Action collective (sociologie)

Une action collective est, en sociologie, un type d'action, collective, résultant d'une coordination non concertée par les agents des buts ou des formes de leurs actions individuelles. Les agents n’ont pas d’engagements les uns à l’égard des autres. Concept La sociologie distingue deux types d'actions collectives :

Lorsque la coordination est simplement induite par les circonstances, l’action collective est dite plurielle : les fins et moyens s’imposent ou sont suggérés. C'est le cas du « sauve qui peut » et des phénomènes de foule.
Lorsque la coordination est prédéterminée par un dispositif social, les actions sont dites complémentaires. Celles-ci peuvent être simultanées, telles celles du conducteur d’autobus et de son passager, ou différée, telle l’action de lire un livre écrit par un autre en une autre époque.

On remarque ainsi deux sens au concept :

au sens large, l'action collective est une action coordonnée de plusieurs individus, comme faire ses courses au

Robotic manipulation to investigate the physical principles of biological self-organization

Fazil Emre Uslu

Self-organization is the spontaneous formation of ordered patterns and networks from a population of comparatively simple elements or individuals with no prior information on neither the formation process nor the final organization. While the construction of tissues and organs is driven by the collective action of many eukaryotic cells, at a higher scale, social insects govern massive colonies via cooperative group behavior. In biological self-organization, unlike inanimate matter, interaction rules of elements are not constant but generally evolve in time and space in a history-dependent fashion. Recent technological advances in molecular biology, genetics, microscopy, and quantitative analysis have made it possible to follow the development of tissues, organs, and entire embryos at the single-cell level with high temporal resolution. Automated video tracking systems based on identification labels allow tracking of all members in insect colonies to identify individual interactions and patterns of social organization. These studies have shown that individuals must allocate themselves to actions or tasks in a dynamic manner following simple rules that incorporate local stimuli received directly from the environment and from interactions with other individuals. The majority of the available platforms provide observation only and do not allow manipulation of conditions for probing the self-organizing systems. Application of spatiotemporally resolved physical stimuli to individuals will reveal a more complete understanding of biological self-organization.In this thesis, I have developed robotic manipulation platforms along with computational models to investigate the principles of self-organization in biological systems. I have worked on two complementary experimental models at different scales to prove the generality of my approach. The first robotic manipulation platform explores the transmission and transduction of mechanical signals within a connected fiber network and associated cellular responses. I developed a biocompatible magnetic microactuator and a magnetic control system to apply physiologically relevant traction forces to cells cultured on fibrous matrices. Along with the experimental platform, I have developed a finite element-modeling framework that simulates stresses on a digital copy of the fiber network. The second robotic manipulation platform controls the temperature on the nest floor of ant colonies. The system is integrated with a real-time tracking system that is capable of following interactions among hundreds of individuals. The ant colony is stimulated to transport their brood by changing the temperature of the next floor in a spatially patterned way. We explored how ants processed thermal signals, coordinated the transport of brood, and interacted with one another.

EPFL2022

Morphogenetic degeneracies in the actomyosin cortex

Sundar Ram Naganathan

One of the great challenges in biology is to understand the mechanisms by which morphogenetic processes arise from molecular activities. We investigated this problem in the context of actomyosin-based cortical flow in C. elegans zygotes, where large-scale flows emerge from the collective action of actomyosin filaments and actin binding proteins (ABPs). Large-scale flow dynamics can be captured by active gel theory by considering force balances and conservation laws in the actomyosin cortex. However, which molecular activities contribute to flow dynamics and large-scale physical properties such as viscosity and active torque is largely unknown. By performing a candidate RNAi screen of ABPs and actomyosin regulators we demonstrate that perturbing distinct molecular processes can lead to similar flow phenotypes. This is indicative for a 'morphogenetic degeneracy' where multiple molecular processes contribute to the same large-scale physical property. We speculate that morphogenetic degeneracies contribute to the robustness of bulk biological matter in development.

ELIFE SCIENCES PUBLICATIONS LTD2018

Robotic manipulation to investigate the physical principles of biological self-organization

Fazil Emre Uslu

EPFL2022

Action collective (sociologie)

Robotic manipulation to investigate the physical principles of biological self-organization

Qualité urbaine, durabilité et action collective: éléments de réflexion

Morphogenetic degeneracies in the actomyosin cortex

Morphogenetic degeneracies in the actomyosin cortex

Robotic manipulation to investigate the physical principles of biological self-organization

Qualité urbaine, durabilité et action collective: éléments de réflexion