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1

Neutrally buoyant tracer in gas cleaning equipment: a case study  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

2

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

3

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

PubMed

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

Sakiyama, S K; Angle, R P

1988-03-01

4

Novel tracer method to measure isotopic labeled gas-phase nitrous acid (HO15NO) in biogeochemical studies.  

PubMed

Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ?60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ?(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ?(15N)=0.2-0.5, the relative standard deviation of ?(15N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15) labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere. PMID:24954648

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

2014-07-15

5

Natural and artificial nobel gas hydrologic tracers  

SciTech Connect

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

Hudson, G.B.

1994-06-01

6

Noble gas tracers for characterisation of flow dynamics and origin of groundwater: A case study in Switzerland  

NASA Astrophysics Data System (ADS)

SummaryThe Grenchen aquifer system in the Swiss Plateau was extensively investigated in order to determine the extent of groundwater contamination and to assess the natural attenuation capacity. Environmental tracer data were applied to estimate groundwater travel times, mixing ratios, and evaluate groundwater origin. Recharge is basically possible in two distinct topographical areas, the immediate vicinity of the town of Grenchen and the elevated plateau of the first Jura Mountain ridge. Groundwater dating was performed with the 3H/ 3He dating method and supplemented by 85Kr measurements. Stable isotope data ( ?18O, ?2H) and dissolved noble gas concentrations allow the determination of the recharge temperature, which is correlated to the recharge elevation. Noble gas temperatures (NGT) decrease in the direction of groundwater flow and range from 10 to 13 C in the upstream area of the town to 7-9 C in the downstream river plain. This trend could suggest the admixture of water from the underlying limestone aquifer recharged under cooler infiltration conditions, e.g. at higher recharge elevations. However, it is shown in this study that the difference in NGT does not require such a recharge. Rather, increasing air temperatures over the last 40 years and the urban heat island effect could possibly explain most of the observed temperature shift. Furthermore, it is concluded that the downstream river plain is hydrologically disconnected from the upstream town area. Consequently most water from the town area is drained by the creek Witibach and recharge in the river plain is higher than previously assumed.

Althaus, R.; Klump, S.; Onnis, A.; Kipfer, R.; Purtschert, R.; Stauffer, F.; Kinzelbach, W.

2009-05-01

7

A new tracer gas method to measure oxygen transfer and enhancement factor on RBC  

Microsoft Academic Search

The aim of this study was to test a new application of tracer gas in rotating biological contactors (RBC). Our method using propane as tracer gas, is able to quantify the purely physical gas liquid exchange. The procedure was utilized on RBC in order to measure: (a) the physical transfer coefficient with clean discs (Kla) in tap water and in

B.-E. Boumansour; J.-L. Vasel

1998-01-01

8

A dual-gas tracer technique for determining trapped gas saturation during steady foam flow in porous media  

SciTech Connect

Foam is a possible mobility control agent for effective oil displacement from reservoirs. Thus, it is important to understand the mechanisms by which foam flows in porous media. Micromodel studies and prior gas-phase tracer experiments show that a significant fraction of the gas in a foam exists as trapped bubbles which, therefore, have a major impact on the flow resistance. Unfortunately, in the tracer experiments performed to date, partitioning of the tracer into the trapped gas has not been accounted for. Currently, only qualitative information is available on the actual amounts of trapped gas. To overcome these limitations and obtain quantitative measurements of trapped gas saturations, we have developed a unique experimental apparatus employing dual gas tracers. During steady foam flow in a porous medium, dilute sulfur hexafluoride (SF{sub 6}) and methane (CH{sub 4}) tracers in a nitrogen carrier are injected, and the effluent concentration is monitored by gas chromatography. The measured tracer histories are fit to a simple mass transfer model which describes any partitioning between the mobil and trapped foam phases. Tracer effluent concentrations predicted by the model are strongly influenced by the solubility of each tracer in the liquid phase. This behavior is observed in the experimental histories as well. Hence, multiple gas tracers provide a discriminating assessment of trapped gas saturation during foam flow through porous media.

Gillis, J.V.; Radke, C.J.

1990-06-01

9

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

NASA Astrophysics Data System (ADS)

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

Deckert, Dirk-Andr; Frhlich, Jrg; Pickl, Peter; Pizzo, Alessandro

2014-06-01

10

A dual-gas tracer technique for determining trapped gas saturation during steady foam flow in porous media  

SciTech Connect

Foam is a possible mobility control agent for effective oil displacement from reservoirs. Micromodel studies and prior gas-phase tracer experiments show that a significant fraction of the gas in a foam exists as trapped bubbles which, therefore, have a major impact on the flow resistance. To obtain quantitative measurements of trapped gas saturations, we have developed a unique experimental apparatus employing dual gas tracers. During steady foam flow in a porous medium, dilute sulfur hexafluoride (SF{sub 6}) and methane (CH{sub 4}) tracers in a nitrogen carrier are injected, and the effluent concentration is monitored by gas chromatography. The measured tracer histories are fit to a simple mass transfer model which describes any partitioning between the mobil and trapped foam phases. Tracer effluent concentrations predicted by the model are strongly influenced by the solubility of each tracer in the liquid phase. Hence, multiple gas tracers provide a discriminating assessment of trapped gas saturation during foam flow through porous media. New trapped gas saturations are reported for an aqueous C{sub 14-16} {alpha}-olefin sulfonate foamer solution and nitrogen flowing through a 2.3-{mu}m{sup 2} fired Berea sandstone at 10{sup 5} Pa (1 atm) back pressure and at room temperature. 26 refs., 7 figs., 1 tab.

Gillis, J.V.; Radke, C.J.

1990-09-01

11

Preliminary Investigation of Tracer Gas Reaeration Method for Shallow Bays  

E-print Network

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

Baker, Sarah H.; Holley, Edward R.

12

Ballistic Motion of a Tracer Particle Coupled to a Bose gas  

E-print Network

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

Juerg Froehlich; Zhou Gang

2013-02-02

13

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

14

Field measurements of tracer gas transport by barometric pumping  

SciTech Connect

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

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

1994-07-28

15

Partitioning Gas Tracer Technology for Measuring Water in Landfills  

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

16

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

SciTech Connect

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

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

1991-06-01

17

Estimating fracture spacing from natural tracers in shale-gas production  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

18

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

19

Isotopologues of Dense Gas Tracers in NGC1068  

NASA Astrophysics Data System (ADS)

We present observations of isotopic lines of dense gas tracers toward the nuclear region of nearby Seyfert 2 galaxy NGC 1068 with the IRAM 30 m telescope and the Atacama Pathfinder Experiment (APEX) 12 m telescope. We detected four isotopic lines (H13CN 1-0, H13CO+ 1-0, HN13C 1-0, and HC18O+ 1-0) at the 3 mm band with the IRAM 30 m telescope and obtained upper limits of other lines. We calculated optical depths of dense gas tracers with the detected isotopic lines of HCN 1-0, HCO+ 1-0, and HNC 1-0. We find that the 14N/15N abundance ratio is greater than 420 if we adopt the upper limit of HC15N(1-0) emission. Combining this with fluxes of 1-0 lines from IRAM 30 m observations and the upper limit of 3-2 lines from APEX 12 m observations, we also estimated the excitation condition of molecular gas in the nuclear region of NGC 1068, which is less dense than that in the extreme starburst regions of galaxies.

Wang, Junzhi; Zhang, Zhi-Yu; Qiu, Jianjie; Shi, Yong; Zhang, Jiangshui; Fang, Min

2014-11-01

20

Gastric activity studies using a magnetic tracer.  

PubMed

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

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

2004-10-01

21

Modeling the phase partitioning behavior of gas tracers under geothermal reservoir conditions  

Microsoft Academic Search

A model of the liquid-vapor phase partitioning behavior of low concentrations of gas tracers in water at geothermal temperatures and pressures is presented. This model uses Henry's coefficient to describe the variation of the gas tracer solubility with temperature and pressure. A new method is described for the determination and representation of Henry's coefficients. The method uses experimentally determined values

Mark Trew; Michael J. O'Sullivan; Yoshio Yasuda

2001-01-01

22

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

EPA Science Inventory

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

23

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

SciTech Connect

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

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

1994-10-01

24

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

PubMed

Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF(6)), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences. PMID:21996285

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

2012-02-01

25

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

USGS Publications Warehouse

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

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

2005-01-01

26

ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED THROUGH FRACTURED MEDIA  

EPA Science Inventory

The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured clay system that is the confin...

27

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

28

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

SciTech Connect

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

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

2011-04-15

29

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

E-print Network

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

Cummings, J. B.

1989-01-01

30

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

NASA Astrophysics Data System (ADS)

Rapid mapping of gas concentrations in air benefits studies of atmospheric phenomena ranging from pollutant dispersion to surface layer meteorology. Here we demonstrate a technique that combines multiple-open-path tunable-diode-laser spectroscopy and computed tomography to map tracer gas concentrations with approximately 0.5 m spatial and 7 s temporal resolution. Releasing CH 4 as a tracer gas in a large (7 m9 m11 m high) ventilated chamber, we measured path-integrated CH 4 concentrations over a planar array of 28 "long" (2-10 m) optical paths, recording a complete sequence of measurements every 7 s during the course of hour-long experiments. Maps of CH 4 concentration were reconstructed from the long path data using a computed tomography algorithm that employed simulated annealing to search for a best fit solution. The reconstructed maps were compared with simultaneous measurements from 28 "short" (0.5 m) optical paths located in the same measurement plane. On average, the reconstructed maps capture 74% of the variance in the short path measurements. The accuracy of the reconstructed maps is limited, in large part, by the number of optical paths and the time required for the measurement. Straightforward enhancements to the instrumentation will allow rapid mapping of three-dimensional gas concentrations in indoor and outdoor air, with sub-second temporal resolution.

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

31

Gas-partitioning tracer test to quantify trapped gas during recharge  

USGS Publications Warehouse

Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

Heilweil, V. M.; Solomon, D. K.; Perkins, K. S.; Ellett, K. M.

2004-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

33

[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

34

Gas-partitioning tracer test to quantify trapped gas during recharge.  

PubMed

Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas. PMID:15318781

Heilweil, Victor M; Solomon, D Kip; Perkins, Kim S; Ellett, Kevin M

2004-01-01

35

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

36

Feasibility study of using line tracer robot under disaster situation  

NASA Astrophysics Data System (ADS)

Line tracer robots are widely accepted in various industry for the purpose of moving objects. In this study feasibility of using line tracer robots under disaster situation is studied as the line tracing capability may be useful in case of disaster. A small scale line tracer robot is designed, implemented, and tested under disaster situation. Specifically, the MCU based robot hardware including sensor, encoder, motor, and power supply is designed and implemented. Also, the software for receiving sensor signal, for driving motor and for implementing line searching algorithm is designed. The devised robot detects the guide line using 6 infrared optical sensors and can adjust the direction of motion with the front steering servo motor according to the sensor signal. In driving test, the robot showed reliable performance both on the straight and curved paths having obstacles under limited visibility condition as in disaster situation.

Kim, Hyung Ki; Choi, Gi Sang; Choi, Gi Heung

2007-12-01

37

Tracer Studies In A Laboratory Beach Subjected To Waves  

EPA Science Inventory

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

38

Optimization and evaluation of fluorescent tracers for flare removal in gas-phase particle image velocimetry  

NASA Astrophysics Data System (ADS)

We report the development of optimized fluorescent dye-doped tracer particles for gas-phase particle image velocimetry (PIV) and their use to eliminate 'flare' from the images obtained. In such applications, micron-sized tracer particles are normally required to accurately follow the flow. However, as the tracer size is reduced the amount of light incident on the particle diminishes and consequently the intensity of emitted light (fluorescence). Hence, there is a requirement to identify dyes with high quantum yield that can be dissolved in conventional tracer media at high concentrations. We describe the selection and characterization of a highly fluorescent blue-emitting dye, Bis-MSB, using a novel method, employing stabilized micro-emulsions, to emulate the fluorescence properties of tracer particles. We present the results of PIV experiments, using 1 m tracer particles of o-xylene doped with Bis-MSB, in which elastically scattered 'flare' has been successfully removed from the images using an appropriate optical filter.

Chennaoui, M.; Angarita-Jaimes, D.; Ormsby, M. P.; Angarita-Jaimes, N.; McGhee, E.; Towers, C. E.; Jones, A. C.; Towers, D. P.

2008-11-01

39

A Tracer Study of Lebanese Upper Secondary School Students  

ERIC Educational Resources Information Center

This paper presents data arising from a tracer study of 90 terminating Beirut upper secondary school students. Nearly all the students intended to transit to university, about half of them to science and technology programmes, and subsequently did so. Median anticipated earnings upon graduation were realistic, but a lack of information or guidance

Vlaardingerbroek, Barend; Dallal, Kamel; Rizkallah, George; Rabah, Jihan

2007-01-01

40

Waste tank ventilation rates measured with a tracer gas method  

Microsoft Academic Search

Passive ventilation with the atmosphere is used to prevent accumulation of waste gases and vapors in the headspaces of 132 of the 177 high-level radioactive waste Tanks at the Hanford Site in Southeastern Washington State. Measurements of the passive ventilation rates are needed for the resolution of two key safety issues associated with the rates of flammable gas production and

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

1998-01-01

41

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

42

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

SciTech Connect

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

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

2013-05-01

43

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

44

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

E-print Network

The Motorola Exhaust Optimization Program strives toward identifying the optimum exhaust requirements for gas panel enclosures to help conserve energy and provide future exhaust capacity for new tools. Various Motorola studies have shown...

Myart, H. R.; Camacho, R.

45

The project MOHAVE tracer study: study design, data quality, and overview of results  

Microsoft Academic Search

In the winter and summer of 1992, atmospheric tracer studies were conducted in support of project MOHAVE, a visibility study in the southwestern United States. The primary goal of project MOHAVE is to determine the effects of the Mohave power plant and other sources upon visibility at Grand Canyon National Park. Perfluorocarbon tracers (PFTs) were released from the Mohave power

Mark C. Green

1999-01-01

46

Tracer Study of Mixing and Transport in the Upper Hudson River  

E-print Network

subject headings: Dams; Dispersion; Hudson River; Mixing; Tracers; Water pollution; VolatizationTracer Study of Mixing and Transport in the Upper Hudson River with Multiple Dams Theodore Caplow1 into the upper Hudson River, a modified natural channel with multiple dams, at Ft. Edward, N.Y. The tracer

Ho, David

47

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

PubMed

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

Keller, Jason M; Brusseau, Mark L

2003-07-15

48

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

50

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

51

Reintegration of child soldiers in Burundi: a tracer study  

PubMed Central

Background Substantial attention and resources are aimed at the reintegration of child soldiers, yet rigorous evaluations are rare. Methods This tracer study was conducted among former child soldiers (N=452) and never-recruited peers (N=191) who participated in an economic support program in Burundi. Socio-economic outcome indicators were measured retrospectively for the period before receiving support (T1; 200506); immediately afterwards (T2; 200607); and at present (T3; 2010). Participants also rated present functional impairment and mental health indicators. Results Participants reported improvement on all indicators, especially economic opportunity and social integration. At present no difference existed between both groups on any of the outcome indicators. Socio-economic functioning was negatively related with depression- and, health complaints and positively with intervention satisfaction. Conclusion The present study demonstrates promising reintegration trajectories of former child soldiers after participating in a support program. PMID:23095403

2012-01-01

52

Tracer studies of SO{sub 2} oxidation in clouds  

SciTech Connect

The quantitative determination of aqueous phase oxidation of S(IV) is critical to determining: (1) the relationship between regional SO{sub 2} emissions and acid deposition at distant receptors; and (2) the size distribution of anthropogenic sulphate aerosols which has consequences on global climate. Husain developed a tracer technique, based on the similarities in physical and chemical behavior of SO{sub 4} and Se aerosols to quantitatively determine SO{sub 2} oxidation in clouds. Extensive investigation of the technique including verification of the assumptions, extension to develop other tracers, its application to study S(IV) oxidation in clouds, comparison of the field data with calculations based on laboratory reaction rates and an assessment of the role of clouds on SO{sub 2} oxidation were the important goals of this dissertation. Field investigations were conducted at Whiteface Mountain, New York during the summers of 1990, 1991, and 1992. Three hundred seventy cloud water samples, usually of 15 min duration were collected from thirteen clouds. Aerosol in cloud free air were also collected for each cloud system. pH of the cloud water ranged between 2.85 and 4.7. Six clouds were selected, based on chemical and meteorological conditions for determination of in-cloud SO{sub 2} oxidation. The amount of SO{sub 4} formed in situ by aqueous phase oxidation (SO{sub 4in}) ranged from none to about 40%. In three clouds, in-cloud oxidation was quantified using Se, As, and Sb as tracers. The results were in good agreement when large amounts of SO{sub 4in} were produced. It is concluded that all three, Se, As, and Sb can be used to determine SO{sub 2} oxidation in clouds. Based on SO{sub 4in}, concentrations of SO{sub 2}, H{sub 2}O{sub 2}, and laboratory reaction rates, progression of the reaction was followed in time using a simple computer model.

Burkhard, E.G.

1994-12-31

53

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

54

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

55

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

SciTech Connect

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

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

2013-02-15

56

The project MOHAVE tracer study: study design, data quality, and overview of results  

NASA Astrophysics Data System (ADS)

In the winter and summer of 1992, atmospheric tracer studies were conducted in support of project MOHAVE, a visibility study in the southwestern United States. The primary goal of project MOHAVE is to determine the effects of the Mohave power plant and other sources upon visibility at Grand Canyon National Park. Perfluorocarbon tracers (PFTs) were released from the Mohave power plant and other locations and monitored at about 30 sites. The tracer data are being used for source attribution analysis and for evaluation of transport and dispersion models and receptor models. Collocated measurements showed the tracer data to be of high quality and suitable for source attribution analysis and model evaluation. The results showed strong influences of channeling by the Colorado River canyon during both winter and summer. Flow from the Mohave power plant was usually to the south, away from the Grand Canyon in winter and to the northeast, toward the Grand Canyon in summer. Tracer released at Lake Powell in winter was found to often travel downstream through the entire length of the Grand Canyon. Data from summer tracer releases in southern California demonstrated the existence of a convergence zone in the western Mohave Desert.

Green, Mark C.

57

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

SciTech Connect

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

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

2006-01-01

58

A novel 83mKr tracer method for characterizing xenon gas and cryogenic distillation systems  

NASA Astrophysics Data System (ADS)

The radioactive isomer 83mKr, has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and ?-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state 83Kr, one does not risk contamination of any low-background experiment with long-lived radionuclides. In this paper, we present a new approach, using 83mKr as a radioactive tracer in noble gases. A method of doping 83mKr, into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. Two applications of this method are presented: firstly, it can be used to characterize the particle flow inside of gas routing systems and determine the circulation speed of gas particles inside of a gas purification system for xenon. Secondly, it is used for rapid estimating of the separation performance of a distillation system.

Rosendahl, S.; Bokeloh, K.; Brown, E.; Cristescu, I.; Fieguth, A.; Huhmann, C.; Lebeda, O.; Levy, C.; Murra, M.; Schneider, S.; V'enos, D.; Weinheimer, C.

2014-10-01

59

A survey of tracer gas techniques for estimation airflow and effective volumes in single and multizone buildings  

SciTech Connect

This paper briefly describes the development of tracer gas techniques. These techniques were introduced over 50 years ago and have evolved into a number of distinct methods. These methods are often tailored to a specific application or to obtain particular information about the flow and volume system. Single-zone techniques are utilized when the structure or zone is relatively well-mixed and can be characterized by a single concentration measurement. Areas or rooms within a single-family residence can sometimes be closely approximated as one well-mixed zone. Multizone techniques are required when the building is composed of two or more zones which communicate with one another through interzonal airflows. Commercial office buildings are usually multizone systems. This paper focuses on single and multiple gas tracer techniques. Traditionally, multizone systems have been analyzed by using a different tracer for each zone. These techniques require equipment capable of accurately injecting and detecting each of the tracers which can be cumbersome in large order systems. Recently, a number of methods have been proposed which use a single tracer gas to estimate flow and effective volumes in multizone systems. 24 refs., 2 figs., 1 tab.

O'Neill, P.J.

1990-10-01

60

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

SciTech Connect

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

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

1984-07-01

61

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

62

Groundwater studies using isotopes and noble gases as a tracer: Review and prospect  

NASA Astrophysics Data System (ADS)

Environmental tracers become a common tool for the groundwater study and a number of methods have been presented in order to understand groundwater flow processes, water budget, origins, chemical reaction processes and retention time. Tracers often used are selected and reviewed for their various methods and advantages as follows; 1) stable 18O, D in water, 2) stable 13C and radioactive 14C in DIC, 3) noble gases such as He, Ne, Ar, Kr, Xe and their isotopes, 4) radioactive 36Cl in dissolved chloride and some heavier isotopes, and 5) inert gaseous species such as CFCs. If they are less reactive species, they likely preserve information at the time of recharge or their origin. Use of D, 18O and the d-value of water is the powerful tool to determine the recharge area because recharged meteoric water have their inherent isotopic ratios correlated with the recharge elevation, distance from the coast, or the local topography. Carbon-bearing species are more reactive though, use of stable isotopes of DIC leads to identify its origin and helps to analyze the chemical reaction between minerals and water or gas addition processes during the groundwater flow in aquifers. Radioactive 14C has been used to estimate groundwater age however special attention should be paid for, i.e., the origin of DIC, before applying the method. Noble gas tracers are the useful species to presume recharge temperature from their concentrations in water using their temperature dependence of solubilities. Radiogenic 4He concentration can be used for the very long-term groundwater dating since the 4He is produced in the crust and is accumulated in the deep aquifers, if the local accumulation rate of 4He is known. Radioactive 36Cl has been used to determine the age of very old saline waters up to million years. This isotope will also be convenient for the dating of very younger waters, by the use of bomb-produced 36Cl resulted from surface nuclear experiments near the seawater in the 1950s. Chlorofluorocarbons (CFCs) are the gas species produced by the recent human activity and dissolve in water during the recharge, therefore, the affected younger groundwater will have equivalent CFCs concentrations with the atmospheric CFCs concentrations at the time of the recharge. As these species are easy to detect with very high sensitivity, this tracer has now been applied not only for the age determination but for the mixing or contamination of shallow young water to a deep old groundwater. As an individual method listed above is valid only for the very simple flow system, appropriate assumptions or coupling of using different tracers is necessary to understand natural complex groundwater flow system where mixing of groundwaters of different origin or age occurs. Combination of tracers helps us simulating the complex system in detail and is being a growing trend in groundwater study.

Kazahaya, Kohei; Yasuhara, Masaya; Takahashi, Hiroshi A.; Morikawa, Noritoshi; Ohwada, Michiko; Tosaki, Yuki; Asai, Kazuyoshi

63

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

PubMed

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

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

1998-05-01

64

Tracer Gas Measurement of Airflow Rates in Spaces with Several Air-Handling Units, Recirculation, or Large Time Constants  

Microsoft Academic Search

Methods to measure airflow rates using tracer gas in single air-handling units are well known. In some buildings, however, in particular in Singapore, rooms are often ventilated with two or more units and present large recirculation rates. Large recirculation ratios homogenize the concentrations, so concentrations in supply and extract ducts are close to each other. In addition, these spaces often

C.-A. Roulet; M. S. Zuraimi; S. C. Sekhar; K. W. Tham

2006-01-01

65

A study of solute transport mechanisms using rare earth element tracers and artificial rainstorms on snow  

E-print Network

A study of solute transport mechanisms using rare earth element tracers and artificial rainstorms and Susan Taylor1,5 Abstract. Rare earth element (REE) tracers and three artificial rain-on-snow storms atmospherically deposited chemical con- taminants throughout the winter, and thus snowmelt often accounts

Kirchner, James W.

