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Using aquaplanets to understand the robust responses of comprehensive climate models to forcing
No full textInternational audienceIdealized climate change experiments using fixed sea-surface temperature are investigated to determine whether zonally symmetric aquaplanet configurations are useful for understanding climate feedbacks in more realistic configurations. The aquaplanets capture many of the robust responses of the large-scale circulation and hydrologic cycle to both warming the sea-surface temperature and quadrupling atmospheric CO2. The cloud response to both perturbations varies across models in both Earth-like and aquaplanet configurations, and this spread arises primarily from regions of large-scale subsidence. Most models produce a consistent cloud change across the subsidence regimes, and the feedback in trade-wind cumulus regions dominates the tropical response. It is shown that these trade-wind regions have similar cloud feedback in Earth-like and aquaplanet warming experiments. The tropical average cloud feedback of the Earth-like experiment is captured by five of eight aquaplanets, and the three outliers are investigated to understand the discrepancy. In two models, the discrepancy is due to warming induced dissipation of stratocumulus decks in the Earth-like configuration which are not represented in the aquaplanet. One model shows a circulation response in the aquaplanet experiment accompanied by a cloud response that differs from the Earth-like configuration. Quadrupling atmospheric CO2 in aquaplanets produces slightly greater adjusted forcing than in Earth-like configurations, showing that land-surface effects dampen the adjusted forcing. The analysis demonstrates how aquaplanets, as part of a model hierarchy, help elucidate robust aspects of climate change and develop understanding of the processes underlying them. © 2014 The Author(s)
Predictability of the Meteorological Conditions Favourable to Radiative Fog Formation During the 2011 ParisFog Campaign
No full textInternational audienceRadiative fog formation is a complex phenomenon involving local physical and microphysical processes that take place when particular meteorological conditions occur. This study aims at quantifying the ability of a regional numerical weather model to analyze and forecast the conditions favourable to radiative fog formation at an instrumental site in the Paris area. Data from the ParisFog campaign have been used in order to quantify the meteorological conditions favorable to radiative fog formation (pre-fog conditions) by setting threshold values on the key meteorological variables driving this process: 2-m temperature tendency, 10-m wind speed, 2-m relative humidity and net infrared flux. Data from the ParisFog observation periods of November 2011 indicate that use of these thresholds leads to the detection of 87 % of cases in which radiative fog formation was observed. In order to evaluate the ability of a regional weather model to reproduce adequately these conditions, the same thresholds are applied to meteorological model fields in both analysis and forecast mode. It is shown that, with this simple methodology, the model detects 74 % of the meteorological conditions finally leading to observed radiative fog, and 48 % 2 days in advance. Finally, sensitivity tests are conducted in order to evaluate the impact of using larger time or space windows on the forecasting skills. © 2013 Springer Science+Business Media Dordrecht
INTERMEDIATE SUMS ON POLYHEDRA II:BIDEGREE AND POISSON FORMULA
No full textAbstract. We continue our study of intermediate sums over polyhedra,interpolating between integrals and discrete sums, whichwere introduced by A. Barvinok [Computing the Ehrhart quasi-polynomial of a rational simplex, Math. Comp. 75 (2006), 1449–1466]. By well-known decompositions, it is sufficient to considerthe case of affine cones s+c, where s is an arbitrary real vertex andc is a rational polyhedral cone. For a given rational subspace L,we integrate a given polynomial function h over all lattice slicesof the affine cone s + c parallel to the subspace L and sum up theintegrals. We study these intermediate sums by means of the intermediategenerating functions SL(s+c)(ξ), and expose the bidegreestructure in parameters s and ξ, which was implicitly used in thealgorithms in our papers [Computation of the highest coefficients ofweighted Ehrhart quasi-polynomials of rational polyhedra, Found.Comput. Math. 12 (2012), 435–469] and [Intermediate sums onpolyhedra: Computation and real Ehrhart theory, Mathematika 59(2013), 1–22]. The bidegree structure is key to a new proof for theBaldoni–Berline–Vergne approximation theorem for discrete generatingfunctions [Local Euler–Maclaurin expansion of Barvinokvaluations and Ehrhart coefficients of rational polytopes, Contemp.Math. 452 (2008), 15–33], using the Fourier analysis with respectto the parameter s and a continuity argument. Our study alsoenables a forthcoming paper, in which we study intermediate sumsover multi-parameter families of polytopes
Proceedings of the Joint Meeting of the Twenty-Third EACSL Annual Conference on Computer Science Logic (CSL) and the Twenty-Ninth Annual ACM/IEEE Symposium on Logic in Computer Science (LICS)
No full textInternational audienc
Tropical Fourier–Motzkin elimination, with an application to real-time verification
