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Non-resonant plasmon energy transfer processes for catalysis
No full textInternational audienceHow can energy transfer catalysis move beyond fragile molecular light absorbers toward more robust and tunable systems? Here we show that tiny gold nanostructures can act as universal energy donors to activate otherwise inactive gold-based catalysts using light. By introducing a molecular mediator, we demonstrate that the localized energy within the nanoparticles can be passed along through a twostep mechanism, ultimately creating a reactive excited state in the gold complex, even when the light does not directly match its energy levels. Spectroscopic measurements confirm the formation and lifetime of this state and provide clear evidence of successful energy transfer. These results establish how plasmonic materials can drive catalytic reactions through controlled energy flow, opening new opportunities for designing durable and versatile systems for light-driven chemistry
Two-point functions in boundary loop models
No full textInternational audienceUsing techniques of conformal bootstrap, we propose analytical expressions for a large class of two-point functions of bulk fields in critical loop models defined on the upper-half plane. Our results include the two-point connectivities in the Fortuin--Kasteleyn random cluster model with both free and wired boundary conditions. We link the continuum expressions to lattice quantities by computing universal ratios of amplitudes for the two-point connectivities, and find excellent agreement with transfer-matrix numerics
ACROPOLIS: Munich urban CO2 sensor network
No full textInternational audienceUrban areas are major contributors to anthropogenic CO2 emissions, yet detailed monitoring remains a challenge due to the cost and operational constraints of traditional sensor networks. As a scalable alternative, we established the ACROPOLIS (Autonomous and Calibrated Rooftop Observatory for MetroPOLItan Sensing) network in the Munich metropolitan area, using mid-cost sensors to enable dense, city-scale observation. This work outlines the development of the hardware and software of the system, its performance and the first 1.5 years of operation, during which more than 90 million CO2 measurements were collected in urban, suburban and rural environments. The primary goal was to evaluate whether mid-cost Vaisala GMP343 sensors, when combined with manufacturer internal corrections and environmental stabilization, can reliably measure CO2 concentrations with sufficient accuracy to resolve urban gradients. We implemented a fully automated 2-point calibration procedure using synthetic dry reference gases and conducted a multi-week side-by-side comparison with a high-precision Picarro reference instrument to assess sensor performance. Our results show that, despite inter-sensor variability in temperature sensitivity, the hourly aggregated mean root mean square error (RMSE) of all sensors is 1.16 ppm with a range of 0.57 to 2.58 ppm. For the specific sensor housed in our second-generation enclosure with PID-controlled heating, the performance improved from 0.9 to 0.6 ppm RMSE. Analysis of spatial and temporal patterns reveal distinct seasonal cycles, urban–rural concentration gradients, and nighttime accumulation events, consistent with expected biogenic and anthropogenic activity, and atmospheric transport mechanisms. We conclude that mid-cost urban networks can provide scientifically valuable, spatially highly resolved greenhouse gas observations when supported by appropriate calibration and stabilization techniques. The open-source design and demonstrated performance of the ACROPOLIS network establish a blueprint for future deployments in other cities seeking to advance emissions monitoring and urban climate policy
Some random media with optimal three-phase boundary lines
No full textInternational audienceMulti components materials show triple phase boundary (TPB) lines at the interface between three components. TPB lines are of primary importance for the performance of electrochemical devices like Solid Oxide Fuel Cells (SOFC). We provide theoretical estimates of the specific length of (TPB) lines LV ijk for a broad range of multi-component random structures. Since analytical results are obtained, random microstructures with optimal LV ijk can be designed. The effects of the composition, through volume fractions, and of the morphology, through the choice of primary grains, are separate, so that "optimal composition" is derived independently on the geometry. Various models designed with the same basic ingredients may show a large range of values for LV ijk , depending on their mode of construction. Much longer LV ijk than experimental measurements in real materials can theoretically be reached, typically over an order of magnitude. This can be used as a guideline to improve the electrochemical behavior of fuel cell components
Cassini on the long term. Practical astronomy, instrumentation and metrology
No full textInternational audienceFrom Giovanni Domenico (1625-1712) to Jean-Dominique (1748-1845), four generations of Cassini succeeded each other at the Paris Observatory from 1669 to 1794. Following the thread of the map-making project proposed by Abbot Jean Picard (1620-1682), I will consider the progressive association of the Cassinis with the general triangulation of France. In particular we’ll see how Picard's project envisages contributing to the study of the “figure” of the Earth, a subject that has been little analyzed by historians – with the exception of the debate that saw Cassinians and Newtonians opposing each other. In the long run, although knowledge by geometric triangulation of the Earth's meridians gradually pushes away the possibility of establishing an “exact” value of the Earth's figure, its investigation leads to an essential development of other forms of scientific knowledge, such as geodesy in its aspects of instrumentation research and metrology
Space explorer: floral evolution and lineage diversification of the Neotropical Sapranthinae clade (Annonaceae)
