Red dwarf stars are one proposed solution to the dark matter problem in the Milky Way Galaxy These cool, low luminosity stars are difficult to detect and segregate in surveys. This study utilizes photometric data obtained on the Kron-Cousins photometric system to develop criteria that classifies stars as red. Two of the color indices are then used to create a two-color diagram to allow separation of giant and dwarf stars. An algorithm based on calculated equations is provided to separate the giant and dwarf stars after detection. A third class of stars, subdwarfs, is addressed as a potential problem in future surveys. Some suggestions for detecting and removing these contaminating stars from the data are offered. Finally, a colormagnitude diagram is developed for red dwarf stars with KronCousins photometry. This curve allows for fairly accurate determination of photometric parallaxes for the red dwarf stars.An attempt was made to segregate the red dwarfs into velocity classes prior to calibrating the color-magnitude diagram. It was found that this approach offered no additional useful information. / Department of Physics and Astronomy

Cataclysmic variable stars (CVs) are interacting binary systems. One of the stars (referred to as the primary) is a white dwarf, the other (referred to as the secondary) is usually a late main sequence star such as a red dwarf. Due to the closeness of the two stars, the white dwarf accretes gasses from the secondary. If the white dwarf does not possess a strong magnetic field, these gasses go into orbit, forming an accretion disk around the primary. If the white dwarf does possess a strong magnetic field, the gasses cannot form an accretion disk because they are entrained by the magnetic field lines. Cataclysmic variable stars in which the magnetic field is strong enough to prevent the formation of the accretion disk are called AM Herculis-type systems, after their prototype. In this study, the time-resolved spectroscopy of two AM Herculis-type binary systems, QQ Vul and EF Eri, are analyzed. In addition, Doppler Tomography, an analysis technique previously applied primarily to cataclysmic variable stars with accretion disks, is applied to these systems. / Department of Physics and Astronomy

There is no abstract available for this thesis. / Department of Physics and Astronomy

Current models of cosmology and galaxy formation are possibly at odds with observations of small-scale galaxies. Such is the case for the dwarf spheroidal (dSph) galaxies of the Milky Way (MW), where tension exists in explaining their observed abundance, mass, and internal structure. Here we present an analysis of the substructure surrounding MW-sized haloes in a Lambda Cold Dark Matter (LCDM) simulation suite. Combined with a semi-analytic model of galaxy formation and evolution, we identify substructures that are expected to host dSph galaxies similar to the satellites of the MW. We subsequently use these simulations to investigate the orbital properties of dSph satellite galaxies to make contact with those orbiting the MW. After accretion into the main halo, the higher mass ``luminous'' substructure remains on highly radial orbits while the orbits of lower mass substructure, which are not expected to host stars, tend to scatter off of the luminous substructure, and thus circularize over time. The orbital ellipticity distribution of the luminous substructure shows little dependence on the mass or formation history of the main halo, making this distribution a robust prediction of LCDM. Through comparison with the ellipticity distribution computed from the positions and velocities of the nine MW dSph galaxies that currently have proper motion estimates as a function of the assumed MW mass, we present a novel means of estimating the virial mass of the Milky Way. The best match is obtained assuming a mass of 1.1 x 10^12 M_sun with 95 per cent confidence limits of (0.6 - 3.1) x 10^12 M_sun. The uncertainty in this estimate is dominated by the large uncertainties in the proper motions and small number of MW satellites used, and will improve significantly with better proper motion measurements from Gaia. We also measure the shape of the gravitational potential of subhaloes likely to host dSphs, down to radii comparable to the half-light radii of MW dSphs. Field haloes are triaxial in general, while satellite haloes become more spherical over time due to tidal interactions with the host. Thus through the determination of the shape of a MW dSph's gravitational potential via line of sight velocity measurements, one could in principle deduce the impact of past tidal interactions with the MW, and thus determine its dynamical history. Additionally, luminous subhaloes experience a radial alignment of their major axes with the direction to the host halo over time, caused by tidal torquing with the host's gravitational potential during close pericentric passages. This effect is seen at all radii, even down to the half-light radii of the satellites. Radial alignment must be taken into account when calibrating weak-lensing surveys which often assume isotropic orientations of satellite galaxies surrounding host galaxies and clusters. / Graduate / 0606

