The range of thermally stable, predominantly a-bonded metal carbonyl derivatives has been expanded to include Pd(I), Pd(II), Ir(III), Os(II), and Ru(II). The new compounds, [Pd(CO)₄][Sb₂F₁₁]₂, cis-Pd(CO)₂(SO₃F)₂, [Pd₂(µ-CO)₂](SO₃F)₂, [Pd₂(µ -CO) ₂][Sb₂₁₁]₂, mer- Ir(CO)₃(SO₃F)₃, [Ir(CO)₅Cl][Sb₂ F₁₁]₂, [Ru(CO)₆][Sb₂F₁₁]₂, [Os(CO)₆][Sb₂F₁₁]₂, and cis- Pt(CO)₂(Sb₂Fn)₂ have been synthesized. The compounds have been characterized using a variety of physico-chemical techniques: elemental analysis, FT-IR and Raman spectroscopy, and ¹³C NMR spectroscopy. For cis-Pd(CO)₂(SO₃F)₂, [Pd₂(µ-CO)₂](SO₃F)₂, mer- Ir(CO)₃(SO₃F)₃, and [Ir(CO)₅Cl][Sb₂F₁₁]₂, the molecular structures have been determined by single crystal X-ray diffraction. [More abstract follows; please see pp.3+ of the accompanying pdf file] / Science, Faculty of / Chemistry, Department of / Graduate

The tap withdrawal response of the nematode Caenorhabditis elegans supports several forms of behavioural plasticity, including habituation (Rankin, Beck, & Chiba, 1990). The relative simplicity of this organism, both in terms of its nervous system and its genetic tractability, suggest that it would be a fruitful model system within which to investigate the neural and molecular substrates of learning. This report examines the production of the tap withdrawal response and the plasticity exhibited by that response at the cellular/circuit level. The neural circuit that mediates the tap response was identified through a program of single-cell laser microsurgery. Further behavioural analyses determined some of the functional properties of the tap withdrawal circuit neurons, both in the production of the tap withdrawal response and in the generation of the plasticity that that response expresses. First, this work demonstrated that the response was not unitary, but rather was composed of two competing reflexive behaviours: forward locomotion in response to posterior mechanosensory input and backward locomotion in response to anterior mechanosensory input. An animal's response to given stimulus was determined by the relative degree to which each of these reflexes were recruited. Second, it was demonstrated that each constituent reflex habituated in the absence of the other, and that habituation of the intact response was a summation of these two processes. Third, a dynamic network simulation of the circuit was used to predict the sign or polarity of the synapses that constitute the circuit. Fourth, it was demonstrated that at least two independent interstimulus interval-dependent processes were recruited during habituation: One that affects habituation kinetics and one that affects recovery from habituation. Finally, an analysis of the effects of tap withdrawal response habituation on other non-mechanosensory withdrawal behaviours was used, in conjunction with ablation studies, to identify potential loci of change within the circuit that might underlie habituation. The implications both of the functional properties of tap withdrawal circuit elements during habituation and the restriction of potential sites of change are discussed. / Medicine, Faculty of / Graduate

Shortly after initiation, shoot and floral organ primordia become determined to particular fates based on their spatial/temporal position in the plant. Many genes are known which affect the proper regulation of this process, and these genes are expressed in spatial/temporal patterns consistent with the developmental decisions they regulate. Little is known about the mechanisms by which these regulatory genes achieve their final patterns in the developing plant. I have identified a novel gene involved in regulation of flower initiation and development in Arabidopsis. This gene is designated UNUSUAL FLORAL ORGANS (UFO). Ufo plants generate more coflorescences than do the wild type and, unlike wild type, coflorescences often appear apical to the first floral shoot, indicating that UFO has a role in regulating coflorescence versus floral fate determination by lateral shoots. In addition, Ufo floral organs exhibit variable homeotic transformations to any of the four organ types in the second, and third whorls, suggesting that ufo mutations result in variable expression levels and/or patterns of the organ identity genes. These hypotheses are supported by phenotypic analysis of double mutants between ufo and other floral initiation and floral organ identity gene mutations. Surprisingly, in situ hybridization analysis revealed no obvious differences in mRNA levels or pattern for any organ identity gene examined. These results suggest that UFO may act post-transcriptionally to regulate the expression of floral organ identity genes. UFO was cloned by homology to the Antirrhinum gene FIMBR1ATA. Sequence analysis revealed no homology to any other gene in the sequence databases. UFO transcription is detected in spatial/temporal patterns consistent with its proposed roles in shoot and organ identity gene regulation, and does not appear to rely directly on any of the floral initiation genes. Collectively, the data indicate that UFO is required as part of the floral initiation process to establish the proper domains of shoot and organ identity gene function, and that this regulation occurs post-transcriptionally. / Science, Faculty of / Botany, Department of / Graduate

