68 results for Thesis, UC Research Repository

  • 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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  • Project Management Internship in Post-Earthquake Christchurch: A review of experiences gained and lessons learned

    Helm, Benjamin (2013)

    Masters thesis
    University of Canterbury Library

    This report discusses the experiences gained and lessons learned during a project management internship in post-earthquake Christchurch as part of the construction industry and rebuild effort.

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  • The effect of the Canterbury earthquakes on alcohol consumption and motivations for drinking among psychologically resilient individuals

    Marie, Leila Michele Anastasia (2014)

    Masters thesis
    University of Canterbury Library

    Individual responses to natural disasters are highly variable. The psychological and behavioural response trajectories of those who manage to cope well with adverse life events are in need of further investigation. Increased alcohol use is often observed in communities exposed to mass traumas, particularly among those exposed to severe levels of trauma, with males drinking more than females. The current study examined patterns of alcohol use and motivations for drinking among a sample of psychologically resilient individuals with varying levels of exposure to the Canterbury earthquakes (N = 91) using structured and semi-structured interviews and self-report measures. As hypothesised, there was a significant increase in alcohol consumption since the earthquakes began, and males reported significantly higher levels of pre-earthquake and current alcohol consumption than females. Contrary to expectations, there was no association between traumatic exposure severity and alcohol consumption. While participants reported anxiety-based coping motives for drinking at levels comparable to those reported by other studies, depression-based coping motives were significantly lower, providing partial support for the hypothesis that participants would report coping motives for drinking at levels comparable to those found by other researchers. No gender differences in drinking motives were found. As expected, current alcohol consumption was positively correlated with anxiety and depression-based coping motives for drinking. Psychological resilience was not significantly associated with alcohol use, however resilience was negatively associated with depression-based coping motives for drinking. These findings have inter-generational and international implications for post-traumatic intervention.

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  • "Western thoughts, Eastern feelings": A study of filial piety and elder mistreatment among Korean immigrants in New Zealand

    Park, Hong-Jae (2011)

    Doctoral thesis
    University of Canterbury Library

    Thesis available in print.

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  • An Independent Review of Project Management Processes for CERA’s Port Hills Land Clearance Programme

    Patterson, Todd Keith (2014)

    Masters thesis
    University of Canterbury Library

    This report to RCP Ltd and University of Canterbury summarises the findings of a 5 month secondment to the CERA Port Hills Land Clearance Team. Improvement strategies were initiated and observed. The Port Hills Land Clearance Programme is the undertaking of the demolition of all built structures from the Crown’s compulsory acquired 714 residential red zoned properties. These properties are zoned red due to an elevated life risk as a result of geotechnical land uncertainty following the 2011 Canterbury Earthquakes.

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  • The treatment of childhood in the novels of Charlotte and Emily Brontë

    Tan, Elis P. N. (1990)

    Masters thesis
    University of Canterbury Library

    In this thesis I have dealt with Charlotte and Emily Brontë's representation of children in their novels, and the significance of childhood as it reflects or suggests the authors' attitudes to morality, character, and society. I have studied what Charlotte and Emily overtly or covertly say about children and the adults that they grow into, as a means of assessing the similarities and differences in the sisters' attitudes, taking into consideration as well, how these attitudes compare with contemporary images of childhood. I have chosen to examine the published novels of Charlotte and Emily, and have used for my research both critical and biographical material written on the Brontës. In chapter one, I introduce both writers vis-à-vis two major influences in Victorian literature, namely, religion and romanticism, comparing the extent to which the sisters are affected by these opposing traditions in their treatment of childhood. Chapters two and three deal separately with Charlotte and Emily and their novels. The final chapter offers a conclusion with regard to the similarities and differences between these authors, including the distinction between their narrative techniques that reflect their differing literary motives. Unlike Charlotte, Emily wrote for personal catharsis and awareness rather than for didactic reasons. While both Brontës reveal their moral attitudes on the question of childhood, Emily, unlike her sister, remains non-judgemental. Also, although both sisters accept harsh reality, Emily seems to do so reluctantly compared to Charlotte who is quite unambiguous about it.

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  • Multi-level voltage and current reinjection ac-dc conversion.

