Welcome to the

International Union of Crystallography

The IUCr is an International Scientific Union. Its objectives are to promote international cooperation in crystallography and to contribute to all aspects of crystallography, to promote international publication of crystallographic research, to facilitate standardization of methods, units, nomenclatures and symbols, and to form a focus for the relations of crystallography to other sciences.

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New developments of the symmetry database

viz-1The symmetry database at http://it.iucr.org/resources/symmetrydatabase/ has now been updated and expanded to include a wealth of new data. Information is now available for the Euclidean, chirality-preserving and affine normalizers of the space groups; these aid many crystallographic calculations including the comparison of different but equivalent coordinate descriptions of a crystal structure (and the accompanying changes in structure factors) and the derivation of phase restrictions for use in direct methods, as described in Chapter 3.5 of the new edition of Volume A. For those interested in molecular symmetry and the physical properties of materials, the generators, general and special positions, and Wyckoff positions of the 3D crystallographic point groups are presented and can be transformed to different settings, enhancing and extending the data presented in Chapter 3.2 of Volume A. Users will also enjoy the simple, clear and instructive interactive visualization of the symmetry elements of the crystallographic point groups. Throughout the database, symmetry operations are now presented in four different ways to suit a range of purposes: as x, y, z-based coordinate triplets, in matrix form, by geometric symbols (indicating the type and order of the operations, and the orientation of the corresponding symmetry elements) and in Seitz notation. Site-symmetry groups, whose oriented symbols show how the symmetry elements at a site are related to the symmetry directions of the crystal lattice, are now also listed for the space and point groups.

Posted 09 Aug 2017 

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A tribute to Professor Philip Coppens

philip coppensThis special issue is dedicated to a lifetime of outstanding scientific achievements by Professor Philip Coppens. Originally a tribute to his recent retirement, this collection of papers – approved by Philip – was submitted by former students, postdocs, close friends and collaborators of Philip. Many of these individuals participated in a symposium 'Advancing structural science: pushing the limits of X-ray crystallography' held at the University at Buffalo in October 2016 that honored Philip's scientific achievements (see https://www.buffalo.edu/ubnow/stories/2016/10/coppens-symposium.html). With Philip's unexpected passing in June 2017, this collection of manuscripts has now become a remembrance of his impactful scientific legacy.

Among the earliest of pioneers of the field of charge density, Philip demonstrated that accurate high-resolution X-ray diffraction was an unparalleled experimental method for mapping and modeling electron density in crystals. In both theory and practice, his contributions impacted every aspect of charge density: helium temperature experiments, data reduction, multipole modeling, combined analysis of charge and spin densities, derived electrostatic properties, multipolar data bases, and applications to chemical bonding and materials science.

Much of Philip's later work involved the development and application of time-resolved X-ray diffraction methods to monitor light-induced transformations in small-molecule systems. Several of his most notable achievements in the area of photocrystallography include the structural determination of metastable intermediates in sodium nitroprusside, photochemistry in supramolecular systems, the development of software for the analysis and refinement of monochromatic and Laue X-ray diffraction, and the picosecond structural dynamics of organometallic complexes.

Philip's extensive influence on the community was felt well beyond his scientific literature and is beautifully described in an excerpt from Philip's eulogy penned by one of his three sons, Eldad Coppens: `He was like a massive star that hurls through the universe with unrestrainable momentum and irrepressible energy affecting the course of everything in its orbit.'

We hope you enjoy reading this collection of manuscripts dedicated to the remembrance of Professor Philip Coppens (1930–2017).

Philip's full eulogy is archived on the IUCr website at http://www.iucr.org/people/crystallographers/philip-coppens-1930-2017.

J. B. Benedict, Y. S. Chen and C. Lecomte
Guest editors


Article taken from a Special issue on charge density photocrystallography and time-resolved crystallography

Posted 07 Aug 2017 

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IUCr Associates Programme

IUCrAssociates_right_squareThe IUCr is excited to announce its new, voluntary Associates Programme. This will launch officially at the IUCr Congress in Hyderabad in August 2017.

The programme offers a series of benefits and tools to help you network, share ideas and discover more about crystallography. In addition, by joining the IUCr Associates Programme you will be supporting the IUCr in its many charitable activities such as sponsoring international meetings and schools, and its OpenLabs initiative.

The benefits of joining include, for example, a 20% discount on the open-access fee for publishing an article in an IUCr journal, the facility to download 6 free articles from Crystallography Journals Online, a 50% discount for individuals purchasing the print version of International Tables for Crystallography, and many others.

There will also be tools for professional networking such as access to the IUCr LinkedIn group, a jobs board and opportunities to participate in the IUCr Outreach and Education programme.

The Associates Programme welcomes individuals at any stage of their career, from undergraduates to postdoctoral and senior researchers (a reduced joining rate is available for students and retired scientists).

The IUCr is offering a pre-launch discount of 20% on the Associates Programme joining fee, which gives you access to all the benefits for a period of 3 years. Anyone signing up before the launch in August will be eligible for this specially discounted rate (USD 160 or USD 48 for students and retired scientists). For more details and to register your interest in this offer, please click here.

