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Abstract: Microglia and astrocytes can quench metal toxicity to maintain tissue homeostasis, but with age, increasing glial dystrophy alongside metal dyshomeostasis may predispose the aged brain to acquire neurodegenerative diseases. The aim of the present study was to investigate age-related changes in brain metal deposition along with glial distribution in normal C57Bl/6J mice aged 2-, 6-, 19- and 27-months (n = 4/age). Using synchrotron-based X-ray fluorescence elemental mapping, we demonstrated age-related increases in iron, copper, and zinc in the basal ganglia (p < 0.05). Qualitative assessments revealed age-associated increases in iron, particularly in the basal ganglia and zinc in the white matter tracts, while copper showed overt enrichment in the choroid plexus/ventricles. Immunohistochemical staining showed augmented numbers of microglia and astrocytes, as a function of aging, in the basal ganglia (p < 0.05). Moreover, qualitative analysis of the glial immunostaining at the level of the fimbria and ventral commissure, revealed increments in the number of microglia but decrements in astroglia, in older aged mice. Upon morphological evaluation, aged microglia and astroglia displayed enlarged soma and thickened processes, reminiscent of dystrophy. Since glial cells have major roles in metal metabolism, we performed linear regression analysis and found a positive association between iron (R2 = 0.57, p = 0.0008), copper (R2 = 0.43, p = 0.0057), and zinc (R2 = 0.37, p = 0.0132) with microglia in the basal ganglia. Also, higher levels of iron (R2 = 0.49, p = 0.0025) and zinc (R2 = 0.27, p = 0.040) were correlated to higher astroglia numbers. Aging was accompanied by a dissociation between metal and glial levels, as we found through the formulation of metal to glia ratios, with regions of basal ganglia being differentially affected. For example, iron to astroglia ratio showed age-related increases in the substantia nigra and globus pallidus, while the ratio was decreased in the striatum. Meanwhile, copper and zinc to astroglia ratios showed a similar regional decline. Our findings suggest that inflammation at the choroid plexus, part of the blood-cerebrospinal-fluid barrier, prompts accumulation of, particularly, copper and iron in the ventricles, implying a compromised barrier system. Moreover, age-related glial dystrophy/senescence appears to disrupt metal homeostasis, likely due to induced oxidative stress, and hence increase the risk of neurodegenerative diseases.

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Abstract: The ability to manipulate the composition of semiconductor alloys on-demand and at nanometer-scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic bandgap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, post-deposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser-driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the constant laser scan speed to achieve indefinitely long Si1-xGex microstructures exhibiting the full range of compositions (0

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Abstract: The use of solar energy to activate chemical pathways in a sustainable manner drives the development in photocatalysis. While catalyst optimisation is a major theme in this pursuit, the development of novel photocatalytic reactors to enhance productivity is also imperative. In this work we combine, for the first time, microstructured optical fibre technology with photocatalysis, creating a photocatalytic microreactor coated with titania decorated with palladium nanoparticles. By doing so, we can create a system capable of effectively combining photons, liquids and gases within a monolithic, highly confined, transparent silica geometry. We utilise a range of characterisation techniques to selectively focus on the photocatalyst that resides exclusively within the internal capillaries of this system. In doing so we validate our design approach, and demonstrate the ability to simultaneously control both nanoparticle size and metal content. Further, we justify our unique design, showing its activity in photocatalytic hydrogen generation from water. In doing so highlighting the importance in developing light propagation properties from optical fibres, and the significant potential of this technology in the expansive photocatalysis landscape.

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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: 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.