6,106 research outputs found
Mechanical properties of the elemental nanocomponents of nacre structure
Sheet nacre is a nanocomposite with a multiscale structure displaying a lamellar âbricks and mortarâ 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 âintracrystallineâ 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
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.% â 40 nm in size) and two organic matrices: (i) the âinterlamellarâ mainly composed of ÎČ-chitin and proteins, and (ii) the âintracrystallineâ 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 nacreâs components, independently. Results reveal various dissipative mechanisms vs. dissipated frictional power: organic thin film lubrication, tabletâs 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 â and especially by its both matrices and respective orientation vs. the sliding direction
Extensive Gene Remodeling in the Viral World: New Evidence for Nongradual Evolution in the Mobilome Network
International audienceComplex nongradual evolutionary processes such as gene remodeling are difficult to model, to visualize, and to investigate systematically. Despite these challenges, the creation of composite (or mosaic) genes by combination of genetic segments from unrelated gene families was established as an important adaptive phenomena in eukaryotic genomes. In contrast, almost no general studies have been conducted to quantify composite genes in viruses. Although viral genome mosaicism has been well-described, the extent of gene mosaicism and its rules of emergence remain largely unexplored. Applying methods from graph theory to inclusive similarity networks, and using data from more than 3,000 complete viral genomes, we provide the first demonstration that composite genes in viruses are 1) functionally biased, 2) involved in key aspects of the arm race between cells and viruses, and 3) can be classified into two distinct types of composite genes in all viral classes. Beyond the quantification of the widespread recombination of genes among different viruses of the same class, we also report a striking sharing of genetic information between viruses of different classes and with different nucleic acid types. This latter discovery provides novel evidence for the existence of a large and complex mobilome network, which appears partly bound by the sharing of genetic information and by the formation of composite genes between mobile entities with different genetic material. Considering that there are around 10E31 viruses on the planet, gene remodeling appears as a hugely significant way of generating and moving novel sequences between different kinds of organisms on Earth
Non-Injectivity of Infinite Interval Exchange Transformations and Generalized Thue-Morse Sequences
In this paper we study the non-injectivity arising in infinite interval
exchange transformations. In particular, we build and analyze an infinite
family of infinite interval exchanges semi-conjugated to generalized Thue-Morse
subshifts, whose non-injectivity occurs at a characterizable finite set of
points.Comment: 23 pages, 8 figure
The Kufrah paleodrainage system in Libya: A past connection to the Mediterranean Sea?
International audiencePaillou et al. (2009) mapped a 900 km-long paleodrainage system in eastern Libya, the Kufrah River, that could have linked the southern Kufrah Basin to the Mediterranean coast through the Sirt Basin, possibly as long ago as the Middle Miocene. We study here the potential connection between the terminal part of the Kufrah River and the Mediterranean Sea through the Wadi Sahabi paleochannel, which may have constituted the northern extension of the lower Kufrah River paleodrainage system. New analysis of SRTM-derived topography combined with Synthetic Aperture Radar images from the Japanese PALSAR orbital sensor allowed the mapping of seven main paleochannels located west of the Kufrah River, each of which is likely to have formed a tributary that supplied water and sediment to the main paleodrainage system. The northernmost four paleochannels probably originated from the Al Haruj relief, a Pliocene alkaline basaltic intracontinental volcanic field, and potentially connected to the Wadi Sahabi paleochannel. The remaining three paleochannels are in the more southerly location of the Sarir Calanscio, North-East of the Tibesti mountains, and barely present a topographic signature in SRTM data. They end in the dunes of the Calanscio Sand Sea, forming alluvial fans. The most southern paleochannel, known as Wadi Behar Belama, was previously mapped by Pachur (1996) using LANDSAT-TM images, and was interpreted by Osborne et al. (2008) as representing part of an uninterrupted sediment pathway from the Tibesti mountains to the Mediterranean Sea. Processing of SRTM topographic data revealed local depressions which allow to connect the seven paleochannels and possibly the terminal alluvial fan of the Kufrah River to the Wadi Sahabi paleochannel, through a 400 km-long, south-north oriented, paleocorridor. These new findings support our previous hypothesis that proposed a connection between the lower Kufrah River in the region of the Sarir Dalmah and the Wadi Sahabi paleochannel, which connected to the Mediterranean Sea. Including the newly mapped paleochannels, the Kufrah River paleowatershed, at its maximum extent, would have covered more than 400,000 km2, representing close to a quarter of the surface area of Libya
Combining mobile-health (mHealth) and artificial intelligence (AI) methods to avoid suicide attempts: the Smartcrises study protocol
The screening of digital footprint for clinical purposes relies on the capacity of wearable technologies
to collect data and extract relevant informationâs for patient management. Artificial intelligence (AI) techniques
allow processing of real-time observational information and continuously learning from data to build
understanding. We designed a system able to get clinical sense from digital footprints based on the smartphoneâs
native sensors and advanced machine learning and signal processing techniques in order to identify suicide risk.
Method/design: The Smartcrisis study is a cross-national comparative study. The study goal is to determine the
relationship between suicide risk and changes in sleep quality and disturbed appetite. Outpatients from the
Hospital FundaciĂłn JimĂ©nez DĂaz Psychiatry Department (Madrid, Spain) and the University Hospital of Nimes
(France) will be proposed to participate to the study. Two smartphone applications and a wearable armband will
be used to capture the data. In the intervention group, a smartphone application (MEmind) will allow for the
ecological momentary assessment (EMA) data capture related with sleep, appetite and suicide ideations.
Discussion: Some concerns regarding data security might be raised. Our system complies with the highest level of
security regarding patientsâ data. Several important ethical considerations related to EMA method must also be
considered. EMA methods entails a non-negligible time commitment on behalf of the participants. EMA rely on
daily, or sometimes more frequent, Smartphone notifications. Furthermore, recording participantsâ daily experiences
in a continuous manner is an integral part of EMA. This approach may be significantly more than asking a
participant to complete a retrospective questionnaire but also more accurate in terms of symptoms monitoring.
Overall, we believe that Smartcrises could participate to a paradigm shift from the traditional identification of risks
factors to personalized prevention strategies tailored to characteristics for each patientThis study was partly funded by FundaciĂłn JimĂ©nez DĂaz Hospital, Instituto
de Salud Carlos III (PI16/01852), DelegaciĂłn del Gobierno para el Plan
Nacional de Drogas (20151073), American Foundation for Suicide Prevention
(AFSP) (LSRG-1-005-16), the Madrid Regional Government (B2017/BMD-3740
AGES-CM 2CM; Y2018/TCS-4705 PRACTICO-CM) and Structural Funds of the
European Union. MINECO/FEDER (âADVENTUREâ, id. TEC2015â69868-C2â1-R)
and MCIU Explora Grant âaMBITIONâ (id. TEC2017â92552-EXP), the French Embassy
in Madrid, Spain, The foundation de lâavenir, and the Fondation de
France. The work of D. RamĂrez and A. ArtĂ©s-RodrĂguez has been partly supported
by Ministerio de EconomĂa of Spain under projects: OTOSIS
(TEC2013â41718-R), AID (TEC2014â62194-EXP) and the COMONSENS Network
(TEC2015â69648-REDC), by the Ministerio de EconomĂa of Spain jointly with
the European Commission (ERDF) under projects ADVENTURE (TEC2015â
69868-C2â1-R) and CAIMAN (TEC2017â86921-C2â2-R), and by the Comunidad
de Madrid under project CASI-CAM-CM (S2013/ICE-2845). The work of P.
Moreno-Muñoz has been supported by FPI grant BES-2016-07762
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