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    Organic complexation in karst cave systems: implications for transition metal incorporation into speleothems
    (The University of Waikato, 2024) Höpker, Sebastian Niels
    The accurate prediction of future climate scenarios heavily relies on the robust understanding of the magnitude and drivers of past climate variability. Amongst the various materials used to study historic climate beyond the instrumental record, secondary cave carbonate deposits, or speleothems, have proven to present particularly valuable archives of numerous environmental processes over a range of temporal and spatial scales. In this context, trace elements included in speleothems are increasingly used to bolster speleothem-based records of past climates and environments (often primarily based on stable isotope proxies), with Mg/Ca and Sr/Ca ratios presenting the most widely interpreted elemental signatures indicative of hydrological processes in the karst. More recently, however, a novel proxy system based on the concentrations of first-row transition metals in stalagmites has been proposed to potentially offer a first means to quantitatively reconstruct past cave drip rates, and hydroclimate by extension. The transport from the surface to the site of speleothem formation of transition metals, such as Co, Ni, or Cu, is understood to be largely governed by the formation of organic metal complexes (OMCs) with ligands present in natural organic matter (NOM). This organic association can evidently facilitate the deposition of organically-complexed metals in response to strong infiltration events, however, has also been suggested to enable a mechanistically distinct and largely undefined inclusion pathway for metals into calcite. Specifically, the availability of transition metals at speleothem surfaces for partitioning into the crystal phase may arguably be driven by the rate-dependant dissociation (or ‘decay’) of OMCs, which is in turn predicted to depend on their residence time at speleothem surfaces. OMC decay kinetics may thus present a potentially viable link between metal concentrations in stalagmites, and the residence time of OMCs at their surfaces. This thesis further investigates these interactions between selected first-row transition metals (Co, Ni, Cu) with NOM, aiming to advance the applicability of respective metal signatures in speleothems to palaeoclimatic reconstructions. In the first research chapter, the decay of OMCs is characterised in a first comparative study of in-cave OMC dissociation kinetic signatures by means of competitive ligand exchange experiments. Performed on water samples and soil extracts from eight Aotearoa New Zealand caves, the findings demonstrated that natural organic ligands decisively limit transition metal availability (by example of Co, Ni, Cu) at the dripwater-speleothem interface, whereas alkaline earth metals (here: Mg, Sr) are essentially unaffected by organic interactions in solution. OMC stability was found to occur in the hierarchy of Cu ≈ Co > Ni, with a variable fraction of all three metals bound very strongly to effectively inert complexes. OMC stability was overall enhanced in soil extracts, presumably due to higher organic content and aromaticity. The study further uses empirical estimates of OMC decay rate constants to assess the time-dependent release of metals at stalagmite surfaces in a simple forward model. This exercise predicted that the decay of transition metal complexes was most sensitive on time-scales relevant to typical cave drip points (up to ca. 40 drips min-1), and increasingly so towards lower flow rates. The second research chapter comprises experimental and field-based measurements of the inclusion rates of Co, Ni, Cu, as well as Mg, Sr. Firstly, a set of ten cave-analogue experiments were aimed to test for kinetic signatures in transition metal concentrations linked to the decay of OMCs during calcite precipitation. Performed at a range of drip rates and with variable concentrations of organic ligands in solution (Suwannee River Fulvic Acid (SRFA) and nitrilotriacetic acid (NTA)), however, the experimental calcite precipitates primarily depicted a direct inclusion of OMCs without prior dissociation. This was particularly pronounced for metal-SRFA complexes due to a considerable degree of co-precipitation of SRFA. Signatures attributable to OMC decay were in turn not discernible, presumably due to experimental conditions preventing their resolution. The study further yielded new estimates of inorganic partition coefficients for Co (≈1.8), Ni (≈0.4), Mg (≈0.04), Sr (≈0.09), and Cu (≈13 on average, but up to ca. 57), with the latter showing a pronounced positive dependency on drip rate. In the second part of this study, a wide range of new and previously published datasets on experimental and in-cave metal partitioning were compiled, which collectively allowed for the establishment of a conceptual framework around hypothesised system-specific conditions determining the dominant drivers of transition metal concentrations in dripwater and stalagmites. The final research chapter explores elemental systematics in two caves on the South Pacific island of Niue, aiming to utilise modern field observations to corroborate stalagmite-based palaeoclimate reconstructions of Holocene climate variability. Intermittent cave monitoring between September 2019 and November 2022 in principle supported the assumption that stalagmites from these caves record environmental conditions in their chemistry and binary lamination. Although reliable chronologies could not be established for the two stalagmite samples analyses in this study, their trace elemental and reconnaissance stable isotope measurements suggested that the most pronounced elemental signal of Mg/Ca ratios reflected a combined control of water-rock interactions, prior calcite precipitation (both indicative of rainfall amount), and marine aerosol inputs. The analysis further implied that Ni/Ca (and Cu, Co, and Zn to a lesser extent) also primarily reflected local hydrology, predominantly exhibiting behaviour consistent with that expected for a pervasive kinetic drip rate control. Based on preliminary interpretations, OMC decay presented the primary driver of transition metal concentrations in the deposits from Anapala Cave, while short-lived ‘soil-flushing’ peaks in various elemental concentrations in response to heavy rainfall events only sporadically defined the record. Collectively, albeit warranting further investigation, the results of this thesis provide new systematic insights into the role of organic complexation for transition metal incorporation into calcite speleothems, thereby presenting important precedent for the further development of a novel (semi-)quantitative class of hydrological proxies.
