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Includes bibliographical references (p. 28-30)

The E895 experiment at the AGS measured strange particle production and collective behavior in Au+Au collisions between 2--8 AGeV. The production of $\Lambda$ Baryons and K$^0$ Mesons as function of energy rises smoothly and exhibits a nonlinear impact parameter dependence. Neutral and positively charged Kaons exhibit a strong anti-flow behavior. $\Lambda$ Baryons show a smaller flow signal than protons.

An important natural phenomenon surfaces that satisfactory synchronization of self-driven particles can be achieved via sharply reduced communication cost, especially for high density particle groups with low external noise. Statistical numerical evidence illustrates that a highly efficient manner is to distribute the communication messages as evenly as possible along the whole dynamic process, since it minimizes the communication redundancy. More surprisingly, it is discovered that there exist some abnormal regions where moderately decreasing the communication cost can even improve the synchronization performance. A phase diagram on the noise-density parameter space is given, where the dynamical behaviors can be divided into three qualitatively different phases: normal phase where better synchronization corresponds to higher communication cost, abnormal phase where moderately decreasing communication cost could even improve the synchronization, and the disordered phase where no coherence among individuals is observed.

Financial markets have been extensively studied as highly complex evolving systems. In this paper, we quantify financial price fluctuations through a coupled dynamical system composed of phase oscillators. We find a Financial Coherence and Incoherence (FCI) coexistence collective behavior emerges as the system evolves into the stable state, in which the stocks split into two groups: one is represented by coherent, phase-locked oscillators, the other is composed of incoherent, drifting oscillators. It is demonstrated that the size of the coherent stock groups fluctuates during the economic periods according to real-world financial instabilities or shocks. Further, we introduce the coherent characteristic matrix to characterize the involvement dynamics of stocks in the coherent groups. Clustering results on the matrix provides a novel manifestation of the correlations among stocks in the economic periods. Our analysis for components of the groups is consistent with the Global Industry Classification Standard (GICS) classification and can also figure out features for newly developed industries. These results can provide potentially implications on characterizing inner dynamical structure of financial markets and making optimal investment tragedies.

Financial markets have been extensively studied as highly complex evolving systems. In this paper, we quantify financial price fluctuations through a coupled dynamical system composed of phase oscillators. We find a Financial Coherence and Incoherence (FCI) coexistence collective behavior emerges as the system evolves into the stable state, in which the stocks split into two groups: one is represented by coherent, phase-locked oscillators, the other is composed of incoherent, drifting oscillators. It is demonstrated that the size of the coherent stock groups fluctuates during the economic periods according to real-world financial instabilities or shocks. Further, we introduce the coherent characteristic matrix to characterize the involvement dynamics of stocks in the coherent groups. Clustering results on the matrix provides a novel manifestation of the correlations among stocks in the economic periods. Our analysis for components of the groups is consistent with the Global Industry Classification Standard (GICS) classification and can also figure out features for newly developed industries. These results can provide potentially implications on characterizing inner dynamical structure of financial markets and making optimal investment tragedies.

This article is from PLoS Computational Biology , volume 10 . Abstract In vitro cultures of endothelial cells are a widely used model system of the collective behavior of endothelial cells during vasculogenesis and angiogenesis. When seeded in an extracellular matrix, endothelial cells can form blood vessel-like structures, including vascular networks and sprouts. Endothelial morphogenesis depends on a large number of chemical and mechanical factors, including the compliancy of the extracellular matrix, the available growth factors, the adhesion of cells to the extracellular matrix, cell-cell signaling, etc. Although various computational models have been proposed to explain the role of each of these biochemical and biomechanical effects, the understanding of the mechanisms underlying in vitro angiogenesis is still incomplete. Most explanations focus on predicting the whole vascular network or sprout from the underlying cell behavior, and do not check if the same model also correctly captures the intermediate scale: the pairwise cell-cell interactions or single cell responses to ECM mechanics. Here we show, using a hybrid cellular Potts and finite element computational model, that a single set of biologically plausible rules describing (a) the contractile forces that endothelial cells exert on the ECM, (b) the resulting strains in the extracellular matrix, and (c) the cellular response to the strains, suffices for reproducing the behavior of individual endothelial cells and the interactions of endothelial cell pairs in compliant matrices. With the same set of rules, the model also reproduces network formation from scattered cells, and sprouting from endothelial spheroids. Combining the present mechanical model with aspects of previously proposed mechanical and chemical models may lead to a more complete understanding of in vitro angiogenesis.

