Open Access Theses

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Open Access
Bound Volume for the degree of Masters of Applied Epidemiology
(2025) Osborne, Aaron
This thesis details projects undertaken during my placement at the North Eastern Public Health Unit (NEPHU) from February 2023 to November 2024. I worked at the public health unit before undertaking my Master of Philosophy (Applied Epidemiology) degree. Recently established in 2021, and as the first MAE student to be placed at the Victorian Public Health Unit. My time was valuable for reflecting on how public health and epidemiology had been in the past and how it could be done differently in the future. My projects comprised of: A group A Streptococcus outbreak in a primary school in Melbourne, Australia; Identifying and characterising geographic areas of Hepatitis B incidence in North Eastern metropolitan Melbourne between 2013 and 2022; Local level Hepatitis B care cascade surveillance: A Feasibility Study; Syndromic surveillance for air quality (PM 2.5) related health events: Relationships between ICD-10 codes and periods of poor air quality. This thesis also describes other experiences and public health activities during my placement. These projects and experiences fulfil the core requirements of the Australian National University Master of Philosophy (Applied Epidemiology) program.
Open Access
Essays on International Trade and Development: Evidence from Indonesian Microdata
(2025) Laksono, Riandy
No country has achieved significant development without engaging in international trade. However, this insight faces scrutiny as developing countries struggle to reach their potential despite open trade regimes. This thesis presents four empirical papers examining how international trade impacts various development aspects, using rich Indonesian microdata at both firm and individual levels. The first analytical chapter (Chapter 4) examines trade liberalization's effect on labor share of income in Indonesian manufacturing from 1990-2015. The analysis reveals that reduced trade protection led to the emergence of superstar firms with superior performance and lower labor costs, ultimately reducing labor's income share through market share redistribution. Unlike developed nations where declining labor share coincided with increased market power, Indonesia's manufacturing firms maintained stable market power, suggesting a unique mechanism of trade reform's influence on labor share dynamics in a developing economy context. Chapter 5 revisits the market discipline hypothesis of trade, which posits that exposure to international trade could limit firms' market power. Using the case of trade liberalization in Indonesian manufacturing, I show that the impact of trade liberalization on competition, measured by markup, will depend on the nature of liberalization itself. While output tariff liberalization creates a market-disciplining effect for firms by reducing markup, this effect is outweighed by input tariff liberalization, which increases firms' markups at a much higher level due to the efficiency effect of cheaper materials. This occurs because competition in Indonesia's manufacturing sector is imperfect, giving firms price-setting power. Thus, the pass-through from cost to price is likely to be incomplete, making the reduction of cost end up in higher markup. In this case, however, although both firms and consumers gain in absolute terms following liberalization, the distribution of the gain favors firms more than consumers. Chapter 6 deals with the trade and productivity nexus but views it through the lens of allocative efficiency rather than within-firm efficiency improvement extensively discussed in existing studies. Chapter 6 examines trade and productivity through allocative efficiency rather than within-firm improvement. The shift of market share towards more productive firms drove productivity growth in Indonesian manufacturing, particularly in the 1990s, though this pace slowed significantly after 2000. Trade liberalization improves allocative efficiency by reallocating market share towards productive incumbents, forcing less productive firms' exit, and reducing industry distortion. This suggests trade liberalization's crucial role in reducing resource misallocation that hinders developing countries' growth potential. The last analytical paper in Chapter 7 aims to understand the impact of export expansion to China on labor market outcomes among workers. To broaden the perspective, we include not only the commodity exports but also the manufacturing ones. We find that individuals living in the regions more exposed to export expansion to China experienced improved formal job opportunities. Export expansion also proved relatively progressive, raising formal employment opportunities and earnings growth particularly for lower- and middle-income classes. These results stem from manufacturing exports' expansion within a largely commodity boom period.
Open Access
Analog Control of the Diamond Quantum Processor
(2025) Stearn, Sophie
Diamond quantum processors, based on the nitrogen-vacancy (NV) centre, offer long coherence times and high-fidelity optical control at room temperature, making them a promising platform for quantum technologies. Until now, they have been operated almost exclusively using the gate-based digital quantum computing (DQC) paradigm. This thesis introduces a novel derivation of the fully controllable Ising model from the diamond control Hamiltonian, laying the groundwork for this architecture to support computational paradigms beyond the gate model. With this result, analog control becomes feasible on diamond hardware for the first time, enabling a novel approach to quantum annealing. Diamond quantum annealing is evaluated through simulations of a room-temperature device based on a single NV-centre cluster, incorporating realistic effects such as decoherence and crosstalk. To improve robustness, open-loop optimisation protocols are introduced for annealing schedule design, showing improved performance. A new hardware-specific quality factor is also proposed, which benchmarks adiabaticity based on the system's minimum transition frequency spacing and decoherence time. This metric suggests that diamond may support purely quantum annealing, without relying on thermalisation. For contrast, the metric is applied to both the proposed diamond quantum annealer and superconducting flux qubit devices, using parameter estimates from D-Wave's Advantage platform. Finally, this work demonstrates that diamond is also capable of stepped digital-analog quantum computation (sDAQC), marking a second potential shift in how quantum algorithms can be realised on this platform. Building on this result, a hardware-specific technique- interleaved circuit compression (ICC)- is also introduced to exploit the newly derived control Hamiltonian. By combining Ising coupling gates with arbitrary-axis rotations, ICC enables substantial compression of gate-based quantum circuits on diamond hardware. This is illustrated using the quantum Fourier transform (QFT), where circuit depth is reduced from O(n^2) under standard digital compilation to O(n) with ICC.