66

Multiple-tracer TESPEL injection for studying impurity behaviour in a magnetically confined plasma  

NASA Astrophysics Data System (ADS)

A new diagnostic method with tracer-encapsulated solid pellet (TESPEL) injection with multiple tracers is developed to study impurity behaviour in a magnetically confined plasma. If a pellet contains multiple tracers, it becomes possible to compare the behaviour of different impurities simultaneously under the same plasma conditions. We injected a TESPEL into the Large Helical Device mainly with triple tracers: vanadium (V), manganese (Mn) and cobalt (Co). The Li-like lines in the vacuum ultraviolet range and the K? lines in the soft x-ray range from these tracers are simultaneously observed with a time resolution of 50 ms. As the charges of the nuclei of intrinsic impurities, chromium (Cr) and iron (Fe), are in between those of the tracers, the behaviour of Cr and Fe can be studied quantitatively by knowing the number of tracer particles and also by comparing the emission intensity change due to the electron temperature change. It is observed that the tracer impurities remain in the plasma core region when the plasma density is higher than 5 1019 m-3. It is also observed that the intrinsic impurities cannot enter the core region when the plasma density is higher than the same level, although the two phenomena appear to be independent.

Sudo, Shigeru; Tamura, Naoki; Suzuki, Chihiro; Muto, Sadatsugu; Funaba, Hisamichi; the LHD Experiment Group

2012-06-01

67

Simulational study of anomalous tracer diffusion in hydrogels  

E-print Network

In this article, we analyze different factors that affect the diffusion behavior of small tracer particles (as they are used e.g.in fluorescence correlation spectroscopy (FCS)) in the polymer network of a hydrogel and perform simulations of various simplified models. We observe, that under certain circumstances the attraction of a tracer particle to the polymer network strands might cause subdiffusive behavior on intermediate time scales. In theory, this behavior could be employed to examine the network structure and swelling behavior of weakly crosslinked hydrogels with the help of FCS.

Fatemeh Tabatabaei; Olaf Lenz; Christian Holm

2010-12-07

68

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 (t 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 t for conversion of portal vein ammonia to urea in the rat liver is ~1011 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 ?78 sec, c) the t for incorporation of blood-borne ammonia into glutamine in the normal rat brain is <3 sec, and d) equilibration between glutamate and aspartate nitrogen in rat liver is extremely rapid (seconds), a reflection of the fact that the components of the hepatic aspartate aminotransferase reaction are in thermodynamic equilibrium. Our work emphasizes the importance of the GDH reaction in rat liver as a conduit for dissimilating or assimilating ammonia as needed. In contrast, our work shows that the GDH reaction in rat brain appears to operate mostly in the direction of ammonia production (dissimilation). The importance of the GDH reaction as an endogenous source of ammonia in the brain and the relation of GDH to the brain glutamine cycle is discussed. Finally, our work integrates with the increasing use of positron emission tomography (PET) and nuclear magnetic resonance (NMR) to study brain ammonia uptake and brain glutamine, respectively, in normal individuals and in patients with liver disease or other diseases associated with hyperammonemia. PMID:21108979

Cooper, Arthur J. L.

2010-01-01

69

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

NASA Technical Reports Server (NTRS)

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

Basu, S. N.

1984-01-01

70

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

SciTech Connect

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

Senum, G.I.

1992-09-01

71

Vital fluorochromes as tracers for fungal growth studies.  

PubMed

Eight fluorescent dyes were tested for staining the spores or mycelia of six fungi and for their translocation into new growth when the preloaded spores or mycelia were incubated on agar coated coverslips. The dyes studied were Cellufluor, Nile red, fluorescein diacetate (FDA), carboxyfluorescein diacetate (CFDA), chloromethylfluorescein diacetate (CMFDA), aminochloromethyl coumarin (CMAC), and the carbocyamines DiIC18(3) and DiOC18(3). The fungi on which the dyes were tested included Botrytis cinerea, Fusarium oxysporum f.sp. lycopersici, Idriella bolleyi, Pythium oligandrum, Sclerotium cepivorum and Trichoderma harzianum. Most of the fluorochromes gave good initial staining of mycelia or spores; however, FDA fluorescence faded rapidly during excitation, making it impractical for use. Also, the spores and mycelia of B. cinerea and T. harzianum sometimes gave weak fluorescence with Nile red, and the spores and mycelia of I. bolleyi gave unusually weak fluorescence with Cellufluor. There were other variations of staining among the different dye/fungus combinations, but each fungus showed strong fluorescence at least one dye. Cellufluor, CMFDA, CMAC and, to a lesser extent, CFDA and Nile red, were efficiently translocated into new growth from preloaded spores or mycelia, whereas FDA, DiIC18(3) and DiOC18(3) were not. The extent of translocation ranged from 0.1 to 1.2 mm in germ tubes arising from spores, and from 0.9 to 9.2 mm in mycelia extending from dye-loaded agar blocks. The findings suggest that fluorescent dyes could be used as markers or tracers in studies of fungal growth and differentiation. PMID:7578589

Stewart, A; Deacon, J W

1995-03-01

72

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...

73

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-...

74

An SF/sub 6/ tracer study for validation of a Terrain Responsive Atmospheric Code  

SciTech Connect

The use of sulfur hexafluoride as a tracer gas has been ongoing for many years. As technologies have improved in the design of the real-time analyzers, so has the number of possible applications. This is a brief synopsis of one such innovative project that was conducted during the summer of 1987. The purpose of this study was to provide data for the evaluation of a dispersion model called TRAC (Terrain Responsive Atmospheric Code). TRAC is a finite element puff model designed to simulate transport and dispersion in complex terrain. The summertime program conducted by NAWC was the first in a series of four planned tests that would cover different climatological regimes. 1 ref., 5 figs.

Brown, K.; Wilkerson, G.; Porter, R.; Langer, G.; Hodgin, R.

1988-01-01

75

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

76

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

77

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

PubMed Central

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

Shen, Xiong; Zong, Chao; Zhang, Guoqiang

2012-01-01

78

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

79

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

80

Gas transport below artificial recharge ponds: insights from dissolved noble gases and a dual gas (SF6 and 3He) tracer experiment.  

PubMed

A dual gas tracer experiment using sulfur hexafluoride (SF6) and an isotope of helium (3He) and measurements of dissolved noble gases was performed at the El Rio spreading grounds to examine gas transport and trapped air below an artificial recharge pond with a very high recharge rate (approximately 4 m day(-1)). Noble gas concentrations in the groundwater were greater than in surface water due to excess air formation showing that trapped air exists below the pond. Breakthrough curves of SF6 and 3He at two nearby production wells were very similar and suggest that nonequilibrium gas transfer was occurring between the percolating water and the trapped air. At one well screened between 50 and 90 m below ground, both tracers were detected after 5 days and reached a maximum at approximately 24 days. Despite the potential dilution caused by mixing within the production well, the maximum concentration was approximately 25% of the mean pond concentration. More than 50% of the SF6 recharged was recovered by the production wells during the 18 month long experiment. Our results demonstrate that at artificial recharge sites with high infiltration rates and moderately deep water tables, transport times between recharge locations and wells determined with gas tracer experiments are reliable. PMID:15984768

Clark, Jordan F; Hudson, G Bryant; Avisar, Dror

2005-06-01

81

GHOST A Novel Airborne Gas Chromatograph for In Situ Measurements of Long-Lived Tracers in the Lower Stratosphere: Method and Applications  

Microsoft Academic Search

A novel fully-automated airborne gas chromatograph for in situmeasurements of long-lived stratospheric tracers hasbeen developed, combining the high selectivity of a megabore PLOTcapillary column with recently developed sampling and separationtechniques. The Gas cHromatograph for theObservation of Stratospheric Tracers (GHOST)has been successfully operated during three STREAM campaigns(Stratosphere TRoposphere Experiment byAirborne Measurement) onboard a Cessna Citation IIaircraft in two different modes: Either

Oliver Bujok; Viceith Tan; Erich Klein; Ralf Nopper; Reimar Bauer; Andreas Engel; Marie-Theres Gerhards; Armin Afchine; Daniel S. McKenna; Ulrich Schmidt; Frank G. Wienhold; Horst Fischer

2001-01-01

82

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

83

Using Biofuel Tracers to Study Alternative Combustion Regimes  

SciTech Connect

Interest in the use of alternative fuels and combustion regimes is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO{sub 2} emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions, and higher noise. Noise and PM have traditionally been the obstacles toward consumer acceptance of Diesel passenger cars in North America, while NOx (a key component in photochemical smog) has been more of an engineering challenge. Diesels are lean burning (combustion with excess oxygen) and reducing NOx to N2 in an oxygen rich environment is difficult. Adding oxygenated compounds to the fuel helps reduce PM emissions, but relying on fuel alone to reduce PM is unrealistic. Keeping peak combustion temperature below 1700 K prevents NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous Charge Compression Ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to validate combustion modeling.

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

2006-02-14

84

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

85

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

86

Long-term slowdown of river tracer pebbles: Generic models and implications for interpreting short-term tracer studies  

NASA Astrophysics Data System (ADS)

We propose generic approaches to modeling the reduction in mobility that occurs as tracer pebbles seeded on the surface are mixed to less active locations (e.g., beneath the bed or high on bars) or advected downstream to reaches with different shear stress or bed grain size. Advection slowdown, which may be negligible, is quantified using a regression equation relating virtual velocity to tracer and reach properties. Mixing slowdown, which is always present, is simulated using a Markov model of exchanges between three stores and assumptions about relative mean velocities of tracers in each store. The model can be calibrated from a full search on one date and at least a surface search on another date. Calibration to six reaches of Allt Dubhaig, Scotland, in which tracers were mapped after 2 and 8 years, suggests mixing took 3-5 years to approach equilibrium in five reaches and was still proceeding in one. Simulated slowdown through mixing is far greater than that through advection and goes much of the way to explaining the 50% observed reduction in virtual velocity over 8 years compared to 2 years. Implications for the design and comparison of tracer-pebble experiments are considered.

Ferguson, R. I.; Hoey, T. B.

2002-08-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

88

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

89

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

90

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

NASA Astrophysics Data System (ADS)

The residence time of water and suspended particles in Fort Point Channel, a sub-region of Boston Harbor containing a major combined sewer overflow and highly contaminated sediment, was determined during three field surveys by measuring the disappearance of fluorescent tracers from the water column. Flushing by advective movement was quantified using Rhodamine WT dye, a dissolved tracer which has negligible interaction with suspended sediment. The fate of suspended particles was inferred from measured concentrations of fluorescent pigment particles which were initially well mixed with Rhodamine dye and which have a size range and settling velocity comparable to the sewage particles of interest. Dye and particle concentrations were measured by fluorescent spectroscopy of water samples obtained throughout the channel over a week following tracer introduction. Dye measurements indicate that channel water is replaced on a scale of 1-27 days, depending on tidal amplitude and phase during tracer release, and the magnitude of freshwater inflow. Ratios of normalized particle concentration to dye concentration suggest effective deposition velocities of 15-33 m day -1; this is an order of magnitude faster than observed in laboratory settling columns suggesting that removal of suspended tracer particles from Fort Point Channel during our surveys may have been the result of scavenging by a bottom ' fluff ' layer. This finding is consistent with our previous observation of particle deposition in Salem Sound, Massachusetts, U.S.A. and in controlled laboratory studies of particle aggregation at the sediment-water interface.

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

1998-03-01

91

TRACER STUDIES IN HYDROGEN-ADAPTED SCENEDESMUS USING ³H AND ¹⁴C  

Microsoft Academic Search

The radioactive tracers H³ and C¹⁴ were used to study the ; generation, properties and metabolic implications of Scenedesmus hydrogenase. ; The use of tritium in the exchange reaction catalyzed by hydrogenase makes it ; possible to make a direct, in vivo estimate of hydrogenase activity. A ; quantitative and qualitative study of carbon fixation in hydrogen-adapted ; Scenedesmus revealed

Goldsby

1961-01-01

92

The use of Na-22 as a tracer for long-term bone mineral turnover studies.  

NASA Technical Reports Server (NTRS)

Sodium-22 has been studied as a tracer for bone mineral metabolism in rats and dogs. When incorporated into bone during growth from birth to adulthood, the bone becomes uniformly tagged with Na-22, which is released through the metabolic turnover of the bone. The Na-22 not incorporated in the bone matrix is rapidly excreted within a few days when animals are fed high, but nontoxic levels of NaCl. The Na-22 tracer can be used to measure bone mineral loss in animals during space flight and in research on bone disease.

Palmer, H. E.; Rieksts, G. A.; Palmer, R. F.; Gillis, M. F.

1979-01-01

93

The 3H-leucine tracer: its use in kinetic studies of plasma lipoproteins.  

PubMed

3H-leucine administered as a bolus has been widely used as a tracer in kinetic investigations of protein synthesis and secretion. After intravenous injection, plasma specific radioactivity decays over several orders of magnitude during the first half-day, followed by a slow decay lasting a number of weeks that results from recycling of the leucine tracer as proteins are degraded and 3H-leucine reenters the plasma pool. In studies in which kinetic data are analyzed by mathematical compartmental modeling, plasma leucine activity is generally used as a forcing function to drive the input of 3H-leucine into the protein synthesis pathway. 3H-leucine is an excellent tracer during the initial hours of rapidly decreasing plasma activity; thereafter, reincorporation of recycled tracer into new protein synthesis obscures the tracer data from proteins with slower turnover rates. Thus, for proteins such as plasma albumin and apolipoprotein (apo) A-I, this tracer is unsatisfactory for measuring fractional catabolic (FCR) and turnover rates. By contrast, the kinetics of plasma very-low-density lipoprotein (VLDL)-apoB, a protein with a residence time of approximately 5 hours, are readily measured, since kinetic parameters of this protein can be determined by the time plasma leucine recycling becomes established. However, measurement of VLDL-apoB specific radioactivity extending up to 2 weeks provides further data on the kinetic tail of VLDL-apoB. Were plasma leucine a direct precursor for the leucine in VLDL-apoB, the kinetics of the plasma tracer should determine the kinetics of the protein. However, this is not the case, and the deviations from linearity are interpreted in terms of (1) the dilution of plasma leucine in the liver by unlabeled dietary leucine; (2) the recycling of hepatocellular leucine from proteins within the liver, where recycled cellular leucine does not equilibrate with plasma leucine; and (3) a "hump" in the kinetic data of VLDL-apoB, which we interpret to reflect recycling or retention of a portion of the apoB protein within the hepatocyte, with its subsequent secretion. Because hepatocellular tRNA is the immediate precursor for synthesis of these secretory proteins, its kinetics should be used as the forcing function to drive the modeling of this system. The VLDL-apoB tail contains the information needed to modify the plasma leucine data, to provide an appropriate forcing function when using 3H-leucine as a tracer of apolipoprotein metabolism. This correction is essential when using 3H-leucine as a tracer for measuring low-density lipoprotein (LDL)-apoB kinetics. The 3H-leucine tracer also highlights the importance of recognizing the difference between plasma and system residence times, the latter including the time the tracer resides within exchanging extravascular pools. The inability to determine these fractional exchange coefficients for apoA-I and albumin explains the failure of this tracer in kinetic studies of these proteins. For apoB-containing lipoproteins, plasma residence times are generally determined, and these measurements can be made satisfactorily with 3H-leucine. PMID:9054478

Fisher, W R; Venkatakrishnan, V; Fisher, E S; Stacpoole, P W; Zech, L A

1997-03-01

94

Stable isotopes applied as water tracers in column and field studies  

Microsoft Academic Search

The stable isotopes deuterium (2H, D) and oxygen 18 (18O) were applied in water for use as tracers in column experiments and in two field studies. Their performance was compared against uranine and was used to characterize saturated and unsaturated water movement and depths of plant water uptake. Deuterium and 18O are completely soluble and chemically and biologically stable. They

Paul Koeniger; Christian Leibundgut; Timothy Link; John D. Marshall

2010-01-01

95

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

E-print Network

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

Eicken, Hajo

96

Glomerular permeability: In vivo tracer studies with polyanionic and polycationic ferritins  

Microsoft Academic Search

Glomerular permeability: In vivo tracer studies with polyanionic and polycationic ferritins. The influence of molecular charge on glomerular permeability to the globular ferritin molecule in vivo was investigated. Mice (Charles River CD strain) and rats (Munich-Wistar strain) were injected intravenously either with native anionic ferritin or various cationized derivatives with different isoelectric points (pI) and the kidneys were examined by

Helmut G Rennke; Manjeri A Venkatachalam

1977-01-01

97

Vascular permeability and hyperpermeability in a murine adenocarcinoma after fractionated radiotherapy: an ultrastructural tracer study  

Microsoft Academic Search

Large radiation doses cause postradiation vascular hyperpermeability by disrupting endothelia. The cumulative sequences of small doses (fractionated radiotherapy) standard in clinical practice cause it too, but not by endothelial disruption: the mechanisms are unknown. In this study, correlated fluorescent and ultrastructural localisation of a tracer revealed the architecture, fine structure and function of microvessels in mouse AT17 tumours, before and

Paul L. Debbage; Sonja Seidl; Alfons Kreczy; Peter Hutzler; Margit Pavelka; Peter Lukas

2000-01-01

98

Isotopic Tracer Studies of Reaction Pathways for Propane Oxidative Dehydrogenation on Molybdenum Oxide Catalysts  

E-print Network

Isotopic Tracer Studies of Reaction Pathways for Propane Oxidative Dehydrogenation on Molybdenum of propane over ZrO2-supported MoOx catalysts. Competitive reactions of C3H6 and CH3 13 CH2CH3 showed combustion of propene, or by direct combustion of propane. A mixture of C3H8 and C3D8 undergoes oxidative

Iglesia, Enrique

99

USING CONTINUOUS MONITORS FOR CONDUCTING TRACER STUDIES IN WATER DISTRIBUTION SYSTEMS  

EPA Science Inventory

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

100

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

SciTech Connect

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

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

2013-12-01

101

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

NASA Astrophysics Data System (ADS)

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

Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

2014-05-01

102

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

PubMed

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

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

2013-04-16

103

Radio-tracer techniques for the study of flow in saturated porous materials  

USGS Publications Warehouse

An experiment was conducted by the U.S. Geological Survey to determine the feasibility of using a radioactive substance as a tracer in the study of microscopic flow in a saturated porous solid. A radioactive tracer was chosen in preference to dye or other chemical in order to eliminate effects of the tracer itself on the flow system such as those relating to density, viscosity and surface tension. The porous solid was artificial "sandstone" composed of uniform fine grains of sand bonded together with an epoxy adhesive. The sides of the block thus made were sealed with an epoxy coating compound to insure water-tightness. Because of the chemical inertness of the block it was possible to use radioactive phosphorus (P32). Ion-exchange equilibrium was created between the block and nonradioactive phosphoric acid. Then a tracer tagged with P32 was injected into the block in the desired geometric configuration, in this case, a line source. After equilibrium in isotopic exchange was reached between the block and the line source, the block was rinsed, drained and sawn into slices. It was found that a quantitative analysis of the flow system may be made by assaying the dissected block. ?? 1961.

Skibitzke, H.E.; Chapman, H.T.; Robinson, G.M.; McCullough, R.A.

1961-01-01

104

Nested Tracer Studies In Catchment Hydrology: Towards A Multiscale Understanding of Runoff Generation and Catchment Funtioning  

NASA Astrophysics Data System (ADS)

Geochemical and isotopic tracers have been shown to have widespread utility in catch- ment hydrology in terms of identifying hydrological source areas and characterising residence time distributions. In many cases application of tracer techniques has pro- vided insights into catchment functioning that could not be obtained from hydromet- ric and/or modelling studies alone. This paper will show how the use of tracers has contributed to an evolving perceptual model of hydrological pathways and runoff gen- eration processes in catchments in the Scottish highlands. In particular the paper will focus on the different insights that are gained at three different scales of analysis; (a) nested sub-catchments within a mesoscale (ca. 200 square kilometers) experimen- tal catchment; (b) hillslope-riparian interactions and (c) stream bed fluxes. Nested hydrometric and hydrochemical monitoring within the mesoscale Feugh catchment identified three main hydrological response units: (i) plateau peatlands which gener- ated saturation overland flow in the catchment headwaters, (ii) steep valley hillslopes which drain from the plateaux into (iii) alluvial and drift aquifers in the valley bottoms. End Member Mixing Analysis (EMMA) in 8 nested sub-catchments indicated that that stream water tracer concentrations can be modelled in terms of 2 dominant runoff pro- cesses; overland flow from the peat and groundwater from the drift aquifers. Ground- water contributions generally increased with catchment size, though this was moder- ated by the characteristics of individual sub-basins, with drift cover being particularly important. Hillslope riparian interactions were also examined using tracers, hydromet- ric data and a semi-distributed hydrological model. This revealed that in the glaciated, drift covered terrain of the Scottish highlands, extensive valley bottom aquifers effec- tively de-couple hillslope waters from the river channel. Thus, riparian groundwater appears to significantly contribute to storm runoff as well as sustain base flows. Water from steeper hillslopes appears to primarily recharge valley bottom aquifers. Fluxes from the drift aquifers into the stream bed were investigated using hydrometric and tracer techniques. Groundwater fluxes through the stream bed appear to be relatively localized relating to geological boundaries or changes in drift characteristics. How- ever, these fluxes are also controlled by morphological features in the river channel which exert a strong control on localized groundwater U surface water interactions. 1 If catchment hydrology is to contribute to a functional understanding of freshwater ecosystems it is argued that integrated tracer studies, at different scales and incorpo- rating both observations from field work and modelling applications, have a key role to play. 2

Soulsby, C.; Rodgers, P.; Malcolm, I. A.; Dunn, S.

105

Brainstem organization of efferent projections to the guinea pig cochlea studied using the fluorescent tracers fast blue and diamidino yellow  

Microsoft Academic Search

Intracochlear injection of the fluorescent retrograde neuronal tracers fast blue and diamidino yellow was used to investigate the distribution within the brainstem of neurones projecting to the cochlea in the guinea pig. The overall pattern of distribution of cells within the brainstem auditory nuclei was the same for both tracers and was also in broad agreement with recent studies in

D. Robertson; K. S. Cole; A. R. Harvey

1987-01-01

106

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

107

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

108

Sample site selection for tracer studies applying a unidirectional circulatory approach  

SciTech Connect

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

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

1987-08-01

109

A novel $^{83\\mathrm{m}}$Kr tracer method for characterizing xenon gas and cryogenic distillation systems  

E-print Network

The radioactive isomer $^{83\\mathrm{m}}$Kr has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and $\\gamma$-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state $^{83}$Kr, one does not risk contamination of any low-background experiment with long- lived radionuclides. In this paper, we present two new applications of $^{83\\mathrm{m}}$Kr. It can be used as a radioactive tracer in noble gases to characterize the particle flow inside of gas routing systems. A method of doping $^{83\\mathrm{m}}$Kr into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. This technique has been used to determine the circulation speed of gas particles inside of a gas purification system for xenon. Furthermore, 83m Kr can be used to...

Rosendahl, S; Brown, E; Cristescu, I; Fieguth, A; Huhmann, C; Lebeda, O; Levy, C; Murra, M; Schneider, S; Vnos, D; Weinheimer, C

2014-01-01

110

A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish  

NASA Astrophysics Data System (ADS)

A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD + WSD, KMD + KV, and KMD + WSD + KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i.e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace. The breakthrough time and peak concentration of RTD curves of model predictions and water modeling results showed a good agreement (all difference within 12.5 pct) for the 100, 150, and 250 mL KCl cases.

Chen, Chao; Jonsson, Lage Tord Ingemar; Tilliander, Anders; Cheng, Guoguang; Jnsson, Pr Gran

2014-09-01

111

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

NASA Astrophysics Data System (ADS)

Tritium tracer techniques are applied to observe behavior of hydrogen (tritium (T)) in near surface regions of Mo and W loaded by gaseous absorption (GAS) and a glow discharge (GDC). GDC produces blisters on both Mo and W surfaces and Tritium Auto-RadioGraph (TARG) showed the thickness of blister skins is larger than the escaping depth of T ?-electrons, around 1 ?m. For GAS specimens, T evolution is likely controlled by diffusion giving diffusion coefficients of, D=1.510-7exp-{41 kJ/mol}/{RT} m s D=4.310-9exp-{38 kJ/mol}/{RT} m s at 273-323 K. GDC specimens show much smaller diffusion coefficients with higher activation energies and T release continues very long, suggesting T release from blisters.

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

2011-10-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

113

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

SciTech Connect

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

Lagunas-Solar, M.C.

1995-02-15

114

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

115

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

Microsoft Academic Search

We present the results of the first HCO+ survey probing the dense molecular gas content of a sample of 16 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). Previous work, based on HCN (1-0) observations, had shown that LIRGs and ULIRGs possess a significantly higher fraction of dense molecular gas compared to normal galaxies. While the picture issued from HCO+

J. Graci-Carpio; S. Garca-Burillo; P. Planesas; L. Colina

2006-01-01

116

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. PMID:21072595

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

2010-01-01

117

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

SciTech Connect

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

Logan, J.

