Synthesis and Reactivity of Martin’s Spirosilane-Derived Chloromethylsilicate

Pentacoordinate silicon derivatives with a chloromethyl ligand are versatile compounds that are usually obtained from the corresponding tetravalent trialkoxy- or trihalogeno(chloromethyl)silane. We describe herein the synthesis of a chloromethylsilicate bearing two Martin’s ligands readily obtained by addition of in situ generated chloromethyllithium to a spirosilane. The reactivity of this new species was evaluated and it has been established that the chloride is displaced by strong nucleophiles such as alkyllithiums and (hetero)aryllithiums. In Lewis acidic conditions, the pentacoordinate silicon species rearranges through a formal insertion of a methylene into one Si–C bond, to form a new tetravalent spirosilane with a six-membered ring. The same kind of rearrangement can be triggered also by addition of a Lewis base. The mechanism of the rearrangement in both conditions has been studied by means of DFT calculations.     

One-Step Gem-Diphosphorylation of Amides and Lactams

We report the extension of an easy one-step synthesis of amino gem-bisphosphonates through the reaction of amides and lactams with trialkylphosphites.     

Optical and Electronic Properties of Organic Photovoltaic Wires and Fabrics

The characteristics of a power producing flexible wire based on organic photovoltaics (OPV) and the processes by which they are produced are described in this paper. A set of materials and coating formulations used on the electrode wires are very similar to those used in the development of two dimensional photovoltaic cells and modules. The active layer of the primary electrode wire comprises the bulk heterojunction-forming P3HT/PCBM (1:1 weight ratio) that has been extensively studied in planar cells. A second wire, which is wrapped around the coated, primary electrode wire, serves as the counter electrode. Ray tracing analysis indicates that light incident on the wires is focused by the cladding onto to the active layer, coated, primary electrode wire even when it is completely shadowed by the counter electrode. Furthermore, when the counter electrode is in a position that partially shadows the primary wire, a significant percentage of the light is reflected by the counter electrode onto the primary electrode.

Many hundreds of feet of OPV wire have been produced continuously for experimental purposes, and the process is capable of producing any length of PV wire desired. Efficiency values of a 200 foot spool of PV wire ranges from 2.79% to 3.27%.     

A Raman Differential Absorption Lidar for Ozone and Water Vapor Measurement in the Lower Troposphere

Abstract

A new way of measuring ozone and water vapor in the Planetary Boundary Layer (PBL) is proposed. The method is based on the simultaneous measurement of the Raman backscattering in the UV by O₂, N₂ and H₂O, using a single pump beam at 266 nm. The ozone concentration is retrieved from the differential absorption of the N₂ and O₂ Raman backscattered signals, while the water vapor is measured using the classical Raman scheme. We present some preliminary results showing daytime ozone measurements in good correlation with a point monitor.     

In situ speciation of trace Fe(II) and Fe(III) in atmospheric waters by the FZ method coupled to GFAAS analysis

Two procedures to characterise atmospheres in piggeries are presented. The first allows delocalised sensorial analysis by trapping volatiles from pig shed emissions in a lipid phase. followed by laboratory analysis of their odour characteristics. The second procedure provides instrumental odour signatures of atmospheres. The volatile compounds are concentrated by solid-phase microextraction (SPME). and analysed directly by mass spectrometry without a chromatographic step (SPME-MS). The information supplied by the two analysis methods proved rich and consistent for the 42 piggeries analysed. In addition. the odour signatures allowed a good estimation of the key dimensions of the odour of the lipid phases. This result indicates that SPME-MS is a promising instrumental method to estimate the degree of odour nuisance in livestock buildings.     

The deformation of thin aluminium films under helium ion bombardment

ABSTRACT : Aluminium films 2000 Å thick have been bombarded with various flu-ences of 5 keV He⁺ ions and the resulting bubble distribution observed by Transmission Electron Microscopy. Scanning Electron Microscopy of the films indicates an areal increase in the unsupported regions of the films, which, if it results from three dimensional swelling of the films, is two orders of magnitude larger than would be calculated from the total bubble volume as observed by T. E. M. In addition features closely resembling blisters observed in bulk materials, form on the supported regions of the film. These blisters like features are thought to result from lateral stresses in the films.     

Revisiting poromechanics in the context of microporous materials

Poromechanics offers a consistent theoretical framework for describing the mechanical response of porous solids, fully or partially saturated with a fluid phase. When dealing with fully saturated microporous materials, which exhibit pores of the nanometre size, aside from the fluid pressure acting on the pore walls additional effects due to adsorption and confinement of the fluid molecules in the smallest pores must be accounted for. From the mechanical point of view, these phenomena result into volumetric deformations of the porous solid: the so-called “swelling” phenomenon. The present work investigates how the poromechanical theory should be refined in order to describe adsorption and confinement induced swelling in microporous solids. Firstly, we report molecular simulation results that show that the pressure and density of the fluid in the smallest pores are responsible for the volumetric deformation of the material. Secondly, poromechanics is revisited in the context of a microporous material with a continuous pore size distribution. Accounting for the thermodynamic equilibrium of the fluid phase in the overall pore space, the new formulation introduces an apparent porosity and an interaction free energy. We use a prototype constitutive relation relating these two quantities to the Gibbs adsorption isotherm, and then calculate the induced deformation of the solid matrix. Agreement with experimental data found in the literature is observed. As an illustrating example, we show the predicted strains in the case of adsorption of methane on activated carbon.     

Hyperbolic manifolds,amalgamated products and critical exponents

We give a new proof of a result due to Y. Shalom: if the fundamental group of a compact real hyperbolic manifold of dimn is a free product of its subgroups A and B over the amalgamated subgroup C, then the critical exponent of C is not smaller than n?2. The proof, which is geometric, allows one to treat the equality case and an extension to variable curvature. To cite this article: G. Besson et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003).