http://www.esrf.eu The latest scientific news daily 1 2006-03-23T07:14:04Z http://www.esrf.eu/news/spotlight/spotlight115/spotlight115 Within the ESRF Upgrade Programmme, the Accelerator Division has increased the brilliance and coherence of the undulator-generated photon beams through a reduction of the electron beam vertical emittance by a factor of six. A value of 5 picometres is now available in User Service Mode, making possible photon beam brilliance values matched nowhere else in the world. 2010-09-07 08:15:00 No publisher admans 2010-09-07T09:40:58Z News Item http://www.esrf.eu/news/spotlight/spotlight114/spotlight114 Phase-contrast X-ray imaging provides substantially enhanced contrast resolution for soft-tissues compared to conventional absorption radiography. Here, researchers demonstrate that phase contrast computed tomography can depict structural properties of cartilage matrix in an excised human sample. The level of detail within the tomographic images is sufficient to differentiate osteoarthritic and intact cartilage matrixes. 2010-08-24 08:30:00 No publisher admans 2010-08-19T09:06:45Z News Item http://www.esrf.eu/news/spotlight/spotlight113/spotlight113 Three-dimensional images of the porous microstructure in plasma-sprayed tungsten are needed to assess whether the material is suitable as a coating for nuclear fusion reactors. High-resolution synchrotron-radiation microtomography (SRµCT) is the only method capable of providing this 3D information - and still the measurements were a challenge. 2010-08-06 14:11:33 No publisher admans 2010-08-24T06:25:23Z News Item http://www.esrf.eu/news/spotlight/spotlight112/spotlight112 Oscillatory chemical reactions are often called chemical ‘clocks’ due to their periodic nature. A well-known system that shows periodic oscillation of reaction rate is the catalytic oxidation of carbon monoxide over platinum and palladium surfaces. A team of researchers from Leiden University and the ESRF have pinpointed a new mechanism that makes this chemical clock ‘tick’. 2010-07-27 08:00:00 No publisher admans 2010-07-26T05:55:52Z News Item http://www.esrf.eu/news/spotlight/spotlight111/spotlight111 A novel combination of infrared spectroscopy and X-ray diffraction, using very hard X-rays, illuminates the structural reactive behaviour of working catalysts. It reveals previously hidden aspects of the fundamental interactions occurring between small molecules and noble metal nanoparticles. 2010-07-13 08:00:00 No publisher admans 2010-06-30T13:35:02Z News Item http://www.esrf.eu/news/spotlight/spotlight110/spotlight110 The combined use of XAS and NMR spectroscopy enabled characterisation of the three-dimensional structure and the metal-binding site of a small Cu(I)/Cu(II)-binding protein involved in bacterial heavy-metal resistance. This protein features a binding cooperativity with enhanced affinity for Cu(II) once Cu(I) is bound. NMR-derived data were used for the determination of the atomic coordinates of the protein moiety in solution while XAS measurements yielded geometric information on the Cu(I) site which is coordinated by four sulphur atoms. This study represents the first example of a XANES and EXAFS characterisation of a tetrathioether Cu(I) site in a protein in which copper is not part of a cluster. Knowledge of this new structure permits the understanding of the previously observed Cu(I)/Cu(II) binding cooperativity from a structural point of view. 2010-06-29 08:59:25 No publisher admans 2010-06-29T08:28:36Z News Item http://www.esrf.eu/news/spotlight/spotlight109/spotlight109 The Earth’s mantle is layered because of successive phase transitions occurring with increasing pressure and temperature. These transitions are understood by comparison between the seismic reflectors and experimentally determined phase diagrams. Nonetheless, peculiar seismic features observed in the D"-layer remain difficult to interpret. Here, a phase transition occurs which transforms the structure of the silicate mineral from its lower pressure stable form, the perovskite phase, to a different structure called post-perovskite. The study of this phase transition, which occurs at ~110 GPa, could help explain some of these anomalies. However, while the transition is well characterised for a simplistic MgSiO3 composition, its mechanisms remain ambiguous for the Earth’s real composition. In particular Al and Fe are known to modify significantly the phase diagram and elastic properties of the mantle minerals. By means of Fe K-edge XANES and X-ray diffraction measurements, scientists investigated the fraction of coexisting perovskite and post-perovskite phases, together with the Fe distribution in a pressure domain extending from 100 to 185 GPa. Their results give evidence for the coexistence of the two silicate phases throughout the whole D"-layer, with a post-perovskite phase depleted in Fe. The phase diagram is incompatible with any sharp seismic reflector in this mantle region. 2010-06-16 15:07:46 No publisher admans 2010-06-16T13:18:42Z News Item http://www.esrf.eu/news/spotlight/spotlight108/spotlight108 Resistive memories are candidates for future non volatile random access memories (RAMs). Their functioning is based on the ability to switch between high and low resistance states. However, the physical mechanism responsible for the low resistivity remains a mystery. Now a team of scientists from the CEA Grenoble and the ESRF have performed non-destructive HAXPES measurements on a NiO device before and after resistive switching. Their results suggest that conduction occurs via defects such as oxygen vacancies. 