I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7525]
Abstract: Red mud leachate (pH 13) collected from Ajka, Hungary is neutralized to < pH 10 by HCl, gypsum, or seawater addition. During acid neutralization >99% Al is removed from solution during the formation of an amorphous boehmite-like precipitate and dawsonite. Minor amounts of As (24%) are also removed from solution via surface adsorption of As onto the Al oxyhydroxides. Gypsum addition to red mud leachate results in the precipitation of calcite, both in experiments and in field samples recovered from rivers treated with gypsum after the October 2010 red mud spill. Calcite precipitation results in 86% Al and 81% As removal from solution, and both are nonexchangeable with 0.1 mol L–1 phosphate solution. Contrary to As associated with neoformed Al oxyhydroxides, EXAFS analysis of the calcite precipitates revealed only isolated arsenate tetrahedra with no evidence for surface adsorption or incorporation into the calcite structure, possibly as a result of very rapid As scavenging by the calcite precipitate. Seawater neutralization also resulted in carbonate precipitation, with >99% Al and 74% As removed from solution during the formation of a poorly ordered hydrotalcite phase and via surface adsorption to the neoformed precipitates, respectively. Half the bound As could be remobilized by phosphate addition, indicating that As was weakly bound, possibly in the hydrotalcite interlayer. Only 5–16% V was removed from solution during neutralization, demonstrating a lack of interaction with any of the neoformed precipitates. High V concentrations are therefore likely to be an intractable problem during the treatment of red mud leachates.
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Jun 2013
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I18-Microfocus Spectroscopy
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Abstract: Herein we report for the first time the detrimental effect of metal poisons on the zeolitic material after deactivation in a commercial FCC unit at the level of a single catalyst particle. Using synchrotron-based hard X-ray radiation, the presence of Ni, V, as well as the crystalline phases can be determined with micrometre resolution in 2D or 3D. Furthermore, the non-invasive nature of the experimental approach avoids the pre-bisection of the FCC particle, avoiding damage and contamination to the catalyst material. Our findings lead to a better understanding of the deactivation processes taking place in real-life FCC catalysis and open the possibility to apply this approach for the study of other important catalytic materials, comprising both metals and crystalline phases.
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Jun 2013
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I18-Microfocus Spectroscopy
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Saloni
Mittal
,
Matthew
Revell
,
Francesca
Barone
,
Michaele J.
Hardie
,
Gulraj
Matharu
,
Alison
Davenport
,
Melissa
Grant
,
Fred
Mosselmans
,
Paul
Pynsent
,
Vaiyapuri P.
Sumathi
,
Owen
Addison
,
Peter
Revell
,
Christopher
Buckley
,
Richard
Martin
Open Access
Abstract: Lymphoid Aggregates That Resemble Tertiary Lymphoid Organs Define a Specific Pathological Subset in Metal-on-Metal Hip Replacements
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May 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7418]
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May 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7450, 7453]
Abstract: Iron from multiple brain regions in Alzheimer’s disease (AD), Parkinson’s disease (PD), and Multiple System Atrophy (MSA) is compared with healthy controls. Altered iron regulation has been observed in various forms in many neurodegenerative disorders; its contribution to disease progression remains an active topic of research. Dysregulation of metal elements besides iron is implicated in various pathological processes, but tracemetals analysis in human brain almost invariably occurs post-mortem. Iron is unusual; it holds particular scope for clinical detection by magnetic resonance imaging (MRI). Iron’s influence on certain MRI parameters is well-demonstrated, but clinical attribution of MRI signal to iron requires validation in context. By testing relationships between regional brain iron in human tissue, and relevant MRI parameters, we are exploring the potential to differentiate between neurodegenerative disorders on the basis of brain iron status. Some iron changes arguably precede the extensive degeneration that is clinically observed in later stages of disease.