Open Access
Ocean Gyres Driven by Wind Stress and Surface Buoyancy Forcing
(2025) Bhagtani, Dhruv
Large-scale ocean circulation is central in modulating weather and climate patterns by distributing heat, nutrients, and carbon dioxide within and across ocean basins. The large-scale circulation is driven by processes at the ocean's surface (such as winds and heat and freshwater fluxes) and steered by processes in the ocean's interior (such as mesoscale eddies and flow-topography interactions). Climate change is expected to alter these surface forcings. Despite the central role of ocean circulation in transporting heat and regulating climate, the impact of physical processes both at the ocean's surface and in the interior on the large-scale ocean circulation -- especially in the context of climate change -- remains inadequately understood. In this thesis, we focus on two large-scale circulatory ocean features: (i) the gyres (primary focus of the thesis), and (ii) the Atlantic Meridional Overturning Circulation (AMOC). Ocean gyres are canonically believed to be driven by wind stress, while the AMOC is thought to be controlled by surface buoyancy forcing (i.e., heat and freshwater fluxes). Using a series of ocean model simulations, we find that in addition to wind stress driving gyres, surface heat fluxes control the near-surface density gradients, which in turn affect the gyre circulation. The relationship between surface heat flux gradients and the gyre circulation is linear for timescales shorter than a decade, after which the relationship becomes non-linear due to density advection by the circulation. A major focus of this thesis is the North Atlantic basin, where the heat carried from the tropics to the Arctic by the subtropical gyre and the AMOC is sensitive to both changes in winds and surface heat fluxes. On timescales shorter than a decade, changes in each circulation's heat transport occurs primarily through anomalies in the circulation strength. On multidecadal timescales, changes in the ocean's temperature feed back to modulate the heat transport response. Last, we focus on a key atmospheric mode of variability, the North Atlantic Oscillation (NAO), and how it affects the ocean circulation. While the NAO impacts the gyres through changes in winds and surface buoyancy fluxes, the relative importance of processes at the ocean's surface and in the interior in shaping the gyres is not fully understood. We find that NAO-induced changes in the surface wind stress drive more than 90\% of the variability in the subtropical gyre. In contrast, in addition to wind stress, the NAO-induced variability in the subpolar gyre is governed by several processes: mesoscale eddies, flow-topography interactions and the ocean's stratification (influenced by surface heat fluxes). Our work emphasizes the under-appreciated role of surface buoyancy fluxes in driving oceanic gyre circulations, with implications for how the gyres, and thus regional climate, may change in the future.
Open Access
Sense of self and belonging in university students participating in orientation program
(2025) Walker, Sarah
Orientation programs and the overall transition period are a critical time for students commencing within higher education. Research has demonstrated what occurs during this time will impact on a student's engagement (Kift, 2009; Krause & Coates, 2008; Tinto, 1994), retention (Krause et al., 2005), and wellbeing (Pascarella & Terenzini, 2005). Similarly, research has highlighted the importance of sense of belonging for university students to support academic engagement (Freeman et al., 2007; Iyer et al., 2009; Smyth et al., 2019) and retention (e.g. Hausmann et al., 2007; Hoffman et al., 2002; Strayhorn, 2019). Sense of belonging has become a cornerstone for improving the experiences and outcomes for students from traditionally underrepresented backgrounds (Hurtado & Carter, 1997; Strayhorn, 2019; Walton & Cohen, 2007, 2011). However, there are clear gaps in the current literature as research on the impact of orientation programs does not measure sense of belonging, even when this is a key purpose of the program. Additionally, while there have been indications that sense of belonging fluctuates over time, there is not an understanding of how or when this occurs, limiting the potential impact of interventions aimed at increasing sense of belonging. This thesis seeks to address these gaps through five studies which examine the limitations within the current literature and to continue building our understanding of the importance of sense of belonging to students transition and ongoing experience within higher education. Utilising a systematic review, primary and institutional survey data, and interviews, these studies demonstrate the importance of sense of belonging during the transition period as well as the impact that it can have for students throughout their studies. The findings will also highlight the need to intentionally focus on sense of belonging for the benefit of all students, and how in particular, it is vital for those students from traditionally underrepresented backgrounds.