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    Envisioning VR theatre: Virtual reality as an assistive technology in theatre performance
    (Thesis, The University of Waikato, 2024-03-20) Srinivasan, Saikrishna
    This research project focuses on exploring the potential artistic advancements provided by the inclusion and incorporation of Virtual Reality (VR) within theatre. The incorporation of VR technology into theatre performance ultimately aims to alter a theatre experience by adding spatial presence for audiences and adding new production considerations for theatre practitioners. This project investigated the conceptual nature and practical aspects of using 360-degree cameras placed on stage to enable virtual teleportation onto the stage from the audience or remote viewing. This thesis constitutes a PhD ‘with publication’ and includes reprints of quality assured peer reviewed scholarly articles produced at different stages on the project. The first study examines the early development and use of three-dimensional theatre prototyping to identify the technical requirements for VR theatre. A digital theatrical prototype was designed, along with mathematical calculations to determine the optimal placement of 360-degree cameras on stage. The study reveals multiple camera angles that can be utilized to capture a 360-degree/VR theatre experience. Building upon the findings of the first study, the second study focuses on practical and technical factors such as visibility, sound, lighting, and visual intensity to enhance audience access and proximity to live performances. Different camera positions were found to be suitable for different theatre styles. The study suggests that the application of VR technology in theatre stages can yield highly satisfying results, as reported by participating actors. Following initial prototyping and planning, the PhD then experienced the impact of COVID-19 that prevented planned collaboration with local theatre practitioners that would have enabled a substantive practical application of VR, technical refinements and, user and audience testing. However, in response to the impact of COVID-19 on the theatre industry, the third study investigated the use of virtually designed spaces and the inclusion of 3D avatars/characters or real actors in performances. It explores the creation of photorealistic virtual worlds that mimic real-world environments and examines audience perceptions of virtual theatre experiences. The study presents a modernization of theatre performance by incorporating 3D virtual spaces, akin to VR games, but with limited interactive freedom for the audience. The fourth and final study involved the development of a post-pandemic experimental theatre performance based on the insights and data collected from the previous studies. It focuses on the virtual teleportation of an audience onto the stage during a performance, facilitated by VR headsets and a 360-degree camera mounted on the actor. Within the experiment participants experienced the performance through VR headsets. The audience and theatre practitioners were then invited to participate in a post interview session, to note their feedback and comments regarding the experience. Despite the limited number of participants due to COVID-19 restrictions, the study highlighted the positive nature of the VR experience pointing to the possibilities for increased virtual access to live theatre beyond this research. Overall, the results of these studies shed light on key practical considerations involved in the integration of VR into theatre performances. The approaches taken in each study support and guide best practice but also opens up VR-assisted theatre to grass roots level community and local theatre so that VR can become a common consideration and tool for all forms of theatre.
