430 research outputs found
Finite element analysis of fretting crack propagation
In this work, the finite elements method (FEM) is used to analyse the growth
of fretting cracks. FEM can be favourably used to extract the stress intensity
factors in mixed mode, a typical situation for cracks growing in the vicinity
of a fretting contact. The present study is limited to straight cracks which is
a simple system chosen to develop and validate the FEM analysis. The FEM model
is tested and validated against popular weight functions for straight cracks
perpendicular to the surface. The model is then used to study fretting crack
growth and understand the effect of key parameters such as the crack angle and
the friction between crack faces. Predictions achieved by this analysis match
the essential features of former experimental fretting results, in particular
the average crack arrest length can be predicted accurately
Dialects in animals: Evidence, development and potential functions
International audienceDialects are one of the parallels that have long been established between human language and animal communication. We discuss the potential functional parallels between human and animal dialects, arguing that in both cases different mechanisms and functions may be at stake where large geographical versus very localized (e.g. social) variations are concerned. Birdsong studies in particular, but also recent studies of mammal vocalizations, show that the use of the term âdialectâ to refer to within-species vocal variations in animal species is more than a metaphor and that animal dialects offer a possibility to explore the causes and functions of linguistic variation and change, one of the challenges in exploring the origin of diversity of language families. We present here an original view, as our approach was not "primate-centered" and take into consideration âhomoplasyâ (analogy) as a potential mechanism to explain that different taxa have evolved the same functional response to social constraints
Développement d'un programme d'intervention basé sur le modÚle de l'ouverture émotionnelle et évaluation de son impact sur le traitement affectif
Contexte thĂ©orique : Lâimportance du traitement affectif est actuellement largement reconnue, notamment dans les domaines de la santĂ© physique et psychique. Câest pourquoi, nous avons dĂ©veloppĂ© un programme dâintervention manualisĂ© de six sĂ©ances explicitement basĂ© sur un modĂšle du traitement Ă©motionnel empiriquement validĂ©, le modĂšle de lâ « Ouverture Emotionnelle », dans le but dâinfluencer positivement le traitement affectif et indirectement, la qualitĂ© de vie des participants. MĂ©thode : Les 102 adultes « tout-venant » de notre recherche ont Ă©tĂ© assignĂ©s dans les conditions contrĂŽles (i.e. sans intervention ou en attente dâintervention) ou expĂ©rimentales (i.e. avec intervention). Puis, ils ont rĂ©pondu Ă trois reprises (i.e. prĂ©-test, post-test et suivi) Ă des questionnaires portant sur le traitement affectif, Ă©valuĂ© notamment par le DOE-trait (Reicherts, 1999b, 2007) et le DOE-IT (Reicherts & Haymoz, 2011), ainsi que sur la qualitĂ© de vie, mesurĂ©e par le WHOQOL-Bref (Skevington, Lofty, & OâConnell, 2004). Les participants bĂ©nĂ©ficiant du programme dâintervention ont Ă©galement cĂŽtĂ© leur affectivitĂ© plusieurs fois par jour au moyen du DOE-self-monitoring, servant Ă la fois dâoutil de mesure et dâapprentissage. RĂ©sultats : La comparaison des deux conditions entre les trois points de mesure montre un effet multi-variĂ© significatif de notre intervention sur toutes les dimensions de lâOuverture Emotionnelle prises ensemble. Le dĂ©tail des rĂ©sultats met en exergue