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General Report of Stable Isotope Separation

Description: Abstract: "The Calutron has been successfully employed to separate the stable isotopes of twenty-one elements. The standard Beta M-2 unit modified to handle charge materials of various temperature ranges has proven adequate for a majority of separations. The problem of K life has received considerable attention but is still to be solved. Other operational problems are similar in most respects to those of uranium. The E design has, of necessity, varied greatly from the "Beta Gloria" type. A desire to keep construction simple, yet adequate for efficient collection and readily adaptable for use with many elements, has dictated the trend in E design. Water cooling on the receiver pockets was necessary with many of the elements separated. The chemical purification of the separated samples, although following a general pattern, varies with the type of pockets used and the element collected."
Date: January 20, 1947
Creator: Ketler, W. R.; Chelius, L. G. & Keim, C. P.
Partner: UNT Libraries Government Documents Department

Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses

Description: The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.
Date: March 5, 2007
Creator: Stolper, Edward
Partner: UNT Libraries Government Documents Department

Chromium isotopes as indicators of hexavalent chromium reduction

Description: This is the final report for a university research project which advanced development of a new technology for identifying chemical reduction of hexavalent chromium contamination in groundwater systems. Reduction renders mobile and toxic hexavalent chromium immobile and less toxic. The new method uses stable isotope ratio measurements, which are made using multicollector ICP-mass spectrometry. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.
Date: March 20, 2012
Creator: Johnson, Thomas M.
Partner: UNT Libraries Government Documents Department

Thermal-neutron capture in light nuclei

Description: We have made considerable progress toward the goal of carrying out thermal-neutron capture {gamma}-ray measurements on all stable isotopes below A=60. Information processed till now has significantly augmented the existing knowledge on the detailed nuclear level structure of many light nuclides. Most of this knowledge comes from our {gamma}-ray energies, level placements, and branching ratios of secondary transitions between low-lying states. Spectroscopic information is also contained in the cross sections of the primary transitions originating from the capturing state. This is deduced from the success of ``direct`` theories of neutron capture for many nuclides, especially those of light and near closed-shell character. 23 refs, 1 tab, 3 figs.
Date: October 1, 1996
Creator: Raman, S.; Jurney, E.T. & Lynn, J.E.
Partner: UNT Libraries Government Documents Department

New approach for the determination of the nuclear level density parameters

Description: The nuclear level density parameters of the stable nuclides have been determined from the neutron resonance data on the basis of new values for the spin dispersion parameter. The latter parameter is deduced from the spin dependent average level spacings of s-wave neutron resonances of odd target nuclides. In addition, the temperature dependence of the level density parameter is studied and an analytical relation for it is presented.
Date: August 1, 1998
Creator: Mughabghab, S.F. & Dunford, C.L.
Partner: UNT Libraries Government Documents Department

Advanced diffusion studies with isotopically controlled materials

Description: The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.
Date: November 14, 2004
Creator: Bracht, Hartmut A.; Silvestri, Hughes H. & Haller, Eugene E.
Partner: UNT Libraries Government Documents Department

High-purity, isotopically enriched bulk silicon

Description: The synthesis and characterization of dislocation-free, undoped, single crystals of Si enriched in all 3 stable isotopes is reported: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (89.8%). A silane-based process compatible with the relatively small amounts of isotopically enriched precursors that are practically available was used. The silane is decomposed to silicon on a graphite starter rod heated to 700-750 C in a recirculating flow reactor. A typical run produces 35 gm of polycrystalline Si at a growth rates of 5 {micro}m/min and conversion efficiency >95%. Single crystals are grown by the floating zone method and characterized by electrical and optical measurements. Concentrations of shallow dopants (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.
Date: November 17, 2004
Creator: Ager III, J.W.; Beeman, J.W.; Hansen, W.L.; Haller, E.E.; Sharp, I.D.; Liao, C. et al.
Partner: UNT Libraries Government Documents Department

Stable isotope customer list and summary of shipments, FY 1977

Description: The compilation of stable isotope customers and shipments is divided into four parts. There are alphabetical lists of domestic and foreign customers, alphabetical list of isotopes with cross-references to customers, alphabetical list of states and customers with cross-reference to customers, and tabulation of shipments, quantities, and dollars. (JSR)
Date: April 1, 1978
Creator: Davis, W.C.
Partner: UNT Libraries Government Documents Department

Phase Preference by Active, Acetate-Utilizing Bacteria at the Rifle, CO Integrated Field Research Challenge Site

