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<p>Silicon oxide films (oxygen-rich or silicon-rich) doped with various rare-earth (RE) [cerium (Ce), terbium (Tb), europium (Eu) and erbium (Er)] elements have been by deposited by electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD). The successful in-situ incorporation of high concentrations of RE elements has been confirmed by Rutherford backscattering spectrometry (RBS), and the optical properties of the films were analyzed by Photoluminescence (PL) spectroscopy.</p><p> Ce, Tb, Eu and Er related emission was observed from the films with corresponding doping and was found to be sensitive to RE concentration, the presence of Si nanoclusters (Si-ncs) and annealing induced structural evolution. The significant enhancement of Ce^3 + emission in Ce-doped oxygen-rich films under annealing in flowing N2 at 1200 °C was found to be related to the formation of cerium silicate whose presence was confirmed by Fourier transform infra-red (FTIR) spectra and high-resolution transmission electron microscopy (HR-TEM) images. The observation of intense Tb^3+ emission from Tb-doped oxygen-rich films under nonresonant excitation revealed the presence of indirect excitation processes. The organic ligands introduced from the Tb(tmhd)3 precursor during deposition was considered as the possible sensitizer. The presence of Si-ncs in Ce or Eu-doped silicon-rich films resulted in the quenching of both RE and Si-ncs PL, while in Tb or Er-doped silicon-rich films the coupling between Si-nes and RE ions can excite RE-related emission efficiently. The formation of Si-ncs with sizes of 2-3 nm in Tb-doped silicon-rich films under annealing in flowing N2 at 1100 and 1200 °C was revealed by HR-TEM images.</p> / Thesis / Master of Applied Science (MASc)

This thesis describes the application of the radioisotope 11C to the synthesis of two analogues of the neurohormone melatonin. The labelled compounds were intended to be used as tracers for the medical imaging technology Positron Emission Tomography (PET). [ 11C]Carbon dioxide, produced in a small on-site cyclotron by the nuclear reaction 14N(p,a)11C, was converted into [11C]CH3COC1 by reaction first with CH3MgBr, followed by reaction with phthaloyl dichloride. The labelled acid chloride was distilled into a solution of an amine, yielding the corresponding 11C-labelled amide, which was purified by a simple solid-phase extraction method. An apparatus was designed and built that allowed the remote synthesis with several hundred millicuries of [11C]C02• The apparatus was mounted in a hot cell and operated remotely with a Macintosh Powerbook programmed in Hypercard. The apparatus and software are generic for these acylation reactions. The individual reaction steps were optimized in terms of reaction time, solvents and equipment; radiosyntheses of a number of purified labelled acetamides were completed in 35 minutes. The radiochemical yields ranged from 15 to 20% with specific activities in the 500 mCi/J..tmol range at the end of the synthesis. 2-Iodo-[11C-acetyl]melatonin (11) and 7-methoxynaphthylenyl-1-ethyl-N-[11Cacetyl] acetamide (15) were synthesized for the first time for PET studies. It was shown that both compounds readily cross the blood-brain-barrier and penetrate into all brain tissues. Specific binding to the melatonin receptors in the suprachiasmatic nuclei of the hypothalamus could not be visualized with either one of the 11C-labelled ligands because of low specific activity and high nonspecific binding. / Thesis / Master of Science (MSc)

The Eppley Precision Spectral Pyranometer (PSP) is a shortwave radiometer that is widely used in global networks to monitor solar irradiances at the earth's surface. Within the instrument, a blackened surface is in intimate thermal contact with the hot junction of a thermopile. The cold junction of the thermopile communicates thermally with the large thermal capacitance of the instrument body, which acts as a heat sink. Radiation arrives at the blackened surface through one or two hemispherical dome-shaped filters that limit the instrument response to the solar spectrum. The voltage developed by the thermopile is then interpreted in terms of the incident irradiance. Measurements taken with the pyranometer are compared with results from theoretical models. Discrepancies between model results and measurements are used to isolate inaccuracies in the optical properties of the atmosphere used in the models. As the accuracy of the models increases, the reliability of the measurements must be examined in order to assure that the models keep up with reality. The sources of error in the pyranometer are examined in order to determine the accuracy of the instrument. Measurements obtained using the pyranometer are known to be influenced by environmental conditions such as ambient temperature, wind, and cloud cover [Bush, et al., 1998]. It is surmised that at least some of the observed environmental variability in these data is due to parasitic thermal exchanges within the instrument [Haeffelin et al., 1999]. Thermal radiation absorbed and emitted by the filters, as well as that reflected and re-reflected among the internal surfaces, influences the net radiation at the detector surface and produces an offset from the signal that would result from the incident shortwave radiation alone. Described is an ongoing effort to model these exchanges and to use experimental results to verify the model. The ultimate goal of the work described is to provide reliable protocols, based on an appropriate instrument model, for correcting measured shortwave irradiance for a variable thermal radiation environment. / Master of Science