2001-04-02

118

Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation  

E-print Network

Observations have revealed prodigious amounts of star formation in starburst galaxies as traced by dust and molecular emission, even at large redshifts. Recent work shows that for both nearby spiral galaxies and distant starbursts, the global star formation rate, as indicated by the infrared luminosity, has a tight and almost linear correlation with the amount of dense gas as traced by the luminosity of HCN. Our surveys of Galactic dense cores in HCN 1-0 emission show that this correlation continues to a much smaller scale, with nearly the same ratio of infrared luminosity to HCN luminosity found over 7-8 orders of magnitude in L_IR, with a lower cutoff around 10^{4.5} L_sun of infrared luminosity. The linear correlation suggests that we may understand distant star formation in terms of the known properties of local star-forming regions. Both the correlation and the luminosity cutoff can be explained if the basic unit of star formation in galaxies is a dense core, similar to those studied in our Galaxy.

Jingwen Wu; Neal J. Evans II; Yu Gao; Philip M. Solomon; Yancy L. Shirley; Paul A. Vanden Bout

2005-11-15

119

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

SciTech Connect

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

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

2014-01-01

120

Adenylate pool and radiological tracer studies of the metabolism of micro-metazoans of the sulfide system  

E-print Network

ADENYLATE POOL AND RADIOLOGICAL TRACER STUDIES OF THE METABOLISM OF MICRO-METAZOANS OF THE SULFIDE SYSTEM A Thesis by CATHERINE ALICE FOX Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE August 1985 Major Subject: Oceanography ADENYLATE POOL AND RADIOLOGICAL TRACER STUDIES OF THE METABOLISM OF MICRO-METAZOANS OF THE SULFIDE SYSTEM A Thesis by CATHERINE ALICE FOX Approved as to style and content by...

Fox, Catherine Alice

2012-06-07

121

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. PMID:16232323

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

2005-01-01

122

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

NASA Astrophysics Data System (ADS)

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

Pera, Sebastian; Marzocchi, Roberto; Bronzini, Simona

2014-05-01

123

Polycyclic aromatic hydrocarbon ionization as a tracer of gas flows through protoplanetary disk gaps  

NASA Astrophysics Data System (ADS)

Context. Planet-forming disks of gas and dust around young stars contain polycyclic aromatic hydrocarbons (PAHs). Aims: We aim to characterize how the charge state of PAHs can be used as a probe of flows of gas through protoplanetary gaps. In this context, our goal is to understand the PAH spectra of four transitional disks. In addition, we want to explain the observed correlation between PAH ionization (traced by the I6.2/I11.3 feature ratio) and the disk mass (traced by the 1.3 mm luminosity). Methods: We implement a model to calculate the charge state of PAHs in the Monte Carlo radiative transfer code MCMax. The emission spectra and ionization balance are calculated in the parameter space set by the properties of the star and the disk. Results: A benchmark modeling grid is presented that shows how PAH ionization and luminosity behave as a function of star and disk properties. The PAH ionization is most sensitive to ultraviolet (UV) radiation and the electron density. In optically thick disks, where the UV field is low and the electron density is high, PAHs are predominantly neutral. Ionized PAHs trace low-density optically thin disk regions where the UV field is high and the electron density is low. Such regions are characteristic of gas flows through the gaps of transitional disks. We demonstrate that fitting the PAH spectra of four transitional disks requires a contribution of ionized PAHs in "gas flows" through the gap. Conclusions: The PAH spectra of transitional disks can be understood as superpositions of neutral and ionized PAHs. For HD 97048, neutral PAHs in the optically thick disk dominate the spectrum. In the cases of HD 169142, HD 135344 B and Oph IRS 48, small amounts of ionized PAHs located in the "gas flows" through the gap are strong contributors to the total PAH luminosity. The observed trend in the sample of Herbig stars between the disk mass and PAH ionization may imply that lower-mass disks have larger gaps. Ionized PAHs in gas flows through these gaps contribute strongly to their spectra.

Maaskant, K. M.; Min, M.; Waters, L. B. F. M.; Tielens, A. G. G. M.

2014-03-01

124

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

SciTech Connect

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

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

1995-07-01

125

New tracers identify hydraulic fracturing fluids and accidental releases from oil and gas operations.  

PubMed

Identifying the geochemical fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil and gas reservoirs has important applications for assessing hydrocarbon resource recovery, environmental impacts, and wastewater treatment and disposal. Here, we report for the first time, novel diagnostic elemental and isotopic signatures (B/Cl, Li/Cl, ?(11)B, and ?(7)Li) useful for characterizing hydraulic fracturing flowback fluids (HFFF) and distinguishing sources of HFFF in the environment. Data from 39 HFFFs and produced water samples show that B/Cl (>0.001), Li/Cl (>0.002), ?(11)B (25-31) and ?(7)Li (6-10) compositions of HFFF from the Marcellus and Fayetteville black shale formations were distinct in most cases from produced waters sampled from conventional oil and gas wells. We posit that boron isotope geochemistry can be used to quantify small fractions (?0.1%) of HFFF in contaminated fresh water and likely be applied universally to trace HFFF in other basins. The novel environmental application of this diagnostic isotopic tool is validated by examining the composition of effluent discharge from an oil and gas brine treatment facility in Pennsylvania and an accidental spill site in West Virginia. We hypothesize that the boron and lithium are mobilized from exchangeable sites on clay minerals in the shale formations during the hydraulic fracturing process, resulting in the relative enrichment of boron and lithium in HFFF. PMID:25327769

Warner, N R; Darrah, T H; Jackson, R B; Millot, R; Kloppmann, W; Vengosh, A

2014-11-01

126

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

USGS Publications Warehouse

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

Busenberg, Eurybiades; Plummer, L. Niel

2010-01-01

127

Using trees to remediate tritium contaminated groundwater: a modeling and tracer study.  

SciTech Connect

Rebel, Karin, T. 2004. Using trees to remediate tritium contaminated groundwater: a modeling and tracer study. Ph.D Dissertation. Cotnell University. Ithaca, New York. 174 pp. Abstract: We have developed a spatially explicit model of water and tritium fluxes in the vadose zone in order to simulate water uptake and subsurface lateral movement in coniferous and mixed hardwood - coniferous forests on Coastal Plain soils of the southern United States. These Coastal Plain soils are characteristically sand overlying slowly permeable clays found at depths of 30 to 200 cm, and can form temporarily saturated, unconfined aquifers. Ten hectares of the modeled watershed was periodically irrigated with tritium enriched water. We used the tritium enriched water as a tracer to validate the model. The model was used to optimize irrigation, to evaluate the amount of tritium entering the atmosphere due to evapotranspiration and to quantify water and tritium fluxes in texture contrast soils. Using tritium as a tracer, we have studied how tree species and canopy position effect water and solutes uptake from different parts of the soil profile. We clipped branches to obtain leaf water from over-and understory laurel oak (Quercus Laurifolia) and over- and understory pine (Pinus elliottii and Pinus taeda), which was then analyzed for tritium. We found that for early successional trees (Pinus spp.) and trees in the overstory proportionally more water was taken up from deeper in the soil compared to the hardwoods or trees in the understory, which took up proportionally more water from the soil surface. These differences are important for understanding competition for resources within a forest and in predicting the hydrologic response to forest management practices such as thinning.

Rebel, Karin, Theodora

2004-01-01

128

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

SciTech Connect

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

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

1999-07-15

129

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

130

New Constraints on Protostellar Jet Collimation from High-Density Gas UV Tracers  

NASA Astrophysics Data System (ADS)

The analysis of high-resolution profiles of the semiforbidden UV lines of C III]1908 and Si III]1892 in the spectra of T Tauri stars (TTSs) shows the following: (1) There is C III]1908 and Si III]1892 emission at velocities that are similar to those observed in the optical forbidden lines formed in the TTSs jets. The luminosity of the UV lines is comparable to that of the optical lines. (2) The comparison between the optical and UV light curves indicates that the C III]1908 and Si III]1892 emission of RY Tau is not associated with accretion shocks, but it is produced farther than 2 R* from the star. (3) The profiles of the UV semiforbidden lines are significantly broader than those of the optical forbidden lines. These profiles cannot be produced in a narrow collimated beam, and they are most likely produced in a bow-shaped shock wave formed at the base of the optical jet, where the hot gas emits in a broad range of projected radial velocities. (4) The atmosphere of RU Lup contributes significantly to the Si III]1892 emission. (5) A puzzling narrow feature is observed close to the C III]1908 line. The feature is blueshifted by -260 km s-1, which corresponds to the wind terminal velocity measured in the P Cygni profile of the Mg II (UV1) lines. Moreover, constraints are derived on the characteristics of the C III]1908 and Si III]1892 emitting region in RY Tau. It is shown that 4.7<=logTe<=5.0 and 109 cm-3<=Ne<=1011 cm-3 provided that the emission is produced in a collisional plasma and that the 1665 feature observed in low-dispersion International Ultraviolet Explorer (IUE) spectra is confirmed to be O III]1665 emission produced in the wind. These very high densities are difficult to generate in the shocks produced by the magnetic pinching of centrifugally driven magnetized disk winds. The data also suggest that the shocked layer has a radius of some few stellar radii and it is closer than ~38 R* to the star. Based on observations made with the International Ultraviolet Explorer (IUE) and with the NASA/ESA Hubble Space Telescope obtained from the HST data archive at the Space Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555.

Gmez de Castro, Ana I.; Verdugo, Eva

2001-02-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

132

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

133

Separation of Emitted and Photochemical Formaldehyde in the Mexico City Metropolitan Area using a Statistical Analysis and a New Pair of Gas-phase Tracers  

NASA Astrophysics Data System (ADS)

In urban air, the presence of formaldehyde (HCHO) is the result of direct emissions from mobile sources (primary HCHO) and of its production by photochemical oxidation of volatile organic compounds (VOC) in the atmosphere (secondary HCHO). HCHO is a known carcinogen, and is further capable to jump-start photochemical smog formation. Pollution control strategies require deconvolution of the amounts of HCHO formed from primary and secondary sources. To separate primary, secondary and background HCHO, a statistical regression analysis of the time series of HCHO from pairs of gas-phase tracer molecules was undertaken. Carbon monoxide (CO) was used as tracer for primary sources; Two different species were compared as tracers for secondary HCHO: glyoxal (CHOCHO) and ozone (O3). These time series were measured at the field campaign supersite located at the National Center for Environmental Research and Training (CENICA) in the Mexico City Metropolitan Area during the MCMA-2003 campaign. In addition, background HCHO measurements were performed outside the city. Correlation coefficients were highest for the CHOCHO-CO tracer pair, indicating that CHOCHO is a better tracer for secondary sources than O3, used previously for this purpose. Results of the analysis are presented for the pre-Easter, Easter week and post-Easter periods. Further, the effect of temperature on the primary and secondary HCHO sources is assessed. On a 24-hour average basis, secondary sources dominate over primary sources. However, during sunrise, when HCHO acts as a radical source to jump-start photochemistry, a significant amount of the HCHO is associated with primary emissions.

Garcia, A.; Volkamer, R.; Molina, L. T.; Molina, M. J.; Samuelsson, J.; Mellqvist, J.; Galle, B.; Herndon, S.; Kolb, C. E.

2004-12-01

134

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

Microsoft Academic Search

The residence time of water and suspended particles in Fort Point Channel, a sub-region of Boston Harbor containing a major combined sewer overflow and highly contaminated sediment, was determined during three field surveys by measuring the disappearance of fluorescent tracers from the water column. Flushing by advective movement was quantified using Rhodamine WT dye, a dissolved tracer which has negligible

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

1998-01-01

135

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

SciTech Connect

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

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

1991-10-01

136

Tracer Testing for Estimating Heat Transfer Area in Fractured Reservoirs  

SciTech Connect

A key parameter governing the performance and life-time of a Hot Fractured Rock (HFR) reservoir is the effective heat transfer area between the fracture network and the matrix rock. We report on numerical modeling studies into the feasibility of using tracer tests for estimating heat transfer area. More specifically, we discuss simulation results of a new HFR characterization method which uses surface-sorbing tracers for which the adsorbed tracer mass is proportional to the fracture surface area per unit volume. Sorption in the rock matrix is treated with the conventional formulation in which tracer adsorption is volume-based. A slug of solute tracer migrating along a fracture is subject to diffusion across the fracture walls into the adjacent rock matrix. Such diffusion removes some of the tracer from the fluid in the fractures, reducing and retarding the peak in the breakthrough curve (BTC) of the tracer. After the slug has passed the concentration gradient reverses, causing back-diffusion from the rock matrix into the fracture, and giving rise to a long tail in the BTC of the solute. These effects become stronger for larger fracture-matrix interface area, potentially providing a means for estimating this area. Previous field tests and modeling studies have demonstrated characteristic tailing in BTCs for volatile tracers in vapor-dominated reservoirs. Simulated BTCs for solute tracers in single-phase liquid systems show much weaker tails, as would be expected because diffusivities are much smaller in the aqueous than in the gas phase, by a factor of order 1000. A much stronger signal of fracture-matrix interaction can be obtained when sorbing tracers are used. We have performed simulation studies of surface-sorbing tracers by implementing a model in which the adsorbed tracer mass is assumed proportional to the fracture-matrix surface area per unit volume. The results show that sorbing tracers generate stronger tails in BTCs, corresponding to an effective enhancement of diffusion. Tailing in BTCs for sorbing tracers may provide adequate sensitivity for quantifying the fracture-matrix interface area. We discuss requirements for tracer sorption and present considerations for designing a tracer test that would determine fracture-matrix interface area.

Pruess, Karsten; van Heel, Ton; Shan, Chao

2004-05-12

137

Tracer diffusion in colloidal gels  

E-print Network

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

Sujin Babu; Jean Christophe Gimel; Taco Nicolai

2007-05-09

138

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

PubMed

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

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

2014-07-16

139

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

ERIC Educational Resources Information Center

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

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

2012-01-01

140

Attenuation and transport of atrazine and picloram in an alluvial gravel aquifer: A tracer test and batch study  

Microsoft Academic Search

A natural?gradient tracer experiment and laboratory batch tests were conducted to study attenuation and transport of atrazine and picloram in an alluvial gravel aquifer. An analytical transport model, AT123D, was used to analyse the field data. Data analysis suggests that there was no retardation and degradation of atrazine and picloram in the aquifer over a distance of 90 m within

Liping Pang; Murray E. Close

1999-01-01

141

Isotopic Tracer Studies of Propane Reactions on H-ZSM5 Zeolite Joseph A. Biscardi and Enrique Iglesia*  

E-print Network

Isotopic Tracer Studies of Propane Reactions on H-ZSM5 Zeolite Joseph A. Biscardi and Enrique unlabeled products from mixtures of propene and propane-2-13C reactants. Aromatic products of propane-2-13C-Parmer) that allowed differential reactor operation (propane reactions were

Iglesia, Enrique

142

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

EPA Science Inventory

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

143

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

NASA Astrophysics Data System (ADS)

The gravel aquifer of the Southern Vienna Basin is a very important backup drinking water resource for the city of Vienna. A discharge location, the Fischa-Dagnitz spring in the Southern Vienna Basin, Austria, was re-investigated in 2011, five years after the gas exchange tracer test published in (Stolp et al., 2010), and sampled for stable isotopes 18O/2H, tritium, 3He, SF6 and 85Kr (Gerber et al., 2012). Additionally, new tritium time series data (Davis et al., 1967), previously not considered in Stolp et al. (2010), were included. These show a higher and earlier tritium peak of >300 TU in 1965 in the discharge of the Fischa-Dagnitz spring as compared to 221 TU in 1972 considered in Stolp et al. (2010). The new 3He, SF6 and 85Kr gas tracer data from 2011 confirm the earlier finding for 3He of Stolp et al. (2010) and indicate a more recent equilibration with the atmosphere than the water bound tracers 18O, 2H and tritium. A new modelling attempt using the Lumpy code (Suckow, 2012) confirmed the discrepancy between the tritium data and the gaseous tracers 3He, SF6 and 85Kr. No steady-state combination of local recharge (represented by an exponential model) and Schwarza river infiltration flowing through the gravel aquifer (represented by a parallel dispersion model) can equally well explain both the tritium time series and the gas tracer results. A revised conceptual model proposes that a pinching of the aquifer at unconformities in the gravel body or a fault zone known in the gravel body forces groundwater along the flow path closer to the surface and exposes it to the atmosphere. This would tend to reset the "dating" clock for the gaseous tracers 3He, SF6 and 85Kr, which can equilibrate quickly with the atmosphere, but not for tritium, which marks the transport behaviour of the water itself. These findings are of importance also for other multi-tracer assessments of groundwater movement in phreatic aquifer systems. References: Davis, G.H., Payne, B.R., Dincer, T., Florkowski, T., Gattinger, T., 1967. Seasonal Variations in the Tritium Content of Groundwaters of the Vienna Basin, Austria, Isotope Hydrology 1967. IAEA, Vienna, Austria, IAEA, Vienna, Austria, pp. 451-473. Gerber, C., Purtschert, R., Kralik, M., Humer, F., Sltenfuss, J., Darling, G.W., Gooddy, D., 2012. Suitability and potential of environmental tracers for base-flow determination in streams: EGU2012-14066, EGU 12. European Geosciences Union, Vienna Stolp, B.J., Solomon, D.K., Suckow, A., Vitvar, T., Rank, D., Aggarwal, P.K., Han, L.-F., 2010. Age dating base flow at springs and gaining streams using helium-3 and tritium: Fischa-Dagnitz system, southern Vienna Basin, Austria. Water Resources Research 46. Suckow, A., 2012. Lumpy - an interactive Lumped Parameter Modeling code based on MS Access and MS Excel., EGU 12. European Geosciences Union, Vienna

Suckow, Axel; Gerber, Christoph; Kralik, Martin; Sltenfuss, Jrgen; Purtschert, Roland

2013-04-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

145

Use of 75Se tracer and autoradiographic techniques in the study of schistosomiasis.  

PubMed

The paper provides an overview of recent studies on the use of 75Se to tag larval schistosomes and to monitor their migration and distribution patterns in naive mice and those previously exposed to cercariae. The principles and techniques of radioassay and autoradiography in studying various aspects of 75Se-labelled larval schistosomes are described. The main shortcoming of radioassay in monitoring location and movement of labelled schistosomula is that some of the label dissociates from the schistosomula and accumulates in host tissues, notably the liver. Dissociated label is indistinguishable from schistosomula-bound label making monitoring of parasite migration extremely difficult. This difficulty is overcome by compressed tissue autoradiography where labelled schistosomula can be seen as reduced silver foci on an autoradiographic film, whereas dissociated label is too diffusely distributed to produce such reduced silver foci. Furthermore, using autoradiography, quantitative information on parasite migration in normal and immunized laboratory animals can be obtained that would be impossible using traditional recovery techniques. In addition to using 75Se tracer in migration studies, the radio-isotope has potential for elucidating various aspects of schistosome transmission ecology and snail population dynamics in natural waters. PMID:3064034

Chandiwana, S K

1988-12-01

146

Developing, Coupling, and Applying a Gas, Aerosol, Transport, and Radiation Model to Study Urban and Regional Air Pollution  

Microsoft Academic Search

This thesis discusses the development of a gas, aerosol, transport, and radiation air quality model (GATOR), the coupling of GATOR to a mesoscale meteorological and tracer dispersion model (MMTD), and the application of the resulting GATOR\\/MMTD air pollution modeling system (APMS) to studies of gas and aerosol pollution buildup in the Los Angeles Basin. GATOR consists of computer algorithms that

Mark Zachary Jacobson

1994-01-01

147

The Santa Monica Basin Tracer Experiment - A study of diapycnal and isopycnal mixing  

NASA Technical Reports Server (NTRS)

Cross isopycnal (diapycnal) and lateral mixing and stirring below the sill of Santa Monica Basin were studied by releasing two tracers, sulfur hexafluoride and perfluorodecalin, as close as possible to an isopycnal surface and measuring their subsequent dispersion. The target for the release was a potential temperature surface at about 790 m depth, roughly 100 m above the bottom and 50 m below the sill. Three surveys, performed immediately after, about 7 weeks after, and about 6 months after the release, showed that the time scales for lateral stirring and mixing in the basin were between 2 and 5 months. The diapycnal diffusivity for the whole period was found to be 0.29 + or - 0.06 sq cm/s near the injection surface, where the buoyancy frequency was about 1.1 cph. This estimate may include some mixing in the turbulent boundary layer near the walls of the basin. The best estimate for the diapycnal diffusivity in the basin interior is 0.25 + or - 0.08 sq cm/s.

Ledwell, James R.; Watson, Andrew J.

1991-01-01

148

Dual-tracer scintigraphy and subtraction studies in the diagnosis of hepatocellular carcinoma  

SciTech Connect

Dual tracer scintigraphy (DTS) (technetium 99m (/sup 99m/Tc) sulfur colloid and gallium 67 citrate (67-gallium citrate)) of the liver and computer subtraction studies (SS) were performed in 26 patients subsequently proven to have hepatocellular carcinoma (HCC) and 32 patients with cirrhosis and focal defects on the colloid scan, with no evidence for HCC after a complete evaluation and a 2-year follow-up period. Both DTS and SS had a sensitivity of 96% and a specificity of 90.6% for HCC. There were three false positive cases (9.4%), two of which were occult abscesses. The predictive value of a positive test was 89% and that of a negative test was 97%. The smallest tumor detected measured 2 cm in diameter and was only visualized with the SS. In the clinical setting, when HCC is suspected (a situation in which tumors are usually larger than 2 cm and the pretest probability of disease is between 20% and 60%) the DTS and SS is an excellent test for the diagnosis or exclusion of HCC. It does not appear to have a role in screening programs.

Sostre, S.; Villagra, D.; Morales, N.E.; Rivera, J.V.

1988-02-15

149

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

150

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

USGS Publications Warehouse

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (318 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 Nha-1yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

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

2012-01-01

151

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

Microsoft Academic Search

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

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

2003-01-01

152

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

Microsoft Academic Search

Tracer kinetic modeling with dynamic contrast enhanced MRI (DCE-MRI) and the quantification of the kinetic parameters are active fields of research which have the potential to improve the measurement of renal function. However, the strong coronal motion of the kidney in the time series inhibits an accurate assessment of the kinetic parameters. Automatic motion correction is challenging due to the

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

2008-01-01

153

The blood-nerve barrier: an in vivo lanthanum tracer study.  

PubMed

The permeability of the blood-nerve barrier was investigated using ionic lanthanum as an electron-dense tracer. The rat sural nerve was microinjected in vivo with lanthanum nitrate solution either into the endoneurial space or into the epineurium. Five to sixty minutes after injection the sural nerves were fixed by vascular perfusion or immersion. Using electron microscopy, lanthanum tracer was observed to be associated with endoneurial vessels in the perivascular spaces, in the inter-endothelial clefts and within the lumina. Furthermore, tracer was present in the spaces between adjacent endothelial cell layers and within vesicles and caveolae of endothelial cells. Epineurial vessels showed a similar distribution of tracer deposits but in greater quantities in inter-endothelial cell spaces and vessel lumina. The results are considered to demonstrate an absence of a blood-nerve barrier to ions as exemplified by lanthanum and are compatible with data from physiological experiments. The blood-nerve and blood-brain barriers are contrasted in their permeability to ions, their related fine structure and their physiological roles. PMID:3446663

MacKenzie, M L; Ghabriel, M N; Allt, G

1987-10-01

154

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

155

Brilliant Blue FCF as a Dye Tracer for Solute Transport StudiesA Toxicological Overview  

Microsoft Academic Search

Brilliant Blue FCF (C.I. 42090) was found to be a useful dye tracer to stain the flow paths of water in soil media. Being neutral or anionic, it is not strongly adsorbed by negatively charged soil constituents. The dye is used in food because its general toxicity is low. However, to stain the flow paths of water in soil, fairly

Markus Flury; Hannes Fltihler

1994-01-01

156

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

157

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

Microsoft Academic Search

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

John F. White; Dorothy Ellingsen; Kevin Burnup

1984-01-01

158

Using mass measurements in tracer studies--a systematic approach to efficient modeling.  