No full textInternational audienceFloral morphology influences angiosperm diversification, yet many lineages maintain ancestral traits due to selection pressures. Although ecological speciation can generate novel floral morphologies, such innovations rarely become widespread. Understanding how floral traits persist, shift, or re-emerge offers crucial insights into the evolutionary patterns that reflect the balance between conservation and innovation in plant diversification. Here, we examine the evolutionary dynamics of floral morphology in the Neotropical Sapranthinae clade (Annonaceae, Magnoliidae) using a phylogenomic framework based on hundreds of nuclear loci. We reconstruct species-level relationships, estimate divergence times, and quantify floral morphospace across the clade. Through multivariate and comparative analyses, we assess floral disparity, convergence, and trait evolution, and evaluate their statistical association with diversification rates. Our analyses recovered three monophyletic genera within the Neotropical Sapranthinae—Desmopsis, Sapranthus, and Tridimeris—with divergence times spanning from the Eocene to the Pliocene. We identified seven distinct floral morphs, each defined by unique morphological features. Ancestral state reconstruction indicates the Desmopsis-type flower as the ancestral condition, with six major transitions and two convergence events contributing to floral disparity. Evolutionary modelling supports multiple adaptive optima, while temporal patterns in floral disparity suggest an early burst of floral innovation followed by episodic shifts coinciding with changes in diversification rates. Sapranthinae illustrates dynamic morphospace exploration within Magnoliidae and highlights the macroevolutionary significance of floral disparity in shaping angiosperm diversity
Écrire l’histoire sur la côte est-africaine au XIXe siècle: Pouvoirs, territoires et usages du passé
No full textInternational audienceÀ la fin du XIXe siècle, sur le littoral de l’actuel Kenya, une cité-État swahili tente de survivre aux bouleversements politiques et aux appétits impériaux. Fondée en 1862 par des élites swahili en exil, Witu se trouve prise entre le sultanat de Zanzibar, la puissance britannique et les rivalités européennes naissantes. Pour défendre leur autorité et leurs territoires, ses dirigeants mobilisent alliés locaux, dépendants – esclaves marrons et clients – et voyageurs allemands, mais aussi le passé lui-même. À travers l’analyse de chroniques, de généalogies et de récits hybrides, cet ouvrage montre comment l’écriture de l’histoire devient une arme politique. À la croisée de l’histoire de l’Afrique, des contacts avec les Européens avant la colonisation et de l’écriture de l’histoire, il révèle comment la mise en récit du passé sert à légitimer des pouvoirs fragilisés et à renégocier des compromis sociaux menacés par les rivalités régionales puis impériales
Science under Threat? A Natural Experiment in Economics
No full textAcademic freedom has come under growing strain across the world. To study whether and how academics react to political pressure, we exploit a natural experiment: the U.S. government's "blacklist" of undesirable words released in early 2025. We find that the release of this list leads to a sharp reduction in the use of banned words in sensitive contexts among economists working at universities that rely heavily on NSF funding. The drop is particularly marked for content related to gender, race, and environment. Our findings are consistent with scholars responding strongly to political pressure through career incentives
South Caucasus greening and Neolithisation: What happened 8200 years ago?
No full textInternational audienceIn the South Caucasus, located north of the Fertile Crescent and between Black and Caspian Seas, the Neolithic way of life emerged relatively late, around 6000 BCE (8000 cal BP). This delay, compared with regions such as Anatolia or the Kopet Dag, has long been discussed by archaeologists and generally attributed to geographical or technical constraints. Climate has also been considered a key factor, particularly the 8.2 ka event, which is often linked to the spread of farming and herding from the Fertile Crescent into neighbouring regions. This event is believed to have triggered a transition from hunter-gathering to agropastoralism. However, its direct impact on the South Caucasus remains debated. Recent palaeoenvironmental studies indicate that the region underwent a major ecological transformation around 8200 cal BP, coinciding with the Early–Middle Holocene Transition. This period was characterised by increased precipitation. As a result, vegetation expanded, particularly grasslands dominated by Poaceae, which provided favourable conditions for livestock grazing and fodder production. Unlike the abrupt 8.2 ka event, this longer-term shift significantly reshaped the environment of the South Caucasus. This review argues that it was not the short-term climatic anomaly but rather the sustained increase in precipitation during the Early–Middle Holocene Transition that created the conditions necessary for the emergence of the Caucasian Neolithic. The expansion of vegetation and natural resources provided an ecological basis for the gradual adoption of agriculture and herding, ultimately leading to the development of an agropastoral system in the region
Tail-Aware Density Forecasting of Locally Explosive Time Series: A Neural Network Approach: CRED WORKING PAPER 2026-02
No full textThis paper proposes a Mixture Density Network specifically designed for forecasting time series that exhibit locally explosive behavior. By incorporating skewed t-distributions as mixture components, our approach offers enhanced flexibility in capturing the skewed, heavy-tailed, and potentially multimodal nature of predictive densities associated with bubble dynamics modeled by mixed causal-noncausal ARMA processes. In addition, we implement an adaptive weighting scheme that emphasizes tail observations during training and hence leads to accurate density estimation in the extreme regions most relevant for financial applications. Equally important, once trained, the MDN produces near-instantaneous density forecasts. Through extensive Monte Carlo simulations and two empirical applications, on the natural gas price and inflation, we show that the proposed MDN-based framework delivers superior forecasting performance relative to existing approaches