Synaptic Coupling Between Two Electronic Neurons

An electrical circuit is proposed to realize an unidirectional coupling between two cells, mimicking chemical synaptic coupling. Each cell represents the FitzHugh–Nagumo (FHN) model of neuron with a modified exitability (MFHN). We present experimental results on frequency doublings and on the chaotic dynamics depending on the coupling strength in a master–slave configuration. In all experiments, we stress the influence of the coupling strength on the control of the slave neuron.     

Helicity Induction in Helicate Self-Organisation from Chiral Tris(bipyridine) Ligand Strands

The chiral tris, and pentakis(bipyridine) ligand strands 3a and 4 were synthesised, each in optically pure form with (S,S)-configuration. Ligand 3a yielded substituted double-helical metal complexes, derived from the parent trihelicate structure 2 , with Cu^I and Ag^I ions. The spectral data, in particular the ¹H-NMR spectra and the large positive Cotton effect, indicate that helicate formation occurs with very high induction of helicity. Together with consideration of the steric effects in the two possible helical diastereoisomers (P)- 1 and (M)- 1 that may be formed, the data favour the preferential generation of the right-handed double helicate (P)- 1 from the tris(bipyridine) strand 3a of(S,S)-configuration.     

Variance of the virtual displacement

We show that the affine structure of the 3-dimensional space is deeply enmeshed with the static laws expression. The relevance of tensorial rules for calculus in mechanics is thus enhanced. The virtual work principle is stated precisely but a little twist is given to the usual statements: the tensorial nature of the so-called virtual displacement vector is asserted to be covariant. To cite this article: C. Vallée et al., C. R. Mecanique 332 (2004).

Résumé

Nous montrons que la structure affine de l'espace tridimensionnel est fortement imbriquée avec l'expression des lois de la statique. La pertinence de l'application des règles du calcul tensoriel à la mécanique est ainsi renforcée. Le principe des travaux virtuels est établi précisément avec une seule entorse aux exposés classiques : la nature tensorielle de l'habituel vecteur déplacement virtuel est affirmée covariante. Pour citer cet article : C. Vallée et al., C. R. Mecanique 332 (2004).     

Intramolecular Cyclization of 1-(ω-Phenylalkyl)-2-(nitromethylene)pyrrolidines in Triflic Acid

1-(ω-Phenylalkyl)-2-(nitromethylene)pyrrolidines in triflic acid undergo a C,O-diprotonation, followed by loss of water, to form conjugated iminium–hydroxynitrilium dications, which react with the tethered phenyl ring by electrophilic aromatic substitution to afford tricyclic iminium compounds as triflate salts. The scope and mechanism of this reaction are discussed.