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Diversification Through Candidate Sampling for a Non-iterated Lin-Kernighan-Helsgaun Algorithm
No full textInternational audienceThe Traveling Salesman Problem (TSP) is a famous NP-hard problem that has been extensively studied. The heuristic first introduced by Lin and Kernighan, is considered one of the most effective methods for solving the TSP and has undergone numerous modifications and extensions. This study examines the fundamental version of Helsgaun's adjustments (LKH) due to the significant improvements it has brought to the heuristic. A key adjustment implemented is the disposition of a candidate set to each city using the α-measure, recognized for its efficacy in approximating the lower bound of the tour cost derived from the minimum 1-tree. To diversify and speed up the process, Helsgaun has applied two main techniques: judicious initial tour, dynamic candidate set reordering.In this paper, we propose a candidate selection strategy aimed at simplifying the diversification process. This approach employs a randomized sampling selection strategy integrated directly into the k-opt search. Compared with LKH-1.3 limited to 2-opt operator, promising results are shown when the noisy move Gain23 is disabled, and comparable results if it is not. The goal of this work is to uphold a high level of quality while making the overall algorithm simpler.</div
Géographie du canyoning en France via les traces géonumériques
No full textInternational audienceLes usages du numérique ont fortement transformé les loisirs sportifs de nature en agissant sur les modalités de pratique en tant que dispositifs d’intermédiation entre l’individu et son environnement. Des collectifs virtuels de pratiquants se structurent et interagissent entre eux (Mao et Obin, 2018). Un grand nombre de pratiques, à l’image de la randonnée (Czegledi et Garcia-Arjona, 2019) ou du ski de randonnée (Davoine et Garat, 2022), sont concernées. Les loisirs sportifs de nature s’inscrivent de ce fait dans une transition numérique marquée par l’équipement et la mobilisation croissante de dispositifs connectés par leurs pratiquants. L’utilisation de ces outils conduit à la production de traces numériques reposant sur un ensemble de données de plusieurs natures : temporelles, physiologiques, spatiales (traces GPS, géolocalisation ponctuelle) et/ou expérientielles (commentaires, échanges virtuels).Le début des années 2000 est marqué par l’affirmation du web 2.0 (O'Reilly, 2009) : les usages collaboratifs se développent. Figure emblématique de cette dynamique, Wikipédia est créé en 2001. Dans les sports de nature, diverses plateformes d’échange d’information apparaissent et des communautés virtuelles se développent. Par exemple, les skieurs de randonnée se regroupent autour du site internet skitour.fr en 2002, ceux des sports de montagne autour de camptocamp.org et les canyonistes autour de descente-canyon.com, tous deux en 2003. Il s’agit d’une forme d’innovation disruptive remettant en question les modalités d’accès aux informations de pratique existantes en offrant un nouveau service aux pratiquants qui permet notamment une actualisation des connaissances quasiment en temps réel sur la base de réseaux élargis au-delà de l’interconnaissance des pratiquants. Cette évolution dessine de nouvelles formes de participation que la recherche peut exploiter à travers le crowdsourcing. Le web collaboratif permet alors « de collecter de grandes quantités de données sur des phénomènes qui étaient jusqu’alors difficilement observables » (Houllier et Merilhou-Goudard, 2016, p. 26).En mobilisant les données de la plateforme descente-canyon.com, nous souhaitons proposer une géographie inédite d’une pratique sportive dans la nature, celle du canyoning en France. Les résultats mettent en évidence les spatialités ou les temporalités de la pratique du canyoning en France et développent des facteurs explicatifs de la fréquentation des canyons. Czegledi O. et Garcia-Arjona N. (2019). Les randonneurs pédestres des sentiers numériques – analyse des consommations numériques sur le littoral français. 18e Congrès international de l’Association des Chercheurs en A.P.S. (ACAPS), Paris, 29-31 octobre 2019.Davoine P-A. et Garat P. (2022). Analyser les pratiques de la randonnée à ski par les données géographiques issues des médias sociaux : l’exemple du forum Skitour à l’échelle du massif des Écrins. Séminaire « Informations Géographiques Volontaires : entre traces et documentation des usages dans le tourisme sportif de montagne », Bourget du Lac, 16 mai 2022.Houllier F. et Merilhou-Goudard J.-B. (2016). Les sciences participatives en France : États des lieux, bonnes pratiques et recommandations. Inra. https://hal.archives-ouvertes.fr/hal-02801940/ Mao, P. et Obin, O. (2018). La transition numérique des sports de nature, vers des sportsnature 3.1. Nature et Récréation, 6, 13-25.O’Reilly T. (2009). What is Web 2.0? Sebastopol : O’Reilly Media, 12 p
