abstract: Isotope ratios of some trace metals have proven useful for tracking Earth’s ocean oxygenation history. As the limitations of some of these isotope systems are realized, it becomes increasingly important to develop new and complementary systems. This dissertation examines the utility of molybdenum (98Mo) and thallium (205Tl) isotope compositions preserved in ancient marine shales to track past ocean oxygenation. My approach is as follows: (1) as an initial exercise, apply the well-established Mo isotope system to a set of ancient shales; (2) validate the use of the newly developed Tl isotope system; and finally (3) examine the potential of applying Mo and Tl isotopes in tandem. Increasingly heavier 98Mo are found in shales deposited during the Neoarchean (2,800 to 2,500 million years ago, or Ma), which would be a predicted consequence of progressive ocean oxygenation across this timeframe. Increasingly heavier 205Tl across a well-documented Mesozoic Oceanic Anoxic Event (~94 Ma), on the other hand, would be a predicted consequence of progressive ocean de-oxygenation. An anti-correlation in the first combined application of Mo and Tl isotopes in ancient shales provides a strong fingerprint for previously unrecognized levels of ocean oxygenation at ~2,500 Ma. Lastly, neither 98Mo or 205Tl behave as predicted in shales deposited during three Ediacaran Ocean Oxygenation Events (~635 Ma, ~580 Ma, and ~560 Ma). These unexpected trends are due, at least in part, to local-scale overprints that must be taken into consideration when pairing together Mo and Tl isotopes in shales. The ability of the Mo and Tl isotope systems to track changes in past ocean oxygenation is confirmed in this dissertation. Both isotope systems have the potential to track these changes independently, but their combined utility is particularly powerful. Under ideal conditions, their combined application can provide an even more robust fingerprint for changes in past ocean oxygenation. Even under non-ideal conditions, their combined application makes it possible to decipher local-scale overprints from signals of past ocean oxygenation. It is therefore ideal, whenever possible, to measure both 98Mo and 205Tl in the same shale samples to assess past changes in ocean oxygenation. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020

The direct determination by Differential Pulse Anodic Stripping Voltammetry (DPASV) on a Mercury Thin Film Electrode of thallous ions in solution, in a slurry of 0.010 M aqueous NaF and gamma-A1203 , is reported at 25•C. An adsorption capacity of 72.8 Mg of Tl (I) per gram of gamma-A1203 was determined by continuous addition experiments with sixty minutes equilibration time. However, continuous addition experiments using 0.010 M aqueous NaC104 , as background electrolyte, showed no adsorption of Tl (I) onto gamma-A1203 . This is attributed to the affinity of Tl (I) for perchlorate over hydroxyl anions. The results obtained for the concentration of Tl (I) in solution in batches of 0. 010 M aqueous NaF with gamma-A1203 , in the range of pH from 7.5 to 10.5, determined by DPASV and Graphite Furnace Atomic Absorption Spectroscopy, agree with a 95% confidence level, given by the regression line analysis. A strong dependence on pH is observed for the adsorption of Tl (I) onto gamma-A1203 , in 0.010 M aqueous NaF. A change from low adsorption values at pH 8, to high adsorption at pH 10 was observed.

The scanning tunneling microscopy is used to study the morphology of Tl adlayer in various stages of Tl desorption from the Si(111) surface and to study behaviour of various adsorbates on the Si(111)/Tl-(1 × 1). The utilization of thallium layer for passivation of the Si(111) was examined closely for various adsorbates. Manganese, aluminium, indium and tin layers which were directly deposited onto the Si(111)-(7 × 7) were compared with the layers prepared by deposition of adsorbate onto the passivating layer after the subsequent thermal desorption of Tl (after annealing at ≈ 400◦ C). Examined adsorbates exhibited signs of extremely high diffusivity and weak bond with the surface Si(111)/Tl- (1 × 1). The passivating layer was stable against the adsorbates.The application of thallium in the role of surfactant caused lowering of temperature and coverage needed for the preparation of reconstructions which were observed on the surfaces prepared by the direct deposition of adsorbate. 1

Two thallium scorpionate complexes: dihydrobis (3-phenyl-4-cyanopyrazolyl) boratothallium(I) (TlBp Ph,4CN), C 20H 14BN 6Tl and dihydrobis(3-tert-butyl-4-cyanopyrazolyl) boratothallium(I) (TlBp t-Bu,4CN), C 16H 22BN 6Tl have been prepared and characterized by X-ray diffraction. Both compounds crystallize in monoclinic space groups, TlBp Ph,4CN in P2 1/n with a = 4.2039(3) Å, b = 26.2211(17) Å, c = 16.611(1) Å, β = 90.199(3)°, and TlBp t-Bu,4CN in P2 1/c with a = 13.8578(5) Å, b = 9.6741(4) Å, c = 14.2790(5) Å, β 95.141(2)°. The two complexes show similar structures with elongated metal-ligand bonds and intermolecular interactions between the metal ion and cyano substituents, allowing the potential construction of cyanobridged coordination polymers.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19962号 / 医博第4152号 / 新制||医||1017(附属図書館) / 33058 / 京都大学大学院医学研究科医学専攻 / (主査)教授 髙橋 良輔, 教授 伊佐 正, 教授 村井 俊哉 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

An accurate and fairly rapid method of analysis of thallium solutions is desirable in order to facilitate further investigation of the chemistry of thallium. The dead-stop titration method which has been successfully applied to other metals of Group 3b, will not be applied to the quantitative determination of the thallium (III) ion in aqueous solution.

No

The difficulties encountered in the determination of equilibrium constants in systems with small, not directly rneasureable free ligand concentrations are discussed. These difficulties are illustrated using the determination of the formation constants of the Tl(III)-Cl- system as a specific example. Four methods are used and evaluated in this study. They are (1) the corresponding solutions method, (2) the method of Fronaeus, (3) the solubility of AgCl in Tl(III) solution method and (4) the method of Hugus. A discussion and derivation of each of these methods is given. The first three methods given and free ligand concentration data from which formation constants are calculated. The last method gives formation constants directly. Only the method of Fronaeus was capable of yielding data from which all four constants of this system can be calculated. The corresponding solutions method can be used only for the determination of β3 and β4, and the solubility measurement method can be used to calculate only β1. The method of Hugus fails completely in the Tl(III)-Cl- system. Using the data obtained from the method of Fronaeus, formation constants are calculated by solving the n̄ equation directly as well as by a graphical technique. The formation constants found in this study are given in the following table.

In this thesis, fundamental questions about the nature of the solvent/counter-ion region of x-ray crystal structures are raised. The ambiguity in the identity and occupancy of the molecular and atomic species in this region is explored experimentally. Anomalous scattering is proposed as a possible method for resolving this ambiguity. To this effect, the properties of rubidium I and thallium I are compared and contrasted to each other and to other group I metals. Finally, the structures of two modified B-DNA dodecamers are determined to explore the effect of monovalent cations on B-DNA structure. The modifications in these structures harbor tethered cations that are covalently linked to the DNA in the major groove. In one structure, the tethered cation causes axial bending of the DNA molecule, while in the second structure the molecule remains linear. We posit that the discrepancy between the two structures is due to lattice packing forces. In addition, we show evidence for the displacement of thallium I cations from the major groove of the bent structure.

Thèse (D.R.M.)--Université du Québec à Chicoutimi, 2001. / Document électronique également accessible en format PDF. CaQCU