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    Enhancing Team Pursuit Performance using Blood Flow Restriction
    (The University of Waikato, 2023) Pugh, Charlie French
    The studies in this thesis investigated the physiological determinants of 4-km team-pursuit (TP) track cycling performance and critically evaluated the use of modelling finite work capacity (W′) and its dynamic balance (W′BAL) during the TP. This thesis also examined the integration of blood flow restriction (BFR) into high-intensity interval training (HIIT) as an intervention to improve factors related to TP performance. A series of related investigations were conducted with trained cyclists up to the Olympic level. Study One recruited male TP squads from International, National, and Regional performance levels. The TP squads were assessed for their critical power (CP) and W′. Maximal 4-km TP efforts confirmed different performance times of 3:49.9, 3:56.7, and 4:05.4 (minutes:s) for International, National, and Regional, respectively. Four TP simulation trials quantified W′ reconstitution from 0 to 100 W below CP. Results showed that the International squad were differentiated from National and Regional performance levels with greater CP (p < 0.05), likely preserving W′ for leading efforts. Furthermore, the International team possessed the fastest rates of W′ reconstitution at recovery intensities within 50 W of CP (p < 0.05), demonstrating the importance of W′ reconstitution at intensities near CP for recovery in the TP. The International team also expended a greater total quantity of W′ than its initial size (104 ± 5%), further demonstrating the capacity to utilise the reconstituted W′. In conclusion, we found that the TP relies on high aerobic capacity and rapid metabolic recovery abilities. An intervention was conceived based on the demands of the TP and the existing training sessions of elite TP cyclists. The training intervention included principles of TP training philosophy where cyclists repeatedly practice competition demands, at their TP lead intensity. As elite TP cyclists engage in substantial training volumes, it was important not to substantially exceed current training workloads. Based on previous BFR research with trained cyclists, an intervention integrating BFR into the recovery between TP efforts was devised. The intervention was performed on an ergometer to enable greater control over conditions and intensity. To evaluate the metabolic demands of the BFR intervention, the Study Two assessed the acute physiological responses in 11 male and female highly-trained cyclists (V̇O2PEAK 65 ± 9 mL·kg-1·minute-1). Using a within-subject design, participants performed two work- and duration-matched HIIT sessions. The HIIT consisted of six high-intensity repetitions with BFR occlusion between work bouts at 200 mmHg for 2-minutes applied proximally on the thighs (BFR) or HIIT alone without BFR (CON). Work intensity was set as 85% of the mean power output of a maximal 30-s test to simulate TP lead intensity. Cardiopulmonary variables (O2 uptake, V̇O2; carbon dioxide production V̇CO2; and ventilation, V̇E) and muscle oxygenation responses were measured during the HIIT, and vascular endothelial growth factor (VEGF) was measured pre- and 3-hours post-HIIT. Results demonstrated that BFR increased V̇CO2 and V̇E (both p < 0.05) during work bouts but did not affect V̇O2 and TSI (both p>0.05). Compared to CON, the BFR intervention significantly decreased V̇O2, V̇CO2, V̇E, and TSI during BFR occlusion (all p<0.05). Following cuff release, there were significantly higher values of V̇O2, V̇CO2, and V̇E, whereas TSI was suppressed (all p < 0.05). There were significant enhancements of serum VEGF concentration at 3-hours post-HIIT after BFR when compared to CON. As BFR appeared to delay recovery, it was hypothesised that BFR may increase metabolic and oxidative stress by delaying recovery processes. The delay in recovery may enhance the adaptations to HIIT without increasing training workload. After demonstrating that applying BFR during recovery in high-intensity work bouts increased markers of physiological stress, Study Three assessed the performance and physiological effects of the training as a chronic intervention. Using a between-subject design, ten performance-matched male trained cyclists (weekly volume >6-hours·week-1) were assigned to BFR or CON conditions. Participants performed pre- and post-intervention tests to determine lactate thresholds, 30-s maximal sprint cycling performance, and an intermittent test designed with high-intensity bouts comparable to the TP. Work bouts were performed at 85% of the mean power output of the maximal 30-s test. Muscle oxygenation and cardiopulmonary measures were continually assessed throughout the intermittent test. Participants performed four-weeks of work- and duration-matched HIIT either with 2-minutes of 200 mmHg thigh BFR between work bouts or HIIT alone (CON). Following BFR intervention, there were significant improvements in intermittent test time to exhaustion, 30-s mean power output, and submaximal lactate thresholds compared to CON (all p < 0.05). Furthermore, BFR led to significant intermittent test improvements for V̇O2PEAK and the rate of muscle tissue reoxygenation (all p < 0.05). There were no significant changes over the intervention period for CON, indicating that HIIT was ineffective in this cohort when BFR was not incorporated. Therefore, it was demonstrated that the integration of BFR between HIIT work bouts improves intermittent performance and a range of physiological factors associated with performance in trained cyclists. Finally, the BFR intervention was integrated into two HIIT sessions within a training camp of an elite TP squad preparing for the Olympic Games to test its potential efficacy and feasibility. As in the previous BFR studies, this case-study (Study Four) applied 2-minutes of 200 mmHg thigh BFR between high-intensity bouts. Work intensities were set at the individual cyclists’ TP lead intensity. A