Open Access Theses
Permanent URI for this collectionhttps://hdl.handle.net/1885/3
To view all theses in this collection, select one of the 'Browse by' options (Issue Date, Author, Title, Subject, Title or Type (of thesis). You can also enter your keyword/s into the text box above and click on Search.
ANU theses are harvested by the National Library of Australia's Trove service and other search engines, making them fully discoverable online.
Find Australian theses.
Full instructions available here
Submit your thesis (Approved ANU research theses only)
Please note: The Abstracts displayed in item metadata are in many cases truncated. For the full Abstracts, see the thesis document files.
Browse
Recent Submissions
Item Open Access Rare earth element mineralisation in Australia(2025) Chandler, RossAustralia hosts a variety of Rare Earth Element (REE) deposits. Whilst carbonatite-associated deposits are the only style currently mined, some peralkaline volcanic and Iron Oxide Copper Gold (IOCG) systems also contain economic concentrations of REE. Despite growing interest in REE, the ore genesis of all three deposit styles in Australia remains understudied, hampering effective utilisation of the nation's Critical Metal resources. This thesis addresses this knowledge gap first by assessing known occurrences, followed by microanalytical and geochemical studies of REE mineralisation nationwide. Firstly this thesis presents a compilation of the geological and isotopic characteristics of Australia's carbonatites. The 16 known carbonatites range from Neoarchean to Jurassic in age, are all hosted within Proterozoic (or older) crust and are extremely geologically diverse. They range from multiphase intrusive complexes dominated by carbonatite (e.g. Gifford Creek and Mt Weld, WA) or silicate rocks (e.g. Cummins Range and Cundeelee, WA), to small volume carbonatite dykes (e.g. Yungal dykes, WA). The diversity is reflected in radiogenic isotopic signatures (Rb/Sr and Sm/Nd), which indicate derivation from a variety of mantle sources. REE and Nb mineralisation is hosted within both primary carbonatite and overlying carbonatite-derived regolith, with dolomite carbonatite displaying greater increases in REE grade during weathering, compared to siderite carbonatites. The second part of this thesis focusses on the Mt Weld carbonatite (WA), which hosts a large REE deposit within the regolith overlying a c. 2.06 Ga carbonatite complex. Samples are taken from an exploration drill hole, and reveal an intrusive architecture of inner REE-mineralised magnesio- to ferrocarbonatite (c. 600m diameter) surrounded by an annulus of REE-poor calciocarbonatite (c. 1.2km thick). Monazite is the main host of REE, with textures and chemistries suggestive of a period of late hydrothermal mineralisation. A comparison of carbonatite and regolith geochemistry suggests minimal horizontal migration of ore elements during regolith formation, displaying a ~5x upgrade in REE during weathering. Thirdly, REE mineralisation within the Bingie Grumble peralkaline trachyte (NSW) is investigated. REE are hosted within magmatic eudialyte that is variably pseudomorphically replaced by intergrown amorphous zircon, hydroxylbastnasite-(Nd) and an array of Ce silicate (Mn) phases. 40Ar/39Ar geochronology confirms a c. 17.1 Ma age for the trachyte. Using mineral and whole-rock chemistries, a model for the deuteric (autometasomatic) alteration of the trachyte is presented, where hydrothermal fluids from the de-volatilisation of the erupting lava interact with eudialyte, causing pseudomorphic replacement by secondary mineral assemblages. The deuteric fluids efficiently oxidised CeIII to CeIV and in some cases, transported trivalent LREE significant distances within flows, forming Ce-deficient hydroxylbastnasite-(Nd), some of the most Nd-rich naturally occurring minerals reported to date (up to 34% Nd2O3). Finally, this thesis presents a study on the Cu-Au-U systems of the eastern Mt Isa Inlier (QLD) which identifies two distinct styles of REE-enriched deposits: F-Ba rich IOCG deposits and U-Cu-Au skarn deposits. The first is characterised by a single phase of REE and Cu mineralisation, and the latter by early REE and U-rich skarn formation followed by a late Cu-Au overprint. REE patterns systematically vary between deposit types, with IOCG deposits characterised by positive Eu anomalies in mineral and whole rock, while skarns have negative Eu anomalies. These observations suggest distinctly different mechanisms of ore formation. The contrasting behaviour of Eu between the two deposit types may reflect the metal source in each deposit type, supported by an association of the skarns with evolved intrusives, and the F-Ba rich IOCGs with regions of albitisation.Item Open Access Developing Novel Methods for High-Field Electron Paramagnetic Resonance Measurements of Biomolecules(2025) Judd, MartynaThe scope of Electron Paramagnetic Resonance (EPR) spectroscopy has expanded dramatically in recent decades as a powerful tool for biomolecular structure determination. Advancements in high-frequency microwave instrumentation have motivated the exploration of novel measurement methods, probehead design, and biomolecular spin technologies, which take advantage of the increased sensitivity and resolution that comes with detecting unpaired electrons at high magnetic fields. High-field EPR provides a promising avenue for visualising molecular events in biological cells and addressing key challenges of modern drug discovery. This thesis aims to contribute to ongoing high-field EPR developments and their application to structural biology. The thesis is divided into two parts. Part I focuses on the Electron-Nuclear Double Resonance (ENDOR) experiment at 94 GHz to measure 5-30 A distances between an electron and nuclear spin. This range is notoriously difficult to capture using standard techniques, but can be accessed by ENDOR through exploiting the spectroscopic advantages of 19F and the S = 7/2 paramagnetic Gd3+ ion at 94 GHz. Chapter 3 shows that 19F ENDOR can resolve distances and conformational dynamics in proteins tagged with Gd3+ and 19F spin labels for dipolar interactions up to 16 A. The 19F ENDOR detection limit is pushed to >20 A by using the distance dependence of the ENDOR intensity, overcoming the chase for linewidth resolution. Systematic 19F ENDOR measurements of molecular rulers with well-defined 19F-Gd3+ distances validate the integrated-intensity approach to reliably access distances up to 30 A in spin-labelled protein. This approach is thoroughly benchmarked by lineshape modelling and statistical error analysis. Lastly, by using a novel, complementary set of luorinated aromatic amino acids, the orientation of buried side chains can be accurately constrained in metalloproteins with rigid Gd3+ sites. In proteins labelled with flexible Gd3+ tags, 19F ENDOR lineshape analysis combined with rotamer simulations provides information on the conformational distribution of trifluoromethyl-labelled side chains. In Chapter 4 this approach is expanded to other magnetically active nuclei. 