Propagating waves in bounded elastic media: a transition from standing wave motion to anguilliform kinematics

Waves propagating in confined geometries usually evolve into spatially stationary patterns, built from the interference between the waves that have been reflected upon hitting the boundaries. However, a recent study on bio-locomotion [1] has reported that traveling wave kinematics can naturally emerge in a forced elastic rod, even with boundary conditions involving significant reflections. It has been shown that this particular behavior is observed only in the presence of strong damping. Based on those observations, we aim at giving a quantitative description of the mechanism involved to prevent the built-up of standing waves and establish traveling fish-like kinematics (that optimizes the global swimming efficiency). The question is discussed here in the framework of hand-made artificial swimmers as an example of practical application. REFERENCE [1] Ramananarivo, S., Godoy-Diana, R., Thiria, B. Passive elastic mechanism to mimic fish-muscle action in anguilliform swimming. Journal of the Royal Society Interface. 2013, 10(88), 20130667

To the Revolution and back: Wordsworth’s painful crossings

Lorsque Wordsworth traverse la Manche en 1791 pour retourner séjourner en France, il accomplit d’un coup diverses transgressions : il désobéit à ses oncles, compromet son avenir professionnel, et rejoint le camp des idées nouvelles. Contraint de rentrer au pays dans l’espoir de trouver des subsides pour la famille illégitime qu’il vient de fonder dans un nouvel acte transgressif, Wordsworth s’aperçoit bien vite que tout retour n’est que chimère. L’Angleterre qu’il retrouve n’est pas celle qu’il a quittée, Annette est devenue impossible à rejoindre. Le passé et son innocence perdue ne sont pas plus accessibles que ne le sont ses futurs lecteurs qu’il craint de ne pouvoir convaincre dans des vers empreints d’une culpabilité déchirante. Le chemin du retour, vers une forme de paix intérieure et d’appartenance apaisée à la communauté nationale, est pavé pour Wordsworth de doubles, choisis ou reniés. Avec Milton, le poète s’invente un frère, compagnon d’infortune, survivant lui aussi d’une révolution manquée. Avec Robespierre, il trouve un bouc émissaire qu’il charge du poids de sa culpabilité, et dont la mort le libère.The crossing of the Channel to revolutionary France was a symbolic transgression for Wordsworth, on various levels: he was disobeying his uncles, compromising his future, and joining the revolutionary side. Forced to go back to get funds for the illegitimate family he had founded in yet another act of transgression, Wordsworth realises that there is in fact no going back. His motherland has changed, his French family cannot be reached, and there is no more going back to the past and its innocence as there is a possibility of crossing over to the reader of The Prelude to win his or her sympathy in lines that transpire with guilt. Eventually, the poet uses historical figures as doubles to help him get back to a safe harbour of inner peace and acceptable Britishness. Wordsworth identifies with Milton as the joint survivor of a failed revolution, and rejects all his sense of guilt onto Robespierre whose death signals the return of innocence

Dans l’ombre de l’ego sublime : portrait de Dorothy Wordsworth en Écho de son frère

Si la figure de Narcisse affleure souvent dans les vers de William Wordsworth, la silhouette effacée de Dorothy, sa sœur, évoque celle de la nymphe Écho. Pourquoi ce silence chez une personnalité passionnée et tout aussi sensible que son frère à la beauté de la nature qui l’environne ? Dans de nombreux poèmes, William réduit au silence une figure féminine, derrière laquelle semble bien se cacher l’ombre de sa sœur. Mais dans les poèmes de Dorothy une poétique de l’écho se fait entendre, et une conscience de sa valeur se fait jour.The figure of Narcissus frequently haunts William Wordsworth’s verse, and conversely, the elusive presence of his sister evokes that of the nymph Echo. Why would such a passionate personality, clearly as sensitive as her brother to nature’s beauties, choose to remain silent? Many poems by William stage a silenced female figure, behind which Dorothy’s features can often be made out. Yet, Dorothy’s own poems reveal a poetic of echoes and a dawning awareness of her own words’ worth