|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.|
It is with great sadness that we report the death of Hugo Rietveld at the age of 84 after a short illness.
Hugo M. Rietveld was born in The Hague, The Netherlands, on 7 March 1932. After completing Grammar School he went to Australia and studied physics at the University of Western Australia in Perth.
In 1964 he obtained his PhD degree in Physics with a thesis entitled 'The Structure of p-Diphenylbenzene and Other Compounds', a single-crystal neutron and X-ray diffraction study. This investigation was the first single-crystal neutron diffraction study in Australia and was conducted at the nuclear reactor, HIFAR, in Sydney.
In 1964 he became a research officer at the Netherlands Energy Research Foundation ECN at Petten, The Netherlands, and was mainly involved in neutron powder diffraction studies of uranates and other ceramic compounds. After a scientific and managerial career with ECN he retired in 1992, but continued to garner a multitude of awards over the following two decades. These included the Gregori Aminoff Prize in 1995, the Barrett Award in 2003 (pictured), the Order of Oranje-Nassau in 2004, and the EPDIC Award for Distinguished Powder Diffractionists and the Hans Kühl Medal, both in 2010.
The work for which he is best known is the Rietveld Refinement Method, first published in J. Appl. Cryst. (1969), 2, 65-71.
Coherent X-ray diffraction imaging (CXDI) has been used to visualise the internal structures of non-crystalline particles with dimensions of micrometers to sub-micrometers in materials science and biology.
Now X-ray free-electron lasers (XFELs) are leading CXDI to a new levels. X-ray pulses with complete spatial coherence and duration are available at XFEL Facilities such as the Linac Coherent Light Source (LCLS) and the Spring-8 Angstrom Compact Free-Electron Laser. One can routinely collect diffraction data before radiation-damage processes occur and owing to the repetition rate of XFEL pulses, a large number of diffraction patterns can be collected within a short period of time.
A group of scientists [Kobayashi et al. (2016), J. Synchrotron. Rad. 23, doi:10.1107/S1600577516007426] have recently proposed XFEL-CXDI experiments for frozen-hydrated biological specimens at cryogenic temperatures. It has been demonstrated previously that cryogenic technologies enable the storage of biological cells at low temperatures, for instance in medical science. Frozen hydrated cells and cellular organelles keep their functional structures, and are still alive after returning to ambient temperatures.
Cryogenic sample preparation enables the storage of frozen-hydrated specimens in liquid nitrogen for CXDI experiments, scientists can therefore harvest a large numbers of cells and isolated unstable cellular organelles at a desired period of the cells cycle. Moreover, frozen-hydrated specimens are free from adiabatic expansion, bubbling of water inside biological specimens and other phenomena.The scientists have developed membranes, devices and procedures to prepare frozen-hydrated biological specimens and standard specimens for cryogenic XFEL-CXDI experiments. The quality of the prepared specimens was examined through a series of diffraction experiments and based on the results, the researchers discussed future developments in specimen preparation, and the characteristics of frozen-hydrated biological specimens in CXDI experiments.
The 1958 Nobel prize to Beadle and Tatum for proposing, in the main, that each gene is responsible for a distinct enzyme is now seen as both foundational to molecular biology and genetics. Some genes for example, code for functional RNAs, while others code for non-enzymatic proteins such as collagen. Yet enzymes remain fundamental to life on earth, catalysing at least 5000 biochemical reactions. Enzymes can increase reaction rates by huge factors, from millions of years to milliseconds per event, so that, from meat tenderizer to washing powder, to muscle contraction, cargo transport in the cell, ion pumps, infection and digestion, no molecular machine is more fundamental to biological function than the enzyme [Spence and Lattman (2016), IUCrJ. 3, 228-229].
In a recent publication [Horrell et al. [(2016), IUCrJ. 3, 271-281] shed some light on the mechanism of the catalytic cycle by creating a kind of atomic resolution X-ray molecular movie. Horrell et al. soaked “large” crystals of recombinant copper nitrite reductase in sodium nitrite for an hour at room temperature before transferring them to a cryo-protectant and plunging into liquid nitrogen, to trap the structure of the room temperature complex. At this stage the reaction does not proceed because no reducing agent is present. The required electrons are provided by free radicals generated by the very X-rays used to image the structure.
The authors then used the Diamond synchrotron fitted with a new fast shutterless detector to obtain 45 low-dose Bragg diffraction datasets in 19s each from the same regions of the crystal. This interval spans the catalytic cycle of nitrite reduction, a vital process in agriculture and in the formation of the greenhouse gas N2O.
In short, the new fast synchrotron detectors, soon to be combined with diffraction-limited sources, may allow us to make movies of enzyme kinetics. If these studies can be used to assist in modelling the atomistic mechanisms for enzymatic catalysis, it may indeed be possible, using recombinant DNA, to develop new enzymes with specifically tuned properties, which will have enormous implications for pharmacology, drug treatment and food production.
The ability of neutrons to penetrate relatively thick metal objects allows the use of various non-destructive testing techniques when other more conventional methods (e.g. laboratory X-ray) cannot be implemented. Neutron imaging with thermal and cold neutrons provides unique contrast and is often used to study internal structure and the presence of defects in various metal samples, as well as the distribution of hydrogen-containing substances within metals, water in proton exchange membrane fuel cells, coolant in heat pipes, diesel in fuel injectors and many others. At the same time, neutron diffraction is widely used for studies of crystallographic properties as the wavelengths of thermal and cold neutrons are comparable to lattice parameters.
The recent development of high-resolution neutron counting detectors capable of simultaneous measurement of >250 000 spectra in combination with the state of the art beamlines at pulsed neutron sources provide the possibility to map both crystallographic properties and elemental composition in various samples with relatively high spatial resolution. Put to the test the technique could hold the key to the non-destructive investigation of the microstructure and elemental composition and uniformity within welds.In a recent publication [Tremsin et al. (2016). J. Appl. Cryst. 49, doi:10.1107/S1600576716006725] a group of scientists from Japan, the UK and the USA demonstrate the possibilities of energy-resolved neutron imaging to study some microstructural features and the bulk distribution of elemental composition in two different sets of dissimilar alloy welds. They also demonstrate the possibility of mapping the distribution of various elements within the welds through resonance absorption imaging with epithermal neutrons.
The International Union of Crystallography is pleased to announce that its new open-access journal, IUCrJ, has received its first impact factor of 3.1 in the 2015 Thomson Reuters Journal Citation Reports.
Other highlights from the 2015 Impact Factor results are as follows:
Peter Strickland, Executive Managing Editor at the IUCr, said “being a small not-for-profit organization we take our mission to share scientific knowledge seriously and feel it is our responsibility to represent our global community fairly and equitably. I would like to take this opportunity to thank our authors, editors and reviewers for their continued contributions and service. It is through their commitment to excellence that we achieve all we do”.
The International Union of Crystallography (IUCr) is an International Scientific Union. Its objectives are to promote international cooperation in 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.The IUCr fulfils its publication objectives by producing primary scientific journals and reference works such as International Tables for Crystallography. IUCr Journals are the leading journals in their field and are produced to the highest quality standards. The IUCr performs numerous global outreach activities including organizing laboratory workshops and international conferences, as well as supporting the development of young crystallographers.