31P Mims ENDOR is used in tandem with EXAFS measurements to validate the binding mode of luminescent lanthanide complexes to different polyphosphates, to understand and optimize these complexes in biological sensing and cell imaging applications. ENDOR provides important insight into binding mode heterogeneity which cannot be easily obtained by other techniques. Part 2 pivots to the development of new resonators for EPR measurements at Q-band (34 GHz) which bridge the requirements of high-sensitivity, narrowband detection for CW EPR, with the need for efficient off-resonance excitation in a broadband resonator for pulse EPR experiments. In Chapter 6 the standard 34 GHz TE011 cavity is modified with a dielectric plate covering the coupling iris to increase the resonator bandwidth while retaining sensitivity. Experiments demonstrate the dependence of the resonator bandwidth on the dielectric thickness, coupling short position, and cavity dimensions and show good agreement with finite elements electromagnetic calculations. This modification was implemented into a movable dielectric coupling short, to easily interchange between the original critically coupled CW mode and the dielectrically overcoupled mode. Finally a new 34 GHz TE01d3 dielectric probe is presented, which outperforms both the TE011 cavity and Bruker EN 5107D2 dielectric resonator sensitivities, and overcomes limitations of standard dielectric resonators, i.e. lack of frequency tunability and sample-size restrictions. The TE01d3 resonator is also compatible with the dielectric coupling mechanism. These developments are well-positioned to allow EPR experiments with different resonator requirements, to be measured in a unified, general-purpose set up.Item Open Access Physiology and Plasticity of Sensory Synapses in the Piriform Cortex(2025) Palmer, DanielIn this thesis, I utilise in vitro slice models to investigate the structure, physiology and plasticity of synapses delivering sensory (afferent) information from the olfactory bulb (OB) to the primary excitatory neurons of the PCx, semilunar (SL) and superficial pyramidal (SP) cells. Given the relationship between postsynaptic morphology and synaptic transmission, I first used enhanced-resolution confocal microscopy to investigate the dendritic structure and distribution of spines on the apical arbours of the two target cell types. SP cells displayed more complex dendritic trees and a higher spine density than SL cells. Interestingly, although arranged at a lower density, spines on the distal apical dendrites of SL cells (where afferent input is received) were significantly larger than those on SP cells. As a result, synaptic opportunity (defined as total spine head surface area per unit dendritic length) was similar for both cell types. In view of the substantial differences in spine structure and distribution, I next combined minimal electrical stimulation with whole-cell somatic recordings to investigate the properties of afferent synaptic transmission. These experiments showed that SL cells receive significantly larger unitary synaptic inputs from the OB than do SP cells. Variance-mean analysis and strontium-evoked asynchronous EPSCs revealed that these powerful inputs to SL cells are driven by both a higher neurotransmitter release probability (Pr) and higher quantal amplitude (Q). As a result, SL cells can be lifted to action potential threshold with fewer afferent inputs than SP cells. Next, I asked whether the disparity in afferent synaptic structure and transmission to SL and SP cells extended to their ability to express synaptic plasticity. Using patterned extracellular stimulation, N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) and depression (LTD) could be observed using field recordings. When isolating unitary inputs, however, LTP and LTD could only be induced at afferent-SL synapses, with no reliable plasticity inducible at afferent-SP inputs. Interestingly, afferent-SL LTD was expressed both pre- and postsynaptically, with variable changes in Pr (presynaptic) and Q (postsynaptic) observed. On the other hand, afferent-SL LTP was predominantly presynaptic and appeared to depend on the prior Pr of the stimulated input, such that low Pr synapses could be potentiated while high Pr synapses could not. In a final set of exploratory experiments, I investigated the excitability of SL and SP cell dendrites. Dendritic NMDA spikes can evoke synaptic potentiation at afferent inputs, so it was important to understand whether the plasticity I observed depended on this mechanism. I made whole-cell recordings from both somas and dendrites of SL and SP cells while systematically increasing the strength of afferent extracellular stimulation. Although putative dendritic electrogenesis was observed at high stimulation strengths, synaptic responses scaled linearly through the minimal stimulation range, indicating that the unitary stimulation strengths used in my plasticity experiments did not evoke active dendritic events. Overall, the experiments presented in this thesis reveal distinct differences in how SL and SP cells receive and process monosynaptic sensory information from the OB. From dendritic spine structure through to synaptic transmission and plasticity, SL and SP cells are markedly distinct. Given that these cells are the dominant glutamatergic cell types of the PCx, and receive the majority of monosynaptic afferent input from the OB, understanding how they process olfactory input will be critical for our ultimate understanding of how information is encoded and stored within this trilaminar sensory cortex.Item Embargo Molecular basis for the folding and autocatalytic processing of beta-helical autotransporter passenger domains(2025) Yuan, XiaojunAutotransporters are a distinct class of outer membrane proteins (OMPs) and the largest family of virulence factors produced by Gram-negative bacterial pathogens. The virulence functions of autotransporters depend on their correct assembly at the bacterial cell surface. Assembly requires the C-terminal beta-barrel domain to be inserted into the outer membrane in a partially folded state to facilitate translocation of the N-terminal passenger domain onto the cell surface, where it folds into its biologically active form. Some passenger domains remain attached to their cognate beta-barrel domains to typically function as adhesins or as mediators of aggregation and biofilm formation, while others are cleaved and released into the extracellular environment to function as toxins or in disruption of host immune response. Once translocated, autotransporter passenger domains predominantly fold into elongated beta-helical stalk-like structures that project outwards from the cell surface. Many studies have provided valuable insights into how autotransporters adopt their functional conformations, yet many mechanistic details are lacking. In this study, we used mutagenesis analysis to test the role of the extracellular loops of the beta-barrel domain belonging to the autotransporter, plasmid-encoded toxin (Pet) in folding of the cognate passenger domain. We found that the fifth extracellular loop (L5), which forms a beta-hairpin structure, is required for Pet passenger folding into its native, protease-resistant conformation in vivo and in vitro. This work revealed that it is the beta-strand propensity of the L5 beta-hairpin, rather than specific amino acid residues, that is important for facilitating passenger folding. Based on these findings, we proposed that L5 mediates Pet passenger folding via beta-augmentation and showed that this folding mechanism is conserved in the Serine Protease Autotransporters of Enterobacteriaceae (SPATE) subfamily. To test if loop-mediated passenger folding is conserved in autotransporters beyond the SPATE subfamily, we used antigen 43 (Ag43) as a model protein. Ag43 is an autotransporter that mediates cell aggregation and biofilm formation. We found that both the fourth and fifth extracellular loops of the beta-barrel domain are required for rapid folding of the passenger domain and for Ag43-mediated bacterial cell aggregation. Together, these findings suggest that loop-mediated passenger folding could be a conserved folding mechanism among autotransporters with a beta-helical structure. We also show that proteolytic processing of Ag43 occurs through autocatalysis, in the absence of host or exogenous proteases, and that autocatalytic processing of