Description: Previous experiments at the Rifle, Colorado Integrated Field Research Challenge (IFRC) site demonstrated that field-scale addition of acetate to groundwater reduced the ambient soluble uranium concentration. In this report, sediment samples collected before and after acetate field addition were used to assess the active microbes via {sup 13}C acetate stable isotope probing on 3 phases [coarse sand, fines (8-approximately 150 {micro}m), groundwater (0.2-8 {micro}m)] over a 24-day time frame. TRFLP results generally indicated a stronger signal in {sup 13}C-DNA in the 'fines' fraction compared to the sand and groundwater. Before the field-scale acetate addition, a Geobacter-like group primarily synthesized {sup 13}C-DNA in the groundwater phase, an alpha Proteobacterium primarily grew on the fines/sands, and an Acinetobacter sp. and Decholoromonas-like OTU utilized much of the {sup 13}C acetate in both groundwater and particle-associated phases. At the termination of the field-scale acetate addition, the Geobacter-like species was active on the solid phases rather than the groundwater, while the other bacterial groups had very reduced newly synthesized DNA signal. These findings will help to delineate the acetate utilization patterns of bacteria in the field and can lead to improved methods for stimulating distinct microbial populations in situ.
Date: February 21, 2011
Creator: Kerkhof, L.; Williams, K.H.; Long, P.E. & McGuinness, L.
Partner: UNT Libraries Government Documents Department

Stable Isotopes Division Semiannual Progress Report for Period Ending November 30, 1956

Description: Report issued by the Oak Ridge National Laboratory discussing progress made by the Stable Isotopes Division. Descriptions of of the progress and studies made are presented. This report includes tables, illustrations, and photographs.
Date: February 12, 1957
Creator: Keim, C. P. & McNally, J. R., Jr.
Partner: UNT Libraries Government Documents Department

Final Project Report: "€œExploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury"€

Description: This is the final project report for award DE-SC0005351, which supported the research project "€œExploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury."€ This exploratory project investigated the use of mercury (Hg) stable isotope measurements as a new approach to study how Hg moves and changes its chemical form in environmental systems, with particular focus on the East Fork of Poplar Creek (EFPC) near the DOE Y-12 plant (a Hg contamination source). This study developed analytical methods and collected pilot data that have set the stage for more detailed studies and have begun to provide insights into Hg movement and chemical changes. The overall Hg stable isotope approach was effective. The Hg isotope analysis methods yielded high-precision measurements of the sediment, water, and fish samples analyzed; quality control measures demonstrated the precision. The pilot data show that the 202Hg/198Hg, 199Hg/198Hg, and 201Hg/198Hg isotope ratios vary in this system. 202Hg/198Hg ratios of the Hg released from the Y-12 plant are relatively high, and those of the regional Hg background in soils and river sediments are significantly lower. Unfortunately, 202Hg/198Hg differences that might have been useful to distinguish early Hg releases from later releases were not observed. However, 202Hg/198Hg ratios in sediments do provide insights into chemical transformations that may occur as Hg moves through the system. Furthermore, 199Hg/198Hg and 201Hg/198Hg ratio analyses of fish tissues indicate that the effects of sunlight-driven chemical reactions on the Hg that eventually ends up in EFPC fish are measureable, but small. These results provide a starting point for a more detailed study (already begun at Univ. of Michigan) that will continue Hg isotope ratio work aimed at improving understanding of how Hg moves, changes chemically, and does or does not take on more highly toxic forms in the Oak Ridge area. ...
Date: August 1, 2012
Creator: Johnson, Thomas M
Partner: UNT Libraries Government Documents Department

Investigations of (Delta)14C, (delta)13C, and (delta)15N in vertebrae of white shark (Carcharodon carcharias) from the eastern North Pacific Ocean

