I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[20611]
Open Access
Abstract: Arc welding is one of the widely used approaches for joining metals. During the arc welding process, an electric arc creates intense heat to fuse metals that forms the melt pool between the parts to be welded together. Intensive flow fields are observable within the fusion weld pools as a result of multiple driving forces. The flow patterns within the melt pool significantly determine the shape of the weld joint and other attributes of the solidified joint, such as microstructure and defects. Porosity is one of the solidification-related defects that can bring a detrimental impact. During the formation and solidification of weld pools, gas bubbles that are formed can be driven in or out from the pool by the flow. In this work, employing in situ synchrotron X-rays, we have observed how different flow conditions and air-liquid interface are contributed to retaining and releasing the gas bubbles that formed during the arc welding. The results suggest that underpinning driving forces, such as electromagnetic forces, act on molten metal to retain the pores inside the weld joints; but, gravity-driven effects can contribute to reduce the porosity, with appropriate process conditions
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Jan 2023
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I03-Macromolecular Crystallography
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Silvia
Gaggero
,
Jonathan
Martinez-Fabregas
,
Adeline
Cozzani
,
Paul K.
Fyfe
,
Malo
Leprohon
,
Jie
Yang
,
F. Emil
Thomasen
,
Hauke
Winkelmann
,
Romain
Magnez
,
Alberto G.
Conti
,
Stephan
Wilmes
,
Elizabeth
Pohler
,
Manuel
Van Gijsel Bonnello
,
Xavier
Thuru
,
Bruno
Quesnel
,
Fabrice
Soncin
,
Jacob
Piehler
,
Kresten
Lindorff-Larsen
,
Rahul
Roychoudhuri
,
Ignacio
Moraga
,
Suman
Mitra
Abstract: Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin-2 (IL-2), a cytokine critical to T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation, and antitumor immunity by CD8+ T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Rα with higher affinity, triggers STAT5 activation, and drives CD8+ T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Last, we show that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.
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Dec 2022
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Krios I-Titan Krios I at Diamond
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Open Access
Abstract: Gene transcription is carried out by RNA polymerase (RNAP) and requires the conversion of the initial closed promoter complex, where DNA is double stranded, to a transcription-competent open promoter complex, where DNA is opened up. In bacteria, RNAP relies on σ factors for its promoter specificities. Using a special form of sigma factor (σ54), which forms a stable closed complex and requires its activator that belongs to the AAA+ ATPases (ATPases associated with diverse cellular activities), we obtained cryo–electron microscopy structures of transcription initiation complexes that reveal a previously unidentified process of DNA melting opening. The σ54 amino terminus threads through the locally opened up DNA and then becomes enclosed by the AAA+ hexameric ring in the activator-bound intermediate complex. Our structures suggest how ATP hydrolysis by the AAA+ activator could remove the σ54 inhibition while helping to open up DNA, using σ54 amino-terminal peptide as a pry bar.
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Dec 2022
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[25542]
Open Access
Abstract: The realisation of post-combustion CO2 capture (PCCC) at industrial scale remains limited; one challenge is the concerns around capital costs and another concern is corrosion of the system itself. Corrosion resistance and mitigation against the amine solvent monoethanolamine (MEA) was studied, using the inhibitor copper (II) carbonate basic (CC). Carbon steel (C1018) was tested in CO2 loaded, 5M aqueous MEA solution, alone and in the presence of CC, to assess the corrosivity of the solution. Immersion testing used mass loss, Fe and Cu ion concentration in solution via ICP-MS, imaging (SEM) and analytical techniques (XRD and EDX) to investigate the effect of corrosion. Generally, the use of CC improved C1018 corrosion resistance relative to C1018 alone. Even at low concentrations (0.9 mM), CC was effective in inhibiting corrosion against CO2 loaded MEA, as the observed corrosion rate was effectively zero and no dissolved Fe was detected in solution. There was no evidence of copper surface adsorption. To clarify the solution chemistry resulting in corrosion inhibition, the local chemical environment of Fe and Cu were probed by Cu and Fe K-edge X-ray Absorption Spectroscopy, respectively. The Cu K- edge HERFD-XANES spectra reveal that a Cu2+ amine complex forms, critical to understanding the structure which is promoting significant corrosion inhibition.
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Dec 2022
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B18-Core EXAFS
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Connaugh M.
Fallon
,
William R.
Bower
,
Brian A.
Powell
,
Francis R.
