3,194 results for UC Research Repository, 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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  • The application of positive leadership in a New Zealand law enforcement organisation.

    MARTIN, Regina Mary (2015)

    Doctoral thesis
    University of Canterbury Library

    This study explored the experiences of 10 leaders in their intentional six-month implementation, during the 2010-2011Christchurch earthquakes, of an adapted positive leadership model. The study concluded that the combination of strategies in the model provided psychological and participative safety for leaders to learn and to apply new ways of working. Contrary to other studies on natural disaster, workplace performance increased and absenteeism decreased. The research contributes new knowledge to the positive leadership literature and new understanding, from the perspective of leaders, of the challenges of leading in a workplace environment of ongoing natural disaster events.

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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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  • Identity and diaspora online: a study of a Chinese network in New Zealand

    Xu, Jingnan (2015)

    Doctoral thesis
    University of Canterbury Library

    This thesis explores the distinctive formation of identity by Chinese diaspora on New Zealand’s most popular Chinese portal site www.skykiwi.co.nz. Following Gee’s framework of discourse analysis, this study is projected to find out the distinctive language produced on Skykiwi and how this language is used to enact social actors’ identities. In particular, different levels and dimensions of discourse analysis, including lexical and intertextual, linguistic and psychological, are deployed as strategic tools to analyze the selected online articles and discussion forum material. The findings of this qualitative research show that there is a distinct mode of hybridity in identity discourse on the site. This thesis argues that this hybrid identity is constructed by maintaining Chinese culture, and meanwhile using the Chinese meaning system to make sense of life in New Zealand so as to promote a partial integration. In this process, a virtual community is built on Skykiwi where the members show a strong sense of belonging and solidarity to the group. The study re-examines theories of transnationalism and hybridization, diaspora and media, sense-making and identity, centripetal and centrifugal forces of the internet, diasporic media and networks, imagined community, and particularly contributes to the knowledge of Chinese diasporic identity and virtual community on the internet.

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  • Light Flicker and Harmonic Modelling of Electrical Lighting

    Frater, Lance Phillip (2015)

    Doctoral thesis
    University of Canterbury Library

    Compact Fluorescent Lamps (CFLs) have emerged as cost-competitive, energy efficient direct replacements of the conventional incandescent lamp. However, little regard has been given to their widescale adoption in terms of the electrical network and power quality. Discrepancies have emerged over the CFLs light flicker sensitivity to voltage fluctuations and concerns at the level of harmonics they generate. This thesis develops an objective measurement method for light flicker, overcoming the limitations of the existing IEC flickermeter standard and develops models using the Harmonic State-Space (HSS) framework and Harmonic Domain (HD) for harmonic studies. The new light flickermeter proposed, measures light directly to quantify flicker, thereby removing the dependency of the incandescent lamp modelled in the current flickermeter standard, IEC 61000.4.15. The light flickermeter methodology resembles the same functional blocks of the IEC Flickermeter to produce equivalent perceptibility levels. This allows for the direct comparison of the two procedures. The Light flickermeter along side the IEC voltage flicker are implemented in the experimental system and fully calibrated to the newly proposed CCU2/CIGRE flickermeter test protocol. The sensitivity of CFLs to common voltage fluctuations are investigated and the light flickermeter is utilised in the design of a new LED fluorescent tube replacement lamp. A linearised Harmonic State-Space (HSS) framework is developed for the modelling of non-linear devices. The methodology includes basic Kirchhoffs voltage and current laws to realise a control block diagram approach to a device’s operation. The HSS is centred around linear time periodic (LTP) systems and the use of harmonic transfer functions to model the switching behaviour (including Switching Instant Variation (SIV)) of converters. Importantly the models are suitable for both transient and steady state simulation. An example of a simplified CFL circuit is presented. An automated sequential harmonic injection technique is developed for the experimental derivation of linearised harmonic admittance matrices of non-linear loads. This technique eliminates the traditional analytical based HD or HSS methods and creates a harmonic domain based model from the actual device. Models are presented for a number of consumer lamps. Detailed validation of these models are achieved under multi-frequency terminal conditions and through the illustration of self distortion by the system impedance. This research paves the way in better understanding, management and coordination of flicker levels in electrical networks. The Light flickermeter apparatus provides a calibrated method for assessing light flicker sensitivity for both current and emerging technologies. The harmonic modelling methods are focussed towards lower powered devices and suited for studying their large scale use.