    Liu, Yonghe (2003)

    Doctoral thesis
    University of Canterbury Library

    This thesis describes a new concept of multi-level reinjection ac-dc conversion, its main purpose being a further reduction of the harmonic content, a solution of dynamic voltage balancing for direct series connected switching devices and an improvement of high power converter efficiency and reliability. It is a combination of the multi-level, soft switching and reinjection concepts. A variety of configurations are proposed, based on the new concept, to achieve efficient voltage and current conversion. For each configuration the firing sequences, waveform analysis, steady and dynamic performances and close-loop control strategies are presented, and particular applications suggested. The ideal reinjection waveforms are first derived for perfect harmonic cancellation and then fully symmetrical approximations are made for more practical implementations. This is followed by a description and comparison of the generation circuits required for the implementation of the multi-level symmetrical reinjection waveforms. A three-level voltage reinjection scheme, implemented by adding a reinjection bridge and a reinj ection transformer to the standard twelve-pulse converter, is discussed in great detail, both for the series and parallel connections. This is followed by an investigation into the possible application of these converters to Back to Back VSC HV de interconnection; the analysis is validated by EMTDC simulations. A multi-level voltage reinjection VSC is also proposed, which uses a controllable de voltage divider to distribute the de source voltage to the two main bridges and produces high quality output waveforms. The voltage and current waveforms, the firing sequences and the capacitor voltage balancing are analyzed and verified by EMTDC simulations. In particular, the proposed VSC is shown to be an ideal solution for the STATCOM application. The multi-level reinjection CSC alternative is also described and shown to exhibit an excellent performance in the STATCOM application.

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  • SYNTHESIS AND COMPLEXES OF BRIDGING HETEROCYCLIC LIGANDS

    Rajan, Siji (2014)

    Doctoral thesis
    University of Canterbury Library

    Ligand–mediated coupling between metal centres is of fundamental importance in inorganic and materials chemistry. Bridging ligands involving azo groups as coordinating π–acceptors can yield complexes with interesting properties. This thesis describes the synthesis of a series of N–heterocyclic compounds containing the azo functionality, designed for potential coordination to the metal through the azo nitrogen and a N–heterocyclic ring. The azo ligands are divided into four categories; ligands based on azobispyridines, ligands containing pyrimidine and fused aromatic azine groups and ligands capable of coordinating in a bis–tridentate fashion to the metal centre. Ligands containing flexible imine subunits connected directly, or through different spacers, are also discussed. Overall twenty one ligands were synthesised, six of which are new compounds. The coordination and metallosupramolecular chemistry of these ligands with ruthenium(II) and silver(I) metal atoms was investigated. A total of thirty five ruthenium(II) and eleven silver(I) complexes were prepared, of which thirty eight were characterised by X–ray crystallography. Mononuclear and dinuclear ruthenium(II) complexes were synthesised and characterised by a combination of spectroscopic and structural techniques. UV/Visible absorption studies and electrochemical methods were used to investigate the nature of metal–ligand and metal–metal interactions. In the mononuclear Ru(II) complexes, N–heterocyclic azo ligands act as chelating ligands forming five–membered chelate rings involving azo–N and heterocyclic–N atoms. The non–coordinated pyridine ring of the azo ligand is twisted with respect to the azo–N atom and is directed towards the adjacent bipyridine rings. Studies reveal that these azo ligands posses extremely low–lying π*–orbitals and are electron deficient. X–Ray structural analysis of the dinuclear complexes revealed short inter–metal separations of ca. 4.9 Å and electrochemical studies indicate that these ligands mediate very strong interactions between the metal centres , due to the excellent π*–acceptor properties of the azo functionality. Varying the pyridine ring of the azo ligand to pyrimidines and fused N–aromatic rings has a considerable effect on the electronic properties of these complexes. Incorporation of a pyrimidine ring facilitates the stabilisation of azo anion radicals and leads to the formation of diruthenium(II) species, bridged by radical species. The X–ray crystal structures of both these complexes were determined. The use of the hexadentate ligands coordinating in a bis–tridentate manner mediate even stronger communication between the two ruthenium centres. Ligands containing bis–pyridylimines result in weaker coupling between the metal centres in dinuclear ruthenium(II) species. A complete absence in the inter–metal communication was observed with increasing the distance and/or flexibility between the two pyridylimine units, contrary to a previous reported claim. Reaction with different silver(I) salts afforded an array of one–dimensional coordination polymers and a discrete dinuclear complex depending on the coordination strengths of the anions. The metallosupramolecular assemblies obtained were characterised mainly by X–ray crystallography, elemental analysis and mass spectrometry.

