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Ground water in excess of one million years old may now be accurately age dated by using the radionuclide Chlorine 36 (36Cl), which has a half-life of 3.01 x 105 years. To maintain a high degree of accuracy in the resultant age it is necessary to take into account the buildup of 36Cl, which is due to thermal neutron activation of 35Cl to 36Cl. The purpose of this research is to determine the thermal neutron flux in various geochemical subsurface environments by conducting field measurements of thermal neutron production rates at discrete locations. These data are then compared with the theoretical thermal neutron flux calculated for each location. The field measurements were conducted from the surface to a maximum depth of 44 meters in a copper, silver and zinc mine. The measured thermal neutron flux was found to be larger than the theoretical thermal neutron flux by a factor of from three to six when below 17 meters depth.

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No description available.

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Call number: LD2668 .T4 1950 K39 / Master of Science

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / The northern sector of the Archaean Superior Craton has been a significant region for diamond exploration, hosting numerous alkaline intrusions of Proterozoic age. The focus of this study is on two kimberlite fields that are situated in eastern Canada, 400 km apart. These are the diamond-rich Renard pipes and dykes, and the Wemindji field, consisting of barren sheeted dykes. The nine diamondiferous Renard igneous bodies were emplaced between 655-630 Ma in the eastern sector of Laurentia into Archaean metamorphic rocks. Thin, subhorizontal Wemindji kimberlite sills were emplaced into granitic gneiss terrane of the Superior Province near Wemindji, Quebec, at 629 ± 29 Ma, along the inferred extension of the Kapuskasing Structural Zone. These kimberlite fields are grouped with the extensive Late Neoproterozoic magmatism of ultramafic and volatile-rich character, which is said to be associated with the breakup of Rodinia. Despite overall compositional similarity of the studied magmatic kimberlites, the material from Renard has higher concentrations of SiO2, Al2O3, MgO, and K2O, which reflects higher phlogopite abundances. The Wemindji sills show higher CaO concentrations due to high primary carbonate contents. Renard and Wemindji kimberlite incompatible trace element distributions are similar, with differences in Cs, Rb, and Sr corresponding to variable modal mineralogy. The initial 87Sr/86Sr ratios for the Renard kimberlites range between 0.70241 and 0.70765, while the Wemindji kimberlites have values between 0.70361 and 0.70442. Initial εNd values for the Renard kimberlites lie between +1.2 and +4.6, whereas the Wemindji kimberlite sills range between +0.2 and +4.8. Initial εHf values for the Renard kimberlites lie between +1.7 and +6.3, whereas the Wemindji kimberlite sills yielded values between +1.1 and +6.5. The overlapping Sr-Nd-Hf isotope compositions of these kimberlite suites indicate melt derivation from moderately depleted mantle sources. Osmium isotope compositions fall at the unradiogenic end for global kimberlites, with initial 187Os/188Os ratios ranging between 0.11539 and 0.12620 for Renard kimberlites, and between 0.11078 and 0.11729 for Wemindji kimberlites, with Os concentrations all below 1.3 ppb. These Os values suggest that an additional input from the CLM (i.e., ancient refractory cratonic peridotite), which is not reflected in the Hf and Nd radiogenic isotopes, is ii required. Both kimberlite suites depict mantle δ13C values (ca. -6 to –4 ‰), with evidence of hydrothermal alteration in the δ18O values (between 10 and 20 ‰ relative to SMOW). Production of an isotopically depleted melt occurred during the breakaway of Laurentia from Rodinia. Wemindji sits on the inferred extension of the Kapuskasing Structural Zone, which is suggested to have been a short-lived reactivated translithospheric rift-like feature, promoting CO2-rich melting conditions during the Late Neoproterozoic. The data from this study suggest that this ascending sublithospheric depleted melt component (more CO2-rich beneath Wemindji) interacted with a maximum input volume of 5% of the MARID-enriched CLM beneath the eastern Superior craton, and between 2% and 30% of ancient refractory cratonic peridotite. The lack of significant diamond in the Wemindji kimberlite dykes could be due to the resorption of the potential diamond in the CO2-rich kimberlite melt.

