3,166 results for University of Canterbury Library, Doctoral

  • Dancing to a different tune: adaptive evolution fine-tunes protein dynamics

    Donovan, Katherine Aleisha (2015)

    Doctoral thesis
    University of Canterbury Library

    The molecular mechanisms that underpin adaptive evolution are not well understood. This is largely because few studies relate evolved alleles (genotype) with their physiological changes (phenotype), which move a population to better fit its environment (adaptation). The work described in this thesis provides a case study exploring the molecular changes underlying adaptive evolution in a key allosteric enzyme. It builds upon a long-term evolution experiment by Richard Lenksi, where twelve replicate populations of Escherichia coli have adapted in parallel to better fit their low-glucose environment. I focused on the allosteric enzyme pyruvate kinase type 1, since this has been shown to adapt to this environment. First, I used X-ray crystallography to determine a higher resolution structure (2.2 Å) than previously available of the wild-type PK1 enzyme for comparison with the evolved enzymes. I resolved the ambiguous space-group problem that affects these crystals, and demonstrated that the kinetic function of the recombinant enzyme is the same as previously reported. In addition, I propose a new model for allosteric activation: a combination of structural and dynamic analyses determined that the allosteric signal is transferred by a series of dynamic changes between the allosteric site, upon fructose-1,6-bisphosphate binding, and the active site for increased substrate binding. The functional analyses demonstrated that all eight evolved PK1 enzymes have a reduced activity compared to the wild-type PK1 at physiological substrate concentrations. Not only did the evolved PK1 enzymes show a parallel decrease in activity, but they all showed changes to substrate binding affinity and seven of the eight showed an altered allosteric activation mechanism. These results suggest that natural selection has selected for enzymes with a reduced activity by altering the functional mechanism of the evolved enzymes. However, in crystal and in solution structure characterisation determined that all of the evolved PK1 enzymes have maintained the same structural fold as the wild-type PK1. Although the fold is the same, substrate binding promiscuity suggested a change in the flexibility of the enzyme, allowing substrates of different sizes and shapes to bind. Computational and experimental dynamics studies determined that natural selection has selected for reduced activity by altering the dynamics in all of the evolved PK1 enzymes, and it has used altered dynamics to change the allostery of the enzymes. Therefore, this study provides the first example of adaptive evolution fine-tuning protein dynamics to alter allostery. This thesis describes the molecular mechanisms underlying one aspect of adaptation of Escherichia coli to the low-glucose environment in Lenski’s long-term evolution experiment. The adaptive mutations in Escherichia coli’s pyruvate kinase type 1 serve to increase the availability of phosphoenolpyruvate for glucose uptake. From a molecular perspective, natural selection has selected for adaptive amino acid substitutions that produce an enzyme with reduced catalytic activity at low phosphoenolpyruvate concentrations, thus decreasing phosphoenolpyruvate consumption. In addition, the adaptive mutations have altered the enzymes’ affinity for the allosteric activator (fructose- 1,6-bisphosphate), fine-tuning them to match the concentration of fructose-1,6- bisphosphate in the cell at the point of glucose re-introduction. Overall, this work describes the intricate relationship between genetic changes and the resulting phenotype and demonstrates the parallel nature of adaptation for this particular case study. Whereby, parallel changes are mapped from organismal fitness, to enzyme function and to enzyme structure. The dynamic changes, however, are not parallel thus making the prediction of specific changes in adaptive evolution difficult.

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  • Primary production of intertidal marine macroalgae: factors influencing primary production over wide spatial and temporal scales

    Tait, Leigh Wayne (2010)

