Les poissons de la Grande Grotte d'Arcy-sur-Cure (Yonne)

Un original método de investigacion, mediante adelgazamiento de la calcita, utilizado por primera vez en una cueva con decoración paleolítica ha permitido sacar a la luz, entre otras cosas, cuatro peces pintados en negro sobre las paredes de la Grande Grotte d'Arcy-sur-Cure (Yonne, France). Dichos peces, salmónidos y lucio, confirman el carácter excepcional el bestiario de esta gruta constituido por animales que no están presentes en las demás, a excepción de la de la cueva Chauvet (Ardechè) ; mamuts, rinocerontes, osos, felino, aves, megáceros. Los vestigios, bien conservados, encontrados sobre su suelo nos han permitido determinar que fue utilizada en la época auriñaciense gravetiense

Hanabi is NP-complete, even for cheaters who look at their cards

This paper studies a cooperative card game called Hanabi from an algorithmic combinatorial game theory viewpoint. The aim of the game is to play cards from 1 to n in increasing order (this has to be done independently in c different colors). Cards are drawn from a deck one by one. Drawn cards are either immediately played, discarded or stored for future use (overall each player can store up to h cards). The main feature of the game is that players know the cards their partners hold (but not theirs. This information must be shared through hints). We introduce a simplified mathematical model of a single-player version of the game, and show several complexity results: the game is intractable in a general setting even if we forego with the hidden information aspect of the game. On the positive side, the game can be solved in linear time for some interesting restricted cases (i.e., for small values of h and c)

Characterisation of Nd-doped calcium aluminosilicate parent glasses designed for the preparation of zirconolite-based glass-ceramic waste forms

4 pagesZirconolite-based (nominally CaZrTi2O7) glass-ceramics belonging to the SiO2-Al2O3-CaO-ZrO2-TiO2 system are good waste forms for the specific immobilisation of actinides. The understanding of their crystallisation processes implies to investigate the structure of the glass. Thus, the environment around Ti, Zr (nucleating agents) and Nd (trivalent actinides surrogate) was characterised in parent glasses. Electron spin resonance (ESR) study of the small amount of Ti3+ occurring in the glass enabled to identify two types of sites for titanium: the main one is of C4v or D4h symmetry. EXAFS showed that Zr occupied a quite well defined 6-7-fold coordinated site with second neighbours which could correspond to Ca/Ti and Zr. Nd environment was probed by optical spectroscopies (absorption, fluorescence), ESR and EXAFS. All these techniques demonstrated that the environment around Nd was very constrained by the glassy network. Notably, Nd occupies a highly distorted 8-9-fold coordinated site in the parent glass

Interlayer Magnetic Frustration in Quasi-stoichiometric Li1-xNi1+xO2

Susceptibility, high-field magnetization and submillimeter wave electron spin resonance measurements of layered quasi-stoichiometric Li1-xNi1+xO2 are reported and compared to isomorphic NaNiO2. A new mechanism of magnetic frustration induced by the excess Ni ions always present in the Li layers is proposed. We finally comment on the possible realization of an orbital liquid state in this controversial compound.Comment: 4 pages, 5 figures, submitted to Phys.Rev.B, Rapid Com

Learning Interpretable Error Functions for Combinatorial Optimization Problem Modeling

In Constraint Programming, constraints are usually represented as predicates allowing or forbidding combinations of values. However, some algorithms exploit a finer representation: error functions. Their usage comes with a price though: it makes problem modeling significantly harder. Here, we propose a method to automatically learn an error function corresponding to a constraint, given a function deciding if assignments are valid or not. This is, to the best of our knowledge, the first attempt to automatically learn error functions for hard constraints. Our method uses a variant of neural networks we named Interpretable Compositional Networks, allowing us to get interpretable results, unlike regular artificial neural networks. Experiments on 5 different constraints show that our system can learn functions that scale to high dimensions, and can learn fairly good functions over incomplete spaces

Jacques Brunet (1942-2017)

Une fois de plus le grand Taureau de Lascaux pleure. Jacques Brunet nous a quitté le 29 mai dernier. Jacques s’engagea très tôt dans la conservation préventive du patrimoine souterrain orné ; responsable du pôle « Grottes ornées » de 1974 à 2006 au LRMH, il parcourut les sites de l’Afrique du Nord, de l’Oural, de l’Amérique centrale et de l’Europe pour dispenser conseils et savoirs. Jacques a beaucoup œuvré pour la conservation de Font de Gaume, Combarelles, Rouffignac, Lascaux et tout autant..