Purpose:  This study aims to investigate the effect of creating individual and collective psychological ownership of the brand for customers on buying from the brand and word-of-mouth advertising through partnership goals with a modifying role of members' activities in Mahan Airlines as a case study. Methodology:  This research is an applied and descriptive survey regarding purpose and method. The sampling method of this study was random, and its number was 384 people. The assessment tool in this study was a researcher-made questionnaire. Statistical analyses were performed using structural equation methods and SPSS and Smart-PLS2 software programs. We used a structural equation modelling method to determine the causal relationship between the variables. Findings:  The results showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership positively and significantly affect members' participation goals. Also, the partnership's goals positively and significantly affect the purpose and intention of buying the brand and word-of-mouth advertising. Originality/Value:  The study showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership have a positive and significant effect on the goals of participation and by modifying the type of activity of members.

Purpose:  This study aims to investigate the effect of creating individual and collective psychological ownership of the brand for customers on buying from the brand and word-of-mouth advertising through partnership goals with a modifying role of members' activities in Mahan Airlines as a case study. Methodology:  This research is an applied and descriptive survey regarding purpose and method. The sampling method of this study was random, and its number was 384 people. The assessment tool in this study was a researcher-made questionnaire. Statistical analyses were performed using structural equation methods and SPSS and Smart-PLS2 software programs. We used a structural equation modelling method to determine the causal relationship between the variables. Findings:  The results showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership positively and significantly affect members' participation goals. Also, the partnership's goals positively and significantly affect the purpose and intention of buying the brand and word-of-mouth advertising. Originality/Value:  The study showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership have a positive and significant effect on the goals of participation and by modifying the type of activity of members.

Purpose:  This study aims to investigate the effect of creating individual and collective psychological ownership of the brand for customers on buying from the brand and word-of-mouth advertising through partnership goals with a modifying role of members' activities in Mahan Airlines as a case study. Methodology:  This research is an applied and descriptive survey regarding purpose and method. The sampling method of this study was random, and its number was 384 people. The assessment tool in this study was a researcher-made questionnaire. Statistical analyses were performed using structural equation methods and SPSS and Smart-PLS2 software programs. We used a structural equation modelling method to determine the causal relationship between the variables. Findings:  The results showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership positively and significantly affect members' participation goals. Also, the partnership's goals positively and significantly affect the purpose and intention of buying the brand and word-of-mouth advertising. Originality/Value:  The study showed that self-efficacy, responsibility, belonging, personal identity, and collective psychological ownership have a positive and significant effect on the goals of participation and by modifying the type of activity of members.

Young children inherently understand the social obligation within the ingroup (Rhodes & Baron, 2019), and they also tend to "punish" those whose behaviors are inconsistent with their groups due to Descriptive to Prescriptive reasoning (Roberts, 2021; Roberts et al., 2017). Meanwhile, there also evidence suggests that children in the same age period infer others' social behavior based on their mental states, and this ability might be influenced by the development of Theory of Mind (ToM) in child perceivers (Chalik et al., 2014). Thus, this study tries to create a dilemma that contrasts collective and individual values for children aged 4 to 6-year-old. More importantly, how children will react in this dilemma, how they would evaluate peers that made different choices, how their evaluation pattern would change across different ages, and the effect of ToM in their evaluations.

