Poly(di(ω-alkylphenyl)stannane)s

Poly(di(ω-alkylphenyl)stannane)s, [Sn(C _n H_2n Ph)₂] _m with n = 2–4, and a copolymer of di(3-propylphenyl)stannane and dibutylstannane of weight-average molar masses of 2–8 · 10⁴ g/mol were synthesized by dehydropolymerization of stannanes of the composition H₂SnR₂ using Wilkinson’s catalyst [RhCl(PPh₃)₃]. At least two methylene groups were required as spacers between the phenyl group and the tin atom for polymerization to occur. The polystannanes were characterized by, among other techniques, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, thermal analysis and X-ray diffraction. The polymers featured properties different from those of the corresponding poly(dialkylstannane)s. Specifically, the [Sn(C _n H_2n Ph)₂] _m family displayed glass transitions at remarkably low temperatures, down to ca. −50 °C, and a lower value for a copolymer (−68 °C). Polymers [Sn(C_nH_2nPh)₂]_m with n = 2 and 3 and a copolymer at room temperature were of a gel-like concistence, which enabled facile orientation with shear forces. Finally, the temperature-dependent electrical conductivity was determined for poly(di(3-propylphenyl)stannane), which followed the law of typical semiconductors, with an activation energy for conduction of 0.12 eV.     

Kinetics and Mechanism of the Water–Gas Shift Reaction Over Platinum Supported Catalysts

A dual-site reaction mechanism is proposed for Pt based water–gas shift catalysts. The sorption equilibrium parameters are evaluated in detail to validate their physical significance. The values of the van ‘t Hoff parameters for CO and H₂ correspond to those for chemisorption on platinum. The sorption parameters of H₂O and CO₂ on the supports have been quantitatively determined from temperature-programmed desorption experiments and have been compared to the values obtained from the kinetic study. Finally the proposed model is able to explain the different activities between the two catalysts.     

Le projet européen PRIME: protection de la vie privée et gestion des identités pour l’Europe

This paper presents an overview of the European project PRIME, with its objectives, main research issues and expected results.     

Parsimonious additive models

A new method for function estimation and variable selection, specifically designed for additive models fitted by cubic splines is proposed. This new method involves regularizing additive models using the l₁-norm, which generalizes the lasso to the nonparametric setting. As in the linear case, it shrinks coefficients and produces some coefficients that are exactly zero. It gives parsimonious models, selects significant variables, and reveals nonlinearities in the effects of predictors. Two strategies for finding a parsimonious additive model solution are proposed. Both algorithms are based on a fixed point algorithm, combined with a singular value decomposition that considerably reduces computation. The empirical behavior of parsimonious additive models is compared to the adaptive backfitting BRUTO algorithm. The results allow to characterize the domains in which our approach is effective: it performs significantly better than BRUTO when model estimation is challenging. An implementation of this method is illustrated using real data from the Cophar 1 ANRS 102 trial. Parsimonious additive models are applied to predict the indinavir plasma concentration in HIV patients. Results suggest that this new method is a promising technique for the research and application areas.     

Systematic sampling is a minimum support design

In order to select a sample in a finite population of N units with given inclusion probabilities, it is possible to define a sampling design on at most N samples that have a positive probability of being selected. Designs defined on minimal sets of samples are called minimum support designs. It is shown that, for any vector of inclusion probabilities, systematic sampling always provides a minimum support design. This property makes it possible to extensively compute the sampling design and the joint inclusion probabilities. Random systematic sampling can be viewed as the random choice of a minimum support design. However, even if the population is randomly sorted, a simple example shows that some joint inclusion probabilities can be equal to zero. Another way of randomly selecting a minimum support design is proposed, in such a way that all the samples have a positive probability of being selected, and all the joint inclusion probabilities are positive.     

Randomized trial of a smoking cessation intervention in hospitalized patients

A hospitalization is a time when perceived vulnerability to dangers from smoking and quitting motivation may be at their peak. Aim was to determine whether a smoking cessation intervention of moderate intensity would increase the smoking cessation rate in hospitalized smokers. Design was randomized trial, conducted in a university-affiliated cardio-pulmonary tertiary care center. Participants were hospitalized smokers aged < or =70 years. Intervention was a smoking cessation intervention consisting of education and psychological support, with or without pharmacological therapy, associated with follow-up phone calls. Patients assigned to the control group received usual care. Measurement was point prevalence cessation rate at 1-year follow-up. A total of 468 patients were screened; 196 were randomized. Although the smoking cessation rates at 12-month follow-up were higher than expected, we found no significant difference between the study groups (intervention: 30.3%; control: 27.8%). Similar results were obtained in patients whose smoking status was validated by urinary cotinine assay. Length of stay and dependence to nicotine were the only significant predictors of smoking cessation. A smoking cessation intervention of moderate intensity delivered in a tertiary cardio-pulmonary center did not increase the smoking cessation rate at 1-year follow-up. The results of this trial should not divert those who deliver care to inpatients from delivering a brief smoking cessation intervention.     

Undecylenic acid: A valuable renewable building block on route to Tyromycin A derivatives

A key intermediate for the synthesis of Tyromycin A, a C‐20 tetrachlorodicarboxylic acid, was produced in six steps starting with the dimerization of methyl 10‐undecenoate which was obtained from a renewable resource, e.g. castor oil. The acyloin condensation product was then oxidized, transformed to the diene, followed by ozonization, chlorination and finally oxidation to the corresponding tetrachlorodicarboxylic acid.     

New methods for the fast simulations of the extrusion process of hot metals

Being able to find alternatives to the costly and time-consuming trial and error current practice in die design based on know-how acquired by practitioners throughout years is of primary importance in the aluminum extrusion industry. In this paper, two programs aimed at helping extruders in estimating the performance and feasibility of processes and simulating in details the flow of material in the press, are presented. Although they have been used so far for aluminum alloys, they could also be applied to other extrusion applications like that of other metals and polymers for instance. Together with a process simulator, which enables one to obtain a fast estimate of the extrusion process performances and computer-aided production of aluminum extrudates, a three-dimensional software dedicated to the design of dies with complicated shapes is also described.     

Mesomorphism of dialkylterthiophene homologues

New dialkylterthiophene liquid crystalline compounds were synthesised and characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized optical microscopy (POM). Upon cooling from the isotropic state to the crystalline phase, these dialkylterthiophenes present different types of smectic mesophases. For the highest ordered smectic phase, XRD analyses have revealed a molecular organisation within the smectic layers and the key structural parameters are determined by molecular modelling simulations. The structural properties of these smectic phases are discussed in relation to the alkyl chain length.