In the growth of anodic oxide films on tantalum, the ionic conduction at a given current density depends on the electrical history of the film. In this thesis, this history effect has been investigated by examining the frequency response of the high field ionic conduction process involved in the growth of anodic oxidation on tantalum. The admittivity, defined as the complex ratio of the ac current density to the ac field, was measured. Ideally, constant dc and ac components of field would be applied. This was approximated by applying a ramp voltage plus an ac voltage, both increasing with the average film thickness. The measured current density includes displacement current.. A series capacitance effect is caused by the ac component of the rate of change in film thickness. After correction for these effects, plots of the real vs. imaginary parts of the admittivity, which yielded arcs of circles with centers above the real axis, were fitted to a Cole-Cole type of expression: A+B/[1+(jωtm)1-θ], where 1 / t m is the angular frequency (o)) at the maximum magnitude imaginary part, π(l-θ) is the central angle subtended by the arc. This result was explained as being due to a distribution of relaxation times being involved in the history effect. This is consistent with the history effect being caused by changes in the structure of the semi-amorphous oxide film depending on formation conditions. tm was found to be close to inversely proportional to the dc ionic current density and almost independent of temperature. This is consistent with a process driven by current density. In anodic oxidation, there is the possibility of incorporation in the film of species from the electrolyte. Experiments were carried out to see if the curvature of the steady-state logJ vs. E relation and the dependence of the stepped-field line slope on the steady-state field can be caused by this incorporation. The steady-state log (J) vs. field (E) relation has been studied for films grown in 0.1M sulphuric acid and 0.1M oxalic acid. The refractive index and thickness of the films were measured using ellipsometry. Films grown in oxalic acid showed 1-2% higher field. Measurement of the oxide capacitance at different film thickness showed the oxide permittivity to be higher for the films grown in sulphuric acid. An overshoot transient in the field (E), with a peak field (Ep ), was observed when the ionic current was stepped from the steady state to a higher value (J2). The field as a function of time, E(t), was derived from the measured voltage divided by the thickness which was equivalent to the integration of ionic charge passed at each time t. Measurement of the initial slope of dE/dt showed the oxide permittivity agreed with the results from the capacitance measurement. The relation of logJ2 vs. Ep at a steady-state current density can approximately describe the stepped-field condition with the history effect held constant during the transient The relation of logJ2 vs. Ep was shown to be linear and the slope of dlogJ2/dEp was shown to be dependent on the initial field for films grown in both electrolyte solutions. Further work is necessary before a definite conclusion can be reached about the contribution of electrolyte incorporation to curvature of the Tafel plot. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

I study the problem of self-organized pattern formation by groups of organisms. "Self-organized" groups are coordinated by interactions between all individuals in the group rather than by a leader or hierarchical organization. The information and stimuli necessary to coordinate individual activities are communicated through the group by these interactions. I begin by describing a modelling philosophy where as many details of the individual behaviours are included in the model as are necessary for both biological and mathematical completeness, but no group behaviours are fed into the model. Two specific phenomena are addressed using this approach. The first phenomenon is honey bee cluster thermoregulation. I address the question "can cluster thermoregulation be explained using only the observed behaviours of individual bees?" and show that a temperature dependent behaviour of the bees is sufficient to produce the observed global thermoregulation of the cluster. Previous models of cluster thermoregulation are discussed in light of this modelling approach. The model also is able to make testable predictions about the density profiles of the cluster. The second phenomenon modelled is the transmission of a pheromone through a honey bee colony. The problem is of interest to beekeepers, since the pheromone is known to suppress swarming. I answer the question "How does congestion within a honey bee colony affect the transmission of a pheromone through the hive?" This question is central to a current hypothesis on the connection between the queen's ability to produce pheromones, colony size and congestion, and swarming. The cluster thermoregulation model involves a behavioural dependence on the cluster temperature. In contrast, the transmission model involves a direct exchange of a chemical pheromone between the bees. Thus, with the thermoregulation model I examine interactions mediated through an environmental state, and with the transmission model I examine direct interactions between individuals. I study these models using both Eulerian and Lagrangian models. The Lagrangian model is studied using cellular automata simulation. The Eulerian model consists of a system of partial integro-differential equations and is studied using a combination of numerical simulations and mathematical analysis. The results of the models suggest that the two interactions produce similar group properties. In the thermoregulation model, information about the global structure of the group diffuses through the cluster as thermal energy. In the transmission model, pheromone diffuses through the colony by the random motions of the bees. / Science, Faculty of / Mathematics, Department of / Graduate

