I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[1793]
Abstract: Al3Ti, Al13Cr2 and Al13Fe4 are important intermetallics in a number of Al alloy systems including complex ultra-high-strength systems with excellent elevated-temperature performance. A full knowledge of their properties and crystallographic structures is a key factor for the understanding of these complex alloys. In the present study samples of the three pure intermetallics were prepared and regions of interest identified in a billet of Al93Fe3Cr2Ti2 alloys and 20 × 10 × 2 µm samples extracted utilizing a Focussed Ion Beam Transmission Electron Microscopy (FIB TEM) sample preparation technique. Using the microfocus spectroscopy beamline I18 at Diamond Light Source we were able to examine 5 µm sections of the samples using X-ray Diffraction (?-XRD) and Extended X-ray Absorption Fine Structure (?-EXAFS) in an attempt to describe the local structure of the second-phase particles and characterized the microstructure of the FIBed samples to selectively illuminate the different phases.
|
Nov 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: The colonization and weathering of young seafloor basaltic glass from the mid-Atlantic Ridge was examined. Microorganisms were localised to fractures in the surface of the basalt and grew on the surfaces of material in the fractures. XAS, Raman Spectroscopy and NanoSIMS analysis of the fracture-filling material shows that it contains non-crystallised iron-enriched altered glass and poorly ordered iron oxides. Organisms, which in places develop into contiguous biofilms, develop on the surface of the material. No putative biogenic alteration textures were observed in the basaltic glass at the fracture boundaries suggesting that the microbial community is restricted to the secondary alteration products. Microbial culturing shows the presence of heterotrophic bacteria including Sufitobacter and Halomonas consistent with observations of photic zone detritus associated with fracture-filling material. These data show that the interior of fresh basaltic glass is an endolithic habitat for microorganisms, but that the glass itself is not a primary source of cations or energy for the developing communities.
|
Oct 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: Thermal spraying is emerging as the leading route for the deposition of protective coatings onto engineering components to improve operation under extreme conditions of temperature, wear or corrosion. Detailed microstructural assessment is a key element in improving coating performance, and this study demonstrates the application of microfocus X-ray techniques to the determination of elemental and structural variations in the coatings.
|
Oct 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 12 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.
|
Sep 2010
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[1125]
|
Sep 2010
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[879]
Abstract: To have any hope of affecting the course of Parkinson's disease, early diagnosis is essential. Rachel Jones assesses progress so far.
When a patient is diagnosed with Parkinson's disease, they usually have two or three of the cardinal symptoms: resting tremor, rigidity and bradykinesia (slowed movement). By this stage, however, they have probably had the disease for years and up to four-fifths of the dopamine-producing neurons in the substantia nigra have been lost. There is currently no way to reverse this damage, but what if doctors could diagnose Parkinson's disease earlier, before so much harm has been done?
The search is on for a biomarker for early Parkinson's disease — a test that can reliably and specifically predict which patients are going to develop the disease while they are still in the early stages (Box 1). Such a biomarker would have several benefits: patients could be warned that they are likely to develop Parkinson's disease; longitudinal studies of these patients could help researchers develop treatments to slow or even halt the progression of the disease; and, if such treatments were to be developed, a reliable biomarker could allow treatment to begin earlier.
|
Aug 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: Shales play an important role in many earth system processes including coastal erosion, and they form the foundations of many engineering structures. The geobiology of the interior of pyrite-containing receding shale cliffs on the coast of northeast England was examined. The surface of the weathered shales was characterised by a thin layer of disordered authigenic iron oxyhydroxides and localised acicular, platy and aggregated gypsum, which was characterised by Raman spectroscopy, XAS and SEM. These chemical changes are likely to play an important role in causing rock weakening along fractures at the micron scale, which ultimately lead to coastal retreat at the larger scale. The surface of the shale hosts a novel, low-diversity microbial community. The bacterial community was dominated by Proteobacteria, with phylotypes closely associating with Methylocella and other members of the γ-subdivision. The second largest phylogenetic group corresponded to Nitrospira. The archaeal 16S rRNA phylotypes were dominated by a single group of sequences that matched phylotypes reported from South African gold mines and possessed ammonia monooxygenase (amoA) genes. Both the phylogenetic and the mineral data show that acidic microenvironments play an important role in shale weathering, but the shale has a higher microbial diversity than previously described pyritic acid mine drainage sites. The presence of a potentially biogeochemically active microbial population on the rock surface suggests that microorganisms may contribute to early events of shale degradation and coastal erosion.
