling Studies at the West Pearl Queen Carbon Sequestration\\/EOR Pilot Site  

Microsoft Academic Search

Recently, a few thousand tons of CO2 were injected into the West Pearl Queen field, a depleted oil reservoir in southeastern New Mexico, for a pilot carbon sequestration project. Small amounts of 3 different perfluorocarbon tracers were injected with the CO2. Approximately 50 capillary absorption tube samplers (CATS) were located across the field within 2m of the grounds surface to

G. S. Bromhal; T. H. Wilson; A. Wells; R. Diehl; D. H. Smith

2003-01-01

257

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

258

Synthesis, characterization, and monkey positron emission tomography (PET) studies of [ 18F]Y1-973, a PET tracer for the neuropeptide Y Y1 receptor  

Microsoft Academic Search

Neuropeptide Y receptor subtype 1 (NPY Y1) has been implicated in appetite regulation, and antagonists of NPY Y1 are being explored as potential therapeutics for obesity. An NPY Y1 PET tracer is useful for determining the level of target engagement by NPY Y1 antagonists in preclinical and clinical studies. Here we report the synthesis and evaluation of [18F]Y1-973, a novel

Eric D. Hostetler; Sandra Sanabria-Bohórquez; Hong Fan; Zhizhen Zeng; Liza Gantert; Mangay Williams; Patricia Miller; Stacey O'Malley; Minoru Kameda; Makoto Ando; Nagaaki Sato; Satoshi Ozaki; Shigeru Tokita; Hisashi Ohta; David Williams; Cyrille Sur; Jacquelynn J. Cook; H. Donald Burns; Richard Hargreaves

2011-01-01

259

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

260

Perfluorocarbon tracer technology  

Microsoft Academic Search

Perfluorocarbon tracer technology developments at Brookhaven is described, including the latest identified as well as available PFTs and air sampling and analysis tools, to demonstrate their utility in a number of different atmospheric tracer experiments as well as in other applications, and to provide food-for-thought on new ways in which the PFTs can be applied in other research objectives. All

1986-01-01

261

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

262

Electrogenic Cl- absorption by Amphiuma small intestine: dependence on serosal Na+ from tracer and Cl- microelectrode studies.  

PubMed

The Na+ requirement for active, electrogenic Cl- absorption by Amphiuma small intestine was studied by tracer techniques and double-barreled Cl- -sensitive microelectrodes. Addition of Cl- to a Cl- -free medium bathing in vitro intestinal segments produced a saturable (Km = 5.4 mM) increase in short-circuit current (ISC) which was inhibitable by 1 mM SITS. The selectivity sequence for the anion-evoked current was Cl- = Br- greater than SCN- greater than NO-3 greater than F- = I-. Current evoked by Cl- reached a maximum with increasing medium Na concentration (KM = 12.4 mM). Addition of Na+, as Na gluconate (10 mM), to mucosal and serosal Na+-free media stimulated the Cl- current and simultaneously increased the absorptive Cl- flux (JCl m----s) and net flux ( JClnet ) without changing the secretory Cl- flux ( JCls ----m). Addition of Na+ only to the serosal fluid stimulated JClm ----s much more than Na+ addition only to the mucosal fluid in paired tissues. Serosal DIDS (1 mM) blocked the stimulation. Serosal 10 mM Tris gluconate or choline gluconate failed to stimulate JClm ----s. Intracellular Cl- activity ( aiCl ) in villus epithelial cells was above electrochemical equilibrium indicating active Cl- uptake. Ouabain (1 mM) eliminated Cl- accumulation and reduced the mucosal membrane potential (psi m) over 2 to 3 hr. In contrast, SITS had no effect on Cl- accumulation and hyperpolarized the mucosal membrane. Replacement of serosal Na+ with choline eliminated Cl- accumulation while replacement of mucosal Na+ had no effect. In conclusion by two independent methods active electrogenic Cl- absorption depends on serosal rather than mucosal Na+. It is concluded that Cl- enters the cell via a primary (rheogenic) transport mechanism. At the serosal membrane the Na+ gradient most likely energizes H+ export and regulates mucosal Cl- accumulation perhaps by influencing cell pH or HCO-3 concentration. PMID:6726790

White, J F; Ellingsen, D; Burnup, K

1984-01-01

263

Tracers in rainfall simulation experiments to study the onset of the wet season in Eastern Mediterranean limestone environments  

NASA Astrophysics Data System (ADS)

The eastern Mediterranean rainfall regime is characterized by dry and hot summers and rainy cold winters. In this climate rocky limestone environments are regarded as major recharge zones due to (a) intensively enlarged fissures by solution weathering and (b) sparse vegetation and shallow soils which limit evapotranspiration losses. However, relatively little is known on hydrological processes during high magnitude rainstorms, which, at the beginning of the rainy season, may occur on both dry and wet soils. These conditions were investigated by a series of sprinkling experiments during two successive days. Rainfall was applied on large plots (143 and 180 m2) to include the variety of different terrain elements (rocky outcrops, bare soil, different vegetation). Sprinkling units were located at each corner of the plot and supplemented by additional ones to balance wind drift. This sprinkling set-up did not guarantee a uniform distribution of applied rainfall, as overlap of sprinkling areas could not be prevented. To assess the spatial rainfall distribution, a large number of totalizers was necessary. During two days of sprinkling these totalizers were regularly measured and spatially interpolated across the plot. The temporal rainfall distribution, a series of two high intensity storms on dry and wet soil, was observed by a tipping bucket raingauge. Tracers were added to the sprinkling water to obtain additional process insights. By end member mixing analysis the contribution of different water types (pre-sprinkling, first day, second day) could be quantified. The first plot was located on a steep rocky hillslope. Significantly different concentration of chloride, nitrate and sulfate in the sprinkling waters helped to identify first day's water in second day's runoff. Surface runoff was a combination of infiltration excess runoff from rocky portions of the plot and saturation excess runoff from areas covered by soil. Soil saturation was accelerated by lateral runoff from adjacent rocky areas. Once the plot was saturated, 80-90% of the applied rainfall became surface runoff. About 14% of the flow collected during the second day originated from water applied during the first day. Both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow. The second plot was located above a karstic cave. Additionally to soil moisture and surface runoff, the drip response of cave stalactites was measured. This time electrical conductivity and bromide were used to study recharge processes, water origin and mixing inside a 28 m vadose zone. Bromide tracing allowed identification of quick direct flow paths. Under dry preconditions, 80 mm of artificial rainfall applied in less than seven hours was not enough to initiate significant downward water percolation. Most water was required to fill uppermost soil and rock storages. During the second day of sprinkling, higher water contents in soils and karst cavities facilitated piston flow effects and a more intense response of the cave drips. Both experiments yielded point estimates for seasonal thresholds of runoff generation and groundwater recharge. The filling of the unsaturated zone, including soil and rock storages, was found to be an important precondition for the onset of surface runoff and groundwater recharge. By mixing analysis, continuously applied tracers identified the dominating processes: saturation excess overland flow for runoff generation and piston flow for water percolation. Overall, a higher seasonal threshold for water percolation than for the generation of surface runoff was found.

Lange, Jens

2010-05-01

264

NPS Gas Gun for Planar Impact Studies  

Microsoft Academic Search

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

Chien Cheong Ho; Robert Hixson

2009-01-01

265

Complex Tracer Diffusion Dynamics in Polymer Solutions  

NASA Astrophysics Data System (ADS)

We employ fluorescence correlation spectroscopy (FCS) and coarse-grained molecular dynamics simulations to study the mobility of tracers in polymer solutions. Excluded volume interactions result in crowding-induced slowdown, depending only on the polymer concentration. With specific tracer-polymer attractions, the tracer is slowed down at much lower concentrations, and a second diffusion component appears that is sensitive to the polymer chain length. The two components can be resolved by FCS, only if the distance traveled by the tracer in the polymer-bound state is greater than the FCS focal spot size. The tracer dynamics can be used as a sensitive probe of the nature and strength of interactions, which—despite their local character—emphasize the role of chain connectivity.

Vagias, Apostolos; Raccis, Riccardo; Koynov, Kaloian; Jonas, Ulrich; Butt, Hans-Jürgen; Fytas, George; Košovan, Peter; Lenz, Olaf; Holm, Christian

2013-08-01

266

Tracer transport in internal wave beams  

NASA Astrophysics Data System (ADS)

Continuously stratified fluids sustain internal waves that propagate like beams under an angle with the vertical. In the ocean, these internal wave beams are believed to transport tracers and contribute to the total abyssal mixing. However, this has not been investigated in the numerous laboratory and numerical studies on this subject. We present laboratory experiments on internal wave beams that are able to transport tracers along the localised beams. The resulting transport depends on the tracer considered, as dynamically active tracers, e.g. buoyancy, are more constrained than free tracers. We observe a horizontal convergence of fluid into the internal wave beam. Internal waves play an important, albeit not quite understood, role in the oceans nutrient exchange and these findings might contribute in our understanding of this process.

Hazewinkel, J.; Dalziel, S. B.; Doelman, A.; Maas, L. R.

2008-12-01

267

Solvent Extraction Behavior of Astatine and Radioiodine at Tracer Concentrations  

Microsoft Academic Search

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

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

2000-01-01

268

Drainage of molecules from subarachnoid space to spinal nerve roots and peripheral nerve of the rat. A study based on Evans blue-albumin and lanthanum as tracers.  

PubMed

The purpose of the present investigation was to find out if a compound injected into the spinal subarachnoid space, after having entered ventral and dorsal nerve roots, can be traced to the epineurial-perineurial sheaths and the endoneurium of peripheral nerves. This would indicate a centrifugal movement of substances from the cerebrospinal fluid along nerves; one route of drainage of cerebrospinal fluid which in the past has been widely discussed. In vivo studies were made using Evans blue-albumin and lanthanum chloride as tracers. Evans blue-albumin is macromolecular in size and emits a red fluorescence after exposure to ultraviolet light. Lanthanum ions are small and easily visible in the electron microscope. The tracers were injected into the cervical subarachnoid space and 15 min to 24 h later samples from roots, dorsal root ganglia, proximal part of spinal nerves and the median nerves were taken and further processed for detection of tracers. Fluorescence microscopy from samples removed 15 min and 24 h after the injection of Evans blue-albumin showed a red fluorescence of low intensity in the endoneurium of nerve roots, ganglia and proximal spinal nerve. After 24 h also the median nerve elicited some fluorescence. The sheaths around these structures were also fluorescent. Lanthanum was detected between cell layers of the nerve root sheath as well as inside the nerve root parenchyma. In about 50% of the samples from dorsal root ganglia extracellular lanthanum was found in the capsule. The tracer was also found in the epineurium of 50% of the spinal nerves and occasionally in the perineurium.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7508671

Pettersson, C A

1993-01-01

269

Chemical tracers in Hybla Gold working room. Final report  

Microsoft Academic Search

Chemical tracers were placed in the working room for the Hybla Gold event to aid in diagnosing flow of high-energy gases down expanding pipes leading from the room. If post-shot reentry is made, the tracers could provide valuable knowledge concerning pipe closure, mixing of gases from various locations, and volume of gas flow into various sizes of pipes.

B. G. Killian; J. H. McQueen

1978-01-01

270

Effect of ionic environment on the transport of cesium ion in alkali chloride solutions from radio tracer studies.  

PubMed

The rate of transport (diffusion) of cesium ion in aqueous solutions of all the alkali metal chlorides together with cesium iodide and cesium fluoride (generalized name MX) at 25 degrees C temperature has been measured by the radioactive tracer technique using (134)Cs as tracer, over the 0.04.0 M. These diffusion data along with other transport data in the literature are used to calculate the velocity correlation coefficients (VCC) for Cs-M, Cs-H(2)O and Cs-X, which actually represent the ensemble average time integrals of the velocity correlation functions of the referred pair of species. The concentration dependence of VCC gives a quantitative estimate of the influence of environment and its dynamics on the transport of cation cesium in a highly correlated system like aqueous solutions of 1-1 electrolytes. PMID:20828659

Chakrabarti, Haimanti; Kundu, Srinanda

2010-05-27

271

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

272

Tracers detect aquifer contamination  

SciTech Connect

The EPA`s National Laboratory (NRMRL) at Ada, OK, along with the University of Florida and the University of Texas, have developed a tracer procedure to detect the amount of contamination in aquifer formations. The tracer procedure has been successfully applied in a highly controlled field experiment in a contaminated cobbly, sandy gravel aquifer at Hill Air Force Base in Layton, UT. The tracer procedure should substantially improve the ability to remediate aquifers and is an improvement over the traditional reliance upon water samples from monitoring wells and core samples.

Enfield, C.

1995-07-01

273

High upwind concentrations observed during an upslope tracer event  

SciTech Connect

In February of 1991 the Rocky Flats Plant conducted twelve tracer experiments to validate an emergency response dispersion model known as the Terrain-Responsive Atmospheric Code (TRAC) (Hodgin 1985). Experimenters released 140 to 260 kilograms of inert tracer gas (sulfur hexafloride) from the plant over an 11 hour period. During each release, one hundred and sixty-five samples, most of which formed concentric rings of 8 and 16 km radius from the plant, recorded cumulative hourly concentrations of the tracer at one meter above ground level (AGL). Figure 1 contains a depiction of the sampler location, the terrain, and the meteorological stations available within the tracer study area. Brown (1991) describes the experimental setup in more detail. The subject of this paper is an event that occurred early in the fifth experiment, on February 9, 1991. In this experiment, tracer material released from 13:00 to 17:00 LST appeared both downwind and upwind of the source, with the highest concentrations upwind. During the fifth experiment, high pressure in Utah produced mostly sunny skis around Rocky Flats. For most of the day, one could find moderate (5 to 10 ms{sup {minus}1}) northerly (from the North) flow within the 700 to 500 mb level of the atmosphere (approximately 3000 to 5500 meters above Mean Sea Level (MSL)). Synoptic scale motions were isolated enough from the surface layer and heating was great enough to produce a 1 km deep upslope flow (flow from the East to the West) by late afternoon. The winds reversed and became downslope at approximately 17:30 LST.