Abnormal vascular reactivity has been suggested to be a hallmark of impending development of hypertension in arteries from diabetic humans. Previous studies from this laboratory have demonstrated an enhancement in both the contractile and signaling response to ai-adrenoceptor stimulation in arteries from male Wistar rats with 12-14 weeks of streptozotocin-induced diabetes. The purpose of the research in this thesis was to study the basis for the increased signaling in diabetic arteries. Direct stimulation of G-proteins with NaF, in the presence of AlCl3, produced contractile responses in mesenteric and caudal arteries from diabetic rats that were significantly elevated compared to control arteries by a similar magnitude as the noradrenaline (NA) enhancement The larger contractile response of the diabetic arteries was not attributable to a difference between control and diabetic arteries in cAMP or cGMP levels, either basally or in the presence of NaF. Ryanodine which depletes intracellular calcium stores, nifedipine which blocks dihydropyridine-sensitive calcium channels and calphostin C which selectively inhibits proteins kinase C, all significantly inhibited maximum contractile responses of mesenteric arteries from control and diabetic rats to NaF. There were no significant differences between control and diabetic arteries in the relative magnitude of the inhibition produced by the three antagonists. These data suggest that there may be increased activation of the same signaling processes that mediate NA-stimulated vasoconstriction, perhaps contraction-associated G-proteins or the effectors coupled to these G-proteins, in response to NaF in mesenteric arteries from diabetic rats. [More abstract follows] / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

The use of (-)-camphor (ent-9) as an enantiopure intermediate in pseudoguaianolide and limonoid synthesis and further aspects of the chemistry df 4-methylcamphor (87) are presented in this thesis. First, the preparation of relay compounds ketal-enone 140, hydroxy-ketone 123, hydroxy-enone 158, and hydroxy-ketone 128 represents a formal, enantiospecific synthesis of the helenanolides carpesiolin (96), helenalin (95), bigelovin (97), mexicanin I (98), and linifolin A (99) and the ambrosanolides damsin (102) and confertin (103). (-)-Camphor (ent-9) was converted in nine steps to ketal-ester 164b. Stereoselective alkylation of 164b with methyl iodide yielded ketal-ester 165 that could be elaborated to the ketal-enone 140 in seven steps. Hydroxy-ketone 123 was obtained from 140 in a further three steps. Similarly, stereoselective alkylation of 164b with allyl bromide yielded ketal-ester 184 that could be converted subsequently to hydroxy-enone 158 in nine steps. Finally, catalytic hydrogenation of 158 provided hydroxy-ketone 128. Secondly, as part of an enantiospecific synthetic approach to the limonoids, the tricyclic enone 257 was prepared. (-)-Camphor (ent-9) was converted to the known bicyclic enone-ester (ent-255) in ten steps. Alkylation of ketal-ester .262, derived from ent-255, with methyl bromoacetate yielded ketal-diester 263, which could be transformed into dimethoxy-enone 267 in three steps. Two successive alkylations of enone 267 yielded the j3,^unsaturated enone 279, and subsequent desilylation, oxidation, and aldol condensation steps provided the tricyclic enone 257, which has potential as a BCD-intermediate for the synthesis of tetracyclic limonoids. Finally, a proposed mechanism for the bromination of endo-3-bromo-4-methylcamphor (327) to yield e«do-3,9-dibromo-4-(bromomethyl)camphor (332) was evaluated using the corresponding deuterium-labelled analogue, e«do-3-bromo-9-deuterio-4-(deuteriomethyl)camphor (351), as substrate. NMR spectroscopic evidence was used to identify the product resulting from the bromination of 351 as g«rfo-3,9-dibromo-9-deuterio-4-(bromodeuteriomethyl)camphor (352). Evidence supporting the proposed existence of unsaturated intermediates 355 and 358 in the bromination mechanism was also obtained. / Science, Faculty of / Chemistry, Department of / Graduate