Li Chak Ming = 18O氧同位素效應對La0.67Ca0.33MnO3薄膜之影響 / 李澤銘. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Li Chak Ming = 18O yang tong wei su xiao ying dui La0.67Ca0.33MnO3 bo mo zhi ying xiang / Li Zeming. / Acknowledgement --- p.i / Abstract --- p.ii / 論文摘要 --- p.iii / Table of Contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.xi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Magnetoresistance (MR) 1 - --- p.1 / Chapter 1.1.1 --- Magnetoresistance (MR) 1 - --- p.1 / Chapter 1.1.2 --- Giant Magnetoresistance (GMR) 1 - --- p.1 / Chapter 1.1.3 --- Anisotropy Magnetoresistance (AMR) 1 - --- p.2 / Chapter 1.1.4 --- Colossal Magnetoresistance (CMR) --- p.1-4 / Chapter 1.1.5 --- Double exchange mechanism 1 - --- p.6 / Chapter 1.1.6 --- Jahn-Teller effect --- p.1-6 / Chapter 1.1.7 --- Tolerance factor 1 - --- p.7 / Chapter 1.1.8 --- The effect of doping --- p.1-10 / Chapter 1.2 --- Possible origin of oxygen isotope effect --- p.1-12 / Chapter 1.3 --- Our approach --- p.1-14 / Chapter 1.4 --- Scope of this thesis work --- p.1-14 / Chapter Chapter 2 --- Experimental methods / Chapter 2.1 --- Thin film deposition --- p.2-1 / Chapter 2.1.1 --- Facing Target Sputering (FTS) --- p.2-1 / Chapter 2.1.2 --- Vacuum system --- p.2-4 / Chapter 2.2 --- Annealing systems --- p.2-6 / Chapter 2.2.1 --- Oxygen annealing system --- p.2-6 / Chapter 2.2.2 --- Oxygen exchange system --- p.2-8 / Chapter 2.2.3 --- Vacuum annealing system --- p.2-10 / Chapter 2.3 --- Characterization --- p.2-12 / Chapter 2.3.1 --- a -step profilometer --- p.2-12 / Chapter 2.3.2 --- X-ray diffraction (XRD) --- p.2-12 / Chapter 2.3.3 --- Resistance measurement --- p.2-15 / Chapter Chapter 3 --- Epitaxial growth of LCMO single layer thin film / Chapter 3.1 --- Fabrications and characterization of La0.67Ca0.33MnO3 target --- p.3-1 / Chapter 3.2 --- Substrate materials --- p.3-6 / Chapter 3.3 --- Preparation of LCMO thin film --- p.3-8 / Chapter 3.3.1 --- Deposition conditions --- p.3-8 / Chapter 3.3.2 --- Deposition procedure --- p.3-10 / Chapter 3.3.3 --- Post-annealing effect --- p.3-13 / Chapter Chapter 4 --- Oxygen in LCMO thin film / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- High Pressure Oxygenation --- p.4-2 / Chapter 4.3 --- Characterization --- p.4-7 / Chapter 4.3.1 --- Determination of oxygen content --- p.4-9 / Chapter 4.3.2 --- "Tolerance factor, t" --- p.4-12 / Chapter Chapter 5 --- Oxygen isotope effect in LCMO thin film / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Identification on successiveness of oxygen exchange --- p.5-4 / Chapter 5.2.1 --- Sample preparation --- p.5-4 / Chapter 5.2.2 --- Oxygen annealing treatment --- p.5-4 / Chapter 5.2.3 --- Identification of 18O by SIMS --- p.5-4 / Chapter 5.3 --- Investigation of isotope effect on LCMO thin film --- p.5-7 / Chapter 5.3.1 --- Sample preparation --- p.5-7 / Chapter 5.3.2 --- Oxygen exchange --- p.5-7 / Chapter 5.3.3 --- Vacuum annealing --- p.5-9 / Chapter 5.3.4 --- Isotope effect --- p.5-9 / Chapter 5.4 --- Conclusions --- p.5-19 / Chapter Chapter 6 --- Isotope effect on the hopping activation energy / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.1.1 --- Variable range hopping --- p.6-2 / Chapter 6.1.2 --- Small polaron models --- p.6-2 / Chapter 6.2 --- Activation energy --- p.6-4 / Chapter 6.3 --- Discussions --- p.6-9 / Chapter Chapter 7 --- Conclusions --- p.7-1

Beginning in the mid-1960's synthetic nucleoside derivatives of polyazaindolizines and polyazaindenes were studied for their anticancer activities. The most promising nucleosides for anticancer activity were pyrrolo-, imidazo-, and s-triazolo- pyrimidines and triazines. Syntheses of 1,2,4-triazolo 3,4c -1,2,4-triazine-7-oxide, 1,2,4-triazolo 3,4c pyrazine-7-oxide and 1,2,4-triazolo 2,3c pyrazine-7-oxide were achieved by the cyclization of the appropriate 3-hydrazinoazine N-oxide with diethoxymethyl acetate. When different one carbon cyclization agents react with the 3-hydrazinoazine-1-oxides they did not produce the expected polyazaindene-7-oxides. The reaction of formic acid with 3-hydrazino-1,2,4-triazine-1-oxide or 3-hydrazinopyrazine-1-oxide produced the 3-formylhydrazino derivatives. Similarly, the reactions of the 3-hydrazino -pyrazine-1-oxide and -triazine-1-oxide with benzaldehyde, acetic anhydride, or phenylisothiocyanate produced the 3-benzylideno, 3-acetyl, and 3-(4-phenylthiosemicarbizide) derivatives, respectively. The direct N-oxidation of imidazo 1,2a pyrazine with meta-chloroperbenzoic acid produced the imidazo 3,4c pyrazine-7-oxide. Proton nuclear magnetic resonance analyses of the polyazaindenes N-oxides has produced a set of shielding and deshielding parameters for ring protons. The mass spectral information obtained for the polyazaindene N-oxides suggests that the five membered ring of polyazaindene N-oxide has a decreased reactivity to electrophilic reagents when compared to the parent compound. The nitrogen-15 nuclear magnetic resonance spectra obtained for selected polyazaindenes were used to predict the percentage of contribution between two ground state resonance contributing structures. The nitrogen-15 nuclear magnetic resonance spectra of several substituted pyridine, pyrazine, pyrimidine and 1,2,4-triazine derivatives and their N-oxides were correlated with substituent contributions and ground state contributing structures. From this data, correlations between the nitrogen-15 chemical shifts and aromatic electron deficiency have been established.

No description available.