48080 research outputs found
Sort by
Advanced Methods for Radiation Protection in Medical and Space Applications
No full textThere is a growing demand for the development of innovative materials and methods to accurately determine the radiation dose delivered to humans. This demand extends to a diverse range of applications including nuclear science, defence, personal dosimetry, medical imaging and radiotherapy, and space exploration.The radiation environment of space is arguably one of the largest risks to astronauts, be it on the International Space Station (ISS), or for future planned deep space missions to the Moon and Mars. In particular, characterising the radiation environment on the surface of the Moon is of great interest within the radiation protection community, as NASA plans to establish a Lunar Gateway and return humans to the Moon for the first time since the 1970s. This is encompassed within NASA’s ARTEMIS missions, where Australia is also contributing through the development of a rover for lunar surface explorations. Therefore, dosimetry measurements are pivotal in assessing the potential risks to electronic components and the radiation-induced biological effects within humans. Experimental measurements are essentially impossible to perform due to the cost of access in space and limited data from previous missions to the Moon. In this case, the utilisation of simulation studies provide a cost-effective means of conducting such assessments. This thesis summarises the results of simulation studies performed to characterise the secondary radiation backscattered from the lunar surface, as well as estimate the daily absorbed doses that can be expected in radio-sensitive organs within the human body.In addition to the complex radiation environment of space, clinical radiotherapy environments require dosimetry methods that can provide accurate and real-time evaluations of patient safety and treatment efficacy. New advancements in radiotherapy treatments have resulted in the need for novel detector technologies with improved performances. These advancements include particle and heavy ion therapies, high dose-rate radiotherapy, and the adaptation of in vivo dosimetry practices for improved patient safety. To address these challenges, novel radiation dosimeters are characterised throughout this study. The detector solutions explored are fabricated from either hydrogenated amorphous silicon (a-Si:H) or organic semiconductor technologies, both of which offer a variety of benefits (such as cheaper manufacturing) compared to traditional solid state devices employing crystalline silicon, germanium or cadmium zinc telluride.The characterisation of these detectors for X-ray dosimetry is presented for both current and emerging External Beam Radiation Therapy (EBRT) treatment modalities. This thesis presents the first characterisations of a-Si:H diode structures on flexible substrates for therapeutic X-ray beams. Potential applications include fully-flexible and minimally perturbing detector solutions for in vivo dosimetry. To achieve this, novel semiconducting materials are explored which provide benefits over currently employed solid-state detector solutions. Organic photodiodes, coupled with plastic scintillators, offer flexibility and improved tissue equivalence in comparison to silicon. Furthermore, the a-Si:H detectors explored in this thesis display superior radiation tolerances in addition to fully flexible detector solutions, identifying them as suitable candidates for prolonged radiation exposures during clinical radiotherapy applications.For a-Si:H detectors, their applications as dosimeters are extended to novel treatment modalities combining high dose-rates and micron-scale spatial fractionation of the treatment beam in a modality known as Microbeam Radiation Therapy. This thesis is the first to document the application of a-Si:H as a solution for beam monitoring and dosimetry of microbeam treatment modalities at synchrotron facilities.</p
Behaviour of Self-Compacting Concrete Members Reinforced with Small Dimension Square Steel Tubes
No full textColumns play a pivotal role in transferring all types of loads imposed on a structure to the foundations of that structure. In an effort to improve the efficacy of concrete columns, this study proposes an innovative way of reinforcing concrete columns by replacing traditional steel bars with small dimension square steel tubes filled with self-compacting concrete (SCC). The main aim of this research study is to investigate the behaviour of square steel tube-reinforced self-compacting concrete (SSTR-SCC) specimens under different loading conditions.The research study was divided into four different sets of experimental programs. The first set of the experimental program focuses on understanding the effect of the unsupported length-to-width (L/B) ratio on the structural stability of square steel tubes with small cross-sectional dimensions subjected to axial compression and tension. Sixty-three small square steel tube specimens with three different cross-sectional dimensions (25 mm × 25 mm, 30 mm × 30 mm, and 35 mm × 35 mm) were tested under