HIGH SPATIAL RESOLUTION FIBRE-OPTIC DOSIMETRY

External beam radiation therapy (EBRT) is one of the most common forms of therapy used to treat cancers worldwide. New EBRT modalities are being developed across a range of therapies to improve patient outcomes. With these new therapies comes unique challenges for dosimetry and quality assurance which is vital for safe and effective treatments. Microbeam radiation therapy (MRT) is a novel form of EBRT that uses spatially fractionated synchrotron sourced kilovoltage x-rays to deliver highly-targeted planes of x-rays to the target volume. These microbeams are typically 25 – 50 µm in thickness, with a peak-to-peak separation of 200 – 400 µm . MRT is currently limited to synchrotron sources, and is therefore only being studied at a small number of facilities worldwide, but the emergence of compact synchrotron technology has the potential to make MRT much more accessible. Due to the extreme dose rates of MRT (in excess of 5000 Gy/s in some configurations) and high spatial fractionation of the microbeams, MRT dosimetry is an ongoing challenge that must be solved if it is to be used in human clinical trials. In this thesis scintillator fibre-optic dosimeters (FODs) with the highest spatial res- olution found in the literature are developed and tested at the Australian Synchrotron on the Imaging and Medical BeamLine, where MRT cell and animal studies are being conducted. These scintillator FODs use plastic scintillator due to its water-equivalence, energy and temperature independence and radiation hardness. The scintillator is fab- ricated to have a thickness equal to the desired one-dimensional spatial resolution for microbeam dosimetry. In this thesis scintillator probes with thicknesses 50 µm , 20 µm , and 10 µm are presented. The scintillator is coupled to an optical fibre with core diameter 1.0 mm. When oriented with the thin edge of the scintillator towards the beam, a microbeam array can be scanned with this high resolution. The FODs were able to resolve microbeams with 50 µm full-width at half-maximum, with the 20µm and 10 µm FODs showing the best agreement to expected values. Only the 10 µm FOD was able to accurately measure the dose in the valleys between the microbeams. Simulations of the detector and the synchrotron beamline were done using the physics particle simulation toolkit Geant4. These simulations were able to provide predictions of the expected intrinsic dose distributions in the microbeam fields, as well as what signals to expect from the FODs. These provided an estimate of the ideal detector responses for the experimental results to be evaluated against. These simulations showed that both the 20 µm and 10 µm detectors measured the full- width at half-maximum that was expected, while the 50 µm detector performed less accurately than could be expected

Rational's experience using Ada for very large systems

The experience using the Rational Environment has confirmed the advantages forseen when the project was started. Interactive syntatic and semantic information makes a tremendous difference in the ease of constructing programs and making changes to them. The ability to follow semantic references makes it easier to understand exisiting programs and the impact of changes. The integrated debugger makes it much easier to find bugs and test fixes quickly. Taken together, these facilites have helped greatly in reducing the impact of ongoing maintenance of the ability to produce a new code. Similar improvements are anticipated as the same level of integration and interactivity are achieved for configuration management and version control. The environment has also proven useful in introducing personnel to the project and existing personnel to new parts of the system. Personnel benefit from the assistance with syntax and semantics; everyone benefits from the ability to traverse and understand the structure of unfamiliar software. It is often possible for someone completely unfamiliar with a body of code to use these facilities, to understand it well enough to successfully with a body of code to use these facilities to understand it well enough to successfully diagnose and fix bugs in a matter of minutes

Oxygen and sulphur heterocycles derived from chloroaldehydes

Includes bibliography.Chloral may be trimerised, tetramised and polymerised, to form parachloral, metachloral and polychloral, respectively. Parachloral has two isomers: the cis-isomer and the trans-isomer. An analysis of the conformational equilibria occuring in solution, was carried out for trans-parachloral, using the techniques of dipole moment measurement and infrared and nmr spectroscopy Both isomers exist in cis-chair conformations, but differ in the chirality of the β-carbon atoms in the side chains. A comparison of the mass spectral fragmentations of parachloral and parabutylchloral is included. The structure of a related five-membered heterocycle, trans-chloralide was also investigated by x-ray crystallography. The cis-isomer of chloralide is reported for the first time. The unusual mechanism, in which carbon monoxide acts as nucleophile, by which chloralide is formed from chloral and fuming sulphuric acid, has been elucidated using 13C-labelling. The dehydrochlorination of chloralide under unexpected conditions, is also discussed. The isomerism in a series sulphur-containing analogues of parachloral was investigated. 2-Trans-dithioparachloral and its dehydrochlorination product, were shown by x-ray crystallography. A comparative study of the effects on the 1H and 13Cnmr spectra, of structural changes in these six-membered heterocycles, is discussed at length. Some introductory preparative work was done, regarding the potential use of 1,3,5-trithiane 1,3,5-trioxides with three axial sulphoxide groups, as terdentate ligands

Use of Rounded Base Turns in General Aviation Traffic Patterns: A Quantitative Analysis

Prevention of in-flight loss of control (I-LOC) in General Aviation (GA) continues to be identified as a most-wanted safety improvement by the National Transportation Safety Board (NTSB), with emphasis on low-altitude maneuvering. A possible technique to mitigate I-LOC is modification of the rectangular traffic pattern used by aircraft arriving and maneuvering within the airspace around an airport. The rectangular pattern is used to align the aircraft with the runway for landing and consists of a “base leg” in which two 90-degree directional changes are accomplished. A “rounded-base” could instead be conducted, consisting of a constant 180- degree turn, potentially resulting in lower angles-of-attack (AOA), thereby keeping the aircraft further from the critical AOA at which I-LOC may occur. Using flight data monitoring equipment, a comparative statistical analysis was conducted between the rectangular method and rounded base method to evaluate variables that influence AOA and determine if the rounded-base method provides an increased level of safety. Results suggest that the rounded base method does allow for lower bank angles, lower pitch attitudes, lower vertical speeds, and more consistent indicated airspeeds throughout the maneuver. Additionally, the rounded-base method considerably reduces the likelihood of runway overshoot during the turn to final

