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  • X-ray diffractionMarsextraterrestrial mineralogyCuriosity rover  (1)
  • X-ray techniquesindustryinnovation  (1)
  • dioxygenaseshistone demethylationDNA/RNA demethylationN6-methyladenosineALKBH5  (1)
  • femtosecond pulseX-ray diffractionpolarizabilityelectron densityrate equations  (1)
  • International Union of Crystallography (IUCr)  (4)
  • Cell Press
  • Periodicals Archive Online (PAO)
  • 2010-2014  (4)
  • 2005-2009
  • 1980-1984
  • 1955-1959
  • 1925-1929
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Keywords
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  • International Union of Crystallography (IUCr)  (4)
  • Cell Press
  • Periodicals Archive Online (PAO)
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  • 2010-2014  (4)
  • 2005-2009
  • 1980-1984
  • 1955-1959
  • 1925-1929
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  • 1
    Publication Date: 2014-11-12
    Description: The time evolution of the electron density and the resulting time dependence of Fourier components of the X-ray polarizability of a crystal irradiated by highly intense femtosecond pulses of an X-ray free-electron laser (XFEL) is investigated theoretically on the basis of rate equations for bound electrons and the Boltzmann equation for the kinetics of the unbound electron gas. The photoionization, Auger process, electron-impact ionization, electron–electron scattering and three-body recombination have been implemented in the system of rate equations. An algorithm for the numerical solution of the rate equations was simplified by incorporating analytical expressions for the cross sections of all the electron configurations in ions within the framework of the effective charge model. Using this approach, the time dependence of the inner shell populations during the time of XFEL pulse propagation through the crystal was evaluated for photon energies between 4 and 12 keV and a pulse width of 40 fs considering a flux of 1012 photons pulse−1 (focusing on a spot size of ∼1 µm). This flux corresponds to a fluence ranging between 0.8 and 2.4 mJ µm−2. The time evolution of the X-ray polarizability caused by the change of the atomic scattering factor during the pulse propagation is numerically analyzed for the case of a silicon crystal. The time-integrated polarizability drops dramatically if the fluence of the X-ray pulse exceeds 1.6 mJ µm−2.
    Keywords: femtosecond pulseX-ray diffractionpolarizabilityelectron densityrate equations
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2014-11-12
    Description: The Mars Science Laboratory landed in Gale crater on Mars in August 2012, and the Curiosity rover then began field studies on its drive toward Mount Sharp, a central peak made of ancient sediments. CheMin is one of ten instruments on or inside the rover, all designed to provide detailed information on the rocks, soils and atmosphere in this region. CheMin is a miniaturized X-ray diffraction/X-ray fluorescence (XRD/XRF) instrument that uses transmission geometry with an energy-discriminating CCD detector. CheMin uses onboard standards for XRD and XRF calibration, and beryl:quartz mixtures constitute the primary XRD standards. Four samples have been analysed by CheMin, namely a soil sample, two samples drilled from mudstones and a sample drilled from a sandstone. Rietveld and full-pattern analysis of the XRD data reveal a complex mineralogy, with contributions from parent igneous rocks, amorphous components and several minerals relating to aqueous alteration. In particular, the mudstone samples all contain one or more phyllosilicates consistent with alteration in liquid water. In addition to quantitative mineralogy, Rietveld refinements also provide unit-cell parameters for the major phases, which can be used to infer the chemical compositions of individual minerals and, by difference, the composition of the amorphous component.
    Keywords: X-ray diffractionMarsextraterrestrial mineralogyCuriosity rover
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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  • 3
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publication Date: 2014-11-12
    Description: The smart specialization declared in the European program Horizon 2020, and the increasing cooperation between research and development found in companies and researchers at universities and research institutions have created a new paradigm where many calls for proposals require participation and funding from public and private entities. This has created a unique opportunity for large-scale facilities, such as synchrotron research laboratories, to participate in and support applied research programs. Scientific staff at synchrotron facilities have developed many advanced tools that make optimal use of the characteristics of the light generated by the storage ring. These tools have been exceptionally valuable for materials characterization including X-ray absorption spectroscopy, diffraction, tomography and scattering, and have been key in solving many research and development issues. Progress in optics and detectors, as well as a large effort put into the improvement of data analysis codes, have resulted in the development of reliable and reproducible procedures for materials characterization. Research with photons has contributed to the development of a wide variety of products such as plastics, cosmetics, chemicals, building materials, packaging materials and pharma. In this review, a few examples are highlighted of successful cooperation leading to solutions of a variety of industrial technological problems which have been exploited by industry including lessons learned from the Science Link project, supported by the European Commission, as a new approach to increase the number of commercial users at large-scale research infrastructures.
    Keywords: X-ray techniquesindustryinnovation
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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  • 4
    Publication Date: 2014-11-12
    Description: Iron(II) and 2-oxoglutarate (2OG)-dependent dioxygenases involved in histone and DNA/RNA demethylation convert the cosubstrate 2OG and oxygen to succinate and carbon dioxide, resulting in hydroxylation of the methyl group of the substrates and subsequent demethylation. Recent evidence has shown that these 2OG dioxygenases play vital roles in a variety of biological processes, including transcriptional regulation and gene expression. In this review, the structure and function of these dioxygenases in histone and nucleic acid demethylation will be discussed. Given the important roles of these 2OG dioxygenases, detailed analysis and comparison of the 2OG dioxygenases will guide the design of target-specific small-molecule chemical probes and inhibitors.
    Keywords: dioxygenaseshistone demethylationDNA/RNA demethylationN6-methyladenosineALKBH5
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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