compression and tension. Specimens with varying L/B ratios ranging from 2 to 12 were tested under axial compression.The second set of the experimental program focuses on investigating the effect of the unsupported length-to-width (L/B) ratio on the axial compressive behaviour of square self-compacting concrete-filled steel tube (SSCFT) specimens. The SSCFT specimens with three different cross-sectional dimensions (25 mm × 25 mm, 30 mm × 30 mm, and 35 mm × 35 mm) and L/B ratios of 2–12 were tested under axial compression. The performance of SSCFT specimens was compared with that of square unfilled steel tube (SUT) specimens of identical cross-sectional dimensions.The third set of the experimental program introduces an innovative approach to replace traditional steel bars with small cross-section steel tubes in self-compacting concrete columns. The structural behaviour of square steel tube-reinforced self-compacting concrete (SSTR-SCC) columns was investigated experimentally. Sixteen specimens were cast and tested under concentric, eccentric, and flexural loads. Four specimens reinforced with 12 mm diameter deformed steel bars were considered as reference specimens, and the remaining 12 specimens were reinforced with small square steel tubes of three different cross-sectional dimensions (25 mm x 25 mm, 30 mm x 30 mm, and 35 mm x 35 mm) and a constant thickness of 2 mm. All the specimens were laterally confined with 10 mm square-shaped steel ties at 50 mm spacing.In the last set of the experimental program, twelve small square steel tube-reinforced self-compacting concrete (SSTR-SCC) columns were tested under symmetric and asymmetric biaxial eccentric loads and their structural behaviour was investigated. Three specimens (reference specimens) were longitudinally reinforced with 12-mm diameter deformed steel bars, and the remaining nine specimens were reinforced with self-compacting concrete filled small square steel tubes of three different cross-sectional dimensions (25 mm x 25 mm, 30 mm x 30 mm, and 35 mm x 35 mm) and a constant thickness of 2 mm. All the specimens were laterally confined using 10-mm diameter steel bar ties at 50-mm centre-to-centre spacing.The experimental findings revealed that the L/B ratio significantly influenced the performance of small square steel tubes. Experimental results of SSCFT specimens revealed that steel tubes effectively confined the infill concrete and demonstrated a 20–40% increase in compressive strength compared with the respective SUT specimens.The SSTR-SCC specimens, under concentric, eccentric and flexural loads, demonstrated the superior load-carrying capacity and ductility compared to the reference specimens. Under biaxial eccentric loads, the SSTR-SCC specimens also demonstrated better performance than the reference specimens in terms of maximum axial load capacity and ductility. The SSTR-SCC specimens were found to be a scientifically significant and structurally efficient alternative to conventional reinforced concrete columns.</p
Emerging evidence of abrupt changes in the Antarctic environment
No full textHuman-caused climate change worsens with every increment of additional warming, although some impacts can develop abruptly. The potential for abrupt changes is far less understood in the Antarctic compared with the Arctic, but evidence is emerging for rapid, interacting and sometimes self-perpetuating changes in the Antarctic environment. A regime shift has reduced Antarctic sea-ice extent far below its natural variability of past centuries, and in some respects is more abrupt, non-linear and potentially irreversible than Arctic sea-ice loss. A marked slowdown in Antarctic Overturning Circulation is expected to intensify this century and may be faster than the anticipated Atlantic Meridional Overturning Circulation slowdown. The tipping point for unstoppable ice loss from the West Antarctic Ice Sheet could be exceeded even under best-case CO2 emission reduction pathways, potentially initiating global tipping cascades. Regime shifts are occurring in Antarctic and Southern Ocean biological systems through habitat transformation or exceedance of physiological thresholds, and compounding breeding failures are increasing extinction risk. Amplifying feedbacks are common between these abrupt changes in the Antarctic environment, and stabilizing Earth’s climate with minimal overshoot of 1.5 °C will be imperative alongside global adaptation measures to minimise and prepare for the far-reaching impacts of Antarctic and Southern Ocean abrupt changes.</p
Understanding microbial mechanisms for integrated management of sulfide, methane, and nitrogen in wastewater systems
No full textThe abstract for this item has not been populated.</p
Assessing the Role of Membrane Interactions and the <i>In Vitro</i> Biological Activity of Novel Bismuth Flavonol Complexes
