Master of Science

thesisThe laser ablation split stream technique allows for concurrent measurement of Lu-Hf and U-Pb isotopes in zircon by consuming one sample volume, ensuring a direct relationship between crystallization age and Hf-isotope ratios. This is an improvement over common in situ techniques that utilize two sample volumes. In this study, we describe a new method for measuring Lu-Hf and U-Pb isotopes on zircons termed Dual Multicollector Laser Ablation Split Stream ICMPS (DM-LASS -ICPMS). The method is thus far unique because it uses two ThermoFinnigan Neptune Plus multicollector mass spectrometers, which allows high precision measurements of U-Pb as well as Hf. The robust nature of this technique is demonstrated through analyses of 5 natural zircons (91500, Ple š ovice, Mudtank, Temora-2, R33) and 3 synthetic zircons (MUNZirc 1, 3, and 4) with a 53 μ m laser spot. Furthermore, the usefulness of this technique is confirmed by 190 measurements on zircons in rhyolites of the Bruneau-Jarbidge volcanic center. The Bruneau-Jarbidge center, located in the central Snake River Plain of Idaho, is an expression of the Yellowstone hotspot (YHS), and was active from 12.7-8 Ma. The ε Hf values of zircons from the Bruneau-Jarbidge volcanic center range from -15 to -1.5, indicating a period of increased basaltic input and suppression of a crustal signature that is associated with increased melt production

SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption

The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve

Nudging towards COVID-19 and influenza vaccination uptake in medically at-risk children : EPIC study protocol of randomised controlled trials in Australian paediatric outpatient clinics

Introduction: Children with chronic medical diseases are at an unacceptable risk of hospitalisation and death from influenza and SARS-CoV-2 infections. Over the past two decades, behavioural scientists have learnt how to design non-coercive ‘nudge’ interventions to encourage positive health behaviours. Our study aims to evaluate the impact of multicomponent nudge interventions on the uptake of COVID-19 and influenza vaccines in medically at-risk children. Methods and analyses: Two separate randomised controlled trials (RCTs), each with 1038 children, will enrol a total of approximately 2076 children with chronic medical conditions who are attending tertiary hospitals in South Australia, Western Australia and Victoria. Participants will be randomly assigned (1:1) to the standard care or intervention group. The nudge intervention in each RCT will consist of three text message reminders with four behavioural nudges including (1) social norm messages, (2) different messengers through links to short educational videos from a paediatrician, medically at-risk child and parent and nurse, (3) a pledge to have their child or themselves vaccinated and (4) information salience through links to the current guidelines and vaccine safety information. The primary outcome is the proportion of medically at-risk children who receive at least one dose of vaccine within 3 months of randomisation. Logistic regression analysis will be performed to determine the effect of the intervention on the probability of vaccination uptake. Ethics and dissemination: The protocol and study documents have been reviewed and approved by the Women’s and Children’s Health Network Human Research Ethics Committee (HREC/22/WCHN/2022/00082). The results will be published via peer-reviewed journals and presented at scientific meetings and public forums. Trial registration number: NCT05613751

ProsCan for Couples: Randomised controlled trial of a couples-based sexuality intervention for men with localised prostate cancer who receive radical prostatectomy

Background: Prostate cancer is the most common male cancer in the Western world. The most substantial long term morbidity from this cancer is sexual dysfunction with consequent adverse changes in couple and intimate relationships. Research to date has not identified an effective way to improve sexual and psychosocial adjustment for both men with prostate cancer and their partners. As well, the efficacy and cost effectiveness of peer counselling as opposed to professional models of service delivery has not yet been empirically tested. This paper presents the design of a three arm randomised controlled trial (peer vs. nurse counselling vs. usual care) that will evaluate the efficacy of two couples-based sexuality interventions (ProsCan for Couples: Peer support vs. nurse counselling) on men's and women's sexual and psychosocial adjustment after surgical treatment for localised prostate cancer; in addition to cost-effectiveness. Methods/design: Seventy couples per condition (210 couples in total) will be recruited after diagnosis and before treatment through urology private practices and hospital outpatient clinics and randomised to (1) usual care; (2) eight sessions of peer-delivered telephone support with DVD education; and (3) eight sessions of oncology nurse-delivered telephone counselling with DVD education. Two intervention sessions will be delivered before surgery and six over the six months post-surgery. The intervention will utilise a cognitive behavioural approach along with couple relationship education focussed on relationship enhancement and helping the couple to conjointly manage the stresses of cancer diagnosis and treatment. Participants will be assessed at baseline (before surgery) and 3, 6 and 12 months post-surgery. Outcome measures include: Sexual adjustment; unmet sexuality supportive care needs; attitudes to sexual help seeking; psychological adjustment; benefit finding and quality of life. Discussion: The study will provide recommendations about the efficacy of peer support vs. nurse counselling to facilitate better sexual and couple adjustment after prostate cancer as well as recommendations on whether the interventions represent efficient health service delivery

