Decidability Problems for Self-induced Systems Generated by a Substitution

International audienceIn this talk we will survey several decidability and undecidability results on topological properties of self-affine or self-similar fractal tiles. Such tiles are obtained as fixed point of set equations governed by a graph. The study of their topological properties is known to be complex in general: we will illustrate this by undecidability results on tiles generated by multitape automata. In contrast, the class of self affine tiles called Rauzy fractals is particularly interesting. Such fractals provide geometrical representations of self-induced mathematical processes. They are associated to one-dimensional combinatorial substitutions (or iterated morphisms). They are somehow ubiquitous as self-replication processes appear naturally in several fields of mathematics. We will survey the main decidable topological properties of these specific Rauzy fractals and detail how the arithmetic properties yields by the combinatorial substitution underlying the fractal construction make these properties decidable. We will end up this talk by discussing new questions arising in relation with continued fraction algorithm and fractal tiles generated by S-adic expansion systems

Connectedness of fractals associated with Arnoux-Rauzy substitutions

Rauzy fractals are compact sets with fractal boundary that can be associated with any unimodular Pisot irreducible substitution. These fractals can be defined as the Hausdorff limit of a sequence of compact sets, where each set is a renormalized projection of a finite union of faces of unit cubes. We exploit this combinatorial definition to prove the connectedness of the Rauzy fractal associated with any finite product of three-letter Arnoux-Rauzy substitutions.Comment: 15 pages, v2 includes minor corrections to match the published versio

La patrimonialisation de l’œuvre du botaniste Henri Gaussen : divers attachements au passé de la science.

Le patrimoine scientifique est polymorphe, à ce titre il ne s’inscrit pas dans un cadre institutionnel unique et stable. Désigner des traces de sciences pour leur valeur patrimoniale relève de diverses pratiques sociales ; la constitution de ce « patrimoine mou » (Rautenberg, 2003) s’effectue au gré d’intérêts et d’opportunités multiples. Pour comprendre la complexité des phénomènes de patrimonialisation des sciences et ce qu’ils révèlent des mondes scientifiques, cette contribution s’emploiera à les décrire via les régimes d’engagement des acteurs impliqués (Thévenot, 2011). Via l’héritage du botaniste et phyto-géographe Henri Gaussen, nous présenterons ici un exemple de diversité de processus à l’œuvre (Davallon, 2006) : les pans des productions choisies et mises en récit au regard des traces omises, les acteurs impliqués et ceux effacés, les opportunités saisies et les archives dispersées… Le « dépliage » (Latour, 2000) des pratiques sociales donne à voir les tensions en jeu lors de la patrimonialisation des traces de l’activité scientifique. Comment valoriser à la fois l’universel et le singulier, le collectif et l’individuel, le global et le local ?The scientific heritage is polymorphous, as such it does not fit into a single and stable institutional framework. Designating science trails for their heritage value is a function of various social practices; the constitution of this "soft heritage" (Rautenberg, 2003) is made according to interests and multiple opportunities. To understand the complexity of the phenomena of patrimonialization of science and what they reveal of scientific worlds, this contribution will be used to describe them via the engagement regimes of the actors involved (Thévenot, 2011). Through the legacy of the botanist and phyto-geographer Henri Gaussen, we will present here an example of the diversity of processes at work (Davallon, 2006): the parts of the productions chosen and put in narrative with regard to the omitted traces, the actors involved and erased, seized opportunities and scattered archives ... The "unfolding" (Latour, 2000) of social practices reveals the tensions involved in the patrimonialization of traces of scientific activity. How to value both the universal and the singular, the collective and the individual, the global and the local 

Anthropologie du mémoriel

Cette contribution présente les origines, la méthodologie et les premiers résultats du programme de recherche « Patrimoine immatériel du Toulouse scientifique moderne (1960-1990) » élaboré à l’intersection des préoccupations patrimoniales de la mission pour la sauvegarde du patrimoine scientifique et technique contemporain de Midi-Pyrénées et des questionnements autour de la mémoire des anthropologues de l’université de Toulous

Le patrimoine universitaire toulousain passé au crible

En 2014 et 2015, l’université Fédérale Toulouse Midi-Pyrénées a mené une étude sur l’ensemble des fonds et collections du site, sur le patrimoine scientifique mais aussi bâti, artistique, écrit et archivistique : l’enjeu était d’établir une méthodologie puis de créer un rapport qui rende compte de la richesse intrinsèque des héritages mais aussi des mécanismes de prises en charge à l’œuvre et de l’implication des acteurs de la communauté universitaire ou des partenaires institutionnels

En reconstruction mammaire : intérêt du dépistage du portage de Staphylococcus aureus dans la prévention de l’infection du site opératoire

