Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Dec. 4, 2007). PDF text: xviii, 149 p. : ill. ; 7 Mb. UMI publication number: AAT 3271931. Includes bibliographical references. Also available in microfilm and microfiche formats.

<p>This thesis is focused on the synthesis and structural determination of a series of quasicrystal approximants in the <i>RE</i>₁₃Zn_~58 (<i>RE</i> = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Ce₁₃Cd_~58and <i>RE</i>Cd₆ (<i>RE</i> = Tb, Ho, Er, Tm and Lu) systems. Structural studies were performed by single crystal X-ray diffraction methods.</p><p>The <i>RE</i>Cd₆ phases are 1/1 cubic approximants to the stable icosahedral quasicrystals. The structure of quasicrystals cannot be solved by conventional crystallography due to the lack of periodicity in three-dimensional space. On the other hand, quasicrystal approximants exhibit long-range order, which makes their structural determination possible by standard methods. Since they are believed to display the same local arrangement as the quasicrystals, the structures of the quasicrystal approximants play a key role in understanding quasicrystals.</p><p>The <i>RE</i>₁₃Zn_~58 and Ce₁₃Cd_~58 quasicrystal approximants show measurable compositional variations coupled to subtle structural differences. The crystal structures are generally rather more complex than previously reported, and exhibit a number of different ordering and disordering modes.</p>

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 194-202).

This dissertation focuses on the synthetic exploratory synthesis of molybdenum chalcogenides and rare earth metal-rich ternary tellurides as a part of an effort to produce molecular building blocks of molybdenum chalcogenide clusters and to explore their structural relationships with solid state cluster networks. The tightly cross-linked Mo3nSe3n+2(n = 2, 3, ...∞) clusters and chain compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675 °C to yield reduced, cyanide-terminated molybdenum chalcogenide clusters that are thermodynamically stable. At temperatures of 650-675 °C, linear chain compounds I6[Mo6Se8(CN)4(CN)2/2] (MI = K, Cs) were prepared from reactions of Mo6Se8 or elemental starting materials, Mo and Se with excess molten cyanide (KCN, CsCN). These are the first known compounds to feature linking of Mo6Se8 clusters via cyanide bridges. Magnetic susceptibility and EPR measurements indicate that there is one unpaired electron per cluster. A new reduced molecular octahedral complex, Na8[Mo6Se8(CN)6]•20H2O was prepared by the reduction of [Mo6Se8(CN)6]7-with Zn in an aqueous NaCN solution. Single crystal structure was determined. Cyclic voltammetric measurements in basic aqueous media show multiple reversible redox waves corresponding to [Mo6Se8(CN)6]6-/7-, [Mo6Se8(CN)6]7-/8-, [Mo6Se8(CN)6]8-/9-redox couples with half-wave potentials of E1/2 = -0.442 V, -0.876 V, and 11.369 V respectively versus the standard hydrogen electrode (SHE). UV-Vis studies support the presence of the reduced cluster compound. New reduced molecular tetrahedral complexes, K7Na[Mo4Se4(CN)12]•5H2O•MeOH, Na4Cs7[Mo4Se4(CN)12]Cl3, Na8[Mo4Se4(CN)12], and Na4K4[Mo4Se4(CN)12]•12H2O were prepared. Preparation of Na8[Mo4Se4(CN)12] is an improved method for the synthesis of the Mo4Se4 core. Half-wave potentials of E1/2 for the [Mo4Se4(CN)12]6-/7-and [Mo4Se4(CN)12]7-/8-couples are 0.233 V, and -0.422 V respectively versus SHE. The molecular cubane clusters [Mo4Se4(CN)12]7-/8-play an essential role in the process by which the discrete [Mo6Se8(CN)6]6-and [Mo6Se8(CN)6]are excised from the CN-linked chain compound, K6Mo6Se8(CN)5. A new rare-earth telluride compound with the empirical composition of Gd4NiTe2 was synthesized from a high-temperature solid-state reaction. Gd4MTe2 (M = Ni) crystallizes in the orthorhombic space group Pnma. This unprecedented structure consists of a cluster condensation of Ni-centered gadolinium tricapped trigonal prisms along the rectangular faces of the trigonal prism such that the Ni atoms act as two of the caps to the trigonal prisms.