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  • Experiments on reciprocity, social comparisons and overconfidence.

    Danková, Katarína (2015)

    Doctoral thesis
    University of Canterbury Library

    This thesis consists of three chapters focusing on negative reciprocity, transparency and job assignment, and overconfidence. To test my hypotheses I use experimental economics methods, which offer control over the data generating process by motivating people financially. Experimental methods are used to identify causal processes and motivations that can be confounded in field settings. Economics experiments reduce response noise, e.g. extreme outliers probably caused by thoughtless, unmotivated subjects (Smith and Walker, 1993). The central theme of my first two experiments is reciprocity – a kind reaction to kind and generous behaviour and retaliation to hostile behaviour. The first chapter discusses reciprocity in connection with violation of the property rights and the source of the endowment on an individual level. In the second chapter the reciprocity is studied in an employer-worker setting, in the presence of social comparisons. The last chapter deals with firm’s overconfidence when deciding about entering the market. All of the chapters study aspects of economic behaviour in social contexts, which have implications for the field. Each of the chapters is described briefly below. My first chapter experimentally explores the impact of the strength of property rights on retaliation decisions. I induce strong property rights by having experimental subjects earn money by performing a real effort task and weak property rights by endowing them with windfall gains. I ask whether people are less likely to respond to a hostile behaviour with retaliation when earned money as opposed to windfall money is at stake. My experimental design identifies two reasons why property rights might influence the size and frequency of retaliation. The first reason is that retaliation might be perceived to be more costly when using earned as opposed to windfall money to pay for retaliation. The second reason is related to the violation of property rights. If another person decreases a decision-maker’s endowment and the endowment consists of earned money rather than windfall money, the decision-maker might consider it to be a stronger violation of his property rights, which in turn could trigger stronger retaliation. The purpose of this experiment is to separate these two effects. While I find support for the fact that subjects retaliate more because of the violation of their property rights, I also find that participants actually retaliate more with their earned money than with windfall. This suggests that participants do not perceive such retaliation to be more costly but rather that their behaviour is driven by violation of property rights. The second chapter focuses on the fairness perceptions of the job assignment process in an employer-worker relationship. In reality, employers have at their disposal jobs of different importance, which have to be assigned to different workers. Workers in more important jobs usually get offered higher wages and workers in less important jobs get offered lower wages. If the interpersonal concerns were absent, the employer would provide a higher wage to the worker in the more important job. When a worker decides what wage to accept, he may compare his wage to the other workers’ wage. An employer anticipating this might adjust the wage policy in order to avoid unnecessary losses or to maximise profits. I experimentally study the fairness perceptions from the workers’ and the employer’s point of view. I ask the following questions: 1. Do workers react to the wages paid to their co-workers and does the job assignment procedure affect workers’ wage rejections? 2. Do employers react to the fact that workers compare themselves with their co-workers and do they compress wages when the job assignment procedure is perceived less fair? These questions have implications for labour market, in particular a firm’s wage policy. If an unfair assignment elicits more wage rejections (i.e. zero profit for the employer and zero wage for the worker) due to social comparisons, it can have detrimental effects on the performance of the firm and thus firms might choose to practice wages secrecy. I examine the impact of job assignment in the presence of social comparisons. In order to test for social comparisons, the worker is only informed about the wage that the employer offered to his co-worker and which job he has been assigned to. Only after workers state their minimum acceptable offers, which determine if the offered wage is accepted or rejected, they come to know their own wage. I posit that a worker’s reaction to a specific job assignment depends on the procedure by which they are allocated to the jobs. An assignment to a less important job will not be perceived as unfair if it arises from an unbiased procedure, for example random assignment with equal probabilities. It will, however, be perceived as unfair if workers think that the employer favours some workers over others for reasons that are unrelated to efficiency concerns. This experiment does not provide evidence on social comparisons or employers compressing wages when the assignment to jobs is perceived unfair. My third chapter is a replication of the high-impact overconfidence and excess entry experiment by Camerer and Lovallo (1999). The topic of overconfidence is crucial for understanding business failures. Camerer and Lovallo were first to directly test overconfidence by measuring economic decisions and personal overconfidence at the same time. Camerer and Lovallo test whether managers’ overconfidence about their skills could predictably influence economic behaviour when entering into markets. I implemented Camerer and Lovallo’s experiment with modifications reflecting the technological progress of economic experiments of past 15 years. While Camerer and Lovallo run their experiment with male participants (who have been shown to be more overconfident than females), my experiment studies the effect of overconfidence of both genders, making it a more conservative test. The thesis employs cutting edge techniques from Experimental Economics to study economic decision-making. My research provides empirical evidence on violation of property rights, fairness considerations in labour markets and impact of overconfidence on market entry decisions.

