Filters
Availability
Publication Year
Resource Type
Faculty
School/Institute
Publication Search Results
Sort
Results per page
1 - 10 of 55
-
(2021)ThesisHigh-resolution optical spectroscopy in solids has attracted an enormous amount of attention over the past few years on the basis of a wide potential range of applications in the fields of communication, biomedical, defence and industrial applications. Transient spectral hole-burning, a laser-based spectroscopic technique, is used throughout this thesis to investigate the optical properties of the chromium(III) systems such as ruby (Al2O4:Cr3+) and alexandrite (BeAl2O4:Cr3+) crystals at their 4A2 to 2E spin-flip transitions (R1-line) at ~2 K. A spin-level pumping enhanced slow light based on the transient spectral hole-burning is reported. The frequency locking and stabilization of an external-cavity diode laser using the Pound-Drever-Hall technique is described. Time-resolved transient spectral hole-burning is performed in the R1-line of different ruby samples in zero field and low magnetic fields at ~2.2 K. The generation of slow light in ruby samples was then investigated using the spectral hole-burning technique. Slow light is caused by the spectral hole in the absorption spectrum of the crystal leading to a strong frequency-dependent normal dispersion, resulting in the delay in pulse propagating through the crystal. An external magnetic field further reduces the width of the spectral hole by reducing the electronic spin-flip rates and even slower light is then observed. A spin-level pumping results in an even slower group velocity of the pulse propagating through the ruby sample when compared without the pumping process. A strong pump pulse applied to the R1(±1/2) line modifies the optical density of the R1(±3/2) line, with the hole-burning performed at the R1(±3/2) line. In addition, the spin-lattice relaxation time of ruby is accurately measured. High-resolution laser transmission measurements are conducted at the R1m-line of alexandrite at 2.1 K, and its strong luminescent properties are studied by fluorescence and fluorescence decay measurements. Polarized time-resolved transient spectral hole-burning is conducted at the R1m-line of alexandrite at 2.1 K in zero and low magnetic fields BIIa, BIIb and BIIc (B < 12 mT). The Zeeman-level splitting, proportional to the applied field strength, is directly observed from the hole patterns and this allows the accurate determination of the g-factor in the excited state.
-
(2020)ThesisThe river water quality plays an important role in our daily life, with rivers providing fresh drinking water and water for industry and agriculture. However, water quality could be affected by the future impacts of climate change on water temperature because of global warming and on streamflow because of changes in precipitation. Nutrients in runoff from farmland and towns will also affect water quality, and may lead to algal blooms. The water-quality model QUAL2K was chosen as the numerical modelling tool to study water quality along the Shoalhaven River, NSW, Australia, in response to changes in the climate and in nutrients in runoff. Three independent variables, air temperature and streamflow representing climate change, and nutrient runoff were varied in eight hypothetical scenarios to determine their impact on water quality, represented by water temperature, and dissolved-oxygen, nitrogen, phosphorus and phytoplankton concentrations. An increase in air temperature by up to 2℃ resulted in an increase in water temperature and phytoplankton concentration, and a decrease in dissolved-oxygen concentration; these changes were more significant when the streamflow was also decreased by 35%. Reducing nutrient runoff reduced the nitrogen and phosphorus concentrations, resulting in a significant increase in the dissolved-oxygen concentration. This study quantifies some of the impacts of climate change and nutrient pollution on water quality and phytoplankton concentration in the Shoalhaven River, providing scientific guidance for managing water quality and algal blooms in future climate-change and nutrient-pollution scenarios.