Ciolek, J.T. Jr.

1993-10-01

274

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

275

Dual-tracer background subtraction approach for fluorescent molecular tomography  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

276

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

277

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

278

Experimental study of the effect of test-well arrangement for partitioning interwell tracer test on the estimation of NAPL saturation  

NASA Astrophysics Data System (ADS)

Partitioning interwell tracer test (PITT) is a method to quantify and qualify a contaminated site with NAPLs through a degree of retardation of partitioning tracers compared to a conservative one. Although PITT is known to be a more effective method to measure the saturation of spatially-distributed NAPL contaminant than the point investigation method, the saturation estimation from PITT is reported to be underestimated due to various factors including heterogeneity of the media, adsorption, source zone NAPL architecture, and long tailing in breakthrough curves of partitioning tracers. Analytical description of PITT assumes that the injection-pumping well pair is on the line of ambient groundwater flow direction, but the test-well pair could easily be off the line in the field site, which could be another erroneous factor in analyzing PITT data. The purpose of this work is to study the influence of the angle of the test-well pair to ambient groundwater flow direction based on the result from PITT. The experiments were conducted in a small-scale 3D sandbox with dimensions of 0.5 m × 0.4 m × 0.15 m (LWH) of stainless steel. The surface is covered and sealed with a plexiglass plate to make the physical model a confined aquifer. Eight full-screened wells of Teflon material were installed along the perimeter of a 50 mm circle with 45 degree intervals in the middle of the physical model. Both ends of the sand box are connected to constant head reservoirs. The physical model was wet-packed with sieved and washed sand. Trichloroethylene (TCE) and bromide were used as the contaminant and the conservative tracer, respectively. Hexanol, 2,4-dimethyl-3-pentanol and 6-methyl-2-heptanol were used as partitioning tracers. Before the injection of TCE, a PITT was conducted to measure adsorption coefficient of partitioning tracers to the sand material. TCE of 4.5 mL, dyed with Sudan IV, was injected into the inner part of the circle of the wells. PITTs using the test-well pair parallel and with angles of 45 and 90 degrees to ambient flow direction were performed. Another PITT was conducted at an increased pumping rate with the test-well pair at a 45 degree angle to examine the effect of pumping rate. From the experiments, it was found that as the angles of the test-well pair to ambient groundwater flow direction increased, the estimated NAPL saturation decreased. Although the increase in pumping rate in this experiment reduces the effect of the obliqueness of the test-well arrangement, the effect of rate-limited transfer of partitioning tracers due to the increased pumping rate on the PITT should be examined in the interpretation. The results of these experiments revealed that the arrangement of the test-well pair is another controlling factor in performing and interpreting PITT in the field, in addition to the factors such as heterogeneity, source zone architecture, and tailing. Key words: PITT, test-well arrangement, ambient groundwater flow direction, NAPL saturation Acknowledgements: This research was supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources (KIGAM) funded by the Ministry of Knowledge Economy of Korea. 11-3414

Kim, B.; Kim, Y.; Yeo, I.; Yongcheol Kim, In Wook Yeo

2011-12-01

279

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

SciTech Connect

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

Dale Spall; Robert Villarreal

1998-08-01

280

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

Microsoft Academic Search

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

1999-01-01

281

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

282

Molecular dynamics studies on nanoscale gas transport  

NASA Astrophysics Data System (ADS)

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress calculations are based on the Irving-Kirkwood method, which divides the stress tensor into its kinetic and virial parts. The kinetic component recovers pressure based on the ideal gas law. The particle-particle virial increases with increased density, while the surface-particle virial develops due to the surface force field effects. Normal stresses within nano-scale confinements show anisotropy induced primarily by the surface force-field and local variations in the fluid density near the surfaces. For dilute and dense gas cases, surface-force field that extends typically 1nm from each wall induces anisotropic normal stress. For liquid case, this effect is further amplified by the density fluctuations that extend beyond the three field penetration region. Outside the wall force-field penetration and density fluctuation regions the normal stress becomes isotropic and recovers the thermodynamic pressure, provided that sufficiently large force cut-off distances are utilized in the computations. Next, non-equilibrium SWMD is utilized to investigate the surface-gas interaction effects on nanoscale shear-driven gas flows in the transition and free molecular flow regimes. For the specified surface properties and gas-surface pair interactions, density and stress profiles exhibit a universal behavior inside the wall force penetration region at different flow conditions. Shear stress results are utilized to calculate the tangential momentum accommodation coefficient (TMAC) between argon gas and FCC walls. The TMAC value is shown to he independent of the now properties and Knudsen number in all simulations. Velocity profiles show distinct deviations from the kinetic theory based solutions inside the wall force penetration depth, while they match the linearized Boltzmann equation solution outside these zones. Afterwards, surface effects are studied as a function of the surface-gas potential strength ratio (epsilon wf/epsilonff) for the shear driven argon gas flows in the early transition and tree molecular flow regimes. Results show that increased epsilonwf/epsilon ff results in increased gas density, leading towards monolayer adsorption on surfaces. The near wall velocity profile shows reduced gas slip, and eventually velocity stick with increased epsilonwf/epsilon ff. Similarly, using MD predicted shear stress values and kinetic theory, TMAC are calculated as a function of epsilonwf/epsilon ff and TMAC values are shown to be independent of the Knudsen number. Results indicate emergence of the wall force field penetration depth as an additional length scale for gas flows in nano-channels, breaking the dynamic similarity between rarefied and nano-scale gas flows solely based on the Knudsen and Mach numbers.

Barisik, Murat

283

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.

284

Comparison of line– and point–source releases of tracer gases  

Microsoft Academic Search

Field measurements were made of greenhouse gas emissions from a wastewater treatment system using open path monitoring with detection by FTIR spectroscopy. Emission rates were determined by the ratio technique using a sulfur hexafluoride tracer gas released from a line source. As a quality control check, a second tracer gas – ethylene – was released from various single point locations.

Bart Eklund

1999-01-01

285

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

286

Rio Vista Gas Leak Study: Belleaire Gas Field, California. Topical Report, April 1989-January 1991.  

National Technical Information Service (NTIS)

The Rio Vista gas leak study evaluated methods for remotely sensing gas leaks from buried pipelines and developed methods to elucidate methane transport and microbial oxidation in soils. Remote-sensing methods were evaluated by staging gas leaks along an ...

P. L. Wilkey

1992-01-01

287

Oxygen tracer diffusion in undoped lanthanum manganites  

Microsoft Academic Search

The oxygen tracer diffusion was studied in cation stoichiometric (LaMnO3±?) and A-site deficient (La0.9MnO3±?) lanthanum manganites by the isotope exchange depth profiling (IEDP) technique using SIMS depth profiling. The measured oxygen tracer diffusion coefficients were in the range of 10?12 to 10?15 cm2 s?1 and these values were comparable with the ones determined in Sr-doped lanthanum manganites. The activation energy

A. V. Berenov; J. L. MacManus-Driscoll; J. A. Kilner

1999-01-01

288

Behavior of organophosphates and hydrophilic ethers during bank filtration and their potential application as organic tracers. A field study from the Oderbruch, Germany.  

PubMed

The behavior of organophosphates and ethers during riverbank filtration and groundwater flow was assessed to determine their suitability as organic tracers. Four sampling campaigns were conducted at the Oderbruch polder, Germany to establish the presence of chlorinated flame retardants (TCEP, TCPP, TDCP), non-chlorinated plasticizers (TBEP, TiBP, TnBP), and hydrophilic ethers (1,4-dioxane, monoglyme, diglyme, triglyme, tetraglyme) in the Oder River, main drainage ditch, and anoxic aquifer. Selected parameters were measured in order to determine the hydro-chemical composition of both, river water and groundwater. The results of the study confirm that organophosphates (OPs) are more readily attenuated during bank filtration compared to ethers. Both in the river and the groundwater, TCPP was the most abundant OP with concentrations in the main drainage ditch ranging between 105 and 958 ng L(-1). 1,4-dioxane, triglyme, and tetraglyme demonstrated persistent behavior during bank filtration and in the anoxic groundwater. In the drainage ditch concentrations of 1,4-dioxane, triglyme, and tetraglyme ranged between 1090 and 1467 ng L(-1), 37 and 149 ng L(-1), and 496 and 1403 ng L(-1), respectively. A positive correlation was found for the inorganic tracer chloride with 1,4-dioxane and tetraglyme. These results confirm the possible application of these ethers as environmental organic tracers. Both inorganic and organic compounds showed temporal variability in the surface- and groundwater. Discharge of the river water, concentrations of analytes at the time of infiltration and attenuation were identified as factors influencing the variable amounts of the analytes in the surface and groundwater. These findings are also of great importance for the production of drinking water via bank filtration and natural and artificial groundwater recharge as the physicochemical properties of ethers create challenges in their removal. PMID:23644568

Stepien, D K; Regnery, J; Merz, C; Püttmann, W

2013-05-03

289

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

290

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

291

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

292

Tracer monitoring of enhanced oil recovery projects  

NASA Astrophysics Data System (ADS)

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

Dugstad, Ø.; Viig, S.; Krognes, B.; Kleven, R.; Huseby, O.

2013-05-01

293

Towards integrating tracer studies in conceptual rainfall-runoff models: recent insights from a sub-arctic catchment in the Cairngorm Mountains, Scotland  

NASA Astrophysics Data System (ADS)

Hydrochemical tracers (alkalinity and silica) were used in an end-member mixing analysis (EMMA) of runoff sources in the 10 km2 Allt a' Mharcaidh catchment. A three-component mixing model was used to separate the hydrograph and estimate, to a first approximation, the range of likely contributions of overland flow, shallow subsurface storm flow, and groundwater to the annual hydrograph. A conceptual, catchment-scale rainfall-runoff model (DIY) was also used to separate the annual hydrograph in an equivalent set of flow paths. The two approaches produced independent representations of catchment hydrology that exhibited reasonable agreement. This showed the dominance of overland flow in generating storm runoff and the important role of groundwater inputs throughout the hydrological year. Moreover, DIY was successfully adapted to simulate stream chemistry (alkalinity) at daily time steps. Sensitivity analysis showed that whilst a distinct groundwater source at the catchment scale could be identified, there was considerable uncertainty in differentiating between overland flow and subsurface storm flow in both the EMMA and DIY applications. Nevertheless, the study indicated that the complementary use of tracer analysis in EMMA can increase the confidence in conceptual model structure. However, conclusions are restricted to the specific spatial and temporal scales examined.

Soulsby, Chris; Dunn, Sarah M.

2003-02-01

294

Nitrate movement and removal along a shallow groundwater flow path in a riparian wetland within a sheep?grazed pastoral catchment: Results of a tracer study  

Microsoft Academic Search

The movement and removal of nitrate (NO3 ) along a groundwater flow path within a riparian wetland was investigated during a 24?day period in late autumn?early winter, using a lithium bromide (LiBr)?potassium nitrate (KNO3) tracer solution containing 19 200 mg\\/litre as Br and 193.8 mg\\/litre as NO3?N. The tracer solution was added as an instantaneous dose of tracer solution at

Douglas A. Burns; Long Nguyen

2002-01-01

295

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

296

Determination of in vivo Bmax and Kd for [11C]GR103545, an agonist PET tracer for kappa opioid receptors: A study in nonhuman primates  

PubMed Central

The kappa opioid receptors (KOR) are involved in mood disorders and addictive conditions. In vivo imaging studies of this receptor in humans have not been reported due to the lack of a selective ligand. We employed a recently developed selective KOR agonist tracer, [11C]GR103545, and performed a study in rhesus monkeys to estimate the in vivo receptor concentration (Bmax) and dissociation equilibrium constant (Kd). Methods Four rhesus monkeys underwent a total of 12 scans with [11C]GR103545 on the Focus 220 scanner under baseline and self-blocking conditions. The injected mass was 0.042±0.014 µg/kg for the baseline scans and ranged from 0.17 to 0.3 µg/kg for the self-blocking scans. The radiotracer was administered in a bolus plus infusion (B+I) protocol, and cerebellum used as reference region in kinetic analysis. Binding potential (BPND) values were computed as [(CROI/CREF)-1], where CROI and CREF are the mean of the radioactivity concentrations from 90 to 120 min post tracer administration in a given region of interest (ROI) and in the cerebellum. In six scans, arterial input functions and free fraction in plasma (fp) were measured, and a 2 -tissue compartment model was used to compute the volume of distribution in the cerebellum (VT_REF), which was then employed to estimate the free to non-displaceable concentration ratio (fND) as fp/VT_REF. A Scatchard plot was used to estimate Bmax, and KdND = Kd/fND, the Kd value with respect to the cerebellar concentration. Individual data were first analyzed separately, then pooled together. When KdND was allowed to vary among ROIs, results were very variable; therefore KdND was constrained to be constant across ROIs whereas Bmax was allowed to be ROI-dependent and animal-dependent. Results A global estimate of 1.72 nM was obtained for KdND. Estimated Bmax ranged from 0.3 to 6.1 nM across ROIs and animals. The Kd estimate of 0.048 nM, obtained by correcting KdND by the factor fND, was between the in vitro Kd values of 0.018 nM to 0.4 nM (obtained from functional assays in rabbit vas deferens and radioligand competition assays using cloned human receptors, respectively). Based on these data, a suitable tracer dose of 0.02 µg/kg was selected for use in humans. Conclusions The use of a B+I protocol with the KOR agonist tracer [11C]GR103545 permitted the successful estimation of Bmax and KdND in vivo. Based on the estimated Kd value, a tracer dose of 1.4 µg (3.38 nmol) for an average body weight of 70 k g was chosen as the mass dose limit in human studies using this novel agonist radiotracer.