Open Access
Low-Power Phase Tracking in Inter-Spacecraft Laser Interferometry
(2025) Sambridge, Callum
Inter-spacecraft laser interferometers perform measurements that are impossible to make from Earth. The Gravity Recovery and Climate Experiment Follow-On mission (GRACE-FO), the first such mission, monitors gravitational anomalies in the Earth's field, inferring critical information about global ice mass, groundwater movement, and sea-level rise. Future missions, such as the Laser Interferometer Space Antenna (LISA), will be the first gravitational-wave observatories capable of probing the millihertz frequency band for gravitational phenomena. These missions provide critical insights into our planet and universe. As light propagates the vast distances in space between satellites, the majority is lost (-70 dB for GRACE-FO), requiring the interferometer to perform measurement with the small amount of light captured. The minimum received optical power with which inter-spacecraft laser links can robustly function is a significant factor in their design and operation. This thesis presents research exploring the low optical power limits of inter-spacecraft optical links. This work focuses on analysing the phasemeter, the digital device within the inter-spacecraft interferometric detection chain where measurement is performed. The work extensively explores phasemeter performance and optimisation for operation with low optical power signals, resulting in robust phasemeter measurement of femtowatt-level optical signals. First, the thesis presents analytical models, numerical simulations, and an optical experiment that explores phasemeter performance in tracking low-power optical interference signals. The experimental system enabled phasemeter tracking of a signal with controllable amplitudes, relative additive noise, and laser frequency noise characteristics. Phasemeter tracking error and cycle slip rate measurements are compared to analytical phase-locked loop models and hardware-in-loop numerical simulations. The findings are used to optimise phasemeter tuning for the low-power regime, resulting in a 90-minute robust measurement of a femtowatt-level optical field. Next, a second experiment is described, performed in collaboration with the NASA Jet Propulsion Laboratory, to determine the optimal phasemeter tuning for low-power tracking of the GRACE-FO flight laser. The results demonstrate robust tracking at an optical power level of 200~femtowatts --- $10$~dB below the tracking requirement of the GRACE-FO mission. This work supports the exploration of future inter-spacecraft interferometric missions operating with relaxed optical power requirements. Following this, the optical power requirements of passive retroreflector inter-spacecraft interferometric architectures are explored using hardware-in-loop numerical simulations and analytical modelling. Observed phasemeter measurement errors are compared between different inter-spacecraft optical configurations, received optical power levels and phasemeter parameter tunings. The work reveals that passive retroreflector architectures can robustly operate with thousands of times less light than their transponder counterparts. Next, an alternate technology for phase tracking DC-centred carrier frequencies is proposed, named here the dual quadrature phasemeter. This approach leverages coherent optical detection to adjust the internal structure of the phasemeter, enabling operation with larger bandwidths and unconstrained carrier frequency (down to and through DC). This technology enables a new class of inter-spacecraft laser link that operates with a simplified optical topology and at a lower cost than traditional transponder methods. The thesis concludes by combining the low-power phasemeter tracking findings with the dual quadrature phasemeter to present a novel optical architecture for a simplified passive-retroreflector mission design. The design's advantages and challenges are outlined, as is the future work required for verification.
Open Access
Three Essays in Life Cycle Modelling
(2025) Huang, Leo
This thesis explores critical aspects of discrete-time life-cycle modeling, focusing on optimization techniques and decision-making strategies for retirement planning and portfolio management. It is composed of three essays, each addressing distinct but interrelated challenges in life-cycle financial models. The first essay establishes a proof of monotonicity between pre-decision and post-decision state variables, with particular focus on the savings function, in the context of stochastic portfolio optimization using the Endogenous Gridpoint Method (EGM). Establishing this proof reinforces the theoretical validity of applying EGM in this setting and helps ensure that a key structural condition, namely monotonicity, is satisfied. This extends the method's applicability to a broader class of problems involving stochastic portfolio returns and addresses a gap in prior literature where this assumption was often left unverified. The second essay investigates a life-cycle retirement planning problem, comparing four different investment strategies: Self-Management with Dynamic Investment, Self-Management with Benchmark Investment, Hire-Management with Flexible Allocation, and Hire-Management with Alpha Focus. Using dynamic programming techniques, this study optimizes investment allocation and consumption patterns during the Defined Contribution accumulation phase, leading to a life annuity purchase at retirement. The results show that while delegated investment options can enhance a worker's retirement outcome, higher fund fees in the US market and associated agency cost may limit their value. The third essay explores the application of the Least-Squares Monte Carlo (LSMC) method to life-cycle utility-based models in retirement savings, a field where its use has been relatively limited. By comparing LSMC's computational efficiency and accuracy with traditional dynamic programming method (i.e., Value Function Iteration), the study highlights its potential to improve decision-making in post-retirement financial planning, particularly in optimizing investment, consumption, and annuitization strategies. Together, these essays contribute to the literature on life-cycle financial planning by offering new insights into the mathematical and computational techniques that enhance decision-making for both individuals and financial institutions.
Open Access
Usable Privacy Documents in Software Systems and Engineering
(2025) Pan, Shidong
Privacy regulations commonly mandate software systems to provide essential privacy documents, such as privacy policies and privacy (nutrition) labels, to inform users about what, why, and how their personal data are collected and used. However, currently these privacy documents often fail to fulfil the needs of users. Privacy documents are often flawed because of the lack of privacy awareness, understanding, and systematic support for privacy among practitioners in software engineering. Software users frequently experience ``Digital Resignation'', which is where users desire to understand and control the information that digital entities own about them, but feel powerless to do so. The low readability and poor usability of privacy documents make it difficult for users to understand the privacy practices of the systems they engage with, leaving them unable to exercise control over their personal privacy. In this thesis, we present five contributions addressing two long-standing research challenges related to privacy documents: Procurability, how to craft privacy documents effectively within the software engineering process; and Utility, the usability of privacy documents for practitioners and stakeholders. Specifically, this line of work originates from a fundamental question: how are problematic privacy documents initially produced? We first examine how software developers employ Automated Privacy Policy Generator (APPGs) to craft privacy policies, unveiling the popularity, characteristics, and compliance of APPGs. Results reveal a 20.1\% adoption rate of APPGs and various incompliance issues against privacy regulations. To tackle the long-standing privacy document generation problem, we then introduce Privacy Bills of Materials (PriBOM) to foster transparent and collaborative privacy notice generation during the software development process. The usability evaluation underscores the usefulness and practicability of PriBOM in fostering a privacy-conscious development workflow. Despite their critical role in protecting digital privacy, privacy documents are often overlooked and poorly engaged with. Leveraging the emergence of privacy labels alongside advances in Large Language Models (LLMs), we first propose an LLM-based agentic framework to automatically generate Privacy Labels from privacy policies to improve readability, evaluated by real-world privacy polices and labels collected from market. Additionally, to build the contextual alignment between privacy notices and real-time privacy events, we present the Contextual Privacy Policies (CPPs) for mobile applications to enhance usability. Evaluated by self-crafted Cpp4App benchmark and a usability evaluation, people exhibit much greater willingness to engage with CPPs, scoring 4.1 out of 5, compared to a mere 2 out of 5 for traditional privacy policies. Lastly, given the widespread adoption of Generative AI (GAI) technologies introduces novel challenges in privacy disclosures, we develop the Repo2Label framework to automatically generate privacy labels for online application repositories. Results show that our framework achieves a precision of 0.81, recall of 0.88, and F1-score of 0.84 under the optimal experimental settings. By targeting the improvement of Procurability and Utility of privacy documents, this thesis aims to strengthen three key areas: compliance between privacy regulations and software privacy documents, alignment between software privacy documents and actual software behaviors, and transparency between software systems and users regarding privacy practices. Keywords: Privacy Documents; Privacy Policy; Privacy Labels; Privacy Laws; Usable Privacy and Security; Software Engineering.