Usages du numérique : utilisation des dispositifs numériques dans les pratiques sportives outdoor
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Lagrangian dispersion in the Red River plume region, Northeast Vietnam, from drifter observations and modeling
No full textInternational audienceThe transport and spatial distribution of materials within river plumes and neighboring waters are stronglyinfluenced by the plume morphology and fronts bounding the plume area. Thus, identifying locations of plumefronts and assessing frontal mixing activity is particularly important for understanding the spatial distribution ofbiogeochemical tracers and the connectivity between source (river mouth) and offshore regions. Statisticalproperties of horizontal dispersion in the Red River (RR) plume region were obtained from drifter experiments,conducted in the Gulf of Tonkin during summer 2022, and also from realistic numerical modeling. Adopting aLagrangian perspective, a method is proposed to characterize the RR plume morphology based on the extractionof Lagrangian Coherent Structures (LCS) from the surface flow field using Finite-Size Lyapunov Exponents(FSLE). Maxima of the attracting FSLE field (FSLE ridge lines) enabled us to identify zones of current convergenceand shear in the flow, which are essential for characterizing the dynamics associated with plumes and mappingthe fronts delimiting them. It became clear that the body of the RR plume is formed by the individual riverplumes of the RR deltaic system. FSLE ridge lines allowed identification of the offshore expansion of individualplumes and revealed a variety of forms, semi-circular or hook-like filaments, characterizing the plume shape. Theballistic regime of dispersion was found inside the plume region, with the dominant direction perpendicular tothe coastal flow direction revealing anisotropic shear dispersion. It was observed at scales of 0.3 to 3 km(submesoscale range), with a maximum value of 10–13 day− 1, as derived from the analysis of the scaledependent relative dispersion of real drifters. In model simulations, the relative dispersion appeared scale independent in the range below 2 km, indicating a significant effect of grid resolution on the model’s representation of lateral mixing
Revealing the Improving Effect and Molecular Mechanism of L-Clausenamide in Combating the Acute Lung Injury: Insights from Network Pharmacology, Molecular Docking, and In Vitro Validation
No full textInternational audienceAcute lung injury is a severe disease with a high mortality rate, which can result in increased oxidative stress and further mitochondrial damage and cell apoptosis. L-Clausenamide is an amide from the fruit wampee. This study combined network pharmacology, molecular docking, and in vitro study to elucidate the effect of combating acute lung injury and the underlying mechanism of L-Clausenamide. Network pharmacology indicated that the 152 targets can treat acute lung injury through regulating oxidative stress. Based on PPI analysis and screening of the central target, AKT1 is the key target of the underlying mechanism. KEGG and GO enrichment analysis demonstrated that apoptosis is an important pathway for this curing effect. In the in vitro study, treatment with L-Clausenamide alleviates intracellular ROS accumulation, mitochondrial membrane potential loss, mitochondrial morphological distortion, ATP decrease, and the CASP3 activity. The SPR analysis was performed to validate the binding between AKT1 and L-Clausenamide. The Western blot result showed that L-Clausenamide increases the phosphorylation of Akt and decreases cleavage of CASP3. L-Clausenamide can alleviate lipopolysaccharide (LPS)-induced acute lung injury through targeting AKT1 and show an improvement in mitochondrial abnormality and inhibition against ROS-activated caspase-3-dependent apoptosis activation
Low clearing asymmetric BTBT mesogens with perfect ambipolar charge transport
No full textInternational audienceTwo new asymmetrically substituted BTBT mesogens were successfully synthesised. These mesogens were designed to achieve low melting and clearing temperatures via the decoration with swallow-tailed chains containing peripheral siloxane units. The aromatic endgroups (phenyl and phthalonitrile) have a significant impact on the bilayer smectic self-assembly. For both materials the aromatic units intercalate completely into double layers, but the phenyl derivative generates a SmC phase and the phthalonitrile derivative a SmA phase. The latter is a weak donor–acceptor system showing outstanding charge transport properties in the mesophase. It exhibits perfectly balanced ambipolar charge carrier mobility in the range of 10−2 cm2 V−1 s−1 resulting in a material that is extremely promising for organic electronic applications