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  • Model-Based Decision Support in Glycaemic Control

    Fisk, Liam Michael (2014)

    Doctoral thesis
    University of Canterbury Library

    Model-based decision support relies on a series of mathematical models and methods to convert raw clinical data into actionable recommendations. High clinical burden associated with measurement, and clinically significant outcomes, make glycaemic control an area where considerable benefit is possible. However, few glycaemic control protocols have been successful in critical care, and fewer exist for outpatient management of diabetes. Challenges faced include high levels of uncertainty and noise, limited measurements, and risk of iatraogenic low blood glucose events. This thesis aims to develop a successful glycaemic control framework, STAR, beyond the critical care environment, and set the stage for an outpatient glycaemic control protocol that individuals with diabetes can use to inform their day-to-day glucose management decisions. To achieve this goal, appropriate models and methods are developed, and validated against both clinical and in-silico data.

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  • Towards understanding the evolution of Banana bunchy top virus and the detection of associated badnaviruses

    Stainton, Daisy Blanche (2015)

    Doctoral thesis
    University of Canterbury Library

    Bananas are an important subsistence and export crop with over 130 tonnes of banana produced annually. Domesticated banana are triploid and sterile and it is thought that wild diploid bananas were domesticated between 7,000 and 10,000 years ago somewhere in the region of Indonesia, Philippines, New Guinea or the Southeast Asia peninsula. Triploid bananas were subsequently moved around the world through vegetative propagules and more recently through tissue culture. A number of diseases are associated with bananas, including banana bunchy top disease (BBTD) and banana streak disease (BSD), both caused by DNA viruses. BBTD is caused by Banana bunchy top virus (BBTV), a single-stranded DNA (ssDNA) virus (genus Babuvirus; family Nanoviridae). Characteristic symptoms of BBTD are severe stunting of the plant and bunching of the leaves, with a green dot-dash streak on the underside of the leaves. Both viruses can cause severe crop loss and are of concern to banana growing regions. BSD is caused by a number of banana-infecting badnaviruses species (Badnavirus; Caulimoviridae), all of which contain a double-stranded DNA (dsDNA) genome. Characteristic symptoms of BSD include chlorotic and necrotic streaks on the leaves, which are not always seen across all leaves, or even across an entire leaf. BBTV is a multi-component virus which is transmitted by the banana aphid Pentalonia nigronervosa. It is the type member of the babuviruses, which contains two other accepted species, Cardamom bushy dwarf virus (CBDV) and Abaca bunchy top virus (ABTV), which infect large cardamom and Musa spp, respectively. It is generally accepted that the genome of BBTV consists of six different components, with each component individually encapsidated. BBTV is able to evolve through recombination, reassortment and mutation. The large numbers of sequenced BBTV components in Chapter Two and Three (927), and publically available component sequences, have allowed for in-depth analyses into the diversity and evolution of this important plant pathogen. Our analysis shows that both reassortment and recombination play a significant role in the evolution of BBTV. Additionally, we found high genetic diversity in two geographic regions, the Southeast Asian / Far East region and the Indian subcontinent. Phylogenetic analysis of all full genomes, with recombinant regions and reassorted components removed, identified that the BBTV genomes circulating in the majority of countries have likely originated from single founder populations. All nanoviruses contain two common regions which are common across species. The common region stem-loop (CR-SL) is involved in initiation of replication and is recognised by the replication-associated protein (Rep), encoded in the DNA-R component. The Rep recognises cognate components through iteron sequences in the CR-SL and nicks the component at the nonanucleotide motif to initiate replication. The common region major (CR-M) is involved in secondary strand replication. The large amount of sequence data generated in Chapters Two and Three, and a recent deposition of a large number of CBDV sequences, allowed a comprehensive analysis of the common regions of the babuviruses. All CR-SL across the three species showed high similarity including the iteron sequences. The CR-M regions however were not similar across the species. Alphasatellites, which only encode a Rep, have previously been found associated with some babuvirus, nanovirus and geminivirus isolates. Therefore these were also analysed for common regions. The babuvirus alphasatellites were more similar to the other alphasatellites than to the babuvirus components. Both BBTV and banana-infecting badnaviruses are DNA viruses which infect the same host species, therefore the banana material that was collected for BBTV analyses was also screened for three species of banana-infecting badnaviruses. Species specific screening primers were designed for Banana streak MY virus (BSMYV), Banana streak OL virus (BSOLV) and Banana streak GF virus (BSGFV) across the movement protein motif located on open reading frame (ORF) three. With these primers we had a higher detection rate, for all three species, compared to previously published primers for banana-infecting badnaviruses. Eighty-two banana samples from 11 countries were found to be positive for at least one badnavirus, with the majority containing BSMYV. Of the 82 positive samples, 51 samples were also positive for BBTV. Banana-infecting badnaviruses are able to exist in two forms, a circular episomal infective form which is transmitted by a number of mealybug species and an endogenous form which is integrated into the banana genome and does not cause symptoms. However, a number of endogenous forms have been identified which are able to reactivate from the Musa genome into the episomal infectious form. As both forms are potentially able to cause infection, detection of either form is important in the identification of clean planting stock. This PhD thesis investigated banana infecting DNA viruses, Banana bunchy top virus and three banana-infecting badnaviruses. In-depth analyses of the global diversity, evolution and the dispersal of BBTV were undertaken. The common regions of the babuviruses and alphasatellites were characterised and screening primers for BSMYV, BSOLV and BSGFV were designed.

