Acoustic dipole surfing on its own acoustic field: toward acoustic quantum analogues

In a recent paper [J. Fluid Mech., 952: A22 (2022)], Roux et al. demonstrated that a translating monopolar acoustic source is subjected to a self-induced radiation force opposite to its motion. This force results from a symmetry breaking of the emitted wave induced by Doppler effect. In the present work, we show that for a dipolar source, the selfinduced radiation force can be aligned with the velocity perturbation, hence amplifying it. This work suggests the possibility of a dipolar acoustic source surfing on its own acoustic wave, hence paving the way towards acoustic quantum analogues

Analyse interlocutoire, dynamiques interactives et étude des mécanismes des progrès cognitifs en situation asymétrique de résolution de problèmes

Le présent travail s’inscrit dans une approche psycho-sociale du développement cognitif. Il est fondé à la fois par les idées théoriques de Vygotski et ses prolongements européens et par la pragmatique, qui étudie la coordination entre la pensée, le langage et les comportements sociaux. Il s’agit de montrer, grâce à la théorie de la logique interlocutoire, que les avancées cognitives individuelles peuvent être considérées comme le produit d’un apprentissage en contexte interactionnel, et que les médiations sémiotiques (et parmi elles tout particulièrement les échanges de signes langagiers) s’accomplissant au sein même du contexte interlocutoire sont consubstancielles aux processus constructeurs eux-mêmes. Les résultats de deux expériences conduites en contexte scolaire attestent d’une part que des enfants jeunes peuvent tirer des bénéfices cognitifs d’une situation asymétrique de résolution de problèmes et d’autre part que les progrès cognitifs constatés peuvent être imputables à des mécanismes différents.This research takes place within a psychosocial approach to cognitive development. It is based on both Vygotskian’s theoretical ideas and the European continuance of these ideas and pragmatics, which study links between thought, language and social behavior. It aims at showing, using the theory of interlocutory logic, that individual cognitive development is the product of learning within a context of interaction, and that semiotic mediations (and particularly exchanges of speech acts) achieved within the interlocutory context are very tightly linked to the constructive process itself. Results of two experiments, carried out within a school context, demonstrate that young children can obtain a substantial cognitive benefit from an asymmetric co-resolution problem-solving device and that these cognitive progresses can be attributed to various mechanisms

Stéphane Yerasimos, La fondation de Constantinople et de Sainte-Sophie dans les traditions turques, Paris, IFEA et Jean Maisonneuve, 1990, 281 p.

Partant de ce qu'il nomme des “ légendes d'Empires ”, en l'occurrence celles relatives à la fondation de Constantinople et de Sainte Sophie, ville et Eglise ainsi liées entres elles indissolublement dès le titre, l'auteur vise au delà de son propos immédiat à expliquer par elles ce qu'est la grande mosquée ottomane (“ un microcosme parfait et immuable de l'univers ”) et les clivages de la société turque moderne

Behavior of a GPI-anchored protein in phospholipid monolayers at the air–water interface

AbstractThe interaction between alkaline phosphatase (AP), a glycosylphosphatidylinositol (GPI)-anchored protein (AP-GPI), and phospholipids was monitored using Langmuir isotherms and PM-IRRAS spectroscopy. AP-GPI was injected under C16 phospholipid monolayers with either a neutral polar head (1,2-dipalmitoyl-sn-glycero-3-phosphocholine monohydrate (DPPC)) or an anionic polar head (1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS)). The increase in molecular area due to the injection of protein depended on the surface pressure and the type of phospholipid. At all surface pressures, it was highest in the case of DPPS monolayers. The surface elasticity coefficient E, determined from the π–A diagrams, allowed to deduct that the AP-GPI–phospholipid mixtures presented a molecular arrangement less condensed than the corresponding pure phospholipid films. PM-IRRAS spectra suggested different protein–lipid interactions as a function of the nature of the lipids. AP-GPI modified the organization of the DPPS deuterated chains whereas AP-GPI affected only the polar group of DPPC at low surface pressure (8 mN/m). Different protein hydration layers between the DPPC and DPPS monolayers were suggested to explain these results. PM-IRRAS spectra of AP-GPI in the presence of lipids showed a shape similar to those collected for pure AP-GPI, indicating a similar orientation of AP-GPI in the presence or absence of phospholipids, where the active sites of the enzyme are turned outside of the membrane

