<p>Drug addiction and behavioural sensitization are associated with reorganization of mesolimbocortical circuitry, which we have attempted to model with glutamatergic-based long-term potentiation (LTP) in the medial prefrontal cortex (mPFC). The objective of the experiments was to examine the effects of dopamine-1 (01) and dopamine-2 (02) receptor family specific agonists and antagonists on LTP in the mPFC in the chronic in vivo preparation using fullyawake, freely-moving rats. Male Long-Evans rats were surgically implanted with stimulating electrodes into the corpus callosum and recording electrodes into the mPFC. Subjects were systemically administered a drug together with high frequency stimulation for the induction of LTP. The rats treated with the 0 1 receptor agonist A68930 (OAmg/kg/ml) showed LTP levels equal to those in the saline LTP group. The 0 1 receptor antagonist SKF83566 (0 . 15m~,/kg/ml) blocked the expression of LTP, and instead induced significant long-term depression. The 02 receptor antagonist sulpiride (3, 6, and 12mg/kg/ml) significantly decreased LTP, compared to the control group, in a dose-dependent fashion. The O2 receptor agonist quinpirole (0.125, 0.25, and 0.5mg/kg/ml) significantly increased LTP, compared to the control group, in a dose-dependent fashion. The O2 receptor agonist also induced behavioural sensitization, the intensity and frequency of which was positively correlated with the LTP effect. This is the first iii work to show that glutamatergic-based LTP in the mPFC is positively modulated by 02 receptors in the chronic in vivo preparation, and behavioural sensitization is, in turn, modulated by LTP induction. As O2 receptor-rich neurons are located largely in mesencephalic nuclei that, in turn, project to the mPFC, the 02 effects may be indirect. This plasticity modulation needs to be more deeply explored to determine its relationship to disorders, such as psychostimulant addiction and schizophrenia that are known to be due to dysregulated dopamime and glutamate function in the mesencephalon and mPFC.</p> / Doctor of Philosophy (PhD)

<p>The state of polarization of photoluminescence that is emitted along (001) and (110) crystallographic orientations has been studied to obtain quantitative information on the interfacial strain, thickness and biaxial strain in InP/InGaAs(P)/InP quantum wells. It is demonstrated that the edge emission from quantum wells is a sensitive function of the strain and thickness of the quantum well. The anisotropic polarization of photoluminescence that is emitted normal to the plane of the quantum well provides information regarding the interfacial features. This anisotropy has been correlated to the anisotropic strain field that is associated with the strained bonds at the interfaces of the quantum wells.</p> / Doctor of Philosophy (PhD)

<p>Quantum wire (QWR) lasers are of interest because of predicted improvement of performance compared to quantum well lasers. For fiber optical communication, lasers are required that operate at wavelengths of 1.3 μm or 1.55 μm. This requires lasers grown in the InP-based materials. In the GaAs-based system, it has been shown that good QWR lasers can be achieved through epitaxial growth onto GaAs substrates having etched V-grooves. However, to date, no InP-based QWRs have been successfully grown in V-grooves. This arises from two problems: (i) the tendency for InP to planarize during growth, in contrast to the resharpening effect of AlGaAs; (ii) the potential for lattice-mismatch between InGaAs(P) and InP, which could result in strain relaxation and defect formation. Therefore, the purpose of this thesis is to establish the conditions whereby InGaAs/InGaAsP QWRs can be achieved and to confirm and characterize the one-dimensional behaviour. V-grooves with both(111)A and(111)B sidewalls are used in this study. They are obtained using chemical etching. The etching process is explained and conditions necessary to achieve each type of V-groove are established. Gas source molecular beam epitaxy has been used to grow various epitaxial structures. For InP layers grown under different growth conditions, it is found that the V/III flux ratio significantly affects the shape of a V-groove bottom and the roughness of both the V-bottom and the sidewalls. With the growth conditions optimized, InP layers can be grown which retain the sharpness and the smoothness of the V-groove. The sharpness of the bottom of the groove is related to growth conditions that decrease the growth rate at the bottom by limiting the supply of the group V component. InGaAs/InP quantum well structures have been grown using the optimized conditions. For (111)A V-grooves, transmission electron microscopy shows that all epilayers are defect-free and that InGaAs/InP quantum wires are successfully obtained with well thickness variation as high as a factor of 6. Lateral subband separations are estimated by a simple one-dimensional parabolic potential model with the thickness determined by TEM. Photoluminescence emission from the InGaAs quantum wires is spatially resolved with a spatially selective etch technique. For (111)B V-grooves, defects such as dislocations are observed in the bottom. However, the growth of bulk InGaAsP and InGaAs/InGaAsP yields different results. No extended defects have been observed in the InGaAsP layer grown in either (111)A or (111)B V-grooves. This is because, at the groove bottom the layer is both P and In rich, as analyzed by using energy dispersive X-rays. This tends to reduce the strain compared to InGaAs deposition, where the absence of P leads to In-rich, strained material. The growth of an InGaAsP layer in a (111)A V-groove results in a flat and wide bottom, which excludes the possibility of forming InGaAs/InGaAsP quantum wires. However, the growth of an InGaAsP layer in (111)B V-grooves results in a sharper bottom, such that crescent-shaped InGaAs/InGaAsP structures are formed when the InGaAs layer is very thin. Quantum-wire behaviour has been confirmed through the observation of lateral subbands in the photoluminescence (PL) spectra. This is further supported by polarization measurements. Also, the subband separation observed in PL spectra is consistent with a calculated value using the one-dimensional parabolic potential model. The InGaAs/InGaAsP QWRs should be able to be incorporated into laser structures.</p> / Doctor of Philosophy (PhD)

