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Abstract: The first experimental results from a new transmissive diagnostic instrument for synchrotron X-ray beamlines are presented. The instrument utilizes a single-crystal chemical-vapour-deposition diamond plate as the detector material, with graphitic wires embedded within the bulk diamond acting as electrodes. The resulting instrument is an all-carbon transmissive X-ray imaging detector. Within the instrument's transmissive aperture there is no surface metallization that could absorb X-rays, and no surface structures that could be damaged by exposure to synchrotron X-ray beams. The graphitic electrodes are fabricated in situ within the bulk diamond using a laser-writing technique. Two separate arrays of parallel graphitic wires are fabricated, running parallel to the diamond surface and perpendicular to each other, at two different depths within the diamond. One array of wires has a modulated bias voltage applied; the perpendicular array is a series of readout electrodes. X-rays passing through the detector generate charge carriers within the bulk diamond through photoionization, and these charge carriers travel to the nearest readout electrode under the influence of the modulated electrical bias. Each of the crossing points between perpendicular wires acts as an individual pixel. The simultaneous read-out of all pixels is achieved using a lock-in technique. The parallel wires within each array are separated by 50 µm, determining the pixel pitch. Readout is obtained at 100 Hz, and the resolution of the X-ray beam position measurement is 600 nm for a 180 µm size beam.

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Abstract: We report on the alteration history of the olivine-phyric, highly depleted (HD) shergottite, Northwest Africa (NWA) 10416, paying particular attention to the origin of the aqueous alteration seen affecting the meteorite’s olivine megacrysts. The rock’s interior displays 1 mm, zoned, altered olivine megacrysts set in a groundmass of clinopyroxene, unzoned olivine, and interstitial plagioclase and maskelynite. Synchrotron micro X-ray diffraction (µ-XRD) and transmission electron microscopy (TEM) show that plagioclase and maskelynite have been partially replaced by kaolinite. The relict olivine megacryst cores display a unique concentric colouration for Martian meteorites, having central amber-coloured zones surrounded by a brown mantle zone, with the rims remaining clear and unaltered. This colouration is a result of fluid alteration and partial replacement, with hydration. TEM analysis revealed the ∼200 nm scale banded and largely amorphous nature of the alteration, but with some (∼ 20%) relict crystalline olivine patches. Although the coloured olivine zones show cation and anion site vacancies compared to stoichiometric olivine, a relict igneous compositional trend is preserved in the megacrysts, from Mg-rich altered cores (Mg# = 76) to unaltered stoichiometric rims (Fo53). Synchrotron Fe-K X-ray absorption near-edge structure (XANES) analysis revealed that the coloured zones of the megacryst have different Fe oxidation values. High ferric contents are present in the brown mantle zones (Fe3+/ΣFe ≤ 0.92) and the amber zones (Fe3+/ΣFe ≤ 0.30), whereas the clear rims are ferrous. This suggests alteration occurred in an oxidising environment and that the sharp contrast in colour of the megacryst (brown to clear) is a record of a relict fluid reaction front. In order to test the terrestrial or extraterrestrial origin of the alteration, olivine material from a shock-melt vein was analysed by TEM. The analysis revealed 0.952 nm curved d-spacing’s from clay alteration undisturbed by any shock effects, strongly suggesting a terrestrial origin. The d-spacing values most likely represent a collapsed saponite or vermiculite, showing that in some places olivine has been replaced by crystalline clay. Oxygen isotope analysis of bulk (Δ17O = 0.309 ± 0.009 (2σ) ‰) and amber-coloured megacryst material (= 0.271 ± 0.002 (2σ) ‰), are also consistent with terrestrial alteration. We propose a model in which, during the meteorite’s time in Northwest Africa, low-temperature, likely acidic, groundwater exploited fractures. The fluid altered the olivine megacrysts in a way that was controlled by the pre-existing, igneous compositional zonation, with Mg-rich olivine being more susceptible to alteration in this fluid environment. The plagioclase and maskelynite were also altered to a high degree. After the alteration event it is likely that NWA 10416 had a significant residence time in Northwest Africa, accounting for terrestrial calcite and the dehydration of some clay phases.

