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12,029 items found (0 items not approved), displaying 31 to 40.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I20-Scanning-X-ray spectroscopy (XAS/XES)	Mixed‐valence Ce/Zr metal‐organic frameworks: Controlling the oxidation state of cerium in one‐pot synthesis approach Maria Ronda‐lloret , Isaac Pellicer-Carreño , Aida Grau-Atienza , Roberto Boada , Sofia Diaz-Moreno , Javier Narciso‐romero , Juan Carlos Serrano‐ruiz , Antonio Sepulveda-Escribano , Enrique V. Ramos‐fernandez Advanced Functional Materials 4 DOI: 10.1002/adfm.202102582 Diamond Proposal Number(s): [19114] Show Abstract ▼ Abstract: The preparation of MOFs including a metal with an easily exchangeable oxidation state, while maintaining the same crystal structure and stability, is of paramount importance for myriad applications. In this work, a new synthesis method is reported that can be used to prepare Ce/Zr‐MOFs (UiO‐66 structure) having only Ce(III), a mixed‐valence Ce(IV)/Ce(III), or only Ce(IV) cations, as desired. The materials are characterized using a large number of techniques, including X‐ray absorption and X‐ray photoelectron spectroscopies.	May 2021
I12-JEEP: Joint Engineering, Environmental and Processing	An in-situ synchrotron diffraction study of stress relaxation in titanium: Effect of temperature and oxygen on cold dwell fatigue Yi Xiong , Phani S. Karamched , Chi-Toan Nguyen , David M. Collins , Nicolò Grilli , Christopher M. Magazzeni , Edmund Tarleton , Angus J. Wilkinson Acta Materialia 97 DOI: 10.1016/j.actamat.2021.116937 Diamond Proposal Number(s): [17222] Show Abstract ▼ Abstract: There is a long-standing technological problem in which a stress dwell during cyclic loading at room temperature in Ti causes a drastic fatigue life reduction. To better understand the material characteristics that control or exacerbate this behaviour, evaluation of the time dependent plasticity of the main prismatic and basal slip systems is critical. Incorporating the influence of operating temperatures and common alloying elements on cold dwell fatigue will be beneficial for future alloy design to address this problem. In this work, characterisation of the time dependent plastic behaviour of two commercially pure titanium samples (grade 1 and grade 4) with different oxygen content at 4 different temperatures (room temperature, 75 C, 145 C and 250 C) was performed during stress relaxation using synchrotron X-ray diffraction. Key parameters that govern the dislocation motion were determined for the major prismatic and basal slip systems as a function of temperature and oxygen content by calibrating a crystal plasticity finite element model with the measured lattice strain relaxation responses. From the temperatures assessed, 75 C was found to be the worse-case scenario, where the macroscopic plastic strain accumulation was significant during a relaxation cycle due to the greatest activity of both prism and basal slip systems. As the temperature increases, the contribution of thermal energy becomes greater than mechanical energy for dislocation glide. Oxygen was found to have a stronger strengthening effect on prism slip over basal slip, through a significant change in their respective critical resolved shear stresses. This effect becomes more significant in high oxygen content commercially pure Ti.	May 2021
I13-2-Diamond Manchester Imaging	A stacked dense denoising–segmentation network for undersampled tomograms and knowledge transfer using synthetic tomograms Dimitrios Bellos , Mark Basham , Tony Pridmore , Andrew P. French Machine Vision And Applications 32 DOI: 10.1007/s00138-021-01196-4 Diamond Proposal Number(s): [9396] Open Access Show Abstract ▼ Abstract: Over recent years, many approaches have been proposed for the denoising or semantic segmentation of X-ray computed tomography (CT) scans. In most cases, high-quality CT reconstructions are used; however, such reconstructions are not always available. When the X-ray exposure time has to be limited, undersampled tomograms (in terms of their component projections) are attained. This low number of projections offers low-quality reconstructions that are difficult to segment. Here, we consider CT time-series (i.e. 4D data), where the limited time for capturing fast-occurring temporal events results in the time-series tomograms being necessarily undersampled. Fortunately, in these collections, it is common practice to obtain representative highly sampled tomograms before or after the time-critical portion of the experiment. In this paper, we propose an end-to-end network that can learn to denoise and segment the time-series’ undersampled CTs, by training with the earlier highly sampled representative CTs. Our single network can offer two desired outputs while only training once, with the denoised output improving the accuracy of the final segmentation. Our method is able to outperform state-of-the-art methods in the task of semantic segmentation and offer comparable results in regard to denoising. Additionally, we propose a knowledge transfer scheme using synthetic tomograms. This not only allows accurate segmentation and denoising using less real-world data, but also increases segmentation accuracy. Finally, we make our datasets, as well as the code, publicly available.	May 2021
