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Unlocking low-power stimulated emission depletion super-resolution microscopy by using upconversion nanocrystals
No full textThesis by publication.Includes bibliographical references.Optical microscopy capable of real-time 3-dimentional imaging for live cells has facilitated modern biological research, especially with the recent development of a series of novel super-resolution techniques that overcome the diffraction limit associated with conventional optical microscopes. Among them, stimulated emission depletion (STED) nanoscopy is the first and optically most straightforward method to effectively break the resolution barrier for far-field microscopes. It has been demonstrated that STED can achieve 3-D imaging even at video rate. However the very high optical intensities required for depletion remain a key challenge for STED to be applied to live biological cells and tissues.This thesis explores the potential to use luminescent probes with long decay lifetimes to lower the optical depletion intensity requirement in STED. In particular, lanthanide-doped upconversion nanomaterials involving multiple intermediate excited states with lifetimes on the microsecond-to-millisecond timescale have been investigated. Such materials have found broad applications in biosensing and imaging due to their unique feature of non-photobleaching and non-photoblinking. Here, their photon upconversion process and depletion capability have been carefully studied, in order to apply them to achieve STED super-resolution imaging at lowered intensity. The thesis is composed of the following research:Firstly, a continuous-wave STED (CW STED) microscope based on a Ti:Sapphire oscillator was established to achieve ~71 nm super-resolution on 20 nm fluorescent nanoparticles. Three components of cellular skeleton and RNA were imaged in fixed cells with super-resolution. This result shows that the CW mode operation reduces the system complexity and cost; however, it cannot relieve the extreme intensity requirement in STED to achieve super resolution for live cell imaging.Secondly, we explored and realized super-resolution imaging via an intermediate-level depletion mechanism using NaYF4:Yb3+/Tm3+ upconversion nanocrystals. Measurement of the depletion efficiency from upconversion nanocrystals with variable doping concentrations showed that the saturation intensity reduces substantially at increased Tm3+ doping concentration. In comparison to conventional organic dyes, the depletion intensity requirement for 8% Tm3+-doped samples is reduced by two orders of magnitude, allowing us to achieve moderate super-resolution on these highly-doped samples at much lower depletion intensities.Thirdly, the mechanism underpinning efficient depletion on highly doped upconversion nanocrystals was studied in detail. We found that the Tm-Tm cross-relaxation rates in the Yb-Tm photon upconversion system increase significantly at high Tm doping concentration. This leads to a photon-avalanche-like process to efficiently establish population inversion on the intermediate excited levels, enabling amplified stimulated emission to depletion/inhibit upconversion luminescence using largely reduced intensity. Meanwhile, for low doping concentration samples, the cross-relaxation rates are not sufficient to achieve photon-avalanche-enhanced stimulated emission depletion.The results embodied in this thesis demonstrate the capability to achieve low-power operation of STED using upconversion nanocrystals for super-resolution imaging for live cells. It suggest that novel luminescence nanoprobes may hold the key to next-generation optical nanoscopy. We further explored the lifetime tunability of upconversion nanocrystals for multiplexed imaging and molecular localization at high throughput, with preliminary results suggesting that upconversion nanoparticles with the same emission wavelengths can be effectively distinguished based on lifetime coding. It is expected that the new bio-friendly upconversion-STED method may find broad applications in life sciences.Mode of access: World wide web1 online resource (xiv, 135 pages) illustrations (some colour
Geophysical signatures of small-scale base metal occurrences in south eastern New South Wales
No full textTheoretical thesis.Bibliography: pages 52-54.1. The geology of base mineralisation in south eastern NSW -- 2. Study localities and research methods -- 3. Geophysical signatures of base metal deposits -- 4. Computational modelling of geophysical signatures -- 5. Interpretation and discussion of geophysical signatures of small-scale deposits -- 6. Conclusion.Ground-based, time-domain electromagnetic, magnetic and gravity datasets were obtained for the southern Gurubang and Rosebank VHMS deposits located approximately 15 km east of Cooma, NSW. The deposits are hosted in a mid-late Silurian sequence of rock composed of shallow marine sediments and felsic volcanic rocks. The aim of this research was to ascertain the usefulness of highresolution geophysical techniques in targeting and evaluating small-scale polymetallic massive sulphide deposits, and to investigate how the detailed geophysics relates to the overall geological framework of the prospect areas. The acquired data was analysed using a forward modelling approach. Due to both deposits containing high concentration of conductive minerals, a coincident loop time-domain electromagnetic 2D survey effectively delineated the sulphide mineralisation and was useful in interpreting and adapting deposit parameters such as the azimuth, dip and strike length. Based on the physical nature of the target deposits, it was determined that high-resolution magnetic and gravity surveys would not be effective methods in directly delineating these smaller-scaled (10’s of m’s) mineral deposits. However, magnetics and gravity did prove effective in depicting the surrounding geology, including potential volcanic intrusions and basement lithologies and structures.1 online resource (vi, 54 pages : illustrations, maps
Are simultaneous interpreters subject to the central processing bottleneck during language production?
