Doctoral Theses

Permanent URI for this collectionhttps://hdl.handle.net/2292/2

Browse

Recent Submissions

Now showing 1 - 20 of 7174
  • No Thumbnail Available
    Item
    Long-term trends and ecological impacts of the subtropical sea urchin Centrostephanus rodgersii in northeastern Aotearoa New Zealand
    (ResearchSpace@Auckland, 2024) Balemi, Celia Anna; Shears, Nick; Taylor, Richard
    Changing climatic conditions along with other anthropogenic stressors can lead to irruptions of native species, with potentially similar widespread effects to that of range extending or invasive species. These are especially profound when they cause the loss of habitat forming organisms (e.g. kelp), resulting in the subsequent degradation of associated biodiversity and ecosystem function. In northeastern Aotearoa New Zealand, there are anecdotal reports that populations of the native subtropical sea urchin Centrostephanus rodgersii are increasing; however, little is known about the long-term trends or associated impacts on reef ecosystems. This thesis aims to examine population trends, feeding preferences and ecological impacts of C. rodgersii in northeastern New Zealand, relative to the common sea urchin Evechinus chloroticus. This study provides the first documentation of long-term increases in C. rodgersii in kelp forests and on invertebrate-dominated rock walls in this region. This has resulted in the emergence of C. rodgersii barrens, both within a long-standing marine reserve and fished archipelago, with a greater depth distribution than historic E. chloroticus barrens. Conversely, densities of E. chloroticus declined and associated barrens disappeared within the marine reserve while remaining stable at the fished location, following the expected response to marine protection. The increase in C. rodgersii coincided with substantial oceanic warming and low numbers of key predatory lobster in both locations. Long-term increases in C. rodgersii on rock walls led to declines in habitat-forming sessile invertebrates and increases in encrusting algae and bare rock. These effects were supported by feeding preference experiments with C. rodgersii exhibiting a more omnivorous diet and consistently feeding at higher trophic levels than E. chloroticus. This reveals that C. rodgersii has potential to impact a greater range of habitats and depths than E. chloroticus and could drive the widespread homogenisation of multiple rocky reef habitats. Overall, these results highlight how a changing climate combined with other stressors can cause changes to the abundance of native species with far-reaching impacts on marine ecosystems. This research demonstrates the novel and unprecedented threat C. rodgersii poses and stresses that steps are urgently needed to help prevent catastrophic shifts in New Zealand’s rocky reef ecosystems.
  • Thumbnail Image
    Item
    The rise and fall of the spiny lobster (Jasus edwardsii) in the Hauraki Gulf, northeastern New Zealand
    (ResearchSpace@Auckland, 2023) Nessia, Hayley Rose; Shears, Nicholas; Radford, Craig A; Taylor, Richard B
    The spiny lobster (Jasus edwardsii) is a critical sea urchin predator on Australasian rocky reefs. In New Zealand, J. edwardsii also supports the country’s most valuable inshore commercial fishery, and subsequently is subjected to intense fishing pressure. While marine reserves have long been shown to be effective in rebuilding lobster populations, declines inside reserves and in fished areas in the Hauraki Gulf, northeastern New Zealand, over the last two decades raise concerns about the plight of this important species. While the recent fisheries assessment suggests improvements in the wider stocks, fisheries-independent assessments are needed to evaluate this. Furthermore, ocean warming has resulted in the expansion of long-spined sea urchins (Centrostephanus rodgersii) in northeastern New Zealand, and it is unknown if this has been facilitated by declines in J. edwardsii populations. The overall aim of this thesis was therefore to investigate the current state of lobster populations in the Hauraki Gulf, and better understand the cause and potential ecological consequences of large-scale declines. This was achieved by carrying out a region-wide dive survey of fished locations and fully protected marine reserves across the Hauraki Gulf, tracking lobster movement in the Cape Rodney-Okakari Point (CROP) marine reserve with a passive acoustic array, and carrying out feeding assays to determine the ability of J. edwardsii to consume C. rodgersii, and its preference for another barren-forming sea urchin, Evechinus chloroticus. Lobster densities in three marine reserves and their adjacent fished locations have not significantly increased following the 2018 catch reduction, and both vulnerable (legal-sized) and spawning stock biomass in the fished population of the Hauraki Gulf are estimated to be ≤5% of reserve biomass. These estimates are in stark contrast to fisheries estimates and suggest the recent stock assessment has grossly overestimated the state of the J. edwardsii population in the Hauraki Gulf. This highlights the value of using marine reserves as a proxy for estimates of unfished biomass to evaluate the status of surrounding fisheries. The passive acoustic array in the CROP marine reserve did not provide adequate simultaneous detections for the signal triangulation necessary for high-resolution data. However, the detections were able to produce weighted positions that allowed tracking of larger-scale movements and diurnal rhythms. The tracking data suggested lobster movements were less extensive than that reported in earlier studies, and there was little evidence to suggest aggregatory behaviour still occurred in contrast to movement data reported from the 1990s. These long-term changes are likely related to declines in overall population size and highlight the inadequate size of the CROP marine reserve in protecting the resident population from the effects of fishing. Feeding assays revealed that J. edwardsii were capable of consuming small C. rodgersii, but they exhibited a clear preference for E. chloroticus. This is likely related to a lobster’s ability to grasp the total diameter of an urchin, which due to longer spines in C. rodgersii translates to lobsters consuming only those with very small test diameters. Nevertheless, the consumptive abilities of J. edwardsii for both barren-forming urchin species in New Zealand reinforces their critical role as an urchin predator and emphasizes the importance of protecting J. edwardsii if urchin barrens are to be controlled or prevented in the Hauraki Gulf. Overall, these findings demonstrate the significant impacts of fishing on population density and behaviour of J. edwardsii and highlight the precarious state of the J. edwardsii population in the Hauraki Gulf. In an uncertain future of climate change stressors, these data strongly suggest a precautionary approach to management of J. edwardsii is necessary if it is to fulfil its functional role within the Hauraki Gulf once again.