A photometric survey of faint galaxies in three high Galactic latitude fields (each ~ 49 arcmin2) with sub-arcsecond seeing is used to study the clustering properties of the faint galaxy population. Multi-colour photometry of the galaxies has been obtained to magnitude limits of V ~ 25, R ~ 25 and I ~ 24. Two approaches are utilized to examine the clustering: close pair and angular correlation analysis. The number of close pairs of galaxies observed to faint magnitude limits, when compared to nearby samples, determines the interaction or merger rate as a function of redshift. The prevalence of mergers at intermediate redshifts is fundamental to understanding how galaxies evolve and the relative population of galaxy types. Mergers have been used to explain the excess of galaxies in faint blue counts above the numbers expected from no-evolution models. Using the deep imaging from one of the fields, a pair fraction is determined which is consistent with the galaxies in the sample being randomly distributed with no significant excess of close pairs. This is contrary to the pair fraction of 34% ± 9% found by other authors for similar magnitude limits and using an identical approach to the pair analysis. Various reasons for this discrepancy are discussed. Colours and morphologies of our close pairs are consistent with the bulk of them being random superpositions although, as indicators of interaction, these criteria are uncertain due to contamination of field galaxies and difficulty in seeing galactic structure at intermediate redshifts, respectively. This observed lack of close pairs is probably linked with the decreasing amplitude of the angular correlation function at faint limits. If our faint samples are comprised of galaxies which have a higher average redshift than brighter samples studied by other workers then either the merger rate has been overestimated or there is a change in its behaviour from what is observed at brighter magnitude limits. [More abstract follows] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The gravitational exchange of fluids between two bodies of water of slightly different density through a channel with a smooth two-dimensional underwater sill is studied theoretically and experimentally. Internal hydraulic theory is extended to incorporate the effects of streamline curvature caused by the sill. The extended theory is applied to both single and two-layer flows. Unlike internal hydraulic theory which fails to predict a whole class of two-layer flows, namely, approach-controlled flows, the extended theory with non-hydrostatic pressure considered achieves excellent agreement with previous experimental measurements. Internal hydraulic theory is further extended to incorporate the effects of friction caused by the channel and the two-layer interface, as well as the streamline curvature. For the exchange flow through a channel of constant width with a sill, maximal exchange occurs when both sill and exit controls are present. With the effects of curvature and friction considered, the sill control is shifted away from the sill crest, and the internal energy is no longer constant. Exchange flows established in the laboratory are studied using flow visualization, particle tracking, and image processing techniques. The friction factors for the sidewalls and bottom are estimated using boundary layer theories, while the interfacial friction factor is determined experimentally. The friction reduces the internal energy throughout the channel, significantly increases the interface slope and reduces the flow rate. The frictional effect is important throughout the channel, whereas the curvature effect is mainly important in the sill region. With both effects included, the exchange flow over a sill is accurately predicted. On the interface of exchange flows, interfacial instabilities are observed, with Kelvin- Helmholtz instabilities at both ends of the channel where shear is strong, and Holmboe instabilities in the middle region where shear is weaker. The Holmboe instabilities have been studied in detail. The existence of the negative shift, i.e., the shear center being lower than the density interface, is confirmed. This shift initially results in non-symmetric Holmboe waves. Later in the experiments, the shift reduces to zero and symmetric Holmboe waves are observed. The growth rate, wave lengths, and wave speeds of the Holmboe instabilities are measured and found to be in agreement with the linear stability theory of Haigh (1995). Variations in wave speeds when the positive and negative waves pass through each other have been observed for the first time experimentally. The Holmboe waves are stabilized when the bulk Richardson number exceeds about 0.8. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This thesis describes studies on the interaction of H₂S with mono- and dinuclear Pd - dpm (bis(diphenylphosphino)methane) complexes with the ultimate goal being to catalyze the conversion of H₂S to H₂ and elemental sulfur (S₈). Solution kinetic and mechanistic studies were performed on the abstraction of sulfur from Pd₂X₂(µ-S)(µ-dpm)₂ [X = Cl (2a), Br (2b), I (2c)] using dpm to give, respectively, Pd₂X₂(dpm)₂ [X = Cl (1a), Br (1b), I (1c)] and dpm(S) (process 2 → 1): [More abstract follows which cannot be rendered here; please see pp.3+ of the accompanying pdf file]. / Science, Faculty of / Chemistry, Department of / Graduate