    Doctoral thesis
    University of Canterbury Library

    Oxygenic photosynthesis is responsible for virtually all of the biochemical production of organic matter in both marine and terrestrial ecosystems. Despite the large amount of research on phytoplankton, macroalgae have received less attention despite them being, on a per-area basis, one of the most productive ecosystems on earth. Furthermore, there has been a tendency of studies to measure primary production in single thalli, or monospecific stands. The lack of studies examining in situ production of whole assemblages using photorespirometry, as is common practice in soft-sediment systems, may be related to a lack of suitable apparatus. This research aimed to develop unique techniques and an apparatus for measuring primary production of intact macroalgal assemblages in laboratory and field conditions. Photorespirometry chambers were developed and tested on in situ macroalgal assemblages, giving information on the role of species identity, biodiversity, irradiance and community structure on overall primary production. Furthermore, the successful application of these methods was used to model annual primary production over local and regional scales, as well as the potential effects of human disturbance on production. In this study, photosynthesis-irradiance relationships (P-E curves) of intact intertidal algal assemblages showed no signs of saturation at high irradiance levels, as is typically seen in single species curves. Furthermore, diverse macroalgal assemblages showed a two-stage rise in production, with a significant enhancement of production at high irradiance. Evidence from this study suggests that the three-dimensional structure of natural assemblages, functional diversity and their interaction with a complex light environment is responsible for the unique P-E curves. The increased efficiency of light use in complex assemblages suggests an important role of species complmentarity in enhancing production with species diversity. This research also shows the potential consequences of disturbance on macroalgal assemblages, with the loss of several species causing a major decline in net production. The methods developed in this thesis have allowed simple modelling of annual rates of primary production and the parameters driving production of macroalgae over long time-scales. Respiration rates have a particularly large influence on production models and indicate that increasing temperature due to climate change could have significant consequences for net carbon fixation of macroalgae. This research gives valuable insight into the production of marine macroalgae and reinforces the notion that they are amongst the most productive systems on earth. These results revealed the importance of examining natural communities, as opposed to randomised assemblages and suggest a vital role of species diversity and community composition. Although there was no functional redundancy of the canopy forming species there did appear to be significant redundancy within the subcanopy assemblage. The identity of subcanopy species had little effect on production, but over longer temporal scales, as species come and go, they may help buffer the communities in terms of primary production. Furthermore, the relationship between biodiversity and ecosystem function (primary production), although driven by diversity, is moderated by resource levels. The complex relationship between irradiance, diversity and production shows the importance of resource levels in the enhancement of function with increasing biodiversity. Due to fundamental differences in terrestrial and marine systems, I was able to examine the effects of discrete levels of irradiance on production, which indicated an important role of complementary light use. This study represents advancements not only in the understanding of primary production in macroalgal assemblages, but also has implications for how diversity may enhance function in other autotrophic systems. The important role of enhanced efficiency of photon capture in multi-canopy layer communities may prove an essential process in ecosystems as diverse as macroalgal beds and tropical rain-forests.

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  • Signal-linear representations of colour for computer vision

    Grant, Robert (2010)

    Doctoral thesis
    University of Canterbury Library

    Most cameras detect colour by using sensors that separate red, green and blue wavelengths of light which is similar to the human eye. As such most colour information available for computer vision is represented in this trichromatic colour model, Red Green Blue or RGB. However this colour model is inadequate for most applications as objects requiring analysis are subject to the reflective properties of light, causing RGB colour to change across object surfaces. Many colour models have been borrowed from other disciplines which transform the RGB colour space into dimensions which are decorrelated to the reflective properties of light. Unfortunately signal noise is present in all acquired video, corrupting the image information. Fortunately most noise is statistically predictable, causing offsets from the true values following a Poisson distribution. When the standard deviation of a noise distribution is known, then noise can be stochastically predicted and accounted for. However transformations inside cameras and transformations between colour models often deform the image information in ways that make the noise distributions non-uniform over the colour model. When computer vision applications need to account for non-uniform noise, wider tolerances are required overall. This results in a loss of useful information and a reduction in discriminative power. This thesis has a focus on the linearity of signal noise distributions in colour representations which are decorrelated to the reflective properties of light. Existing colour models are described and each of their components examined with their strengths and weaknesses discussed. The results show that the proposed Signal Linear RGB (SLRGB) colour model achieves a transformation of the RGB colour space with uniform noise distributions along all axes under changes to camera properties. This colour space maintains a signal noise with a standard deviation of one unit across the space under changes of the camera parameters: white balance, exposure and gain. Experiments demonstrated that this proposed SLRGB model consistently provided improvements to linearity over RGB when used as a basis for other colour models. The proposed Minimum Weighted Colour Comparison (MWCC) method allows reflectively decorrelated colour models to make colour comparisons which counter the deforming effects of their coordinate systems. This was shown to provide substantial improvements to linearity tests in every case, making many colour models have a comparative noise linearity to undeformed colour models. The proposed Planar Hue Luminance Saturation (PHLS) and Spherical Hue Luminance Saturation (SHLS) colour models are decorrelated to reflective properties of light and allow for signal linear colour comparisons. When used for pixel classification of coloured objects the PHLS and SHLS colour models used only 0.26% and 0.25% of the colour volume to classify all of the objects, with the next best using 0.88% without MWCC and 0.45% with. The proposed Gamut Limit Invariant (GLI) colour model extends the decorrelation of reflective properties of light further by correcting for colours which are too bright and are clipped by the limits of the RGB space. When clipping occurs the properties become no longer decorrelated and shift. GLI models these changes to estimate the original values for clipped colours. The results show that this method improves decorrelation when performing pixel classification of coloured objects with varying proportions of clipped colours. Overall, the results show that the proposed framework of colour models and methods are a significant improvement over all prior colour models in enabling the most accurate information possible for processing colour images.