This thesis is focused on the synthesis and structural determination of a series of quasicrystal approximants in the RE13Zn~58 (RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Ce13Cd~58 and RECd6 (RE = Tb, Ho, Er, Tm and Lu) systems. Structural studies were performed by single crystal X-ray diffraction methods. The RECd6 phases are 1/1 cubic approximants to the stable icosahedral quasicrystals. The structure of quasicrystals cannot be solved by conventional crystallography due to the lack of periodicity in three-dimensional space. On the other hand, quasicrystal approximants exhibit long-range order, which makes their structural determination possible by standard methods. Since they are believed to display the same local arrangement as the quasicrystals, the structures of the quasicrystal approximants play a key role in understanding quasicrystals. The RE13Zn~58 and Ce13Cd~58 quasicrystal approximants show measurable compositional variations coupled to subtle structural differences. The crystal structures are generally rather more complex than previously reported, and exhibit a number of different ordering and disordering modes.

No description available.

Rare earth ferrosilicon alloy is an important additive for ferrous metallurgy. It is mainly used to control the detrimental effects of sulfur in steel and to modify graphite structures in cast iron. The aim of this study was to optimize the conditions for the production of rare earth ferrosilicon alloy by metallothermic reduction process using a preconcentrate prepared from a bastnasite type of ore present in the Beylikahir-EskiSehir region of Turkey. In this study, the rare earth preconcentrate was reduced by aluminum together with ferrosilicon and rare earth ferrosilicon alloys were produced. The optimum conditions of reduction, which are time, temperature, reducer amounts and the basicity of the slag phase, were investigated by smelting in an induction furnace. At the end of the study, a rare earth ferrosilicon alloy containing 39.3 % rare earths, 37.5 % silicon, 19.3 % iron and 3.9 % aluminum was produced under the optimum conditions determined with 57.7 % rare earth metal recovery.

This dissertation focuses on two areas of garnet porphyroblast crystallization that have until now remained largely uninvestigated: epitaxial nucleation of garnet porphyroblasts and yttrium and rare earth (Y+REE) uptake in metamorphic garnet. The mechanism of epitaxial nucleation is explored as a step towards determining which aspects of interfaces are significant to interfacial energies and nucleation rates. Garnet from the aureole of the Vedrette di Ries tonalite, Eastern Alps, shows a clear case of epitaxial nucleation in which garnet nucleated on biotite with (110)grt / (001)bt with [100]grt / [100]bt. The occurrence is remarkable for the clear genetic relationships revealed by the microstructures and for its preservation of the mica substrate, which allows unambiguous determination of the coincident lattice planes and directions involved in the epitaxy. Not all epitaxial nucleation is conspicuous; to increase the ability to document epitaxial relationships between garnet and micas, I develop and apply a method for determining whether evidence for epitaxial nucleation of garnet is present in porphyroblasts containing an included fabric. Although the magnitude of uncertainties in orientation measurements for garnets from Passo del Sole (Switzerland), the Nevado Filabride Complex (Spain), and Harpswell Neck (USA) preclude definitive identification of epitaxial relationships, the method has potential to become a viable technique for creating an inventory of instances and orientations of epitaxial nucleation with appropriate sample selection. Using lattice-dynamics simulations, I explore the most commonly documented epitaxial relationship, (110)grt / (001)ms. The range of interfacial energies resulting from variations in the intracrystalline layer within garnet at the interface, the initial atomic arrangement at the interface, and the rotational orientation of the garnet structure relative to the muscovite structure shows that the intracrystalline layer within garnet has the greatest effect on interfacial energy. A complete understanding of the role of intergranular diffusion for yttrium and rare-earth-element uptake in porphyroblastic garnet is critical because the complexities of Y+REE zoning in garnets and the mechanisms of Y+REE uptake have implications for petrologic interpretations and garnet-based geochronology. Y+REE distributions in garnets from the Picuris Mountains (USA), Passo del Sole (USA), and the Franciscan Complex (USA) imply diverse origins linked to differing degrees of mobility of these elements through the intergranular medium during garnet growth. / text

