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Caprine dairy exploitation on the Iranian Plateau from the seventh millennium BC
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Étude géoarchéologique du système d’irrigation de Sarazm (IVe-IIIe millénaires av. n. è.). De la gestion de l’eau à la fabrique du paysage fluvial dans la moyenne vallée semi-aride et tectoniquement active du Zeravshan (Tadjikistan, Asie centrale).
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Parcourir le fonds Q28: les catalogues des cabinets de lecture dans les collections de la Bibliothèque nationale de France (BnF) 1764-1830
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Idealized modeling of stratospheric aerosol injection deployment scenarios with two non-cooperative actors
No full textInternational audienceWe investigate solar radiation management scenarios of two non-cooperative actors deploying stratospheric aerosol injection (SAI). We perform the idealized experiments with a four-box Energy Balance Model capable of predicting hemispheric temperatures and monsoon precipitation, coupled to PI-controllers. The controller models the behaviour of an actor that deploys SAI at a certain location in order to reach a certain climatic goal, such as an average temperature or a monsoon precipitation target. The goal of this work is to assess through case studies of idealized scenarios what could go wrong in a non-cooperative deployment. Continuous non-cooperative deployment by two actors provides the expected climate result in most of the cases studied, but it can lead to the actors not fully reaching their targets. Intermittent deployment, related to policy instability in our scenario design, can lead to a free-riding situation, or missing the climatic targets due to temperature oscillations induced by the intermittency. These results of our case studies point out the need for exploring more politically plausible scenarios in SRM modelling studies. More complex experiments, including multi-target controllers and coalitions of actors, will be possible with a future version of the mode
Pollinators in blackcurrant orchards: Spatio-temporal environmental effects and no evidence of competition with co-flowering resources
No full textAgricultural intensification is threatening pollinators and associated ecosystem services. Flower strips and spontaneous floral cover are commonly recommended to support pollinators, but farmers often hesitate to adopt them, fearing competition with their crops. Here, we studied nine blackcurrant orchards in Burgundy, France, differing in local floral resources and surrounding landscape composition. We thus investigated (i) the potential competition for pollinators between blackcurrant flowers and flowers in adjacent inter-rows, and (ii) the effects of local and landscape factors through time on the abundance of five pollinator morpho-groups: Bombus spp., Apis mellifera, large bees, small bees, and hoverflies. We conducted transects in orchards at three different periods in spring to quantify the abundance of local flowers and pollinators. We characterised the landscape composition around sites within a 100 m and 500 m radii. We showed that in each morpho-group, pollinator abundance in blackcurrant bushes increased with pollinators in adjacent inter-rows and was unaffected by flower abundance there, suggesting an absence of competition. Pollinator morpho-groups responded differently to environmental factors, with variations throughout spring. Small bees were the most negatively affected by the distance from orchard edge, while hoverfly abundance highly increased with the number of flowers at the end of spring. Floral resources in the inter-row could support pollinators in spring, particularly hoverflies and poor dispersers like small bees. Given the variability in pollinator traits and rapid environmental changes, future research should focus on functional groups and fine-scale spatio-temporal analysis to better understand environmental impacts on pollinators and effectively guide conservation efforts
Living on the edge: Pleistocene ice‐free refugia and collared lemming ( Dicrostonyx sp.) in the North American High Arctic
No full textInternational audienceCollared lemmings (genus Dicrostonyx ) are an emblematic group of Arctic‐tundra mammalian communities, comprising six different species in North America. As other northern fauna, most of their diversity is impacted by Pleistocene glacial–interglacial cycles. While D. hudsonius and D. richardsoni have a restricted distribution area on both sides of the Hudson Bay, D. groenlandicus is widespread in all Nearctic northernmost regions, from Alaska and Canadian mainland to the High Arctic Archipelago and Greenland, occupying a highly fragmented area. Using extensive data, this paper investigates the morphological variability of the molar of Nearctic Dicrostonyx using geometric morphometrics. Our results show weak interspecific differences among Nearctic Dicrostonyx , while demonstrating the existence of a clear geographical structure: a north–south gradient that structures collared lemming's phenotype, surpassing interspecific differences. The possible causes of such patterns are explored, whether they are environmental (e.g. due to local to regional climatic conditions) or phylogeographic (e.g. isolation of the populations during the glacial periods) using ERA5‐Land reconstruction climatic data, and a reconstruction of the Laurentide Ice Sheet extent with isometric variations. The peculiar status of several populations, including Greenland and Victoria Island specimens, can be linked with their survival and isolation in Pleistocene ice‐free refugia in the High Arctic in agreement with both genetic and morphological signals. We argue that studying present‐day morphological variability can provide meaningful information on the Quaternary biogeography of modern species
