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  • 1
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    Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow (2003)
    In:  Science, New York, Conseil de l'Europe, vol. 301, no. 5637, pp. 1227-1230, pp. L07312, (ISSN 0343-5164)
    Details
    Publication Date: 2003
    Keywords: Plate tectonics ; ConvolutionE ; Subduction zone ; Stress ; STARI ; Anisotropy
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Natural dissociation of olivine to (Mg,Fe)SiO3 perovskite and magnesiowustite in a shocked Martian meteorite [Geology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-04-13
    Description: We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine (Fa34-41) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO3 perovskite (Pv)+magnesiowüstite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular (Mg,Fe)SiO3 Pv and Mw have 50–100 nm in diameter, and lamellar (Mg,Fe)SiO3 Pv and Mw have approximately 20 and approximately 10 nm in thickness, respectively. Partitioning coefficient, KPv/Mw = [FeO/MgO]/[FeO/MgO]Mw, between (Mg,Fe)SiO3 Pv and Mw in equigranular and lamellar textures are approximately 0.15 and approximately 0.78, respectively. The dissociation of olivine implies that the pressure and temperature conditions recorded in the shock melt vein and melt pockets during the dynamic event were approximately 25 GPa but 700 °C at least.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Mantle superplasticity and its self-made demise (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-12-24
    Description: The unusual capability of solid crystalline materials to deform plastically, known as superplasticity, has been found in metals and even in ceramics. Such superplastic behaviour has been speculated for decades to take place in geological materials, ranging from surface ice sheets to the Earth's lower mantle. In materials science, superplasticity is confirmed when the material deforms with large tensile strain without failure; however, no experimental studies have yet shown this characteristic in geomaterials. Here we show that polycrystalline forsterite + periclase (9:1) and forsterite + enstatite + diopside (7:2.5:0.5), which are good analogues for Earth's mantle, undergo homogeneous elongation of up to 500 per cent under subsolidus conditions. Such superplastic deformation is accompanied by strain hardening, which is well explained by the grain size sensitivity of superplasticity and grain growth under grain switching conditions (that is, grain boundary sliding); grain boundary sliding is the main deformation mechanism for superplasticity. We apply the observed strain-grain size-viscosity relationship to portions of the mantle where superplasticity has been presumed to take place, such as localized shear zones in the upper mantle and within subducting slabs penetrating into the transition zone and lower mantle after a phase transformation. Calculations show that superplastic flow in the mantle is inevitably accompanied by significant grain growth that can bring fine grained (〈/=1 mum) rocks to coarse-grained (1-10 mm) aggregates, resulting in increasing mantle viscosity and finally termination of superplastic flow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hiraga, Takehiko -- Miyazaki, Tomonori -- Tasaka, Miki -- Yoshida, Hidehiro -- England -- Nature. 2010 Dec 23;468(7327):1091-4. doi: 10.1038/nature09685.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan. hiraga@eri.u-tokyo.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21179165" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
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    Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-08-30
    Description: One of the principal means of understanding upper mantle dynamics involves inferring mantle flow directions from seismic anisotropy under the assumption that the seismic fast direction (olivine a axis) parallels the regional flow direction. We demonstrate that (i) the presence of melt weakens the alignment of a axes and (ii) when melt segregates and forms networks of weak shear zones, strain partitions between weak and strong zones, resulting in an alignment of a axes 90 degrees from the shear direction in three-dimensional deformation. This orientation of a axes provides a new means of interpreting mantle flow from seismic anisotropy in partially molten deforming regions of Earth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Holtzman, B K -- Kohlstedt, D L -- Zimmerman, M E -- Heidelbach, F -- Hiraga, T -- Hustoft, J -- New York, N.Y. -- Science. 2003 Aug 29;301(5637):1227-30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA. holtz007@umn.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12947196" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Olivine crystals align during diffusion creep of Earth's upper mantle (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-10-18
    Description: The crystallographic preferred orientation (CPO) of olivine produced during dislocation creep is considered to be the primary cause of elastic anisotropy in Earth's upper mantle and is often used to determine the direction of mantle flow. A fundamental question remains, however, as to whether the alignment of olivine crystals is uniquely produced by dislocation creep. Here we report the development of CPO in iron-free olivine (that is, forsterite) during diffusion creep; the intensity and pattern of CPO depend on temperature and the presence of melt, which control the appearance of crystallographic planes on grain boundaries. Grain boundary sliding on these crystallography-controlled boundaries accommodated by diffusion contributes to grain rotation, resulting in a CPO. We show that strong radial anisotropy is anticipated at temperatures corresponding to depths where melting initiates to depths where strongly anisotropic and low seismic velocities are detected. Conversely, weak anisotropy is anticipated at temperatures corresponding to depths where almost isotropic mantle is found. We propose diffusion creep to be the primary means of mantle flow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Miyazaki, Tomonori -- Sueyoshi, Kenta -- Hiraga, Takehiko -- England -- Nature. 2013 Oct 17;502(7471):321-6. doi: 10.1038/nature12570.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24132289" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 6