Open Access
Assessing Assemblage Integrity and Temporal Associations in Three Sand Bodies on the Cumberland Plain, Sydney
(2025) Richardson, Norma
Archaeological investigations of sand bodies on the Cumberland Plain in Sydney have reported Pleistocene dates for occupation, however debate over the suspected impact of bioturbation on assemblage integrity raised questions regarding the reliability of these age estimates. Analysis of three assemblages from these sand bodies was structured to address a series of research questions involving the age and depositional context of this archaeological material. A range of analytical methods were employed to investigate the impact of site formation processes on assemblage integrity. These impacts include both the transformation of individual artefacts and redistribution of assemblage components from syn-depositional and post-depositional processes. A 'whole of assemblage' approach provided the opportunity to utilise 'waste' material, such as heat shatter, frequently ignored or discarded by archaeologists. Identification of heat induced fractures assisted not only with estimates of artefact breakage rates and the identification of fire use behaviour, but also provided samples for luminescence dating to obtain age determinations for these burning events. Raw material analysis, refitted artefact sequences and conjoined non-artefactual pieces provided evidence of a range of cultural activities as well as contributing to spatial analysis and assessments of displacement. The validity and timeliness of this study are reinforced by an examination of specific research questions raised in recent archaeological studies in the Sydney region and adjacent areas. Although this thesis does not attempt to support or refute any claims of antiquity or propose any new regional chronologies for archaeological sites outside the Sydney Basin, the findings do contribute to the debate regarding direct temporal association between stone artefacts and dated sediments in other sites. The results indicate that site formation processes can have a significant impact on the accuracy of dating cultural remains using age estimates obtained using luminescence procedures on sediments.
Open Access
On triangulated categories with metrics
(2025) Manali Rahul, Kabeer
Neeman has recently initiated the use of metrics, and approximations via metrics, to study triangulated categories. In this thesis, we use these techniques to prove results which have application in algebraic geometry. First of all we define a generalisation of the notion of approximable triangulated categories. We prove some Brown representability type theorems for the compact objects of such categories. Further, we show that for nice schemes, the homotopy category of injectives satisfies the conditions of this new definition, which gives us Brown representability type theorems for the corresponding bounded derived category of coherent sheaves. The second major application is to the construction of new semiorthogonal decompositions from gives ones. This generalises recent work by Kuznetsov, Shinder, and Bondarko. Finally, we discuss joint work on bounded t-structures and the finitistic dimension of a triangulated category, which generalises a powerful new theorem by Neeman.
Open Access
Dynamic Load Balancing and Elasticity in a Distributed Heterogeneous Task-based Dataflow Runtime
(2025) John, Joseph
For over three decades, scientific computing software has heavily relied on process-centric distributed programming models. In this paradigm, individual processes divide the workload between nodes, and threads further divide the tasks within each node. This model proved efficient when hardware was homogeneous, and applications were regular and balanced. However, with the advent of hardware heterogeneity and increased application irregularity, process-centric model is exhibiting significant limitations. As computing nodes become more efficient at managing asynchronous events, thus enhancing the capacity to better scale applications, it becomes imperative for programming models to identify and expose asynchronicity within applications. Nevertheless, process-centric programming models often struggle to fully exploit this asynchronicity. Another critical drawback of the process-centric programming model is the degree of low-level decisions that a programmer must engage in, such as data distribution, GPU offloading, synchronization, and communication. Compounding these challenges is the absence of automatic load balancing in process-centric models. To meet the current requirements, we need a programming model capable of managing multi-node applications while effectively managing the heterogeneity among individual computing nodes. In this regard, the task-based dataflow programming model has emerged as a viable alternative to the process-centric programming model for extreme-scale applications. In this model, the application is conceptualized as a collection of tasks with data flowing between them. Decomposing the problem at the task level helps expose more asynchronicity within an application. An additional benefit of the task-based programming model is the shift of low-level responsibilities from the programmer to the runtime. Despite these advantages, dynamic automatic load balancing remains a challenge in task-based dataflow programming models. This thesis employs the task-based dataflow programming model, PaRSEC, to investigate the challenges associated with dynamic and automatic load balancing. This research delves into the realm of distributed load balancing and provides an in-depth analysis of design and policy choices that impact application performance when migrating tasks from one compute node to another. The research demonstrates that distributed work stealing, even without having to collect any load information, is an effective load-balancing mechanism and introduces new work stealing strategies that consider future tasks in the decision-making process for work stealing. Further, this research addresses the unique challenges and solutions related to load balancing among different GPUs within a compute node. In today's high-performance computing systems, multi-GPU computing nodes have become integral. Despite notable strides in programmability, efficiently harnessing the power of all GPUs in a computing node remains a substantial challenge. This thesis demonstrates, for the first time, the enhancement of application performance in a task-based dataflow runtime by implementing work sharing among GPUs within a computing node, with a specific focus on optimizing GPU utilization. Additionally, this research introduces the first instance of migrating tasks whose data is already resident in GPU memory to another GPU, showing that such task migration incurs no disadvantages. Further, this thesis explores the mechanism of distributed work stealing to migrate tasks intended for GPUs across compute nodes. This research demonstrates the utility of this work stealing approach, for the first time, as a mechanism to implement elasticity within the task-based dataflow runtime. Through these investigations, this thesis aims to contribute valuable insights into overcoming challenges associated with load balancing in complex high-performance computing environments.