Does Heterogeneous Strain Act as a Control on Seismic Anisotropy in Earth’s Lower Mantle?

Plastic deformation and texture development in minerals of the lower mantle can result in seismic anisotropy, and studying deformation of lower mantle materials is therefore important for interpreting lower mantle flow. Most previous deformation experiments documenting texture development at lower mantle pressures have been conducted on single-phase samples and/or at room temperature. However, real rocks deform at high temperature and are poly-phase and deformation is therefore likely different from that of a single phase. Here we report on high temperature diamond anvil cell deformation experiments on a multiphase assemblage of bridgmanite, ferropericlase, and ringwoodite compressed from ∼28 to ∼39 GPa and resistively heated at a constant temperature of 1,000 K. We employ the elasto-viscoplastic self-consistent method to model both texture and lattice strain of bridgmanite as a function of deformation mechanisms. Simulations indicate deformation of bridgmanite is accommodated by about half of slip activity on (100)[010] with the remainder split between (100)[001] and/or (100)〈011〉. Texture in bridgmanite is consistent with most seismic observations in the lowermost mantle. Although there is texture development in both bridgmanite and ringwoodite, ferropericlase does not develop coherent texture throughout the course of the experiment. Analysis of lattice strains suggests that the lack of coherent texture development in ferropericlase is due to heterogeneous plastic deformation resulting from microstructural interactions imposed by other phases. Variations in texturing of bridgmanite and ferropericlase could therefore cause laterally varying, complex anisotropy. Our models for binary mantle-like mixtures of bridgmanite and ferropericlase show that changes in strain and texture partitioning can explain the range of observed lower mantle anisotropies

Texture Development and Stress–Strain Partitioning in Periclase + Halite Aggregates

© 2019 by the authors.Multiphase materials are widely applied in engineering due to desirable mechanical properties and are of interest to geoscience as rocks are multiphase. High-pressure mechanical behavior is important for understanding the deep Earth where rocks deform at extreme pressure and temperature. In order to systematically study the underlying physics of multiphase deformation at high pressure, we perform diamond anvil cell deformation experiments on MgO + NaCl aggregates with varying phase proportions. Lattice strain and texture evolution are recorded using in-situ synchrotron x-ray diffraction and are modeled using two-phase elasto-viscoplastic self-consistent (EVPSC) simulations to deduce stress, strain, and deformation mechanisms in individual phases and the aggregate. Texture development of MgO and NaCl are affected by phase proportions. In NaCl, a (100) compression texture is observed when small amounts of MgO are present. In contrast, when deformed as a single phase or when large amounts of MgO are present, NaCl develops a (110) texture. Stress and strain evolution in MgO and NaCl also show different trends with varying phase proportions. Based on the results from this study, we construct a general scheme of stress evolution as a function of phase proportion for individual phases and the aggregate.L.M. acknowledges support from the National Science Foundation through EAR-1654687. This work has been supported by the US Department of Energy, National Nuclear Security Administration, through the Capital-DOE Alliance Center (DE-NA0003858) which provided graduate student financial support for M.J. and S.C. as well as support for beamtime.Peer reviewe

Deformation of NaCoF3_ 3 perovskite and post-perovskite up to 30 GPa and 1013 K: implications for plastic deformation and transformation mechanism

