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New knowledge of Holocene hydroclimate and freshwater availability at Murujuga
(Australian Archaeological Association, 2024-12-03) Mather, C; Tucker, M; Leopold, M; Levchenko, VA; Skrzypek, G; O'Leary, M; McDonald, J
Extensive rock art engravings and archaeological evidence of human occupation are documented around waterholes at Murujuga, highlighting their cultural significance and importance as sources of freshwater. Frequently, these waterholes have thick deposits of tufa (carbonate): evidence of the past environment and climatic conditions under which the carbonate precipitated. Here we discuss how we have refined our knowledge of the hydrology and water permanence of the waterholes at Murujuga using tufa as geo-archives of environmental and hydroclimatic change over time. Rainfall, surface water levels and geochemistry demonstrate that some waterholes are long-lasting (semi-permanent) and fed by perched seepage after large recharge events: other ephemeral waterholes evaporate quickly after rainfall events. Semi-permanent waterholes on Murujuga’s islands would be important for supporting humans as well as plant and animal life. The formation of tufa is dependent on moderate to large rainfall events that recharge the landscape and can generate significant surface water flows and allow for precipitation of calcium carbonate. Radiocarbon ages of Murujuga tufas range from 0.5 to 9.7 cal ka BP and constrain tufa formation to the Holocene. The initiation of tufa formation in the early- to mid-Holocene coincides with changing hydroclimatic conditions, following sea level rise and formation of the archipelago since the Last Glacial Maximum. Further insights from stable isotope and geochemical data from tufa will enhance our knowledge of hydroclimatic variability throughout the Holocene. This tufa palaeoenvironmental proxy record allows us to understand at what times during the Holocene water resources were abundant or sparse, meaning we can better contextualise the archaeological record at Murujuga. © The Authors
From phase separation to food science
(Institut Laue Langevin, 2024-07-19) Gilbert, EP
Experimental scattering methods, primarily X-ray and neutron, can reveal insight into the structure and dynamics of condensed matter systems, an area in which Professor John White made an enormous contribution over more than five decades. Through his mentoring, guidance and friendship, he helped launch the careers of countless international scientists over multiple (both academic and actual) generations. In the context of (mostly) small-angle scattering, I will offer here my personal reflections on John’s contributions to my own career trajectory which began as his PhD student more than (and quite astonishingly) 30 years ago.
Impact of the freshwater reservoir effect on the radiocarbon dating of shells from the lower and Central Murray River
(Australian Archaeological Association, 2024-12-03) Stringer, C; Prendergast, A; Garvey, J; May, JH; Lvchenko, VA
Since the 1950s, archaeological research conducted along the lower and central Murray River, on Ngintait, Latji Latji, Barkandji, Yorta Yorta, and Ngaiawang Countries, has relied on radiocarbon dating of freshwater mollusc shell to help confirm the chronology of human occupation in this region as well as support larger models of human occupation timing in Australia. The popularity of freshwater mollusc shell for radiocarbon dating in this region is partially due to the prevalence of shell in a variety of Aboriginal cultural sites. However, radiocarbon dating of freshwater organisms, such as molluscs, is complex as the carbon reservoir of the water bodies in which they live may differ from atmospheric values. Therefore, radiocarbon dates which do not consider this freshwater reservoir effect may be inaccurate. While Gillespie and colleagues (2009) investigated the freshwater reservoir effect in the Murray-Darling Basin around Willandra Lakes World Heritage Area, the effect present in the Murray River has yet to be explored. Therefore, this research analysed historically live-collected freshwater mussel samples collected from Ngintait, Latji Latji, Barkandji, Yorta Yorta, and Ngaiawang Countries, near Mildura (VIC), Echuca (VIC), and Morgan (SA), to establish a freshwater reservoir effect for the lower and central Murray River. We also dated modern water and freshwater shell samples from across this region to better understand the source of this offset. The calculated average offset of approximately 136-56 years will have an impact on chronologically recent sites and improve overall precision. These results will help us improve chronologies in the region and better understand the important relationship between people, molluscs, and Country. © The Authors
Untitled
(BHRA Fluid Engineering, 1983-04-19) Dalton, AW
A computer program, NAIADQ, has been developed to simulate the dynamic response of water, in a one—dimensional flow path, to rapid changes in the axial distribution of the power input to the channel. The dynamic behaviour of the coolant is described, in the single—phase state, in terms of three equations representing the conservation of its mass, momentum and energy. For the two—phase state a fourth equation, representing the conservation of the vapour mass is introduced in which the vapour is generated at a nonequilibrium rate; to compensate for this, the liquid phase is allowed to superheat. It is further assumed that the vapour is always in a saturated state, that the two phases have the same axial velocity and that the pressure at each axial location is the same for both phases. To describe the redistribution of the heat, injected into the flow path, between the heat source and the coolant fluid, a simple pipe model and a range of heat transfer options are available in the code together with equations of state for both the liquid and two—phase state. The code has been used to simulate published data on two different types of experiments, one relating to the expulsion of water from a rapidly heated channel and the other to reactivity induced power transients in an experimental water—cooled nuclear reactor.
Characterization of thermally stable diamond composite material
(2013-09) Boland, JN; Luzin, V; Lin, XS
Diamond composite materials are being used increasingly in cutting tools for both the mining and manufacturing industries. Except for the low pressure CVD and SPS methods, most SiC based diamond composites are produced under high pressure and high temperature (HPHT). The dominant binder phase is SiC and these composites are classed as thermally stable and are referred to as TSDC (thermally stable diamond composite). TSDC composites are produced by reactive sintering either within the diamond stability field, ~1500°C and ~5.5 GPa, or in the graphite phase field at ~1550°C and ~2 - 3.5 GPa as originally patented by Ringwood. Unlike the traditional polycrystalline diamond composite (PCD) that use Co as the binder phase and operate under restricted temperature conditions, usually less the 800°C, TSDC is Co-free allowing the operational temperature range for TSDC to be extended substantially. Extensive experimental research has been conducted at the CSIRO (Commonwealth Scientific & Industrial Research Organization) Rock Cutting Laboratory to assess the quality of TSDC products through a series of in-house tests that have been developed (abrasive wear test, compressive and shear testing) to facilitate their use in the mining industry. The focus is to prevent TSDC from premature failures in drilling and cutting operations. Since the wear resistance and performance in general, of TSDC cutting elements are strongly dependent on the phase composition, phase distribution (microstructures) and phase interaction (microstresses), detailed studies of TSDC have been undertaken using optical, SEM (with EDS and CL), Raman microscopy and radiographic imaging of macro defects as well as x-ray and neutron diffraction. Residual stress measurements were made using the neutron diffractometer Kowari at OPAL research reactor in the diamond and SiC phases in two TSDC samples. The microstresses that developed in these phases as a result of quenching from high sintering pressure and temperature and the mismatch of the thermo-mechanical properties of SiC matrix and diamond inclusions were evaluated. The matrix-inclusion concept has also been used to calculate stress partition in the phases of the TSDC products that can be directly comparable with the experimental data and give clearer interpretation of the experimental results

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