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Coalescence in small generations for the diffusive randomly biased walk on Galton-Watson trees
No full textInternational audienceWe investigate the range R_T of the diffusive biased walk X on a Galton-Watson tree T in random environment, that is to say the sub-tree of T of all distinct vertices visited by this walk up to the time T. We study the volume of the range with constraints and more precisely the number of k-tuples (k ≥ 2) of distinct vertices in this sub-tree, in small generations and satisfying an hereditary condition. A special attention is paid to the vertices visited during distinct excursions of X above the root of the Galton-Watson tree as we observe they give the major contribution to this range. As an application, we study the genealogy of k ≥ 2 distinct vertices of the tree R_T picked uniformly from those in small generations. It turns out that two or more vertices among them share a common ancestor for the last time in the remote past. We also point out an hereditary character in their genealogical tree due to the random environment
Probability-graphons: Limits of large dense weighted graphs
No full textInternational audienceWe introduce probability-graphons which are probability kernels that generalize graphons to the case of weighted graphs. Probability-graphons appear as the limit objects to study sequences of large weighted graphs whose distribution of subgraph sampling converge. The edge-weights are taken from a general Polish space, which also covers the case of decorated graphs. Here, graphs can be either directed or undirected. Starting from a distance inducing the weak topology on measures, we define a cut distance on probability-graphons, making it a Polish space, and study the properties of this cut distance. In particular, we exhibit a tightness criterion for probability-graphons related to relative compactness in the cut distance. We also prove that under some conditions on the distance , which are satisfied for some well-know distances like the Prohorov distance, and the Fortet-Mourier and Kantorovitch-Rubinstein norms, the topology induced by the cut distance on the spaceof probability-graphons is independent from the choice of . Eventually, we prove that this topology coincides with the topology induced by the convergence in distribution of the sampled subgraphs
Social insects behind the microgranular structure of Ferralsols: Consequences for their physical fertility when cultivated
No full textInternational audienceIt was long accepted that the microgranular structure which is characteristic of many Ferralsols was mainly related to physico-chemical processes and to their mineralogical composition. It now appears, however, that this microgranular structure originates from the burrowing activity of termites and ants. Given its importance for the physical properties of Ferralsols, it will be necessary to study the different termite and ant species responsible for this microgranular structure and the characteristics of the burrowing activity associated with species. This is a major point to better understand the possible long-term consequences of agriculture on Ferralsol properties because it strongly affects soil faunal biodiversity Most yellow or red soils found in the South American, African and Asian tropics are classified as Ferralsols in the World Reference Base (IUSS Working Group WRB, 2015). They correspond to Latosols in the Brazilian taxonomy (Embrapa, 2006), mainly to Ferrallisols in the Genetic Soil Classification of China and to Ferrosols in the Chinese Soil Taxonomy (Shi et al., 2004 and 2006), and to Oxisols or Ultisols in the Soil Taxonomy (Soil Survey Staff, 2006). They represent a large land surface area with 750 million hectares worldwide (IUSS Working Group WRB, 2015), which corresponds in the tropics to about 14 % of the land surface area. They result from a long sequence of deep weathering under conditions that in most cases have prevailed for at least several tens of thousands of years (van Wambeke, 1992; Scholten et al., 1997; Schaefer, 2001). In such soils, easily weatherable primary minerals such as feldspar and micas have disappeared, resulting in a fine material essentially made up of kaolinite and of iron and aluminium sesquioxides (Pédro, 1968; Melfi and Pédro, 1977, 1978). As a result, Ferralsols are characterized by extremely low native chemical fertility, resulting from very low nutrient reserves, low pH, high phosphorus retention by oxide minerals, and low cation exchange capacity (Yu, 1997; Kögel-Knabner and Amelung, 2014). On the other hand, most Ferralsols are characterized by a well-developed microgranular structure and consequently exhibit high physical fertility resulting from high porosity, low resistance to root penetration, high infiltration rate and high available water retention (Stoop
The medieval chisels from Castel-Minier, France (14th-15th centuries), an experimental and computational approach.
