Browsing by Author "Nelson, ARJ"

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    Advice on describing Bayesian analysis of neutron and X-ray reflectometry
    (International Union of Crystallography (IUCr), 2023) McCluskey, AR; Caruana, AJ; Kinane, CJ; Armstrong, AJ; Arnold, T; Cooper, JFK; Cortie, DL; Hughes, AV; Moulin, JF; Nelson, ARJ; Potrezbowski, W; Starostin, V
    As a result of the availability of modern software and hardware, Bayesian analysis is becoming more popular in neutron and X-ray reflectometry analysis. The understandability and replicability of these analyses may be harmed by inconsistencies in how the probability distributions central to Bayesian methods are represented in the literature. Herein advice is provided on how to report the results of Bayesian analysis as applied to neutron and X-ray reflectometry. This includes the clear reporting of initial starting conditions, the prior probabilities, the results of any analysis and the posterior probabilities that are the Bayesian equivalent of the error bar, to enable replicability and improve understanding. It is believed that this advice, grounded in the authors' experience working in the field, will enable greater analytical reproducibility in the work of the reflectometry community, and improve the quality and usability of results. © 2023 The Authors. Open Access published under a CC BY 4.0 licence.
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    Advice on describing Bayesian analysis of neutron and x-ray reflectometry
    (International Union of Crystallography, 2023-02-01) McCluskey, AR; Caruana, AJ; Kinane, CJ; Armstrong, AJ; Arnold, T; Cooper, JFK; Cortie, DL; Hughes, AV; Moulin, JF; Nelson, ARJ; Potrzebowski, W; Starostin, V
    As a result of the availability of modern software and hardware, Bayesian analysis is becoming more popular in neutron and X-ray reflectometry analysis. The understandability and replicability of these analyses may be harmed by inconsistencies in how the probability distributions central to Bayesian methods are represented in the literature. Herein advice is provided on how to report the results of Bayesian analysis as applied to neutron and X-ray reflectometry. This includes the clear reporting of initial starting conditions, the prior probabilities, the results of any analysis and the posterior probabilities that are the Bayesian equivalent of the error bar, to enable replicability and improve understanding. It is believed that this advice, grounded in the authors' experience working in the field, will enable greater analytical reproducibility in the work of the reflectometry community, and improve the quality and usability of results. © The Authors CC BY 4.0
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    The assembly mechanism and mesoscale architecture of protein–polysaccharide complexes formed at the solid–liquid Interface
    (American Chemical Society, 2022-10-04) Biswas, S; Melton, LD; Nelson, ARJ; Le Brun, AP; Heinrich, F; McGillivray, DJ; Xu, AY
    Protein-polysaccharide composite materials have generated much interest due to their potential use in medical science and biotechnology. A comprehensive understanding of the assembly mechanism and the mesoscale architecture is needed for fabricating protein-polysaccharide composite materials with desired properties. In this study, complex assemblies were built on silica surfaces through a layer-by-layer (LbL) approach using bovine beta-lactoglobulin variant A (βLgA) and pectin as model protein and polysaccharide, respectively. We demonstrated the combined use of quartz crystal microbalance with dissipation monitoring (QCM-D) and neutron reflectometry (NR) for elucidating the assembly mechanism as well as the internal architecture of the protein-polysaccharide complexes formed at the solid-liquid interface. Our results show that βLgA and pectin interacted with each other and formed a cohesive matrix structure at the interface consisting of intertwined pectin chains that were cross-linked by βLgA-rich domains. Although the complexes were fabricated in an LbL fashion, the complexes appeared to be relatively homogeneous with βLgA and pectin molecules spatially distributed within the matrix structure. Our results also demonstrate that the density of βLgA-pectin complex assemblies increased with both the overall and local charge density of pectin molecules. Therefore, the physical properties of the protein-polysaccharide matrix structure, including density and level of hydration, can be tuned by using polysaccharides with varying charge patterns, thus promoting the development of composite materials with desired properties. © 2024 American Chemical Society
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    Spatz: the time-of-flight neutron reflectometer with vertical sample geometry at the OPAL research reactor
    (International Union of Crystallography, 2023-02) Le Brun, AP; Huang, TY; Pullen, SA; Nelson, ARJ; Spedding, J; Holt, SA
    The Spatz neutron beam instrument is the second time-of-flight neutron reflectometer to be installed at the OPAL research reactor. The instrument was formerly the V18 BioRef reflectometer at the BER-II reactor in Berlin and was transferred to Australia in 2016. Subsequently the instrument was re-installed in the neutron guide hall of the OPAL reactor at the end position of the CG2B cold-neutron guide and recommissioned. The instrument performance has not been compromised by the move, with reflectivity achieved down to 10−7 and good counting statistics within a reasonable time frame using a wavelength range of 2–20 Å. Several different samples at the solid–air interface and the solid–liquid interface have been measured to demonstrate the instrument's capabilities. © The Authors - CC BY 4.0.