Open Access
Sputter deposition and plasma modification of tungsten alloys for nuclear fusion applications
(2025) Mahoney, Nicholas
The ITER reactor aims to be first thermonuclear fusion device to demonstrate net fusion power. Critical plasma-facing components in the reactor will be made of tungsten, but helium plasma irradiation is known to embrittle tungsten metal. A future reactor will therefore need an alternative material to extend the lifetime of the components. This thesis investigated the use of tungsten alloy films as a plasma-facing material for a future reactor. Tantalum and chromium were chosen as the alloying elements, and 60 − 100 nm films were manufactured using magnetron sputter deposition at a variety of alloy concentrations. Tungsten alloy films are known to deposit in an undesirable A15 crystal phase. The films were heat treated at 650◦C for 1 hour, 2 hours and 4 hours to induce and investigate the phase transition from A15 to BCC structure. X-ray diffraction patterns confirmed the presence of an A15 structure prior to annealing. The A15 phase was very stable in comparison with past results, requiring over 2 hours at 650◦C to transition to BCC. This was speculated to be linked to oxygen trapped in the films during deposition. The phase transition was slower in alloyed films than a pure tungsten control, with the retarding effect of tantalum stronger than chromium, which suggested the alloying atoms further stabilised the deposited A15 structure. Resistivity of the films saw a reduction with annealing time characteristic of the phase transition. The annealed alloy films were then exposed to helium plasma in the Magnetised Plasma Interaction Experiment at 300◦C, 500◦C and 800◦C. Surface morphology changes were tracked with secondary electron imaging. At 800◦C, surface pits were seen, which were larger in a pure tungsten film than in low concentration alloy films. Advanced surface roughening was observed in the chromium films, while a high concentration tantalum film had no surface damage at all. X-ray diffraction patterns confirmed these trends, and showed an increase in microstrain with the surface roughening in the chromium alloys. These results suggest W-Ta alloy films may have superior irradiation resistance than W-Cr alloy films, but more work is needed to confirm the trends in alloy concentration.
Open Access
Recent Developments in Applying Quantile Regression for Missing Data in Longitudinal Studies
(2025) Tao, Dehua
In this thesis, we propose new approaches based on a quantile regression model to handle missing data in longitudinal studies. In Chapters 2 and 3, we develop univariate quantile regression imputation models for longitudinal data that may exhibit population heterogeneity. In Chapter 4, we propose a multivariate quantile regression imputation model capable of handling missing values across multiple responses, as well as imputations for censored observations. Our proposed models are evaluated using three HIV longitudinal datasets collected from the Multicenter AIDS Cohort Study and the Women's Interagency HIV Study (also known as the MACS/WIHS Combined Cohort Study). We believe these models can also be applied to other longitudinal datasets. All our models are built within the Bayesian framework, with estimation and inference implemented using the Markov Chain Monte Carlo (MCMC) procedure. In Chapter 2, considering the presence of population heterogeneity in the longitudinal data, we construct a latent class mixture quantile regression model for imputation. To address missing values under the Missing Not at Random (MNAR) assumption, we propose an additional model to capture the missingness indicator, thereby facilitating the imputation of missing values. We test the proposed approach under various simulation settings, and find the proposed model consistently yields accurate parameter estimations across the simulation scenarios. The model is also evaluated using real data from the MACS study. Based on the real-data analysis results, we conclude that the model fit can be improved with the addition of a latent class structure when a clustering effect exists in the data. In Chapter 3, we extend the imputation model introduced in Chapter 2 by incorporating semiparametric random effects terms, assuming a Dirichlet process prior. This imputation model can be treated as a semiparametric latent class mixture quantile regression model. Additionally, we include the same random effects terms in the model for the missingness indicator, thus building a shared-parameter model structure for MNAR. Simulation results demonstrate that the proposed model can not only provide consistent and accurate results for the estimation of parameters of interest, but can also recover the shape of the random effects terms when the response variable contains missing observations. We also test the proposed model using longitudinal data from the MACS HIV study. Compared to the model presented in Chapter 2, the Chapter 3 model returns a better fit. In Chapter 4, we propose a multivariate imputation approach within the quantile regression framework to address missing values in multiple responses within longitudinal studies. This model is motivated by real data from the WIHS HIV study. The response variable, HIV viral load, contains missing values and is also subject to upper detection limits, which can be treated as left-censored observations. Other variables of interest, such as CD4 and CD8 cell counts, also contain missing observations. Additionally, we incorporate an autocorrelated error structure in the imputation model, as current values can be influenced by previous observations. We test the model under various simulation settings and show that our model can provide accurate and consistent parameter estimation results by imputing the missing observations and recovering the censored observations. In the real data setting, we assess our model's performance compared to models without autocorrelated error structures and those using multivariate linear mixed effects models as imputation models, and we find that our model yields a better fit. In Chapter 5, we summarize the thesis and outline directions for future research.
