1,446 research outputs found

    Integrated stratigraphy and astrochronology of the Messinian GSSP at Oued Akrech (Atlantic Morocco)

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    A much improved high-resolution integrated stratigraphy (calcareous plankton biostratigraphy, magnetostratigraphy, cyclostratigraphy) is presented for the classic section of Oued Akrech (Atlantic Morocco) straddling the Tortonian^Messinian boundary. Magnetobiostratigraphic correlations with time-equivalent and astronomically dated sections in the Mediterranean indicate that cyclic alternations of indurated light beige coloured marls and softer, more clayey and reddish coloured marls are dominantly precession-controlled. Characteristic sedimentary cycle patterns, in particular those reflecting precession^obliquity interference, allow for one possible tuning, thus providing accurate astronomical ages for cycles, calcareous plankton events and magnetic reversals. The tuning further indicates that the reddish layers are the equivalent of sapropels in the Mediterranean. The Messinian Global boundary Stratotype Section and Point (GSSP) has recently been formally defined at the base of the reddish layer of cycle No. 15 in section Oued Akrech. This level coincides closely with the first regular occurrence of the Globorotalia miotumida group and is astronomically dated at 7.251 Ma. The global correlation potential is guaranteed by the straightforward calibration of the Oued Akrech magnetostratigraphy to the geomagnetic polarity time scale, locating the GSSP within C3Br.1r. In the marine realm the calcareous nannofossil genus Amaurolithus provides a series of extremely useful events to delimit the boundary on a global scale. The astronomical tuning guarantees a direct first-order calibration of the Messinian GSSP to the standard geological time scale once, as anticipated, the late Miocene part of the astronomical time scale has been incorporated

    Scalable Environment for Quantification of Uncertainty and Optimization in Industrial Applications (SEQUOIA)

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143027/1/6.2017-1327.pd

    Clastic vs. primary precipitated evaporites in the Messinian sicilian Basins

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    The Messinian stratigraphy of Sicily has a particular importance for the comprehension ofthe Messinian salinity crisis as its successions bear the greatest similarity with those of thedeep Mediterranean basins. Despite the large number of studies carried out in the last 30years, we believe that the true time and genetic relationships between the different evaporiticand non evaporitic rock bodies are still not well established. This is probably due to thelimited, partial view offered by the central Sicilian basin, despite its complete Messinianstratigraphic record.Clastic and chaotic evaporitic deposits emplaced by tectonically-driven small to largescaleresedimentation processes form an important part of the MSC record of Sicily in theBelice and Caltanissetta basins. Facies characteristics of clastic evaporites, the stratigraphicrelationships with the other Messinian deposits, their possible significance in the regionalgeological evolution and the implications at a Mediterranean scale will be discussed in thefield. Attention also will be paid to primary precipitated facies of Lower and UpperEvaporites.The main aim of this field trip is to visit and discuss, beside some of the classic localitiesof the Caltanissetta basin, other less known outcrops of western Sicily (Belice basin), inorder to have a more complete regional geological framework of the MSC events in Sicily.This will give the participants the opportunity to discuss many of the still open problemsconcerning the MSC. In this section we suggest some topics for discussion during the fieldtrip

    Ultimate strength

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    Concern for the ductile behaviour of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and in-service damage and degradation on reserve strength

    Glucose-6-phosphate dehydrogenase plays a crucial role in the protection from redox-stress induced apoptosis.

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    Glucose-6-phosphate dehydrogenase-deleted embryonic stem (ES) cells (G6pdD) proliferate in vitro without special requirements, but when challenged with oxidants fail to sustain glutathione disulphide reconversion to reduced glutathione (GSH), entering a condition of oxidative stress. Here, we investigate the signalling events downstream of GSH oxidation in G6pdD and wild-type (wt) ES cells. We found that G6pdD ES cells are very sensitive to oxidants, activating an apoptotic pathway at oxidant concentrations otherwise sublethal for wt ES cells. We show that the apoptotic pathway activated by low oxidant concentrations is accompanied by mitochondria dysfunction, and it is therefore blocked by the overexpression of Bcl-XL. Bcl-XL does not inhibit the decrease in cellular GSH and reactive oxygen species formation following oxidant treatment. We also found that oxidant treatment in ES cells is followed by the activation of the MEK/ extracellular signal-regulated kinase (ERK) pathway. Interest¬ingly, ERK activation has opposite outcomes in G6pdD ES cells compared to wt, which has a proapoptotic function in the first and a prosurvival function in the latter. We show that this phenomenon can be regulated by the cellular GSH level
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