No full textTheoretical thesis.Bibliography: pages 117-138Chapter 1. Introduction -- Chapter 2. Literature review -- Chapter 3. Methodology -- Chapter 4. Results and analysis -- Chapter 5. Conclusion, limitations and avenues for further research.Simultaneous interpreting (SI), the mode of interpreting generally used at international conferences, is an exceptionally complex language-processing task, which requires interpreters to continuously receive source language (SL) utterances, store the information in memory, transcode utterances into the target language (TL), and articulate the previous segments. What makes SI particularly difficult to perform is that all the above processes are carried out in real time.Almost all models of cognitive processing during SI share the assumption that cognitive resources are limited and shared by all the components of processing that need to occur concurrently (Gerver, 1976; Gile, 1997; Liu et al., 2004; Christoffels & De Groot, 2004; Padilla, Bajo & Macizo, 2005). This assumption has gone largely unchallenged, and yet psycholinguistic research on language performance has suggested that language production is subject to a central processing bottleneck (Welford, 1952) which allows only one task to be performed at a time.This raises the as-yet-unanswered question of whether interpreters, despite their professional experience, are also subject to the central processing bottleneck during language production, or whether interpreters’ extensive experience leads to more efficient lemma and phonological word-form selection than is the case for bilinguals and monolinguals, alleviating the bottleneck. In this study, I investigate these questions using an experiment in the dual-task paradigm. The results suggest that even language experts such as simultaneous interpreters are subject to the central processing bottleneck during word production. No significant difference was found between the three matched groups of professional interpreters, bilinguals and monolinguals on the duration of the bottleneck stage during word production. In addition, the results indicate that interpreters are as good at anticipating the upcoming word as monolinguals, and better than proficient bilinguals.Mode of access: World wide web1 online resource (xvi, 141 pages
Rhetorical strategies of the first chapter of 1 Timothy: the relationship of the first chapter to the purpose of the letter
No full textTheoretical thesis.Bibliography: pages 324-360.Chapter 1. The present life (1 Tomothy 4:8 : 1 Timothy as a historical document -- Chapter 2. The author and the letter -- Chapter 3. The letter writer and his son -- Chpater 4. The command and the instruction -- Chapter 5. The education of the young man -- Chapter 6. The orator : persuading the "certain men" -- Chapter 7. The goal of the command entrusted to Timothy -- Conclusion -- Bibliography.There are a number of problems that face the scholar wishing to interpret 1 Timothy. These problems are epitomized by the following comment from Marin Dibelius and Hans Conzelmann in their 1972 commentary on the Pastoral Epistles : We cannot with equal certainty identify a basic body of material in 1 Tim [as it can be for Titus]. For there the interest is directed to two main points: church order and the refutation of heretics…But even apart from this twofold interest, the character of the church order materials themselves does not seem uniform. 1 Timothy looks like an assortment of materials, and it is difficult to perceive how they function together as a cohesive whole. Lewis Donelson in his, Pseudepigraphy and Ethical Argument in the Pastoral Epistles (1986), argued that each of the Pastoral Epistles could be understood as offering cohesive arguments when compared to other Graeco-Roman ethical documents. However, Donelson’s insistence that the Pastoral Epistles fit within a pseudepigraphical letter category has not gone without criticism.This thesis will argue that the opening command, verses 3—4 of 1 Timothy 1 is the key to understanding how the letter functions as a persuasive literary unit. As Donelson has pointed out, rhetorical devices are at work in this letter. However, there are important ideological and thematic threads that need to be considered including the ideologically important father-son motif, civic ideals, educational motifs, stereotypes of young men and older men, cultural anxieties and aspirations. What will be demonstrated in this thesis is that these threads, among others, are drawn in by the writer in order to develop a strategy in the rhetorically significant digression, 1 Timothy 1:5—20, to persuade the “certain men” to desist in “teaching strange doctrines” and pursuing other unhelpful activities. It will be concluded that the “certain men” are being persuaded to turn to the “administration of God which is by faith,” and it is this persuasive strategy that ties the commands that follow later in the letter to the command given at 1 Timothy 1:3—4.1 online resource (360 pages
