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A suite of four samples of nitrogen doped carbon microspheres, each with a di erent level of nitrogen dopant, was synthesised in a horizontal chemical vapour deposition reaction. The samples were characterized using scanning electron microscopy, Raman spectroscopy and electron paramagnetic resonance spectroscopy. Scanning electron microscopy showed that microspheres were produced by the reaction. Raman spectroscopy con rmed the graphitic nature of the samples. Electron paramagnetic resonance spectroscopy determined that nitrogen was present in the graphitic lattice and was used as a non-destructive technique to measure the amount of substitutional nitrogen present in the samples. In order to perform electrical transport measurements an automated magneto-transport measurement station was developed in the laboratory. This transport station was computer controlled and contained all of the necessary hardware and software required to perform magneto-electrical transport measurements. Variable temperature electrical transport measurements were performed on all samples to determine their conductive properties. Resistance measurements showed that two of the samples were semiconductors while the other two samples displayed a transition to metallic behaviour at higher temperatures. This transition can be ascribed to the thermal desorption of nitrogen dopant. Models were tted to the data and the semiconducting behaviour is best explained by a model of uctuation induced tunnelling while the metallic behaviour is best explained by a quasi-1 dimensional metallic term based on electron-phonon interactions. The IV characteristics of two of the samples display increasing non-linearity of the current's voltage dependence with decreasing temperature. The other two samples exhibit this behaviour at lower temperatures while higher temperature IV data displays a current saturation with increasing voltage. The same models used to explain the resistance measurements can be used to explain the IV characteristics data extremely well. The magnetoresistance data taken with the direction of current ow orientated both parallel and perpendicular to the eld, show a transition from negative to positive magnetoresistance with decreasing temperature. The results of these experiments are inconclusive, as a theoretical model of magnetoresistance in systems that conduct via uctuation induced tunnelling is not well de ned. A comparison between the resistance measurements of all four samples was made to determine the e ect of nitrogen doping on the samples' electronic transport properties. The result of this comparison was indeterminate. This was due to samples with identical nitrogen dopant levels displaying vastly di erent conductive properties and indicates that very strict synthesis conditions need to be adhered to in order to ensure sample quality. Resistance measurements were rerun on the two samples that displayed purely semiconducting behaviour to investigate the possibility of atmospheric doping. It was found that the samples now displayed a transition to metallic behaviour and a reduced resistance. These results are suggestive of atmospheric doping by oxygen and water vapour.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. April 2016. / Chemical vapour deposition was used to synthesise four carbon microspheres (CMS) samples. Introduction of acetonitrile in different quantities produced spheres of differing nitrogen concentration. The structure of the spheres was investigated using Raman spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy techniques. The Raman investigation revealed a decrease in average graphitic flake size which forms the surface layers of the spheres with nitrogen incorporation. XPS showed that increased nitrogen doping caused a larger proportion of pyridinic nitrogen, which process likely restricts the growth of the crystallite flakes detected with the Raman technique. Microscopy revealed spheres with differing morphologies which did not correlated with the level of nitrogen doping. Electron paramagnetic resonance techniques were employed to investigate the impact of nitrogen doping on the spin system of the samples. Electrical transport and Hall effect data were collected with an automated experiment station purpose built for this work. Samples displayed semiconducting behaviour at low temperatures which was ascribed to fluctuation assisted tunnelling. At higher temperatures all four samples display a transition to metallic behaviour. Models for conduction, which were tested but ultimately rejected, include variable range hopping in all its dimensional forms, Efros-Shklovskii VRH and weak localisation. A comparison of the conduction results and the structural information showed the conductivity to be more closely affected by the structure of the spheres than the overall doping level. A case is made for the dominant conduction mechanism being determined by the intersphere rather than the intrasphere conduction. This research shows that creating carbon microspheres with specific electrical properties requires control of the structure induced during synthesis. Nitrogen doping alone does not determine the final physical and electrical transport properties. / LG2017

by Yee-kwan Lau. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 65-67. / Chapter I. --- Acknowledgements --- p.1 / Chapter II. --- List of Nomenclature --- p.2 / Chapter III. --- Abstract --- p.10 / Chapter IV. --- Introduction --- p.11 / Chapter V. --- Results and Discussion: / Chapter i. --- Synthesis of ortho-quinonoid compounds related to miltirone ( / ) --- p.17 / Chapter ii. --- Pharmacological profile of synthetic compounds --- p.37 / Chapter VI. --- Conclusion --- p.33 / Chapter VII. --- Experimental Section --- p.39 / Chapter VIII. --- References and Notes --- p.55 / Chapter IX. --- Spectra --- p.68

