Mechanical properties of the elemental nanocomponents of nacre structure

Sheet nacre is a nanocomposite with a multiscale structure displaying a lamellar “bricks and mortar” microarchitecture. In this latter, the brick refer to aragonite platelets and the mortar to a soft organic biopolymer. However, it appears that each brick is also a nanocomposite constituted as CaCO3 nanoparticles reinforced organic composite material. What is the role of this “intracrystalline” organic phase in the deformation of platelet? How does this nanostructure control the mechanical behaviour of sheet nacre at the macroscale? To answer these questions, the mechanical properties of each nanocomponents are successively investigated and computed using spherical and sharp nanoindentation tests combined with a structural model of the organomineral platelets built from AFM investigations

Bivariate censored regression relying on a new estimator of the joint distribution function

Abstract In this paper we study a class of M −estimators in a regression model under bivariate random censoring and provide a set of sucient conditions that ensure asymptotic n 1/2 −convergence. The cornerstone of our approach is a new estimator of the joint distribution function of the censored lifetimes. A copula approach is used to modelize the dependence structure between the bivariate censoring times. The resulting estimators present the advantage of being easily computable. A simulation study enlighten the nite sample behaviour of this technique

A multiscale tribological study of nacre : Evidence of wear nanomechanisms controlled by the frictional dissipated power

Sheet nacre is a hybrid biocomposite with a multiscale structure, including nanograins of CaCO3 (97% wt.% – 40 nm in size) and two organic matrices: (i) the “interlamellar” mainly composed of β-chitin and proteins, and (ii) the “intracrystalline” mainly composed by silk-fibroin-like proteins. This material is currently studied as small prostheses with its tribological behaviour. In this work, the latter is studied by varying the frictional dissipated power from few nW to several hundreds mW, in order to study the various responses of the different nacre’s components, independently. Results reveal various dissipative mechanisms vs. dissipated frictional power: organic thin film lubrication, tablet’s elastoplastic deformations, stick-slip phenomenon and/or multiscale wear processes, including various thermo-mechanical processes (i.e., mineral phase transformation, organics melting and friction-induced nanoshocks process on a large range). All these mechanisms are controlled by the multiscale structure of nacre – and especially by its both matrices and respective orientation vs. the sliding direction

Multiscale structure of nacre biomaterial: Thermomechanical behavior and wear processes

Sheet nacre is a hybrid biocomposite with a multiscale structure, including nanograins of CaCO 3 (97% wt.% – 40 nm in size) and two organic matrices: (i) the interlamellar mainly composed of β-chitin and proteins, and (ii) the intracrystalline composed by silk-fibroin-like proteins. This material is currently contemplated for the manufacture of small prostheses (e.g. rachis and dorsal vertebra prostheses) which are subjected to micro-slip or fretting motion. In this work, the tribological behaviour of nacre is studied by varying the frictional dissipated power from few nW to several hundreds mW, in order to assess the various responses of the different nacre’s components, independently. Results reveal various dissipative mechanisms vs. dissipated frictional power: organic thin film lubrication, tablet’s elastoplastic deformations, stick-slip phenomenon and/or multiscale wear processes, including various thermo-mechanical processes (i.e., mineral phase transformation, organics melting and friction-induced nanoshocks process on a large range). All these mechanisms are controlled by the multiscale and anisotropy of its structure – and especially by its both matrices and respective orientation vs. the sliding direction

CASSIOPE: An expert system for conserved regions searches

<p>Abstract</p> <p>Background</p> <p>Understanding genome evolution provides insight into biological mechanisms. For many years comparative genomics and analysis of conserved chromosomal regions have helped to unravel the mechanisms involved in genome evolution and their implications for the study of biological systems. Detection of conserved regions (descending from a common ancestor) not only helps clarify genome evolution but also makes it possible to identify quantitative trait loci (QTLs) and investigate gene function.</p> <p>The identification and comparison of conserved regions on a genome scale is computationally intensive, making process automation essential. Three key requirements are necessary: consideration of phylogeny to identify orthologs between multiple species, frequent updating of the annotation and panel of compared genomes and computation of statistical tests to assess the significance of identified conserved gene clusters.</p> <p>Results</p> <p>We developed a modular system superimposed on a multi-agent framework, called CASSIOPE (Clever Agent System for Synteny Inheritance and Other Phenomena in Evolution). CASSIOPE automatically identifies statistically significant conserved regions between multiple genomes based on automated phylogenies and statistical testing. Conserved regions were searched for in 19 species and 1,561 hits were found. To our knowledge, CASSIOPE is the first system to date that integrates evolutionary biology-based concepts and fulfills all three key requirements stated above. All results are available at <url>http://194.57.197.245/cassiopeWeb/displayCluster?clusterId=1</url></p> <p>Conclusion</p> <p>CASSIOPE makes it possible to study conserved regions from a chosen query genetic region and to infer conserved gene clusters based on phylogenies and statistical tests assessing the significance of these conserved regions.</p> <p><b>Source code </b>is freely available, please contact: <email>[email protected]</email></p