<p>InP and related materials have become important materials for applications in many electronic and photonic devices because of their high electron mobilities and high saturation electron drift velocities. InGaAs and InGaAsP, grown lattice matched to InP, are the materials of choice for making light sources and detectors in the wavelength range of 1.3-1.6 μm for the present day high data rate, long haul, fibre-optic communication systems. InGaAs metal-semiconductor-metal (MSM) photodetectors, InGaAs high-electron mobility transistors (HEMTs) and their monolithic integration as photoreceivers are promising devices for opto-electronic integrated circuits (OEICs). In the fabrication of the InGaAs MSM-PDs and HEMTs, good Schottky contacts are critical to achieve high performance, such as low dark current and high breakdown voltage, of the devices. However, the Schottky barrier height of metal/InGaAs contacts is only about 0.2-0.3 eV, which is not high enough for device applications. InP was chosen as the contact material in our fabrications of InGaAs MSM-PDs and HEMTs because of its compatibility in growth and lattice matched to In₀₅₃Ga₀₄₇As. In this research, the following investigations were carried out to understand the physics of the InP Schottky barrier, to obtain good Schottky contacts to InP, and to improve the performance of the InP/InGaAs MSM-PDs. (1) It was found that the current-voltage characteristics of metal(s)-InP Schottky contacts depart from the behavior predicted for the thermionic emission model. To explain these barrier anomalies. a modified current-voltage relationship was developed based on the inhomogeneous Schottky barrier. (2) A systematic investigation on metallization schemes shows that the Schottky barrier height of metal(s)-InP ranges from 0.38 to 0.5 eV, depending on the metal(s) and deposition techniques and the surface conditions of the InP. Among them, Au/Ti/Pt produces the highest barrier height while Au/Ni/Pt has the best uniformity in metal(s)-InP Schottky contacts. To further increase the Schottky barrier height, a thin In1-xGxP (x ranges from 0.1 to 0.3) layer of 100-200 Å grown on top of InP was employed. The barrier height obtained is found between 0.56 to 0.65 eV. The dark current is significantly reduced while the reverse breakdown voltage is increased from about 15 V to 20 V. (3) High-performance InGaAs MSM-PDs with InP as the barrier layer was fabricated. The MSM-PDs with a finger width of 2μm, finger spacing of 2μm, and an active area of 50 x 50 μm², have a dark current of about 200 nA at a bias of 10 V, a low capacitance of 0.2 pF, and breakdown voltages of about 15 V. A fairly high responsivity of 0.75±0.05 A/W at λ=1.3 μm was obtained. The temporal response is characterized by a rise time of about 4.0±0.2 ps, fall time of 8.0±0.2 ps, and FWHM of 8.5±0.2 ps which corresponds to a 3-dB frequency (unit current gain cut-off frequency), f3dB, of 20 GHz. The performance is comparable to the best of those InGaAs MSM-PDs with InAlAs as the contact layer. (4) Because of the lateral conduction in MSM-PDs and the Fermi-level pinning in InP due to surface states, the surface conditions play an important role in device performance. Surface passivation using (NH₄)₂Sx solution was successfully implemented to improve the performance of InGaAs/InP MSM-PDs.</p> / Doctor of Philosophy (PhD)

