In this study, the generalized and traditional interferometric techniques (GINTY and TINTY) are used to investigate some of the important aspects of Polarization Mode Dispersion (PMD) phenomenon in optical fibres. Measurements of PMD and chromatic dispersion (CD) are performed on buried optical fibre cable in the Pretoria Telkom’s metropolitan network. The upgradeability of this network was investigated, and it was observed that just over a half of the fibres are upgradeable to 10 Gb.s-1 transmissions. Long-haul aerial network in the Northern Cape was also tested for upgradeability to 10 Gb.s-1. It was found that 41 percent of the fibres tested are upgradeable to 10 Gb.s-1. Long-term monitoring showed that PMD varies rapidly in aerial fibres and, on the other hand, it is relatively stable in buried cables. Investigations on the accuracy of the techniques showed that polarization scrambling is essential for the reduction of the measurements uncertainties. Furthermore, it was observed that TINTY underestimates the single scan PMD distributions. The study on the effect of the change in mode coupling on various fibre configurations was performed, and fibres showed a reduction in PMD after the introduction of mode coupling. Measurements of PMD conducted in the laboratory on cabled fibre with low PMD showed the floor sensitivity of TINTY. Comparison between GINTY and Jones Matrix Eigeanalysis (JME) PMD measurements methods were performed on an emulator, and the results showed a good agreement in the measured PMD.

An atomic beam type of apparatus designed to produce a polarized He³ beam with an intensity of approximately one microampere and 90% polarization is described. He³ is a monatomic gas consisting of atoms with zero electronic magnetic moment and nuclear spin of ½. As no initial molecular dissociation is required, an intense, supersonic neutral beam can be produced with a miniature Laval nozzle cooled to liquid He⁴ temperatures. The velocity distribution of the particles in the Laval beam and the trajectories of these particles in a radially symmetric hexapole magnet have been computed. Sufficient separation of the two beams, consisting of particles in the two possible nuclear spin states, is achieved with a magnet in which the diameter of the gap between the pole pieces increases from 3mms at the entrance to 6mm in 15 cms and is then constant for 35cms. After ionization the nuclear polarization of the singly ionized particles depends upon the magnetic field strength at the position of the ion. Theoretical calculations show that field strengths of 6000 gauss at both the ionizer and target (in reaction studies) are sufficient to give 90% nuclear polarization. For an input gas temperature and pressure of 2.2°K and 15 mm.Hg. the Laval nozzle (throat diameter, 0.2 mm) has been designed to produce a supersonic beam of Mach number 4 with an intensity of 6.5x10¹⁵ particles/sec at the magnet entrance. Assuming 40% transmission through the magnet (one half of the beam being removed by the polarization process) and an ionization efficiency of 0.25%, the resulting ion beam intensity is 6.5x10¹² ions per second or approximately one microampere. The low temperature atomic beam source has been tested at liquid nitrogen temperature with a He⁴ beam. The measured beam intensity of 9x10¹³ particles/cm²/sec at the magnet exit, 76 cms from the nozzle, agrees favourably with the calculated intensity of 1.2x10¹⁴ atoms/ cm² sec under these operating conditions. The measured field gradient of 70,000 gauss/cm. near the pole tips of the hexapole splitting magnet is more than required for separating the atoms in the two nuclear spin states. A pulsed nuclear magnetic resonance method for measuring the nuclear polarization of the neutral He^ beam prior to ionization is described. The angular distribution and polarization of the protons produced by the D(He³,p)He⁴ reaction with an incident, polarized He³ beam of 150 Kev bombarding energy has been calculated, This angular distribution is isotropic. In the plane of the reaction, the proton polarization, which may be measured by a second scattering experiment, is -2/3 the incident He³ polarization. The angular distribution and polarization of the protons from this reaction has been calculated for the case of polarized and unpolarized He³ beams incident on a polarized deuteron target. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Microstructuring of silicon is performed to alter its optical and electrical properties for use in photonic devices. Femtosecond lasers are a favourable structuring tool because they are extremely precise due to the confinement of their interaction to the focal volume. Experiments were carried out on N-type, P-type, and intrinsic silicon with a femtosecond laser operating at 800 nm, with pulse duration of 40 fs, and 1 kHz repetition rate. A single pulse produced a micro-ring structure surrounding a crater. It is caused by the motion of material according to the pressure gradient induced by the Gaussian profile of the laser. Multiple-pulse structures were similar to the single pulse except for the central protrusion of material. Two factors are responsible for multiple-pulse structures: (1) geometrical difference of the plasma compared to the single pulse (2) reflections of shockwaves produce protruding structures. Polarization dependence of all structures was observed.

