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Les besoins conflictuels optiques et mécaniques déterminent l'évolution de l'épaisseur de la membrane de l'aile chez les papillons transparents ithomiines
No full textTransparent animals are often thin, which raises the question of their fragility. In clearwing Lepidoptera, the wing thickness is the evolutionary result of conflicting optical and mechanical needs. All else being equal, a thinner membrane lets light better go through, can still sustain the reduced scales it often bears, it has a low stiffness advantageous for flight but it resists less to fatigue and failure, a crucial point. An evolutionary way out of these conflicting needs can be spatial heterogeneity in stiffness, with thicker opaque patches compensating for thinner transparent ones, especially when transparency covers a great wing surface proportion. We tested these predictions in Ithomiine butterflies, a tribe comprising closely-related opaque and transparent unpalatable species. We found that species with partially transparent wings have a thinner membrane in the transparent zone than in the opaque one, which likely helps light getting through and agrees with the lighter weight wings have to support in the transparent zone. Surprisingly, more transparent species have a thicker membrane in their transparent zone. We find no relationship between membrane thickness and scale density, ruling out a predominant role of membrane thickness as a mechanical support for scales. Finally, species with a higher wing proportion occupied by transparency have thicker membranes on their transparent patch, and a greater ratio in thickness between opaque and transparent zones. These latter two results support the hypothesis that clearwing butterflies with larger transparent patches are potentially more fragile and that this frailty is offset by thicker surrounding opaque patches offering higher mechanical resistance, like tubules framing a kite sail. In clearwing butterflies, wing membrane thickness has likely evolved under optical and mechanical selective pressures and further research should experimentally measure the costs, if any, of thinner transparent membranes.Les animaux transparents sont souvent minces, ce qui soulève la question de leur fragilité. Chez les Lépidoptères à ailes transparentes, l’épaisseur de l’aile est le résultat évolutif de besoins optiques et mécaniques contradictoires. Toutes choses égales par ailleurs, une membrane plus fine laisse mieux passer la lumière, et peut pourtant supporter les écailles réduites qu’on trouve souvent dans les zones transparentes. Elle présente une faible rigidité avantageuse pour le vol, mais résiste moins bien mécaniquement à la rupture, un point crucial. Une solution évolutive à ces contraintes opposées peut passer par une hétérogénéité spatiale de la rigidité, avec des zones opaques plus épaisses compensant les zones transparentes plus fines, en particulier lorsque la transparence occupe une grande proportion de la surface alaire.Nous avons testé ces prédictions chez les papillons ithomiines, une tribu comprenant des espèces toxiques étroitement apparentées, à ailes opaques ou transparentes. Nous avons constaté que les espèces partiellement transparentes possèdent une membrane plus fine en zone transparente qu’en zone opaque, ce qui favorise le passage de la lumière et peut quand même soutenir la masse plus faible que les ailes doivent supporter en zone transparente. De manière surprenante, les espèces les plus transparentes présentent une membrane plus épaisse dans leur zone transparente. Nous ne trouvons aucune relation entre l’épaisseur de la membrane et la densité des écailles, ce qui exclut un rôle prédominant de l’épaisseur membranaire comme support mécanique des écailles.Enfin, les espèces dont une plus grande proportion de l’aile est occupée par des zones transparentes présentent des membranes plus épaisses en zone transparente, et un ratio d’épaisseur plus élevé entre les zones opaques et transparentes. Ces deux derniers résultats soutiennent l’hypothèse selon laquelle les papillons à ailes transparentes dotés de larges zones transparentes sont potentiellement plus fragiles, et que cette fragilité est compensée par des zones opaques environnantes plus épaisses, offrant une plus grande résistance mécanique, à la manière de tubulures encadrant la voile d’un cerf-volant. Chez les papillons à ailes transparentes, l’épaisseur de la membrane alaire a probablement évolué sous l’effet de pressions de sélection à la fois optiques et mécaniques, et des recherches futures devraient mesurer expérimentalement les coûts éventuels de membranes transparentes plus fines
Signal Injection for Systems with Direct Feedthrough - Application to Water Content Estimation in Fuel Cells
No full textInternational audienceProton exchange membrane fuel cells (PEMFCs) suffer from water-management issues that can lead to drying or flooding, thereby reducing performance and durability. Accurate estimation of water content is therefore essential for Fuel Cell Management Systems design. In this work, we investigate how the introduction of a known high-frequency excitation into the system input enhance estimation capabilities. This paper extends signal-injection techniques to nonlinear feedthrough dynamical systems, such as the ones used to model PEMFCs. It proposes a signal injection procedure tailored for systems with nonlinear input dependencies in both state and output equations. The approach is applied to an open-cathode PEMFC model to recover temperature, liquid water saturation in the cathode catalyst layer and ohmic resistance from the sole voltage measurement. Numerical simulations confirm the interest of the proposed method and show that estimation precision improves as the excitation frequency increases
