published_or_final_version / Chemistry / Master / Master of Philosophy

A critical survey has been conducted on the research done in oxygen isotopes. Only those aspects are considered which are of interest to the earth scientists. Oxygen isotopes have been used for geothermometric purposes and for rock genesis problems. The physical principles underlying these two lines of research are stressed. Assumptions which are usually implied are explicitly stated. It is shown that the influence of pressure on the equilibrium constant of oxygen isotope exchange reactions is only a minor one in comparison with the temperature influence. The significance of determined temperatures is discussed in the light of possible oxygen diffusion in silicates and carbonates. It is concluded that diffusion is usually neglected without justification. As far as data are available it is shown that diffusion can be responsible for many discrepancies between oxygen isotope temperatures and' temperatures derived by other means. Studies on the origin of rocks by means of oxygen isotopes are discussed. Attention is focussed on the Southern Californian batholith. The results of Taylor and Epstein's preliminary study of this batholith are interpreted here as evidence in favour of a metamorphic origin of this huge rock body. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An automated sample preparation line has been developed to equilibrate water samples for determination of their oxygen isotope ratio. Preliminary estimates put the repeatability of the sample preparation methods at approximately 0.04°/oof a figure that compares very favourably with the present state of the art. A noteworthy feature of our sample line, is that temperature control is unnecessary during sample equilibration. Errors arising from non-constant temperature conditions are prevented by simultaneously saving all of the equilibrated gas samples in separate reservoirs when the equilibration reaction is complete. Several other innovations in sample rack design are also described. These are: a circular rack geometry; an improved, inexpensive, magnetic stirrer design to agitate water samples; a Peltier cooling device to trap water vapour; and the use of standard Pyrex test tubes as equilibration flasks. The preparation line is highly modular. Up to sixteen racks, each capable of preparing sixteen samples, can be included in the system. Racks may be removed, repaired or modified, and replaced, without disturbing the operation of any other racks in the system. The current configuration is a minimum system with only one rack. The programming concepts used to control operation of the system are new to this application, and hence are a significant contribution. A multi-tasking executive allocates resources amongst the racks on a priority basis. By using linked list structures, the operating system maximises resource and processor utilisation, but does not compromise flexibility and modularity. The operator can submit any rack for preparation at any time, and the system could, with sixteen racks, prepare a full load of 256 samples in a day. A simple handshaking interface has been provided to control the release of samples for analysis. This should make it possible to connect the sample line to any mass spectrometer capable of the automated analysis of carbon dioxide. The user controls sample line operation by commands entered on a teletype keyboard. The command language is deliberately unstructured, and users can type in "natural" English sentences if they wish. All system operations and user sentences are printed on the teletype to provide a permanent record for later scrutiny. Finally a manual command repertoire has been provided. It allows the operator complete control over any rack. All solenoids, registers, and control lines, can be manipulated on an individual basis from the teletype keyboard. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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

Thesis (Ph. D.)--Columbia University, 1934. / Vita. Bibliography: p. 34-35.

No description available.

A completely automated mass spectrometer system has been developed to measure the oxygen isotope ratio of carbon dioxide samples. The system has been shown to have a precision of 0.03°/oo, which is comparable to that quoted for any other system in the world. In addition, the facility is capable of analyzing over one hundred samples per day. The system uses an Interdata minicomputer as the primary controller. The minicomputer monitors the quality of analyses, on-line, and thereby insures that all DEL values are measured to at least 0.04°/oo. Host of the sophistication resides in intelligent controllers within the mass spectrometer console. This design gives a technician considerable power when operating the system in a manual mode. The intelligence of the system is contained within hardware circuits, software within the minicomputer and firmware written for a Motorola 6802 microprocessor. A major contribution of this thesis has been the design and installation of an automated mass spectrometer inlet system. A microprocessor based inlet system controller maximizes the throughput of carbon dioxide samples within the inlet system. The inlet system normally contains four different aliquots of carbon dioxide and introduces these samples to the mass spectrometer, in proper sequence, through a single mass spectrometer admittance leak. The system has been used in the analysis of 111 samples of ice taken from the Steele Glacier, Yukon Territory. The samples taken from a vertical borehole, displayed a sawtooth variation of the oxygen isotope ratio with depth. The data have been explained by a physical model described in an appendix to this thesis. If our interpretation is correct, the isotopic variations have recorded at least four surges of the Steele Glacier. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

>Magister Scientiae - MSc / In this study a complete set of exclusive (~p; 2p) polarization transfer observables of closed-shell oxygen isotopes are calculated using both direct and inverse kinematics using the relativistic plane wave impulse approximation. The interaction matrix is written in terms of the SPVAT (scalar, pseudoscalar, vector axial vector, tensor) covariants where each amplitude is obtained directly from experimental phase shifts. A relativistic mean eld theory approximation is used to compute boundstate wave functions of the nucleons. We study the evolution of polarization transfer observables within oxygen isotopes and identify observables which may discriminate between these isotopes. The same kinematical conditions are considered for both direct and inverse kinematics: the incident energy is set at 504 MeV and coplanar angles are xed at (22:12 ;􀀀40:30 ). The results indicate that only three spin observables, namely, Ay, P and Dnn distinguish di erent oxygen isotopes at these kinematical conditions in the inverse kinematics.

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My study was designed to identify the relationships between climate variables, such as precipitation and temperature, and δ 18 O values of tree ring &alpha-cellulose extracted from exactly dated tree rings of Pterocarpus angolensis growing in the arid to semiarid Mzola region of western Zimbabwe. This species is known to be sensitive to seasonal variation in rainfall. In this region, the wet season occurs during the austral summer from mid November to early April followed by a dry winter season from around June through October. Overall, the total annual rainfall exhibits a high degree of spatial and temporal variation with a mean of less than 600 mm per year. I applied the Modified Brendel technique to isolate &alpha-cellulose from raw wood samples extracted from two P. angolensis trees and measured the α-cellulose δ 18 O values using continuous flow isotope ratio mass spectrometry. I developed a 30-year (1955-1984) &alpha-cellulose δ 18 O chronology and correlated it with tree-ring width, meteoric water δ 18 O values, monthly and seasonal precipitation totals, and mean seasonal temperature. The δ 18 O values of meteoric water for this region were obtained from the Global Network of Isotopes in Precipitation (GNIP) and correlated with the δ 18 O values of tree ring &alpha-cellulose. The strongest correlations were observed between &alpha-cellulose δ 18 O values and February total precipitation (r = -0.49, p = 0.006) and to a lesser degree total wet season (NDJFMA) precipitation, In particular, unusually rainy wet seasons were significantly correlated (r = -0.79, P = 0.007) with &alpha-cellulose δ 18 O. This relationship is consistent with 18 O-depleted values measured in summer precipitation during periods of high rainfall, which is most likely the result of the isotopic amount effect reported in tropical regions. I also identified a positive correlation (r = 0.49, p = 0.03) between &alpha-cellulose δ 18 O and the δ 18 O values of meteoric water, and investigated the possibility of an isotopic temperature effect for δ 18 O in meteoric water, which also may be reflected in the δ 18 O values in tree ring &alpha-cellulose. The strongest correlation with mean temperature was observed during the wet summer season (r = 0.56, p = 0.01). My results suggest that the δ 18 O values of P. angolensis tree rings can be used as natural indicators of paleoclimate in southern Africa.