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Abstract: This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe-Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe3+ and the Ni is octahedrally co-ordinated Ni2+. Structural analysis supports the suggestion that non-stoichiometric Fe2NiO4 trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.

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Abstract: Purpose : The purpose of this study was to investigate the distribution of Ca, Fe and Zn using X-ray fluorescence in human RPE/Bruch’s membrane/choroid with and without early AMD. Methods : We used a set of unfixed frozen human retinal pigment epithelium (RPE)/choroid samples from young (n=1, female aged 34) and aged donors with (n=4, males, aged 73-78) and without (n=3, one female, aged 75-77) early AMD from Manchester Eye Tissue Repository. Using X-ray fluorescence microscopy (I18 Diamond light source, UK) with a 2 um beam, we obtained high-resolution Ca, Zn, Fe, sulphur, potassium, chloride and phosphorus maps covering areas up to 100 x 600 um2 of 30 um thick sections placed on quartz holders and scanned at room temperature Results : Calcification was observed in the 3 groups. In the 34-year old sample, sparse small Ca spherules (2x2 um2) at the RPE/Bruch’s membrane interface not colocalising with Zn or Fe. In aged samples, with and without AMD, calcified nodules within RPE cells, at RPE/Bruch’s membrane interface and within druse in AMD. Every calcified nodule colocalised with Zn. Quantification revealed two types (high Zn content, low Zn content). In aged donors without AMD, high-Zn calcified nodules with Ca concentration of 3083+1679 ppm (mean+SD) (maximum 12809+9311) and Zn 66+55 ppm (max 125+75). The average size was 27+15 um2. In aged samples with AMD, high-Zn calcified nodules with average Ca concentration of 4316+1723 ppm (max 13105+7563) and Zn 97+57 ppm (max 201+143). Size 26x10 um2. In the aged non-AMD group, the low zinc-calcification nodules contained an average Ca ppm of 915+259 (max 1475+380) and Zn 33+18 ppm (max 40+21). The average size 28x16 um2. In the AMD group, the low Zn calcified nodules average Ca ppm 1544+1450 (max 3526+5289) and average Zn ppm 47+23 (max 64+37). Average size 19x10 um2. Calcified plaques in Bruch’s membrane from aged donors with and without AMD. Some of these plaques colocalised with Zn and also Fe. Fe-loaded structures in the choriocapillaris underlying calcified nodules and plaques. Conclusions : Calcific nodules contain zinc in older eyes with and without AMD. Calcified nodules with lower amounts of Ca contained lower amounts of Zn, so the accumulation of Ca may occur in parallel to Zn. It is possible that iron-loaded structures in the choriocapillaris are macrophages.

Open Access

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Abstract: The imaging of catalysts and other functional materials under reaction conditions has advanced significantly in recent years. The combination of the computed tomography (CT) approach with methods such as X-ray diffraction (XRD), X-ray fluorescence (XRF) and X-ray absorption near-edge spectroscopy (XANES) now enables local chemical and physical state information to be extracted from within the interiors of intact materials which are, by accident or design, inhomogeneous. In this work, we follow the phase evolution during the initial reduction step(s) to form Co metal, for Co-containing particles employed as Fischer–Tropsch synthesis (FTS) catalysts; firstly, working at small length scales (approx. micrometre spatial resolution), a combination of sample size and density allows for transmission of comparatively low energy signals enabling the recording of ‘multimodal’ tomography, i.e. simultaneous XRF–CT, XANES–CT and XRD–CT. Subsequently, we show high-energy XRD–CT can be employed to reveal extent of reduction and uniformity of crystallite size on millimetre-sized TiO2 trilobes. In both studies, the CoO phase is seen to persist or else evolve under particular operating conditions and we speculate as to why this is observed.

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Abstract: The chemistry of molybdenum species in artificial corrosion pits on 316L stainless steel was investigated using X-ray absorption spectroscopy (XANES). It was found that the K-edge spectra are consistent with the presence of an Mo(III) species. The presence of Mo(VI) polymolybdates as been proposed to explain the well-known beneficial effects of Mo in decreasing the susceptibility of stainless steel to localised corrosion, but no evidence of these species was found. High resolution measurements (with a spatial resolution of 3.5 μm in the vertical direction) through the dissolving metal interface did not detect the presence of any different Mo-containing species in the vicinity of the salt film. However, the spatial resolution was insufficient to detect the presence of submonolayer species on the dissolving metal surface that have been proposed to block active dissolution.

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Abstract: Zinc is known to play an important role in many cellular processes, and the levels of zinc are controlled by specific transporters from the ZIP (SLC39A) influx transporter group and the ZnT (SLC30A) efflux transporter group. The distribution of zinc was measured in 59 samples of invasive ductal carcinoma of breast using synchrotron radiation micro probe x-ray fluorescence facilities. The samples were formalin fixed paraffin embedded tissue micro arrays (TMAs) enabling a high throughput of samples and allowing us to correlate the distribution of trace metals with tumour cell distribution and, for the first time, important biological variables. The samples were divided into two classes, 34 oestrogen receptor positive (ER+ve) and 25 oestrogen receptor negative (ER-ve) based on quantitative immunohistochemistry assessment. The overall levels of zinc (i.e. in tumour and surrounding tissue) in the ER+ve samples were on average 60% higher than those in the ER-ve samples. The zinc levels were higher in the ER+ve tumour areas compared to the ER-ve tumour areas with the mean levels in the ER+ve samples being approximately 80% higher than the mean ER-ve levels. However, the non-tumour tissue regions of the samples contained on average the same levels of zinc in both types of breast cancers. The relative levels of zinc in tumour areas of the tissue were compared with levels in areas of non-tumour surrounding tissue. There was a significant increase in zinc in the tumour regions of the ER+ve samples compared to the surrounding regions (P < 0.001) and a non-significant increase in the ER-ve samples. When comparing the increase in zinc in the tumour regions expressed as a percentage of the surrounding non-tumour tissue zinc level in the same sample, a significant difference between the ER+ve and ER-ve samples was found (P < 0.01).