Asymptotic ordination of artificial satellite Hamiltonian

Spatial Agencies’ projects for future artificial satellites continue to grow in number and complexity. These projects need the development of analytical theories in order to place the satellites in the most suitable orbit. The most common technique for constructing analytical theories is the Lie–Deprit method, which requires to expand in series of a small parameter the Hamiltonian of the problem. This expansion is not trivial but, usually, it is made without care. In this paper we provide a unified and systematic framework to get that development in a rigorous way.     

Synthesis of novel ionic polymers containing arsonic acid group

Synthesis of ortho‐ and para‐acryloylaminophenylarsonic acids (o‐AAPHA and p‐AAPHA) monomers and their homopolymers, useful as ion‐exchange materials, are reported. Both the monomers and homopolymers are synthesized with >90% yield. The structures of the new compounds are determined by NMR and FTIR spectroscopy. Molecular weights of the polymers are determined from light scattering measurements and found to be M_w = 38,759 g/mol for o‐AAPHA polymer and M_w = 31,347 g/mol for p‐AAPHA polymer. Good thermal stability of the new compounds derived from their intra‐ or intermolecular hydrogen bondings suggests their applications as proton‐exchange membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1627–1634, 2006     

ADHD candidate gene (DRD4 exon III) affects inhibitory control in a healthy sample

Background  

Dopamine is believed to be a key neurotransmitter in the development of attention-deficit/hyperactivity disorder (ADHD). Several recent studies point to an association of the dopamine D4 receptor (DRD4) gene and this condition. More specifically, the 7 repeat variant of a variable number of tandem repeats (VNTR) polymorphism in exon III of this gene is suggested to bear a higher risk for ADHD. In the present study, we investigated the role of this polymorphism in the modulation of neurophysiological correlates of response inhibition (Go/Nogo task) in a healthy, high-functioning sample.     

Interaction between water and polymer chains in poly(hydroxyethyl acrylate) hydrogels

Polymer networks of different cross-linking densities were prepared by copolymerisation of hydroxyethyl acrylate and ethylene glycol dimethacrylate. The average molecular weight between cross-links as well as the polymer chain mobility were characterised by means of dynamic–mechanical spectroscopy. Equilibrium sorption isotherms and the water uptake in immersion in liquid water allowed the determination of the Flory–Huggins interaction parameter between water molecules and polymer chain segments, which decreased with the water activity in the hydrogel and increased with the cross-linking density as a consequence of the hydrophobic character of the cross-linking agent. Dynamic sorption and desorption experiments were used to determine the diffusion coefficient. Received: 11 November 1999 Accepted: 28 July 2000     

Optical study and structure modelling of PPI liquid crystalline dendrimer derivatives

Optical study of two families of poly(propylene imine) (PPI) dendrimers (G = 1–5) are reported. The enlarging of the chain number (generations) of the PPI dendrimer leads to the spectra shift to IR region in solvent until 8 and 19 nm for both families, respectively. The theoretical modelling of the dendrimer structure was performed. The geometric characterization of dendrimer structure demonstrates that the preferable free space for encapsulation is periphery of the PPI dendrimer.     

-convergence of quadratic functionals with oscillating linear perturbations

We explore the Γ-convergence of quadratic functionals perturbed by linear terms with oscillatory coefficients. In particular, we are interested in understanding the interaction between the oscillations of the quadratic part and the linear term. We also look at this issue from the perspective of the associated equations of optimality as in homogenization.     

Palladium nanoparticles-catalyzed chemoselective hydrogenations, a recyclable system in water

Chemoselective hydrogenation of double bonds in the presence of various functional groups occurred in high yields using water or toluene as solvent, and Pd nanoparticles as catalyst. Up to nine recyclings were achieved in water without decrease of the catalyst activity.     

Fast prediction of the fatigue behavior of short-fiber-reinforced thermoplastics based on heat build-up measurements: application to heterogeneous cases

Short-fiber-reinforced thermoplastics components for structural applications are usually very complex parts as stiffeners, ribs and thickness variations are used to compensate the quite low material intrinsic stiffness. These complex geometries induce complex local mechanical fields but also complex microstructures due to the injection process. Accounting for these two aspects is crucial for the design in regard to fatigue of these parts, especially for automotive industry. The aim of this paper is to challenge an energetic approach, defined to evaluate quickly the fatigue lifetime, on three different heterogeneous cases: a classic dog-bone sample with a skin-core microstructure and two structural samples representative of the thickness variations observed for industrial components. First, a method to evaluate dissipated energy fields from thermal measurements is described and is applied to the three samples in order to relate the cyclic loading amplitude to the fields of cyclic dissipated energy. Then, a local analysis is detailed in order to link the energy dissipated at the failure location to the fatigue lifetime and to predict the fatigue curve from the thermomechanical response of one single sample. The predictions obtained for the three cases are compared successfully to the Wöhler curves obtained with classic fatigue tests. Finally, a discussion is proposed to compare results for the three samples in terms of dissipation fields and fatigue lifetime. This comparison illustrates that, if the approach is leading to a very relevant diagnosis on each case, the dissipated energy field is not giving a straightforward access to the lifetime cartography as the relation between fatigue failure and dissipated energy seems to be dependent on the local mechanical and microstructural state.