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On Runs Tests for Directional Data and Their Local and Asymptotic Optimality Properties
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#Museumchallenges : La copie créative d'oeuvres d'art en régime numérique
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RNA Triplet Repeats: Improved Algorithms for Structure Prediction and Interactions
No full textExtended version of WABI 2024, under review at Algorithms for Molecular BiologyInternational audienceRNAs composed of Triplet Repeats (TR) have recently attracted much attention in the field of synthetic biology. We study the mimimum free energy (MFE) secondary structures of such RNAs and give improved algorithms to compute the MFE and the partition function. Furthermore, we study the interaction of multiple RNAs and design a new algorithm for computing MFE and partition function for RNA-RNA interactions, improving the previously known factorial running time to exponential. In the case of TR, we show computational hardness but still obtain a parameterized algorithm. Finally, we propose a polynomial-time algorithm for computing interactions from a base set of RNA strands and conduct experiments on the interaction of TR based on this algorithm. For instance, we study the probability that a base pair is formed between two strands with the same triplet pattern, allowing an assessment of a notion of orthogonality between TR
Improved branching-fraction measurements of decays and first observation of
No full textInternational audienceThis paper presents a study of the charmless three-body decays (where ), using a sample of collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9\mbox{\,fb}^{-1}. The decay is observed for the first time, and the following ratios of branching fractions are measured: \begin{alignat*}{6} &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.578 &&\pm 0.007 &&\pm 0.017\,, &\frac{{\cal B}(B^0 \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.1363 &&\pm 0.0035 &&\pm 0.0051\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} π^+π^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.269 &&\pm 0.011 &&\pm 0.015 && \pm 0.008\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^+ K^-)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 0.0303 &&\pm 0.0041 &&\pm 0.0025 && \pm 0.0009\,, &\frac{{\cal B}(B^0_s \to K^0_{\mathrm{S}} K^\pmπ^\mp)}{{\cal B}(B^0 \to K^0_{\mathrm{S}} π^+π^-)} &&= 1.818 &&\pm 0.021 &&\pm 0.031 && \pm 0.056\,, \end{alignat*} where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the and mesons, respectively
Platform Information Provision: Evidence from an Online Auction Platform
No full textDigital platforms have reduced search costs, fostering niche product markets. However, these markets often suffer from limited and asymmetric information due to a lack of consumer feedback, risking market failure. This paper examines Catawiki's solution, where over 240 experts provide value estimates for rare collectibles being auctioned on a digital platform. Using data from 57,000 listings, we analyze the impact of these estimates on final prices and seller behavior. By leveraging both minimum and maximum expert estimates, we isolate the effect of increasing the maximum estimate while holding the minimum estimate fixed. Our findings indicate that higher expert estimates increase final bidden prices, suggesting buyer trust. Sellers also adjust their behavior by setting fewer reserve prices for items with high estimates, leading to more bids. Despite potential conflicts of interest stemming from the platform's dual role as matchmaker and advisor, our results show that expert estimates are influential even when potentially overinflated. This study underscores the critical role of platform-provided information in enhancing market efficiency
The second H.E.S.S. gamma-ray burst catalogue: 15 years of observations with the H.E.S.S. telescopes
No full textInternational audienceRecent observational efforts using imaging atmospheric Cherenkov telescopes (IACTs) have led to firm detections of very-high-energy (VHE) signals from bright gamma-ray bursts (GRBs), often at moderate redshifts. This work presents 15 years of H.E.S.S. GRB observations and examines their implications through population comparisons and selected modelling cases. GRBs are a key science target of the High Energy Stereoscopic System (H.E.S.S.). With a low-energy threshold (100 GeV) and rapid repointing capabilities, H.E.S.S. can begin follow-up observations within tens of seconds after a GRB trigger, covering the late prompt or early afterglow phases. We report GRB follow-up observations with H.E.S.S. from 2004 to 2019, which resulted in no significant VHE signals (aside from the detections of GRB~180720B and GRB~190829A). The resulting upper limits comprise the largest set available for GRBs at VHE. A subset of bursts with favourable conditions were selected for X-ray analysis and emission modelling. Population studies were performed to compare detected and non-detected GRBs. The results indicate that VHE-detected GRBs are not a distinct population, but tend to feature luminous X-ray emission and favourable redshift and observing conditions. This highlights the potential of next-generation IACTs such as the Cherenkov Telescope Array Observatory (CTAO), whose lower energy threshold will enhance the detection of fainter and more distant GRBs