the passenger domain from its cognate beta-barrel is not required for Ag43 function. This study provides new mechanistic understanding of how autotransporter passenger domains fold and undergo proteolytic processing. Our results suggest that the autotransporter beta-barrel domain is a folding vector that mediates passenger domain folding directly via the extracellular loop(s). We show that inhibition of passenger domain folding through deletion of the extracellular loop(s) inhibits autotransporter-mediated virulence functions, and thereby propose that the extracellular loops are potential therapeutic targets in treating and preventing bacterial infections.Item Open Access Efficient Policy Gradient Reinforcement Learning in High-Noise Long Horizon Settings(2025) Aitchison, MatthewThis thesis explores the enhancement of Policy Gradient (PG) methods in reinforcement learning (RL), focusing on their application in real-world scenarios. It addresses challenges in efficient evaluation, noise reduction, and long-horizon discounting in RL. Key contributions include the Atari-5 dataset, reducing evaluation time in the Arcade Learning Environment, and the Dual Network Architecture (DNA) algorithm, improving Proximal Policy Optimization's (PPO) performance in vision-based tasks. The TVL algorithm, capable of learning over long horizons without discounting, demonstrates potential in high-noise environments. This research advances the understanding and application of PG methods, highlighting their practical implications in complex decision-making and robotics.Item Open Access Examining Skill Enactment and Knowledge Acquisition in Digital Cognitive Behavioural Therapy for Depression and Anxiety(2025) Jackson, HayleySubstantial evidence supports the effectiveness of digital mental health interventions (DMHIs) in treating and preventing depression and anxiety disorders. Interventions based on cognitive behavioural therapy (CBT) show the most robust evidence. However, challenges remain in effectively engaging users with DMHIs. Most research has relied on usage metrics such as the number of logins or modules accessed to measure engagement. This approach may not fully capture other important processes, such as the application of intervention strategies in daily life (i.e., skill enactment) or the acquisition of knowledge about mental health and strategies to address symptoms (i.e., knowledge acquisition). Accordingly, this thesis aimed to investigate skill enactment (primary aim) and knowledge acquisition (secondary aim) in digital CBT interventions for depression and anxiety. Four studies were conducted that used narrative synthesis, quantitative, and/or qualitative approaches. Study 1 was a systematic review that synthesised the literature on skill enactment and knowledge acquisition in randomised controlled trials (RCTs) of digital CBT interventions for depression and anxiety. Study 2 examined predictors of engagement and explored the relationship between skill enactment and mental health outcomes among adolescents in a cluster-randomised controlled trial (cRCT) of a school-based online depression prevention program. Study 3 employed mixed methods to assess the effects of a video-based intervention on skill enactment, evaluate the impact of skill enactment on mental health outcomes, and explore experiences of skill enactment among university students with mild to moderate psychological distress. Study 4 qualitatively explored experiences of learning and enacting skills among adult users of publicly available digital CBT interventions. Results suggest that digital CBT interventions can enhance skill enactment and knowledge acquisition among adults with elevated symptoms or those who recognise a need for treatment (Studies 1 and 4). While both constructs are likely important for mental health outcomes in these contexts, their significance may vary depending on the specific type or aspect of skill enactment or knowledge, as well as factors such as perceived control, motivation to change, and active coping. In contrast, no significant changes in skill enactment were observed among young adult users of a digital CBT program (Study 3), nor was skill enactment found to influence mental health outcomes among adolescents or young adults (Studies 2 and 3). Key factors influencing skill enactment included perceived learning and knowledge reinforcement, the relevance and usefulness of intervention strategies to the individual user, and barriers such as time constraints and low motivation. The thesis advances understanding of engagement with digital CBT interventions by consolidating evidence on skill enactment and knowledge acquisition, while offering new insights into skill enactment among different groups of young people and user experiences of learning and implementing skills outside trial settings. The thesis findings suggest that personalised content, learning support strategies, and ongoing resources beyond the intervention may help support the acquisition, retention, and use of knowledge and skills. Enhancing skill enactment and knowledge acquisition may be critical for optimising the impact of DMHIs, although further investigation into the mechanisms by which these constructs influence mental health outcomes is warranted.Item Open Access Gut Instincts: Applied Epidemiology of Enteric Viruses, Bacteria and Parasites(2025) Alland, SarahHunter New England (HNE) Health Protection is responsible for prevention, surveillance and response to threats to human health in the Hunter New England Local Health District (HNELHD) region of New South Wales (NSW). From February 2023 to October 2024, I undertook my MAE field placement within HNE Health Protection. This thesis describes the projects I undertook during the field placement. The projects that fulfill the MAE competencies are: 1) a capture-recapture analysis of acute flaccid paralysis surveillance in the Australian Capital Territory, 2) a case-control study of Clostridioides difficile infection and antibiotic use at a large, regional hospital, 3) investigation of an increase in cryptosporidiosis notifications in the HNE region, 4) an evaluation of Salmonella Enteritidis human health surveillance in NSW and 5) teaching of epidemiological concepts to other MAE scholars and colleagues. This thesis also describes other public health activities I contributed to during the field placement, including: local and national foodborne outbreak investigations through OzFoodNet; a data analysis summarising Australian listeriosis outbreaks from 2012 to 2022; routine follow-up of notifiable diseases in HNELHD; ad hoc data analyses to inform surveillance of notifiable diseases in HNELHD; development of HNE Health Protection incident response management system and processes for highly pathogenic avian influenza; and amendments to HNE Health Protection's Standard Operating Procedures for cryptosporidiosis follow-up. These projects and activities fulfil the core requirements of the Australian National University Master of Philosophy (Applied Epidemiology) program.Item Open Access Investigation of cost effective III-V semiconductor solar energy device architecture(2024) Gupta, BikeshThis thesis is dedicated to exploring novel device structures and strategies for cost-effective III-V semiconductor solar energy devices. It includes experimental work and addresses fundamental constraints to develop high-efficiency, cost-effective III-V semiconductor solar devices. The thesis is structured as follows: Chapter 2: This chapter identifies and analyzes the factors contributing to the high cost of III-V semiconductor photovoltaic devices. It aims to overcome cost-related challenges through innovative designs that improve efficiency and economic viability. Chapter 3: This chapter