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  • Karl Popper’s critical rationalism and the politics of liberal-communitarianism.

    Afisi, Oseni Taiwo (2015)

    Doctoral thesis
    University of Canterbury Library

    Whether there are prospects for a liberal-communitarian philosophy with aims and objectives that enhance Karl Popper’s project of the open society I here argue in the affirmative. Such a philosophy promotes both self-determination by individuals and community enhancement of individual well-being. My argument for a liberal-communitarian philosophy develops out of Popper’s critical rationalism, exploiting the fact that in Popper’s philosophy, science and politics are intertwined and each is defined by both individual and social elements. In particular, Popper’s politics of liberalism are derived from the ethical and epistemological core of his critical rationalism, the latter originating in his philosophy of science, the former preceding it. Individuals become socially embedded with others as they engage in mutual criticism that is based upon a rational understanding of mutual respect, unity, and tolerance. I defend ontological claims about the social nature of the self and normative claims about the value of community which together make intelligible the idea that the self cannot exist outside of the context of community. This implies that the very consciousness of the self is constituted by interaction, interconnectedness and interrelationship with others. How well a philosophy that upholds individualism marries with the idea of the community, I show that Popper’s critical rationalism fruitfully addresses. Society must protect the individual’s capacity for rational criticism. Rational criticism is mutualistic. Critical rationalism as regards both science and politics is implicitly communitarian. Although Popper’s politics of liberalism are overtly individualistic, they also are implicitly communitarian. Popper’s ideas offer a basis for rational engagement with non-liberal ideologies that emphasis social and community togetherness.

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  • Allophonic imitation within and across word positions

    Fiasson, Romain Gines Michel (2015)

    Doctoral thesis
    University of Canterbury Library

    This dissertation investigates imitation in speech, which is the general tendency shown by a speaker to become more similar to another speaker in the way they speak. Many of us have experienced this while talking to someone who is speaking the same language but with a different accent. Conversing with such a person can affect some characteristics of our speech, so that we come to sound more like them. Imitation in speech has been very extensively studied, especially over recent years. To contribute to this line of research we provide an account of imitation in speech at the allophonic level, that is at the level of the possible phonetic realisations of a phoneme. We are interested in whether imitation of the sound of a given phoneme in a particular word position can influence the other possible realisations of that phoneme in the same word position. We are also interested in determining whether imitation of a speech sound in a particular word position for a given phoneme can affect the realisations of that phoneme in a different word position. New Zealand English provides of wealth of allophonic variation across word positions for the phoneme /t/. Therefore it is an ideal language to investigate imitation and allophony. Before presenting our experimental designs and our results on imitation however, we verified and further extended the work that has been conducted on the dialect. We analysed large corpora of spoken NZE and found new allophones of /t/. We discuss a fricative realisation in particular. The fricative realisation in NZE was further examined by means of a palatographic pilot experiment, as well as a perception experiment. Building on our findings from the perception experiment, we investigated imitation in speech towards an artificially created novel fricative allophone in medial position using acoustic and EPG data. For some speakers, the mere exposure to the novel allophone affected the realisation of other allophones in the same word position. A series of acoustic experiments were then conducted to examine allophonic imitation across word positions. We found that repeated exposure to a given allophone can drive allophonic selection across word positions. We also found that positional transfer can occur, such that exposure to an acoustically manipulated allophone can affect the same allophones in a different word position. Interestingly it can also affect other allophones in a different word position. Our results are discussed according to hybrid exemplar models and the Direct Realist view. We discuss which theoretical framework best accounts for the results we obtained.

