Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S03: Physics of Social Interactions IIFocus Recordings Available
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Sponsoring Units: DBIO Chair: Greg Stephens, OIST and Vrije Universiteit Amsterdam Room: McCormick Place W-176A |
Thursday, March 17, 2022 8:00AM - 8:12AM |
S03.00001: Wetting, speed, and contact geometry in cell-cell collisions Pedrom Zadeh, Brian A Camley Collective cell migration, in which cells crawl in coordination, is crucial in many biological processes. The extent of collective migration is controlled by how cells interact, which is often studied in cell pairs. A recent study observed head-on collisions between trains of MDCK cells in narrow confinement [1]. One feature controlling the outcome was contact geometry—the leading cell that formed a smaller contact angle with the substrate had a larger probability of maintaining its polarity. We build a phase-field model for two-body collisions, in which cells are treated as continuously deformable objects. We hypothesize that cells can sense their velocity and align to it over a finite timescale. We control the cell’s contact angle via its strength of adhesion to the substrate, surface tension, and strength of active force in the leading edge and track its contact angle and speed. Within this model, we show that contact angle does predict collision outcome, but that this is potentially misleading as contact angle correlates with cell speed, which is a better predictor of whether a cell remains persistent upon collision. |
Thursday, March 17, 2022 8:12AM - 8:24AM |
S03.00002: Modeling evolution of firefly-like signal vocabularies Chantal Nguyen, Isabella Huang, Orit Peleg Fireflies communicate by producing bioluminescence to signal their presence and court mates. In particular, some species emit patterns of short flashes with the potential to encode information; males flash according to a species-specific pattern in order to attract and locate females. Multiple firefly species with different characteristic patterns can share the same habitat, leading to visual clutter that could potentially hinder successful communication among conspecifics. We investigate how flash sequences can co-evolve to be distinguishable by developing a "vocabulary generator" model. We use this model to simulate sequences that minimize both their mutual similarity with each other and their individual predation risks. We observe an emergent periodicity in the resulting optimal sequences despite the lack of any constraints on the sequences to be periodic. We also demonstrate a method of reconstructing potential cost functions from the phylogenetic relationships of extant species alongside their characteristic flash patterns. |
Thursday, March 17, 2022 8:24AM - 8:36AM |
S03.00003: Socially isolated bumblebees display frequent antennation and close interactions compared to socially reared bumblebees Grace C McKenzie-Smith, Z. Yan Wang, Hyo Jin Cho, Talmo D Pereira, Sarah D Kocher, Joshua W Shaevitz Bumblebees are eusocial insects that must correctly give and receive social cues to function as a group. Newly eclosed bumblebees go through a nine day period of rapid brain development as they take on tasks within the hive. To probe how social interaction during this time affects later behavior we removed newly eclosed bees from the colony and isolated them for nine days. We observed the behavior of age-matched bees from extra-hive isolated and grouped rearing conditions and hive reared bees. We used SLEAP1 to track posture and quantified the behavioral repertoire of bees in both individual and paired trials. We find broad behavior differences between isolated bees and their socially reared counterparts. We also find that isolated bees paired with any other bee (isolated, grouped control, or hive reared) have increased antennal interactions and prefer closer interthorax distances with their partner than socially reared bees. |
Thursday, March 17, 2022 8:36AM - 8:48AM |