No full textFlavonols (Flavs) are a diverse group of naturally occurring polyphenolic compounds with well-documented anti-oxidant, anti-microbial and anti-cancer properties. Their ability to interact with biological membranes and modulate cellular processes has led to increased interest in their therapeutic potential. Metal-flavonol complexes have emerged as promising candidates for enhancing the biological activity of flavonoids. Recently, studies of Bi-flavonoid complexes (BiFlavs) have been performed to determine if their properties can be harnessed as a novel strategy to overcome drug resistance and improve bioavailability in cancer therapy. This Thesis systematically investigates the bioactivity of BiFlavs by assessing their membrane interactions, uptake in cancer cells, cytotoxicity, and binding to serum proteins using combined biophysical, biochemical, and cellular techniques.The ability of Flavs and BiFlavs to interact with membrane mimics was examined using electrical impedance spectroscopy (EIS), quartz crystal microbalance with dissipation (QCM-D) monitoring and neutron reflectometry (NR). Flavs transiently increased membrane conductance in EIS studies, indicative of pore formation, with interactions largely reversible. In contrast BiFlavs, particularly BiPh(Flav)2 and BiPh(BrFlav)2, exhibited stronger and more persistent membrane interactions which was evident by significant mass deposition on lipid bilayers in QCM-D experiments. NR data indicated that the free Flavs interacted with the head group region of the lipid membrane mimic. The BiFlavs, BiPh(Flav)2 and BiPh(BrFlav)2, were found to interact with the hydrophobic core and the polar head groups of the membrane mimic, while Bi(BrFlav)3 primarily disrupted the organisation of the head group region. These findings suggested that Bi coordination influences membrane penetration and stability, potentially affecting cellular uptake and bioactivity.The cellular accumulation of BiFlavs was assessed in a range of cancer and noncancer cell lines using graphite furnace atomic absorption spectroscopy (GFAAS). The accumulation of Bi was assessed in colorectal (HCT-8, HCT-116 and HT-29) and pancreatic (MIA PaCa-2 and BxPC-3) cancer cells as well as leukemia (K562) cells, osteosarcoma (U-2 OS) cells and human peripheral blood mononuclear cells (PBMCs). Intracellular Bi concentrations of the different BiFlavs were consistent with the extent of membrane disruption observed in model membrane studies, suggesting that permeability may influence uptake efficiency. However, differences observed between cancer cell lines indicated that alternative transport mechanisms, such as receptor-mediated transport, may also contribute.The in vitro anti-cancer activity of BiFlavs was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay. Free flavonoids exhibited limited cytotoxicity, with Flav and BrFlav displaying particularly weak anti-cancer effects. The BiFlavs were found to have significantly greater cytotoxicity compared to the free ligands. Among the BiFlav complexes, BiPh(Flav)2 exhibited the greatest cytotoxicity across multiple cancer cell lines. Despite promising uptake studies, BiFlavs exhibited cytotoxicity in non-cancerous PBMCs, raising concerns about selectivity. Flow cytometry assays of apoptotic and necrotic markers confirmed that apoptosis was the predominant mode of cell death in all cell lines studied.To understand the potential in vivo transport and bioavailability of BiFlavs, the binding interactions of BiFlavs and the free ligands with major serum transport proteins, human serum albumin (HSA), human lactoferrin (hLf) and human transferrin (hTf), were investigated using UV-visible spectroscopy. BiFlavs exhibited significantly stronger protein binding than free flavonoids. BiPh(Flav)2 and BiPh(BrFlav)2 demonstrated preferential binding to hTf. This aligned with cellular uptake trends, where transferring receptor (TfR)-rich leukemia (K562) and osteosarcoma (U-2 OS) cells displayed elevated BiFlav accumulation, suggesting a potential mechanism for targeted delivery.The studies of BiFlav complexes in this Thesis demonstrated a promising relationship between membrane interactions and in vitro activity. Consequentially future investigations are warranted to optimise selectivity, minimise off-target toxicity and improve bioavailability. Additionally, in vivo studies are required to validate the biological relevance of these findings by assessing the biodistribution and in vivo safety profile of the BiFlavs, particularly in cancer and inflammatory disease animal models.</p
Treading lightly on Country: developing a co-designed pathway for the study of the Willandra’s ancient environments
No full textThe history of geological and geographical research within the Willandra Lakes Region World Heritage Area (WLRWHA) and the majority of the Australian continent has been one of entrenched colonial ideology. While archaeological researchers have championed the decolonisation of their research field by building trusting relationships with Traditional Owners and Indigenous communities, the same is, sadly, not the case within the sphere of Earth Science. The establishment of the Willandra Lakes Region Aboriginal Advisory Group’s (WLRAAG) Research Code of Practice in May 2021 put forward a series of Research Principals and practical guidance for the co-development of Research Protocols for all research taking place within the boundaries of the WLRWHA.
