Tracer characterization

Food authentication, application of stable isotope tracers, characterization of complex metallobiomolecules, and investigation of their role in biological processes are all areas in which ICP-MS can play a more and more critical role. Speciation will continue to be a very dynamic field of investigation and the integration of speciation and metabolism studies with the use of stable isotopes as species-specific tracers is likely to become a research area of vital importance. On... 

Figure 6 is a schematic of the time history of representative tracers characterized by the first two types of release styles for the northern hemisphere. Three of the tracers (radiocarbon and the CFCs) are gaseous phase tracers, and are consequently relatively homogeneously distributed between the hemispheres, with the northern hemisphere leading the southern hemisphere by l-2yr both CFCs and radiocarbon were released preferentially in the northern hemisphere. Radiocarbon was released from atmospheric nuclear weapons tests that were almost solely in the northern hemisphere, and CFC releases were dominated by North American, European, and Soviet production. The time lag... 

There should be specific, saturable binding to the receptor, accompanied by pharmacological characteristics appropriate to the functional effects, demonstrable using a radioactive, eg, tritium or iodine-125, ligand to label the receptor. Radioligand binding assays (1,6) have become a significant means by which to identify and characterize receptors and enzymes (see Immunoassays Radioactive tracers). Isolation of the receptor or expression of the receptor in another cell, eg, an oocyte can be used to confirm the existence of a discrete entity. 

NRA is an effective technique for measuring depth profiles of light elements in solids. Its sensitivity and isotope-selective character make it ideal for isotopic tracer experiments. NRA is also capable of profiling hydrogen, which can be characterized by only a few other analytical techniques. Future prospects include further application of the technique in a wider range of fields, three-dimensional mapping with microbeams, and development of an easily accessible and comprehensive compilation of reaction cross sections. 

P0O3 may have been detected on a tracer scale but has not been characterized with weighable amounts of the element. 

His researches and those of his pupils led to his formulation in the twenties of the concept of active catalytic centers and the heterogeneity of catalytic and adsorptive surfaces. His catalytic studies were supplemented by researches carried out simultaneously on kinetics of homogeneous gas reactions and photochemistry. The thirties saw Hugh Taylor utilizing more and more of the techniques developed by physicists. Thermal conductivity for ortho-para hydrogen analysis resulted in his use of these species for surface characterization. The discovery of deuterium prompted him to set up production of this isotope by electrolysis on a large scale of several cubic centimeters. This gave him and others a supply of this valuable tracer for catalytic studies. For analysis he invoked not only thermal conductivity, but infrared spectroscopy and mass spectrometry. To ex-... 

Dunn et al. (D7) measured axial dispersion in the gas phase in the system referred to in Section V,A,4, using helium as tracer. The data were correlated reasonably well by the random-walk model, and reproducibility was good, characterized by a mean deviation of 10%. The degree of axial mixing increases with both gas flow rate (from 300 to 1100 lb/ft2-hr) and liquid flow rate (from 0 to 11,000 lb/ft2-hr), the following empirical correlations being proposed ... 

Schiesser and Lapidus (S3), in later studies, measured the liquid residencetime distribution for a column of 4-in. diameter and 4-ft height packed with spherical particles of varying porosity and nominal diameters of in. and in. The liquid medium was water, and as tracers sodium chloride or methyl orange were employed. The specific purposes of this study were to determine radial variations in liquid flow rate and to demonstrate how pore diffusivity and pore structure may be estimated and characterized on the basis of tracer experiments. Significant radial variations in flow rate were observed methods are discussed for separating the hydrodynamic and diffusional contributions to the residence-time curves. 