-
(2020)ThesisThe tiara[n]uril (Tu[n]) family is a novel class of water-soluble macrocyclic hosts, structurally characterised by the presence of a positively charged cavity comprised of glycoluril units connected to a dipyrazolium moiety. Being a newly developed macrocyclic host, only a few examples of Tu[n] with different substitutions have been reported. However, this has left open the opportunity to explore this novel class of host molecules to further develop functionality, which could potentially be modified for use in the synthesis of more complex supramolecular structures such as amphiphilic Tu[n] derivatives or hydrogels. This potential was explored through two main approaches – derivatisation of the glycoluril precursors or – derivatisation of the methyl groups on the dipyrazolium moiety in Tu[n]. This thesis demonstrates the synthesis of two novel Tu[n] derivatives with functionality aimed at the preparation of amphiphilic Tu[n] derivatives. In the first approach – the primary objective was the preparation of functionalised Tu through derivatisation of the glycoluril precursors. In this regard, we explored the synthesis of THTn-m-xylene-tmdpzm-Tu[n] and AcidCyPnTu[n] from tetrahydrothiophene glycoluril diether and cyclopentano diethyl dicarboxylate glycoluril diether respectively. These explorations revealed the formation of THT2-m-xylene-tmdpzm-Tu[2] and AcidCyP3Tu[3] that were analysed and elucidated using 1H NMR and high-resolution mass spectroscopy. The preparation of these functional Tu[n] provided some hope for future opportunities for amphiphilic compounds and/or hydrogels. As water-soluble cationic macrocycles, these Tu could be suitable precursors for derivatisation with lipophilic substituents in order to achieve the long-term objective. The second objective of the work presented in this thesis was to investigate the synthesis of Tu[n] derivatives through derivatisation of the methyl groups on the dipyrazolium moiety. This investigation focused on base catalysed alkylation reactions on the methyl groups which were acidic, to provide an alternative route to the synthesis of Tu[n] derivatives in order to obtain amphiphiles. The investigations toward the synthesis of alkyl-substituted derivatives of Me10Tu[3](PF6)2 were initially performed through a short-chain alkylation reaction employing ethyl iodide as an alkylating agent as a proof of concept, which formed propyl-substituted derivatives of Me10Tu[3](PF6)2. These preliminary investigations revealed the formation of mono-substituted and di-substituted products - Methyl9Propyl1Tu[3](PF6)2 and Methyl8Propyl2Tu[3](PF6)2 respectively that were analysed using 1H NMR and high-resolution mass spectroscopy. As a follow up, a preliminary study toward long-chain alkylation of Me10Tu[3](PF6)2 was examined using octyl bromide as an alkylating agent. Although alkylation was not observed, the potential remains. A study of the alkylation process using different base catalysts is discussed as well as other improvements that could be made to achieve the objective. Both of the approaches discussed in this thesis for the synthesis of Tu[n] derivatives provide a useful preliminary study toward the objective of developing amphiphilic molecules that may provide opportunities in drug delivery systems such as micelles or hydrogels.
-
(2020)ThesisIn confronting the emerging shocks and stresses triggered by neoliberal urbanism and climate change impacts, global efforts toward ‘urban resilience’ building have proliferated. The current discourse has conceived ‘urban resilience’, the capacity of urban systems to adapt and withstand disturbances, as a complex, contradictory, and context-specific concept. Drawing on ‘urban resilience planning’, this thesis focuses on the strategic approach and performance in urban resilience building in the context of a developing country, Cambodia, where the aims of both building modernity and promoting the resilience of its urban areas have been formulated. To realise these long-term goals, the Cambodian government has introduced many institutional reforms along with the development of various urban development policies and plans. Despite these reforms, urban challenges and vulnerabilities of urban poor communities remain unsolved, in a context where many urban renewal projects have been undertaken. It is argued that the effective implementation of a participatory approach reflects a radical change in urban planning and can potentially underpin the effectiveness of urban resilience building in the modern development process. While the participatory planning approach is not entirely new to Cambodia, it has been inadequately and ineffectively applied in the process of promoting the resilience of its urban areas. The thesis is developed within the paradigm of postmodernism. Three main concepts were integrated to frame the analysis of the contemporary process of urban resilience building in the context of neoliberal urbanisation: the participatory planning approach; the sustainable livelihood framework; and sustainable development. Using a Phnom Penh city case study, this thesis adopted a mixed methods approach to the data collection. This thesis will argue that controversial approaches to contemporary urban upgrading are influenced by modernisation and an adherence to the ‘growth machine’ ethos that is deepening urban inequality and leading to poor decision making about the distribution of urban resources, and limiting the adaptive capacities of citizens to cope with livelihood disruptions. Efforts in building urban resilience thus becomes more difficult for marginalised urban dwellers. The thesis advocates for a paradigm shift in contemporary urban resilience planning that focuses on balancing the power of stakeholders and promotes effective collaboration among urban stakeholders for inclusive, sustainable and resilient urban areas.