|
Aug 2010
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[684]
Abstract: X-ray absorption near-edge structure (XANES) spectroscopy was used to examine the oxidation state of Zn, Fe and Cu in 22 normal and 23 tumour regions spread over 30 formalin-fixed, paraffin-embedded tissue samples of human primary invasive breast cancer. A micro-mapping analysis of the metal distribution in the tissue was performed prior to the XANES analysis to identify and localise the metals in the tumour and normal tissue regions. The aim of this study was to identify the oxidation state of Zn, Fe and Cu in normal and tumour tissues of the breast, in order to correlate the oxidation state of these elements with the carcinogenesis process. The position of the Zn K-edge in normal and tumour tissues suggests that Zn exists in a bounded form. The shape of the Cu K-edge XANES spectra and the first derivative spectra of normal and tumour tissues shows that a significant portion of the total copper is present as Cu (I). Nevertheless, the position of the edges in the normal and tumour tissue spectra does not exclude the presence of Cu (II). The shape and position of both normal and tumour regions of the tissue suggest that they contain mixtures of Fe (II) and Fe (III) ions with a significant fraction being Fe (III). However, normal tissue regions were found to have a higher fraction of Fe (II) compared to the tumour tissues. In order to estimate the best target for therapy, more information is required about the relative abundance of Zn, Fe and Cu binding proteins, their oxidation state and their localisation at the subcellular level. Copyright © 2010 John Wiley & Sons, Ltd.
|
Aug 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: Several amyloidogenic proteins including insulin, ?-lactoglobulin, and albumin form spherulites in vitro under non-physiological conditions. These micrometer-sized, roughly spherical structures are composed of ordered arrays of amyloid fibrils in radial arrangements which, characteristically, show a typical Maltese cross pattern of light extinction under the polarizing microscope. The physiological significance of amyloid spherulites is unknown though in Alzheimer's disease, senile plaques composed primarily of ? sheets of amyloid-? (A?){42} have, very occasionally, been shown to give a Maltese cross pattern of light extinction under crossed polarizers. Herein we describe the first observation of the formation in vitro of spherulites of A?{42}. They were formed under near-physiological conditions in which the ? sheet conformation of pre-formed aggregates of A?{42} had been abolished following the addition of an excess of copper. Incubation of these preparations at 37°C for up to 9 months resulted in the formation of globular structures, 5–20 ?m in diameter, which exhibited a Maltese cross pattern of light extinction typical of spherulites. Near-identical spherulitic structures were also observed in abundance in 30 ?m thick sections of Alzheimer's disease brain tissue. Synchrotron x-ray fluorescence showed that the location of these spherulites in AD tissue coincided with locally elevated concentrations of tissue copper. The formation in vitro of spherulites of A?{42} which morphologically appeared analogous to spherulitic structures observed in vivo strongly supports the hypothesis that spherulites and senile plaques in AD tissue are one and the same structures and that their ultimate formation may involve copper.
|
Jul 2010
|
|
I18-Microfocus Spectroscopy
|
Abstract: The Moa Bay NiCo laterite deposits, placed in the so-called MayariBaracoa ophiolitic belt (eastern Cuba), are oxide type. Despite its geological relevance and economical impact no detailed studies exist with regards to cristallochemical characterization of Ni incorporated in (or attached to) the main Ni-containing minerals forming the lateritic profile. A sample corresponding to the ore limonite horizon has been studied by microfocus Raman, micro X-ray diffraction (μXRD), electron probe micro analysis (EPMA) and synchrotron radiation microfocus X-ray absorption spectroscopy (XAS) to gain structural and chemical information on Ni. The data obtained has revealed that Ni is preferably accumulated in quantities up to 21 wt.% in lithiophoriteasbolane intermediates. The local environment of Ni shows NiMn distances ∼3.5 Å suggesting that Ni is sorbed mostly in inner-sphere complexes sitting on Mn vacancies and at the edge of the Mn layers. However it is shown that in the presence of Al the Ni is incorporated within the lithiophoriteasbolane intermediate by developing brucite-like interlayers. The understanding of Ni sorption mechanisms within the limonite horizon suggests that combined physicochemical factors such as soil porosity and pH regime have important implications for Ni mobility across the profile.
|
Jun 2010
|
|