Browsing by Author "Bennett, JW"
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- ItemApplication of acoustical methods to the measurement of water content in sand(Australian Nuclear Science and Technology Organisation, 2000-10) Nazarov, VE; Radostin, AV; Stepanyants, YA; Bennett, JWResults of laboratory experiments on the propagation of high-frequency acoustic waves (f = 100 kHz) in a glass tube filled with river sand are presented. Several sand samples have been used with different water content: dry unsaturated and completely water saturated. It is shown that the dissipative coefficient of acoustic waves decreases with increasing wave amplitude. This 'self-brightening' phenomenon takes place over the whole range of moisture content from zero to 100% but its degree of manifestation depends on the moisture content. The exponent of the dissipative nonlinearity α is found to be the most sensitive parameter to the moisture content and is determined on the basis of measurements. It is considered to be a good indicator of water content in porous media and provides an opportunity to measure water content in such materials indirectly by means of an acoustic method. A simple phenomenological model is presented to explain the experimental results.
- ItemCommissioning of NAA at the new OPAL reactor in Australia(Springer, 2008-12) Bennett, JWIn April 2007 the new nuclear research reactor, OPAL, was opened at Lucas Heights in Sydney. OPAL is a 20 MW open pool light water reactor with a heavy water reflector vessel and contains a cold neutron source. It is a multi-purpose facility for radioisotope production, irradiation services and neutron beam research. The OPAL design includes purpose-built facilities for instrumental neutron activation analysis (INAA) and delayed neutron activation analysis (DNAA). For INAA there is a short residence time facility in a neutron flux of around 2 center dot 10(13) cm(-2)center dot s(-1) and a number of long residence time facilities providing fluxes from 3 center dot 10(12) to 1 center dot 10(14) cm(-2) center dot s(-1). The flux at the short residence time DNAA facility is around 6 center dot 10(12) cm(-2) center dot s(-1). The main focus for INAA at OPAL is the research community, meeting the needs of a wide range of disciplines, including mineral processing, geology, the environment, health and archaeology. Both the relative (comparator) method and the k(0)-method of standardization for INAA are being established in OPAL. A description of progress, plans and capabilities are presented. © 2008, Springer.
- ItemDose enhancement effects to the nucleus and mitochondria from gold nanoparticles in the cytosol(IOP Publishing, 2016-07-20) McNamara, AL; Kam, WWY; Scales, N; McMahon, SJ; Bennett, JW; Byrne, HL; Schuemann, J; Paganetti, H; Banati, RB; Kuncic, ZGold nanoparticles (GNPs) have shown potential as dose enhancers for radiation therapy. Since damage to the genome affects the viability of a cell, it is generally assumed that GNPs have to localise within the cell nucleus. In practice, however, GNPs tend to localise in the cytoplasm yet still appear to have a dose enhancing effect on the cell. Whether this effect can be attributed to stress-induced biological mechanisms or to physical damage to extra-nuclear cellular targets is still unclear. There is however growing evidence to suggest that the cellular response to radiation can also be influenced by indirect processes induced when the nucleus is not directly targeted by radiation. The mitochondrion in particular may be an effective extra-nuclear radiation target given its many important functional roles in the cell. To more accurately predict the physical effect of radiation within different cell organelles, we measured the full chemical composition of a whole human lymphocytic JURKAT cell as well as two separate organelles; the cell nucleus and the mitochondrion. The experimental measurements found that all three biological materials had similar ionisation energies ~70 eV, substantially lower than that of liquid water ~78 eV. Monte Carlo simulations for 10–50 keV incident photons showed higher energy deposition and ionisation numbers in the cell and organelle materials compared to liquid water. Adding a 1% mass fraction of gold to each material increased the energy deposition by a factor of ~1.8 when averaged over all incident photon energies. Simulations of a realistic compartmentalised cell show that the presence of gold in the cytosol increases the energy deposition in the mitochondrial volume more than within the nuclear volume. We find this is due to sub-micron delocalisation of energy by photoelectrons, making the mitochondria a potentially viable indirect radiation target for GNPs that localise to the cytosol. © 2016 Institute of Physics and Engineering in Medicine
- ItemModel for the description of oxidation in sulfidic waste rock dumps.(Australian Nuclear Science and Technology Organisation, 2000-03) Pantelis, G; Ritchie, AIM; Stepanyants, YA; Bennett, JWBasic mathematical equations which describe the processes of sulfide oxidation and gas and water transport in waste rock dumps are presented and discussed. The governing equations account for gas and water flow vaporisation and condensation with latent heat effects heat transport and mass balance. Gas water and solid phases are assumed to be in local thermal equilibrium at all times. Air is approximated as an ideal three-component gas. Different semi-empirical relationships between physical values are used: Darcy's law for fluid flow ideal gas law the Van Genuchten formula for the relationship between degree of water saturation and pressure head Mualem's formula for the relative hydraulic conductivity as a function of pressure head etc. Some important global quantities such as the fraction of sulfide sulfur oxidised and the global oxidation rate are defined and considered as functions of time. The full set of equations is collected and presented in explicit form convenient for further numerical modelling. The glossary of some technical terms and the table of definitions of the main parameters as well as their units and characteristic values are displayed.
