Two-color laser-induced incandescence and cavity ring-down spectroscopy for sensitive and quantitative imaging of soot and PAHs in flames

Laser-induced incandescence is a technique which enables the measurement of soot volume fractions. However, the laser-induced soot emission might be affected by a fluorescence background generally ascribed to the polycyclic aromatic hydrocarbon compounds (PAHs) present at the soot location. In this paper, spatially resolved distributions of PAH absorbance and soot are obtained in sooting diffusion flames. The original method developed here consists in comparing the emission distributions induced by two different laser wavelengths: (1) at 1064 nm emission signals are exempt from PAH fluorescence and (2) at 532 nm both soot incandescence and PAH emission contribute to the total signal. In addition, the absolute absorption coefficient of the PAH mixture is determined by comparing absorption measurements obtained by cavity ring-down spectroscopy (CRDS) at 1064 nm and 532 nm. The proposed method can provide highly sensitive 2D imaging of PAHs and soot using the fundamental and the second-harmonic frequencies of a single YAG laser. Finally, 2D distributions of PAH absorbance and soot volume fraction calibrated by CRDS are obtained in two diffusion flames, particularly in a very low-sooting flame exhibiting a maximum PAH absorbance of 6×10^-4 cm^-1 and a maximum soot volume fraction of 3 ppb only. The respective spatial distributions of PAHs and soot are shown to vary with the initial C/O ratio. PACS 33.20.Lg; 42.62.Fi; 44.40.+a     

Solid-phase synthesis of model libraries of 3 α17β-dihydroxy-16α-(aminoethyl-N-substituted)-5α-androstanes for the development of steroidal therapeutic agents

The solid-phase synthesis of 16-derivatives of 5-androstane-3,17-diol with one, two or three levels of molecular diversity was accomplished using the diethylsilyloxy linker. Libraries with one level of diversity (10 members) and two levels of diversity (40 members) were synthesized in a parallel fashion in good yields and acceptable HPLC purities for the majority of library members. Compounds with three levels of diversity (15 pools) were realized in a split and pool fashion to allow further deconvolution by the positional scanning method. The screening of the generated model libraries revealed interesting preliminary structure–activity relationships related to their antiproliferative activities on androgen-sensitive Shionogi cells. In the case of the two-level library, the presence of a hydrophobic amino acid at R₁ (isoleucine (Ile) or phenylalanine (Phe)) and a six-membered ring (aromatic or not) at R₂ seems an important requirement for activity. In the three-level library, the amino acid residues isoleucine and phenylalanine clearly provided a better antiproliferative activity than glycine (Gly) and proline (Pro). These model libraries will serve as basis for the generation of larger libraries of peptidosteroids toward the development of therapeutic agents.     

Une formule asymptotique pour\sum\limits_{n \leqq x} {a_z (n)d(n + 1)}

Sans résumé     

Sur une voie d'acces potentiellement generale aux phosphines fonctionnelles a phosphore optiquement actif

Optically active methyl-phenyl-cyclohexylphosphine sulfide is metallated by BuLi and reacted with ethyl carbonate to yield carbethoxymethyl-phenyl-cyclohexylphosphine sulfide with retention of the optical activity at phosphorus ; this sulfide is converted into the corresponding optically active functional phosphine through a nickelocene reduction-complexation.     

Magnetoelectric effect and magnetization process in Fe5LiO8

After showing the existence of second order M.E. effect β, in Fe₅LiO₈ [1], we try to verify Lee and Rado's assumptions. These authors suppose that the existence of β is connected with the rotation of magnetic domains. We compare the magnetoelectric β and the magnetization σ curves vs the magnetic field H₀. The latter curve reveals the different magnetic modes, and therefore illustrates the behavior of the magnetic domains. This comparison has been made for several directions of the applied field in order to illustrate all possible cases of rotation of the domains and allows us to confirm the basic assumption.     

Stereochimie de l'addition des derives zinciques des ethers propargyliques sur les composes carbonyles

The stereochemistry of the addition of the zinc derivative of ether PhCCCH₂OMe, to aldehydes and ketones has been studied. In the case of saturated carbonyl compounds, the results can be explained by a mechanism which takes into account the steric effects of the substituents. However, with those which contain phenyl, vinyl or alkynyl groups in the α position, conformational and electronic factors must be considered.     

Modelling of dynamic ductile fracture and application to the simulation of plate impact tests on tantalum

A model of dynamic damage by void nucleation and growth is proposed for elastic-viscoplastic materials sustaining intense loading. The model is dedicated to ductile materials for which fracture is caused by microvoiding. The material contains potential nucleation sites where microvoids are generated when the local pressure overcomes the nucleation pressure. A probability density function is adopted to describe the fluctuation of the nucleation pressure within the material. The void growth is described by using a hollow sphere model where micro-inertia effects are accounted for. The matrix weakening due to void growth is also included.The model has been first tested under uniaxial deformation. When the strain rate is assumed constant, the pressure inside the material has nearly a linear response up to a maximum. An analytical expression for the maximum pressure is proposed.Finite element simulations of plate impact tests have been carried out and compared to experiments on tantalum. From simulations based on the proposed model, an increase of the spall strength is observed with higher shock intensities. Therefore, the relationship between the velocity pullback and spall strength usually assumed in the literature (based on the acoustic approach) seems to be inadequate. Velocity profiles are simulated for different flyer thicknesses and different impact velocities with close agreement with experiments.     

Water vapor sorption in naphthalenic sulfonated polyimide membranes

The water vapor uptake of sulfonated polyimides (SP) was investigated by electronic microbalance (IGA, Hiden) from 15 to 55°C. The sigmoïdal isotherms obtained (BET II type) are considered as dual sorption (concave part) plus clustering (convex part) and are fitted with good agreement by Park’s equation. Zimm–Lundberg’s method is used to study the clustering process of water molecules: limit clustering activity, a^*, and the number of molecules per cluster are estimated.

To obtain a better understanding of polymer structure and isotherm analysis, H⁺ (counter-ions of sulfonic groups) were replaced by ions with a smaller hydration shell (Cs⁺ and EDAH⁺). Comparison of the three isotherms shows no significant difference in the water affinity of the cations. This is attributed to a partial control of the sorption by microcavities existing in the membrane.