MODNet -- accurate and interpretable property predictions for limited materials datasets by feature selection and joint-learning

In order to make accurate predictions of material properties, current machine-learning approaches generally require large amounts of data, which are often not available in practice. In this work, an all-round framework is presented which relies on a feedforward neural network, the selection of physically-meaningful features and, when applicable, joint-learning. Next to being faster in terms of training time, this approach is shown to outperform current graph-network models on small datasets. In particular, the vibrational entropy at 305 K of crystals is predicted with a mean absolute test error of 0.009 meV/K/atom (four times lower than previous studies). Furthermore, joint-learning reduces the test error compared to single-target learning and enables the prediction of multiple properties at once, such as temperature functions. Finally, the selection algorithm highlights the most important features and thus helps understanding the underlying physics.Comment: 5 pages, 2 figure

Bright Light as a Personalized Precision Treatment of Mood Disorders

Background: The use of light for its antidepressant action dates back to the beginnings of civilization. Three decades ago, the use of bright-light therapy (BLT) for treating Seasonal Affective Disorder (SAD) was officially proposed. Since then, a growing scientific literature reports its antidepressant efficacy in both unipolar and bipolar disorders (BD), with or without seasonal patterns. This review aims to examine the management of BLT as a personalized and precision treatment in SAD, unipolar, and BD.Methods: We conducted a narrative review using Medline and Google Scholar databases up to June 2018.Results: BLT has physiological effects by resynchronizing the biological clock (circadian system), enhancing alertness, increasing sleep pressure (homeostatic system), and acting on serotonin, and other monoaminergic pathways. Effects of BLT on mood depend on several factors such as light intensity, wavelength spectrum, illumination duration, time of the day, and individual circadian rhythms. A growing body of evidence has been generated over the last decade about BLT evolving as an effective depression treatment not only to be used in SAD, but also in non-seasonal depression, with efficiency comparable to fluoxetine, and possibly more robust in patients with BD. The antidepressant action of BLT is fast (within 1-week) and safe, with the need in BD to protect against manic switch with mood stabilizers. Side effects might be nausea, diarrhea, headache, and eye irritation, and are generally mild and rare. This good safety profile may be of particular interest, especially in women during the perinatal period or for the elderly. The management of BLT needs to be clarified across mood disorders and future studies are expected to compare different dose-titration protocols, to validate its use as a maintenance treatment, and also to identify predictive biomarkers of response and tolerability. We propose clinical guidelines for BLT use in SAD, non-seasonal depression, and BD.Conclusions : BLT is an efficient antidepressant strategy in mono- or adjunct-therapy, that should be personalized according the unipolar or bipolar subtype, the presence or absence of seasonal patterns, and also regarding its efficacy and tolerability

Condensation of helium in aerogels and athermal dynamics of the Random Field Ising Model

High resolution measurements reveal that condensation isotherms of $^4$He in a silica aerogel become discontinuous below a critical temperature. We show that this behaviour does not correspond to an equilibrium phase transition modified by the disorder induced by the aerogel structure, but to the disorder-driven critical point predicted for the athermal out-of-equilibrium dynamics of the Random Field Ising Model. Our results evidence the key role of non-equilibrium effects in the phase transitions of disordered systems.Comment: 5 p + suppl. materia