Directional Search for Persistent Gravitational Waves: Results from the First Part of LIGO-Virgo-KAGRA's Fourth Observing Run
No full textInternational audienceThe angular distribution of gravitational-wave power from persistent sources may exhibit anisotropies arising from the large-scale structure of the Universe. This motivates directional searches for astrophysical and cosmological gravitational-wave backgrounds, as well as continuous-wave emitters. We present results of such a search using data from the first observing run through the first portion of the fourth observing run of the LIGO-Virgo-KAGRA Collaborations. We apply gravitational-wave radiometer techniques to generate skymaps and search for both narrowband and broadband persistent gravitational-wave sources. Additionally, we use spherical harmonic decomposition to probe spatially extended sources. No evidence of persistent gravitational-wave signals is found, and we set the most stringent constraints to date on such emissions. For narrowband point sources, our sensitivity estimate to effective strain amplitude lies in the range across all sky and frequency range Hz. For targeted sources -- Scorpius X-1, SN 1987A, the Galactic Center, Terzan 5, and NGC 6397 -- we constrain the strain amplitude with best limits ranging from to . For persistent broadband sources, we constrain the gravitational-wave flux F_{α, \hat{n}}^{95\%, \mathrm{UL}}(25\, \mathrm{Hz}) < (0.008 - 5.5) \times 10^{-8}\, \mathrm{erg\, cm^{-2}\, s^{-1}\, Hz^{-1}}, depending on the sky direction and spectral index . Finally, for extended sources, we place upper limits on the strain angular power spectrum C_\ell^{1/2} < (0.63 - 17) \times 10^{-10} \,\mathrm{sr}^{-1}
Ecrire le terrain end Asie du Sud: vers un "tournant alternatif"?
No full textL’objet de ce dossier, au cœur d’une revue précisément dédiée à une aire culturelle –et donc, par nature, interdisciplinaire –est d’interroger le «tournant alternatif» des SHS au prisme des travaux sur l’Asie du Sud, et en particulier de la pratique et de la restitution du terrain: quels types de modalités alternatives sont mobilisés et produits dans la recherche sur l’Asie du Sud, et à quelles fins? Qu’apportent-elles aux chercheur.es, aux lecteurs et lectrices, aux acteurs et actrices du terrain? Les écritures alternatives témoignent-elles ou non d’une spécificité (culturelle, sociale, religieuse, politique) du terrain sud-asiatique, imposant là une spécificité dans la restitution de la recherche
Characterization and modeling of continuous dynamic recrystallization (CDRX): Application to 2139 aluminum alloy
No full textInternational audienceControlling microstructure is a key factor in hot metal forming as it affects the performance of metallic materials. In high stacking-fault-energy materials, including aluminum alloys, continuous dynamic recrystallization (CDRX) drives microstructural evolution. In this study, hot compression tests were conducted on the AA2139 alloy across a wide range of thermomechanical conditions to (i) characterize the CDRX mechanism and (ii) generate experimental data for model calibration. Microstructural investigations were conducted to examine the development of grain and subgrain structures, and the evolution of disorientation distributions. Evidence of CDRX was observed through the formation of low-angle grain boundaries (LAGBs), their progressive increase in disorientation, and their transformation into high-angle grain boundaries (HAGBs), both in grain interiors and near original grain boundaries. Increasing strain promoted the progressive disorientation of LAGBs. Strain rate and temperature strongly influenced subgrain size, LAGB density, and dynamic recovery. Based on these results, a physically based CDRX model was developed by extending the work of Gourdet and Montheillet. The proposed improvements introduce the contribution of LAGB energy and disorientation angle to the subgrain-rotation law, a crystallite-size-dependent rate of LAGB creation through a refined physical description of the parameter , and the incorporation of self-heating effects during deformation. Together, these developments significantly enhance the physical consistency of the model. The overall experimental trends were reproduced, including the decrease in crystallite size and the increase in LAGB density at higher strain rates and lower temperatures, as well as the higher mean LAGB disorientation angle observed at lower strain rates. In addition, the model captures the macroscopic flow stress under various thermomechanical conditions