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  • Some aspects of the biology of Anthoxanthum odoratum L.

    Lambrechtsen, N. C. (1968)

    Doctoral thesis
    University of Canterbury Library

    Several aspects of the biology of Anthoxanthum odoratum have been studied in this thesis. The results are based on evidence obtained from the literature and on findings from experiments carried out by the candidate. This thesis has been arranged to give a balanced picture of the biology of sweet vernal grass without over-emphasis on the experiments carried out as it was felt that this would disjoint the lay-out. The main experiments are contained in Chapters 2, 5, 6 and 7. Since A. odoratum is a very polymorphic grass, plants have been collected from five localities in New Zealand (Kaikohe, Te Awa, Lincoln, Gore, and Porter's Pass) to reduce bias in the experimental results. Although this grass has been in New Zealand for about one hundred years only, physiological and morphological differences were found to occur among the plants from these localities. These findings may reduce the significance of the results obtained with A. odoratum as an indicator plant for nutrient availability in different soils. Therefore, it has been recommended in Chapter 6 to use only those A. odoratum plants with known-fertility response pattern for nutrient availability studies. In Chapter 10, the importance of this ecotypic differentiation, its evolutionary significance and its use for plant breeders has been discussed. Only incipient ecotypy could be recognized and no new taxa have been described.

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  • Light regimes as a control of terrestrial orchid distribution in New Zealand.

    Abernethy, Angela (2002)

    Doctoral thesis
    University of Canterbury Library

    This thesis examines how, and to what extent, do light regimes control the distribution of terrestrial orchids, through field studies of orchid populations under different forest types, manipulated light environment trials, and seasonal studies of orchids growing under different light environments. The significance of understorey light environment as a determining factor on terrestrial orchid occurrence and distribution is examined. A survey is performed over two primary (Nothofagus and Podocarp) and two secondary (Broadleaf and Manuka) forest types at selected South and Stewart Island sites. Hemispherical photography is used to record canopy architecture. Four parameters are used to represent canopy and understorey light characteristics. Broadleaf sites are significantly darker than the other three forest types. Of the 23 orchid species identified at these forest sites, the thirteen most abundant are classified into three categories based on the four light parameters. Pour species are considered to be low-light plants, all of which are of the genus Pterostylis. A further three species are classified as occurring under medium light conditions, with the remaining six species assigned to a high-light group. Light environment is a key factor controlling orchid occurrence under the sampled forests (R2 = 0.37 - 0.74). Even stronger correlations are identified for plant density (R2 = 0.73 - 0.93). The adaptability of Pterostylis banksii, P. graminea, Thelymitra longifolia and T. pauciflora to different light environments is examined using transplanting trials. Plant occurrence, morphology and physiology is compared under three different light regimes, with comparisons made to the original field populations. P. banksii is able to successfully adapt from the low-light Broadleaf environment to significantly higher enclosure light regimes. T. longifolia specimens are able to successfully adapt to both higher and lower light regimes than the field conditions. These plants also exhibit modified metabolism with leaf efficiency (Pmax/Rdark) of T. longifolia enclosure plants significantly lower than field plants. Morphological changes are also evident with the production of multiple replacement tubers in enclosure individuals. Results for P. graminea and T. pauciflora are inconclusive due to high mortality rates. It is believed that P. graminea is unable to adapt to the significantly higher light conditions, with T. pauciflora intolerant of transplanting. The relationship between understorey light environment and the morphology and phenology of natural populations of P. banksii, P. graminea, T. longifolia and T. pauciflora is examined. Dry weight and total non-structural carbohydrate concentrations of organs are recorded over a 12 month period. The two Pterostylis species have a similar phenology and morphology, with biomass and carbohydrate allocation patterns generally following similar trends. Inflorescence production precedes replacement tuber development, suggesting that floral induction is based on cues from the previous season. Replacement tuber development occurs late in the growing season, only two months prior to plant senescence, making November and December key months for carbohydrate acquisition. The two Thelymitra species have similar morphology and phenology, with equivalent biomass and carbohydrate allocation patterns. Photosynthetic characteristics vary significantly with plant age for T. longifolia, but not T. pauciflora. Inflorescence production occurs several months after replacement tuber initiation. The results of this study demonstrate that understorey light environment is a key environmental factor for terrestrial orchids, inducing changes in orchid morphology and physiology. The influence of light regime on orchid occurrence and density is significant, but only fully apparent when understorey conditions are represented using multi-parameter models.

