Higher-Order Temporal Network Prediction

A social interaction (so-called higher-order event/interaction) can be regarded as the activation of the hyperlink among the corresponding individuals. Social interactions can be, thus, represented as higher-order temporal networks, that record the higher-order events occurring at each time step over time. The prediction of higher-order interactions is usually overlooked in traditional temporal network prediction methods, where a higher-order interaction is regarded as a set of pairwise interactions. We propose a memory-based model that predicts the higher-order temporal network (or events) one step ahead, based on the network observed in the past and a baseline utilizing pair-wise temporal network prediction method. In eight real-world networks, we find that our model consistently outperforms the baseline. Importantly, our model reveals how past interactions of the target hyperlink and different types of hyperlinks that overlap with the target hyperlinks contribute to the prediction of the activation of the target link in the future.Comment: Submitted to the Conference on Complex Networks and Their Applications XI

Caractérisation physico-chimique et comportement hydromécanique d'une argile échangée avec l'ammonium dans le contexte des sites de stockage

International audienceEn 2007, près de 38 millions de tonnes de déchets d'origine ménagère ont été collectés par les collectivités en France (ADEME, 2009). Malgré l'essor constant du recyclage et du compostage, 31% de ces déchets municipaux traités ont été envoyé dans des installations de stockage des déchets non dangereux (ISDND) cette même année. A l'échelle européenne, ce pourcentage augmente considérablement. Dans ces sites de stockage, la percolation de l'eau à travers les déchets produit une grande quantité de lixiviats chargés en polluants de diverses natures. L'étanchéité en fond de site est notamment assurée par une couche argileuse (barrière passive). Son rôle est notamment de limiter la pollution des sols et des nappes phréatiques. Les argiles utilisées en fond de site de stockage sont principalement des smectites qui possèdent une forte capacité de rétention. Dans les analyses de lixiviats, de nombreux auteurs ont mis en évidence une très grande quantité d'ammonium susceptible de s'échanger avec le sodium ou le calcium initialement présent la barrière argileuse. Si ces dernières ont largement été décrites dans la littérature, les argiles ammoniées sont beaucoup moins connues. Le travail présenté ici s'est donc intéressé à la caractérisation complète d'une argile totalement échangée avec des cations ammonium. L'objectif de ce travail est de mieux comprendre et appréhender le comportement d'une argile ammoniée dans le contexte de la mise en décharge des déchets. En raison du poids des déchets, la barrière d'argile en fond de site subit des pressions élevées. Le deuxième objectif est de comprendre les phénomènes microscopiques et macroscopiques liées au comportement hydromécanique des matériaux argileux. Des cellules oedométriques équipées d'un système d'injection sous pression contrôlée ont été utilisés. Des différences significatives sur les capacités d'hydratation de l'argile ammoniée et sur la perméabilité de cette dernière ont été mises en évidence au cours de ce travail. L'ensemble des résultats présentés souligne l'importance du suivi des sites de stockage sur le long terme, notamment pour prévenir des pollutions des nappes phréatiques

Federated learning compression designed for lightweight communications

Federated Learning (FL) is a promising distributed method for edge-level machine learning, particularly for privacysensitive applications such as those in military and medical domains, where client data cannot be shared or transferred to a cloud computing server. In many use-cases, communication cost is a major challenge in FL due to its natural intensive network usage. Client devices, such as smartphones or Internet of Things (IoT) nodes, have limited resources in terms of energy, computation, and memory. To address these hardware constraints, lightweight models and compression techniques such as pruning and quantization are commonly adopted in centralised paradigms. In this paper, we investigate the impact of compression techniques on FL for a typical image classification task. Going further, we demonstrate that a straightforward method can compresses messages up to 50% while having less than 1% of accuracy loss, competing with state-of-the-art techniques

NH4-smectite: Characterization, hydration properties and hydro mechanical behaviour

International audienceLeachates in waste landfills are characterized by the presence of ammonium ions in large excess. These ammonium ions can be exchanged with the interlayer cations in clay and modify the physical and chemical properties of clay geochemical barriers in waste landfills and drive to environmental problems. The purpose of this study was to understand the hydro-physical changes of a smectite in the presence of ammonium ions. An ammonium smectite was prepared by cation exchange from a natural montmorillonite (Wyoming). The samples were characterized and their properties were compared by the use of a set of complementary techniques (X-ray diffraction, infrared spectroscopy, N2 adsorption-desorption BET technique, thermal analysis, and percolation experiments). The main effect was a modification of the porosity and its network, and reduced crystalline swelling. These effects changed the hydraulic conductivity and macroscopic swelling of the clay. The oedometer experiments, which allow simulating the pressure on small amounts of samples, proved the strong increase of the permeability of NH4-smectite. This last point is of great importance in an environment point of view and raises questions on the impermeability behaviour on the long term of the clay geochemical barriers with the presence of ammonium ions in waste landfills

Interactions of ammonium smectite with low molecular weight carboxylic acids.