questionnaire was developed to assess the pain, tolerance, enjoyment, and compare the intervention to other training modalities. Questionnaire responses indicated that the elite cyclists enjoyed and positively perceived the intervention, appreciating the variety and efficiency of the training stimulus. All but one elite cyclist tolerated that intervention. Further investigation in conjunction with medical staff indicated that the intolerant cyclist had a pre-existing undiagnosed cardiovascular condition and presented with femoral artery claudication (discussed in the addendum). Thus, integrating BFR into HIIT for elite track cyclists was feasible and tolerable when no contraindications existed. In summary, elite TP performance relies on high sustained aerobic power output and rapid W′ recovery between efforts. This thesis showed integrating BFR between HIIT work bouts provides an additional training stimulus and can improve factors related to aerobic capacity and high-intensity intermittent performance in trained cyclists. The BFR intervention is tolerable within an elite cohort and may improve TP performance without increasing training workload.
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    Studies on Paphies australis (Mesodesmatidae) in Whangārei, Aotearoa New Zealand: an investigation into their declining health.
    (The University of Waikato, 2023) Howells, Joanne Elizabeth
    Disease outbreaks in marine species can have devastating consequences, including increasing host mortality, destabilising commercial production, altering ecosystem functioning, and jeopardising human health. A changing ocean climate is expected to increase host stress and the risk of disease outbreaks. Particularly through new and emerging diseases and opportunistic infections. Wild bivalve molluscs provide economic, ecological, and socio-cultural benefits. Healthy and sustainable kaimoana (shellfish/bivalves, seafood) are intrinsically linked to the wellbeing of many communities in New Zealand. Over the past decade there has been a noticeable decline in the general health of native marine bivalves, characterised by an increase in observation of mass die-offs. Reasons for this are not clear and could be due to a number of factors, such as sedimentation, harvesting pressures, or disease. Baseline health data on wild bivalve populations are very rare and therefore it is very difficult to identify the causation of ill health. There is a need to establish health baselines to help benchmark changes in infection prevalence and intensity and identify drivers of bivalve mortality events. Wild bivalve populations are often located in remote and isolated parts of New Zealand. When a mortality event occurs, the logistics of obtaining quality samples for accurate diagnosis can be hindered due to time delays and sample degradation. To gain a better understanding of these limitations for diagnostics using bacteriology, in Chapter 2 I investigate typical sample collection methods (i.e., samples collected and sent to a testing laboratory) and sample collections immediately in the field to understand what effect different sample methods have on number and types of bacteria isolated. Although the results of Chapter 2 found there were limitations to both sampling methods, it did identify that typical sampling techniques were not wholly optimal, and the information gained by sampling immediately in the field retained additional information that could be essential for disease diagnostics. Field sampling for bacteriology was applied throughout this thesis research. Pipi (Paphies australis) are native bivalves to New Zealand, inhabiting the shallow subtidal of estuaries and bays. Pipi have suffered serious population declines in an area of northern New Zealand (Whangārei) since 2009. I investigate possible drivers of the poor health of pipi in Whangārei, with the objective of identifying the mechanisms that have contributed to the decline, and prevention of the recovery of pipi in Whangārei, with a primary focus of disease as a causative agent. I establish a health baseline of pipi from Whangārei using histopathology, bacteriology, and qPCR of Endozoicomonas spp., a bacteria previously identified in mortality bivalves (Chapter 3). The health baseline was compared against samples collected during three mass mortality events to help identify drivers of mass mortality events (Chapter 4). Through laboratory experimentation, I test whether pipi exposed to stressors had higher infection intensity and prevalence of Endozoicomonas spp. (Chapter 5). Finally, using archived samples, I test whether the baseline data established was consistent through time and help to provide insights into considerations when analysing bivalve mass mortality events (Chapter 6). I found that Endozoicomonas spp. make an important part of pipi host microbiome. Although Endozoicomonas spp. are highly prevalent in pipi collected during a mass mortality event, their infection intensity was significantly lower in moribund pipi than healthy pipi. The prevalence and infection intensity of Endozoicomonas spp. were not driven by environmental stressors. The stressors, however, did appear to impact host health, with high suspended sediment loads and water temperatures of 24°C appeared to be unfavourable to pipi. Overall, Endozoicomonas sp. does not appear to be a main driver in the declining population of pipi from Whangārei and is probably not important to bivalve health. The reduced prevalence and infection intensity of Endozoicomonas sp. in healthy pipi strongly suggests these bacteria are symbiotic. A relationship that has been reported for this bacterial group in species of coral and sponges. The establishment of a health baseline represents a significant step forward towards biosecurity preparedness by being able to identify changes in infection prevalence and intensity against it. The operational use of these data when paired with historical data will be a powerful tool to identify patterns of disease dynamics and emerging disease.
