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Dittmar Bockler - One of the best experts on this subject based on the ideXlab platform.

  • elevated Wall shear stress in aortic type b dissection may relate to retrograde aortic type a dissection a computational fluid dynamics pilot study
    European Journal of Vascular and Endovascular Surgery, 2017
    Co-Authors: Anja Osswald, Christof Karmonik, Jeff R Anderson, Fabian Rengier, Matthias Karck, J Engelke, Klaus Kallenbach, Drosos Kotelis, Sasan Partovi, Dittmar Bockler
    Abstract:

    Objective Retrograde aortic type A dissection (RTAD) is a known complication in patients with aortic type B dissection. The purpose of this computational fluid dynamics (CFD) study was to identify haemodynamic risk factors for the occurrence of RTAD. Methods Computed tomographic angiography (CTA) images of 10 patients with type B dissections, who subsequently developed a RTAD, were retrospectively analysed together with patients constituting a control group (n = 10) where no further vascular events after the initial type B dissection occurred. CFD simulations were conducted based on 3D surface models of the aortic lumen derived from CTA datasets. For both groups, pressures, velocity magnitudes and Wall shear stress (WSS) were compared at the site of the future RTAD entry tear and the Surrounding aortic Wall. Results WSS at the site of the future entry tear was significantly elevated compared with the Surrounding Wall (15.10 Pa vs. 5.15 Pa, p  Conclusions Increased WSS accompanies the occurrence of RTAD. The results merit the design for a prospective study to confirm whether WSS is a risk factor for the occurrence of RTAD.

Anja Osswald - One of the best experts on this subject based on the ideXlab platform.

  • elevated Wall shear stress in aortic type b dissection may relate to retrograde aortic type a dissection a computational fluid dynamics pilot study
    European Journal of Vascular and Endovascular Surgery, 2017
    Co-Authors: Anja Osswald, Christof Karmonik, Jeff R Anderson, Fabian Rengier, Matthias Karck, J Engelke, Klaus Kallenbach, Drosos Kotelis, Sasan Partovi, Dittmar Bockler
    Abstract:

    Objective Retrograde aortic type A dissection (RTAD) is a known complication in patients with aortic type B dissection. The purpose of this computational fluid dynamics (CFD) study was to identify haemodynamic risk factors for the occurrence of RTAD. Methods Computed tomographic angiography (CTA) images of 10 patients with type B dissections, who subsequently developed a RTAD, were retrospectively analysed together with patients constituting a control group (n = 10) where no further vascular events after the initial type B dissection occurred. CFD simulations were conducted based on 3D surface models of the aortic lumen derived from CTA datasets. For both groups, pressures, velocity magnitudes and Wall shear stress (WSS) were compared at the site of the future RTAD entry tear and the Surrounding aortic Wall. Results WSS at the site of the future entry tear was significantly elevated compared with the Surrounding Wall (15.10 Pa vs. 5.15 Pa, p  Conclusions Increased WSS accompanies the occurrence of RTAD. The results merit the design for a prospective study to confirm whether WSS is a risk factor for the occurrence of RTAD.

Stephen F Foley - One of the best experts on this subject based on the ideXlab platform.

  • vein plus Wall rock melting mechanisms in the lithosphere and the origin of potassic alkaline magmas
    Lithos, 1992
    Co-Authors: Stephen F Foley
    Abstract:

