Proterozoic crustal growth in the southeastern Gawler Craton: the development of the Barossa Complex, and an assessment of the detrital zircon method

The Barossa Complex, southeast Gawler Craton, South Australia, forms the southeastern-most exposure of pre-Neoproterozoic crust in Australia. Understanding the geodynamic evolution of this area can improve paleogeographic reconstructions of the economically significant Gawler Craton, as well as global reconstructions in the Proterozoic. The first part of this thesis addresses the geological development of the Barossa Complex during the Palaeo-Mesoproterozoic. The Barossa Complex is composed of metasedimentary and metaigneous gneisses. These include calcsilicate, quartzofeldspathic, psammopelitic, and pelitic gneisses. In the northern inliers, the protoliths to these gneisses are indicative of a progressively deepening basin. Syndepositional felsic orthogneisses and mafic amphibolites indicate a tectonically active basin. Deposition of the metasedimentary protoliths to the Barossa Complex occurred between 1730-1655 Ma, synchronous to the onset of the Kimban Orogeny in the Gawler Craton and the deposition of the Willyama Supergroup in the Curnamona Province. U-Pb and Hf isotopic analyses from detrital zircon indicates sediment was largely derived from the Gawler Craton. Syndepositional granite intrusions occurred in the northern extent of the Barossa Complex at 1717 ±7 Ma. Metamorphism initiated in the Barossa Complex at c. 1630 Ma with the development of a low angle metamorphic fabric. Peak granulite conditions of approximately 8-9 kbar and 800-850 °C occurred at c. 1590 Ma in the southern Barossa Complex. The northern Barossa Complex preserves lower grade metamorphic features and c. 1600 Ma zircon with hydrothermal Rare Earth Element (REE) signatures, which are potentially linked to the Hiltaba event in the Gawler Craton. Post peak metamorphism continued until c. 1550 Ma and is associated with retrograde shear zones in the southern Barossa Complex, and late pegmatites in the northern inliers. The Barossa Complex shares a depositional and metamorphic history with the Willyama Supergroup in the Curnamona Province and Mt. Isa Inlier basin sequences, and was part of a transcontinental plate margin system during the Late Palaeo- Early Mesoproterozoic. East dipping subduction was the likely driver for extensive rift basin development across the eastern margin of Proterozoic Australia before the Isan-Olarian Orogeny inverted these basins. The Barossa Complex is the southern-most exposure of this system. The second part of this thesis addresses the use of detrital zircon in modern sediment as a means of characterising the bedrock of a catchment area, which has been used previously in the Gawler Craton and Curnamona Province. In the Broken Hill area of the Curnamona Province, stream sediments were sampled from drainage pathways with catchments that have stratigraphically and chronologically well characterised bedrock lithologies. Zircon ages from the modern sediment found up to 30% of the zircons were significantly younger than what expected from the bedrock sources (>1.6 Ga). Aeolian dune sands from the Strzelecki Desert to the north of the study area are found to contain zircon with U-Pb and Lu-Hf isotopic compositions matching the ‘exotic’ zircon populations in Broken Hill. Aeolian detritus is considered to have contributed zircon to the stream sediments in Broken Hill, and should be considered in any study utilising modern detritus in arid environments. Detrital zircon provenance studies of the geological record should be interpreted cautiously if aeolian input may have occurred.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 201

Molecular Genetic Typing of Staphylococcus aureus from Cows, Goats, Sheep, Rabbits and Chickens

End of project reportsS. aureus can also cause a number of infections in animals such as tick-associated pyaemia in lambs, staphylococcosis in rabbits, septicaemia, abscesses and chondronecrosis in chickens and pneumonia and osteomyelitis complex in turkeys. S. aureus is the most frequent cause of bovine mastitis, a disease that is of economic importance worldwide (Beck et al., 1992). Typically staphylococcal mastitis is chronic in nature, with subclinical mastitis being the most common form

Molecular Characterisation of Bacteriophage K Towards Applications for the Biocontrol of Pathogenic Staphylococci

