I07-Surface & interface diffraction
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Cem
Ornek
,
Fan
Zhang
,
Alfred
Larsson
,
Mubashir
Mansoor
,
Gary S.
Harlow
,
Robin
Kroll
,
Francesco
Carla
,
Hadeel
Hussain
,
Dirk L.
Engelberg
,
Bora
Derin
,
Jinshan
Pan
Diamond Proposal Number(s):
[23388]
Open Access
Abstract: The passive film stability on stainless steel can be affected by hydrogen absorption and lead to microstructure embrittlement. This work shows that the absorption of hydrogen results in surface degradation due to oxide reduction and ionic defect generation within the passive film, which decomposes and eventually vanishes. The passive film provides a barrier to entering hydrogen, but when hydrogen is formed, atomic hydrogen infuses into the lattices of the austenite and ferrite phases, causing strain evolution, as shown by synchrotron x-ray diffraction data. The vacancy concentration and hence the strains increase with increasing electrochemical cathodic polarization. Under cathodic polarization, the surface oxides are thermodynamically unstable, but the complete reduction is kinetically restrained. As a result, surface oxides remain present under excessive cathodic polarization, contesting the classical assumption that oxides are easily removed. Density-functional theory calculations have shown that the degradation of the passive film is a reduction sequence of iron and chromium oxide, which causes thinning and change of the semiconductor properties of the passive film from n-type to p-type. As a result, the surface loses its passivity after long cathodic polarization and becomes only a weak barrier to hydrogen absorption and hence hydrogen embrittlement.
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Aug 2023
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[28557]
Open Access
Abstract: Swelling of shale in response to interaction with water is an important consideration within subsurface energy systems. In the case of waste disposal, swelling can provide important barriers around the waste and enhance the sealing ability of rocks. For shale gas exploration purpose, however, swelling may cause wellbore instability. Therefore, a careful study of shale swelling is critical for subsurface energy related applications. Here, the swelling effects of shale were imaged at nanoscale using an advanced synchrotron Transmission X-ray Microscopy (TXM) imaging technique for the first time, with a spatial resolution down to 40.9 nm. Organic matter and clays within the analysed sample were observed to display large swelling effects which resulted in a 50% reduction in porosity. Strain maps generated using Digital Volume Correlation (DVC) show deformation and significant strain were mostly localized to between the contact boundaries of sharp brittle minerals and softer organic matter and clays. This is the first study, to our knowledge, to directly image the swelling deformation of shale at the tens of nanometer scale and provide local information on the strain evolution.
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Jul 2023
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I10-Beamline for Advanced Dichroism
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Open Access
Abstract: Element-specific spectroscopies using synchrotron-radiation can provide unique insights into materials properties. The recently developed technique of X-ray detected ferromagnetic resonance (XFMR) allows studying the magnetization dynamics of magnetic spin structures. Magnetic sensitivity in XFMR is obtained from the X-ray magnetic circular dichroism (XMCD) effect, where the phase of the magnetization precession of each magnetic layer with respect to the exciting radio frequency is obtained using stroboscopic probing of the spin precession. Measurement of both amplitude and phase response in the magnetic layers as a function of bias field can give a clear signature of spin-transfer torque (STT) coupling between ferromagnetic layers due to spin pumping. In the last few years, there have been new developments utilizing X-ray scattering techniques to reveal the precessional magnetization dynamics of ordered spin structures in the GHz frequency range. The techniques of diffraction and reflectometry ferromagnetic resonance (DFMR and RFMR) provide novel ways for the probing of the dynamics of chiral and multilayered magnetic materials, thereby accessing key information relevant to the engineering and development of high-density and low-energy consumption data processing solutions.