Novel zinc alloy castings for medical implants
No full textEmpirical thesis.Bibliography: pages 47-48.1. Introduction -- 2. Literature review -- 3. Experimental procedures -- 4. Results -- 5. Discussion -- 6. Conclusions -- 7. Future work -- 8. Abbreviations -- Appendices -- References.There have been many studies of biodegradable metals, mainly involving magnesium and iron, with new studies of zinc. Zinc being an essential element of the human body and biocompatible, this makes it a potential candidate for a biodegradable metal. However, zinc is brittle and has low mechanical properties, but it excels in corrosion resistance. Therefor the focus of this research is to experiment with different compositions of magnesium and calcium, to see how they affect the characteristics of zinc. With the success of the characterisation, it will lead on to using zinc alloys in 3D printing for medical implants.Mode of access: World wide web.1 online resource (xiii, 48 pages illustrations (some colour)
Microstructural analysis of 3D printed 316L stainless steel
No full textEmpirical thesis.Bibliography: pages 50-51.1. Introduction -- 2. Background and literature review -- 3. Experimental procedures and methods -- 4. Results and discussion -- 5. Conclusion -- 6. Future work -- 7. Nomenclature -- 8. References.This study investigates the important, rapidly emerging, latest manufacturing technology which is revolutionising the manufacturing industries. Additive manufacturing (AM), also referred to as 3D printing, in comparison to traditional subtracting manufacturing techniques, involves manufacturing a part by depositing material layer by layer until the final product is achieved. Once the 316L stainless steel part is printed, microstructural crystal grain analysis of the part will be carried out on the longitudinal and latitudinal cross-sectional surfaces with varying heights, and comparing the results obtained with that of conventional manufacturing methods being currently used.Mode of access: World wide web.1 online resource (51 pages illustrations (some colour)
Development of rotation mechanism for beam-steering antenna
No full textEmpirical thesis.Bibliography: pages 93-101.Chapter 1. Introduction and background -- Chapter 2. Existing rotation system design -- Chapter 3. Planner holder -- Chapter 4. Concept development -- Chapter 5. Engineering analysis -- Chapter 6. Prototyping and fabrication -- Chapter 7. Testing and refinement -- Chapter 8. Discussion -- Chapter 9. Conclusions -- Appendices -- References.During the last thirty years antenna application technology has significantly improved. Advances in antenna technology has allowed for an increased reception range for both the Internet and mobile phones. Macquarie University has invented a new class of planner high-gain antennas as a solution to get more efficient mobile phone reception and Internet connectivity. The antenna accomplishes this goal by gaining satellite radiation waves at any region on the ground, on water or even in the atmosphere. This type of planner antenna requires a beam steering system to be rotated and aligned in a specific direction to ensure efficient functionality. In addition, this rotation system requires speed and accuracy to track the satellite radiation waves. Many researchers have developed antenna control systems using a range of different methods to track the signal resource. This thesis presents the control system development within Macquarie's antenna planners. The system development began with four designs. These were produced after examining several antenna mechanism research studies and improved upon by utilising these studies to produce a flexible system free from systemic error. The implementation of worm gears and roller methods to the mechanism are introduced to improve the way the antenna performs. This specific development method is not used in any normal antenna control systems and has been designed specifically for Macquarie University's antenna planner system. The simulation and outcome results show that the methods have eliminated any systemic errors and have been shown to improve the overall performance of the mechanism.Mode of access: World wide web.1 online resource (xv, 101 pages colour illustrations
