I08-Scanning X-ray Microscopy beamline (SXM)
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Open Access
Abstract: This study explores the delivery of phosphorus to the upper atmospheres of Earth, Mars, and Venus via the ablation of cosmic dust particles. Micron-size meteoritic particles were flash heated to temperatures as high as 2900 K in a Meteor Ablation Simulator (MASI), and the ablation of PO and Ca recorded simultaneously by laser induced fluorescence. Apatite grains were also ablated as a reference. The speciation of P in anhydrous chondritic porous Interplanetary Dust Particles was made by K-edge X-ray absorption near edge structure (XANES) spectroscopy, demonstrating that P mainly occurs in phosphate-like domains. A thermodynamic model of P in a silicate melt was then developed for inclusion in the Leeds Chemical Ablation Model (CABMOD). A Regular Solution model used to describe the distribution of P between molten stainless steel and a multicomponent slag is shown to provide the most accurate solution for a chondritic-composition, and reproduces satisfactorily the PO ablation profiles observed in the MASI. Meteoritic P is moderately volatile and ablates before refractory metals such as Ca; its ablation efficiency in the upper atmosphere is similar to Ni and Fe. The speciation of evaporated P depends significantly on the oxygen fugacity, and P should mainly be injected into planetary upper atmospheres as PO2, which will then likely undergo dissociation to PO (and possibly P) through hyperthermal collisions with air molecules. The global P ablation rates are estimated to be 0.017 t d−1 (tonnes per Earth day), 1.15 × 10−3 t d−1 and 0.024 t d−1 for Earth, Mars and Venus, respectively.
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Apr 2020
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[19228, 22730]
Abstract: Hydrothermal carbonisation (HTC) has been demonstrated to be a sustainable thermochemical process, capable of producing functionalised carbon materials for a wide range of applications. In order to better apply such materials, the local chemistry and reaction pathways governing hydrothermal carbon growth must be understood. We report the use of scanning transmission X-ray microscopy (STXM) to observe chemical changes in functionality of carbon between the interface and bulk regions of HTC. Spatially-resolved, element-specific X-ray photo-absorption spectra show the presence of differing local carbon chemistry between bulk “core” and interface “shell” regions of a glucose-derived hydrothermal carbon spherule. STXM provides direct evidence to suggest that mechanistic pathways differ between the core and shell of the hydrothermal carbon. In the shell region, at the water-carbon interface, more aldehyde and/or carboxylic species are suspected to provide a reactive interface for bridging reactions to occur with local furan-based monomers. In contrast, condensation reactions appear to dominate in the core, removing aryl-linking units between polyfuranic domains. The application of STXM to HTC presents opportunities for a more comprehensive understanding of the spatial distribution of carbon species within hydrothermal carbon, especially at the solvent-carbon interface.
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Jan 2020
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Data acquisition
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A. D.
Parsons
,
S.
Ahmed
,
M.
Basham
,
D.
Bond
,
B.
Bradnick
,
M.
Burt
,
T.
Cobb
,
N.
Dougan
,
M.
Drakopoulos
,
F.
Ferner
,
J.
Filik
,
C.
Forrester
,
L.
Hudson
,
P.
Joyce
,
B.
Kaulich
,
A.
Kavva
,
J.
Kelly
,
J.
Mudd
,
B.
Nutter
,
P.
Quinn
,
K.
Ralphs
,
C.
Reinhard
,
J.
Shannon
,
M.
Taylor
,
T.
Trafford
,
X.
Tran
,
E.
Warrick
,
A.
Wilson
,
A. D.
Winter
Open Access
Abstract: We present a beamline analogue, capable of system pro- totyping, integrated development and testing, specifically designed to provide a facility for full scientific testing of instrument prototypes. With an identical backend to real beamline instruments the P99 development rig has allowed increased confidence and troubleshooting ahead of final scientific commissioning. We present detail of the software and hardware components of this environment and how these have been used to develop functionality for the new operational instruments. We present several high impact examples of such integrated prototyping development in- cluding the instrumentation for DIAD (integrated Dual Im- aging And Diffraction) and the J08 (Soft X-ray ptychogra- phy) beamline end station.
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Oct 2019
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I08-Scanning X-ray Microscopy beamline (SXM)
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Alastair J. M.
Lough
,
Douglas P.
Connelly
,
William B.
Homoky
,
Jeffrey A.
Hawkes
,
Valerie
Chavagnac
,
Alain
Castillo
,
Majid
Kazemian
,
Ko-ichi
Nakamura
,
Tohru
Araki
,
Burkhard
Kaulich
,
Rachel A.