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  • Advances in Visibility Modelling in Urban Environments to Support Location Based Services

    Bartie, Philip James (2011)

    Doctoral thesis
    University of Canterbury Library

    People describe and explore space with a strong emphasis on the visual senses, yet modelling the field of view has received little attention within the realm of Location Based Services (LBS), in part due to the lack of useful data. Advances in data capture, such as Light Detection and Ranging (LiDAR), provide new opportunities to build digital city models and expand the range of applications which use visibility analysis. This thesis capitalises on these advances with the development of a visibility model to support a number of innovative LBS functions in an urban region and particular focus is given to the visibility model‟s supporting role in the formation of referring expressions, the descriptive phrases used to identify objects in a scene, which are relevant when delivering spatial information to the user through a speech based interface. Speech interfaces are particularly useful to mobile users with restricted screen viewing opportunities, such as navigational support for motorists and a wider range of tasks including delivering information to urban pedestrians. As speech recognition accuracies improve so new interaction opportunities will allow users to relate to their surroundings and retrieve information on buildings in view through spoken descriptions. The papers presented in this thesis work towards this goal, by translating spatial information into a form which matches the user‟s perspective and can be delivered over a speech interface. The foundation is the development of a new visual exposure model for use in urban areas, able to calculate a number of metrics about Features of Interest (FOIs), including the façade area visible and the percentage on the skyline. The impact of urban vegetation as a semi-permeable visual barrier is also considered, and how visual exposure calculations may be adjusted to accommodate under canopy and through canopy views. The model may be used by pedestrian LBSs, or applied to vehicle navigation tasks to determine how much of a route ahead is in view for a car driver, identifying the sections with limited visibility or the best places for an overtaking manoeuvre. Delivering information via a speech interface requires FOI positions to be defined according to projective space relating to the user‟s viewpoint, rather than topological or metric space, and this is handled using a new egocentric model. Finally descriptions of the FOIs are considered, including a method to automatically collect façade colours by excluding foreground objects, and a model to determine the most appropriate description to direct the LBS user‟s attention to a FOI in view.

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  • Molecular cloning of cDNA encoding alliinase from onion (Allium cepa L.)

    Clark, Sonya A. (1993)

    Doctoral thesis
    University of Canterbury Library

    Alliinase catalyses the release of a range of volatile sulphur compounds which are responsible for the distinctive flavour and odour of Allium species. Clones encoding this vacuolar enzyme were isolated by immunoscreening a cDNA expression library constructed in the vector λZAPII with mRNA extracted from sprouting A. cepa bulb shoots. Six clones were characterized by DNA sequencing. Four of the cDNA sequences (Alli6, 7, 8B and 9) were found to be identical apart from variation in the length of their 5' ends. These sequences contained three putative polyadenylation signals. A fifth clone, Alli4B, was also very similar but displayed a truncated 3' end with six divergent bases just prior to the polyadenylate tail and lacked the most 3' polyadenylation signal present within the sequences of the other clones. It was evident from these differences that the clones were unique. However, their high sequence homology suggested they were encoded by a single gene, or two that are very closely related. The sixth clone sequenced, Alli4A, showed no homology to the other five clones, nor to any sequences within the GenBank database. The five highly homologous cDNA sequences ranged in length from 1604 bp to 1757 bp, and all appeared to contain a complete longest open reading frame encoding a polypeptide with a predicted size of 54 884 Da. Four peptide sequences derived from purified A. cepa alliinase were aligned, and showed 93% homology with the corresponding amino acid sequences deduced from the cDNA clones. Alignment of the native alliinase N-terminal peptide to the cDNA-inferred protein sequence predicted a hydrophobic 34-residue prepeptide sequence terminating in a peptidase cleavage site. Given the vacuolar location of this enzyme, it is probable that this region functions in targeting of the alliinase precursor to the endoplasmic reticulum. The inferred mature alliinase subunit polypeptide contained sequence motifs compatible with both Asn-linked glycosylation and pyridoxal phosphate cofactor binding. Conversion of clones to the phagemid form allowed the protein expressed in Escherichia coli from Alli6 to be western blotted. This analysis revealed protein moieties with molecular masses of 47 and 41.4 kDa. Southern hybridization analysis of A. cepa genomic DNA using an alliinase cDNA probe demonstrated the presence of a small multigene family with at least four members. Further genomic DNA hybridization analysis using a probe encompassing the 3' untranslated region of the alliinase clones demonstrated that the highest identity was to a single fragment, suggesting some alliinase gene family members may be transcriptionally inactive in sprouting bulb shoot tissue. A 1.7 kb transcript was detected by northern analysis of RNA extracted from developing A. cepa seedlings, indicating that the cDNA clones were near-full-length. Alliinase mRNA could be easily detected in seedlings up to 14 days after germination. Visual assessment and densitometer analysis of hybridization intensities suggested that alliinase transcripts were most abundant two to six days after germination and declined rapidly over the ensuing eight days. This indicated that alliinase expression is regulated at the transcriptional level during this period.

