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3D imaging techniques are very fashionable nowadays, and allow enormous progress in understanding ceramic microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this feature article, we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. While the techniques are limited by the X-ray absorption of the material under investigation, we demonstrate showcases of ceramics and composite materials, where understanding of process parameter influence or simply of microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. (C) 2016 Elsevier Ltd. All rights reserved.
Talbot-Lau interferometry provides X-ray imaging techniques with significant enhancement of the radiographic contrast of weakly absorbing objects. The grating based technique allows separation of absorption, refraction and small angle scattering effects. The different efficiency of rectangular and triangular shaped phase gratings at varying detector distances is investigated. The interference patterns (Talbot carpets) are modeled for parallel monochromatic radiation and measured by synchrotron radiation. In comparison to rectangular shapes of phase gratings much higher visibility is obtained for triangular shapes which yield enhanced contrast of a glass capillary test specimen.
An important tool for understanding deformation occurring within a subduction zone is the measurement of seismic anisotropy through observations of shear wave splitting (SWS). In Sumatra, two temporary seismic networks were deployed between December 2007 and February 2009, covering the fore arc between the fore-arc islands to the back arc. We use SKS and local SWS measurements to determine the type, amount, and location of anisotropy. Local SWS measurements from the fore-arc islands exhibit trench-parallel fast directions which can be attributed to shape preferred orientation of cracks/fractures in the overriding sediments. In the Sumatran Fault region, the predominant fast direction is fault/trench parallel, while in the back-arc region it is trench perpendicular. The trench-perpendicular measurements exhibit a positive correlation between delay time and raypath length in the mantle wedge, while the fault-parallel measurements are similar to the fault-parallel fast directions observed for two crustal events at the Sumatran Fault. This suggests that there are two layers of anisotropy: one due to entrained flow within the mantle wedge and a second layer within the overriding crust due to the shear strain caused by the Sumatran Fault. SKS splitting results show a NNW-SSE fast direction with delay times of 0.8-3.0s. The fast directions are approximately parallel to the absolute plate motion of the subducting Indo-Australian Plate. The small delay times exhibited by the local SWS (0.05-0.45s), in combination with the large SKS delay times, suggest that the anisotropy generating the teleseismic SWS is dominated by entrained flow in the asthenosphere below the slab.
On 12 September 2007, an M-w 8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of high Vp (8.0 km/s), which can be a traced to similar to 50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5-5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the M-w 7.7 Mentawai tsunami earthquake on 25 October 2010.
We focus on the relation between seismic and total postseismic afterslip following the Maule M-w 8.8 earthquake on 2010 February 27 in central Chile. First, we calculate the cumulative slip released by aftershock seismicity. We do this by summing up the aftershock regions and slip estimated from scaling relations. Comparing the cumulative seismic slip with afterslip modelswe showthat seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints. As the afterslip model implicitly contains the displacements from the aftershocks, this reflects the tendency of afterslip models to smear out the actual slip pattern. However, it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor. This effect, seen weakly for the Maule 2010 and also for the Tohoku 2011 earthquake, can be explained by taking into account the uncertainties of the seismicity and afterslip models. In spite of uncertainties, the hypocentral region of the Nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically. Therefore, these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture. In a second step, we divide the megathrust of the Maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time. We then compare this number to a time-dependent afterslip model by defining the 'afterslip to aftershock ratio' (ASAR) for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count. Although we find a linear relation between afterslip and aftershocks for most cells, there is significant variability in ASAR in both the downdip and along-strike directions of the megathrust. We compare the spatial distribution of ASAR with the spatial distribution of seismic coupling, coseismic slip and Bouguer gravity anomaly, and in each case we find no significant correlation.
A catalog of genetic loci associated with kidney function from analyses of a million individuals
(2019)
Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through transancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these,147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.