J. Appl. Cryst.の発刊に際して
10 Mar 1970-Vol. 12, Iss: 1, pp 1-1
About: The article was published on 1970-03-10 and is currently open access. It has received 8159 citations till now.
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05 Feb 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors used synchrotron X-ray diffraction measurements to determine the through-thickness distribution of axial and tangential residual stresses in an Al6022 deep drawn cup.
Abstract: Fueled by pressures to reduce scrap and tooling costs, the modeling and prediction of springback has become a major focus of interest in sheet metal forming. Finite element codes and packages are being developed or improved but face the demand for higher predictive accuracy which, in turn, requires accurate property data and a more complete understanding of the stresses that are responsible for the elastic part of the springback. In order to provide experimental data for these calculations, synchrotron X-ray diffraction measurements were carried out in order to determine the through-thickness distribution of axial and tangential residual stresses in an Al6022 deep drawn cup. The technique is able to provide true spatial resolutions of 0.05 mm for a strain measurement on a cup with 0.92 mm wall thickness. It is found that both axial and tangential stresses exhibit non-linear gradients through thickness and both exhibit a pronounced dependency on the axial position. The springback measured on a split ring cut from the cup agrees within 3% accuracy with the value predicted from the average of measured through-thickness stresses.
45 citations
TL;DR: In this paper, the authors used tomographic and topographic imaging techniques to reconstruct the three-dimensional grain shape inside a polycrystalline sample, which can be performed from projection images with the detector positioned either in the diffracted-beam or in the direct-beam position.
Abstract: By orienting a crystal grain with its diffraction vector along the sample rotation axis, it is possible to use powerful tomographic and topographic imaging techniques to reconstruct the three-dimensional grain shape inside a polycrystalline sample. The acquisition and reconstruction can be performed from projection images with the detector positioned either in the diffracted-beam or in the direct-beam position. In the first case, the projection data consist of a series of integrated, monochromatic beam X-ray diffraction topographs of the grain under investigation. In the second case, the corresponding diffraction contrast in the transmitted beam may be interpreted as an additional contribution to the X-ray attenuation coefficient of the material. This latter variant is restricted to grains with small orientation spread but offers the possibility to characterize simultaneously the three-dimensional grain shape and the absorption microstructure of the surrounding sample material. The contrast mechanism is sensitive to local strain fields and can, in certain cases, reveal details of the grain microstructure, such as the presence of second-phase inclusions. The methodology is successfully demonstrated on an aluminium polycrystal, with a resulting three-dimensional mapping accuracy better than 7 µm. The possibilities and limitations of the technique are listed and its performance relative to other three-dimensional mapping techniques is discussed.
45 citations
Cites background from "J. Appl. Cryst.の発刊に際して"
...Ideally, topotomography should therefore be combined with a polycrystal indexing procedure (Lauridsen et al., 2001) providing access to grain orientations and possibly also the centre of mass positions of the grains....
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TL;DR: A new dinuclear copper complex and several Cu-amino acid complexes inhibit protein tyrosine phosphatase 1B competitively at submicromolar levels, suggesting that copper complexes may interfere with cellular signaling pathways by inhibiting protein tyrolysis phosphatases.
45 citations
TL;DR: High-energy ball-milling in an oxidative atmosphere caused gradual transition of pure zincite into zinc ferrite due to the oxidation of steel contamination, while in an inert atmosphere the rate of contamination increased dramatically.
45 citations
TL;DR: Advancements in source stability, X-ray optics, detectors, goniometry, data-collection strategies and data reduction and phasing software made over the past decade have placed native SAD at the verge of becoming a ‘first-choice’ method for both de novo and molecular-replacement structure determination.
45 citations
Cites background from "J. Appl. Cryst.の発刊に際して"
...Recent studies (Alkire et al., 2008, 2013) illustrate the effect of pin–loop design on data quality....
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...…of fast photon-counting and CCD detectors can collect data at an astonishing rate (10 Hz to 100 Hz or greater), and this coupled with ultrafine data slicing (e.g. 0.05 per frame) make data storage, data transfer and data reduction very demanding if not overwhelming in the home laboratory....
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References
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TL;DR: The goals of the PDB are described, the systems in place for data deposition and access, how to obtain further information and plans for the future development of the resource are described.
Abstract: The Protein Data Bank (PDB; http://www.rcsb.org/pdb/ ) is the single worldwide archive of structural data of biological macromolecules. This paper describes the goals of the PDB, the systems in place for data deposition and access, how to obtain further information, and near-term plans for the future development of the resource.
34,239 citations
TL;DR: New features added to the refinement program SHELXL since 2008 are described and explained.
Abstract: The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.
28,425 citations
TL;DR: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics.
Abstract: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics. The map-fitting tools are available as a stand-alone package, distributed as `Coot'.
27,505 citations
TL;DR: The PHENIX software for macromolecular structure determination is described and its uses and benefits are described.
Abstract: Macromolecular X-ray crystallography is routinely applied to understand biological processes at a molecular level. However, significant time and effort are still required to solve and complete many of these structures because of the need for manual interpretation of complex numerical data using many software packages and the repeated use of interactive three-dimensional graphics. PHENIX has been developed to provide a comprehensive system for macromolecular crystallographic structure solution with an emphasis on the automation of all procedures. This has relied on the development of algorithms that minimize or eliminate subjective input, the development of algorithms that automate procedures that are traditionally performed by hand and, finally, the development of a framework that allows a tight integration between the algorithms.
18,531 citations
TL;DR: A description is given of Phaser-2.1: software for phasing macromolecular crystal structures by molecular replacement and single-wavelength anomalous dispersion phasing.
Abstract: Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For molecular replacement, the new algorithms have proved to be significantly better than traditional methods in discriminating correct solutions from noise, and for single-wavelength anomalous dispersion experimental phasing, the new algorithms, which account for correlations between F+ and F−, give better phases (lower mean phase error with respect to the phases given by the refined structure) than those that use mean F and anomalous differences ΔF. One of the design concepts of Phaser was that it be capable of a high degree of automation. To this end, Phaser (written in C++) can be called directly from Python, although it can also be called using traditional CCP4 keyword-style input. Phaser is a platform for future development of improved phasing methods and their release, including source code, to the crystallographic community.
17,755 citations