S03.00004: Modeling ant pontoon bridging using a robophysical active matter system Noah Egan, Shengkai Li, Ram Avinery, Haolin Zeng, Takao Sasaki, Daniel I Goldman Laboratory experiments demonstrate that when groups of fire ants [S. invicta] detect food located on the surface of water a short distance from a rigid boundary, the ants self-assemble into a floating pontoon bridge, allowing the colony to reach the food. The bridge grows from the boundary via a complex interplay of individual water walking, collective clumping and edge connection. Once formed, the ants rapidly travel across the bridge to and from the food source. To begin to robophysically model the bridge formation behavior we use BOBbots [Li et al, Sci. Adv. 2021] an active matter system composed of 6 cm diameter disc-shaped robots which move via vibratory motors and connect via loose magnets. To systematically determine individual behavioral rules of the BOBbots leading to the emergent bridge-building behavior, we first test bridge-building in a Discrete Element Method simulation of the BOBbots. Simulations qualitatively replicate aspects of the bridge formation dynamics including slow growth from a boundary and stochastic clumping and aggregation. Study of the directed aggregation (bridging) effect revealed by the simulation gives insight into relevant ant behaviors which contribute to formation of these on-demand biological pontoon bridges. |
Thursday, March 17, 2022 8:48AM - 9:00AM |
S03.00005: Spatiotemporal patterns of flash synchrony in firefly mating swarms Raphael Sarfati, Julie Hayes, Orit Peleg On a midsummer night, firefly swarms might appear as a cloud of uncorrelated sparks, but they likely present a structured internal dynamics, shaped by evolution to optimize mating outcomes. As a blatant example of collective behavior, some species spontaneously synchronize their flashes, and at high density they create large-scale displays of blinking lights with complex correlations. Using stereoscopic reconstructions of swarms, we investigate how individual flash motifs and the structure of social interactions induce collective flash patterns of various kinds. We focus on two different species exhibiting either continuous or intermittent synchrony with an emergent frequency. Finally, we use the analysis of 3D trajectories to reveal social differentiation, information propagation, and broadly explore the interplay between movement and flashing behavior. |
Thursday, March 17, 2022 9:00AM - 9:12AM |
S03.00006: Larval zebrafish exhibit collective circulation in confined spaces Haider Zaki, Enkeleida Lushi, Kristen Severi Collective behavior may be elicited or can spontaneously emerge by a combination of interactions with the physical environment. To investigate the relative contributions of these factors for a millimeter-scale swimming organism, we observed larval zebrafish interacting at varying densities under circular confinement. If left undisturbed, larval zebrafish swim intermittently in a burst and coast manner and are socially independent at this developmental stage, before shoaling behavioral onset. We explore the behavior these larvae as they swim together inside dishes. We report our analysis of a new observation for this well-studied species: in circular confinement and at sufficiently high densities, the larvae collectively circle rapidly alongside the boundary. This is a new physical example of self-organization of mesoscale living active matter driven by not only by boundaries and environment geometry, but also influenced by social interactions. |
Thursday, March 17, 2022 9:12AM - 9:24AM |
S03.00007: An Agent Based Force Vector Model of Human Social Influence G J Maclay, Moody Ahmad The model is based on a vector representation of each agent. The components of the vector are the continuous “attributes” that determine the social behavior of the agent. A force vector model gives the effect of each agent on all other agents. It assumes that the force between two agents is proportional to the "similarity of attributes" given by the dot product of the vectors representing the attributes, and goes inversely as the distance in attribute space between the two vectors. The force between the agents may be positive (attractive), zero, or negative (repulsive) depending on the angle between the vectors. A positive force causes the attributes of the agents to become more similar and the corresponding vectors to become more nearly parallel. Interaction between all agents is allowed unless the distance between the agents exceeds a confidence limit, the Attribute Influence Bound (AIB). Agents with similar attributes tend to form groups. For small values of the AIB, numerous groups remain scattered in attribute space at the end of a simulation. As the AIB is increased the few remaining groups have increasingly different characteristic attributes and approximately equal sizes. With a large AIB all agents are connected and extreme bi- or tri-polarization results. |
Thursday, March 17, 2022 9:24AM - 9:36AM |
