Conductivité Anionique des Phases Isolées dans les Systèmes PbF2?SnF4 et PbF2?GeF4

Ionic Conductivity of the Phases Isolated in the Binary Systems PbF₂? SnF₄ and PbF₂? GeF₄ The study of PbF₂? MF₄ (M ?; Sn, Ge) systems reveals a restricted solid solution domain, with a fluorine structure and edfinite Pb₃GeF₁₀, Pb₃Ge₂F₁₄ and PbMF₆ phases. The ionic conductivity has been measured by complex impedance technic. It appears that, in the solid solutions the M⁴⁺ cations adopt a distorted octahedral environment.     

Organized self-assembled monolayers from organosilanes containing rigid pi-conjugated aromatic segments

The morphology of surfaces modified by pi-conjugated arylsilanes depends on various parameters such as the nature and the number of the hydrolyzable functions or the length of the aromatic segment. The grafting of phenyltrichlorosilane and phenyltrimethoxysilane leads to multilayers even when the reactions are carried out at 0 degrees C, the films obtained from phenyltrichlorosilane being much thicker than the one obtained from phenyltrimethoxysilane. A submonolayer is obtained using phenyltriethoxysilane. Whereas the trifunctional phenyltrichlorosilane forms an inhomogeneous multilayer, the difunctional phenyldichlorosilane (PhSiHCl2) and the monofunctional phenylchlorosilane (PhSiH2Cl) (the SiH bond is not reactive under these experimental conditions) deposit as dense homogeneous monolayers. For these two phenylchlorosilanes, the surface analytical data are similar except for contact angle measurements, which can be explained by a different orientation of the phenyl group at the surface. Concerning the influence of the length of the aromatic segment on the quality of the film, styryltrimethoxysilane and methylstilbenyltrimethoxysilane lead to dense monolayers indicating that adding a short group such as the vinyl group is sufficient to induce an organization between aromatic groups and to achieve a dense monolayer.     

The effect of slow heating rates on the reaction mechanisms of nano and micron composite thermite reactions

Thermal analyses were performed on Al+MoO₃ thermite reactions as a function of Al particle size (ranging from 50 to 20 μm) and heating rate (from 2.5 to 15 K min^–1 ). Results include ignition (onset) temperatures and heats of reaction. The nano-thermites initiate prior to reactant phase changes and at least 300°C below micron-thermites. The differences in ignition temperatures are suggestive of different ignition mechanisms. Nano-thermites display higher heats of reaction that are dependent on experimental conditions.     

The Rigidification of the x-Conjugated System: An Effcient New Strategy Towards Small Bandgap Semi-Conductors

Abstract

A new synthetic approach for the reduction of the bandgap of molecular and polymeric conjugated systems is presented.     

Heterodyne beatings between frequency-shifted feedback lasers

Frequency-shifted feedback (FSF) lasers are potential candidates for long distance telemetry due to the appearance of beatings in the noise spectrum at the output of a homodyne interferometer: the frequencies of these beatings vary linearly with the path delay. In this Letter we demonstrate that these beatings also occur in the heterodyne mixing of two identical, but distinct, FSF lasers. This phenomenon is explained by the passive cavity model and is exploited to characterize the time-spectrum properties of FSF lasers. Consequences on telemetry with FSF lasers are presented.     

Population inversion in a single InGaAs quantum dot using the method of adiabatic rapid passage

Preparation of a specific quantum state is a required step for a variety of proposed quantum applications. We report an experimental demonstration of optical quantum state inversion in a single semiconductor quantum dot using adiabatic rapid passage. This method is insensitive to variation in the optical coupling in contrast with earlier work based on Rabi oscillations. We show that when the pulse power exceeds a threshold for inversion, the final state is independent of power. This provides a new tool for preparing quantum states in semiconductor dots and has a wide range of potential uses.