Tomasi, Giampaolo; Nabulsi, Nabeel; Zheng, Ming-Qiang; Weinzimmer, David; Ropchan, Jim; Blumberg, Laura; Brown-Proctor, Clive; Ding, Yu-Shin.; Carson, Richard E.; Huang, Yiyun

2013-01-01

297

Atmospheric tracer technology and applications  

Microsoft Academic Search

This book presents information on atmospheric tracer technology and applications. It summarizes the state of the art, provides information exchange for members of the atmospheric community, defines areas for future applications of tracers, and identifies requirements for tracer techniques. A major objective of research in atmospheric science over the past several decades has been to obtain an enhanced description of

Heiken

1986-01-01

298

Modeling surf zone tracer plumes: 2. Transport and dispersion  

NASA Astrophysics Data System (ADS)

Five surf zone dye tracer releases from the HB06 experiment are simulated with a tracer advection diffusion model coupled to a Boussinesq surf zone model (funwaveC). Model tracer is transported and stirred by currents and eddies and diffused with a breaking wave eddy diffusivity, set equal to the breaking wave eddy viscosity, and a small (0.01 m2 s-1) background diffusivity. Observed and modeled alongshore parallel tracer plumes, transported by the wave driven alongshore current, have qualitatively similar cross-shore structures. Although the model skill for mean tracer concentration is variable (from negative to 0.73) depending upon release, cross-shore integrated tracer moments (normalized by the cross-shore tracer integral) have consistently high skills (?0.9). Modeled and observed bulk surf zone cross-shore diffusivity estimates are also similar, with 0.72 squared correlation and skill of 0.4. Similar to the observations, the model bulk (absolute) cross-shore diffusivity is consistent with a mixing length parameterization based on low-frequency (0.001-0.03 Hz) eddies. The model absolute cross-shore dispersion is dominated by stirring from surf zone eddies and does not depend upon the presence of the breaking wave eddy diffusivity. Given only the bathymetry and incident wave field, the coupled Boussinesq-tracer model qualitatively reproduces the observed cross-shore absolute tracer dispersion, suggesting that the model can be used to study surf zone tracer dispersion mechanisms.

Clark, David B.; Feddersen, Falk; Guza, R. T.

2011-11-01

299

Application of the Tracer-Aerosol Gradient Interpretive Technique to Sulfur Attribution for the Big Bend Regional Aerosol and Visibility Observational Study  

Microsoft Academic Search

A simple data analysis method called the Tracer-Aerosol Gradient Interpretive Technique (TAGIT) is used to attribute particulate S and SO2 at Big Bend National Park in Texas and nearby areas to local and regional sources. Particulate S at Big Bend is of concern because of its effects on atmospheric visibility. The analysis used particulate S, SO2 , and perfluorocarbon tracer

Mark Green; Hampden Kuhns; Marc Pitchford; Russell Dietz; Lowell Ashbaugh; Tom Watson

2003-01-01

300

Preliminary studies of gas fillings in gas scintillation proportional counters  

NASA Astrophysics Data System (ADS)

Results are presented on improvements in the performance of medium energy large area gas scintillation proportional counters for use in X-ray astronomy. By a suitable choice of gas mixture the electron transit time through the drift region can be significantly lowered with a consequent reduction in the detector dead time. In addition, the electron diffusion is also reduced and this should result in an increase in the background rejection efficiency.

Manzo, G.; Peacock, A.; Andresen, R. D.; Taylor, B. G.

1980-02-01

301

The Star Formation Rate and Gas Surface Density Relation in the Milky Way: Implications for Extragalactic Studies  

NASA Astrophysics Data System (ADS)

We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) and massive dense clumps. Our YSO sample consists of objects located in 20 large molecular clouds from the Spitzer cores to disks (c2d) and Gould's Belt (GB) surveys. These data allow us to probe the regime of low-mass star formation, essentially invisible to tracers of high-mass star formation used to establish extragalactic SFR-gas relations. We estimate the gas surface density (?gas) from extinction (AV ) maps and YSO SFR surface densities (?SFR) from the number of YSOs, assuming a mean mass and lifetime. We also divide the clouds into evenly spaced contour levels of AV , counting only Class I and Flat spectral energy distribution YSOs, which have not yet migrated from their birthplace. For a sample of massive star-forming clumps, we derive SFRs from the total infrared luminosity and use HCN gas maps to estimate gas surface densities. We find that c2d and GB clouds lie above the extragalactic SFR-gas relations (e.g., Kennicutt-Schmidt law) by factors of up to 17. Cloud regions with high ?gas lie above extragalactic relations up to a factor of 54 and overlap with high-mass star-forming regions. We use 12CO and 13CO gas maps of the Perseus and Ophiuchus clouds from the COMPLETE survey to estimate gas surface densities and compare to measurements from AV maps. We find that 13CO, with the standard conversions to total gas, underestimates the AV -based mass by factors of ~4-5. 12CO may underestimate the total gas mass at ?gas >~ 200 M sun pc-2 by gsim30%; however, this small difference in mass estimates does not explain the large discrepancy between Galactic and extragalactic relations. We find evidence for a threshold of star formation (?th) at 129 ± 14 M sun pc-2. At ?gas>?th, the Galactic SFR-gas relation is linear. A possible reason for the difference between Galactic and extragalactic relations is that much of ?gas is below ?th in extragalactic studies, which detect all the CO-emitting gas. If the Kennicutt-Schmidt relation (?SFR vprop ?1.4 gas) and a linear relation between dense gas and star formation are assumed, the fraction of dense star-forming gas (f dense) increases as ~?0.4 gas. When ?gas reaches ~300 ?th, the fraction of dense gas is ~1, creating a maximal starburst.

Heiderman, Amanda; Evans, Neal J., II; Allen, Lori E.; Huard, Tracy; Heyer, Mark

2010-11-01

302

Rio Vista gas leak study: Belleaire Gas Field, California. Topical report, April 1989January 1991  

Microsoft Academic Search

The Rio Vista gas leak study evaluated methods for remotely sensing gas leaks from buried pipelines and developed methods to elucidate methane transport and microbial oxidation in soils. Remote-sensing methods were evaluated by singing gas leaks along an abandoned Pacific Gas and Electric (PG&E) gas field collection line in northern California and applying surface-based and airborne remote-sensing techniques in the

Wilkey

1992-01-01

303

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

304

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

Microsoft Academic Search

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

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

1998-01-01

305

Tracers and Tracer Testing: Design, Implementation, Tracer Selection, and Interpretation Methods  

SciTech Connect

Conducting a successful tracer test requires adhering to a set of steps. The steps include identifying appropriate and achievable test goals, identifying tracers with the appropriate properties, and implementing the test as designed. When these steps are taken correctly, a host of tracer test analysis methods are available to the practitioner. This report discusses the individual steps required for a successful tracer test and presents methods for analysis. The report is an overview of tracer technology; the Suggested Reading section offers references to the specifics of test design and interpretation.

G. Michael Shook; Shannon L.; Allan Wylie

2004-01-01

306

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

307

Solar-gas systems impact analysis study  

NASA Astrophysics Data System (ADS)

The impacts of solar/gas technologies on gas consumers and on gas utilities were 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 benefits or penalties of solar/gas systems on a combined basis for consumers sand distribution companies. It is shown that the combined benefits associated with solar/gas systems are generally greatest when the systems are purchased by customers who would have otherwise chosen high-efficiency electric systems (were solar/gas systems not available in the market place). The role of gas utilities in encouraging consumer acceptance of solar/gas systems was also examined ion a qualitative fashion. A decision framework for analyzing the type and level of utility involvement in solar/gas technologies was developed.

Neill, C. P.; Hahn, E. F.; Loose, J. C.; Poe, T. E.; Hirshberg, A. S.; Haas, S.; Preble, B.; Halpin, J.

1984-07-01

308

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2010 CFR

...during exercise. No blood-gas study shall be performed if medically...contraindicated. (b) A blood-gas study shall initially be administered at rest and in a sitting position. If the results of the...Any report of a blood-gas study submitted in connection...

2009-04-01

309

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2010 CFR

...during exercise. No blood-gas study shall be performed if medically...contraindicated. (b) A blood-gas study shall initially be administered at rest and in a sitting position. If the results of the...Any report of a blood-gas study submitted in connection...

2010-04-01

310

Experimental depression of junctional membrane permeability in mammalian cell culture. A study with tracer molecules in the 300 to 800 dalton range  

Microsoft Academic Search

Summary Cell-to-cell junctional permeability in mammalian cell cultures was probed with a series of fluorescent tracers ranging 300 to 800 in molecular weight, during treatment with metabolic inhibitors, Ca-transporting ionophore, and carbon dioxide. Treatment with the combination of cyanide and iodoacetic acid (1–2mm each), but not with either one alone, caused reversible junctional blockade to all tracer molecular species, large

J. Flagg-Newton; W. R. Loewenstein

1979-01-01

311

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

312

The active magnetospheric particle tracer explorers (AMPTE) program  

Microsoft Academic Search

The Active Magnetospheric Particle Tracer Explorers (AMPTE) will carry out the release and monitoring of tracer ions (lithium and barium) in the solar wind and within the distant magnetosphere in order to study access of solar wind ions to the magnetosphere and the convective-diffusive transport and energization of magnetospheric particles. In addition, a single massive release of barium in the

S. M. Krimigis; G. Haerendel; R. W. McEntire; G. Paschmann; D. A. Bryant

1982-01-01

313

Use of injected helium as a hydrological tracer  

Microsoft Academic Search

Helium has several characteristics which make it attractive for use as a tracer in hydrological studies. These include its inert nature, relatively high solubility in water (~ 1 %), low molecular diffusion in water, ready availability in commercial quantities, nontoxic nature, and low background atmospheric concentration. The use of helium as a tracer of water movement has become possible through

SUSHIL K. GUPTA; PHILIP S. MORAVCIK; L. STEPHEN LAU

1994-01-01

314

Use of iiyected helium as a hydrological tracer  

Microsoft Academic Search

Helium has several characteristics which make it attractive for use as a tracer in hydrological studies. These include its inert nature, relatively high solubility in water ( ~ 1 %), low molecular diffusion in water, ready availability in commercial quantities, nontoxic nature, and low background atmospheric concentration. The use of helium as a tracer of water movement has become possible

SUSHIL K. GUPTA; PHILIP S. MORAVCIK; L. STEPHEN LAU

315

Echo tracer dispersion in model fractures with a rectangular geometry  

Microsoft Academic Search

We report an experimental study of tracer dispersion in model rectangular fractures with rough or smooth walls and with different mean apertures. We use an echo dispersion technique in which tracer is first injected into the fracture and then pumped back through a detector. in a parallel flow regime, echo dispersion combines a geometrical mechanism due to the fracture roughness

I. Ippolito; G. Daccord; E. J. Hinch; J. P. Hulin

1994-01-01

316

Field tracer-transport tests in unsaturated fractured tuff  

Microsoft Academic Search

This paper presents the results of a field investigation in the unsaturated, fractured welded tuff within the Exploratory Studies Facility (ESF) at Yucca Mountain, NV. This investigation included a series of tests during which tracer-laced water was released into a high-permeability zone within a horizontal injection borehole. The tracer concentration was monitored in the seepage collected in an excavated slot

Qinhong Hu; Rohit Salve; William T Stringfellow; Joseph S. Y Wang

2001-01-01

317

MINERAL BIOAVAILABILITY AND METABOLISM DETERMINED BY USING STABLE ISOTOPE TRACERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

318

The dispersion of atmospheric tracers in nocturnal drainage flows  

Microsoft Academic Search

This paper summarizes the results of a series of perfluorocarbon tracer experiments that were carried out in the Brush Creek Valley in western Colorado under the auspices of the Atmospheric Studies in Complex Terrain (ASCOT) program. The results indicate that tracers entrained within the valley's nocturnal drainage flows displayed well defined plumes that were not influenced significantly by the larger

Paul H. Gudiksen; Donald L. Shearer

1989-01-01

319

Landfill methane emissions measured by enclosure and atmospheric tracer methods  

NASA Astrophysics Data System (ADS)

Methane (CH4) emissions were measured from the Nashua, New Hampshire municipal landfill using static enclosure and atmospheric tracer methods. The spatial variability of emissions was also examined using geostatistical methods. One hundred and thirty nine enclosure measurements were performed on a regular grid pattern over the emitting surface of the landfill resulting in an estimate of whole landfill emissions of 15,800 L CH4 min-1. Omnidirectional variograms displayed spatial correlation among CH4 fluxes below a separation distance of 7 m. Eleven tracer tests, using sulfur hexafluoride (SF6) as a tracer gas, resulted in a mean emissions estimate of 17,750 L CH4 min-1. The favorable agreement between the emission estimates was further refined using the observed relationship between atmospheric pressure and CH4 flux. This resulted in a pressure-corrected tracer flux estimate of whole landfill emissions of 16,740 L CH4 min-1.

Czepiel, P. M.; Mosher, B.; Harriss, R. C.; Shorter, J. H.; McManus, J. B.; Kolb, C. E.; Allwine, E.; Lamb, B. K.

