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Initial results and observations on a radiocarbon dating program in the Riverland region of South Australia
No full textThis paper presents a preliminary occupation chronology for the Riverland region of South Australia, based on 31 radiocarbon age determinations. This region has represented a significant geographic gap in understanding occupation chronologies for the broader Murray-Darling Basin. The dating forms part of an ongoing research program exploring the long-term engagements of Aboriginal people with the habitat mosaics of the central River Murray corridor. Dating targets were selected on the basis of their landscape context. Results relate occupation evidence to an evolving riverine landscape through the period extending from approximately 29 ka to the late Holocene. These results include the first pre-Last Glacial Maximum ages returned on the River Murray in South Australia and extend the known Aboriginal occupation of the Riverland by approximately 22,000 years. © 2020 Informa UK Limite
Upper Hunter Valley Particle Characterization Study 2nd Progress Report
Full text linkThe 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 2nd Progress Report presents an update on the project, some preliminary results, and a description of the CSIRO analysis technique.© 2012 CSIR
Hot isostatically pressed (HIPed) fluorite glass‐ceramic wasteforms for fluoride molten salt wastes
No full textMolten pyroprocessing salts can be used to dissolve used nuclear fuel from a reactor allowing recovery of the actinides. Previously, ANSTO have demonstrated hot isostatically pressed (HIPed) sodalite glass‐ceramic wasteforms for eutectic (Li,K)Cl salts containing fission products, but this system cannot be used for the analogous molten alkali fluoride salts (eg, FLiNaK), which have utility in the application of the next generation of nuclear reactors. In this work, a novel glass‐ceramic composite wasteform has been prepared by HIPing, as a candidate for the immobilization of fission product‐bearing FLiNaK salts. The wasteform has been tailored to immobilize the high fluoride content of the waste within fluorite, whereas the waste alkali elements are incorporated in a durable sodium aluminoborosilicate glass, with total waste loadings of ~17‐21 wt% achieved. It was also demonstrated that the speciation of Mo‐ and Sb‐simulated fission products was altered by adding Ti metal due to a controlled redox environment. The resulting candidate wasteform has been studied by X‐ray diffraction and scanning electron microscopy, including the HIP canister‐wasteform interaction zone, and its performance assessed via leaching studies using the PCT and ASTM C1220 leaching protocols. Dr Vance very much enjoyed the challenge of wasteform design for problematic nuclear wastes, for which fission product‐bearing FLiNaK salts are a clear example. His ability to hone in on a wasteform solution with viable waste loadings that meet performance requirements was testament to his nearly 40 years experience in nuclear waste immobilization. The samples discussed in this work represent the last wasteform materials that he prepared. © 1999-2020 John Wiley & Sons, Inc
Evaluation of isotopic boron (11B) for the fabrication of low activation Mg11B2 superconductor for next generation fusion magnets
No full textIn this study, we analyze the properties of boron isotope (11B)‐rich powders from three different sources, that is, American, Cambridge, and Pavezyum, to fabricate the bulk Mg11B2 superconductors and evaluate their superconducting properties. While 11B‐rich powder is an essential precursor to fabricate Mg11B2 superconductors for fusion magnet applications, the properties of the 11B powder turned out to be critical to determine the quality of the final superconducting product. Therefore, appropriate control of processing conditions is needed to comply with the requirements of the nuclear fusion application. Analysis of the B isotope ratio by accelerator mass spectroscopy and neutron transmission revealed that all three types of powder are enriched with 11B to better than 99 at % quality. In addition, Pavezyum's 11B shows the lowest crystallinity and smallest crystalline domain size as evidenced by the high‐resolution X‐ray diffractometer and scanning electron microscopy. The chemical states of the boron isotope investigated with near edge X‐ray absorption fine structure spectroscopy and X‐ray photoemission spectroscopy also reveals that Pavezyum boron has amorphous structure. Mg11B2 bulks and multi‐filamentary (12‐filament) wires have been manufactured, sintered