Open Access
Three essays in Corporate Finance
Cui, Hedda
This thesis consists of three chapters. The first chapter is titled "The Glass Cliff: Are Promotions to CEOs Precarious for Women?" This study investigates the "glass cliff" phenomenon, wherein female CEOs are disproportionately appointed to precarious leadership positions. Our analysis demonstrates that female CEOs are approximately 19\% more likely than their male counterparts to be appointed under such challenging conditions. We empirically test two competing hypotheses for the glass cliff: discrimination and preference. We find that the sensitivity of female CEO appointments to firm performance varies with product market competitiveness; it diminishes when industry competition intensifies. Contrary to the preference hypothesis, which suggests that firms may appoint female CEOs for performance recovery, our finding does not support superior post-appointment performance for firms led by women compared to those led by men. Our further analysis shows that while the presence of female directors on the board is associated with an increased likelihood of female CEO appointments, it does not mitigate the glass cliff effect, suggesting that boardroom gender diversity alone is insufficient to address deeper issues related to gender bias in leadership appointments. Overall, our findings imply that the glass cliff is primarily a consequence of gender discrimination rather than a strategic preference for female leadership during precarious situations. The second chapter is titled "Corporate Governance and Performance of Australia Family Firms". While the performance of family firms has been extensively studied in international markets, there is limited understanding of their corporate governance structures and impact on firm performance within the Australian context. In this study, we analyse a large sample of Australian firms to assess the performance of family firms from a corporate governance perspective. We first compare key governance mechanisms between family and non-family firms, including board independence, board size, managerial power concentration, and overall governance quality. Our findings reveal a significant substitutive relationship between family control and conventional governance mechanisms, indicating that family firms often rely on internal governance practices rather than external oversight. When examining performance, we find that family firms exhibit higher profitability; however, this advantage diminishes for market-based valuation once governance heterogeneity is considered. Our results remain robust across various tests, including propensity score matching (PSM) and instrumental variable (IV) analyses. The third chapter is titled "Bank CEOs' Financial Distress Experience and Risk Inertia in Risk-Taking". This study investigates the relation between banks' risk-taking behaviour and bank CEOs' experience in financial distress under regular market conditions. We document strong evidence showing the relationship to be positive: banks of high-risk levels are associated with CEOs with distress experience. This finding is in contrast to previous studies that report a negative influence of CEOs' experiences in crises or early career disasters. Our results remain robust through propensity score matching (PSM) and are further validated with placebo tests. To understand the mechanisms behind the positive relationship, we compare risk levels before and after the appointment of distress-experienced CEOs. Our results show that bank risk-taking does not significantly change following the appointment, suggesting that these CEOs do not actively escalate risk. Instead, the evidence suggests a role of matching in top-management appointments, whereby risk-prone banks strategically choose CEOs with distress experience to align with their existing risk culture.
Open Access
Relational Care and Wellbeing: Applied Epidemiology in Aboriginal Community Controlled Health settings
(2025) White, Antoinette
This thesis presents the projects and the experience I acquired to fulfil the competencies of the Master of Applied Epidemiology (MAE), Australian National University. From March 2023 to December 2024, I undertook an MAE field placement with the Institute for Urban Indigenous Health (IUIH), Brisbane, Queensland. In 2009, IUIH was established to create a unified network of Aboriginal and Torres Strait Islander Community Health Services (ATSICHS) in Southeast Queensland. The network works collaboratively to provide culturally tailored and appropriate healthcare services that are accessible, affordable and place based. This was IUIH's first experience at offering a field placement for an MAE Scholar and the majority of the MAE projects were completed at this placement. To fulfil the requirement of an investigation of an acute public health problem or threat, I undertook a short-term field placement with the Public Health Intelligence Branch (PHI), Queensland Health, for an outbreak investigation and response. Presented in this bound volume are the major competencies of an evaluation of a public health surveillance system, investigation of an acute public health problem or threat, analysis of a public health dataset and an epidemiological study. Included within are the minor competencies of a literature review, lay summary, conference presentation, peer-review publication and the teaching of field epidemiology. The first chapter outlines the activities undertaken during the MAE field placement to meet my MAE core competencies. The second chapter is an evaluation of the ATLAS Indigenous Primary Care Surveillance and Research Network for sexually transmissible infections (STIs), blood-borne viruses (BBVs) and vaccine preventable diseases (VPDs). The second chapter describes the system nationally and from the perspective of one of its clinical hubs, IUIH. Stakeholder yarns, a survey, continuous quality improvement (CQI) focus groups, and the ATLAS national workshop were used to examine the attributes of acceptability, simplicity, flexibility, timeliness and stability. In addition, a data quality assessment of a subset of hepatitis C data were examined for the clinical hub. The third chapter describes the first outbreak of locally acquired mpox in Southeast Queensland which included the establishment of a Incident Management Team (IMT) to manage the response to this public health incident of state significance. It highlights the role communication and relationships play in an effective public health response. The fourth chapter is a combined Data Analysis and Epidemiological study. This retrospective cross-sectional study examined data collected from the adult client populations of two urban ATSICHS within the IUIH network during 2020-2023. A descriptive analysis was conducted to develop a wellbeing client profile for each clinic. This was followed by regression analysis to explore the relationship between relational care, client enablement and wellbeing outcomes. The final chapter in this volume describes my experiences teaching field epidemiology, including delivering a tutorial on How to create a simple survey using Qualtrics and REDcap to the first year MAE scholars, and delivering a lesson from the field on What can I or should I do about my missing data?
