An investigation into the effect of oxygen on the three ultraviolet optical absorption bands in magnesium oxide was carried out. These peaks were located at 5.75, 5.0 and 4.40 eV within the range 212 to 350 mu. The single crystal platelets were heated in air or oxygen for increasing times at various temperatures. It was found that the increase in peak height with time followed a diffusion relation. A mechanism of formation of the centers causing the 5.75 and 4.40 eV peaks was proposed. The mechanism was based on the oxidation of iron and manganese impurities and the diffusion of magnesium to the crystal surface. The absorbing center was defined as (Fe⁺³∙VMg⁺²). From this it was shown that the diffusion process governing both the 5.75 and the 4.40 eV peaks followed the same Arrhenius relation: D=1.7 X 10⁵ e -77,000/RT cm²/sec. over the temperature range of 800 to 1100° C. No similar conclusions could be drawn concerning the 5.0 eV peak. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A study of the quenching abilities of a series of compounds containing heavy atoms was undertaken to ascertain whether or not 0₂(¹Σ⁺[formula omitted]) quenching is subject to heavy atom enhancement. Presence of a heavy atom effect would suggest significant quenching via the 0₂(¹Σ⁺[formula omitted] → ³Σˉ[formula omitted]) transition. The fact that no such effect is observed supports the generally assumed quenching mode: 0₂(¹Σ⁺[formula omitted] → ¹Δ[formula omitted]). A systematic investigation of the use of overlap of absorption spectrum of quencher with emission spectrum of 0₂(¹Σ⁺[formula omitted]) to obtain calculated quenching rate constants was undertaken. The correlation between calculated and experimental rate constants are examined and shortcomings of the method are presented. / Science, Faculty of / Chemistry, Department of / Graduate

In Part I of this work, the decay of O₂(¹Δg) was studied at room temperature in the flow system in the absence of oxygen atoms. The decay of O₂(¹Δg) was classified into first and second order decay with respect to O₂(¹Δg). The rate constant of the main first order decay with respect to O₂(¹Δg), which is considered to be caused by collisions of O₂(¹Δg) with wall of the reaction tube, was found to be 0.25 sec. The total second order decay constant was found to be 2.9 x 10⁴ 1/ mole sec. In Part II the reactions of excited oxygen molecules with some olefins were investigated. 2,3-Dimethyl-3-hydroperoxybutene-1 was identified as the product of the reaction of excited oxygen molecules with 2,3-dimethylbutene-2, 3-Methyl hydroperoxybutene-1 and 2-methyl-3hydro-peroxybutene-1 were produced by the reaction of excited oxygen molecule with 2-methylbutene-2. The decay of O₂(¹Δg) with 2,3-dimethylbutene-2 was also studied but the results could not be explained by any simple mechanism. / Science, Faculty of / Chemistry, Department of / Graduate

The reactions: [formulae omitted] have been studied here in a discharge flow system. Using two temperatures, the rate constant for wall deactivation was found to be 3.8 x 10² exp [fomula omitted] sec⁻¹. It was concluded that the deactivation was not diffusion controlled as previously suggested but controlled by the surface deactivation process on the walls. The rate constant for production of O₂(¹Σg＊) was found to be 6.7 x 10⁴ exp [formula omitted] litres mole⁻¹sec⁻¹, in reasonable agreement with the room temperature value determined by Arnold. An upper limit of 1.6 x 10⁴ litres mole⁻¹sec⁻¹ was obtained for the rate constant of the reaction: N + O₂ (¹Δg ) → NO + 0 showing that the reaction is considerably slower than expected from comparison with the analogous reaction of ground state oxygen. This is rationalized by showing that the two reactions require different transition states. Whilst studying the above reaction several surface catalysed glows from molecular nitrogen and nitric oxide were seen. These glows were found to require O₂ (¹Δg) for their production and not atomic oxygen as previously thought. Several qualitative and spectroscopic experiments were performed and in the light of the information gained various possible mechanisms are discussed. / Science, Faculty of / Chemistry, Department of / Graduate

The currently used BOD test attempts to predict oxygen level depletion in a given environment, e.g. a moving stream, and is also a parameter for the design and operation of biological processes. It is run under conditions similar to those occurring in nature, but it has been reported that the oxidation rate in a stream is higher than the corresponding rate obtained from the laboratory BOD test. This study was undertaken to observe the effect of turbulence, light and turbidity, separately and in combinations, on the standard BOD test, using raw sewage samples. Mixing was found to increase the BOD, by an average of 15$. reduce the lag period and increase the ultimate BOD value. Light did not show any appreciable change on the standard BOD test, since only an average 4% increase in BOD^ was found. However, turbidity demonstrated an average reduction of 25% on BOD,, values. When the above physical changes were observed in combinations, the results were not additive. As an example, light and turbidity, in combination, did not reduce the BOD,-decrease to 21% (25%-k%). Instead, the decrease in BOD^ value was 5%. This clearly points out that physical changes to the BOD test should not only be studied separately, but also in combinations. Therefore, this study appears to expose the inade quacy of the present BOD test for actual stream conditions. It has also shown that without further research, extrapolating from the existing standard BOD test,yields questionable results. Inclusion in the BOD test, of the physical characteristics of the stream, is a possible solution to obtaining reliable results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

