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(394) Production(s) de l'année 2014
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Morphology and Intrinsic Excitability of Regenerating Sensory and Motor Neurons Grown on a Line Micropattern
Auteur(s): Benzina O., Cloitre T., Martin Fernandez M., Raoul Cedric, Gergely C., Scamps Frédérique
(Article) Publié:
Plos One, vol. 9 p.e110687 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01084010_v1
PMID 25329060
DOI: 10.1371/journal.pone.0110687
WoS: 000343942100082
Exporter : BibTex | endNote
4 Citations
Résumé: Axonal regeneration is one of the greatest challenges in severe injuries of peripheral nerve. To provide the bridge needed for regeneration, biological or synthetic tubular nerve constructs with aligned architecture have been developed. A key point for improving axonal regeneration is assessing the effects of substrate geometry on neuronal behavior. In the present study, we used an extracellular matrix-micropatterned substrate comprising 3 mm wide lines aimed to physically mimic the in vivo longitudinal axonal growth of mice peripheral sensory and motor neurons. Adult sensory neurons or embryonic motoneurons were seeded and processed for morphological and electrical activity analyses after two days in vitro. We show that micropattern-guided sensory neurons grow one or two axons without secondary branching. Motoneurons polarity was kept on micropattern with a long axon and small dendrites. The micro-patterned substrate maintains the growth promoting effects of conditioning injury and demonstrates, for the first time, that neurite initiation and extension could be differentially regulated by conditioning injury among DRG sensory neuron subpopulations. The micro-patterned substrate impacts the excitability of sensory neurons and promotes the apparition of firing action potentials characteristic for a subclass of mechanosensitive neurons. The line pattern is quite relevant for assessing the regenerative and developmental growth of sensory and motoneurons and offers a unique model for the analysis of the impact of geometry on the expression and the activity of mechanosensitive channels in DRG sensory neurons.
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Initial stem cell adhesion on porous silicon surface: molecular architecture of actin cytoskeleton and filopodial growth
Auteur(s): Collart Dutilleul Pierre-Yves, Panayotov Ivan, Secret Emilie, Cunin Frédérique, Gergely C., Cuisinier Frédéric, Martin Fernandez M.
(Article) Publié:
Nanoscale Research Letters, vol. 9 p. (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01084004_v1
PMID 25386101
DOI: 10.1186/1556-276X-9-564
WoS: 000347641900001
Exporter : BibTex | endNote
33 Citations
Résumé: The way cells explore their surrounding extracellular matrix (ECM) during development and migration is mediated by lamellipodia at their leading edge, acting as an actual motor pulling the cell forward. Lamellipodia are the primary area within the cell of actin microfilaments (filopodia) formation. In this work, we report on the use of porous silicon (pSi) scaffolds to mimic the ECM of mesenchymal stem cells from the dental pulp (DPSC) and breast cancer (MCF-7) cells. Our atomic force microscopy (AFM), fluorescence microscopy, and scanning electron microscopy (SEM) results show that pSi promoted the appearance of lateral filopodia protruding from the DPSC cell body and not only in the lamellipodia area. The formation of elongated lateral actin filaments suggests that pores provided the necessary anchorage points for protrusion growth. Although MCF-7 cells displayed a lower presence of organized actin network on both pSi and nonporous silicon, pSi stimulated the formation of extended cell protrusions.
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Stochastic 3D optical mapping by holographic localization of Brownian scatterers
Auteur(s): Martinez-Marrades Ariadna, Rupprecht Jean François, Gross M., Tessier Gilles
(Article) Publié:
Optics Express, vol. 22 p.29191-29203 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01083885_v1
DOI: 10.1364/OE.22.029191
WoS: 000345268500139
Exporter : BibTex | endNote
20 Citations
Résumé: We present a wide-field microscopy technique for the 3D mapping of optical intensity distributions using Brownian gold nanopar-ticles as local probes, which are localized by off-axis holography. Fast computation methods allow us to localize hundreds of particles per minute with accuracies as good as 3 × 3 × 10nm3 for immobilized particles. Factors limiting this accuracy are discussed and the possibilities of the technique are illustrated through the 3D optical mapping of an evanescent and a propagative wave. Our results pave the way for a new stochastic imaging technique, well adapted to subwavelength optical characterization in water-based systems.
