Self-Organized Criticality and Thermodynamic formalism

We introduce a dissipative version of the Zhang's model of Self-Organized Criticality, where a parameter allows to tune the local energy dissipation. We analyze the main dynamical features of the model and relate in particular the Lyapunov spectrum with the transport properties in the stationary regime. We develop a thermodynamic formalism where we define formal Gibbs measure, partition function and pressure characterizing the avalanche distributions. We discuss the infinite size limit in this setting. We show in particular that a Lee-Yang phenomenon occurs in this model, for the only conservative case. This suggests new connexions to classical critical phenomena.Comment: 35 pages, 15 Figures, submitte

Yeast cytochrome c oxidase: a model system to study mitochondrial forms of the haem-copper oxidase superfamily.

The known subunits of yeast mitochondrial cytochrome c oxidase are reviewed. The structures of all eleven of its subunits are explored by building homology models based on the published structures of the homologous bovine subunits and similarities and differences are highlighted, particularly of the core functional subunit I. Yeast genetic techniques to enable introduction of mutations into the three core mitochondrially-encoded subunits are reviewed

Interface tactile pour la saisie guidée de connaissances

International audienceIn recent years, artificial intelligence tools have democratized and are increasingly used by people who are not experts in the field. These artificial intelligence tools, like rule-based or constraint-based systems require the input of human expertise to replicate the desired reasoning. Despite the explosion of new devices and new input paradigms, such as tablets and other touch interfaces, it seems that the usability of these tools have not taken advantage of these recent advances. In this article, we illustrate our concept with the rule edition in a fuzzy expert system. The special feature of fuzzy logic is that these rules look closer to natural language than classical logic. We present our work that involves the use of new touch interfaces to edit a fuzzy rule base with one finger. We end this section by the evaluation of the interface with a user panel.Au cours de ces dernières années, les outils d'intelligence artificielle se sont démocratisés et sont de plus en plus sou-vent utilisés par des personnes qui ne sont pas expertes du domaine. Parmi ces outils d'intelligence artificielle, les systèmes à base de règles ou de contraintes nécessitent la saisie de l'expertise humaine afin de reproduire le comporte-ment souhaité. Malgré l'explosion des nouveaux périphé-riques et de nouveaux paradigmes de saisie, comme les tablettes et autres interfaces tactiles, l'ergonomie de ces outils semble ne pas avoir profité de toutes ces avancées récentes. Dans cet article, nous prenons l'exemple d'un système expert flou pour lequel il faut rédiger des règles. La particu-larité de la logique floue est que ces règles sont construites d'une manière plus proche du langage naturel qu'en lo-gique classique. Nous présentons notre travail qui consiste en l'exploitation des nouvelles interfaces tactiles afin de rédiger une base de règles floues avec un seul doigt. Nous terminons cet article par l'évaluation de l'interface auprès d'un panel d'utilisateurs

Stay or drift? Queen acceptance in the ant Formica paralugubris

Abstract.: The acceptance of new queens in ant colonies has profound effects on colony kin structure and inclusive fitness of workers. Therefore, it is important to study the recognition and discrimination behaviour of workers towards reproductive individuals entering established colonies. We examined the acceptance rate of queens in populations of the highly polygynous ant F. paralugubris, where the genetic differentiation among nests and discrimination ability among workers suggest that workers might reject foreign queens. We experimentally introduced young queens in their natal nest and in foreign nests. Surprisingly, the survival rate of mated queens did not differ significantly when introduced in a foreign male-producing nest, a foreign female-producing nest, or the natal nest. Moreover, the survival of virgin queens in their natal nest was twice the one of mated queens, suggesting that mating status plays an important role for acceptance. The results indicate that other factors than queen discrimination by workers are implicated in the limited longdistance gene flow between nests in these population

Rcf2 revealed in cryoEM structures of hypoxic isoforms of mature mitochondrial III-IV supercomplexes

The organisation of the mitochondrial electron transport chain proteins into supercomplexes (SCs) is now undisputed, however their assembly process, or the role of differential expression isoforms, have yet to be determined. In Saccharomyces cerevisiae, cytochrome c oxidase (CIV) forms SCs of varying stoichiometry with cytochrome bc1 (CIII). Recent studies have revealed, in normoxic condition of growth, an interface made exclusively by Cox5A, the only yeast respiratory protein that exists as one of two isoforms depending on oxygen levels. Here, we present the cryo-EM structures of the III2-IV1 and III2-IV2 SCs containing the hypoxic isoform Cox5B solved at 3.4 and 2.8 Å, respectively. We show that the change of isoform doesn’t affect SC formation or activity and that SC stoichiometry is dictated by the level of CIII/CIV biosynthesis. Comparison of the CIV5B and CIV5A-containing SC structures highlighted few differences, mainly found in the region of Cox5. Additional density was revealed in all SCs, independent of CIV isoform, in a pocket formed by Cox1, Cox3, Cox12 and Cox13, away from the CIII-CIV interface. In the CIV5B-containing hypoxic SCs, this could be confidently assigned to the hypoxia-induced gene 1 (Hig1) type 2 protein Rcf2. With conserved residues in mammalian Hig1 proteins and Cox3/Cox12/Cox13 orthologues, we propose that Hig1 type 2 proteins are stoichiometric subunits of CIV, at least when within a III-IV SC

Library Technology and Innovation as a Force for Public Good: A Case study from UCL Library Services

Whilst there have been many innovations and new technology deployed in academic libraries around the world over the past ten years, as digital libraries have grown massively and physical library space has been reconfigured to meet student needs, few of these developments have had a profound impact outside of the university campus. This paper sets out the journey of UCL Library Services over the past 10 years. In line with UCL’s radical tradition and drawing from Jeremy Bentham’s utilitarian principle of “the greatest happiness of the greatest number”, the library is playing a key role in opening access to education and research. First, the paper establishes how the library’s role is being extended, as libraries become providers of excellent customer service, focused on providing an outstanding user experience. As students are seen increasingly as partners, their participation within the university is growing, and education, research and public engagement are intertwining as components of the student experience. The Connected Curriculum at UCL provides a framework for this (r)evolution in higher education. The library’s use of Open Access tools, particularly with UCL Press, helps to connect high-quality science and student outputs with a wide public, enabling this research to be accessed and utilised on a global scale. Finally, the paper looks at innovative approaches to public engagement, leveraging social science and technology to deliver benefits to local communities, particularly in East London. Libraries should work together, across sectors, to address the current need for evidence-based information, and to provide opportunities for citizens to acquire transferable research skills

The smectitic minerals in a bentonite deposit from melo (Uruguay)

International audienceA nearly monomineralic 1.5 m thick bentonite bed sampled in Melo (Uruguay) appears to be a pure high-charge montmorillonite: [Si3.94 Al0.06] (Al1.40 Fe 3+ 0.11 Ti0.02 Mg0.49 Mn0.01) O10 (OH)2 Na0.01 K0.08 Ca0.18. However, contrasting swelling behaviors have been evidenced by fitting the experimental X-ray diffraction patterns recorded on oriented preparations of the same sample in different saturation states. According to the expandability of the layers in the Ca-, K- and K-Ca-saturated (that is saturated first with K + and subsequently with Ca2+) states, three "layer types" were defined. Low-, intermediate-, and high-charge layers are fully, partly, and not expandable, respectively, after K-saturation. Collapse of high-charge layers is not reversible after subsequent Ca-saturation, most likely because of tetrahedral substitutions. These three different layer types are segregated in two distinct randomly interstratified mixedlayer phases. TSA and CEC are shown to depend on the interlayer cation composition