Description: The white shark (Carcharodon carcharias) has a complex life history that is characterized by large scale movements and a highly variable diet. Estimates of age and growth for the white shark from the eastern North Pacific Ocean indicate they have a slow growth rate and a relatively high longevity. Age, growth, and longevity estimates useful for stock assessment and fishery models, however, require some form of validation. By counting vertebral growth band pairs, ages can be estimated, but because not all sharks deposit annual growth bands and many are not easily discernable, it is necessary to validate growth band periodicity with an independent method. Radiocarbon ({sup 14}C) age validation uses the discrete {sup 14}C signal produced from thermonuclear testing in the 1950s and 1960s that is retained in skeletal structures as a time-specific marker. Growth band pairs in vertebrae, estimated as annual and spanning the 1930s to 1990s, were analyzed for {Delta}{sup 14}C and stable carbon and nitrogen isotopes ({delta}{sup 13}C and {delta}{sup 15}N). The aim of this study was to evaluate the utility of {sup 14}C age validation for a wide-ranging species with a complex life history and to use stable isotope measurements in vertebrae as a means of resolving complexity introduced into the {sup 14}C chronology by ontogenetic shifts in diet and habitat. Stable isotopes provided useful trophic position information; however, validation of age estimates was confounded by what may have been some combination of the dietary source of carbon to the vertebrae, large-scale movement patterns, and steep {sup 14}C gradients with depth in the eastern North Pacific Ocean.
Date: June 8, 2006
Creator: Kerr, L A; Andrews, A H; Cailliet, G M; Brown, T A & Coale, K H
Partner: UNT Libraries Government Documents Department

Annual Growth Bands in Hymenaea courbaril

Description: One significant source of annual temperature and precipitation data arises from the regular annual secondary growth rings of trees. Several tropical tree species are observed to form regular growth bands that may or may not form annually. Such growth was observed in one stem disk of the tropical legume Hymenaea courbaril near the area of David, Panama. In comparison to annual reference {Delta}{sup 14}C values from wood and air, the {Delta}{sup 14}C values from the secondary growth rings formed by H. courbaril were determined to be annual in nature in this one stem disk specimen. During this study, H. courbaril was also observed to translocate recently produced photosynthate into older growth rings as sapwood is converted to heartwood. This process alters the overall {Delta}{sup 14}C values of these transitional growth rings as cellulose with a higher {Delta}{sup 14}C content is translocated into growth rings with a relatively lower {Delta}{sup 14}C content. Once the annual nature of these growth rings is established, further stable isotope analyses on H. courbaril material in other studies may help to complete gaps in the understanding of short and of long term global climate patterns.
Date: February 9, 2004
Creator: Westbrook, J A; Guilderson, T P & Colinvaux, P A
Partner: UNT Libraries Government Documents Department

Temperature and vital effect controls on Bamboo coral (Isididae) isotopegeochemistry: A test of the "lines method"

Description: Deep-sea bamboo corals hold promise as long-term climatic archives, yet little information exists linking bamboo coral geochemistry to measured environmental parameters. This study focuses on a suite of 10 bamboo corals collected from the Pacific and Atlantic basins (250-2136 m water depth) to investigate coral longevity, growth rates, and isotopic signatures. Calcite samples for stable isotopes and radiocarbon were collected from the base the corals, where the entire history of growth is recorded. In three of the coral specimens, samples were also taken from an upper branch for comparison. Radiocarbon and growth band width analyses indicate that the skeletal calcite precipitates from ambient dissolved inorganic carbon and that the corals live for 150-300 years, with extension rates of 9-128 {micro}m/yr. A linear relationship between coral calcite {delta}{sup 18}O and {delta}{sup 13}C indicates that the isotopic composition is influenced by vital effects ({delta}{sup 18}O:{delta}{sup 13}C slope of 0.17-0.47). As with scleractinian deep-sea corals, the intercept from a linear regression of {delta}{sup 18}O versus {delta}{sup 13}C is a function of temperature, such that a reliable paleotemperature proxy can be obtained, using the 'lines method.' Although the coral calcite {delta}{sup 18}O:{delta}{sup 13}C slope is maintained throughout the coral base ontogeny, the branches and central cores of the bases exhibit {delta}{sup 18}O:{delta}{sup 13}C values that are shifted far from equilibrium. We find that a reliable intercept value can be derived from the {delta}{sup 18}O:{delta}{sup 13}C regression of multiple samples distributed throughout one specimen or from multiple samples within individual growth bands.
Date: March 1, 2011
Creator: Hill, T M; Spero, H J; Guilderson, T P; LaVigne, M; Clague, D; Macalello, S et al.
Partner: UNT Libraries Government Documents Department

