I18-Microfocus Spectroscopy
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Nilay
Lakhkar
,
Jeong-hui
Park
,
Nicola J.
Mordan
,
Vehid
Salih
,
Ivan B.
Wall
,
Hae-won
Kim
,
Scott P.
King
,
John V.
Hanna
,
Richard
Martin
,
Owen
Addison
,
Jonathan C.
Knowles
,
J.f.w.
Mosselmans
Diamond Proposal Number(s):
[5770]
Abstract: We have demonstrated the successful production of titanium phosphate glass microspheres in the size range of ?10–200 ?m using an inexpensive, efficient, easily scalable process and assessed their use in bone tissue engineering applications. Glasses of the following compositions were prepared by melt-quench techniques: 0.5P2O5–0.4CaO–(0.1 ? x)Na2O–xTiO2, where x = 0.03, 0.05 and 0.07 mol fraction (denoted as Ti3, Ti5 and Ti7 respectively). Several characterization studies such as differential thermal analysis, degradation (performed using a novel time lapse imaging technique) and pH and ion release measurements revealed significant densification of the glass structure with increased incorporation of TiO2 in the glass from 3 to 5 mol.%, although further TiO2 incorporation up to 7 mol.% did not affect the glass structure to the same extent. Cell culture studies performed using MG63 cells over a 7-day period clearly showed the ability of the microspheres to provide a stable surface for cell attachment, growth and proliferation. Taken together, the results confirm that 5 mol.% TiO2 glass microspheres, on account of their relative ease of preparation and favourable biocompatibility, are worthy candidates for use as substrate materials in bone tissue engineering applications.
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Jul 2012
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[1573]
Abstract: Globally, more than 1000 tonnes of titanium (Ti) is implanted into patients in the form of biomedical devices on an annual basis. Ti is perceived to be ‘biocompatible’ owing to the presence of a robust passive oxide film (approx. 4 nm thick) at the metal surface. However, surface deterioration can lead to the release of Ti ions, and particles can arise as the result of wear and/or corrosion processes. This surface deterioration can result in peri-implant inflammation, leading to the premature loss of the implanted device or the requirement for surgical revision. Soft tissues surrounding commercially pure cranial anchorage devices (bone-anchored hearing aid) were investigated using synchrotron X-ray micro-fluorescence spectroscopy and X-ray absorption near edge structure. Here, we present the first experimental evidence that minimal load-bearing Ti implants, which are not subjected to macroscopic wear processes, can release Ti debris into the surrounding soft tissue. As such debris has been shown to be pro-inflammatory, we propose that such distributions of Ti are likely to effect to the service life of the device.
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Jul 2012
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I18-Microfocus Spectroscopy
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Abstract: The variation in geographical distribution of selenium (Se) in environmental settings and the food chain can cause serious human health deficiencies, or poisoning and fatal death. Although Se toxicity is usually inferred as caused by local geology or human activities, the current food trade practices raise Se concerns to a global level, as the Se contained in agricultural products is often unknown. In most natural settings, the prime -. source of Se are shale rocks. Yet, Se weathering pathways and release mechanisms are poorly understood because the locus and the distribution of Se in shales are unknown. Therefore, this thesis assessed the geochemical environment surrounding Se in shales and identified the main inorganic and organic host phases and elucidated the Se speciation and the way this may affect the Se mobilization pathways. This was done by combining simple and complex geochemical, mineralogical and spectroscopic techniques -that were statistically validated to analyse shale samples from the UK, Colombia and China that were representative for typical (1 - 10 ug/g) and extreme (>1 %) Se concentrations. The first important result was the identification of pyrite and organic matter as the two main Se host phases. Additionally, the data showed that in typical shales (e.g. with <6% organic C and 1-2% reduced inorganic S) Se was preferentially associated to pyrite, while in low pyrite shales the association between Se and organic matter was favoured. Interestingly, the data also revealed that depending on the formation pathways pyrite morphology also differentially bound Se with euhedrals concentrating more Se than framboids. Finally, the spectroscopic data showed that Se was not substituting S in pyrite, instead Se was present as an independent FeSex species in close association with both euhedral and framboidal pyrite. Conversely, in the organic matrix, nanosized elemental Se and organo-Se species (Se=C, Se-Se and Se-C bonds) were the main Se carriers.