at different temperatures and characterized via the transport critical current density. The wire with Pavezyum 11B shows three times higher current carrying capacity at a particular magnetic field compared to the wire using Cambridge 11B and hence, Pavezyum 11B boron has the potential for manufacturing fusion grade Mg11B2 based magnets. The results of this study demonstrated that Boron powders with higher purity, smaller grain size and lower crystallinity are critical for improving the superconducting and electronic properties of Mg11B2 samples fabricated from the powder. Thus, the low‐neutron‐activation Mg11B2 is possibly an affordable and technically viable candidate to replace NbTi superconductors in the low field poloidal field and correction coils for the next‐generation fusion reactors. © 1999-2020 John Wiley & Sons, Inc
Using inherited OSL signals to quantify landscape dynamics: examples from the Jalisco Block to the faults of Sierra de Juarez (Mexico)
No full textCosmogenic radionuclides (CRN) and optically stimulated luminescence (OSL) are two recent geochronological techniques that have expanded the capabilities of quantifying geomorphic processes and the age of landforms. Traditionally, OSL has been used to date the age of deposits (< 0.5 Ma) and in some cases such ages complement the results obtained from CRNs. Here we extend the usage of OSL signals in order to: (1) determine the presence of erosional pulses in low energy depositional settings and (2) explore if OSL signals can provide additional information about the erosion rates in the landscape as 10Be-based catchment-averaged denudation rates do.
For the first approach we extracted and analyzed two cores from Sayula and San Marcos lakes located in the triple junction of the Jalisco Block (west-central Mexico). Even though OSL signals exhibit the expected pattern of increasing luminescence age with depth, our analysis of cores using a Pulsed Photon Stimulated Luminescence unit indicate that there has been different rates of deposition and changes in the precedence of sediment. These results are also supported with geochemical analysis of major elements. For the second approach we analyzed the faults of Oaxaca and Donají which form the front of Sierra de Juarez (southern Mexico). From the active channels incising across thefaults we extracted sediment samples to determine the 10Be catchment-averaged erosion rates and to measure the OSL signals. At Donají fault, OSL signals closely scale with 10Be catchment-averaged denudation rates (R2 = 0.78 for IRSL and R2 = 0.71 for BLSL) and the last correlates with the mean basin rainfall (R2 = 0.86). At Oaxaca fault, OSL signals are negatively correlated with 10Be catchment-averaged denudation rates. Based on our OSL and 10Be data, as well as on topographic analyses we propose that the landscape along the Oaxaca fault is in disequilibrium due to the fault offset, whereas in Donají, which is known to be a transfer fault, the landscape seems to have reach a state close to equilibrium. Here we demonstrate that OSL signals, supported with 10Be-derived denudation rates, can yield information on the rates that prevail in the landscape. © 2016 The Geological Society of America(GSA
Gloria Knolls Slide: a prominent submarine landslide complex on the Great Barrier Reef margin of north-eastern Australia
No full textWe investigate the Gloria Knolls Slide (GKS) complex on the Great Barrier Reef margin of north-eastern Australia, the largest extant mixed carbonate-siliciclastic province in the world. Based on the most complete bathymetric and sub-bottom profile datasets available for the region, we describe the main surface and subsurface geomorphologic characteristics of this landslide complex. The GKS forms a 20 km along-slope and 8 km across-slope indentation in the margin, extending from 250 to 1350 m depth, and involves a volume of 32 km3 of sediment remobilized during three events. Three main seafloor terrains can be distinguished based on seafloor morphology: a source area, a proximal depositional area and a distal depositional area. The source area includes a main headwall scarp with a maximum height of 830 m and a secondary scarp at 670 m depth. The proximal depositional area is flat and smooth, and lacks debris exposed on the seafloor. The distal depositional area has a hummocky surface showing a distinctive cluster of eight knolls and over 70 small debris blocks. A dredge sample from the top of the largest knoll at a depth of 1170 m reveals the presence of a cold-water coral community. In the sub-bottom profiles, the mass-transport deposits in the