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Aminocyclopropane Chemistry for the Construction of Nitrogen containing Polycyclic Systems
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Towards complete band structure of microscopic MoS 2 flakes
No full textInternational audienceThe occupied and unoccupied electronic states of MoS2 monolayer isolated flake were studied using laboratory based photoemission electron microscope (PEEM) nanoESCA equipped with He-I photon source. PEEM real-space imaging allowed selecting the high quality flake. Altogether, the data will allow accurately recovering the band structures of MoS2. The band structures will be used in future pump-probe experiments to explore the dynamics of electrons in the conduction band and photo-induced multitopological states using trefoil polarization
Palladium-catalyzed cycloadditions towards medium-sized N-heterocycles
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Les mots et les choses in Outer Space. How do words relate to things in outer space?
No full textInternational audienceThis essay develops a practice it calls extraordinary ordinary philosophy, emergent from latent thought lines in the writings of Thomas Kuhn and Stanley Cavell, to think the consequences of speaking about the Martian world viewed using everyday terrestrial words. Exposing how our planet haunts our ordinary language and entangles itself in the claims of what we normally call reason, it presents a fragment of a critique of planetary reason. It sounds out, via a focused encounter with alien objects, and against the background of the scientific exploration of the red planet and its history, how and in which contexts our terrestrial words can be confidently projected beyond the Earth with something resembling the confident universality of the language of natural science. But it also pushes for the acknowledgement of the planetary limits that inhere within our ordinary uses of many everyday words. In so doing, the essay illustrates that acknowledging what Cavell calls the truth of skepticism is critical for developing an awareness of the degree to which we, our words, and what we are inclined to call reason, are planetary: earthly. Attending to the proximity and distance of Mars viewed, extraordinary ordinary philosophy brings out the stakes of speaking in situations in which we acknowledge that we are not sure that we want to mean what we say, and so offers orientation in our planetary age
How to Bring the Social Sciences into the Post-Planetary Age
No full textInternational audienceThis presentation will make two interrelated claims.First, we will highlight the problems and the limits of traditional social science methodologies with respect to thinking about astroculture– the relationship between human beings and outer space. In particular, it will bring out the ways in which these methods are either of limited use, or are even actively stultifying, when studying the human relationship to objects and information that is derived from situations located outside of immediate embodied experience of human knowers (which is the prevailing epistemic condition with respect to the majority of our robotic activities in space).Second, the presentation will suggest an alternate way forward towards thinking about social science in space, highlighting the importance of thinking about the intersections between the logics of information, classical, or terrestrial and embodied epistemologies, and logics of belief.The aim of the presentation is thus to illustrate why existing methodologies are mostly inadequate for thinking about the relationship between society and the extra-terrestrial, and to gesture towards alternative approaches that offer better epistemic prospects for understanding our post-planetary condition
A Palladium-Catalyzed Strategy for the Preparation of Enantioenriched Lactams
No full textInternational audienceLactams are ubiquitous in biologically active natural products or pharmaceuticals and prompted organic chemists to involve practical synthetic equivalents of the highly desired {C–C(=O)–N} synthon in cycloaddition reactions. In this context, α-haloamides have been extensively described as versatile precursors of this important synthon but, despite a myriad of known synthetic methodologies [1], asymmetric cycloadditions of these substrates are scarce [2] and a general strategy to access enantioenriched cycloadducts would be of high importance. Our research group is interested in catalytic cycloadditions involving π-allylpalladium zwitterionic dipoles [3-5]. We have recently identified original vinyloxazolidine-2,4-diones as competent synthetic equivalents of the {C–C(=O)–N} synthon. Under Pd(0) catalysis, the resulting π-allylpalladium(II) intermediates can act as aza-1,3-dipoles in (3+2) cycloadditions towards enantioenriched lactams
Influence of shaft stiffness on the performance of a plane-like hydrofoil