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  • Nature nationalism : the New Zealand wilderness myth and Pākehā identity in the South Island

    Boyle, Cameron (2016)

    Masters thesis
    University of Canterbury Library

    New Zealand’s landscapes have played a central role in settler and Pākehā cultural imagination, probably none more so than those that are considered to be wild or wilderness. These are the mountains, forests, wetlands, and other environments that are unfarmed, nonurbanized, perceived to be natural, and mostly composed of indigenous plant and animal species. I draw on a range of literature relating to New Zealand’s wilderness, from the journals of explorers and settlers, to contemporary advertising in conservation and tourism. I argue for the existence of a dominant settler and Pākehā understanding of such landscapes as uninhabited and primeval, which I refer to as the New Zealand wilderness myth. I contend that this myth relies heavily on what I term the regional construction of the South Island, which represents the South Island as the true place of New Zealand’s wilderness. I utilize critical regionalism to investigate the myriad ways in which this myth arises out of the transmutation of European understandings of the wild and landscape, particularly romantic and Victorian ones, within the context of New Zealand. I suggest that, according to this myth, New Zealand’s wilderness signifies the pre-human past of origin. Moreover, as this past is not only inaccessible but also imaginary, the wild stands in for its lack of existence, allowing it to be experienced within the present. This past, which I theorize exists through what I label the simulacrum of wilderness, is longed for through the emotion of nostalgia. I assert that via this myth, and the nostalgia that underpins it, Pākehā form a politics of nature nationalism, as I call it, through which they claim that New Zealand’s wilderness is their home and place of origin. Finally, I critique this simulacral landscape and Pākehā claim of neo-indigeneity to it, and ask the following question: what is the possibility of a postcolonial wilderness in New Zealand?

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  • ‘NOW I WANNA GO UNDERGROUND’ FINDING PETER GUTTERIDGE

    Herchenbach, Hannah (2015)

    Bachelors with Hnours thesis
    University of Canterbury Library

    The South Island record label Flying Nun has arguably produced some of New Zealand’s most celebrated cultural exports since 1981. Peter Gutteridge is considered a giant in New Zealand music for having a hand in forming some of the label’s most celebrated bands, such as The Clean, The Chills, The Great Unwashed, and Snapper. Yet little of substance has been written about him. There is an emerging historiographical narrative in which both the label and its surrounding music scenes have been mythologised and historicised. An analysis of the shared experiences of those who played with Peter Gutteridge illuminates the differences between the myths of the Dunedin music community and the reality of those who experienced it. Rather than representing a particular place, the Dunedin music community was a fluid group of highly migratory musicians that came from all over New Zealand. Dunedin was a popular base due to having the most fertile economic, geographic and social conditions out of all the regional centres for music as a social practice. Peter’s role within the constructed narrative could be described as that of a trickster, the mythological character whose mediation of oppositions both supports and subverts the myth. His interest in the next generation of musicians also brings the historicised ‘Dunedin Sound’ into the present. This dissertation helps fill an existing gap in New Zealand music and cultural history by contributing 15 semi-structured oral histories with New Zealand musicians who knew Peter Gutteridge between 1978 and 2014. This data was corroborated by articles on the Dunedin music scene in local and international newspapers, niche music magazines and fanzines.

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  • Knowledge and falling in Milton's Paradise lost and Imre Madách's The tragedy of man

    Liebert, Elisabeth (2003)

    Masters thesis
    University of Canterbury Library

    Milton's Paradise Lost and Imre Madách's Az ember tragédiája [The Tragedy of Man] were written in different centuries, in different languages. Yet as reworkings of the story of the Fall of Man both attempt to explicate the phenomenon of human selfawareness. A comparison of their treatment of knowledge and its relationship to the Fall discloses this similarity of intent, as well as the fundamental difference that underlies the philosophical position of the two authors. The thesis is divided into chapters that examine prelapsarian knowledge, the Fall itself, and postlapsarian knowledge in Paradise Lost and The Tragedy of Man respectively, with occasional reference to the Biblical story and literary analogues in order to illustrate the development of central themes. As elements of the story are considered - Adam's conversation with God in Eden, the injunction against the Tree of Knowledge, the role of Satan or Lucifer, Eve's otherness, the consequences of the Fall, expulsion from the garden, and Adam's postlapsarian [re]discovery of knowledge - it becomes clear that Milton and Madách deploy them differently to different ends: for Milton self-knowledge is only possible within the context of a relationship with God, while for Madách selfknowledge begins when man has abandoned God and, although the final stage of selfunderstanding can only be achieved by returning to a relationship with the divine, certain knowledge is never possible. The comparison of Paradise Lost and The Tragedy of Man illustrates the fact that the desire to know remains a constant through the vagaries of human development, but the approach to knowledge taken by different generations shifts, drawing the story of the Fall away from its original context of religious mythology into the realms of anthropocentric philosophy.

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  • Mating strategies and sperm competition in New Zealand geckos (Family Gekkonidae).