1996-07-01

320

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

321

TRACERS TEST EFFICIENCY OF AIRCOMPRESSOR FILTERS  

Microsoft Academic Search

A study was conducted of filter efficiency in high-speed and high-; temperature air compressors, Oil particles tend to form varnishlike deposits in ; critical parts of airbrake equipment. A tracer of Sb¹²⁴ in ; triphenylstibine was used to evaluate the efficiency of each filter tested. The ; method used in the testing of the filters is presented. (B.O.G.);

R. L. Jr. Ely; J. R. Pier

1960-01-01

322

Modeling the CAPTEX Vertical Tracer Concentration Profiles  

Microsoft Academic Search

Perfluorocarbon tracer concentration profiles measured by aircraft 600-900 km downwind of the release locations during CAPTEX are discussed and compared with some model results. In general, the concentrations decreased with height in the upper half of the boundary layer where the aircraft measurements were made. The results of a model sensitivity study suggested that the shape of the profile was

Roland R. Draxler; Barbara J. B. Stunder

1988-01-01

323

CityFlux perfluorocarbon tracer experiments  

Microsoft Academic Search

In June 2006, two perfluorocarbon tracer experiments were conducted in central Manchester UK as part of the CityFlux campaign. The main aim was to investigate vertical dispersion in an urban area during convective conditions, but dispersion mechanisms within the street network were also studied. Paired receptors were used in most cases where one receptor was located at ground level and

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

2010-01-01

324

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

325

Dense gas in the Galaxy  

Microsoft Academic Search

The large-scale distribution of gas in the Galaxy is discussed by means of a review of recent studies of molecular gas and statistical analyses of giant molecular clouds (GMCs) as derived from CO-line surveys. The use of CO as a tracer of the galactic H2 is discussed, and the large-scale distribution is analyzed both in terms of the radius and

N. Z. Scoville

1990-01-01

326

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

327

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

328

Geochemical tracers of mantle processes  

NASA Astrophysics Data System (ADS)

The mantle can be sampled directly only very rarely. Geochemists have thus come to rely heavily on mantle-derived magmas to study the composition and evolution of the mantle. Only those compositional features that are unaffected by magmatic processes are useful as tracers of mantle processes. These include radiogenic isotope ratios such as those of He, Sr, Hf, and Os, stable isotope ratios, and ratios of highly incompatible elements or elements of similar incompatibility, such as Ba/Nb or Pb/Ce. The term "incompatible" denotes a preference of the element for a melt over mantle minerals. Highly incompatible elements will partition entirely into the melt under most circumstances, so that the ratio of two such elements in a basalt will be virtually identical to that ratio in its source. This is also true to a lesser degree of ratios such as La/Sm and Zr/Nb, as Zr and Sm are not highly incompatible elements.

White, William M.

1995-07-01

329

Cellular accumulation of 18F-labelled boronophenylalanine depending on DNA synthesis and melanin incorporation: a double-tracer microautoradiographic study of B16 melanomas in vivo.  

PubMed Central

The cellular distribution of 4-borono-2-[18F]fluoro-L-phenylalanine ([18F]FBPA, an analog of p-boronophenylaline), a potential agent for boron neutron capture therapy (BNCT), and [6-3H]thymidine ([3H]Thd, a DNA precursor) in murine two B16 melanoma sublines and FM3A mammary carcinoma was studied in vivo using double-tracer microautoradiography. Tumour volume, tumour age, cell density in the tissues and the proportion of S phase cells in the cell cycle were the same in the three tumour models. Volume doubling time, which represents tumour growth rate, was fastest in B16F10, followed by B16F1 (P < 0.05), the slowest being in FM3A (P < 0.001). The rate of DNA synthesis in S phase cells corresponded to the volume doubling time. The greatest amount of [18F]FBPA was observed in S phase melanocytes and the lowest amount was found in non-S phase non-melanocytes. The [18F]FBPA accumulation was primarily related to the activity of DNA synthesis and, secondarily, to the degree of pigmentation in melanocytes. The therapeutic efficacy of BNCT with p-boronophenylalanine may be greater in melanoma that exhibits greater DNA synthesis activity and higher melanin content. Images Figure 1

Kubota, R.; Yamada, S.; Ishiwata, K.; Tada, M.; Ido, T.; Kubota, K.

1993-01-01

330

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

331

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

332

The Advection-Diffusion Problem for Stratospheric Flow. Part II: Probability Distribution Function of Tracer Gradients  

Microsoft Academic Search

This paper is a continuation of the study of the advection-diffusion problem for stratospheric flow, and deals with the probability distribution function (PDF) of gradients of a freely decaying passive tracer. Theoretical arguments are reviewed and extended showing that mixing of a weakly diffused tracer by random large-scale flows produces a tracer gradient field whose probability distribution function has ''stretched

YONGYUN H UA; T. P IERREHUMBERT

333

Soil ingestion estimates for use in site evaluations based on the best tracer method  

Microsoft Academic Search

This paper develops a novel methodology, the Best Tracer method (BTM), that substantially overcomes the principal limitations (intertracer inconsistencies, and poor precision of recovery) of estimating soil ingestion by specific soil?based tracers in massbalance studies. The BTM incorporates a biological and statistical framework that improves precision of recovery of tracer estimates, markedly reducing input?output misalignment error resulting from a lack

Edward J. Stanek III; Edward J. Calabrese

1995-01-01

334

Helium Tracer Tests for Assessing Air Recovery and Air Distribution During In Situ Air Sparging.  

National Technical Information Service (NTIS)

Helium tracer tests are used as an alternative to soil-gas pressure measurements to assess the effectiveness of soil vapor extraction (SVE) systems for capturing contaminant vapors liberated by in situ air sparging (IAS). The tracer approach is simple to ...

R. L. Johnson P. C. Johnson T. L. Johnson A. Leeson

2001-01-01

335

Rio Vista gas leak study: Belleaire Gas Field, California. Topical report, April 1989--January 1991  

SciTech Connect

The Rio Vista gas leak study evaluated methods for remotely sensing gas leaks from buried pipelines and developed methods to elucidate methane transport and microbial oxidation in soils. Remote-sensing methods were evaluated by singing gas leaks along an abandoned Pacific Gas and Electric (PG&E) gas field collection line in northern California and applying surface-based and airborne remote-sensing techniques in the field, including thermal imaging, laser imaging, and multispectral imagery. The remote-sensing techniques exhibited limitations in range and in their ability to correlate with ground truth data. To elucidate methane transport and microbial oxidation in soils, a study of a controlled leak permitted field testing of methods so that such processes could be monitored and evaluated. Monitoring and evaluation techniques included (1) field measurement of soil-gas concentrations, temperatures, and pressures; (2) laboratory measurement of soil physical/chemical properties and activity of methane-oxidizing microorganisms by means of field samples; and (3) development of a preliminary numerical analysis technique for combined soil-gas transport/methane oxidation. Soil-gas concentrations at various depths responded rapidly to the high rate of gas leakage. The number of methane-oxidizing microorganisms in site soils rapidly increased when the gas leak was initiated and decreased after the leak was terminated. The preliminary field, laboratory, and numerical analysis techniques tested for this study of a controlled gas leak could be successfully applied to future studies of gas leaks. Because soil-gas movement is rapid and temporally variable, the use of several complementary techniques that permit generalization of site-specific results is favored.

Wilkey, P.L. [Argonne National Lab., IL (United States)

1992-08-01

336

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

337

Assessment of zinc loading in an acid rock drainage alpine catchment using a tracer-injection and synoptic-sampling study  

NASA Astrophysics Data System (ADS)

Seasonal low flow conditions in acid rock drainage (ARD) streams result in increased acidity and metal ion concentrations - changes that have been shown to become more pronounced with longer dry periods. These resulting increases in acidity and metals concentrations may pose an increasing danger to aquatic ecosystems and drinking water supplies. For example, in many ARD-impacted mountain streams, fish populations are not self-sustaining. The study site in the Upper Snake River watershed in Colorado is an alpine catchment impacted by acid rock drainage thought to originate from the natural weathering of pyrite whereas the main stem of the Snake River and its other tributaries are impacted by accelerated ARD resulting from historic mining activities. Because concentrations toxic to aquatic life persist well downstream of the ARD inputs, dissolved zinc is the primary metal of concern in this study. A compilation of historic data from the Snake River Watershed during the low flow months of September and October indicates that zinc concentrations have increased four-fold over the past 30 years. We hypothesize that this increase is due to changes in groundwater flow patterns caused by climate change and associated earlier peak snowmelt (by 2-3 weeks), resulting in lower stream flows and drier soils in late summer. The observed increase in background metals concentrations has implications for mitigation of former mining sites. A synoptic study to identify discrete surface water sources of zinc loading indicated a significant input from a tributary on the north side of the catchment. Zinc concentrations here measured an order of magnitude higher than in the main stem of the stream, and were correlated with increases in sulfate, hardness, and total metals, supporting our contention that increasing zinc concentrations are driven by the acceleration of ARD in the watershed. The current research further investigates sources of metal-rich inflows to the tributary using a tracer injection study with synoptic sampling.

Crouch, C. M.; McKnight, D. M.; Todd, A.

2010-12-01

338

Methyl-?-cyclodextrin: an alternative carrier for intravenous infusion of palmitate during tracer studies in swine ( Sus scrofa domestica)  

Microsoft Academic Search

Fatty acid-free albumin has been the standard carrier for intravenous infusion of fatty acids to study in vivo lipid metabolism. However, subjects can have adverse reactions to infusion of albumin. We sought an alternative to albumin as a carrier for intravenous infusion of fatty acids, using the pig as a model. Cyclodextrins are naturally occurring water-soluble molecules that can serve

Diane Wray-Cahen; Thomas J Caperna; Norman C Steele

2001-01-01

339

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

Microsoft Academic Search

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

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

2000-01-01

340

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

PubMed

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 (18)F-fluorodeoxyglucose (FDG) and (18)F-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), K(net), and K(1) as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k(2), k(3)) 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. PMID:23296314

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

2013-01-08

341

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

342

The study of the existence of unknown and unstable compounds through mixed crystal formation using radioactive tracers  

Microsoft Academic Search

A heterogeneous distribution study with internally formed lead chromate as host and110Ag as guest indicates the existence of a new variety of lead chromate, which forms mixed crystals with silver chromate, and\\u000a differs in morphology from the aged variety. It is inferred that the formation of mixed crystals is probably due to breeding\\u000a of a morphologically analogous and unstable species

B. C. Purkayastha; Nityaranjan Das

1974-01-01

343

Oxygen tracer diffusion in polycrystalline calcium-doped lanthanum chromites  

SciTech Connect

Acceptor-doped lanthanum chromites have been considered as one of the most promising materials for interconnectors in solid-oxide fuel cells (SOFCs). Oxygen tracer diffusion in polycrystalline (La,Ca)CrO{sub 3{minus}{delta}} was studied by the gas-solid isotope exchange reaction in combination with a depth-profiling technique using secondary-ion mass spectroscopy, which allowed determination of coefficients of lattice and grain-boundary diffusion separately. A significant contribution of fast grain-boundary diffusion was confirmed. The lattice diffusion coefficient increased with increased acceptor content and decreased oxygen partial pressure, which was consistent with the currently established point defect model and, thereby, suggested that the lattice oxide ions diffused by a vacancy mechanism.

Yasuda, Isamu; Ogasawara, Kei; Hishinuma, Masakazu [Tokyo Gas Co., Ltd. (Japan). Fundamental Technology Research Lab.

1997-12-01

344

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

345

Proceedings of the atmospheric tracers and tracer application workshop  

SciTech Connect

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

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

1979-12-01

346

Radioactive tracers as a tool for the study of in situ meiofaunal-microbial trophic interactions in marine sediments  

SciTech Connect

Three methods of delivering labeled substrates to natural cores of sediments were compared. Slurried sediments disrupted the sedimentary structure and significantly altered uptake of labeled substrates by copepod species. Thus, disruption of sedimentary structure can significantly alter microbial-meiofaunal interactions and influence the results of grazing studies. The ({sup 3}H)-thymidine technique for measuring bacterial production was evaluated. The metabolic fate of labeled thymidine in a coastal marine sediment was not consistent with assumptions necessary for measuring bacterial production or its consumption by meiofauna. Microautoradiography was used to demonstrate the sedimentary microalgae and heterotrophic bacteria can be selectively labeled with ({sup 14}C)bicarbonate and labeled organic substrates, respectively. A study was performed to determine if radioactivity measured in copepods from grazing experiments was the result of ingestion of labeled microorganisms or the result of uptake by non-feeding processes. Uptake of label by copepods from ({sup 14}C)-bicarbonate was due almost exclusively to grazing on microalgae. Uptake of label by copepods from ({sup 14}C)-acetate, however, resulted from activity by epicuticular bacteria and was not due to ingestion of labeled bacteria.

Carman, K.R.

1989-01-01

347

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...

348

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

SciTech Connect

This research program has moved ahead with success in several areas. The isotopic composition of osmium in seawater and in some rivers was directly determined for the first time. The concentration of osmium was first estimated in both seawater and rivers. A major effort was directed toward the transport of the U,Th series nuclides in a watershed in Sweden. A serious effort was directed at developing a transport model for the U,Th series nuclides in aquifers. A detailed study of {sup 238}U-{sup 230}Th dating of a cave in Israel was carried out collaboratively. The Os-Re fractionation between silicate and sulfide melts were determined in MORB basalts and glasses and the isotopic composition of Os was measured in sulfide samples.

Wasserburg, G.J.

1999-02-01

349

A mercuric iodide detector unit implantable and externally powered for use in radionuclide tracer studies in small animals.  

