Generation of Accurate Finite Element Models of Nonlinear Systems – Application to an Aeroplane-Like Structure

Model updating and validation is currently a central issue in the fields of computational structural mechanics and dynamics. The vast majority of applications however concerns linear structures. On the other hand, updating nonlinear models is something the structural dynamicist prefers to avoid mainly because tools such as modal analysis are no longer available. The objective of the present study is to propose a two-step methodology for dealing with nonlinear systems. Its most appealing feature is that it decouples the estimation of the linear and nonlinear parameters. A numerical application consisting of an aeroplane-like structure is used to assess the efficiency of the procedure.     

Regioselective electrophilic trifluoromethylation of substituted anilines and derivatives in superacid

In a one pot procedure, treatment of chloro or methyl substituted acetanilides in HF/SbF₅/CCl₄ followed by addition of HF/pyridine yields trifluoromethyl derivatives with high regioselectivity.     

Synthetic sulfated glucuronosyl paragloboside (SGPG) and its use for the detection of autoimmune peripheral neuropathies

The sulfated glucuronosyl paragloboside SO₄-3-GlcA(β1-3)Gal-(β1-4)GlcNAc(β1-3)Gal-(β1-4)Glcβ(1-1′)Cer (SGPG) is a specific constituent of the peripheral nervous system involved in human dysimmune neuropathies. Although it is highly immunogenic in human pathology, it is not a major constituent of peripheral nerve in humans. Pure SGPG is very difficult to obtain from natural sources, but is needed for the design of efficient and reproducible immunoassays. We describe a new chemical synthesis of this important glycolipid with a stearic tail, including its complete characterization by mass spectrometry and its use in the detection of autoimmune neuropathies.     

Dépose dynamique d'un micro-objet saisi par adhésionManipulation of micro-objects using adhesion forces and dynamical effects

This paper describes a dynamical strategy for releasing micro objects picked-up by means of adhesion forces. While sticking effects are used in order to capture an object by adequately choosing a high surface energy constitutive material for the end-effector, these same effects handicap considerably the release. We propose to take advantage of the inertial effects of both the end-effector and the manipulated object to overbalance adhesion forces and to achieve the release. Simulations show that for this purpose, accelerations as high as 10⁵ m/s² are needed. Successful manipulation of a 40 μm radius glass sphere is demonstrated. To cite this article: S. Haliyo et al., C. R. Mecanique 331 (2003).     

Lp resolvent estimates for magnetic Schrödinger operators with unbounded background fields

We prove L^p and smoothing estimates for the resolvent of magnetic Schrödinger operators. We allow electromagnetic potentials that are small perturbations of a smooth, but possibly unbounded background potential. As an application, we prove an estimate on the location of eigenvalues of magnetic Schrödinger and Pauli operators with complex electromagnetic potentials.     

Variational forms for the inverses of integral logarithmic operators over an interval

We present explicit and exact variational formulations for the weakly singular and hypersingular operators over an interval as well as for their corresponding inverses. By decomposing the solutions in symmetric and antisymmetric parts, we precisely characterize the associated Sobolev spaces. Moreover, we are able to define novel Calderón-type identities in each case.     

Synthesis of nitrogen bicyclic scaffolds: pyrimido[1,2-a]pyrimidine-2,6-diones

The multi-step synthesis of 1,3,7-trisubstituted pyrimido[1,2-a]pyrimidinediones starting from isothiocyanates is described. These nitrogen bicycles were prepared by an iterative sequence of functionalization/cyclocondensation reactions. [4+2] Cycloaddition reactions took place between diazadienic chains and various acyl chlorides providing sophisticated heterobicycles.     

Molecular rearrangement of epoxide derived from sesquiterpenes by Lewis acid catalysis

The molecular rearrangement under mild conditions of two epoxides derived from the sesquiterpenic himachalenes has been studied using BF₃·Et₂O as the Lewis acid catalyst. Both reactions are efficient and selective affording in each case one new enantiomerically pure ketone isolated in good yield. Their structures have been fully characterized by spectroscopic methods. Mechanisms for the BF₃-catalyzed reactions are proposed.     

New macrolactones from the defensive salivary secretion of soldiers of the african termite Pseudacanthotermes spiniger

The salivary defensive secretion of large soldier termites of the species Pseudacanthotermes spiniger contains two novel macrocyclic lactones [22-keto-hexacosanolide (2) and 2-hydroxy-24-keto-octacosanolide (3)] together with the already known macrolactone hexacosanolide (1). In addition, the secretion contains important amounts of a polysaccharide based mainly upon β-glucopyranose, β-glucosamine and N-acetyl-β-glucosamine in equal amount.