As part of the project EC2 (ec2project.eu) aimed at exploring the multifaceted nature of human agency within the context of climate change and the energy transition, this study investigates the association between social descriptive trending norms, collective efficacy beliefs, and pro-environmental action intentions. Covering a range of behavior (-intentions) in relation to the energy transition in Germany as part of a broader set of climate crisis mitigation efforts, collective action intentions (i.e., participating in the energy transition as part of a collective such as in energy communities), as well as individual energy behavior will be investigated. Additionally, policy acceptance regarding current legislative changes in the context of the German energy transition will be considered, recognizing that large-scale socio-ecological changes such as those in the energy sector necessitate significant political and legislative transformations. As suggested by previous research, successful implementation requires widespread acceptance from citizens next to actual behavior changes (Gerdes et al., 2023; Kaiser et al., 2023). Based on models of environmental collective action (i.e., Fritsche et al., 2018; van Zomeren et al., 2008) and empirical research, both social trending norms and collective efficacy beliefs as two components of collective agency are assumed to motivate pro-environmental behavior. Both have been established as important predictors of collective (as well as individual) environmental action (e.g., Bergquist et al., 2019; Cialdini et al., 1990; Goldstein et al., 1990; Fritsche et al., 2018; Mortensen et al., 2019; Wang & Lin, 2017; Jugert et al., 2016; Carmi & Mostovoy, 2018; Wang, 2018; Thao et al., 2016; Hamann, 2021) – representing an informational (social) source of the prevalence and perceived feasibility of an action, respectively. Moreover, within a social identity framework, identification with a relevant social group has shown to be a moderating factor for their influence, suggesting that social identification positively influences group-based perceptions such as efficacy beliefs and ingroup norms (Dunlap & McCright, 2008; Fritsche et al., 2018; Masson & Fritsche, 2021). In an experimental study, I centrally focus on those two facets of collective agency: collective efficacy beliefs (low vs. efficacy control group) and (goal-directed) descriptive social trending norms (high vs. low). In order to investigate underlying mechanisms of social normative influence this study aims to test a mediator model that assumes collective efficacy to act as a core process for collective agency, that is, efficacy beliefs are considered a potential mediator for the effect of descriptive trending norms on pro-environmental behavior. Based on the notion that social trending norms (as an indicator that a certain increasing/decreasing majority is already engaging in a behavior, here, energy-relevant behavior), can positively influence collective efficacy beliefs (van Zomeren et al., 2004; Doherty & Webler, 2016; Swim et al., 2019) and prior research indicating a positive social normative influence on pro-environmental action intentions via efficacy beliefs (Wang & Lin, 2017; correlational pre-study) I thus assume that collective efficacy beliefs mediate the effect of social trending norms on individual and collective action intentions as well as policy acceptance. The underlying assumption is that in order for social norms to exert a positive influence, a feeling of collective efficacy is essential to motivate behavior intentions – in other words, collective efficacy beliefs being so crucial that they cannot be compensated by other indicators of agency. Relatively few studies, however, have focused experimentally on this connection between social norms and efficacy beliefs on public/activist behavior in the environmental domain and, specifically, the energy transition. Following the social identity reason, people acting as group members (i.e., when they highly identify with a social group) are assumed to more strongly embrace collective norms as collective goals (here: participating in the energy transition in the city of Leipzig) and act accordingly (e.g., Hoppe, 2023; Fritsche & Masson, 2014; van Zomeren et al., 2008; Fielding et al, 2020; Chung, 2020). Moreover, social identification has shown to foster collective efficacy beliefs (Hamann et al. 2021; van Zomeren et al., 2008). I thus expect social identification to positively influence the assumed association between social trending norms and efficacy beliefs, that is, a stronger effect of social norms on pro-environmental behavior when individuals highly identify with a group and collective goals appear as attainable through collective efforts of the group. Additionally, this study aims to examine potential boundary conditions for perceived collective agency. Environmental action and the acceptance of policy measures may also be influenced by perceived and/or actual behavioral barriers and costs (e.g., financial or time resources) of an action despite social influence, its perceived effectiveness or prevailing positive (environmental) attitudes (Kaiser et al., 2023; Huang et al., 2020; Stern, 2000), Furthermore, the experience of efficacy may also manifest on a more personal level (i.e., self-efficacy) and may be accompanied by or translated into action by emotional reactions (i.e., efficacy affect, Hamann, 2021; Bandura, 1997). Efficacy beliefs (on a collective level) are also assumed to be influenced by autonomous group goals, representing intrinsic motivation towards collective goals. Therefore, the effects of perceived behavioral barriers on the effect of efficacy beliefs will be considered as well as, exploratory, the influence of efficacy affect and collective autonomous motivation.

