4051 research outputs found
Sort by
Isotopes in the hydrological cycle
No full textNot available. Physical copy available in ANSTO Library at 621.48/1
PET imaging of neuroinflammation: preclinical imaging of disease progression in epilepsy and other neurological disorders
No full textNot available. Physical copy available in ANSTO Library at 621.48/1
12,000-Year-old Aboriginal rock art from the Kimberley region, Western Australia
No full textThe Kimberley region in Western Australia hosts one of the world’s most substantial bodies of indigenous rock art thought to extend in a series of stylistic or iconographic phases from the present day back into the Pleistocene. As with other rock art worldwide, the older styles have proven notoriously difficult to date quantitatively, requiring new scientific approaches. Here, we present the radiocarbon ages of 24 mud wasp nests that were either over or under pigment from 21 anthropomorphic motifs of the Gwion style (previously referred to as “Bradshaws”) from the middle of the relative stylistic sequence. We demonstrate that while one date suggests a minimum age of c. 17 ka for one motif, most of the dates support a hypothesis that these Gwion paintings were produced in a relatively narrow period around 12,000 years ago. © 2020 American Association for the Advancement of Science.This research was funded by Australian Research Council Linkage Projects LP130100501 and LP170100155 with funding partner the Kimberley Foundation Australia, with in-kind support from Dunkeld Pastoral Co. Pty Ltd. and Balanggarra Aboriginal Corporation especially for fieldwork. D.F. is supported by an Australian Postgraduate Award and an AINSE Post Graduate Research Award. The Kimberley Foundation Australia also provided a grant to D.F. to establish the radiocarbon pretreatment facility at the University of Melbourne
Mercury vapor sensor enhancement by nanostructured gold deposited on nickel surfaces using galvanic replacement reactions
No full textAnthropogenic mercury emission is a serious global environmental problem because of its toxicity to humans, plants and wildlife. In order to control these emissions, accurate and reliable online continuous mercury monitoring systems (CMMs) are critical. Such systems can notify appropriate authorities or provide feedback signals to a process control system in time, thus making them an integral part of monitoring and controlling Hg emissions. We demonstrate how nanostructured gold can easily be deposited in small quantities on nickel electrode based QCMs using galvanic replacement (GR) reactions with the resultant surface having excellent Hg monitoring properties. The developed GR surfaces were observed to have higher sensitivity and selectivity in the presence of interfering gas species (NH3 and H2O), as well as to have ∼80% higher mercury sorption capacity than the most efficient mercury sorbents reported to date. Investigations towards the Hg-sensing capabilities of the resultant Ni–Au surface based Hg sensors showed ∼50% better sensitivity and detection limit over control Au films. Furthermore, the GR based QCMs were found to self-regenerate without changing the operating temperature of the sensor, undergoing Hg desorption with sensor recoveries of 93.7–99.3% following Hg exposure at an operating temperature of 90 °C. Surface depth profile analysis of the Ni–Au electrode surfaces showed that the high recovery rate of the sensors was primarily due to the Ni–Au structures, which unlike continuous Au thin-films more commonly used for Hg sensing applications, do not accumulate Hg at the sensitive-layer–substrate interface. Furthermore, the GR Ni–Au surfaces were found to be highly selective towards Hg vapor in the presence of NH3 and H2O interfering gas species which makes them potentially suitable for operating in harsh industrial effluent environments.© The Royal Society of Chemistry 201
Upper Hunter Valley particle characterization study: 1st progress report – site commissioning and methodology
Get PDFThe objective of the Upper Hunter Valley Particle Characterization Study is to determine the major components and sources of particulate matter (as PM2.5 – particles with a diameter of less than 2.5
micrometres) in the two main population centres in the Upper Hunter Valley, namely Singleton and Muswellbrook.
This 1st Progress Report outlines the design of the project, the methodology, and the commissioning phase.© 2012 CSIR
Radiocarbon dating of a young speleothem record of paleoclimate for Angkor, Cambodia
No full textWe report the chronological construction for the top portion of a speleothem, PC1, from southern Cambodia with the aim of reconstructing a continuous high-resolution climate record covering the fluorescence and decline of the medieval Khmer kingdom and its capital at Angkor (~9th–15th centuries AD). Earlier attempts to date PC1 by the standard U-Th method proved unsuccessful. We have therefore dated this speleothem using radiocarbon. Fifty carbonate samples along the growth axis of PC1 were collected for accelerator mass spectrometry (AMS) analysis. Chronological reconstruction for PC1 was achieved using two different approaches described by Hua et al. (2012a) and Lechleitner et al. (2016a). Excellent concordance between the two age-depth models indicates that the top ~47 mm of PC1 grew during the last millennium with a growth hiatus during ~1250–1650 AD, resulting from a large change in measured 14C values at 34.4–35.2 mm depth. The timing of the growth hiatus covers the period of decades-long droughts during the 14th–16th centuries AD indicated in regional climate records.© 2017 by the Arizona Board of Regents on behalf of the University of ArizonaVolume 59, Special Issue 6 (8th International Symposium, Edinburgh, 27 June – 1 July, 2016 Part 2 of 2). Includes corrected reference: Hua, Q., Cook, D., Fohlmeister, J., Penny, D., Bishop, P., & Buckman, S. (2018). Radiocarbon Dating of a Speleothem Record of Paleoclimate for Angkor, Cambodia – Corrigendum. Radiocarbon, 60(2), v-v. doi:10.1017/RDC.2018.13
Oldest directly dated remains of sheep in China
