I10-Beamline for Advanced Dichroism
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Diamond Proposal Number(s):
[20182]
Open Access
Abstract: A chiral bobber is a localized three-dimensional magnetization configuration, terminated by a singularity. Chiral bobbers coexist with magnetic skyrmions in chiral magnets, lending themselves to new types of skyrmion-complementary bits of information. However, the on-demand creation of bobbers, as well as their direct observation remained elusive. Here, we introduce a new mechanism for creating a stable chiral bobber lattice state via the proximity of two skyrmion species with comparable size. This effect is experimentally demonstrated in a
Cu
2
OSeO
3
/
[
Ta
/
CoFeB
/
MgO
]
4
heterostructure in which an exotic bobber lattice state emerges in the phase diagram of
Cu
2
OSeO
3
. To unambiguously reveal the existence of the chiral bobber lattice state, we have developed a novel characterization technique, magnetic truncation rod analysis, which is based on resonant elastic x-ray scattering.
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Jan 2021
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I13-2-Diamond Manchester Imaging
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Paolo
Miocchi
,
Alejandra
Sierra
,
Laura
Maugeri
,
Eleonora
Stefanutti
,
Ali
Abdollahzadeh
,
Fabio
Mangini
,
Marta
Moraschi
,
Inna
Bukreeva
,
Lorenzo
Massimi
,
Francesco
Brun
,
Jussi
Tohka
,
Olli
Gröhn
,
Alberto
Mittone
,
Alberto
Bravin
,
Charles
Nicaise
,
Federico
Giove
,
Alessia
Cedola
,
M.
Fratini
Abstract: Purpose: Image processing plays a fundamental role in the study of central nervous system, for example in the analysis of the vascular network in neurodegenerative diseases. Synchrotron X-ray Phase-contrast micro-Tomography (SXPCT) is a very attractive method to study weakly absorbing samples and features, such as the vascular network in the spinal cord (SC). However, the identification and segmentation of vascular structures in SXPCT images is seriously hampered by the presence of image noise and strong contrast inhomogeneities, due to the sensitivity of the technique to small electronic density variations. In order to help with these tasks, we implemented a user-friendly ImageJ plugin based on a 3D Gaussian steerable filter, tuned up for the enhancement of tubular structures in SXPCT images. Methods: The developed 3D Gaussian steerable filter plugin for ImageJ is based on the steerability properties of Gaussian derivatives. We applied it to SXPCT images of ex-vivo mouse SCs acquired at different experimental conditions. Results: The filter response shows a strong amplification of the source image contrast-to-background ratio (CBR), independently of structures orientation. We found that after the filter application, the CBR ratio increases by a factor ranging from ~6 to ~60. In addition, we also observed an increase of 35% of the contrast to noise ratio in the case of injured mouse SC. Conclusion: The developed tool can generally facilitate the detection/segmentation of capillaries, veins and arteries that were not clearly observable in non-filtered SXPCT images. Its systematic application could allow obtaining quantitative information from pre-clinical and clinical images.
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Jan 2021
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B21-High Throughput SAXS
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Diamond Proposal Number(s):
[21035]
Open Access
Abstract: The object of this study is a comparison between solid lipid nanoparticles and ethosomes for caffeic acid delivery through the skin. Caffeic acid is a potent antioxidant molecule whose cutaneous administration is hampered by its low solubility and scarce stability. In order to improve its therapeutic potential, caffeic acid has been encapsulated within solid lipid nanoparticles and ethosomes. The effect of lipid matrix has been evaluated on the morphology and size distribution of solid lipid nanoparticles and ethosomes loaded with caffeic acid. Particularly, morphology has been investigated by cryogenic transmission electron microscopy and small angle X-ray scattering, while mean diameters have been evaluated by photon correlation spectroscopy. The antioxidant power has been evaluated by the 2,2-diphenyl-1-picrylhydrazyl methodology. The influence of the type of nanoparticulate system on caffeic acid diffusion has been evaluated by Franz cells associated to the nylon membrane, while to evaluate caffeic acid permeation through the skin, an amperometric study has been conducted, which was based on a porcine skin-covered oxygen electrode. This apparatus allows measuring the O2 concentration changes in the membrane induced by polyphenols and H2O2 reaction in the skin. The antioxidative reactions in the skin induced by caffeic acid administered by solid lipid nanoparticles or ethosomes have been evaluated. Franz cell results indicated that caffeic acid diffusion from ethosomes was 18-fold slower with respect to solid lipid nanoparticles. The amperometric method evidenced the transdermal delivery effect of ethosome, indicating an intense antioxidant activity of caffeic acid and a very low response in the case of SLN. Finally, an irritation patch test conducted on 20 human volunteers demonstrated that both ethosomes and solid lipid nanoparticles can be safely applied on the skin.