National audienceThe incidence of prosthesis infections after breast reconstruction is of the order of 4% to 13% according to the literature. In surgical patients, Staphylococcus aureus (S. aureus) is the bacterial species most often responsible for surgical site infections. In cardiac surgery, screening for carriage of S. aureus and preoperative decontamination are carried out routinely before prosthetic surgery. We retrospectively reviewed data from patients at our institution between January 2011 and December 2013. Our series showed that the prosthesis infection rates were in the range of 5.92% in 2008 with an ISO rate of S. aureus 3.61%. Routine screening for prosthetic reconstructions was performed to assess the impact of preoperative decontamination patients in carriers of S. aureus. This screening was done in 381 patients: 17.8% of patients were carriers of S. aureus ; 11 patients have an ISO (or an incidence rate of 2.88%) ; 5 patients have an ISO S. aureus (an incidence of S. aureus ISO 1.3%). The introduction of the screening process, allowed a drop of 5.92% ISO rate at 1.46% with a passage of S. aureus SSI rates of 3, 60% to 0.72%. In the near future, studies are needed to confirm these encouraging results, to demonstrate the efficacy of preoperative decontamination in carriers of S. aureus patients before laying prosthesis

Detection of slow slip events along the southern Peru - northern Chile subduction zone

Detections of slow slip events (SSEs) are now common along most plate boundary fault systems at the global scale. However, no such event has been described in the south Peru - north Chile subduction zone so far, except for the early preparatory phase of the 2014 Iquique earthquake. We use geodetic template matching on GNSS-derived time series of surface motion in Northern Chile to extract SSEs hidden within the geodetic noise. We detect 33 events with durations ranging from 9 to 40 days and magnitudes from Mw 5.6 to 6.2. The moment released by these aseismic events seems to scale with the cube of their duration, suggesting a dynamic comparable to that of earthquakes. We compare the distribution of SSEs with the distribution of coupling along the megathrust derived using Bayesian inference on GNSS- and InSAR-derived interseismic velocities. From this comparison, we obtain that most SSEs occur in regions of intermediate coupling where the megathrust transitions from locked to creeping or where geometrical complexities of the interplate region have been proposed. We finally discuss the potential role of fluids as a triggering mechanism for SSEs in the area

Les documents scientifiques informels: un patrimoine peu exploré, témoin de la construction des savoirs

L'objectif du projet ECRITO était de contribuer à préserver et à valoriser les documents scientifiques produits quotidiennement par les chercheurs de Midi-Pyrénées, en amont des publications formelles : non seulement les articles, communications ou monographies, qui constituent la partie visible de la recherche, mais aussi tous les matériaux et informations accumulés par les chercheurs, et sur la base desquels se construit leur travail. Ces matériaux sont de types très divers : littérature " grise " (rapports, mémoires, documentation techniques...), documents textuels " informels " (carnets, notes, brouillons, correspondances, cahiers de laboratoires), corpus visuels, sonores ou multimédia (campagnes photographiques, campagnes d'enquêtes, enregistrements audio ou vidéo), données électroniques (bases de données, fichiers informatiques), etc. Le projet visait également à prolonger, de manière exploratoire, le questionnement sur le patrimoine scientifique à partir des traces matérielles produites quotidiennement par les chercheurs dans leurs activités de recherche. Ces traces représentent en effet une fenêtre irremplaçable sur la science en train de se construire : elles permettent de rendre visible et compréhensible le processus habituellement dissimulé de production de la science, ce qui constitue un enjeu scientifique et pédagogique fondamental

Modelling trace metal background to evaluate anthropogenic contamination in arable soils of south-western France

The trace metal (TM) content in arable soils has been monitored across a region of France characterised by a large proportion of calcareous soils. Within this particular geological context, the objectives were to first determine the natural levels of trace metals in the soils and secondly, to assess which sites were significantly contaminated. Because no universal contamination assessment method is currently available, four different methods were applied and compared in order to facilitate the best diagnosis of contamination. First, the TM geochemical background was determined by using basic descriptive statistics and linear regression models calculated with semi-conservative major elements as predictors. The natural concentrations of trace metals varied greatly due to the high soil heterogeneity encountered on the regional scale and were more-or-less accurately modelled according to the considered TM. Second, the basic descriptive statistics and the linear regression methods were then compared with the enrichment factor (EF) method and multivariate analysis (PCA), in order to evaluate whether the concentrations measured in soils were abnormally high or not. The advantages and disadvantages of each method were discussed and their results used to identify the most probable contamination cases, the influence of the soils characteristics, as well as the agricultural land cover. The basic descriptive method was good as a first and easy approach to describe the TM ambient concentrations, but may misinterpret the natural anomalies as contaminations. Based on geochemical associations, the linear regression method provided more realistic results even if the relationships between major and trace metals were not significant for the most mobile TM. The EF method was useful to identify high point source contaminations, but it was not suitable when considering a large dataset of low TM concentrations. Finally, the PCA method was a good preliminary tool for the description of the global TM concentrations in a studied area, but it could only give indication on the highest contaminated points. By comparing the results of the different methods in the studied region, we estimated that 24% of the arable soils were contaminated by at least one trace metal, mainly Cu in vineyards/orchards and Cd, Pb and/or Zn in grazing lands. In addition, the calcareous soils exhibited globally higher natural and anthropogenic TM concentrations than non-calcareous soils, probably because of the lower TM mobility at alkaline pH