If you have any questions about the Associates Programme, please do not hesitate to contact us at associates@iucr.org

Posted 09 Mar 2017 

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Quality assurance in microbeam radiation therapy

Microbeam radiation therapy (MRT) is an innovative preclinical radiotherapy procedure consisting of many micrometre-sized spatially fractionated radiation fields, obtained by collimating a beam of synchrotron radiation with a multi-slit collimator. A typical radiation field of MRT consists of an array of microbeams, each with a width of 50 µm and a centre-to-centre distance of 400 µm.

MRT differs from external beam radiation therapy (EBRT) due to the properties of synchrotron radiation, such as the small angular divergence of the photon beam, the broad spectrum of energies available and the pulsed high-intensity radiation that is produced. The low divergence of the beam ensures that the field does not spread out as it passes through the patient, thus maintaining the spatial fractionation at depth; the high-intensity radiation allows treatment time to be reduced, thus reducing smearing of the microbeam paths in the tissues due to breathing or cardiosynchronous motion.

The most significant advantage of MRT over EBRT is the different radiobiological response of cancerous and healthy tissues to the micrometre-sized MRT field. As the size of the radiation field decreases to the order of micrometres the dose tolerated by normal tissue increases dramatically, whilst maintaining tumour control. This phenomenon, called the dose-volume effect, makes MRT a promising treatment for radioresistant tumours such as osteosarcomas, or tumours located within or near sensitive structures (e.g. glioblastomas in paediatric patients).

Routine dosimetry quality assurance (QA) prior to treatment is necessary to identify any changes in beam condition from the treatment plan, and is undertaken using solid homogeneous phantoms. Solid phantoms are designed for, and routinely used in, megavoltage X-ray beam radiation therapy. These solid phantoms are not necessarily designed to be water-equivalent at low X-ray energies, and therefore may not be suitable for MRT QA.

Cameron et al. (2017). J. Synchrotron Rad. 24, 866-876 simulated dose profiles of various phantom materials and compared them with those calculated in water under the same conditions, so demonstrating quantitatively the most appropriate solid phantom to use in dosimetric MRT QA.

Based on the study, the adoption of virtual water, plastic water DT, RW3 and RM1457 solid water were recommended for MRT QA as water-equivalent solid phantom materials.

Posted 31 Jul 2017 

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Preclinical radiotherapy at the Australian Synchrotron Imaging and Medical Beamline

mo5155Therapeutic applications of synchrotron X-rays such as microbeam (MRT) and minibeam (MBRT) radiation therapy promise significant advantages over conventional clinical techniques for some diseases if successfully transferred to clinical practice. Preclinical studies show clear evidence that a number of normal tissues in animal models display a tolerance to much higher doses from MRT compared with conventional radiotherapy. However, a wide spread in the parameters studied makes it difficult to come to any conclusions about the associated tumor control or normal tissue complication probabilities. To facilitate more systematic and reproducible preclinical synchrotron radiotherapy studies, a dedicated preclinical station including small-animal irradiation stage was designed and installed at the Imaging and Medical Beamine (IMBL) at the Australian Synchrotron [Livingstone et al. (2017). J. Synchrotron Rad. 24, 854-865].

The stage was characterised in terms of the accuracy and reliability of the vertical scanning speed, as this is the key variable in dose delivery. The measured speed was found to be within 1% of the nominal speed for the range of speeds measured by an interferometer. Furthermore, dose measurements confirmed the expected relationship between speed and dose and showed that the measured dose is independent of the scan direction.

These and further studies covered in the paper demonstrate that the IMBL preclinical synchrotron radiotherapy irradiation stage can provide unique opportunities for reproducible radiobiology studies in small animals to answer fundamental questions on biological pathways in high-dose-rate synchrotron radiotherapy. The tool also represents a unique opportunity to set the medical physics codes of practice for spatially fractionated submillimetric beams, such as dosimetry protocols, treatment planning benchmarking platform, patient safety procedures and patient safety systems.

Posted 27 Jul 2017 

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Pioneering X-ray technique to analyse ancient artefacts

sc5013aA pioneering X-ray technique that can analyse artefacts of any shape or texture in a non-destructive way has been developed by an international team of scientists. The method uses X-ray diffraction (XRD) in order to determine crystallographic phase information in artefacts with very high accuracy and without causing damage to the object being scanned [Hansford et al. (2017). Acta Cryst. A73, 293-311].

Using the technique, researchers can identify pigments in paintings and on painted objects – which could potentially be applied in the future to help to clamp down on counterfeit artwork and artefacts and verify authenticity.

The research suggests that the non-invasive technique could also eliminate the frequent need to compromise between archaeological questions that can be solved and the analytical methods available to do so.

Dr Graeme Hansford, from the University of Leicester, explained, “What makes this method really unique is that the shape and texture of the sample become immaterial. I expect future studies to make significant contributions to determining the provenance of a range of archaeological objects, and this data will ultimately provide vital context information for museum collections.

“In paintings, the type of pigment used frequently yields useful insights into methods of production and the organisation of ancient industries, as well as restricting the possible date of manufacture. This could help to determine if the provenance of an artefact is as purported.”

The research was supported by the UK’s Science and Technology Facilities Council.

This news story is an excerpt taken from a press release published by the University of Leicester.
Posted 24 Jul 2017