Building materials are a major source of indoor air contaminants. Volatile organic compounds (VOCs) are an important class of contaminants prevalent in indoor air. Attempts have been made to model the emission of VOCs from building materials. Diffusion has been shown to control the rate of mass transfer within certain types of building materials. The primary objective of this research is to develop a fundamental diffusion-based model for single and double layer building materials. The single-layer model considers a slab of material located on the floor of a chamber or room with the material acting either as a source or a sink for VOCs. The behavior of the model is governed by the material phase diffusion coefficient (D), the material/air partition coefficient (K), the concentration of VOC in the influent air stream, and the initial concentration within the material phase. The single-layer model extends a previously developed version, incorporating the non-uniform initial concentration inside the building material and a transient influent concentration. Experimental work is performed to check the validity of the model. A steel chamber housing a piece of vinyl flooring is used to simulate building material within a room. D and K values for two representative VOCs, n-dodecane and phenol, are available from earlier experiments. These parameters are used in the model to predict the VOC concentration inside the chamber. The predicted values compare very well to the observed experimental data. A double layer version of the model is developed and studied from a theoretical perspective. The model also permits a time dependent influent concentration and a non-uniform initial concentration profile within each of the two layers. A parametric analysis is performed varying the ratio of the diffusion coefficients, the partition coefficients and the thickness of the two layers. Three cases of practical interest are studied using the double-layer model. The use of a thin low-permeability barrier layer placed on top of a building material is shown to hold considerable promise for reducing the emission rate of VOCs into indoor air. / Master of Science

Velocity tomography is a noninvasive technique that can image the interior of a rock structure. To apply tomography to rock specimens, a propagation wave, which acts as a probe, is used. The propagation wave propagates from a source until it reaches a sensor on the surface of the rock specimen. Tomograms can then be generated from the velocity distribution within the rock structure. Areas of higher velocity are typically representative of higher stress concentrations, whereas areas of low velocity can be areas of fracturing. The variation of velocity tomography described in this thesis uses acoustic emissions as sources for the propagation wave. Acoustic emission sources provide advantages over mechanical sources, since the acoustic emission source is generated by the rock as a result of deformation and fracturing. Velocity tomography of rock structures in the field has numerous applications and advantages. Velocity tomography can be used to monitor rock structures surrounding tunnels and underground openings such as mines. To monitor the rock structure, velocity tomography is used to determine areas of higher stress concentration that may be precursors to rock failure. However, velocity tomography must first be used in a laboratory environment to determine failure in rock samples before being applied to the field. The research presented includes the unconfined compression strength testing of 19 Berea sandstone samples. These samples were loaded to failure and during the experiment the acoustic emission events within the samples were monitored using a commercial acquisition system manufactured by Engineering Seismology Group (ESG) Canada. Source location software, also produced by ESG, was used for the location of the acoustic emission events. Ray inversions were performed on the data from the experiments to generate tomograms. The tomograms generated display the p-wave velocity distribution imaged within the Berea sandstone samples with the ultimate goal of being able to predict rock failure. Based on the experiments discussed in this thesis it can be inferred that velocity tomography is a useful tool for imaging the inside of the Berea sandstone samples. Precursors of rock failure could not be determined in this early stage of research. However, the tomograms do image the p-wave velocity distribution and do show a gradual progression of the p-wave velocity from the initial velocity model to higher velocities. Results of these 19 experiments do provide reasonable confidence in the method and warrant pursuit of further research to refine and improve this method of monitoring velocity tomography. / Master of Science