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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Induced polarization: Electrochemistry, fractal geometry, and geohydrologic applications.

Fink, James Brewster. January 1989 (has links)
The application of spectral induced polarization (SIP) to geohydrologic and geotechnical problems is considered. Some fundamental electrochemical characteristics of sulfides are reviewed. An alternate theory of the underlying cause of IP is presented. A modified field method is proposed. Two field sites are studied. Prevailing electrochemical thought is that most sulfides, especially pyrite and chalcopyrite, have passivating surface coatings. With this thought in mind, existing geophysically-oriented electrochemical measurements may be reinterpreted quite differently than has previously been done. Large impedances at low frequencies have traditionally been attributed by geophysicists to diffusional phenomena related to rapid reactions occurring at the sulfide surface. Large impedances at low frequencies with clays have traditionally been attributed to restrained ionic diffusion between zones of clay particles. Although they appear to be due to quite different mechanisms, both of these low frequency dispersions may be explained by a single rate limiting mechanism. Using fractal geometry, the large low frequency dispersions observed on sulfides may be explained by distributed high charge-transfer resistances on rough surfaces. With high surface resistances sulfides may behave like insulating clay particles and allow charge separation to occur in surface conduction current flow. Although displacement currents may flow in sulfides they are considered to be minimal in comparison to the surface conduction currents. The concept of a common polarization phenomenon allows the previous studies on rock samples containing clay particles and/or sulfides to be equated on the basis of particle size. With clay-coated sand grains it may be possible to estimate intrinsic hydraulic conductivity based on the interpreted polarizable grain size. Aquifers, and partially water saturated zones, may be IP targets if they have small amounts of polarizable clay minerals. Aquifer detection and grain size estimation are demonstrated. Theoretical work and field studies show the advantages of using a modified dipole-dipole array and data presentation methods. The large amounts of data gathered during broad-band SIP surveys are demonstrated to be very useful in layered-earth geohydrologic problems. The higher frequency data contain much earth-structure information, are easily gathered, and allow immediate qualitative structural interpretation. Lower frequency data contain information useful in aquifer characterization.
2

ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF THIOETHER COORDINATION COMPLEXES (CYCLIC VOLTAMMETRY, OCTAHEDRAL LOW-SPIN METALS, BLUE COPPER PROTEINS, ELECTRON PARAMAGNETIC RESONANCE).

SWANSON, DALE DORSETT. January 1985 (has links)
The bis 1,4,7-trithiacyclononane (1,4,7-TTCN) complexes of iron, cobalt, nickel and copper are reported in this work. Their properties have been examined using computer-controlled electrochemical and spectroscopic techniques. These TTCN complexes form readily, are unusually symmetrical and support electron transfer reactions at the metal center. The cobalt(II) complex is octahedral, low spin and symmetrical. Four oxidation states of cobalt-TTCN complex are observed; two one-electron transfer processes are reversible. Copper (II) bis 1,4,7-TTCN is unusually symmetrical evidenced by both solid phase and ambient temperature aqueous phase electron paramagnetic resonance spectra. An unusually high redox potential for the copper complex indicates extraordinary stability of the Cu(I) oxidation state but evidently not at the expense of Cu(II) stability. The complex also has a high formation constant compared to other copper-thioether complexes. This unusual strength of thioether donor is attributed to ligand geometry. The 1,4,7-TTCN molecule is the only known cyclic polythioether to have all sulfur atoms endodentate. This structure contributes to thermodynamic stability of complexes as the ground state configuration of the free ligand is maintained in the complex.

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