Le désapprentissage, une rudologie de l’esprit

International audienceLes auteurs proposent la courbe « espoir vs déception » pour décrire le cycle de vie des représentations mentales. Ils mettent en évidence qu’en fin du cycle, ces représentations mentales deviennent d’abord inutiles puis mentalement toxiques et doivent être désapprises, c’est-à-dire éliminées du moins si l’acteur veut préserver sa santé mentale, continuer à piloter la suite de sa vie de façon à maintenir son employabilité. Les auteurs considèrent cette élimination comme semblable à celles du traitement de déchets : une sorte de rudologie de l’esprit

La dangerosité sociale est-elle inhérente à la path dependence?

International audienceAu sein de la doctrine providentielle sociale française, règne la path dependence : un attachement indéfectible au passé et un rejet aversif du risque et du futur. Il en résulte une protection sociale inadaptée qui est devenue un prédateur économique jetant les classes moyennes dans la pauvreté. Pourtant les élus n’y renoncent pas car elle constitue un acquis de la Résistance. Son maintien absolu provoque des problèmes de régulation justifiant l’entretien de coûteux complexes juridiques et organisationnels, dont les vagues successives d’élus amplifient encore la complexité au fil du temps. Or, d’après la théorie cybernétique, tout organisme qui se complexifie, chemine inéluctablement vers un état provisoire - le chaos -avant d’atteindre un état final : l’effondrement. Ainsi, une société ancrée dans une dépendance au passé, est-elle menacée par un risque civilisationnel majeur, celui de sa disparition. Ce risque devient prédictible à travers 7 signaux faibles : l’effet « tâche d’huile », l’effet « tunnel », l’effet « boomerang », l’effet « matelas à eau », l’effet « démoralisation », l’effet « intolérance aux immigrés » et l’effet « cliquet »

Quand la cybernétique et la sociologie de la traduction mettent en évidence la dangerosité sociale inhérente à la protection sociale.

International audienceLa mobilisation de la cybernétique et de la sociologie de la traduction permet de mettre en évidence que, dans le domaine social, les mécanismes de la prédation et de la protection sont indissociables. L’un s’appuie sur l’autre et aucun des deux ne peut exister sans l’autre. Or, ce lien indestructible entre ces deux opposés généralise le chaos, au risque de provoquer à terme l’effondrement du système. Quelques exemples emblématiques tirés des politiques de la sécurité et du travail permettent d’illustrer comment la protection sociale développe cette forte Dangerosité Sociale Inhérente (DSI) à la prédation par l’intermédiaire des Interactants vs Actants

Homo-coupling of terminal alkynes on a noble metal surface

The covalent linking of acetylenes presents an important route for the fabrication of novel carbon-based scaffolds and two-dimensional materials distinct from graphene. To date few attempts have been reported to implement this strategy at well-defined interfaces or monolayer templates. Here we demonstrate through real space direct visualization and manipulation in combination with X-ray photoelectron spectroscopy and density functional theory calculations the Ag surface-mediated terminal alkyne Csp−H bond activation and concomitant homo-coupling in a process formally reminiscent of the classical Glaser–Hay type reaction. The alkyne homo-coupling takes place on the Ag(111) noble metal surface in ultrahigh vacuum under soft conditions in the absence of conventionally used transition metal catalysts and with volatile H2 as the only by-product. With the employed multitopic ethynyl species, we demonstrate a hierarchic reaction pathway that affords discrete compounds or polymeric networks featuring a conjugated backbone. This presents a new approach towards on-surface covalent chemistry and the realization of two-dimensional carbon-rich or all-carbon polymers