Bibliography: leaves 186-209. / xiii, 218 leaves : ill. (some col.), 1 col. map ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Agronomy and Farming Systems, 2000

Thesis (Ph. D.)--Oregon State University, 1977. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Plant production and soil microbial biomass (SMB) in grassland ecosystems are linked by flows of carbon (C) and nitrogen (N) between the two groups of organisms. In native mixed grasslands of the southern Great Plains, these cycles are strongly influenced by climate. They may also be modulated by the timing and intensity of disturbances such as fire and clipping. We assessed the relative influence of climate and disturbance on plant community and soil C and N dynamics. Combined effects of fire and clipping were assessed in a 2x3 factorial design including spring fire and light clipping or continuous clipping. Seasonal fire effects were evaluated in a one-way analysis incorporating spring and fall fire in unclipped plots. Plant cover and biomass (by functional type), litter mass, SMB C and N, soil density fraction concentration and composition, soil organic C, total N, and inorganic N, soil temperature and moisture, soil respiration, and net N mineralization were measured at monthly intervals. C4 grasses were unaffected by fire or clipping, probably as a result of summer drought in both studyyears. Clipping reduced cover of C3 annual grasses but increased that of C3 perennials, resulting in no net change in C3 grass biomass. Fire did not affect C3 grass cover or biomass. Both fire and clipping reduced litter mass. This was reflected in seasonal declines in SMB C in fire treatments, suggesting that the primary input of microbial C in this ecosystem occurs by decomposition of current-season plant litter. Litter removal offers a single mechanism by which fire-induced increases in soil temperature and reductions in light soil density fraction concentration, soil moisture, and net N mineralization rates may be explained. Lack of treatment effects on soil respiration rates suggest that plant roots represent an important component of the plant-soil C cycle, not quantified in this research. Overall, treatment effects were relatively minor compared to seasonal climate-related changes in response variables, particularly in light of repeated summer drought.

Thesis (M.S.)--Middle East Technical University, 2003. / Keywords: Azotobacter chroococcum, Nitrogen Fixation, OMW, Bioremediation.

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The diesel engine currently accounts for 32 per cent of the new passenger car sales in Europe. In the US, diesel-power is responsible for 94 per cent of all freight movement. Comparing European Stage III standard petrol and diesel passenger car emissions, diesel NOx emissions are still considered a concern. This thesis investigates the mechanisms by which oxides of nitrogen are formed during diesel combustion. It reviews the current methods of controlling NOx emissions, such as retarding fuel injection timing, exhaust gas re-circulation (EGR), water injection and exhaust after-treatment. Modelling using a phenomenological model, is used to demonstrate the extended Zeldovich mechanism and formation trends, the effects of EGR and the significance of the Zeldovich mechanism rate constants. Modified Zeldovich rate constants are proposed to improve the correlation to measured data. Clearly, EGR is currently the most effective method of reducing NOx emissions from passenger car diesel engines. The way EGR works in suppressing NOx formation is reviewed in detail. Experimentation on a 1.8 litre inline 4-cylinder 4-valve per cylinder DI diesel with a variable nozzle turbine (VNT) turbocharger was used to demonstrate the concept of "additional" EGR on this small automotive engine. "Additional" EGR is the concept whereby a proportion of the EGR is added to the total charge, so that the volumetric efficiency increases as EGR is introduced. By using "additional" EGR, the benefits of lower NOx emissions combined with reduced particulates emissions and improved fuel consumption were clearly demonstrated at two test conditions. The reasons for achieving lower NOx emissions when using a VNT turbocharger and EGR have been explained. Finally, several methods of calculating EGR proportion were used and compared against true mass flow. The use of a CO2 balance was found to be the most accurate method.