MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Journal of Applied Crystallography' source. Thu, 09 Feb 2012 20:29:17 +0100 http://www.medworm.com/index.php?rid=5674298&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5538 X-ray diffraction experiments at very low temperatures require samples to be isolated from atmospheric conditions and held under vacuum. These conditions are usually maintained via the use of beryllium chambers, which also scatter X-rays, causing unwanted contamination of the sample's diffraction pattern. The removal of this contamination requires novel data-collection and processing procedures to be employed. Herein a new approach is described, which utilizes the differences in origin of scattering vectors from the sample and the beryllium to eliminate non-sample scattering. The program Masquerade has been written to remove contaminated regions of the diffraction data from the processing programs. Coupled with experiments at different detector distances, it allows for the acquisition of d... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674298 Fri, 10 Feb 2012 01:11:50 +0100 5674298 http://www.medworm.com/index.php?rid=5674306&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fpf0094 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674306 Thu, 09 Feb 2012 05:00:00 +0100 5674306 http://www.medworm.com/index.php?rid=5674305&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frg5007 A novel grazing-incidence in-plane X-ray diffraction setup based on a commercial four-circle diffractometer with a sealed-ceramic copper X-ray tube, upgraded with parabolic graded multilayer X-ray optics and a one-dimensional position-sensitive detector, is presented. The high potential of this setup is demonstrated by a phase analysis study of pentacene thin films and the determination of in-plane lattice constants of pentacene mono- and multilayers. The quality of the results compare well to studies performed at synchrotron radiation facilities. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674305 Thu, 09 Feb 2012 05:00:00 +0100 5674305 http://www.medworm.com/index.php?rid=5674304&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5542 SIR2011, the successor of SIR2004, is the latest program of the SIR suite. It can solve ab initio crystal structures of small- and medium-size molecules, as well as protein structures, using X-ray or electron diffraction data. With respect to the predecessor the program has several new abilities: e.g. a new phasing method (VLD) has been implemented, it is able to exploit prior knowledge of the molecular geometry via simulated annealing techniques, it can use molecular replacement methods for solving proteins, it includes new tools like free lunch and new approaches for electron diffraction data, and it visualizes three-dimensional electron density maps. The graphical interface has been further improved and allows the straightforward use of the program even in difficult cases. (Source: Jour... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674304 Thu, 09 Feb 2012 05:00:00 +0100 5674304 http://www.medworm.com/index.php?rid=5674303&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fkk5095 Fragment Finder 2.0 is a web-based interactive computing server which can be used to retrieve structurally similar protein fragments from 25 and 90% nonredundant data sets. The computing server identifies structurally similar fragments using the protein backbone Cα angles. In addition, the identified fragments can be superimposed using either of the two structural superposition programs, STAMP and PROFIT, provided in the server. The freely available Java plug-in Jmol has been interfaced with the server for the visualization of the query and superposed fragments. The server is the updated version of a previously developed search engine and employs an in-house-developed fast pattern matching algorithm. This server can be accessed freely over the World Wide Web through the URL http://cluster... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674303 Thu, 09 Feb 2012 05:00:00 +0100 5674303 http://www.medworm.com/index.php?rid=5674302&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fnb5010 The six orientation relationships (ORs) found in the Mg/γ-Mg17Al12 precipitation system were summarized and systematically interpreted based on the atomic structure of the precipitate γ-Mg12Al17 and the invariant deformation element (IDE) model for diffusional phase transformations. It was found that the pseudo-twinning relationship between the six ORs is a reflection of the pseudo-twinning relationship between the close- or near-close-packing planes ({\overline 8}\hskip.75{\overline 7}\hskip.75{\overline 7}), ({\overline 4}11), (033), (411) and (8{\overline 7}\hskip.75{\overline 7}) in the precipitate γ-Mg12Al17. As a result, the Pitsch–Schrader OR is the starting point for the other five ORs. Multiple morphologies, growth directions and habit planes could be rationally interpreted b... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674302 Thu, 09 Feb 2012 05:00:00 +0100 5674302 http://www.medworm.com/index.php?rid=5674301&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5537 This article presents an automated sample-loading system for BioSAXS beamlines, which combines single-channel disposable-tip pipetting with a vacuum-enclosed temperature-controlled capillary flow cell. The design incorporates an easily changeable capillary to reduce the incidence of X-ray window fouling and cross contamination. Both the robot-control and the data-processing systems are written in Python. The data-processing code, RAW, has been enhanced with several new features to form a user-friendly BioSAXS pipeline for the robot. The flow cell also supports efficient manual loading and sample recovery. An effective rinse protocol for the sample cell is developed and tested. Fluid dynamics within the sample capillary reveals a vortex ring pattern of circulation that redistributes radiati... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674301 Thu, 09 Feb 2012 05:00:00 +0100 5674301 http://www.medworm.com/index.php?rid=5674300&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5304 Vertically aligned undoped ZnO and Sb-doped ZnO nanowires have been synthesized on a silicon substrate using the vapor–solid technique, without using a catalyst or predeposited buffer layers. The structure and morphology of the as-synthesized nanowires are characterized using X-ray diffraction, scanning and transmission electron microscopies, selected area electron diffraction, and electron dispersive X-ray spectroscopy. The results showed that the use of Si(111) is a critical factor for the growth of vertically aligned nanowires. This is a result of the lattice match on Si(111), which is more favorable with the ZnO lattice structure because the Si(111) surface is hexagonal and has a smaller lattice constant of 3.840 Å. The photoluminescence properties were also investigated at room t... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674300 Thu, 09 Feb 2012 05:00:00 +0100 5674300 http://www.medworm.com/index.php?rid=5674299&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5138 Very high resolution powder diffraction structural studies of the potentially room temperature multiferroic Ga2−xFexO3 solid solution series (x = 0.7–1.3, 0.1 steps) have been undertaken using a fixed angle of incidence geometry. The applied absorption correction was seen to improve the goodness of fit (χ2) of the Rietveld refinements from an average of 1.41 to 1.06. The correction also resulted in an increased mean isotropic displacement parameter from 0.5 to 0.65. The mean difference in the fractional coordinates of the atoms between the refined models from the corrected and uncorrected data was 0.0007 Å, compared with the mean fractional coordinate error of 0.0003 Å. It is concluded that the final crystal structures refined from the corrected and uncorrected data are not sign... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5674299 Thu, 09 Feb 2012 05:00:00 +0100 5674299 http://www.medworm.com/index.php?rid=5617361&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5539 Gravity distorts the circular contours found for small-angle neutron scattering data from azimuthally symmetric scattering systems when taken at long wavelength and with large wavelength spreads. The resolution is calculated for a Debye–Scherrer ring and compared with results from measurements taken on a sample of opal. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617361 Sat, 14 Jan 2012 05:00:00 +0100 5617361 http://www.medworm.com/index.php?rid=5617360&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5525 In this study, the change in internal lattice strain in an iron plate during tensile deformation was investigated by performing in situ measurements under applied force. The lattice strain was evaluated by neutron diffraction and Bragg-edge transmission. The neutron diffraction results showed that the averaged 110 lattice strain along the direction perpendicular to the applied force was between −422 and −109 × 10−6. The position dependence of the lattice strain and the change in the distribution of elastic strain in an iron plate with notches during tensile deformation was obtained by Bragg-edge transmission. It was also observed that, when the load increased over 30 kN, the area of plastic deformation increased around the positions of the notches. (Source: Journal of Applied ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617360 Sat, 14 Jan 2012 05:00:00 +0100 5617360 http://www.medworm.com/index.php?rid=5617359&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fto5007 Combined refinements of local atomic structure that involve simultaneous fitting of powder-averaged and single-crystal data were implemented as an extension to the publicly available RMCProfile software. The refinements employ the reverse Monte Carlo method to fit neutron total scattering data, the neutron Bragg profile, extended X-ray absorption fine structure (EXAFS) and structured diffuse scattering in electron diffraction. The procedure was tested using simulated data generated for a realistic model of perovskite-like KNbO3, which exhibits strongly correlated Nb and O displacements. The results indicated that fitting the powder data (i.e. total scattering or total scattering plus EXAFS) alone fails to reproduce the nanoscale range of displacement correlations. Simultaneous fitting of t... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617359 Sat, 14 Jan 2012 05:00:00 +0100 5617359 http://www.medworm.com/index.php?rid=5617357&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fnb5006 Nanocrystalline Ni thin films have been produced by direct current electrodeposition with different additives and current density in order to obtain 〈100〉, 〈111〉 and 〈211〉 major fiber textures. The dislocation density, the Burgers vector population and the coherently scattering domain size distribution are determined by high-resolution X-ray diffraction line profile analysis. The substructure parameters are correlated with the strength of the films by using the combined Taylor and Hall–Petch relations. The convolutional multiple whole profile method is used to obtain the substructure parameters in the different coexisting texture components. A strong variation of the dislocation density is observed as a function of the deposition conditions. (Source: Journal of Applied Crysta... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617357 Sat, 14 Jan 2012 05:00:00 +0100 5617357 http://www.medworm.com/index.php?rid=5617356&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5301 Anisotropic broadening correction in X-ray powder diffraction by an ellipsoidal formula is applied on samples with nanosized crystals. Two cases of minerals with largely anisotropic crystallite shapes are presented. The properly applied formalism not only improves the fitting of the theoretical and observed diffraction diagrams but also gives direct information about realistic crystallite shapes and sizes. The approach is demonstrated using the Rietveld refinement program TOPAS and it is easily adaptable to other similar software. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617356 Sat, 14 Jan 2012 05:00:00 +0100 5617356 http://www.medworm.com/index.php?rid=5617364&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fpf0090 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617364 Wed, 04 Jan 2012 05:00:00 +0100 5617364 http://www.medworm.com/index.php?rid=5617363&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fme0458 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617363 Wed, 04 Jan 2012 05:00:00 +0100 5617363 http://www.medworm.com/index.php?rid=5617362&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5310 Errors in the paper by Liu, Waclawik & Luo [J. Appl. Cryst. (2010), 43, 448–454] are corrected. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617362 Wed, 04 Jan 2012 05:00:00 +0100 5617362 http://www.medworm.com/index.php?rid=5617358&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fkk5086 Multiple Bragg reflections (MBRs), which can be realized in a bent perfect crystal (BPC) slab and are mutually in dispersive diffraction geometry, provide a monochromatic beam of excellent resolution. After identifying many MBR effects in a BPC Si crystal by using the method of θ–2θD scanning, we have turned our attention to the study of selected effects using the method of azimuthal rotation of the crystal lattice around the scattering vector of the primary reflection for a fixed chosen wavelength. In this paper, several azimuthal scans with the intention of possible practical exploitation for very high resolution diffractometry are presented. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5617358 Wed, 04 Jan 2012 05:00:00 +0100 5617358 http://www.medworm.com/index.php?rid=5534015&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frw5007 An unexpected precipitate phase was observed in Mg–20 wt% Dy alloy, with a cuboid morphology not compatible with any shown in the Mg–Dy binary phase diagram. As observed by scanning electron microscopy and energy-dispersive X-ray analysis, the ratio of atomic percent of Dy to Mg is very high in these particles, probably largely because of the poor spatial resolution of that technique but already showing the mismatch with any previously characterized Mg–Dy compound. High-brilliance synchrotron diffraction and transmission electron microscopy experiments confirmed that these particles are composed of DyH2. They are formed during sample preparation at room temperature when hydrogen-containing sources such as water are used. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5534015 Fri, 23 Dec 2011 14:18:29 +0100 5534015 http://www.medworm.com/index.php?rid=5534018&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Ffs5009 A prototype jig to attach a protein crystallization plate to a standard X-ray goniometer has been designed and constructed in partnership with an engineering firm. This allows a low-cost implementation of in situ diffraction using the available home-laboratory X-ray source. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5534018 Thu, 22 Dec 2011 05:00:00 +0100 5534018 http://www.medworm.com/index.php?rid=5534017&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5185 This article describes the development of a curated online protein block sequence database, PDB-2-PB. The protein block sequences for protein structures with complete backbone coordinates have been encoded using the encoding procedure of de Brevern, Etchebest & Hazout [Proteins (2000), 41, 271–287]. In the current release of the PDB-2-PB database (version 1.0), the protein entries from a recent release of the World Wide Protein Data Bank (wwPDB), which has 74 297 solved PDB entries as of 7 July 2011, have been used as a primary source. The PDB-2-PB database stores the protein block sequences for all the chains present in a protein structure. PDB-2-PB version 1.0 has the curated protein block sequences for 103 252 PDB chain entries (93 547 X-ray, 7033 NMR and 2672 other experimental... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5534017 Thu, 22 Dec 2011 05:00:00 +0100 5534017 http://www.medworm.com/index.php?rid=5534016&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fto5009 Two static high-pressure X-ray diffraction (XRD) studies of potassium chlorate have been performed at pressures of up to ∼14.3 GPa in a diamond anvil cell at ambient temperature using the 16 ID-B undulator beamline at the Advanced Photon Source for the X-ray source. The first experiment was conducted to ascertain decomposition rates of potassium chlorate as a function of pressure. Below 2 GPa, the sample was observed to decompose rapidly in the presence of the X-ray beam and release oxygen. Above 2 GPa (near the phase I → phase II transition), the decomposition rate dramatically slowed so that good quality XRD patterns could be acquired. This suggests a phase-dependent decomposition rate. In the second study, X-ray diffraction spectra were collected at pressures from 2 to 14.3 ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5534016 Thu, 22 Dec 2011 05:00:00 +0100 5534016 http://www.medworm.com/index.php?rid=5501458&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5193 The recently developed GEO-MIX-SELF approximation (GMS) is applied to interpret the pressure dependence of the longitudinal ultrasonic wave velocities in a polycrystalline graphite sample that has already been investigated in a wide range of experimental contexts. Graphite single crystals have extremely anisotropic elastic properties, making this sample a challenging test to demonstrate the potential of the GMS method. GMS combines elements of well known self-consistent algorithms and of the geometric mean approximation. It is able to consider mixtures of different polycrystalline phases, each with its own nonspherical grain shape and preferred orientation (texture). Pores and `cracks', typical for bulk graphite, are modeled as phases with `empty' grains. The pressure dependence (up to 150... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501458 Wed, 14 Dec 2011 15:17:34 +0100 5501458 http://www.medworm.com/index.php?rid=5501468&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fnb5007 A low-budget automatic sample changer that allows the rapid analysis of powder or polycrystalline samples using an X-ray single-crystal diffractometer equipped with an area detector is here described. It uses control software that synchronizes the movement of a linear stage with the collection of frames by the diffractometer. Small pieces of thin solid samples are directly attached to a 30 cm ruler, which is used as a disposable magazine, while loose powder samples are loaded into holes on an acetate strip covered on both sides with Kapton tape and attached to the ruler. The use of this type of diffractometer with a sample changer is a simple, low cost and effective solution for studies requiring the analysis of a large number of samples by X-ray powder diffraction. With the current desi... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501468 Tue, 13 Dec 2011 05:00:00 +0100 5501468 http://www.medworm.com/index.php?rid=5501467&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5181 Stereographic projection is one of the most powerful research tools for crystallography in materials science. A new program for full operation of stereographic projections and in-depth exploration of crystallographic orientation relationships is described. It is specifically designed for materials researchers who are in need of tools for extensive crystallographic analysis. The difference from other popular commercial software for crystallography is that this program provides new options for users to plot and fully control stereographic projections of an arbitrary pole centre for an arbitrary crystal structure and to illustrate composite stereographic projections, which are necessary to explore the orientation relationships between two phases. The program is able to perform a range of esse... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501467 Tue, 13 Dec 2011 05:00:00 +0100 5501467 http://www.medworm.com/index.php?rid=5501466&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Ffs5008 A method is derived to calculate the attenuation correction factors for elastic or inelastic X-ray or neutron scattering experiments using a spherical sample. The method can be applied to a sphere that is either fully or partially illuminated by an incident beam of rectangular cross-sectional area. The required input parameters are the energy-dependent attenuation coefficients, the radius of the sphere and the dimensions of the incident beam. In-plane scattering is assumed. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501466 Tue, 13 Dec 2011 05:00:00 +0100 5501466 http://www.medworm.com/index.php?rid=5501465&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frg5006 Anomalous dispersion at the Si K absorption edge has been used to control the reflection from the interface between a film and an Si substrate, which otherwise complicates the nanostructure analysis of such a film, particularly for the soft-matter case, in grazing-incidence small-angle scattering. Such a reflectionless condition has been chosen for a triblock copolymer thin film, and two-dimensional grazing-incidence small-angle scattering patterns were obtained without the effect of the reflection. The present approach is useful for analysing nanostructures without introducing complicated corrections arising from the reflection. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501465 Tue, 13 Dec 2011 05:00:00 +0100 5501465 http://www.medworm.com/index.php?rid=5501464&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5294 A new crystallization system is described, which makes it possible to use an evaporation-based microfluidic crystallization technique for protein crystallization. The gas and water permeability of the used polydimethylsiloxane (PDMS) material enables evaporation of the protein solution in the microfluidic device. The rates of evaporation are controlled by the relative humidity conditions, which are adjusted in a precise and stable way by using saturated solutions of different reagents. The protein crystals could nucleate and grow under different relative humidity conditions. Using this method, crystal growth could be improved so that approximately 1 mm-sized lysozyme crystals were obtained more successfully than using standard methods. The largest lysozyme crystal obtained reached 1.57�... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501464 Tue, 13 Dec 2011 05:00:00 +0100 5501464 http://www.medworm.com/index.php?rid=5501463&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frg5004 Specialized software has been developed to calculate the absorption factor for the infinite-cylinder transmission Debye–Scherrer geometry (including inclined beams) to be used with two-dimensional area powder pattern registration. The diffracted beams are defined by the direction cosines in the laboratory Cartesian coordinate system. Modern two-dimensional area detectors have a large number of pixels, so an interpolation is made by the triangulation procedure to save computer time. The absorption correction is allowed for so that the intensity in each pixel is reduced on the same scale and the final diffraction-angle-dependent intensity, I(2θ), does not require any further absorption correction. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501463 Tue, 13 Dec 2011 05:00:00 +0100 5501463 http://www.medworm.com/index.php?rid=5501462&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5198 A prototype X-ray pixel area detector (XPAD3.1) has been used for X-ray diffraction experiments with synchrotron radiation. The characteristics of this detector are very attractive in terms of fast readout time, high dynamic range and high signal-to-noise ratio. The prototype XPAD3.1 enabled various diffraction experiments to be performed at different energies, sample-to-detector distances and detector angles with respect to the direct beam, yet it was necessary to perform corrections on the diffraction images according to the type of experiment. This paper is focused on calibration and correction procedures to obtain high-quality scientific results specifically developed in the context of three different experiments, namely mechanical characterization of nanostructured multilayers, elasti... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501462 Tue, 13 Dec 2011 05:00:00 +0100 5501462 http://www.medworm.com/index.php?rid=5501461&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fto5004 An in situ energy-dispersive X-ray diffraction experiment was undertaken on operational titanium electrowinning cells to observe the formation of rutile (TiO2) passivation layers on Magnéli-phase (TinO2n−1; n = 4–6) anodes and thus determine the relationship between passivation layer formation and electrolysis time. Quantitative phase analysis of the energy-dispersive data was undertaken using a crystal-structure-based Rietveld refinement. Layer formation was successfully observed and it was found that the rate of increase in layer thickness decreased with time, rather than remaining constant as observed in previous studies. The limiting step in rutile formation is thought to be the rate of solid-state diffusion of oxygen within the anode structure. (Source: Journal of Applied Crystal... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501461 Tue, 13 Dec 2011 05:00:00 +0100 5501461 http://www.medworm.com/index.php?rid=5501460&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5534 In conclusion, the main concern is the availability of the nanobeam, how it was generated and the fact that a beam out of a two-dimensionally confining waveguide was used for diffraction experiments for the first time. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501460 Tue, 13 Dec 2011 05:00:00 +0100 5501460 http://www.medworm.com/index.php?rid=5501459&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5201 The formation of GeSi nanoparticles on an SiO2 matrix is studied here by synchrotron-based techniques. The shape, average diameter and size dispersion were obtained from grazing-incidence small-angle X-ray scattering data. X-ray diffraction measurements were used to obtain crystallite sizes and composition via resonant (anomalous) measurements. By using these techniques as input for extended X-ray absorption fine structure analysis, the local composition surrounding the Ge atoms is investigated. Although the results for each of the methods above are commonly analyzed separately, the combination of such techniques leads to an improved understanding of nanoparticle structural and chemical properties. Crucial indirect parameters that cannot be quantified by other means are accessed in this wo... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5501459 Tue, 13 Dec 2011 05:00:00 +0100 5501459 http://www.medworm.com/index.php?rid=5404883&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5119 The VLD algorithm relies on the properties of the difference Fourier synthesis and is designed for solving crystal structures in the correct space group, starting from random models. The standard approach has been modified by integrating it with the RELAX procedure, for translating to the correct position misplaced but correctly oriented models. A better control of the parameters and additional phase refinement cycles were able to improve the quality of the solutions and to make superfluous, for macromolecules and medium-sized molecules, the least-squares refinement cycles that, in the standard VLD approach, follow the phasing step. As a result, the efficiency of the new VLD algorithm is strongly increased; it has been checked using a wide variety of practical cases and compared with the e... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404883 Mon, 14 Nov 2011 12:51:08 +0100 5404883 http://www.medworm.com/index.php?rid=5404896&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5118 Determining the effects of stress on the internal structure of high-performance fibres may provide insight into their structure–property relationships. The deformation of voids inside a poly(p-phenylene terephthalamide) (PPTA) fibre upon application of stress is one such effect which may be observed using in situ small-angle X-ray scattering. For this purpose, a compact in-vacuum stretching device is described here, capable of applying a force of up to 500 N using specially designed fibre clamps. Furthermore, a small radiative heater is placed around the fibre at the measurement position, so that the effects of the application of heat during tensile load can also be determined. Initial results show a slight but significant effect of stress and heating on the internal void structure of ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404896 Sat, 12 Nov 2011 05:00:00 +0100 5404896 http://www.medworm.com/index.php?rid=5404895&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5182 A new octuple cuvette has been developed to reduce the experimental time in small-angle X-ray scattering (SAXS). Since each chamber has uniform dimensions, identical scattering curves for bovine serum albumin are obtained within an average deviation of 1%. The cuvette can be used to record SAXS curves for seven sample concentrations quasi-simultaneously by interchamber subtraction, i.e. calculating the difference in scattering intensity between the sample in any of the first seven chambers and a matching buffer in the eighth chamber. This enables fast acquisition of a data set and its extrapolation to infinite dilution, and increases the throughput of SAXS experiments. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404895 Sat, 12 Nov 2011 05:00:00 +0100 5404895 http://www.medworm.com/index.php?rid=5404894&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Ffs5005 The new program ANODE estimates anomalous or heavy-atom density by reversing the usual procedure for experimental phase determination by methods such as single- and multiple-wavelength anomalous diffraction and single isomorphous replacement anomalous scattering. Instead of adding a phase shift to the heavy-atom phases to obtain a starting value for the native protein phase, this phase shift is subtracted from the native phase to obtain the heavy-atom substructure phase. The required native phase is calculated from the information in a Protein Data Bank file of the structure. The resulting density enables even very weak anomalous scatterers such as sulfur to be located. Potential applications include the identification of unknown atoms and the validation of molecular replacement solutions.... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404894 Sat, 12 Nov 2011 05:00:00 +0100 5404894 http://www.medworm.com/index.php?rid=5404893&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fkk5092 ShelXle is a graphical user interface for SHELXL [Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122], currently the most widely used program for small-molecule structure refinement. It combines an editor with syntax highlighting for the SHELXL-associated .ins (input) and .res (output) files with an interactive graphical display for visualization of a three-dimensional structure including the electron density (Fo) and difference density (Fo–Fc) maps. Special features of ShelXle include intuitive atom (re-)naming, a strongly coupled editor, structure visualization in various mono and stereo modes, and a novel way of displaying disorder extending over special positions. ShelXle is completely compatible with all features of SHELXL and is written entirely in C++ using the Qt4 and FFTW libra... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404893 Sat, 12 Nov 2011 05:00:00 +0100 5404893 http://www.medworm.com/index.php?rid=5404892&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frg5002 SAAF is a tool for analyzing small-angle neutron scattering (SANS) data using analytical model functions. It is implemented in Perl and uses Gnuplot as its engine for curve fitting and data display. A set of standard models is provided with the program. New models are easy to implement at the user level. One of its features is the ability to perform de-smearing on data sets with variable and convoluted instrument resolutions. For SANS experiments, data de-smearing is often required, especially for data with small neutron scattering vector (Q) values or sharp scattering features. On time-of-flight instruments, the uncertainty in Q is a convolution of the contributions from neutrons with different wavelengths and beam intensities. SAAF is designed to take such Q resolution into account for d... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404892 Sat, 12 Nov 2011 05:00:00 +0100 5404892 http://www.medworm.com/index.php?rid=5404891&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5199 The microstructural and crystallographic characteristics of 5M martensite in an Ni50Mn28Ga22 alloy were investigated by electron backscatter diffraction (EBSD) analysis. The microstructure of 5M martensite observed at room temperature can be characterized by broad plates with alternately distributed fine lamellae (variants). With the accurate EBSD orientation measurements and by application of monoclinic superstructure information, four twin-related variants in one broad plate were identified. On the basis of the correct orientation data of martensite variants acquired from the EBSD measurements, the more favourable orientation relationship between austenite and 5M martensite was revealed to be the Pitsch relation with (101)A//(1 {\overline 2} \hskip1{\overline 5})5M and [10 {\overline 1}]... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404891 Sat, 12 Nov 2011 05:00:00 +0100 5404891 http://www.medworm.com/index.php?rid=5404890&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frg5003 A surface structure refinement procedure is introduced, which uses both anomalous and non-anomalous crystal truncation rod data simultaneously. It is shown how a single structural model can be refined against data sets measured at different wavelengths and how this can greatly reduce correlations between fit parameters. The structure factors are computed taking into account the anomalous dispersion corrections and are scaled to the data, whereby each data set is assigned its own scale factor. The procedure is implemented in the widely used surface diffraction program ROD. The structure of a one unit cell thin LaAlO3 film on an SrTiO3(001) substrate is refined by making use of a non-anomalous data set and one taken at the La L1-edge. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404890 Sat, 12 Nov 2011 05:00:00 +0100 5404890 http://www.medworm.com/index.php?rid=5404889&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5196 An efficient method for X-ray diffraction data collection mapping on a given curved surface has been developed. The method uses a laser–video auto z alignment system to collect a map of heights on a fine mesh grid. It also reconstructs the surface geometry and determines surface normals on a three-dimensional surface fit. An algorithm was used to calculate the required rotation and tilt angles to coincide the sample normal with the diffraction center before each exposure. A set of diffraction frames collected using this technique was analyzed in order to superimpose a phase transformation map onto a typical zirconia ceramic sample. With this method, mapping of phase and stresses on a complex surface has been demonstrated. This approach is broadly applicable to many important areas of stu... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404889 Sat, 12 Nov 2011 05:00:00 +0100 5404889 http://www.medworm.com/index.php?rid=5404888&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5133 Seven diffraction patterns were collected on a 100 nm Gd-doped ceria layer deposited on a silicon wafer under asymmetric reflection conditions. As the grazing-incidence angle decreases, large shifts (a few tens of degrees) and broadenings (two degrees below the critical angle) of hkl reflections are apparent in the diffraction patterns. The impact of these aberrations on the positions and profiles of the Bragg peaks is studied in detail in this work. On the basis of this analysis, diffraction patterns collected at different angles of incidence could then be refined using a unique structural model. From these refinements, the evolution of the coherent diffracting domains, the strain and the microstrain can clearly be traced as a function of depth. (Source: Journal of Applied Crystallograp... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404888 Sat, 12 Nov 2011 05:00:00 +0100 5404888 http://www.medworm.com/index.php?rid=5404887&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5178 Differential evolution is a global optimization algorithm that has started to find widespread use in the scattering community because of its proven effectiveness. In this article the performance of the algorithm is evaluated by fitting an X-ray reflectivity data set and investigating its convergence behavior as a function of its tuning parameters. The results offer important insights for applying differential evolution algorithms to scattering problems and provide some rules of thumb on how to tune the parameters. It is shown that, by choosing optimal tuning parameter values, the speed of the fitting process can be increased by an order of magnitude. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404887 Sat, 12 Nov 2011 05:00:00 +0100 5404887 http://www.medworm.com/index.php?rid=5404886&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5120 The newly developed multiphase transformation-induced plasticity (TRIP) steels are of interest for industrial applications because of their excellent combination of high strength and ductility. Their performance can be successfully controlled by designing an optimum balance in the volume fractions of ferrite, bainite and retained austenite. The characteristics of the retained austenite are considered to be the main key to achieving the desired final properties. Against this background, the effects of retained austenite characteristics, such as volume fraction, carbon concentration, size and shape, on the behaviour of TRIP steels have been studied. The crystallographic orientation of the retained austenite was measured by electron backscattered diffraction (EBSD). The effect of initial cold... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404886 Sat, 12 Nov 2011 05:00:00 +0100 5404886 http://www.medworm.com/index.php?rid=5404885&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fto5005 It is shown that an extremely inclined X-ray double-crystal monochromator can diffract a beam with the required wavelength and at the same time may reflect a great deal of unwanted radiation in a broad range of Bragg angles. This is a generalization of the idea of Cowan & Brennan [Rev. Sci. Instrum. (1989), 60, 1987–1990], which partially solves the radiation heat load problem. The properties of such a device are discussed. It is shown that in some cases the diffracted beam may be significantly broadened as a result of refraction effects. In these cases a four-crystal arrangement or an additional mirror is necessary. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404885 Sat, 12 Nov 2011 05:00:00 +0100 5404885 http://www.medworm.com/index.php?rid=5404884&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5202 Knowledge of the geometry of grain boundaries in polycrystalline materials is essential for predicting boundary properties. The issue of cataloging the geometrically characterized groups of twist and tilt boundaries is addressed. All distinct types of pure-twist and pure-tilt boundaries are determined for misorientations corresponding to highly coincident (3 ≤ Σ ≤ 13) lattices of cubic symmetry. For these particular misorientations, the number of distinct twist boundaries and zones of tilt boundaries ranges from 5 (Σ = 3) to 11 (Σ = 9 or 11). Maps displaying the locations of twist and tilt boundary planes indicate boundaries having particular geometries with two-dimensional periodicities. This is of significance for identification of special boundary structures. Moreover, the maps a... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5404884 Sat, 12 Nov 2011 05:00:00 +0100 5404884 http://www.medworm.com/index.php?rid=5376131&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fpf0084 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376131 Sat, 29 Oct 2011 04:00:00 +0100 5376131 http://www.medworm.com/index.php?rid=5376130&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fdb5098 VESTA is a three-dimensional visualization system for crystallographic studies and electronic state calculations. It has been upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphology of crystals; superimposing multiple structural models, volumetric data and crystal faces; calculation of electron and nuclear densities from structure parameters; calculation of Patterson functions from structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels; determination of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex molecules and cage-like structures; undo and redo in graphical... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376130 Sat, 29 Oct 2011 04:00:00 +0100 5376130 http://www.medworm.com/index.php?rid=5376129&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5135 iotbx.cif is a new software module for the development of applications that make use of the CIF format. Comprehensive tools are provided for input, output and validation of CIFs, as well as for interconversion with high-level cctbx [Grosse-Kunstleve, Sauter, Moriarty & Adams (2002). J. Appl. Cryst. 35, 126–136] crystallographic objects. The interface to the library is written in Python, whilst parsing is carried out using a compiled parser, combining the performance of a compiled language (C++) with the benefits of using an interpreted language. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376129 Sat, 29 Oct 2011 04:00:00 +0100 5376129 http://www.medworm.com/index.php?rid=5376128&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5180 A new method for determination of the orientation matrix of Laue X-ray data is presented. The method is based on matching of the experimental patterns of central reciprocal lattice rows projected on a unit sphere centered on the origin of the reciprocal lattice with the corresponding pattern of a monochromatic data set on the same material. This technique is applied to the complete data set and thus eliminates problems often encountered when single frames with a limited number of peaks are to be used for orientation matrix determination. Application of the method to a series of Laue data sets on organometallic crystals is described. The corresponding program is available under a Mozilla Public License-like open-source license. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376128 Sat, 29 Oct 2011 04:00:00 +0100 5376128 http://www.medworm.com/index.php?rid=5376127&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5194 This paper proposes a method to identify the type and the Burgers vector of dislocations visualized via transmission electron microscopy (TEM). The first step is to determine experimentally the orientation, with respect to the sample holder, of a grain of known crystal structure whose dislocation slip systems have been previously reported. With this determined orientation of the grain, the method calculates the orientation of the projections of the possible dislocation line vectors in the transmission electron microscope screen coordinate system and then compares them with the observed dislocations to identify their type and the Burgers vector. The coordinate transformations underlying the method are outlined, and its validity is demonstrated using TEM measurements on a titanium sample. Th... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376127 Sat, 29 Oct 2011 04:00:00 +0100 5376127 http://www.medworm.com/index.php?rid=5376126&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5124 The morphology of epitaxial alloy nanostructures grown on a van der Waals-type WSe2(0001) surface was studied using grazing-incidence small-angle X-ray scattering (GISAXS). Assemblies of 111-oriented islands of (Co,Cr)Pt3 and (Co,Fe)Pt alloys were grown at different deposition temperatures, with nominal thicknesses from 0.1 to 3 nm, resulting in various island densities. Evaluation of the GISAXS patterns indicates that for similar growth conditions CrPt3 islands are flatter than CoPt or FePt islands and exhibit larger island volumes. These features are correlated with the better wetting behaviour and more negative formation enthalpy of the CrPt3 alloy. For dense arrays of self-assembled CoPt islands, much smaller island volumes are extracted from GISAXS experiments than are observed by s... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5376126 Sat, 29 Oct 2011 04:00:00 +0100 5376126 http://www.medworm.com/index.php?rid=5281919&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fto5002 Some new sets of special directions (SDs) in the Brillouin zone for cubic structures are presented. They allow for construction in the reciprocal space of anisotropic quantities, having Γ1 symmetry, from knowledge of such quantities along a limited number of SDs. These SDs also define which spectra, measured, for example, in Compton scattering experiments, are the most efficient for reconstructing three-dimensional densities from their one-dimensional projections. The new SDs are compared with results obtained by other authors. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281919 Tue, 04 Oct 2011 14:54:32 +0100 5281919 http://www.medworm.com/index.php?rid=5281926&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Frw5003 The conventional zero-background holder technique has been adapted for handling small bulk samples by adding one-axis mobility to a single-crystal wafer using a Newport optical stage. Experiments showed that an a-plane (11{\overline 2}0) sapphire crystal with a surface-to-crystal-plane angle of ∼3° can be used as a zero-background holder. Such a crystal is a viable alternative to the commercial Rigaku product and shows better performance in the intermediate angle range (2θ = 60–110° for Cu Kα radiation). It has also been demonstrated that the proposed scheme of hardware stacking is operational. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281926 Tue, 04 Oct 2011 04:00:00 +0100 5281926 http://www.medworm.com/index.php?rid=5281925&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Ffs5004 A sample holder for handling samples of protein for in-house X-ray powder diffraction (XRPD) analysis has been made and tested on lysozyme. The use of an integrated pinhole reduced the background, and good signal-to-noise ratios were obtained from only 7 µl of sample, corresponding to approximately 2–3 mg of dry protein. The sample holder is further adaptable to X-ray absorption spectroscopy (XAS) measurements. Both XRPD and XAS at the Zn K-edge were tested with hexameric Zn insulin. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281925 Tue, 04 Oct 2011 04:00:00 +0100 5281925 http://www.medworm.com/index.php?rid=5281924&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Ffs5003 DADIMODO is a program for refining atomic models of multidomain proteins or complexes against small-angle X-ray scattering data. Interdomain distance and orientational restraints, such as those derived from NMR measurements, can be included in the optimization process. While domain structures are mainly kept rigid, flexible regions can be user defined. Stepwise generic conformational changes, specified by the user, are applied cyclically in a stochastic optimization algorithm that performs a search in the protein conformation space. The convergence for this genetic algorithm is driven by an adaptable selection pressure. The algorithmic structure guarantees that a physically acceptable full atomic model of the structure is present at all stages of the optimization. A graphical user interfac... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281924 Tue, 04 Oct 2011 04:00:00 +0100 5281924 http://www.medworm.com/index.php?rid=5281923&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5094 Quasi-mosaicity is an effect of secondary bending within a crystal driven by crystalline anisotropy. This effect can be used to fabricate a series of curved crystals for the realization of a Laue lens. It is highlighted that crystals bent by the quasi-mosaic effect allow very high resolution focusing with respect to mosaic crystals. Under the same conditions for energy passband, crystal size and flux of incident photons, a Laue lens based on quasi-mosaic crystals would increase the signal-to-noise ratio by about an order of magnitude compared to the same lens with mosaic crystals. Moreover, no mosaic defocusing occurs for quasi-mosaic crystals. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281923 Tue, 04 Oct 2011 04:00:00 +0100 5281923 http://www.medworm.com/index.php?rid=5281922&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5192 Marble has historically been used as an ornamental stone because of its aesthetic appeal, ease of polishing and ex;cellent physical properties. One of the main factors affecting the durability of marbles is their thermal behaviour. Although marble is used extensively in Spain as a building and decorative material, little research has been done into its thermal behaviour. In this work, the textural and microstructural properties of seven calcitic and dolomitic marbles from Andalusia (southern Spain) were characterized to assess how these properties affect their thermal response. Rock fabric properties (grain morphology, boundaries and micro-crack populations) were studied by polarized microscopy and lattice preferred orientation using X-ray texture goniometry. Elastic properties were measur... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281922 Tue, 04 Oct 2011 04:00:00 +0100 5281922 http://www.medworm.com/index.php?rid=5281921&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5531 The structure of porous TiO2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40–60 Å at the pore wall (i.e. the interface between the pore and the TiO2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281921 Tue, 04 Oct 2011 04:00:00 +0100 5281921 http://www.medworm.com/index.php?rid=5281920&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5293 In the case of neutron (and X-ray) scattering by objects that are about 105 times larger than the wavelength, the objects can be considered as (inhomogeneous) phase-shifting media. In contrast with small-angle scattering, the scattering patterns from phase-shifting objects are calculated by the superposition of coherent partial waves that penetrate the object. In order to determine the scattering patterns from large complicated objects, it is proposed to use the two-dimensional Radon transform of the objects and Fraunhofer diffraction. This approach is much easier than using the small-angle scattering treatment, as is shown in this paper. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5281920 Tue, 04 Oct 2011 04:00:00 +0100 5281920 http://www.medworm.com/index.php?rid=5204567&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko9123 Errors in the paper by Ciccariello, Melnichenko & He [J. Appl. Cryst. (2011), 44, 43–51] are corrected. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204567 Thu, 08 Sep 2011 04:00:00 +0100 5204567 http://www.medworm.com/index.php?rid=5204566&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5174 EDIFF is a new user-friendly software suite for unit-cell determination of three-dimensional nanocrystals from randomly oriented electron diffraction patterns with unknown independent orientations. It can also be used for three-dimensional cell reconstruction from diffraction tilt series. In neither case is exact knowledge of the angular relationship between the patterns required. The unit cell can be validated and the crystal system assigned. EDIFF can index the reflections in electron diffraction patterns. Thus, EDIFF can be employed as a first step in reconstructing the three-dimensional atomic structure of organic and inorganic molecules and of proteins from diffraction data. An example illustrates the viability of the EDIFF approach. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204566 Thu, 08 Sep 2011 04:00:00 +0100 5204566 http://www.medworm.com/index.php?rid=5204565&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5116 Most melt-crystallized polymers present a lamellar nanostructure of alternating crystalline and amorphous lamellae which is coherent enough to display a broad interference peak in small-angle X-ray scattering experiments (SAXS). Nascent semi-crystalline polymers, on the other hand, though highly crystalline, hardly show an interference peak. This has long been attributed either to the formation of extended chain crystals or to a highly incoherent lamellar stacking. Here it is shown that a coherent lamellar order is shaded by a large scattering contribution from the air/grain interface. This is revealed by a SAXS contrast variation technique that suppresses the air/grain interface scattering and leaves only the scattering contribution from the internal lamellae. (Source: Journal of Applied ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204565 Thu, 08 Sep 2011 04:00:00 +0100 5204565 http://www.medworm.com/index.php?rid=5204564&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5117 Initial experimental results are reported from the extended Q-range small-angle neutron scattering (EQ-SANS) diffractometer at the Spallation Neutron Source at Oak Ridge National Laboratory (ORNL). A generation-8 polyamidoamine dendrimer was measured and the conformation parameters (radius of gyration, thickness of the soft shell etc.) extracted by model fitting to the scattering data. The results are compared with data collected at the general-purpose small-angle neutron scattering (GP-SANS) beamline at the High-Flux Isotopic Reactor at ORNL and show that EQ-SANS is ready for scientific studies for the small-angle neutron scattering community. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204564 Thu, 08 Sep 2011 04:00:00 +0100 5204564 http://www.medworm.com/index.php?rid=5204563&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5297 The resolution ellipses for neutron diffraction peaks at small scattering vectors lie along lines that point to a position vertically above the beam center on the small-angle scattering detector. This gravity effect is only noticeable for neutron beams at long wavelengths and with large wavelength spreads. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204563 Thu, 08 Sep 2011 04:00:00 +0100 5204563 http://www.medworm.com/index.php?rid=5204562&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5127 It is demonstrated that scanning X-ray diffraction tomography of heterogeneous and polycrystalline samples can provide real-space semi-quantitative three-dimensional structural information at a submicrometre spatial resolution. The capabilities of this technique are illustrated by the study of a slice of a spherical particle consisting of a UMo core (about 37 µm in diameter) surrounded by a UMoAl shell (5 µm thick). The technique allows precise characterization of the embedded UMo/UMoAl interface where the phases α-U (in the core), UAl2 and U6Mo4Al43 (in the shell) are found. Moreover, an unexpected phase (UC) is detected at a trace level. It is shown that the thickness of the UMoAl shell is locally anticorrelated with the amount of UC, suggesting that this phase plays a protective ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204562 Thu, 08 Sep 2011 04:00:00 +0100 5204562 http://www.medworm.com/index.php?rid=5204561&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5115 Several nonlinear crystals that are used in laser and optical signal processing technologies belong to the {\overline 4}2m point group. This group exhibits as primary effects natural birefringence, optical activity, linear and quadratic electro-optic effects, and linear and quadratic electro-gyration effects, and, as secondary effects, photo-elasticity and piezo-gyration via the inverse piezo-electric phenomenon. The combination of these effects makes the study of light propagation a complicated task. In this work, the influence of each of these effects on light propagation is analytically reviewed, and suitable configurations for the light propagation and applied electric field directions are identified, which decouple the contribution of the individual effects. It is found that the compl... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204561 Thu, 08 Sep 2011 04:00:00 +0100 5204561 http://www.medworm.com/index.php?rid=5204560&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5129 In situ biaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate using a biaxial testing machine developed on the DiffAbs beamline at the Synchrotron SOLEIL. The mechanical behaviour of the nanocomposite was characterized at the micro- and macroscales using synchrotron X-ray diffraction and digital image-correlation techniques simultaneously. Strain analyses for equibiaxial and non-equibiaxial loading paths were carried out. The results show that the two strain measurements match to within 1 × 10−4 in the elastic domain for strain levels less than 0.3% and for both loading paths. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204560 Thu, 08 Sep 2011 04:00:00 +0100 5204560 http://www.medworm.com/index.php?rid=5204559&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5132 A single-crystal charge-flipping algorithm has been applied to two-dimensional projections derived from X-ray powder diffraction data to retrieve structure-factor phases. These phases proved to be as reliable as those obtained from high-resolution transmission electron microscopy (HRTEM) images or from precession electron diffraction data. In particular, the stronger reflections tend to be correctly phased. The two-dimensional electron-density `images' obtained in this way show the same features as the corresponding HRTEM images, but with higher resolution. Application of the powder charge-flipping algorithm to the full three-dimensional powder diffraction data in conjunction with phases derived from several such (arbitrarily selected) projections was found to have a significant and benefi... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204559 Thu, 08 Sep 2011 04:00:00 +0100 5204559 http://www.medworm.com/index.php?rid=5204558&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fkk5088 A summary of the features for investigating absolute structure available in the crystallographic refinement program CRYSTALS is presented, together with the results of analyses of 150 light-atom structures collected with molybdenum radiation carried out with these tools. The results confirm that the Flack and Hooft parameters are strongly indicative, even when the standard uncertainties are large compared to the thresholds recommended by Flack & Bernardinelli [J. Appl. Cryst. (2000), 33, 1143–1148]. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204558 Thu, 08 Sep 2011 04:00:00 +0100 5204558 http://www.medworm.com/index.php?rid=5204557&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5092 The influence of annealing on crystal growth and the micro- and mesoscopic structures of Mn-substituted nanocrystalline zinc oxide (ZnO) has been investigated using X-ray diffraction, high-resolution transmission electron microscopy and small-angle neutron scattering (SANS). Average particle sizes and their distributions have been estimated from scattering experiments as well as a microscopy study, and found to be in the nanometre range. The SANS study indicates that the fractal dimension, which describes the nature of the agglomerate, is almost unchanged up to an annealing temperature of 1023 K. However, at 1223 K, the fractal dimension increases to 3. An attempt has also been made to understand the influence of the annealing temperature on the growth of the structural morphology of t... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204557 Thu, 08 Sep 2011 04:00:00 +0100 5204557 http://www.medworm.com/index.php?rid=5204556&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5099 The electrical and optical properties of molecular thin films are widely used, for instance in organic electronics, and depend strongly on the molecular arrangement of the organic layers. It is shown here how atomic structural information can be obtained from molecular films without further knowledge of the single-crystal structure. C60 fullerene was chosen as a representative test material. A 250 nm C60 film was investigated by grazing-incidence X-ray diffraction and the data compared with a Bragg–Brentano X-ray diffraction measurement of the corresponding C60 powder. The diffraction patterns of both powder and film were used to calculate the pair distribution function (PDF), which allowed an investigation of the short-range order of the structures. With the help of the PDF, a structu... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204556 Thu, 08 Sep 2011 04:00:00 +0100 5204556 http://www.medworm.com/index.php?rid=5204555&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5143 Dynamical theory (DT) calculations have been successfully developed to explain neutron spin-echo resolved grazing-incidence scattering from diffraction gratings. The theory, without any adjustable parameters, has been shown in previous publications to accurately reproduce the sensitivity of the spin-echo polarization signal to sample specifications and scattering geometry. The phase-object approximation (POA), which is computationally less demanding than the DT, has also been used to analyze neutron spin-echo polarization data obtained from diffraction gratings. In this paper, POA and DT calculations are compared for neutron scattering from various diffraction gratings in different geometrical settings. POA gives a good description of the data for transmission cases, where the neutron beam... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204555 Thu, 08 Sep 2011 04:00:00 +0100 5204555 http://www.medworm.com/index.php?rid=5204554&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5151 A new methodology is proposed for structure refinement using powder diffraction data, from which models for particle statistics and any other statistical errors can be formally optimized. This method is nothing but a straightforward implementation of the maximum-likelihood method, extended to the error estimation. Structure parameters refined by the method for fluorapatite [Ca5(PO4)3F], anglesite (PbSO4) and barite (BaSO4) become significantly closer to those obtained by single-crystal structure analyses in comparison with the results of the conventional Rietveld method. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204554 Thu, 08 Sep 2011 04:00:00 +0100 5204554 http://www.medworm.com/index.php?rid=5204553&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5096 The high-temperature phase transition of single crystals of l-asparagine monohydrate was investigated by X-ray diffraction in association with Rietveld refinement and dilatometer measurements as a function of annealing time. The X-ray results showed that, for samples annealed at 343 K (or even 333 K) for 5 h, the expected anhydrous l-asparagine phase has been formed, monoclinic system (space group P21), with lattice parameters a = 5.0677 (2), b = 6.7657 (2), c = 8.0742 (3) Å and β = 91.276 (4)°. The results obtained from measurements as a function of annealing time confirmed that the phase transition associated with loss of the water molecule is time dependent. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204553 Thu, 08 Sep 2011 04:00:00 +0100 5204553 http://www.medworm.com/index.php?rid=5204552&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5175 A numerical procedure to carry out the integral on the powder diffraction sphere in reciprocal space and obtain accurate powder diffraction peak profiles for small crystallites is presented. In doing so, the literature surrounding the effect of crystallite size and shape on the powder peak profile is briefly reviewed. Powder patterns simulated by this technique are compared with those calculated by the tangent plane approximation and Debye function for spherical, cubic and cylindrical crystallites having sizes of only a few nanometres. The tangent plane approximation is found to produce inaccurate peak profiles and peak positions in simulated patterns of the cubic and cylindrical nanocrystallites. This performance is in contrast to that of the proposed powder integration technique, which r... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5204552 Thu, 08 Sep 2011 04:00:00 +0100 5204552 http://www.medworm.com/index.php?rid=5156150&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5188 The classical external-standard method derived from the work of O'Connor & Raven [Powder Diffr. (1988), 3, 2–6] was used to examine the hydration of the major phase, alite, of ordinary Portland cements at different temperatures and different water/alite ratios. In order to estimate the accuracy of the method, heat-flow curves were calculated from the alite dissolution curves obtained from X-ray diffraction in situ experiments. The heat-flow curves calculated in this way were compared with heat-flow curves recorded using a calorimeter. It is shown that the calculated curves agree well with the curves obtained from heat-flow experiments. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156150 Thu, 25 Aug 2011 09:32:08 +0100 5156150 http://www.medworm.com/index.php?rid=5156164&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fea5145 CrysPage is a program to facilitate the rapid evaluation of high-throughput crystallization trials by experienced crystallographers. Emphasis is placed on a clear overview and the display of individual drops. Chemical space can be searched and selected drops can be displayed for detailed inspection, allowing the user to narrow down the range of trial conditions for further optimization. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156164 Wed, 17 Aug 2011 23:00:00 +0100 5156164 http://www.medworm.com/index.php?rid=5156163&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fea5144 A new microfluidic sample-preparation system is presented for the structural investigation of proteins using small-angle X-ray scattering (SAXS) at synchrotrons. The system includes hardware and software features for precise fluidic control, sample mixing by diffusion, automated X-ray exposure control, UV absorbance measurements and automated data analysis. As little as 15 µl of sample is required to perform a complete analysis cycle, including sample mixing, SAXS measurement, continuous UV absorbance measurements, and cleaning of the channels and X-ray cell with buffer. The complete analysis cycle can be performed in less than 3 min. Bovine serum albumin was used as a model protein to characterize the mixing efficiency and sample consumption of the system. The N2 fragment of an adapt... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156163 Wed, 17 Aug 2011 23:00:00 +0100 5156163 http://www.medworm.com/index.php?rid=5156162&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5182 Orientation distribution functions, essential for making a quantitative connection between single-crystal and polycrystal properties, have been determined for extruded α-phase alumina, hot-pressed Ti3AlC2 and cold isostatically pressed Ti3AlC2 using experimental pole figures recorded on the fixed-wavelength neutron diffractometer KOWARI. Some practical improvements to the calculation of the pole-figure density from the raw area-detector data, and for constructing pole figures on an n × n° hemispherical grid, are presented. The textures give some insight into particle flow during manufacture. Directly measured material textures were compared with one-dimensional pole density functions, such as the March and Rietveld functions commonly used for the correction of preferred orientation in R... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156162 Wed, 17 Aug 2011 23:00:00 +0100 5156162 http://www.medworm.com/index.php?rid=5156161&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5189 (KxNa1−x)NbO3 ceramics modified with Li+ and Ta5+ have been produced using the mixed-oxide synthesis method. Synchrotron X-ray diffraction measurements were made on the samples from 12 K to temperatures above their ferroelectric–paraelectric transition points with 10 K measurement steps. Rietveld refinement was used to refine the patterns. Depending on the composition and temperature, rhombohedral phases, orthorhombic phases, tetragonal phases, cubic phases and two-phase mixtures were obtained. Space groups R3c (161), Amm2 (38), P4mm (99) and Pm{\overline 3}m (221) and their combinations were used to refine the rhombohedral, orthorhombic, tetragonal, cubic and mixed phases, respectively. Li+ addition suppressed the formation of the rhombohedral low-temperature phase and increased t... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156161 Wed, 17 Aug 2011 23:00:00 +0100 5156161 http://www.medworm.com/index.php?rid=5156160&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5287 A collimator and beam-stop assembly that can be inserted inside a temperature-controlled pressure vessel, to reduce dramatically the parasitic Bragg scattering from the vessel, has been designed and evaluated. High-energy X-ray powder diffraction data, suitable for the Rietveld refinement of simple crystal structures, were collected using this background-reducing internal mask (BRIM). ZrW2O8 was examined at up to 540 K and 124 MPa, using quite large pressure and temperature steps. No pressure dependence of the order–disorder transition temperature of this material was apparent. An orthorhombic to monoclinic phase transition (onset ∼83 MPa) was observed for Al2W3O12. Upon going through the transition, the bulk modulus of the material decreased from 41.8 to 20.8 GPa. Bulk moduli ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156160 Wed, 17 Aug 2011 23:00:00 +0100 5156160 http://www.medworm.com/index.php?rid=5156159&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5148 A study of the effect of Cr3+ doping in zinc tris(thiourea)sulfate (ZTS, a well known nonlinear optical material) single crystals on crystalline perfection and optical properties was carried out. Pure and chromium-doped (1 and 2 mol%) ZTS single crystals were grown by the slow evaporation solution technique. The actual concentration of chromium incorporated into the crystal lattice was found to be different, as evaluated by flame atomic absorption spectroscopy. High-resolution X-ray diffraction (HRXRD) analysis revealed that chromium doping led to the creation of vacancies in the grown single crystals. The photoluminescence emission spectra of pure and doped crystals supported the HRXRD findings. The optical band gap of the single crystals increased as a result of the Cr3+ doping, but th... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156159 Wed, 17 Aug 2011 23:00:00 +0100 5156159 http://www.medworm.com/index.php?rid=5156158&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5187 The preferred martensitic variant distribution in Ni53Mn25Ga22 ferromagnetic shape memory alloy (FSMA) samples annealed without and with a high magnetic field of 12 T applied during the annealing process was investigated by electron backscatter diffraction. It is revealed that the high magnetic field applied during annealing enhances the regular arrangement of martensitic variants from the morphological point of view and effectively modifies the preferred orientation distribution of martensitic variants without changing the misorientation between them from the crystallographic point of view. Only one texture component, \{ 1{\overline 1}0\} \langle 33{\overline 2}\rangle, exists in the sample annealed without a magnetic field, whereas two additional texture components, \{ 4{\overline 6} 3... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156158 Wed, 17 Aug 2011 23:00:00 +0100 5156158 http://www.medworm.com/index.php?rid=5156157&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5184 The ability to resolve the wavelength in neutron transmission experiments has opened up a wide range of applications investigating crystallographic structures and properties. The investigations presented in this paper apply the Bragg edge transmission technique to the study of texture in a cylindrical aluminium specimen. The feasibility of this method is the main focus of this work; hence, conventional pole-figure measurements have been conducted with neutron diffraction to provide reference data for the evaluation of the transmission results. Furthermore, a Monte Carlo simulation has been developed to emulate the experimental conditions and allow investigations of instrument effects. The results have been compared and are discussed with respect to quantitative texture analysis. (Source: J... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156157 Wed, 17 Aug 2011 23:00:00 +0100 5156157 http://www.medworm.com/index.php?rid=5156156&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5183 Owing to its selectivity, diffraction is a powerful tool for analysing the mechanical behaviour of polycrystalline materials at the mesoscale (phase and/or grain scale). In situ neutron diffraction during tensile tests and elastoplastic self-consistent modelling were used to study slip phenomena occurring on crystallographic planes at small and large deformation. The critical resolved shear stresses in both phases of duplex stainless steel were found for samples subjected to different thermal treatments. The evolution of grain loading was also determined by showing the large differences between stress concentration for grains in ferritic and austenitic phases. It was found that, for small loads applied to the sample, linear elastic deformation occurs in both phases. When the load increases... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156156 Wed, 17 Aug 2011 23:00:00 +0100 5156156 http://www.medworm.com/index.php?rid=5156155&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5288 ABX3 post-perovskite (PPV) phases that are stable (or strongly metastable) at ambient pressure are important as analogues of PPV-MgSiO3, a deep-Earth phase stable only at very high pressure. The thermoelastic and structural properties of orthorhombic PPV-structured CaPtO3 have been determined to 9.27 GPa at ambient temperature and from 2 to 973 K at ambient pressure by time-of-flight neutron powder diffraction. The equation-of-state from this high-pressure study is consistent with that found by Lindsay-Scott, Wood, Dobson, Vočadlo, Brodholt, Crichton, Hanfland & Taniguchi [(2010). Phys. Earth Planet. Inter. 182, 113–118] using X-ray powder diffraction to 40 GPa. However, the neutron data have also enabled the determination of the crystal structure. The b axis is the most compressi... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156155 Wed, 17 Aug 2011 23:00:00 +0100 5156155 http://www.medworm.com/index.php?rid=5156154&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5279 Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so-called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of γ′ morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre-straining. In situ small-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towa... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156154 Wed, 17 Aug 2011 23:00:00 +0100 5156154 http://www.medworm.com/index.php?rid=5156153&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5171 In this study, the texture (lattice preferred orientation) of the crystallites in cortical bone samples has been studied by means of synchrotron hard X-ray diffraction, performing a combined analysis with the Rietveld method to quantify fully the preferred orientation features and to obtain lattice and microstructural parameters (such as crystallite size) simultaneously. The samples were ribs from four adult female macaques of different ages, and two femurs chosen for comparison, one from a human child and one from an adult cow. The effect of the preferred orientation of the mineral component on the elastic properties is also briefly discussed. All six samples, averaging volumes of ∼0.5 mm3, show strong preferred orientation, with the hydroxylapatite c axis parallel to the bone axis. T... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156153 Wed, 17 Aug 2011 23:00:00 +0100 5156153 http://www.medworm.com/index.php?rid=5156152&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5130 Particle statistics in synchrotron powder diffractometry measured in a capillary transmission mode have been theoretically and experimentally investigated. General mathematical formulae for statistical analysis of observed intensities measured by a spinner-scan method are derived. It is shown that an additional parameter to characterize the size distribution of crystallites can be evaluated from the skewness of the distribution of measured diffraction intensities obtained by the spinner-scan method applied to capillary specimens. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156152 Wed, 17 Aug 2011 23:00:00 +0100 5156152 http://www.medworm.com/index.php?rid=5156151&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5190 Studies of the extraction of nickel from low-grade laterite ores require a much better quantitative understanding of the poorly ordered mineral phases present, including turbostratically disordered nontronite. Whole pattern refinements with nontronite X-ray diffraction data from a Western Australian nickel deposit (Bulong) using a nontronite lattice model (Pawley phase) with two space groups (P3 and C2/m) and a peaks phase group model were performed to improve the accuracy of quantitative X-ray diffraction of nickel laterite ore samples. Modifications were applied when building the new models to accommodate asymmetric peak shape and anisotropic peak broadening due to the turbostratic disorder. Spherical harmonics were used as convolution factors to represent anisotropic crystal size and st... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5156151 Wed, 17 Aug 2011 23:00:00 +0100 5156151 http://www.medworm.com/index.php?rid=5027084&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5186 A description of the gsaslanguage software is presented. The software provides input to and processes output from the GSAS package. It allows the development of scripts for the automatic evaluation of large numbers of data sets and provides documentation of the refinement strategies employed, thus fostering the development of efficient refinement strategies. Use of the bash shell and standard Unix text-processing tools, available natively on Linux and Mac OSX platforms and via the free cygwin software on Windows systems, make this software platform independent. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027084 Tue, 12 Jul 2011 23:00:00 +0100 5027084 http://www.medworm.com/index.php?rid=5027083&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5178 The temperature-induced phase transition in an as-deposited amorphous Ge2Sb2Te5 (GST) thin film was studied by a unique combination of in situ synchrotron techniques (diffraction and reflectivity of X-rays) and sheet resistance measurements. The combination of these characterization techniques allowed the simultaneous extraction of structural (density and film thickness) and electrical characteristics of the GST film during its thermal annealing. It is shown that, at 425 (3) K, the appearance of diffraction peaks associated with a metastable crystalline cubic phase is unambiguously correlated to a density increase in combination with a layer thickness reduction and a resistivity switch towards a lower-resistance state. Under the present annealing conditions, the Ge2Sb2Te5 film consists... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027083 Tue, 12 Jul 2011 23:00:00 +0100 5027083 http://www.medworm.com/index.php?rid=5027082&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5126 Although the structures of pure Sc2Si2O7 and β-Y2Si2O7 have been described in the literature using the C2/m space group, 29Si magic angle spinning (MAS) NMR measurements of the intermediate members of the Sc2Si2O7–β-Y2Si2O7 system indicate a lowering of the symmetry to the C2 space group. Indeed, these compositions exhibit a unique Si crystallographic site and an Si—O—Si angle lower than 180°, incompatible with the C2/m space group. C2 is the only possible alternative. Space group Cm can be discarded with regard to its two different Si sites per unit cell. Moreover, 89Y MAS NMR data have revealed the existence of two different Y sites in the structure of the intermediate members of the Sc2Si2O7–β-Y2Si2O7 system, confirming the lowering of the symmetry to the C2 space group. The... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027082 Tue, 12 Jul 2011 23:00:00 +0100 5027082 http://www.medworm.com/index.php?rid=5027081&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5144 The remarkable enhancement of the crystalline perfection of benzophenone (BP) crystals induced by liquid crystal (LC) doping has been investigated, and has in turn led to better optical properties. High-resolution X-ray diffractometry demonstrates that the structural grain boundaries present in pure crystals can be eliminated when the crystal is grown with LC doping. Thus, the high alignment capability of LCs has for the first time been utilized to enhance the quality of BP bulk single crystals. The LC-doped crystal exhibits higher optical transparency over its entire transparent region. The optical polarizing behaviour of the doped BP crystal is also improved. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027081 Tue, 12 Jul 2011 23:00:00 +0100 5027081 http://www.medworm.com/index.php?rid=5027080&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5512 This article presents the methods developed to mount and centre the sample accurately on the instrument; to reduce the background and hence increase the precision of the measured reflection intensities; and to increase further the accessible region of reciprocal space with a single sample loading. Developments are also highlighted, with a view to increasing the range of both science and pressures that can be achieved at the Institut Laue–Langevin reactor source using single-crystal techniques. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027080 Tue, 12 Jul 2011 23:00:00 +0100 5027080 http://www.medworm.com/index.php?rid=5027079&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5181 A new approach is proposed to determine unambiguously the location of four cations within the crystal structure of a natural AB2O6 columbite-type compound and derivatives, when submitted to order–disorder transitions caused by heat treatments. This method is based on the successive use of electron microprobe analysis to determine the cation concentration, Mössbauer spectroscopy to identify the Fe occupation, and a crystal structure determination of the samples combining Rietveld refinements of both neutron and X-ray diffraction. This approach is tested successfully to investigate (Fe, Mn, Nb, Ta) natural minerals as well as oxides obtained by heat treatment of the initial AB2O6 columbite-type compound. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027079 Tue, 12 Jul 2011 23:00:00 +0100 5027079 http://www.medworm.com/index.php?rid=5027078&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5090 The pore–solid structure of selected high-compressive-strength metakaolin geopolymers has been characterized to facilitate quantitative prediction of their physical properties. Geopolymers are multiphase materials with pore widths ranging from subnanometre to several tenths of a millimetre. Ultramicrotoming of resin-embedded grains was found to be an effective method for producing electron-transparent sections. Scanning and transmission electron microscopy showed the existence of a bi-level pore system and heterogeneity of the pore morphology. Ultra-small-angle neutron scattering, of sufficiently thin specimens, was found to be useful in detecting the length scales on which statistically significant structural changes occur as the geopolymer chemical composition is varied. Contrast varia... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027078 Tue, 12 Jul 2011 23:00:00 +0100 5027078 http://www.medworm.com/index.php?rid=5027077&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5173 In sample-scanning Laue microdiffraction, the local crystal orientation and local deviatoric strain tensor are obtained by illuminating the polycrystalline sample with a broadband `white' (5–30 keV) X-ray microbeam and analyzing the spot positions in the resulting local Laue pattern. Mapping local hydrostatic strain is usually slower, owing to the need to alternate between white and tunable-energy monochromatic microbeams. A technique has been developed to measure hydrostatic strain while keeping the white beam. The energy of one of the Laue spots of the grain of interest is measured using an energy-dispersive point detector, while simultaneously recording the Laue pattern on the two-dimensional detector. The experimental spot energy, Eexp, is therefore measured at the same time as Eth... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027077 Tue, 12 Jul 2011 23:00:00 +0100 5027077 http://www.medworm.com/index.php?rid=5027076&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5280 In this work, a study of the crystalline perfection of an aluminium single crystal is presented. The study shows that, from three-dimensional neutron diffraction rocking curves, it is possible to characterize the individual crystalline domains of a multidomain crystal. From a macroscopic point of view, the determination of the domains allows an evaluation of the crystalline perfection of the crystal under study. Three-dimensional rocking curves have been obtained by neutron diffraction from a large mosaic aluminium crystal. Construction of a contour map of individual domains made it easier to determine the breadth and relative intensity of each domain. The angular distances between domains were also determined. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=5027076 Tue, 12 Jul 2011 23:00:00 +0100 5027076 http://www.medworm.com/index.php?rid=4974857&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5093 MetLigDB (http://silver.sejong.ac.kr/MetLigDB) is a publicly accessible web-based database through which the interactions between a variety of chelating groups and various central metal ions in the active site of metalloproteins can be explored in detail. Additional information can also be retrieved, including protein and inhibitor names, the amino acid residues coordinated to the central metal ion, and the binding affinity of the inhibitor for the target metalloprotein. Although many metalloproteins have been considered promising targets for drug discovery, it is difficult to discover new inhibitors because of the difficulty in designing a suitable chelating moiety to impair the catalytic activity of the central metal ion. Because both common and specific chelating groups can be identifie... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974857 Mon, 27 Jun 2011 23:00:00 +0100 4974857 http://www.medworm.com/index.php?rid=4974856&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fgm5016 Crystallographic Fourier maps may contain barely interpretable or non-interpretable regions if these maps are calculated with an incomplete set of diffraction data. Even a small percentage of missing data may be crucial if these data are distributed non-uniformly and form connected regions of reciprocal space. Significant time and effort can be lost trying to interpret poor maps, in improving them by phase refinement or in fighting against artefacts, whilst the problem could in fact be solved by completing the data set. To characterize the distribution of missing reflections, several types of diagrams have been suggested in addition to the usual plots of completeness in resolution shells and cumulative data completeness. A computer program, FOBSCOM, has been developed to analyze the spatia... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974856 Mon, 27 Jun 2011 23:00:00 +0100 4974856 http://www.medworm.com/index.php?rid=4974855&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5125 An ex situ characterization study has been performed on rutile passivation layers on inert anodes used for molten salt electrochemical studies. Rutile layer thicknesses were estimated using a number of ex situ methods, including laboratory and synchrotron X-ray diffraction and optical microscopy. The only phases in the anode detected by diffraction were the Magnéli phases (TinO2n−1, n = 5–6) of the unreacted anode and rutile (TiO2), which forms on electrolysis. These measurements validate a previously developed in situ energy-dispersive X-ray diffraction analysis technique [Scarlett, Madsen, Evans, Coelho, McGregor, Rowles, Lanyon & Urban (2009). J. Appl. Cryst. 42, 502–512]. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974855 Mon, 27 Jun 2011 23:00:00 +0100 4974855 http://www.medworm.com/index.php?rid=4974854&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5142 The decomposition of hexacarbonyltungsten, W(CO)6, has been studied. The decomposition was induced by heating W(CO)6 in an autoclave at 523 K and pressures up to 1.8 MPa, and by laser heating in a diamond anvil cell at pressures between 5 and 18 GPa. The products have been characterized using synchrotron X-ray diffraction, pair distribution function analysis, Raman spectroscopy and scanning electron microscopy. Decomposition in the autoclave at the lower pressures resulted in the formation of a metastable tungsten carbide, W2C, with an average particle size of 1–2 nm, and an unidentified nanocrystalline tungsten oxide and nanocrystalline graphite with average particle sizes of 1–2 and 11 nm, respectively. The existence of nanocrystalline graphite was deduced from micro-Raman ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974854 Mon, 27 Jun 2011 23:00:00 +0100 4974854 http://www.medworm.com/index.php?rid=4974853&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fnb5001 Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels with low stacking fault energy leads typically to the formation of ∊-martensite within the original austenite. The ∊-martensite is often described as a phase having a hexagonal close-packed crystal structure. In this contribution, an alternative structure model is presented that describes ∊-martensite embedded in the austenitic matrix via clustering of stacking faults in austenite. The applicability of the model was tested on experimental X-ray diffraction data measured on a CrMnNi TRIP steel after 15% compression. The model of clustered stacking faults was implemented in the DIFFaX routine; the faulted austenite and ∊-martensite were represented by different stacking fault arrangements... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974853 Mon, 27 Jun 2011 23:00:00 +0100 4974853 http://www.medworm.com/index.php?rid=4974852&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5176 Small-angle X-ray scattering interface distribution function (IDF) analysis is successfully applied to evaluate the two- and three-phase inter-platelet gallery structure in synthetic montmorillonite (MMT) modified with a mixture of chemically grafted and physically adsorbed chains of a typical organic modifier, octadecyl trimethyl ammonium bromide. Two distinctly different states of adsorbed chains in the inter-platelet galleries are identified. The first one corresponds to a fully cation-exchanged structure with an inter-platelet distance of about 21 Å. In this case the organic modifier is in a liquid-like state, and the system does not exhibit any structural or thermal transitions between ambient temperature and 433 K. When the number of adsorbed chains exceeds the cation-exchange c... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974852 Mon, 27 Jun 2011 23:00:00 +0100 4974852 http://www.medworm.com/index.php?rid=4974851&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5138 This study provides specific information for choosing the instrument configuration suitable for most strain-scanning experimental tasks. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974851 Mon, 27 Jun 2011 23:00:00 +0100 4974851 http://www.medworm.com/index.php?rid=4974850&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fea5140 This paper highlights a parallelization of the FMLSQ program, which allows full-matrix least-squares refinement of large macromolecular structures. The detailed elapsed time profiling of FMLSQ and analysis of its execution on two different Intel architectures has led to a dramatic speedup due to parallelization of all stages of the algorithm. Amdahl's law proved to be very useful during this analysis. It has been shown that processor memory bandwidth may be more important than raw processing power for parallel crystallographic calculations. The new parallelized version of the program has been tested on several protein structures at high resolution. Requirements for a computing architecture intended for full-matrix refinement are discussed in detail. (Source: Journal of Applied Crystallogra... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974850 Mon, 27 Jun 2011 23:00:00 +0100 4974850 http://www.medworm.com/index.php?rid=4974849&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fdb5092 Powder pattern indexing routines frequently yield multiple solutions, i.e. different reciprocal lattices and unit cells. Here, a method is suggested that reveals whether or not there are numerical and geometric relationships between the solutions. It is based on the detection of a reciprocal vector triplet that is common to two or more proposed reciprocal lattices. Hence, the method can be termed a common reciprocal metric tensor approach. If no such common tensor exists, the different reciprocal lattices are unrelated, but if one exists the lattices are either in a sublattice/superlattice or in a coincidence-site lattice relationship, depending on the character of the respective orientation matrix. Furthermore, the approach can also be used to generate, from a given indexing solution, fur... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974849 Mon, 27 Jun 2011 23:00:00 +0100 4974849 http://www.medworm.com/index.php?rid=4974848&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fkk5082 The use of nonlinear tapered guides is becoming more common in advanced neutron scattering facilities around the world. Elliptical guides offer the promise of high performance not only as focusing devices but as an efficient way to transport neutrons over long distances. Here, the analytical expressions to determine their performance are derived and discussed. Under certain conditions, an increase in flux delivery is observed with increasing guide length, due to an increase in the angular spread of the neutrons reflected in the guide. The performance is only limited by the distance between the source and the guide entrance, the dimensions of the instrument placed after it, and the supermirror coating. As an example of the potential of elliptical geometry in instrumentation, a new small-ang... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974848 Mon, 27 Jun 2011 23:00:00 +0100 4974848 http://www.medworm.com/index.php?rid=4974847&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5091 A general method is described for reducing white-beam X-ray total scattering raw data to the differential scattering cross section and pair distribution function. The method incorporates corrections for X-ray fluorescence, Bremsstrahlung radiation, polarization, attenuation, multiple scattering and sample container scattering, and invokes the Krogh-Moe and Norman method to put the data on an absolute scale. An accurate method to convert the differential scattering cross section to the pair distribution function is also described, and a rigorous and revised Lorch function is proposed for removing the effects of Fourier truncation oscillations. The method can be equally applied to synchrotron X-ray data, where the data analysis can be simpler than at a laboratory source. (Source: Journal of ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4974847 Mon, 27 Jun 2011 23:00:00 +0100 4974847 http://www.medworm.com/index.php?rid=4910654&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5128 The performance of a bent Laue crystal monochromator crucially depends on the sagittal and meridional bending curvatures of the crystal. To optimize the design of monochromator crystals, the surface curvatures and diffraction profiles of a set of sagittally bent Laue crystals with different aspect ratios have been studied experimentally by optical metrology and X-ray measurements. The results were confirmed with finite-element analysis using large-deformation theory. The nonlinear relationship between the curvatures necessitates an experimentally determined parameter in the theoretical modeling of the diffraction profiles. By taking into account the local stress and the aspect ratio of the sagittally bent Laue crystal, the modified analytical approach successfully predicts the rocking-curv... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910654 Wed, 08 Jun 2011 23:46:21 +0100 4910654 http://www.medworm.com/index.php?rid=4910663&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fpf0081 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910663 Tue, 07 Jun 2011 23:00:00 +0100 4910663 http://www.medworm.com/index.php?rid=4910662&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fes0387 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910662 Tue, 07 Jun 2011 23:00:00 +0100 4910662 http://www.medworm.com/index.php?rid=4910661&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5529 A collection of new software tools is presented for the analysis of geometrical, chemical and crystallographic data from the Cambridge Structural Database (CSD). This software supersedes the program Vista. The new functionality is integrated into the program Mercury in order to provide statistical, charting and plotting options alongside three-dimensional structural visualization and analysis. The integration also permits immediate access to other information about specific CSD entries through the Mercury framework, a common requirement in CSD data analyses. In addition, the new software includes a range of more advanced features focused towards structural analysis such as principal components analysis, cone-angle correction in hydrogen-bond analyses and the ability to deal with topologica... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910661 Tue, 07 Jun 2011 23:00:00 +0100 4910661 http://www.medworm.com/index.php?rid=4910660&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5523 Fragment-based drug discovery (FBDD), which is a molecular build-up strategy from small scaffolds, has recently become a promising approach for lead-compound generation. Although high-throughput protein crystallography is usually used to determine the protein–ligand complex structure and identify potential hit compounds, the relationship between the quality of the Fo–Fc maps of hit compounds and their inhibitory activities has rarely been examined. To address this issue, crystallographic competition experiments were carried out to determine the relative order of the in-crystal binding affinities using five hit compounds of bovine pancreatic trypsin inhibitors. Soaking experiments of all combinations of the five hit compounds were used to define the in-crystal affinity ranking. Based on... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910660 Tue, 07 Jun 2011 23:00:00 +0100 4910660 http://www.medworm.com/index.php?rid=4910659&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5087 Information on the size and structure of nanoparticles can be obtained via analysis of the atomic pair distribution function (PDF), which is calculated as the Fourier transform of X-ray/neutron total scattering. The structural parameters are commonly extracted by fitting a model PDF calculated from atomic coordinates to the experimental data. This paper discusses procedures for minimizing systematic errors in PDF calculations for nanoparticles and also considers the effects of noise due to counting statistics in total scattering data used to obtain the PDF. The results presented here demonstrate that smoothing of statistical noise in reciprocal-space data can improve the precision of parameter estimates obtained from PDF analysis, facilitating identification of the correct model (from mult... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910659 Tue, 07 Jun 2011 23:00:00 +0100 4910659 http://www.medworm.com/index.php?rid=4910658&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5530 In recent years, microsource sealed tubes in combination with multilayer optics have been adopted in many crystallography laboratories for very low power X-ray generation, monochromatization and high-brilliance microfocusing. All these factors allow high-performance experiments on a laboratory scale. However, a fundamental defect of this technology has been discovered, namely a significant contamination of the characteristic radiation by low-energy photons. Some simple experiments are reported, showing that the contamination can significantly reduce the accuracy of the measured intensities, especially when Mo Kα radiation is used. A simple and economic solution to the problem is proposed: an aluminium filter approximately 100 µm thick, which efficiently removes the low-energy contami... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910658 Tue, 07 Jun 2011 23:00:00 +0100 4910658 http://www.medworm.com/index.php?rid=4910657&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fdz5227 This paper reports on several developments of X-ray fluorescence techniques for macromolecular crystallography recently implemented at the National Institute of General Medical Sciences and National Cancer Institute beamlines at the Advanced Photon Source. These include (i) three-band on-the-fly energy scanning around absorption edges with adaptive positioning of the fine-step band calculated from a coarse pass; (ii) on-the-fly X-ray fluorescence rastering over rectangular domains for locating small and invisible crystals with a shuttle-scanning option for increased speed; (iii) fluorescence rastering over user-specified multi-segmented polygons; and (iv) automatic signal optimization for reduced radiation damage of samples. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910657 Tue, 07 Jun 2011 23:00:00 +0100 4910657 http://www.medworm.com/index.php?rid=4910656&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5524 This article describes a protocol to crystallize the acidic protein bovine β-lactoglobulin in the presence of yttrium to yield high-quality crystals that belong to a new space group. The yttrium ions not only are used to engineer the crystallization, but are an integral part of the crystal lattice and can therefore be used to solve the phase problem using anomalous dispersion methods. Protein crystallization conditions were first optimized using an experimental phase diagram in the protein and salt concentration plane. Crystal growth strongly depends on the position in the phase diagram, and the best crystals grow near the phase transition boundaries. The structure analysis demonstrates the specific binding of yttrium ions to surface-exposed glutamate and aspartate side chains contributed... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910656 Tue, 07 Jun 2011 23:00:00 +0100 4910656 http://www.medworm.com/index.php?rid=4910655&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5107 A method is proposed for extracting the relevant structural information from powder diffraction data. The pattern is fitted and a reduced number of intensity values, called `pseudo-intensities', are extracted and used as a substitute for the full pattern in the structure determination algorithm. Since the number of pseudo-intensities is one order of magnitude smaller than the number of data points in the experimental data, the calculation of the agreement factor (Rwp), and hence the evaluation of a trial structure, is carried out more quickly. The method consists of a procedure for stripping out the influence of the profile fit from the full pattern Rwp factor, leaving just the important intensity information needed in the structure determination process. (Source: Journal of Applied Crysta... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4910655 Tue, 07 Jun 2011 23:00:00 +0100 4910655 http://www.medworm.com/index.php?rid=4827749&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fpf0082 (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827749 Fri, 13 May 2011 23:00:00 +0100 4827749 http://www.medworm.com/index.php?rid=4827748&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5526 CIFXML applies the XML strategies and technologies to create a general interface for processing CIF documents that conform to the CIF syntax and DDL1. Both a DTD and an XML schema for CIFs are presented. CIFs can be read, edited, validated syntactically, sorted, normalized, filtered, stored as an XML document object model, transformed and output. CIFXOM provides an easy way of converting CIFs to XML and vice versa using Java. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827748 Fri, 13 May 2011 23:00:00 +0100 4827748 http://www.medworm.com/index.php?rid=4827747&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5510 First results are presented for a uniaxial tensile stage designed to operate on a scanning micro X-ray diffraction synchrotron beamline. The new tensile stage allows experiments at typical loading cycles used in standard engineering stress–strain tests. Several key features have been implemented to support in situ loading experiments at the intragranular length scale. The physical size and weight of the load cell were minimized to maintain the correct working distance for the X-ray focusing optics and to avoid overloading the high-resolution raster scan translation stages. A high-magnification optical microscope and image correlation code were implemented to enable automated online tracking capabilities during macroscopic elongation of the sample. Preliminary in situ tensile loading expe... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827747 Fri, 13 May 2011 23:00:00 +0100 4827747 http://www.medworm.com/index.php?rid=4827746&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5111 The relaxor ferroelectric PbMg1/3Ta2/3O3 was studied by single-crystal neutron and synchrotron X-ray diffraction, and its detailed atomic structure modelled in terms of static Pb displacements that lead to the formation of polar nanoregions. Similar to the other members of the Pb-based relaxor family like PbMg1/3Nb2/3O3 or PbZn1/3Nb2/3O3 the diffuse scattering in the [H00]/[0K0] scattering plane has a butterfly shape around the h00 Bragg reflections and is orthogonal to the scattering vector for hh0 peaks. In the [HH0]/[00L] plane the diffuse scattering is elongated along the 〈112〉 directions and is orthogonal to the scattering vector for hhh reflections. It is found that a model consisting of correlated Pb displacements along the 〈111〉 directions reproduces adequately the main fea... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827746 Fri, 13 May 2011 23:00:00 +0100 4827746 http://www.medworm.com/index.php?rid=4827745&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5515 SrLaCuNbO6 and SrLaCuTaO6 are Jahn–Teller distorted double perovskites with complete B-site ordering. The crystal structure of SrLaCuTaO6 has been solved by refinement of neutron powder diffraction data at 323 (triclinic), 573 (monoclinic) and 923 K (body-centered monoclinic). Synchrotron X-ray and electron diffraction reveal local-scale features similar to those seen in ferroelectric perovskites, and also in A-site ordered perovskites exhibiting nanoscale periodicities. The crystal structure of SrLaCuNbO6 was solved by refinement of synchrotron X-ray powder diffraction data at 673 and 1273 K. Because of the high resolution of the synchrotron, adjustments to these structure models were necessary in order to account for profile irregularities resulting from the local-scale behavior. (... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827745 Fri, 13 May 2011 23:00:00 +0100 4827745 http://www.medworm.com/index.php?rid=4827744&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5090 It is shown that textures with double-axis averaging similar to the a-texture, or Keller–Machin Type I texture, are not specific to semicrystalline polymers exhibiting twisted lamellar growth. In this work, such texture is observed in extruded fibers of a typical discotic molecule, trans-diC60-Zn porphyrin. Experimentally, these textures can be detected from the characteristic `comma'-like azimuthal profiles of the non-equatorial diffraction peaks in two-dimensional X-ray patterns. Analytical expressions for the azimuthal intensity distribution are developed, which are in good agreement with the experiment. In the proposed generalized coordinates, the diffraction peak shape becomes universal. This provides a simple means of checking the closeness of the sample morphology to the a-texture... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827744 Fri, 13 May 2011 23:00:00 +0100 4827744 http://www.medworm.com/index.php?rid=4827743&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5102 By combining two methods of selective doping of paramagnetic species into a microdomain and small-angle neutron scattering (SANS), the spatially inhomogeneous proton polarization created by dynamic nuclear polarization (DNP) has been precisely evaluated. A lamella-forming diblock copolymer composed of polystyrene (PS) and polyisoprene (PI) block chains (PS-b-PI) was employed, the SANS profile of which clearly shows scattering peaks up to the third order due to interlamellar interference. As a source of electron spin for DNP, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) was doped into one or other of the microdomains; samples with PS or PI microdomains selectively doped with TEMPO are designated PS.-b-PI and PS-b-PI., respectively. The SANS intensity at the first- and third-order peaks is w... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827743 Fri, 13 May 2011 23:00:00 +0100 4827743 http://www.medworm.com/index.php?rid=4827742&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5272 This combined study using small-angle neutron scattering (SANS), X-ray powder diffraction (XRPD), transmission electron microscopy (TEM) and adsorption isotherm techniques demonstrates radical changes in the microstructure of porous hematite (α-Fe2O3) nanoparticles upon calcination in air. TEM images of the as-synthesized hematite sample show that it consists of subrounded nanoparticles [50 (8)–61 (11) nm in average minimum and maximum diameters] with an apparent porous structure of nanosized pores/channels or cracks. SANS data confirm the presence of two characteristic sizes, one originating from the particle size and the other from the pore/void structure. Furthermore, the TEM images show that the particle sizes are nearly unaffected by calcination at 623 K, whereas their pore... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4827742 Fri, 13 May 2011 23:00:00 +0100 4827742 http://www.medworm.com/index.php?rid=4788314&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5139 A four-circle neutron diffractometer with a new multi-wafer 331 Si monochromator has been installed and commissioned on a thermal beamline at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The instrument is well suited to studies of nuclear and magnetic structures as a function of composition and temperature, resolving symmetry changes (lattice distortions and local structural changes), mapping the evolution of complex magnetic phases, determining hydrogen bonding, analyzing nuclear and spin densities, mapping diffuse scattering, and exploring fiber diffraction. Three incident wavelengths are available, 1.000, 1.536 and 2.540 Å, with intensities of 2.5 × 106, 2.2 × 107 and 8.0 × 106 neutrons cm−2 s−1, respectively. Either high-resolution or high-intensity m... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788314 Thu, 05 May 2011 23:00:00 +0100 4788314 http://www.medworm.com/index.php?rid=4788313&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fwf5088 The order–disorder contributions to the ferroelectric properties of Cd2Nb2O7 (CNO) have been studied by Monte Carlo simulation of a 12-state modified Potts model on the pyrochlore lattice. Spin configurations obtained by these simulations are mapped to local Nb displacements. Secondary Cd displacements normal to the Nb displacement directions are considered as well. The model correctly reproduces diffuse scattering experimentally observed in CNO. A first-order phase transition is observed for kTp/J = 0.3891 (k is the Boltzmann constant, Tp is the model phase transition temperature and J is the interaction energy). To further adapt the model to the properties of CNO, coupling of local Nb displacements to the T2u soft mode is simulated via the addition of an appropriate field term in the m... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788313 Thu, 05 May 2011 23:00:00 +0100 4788313 http://www.medworm.com/index.php?rid=4788312&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5283 Methods to obtain and analyze high-resolution real-time X-ray diffraction (XRD) measurements from shock-compressed single crystals are presented. Procedures for extracting microstructural information – the focus of this work – from XRD line profiles are described. To obtain quantitative results, careful consideration of the experimental geometry is needed, including the single-crystal nature of the sample and the removal of instrumental broadening. These issues are discussed in detail. Williamson–Hall (WH) and profile synthesis (PS) analysis procedures are presented. More accurate than WH, the PS procedure relies on a forward calculation in which a line profile is synthesized by convoluting the instrumental line profile with a line profile determined from a diffraction simulation. Th... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788312 Thu, 05 May 2011 23:00:00 +0100 4788312 http://www.medworm.com/index.php?rid=4788311&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5177 The tympanum of the entrance of the Zaouïa Moulay Idriss II in Fez contains the only known example of a dodecagonal cartwheel quasiperiodic pattern in Islamic art, dating possibly from the Merinid epoch. This pattern, carved in a marble plate, is based on a type of Ammann quasilattice known also from modern mathematical literature. The central portions of this pattern were used as elements in a periodic pattern on the walls of the Saadian mausoleum in Marrakech. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788311 Thu, 05 May 2011 23:00:00 +0100 4788311 http://www.medworm.com/index.php?rid=4788310&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fko5120 This article introduces methods for the correction of nanoparticle, bulk crystalline and amorphous powder neutron scattering data with significant incoherent contributions from hydrogen, and describes the effects the corrections have on the resulting atomic pair distribution function data sets. The approach is presented in the context of the PDFgetN data-reduction program [Peterson, Gutmann, Proffen & Billinge (2000). J. Appl. Cryst. 33, 1192]. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788310 Thu, 05 May 2011 23:00:00 +0100 4788310 http://www.medworm.com/index.php?rid=4788309&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5117 This article reports the three-dimensional X-ray diffraction imaging and visualization of the structure of these dislocations. A series of X-ray section topographs of both the indents and the dislocation loops were taken at the ANKA Synchrotron, Karlsruhe, Germany. The topographs were recorded on a CCD system combined with a high-resolution scintillator crystal and were measured by repeated cycles of exposure and sample translation along a direction perpendicular to the beam. The resulting images were then rendered into three dimensions utilizing open-source three-dimensional medical tomography algorithms that show the dislocation loops formed. Furthermore this technique allows for the production of a video (avi) file showing the rotation of the rendered topographs around any defined axis.... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788309 Thu, 05 May 2011 23:00:00 +0100 4788309 http://www.medworm.com/index.php?rid=4788308&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fks5277 High-resolution X-ray diffraction imaging of 200 mm silicon wafers following rapid thermal annealing at a temperature of 1270 K has revealed the presence of many early stage sources of thermal slip associated with the wafer edge. Dislocation sources are primarily at the wafer extremity, though many are generated by damage at the edge of the bevel incline on the wafer surface. A smaller fraction of sources is associated with other regions of localized damage, probably relating to protrusions on the wafer support. The geometry of the latter is similar to that of dislocation sources generated by controlled indentation on the wafer surface. It is concluded that rapid spike annealing at high temperature does not suppress the nucleation of slip, but rather the rapidity of the process prevent... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788308 Thu, 05 May 2011 23:00:00 +0100 4788308 http://www.medworm.com/index.php?rid=4788307&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5498 This paper describes the optimization of an entire neutron guide system, from the moderator to the sample position for several instruments simultaneously, using no more than a desktop computer and a few days of CPU time. This is made possible by merging two relatively advanced computational techniques. Neutron acceptance diagram shading is a fast new method for modelling neutron beams, using an approach based on polygons similar to those featuring in computer games. Optimization algorithms based on swarm intelligence are efficient and reliable ways to maximize numerically calculable figures of merit with many strongly coupled geometry parameters. Recent developments in these methods are described, as well as their combination to optimize the geometry of the H5 beamlines at the Institut Lau... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788307 Thu, 05 May 2011 23:00:00 +0100 4788307 http://www.medworm.com/index.php?rid=4788306&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5100 The structure of large block copolymer micelles is traditionally determined by small-angle neutron scattering (SANS), covering a large range of scattering vectors and employing contrast variation to determine the overall micelle morphology as well as the internal structure on shorter length scales. The present work shows that the same information can be obtained by combining static light scattering (SLS) and small-angle X-ray scattering (SAXS), which provide information on, respectively, large and short length scales. Micelles of a series of block copolymers of poly(ethylene propylene)-b-poly(ethylene oxide) (PEP–PEO) in a 70% ethanol solution are investigated. The polymers have identical PEP blocks of 5.0 kDa and varying PEO blocks of 2.8–49 kDa. The SLS contrasts of PEP and PEO a... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788306 Thu, 05 May 2011 23:00:00 +0100 4788306 http://www.medworm.com/index.php?rid=4788305&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5121 Cold-neutron backscattering spectrometers are designed for inelastic neutron scattering experiments at a high energy resolution, where 0.5 µeV FWHM can routinely be achieved at the incident wavelength λ ≃ 6.3 Å. The phase-space transformation (PST) technique can be used to enhance the neutron flux at the sample position of such backscattering spectrometers at the expense of an acceptable increase of the beam divergence. Technically, the PST is achieved by a rotating disc carrying mosaic crystals on its circumference. Here a new analytical framework to describe the Bragg reflection of a divergent polychromatic beam from a moving mosaic crystal is discussed. Results obtained using this framework are compared with detailed Monte Carlo numerical simulations. The results presented here... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788305 Thu, 05 May 2011 23:00:00 +0100 4788305 http://www.medworm.com/index.php?rid=4788304&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5122 The behaviour of ferroelectric domains at high temperatures near the Curie temperature in a periodically poled rubidium-doped potassium titanyl phosphate crystal (Rb:KTP) has been studied by Bragg–Fresnel X-ray diffraction imaging in situ using a compact coherence-preserving furnace. The development and partial disappearance of the inverted domain structure as the temperature increases has been successfully modelled, and is explained by invoking a built-in electric field produced under heating in a low vacuum by out-diffusion of atoms from the sample. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4788304 Thu, 05 May 2011 23:00:00 +0100 4788304 http://www.medworm.com/index.php?rid=4758230&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5109 The single-particle small-angle scattering properties of five Platonic solids, including the tetrahedron, hexahedron, octahedron, dodecahedron and icosahedron, are systematically investigated. For each given geometry, the Debye spatial autocorrelation function, pair distance distribution function and intraparticle structure factor (form factor) are calculated and compared with the corresponding scattering function of a spherical reference system. From the theoretical models, the empirical relationship between the dodecahedral and icosahedral structural characteristics and those of the equivalent spheres is found. Moreover, the single-particle scattering properties of icosahedral and spherical shells with identical volume are investigated, and the prospect of using different data analysis a... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4758230 Tue, 26 Apr 2011 23:00:00 +0100 4758230 http://www.medworm.com/index.php?rid=4741870&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fce5101 In the presence of phosphate anions, spindle-shaped mesoscale hematite particles can be prepared via controlled precipitation of iron(III) chloride. The aspect ratio of the particles is determined by the concentration of phosphate anions selectively covering specific crystal surfaces and thus enabling anisotropic growth of the particles. The scattering function for suspensions of polydisperse spindles is derived and used to analyse the small-angle scattering resulting from these particles. In the presence of an external magnetic field, the particles align perpendicular to the field direction as a result of the negative anisotropy of their magnetic susceptibility \Delta\chi. Hereby, an isotropic–nematic phase transition can be induced in external magnetic fields. (Source: Journal of Appli... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4741870 Sat, 23 Apr 2011 06:08:21 +0100 4741870 http://www.medworm.com/index.php?rid=4741874&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5170 Modern materials science diffractometers are generally equipped with area detectors that allow a high time efficiency to be achieved by simultaneously collecting the scattering pattern over large angular regions. These area-detector-based instruments, however, produce a huge amount of data, especially if they are located at large-scale neutron or synchrotron sources. The software StressTextureCalculator (STeCa) was designed to facilitate fast, easy and automated access to such area-detector data. Its outstanding features are direct calculation of diffraction patterns from different types of area-detector measurements, automatic data treatment and peak fitting using several implemented fit options. The resulting information on intensity, peak shift and broadening can then be exported into s... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4741874 Thu, 21 Apr 2011 23:00:00 +0100 4741874 http://www.medworm.com/index.php?rid=4741873&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Faj5173 A method is proposed for the initial identification of non-hydrogen atomic species in a crystal from X-ray diffraction intensities when the chemical composition is not available. When atom positions are determined, a portion of the scattering factor curve for each atom can be obtained by Fourier synthesis with reflections from concentric shells. From these curves, the atomic number and the isotropic displacement parameter for all non-H atoms, and the scaling constant of the structure factors, can be approximately determined. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4741873 Thu, 21 Apr 2011 23:00:00 +0100 4741873 http://www.medworm.com/index.php?rid=4741872&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5516 A novel X-ray diffraction (XRD) technique, which exhibits almost complete insensitivity to the morphology of and distance to the sample, is presented for the first time. This technique applies energy-dispersive XRD (EDXRD) in a back-reflection geometry, with 2θ ≃ 180°. Although this geometry leads to low resolution of diffraction peaks and the greatest overlap with fluorescence peaks, it nevertheless yields a combination of properties that are unique in the field of X-ray diffractometry. It is likely that diffraction patterns can be obtained with no or very minimal sample preparation. Furthermore, the intrinsic geometry of the method and the simplicity inherent to EDXRD enables a compact lightweight instrument design, suitable for field-portable or hand-held XRD and X-ray fluorescence ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4741872 Thu, 21 Apr 2011 23:00:00 +0100 4741872 http://www.medworm.com/index.php?rid=4741871&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fcg5175 The textures of an Al thin film and of α-MnS nanocrystals deposited on a carbon film grid have been analysed using powder electron diffraction. For each sample a series of powder electron diffraction patterns tilted with respect to two orthogonal axes were collected, to adapt to this type of data the texture analysis procedures commonly used in synchrotron X-ray transmission geometry. Both pattern sets have been analysed with the Rietveld procedure embedded in the software MAUD. The fit is satisfactory with agreement factors of 7.03% for the Al film and 3.42% for α-MnS and reveals in both cases a (111) preferred orientation with a pronounced cylindrical symmetry. The (111) and (100) pole figures, plotted in terms of multiples of random distribution (m.r.d.), show a fairly strong lattice ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4741871 Thu, 21 Apr 2011 23:00:00 +0100 4741871 http://www.medworm.com/index.php?rid=4669693&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fdb5094 Ab initio crystal structure determination from powder diffraction data is not yet a straightforward process: it is strongly disrupted by the low quality of the estimated Bragg reflection intensities. In a two-stage method the integrated intensities calculated from a powder pattern are immediately submitted to direct methods to obtain phases. The larger the accuracy of the integrated intensities, the more efficient the phasing process. A systematic decomposition procedure was introduced in the EXPO2004 program to improve the efficiency of the phasing process. The disadvantage of this approach is that a large number of feasible trial structures are generated, among which the correct solution must be recognized. A new procedure is described aiming at introducing strategies to reduce the total... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4669693 Sun, 03 Apr 2011 14:34:47 +0100 4669693 http://www.medworm.com/index.php?rid=4669698&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhe5519 The Basic Local Alignment Search Tool (BLAST) is one of the most widely used sequence alignment programs with which similarity searches, for both protein and nucleic acid sequences, can be performed against large databases at high speed. A large number of tools exist for processing BLAST output, but none of them provide three-dimensional structure visualization. This shortcoming has been addressed in the proposed tool BLAST Server for Structural Biologists (BSSB), which maps a BLAST output onto the three-dimensional structure of the subject protein. The three-dimensional structure of the subject protein is represented using a three-color coding scheme (identical: red; similar: yellow; and mismatch: white) based on the pairwise alignment obtained. Thus, the user will be able to visualize a ... Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4669698 Fri, 01 Apr 2011 23:00:00 +0100 4669698 http://www.medworm.com/index.php?rid=4669697&cid=s_37345_75_f&fid=37345&url=http%3A%2F%2Fscripts.iucr.org%2Fcgi-bin%2Fpaper%3Fhx5119 Scattering maps from strained or disordered nanostructures around a Bragg reflection can be either computed quickly using approximations and a (fast) Fourier transform or obtained using individual atomic positions. In this article, it is shown that it is possible to compute up to 4 × 1010 reflections atoms s−1 using a single graphics card, and the manner in which this speed depends on the number of atoms and points in reciprocal space is evaluated. An open-source software library (PyNX) allowing easy scattering computations (including grazing-incidence conditions) in the Python language is described, with examples of scattering from non-ideal nanostructures. (Source: Journal of Applied Crystallography) Journal of Applied Crystallography journals http://www.medworm.com/rss/comments.php?id=4669697 Fri, 01 Apr 2011 23:00:00 +0100 4669697