Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Receptor. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

Wetting transitions on rough surfaces

Abstract: We consider microscopic contact states of a drop deposited on textured rough surfaces. The energies of three possible (meta)stable wetting states are compared and the lowest energy state is regarded as the "phase". We present the "phase diagrams" in the two-dimensional space of texture parameters, which suggests transitions between the wetting states. We propose a model which allows the description of transition states between (meta)stable contact states and quantify the energy barriers between them. Thereby, we theoretically suggest that the actually realized state is not always the lowest energy state.

Controlled Design of Size-Tunable Monodisperse Nickel Nanoparticles

Abstract: We present here a complete study on a synthesis of nickel nanoparticles involving the reaction of [Ni(acac)2] with oleylamine (OA) and trioctylphosphine (TOP) reactants, whose simultaneous presence and relative amounts are paramount. The role of every reactant in the nucleation and growth of the nanoparticles has been delineated: OA is the reductant and thus controls the nucleation rate, meanwhile TOP provides a tunable surface stabilization through coordination on the Ni(0) surface. This result leads us to a design synthesis providing tailored monodispersed nanoparticles in a wide range (2−30 nm), which allows self-consistent studies of size-induced changes in catalytic and magnetic properties. Additionally, the growth mechanism is demonstrated to include an aggregation step which thus correlates with the polycrystalline feature of the nanoparticles obtained through this process. Moreover, the critical influence of the phosphine in this system was demonstrated a) for the outcome of the ripening mechanism...

Noncovalent Modification of Carbon Nanotubes with Pyrene‐Functionalized Nickel Complexes: Carbon Monoxide Tolerant Catalysts for Hydrogen Evolution and Uptake

Abstract: Hydrogen production through the reduction of water appears to be a very attractive solution for the long-term storage of renewable energy. However, economically viable processes require platinum-free catalysts, since this expensive and scarce metal is not a sustainable resource. We recently showed that the combination of a bioinspired molecular approach with nanochemical tools, through the covalent attachment of mimics 3] of the active site of hydrogenase enzymes onto carbon nanotubes (CNTs), results in a noblemetal-free electrocatalytic nanomaterial with low overpotential and exceptional stability for H2 evolution or uptake. [4,5] In this initial study, we used the electroreduction of a diazonium salt to decorate multiwalled carbon nanotubes (MWCNTs) deposited on the electrode support with a polyphenylene layer bearing amino groups. These amino groups were then used to attach an activated ester derivative [Ni(P2N Ar 2)2] 2+

Negative effect of Hox gene expression on the development of the neural crest-derived facial skeleton

Abstract: Diencephalic, mesencephalic and metencephalic neural crest cells are skeletogenic and derive from neural folds that do not express Hox genes. In order to examine the influence of Hox gene expression on skull morphogenesis, expression of Hoxa2, Hoxa3 and Hoxb4 in conjunction with that of the green fluorescent protein has been selectively targeted to the Hox-negative neural folds of the avian embryo prior to the onset of crest cell emigration. Hoxa2 expression precludes the development of the entire facial skeleton. Transgenic Hoxa2 embryos such as those from which the Hox-negative domain of the cephalic neural crest has been removed have no upper or lower jaws and no frontonasal structures. Embryos subjected to the forced expression of Hoxa3 and Hoxb4 show severe defects in the facial skeleton but not a complete absence of facial cartilage. Hoxa3 prevents the formation of the skeleton derived from the first branchial arch, but allows the development (albeit reduced) of the nasal septum. Hoxb4, by contrast, hampers the formation of the nasal bud-derived skeleton, while allowing that of a proximal (but not distal) segment of the lower jaw. The combined effect of Hoxa3 and Hoxb4 prevents the formation of facial skeletal structures, comparable with Hoxa2. None of these genes impairs the formation of neural derivatives of the crest. These results suggest that over the course of evolution, the absence of Hox gene expression in the anterior part of the chordate embryo was crucial in the vertebrate phylum for the development of a face, jaws and brain case, and, hence, also for that of the forebrain.