Livens
,
Ian C.
Lyon
,
Alana E.
Mcnulty
,
Kathryn
Peruski
,
J. Frederick W.
Mosselmans
,
Daniel I.
Kaplan
,
Daniel
Grolimund
,
Peter
Warnicke
,
Dario
Ferreira-Sanchez
,
Marja Siitari
Kauppi
,
Gianni F.
Vettese
,
Samuel
Shaw
,
Katherine
Morris
,
Gareth T. W.
Law
Diamond Proposal Number(s):
[16611, 16939, 17243]
Open Access
Abstract: Uranium dioxide (UO2) and metaschoepite (UO3•nH2O) particles have been identified as contaminants at nuclear sites. Understanding their behavior and impact is crucial for safe management of radioactively contaminated land and to fully understand U biogeochemistry. The Savannah River Site (SRS) (South Carolina, USA), is one such contaminated site, following historical releases of U-containing wastes to the vadose zone. Here, we present an insight into the behavior of these two particle types under dynamic conditions representative of the SRS, using field lysimeters (15 cm D x 72 cm L). Discrete horizons containing the different particle types were placed at two depths in each lysimeter (25 cm and 50 cm) and exposed to ambient rainfall for 1 year, with an aim of understanding the impact of dynamic, shallow subsurface conditions on U particle behavior and U migration. The dissolution and migration of U from the particle sources and the speciation of U throughout the lysimeters was assessed after 1 year using a combination of sediment digests, sequential extractions, and bulk and μ-focus X-ray spectroscopy. In the UO2 lysimeter, oxidative dissolution of UO2 and subsequent migration of U was observed over 1–2 cm in the direction of waterflow and against it. Sequential extractions of the UO2 sources suggest they were significantly altered over 1 year. The metaschoepite particles also showed significant dissolution with marginally enhanced U migration (several cm) from the sources. However, in both particle systems the released U was quantitively retained in sediment as a range of different U(IV) and U(VI) phases, and no detectable U was measured in the lysimeter effluent. The study provides a useful insight into U particle behavior in representative, real-world conditions relevant to the SRS, and highlights limited U migration from particle sources due to secondary reactions with vadose zone sediments over 1 year.
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Dec 2022
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E02-JEM ARM 300CF
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Haobo
Dong
,
Ruirui
Liu
,
Xueying
Hu
,
Fangjia
Zhao
,
Liqun
Kang
,
Longxiang
Liu
,
Jianwei
Li
,
Yeshu
Tan
,
Yongquan
Zhou
,
Dan J. L.
Brett
,
Guanjie
He
,
Ivan
Parkin
Diamond Proposal Number(s):
[30614, 29809]
Open Access
Abstract: A stable cathode–electrolyte interface (CEI) is crucial for aqueous zinc-ion batteries (AZIBs), but it is less investigated. Commercial binder poly(vinylidene fluoride) (PVDF) is widely used without scrutinizing its suitability and cathode-electrolyte interface (CEI) in AZIBs. A water-soluble binder is developed that facilitated the in situ formation of a CEI protecting layer tuning the interfacial morphology. By combining a polysaccharide sodium alginate (SA) with a hydrophobic polytetrafluoroethylene (PTFE), the surface morphology, and charge storage kinetics can be confined from diffusion-dominated to capacitance-controlled processes. The underpinning mechanism investigates experimentally in both kinetic and thermodynamic perspectives demonstrate that the COO− from SA acts as an anionic polyelectrolyte facilitating the adsorption of Zn2+; meanwhile fluoride atoms on PTFE backbone provide hydrophobicity to break desolvation penalty. The hybrid binder is beneficial in providing a higher areal flux of Zn2+ at the CEI, where the Zn-Birnessite MnO2 battery with the hybrid binder exhibits an average specific capacity 45.6% higher than that with conventional PVDF binders; moreover, a reduced interface activation energy attained fosters a superior rate capability and a capacity retention of 99.1% in 1000 cycles. The hybrid binder also reduces the cost compared to the PVDF/NMP, which is a universal strategy to modify interface morphology.
