Vers une psychophysique à l'échelle urbaine

Summary The reproduction at scale 1/1 of the size of 13 public squares in different towns, varying from 350 m² to 6 400 m², was studied with 120 Ss. After a period of observation in a square, the S was asked to mark, with stakes in a big field, the perimeter of the space he had explored. Each S was tested only in one public square. In general, underestimation increases with size. Moreover individual responses show a variation which is characteristic for squares less than 2 000 m2 (20 Ss overestimate and 48 Ss underestimate size). On the contrary, above 2 000 m2, ail Ss (except one) underestimate size. Therefore we may consider that at 2 000 m2 there is a « change of scale » of the squares.RÉSUMÉ Nous avons étudié la reproduction en échelle 1/1 de la surface de 13 places de différentes villes, variant de 350 m² à 6 400 m², avec 120 sujets. Après avoir observé à loisir la place, le sujet est prié de marquer avec des tiges dans un grand terrain le périmètre de l'espace qu'il vient d'explorer. Chaque sujet fait l'expérience pour une seule place. En général, la sous-estimation augmente avec la surface. Les réponses individuelles présentent des variations pour les places inférieures à 2 000 m2 (20 sujets surestiment et 48 sous-estiment les places). Par contre, pour les surfaces supérieures à 2 000 m2 tous les sujets (sauf un) sous-estiment les places. Du point de vue psychophysique on pourrait considérer que pour 2 000 m2 il se produit un « changement d'échelle » des places.Battro A. M., Mazzotti Tarso Bonilha, Gerassi Cabral Reinaldo J. Vers une psychophysique à l'échelle urbaine. In: L'année psychologique. 1975 vol. 75, n°1. pp. 147-152

Modification of a Single Atom Affects the Physical Properties of Double Fluorinated Fmoc-Phe Derivatives

Supramolecular hydrogels formed by the self-assembly of amino-acid based gelators are receiving increasing attention from the fields of biomedicine and material science. Self-assembled systems exhibit well-ordered functional architectures and unique physicochemical properties. However, the control over the kinetics and mechanical properties of the end-products remains puzzling. A minimal alteration of the chemical environment could cause a significant impact. In this context, we report the effects of modifying the position of a single atom on the properties and kinetics of the self-assembly process. A combination of experimental and computational methods, used to investigate double-fluorinated Fmoc-Phe derivatives, Fmoc-3,4F-Phe and Fmoc-3,5F-Phe, reveals the unique effects of modifying the position of a single fluorine on the self-assembly process, and the physical properties of the product. The presence of significant physical and morphological differences between the two derivatives was verified by molecular-dynamics simulations. Analysis of the spontaneous phase-transition of both building blocks, as well as crystal X-ray diffraction to determine the molecular structure of Fmoc-3,4F-Phe, are in good agreement with known changes in the Phe fluorination pattern and highlight the effect of a single atom position on the self-assembly process. These findings prove that fluorination is an effective strategy to influence supramolecular organization on the nanoscale. Moreover, we believe that a deep understanding of the self-assembly process may provide fundamental insights that will facilitate the development of optimal amino-acid-based low-molecular-weight hydrogelators for a wide range of applications