PubMed

A small externally powered implantable gamma-radiation detector unit (35 X 12 mm diameter containing a mercuric iodide detector (HgI2), charge amplifier, radiotransmitter and an inductive power supply has been constructed. Since the total weight of the device is 5 g, it is suitable for implantation in laboratory animals such as rats or hamsters. A comparison between the implanted HgI2 detector unit and a conventional stationary 2 X 2 inch NaI(TI) detector has been performed by simultaneous measurements of the 133Xe clearance from a depot. Using 125I-iothalamate a kidney function study of an unrestrained hamster is shown as an example of measurements in the unrestrained animal. PMID:7337823

Singh, B; Vadstrup, S; Pearce, G; Bunce, R W; Bojsen, J

1981-01-01

350

Validation And Application Of Global Atmospheric Tracer Model (NIES-08) For Studies Of The Regional And Global Budgets Of Carbon Dioxide  

NASA Astrophysics Data System (ADS)

In this work, we present validation of flux version of the NIES-08 (National Institute for Environmental Studies) off-line global atmospheric tracer transport model. This version was improved by adding a wind correction that guarantees exact mass conservation, and high order advection algorithm. As previous, the model transport is driven by analyzed meteorological fields and designed to simulate seasonal and diurnal cycles, synoptic variations, and spatial distributions of atmospheric chemical constituents in the troposphere. Several configurations have been tested and validated against observations and other models. Comparison of inter hemispheric gradients in fossil fuel carbon dioxide, radon-222 averaged concentration and SF6 show better model performance compared to previous version. In addition, we optimized Carnegie-Ames-Stanford Approach (CASA) using the data from several airborne observation sites globally. We applied the atmospheric transport inversion method, which is widely used to estimate regional fluxes of CO2, to estimate two parameters of the CASA flux model independently for each of the 11 vegetation types. By analyzing the vertical profiles of simulated and observed carbon dioxide, it was found that the transport model used in this study has a weak vertical mixing especially in the northern mid latitude during winter and this inaccuracy of the mixing led to the underestimation of NEP seasonality when near-surface data was used exclusively. The optimization with partial column data of CO2, on the other hand, is less affected by mixing scheme of a transport model and expected to result in more accurate optimization of seasonal cycles of NEP field. The optimized global flux dataset was used for simulation of seasonal cycles and vertical profiles of carbon dioxide. Comparison with old fluxes and observation data show better model performance.

Belikov, D.; Maksyutov, S.; Nakatsuka, Y.

2008-12-01

351

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2013 CFR

...miner's death, then any such study must be accompanied by a physician's...reliance on the blood-gas study as evidence that the miner was...disabled at death. (e) In the case of a deceased miner, where...paragraph (d) for any blood gas study administered during a...

2013-04-01

352

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

353

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

NASA Astrophysics Data System (ADS)

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 ?m), and particulate (>1 ?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 (log Kc ? 6) were shown to be much more efficient sorbents for Be-7 than the suspended particles (log Kp 4-5). Particle concentrations Cp ranged from 0.5 to 2 mg/L. The ratio of colloid (>10 kD) to particle concentration Cc/ Cp 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 (? coag ? 0.4 d -1) along with the lowest Kc (log Kc ? 5.2) were found after an algal bloom in spring.

Steinmann, P.; Billen, T.; Loizeau, J.-L.; Dominik, J.

1999-06-01

354

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

355

Delta N-15 of N[sub 2] in air trapped in polar ice - a tracer of gas transport in the firn and a possible constraint on ice age-gas age differences  

SciTech Connect

Factors which influence the distribution of air in present-day firn are examined on the basis of the analysis of delta N-15 of trapped N[sub 2] in 12 ice-core samples taken from Greenland and Antarctica, and this information is used to determine how air may have been mixed in glacial firn. The upper and the lower limits of ice-age/gas-age differences (Delta age) are then calculated for the ice core at the Vostok, the Dome C, and the Byrd locations, and the results are compared with previous estimates. Finally, the surface-temperature and CO[sub 2] records from Byrd and Vostok over the last 30,000 years are compared to provide independent means of establishing the best estimates of the Delta age difference for Vostok, and of the nature of gas transport in firn during the last glacial termination. 39 refs.

Sowers, T.; Bender, M.; Raynaud, D.; Korotkevich, IU.S. (Rhode Island Univ., Narragansett (United States) CNRS, Lab. de Glaciologie et Geophysique de l'Environnement, St.-Martin-d'Heres (France) Arctic and Antarctic Research Inst., St. Petersburg (Russian Federation))

1992-10-01

356

Application of Fluorescent-and Radioactive Tracers in Sedimentology.  

National Technical Information Service (NTIS)

The development of techniques of sediment labelling, creating the possibility of using fluorescent and radioactive tracers not yet applied in Brazil, in the area of sedimentology, is studied. (Atomindex citation 14:771486)

L. M. L. de Alencar

1981-01-01

357

Some design considerations for the proposed Dixie Valley tracer test  

SciTech Connect

A tracer test for the Dixie Valley, Nevada, geothermal resource is planned for the summer of 1988, in order to study the fluid flow paths that will develop under typical operating conditions. During the test six production wells will provide the power plant with steam sufficient for generation of 60 MWe, requiring fluid production at a rate of approximately 600 kg/sec. Up to 75% by mass of the extracted fluid will be reinjected into the reservoir, using four injection wells. Tracer will be added to the injected fluid for a twenty-minute period, and subsequently the produced fluid will be monitored for the tracer. 5 refs., 9 figs., 5 tabs.

Doughty, C.; Bodvarsson, G.S.

1988-06-01

358

Infill Drilling for Shale Gas Development: A Field Case Study  

Microsoft Academic Search

The U.S. Department of Energy has conducted a reservoir simulation study of a producing Devonian shale reservoir in Meigs Co., Ohio, following an extensive field testing program to determine the parameters controlling production from this unconventional gas resource. The purpose of the study was to determine the possible impact of infill drilling in established areas of Eastern gas shales production.

Andrea Horton; James Mercer; Walter Sawyer

1982-01-01

359

Quantifying Methane Fluxes Simply and Accurately: The Tracer Dilution Method  

NASA Astrophysics Data System (ADS)

Methane is an important atmospheric constituent with a wide variety of sources, both natural and anthropogenic, including wetlands and other water bodies, permafrost, farms, landfills, and areas with significant petrochemical exploration, drilling, transport, or processing, or refining occurs. Despite its importance to the carbon cycle, its significant impact as a greenhouse gas, and its ubiquity in modern life as a source of energy, its sources and sinks in marine and terrestrial ecosystems are only poorly understood. This is largely because high quality, quantitative measurements of methane fluxes in these different environments have not been available, due both to the lack of robust field-deployable instrumentation as well as to the fact that most significant sources of methane extend over large areas (from 10's to 1,000,000's of square meters) and are heterogeneous emitters - i.e., the methane is not emitted evenly over the area in question. Quantifying the total methane emissions from such sources becomes a tremendous challenge, compounded by the fact that atmospheric transport from emission point to detection point can be highly variable. In this presentation we describe a robust, accurate, and easy-to-deploy technique called the tracer dilution method, in which a known gas (such as acetylene, nitrous oxide, or sulfur hexafluoride) is released in the same vicinity of the methane emissions. Measurements of methane and the tracer gas are then made downwind of the release point, in the so-called far-field, where the area of methane emissions cannot be distinguished from a point source (i.e., the two gas plumes are well-mixed). In this regime, the methane emissions are given by the ratio of the two measured concentrations, multiplied by the known tracer emission rate. The challenges associated with atmospheric variability and heterogeneous methane emissions are handled automatically by the transport and dispersion of the tracer. We present detailed methane flux results from four different landfills in the United States, using a commercially available Cavity Ringdown Spectroscopy (CRDS) dual-species (methane - acetylene) analyzer. This instrument, because of its high precision, mobility, and ease-of-use, enables quantification of the methane flux from a variety of extended area sources. The instrument was operated off of batteries and was mounted in a four-wheel drive vehicle. A high-precision GPS and two-dimensional self-aligning anemometer were integrated directly with the instrument. Concentration data on methane and acetylene were collected every second, and, together with the wind and GPS data, were processed to provide quantitative measurements of total methane fluxes, on a time scale of just minutes. The landfills studied varied widely in their size, location, topography, and physical access. Data were collected using three variants of the method: the Mobile Transect Method, in which the dual-species analyzer is transported rapidly through the plumes in the far-field; the Stationary Plume Method, in which the analyzer is situated in a fixed location downwind of the release point; and a new method called the Mid-Field Stationary Method, in which the instrument is located at a fixed location at a closer distance than the true far-field, where the plume overlap is not ideal. The resulting methane fluxes varied over a wide range of values, from just a few kg methane / minute, to over 20 kg methane / minute. Finally, we describe how these methods can be used to quantify methane emissions from other natural and anthropogenic extended-area sources, such as wetlands.

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

2010-05-01

360

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...

361

Study on distributed optic fiber gas sensors  

Microsoft Academic Search

Online detection of gas concentrations is important research topic recently. Based on the analysis of near infrared spectral absorption of acetylene, ammonia and carbon monoxide, a system using absorption type optic fiber for high sensitivity distributed detection of gases with wideband light source is demonstrated. Light source modulation harmonic measurement is presented in this paper. Wavelength modulation is realized by

Jin Liu; Haima Yang; Yan Yue

2009-01-01

362

Experimental studies of gas-aerosol reactions  

NASA Astrophysics Data System (ADS)

The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than pure (NH4)2SO4 particles. The chemical mechanism for these surface reactions remains to be elucidated. Observed growth rates extrapolated to ambient SO2 and H2O2 concentrations are 10 to 100 times smaller than those observed by McMurry and Wilson (1983) for ambient aerosols.

Gupta, Anand

1991-05-01

363

Tracer-based Metabolomics: Concepts and Practices  

PubMed Central

Tracer-based metabolomics is a systems biology tool that combines advances in tracer methodology for physiological studies, high throughput “-omics” technologies and constraint based modeling of metabolic networks. It is different from the commonly known metabolomics or metabonomics in that it is a targeted approach based on a metabolic network model in cells. Because of its complexity, it is the least understood among the various “-omics”. In this review, the development of concepts and practices of tracer-based metabolomics is traced from the early application of radioactive isotopes in metabolic studies to the recent application of stable isotopes and isotopomer analysis using mass spectrometry; and from the modeling of biochemical reactions using flux analysis to the recent theoretical formulation of the constraint based modeling. How these newer experimental methods and concepts of constraint-based modeling approaches can be applied to metabolic studies is illustrated by examples of studies in determining metabolic responses of cells to pharmacological agents and nutrient environment changes.

Lee, W-N. Paul; Wahjudi, Paulin N.; Xu, Jun; Go, Vay Liang

2010-01-01

364

Trans-Caspian gas pipeline feasibility study. Volume 1  

SciTech Connect

This study, conducted by Enron Engineering and Construction Company, was funded by the US Trade and Development Agency. The study provides detailed information concerning natural gas demand in Turkey and Southern Europe. The purpose of the study is to estimate the rate at which new gas can be absorbed in the Turkish market and be re-exported to the markets in Europe, as well as to forecast Turkish natural gas demand for the period up to 2020. The study also evaluates gas demand and pricing for the market in the 2002--2005 time frame. This is Volume 1 of a 3-volume report, and is divided into the following sections: (1) Task A: Gas Sales; (2) Task B: Initial Economic Screening; (3) Task D: Project Cost Analysis.

NONE

1999-03-01

365

Gas jet study in microgravity environment  

Microsoft Academic Search

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

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

2006-01-01

366

Delineation and segmentation of cerebral tumors by mapping blood-brain barrier disruption with dynamic contrast-enhanced CT and tracer kinetics modeling–a feasibility study  

Microsoft Academic Search

Dynamic contrast-enhanced (DCE) imaging is a promising approach for in vivo assessment of tissue microcirculation. Twenty\\u000a patients with clinical and routine computed tomography (CT) evidence of intracerebral neoplasm were examined with DCE-CT imaging.\\u000a Using a distributed-parameter model for tracer kinetics modeling of DCE-CT data, voxel-level maps of cerebral blood flow (F), intravascular blood volume (v\\u000a i) and intravascular mean transit

S. Bisdas; X. Yang; C. C. T. Lim; T. J. Vogl; T. S. Koh

2008-01-01

367

Isolation of aminoacyl-tRNA and its labeling with stable-isotope tracers: Use in studies of human tissue protein synthesis  

SciTech Connect

The authors isolated aminoacyl-tRNA from human and rat tissues and measured, by GC/MS, its labeling in vivo by ({sup 15}N)-and ({sup 13}C)leucine. Tracer dilution artifacts seemed unlikely since, after infusion of L-(1-{sup 13}C, {sup 15}N)leucine into rats, (1) muscle leucyl-tRNA labeling exceeded tissue free leucine labeling, (2) values were largely unaffected by storing over 5 min at 22C, and (3) L-(2,4,5-methyl-{sup 13}C)leucine was not incorporated into leucyl-tRNA during homogenization. Leucyl-tRNA labeling in liver and muscle suggested charging from extra- and intracellular pools: e.g., after infusing L-(1-{sup 13}C, {sup 15}N)leucine, rat muscle tissue free leucine {sup 13}C labeling exceeded that by {sup 15}N and both were significantly lower than venous plasma indicating tracer dilution by transamination and by proteolysis; however, leucyl-tRNA labeling by either isotope was significantly above mixed tissue free leucing. Human placental leucyl-tRNA labeling (after predelivery tracer infusion) was 37% lower than maternal uterine vein labeling but not significantly different from placental free leucine or umbilical arterial leucine.

