Ref HAL: hal-02024615_v1
DOI: 10.1016/j.jcis.2019.02.017
WoS: 000461536400040
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10 Citations
Résumé:

Hypothesis: Rotational Brownian diffusions of colloidal particles at a fluid interface play important roles in particle self-assembly and in surface microrheology. Recent experiments on translational Brownian motion of spherical particles at the air-water interface show a significant slowing down of the translational diffusion with respect to the hydrodynamic predictions (Boniello et al., 2015). For the rotational diffusions of partially wetted colloids, slowing down of the particle dynamics can be also expected.Experiments: Here, the rotational dynamics of Janus colloids at the air-water interface have been experimentally investigated using optical microscopy. Bright field and fluorescent microscopies have been used to measure the in-plane and out-of-plane particle rotational diffusions exploiting the Janus geometry of the colloids we fabricated.Findings: Our results show a severe slowing down of the rotational diffusion Dr,⊥ connected to the contact line motion and wetting-dewetting dynamics occurring on particle regions located at opposite liquid wedges. A slowing down of the particle rotational diffusion about an axis parallel to the interfacial normal Dr,|| was also observed. Contact line fluctuations due to partial wetting dynamics lead to a rotational line friction that we have modelled in order to describe our results.

Ref HAL: hal-02023484_v1
Ref Arxiv: 1902.02811
Ref. & Cit.: NASA ADS
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We consider classical and quantum integrable sigma models and their relations with the solutions of renormalization group equations. We say that an integrable sigma model possesses the "nice" duality property if the dual quantum field theory has the weak coupling region. As an example, we consider the deformed $CP(n-1)$ sigma model with additional quantum degrees of freedom. We formulate the dual integrable field theory and use perturbed conformal field theory, perturbation theory, $S$-matrix, Bethe Ansatz and renormalization group methods to show that this field theory has the "nice" duality property. We consider also an alternative approach to the analysis of sigma models on the deformed symmetric spaces, based on the perturbed rational conformal field theories.

Commentaires: 37 pages

Ref HAL: hal-02022558_v1
Ref Arxiv: 1810.01213
DOI: 10.1103/PhysRevE.99.012107
WoS: WOS:000455062400003
Ref. & Cit.: NASA ADS
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11 Citations
Résumé:

A novel form of amorphous matter characterized by marginal stability was recently discovered in the mean-field theory of structural glasses. Using this approach, we provide complete phase diagrams delimiting the location of the marginally stable glass phase for a large variety of pair interactions and physical conditions, extensively exploring physical regimes relevant to granular matter, foams, emulsions, hard and soft colloids, and molecular glasses. We find that all types of glasses may become marginally stable, but the extent of the marginally stable phase highly depends on the preparation protocol. Our results suggest that marginal phases should be observable for colloidal and non-Brownian particles near jamming and for poorly annealed glasses. For well-annealed glasses, two distinct marginal phases are predicted. Our study unifies previous results on marginal stability in mean-field models and will be useful to guide numerical simulations and experiments aimed at detecting marginal stability in finite-dimensional amorphous materials.

Ref HAL: hal-01996796_v1
DOI: 10.1101/509190
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Résumé:

During embryogenesis of all vertebrates, haematopoietic stem/progenitor cells 16 (HSPCs) extrude from the aorta by a complex process named Endothelial-to-17 Haematopoietic Transition (EHT). HSPCs will then colonize haematopoietic organs 18 allowing haematopoiesis throughout adult life. The mechanism underlying EHT 19 including the role of each aortic endothelial cell within the global aorta dynamics 20 remains unknown. In the present study, we show for the first time that EHT involves the 21 remodelling of individual cells within a collective migration of endothelial cells which is 22 tightly orchestrated, resulting in HSPCs extrusion in the sub-aortic space without 23 compromising aorta integrity. By performing a cross-disciplinary study which combines 24 high resolution 4D imaging and theoretical analysis based on the concepts of classical 25 mechanics, we propose that this complex developmental process is dependent on 26 mechanical instabilities of the aorta preparing and facilitating the extrusion of HSPCs. 27 28 29 We dedicate this work to the memory of our friend and colleague, V. Lorman. 30 31 All rights reserved. No reuse allowed without permission. (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

Ref HAL: hal-02010278_v1
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Résumé:

How glasses break: A randomcritical point for yielding

Ref HAL: hal-02010215_v1
DOI: 10.1039/C8CP06817H
WoS: 000459584900045
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4 Citations
Résumé:

Adsorption studies in flexible metal–organic frameworks are challenging and time-consuming. It ismainly because the mechanism of adsorption, defined by structural framework properties, is constantlymodified during the process, as the framework transformation depends on the adsorption uptake. Wepropose here a new approach to investigate adsorption in such complex systems, in which thesimulations of adsorption in a deforming framework are replaced by the analysis of adsorption inintermediate rigid structures. As a proof of concept we analyze carbon dioxide, hexane, and methaneadsorption in MIL-53. 19 intermediate structures were generated using geometrical interpolationbetween the open and the closed MOF forms and optimized with quantum DFT calculations. The grandcanonical Monte Carlo method was applied to calculate adsorption isotherms in all intermediatestructures. The comparison with experimental results enabled the identification of the intermediateadsorption states. The analysis of the microscopic configurations of the adsorbed molecules in thesestructures allowed us to propose a new mechanism of adsorbate evolution over the entire process.

Ref HAL: hal-01993807_v1
Ref Arxiv: 1804.08765
DOI: 10.1038/s41467-018-07978-1
WoS: 000454756900003
Ref. & Cit.: NASA ADS
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41 Citations
Résumé:

We numerically study the evolution of the vibrational density of states $D(\omega)$ of zero-temperature glasses when their kinetic stability is varied over an extremely broad range, ranging from poorly annealed glasses obtained by instantaneous quenches from above the onset temperature, to ultrastable glasses obtained by quenching systems thermalised below the experimental glass temperature. The low-frequency part of the density of states splits between extended and quasi-localized modes. Extended modes exhibit a boson peak crossing over to Debye behaviour ($D(\omega) \sim \omega^2$) at low-frequency, with a strong correlation between the two regimes. Quasi-localized modes instead obey $D(\omega) \sim \omega^4$, irrespective of the glass stability. However, the prefactor of this quartic law becomes smaller in more stable glasses, and the corresponding modes become more localized and sparser. Our work is the first numerical observation of quasi-localized modes in a regime relevant to experiments, and it establishes a direct connection between glass stability and soft vibrational motion in amorphous solids.

Commentaires: 8 pages, 6 figures.Nat. Commun. 10, 26 (2019), https://rdcu.be/bfkWJ