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Isotopic labeling of methane and ethylene by uranium hydride-hydrocarbon exchangeLumba, Linda Gamboa, January 1969 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Understanding the non-conservative behaviour of fluoresceinSmith, Simon Alastair. January 2002 (has links)
Thesis (M.Sc.(Water Utilisation))--University of Pretoria, 2001. / Summaries in Afrikaans and English. Includes bibliographical references.
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Marker studies of nickel silicide formationMcLeod, John Edward January 1988 (has links)
Includes bibliographical references. / Atomic diffusion during the solid state formation of thin films of nickel silicides (Ni2Si and NiSi) from nickel and amorphous silicon has been investigated using 31Si radioactive tracer and inert marker techniques. Samples were prepared by vacuum deposition of thin films of nickel and silicon, followed by thermal annealing to effect silicide growth. The radioactive tracer investigation of Ni2Si showed nickel to be the diffusing species during silicide growth. Sharply defined Ni2si* profiles of 100% radioactive concentration at the sample surface were - obtained. The results are compared with previous results in which the profiles were more spread out and of lower surface concentration. The radioactive tracer investigation of NiSi formation showed that nickel is also the diffusing species during second phase growth. The NiSi * layer was found to be of 100% concentration. Some spreading of the activity profile near the NiSi/NiSi* interface was observed. The results were consistent with previous 31Si tracer work on NiSi formation and also with the present Ni * 2Si results. The inert marker investigation used an ultra-thin (5-10 A) continuous layer of Mo or Ta to monitor atomic movement during silicide growth. The results confirmed nickel to be the diffusing species during the growth of both phases. These results are in excellent agreement with previous inert marker studies of nickel silicide growth.
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IN SITU MEASUREMENT OF GAS DIFFUSION CHARACTERISTICS IN UNSATURATED POROUS MEDIA BY MEANS OF TRACER EXPERIMENTS.KREAMER, DAVID KENNETH. January 1982 (has links)
A gas-diffusion tracer experiment was conducted at the ChemNuclear, Inc., nuclear waste burial site near Barnwell, South Carolina, on June 1-10; 1981, testing a new methodology to measure the in situ gaseous diffusion characteristics of unsaturated porous media for the purpose of estimating the diffusive flux of volatile contaminants from the burial ground. The tracers used were CClBrF₂ and SF₆. They were released in the subsurface from permeation devices that closely approximate an ideal point-diffusion source. The permeation devices contain the tracer in liquid form and allow the tracer to escape at a constant rate by diffusion through a Teflon membrane. The release rates for CClBrF₂ and SF6 during the test were 105 and 3.3 nanograms/second, respectively. These compounds were selected on the basis of their compatabi1ity with the permeation-release device, their absence in the subsurface, and detectability in the part-per-tri11ion range in soil gas. Analyses were made in the field on a Varian 3700 series gas chromatograph equipped with an electron-capture detector. The instrument was modified to introduce soil gas through sampling valves and a Nafion tube desiccant. The diffusion sources were placed in the unsaturated soil at depths of 2 meters and 13 meters below land surface. Diffusive movements of tracer were monitored for a period of 7 days and tracer breakthrough was observed at points up to 3.5 meters away. Diffusion was modeled using a three-dimensional, continuous point source, transient-state, analytical model which allowed estimation of the effective diffusion coefficient of the porous media, and an independent assessment of the media's sorptive effects on the tracer gas. The model was calibrated using least squares and curve matching techniques, the latter of which enables a field technician to quickly interpret observed field data. Field values obtained for effective diffusion coefficient ranged from 0.026 to 0.037 cm²/sec. The average tortuosity factor observed for test site was 0.705.