PubMed

Tracer enrichment data are fitted by multicompartmental models to estimate rate constants and fluxes or transport rates. In apolipoprotein turnover studies, mass measurements are also available, for example, apolipoprotein B levels in very low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein, and are often essential to calculate some of the rate constants. The usual method to use mass measurements is to estimate pool masses along with rate constants. A systematic alternative approach is developed to use flux balances around pools to express some rate constants in terms of the other rate constants and the measured masses. The resulting reduction in the number of parameters to be estimated makes the modeling more efficient. In models that would be unidentifiable without mass measurements, the usual approach and the proposed approach yield identical results. In a simple two-pool model, the number of unknown parameters is reduced from 4 to 2. In a published five-pool model for apolipoprotein B kinetics with three mass measurements, the number of parameters is reduced from 12 to 9. With m mass measurements, the number of responses to be fitted and the number of parameters to be estimated are each reduced by m, a simplification by 1/4 to 1/3 in a typical pool model. Besides a proportionate reduction in computational effort, there is a further benefit because the dimensionality of the problem is also decreased significantly, which means ease of convergence and a smaller likelihood of suboptimal solutions. Although our approach is conceptually straightforward, the dependencies get considerably more complex with increasing model size. To generate dependency definitions automatically, a Web-accessible program is available at http://biomath.info/poolfit/constraints. PMID:18640385

Ramakrishnan, Rajasekhar; Ramakrishnan, Janak D

2008-08-01

159

Tracer airflow measurement system (TRAMS)  

DOEpatents

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

Wang, Duo (Albany, CA)

2007-04-24

160

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

161

Exploring Hydrofluorocarbons as Groundwater Age Tracers (Invited)  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

162

Nitrogen tracers in nitrogen cycle studies: past use and future needs  

Microsoft Academic Search

Nitrogen research is directed toward two main objectives, food and fiber ; production and environmental control. To achieve N balance in productive ; ecosystems, better quantitative estimates of N transformation rates are needed. ; Nitrogen tracers are indispensable for making many of these estimates. Either \\/; sup 15\\/Ndepleted or ¹⁵N-enriched materials can be used. The use of ¹⁵; Ndepleted materials

Roland D. Hauck

1973-01-01

163

Seston dynamics in a tidal inlet with shellfish aquaculture: a model study using tracer equations  

NASA Astrophysics Data System (ADS)

A process-oriented modelling study is used to examine biophysical control of the distribution of particulate organic matter, or seston, in a tidal embayment with shellfish aquaculture. The focus is on the spatio-temporal dynamics of seston as influenced by the processes of water motion and mixing, internal primary production of seston, and the clearance of the water volume by the grazing activity of a large bivalve population. A fluid dynamical framework is used wherein seston is treated as a non-conservative tracer in an advection-diffusion equation with additional source and sink terms. An idealized one-dimensional (1D) tidal inlet is first used to examine the sensitivity of tidally averaged seston concentration and flux to variations in tidal transport, internal production, and shellfish grazing. This model is then applied to Tracadie Bay, a tidal inlet off Canada's east coast, to illustrate temporal variability in seston level and flux for a more complex tidal regime. The results of this study suggest that seston flux is mainly under physical control, with its spatial distribution set by tidal transport processes. Seston level, on the other hand, is affected by both grazing and production, with the magnitude of these effects being spatially dependent as dictated by the tidal currents. Grazing and production effects on seston are most pronounced near the head of the inlet, which depends on internal, or local, processes. More seaward areas are buffered against these changes due the advection of seston from the adjacent open ocean. Variation in the spatial distribution of grazing activity demonstrates how local processes have inlet-wide effects. The temporal response of the inlet to tidal changes in the incoming far-field seston flux resembles a low-pass filter with a phase lag; temporal changes in seston at the head of the inlet are highly dampened and occur later than the forcing flux at the mouth. The implications of these results for marine bivalve aquaculture in terms of growth potential (seston level) and carrying capacity (seston flux) are discussed.

Dowd, Michael

2003-06-01

164

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

PubMed

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the ?C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the ?H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H? gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE+VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the BA was intensive only in wells where an amendment was distributed during injection, it is necessary to adequately distribute the amendments throughout the fractured rock to achieve substantial bioremediation. The slowdown in BA effect after a year is due to some extend to the decrease abundant of appropriate microbes, but more likely the decreased concentration of electron donor. PMID:24270158

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

2014-01-01

165

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. PMID:23547943

2013-01-01

166

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

SciTech Connect

Three-dimensional high-resolution numerical simulations of a gassolid jet in a high-density riser flow were conducted. The impact of gassolid injection on the riser flow hydrodynamics was investigated with respect to voidage, tracer mass fractions, and solids velocity distribution. The behaviors of a gassolid 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 gassolid jet were reasonably predicted compared with the experimental measurements made at NETL.

Li, Tingwen; Guenther, Chris

2012-03-01

167

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

NASA Astrophysics Data System (ADS)

We present the first results from a gas tracer injection experiment in the ocean crust on the eastern flank of the Juan de Fuca Ridge, in an area of vigorous hydrothermal circulation. A mixture of tracers was injected in Hole 1362B in 2010, during IODP Expedition 327, as part of a 24-hour pumping experiment. Fluid samples were subsequently collected from this hole and three additional holes (1026B, 1362A, and 1301A), located 300 to 500 m away. The array of holes is located on 3.5 M.y. old seafloor, and oriented N20E, subparallel to the Endeavor Segment of Juan de Fuca Ridge, 100 km to the west. Sulfur hexafluoride (SF6) was injected at a concentration of 0.0192 mol/min, with fluid pumping rate of 6.7 L/s for 20.2 h, resulting in a mean concentration of 47.6 ?M and 23.3 mol of SF6 being added to crustal fluids. Borehole fluid samples were collected in copper coils using osmotic pumps attached to the wellheads of several long-term, subseafloor observatories (CORKs). These samples were recovered from the seafloor using a remotely-operated vehicle in 2011 and 2013. Analyses of SF6 concentrations in samples recovered in 2011 indicate the first arrival of SF6 in Hole 1301A, 550 m south of the injection Hole 1362B, ~265 days after injection. This suggests that the most rapid lateral transport of gas (at the leading edge of the plume) occurred at ~2 m/day. Samples recovered in 2013 should provide a more complete breakthrough curve, allowing assessment of the mean lateral transport rate. Additional insights will come from analysis of metal salts and particle tracers injected contemporaneously with the SF6, the cross-hole pressure response to injection and a two-year fluid discharge experiment. Additional wellhead samples will be collected in Summer 2014, as will downhole osmosamplers deployed in perforated casing within the upper ocean crust in Holes 1362A and 1362B.

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

2013-12-01

168

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

169

Effects of resolution and model physics on tracer transports in the NASA Goddard Institute for Space Studies general circulation models  

NASA Astrophysics Data System (ADS)

We explore the dependency of general circulation model tracer transports on model physics and horizontal and vertical resolution. We use NASA Goddard Institute for Space Studies (GISS) Model E at 4 5 with 20 and 23 layers and the GISS Global Climate Middle Atmosphere Model 3 at 4 5 with 23 and 53 layers and at 2 2.5 with 53 and 102 layers. The online tracers employed are CO2, CH4, N2O, CFC-11, SF6, 222Rn, bomb 14C, and O3. Model experiments are done two ways: with specified stratospheric ozone or with the stratospheric ozone tracer used for atmospheric radiation calculations. The results show that when model physics produces greater precipitation over land in the Northern Hemisphere summer monsoon region, as occurs in Model 3, the associated dynamics (stronger Hadley cell) and subgrid-scale transports lead to faster and more realistic interhemispheric transport. Increased vertical resolution results in some increase in vertical mixing between the boundary layer and upper troposphere, due to both convective and synoptic-scale influences. A better resolved boundary layer does not result in higher surface concentrations, as the influence of various processes (convection, turbulence, rainfall) contribute in different ways. Transport into, within, and out of the stratosphere is faster (less realistic) with the coarser resolution models as wave forcing generates a stronger residual circulation. It is also faster in Model E as a result of its larger parameterized orographic gravity wave drag; the latter also results in a more "leaky" stratospheric tropical pipe. Horizontal resolution in this range by itself has minimal impact on most transports (although for active chemical tracers, photochemistry has been shown to be resolution-dependent). In contrast, finer vertical resolution leads to faster interhemispheric transport, slower mixing into and out of the stratosphere, and greater age of stratospheric air. When both resolutions are increased, the largest changes are seen. The interactive stratospheric ozone tracer, without an ozone hole parameterization, produced (as expected) greater ozone values than observations in the lower stratosphere. The associated temperature warming of a few degrees Celsius increased atmospheric stability and altered the tropospheric wave forcing of the Brewer Dobson circulation such that the stratospheric age of air increased by some 30%. This large sensitivity has implications for past and future stratospheric circulations and for the ability of climate perturbations to affect the stratosphere.

Rind, D.; Lerner, J.; Jonas, J.; McLinden, C.

2007-05-01

170

AIR INFILTRATION MEASUREMENTS USING TRACER GASES: A LITERATURE REVIEW  

EPA Science Inventory

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

171

Warm gas TVC design study  

NASA Technical Reports Server (NTRS)

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

Moorhead, S. B., Jr.

1973-01-01

172

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. PMID:16535046

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

1995-01-01

173

Viral tracer studies indicate contamination of marine waters by sewage disposal practices in key largo, Florida.  

PubMed

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. PMID:16535046

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

1995-06-01

174

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

NASA Astrophysics Data System (ADS)

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

Rood, Arthur S.

2014-06-01

175

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

SciTech Connect

Near-surface monitoring and subsurface characterization activities were undertaken in collaboration with the Southwest Regional Carbon Sequestration Partnership on their San Juan Basin coal-bed methane pilot test site near Navajo City, New Mexico. Nearly 18,407 short tons (1.670 107 kg) of CO{sub 2} were injected into 3 seams of the Fruitland coal between July 2008 and April 2009. Between September 18 and October 30, 2008, two additions of approximately 20 L each of perfluorocarbon (PFC) tracers were mixed with the CO{sub 2} at the injection wellhead. PFC tracers in soil-gas and in the atmosphere were monitored over a period of 2 years using a rectangular array of permanent installations. Additional monitors were placed near existing well bores and at other locations of potential leakage identified during the pre-injection site survey. Monitoring was conducted using sorbent containing tubes to collect any released PFC tracer from soil-gas or the atmosphere. Near-surface monitoring activities also included CO{sub 2} surface flux and carbon isotopes, soil-gas hydrocarbon levels, and electrical conductivity in the soil. The value of the PFC tracers was demonstrated when a significant leakage event was detected near an offset production well. Subsurface characterization activities, including 3D seismic interpretation and attribute analysis, were conducted to evaluate reservoir integrity and the potential that leakage of injected CO{sub 2} might occur. Leakage from the injection reservoir was not detected. PFC tracers made breakthroughs at 2 of 3 offset wells which were not otherwise directly observable in produced gases containing 2030% CO{sub 2}. These results have aided reservoir geophysical and simulation investigations to track the underground movement of CO{sub 2}. 3D seismic analysis provided a possible interpretation for the order of appearance of tracers at production wells.

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

2012-05-01

176

Petroleum characterization by perfluorocarbon tracers  

SciTech Connect

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

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

1992-02-01

177

PET radiopharmaceuticals for imaging integrin expression: tracers in clinical studies and recent developments.  

PubMed

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

Haubner, Roland; Maschauer, Simone; Prante, Olaf

2014-01-01

178

Communication: Ab initio study of O4H+: A tracer molecule in the interstellar medium?  

NASA Astrophysics Data System (ADS)

The structure and energetics of the protonated molecular oxygen dimer calculated via ab initio methods is reported. We find structures that share analogies with the eigen and zundel forms for the protonated water dimer although the symmetrical sharing of the proton is more prevalent. Analysis of different fragmentation channels show charge transfer processes which indicate the presence of conical intersections for various states including the ground state. An accurate estimate for the proton affinity of O4 leads to a significantly larger value (5.6 eV) than for O2 (4.4 eV), implying that the reaction H_3^+ + O4 ? O4H+ + H2 is exothermic by 28 Kcal/mol as opposed to the case of O2 which is nearly thermoneutral. This opens up the possibility of using O4H+ as a tracer molecule for oxygen in the interstellar medium.

Xavier, George D.; Bernal-Uruchurtu, Margarita I.; Hernndez-Lamoneda, Ramn

2014-08-01

179

Communication: Ab initio study of O4H(+): A tracer molecule in the interstellar medium?  

PubMed

The structure and energetics of the protonated molecular oxygen dimer calculated via ab initio methods is reported. We find structures that share analogies with the eigen and zundel forms for the protonated water dimer although the symmetrical sharing of the proton is more prevalent. Analysis of different fragmentation channels show charge transfer processes which indicate the presence of conical intersections for various states including the ground state. An accurate estimate for the proton affinity of O4 leads to a significantly larger value (5.6 eV) than for O2 (4.4 eV), implying that the reaction H3 (+) + O4 ? O4H(+) + H2 is exothermic by 28 Kcal/mol as opposed to the case of O2 which is nearly thermoneutral. This opens up the possibility of using O4H(+) as a tracer molecule for oxygen in the interstellar medium. PMID:25172995

Xavier, George D; Bernal-Uruchurtu, Margarita I; Hernndez-Lamoneda, Ramn

2014-08-28

180

A study of the accuracy of neutrally buoyant bubbles used as flow tracers in air  

NASA Technical Reports Server (NTRS)

Research has been performed to determine the accuracy of neutrally buoyant and near neutrally buoyant bubbles used as flow tracers in air. Theoretical, computational, and experimental results are presented to evaluate the dynamics of bubble trajectories and factors affecting their ability to trace flow-field streamlines. The equation of motion for a single bubble was obtained and evaluated using a computational scheme to determine the factors which affect a bubble's trajectory. A two-dimensional experiment was also conducted to experimentally determine bubble trajectories in the stagnation region of NACA 0012 airfoil at 0 deg angle of attack using a commercially available helium bubble generation system. Physical properties of the experimental bubble trajectories were estimated using the computational scheme. These properties included the density ratio and diameter of the individual bubbles. the helium bubble system was then used to visualize and document the flow field about a 30 deg swept semispan wing with simulated glaze ice. Results were compared to Navier-Stokes calculations and surface oil flow visualization. The theoretical and computational analysis have shown that neutrally buoyant bubbles will trace even the most complex flow patterns. Experimental analysis revealed that the use of bubbles to trace flow patterns should be limited to qualitative measurements unless care is taken to ensure neutral buoyancy. This is due to the difficulty in the production of neutrally buoyant bubbles.

Kerho, Michael F.

1993-01-01

181

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

182

Novel and nontraditional use of stable isotope tracers to study metal bioavailability from natural particles.  

PubMed

We devised a novel tracing approach that involves enriching test organisms with a stable metal isotope of low natural abundance prior to characterizing metal bioavailability from natural inorganic particles. In addition to circumventing uncertainties associated with labeling natural particles and distinguishing background metals, the proposed "reverse labeling" technique overcomes many drawbacks inherent to using radioisotope tracers. Specifically, we chronically exposed freshwater snails ( Lymnaea stagnalis ) to synthetic water spiked with Cu that was 99.4% (65)Cu to increase the relative abundance of (65)Cu in the snail's tissues from ~32% to >80%. The isotopically enriched snails were then exposed to benthic algae mixed with Cu-bearing Fe-Al particles collected from the Animas River (Colorado), an acid mine drainage impacted river. We used (63)Cu to trace Cu uptake from the natural particles and inferred their bioavailability from calculation of Cu assimilation into tissues. Cu assimilation from these particles was 44%, indicating that 44% of the particulate Cu was absorbed by the invertebrate. This demonstrates that inorganic particulate Cu can be bioavailable. The reverse labeling approach shows great potential in various scientific areas such as environmental contamination and nutrition for addressing questions involving uptake of an element that naturally has multiple isotopes. PMID:23458345

Croteau, Marie-Nole; Cain, Daniel J; Fuller, Christopher C

2013-04-01

183

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

184

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

E-print Network

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 3-D 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 mass distribution. Methods. We used the Leiden/Argentine/Bonn all sky 21-cm line survey. The transformation from brightness temperatures to densities depends on the rotation curve. We explored several models, reflecting different dark matter distributions. Each of these models was set up to solve the combined Poisson-Boltzmann equation in a self-consistent way and optimized to reproduce the observed flaring. Results. Besides a massive extended halo of M ~ 1.8 10^{12} Msun, we find a self-gravitating dark matter disk with M=2 to 3 10^{11} Msun, including a dark matter ring at 13 gas layer is strongly flaring. The HWHM scale height is 60 pc at R = 4 kpc and increases to ~2700$ pc at R=40 kpc. Spiral arms cause a noticeable imprint on the gravitational field, at least out to R = 30 kpc. Conclusions. Our mass model supports previous proposals that the giant stellar ring structure is due to a merging dwarf galaxy. The fact that the majority of the dark matter in the Milky Way for $R \\la 40$ kpc can be successfully modeled by a self-gravitating isothermal disk raises the question of whether this massive disk may have been caused by similar merger events in the past.

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

2007-04-30

185

Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions  

E-print Network

Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical and chemical information. Five of the sources observed were protostellar, ranging in energetics from 1 - 500L_sun, while the other two sources were located at a shock front and within a photodissociation region (PDR). Statistical equilibrium calculations were used to deduce from the measured line strengths the physical conditions within each source and the abundance of each molecule. In all cases except the shock and the PDR, the abundance of CO with respect to H_2 appears significantly below (factor of ten) the general molecular cloud value of 10^-4. {Formaldehyde measurements were used to estimate a mean temperature and density for the gas in each source. Evidence was found for trends between the derived abundance of CO, H_2CO, CH_3OH, and CS and the energ...

Johnstone, D; Van Dishoeck, E F; Johnstone, Doug; Boonman, Annemieke M. S.; Dishoeck, Ewine F. van

2003-01-01

186

Investigation of helical flow by using tracer technique  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

187

Determination of stream reaeration coefficients by use of tracers  

USGS Publications Warehouse

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

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

1987-01-01

188

Elemental Abundances as Tracers of Star Formation  

E-print Network

have Z Cycle of GAS and STARS in Galaxies Gas is transformed into stars Each star into the interstellar gas at the end of the star's life Through winds and supernovae explosions Some fractionElemental Abundances as Tracers of Star Formation S. Veilleux (U. Maryland) (Tremonti+04) Three

Veilleux, Sylvain

189

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

190

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

191

An analysis of whole body tracer kinetics in dynamic PET studies with application to image-based blood input function extraction.  

PubMed

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

Huang, Jian; O'Sullivan, Finbarr

2014-05-01

192

Optimizing Natural Gas Use: A Case Study  

E-print Network

OPTIMIZING NATURAL GAS USE: A CASE STUDY VEN V. VENKATESAN, PATRICK SCHWEIKERT, General Manager, Senior Manager (Maintenance), VGA Engineering Consultants, Inc. Baker Petrolite 8030 Sandberry Blvd. 9100 W, 21st Street...OPTIMIZING NATURAL GAS USE: A CASE STUDY VEN V. VENKATESAN, PATRICK SCHWEIKERT, General Manager, Senior Manager (Maintenance), VGA Engineering Consultants, Inc. Baker Petrolite 8030 Sandberry Blvd. 9100 W, 21st Street...

Venkatesan, V. V.; Schweikert, P.

2007-01-01

193

Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions  

E-print Network

Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical and chemical information. Five of the sources observed were protostellar, ranging in energetics from 1 - 500L_sun, while the other two sources were located at a shock front and within a photodissociation region (PDR). Statistical equilibrium calculations were used to deduce from the measured line strengths the physical conditions within each source and the abundance of each molecule. In all cases except the shock and the PDR, the abundance of CO with respect to H_2 appears significantly below (factor of ten) the general molecular cloud value of 10^-4. {Formaldehyde measurements were used to estimate a mean temperature and density for the gas in each source. Evidence was found for trends between the derived abundance of CO, H_2CO, CH_3OH, and CS and the energetics of the source, with hotter sources having higher abundances.} Determining whether this is due to a linear progression of abundance with temperature or sharp jumps at particular temperatures will require more detailed modeling. The observed methanol transitions require high temperatures (T>50 K), and thus energetic sources, within all but one of the observed protostellar sources. The same conclusion is obtained from observations of the CS 7-6 transition. Analysis of the HCN and HNC 4-3 transitions provides further support for high densities n> 10^7 cm^-3 in all the protostellar sources.

Doug Johnstone; Annemieke M. S. Boonman; Ewine F. van Dishoeck

2003-10-06

194

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

SciTech Connect

The Yucca Mountain Project is a US Department of Energy (DOE) scientific study to evaluate the potential for geologic disposal of high-level radioactive waste in an unsaturated-zone desert environment. The US Geological Survey (USGS) has been conducting geologic and hydrologic studies of the potential repository site for the DOE. These studies are to quantify the geologic and hydrologic characteristics of Yucca Mountain and to conceptualize and model gas and liquid flow at the potential repository site. Single-hole and cross-hole air-injection and tracer testing was conducted in alcoves located in the underground Exploratory Studies Facility (ESF) to quantify the permeability and porosity values of the fractured and unfractured volcanic rocks (tuff). The permeability and porosity of these tuffs control the movement of fluids in Yucca Mountain. Study of these parameters provides an understanding of fluid flow in the unsaturated zone, and the parameters can be used in unsaturated-zone numerical modeling to estimate fluid flux through the mountain. This report presents the results from air-injection and tracer testing conducted in the upper Tiva Canyon alcove (UTCA), the Bow Ridge Fault alcove (BRFA), and the upper Paintbrush contact alcove (UPCA) by the USGS from August 1994 through July 1996. The locations of the alcoves and their relations to the potential repository are shown in a figure.

LeCain, G.D.

1998-09-01

195

A groundwater separation study in boreal wetland terrain: the WATFLOOD hydrological model compared with stable isotope tracers.  

PubMed

Monitoring of stable water isotopes (18O and 2H) in precipitation and surface waters in the Mackenzie River basin of northern Canada has created new opportunities for researchers to study the complex hydrology and hydroclimatology of this remote region. A number of prior studies have used stable isotope data to investigate aspects of the hydrological regime of the wetland-dominated terrain near Fort Simpson, Northwest Territories, Canada. The present paper compares estimates of groundwater contributions to streamflow derived using the WATFLOOD distributed hydrological model, equipped with a new water isotope tracer module, with the results of conventional isotope hydrograph separation for five wetland-dominated catchments along the lower Liard River. The comparison reveals highly promising agreement, verifying that the hydrological model is simulating groundwater flow contributions to total streamflow with reasonable fidelity, especially during the crucial snowmelt period. Sensitivity analysis of the WATFLOOD simulations also reveals intriguing features about runoff generation from channelized fens, which may contribute less to streamflow than previously thought. PMID:15823857

Stadnyk, T; St Amour, N; Kouwen, N; Edwards, T W D; Pietroniro, A; Gibson, J J

2005-03-01

196

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

SciTech Connect

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

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

1989-05-01

197

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

198

Evaluation of lanthanide tracer methods in the study of mammalian pulmonary parenchyma and cardiac muscle by electron energy-loss spectroscopy.  