A study of the dielectric properties of some phosphonitrilic fluorides, chlorides and chloride-fluorides in cyclohexane solutions was carried out and evidence was found to support the hypothesis that these compounds all have a non-negligible atom polarization caused by low frequency vibrations of the molecules. The distortion polarization of one of the geminally substituted isomers of the compound N₄P₄F₄Cl₄ was measured and this datum was used as support for assigning the 1,1,3,3-isomer structure to the compound. / Science, Faculty of / Chemistry, Department of / Graduate

The polarization of light from helium atoms excited by the impact of low energy electrons has been measured for the spectral lines 2³P - 2³S (10,829 Å) and 3³P - 2³S (3889 Å). An electron beam carrying a current of 10μA was directed into helium gas at a pressure of 4 x 10⁻³ torr or less. Polarization was measured as a function of electron energy in a range from the excitation threshold (approximately 23 electron volts) to 50 e.v. For the 2³T - 2³S line, this work represents the first reported measurement of this type. There is special interest in the value of polarization near the excitation threshold. The theoretical threshold polarization for both lines studied in this thesis is 36.6%. In the experiment of this thesis, the observed polarization of the 2³P line rises to 21% near threshold, and by means of a curve fitting procedure may be extrapolated to 32 ± 6%. The polarization of the 3³P - 2³S line rises to 11% and may be extrapolated to 15 ± 3%. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A proton polarimeter employing multi-wire delay-line drift chambers (MWDDCs) has been built for ongoing pion absorption studies in the meson area at TRIUMF. A brief introduction of the theoretical basis of polarimeter and MWDCC operation is offered. An in-depth study of our own system is presented including an account of the data acquisition readout electronics and the procedures used for wire chamber position calibration. Detailed performance specifications of all aspects of our chamber are given, notably for the method used to solve the drift chamber left/right ambiguity. The chambers are found to operate reliably and efficiently with very good spatial resolution, σ = ~200µm. The systematic artificial asymmetry in the polarimeter is also studied. Finally, scattering-efficiency and figure-of-merit ([formula omitted]) results are presented for 230 MeV protons scattering off a 7cm carbon analyzer in the three cases of ø + π and 2π azimuthal scattering acceptance symmetry, and full polarimeter acceptance. In particular, it is found that when employing the Besset weighted-sums polarization extraction technique, imposition of ø + π azimuthal scattering symmetry results in only a small increase in measured statistical error compared to results obtainable from a full Fourier spectrum analysis with no applied acceptance symmetry. Suggestions for improvements to established practices are offered throughout. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

It is shown that light emitted by mercury vapour at 253.7 nm can be polarized by passing the light through mercury absorption gas embedded in a magnetic field which is transverse to the direction of propagation of the light. The absorption lines of the mercury are split by the Zeeman effect, so that the absorber has an absorption coefficient which depends on both the polarization and wavelength of the transmitted light. A complete theory for the Hg²⁰² isotope is presented and the results are compared to measurements made with a natural mercury emitter and absorber. The observations are in qualitative agreement with the theory once isotope and hyperfine structure of the isotopes in natural mercury are included in the theory. Quantitative analysis was not possible because the emission line profiles could not be measured with the available equipment. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In this work, liquid phase Carbon-thirteen DNP experimental data were collected in a flow transfer system for different mono-substituted aromatic compounds, such as, anisole, nitrobenzene and halobenzenes. These substitute groups covered a wide range of electronic effects from strong electron donating groups to strong electron withdrawing groups. Hammett linear free energy relationship was used to quantitatively study the electronic effect of substituent on the carbon-thirteen DNP enhancement. It was found that the carbon-thirteen DNP enhancements at meta and para positions exhibits a reasonable correlation. A better correlation of carbon-thirteen DNP enhancements with the Hammett inductive factor was observed. A large scalar dominated enhancement at ipso (C-1) position was observed for iodobenzene. This suggests that facile transfer of spin polarization to the C-1 carbon via the highly polarizable iodine atom is possible and the dominate electron transfer mechanism for this system. A model of polarization transfer via spin diffusion of abundant proton spins was examined. The results indicate that it is not important. / Master of Science

