66 research outputs found

    The SNC meteorites: basaltic igneous processes on Mars

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    A group of 31 meteorites (SNC group) was derived from Mars as a product of 4 – 7 ejection events, probably from Tharsis and Elysium-Amazonis. The SNCs either have basaltic mineralogy or some are ultramafic cumulates crystallised from basaltic melts. The SNCs can be classified both petrographically and geochemically. We classify the shergottite SNC meteorites on the basis of their LREE-depletion into Highly Depleted, Moderately Depleted and Slightly Depleted. The Slightly Depleted samples (which are mainly but not exclusively aphyric basalts) show high log oxygen fugacity values (QFM -1.0). Highly Depleted samples - which are mainly olivine-phyric basalts - have low log oxygen fugacity values (QFM -3.5). On the basis of mixing calculations between La/Lu and 87-Sr/86-Sr we favour models linking the correlation between LREE abundances and log oxygen fugacity to mantle heterogeneity rather than contamination by oxidised, LREE-rich crustal fluids. SNC chemistry in general reflects the Fe-rich mantle of Mars (x2 FeO that of the Earth), the late accretion of chondritic material into the mantle, and possibly the presence of a plagioclase-rich magma ocean which acted to variably deplete the mantle in Al. The high FeO contents of the SNC melts are associated with high melt densities (allowing the ponding of large magma bodies) and low viscosities, both of which are consistent with the large scale of many observed martian lava flows

    A Nonlinear Electro-Thermal Scalable Model for High-Power RF LDMOS Transistors

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    The LHCb upgrade I

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    The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software
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