Texture, plastic deformation, and phase transformation mechanisms in perovskite and post-perovskite are of general interest for our understanding of the Earth's mantle. Here, the perovskite analogue NaCoF$_3$ is deformed in a resistive-heated diamond anvil cell (DAC) up to 30 GPa and 1013 K. The in situ state of the sample, including crystal structure, stress, and texture, is monitored using X-ray diffraction. A phase transformation from a perovskite to a post-perovskite structure is observed between 20.1 and 26.1 GPa. Normalized stress drops by a factor of 3 during transformation as a result of transient weakening during the transformation. The perovskite phase initially develops a texture with a maximum at 100 and a strong 010 minimum in the inverse pole figure of the compression direction. Additionally, a secondary weaker 001 maximum is observed later during compression. Texture simulations indicate that the initial deformation of perovskite requires slip along (100) planes with significant contributions of {110} twins. Following the phase transition to post-perovskite, we observe a 010 maximum, which later evolves with compression. The transformation follows orientation relationships previously suggested where the c axis is preserved between phases and hh0 vectors in reciprocal space of post-perovskite are parallel to [010] in perovskite, which indicates a martensitic-like transition mechanism. A comparison between past experiments on bridgmanite and current results indicates that NaCoF$_3$ is a good analogue to understand the development of microstructures within the Earth's mantle

Trends in bulk compressibility of Mo2-xWxBC solid solutions

The Mo2-xWxBC system is of interest as a material with high hardness while maintaining moderate ductility. In this work, synchrotron diffraction experiments are performed on Mo2-xWxBC solid solutions, where x = 0, 0.5, and 0.75, upon hydrostatic compression to ~54 GPa, ~55 GPa, and ~60 GPa, respectively. Trends in bulk modulus, K0, are evaluated by fitting collected pressure-volume data with a third-order Birch-Murnaghan equation of state, finding K0 = 333(9) GPa for Mo2BC, K0 = 335(11) GPa for Mo1:5W0:5BC, and K0 = 343(8) GPa for Mo1:25W0:75BC. While K0 demonstrates a slight increase when Mo is substituted by W, calculated zero pressure unit cell volume, V0, exhibits the opposite trend. The decrease in V0 corresponds to an increase in valence electron density, hardness, and K0. Observations corroborate previously reported computational results and will inform future efforts to design sustainable materials with exceptional mechanical properties

Machine Learning Directed Search for Ultraincompressible, Superhard Materials

In the pursuit of materials with exceptional mechanical properties, a machine-learning model is developed to direct the synthetic efforts toward compounds with high hardness by predicting the elastic moduli as a proxy. This approach screens 118 287 compounds compiled in crystal structure databases for the materials with the highest bulk and shear moduli determined by support vector machine regression. Following these models, a ternary rhenium tungsten carbide and a quaternary molybdenum tungsten borocarbide are selected and synthesized at ambient pressure. High-pressure diamond anvil cell measurements corroborate the machine-learning prediction of the bulk modulus with less than 10% error, as well as confirm the ultraincompressible nature of both compounds. Subsequent Vickers microhardness measurements reveal that each compound also has an extremely high hardness exceeding the superhard threshold of 40 GPa at low loads (0.49 N). These results show the effectiveness of materials development through state-of-the-art machine-learning techniques by identifying functional inorganic materials

CLEC-2 expression is maintained on activated platelets and on platelet microparticles

The C-type lectin-like receptor CLEC-2 mediates platelet activation through a hem-immunoreceptor tyrosine-based activation motif (hemITAM). CLEC-2 initiates a Src- and Syk-dependent signaling cascade that is closely related to that of the 2 platelet ITAM receptors: glycoprotein (GP)VI and FcγRIIa. Activation of either of the ITAM receptors induces shedding of GPVI and proteolysis of the ITAM domain in FcγRIIa. In the present study, we generated monoclonal antibodies against human CLEC-2 and used these to measure CLEC-2 expression on resting and stimulated platelets and on other hematopoietic cells. We show that CLEC-2 is restricted to platelets with an average copy number of ∼2000 per cell and that activation of CLEC-2 induces proteolytic cleavage of GPVI and FcγRIIa but not of itself. We further show that CLEC-2 and GPVI are expressed on CD41+ microparticles in megakaryocyte cultures and in platelet-rich plasma, which are predominantly derived from megakaryocytes in healthy donors, whereas microparticles derived from activated platelets only express CLEC-2. Patients with rheumatoid arthritis, an inflammatory disease associated with increased microparticle production, had raised plasma levels of microparticles that expressed CLEC-2 but not GPVI. Thus, CLEC-2, unlike platelet ITAM receptors, is not regulated by proteolysis and can be used to monitor platelet-derived microparticles