    Todd, Amanda Claire (2003)

    Doctoral thesis
    University of Canterbury Library

    Most species of reptile studied to date have polygynandrous mating systems and possess specialised sperm storage regions. Consequently, there is a high potential for sperm competition in this group. Using comparative analyses, I examined the level of sperm competition in New Zealand geckos and how this has influenced the evolution of their reproductive morphology. Across lizards and snakes, there was more than a 40-fold variation in relative testis size. New Zealand geckos fell in the middle of this range and lacked sexual dimorphism in head size, suggesting that most species have polygynandrous mating systems. I confirmed this for one species, Hoplodactylus maculatus, which is gregarious, lacks territoriality and has a courtship pattern that suggests a high level of promiscuity for both sexes. I found that hemipenis size in New Zealand geckos was positively correlated with relative testis size, suggesting that sperm competition has resulted in the evolution of larger intromittent organs. However, the surface features of the hemipenis were relatively conservative across species. Although there was no relationship between sperm length or putative sperm storage site (SST) morphology and relative testis size, species with fewer SSTs, and thus more intense sperm competition, had longer sperm. H maculatus males produced two types of sperm which differed not only in length but also in fertilising capacity, the short morph lacking DNA. This is the first known example of such sperm polymorphism in a vertebrate and may have evolved in response to sperm competition, the non-fertilising morph potentially helping to block the sperm of rival males or filling sperm storage sites. The motility of these short sperm was positively correlated with temperature; however, at higher temperatures motility declined with time, suggesting a trade-off between motility and longevity. Such temperature influences on male reproductive physiology have important implications for males of ectothermic species under sperm competition.

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  • Characterisation and Control of 3-Deoxy-D-arabino-heptulosonate 7-phosphate Synthase from Geobacillus sp

    Othman, Mohamad (2014)

    Masters thesis
    University of Canterbury Library

    3-Deoxy-D-arabino heptulosonate 7-phosphate synthase (DAH7PS) catalyses the first step of the shikimate pathway, responsible for the biosynthesis of aromatic amino acids. This pathway is found in microorganisms, plants and apicomplexan parasites and its absence in mammals makes it a viable target for antimicrobial drug design. DAH7PS enzymes differ in the regulatory machinery that decorates the catalytic (β/α)8 barrel. Some DAH7PS enzymes are fused to chorismate mutase (CM), another enzyme in the shikimate pathway. This fusion protein is allosterically regulated by chorismate (CA) or prephenate (PA), the precursor of tyrosine and phenylalanine. It has been suggested that DAH7PS enzymes evolved these extensions to the core barrel for the sole purpose of regulation. Geobacillus sp DAH7PS (GspDAH7PSWT) is a thermophilic type Iβ DAH7PS enzyme with an N-terminal CM domain fused through a linker region. This thesis describes the functional characterisation work carried out on GspDAH7PSWT, in attempt to help determine how DAH7PS enzymes evolved such diverse methods of regulation. Chapter 2 describes the functional characterisation work carried out on the catalytic and regulatory domains of GspDAH7PSWT. The enzyme demonstrated both DAH7PS and CM activities with the DAH7PS domain determined to be metal dependent and most activated by Cd2+. PA completely inhibited the catalytic activity of GspDAH7PSWT, and AUC demonstrated an equilibrium exists between the dimeric and tetrameric quaternary states of the enzyme in solution. Chapter 3 describes the domain truncation of GspDAH7PSWT carried out at the linker region in order to obtain two separate protein domains, the catalytic domain lacking the N-terminal domain (GspDAH7PSDAH7PS) and the regulatory domain without the catalytic domain (GspDAH7PSCM). Both variants were fully characterised, and information obtained from each domain was compared to the respective catalytic and regulatory domains of the wild-type enzyme, which was also characterised. Like GspDAH7PSWT, GspDAH7PSDAH7PS showed greatest activation in the presence of Cd2+, with other metals having varying effects on activation rates and stability of the enzyme. Both truncated variants followed Michaelis-Menten kinetics where GspDAH7PSDAH7PS was found to be more active than GspDAH7PSWT and unaffected by PA, whereas GspDAH7PSCM was a less efficient catalyst than the CM domain of GspDAH7PSWT. AUC demonstrated that in solution an equilibrium occurs between the monomeric and tetrameric oligomeric states of GspDAH7PSDAH7PS. Chapter 4 summarises the findings of the thesis along with future directions of this research, combining the results obtained and expanding upon them. It is concluded that the catalytic regulatory CM domain supports both protein structure and allosteric regulation of GspDAH7PSWT

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  • Novel biomarkers for diabetic patients at risk of developing secondary complications.