2010-06-01 09:14:58 No publisher admans 2010-06-02T13:52:33Z News Item http://www.esrf.eu/news/spotlight/spotlight107/spotlight107 A multi quantum well electroabsorption-modulated laser is a semiconductor device employed in long-distance, high-frequency optical-fibre communication. The most advanced devices involve monolithic integration of two functions, electroabsorption modulator and distributed feedback laser, at the chip level. Devices are manufactured by state-of-the-art methods of substrate masking and vapour deposition, but the results of this process are judged empirically. Here scientists have used an ESRF hard X-ray microprobe to characterise the semiconductor material constituents of such a device with unprecedented detail. 2010-05-18 08:05:00 No publisher admans 2010-05-27T12:13:29Z News Item http://www.esrf.eu/news/spotlight/spotlight106/spotlight106 The transfer of phosphoryl groups is probably the most important enzyme-catalysed reaction in biology. All organisms use phosphate in the form of ATP to store and transmit energy but phosphoryl transfer is also used to control processes as diverse as cell signalling, regulation of cellular division, membrane structure and enzyme function. Consequently, a huge number of enzymes, up to 10% of the human genome, have evolved to catalyse phosphoryl transfer. Dissecting how these enzymes catalyse the reaction is of vital importance in understanding the cellular processes they regulate and perhaps designing drugs to target specific pathways. Structural studies of two analogues of the transition state of phosphoryl transfer, magnesium trifluoride and aluminium tetrafluoride, using high resolution X-ray crystallography in combination with 19F-NMR, has provided exceptional details of the mechanism of the reaction in two archetypal phosphoryl transfer enzymes.  2010-05-04 07:45:00 No publisher admans 2010-06-18T13:26:16Z News Item http://www.esrf.eu/news/spotlight/spotlight105/spotlight105 Bacteria sense external events and send signals to the cell interior via two-component systems formed by a membrane protein, histidine kinase, that has extracellular and intracytoplasmic domains and a soluble intracellular response regulator. The crystal structure of such a system from Thermotoga maritima provides the paradigm for a structural understanding of signalling in bacteria and for its perturbation using structure-based inhibitors. An additional highlight of this study is the demonstration that the histidine kinase component can autophosphorylate in cis geometry, refuting the belief that trans autophosphorylation is universal for histidine kinases. 2010-04-20 07:45:00 No publisher admans 2010-04-19T15:20:02Z News Item http://www.esrf.eu/news/spotlight/spotlight104/spotlight104 Biaxial liquid crystals in goethite dispersions were discovered using small-angle X-ray scattering. Uniaxial liquid crystals, with only one optical axis, are widely used in liquid crystal displays (LCDs). Biaxial liquid crystals, with full 3D optical anisotropy, can make displays and optical switches much faster and might open doors to new 3D technologies. 2010-04-06 07:45:00 No publisher admans 2010-04-06T06:29:42Z News Item http://www.esrf.eu/news/spotlight/spotlight103/spotlight103 Molecular dynamics computer simulation for a model glass permitted the exploration of a previously inaccessible region of wavelength for acoustic excitations in glasses. New characteristic properties of the acoustic excitations were found in this region that are anomalous with respect to crystals. Such acoustic properties are at the origin of the universal behaviour found in the specific heat of glasses in the ~10 K temperature range. 2010-03-23 08:45:00 No publisher admans 2010-03-22T13:40:03Z News Item http://www.esrf.eu/news/spotlight/spotlight102/spotlight102 Magnetic imaging with nanoscale domain resolution is now possible thanks to a new way of carrying out soft X-ray holography. The key feature of this microscopy-like imaging technique is a movable field-of-view that can be freely positioned on the sample. The microscope allows imaging of extended samples with some tens of nanometres resolution and provides chemical as well as magnetic contrast. 2010-03-09 08:45:00 No publisher admans 2010-03-09T07:54:34Z News Item http://www.esrf.eu/news/spotlight/spotlight101/spotlight101 Solid carbon dioxide undergoes a radical change from a molecular solid to a non-molecular “polymeric” state at elevated pressures and temperatures [1]. The polymeric state is characterised by the disappearance of the double bonds between the carbon and oxygen atoms and the formation of new single bonds. Whether this transformation occurs as a result of solid-state chemical reactions between molecules reaching a critical separation, or via intermediate states where molecules gradually distort as pressure increases, remains unknown. To solve this mystery, researchers from Université Pierre et Marie Curie have determined the structure of CO2 in the high-pressure phase IV, the ultimate molecular phase before its polymerisation into phase V. 2010-02-23 08:45:00 No publisher admans 2010-02-22T09:00:07Z News Item