-
(2022)ThesisSince the 1990s the fast fashion industry has garnered a reputation for the use of exploitive and unethical practices, prompting an enquiry into the fashion industry by geographers, particularly regarding the exploitation of workers within developing nations. However, despite focused efforts to eliminate the unethical practices that have become so synonymous with fast fashion, only small improvements have been made. Academics acknowledge consumers have a key role to play in fashion’s current problematic state yet attempts to actualise consumers as key actors in the industry’s upheaval have produced lacklustre results producing a shift in focus back to the brands and host countries. Taking seriously Gilles Deleuze’s statement that every ‘problem has the solution it deserves in proportion to its own truth or falsity’ (Deleuze & Guattari, 1994, p. 159), the lack of movement on this issue is in part due to the questions being posed to it. Rather than questioning how to reconstitute fast fashion to exist within a morally acceptable framework, first both fashion and ethical production need to be separately dissected into their composites so as to identify and critique their assumptions and generalities. In following this approach, fashion’s genesis as both commodity and cultural phenomenon is re-examined through the works Gilbert Simondon and Gillies Deleuze, providing a basis for fashion as both an aesthetic object of sensation and desiring-machine. Here fashion’s productive nature is elucidated. Through the amplifying nature of aesthetics, I outline how fashion’s engagement is more than a tool for reproducing and solidifying concurrent collective thought or fulfilling a desire produced through a perceived feeling of lack, but a productive medium for novel individuations, new subjectivities, and the ability to produce a more active or joyful existence. Finally, seen in such a way, we can examine ways to reposition the question of fashion and ethical manufacture so that it does not immediately cut off those affected by the fashion industry, from their capacity to act leading to a more ethical industry.
-
(2021)ThesisThe North West Shelf (NWS) of Australia is an ecologically sensitive region susceptible to extreme ocean and atmospheric events driven by large-scale and climate variability. This thesis investigates the drivers of the 2012/2013 strong marine heatwave (MHW) and how tropical cyclones (TCs) affect the temperature and energy of the ocean in the NWS region. In part 1, a high-resolution regional numerical model based on the Regional Ocean Modelling System (ROMS) is implemented to simulate the variability of the upper ocean temperature and circulation in order to understand the mechanisms that drive the evolution of the 2012/2013 MHW. An upper ocean heat budget is used to quantify the roles of air-sea heat flux and ocean circulation in the development of extreme temperature anomalies over the continental shelf. Results indicate that during December 2012 an increase of net air-sea heat flux combined with positive horizontal advective heat flux anomaly led to development of the MHW. Despite a decrease in net air-sea flux warming, during the peak in January-February 2013 high-temperature anomalies were maintained by a combination of positive anomalies of heat advection and vertical mixing. The delayed onset of the 2012–2013 Australian monsoon resulted in alongshore wind anomalies on the NWS which in turn caused the advection and mixing anomalies. Part 2 focuses on characterizing the changes produced by TCs over the NWS of Australia on the ocean structure and ocean thermal energy budget using a 20-year composite of cyclone data (1996-2016) created from Bluelink ReANalysis data (BRAN). The passage of a TC can have strong effects over a large area as the strong winds cause vertical mixing and upwelling through the water column near the TC core as well as downwelling in the periphery of the TC circulation. Cold temperature anomalies develop at the ocean surface beneath the TC core in response to strong mixing and deep upwelling driven by surface divergence and Ekman pumping. In the TC outer circulation surface cold anomalies also develop. However, in the subsurface warm temperature anomalies appear below the mixed layer due to wind-driven mixing across the mixed layer. In the month following the passage of the TC, the surface cold temperature anomalies recover relatively quickly due to air-sea fluxes, while the subsurface warm anomalies take longer to recover, mostly due to a reduction in mixing once the TC has left the region. Different TC and ocean characteristics such as location with respect to the shelf edge, period of the year, intensity and translation speed, and the presence of a barrier layer are examined to assess their effects on thermal changes occurring in the ocean. Stronger cold anomalies develop at the surface over the shelf locations, over locations with a shallow or non-existent barrier layer, for strong TCs (category 3 or above on the Australian intensity category scale), and for slow-moving (< 4 m/s) TCs. The period of the year influences the recovery of the surface anomalies, which happens faster for TCs between December and February than for TCs that occur during or after March. The warm anomalies in the subsurface are stronger for more intense TCs and over locations with a shallow barrier layer as the vertical mixing processes are more efficient. Ocean heat content (OHC) integrated heat through the water column is examined as a proxy for the energy exchange between the atmosphere and ocean during the TC passage. The processes that produce changes in OHC during and after the passage of the TC are separated into regions near the TC core, in the TC outer structure, and at different depths in the ocean during the passage and the subsequent 30-day recovery period. The OHC in the top 500 m of the region within 1000 km from the TC centre recovers more than 30 days after the passage of the TC. During the passage of the TC the majority of the OHC losses are located beneath the TC core and in the surface layer, while the OHC increases in the subsurface layer in the region between 500 and 1000 km from the TC centre. When the temperature anomalies start to recover, the OHC increases at a stronger rate in the surface layer due to the air-sea heat fluxes and in the TC core region where the strong upwelling relaxes to downwelling. Strong TCs produce an overall increase in the OHC within a month after the TC passage, while weak TCs of categories 1 and 2 cause an overall decrease in the OHC.
