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Concurrent heat waves and their linkage to large-scale meridional heat transports through planetary-scale waves
No full textInternational audienceWe investigate concurrent heatwaves across the Northern Hemisphere through the linkage between extremes in Meridional Heat Transport (MHT) and in hemispheric land surface temperature (LST). MHT provides fundamental insight on how large-scale thermodynamics links to atmospheric large-scale dynamics, especially through the action of the eddy planetary-scale circulation in the mid-latitudes. The phase and amplitude of these waves can in fact favor the simultaneous occurrence of heatwaves in remote regions, but how this relates to the amount of heat carried by them has not yet been discussed. In this work, we find that the conditional occurrence of extremely weak MHT and extremely warm hemispheric LSTs is significantly more frequent than other conditional occurrences, both in Summer (JJA) and in Winter (DJF). We argue that the combination of extremely weak, in some cases equatorward, MHTs and warm LSTs in JJA are associated with the reversal of the MHT contribution by zonal wavenumber 3, which is in turn associated with the frequency of atmospheric blocking in western Eurasia and the intensity of blockings and jet stream over the Northwestern Pacific. In DJF, the weak, albeit never equatorward, MHT – warm LST events are characterized by a suppression of the climatologically dominant wavenumber 2, which weakens the overall MHT. The flow is anomalously zonal across much of North America and Eurasia, with reduced frequency of atmospheric blockings and downstream displacement of the jet stream, advecting moist and mild air eastward into the continents. Overall, such dynamical pattern correspond to abnormally warm and widespread temperatures in North America, Eastern Europe, and China. The conditional occurrence of extremely weak MHTs and warm hemispheric LSTs is found to be related to between 30 % and over 40 % of extremely warm hemispheric LST days in both seasons
Combination of ATLAS and CMS searches for Higgs boson pair production at TeV
No full textInternational audienceThis Letter presents a combination of searches for Higgs boson pair (HH) production performed by the ATLAS and CMS Collaborations using proton-proton collision data sets recorded at TeV during the Large Hadron Collider Run 2, corresponding to integrated luminosities ranging between 126 and 140 . The upper limit at the 95% confidence level on the total HH signal strength, defined as the ratio of the measured cross section to the SM prediction, corresponds to 2.5, with an expected value of 1.7 (2.8) assuming the absence (presence) of the standard model (SM) HH signal. The strength of the HH signal is measured to be relative to the SM prediction. The observed significance is found to be 1.1 standard deviations whereas 1.3 are expected for the SM HH signal. Constraints are set on the Higgs boson trilinear self-coupling and on the couplings of two Higgs bosons to two vector bosons, both normalized to the SM predictions and denoted as and , respectively. The observed individual constraints at the 95% confidence level are and , while the expected constraints assuming the presence of the SM HH signal are and
TRAKNN: Efficient Trajectory Aware Spatiotemporal kNN for Rare Meteorological Trajectory Detection
No full textExtreme weather events, such as windstorms and heatwaves, are driven by persistent atmospheric circulation patterns that evolve over several consecutive days. While traditional circulation-based studies often focus on instantaneous atmospheric states, capturing the temporal evolution, or trajectory, of these spatial fields is essential for characterizing rare and potentially impactful atmospheric behavior. However, performing an exhaustive similarity search on multi-decadal, continental-scale gridded datasets presents significant computational and memory challenges. In this paper, we propose TRAKNN (TRajectory Aware KNN), a fully unsupervised and data-agnostic framework for detecting geometrically rare short trajectories in spatio-temporal data with an exact kNN approach. TRAKNN leverages a recurrence-based algorithm that decouples computational complexity from trajectory length and efficient batch operations, maximizing computational intensity. These optimizations enable exhaustive analysis on standard workstations, either on CPU or on GPU.We evaluate our approach on 75 years of daily European sea-level pressure data. Our results illustrate that rare trajectories identified by TRAKNN correspond to physically coherent atmospheric anomalies and align with independent extreme-event databases
Optimizing fertilizer use for sustainable crops with Agrivoltaics in Mediterranean climates
No full textInternational audienceAgrivoltaics (AV), a fast-growing technology integrating photovoltaic panels with agriculture, can offer the dual benefit of clean energy and crop yield gains, especially in the Mediterranean basin. However, its interaction with fertilizers -key for crops productivity but major contributors to environmental degradation- remains unexplored. This study applies a regional AV model over the Iberian Peninsula (1991–2020) using the ORCHIDEE land surface model to assess AV under varying synthetic fertilizers scenarios. We examine its effects on crop productivity, nitrogen and water use efficiency, and fertilizer-induced greenhouse gas emissions. Results show that AV can enhance productivity and reduce environmental costs, particularly in water-scarce conditions. However, trade-offs arise at critical fertilizer levels varying by crop type and climate. A region-specific strategy that considers climate, crop responses, and environmental impacts is essential to optimize AV sustainability potential
Stamps for Pattern Applications for DIC or Markers Tracking