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Jul 2023
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B18-Core EXAFS
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Diamond Proposal Number(s):
[15151]
Abstract: Lignin is one of the most promising feedstocks for renewable aromatics production. Conversion of such feedstock into aromatics can be attained through catalytic hydrogenolysis. In this work, NixFey/TiN bimetallic catalysts were evaluated in the hydrogenolysis of both: (i) benzyl phenyl ether (BPE) as a model compound for lignin and (ii) real organosolv lignin feedstock under low temperature (150 °C) and low H2 pressure (12 bar). All bimetallic catalysts exhibited superior performance over single-component materials and were shown to compose of uniformly/highly dispersed and intimately mixed Ni and Fe nanoparticles. Among bimetallic materials, Ni5Fe2/TiN possesses the highest activity in BPE hydrogenolysis, which is comparable to that of a 5% Pd/C commercial catalyst while showing significantly higher aromatic selectivity. Ni5Fe2/TiN catalyst also outperformed Pd/C in hydrogenolysis of organosolv lignin, shown by its higher oil yield, greater content of phenolic monomers, and lower content of dimers. This material exhibited good stability in BPE conversion with no noticeable deactivation over 5 recycling cycles. XANES analysis suggests the electron transfer from Ni to Fe, which explains the superior activity observed with Ni5Fe2/TiN.
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Jul 2023
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VMXi-Versatile Macromolecular Crystallography in situ
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Halina
Mikolajek
,
Juan
Sanchez-Weatherby
,
James
Sandy
,
Richard J.
Gildea
,
Ivan
Campeotto
,
Harish
Cheruvara
,
John D.
Clarke
,
Toshana
Foster
,
Sotaro
Fujii
,
Ian T.
Paulsen
,
Bhumika S.
Shah
,
Michael A.
Hough
Open Access
Abstract: The utility of X-ray crystal structures determined under ambient-temperature conditions is becoming increasingly recognized. Such experiments can allow protein dynamics to be characterized and are particularly well suited to challenging protein targets that may form fragile crystals that are difficult to cryo-cool. Room-temperature data collection also enables time-resolved experiments. In contrast to the high-throughput highly automated pipelines for determination of structures at cryogenic temperatures widely available at synchrotron beamlines, room-temperature methodology is less mature. Here, the current status of the fully automated ambient-temperature beamline VMXi at Diamond Light Source is described, and a highly efficient pipeline from protein sample to final multi-crystal data analysis and structure determination is shown. The capability of the pipeline is illustrated using a range of user case studies representing different challenges, and from high and lower symmetry space groups and varied crystal sizes. It is also demonstrated that very rapid structure determination from crystals in situ within crystallization plates is now routine with minimal user intervention.
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Jul 2023
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I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[21970]
Open Access
Abstract: Oral and gut microbiomes are important for the maintenance of homeostasis in the human body. Altered or disturbed mutualism between their members results in dysbiosis with local injury and subsequent systemic diseases. The high bacterial density causes intense competition among microbiome residents to acquire nutrients, including iron and heme, the latter of high importance for heme auxotrophic members of the Bacteroidetes phylum. Our main hypothesis is that the heme acquisition mechanism, with the leading role played by a novel HmuY family of hemophore-like proteins, can be used to fulfill nutritional requirements and increase virulence. We characterized HmuY homologs expressed by Bacteroides fragilis and compared their properties with the first representative of this family, the HmuY protein of Porphyromonas gingivalis. In contrast to other Bacteroidetes members, B. fragilis produces three HmuY homologs (Bfr proteins). All bfr transcripts were produced at higher levels in bacteria starved of iron and heme (fold change increase ~60, ~90, and ~70 for bfrA, bfrB, and bfrC, respectively). X-ray protein crystallography showed that B. fragilis Bfr proteins are structurally similar to P. gingivalis HmuY and to other homologs, except for differences in the potential heme-binding pockets. BfrA binds heme, mesoheme, and deuteroheme, but preferentially under reducing conditions, using Met175 and Met146 to coordinate heme iron. BfrB binds iron-free protoporphyrin IX and coproporphyrin III, whereas BfrC does not bind porphyrins. HmuY is capable of heme sequestration from BfrA, which might increase the ability of P. gingivalis to cause dysbiosis also in the gut microbiome.
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Jul 2023
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[23975]
Abstract: The strength and fracture toughness of Additively Manufactured (AM) components are significantly influenced by the concentration and size of oxides and precipitate inclusions within the build powders. These features are highly sensitive to powder production parameters, as well as the number of times a powder has been reused. In this study synchrotron X-ray powder diffraction was performed in an inert atmosphere at room temperature and during in-situ heating, providing crucial insights into growth rates and distribution of oxides and precipitates as a function of temperature. From the high angular resolution data collected, the structural refinement showed that plasma wire arc atomisation shows lower residual strain than gas atomised powder samples at room temperature after atomisation likely due to lower temperatures achieved during the production process. Additionally, the results from the diffraction patterns collected during in-situ heating provide key insights to the four metal powders considered in this study, Ti-6Al-4 V, Ni718, AlSi10Mg, and Scalmalloy. This paper also highlights the potential that using synchrotron X-ray diffraction to study AM parts and constituent AM powder has to gain crucial insight into material properties and the build reliability of end use production quality parts from AM.