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Sub-meV linewidth in GaN nanowire ensembles: Absence of surface excitons due to the field ionization of donors
Auteur(s): Corfdir Pierre, Zettler Johannes K., Hauswald Christian, Fernandez-Garrido Sergio, Brandt Oliver, Lefebvre P.
(Article) Publié:
-Physical Review B Condensed Matter And Materials Physics (1998-2015), vol. 90 p.205301 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01083398_v1
DOI: 10.1103/PhysRevB.90.205301
WoS: 000348767800007
Exporter : BibTex | endNote
25 Citations
Résumé: We observe unusually narrow donor-bound exciton transitions (400 µeV) in the photoluminescence spectra of GaN nanowire ensembles grown on Si(111) substrates at very high (>850 ∘C) temperatures. The spectra of these samples reveal a prominent transition of excitons bound to neutral Si impurities which is not observed for samples grown under standard conditions. Motivated by these experimental results, we investigate theoretically the impact of surface-induced internal electric fields on the binding energy of donors by a combined Monte Carlo and envelope function approach. We obtain the ranges of doping and diameter for which the potential is well described using the Poisson equation, where one assumes a spatially homogeneous distribution of dopants. Our calculations also show that surface donors in nanowires with a diameter smaller than 100 nm are ionized when the surface electric field is larger than about 10 kV/cm, corresponding to a doping level higher than 2×1016cm−3. This result explains the experimental observation: since the (D+,X) complex is not stable in GaN, surface-donor-bound excitons do not contribute to the photoluminescence spectra of GaN nanowires above a certain doping level, and the linewidth reflects the actual structural perfection of the nanowire ensemble.
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Light-Emitting-Diodes based on ordered InGaN nanocolumns emitting in the blue, green and yellow spectral range.
Auteur(s): Bengoechea-Encabo Ana, Albert Steven, Lopez-Romero D., Lefebvre P., Barbagini Francesca, Torres-Pardo A., González-Calbet Jose M., Sanchez-Garcia M.A., Calleja E.
(Article) Publié:
Nanotechnology, vol. 25 p.435203 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01073992_v1
PMID 25297338
DOI: 10.1088/0957-4484/25/43/435203
WoS: 000344159600003
Exporter : BibTex | endNote
18 Citations
Résumé: The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN (planar) layers of similar composition and thickness. Electroluminescence spectra show a very small blue shift with increasing current (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.
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Terahertz Plasma Field Effect Transistors
Auteur(s): Knap W., Coquillat D., Diakonova N., But D., Otsuji T., Teppe F.
Chapître d'ouvrage: Physics And Applications Of Terahertz Radiation, vol. p.77 (2014)
Ref HAL: hal-01101033_v1
DOI: 10.1007/978-94-007-3837-9_3
Exporter : BibTex | endNote
Résumé: The channel of the field effect transistor can operate as a cavity for plasma waves. For the electrons with high enough mobility, the plasma waves can propagate in field effect transistors (FETs) channel leading to resonant Terahertz (THz) emission or detection. In the low mobility case, plasma oscillations are overdamped, but a plasma density perturbation can be induced by incoming THz radiation. This perturbation can lead to efficient broadband THz detection. We present an overview of the main experimental results concerning the plasma oscillations in field effect transistors for the generation and the detection of terahertz radiations.
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Terahertz photodetectors based on tapered semiconductor nanowires
Auteur(s): Romeo L., Coquillat D., Husanu E., Ercolani D., Tredicucci A., Beltram F., Sorba L., Knap W., Vitiello M.
(Article) Publié:
Applied Physics Letters, vol. p.231112 (2014)
Ref HAL: hal-01101034_v1
DOI: 10.1063/1.4903473
WoS: 000346266000012
Exporter : BibTex | endNote
14 Citations
Résumé: We report on the demonstration of Terahertz (THz) broadband detectors based on field effect transistors exploiting tapered semiconductor nanowires. The intrinsic asymmetry provided by the nanowires geometry allows to achieve responsivity values as high as 55 V/W (2.5 mA/W) and a noise-equivalent-power of 3 × 10−10 W/Hz1/2 independent of the specific gate voltage applied. The possibility to reduce the number of terminals required to the source and drain contacts only and the technological feasibility of multi-pixel arrays are promising for the realization of compact and integrated THz matrix array detection systems.
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