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.

The neural crest

Abstract: This 1999 edition of The Neural Crest contains comprehensive information about the neural crest, a structure unique to the vertebrate embryo, which has only a transient existence in early embryonic life. The ontogeny of the neural crest embodies the most important issues in developmental biology, as the neural crest is considered to have played a crucial role in evolution of the vertebrate phylum. Data that analyse neural crest ontogeny in murine and zebrafish embryos have been included in this revision. This revised edition also takes advantage of recent advances in our understanding of markers of neural crest cell subpopulations, and a full chapter is now devoted to cell lineage analysis. The major research breakthrough since the first edition has been the introduction of molecular biology to neural crest research, enabling an elucidation of many molecular mechanisms of neural crest development. This book is essential reading for students and researchers in developmental biology, cell biology, and neuroscience.

A decade of molecular biology of retinoic acid receptors.

Abstract: Retinoids play an important role in development, differentiation, and homeostasis. The discovery of retinoid receptors belonging to the superfamily of nuclear ligand-activated transcriptional regulators has revolutionized our molecular understanding as to how these structurally simple molecules exert their pleiotropic effects. Diversity in the control of gene expression by retinoid signals is generated through complexity at different levels of the signaling pathway. A major source of diversity originates from the existence of two families of retinoid acid (RA) receptors (R), the RAR isotypes (alpha, beta, and gamma) and the three RXR isotypes (alpha, beta, and gamma), and their numerous isoforms, which bind as RXR/RAR heterodimers to the polymorphic cis-acting response elements of RA target genes. The possibility of cross-modulation (cross-talk) with cell-surface receptors signaling pathways, as well as the finding that RARs and RXRs interact with multiple putative coactivators and/or corepressors, generates additional levels of complexity for the array of combinatorial effects that underlie the pleiotropic effects of retinoids. This review focuses on recent developments, particularly in the area of structure-function relationships.

Perspectives in Supramolecular Chemistry—From Molecular Recognition towards Molecular Information Processing and Self‐Organization

Abstract: The selective binding of a substrate by a molecular receptor to form a supramolecular species involves molecular recognition which rests on the molecular information stored in the interacting species. The functions of supermolecules cover recognition, as well as catalysis and transport. In combination with polymolecular organization, they open ways towards molecular and supramolecular devices for information processing and signal generation. The development of such devices requires the design of molecular components performing a given function (e.g., photoactive, electroactive, ionoactive, thermoactive, or chemoactive) and suitable for assembly into an organized array. Light-conversion devices and charge-separation centers have been realized with photoactive cryptates formed by receptors containing photosensitive groups. Eleclroactive and ionoactive devices are required for carrying information via electronic and ionic signals. Redox-active polyolefinic chains, like the “caroviologens”, represent molecular wires for electron transfer through membranes. Push-pull polyolefins possess marked nonlinear optical properties. Tubular mesophases, formed by organized stacking of suitable macro-cyclic components, as well as “chundle”-type structures, based on bundles of chains grafted onto a macrocyclic support, represent approaches to ion channels. Lipophilic macrocyclic units form Langmuir-Blodgett films that may display molecular recognition at the air-water interface. Supramolecular chemistry has relied on more or less preorganized molecular receptors for effecting molecular recognition, catalysis, and transport processes. A step beyond preorganization consists in the design of systems undergoing self-organization, that is, systems capable of spontaneously generating a well-defined supramolecular architecture by self-assembling from their components under a given set of conditions. Several approaches to self-assembling systems have been pursued: the formation of helical metal complexes, the double-stranded helicates, which result from the spontaneous organization of two linear polybipyridine ligands into a double helix by binding of specific metal ions; the generation of mesophases and liquid crystalline polymers of supramolecular nature from complementary components, amounting to macroscopic expression of molecular recognition; the molecular-recognition-directed formation of ordered solid-state structures. Endowing photo-, electro-, and ionoactive components with recognition elements opens perspectives towards the design of programmed molecular and supramolecular systems capable of self-assembly into organized and functional supramolecular devices. Such systems may be able to perform highly selective operations of recognition, reaction, transfer, and structure generation for signal and information processing at the molecular and supramolecular levels.

A flat Universe from high-resolution maps of the cosmic microwave background radiation

Abstract: The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole l_(peak) = (197 ± 6), with an amplitude ΔT_(200) = (69 ± 8) µK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

Mean Field Games

Abstract: We survey here some recent studies concerning what we call mean-field models by analogy with Statistical Mechanics and Physics. More precisely, we present three examples of our mean-field approach to modelling in Economics and Finance (or other related subjects...). Roughly speaking, we are concerned with situations that involve a very large number of “rational players” with a limited information (or visibility) on the “game”. Each player chooses his optimal strategy in view of the global (or macroscopic) informations that are available to him and that result from the actions of all players. In the three examples we mention here, we derive a mean-field problem which consists in nonlinear differential equations. These equations are of a new type and our main goal here is to study them and establish their links with various fields of Analysis. We show in particular that these nonlinear problems are essentially well-posed problems i.e., have unique solutions. In addition, we give various limiting cases, examples and possible extensions. And we mention many open problems.