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  • Go, and you will return: Locating meanings in young Muslims’ lived experience at schools in Christchurch, New Zealand via an adapted IPA method influenced by Ramadanian philosophies (IPA-R).

    Loo, Erin WH (2015)

    Doctoral thesis
    University of Canterbury Library

    This thesis explored the lived experience of Muslim students in schools in Christchurch, New Zealand; how they made sense of their experience and the meanings they placed on it, and their coping strategies. Its central argument is that young Western Muslims engage in a highly personalized version of everyday ijtihad in managing their social affairs within their everyday encounters of a secularised environment. For this group of participants, their acts of sensemaking helped them construct meaning frameworks in building their social identity. As the findings of this study suggest, this identity is constantly shaped and re-shaped along dimensions of time and space. It is a result of individual awakenings that find synergy within their own critical reasoning, a form of everyday ijtihad. The use of an adapted IPA method influenced by Ramadanian philosophies (IPA-R) was necessary to enable the exploration of the participants’ Muslim consciousness while the small sample size made it possible to study the personal experiences of a group of young Muslims from an idiographic approach. A limitation of this study stemmed from the constraints of member-checking that was substituted with the peer-review process. This study conceptualized that understanding young Muslims’ sensemaking and meaning-making is part of inclusive practice and within the broader context, suggests that the IPA-R approach is a solution to the ‘textbook Muslims’ approach.

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  • The role of body size in predator-prey interactions and community structure

    Warburton, Helen J. (2015)

    Doctoral thesis
    University of Canterbury Library

    Body size is a fundamental property of an organism. Consistent body size-related patterns, relevant to food webs, have been found at the individual (e.g. metabolism), population (e.g. predator-prey interactions), and community (e.g. body-size scaling with abundance) levels of ecological organisation. These patterns represent key components of food webs, so body-size distributions should be representative of a wide range of food web processes. Therefore, knowledge on the controls of the distribution of body sizes within a community should aid in the understanding of community structure and stability. I focused on two key body size-associated relationships in food webs: the relationship between body mass/size (M) and abundance (N), and relationships between body size and predator-prey interaction strengths. Analysis of M-N data, collected from stream communities spanning habitat size and flooding disturbance gradients, indicated that habitat size limited top predator size, whereas disturbance limited their abundance. These results highlight how M-N relationships, and changes in body size patterns across communities in general, are particularly useful tools for understanding influences on community structure. Mesocosm experiments were used to investigate how relationships between predator-prey body mass ratios (PPMR) and predator-prey interaction strengths differed when prey defences and density varied. Larger predators generally had stronger per-capita interaction strengths however, prey morphological defences and prey abundance significantly altered the relationship between body size and per-capita interaction strengths. Defended prey were eaten less than undefended prey and the relationship between PPMR and interaction strength was steeper at higher prey densities. These results indicated that while PPMRs are generally good predictors of interaction strengths, the incorporation of other general traits, beyond body size, into current theory would improve prediction of interaction strengths in food webs. An in-stream channel experiment was conducted to investigate the population, compared to per-capita, effects of top-predator body size and abundance on the strength of top-down interactions in food webs. By manipulating top-predator size and abundance, but keeping top-predator (brown trout) biomass constant, I showed that smaller, more abundant top predators had greater top-down effects compared to, fewer large predators of equivalent biomass. Overall, my results indicate that body size-related relationships can be used to describe changes in predator-prey interaction strengths, community structure and by extension possibly community stability. However, the usefulness of these relationships could be improved by incorporating traits over and above body size, which would aid in the prediction of community stability as communities face ongoing anthropogenic pressures.