    Orban, Thomas (2015)

    Masters thesis
    University of Canterbury Library

    Diabetes is a chronic, incurable disease characterized by chronic hyperglycemia. Patients who control their diabetes poorly are at risk of developing long-term complications, such as cardiovascular diseases, renal failure and retina damage. Glycated hemoglobin (HbA1c), formed by the reaction of glucose with hemoglobin, is considered the gold standard for the monitoring of glycemic control, but it does not discriminate between the different types of secondary complications associated with diabetes. Diabetes and its complications are linked to oxidative stress and the resulting lipid peroxidation produce reactive aldehydes including acrolein. Acrolein forms adducts with nucleophilic residues of proteins, which can be used as biomarkers of oxidative stress. It is hypothesized in the present study that specific adducts of acrolein with hemoglobin could be used as reliable biomarkers for secondary complications linked with diabetes. In this context, reactions of acrolein with the two nucleophilic amino acids cysteine and lysine have been studied. The formation of adducts was confirmed for both of these amino acids, and lead to the discovery of the novel compound FTT-cysteine. Studies on hemoglobin itself were conducted in order to understand how acrolein influences the structure and function of this protein and where the preferential sites of modification were located. It was concluded that acrolein does not significantly alter the structure of hemoglobin and actually tends to stabilize it due to the formation of internal cross-links. MS studies revealed that both the single addition of acrolein and the formation of the aromatic compound MP-lysine, arising from reaction with two molecules of acrolein, occur in hemoglobin samples. ELISA tests were developed that could successfully determine the presence of naturally forming hemoglobinacrolein adducts in vivo. X-ray crystallography could show the presence of extra electron density in the vicinity of Cys 93 on the β subunit. A proteomics search determined the sites of preferential reaction on hemoglobin, one of which is Cys 93. These results paved the way for the design of two novel synthetic hexapeptides, Ser-Ala-Gln-Val-Lys-Gly and Leu-His-Cys-Asp-Lys-Leu,whose reactivity towards acrolein was then studied. Both peptides were successfully modified by reaction with acrolein: MS studies revealed the formation of MP-lysine for Ser-Ala-Gln-Val-Lys-Gly and of a single cysteine Michael adduct for Leu-His-Cys-Asp-Lys-Leu. Future work will include the synthesis of 16-residue peptide chains as determined by the results from the proteomics search, against which antibodies will be raised. The antibodies will be used to develop highly specific ELISA assays that will hopefully correlate with secondary complications of diabetes. The outcome of this research could lead to the development of a convenient product that could be used to evaluate the risks that diabetic patients have of developing specific secondary complications.

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  • Superconductivity in nanocluster films

    Nande, Amol V.

    Thesis
    University of Canterbury Library

    Superconductivity in a bulk material is generally characterizing by a sharp drop in the resistance of the sample as a result of formation of a quantum condensate of paired electrons when the temperature is reduced below the critical temperature. However, superconducting behaviour changes dramatically with reducing dimensions of the superconducting structure. Several different behaviours have been reported in this dirty limit such as quantum phase slips, total suppression of superconductivity and a transition from the superconducting state to an insulating state. The question of how small a superconducting object can be before it loses its superconducting behaviour and what are the mechanisms that determine nanomaterials different behaviour at low temperatures are of fundamental importance of understanding the nature of superconductivity at the nanoscale and have the tremendous technological importance. Nanocluster films are ideal for addressing these questions, as they provide independent control of both cluster size and surface coverage and allow the study of local as well as global suppression of superconductivity. In particular, the percolating properties of the groups of clusters play vital role in the superconducting behaviour of the film. In this research clusters were produced in an inert gas aggregation source and deposited in ultra high vacuum. We present results obtained from the electrical characterization of films of ~ 30 nm diameter Pb nanoclusters deposited on SiN substrates at temperatures 10 K and 300 K; these substrates have pre-fabricated gold electrodes to monitor conductance of the percolating nanocluster film. A wide range of samples, with normal state resistances from 30 Ω and 5 MΩ, were prepared. The main focus of the study is on transport measurements for 10 K deposited samples. For low coverage films (above the percolation threshold) with RN ≳ 1 kΩ, low current V(I) and R(T) data show clear evidence of phase slips which appear to occur in the narrow 1 dimensional necks between the clusters. However, high coverage samples (with RN < 1 kΩ) exhibit a Berezinskii-Kosterlitz-Thouless (BKT) transition which is a signature of vortex unbinding in 2D system. Above critical current, it is found that V ~ (I – IC)a, with a ~ 2.1 ± 0.2. The exponent, a, is independent of temperature and particle coverage which is due to the underlying percolating nature of the sample. We have also prepared cluster films with coverage well below the percolation threshold. In these samples coupling between adjacent cluster groups is in the tunnelling regime and the films show a superconductor to insulator (SIT) transition. Furthermore, we have shown the SIT transition can be driven by change in either current or voltage.