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Polar organic compounds as tracers of environmental processesMedeiros, Patricia Matheus de 01 June 2006 (has links)
Sources of polar/water-soluble organic compounds conjunctly with apolar
biomarkers were characterized in natural organic matter. This multi-biomarker
approach was accomplished by a simple analytical method consisting of extraction
with dichloromethane:methanol (2:1, v/v), silylation and analysis by gaschromatography-
mass spectrometry (GC-MS). Polar and apolar biomarkers, derived
mainly from higher plants and microorganisms, were used as tracers of processes
occurring in the environmental compartments and registered in aerosol, soil and
sediment samples. Sugars (monosaccharides, disaccharides, anhydrosugars and sugar
alcohols) were utilized to trace seasonal variation inputs of biogenic organic carbon to
aerosols over a pristine forest and the passage of a smoke plume from the long-range
transport wildfire emissions. Sugars and fatty acid methyl esters were target
compounds used to better understand the plant-microorganism dynamics in a ryegrass
soil over a one-year period. Distributions and abundances of straight chain
homologous series (n-alkanes, n-alkanols, n-alkanoic acids), cyclic components (e.g.,
diterpenoids, triterpenoids, steroids) and polar biomakers (e.g., sugars) were
determined for sediment and smoke samples. In the first study, the transport and
alterations of major terrestrial biomarkers were assessed for small rivers draining the
northwestern US. In the latter, biomarkers and their thermal alteration derivatives
were identified in smoke emissions from known temperate and semi-arid green
vegetation to be applied as tracers of wildfires. This work demonstrated that a multi-biomarker
tracer analysis is a useful tool for describing and understanding the
biogeochemistry occurring in various environmental compartments. / Graduation date: 2006
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Zero-Valent Iron Decolorization of the Anthraquinone Dye Reactive Blue 4 and Biodegradation Assessment of its Decolorization ProductsYang, Hanbae 18 April 2005 (has links)
Anthraquinone dyes constitute the second largest class of textile dyes, and are used extensively in the textile industry. A high fraction of the initial reactive dye mass used in the dyeing process remains in the spent dyebath. Reactive dyes are not readily removed by typical wastewater treatment processes and the high salt concentration typical of reactive dyeing further complicates the management of spent reactive dyebaths. Investigation of the reductive transformation of reactive anthraquinone dyes and their decolorization products has been very limited. Additionally, very limited research has been conducted on the decolorization of spent reactive dyebaths.
Research was conducted to investigate the key operational parameters of batch and continuous-flow ZVI decolorization of a reactive anthraquinone dye, Reactive Blue 4 (RB4), under anoxic conditions, as well as the potential for the biodegradation of its decolorization products in a halophilic culture under aerobic conditions. The effect of two operational parameters, such as mixing intensity and initial dye concentration, on the ZVI batch decolorization kinetics indicates that ZVI decolorization of RB4 is a surface-catalyzed, mass transfer-limited process. The high salt and base concentrations enhanced the rate of RB4 decolorization. Based on parameters such as porosity, hydraulic conductivity, pore water velocity, and dispersion coefficient, non-ideal transport characteristics were observed in a continuous-flow ZVI column. The results of a long-term continuous-flow ZVI decolorization kinetics demonstrated that continuous-flow ZVI decolorization is feasible. However, column porosity losses and a shift of reaction kinetics occur in long-term column operation. ZVI decolorization of RB4 was successfully described with a pseudo first-order or a site saturation model. Lastly, the RB4 decolorization products generated by ZVI treatment had no inhibitory effect on the halophilic culture. However, biodegradation and/or mineralization of RB4 decolorization products was not observed after a long-term incubation of the culture.
This research demonstrated the feasibility of ZVI decolorization of reactive anthraquinone dyes, which will help in the development of a continuous-flow, dyebath decolorization process and the possible reuse of the renovated dyebath in the dyeing operation. Such a system could lead to substantial reduction of water usage, as well as a decrease of salt and dye discharges.
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Tracer monitoring techniques for shallow land burial of toxic wasteBetsill, Jeffrey David. January 1982 (has links) (PDF)
Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1982. / Includes bibliographical references (leaf 52).
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Géochimie isotopique Re-Os et Pb-Pb : approches environnementale et météoritique /Poirier, André, January 2005 (has links)
Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, programme en association avec l'Université du Québec à Montréal, 2006. / Bibliogr.: f. 95-101. Document électronique également accessible en format PDF. CaQCU
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Importance de la captation lymphocytaire du traceur 99mTc-MIBI et ses aspects radiobiologiquesTaibi, Naima January 2005 (has links)
Doctorat en Sciences / info:eu-repo/semantics/nonPublished
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A global three-dimensional model of the circulation and chemistry of long-lived atmospheric speciesGolombek, Amram January 1982 (has links)
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 194-201. / by Amram Golombek. / Ph.D.
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