- ItemMulti-proxy evidence for trans-Pacific tsunamis in the Hawai'ian Islands(Elsevier, 2012-03-01) Chagué-Goff, C; Goff, JR; Nichol, SL; Dudley, W; Zawadzki, A; Bennett, JW; Mooney, SD; Fierro, D; Heijnis, H; Dominey-Howes, D; Courtney, CThe origin of two sand layers buried in Pololū wetland, on the northeast coast of the island of Hawai'i, was investigated using a multi-proxy approach, including radiometric dating, sedimentology, geochemistry, micropalaeontology, palynology and historical records. Based on 210Pb, 137Cs and pollen data, the lower sand unit extending 250 to 350 m inland is attributed to the 1946 Aleutian tsunami, while the upper sand unit was laid down by the 1957 Aleutian tsunami. Chronological information does not appear to support any link between these deposits and historical storm events. Furthermore, sedimentological, geochemical, diatom and pollen results suggest deposition of marine and near-beach sediments under high energy conditions typically associated with tsunami inundation. This work presents the first conclusive sedimentary evidence for distantly-generated tsunamis on the Hawai'ian Islands, opening the way for more comprehensive historical and palaeotsunami studies. Indeed, a brief review of archaeological data suggests that the Hawai'ian coast may have experienced similar large magnitude events in the past, from both local and distant sources. © 2012 Elsevier
- ItemNuclear science and the story of a preserved leaf from a copy of the great bible(Elsevier, 2013-04-01) Dodson, JR; Grierson, P; Bennett, JW; de Howard, SM; Wong, HKYThree pressed leaves of Ulmus glabra (Wych Elm) were found within the pages of a copy of the Great Bible in the Library of the University of Western Australia. The Bible dates from AD 1540 and was originally housed at Ely Cathedral in Cambridgeshire. A radiocarbon age on one of the leaves found it was about as old as the Great Bible itself, and stable C and N isotope and neutron activation analyses were carried out on the same leaf. The δ15N values were elevated and the content of iron, arsenic, bromine, silver, gold and mercury were relatively high. These analyses are consistent with an environment where water logging is present, as at Ely at the time, and the silver and gold content are probably consistent with the cathedral setting. The mercury was found to be associated with the red ink in the Bible. It is intriguing to ponder why Wych elm leaves were placed in the Bible, especially in the light that a copy of an original edition of the King James version of the Bible from Ely, also in the library in Perth has many dozens of U. glabra leaves also preserved within in its pages.© 2012, Elsevier Ltd.
- ItemOchre through the late Quaternary at Gledswood Shelter 1, northwest Queensland(Australasian Quaternary Association Inc, 2014-06-29) Wallis, LA; Lowe, KM; Popelka-Filcoff, RS; Bennett, JW; St George, C; Watson, C; Fitzsimmons, KE; Wight, C; Watchman, A; Lenehan, CE; Matthews, JGledswood Shelter 1 (GS1) is a sandstone rockshelter located in northwest Queensland containing archaeological evidence for human occupation dating from at least 35 ka to the recent past. Considerable quantities of ochre fragments (many with striations caused by grinding) have been recovered from the 2.5 m deep cultural sequence, particularly in the pre-LGM levels. The abundance of ochre varies through time, in line with recovered stone artefacts, suggesting that these materials reflect different periods and intensities of site use. This evidence possibly indicates that the production of painted or stencilled art in this region may be earlier than previous evidence suggests (ca 9,000 years ago). The GS1 ochre samples were initially characterised according to visual characteristics including colour, texture and inclusions using low powered microscopy. This work suggests there are several groups of pigment present, including fragments that would more normally be referred to as ironstone and not considered as an 'ochre', but that have anthropogenic ground surfaces indicating their use as a source of pigment. In this paper we present the initial characterisation and preliminary neutron activation analysis results of the GS1 ochres, and consider their implications for the human history of the northwest Queensland region.
- ItemTrace metal content in inhalable particulate matter (PM10 and PM2.5 collected from historical mine waste deposits using a laboratory-based approach(Springer, 2016-05-05) Martin, R; Dowling, K; Pearce, DC; Florentine, S; McKnight, S; Stelcer, E; Cohen, DD; Stopic, A; Bennett, JWMine wastes and tailings are considered hazardous to human health because of their potential to generate large quantities of highly toxic emissions of particulate matter (PM). Human exposure to As and other trace metals in PM may occur via inhalation of airborne particulates or through ingestion of contaminated dust. This study describes a laboratory-based method for extracting PM2.5–10 (coarse) and PM2.5 (fine) particles from As-rich mine waste samples collected from an historical gold mining region in regional, Victoria, Australia. We also report on the trace metal and metalloid content of the coarse and fine fraction, with an emphasis on As as an element of potential concern. Laser diffraction analysis showed that the proportions of coarse and fine particles in the bulk samples ranged between 3.4–26.6 and 0.6–7.6 %, respectively. Arsenic concentrations were greater in the fine fraction (1680–26,100 mg kg−1) compared with the coarse fraction (1210–22,000 mg kg−1), and Co, Fe, Mn, Ni, Sb and Zn were found to be present in the fine fraction at levels around twice those occurring in the coarse. These results are of particular concern given that fine particles can accumulate in the human respiratory system. Our study demonstrates that mine wastes may be an important source of metal-enriched PM for mining communities.© 2016, Springer Science+Business Media Dordrecht.