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.

Large First Hyperpolarizabilities in Push-Pull Polyenes by Tuning of the Bond Length Alternation and Aromaticity

Abstract: Conjugated organic compounds with 3-phenyl-5-isoxazolone or N,N'-diethylthiobarbituric acid acceptors have large first molecular hyperpolarizabilities (β) in comparison with compounds with 4-nitrophenyl acceptors. For example, julolidinyl-(CH=CH)_3-CH=N,N'- diethylthiobarbituric acid, which has 12 atoms between the donor and acceptor, has a β(0) of 911 x 10^(-30) electrostatic units, whereas (CH_3)_2NC_6H_4,–(CH=CH)_4–C_6H_4NO_2, with 16 atoms between its donor and acceptor, has a β(0) of 133 x 10^(-30) electrostatic units. The design strategies demonstrated here have resulted in chromophores that when incorporated into poled-polymer electrooptic modulators exhibited significant enhancements in electrooptic coefficients relative to polymers containing the commonly used dye Disperse Red-1. Poled polymer devices based on these or related chromophores may ultimately lead to high-speed electrooptic switching elements with low drive-power requirements, suitable for telecommunications applications.

Anionic redox processes for electrochemical devices.

Abstract: Understanding and controlling the anionic redox processes is pivotal for the design of new Li-ion battery and water splitting materials.

Transport Phenomena in Helium II

Abstract: F. LONDON1 has recently proposed a new conception of helium II, according to which this liquid can be regarded as a degenerate Bose-Einstein gas, that is, as a system in which one fraction of the substance—say, n atoms per cm.3—is distributed over the excited states in a way determined by the temperature, while the rest—n0–n atoms per cm.3—is 'condensed' in the lowest energy level. If T0 denotes the temperature of degeneracy, the ratio n/n0 is given by For an ideal Bose-Einstein gas, according to London, s = 3/2, but for the real fluid one should rather insert s = 5 in order to fit Keesom's specific heat measurements. The rapid pace of discovery that characterized early experimental work in superfluidity [see Nature 141, 243-244 (1938)] was equalled by theorists. In one of the great conceptual leaps in the history of physics, Fritz London proposed in April 1938 that the λ-transition in liquid helium was analogous to Bose-Einstein condensation, predicted by Einstein to occur in dilute gases. Just one month later, Laszlo Tisza extended London's proposal by invoking a two-fluid model for helium II, which could qualitatively explain the observed transport phenomena, including the fountain effect.

Posttranslational glutamylation of alpha-tubulin

Abstract: The high degree of tubulin heterogeneity in neurons is controlled mainly at the posttranslational level. Several variants of alpha-tubulin can be posttranslationally labeled after incubation of cells with [3H]acetate or [3H]glutamate. Peptides carrying the radioactive moiety were purified by high-performance liquid chromatography. Amino acid analysis, Edman degradation sequencing, and mass spectrometric analysis of these peptides led to the characterization of a posttranslational modification consisting of the successive addition of glutamyl units on the gamma-carboxyl group of a glutamate residue (Glu445). This modification, localized within a region of alpha-tubulin that is important in the interactions of tubulin with microtubule-associated proteins and calcium, could play a role in regulating microtubule dynamics.

Gastric mucosa abnormalities and tumorigenesis in mice lacking the pS2 trefoil protein.

Abstract: To determine the function of the pS2 trefoil protein, which is normally expressed in the gastric mucosa, the mouse pS2 (mpS2) gene was inactivated. The antral and pyloric gastric mucosa of mpS2-null mice was dysfunctional and exhibited severe hyperplasia and dysplasia. All homozygous mutant mice developed antropyloric adenoma, and 30 percent developed multifocal intraepithelial or intramucosal carcinomas. The small intestine was characterized by enlarged villi and an abnormal infiltrate of lymphoid cells. These results indicate that mpS2 is essential for normal differentiation of the antral and pyloric gastric mucosa and may function as a gastric-specific tumor suppressor gene.