Agrégats et forêts IDLA avec sources dans un hyperplan de Zd
No full textInternal Diffusion Limited Aggregation (idla) is a process used to construct random aggregates in Zd. At the start, it was introduced to model certain industrial chemical techniques such as electropolishing. Since then, many variants of this model have been studied, and have led to results describing the overall shape of the aggregate. Such results are referred to as shape theorems. This thesis handles several idla models in Zd, with d ≥ 2. We study various families of random aggregates, whose construction is based on an idla protocol with an infinite number of sources. We establish stabilization results for these aggregates as well as shape theorems. We begin by studying a multi-source idla model built by sending a deterministic number of particles from infinitely many sources. We establish properties of stationarity for this model, along with a global upper bound, which roughly describes the shape of the aggregate far away from the origin. This result allows us to then show a stabilization result, which turns out to be crucial in the second part of our study. The second part is devoted to the study of a multi-source model similar to the previous one, built this time by sending a random number of particles from infinitely many sources, in a random order. We study this model with the goal of building a translation invariant forest, called the directed infinite-volume idla forest. Its existence is non-trivial due to issues of consistancy, and forces us to adapt results obtained for the previous model to this one, requiring even to sharpen some of these results. In this second part, we prove a stabilization result for forests, whose proof is based on arguments of percolation, allowing us to prove the existence of the directed infinite-volume idla forest.L’Agrégation Limitée par Diffusion Interne (idla) est un processus permettant de construire des agrégats aléatoires dans Zd. Il a initialement été introduit pour modéliser des problèmes de chimie industrielle tels que l’électro-polissage. Depuis, de nombreuses variantes de ce modèle ont été étudiées, et ont donné lieu à des résultats permettant de décrire la forme des agrégats obtenus. De tels résultats sont qualifiés dans la littérature de shape theorems. Cette thèse traite de plusieurs modèles d’agrégation limitée par diffusion interne sur Zd, avec d ≥ 2. Nous étudions différentes familles d’agrégats aléatoires, dont la construction se base sur un protocole idla comportant une infinité de sources. Nous établissons des résultats de stabilisation pour ces agrégats, ainsi que des shape theorems. Dans un premier temps, nous étudions un modèle d’idla multi-sources construit en envoyant un nombredéterministe de particules depuis un nombre infini de sources. Nous établissons des propriétés de stationnarité pour ce modèle, ainsi qu’une borne globale permettant de contrôler de façon grossière l’agrégat loin de l’origine. Ce résultat nous permet ensuite de montrer un résultat de stabilisation, qui se révèle être crucial pour la seconde partie de notre étude. La seconde partie est dévouée à l’étude d’un modèle multi-sources similaire au premier, mais construit cette fois-ci en envoyant un nombre aléatoire de particules depuis un nombre infini de sources, selon un ordre aléatoire. Nous étudions ce modèle dans le but de construire une forêt invariante par translation, appelée forêt idla dirigée de volume infini. L’existence de cette forêt est non-triviale à cause de problèmes de consistance, et nous amène à adapter et à affiner les résultats du précédent modèle pour le second. Nous démontrons dans cette seconde partie un résultat de stabilisation pour des forêts, dont la preuve est basée sur un argument de percolation, nous permettant de démontrer l’existence de la forêt idla dirigée de volume infini
Impact of internal tides on chlorophyll distribution and primary production off the Amazon shelf from glider measurements and satellite observations