GKS are identified below the background sediment drape as partially confined, wedge-shaped bodies of mostly weak amplitude, transparent reflectors in the proximal depositional area; and more discontinuous and chaotic in the distal depositional area. The failed sediment slabs of the GKS were evacuated, transported and disintegrated downslope in three events following a sequential failure process spreading successively from the lower slope to the upper slope. The first event initiated at the lower slope at the depth of the secondary scarp, moved downslope and disintegrated over the basin floor leaving coherent blocks. The subsequent second and third events were responsible for the formation upslope of the main scarp in the GKS. The timing of emplacement of the first GKS event, constrained by radiometric age of fossil biota from the surface of the largest slide block, was at least before 302 ± 19 ka. The presence of alternating mixed carbonate and siliciclastic lithologies that build the slope might have played an important role as a preconditioning factor in this region. Preliminary estimations suggest that unusually large seismic events were the most likely triggering mechanism for the GKS. This work contributes to the understanding of large mass-movement deposits in mixed carbonate-siliciclastic margins and provides a useful morphologic characterization and evolutionary model for assessing its tsunamigenic potential with further numerical simulations. In addition, the discovery of a cold-water coral community on top of the largest knoll has implications for identifying similar landslide-origin cold-water coral communities on the GBR margin. © 2016 Elsevier B.V
Optimization of nucleophilic 18F radiofluorinations using a microfluidic reaction approach
No full textMicrofluidic techniques are increasingly being used to synthesize positron-emitting radiopharmaceuticals. Several reports demonstrate higher incorporation yields, with shorter reaction times and reduced amounts of reagents compared with traditional vessel-based techniques. Microfluidic techniques, therefore, have tremendous potential for allowing rapid and cost-effective optimization of new radiotracers. This protocol describes the implementation of a suitable microfluidic process to optimize classical 18F radiofluorination reactions by rationalizing the time and reagents used. Reaction optimization varies depending on the systems used, and it typically involves 5–10 experimental days of up to 4 h of sample collection and analysis. In particular, the protocol allows optimization of the key fluidic parameters in the first tier of experiments: reaction temperature, residence time and reagent ratio. Other parameters, such as solvent, activating agent and precursor concentration need to be stated before the experimental runs. Once the optimal set of parameters is found, repeatability and scalability are also tested in the second tier of experiments. This protocol allows the standardization of a microfluidic methodology that could be applied in any radiochemistry laboratory, in order to enable rapid and efficient radiosynthesis of new and existing [18F]-radiotracers. Here we show how this method can be applied to the radiofluorination optimization of [18F]-MEL050, a melanoma tumor imaging agent. This approach, if integrated into a good manufacturing practice (GMP) framework, could result in the reduction of materials and the time required to bring new radiotracers toward preclinical and clinical applications. © 2014, Nature Publishing Grou
Simultaneous scanning of two mice in a small-animal PET scanner: a simulation-based assessment of the signal degradation
No full textIn PET imaging, research groups have recently proposed different experimental set ups allowing multiple animals to be simultaneously imaged in a scanner in order to reduce the costs and increase the throughput. In those studies, the technical feasibility was demonstrated and the signal degradation caused by additional mice in the FOV characterized, however, the impact of the signal degradation on the outcome of a PET study has not yet been studied. Here we thoroughly investigated, using Monte Carlo simulated [18F]FDG and [11C]Raclopride PET studies, different experimental designs for whole-body and brain acquisitions of two mice and assessed the actual impact on the detection of biological variations as compared to a single-mouse setting. First, we extended the validation of the PET-SORTEO Monte Carlo simulation platform for the simultaneous simulation of two animals. Then, we designed [18F]FDG and [11C]Raclopride input mouse models for the