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  • Investigations into the Effects of Middle Ear Surgery on Inner Ear Function

    Babbage, Melissa Jane (2015)

    Doctoral thesis
    University of Canterbury Library

    Middle ear surgical procedures are typically associated with a high rate of improvement in air-conduction thresholds and a low rate of sensorineural hearing loss in the conventionally assessed frequency range (0.25 – 8 kHz). Hearing loss in the extended high-frequency (EHF) range (8 – 16 kHz), however, may be common, although its characteristics are not well understood. To elucidate the effects of middle ear surgery on auditory function, prospective investigations were performed to provide data that allowed transient and permanent changes in EHF hearing to be distinguished, and to establish the nature of EHF hearing loss. Changes in hearing at 0.25 to 16 kHz were documented in 88 patients following stapedectomy, ossiculoplasty, and tympanoplasty. Hearing was measured preoperatively, and 1 week, 1, 3, 6, and 12 months postoperatively. Results showed that elevation of EHF air-conduction thresholds occurred frequently following all three surgeries and was most severe one week postoperatively. Although significant recovery of hearing was recorded by three months, 12 months after surgery, 50% of patients who underwent stapedectomy, 42% who had a tympanoplasty and 20% who underwent ossiculoplasty retained a reduction in their highest audible frequency. A TEAC HP-F100 bone-conduction transducer was modified for use in EHF audiometry and used in a small pilot study to demonstrate that EHF hearing loss following stapedectomy may be composed of both conductive and sensorineural elements. It was hypothesised that changes to utricular responses reflective of trauma to the vestibular portion of the inner ear may also occur following middle ear surgery. Measurements of tap-evoked ocular vestibular evoked myogenic potentials (oVEMPs) were performed in the same group of patients in which audiometric data was collected. Overall, the oVEMP data provided no evidence of a postoperative change in utricular responses. To assess clinical importance of EHF hearing loss, its role in one aspect of auditory function, localisation ability, was investigated in 46 participants; 23 with EHF hearing loss and 23 with normal EHF hearing. Overall, the results agreed with previous studies that localisation accuracy decreased when was EHF spectral content was removed by filtering, however the difference between hearing groups was significant only when speakers were positioned in the lateral vertical orientation. Regardless of the clinical consequences, the increased vulnerability of EHF hearing acuity to the effects of middle ear surgery provides a useful model which could be used to efficiently assess the effect of technical factors of surgery or the efficacy of ototherapeutic treatments on hearing outcomes.

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  • Intergenerational literacy engagement : literacy intervention for teenage mothers and their children.

    Scott, Amy (2015)