PubMed

Lanthanum (La) has widely been used as a tracer to study the integrity of plasma membranes. With conventional transmission electron microscopy (cTEM), the absence of electron scattering deposits from the cytoplasm has generally been assumed to reflect an intact cell membrane. However, the application of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS) reveals that electron scattering deposits may be present which do not contain La. However, La could be detected in regions of pulmonary parenchyma and cardiac muscle that were devoid of electron scattering deposits. Therefore, to exclude misinterpretations based on cTEM the application of microanalytical techniques is strongly recommended for the study of the integrity of plasma membranes by means of La tracers. In addition, ESI and EELS are shown to distinguish between different tracers in simultaneous applications of La and terbium (Tb) which were used at the different faces of the pulmonary air-blood barrier. The analysis of the distribution of both tracers which form electron scattering deposits, indistinguishable by cTEM, may help us to understand the different functional significances of cellular alterations of both cellular borders of the barrier. As was shown for La, however, strictly controlled conditions are mandatory during the fixation procedure because an increase in the incubation time to more than 1 h in samples of pulmonary parenchyma may result in the occurrence of La deposits within the cytoplasm. In the absence of electron scattering deposits, the presence of La in glycogen granules and ribosome-containing areas of various types of alveolar septal cells even after 15 min incubation indicates that the absence of deposits does not necessarily correspond to the absence of the tracer. PMID:8071989

Fehrenbach, H; Schmiedl, A; Brasch, F; Richter, J

1994-06-01

199

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

E-print Network

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

Mohan, Anand

2012-06-07

200

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

201

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

202

Stable Isotope Composition of Molecular Oxygen in Soil Gas and Groundwater: A Potentially Robust Tracer for Diffusion and Oxygen Consumption Processes  

NASA Astrophysics Data System (ADS)

We have measured the concentration and isotopic composition of molecular oxygen in soil gas and groundwater. At a site near Lincoln, Nebraska, USA, soil gas oxygen concentrations ranged from 13.8 to 17.6% at depths of 3-4 m and the ? 18O values ranged mostly from 24.0 to 27.2 (SMOW). The concentration of dissolved oxygen in a perched aquifer in the Texas Panhandle (depth to water 76 m) was about 5 mg/L and the ? 18O values were 21.2-22.9. The ? 18O of soil gas oxygen in our study are higher and those of dissolved oxygen are lower than the ? 18O of atmospheric oxygen (23.5). A model for the oxygen concentration and isotopic composition in soil gas was developed using the molecular diffusion theory. The higher ? 18O values in soil gas at the Nebraska site can be explained by the effects of diffusion and soil respiration (plant root and bacterial) on the isotopic composition of molecular oxygen. The lower ? 18O of dissolved oxygen at the Texas site indicates that oxygen consumption below the root zone in the relatively thick unsaturated zone here may have occurred with a different fractionation factor (either due to inorganic consumption or due to low respiration rates) than that observed for the dominant pathways of plant root and bacterial respiration. It is concluded that the use of the concentration and isotopic composition of soil gas and dissolved oxygen should provide a robust tool for studying the subsurface gaseous diffusion and oxygen consumption processes.

Aggarwal, Pradeep K.; Dillon, M. A.

1998-02-01

203

Effect of molecular charge on choroid-plexus permeability: Tracer studies with cationized ferritins  

Microsoft Academic Search

The permeability of the choroid plexus and renal glomerulus to intravenously injected native, anionic ferritin and various cationic ferritin derivatives was studied in normal rats by electron microscopy. In both structures, anionic, native ferritin was largely confined to the circulatory compartment while the cationic forms penetrated and accumulated within the filtration barriers. In the choroid plexus, cationic ferritin concentrated in

Nancy S. Peress; David Tompkins

1981-01-01

204

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

E-print Network

distributions as a supplementary tool for modern and paleoclimate isotope studies to bridge this gap significant potential for ground-truthing paleoclimate simulations extending back tens to hundreds-CN-80/66 [1]). The GNIP database has long been used for calibrating isotopic indicators of paleoclimate

Edwards, Thomas W.D.

205

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

EPA Science Inventory

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

206

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

207

Mixing of secondary gas injection in a bubbling fluidized bed  

Microsoft Academic Search

In this work, three-dimensional numerical simulations with the aim of investigating the mixing of secondary gas in a bubbling fluidized bed are performed. Single and multiple horizontal gas jet injections into a small scale rectangular bubbling fluidized bed are studied. A tracer gas is introduced through the jet orifice to study the gas mixing in the system. Both transient and

Tingwen Li; Konstantin Pougatch; Martha Salcudean; Dana Grecov

2009-01-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

209

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

2008-10-01

210

An airborne perfluorocarbon tracer system and its first application for a Lagrangian experiment  

NASA Astrophysics Data System (ADS)

A perfluorocarbon tracer system (PERTRAS), specifically designed for Lagrangian aircraft experiments, has been developed by the Deutsches Zentrum fr Luft- und Raumfahrt (German Aerospace Center, DLR). It consists of three main parts: a tracer release unit (RU), an adsorption tube sampler (ATS) and a tracer analytical system. The RU was designed for airborne tracer release experiments; meanwhile, it can be used on various platforms for different experimental purpose (here research vessel). PERTRAS was for the first time applied in the field campaign Stratospheric ozone: halogen Impacts in a Varying Atmosphere (SHIVA) in November 2011. An amount of 8.8 kg perfluoromethylcyclopentane (PMCP) was released aboard the research vessel Sonne (RV Sonne) near the operational site of this campaign, Miri, Malaysia, on 21 November. The tracer samples collected using the ATS on board the DLR research aircraft Falcon were analyzed in the laboratory using a thermal desorber/gas chromatography/mass spectrometry (TD/GC/MS) system. Guided by forecasts calculated with the Lagrangian model, Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT), 64 tracer samples were collected onboard the Falcon approximately 5 and 25 h after the release, respectively, mostly with a time resolution of 1 min. Enhanced PMCP concentrations relative to ambient PMCP background values (mean: 6.62 fmol mol-1) were detected during three intersects of the fresh tracer plume (age 5 h), with a maximum value of 301.33 fmol mol-1. This indicates that the fresh tracer plume was successfully intercepted at the forecasted position. During the second flight, 25 h after the release, the center of tracer plume was not detected by the sampling system due to a faster advection of the plume than forecasted. The newly developed PERTRAS system has been successfully deployed for the first time. The instrumental set-up and comparisons between the measurements and HYSPLIT simulations are presented in this study.

Ren, Y.; Baumann, R.; Schlager, H.

2014-07-01

211

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

SciTech Connect

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

Wasserburg, Gerald J

2008-07-31

212

The ketogenic diet increases brain glucose and ketone uptake in aged rats: a dual tracer PET and volumetric MRI study.  

PubMed

Despite decades of study, it is still unclear whether regional brain glucose uptake is lower in the cognitively healthy elderly. Whether regional brain uptake of ketones (?-hydroxybutyrate and acetoacetate [AcAc]), the main alternative brain fuel to glucose, changes with age is unknown. We used a sequential, dual tracer positron emission tomography (PET) protocol to quantify brain (18)F-fluorodeoxyglucose ((18)F-FDG) and (11)C-AcAc uptake in two studies with healthy, male Sprague-Dawley rats: (i) Aged (21 months; 21M) versus young (4 months; 4M) rats, and (ii) The effect of a 14 day high-fat ketogenic diet (KD) on brain (18)F-FDG and (11)C-AcAc uptake in 24 month old rats (24M). Similar whole brain volumes assessed by magnetic resonance imaging, were observed in aged 21M versus 4M rats, but the lateral ventricles were 30% larger in the 21M rats (p=0.001). Whole brain cerebral metabolic rates of AcAc (CMR(AcAc)) and glucose (CMR(glc)) did not differ between 21M and 4M rats, but were 28% and 44% higher, respectively, in 24M-KD compared to 24M rats. The region-to-whole brain ratio of CMR(glc) was 37-41% lower in the cortex and 40-45% lower in the cerebellum compared to CMR(AcAc) in 4M and 21M rats. We conclude that a quantitative measure of uptake of the brain's two principal exogenous fuels was generally similar in healthy aged and young rats, that the % of distribution across brain regions differed between ketones and glucose, and that brain uptake of both fuels was stimulated by mild, experimental ketonemia. PMID:23063891

Roy, Maggie; Nugent, Scott; Tremblay-Mercier, Jennifer; Tremblay, Sbastien; Courchesne-Loyer, Alexandre; Beaudoin, Jean-Franois; Tremblay, Luc; Descoteaux, Maxime; Lecomte, Roger; Cunnane, Stephen C

2012-12-01

213

Brainstem Reticular Nuclei that Project to the Thalamus in Rats: A Retrograde Tracer Study; pp. 122  

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

214

Application of INAA in the Characterisation and Quantification of Dy-Labeled Ceramic Spheres and Their Use as Inert Tracers in Soil Studies  

Microsoft Academic Search

An inert, activable tracer method, using sized ceramic spheres custom labeled with 15% Dy2O3 during manufacture, has been developed to study soil aggregation. Instrumental neutron activation analysis (INAA) with a Slowpoke reactor, using 165mDy (T\\u000a1\\/2 = 1.26 min), provides an extremely rapid means with which to characterise the Dy-content of the various size fractions of labeled spheres from different

M. J. M. Duke; A. F. Plante; W. B. McGill

2000-01-01

215

Constraining North Atlantic circulation with transient tracer observations  

E-print Network

The capability of transient tracers to constrain the ocean circulation in the North Atlantic is explored. Study of an idealized tracer shows that inferences of circulation properties from transient state distributions are ...

Li, Xingwen, 1968-

2003-01-01

216

Isotope-specific analysis of Ni by ICP-MS: applications of stable isotope tracers to biokinetic studies.  

PubMed

Inductively coupled plasma mass spectrometry (ICP-MS) offers excellent detection limits and isotopic analysis of Ni in aqueous standards, but is prone to interferences--mainly from Ca-containing polyatomics--when biological matrices are analyzed for Ni. We have used multivariate calibration with principal components analysis (PCA) to correct for mass overlaps in serum digests. The resulting detection limit for Ni is below 1 microgram/l and the within-run imprecision is 6% at 1.46 micrograms Ni/l. In urine, the higher Ca content renders routine application of PCA problematic. We evaluated several methods of pre-concentration, and have developed a method of Ca oxalate precipitation that allows direct analysis of Ni in the diluted supernatant. The stable isotope 62Ni and the radiosotope 63Ni were co-administered i.v. to rats and the serum and urinary clearances were determined by liquid scintillation counting and ICP-MS. Ni measurements by both methods were in excellent agreement, and serum clearance fit a double exponential decay consistent with the two-compartment model of Onkelinx et al. [24]. A human volunteer ingested 61Ni (20 micrograms Ni/kg body wt.) in water after an overnight fast. Identical serum levels, peaking near 35 micrograms/l at 2 h, were measured by electrothermal atomic absorption spectrometry and ICP-MS with PCA. Urinary excretion of 61Ni measured by ICP-MS demonstrated absorption of 30% of the administered dose. We conclude that Ni isotopes can be measured in body fluids by ICP-MS at levels that allow stable isotope tracer studies in humans. PMID:8029700

Templeton, D M; Xu, S X; Stuhne-Sekalec, L

1994-06-01

217

Combined use of tracer approach and numerical simulation to estimate groundwater recharge in an alluvial aquifer system: A case study of Nasunogahara area, central Japan  

NASA Astrophysics Data System (ADS)

In this study, we simulate the spatial and temporal distribution of groundwater recharge in an alluvial aquifer system in the Nasunogahara area of Japan. Natural stable isotopes (18O, D) were considered as additional calibration targets in a numerical model. The reliability of the model outputs was further validated by comparing the results from the numerical simulation and an independent tracer approach. The results indicated that the calibrated model can effectively simulate the spatial and temporal characteristics of the contribution ratios of recharge sources to groundwater in the Nasunogahara area. However, the tracer approach (i.e., end member mixing analysis) provided more reliable results at point scale, particularly for the estimated contribution ratios of paddy field water. The precipitation in the Nasunogahara area is the major recharge source; its mean contribution ratio is 58% for a one-year period over the entire alluvial fan. River seepage is significant in the upstream area of the alluvial fan, and the contribution ratio of river waters along the river channels in the upstream area increases during the wet season. Paddy field water is a highly important recharge source in the midstream and downstream areas of the alluvial fan, and the contribution ratio of paddy field water obviously increases from dry season to wet season because of irrigation. This study demonstrates that combined use of the tracer approach and numerical simulation with stable isotopes as additional calibration targets can eliminate their respective limitations and can assist in better understanding the groundwater recharge mechanism in alluvial aquifer systems.

Liu, Yaping; Yamanaka, Tsutomu; Zhou, Xun; Tian, Fuqiang; Ma, Wenchao

2014-11-01

218

Fundamental study on gas monitoring in CELSS  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

219

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.

220

New physical Lagrangian tracer  

Microsoft Academic Search

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

Zak

1984-01-01

221

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

PubMed

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

Steinbrecht, R A

1992-09-01

222

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, whichdespite their local characteremphasize the role of chain connectivity.

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

2013-08-01

223

Effect of motion on tracer activity determination in CT attenuation corrected PET images: a lung phantom study.  

PubMed

Respiratory motion is known to affect the quantitation of 18FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with 18FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere's activity concentration from one PET/CT scan to another acquired with standard helical/clinical protocol can arise as a consequence of spatial mismatch between the sphere's location in PET emission and the CT data. PMID:16121593

Pevsner, Alex; Nehmeh, Sadek A; Humm, John L; Mageras, Gig S; Erdi, Yusuf E

2005-07-01

224

Effect of motion on tracer activity determination in CT attenuation corrected PET images: A lung phantom study  

SciTech Connect

Respiratory motion is known to affect the quantitation of {sup 18}FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with {sup 18}FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere's activity concentration from one PET/CT scan to another acquired with standard helical/clinical protocol can arise as a consequence of spatial mismatch between the sphere's location in PET emission and the CT data.

Pevsner, Alex; Nehmeh, Sadek A.; Humm, John L.; Mageras, Gig S.; Erdi, Yusuf E. [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States)

2005-07-15

225

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

226

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

227

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

228

FLUE GAS DESULFURIZATION PILOT STUDY. PHASE II. APPLICABILITY STUDY  

EPA Science Inventory

The North Atlantic Treaty Organization Committee on the Challenges of Modern Society (NATO-CCMS) Flue Gas Desulfurization (FGD) Study Group prepared status reports on 12 FGD processes. Results of this work are summarized in NATO Report No. 95 titled 'Flue Gas Desulfurization Pilo...

229

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

230

Tracer attenuation in groundwater  

NASA Astrophysics Data System (ADS)

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

Cvetkovic, Vladimir

2011-12-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

232

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

233

Dual-tracer background subtraction approach for fluorescent molecular tomography  

PubMed Central

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

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

2013-01-01

234

Gas Cylinders and Safety A Case Study in Chemistry  

NSDL National Science Digital Library

This case study, developed for an introductory chemistry course as part of a two-year dental hygiene curriculum, teaches students how to apply gas properties and gas storage identification systems to identify a mishandled or mislabeled gas cylinder.

Box, Melinda

2006-01-01

235

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

SciTech Connect

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

Allwine, K Jerry; Flaherty, Julia E.

2007-08-01

236

Experimental Determination of Tracer Dispersivity in Fractures  

SciTech Connect

Reinjection of waste hot water is commonly practiced in most geothermal fields, primarily as a means of disposal. Surface discharge of these waste waters is usually unacceptable due to the resulting thermal and chemical pollution. Although reinjection can help to main reservoir pressure and fluid volume, in some cases a decrease in reservoir productivity has been observed. This is caused by rapid flow of the reinjected water through fractures connecting the injector and producers. As a result, the water is not sufficiently heated by the reservoir rock, and a reduction in enthalpy of the produced fluids is seen. Tracer tests have proven to be valuable to reservoir engineers for the design of a successful reinjection program. By injecting a slug of tracer and studying the discharge of surrounding producing wells, an understanding of the fracture network within a reservoir can be provided. In order to quantify the results of a tracer test, a model that accurately describes the mechanisms of tracer transport is necessary. One such mechanism, dispersion, is like a smearing out of a tracer concentration due to the velocity gradients over the cross section of flow. If a dispersion coefficient can be determined from tracer test data, the fracture width can be estimated. The purpose of this project was to design and construct an apparatus to study the dispersion of a chemical tracer in flow through a fracture.

Gilardi, J.; Horns, R.N.

1985-01-22

237

Nanotomography based study of gas diffusion layers  

Microsoft Academic Search

Nano-computed tomography (nanoCT) was used for non-invasive 3D visualization and characterization of porous gas diffusion layer (GDL) for polymer electrolyte membrane fuel cells (PEMFC). The study was conducted using reconstruction of 3D images of a GDL of polymer electrolyte fuel cell to determine the critical nanostructural parameters of the layer, such as porosity, mean pore radii, structure model index and

H. Ostadi; P. Rama; Y. Liu; R. Chen; X. Zhang; K. Jiang

2010-01-01

238

Measuring magnesium, calcium and potassium isotope ratios using ICP-QMS with an octopole collision cell in tracer studies of nutrient uptake and translocation in plants.  

PubMed

The ability of a quadrupole-based ICP-MS with an octopole collision cell to obtain precise and accurate measurements of isotope ratios of magnesium, calcium and potassium was evaluated. Hydrogen and helium were used as collision/reaction gases for ICP-MS isotope ratio measurements of calcium and potassium in order to avoid isobaric interference with the analyte ions from (mainly) argon ions 40Ar+ and argon hydride ions 40Ar1H+. Mass discrimination factors determined for the isotope ratios 25Mg/24Mg, 40Ca/44Ca and 39K/41K under optimized experimental conditions varied between 0.044 and 0.075. The measurement precisions for 25Mg/24Mg, 40Ca/44Ca and 39K/41K were found to be 0.09%, 0.43% and 1.4%, respectively. This analytical method that uses ICP-QMS with a collision cell to obtain isotope ratio measurements of magnesium, calcium and potassium was used in routine mode to characterize biological samples (nutrient solution and small amounts of digested plant samples). The mass spectrometric technique was employed to study the dynamics of nutrient uptake and translocation in barley plants at different root temperatures (10 degrees C and 20 degrees C) using enriched stable isotopes (25Mg, 44Ca and 41K) as tracers. For instance, the mass spectrometric results of tracer experiments demonstrated enhanced 25Mg and 44Ca uptake and translocation into shoots at a root temperature of 20 degrees C 24 h after isotope spiking. In contrast, results obtained from 41K tracer experiments showed the highest 41K contents in plants spiked at a root temperature of 10 degrees C. PMID:17962924

Becker, J S; Fllner, K; Seeling, U D; Fornalczyk, G; Kuhn, A J

2008-01-01

239

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

240

Quantitative structure-polarization relationships (QSPR) study of BTEX tracers for the formation of antibody-BTEX-EDF complex.  

PubMed

The multiple linear regression (MLR) analysis and back propagation neural networks (NN) were performed to examine the quantitative structure-polarization relationships (QSPR) for the formation of antibody-BTEX-EDF complex. Five descriptors out of 18 ones were selected for both MLR and NN, respectively, and the selected descriptors in MLR were the same as those in NN. These descriptors were the number of atoms, which can form hydrogen bonds (HA), connolly surface area (Area), the highest occupied molecular orbital energy (HOMO), partial charge of C3 carbon atom (C3), and HOMO pi coefficient of C2 carbon atom (P2). The fact that the descriptors in MLR are identical to those in NN suggests that these descriptors have good linear relationships and play a significant role in the formation of antibody-tracer complex. PMID:15177453

Moon, Taesung; Chi, Myung Whan; Choi, Myung Ja; Yoon, Chang No

2004-07-01

241

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

PubMed

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

Lu, Hsueh-Yu

2014-01-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

243

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

NASA Astrophysics Data System (ADS)

Thermal-lifetime prediction is a traditional endeavour of inter-well tracer tests conducted in geothermal reservoirs. Early tracer test signals (detectable within the first few years of operation) are expected to correlate with late-time production temperature evolutions ('thermal breakthrough', supposed to not occur before some decades of operation) of a geothermal reservoir. Whenever a geothermal reservoir can be described as a single-fracture system, its thermal lifetime will, ideally, be determined by two parameters (say, fracture aperture and porosity), whose inversion from conservative-tracer test signals is straightforward and non-ambiguous (provided that the tracer tests, and their interpretation, are performed in accordance to the rules of the art). However, as soon as only 'few more' fractures are considered, this clear-cut correlation is broken. A given geothermal reservoir can simultaneously feature a single-fracture behaviour, in terms of heat transport, and a multiple-fracture behaviour, in terms of solute tracer transport (or vice-versa), whose effective values of fracture apertures, spacings, and porosities are essentially uncorrelated between heat and solute tracers. Solute transport parameters derived from conservative-tracer tests will no longer characterize the heat transport processes (and thus temperature evolutions) taking place in the same reservoir. Parameters determining its thermal lifetime will remain 'invisible' to conservative tracers in inter-well tests. We demonstrate this issue at the example of a five-fracture system, representing a deep-geothermal reservoir, with well-doublet placement inducing fluid flow 'obliquely' to the fractures. Thermal breakthrough in this system is found to strongly depend on fracture apertures, whereas conservative-solute tracer signals from inter-well tests in the same system do not show a clear-cut correlation with fracture apertures. Only by using thermosensitive substances as tracers, a reliable correlation between (early) tracer signals and (later) thermal breakthrough can be re-established. Thus, thermosensitive tracers are indispensable for predicting thermal breakthrough, in such geothermal reservoirs whose 'hydrogeological personality' is given by a finite set of fractures, with flow occurring both across and along the fractures. In terms of the 'gebo benchmark-model' typology investigated by Hrdt et al. (2011) [http://eposters.agu.org/abstracts/models-of-geothermal-reservoirs-as-a-basis-for-interdisciplinary-cooperation/] , such systems combine flow and transport patterns of the 'petrothermal' type and of the so-called 'deep-aquifer' type: across the fractures, heat is travelling faster than conservative-solute tracers; along the fractures, conservative-solute tracers experience much less retardation by transversal exchange (matrix diffusion), than heat; fluid (and tracer) flow is not limited to the fractures; matrix flow yields essential contribution to prolonging the fluid (and tracer) residence time. Thermal lifetime results from the opposite effects of fracture aperture as an: advection-related parameter: fluid travel time increases with increasing fracture aperture advection-unrelated parameter: fracture - matrix exchange rate increases with decreasing fracture aperture, which accelerates transport across the fracture, but retards transport along the fracture. In conservative-solute tracer signals, all these fracture aperture effects on tracer transport are masked by the very long residence time associated with the matrix flow component. Thermosensitive tracers are able to 'magnify' the visibility of fracture aperture effects against matrix flow effects. Acknowledgment: This study benefits from thermosensitive-tracer research conducted within the projects Smart Tracers and LOGRO, funded by the German Ministry for Environment, Nature Conservation and Nuclear Safety (BMU, 0327579 and 0325111B) and by Energie Baden-Wrttemberg (EnBW).

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

2012-04-01

244

Gas Gun Studies of Interface Wear Effects  

NASA Astrophysics Data System (ADS)

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

Jackson, Tyler; Kennedy, Greg; Thadhani, Naresh

2011-06-01

245

Evaluation of C-14 as a natural tracer for injected fluids at the Aidlin sector of The Geysers geothermal system through modeling of mineral-water-gas Reactions  

E-print Network

the geothermal reservoir rocks. Initial simulation resultssimulation program for non- isothermal multiphase reactive geochemical transport in variably saturated geologic media: Applications to geothermalsimulations of the interactions between injectate water and the mineral, gas, and steam phases present in the geothermal

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

2006-01-01

246

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 0.0420.014 g/kg for the baseline scans and ranged from 0.17 to 0.3 g/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 g/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 g (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. PMID:23424192

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

247

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

2013-05-01

248

Determination of stream reaeration coefficients by use of tracers  

USGS Publications Warehouse

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

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

1989-01-01

249

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

USGS Publications Warehouse

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

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

2012-01-01

250

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

USGS Publications Warehouse

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

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

2013-01-01

251

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Arterial blood-gas studies. 718.105 Section 718.105... Criteria for the Development of Medical Evidence 718.105 Arterial blood-gas studies. (a) Blood-gas studies are performed to detect an...

2013-04-01

252

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

253

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Arterial blood-gas studies. 718.105 Section 718.105... Criteria for the Development of Medical Evidence 718.105 Arterial blood-gas studies. (a) Blood-gas studies are performed to detect an...

2012-04-01

254

20 CFR 718.105 - Arterial blood-gas studies.  

...2014-04-01 false Arterial blood-gas studies. 718.105 Section 718.105... Criteria for the Development of Medical Evidence 718.105 Arterial blood-gas studies. (a) Blood-gas studies are performed to detect an...

2014-04-01

255

20 CFR 718.105 - Arterial blood-gas studies.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

257

3-D numerical evaluation of density effects on tracer tests.  

