Flowing active liquids in a pipe: Hysteretic response of polar flocks to external fields

We investigate the response of colloidal flocks to external fields. We first show that individual colloidal rollers align with external flows as would a classical spin with magnetic fields. Assembling polar active liquids from colloidal rollers, we experimentally demonstrate their hysteretic response: confined colloidal flocks can proceed against external flows. We theoretically explain this collective robustness, using an active hydrodynamic description, and show how orientational elasticity and confinement protect the direction of collective motion. Finally, we exploit the intrinsic bistability of confined active flows to devise self-sustained microfluidic oscillators.Comment: 12 pages, 7 figure; accepted for publication in Physical Review

Collective Motion with Anticipation: Flocking, Spinning, and Swarming

We investigate the collective dynamics of self-propelled particles able to probe and anticipate the orientation of their neighbors. We show that a simple anticipation strategy hinders the emergence of homogeneous flocking patterns. Yet, anticipation promotes two other forms of self-organization: collective spinning and swarming. In the spinning phase, all particles follow synchronous circular orbits, while in the swarming phase, the population condensates into a single compact swarm that cruises coherently without requiring any cohesive interactions. We quantitatively characterize and rationalize these phases of polar active matter and discuss potential applications to the design of swarming robots.Comment: 6 pages, 4 figure

Le Saix – Barnèche 2

Identifiant de l'opération archéologique : 8223 Date de l'opération : 2007 (SD) Le site de Barnèche 2 est implanté à 847 m d’altitude dans la petite vallée du torrent de Barnèche, affluent du torrent de la Maraize, sur la commune du Saix. Ce site, découvert par Henri Faure, a fourni lors des ramassages de surface plusieurs centaines de pièces, essentiellement des silex taillés, se rapportant à des ambiances chronoculturelles néolithiques. La cartographie des ramassages montre que le site s’ét..

Disentangling shape from level effects in person-centered analyses : An illustration based on university teachers' multidimensional profiles of effectiveness

This study compares alternative ways of disentangling the effects of level (the tendency for a person to be high, medium, or low across all factors) and shape (the tendency for a person to have a distinct pattern of factors on which they are high, medium, or low) in profile analyses. This issue is particularly relevant to performance appraisals where it is often useful to identify specific strengths and weaknesses over and above a person global performance, but also to person-centered analyses more generally where the observation of qualitative (shape) differences between profiles is often used as justification for the added value of profiles. Substantively, this study illustrates these issues in the identification of profiles of teachers based on multidimensional students’ ratings of their effectiveness, using an archival data set of 31,951 class-average ratings based on the Students’ Evaluations of Educational Quality (SEEQ) instrument collected over a 13-year period. The results show the superiority of a factor mixture operationalization of teaching effectiveness in which a global effectiveness factor was used to control for unnecessary level effects in the profiles

Spontaneous Demixing of Binary Colloidal Flocks

Population heterogeneity is ubiquitous among active living systems, but little is known about its role in determining their spatial organization and large-scale dynamics. Combining evidence from synthetic active fluids assembled from self-propelled colloidal particles along with theoretical predictions at the continuum scale, we demonstrate the spontaneous demixing of binary polar liquids within circular confinement. Our analysis reveals how both active speed heterogeneity and non-reciprocal repulsive interactions lead to self-sorting behavior. By establishing general principles for the self-organization of binary polar liquids, our findings highlight the specificity of multi-component active systems.Comment: 6 pages, 4 figure

Sainte-Marie-du-Mont, Chapareillan – Structures des Hauts de Chartreuse

Identifiant de l'opération archéologique : 229396 Date de l'opération : 2007 (PT) Inventeur(s) : Carron Pierre-Yves (COL) Une opération de prospection sur les structures pastorales (Fig. n°1 : Plan d'ensemble des structures pastorales des Haberts de Barraux, alpage de l'Alpe) s’est déroulée sur les Hauts de Chartreuse, sur les alpages de l’Alpe, du Pinet et de l’Alpette (Sainte-Marie-du-Mont et Chapareillan, Isère), avec les soutiens financiers de la réserve naturelle des Hauts de Chartreuse..

Sainte-Marie-du-Mont, Chapareillan

Identifiant de l'opération archéologique : 229396 Date de l'opération : 2007 (PT) Inventeur(s) : Carron Pierre-Yves (COL) Une opération de prospection sur les structures pastorales (Fig. n°1 : Plan d'ensemble des structures pastorales des Haberts de Barraux, alpage de l'Alpe) s’est déroulée sur les Hauts de Chartreuse, sur les alpages de l’Alpe, du Pinet et de l’Alpette (Sainte-Marie-du-Mont et Chapareillan, Isère), avec les soutiens financiers de la réserve naturelle des Hauts de Chartreuse..

Examination of the structure and grade-related differentiation of multidimensional self-concept instruments for children using ESEM

This study is a substantive-methodological synergy in which exploratory structural equation modeling is applied to investigate the factor structure of multidimensional self-concept instruments. On the basis of a sample of German students (N = 1958) who completed the Self-Description Questionnaire I and the Self-Perception Profile for Children, the results supported the superiority of exploratory structural equation modeling compared with confirmatory factor analyses for both instruments. Exploratory structural equation modeling resulted in lower factor correlations and substantively meaningful cross-loadings. The authors also proposed and contrasted 3 mechanisms for testing grade-related differences in the differentiation of self-concept facets and found no evidence of increased differentiation between Grades 3 to 6

Mixture modeling for lifespan developmental research

As part of the Generalized Structural Equation Modeling framework, mixture models are person-centered analyses seeking to identify distinct subpopulations, or profiles, of participants differing quantitatively and qualitatively from one another on a configuration of indicators and/or relations among these indicators. Mixture models are typological (resulting in a classification system), probabilistic (each participant having a probability of membership into all profiles based on prototypical similarity), and exploratory (the optimal model is typically selected based on a comparison of alternative specifications) in nature, and can take different forms. Latent profile analyses seek to identify subpopulations of participants differing from one another on a configuration of indicators and can be extended to factor mixture analyses allowing for the incorporation of latent factors to the model. In contrast, mixture regression analyses seek to identify subpopulations of participants’ differing from one another in terms of relations among profile indicators. These analyses can be extended to the multiple-group and/or longitudinal analyses, allowing researchers to conduct tests of profile similarity across different samples of participants or time points, and latent transition analyses can be used to assess probabilities of profiles transition over time among a sample of participants (i.e., within person stability and change in profile membership). Finally, growth mixture analyses are built from latent curve models and seek to identify subpopulations of participants following quantitatively and qualitatively distinct trajectories over time. All of these models can accommodate covariates, used either as predictors, correlates, or outcomes, and can even be extended to tests of mediation and moderation