-
(2022)ThesisStorage phosphors have found widespread applications in dosimetry and computed radiography. To date, BaFBr(I):Eu2+ is the most commercially successful phosphor used in computed radiography. Due to their limited signal to noise ratio and erasure of stored information, investigations of alternative phosphor materials are crucial and BaLiF3 has emerged as a potential candidate. This thesis focuses on a thorough understanding of the luminescence phenomena and X-ray storage capability of single- doped (BaLiF3:Eu3+, BaLiF3:Sm3+ and BaLiF3:Tm3+), co-doped (BaLiF3:Yb3+, Er3+), and undoped BaLiF3. The doped and undoped BaLiF3 powder were prepared by ball milling and characterized using powder X-ray diffraction, transmission and scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Their optical properties were characterized by photoluminescence, upconversion luminescence and photoluminescence excitation spectroscopy in external magnetic field (9 T). Photoluminescence properties of nanocrystalline BaLiF3:Eu3+, BaLiF3:Sm3+ and BaLiF3:Tm3+ before and after X-irradiation was studied to quantify their X-ray storage capability of such host-activator systems. It is demonstrated that BaLiF3 is a potential host which can enable luminescence within a broad optical range (UV–infrared) depending on the activator. In addition, upconversion luminescence in BaLiF3:Yb3+, Er3+ was investigated and shown to increase by 2 orders of magnitude upon treatment by annealing at higher temperatures. Furthermore, the reduction of Er3+ upconversion luminescence as well as Yb3+ and Er3+ photoluminescence in BaLiF3:Yb3+, Er3+ as a function of increasing X-ray doses were explored in detail. It is demonstrated that Yb3+ and Er3+ co-doped BaLiF3 exhibits desirable sensitivity to X-ray radiation. 2D X-ray images were recorded based on the observed upconversion luminescence which demonstrated their potential for X-ray imaging along with dosimetry. Finally, a F3+ colour centre is reported in undoped BaLiF3 upon annealing, which display a zero-phonon line at 764.8 nm. The zero-phonon line exhibited Zeeman effects in large magnetic fields due to a triplet ground state. This is the first observation of singlet to triplet luminescence of colour centre. The photoluminescence properties and X-ray storage capability of the F3+ centre was rigorously explored. Significantly, this thesis advances the understanding of luminescent properties of activated and pure BaLiF3 and sheds light on the utilization of these nanocrystals for practical implementations.
-
(2021)ThesisGenetic differentiation is a vital aspect of population genetics and is a direct consequence of evolutionary forces acting on genetic diversity. By interpreting patterns of genetic differentiation, we can detect, infer and estimate the extent to which natural selection, genetic drift and gene flow affect genetic diversity. In this thesis, estimation of genetic differentiation is used as a tool to answer the following questions, three mainly theoretical, and the other an applied study on platypus conservation. 1. Can a form of linked selection termed associative overdominance (AOD) explain lower levels of genetic differentiation between populations (FST), and higher heterozygosity, than expected under neutrality in experimental populations (Drosophila melanogaster) and in a feral population (Bos taurus)? 2. Under which circumstances does AOD affect FST and heterozygosity? 3. Can AOD be detected in natural populations? 4. Do dams restrict gene flow among platypus groups? AOD is triggered by the occurrence of recessive deleterious mutations that are physically linked and form haplotypes when recombination events are scarce, as in small populations. When haplotypes within an individual contain recessive deleterious mutations at different positions, a heterozygote for two different haplotypes is fitter than either one of the homozygotes. As a result, heterozygosity is higher, and FST lower than expected under neutrality. Here, using feral, experimental and computer- simulated populations, it is demonstrated how AOD might be prevalent in small populations, and a framework for predicting and detecting AOD is provided. The extent to which dams disrupt gene flow among platypus populations is investigated by using four rivers regulated by dams and three unregulated rivers. It was found that: genetic differentiation is significantly correlated with the number of generations since the dams were built; populations and individuals separated by dams are genetically more different than otherwise; and areas of high genetic differentiation coincide with the location of dams. It is suggested that dams jeopardise the long-term viability of platypus populations.