Open Access
Thermodiffusion for sustainable desalination, brine treatment, and crystallisation
(2025) Xu, Shuqi
Open Access
Genomic epidemiology of oat crown rust disease in Australia and abroad uncovers diverse mechanisms to generate diversity
(2025) Henningsen, Eva
Rust fungi are a diverse group of plant pathogens consisting of over 8,000 species in the Basidiomycete order Pucciniales. They parasitize numerous plants of agricultural and ecological importance, such as cereals, legumes, and trees. Like plants, rust fungi undergo alternation of generations during their life cycle. This means that their cells either have one haploid nucleus or two haploid nuclei (dikaryon) at different stages of reproduction. Rust fungi are typically dikaryotic during asexual reproduction, which can occur indefinitely through infection by urediniospores. Host adaptation by mutation during asexual propagation may occur rapidly in rust fungi, but diversification is further accelerated when the sexual cycle is active. The dikaryon enables a third mechanism for generating diversity in the absence of the sexual cycle, in which two individuals exchange entire nuclei without recombination (nuclear exchange). However, it is not understood how much these three mechanisms may contribute to host adaptation at a population scale in most rust species. A pathosystem which is well-suited to explore this is Puccinia coronata f. sp. avenae (Pca), which causes crown rust of oats. Pca is a heteroecious rust which infects oat (Avena spp.) as its telial host and buckthorns (Rhamnus spp.) as its sexual host. Compared to other cereal rusts, Pca is unique in being able to infect globally distributed wild grass species which serve as a reservoir for inoculum. In addition, different modes of reproduction vary in their relevance to Pca populations from different regions, as Rhamnus species are not distributed globally. Australia is a major oat exporter and in epidemic years Pca represents a constraint to production, but the population in Australia has not been characterized with contemporary molecular methods. To characterize the Australian population, Pca samples from across the country were phenotyped on two oat differential sets and their genomes were sequenced with short reads. Previous reports of high phenotypic diversity were confirmed but a high number of lineages were detected, which was unexpected considering the previous assumption of clonality. Chromosome level genome references for diverse Pca isolates from the USA, Australia, South Africa, Egypt, Israel, Switzerland, and the United Kingdom were generated to build resources for characterizing a broader set of Pca isolates. At the haplotype level, previous reports of genetic recombination in the USA population were confirmed and either sexual or cryptic recombination between Australian isolates was detected. The recent invasive ornamental shrub R. alaternus could be acting as a sexual host for Pca in Australia, but this requires further validation. Nuclear exchange events were identified between Pca isolates that are not only associated with significant changes in fitness but also imply intercontinental migration of haplotypes, which provides further impetus for molecular monitoring of rust pathogen populations on a global scale. The haplotype atlas generated through this work represents a significant resource for exploring how virulence evolves in Pca.
Open Access
Bone decomposition in aquatic environments
(2025) Macfarlane, Nicole
Numerous studies have been undertaken on decomposing human remains in different terrestrial contexts. Determining postmortem interval and bone decomposition rate in cases where remains have been located in aquatic contexts, however, has been problematic due to numerous variables in the aquatic environment. These include but are not limited to water temperature, chemistry, bacteria, scavengers and current or tidal activity. Hence, research in this field has occurred in a somewhat limited capacity, with studies mainly focusing on the effects of water temperature and microorganisms on the decomposition of remains. This study used a controlled animal model experiment over 12 months between January 2019 and December 2019 in the Gold Coast region of Australia. Forty-eight de-fleshed pig femora were placed in tanks replicating differing types of aquatic environments, including riverine, oceanic, estuarine and dam, with a further four femora situated terrestrially to act as controls. Twelve femora were placed in each water type, with three removed at intervals of three, six, nine and twelve months, and four femora on a gravel surface (terrestrial control) surrounded by a cage, with one removed at the previously mentioned intervals. All femora were recorded before and during the fieldwork to examine the effects of taphonomic variables such as individual environment, water chemistry, marine scavenger activity and weathering. Following the removal and collection of the femora at the three-, six---, nine--- and twelve- month intervals, additional analysis was undertaken on the remains, including macro and microscopic quantification of bone surface modifications. This analysis, including measuring any increase in porosity to the surface of the bones, assessing changes in the weight of the bone from commencement to completion of the study, measuring the staining to the interior surface of the bone once cut into a thick section, and histologically inspecting and measuring any inclusions and infiltrations to the thin sections of bone, was used to determine the potential use of each in estimating bone decomposition rate in aquatic environments. The results demonstrated that water chemistry in differing locations plays a large part in the way in which remains decompose. For example, bones subject to the replicated ocean and estuarine environments were slower to decompose due to the scale-forming nature of the water, whereas bones subjected to the more corrosive environments of the riverine and weir environments were more rapidly degraded. It was found that it is indeed possible to measure and quantify bone diagenesis in differing aquatic environments and formulate methods to determine how long remains potentially may have been exposed to water, a bone decomposition, rate using both macroscopic and microscopic techniques. The implications are that in forensic cases where an isolated bone is located in an aquatic environment, researchers may be able to better determine how long this bone had been exposed to water in situ using the techniques developed with this research.