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  • Transport development and the rural economy : insights from Indonesia.

    Sabandar, William Palitondok (2004)

    Doctoral thesis
    University of Canterbury Library

    This thesis examines the roles of transport development in the rural economy. It is based on the fact that very little knowledge has been gained on how transport should be developed to bring maximum benefits to the rural population. The fundamental premises are that the relationship between transport development and the rural economy is highly multifaceted and that any explanation which does not consider context can never be sufficient. An institutional approach, based primarily on the new institutionalism theory, was employed as the theoretical basis for the analysis. The research was implemented at four levels of Indonesian institutions: national, district, village and household. Information was collected in Jakarta and four rural districts in Eastern Indonesia through key informant interviews, questionnaire surveys, field observation and library materials. The analyses explored the roots of ineffective rural transport development at each level of these institutions. At the national level, doctrines are chosen, organisations are created and policies are designed, all based on an "adopted" neo-classical assumption and without an appropriate understanding of the specific characteristics of transport and the rural economy. At the district level, there are few mechanisms available for people engaging in the practical development process to inform transport policy makers of the particular benefits and/or limitations of specific transport and rural development initiatives. At the village level, rural people have mainly been passive agents in the development process, without opportunities to determine the transport intervention that they need most. At the household level, individuals are not always able to respond to the opportunities created by transport improvements. All these have contributed to the failure of transport development to effectively promote the rural economy. Based on the empirical analysis, the linkages between transport development and the rural economy are conceptualised. Transport development needs to be approached as conscious and systematic efforts to improve rural accessibility and mobility. Such an approach should be supported by an environment conducive to greater recognition and participation of societal institutions in the development process. This thesis has important implications for the discourses on transport policy and research. There is a crucial need for transport policy and research to go beyond their conventional boundaries and to incorporate wider development perspectives that include the social, political, cultural and the economic relationships of rural regions and rural people.

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  • Isolation and characterisation of genomic clones of alliinase from Allium cepa L.

    Gilpin, Brent John (1995)

    Doctoral thesis
    University of Canterbury Library

    The culinary and medicinal attributes of Alliums are derived from the high levels of nonprotein sulfur compounds which they contain. When onion cells are disrupted, the vacuolar enzyme alliinase hydrolyses the cytoplasmic S-alk(en)yl cysteine sulfoxide flavour precursors to produce pyruvate, ammonia and the many volatile sulphur compounds associated with flavour and odour. cDNA clones of alliinase have been previously isolated by immunoscreening an onion cDNA expression library. In this thesis, a genomic library of A. cepa was constructed and screened using the alliinase cDNA clone as a probe. Positively hybridising clones were screened initially using alliinase specific primers. Sequencing of PCR products, intact lambda and plasmid clones was performed to determine the sequence of the clones. One of the clones isolated encoded the previously isolated cDNA clones, while another contained a number of nucleotide differences. Both clones contained four small introns within the coding region. The predicted proteins of each clone are very similar, but nucleotide differences within the upstream, downstream, intron and mRNA regions may influence gene expression. An alliinase promoter from one of the genomic clones was cloned adjacent to a β-glucuronidase gene to determine the promoter functionality. These constructs were used for Agrobacterium mediated transformation of tobacco, and microprojectile bombardment of onion mini-bulbs. In tobacco, the alliinase promoter was expressed to a limited extent in some vascular tissue. Expression in onion minibulbs, although only evaluated transiently, indicated that this is a functional monocotyledonous promoter, which may have many applications in the genetic manipulation of onions. The expression level of the alliinase promoter was approximately half that of CaMV 35S promoter suggesting that features of the mRNA and protein are mainly responsible for the high expression level of alliinase.

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  • Physiological stress, smoltification and seawater adaptation in New Zealand's sockeye and quinnat salmon.

