Université PSL

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RECHERCHER

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Microporous electrostrictive materials for vibrational energy harvesting
MIE - Matériaux Innovants pour l'Energie - Mickaël Pruvost, Wilbert J Smit, Cécile Monteux, Philippe Poulin, Annie Colin
Multifunctional Materials - 1 015004 - - 2018
We present electrostrictive materials with excellent properties for vibrational energy harvesting applications. The developed materials consist of a porous carbon black composite, which is processed using water-in-oil emulsions. In combination with an insulating layer, the investigated structures exhibit a high effective relative dielectric permittivity (up to 182 at 100 Hz) with very low effective conductivity (down to 2.53 10− 8 S m− 1). They can generate electrical energy in response to mechanical vibrations with a power density of 0.38 W m− 3 under an applied bias electric field of 32 V. They display figures or merit for energy harvesting applications well above reference polymer materials in the field, including fluorinated co-and ter-polymers synthetized by heavy chemical processes. The production process of the present materials is based on non hazardous and low-cost chemicals. The soft dielectric materials are …
Shear Rheology Control of Wrinkles and Patterns in Graphene Oxide Films
MIE - Matériaux Innovants pour l'Energie - Franco Tardani, Wilfrid Neri, Cécile Zakri, Hamid Kellay, Annie Colin, Philippe Poulin
Langmuir - 9(34) 2996-3002 - - 2018
Drying graphene oxide (GO) films are subject to extensive wrinkling, which largely affects their final properties. Wrinkles were shown to be suitable in biotechnological applications; however, they negatively affect the electronic properties of the films. Here, we report on wrinkle tuning and patterning of GO films under stress-controlled conditions during drying. GO flakes assemble at an air–solvent interface; the assembly forms a skin at the surface and may bend due to volume shrinkage while drying. We applied a modification of evaporative lithography to spatially define the evaporative stress field. Wrinkle alignment is achieved over cm2 areas. The wavelength (i.e., wrinkle spacing) is controlled in the μm range by the film thickness and GO concentration. Furthermore, we propose the use of nanoparticles to control capillary forces to suppress wrinkling. An example of a controlled pattern is given to elucidate the …
All-organic microelectromechanical systems integrating electrostrictive nanocomposite for mechanical energy harvesting
MIE - Matériaux Innovants pour l'Energie - Hussein Nesser, Hélène Debéda, Jinkai Yuan, Annie Colin, Philippe Poulin, Isabelle Dufour, Cédric Ayela
Nano energy - 44 1-6 - - 2018
Recent advances in the field of microelectromechanical systems (MEMS) have generated great interest in the substitution of inorganic microcantilevers by organic ones, due to their low cost, high flexibility and a simplified fabrication by means of printing methods. Here, we present the integration of electrostrictive nanocomposites into organic microcantilever resonators specifically designed for mechanical energy harvesting from ambient vibrations. Strain sensitive nanocomposite materials composed of reduced graphene oxide (rGO) dispersed in polydimethylsiloxane (PDMS) are integrated into all-organic MEMS by means of an innovative low-cost and environment friendly process by combining printing techniques and xurography. Static tests of the electrostrictive nanocomposite with 3.7 wt% rGO show good performances with variations of capacitance that exceeds 4% for strain values lower than 0.55% as the …
Giant Electrostriction of Soft Nanocomposites Based on Liquid Crystalline Graphene
MIE - Matériaux Innovants pour l'Energie - Jinkai Yuan, Alan Luna, Wilfrid Neri, Cécile Zakri, Annie Colin, Philippe Poulin
ACS nano - 12(2) 1688-1695 - - 2018
High electromechanical coupling is critical to perform effective conversion between mechanical and electrical energy for various applications of electrostrictive polymers. Herein, a giant electrostriction effect is reported in liquid crystalline graphene-doped dielectric elastomers. The materials are formulated by a phase-transfer method which allows the solubilization of graphenic monolayers in nonpolar solvents. Dielectric spectroscopy is combined with tensile test devices to measure the true electrostriction coefficients with differentiating the Maxwell stress effect. Because of their liquid crystal structure, the resultant composites show an ultralarge electrostriction coefficient (∼10–14 m2/V2 at 0.1 Hz) coupled with good reproducibility during cycles at high deformation rates. This work offers a promising pathway to design high-performance electrostrictive polymer composites as well as to provide insights into mechanisms …