S03.00008: Third-party restoration and annihilation of attractor basins in a dynamical model of coordination Joseph C McKinley, Mengsen Zhang, Alice Wead, Christine Williams, Emmanuelle Tognoli, Christopher Beetle The Haken-Kelso-Bunz (HKB) equations, as generalized by Zhang to arbitrarily large ensembles of oscillators, model empirical observations in systems exhibiting emergent behavioral and social coordination. The hallmark of the generalized HKB model is its conditional bistability: the existence of stable, rhythmic motions with subpopulations of oscillators clustered in either in-phase or antiphase relative motions for some parameter values, with bifurcations from states exhibiting only in-phase coordination for other values. This work explores a phenomenon whereby a dyad of oscillators, which would be only monostable in isolation, can exhibit bistable coordination when embedded in a larger system. We focus particularly on how breaking symmetry among the oscillators' natural frequencies affects attractor landscapes, yielding quantitative limits on the third-party restoration of dyadic bistability. Our findings illustrate how the whole of a complex system can differ crucially from the sum of its parts. This theoretical work has applications in the social sciences, as well as in healthcare, where it is being used to design interventions aimed at the enhancement of complex behavioral patterns within heterogeneous groups whose members have varying affinities for social coordination. |
Thursday, March 17, 2022 9:36AM - 9:48AM |
S03.00009: The Physics of Team Formation: Modeling the Catalysis of Collaboration at In-Person and Virtual Conferences Emma R Zajdela, Daniel M Abrams, Richard J Wiener, Andrew L Feig The impact of interaction on the scientific process was brought to the fore as the COVID-19 pandemic forced gatherings to shift to a virtual setting. In this talk, we present a new nonlinear dynamical model for the origin of scientific collaborations at conferences, inspired by the physics of catalytic processes. Our model takes as input the pattern of interactions among participants and predicts the probability that any given team will form. We test the model with a novel dataset tracking multi-year “Scialog” scientific conferences, including room-level participation data from 12 in-person and six virtual meetings, each with about 50 participants. Our model agrees well with data and outperforms seven other candidate models. |
Thursday, March 17, 2022 9:48AM - 10:24AM |
S03.00010: The Mirror Game Invited Speaker: Uri Alon
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Thursday, March 17, 2022 10:24AM - 10:36AM |
S03.00011: Causality analysis of synchronized 2D neuron monolayer network Guanyu Li, Bo Sun, Andrew Mugler, Ryan W LeFebre, Patrick Chappell, Alia Starman Cells are constantly detecting their local chemical environment. It is important for cells to be able to detect the change of the environment and employ correct strategies to make correct response. During the chemosensing process, cell colony would be able to generate highly regulated, consistent response, but for individual cell, the response would be intrinsically stochastic. The highly regulated, consistent response is vital to maintain the normal functionality of organism or larger biological system. Here we aim to understand how communication would play a role in the chemosesing process by using statistical causality analysis. In particular, we study KTaR cells, an immortalized neuronal cell line, with periodic ATP stimulations. We systematically vary the concentration and period of the stimuli. By analyzing the resulted Ca2+ oscillation, we use Granger Causality test to determine the connection between cells in the cell colony and to reconstruct the communicational network with the cells. Our results show that the temporal aspect of the external stimuli modulates self-organized multicellular network more than varying chemical concentration and revealed network evolution properties. |
Thursday, March 17, 2022 10:36AM - 10:48AM |
S03.00012: Escaping Confinement: How Bacteria Reshape Their Surroundings to Enable Migration R. Konane Bay, Hao Nghi Luu, Sujit Datta While studies of bacteria typically focus on their behavior in liquid or at flat surfaces, most bacteria inhabit structured environments such as biological tissues and organs, soils, and sediments. In these cases, physical confinement strongly impedes the ability of cells to move. Here, by monitoring the dynamics of 3D-printed populations of Escherichia coli and Vibrio Cholerae in jammed hydrogel matrices, we demonstrate how bacteria can in turn reshape their surroundings to promote their active motion and dispersal. Our results thus provide fundamental insights into the interactions between bacteria and their environment. |
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