End of project reportThe aim of this work was to characterise staphylococcal bacteriophage (a bacterial virus) and to assess their potential as therapeutic agents against pathogenic strains of Staphylococcus aureus, particularly mastitis-causing strains. The project included the use of two newly isolated phage CS1 and DW2, and an existing polyvalent phage. The new phage were isolated from the farmyard and characterised by electron microscopy and restriction analysis. Both phage were shown to belong to the Siphoviridae family and were lytic for representatives of all three clonal groups of Irish mastitis-associated staphylococci. A cocktail of three phage (CS1, DW2 and K) at 108 (plaque forming units) PFU/ml was infused into cows teats in animal trials. The lack of an increase in somatic cell counts in milks indicated strongly that the phage did not irritate the animal. In addition, the most potent phage used in this study, phage K, was further studied by genome sequencing, which revealed a linear DNA genome of 127,395 base pairs, which encodes 118 putative ORFs (open reading frames)

Microstructural Correlates of Resilience against Major Depressive Disorder: Epigenetic Mechanisms?

Mental disorders are a major cause of long-term disability and are a direct cause of mortality, with approximately 800.000 individuals dying from suicide every year worldwide - a high proportion of them related to major depressive disorder (MDD)^1^. Healthy relatives of patients with major depressive disorder (MDD) are at risk to develop the disease. This higher vulnerability is associated with structural^2-4^ and functional brain changes^5^. However, we found using high angular resolution diffusion imaging (HARDI) with 61 diffusion directions that neuron tracts between frontal cortices and limbic as well as temporal and parietal brain regions are characterized by better diffusion coefficients in unaffected relatives (UHR), who managed to stay healthy, compared to healthy volunteers without any family history for a psychiatric disease (HC). Moreover, those UHR with stronger fibre connections better managed incidences of adversity in early life without later developing depression, while in HC axonal connections were found to be decreased when they had early-life adversity. Altogether these findings indicate the presence of stronger neural fibre connections in UHR, which seem to be associated with resilience against environmental stressors, which we suggest occur through epigenetic mechanisms

Effect of Motion on the ADC Quantification Accuracy of Whole-Body DWIBS

y Diffusion-weighted whole-body imaging with background body signal subtraction was introduced as a qualitative approach to detecting metastases in the body. A liver-mimicking phantom with embedded tumours that could be moved to replicate respiratory motion was developed to assess its ability to accurately quantify ADC values. RESULTS: Mean tumour ADC values were unaltered by the motion; however, a significant (p \u3c 0.05) increase in the spread of ADC values was measured, even for relatively large tumours. CONCLUSIONS: These findings may be of significance in cancer therapy monitoring where subtle changes in ADC histograms may reveal changes in tumour heterogeneity

A Novel Anthropomorphic Flow Phantom for the Quantitative Evaluation of Prostate DCE-MRI Acquisition Techniques

A novel anthropomorphic flow phantom device has been developed which can be used for quantitatively assessing the ability of MRI scanners to accurately measure signal / concentration time-intensity curves (CTCs) associated with dynamic contrast-enhanced (DCE) MRI. Modelling of the complex pharmacokinetics of contrast agents as they perfuse through the tumour capillary network has shown great promise for cancer diagnosis and therapy monitoring. However, clinical adoption has been hindered by methodological problems, resulting in a lack of consensus regarding the most appropriate acquisition and modelling methodology to use and a consequent wide discrepancy in published data. A heretofore overlooked source of such discrepancy may arise from measurement errors of tumour CTCs deriving from the imaging pulse sequence itself, while the effects on the fidelity of CTC measurement of using rapidly-accelerated sequences such as parallel imaging and compressed sensing remain unknown. The present work aimed to investigate these features by developing a test device in which „ground truth‟ CTCs were generated and presented to the MRI scanner for measurement, thereby allowing for an assessment of the DCE-MRI protocol to accurately measure this curve-shape. The device comprised of a 4-pump flow system wherein CTCs derived from prior patient prostate data were produced in measurement chambers placed within the imaged volume. The ground truth was determined as the mean of repeat measurements using an MRI-independent, custom-built optical imaging system. In DCE-MRI experiments, significant discrepancies between the ground truth and measured CTCs were found for both tumorous and healthy tissue-mimicking curve shapes. Pharmacokinetic modelling revealed errors in measured Ktrans, ve and kep values of up to 42%, 31%, and 50% respectively, following a simple variation of the parallel imaging factor and number of signal averages in the acquisition protocol The device allows for the quantitative assessment and standardisation of DCE-MRI protocols (both existing and emerging)

Population and Virulence Factor Analysis of Staphylococcus aureus from Bovine Mastitis.

