Mineralogy and petrology of comet 81P/wild 2 nucleus samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk

Methodologie des etudes d'evenements Nouvelles approches

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : DO 5682 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Tuning Coulomb blockade in ultra-small metallic nanoparticle self-assemblies, at room-temperature

International audienceTuning Coulomb blockade at room temperature in nanoparticle self-assemblies can open the door to the development of a new class of nanoelectronics. Here, we describe self-assemblies of ultrasmall platinum nanoparticles, the morphology and electrical properties of which can be tuned through slight modifications of their aryl- or alkyl thiol ligand backbones or chain length. Three parameters have been modified independently at an unprecedented fine level to control the Coulomb blockade energy: the size of the nanoparticles (between 1.2 and 1.7 nm), the distance between them (between 1.9 and 2.5 nm) and the dielectric constant of the ligands (between 2.7 and 7.1). Elaborating such systems, stable in air for months, and understanding their electrical properties are first steps towards nanoelectronic systems where the charging energy of the nanoparticles can be tuned by the nature of the ligands

Tuning Coulomb blockade in ultra-small metallic nanoparticle self-assemblies, at room-temperature

International audienceTuning Coulomb blockade at room temperature in nanoparticle self-assemblies can open the door to the development of a new class of nanoelectronics. Here, we describe self-assemblies of ultrasmall platinum nanoparticles, the morphology and electrical properties of which can be tuned through slight modifications of their aryl- or alkyl thiol ligand backbones or chain length. Three parameters have been modified independently at an unprecedented fine level to control the Coulomb blockade energy: the size of the nanoparticles (between 1.2 and 1.7 nm), the distance between them (between 1.9 and 2.5 nm) and the dielectric constant of the ligands (between 2.7 and 7.1). Elaborating such systems, stable in air for months, and understanding their electrical properties are first steps towards nanoelectronic systems where the charging energy of the nanoparticles can be tuned by the nature of the ligands