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.

Colloid & Polymer Science

Abstract: Certain water soluble polymers may have a repulsive two-body interaction, but an attractiven-body interaction induced by certain “clustering” effects. In the bulk this may lead to a “ $$\bar \theta $$ point” in the phase diagram. Here, with polymer brushes, we construct the theoretical density profiles, using a local mean-field approximation. The brush often shows two layers (one dense near the wall, and one dilute), but the concentrations in both layers depend on the distance to the wall. The location of the interlayer boundary can be derived from a Maxwell construction.

Quantum Kibble-Zurek mechanism and critical dynamics on a programmable Rydberg simulator

Abstract: Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations. These fluctuations play a dominant role in the quantum critical region surrounding the transition point, where the dynamics are governed by the universal properties associated with the QPT. While time-dependent phenomena associated with classical, thermally driven phase transitions have been extensively studied in systems ranging from the early universe to Bose Einstein Condensates, understanding critical real-time dynamics in isolated, non-equilibrium quantum systems is an outstanding challenge. Here, we use a Rydberg atom quantum simulator with programmable interactions to study the quantum critical dynamics associated with several distinct QPTs. By studying the growth of spatial correlations while crossing the QPT, we experimentally verify the quantum Kibble-Zurek mechanism (QKZM) for an Ising-type QPT, explore scaling universality, and observe corrections beyond QKZM predictions. This approach is subsequently used to measure the critical exponents associated with chiral clock models, providing new insights into exotic systems that have not been understood previously, and opening the door for precision studies of critical phenomena, simulations of lattice gauge theories and applications to quantum optimization.

Optical Switching and Fluorescence Modulation Properties of Photochromic Metal Complexes Derived from Dithienylethene Ligands

Abstract: Novel perfluorocyclopentene-derived metallic complexes exhibit pronounced photochromic properties that can form the basis of nondestructive read-out models in optical memory devices. The methodology is described, discussed, and illustrated here by a scheme that represents the interconversion between the open form and the closed form of a tungsten photochromic complex.

Nicotinic receptors in the rat prefrontal cortex: increase in glutamate release and facilitation of mediodorsal thalamo-cortical transmission.

Abstract: The modulatory influence of nicotinic acetylcholine receptor (nAChRs) on thalamocortical transmission was characterized in the prelimbic area (PrL) of the rat prefrontal cortex. In the first experiment, rats received a unilateral excitotoxic lesion centred on the mediodorsal thalamic nucleus (MD), and were sacrificed 1 week later. The lesion resulted in a 40% reduction of 3H-nicotine autoradiographic labelling in the ipsilateral prefrontal cortex, particularly in areas that are innervated by the MD. Electrophysiological experiments were subsequently performed in non-lesioned anaesthetized animals, in order to study modulation of short- and long-latency responses of PrL neurons evoked by electrical stimulation of the MD. The short-latency responses result from activation of the MD–PrL pathway and are mediated via AMPA-type glutamatergic receptors, whereas the long-latency responses reflect activation of the recurrent collaterals of cortical pyramidal neurons. Iontophoretic application of nicotinic agonists (nicotine, DMPP) facilitated both types of response. Local application of the nAChR antagonists dihydro-beta-erythroidine, mecamylamine and methyllycaconitine, prevented both kinds of facilitation. Finally, intracerebral microdialysis experiments were performed in order to test for nicotinic modulation of extracellular glutamate concentrations in the PrL. Direct application of nicotine via the dialysis probe increased glutamate levels in a dose-dependent manner. This effect was blocked by local perfusion of dihydro-beta-erythroidine. These findings therefore provide anatomical and functional evidence for nAChR-mediated modulation of thalamocortical input to the prefrontal cortex. Such a mechanism may be relevant to the cognitive effects of nicotine and nicotinic antagonists.