  • No Thumbnail Available
    Item
    Residual Capacity and Repairability of Reinforced Concrete Frame Buildings
    (ResearchSpace@Auckland, 2024-02) Kuwabara, Ryo ; Hogan, Lucas ; Elwood, Kenneth ; Opabola, Eyitayo
    Reinforced concrete (RC) frame buildings designed according to modern design standards achieved life-safety objectives during the Canterbury earthquakes in 2010-11 and the Kaikōura earthquake in 2016. These buildings formed ductile plastic hinges as intended and partial or total building collapse was prevented. However, despite the fact that the damage level of these buildings was relatively low to moderate, over 60% of multi-storey RC buildings in the Christchurch central business district were demolished due to insufficient insurance coverage and significant uncertainty in the residual capacity and repairability of those buildings. This observation emphasized an imperative need to improve understanding in evaluating the post-earthquake performance of earthquake-damaged buildings and to develop relevant post-earthquake assessment guidelines. This thesis focuses on improving the understanding of the residual capacity and repairability of RC frame buildings. A large-scale five-storey RC moment-resisting frame building was tested to investigate the behaviour of earthquake-damaged and repaired buildings. The original test building was tested with four ground motions, including two repeated design-level ground motions. Subsequently, the test building was repaired using epoxy injection and mortar patching and re-tested with three ground motions. The test building was assessed using key concepts of the ATC-145 post-earthquake assessment guideline to validate its assessment procedures and highlight potential limitations. Numerical models were developed to simulate the peak storey drift demand and identify damage locations. Additionally, fatigue assessment of steel reinforcement was conducted using methodologies as per ATC-145. The residual capacity of earthquake-strained steel reinforcement was experimentally investigated in terms of the residual fatigue capacity and the residual ultimate strain capacity. In addition to studying the fatigue capacity of steel reinforcement, the fatigue damage demand was estimated using 972 ground motion records. The deformation limit of RC beams and columns for damage control was explored to achieve a low likelihood of requiring performance-critical repair. A frame component test database was developed, and the deformation capacity at the initiation of lateral strength loss was examined in terms of the chord rotation, plastic rotation and curvature ductility capacity. Furthermore, the proposed curvature ductility capacity was discussed with the current design curvature ductility limits as per NZS 3101:2006.
  • No Thumbnail Available
    Item
    Talent management: how is it practised and how do employees respond to it?
    (ResearchSpace@Auckland, 2024) Sultana, Nigar; Boxall, Peter; Cheung, Gordon; George, Elizabeth
    Although scholars call for contextualised research on talent management, particularly in emerging economies, few studies have been conducted in these contexts. In response to this call, this thesis examines talent management in Bangladesh, an emerging economy in South Asia. Using mixed methods, including multiple qualitative case studies on six organisations and a quantitative survey of 210 employees from a single organisation, the thesis aims to respond to scholarly calls for multilevel research in the talent management literature. It addresses the question of how talent management is practised in Bangladesh and how employees respond to it. The qualitative study reveals how managers conceptualise and implement talent management, considering broader environmental and organisational factors. It is found that economic (e.g., national economic growth), demographic (e.g., Gen Z trends), and sociocultural (e.g., tadbir, toshamodi (sycophancy) and instrumentalism) factors, along with organisational infrastructure, resources, and the values and philosophies of top management and line managers, significantly impact the adoption and implementation of talent management. The data suggest a flexible approach to talent management and the coexistence of contextualised and international standard practices in these organisations. The case study data are also used to develop items for measuring talent management practices in the subsequent quantitative study. Based on HR attribution and signalling theory, this study finds a significant impact of perceived talent management practices on employee responses in terms of affective commitment and intention to stay and commitment-focused talent management attributions. The study also shows a significant impact of the individual-level sociocultural variable of instrumentalism on the relationship between perceived talent management practices and commitment-focused attributions. Adopting a contextualised approach, this thesis provides valuable insights into the interconnected effects between macro (national), meso (organisational), and micro (individual) level factors and their independent or combined impacts on talent management. By incorporating perspectives from management (including line managers) from the qualitative study, and employees from the quantitative study, a system model of talent management is developed. The thesis has practical implications for managers in Bangladesh and other emerging economies with similar sociocultural, demographic, and economic conditions.
  • No Thumbnail Available
    Item
    Variation in thermal tolerance: the interactive effects of thermal stress on cardiac mitochondrial parameters in the family Labridae
    (ResearchSpace@Auckland, 2024-04-28) Harford, Alice Rebecca; Hickey, Tony; Herbert, Neill
    Mitochondria are essential for almost all complex multicellular life, supplying ~90% cellular power as ATP. Just below upper habitat temperatures, mitochondria fail (mtTcrit), mediating heart failure and death in ectotherms. While work has examined mitochondrial bioenergetics with thermal stress, the exact mechanisms that induce mitochondrial disruption remain unclear, and limited work has examined the impact on mitochondrial ultrastructure. The primary aims of this thesis were to determine the interactive effects of temperature and oxygen (O2) on cardiac mitochondria as temperatures reach mtTcrit in wrasse species from different thermal environments, cold-temperate Notolabrus fucicola and tropical Scarus ghobban, and to explore whether mitochondrial mechanisms are involved in variations in thermal-tolerance. Using high-resolution-respirometers coupled with fluorometric measures, we explored mitochondrial bioenergetic interactions between mitochondrial O2 consumption efficiency, mitochondrial membrane potential (mtMP), mitochondrial work (Jmt) and ATP dynamics, and whether mitochondrial failure at mtTcrit results from disruption to mitochondrial ultrastructure. These measurements were performed from saturated O2 tensions to anoxia, in order to span from traditional hyperoxic experimental conditions to in situ heart mitochondrial environment. In translation to whole organism aerobic scope, we explored mitochondrial scope, which informs on the surplus proportion of mitochondrial respiration available above basal metabolism. Analysis of mitochondrial scope showed species were able to support mitochondrial respiration until species respective mtTcrit (N. fucicola 26oC; S. ghobban between 32oC-35oC). Importantly, mitochondrial scope was more severely impacted by temperature at subcellular O2 tensions, indicating mitochondrial oxidative phosphorylation is sensitive to small changes in O2, and can be limiting under physiological conditions. At mtTcrit, mitochondria in OXPHOS state from N. fucicola showed mtMP depolarisation, increased Jmt, and a mis-match in ATP production relative to hydrolysis. This in conjunction with changes in metabolite levels, may indicate progressive disruption of the electron transport system, directing metabolism to anaerobic pathways. In contrast, Scarus ghobban mitochondria sustained mtMP, Jmt and normal levels of ATP hydrolysis above mtTcrit, despite decreases in ATP production. Electron microscopy on intact cardiac tissue showed changes in mitochondrial cristae structure mediating progressive matrix swelling in response to warming. Importantly, changes in ultrastructure occurred at temperatures below mtTcrit. This thesis confirms that mitochondrial ultrastructure disruption mediates the loss of mitochondrial bioenergetics at mtTcrit, and loss of mitochondrial function fails the hot heart of N. fucicola and S. ghobban approaching their respective habitat thermal range.
  • No Thumbnail Available
    Item
    Physical activity and sedentary behaviour in people living with cervical dystonia
    (ResearchSpace@Auckland, 2025) Yaqoob, Irum ; Meiring, Rebecca; Gusso, Silmara
    Physical activity (PA) and sedentary behaviour (SB) have a significant impact on symptoms, disease progression, and quality of life of people having neurological disorders. Hence, measuring these behaviors and determining their impact on health helps PA-based treatment approaches to improve health and manage disease progression. Cervical dystonia (CD) is a neurological disorder having associated motor and non-motor symptoms, causing a significant impact on health and activity behaviours. This PhD assessed and described the PA and SB in CD using currently available best practice guidelines for device-based acquisition, extraction, and analysis of activity data. The project also aimed to explore the likelihood of PA resulting in aggravation of dystonia-related symptoms in this population. To begin making recommendations for future research regarding exercise prescription in CD, a systematic review was initially conducted to synthesize how accelerometer-based activity data is currently collected and processed and to summarize the associations between activity behaviours and health outcomes in neurological populations. Five databases were searched to include accelerometer-based studies in adults with idiopathic neurological conditions. Results showed that the most used accelerometers were the Actigraph (AG) and activPAL. There was high compliance (> 85%) to wear, but studies lacked consensus on best practice criteria for data processing. Some recommendations are still drawn based on the majority of studies in systematic review, including 10 hours of waking wear to validate day, 3 out of 7 consecutive days of valid wear for habitual activity measurement, sedentary behaviour was accurately measured using activPAL, while AG was more accurate measuring activity. Based on these recommendations the second and third part of the Ph.D. was designed. The second study validated the activPAL accelerometer against direct observation in CD for activities such as stepping and transitions. Results supported the preliminary findings on activPAL being valid in assessing these measures. For the third part, the cohort of participants then wore the activPAL for seven days for the measurement of their habitual activity behaviours, completed health-related questionnaires (for disease rating, sleep, anxiety, depression, fatigue, quality of life, behavioral regulation, and self-efficacy to exercise), and performed supervised functional assessments including grip strength and usual gait speed. Based on recommendations from systematic review, the device data was analysed using the best practice suggestions. Analysis of the seven-day activity data showed that although participants spent most of their waking time either sedentary or accumulating low-intensity activities, they were also accumulating the recommended levels of moderate-vigorous intensity activity per week through incidental activities and their functional measures were comparable to healthy adults. PA wasn't significantly associated with any health-related measures except exercise self-efficacy and behavioural regulation. SB exhibited no significant associations with any of the health outcomes measured. Finally, based on previous reports that people with CD experience an increase in the severity of their symptoms after performing high intensity exercise, the fourth study was designed that aimed to determine the exercise threshold for symptom aggravation after exercise. This final study in the PhD was a test-retest reliability study in which an exercise tolerance test was repeated a minimum of one week apart to see whether exercise resulted in a consistent change in symptoms. In this study, participants performed two bouts of submaximal exercise on a recumbent bike separated by a week and reported their dystonia-related symptom severity during and a week after the exercise bouts. According to the results, participants seemed to achieve a moderate-vigorous exercise intensity without significant symptom exacerbation, but the reliability of the test was poor, indicating variations in symptoms between two bouts. In short, this project has improved the knowledge base regarding a rare neurological disorder, cervical dystonia. It also highlighted the current physical activity and sedentary behaviour this population accumulates, their association with motor and non-motor symptoms, and the intensity of exercise that can be safely achieved without symptoms aggravation. Hence highlighting the role of physical activity as a holistic approach to managing cervical dystonia.
  • No Thumbnail Available
    Item
    Being an immigrant teacher is a tough road: a self-study of teaching praxis
    (ResearchSpace@Auckland, 2024-11-19) Cardoso Kucera, Carlos Augusto; Ovens, Alan; Bennett, Blake
    Immigrating and becoming a teacher in a new country is challenging and brings with it a necessity to shape personal and professional feelings, assumptions and practices. Challenges, and the necessity to shape these elements, also happen when changing suddenly from presential to remote teaching. Major shifts can challenge educators to question their educational paradigms and adapt their praxis to a new educational system. This thesis is about my journey of immigration to Aotearoa New Zealand from Brazil and my journey teaching during the Covid-19 pandemic, including the effect these shifts had on the way I enact my teaching, my praxis, as a physical education (PE) teacher. Using a self-study methodology with elements of bricolage to support the research design, I sought to examine the ways in which my teaching in a primary school were influenced by and adapted to a new cultural setting and education system. Data sources included teaching artefacts, journaling, personal history through narratives and meeting with critical friends and supervisors. Using thematic analysis of the data suggests that divergent points, such as (1) language, (2) feeling of belonging, (3) understanding of praxis, (4) pedagogical strategies and (5) personal assumptions influenced and shaped my praxis and, therefore, the way I enacted my teaching. By engaging with praxis as a theoretical framework and a way to understand my actions, I came to understand that I adapted my praxis due to the new contexts. I also had to shape the way I teach both in a macro and micro pedagogical context because of the divergent topics found in this research. Ultimately, this thesis illuminates the way I built my praxis as an immigrant teacher, teaching both face to face and online, and offers suggestions on how to support other teachers migrating to new countries and starting their journey as educators in a new cultural and teaching context.
  • No Thumbnail Available
    Item
    Decision-Making in the Design of Large Complex Composite Structures
    (ResearchSpace@Auckland, 2024) Lorimer, Tobias; Allen, Tom; Wynn, David
    Fibre Reinforced Plastics are increasingly utilised in the form of Large Complex Composite Structures where attributes like efficiency and specific performance are highly sought after. Common usage includes racing yachts, rockets, wind turbine blades and throughout aeroplane structures. However, contemporary design practices can fail to maximise structural efficiency. The benefits of increased efficiency are numerous, but improved system-wide design approaches are required for improved utilisation of Fibre Reinforced Plastics. A holistic early-stage design approach has been developed for the design of LCCSs. It allows the concurrent determination of optimal FRP laminate and structural arrangements in the early stages of LCCS design. It relies on a Genetic Algorithm (GA) -based optimisation approach designed to concurrently determine the optimal stacking sequence, ply orientations, and the ply count for a laminate subject to complex loading. The GA-based optimisation approach was shown to return optimal or nearoptimal solutions in search spaces up to and including 194 billion points. This demonstrates the GA-based optimisation approach’s ability to find near-optimal solutions when they made up less than 0.1% of the search space. The influence of the FRP Failure Criteria (FC) on optimal laminate configurations was also investigated. Puck’s FC was consistently the most accurate and most conservative out of a range of five well-established FC. It has been implemented in the GA-based optimisation approach and is recommended for future use. Experimental testing was undertaken using a newly designed Biaxial Testing Apparatus (BTA) and cruciform specimens optimised using each of the five FC. The testing accompanied and endorsed a series of numerical simulations investigating the ultimate performance of the GA-based optimisation approach. The influence of FC in the optimisation formulation was quantified, and the effectiveness of the GA-based optimisation at a lab scale was confirmed. Finally, a case study was conducted to assess the efficacy of the newly developed approach compared to a contemporary design process for an IMOCA 60 race yacht. While the results demonstrated the effectiveness of the developed method, the primary emphasis remains on the successful development of the early-stage design philosophy.
  • Thumbnail Image
    Item
    Novel Formal Methods for the Safety and Security of Cyber-Physical Systems
    (2024) Baird, Alexander John Renfree; Roop, Partha; Patel, Nitish
    The ongoing digital revolution is now augmenting physical processes with embedded controllers. This results in Cyber-Physical Systems (CPSs), where the physical and cyber worlds become one integrated system. There is a growing group of emerging industries (Internet of Things (IoT) devices, Unmanned Aerial Vehicles (UAVs), and 3D printers) that fall into grey areas where regulations may be lacking, and industry practice is inconsistent. Robust methods in the field of formal runtime assurance can be used to verify safety and security policies. They have lower resource overheads than traditional formal methods, appealing to designers with resource constraints. Runtime verification, an area within runtime assurance, verifies policies during the system’s execution and produces alerts if a policy is violated. For example, a smart watch alerting if it detects abnormal heart rhythm. For CPSs with the ability to take action, runtime enforcement is well suited to ensure safety and security policies are upheld. Runtime enforcement extends runtime verification with the ability to intervene before a violation occurs (important for safety critical systems where failure may cause loss of life). Existing runtime enforcement work has not considered the attacker’s perspective, which can undermine defensive strategies. Additionally, as CPSs become more capable, the need for scalable enforcement of multiple policies grows. This thesis presents a set of novel runtime assurance methods using runtime verification and runtime enforcement to verify safety and security. Firstly, we present formal models of abnormal heart rhythms detectable in Electrocardiograms (ECGs). Our approach has comparable performance to existing methods with the benefit of producing clinically explainable alerts. Secondly, we propose enforcer interchange to orchestrate sophisticated runtime enforcer attacks. We model a set of attacks on UAV communication and successfully launch these on a high fidelity drone simulator. Thirdly, we present a framework to compose runtime enforcers in parallel to defend against attacks on complex CPSs. We demonstrate improved scalability with (a set of) defensive policies for a 3D printer. In a constantly evolving technological landscape, designers are creating more capable CPSs. We present the aforementioned approaches to aid designers in the pursuit of safety and security.
  • No Thumbnail Available
    Item
    High Throughput Platform for the Rapid Stretching of Brain Cells
    (ResearchSpace@Auckland, 2024) Jayatissa, Canangama Arachchige Vimantha Sahan; Anderson, Iain; Shim, Vickie; Rosset, Samuel
    New Zealand has the highest incidence of Traumatic Brain Injury (TBI) in the world. It is an injury where an external impact causes damage to the tissue of the brain and it is speculated that high incidence is a result of the interest in contact sports in the country. TBI is also the leading cause of injury-related death and disability in children across the globe and despite the large body of research carried out, there are currently no therapeutic or biological diagnostic methods for TBI. The mild form of TBI (mTBI), also known as concussions, have proven a challenge for both diagnosis even though it accounts for 90% of the cases. Several in-vitro and in-vivo models have been presented for the study of mTBI but the lack of a clear indicator for the injury shows that a large amount of research and experiments still needs to be done. There is a clear need for a tool to carry out high throughput experimentation to understand this complex injury. This study presents the development and characterization of a High Throughput Cell Stretching Platform that utilises a Dielectric Elastomer Actuator (DEA), a form of soft actuator, to apply mechanical insults onto brain tissue. The device design allows for quick fabrication and the development of a experimental tools allows for quick and easy experimentation creating the potential for a large amount of experimentation to be carried out. A novel method for the optimization of the first part of fabrication process is presented. The device is rigorously characterized to determine strain and thickness homogeneity and can consistently produce strains of up to 20% onto the cells. The combination of an open loop control system for strain and head impact data from a rugby player was used to recreate the strain profile of a real life head impact data. Finally, the simple addition of a infrared LED array is used to demonstrate its versatility in high throughput applications beyond mTBI. The device presented in this study is expected to be a valuable tool for carrying out high throughput mechanobiological experiments including identifying a therapeutic target for mTBI which has been elusive while also paving a new pathway in global cell stretching research.
  • Thumbnail Image
    Item
    Develop a Sulfur-driven Autotrophic Denitrification Process for The Treatment of Industrial Wastewater Containing High Levels of Salinity in an Alkaline Environment
    (ResearchSpace@Auckland, 2024-05-30) Yao, Bo; Zhuang, Wei-Qin; Quenneville, Pierre; Craggs, Rupert
    This research aimed to develop a rapid start-up procedure for Sulfur-driven Autotrophic Denitrification (SdAD) tailored for the remediation of wastewater with varying salinity levels, mainly targeting saline industrial wastewater with specific alkalinity. The study focused on evaluating the efficiency of two systems, Sulfide-based Autotrophic Denitrification (SbAD) and Thiosulfate-based Autotrophic Denitrification (TbAD), under different salinities (0.1%, 3.5%, and 6%). The SbAD process was initially assessed, revealing that after 186 extensive enrichments, consistent nitrogen removal was achieved. The results indicated that while the system performed well at 0.1% and 3.5% salinities, its efficiency decreased significantly at a 6% salinity level. Subsequently, the TbAD system was evaluated, demonstrating a more rapid achievement of consistent nitrogen removal within 57 days of enrichments. Further enhancement was achieved through subculture purification, which increased the nitrate removal efficiencies to 161.689 mg NL-1day-1 at 0.1% salinity, 94.039 mg NL-1day-1 at 3.5% salinity and 40.663 mg NL-1day-1 at 6% salinity. Metagenomics and proteomics analyses were conducted to understand microbial community dynamics and their roles in the SdAD system. These analyses revealed that Proteobacteria and Bacteroidota dominated at the phylum level. The critical species from Halomonas, Thiobacillus, and Rhodanobacter show a strong positive correlation with the system's salinity, denitrification rate, and sulfur conversion rate, respectively. The innovations of this study are significant. Firstly, it demonstrated the effectiveness of the SbAD system in treating saline wastewater in an alkaline environment. Secondly, it developed a rapid initiation method for the TbAD system, which shows practical applicability in industrial settings for high-salinity wastewater treatment. Thirdly, a method for improving treatment efficiency using TbAD subculture purification with thiosulfate was established. In conclusion, the SdAD system developed in this research represents a promising biological method for treating nitrate contamination in saline wastewater. The findings advanced our understanding of how salinity affected the microbial community structure and functional dynamics within the SdAD system, thereby promoting the application of this sustainable bioprocess in industrial wastewater treatment contexts.
  • No Thumbnail Available
    Item
    Synthetic Studies Towards Pallamolide A
    (ResearchSpace@Auckland, 2024-03) Drummond, Grace; Brimble, Margaret; Furkert, Dan
    Pallamolides A–E (20–24) are 7,8-seco-labdanes isolated from the Chinese liverwort Pallavicinia ambigua. The tautomeric pair 23 and 24 exhibits anti-fungal activity, by inhibition of mycelium hyphae formation in a dose dependent manner, with an MIC of 32 μg/mL. Additionally, 23 and 24 were found to significantly destroy the biofilm structure of DSY654 cells at 16 μg/mL. The unique structural complexity of 20–24, and the promise held by 23 and 24 as antifungal therapeutics, make them desirable targets for total synthesis. Herein, the evolution of an asymmetric synthetic strategy towards pallamolide A (20) is described. The initial aim targeted the construction of the caged bicyclo[2.2.2]octane core (177) of pallamolide A (20). Access to keto-aldehyde 252 was secured first by synthesis of ketone 182, followed by a 7-step sequence hinging on a modified Shapiro reaction to effect ring opening. Unfortunately, NHC-catalysed acyloin condensation of 252 to 253 could not be effected, however, the intramolecular aldol reaction of its homologue, aldehyde 268, to 269 was successful. Despite access to the caged core of pallamolide A (20), an alternative strategy towards the total synthesis of 20 was employed, hinging on an intramolecular vinylogous Mukaiyama aldol (VMA) reaction of 274, accessed by the hydration of bicyclic dihydropyran 276. A model study demonstrated that a robust synthesis of lactol 299 could be achieved, but investigation of the key VMA reaction was hindered by failure to capture any analogues of the ring-opened tautomers of 311 or lactone 316. The revised strategy employed the autoxidation of 333 to 378, from which a VMA reaction with 414 provided intermediate 413. Upon purification, 413 serendipitously underwent an intramolecular vinylogous aldol reaction to provide 411, possessing the central core and spiro butenolide moiety of pallamolide A (20). Introduction of the hydroxymethyl group of pallamolide A (20) at C8 was demonstrated via a palladium-catalysed CH activation sequence on intermediate 435, providing alcohol 438. The synthetic approaches investigated herein have provided a sound foundation for the total synthesis of pallamolide A (20). The current synthetic strategy provided a highly decorated intermediate possessing the central scaffold of 20, and elaboration of this approach towards the synthesis of pallamolide A (20) remains an ongoing pursuit within this research group.
  • No Thumbnail Available
    Item
    Understanding Situational Factors in Human-centred Phishing Susceptibility
    (ResearchSpace@Auckland, 2025) Zhuo, Sijie ; Russello, Giovanni ; Lottridge, Danielle
    Phishing is a type of social engineering attack that deceives individuals into disclosing sensitive information or downloading malware. It poses a significant threat to both individuals and organisations, causing substantial financial losses. This thesis aims to enhance the understanding of human-centred phishing susceptibility by investigating the factors influencing users' vulnerability to phishing attacks. The thesis begins by categorising phishing susceptibility factors into long-term stable variables, situational variables, and in-the-moment variables. This categorisation leads to the development of a Phishing Susceptibility Model (PSM) and highlights the research gap in exploring situational factors that influence users' email processing behaviour and phishing susceptibility. To address this gap, we conducted a large-scale simulated phishing campaign to explore the impact of device type and link presentation on users' tendency to click on phishing links. Our study reveals that while the device used (mobile vs. computer) does not significantly influence susceptibility, masking the phishing link with hypertext significantly increases the likelihood of user clicks. Additionally, we identified a novel research method in phishing susceptibility, the Precision Email Interaction Study (PEIS), to closely observe users' interactions with phishing emails in a controlled yet realistic environment. PEIS allows precise measurement of user interactions with phishing emails under various conditions. To support the PEIS, we developed the Precision Email Simulator, which provides customisation for various research needs. Using PEIS, we conducted two user studies to explore the impact of workload on phishing susceptibility. We found that high workload is associated with shorter email reading times and an increased tendency to interact with task-relevant phishing emails. Additionally, paying attention to the email sender can significantly reduce phishing susceptibility. This thesis concludes by discussing the implications of these findings for designing anti-phishing interventions and training programmes. By providing actionable insights into the human factors of phishing susceptibility, this work contributes to developing more effective strategies to mitigate the risk of phishing attacks. We also discuss future research directions that could build on our findings and further enhance email security.
  • No Thumbnail Available
    Item
    The Systematisation of Safety in Design Implementation in the New Zealand Construction Industry
    (ResearchSpace@Auckland, 2024) Shi, Weifang; Chang-Richards, Alice; Ingham, Jason
    Compared to other industries, the construction sector performs poorly in health and safety, with a staggering number of injuries and fatalities. A significant percentage of accidents were closely linked to a lack of consideration for ‘Safety in Design’ (SiD) and its implementation. The gaps lie in the unrevealed SiD factors, dynamics interactions, SiD maturity metrics, safe design knowledge shortage, and effective methods to educate designers. This research aims to develop a comprehensive framework for effectively and strategically implementing SiD. The research explored factors influencing SiD and investigated strategies advancing its implementation and improving workers’ health and safety through design activities. This study identifies five aspects of implementing SiD: (1) Critical factors affecting SiD implementation. (2) Motives within system dynamics interactions. (3) Leading indicators measuring the SiD maturity. (4) Significant design features mitigating hazards. (5) A Conceptual framework including safe design practice training. This research applied in-depth interviews with participants with SiD experience in New Zealand and this research proceeded through: (1) Grounded theory to reveal unearthing underpinned theories. (2) System dynamics analysis to investigate inherent motives and interactions. (3) Rigid programmatic triangulation method to decide leading indicators. (4) Computational methods in finalising significant design features. (5) Prototype integrating the elements of high technologies. The results suggested that the potential factors were attributed to a theoretical framework, including critical factors, challenges and opportunities. The identified leading indicators are legislation change and designers’ knowledge, while significant design features mitigating highly lethal hazards were investigated in the built environment, such as accessibility and spatiality. This research added significant value to theory and practice: (1) An analytical framework that includes research trends and potentials guiding future research. (2) A theoretical framework initiated with unified terminology to guide decisionmaking. (3) A system dynamics model revealing motives and interactions. (4) A programmatic method determining leading indicators. (5) The computational method pioneered the generation of significant design features. (6) A framework conceptualised in safe design training with explicit development processes outlined in the prototype. (7) A comprehensive framework encompassing enabling factors and strategies was developed.
  • No Thumbnail Available
    Item
    Enhancing Reinforcement Learning Efficiency: Novel Distributed Algorithms, Human-Inspired Reward Mechanisms, and State Space Analysis for Simulated and Real-World Applications
    (ResearchSpace@Auckland, 2025) Valencia Redrovan, David Patricio; MacDonald, Bruce A. ; Williams, Henry
    Reinforcement Learning (RL), a subset of Machine Learning (ML), has garnered significant attention because of its capacity to enable systems to learn problem-solving without the need for pre-collected datasets. Despite its historical roots and its efficacy in tackling tasks, mostly in simulation and video games, RL algorithms encounter various limitations. These include a lack of standardisation in definitions and concepts, sample inefficiency in sparse reward environments, challenges with high-dimensional state spaces, bridging of the sim-to-real gap, complex training strategies, and the necessity for meticulous hyperparameter tuning. Consequently, the widespread application of RL in solving intricate real-world scenarios with straightforward implementations remains an unresolved challenge. This thesis endeavours to address these challenges by first providing clear explanations of RL concepts and definitions. Subsequently, it identifies and analyses the limitations in diverse RL algorithms before presenting two novel solutions inspired by the human brain and the contextual intricacies of the real world. Specifically, two new algorithms named NaSA-TD3 and CTD4 are introduced. NaSA-TD3 explores the impact of human-inspired stimuli presented as a reward bonus to improve the exploration of the environment and sample efficiency in dense and sparse environments. CTD4 mitigates the overestimation bias of the Q-values and eases the implementation and training strategies of traditional categorical RL methods. Further, this thesis critically examines the applicability of Model-Based Reinforcement Learning (MBRL) in a real-world scenario in terms of sample efficiency and hyperparameter robustness by identifying its strengths and weaknesses in using dynamic model representations. Through rigorous experimentation and analysis in both real-world and simulated environments, this thesis contributes to advancing the understanding and application of RL. Validation on physical robots and standardised virtual platforms confirms the applicability of the proposed algorithms. Furthermore, detailed experiences and recommendations are presented. By providing clear definitions, thorough explanations, effective and innovative algorithms with trustworthy implementation, this thesis opens new avenues for the practical implementation of RL in diverse domains where all source codes and clear instructions on their usage are provided.
  • Thumbnail Image
    Item
    “It Belongs to Us”: Chinese Youth’s Imagined Futures
    (ResearchSpace@Auckland, 2024) Meng, Fanqi; Showden, Carisa; France, Alan
    The imagined future of young people has become a significant area of research in sociology and youth studies, providing insights into youth identities, agency, and autonomy. In western academia, researchers have adopted a dual approach to exploring imagined futures, distinguishing between short-term, personal futures and long-term, societal futures (Cook, 2018; Leahy et al., 2010). This study strives to evaluate the applicability of the western frameworks in a distinctive social context. By examining the future imaginaries of 86 middle-class young people (aged 14-15) in three schools situated in Guangzhou, China, this study posits that there are four categories of future that these adolescents envision: (1) the temporary future; (2) the personal future; (3) the national future; and (4) the societal future. Based on a Bourdieusian analysis, these categories of future imaginaries can be attributed to the hybridity and complexity of Chinese youth’s habitus, field, and capital. Dominated by both western ideologies such as neoliberalism and individualism as well as indigenous philosophies like Confucianism and collectivism, these young people’s imagined futures exhibit diverse constructs, influences, and representations in contrast to those of their western counterparts, contingent on their unique living experiences and socio-cultural circumstances. This research deconstructs the entangled everyday experiences of Chinese youth, providing valuable data to decipher the factors driving the distinctiveness of their imagined futures. Furthermore, this research examines the applicability of western theories in a distinctive social setting, providing perspectives and tools for researchers to study Chinese youth. The practical implications which arise from the methodology of this thesis, centre around a revised adaptation of Pierre Bourdieu’s thinking tools, transforming young people’s imagined futures into processes of social practice rather than simple actions, thus manifesting Bourdieu’s advancement in social research.
  • Thumbnail Image
    Item
    The Association of Arterial Stiffness with Diabetes and Microvascular Disease
    (ResearchSpace@Auckland, 2024) Beros, Angela Lukrica; Scragg, Robert; Sluyter, John
    Aim This thesis aimed to identify if arterial stiffness, predominantly assessed by pulse wave velocity (PWV), is a risk factor for diabetes and microvascular disease, and if so, whether aortic PWV estimated with a single cuff oscillometric device PWV (oPWV), which is easy-to-apply in clinical practice, can predict future disease incidence. Methods Four systematic reviews were conducted based on existing observational studies, incorporating where possible meta-analysis, to investigate the association of arterial stiffness with each of diabetes, chronic kidney disease (CKD), microvascular eye disease and neuropathy. These reviews also investigated the temporality of the associations. Three analyses were undertaken of the Vitamin D Assessment (ViDA) Study, a population-based cohort of 5108 people in Auckland, New Zealand, aged 50-84 years, to determine if arterial stiffness, estimated using oPWV, predicted incident diabetes/prediabetes, CKD and glaucoma. Findings The systematic reviews established that there appears to be a bi-directional association between increased arterial stiffness and diabetes and that increased arterial stiffness may predict incident CKD. Further, increased arterial stiffness appears to be associated with the development of age-related macular degeneration, glaucoma, retinal vein occlusion, and retinopathy. Though there is a lack of longitudinal evidence, increased arterial stiffness also appears to be associated with incident peripheral neuropathy and cardiac autonomic neuropathy. The ViDA Study confirmed that over a mean period of 10.5 years, arterial stiffness, estimated using oPWV, is associated with the development of diabetes/prediabetes, CKD and glaucoma. Conclusions Increased arterial stiffness could be an additional risk factor to be incorporated into clinical practice when determining a person’s future risk of diabetes and microvascular disease. Validated risk-prediction models incorporating increased arterial stiffness, however, must first show the utility of increased arterial stiffness as a risk factor, and investigation must be undertaken as to whether lifestyle and pharmacological interventions which lower arterial stiffness also translate into reduced incidence of these conditions.
  • No Thumbnail Available
    Item
    Tracking the Path of Alzheimer's Disease: Insights from the Integration of Cognitive and Structural Measures
    (ResearchSpace@Auckland, 2023) Chaffey, Tessa Elizabeth; Tippett, Lynette; Roberts, Reece
    Mild cognitive impairment (MCI) is recognised as a transitory state between healthy aging and Alzheimer’s disease (AD) dementia, although not all individuals with MCI progress to AD dementia. The cognitive and brain structural profiles of individuals along the at-risk AD clinical continuum remain under investigation, and determinants of whether an individual with MCI will progress to AD dementia remain unclear. The overall aim of this study was to identify markers of early cognitive and structural changes in individuals with subjective cognitive decline (SCD), amnestic MCI (aMCI), multi-domain MCI (mMCI), and AD dementia. We investigated the relationship between these measures and their ability to predict MCI outcomes. Participants from the Dementia Prevention Research Clinics underwent comprehensive neuropsychological assessment and magnetic resonance imaging at baseline (n = 237) and at two-year follow-up (n = 167 for cognitive data, n = 136 for imaging data). T1 weighted scans enabled analyses of structural measures of cortical thickness and volume. We utilised a combination of general linear model and non-parametric partial least squares (PLS) approaches. Our cross-sectional analysis identified early volumetric atrophy and cortical thinning, predominantly observable in the temporal, frontal, and inferior parietal cortices across individuals along the at-risk AD continuum. Our brain-behaviour PLS analysis revealed unique correlations between cognitive domains and structural measures, which were generally stronger in the cognitively impaired group. Our longitudinal PLS analysis indicated that atrophy rates increased along the at-risk AD continuum, particularly in the middle temporal, cingulate, and insula regions. The MCI groups demonstrated differential longitudinal changes in cognitive performance in the Attention/Working Memory, Processing Speed, Language/Semantic, Verbal Learning and Memory, and Executive Function Inhibition domains compared to Cognitively Normal (CN) and SCD groups. Finally, MCI conversion to AD dementia was associated with poorer baseline performance in memory and executive measures and widespread baseline atrophy, particularly in the temporal, middle frontal, and cingulate regions. Understanding the cognitive and structural patterns along the at-risk AD continuum and elucidating the relationship between these measures can aid the differentiability of groups along this continuum and facilitate early detection and intervention of individuals at increased risk of progressing to AD dementia.
  • No Thumbnail Available
    Item
    Novel Imaging Of Human Fascia in vivo Using Advanced MRI
    (ResearchSpace@Auckland, 2024) Perera, Meeghage Randika ; Handsfield, Geoffrey
    Fascia is an abundant connective tissue that may be involved in force transmission in ways that are poorly understood. Prior experiments suggest that fascia may play a consid- erable role on musculoskeletal force distribution in animals and humans. There is a growing interest in modelling the mechanical contribution of this tissue, which is challenging con- sidering the thin structure of the tissue and the difficulty of obtaining details from imaging. Here, I use advanced MRI to image the fascia in vivo to create physics-based simulations to explore fascia mechanics and probe its role in force transmission in the musculoskele- tal system. This thesis comprises four primary studies: firstly, the development of an MRI protocol for human fascia, followed by the application of image processing techniques to enhance image quality; an in vivo assessment of fascia and surrounding lower leg muscles in adult humans, followed by the building of a finite element geometry of several lower leg muscles and its surrounding fascia to probe the biomechanics of the tissue. In this work, using advanced MRI, this novel study involves the successful imaging of lower limb fascia in high resolution. This MRI protocol was used to image 30 healthy volunteers to create a first-ever in vivo human fascia dataset. Using this dataset, I measure human fascia thickness in vivo and show that these are consistent with available literature from dissection studies which ranges from 0.7-1.1 mm. Finite element simulations demonstrate that the presence of fascia may increase the forces transmitted from muscle to tendon compared to a system that lacks fascia. We conducted simulations on different lower limb muscles to understand the impacts of different muscle architecture, and consistently, the simulation results arrive at the same conclusion. This work is the first to my knowledge to take advantage of in vivo MRI of human fascia and build physics-based models to explore human muscle-fascia biomechanics.
  • No Thumbnail Available
    Item
    Deep and Sustained Engagement in Second Language Learning: An Exploration of Directed Motivational Currents among Chinese Adolescents
    (ResearchSpace@Auckland, 2024) Huo, Chuanwei; Stephens, Jason; Zhang, (Lawrence) Jun
    Motivation has consistently been a central concern in the study of second language (L2) and English as a Foreign Language (EFL) education. In China, many English teachers recognize the importance of motivation in addressing challenges related to low language learning efficiency, diminished learning motivation, and the problem of “dumb English”. Many scholars of second language acquisition (e.g., Larsen-freeman, 2014; Dörnyei et al., 2015; Muir & Dörnyei, 2013; Henry et al., 2015) have drawn on theories from mainstream psychology and educational psychology to understand students’ L2 or EFL learning motivation and behavior. This thesis project used Dörnyei et al.’s (2016) theory of Directed Motivational Currents (DMCs) to explore periods of intense and sustained L2 motivation among Chinese adolescent EFL learners in senior high school and university. DMCs are defined as periods of intense, highly motivated behavior aimed at achieving a specific, personally meaningful goal (Dörnyei et al., 2015). They are marked by sustained effort, deep engagement, and a positive emotional state, leading individuals to exceed initial expectations across various contexts. This thesis project employed a mix-methods sequential explanatory design procedure, consisting of two studies. In Study 1, a cross-sectional survey of Chinese high school (n = 397) and university (n = 343) students, 86.2% of participants recognized the intense motivation characteristic of DMCs, 73.5% reported having a DMC-like experience somewhere, and 64.6% indicated having DMC-like experience while learning English. Results from MANOVA indicated that students majoring in English reported higher DMC scores in English learning compared to students who were not majoring in English. Paired sample t-test showed that participants self- assessed English proficiencies improved after experiencing a DMC in English. Results from correlational analysis, indicated that participants’ expectancy-value appraisals (i.e., expectancy for success, intrinsic interest, utility value), perception of parental encouragement, and evaluation of English teachers and course were significantly correlated with DMC scores. However, after controlling for demographic and personal salience variables, results from regression analysis revealed that only expectancy for success, and parental encouragement were significant correlates of DMC scores. Additionally, qualitative data from the survey highlighted that external influences, outcome-led factors, and intrapersonal reasons initiated DMCs were mainly shaped by Chinese educational environments. Study 2 employed individual interviews with participants (n = 10) from Study 1, to explore more deeply the development and impact of the motivation process on individual EFL learners. Results revealed what conditions led to a DMC, what a DMC-cycle entailed, and how participants made use of a salient structure. Specifically, results indicated that establishing a facilitative structure right at the onset of a DMC was crucial for the sustain of the current. This importance stemmed from the impact of behavioral routines, which played a significant role in maintaining continued engagement and protecting it from potential distractions. Additionally, many participants (six out of ten) reported that their cognitive skills (e.g., attention, processing speed, executive functions, logic, and reasoning) were activated while experiencing a DMC, which encouraged them to engage more deeply in daily English learning activities.