A comparison of knee conditions before and after total knee arthroplasty (TKA)
No full textEmpirical thesis.Bibliography: pages 37-38.1. Introduction -- 2. Background and related work -- 3. Methodology -- 4. Findings -- 5. Discussion -- 6. Conclusion and future work -- 7. Abbreviations -- Bibliography.Total knee arthroplasty (TKA) is a common procedure intended to restore function to damaged knees resulting from injuries or common diseases such as late stage osteoarthritis (OA). The end goal is to improve a patient's range of motion, as well as reducing pain levels to an acceptable level comparable to that of a healthy knee. The procedure involves replacing both the femoral and tibial components with metallic implants adjoined together with a synthetic polyethylene insert to replicate a real knee. The goal of this project is to analyse the differences in knee biomechanics before and after the TKA procedure using medial pivot implants. If time and resources permit, comparisons between traditional knee implants and medial pivot implants may also be researched.Mode of access: World wide web.1 online resource (xiii, 39, [18] pages illustrations (some colour)
Solar fuels production from water splitting with sunlight
No full textEmpirical thesis.Bibliography: pages 41-44.1. Introduction -- 2. Literature review -- 3. Approach and methodology -- 4. Results -- 5. Conclusion -- 6. Future work -- 7. Abbreviations -- Appendices -- References.With the increase in the depletion of fossil fuel resources and its accompanying harmful environmental effects, a clean, efficient and portable fuel is in need of development. As a result, hydrogen fuel has attracted much attention because of its favourable characteristics, but due to its limiting technology to produce it, hydrogen fuel is not widely used. Photocatalytic water splitting is a recent development that can potentially lead to an economical and efficient process to produce hydrogen. The power that drives this technology is sunlight, an environmentally free and renewable resource, making it a valuable approach to producing hydrogen fuel in the future. This thesis aims to conduct further work on the development of an efficient photocatalyst, which initiates the splitting of water into hydrogen and oxygen.The project fabricated iron oxide/carbon nitride nanotubes (FeOx/C3N4 NTs, and then tested its hydrogen generation performance, by emitting artificial visible-light on the chemical product submerged in water. The results showed an increase in photocatalytic performance as compared to the bulk graphitic C3N4, and C3N4 NTs by itself. In essence, the nanoparticles, FeOx, reduced the negative effect of recombinant rate and increased the visible-light absorption capacity. In addition, different weight percentages of FeOx/C3N4 NTs were synthesised (1 wt%, 3 wt%, 5 wt%, 7 wt% and 9 wt%). The photocatalytic test determined the optimum weight percentage for hydrogen evolution is 5 wt%. Any subsequent testing wt% values that were either above of below 5 wt% showed a reduction in hydrogen production. The morphological structure of the synthesised FeOx/C3N4 NTs was characterised by TEM, while its crystal phase was determined by the XRD. TEM images proved that FeOx particles are indeed anchored on the C3N4 NTs. However, many agglomerated on the NT surface, suggesting that the adopted method was not successful in synthesisin distinct NPs adhered onto the host photocatalyst. XRD results showed evidence of Fe3O4, Fe2O3 and Fe NPs. UV-vis absorption and PL spectra analysis showed that the hybrid photocatalyst is a visible-light driven photocatalyst and has a low recombination rate when exposed to visible light.Mode of access: World wide web.1 online resource (xii, 44 pages illustrations(some colour)
Final report
No full textEmpirical thesis.Bibliography: pages 63-65.1. Introduction -- 2. Background and literature review -- 3. System design and testing -- 4. Results -- 5. Discussion -- 6. Conclusions -- 7. Future work -- 8. Abbreviations -- Appendices -- References.With the adoption of phased array feeds on telescopes such as the Australian Square Array Pathfinder comes problems in processing data coming from the array. One such problem is the calculation of beam weights for beam formers. A need has been identified for a fast matrix inversion algorithm capable of supporting these data rates. A hardware implementable algorithm addressing the matrix inversion problem will be presented along with its limitations and advantages. Several other algorithms were also tested for suitability with the results presented.Mode of access: World wide web.1 online resource (xiii, 65 pages colour illustrations