Mills
Diamond Proposal Number(s):
[12738]
Open Access
Abstract: Iron (Fe) limits primary productivity and nitrogen fixation in large regions of the world’s oceans. Hydrothermal supply of Fe to the global deep ocean is extensive; however, most of the previous work has focused on examining high temperature, acidic, focused flow on ridge axes that create “black smoker” plumes. The contribution of other types of venting to the global ocean Fe cycle has received little attention. To thoroughly understand hydrothermal Fe sources to the ocean, different types of vent site must be compared. To examine the role of more diffuse, higher pH sources of venting, a hydrothermal plume above the Von Damm vent field (VDVF) was sampled for Total dissolvable Fe (unfiltered, TDFe), dissolved Fe (<0.2 μm, dFe) and soluble Fe (<0.02 μm, sFe). Plume particles sampled in situ were characterized using scanning electron microscopy and soft X-ray spectromicroscopy. The VDVF vents emit visibly clear fluids with particulate Fe (TDFe-dFe, >0.2 μm) concentrations up to 196 nmol kg–1 comparable to concentrations measured in black smoker plumes on the Mid-Atlantic Ridge. Colloidal Fe (cFe) and sFe increased as a fraction of TDFe with decreasing TDFe concentration. This increase in the percentage of sFe and cFe within the plume cannot be explained by settling of particulates or mixing with background seawater. The creation of new cFe and sFe within the plume from the breakdown of pFe is required to close the Fe budget. We suggest that the proportional increase in cFe and sFe reflects the entrainment, breakdown and recycling of Fe bearing organic particulates near the vents. Fe plume profiles from the VDVF differ significantly from previous studies of “black smoker” vents where formation of new pFe in the plume decreases the amount of cFe. Formation and removal of Fe-rich colloids and particles will control the amount and physico-chemical composition of dFe supplied to the deep ocean from hydrothermal systems. This study highlights the differences in the stabilization of hydrothermal Fe from an off-axis diffuse source compared to black smokers. Off-axis diffuse venting represent a potentially significant and previously overlooked Fe source to the ocean due to the difficulties in detecting and locating such sites.
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Jul 2019
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[12738]
Abstract: Iron (Fe) limits or co-limits primary productivity and nitrogen fixation in large regions of the world's oceans, and the supply of Fe from hydrothermal vents to the deep ocean is now known to be extensive. However, the mechanisms that control the amount of hydrothermal Fe that is stabilized in the deep ocean, and thus dictate the impact of hydrothermal Fe sources on surface ocean biogeochemistry, are unclear. To learn more, we have examined the dispersion of total dissolvable Fe (TDFe), dissolved Fe (dFe) and soluble Fe (sFe) in the buoyant and non-buoyant hydrothermal plume above the Beebe vent field, Caribbean Sea. We have also characterized plume particles using electron microscopy and synchrotron based spectromicroscopy.
We show that the majority of dFe in the Beebe hydrothermal plume was present as colloidal Fe (dFe − sFe = cFe). During ascent of the buoyant plume, a significant fraction of particulate Fe (pFe = TDFe − dFe) was lost to settling and exchange with colloids. Conversely, the opposite was observed in the non-buoyant plume, where pFe concentrations increased during non-buoyant plume dilution, cFe concentrations decreased apparently due to colloid aggregation. Elemental mapping of carbon, oxygen and iron in plume particles reveals their close association and indicates that exchanges of Fe between colloids and particles must include transformations of organic carbon and Fe oxyhydroxide minerals. Notably, sFe is largely conserved during plume dilution, and this is likely to be due to stabilization by organic ligands, in contrast to the more dynamic exchanges between pFe and cFe.
This study highlights that the size of the sFe stabilizing ligand pool, and the rate of iron-rich colloid aggregation will control the amount and physico-chemical composition of dFe supplied to the ocean interior from hydrothermal systems. Both the ligand pool, and the rate of cFe aggregation in hydrothermal plumes remain uncertain and determining these are important intermediate goals to more accurately assess the impact of hydrothermalism on the ocean's carbon cycle.
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Jan 2019
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I08-Scanning X-ray Microscopy beamline (SXM)
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Abstract: Primitive CO3 carbonaceous chondrite meteorites provide a detailed record of the geological processes and events that have shaped our solar system over the last 4.5 billion years. They contain a fine-grained (≤ 1 μm) matrix (> 50 vol%) of amorphous and crystalline silicates, oxides, sulphides and metals that have remained largely unaltered since the time they accreted into an asteroid. The matrix of CO3 carbonaceous chondrites also contains ~5 wt% carbon in a wide variety of organic materials including soluble molecules, kerogen-like insoluble organic matter (IOM), and carbonaceous nanoglobules. The formation and evolution of the organic materials and their relationship to the mineralogy remains poorly understood mainly because of the fine-grained and heterogeneous nature of the matrix. However, new analytical techniques are now making it possible to study the relationship between organics and minerals in extra-terrestrial materials in-situ at high spatial resolution. Here, we present C K-edge X-ray absorption near edge structure (XANES) analyses of carbonaceous phases in the CO chondrites DOM 08006, NWA 7892 and Moss.