Watt, P.W.; Lindsay, Y.; Scrimgeour, C.M.; Chien, P.A.F.; Taylor, D.J.; Rennie, M.J. (Univ. of Dundee (England)); Gibson, J.N.A. (Univ. of Dundee (England) Univ. of Edinbergh (England))

1991-07-01

368

A prospective comparative study to assess the contribution of radioisotope tracer method to dye-only method in the detection of sentinel lymph node in breast cancer  

PubMed Central

Background Metastasis in the axillary lymph nodes is the most important known prognostic factor for breast cancer. We aimed to investigate the contribution of the radioisotope tracer method to the dye-only method by performing sentinel lymph node biopsy on the same patient group during a single surgical session. Methods Forty-two patients who underwent operations in our clinic from February 2010 to October 2011 and with masses of <5 cm and clinically and radiologicallly negative axilla (T1-2 N0) were prospectively included in this study. After paraffin examination results were obtained, the numbers and metastatic states of the lymph nodes that were unidentifiable during surgery (although they were stained) but were detected by a gamma probe, lymph nodes that were only stained, lymph nodes that were only radioactive (hot), and lymph nodes that were both stained and radioactive (stained-hot) were determined in all patients. In patients who underwent axillary lymph node dissection, the total numbers of lymph nodes removed and their metastatic states were determined separately. Results At least one blue-stained sentinel lymph node was identified in all patients during the blue-stained lymph node detection stage. The average number of sentinel nodes removed at this stage was 2.1?±?1.1. In the second surgical stage (the stage in which nodes with axillary counts were investigated with the gamma probe) in these 41 patients, at least one additional hot node was removed, or at least one of the nodes that was removed because it was blue was also hot. In addition to the lymph nodes removed in the dye stage, 34 hot lymph nodes were excised from 21 patients. Overall, the average number of hot lymph nodes removed was 2.9?±?1.5. In all patients, subsequent frozen sections and histopathological examinations were 100% concordant with the sentinel lymph nodes that were removed; the stained sentinel lymph nodes that were removed first did not affect the decision to perform axillary dissection. Conclusion The results of our study indicate that performing sentinel lymph node biopsy with dye only is sufficient and as effective as the combined method.

2013-01-01

369

LANDFILL GAS ENERGY UTILIZATION: TECHNOLOGY OPTIONS AND CASE STUDIES  

EPA Science Inventory

The report discusses technical, environmental, and other issues associated with using landfill gas as fuel, and presents case studies of projects in the U.S. illustrating some common energy uses. he full report begins by covering basic issues such as gas origin, composition, and ...

370

Little study sees large growth in Asian natural gas market  

Microsoft Academic Search

Power capacity additions in Asia will at least triple by 2010, and Arthur D. Little Inc. predicts natural gas can pick up a good 15 percent of that market. The study predicts Asia potentially will need 720 gigawatts of new power generation by 2010, of which 15 percent may be gas-based. This represents a market three times the size of

ODriscoll

1993-01-01

371

Results of Repeat Tracer Tests at Ohaaki, NZ  

SciTech Connect

During 20 years of tracer testing at Ohaaki a number of wells have been used more than once as tracer injection sites. In studying the various responses obtained it has been necessary to consider variations in the experimental test conditions before making comparisons which relate to field conditions. Some very significant changes have occurred in the field hydrology in recent years and water flow speeds as high as those encountered at Wairakei have been demonstrated.

McCabe, W.J.; Clotworthy, A.W.; Morris, C.

1995-01-01

372

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

SciTech Connect

Researchers from Brookhaven National Laboratory (BNL) tested perfluorocarbon (PFT) gas tracers on a subsurface barrier with known flaws at the Waldo test facility [operated by Science and Engineering Associates, Inc (SEA)]. The tests involved the use of five unique PFT tracers 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 a 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 lane 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.

SULLIVAN,T.; HEISER,J.; SENUM,G.; MILLIAN,L.

2000-02-27

373

Dyes as tracers for vadose zone hydrology  

NASA Astrophysics Data System (ADS)

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

Flury, Markus; Wai, Nu Nu

2003-03-01

374

THE STAR FORMATION RATE AND GAS SURFACE DENSITY RELATION IN THE MILKY WAY: IMPLICATIONS FOR EXTRAGALACTIC STUDIES  

SciTech Connect

We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) and massive dense clumps. Our YSO sample consists of objects located in 20 large molecular clouds from the Spitzer cores to disks (c2d) and Gould's Belt (GB) surveys. These data allow us to probe the regime of low-mass star formation, essentially invisible to tracers of high-mass star formation used to establish extragalactic SFR-gas relations. We estimate the gas surface density ({Sigma}{sub gas}) from extinction (A{sub V}) maps and YSO SFR surface densities ({Sigma}{sub SFR}) from the number of YSOs, assuming a mean mass and lifetime. We also divide the clouds into evenly spaced contour levels of A{sub V} , counting only Class I and Flat spectral energy distribution YSOs, which have not yet migrated from their birthplace. For a sample of massive star-forming clumps, we derive SFRs from the total infrared luminosity and use HCN gas maps to estimate gas surface densities. We find that c2d and GB clouds lie above the extragalactic SFR-gas relations (e.g., Kennicutt-Schmidt law) by factors of up to 17. Cloud regions with high {Sigma}{sub gas} lie above extragalactic relations up to a factor of 54 and overlap with high-mass star-forming regions. We use {sup 12}CO and {sup 13}CO gas maps of the Perseus and Ophiuchus clouds from the COMPLETE survey to estimate gas surface densities and compare to measurements from A{sub V} maps. We find that {sup 13}CO, with the standard conversions to total gas, underestimates the A{sub V} -based mass by factors of {approx}4-5. {sup 12}CO may underestimate the total gas mass at {Sigma}{sub gas} {approx}> 200 M{sub sun} pc{sup -2} by {approx}>30%; however, this small difference in mass estimates does not explain the large discrepancy between Galactic and extragalactic relations. We find evidence for a threshold of star formation ({Sigma}{sub th}) at 129 {+-} 14 M{sub sun} pc{sup -2}. At {Sigma}{sub gas}>{Sigma}{sub th}, the Galactic SFR-gas relation is linear. A possible reason for the difference between Galactic and extragalactic relations is that much of {Sigma}{sub gas} is below {Sigma}{sub th} in extragalactic studies, which detect all the CO-emitting gas. If the Kennicutt-Schmidt relation ({Sigma}{sub SFR} {proportional_to} {Sigma}{sup 1.4}{sub gas}) and a linear relation between dense gas and star formation are assumed, the fraction of dense star-forming gas (f{sub dense}) increases as {approx}{Sigma}{sup 0.4}{sub gas}. When {Sigma}{sub gas} reaches {approx}300 {Sigma}{sub th}, the fraction of dense gas is {approx}1, creating a maximal starburst.

Heiderman, Amanda; Evans, Neal J. II [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Allen, Lori E. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Huard, Tracy [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Heyer, Mark, E-mail: alh@astro.as.utexas.ed, E-mail: nje@astro.as.utexas.ed, E-mail: lallen@noao.ed, E-mail: thuard@astro.umd.ed, E-mail: heyer@astro.umass.ed [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States)

2010-11-10

375

X-ray clusters of galaxies as tracers of structure in the Universe.  

PubMed

Clusters of galaxies are visible tracers of the network of matter in the Universe, marking the high-density regions where filaments of dark matter join together. When observed at X-ray wavelengths these clusters shine like cosmic lighthouses, as a consequence of the hot gas trapped within their gravitational potential wells. The X-ray emission is linked directly to the total mass of a cluster, and so can be used to investigate the mass distribution for a sizeable fraction of the Universe. The picture that has emerged from recent studies is remarkably consistent with the predictions for a low-density Universe dominated by cold dark matter. PMID:11343106

Borgani, S; Guzzo, L

2001-01-01

376

Predictions of PuO{sub 2} and tracer compound release from ISV melts  

SciTech Connect

Two field tests were conducted at the Idaho National Engineering Laboratory (INEL) to assess in situ vitrification (ISV) suitability for long-term stabilization of buried radioactive waste. Both tests contained rare-earth oxide tracers (DY{sub 2}O{sub 3}, Yb{sub 2}O{sub 3}, and Tb{sub 4}O{sub 7}) to simulate the presence of plutonium in the form of PuO{sub 2}. In the first test, Intermediate Field Test (IFT)-l, approximately 4-% release of tracer material occurred during soil melting and associated off-gassing, while essentially nil release was observed for the second experiment (IFT-2) for which off-gassing was much reduced. This report presents an evaluation of the IFT test data in terms of governing release processes. Prediction of tracer release during ISV melting centered on an assessment of three potential transport mechanisms, (a) tracer diffusion through stagnant pool, (b) tracer transport by convective currents, and (c) tracer carry-off by escaping gas bubbles. Analysis indicates that tracer release by escaping gas is the dominant release mechanism, which is consistent with video records of gas bubble escape from the ISV melt surface. Quantitative mass transport predictions were also made for the IFT-I test conditions, indicating similarity between the 4-% release data and calculational results at viscosities of {approx} poise and tracer diffusivities of {approx}10{sub {minus}6} CM{sup 2}/s. Since PuO{sub 2} has similar chemical and transport (diffusivity) properties as the rare-earth tracers used in the rare earth tracers used in the IFT experiments, release of PuO{sub 2} is predicted for similar off-gassing conditions. Reduced off-gassing during ISV would thus be expected to improve the overall retention of heavy-oxides within vitrified soil.

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

1992-04-01

377

Predictions of PuO sub 2 and tracer compound release from ISV melts  

SciTech Connect

Two field tests were conducted at the Idaho National Engineering Laboratory (INEL) to assess in situ vitrification (ISV) suitability for long-term stabilization of buried radioactive waste. Both tests contained rare-earth oxide tracers (DY{sub 2}O{sub 3}, Yb{sub 2}O{sub 3}, and Tb{sub 4}O{sub 7}) to simulate the presence of plutonium in the form of PuO{sub 2}. In the first test, Intermediate Field Test (IFT)-l, approximately 4-% release of tracer material occurred during soil melting and associated off-gassing, while essentially nil release was observed for the second experiment (IFT-2) for which off-gassing was much reduced. This report presents an evaluation of the IFT test data in terms of governing release processes. Prediction of tracer release during ISV melting centered on an assessment of three potential transport mechanisms, (a) tracer diffusion through stagnant pool, (b) tracer transport by convective currents, and (c) tracer carry-off by escaping gas bubbles. Analysis indicates that tracer release by escaping gas is the dominant release mechanism, which is consistent with video records of gas bubble escape from the ISV melt surface. Quantitative mass transport predictions were also made for the IFT-I test conditions, indicating similarity between the 4-% release data and calculational results at viscosities of {approx} poise and tracer diffusivities of {approx}10{sub {minus}6} CM{sup 2}/s. Since PuO{sub 2} has similar chemical and transport (diffusivity) properties as the rare-earth tracers used in the rare earth tracers used in the IFT experiments, release of PuO{sub 2} is predicted for similar off-gassing conditions. Reduced off-gassing during ISV would thus be expected to improve the overall retention of heavy-oxides within vitrified soil.

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

1992-04-01

378

An aging study of a gas electron multiplier with micro-strip gas chamber readout  

SciTech Connect

The authors have performed an aging study of a Gas Electron Multiplier (GEM) readout with a Micro-Strip Gas Chamber (MSGC). The GEM is constructed from Kapton and copper, and the MSGC is constructed from semiconductive glass and gold. When the detector (GEM+MSGC) is operated in an argon-dimethyl ether (DME) gas mixture and irradiated with a 5.4 keV photon beam, about 220 mC/cm of charge can be accumulated without degradation of the detector performance. This corresponds to about 20 years of operation at the LHC.

Miyamoto, J.; Shipsey, I.P.I. [Purdue Univ., W. Lafayette, IN (United States). Dept. of Physics

1999-06-01

379

Experimental study on the dynamic characteristics of a gas turbine combustor burning syn-gas  

Microsoft Academic Search

The present study focused on the development of a full-scale gas turbine combustor burning syn-gas from the coal-based multi-production.\\u000a The dynamic features of a variety of parameters of the combustor, such as temperature and pressure during the procedures of\\u000a startup and thermal load shifting, were measured and analyzed. The frequency and power spectrum of pressure fluctuation were\\u000a analyzed by applying

Yu Lei; Gang Xu; Aibing Fang; Chaoqun Nie; Weiguang Huang

2004-01-01

380

Trans-Caspian gas pipeline feasibility study. Volume 3  

SciTech Connect

This study, conducted by Enron Engineering and Construction Company, was funded by the US Trade and Development Agency. The study provides detailed information concerning natural gas demand in Turkey and Southern Europe. The purpose of the study is to estimate the rate at which new gas can be absorbed in the Turkish market and be re-exported to the markets in Europe, as well as to forecast Turkish natural gas demand for the period up to 2020. The study also evaluates gas demand and pricing for the market in the 2002--2005 time frame. This is Volume 3 of a 3-volume report, and it is divided into the following sections: (1) Executive Summary; (2) Task C: Technical Feasibility and Preliminary Design; (3) Task F: Project Implementation Strategy.

NONE

1999-03-01

381

Trans-Caspian gas pipeline feasibility study. Volume 2  

SciTech Connect

This study, conducted by Enron Engineering and Construction Company, was funded by the US Trade and Development Agency. The study provides detailed information concerning natural gas demand in Turkey and Southern Europe. The purpose of the study is to estimate the rate at which new gas can be absorbed in the Turkish market and be re-exported to the markets in Europe, as well as to forecast Turkish natural gas demand for the period up to 2020. The study also evaluates gas demand and pricing for the market in the 2002--2005 time frame. This is Volume 2 of a 3-volume report, and it is divided into the following sections: (1) Executive Summary; (2) Policy, Legal and Administrative Framework; (3) Assessment of Alternatives; (4) Baseline Conditions in the Project Area; (5) Potential (Unmitigated) Environment, Health and Safety Impacts; (6) Proposed Environmental Prevention and Mitigation; (7) Projected Net Environmental Impacts; (8) Bibliography.

NONE

1999-03-01

382

SENSITIVITY ANALYSIS AND THE DESIGN OF GAS UPTAKE INHALATION STUDIES  

EPA Science Inventory

Gas uptake studies analyzed by physiologically based pharmacokinetic (PBPK) models have been used to estimate metabolic parameters for many volatiles. he metabolic constants Vmax, Km, and Kf are typically inferred from the decline in chemical concentration observed in closed cham...