    Abstract A model is developed for the origin of ultrapotassic melts by melting of veined lithosphere; the veins are rich in clinopyroxene and mica, whereas the Wall-rocks consist principally of peridotites. The veins originate by solidification of low-degree melts which are themselves the results of earlier, deeper, multistage processes ultimately due to the presence of a transition zone between large-scale channelled and porous flow regimes. The melting event producing the ultrapotassic magma begins in the veins due to the concentration of hydrous phases and incompatible elements, but spreads to include the Surrounding Wall-rocks by a combination of two mechanisms. The alkaline magma composition is thus a hybrid of vein (V) and Wall-rock (W) components. The melt hybridization mechanisms are: (i) Solid-solution melting: Minerals which from extensive solid-solutions are abundant in the vein assemblages (Cr/Al spinel, F/OH mica, amphibole and apatite). The breakdown of these phases take place over a temperature range between the solidus of the vein assemblage and the elimination of the more refractory end-members. This process bridges the temperature gap between the solid of vein and Wall-rock, so that a melt component from the Wall-rock is added to that from the vein before elimination of all vein minerals. Phlogopite forms the most effective of these sliding reactions, resulting in its stability at near-liquids temperatures in experiments. (ii) Dissolution of Wall-rock minerals: The initial melt fraction in the vein infiltrates the Surrounding Wall-rock due to the dominance of surface energy minimization on melt flow at the intergranular scale. Following infiltration, dissolution of Wall-rock minerals occurs at temperatures lower than their melting temperatures, thus imparting a refractory Wall-rock component to the melt composition. Dissolution of olivine and/or orthopyroxene occurs preferentially, since these minerals are furthest from equilibrium with the strongly alkaline, vein-derived melt. Remobilisation of several generations of veins explains the occurrence within a restricted space and time of rocks bearing chemical characteristics which are generally thought to indicate contrasting tectonic settings (e.g. central Italy). The ultrapotassic rocks are explained as being dominanyly vein-derived (i.e. high V/W ratio): further dilution of the V-component by Wall-rock, supplemented by asthenospheric melt in advanced cases, leads to the production of more voluminous basaltic rocks bearing incompatible element signatures reminiscent of those of ultrapotassic rocks.

M. Santosh - One of the best experts on this subject based on the ideXlab platform.

  • the jiaodong type gold deposits characteristics origin and prospecting
    Ore Geology Reviews, 2015
    Co-Authors: M. Santosh
    Abstract:

    Abstract The Jiaodong type comprises a unique class of gold mineralisation which includes the Linglong type quartz-vein hosted and the Jiaojia type fracture-disseminated style deposits. Although the type area is in the Jiaodong Peninsula in NE China, where some of the world's richest gold reserves occur, we identify similar occurrences in other parts of China and elsewhere in the world under this category. The ore fluids migrated upwards forming quartz vein type of gold ore (Linglong type) wherever the ore-controlling fractures are at high angles. Fluid infiltration into the Surrounding Wall rocks and generation of the Jiaojia type disseminated style deposits resulted where the ore-bearing fluids encountered low angle fractures. On a regional scale, the Jiaodong type gold mineralisation occurs along the margins of reactivated cratons, within the interior of cratons along paleosuture zones, or along the junctions of micro-blocks, and is distinctly different from the classic orogenic gold in terms of their tectonic setting, ore characteristics and genetic history. Unlike skarn and porphyry type of deposits, the Jiaodong type gold deposits do not always show close spatial relationship with magmatic intrusives and some of the deposits occur distal to plutons (> 10 km). In this paper, we evaluate the salient geological, geochronological, geochemical and isotopic features of the Jiaodong type gold deposits and propose some general guidelines for gold prospecting. Based on case studies, we predict that the gold lodes in the Jiaodong type mineralised zones might extent vertically up to 3000 m with only minor mineralogical and geochemical variations.

Federica Brandizzi - One of the best experts on this subject based on the ideXlab platform.

  • the plant secretory pathway an essential factory for building the plant cell Wall
    Plant and Cell Physiology, 2014
    Co-Authors: Sang Jin Kim, Federica Brandizzi
    Abstract:

    For building and maintaining the complex structure of the Surrounding Wall throughout their life, plant cells rely on the endomembrane system, which functions as the main provider and transporter of cell Wall constituents. Efforts to understand the mechanisms of synthesis and transport of cell Wall materials have been generating valuable information for diverse practical applications. Nonetheless, the identity of the endomembrane components necessary for the transport of cell Wall enzymes and polysaccharides is not well known. Evidence indicates that plant cells can accomplish secretion of cell Wall constituents through multiple pathways during development or under stress conditions and, that compared with other eukaryotes, they rely on a highly diversified toolkit of proteins for membrane traffic. This suggests that production of the cell Wall in plants consists of intricate and highly regulated pathways. In this review, we summarize important discoveries that have allowed the activities of the plant secretory pathway to be linked to the production and deposition of cell Wall-synthesizing enzymes and polysaccharides.