    Doctoral thesis
    University of Canterbury Library

    The language and literacy development of young children starts in the home, and is strongly influenced by the experiences and beliefs they are exposed to by their parents. Teenage mothers are reported to have an increased risk of low levels of educational attainment, with preliminary data suggesting literacy development is also impeded. Further, their potentially negative experiences with reading may influence their beliefs and perceptions of the activity. Children of teenage mothers are at greater risk of delayed language and literacy development, and their mothers may be less able to provide the enriched experiences required to facilitate optimal development. Therefore, interventions to support both the mother’s own literacy beliefs and skills, and the literacy environment in which they raise their children are a potentially useful way of optimising the developmental opportunities available. Despite the identified intergenerational nature of literacy learning, interventions targeting the literacy skills of teenage mothers and their children, particularly in the New Zealand context, are sparse. The experiments in this thesis addressed the need to better understand the language and literacy development of New Zealand teenage mothers and their children, and determine the effectiveness of interventions to target these important areas. The first study explored the home literacy environments provided by 41 New Zealand teenage mothers. This experiment utilised an online survey to gather qualitative and quantitative data on four key aspects of the home literacy environment. The findings suggest that teenage mothers recognise the importance of engaging children in shared reading interactions, but they lack knowledge on other aspects of children’s early literacy experience. For example, the role their own reading behaviours may contribute, the importance of providing a home environment enriched with literacy resources, and developmentally appropriate behaviours demonstrated by young children during shared reading. The first study explored the home literacy environments provided by 41 New Zealand teenage mothers. This experiment utilised an online survey to gather qualitative and quantitative data on four key aspects of the home literacy environment. The findings suggest that teenage mothers recognise the importance of engaging children in shared reading interactions, but they lack knowledge on other aspects of children’s early literacy experience. For example, the role their own reading behaviours may contribute, the importance of iii providing a home environment enriched with literacy resources, and developmentally appropriate behaviours demonstrated by young children during shared reading. The third study explored the effectiveness of a multi-component literacy intervention targeting the literacy skills of 10 mothers (M = 18;10) identified as low-achieving in reading comprehension. Using a pre-test/post-test research design with general comparison group (M = 18;6), the 26-session classroom-based intervention used same-language subtitled movies and a range of integrated literacy activities to target passage and word comprehension, oral reading fluency, vocabulary, morphology and spelling. Results showed no significant improvement in passage comprehension, oral reading fluency, spelling or vocabulary from pre- to post-intervention testing. Statistically significant improvement was noted for The third study explored the effectiveness of a multi-component literacy intervention targeting the literacy skills of 10 mothers (M = 18;10) identified as low-achieving in reading comprehension. Using a pre-test/post-test research design with general comparison group (M = 18;6), the 26-session classroom-based intervention used same-language subtitled movies and a range of integrated literacy activities to target passage and word comprehension, oral reading fluency, vocabulary, morphology and spelling. Results showed no significant improvement in passage comprehension, oral reading fluency, spelling or vocabulary from pre- to post-intervention testing. Statistically significant improvement was noted for The third study explored the effectiveness of a multi-component literacy intervention targeting the literacy skills of 10 mothers (M = 18;10) identified as low-achieving in reading comprehension. Using a pre-test/post-test research design with general comparison group (M = 18;6), the 26-session classroom-based intervention used same-language subtitled movies and a range of integrated literacy activities to target passage and word comprehension, oral reading fluency, vocabulary, morphology and spelling. Results showed no significant improvement in passage comprehension, oral reading fluency, spelling or vocabulary from pre- to post-intervention testing. Statistically significant improvement was noted for morphological awareness. When comparing results to a general comparison group, no significant improvement was detected in any area. The fourth study aimed to describe the language and development of 36 children of teenage mothers (M = 17 months). A range of standardised and parent-report assessment measures were used. Results varied considerably within the group on all measures. On clinician measures of language development, younger children performed more poorly than older children. Discrepancies were also observed between parent- and clinician-report measures. Parent measures primarily indicated children were performing within or at above average range in language and development. Conversely, clinician-report measures highlighted concerns with regards to children’s language development. In consideration of the risk profiles associated with teenage motherhood, the results suggested that these children may benefit from enriched language and literacy opportunities through quality shared reading interactions with their mothers. Given the home literacy environment was reported as lacking in enriched opportunities for literacy development, and children’s language development was identified as at-risk, the fifth study implemented a parent-targeted intervention to enrich the shared reading interactions experienced by 27 children of teenage mothers (M = 19;6). Using a pretest/ post-test research design mothers completed a seven week intervention based in the classroom, targeting a range of emergent literacy skills that they could utilise when reading with their children. A comparison cohort (n = 10; M = 18;3) was utilised to establish if assessed behaviours were commensurate with a similar population of teenage mothers. Assessments tracked changes in the type and frequency of mothers’ reading behaviours demonstrated during videoed shared reading interactions with their young children, as well as changes to aspects of the home literacy environment. A blinded, independent coder completed the data analysis. Results indicated significantly greater frequency of vocabulary, questioning and book/print features-focused reading behaviours from pre-test to post-test. No changes were observed in reading behaviours relating to letter/sound features. The sixth study provided an in-depth analysis of the quality and quantity of language used by mothers and children during the shared reading interactions collected in study five. Using a pre-test/post-test research design, language quality and quantity was measured during the shared reading interactions of 14 mother/child dyads (M = 19;9). Analysis examined MLU-m and total number of words and utterances used by mother and child, mother’s use of rare/sophisticated words, and children’s use of word classes. Discourse-level analysis was also completed, which examined five different types of conversational acts. Results demonstrated significant and meaningful changes in both language quality and quantity following the emergent literacy intervention. Changes at the discourse level were also observed. This thesis revealed that the language and literacy profiles of teenage mothers and their children are heterogeneous in nature, and may reflect a wide range of experiences and circumstances that existed before parenthood. This comprehensive collection of data is the first of its kind and provides detailed information on the language and literacy skills of this population. Despite the observed variability, it was determined that there is a need within this population for literacy support for both mothers and their children. This research also demonstrated differential changes in response to intervention when targeting the literacy skills of the mothers, and the way in which they share books with their children. The most positive changes were observed from the intervention that targeted shared book reading at both a behavioural and linguistic level. Analysis of the linguistic characteristics of shared reading interactions is a novel method of exploring response to intervention, and has not previously been examined in the literature.