Get PDFThe origins of domesticated sheep (Ovis sp.) in China remain unknown. Previous workers have speculated that sheep may have been present in China up to 7000 years ago, however many claims are based on associations with archaeological material rather than independent dates on sheep material. Here we present 7 radiocarbon dates on sheep bone from Inner Mongolia, Ningxia and Shaanxi provinces. DNA analysis on one of the bones confirms it is Ovis sp. The oldest ages are about 4700 to 4400 BCE and are thus the oldest objectively dated Ovis material in eastern Asia. The graphitisised bone collagen had δ13C values indicating some millet was represented in the diet. This probably indicates sheep were in a domestic setting where millet was grown. The younger samples had δ13C values indicating that even more millet was in the diet, and this was likely related to changes in foddering practices. © 2014, Macmillan Publishers Limite
Indo-Pacific hydroclimate over the past millennium and links with global climate variability
No full textThe El Niño-Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) are the dominant modes of hydroclimate variability in the tropical Pacific and have far-reaching impacts on Earth’s climate. Experiments combining instrumental records with climate-model simulations have highlighted the dominant role of the Pacific Walker circulation in shaping recent trends in global temperatures (Kosaka and Xie, 2013, 2016). However, the paucity of high-resolution terrestrial paleoclimate records of deep atmospheric convection over the Indo-Pacific Warm Pool (IPWP) precludes a comprehensive assessment as to role of the tropical Pacific in modulating radiative-forced shifts in global temperature on multidecadal to centennial timescales. Here we present a suite of new high-resolution oxygen-isotope records from Indo-Pacific speleothems, which, based on modern rainfall and cave drip-water monitoring studies, along with trace element (Mg/Ca, Sr/Ca) analyses, are interpreted to reflect changes in Australasian monsoon variability during the Common Era (C.E.).
Our results reveal a protracted decline in southern Indonesian monsoon rainfall between ~1000-1400 C.E. but stronger between ~1500-1900 C.E. These centennial-scale patterns over southern Indonesia are consistent with other proxy records from the region but anti-phased with records from India and China, supporting the paradigm that Northern Hemisphere cooling increased the interhemispheric thermal gradient, displacing the Australasian ITCZ southward. However, our findings are also compatible with a recent synthesis of paleohydrologic records for the Australasian monsoon region, which, collectively, suggest that rather than moving southward during the LIA, the latitudinal range of monsoon-ITCZ migration probably contracted equatorward (Yan et al., 2015). This proposed LIA ITCZ contraction likely occurred in parallel with a strengthening of the Walker circulation (as indicated through comparison with our hydroclimate records from the central-eastern equatorial Pacific Ocean and western Indian Ocean, and eastern Australia), and thus, the tropical Pacific may have played a critical role in amplifying the radiative-forced global cooling already underway. © 2016. American Geophysical Unio
A carved ivory cylinder from Akchakhan-kala, Uzbekistan: problems of dating and provenance
No full textExcavations at Akchakhan-kala in Uzbekistan, a region known in antiquity as Chorasmia, recovered a large, elaborately carved and heavily burned cylinder of some very solid material. Its poor condition made identification of the raw material difficult. Here we used neutron tomography to examine the internal structure in a non-destructive way, and X-ray Diffraction to determine the main chemical composition of the material which confirmed it as ivory. This was followed by preparation for stable isotope and radiocarbon analysis. The stable isotope analysis suggests a tropical or subtropical grassland source for the ivory, which is unlikely to be from Uzbekistan. The dating shows the ivory to be much earlier than the context in which it was found. Whatever its origin, the ivory travelled far to reach Chorasmia, perhaps in its raw state, and perhaps also for some time in its carved form. © 2015 Elsevier Ltd
Tuning the grade of graphene: gamma ray irradiation of free-standing graphene oxide films in gaseous phase
No full textA direct approach to functionalize and reduce pre-shaped graphene oxide 3D architectures is demonstrated by gamma ray irradiation in gaseous phase under analytical grade air, N2 or H2. The formation of radicals upon gamma ray irradiation is shown to lead to surface functionalization of the graphene oxide sheets. The reduction degree of graphene oxide, which can be controlled through varying the γ-ray total dose irradiation, leads to the synthesis of highly crystalline and near defect-free graphene based materials. The crystalline structure of the graphene oxide and γ-ray reduced graphene oxide was investigated by x-ray diffraction and Raman spectroscopy. The results reveal no noticeable changes in the size of sp2 graphitic structures for the range of tested gases and total exposure doses suggesting that the irradiation in gaseous phase does not damage the graphene crystalline domains. As confirmed by X-ray photoemission spectroscopy, the C/O ratio of γ-ray reduced graphene oxide is increasing from 2.37 for graphene oxide to 6.25 upon irradiation in hydrogen gas. The removal of oxygen atoms with this reduction process in hydrogen results in a sharp 400 times increase of the electrical conductivity of γ-ray reduced graphene oxide from 0.05 S cm−1 to as high as 23 S cm−1. A significant increase of the contact angle of the γ-ray reduced graphene oxide bucky-papers and weakened oxygen rich groups characteristic peaks across the Fourier transform infrared spectra further illustrate the efficacy of the γ-ray reduction process. A mechanism correlating the interaction between hydrogen radicals formed upon γ-ray irradiation of hydrogen gas and the oxygen rich groups on the surface of the graphene oxide bucky-papers is proposed, in order to contribute to the synthesis of reduced graphene materials through solution-free chemistry routes. © 2014 Elsevier B.V