This study is the fourth of a research line investigating the relations between various kind of social identities, climate change conspiracy beliefs and climate science acceptance. In this experimental study, we want to test whether national collective narcissism saliency, under climate change threat, increases climate change conspiracy beliefs, which in turn decreases pro-environmental behavioral intentions.

This study is the fourth of a research line investigating the relations between various kind of social identities, climate change conspiracy beliefs and climate science acceptance. In this experimental study, we want to test whether national collective narcissism saliency, under climate change threat, increases climate change conspiracy beliefs, which in turn decreases pro-environmental behavioral intentions.

This study is the fourth of a research line investigating the relations between various kind of social identities, climate change conspiracy beliefs and climate science acceptance. In this experimental study, we want to test whether national collective narcissism saliency, under climate change threat, increases climate change conspiracy beliefs, which in turn decreases pro-environmental behavioral intentions.

In this paper, we propose an approach for modeling and analysis of a number of phenomena of collective behavior. By collectives we mean multi-agent systems that transition from one state to another at discrete moments of time. The behavior of a member of a collective (agent) is called conforming if the opinion of this agent at current time moment conforms to the opinion of some other agents at the previous time moment. We presume that at each moment of time every agent makes a decision by choosing from the set {0,1} (where 1-decision corresponds to action and 0-decision corresponds to inaction). In our approach we model collective behavior with synchronous Boolean networks. We presume that in a network there can be agents that act at every moment of time. Such agents are called instigators. Also there can be agents that never act. Such agents are called loyalists. Agents that are neither instigators nor loyalists are called simple agents. We study two combinatorial problems. The first problem is to find a disposition of instigators that in several time moments transforms a network from a state where a majority of simple agents are inactive to a state with a majority of active agents. The second problem is to find a disposition of loyalists that returns the network to a state with a majority of inactive agents. Similar problems are studied for networks in which simple agents demonstrate the contrary to conforming behavior that we call anticonforming. We obtained several theoretical results regarding the behavior of collectives of agents with conforming or anticonforming behavior. In computational experiments we solved the described problems for randomly generated networks with several hundred vertices. We reduced corresponding combinatorial problems to the Boolean satisfiability problem (SAT) and used modern SAT solvers to solve the instances obtained.

In this paper, we propose an approach for modeling and analysis of a number of phenomena of collective behavior. By collectives we mean multi-agent systems that transition from one state to another at discrete moments of time. The behavior of a member of a collective (agent) is called conforming if the opinion of this agent at current time moment conforms to the opinion of some other agents at the previous time moment. We presume that at each moment of time every agent makes a decision by choosing from the set {0,1} (where 1-decision corresponds to action and 0-decision corresponds to inaction). In our approach we model collective behavior with synchronous Boolean networks. We presume that in a network there can be agents that act at every moment of time. Such agents are called instigators. Also there can be agents that never act. Such agents are called loyalists. Agents that are neither instigators nor loyalists are called simple agents. We study two combinatorial problems. The first problem is to find a disposition of instigators that in several time moments transforms a network from a state where a majority of simple agents are inactive to a state with a majority of active agents. The second problem is to find a disposition of loyalists that returns the network to a state with a majority of inactive agents. Similar problems are studied for networks in which simple agents demonstrate the contrary to conforming behavior that we call anticonforming. We obtained several theoretical results regarding the behavior of collectives of agents with conforming or anticonforming behavior. In computational experiments we solved the described problems for randomly generated networks with several hundred vertices. We reduced corresponding combinatorial problems to the Boolean satisfiability problem (SAT) and used modern SAT solvers to solve the instances obtained.