introduces the experimental methods and fabrication techniques used in subsequent chapters (Chapters 4 to 7) to demonstrate high-efficiency and cost-effective InP solar energy devices. Chapter 4: In this chapter, InP heterojunction solar cells are presented, which utilize carrier selectivity and eliminate the need for costly metal organic chemical vapor deposition. TiO2 serves as the electron-selective layer, and H2 plasma exposure modifies the InP surface, resulting in an efficiency of 19.3% and an open-circuit voltage of approximately 800 mV. The effects of H2 plasma exposure on InP photovoltaic devices are discussed. Chapter 5: This chapter introduces an InP heterojunction solar cell with a simplified, cost-effective approach for processing the electron-selective contact layer. A solution-processed ferrihydrite layer is employed as the electron-selective contact, achieving a noteworthy short-circuit current density of 24.7 mA cm-2, comparable to atomic layer-deposited TiO2 (25.8 mA cm-2). Ferrihydrite also acts as a protective shield against InP photocathode photo-corrosion and offers long-term stability, with a photoelectrochemical half-cell water reduction efficiency of 8.4%. Calculations suggest the potential for exceeding 25% efficiency. Chapter 6: This chapter presents a low bandgap InGaAsP solar cell with an efficiency of 19.1% and an open-circuit voltage of 658 mV, rivaling cutting-edge InGaAsP homojunction solar cells. The role of a thin InP surface passivation layer and a TiO2 electron-selective layer in achieving high efficiency is discussed. A mechanically stacked tandem solar cell configuration is developed, achieving an impressive efficiency of 27.7% and an excellent open-circuit voltage of 1.7 V, eliminating the need for lattice-matched tunnel layers. Chapter 7: This chapter addresses cost concerns associated with III-V semiconductor solar cells, particularly related to the use of entire wafers in the manufacturing process. The technique of mechanical peeling off thin InP films from bulk InP wafers (spalling) is introduced. The chapter includes a meticulous assessment of the surfaces of spalled InP thin films to identify potential surface damage. Successful production of InP heterojunction solar cells with an efficiency of 13.3% using spalled thin films is discussed, as well as the creation of a photoanode with promising water oxidation efficiency. Chapter 8: The final chapter consolidates the primary research findings and analyses from the thesis. It also explores potential future research directions for achieving cost-efficient III-V semiconductor solar energy devices. In summary, this thesis contributes significantly to the field of solar energy technology by improving the efficiency and reducing the cost of III-V semiconductor solar cells. The research presents innovative solutions and insights with the potential to advance sustainable and economically viable solar energy technologies.Item Open Access Efficient zero-knowledge range arguments and privacy-preserving applicationsZhou, YueThis thesis primarily explores efficient zero-knowledge range arguments as first part and privacy-preserving applications within distributed systems as second part. The first part focuses on zero-knowledge range arguments, a fundamental cryptographic primitive that enables a prover to convince a verifier that a secret value lies within a predefined range without disclosing any unnecessary information. However, deploying range arguments in practice faces significant challenges due to high gas costs and computational overhead. This part contributes to optimizing the {\em verification efficiency} of range arguments to reduce deployment costs on blockchains and other decentralized platforms. We introduce four new zero-knowledge range arguments in the discrete logarithm setting that require only $c \sqrt{\tfrac{N}{\log N}}$ group exponentiations in verification, where $N$ is the number of bits to represent a range and $c$ is a small constant. These improvements make the arguments concretely efficient for blockchain deployment with minimal gas costs. The second part proposes two privacy-enhancing secure distributed systems and applications. First, we introduce a novel paradigm for decentralized privacy-preserving group purchasing for energy plans. Leveraging privacy-preserving blockchain technology and secure multi-party computation, this approach enables users to form coalitions for coordinated switch decisions in a decentralized manner without relying on a trusted third party. We develop an effective solution to support decentralized privacy-preserving group purchasing, which includes a competitive online algorithm for decision-making, secure multi-party computation for enhancing privacy, and zero-knowledge proofs on the blockchain for verifying the private input data used in our online algorithm. Second, we propose a novel scheme zk-qrcode based on anonymous credentials and zk-SNARK. Our scheme leverages the following features: Blockchain-based credential issuance, we eliminate the need for credential issuers to hold signing keys by allowing them to issue credentials to a smart contract on the blockchain; Flexible and composable identity statements, enables users to prove complex statements about their credentials without revealing unnecessary information; QR code based verification: enables user interaction with service providers through QR codes displayed or scanned on mobile phones, incorporating identity proof and access control requests. We implement and evaluate our zk-qrcode scheme in practical use cases for entering bar anonymously. Our results demonstrate that the scheme is efficient and practical, with access control proof generation and verification taking less than 650 milliseconds.Item Open Access Security for the Internet of Things in Terrestrial and Non-Terrestrial Networks(2025) Khan, SaudThe IoT revolution is transforming various sectors by enabling seamless connectivity and data exchange between devices. However, this rapid expansion brings significant security challenges due to IoT devices' constrained resources and diverse nature. This thesis presents a comprehensive security framework addressing these challenges through three interconnected components: detection, identification, and authentication. This integrated approach is crucial for establishing a robust IoT security framework capable of mitigating various threats effectively. First, we focus on the detection and identification components by investigating the multi-user detection (MUD) problem in uplink grant-free NOMA. This scenario involves identifying the number of active IoT devices and decoding their transmitted data without prior knowledge of device activity levels. The proposed solution leverages an attention-based bidirectional long short-term memory (BiLSTM) network, exploiting the temporal correlation of IoT device transmissions. The BiLSTM network processes the device activation history through forward and reverse-pass LSTMs, while the attention mechanism highlights crucial activation points. This approach forms a hierarchical pathway for detecting active IoT devices and performs blind data detection using complex spreading sequences. The results indicate that this method significantly outperforms existing benchmark schemes, providing superior detection accuracy and flexibility without requiring prior knowledge of device sparsity or channel conditions. Next, we investigate the IoT authentication component by introducing an innovative physical-layer authentication scheme tailored for terrestrial IoT devices with limited computational capabilities. The scheme eliminates the need for repeated key generation and verification by verifying access time slots and spreading sequences. This approach