No full textAlso arXiv:1308.2122International audienceWe introduce a generalization of tropical polyhedra able to express both strict and non-strict inequalities. Such inequalities are handled by means of a semiring of germs (encoding infinitesimal perturbations). We develop a tropical analogue of Fourier-Motzkin elimination from which we derive geometrical properties of these polyhedra. In particular, we show that they coincide with the tropically convex union of (non-necessarily closed) cells that are convex both classically and tropically. We also prove that the redundant inequalities produced when performing successive elimination steps can be dynamically deleted by reduction to mean payoff game problems. As a complement, we provide a coarser (polynomial time) deletion procedure which is enough to arrive at a simply exponential bound for the total execution time. These algorithms are illustrated by an application to real-time systems (reachability analysis of timed automata)
INTERMEDIATE SUMS ON POLYHEDRA: COMPUTATION AND REAL EHRHART THEORY
No full textWe study intermediate sums, interpolating between integrals and discrete sums, which were introduced by A. Barvi-nok [Computing the Ehrhart quasi-polynomial of a rational simplex, Math. Comp. 75 (2006), 1449–1466]. For a given semi-rational polytope p and a rational subspace L, we integrate a given polyno-mial function h over all lattice slices of the polytope p parallel to the subspace L and sum up the integrals. We first develop an al-gorithmic theory of parametric intermediate generating functions. Then we study the Ehrhart theory of these intermediate sums, that is, the dependence of the result as a function of a dilation of the polytope. We provide an algorithm to compute the resulting Ehrhart quasi-polynomials in the form of explicit step polynomi-als. These formulas are naturally valid for real (not just integer) dilations and thus provide a direct approach to real Ehrhart theory
Etude des interactions multivalentes carbohydrate/protéine sur des biocapteurs de silicium
No full textSpecific carbohydrate/protein interactions play an important role in numerous physiological and pathological processes. Silicon-based biosensors have been envisaged for studying such interactions here. In a first approach, a multistep functionalization strategy was established on crystalline silicon via robust covalent Si-C bonds to incorporate oligo(ethylene glycol) units and generate a glycan-terminated monolayer by “click” chemistry. The functionalization process was carefully characterized by IR-ATR, AFM and XPS, leading to the formation of highly compact organic monolayers. The as-fabricated glycan-terminated surface showed good antifouling property towards non-specific lectins and excellent selectivity towards specific lectins. By using quantitative IR-ATR analysis and numerical simulation, we demonstrated the importance of the surface concentration of glycans to favor the multivalent binding of the glycan ligands on the surface with the specific lectins. In a second approach, the amorphous silicon-carbon alloy thin films coated on gold nanoparticles were used as the substrate for the elaboration of glycan microarray. Fluorescence imaging was used for the recognition specificity of the glycans clicked on the surface with the dye-labeled lectins. By optimizing the distance between the fluorophore and the nanoparticles, best localized surface plasmon resonance (LSPR)-enhanced fluorescence was achieved to improve the microarray sensitivity with a limit of detection at the picomolar level.Les interactions spécifiques carbohydrate/protéine joue un rôle important dans de nombreux processus physiologiques et pathologiques. Cette thèse a mis au point des biocapteurs sur silicium pour l’étude de telles interactions. Dans une première approche, on a établi une stratégie de fonctionnalisation multi-étapes du silicium cristallin via des liaisons covalentes Si-C robustes pour accrocher des précurseurs propargyl-glycanes par chimie click. Chaque étape a été soigneusement caractérisée par IR-ATR, AFM et XPS, conduisant à la formation de monocouches denses composées d’entités oligo(éthylène glycol) et terminées par une fonction glycane (mannose ou lactose). Ces nouvelles surfaces de glycane ont montré une très bonne biorésistance aux lectines non spécifiques et une excellente sélectivité vis-à-vis de lectines spécifiques. En utilisant la spectroscopie IR quantitative et la simulation numérique, on a démontré l’importance de la concentration surfacique en glycane pour favoriser des interactions multivalentes entre les glycanes et la lectine spécifique (constantes d’affinité proche du micromolaire). Dans une seconde approche, on a mis au point une puce à glycanes constituée d’une couche mince de silicium amorphe carboné déposée sur des nanoparticules d’or sur verre. L’imagerie par fluorescence a validée la spécificité des interactions entre les glycanes clickées à la surface de la biopuce et des lectines fluorescentes. En optimisant la distance entre les lectines et les nanoparticules, l’exaltation de la fluorescence par les plasmons de surface localisées a permis d’augmenter la sensibilité de la biopuce au niveau du picomolaire
Black-box complexity: from complexity theory to playing Mastermind
No full textTutorial slides, published in Gecco companion materialTutorial given at GECCO 201
Un novel accès radicalaire à des benzazèpinones, naphtylamides et naphtylhydrazides