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  • Understanding the ecophysiological and biomechanical properties of juvenile pinus radiata in response to water deficits.

    Waghorn, Matthew J.

    Thesis
    University of Canterbury Library

    As the frequency and severity of drought events are expected to increase globally, drought induced reductions in plantation productivity are likely to become more important. This will concern forest managers who wish to improve forest productivity during the establishment and initial growth phases of plantation-grown Pinus radiata D. Don. Wood grown during the initial growth phases is in the corewood zone, which in Pinus radiata generally has poor wood properties. This restricts its usability, particular for solid timber applications. Therefore, understanding how water deficits impact on patterns of juvenile P. radiata productivity and wood variation is important. The objective of this research was to assess how key morphological and physiological processes, carbon fluxes and partitioning, and wood property formation in juvenile P. radiata responded to the timing and duration of water deficits. Using two-year-old P. radiata cultivated in a controlled environment, trees were subjected to a well watered control, plus early season cyclical drought, late season cyclical drought and summer drought treatments over the course of one growing season. Needle water potential, tree growth, crown characteristics, biomass partitioning, leaf characteristics, physiological processes and water use efficiency were measured. A carbon balance approach was used to examine how the timing and duration of water deficits modified gross primary production (GPP), net primary production (NPP), carbon fluxes to aboveground net primary production (ANPP) and total belowground carbon flux (TBCF), and the partitioning of GPP to ANPP and TBCF. Wood samples were analysed by X-ray absorption, X-ray diffraction and automated image analysis using Silviscan. Measures of wood density, microfibril angle (MFA), fibre dimensions and modulus of elasticity (E) were examined by matching seasonal variation in growth, measured temporally, with variation in wood properties, measured spatially. Further wood samples were assessed for longitudinal shrinkage and acoustic velocity. Cyclical drought treatments resulted in large fluctuations in needle water potential, while the summer drought treatment resulted in a sustained negative needle water potential over the summer months. Water stress integrals (Sψ) were 41.4, 66.8, 55.2 and 97.6 MPa-days for the well watered, early season cyclical drought, late season cyclical drought and summer drought treatments, respectively. In general, water deficits decreased tree growth, reduced crown size, reduced biomass accumulation and leaf area, reduced physiological activity and resulted in more enriched values of δ13C, all of which were significantly (P < 0.05) affected by treatment. Although the early season drought treatment experienced greater levels of water stress, growth and productivity were superior to those of the late season drought treatment. Summer drought reduced height, diameter and basal area by 24.7%, 33.1%, and 52.3%, respectively, while aboveground biomass was reduced by 68.3% and total leaf area by 40.0%. Water deficits substantially decreased fluxes to GPP, NPP, ANPP and TBCF following gradients of tree productivity. Treatment values of GPP were between 1470 and 4142 g C per tree per year. Partitioning of GPP to ANPP and TBCF was not affected by treatment, nor were the FS /ΔCR, TBCF/ANPP and ΔCR/ANPP ratios. Partitioning of GPP was predominantly to TBCF (45 - 56%) for all treatments. Partitioning of soil respiration (FS) did not significantly differ with treatment but FS was the dominant component of TBCF (77 - 88%) for all treatments. Wood properties of juvenile P. radiata were sensitive to temporal changes in water availability and associated growth rates. Imposition of seasonal water deficits resulted in higher values of air-dry density and modulus of elasticity (E) and decreases in microfibril angle (MFA). These differences were more evident for the late season drought treatment than for the early season drought treatment when compared to the well watered treatment. Late season drought increased density by 10%, E by 18% and decreased MFA by 5%, compared with the well watered trees. Seasonal water deficits had no impact on annual average values of density, E and MFA in this experiment but significant annual differences existed in cell wall thickness, cell radial diameter and cell populations between the faster and slower growing trees. Well watered trees had higher velocity and also greater longitudinal shrinkage which were significantly different (P < 0.05) from the water deficit treatments. Within treatment variation for acoustic velocity and longitudinal shrinkage was greatest for the well watered treatment. Weak to non-existent relationships were observed between longitudinal shrinkage and other wood properties. The results provide insight for forest managers of P. radiata into the importance of managing water deficits to maximise forest production and improve wood quality of juvenile trees. This study demonstrated that late season drought has a more marked impact on absolute growth and wood properties than early season drought, and that water deficits have a greater impact on growth than on partitioning of carbon or ring level wood properties.