<p>For decades, microwaves have been used to create gas discharges for many applications. This thesis deals with the use of microwaves to excite gas discharges for incoherent optical sources, with particular emphasis on excimer systems. In addition, microwave excitation of a gas laser is considered. A novel apparatus was designed and built to couple 2.45-GHz microwave radiation into a gas discharge. The microwave resonator is the essential part of this equipment, and a detailed discussion of its design and performance is given. The resonator is characterized both theoretically and experimentally in order to determine the coupling efficiency and peak electric-field strength. Specialized theory is developed in order to evaluate many parameters of a microwave-excited discharge. The phenomenon of skin effect is investigated quantitatively and expressions for the plasma frequency and electron density are developed in terms of collision frequency and observable parameters (e.g., skin depth). Expressions for peak electric-field strength, ionization coefficient and collisionless electron energy are also developed. The results of an extensive investigation of continuous-wave microwave-excited excimer fluorescence are reported. Rare-gas halide, homonuclear halogen and heteronuclear halogen systems are examined and the corresponding ultraviolet spectra are presented. Truly continuous excimer emission has been achieved (for the first time) on several transitions. For systems of particular interest (e.g. XeCl and KrCl), the effects of total pressures and gas composition on fluorescence output are investigated, and the appropriate spectra are presented. Finally, the potential operation of microwave-excited carbon dioxide and argon-ion gas lasers is investigated, and upper limits are deduced for the small-signal gain under various conditions.</p> / Doctor of Philosophy (PhD)

<p>A technique for obtaining maps of the spatially-resolved and polarization-resolved electroluminescence of 1.3 μm semiconductor diode lasers has been developed. It reveals information about the strain, scattering and absorption which exist in the active region of lasers. These data have been correlated with the spectral output of the lasers, and models have been developed which explain the correlation.</p> / Doctor of Philosophy (PhD)

<p>An experimental investigation of graft copolymerization of styrene in wood was performed utilizing (1) Cobalt-60 radiation initiation, 2) impregnating solutions of styrene, methanol and water and (3) heat during the irradiation period. It was found that heating did not increase the grafting efficiency of the system. The grafting process was found to be dependent upon (1) the method of impregnation, (2) the density of the wood and (3) the amount of swelling agents in the impregnating solution. Wood treated with styrene and swelling agents was weakened in all mechanical properties except the maximum crushing strength and properties associated with compression. In genaral, wood treated with pure styrene was strengthened. It is felt that the use of radiation in the formation of wood-plastic composites is commercially unjustified.</p> / Master of Engineering (ME)

<p>The variety and heterogeneity of information communication standards in different application domains are the main sources of complexity in interoperability provision among those application domains. The maturity of application domains can be assessed by the ease of communication of terms between different stakeholders in the same domain, which is central in defining standards for communication of information among organizatiuns. Currently. most research activities are focused towards standardization and illteroperabiliry among information systems within the same domain.</p> <p><br />However. an emerging challenge is to address the exchange of information among heterogeneous applications in different domains, such as healthcare and insurance. This requires data extraction to obtain common subsets of information in the collaborating domains. The second step would be to provide intra-domain and inter-domain semantic interoperability through proprietary and shared ontology systems.</p> <p><br />In this context, we address the above challenges through description of a framework that employs healthcare standard development frameworks and clinical terminology systems to achieve semantic interoperability between distributed systems among different application domains. A real world case study, which addresses message-oriented integration of business processes between healthcare and insurance is demonstrated.</p> / Master of Applied Science (MASc)

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