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Synchrotron X-rays (synchrotron + x-ray)
Terms modified by Synchrotron X-rays Selected AbstractsChemInform Abstract: Crystal Structure of Superconducting K3Ba3C60: A Combined Synchrotron X-Ray and Neutron Diffraction Study.CHEMINFORM, Issue 1 2001Serena Margadonna Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synchrotron X-ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p,-bibenzoate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Ernesto Pérez Abstract Time-resolved synchrotron X-ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p,-bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110,°C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained. Scattering profiles corresponding to sample PDEB85 in a melting experiment. [source] Re-investigation of the structure and crystal chemistry of the Bi2O3,W2O6 `type (Ib)' solid solution using single-crystal neutron and synchrotron X-ray diffractionACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010Neeraj Sharma Single crystals of composition Bi35.66W4.34O66.51 (or Bi8.2WO15.3, bismuth tungsten oxide), within the type (Ib) solid-solution region of the Bi2O3,WO3 system, were synthesized using the floating-zone furnace method. Synchrotron X-ray and neutron single-crystal diffraction data were used to confirm the previously tentative assignment of the room-temperature space group as I41. Fourier analysis of the combined X-ray and neutron datasets was used to elucidate and refine fully the cation and anion arrays for the first time. The mixed cation site M1 is shown to be coordinated by eight O atoms in an irregular cube when M = Bi, and by six O atoms in an octahedron when M = W. The resulting disorder in the average structure around M1 is discussed in the context of experimentally observed oxide-ion conductivity. [source] ChemInform Abstract: Pressure-Induced Spin-State Transition in BiCoO3.CHEMINFORM, Issue 41 2010Kengo Oka Abstract Synchrotron X-ray and neutron powder diffraction measurements show that the structure of the title compound changes from a polar tetragonal PbTiO3 -type (space group P4mm) to a centrosymmetric orthorhombic GdFeO3 -type (space group Pbnm) above 3 GPa with a large volume decrease of 13% at room temperature revealing a spin-state change. [source] Microstrain and grain-size analysis from diffraction peak width and graphical derivation of high-pressure thermomechanicsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2008Yusheng Zhao An analytical method is presented for deriving the thermomechanical properties of polycrystalline materials under high-pressure (P) and high-temperature (T) conditions. This method deals with non-uniform stress among heterogeneous crystal grains and surface strain in nanocrystalline materials by examining peak-width variation under different P,T conditions. Because the method deals directly with lattice d spacing and local deformation caused by stress, it can be applied to process any diffraction profile, independent of detection mode. In addition, a correction routine is developed using diffraction elastic ratios to deal with severe surface strain and/or strain anisotropy effects related to nano-scale grain sizes, so that significant data scatter can be reduced in a physically meaningful way. Graphical illustration of the resultant microstrain analysis can identify micro/local yields at the grain-to-grain interactions resulting from high stress concentration, and macro/bulk yield of the plastic deformation over the entire sample. This simple and straightforward approach is capable of revealing the corresponding micro and/or macro yield stresses, grain crushing or growth, work hardening or softening, and thermal relaxation under high- P,T conditions, as well as the intrinsic residual strain and/or surface strain in the polycrystalline bulk. In addition, this approach allows the instrumental contribution to be illustrated and subtracted in a straightforward manner, thus avoiding the potential complexities and errors resulting from instrument correction. Applications of the method are demonstrated by studies of ,-SiC (6H, moissanite) and of micro- and nanocrystalline nickel by synchrotron X-ray and time-of-flight neutron diffraction. [source] Synchrotron X-ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p,-bibenzoate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Ernesto Pérez Abstract Time-resolved synchrotron