Homo-coupling of terminal alkynes on a noble metal surface

The covalent linking of acetylenes presents an important route for the fabrication of novel carbon-based scaffolds and two-dimensional materials distinct from graphene. To date few attempts have been reported to implement this strategy at well-defined interfaces or monolayer templates. Here we demonstrate through real space direct visualization and manipulation in combination with X-ray photoelectron spectroscopy and density functional theory calculations the Ag surface-mediated terminal alkyne Csp−H bond activation and concomitant homo-coupling in a process formally reminiscent of the classical Glaser–Hay type reaction. The alkyne homo-coupling takes place on the Ag(111) noble metal surface in ultrahigh vacuum under soft conditions in the absence of conventionally used transition metal catalysts and with volatile H2 as the only by-product. With the employed multitopic ethynyl species, we demonstrate a hierarchic reaction pathway that affords discrete compounds or polymeric networks featuring a conjugated backbone. This presents a new approach towards on-surface covalent chemistry and the realization of two-dimensional carbon-rich or all-carbon polymers

Five-vertex Archimedean surface tessellation by lanthanide-directed molecular self-assembly

The tessellation of the Euclidean plane by regular polygons has been contemplated since ancient times and presents intriguing aspects embracing mathematics, art, and crystallography. Significant efforts were devoted to engineer specific 2D interfacial tessellations at the molecular level, but periodic patterns with distinct five-vertex motifs remained elusive. Here, we report a direct scanning tunneling microscopy investigation on the cerium-directed assembly of linear polyphenyl molecular linkers with terminal carbonitrile groups on a smooth Ag(111) noble-metal surface. We demonstrate the spontaneous formation of fivefold Ce-ligand coordination motifs, which are planar and flexible, such that vertices connecting simultaneously trigonal and square polygons can be expressed. By tuning the concentration and the stoichiometric ratio of rare-earth metal centers to ligands, a hierarchic assembly with dodecameric units and a surface-confined metal-organic coordination network yielding the semiregular Archimedean snub square tiling could be fabricated

Chemical Transformations Drive Complex Self-Assembly of Uracil on Close-Packed Coinage Metal Surfaces

We address the interplay of adsorption, chemical nature, and self-assembly of uracil on the Ag(111) and Cu(111) surfaces as a function of molecular coverage (0.3 to 1 monolayer) and temperature. We find that both metal surfaces act as templates and the Cu(111) surface acts additionally as a catalyst for the resulting self-assembled structures. With a combination of STM, synchrotron XPS, and NEXAFS studies, we unravel a distinct polymorphism on Cu(111), in stark contrast to what is observed for the case of uracil on the more inert Ag(111) surface. On Ag(111) uracil adsorbs flat and intact and forms close-packed two-dimensional islands. The self-assembly is driven by stable hydrogen-bonded dimers with poor two-dimensional order. On Cu(111) complex structures are observed exhibiting, in addition, a strong annealing temperature dependence. We determine the corresponding structural transformations to be driven by gradual deprotonation of the uracil molecules. Our XPS study reveals unambiguously the tautomeric signature of uracil in the contact layer and on Cu(111) the molecule’s deprotonation sites. The metal-mediated deprotonation of uracil and the subsequent electron localization in the molecule determine important biological reactions. Our data show a dependence between molecular coverage and molecule–metal interaction on Cu(111), as the molecules tilt at higher coverages in order to accommodate a higher packing density. After deprotonation of both uracil N atoms, we observe an adsorption geometry that can be understood as coordinative anchoring with a significant charge redistribution in the molecule. DFT calculations are employed to analyze the surface bonding and accurately describe the pertaining electronic structure

Dynamics of Spatially Confined Bisphenol A Trimers in a Unimolecular Network on Ag(111)

Bisphenol A (BPA) aggregates on Ag(111) shows a polymorphism between two supramolecular motifs leading to formation of distinct networks depending on thermal energy. With rising temperature a dimeric pairing scheme reversibly converts into a trimeric motif, which forms a hexagonal superstructure with complex dynamic characteristics. The trimeric arrangements notably organize spontaneously into a self-assembled one-component array with supramolecular BPA rotors embedded in a two-dimensional stator sublattice. By varying the temperature, the speed of the rotors can be controlled as monitored by direct visualization. A combination of scanning tunneling microscopy and dispersion corrected density-functional tight-binding (DFTB-vdW(surf)) based molecular modeling reveals the exact atomistic position of each molecule within the assembly as well as the driving force for the formation of the supramolecular rotors