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Dec 2018
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I08-Scanning X-ray Microscopy beamline (SXM)
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Abstract: Fluoroacetate (FA), a plant toxin and intermediate product of anticancer agents, integrates itself into the Krebs cycle by substituting for acetate to form fluorocitrate. The function of this key metabolic cycle in glucose metabolism is disabled when fluorocitrate binds to aconitase. FA purportedly disrupts the Krebs cycle selectively in non-neuronal cells, i.e. glia/astrocytes, making it the substance of choice by which to assess the importance of glia for brain function in the living animal. However, since acetate, considered a marker of glial oxidative metabolism, can also be transported into neurons begs the question whether FA uptake, metabolism, and compartmentation is glial-selective in vivo, and whether this can be experimentally imaged; as important, is whether the first phase of brain glucose metabolism, i.e. glycolysis is affected. Dynamic cerebral 18FDG (glucose) PET in the living rat, and low energy x-ray fluorescence chemical imaging of such brains, albeit freeze substitution-fixed and epon infiltrated, were implemented to address these questions, and enabled testing our working hypothesis that sexual dimorphism of brain structure and function extends to metabolism as well.
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Aug 2018
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[11016]
Open Access
Abstract: Glaciers and ice sheets are a significant source of nanoparticulate Fe, which is potentially important in sustaining the high productivity observed in the near-coastal regions proximal to terrestrial ice cover. However, the bioavailability of particulate iron is poorly understood, despite its importance in the ocean Fe inventory. We combined high-resolution imaging and spectroscopy to investigate the abundance, morphology and valence state of particulate iron in glacial sediments. Our results document the widespread occurrence of amorphous and Fe(II)-rich and Fe(II)-bearing nanoparticles in Arctic glacial meltwaters and iceberg debris, compared to Fe(III)-rich dominated particulates in an aeolian dust sample. Fe(II) is thought to be highly biolabile in marine environments. Our work shows that glacially derived Fe is more labile than previously assumed, and consequently that glaciers and ice sheets are therefore able to export potentially bioavailable Fe(II)-containing nanoparticulate material to downstream ecosystems, including those in a marine setting. Our findings provide further evidence that Greenland Ice Sheet meltwaters may provide biolabile particulate Fe that may fuel the large summer phytoplankton bloom in the Labrador Sea, and that Fe(II)-rich particulates from a region of very high productivity downstream of a polar ice sheet may be glacial in origin.
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Jul 2018
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[14799, 17780]
Open Access
Abstract: We are investigating the effects of thermal meta-morphism on crystalline and amorphous silicates in the matrices of CO carbonaceous chondrites, which range in petrologic type from 3.0 to 3.8. Our aim is to better understand the initial formation conditions of the sili-cates, and to quantify how the degree of asteroidal heating has influenced their abundance, structure, chemistry and transformation behaviour. Here we pre-sent results from the CO chondrites DOM 08006 (CO 3.0), Kainsaz (CO 3.2) and Moss (CO 3.6).
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Mar 2018
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[11426]
Open Access
Abstract: Many studies have described petrographic evidence for in situ aqueous alteration
on the asteroid parent body(ies) of CM chondrites [1]. However, the origin of finegrained
rims (FGRs) of phyllosilicates that surround pristine anhydrous fragments in
CM chondrites remains controversial. The textures of FGRs suggest that they formed
through accretion onto their host objects, but it’s not clear whether hydration of the
dust occurred in a nebula [2] or asteroid [3] environment. The settings of aqueous
alteration in the early solar system may be inferred from crystal chemical variations
within the sub-micron mineralogy of FGRs and matrix within the CM chondrites.
Using synchrotron μXANES we observed systematic variations in Fe3+/ΣFe
across FGRs but not within the matrix [4]. To identify the source of this variation we
used STXM and nanoscale XRF to compare the crystal-chemical relationships of the
matrix mineralogy with that of the FGRs. Changes in Fe L- and O K-edge spectra
from matrix areas can be attributed to oxide and phyllosilicate minerals. For FGRs,
small changes in the relative intensities of the Fe L3 edge main peaks suggest
variations in the Fe3+/ΣFe ratio. More grain-scale variability is observed in the FGR
than in the matrix, and Fe-sulphides are detected in the FGR but not in the matrix.
Our data show that the composition of the FGR is mineralogically distinct from
the matrix, showing it was surrounding the chondrules in their nebular sojourn prior to
accretion and hence has sampled a different reservoir of dust to the matrix. A
possible explanation for the data is the incorporation of ice and/or carbonaceous
grains in the FGR which would cause local variability in redox states when these
phases reacted on the asteroidal parent body.
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Dec 2017
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