Shear thinning in non-Brownian suspensions
MIE - Matériaux Innovants pour l'Energie - Guillaume Chatté, Jean Comtet, Antoine Niguès, Lydéric Bocquet, Alessandro Siria, Guylaine Ducouret, François Lequeux, Nicolas Lenoir, Guillaume Ovarlez, Annie Colin
Soft Matter - 6(14) 879-893 - - 2018
We study the flow of suspensions of non-Brownian particles dispersed into a Newtonian solvent. Combining capillary rheometry and conventional rheometry, we evidence a succession of two shear thinning regimes separated by a shear thickening one. Through X-ray radiography measurements, we show that during each of those regimes, the flow remains homogeneous and does not involve particle migration. Using a quartz-tuning fork based atomic force microscope, we measure the repulsive force profile and the microscopic friction coefficient μ between two particles immersed into the solvent, as a function of normal load. Coupling measurements from those three techniques, we propose that (1) the first shear-thinning regime at low shear rates occurs for a lubricated rheology and can be interpreted as a decrease of the effective volume fraction under increasing particle pressures, due to short-ranged repulsive …
Derivation of nearest-neighbor DNA parameters in magnesium from single molecule experiments.
Laboratoire Biochimie - Huguet JM1,2, Ribezzi-Crivellari M3, Bizarro CV4, Ritort F1,5.
Nucleic Acids Res. - 120 158101 - doi: 10.1093/nar/gkx1161. - 2017
DNA hybridization is an essential molecular reaction in biology with many applications. The nearest-neighbor (NN) model for nucleic acids predicts DNA thermodynamics using energy values for the different base pair motifs. These values have been derived from melting experiments in monovalent and divalent salt and applied to predict melting temperatures of oligos within a few degrees. However, an improved determination of the NN energy values and their salt dependencies in magnesium is still needed for current biotechnological applications seeking high selectivity in the hybridization of synthetic DNAs. We developed a methodology based on single molecule unzipping experiments to derive accurate NN energy values and initiation factors for DNA. A new set of values in magnesium is derived, which reproduces unzipping data and improves melting temperature predictions for all available oligo lengths, in a range of temperature and salt conditions where correlation effects between the magnesium bound ions are weak. The NN salt correction parameters are shown to correlate to the GC content of the NN motifs. Our study shows the power of single-molecule force spectroscopy assays to unravel novel features of nucleic acids such as sequence-dependent salt corrections.
Information-theoretic analysis of the directional influence between cellular processes
Laboratoire Biochimie - Sourabh Lahiri, Philippe Nghe, Sander J. Tans, Martin Luc Rosinberg, David Lacoste
Nucleic Acids Res. - - doi.org/10.1371/journal.pone.0187431 - 2017
Inferring the directionality of interactions between cellular processes is a major challenge in systems biology. Time-lagged correlations allow to discriminate between alternative models, but they still rely on assumed underlying interactions. Here, we use the transfer entropy (TE), an information-theoretic quantity that quantifies the directional influence between fluctuating variables in a model-free way. We present a theoretical approach to compute the transfer entropy, even when the noise has an extrinsic component or in the presence of feedback. We re-analyze the experimental data from Kiviet et al. (2014) where fluctuations in gene expression of metabolic enzymes and growth rate have been measured in single cells of E. coli. We confirm the formerly detected modes between growth and gene expression, while prescribing more stringent conditions on the structure of noise sources. We furthermore point out practical requirements in terms of length of time series and sampling time which must be satisfied in order to infer optimally transfer entropy from times series of fluctuations