Origin of groundwater discharge at Burney Falls, Shasta Co., California

Description: Stable isotope measurements of surface water and groundwater from the Burney Basin and northern Hat Creek Basin indicate that spring discharge at Burney Falls is a mixture of water derived from both basins. Relative mixing proportions depend on the assumed isotopic composition of each end-member, but plausible mixing models suggest that approximately 40 to 60% of the spring water originates from the Burney Basin. The isotope data also indicate that Burney Creek cannot be the dominant source of Burney Falls Springs. The proposed development of a new power plant (Three Mountain Project) in the Burney Basin area of northeastern California provided the impetus for this brief report on the origin of groundwater discharge at Burney Falls Springs. The proposed project is situated {approx} 13 km up-gradient of McArthur-Burney Falls Memorial State Park, where groundwater emanates from a group of large springs at a rate of approximately 4.2 to 6.4 m{sup 3}s{sup -1} (150-225 ft{sup 3}s{sup -1}). This report discusses stable isotope data for water samples that were gathered from this region by the author in the mid-1990's. The intent is to provide impartial scientific evidence that may assist in the environmental risk assessment process.
Date: February 9, 2000
Creator: Rose, T P
Partner: UNT Libraries Government Documents Department

Quantifying human vitamin kinetics using AMS

Description: Tracing vitamin kinetics at physiologic concentrations has been hampered by a lack of quantitative sensitivity for chemically equivalent tracers that could be used safely in healthy people. Instead, elderly or ill volunteers were sought for studies involving pharmacologic doses with radioisotopic labels. These studies fail to be relevant in two ways: vitamins are inherently micronutrients, whose biochemical paths are saturated and distorted by pharmacological doses; and while vitamins remain important for health in the elderly or ill, their greatest effects may be in preventing slow and cumulative diseases by proper consumption throughout youth and adulthood. Neither the target dose nor the target population are available for nutrient metabolic studies through decay counting of radioisotopes at high levels. Stable isotopic labels are quantified by isotope ratio mass spectrometry at levels that trace physiologic vitamin doses, but the natural background of stable isotopes severely limits the time span over which the tracer is distinguishable. Indeed, study periods seldom ranged over a single biological mean life of the labeled nutrients, failing to provide data on the important final elimination phase of the compound. Kinetic data for the absorption phase is similarly rare in micronutrient research because the phase is rapid, requiring many consecutive plasma samples for accurate representation. However, repeated blood samples of sufficient volume for precise stable or radio-isotope quantitations consume an indefensible amount of the volunteer's blood over a short period. Thus, vitamin pharmacokinetics in humans has often relied on compartmental modeling based upon assumptions and tested only for the short period of maximal blood circulation, a period that poorly reflects absorption or final elimination kinetics except for the most simple models.
Date: February 19, 2004
Creator: Hillegonds, D; Dueker, S; Ognibene, T; Buchholz, B; Lin, Y; Vogel, J et al.
Partner: UNT Libraries Government Documents Department

High-resolution metagenomics targets major functional types in complex microbial communities

Description: Most microbes in the biosphere remain uncultured and unknown. Whole genome shotgun (WGS) sequencing of environmental DNA (metagenomics) allows glimpses into genetic and metabolic potentials of natural microbial communities. However, in communities of high complexity metagenomics fail to link specific microbes to specific ecological functions. To overcome this limitation, we selectively targeted populations involved in oxidizing single-carbon (C{sub 1}) compounds in Lake Washington (Seattle, USA) by labeling their DNA via stable isotope probing (SIP), followed by WGS sequencing. Metagenome analysis demonstrated specific sequence enrichments in response to different C{sub 1} substrates, highlighting ecological roles of individual phylotypes. We further demonstrated the utility of our approach by extracting a nearly complete genome of a novel methylotroph Methylotenera mobilis, reconstructing its metabolism and conducting genome-wide analyses. This approach allowing high-resolution genomic analysis of ecologically relevant species has the potential to be applied to a wide variety of ecosystems.
Date: August 1, 2009
Creator: Kalyuzhnaya, Marina G.; Lapidus, Alla; Ivanova, Natalia; Copeland, Alex C.; McHardy, Alice C.; Szeto, Ernest et al.
Partner: UNT Libraries Government Documents Department

Use of Stable Noble Gases as a Predictor of Reactor Fuel Type and Exposure

Description: Ensuring spent reactor fuel is not produced to provide weapons-grade plutonium is becoming a major concern as many countries resort to nuclear power as a solution to their energy problems. Proposed solutions range from the development of proliferation resistant fuel to continuous monitoring of the fuel. This paper discusses the use of the stable isotopes of the fissiogenic noble gases, xenon and krypton, for determining the burnup characteristics, fuel type, and the reactor type of the fuel from which the sample was obtained. The gases would be collected on-stack as the fuel is reprocessed, and thus confirm that the fuel is as declared.
Date: August 30, 1999
Creator: Fearey, B.L.; Charlton, W.S.; Perry, R.T.; Poths, J.; Wilson, W.B.; Hemberger, P.H. et al.
Partner: UNT Libraries Government Documents Department