Discovery of anti-cancer cisplatin was a great success in anti-cancer chemotherapy. Numerous analogues of cisplatin such as carboplatin and oxaliplatin, were developed to improve the clinical effectiveness. Nevertheless, the clinical uses of these platinum-based drugs are limited by the occurrence of drug-resistance, narrow range of susceptible cancer types and severe toxicity. These drawbacks have stimulated the development of other metal-based compounds with distinct mechanisms of anti-cancer action. In this study, a series of ytterbium(III) porphyrin and iron(II) polypyridyl complexes were synthesized. Their anti-cancer activities were examined. With the aid of gene expression profiling and bioinformatics analysis, the mechanisms of these anti-cancer active complexes have been examined. A series of ytterbium(III) porphyrin complexes have been prepared and structurally characterized. An ytterbium(III) octaethylporphyrin complex (1) was found to exhibit potent anti-cancer activities with cytotoxic IC50 values down to sub-micromolar range. Complex (1) was shown to exist as a dimeric hydroxyl-bridged complex [Yb2(OEP)2(μ-OH)2] (where H2OEP = octylethylporphyrin) in CH2Cl2 and in solid state, and as monomeric [Yb(OEP)(DMSO)(OH)(OH2)] in DMSO/aqueous solution. Unlike various anti-cancer lanthanide complexes which are commonly proposed to target cellular DNA, our transcriptomics data, bioinformatics connectivity map analysis and cellular experiments altogether indicate that (1) exerts its anticancer effect through apoptosis which is highly associated with endoplasmic reticulum stress pathway. Two iron(II) polypyridyl complexes [Fe(qpy)(CH3CN)2](ClO4)2 (Fe-1a) (qpy =2,2’:6’,2”:6”,2’”:6”’,2””-quinquepyridine) and [Fe(Py5-OH)(CH3CN)](ClO4)2 (Fe-2a) (Py5-OH = 2,6-bis[hydroxybis(2-pyridyl)methyl]pyridine) were found to display selective cytotoxicity towards cancer cell lines over a normal lung fibroblast cell line. Affymetrix oligonucleotide microarray and bioinformatics analysis suggested that the anti-cancer mechanisms of Fe-1a and Fe-2a involve apoptosis, cell cycle arrest, activation of p53 and mitogen activated protein kinase (MAPK). Complex Fe-1a induced the formation of reactive oxygen species (ROS) in a concentration-dependent manner. Both iron complexes could cleave supercoiled plasmid DNA. The cellular DNA damage induced by both complexes was confirmed by comet assay and phospho-histone protein ( -H2AX) immunofluorescence assay. Cell cycle progression analysis revealed that Fe-1a induced both S- and G2/M-phase cell cycle arrests, whereas Fe-2a induced a G0/G1-phase arrest. Apoptosis induced by both complexes was confirmed by annexin-V/SYTOX green flow cytometry analysis and western blotting. Moreover, p53 and MAPK activation were found to be associated with the induced apoptosis. By employing the cationic porphyrin ligand, 5-(p-N-methylpyridyl)triphenylporphyrin [H2(5-MePyTPP)]+, a series of cationic metalloporphyrin complexes formulated as [M(porphyrinato)]n+ (where M = PtII, RuII, CoII or AuIII, n = 1 or 2) were prepared. The cytotoxicities of these complexes were examined. The platinum(II) and ruthenium(II) complexes were relatively non-cytotoxic towards the examined cancer cell lines with IC50 >24 μM. [CoII(5-MePyTPP)]Cl displayed a more pronounced anti-cancer activity with IC50 values between 7.48 – 17.7 μM. However, this Co(II) complex displayed poor selectivity towards the cancer cell lines compared to the normal cell line. The gold(III) porphyrin complex [AuIII(5-MePyTPP)]Cl2 showed a much higher potency (IC50 =3.01 -10.7μM) than the other [M(5-MePyTPP)]n+ prepared. By means of flow cytometry and fluorescence microscopy, [AuIII(5-MePyTPP)]Cl2 was found to induce G2/M-phase cell cycle arrest and necrotic cell death in HeLa cells. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy