Science: Theses and Dissertations

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Open Access
Southern Ocean dimethyl sulfide and marine aerosol production simulated with an earth system model
(University of Canterbury, 2024) Bhatti, Yusuf A.
This thesis explores the complex interplay between dimethyl sulfide (DMS) emissions, sulfate aerosols, and climate dynamics, focusing predominantly on the Southern Ocean. Understanding the role of dimethyl sulfide in aerosol production and its subsequent impact on climate models is crucial for accurate climate predictions. This thesis addresses the complexity and influence of natural biogenic aerosol production from DMS in the Southern Ocean (40 ◦S to 60 ◦S), a region with high uncertainty in simulating clouds and aerosol in current climate models. Using Earth System Models (ESMs) focusing on the UK Earth System Model (UKESM1-AMIP) addresses the uncertainties associated with DMS sources, emissions, and sulfate chemistry.
Open Access
Jesting boundaries : the impact of context on offensive humor and censorship.
(2025) Robertson, K. L.
This research examines the psychology behind people supporting censorship and “cancelling” of comedians for telling “offensive” jokes. We argue that people don’t cancel comedians because of bad jokes, but because of the inferred meaning behind the jokes, and what the audience thinks a joke reveals about the comedian’s mind (Gray, et al., 2012; Waytz, et al., 2010). Sometimes the way a joke is told reveals more about the person’s character than the words in the joke itself. We used a model of mind perception, the Heuristic of Sufficient Explanation (HOSE) to help unpack when jokes reveal bad character versus not (Vonasch, et al., 2024). We predicted that people will be more likely to be offended and support censorship when they are told a joke with offensive content that is not justified by context in how the joke is being told. Results from two experimental studies showed that missing context led to the audience misperceiving the intentions of the comedian, their mind, and their overall character due to greater offense taken, and thus audiences were more likely to support censorship in conditions where the context was missing. However, the extent to which they supported censorship across all contexts was minimal, supporting the hypothesis that a vocal minority of people are driving support for censorship of comedians telling offensive jokes (Mustafaraj et al., 2011). Understanding why individuals and groups may choose to censor comedy it allows us to examine the balance between protecting societal sensitivities and preserving comedy’s vital role in promoting free expression, challenging norms, and fostering democratic discourse.
Open Access
Detaching to recovery : exploring the role of psychological detachment on energy levels in remote workers: an 8-day diary study.
(2025) O'Toole, Regan
This study examined the relationship between telepressure and energy levels, and the relationship between telepressure and sleep quality among remote workers, while also considering the mediating effect of psychological detachment in both relationships. These relationships were investigated using an 8-day diary study design. Nineteen full-time remote workers from a range of industries in New Zealand and Australia completed two short surveys daily starting on a Wednesday and concluding the following Wednesday. The mediation analyses found no significant relationship between telepressure and evening energy, but a significant negative association between telepressure and morning energy at the between-person level was observed. Similarly, no significant associations were found between telepressure and sleep quality, psychological detachment and sleep quality, and the hypothesised mediating effect of psychological detachment on telepressure and energy levels. Interestingly, the study found a significant positive association between telepressure and psychological detachment, and psychological detachment was unexpectedly linked to lower next day morning energy levels at the between-person level. These findings highlight complexities in the recovery process in the context of remote work, suggesting that adequate recovery for remote workers might require a combination of recovery strategies rather than just psychological detachment alone. The limitations of this study are discussed along with implications for organisations looking to better support the recovery process of their remote workers by understanding the importance of effective recovery strategies and their role in promoting health and well-being.
Open Access
Imperfect detection can underestimate urban bird and butterfly richness predictions in joint species distribution models.
(2025) Anderson, Jack Liam
Urbanization has clear and significant effects on biodiversity, leading to habitat loss and degradation, homogenisation, and introduction of exotic species. As the global population increases and urbanization continues to threaten natural ecosystems, it becomes more vital to mitigate biodiversity loss by making well informed management decisions. A tool that is being used increasingly to understand how the land cover affects species, thereby assisting these management decisions, is the joint species distribution model. Joint species distribution models allow for species- and community level inferences; however, the ecological data they take is prone to biases due to variation in detectability of the species or environment. This can lead to inaccurate inferences on the drivers of occupancy and significant underestimations of species richness, both of which can hinder efforts to maintain biodiversity as urbanization and other global change drivers take effect. Nonetheless, few studies consider imperfect detection when analysing urban ecological data. Here, I conduct a historical literature review of the development of joint species distribution models to give context to the current state of this methodology, showing where each component of the model has its origin and when each line of research has converged. Following this, I develop a framework that accounts for imperfect detection in joint species distribution models, as well as providing a stepby- step user guide for future reference and to aid in usability of the framework described, using Just Another Gibbs Sampler (JAGS) and R. Finally, I use the developed framework in the context of bird and butterfly communities in Singapore with the aim of understanding how urbanization and detectability affect both bird and butterfly occupancy. By doing this I fill the gap in accounting for imperfect detection in joint species distribution models in urban ecosystems. I make comparisons between my analysis and models that overlook detectability by using information criteria, and I compare occupancy and detection responses of birds and butterflies to land cover variables including various vegetation types and traffic density. In doing so, I found that accounting for detectability increased prediction accuracy of the model, and that when detectability was overlooked while making species richness predictions, the values were considerably lower than when detectability was accounted for. This work shows the importance of accounting for detectability when making predictions of species richness, and it describes the species– and community–environment relationships that can guide effective conservation decisions in urban ecosystems. Using this framework can help with the identification of effective indicator species, as well as guide urban development to minimise loss of essential habitat and consequently urban biodiversity.
Open Access
Fault-rupture induced river avulsion susceptibility: developing a national model for New Zealand.
(2025) Anderson, Gavin
Surface-rupturing earthquakes can trigger the sudden avulsion of river channels, causing rapid and persistent coseismic flooding of previously unaffected areas. This phenomenon, known as fault-rupture-induced river avulsion (FIRA), occurs when fault displacement significantly alters river channel topography. The importance of understanding FIRA as a secondary seismic hazard was highlighted by events during the 2010 Darfield and 2016 Kaikoura earthquakes in New Zealand. This thesis develops a national model to identify and quantify FIRA susceptibility across New Zealand by integrating hydrological datasets (NIWA RiverMaps and Flood Statistics) with active fault information (NZ Active Faults Database and RSQSim earthquake simulations). The methodology applies the F-index framework proposed by McEwan et al. (2023), which quantifies FIRA potential based on the ratio of fault throw plus discharge-dependent depth to bank full depth at each fault-river intersection. The model successfully identified 3,796 potential FIRA-susceptible fault-river intersections nationwide, with 451 involving waterways equal to or larger than the Hororata River. Regional analysis revealed higher concentrations of FIRA-susceptible sites in the Bay of Plenty, Canterbury, and Marlborough regions. Validation against historical events showed the model effectively located known FIRA occurrences from the Kaikoura and Darfield earthquakes, though with some limitations in accurately predicting F-index values due to complex fault displacement patterns and challenges in modelling bank full depths of large, braided rivers. This research establishes New Zealand's first nationwide assessment of fault-induced river avulsion susceptibility. The approach creates a structured methodology for identifying high-risk fault-river intersections and determining which sites require thorough localised examination. The methodology developed offers a template for similar assessments in other tectonically active regions and contributes to improving earthquake hazard assessment and disaster preparedness planning.
Open Access
Turnover intention of new graduates in Japan : a cross-cultural study on the effects of person-job fit, the mediating effect of employee wellbeing and the moderating effect of recruitment systems..
(2025) Matsumoto, Keito
Over the past 30 years, Japan’s three-year turnover rate for new graduate employees has never dropped below 30%. Analysing Japan’s societal context reveals the possibility that the country’s unique simultaneous recruitment system, which fails to foster person-job fit, may be responsible for its high turnover. Thus, following the theory of met expectations, the current study investigated whether differing recruitment systems moderated the direct and indirect relationship between person-job fit and turnover intention via workplace wellbeing in Japanese and New Zealand new graduate employees. This cross-cultural study analysed cross-sectional quantitative and qualitative data from 157 Japanese and 142 New Zealand new graduate employees to conduct mediation, moderated mediation and content analyses. Mediation analyses supported the negative indirect effect of person-job fit on turnover intention via workplace wellbeing in Japanese new graduates, suggesting the importance of facilitating person-job fit to minimise Japanese new graduates’ workplace wellbeing and subsequent turnover intentions. However, this indirect effect was not found among New Zealand new graduates. Moderated mediation analyses supported the moderating role of recruitment systems, where the indirect effect of person-job fit on turnover intention via workplace wellbeing was stronger in Japanese new graduates than in New Zealand new graduates. This study makes vital contributions to the limited literature by establishing the importance of person-job fit in influencing Japanese new graduates’ workplace wellbeing and subsequent turnover intention and revealing the exacerbating role of the simultaneous recruitment system on this negative indirect relationship that amplifies Japanese new graduates’ expectations to enter a job that aligns with their knowledge, skills and abilities (KSAs). Thus, these results suggest the need for Japanese organisations to rethink their approach to recruitment to ensure that new graduates’ person-job fit is facilitated.
Open Access
Investigating γ Doradus pulsating stars in spectroscopic binary systems.
(2025) Simmonds, Noah
This thesis presents the results of an orbital and asteroseismologic analysis of three γ Doradus stars in spectroscopic binary systems. The three binary systems are HD 147787, HD 214291, HD 10167 and they were observed using photometry and spectroscopy. Photometric data was obtained from the Transiting Exoplanet Survey Satellite (TESS) and spectroscopic data was obtained using the 1.0-m McLellan telescope with the High Efficiency and Resolution Canterbury University Large Echelle Spectrograph (HERCULES) at the University of Canterbury Mt John Observatory. A total of 7 sectors of data from TESS were analysed and over a thousand spectroscopic observations from Mt John were reduced using the MEGARA pipeline. Cross-correlated line profiles were obtained for each spectroscopic observation and were analysed. The Specbin spectroscopic binary analysis software was used to conduct an orbital analysis of all three systems. HD 147787 was determined to have an orbital period of 39.88 days, HD 214291 had an orbital period of 1.742 days, and HD 10167 had an orbital period of 9.319 days. Other orbital parameters were calculated, and the artificial orbital fit data were used to remove the orbital velocities from the components in each of the binary systems. Gaussian fits to the cross-correlated line profile were used to model and remove the non-pulsating stars from the combined line profile. Using the software packages FAMIAS and SigSpec for frequency analysis of photometric and spectroscopic data, pulsation frequencies were identified for the pulsating component in each binary system. HD 147787 had six identified pulsation frequencies, HD 214291 had three frequencies for star 1 and two for star 2, while HD 10167 had three frequencies determined. All measured frequencies were within the γ Doradus frequency range of 0.3 to 3 days⁻¹. From the spectroscopic mode identification with the FAMIAS software, all identified pulsation modes are low-degree modes (l ≤ 3). From the frequency analysis and mode identification, all stars were confirmed to be γ Dor stars, with refined pulsational frequencies and improved orbital parameters.
Open Access
Evaluation of MRI protocols for gynaecological brachytherapy at Wellington Blood and Cancer Centre.
(2025) Cayanan, Chrizia
High dose rate (HDR) brachytherapy (BT) is a treatment technique for cervical cancer that relies on placing radioactive sources within the patient using applicators to deliver high radiation doses to the tumour. Given the high doses associated with HDR BT, imaging plays a critical role in ensuring accurate tumour localisation and source placement within the patient. At the Wellington Blood and Cancer Centre (WBCC), the current workflow relies on computed tomography (CT) for applicator reconstruction and magnetic resonance imaging (MRI) for target contouring. This process involves multiple patient transfers and long treatment planning times, increasing the risk of discrepancies between the planned and delivered dose. Implementing an MRI-only workflow or reducing the number of images acquired will substantially simplify the imaging protocol, with a consequent improvement in treatment accuracy. This thesis aims to develop the methodologies for evaluation of MRI sequences and the resulting workflows to be used for cervix HDR BT planning at WBCC. An MRI-safe phantom was fabricated for MRI sequence optimisation, and a methodology for assessing image quality was developed to compare new MR sequences against the current protocol. Processes for evaluating the equivalence of treatment planning on test workflows involving a new MR sequence against the standard workflow in terms of applicator reconstruction and high-risk clinical target volume (HRCTV) contouring variability, as well as resource efficiency, were established and tested on three patients. The current workflow consists of four 2D MR sequences and a CT scan for at least the first treatment fraction. Two test workflows were considered: Test1 consisted of sagittal and high-resolution axial 2D MR sequences for target contouring, and a CT scan for applicator reconstruction; and Test2 comprised a sagittal and high-resolution 2D MR sequences for both applicator reconstruction and target contouring. An MR-based applicator reconstruction methodology was developed for the titanium ring and tandem (R&T) applicator and titanium needles for the Test2 workflow. Among the workflows, Test2 was the most time-efficient, reducing the time required for image registration, contouring and applicator reconstruction by approximately half compared to the standard workflow. Inter-observer applicator reconstruction variability was higher for the MR-based method (Test2) than the CT-based method (Test1 and standard). For MR-based applicator reconstruction, the mean inter-observer distance for the ring, tandem and needles were 0.9 mm, 1.5 mm, and 0.7 mm, respectively. Whereas for CT-based applicator reconstruction, the respective mean inter-observer distances were 0.4 mm, 0.2 mm, and 0.5 mm. On the other hand, the standard workflow appeared to have the highest inter-observer contouring variability for the HRCTV, with a mean conformity index (CI) and average Hausdorff distance (HDave) of 0.68 and 2.2 mm, respectively. Test1 had a mean CI and HDave of 0.73 and 1.9 mm, respectively, while the respective values for Test2 were 0.72 and 1.9 mm. The test workflows demonstrated improved inter-observer contouring agreement, suggesting that these workflows may enhance clinical consistency. This thesis successfully developed the methodologies needed to evaluate MR sequences. Although the small sample size prevents definitive conclusions on the optimal workflow, the findings provide valuable insight into contouring and applicator reconstruction uncertainties at WBCC. The results indicate that the number of of MRI sequences in the current protocol could be safely reduced from four to two. The developed methodologies for MRI sequence evaluation in this project will support future research and clinical implementation of an optimised imaging protocol. While further work is necessary for MR-based applicator reconstruction, the findings from this project are promising.
Open Access
Exploring leadership and employee perspectives on the value of workplace wellbeing and how it should be supported.
(2025) Richardson, Ella Grace
In an era where 'wellbeing' is becoming a corporate buzzword, there is a growing need for clarity on what constitutes meaningful support for employees, and how both leaders and employees can work together to move beyond tokenistic gestures toward creating supportive work environments. Historically, literature has primarily focused on the broader effects of wellbeing support in the workplace, often overlooking the nuanced perceptions of different organisational levels on their understanding of wellbeing support. To explore this, the current study examined how leaders and employees perceive, prioritise and support workplace wellbeing, highlighting key areas of alignment and discrepancy. Using a qualitative approach within a case study framework, the research investigated leaders' and employees' lived experiences and perspectives. Twelve semi-structured interviews were conducted with seven leaders and five employees from within the organisation. Thematic analysis revealed two overarching themes describing participants’ conceptualisation of wellbeing and the support mechanisms at the individual, leadership and organisational levels. The findings suggest that workplace wellbeing is shaped by a dynamic interplay of factors that are different for everyone, emphasising that workplace wellbeing cannot be approached as a one-size-fits-all solution. These findings offer practical implications for organisations by providing insight into the factors that shape leaders’ and employees’ understanding of workplace wellbeing within a specific organisational context, highlighting the importance of effective leadership and tailoring support to meet employee expectations and organisational goals.
Open Access
Aroha and manaakitanga : the effects of a compassion-based event on happiness, loneliness, and social connectedness.
(2025) Park, Eddie Sang-Yool
Over the past decades, there has been growing interest in the benefits of compassion and its role in psychological well-being. However, research investigating structured, guided interventions designed to enhance these factors remains limited. The present study investigated whether participating in an Unchatter event – a structured workshop involving guided compassion-based exercises – would lead to increased happiness and social connectedness, and reduced loneliness. A sample of 26 participants completed self-report measures of happiness, loneliness, and social connectedness before and immediately after the event, with weekly follow-up questionnaires administered over a four-week period. Results indicated a significant increase in happiness and a significant decrease in loneliness after the event, although no significant changes were detected for social connectedness. Over the four-week follow-up period, results from repeated measures ANOVAs indicated no statistically significant changes in happiness, loneliness, or social connectedness. However, mean difference analyses indicated a trend of gradual increases in happiness and social connectedness, and a steady decline in loneliness over time. Additionally, a sensitivity analysis indicated that the study was likely underpowered to detect smaller effects, as only very large effects (f > 1.166) could be reliably detected. The findings from this study suggest that although structured compassion-based events may result in immediate psychological benefits, sustaining these positive effects over time may require repeated sessions. Future research could build on these findings by further investigating the long-term impacts of compassion-based interventions and employing strategies to improve their sustained positive impacts on psychological well-being.
Open Access
Co-occurrences of estuarine foundation species and associated epibiota along environmental gradients – with implication for future warming.
(2025) Clemente, Ken Joseph E.
Estuarine ecosystems are stressful yet productive environments, where foundation species (FS) such as seagrasses, seaweeds, and bivalves play key roles in sustaining biodiversity, ecological functions, and ecosystem services. However, the outcomes of interactions among co-occurring FS, and their cascading community effects may vary along spatiotemporal stress gradients. This complexity remains poorly understood, especially regarding if and how FS-driven facilitative interactions become more pronounced, and thus more valuable, in a conservation context. To address this research gap, this thesis used supplementary methods to disentangle temperature-related spatiotemporal drivers that affect the abundance, distribution, and facilitation among co-occurring FS and their wider consequences for biodiversity. Specifically, I examined: (i) reciprocal impacts among ubiquitous aquatic FS (angiosperms, seaweeds, bivalves) using a global meta-analysis, (ii) the response of seagrass to marine heatwaves using satellite-based remote sensing, (iii) co-occurrence patterns of seagrass, seaweeds, and shells across estuarine stress gradients, (iv) spatiotemporally contingent facilitation cascades arising from shell–seaweed interactions, and (v) the potential to monitor facilitation cascades across spatial resolutions. Spatiotemporal factors that covary with temperature - such as latitude, tidal elevation and seasonal variation - were central to understand ecological responses of FS, reflecting the broad importance of temperature as a fundamental driver of community structures. In Chapter 2, I analysed 1942 effect sizes extracted from 148 studies to assess reciprocal impacts among aquatic FS. This global meta-analysis showed that seaweeds consistently had negative effects on angiosperms and that angiosperms and bivalves generally facilitated each other, though some responses (e.g., bivalve growth, angiosperm abundance) were not always enhanced. Furthermore, bivalves generally elevated seaweed growth, while seaweeds had minimal effects on bivalves. Importantly, bivalve interactions with other FS were generally more positive at higher temperatures, suggesting that facilitation involving bivalves, may become increasingly important in restoration as the climate continues to warm. In Chapter 3, I used high-resolution PlanetScope satellite imagery to monitor intertidal and shallow subtidal seagrass (Zostera muelleri) across 20 New Zealand estuaries over five years, encompassing the 2017/18 marine heatwave - the warmest summer on record in New Zealand. This study showed that Zostera was resilient to heatwaves but also that abundances were highly dynamic on both seasonal and annual scales. In Chapter 4, I conducted extensive drone and camera-based surveys to test how abundances and co-occurrences of seagrass (Z. muelleri), seaweeds (Ulva spp., Gracilaria chilensis), and shells (mainly the cockle Austrovenus stutchburyi) varied across spatiotemporal gradients, reflecting temperature (latitudes, seasons, intra-seasonal sampling), salinity (site effects) and desiccation (elevation) stressors. I found that spatial gradients had a stronger influence on FS than temporal factors and that seagrass was most abundant often co-occurring with entangled seaweeds and embedded shells. This study highlighted that estuarine FS are rarely monocultures but instead create multi-FS assemblages with high habitat heterogeneity. In Chapter 5 I tested, using high-order factorial mensurative and manipulative experiments, how facilitation cascades with shells and seaweeds varied across spatiotemporal contingencies, like seasons, intraseason, latitudes, tidal elevations, habitat matrices, and FS sizes. I identified and counted >65,000 small mobile epifaunal invertebrates associated with the FS and found that higher-order interactions were much less important compared to simpler two-way interactions or single factor effects. Specifically, facilitation of epifauna was strongest on larger and more complex seaweeds, at near-ocean sites, in deeper intertidal zones, and during warmer seasons. This study highlighted a relatively tidy, not messy, control of biodiversity of estuarine epifauna, and that high-order factorial sampling can help unravel and rank co-occurring environmental drivers and better understand ecological contingencies. Finally, in Chapter 6, I integrated satellite, drone, camera, field collections, and laboratory measurements to assess co-occurrences of Austrovenus and Ulva and their facilitation of mobile epifauna. I found, across wide spatiotemporal scales, that Ulva frequently attached to live or dead Austrovenus, that Ulva was more abundant in winter while Austrovenus were more abundant near the ocean, and that larger Ulva provided a better habitat for epifauna than Austrovenus. This study also showed that remote sensing can efficiently monitor these processes, with potential applications for estuarine management strategies. Overall, this thesis advances the understanding of how temperature-related spatiotemporal drivers influence interactions among co-occurring estuarine FS. The findings emphasize the importance of considering spatial heterogeneity and temperature in conservation and management strategies. By highlighting the resilience of FS to climatic extremes and the predictable nature of facilitation cascades, my work provides valuable insights for predicting ecological responses to climate change and for preserving the biodiversity and functionality of estuarine ecosystems.
Open Access
Is everyone a transport planner? An analysis of opinions on streetscape changes in Ōtautahi Christchurch.
(2025) Smith, Tanya
The way our streets change over time is a consistently contested issue amongst communities and governments. Streetscape changes, such as the development of cycleways, roads, traffic calming, and management systems, often face perceived and tangible challenges related to cost, convenience, and the overall appeal of the project. The resulting contestation goes beyond the formal realm of councils and government bodies; it directly impacts members of the community, with public opinions increasingly voiced on digital and external platforms. This heightened visibility often contributes to the spread of misinformation, complicating the public’s understanding of project intentions and outcomes. Historically, streetscapes have played a pivotal role in urban planning, reflecting shifts in societal needs and values (Said & Samadi, 2016). Whether designed for efficient traffic flow, pedestrian comfort, or social interaction, the design of streets shapes our daily experiences and, in turn, our neighbourhoods. As such, it is not surprising that streetscape changes can be met with resistance, particularly when they challenge the status quo. However, what happens over time to that resistance? This thesis examines how public opinions evolve following the implementation of major streetscape alterations, identifying opinions about changes in both before and after the implementation and comparing them. Initial perceptions will be drawn from consultation submissions, which will be analysed to identify key themes. These findings will be compared with primary data collected through semi-structured interviews with residents, businesses, and frequent users of the affected streets. The combination of qualitative thematic analysis and submission review will provide insights into both attitudes toward transport projects and the consultation process itself. By examining shifts in community sentiment and identifying perceived gaps in engagement, this research aims to highlight areas for improvement in future consultation practices. Despite initial resistance, many respondents developed strong support for the projects after experiencing the changes, particularly those using active transport or with children benefiting from improvements. Concerns about safety and aesthetics shifted to praise, highlighting the role of firsthand experience in acceptance. However, consultation shortcomings led to frustration, with many feeling their feedback was overlooked. Confusion over project objectives and design fuelled resistance. Trials and temporary activations emerged as valuable tools for increasing acceptance. The discussion underscores the importance of clear communication, transparent decision-making, and inclusive engagement to maximize community wellbeing and ensure socially beneficial urban projects.
Open Access
Landslide dam hazard and exposure modelling for an alpine fault earthquake.
(2025) Bain, Daniel
The natural blockage of a river via landsliding is a common phenomenon in mountainous landscapes known as a landslide dam. Landslide dams can fail suddenly and catastrophically, releasing impounded water that can put downstream communities at risk of outburst flooding. The impoundment of water can inundate the area upstream and form a lake, which in some cases can remain in the landscape for millennia. Thus, there is a growing body of research focused on the processes involved in the formation and failure of landslide dams. However, there is a limited understanding of landslide dam hazard and exposure prior to their formation. This thesis develops new methods for assessing pre-formation landslide dam hazard and exposure, applying these to a future earthquake scenario on the Alpine Fault in Aotearoa New Zealand. In the absence of empirical Alpine Fault landslide data, this study investigates the New Zealand Landslide Dam Database to inform critical modelling decisions. In doing so, this thesis develops a method framework that considers the likelihood and intensity of landslide dam formation to quantify the hazard posed by rivers. To determine whether future landslide dam formation may expose communities to outburst flooding, this study models a potential flood area for each catchment. Using both hazard and exposure, this research identifies catchments that pose high landslide dam threat, which is critical for improving Aotearoa New Zealand’s disaster resilience. In an Mw 8.0 Alpine Fault earthquake scenario, this thesis finds that > 28,700 permanent residents are exposed to the 100 most threatening catchments. The highest threat catchment is the Callery River in Franz Josef, exposing ~570 permanent residents and potentially > 3,000 tourists to landslide dam hazard within the 99th percentile. Having similar landslide dam hazard to the Callery River, the Cleddau River in Milford Sound exposes ~80 permanent residents and potentially ~3,700 tourists. The Shotover River in Queenstown also poses high landslide dam threat as it exposes > 8,800 permanent residents to high landslide dam hazard. Another notable example is the Haupiri River, which exposes > 700 permanent residents including the Gloriavale Christian Community. The results of this thesis show that landslide dam hazard and threat in an Alpine Fault earthquake is concentrated in catchments west of the Southern Alps. For example, 58 of the 100 most threatening catchments are in the Westland District, with 28 of these exposing Franz Josef. This research contributes to the wider body of landslide dam literature by developing methods for the assessment of landslide dam hazard and exposure before their formation. While these methods are applied to an earthquake scenario, the conceptual model is trigger-agnostic and can be altered for aseismic landslide dam modelling. Such modelling is critical for identifying locations where future landslide dam formation is likely as well as determining whether communities are exposed to potential outburst flooding. There is an opportunity for future research to focus on the catchments identified within this study. Furthermore, the identification of specific high-threat catchments can guide emergency planning and response for a future earthquake on the Alpine Fault.
Open Access
Purple non-sulphur bacteria biofilm : the effect of mixing speed and settling time on biofilm growth.
(2025) Attamimi, Nida Nafila
There is an increasing interest throughout the world in alternative wastewater treatment systems with lower power consumption than those of conventional aerated systems. Reactors based on purple non-sulfur bacteria (PNSB) present a promising alternative as they can function under anaerobic or microaerophilic conditions. This means they utilize little or no aeration, which is typically the largest energy use in a wastewater treatment plant. In bioreactors, the formation of biofilms enhances the retention of bacteria and biomass accumulation, consequently improving reactor performance and increasing treatment efficiency. This study examines the effects of mixing speed, substrate concentration, and settling time on biofilm growth and reactor performance in a sequencing batch reactor (SBR) enriched for PNSB. Three identical 1.5 L reactors were operated at different mixing speeds (100, 150, and 200 rpm) to evaluate biofilm formation on 1 cm² square mesh media and to evaluate the impact of mixing intensity on reactor efficiency. The study was divided into three phases: Phase 1 focused on biofilm formation and suspended biomass dynamics affected by the mixing speeds, and Phase 2 focused on how substrate concentration change can influence biofilm growth. At the same time, Phase 3 analysed the influence of reduced settling time on reactor performance. Key parameters assessed included total suspended solids (TSS), volatile suspended solids (VSS), particle size distribution, extracellular polymeric substances (EPS), and total organic carbon (TOC) removal. Results indicate that lower mixing speeds (100 rpm) promoted higher biomass retention and biofilm thickness, while higher speeds (200 rpm) enhanced microbial activity but led to lower settling ability. The increase in substrate concentration (1.5 times the original concentration) required an adaptation period of 23 days, after which all reactors exhibited increased biomass production. Reactor 1 consistently demonstrated higher TSS concentrations and improved settling characteristics, while Reactors 2 and 3 showed lower settling efficiency due to the formation of smaller aggregates from increased shear forces. Biofilm on mesh media developed faster and more robustly under increased substrate availability, with Reactor 1 forming the densest biofilm and Reactor 3 producing more elongated, thinner structures. The final phase of the study, which involved reducing the settling time from 45 minutes to 30 minutes, demonstrated that lower settling times influenced biofilm stability, as evidenced by a reduction in carbohydrate and protein concentrations after the change. In conclusion, hydrodynamic forces, substrate concentration, and settling time affect biofilm development on the mesh media in the PNSB system using SBR. Increased mixing speeds facilitate initial biofilm adhesion, while reduced mixing speeds promote biofilm stability over time. Reduced settling time can significantly change the production and structure of extracellular polymeric substances (EPS), which in turn can influence biofilm development. However, due to time constraints, the study was limited in assessing the long-term effects and in reaching an equilibrium, thus requiring further monitoring to confirm the sustained impact of these changes. Adjusting the operational settings to balance mixing forces, substrate concentration, and settling behaviour is important. The findings of this study will help improve PNSB based wastewater treatment efficiency and improve biofilm stability. These outcomes will potentially promote low-energy treatment processes using PNSB for sustainable wastewater treatment.
Open Access
Exploring spillover, turnover intention, burnout and family configuration dynamics among experienced audiologists.
(2025) Kokatnur, Sonia
Objective: This study addresses the research gap in work-family dynamics among audiologists by examining family structures' influence. It explores the intersection of spillover, burnout, turnover intentions and family structure, an underexplored area in audiology. The study also focuses on four spillover components (negative work-to-family, negative family-to-work, positive work-to-family, and positive family-to-work), to identify key work and family domain predictors and their professional implications. Design: An online questionnaire was administered, comprising self-made questions for the demographics, work and family domain sections. The MIDUS 2 questionnaire was used to examine all four domains of spillover, Maslach's Burnout Inventory was used to assess burnout and the 5-item Turnover Intention Scale from Rahman (2020), an adaptation of Roodt’s (2004) scale, was also utilized to assess turnover intention. Study Sample: 98 clinicians completed the survey, which included 49 parents and 49 non-parents. These clinicians practiced in Australia, Canada, Denmark, Germany, Ireland, Israel, Japan, New Zealand, Portugal, the U.K., and the U.S.A. Results: The results indicate significant differences in all four forms of spillover between parents and non-parents, with NWFS being the only form of spillover showing significant differences between partnered and single parents. Work predictors (work hours, work flexibility, work support, job position, and parental status) revealed that work flexibility had a significant negative association with NWFS and job position showed a significant positive association with NWFS. Parental status also showed a significant negative association with NWFS, with parents experiencing less NWFS than non-parents. When exploring the same work predictors on PWFS, work flexibility showed a significant positive association, while parental status had a significant negative association, showing parents experiencing less PWFS than non-parents. All other predictors were not significant for NWFS or PWFS. Additionally, relationship status, rather than parental status, was used with the same work predictors. Only work flexibility showed a significant negative association with NWFS, while other predictors were not significant. Family predictors (number of children, age of the youngest/only child, family support, and relationship status) indicated that the number of children had a significant negative association with NFWS, while the other predictors were not significant. Additionally, the overall model examining family predictors for PFWS was not significant. When exploring burnout, NWFS was significantly positively associated with emotional exhaustion, whereas PFWS and parental status were significantly negatively associated with emotional exhaustion, with parents experiencing less emotional exhaustion than non-parents. The model examining NWFS and parental status for depersonalization was not significant. Lastly, emotional exhaustion and parental status were significantly positively associated with higher turnover intentions. Similarly, depersonalization and parental status also showed a significant positive relationship with turnover intentions. Both analyses indicate that parents experience greater turnover intentions than non-parents. Conclusion: This study examined spillover, burnout, turnover intentions, and family structure among audiologists. Parental status significantly predicted spillover, while relationship status affected only NWFS. Workplace flexibility and support were also found to be key in reducing negative spillover and enabling positive spillover, whereas family predictors had less impact, which is possibly unique to audiology. Additionally, negative spillover was strongly correlated with emotional exhaustion, while positive spillover mitigated its effects. Parent audiologists also reported lower emotional exhaustion but higher turnover intentions, highlighting work-family balance challenges. Hence, these findings highlight the need for organizational strategies to improve clinician well-being and retention.
Open Access
Rockfall risk and mitigation performance following the 2016 Kaikōura earthquake.
(2024) Mabin, S. G.
The 14th November M7.8 Kaikōura earthquake struck the northeastern coast of the South Island of New Zealand and caused intense shaking that resulted in over 30,000 coseismic landslides. State Highway 1 and Main North Railway Line were affected by landslides at 40 sites north and south of the Kaikōura township, cutting it off from the outside world. The government prioritised re-opening of these transport links within one year and this was effectively achieved as a result of major engineering works to clear and stabilise slopes above the transport corridor. Many active and passive rockfall mitigation measures were designed and constructed, and a monitoring program was set in place to document the success of these works. This thesis analyses these monitoring data and the main research questions addressed were: • How has the rate of rockfall varied with time along the transport corridor south of Kaikōura since the 2016 earthquake? • What is the quantified performance of the mitigation measures at reducing the rockfall impacts on the transport corridor? Three distinct rockfall rate and volume periods were observed: an initial 10-month period of high rockfall rate with one rockfall event every 22 hours, a 3 year and 8 month period of declining but still moderately high rates of one rockfall event every 80 hours, and after 4 years and 6 months a return to assumed pre-earthquake background rate of rockfall of one rockfall event every 300 hours. Rainfall has a weak correlation to rockfall count and volume and therefore time since the earthquake is suggested to be the main influencing factor. Rockfall is equally as likely to occur at mitigated sites as non-mitigated sites, but most of the rockfall volume comes from non-mitigated sites, when excluding a very large outlier. Most rockfall volume appears to have been unsuccessfully captured by mitigation, or occurred where mitigation wasn’t present. However, the initial definition of success used was considered inadequate, and a new definition and tolerances of success were explored, including whether mitigation was able to capture block sizes of < 0.2 m3 and volumes of < 0.5 m3. These metrics more closely align with mitigation design practices and are therefore considered a ‘fairer’ measure of mitigation performance. For both these measures, anchored mesh and active mitigation types had the highest percentage increases from the previous definition of success. The results help to understand the effectiveness of the approach taken by NCTIR and highlight the use of the New South Wales Guide to Slope Risk Assessment in New Zealand setting. This research may form a basis for design of future earthquake recoveries in a future earthquake event such as an Alpine Fault or Wellington Fault earthquake.
Open Access
Development of a TOPAS/Python based toolkit for nuclear medicine imaging applications.
(2025) du Toit, Robert Pierre
Computer simulations are a powerful tool for modelling and predicting complex phenomena in the natural world, where they model the environment, financial markets, and medicine. The application of simulations in the world of medical physics are evident, with examples such as modelling particle transport. In this research, a functioning simulation of a single-photon emission computed tomography system was developed as a tool for medical physicists to use for validation and experimentation. Computer simulations are particularly useful in medical physics as they allow for non-invasive experimentation without the potential for harm to any patients. A collimator extension was successfully developed in the TOPAS C++ extension framework. The extension allows users to create hexagonal-holed collimators of any size, and allows modification of key parameters such as: material, hole length, hole diameter, and septal thickness in a way akin to definitions of other geometry components. The collimator behaviour was validated, showing that it successfully absorbed diagnostic energy photons at non-perpendicular angles, allowing for the resolution of sources of different shapes. Measuring collimator efficiency showed that efficiency was typically higher than expected, however this result was inconclusive. A digitiser element was developed to simulate the non-collimator elements of the gamma camera, namely the scintillation crystal, photomultiplier tubes, and associated electronics. The Python-based solution was able to match the behaviour of a real system in terms of energy resolution and windowing across multiple tests. The spatial blurring and resolution tests showed that the digitiser consistently over-blurred detected photons leading to unrealistically poor spatial resolution performance over a range of target resolutions in the typical system range. Finally, the capabilities of both sections integrated together were tested by simulating a myocardial perfusion imaging study. Sources simulating a normal and abnormal heart were imaged at a range of projection angles before then having a central slice processed into a sinogram and reconstructed. The projection images were transformed into sinograms and those were successfully reconstruction with both a backprojection and filtered backprojection method. Unfortunately, low photon counts in each projection image, especially in the abnormal heart simulation, led to poor quality reconstructions where it was not clear if a slice corresponded to the normal or abnormal heart source.
Open Access
Paws and effect : oxytocin’s impact on canine social dynamics in a doggy daycare environment.
(2024) de Rybel, Elysha Maiwenn
I investigated the role of oxytocin in modulating social behaviours and stress regulation in dogs within a high-energy doggy daycare environment, focusing on how diverse social contexts influence physiological and behavioural responses. Given oxytocin’s involvement in social bonding and pro-social behaviours, I aimed to explore its effects on canine sociability and stress resilience by examining hormonal and behavioural data across varied daycare conditions. Two primary approaches were employed: (1) measuring oxytocin concentrations through saliva swabs in three key contexts; arrival, play, and nap, and (2) analysing behavioural observations, including Play, Avoidance, Human Approach, and Dog Approach, within the play area. Significant relationships emerged between oxytocin levels and certain behaviours, with heightened Human Approach Behaviour correlating with increased oxytocin levels in the play area, suggesting dogs rely on familiar handlers as a source of emotional support in socially stimulating environments. Oxytocin levels were highest in the nap area, where dogs anticipated social re-engagement, highlighting an anticipatory hormonal response. Additionally, findings revealed important trends related to daycare experience and sex; male dogs exhibited greater variability in oxytocin levels, and those with moderate daycare experience showed fluctuating responses, suggesting that structured socialization affects hormonal adaptation over time. These results underscore the impact of social environments on both physiological and behavioural outcomes, with significant implications for enhancing welfare strategies in high-stimulation settings like shelters and pounds. By understanding oxytocin’s role in promoting pro-social behaviours and stress reduction, my study offers insights into designing structured routines and socialization programs to support canine well-being in both daycare and shelter contexts.
Open Access
The migrant experience of decent and meaningful work : a qualitative exploration.
(2025) Hulston, Paul
New Zealand increasingly attracts skilled migrants seeking personal and professional growth, safety, and political freedoms. However, many migrants arrive in New Zealand and realise that their qualifications are not recognised by employers, often forcing them into work for which they are overqualified. Under these conditions, questions arise about migrants' access to – and experiences of – decent and meaningful work. Research examining decent and meaningful work among migrants, particularly those who are overqualified, is scarce and primarily has focused on barriers to accessing decent and meaningful work. The present study addresses gaps in the literature by qualitatively exploring how skilled migrants’ views and experiences of decent and meaningful work evolve and inform career and life decisions and outcomes. Sixteen semi-structured interviews were conducted with skilled migrants in New Zealand who had worked in roles for which they were overqualified at some stage in their careers. Thematic analysis identified four key themes that characterise skilled migrants’ experience of decent and meaningful work: access to meaningful work, redefining the role of work, deriving meaning amidst occupational change and professional identity resilience. This study makes important contributions to the literature by providing insight into the subjective and evolving nature of decent work, and how migrants experience meaningfulness in work roles and environments where traditional sources of work meaning may be compromised. This study offers valuable practical implications, demonstrating that promoting and facilitating decent and meaningful work for skilled migrants enhances their overall wellbeing and quality of life and how doing so, is in the best interests of organisations.
Open Access
Intersectionality of gender pay gap and hearing impairment in the workforce.
(2025) Dyson, Ella
More than 1.5 billion people worldwide have hearing loss to some degree (World Health Organization, 2024). Hearing loss has been associated with higher rates of unemployment and lower income levels (Kim et al., 2021). Similarly, an abundance of literature conveys that women are often paid less than their male counterpart (Fortin et al., 2022; Narayan, 2024). This is significant considering economic comfort has been shown to affect individual wellbeing (Lamu & Olsen, 2016). Therefore, the current study aimed to examine the intersectionality between the gender pay gap and hearing impairment pay gap for workers in the United States of America. Participants were administered a survey that collected data regarding hearing level status, hourly rate and nature of work. An ANOVA analysis revealed significant differences on pay rate based on hearing impairment and/or gender across all job professions included in the study. Additionally, the analysis revealed an intersectional relationship between gender and hearing impairment on pay rate. Therefore, it is suggested that employers and organizations are encouraged to develop their understanding about disabilities in the workforce and educate themselves about the necessary accommodations that can be made to support disabled workers. Further, evidence of intersectionality in the current study reinforces the need for intersectional research and advocacy. Keywords: hearing impairment, gender, pay gap, intersectionality.