X-ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p,-bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110,°C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained. Scattering profiles corresponding to sample PDEB85 in a melting experiment. [source] Revision of the structure of Cs2CuSi5O12 leucite as orthorhombic PbcaACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2010A. M. T. Bell The crystal structure of a hydrothermally synthesized leucite analogue Cs2CuSi5O12 has been determined and refined using the Rietveld method from high-resolution synchrotron X-ray and neutron powder diffraction data. This structure is based on the topology and cation-ordering scheme of the Pbca leucite structure of Cs2CdSi5O12, and exhibits five ordered Si sites and one ordered Cu tetrahedrally coordinated (T) site. This structure for Cs2CuSi5O12 is topologically identical to other known leucite structures and is different from that originally proposed by Heinrich & Baerlocher [(1991), Acta Cryst. C47, 237,241] in the tetragonal space group . The crystal structure of a dry-synthesized leucite analogue Cs2CuSi5O12 has also been refined; this has the cubic pollucite structure with disordered T sites. [source] Structures of 6H perovskites Ba3CaSb2O9 and Ba3SrSb2O9 determined by synchrotron X-ray diffraction, neutron powder diffraction and ab initio calculationsACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2008Budwy Rowda The structures of the 6H perovskites Ba3B2+Sb5+2O9, B = Ca and Sr, have been solved and refined using synchrotron X-ray and neutron powder diffraction data. Ba3CaSb2O9 and Ba3SrSb2O9 have monoclinic C2/c and triclinic space-group symmetries, respectively, while Ba3MgSb2O9 has ideal hexagonal P63/mmc space-group symmetry. The symmetry-lowering distortions are a consequence of internal `chemical pressure' owing to the increasing effective ionic radius of the alkaline-earth cation in the perovskite B site from Mg2+ (0.72,Å) to Ca2+ (1.00,Å) to Sr2+ (1.18,Å). Increasing the effective ionic radius further to Ba2+ (1.35,Å) leads to decomposition at room temperature. The driving force behind the transition from P63/mmc to C2/c is the need to alleviate underbonding of Ba2+ cations in the perovskite A site via octahedral rotations, while the transition from C2/c to is driven by the need to regularize the shape of the Sb2O9 face-sharing octahedral dimers. Ab initio geometry-optimization calculations were used to find a triclinic starting model for Ba3SrSb2O9. [source] Texture analysis from synchrotron diffraction images with the Rietveld method: dinosaur tendon and salmon scaleJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2005Mark Goodwin A Rietveld method is described which extracts information on crystal structure, texture and microstructure directly from two-dimensional synchrotron diffraction images. This is advantageous over conventional texture analysis that relies on individual diffraction peaks, particularly for low-symmetry materials with many overlapping peaks and images with a poor peak-to-background ratio. The method is applied to two mineralized biological samples with hydroxylapatite fabrics: an ossified pachycephalosaurid dinosaur tendon and an Atlantic salmon scale. Both are measured using monochromatic synchrotron X-rays. The dinosaur tendon has very strongly oriented crystals with c -axes parallel to the tendon direction. The salmon scale displays a weak texture. [source] Time-resolved measurements of supersonic fuel sprays using synchrotron X-raysJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2000Christopher F. Powell A time-resolved radiographic technique has been developed for probing the fuel distribution close to the nozzle of a high-pressure single-hole diesel injector. The measurement was made using X-ray absorption of monochromatic synchrotron-generated radiation, allowing quantitative determination of the fuel distribution in this optically impenetrable region with a time resolution of better than 1,µs. These quantitative measurements constitute the most detailed near-nozzle study of a fuel spray to date. [source] Polarization-dependent six-beam X-ray pinhole topographsACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2006Kouhei Okitsu X-ray six-beam pinhole topograph images were obtained for a silicon crystal with incident synchrotron X-rays. The polarization state of X-rays incident on the sample crystal was controlled by using a four-quadrant phase-retarder system [Okitsu et al. (2002). Acta Cryst. A58, 146,154] that can be rotated around the transmitted beam axis to generate arbitrarily polarized