reduces computational overhead and enhances security by concealing seed information from potential attackers. The results demonstrate a near threefold reduction in the misdetection rate of illegitimate devices and a false alarm rate close to zero, even with varying numbers of active devices and signal-to-noise ratios. The scheme boasts at least half the computational cost of benchmark methods, underscoring its practicality for real-world IoT deployments. Finally, we address the unique security challenges associated with IoT authentication in non-terrestrial Low Earth Orbit (LEO) satellite-based IoT networks. This work proposes a modified AKMA framework incorporating local key refreshment for decentralized and continuous authentication. This modification reduces the need for repeated authentication attempts with satellites, mitigating the risks of man-in-the-middle and spoofing attacks. The framework's performance is evaluated in the presence of an illegitimate Unmanned Aerial Vehicle (UAV), showing improved authentication rates for legitimate devices and reduced misdetection rates for illegitimate devices compared to existing shared key and physical channel-based authentication schemes. The modified AKMA framework demonstrates its applicability and effectiveness in enhancing security for LEO satellite-based IoT networks. In summary, this thesis presents a holistic IoT security framework that effectively addresses the critical detection, identification, and authentication components. Each component offers significant advancements in its respective domain, and their integration forms a comprehensive framework to safeguard IoT devices against a broad spectrum of security threats. This work not only contributes valuable insights into IoT security but also provides practical solutions that can be implemented to ensure the secure operation of IoT networks in various environments. The results underscore the importance of a multi-faceted approach to IoT security, paving the way for future research and development in this vital field.Item Open Access Observing the Dynamic Infrared Sky(2025) Soon, JamieThe entirety of the dynamic infrared sky has only just begun to be explored. The field of multi-messenger time-domain astronomy has grown significantly over the past years with astronomical transient and variable events including, but not limited to, supernovae, gravitational waves, and neutrino events. Whilst there are a significant number of all-sky optical surveys that are observing these events, there are a substantially less number in the near-infrared even though it is known that extinction due to dust means that a proportion of these events cannot be seen in the optical regime. One of the main reason for the lack of infrared survey telescopes is that astronomy has, for many years, traditionally relied on Mercury Cadium Telluride detectors which are orders of magnitude more expensive than equivalent optical detectors. However, a recent change has been the development of large format Indium Gallium Arsenide detectors which may allow astronomers to bridge this gap between optical and infrared surveys. In this thesis, two wide-field fully robotic near-infrared surveys are discussed, Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey. Palomar Gattini-IR is a 0.3m telescope located at Palomar Observatory in California, United States of America operated by the California Institute of Technology. The Dynamic REd Allsky Monitoring Survey is a survey that will be located at Siding Spring Observatory in New South Wales, Australia utilising a 0.5m telescope and will be operated by the Research School of Astronomy and Astrophysics of the Australian National University. The Dynamic REd All-sky Monitoring Survey will take advantage of the development of Indium Gallium Arsenide technologies to achieve its goals. This thesis describes the initial commissioning and subsequent operations of Palomar Gattini-IR and the path from a conceptual design through to the development for the Dynamic REd All-sky Monitoring Survey. This thesis also describes the feedback loop that is required for the design of an instrument from observations to follow-up to identification to statistics to survey requirements and back to the initial design. This thesis also describes the development of supporting tools and infrastructure for multi-wavelength, multi-colour, and multi-messenger time-domain astronomy. The observations from Palomar Gattini-IR and the design for the Dynamic REd All-sky Monitoring Survey have shown that there is a substantial amount of interest in the near-infrared astronomical sky and bodes well for the future with the on-going automation of the Australian National University 2.3m telescope and synergies with the Vera Rubin Observatory.Item Open Access Functional characterisation of the evolutionary intermediates of the prokaryotic adaptive immune system CRISPR-Cas12(2025) D Silva, JovitaProkaryotes have developed an array of defence mechanisms against invading mobile genetic elements (MGE's) such as bacteriophages and plasmids. Among them, CRISPR-Cas (Clustered regularly interspaced short palindromic repeats- CRISPR associated proteins) is the only known adaptive defence system. CRISPR-Cas systems generate an RNA from a memory cassette of past infections, which guides the Cas protein to bind to and interfere with complementary invading DNA during a subsequent infection. This RNA guided nuclease activity is programmable and thus over the last decade has been explored for gene editing and molecular diagnostics. CRISPR-Cas systems are numerous and diverse, thus classified into 2 classes and 6 types. The type V systems, also called CRISPR-Cas12 embodies an effector protein with a conserved RuvC catalytic site that causes double-stranded breaks in the target DNA (some Cas12 harbour inactive RuvC). The Cas12 family by itself is very diverse and over the last few years, there has been a growing interest in understanding the evolution of the type V CRISPR Cas systems to unravel how these systems have evolved? Several CRISPR-Cas systems have been evolutionarily linked to transposable elements. Cas12 systems have evolved from a transposon associated element IS200/IS605 or IS607, called 'TnpB'. TnpB is also an RNA guided nuclease, but instead of defence, it functions to identify its targeted site for transposition. This raises the question: how did a transposon such as TnpB evolve to acquire the ability to protect its host against foreign genetic elements? In order to understand the evolution of TnpB into a fully functional Cas12 system (such as Cas12a), this thesis focusses on the identification and characterisation of their evolutionary intermediates. I undertook a computational analysis identifying Cas12 and TnpB effectors from a large dataset of assembled metagenomes which was then subjected to phylogenetic analysis. Evolutionary intermediates sub-types of Cas12 were identified as those that were closely linked to typical TnpB's and did not occur with adaptation proteins such as Cas1 and Cas2. Three such sub-types, type V-U1, type V-U2 and type V-U4 were then investigated by selectively characterising representative of each sub-type. All systems were structurally aligned with pre-existing structures to identify similarities and unique features that tied them to TnpB. Their loci were heterologously expressed to study their expression profiles and identify the small RNA require for interference. The candidate effectors were then subjected to in vitro assays, bacteriophage infection assays and plasmid interference assays to assess their programmability, interference, to understand their mechanism of action and validate their ability to function as ancestral defence systems. Through functional