Experimental Geochemical Studies Relevant to Carbon Sequestration

Description: The authors are conducting laboratory studies to determine: (i) the thermophysical properties and phase relations of CO{sub 2}CH{sub 4}-H{sub 2}O fluids; (ii) the magnitude of stable isotope partitioning during calcite precipitation; and (iii) the utility of natural isotopic tracers in quantifying CO{sub 2} residence times, storage capacity and reaction mechanisms in the subsurface. The ultimate aim of the research on CO{sub 2}-CH{sub 4}H{sub 2}O fluids is to develop a comprehensive equation of state for binary and ternary mixtures of CO{sub 2}, CH{sub 4} and H{sub 2}O at pressure-temperature (P-T) conditions representative of those in deep gas fields and saline aquifers. To acquire the data needed to create the model, two unique, custom-designed devices at the Oak Ridge National Laboratory--a high pressure vibrating-tube densimeter, and a hydrogen-service internally heated pressure vessel--are being used to measure the densities, excess molar volumes, miscibility limits and activity-composition relations of CO{sub 2}H{sub 2}O, CH{sub 4}-H{sub 2}O and ternary CO{sub 2}-CH{sub 4}-H{sub 2}O mixtures at P-T conditions near the vapor-saturation phase boundary in the H{sub 2}O system. In another project, experiments are being conducted to determine the kinetics of carbonate precipitation from CO{sub 2}-rich saline waters, and associated isotope partitioning. Both inorganic and microbially mediated processes are being investigated under environmental conditions encountered during CO{sub 2} injection into the subsurface. Our results indicate that the behavior of isotopes, especially oxygen isotopes, is affected by the composition of water and the precipitation rate of carbonate minerals. We have also observed significant carbon isotope partitioning (4 to 8{per_thousand}) between CO{sub 2} and hydrocarbon-saturated rock (an EOR injection scenario) reacted statically at 25 C. These preliminary results suggest that a light isotopic component of CO{sub 2} may be retained in the reservoir, leading to isotopically heavier CO, further down the flow path.
Date: January 10, 2001
Creator: Blencoe, J. G.
Partner: UNT Libraries Government Documents Department

Effect of CH4 and O2 variations on rates of CH4 oxidation and stable isotope fractionation in tropical rain forest soils

Description: Methane-oxidizing bacteria are the primary sink for CH{sub 4} in reduced soils, and account for as much as 90 percent of all CH{sub 4} produced. Methanotrophic bacteria strongly discriminate against the heavy isotopes of carbon, resulting in CH{sub 4} emissions that are significantly more enriched in {sup 13}C than the original source material. Previous studies have used an isotope mass balance approach to quantify CH{sub 4} sources and sinks in the field, based on the assumption that the fractionation factor for CH{sub 4} oxidation is a constant. This study quantifies the effect of systematic variations in CH{sub 4} and O{sub 2} concentrations on rates of CH{sub 4} oxidation and stable isotope fractionation in tropical rain forest soils. Soils were collected from the 0-15 cm depth, and incubated with varying concentrations of CH{sub 4} (100 ppmv, 500 ppmv, 1000 ppmv, and 5000 ppmv) or O{sub 2} (3 percent, 5 percent, 10 percent, and 21 percent). The isotope fractionation factor for CH{sub 4} oxidation was calculated for each incubation using a Rayleigh fractionation model. Rates of CH{sub 4} oxidation varied significantly between CH{sub 4} treatments, with the 100 ppmv CH{sub 4} treatment showing the lowest rate of CH{sub 4} uptake, and the other 3 treatments showing similar rates of CH{sub 4} uptake. Rates of CH{sub 4} oxidation did not vary significantly between the different O{sub 2} treatments. The fractionation factor for CH{sub 4} oxidation varied significantly between the different CH{sub 4} treatments, with the 5000 ppmv CH{sub 4} treatment showing the largest {sup 13}C-enrichment of residual CH{sub 4}. In treatments where CH{sub 4} concentration was not rate-limiting (> 500 ppmv CH{sub 4}), the fractionation factor for CH{sub 4} oxidation was negatively correlated with CH{sub 4} oxidation rate (P < 0.003, r{sup 2} = 0.86). A multiple regression model that included initial CH{sub ...
Date: October 1, 2003
Creator: Teh, Yit Arn; Conrad, Mark; Silver, Whendee L. & Carlson, Charlotte M.
Partner: UNT Libraries Government Documents Department

Is Lutein a Physiologically Important Ligand for Transthyretin in Humans?