Exploring the environmental distribution of the oyster parasite Haplosporidium costale
No full textInternational audienceThe protozoan parasite Haplosporidium costale is known to occur in the USA where it has been associated with sharp seasonal mortality of the Eastern oyster Crassostrea virginica since the 1960’s. In 2019, the parasite was detected for the first time in the Pacific oyster Magallana gigas in France in the context of light mortality and was subsequently detected in archived material collected since 2008. This detection raised several questions regarding the ability of the parasite to maintain in the ecosystem and the potential involvement of other species in its life cycle. To answer these questions, an integrated sampling approach was deployed seasonally in three oyster farming areas where the parasite was already known to occur. Parasite presence was evaluated after checking the presence of PCR inhibitors and using a previously developed and validated Real Time PCR assay, optimized in this study to detect parasite DNA in various environmental compartments. Parasite DNA was almost only detected in cupped oysters. Considering the high number of oysters found positive with low infection intensity, a complementary experiment was undertaken to better characterize sub-clinical infections in oysters. The presence of the parasite was tested twice a week in water and sediment from aquaria hosting cupped oysters from a known infected site. After one month, oysters were sacrificed and tested regarding the presence of the parasite at the tissular level. Altogether, field and experimental results indicate that the parasite is stably established in oyster, particularly in gills, which may act as a reservoir all along the year. The detection of parasite DNA in nanoplankton and sediment suggests that H. costale is released from the oysters outside mortality event. Our results do not support the involvement of other species than cupped oyster in the parasite life cycle except periwinkles, whose role would deserve to be further investigate
StripesCounter: A new image software for increment measurement in paleoclimate archives
No full textInternational audienceMost natural paleoclimate archives are accretionary material presenting periodic structures that bear environmental and/or chronological information. Here we present StripesCounter, an open access Python software designed for automated banding detection and measurement. As a study case, 16-year long profiles of daily growth increment measurements were conducted on a modern shell of the giant clam Tridacna gigas. High resolution images of shell thin sections were obtained using a confocal laser scanning microscopy and processed using StripesCounter. We demonstrate that StripesCounter provides highly reproducible and accurate results. The long time series of daily increments indicate that Tridacna gigas growth is strongly modulated by seasonal oceanographic variations, reflecting changes in sea surface temperature, precipitation, and salinity. Notably, growth profiles reveal semi-annual variations related to semi-annual variations in environmental factors, potentially linked to ENSO events. This automated growth increment analysis can be extended to other archives with cyclic structures, including tree rings, corals, and other biogenic or abiotic laminated materials. StripesCounter offers a powerful and accessible tool for generating long high-resolution, temporally explicit datasets, opening new perspectives for investigating rapid environmental changes across diverse ecosystems and geological timescales
Subsoils, but not toeslopes, store millennia-old PyC in a gently sloping catchment under temperate climate after centuries of cultivation
No full textInternational audiencePyrogenic carbon (PyC) is the carbonaceous solid residue of incomplete combustion of biomass. It is a continuum of mostly condensed and aromatic molecules. PyC persists for longer in soils relative to non-PyC organic carbon. However, estimates of PyC residence time vary greatly. The time and spatial scales investigated are not always adapted to the long-residence time and vertical and lateral mobility of PyC in the soil profile and the landscape. In addition, agricultural land-use and shallow slopes are under-represented in the PyC literature.We measured the concentrations and stocks of PyC down to 60 cm along three toposequences in a small agricultural catchment with shallow slopes and homogeneous soil parent material in the west of France. We used two methods (chemo-thermal oxidation – CTO and hydropyrolysis – HyPy) of PyC quantification that cover the intermediate to highly condensed part of the PyC continuum, and also measured the radiocarbon values in both total soil organic carbon (SOC) and the PyC fraction. There was likely little persistent PyC inputs to the catchment in the last 150 years which gave us access to the resultant, long term PyC distribution in the landscape. In particular, we aimed to investigate whether the vertical and horizontal distribution of PyC were similar or differed from SOC and whether they were affected by the soil types along the slope.Topographic position was not the main driver of PyC stocks in this landscape. The stock of PyCCTO to 60 cm depth averaged 2.5 ± 0.22 t ha−1 across topographic positions. PyC stocks were the highest in a Solimovic Cambisol at the toeslope (3.3 ± 0.26 t ha−1), likely formed following changes in erosion dynamics with land-use. Contrary to previous reports, erosion redistributed already aged PyC without enrichment or depletion. PyCHyPy concentrations in the topsoil decreased from