No full textInternational audienceThe ocean region off the Amazon shelf including the shelf break presents a hotspot for internal tide (IT) generation, yet its impact on phytoplankton distribution remains poorly understood. While previous studies have extensively examined the physical characteristics and dynamics of ITs, their biological implications – particularly in nutrient-limited environments – remain underexplored. To address this question, we analyzed a 26 d glider mission deployed over September–October 2021 sampling hydrographic and optical properties (chlorophyll a) at high resolution along an IT pathway as well as satellite chlorophyll a and altimetry data to assess mesoscale interactions. Chlorophyll a dynamics were analyzed under varying IT intensities, comparing strong (HT) and weak (LT) internal tide conditions. Results reveal that ITs drive vertical displacements of the deep chlorophyll maximum (DCM) from 15 to 45 m, accompanied by 50 % expansion in its thickness during HT events. This expansion is observed with a dilution of the chlorophyll a maximum concentration within the DCM depth. While direct turbulence measurements were not collected, the observed vertical redistribution of chlorophyll a is indicative of tidally driven cross-isopycnal exchanges, the only physical mechanism explaining the transfer of biomass above and below the DCM. At the surface, turbulent fluxes provide 38 % of the chlorophyll a input, while the remainder is supplied by in situ biological activity. Notably, total chlorophyll a in the water column increases by 14 %–29 % during high internal tide phases, indicating a net enhancement of primary productivity driven by the combined effects of vertical mixing and stimulated surface-layer biological activity. These findings indicate that internal tides can be an important driver of chlorophyll a distribution and short-term biological variability in our study region. By reshaping the vertical chlorophyll a profile through vertical mixing, active internal tides influence primary productivity and may contribute to carbon cycling, particularly in oligotrophic oceanic environments where both a deep chlorophyll maximum and strong internal tides are present
Matrix symmetric and quasi-symmetric functions and noncommutative representation theory
No full textA fundamental result by L. Solomon in algebraic combinatorics and representation theory states that Mackey formulas for products of characters of a symmetric group, or equivalently the computation of tensor products of representations thereof, can be lifted to the corresponding Solomon's descent algebra, a subalgebra of the group algebra with a very rich structure. Motivated by the structure of the product formula in these algebras and by other results and ideas in the field, we introduce and investigate in the present article a two dimensional analogue of descent algebras based on packed integer matrices that inherits most of their fundamental properties. One of the various bialgebra structures we introduce on packed integer matrices identifies with a bialgebra recently introduced by J. Diehl and L. Schmitz to define a two dimensional generalisation of Chen's iterated integrals signatures
Best Practices for Optimization of Phytoplankton Analysis in Natural Waters Using CytoSense Flow Cytometers
No full textInternational audienceABSTRACT The use of flow cytometry to investigate phytoplankton functional groups is rapidly expanding worldwide, using lab‐ or ship‐based instruments or autonomous environmental monitoring platforms. Automation, coupled with greater autonomy, allows for higher spatial and temporal resolution of phytoplankton groups, enhancing understanding of their dynamics and patterns, generating large datasets. The level of resolution is determined by both instrumental capabilities and optimization of its acquisition settings. Sharing these datasets with the scientific community, whether to improve global phytoplankton distribution resolution or facilitate the intercomparison of environmental indicators among monitoring laboratories, strongly relies on quality‐controlled instruments and standardized data acquisition and analysis. This article focuses on CytoSense‐type (CytoBuoy, NL) flow cytometers, which operate by recording the optical pulse shapes of particles as they pass through a laser beam. Different configurations such as laser wavelength and power, sheath fluid management, sample inlet design, and dataset output format were not considered, in order to focus on optimization and protocol standardization to resolve the whole phytoplankton size spectrum, from the smallest autofluorescing prokaryotes to colonies and chain‐forming species. In this study, coincidence, PMT voltage, trigger threshold optimization, and regular quality control procedures are considered and discussed, using datasets from three types of instruments and two contrasted marine coastal waters as case studies. The primary goal of this study is to establish a framework to guide and support the exploration and application of this type of flow cytometer, ultimately achieving a reliable and optimal resolution for sample acquisition of natural waters