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Research Commons is the University of Waikato's open access research repository, housing research publications and theses produced by the University's staff and students.
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Publication The biology of Asparagopsis armata for closed-life cycle cultivation in New Zealand(Thesis, The University of Waikato, 2024)The red seaweed Asparagopsis armata is a target species for aquaculture due to its efficacy as an anti-methanogenic ruminant feed additive. However, limited knowledge regarding its reproductive biology and methods for closed-life cycle cultivation has delayed adoption of this method in aquaculture. This thesis therefore aimed to address these knowledge gaps by investigating (1) reproductive phenology, (2) techniques for inducing life-cycle transitions, (3) nursery requirements, and (4) internal mechanisms regulating reproductive processes in A. armata. A comparative analysis of A. armata reproductive phenology in New Zealand from 2021 to 2022, compared to 1978 to 1981, identified potential climate-driven shifts in phenology. Specifically, the occurrence period of gametophytes was shorter, and cystocarp production and viable carpospore release were delayed in comparison to 1978–1981. Discoloration, low reproductive output, and low survival rates in 2022 were likely caused by heat stress. These findings will help guide aquaculture practises and advance our understanding of climate change effects on seaweed reproductive phenology through future comparative studies. Mass production and release of tetraspores in domesticated A. armata tetrasporophytes was demonstrated through a 14-day exposure to a reduced critical photoperiod of 8 h L:16 h D. Increasing the temperature from 15 to 18 °C resulted in a marked increase in tetraspore release, whereas exposure to 11 and 13 °C, along with lower light intensities and nutrient concentrations, did not initiate tetrasporogenesis. These results highlight the importance of temperature, among other environmental factors, in controlling reproductive output. A distinct bimodal pattern in tetraspore release was observed, and tetrasporogenesis could be re-induced in the same biomass by adjusting key environmental parameters. These findings collectively offer precise control over tetrasporogenesis, facilitating commercial hatchery production. Key parameters for enhancing the growth and development of juvenile gametophytes of A. armata were identified, notably moderate temperature and water flow, which resulted in substantial biomass productivity increases. Gametophytes developed more rapidly under a 12h L:12h D photoperiod, while growth was enhanced under lower irradiances. Additionally, lowering nutrient concentrations resulted in cleaner cultures without compromising growth. These results elucidate the influence of environmental factors during the early life stages of A. armata, providing essential insights to enable large-scale nursery operations. Finally, an analysis of metabolomic and transcriptomic dynamics during induction of tetrasporogenesis identified marked changes in gene expression. While metabolomic changes were less prominent, accumulation of several metabolites occurred. Multiple pathways and genes, such as those related to polyamine and steroid hormone production, environmental signalling, and carbon metabolism, were upregulated during induction. These results demonstrate a dynamic biochemical and molecular response, particularly in the early stages of initiating tetrasporogenesis, laying the groundwork for identifying candidate genes and metabolites that regulate this process. In summary, this thesis significantly advances the science and knowledge required for the successful cultivation of A. armata by creating foundations to (1) guide the selection of cultivation techniques, (2) develop climate-resilient management strategies, (3) enable the implementation of streamlined commercial hatcheries and nurseries, and (4) direct future research aimed at deciphering the fundamental internal mechanisms of reproductive transitions in seaweed.Item Recyclable hemp hurd fibre-reinforced PLA composites for 3D printing(Journal Article, Elsevier, 2024)In this study, 3D printing filaments were produced from hemp hurd fibre-reinforced polylactide (PLA) composites. Hemp hurd microfibres were obtained through alkaline digestion followed by a bleaching treatment and were used to produce PLA-based composites with 20–40 wt% fibre content for fused deposition modelling. Tensile testing of 3D printed composites revealed a gradual increase of Young's modulus with the addition of fibres, reaching a maximum of 7.1 GPa for the 40 wt% composite - a two-fold increase to neat PLA. However, tensile strength was only improved for the 20 wt% formulation, with an increase of 8% in comparison with neat PLA. Nevertheless, the thermo-mechanical properties of the composites were significantly enhanced with the addition of fibres. In addition, physical objects were printed from the recycled filaments to assess their recyclability and printability. It was found that the recycled filaments maintained comparable mechanical properties and printability after three recycling cycles.Publication A decision support system for predicting the complications of diabetes mellitus: A design science research approach(Thesis, The University of Waikato, 2024)Health information systems (HIS) serve as the cornerstone of modern healthcare, seamlessly weaving data into actionable insights and empowering professionals to make informed decisions and elevate patient care. Decision support systems became a prominent research area in the discipline of HIS, where clinical decision support systems (CDSSs) with the ability to diagnose and prognosis of disease are recognised as the most common and beneficial information systems. Moreover, the high prevalence and adverse effects of diabetes all over the globe evidently make it vital to predict diabetes and its complications. The current study aims to resolve an issue at Te Whatu Ora, by generating a CDSS which can predict the complications of diabetes mellitus (CoDM) while answering the knowledge gap. Although a rich data set of diabetes patients’ is maintained at Te Whatu Ora, their involvement in decision-making is unsatisfactory. This study created a CDSS to resolve the issue at Te Whatu Ora while considering two perspectives of the question: design and data analysis. The system design followed design science research methodologies (DSRM) while selecting suitable techniques in the steps of the empirical cycle to confirm their applicability