No full textInternational audienceDigital image correlation requires a surface pattern to monitor deformation, and while spray paint is widely used for this purpose, it suffers from drawbacks such as limited reproducibility and poor control over speckle characteristics. This study aims to develop stamps to apply patterns with greater consistency and control, and to demonstrate that such pattern speckle performs comparably to traditional spray paint speckle. For that purpose, speckles were applied to polymer surfaces using two techniques, ink stamping of circular dots and conventional spray painting. Their quality was first evaluated through numerical assessments, followed by digital image correlation analyses under both small and large strains. Small-strain behavior was studied using synthetically deformed images based on sinusoidal displacements, while large-strain performance was assessed via uniaxial stretching of a holed elastomer sample. Both speckle application methods yielded similar results in terms of image correlation accuracy and robustness across deformation scales proving that the produced stamps offer a viable alternative to spray paint, providing significant advantages in terms of control, reproducibility, and customizability of the speckle pattern, without compromising performance
Magnetohydrodynamic thermal rotating shallow water systems
No full textInternational audienceWe introduce the Magnetohydrodynamic Thermal Rotating Shallow Water (MTRSW) model as a framework to study magnetized rotating fluids influenced by thermal gradients and stratification. The model is derived from the full magnetohydrodynamic equations incorporating Coriolis forces, magnetic induction, and thermal effects. To extend its applicability to small-scale magnetic dynamics, Hall MTRSW corrections are included.The proposed MTRSW systems are particularly applicable for thin, magnetized, rotating stratified layers, such as the solar tachocline, neutron star oceans, and accretion disks with shallow vertical extent. Numerical simulations confirm that thermal and magnetic coupling substantially impacts the stability and evolution of vortices, with nontrivial temperature gradients fostering prolonged instabilities.</div
Shifting and Persisting Neighborhood Hierarchies: Immigrant Influx and the Gentrification of Black Neighborhoods in the Twenty-first Century
No full textInternational audienceIn recent decades, U.S. cities have experienced an increasing prevalence of gentrification, especially in Black urban neighborhoods, and the growth and dispersal of new immigrants. Although scholarship suggests links between immigrant settlement and gentrification, few quantitative studies examine this relationship and consider differences across neighborhood ethnoracial contexts and city-level contexts of immigrant reception. This study draws on U.S. Census and American Community Survey data from 1990 to 2019 to examine this relationship across the United States. We find that higher shares of recent immigrants lower the likelihood that neighborhoods gentrify, except in Black neighborhoods. In Black neighborhoods, the share of recent immigrants is positively associated with gentrification, particularly since the 2000s and in newer immigrant destination cities. Findings suggest that new immigrants serve as pioneers of gentrification and buffers in Black neighborhoods but that this pathway is contingent on the broader context of immigrant reception
Exceptions in the Algorithmic Age: Evidence from the Case of Tenant Screening
No full textInternational audienceOrganizations have long used records of individuals’ pasts to assess risk, and increasingly they do so with algorithms. This may seem to eliminate leniency for problematic pasts, yet scholars note algorithms do not erase discretion, only relocate it. Extending this insight, we offer a theory of how organizations continue to make exceptions, through rules rather than in opposition to them. We leverage the case of tenant screening, where gatekeepers consider unpaid debts, criminal records, and eviction histories with both rules-based algorithms and traditional judgment. Interviews with landlords, property managers, and real estate and tenant screening executives reveal that, to decide which records to overlook, gatekeepers of both sorts rely on narrative and analogy. Yet with algorithms, exceptions must be codified in advance and interoperable with records’ classification systems. The result is that only applicants with culturally salient and institutionally legible circumstances benefit. We discuss implications for theories of algorithms, exceptions, and inequality
What is AI Doing to Job Quality? Platformization, Fissured Workplaces and Dispersion
No full textInternational audienceDebates about AI and labour are focused on job losses, yet give little consideration to how this technology affects actual working experiences. This chapter examines the impact of AI on job quality through its use and through the invisibilized labour that sustains it, using the framework of the European Job Quality Index. AI deployment often intensifies work, increases surveillance and limits worker autonomy, while its production relies on a highly stratified global workforce of engineers and hidden data workers. These arrangements have resulted in companies outsourcing functions while maintaining control over production in what is known as a ‘fissured workplace’. Furthermore, AI-driven workplaces are creating a ‘regime of dispersion’ where workers juggle numerous fragmented tasks. The chapter explores these phenomena, correlated as they are in terms of AI and job quality, while identifying the research agenda and policy implications which would safeguard all users in AI’s global supply chains
Laissés-pour-compte : les effets locaux de la désindustrialisation en France
No full textNotes IPP n°123Comment la désindustrialisation a-t-elle remodelé la vie économique et sociale locale en France? Cette note montre que les communes ayant connu les plus fortes baisses de l’emploi industriel ont fait face à un chômage durablement plus élevé, à des revenus plus faibles, à une croissance démographique plus lente et à un isolement social accru. La désindustrialisation a également réduit la participation civique, en diminuant la participation électorale et le soutien à l’intégration européenne. Elle a aussi augmenté la part des voix en faveur de l’extrême droite. Nous montrons en outre que ces territoires se distinguent nettement dans la vie communautaire contemporaine : les communes les plus exposées au déclin industriel disposent aujourd’hui de moins d’équipements de proximité – tels que des commerces, services de santé et équipements culturels – et voient émerger moins d’associations. Ensemble, ces résultats documentent comment le recul de l’industrie a transformé non seulement les économies locales, mais aussi le tissu social et civique des communautés françaises