characterisation of three different evolutionary intermediate sub-types, the key findings emphasised on the independent evolution of each subtype from a different TnpB on multiple independent occurrences. I characterised the sub-type V-U1 to have evolved from be a nuclease inactive variant, that interfered with dsDNA bacteriophages and plasmidic elements through binding to its target sequence thereby causing CRISPR interference. Conversely, type V-U2, did not exhibit any bacteriophage defence against bacteriophages, but harboured a RuvC active catalytic centre that facilitated plasmidic interference. Type V-U4 was most similar to the only characterised TnpB, ISDra2. It harboured a RuvC intact catalytic domain that together with small functional RNAs targeted double-stranded DNA bacteriophage. Overall, identifying and understanding the elemental characteristics of three independent evolutionary inter-mediatory Cas12 subtypes, revealed properties that are ancestral and most essential in the functioning of Cas12 systems. This works more predominantly unravels the blueprint of Cas12's evolution from TnpB transposable elements.Item Open Access The end of time as we know it: ethics and inequalities in mothers and fathers experience of time for work, family and health(2025) Wales, MandyParents in Australia have higher total time commitments and more gendered time-use patterns than other adults, with most 'juggling' their time between paid work and family caring responsibilities. Responding to the time demands of both the labour market and the family presents considerable challenges. Parents are routinely described as being time scarce and time pressured. Exercise and a healthy diet are considered to be vital for good health but both also require time and effort on a daily basis. In view of the time constraints experienced by parents, is there time for health? This study examines the intersection of work, family and health in the daily lives of parents in Australia. Using a qualitative and interpretative framework, and drawing on data from questionnaires and interviews with 43 mothers and fathers in Western Sydney, it explores experiences of time, and attitudes and priorities articulated by parents while engaging in work, caring for their children and in being healthy. Thematic analysis was used along with social practice theory to identify key themes and issues. The results highlight the difficulty that many parents face in satisfactorily balancing time for paid work in addition to caring for their children as well as they wish. Time for paid work was found to be privileged, and valued by most mothers and fathers in the study as a source of dignity, respect, social connection, personal development and fulfillment as well as generating income. The evidence demonstrated that in terms of absolute time commitments however, unpaid family work overwhelmingly trumped time for work. Many parents expressed sentiments about the vast array of responsibilities and invisible tasks required to 'properly' care for children in the modern age and a sense that expectations had increased over time in accord with a practice of 'intensive parenting'. These pressures exacerbated parents' experience of time as a problem: time that sped by too fast, and yet was characterised by interruptions and challenges of sequencing and scheduling. Importantly, parents described the way that time was used, controlled and understood in ways that evidenced gendered inequality and challenges to their capacity to meet their own and societal expectations. The research also confirmed that time is an important resource for health and that busy and time-pressured parents often compromise self-care and the diet and exercise behaviours necessary for healthy living. Parents were well aware of the need for healthy behaviours and also expressed a desire to support their children to lead healthy lives. This study suggests that the ability of some parents to 'choose health' is constrained and compromised by their personal experiences of time, and provides explanations for the ways in which time can compromise health behaviours. It demonstrates that these are issues that also confront families who are economically and socially disadvantaged. The study offers a novel approach to the analysis of time barriers by also investigating the complex ways that time is valued, adding the concept of 'morality of time' to the multitude of ways that time influences health.Item Open Access Identification of Resonantly Coupled Ion Pairs in Eu3+:Y2SiO5(2024) Lennon, AnnaliseRare-earth-ion-doped crystals are being increasingly studied for quantum information, due to their highly coherent and long-lived optical and spin levels. In these systems, interactions between dopants form the basis of quantum computation. However, these interactions remains poorly understood at small inter-ion distances. In particular, there has been little work toward understanding off-diagonal interactions, which delocalise the excited states of the two interacting ions. This thesis presents an experimental investigation into the off-diagonal resonant coupling interaction that arises between symmetry-related pairs of Eu3+ ions in Eu3+:Y2SiO5, to investigate both its strength and extent. The strength determines the variation of the coupled ion properties from their uncoupled counterparts, while the extent informs on the number of impacted ions. This thesis presents two new methods for the identification of resonantly coupled ion pairs in rare-earth-ion-doped materials. The first method uses variations in both the frequency and homogeneity of the optical and hyperfine transitions to identify ion pairs with strong resonant coupling interactions. Using this method, I have identified three resonantly coupled ion pairs. The second method uses the change in the permanent electric dipole moment due to the delocalisation of the excited states to identify ion pairs with weaker resonant coupling interactions. Using this method, I identified an additional two resonantly coupled ion pairs. The strength of the resonant coupling interaction can theoretically be deduced from this method. I present the first steps to this analysis, and highlight the current limitations to this approach. The strength of the interaction is additionally investigated through changes to the transition selection rules that are induced by the delocalisation of the excited states. Using this method, I determine the interaction strength for one resonantly coupled ion pair and provide an estimate for the remaining pairs. The number of observed resonantly coupled ion pairs is used to produce a lower bound on the extent of the interaction.Item Open Access Unraveling the Influence of the North Atlantic Ocean on Atmospheric CO2 through Carbonate Chemistry: Insights from ODP Site 984(2025) Wu, JiadeIn the modern climate, the North Atlantic - the portion of the Atlantic Ocean which lies north of the Equator - serves as a significant carbon dioxide (CO2) sink; however, its role in past atmospheric CO2 fluctuations remains enigmatic. To address this, the thesis employs a comprehensive examination of a long, continuous, and high-resolution marine sediment core from Ocean Drilling Program site 984 (ODP 984), situated at the heart of the Northern Component Water (NCW) endmember. Various analyses, including faunal and detrital counting, and benthic foraminifera stable isotopes and trace element compositions, are employed to interpret the chemical and physical attributes of past seawaters and porewaters, thereby illuminating the North Atlantic's role in atmospheric CO2 dynamics across different timescales. The thesis probes the potential significance of the North Atlantic in glacial-interglacial atmospheric CO2 variability. Despite a