Spin-motion coupling in a circular Rydberg state quantum simulator: case of two atoms

Rydberg atoms are remarkable tools for the quantum simulation of spin arrays. Circular Rydberg atoms open the way to simulations over very long time scales, using a combination of laser trapping of the atoms and spontaneous-emission inhibition, as shown in the proposal of a XXZ spin-array simulator based on chains of trapped circular atoms [T.L. Nguyen $\textit{et al.}$, Phys. Rev. X 8, 011032 (2018)]. Such simulators could reach regimes (thermalization, glassy dynamics) that are out of the reach of those based on ordinary, low-angular-momentum short-lived Rydberg atoms. Over the promised long time scales, the unavoidable coupling of the spin dynamics with the atomic motion in the traps may play an important role. We study here the interplay between the spin exchange and motional dynamics in the simple case of two interacting circular Rydberg atoms confined in harmonic traps. The time evolution is solved exactly when the position dependence of the dipole-dipole interaction terms can be linearized over the extension of the atomic motion. We present numerical simulations in more complex cases, using the realistic parameters of the simulator proposal. We discuss three applications. First, we show that realistic experimental parameters lead to a regime in which atomic and spin dynamics become fully entangled, generating interesting non-classical motional states. We also show that, in other parameter regions, the spin dynamics notably depends on the initial temperature of the atoms in the trap, providing a sensitive motional thermometry method. Last, and most importantly, we discuss the range of parameters in which the motion has negligible influence over the spin dynamics.Comment: 18 pages, 12 figure

Staphylococcus aureus gene expression in a rat model of infective endocarditis

Background: Diabetes mellitus is a frequent underlying comorbidity in patients with Staphylococcus aureus endocarditis, and it represents a risk factor for complications and a negative outcome. The pathogenesis of staphylococcal endocardial infections in diabetic hosts has been poorly characterized, and little is known about S. aureus gene expression in endocardial vegetations. Methods: We utilized a rat model of experimental S. aureus endocarditis to compare the pathogenesis of staphylococcal infection in diabetic and nondiabetic hosts and to study the global S. aureus transcriptome in endocardial vegetations in vivo. Results: Diabetic rats had higher levels of bacteremia and larger endocardial vegetations than nondiabetic control animals. Microarray analyses revealed that 61 S. aureus genes were upregulated in diabetic rats, and the majority of these bacterial genes were involved in amino acid and carbohydrate metabolism. When bacterial gene expression in vivo (diabetic or nondiabetic endocardial vegetations) was compared to in vitro growth conditions, higher in vivo expression of genes encoding toxins and proteases was observed. Additionally, genes involved in the production of adhesins, capsular polysaccharide, and siderophores, as well as in amino acid and carbohydrate transport and metabolism, were upregulated in endocardial vegetations. To test the contribution of selected upregulated genes to the pathogenesis of staphylococcal endocarditis, isogenic deletion mutants were utilized. A mutant defective in production of the siderophore staphyloferrin B was attenuated in the endocarditis model, whereas the virulence of a surface adhesin (ΔsdrCDE) mutant was similar to that of the parental S. aureus strain. Conclusions: Our results emphasize the relevance of diabetes mellitus as a risk factor for infectious endocarditis and provide a basis for understanding gene expression during staphylococcal infections in vivo. Electronic supplementary material The online version of this article (doi:10.1186/s13073-014-0093-3) contains supplementary material, which is available to authorized users