724 research outputs found
Effect of the anisotropy of the cells on the topological properties of two- and tree-dimensional froths
URL: http://www-spht.cea.fr/articles/T00/164 Effet de l'anisotropie des cellules sur les propriétés topologiques des mousses 2D et 3DInternational audienceWe study the effect of the anisotropy of the cells on the topological properties of monodisperse 2D and 3D froths. These froths are built by Voronoï tessellation of actual assemblies of monosize disks (2D) and of many numerical packings of monosize disks (2D) and spheres (3D). We show that topological properties of these froths depend universally on the anisotropy of the cells
Intoxication expérimentale par la glycérie aquatique
Guilhon Jean, Oger C. Intoxication expérimentale par la glycérie aquatique. In: Bulletin de l'Académie Vétérinaire de France tome 104 n°7, 1951. pp. 383-386
MPGDs in Compton imaging with liquid-xenon
The interaction of radiation with liquid xenon, inducing both scintillation
and ionization signals, is of particular interest for Compton-sequences
reconstruction. We report on the development and recent results of a
liquid-xenon time-projection chamber, dedicated to a novel nuclear imaging
technique named "3 gamma imaging". In a first prototype, the scintillation is
detected by a vacuum photomultiplier tube and the charges are collected with a
MICROMEGAS structure; both are fully immersed in liquid xenon. In view of the
final large-area detector, and with the aim of minimizing dead-zones, we are
investigating a gaseous photomultiplier for recording the UV scintillation
photons. The prototype concept is presented as well as preliminary results in
liquid xenon. We also present soft x-rays test results of a gaseous
photomultiplier prototype made of a double Thick Gaseous Electron Multiplier
(THGEM) at normal temperature and pressure conditions.Comment: presented at MPGD09, CRETE, June 2009; to be published in JINST
Proceedings, PDF, 10 pages, 11 figure
Shocks in supersonic sand
We measure time-averaged velocity, density, and temperature fields for steady
granular flow past a wedge and calculate a speed of granular pressure
disturbances (sound speed) equal to 10% of the flow speed. The flow is
supersonic, forming shocks nearly identical to those in a supersonic gas.
Molecular dynamics simulations of Newton's laws and Monte Carlo simulations of
the Boltzmann equation yield fields in quantitative agreement with experiment.
A numerical solution of Navier-Stokes-like equations agrees with a molecular
dynamics simulation for experimental conditions excluding wall friction.Comment: 4 pages, 5 figure
Quaterthiophenes with Terminal Indeno[1,2-b]thiophene Units as p-Type Organic Semiconductors
Quaterthiophenes 4T, Oct-4T, and Tol-4T based on a central 2,2âČ-bithiophene core α,Ï-terminated with 4,4-unsubstituted and 4,4-disubstituted n-octyl or p-tolyl indeno[1,2-b]thiophene have been synthesized by Stille or MiyauraâSuzuki couplings. Compound 4T was also synthesized by an alternative route involving a soluble precursor bearing solubilizing trimethylsilyl groups which have been eliminated in the last step. The electronic properties of the compounds have been analyzed by cyclic voltammetry, UVâvis absorption and fluorescence emission spectroscopy. Thermal evaporation of 4T and Oct-4T leads to crystalline thin films and UVâvis absorption and X-ray diffraction data for these films suggest that the molecules adopt a quasi-vertical orientation onto the substrate. Strong Ï-Ï intermolecular interactions have been observed for 4T but not for molecules Oct-4T due to the presence of n-octyl chains. Sublimed thin films of Tol-4T show an amorphous character. The characterization of field-effect transistors fabricated from these three materials gave a hole-mobility of 2.2 Ă 10â2 cm2 Vâ1 sâ1 with an on/off ratio of 2.2 Ă 104 for 4T while no field-effect was observed for Oct-4T and Tol-4T
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