X-rays. Quantitative agreement was found between the experimental and computer-simulated topograph images based on the n -beam Takagi,Taupin dynamical theory under the assumption that the polarization state of the incident X-rays was identical with the experiment. This result confirmed the validity of the computer algorithm to solve the n -beam dynamical theory and the proper operation of the rotating four-quadrant phase-retarder system simultaneously. [source] A lamellar model for the X-ray rocking curves of sagittally bent Laue crystalsACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2003Z. Zhong The use of sagittally bent asymmetric Laue crystals in horizontally focusing monochromators for high-energy synchrotron X-rays necessitates simulation of the X-ray reflectivity by such crystals. Based on the theory of the lattice distortion in the diffraction plane of sagittally bent Laue crystals, a lamellar model was developed to predict their rocking curves. The model was experimentally verified by rocking-curve measurements from various reflections on silicon crystals of four representative orientations, sagittally bent to various radii, using X-rays of 67,keV energy. [source] Crystallization and preliminary X-ray crystallographic studies of the sixth PDZ domain of glutamate-receptor interacting protein 1 (GRIP1) from Rattus norvegicusACTA CRYSTALLOGRAPHICA SECTION D, Issue 6-2 2002Seong Ho Park The sixth PDZ domain from GRIP1 and its complex with the octapeptide of the liprin-,1 C-terminus were crystallized at 294,K by the hanging-drop vapour-diffusion method. The native crystal belongs to space group P6122 (or P6522), with unit-cell parameters a = b = 40.3, c = 222.9,Å. The complex crystal belongs to space group R32, with unit-cell parameters a = b = 117.8, c = 102.0,Å. Native and peptide-complex diffraction data were collected to resolutions of 1.5 and 1.8,Å, respectively, using synchrotron X-rays. [source] Crystallization and preliminary X-ray crystallographic analysis of deoxyuridine triphosphate nucleotidohydrolase from Saccharomyces cerevisiaeACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2001Byung Woo Han Deoxyuridine triphosphate nucleotidohydrolase (dUTPase) from Saccharomyces cerevisiae is essential for cell viability. It has been overexpressed in Escherichia coli and has been crystallized at 296,K using polyethylene glycol (PEG) 1500 as a precipitant. The crystals belong to the orthorhombic space group P212121, with unit-cell parameters a = 59.48, b = 138.54, c = 157.91,Å, , = , = , = 90°. Two molecules of trimeric dUTPase from S. cerevisiae are present in the asymmetric unit, giving a crystal volume per protein mass (VM) of 3.36,Å3,Da,1 and a solvent content of 63%. The diffraction limit of the crystals could be significantly extended by the crystal-annealing procedure. A set of native data extending to 2.7,Å resolution has been collected at 100,K using synchrotron X-rays. [source] Crystallization of human complement component C3b in the presence of a staphylococcal complement-inhibitor protein (SCIN)ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009Brandon L. Garcia Staphylococcus aureus secretes a number of small proteins that effectively attenuate the human innate immune response. Among these, the staphylococcal complement-inhibitor protein (SCIN) disrupts the function of the complement component 3 (C3) convertase that is initiated through either the classical or the alternative pathway and thereby prevents amplification of the complement response on the bacterial surface. Recent studies have shown that SCIN may affect the activities of the C3 convertase by binding in an equimolar fashion to C3b, which is itself an integral although non-enzymatic component of the convertase. In order to better understand the nature of the C3b,SCIN interaction, the hanging-drop vapor-diffusion technique was used to crystallize human C3b in the presence of a recombinant form of SCIN. These crystals diffracted synchrotron X-rays to approximately 6,Å Bragg spacing and grew in a primitive tetragonal space group (P41212 or P43212; unit-cell parameters a = b = 128.03, c = 468.59,Å). Cell-content analysis of these crystals was consistent with the presence of either two 1:1 complexes or a single 2:2 assembly in the asymmetric unit, both of which correspond to a solvent content of 51.9%. By making use of these crystals, solution of the C3b,SCIN structure should further our understanding of complement inhibition and immune evasion by this pathogen. [source] | ||||||||||