    Franklin, Craig E. (1989)

    Doctoral thesis
    University of Canterbury Library

    This study investigated smoltification and seawater adaptability of sockeye (Oncorhynchus nerka) and quinnat salmon (O. tshawytscha). Both species were introduced into New Zealand with an anadromous population of quinnat and a totally freshwater population of sockeye salmon becoming established. The sockeye were found to be capable of successfully adapting to sea water and appeared not to have lost their hypoosmoregulatory ability despite being landlocked for approximately 90 years. The physiological changes associated with smoltification and seawater adaptation were studied and were viewed in part with reference to physiological stress. Salmon exposed to a handling or temperature stressor showed an increase in plasma cortisol concentrations and depending on the severity of the stressor, a change in haematocrit and an osmotic imbalance could also result. The physiological state of the salmon (pre-smoltified, smoltified, desmoltified) was assessed in a variety of ways and the reliability of the parameters measured related to the seawater adaptability of the salmon. Increased gill Na+-K+-ATPase activity provided the best indicator of smoltification. Plasma cortisol concentrations also increased in smoltifying salmon. The seawater adaptability of the salmon was found to be dependent on both the degree of smoltification that had occurred in the salmon and on the temperature of the sea water. High seawater temperatures limited the ability of the salmon to successfully adapt. Rapid increases in plasma cortisol occurred when salmon were transferred directly to sea water, but returned to basal levels within 12 hours in the fish that successfully adapted. Plasma cortisol concentrations remained elevated in the salmon that failed to adapt to the sea water. Morphological changes in the gills of sockeye salmon that successfully and unsuccessfully adapted to sea water were also investigated.

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  • Aspects of electromagnetic scattering.

    Hunter, J. D. (1970)

    Doctoral thesis
    University of Canterbury Library

    An expression for the field scattered by a perfectly conducting wedge with a deformed apex is formulated as a finite matrix equation to illustrate the application of the current density replacement technique. This technique enables the scattering from any size of body to be determined to a given accuracy after the inversion of one finite matrix, provided that the shape of the body can be derived by inwardly deforming a finite part of a body from which the scattering is known explicitly. The size of only the deformed part of the body is limited by available computational facilities. The field scattered from truncated and rounded wedges is calculated. These results not only enable the effect of edge deformation to be studied, but are also used to evaluate the accuracy of the geometrical theory of diffraction and physical optics estimates of the diffracted field. Expressions for the field scattered by a perfectly conducting wedge in the presence of transversely polarized line sources are found. These results are used with an iterative current density replacement technique to formulate expressions for the field scattered by a truncated wedge, and thus derive a secondary edge diffraction coefficient for use with the geometrical theory of diffraction. This coefficient is applicable to perfectly conducting bodies with small or large separation between edges. The increased accuracy obtainable with this coefficient, and a modification to the physical optics representation of the current density on a body with edges, are discussed.

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  • Matrix-isolation magneto-optical spectroscopy of diatomic radical monohydrides.

    Harrison, Jeremy J. (2003)

    Doctoral thesis
    University of Canterbury Library

    This PhD thesis presents the results of electronic magnetic-circular-dichroism (MCD) and absorption spectroscopy of CH, NH, OH, PH, and SH isolated in various noble-gas (argon, krypton, and xenon) matrices (XH/NG) at cryogenic temperatures, using a high-resolution simultaneous MCD and absorption spectrometer, MOD4. Experimental problems prevented the study of CH/Xe, NH/Xe, or OH/Xe matrices. The results were interpreted in terms of a randomly oriented spin-orbit (SO) - crystal-field (CF) model previously developed by workers in this research group. SO and CF parameters were extracted by fitting the resulting data with parameterised equations derived from group-theoretical and quantum-mechanical considerations of the SO-CF model. In the cases of NH and PH, zero-field splitting (ZFS) parameters were also extracted. The SO-CF model worked well for CH, NH, and PH, but was found to fail for OH and SH. Trends in the parameters of XH with varying noble-gas host were attributed to the external heavy-atom effect and/or motional effects within the matrix. Preliminary attempts have been made to interpret spectral structure in terms of free or hindered rotation of the guest radicals within the host matrix. This has had a degree of success, especially for NH/Ar, however more theoretical work still needs to be done.

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  • The ecological role of bryophytes in alpine streams of New Zealand.