End of Project ReportsStaphylococcus aureus is a major cause of bovine mastitis and the disease is responsible for substantial economic losses in the dairy industry world-wide. A large number of commonly accepted virulence factors are associated with S. aureus but it is yet to be elucidated which of these are important for infection of the bovine udder. A rational and effective strategy for the control of intramammary infections may need to be directed against clones of S. aureus that commonly cause disease. The objective of this study was to characterise the genetic variance of S. aureus isolate populations from infected udders in Ireland using RAPD-PCR, ribotyping and multilocus enzyme electrophoresis (MLEE). Similar S. aureus isolates collected in the USA were also typed in order to compare strain differences in staphylococcal populations in a different environment. Phenotypic diversity based on a number of presumed virulence factors together with antibiotic sensitivity was examined and correlations between phenotype and genotype were identified, if present. In addition, a pathogenicity island encoding multiple superantigens was completely sequenced and characterised. Knockout mutants of these superantigens were also constructed and in vitro functional analysis performed. Laboratory animal experiments (mice and rabbits) were used to study the relative pathogenicity of individual staphylococcal strains (mice) and also to measure the immunological responses after prolonged exposure to the predominant strains (rabbits)

Optimisation of the transmit beam parameters for generation of subharmonic signals in native and altered populations of a commercial microbubble contrast agent SonoVue®

The aim of this work was to establish the optimum acoustic characterisation approach and insonation transmit beam parameters for subharmonic signal generation with ‘native’ and ‘altered’ populations of a commonly-used microbubble contrast agent. Dynamic contrast-enhanced (DCE) ultrasound is a non-invasive method of imaging the microvasculature, typically implemented using harmonic imaging. Subharmonic imaging, in which echoes at half the fundamental frequency are detected, detects signals which are generated by the ultrasound contrast agents (UCAs) but not by tissue. However, optimal transmission parameters and furthermore, the optimum acoustic characterisation method have not been established. The subharmonic response of ‘native’ and ‘altered’ UCA, altered through decantation, was investigated at transmit centre frequencies 1.8–5 MHz and pulse lengths 1–8 cycles. The ‘altered’ UCA had reduced polydispersity (1–4 µm: 82% bubble volume), compared to ‘native’ (4–10 µm: 57% bubble volume). A custom-built narrow-band acoustic characterisation system was found to be more appropriate for acoustic characterisation compared to the commonly used broadband pulse-echo approach. Both UCA generated the highest subharmonic signal at pulse length of 3-cycles. The maximum ‘native’ subharmonic signal was generated at a transmit centre frequency of 1.9 MHz, corresponding to a subharmonic at 0.95 MHz. This optimal frequency increased in the ‘altered’ population to 2.3–2.5 MHz, bringing the subharmonic above 1 MHz and hence into a range amenable to clinical abdominal imaging transducers. The use of subharmonic signal detection coupled with a modified UCA size distribution has potential to significantly improve the quantification sensitivity and accuracy of DCE ultrasound imaging. Keywords: Ultrasound contrast agent; Acoustic characterisation; Subharmonic imagin

An Anthropometric Study of 38 Individuals With Prader-Labhart- Willi Syndrome

Weight, height, sitting height, and 24 other anthropometric variables (5 body circumferences, skinfolds at 7 sites, 4 head dimensions, and 8 hand and foot measurements) were obtained on 38 Prader-Labhart-Willi syndrome (PLWS) individuals (21 with apparent chromosome 15 deletions and 17 nondeletion cases) with an age range of 2 weeks to 38½ years. More than half of these individuals were measured on more than one occasion. The measurements confirmed the presence of short stature, small hands and feet, obesity, and narrow bi-frontal diameter in PLWS. No differences were found for the anthropometric measurements between the 2 chromosome subgroups. Inverse correlations were produced with linear measurements (eg, height, hand and foot lengths) and age, which indicated a deceleration of linear growth relative to normal individuals with increasing age