Partial Melting Experiments On Phlogopite-bearing Model Mantle Sources And The Role Of Carbon Dioxide- And Alkali-rich Melts In Metasomatic Processes

Experiments at 3.0 GPa were done to define the nature of near-solidus melts formed from phlogopite lherzolite (PLZ) and carbonated phlogopite lherzolite (CPL) model mantle sources. The reactivity of these melts towards harzburgite and wehrlite were then investigated at 2.0 GPa and 1000{dollar}\sp\circ{dollar}C.;At 3.0 GPa and 1225{dollar}\sp\circ{dollar}C, PLZ yields 7 wt% of melt. The partial breakdown of phlogopite to olivine and liquid results in a silicate melt enriched in K, OH, Al and Fe and a residual phlogopite enriched in Ti. This alkaline silicate melt is only slightly reactive towards harzburgite and wehrlite at 2.0 GPa and 1000{dollar}\sp\circ{dollar}C.;In CPL, at 3.0 GPa and 1100{dollar}\sp\circ{dollar}C, 4 wt% of alkali-bearing dolomitic melt coexists with residual garnet phlogopite lherzolite. The alkalinity is related to the partial breakdown of phlogopite to olivine and pyrope yielding K and OH to the melt. At 2.0 GPa and 1000{dollar}\sp\circ{dollar}C, this dolomitic melt metasomatizes a harzburgite to a phlogopite wehrlite, whereas infiltration into wehrlite could result in the formation of calcite- and phlogopite-bearing dunite.;A process active below continental rifts is proposed in which a carbonated phlogopite lherzolite horizon, formed at the base of the lithosphere by the release of dense alkaline fluids, migrates via melting-migrating-solidifying/reacting cycles. The results of the CPL and PLZ experiments suggest that fractional melting of the carbonated phlogopite lherzolite horizon at 100 km depth could yield a dolomitic melt followed by an alkali-rich silicate melt. The consecutive infiltration of these distinct agents into lithospheric mantle at 65km depth could result in a decoupled metasomatic/enrichment event. The dissociation of the carbonate components of the dolomitic melt will create an harzburgite {dollar}\to{dollar} wehrlite metasomatic trend. The infiltration of the silicate melt will enrich the metasomatized rocks in clinopyroxene and phlogopite. The variety of rocks that result bear similarities with a suite of mantle xenoliths from the West Eifel, Germany

Wood wasp inspired space and earth drill

In this chapter, we explain why the low gravity encountered on Mars or on the Moon and the low mass of the probes, landers and rovers that carry drilling devices limit classical drilling techniques. Novel boring solutions optimised in mass and power consumption are thus needed for space applications. Biologists have identified the wood wasp, an insect that is capable of "drilling" into wood to lay its eggs. A low mass and low power system, like an insect, capable of drilling into wood is of the highest interest for planetary drilling and terrestrial drilling alike. The general working principle of the wood wasp drill ("dual reciprocating drilling") will be exposed and the potential benefits of imitating the wood wasp for planetary drilling will be highlighted. Since the nature of wood is highly fibrous but the nature of extraterrestrial and terrestrial soils are not, it is necessary to adapt the wood wasp ovipositor to our target soils. A test bench to evaluate the influence of the different geometries and operational parameters was produced and is presented here. The dual reciprocating drilling experimental results obtained on this test bench are also highlighted. They should lead to a new and enhanced model and comprehension of dual-reciprocating-drilling

Regular updating

We study the Full Bayesian Updating rule for convex capacities. Following a route suggested by Jaffray (1992), we define some properties one may want to impose on the updating process, and identify the classes of (convex and strictly positive) capacities that satisfy these properties for the Full Bayesian updating rule.

Parameter estimation for peaky altimetric waveforms

Much attention has been recently devoted to the analysis of coastal altimetric waveforms. When approaching the coast, altimetric waveforms are sometimes corrupted by peaks caused by high reflective areas inside the illuminated land surfaces or by the modification of the sea state close to the shoreline. This paper introduces a new parametric model for these peaky altimetric waveforms. This model assumes that the received altimetric waveform is the sum of a Brown echo and an asymmetric Gaussian peak. The asymmetric Gaussian peak is parameterized by a location, an amplitude, a width, and an asymmetry coefficient. A maximum-likelihood estimator is studied to estimate the Brown plus peak model parameters. The Cramér–Rao lower bounds of the model parameters are then derived providing minimum variances for any unbiased estimator, i.e., a reference in terms of estimation error. The performance of the proposed model and the resulting estimation strategy are evaluated via many simulations conducted on synthetic and real data. Results obtained in this paper show that the proposed model can be used to retrack efficiently standard oceanic Brown echoes as well as coastal echoes corrupted by symmetric or asymmetric Gaussian peaks. Thus, the Brown with Gaussian peak model is useful for analyzing altimetric easurements closer to the coast