No full textInternational audienceCastel-Minier was a polymetallic production site settled in the Viscounty of Couserans in French Pyrenees and isolated in the valley four kilometers from Aulus-les-Bains village. From the XIIIth to the XVth century, silver, lead and copper were produced with ore extracted on-site and in closed valleys. Besides, by necessity and opportunism, the metallurgists also produced iron for export and on-site use, using ore extracted from the Rancié iron mine. The archaeological excavations carried out over the last twenty years have brought to light a series of tools associated with mining, including 47 handheld chisels (complete or fragmentary) and 2 scrap bars. These chisels represent rare specimens in Western Europe for this period and are the only ones discovered in the French Pyrenees.We previously highlighted the durability and variability of the manufacturing methods of chisels, whether the body or the tip (Méaudre et al., ARN, 28: 69–83, 2023). To continue our discussion, we choose an experimental approach carried out on the "Arts du feu" experimental archaeology platform in Melle and at the "Forges de Pyrene", an ecomuseum with a hydraulic hammer. The purpose is to produce metal from archaeological ore and then to shape type C tools. For this initial approach, the blacksmiths worked without viewing the metallographic analyses, referring only to the metrological data. The aim is to observe the shaping process (welding, shaping the eye ... ) and to collect their feedback
A case of the circular economy: Excavating up and experimenting with the ancient production of manganese iron
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Thermal properties of some African tropical woods: Okoume, Bilinga, Movingui, Ozigo, and Nove and their potential in bioenergy utilisation
No full textInternational audienceTropical wood biomass’s thermal properties, influenced by density, porosity, moisture content, and temperature, require precise characterisation for optimal biofuel production and thermal-based applications. In that regard, the thermal properties such as thermal conductivity, thermal diffusivity, and specific heat capacity of Okoume, Bilinga, Movingui, Ozigo, and Nove wood species were investigated using a hot-disk thermal constant analyser. Ozigo has the highest porosity level of 0.82, attributed to its lower bulk density, while Movingui’s porosity is 0.45. The study found that increasing relative humidity significantly affected the thermal conductivity of wood species, with Okoume and Ozigo showing a 69% and 58% increase, respectively. In contrast, Bilinga and Movingui showed a slight decrease. When the samples were oven-dried at 60 °C, there was a significant difference in the thermal diffusivity values for all the wood samples, excluding Movingui with 1.13 mm2/s. After 103 °C oven-drying, the thermal diffusivities of Bilinga, Movingui, and Nove increased with increasing moisture content in the wood. Ozigo and Bilinga had the highest specific heat capacity (Cp) of 1656 J/kg/K and 1440 J/kg/K, respectively. Ozigo’s higher Cp suggests potentially superior insulation and fire resistance compared to the others. Movingui had the highest thermal conductivity (k) of 0.3050 W/mK, followed by Nove at 0.2750 W/mK, and Okoume was the lowest at 0.1752 W/(m. K), indicating less effectiveness in heat transmission. Movingui exhibited the highest thermal diffusivities at both oven-dry temperatures. The study reveals that the high thermal conductivity and diffusivity of Movingui, Ozigo, Okoume, and Nove can enhance thermochemical conversion processes. In contrast, moderate thermal properties could be used as complementary feedstocks in blended biofuel systems, enhancing efficiency and sustainability. Future research should examine the biochemical composition of these wood species to assess their efficiency in biofuel conversion processes, optimise their utilisation as feedstocks, and evaluate their environmental impacts for sustainability and economic viability
Signatures of local acceleration of quark-gluon plasma in the dilepton production
No full textInternational audienceDilepton production is one of the key probes of the Quark-Gluon Plasma (QGP) that encodes the imaginary part of the electromagnetic current-current correlator. We investigate the effect of local acceleration on the dilepton production by treating acceleration as a small perturbation. Using the thermal Dirac propagator in an accelerated frame within the imaginary-time formalism, we compute the photon polarization tensor and extract its imaginary part. Comparison with the zero-acceleration case isolates the distinct contributions of acceleration to dilepton yields
Confidence-Driven Deep Learning Framework for Early Detection of Knee Osteoarthritis
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Attitude-behavior gap in sustainable products in the fashion industry
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Prospectivity Mapping of Tungsten–Tin Deposits Integrating Multiple Geological, Geophysical, and Geochemical Datasets with the DBA–RF Method: Application to the Puy-les-Vignes/Saint-Goussaud District (Massif Central, France)
No full textInternational audienceThis paper evaluates the impact of integrating various geological, geophysical, and geochemical datasets into mineral prospectivity mapping for undiscovered tungsten (W) and tin (Sn) deposits, using the Variscan French Massif Central (FMC) as a case study. Previous studies on the prospectivity of W–Sn deposits in Variscan terranes have primarily focused on geological and geochemical datasets, rarely integrating multi-method geophysical data. The FMC, located in the internal zone of the Western European Variscan belt, is a historic mining region known to host numerous granite-related W–Sn deposits. However, a comprehensive assessment is required to identify new prospective areas, including possible targets at depth. We applied a data-driven predictive approach using the disk-based association method coupled with random forest classification (DBA–RF) to predict the likelihood of undiscovered W–Sn deposits in the Puy-les-Vignes/Saint-Goussaud district (approximately 800 km2) located in the northern FMC. Favorable criteria from geological maps (lithostratigraphy, distance to faults, and known mineral occurrences) were analyzed, along with multiple datasets from airborne and ground geophysics (gravimetry, magnetics, electromagnetics, and gamma spectrometry), and stream sediment geochemistry (As, B, Be, Cu, Sn, and W concentration maps). The resulting prospectivity maps highlight several zones with a total area of 67 km2 for W and 33 km2 for Sn, which represent 8.3% and 4.1% of the study area, respectively. These zones coincide with known mineral occurrences, thereby validating the predictive model’s effectiveness. Additionally, new prospective zones extending well beyond (>2 km) the known mineral occurrences were identified, suggesting potential for discovery. This research demonstrates the value of using the DBA–RF method to integrate multiple geological, geophysical, and geochemical datasets in former mining districts where W–Sn occurrences are already known. The DBA–RF appears as a promising method for making the most of datasets acquired through historical and recent exploration surveys, and for enhancing mineral exploration programs by efficiently reducing the size of prospective areas. This methodological approach can serve as a robust framework in other prospective regions as a regional targeting tool to search for W–Sn deposits spatially associated with buried granitic intrusion