Au fil des residences de Napoleon. De la “petite maison” au palais de l’Élysée

Nel 1797 Napoleone Bonaparte si stabilì nella petite maison di rue Chantereine allora occupata da Giuseppina. Dopo il colpo di stato del 18 Brumario, la coppia si insediò ufficialmente nelle residenze del Petit Luxembourg e del palazzo delle Tuileries, mentre il castello della Malmaison svolse la funzione di ritiro campestre.Nel dicembre del 1804, la proclamazione dell’impero cambiò radicalmente la situazione. Le Tuileries, per quanto rappresentative non erano habitables. Napoleone cercò cosi una residenza vicina alla nuova cittadella imperiale, allora in costruzione sulla collina di Chaillot. La scelta cadde sull’hôtel particulier un tempo appartenuto a Madame de Pompadour: l’hôtel d’Évreux, poi ribattezzato Elysée.Allo stesso tempo palazzo cittadino e maison de plaisance suburbana aperta sugli Champs-Élysées, il palazzo dell’Eliseo era stato acquistato nel 1806 dai Granduchi di Berg, Giacchino Murat e Carolina Bonaparte, e completamente ristrutturato dagli architetti Vignon e Thibault. Nuovi saloni di rappresentanza furono allora creati, affiancati da lussuosi appartamenti privati.Dal 1808, l’Eliseo servì così da dimora privata per la coppia imperiale, prima di essere recuperato da Giuseppina, al momento del divorzio, e da Napoleone dopo il matrimonio con Maria-Luigia.La nascita del Re di Roma donò a Napoleone lo statuto di capo di una dinastia regnante. L’Eliseo passò così da semplice residenza privata a vero palazzo imperiale, e come tale sottoposto a una ingente opera di ristrutturazione diretta dal primo architetto di corte Pierre-François-Léonard Fontaine. Tuttavia fu durante i Cento Giorni che il palazzo acquisì il suo ruolo più importante, che conserva tutt’ora, quello di residenza del capo dello Stato.En 1797, Napoléon s’installa dans la «petite maison» alors occupée par Joséphine rue Chantereine. Ce lieu raffiné et élégant, fut un témoin de l'ascension du jeune Bonaparte. Après le coup d'état du 18 brumaire, Napoléon et Joséphine quittèrent leur petite maison. Leur vie désormais publique eut pour cadre la résidence officielle du Petit Luxembourg, puis du palais de Tuileries, tandis que la Malmaison, offrait un retrait champêtre d'une maison de plaisance. Pour eux le temps de la rue de la Victoire était désormais terminé.En décembre 1804, la proclamation de l’Empire changea profondément la situation. Les Tuileries, lui offrant le cadre officiel nécessaire au train de vie de l’Empereur, n’étaient toutefois pas «habitables». N’aimant guère ce palais, Napoléon chercha une résidence proche de la nouvelle cité impériale en création, dans laquelle il aurait pu se retirer. Il fit le choix d'un hôtel particulier ayant jadis appartenu à Madame de Pompadour, et à deux reprises au Roi: l'ancien hôtel d'Évreux.À la fois palais de ville et maison de plaisance ouverte sur les Champs-Élysées, l'Élysée avait été acheté en 1806 par les grands ducs de Berg. La résidence avait été complètement réhabilitée par les architectes Vignon et Thibault. Elle comportait des riches pièces d'apparat et des luxueux appartements privés.L’Elysée servit ainsi de résidence privée pour le couple impérial, avant de n’être récupérée par Joséphine au moment du divorce, puis repris par Napoléon après le mariage avec Marie-Louise.La naissance du Roi de Rome rendit Napoléon le chef d'une dynastie, légitimant ainsi finalement sa position. L'Élysée passa donc de simple maison privée à vrai palais impérial. Des Grands travaux de réaménagement furent alors commandés à l'architecte Fontaine, visant alors à créer l'appartement pour le roi de Rome au deuxième étage. Mais ce fut pendant les Cent Jours que le palais acquit son rôle le plus fondamental – qu’il conserve encore aujourd’hui –, celui de résidence du chef de l’Etat.En 1797, Napoléon s’installa dans la «petite maison» alors occupée par Joséphine rue Chantereine. Ce lieu raffiné et élégant, fut un témoin de l'ascension du jeune Bonaparte. Après le coup d'état du 18 brumaire, Napoléon et Joséphine quittèrent leur petite maison. Leur vie désormais publique eut pour cadre la résidence officielle du Petit Luxembourg, puis du palais de Tuileries, tandis que la Malmaison, offrait un retrait champêtre d'une maison de plaisance. Pour eux le temps de la rue de la Victoire était désormais terminé.En décembre 1804, la proclamation de l’Empire changea profondément la situation. Les Tuileries, lui offrant le cadre officiel nécessaire au train de vie de l’Empereur, n’étaient toutefois pas «habitables». N’aimant guère ce palais, Napoléon chercha une résidence proche de la nouvelle cité impériale en création, dans laquelle il aurait pu se retirer. Il fit le choix d'un hôtel particulier ayant jadis appartenu à Madame de Pompadour, et à deux reprises au Roi: l'ancien hôtel d'Évreux.À la fois palais de ville et maison de plaisance ouverte sur les Champs-Élysées, l'Élysée avait été acheté en 1806 par les grands ducs de Berg. La résidence avait été complètement réhabilitée par les architectes Vignon et Thibault. Elle comportait des riches pièces d'apparat et des luxueux appartements privés.L’Elysée servit ainsi de résidence privée pour le couple impérial, avant de n’être récupérée par Joséphine au moment du divorce, puis repris par Napoléon après le mariage avec Marie-Louise.La naissance du Roi de Rome rendit Napoléon le chef d'une dynastie, légitimant ainsi finalement sa position. L'Élysée passa donc de simple maison privée à vrai palais impérial. Des Grands travaux de réaménagement furent alors commandés à l'architecte Fontaine, visant alors à créer l'appartement pour le roi de Rome au deuxième étage. Mais ce fut pendant les Cent Jours que le palais acquit son rôle le plus fondamental – qu’il conserve encore aujourd’hui –, celui de résidence du chef de l’Etat