more efficient glacial carbon pump, the biological production inferred from foraminiferal U/Mn might have been diminished by enhanced glacial stratification at various levels, as indicated by ice-rafted debris, and benthic foraminifera d13C and [CO32-] gradients between intermediate and deep Atlantic. These records imply the North Atlantic has sequestered a large deep carbon reservoir prior to the LGM therefore leaving a nutrient-depleted upper cell that support a more efficient but likely more static carbon pump. A comparative analysis of the Last Glacial Maximum (LGM) and the Preindustrial ocean, based on the compilation of global ocean carbon cycle parameters, reveals that the LGM global ocean had a much higher alkalinity, facilitating greater carbon storage. An elevated regional alkalinity was also observed in the North Atlantic at a depth of 2-3 km, suggesting a unique water mass possibly acting as a buffer between the shallow and deep Atlantic. The thesis further scrutinizes millennial scale climatic oscillations during periods of stable external forcing, exemplified by the Marine Isotope Stage 3 (MIS3, 29,000 - 57,000 years ago). The synthesis of carbon cycle parameters and ocean circulation state data indicates that Heinrich stadials were marked by low Dissolved Inorganic Carbon (DIC) and comparatively weak Atlantic Meridional Overturning Circulation (AMOC) in the intermediate depth North Atlantic, which may have contributed to atmospheric CO2 increases during these periods. In summary, this research elucidates the past role of the North Atlantic in atmospheric CO2 variability. Low glacial atmospheric CO2 concentrations are facilitated by high alkalinity and stratification in the ocean, both of which enable larger ocean carbon storage. On a shorter timescale, abrupt CO2 increases during Heinrich stadials are closely linked to marine biology in the North Atlantic. These findings improve the understanding of the ocean-atmospheric carbon cycle, offering invaluable insights for understanding our climate system.Item Open Access Monster ecology: Australian Bunyips and thylacines interacting with people in changing environments.(2025) Weinstein, PhilipMy thesis explores how two contrasting monsters are constituted, and how they interact with the people who believe in them: the cryptid Bunyip, an ancient monster with origins in Australian Aboriginal mythology; and the ghost thylacine, a more recent being with a clear connection to the zoologically recognised but extinct Thylacinus cynocephalus. I use participant-observation, semi-structured interviews, and published historical material to document firstly current understandings of the Ngarrindjeri Bunyip (Mulyawonk) and its antecedents among a group of Aboriginal people of the lower Murray River in South Australia, and secondly the being sighted and pursued by members of The Thylacine Awareness Group of Australia (TAGOA), also in South Australia. Both beings are integral to the cultural landscapes that they share with the people who believe in them, and reflect the anxieties and concern of those communities. They illustrate the mechanisms of monster change, and to our existing understanding of these processes I add two novel interpretations: monster radiation (in the evolutionary sense), and monster-human mutualism. The interactions between monsters, people, and the cultural landscapes that support both can be contextualised as 'monster ecology' - an ecology that is likely to change rapidly under the influence of global environmental crises such as climate change and biodiversity loss. I predict that the Anthropocene is likely to put some monsters at risk of extinction, but create opportunities for others to emerge.Item Open Access Studies in sparsity constrained approaches to geophysical inversion(2025) Turunctur, BuseTomography is an indispensable tool in Earth sciences, providing essential insights into the planet's internal structures and the geological processes that shape them. However, traditional tomographic techniques often struggle to accurately represent complex geological features, especially those that vary across multiple scales. These methods typically produce images that are overly smoothed, blurring sharp boundaries that are crucial for detailed geological interpretation. Additionally, the need for intricate parameter optimisation in these traditional approaches can make the interpretation of large datasets challenging. To address these challenges and fully harness the potential of tomographic imaging, this thesis introduces a pioneering methodology known as `overcomplete tomography'. This novel approach uses an expanded set of mathematical functions to represent the Earth's interior, allowing for high-resolution imaging even from relatively sparse datasets. By employing more functions than traditionally required, overcomplete tomography can capture a wider range of geological features with enhanced precision, leading to more accurate reconstructions of complex structures. This technique not only improves image quality but also simplifies the process of building models, making the inversion more intuitive and less dependent on arbitrary parameter settings. A key aspect of our method is the use of a mathematical technique called L1 regularisation in the inversion process. This approach encourages simpler models by promoting sparsity, meaning that only the most significant features are represented in the final images. This ensures that the images are both precise and concise, making them easier to interpret and preserving critical structural details often lost in conventional tomographic reconstructions. Furthermore, we extend the application of overcomplete tomography to include temporal analyses, thereby enhancing its utility for dynamic studies. This temporal dimension is critical for monitoring and understanding natural phenomena such as crustal deformation, seismic activity, and volcanic eruptions. Capturing changes over time not only enhances our ability to track and predict geological hazards but also provides deeper insights into the dynamic processes shaping the Earth's crust. Overall, this research significantly advances the field of geophysical tomography. By overcoming the inherent limitations of traditional methods and introducing a high-resolution approach, overcomplete tomography promises to revolutionise our understanding of the Earth's interior and its dynamic behaviours.Item Open Access 3D Point Cloud Shapes Latent Representation Learning and Applications(2025) Li, ShidiDue to the rapid advancement of machine learning, 3D object modeling has become a central focus in computer vision. A significant challenge lies in acquiring a latent representation for diverse 3D objects that is information-rich, efficient, and ubiquitous. This thesis tackles the above challenge from three fronts -- 1) how to learn information-rich disentangled latent representations in an unsupervised manner? 2) how to organize the learned disentangled latent representation efficiently in an unsupervised manner? 