    Suren, Alastair M. (1990)

    Doctoral thesis
    University of Canterbury Library

    The ecological roles of aquatic bryophytes in 2 small New Zealand alpine streams were investigated. The streams differed with respect to algal biomass and detrital inputs, reflecting their location either above the tree-line (Mouse Stream) or flowing through mountain beech forest (Tim's Creek). Streambed instability was also higher in the forested site. Quantitative sampling of bryophytes and riffles over 18 months revealed the existence of discrete macroinvertebrate (>250 µm) and meiofaunal (i.e., 5% of bryophyte material in their guts. The cranefly Limonia hudsoni was the only taxa that appeared to graze bryophytes extensively. Lack of consumption may be related to that fact that bryophytes contained more refractory, and less "digestible" material than selected riparian vegetation, or to the presence of antiherbivore compounds within some species. The importance of bryophytes in affecting energy inputs into streams was finally examined. Algal biomass was higher on structures mimicking bryophytes than stones, and biomass was higher above the tree-line than below. Natural bryophytes trapped more FPOM than riffles, and mimics at Tim's Creek trapped more FPOM than at Mouse Stream. Bryophyte biomass at both sites however was similar, reflecting the ability of these plants to tolerate a wide range of light regimes. Retention of introduced organic matter into streams was influenced by bryophytes, whereby streams with these plants retained material better than streams without.

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  • Space-time processing : an experimental test platform and algorithms.

    Green, Peter John (2002)

    Doctoral thesis
    University of Canterbury Library

    This Thesis describes the concept, architecture, development and demonstration of a Smart Antenna Software Radio Test System (SASRATS). SASRATS was designed and developed as a functional and flexible system to facilitate the field testing of space-time processing architectures and algorithms. It is designed to facilitate the correlation of theoretical, simulated and measured performance. The SASRATS architecture has the capability of batch, pseudo-real and real time implementation of signal processing algorithms. It is used here to verify the work done by the author and others in the field of signal enumeration and blind beamforming. The Thesis develops a robust method to enumerate the incident signals impinging on a uniform but variable size linear array independent of the extent of their correlation in a Rayleigh flat fading channel environment. The method self-optimizes the array size by minimizing the number of antennas with respect to the number of signals and adapts continuously to maintain optimum performance in a mobile environment where users (signals) come and go. An algorithm is formulated with simulation and field results presented. A robust channel order estimation algorithm using multiple antennas is also presented. We show that the approach has better performance than the conventional information theoretic based channel order estimation algorithms. It operates over a wide range of signal-to-noise ratios and is tolerant to correlation between channels. Algorithm performance is evaluated via computer simulation.

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  • Social organisation of the Adelie Penguin, Pygoscelis adeliae.

    Spurr, E. B. (1972)

    Doctoral thesis
    University of Canterbury Library

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  • The Synthesis of Conformationally Restricted Amino Acides and Peptide Mimics Using Ring-Closed Metathesis.

    Gardiner, James (2003)

    Doctoral thesis
    University of Canterbury Library

    Peptidomimetics have found wide application as biostable, bioavailable, and often potent mimics of natural peptides. Examples of peptidomimetics have been isolated as natural products, synthesized as libraries from novel subunits, and designed on the basis of X-ray crystallographic studies and through an intricate knowledge of the biological mode of action of natural peptides. They offer challenging synthetic targets and are increasingly important medicinal agents and biological probes. Chapter One introduces the fields of peptidomimetics and peptidomimetic design, with relevant examples taken from biochemistry, synthesis, and medicinal chemistry used to illustrate important concepts. The sources of peptidomimetics, along with common tools used for the conformational restriction of peptides, is then reviewed. Ring-closing metathesis (RCM), an important new method for the formation of carbocyclic rings is then reviewed, and discussed in terms of its application towards the synthesis of conformationally restricted peptidomimetics. This section emphasises the importance of RCM as a new and versatile tool for use in peptidomimetic synthesis. Chapter Two describes the enantioselective synthesis of the conformationally constrained, substituted tetrahydropyridine, and piperidine peptide mimics, 2.9 and 2.12 respectively, via RCM. The solid-state conformations of 2.9 and 2.12 are examined and their application as potential cis-amide bond mimics discussed. Further derivatisation of 2.9 gave dihydroxy analogues 3.13, and dibromo analogues 2.14. A novel bicyclic lactone 2.16 was also formed upon crystallisation of the major isomer of 2.14. The enantiomeric purity of a key intermediate 2.7 was analysed, and determined to be >95%, confirming the stereoselectivity of a key alkylation step.