Impact of three-dimensional standing waves on a flat horizontal plate

International audienceA set-up is designed in order to study the wave impact on structures. These structures can be the stern part of cruiser, a fixed structure as a pier or the roof of LNG-tank. The traveling waves impact was already studied by Smith et al. (1998) but it seems difficult to elaborate a model except some empirical formulæ linking the drop height, the wavelength and the wave steepness. Barrholm (2001) as well studied the travelling wave impact underneath decks of platforms. His modelling is based on a two-dimensional Wagner model where the determination of the wetted surface is not a simple task. Here a simplified impact phenomenon is investigated since standing waves are generated

Successful rescue therapy with tenofovir in a patient with hepatic decompensation and adefovir resistant HBV mutant

BACKGROUND: Prolonged adefovir therapy exposes to the emergence of adefovir resistant hepatitis B virus mutants. Initial reports of the rtN236T mutation showed preserved sensitivity to lamivudine; however, complex mutations are emerging with reduced susceptibility to lamivudine. CASE PRESENTATION: After 2 years of therapy, a cirrhotic patient developed the rtN236T and rtA181T adefovir resistant mutations. He had been previously treated with lamivudine, developed lamivudine resistance and, despite good compliance, had an incomplete response to adefovir. Adefovir resistance resulted in viral breakthrough with hepatitis flare-up and liver decompensation. Tenofovir had an excellent antiviral effect allowing sustained control of viral replication and reversal of hepatic failure. CONCLUSION: In patients with cirrhosis, adefovir resistance can lead to severe hepatitis. Tenofovir appears to be an effective treatment of adefovir resistant mutants. Incomplete control of viral replication with adefovir requires monitoring for viral resistance and should prompt a change in antiviral treatment

A Semi-Analytical Model for Delay/Doppler Altimetry and Its Estimation Algorithm

International audienceThe concept of delay/Doppler (DD) altimetry (DDA) has been under study since the mid-1990s, aiming at reducing the measurement noise and increasing the along-track resolution in comparison with the conventional pulse-limited altimetry. This paper introduces a new model for the mean backscattered power waveform acquired by a radar altimeter operating in synthetic aperture radar mode, as well as an associated least squares (LS) estimation algorithm. As in conventional altimetry (CA), the mean power can be expressed as the convolution of three terms: the flat surface impulse response (FSIR), the probability density function of the heights of the specular scatterers, and the time/frequency point target response of the radar. An important contribution of this paper is to derive an analytical formula for the FSIR associated with DDA. This analytical formula is obtained for a circular antenna pattern, no mispointing, no vertical speed effect, and a uniform scattering. The double convolution defining the mean echo power can then be computed numerically, resulting in a 2-D semi-analytical model called the DD map (DDM). This DDM depends on three altimetric parameters: the epoch, the sea surface wave height, and the amplitude. A multi-look model is obtained by summing all the reflected echoes from the same along-track surface location of interest after applying appropriate delay compensation (range migration) to align the DDM on the same reference. The second contribution of this paper concerns the estimation of the parameters associated with the multi-look semi-analytical model. An LS approach is investigated by means of the Levenberg-Marquardt algorithm. Simulations conducted on simulated altimetric waveforms allow the performance of the proposed estimation algorithm to be appreciated. The analysis of Cryosat-2 waveforms shows an improvement in parameter estimation when compared to the CA

A Unified Framework for Adversarial Attack and Defense in Constrained Feature Space

The generation of feasible adversarial examples is necessary for properly assessing models that work in constrained feature space. However, it remains a challenging task to enforce constraints into attacks that were designed for computer vision. We propose a unified framework to generate feasible adversarial examples that satisfy given domain constraints. Our framework can handle both linear and non-linear constraints. We instantiate our framework into two algorithms: a gradient-based attack that introduces constraints in the loss function to maximize, and a multi-objective search algorithm that aims for misclassification, perturbation minimization, and constraint satisfaction. We show that our approach is effective in four different domains, with a success rate of up to 100%, where state-of-the-art attacks fail to generate a single feasible example. In addition to adversarial retraining, we propose to introduce engineered non-convex constraints to improve model adversarial robustness. We demonstrate that this new defense is as effective as adversarial retraining. Our framework forms the starting point for research on constrained adversarial attacks and provides relevant baselines and datasets that future research can exploit