Open Access
Actor and Factor Dynamics in Urban Waste Management Experiments: Insights from China
(2025) Wang, Shengnan
Effective municipal solid waste (MSW) management is critical due to its significant environmental and public health impacts. Cities play a key role in addressing MSW challenges, while generating the most waste and facing the greatest impacts, with their resources and ability to coordinate stakeholders, they are well-positioned to implement swift, transformative waste management solutions. However, MSW management in cities is a "wicked problem," marked by complex stakeholder interactions, multifaceted challenges, and uncertainties.The concept of sustainability transitions offers a valuable theoretical framework to examine the intricate processes by which MSW management can evolve. It highlights the interactions between actors and systemic factors across multiple levels of governance and practice. Given the uncertainties surrounding both the nature of the problem and potential solutions, small-scale experimentation has emerged as a promising approach to foster sustainable practices. While sustainability experiments are increasingly driven by diverse actors, there is limited understanding of how their roles, interactions, and strategies evolve across developmental stages of sustainability experiments formed in different settings. Moreover, the critical factors and their joint impact that influence outcomes remain poorly explored. Using China,the world's largest producer of MSW and characterized by a top-down governance system, as a case study, this research examines the development of waste management experiments within a centralized policy framework. We explore the primary question: How do actors' roles and strategies evolve in sustainability experiments, and what critical factors and synergies determine their outcomes within China's socio-political and institutional framework?Through four interrelated chapters, this research systematically examines the dynamics of actor roles, interactions, and contextual factors in forming urban waste management experiments across varied settings. The findings demonstrate that non-governmental organizations (NGOs), municipal governments, businesses, and inter-organizational alliances play critical roles in mobilizing resources, strengthening networks, aligning stakeholder interests, and building long-term linkages to address waste challenges collaboratively, albeit their roles and influence evolve over time. This research also identifies three successful causal pathways that underpin effective waste experiments:1. dedicated participants supported by strong community engagement, 2. committed actors backed by local government involvement, and 3. robust grassroots leadership enabled by responsible and responsive local governance. These pathways underscore the critical interplay of social, organizational, and behavioral factors in addressing the complexities of MSW management.By focusing on China's urban waste management, this PhD research makes several key contributions to the field of sustainability transitions. First, it advances understanding of how diverse actors and their interactions evolve across different stages of sustainability experiments, providing nuanced insights into actor dynamics and strategies. Second, it identifies and contextualizes the critical factors and their synergies that drive successful outcomes in sustainability experiments. This research also expands the geographical scope of sustainability transitions research, addressing a notable gap in understanding experimentation within China's unique institutional and socio-political environment. Finally, this work offers practical guidance for policymakers, practitioners, and researchers aiming to design and implement effective waste management initiatives in complex urban contexts.
Open Access
Positron Scattering From Small Hydrocarbons
(2025) Cheong, Zoe
Positrons are anti-matter electrons and have applications in testing of fundamental physics and non-invasive imaging. Positrons can also bind with electrons to form positronium atoms, Ps, and can also bind to atoms and molecules. A phenomenon related to positron binding is scattering resonances, where an incident charged particle is temporarily bound to a target molecule. Contrary to electron scattering, there is limited experimental evidence for positron resonances, only the Surko group in UC San Diego have managed to observe Feshbach resonances via the annihilation cross section for positron scattering from hydrocarbons. This PhD aimed to search for more evidence of the Feshbach resonances for molecules and generate new cross sections for these molecules as well. The resonances observed by the Surko group are vibrational Feshbach resonances (VFR). There is a theoretical framework developed that uses the positron binding energy as a free parameter and assumes that the annihilation escape channel for the VFR decay is small compared to other channels, and it predicts the VFR structure in the annihilation cross section well. However, a corollary of this framework is that the resonance structure can couple to vibrational states lower in energy and allow the positron to escape the resonance structure, known as intramolecular vibrational redistribution (IVR), which is information that the annihilation cross section is unable to provide. The hydrocarbons chosen for the experiment in this PhD were ethane, ethylene and acetylene, which are all two-carbon molecules with an increasing number of bonds between the two carbon atoms. The measurements in this PhD set out to conduct were primarily the vibrational excitation cross sections to search for evidence of inelastic escape of positron from the VFR structure as well as the effects of IVR. Despite strong resonance structure in the annihilation cross section associated with the CH stretch mode of all three target molecules, the CH stretch excitation cross section show no enhancement in the cross section for all three target molecules. The CH3 deformation mode cross section for ethane shows no resonance enhancement either, while the CH2 deformation mode for ethylene shows evidence of multimode VFR structure. The CC stretch mode for both ethylene and acetylene are dipole forbidden, and that of ethylene has a very small cross section and it is unclear if it is real, while that of acetylene shows a clear resonance structure that can only be a VFR coupling into this vibrational mode via IVR. The total cross section for positron scattering from ethane, ethylene and acetylene for this energy range was also measured and showed no resonance structure in the cross section. Consequently, it can be interpreted that for these three molecules, the VFR does not decay via elastic escape. This, combined with the limited evidence for inelastic escape is contrary to the assumptions used by the theoretical calculations. While there is evidence for IVR, it remains that the theory needs to be improved upon. Next, the differential cross section (DCS) of all three target molecules were measured, and are all strongly forward peaked. Such behaviour is typically attributed to molecules with a dipole moment, which ethane, ethylene and acetylene lack, and the strong forward scattering must then be due to the polarizability of the target molecules, which is not accounted for well by the theory. The current grand total cross sections measured were all consistently around 10 angstrom squared larger than the previous measurements, which is attributed to the previous experiments missing a larger portion of the cross section due to the strongly forward peaked DCS. The total elastic, total electronic excitation, positronium and ionisation cross sections are presented as well, where the theory again misses the forward scattering and is smaller than the experimental total elastic cross sections.

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