The eclipsing binary ò Aur is unique in being a very-long-period binary involving an evolved, variable F star and a suspected B main-sequence star enshrouded in an opaque circumstellar disk. The geometrical arrangement is that the disk is viewed almost perfectly edge on, with the alignment leading to a partial eclipse of the F star. Despite a global observing campaign for the 2009–11 eclipse, there remain outstanding questions about the nature of the binary, its components, the disk, and the evolutionary state of the system. We analyze optical-band polarimetry in conjunction with broadband color variations to interpret brightness variations across the surface of the F star. We model this both during and after the 1982–84 eclipse for which an extensive and dense data set exists. We develop a model in terms of surface temperature variations characterized by a small global variation overlaid with a temperature variation described with low-order spherical harmonics. While not providing a detailed fit to the data set, our modeling captures the overall characterization of the color and polarimetric variability. In particular, we are able to recover the gross behavior of the polarimetric excursion in the Q–U plane as observed during eclipse of the F star when compared to posteclipse behavior.

This thesis examines urban inequalities in the Canadian context and focuses on Ottawa, the capital city. Firstly, income inequality in the eight largest Census Metropolitan Areas in Canada, between 1971 and 2016, is examined through an analysis of income polarization and its spatial patterns. The middle-income group has declined across CMAs, while the low-income group has usually expanded. Concurrently, increasing spatial fragmentation is identified in every CMA examined. Local spatial autocorrelation identified clustering of high-income Census Tracts (CTs) suggesting that these areas are more resilient to fragmentation. Therefore, patterns of urban inequality are ones of an unequivocally disappearing middle-income population with an increasingly spatially fragmented urban income-scape. At local levels, inequality is manifest in processes such as gentrification. To increase the spatial and temporal ability to monitor and map gentrification in a large city, artificial intelligence and Google Street View imagery were used to identify visual improvements to properties that are indicative of gentrification between 2007 and 2016. A deep Siamese convolutional neural network (SCNN) and VGG19 backbone was trained to recognize visual gentrification-like changes of properties over time. This deep mapping model achieved a 95.6% level of accuracy in identifying the visual signs of property improvement using 86110 georeferenced photographs of individual properties in Ottawa, Canada. Given that the residential/commercial property itself is the atomic object of gentrification, properties identified as having undergone a gentrification like visual change were mapped as points to produce kernel density maps that reduce noise and identify regions of high visual property change intensity (hot spots). The intensity of visual property improvements exhibited strong concordance with the spatial pattern of building permits between 2011 and 2016. The results confirmed areas known to be undergoing gentrification and also presented areas where the process was not previously suspected of occurring. Thirdly, a select set of census-based quantitative methods of modelling gentrification were compared between 2006 and 2016 at both the CT and the finer dissemination area unit of analysis. All models were tested against their ability to predict the density of GSV-points per unit residential area that were predicted by the Siamese deep learning model. For the CT level, two new regression models were created using all the census variables identified within the learned literature. An OLS multivariable regression model was created using backward stepwise regression, after which only age (youth), dwelling-value, income & occupation were retained. Residual spatial dependence in the OLS required a spatial linear model specification. A spatially lagged simultaneous autoregressive model (SAR Lag_y) explained 57% of the variance in GSV-point density in Ottawa. Out of all the models tested, the SAR Lag_y possessed the strongest spatial correlation with the original pattern of GSV point density as measured using Lee's L bivariate spatial autocorrelation statistic. A second model was produced using quasibinomial regression in order to predict the probability of a given CT being gentrified. That model achieved 91.7% accuracy. Out of the five reproduced models from the literature, one preformed close to as well as our new models in predicting GSV-point density per unit residential area. While there is some agreement between models that purport to measure gentrification, there are considerable differences between models, which suggests that census-based gentrification measure should be locally focused.