No full textInternational audienceHydrofoils are now widely used to reduce hydrodynamic resistance, leading to increased velocities and sailing crafts performance. However, designing hydrofoils for sailing vessels such as windfoils and kitefoils remains a complex challenge, as the ride height plays a critical part on the stability and performance of foiling vessels. Furthermore, the strut between the board and the plane-like foil (called the shaft) is highly loaded and subject to significant deformation, leading to potentially important Fluid-Structure Interaction (FSI) effects. Consequently, it is now critical to consider the ride height and the FSI effects in Velocity Prediction Programs (VPP). This work first presents the development of a novel five degree-of-freedom (DoF) Velocity Prediction Program (VPP) for foiling crafts, which includes the FSI effects on the shaft of the vessel. Hydrodynamic forces are computed using a vortex lattice model with a viscous correction, solved by the panel method implemented in the software Athena Vortex Lattice (AVL). The structural behavior of the shaft is introduced in the VPP in the form of an analytical model derived from experimental tests on real shafts. This improved VPP is then applied to a generic plane-like hydrofoil, typical of a windfoil sailing upwind at a speed of 9m/s (18kts) and approximately a 20° windward-heel. Twenty shafts of different stiffness are tested, and their respective deflections, as well as the equilibrium state computed by the VPP, are compared. Results show that for a static analysis the equilibrium state and the performance are barely affected by the stiffness of the shaft. However, the use of a flexible shaft leads to a different distribution of the lateral hydrodynamic force (anti-drift) onto the different parts of the foil
Remote Monitoring of Mediterranean Hurricanes Using Infrasound
No full textInternational audienceMediterranean hurricanes, or medicanes, are tropical-like cyclones forming once or twice per year over the waters of the Mediterranean Sea. These mesocyclones pose a serious threat to coastal infrastructure and lives because of their strong winds and intense rainfall. Infrasound technology has already been employed to investigate the acoustic signatures of severe weather events, and this study aims at characterizing, for the first time, the infrasound detections that can be related to medicanes. This work also contributes to infrasound source discrimination efforts in the context of the Comprehensive Nuclear-Test-Ban Treaty. We use data from the infrasound station IS48 of the International Monitoring System in Tunisia to investigate the infrasound signatures of mesocyclones using a multi-channel correlation algorithm. We discuss the detections using meteorological fields to assess the presence of stratospheric waveguides favoring propagation. We corroborate the detections by considering other datasets, such as satellite observations, a surface lightning detection network, and products mapping the simulated intensity of the swell. High-and low-frequency detections are evidenced for three medicanes at distances ranging between 250 and 1100 km from the station. Several cases of non-detection are also discussed. While deep convective systems, and mostly lightning within them, seem to be the main source of detections above 1 Hz, hotspots of swell (microbarom) related to the medicanes are evidenced between 0.1 and 0.5 Hz. In the latter case, simulations of microbarom detections are consistent with the observations. Multi-source situations are highlighted, stressing the need for more resilient detection-estimation algorithms. Cloud-to-ground lightning seems not to explain all high-frequency detections, suggesting that additional sources of electrical or dynamical origin may be at play that are related to deep convective systems
Validation of a corner reflector installation at Côte d’Azur multi-technique geodetic observatory
No full textInternational audienceWe present the procedure we followed to design an artificial corner reflector (CR) at the Calern site of Côte d'Azur Observatory (France). Although still few in number, such reflectors are an integral part of the Global Geodetic Observing System (GGOS) infrastructure. They can be used as a stable radar target in SAR images to connect local InSAR deformation maps to the global Terrestrial Reference Frame and for SAR absolute determination. During a test phase, the orientation of the CR was changed in order to be aligned toward all possible orbits of Sentinel-1A/1B satellites. On the different SAR images, the CR exhibits a high backscattering signal, and provides a Signal-to-Clutter Ratio larger than 26 dB. Since December 2018, the CR is specifically oriented toward the relative orbit 88. It is clearly detected as a PS in our InSAR analyses and as expected, the standard deviation of displacement measured on the CR is lower than on surrounding PS. A first local survey was performed to locate precisely this CR with respect to the existing geodetic instruments and annual campaigns have been carried out since then to insure its stability over time