un changement positif dans la capacitĂ© Ă pouvoir distinguer ses Ă©tats affectifs et Ă se les reprĂ©senter prĂ©cisĂ©ment (REPCOG) ainsi que dans la rĂ©gulation des Ă©motions (REGEMO), Ă©valuĂ©es par le DOE-trait. En ce qui concerne lâusage et lâefficacitĂ© des stratĂ©gies de rĂ©gulation des Ă©motions exercĂ©es en sĂ©ance et Ă©valuĂ©es par le DOE-IT, nous observons un changement positif dans lâusage de lâ « acceptation » et de la « dĂ©tente mentale » face Ă un affect nĂ©gatif, dans lâefficacitĂ© perçue quant Ă lâusage de la « dĂ©tente mentale » pour la gestion dâun affect nĂ©gatif ainsi que de la « dĂ©tente corporelle » pour un affect positif. Finalement, les rĂ©sultats obtenus au DOE-self-monitoring mettent en Ă©vidence une Ă©volution positive entre les points de mesure de la tendance Ă rĂ©guler ses Ă©motions afin de les augmenter ou les maintenir (REGEMO_up) et Ă percevoir les indicateurs corporels externes accompagnant le vĂ©cu affectif (PEREXT). En outre, les rĂ©sultats nâindiquent aucune influence de notre intervention sur la qualitĂ© de vie des participants. Conclusion : Les rĂ©sultats rĂ©vĂšlent globalement un impact positif de notre programme sur les dimensions susmentionnĂ©es, malgrĂ© lâabsence de rĂ©sultats significatifs sur la qualitĂ© de vie. Au regard de ces rĂ©sultats encourageants, nous souhaitons adapter notre programme Ă des Ă©chantillons cliniques, dont les difficultĂ©s en termes de traitement affectif sont rĂ©guliĂšrement reportĂ©es
Combined XRF, XRD, SEM-EDS, and Raman Analyses on Serpentinized Harzburgite (Nickel Laterite Mine, New Caledonia): Implications for Exploration and Geometallurgy
International audienceDifferent techniques have been combined to determine the crystallography and the chemical composition of serpentinized harzburgite sampled in a drill core coming from the lower part of the New Caledonia ophiolite. Specifically, this serpentinized harzburgite is the common bedrock of most of the nickel laterite mines in New Caledonia. Most of the minerals present in serpentinized harzburgite were analyzed by Raman spectroscopy and XRD. In this study, Raman spectroscopy has been applied for the first time to estimate the nickel content in lizardite, forsterite, talc, and goethite. The analyses confirm that the major serpentine minerals show two varieties: (1) Ni-bearing lizardite and (2) Ni-free lizardite. Furthermore, Ni-rich forsterite, enstatite, Ni-rich talc, sepiolite, periclase (MgO), and quartz were detected. Additionally, Raman spectroscopy evidence minor phases not detected by XRD: anatase, rutile, pyrite, hematite, chromite, magnesiochromite, and Ni-rich goethite. Our results show that the Ni substitution is only present in lizardite exhibiting turbostratic-stacking disorder. This finding has potential for being used as an exploration tool using short-wave-infrared spectroscopy online or as a portable instrument, and for defining geometallurgical parameters for processing these complex ores
Evaluation du projet de lâAssociation RĂ©seau Orientation SantĂ© Social (AROSS)
Dans le cadre des travaux de la planification mĂ©dico-sociale (PMS) du canton de NeuchĂątel et afin dâamĂ©liorer lâorientation des personnes ĂągĂ©es de plus de 65 ans dans le rĂ©seau socio-sanitaire du canton, le rapport « RĂ©seau et entretiens dâorientation » prĂ©conisait la crĂ©ation dâun dispositif dâinformation, dâorientation et de coordination Ă lâĂ©chelle cantonale, portĂ©e par un Ă©tablissement autonome de droit public. La finalitĂ© annoncĂ©e de ce dispositif est « dâaugmenter lâespĂ©rance de vie sans incapacitĂ© », par la dĂ©tection et la prise en charge prĂ©coce et adaptĂ©e des personnes prĂ©-fragiles et fragiles.