An unstructured conservative level-set algorithm coupled with dynamic mesh adaptation for the computation of liquid-gas flows

International audienceAccurate and efficient simulations of 3D liquid-gas flows are of first importance in many industrial applications, such as fuel injection in aeronautical combustion chambers. In this context, it is mandatory to handle complex geometries. The use of unstructured grids for two-phase flow modeling fulfills this requirement and paves the way to isotropic adaptive mesh refinement. This work presents a narrow-band conservative level-set algorithm implemented in the YALES2 incompressible flow solver, which is combined to dynamic mesh adaptation. This strategy enables resolving the small physical scales at the liquid-gas interface at a moderate cost. It is applied to predicting the outcome of a droplet collision with reflexive separation. In the accurate conservative level set framework, the interface is represented using a hyperbolic tangent profile, which is advected by the fluid, and then reshaped using a reinitialization equation. The classical signed-distance function is reconstructed at nodes in the narrow band around the interface using a geometric projection/marker method (GPMM), to calculate the smallest distance to the interface. The interface normal and curvature are computed using this signed-distance function. Within a mesh cell, the interface is approximated by a segment (2D) or one or several triangles (3D). The distance at the nodes is simply obtained by projection to the closest surface elements. If a node is connected to n elements containing interface fragments, it has a n-marker list (a marker contains the coordinates of the crossing points and the distance). To speed-up the algorithm, the markers stored at each node are sorted based on their distance. Markers are propagated from one band to another: each node compares its markers to its neighbors' and keeps the closest only. The GPMM approach for the reconstruction of the level-set signed-distance function used in conjunction with the reinitialization of Chiodi et al. (2017) leads to significant improvement in the interface quality and overall accuracy compared to the reinitialization of Desjardins et al. (2008) in the calculations performed on unstructured grids. Since the accuracy of the interface normal and curvature directly depends on the signed-distance function reconstruction, less spurious currents occur on the implicit surface. The improved level-set algorithm leads to accurate predictions of the outcome of a droplet collision with reflexive separation, and is validated against the experimental results of Ashgriz et al. (1990). Introduction Two-phase flows are ubiquitous in nature and in industrial systems. The understanding of the various phenomena occurring in liquid-gas flows is crucial for aeronautical combustors, in which a fuel is injected in liquid form, goes under an atomization process, evaporation, mixing with air and eventually combustion. Understanding the atomization process and the resulting droplet distribution is of first importance for aircraft engine performance and operability. The prediction of the atomization process is complex, due to many non-linear phenomena such as interface break-up, droplet convection, or droplet collision. Atomization also involves a wide range of time and space scales, which leads to important calculation costs. Thus, the use of dynamic mesh adaptation for unstructured meshes is particularly helpful for simulating industrial liquid-gas flow problems, as it allows implicit interface dynamics calculation in complex geometries at a reasonable cost [1]. To capture the interface, the conservative level set method is used, which accurately predicts the interface dynamics while conserving liquid mass [2]. This article presents a method to compute the signed-distance function on unstructured grids, and an implementation of the reinitialization of [3], adapted to unstructured meshes. Classic test cases are run to check the overall accuracy and robustness of the method, and a droplet collision case is simulated to validate the global algorithm with a front merging scenario against the experimental results of [4]

Critical behavior of the liquid gas transition of 4 He confined in a silica aerogel

6 pagesInternational audienceWe have studied 4 He confined in a 95% porosity silica aerogel in the vicinity of the bulk liquid gas critical point. Both thermodynamic measurements and light scattering experiments were performed to probe the effect of a quenched disorder on the liquid gas transition, in relation with the Random Field Ising Model (RFIM). We find that the hysteresis between condensation and evaporation present at lower temperatures disappears at a temperature T ch between 25 and 30 mK below the critical point. Slow relaxations are observed for temperatures slightly below T ch , indicating that some energy barriers, but not all, can be overcome. Above T ch , no density step is observed along the (reversible) isotherms, showing that the critical behavior of the equilibrium phase transition in presence of disorder, if it exists, is shifted to smaller temperatures, where it cannot be observed due to the impossibility to reach equilibrium. Above T ch , light scattering exhibits a weak maximum close to the pressure where the isotherm slope is maximal. This behavior can be accounted for by a simple model incorporating the compression of 4 He close to the silica strands