International audienceThis study aims at better understanding the interaction between an ammonium smectite and carboxylic acids. The SWy-2 (Wyoming smectites) has been exchanged with NH4 + and then batched with carboxylic acids (acetic, formic, chloroacetic and oxalic) in concentrations between 0,01M and 1M. The obtained solid phases have been chemically analyzed and characterized by infrared absorption spectroscopy and X-ray powder diffraction. The ionic chromatography has been used for the quantitative measurement of ammonium in the solution after interaction. For the four acids, the interaction is characterized by a cationic exchange of NH4+ to H3O+. A partial exchange to Al3+ due to a partial dissolution of the sample in strong acidic medium is observed with chloroacetic and oxalic acids. For these two last acids, the adsorption of molecules on the clay sample occurs, mainly through H-bonding with the cation. Moreover, the intercalation of oxalic acid in the interlayer space has been highlighted

Quantum Cascade Lasers as Broadband Sources via Strong RF Modulation

In this work, we demonstrate that in a regime of strong modulation, by generating pulses of the length of the order of a few cavity lifetimes (hundreds of ps), a broadband quantum cascade laser can be driven to lase on a bandwidth (250cm-1) limited by the gain. In addition, the amplitude noise of the radiation was shown to be limited by the detector. A laser linewidth study has been performed under different operating conditions finding values spanning from 20MHz to 800MHz, indicating a trade-off between emission bandwidth, amplitude stability and coherence

Adaptation of the semi-Hertzian method to wheel/rail contact in turnouts

A procedure is described in order to assess loads applied on a turnout due to track-train interaction. Co-simulation is used between a finite element method (FEM) model of the turnout and a multibody system (MBS) of the vehicle. Wheel/rail contact forces are computed in the MBS and applied to the rails of the turnout modelled as FEM beams. FEM displacements under the wheel are accounted in the MBS in the next time step. A modification has been applied to the semi-Hertzian (SH) method used to assess wheel/rail forces. This adapted SH method is designed to take in account the relative flexibility of the components of the turnout, like the stock rail and the switch rail. Such parts have their own degree of freedom and may in some extent behave independently: the proposed method takes it in account in the contact search. The co-simulation has been first used in a referenced case-study

Developing a French FrameNet: Methodology and First results

International audienceThe Asfalda project aims to develop a French corpus with frame-based semantic annotations and automatic tools for shallow semantic analysis. We present the first part of the project: focusing on a set of notional domains, we delimited a subset of English frames, adapted them to French data when necessary, and developed the corresponding French lexicon. We believe that working domain by domain helped us to enforce the coherence of the resulting resource, and also has the advantage that, though the number of frames is limited (around a hundred), we obtain full coverage within a given domain

Organellar inheritance in the green lineage: insights from Ostreococcus tauri

Along the green lineage (Chlorophyta and Streptophyta), mitochondria and chloroplast are mainly uniparentally transmitted and their evolution is thus clonal. The mode of organellar inheritance in their ancestor is less certain. The inability to make clear phylogenetic inference is partly due to a lack of information for deep branching organisms in this lineage. Here, we investigate organellar evolution in the early branching green alga Ostreococcus tauri using population genomics data from the complete mitochondrial and chloroplast genomes. The haplotype structure is consistent with clonal evolution in mitochondria, while we find evidence for recombination in the chloroplast genome. The number of recombination events in the genealogy of the chloroplast suggests that recombination, and thus biparental inheritance, is not rare. Consistent with the evidence of recombination, we find that the ratio of the number of nonsynonymous to the synonymous polymorphisms per site is lower in chloroplast than in the mitochondria genome. We also find evidence for the segregation of two selfish genetic elements in the chloroplast. These results shed light on the role of recombination and the evolutionary history of organellar inheritance in the green lineage

Ten simple rules for developing visualization tools in genomics

Our following 10 simple rules are dedicated to biologists and bioinformaticians who, while already being at the crossroads of many fields, want to venture further into the land of Data Visualization (“datavis” or “dataviz” for short). They combine tips and advice that we would have wanted when we first started our own journeys, gathered from our experiences in building genomic and/or datavis tools, and the time spent with related communities. Additionally, they address current challenges in computational biology and the needs of the community