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Jul 2012
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[6303]
Abstract: Tris(8-quinolinolato)gallium(III) (1, KP46) is a very promising investigational anticancer drug. Its interaction with serum proteins, elemental distribution, and coordination in tissue were investigated with X-ray absorption (XAS) methods. Model compounds with mixed O, N, and/or S donor atoms are reported. The coordination and structure of 1 in cell culture medium (minimum essential medium, MEM) and fetal calf serum (FCS) were probed by XANES and EXAFS. The interaction of 1 with the serum proteins apotransferrin (apoTf) and human serum albumin (HSA) was addressed as well. By application of micro-XAS to tissue samples from mice treated with 1, the gallium distribution pattern was analyzed and compared to those of physiological trace elements. The complex 1 turned out to be very stable under physiological conditions, in cell culture media and in tissue samples. The coordination environment of the metal center remains intact in the presence of apoTf and HSA. The gallium distribution pattern in tumor and liver tissue revealed high similarities to the distribution patterns of Zn and Fe, minor similarities to Cu and Ni, and no similarity to Ca.
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Jun 2012
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I18-Microfocus Spectroscopy
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Alister J
Hart
,
Paul D
Quinn
,
Ferdinand
Lali
,
Barry
Sampson
,
John A
Skinner
,
Jonathan J
Powell
,
John
Nolan
,
Keith
Tucker
,
Simon
Donell
,
Adrienne
Flanagan
,
J Fred W
Mosselmans
Diamond Proposal Number(s):
[1918]
Abstract: Some types of metal-on-metal (MOM) hip replacements have unacceptably high rates of failure, such as the Ultima TPS MOM hip, with 13.8% failure at 5 years. This has been attributed to an inflammatory reaction following the release of cobalt (Co) and chromium (Cr) from the bearing surfaces and modular junctions. There is in vitro evidence that Co is more important than Cr in the inflammatory process, but there are no reported human tissue studies of the analysis of implant-derived metals.
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Jun 2012
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I18-Microfocus Spectroscopy
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Abstract: Gas-phase Fe nanoparticles with a diameter ~ 2nm, have been used in all the nanostructured material in this thesis. In pure Fe nanoparticle systems with different thicknesses, two important parameters the exchange interaction (Hex) and random anisotropy (Hr) were investigated using the Random Anisotropy Model (RAM). This reveals that for the same particle size Hex remains almost constant for varying Fe thicknesses; whereas Hr increases with the increase of Fe film thickness. This is ascribed to increasing strain imposed at the nanoparticle level. The observed high values of Hr are related to an oxide on the cluster surface in these films, whose effect is also observed in low temperature magnetometry data. This shows the appearance of exchange bias in the films. The RAM approach when applied to Fe clusters in Co matrices, reveals much lower values of Hr than found in pure Fe nanoparticles and both Hr and Hex show an increase with the Volume Fraction (VF) of Fe in Co. The increase in Hex is ascribed to the increasing spin moment with Fe volume fraction. The nature of Fe clusters in very thick layers produce a high frequency Ferromagnetic Resonance response in the radio frequency range, which is an important finding for many applications. The EXAFS study of Fe nanoparticles in Cr matrices show no structural modification relative to the bulk bcc structure of both elements. The magnetometry results suggest that in dilute Fe concentration films, the observed decrease in the overall magnetization is due to the development of a nonmagnetic shell at the interface between Fe and Cr at each cluster boundary. This is reinforced by the lack of any evidence of EB. With increasing VF at about 10% of Fe there is strong evidence of the formation of a super-spin-glass (SSG) that shows the characteristic memory effect. Increasing the Fe nanoparticles VF to 20% Fe in Cr, the magnetization exceeds that expected for Fe indicating that the interaction induces some of the Cr to order ferromagnetically. Core-shell nanoparticle systems have been synthesised by a method that allows a complete control over the morphology of these assemblies. Atomic investigations in Fe@Cu CS nanoparticles reveal that Fe nanoparticles adopt the fcc structure with a 20 monolayer Cu shell thickness and stay in the bcc structure for 1-2 monolayer thick Cu shells. No alteration in the Fe atomic structure has been reported for different Au shell thicknesses in Fe@Au. The magnetic data show a reduced magnetization of the FM-AFM Fe@Cr CS nanoparticles as compared to the bulk value which is also ascribed to the formation of a non-magnetic Fe shell at the interface.