PubMed

In this paper we present numerical simulations carried out to assess the importance of density-dependent flow on tracer plume development. The scenario considered in the study is characterized by a short-term tracer injection phase into a fully penetrating well and a natural hydraulic gradient. The scenario is thought to be typical for tracer tests conducted in the field. Using a reference case as a starting point, different model parameters were changed in order to determine their importance to density effects. The study is based on a three-dimensional model domain. Results were interpreted using concentration contours and a first moment analysis. Tracer injections of 0.036 kg per meter of saturated aquifer thickness do not cause significant density effects assuming hydraulic gradients of at least 0.1%. Higher tracer input masses, as used for geoelectrical investigations, may lead to buoyancy-induced flow in the early phase of a tracer test which in turn impacts further plume development. This also holds true for shallow aquifers. Results of simulations with different tracer injection rates and durations imply that the tracer input scenario has a negligible effect on density flow. Employing model cases with different realizations of a log conductivity random field, it could be shown that small variations of hydraulic conductivity in the vicinity of the tracer injection well have a major control on the local tracer distribution but do not mask effects of buoyancy-induced flow. PMID:16183165

Beinhorn, M; Dietrich, P; Kolditz, O

2005-12-01

258

Combined use of ?(13)C, ?(15)N, and ?(34)S tracers tostudy anaerobic bacterial processes in groundwater flow systems.  

PubMed

We present an approach for determining the major anaerobic bacterial processes in aquifers, using the combined stable isotope ratios of major elements (C, N, and S) as net recorders of the biogeochemical reactions. The Kumamoto groundwater is constituted of two major flow systems, A-A' and B-B', within 10(3)km-scale area. Previous study [Hosono, T., Tokunaga, T., Kagabu, M., Nakata, H., Orishikida, T., Lin, I-T., Shimada, J., 2013. The use of ?(15)N and ?(18)O tracers with an understanding of groundwater flow dynamics for evaluating the origins and attenuation mechanisms of nitrate pollution. Water Res. 47, 2661-2675.] investigated the nitrate sources and extent of denitrification using [Formula: see text] and [Formula: see text] tracers. In the present study, we studied a type of denitrification (heterogenic vs. autotrophic) and occurrence of sequential anaerobic processes along the flow systems with newly measured ?(13)CDIC and [Formula: see text] . In A-A' flow system, C, N, and S isotopic compositions did not change along the flow direction. However, in B-B' flow system significant sulfate reduction (with a maximum [Formula: see text] enrichment of +55) occurred along with denitrification (with a maximum [Formula: see text] enrichment of +38) as the groundwater flowed down-gradient. Depletions in [Formula: see text] (-8 maximum) were found only sporadically. These observations imply that autotrophic denitrification could occur in very limited parts of the study area. Moreover, the occurrence of methanogenic reactions was suggested by the enriched ?(13)CDIC signature (+8 maximum) at a denitrification hotspot. By characterizing C, N, and S isotope compositional changes in wide redox range (from aerobic oxidation of organic carbon, through denitrification, to sulfate reduction, until methanogenesis), we could develop the model of C, N, and S isotopic evolutional patterns under different redox scenarios. Proposed model is useful in obtaining a comprehensive understanding of the major anaerobic bacterial processes in aquifer systems, including distinguishing between heterotrophic and autotrophic denitrification. PMID:24583520

Hosono, Takahiro; Tokunaga, Takahiro; Tsushima, Akane; Shimada, Jun

2014-05-01

259

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

EPA Science Inventory

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

260

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

USGS Publications Warehouse

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

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

2000-01-01

261

Ultrastructural examination of the corticocollicular pathway in the guinea pig: a study using electron microscopy, neural tracers, and GABA immunocytochemistry  

PubMed Central

Projections from auditory cortex (AC) can alter the responses of cells in the inferior colliculus (IC) to sounds. Most IC cells show excitation and inhibition after stimulation of the AC. AC axons release glutamate and excite their targets, so inhibition is presumed to result from cortical activation of GABAergic IC cells that inhibit other IC cells via local projections. However, it is not known whether cortical axons contact GABAergic IC cells directly. We labeled corticocollicular axons by injecting fluorescent dextrans into the AC in guinea pigs. We visualized the tracer with diaminobenzidine and processed the tissue for electron microscopy. We identified presumptive GABAergic profiles with post-embedding anti-GABA immunogold histochemistry on ultrathin sections. We identified dextran-labeled cortical boutons in the IC and identified their postsynaptic targets according to morphology (e.g., spine, dendrite) and GABA-reactivity. Cortical synapses were observed in all IC subdivisions, but were comparatively rare in the central nucleus. Cortical boutons contain round vesicles and few mitochondria. They form asymmetric synapses with spines (most frequently), dendritic shafts and, least often, with cell bodies. Excitatory boutons in the IC can be classified as large, medium or small; most cortical boutons belong to the small excitatory class, while a minority (~14%) belong to the medium excitatory class. Approximately 4% of the cortical targets were GABA-positive; these included dendritic shafts, spines, and cell bodies. We conclude that the majority of cortical boutons contact non-GABAergic (i.e., excitatory) IC cells and a small proportion (4%) contact GABAergic cells. Given that most IC cells show inhibition (as well as excitation) after cortical stimulation, it is likely that the majority of cortically-driven inhibition in the IC results from cortical activation of a relatively small number of IC GABAergic cells that have extensive local axons. PMID:23734104

Nakamoto, Kyle T.; Mellott, Jeffrey G.; Killius, Jeanette; Storey-Workley, Megan E.; Sowick, Colleen S.; Schofield, Brett R.

2013-01-01

262

Tracers in vascular casting resins enhance backscattering brightness.  

PubMed

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

Schraufnagel, Dean E; Ganesan, Dhanalakshmi P

2002-01-01

263

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

264

Atmospheric trace gas studies in Antarctica  

SciTech Connect

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

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

1988-08-01

265

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

USGS Publications Warehouse

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

LeCain, Gary D.

1998-01-01

266

Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test  

NASA Technical Reports Server (NTRS)

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

Eberhard, Wynn L.; Willis, Ron J.

1992-01-01

267

Local and regional contributions to the atmospheric aerosol over Tel Aviv, Israel: a case study using elemental, ionic and organic tracers  

NASA Astrophysics Data System (ADS)

Changes in aerosol composition associated with a cold front passage were examined during a field experiment in Tel Aviv, Israel (2-15 Dec, 2000). In addition to monitoring aerosol scattering and optical thickness, aerosol samples were collected for detailed chemical analyses. Data were compared to simultaneous measurements made at Sde Boker, a semi-remote site in the Negev Desert, to help determine what changes were due to local pollution as opposed to regional phenomena. During the pre-frontal period (2-7 Dec) both sites were influenced by air masses containing a relatively high content of sulphate and dust, originating from neighbouring regions of the Middle East. A steady build-up of local pollution was then observed in Tel Aviv due to vehicular emissions/industrial activities, as indicated by increasing concentrations of black carbon, organic carbon, V, Cu, Ni, Zn, Br, Pb, NO 3- and PAHs. Identification of a number of organic biomass burning tracers (e.g., levoglucosan) indicates that smoke also contributed to the pollution build-up in Tel Aviv, while a range of sugars/sugar alcohols point to a microbial/bioaerosol component. Locally emitted pollutants tended to exhibit higher nighttime concentrations due to trapping of pollution under a nocturnal inversion. Fine aerosol iodine was the only element exhibiting higher daytime concentrations, hinting at a photochemical source. Post-frontal measurements (12-15 Dec) revealed a significant decrease in all pollutants due to dispersal of the haze by the cold front (8-9 Dec), with the air initially being dominated by marine aerosol. Concentrations of pollutants then began to increase, with backward trajectories indicating a possible contribution from Eastern Europe. Overall, the study identified a range of useful tracers for monitoring the contribution of different sources to the aerosol over Israel.

Graham, Bim; Falkovich, Alla H.; Rudich, Yinon; Maenhaut, Willy; Guyon, Pascal; Andreae, Meinrat O.

268

Tracer for circulation determinations  

SciTech Connect

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

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

1985-03-19

269

Cancer Tracer Synthesis Resources  

Cancer.gov

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

270

Isotopes and Tracers  

NSDL National Science Digital Library

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

Meixner, Thomas

271

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

SciTech Connect

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

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

2006-06-01

272

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-Jrgen

2013-02-01

273

Dynamics of advected tracers with varying buoyancy  

NASA Astrophysics Data System (ADS)

We study the dynamics of passively advected Lagrangian tracers undergoing small vertical oscillations around an horizontal reference density surface, in an Eulerian velocity field depending only on the horizontal coordinates. The motion of the advected particles may be chaotic even though the fluid (or, equivalently, the non-oscillating) particles undergo regular motion and follow the streamlines of the Eulerian flow. Slowly oscillating particles undergo large-time dispersion, a behavior which cannot be observed in the motion of non-oscillating particles in the same fluid flow. The system studied here may be considered as an idealized representation of the dynamics of free subsurface buoys or free balloons in the atmosphere; the results of this study indicate that a proper evaluation of the parameters of the Lagrangian tracers should be pursued in order to verify the motion of the Lagrangian tracers properly represents the behavior of true fluid particles.

Tanga, P.; Provenzale, A.

1994-09-01

274

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

E-print Network

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

J. Christopher Howk; Kenneth R. Sembach

1999-07-29

275

Water-Gas Shift Membrane Reactor Studies  

E-print Network

Reactor Fuels and Chemicals Generator Steam Turbine Combustion Turbine Heat Recovery Steam Generator Coal, Petroleum coke, Biomass, Waste, etc. Gasifier Particulate Removal Air Separator Oxygen Air Steam Particulates Steam Solid Waste Gas Cleanup Sulfur Byproduct Compressed Air Synthesis Gas Conversion Shift

276

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

277

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

278

222Rn flux and soil air concentration profiles in West-Germany. Soil 222Rn as tracer for gas transport in the unsaturated soil zone  

NASA Astrophysics Data System (ADS)

Measurements of the 222Rn activity concentration profile in the soil and the 222Rn flux in West-Germany are presented. The spatial pattern of the 222Rn flux depends more on soil type than on the 226Ra activity of the soil material. The average 222Rn flux from sandy soils is 1000 2000 dpm m-2h-1 and 4000 6000 dpm m-2h-1 from loamy and clayey soils. Weekly 222Rn flux measurements during a period of 1year at a sandy site show no significant temporal variations. At a clayey site, the 222Rn flux tends to be higher in summer than in winter. The permeability coefficient PRn, obtained from simultaneous 222Rn flux and concentration profile measurements in various soils, can be expressed as a function of the soil parameters total porosity e0, soil moisture F, tortuosity k and the molecular diffusion coefficient D0 of 222Rn in air: P=D0((e0-F)/k const.). The flux of any other gas into or out of the soil can thus be calculated from its measured concentration profile in the soil and from the 222Rn permeability coefficient, replacing the molecular diffusion coefficient of 222Rn by that of the specific gas under consideration. As an example, this method of flux determination is demonstrated for the soil CO2 flux to the atmosphere and for the flux of atmospheric CH4 into the soil.

Drr, Helmut; Mnnich, Karl Otto

1990-02-01

279

Inhalation pharmacokinetics based on gas uptake studies  

Microsoft Academic Search

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

J. G. Filser; H. M. Bolt

1981-01-01

280

Theoretical and experimental studies of optically pumped molecular gas lasers.  

E-print Network

??Optically pumped molecular gas lasers based on vibrational-rotational transitions in the infrared spectral region were studied experimentally and theoretically. A model was developed to predict (more)

Amarin, Ratanavis

2010-01-01

281

Kinetic analysis of the metabotropic glutamate subtype 5 tracer [18F]FPEB in bolus and bolus-plus-constant-infusion studies in humans  

PubMed Central

[18F]FPEB is a positron emission tomography tracer which, in preclinical studies, has shown high specificity and selectivity toward the metabotropic glutamate receptor 5 (mGluR5). It possesses the potential to be used in human studies to evaluate mGluR5 function in a range of neuropsychiatric disorders, such as anxiety and Fragile X syndrome. To define optimal scan methodology, healthy human subjects were scanned for 6?hours following either a bolus injection (n=5) or bolus-plus-constant-infusion (n=5) of [18F]FPEB. Arterial blood samples were collected and parent fraction measured by high-performance liquid chromatography (HPLC) to determine the metabolite-corrected plasma input function. Time activity curves were extracted from 13 regions and fitted by various models to estimate VT and BPND. [18F]FPEB was well fitted by the two-tissue compartment model, MA1 (t*=30), and MRTM (using cerebellum white matter as a reference). Highest VT values were observed in the anterior cingulate and caudate, and lowest VT values were observed in the cerebellum and pallidum. For kinetic modeling studies, VT and BPND were estimated from bolus or bolus-plus-constant-infusion scans as short as 90?minutes. Bolus-plus-constant-infusion of [18F]FPEB reduced intersubject variability in VT and allowed equilibrium analysis to be completed with a 30-minute scan, acquired 90120?minutes after the start of injection. PMID:23250105

Sullivan, Jenna M; Lim, Keunpoong; Labaree, David; Lin, Shu-fei; McCarthy, Timothy J; Seibyl, John P; Tamagnan, Gilles; Huang, Yiyun; Carson, Richard E; Ding, Yu-Shin; Morris, Evan D

2013-01-01

282

Measurement of human mixed muscle protein fractional synthesis rate depends on the choice of amino acid tracer.  

PubMed

The goal of this study was to discover whether using different tracers affects the measured rate of muscle protein synthesis in human muscle. We therefore measured the mixed muscle protein fractional synthesis rate (FSR) in the quadriceps of older adults during basal, postabsorptive conditions and mixed meal feeding (70 mg protein x kg fat-free mass(-1) x h(-1) x 2.5 h) by simultaneous intravenous infusions of [5,5,5-(2)H(3)]leucine and either [ring-(13)C(6)]phenylalanine or [ring-(2)H(5)]phenylalanine and analysis of muscle tissue samples by gas chromatography-mass spectrometry. Both the basal FSR and the FSR during feeding were approximately 20% greater (P < 0.001) when calculated from the leucine labeling in muscle tissue fluid and proteins (fasted: 0.063 +/- 0.005%/h; fed: 0.080 +/- 0.007%/h) than when calculated from the phenylalanine enrichment data (0.051 +/- 0.004 and 0.066 +/- 0.005%/h, respectively). The feeding-induced increase in the FSR ( approximately 20%; P = 0.011) was not different with leucine and phenylalanine tracers (P = 0.69). Furthermore, the difference between the leucine- and phenylalanine-derived FSRs was independent of the phenylalanine isotopomer used (P = 0.92). We conclude that when using stable isotope-labeled tracers and the classic precursor product model to measure the rate of muscle protein synthesis, absolute rates of muscle protein FSR differ significantly depending on the tracer amino acid used; however, the anabolic response to feeding is independent of the tracer used. Thus different precursor amino acid tracers cannot be used interchangeably for the evaluation of muscle protein synthesis, and data from studies using different tracer amino acids can be compared qualitatively but not quantitatively. PMID:17535855

Smith, Gordon I; Villareal, Dennis T; Mittendorfer, Bettina

2007-09-01

283

Vapor-phase transport of trichloroethene in an intermediate-scale vadose-zone system: retention processes and tracer-based prediction.  

PubMed

Gas-phase transport experiments were conducted using a large weighing lysimeter to evaluate retention processes for volatile organic compounds (VOCs) in water-unsaturated (vadose-zone) systems, and to test the utility of gas-phase tracers for predicting VOC retardation. Trichloroethene (TCE) served as a model VOC, while trichlorofluoromethane (CFM) and heptane were used as partitioning tracers to independently characterize retention by water and the air-water interface, respectively. Retardation factors for TCE ranged between 1.9 and 3.5, depending on water content. The results indicate that dissolution into the bulk water was the primary retention mechanism for TCE under all conditions studied, contributing approximately two-thirds of the total measured retention. Accumulation at the air-water interface comprised a significant fraction of the observed retention for all experiments, with an average contribution of approximately 24%. Sorption to the solid phase contributed approximately 10% to retention. Water contents and air-water interfacial areas estimated based on the CFM and heptane tracer data, respectively, were similar to independently measured values. Retardation factors for TCE predicted using the partitioning-tracer data were in reasonable agreement with the measured values. These results suggest that gas-phase tracer tests hold promise for characterizing the retention and transport of VOCs in the vadose-zone. PMID:23333418

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

2013-02-01

284

Study of tropospheric CO and O3 enhancement episode over Indonesia during Autumn 2006 using the Model for Ozone and Related chemical Tracers (MOZART-4)  

NASA Astrophysics Data System (ADS)

An intense biomass burning event occurred over Indonesia in Autumn of 2006. We study the impact of this event on the free tropospheric abundances of carbon monoxide (CO) and ozone (O3) using MOPITT (Measurements of Pollution In The Troposphere) observations, ozonesonde measurements and 3D chemistry transport model MOZART (Model for Ozone and Related chemical Tracers). MOPITT observations showed an episode of enhanced CO in the free troposphere over the Indonesian region during October-November 2006. This feature is reproduced well by MOZART. The model mass diagnostics identifies the source of enhanced CO mixing ratio in the free troposphere (100-250 ppbv) as due to convective processes. The implication of the fire plume on the vertical distribution of O3 over Kuala Lumpur has been studied. The tropospheric O3 increased over this location by 10-25 ppbv during Autumn 2006 as compared to Autumn 2005 and 2007. The MOZART model simulation significantly underestimated this tropospheric O3 enhancement. The model is run both with and without Indonesian biomass burning emissions to estimate the contribution of fire emission in CO and O3 enhancement. Biomass burning emission is found to be responsible for an average increase in CO by 104 56 ppbv and O3 by 5 1 ppbv from surface to 100 hPa range. The model results also showed that biomass burning and El Nio related dynamical changes both contributed (4 ppbv-12 ppbv) to the observed increase in tropospheric O3 over the Indonesian region during Autumn 2006.

Srivastava, Shuchita; Sheel, Varun

2013-03-01

285

Gas release and conductivity modification studies  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

286

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

287

Pore-scale studies of gas shale  

NASA Astrophysics Data System (ADS)

Natural gas is the cleanest hydrocarbon fuel. The contribution of natural gas produced from shale to the United States energy portfolio has been steadily increasing over the past several years. The projections into the coming decades expect this trend to remain stable. Although the advancements in well stimulation technologies have made it possible to convert huge resources into recoverable reserves, the mechanisms of gas recovery from these practically impermeable rocks are not yet fully understood. We employed the powerful imaging facilities at Lawrence Berkeley National Laboratory to gain insights into the pore geometry and structure of shale at micron and submicron scales. The X-ray micro-tomography facility at the Advanced Light Source produces 3D reconstructions of the pore space at resolutions approaching one micron. The Focused Ion-Beam sequential milling and imaging at the Molecular Foundry and National Center for Electron Microscopy allows for 3D shale structure and mineral composition at a resolution on the order of ten nanometers. We find that even a miniscule volume of reservoir shale includes an extremely rich diversity of minerals and geometries. Organic matter is consistently present as pore filling among solid grains. Some samples show a connected networks of pores in kerogen, apparently indicating its thermal maturity. Understanding the features controlling gas flow will help increase the ultimate recovery and extend the productive lifetime of a given well.

Silin, D.; Ajo Franklin, J. B.; Cabrini, S.; Kneafsey, T. J.; MacDowell, A.; Nico, P. S.; Radmilovic, V.

2010-12-01

288

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...

289

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

290

Identifying Water Main Leaks With Trihalomethane Tracers  

Microsoft Academic Search

In this study, the trihalomethanes (THMs) chloroform and dichlorobromomethane, present in chlorinated drinking water, were used as tracer compounds to identify the presence of treated city water in samples of seepage collected at leak sites in the distribution system. Using physical and chemical tests such as alkalinity, hardness, conductivity, and pH, the origin of leakage water samples often could not

Erika E. Hargesheimer

1985-01-01

291

Dynamics of advected tracers with varying buoyancy  

Microsoft Academic Search

We study the dynamics of passively advected Lagrangian tracers undergoing small vertical oscillations around an horizontal reference density surface, in an Eulerian velocity field depending only on the horizontal coordinates. The motion of the advected particles may be chaotic even though the fluid (or, equivalently, the non-oscillating) particles undergo regular motion and follow the streamlines of the Eulerian flow. Slowly

P. Tanga; A. Provenzale

1994-01-01

292

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

293

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 PMID:8471428

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

1993-01-01

294

Study of gas purifiers for the CMS RPC detector  

E-print Network

The CMS RPC muon detector utilizes a gas recirculation system called closed loop (CL) to cope with large gas mixture volumes and costs. A systematic study of CL gas purifiers has been carried out over 400 days between July 2008 and August 2009 at CERN in a low-radiation test area, with the use of RPC chambers with currents monitoring, and gas analysis sampling points. The study aimed to fully clarify the presence of pollutants, the chemistry of purifiers used in the CL, and the regeneration procedure. Preliminary results on contaminants release and purifier characterization are reported.

Benussi, L; Colafranceschi, S; Fabbri, F L; Felli, F; Ferrini, M; Giardoni, M; Greci, T; Paolozzi, A; Passamonti, L; Piccolo, D; Pierluigi, D; Russo, A; Saviano, G; Buontempo, S; Cimmino, A; de Gruttola, M; Fabozzi, F; Iorio, A O M; Lista, L; Paolucci, P; Baesso, P; Belli, G; Pagano, D; Ratti, S P; Vicini, A; Vitulo, P; Viviani, C; Guida, R; Sharma, A

2012-01-01

295

Study of gas purifiers for the CMS RPC detector  

E-print Network

The CMS RPC muon detector utilizes a gas recirculation system called closed loop (CL) to cope with large gas mixture volumes and costs. A systematic study of CL gas purifiers has been carried out over 400 days between July 2008 and August 2009 at CERN in a low-radiation test area, with the use of RPC chambers with currents monitoring, and gas analysis sampling points. The study aimed to fully clarify the presence of pollutants, the chemistry of purifiers used in the CL, and the regeneration procedure. Preliminary results on contaminants release and purifier characterization are reported.

L. Benussi; S. Bianco; S. Colafranceschi; F. L. Fabbri; F. Felli; M. Ferrini; M. Giardoni; T. Greci; A. Paolozzi; L. Passamonti; D. Piccolo; D. Pierluigi; A. Russo; G. Saviano; S. Buontempo; A. Cimmino; M. de Gruttola; F Fabozzi d A. O. M. Iorio; L. Lista; P. Paolucci; P. Baesso; G. Belli; D. Pagano; S. P. Ratti; A. Vicini; P. Vitulo; C. Viviani; R. Guida; A. Sharma

2010-12-26

296

Water quality studies in Kranji Catchment, Singapore : use of organic tracer and PEDs for identifying potential sewage sources  

E-print Network

The objective of this study was to identify organic compounds that could serve as indicators of potential human fecal contamination sources to the Kranji Reservoir in Singapore that could be used as confirmation indicators ...

Mendez Sagel, Adriana (Adriana Raquel)

2010-01-01

297

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

USGS Publications Warehouse

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

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

2006-01-01

298

Balloon tracer for atmospheric pollutants  

Microsoft Academic Search

An operational prototype of the Balloon Tracer was developed and described. This prototype was designed to be capable of meeting all of the desired specifications for the Balloon Tracer. Its buoyancy adjustment subsystem is shown. Three Gilian instrument pumps operating in parallel provide a flow of about 12 litres per minute, depending upon backpressure. The miniature Klippard mechanical valves are

E. W. Lichfield; M. D. Ivey; B. D. Zak; H. W. Church

1985-01-01

299

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

300

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

301

RADIOACTIVE TRACER STUDIES ON THE CORROSION RESISTANCE OF SOLID SOLUTIONS OF METALS. II. THE SYSTEM Mg-Cd  

Microsoft Academic Search

A study was made of the formation of a surface layer on Mg--Cd alloys in ; O.1N HSO at room temperature. The radioactive isotope Rb⁸⁶ ; was used to determine the depth of the micropores at the metal and alloy surfaces. ; As a result the following mean values for the depths of the micropores before ; corrosion were obtained:

N. N. Gratsianskii; P. F. Kaluzhnaya

1959-01-01

302

Numerical study of a helicon gas discharge  

NASA Astrophysics Data System (ADS)

Plasma sources based on the helicon gas discharge are widely used in industry [1] due to their high efficiency. We investigate performance of a particular helicon plasma sources designed for the VASIMR [2] plasma thruster. Specifically we are interested in the VX-10 configuration [3] operating with hydrogen or helium plasmas. Firstly, we use our zero-dimensional model to characterize plasma condition and composition [4]. Next we couple it to one-dimensional hybrid model [5] for a rarified gas flow in the system feeding pipe - quartz tube of the helicon. We perform numerical analysis of plasma source operation in different regimes. Results are compared and used to explain experimental data [3]. Finally, we'll discuss more detailed fully kinetic models for the gas and plasma species evolution in the helicon discharge with parameters typical to that of the VASIMR plasma thruster. [1] M.A. Lieberman and A.J.Lihtenberg, , 'Principles of plasma discharges and materials processing', Wiley, NY, 1994; [2] F.Chang-Diaz et al, Bull. APS 45 (7) 129, 2000; [3] J. Squire et al., Bull. APS 45 (7) 130, 2000; [4] O.Batishchev and Kim Molvig, AIAA technical paper 2000-3754, 2000; [5] O.Batishchev and Kim Molvig, AIAA technical paper 2001-0963, 2001.

