Browsing by Author "Williams, R"

Now showing 1 - 4 of 4
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    The application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)
    (Springer Nature, 2018-02-06) Kristo, MJ; Williams, R; Gaffney, AM; Kayzar-Boggs, TM; Schorzman, KC; Lagerkvist, P; Vesterlund, A; Ramebäck, H; Nelwamondo, AN; Kotze, D; Song, K; Lim, SH; Han, SH; Lee, CG; Okubo, A; Maloubier, D; Cardona, D; Samuleev, P; Dimayuga, I; Varga, Z; Wallenius, M; Mayer, K; Loi, E; Keegan, EA; Harrison, JJ; Thiruvoth, S; Stanley, FE; Spencer, KJ; Tandon, L
    In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched uranium oxide samples, providing 12 analytical results using three different parent-daughter pairs serving as independent chronometers. The vast majority of the results were consistent with one another and consistent with the known processing history of the materials. In general, for these particular samples, mass spectrometry gave more accurate and more precise analytical results than decay counting measurements. In addition, the concordance of the 235U–231Pa and 234U–230Th chronometers confirmed the validity of the age dating assumptions, increasing confidence in the resulting conclusions. © 2018 U.S. Government
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    Changes in small-angle x-ray scattering parameters observed upon binding of ligand to rabbit muscle pyruvate kinase are not correlated with allosteric transitions
    (American Chemical Society, 2010-08-24) Fenton, AW; Williams, R; Trewhella, J
    Protein fluorescence and small-angle X-ray scattering (SAXS) have been used to monitor effector affinity and conformational changes previously associated with allosteric regulation in rabbit muscle pyruvate kinase (M-1-PYK). In the absence of substrate [phosphoenolpyruvate (PEP)], SAXS-monitored conformational changes in M-1-PYK elicited by the binding of phenylalanine (an allosteric inhibitor that reduces the affinity of M-1-PYK for PEP) are similar to those observed upon binding of alanine or 2-aminobutyric acid. Under our assay conditions, these small amino acids bind to the protein but elicit a minimal change in the affinity of the protein for PEP. Therefore, if changes in scattering signatures represent cleft closure via domain rotation as previously interpreted, we can conclude that these motions are not sufficient to elicit allosteric inhibition. Additionally, although PEP has similar affinities for the free enzyme and the M-1-PYK small amino acid complexes (i.e., the small amino acids have minimal allosteric effects), PEP binding elicits different changes in the SAXS signature of the free enzyme versus the M-1-PYK small amino acid complexes. © 2010, American Chemical Society
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    Developing a model of upland swamp structure, function and evolution for biodiversity conservation and rehabilitation: the case of threatened Temperate Highland Peat Swamps on Sandstone (THPSS)
    (University of Melbourne, 2014-07-27) Fryirs, K; Freidman, B; Williams, R; Jacobsen, GE; Hose, G
    Temperate highland peat swamps on sandstone (THPSS) (called upland swamps) are a form of topogenous mire which occur on the plateau areas of eastern Australia. These systems are well recognised for their ecological value, under several State and Federal policies. However, our understanding of their structure, function and evolution remains limited. This study examines the sedimentology, age structure, hydrological function and stygofauna diversity of 19 valley-bottom swamps in the Blue Mountains and Southern Highlands of NSW to produce a regional model of THPSS geo-ecological function. This regional model provides a template for environmental health assessment and rehabilitation of these systems, and to inform State and Federal policy making on the conservation status of these systems. © 2014 University of Melbourne
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    Nuclear forensic analysis of an unknown uranium ore concentrate sample seized in a criminal investigation in Australia
    (Elsevier, 2014-07) Keegan, EA; Kristo, MJ; Colella, M; Robel, M; Williams, R; Lindvall, R; Eppich, G; Roberts, SK; Borg, L; Gaffney, AM; Plaue, J; Wong, HKY; Davis, J; Loi, E; Reinhard, MI; Hutcheon, I
    Early in 2009, a state policing agency raided a clandestine drug laboratory in a suburb of a major city in Australia. During the search of the laboratory, a small glass jar labelled “Gamma Source” and containing a green powder was discovered. The powder was radioactive. This paper documents the detailed nuclear forensic analysis undertaken to characterise and identify the material and determine its provenance. Isotopic and impurity content, phase composition, microstructure and other characteristics were measured on the seized sample, and the results were compared with similar material obtained from the suspected source (ore and ore concentrate material). While an extensive range of parameters were measured, the key ‘nuclear forensic signatures’ used to identify the material were the U isotopic composition, Pb and Sr isotope ratios, and the rare earth element pattern. These measurements, in combination with statistical analysis of the elemental and isotopic content of the material against a database of uranium ore concentrates sourced from mines located worldwide, led to the conclusion that the seized material (a uranium ore concentrate of natural isotopic abundance) most likely originated from Mary Kathleen, a former Australian uranium mine. © 2014 Elsevier Ireland Ltd.