Dissipation and adhesion hysteresis between (010) forsterite surfaces using molecular-dynamics simulation and the Jarzynski equality

Dissipation and adhesion are important in many areas of materials science, including friction and lubrication, cold spray deposition, and micro-electromechanical systems (MEMS). Another interesting problem is the adhesion of mineral grains during the early stages of planetesimal formation in the early solar system. Molecular-dynamics (MD) simulation has often been used to elucidate dissipative properties, most often in the simulation of sliding friction. In this paper, we demonstrate how the reversible and irreversible work associated with interactions between planar surfaces can be calculated using the dynamical contact simulation approach based on MD and empirical potentials. Moreover, it is demonstrated how the approach can obtain the free-energy $\Delta A(z)$ as a function of separation between two slabs using the Jarzynksi equality applied to an ensemble of trajectories which deviate significantly from equilibrium. Furthermore, the dissipative work can also be obtained using this method without the need to compute an entire cycle from approach to retraction. It is expected that this technique might be used to efficiently compute dissipative properties which might enable the use of more accurate approaches including density-functional theory. In this paper, we present results obtained for forsterite surfaces both with and without MgO-vacancy surface defects. It is shown that strong dissipation is possible when MgO-vacancy defects are present. The mechanism for strong dissipation is connected to the tendency of less strongly-bound surface units to undergo large displacements including mass transfer between the two surfaces. Systems with strong dissipation tend to exhibit a long-tailed distribution rather than the Gaussian distribution often anticipated in near-equilibrium applications of the JE.Comment: 26 pages, 15 figure

Annotating sign language using a dedicated glyph system (the project Typannot)

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Création d'un corpus de traces graphiques de la Langue des Signes Française

International audienceThis work constitutes a contribution to the emergence of a common writing for French Sign Language in a graphical or even a typographical framework. Our hypothesis is as follows : in its execution, the gestural sign contains a readable graphic trace that can be visualized with a photographic device. In order to evaluate this hypothesis, we gather a photographic corpus made of isolated elicited signs.Le projet GestuelScript se présente comme une contribution à l'émergence d'une écriture courante pour la Langue des Signes Française dans un cadre de travail essentiellement graphique, voire typographique. Notre hypothèse : le signe gestuel décrirait, dans sa réalisation, une trace graphique lisible qu'un dispositif photographique permet de visualiser. Pour la tester, nous constituons un corpus de travail photographique fait de signes isolés élicités

Evolution of the sex-Related Locus and Genomic Features Shared in Microsporidia and Fungi

Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that microsporidia share a particularly close evolutionary relationship with the zygomycetes.Here we expanded this analysis and also examined a putative sex-locus for variability between microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and microsporidians. One locus previously found to be conserved in many microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sex-related locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and microsporidians.The unique genomic hallmarks between microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in microsporidia and zygomycetes

Annotating Sign Language using a dedicated glyph System

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Typannot: a glyphic system for the transcription of handshapes

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PARCOURS ATTENTIONNEL ET RÉGULARITÉS VISUOSPATIALES DANS L’ÉCRITURE

International audienceL’apprentissage de l’écriture est une activité complexe qui implique d’importantes modifications au niveau psychomoteur et cognitif chez l ’apprenant. Bien qu’essentiellement centrées sur la problématique du contrôle graphomoteur dans des tâches de tracés discrétisés (dimensions finies), les recherches et théories sur l’apprentissage de l’écriture mentionnent l’importance des régularités visuo-spatiales régissant les tracés entre eux dans l’espace d’écriture (dimensions ouvertes de type topologique). L’étude de la nature, du rôle et du fonctionnement de l’attention vis-à-vis de ces régularités nous guidera vers des hypothèses didactiques pouvant être complémentaires des approches existantes. Nous testerons celles-ci au travers de la conception et de l’expérimentation de dispositifs adaptatifs d’entrainement attentionnel (au sein du projet DESCRIPT, UTC, Gapenne), qui devront nous permettre d’observer l’émergence d’une pratique attentionnelle porteuse de stabilité et d’adaptabilité pour le tracé

Structural Correlation between Location and Movement of Signs: Lacking Motion Economy for cospeech gestures

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Sacrificial templates for manufacturing multidimensional vasculature

Biological systems employ complex, composite architectures that are intimately related to homeostatic functionality. A common necessity underlying many of these systems is the transport of fluids that distribute nutrients, remove waste, and provide thermal regulation. Parallels exist in engineered materials; however, the architectures are comparatively less complex. No single fabrication technique has emerged with the flexibility to create architectures of various size-scale and dimensionality. Esser-Kahn et al. introduced a technique referred to as vaporization of sacrificial components (VaSC) [1]. Poly(lactic acid) PLA fibers are first treated with a catalyst, tin oxalate (SnOx), to lower their depolymerization temperature. The fibers are embedded in a thermoset matrix and then vaporized to leave behind straight channels (1D dimensionality). In this study, we extend the application of sacrificial PLA and VaSC to all levels of spatial dimensionality (0D–3D). Sacrificial PLA templates of each level of dimensionality: 0D-spheres, 1D-fibers, 2D-sheets, and 3D-printed structures are fabricated. Two different tin catalysts (tin oxalate, SnOx, and tin octoate, SnOc) are incorporated into PLA to promote depolymerization at modest temperatures (~200°C). Spheres with diameters averaging 23 μm are fabricated using an emulsion/solvent evaporation technique. Fibers spanning two orders of magnitude in diameter are fabricated using electrospinning (~5 μm) and melt-spinning (~300 μm) techniques. Sheets (~550 μm thick) are hot-pressed and laser cut to form branched planar networks. Fused deposition modeling is used to create a 3D branching tree-like structure. Each template is embedded in epoxy and removed using VaSC (200°C in a vacuum oven, 24–48 h) to reveal the inverse of the template architecture. The effectiveness of VaSC is evaluated using isothermal thermogravimetric analysis (iTGA) at 200°C (ex situ), and by tracking weight of the embedded °C in a vacuum oven (in situ). The templates in epoxy subjected to 200°C choice of catalyst influences the vaporization time with SnOc promoting more rapid removal. Comparison of in situ and ex situ tests reveals a delay in VaSC completion in the embedded state. The structures created using template materials from each level of dimensionality (0D–3D) are evaluated by flow rate testing. Experiments were performed under laminar flow conditions and compared to appropriate predictive models. Structures tested include porous sheets, 1D channels, a 2D-bifurcating network, and a 3D-branched tree-like structure. Flow in porous sheets is compared to Darcy’s law using a porosity-permeability correlation, whereas flow in one-dimensional channels is compared to the Hagen–Poiseuille equation. Computational fluid dynamics simulations of flow in both the 2D and 3D structure are performed in ANSYS FLUENT. Experimental data agreed well with modeling/simulation for every level of dimensionality. Sacrificial templates provide a technique to form multiscale, multidimensional, and interconnected vascular and porous networks in thermosetting polymers. Further work in this area will focus on extending the concept to more types of polymers and improving precision and resolution in complex 2D and 3D structures. REFERENCE [1] Esser-Kahn et al.. Adv. Mater. 2011, 23, 3654