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  • Training in massive MIMO systems.

    Wan Mohd Mahyiddin, Wan Amirul

    Thesis
    University of Canterbury Library

    Massive multiple-input multiple-output (MIMO) systems have been gaining interest re cently due to their potential to achieve high spectral efficiency [1]. Despite their po tential, they come with certain issues such as pilot contamination. Pilot contamination occurs when cells simultaneously transmit the same pilot sequences, creating interfer ence. Unsynchronizing the pilots can reduce pilot contamination, but it can produce data to pilot interference. This thesis investigates the impact of pilot contamination and other interference, namely data to pilot interference, on the performance of finite massive MIMO systems with synchronized and unsynchronized pilots. Two unsynchro nized pilot schemes are considered. The first is based on an existing time-shifted pilot scheme, where pilots overlap with downlink data from nearby cells. The second time shifted method overlaps pilots with uplink data from nearby cells. Results show that if there are small numbers of users, the first time-shifted method provides the best sum rate performance. However, for higher numbers of users, the second time-shifted method pro vides better performance than the other methods. We also show that time-synchronized pilots are not necessarily the worst case scenario in terms of sum rate performance when shadowing effects are considered. The wireless channel can be time and frequency varying due to the Doppler effect from mobile user equipment (UE) and a multipath channel. These variations can be simulated by using a selective channel model, where the channel can vary within the coherence block in both time and frequency domains. The block fading channel model approxi mates these variations by assuming the channel stays constant within a coherence block, but changes independently between blocks [2]. Due to its simplicity, the block fading model is widely used in massive MIMO studies [3–8]. Our research compares the impact of block fading and time-selective fading channel models in massive MIMO systems. To achieve this, we derive a novel closed form sum rate expression for time-selective channels. Results show that there are significant differences in sum rate performance between these models. In addition to time variation from Doppler effect, the channel can also experience fre quency variation due to delay spread from multipath signal propagation. The combi nation of time and frequency selective channels can be described as a doubly-selective channel. Hence, the sum rate expression for time-selective channels can also be extended to doubly-selective channels. We investigate two types of pilot sequences, namely con stant amplitude pilots and zero padded pilots in doubly-selective channels. Results show that a zero padded pilot has a better sum rate performance than a constant amplitude pilot for a wide range of antenna numbers and time-frequency correlation values. Two different type of training optimization, namely average optimum training and adaptive optimum training, are investigated. Both methods shows similar sum rate performance. In addition, we also study the effect of increasing frequency reuse and the pilot reuse factor. Even though these methods can reduce intercell interference, they also result to lower sum rate due to inefficient use of time-frequency resources.

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  • “Social and environmental reporting in New Zealand : analysing the (non)-institutionalisation of practice”.

    Wright, Helen Anne (2014)

    Masters thesis
    University of Canterbury Library

    The purpose of this thesis is to better understand why the social and environmental reporting practices of New Zealand business entities are ‘starting behind’ international counterparts. An integral aspect is gaining an understanding of the role of key players in the organisational field who have the potential to influence social and environmental reporting in New Zealand. This thesis is motivated by the importance of business entities pursuing sustainability-related practices, and being accountable for their actions through providing external social and environmental reports. The theoretical framework for this research is neo-institutional theory. The research method involved mapping the organisational field in order to identify players that influence, or have the potential to influence the social and environmental reporting practices of New Zealand business entities. Initially comprehensive background information was collected from websites, academic articles, surveys and a University of Canterbury archive. Subsequently semi-structured interviews were conducted with key players, Chief Executives from three Sustainable Business Intermediaries and Senior Executives from 11 of their members. Findings from the interviews were analysed through an iterative process allowing for emerging themes to be analysed using prior literature and explained through the lens of neo-institutional theory. The findings and analysis chapters are structured according to the research questions. Chapter six finds weak isomorphic pressures have influenced New Zealand business entities’ social and environmental reporting practices, but have not institutionalised this practice. The rationales of accountability and the business case have both motivated and caused resistance to business entities’ engagement in social and environmental reporting. Chapter seven finds the role of Sustainable Business Intermediaries facilitates weak isomorphic pressures on members’ social and environmental reporting practice. However, the business case rationale results in resistance to the practice of social and environmental reporting with legitimacy a key focus of these field players. Although coercive pressure in New Zealand is weak or lacking there is potential through field players’ roles to influence or enforce coercive pressure. The research concludes with recommendations that the New Zealand government should regulate social and environmental reporting. There has been extensive research focusing on various aspects of social and environmental reporting. However, there is little work focusing on the role and influence of field players through engagement-based research. Hence filling this gap extends the understanding of key field players’ influence on and interest in institutionalising social and environmental reporting and why this practice is resisted. Ultimately this research offers policy recommendations for the New Zealand government.