simulation of realistic whole-body and brain PET studies. Simulated studies allowed us to accurately estimate the differences in detection between single- and dual-mode acquisition settings that are purely the result of having two animals in the FOV. Validation results showed that PET-SORTEO accurately reproduced the spatial resolution and noise degradations that were observed with actual dual phantom experiments. The simulated [18F]FDG whole-body study showed that the resolution loss due to the off-center positioning of the mice was the biggest contributing factor in signal degradation at the pixel level and a minimal inter-animal distance as well as the use of reconstruction methods with resolution modeling should be preferred. Dual mode acquisition did not have a major impact on ROI-based analysis except in situations where uptake values in organs from the same subject were compared. The simulated [11C]Raclopride study however showed that dual-mice imaging strongly reduced the sensitivity to variations when mice were positioned side-by-side while no sensitivity reduction was observed when they were facing each other. This is the first study showing the impact of different experimental designs for whole-body and brain acquisitions of two mice on the quality of the results using Monte Carlo simulated [18F]FDG and [11C]Raclopride PET studies. © 2016 Institute of Physics and Engineering in Medicin
Synthesis and in vivo biological evaluation of 68Ga labelled carbonic anhydrase IX targeting small molecules for positron emission tomography
No full textTumor hypoxia contributes resistance to chemo- and radiotherapy, while oxygenated tumors are sensitive to these treatments. The indirect detection of hypoxic tumors is possible by targeting carbonic anhydrase IX (CA IX), an enzyme overexpressed in hypoxic tumors, with sulfonamide-based imaging agents. In this study, we present the design and synthesis of novel gallium-radiolabeled small-molecule sulfonamides targeting CA IX. The compounds display favorable in vivo pharmacokinetics and stability. We demonstrate that our lead compound, [68Ga]-2, discriminates CA IX-expressing tumors in vivo in a mouse xenograft model using positron emission tomography (PET). This compound shows specific tumor accumulation and low uptake in blood and clears intact to the urine. These findings were reproduced in a second study using PET/computed tomography. Small molecules investigated to date utilizing 68Ga for preclinical CA IX imaging are scarce, and this is one of the first effective 68Ga compounds reported for PET imaging of CA IX. © 2016 American Chemical Societ
Reduced sensitivity to MDMA-induced facilitation of social behaviour in MDMA pre-exposed rats
No full textThe acute effects of the party drug 3,4-methylenedioxymethamphetamine (MDMA, “Ecstasy”) in humans include feelings of love, closeness towards other people and an increased acceptance of others views and feelings. Some evidence suggests that regular MDMA users develop a subsensitivity to the positive effects of the drug and escalate their intake of the drug over time as a result. The current study investigated whether brief exposure to relatively high doses of MDMA in rats produces a subsequent attenuation in the ability of MDMA to enhance social interaction. Male Wistar rats were exposed to either MDMA (4 × 5 mg/kg over 4 h) or vehicle on two consecutive days. Twelve weeks later, MDMA pre-exposed rats displayed a significantly shorter period of time spent in social interaction than controls when tested in the drug-free state. MDMA pre-exposed rats also showed a blunted prosocial response to MDMA (2.5 mg/kg) relative to controls. This difference was overcome by increasing the MDMA dose to 5 mg/kg. The 5-HT1A agonist 8-OH-DPAT (250 µg/kg but not 125 µg/kg) increased social interaction and this effect did not differ in MDMA and vehicle pre-exposed rats. HPLC analysis showed a small but significant depletion of prefrontal 5-HT and 5-HIAA in MDMA pre-exposed rats. Prefrontal 5-HIAA concentrations were also reduced in the subset of vehicle and MDMA pre-exposed rats that received additional testing with MDMA. These results indicate that treatment with MDMA not only causes lasting reductions in social interaction in rats but causes an attenuation of the prosocial effects of subsequent MDMA administration. The lack of a differential response to 8-OH-DPAT agrees with other findings that the 5-HT1A receptor system remains functionally intact following MDMA pre-exposure and suggests that other neuroadaptations may underlie the lasting social deficits caused by MDMA. © 2008 Elsevier Inc