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December 2023 issue
Cover illustration: Highlighting some recent developments in instrumentation and apparatus: the FALCON double-detector Laue diffractometer add-on for grain mapping at POLDI, Paul Scherrer Institute [Samothrakitis et al. (2023). J. Appl. Cryst. 56, 1792–1801]; an upgrade of the small-angle neutron scattering diffractometer SANS-J at JRR-3, Japan Atomic Energy Agency [Kumada et al. (2023). J. Appl. Cryst. 56, 1776–1783]; development of a D2O/H2O vapor generator for contrast-variation neutron scattering [Arima-Osonoi et al. (2023). J. Appl. Cryst. 56, 1802–1812]; and HETU, the high-resolution stress and texture neutron diffractometer at China Mianyang Research Reactor [Wang et al. (2023). J. Appl. Cryst. 56, 1674–1682].
editorial
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A new virtual special issue highlights some of the most exciting work presented at the 18th International Small Angle Scattering Conference (SAS2022), which took place in Campinas, Brazil. The articles included here were originally published in recent regular issues of Journal of Applied Crystallography and Acta Crystallographica Section D. The SAS2022 special issue is available at http://journals.iucr.org/special_issues/2023/sas2022/.
research papers
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A data-analysis round robin was performed using four real-world datasets to quantify the role of the human factor in analysis; the 46 responses show that the analyses by different researchers and laboratories may not be directly comparable, with large reporting inconsistencies in distribution widths and volume fractions. Several underlying causes for these inconsistencies are highlighted that can be addressed by the community.
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The twinning and homo-epitaxy that operate in aragonite have been investigated by experimental and theoretical studies.
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A purely experimental method to determine absolute scales from small-angle X-ray scattering (SAXS) data of lipid bilayers with the aid of grazing-incidence X-ray off-specular scattering (GIXOS) data from lipid monolayers at the air–water interface is presented.
A straightforward yet smart glutathione-responsive drug delivery system based on aptamer-coated mesoporous silica has been developed and characterized through various analytical techniques.
The elastic behaviour of orientation-correlated subsets of grains in textured polycrystals is analysed with respect to different modelling approaches. Novel concepts discussed here are the upper bound and lower bound formulation of the self-consistent model, the calculation of diffraction elastic constants (DECs) using discrete grain orientations based on electron backscatter diffraction (EBSD) data, the fitting of single-crystal elastic constants from measured DECs, and the calculation of overall elastic constants for multiphase aggregates in the presence of texture and non-spherical grain shapes. EBSD data allow calculations that include individual grain shapes, orientations and grains that are immediate neighbours to diffracting grains.
A new high-resolution stress and texture neutron diffractometer that utilizes long-wavelength neutrons to evaluate residual stress and analysis texture is presented.
Details of the microstructures in soft-matter systems and their evolution following a change in environment can be revealed by combining in situ X-ray scattering data with two-dimensional correlation spectroscopy.
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Silica-rich sedimentary rocks (chert) exhibit an evolving microstructure able to preserve organic matter mostly in mesopores during geological timescales. Under compaction, silica porous matrices experience porosity reduction, dehydration of silica and redistribution of organics inside the pore network.
A method is presented for calculating the reference intensity ratio of crystalline phases with unknown atomic arrangements using just the composition and lattice parameters.
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A general formalism is presented for the single-chain scattering function of helices and twisted fibres with easy adaptation of number of strands and cross-sectional symmetry.
A method for obtaining the crystallographic texture of polycrystalline samples through analysis of Bragg edges is presented and applied to the case of a cubic material.
A multiplexing heater that can probe up to 18 reactions in solutions, molten fluxes and solids – in parallel – is presented.
A penalized iterative regression method using a gradient descent algorithm with regularization is presented to eliminate size-distribution-induced smearing effects in small-angle X-ray scattering (SAXS) profiles, enabling retrieval of the characteristic Bessel-type SAXS oscillations (including both peaks and valleys) of representative nanoparticles of varying shape.
A simple and robust procedure for determining the degree of crystallinity (DOC) has been developed. Misestimation of the background level can automatically be corrected to improve the accuracy. The procedure has been tested using experimental and computer-generated intensity data, and here the routine determination of the DOC within an error of 1–2% for samples with DOC < 50% is demonstrated.
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A method for verifying that coordinate systems are conserved while performing texture analysis using MAUD is demonstrated for neutron diffraction data of a quartz single crystal.
The combination of the existing position-sensitive photomultiplier and 3He main detectors with the newly installed front detectors in SANS-J at JRR-3, Tokai, Japan, allows small-angle neutron scattering signals to be covered in the range 0.002–6 nm−1 for the magnitude of the scattering vector Q without gaps using three standard device layouts. Installation of the front detector and a graphical user interface have greatly improved the usability of SANS-J.
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Time-resolved high-energy X-ray diffraction was used during growth of ultrathin NixFe3−xO4 films of varying Ni content (0 ≤ x ≤ 1.5) on MgO(001). For low Ni contents (x ≤ 1), the films grow initially in a rock salt phase followed by an inverse spinel structure, while overstoichiometric films (Ni contents x > 1) grow completely in a rock salt structure.
This article introduces the commissioning of the FALCON double-detector system used for Laue 3D neutron diffraction tomography experiments at the POLDI instrument of SINQ, Paul Scherrer Institute.
This work presents a novel water vapor generator designed for neutron scattering experiments that allows continuous control of the isotopic H/D ratio, which is particularly useful for contrast-variation measurements.
The structure of opal represents a missing link in the length scale between amorphous and crystalline states. This work revisits a long-standing debate about the intermediate-range order in natural opal (opal-CT) and presents a complete multilevel structural description for local distortions and interstratification features observed in powder diffraction and pair distribution function datasets.
teaching and education
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The International Tables Symmetry Database (https://symmdb.iucr.org/), part of International Tables for Crystallography, is a collection of individual databases of crystallographic space-group and point-group information. Programs are provided to access and interactively visualize the data, and also allow new data to be calculated `on the fly', facilitating the in-depth study of group–subgroup relations, domain structures and twinning, families of related crystal structures and phase transitions, and the prediction of new crystal structures.
computer programs
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New features of the RootProf program for model-free analysis of unidimensional profiles are presented and discussed.
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A computer program that implements a new approach to quantifying distortions in coordination polyhedra, molecules and cages by optimizing dynamic model shapes is presented.
AutoEMage is a new open-source software package that automates data transfer, preprocessing, real-time display and data monitoring during cryo-electron microscopy (cryo-EM) data collection. It is equipped with an easy-to-use graphical user interface that provides seamless data screening and real-time feedback on data quality and microscope status.
A command-line utility to calculate the intensity distribution in reciprocal space using input files with CIF syntax is described
laboratory notes
Powder packing fraction strongly impacts the kinetics and progress of solid-state reactions.
crystallographers
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