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Jun 2012
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[4842]
Abstract: Timescales of magma chamber assembly and recharge are investigated here by applying 1D and 2D diffusion modeling techniques to high-resolution maps of titanium in quartz from a large-volume ignimbrite eruption in the Taupo Volcanic Zone, New Zealand. We compare quartz zonation patterns and associated diffusion timescales from the ?340?ka Whakamaru super-eruption (magma volume ?1000?km3) with the Younger Toba Tuff super-eruption, 74?ka (2000?km3), Sumatra, and the smaller volume ?50?ka Earthquake Flat eruption (10?km3), Okataina Caldera Complex, New Zealand. Two principal timescales are presented: that of chamber recharge and eruption triggering events, and that of magma generation (involving long-term assembly, stirring and reactivation). Synchrotron micro-X-ray fluorescence maps of core–rim quartz transects provide a high-resolution record of magma chamber conditions throughout quartz crystallization. Quartz crystals from the Whakamaru magma display complex zonation patterns indicating fluctuating pressure–temperature conditions throughout the crystallization history. Toba and Earthquake Flat, in contrast, display simple quartz-zoning patterns and record slightly longer periods of crystal residence in the chamber that fed the eruption. We apply Lattice Boltzmann 2D diffusion modeling to reconstruct the timescales of quartz crystal zonation, accounting for crystal boundary complexities. Quartz crystal orientation is also accounted for by using geometry constraints from the synchrotron data. Our calculations suggest that crystal-mush reactivation for the main Whakamaru magma reservoir occured over a period of the order of 103–104 years. Both the Earthquake Flat and Toba eruptions experienced a significant recharge event (causing a temperature and pressure change), which occurred within ?100 years of eruption. In comparison, the complex Whakamaru quartz zoning patterns suggest that the magma body experienced numerous thermal and compositional fluctuations in the lead-up to eruption. The final magma recharge event, which most probably triggered the eruption, occurred within ?10–60 years of the eruption. Even though the volume of these systems spans two orders of magnitude, there does not appear to be a relationship between magma volume and diffusion timescale, suggesting similar histories before eruption.
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Apr 2012
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I18-Microfocus Spectroscopy
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Abstract: X-ray Absorption Fine Structure techniques have been used on Comet Wild2/81P tracks from the Stardust mission. Fe-XANES and EXAFS have been performed on aerogel sections from Tracks 41 and 162 as well as the mid and terminal positions of Track 134. This is the first use of EXAFS in the study of early Solar System materials. With EXAFS, we have measured FeO and FeS bond lengths and thus, together with complementary XANES measurements, identified Fe-rich phases. In particular, we show that ferric-rich phases in 2 Tracks (41, 162) have FeO bond 1st shell bond lengths of 1.992.01 Å and Fe K absorption edge and pre edge centroid positions consistent with being hematite-dominated grains. These iron oxides can be clearly distinguished from a magnetite grain, present in Track 134. We also demonstrate the identification of the Mg-rich end member olivine using EXAFS with XANES in Track 162. The terminal grain of Track 134 is pyrrhotite, its first atomic shell has an FeS structure, with 4 nearest neighbouring S atoms at a distance of 2.29 ± 0.05 Å. Our XANES results show the presence of Fe3+-bearing grains along the Stardust tracks and suggest either flash-cooling of an FeSSiOO2 gas during capture or the presence of a FeNiSO melt along the cometary tracks during impact capture in the aerogel, rather than the capture process being solely associated with reduction of cometary phases. Accurate determination of Comet Wild2 redox conditions requires the identification of phases, in particular terminal grains, which have not experienced this melting. For instance, the larger hematite-rich grains (>10 μm) are more likely to be cometary in origin. EXAFS provides a valuable new analytical technique to study fine-grained early Solar System materials.
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Apr 2012
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[7058]
Abstract: Results are presented from X-ray absorption spectroscopy based analysis of As, Cr, and V speciation within samples of bauxite ore processing residue (red mud) collected from the spill site at Ajka, Western Hungary.
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Mar 2012
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I18-Microfocus Spectroscopy
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Mar 2012
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