3) how to develop an ubiquitous general-purpose latent representation that can be readily applied to various downstream tasks with minimal additional training. This thesis first proposes a novel framework, namely \editvae, for unsupervised learning of disentangled latent representations of 3D objects. \editvae\ enables direct generation of individual object parts by training the model with whole object data. In particular, the learnt latent representation can be decomposed into a disentangled representation for each part of the shape. These parts are further decomposed into a shape primitive and a point cloud representation, along with a standardising transformation to a canonical coordinate system. Importantly, the dependencies between these transformations preserve spatial relationships between parts, facilitating meaningful parts-aware point cloud generation and shape editing. Further, beyond the learned information-rich latent representation, this thesis proposes \spavae\ with an unsupervised similar parts assignment module to organize the explicit disentangled representation. To be specific, \spavae\ infers a set of latent canonical candidate shapes for an object, along with a set of rigid body transformations for each such candidate shape to one or more locations within the assembled object. In this way, noisy samples on the surface of, say, each leg of a 3D point cloud table, are effectively organized and combined to estimate a single leg prototype. When parts-based self-similarity exists in the raw data, sharing data among parts in this way confers numerous advantages: modeling accuracy, appropriately self-similar generative outputs, precise in-filling of occlusions, and model parsimony. Finally, this thesis proposes a unified latent representation that facilitates its application to diverse downstream tasks. This thesis propose a novel sparse transformer, \textit{sampled transformer}, with $O(n)$ complexity that can efficiently process point set elements with little additional inductive bias. This transformer is then integrated into a Masked Auto-Encoder (MAE) pre-training framework for learning an ubiquitous latent representation. The success of this representation in fine-tuning tasks like classification, transfer learning, few-shot learning, and generation demonstrates its effectiveness in capturing rich object information.Item Open Access Catalytic Diplomacy: International Institutional Complexity and the Acceleration of Cooperation in the Asia-Pacific(2024) Ramasubramanian, GiridharanIn recent years, countries in the Asia-Pacific have created a diversity of international institutions across a range of different issue areas to harness cooperation within their broader institutional landscape. This thesis studies the dynamics of institutional evolution by investigating how the architecture of existing arrangements has shaped the negotiations of small group institutions in the Asia-Pacific and how these agreements, in turn, have shaped that architecture. It poses the puzzle: Why has institutionalization of inter-state cooperation accelerated in some issue areas while evolving incrementally in other issue areas? What role has small group institutions - regional and bi/pluri/mini-lateral institutions - played in accounting for this variation in institutionalisation? The thesis engages with the rational design, institutional interplay, orchestration, historical institutionalism, institutional diffusion, and complex adaptive systems literatures. It conceptualises a new analytical lens, "institutional catalyst" and elaborates on a framework of "catalytic diplomacy" that has the following properties: (1) amplification - ability to shape the momentum and direction of an institutional complex, (2) attraction - attract different actors to become a focal node within the complex and, (3) assimilation - channel fragmentation to make a complex system more manageable. It asks: How are institutional catalysts created within an institutional complex and how do they end up shaping that complex? It distinguishes between different types of small group institutions and characterises them according to their roles within an institutional ecosystem: building blocks, facilitators, or catalysts. The thesis challenges the rational design literature and the building/stumbling block conception of small group cooperation and explores how institutions in the Asia-Pacific and global institutions co-evolve in a non-linear and dynamic manner. The thesis integrates case studies methods and process tracing to investigate the dynamics of institutional interactions and evolution within four different issue areas - Trade, Climate Change, Arms Control, and Finance - to provide a structured comparative analysis across two detailed case studies and two counter-examples. The thesis first maps the different institutional complexes. It then explores the temporal sequence of emergence, transformation, and establishment of small group institutions within their respective institutional complexes. Through data collected from interviews with diplomats and policymakers as well as through primary and secondary documents, it explores the emergence and impact of institutional catalysts such as the Trans-Pacific Strategic Economic Partnership and the US - China bilateral climate agreement. This thesis argues that international institutions are catalytic when they scale out; scale up; are adaptive and open; align; act as pathfinders; and integrate past processes. It shows that institutional catalysts are the products of interactions between building blocks and facilitators when global multilateral institutions are deadlocked. It further illustrates that institutional catalysts will interact with institutional facilitators to transform an institutional complex and potentially overcome multilateral deadlocks. By surveying regional and minilateral institutions in two other issue areas - Arms Control (Proliferation Security Initiative) and Finance (Chiang Mai Initiative) - where system transformation did not occur, it analyses the boundaries of catalytic diplomacy. This thesis shows that institutional catalysts have the capacity to engage in incremental problem solving and simultaneously, shape the long-term emergence of new institutions, accelerating the process of institutionalisation within an issue area. Thus, this thesis contributes to a better understanding of the use of catalytic diplomacy in navigating and managing international institutional complexity.Item Open Access Navigating Ideational Dynamics: Actor-Policy Interactions in the Implementation of Indonesia's Higher Education Reform(2025) Aprimadya, Muhammad HaliThis thesis explores the diversity of actors' ideas, beliefs, and traditions in influencing and shaping their implementation of public policies. Drawing on the experience of higher education reform in Indonesia between 1999 and 2019, this thesis illuminates the intricate nature of actor-policy interactions by asking: how do actors' held beliefs and traditions shape their responses to 'new' ideas propagated by policies? And what do these interpretations and actions mean for policy implementation? This thesis uses an interpretive approach to explore academics' interpretations of a series of regulatory changes intended to shape their behaviour. This study demonstrates that the implementation of research-related policies in Indonesian higher education constitutes complex actor-policy ideational interactions that might not always be goal-oriented endeavours but also expressive acts. Central to these interactions are dilemmas that might arise from individual academics' ideational and institutional contexts. Facilitated by their 'situated' agency, Indonesian academics' interpretations and actions in response to dilemmas may constitute diverse acts that display a degree of discord with policy intents. This thesis contends that these incongruities depict academics' improvisations to overcome institutional conflicts rather than mere acts of negligence. Through decentred analysis, the thesis illuminates how policy implementation is an art and craft instead of a mere technocratic and structured effort. By combining the cultural approach and interpretivism, it also provides an alternative framework and methodological approach to study policy implementation. Finally, this thesis contributes to understanding the governance complexities of Indonesian higher education as one of the region's most dynamic higher education sectors.