383

North American Natural Gas Markets: Selected technical studies  

SciTech Connect

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

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

1989-04-01

384

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

SciTech Connect

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

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

1989-04-01

385

Study of Bad-Smell Sensing Using Gas Detector Tube  

NASA Astrophysics Data System (ADS)

Although GC/MS(Gas Chromatograph/Mass Spectrum) method is often used to analyze gases, a rapid and low-cost method is required. Since a gas detector tube is well known as a simple measurement method, we focused on it to perform bad-smell sensing for monitoring living environment. We developed a simple system for automatically and continuously measuring color change of the gas detector tube. It is originally a disposable one for manually measuring the gas concentration only once at a certain time. The developed system enables the real-time measurement of the gas concentration change and the reduction of the read-out error. In the present study, we proposed the method for eliminating the influence of the noise to determine the boundary of the color-change region. The measurements of methyl mercaptan and hydrogen sulfide were reproducibly performed under the humidity-rich environment using the proposed method.

Tanaka, Yukinobu; Yoshioka, Masahiro; Nakamoto, Takamichi; Moriizumi, Toyosaka

386

Studying Gas in Young and Debris Disks Using Spitzer  

NASA Astrophysics Data System (ADS)

We present results from models that self-consistently calculate the gas chemistry, gas temperature, dust temperature, and vertical density distribution in circumstellar disks around young stars, and that predict the emergent infrared spectra. A parameter study of optically thin disks shows that fine structure lines such as [SI] 25 ?m are generally stronger than the H2 rotational lines. Spitzer can detect lines from disks ? 100 pc with gas masses of ? 0.01 MJ and some dust present (? 10-7 MJ) to heat the gas. We model Spitzer upper limits on line fluxes from HD 105, a 30 Myr old G0V star, and provide upper limits on the gas surface density and mass (? 1 MJ) in the planet-forming region (1-40 AU). Preliminary results for younger, optically thick disks are briefly discussed.

Hollenbach, D.; Gorti, U.

2006-12-01

387

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

388

Bioethics. LC Science Tracer Bullet.  

ERIC Educational Resources Information Center

|This guide lists published materials on many aspects of bioethics, the literature of which is varied and scattered. Related guides in the LC Science Tracer Bullet series are TB 80-9, Terminal Care, TB 80-11, Drug Research on Human Subjects, TB 83-4, Science Policy, and TB 84-7, Biotechnology. Not intended to be a comprehensive bibliography, this…

Martin, Cathy, Comp.; Cadoree, Michelle

389

Sensitivity of tracers and a stratospheric aircraft perturbation to two-dimensional model transport variations  

NASA Astrophysics Data System (ADS)

We examine the sensitivity of two-dimensional model simulations of stratospheric tracers to uncertainties in the model transport and explore how such uncertainties impact the simulation of a lower stratospheric perturbation due to high-speed civil transport (HSCT) aircraft emissions. To define the transport uncertainty, we vary the model transport fields so that the resulting tracer simulations roughly bracket the observations. This provides an estimate of the upper and lower limits on realistic transport rates in our two-dimensional (2-D) model. Increasing the advective residual circulation strength or the lower stratospheric vertical diffusion (Kzz) decreases the mean age and residence time of the HSCT emissions and diminishes the negative response in total column ozone globally. Increasing the stratospheric horizontal diffusion (Kyy) either globally or in the tropics only has the opposite effect of increasing the age and emission residence time and enhancing the negative total ozone response. Uncertainties in the mechanical eddy forcing derivation affect both Kyy and the residual circulation simultaneously, resulting in some cancellation of effects. This produces a smaller range of uncertainty in the tracer and perturbation simulations than given by uncertainties in the circulation or Kyy components separately. The model simulations in the lower and middle stratosphere are relatively insensitive to the strength of the mesospheric gravity wave effects and the magnitude of the horizontal diffusive transport across the tropopause. The base model transport compares most favorably with tracer data and gives a global and annual mean steady state HSCT perturbation response in total ozone of -0.62%, assuming a NOx emission index of 5 g/kg, 500 airplanes, and a 10% gas-to-particle conversion of the SO2 emission. For the range of transport uncertainty examined in this study, the global total ozone perturbation response ranges from -0.34% to -0.74%, with a mainly strong correlation between the total ozone response and mean age.

Fleming, Eric L.; Jackman, Charles H.; Considine, David B.; Stolarski, Richard S.

2001-07-01

390

Aircraft measurements of polar organic tracer compounds in tropospheric particles (PM10) over Central China  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol samples were collected by aircraft at low to middle altitudes (0.8-3.5 km a.g.l.) over Central East to West China during summer 2003 and spring 2004. The samples were analyzed for polar organic compounds using a technique of solvent extraction/BSTFA derivatization/gas chromatography-mass spectrometry. Biogenic secondary organic aerosol (SOA) tracers from the oxidation of isoprene were found to be more abundant in summer (3.3-138 ng m-3, mean 39 ng m-3) than in spring (3.2-42 ng m-3, 15 ng m-3), while ?/?-pinene and ?-caryophyllene SOA tracers showed similar abundance between these two seasons. A strong positive correlation (R2=0.83) between levoglucosan and ?-caryophyllinic acid was found in the spring samples versus a weak correlation (R2=0.17) in the summer samples, implying substantial contributions from biomass burning to the ?-caryophyllinic acid production in spring. Two organic nitrogen species (oxamic acid and carbamide) were detected in the aircraft aerosol samples and their concentrations were comparable to those of biogenic SOA tracers. Most of the POA and SOA tracers were less abundant at higher altitudes, suggesting they are of ground surface origin, either being directly emitted from anthropogenic/natural sources on the ground surface, or rapidly formed through photooxidation of their precursors emitted from the ground surface and then diluted during uplifting into the troposphere. This study demonstrates that primary biological aerosols, biogenic SOA, and organic nitrogen species are important components of organic aerosols in the troposphere over Central China.

Fu, P. Q.; Kawamura, K.; Cheng, Y. F.; Hatakeyama, S.; Takami, A.; Li, H.; Wang, W.

2013-09-01

391

Development of Miniaturized Difference Frequency Generation, Fiber Optic, and Quantum Cascade Laser Systems in Conjunction With Integrated Electronics for Global Studies of Atmospheric Tracers Using UAVs.  

NASA Astrophysics Data System (ADS)

In order to harness the power of UAVs (Unmanned Aerial Vehicles) for in situ atmospheric monitoring of tracers such as CO2, N2O, CH4, and H2O, we have developed small, lightweight, single mode laser systems with co- developed integrated electronics. The laser sources are of various types including newly developed cavity- enhanced difference frequency generation (CE DFG), distributed feedback quantum cascade lasers (DFB QCLs), and new types of commercially available DFB diode lasers. All are continuous wave (cw) and thermo-electrically cooled, ensuring a high instrument duty cycle in a compact, low maintenance package. The light sources are collimated with miniature aspherical lenses and coupled into a home-built astigmatic Herriott cell for detection of the various targets using direct absorption. In parallel with the optical components, we have developed integrated electrical systems for laser control, data processing, and acquisition. A prototype instrument suite is described that illustrates the importance of parallel development of optical and electrical components in achieving an apparatus that is compact, fully automated, and highly capable scientifically. Although the emphasis here is on atmospheric tracers, this technology could be applied to spectroscopic measurements of other atmospheric species such as isotopes, free radicals, and reactive intermediates.

Witinski, M. F.; Lapson, L. B.; Anderson, J. G.

2007-12-01

392

Water Alternating Gas (WAG) Injection Micromodel Studies  

Microsoft Academic Search

SUMMARY A research project consisting of experimental studies using micromodels, together with mathematical network modelling is currently underway to generate information required for simulating the performance of the oil reservoirs when produced with the WAG injection recovery method. This paper covers the progress made on mi cromodel studies during the first year of the project. In this study a physical

M. Sohrabi

393

Geophysical studies of marine gas hydrate in northern cascadia  

NASA Astrophysics Data System (ADS)

This paper reviews the extensive geophysical studies and Ocean Drilling Project (ODP) results that have provided constraints on the occurrence, distribution, and concentration of gas hydrate and underlying free gas beneath the continental slope of the northern Cascadia subduction zone. On this margin there is a large clastic accretionary sedimentary prism, the most common environment for high concentrations of marine gas hydrates. Most information on the gas hydrate has come from a wide range of seismic surveys, including mapping the area of the characteristic bottom-simulating reflector (BSR), determining the depth distribution of hydrate and underlying free gas, and the geological controls of hydrate formation. BSRs are evident beneath about half of the mid-continental slope. Special seismic studies include BSR reflection coefficients, the frequency dependence of the BSR amplitude, BSR amplitude-versus-offset (AVO), and full waveform inversions. Additional information on hydrate concentration is provided by electrical resistivity profiling, and measurements of seafloor compliance. Detailed heat flow surveys have mapped the thermal regime that controls the depth to which gas hydrate is stable. Ocean Drilling Program Leg 146 drilled through the gas hydrate on the midcontinental slope and a reference hole in the adjacent deep sea Cascadia basin. Downhole geophysical logs and core analyses have constrained the concentrations of hydrate and free gas at the drill sites, and provided calibration of the regional geophysical data. In the region of the ODP site, the estimated concentration of hydrate from both geophysical and borehole data is 20-30% of the pore space (10-15% of total volume) over 100 m above the BSR, with an underlying 10-20 m layer of less than 1% free gas.

Hyndman, R. D.; Spence, G. D.; Chapman, R.; Riedel, M.; Edwards, R. N.

394

Fuel cell/gas turbine system performance studies  

SciTech Connect

Because of the synergistic effects (higher efficiencies, lower emissions) of combining a fuel cell and a gas turbine into a power generation system, many potential system configurations were studied. This work is focused on novel power plant systems by combining gas turbines, solid oxide fuel cells, and a high-temperature heat exchanger; these systems are ideal for the distributed power and on- site markets in the 1-5 MW size range.

Lee, G.T.; Sudhoff, F.A.

1996-12-31

395

A study of gas in marine sediments in Hong Kong  

NASA Astrophysics Data System (ADS)

During the course of an offshore investigation for sand sources in Hong Kong, seismic reflection profiles revealed areas of acoustic turbidity in Holocene marine sediments. These areas assumed particular significance during a subsequent comprehensive planning study for Hong Kong's new airport. Acoustic turbidity is generally regarded as a possible indicator of gas within sediments, which may have an important effect on the engineering properties of the sediments. To investigate the presence of the gas and to assess its significance, an extensive in situ testing programme was initiated. The test utilized the offshore BAT system developed at the Norwegian Geotechnical Institute (NGI) in cooperation with the BAT company in Sweden. This system was considered to be the most direct and reliable means of determining the presence of pore gas. A total of 96 BAT tests were carried out at 11 test sites, at about nine different depths at each site. Test results indicated that some occluded gas bubbles exist in the areas of acoustic turbidity. The free gas was shown to be mainly composed of nitrogen and methane, while carbon dioxide was the dominant dissolved gas. These constitutents were considered to have been generated by biogenic degradation of organic matter. No free gas was detected at the control stations where acoustic turbidity had not been observed on seismic records.

Premchitt, J.; Rad, N. S.; To, P.; Shaw, R.; James, J. W. C.

1992-10-01

396

Drawing the line on natural gas regulation: The Harvard study on the future of natural gas  

SciTech Connect

The Harvard Study on the Future of Natural Gas Policy reflects the ideas, discussions, and debates of nine authors and more than seventy experts from business, government, and academia. These study participants constituted the Executive Working Group, which met in three sessions during 1984-1985. The executive sessions provided forums for the authors to present versions of their chapters at progressive stages of development. The results were invaluable insights and perspectives from parties directly involved in the ongoing debates over the reform of natural gas policy. In addition, a number of participants have contributed written comments on the various chapters of this book.

Kalt, J.P.; Schuller, F.C. (eds.)

1987-01-01

397

FTIR gas chromatographic analysis of perfumes  

NASA Astrophysics Data System (ADS)

Perfumes, natural or synthetic, are complex mixtures consisting of numerous components. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques have been extensively utilized for the analysis of perfumes and essential oils. A limited number of perfume samples have also been analyzed by FT-IR gas chromatographic (GC-FTIR) techniques. Most of the latter studies have been performed using the conventional light pipe (LP) based GC-FTIR systems. In recent years, cold-trapping (in a matrix or neat) GC-FTIR systems have become available. The cold-trapping systems are capable of sub-nanogram sensitivities. In this paper, comparison data between the LP and the neat cold-trapping GC- FTIR systems is presented. The neat cold-trapping interface is known as Tracer. The results of GC-FTIR analysis of some commercial perfumes is also presented. For comparison of LP and Tracer GC-FTIR systems, a reference (synthetic) mixture containing 16 major and numerous minor constituents was used. The components of the mixture are the compounds commonly encountered in commercial perfumes. The GC-FTIR spectra of the reference mixture was obtained under identical chromatographic conditions from an LP and a Tracer system. A comparison of the two sets of data thus generated do indeed show the enhanced sensitivity level of the Tracer system. The comparison also shows that some of the major components detected by the Tracer system were absent from the LP data. Closer examination reveals that these compounds undergo thermal decomposition on contact with the hot gold surface that is part of the LP system. GC-FTIR data were obtained for three commercial perfume samples. The major components of these samples could easily be identified by spectra search against a digitized spectral library created using the Tracer data from the reference mixture.

Diederich, H.; Stout, Phil J.; Hill, Steve L.; Krishnan, K.