I04-1-Macromolecular Crystallography (fixed wavelength)	Comprehensive analysis of binding sites in tubulin Tobias Muhlethaler , Dario Gioia , Andrea Enrico Prota , May E. Sharpe , Andrea Cavalli , Michel O. Steinmetz Angewandte Chemie International Edition DOI: 10.1002/anie.202100273 Diamond Proposal Number(s): [17334] Open Access Show Abstract ▼ Abstract: Tubulin plays essential roles in vital cellular activities and is the target of a wide range of proteins and ligands. Here, using a combined computational and crystallographic fragment screening approach, we addressed the question of how many binding sites exist in tubulin. We identified 27 distinct sites, of which 11 have not been described previously, and analyzed their relationship to known tubulin–protein and tubulin–ligand interactions. We further observed an intricate pocket communication network and identified 56 chemically diverse fragments that bound to 10 distinct tubulin sites. Our results offer a unique structural basis for the development of novel small molecules for use as tubulin modulators in basic research applications or as drugs. Furthermore, our method lays down a framework that may help to discover new pockets in other pharmaceutically important targets and characterize them in terms of chemical tractability and allosteric modulation.	May 2021
I13-1-Coherence	X-ray ptychography with a laboratory source Darren Batey , Frederic Van Assche , Sander Vanheule , Matthieu N. Boone , Andrew J. Parnell , Oleksandr O. Mykhaylyk , Christoph Rau , Silvia Cipiccia Physical Review Letters 126 DOI: 10.1103/PhysRevLett.126.193902 Open Access Show Abstract ▼ Abstract: X-ray ptychography has revolutionized nanoscale phase contrast imaging at large-scale synchrotron sources in recent years. We present here the first successful demonstration of the technique in a small-scale laboratory setting. An experiment was conducted with a liquid metal-jet x-ray source and a single photon-counting detector with a high spectral resolution. The experiment used a spot size of 5 μ m to produce a ptychographic phase image of a Siemens star test pattern with a submicron spatial resolution. The result and methodology presented show how high-resolution phase contrast imaging can now be performed at small-scale laboratory sources worldwide.	May 2021
I11-High Resolution Powder Diffraction	Discovery of a low thermal conductivity oxide guided by probe structure prediction and machine learning Christopher M. Collins , Luke M. Daniels , Quinn Gibson , Michael W. Gaultois , Michael Moran , Richard Feetham , Michael J. Pitcher , Matthew S Dyer , Charlene Delacotte , Marco Zanella , Claire A. Murray , Gyorgyi Glodan , Olivier Perez , Denis Pelloquin , Troy D. Manning , Jonathan Alaria , George R. Darling , John B. Claridge , Matthew J. Rosseinsky Angewandte Chemie International Edition DOI: 10.1002/anie.202102073 Show Abstract ▼ Abstract: We report the aperiodic titanate Ba 10 Y 6 Ti 4 O 27 with a room temperature thermal conductivity that equals the lowest reported for an oxide. The structure is characterised by discontinuous occupancy modulation of each of the sites, and can be considered as a quasicrystal. The resulting localisation of lattice vibrations suppresses phonon transport of heat. This new lead material for low thermal conductivity oxides is metastable and located within a quaternary phase field that has been previously explored – its isolation thus requires a precisely‐defined synthetic protocol. The necessary narrowing of the search space for experimental investigation is achieved by evaluation of titanate crystal chemistry, prediction of unexplored structural motifs that will favour synthetically accessible new compositions and assessment of their properties with machine learning models.	May 2021
I04-Macromolecular Crystallography I24-Microfocus Macromolecular Crystallography	Transfer of stabilising mutations between different secondary active transporter families Cristina Cecchetti , Nicola J. Scull , Thotegowdanapalya C. Mohan , Yilmaz Alguel , Alexandra M. C. Jones , Alexander D. Cameron , Bernadette Byrne Febs Open Bio DOI: 10.1002/2211-5463.13168 Diamond Proposal Number(s): [23620, 17221] Open Access Show Abstract ▼ Abstract: Integral membrane transporters play essential roles in the movement of substrates across biological membranes. One approach to produce transporters suitable for structural studies is to introduce mutations that reduce conformational flexibility and increase stability. However, it can be difficult to predict which mutations will result in a more stable protein. Previously, we stabilised the uric‐acid xanthine transporter, UapA, a member of the SLC23 family, through introduction of a single point mutation, G411V, trapping the protein in the inward facing conformation. Here we attempted to stabilise the structurally related BOR1 transporter from Arabidopsis thaliana, a member of the SLC4 family, by introducing the equivalent substitution. We identified possible residues, P362 and M363, in AtBOR1, likely to be equivalent to the G411 of UapA, and generated four mutants, P362V or L and M363F or Y. Stability analysis using heated Fluorescent Size Exclusion Chromatography indicated that the M363F/Y mutants were more stable than the WT AtBOR1 and P362V/L mutants. Furthermore, functional complementation analysis revealed that the M363F/Y mutants exhibited reduced transport activity compared to the P362V/L and WT proteins. Purification and crystallisation of the M363F/Y proteins yielded crystals that diffracted better than WT (5.5 vs 7 Å). We hypothesize that the increased bulk of the F and Y substitutions limits the ability of the protein to undergo the conformational rearrangements associated with transport. These proteins represent a basis for future studies on AtBOR1.	May 2021