The purpose of this experiment is to investigate the chain mediating role of psychological safety and felt responsibility between information overload and knowledge sharing, and to further examine the moderating role of hierarchical distance on psychological safety, felt responsibility and information overload within online collective spaces in the project team context. The study was conducted with project team members and used a situational experiment to collect data and assess the moderating effects and mediating mechanisms by measuring each study variable through scales. This study helps to reveal how information overload hierarchical distance affects the psychological state and behavioral responses of team members, and then provides a theoretical basis and practical guidance for organizations to indirectly strengthen employees' felt responsibility by creating a good atmosphere of psychological safety, alleviate the adverse effects of information overload on psychological safety, and promote knowledge sharing, so as to optimize knowledge management and enhance organizational innovation. This study has received ethical approval by Yangzhou University (YXYLL-2025-84).

The purpose of this experiment is to investigate the chain mediating role of psychological safety and felt responsibility between information overload and knowledge sharing, and to further examine the moderating role of hierarchical distance on psychological safety, felt responsibility and information overload within online collective spaces in the project team context. The study was conducted with project team members and used a situational experiment to collect data and assess the moderating effects and mediating mechanisms by measuring each study variable through scales. This study helps to reveal how information overload hierarchical distance affects the psychological state and behavioral responses of team members, and then provides a theoretical basis and practical guidance for organizations to indirectly strengthen employees' felt responsibility by creating a good atmosphere of psychological safety, alleviate the adverse effects of information overload on psychological safety, and promote knowledge sharing, so as to optimize knowledge management and enhance organizational innovation. This study has received ethical approval by Yangzhou University (YXYLL-2025-84).

This study aims to answer the question of how framings of responsibility for the climate crisis and frames of fairness in current mitigation action influence attitudes toward individual behaviors (e.g., energy consumption, mobility behavior, dietary choices, general consumption) and collective/political behaviors (e.g., voting behavior, protesting, engagement in NGOs or political parties, civil disobedience). Frames of responsibility are defined as communicative tools to assign responsibility for both the causes and mitigation of the climate crisis to specific people or institutions (Iyengar, 1989). In this study, responsibility will be either assigned to individuals or to corporations and political stakeholders and then participants’ attitudes towards different climate crisis behaviors will be assessed. Likewise, frames of fairness state whether others are putting in the effort to solve the public good dilemma of the climate crisis (Jamieson, 2009; Markowitz, 2012). Furthermore, we will investigate whether these effects are moderated by different environmental identities and the strength of these identities. By filling the gaps in the existing literature on responsibility framings, perceptions of fairness, and climate crisis behavior, this study could offer important insights into how the public discourse on the climate crisis affects what individuals perceive as good and efficient to combat the existential threat of the climate crisis. It could further practical implications for scientists, the media, political stakeholders, NGOs, and activists on how to communicate about the climate crisis more efficiently and how to evoke climate crisis behavior in the general public.

This study is conducted as part of the project EC2 (ec2project.eu). We test the longitudinal relations between collective agency (collective autonomous goals, descriptive norms, injunctive norms, collective efficacy), and participative efficacy on the energy community level with public/activist behavior and volunteer hours.

This pilot study examines how discrimination based on racial lumping influences Asian American political behavior. Specifically, this study tests the strength of Asian American pan-ethnic identity during a heightened era of xenophobia, discrimination, and hate crime amidst covid-19. The project examines how discrimination due to racial lumping affects pan-ethnic collective identity and action. This study was approved by Indiana University's IRB #10400.

Previous research has revealed diverse explanatory approaches to elucidate the persistence and intractability of some particularly hostile and prolonged intergroup conflicts. The present study seeks to contribute to this effort by examining the consequences of inducing feelings of grievance, which is a significant and encrusted perception that the ingroup has been or is the target of an offense or injustice by the outgroup. By focusing on the intergroup conflict that exists between secessionist Catalans and Spaniards, this investigation aims to examine how the experience of grievance experienced by Spaniards in response to the actions undertaken by secessionist Catalans may contribute to the heightened dehumanization of secessionist Catalans and, in turn, to higher willingness to participate in collective action (normative or not) in favor of the unity of Spain and to more aggressive inclinations against secessionist Catalans. Furthermore, the current study seeks to explore whether individuals' ideological orientations moderate the relationship between grievance and dehumanization, as well as between grievance and collective action and aggressive inclinations.