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    Grain- to multiple-grain-scale deformation processes during diffusion creep of forsterite + diopside aggregate I: Direct observations (2017)
    Wiley
    Details
    Publication Date: 2017-07-08
    Description: We uniaxially deformed fine-grained (~ 1 μm) forsterite + diopside (5 and 20 vol%) aggregates in the diffusion creep regime. Prior to deformation, line markers were milled on a lateral surface of a cylindrical sample to detect single- to multiple-grain-scale deformation. We performed deformation experiments and observations of the marker-etched surface after sample cooling multiple times on the same specimens. The strain measured at the scale of several tens of grains from macroscopic shortening of the markers parallel to the compression axis is consistent with the total strain of the sample. However, microscopically, the markers are intensely segmented and rotated at the grain scale increasing with the sample strain. Meanwhile, essentially no deformation is observed within the grains in most of the samples. The surface microstructures, including the deformation of the markers, reveal the serial operations of grain boundary migration, grain boundary sliding, rigid-body grain rotation and grain-neighbor switching, which correspond well to processes expected in diffusion-controlled superplasticity. This sequence is commonly observed in both samples consisting with forsterite grains of tabular- and equiaxed- grain shapes, which have been shown to develop notable crystallographic preferred orientation (CPO) and random (or weak) CPO, respectively, during diffusion creep. Intragranular regions of relatively larger forsterite grains in the specimens deformed at stresses near the transition between deformation mechanisms from diffusion creep to dislocation creep reveal marker deformation and formation of surface creases and sub-grain boundaries, which indicate intragranular dislocation processes. Overall, the surface microstructures reflect the deformation state of the materials well.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Grain- to multiple-grain-scale deformation processes during diffusion creep of forsterite + diopside aggregate II: Grain-boundary-sliding induced grain rotation and its role in crystallographic preferred orientation in rocks (2017)
    Wiley
    Details
    Publication Date: 2017-07-08
    Description: Polycrystalline samples composed of either tabular or equiaxed forsterite grains + diopside (5 and 20 vol%) were deformed with a grid etched onto the lateral surface. In Part I of this study, we identified grain boundary sliding (GBS) and rigid body-like grain rotation during deformation by diffusion creep where samples with tabular forsterite grains were shown to develop low-index plane grain boundaries that result in crystallographic preferred orientation (CPO). Here we examine how grain rotation depends on the sample strain, grain size, phases, grain shapes, and orientations relative to the compression axis and long-axes of tabular forsterite grains. Based on these results, we model grain rotation due to GBS that occurs preferentially along low-index plane boundaries. The model reproduces all of the characteristics of grain rotation and together with the observed grain rotation rates in tabular- and equiaxed-grain samples, we estimate that low-index plane boundaries have a lower viscosity by a factor of ~3 relative to general grain boundaries, which results in the development of CPO during diffusion creep. The observed constant rotation rate of ~0.4 (median/strain) in equiaxed-grain samples and in tabular-grain samples deformed to a strain of 〉0.5 is considered to be a minimum and further, a material-independent rotation rate during diffusion creep, indicating grain rotation as a primary micro-process during diffusion creep. We discuss the possible consequences of GBS-induced grain rotation and CPO development in rock microstructure and the seismic properties of the Earth's mantle.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    Characteristics of Porcine Coronary Artery Endothelial Cells in Culture: Comparison with Aortic Endothelium
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 202 (1994), S. 504-511 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/bbrc.1994.1957
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Femtosecond pulse compression by intracavity third-order nonlinear organic elements in CPM lasers
    Amsterdam : Elsevier
    Optics Communications 79 (1990), S. 107-110 
    Details
    ISSN: 0030-4018
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0030-4018(90)90186-W
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  • 10
    Electronic Resource
    Electronic Resource
    The structure of grain boundaries in granite-origin ultramylonite studied by high-resolution electron microscopy (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 617-623 
    Details
    ISSN: 1432-2021
    Keywords: Key words Grain boundary ; Lattice fringe ; High-resolution electron microscopy ; Ultramylonite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The structure of grain boundaries in a granite-origin ultramylonite, composed mainly of fine-grained feldspar and quartz, was studied by high-resolution electron microscopy (HREM). At most of the boundaries, not only between the same minerals but also between different minerals, lattice fringes in adjacent grains meet at the interface with no other appreciable phases. In these boundaries, some of the straight segments correspond to a low-index plane of one of the connected grains. Boundaries containing voids, with a spheroidal shape elongated along the boundaries, were observed only between quartz grains. It is suggested that these boundaries were formed by healing of microcracks. The structural width of major boundaries, deduced from lattice-fringe imaging, is less than about 0.5 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050226
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