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Dec 2022
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Open Access
Abstract: In this paper we carry out a surface study of promising supported solid acid catalysts commonly used for the production of high value chemicals derived from glycerol. In particular, γ, θ and α alumina (Al2O3) were modified by (i) grafting with 5 wt% zirconia, (ii) doping with 30 wt% silicotungstic acid (STA), and (iii) using both zirconia and STA. The aim is to rationalise the effect of these different parameters on structural properties and surface adsorption through a comprehensive multi-technique approach, including recently developed NMR relaxation techniques. XRD and laser Raman spectroscopy confirmed a strong interaction between STA and the γ-/θ-Al2O3 resulting in a distortion of the supported STA Keggin structure relative to that of bulk STA. Conversely, a much weaker interaction between the supported STA and α-Al2O3 was measured. NMR relaxation demonstrated that the STA doping increases the adsorption properties of the catalyst, particularly for γ-/θ-Al2O3. For catalysts based on α-Al2O3, such effect was negligible. Thermogravimetric/differential thermogravimetry (TGA/DTG) analysis suggested that zirconia-grafted and non-grafted θ-Al2O3 and γ-Al2O3 are suitable materials for increasing the thermal stability of STA whereas α-Al2O3 (both grafted and non-grafted) does not improve the thermal stability of STA.
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Dec 2022
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I09-Surface and Interface Structural Analysis
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Open Access
Abstract: Understanding a material’s electronic structure is crucial to the development of many functional devices from semiconductors to solar cells and Li-ion batteries. A material’s properties, including electronic structure, are dependent on the arrangement of its atoms. However, structure determination (the process of uncovering the atomic arrangement), is impeded, both experimentally and computationally, by disorder. The lack of a verifiable atomic model presents a huge challenge when designing functional amorphous materials. Such materials may be characterised through their local atomic environments using, for example, solid-state NMR and XAS. By using these two spectroscopy methods to inform the sampling of configurations from ab initio molecular dynamics we devise and validate an amorphous model, choosing amorphous alumina to illustrate the approach due to its wide range of technological uses. Our model predicts two distinct geometric environments of AlO5 coordination polyhedra and determines the origin of the pre-edge features in the Al K-edge XAS. From our model we construct an average electronic density of states for amorphous alumina, and identify localized states at the conduction band minimum (CBM). We show that the presence of a pre-edge peak in the XAS is a result of transitions from the Al 1s to Al 3s states at the CBM. Deconvoluting this XAS by coordination geometry reveals contributions from both AlO4 and AlO5 geometries at the CBM give rise to the pre-edge, which provides insight into the role of AlO5 in the electronic structure of alumina. This work represents an important advance within the field of solid-state amorphous modelling, providing a method for developing amorphous models through the comparison of experimental and computationally derived spectra, which may then be used to determine the electronic structure of amorphous materials.
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Dec 2022
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B18-Core EXAFS
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Diamond Proposal Number(s):
[15151]
Open Access
Abstract: The perovskite CaCu3Ti4O12 is known for its ability to photocatalytically degrade model dye molecules using visible light. Here in we show the influence of ball milling on the catalysts structure and performance in the degradation of Rhodamine B. The surface area of CaCu3Ti4O12 increased from 1 m2g-1 to >80 m2g-1 on milling with a retention of 96% CaCu3Ti4O12 phase purity, as determined by X-ray diffraction and extended X-ray absorption fine structure analysis. Multiple characterisation techniques showed an increase in structural defects on milling. Specifically, X-ray absorption near edge spectroscopy, supported by simulation, showed changes in the local electronic structure from the perspective of Cu and Ti. Photocatalytic degradation was notably higher with the milled sample than that observed for the as-synthesized sample, even after normalisation for surface area, with a doubling of surface normalised rate constant from 4.91x10-4 to 9.11x10-4 L min-1m2. The improvement in catalytic performance can be correlated to the structural changes observed.
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Dec 2022
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I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[20221]
Open Access
Abstract: De novo design methods hold the promise of reducing the time and cost of antibody discovery while enabling the facile and precise targeting of predetermined epitopes. Here, we describe a fragment-based method for the combinatorial design of antibody binding loops and their grafting onto antibody scaffolds. We designed and tested six single-domain antibodies targeting different epitopes on three antigens, including the receptor-binding domain of the SARS-CoV-2 spike protein. Biophysical characterization showed that all designs are stable and bind their intended targets with affinities in the nanomolar range without in vitro affinity maturation. We further discuss how a high-resolution input antigen structure is not required, as similar predictions are obtained when the input is a crystal structure or a computer-generated model. This computational procedure, which readily runs on a laptop, provides a starting point for the rapid generation of lead antibodies binding to preselected epitopes.
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Nov 2022
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