Previous research has revealed diverse explanatory approaches to elucidate the persistence and intractability of some particularly hostile and prolonged intergroup conflicts. The present study seeks to contribute to this effort by examining the consequences of inducing feelings of grievance, which is a significant and encrusted perception that the ingroup has been or is the target of an offense or injustice by the outgroup. By focusing on the intergroup conflict that exists between secessionist Catalans and Spaniards, this investigation aims to examine how the experience of grievance experienced by Spaniards in response to the actions undertaken by secessionist Catalans may contribute to the heightened dehumanization of secessionist Catalans and, in turn, to higher willingness to participate in collective action (normative or not) in favor of the unity of Spain and to more aggressive inclinations against secessionist Catalans. Furthermore, the current study seeks to explore whether individuals' ideological orientations moderate the relationship between grievance and dehumanization, as well as between grievance and collective action and aggressive inclinations.

We consider the dynamics of systems of self propelling particles with nonholonomic constraints. A continuum model for a discrete algorithm used in works by T. Vicsek et al. is proposed. For a case of planar geometry the finite flocking behavior is obtained. The circulation of the velocity field is found not to be conserved as a consequence of the nonholomicity. The stability of ordered motion with respect to noise is discussed. An analogy with the kinetics of charges in superconductors is noted.

Several models of flocking have been promoted based on simulations with qualitatively naturalistic behavior. In this paper we provide the first direct application of computational modeling methods to infer flocking behavior from experimental field data. We show that this approach is able to infer general rules for interaction, or lack of interaction, among members of a flock or, more generally, any community. Using experimental field measurements of homing pigeons in flight we demonstrate the existence of a basic distance dependent attraction/repulsion relationship and show that this rule is sufficient to explain collective behavior observed in nature. Positional data of individuals over time are used as input data to a computational algorithm capable of building complex nonlinear functions that can represent the system behavior. Topological nearest neighbor interactions are considered to characterize the components within this model. The efficacy of this method is demonstrated with simulated noisy data generated from the classical (two dimensional) Vicsek model. When applied to experimental data from homing pigeon flights we show that the more complex three dimensional models are capable of predicting and simulating trajectories, as well as exhibiting realistic collective dynamics. The simulations of the reconstructed models are used to extract properties of the collective behavior in pigeons, and how it is affected by changing the initial conditions of the system. Our results demonstrate that this approach may be applied to construct models capable of simulating trajectories and collective dynamics using experimental field measurements of herd movement. From these models, the behavior of the individual agents (animals) may be inferred.

We perform 3+1D viscous hydrodynamic calculations of proton-lead and lead-lead collisions at top LHC energy. We show that existing data from high-multiplicity p-Pb events can be well described in hydrodynamics, suggesting that collective flow is plausible as a correct description of these collisions. However, a more stringent test of the presence of hydrodynamic behavior can be made by studying the detailed momentum dependence of two-particle correlations. We define a relevant observable, $r_n$, and make predictions for its value and centrality dependence if hydrodynamics is a valid description. This will provide a non-trivial confirmation of the nature of the correlations seen in small collision systems, and potentially to determine where the hydrodynamic description, if valid anywhere, stops being valid. Lastly, we probe what can be learned from this observable, finding that it is insensitive to viscosity, but sensitive to aspects of the initial state of the system that other observables are insensitive to, such as the transverse length scale of the fluctuations in the initial stages of the collision.

We perform the analog to the "water bell" experiment using non-cohesive granular material. When a jet of granular material, many particles wide, rebounds from a fixed cylindrical target, it deforms into a sharply-defined sheet or cone with a shape that mimics a liquid with zero surface tension. The particulate nature of granular material becomes apparent when the number of particles in the cross-section of the jet is decreased and the emerging sheets and cones broaden and gradually disintegrate into a broad spray. This experiment has its counterpart in the behavior of the quark-gluon plasma generated by collisions of gold ions at the Relativistic Heavy Ion Collider. There a high density of inter-particle collisions gives rise to collective behavior that has also been described as a liquid.

