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| 2. |
- Choi, J., et al.
(author)
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Spatially inhomogeneous competition between superconductivity and the charge density wave in YBa2Cu3O6.67
- 2020
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Journal article (peer-reviewed)abstract
- The charge density wave in the high-temperature superconductor YBa2Cu3O7−x (YBCO) has two different ordering tendencies differentiated by their c-axis correlations. These correspond to ferro- (F-CDW) and antiferro- (AF-CDW) couplings between CDWs in neighbouring CuO2 bilayers. This discovery has prompted several fundamental questions: how does superconductivity adjust to two competing orders and are either of these orders responsible for the electronic reconstruction? Here we use x-ray diffraction to study YBa2Cu3O6.67 as a function of magnetic field and temperature. We show that regions with F-CDW correlations suppress superconductivity more strongly than those with AF-CDW correlations. This implies that an inhomogeneous superconducting state exists, in which some regions show a fragile form of superconductivity. By comparison of F-CDW and AF-CDW correlation lengths, it is concluded that F-CDW ordering is sufficiently long-range to modify the electronic structure. Our study thus suggests that F-CDW correlations impact both the superconducting and normal state properties of YBCO.
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| 3. |
- Pagnamenta, A. T., et al.
(author)
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An ancestral 10-bp repeat expansion in VWA1 causes recessive hereditary motor neuropathy
- 2021
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In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 144, s. 584-600
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Journal article (peer-reviewed)abstract
- The extracellular matrix comprises a network of macromolecules such as collagens, proteoglycans and glycoproteins. VWA1 (von Willebrand factor A domain containing 1) encodes a component of the extracellular matrix that interacts with perlecan/collagen VI, appears to be involved in stabilizing extracellular matrix structures, and demonstrates high expression levels in tibial nerve. Vwa1-deficient mice manifest with abnormal peripheral nerve structure/function; however, VWA1 variants have not previously been associated with human disease. By interrogating the genome sequences of 74 180 individuals from the 100K Genomes Project in combination with international gene-matching efforts and targeted sequencing, we identified 17 individuals from 15 families with an autosomal-recessive, non-length dependent, hereditary motor neuropathy and rare biallelic variants in VWA1. A single disease-associated allele p.(G25Rfs*74), a 10-bp repeat expansion, was observed in 14/15 families and was homozygous in 10/15. Given an allele frequency in European populations approaching 1/1000, the seven unrelated homozygote individuals ascertained from the 100K Genomes Project represents a substantial enrichment above expected. Haplotype analysis identified a shared 220 kb region suggesting that this founder mutation arose 47000 years ago. A wide age-range of patients (6-83 years) helped delineate the clinical phenotype over time. The commonest disease presentation in the cohort was an early-onset (mean 2.0 +/- 1.4 years) non-length-dependent axonal hereditary motor neuropathy, confirmed on electrophysiology, which will have to be differentiated from other predominantly or pure motor neuropathies and neuronopathies. Because of slow disease progression, ambulation was largely preserved. Neurophysiology, muscle histopathology, and muscle MRI findings typically revealed clear neurogenic changes with single isolated cases displaying additional myopathic process. We speculate that a few findings of myopathic changes might be secondary to chronic denervation rather than indicating an additional myopathic disease process. Duplex reverse transcription polymerase chain reaction and immunoblotting using patient fibroblasts revealed that the founder allele results in partial nonsense mediated decay and an absence of detectable protein. CRISPR and morpholino vwa1 modelling in zebrafish demonstrated reductions in motor neuron axonal growth, synaptic formation in the skeletal muscles and locomotive behaviour. In summary, we estimate that biallelic variants in VWA1 may be responsible for up to 1% of unexplained hereditary motor neuropathy cases in Europeans. The detailed clinical characterization provided here will facilitate targeted testing on suitable patient cohorts. This novel disease gene may have previously evaded detection because of high GC content, consequential low coverage and computational difficulties associated with robustly detecting repeat-expansions. Reviewing previously unsolved exomes using lower QC filters may generate further diagnoses.
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| 4. |
- Villanueva-Perez, P., et al.
(author)
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Scanning Compton X-ray microscopy
- 2021
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In: Optics Letters. - 0146-9592. ; 46:8, s. 1920-1923
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Journal article (peer-reviewed)abstract
- X-ray microscopy offers the opportunity to image biological and radiosensitive materials without special sample preparations, bridging optical and electron microscopy capabilities. However, the performance of such microscopes, when imaging radiosensitive samples, is not limited by their intrinsic resolution, but by the radiation damage induced on such samples. Here, we demonstrate a novel, to the best of our knowledge, radio-efficient microscope, scanning Compton X-ray microscopy (SCXM), which uses coherently and incoherently (Compton) scattered photons to minimize the deposited energy per unit of mass for a given imaging signal. We implemented SCXM, using lenses capable of efficiently focusing 60 keV X-ray photons into the sub-micrometer scale, and probe its radio-efficient capabilities. SCXM, when implemented in high-energy diffraction-limited storage rings, e.g., European Synchrotron Radiation Facility Extremely Brilliant Source and PETRA IV, will open the opportunity to explore the nanoscale of unstained, unsectioned, and undamaged radiosensitive materials.
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| 6. |
- Hejral, U., et al.
(author)
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Composition-Dependent Alloy Nanoparticle Shape Changes under Reaction Conditions : Kinetic and Thermodynamic Effects
- 2024
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In: The Journal of Physical Chemistry C. - 1932-7447 .- 1932-7455. ; 128:10, s. 4330-4342
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Journal article (peer-reviewed)abstract
- Particle sintering and reshaping constitute the main cause for catalyst deactivation. An atomic-scale understanding of the correlation among the catalyst structure, its support, and the gas phase under realistic reaction conditions is required for its suppression. In this study, we combined high-energy grazing incidence X-ray diffraction, in situ mass spectrometry, ex situ scanning electron microscopy, and density functional theory calculations to unravel the driving force behind the composition-dependent particle shape changes and sintering processes of alpha-Al2O3(0001)-supported Pt-Pd alloy nanoparticles under realistic reaction conditions for CO oxidation. We find that pure Pt and Pt-rich particles, initially kinetically trapped in metastable flat particle shapes, undergo a strong reaction-induced height increase to adopt a more stable, theoretically predicted compact equilibrium shape. Contrarily, Pd-rich particles prove to be more resistant against shape changes, since they exhibit already a shape close to equilibrium. We thus conclude that the observed initial deviations in particle shape from the theoretical predictions are due to kinetic limitations during growth. Our data provide information on the segregation state of the alloy particles, indicating a Pt core and Pd shell structure under strongly reducing conditions and the alloying of Pt and Pd under the reaction conditions for CO oxidation close to stoichiometry.
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| 7. |
- Li, Tang, et al.
(author)
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Dose-efficient scanning Compton X-ray microscopy
- 2023
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In: Light: Science and Applications. - 2095-5545. ; 12:1
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Journal article (peer-reviewed)abstract
- The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure, induced by the necessarily high energy of short-wavelength radiation. Imaging the inelastically scattered X-rays at a photon energy of 60 keV (0.02 nm wavelength) offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography. We present images of dried, unstained, and unfixed biological objects obtained by scanning Compton X-ray microscopy, at a resolution of about 70 nm. This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision, a new wavefront measurement scheme for hard X rays, and efficient pixel-array detectors. The doses required to form these images were as little as 0.02% of the tolerable dose and 0.05% of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy. The images obtained provide a quantitative map of the projected mass density in the sample, as confirmed by imaging a silicon wedge. Based on these results, we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.
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