1992-03-01

398

Cytogenetic studies of stainless steel welders using the tungsten inert gas and metal inert gas methods for welding  

Microsoft Academic Search

Cytogenetic damage was studied in lymphocytes from 23 welders using the Tungsten Inert Gas (TIG), and 21 welders using the Metal Inert Gas (MIG) and\\/ or Metal Active Gas (MAG) methods on stainless steel (SS). A matched reference group I, and a larger reference group II of 94 subjects studied during the same time period, was established for comparison. Whole

Øyvind Jelmert; Inger-Lise Hansteen; Sverre Langård

1995-01-01

399

Post-experiment correction for release rate in permeation tubes improves the accuracy of the sulphur hexafluoride (SF 6) tracer technique in deer  

Microsoft Academic Search

The sulphur hexafluoride (SF6) tracer technique is a means to estimate CH4 emissions from individual ruminants, particularly whilst grazing. The success of the SF6 technique is reliant upon accurate determination of the release rate of SF6 gas from the permeation tubes (PT). Our study aimed to determine effects of SF6 PT rumen residence time on the release rate of SF6

N. M. Swainson; I. M. Brookes; S. O. Hoskin; H. Clark

2011-01-01

400

Perfluorocarbon tracer tagging of drilling muds for the assessment of sample contamination  

Microsoft Academic Search

Perfluorocarbon tracers, PFTs, a multitracer technology of seven chemical tracers, were used to tag the drilling muds used in the Fourth Investigators Hole of the Deep Probe experiments. PFTs are fully fluorinated alkyl substituted cycloalkanes, which are inert, non-toxic and chemically non-reactive, detectable in these applications to 1 picoliter\\/gram of sample by gas chromatographic electron capture detection. PFTs were incorporated

G. I. Senum; R. N. Dietz

1990-01-01

401

NEXT GENERATION GAS TURBINE (NGGT) SYSTEMS STUDY  

SciTech Connect

The ADL NGGT analysis focuses on intermediate load applications, but recognizes peaking, repowering, ancillary services, cogen, and green power requirements. In light of identifying new markets, GE will re-examine the changing customer needs since the original ADL study. The priorities of this potential customer base can be structured into key requirements for a broader cross-section of customers and applications, and a balanced view identifying the key potential customer segments will result. Given the potential for non-U.S. market segments, a broader global approach will be adopted. GEPS will translate these customer segments into customer needs, further testing the requirements listed in the original study. These customer needs will be prioritized and compared so that a balanced view of performance requirements will be identified. The performance requirements will be translated in specific design requirements for a potential AMGT-type product.

NONE

2000-10-12

402

Simple light gas guns for hypervelocity studies  

Microsoft Academic Search

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 â5 km\\/s. These guns are relatively small and simple (thus, easy to operate), allowing a significant number of

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

1990-01-01

403

Study of liquid retention in fixed-bed reactors with upward flow of gas and liquid  

SciTech Connect

A literature survey of the measurement techniques for the determination of liquid retention in cocurrent upward gas and liquid flow in fixed-bed reactors is presented. A number of these techniques were used in this work in columns of different diameters (Dc = 0.05 m, 0.10 m, and 0.15 m). Porous alumina particles of two different diameters (dp = 0.002 m and 0.0028 m) with both nonfoaming (water, cyclohexane, heptane, and propanol) and foaming liquids (kerosene, LCO, and diesel fuel) have been investigated. The gas used was either air or N[sub 2]. The methods investigated include volumetry, gravimetry, gammametry, and determination of residence-time distribution by tracer technique. A simple correlation for the prediction of total gas and liquid retention for bubble and pulsed flow is proposed and verified.

Yang, X.L.; Euzen, J.P. (Inst. Francais du Petrole, Vernaison (France)); Wild, G. (Lab. des Sciences du Genie Chimique, Nancy (France))

1993-01-01

404

Study on the wiping gas jet in continuous galvanizing line  

NASA Astrophysics Data System (ADS)

In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.

Kweon, Yong-Hun; Kim, Heuy-Dong

2011-09-01

405

FISSION GAS HOLDUP TESTS ON HRT CHARCOAL BEDS  

Microsoft Academic Search

Fission gas holdup tests on the HRT charcoal beds under simulated ; operating conditions are complete. A radioactive tracer technique developed for ; use in laboratory absorption studies was utilized. The efficiency of the ; charcoal beds, in regard to holdup of fission gases, exceeds design ; specifications. On the basis of these tests, the charcoal beds should perform ;

R. E. Adams; W. E. Browning

1958-01-01

406

A perfluorocarbon tracer transport and dispersion experiment in the North Sea Ekofisk oil field  

Microsoft Academic Search

A perfluorocarbon tracer (PFT) transport and dispersion experiment has been performed in the Ekofisk section of the North Sea Oil fields. Fifty grams each of three PFTs were injected into a well and 28 surrounding wells were sampled for the presence of PFT. Sampling was accomplished by initially collecting bottles of reservoir hydrocarbon gas and subsequently transferring 5 liter (gas

G. I. Senum; R. N. Dietz; T. W. DOttavio; R. W. Goodrich; E. A. Cote; D. J. Spandau

1990-01-01

407

A perfluorocarbon tracer transport and dispersion experiment in the North Sea Ekofisk oil field  

Microsoft Academic Search

A perfluorocarbon tracer (PFT) transport and dispersion experiment has been performed in the Ekofisk section of the North Sea oil fields. Fifty grams each of three PFTs were injected into a well and 28 surrounding wells were sampled for the presence of PFT. Sampling was accomplished by initially collecting bottles of reservoir hydrocarbon gas and subsequently transferring 5 liter (gas

G. I. Senum; R. N. Dietz; T. W. DOttavio; R. W. Goodrich; E. A. Cote; D. J. Spandau

1989-01-01

408

Determination of hydrogen diffusivity and permeability in W near room temperature applying a tritium tracer technique  

NASA Astrophysics Data System (ADS)

Tungsten is a primary candidate of plasma facing material in ITER and beyond, owing to its good thermal property and low erosion. But hydrogen solubility and diffusivity near ITER operation temperatures (below 500 K) have scarcely studied. Mainly because its low hydrogen solubility and diffusivity at lower temperatures make the detection of hydrogen quite difficult. We have tried to observe hydrogen plasma driven permeation (PDP) through nickel and tungsten near room temperatures applying a tritium tracer technique, which is extremely sensible to detect tritium diluted in hydrogen.The apparent diffusion coefficients for PDP were determined by permeation lag times at first time, and those for nickel and tungsten were similar or a few times larger than those for gas driven permeation (GDP). The permeation rates for PDP in nickel and tungsten were larger than those for GDP normalized to the same gas pressure about 20 and 5 times larger, respectively.

Ikeda, T.; Otsuka, T.; Tanabe, T.

2011-08-01

409

Human calcium metabolism including bone resorption measured with {sup 41}Ca tracer  

SciTech Connect

Accelerator mass spectrometry is so sensitive to small quantities of {sup 41}Ca that it might be used as a tracer in the study of human calcium kinetics to generate unique kinds of data. In contrast with the use of other Ca isotopic tracers, {sup 41}Ca tracer can be so administered that the tracer movements between the various body pools achieve a quasi steady state. Resorbing bone may thus be directly measured. We have tested such a protocol against a conventional stable isotope experiment with good agreement.

Freeman, S.P.H.T. [Lawrence Livermore National Lab., CA (United States); King, J.C. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Vieira, N.E. [National Inst. of Child Health and Human Development, Bethesda, MD (United States); Woodhouse, L.R. [California Univ., Berkeley, CA (United States). Dept. of Nutritional Science; Yergey, A.L. [National Inst. of Child Health and Human Development, Bethesda, MD (United States)

1996-08-01

410

Gas cooled leads. Part 1, Theoretical study  

SciTech Connect

The intent of this paper is to cover as completely as possible and in sufficient detail the topics relevant to lead design. The first part identifies the problems associated with lead design, states the mathematical formulation, and shows the results of numerical and analytical solutions. The second part presents the results of a parametric study whose object is to determine the best choice for cooling method, material, and geometry. These findings axe applied in a third part to the design of high-current leads whose end temperatures are determined from the surrounding equipment. It is found that cooling method or improved heat transfer are not critical once good heat exchange is established. The range 5 < RRR < 100 is found to be acceptable for the relative resistivity ratio of the material. Use of high transition temperature super conductor materials is not warranted for this application. The optimal geometry (L:length, A:cross-section) for given current (1) follows the relation LI/A = 2 {times} 10{sup 5} but extends over a large of values. Mass flow needed to prevent thermal runaway varies linearly with current above a given threshold. Below that value, the mass flow is constant with current. Transient analysis shows no evidence of hysteresis. If cooling is interrupted, the mass flow needed to restore the lead to its initially cooled state grows exponentially with the time that the lead was left without cooling.

Shutt, R.P.; Rehak, M.L.; Hornik, K.E.

1993-12-07

411

First Deployment of a New Mobile Laboratory for Greenhouse Gas Attribution Studies  

NASA Astrophysics Data System (ADS)

Anthropogenic sources of carbon dioxide represent a significant portion of the global carbon budget, but partitioning CO2 measurements into their biogenic and anthropogenic sources has been difficult using only measurements of CO2 abundances and those of a small number of additional tracers. An intensive field campaign was conducted in Fall 2010 at the ARM-SGP Central facility near Lamont, OK to measure CO2 and several tracers for its sources using a new mobile laboratory. Two trucks carrying over fifteen instruments for gases and particles were deployed along with a gas-calibration system. Air was drawn into both trucks from a 10-m tall mast. All measurements were made either from a common inlet or closely located inlets. Instruments were selected to provide measurements of tracers of both biogenic and anthropogenic sources. High-frequency measurements of abundances of CO2 and its stable isotopologues (13CO2 and C18OO) were made simultaneously with measurements of CO, SO2, NOx, O3, CH4, water vapor isotopologues (H2O, HDO, and H218O), volatile organic compounds, black and organic carbon aerosol, and particle count. Automated flask samplers collected whole air samples for off-line 14C analysis using accelerator mass spectrometry. Redundancy between CO2, CH4, and H2O measurements provided a valuable crosscheck for the calibrations and the measurements. Good agreement between CO2 measurements from four different instruments was attained following careful post-processing and calibrations. Similarly good agreement was demonstrated between four instruments that measured water vapor and two instruments that measured CH4. Correlations between various tracers and CO2 provide insight into the different sources, including the anthropogenic component, which includes biomass and fossil fuel combustion. These results are supported by back-trajectory analysis.

Bambha, R.; Michelsen, H. A.; Schrader, P.; Helsel, F.; Ivey, M.; Zak, B. D.; LaFranchi, B. W.; Flowers, B. A.; Rahn, T.; Dubey, M. K.; Guilderson, T. P.; Biraud, S. C.; Fischer, M. L.; Torn, M. S.; Berry, J. A.; Karion, A.; Novelli, P. C.; Sweeney, C.

2011-12-01

412

Tracer transport in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

Transport is crucial to understanding and reproducing the Martian dust and water cycles, and to interpreting putative methane and other trace gas (e.g. Argon) observations. However, as quantified by comparing model predictions with Argon measurements made by the Gamma Ray Spectrometer [e.g. Sprague et al., 2004, 2007], current Mars general circulation models (GCM's) appear to do a poor job at tracer transport [e.g. Nelli et al., 2007]. This invalidates a core assumption of GCM modeling in the last decade - that transport is sufficiently well treated in models that we need focus only on improving physical parameterizations, and that differences between results from different GCM's stem purely from their treatment of physical processes. If instead it is the simulated dynamical processes that need better treatment we need to move towards higher-quality numerics, e.g. based on the finite volume formulation, and introduce a more sophisticated approach to advection following work done for terrestrial chemical transport modeling. Here we present the results of non-condensable tracer transport simulations using our newly developed Mars MITgcm, which has both of the aforementioned desirable attributes: a finite volume core and access to a range of sophisticated advection schemes. Our results are encouraging in that we are able to reproduce the observed peak polar Argon enhancement factor of six (about double that attainable with most other Mars GCMs). Our diagnostics show that the time-averaged zonal-mean advection produces net increases of Argon at the winter poles, while stationary and transient eddies transport Argon away from the poles. Using less diffusive nonlinear advection schemes with flux limiters tends to produce more advective fluxes of tracers into the southern winter pole than the more diffusive linear advection schemes, resulting in a greater net increase of polar Argon abundance. We further utilize a more realistic k-distribution radiative transfer model, an improvement over the wide-band models often used in Mars GCM's, and find that the improved radiative transfer in combination with an appropriate advection scheme can quantitatively reproduce the observed Argon distribution. Our results suggest that both advection schemes and physics parameterizations are equally important in good simulation of transport-sensitive climate components, and that newer finite-volume based models (such as our MITgcm and the GFDL / NASA Ames finite volume GCM) are likely necessary for further progress in these areas.

Lian, Y.; Richardson, M. I.; Newman, C. E.; Lee, C.; Toigo, A. D.; Campin, J.

2011-12-01

413

The use of microbial tracers to monitor seasonal variations in effluent retention in a constructed wetland.  

PubMed

Effluent retention in a constructed wetland was determined using both microbial and chemical tracers. Seasonal variation in effluent retention was the main focus of the study. The biotracers used in the study were the coliphage MS2, a bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii. Two separate tracer runs were conducted, Winter high flow (January 2002) and Summer low flow (June 2002). The three biotracers were evaluated simultaneously on both occasions, with the commonly used chemical tracer, rhodamine WT, a bright red fluorescent dye, being evaluated during the final experiment. The Winter tracer run was conducted during a typical Winter storm, with a mean effluent discharge of 4.1 ls(-1). Tracer recovery was 98% MS2, 91% Ent. cloacae phage and 2% endospore. Effluent retention was estimated at between 2 and 4 h at 90% phage tracer recovery. The Summer tracer run was conducted at a typical site operating discharge rate of 0.8 ls(-1). Tracer recovery was 23% MS2, 36% Ent. cloacae phage, 8% rhodamine and 14% for the endospores. Effluent retention was estimated at between 11 and 18 h at 90% of phage tracer recovery. Initial results are encouraging and indicate bacteriophage to have further potential as tracing agents in wetlands. PMID:15380974

Hodgson, C J; Perkins, J; Labadz, J C

2004-11-01