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  • Allophonic imitation within and across word positions

    Fiasson, Romain Gines Michel (2015)

    Doctoral thesis
    University of Canterbury Library

    This dissertation investigates imitation in speech, which is the general tendency shown by a speaker to become more similar to another speaker in the way they speak. Many of us have experienced this while talking to someone who is speaking the same language but with a different accent. Conversing with such a person can affect some characteristics of our speech, so that we come to sound more like them. Imitation in speech has been very extensively studied, especially over recent years. To contribute to this line of research we provide an account of imitation in speech at the allophonic level, that is at the level of the possible phonetic realisations of a phoneme. We are interested in whether imitation of the sound of a given phoneme in a particular word position can influence the other possible realisations of that phoneme in the same word position. We are also interested in determining whether imitation of a speech sound in a particular word position for a given phoneme can affect the realisations of that phoneme in a different word position. New Zealand English provides of wealth of allophonic variation across word positions for the phoneme /t/. Therefore it is an ideal language to investigate imitation and allophony. Before presenting our experimental designs and our results on imitation however, we verified and further extended the work that has been conducted on the dialect. We analysed large corpora of spoken NZE and found new allophones of /t/. We discuss a fricative realisation in particular. The fricative realisation in NZE was further examined by means of a palatographic pilot experiment, as well as a perception experiment. Building on our findings from the perception experiment, we investigated imitation in speech towards an artificially created novel fricative allophone in medial position using acoustic and EPG data. For some speakers, the mere exposure to the novel allophone affected the realisation of other allophones in the same word position. A series of acoustic experiments were then conducted to examine allophonic imitation across word positions. We found that repeated exposure to a given allophone can drive allophonic selection across word positions. We also found that positional transfer can occur, such that exposure to an acoustically manipulated allophone can affect the same allophones in a different word position. Interestingly it can also affect other allophones in a different word position. Our results are discussed according to hybrid exemplar models and the Direct Realist view. We discuss which theoretical framework best accounts for the results we obtained.

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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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  • 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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  • Natural Hand Interaction for Augmented Reality

    Piumsomboon, Thammathip (2015)

    Doctoral thesis
    University of Canterbury Library

    Despite the increasing prevalence of Augmented Reality (AR) interfaces, there is still a lack of interaction techniques that allow full utilization of the medium. Natural hand interaction has the potential to offer these affordances however, as of yet, has not been well explored. The aim of this thesis is to improve the understanding of natural hand interaction and ultimately create a novel natural hand interaction technique that enhances user experience when interacting with AR. To better understand natural hand interaction, two prototype AR systems featuring environmental awareness and physical simulation were developed, one featuring interaction on a tabletop, and the other in a mobile tablet setting. Observations and feedback from public demonstrations of the systems were collected, and it was found that users felt that interacting physically using their hands and other tangible objects was natural and intuitive. Following this, a guessability study was conducted to elicit hand gestures for AR and obtain qualitative feedback from users in a video-see through head mounted display (HMD). From the results, a user-defined gesture set was created to guide the design of natural hand interaction for AR. Utilizing this deeper understanding and set of design guidelines, a gesture interface was developed that enabled hand tracking and gesture recognition based on depth sensing input. An AR framework that supports natural interaction as the primary input, called G-SIAR, was created, and a novel direct manipulation natural hand interaction technique, Grasp-Shell (G-Shell), was developed. This interaction technique was validated by comparing it to a traditional indirect manipulation gesture and speech interaction technique, Gesture-Speech (G-Speech), in a usability study. From the study, we gained insights into the strengths and weaknesses of each interaction technique. We found impacts on performance, usability, and user preference when comparing G-Shell’s direct interaction, where the user physically manipulates the object they are interacting with, and G-Speech’s indirect interaction, where the user interacts with the object remotely using gestures and speech commands, depending on the task. We concluded that these interaction techniques were complementing each other and should be offered together. The primary contributions of this thesis include a literature review of AR and its interaction techniques, the implementation of two AR systems and findings from the public demonstrations, findings from a guessability study on hand gestures for AR, the design and development of gesture interface and multimodal AR framework, and the design and evaluation of two natural interaction techniques, G-Shell and G-Speech. This research offers knowledge gained into natural hand interaction for AR and forms a new layer of foundation for research into interaction techniques in AR.

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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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