Non-destructive three-dimensional crystallographic orientation analysis of olivine using laboratory diffraction contrast tomography

X-ray laboratory diffraction contrast tomography (LabDCT) produces three-dimensional (3D) maps of crystallographic orientation. The non-destructive nature of the technique affords the key benefit of full 3D context of these, and other, in situ measurements. This study is the first to apply the technique to any material other than a metal or silicon. We report the first 3D measurements of the crystallographic orientation of olivine, which also makes this study the first to apply LabDCT to (1) a non-metallic, non-cubic system and (2) geological material. First, we scanned fragments of olivine set in resin alongside glass microbeads using LabDCT and absorption contrast tomography (ACT). Then we reconstructed these data assuming an orthorhombic crystal system. We show that: (1) the regions within the sample that index well according to the orthorhombic system correspond to olivine fragments in the ACT image; (2) crystalline regions not corresponding to olivine are not indexed assuming the same lattice parameters; and (3) the diffraction data discriminates crystalline from non-crystalline materials as expected. Finally, we demonstrate that the method resolves sub-degree orientation differences between distinct regions within individual olivine fragments. We conclude that DCT can be applied to the study of rocks and other crystalline materials, and offers advantages over conventional techniques. We also note that LabDCT may offer a solution to the crystallographic measurement of substances that would otherwise be difficult to measure due to challenges in obtaining a perfect sample polish. Future developments to accommodate larger experimental volumes and additional crystallographic systems within a sample promises to expand the applicability and impact of DCT

Exploring the infiltrative and degradative ability of Fusarium oxysporum on polyethylene terephthalate (PET) using correlative microscopy and deep learning

Abstract Managing the worldwide steady increase in the production of plastic while mitigating the Earth’s global pollution is one of the greatest challenges nowadays. Fungi are often involved in biodegradation processes thanks to their ability to penetrate into substrates and release powerful catabolic exoenzymes. However, studying the interaction between fungi and plastic substrates is challenging due to the deep hyphal penetration, which hinders visualisation and evaluation of fungal activity. In this study, a multiscale and multimodal correlative microscopy workflow was employed to investigate the infiltrative and degradative ability of Fusarium oxysporum fungal strain on polyethylene terephthalate (PET) fragments. The use of non-destructive high-resolution 3D X-ray microscopy (XRM) coupled with a state-of-art Deep Learning (DL) reconstruction algorithm allowed optimal visualisation of the distribution of the fungus on the PET fragment. The fungus preferentially developed on the edges and corners of the fragment, where it was able to penetrate into the material through fractures. Additional analyses with scanning electron microscopy (SEM), Raman and energy dispersive X-ray spectroscopy (EDX) allowed the identification of the different phases detected by XRM. The correlative microscopy approach unlocked a more comprehensive understanding of the fungus-plastic interaction, including elemental information and polymeric composition

3D X-ray tomographic analysis reveals how coesite is preserved in Muong Nong-type tektites

International audienceMuong Nong-type (MN) tektites are a layered type of tektite associated to the Australasian strewn field, the youngest (790 kyr) and largest on Earth. In some MN tektites, coesite is observed in association with relict quartz and silica glass within inclusions surrounded by a froth layer. The formation of coesite-bearing frothy inclusions is here investigated through a 3D textural multiscale analysis of the vesicles contained in a MN tektite sample, combined with compositional and spectroscopic data. The vesicle size distribution testifies to a post-shock decompression that induced melting and extensive vesiculation in the tektite melt. Compared to free vesicles, nucleated homogeneously in the tektite melt, froth vesicles nucleated heterogeneously on relict quartz surfaces at the margins of coesite-bearing inclusions. The rapid detachment of the froth vesicles and prompt reactivation of the nucleation site favoured the packing of vesicles and the formation of the froth structure. Vesicle relaxation time scales suggest that the vesiculation process lasted few seconds. The formation of the froth layer was instrumental for the preservation of coesite, promoting quenching of the inclusion core through the subtraction of heat during froth expansion, thereby physically insulating the inclusion until the final quench of the tektite melt