I19-Small Molecule Single Crystal Diffraction	The effect of tether groups on the spin states of iron(ii)/bis[2,6-di(pyrazol-1-yl)pyridine] complexes Izar Capel Berdiell , Victor García-López , Mark J. Howard , Miguel Clemente-León , Malcolm A. Halcrow Dalton Transactions 233–235 DOI: 10.1039/D1DT01076J Diamond Proposal Number(s): [20570] Show Abstract ▼ Abstract: The synthesis of six 2,6-di(pyrazol-1-yl)pyridine derivatives bearing dithiolane or carboxylic acid tether groups is described: [2,6-di(pyrazol-1-yl)pyrid-4-yl]methyl (R)-lipoate (L1), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]ethyl (R)-lipoate (L2), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxy]ethyl (R)-lipoate (L3), N-([2,6-di(pyrazol-1-yl)pyrid-4-ylsulfanyl]-2-aminoethyl (R)-lipoamide (L4), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]acetic acid (L5) and 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]propionic acid (L6). The iron(II) perchlorate complexes of all the new ligands exhibit gradual thermal spin-crossover (SCO) in the solid state above room temperature, except L4 whose complex remains predominantly high-spin. Crystalline [Fe(L6)2][ClO4]2·2MeCN contains three unique cation sites which alternate within hydrogen-bonded chains, and undergo gradual SCO at different temperatures upon warming. The SCO midpoint temperature (T1/2) of the complexes in CD3CN solution ranges between 208–274 K, depending on the functional group linking the tether groups to the pyridyl ring. This could be useful for predicting how these complexes might behave when deposited on gold or silica surfaces.	May 2021
I22-Small angle scattering & Diffraction	RAFT polymerisation of renewable terpene (meth)acrylates and the convergent synthesis of methacrylate–acrylate–methacrylate triblock copolymers Rachel L. Atkinson , Olivia R. Monaghan , Matthew T. Elsmore , Paul D. Topham , Daniel T. W. Toolan , Matthew J. Derry , Vincenzo Taresco , Robert A. Stockman , Davide S. A. De Focatiis , Derek J. Irvine , Steven M. Howdle Polymer Chemistry 16 DOI: 10.1039/D1PY00326G Open Access Show Abstract ▼ Abstract: Terpenes are ideal candidates for sustainable polymer feedstocks, due to their natural abundance and availability from existing waste streams. Previously, we have shown that a range of terpene(meth)acrylate monomers can be synthesised from the most commonly available terpenes (α-pinene, β-pinenene and limonene) and that these readily undergo radical polymerisation. We now report the synthesis of well-defined polymers and precise di- and multiblock copolymer architectures by use of RAFT control. A very wide range of Tg values are observed for the terpene (meth)acrylate homopolymers, from −3 °C for poly(limonene acrylate), up to +168 °C for poly(α-pinene methacrylate), and we exploit these to create renewably-sourced hard–soft block copolymers. We also report the synthesis of difunctional poly(α- and β-pinene methacrylate) macro-RAFT agents and the preparation of ABA triblock copolymers. Promising adhesive properties are observed for a triblock copolymer comprised of poly(α-pinene methacrylate) and poly(butyl acrylate) blocks. A range of fully terpene-based triblock copolymers containing poly(limonene acrylate) soft blocks are also reported.	May 2021
I22-Small angle scattering & Diffraction	Gyroid‐nanostructured all‐solid polymer films combining high H+ conductivity with low H2 permeability Tsubasa Kobayashi , Ya‐xin Li , Yuichiro Hirota , Asako Maekawa , Norikazu Nishiyama , Xiang‐bing Zeng , Takahiro Ichikawa Macromolecular Rapid Communications 451 DOI: 10.1002/marc.202100115 Open Access Show Abstract ▼ Abstract: Gyroid‐nanostructured all‐solid polymer films with exceedingly high proton conductivity and low H2 gas permeability have been created via crosslinking polymerization of mixtures of a zwitterionic amphiphilic monomer and a polymerizable imide‐type acid that co‐organize into bicontinuous cubic liquid‐crystalline phases. The gyroid nanostructures are visualized by reconstructing a 3D electron map from the synchrotron X‐ray diffraction patterns. These films exhibit high proton conductivity of the order of 10−1 S cm−1 and extremely low H2 gas permeability of the order of 10−15 mol m m−2 s−1 Pa−1. These properties can be ascribed to the presence of the ionic liquid‐like layer along the gyroid minimal surface. Since these two characteristics are required for improving the performance of proton‐exchange membrane fuel cells, the present membrane design represents a promising strategy for the development of advanced devices, pertinent to establishing sustainable energy sources.	May 2021

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