Lake Winnipeg has the second largest walleye fishery in North America. The North and South Basins of the lake differ in many ways, e.g. water temperature, turbidity, and fish community. The study objectives were to determine if (a) growth, condition or diet of walleye, sauger or dwarf walleye differed between basins, (b) among seasons, and (c) whether the invasive rainbow smelt are associated with these differences. Walleye, sauger and dwarf walleye were caught using gill-nets and analysed for growth, condition and diet in all seasons. Walleye and sauger in the North Basin showed higher growth rates and condition than in the South Basin. Diet in the South Basin had more diverse species composition, whereas in the North Basin, the diet consisted almost entirely of rainbow smelt. Some seasonal variation was also documented and the impact of rainbow smelt seems to be positive for these piscivorous fish in Lake Winnipeg.

Current models of cosmology and galaxy formation are possibly at odds with observations of small-scale galaxies. Such is the case for the dwarf spheroidal (dSph) galaxies of the Milky Way (MW), where tension exists in explaining their observed abundance, mass, and internal structure. Here we present an analysis of the substructure surrounding MW-sized haloes in a Lambda Cold Dark Matter (LCDM) simulation suite. Combined with a semi-analytic model of galaxy formation and evolution, we identify substructures that are expected to host dSph galaxies similar to the satellites of the MW. We subsequently use these simulations to investigate the orbital properties of dSph satellite galaxies to make contact with those orbiting the MW. After accretion into the main halo, the higher mass ``luminous'' substructure remains on highly radial orbits while the orbits of lower mass substructure, which are not expected to host stars, tend to scatter off of the luminous substructure, and thus circularize over time. The orbital ellipticity distribution of the luminous substructure shows little dependence on the mass or formation history of the main halo, making this distribution a robust prediction of LCDM. Through comparison with the ellipticity distribution computed from the positions and velocities of the nine MW dSph galaxies that currently have proper motion estimates as a function of the assumed MW mass, we present a novel means of estimating the virial mass of the Milky Way. The best match is obtained assuming a mass of 1.1 x 10^12 M_sun with 95 per cent confidence limits of (0.6 - 3.1) x 10^12 M_sun. The uncertainty in this estimate is dominated by the large uncertainties in the proper motions and small number of MW satellites used, and will improve significantly with better proper motion measurements from Gaia. We also measure the shape of the gravitational potential of subhaloes likely to host dSphs, down to radii comparable to the half-light radii of MW dSphs. Field haloes are triaxial in general, while satellite haloes become more spherical over time due to tidal interactions with the host. Thus through the determination of the shape of a MW dSph's gravitational potential via line of sight velocity measurements, one could in principle deduce the impact of past tidal interactions with the MW, and thus determine its dynamical history. Additionally, luminous subhaloes experience a radial alignment of their major axes with the direction to the host halo over time, caused by tidal torquing with the host's gravitational potential during close pericentric passages. This effect is seen at all radii, even down to the half-light radii of the satellites. Radial alignment must be taken into account when calibrating weak-lensing surveys which often assume isotropic orientations of satellite galaxies surrounding host galaxies and clusters. / Graduate / 0606

