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  • X-ray lasersXFELsbiologystructuredynamics  (2)
  • protein crystallizationX-ray diffractionserial crystallographymicrofluidic devices  (2)
  • quasicrystalssuperspace crystallographystructure analysisphasonsX-ray diffuse scattering  (2)
  • Al/Si orderingvacancy orderingceramicssuperspaceincommensurate structures  (1)
  • Allgemeine Physik
  • International Union of Crystallography (IUCr)  (7)
  • American Institute of Physics (AIP)
  • 2015-2019  (7)
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Verlag/Herausgeber
  • International Union of Crystallography (IUCr)  (7)
  • American Institute of Physics (AIP)
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  • 2015-2019  (7)
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  • 1
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publikationsdatum: 2018-06-26
    Beschreibung: Synchrotron single-crystal X-ray diffraction has revealed diffuse scattering alongside sharp satellite reflections for different samples of mullite (Al4+2xSi2−2xO10−x). Structural models have been developed in (3+1)-dimensional superspace that account for vacancy ordering and Al/Si ordering based on harmonic modulation functions. A constraint scheme is presented which explains the crystal-chemical relationships between the split sites of the average structure. The modulation amplitudes of the refinements differ significantly by a factor of ∼3, which is explained in terms of different degrees of ordering, i.e. vacancies follow the same ordering principle in all samples but to different extents. A new approach is applied for the first time to determine Al/Si ordering by combining density functional theory with the modulated volumes of the tetrahedra. The presence of Si–Si diclusters indicates that the mineral classification of mullite needs to be reviewed. A description of the crystal structure of mullite must consider both the chemical composition and the degree of ordering. This is of particular importance for applications such as advanced ceramics, because the physical properties depend on the intrinsic structure of mullite.
    Schlagwort(e): Al/Si orderingvacancy orderingceramicssuperspaceincommensurate structures
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publikationsdatum: 2017-07-01
    Schlagwort(e): X-ray lasersXFELsbiologystructuredynamics
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publikationsdatum: 2017-05-11
    Beschreibung: The development and application of the free-electron X-ray laser (XFEL) to structure and dynamics in biology since its inception in 2009 are reviewed. The research opportunities which result from the ability to outrun most radiation-damage effects are outlined, and some grand challenges are suggested. By avoiding the need to cool samples to minimize damage, the XFEL has permitted atomic resolution imaging of molecular processes on the 100 fs timescale under near-physiological conditions and in the correct thermal bath in which molecular machines operate. Radiation damage, comparisons of XFEL and synchrotron work, single-particle diffraction, fast solution scattering, pump–probe studies on photosensitive proteins, mix-and-inject experiments, caged molecules, pH jump and other reaction-initiation methods, and the study of molecular machines are all discussed. Sample-delivery methods and data-analysis algorithms for the various modes, from serial femtosecond crystallography to fast solution scattering, fluctuation X-ray scattering, mixing jet experiments and single-particle diffraction, are also reviewed.
    Schlagwort(e): X-ray lasersXFELsbiologystructuredynamics
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Unbekannt
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publikationsdatum: 2016-06-28
    Schlagwort(e): quasicrystalssuperspace crystallographystructure analysisphasonsX-ray diffuse scattering
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2016-06-15
    Beschreibung: The detailed atomic structure of the binary icosahedral (i) ScZn7.33 quasicrystal has been investigated by means of high-resolution synchrotron single-crystal X-ray diffraction and absolute scale measurements of diffuse scattering. The average atomic structure has been solved using the measured Bragg intensity data based on a six-dimensional model that is isostructural to the i-YbCd5.7 one. The structure is described with a quasiperiodic packing of large Tsai-type rhombic triacontahedron clusters and double Friauf polyhedra (DFP), both resulting from a close-packing of a large (Sc) and a small (Zn) atom. The difference in chemical composition between i-ScZn7.33 and i-YbCd5.7 was found to lie in the icosahedron shell and the DFP where in i-ScZn7.33 chemical disorder occurs on the large atom sites, which induces a significant distortion to the structure units. The intensity in reciprocal space displays a substantial amount of diffuse scattering with anisotropic distribution, located around the strong Bragg peaks, that can be fully interpreted as resulting from phason fluctuations, with a ratio of the phason elastic constants K2/K1 = −0.53, i.e. close to a threefold instability limit. This induces a relatively large perpendicular (or phason) Debye–Waller factor, which explains the vanishing of `high-Qperp' reflections.
    Schlagwort(e): quasicrystalssuperspace crystallographystructure analysisphasonsX-ray diffuse scattering
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Publikationsdatum: 2015-08-19
    Beschreibung: The name of one of the authors in the article by Heymann et al. [(2014), IUCrJ, 1, 349–360] is corrected.
    Schlagwort(e): protein crystallizationX-ray diffractionserial crystallographymicrofluidic devices
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Publikationsdatum: 2015-08-16
    Beschreibung: An emulsion-based serial crystallographic technology has been developed, in which nanolitre-sized droplets of protein solution are encapsulated in oil and stabilized by surfactant. Once the first crystal in a drop is nucleated, the small volume generates a negative feedback mechanism that lowers the supersaturation. This mechanism is exploited to produce one crystal per drop. Diffraction data are measured, one crystal at a time, from a series of room-temperature crystals stored on an X-ray semi-transparent microfluidic chip, and a 93% complete data set is obtained by merging single diffraction frames taken from different unoriented crystals. As proof of concept, the structure of glucose isomerase was solved to 2.1 Å, demonstrating the feasibility of high-throughput serial X-ray crystallography using synchrotron radiation.
    Schlagwort(e): protein crystallizationX-ray diffractionserial crystallographymicrofluidic devices
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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