In order to design a successful space system, the unique challenges of the space environment it will operate in must be considered during the design process. Atomic oxygen (AO) is a detrimental environmental effect found in Low Earth Orbit (LEO) that affects spacecraft surfaces by oxidizing and eroding material over time, particularly polymers. Carbon fiber/epoxy composites are a commonly used spacecraft material affected by AO exposure. Carbon composites are used as a structural material, such as on solar panels; their large surface area therefore is a potential contamination source to sensitive components. The Space Environments and Testing Lab at California Polytechnic State University, San Luis Obispo (Cal Poly SLO) includes an apparatus that can simulate AO in the LEO environment. This apparatus was used to expose carbon composite samples to AO before being tested for short beam strength to measure the effect on material properties. Results showed no significant difference in short beam strength for a 24-hour AO exposure compared to unexposed samples, but a 4% decrease for samples with a 48-hour exposure. Previous work at Cal Poly SLO found that AO-exposed composite generated particulate contaminants. Tape lift tests and mass measurements of samples were conducted before and after AO exposure to characterize the particulate contamination generated and percent mass loss. It was found that AO exposure increased the percent mass loss by 1.5% for 24-hour exposure and 3% for 48-hour exposure. The tape lift percent area coverage increased by 2.5% near sample ends and 0.35% in the middle after AO exposure.

Ischemic events of even a very short duration are not tolerated Ill in humans. The human cost of ischemia, when looked at as combined cardiovascular disease, dwarfs all other causes of death in the United States. Annually, CVD kills as many people in the US as does cancer, chronic lower respiratory disease, accidents, and diabetes mellitus combined. In 2005 (the latest year for which final statistics are available), CVD was responsible for 864,480 deaths or 35.3 percent of total deaths for the year. In my study, I have used the nematode Caenorhabditis elegans to determine genetic and environmental modulators of oxygen deprivation a key component of ischemia. I have found that animals with mutations in insulin like signaling pathways, neuronal function, electron transport chain components, germline function, and animals that are preconditioned by being raised on a diet of E. coli HT115 bacteria at 25°C have an enhanced ability to survive long-term (>72 hours) anoxia (<.005 kPa O2) at 20°C. The enhanced anoxia survival phenotype partially correlates with increased levels of carbohydrate stores in the nematodes. Suppression of this enhanced anoxia survival phenotype is possible by altering expression of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase, the FOXO transcription factor DAF-16, and 5’-AMP kinase.

The purpose of this study was to examine the possibility of methane as a replacement to traditional fuels. Methane provides several advantages over fuels such as hydrogen. The LABROC VI was used to examine the performance of a small methane and oxygen rocket engine. A theoretical analysis was performed on the LABROC nozzle to compare the effects of changing the mixture ratio and the chamber pressure. The LABVIEW control program was altered to only take data due to problems with the spark plug. The hardware used within the LABROC and the procedure for operation was examined and possible problems are noted. The existing LABVIEW control program was modified to only record data. Experimental data was taken from firing the LABROC and compared to the theoretical values. To check the viability of a methane motor, a nozzle was designed that produces the approximate thrust of small, commercially available, solid rocket motors.

A review of the theory and evolution of fO2 cells is given. Particular attention is paid to the double cell design of Sato (1971). The incorporation of a servo mechanism after Sato (1971) is discussed. Calibration procedures for the entire system are presented with some emphasis on the use of nickel-neckel oxide and synthetic magnetite. The petrology of the Bushveld is reviewed in light of a possible fO2 hypothesis for the Critical Zone. Results of an examination of the E-F contact, Critical Zone, Eastern Bushveld, show a last equilibration at 1075 C and at a log10 fO2 value of -12.20. Two explanations are suggested for this intersection point: 1. It is the solidus, fO2 and temperature of the Bushveld magma at this horizon. 2. It is the post-cumulus, i.e., sub-solidus, fO2 and temperature of equilibration for the Bushveld rocks at the F-horizon. The first explanation is favored by the author and is being pursued currently. The second explanation requires ferrous/ferric equilibration but not chemical equilibration. This phenomenon is discussed from the consideration of diffusion rates for various ions. / Earth and Environmental Science

<p> A study was made to determine the elimination rate of soluble organic and inorganic compounds during anaerobic storage. Using aerobic storage as a comparison, some insight could then be gained into the metabolic activities of a mixed culture.</p> <p> The rate of oxygen utilization following anaerobic storage appeared to be dependent on the level of aeration within the reactor prior to storage. There was no liberation of carbon to account for the increased oxygen uptake following storage. Although there was a slight decrease in the solids level, it was independent of the type of storage.</p> <p> The nitrate ion appeared to act as a hydrogen acceptor during anaerobic storage and, upon reaeration, the nitrate level tended to level off. There was a production of ammonia during both aerobic and anaerobic storage indicating a deamination of cellular material (loss of solids).</p> / Thesis / Master of Engineering (MEngr)