Un plongement renversant l'ordre des degrés de Turing dans les degrés d'Arthur-Nimué-Merlin
No full textThe Arthur-Nimue-Merlin degrees are a generalization of the Turing degrees introduced by Kihara as a tangible description of the partially ordered set of Lawvere-Tierney topologies on the effective topos (equivalently, subtoposes of the effective topos). They are defined in terms of a three-player game that introduces both angelic and demonic nondeterminism into oracle queries. We construct an order embedding of the Turing degrees with their order reversed into the Arthur-Nimue-Merlin degrees, whose image we call the "co-Turing degrees"; we then study the order relationship of these co-Turing degrees with the (naturally embedded) Turing degrees within the Arthur-Nimue-Merlin degrees.Les degrés d'Arthur-Nimué-Merlin sont une généralisation des degrés de Turing introduite par Kihara pour donner une description tangible de l'ensemble partiellement ordonné des topologies de Lawvere-Tierney sur le topos effectif (de façon équivalente, des sous-topos du topos effectif). Ils sont définis en termes d'un jeu à trois joueurs qui introduit à la fois un non-déterminisme angélique et démoniaque dans les requêtes à l'oracle. Nous construisons un plongement comme ensemble partiellement ordonné des degrés de Turing avec leur ordre renversé dans les degrés d'Arthur-Nimué-Merlin, dont nous appelons l'image les «degrés de co-Turing»; nous étudions aussi les relations d'ordre de ces degrés de co-Turing avec les degrés de Turing (naturellement plongés) dans les degrés d'Arthur-Nimué-Merlin.</div
Kink-bands as drivers of hygroscopic response in flax fibres: A multi-scale investigation
No full textInternational audienceFlax fibres are increasingly explored as sustainable reinforcements in high-performance composites due to their remarkable stiffness and strength. However, their hygroscopic nature and complex hierarchical organisation pose challenges for dimensional stability and long-term durability. Among the intrinsic microstructural heterogeneities, kink-bands, localised deformations associated with cellulose misalignment and increased porosity, may affect water uptake and swelling. Despite their potential impact, the effect of kink-bands on water sorption and moisture-induced structural changes has not been directly investigated. This study investigates the influence of kink-band density on the hygroscopic behaviour of flax fibres using an integrated multi-scale approach combining Dynamic Vapour Sorption (DVS), Environmental Scanning Electron Microscopy (ESEM), X-ray microtomography, and solid-state Nuclear Magnetic Resonance (ss-NMR). Three flax fibre batches with distinct kink-band frequencies were prepared through controlled mechanical processing. DVS results revealed no significant difference in overall water sorption capacity between batches, indicating that kink-bands do not markedly affect global hygroscopicity. However, ESEM and X-ray tomography analyses highlighted heterogeneous swelling behaviour at the bundle and fibre scales, with kink-band regions exhibiting lower expansion than intact zones, suggesting a compensating effect of internal pores on local deformation. Solid-state NMR analyses revealed that, although fibril dimensions and overall crystallinity were unchanged, fibres with higher kink-band content exhibited increased water accessibility and subtle nanoscale polymer reorganisation. This suggests that kink-bands promote local water penetration and interactions with surrounding non-cellulosic components, without altering overall bulk hygroscopicity. Together, these results indicate that kink-bands modulate local moisture dynamics, providing new insights into the structural–functional relationships governing flax fibre behaviour in humid environments. They are also relevant for natural fibre composites, as understanding how kink-bands influence local moisture dynamics can inform predictions of dimensional stability, fibre–matrix interactions, and long-term durability