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  • The determinants of consumer responses in the LGBT community : an exploratory study of LGBT marketing in the context of New Zealand and USA advertisements.

    Kaur, Harpreet (2016)

    Masters thesis
    University of Canterbury Library

    The Lesbian, Gay, Bisexual and Transgender (LBGT) community faces significant discrimination in today’s society. Discrimination is not limited only to various sectors such as health, education, housing, employment, politics, sociocultural representation, and within the mainstream marketing (Badgett, 2014). In the media their portrayal has been very suppressive, often having the media reinforce already existing stereotypes Hart, 2004). Marketing, being a vector for change, bring about social acceptance as it has the right tools for instigating evolved attitudes in society (Zinkhan & Carlson, 1995). Due to the institutionalized expressions of homophobia that have been present within societies (Abelove, Barlae & Halperin, 1993), the amount of research on marketing responses from LGBT members is very limited (Tsai, 2011). The objective of this study is to highlight LGBT participants’ perceptions towards the marketing style that features LGBT styles in advertisements. Organizations try to promote ethical diversity through marketing to appeal to both the LGBT community and non-LGBT people/members of society (Borgerson, et al., 2006). In the current study, 12 in-depth interviews were conducted to investigate LGBT participants’ perceptions on the marketing styles that feature the LGBT community. The participants included gay, bisexual and transgender individuals. Through using qualitative analysis along with photo-elicitation to demonstrate how organizations have used the LGBT community in their marketing, participants were able to provide insightful opinions paired with their experiences while ‘coming out’. They also explained how the use of LGBT marketing influences their experience of being ‘normalized’ into society. It was found that organizations reinforced negative stereotypes through their marketing strategies. Furthermore, the language used in the marketing materials involved derogatory terms and involved objectification of their sexual orientation and identity. Lastly, the research concludes on how marketing can engage and integrate LGBT members in a socially acceptable practice. Organizations can establish a trustbased relationship with the LGBT community and feature them in advertisements in a realistic way, thus establishing a robust framework to eradicate the social stigma associated with the LGBT community.

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  • Aranuian pollen diagrams from montane Canterbury, New Zealand.

    Russell, John Blair (1980)

    Doctoral thesis
    University of Canterbury Library

    Detailed site histories are developed from pollen analyses at six sites in three areas of montane Canterbury: Upper Rakaia Valley, Mt. Somers, Lake Sumner. A post-glacial (Aranuian) vegetational and climatic history for central montane Canterbury is developed from these site histories and pollen analyses published from other areas. The site histories relate broadly to existing knowledge, but it is shown that pollen diagrams from montane areas may not be taken as being directly representative of the regional vegetation. Forest in montane Canterbury became widespread in the upper Rakaia Valley 10,000 years ago. The subsequent spread of beech forest (species of the Nothofagus fusca pollen group) in montane Canterbury occurred about 6,000 years ago in the Waimakariri and Hurunui catchments; more than 4,500 years ago in the Harper tributary of the Rakaia River; and about 1,000 years ago in the vicinity of Prospect Hill in the upper Rakaia Valley. The isolated occurrence of silver beech (N. menziesii) in the Lake Stream tributary of the Rakaia River has a probable history of about 8,000 years, and at Prospect Hill, a local history of 2,000 years. Beech forests of the Hurunui catchment originated from a northern mixed beech source, while the beech forests of the Waimakariri and Rakaia catchments, and Mt. Somers, originated mainly from mountain beech (N. solandri var. cliffortioides) sources, scattered most probably in the foothills of the central Canterbury Alps. Present evidence suggests that there was a marked improvement in climate 10,000 years ago from cold early Aranuian conditions. It is thought that climatic conditions were most equable between 10,000 and about 6,000 yr B.P. when precipitation was higher than at present. Conditions deteriorated at about 6,000 yr B.P. becoming drier and less equable, approaching present conditions. Pollen and charcoal evidence of European, Polynesian, and prehistoric fires in the study areas contributes to the history man-caused and natural fires in Canterbury. Polynesian fires in the Upper Rakaia - Lake Heron - Mt. Somers region are seen as the coup de grace in a long established history of decline of montane podocarp forest there.

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