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Jan 2021
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[23480]
Abstract: Although circular helicates can be assembled with a range of labile transition-metal centers, solely “chiral-at-metal” examples (i.e., systems without chiral ligands) and heterometallic (i.e., mixed metal systems, racemic or chiral) circular helicates both remain unexplored. Here, we report on the enantioselective synthesis of a heterometallic (Ir2Zn4) hexameric circular helicate and its elaboration into the corresponding triply interlocked Star of David [2]catenane. The relative inertness of Ir(III) enables enantiospecific synthesis of the hexameric circular helicate using chiral-at-metal building blocks. The resulting Star of David [2]catenane, which is a chiral 6-2-1 link, is formed as a single topological enantiomer. The X-ray crystal structure of the (Ir2Zn4)-catenane shows each of the two 95-atom-long macrocycles entwined around the six metal octahedral metal ions and each other, forming a triply interlocked circular double helix. Two PF6– anions reside above and below the central cavity. The Star of David [2]catenane, both with and without coordinated Zn(II) ions, retains the photophysical properties characteristic of cyclometalated Ir(III) complexes. The synthetic strategy opens up new research directions and opportunities for the assembly of other chiral knots, links, and heterometallic circular helicates.
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Jan 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[15478, 14948, 12950]
Open Access
Abstract: Graphene oxide (GO) forms a well-aligned lyotropic liquid crystal (LC) phase in aqueous dispersions at relatively low concentrations. Under a remarkably wide range of shear rates, we report hitherto unobserved shear-induced polarized light image patterns, a Maltese cross combined with shear banding, recorded in real time and in situ during rheological measurements. This is shown to be a result of elastic flow instabilities that manifest as a helical flow in alternating bands of left- and right-handed helices, arising from a combination of shear flow and Taylor-type vortex flow. The instability is observed for LCs formed from large aspect ratio GO particles owing to their unique viscoelastic properties, but not for smaller aspect ratio particles. This phenomenon coincides with rheopecty and anomalous small-angle X-ray scattering patterns under shear flow, which confirm the instabilities. The results presented here could lead to advanced control over macroscopic periodic alignment in technologically relevant dispersions of two-dimensional material particles.
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Jan 2021
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[22477]
Open Access
Abstract: Defects are emerging as a key tool for fine-tuning the stimuli-responsive behavior of coordination polymers and metal–organic frameworks. Here, we study the ramifications of defects on the mechanical properties of the molecular perovskite [C(NH2)3]MnII(HCOO)3 and its defective analogue [C(NH2)3]Fe2/3III□1/3(HCOO)3, where □ = vacancy. Defects reduce the bulk modulus by 30% and give rise to a temperature-driven phase transition not observed in the nondefective system. The results highlight the opportunities that come with defect-engineering approaches to alter the mechanical properties and underlying thermodynamics, with important implications for the research on stimuli-responsive materials.
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Jan 2021
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[19067]
Open Access
Abstract: High-end organic–inorganic lead halide perovskite semitransparent p–i–n solar cells for tandem applications use a phenyl-C61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)3 and (Cs,FA)Pb(Br,I)3 and in this study on Cs0.05FA0.79MA0.16PbBr0.51I2.49 (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p–i–n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 °C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20–50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.
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Jan 2021
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Krios I-Titan Krios I at Diamond
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Diamond Proposal Number(s):
[14769]
Open Access
Abstract: The Tuberous Sclerosis Complex (TSC) protein complex (TSCC), comprising TSC1, TSC2, and TBC1D7, is widely recognised as a key integration hub for cell growth and intracellular stress signals upstream of the mammalian target of rapamycin complex 1 (mTORC1). The TSCC negatively regulates mTORC1 by acting as a GTPase-activating protein (GAP) towards the small GTPase Rheb. Both human TSC1 and TSC2 are important tumour suppressors, and mutations in them underlie the disease tuberous sclerosis.