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May 2013
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I18-Microfocus Spectroscopy
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Abstract: Luminescent quantum dots were synthesized using bacterially derived selenide (SeII-) as the precursor. Biogenic SeII- was produced by the reduction of Se-IV by Veillonella atypica and compared directly against borohydride-reduced Se-IV for the production of glutathione-stabilized CdSe and beta-mercaptoethanol-stabilized ZnSe nanoparticles by aqueous synthesis. Biological SeII- formed smaller, narrower size distributed QDs under the same conditions. The growth kinetics of biologically sourced CdSe phases were slower. The proteins isolated from filter sterilized biogenic SeII- included a methylmalonyl-CoA decarboxylase previously characterized in the closely related Veillonella parvula. XAS analysis of the glutathione-capped CdSe at the S K-edge suggested that sulfur from the glutathione was structurally incorporated within the CdSe. A novel synchrotron based XAS technique was also developed to follow the nucleation of biological and inorganic selenide phases, and showed that biogenic SeII- is more stable and more resistant to beam-induced oxidative damage than its inorganic counterpart. The bacterial production of quantum dot precursors offers an alternative, 'green' synthesis technique that negates the requirement of expensive, toxic chemicals and suggests a possible link to the exploitation of selenium contaminated waste streams.
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Apr 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[2000]
Abstract: This paper investigates the incorporation of Sr into biomineralized calcium carbonate granules secreted by the earthworm Lumbricus terrestris. Experiments were conducted using an agricultural soil amended with Sr(NO3)2 to give concentrations in the range 50–500 mg kg?1 Sr and a naturally Sr-rich, Celestine-bearing soil containing up to 11 000 mg kg?1 Sr. Granule production rates were in the range 0.26–2.3 mgCaCO3 earthworm?1 day?1; they showed no relationship with soil or soil solution Sr concentration but decreased with decreasing pH. Strong relationships exist (r2 ? 0.8, p ? 0.01) between the Sr concentrations and Sr/Ca ratios of the granules and those of the soil, soil solution and earthworms. The highest bulk Sr concentration we recorded in the calcium carbonate granules was 5.1 wt.% Sr whilst electron microprobe analysis recorded spot concentrations of up to 4.3 wt.% Sr. X-ray diffraction and X-ray absorption spectroscopy indicate that the majority of the calcium carbonate is present as Sr-bearing calcite with trace amounts of Sr-bearing vaterite also being present. The granules produced in the Sr-amended soils concentrated Sr relative to Ca from the bulk soil and the earthworms. This suggests that earthworm secreted calcium carbonate may be significant in the cycling of 90Sr released into soils via nuclear accidents or leakage from nuclear waste storage facilities.
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Apr 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[6180, 7048]
Open Access
Abstract: Fluid catalytic cracking (FCC) is the main conversion process used in oil refineries. An X-ray microscopy method is used to show that metal poisoning and related structural changes in the zeolite active material lead to a non-uniform core–shell deactivation of FCC catalyst particles. The study links the detrimental effect of V and Ni poisoning with zeolite destruction and dealumination in a spatial manner within a single FCC catalyst particle.
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Apr 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[2952, 923]
Abstract: We have used synchrotron-based X-ray fluorescence and absorption techniques to establish both metal distribution and complexation in mature wheat grains. In planta, extended X-ray absorption fine structure (EXAFS) spectroscopy reveals iron phytate and zinc phytate structures in aleurone cells and in modified aleurone cells in the transfer region of the grain: iron is coordinated octahedrally by six oxygen atoms and fewer than two phosphorous atoms. Zinc is coordinated tetrahedrally by four oxygen atoms and approximately 1.5 phosphorus atoms in an asymmetric coordination shell. We also present evidence of modified complexation of both metals in transgenic grain overexpressing wheat ferritin. For zinc, there is a consistent doubling of the number of complexing phosphorus atoms. Although there is some EXAFS evidence for iron phytate in ferritin-expressing grain, there is also evidence of a structure lacking phosphorus. This change may lead to an excess of phosphorus within the storage regions of grain, and in turn to the demonstrated increased association of phosphorus with zinc in ferritin-expressing grains. Derivative X-ray absorption spectra also suggest that mineral complexation in the transfer region of ferritin-expressing grains is quite different from that in wild-type grain. This may explain why the raised levels of minerals transported to the developing grain accumulate within the crease region of the transgenic grain.
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Apr 2013
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7418, 8377]
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Apr 2013
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