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 & Dopamine. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

Molecular layering in the spreading of wetting liquid drops

Abstract: THE details of the mechanisms involved in the spreading of liquids on solid substrates are still poorly understood, partly because dominant phenomena may occur in the range 0 to 100 A from the substrate. Experimental investigation at the molecular level should provide information on the basic physical process involved. Here we present the results of studies on the time-dependent thickness profile of tiny drops spreading completely on a smooth surface (a silicon wafer). We use simple liquids which lack any orientational or structural order in the bulk. Using ellipsometry, an optical technique that provides measurements of thickness with sub-molecular resolution, we show that there is strong, dynamic structuring of the fluid near the solid surface, in that the spreading droplet advances as a series of distinct molecular layers. These observations may provide a clue to the nature of the molecular interactions or fluid flow phenomena involved in the spreading process.

Delta-Notch signaling controls the generation of neurons/glia from neural stem cells in a stepwise process.

Abstract: We examined the role of Notch signaling on the generation of neurons and glia from neural stem cells by using neurospheres that are clonally derived from neural stem cells. Neurospheres prepared from Dll1 lacZ/lacZ mutant embryos segregate more neurons at the expense of both oligodendrocytes and astrocytes. This mutant phenotype could be rescued when Dll1 lacZ/lacZ spheres were grown and/or differentiated in the presence of conditioned medium from wild-type neurospheres. Temporal modulation of Notch by soluble forms of ligands indicates that Notch signaling acts in two steps. Initially, it inhibits the neuronal fate while promoting the glial cell fate. In a second step, Notch promotes the differentiation of astrocytes, while inhibiting the differentiation of both neurons and oligodendrocytes.

Exact and approximate controllability for distributed parameter systems

Abstract: We consider a system whose state is given by the solution y to a Partial Differential Equation (PDE) of evolution, and which contains control functions, denoted by v.