upslope (median = 1.6, IQR = 0.22 g C kg−1 soil) to downslope positions (median = 1.10, IQR = 0.40 g C kg−1 soil), which we tentatively attribute to PyCHyPy leaching following the destabilisation of mineral associations with iron oxides in the water-table affected portion of the transects. The subsoil (30–60 cm) represented between 37 % and 51 % of the PyCCTO stock. PyCHyPy proportion in SOC increased with depth and reached an average of 11 ± 3.3 % at 50–60 cm depth. PyCHyPy had an uncalibrated radiocarbon age of 2520 to 9600 years BP at this depth, significantly older than bulk SOC at the same depth and than PyCHyPy at 0–10 cm (1530 to 2630 years BP). These results confirm the long persistence of PyC in soils and point to a slow advection of PyC towards the soil depth under the pedoclimatic conditions of our study area.Future studies should assess whether erosion modalities and age and quality of PyC affect its fate during erosion events. Identifying the proportion of PyC produced which is quickly transported away from the watershed and that which remains and is stabilised in soils for millennia after a fire is an important knowledge gap that still needs to be investigated to close the terrestrial PyC budget
Spherically symmetric solutions in quasi-local Einstein-Weyl gravity
No full textInternational audienceQuantum-gravitational effective actions with higher-derivative and non-local operators are expected to regularize the singularities of general relativity. Here we focus on quasi-local Einstein-Weyl gravity and obtain a classification of Frobenius solutions in static spherical symmetry. In contrast to local Einstein-Weyl gravity, and more generally quadratic gravity, we find that the quasi-local theory admits only regular solutions at the radial core. In addition, we find asymptotic -corrections to the Schwarzschild geometry at large radial distances. Other solution classes around generic expansion points describe Schwarzschild-like and other types of horizons, as well as symmetric and non-symmetric wormhole throats
Nonconservative Lie series: post-Newtonian binary dynamics at 2.5PN
No full textInternational audienceWe present a fully analytical solution to the dynamics of the non-spinning 2.5 post-Newtonian binary problem, accounting for both the long-term (secular) and short-term (oscillatory) temporal behavior, with no restriction on eccentricity. The radiative degrees of freedom are handled within the nonconservative Hamiltonian framework introduced in a companion paper. In this work, we apply the Lie series method to construct a resonant Birkhoff normal-form and the corresponding generator of the radiation-reaction dynamics. The secular piece reconstructs exactly the Peters-Mathews relations for semi-major axis and eccentricity. The oscillatory piece completes the dynamics and is well suited for gravitational wave templates. The procedure we present in this paper can be systematically employed to cast arbitrary nonconservative systems into extended Hamiltonian form so that the Lie method can be applied
Weak Scale Triggers in the SMEFT
No full textInternational audienceThere are no weak scale triggers in the SMEFT up to dimension six that can solve the hierarchy problem far above the weak scale. Our arguments can be used to show that the same is true at dimension eight. Weak scale triggers are local operators sensitive to the Higgs mass squared and they are needed in a large number of qualitatively different cosmological solutions to the hierarchy problem. These solutions have little in common besides the use of a trigger operator. We argue that focusing on the signatures of the three already-known trigger operators can lead to discover or exclude this class of solutions to the hierarchy problem
Block structures of graphs and quantum isomorphism
No full textWe prove that for every pair of quantum isomorphic graphs, their block trees and their block graphs are isomorphic, and that such an isomorphism can be chosen so that the corresponding blocks are quantum isomorphic -in particular, 2-connectedness is preserved under quantum isomorphism. We conclude with some corollaries, including obtaining some necessary conditions on a pair of quantum isomorphic, not isomorphic graphs with a minimal number of vertices
Legal arguments against emotions - how the law silences militant disillusionment with the identity evolution of a non-religious organisation
No full textInternational audienceThis article aims to show how the law can be used to silence the emotions of activists and counter any opposition to the strategic and doctrinal evolutions of a French non-religious organisation.At the end of the 1980s, France's biggest confederation of associations, the Ligue de l'enseignement, shifted its doctrinal base from a secularism closed to any dialogue with religions to a recognition of their importance as a cultural fact. Discussions have been held with leaders of the main religions present in France, the teaching of religion (in historical and sociological perspectives) has been advocated, and reflections on Islam have been carried out. But this evolution was initiated by the sole organisation's leaders and not by the whole confederation. Some militants have expressed skepticism, disillusionment and even incomprehension about these changes. Others rejected the organisation's positions, particularly on the issue of the veil. However, to counter this militant “unhappiness” and the divisions within the movement, those in charge put forward the legislative argument: the Goblet law of 1886 was put forward as a reminder of the long-standing legal recognition of religious establishments; the law on religious signs passed in 2004 was mobilized to silence opposition on the issue