-
(2020)ThesisTiara[n]uril is a new class of glycoluril-based macrocyclic hosts, characterized by the presence of a positively charged cavity comprising of glycoluril moieties linked to two pyrazolium groups. Being a recently discovered macrocycle, only a few Tu[n] derivatives have been synthesized and reported. However, these Tu[n]s are restricted to homologues no larger than Tu[3], which indicates synthetic opportunities towards the attainment of higher homologues through variation of substitutions on the glycoluril moieties. Presented in this thesis is the synthesis of new members of Tu[n] family - tetrahydrothiophenetiara[n]uril (THTnTu[n]). A reaction sequence was designed to achieve homologues of Tu[n] (n>3) through equatorial introduction of THT functionality. This synthetic route provided access to two THT functionalized Tu[n]s - THT3Tu[3]2+ and THT4Tu[4]2+, where the later represents the first example of higher homologue in Tu[n] family. The structural properties of purified THT3Tu[3]2+ and THT4Tu[4]2+ were fully elucidated using different techniques. Furthermore, attempts to bias the product distribution towards THT4Tu[4]2+ was illustrated through the use of different acids, which indicated the influence of an anionic template in attaining improved higher homologue (n=4) proportion. The second objective of the work was to develop an understanding of the binding capabilities of methyl and THT substituted Tu[n]s to establish their potential for functional applications. The binding association of Me10Tu[3]2+, THT3Tu[3]2+ and THT4Tu[4]2+ were explored with a selection of guests suitable for the testing of a preliminary understanding. The association towards an inorganic (HCl), and organic guest (L-glutamine) was demonstrated through an increase in pKa for HCl and changes in CD and fluorescence outcome for the amino acid. In addition, the cavity encapsulating feature of THT4Tu[4]2+ was established with the guests - dioxane and d8-dioxane. The binding constants were determined using comparative binding and d8-dioxane was found to bind more strongly than dioxane. Furthermore, Me10Tu[3]2+ was investigated for it’s possible effectiveness as a solubilizing excipient for the poorly soluble oral drugs. The preliminary results indicated formation of association complexes as reflected by changes in their solubilities at two pH conditions - 3.5 and 7.4. These solubility results suggests that Me10Tu[3]2+ or related Tu[n]s may have potential in future drug delivery applications.
-
(2020)ThesisEcosystems can be stressed when an environment is under pressure, such as when resources deplete due to biological invasion. Randomness in nature is an inherent source of environmental stress affecting resident species. Central to ecologists is the concept of a carrying capacity -- maximum population sustained by an environment. Many models consider the carrying capacity, a proxy for the environment, as unchanging. It is recognised that this is not the case. We propose an approach that accounts for a variable carrying capacity. This permits us to model changes in a population due to environment stress. A couple of different approaches to modelling the dynamics of a reindeer population is discussed. One is based on survival modelling -- the effects of a stressed environment on a reindeer population is investigated employing well known survival functions. Survival probability is calculated by applying a hazard function directly and indirectly to the reindeer. The second is based on a system of differential equations that couples the population to the environment via the carrying capacity. We employ seven different response functions in an effort understand their population dynamics. We find that a Type II response function is suited to reindeer populations that show a gradual decline in the population size, such as on St. George Island and George Reserve. Whereas a Type VI (ratio-dependent) response function for populations that exhibit a sharp decline, as on St. Paul and Svalbard Islands. We also consider the role of lichen regrowth and the effects of an environmental delay in response to grazing by reindeer. We show that regrowth is an important ingredient in the model even though its growth rate is very slow compared to its consumption rate by reindeer. Further, the inclusion of a delay greatly improves the model for the reindeer on St. George Island.