Thesis (Ed.D.)--Boston University.

Analytical methods were developed and validated for the determination of the total concentration of trace elements (Se, Fe, Cu, Zn, Mg, Ca, Mn, Mo, I, Cd and Pb) and the various organic and inorganic selenium species present in human body fluids. Total elemental analysis involved the use of inductively coupled plasma mass spectrometry (ICP-MS). Speciation analysis utilised ion-pair high performance liquid chromatography (HPLC) coupled on-line to a hexapole collision cell ICP-MS. The methods that were developed were then applied to three separate studies. The effect of psychological stress on human fertility was determined by comparing the trace element levels in blood serum from 47 infertile women undergoing in-vitro fertilisation (IVF) treatment. Elemental data was compared with stress-hormone (plasma prolactin and serum cortisol) levels and Spielberger stress questionnaires. Statistical analysis showed no relationship between stress-hormones and blood serum trace element levels and that stress-hormones do not have an adverse effect on human fertility. A further study examined the total trace element levels of blood serum, follicular fluid, endometrial fluid and scalp hair from a study population of 97 women aged between 24 - 44 years undergoing IVF treatment. Selenium levels in blood serum were significantly lower in IVF patients in contrast to 18 (age and gender matched) control cases (P = 0.001, 35 degrees of freedom). This was in agreement with a previous study with infertile women, aged < 35 years. Zinc and manganese were determined in endometrial fluid, both showing a high degree of correlation (P = 0.001, 17 degrees of freedom) in the IVF population (no control samples were available for analysis). The levels of each element measured in scalp hair showed no correlation with the levels determined in any other matrix. A major contribution of this research involved speciation analysis of selenium in blood serum, seminal plasma and urine. Commercial selenium supplements were consumed over 28 days and the effect that this had on selenium levels (total and species) within the human body fluids was investigated. Consumption caused an increase in the levels of selenium within all human body fluids and in general, the total level of selenium was found to be higher than the sum of the species present. An in-vitro bioavailability procedure was performed on the supplements and showed that two selenium yeast commercial products contained different selenium species. Some selenium species were identified and the implications of this are discussed.

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Erbium, a rare earth element, has been shown to exhibit characteristic luminescence at 1.54mum due to its internal 4f transition from the first excited state (4pi3/2) to the ground state (4pi5/2). As this emission wavelength falls inside the maximum transmission window of silicon based optical fibers, erbium doped silicon might lead to the opportunity of silicon based optoelectronics. The introduction of erbium in silicon allows excitation through electron-hole recombination and subsequent radiative emission from the rare earth centers. The works reported here describe the structural, electrical and optical properties of crystalline silicon codoped with erbium and boron by ion implantation technique. Four sets of samples, co-implanted with erbium and boron at different Er dose, implantation energy and at different conditions, were prepared. Post-implantation annealing has been performed to recover the implantation damage to an acceptable value and to activate the dopant atoms optically and electrically. PL and EL measurements have been performed in the temperature range between 80K to room temperature. The sample with the lowest erbium concentration and energy gives the best PL and EL results. The observed emission peaks in both PL and EL measurements were at around 1.129mum, ~1.303mum, 1.50mum and 1.597mum at 80K. At higher temperatures, a broader peak at around 1.50mum with long tail towards the both end of wavelength has been observed. The peak at 1.129mum corresponding to the Si band edge emission, the reason for the peaks at around l.303mum has not been identified while the remaining two peaks correspond the Er3+ emission. Virtually no temperature quenching of Er luminescence is observed in some samples rather room temperature intensity is higher than that at 80K. The improvement of the temperature quenching effect on Er luminescence at room temperature has been attained in our results, which is significant improvement in comparison to the result found in the literature. The structural properties were studied by TEM in both cross-sectional and plan view configurations. TEM analyses showed dislocation loops and other defects of random size and distribution from the surface to 600nm below the surface. Er precipitates defects were also seen in the sample doped with Er comparatively at higher dose (1x1015Er/cm2) and energy (1.0 MeV). No detectable room temperature PL and EL signals were observed from the sample implanted at higher doses and energies.

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Please read the abstract in the section 03back of this document / Dissertation (MSc (Applied Mineralogy))--University of Pretoria, 2005. / Mathematics and Applied Mathematics / unrestricted

The reactions between the lanthanide nitrate salts and the ligand triphenylphosphine oxide (TPPO) gave rise to nine-coordinated complexes of the nature Ln(TPPO)3(NO3)3, for Ln = La – Dy, Er, Tm, in which the Ln(III) centre is coordinated to three phosphoryl oxygen atoms and three bidentate nitrate ligands. Generally, the geometry can be described as being mer-octahedral, where the nitrate ligands are considered as monoatomic species. The product of the reaction between Yb(NO3)3·5H2O and TPPO, however, was a highly symmetrical eight-coordinated complex, in which the Yb(III) centre was coordinated to two bidentate nitrate groups and four TPPO molecules. The geometry in this case is best described as being trans-octahedral, with the two nitrate ligands coordinated practically perpendicular to one another. The complexes isolated from the reactions of lanthanide nitrate salts with the ligand bis(pentamethylene)urea (PMU) had the general formula Ln(PMU)3(NO3)3, where Ln = La – Dy, Yb, Lu. The complexes were found to be nine-coordinated with distorted trigonal prismatic geometry, in which the one base of the prism is composed of the oxygen atoms of the three PMU ligands and the other base is made up by one oxygen atom from each of the bidentate nitrate groups. The second oxygen atoms of each of the nitrate groups protrude upward, occupying capping positions. The reactions of the La and Pr nitrate salts with the ligand 2,2’-dipyridyl-N,N’-dioxide (DPDO) produced two novel complexes of the nature [Ln(DPDO)(H2O)2(NO3)3]. These complexes are remarkable in that their crystal structures reveal the Ln(III) centres to be ten-coordinated. The geometry around the Ln(III) centres was complex, due to the presence of a seven-membered chelate ring, formed by the bidentate coordination of the oxygen atoms from the DPDO ligands to the metal centres. The chelate ring did not lie in a single plane, but was twisted at the pyridyl bridgeheads to lie above and below the coordination plane.

The extraction of the Rare Earths from two kilograms of Lindsay Light and Chemical Company's "monazite residues" (hydrated Rare Earth oxides), from two kilograms of Norwegian gadolinite, and from five kilograms of Lindsay's "didymium carbonate" (Code 411) gave a mixture of Rare Earths which, after purification, fractional crystallisation as the double magnesium nitrates and ion exchange separation, showed some evidence for the existence of naturally occurring element number 610. This evidence took the form of unexplained lines in the arc spectra, anomalous absorption bands, aid an unexplained peak in the elution curve obtained from the ion exchange work. The evidence presented is far from conclusive and the suggestion is made that further research along these lines be carried out. / Science, Faculty of / Chemistry, Department of / Graduate