Evolutionary Applications
Laboratoire Biochimie - Calcagno, V., Mitoyen, C., Audiot, P., Ponsard, S., Gao, G.-Z., Lu, Z.-Z., Wang, Z.-Y., He, K.-L., and Bourguet, D. Parallel
Semin Cell Dev Biol. - 10 9 - DOI: 10.1111/eva.12481 - 2017
Maize was introduced into opposite sides of Eurasia 500 years ago, in Western Europe and in Asia. This caused two host-shifts in the phytophagous genus Ostrinia; O. nubilalis (the European corn borer; ECB) and O. furnacalis (the Asian corn borer; ACB) are now major pests of maize worldwide. They originated independently from Dicot-feeding ancestors, similar to O. scapulalis(the Adzuki bean borer; ABB). Unlike other host-plants, maize is yearly harvested, and harvesting practices impose severe mortality on larvae found above the cut-off line. Positive geotaxis in the ECB has been proposed as a behavioural adaptation to harvesting practices, allowing larvae to move below the cut-off line and thus escape harvest mortality. Here, we test whether the same behavioural adaptation evolved independently in Europe and in Asia. We sampled eight genetically differentiated ECB, ACB and ABB populations in France and China and monitored geotaxis through the entire larval development in artificial stacks mimicking maize stems. We find that all ECB and ACB populations show a similar tendency to move down during the latest larval stages, a behaviour not observed in any European or Asian ABB population. The behaviour is robustly expressed regardless of larval density, development mode or environmental conditions. Our results indicate that maize introduction triggered parallel behavioural adaptations in Europe and Asia, harvest selection presumably being the main driver.
Caveolin-1 Expression Increases upon Maturation in Dendritic Cells and Promotes Their Migration to Lymph Nodes Thereby Favoring the Induction of CD8 T Cell Responses.
Laboratoire Biologie cellulaire systémique de la polarité et de la division - Oyarce C, Cruz-Gomez S, Galvez-Cancino F, Vargas P, Moreau HD, Diaz-Valdivia N, Diaz J, Salazar-Onfray FA, Pacheco R6, Lennon-Dumenil AM, Quest AFG, Lladser A.
Front Immunol - 13;8 1794 - doi: 10.3389/fimmu.2017.01794 - 2017
Dendritic cell (DC) trafficking from peripheral tissues to lymph nodes (LNs) is a key step required to initiate T cell responses against pathogens as well as tumors. In this context, cellular membrane protrusions and the actin cytoskeleton are essential to guide DC migration towards chemotactic signals. Caveolin-1 (CAV1) is a scaffolding protein that modulates signaling pathways leading to remodeling of the actin cytoskeleton and enhanced migration of cancer cells. However, whether CAV1 is relevant for DC function and specifically for DC migration to LNs is unknown. Here, we show that CAV1 expression is upregulated in DCs upon LPS- and TNF-α-induced maturation. CAV1 deficiency did not affect differentiation, maturation, or the ability of DCs to activate CD8+ T cells in vitro. However, CAV1-deficient (CAV1-/-) DCs displayed reduced in vivo trafficking to draining LNs in control and inflammatory conditions. In vitro, CAV1-/- DCs showed reduced directional migration in CCL21 gradients in transwell assays without affecting migration velocity in confined microchannels or three-dimensional collagen matrices. In addition, CAV1-/- DCs displayed reduced activation of the small GTPase Rac1, a regulator of actin cytoskeletal remodeling, and lower numbers of F-actin-forming protrusions. Furthermore, mice adoptively transferred with peptide-pulsed CAV1-/- DCs showed reduced CD8+ T cell responses and antitumor protection. Our results suggest that CAV1 promotes the activation of Rac1 and the formation of membrane protrusions that favor DC chemotactic trafficking toward LNs where they can initiate cytotoxic T cell responses.
Forcing Entry into the Nucleus.
Laboratoire Biologie cellulaire systémique de la polarité et de la division - AlexisLomakin, GuilhermeNader, MatthieuPiel
Cell - 43 547-548 - https://doi.org/10.1016/j.devcel.2017.11.015 - 2017
Nuclear pore complexes tightly regulate nucleo-cytoplasmic transport, controlling the nuclear concentration of several transcription factors. In a recent issue of Cell, Elosegui-Artola et al. (2017) show that nuclear deformation modulates the nuclear entry rates of YAP/TAZ via nuclear pore stretching, clarifying how forces affect gene transcription.

410 publications.