in the domain. The data analysis perspective of the study focused on survival analysis methods due to their appropriateness in fulfilling the identified research gaps. The created CDSS is the primary outcome of the research, which resolves the real-world issue while addressing the recognised research gaps. The solution's design perspective confirms the applicability of adopting design science research approaches in the context of a systematic solution-design process. The data analytics perspective confirms the appropriateness of survival techniques in the domain while validating the system’s performance. The outcome of this research has significant academical, and managerial implications. The implemented CDSS is capable of providing a chronological risk percentage for 10 CoDM in a cohort of New Zealand. The systematic procedure adopted in the research contributes to the existing knowledge gaps while answering the design, implementation, and evaluation stages. The managerial implications of the study expand through policy-makers, resource-allocators, iii and healthcare administrators to doctors, nurses, and patients. The predicted risk of CoDM may be beneficial in managing the patients by issuing early warnings, starting treatment plans, conducting diagnosis tests, recommending dietary/exercise routines and more from the perspective of patient care. The visualisation of the statistical details and the survival curves in the system may assist in managing diabetes data repositories efficiently. This study creates a cohort-specific risk prediction model based on the New Zealand cohort. The interoperability challenges in the CDSS could occur due to the variety of practices in real life. Future research studies in this domain can concentrate on increasing the accuracy of the models with more features of a rich dataset while protecting the patents’ confidentiality. Additionally, the cohort specificity of the CDSS can be avoided with the engagement of a global dataset.Publication Exploring cross-modal association in canine (canis familiaris) scent detection: A framework for training dogs to identify multiple odours(Thesis, The University of Waikato, 2024-04-19)Dog’s olfaction abilities and trainability have made them valuable companions in scent detection tasks for centuries. While research has focused on dogs detecting single odours, there is a gap in understanding if they can emit different responses to different odours. Based on the principles of stimulus control and existing evidence of dogs’ ability to learn to perform similar tasks, it was hypothesised that dogs, using cross-modal association through olfaction and vision modalities, can match odours to corresponding shapes. Using an automated scent delivery apparatus, four dogs were trained using operant conditioning procedures to discriminate between two odours and select a corresponding shape. One dog met the mastery criteria and progressed to three odours. It was found that dogs were able to discriminate between odours at greater accuracy than chance, confirming our hypothesis. Yet, all dogs did display a bias towards one of the four touchscreen quadrants. The findings were similar to those observed in other studies involving different animal species, but the accuracy rates observed in this study were lower than those reported in other similar studies. These findings have implications for tasks the detection of multiple scents and further the understanding of dogs’ abilities to perform cross-modal discrimination tasks. This study established a methodological framework for cross-modal scent discrimination tasks but there are several improvements to the methods that might enhance dogs’ performance in future research.Publication Ceremonious storytelling: Exploring experiences within the publicly funded health service(Thesis, The University of Waikato, 2024-07-27)Background: Chronic disease is defined as a condition impacting organs or organ systems causing dysfunction or dysregulation that lasts longer than six months or remains, despite medical intervention or treatment. Research has shown that barriers, including those of a financial, physical, institutional and patient orientated nature significantly impact on outcomes. Māori are significantly over-represented in chronic health condition statistics, particularly relating to cardiac, respiratory, renal and mental health. Further, Māori are more likely to have a negative experience engaging with primary and secondary health services, leading to disempowerment and dis-engagement. Therefore, research which explores how quality of care for Māori can be improved is of pressing value. Objective: This study seeks to explore the experiences of Māori and non-Māori health-care consumers and providers within the publicly funded health service of Aotearoa. Participants: Advertising across primary and secondary care settings resulted in a total of 37 responses from health care consumers (31 respondents contributing to pūrākau) and 37 responses from health professionals (27 respondents contributing to pūrākau). Methods: This study utilised kaupapa Māori methodological approaches, frameworks and models to guide and intertwine qualitative and quantitative research methods. Participants were able to engage with any subset of questions, defining their responses through pūrākau, which supports the development of narratives within questions that are outside the limits of other worldviews. Māori methods such as pūrākau are flexible, enabling the development of research methods that are culturally aware and safe for Indigenous and non-Indigenous people globally Results: Key themes found within pūrākau highlighted the importance of meaningful engagement, person focused, trauma informed care to positively impact willingness and ability to engage with primary, secondary and tertiary services. The study reported that consumers had a strong willingness to engage with services. Conclusion: Health is personal and impacts people in various ways. Access to health services, while funded in Aotearoa, still create barriers for some people and perpetuates the gap between prevention and diagnosis of chronic disease. Kaupapa Māori methods within research support Māori engagement and definition within research through historical ways of being, knowing and conducting research. Participants of this study detailed experiences within health services, highlighting willingness and ability to engage with health services. Prior research defined the development of the Levesque access and accessibility framework, which correlates with the findings within this study."
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