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Publisher: Oxford [u.a.] : Blackwell ×

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    Small-angle X-ray scattering from GaN nanowires on Si(111): facet truncation rods, facet roughness and Porod's law
    (Oxford [u.a.] : Blackwell, 2021) Kaganer, Vladimir M.; Konovalov, Oleg V.; Fernández-Garrido, Sergio
    Small-angle X-ray scattering from GaN nanowires grown on Si(111) is measured in the grazing-incidence geometry and modelled by means of a Monte Carlo simulation that takes into account the orientational distribution of the faceted nanowires and the roughness of their side facets. It is found that the scattering intensity at large wavevectors does not follow Porod's law I(q) ∝ q-4. The intensity depends on the orientation of the side facets with respect to the incident X-ray beam. It is maximum when the scattering vector is directed along a facet normal, reminiscent of surface truncation rod scattering. At large wavevectors q, the scattering intensity is reduced by surface roughness. A root-mean-square roughness of 0.9 nm, which is the height of just 3-4 atomic steps per micrometre-long facet, already gives rise to a strong intensity reduction. open access.
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    X-ray diffraction from strongly bent crystals and spectroscopy of X-ray free-electron laser pulses
    (Oxford [u.a.] : Blackwell, 2020) Kaganer, Vladimir M.; Petrov, Ilia; Samoylova, Liubov
    The use of strongly bent crystals in spectrometers for pulses of a hard X-ray free-electron laser is explored theoretically. Diffraction is calculated in both dynamical and kinematical theories. It is shown that diffraction can be treated kinematically when the bending radius is small compared with the critical radius given by the ratio of the Bragg-case extinction length for the actual reflection to the Darwin width of this reflection. As a result, the spectral resolution is limited by the crystal thickness, rather than the extinction length, and can become better than the resolution of a planar dynamically diffracting crystal. As an example, it is demonstrated that spectra of the 12 keV pulses can be resolved in the 440 reflection from a 20 µm-thick diamond crystal bent to a radius of 10 cm. open access.
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    Agricultural fertilization with poultry manure results in persistent environmental contamination with the pathogen Clostridioides difficile
    (Oxford [u.a.] : Blackwell, 2021) Frentrup, Martinique; Thiel, Nadine; Junker, Vera; Behrens, Wiebke; Münch, Steffen; Siller, Paul; Kabelitz, Tina; Faust, Matthias; Indra, Alexander; Baumgartner, Stefanie; Schepanski, Kerstin; Amon, Thomas; Roesler, Uwe; Funk, Roger; Nübel, Ulrich
    During a field experiment applying broiler manure for fertilization of agricultural land, we detected viable Clostridioides (also known as Clostridium) difficile in broiler faeces, manure, dust and fertilized soil. A large diversity of toxigenic C. difficile isolates was recovered, including PCR ribotypes common from human disease. Genomic relatedness of C. difficile isolates from dust and from soil, recovered more than 2 years after fertilization, traced their origins to the specific chicken farm that had delivered the manure. We present evidence of long-term contamination of agricultural soil with manure-derived C. difficile and demonstrate the potential for airborne dispersal of C. difficile through dust emissions during manure application. Clostridioides genome sequences virtually identical to those from manure had been recovered from chicken meat and from human infections in previous studies, suggesting broiler-associated C. difficile are capable of zoonotic transmission.
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    Organic acids, siderophores, enzymes and mechanical pressure for black slate bioweathering with the basidiomycete Schizophyllum commune
    (Oxford [u.a.] : Blackwell, 2019) Kirtzel, Julia; Ueberschaar, Nico; Deckert-Gaudig, Tanja; Krause, Katrin; Deckert, Volker; Gadd, Geoffrey Michael; Kothe, Erika
    Although many fungi are known to be able to perform bioweathering of rocks and minerals, little information is available concerning the role of basidiomycetes in this process. The wood-rotting basidiomycete Schizophyllum commune was investigated for its ability to degrade black slate, a rock rich in organic carbon. Mechanical pressure of hyphae and extracellular polymeric substances was investigated for biophysical weathering. A mixed ß1-3/ß1-6 glucan, likely schizophyllan that is well known from S. commune, could be identified on black slate surfaces. Secretion of siderophores and organic acids as biochemical weathering agents was shown. Both may contribute to biochemical weathering in addition to enzymatic functions. Previously, the exoenzyme laccase was believed to attack organic the matter within the black slate, thereby releasing metals from the rock. Here, overexpression of laccase showed enhanced dissolution of quartz phases by etching and pitting. At the same time, the formation of a new secondary mineral phase, whewellite, could be demonstrated. Hence, a more comprehensive understanding of biophysical as well as biochemical weathering by S. commune could be reached and unexpected mechanisms like quartz dissolution linked to shale degradation. © 2019 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.