Batishchev, Oleg; Molvig, Kim

2001-06-01

303

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

PubMed Central

Purpose The tracer 123I-2-([2-({dimethylamino}methyl)phenyl]thio)-5-iodophenylamine ([123I]ADAM) has been developed to image serotonin transporters (SERTs) with SPECT. Preclinical studies have shown that [123I]ADAM binds selectively to SERTs. Moreover, initial human studies have shown that [123I]ADAM binding could be blocked by selective serotonin reuptake inhibitors (SSRIs). However, in humans it has not been proven that [123I]ADAM binds selectively to SERTs. Methods We examined the in vivo availability of SERTs in 12 healthy young volunteers 5 h after bolus injection of [123I]ADAM. To evaluate the selectivity of binding, four participants were pretreated (double-blinded design) with placebo, four with paroxetine (20mg) and four with the dopamine/norepinephrine blocker methylphenidate (20mg). SPECT studies were performed on a brain-dedicated system (Neurofocus), and the SPECT images were coregistered with individual MR scans of the brain. ADAM binding in SERT-rich brain areas and cerebellar cortex (representing non-specific binding) was assessed by drawing regions of interest (ROIs) on the individual MR images. Specific to non-specific ratios were used as the outcome measure. Results We found that specific to non-specific ratios were statistically significantly lower in paroxetine-pretreated participants than in placebo- or methylphenidate-pretreated participants. No such difference was found between groups pretreated with placebo or methylphenidate. Conclusion Our preliminary findings suggest that [123I]ADAM binds selectively to SERTs in human brain. PMID:20309682

van de Giessen, Elsmarieke

2010-01-01

304

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

305

DEVELOPMENT OF A TRACER FLUID IN A VERTICAL TUBE WITH GRAVITY ASSISTED AND RESISTED MOTIONS  

Microsoft Academic Search

This study provides procedural tools that can be used in concert with a computer algorithm to simulate the two-phase flow development of a higher density, tracer fluid inside a vertical tube. The problem arises in the context of a tracer fluid (e.g., a contrast agent) being injected into a neutral fluid such as blood. Based on cell fractions of tracer

Joseph Majdalani; Chong Zhou; Christopher A. Dawson

306

High-performance liquid chromatographic separation of iodoamino acids for tracer turnover studies of thyroid hormones in vivo.  

PubMed

A reversed-phase high-performance liquid chromatographic technique was developed to separate radioiodinated thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3',5'-triiodothyronine (rT3) and two diiodothyronines (3,3'-T2 and 3',5'-T2), in extracts from either serum or urine. Chromatography was performed with 10-micron C18 silica gel, packed in a glass column (3 X 300 mm); the mobile phase was methanol-water (55:45) adjusted to pH 3 with H3PO4, at a flow-rate of 1.2 ml/min and a pressure of 2800 p.s.i. The results demonstrate the ability of the system to yield a clear-cut separation of the iodothyronines involved in in vivo turnover studies, i.e., T4, T3, rT3, and the two T2 compounds together. PMID:6490771

Bianchi, R; Molea, N; Cazzuola, F; Fusani, L; Lotti, M; Bertelli, P; Ferdeghini, M; Mariani, G

1984-08-01

307

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 ...

308

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

SciTech Connect

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

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

1999-06-01

309

Using Neural Networks to Describe Tracer Correlations  

NASA Technical Reports Server (NTRS)

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

Lary, D. J.; Mueller, M. D.; Mussa, H. Y.

2003-01-01

310

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

SciTech Connect

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

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

1982-03-01

311

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

2013-02-01

312

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

313

Comparison of different tracers for PIV measurements in EHD airflow  

NASA Astrophysics Data System (ADS)

In this study, a proposed method for selecting a tracer for particle imaging velocimetry (PIV) measurement in electrohydrodynamics flows was developed. To begin with, several published studies were identified that exploit different tracers, such as oil smoke, cigarette smoke and titanium dioxide (TiO2). An assortment of tracers was then selected based on comparisons with conventional dimensionless numbers; Stokes number ( St), Archimedes number ( Ar) and electrical mobility ratio ( M). Subsequently, an experimental study for testing tracers was developed, which enabled the velocity profile of an ionic wind generated by a needle/ring configuration to be measured. Air velocity measurements carried out with a Pitot tube, considered as the reference measurements, were compared to PIV measurements for each tracer. In addition, the current-voltage curves and the evolution of the current during seeding were measured. All the experimental results show that TiO2, SiO2 microballoons and incense smoke are the ideal tracers in the series of tracers investigated.

Hamdi, M.; Havet, M.; Rouaud, O.; Tarlet, D.

2014-04-01

314

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

315

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

Microsoft Academic Search

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

Lars Sproge; John gren

1988-01-01

316

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...

317

A study of water driven oil encroachment into gas caps  

E-print Network

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

Ritch, Harlan J

2012-06-07

318

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

319

Inorganic Tracer Use - Lake Fryxell  

NSF Publications Database

... EAM NSF Org: OD / OPP Date : June 27, 1991 File : opp93031 DIVISION OF POLAR PROGRAMS OFFICE OF ... Inorganic Tracer Use at Lake Fryxell) To: Files (S.7 - Environment) Manager, Polar Biology and ...

320

Small Gas Turbine Combustor Primary Zone Study  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

321

Study of the MWPC gas gain behaviour as a function of the gas pressure and temperature  

E-print Network

The Muon System of the LHCb experiment is composed of five detection stations (M1-M5) equipped with 1368 Multi-Wire Proportional Chambers (MWPC) and 24 Triple-GEM detectors. The Multi Wire Proportional Chamber (MWPC) performances (detection efficiency, time resolution, pad-cluster size and ageing properties) are heavily dependent on the gas gain. The chamber gain depends on the gas density and therefore on the gas temperature and pressure. The impact of the environmental parameters on the MWPC gain has been studied in detail. The results, togheter with a simple method proposed to account for the gain variations, are reported in this note. The absolute gas gain at the testing voltage of 2750 V was also measured to be (1.2 +- 0.1)*10^5.

Pinci, D

2005-01-01

322

Microfluidic Investigation of Tracer Dye Diffusion in Alumina Nanofluids  

E-print Network

. Under conditions matching previously reported studies, strong complexation interactions between the dye and nanoparticles at the interface between fluid streams was observed. When the tracer dye and surfactant were carefully chosen to minimize...

Ozturk, Serdar 1979-

2012-10-05

323

An investigation of longwall gob gas behavior and control methods  

SciTech Connect

The National Inst. for Occupational Safety and Health (NIOSH) has initiated the use of a tracer gas in field studies to characterize geologic and mining factors influencing the migration of longwall gob gas. Three studies have been conducted using sulfur hexafluoride (SF{sub 6}) at a coal mine in the Northern Appalachian Basin operating in the Pittsburgh Coalbed. Eight underground tracer gas releases and one gob gas venthole release are summarized. The results indicate that the gas flow in the bleeder network and in the interior regions of longwall panel gobs do not strongly interact and that the negative pressure provided by gob gas venthole exhausters is very significant in maintaining this behavior. The data also show that ventilation practices employed in a large multi-panel gob area are functioning in accordance with the intent of the engineering design, a fact which would be difficult to evaluate using conventional mine ventilation measurement methods.

Schatzel, S.J.; Diamond, W.P.; Garcia, F.; LaScola, J.C.; McCall, F.E.; Jeran, P.W.; Mucho, T.P.

1999-07-01

324

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 <5cm and clinically and radiologicallly negative axilla (T1-2N0) 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. PMID:23617459

2013-01-01

325

Collective dynamics effect transient subdiffusion of inert tracers in flexible gel networks  

NASA Astrophysics Data System (ADS)

Based on extensive Brownian dynamics simulations we study the thermal motion of a tracer bead in a cross-linked, flexible gel in the limit when the tracer particle size is comparable to or even larger than the equilibrium mesh size of the gel. The analysis of long individual trajectories of the tracer demonstrates the existence of pronounced transient anomalous diffusion. From the time averaged mean squared displacement and the time averaged van Hove correlation functions we elucidate the many-body origin of the non-Brownian tracer bead dynamics. Our results shed new light onto the ongoing debate over the physical origin of steric tracer interactions with structured environments.

Godec, Alja; Bauer, Maximilian; Metzler, Ralf

2014-09-01

326

Chemical Tracers as an Indicator of Transport in the UT/LS  

NASA Astrophysics Data System (ADS)

Previous airborne studies have proven the scientific value of chemical tracers in examining transport of the Upper Troposphere and Lower Stratosphere (UT/LS). ESRL scientists operated two airborne gas chromatographs on the NCAR G-V during the NSF sponsored Stratosphere-Troposphere Analyses of Regional Transport START-08 campaign over the midlatitudes of central North America. The Unmanned aircraft systems Chromatograph for Atmospheric Trace Species (UCATS) is comprised of a two-channel electron capture detection-gas chromatograph (ECD-GC), an ozone absorption photometer, and a water vapor tunable diode laser spectrometer. It measures N2O and SF6 every 70 seconds on one EC-GC channel, and H2, CO, and CH4 every 140 seconds on the second channel. PAN and Trace Hydrohalocarbon ExpeRiment (PANTHER) is a six-channel gas chromatograph with four ECD-GC channels and two mass selective detector-gas chromatograph (MSD-GC) channels that double the sampling rate to 180 seconds by using two traps and columns. The ECD-GC channels measure N2O, SF6, CFC-11, CFC-12, halon-1211, and PAN once every 70 seconds, H2, CH4, and CO once every 140 seconds. The two MSD-GC channels measure methyl halides (CH3I, CH3Cl, CH3I), HCFCs (22, 141b, 142b), HFC-134a, sulfur gases (COS and CS2) once every 180 seconds. These data represent a diversity of atmospheric lifetimes and are useful in examining transport in UT/LS. One example is the tracer-tracer correlation plot of N2O versus SF6, which shows three distinction regions of transport, LS, tropospause transition, and UT. Tropospheric gradients for both gases are apparent in the UT region. Other correlations will be shown in this presentation. A comparison of common species measured between UCATS and PANTHER shows a better than one percent agreement between the two instruments.

Moore, F. L.; Hurst, D. F.; Elkins, J. W.; Nance, J. D.; Dutton, G. S.; Hall, B. D.

2009-12-01

327

Tracer Diffusion in a Soft Glassy Material  

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

328

Evaluating 10B-enriched Boric Acid, Bromide, and Heat as Tracers of Recycled Groundwater Flow near MAR Operations  

NASA Astrophysics Data System (ADS)

Coupled with the unpredictability of a changing climate, the projected growth in human population over the next century requires new and innovative ways to augment already-depleted water supplies. An increasingly popular and promising development is managed aquifer recharge (MAR), a cost-effective method of intentionally storing potable water in groundwater aquifers at engineered sites worldwide. Reclaimed (or recycled) water, defined as cleaned and treated wastewater, will account for a larger portion of MAR water in future years. A crucial component for managing groundwater recharged with reclaimed water is its subsurface travel time. The California Department of Public Health (CDPH), with the most recent draft of regulations issued on November 21, 2011, requires the application of groundwater tracers to demonstrate subsurface residence time. Residence time increases the quality of reclaimed water via soil-aquifer treatment (SAT), which includes mechanisms such as sorption, biological degradation, and microbial inactivation to remove potential contaminants or pathogens. This study addresses the need for an appropriate tracer to determine groundwater residence times near MAR facilities. Standard shallow groundwater dating techniques, such as T/3He and chlorofluorocarbon (CFC) methods, cannot be used because their uncertainties are typically 2 years, longer than the target CDPH retention time of ~6 months. These methods also cannot map preferential flow paths. Sulfur hexafluoride (SF6), a nonreactive synthetic gas, is well-established as a deliberate tracer for determining subsurface travel time; however, SF6 is a very strong greenhouse gas and the California Air Resources Board (CARB) is regulating its emission. Other tracers, such as noble gas isotopes, that have successfully determined subsurface retention times are impractical due to their high cost. A multi-tracer experiment at the San Gabriel Spreading Grounds test basin (Montebello Forebay, Los Angeles County, CA, USA) has been in progress since September 6, 2011, following injection of boric acid enriched in boron-10 (10B) and bromide (Br-) tracers. Tracer concentrations are collected at 9 monitoring wells that have pre-experiment estimated travel times between 0.5 to 180 days. Results indicate that 10B-enriched boric acid is an effective deliberate tracer at MAR sites; however, the ion's movement is slightly retarded relative to bromide by the substrate. 10B/Br- travel time ratios range from 1 to 1.4. In addition to the two deliberate geochemical tracers, heat is being evaluated as a possible intrinsic tracer at MAR sites. At the time of the experiment (late summer), reclaimed water was significantly warmer (~20F) than the native groundwater as it entered the system. Time series are developed from loggers outfitted at each monitoring well, with measurements recorded hourly accurate to one thousandth of a degree. Results are similar to 10B & Br- travel times and validate the potential of heat as an intrinsic tracer.

Becker, T.; Clark, J. F.

2012-12-01

329

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

330

Multibreath tracer species dynamics in the lung  

Microsoft Academic Search

By studying the behavior of various tracer species in the lungs, one can assess many important characteristics which distinguish\\u000a normal and abnormal function. Quantitative evaluation of function depends on the use of an appropriate model in conjunction\\u000a with experimental data. A multi-compartment model is derived from mass balances to describe dynamic as well as (breath-averaged)\\u000a steady-state transport processes between the

Gerald M. Saidel; Gerald M. Burma

1981-01-01

331

Characterizing building ventilation with the pollutant concentration index: Results from field studies  

SciTech Connect

A new method for characterizing ventilation in commercial buildings using the Pollutant Concentration Index (PCI) was evaluated via field studies in four buildings. The PCI parameter quantifies the effectiveness of ventilation in controlling air pollutant exposures for pollutants released continuously and spatially uniformly within the building. For the measurements, passive tracer gas sources spaced uniformly per unit floor area, simulated an indoor pollutant. The sources continuously released the tracer gas at a known rate. During the occupied periods of several days, air samples from seated breathing-level locations were collected in gas storage bags. The PCI values were based on the tracer gas concentrations in the sample storage bags and on the indoor tracer gas emission rate. The technique was successfully implemented in buildings ranging in floor area from 129 m{sup 2} to 4475 m{sup 2}. Results of these studies indicated that the spacing of tracer gas sources, between 8 and 73 m{sup 2}/source, had little effect upon measured values of the PCI. The agreement between PCI values measured simultaneously with two different tracers was usually within 15%. The precision of PCI measurements made with a single tracer gas was approximately 5%. Measured PCI values were referenced to predicted values for buildings that meet minimum ventilation standards. PCI values also indicated the spatial and temporal variability of the effectiveness of ventilation in controlling pollutant exposures.

Faulkner, D.; Fisk, W.J.; Sullivan, D.P.; Thomas, J.M. Jr.

1997-04-01

332

Off-gassing induced tracer release from molten basalt pools  

SciTech Connect

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

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

1994-01-01

333

Biological conversion of synthesis gas. Topical report: Bioreactor studies  

SciTech Connect

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

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

1993-09-01

334

PET tracers in musculoskeletal disease beyond FDG.  

PubMed

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

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

2014-04-01

335

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

336

Tracer-encapsulated solid pellet injection system.  

PubMed

The method of tracer-encapsulated solid pellet (TESPEL) is now flourishing in various fields. The original purpose to study impurity transport without giving substantial perturbation on the plasma is implemented successfully for years. In addition to this, TESPEL is being intensively applied to study thermal (especially non-local) transport, high energy particles with the use of TESPEL ablation cloud, and spectroscopy from the viewpoint of atomic data. It is now further growing up to the utilization of multiple tracer methods which was not planned at the initial phase of the project. The proof-of-principle experiment using triple tracers has been successfully implemented. This opens a way to compare the Z dependence or mass dependence of impurity transport. In this article, as TESPEL is used in a variety of fields, the TESPEL injection system is summarized together with the method of TESPEL production, TESPEL storage disk, TESPEL guide system, and the differential pumping system. Also, the observation system for TESPEL flight and TESPEL ablation is explained. PMID:22380087

Sudo, Shigeru; Tamura, Naoki

2012-02-01

337

Tracer-encapsulated solid pellet injection system  

NASA Astrophysics Data System (ADS)

The method of tracer-encapsulated solid pellet (TESPEL) is now flourishing in various fields. The original purpose to study impurity transport without giving substantial perturbation on the plasma is implemented successfully for years. In addition to this, TESPEL is being intensively applied to study thermal (especially non-local) transport, high energy particles with the use of TESPEL ablation cloud, and spectroscopy from the viewpoint of atomic data. It is now further growing up to the utilization of multiple tracer methods which was not planned at the initial phase of the project. The proof-of-principle experiment using triple tracers has been successfully implemented. This opens a way to compare the Z dependence or mass dependence of impurity transport. In this article, as TESPEL is used in a variety of fields, the TESPEL injection system is summarized together with the method of TESPEL production, TESPEL storage disk, TESPEL guide system, and the differential pumping system. Also, the observation system for TESPEL flight and TESPEL ablation is explained.

Sudo, Shigeru; Tamura, Naoki

2012-02-01

338

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

339

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

340

Quantification of brain perfusion with tracers retained by the brain  

SciTech Connect

Almost a decade ago, tracers, labelled with {sup 123}I and {sup 99m}Tc, that are retained by the brain, started to be used for studies of regional brain perfusion (regional cerebral blood flow, rCBF). To date, these tracers have been used for brain perfusion imaging with SPECT in brain disorders as well as for physiological activation protocols. Only seldom, however, have they been used in protocols that quantitatively measure rCBF. Nevertheless, comparative studies with perfusion reference tracers have repeatedly demonstrated that the brain uptake of these brain-retained tracers is correlated to perfusion, the major determinant of the distribution of these tracers in the brain. The brain kinetics of {sup 99m}Tc HMPAO, which is the tracer most commonly used, was described with a two-compartment tissue model. The theoretical approach, which is, in itself, sufficient for modeling quantitative measurements with {sup 99m}Tc HMPAO, initially suggested the possibility of empirically narrowing the distance between the brain`s regional uptake of the tracer and rCBF with a linearization algorithm which uses the cerebellum as the reference region. The value of this empirical method is hampered by the fact that the cerebellum can be involved in cerebrovascular disease (i.e. cerebellar diaschisis) as well as in several other brain disorders (e.g. anxiety, and dementia of the Alzheimer type). It also was proposed that different reference regions (occipital, whole slice, or whole brain) should be selected in relation to the brain disorder under study. However, this approach does not solve the main problem because it does not equip us with a reliable tool to evaluate rCBF with a high predictive value, and, at the same time, to reduce intersubject variability. The solution would be to measure a quantitative parameter which directly reflects rCBF, such as the unidirectional influx constant of the freely diffusible flow-limited tracers. 45 refs., 3 figs., 1 tab.

Pupi, A.; Bacciottini, L.; De Cristofaro, M.T.R.; Formiconi, A.R.; Castagnoli, A. [Univ. of Florence (Italy)

1991-12-31

341

Sensitivity of tracer transport to model resolution, prescribed meteorology and tracer lifetime in the general circulation model ECHAM5  

NASA Astrophysics Data System (ADS)

Atmospheric transport of traces gases and aerosols plays an important role in the distribution of air pollutants and radiatively active compounds. For model simulations of chemistry-climate interactions it is important to know how the transport of tracers depends on the geographical resolution of the general circulation model. However, this aspect has been scarcely investigated until now. Here, we analyse tracer transport in the ECHAM5 general circulation model using 6 independent idealized tracers with constant lifetimes, which are released in two different altitudes at the surface and in the stratosphere, respectively. Model resolutions from T21L19 to T106L31 were tested by performing multi-annual simulations with prescribed sea surface temperatures and sea ice fields of the 1990s. The impacts of the tracer lifetime were investigated by varying the globally uniform exponential decay time between 0.5 and 50 months. We also tested the influence of using prescribed meteorological fields (ERA40) instead of climatological sea surface temperature and sea ice fields. Meridional transport of surface tracers decreases in the coarse resolution model due to enhanced vertical mixing, with the exception of the advection into the tropical region, which shows an inconsistent trend between the resolutions. Whereas, the meridional transport of tracers released in the stratosphere was enhanced with higher model resolutions, except in the transport from tropical stratosphere to the Southern Hemisphere, which exhibits an increase trend with increasing model resolution. The idealized tracers exhibit a seasonal cycle, which is modulated by the tracer lifetime. In comparison to the run with prescribed sea surface temperature and sea ice fields, the simulation with prescribed meteorological fields did not exhibit significant change in the meridional transport, except in the exchange of stratospheric tracers between both hemispheres, where it causes about 100% increase. The import of the surface tracers into the stratosphere is increased by up to a factor of 2.5, and the export from the stratosphere into the troposphere was increased by up to 60% when prescribed meteorological fields is used. The ERA40 simulation also showed larger interannual variability (up to 24% compared to 12% in the standard simulations). Using our surface tracers released in either the northern or Southern Hemisphere, respectively, we calculate inter-hemispheric transport times between 11 and 17 months, consistent with values reported in the literature. While this study cannot be used to relate differences in model results to specific changes in transport processes, it nevertheless provides some insight into the characteristics of tracer transport in the widely used ECHAM5 general circulation model.

Aghedo, A. M.; Rast, S.; Schultz, M. G.

2010-04-01

342

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

343

The use of tracers to assess leakage from the sequestration of CO2 in a depleted oil reservoir, New Mexico, USA  

SciTech Connect

Geological sequestration of CO2 in depleted oil reservoirs is a potentially useful strategy for greenhouse gas management and can be combined with enhanced oil recovery. Development of methods to estimate CO2 leakage rates is essential to assure that storage objectives are being met at sequestration facilities. Perfluorocarbon tracers (PFTs) were added as three 12 h slugs at about one week intervals during the injection of 2090 tons of CO2 into the West Pearl Queen (WPQ) depleted oil formation, sequestration pilot study site located in SE New Mexico. The CO2 was injected into the Permian Queen Formation. Leakage was monitored in soilgas using a matrix of 40 capillary adsorbent tubes (CATs) left in the soil for periods ranging from days to months. The tracers, perfluoro-1,2-dimethylcyclohexane (PDCH), perfluorotrimethylcyclohexane (PTCH) and perfluorodimethylcyclobutane (PDCB), were analyzed using thermal desorption, and gas chromatography with electron capture detection. Monitoring was designed to look for immediate leakage, such as at the injection well bore and at nearby wells, and to develop the technology to estimate overall CO2 leak rates based on the use of PFTs. Tracers were detected in soilgas at the monitoring sites 50 m from the injection well within days of injection. Tracers continued to escape over the following years. Leakage appears to have emanated from the vicinity of the injection well in a radial pattern to about 100 m and in directional patterns to 300 m. Leakage rates were estimated for the 3 tracers from each of the 4 sets of CATs in place following the start of CO2 injection. Leakage was fairly uniform during this period. As a first approximation, the CO2 leak rate was estimated at about 0.0085% of the total CO2 sequestered per annum.