Avant le dĂ©ploiement Ă grande Ă©chelle de ce dispositif, lâĂtat a souhaitĂ© lâexpĂ©rimenter sur un territoire du canton. LâAssociation RĂ©seau Orientation SantĂ© Social (AROSS) a ainsi Ă©tĂ© crĂ©Ă©e en mars 2015 afin de promouvoir le dĂ©veloppement dâun rĂ©seau socio-sanitaire assurant lâinformation, lâorientation et lâefficience de lâaccompagnement des personnes ĂągĂ©es de plus de 65 ans, dans une optique de continuitĂ© des soins.
Un projet-pilote, sous la forme dâune structure dâinformation et dâorientation destinĂ©e aux personnes ĂągĂ©es, Ă leurs proches et aux partenaires socio-sanitaires, a Ă©tĂ© mis en place depuis le 1er janvier 2016 sur les communes du Locle et des Brenets, puis Ă©tendu sur lâensemble du district du Locle au 1er janvier 2017, afin de tester et valider lâapproche
The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
We present an analysis of the deepest Herschel images in four major extragalactic fields GOODS-North, GOODS-South, UDS and COSMOS obtained within the GOODS-Herschel and CANDELS-Herschel key programs. The picture provided by 10497 individual far-infrared detections is supplemented by the stacking analysis of a mass-complete sample of 62361 star-forming galaxies from the CANDELS-HST H band-selected catalogs and from two deep ground-based Ks band-selected catalogs in the GOODS-North and the COSMOS-wide fields, in order to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. We show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe our method called "scatter stacking" that may be easily generalized to other experiments. We demonstrate that galaxies of all masses from z=4 to 0 follow a universal scaling law, the so-called main sequence of star-forming galaxies. We find a universal close-to-linear slope of the logSFR-logM* relation with evidence for a flattening of the main sequence at high masses (log(M*/Msun) > 10.5) that becomes less prominent with increasing redshift and almost vanishes by z~2. This flattening may be due to the parallel stellar growth of quiescent bulges in star-forming galaxies. Within the main sequence, we measure a non varying SFR dispersion of 0.3 dex. The specific SFR (sSFR=SFR/M*) of star-forming galaxies is found to continuously increase from z=0 to 4. Finally we discuss the implications of our findings on the cosmic SFR history and show that more than 2/3 of present-day stars must have formed in a regime dominated by the main sequence mode. As a consequence we conclude that, although omnipresent in the distant Universe, galaxy mergers had little impact in shaping the global star formation history over the last 12.5 Gyr
Extracellular Bacterial Pathogen Induces Host Cell Surface Reorganization to Resist Shear Stress
Bacterial infections targeting the bloodstream lead to a wide array of devastating diseases such as septic shock and meningitis. To study this crucial type of infection, its specific environment needs to be taken into account, in particular the mechanical forces generated by the blood flow. In a previous study using Neisseria meningitidis as a model, we observed that bacterial microcolonies forming on the endothelial cell surface in the vessel lumen are remarkably resistant to mechanical stress. The present study aims to identify the molecular basis of this resistance. N. meningitidis forms aggregates independently of host cells, yet we demonstrate here that cohesive forces involved in these bacterial aggregates are not sufficient to explain the stability of colonies on cell surfaces. Results imply that host cell attributes enhance microcolony cohesion. Microcolonies on the cell surface induce a cellular response consisting of numerous cellular protrusions similar to filopodia that come in close contact with all the bacteria in the microcolony. Consistent with a role of this cellular response, host cell lipid microdomain disruption simultaneously inhibited this response and rendered microcolonies sensitive to blood flowâgenerated drag forces. We then identified, by a genetic approach, the type IV pili component PilV as a triggering factor of plasma membrane reorganization, and consistently found that microcolonies formed by a pilV mutant are highly sensitive to shear stress. Our study shows that bacteria manipulate host cell functions to reorganize the host cell surface to form filopodia-like structures that enhance the cohesion of the microcolonies and therefore blood vessel colonization under the harsh conditions of the bloodstream
TLR9 activation induces normal neutrophil responses in a child with IRAK-4 deficiency: involvement of the direct PI3K pathway.