Characterization of the bacterioplankton communities in the melt-water ponds of Bratina Island, Victoria Land, Antarctica

Antarctic ecosystems (such as the ponds by Bratina Island, Antarctica) provide an excellent opportunity to examine organisms that can live in one of the most extreme and geochemically varied environments in the world. These ponds are of interest as each one can vary greatly in size, depth, and age as well as profiles of dissolved oxygen, metal concentrations, pH and salinity. Even within ponds geochemically distinct stratified layers can form which can greatly influence their microbial communities. There are a number of studies which indicate that microbial populations found in Antarctic ponds will be highly diverse and variable due to the uniqueness of the environment. This study aims to increase our knowledge of microbial biodiversity and the environmental factors which structure them, in particular the stratification transition zones within ponds water columns. A thorough set of biological samples were taken from five selected ponds during mid-summer in the 09-10 season to complement those taken during the winter freeze-up in the 07-08 extended season by Hawes and co-workers. Oxygen concentration, pH, conductivity and temperature of each pond water sample were measured in the field and water samples were taken back to the University of Waikato for further analysis. This research primarily used the DNA fingerprinting technique ARISA, matched with geochemistry to identify and characterise the resident and functional members of the microbial community and understand how the community is structured in relation to environmental conditions. We found that the planktonic populations of the Bratina Island ponds do vary between ponds, that each pond has its own chemical signature and that populations do change with depth. One of the studied ponds, Egg, was found to have an extreme chemical stratification leading to significantly different populations at each depth. Data analysis using BEST analysis determined that the changes in the bacterial populations in Egg are primarily in relation to the pH and conductivity at each depth which changes dramatically in the lower depths

Characterisation of bacterioplankton communities in the meltwater ponds of Bratina Island, Victoria Land, Antarctica

A unique collection of Antarctic aquatic environments (meltwater ponds) lies in close proximity on the rock and sediment-covered undulating surface of the McMurdo Ice Shelf, near Bratina Island (Victoria Land, Antarctica). During the 2009–10 mid-austral summer, sets of discrete water samples were collected across the vertical geochemical gradients of five meltwater ponds (Egg, P70E, Legin, Salt and Orange) for geochemical and microbial community structure analysis. Bacterial DNA fingerprints (using Automated Ribosomal Intergenic Spacer Analysis) statistically clustered communities within ponds based on ANOSIM (R = 0.766, P = 0.001); however, one highly stratified pond (Egg) had two distinct depth-related bacterial communities (R = 0.975, P = 0.008). 454 pyrosequencing at three depths within Egg also identified phylum level shifts and increased diversity with depth, Bacteroidetes being the dominant phyla in the surface sample and Proteobacteria being dominant in the bottom two depths. BEST analysis, which attempts to link community structure and the geochemistry of a pond, identified conductivity and pH individually, and to a lesser extent Ag109, NO2 and V51 as dominant influences to the microbial community structure in these ponds. Increasing abundances of major halo-tolerant OTUs across the strong conductivity gradient reinforce it as the primary driver of community structure in this stud

Macrolichens of Mount Wellington, Tasmania

A census of the fruticose, foliose and squamulose lichens, also referred to as "macrolichens", was carried out on Mount Wellington, Tasmania, between November 1980 and December 1985. A total of 95 taxa was found, including 32 taxa of Cladia, Cladina and Cladonia. This contrasts with the findings of a recent survey of macrolichens in Tasmanian rainforests, which reported only eight species from those genera. Mount Wellington had fewer species of Collema, Menegazzia, Pseudocyphellaria and Sphaerophorus. Thirty-seven species of macrolichens were common to both survey areas. Ramalea cochleata is reported from Tasmania for the first time. SEE ALSO: Wilson, Francis RM (1892) Tasmanian lichens - Part 1. Papers & Proceedings of the Royal Society of Tasmania . pp. 133-178. http://eprints.utas.edu.au/16016

Benthic microbial communities of coastal terrestrial and ice shelf Antarctic meltwater ponds.

The numerous perennial meltwater ponds distributed throughout Antarctica represent diverse and productive ecosystems central to the ecological functioning of the surrounding ultra oligotrophic environment. The dominant taxa in the pond benthic communities have been well described however, little is known regarding their regional dispersal and local drivers to community structure. The benthic microbial communities of 12 meltwater ponds in the McMurdo Sound of Antarctica were investigated to examine variation between pond microbial communities and their biogeography. Geochemically comparable but geomorphologically distinct ponds were selected from Bratina Island (ice shelf) and Miers Valley (terrestrial) (<40 km between study sites), and community structure within ponds was compared using DNA fingerprinting and pyrosequencing of 16S rRNA gene amplicons. More than 85% of total sequence reads were shared between pooled benthic communities at different locations (OTU0.05), which in combination with favorable prevailing winds suggests aeolian regional distribution. Consistent with previous findings Proteobacteria and Bacteroidetes were the dominant phyla representing over 50% of total sequences; however, a large number of other phyla (21) were also detected in this ecosystem. Although dominant Bacteria were ubiquitous between ponds, site and local selection resulted in heterogeneous community structures and with more than 45% of diversity being pond specific. Potassium was identified as the most significant contributing factor to the cosmopolitan community structure and aluminum to the location unique community based on a BEST analysis (Spearman's correlation coefficient of 0.632 and 0.806, respectively). These results indicate that the microbial communities in meltwater ponds are easily dispersed regionally and that the local geochemical environment drives the ponds community structure