Description: Lutein and zeaxanthin are the only carotenoids accumulated in the macula of the human retina and are known as the macular pigments (MP). These pigments account for the yellow color of the macula and appear to play an important role in protecting against age-related macular degeneration (AMD). The uptake of lutein and zeaxanthin in human eyes is remarkably specific. It is likely that specific transport or binding proteins are involved. The objective is to determine whether transthyretin (TTR) is a transport protein in human plasma and could thus deliver lutein from the blood to the retina. In this study, they used a biosynthetic {sup 13}C-lutein tracer and gas chromatography-combustion interfaced-isotope ratio mass spectrometry (GCC-IRMS) to gain the requisite sensitivity to detect the minute amounts of lutein expected as a physiological ligand for human transthyretin. The biosynthetic {sup 13}C-labeled lutein tracer was purified from algae. Healthy women (n = 4) each ingested 1 mg of {sup 13}C-labeled lutein daily for 3 days and a blood sample was collected 24 hours after the final dose. Plasma TTR was isolated by retinol-binding protein (RBP)-sepharose affinity chromatography and extracted with chloroform. The {sup 13}C/{sup 12}C ratio in the TTR extract was measured by GCC-IRMS. There was no {sup 13}C-lutein enrichment in the pure TTR extract. This result indicated that lutein is not associated with TTR in human plasma after ingestion in physiological amounts. Some hydrophobic compounds with yellow color may bind to human TTR in the plasma. However, this association needs to be further proved by showing specificity. The study provides a new approach for carotenoid-binding protein studies using a stable isotope tracer method combined with the high precision of GCC-IRMS. The mechanism of selective transport, uptake, and accumulation of lutein in human macula remain to be determined.
Date: May 31, 2003
Creator: Chen, Liwei
Partner: UNT Libraries Government Documents Department

Natural Strontium, Iodine, Cesium, and Cobalt in Savannah River Site Groundwater: Data Report

Description: The purpose of this investigation was to obtain baseline groundwater concentrations for naturally occurring stable isotopes of Sr, I, Cs, and Co in shallow aquifers at the Savannah River Site. These data are necessary to fully understand migration and remediation of 90Sr, 129I, 137Cs, and 60Co. Fourteen P-wells were selected and sampled based on their close proximity to facilities, available water table and Gordon aquifer wells, and archived core. This report provides the analytical results from the groundwater sampling and core leaching studies. Several radioactive contaminants have naturally occurring counterparts that are non-radioactive, but have chemical behavior that is identical to the radioactive contaminants. These naturally occurring isotopes are typically present in groundwater at mass concentrations that are orders of magnitude greater than their associated radionuclides. A consequence of this is that the natural constituents compete for adsorption and cation exchange site s with their radioactive counterparts, reducing retardation of the radioactive species. Hence, the concentrations of these natural species are important to the modeling of monitored natural attenuation, performance assessments, and other regulatory documents that require a fate and transport analysis.
Date: December 15, 2003
Creator: Denham, M.E.
Partner: UNT Libraries Government Documents Department

Origin and recharge rates of alluvial ground waters, Eastern Desert, Egypt.

Description: Stable isotope and tritium analyses of shallow ground waters in the Eastern Desert of Egypt showed that the waters were derived largely by evaporation of regional precipitation and at least partly from precipitation in the past 45 y. To estimate the ground water recharge rate, we developed an integrated hydrologic model based on satellite data, geologic maps, infiltration parameters, and spatial rainfall distribution. Modeling indicated that during a severe 1994 storm, recharge through transmission loss in Wadi El-Tarfa was 21% of the precipitation volume. From archival precipitation data, we estimate that the annual recharge rate for the El-Tarfa alluvial aquifer is 4.7 x 10{sup 6} m{sup 3}. Implications for the use of renewable ground waters in arid areas of Egypt and in neighboring countries are clear.
Date: April 12, 2002
Creator: Sultan, M.; Gheith, H.; Sturchio, N. C.; El Alfy, Z. & Danishwar, S.
Partner: UNT Libraries Government Documents Department