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  • The Chinese Approach To Web Journalism: A Comparative Analysis

    Xin, Jing (2010)

    Doctoral thesis
    University of Canterbury Library

    This thesis explores the distinctive forms of journalism that have emerged in mainstream news websites in mainland China. Two case studies, the 2008 Beijing Olympic Games and the H1N1 influenza pandemic in 2009, are employed to identify features in Chinese and Western news online. Specifically, a comparison is made between the in-depth news sections of popular mainstream news websites in China and those in the United States, the United Kingdom, and New Zealand. The study finds that the Chinese version of mainstream web news genre differs significantly from the Western version. This thesis argues that journalists’ practice is strongly context dependent. Distinctive economic, organizational, social and cultural factors contribute to shaping Chinese web journalism in a way that contradicts the notion of a homogeneous worldwide journalism or of a single set of norms for journalism. The study challenges the dominance of the political explanatory framework that considers political factors as the most important approach to study Chinese web-based media. In the face of a sparse literature and sporadic studies concerning the development of the internet as a novel platform in China for news production and transmission, this thesis aims to bring more academic interest to an overlooked research area and to contribute to a broader understanding of the actual diversity of global communication research.

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  • Fast evaluation of radial basis functions : theory and application.

    Cherrie, J. B. (2000)

    Doctoral thesis
    University of Canterbury Library

    Radial Basis Functions (RBFs) have proven to be successful interpolants to scattered data. However, the perceived high computational costs for fitting and evaluating the RBFs associated with large data sets have hindered their application to many real world problems. This thesis is concerned with the "fast" evaluation of RBFs: the O(N2) process of evaluation at all centres is reduced to O(N log N) or even O(N). The required theory is developed for polyharmonic RBFs in 4-dimensions and for multiquadric RBFs in arbitrary dimensions. These methods are applied to fit surfaces to scattered data containing many tens of thousands of points.

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  • A Traditional Institutionsurviving in a Modern Setting?The Reinterpretation of Caste in the IndianIT Industry

    Lindt, Benjamin (2011)

    Doctoral thesis
    University of Canterbury Library

    This thesis aims to explore and understand the changes to the social institution of caste that arise from the ongoing modernisation of Indian society. The research setting is the IT industry in Bangalore and Hyderabad. As the Indian IT industry is the economic sector most exposed to globalised modernisation, it has come to represent a social milieu deemed particularly modern in India. The thesis discusses the social role of the IT industry in India; the rise of the new middle classes, and the specifics of the locality of Bangalore. It is argued that caste as a social institution systematically connects three different dimensions of human existence; the economic (caste-wise division of labour); the biological (rules concerning exogamy and endogamy); and the ideational (various rationalisations for caste). While the economic dimension of caste is increasingly losing its meaning, caste endogamy remains largely intact and is rationalised in forms much more compatible with modernity. This composite model of caste is then contrasted with a model of modernity based arguments presented by the most relevant sociologists, from Max Weber to Peter Wagner. In the analysis here, the contemporary, ‘quasiethnic’ reinterpretation of caste appears still to conflict with the implications of modernity. Even though caste provides actual benefits for those who employ the concept and practise it – ranging from political to economic to private – its rationale nevertheless contrasts with the motives that are generally attributed to modernity. The empirical research, employing qualitative, semi-structured interviews, participant observation, and hermeneutic interpretation of first-hand sources, produces a complex picture. The interviews with more than 70 IT employees of various caste backgrounds (including over 40 from SC/ST categories – underrepresented in the industry) indicate that caste is seemingly irrelevant in professional settings. In support of this conclusion, additional research hints at the prevalence of widespread anonymity in the IT industry and limited understanding of caste amongst IT employees. By contrast, participant observation during seven months living amongst IT engineers suggests that caste still matters: In private, the consequences of the practise of caste are still apparent, even though ritual restrictions are waning in importance. Thus, a pronounced caste-wise compartmentalisation of Indian society remains visible even amongst young IT engineers. The thesis concludes that caste is not disappearing from Indian society; rather, it is dramatically adapting to modern circumstances.

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  • Three phase integrated load and harmonic flows.

    Callaghan, C. D. (1989)

    Doctoral thesis
    University of Canterbury Library

    This thesis investigates two algorithms for the steady state analysis of HVDC convertor plant. The first is an already well established frequency domain technique, known as IHA (Iterative Harmonic Analysis), and the investigation centres on the nature of the algorithm under divergent conditions. In particular, a mathematical analysis of the algorithm is used to prove that divergence of the algorithm is not necessarily indicative of a physical harmonic instability. The second algorithm is developed to exploit the IHA technique within the context of the three phase a.c.-d.c. loadflow as an alternative convertor model which incorporates (rather than ignores) the effects of harmonics. The resulting three phase integrated load and harmonic flow algorithm is a significant improvement on the existing single phase load & harmonic flow algorithms. Finally, the integrated algorithm is applied to two test systems drawn from the New Zealand primary network, and is shown to be a significant improvement over the IRA algorithm alone, resolving the inconsistencies which exist between the fundamental frequency and harmonic models of the convertor.

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