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.

Disc-Like Mesogen Polymorphism

Abstract: Among the various mesogenic polyaromatic cores, only benzene, triphenylene, truxene and anthraquinone hexasubstituted derivatives exhibit one or several D columnar phases and/or a ND lenticular nematic phase. A simple scheme of nomenclature is suggested for the six different types of columnar phase requiring only two structural parameters: firstly the symmetry of the lattice (hexagonal: Dh, rectangular: Dr, oblique: Dob), and secondly the order or disorder within the column. Several examples of disc-like compounds which form phases Dho, Dhd, Drd(P21/a) , Drd(P2/a), Drd(C2/m), Dod.d are described and a discussion of the specificity of the corresponding optical textures is given. Then the complex polymorphism of these new mesogenic materials (normal, inverse, reentrant columnar-nematic sequences) is reviewed. Finally, a simple classification of the various types of lyotropic and thermotropic phase is proposed, based on the shape of the structural element (finite or infinite cylinder, disc, infinite...

Slippy and sticky microtextured solids

Abstract: The aim of this paper is to describe the possibility of achieving super-hydrophobic materials by tailoring their surface topography. Water droplets easily slip or roll down on such surfaces. However, it is found that microtextures on a solid can generate sticky surfaces as well, and the conditions for avoiding such an effect are discussed.

Chromosomal assignment of the second locus for autosomal dominant cerebellar ataxia (SCA2) to chromosome 12q23–24.1

Abstract: The autosomal dominant cerebellar ataxias (ADCA) are a group of neurodegenerative disorders characterized by onset with gait ataxia, dysarthria, dysmetria and dysdiadochokinesia. We have demonstrated previously genetic heterogeneity within these disorders by excluding the disease locus from the documented spinocerebellar ataxia locus (SCA1) on chromosome 6p in a large Cuban founder population. We now report the assignment of a second locus for ADCA (SCA2) to chromosome 12q23–24.1 following linkage analyses carried out for the Cuban pedigrees, with probable flanking markers D12S58 and phospholipase A2. Investigation of linkage to the interval containing SCA2 for seven French ADCA families, previously excluded from linkage to SCA1, provides preliminary data suggesting the existence of a third ADCA locus (SCA3).

Intercellular calcium signaling and gap junctional communication in astrocytes.

Abstract: Two main characteristics of astrocytes are their elaborated intracellular calcium signaling and their high degree of intercellular communication mediated by gap junctional channels. In these cells a number of studies have contributed to demonstrate that the combination of these two properties provides a basis for a long-range signaling system within the brain. Intercellular calcium signaling, also termed calcium waves, allows astrocytes to communicate with each other and to interact with adjacent neurons. Most of the intra- and inter-cellular events involved in the initiation and propagation phases of this process has now been identified. This sequence of events includes the permeability of gap junction channels, which at the time-scale for calcium waves propagation, are likely permeated rather than closed by Ca 21 and/or related signaling molecules like IP3. In addition, in some studies an external component have been reported to participate to the propagation process. Finally, the control of the spread of intercellular calcium signaling has been demonstrated to occur at several levels including phospholipase C, IP3 receptors, intracellular Ca 21 stores, and cytoplasmic Ca 21 buffering. Accordingly, normal and pathological situations that affect one or several of these steps can be predicted to influence on astrocytic calcium waves. GLIA 24:50-64, 1998. r 1998 Wiley-Liss, Inc.