This presentation presents the narrative of connections and interactions that have taken place between the Elders of the WLRAAG and myself–-a geologist interested in exploring the Willandra’s ancient environments. Together, we have co-designed the Research Protocol that governs both my DECRA research project and how the research team interacts with the landscape. As we build our relationship, I continue to work and walk alongside the WLRAAG as they teach me how we can go about understanding their Country but also how I can ‘tread lightly’ in the process.</p
Significant Improvement in Tribological Properties of CoCrNi Medium-Entropy Alloy by Silicon Addition
No full textThe development of medium-entropy alloys (MEAs) has attracted significant attention due to their unique combination of superior mechanical properties and potential for high-temperature applications. Among these, CoCrNi-based MEAs have emerged as a promising class of materials known for their excellent strength and stability. The enhancement of these properties through the addition of Si has been reported but not thoroughly explored. This study investigated the effect of varying Si content on the microstructure, hardness, and wear resistance of CoCrNiSix MEAs.In this work, CoCrNiSix (x = 0.1, 0.2, 0.3) MEAs were fabricated by casting. The ingots were homogenized, cold-rolled, and subsequently annealed at two different temperatures, namely 500°C and 800°C for 30 minutes to study the effect of thermal treatment on microstructure and mechanical properties. Wear tests were carried out under dry sliding condition using a ball-on-disc tribometer. The tests were conducted at room temperature (RT) and high temperatures (HT) of 400°C, 600°C, and 800°C to evaluate the coefficient of friction (CoF) and wear resistance of the alloys. The microstructure, hardness, and wear resistance of the CoCrNiSix MEAs were studied in detail.The research found that increasing Si content significantly refined the microstructure and enhanced the phase stability, particularly in the CoCrNiSi0.3 alloy. Annealing at 500°C improved the hardness of the alloys, leading to superior wear resistance, while annealing at 800°C induced extensive recrystallization and grain growth, resulting in a reduction in hardness. However, this reduction was less pronounced in alloys with higher Si content.Wear testing from RT to 800°C revealed that higher Si content consistently reduced the CoF and improved wear resistance. The CoCrNiSi0.3 alloy demonstrated the best overall performance, especially after 500°C annealing. At HT, the wear mechanisms varied with temperature, with 800°C showing the most pronounced plastic deformation and oxidation. Despite the reduced mechanical strength at this temperature, the formation of protective oxide layers led to lower wear rates, particularly in the CoCrNiSi0.3 alloy.This study highlighted the critical role of Si in enhancing the microstructure, hardness, and wear resistance of CoCrNiSix MEAs, making these alloys promising candidates for applications requiring high durability and performance at elevated temperatures.</p
Home-neighbourhood: a material-affective infrastructure for the Creative City
No full textDebates on the relationship between urban spaces and creative industries have traversed multiple dimensions and spatialities. Yet, with some notable exceptions, analytical focus rarely lands on domestic space. This article engages with the domestic geographies of creative work in the city to explore the growing centrality of home both as a locus for this work and as material–affective infrastructure sustaining creative production. Drawing on longitudinal research with musicians in Sydney, Australia, we use the lens of creative practitioners’ experience through COVID-19 – wherein home and neighbourhood were necessarily centred – to unpack the intensification of home’s importance to creative work. The article explores how home, understood relationally as encompassing home–neighbourhood, plays a pivotal role as an informal, low-risk and supportive creative production space. Relational spaces of home – enrolling kitchens, bedrooms, home studios and gardens, as well as nearby local venues and scenes in the self-reinforcing affects of creative collaboration and performance – provide vital material–affective infrastructure for the process of collaborative creativity. Participants revealed the geographies of ‘creative homes in creative neighbourhoods’ fashioned via the self-intensifying affects of levity, appreciation and sociality, enabling and supporting ongoing creation. Home–neighbourhoods were central to worlds of creative work, intensified by COVID-19’s tempering effect alongside digitalisation, assetification and financialisation. Foregrounding the intertwining of neoliberal urbanism, housing (in)security and creative work, we conceptualise home–neighbourhood in relation to the emerging geographies of hybrid and home-supported work, with key implications for urban cultural and housing policy.</p
A Minimum Variance Controller for SISO Linear Time Variant Systems
No full textAn optimal controller is developed for linear time variant systems described using transfer operators, where the noise response is described using a time variant moving average autoregressive model and the control response is described using a time variant autoregressive moving average model. Following the line of minimum variance control methods, this controller can achieve minimum variance output tracking without using noise variance information even when the speed of parameter variation in the system is arbitrarily fast.</p
The Role of Community in Shaping Authentic and Meaningful Work: A Study of Artists on the South-Coast
No full textThis thesis examines the significance of ‘meaningful work’ and the role of ‘place’ in the construction of authentic selfhood. It utilises interview based case‐studies of the subjective experiences of artists in a small coastal town, one hour south of Sydney. In‐depth interviews with seven participants produce a rich analysis into how these individuals craft identity and locate meaning through their work. The core theme explored is how this experience is crafted through place and community. This research contributes to the underdeveloped sociological discourse of ‘meaningful work’, in contrast to the long-established discourse of ‘meaningless work’. ‘The city’ is framed in this thesis as a place constrained by the dominant neoliberal ideology; inherently problematic for doing meaningful work; with ‘communities’ outside of the city subsequently framed as an alternative to this, where there is greater potential to locate experiences of authentic, creative and meaningful work. Through empirical exploration, the thesis finds that the emotional experience of meaningful work is highly dependent on the construction of the authentic creative self in response to authentic place in community.</p