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Jun 2023
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I07-Surface & interface diffraction
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Cem
Ornek
,
Mubashir
Mansoor
,
Alfred
Larsson
,
Fan
Zhang
,
Gary S.
Harlow
,
Robin
Kroll
,
Francesco
Carla
,
Hadeel
Hussain
,
Bora
Derin
,
Ulf
Kivisäkk
,
Dirk L.
Engelberg
,
Edvin
Lundgren
,
Jinshan
Pan
Diamond Proposal Number(s):
[23388]
Open Access
Abstract: Various mechanisms have been proposed for hydrogen embrittlement of duplex stainless steel, but the causation of hydrogen-induced material degradation has remained unclear. This work shows that phase instability (decomposition) of the austenite phase and ductile-to-brittle transition of the ferrite phase precedes hydrogen embrittlement. In-situ diffraction measurements revealed that Ni-rich sites of the austenite phase decompose into metastable hydrides. Hydride formation is possible by increasing the hydrogen chemical potential during electrochemical charging and low defect formation energy of hydrogen interstitials. Our findings demonstrate that hydrogen embrittlement can only be understood if measured in situ and in real-time during the embrittlement process.
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Jun 2023
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[28804]
Open Access
Abstract: Melt flow is critical to build quality during additive manufacturing (AM). When an external magnetic field is applied, it causes forces that alter the flow through the thermoelectric magnetohydrodynamic (TEMHD) effect, potentially altering the final microstructure. However, the extent of TEMHD forces and their underlying mechanisms, remain unclear. We trace the flow of tungsten particles using in situ high-speed synchrotron X-ray radiography and ex situ tomography to reveal the structure of TEMHD-induced flow during directed energy deposition AM (DED-AM). When no magnetic field is imposed, Marangoni convection dominates the flow, leading to a relatively even particle distribution. With a magnetic field parallel to the scan direction, TEMHD flow is induced, circulating in the cross-sectional plane, causing particle segregation to the bottom and side of the pool. Further, a downward magnetic field causes horizontal circulation, segregating particles to the other side. Our results demonstrate that TEMHD can disrupt melt pool flow during DED-AM.
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Jun 2023
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[24948]
Open Access
Abstract: Chagas disease is a neglected tropical disease (NTD) caused by Trypanosoma cruzi, whilst leishmaniasis, which is caused by over 20 species of Leishmania, represents a group of NTDs endemic to most countries in the tropical and subtropical belt of the planet. These diseases remain a significant health problem both in endemic countries and globally. These parasites and other trypanosomatids, including T. theileri, a bovine pathogen, rely on cysteine biosynthesis for the production of trypanothione, which is essential for parasite survival in hosts. The de novo pathway of cysteine biosynthesis requires the conversion of O-acetyl-L-serine into L-cysteine, which is catalysed by cysteine synthase (CS). These enzymes present potential for drug development against T. cruzi, Leishmania spp. and T. theileri. To enable these possibilities, biochemical and crystallographic studies of CS from T. cruzi (TcCS), L. infantum (LiCS) and T. theileri (TthCS) were conducted. Crystal structures of the three enzymes were determined at resolutions of 1.80 Å for TcCS, 1.75 Å for LiCS and 2.75 Å for TthCS. These three homodimeric structures show the same overall fold and demonstrate that the active-site geometry is conserved, supporting a common reaction mechanism. Detailed structural analysis revealed reaction intermediates of the de novo pathway ranging from an apo structure of LiCS and holo structures of both TcCS and TthCS to the substrate-bound structure of TcCS. These structures will allow exploration of the active site for the design of novel inhibitors. Additionally, unexpected binding sites discovered at the dimer interface represent new potential for the development of protein–protein inhibitors.
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Jun 2023
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