Advances in constitutive modelling of jointed rock hydro mechanical interactions at laboratory scale

Cette étude s’inscrit dans une recherche multi échelles basée sur des expérimentations in situ et des essais de laboratoire. Les essais, injections radiales d’eau au centre de l’éponte inférieure, sont fait à contrainte normale constante de 0 à 110 MPa et pour des pressions de 0 à 4 MPa. Quatre essais hydromécaniques ont été réalisés au laboratoire L3S sur des échantillons de calcaire fracturé (deux diaclases et deux joints de stratification). L’analyse des mesures montre une corrélation entre les variations de la surface de contact et le débit hydraulique dans la fracture. La modélisation hydromécanique réalisée à l’aide du code 3DEC peut être améliorée à partir de l’analyse précédente à travers la modification de la relation entre l’ouverture hydraulique et la fermeture mécanique du joint. L’écart entre les valeurs mesurées et calculées est lié en particulier à la dégradation des aspérités de la fracture sous forte contrainte et à la turbulence des écoulements non prises en compte dans la modélisation

Introducing Trait Networks to Elucidate the Fluidity of Organismal Evolution Using Palaeontological Data

International audienceExplaining the evolution of animals requires ecological, developmental, paleontological, and phylogenetic considerations because organismal traits are affected by complex evolutionary processes. Modeling a plurality of processes, operating at distinct timescales on potentially interdependent traits, can benefit from approaches that are complementary treatments to phylogenetics. Here, we developed an inclusive network approach, implemented in the command line software ComponentGrapher, and analyzed trait co-occurrence of rhinocerotoid mammals. We identified stable, unstable, and pivotal traits, as well as traits contributing to complexes, that may follow to a common developmental regulation, that point to an early implementation of the postcranial Bauplan among rhinocerotoids. Strikingly, most identified traits are highly dissociable, used repeatedly in distinct combinations and in different taxa, which usually do not form clades. Therefore, the genes encoding these traits are likely recruited into novel gene regulation networks during the course of evolution. Our evo-systemic framework, generalizable to other evolved organizations, supports a pluralistic modeling of organismal evolution, including trees and networks

ROOT for the HL-LHC: data format

This document discusses the state, roadmap, and risks of the foundational components of ROOT with respect to the experiments at the HL-LHC (Run 4 and beyond). As foundational components, the document considers in particular the ROOT input/output (I/O) subsystem. The current HEP I/O is based on the TFile container file format and the TTree binary event data format. The work going into the new RNTuple event data format aims at superseding TTree, to make RNTuple the production ROOT event data I/O that meets the requirements of Run 4 and beyond

New Species in the Old World: Europe as a Frontier in Biodiversity Exploration, a Test Bed for 21st Century Taxonomy

The number of described species on the planet is about 1.9 million, with ca. 17,000 new species described annually, mostly from the tropics. However, taxonomy is usually described as a science in crisis, lacking manpower and funding, a politically acknowledged problem known as the Taxonomic Impediment. Using data from the Fauna Europaea database and the Zoological Record, we show that contrary to general belief, developed and heavily-studied parts of the world are important reservoirs of unknown species. In Europe, new species of multicellular terrestrial and freshwater animals are being discovered and named at an unprecedented rate: since the 1950s, more than 770 new species are on average described each year from Europe, which add to the 125,000 terrestrial and freshwater multicellular species already known in this region. There is no sign of having reached a plateau that would allow for the assessment of the magnitude of European biodiversity. More remarkably, over 60% of these new species are described by non-professional taxonomists. Amateurs are recognized as an essential part of the workforce in ecology and astronomy, but the magnitude of non-professional taxonomist contributions to alpha-taxonomy has not been fully realized until now. Our results stress the importance of developing a system that better supports and guides this formidable workforce, as we seek to overcome the Taxonomic Impediment and speed up the process of describing the planetary biodiversity before it is too late