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    Sociocultural and academic adjustment experiences of Omani international students at a New Zealand university
    (The University of Waikato, 2024) Al-Tamimi , Muwafaq
    Promoting international student mobility is a key consideration in the internationalisation of higher education. Due to this attention, it has become increasingly important to understand international students’ experiences. Previous research on international students’ adjustment experiences has reported various issues and unique aspects depending on the context of their adjustment. However, there is a need for research on Omani international students in New Zealand to provide insight into what might affect students’ academic, social, and cultural adjustment. This study explored how Omani students described their sociocultural and academic adjustment experiences and how they gave meaning to these from their viewpoints. A qualitative phenomenological approach underpinned by an interpretive research paradigm was used to investigate the adjustment experiences of 12 Omani student participants. Data were gathered through semi-structured interviews from January to September 2020 at one New Zealand university. Two rounds of interviews were held for each participant. During data collection, Omani participants were enrolled in bachelor degree programmes in Engineering, Education, Earth Science, and Management. NVivo 11 was used to assist in organising and analysing data from the interviews using a thematic approach. Findings suggest that Omani students experienced adjustment as an interactive social, cultural, and academic experience. For most of them, their initial experience was facilitated by their homestay, attendance at language school, and participation in the Omani Students’ Association. This triad of interactions and support meant Omani students felt happy and included in the local community. However, after this initial stage of comfort, many experienced negative emotions, such as homesickness, especially during Islamic holidays. Omani students’ sociocultural adjustment was made easier by them engaging in social interaction and seeking out friendships. However, they reported little interaction with hostnational students; most interactions and friendships were with co-nationals and international friends. Omani students did not experience cultural distance as a barrier to their adjustment process despite the move from a Muslim-majority country to a Western country. Thus, overall, students reported being satisfied with their lives in New Zealand. They were conscious they had developed self-discipline and self-reliance, which they viewed as important in their successful adjustment. Academic adjustment was promoted by interaction with other students in group work and academic support from their lecturers. Group work was reported as an opportunity to interact with degree programme classmates and make new friends, but six of the 12 students described difficulties interacting in group work. Interactions with lecturers were described as informal and positive for academic success. Across both their social and academic lives, the participating Omani students identified their proficiency with English as a barrier to communication and adjustment. As a result, they were eager to improve their English levels to integrate into the host culture and community. The U-curve model (Lysgaard, 1955) and the ABC model (Ward et al., 2001) were used as lenses to explain the above findings. The U-curve model describes the adjustment process as four stages: “honeymoon”, “culture shock”, “adjustment”, and “mastery”. The U-curve model was able to describe and explain the adjustment experiences of eight of the 12 students in this study in suggesting a honeymoon period on arrival. However, four students reported difficulty in terms of homesickness and loneliness upon arrival. This fits with the ABC model, which proposes that adjusting to a new culture can be initially difficult and stressful, but, over time, individuals can manage stress and learn the social skills needed for effective interactions, leading to adjustment. Hence, the study findings indicate the need for a model that allows for two different initial experiences and acknowledges that international students move through stages of adjustment. The culture learning process in the ABC model can explain the mechanism of moving between the stages of the U-curve model. Findings have implications for Omani scholarship providers, future Omani international students, New Zealand policy makers, and New Zealand universities. They are advised to consider the importance of homestays in providing a comfortable, safe environment for students to interact with host nationals. It is also recommended that the value of having intercultural friendships and being open to other cultures is promoted to Omani students, as this can ease the adjustment process.

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