Cocoa (Theobroma cacao L.) is an important cash crop in the coastal areas of Papua New Guinea (PNG). In 2000, a mutant cocoa genotype MJ 12-226, with abnormal growth characteristics was identified at the Cocoa and Coconut Institute of PNG. The mutant, found among progenies of the cross Scavina 12 x Nanay 149, was characterized by dwarfing, small and narrow leaves, a small root system and strong branching habit. This study was designed to improve the understanding of the dwarf cocoa mutant and identify its relevance to future cocoa farming. The specific objectives are to investigate the feasibility of using a dwarf mutant of cocoa as a commercial rootstock for various hybrid cocoa clones, to study the genetics of this dwarf mutant and the role of plant hormones in differentiating this mutant from the normal phenotype. This study was carried out at the Cocoa and Coconut Institute of PNG, Rabaul, Papua New Guinea, and at the University of Queensland, Gatton Campus, Australia. The comparative study of mutant and normal cocoa seedlings revealed distinct vegetative differences between the two genotypes at the nursery stage. The largest effects of the mutant genotype are on stem elongation, short internodes, multiple stems, root growth and leaf growth. The agronomic results indicated that the mutant rootstock significantly reduced tree vigour at least in the early years. When used as a rootstock, the mutant had a significant dwarfing effect on scion growth of cocoa clones in the nursery and persisted in the field 12 months after planting. After that, the cocoa clones grafted on mutant rootstock reverted to normal growth. It was postulated that the accumulation of endogenous growth substances and cambial activity between the scion (normal) and the rootstock overcame the dwarfing effect of the mutant genotype. Yield and vegetative data collection from this trial ceased on May 2006 and recommenced in May 2007 to allow trees to recover from heavy canopy pruning due to cocoa pod borer attack. This resulted in one year loss of yield and vegetative data from this experiment. The first two years’ yield data indicated no significant differences between mutant, normal segregants and commercial rootstocks. However, cocoa clones bud grafted on these mutant rootstocks produced significantly greater yield at higher planting density compared with lower densities and this was sustained for two years. However, it might be expected that competition among cocoa trees would increase with increased size of trees, favouring low density planting and reducing the differential performance of the trees under high density planting with time. The major advantages of reducing tree vigour are to improve the harvest index, ease of harvesting, pruning and overall management of the trees. The continuation of this study to collect mature tree yield data (from fifth to eighth years) would confirm these results. This work has also demonstrated for the first time that cocoa clones grafted on mutant rootstock can produce similar yields to clones grafted on normal or commercial rootstocks. Moreover, this study has also established that cocoa clones derived from orthotropic scions can yield the same as plagiotropic scions when grafted on to either mutant or normal rootstocks. Therefore, it is proposed that mutant rootstocks and orthtropic scions should also be considered for future use in cocoa farming. The strong branching habit and dwarfing stature of the mutant suggested that the mutation affects the quantity or the balance of plant growth hormones, or both. The effect of exogenously applied gibberellic acid (GA3) on developmental processes in dwarf mutant and normal cocoa seedlings was studied. Both dwarf mutant and normal one month old cocoa seedlings responded to gibberellic acid (GA3) by accelerated longitudinal growth, especially seedling height. Paclobutrazol (PBZ) applied to normal cocoa seedlings altered the growth so that they almost resembled the mutant phenotype. It was postulated that PBZ prevented GA biosynthesis in the normal cocoa seedlings and therefore decreased bioactive auxin (IAA) which, in turn, then promoted lateral shoot growth; PBZ also slightly retarded plant growth. Synthetic auxin (IBA/NAA) significantly inhibited lateral bud sprouting and growth of intact, decapitated and nodal segments of mutant and normal cocoa seedlings compared with control and those treated with IAA. It appears that the mutant and normal cocoa genotypes have a similar capacity to metabolize IAA and this capacity was much greater than for synthetic auxins. The results suggested that auxin levels in the mutant seedlings were probably limiting, and therefore affected biosynthesis of gibberellic acid thus resulting in the dwarfing characteristics of the mutant cocoa genotype. However, analysis of endogenous IAA and GA1 levels at four months old did not reveal differences between the mutant and normal seedlings. The present genetic studies which included backcrossing, test crossing and selfing of F1 progenies confirmed earlier work on the mutant and showed that the mutant was probably heterozygous (Dd). The allele (DD) in mutant cocoa is probably lethal in nature because the phenotype of the homozygote was not observed amongst the mutant progenies. Mutant segregants were obtained in a 1:1 ratio only when the mutant clone was used as the female; however, when the mutant was used as male, very few mutant segregants were obtained. This suggested selective pollen viability (pollen grains carrying the D allele are nonviable) or an incompatible reaction between pollen tubes (D carrying pollen) and style or ovule. The selfing and test-crosses of F1 progenies resulted in deviation from the expected 3:1 segregation ratio to a 1:1 ratio.

Thesis (Ph.D.)--McMaster University (Canada), 1995. / Source: Dissertation Abstracts International, Volume: 57-03, Section: B, page: 1862. Adviser: W. E. Harris.

Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Science, 1996? / Includes bibliographical references.

Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 2001. / Errata attached to inside front cover. Bibliography: leaves [156-188].