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Abstract: The hallmark of neurodegenerative disease in humans, including Alzheimer’s, Amyotrophic Lateral Sclerosis and Parkinson’s, lies in our inability to efficiently restore damaged neurons. Contrary to widespread belief, humans can regenerate neurons within the Peripheral Nervous System (PNS) and some areas of the Central Nervous System (CNS), however the underlying mechanisms which drive or repress complete functional and structural neuronal regeneration remain elusive. To develop our understanding of this natural phenomenon one should focus on species which are capable of efficient neuronal regeneration following neurotrauma. The earthworm species Eisenia fetida can regenerate their Cerebral Ganglion (CG) - loosely defined as the brain, within a few weeks following surgical removal. The characterization of fundamental aspects of neuronal regeneration in the earthworm promises to provide an insight as to why humans have largely lost that capability. Here we present a detailed micro-dissection protocol that has been developed to excise the CG and study the progression of its regeneration. The Ventral Nerve Cord (VNC) of the worm is a tissue which connects the CG to the rest of the nervous system via the Circumpharyngeal Connectives (CC). Exploration of molecular dynamics through changes in the transcriptome were determined in the VNC and CC at 1 week and 5-week post-decerebration using an RNAseq approach (90 million reads/condition, 100bp Paired End). RNAseq established that specific groups of genes are up- or downregulated in the regenerating VNC. More than 500 significantly enriched biological processes were identified throughout the regeneration process, including vascular development, neurogenesis and extracellular matrix organization, as well as more than 100 significantly enriched molecular functions, including calcium ion binding, metal ion binding and metalloendopeptidase activity. Differential expression of transcripts was confirmed via qPCR. Examples of transcripts which have been validated at 1w post-decerebration, include catalase (~34-fold), superoxide dismutase 1 (sod-1) (~12-fold) and transcription factor jun-B (junb) (~3-fold). On the other hand, examples of transcripts which have been validated at 5w post-decerebration, include Glial Fibrillary Acidic Protein (GFAP) (~101-fold), adam19 (~17-fold) and Bone Morphogenetic Protein 1 (BMP1) (~3-fold). Moreover, the large number of differentially expressed metalloproteins (ADAMs, BMPs, MMPs, metallothionein) identified in the transcriptome, led to the hypothesis that metal trafficking could play a role in the course of regeneration. This was confirmed using a synchrotron-based approach, namely X-Ray Fluorescence (XRF) spectroscopy, where Zinc (Zn) and Iron (Fe) show a differential distribution pattern across different stages (at 1 week to 10-weeks post-decerebration) of regeneration. Lastly, various histological techniques were implemented to characterize/describe neuronal structures during the regenerating process, including immunohistochemistry and Terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL). Furthermore, numerous novel markers and biological processes have been identified which, to date, have not been linked to neuronal regeneration. In summary, the results suggest that the increase of axon growth promoting factors as well the decrease of growth inhibitory factors act in conjunction to ensure efficient neuronal regeneration in the earthworm.

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Abstract: Techniques employing synchrotron radiation (SR) have had a major and growing impact on catalytic science. They have made key contributions to our understanding of structural properties of catalytic systems and of structural changes during the operation of a catalytic process. They can also improve our understanding of electronic and vibrational properties, which can contribute to the understanding of mechanisms. SR techniques are now key components of the experimental tool box of the catalytic scientist.

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Abstract: From oxic atmosphere to metallic core, the Earth's components are broadly stratified with respect to oxygen fugacity. A simple picture of reducing oxygen fugacity with depth may be disrupted by the accumulation of oxidised crustal material in the deep lower mantle, entrained there as a result of subduction. While hotspot volcanoes are fed by regions of the mantle likely to have incorporated such recycled material, the oxygen fugacity of erupted hotspot basalts had long been considered comparable to or slightly more oxidised than that of mid-ocean ridge basalt (MORB) and more reduced than subduction zone basalts. Here we report measurements of the redox state of glassy crystal-hosted melt inclusions from tephra and quenched lava samples from the Canary and Cape Verde Islands, that we can independently show were entrapped prior to extensive sulphur degassing. We find high ferric iron to total iron ratios (Fe3+/∑Fe) of up to 0.27–0.30, indicating that mantle plume primary melts are significantly more oxidised than those associated with mid-ocean ridges and even subduction zone. These results, together with previous investigations from the Erebus, Hawaiian and Icelandic hotspots, confirm that mantle upwelling provides a return flow from the deep Earth for components of oxidised subducted lithosphere and suggest that highly oxidised material accumulates or is generated in the lower mantle. The oxidation state of the Earth's interior must therefore be highly heterogeneous and potentially locally inversely stratified.