Glaser and Lichtenstein (G3) measured the liquid residence-time distribution for cocurrent downward flow of gas and liquid in columns of -in., 2-in., and 1-ft diameter packed with porous or nonporous -pg-in. or -in. cylindrical packings. The fluid media were an aqueous calcium chloride solution and air in one series of experiments and kerosene and hydrogen in another. Pulses of radioactive tracer (carbon-12, phosphorous-32, or rubi-dium-86) were injected outside the column, and the effluent concentration measured by Geiger counter. Axial dispersion was characterized by variability (defined as the standard deviation of residence time divided by the average residence time), and corrections for end effects were included in the analysis. The experiments indicate no effect of bed diameter upon variability. For a packed bed of porous particles, variability was found to consist of three components (1) Variability due to bulk flow through the bed... 

The residence time is the time spent in a reservoir by an individual atom or molecule. It is also the age of a molecule when it leaves the reservoir. If the pathway of a tracer from the source to the sink is characterized by a physical transport, the word transit time can also be used. Even for a single chemical substance, different atoms and molecules will have different residence times in a given reservoir. Let the probability density... 

Swarzenski PW, Reich CD, Spechler RM, Kindinger JL Moore WS (2001) Using multiple geochemical tracers to characterize the hydrogeology of the submarine spring off Crescent Beach, Florida. Chem Geol 179 187-202... 

Resolving some of the issues surrounding the use of " Th as a tracer for POC flux, as well as collecting simultaneous °Po and °Pb data, will enable a better characterization of other components of the particulate flux, such as biogenic silica (Buesseler et al. 2001 Friedrich and Rutgers van der Loeff 2002) and particle-associated... 

Dye structures of passive tracers placed in time-periodic chaotic flows evolve in an iterative fashion an entire structure is mapped into a new structure with persistent large-scale features, but finer and finer scale features are revealed at each period of the flow. After a few periods, strategically placed blobs of passive tracer reveal patterns that serve as templates for subsequent stretching and folding. Repeated action by the flow generates a lamellar structure consisting of stretched and folded striations, with thicknesses s(r), characterized by a probability density function, f(s,t), whose... 

TFSA-WATERFLOOD PILOT. A 36 acre (1.14 x lO m2) TFSA-waterflood pilot was recently conducted in the Torrance Field in the Los Angeles Basin of Southern California. To characterize the fluid floi patterns within the pilot, an interwell chemical tracer study was conducted with sodium thiocyanate. Results of the tracer study are shown in Table IV. Only 61.6 % of the injected tracer was recovered in the produced fluids, indicating that as much as 38.4 % of the injected fluids were flowing out of the pattern. Furthermore, since only 1604 bbl/d (255 m3/d) of brine was injected into the pattern, as much as 75.9 % of the total fluids produced by pilot wells were from outside the pattern. 

Fluid flow patterns within the pilot pattern were characterized by an interwell chemical tracer study which showed that as much as 38.4 % of the fluids injected into the pilot flowed out of the unconfined pattern and 75.9 % of the produced fluids are from outside the pattern. 

At time t the fraction of the effluent fluid characterized by an age less than t (and thus with a composition Wo) is just equal to F(t). At the same time, the fraction of the effluent characterized by an age greater than t (with the original inlet composition Wo) is equal to 1 — F(t). The time dependence of the weight fraction tracer in the effluent (w ) is then given by... 

Kraehenbuhl, J.P., Calardy, R.E., and Jamieson, J.D. (1974) Preparation and characterization of an immu-noelectron microscope tracer consisting of a heme-octapeptide coupled to Fab. J. Exp. Med. 139, 208. 

In the second model, the distribution and removal rates of tracers in the ocean are characterized through a one dimensional, (vertical) diffusion-advection equation. In this model, which ignores all horizontal processes, the equation governing the distribution of tracer in the soluble phase is [51,52,53,54] ... 

If it is suspected (or known) that the plug flow assumption does not hold, a separate tracer study is needed to characterize the flow distribution within the pipes. These data are then used to adjust both the concentration and the sampling time, as required. If the nature of flow and mixing in the vessel is independent of the flow characteristics in the pipes, then the o1 curve for the vessel may be calculated from... 

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