We used single-particle cryo-EM to reveal the organisation and architecture of the complete human TSCC. We show that TSCC forms an elongated scorpion-like structure, consisting of a central “body”, with a “pincer” and a “tail” at the respective ends. The “body” is composed of a flexible TSC2 HEAT repeat dimer, along the surface of which runs the TSC1 coiled-coil backbone, breaking the symmetry of the dimer. Each end of the body is structurally distinct, representing the N- and C-termini of TSC1; a “pincer” is formed by the highly flexible N-terminal TSC1 core domains and a barbed “tail” makes up the TSC1 coiled-coil-TBC1D7 junction. The TSC2 GAP domain is found abutting the centre of the body on each side of the dimerisation interface, poised to bind a pair of Rheb molecules at a similar separation to the pair in activated mTORC1.
Our architectural dissection reveals the mode of association and topology of the complex, casts light on the recruitment of Rheb to the TSCC, and also hints at functional higher order oligomerisation, which has previously been predicted to be important for Rheb-signalling suppression.
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Jan 2021
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I05-ARPES
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Ryo
Noguchi
,
Masaru
Kobayashi
,
Zhanzhi
Jiang
,
Kenta
Kuroda
,
Takanari
Takahashi
,
Zifan
Xu
,
Daehun
Lee
,
Motoaki
Hirayama
,
Masayuki
Ochi
,
Tetsuroh
Shirasawa
,
Peng
Zhang
,
Chun
Lin
,
Cédric
Bareille
,
Shunsuke
Sakuragi
,
Hiroaki
Tanaka
,
So
Kunisada
,
Kifu
Kurokawa
,
Koichiro
Yaji
,
Ayumi
Harasawa
,
Viktor
Kandyba
,
Alessio
Giampietri
,
Alexei
Barinov
,
Timur K.
Kim
,
Cephise
Cacho
,
Makoto
Hashimoto
,
Donghui
Lu
,
Shik
Shin
,
Ryotaro
Arita
,
Keji
Lai
,
Takao
Sasagawa
,
Takeshi
Kondo
Diamond Proposal Number(s):
[20445]
Abstract: Low-dimensional van der Waals materials have been extensively studied as a platform with which to generate quantum effects. Advancing this research, topological quantum materials with van der Waals structures are currently receiving a great deal of attention. Here, we use the concept of designing topological materials by the van der Waals stacking of quantum spin Hall insulators. Most interestingly, we find that a slight shift of inversion centre in the unit cell caused by a modification of stacking induces a transition from a trivial insulator to a higher-order topological insulator. Based on this, we present angle-resolved photoemission spectroscopy results showing that the real three-dimensional material Bi4Br4 is a higher-order topological insulator. Our demonstration that various topological states can be selected by stacking chains differently, combined with the advantages of van der Waals materials, offers a playground for engineering topologically non-trivial edge states towards future spintronics applications.
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Jan 2021
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[19787]
Open Access
Abstract: Insulin mucoadhesive buccal films (MBF) are a noninvasive insulin delivery system that offers an advantageous alternative route of administration to subcutaneous injection. One major concern in the formulation of insulin MBF is the preservation of an insulin secondary structure in the presence of the other film components. Buccal films were formulated using chitosan, glycerin, and L-arginine. The MBF-forming solutions (MBF-FS) and the films (MBF) were examined for their chemical and structural stability and for their in vivo activity. Enzyme-Linked Immunosorbent Assay (ELISA) of the insulin-loaded MBF showed that each individualized unit dose was at least loaded with 80% of the insulin theoretical dose. Results of Synchrotron Radiation Circular Dichroism (SRCD) measurements revealed that MBF-FS retained the α-helices and β–sheets conformations of insulin. Fourier transform infrared (FTIR)-microspectroscopy (FTIR-MS) examination of insulin MBF revealed the protective action of L-arginine on insulin structure by interacting with chitosan and minimizing the formation of an unordered structure and β-strand. A blood glucose-lowering effect of insulin MBF was observed in comparison with subcutaneous (S.C) injection using a rat model. As a result; chitosan-based MBFs were formulated and characterized using SRCD and FTIR-MS techniques. Furthermore, the results of in vivo testing suggested the MBFs as a promising delivery system for insulin.
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Jan 2021
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