Wells, A.W.; Diehl, J.R.; Bromhal, G.S.; Strazisar, B.R.; Wilson, T.H. (West Virginia University, Morgantown, WV); White, C.M. (Parsons Corp., South Park, PA)

2007-05-01

344

Commercial applications of perfluorocarbon tracer (PFT) technology  

SciTech Connect

Tracer technology can be successfully applied to many leak-checking and monitoring evaluations of operating systems (e.g., building HVACs), manufacturing processes and products (e.g., air conditioners), and subsurface components and systems (e.g., underground storage tanks). Perfluorocarbon tracer (PFT) technology is the most sensitive of all tracer technologies because the ambient background levels of the five (5) routinely-used PFTs are in the range of parts per 10{sup 15} parts of air (i.e., parts per quadrillion-ppq) and this technology's instrumentation can measure down to those levels. The effectiveness of this technology is achieved both in terms of cost (very little PFT need to be used) and detectability; for example, very small leaks can be rapidly detected. The PFT compounds, which are environmentally and biologically safe to use, are commercially available as are the sampling and analysis instrumentation. This presentation concerns (1) the steps being taken to commercialize this technology, (2) new applications of processes currently under study, and (3) applications in areas of use that will be particularly beneficial to the environment. 21 refs., 2 figs., 2 tabs.

Dietz, R.N.

1991-06-01

345

Molecular tracers of high mass star-formation in external galaxies  

E-print Network

Hot core molecules should be detectable in external active galaxies out to high redshift. We present here a detailed study of the chemistry of star-forming regions under physical conditions that differ significantly from those likely to be appropriate in the Milky Way Galaxy. We examine, in particular, the trends in molecular abundances as a function of time with respect to changes in the relevant physical parameters. These parameters include metallicity, dust:gas mass ratio, the H$_{2}$ formation rate, relative initial elemental abundances, the cosmic ray ionization rate, and the temperature of hot cores. These trends indicate how different tracers provide information on the physical conditions and on evolutionary age. We identify hot core tracers for several observed galaxies that are considered to represent spirals, active galaxies, low-metallicity galaxies, and high-redshift galaxies. Even in low-metallicity examples, many potential molecular tracers should be present at levels high enough to allow unresolved detection of active galaxies at high redshift containing large numbers of hot cores.

E. Bayet; S. Viti; D. A. Williams; J. M. C. Rawlings

2007-12-17

346

Nicotelline: A Proposed Biomarker and Environmental Tracer for Particulate Matter Derived from Tobacco Smoke  

PubMed Central

Particulate matter (PM) derived from tobacco smoke contains numerous toxic substances. Since the PM and gas phase of tobacco smoke may distribute differently in the environment, and substances in them may have different human bioavailability, multiple tracers and biomarkers for tobacco smoke constituents are desirable. Nicotelline is a relatively non-volatile alkaloid present in tobacco smoke, and therefore it has the potential to be a suitable tracer and biomarker for tobacco smoke-derived PM. We describe experiments demonstrating that nicotelline is present almost entirely in the PM, in both freshly generated cigarette smoke and aged cigarette smoke. An excellent correlation between the mass of nicotelline and the mass of the PM in aged cigarette smoke was found. We also describe experiments suggesting that the main source of nicotelline in tobacco smoke is dehydrogenation of another little-studied tobacco alkaloid, anatalline, during the burning process. We show that nicotelline metabolites can be measured in urine of smokers, and that nicotelline can be measured in house dust from homes of smokers and non-smokers. We conclude that nicotelline should be useful as a tracer and biomarker for PM derived from tobacco smoke. PMID:24125094

Jacob, Peyton; Goniewicz, Maciej L.; Havel, Christopher; Schick, Suzaynn F.; Benowitz, Neal L.

2013-01-01

347

B-10 enriched boric acid, bromide, and heat as tracers of recycled groundwater flow near managed aquifer recharge operations  

NASA Astrophysics Data System (ADS)

Recycling wastewater for potable and nonpotable use by artificially recharging aquifers is a decades-old but increasingly popular practice. Natural attenuation processes in the subsurface, known as soil aquifer treatment (SAT), purify recycled water during recharge and subsequent groundwater flow. Travel time criteria are often used to regulate managed aquifer recharge (MAR) operations. California state draft regulations currently gives preference to groundwater tracers to quantify underground residence time, with a target retention time of >6 months from infiltration to drinking water extraction for surface spreading projects using tertiary treated wastewater (less time may be possible if full advanced treated water is utilized). In the past sulfur hexafluoride, a very strong greenhouse gas, has been the principle deliberate tracer for this work. However, its emission has recently become regulated in California and new tracers are needed. Here, two prospective tracers are evaluated: boron-10 (B-10), the least abundant boron isotope, and heat (with recharging water naturally warmed at the sewage treatment plants and in surface-spreading basins). An additional deliberate tracer, bromide (Br), which is a well-studied conservative tracer, was released as a control. Tracer injection occurred at the San Gabriel Spreading Grounds research test basin in Los Angeles County, CA, USA. The basin was constructed and characterized by the US Geological Survey in the mid-1990s. Recycled wastewater was piped directly to this basin at a known rate (about 1.5 m3/day). Down gradient from the test basin are nine high quality monitoring wells in a line that extends from the center of the basin to 150 m down gradient. All of the wells were equipped with temperature loggers that recorded groundwater temperatures every hour with an accuracy of one thousandth of a degree. The pre-experiment expected arrival times ranged from less than one day to six months. Arrival of Br was always coincident or preceded the B-10 arrival, reflecting retardation of B-10 presumably due to exchange with clay surfaces. B-10/Br travel time ratios determined from the center of mass range from 1 to 1.4. Temperature time series were developed from data loggers. The 1.5 C diurnal temperature variation observed in the spreading pond was only apparent at one well that is screen about 3 m below the pond bottom. At the other wells, we observed temperature increases over a period of days to weeks. Basic analysis of temperature profiles yields a reliable estimate of the underground residence time; heat flow travel times are in good agreement with those derived from the geochemical tracers.

Clark, J. F.; Becker, T.; Johnson, T. A.

2013-12-01

348

A Role for Altimeter Radars in Gas Exchange Studies  

NASA Astrophysics Data System (ADS)

Accurate estimates of air-sea transfer rates of radiatively active gases are needed for studies of regional and global gas cycling and for climate change studies. However, estimates using traditional wind speed - gas transfer velocity parameterizations vary by a factor of 2- 3, contributing significantly to error budgets in global modeling of gas exchange and the carbon cycle. A decade of research has shown the utility of sea surface roughness, represented by the mean square surface slope (mss) due to gravity-capillary scale waves, as a proxy for gas exchange. Normalized backscatter of altimeter radars can be used in scattering models to estimate mss by combining coordinated ship-based measurements of mss with satellite overflights. These coordinated field experiments over the last decade have begun to provide the data necessary to calibrate mss estimates from altimeter radars. Now we have developed this technique into an alternative approach for assessing global gas transfer velocity fields remotely. This paper will trace the evolution of this concept from key laboratory and in situ observations to remote sensing observations and construction of a decade-long time series from the TOPEX and Jason-1 data streams.

Frew, N. M.; Glover, D. M.; McCue, S. J.

2006-07-01

349

Atmospheric dispersion and tracer ventilation in a deep mountain valley  

SciTech Connect

During September and October 1984, a major meteorological and tracer study was conducted in Colorado's Brush Creek valley. The characteristics of atmospheric dispersion during the nighttime and morning transition periods are discussed in this paper. Tracer released near the valley floor did not reach the ridgetops (escape from the valley) during the nighttime but was confined to the valley, being carried in down-valley flows. After sunrise, with the onset of convective boundary-layer growth and initiation of upslope flows, the tracer within the valley was carried into the upper elevations of the valley atmosphere and ventilated from the valley. This was confirmed by the ridgetop tracer samplers and by a tracer mass budget applied to a valley atmosphere control volume. The ventilation rate of tracer from the valley atmosphere to the above-ridgetop flows was calculated from the tracer mass budget. A dimensionless form of the ventilation rate is proposed. The Gaussian plume equation adequately represented (16% average deviation) the average nighttime plume centerline concentration, out to 8 km from the release, when the plume was fully contained in down-valley flows. This agreement was attained by accounting for plume reflections from the valley sidewalls and using measured turbulence statistics in the calculation of the dispersion coefficients. Beyond 8 km down valley from the release, the Brush Creek valley merged with the Roan Creek valley and the two airstreams mixed, resulting in a sudden dilution of the tracer plume. The Gaussian plume equation was not valid after the two airstreams merged. 35 refs., 22 figs., 4 tabs.

Allwine, K.J. (Pacific Northwest Lab., Richland, WA (United States))

1993-06-01

350

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

351

A Study of Formation and Dissociation of Gas Hydrate  

E-print Network

and initial pressure. The aim of the second part of the study was the evaluation of the formation of gas hydrate and ice phases in a super-cooled methane-water system under the cooling rates of 0.45 and 0.6 degrees C/min, and the initial pressures of 1500...

Badakhshan Raz, Sadegh

2012-07-16

352

Eye-Tracking Study of Complexity in Gas Law Problems  

ERIC Educational Resources Information Center

This study, part of a series investigating students' use of online tools to assess problem solving, uses eye-tracking hardware and software to explore the effect of problem difficulty and cognitive processes when students solve gas law word problems. Eye movements are indices of cognition; eye-tracking data typically include the location,

Tang, Hui; Pienta, Norbert

2012-01-01

353

Study of VHF-band QCM gas sensor  

Microsoft Academic Search

A VHF-band quartz crystal microbalance (QCM) gas sensor made up of a resonator with its thin quartz plate and a sensing film was studied to raise its sensitivity. The fundamental mode was used instead of the harmonic mode because of its high sensitivity. The sample flow system using a diffusion method was constructed and the experiment on the vapor exposure

T. Nakamoto; Y. Suzuki; T. Moriizumi

2002-01-01

354

The use of synthetic colloids in tracer transport experiments in saturated rock fractures  

SciTech Connect

Studies of groundwater flow and contaminant transport in saturated, fractured geologic media are of great interest to researchers studying the potential long-term storage of hazardous wastes in or near such media. A popular technique for conducting such studies is to introduce tracers having different chemical and physical properties into a system and then observe the tracers at one or more downstream locations, inferring flow and transport mechanisms from the breakthrough characteristics of the different tracers. Many tracer studies have been conducted in saturated, fractured media to help develop and/or refine models capable of predicting contaminant transport over large scales in such media.

Reimus, P.W.

1995-08-01

355

Tracer Lamination in the Stratosphere: A Global Climatology  

NASA Technical Reports Server (NTRS)

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

Appenzeller, Christof; Holton, James R.

1997-01-01

356

Gas absorption using a nanofluid solvent: kinetic and equilibrium study  

NASA Astrophysics Data System (ADS)

An experimental study has been performed to explore gas absorption in a nanofluid solvent. Propane and propylene were separately absorbed in a non-aqueous based nanofluid composed of N-methyl 2-pyrolidone (NMP) + small amount of TiO2 nanoparticle. Absorption was performed at different initial pressures and nanoparticle concentrations. Results showed that the addition of small amount of nanoparticle enhances the rate of absorption. Nanofluid decreased the time needed to achieve equilibrium and increased the maximum amount of gas absorbed.

Azizi, S.; Peyghambarzadeh, S. M.; Saremi, M.; Tahmasebi, H.

2014-05-01

357

Setup optimization toward accurate ageing studies of gas filled detectors  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

358

Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction  

NASA Astrophysics Data System (ADS)

Denitrification was measured within a nitrate-contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 ?M) and nitrous oxide (up to 143 ?M) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small-scale (15-24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down-gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one-dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036-0.047 ?mol N (L aquifer)-1 d-1) was faster than the subsequent denitrification steps (0.013-0.016 ?mol N (L aquifer)-1 d-1 for nitrous oxide and 0.013-0.020 ?mol N (L aquifer)-1 d-1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down-gradient before being completely consumed.

Smith, Richard L.; BHlke, John Karl; Garabedian, Stephen P.; Revesz, Kinga M.; Yoshinari, Tadashi

2004-07-01

359

Study of Mixed Collisionality Gas Flow in the VASIMR Thruster  

NASA Astrophysics Data System (ADS)

The degree of gas ionization in the VASIMR plasma thruster [1] is about one percent. This allows separating of the gas propellant flow from the plasma dynamics. The Knudsen number of the hydrogen (deuterium) or helium gas flow in a system of pipes of varying diameter falls into the .2-5 range. This indicates that the kinetic approach is required. First we present results from 1D hybrid Poiseuille-Knudsen model for viscous - free molecular pipe flow [2]. We compare simulation results to the experimental measurements. Next we study effects of (i) internal baffles to assist the retaining of the propellant, and (ii) gas pre-heating. Finally, we describe an extension of our 1D2V fully kinetic finite volume method [3] to a semi-collisional gas flow simulation. [1] F. Chang-Daz et al., Bulletin of APS, 44 (1999) 99. [2] O. Batishchev and K. Molvig, AIAA 2000-3754 paper (2000). [3] Batishchev O. et al., J. Plasma Phys. 61 (1999) 347.

Batishchev, Oleg; Molvig, Kim

2000-11-01

360

Transport of Passive Tracers in Baroclinic Wave Life Cycles  

NASA Technical Reports Server (NTRS)

The transport of passive tracers in idealized baroclinic wave life cycles is studied using output from the National Center for Atmospheric Research Community Climate Model (CCM2). Two life cycles, LCn and LCs, are simulated, starting with baroclinically unstable initial conditions similar to those used by Thorncroft et al. in their study of two life cycle paradigms. The two life cycles LCn and LCs have different initial horizontal wind shear structures that result in distinctive nonlinear development. In terms of potential vorticity-potential temperature (PV-theta) diagnostics, the LCn case is characterized by thinning troughs that are advected anti-cyclonically and equatorward, while the LCs case has broadening troughs that wrap up cyclonically and poleward. Four idealized passive tracers are included in the model to be advected by the semi-Lagrangian transport scheme of the CCM2, and their evolutions are investigated throughout the life cycles. Tracer budgets are analyzed in terms of the transformed Eulerian mean constituent transport formalism in pressure coordinates and also in isentropic coordinates. Results for both LCn and LCs show transport that is downgradient with respect to the background structure of the tracer field, but with a characteristic spatial structure that maximizes in the middle to high latitudes. For the idealized tropospheric tracers in this study, this represents a net upward and poleward transport that enhances concentrations at high latitudes. These results vary little with the initial distribution of the constituent field. The time tendency of the tracer is influenced most strongly by the eddy flux term. with the largest transport occurring during the nonlinear growth stage of the life cycle. The authors also study the transport of a lower-stratospheric tracer, to examine stratosphere-troposphere exchange for baroclinic waves.

Stone, Elizabeth M.; Randel, William J.; Stanford, John L.

1999-01-01

361

Diffusion NMR methods applied to xenon gas for materials study.  

PubMed

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

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

2002-12-01

362

Diffusion NMR methods applied to xenon gas for materials study  

NASA Technical Reports Server (NTRS)

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. c2002 John Wiley & Sons, Ltd.

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

2002-01-01

363

Tracer Tests in flooded underground mines  

Microsoft Academic Search

Tracer tests are a common means to investigate the hydrogeological conditions in the hydro- sphere. Nevertheless, only few successful tracer tests in flooded underground mines have been described. In two flooded German underground mines tracer tests with club moss spores (Lycopodium clavatum) and mi- crospheres had been conducted by the use of the LydiA technique. Both times, effective velocities between

Ch. Wolkersdorfer

364

Gas fueling studies in the PDX tokamak: II  

SciTech Connect

Measurements of the gas fueling characteristics of the PDX tokamak have been extended in parameter range. An earlier study presented the gas fueling efficiency for H/sub 2/ and D/sub 2/ for the standard PDX divertor configurations with a large conductance between the divertor and main plasma chambers. This study presents the observed variations in H/sub 2/, D/sub 2/, and He neutral pressure and ionization light emission for divertor configurations with a restricted conductance between the divertor and main plasma chambers. The restricted conductance improved the divertor/main-chamber compression ratio by more than an order of magnitude. For the same plasma density, gas fueling from the divertor chamber was twice as efficient as fueling from the main chamber. At the highest plasma densities that were investigated, anti n/sub e/ approx. = 4 x 10/sup 13/ cm/sup -3/, a decrease in the plasma temperature in the divertor was indicated by a decrease in the ionization light at the divertor throat for D/sub 2/ and He fueled discharges. These observations are consistent with a Monte-Carlo model of neutral gas transport in the divertor.

Dylla, H.F.; Bell, M.G.; Fonck, R.J.; Jaehnig, K.; Kaye, S.M.; Owens, D.K.; Heifetz, D.B.; Schmidt, G.L.

1984-01-01

365

A 2D multiwavelength study of the ionized gas and stellar population in the giant H II region NGC 588  

NASA Astrophysics Data System (ADS)

Giant H II regions (GHIIRs) in nearby galaxies are a local sample in which we can study in detail processes in the interaction of gas, dust and newly formed stars which are analogous to those which occurred in episodes of higher intensity in which much of the current stellar population was born. Here, we present an analysis of NGC 588, a GHIIR in M33, based on optical Integral Field Spectroscopy data obtained with the Potsdam Multi-Aperture Spectrophotometer at the 3.5-m telescope of the Calar Alto Observatory, CAHA, together with Spitzer infrared images at 8 and 24 ?m. The extinction distribution measured in the optical shows complex structure, with three maxima which correlate in position with those of the emission at 24 and 8 ?m. Furthermore, the H? luminosity absorbed by the dust within the H II region reproduces the structure observed in the 24-?m image, supporting the use of the 24-?m band as a valid tracer of recent star formation. A velocity difference of 50 km s-1 was measured between the areas of high and low surface brightness, which would be expected if NGC 588 were an evolved GHIIR. We have carefully identified the areas which contribute most to the line ratios measured in the integrated spectrum. Those line ratios which are used in diagnostic diagrams proposed by Baldwin, Phillips & Terlevich (i.e. the BPT diagrams) show a larger range of variation in the low surface brightness areas. The ranges are 0.5-1.2 dex for [N II]?6584/H?, 0.7-1.7 dex for [S II]??6717,6731/H? and 0.3-0.5 dex for [O III]?5007/H?, with higher values of [N II]?6584/H? and [S II]??6717,6731/H?, and lower values of [O III]?5007/H? in the areas of lower surface brightness. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in H? and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as 0.8 dex, notably when using [O III]??4959,5007/[O II]??3726,3729 and in the high surface brightness spaxels. [O II]??3726,3729/H? and [O III]??4959,5007/[O II]??3726,3729 yield similar local values for the ionization parameter, which are consistent with those expected from the integrated spectrum of an H II region ionized by a single star. The ratio [S II]??6717,6731/H? departs significantly from the range predicted by this scenario, indicating the complex ionization structure in GHIIRs. There is a significant scatter in derivations of the metallicity using strong line tracers as a function of position, caused by variations in the degree of ionization. The scatter is smaller for N2O3 which points to this tracer as a better metallicity tracer than N2. One interesting result emerges from our comparison between integrated and local line ratio values: measurements of the line ratios of GHIIRs in galaxies at distances ?25 Mpc may be dominated by the ionization conditions in their low surface brightness areas.

Monreal-Ibero, A.; Relao, M.; Kehrig, C.; Prez-Montero, E.; Vlchez, J. M.; Kelz, A.; Roth, M. M.; Streicher, O.

2011-05-01

366

Selected Examples of Gas-Phase Ion Chemistry Studies  

PubMed Central

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

Nibbering, Nico M. M.

2013-01-01

367

Tracing Molecular Gas Mass in Extreme Extragalactic Environments: An Observational Study  

NASA Astrophysics Data System (ADS)

We present a new observational study of the 12CO(1-0) line emission as an H2 gas mass tracer under extreme conditions in extragalactic environments. Our approach is to study the full neutral interstellar medium (H2, H I, and dust) of two galaxies whose bulk interstellar medium (ISM) resides in environments that mark (and bracket) the excitation extremes of the ISM conditions found in infrared luminous galaxies, the starburst NGC 3310, and the quiescent spiral NGC 157. Our study maintains a robust statistical notion of the so-called X = N(H2)/I CO factor (i.e., a large ensemble of clouds is involved) while exploring its dependence on the very different average ISM conditions prevailing within these two systems. These are constrained by fully sampled 12CO(3-2) and 12CO(1-0) observations, at a matched beam resolution of half-power beam width ~15'', obtained with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii) and the 45 m telescope of the Nobeyama Radio Observatory in Japan, combined with sensitive 850 ?m and 450 ?m dust emission and H I interferometric images which allow a complete view of all the neutral ISM components. Complementary 12CO(2-1) observations were obtained with the JCMT toward the center of the two galaxies. We found an X factor varying by a factor of 5 within the spiral galaxy NGC 157 and about two times lower than the Galactic value in NGC 3310. In addition, the dust emission spectrum in NGC 3310 shows a pronounced submillimeter "excess." We tried to fit this excess by a cold dust component but very low temperatures were required (T C ~ 5-11 K) with a correspondingly low gas-to-dust mass ratio of ~5-43. We furthermore show that it is not possible to maintain the large quantities of dust required at these low temperatures in this starburst galaxy. Instead, we conclude that the dust properties need to be different from Galactic dust in order to fit the submillimeter "excess." We show that the dust spectral energy distribution can be fitted by an enhanced abundance of very small grains and discuss different alternatives.

Zhu, Ming; Papadopoulos, Padeli P.; Xilouris, Emmanuel M.; Kuno, Nario; Lisenfeld, Ute

2009-12-01

368

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

SciTech Connect

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

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

2009-12-01

369

Hydrological tracers using nanobiotechnology: proof of concept.  

PubMed

In order to answer questions that involve differentiating among multiple and potentially interacting hydrological flowpaths, it would be ideal to use multiple tracers with identical transport properties that can nonetheless be distinguished from each other. This paper describes the development and proof of concept of a new kind of 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, and paramagnetic iron oxide nanoparticles are included in the tracer to facilitate magnetic concentration of the tracers in potentially dilute water samples. Some potential advantages of this tracer concept include: virtually limitless uniquely labeled tracers, highly sensitive detection, and relatively moderate expense. Three proof-of-concept experiments at scales ranging from orders of 10 cm to 100 m demonstrated the use of the tracer system. PMID:22831647

Sharma, Asha N; Luo, Dan; Walter, M Todd

2012-08-21

370

Suzaku study of gas properties along filaments of A2744  

NASA Astrophysics Data System (ADS)

Context. We present the results of Suzaku observations of a massive galaxy cluster A2744, which is an active merger at z = 0.308. Aims: By using long X-ray observations of A2744, we aim to understand the growth of the cluster and the gas heating process through mass accretion along the surrounding filaments. Methods: We analyzed data from two-pointed Suzaku observations of A2744 to derive the temperature distribution out to the virial radius in three different directions. We also performed a deprojection analysis to study radial profiles of gas temperature, density, and entropy and compared the X-ray results with multiwavelength data to investigate correlations with the surface density of galaxies and with radio relics. Results: The gas temperature was measured out to the virial radius r200 in the north-eastern region and to about 1.5r200 in the northwestern and southern regions. The radial profile of the gas temperature is rather flat and the temperature is very high (even near r200), which makes it comparable to the mean temperature of this cluster (kT = 9 keV). These characteristics have not been reported in any other cluster. We find a hint of temperature jump in the north-eastern region whose location coincides with a large radio relic, indicating that the cluster experienced gas heating because of merger or mass accretion onto the main cluster. The temperature distribution is anisotropic and shows no clear positive correlation with the galaxy density, which suggests an inhomogeneous mass structure and a complex merger history in A2744.

Ibaraki, Y.; Ota, N.; Akamatsu, H.; Zhang, Y.-Y.; Finoguenov, A.

2014-02-01

371

Thermal tracer tests for characterizing a shallow alluvial aquifer  

NASA Astrophysics Data System (ADS)

Using heat as an active tracer in different types of aquifers is a topic of increasing interest [e.g. Vandenbohede et al.; 2008, Wagner et al., 2013; Read et al., 2013]. In this study, we investigate the potential interest of coupling heat and solute tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in nine monitoring wells located according to three transects with regards to the main groundwater flow direction. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. Temperature and concentrations in the recovery well are then used for estimating the specific heat capacity with the energy balance approach and the estimated value is found to be consistent with those found in the literature. Temperature breakthrough curves in other piezometers are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. By means of a numerical heat transport model, we provide a preliminary interpretation of these temperature breakthrough curves. Furthermore, these data could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling.

Wildemeersch, Samuel; Klepikova, Maria; Jamin, Pierre; Orban, Philippe; Hermans, Thomas; Brouyre, Serge; Dassargues, Alain

2014-05-01

372

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

SciTech Connect

Brookhaven Labs perfluorocarbon tracer (PFT) technology can be viewed as a hamm