International audiencePolymorphonuclear neutrophils (PMN) play a key role in innate immunity. Their activation and survival are tightly regulated by microbial products via pattern recognition receptors such as TLRs, which mediate recruitment of the IL-1R-associated kinase (IRAK) complex. We describe a new inherited IRAK-4 deficiency in a child with recurrent pyogenic bacterial infections. Analysis of the IRAK4 gene showed compound heterozygosity with two mutations: a missense mutation in the death domain of the protein (pArg12Cys) associated in cis-with a predicted benign variant (pArg391His); and a splice site mutation in intron 7 that led to the skipping of exon 7. A nontruncated IRAK-4 protein was detected by Western blotting. The patient's functional deficiency of IRAK-4 protein was confirmed by the absence of IRAK-1 phosphorylation after stimulation with all TLR agonists tested. The patient's PMNs showed strongly impaired responses (L-selectin and CD11b expression, oxidative burst, cytokine production, cell survival) to TLR agonists which engage TLR1/2, TLR2/6, TLR4, and TLR7/8; in contrast, the patient's PMN responses to CpG-DNA (TLR9) were normal, except for cytokine production. The surprisingly normal effect of CpG-DNA on PMN functions and apoptosis disappeared after pretreatment with PI3K inhibitors. Together, these results suggest the existence of an IRAK-4-independent TLR9-induced transduction pathway leading to PI3K activation. This alternative pathway may play a key role in PMN control of infections by microorganisms other than pyogenic bacteria in inherited IRAK-4 deficiency
Ătude numĂ©rique des champs mĂ©caniques locaux dans les agrĂ©gats polycristallins sous chargements cycliques
Dans les piĂšces mĂ©caniques soumises Ă des sollicitations cycliques, les dĂ©formations rĂ©pĂ©tĂ©es engendrent le phĂ©nomĂšne de fatigue. Dans le cas des polycristaux, on constate une localisation de ces dĂ©formations qui conduit Ă la formation de fissures courtes dont l'amorçage et la micropropagation sont pilotĂ©s par les paramĂštres de la microstructure du matĂ©riau, comme l'orientation des grains et les joints de grains. Cette dĂ©pendance, associĂ©e aux multitudes de configurations microstructurales possibles, explique la forte dispersion des rĂ©sultats d'essais en fatigue. L'Ă©tude numĂ©rique proposĂ©e se base sur des calculs d'agrĂ©gats polycristallins par ĂlĂ©ments Finis avec un modĂšle de plasticitĂ© cristalline sous diffĂ©rentes conditions de chargements cycliques. Ces derniers sont rĂ©alisĂ©s sur des microstructures tridimensionnelles synthĂ©tiques (dĂ©composition de VoronoĂŻ) et rĂ©elles (EBSD avec polissages successifs). Plusieurs configurations d'orientations sont prises en compte afin de reproduire les effets de dispersion observĂ©s expĂ©rimentalement. Les rĂ©sultats des simulations sont analysĂ©s au cas par cas d'une part, et par traitement statistique d'autre part. L'objectif est de rendre compte de l'effet des paramĂštres de la microstructure, tels que le facteur de Schmid sur la formation des fissures courtes de fatigue. Les marches d'extrusion et intrusion en surface, considĂ©rĂ©s comme les sites critiques menant Ă l'amorçage des fissures courtes, sont reproduites numĂ©riquement et comparĂ©es Ă la microstructure rĂ©elle fissurĂ©e. La prĂ©diction de ces marches est en bonne concordance avec les observations expĂ©rimentales, dĂšs lors qu'elles apparaissent dans des grains assez larges en surface. On observe Ă©galement une nocivitĂ© accrue sous chargement Ă©quibiaxial. L'analyse des distributions des champs locaux permet d'analyser quantitativement l'hĂ©tĂ©rogĂ©nĂ©itĂ© des contraintes Ă l'Ă©chelle locale
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