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Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 205-209). Also available via World Wide Web.

Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2009/06/11). Includes bibliographical references.

In this work, the phase behavior of binary systems comprising nitrogen and a noble element (nitrogen + argon and nitrogen + krypton) was studied at high density in the condensed state. Following the work of Lotz et al.[2001], the main goal of this work was to further investigate the pressure-concentration phase diagram as well as to look for the possible formation of van der Waals compounds at elevated pressures and room temperature and study their physical properties, using both vibrational spectroscopy and X-ray diffraction. The observed phases, formed by single atoms and/or simple molecules in the binary systems were solved and modeled for their corresponding crystalline structures. From experimental results, lattice parameters for all crystalline structures and phase transitions, if detected, have been observed to shift with respect to that of the pure substances. The analyses and characterization of these binary systems are discussed in detail.

This dissertation discusses research that focuses on understanding transneptunian objects (TNOs) using a variety of techniques and approaches. In Chapter 1, I introduce the main concepts used throughout this dissertation and discuss the current understanding of the transneptunian region. In Chapter 2, I discuss my efforts to understand how Neptune's late stages of migration affect the Haumea family, the only known collisional family in the transneptunian region. Using advanced simulations of Neptune migration, I find that the Haumea family can plausibly form before the termination of giant planet migration and show that this extensively mixes the family. The simplest explanation for the formation of Haumea and its family is a slow disruption of a large, primordial binary system. In Chapter 3, I examine the detectability of non-Keplerian effects in the mutual orbits of transneptunian binaries. I find non-Keplerian effects are common, with 20% of TNBs best explained by a non-Keplerian orbit. I also demonstrate that one of the components of TNB (66652) Borasisi-Pabu is a contact binary. In Chapter 4, I examine the non-Keplerian orbits of Hi'iaka and Namaka, the satellites of Haumea, showing that they are strongly affected by both inter-satellite gravitational interactions and precession caused by Haumea's nonspherical gravitational field. Future observations of the Haumea system, combined with non-Keplerian fitting, will sensitively probe Haumea's interior. Lastly, in Chapter 5, I explore the mutual orbits of Cold Classical TNO binaries using non-Keplerian orbit fitting. Out of a sample of 18 binaries, 6 have significantly non-Keplerian orbits, allowing detailed characterization of their system architecture. I find that 3 of these systems are best explained as hierarchical systems, while the remaining 3 are consistent with precession due to the Sun's gravitational influence. The hierarchical systems I find strongly support the streaming instability theory of planetesimal formation.

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Phase equilibria studies of two ternary systems, the vanadium rhodium-silicon system and the niobium-rhodium-silicon system, were made to obtain information about the formation of the Cr₃O-type structure in these systems. All samples had compositions in the . vicinity of the stoichiometric Cr₃O composition line and were prepared by powder metallurgy techniques. The compacts were then arc-melted, given a homogenization anneal, and examined by x-ray diffraction. Complete solid solubility of silicon for rhodium was found across the V-Rh-Si system in the Cr₃O-type structure. A large range of vanadium compositions for the formation of the Cr₃O-type structure in the V-Rh-Si system was also found. A minimum lattice parameter was found for samples closely approximating the stoichiometric Cr₃O composition in the V-Rh-si system. Either an increase or a decrease in vanadium composition from stoichiometry caused an increase in the lattice parameter of the Cr₃O-type structure formed. No solid solubility of silicon for rhodium was found in the niobium-rhodium-silicon system. Apparently the only Cr₃O-type structure which forms in the Nb-Rh-Si system is of' the stoichiometric composition Nb₃Rh. / Master of Science

1. From a study of the system salicylic acid-biphenyl it was concluded that there was no compound formation in the system. The solution is very nearly ideal, having an eutectic temperature of 67.6℃ at a mole fraction of .903 for the biphenyl. 2. The system salicylic acid-diphenylamine was studied and no compound formation was found to be present. The system and no compound formation was found to be present. The system is not as ideal as the salicylic acid-biphenyl system, but follows the ideal solution curve fairly well. The system has an eutectic temperature of 48.5℃ at .926 mole fraction of diphenylamine. / M.S.

I have used blue near-infrared colours to select a group of UKIDSS T dwarfs with spectral types later than T4. From amongst these I identify two kinematic halo T-dwarf candi- dates. Blue near-infrared colours have been attributed to collisionally-induced hydrogen absorption, which is enhanced by either high surface gravity or low metallicity. Proper motions are measured and distances estimated, allowing the determination of tangential velocities. U and V components are estimated for our objects by assuming Vrad = 0. From this, ULAS J0926+0835 is found to have U = 62 kms−1 and V = −140 kms−1 and ULAS J1319+1209 is found to have U = 192 kms−1 and V = −92 kms−1. These values are consistent with potential halo membership. However, surprisingly, these are not the bluest objects in the selection. The bluest is ULAS J1233+1219, with J −K = −1.16±0.07, and surprisingly this object is found to have thin disc-like U and V . Our sample also contains Hip 73786B, which I find to be a companion to the star Hip 73786. Hip 73786 is a metal- poor star, with [Fe/H]= −0.3 ± 0.1 and is located at a distance of 19±0.7 pc. U, V,W space velocity components are calculated for Hip 73786A and B, finding that U = −48±7 kms−1, V = −75 ± 4 kms−1 and W = −44 ± 8 kms−1. From the properties of the pri- mary, Hip 73786B is found to be at least 1.6Gyr old. As a metal poor object, Hip 73786B represents an important addition to the sample of known T dwarf benchmarks. Using mid-infrared data from WISE, I also identify T dwarfs with abnormally-red H − W2 and consider possible causes for their extreme colours. In particular I exam- ine three prominent examples of this phenomenon, ULAS J1416+1348B, 2MASS J0939- 2448 and BD+01o 2920B. A plot of spectral type against MW2-magnitude suggests that ULAS J1416+1348B is potentially an unresolved binary, similar to 2MASS J0939-2448. However, the plot also indicates that BD+01o 2920B is not an unresolved binary. I also present new FIRE spectroscopy for ULAS J1416+1348B and 2MASS J0939-2448. These data show that ULAS J1416+1348B has a similar shape to the Y -band spectrum to that of BD+01o 2920B, thus suggesting that the two objects have a similar metallicity, whereas 2MASS J0939-2448 appears to be a more metal-rich object. Using a new parallactic dis- tance, I derive a luminosity of (6.9±0.7)×1020W for ULAS J1416+1348B. I also find a radial velocity of −39 ± 1 kms−1 for this object. The agreement between this and that of the L dwarf SDSS J1416+1348A confirms that these two objects are physically-associated. I also present a set of simulated unresolved binaries; the colours of these systems do not appear to redden significantly with the addition of cooler companions. From this, I suggest that the colours of ULAS J1416+1348B and BD+01o 2920B cannot be solely attributed to any possible unresolved companions; for these two objects, composition and/or surface gravity must be playing a substantial role. Consideration of model predictions provides extra evidence for this argument, showing as it does that high log g and low metallicity can redden H − W2 colours by as much as »0.5mag as compared to a high-metallicity and low log g object of the same effective temperature. I also present kinematics and photometry for several more new candidate low-metallicity T dwarfs. Spectra are also presented, where available. In addition I provide new follow-up JHK spectroscopy for ULAS J0926+0835, ULAS J1233+1219 and ULAS J1319+1209. These new spectra allow full JHK-based spectral typing for these objects.