No full textThe work presented in this manuscript highlights some further sometimes unusual aspects of the radical chemistry of xanthates. The study of the cyclisations onto the aromatic ring of hydroxamates has revealed an unexpected fragmentation and a brief investigation provided solid evidence for the homolytic rupture of the N-O bond. Consequently, a new methodology to access the family of N-unsubstituted benzazepinones based on the xanthate chemistry was developed. Benzazepinones with various substituents including sugar and boronate could be readily prepared by this route. The process is flexible, convergent and very suitable for the construction of libraries.Alpha-Tetralones are readily prepared by the xanthate-based addition/cyclisation sequence and are important intermediates for the synthesis of various aromatic structures. An efficient and general methodology to access regioselectively substituted naphthylamides by aromatisation of the corresponding alpha-tetralones was established. Naphthylhydrazides were synthesized in the same fashion, but in this case, the alpha-tetralones were reacted with Boc-protected hydrazines before undergoing the aromatisation.Les travaux, présentés dans ce manuscrit, mettent en valeur certains aspects inhabituels de la chimie radicalaire desxanthates.Via l’étude de la cyclisation par formation d’un noyau aromatique à partir d’hydroxamates, une fragmentation inattendue a été observée et une recherche suivie et approfondie a permis de mettre en évidence une rupture homolytique de la liaison N-O. Par conséquent, une nouvelle méthodologie basée sur la chimie des xanthates a été développée afin d’accéder à des composés de la famille des benzazépinones avec atome d’azote non substitué. Des benzazépinones avec des substituants variés, comme des sucres ou des boronates, ont pu ainsi être facilement préparées grâce à cette nouvelle voie. Ce procédé est facilement modulable, convergent et très pratique dans le but d’avoir une chimiothèque avec un grand nombre de composés organiques.La synthèse d’alpha-tetralones, qui sont des intermédiaires très importants pour la synthèse de structures aromatiques variées, a également été envisagée via une réaction de type addition/cyclisation basée sur la chimie des xanthates. Une méthodologie générale et efficace a été développée afin d’obtenir régiosélectivement des naphthylamides substituées par aromatisation des tetralones correspondantes. De la même manière, la synthèse de naphthylhydrazides a été envisagée. Cependant, dans ce cas, les alpha-tetralones réagissent avec des hydrazines protégées par des groupements Boc avant que l’étape d’aromatisation soit réalisée
Constraining physics of very hot super-Earths with the James Webb Telescope. The case of CoRot-7b
No full textInternational audienceContext. Transit detection from space using ultra-precise photometry led to the first detection of super-Earths with solid surfaces: CoRot-7b and Kepler-10b. Because they lie only a few stellar radii from their host stars, these two rocky planets are expected to be extremely hot.Aims. Assuming that these planets are in a synchronous rotation state and receive strong stellar winds and fluxes, previous studies have suggested that they must be atmosphere-free and that a lava ocean is present on their hot dayside. In this article, we use several dedicated thermal models of the irradiated planet to study how observations with NIRSPEC on the James Webb Space Telescope (JWST) could further confirm and constrain, or reject the atmosphere-free lava ocean planet model for very hot super-Earths.Methods. Using CoRoT-7b as a working case, we explore the consequences on the phase-curve of a non tidal-locked rotation, with the presence/absence of an atmosphere, and for different values of the surface albedo. We then simulate future observations of the reflected light and thermal emission from CoRoT-7b with NIRSPEC-JWST and look for detectable signatures, such as time lag, of those peculiarities. We also study the possibility to retrieve the latitudinal surface temperature distribution from the observed SED.Results. We demonstrate that we should be able to constrain several parameters after observations of two orbits (42 h) thanks to the broad range of wavelengths accessible with JWST: i) the Bond albedo is retrieved to within ±0.03 in most cases. ii) The lag effect allows us to retrieve the rotation period within 3 h of a non phase-locked planet, whose rotation would be half the orbital period; for longer period, the accuracy is reduced. iii) Any spin period shorter than a limit in the range 30–800 h, depending on the thickness of the thermal layer in the soil, would be detected. iv) The presence of a thick gray atmosphere with a pressure of one bar, and a specific opacity higher than 10-5 m-2 kg-1 is detectable. v) With spectra up to 4.5 μm, the latitudinal temperature profile can be retrieved to within 30 K with a risk of a totally wrong solution in 5% of the cases. This last result is obtained for a signal-to-noise ratio around 5 per resel, which should be reached on Corot-7 after a total exposure time of ~70 h with NIRSPEC and only three hours on a V = 8 star.Conclusions. We conclude that it should thus be possible to distinguish the reference situation of a lava ocean with phase-locking and no atmosphere from other cases. In addition, obtaining the surface temperature map and the albedo brings important constraints on the nature or the physical state of the soil of hot super-Earths