A simple system composed of electronic oscillators capable of emitting and detecting light-pulses is studied. The oscillators are biologically inspired, their behavior is designed for keeping a desired light intensity, W, in the system. From another perspective, the system behaves like modified integrate and fire type neurons that are pulse-coupled with inhibitory type interactions: the firing of one oscillator delays the firing of all the others. Experimental and computational studies reveal that although no driving force favoring synchronization is considered, for a given interval of W phase-locking appears. This weak synchronization is sometimes accompanied by complex dynamical patterns in the flashing sequence of the oscillators.

blumer social problems as collective behavior

Femtoscopy measures space-time characteristics of the particle emitting source created in relativistic heavy-ion collisions. It is argued that collective behavior of matter (radial flow) produces specific femtoscopic signatures. The one that is best known, the m_T dependence of the pion ``HBT radii'', can be explained by the alternative scenario of temperature gradients in an initial state thermal model. We identify others that can invalidate such alternatives, such as non-identical particle correlations and m_T scaling for particles of higher mass. Studies with a simple rescattering code show that as the interaction cross-section is increased the system develops collective behavior and becomes more thermalized at the same time, the two effects being the natural consequence of increased number of particle rescatterings. Repeating calculations with a more realistic rescattering model confirmed all of these conclusions and provided deeper insight into the mechanisms of collectivity buildup, showing a preference for a thermal model with uniform temperature.

Microtubules (MTs) nucleated by centrosomes form star-shaped structures referred to as asters. Aster motility and dynamics is vital for genome stability, cell division, polarization and differentiation. Asters move either towards the cell center or away from it. Here, we focus on the centering mechanism in a membrane independent system of Xenopus cytoplasmic egg extracts. Using live microscopy and single particle tracking, we find that asters move towards chromatinized DNA structures. The velocity and directionality profiles suggest a random walk with drift directed towards DNA. We have developed a theoretical model that can explain this movement as a result of a gradient of MT length dynamics and MT gliding on immobilized dynein motors. In simulations, the antagonistic action of the motor species on the radial array of MTs leads to a tug-of-war purely due to geometric considerations and aster motility resembles a directed random-walk. Additionally our model predicts that aster velocities do not change greatly with varying initial distance from DNA. The movement of asymmetric asters becomes increasingly super-diffusive with increasing motor density, but for symmetric asters it becomes less super-diffusive. The transition of symmetric asters from superdiffusive to diffusive mobility is the result of number fluctuations in bound motors in the tug-of-war. Overall, our model is in good agreement with experimental data in Xenopus cytoplasmic extracts and predicts novel features of the collective effects of motor-MT interactions.

Replicating and extending the previous correlational study, I will conduct an experimental study in which perceived collective efficacy is manipulated. This experiment will allow me to investigate the causal role of White Americans’ perception of Blacks' collective efficacy in their efforts to reduce the racial wealth gap. I will test the hypothesis that egalitarian values, sociopolitical self-efficacy, and perceived collective efficacy will jointly predict different types of ally behavior.

In the context of climate change, we will examine the relationship between personal and collective behavior, and between adaptation and mitigation behavior.

This study is conducted as part of the project EC2 (ec2project.eu). We test the longitudinal relations between collective agency (collective autonomous goals, descriptive norms, injunctive norms, collective efficacy), and participative efficacy on the neighborhood/community level with public/activist behavior.

We investigate the collective behavior of a system of chaotic Rossler oscillators indirectly coupled through a common environment that possesses its own dynamics and which in turn is modulated by the interaction with the oscillators. By varying the parameter representing the coupling strength between the oscillators and the environment, we find two collective states previously not reported in systems with environmental coupling: (i) nontrivial collective behavior, characterized by a periodic evolution of macroscopic variables coexisting with the local chaotic dynamics; and (ii) dynamical clustering, consisting of the formation of differentiated subsets of synchronized elements within the system. These states are relevant for many physical and biological systems where interactions with a dynamical environment are frequent.

The purpose of this essay is to propose a different explanation of collective behavior and also to hypothesize how communication functions in this process. Using the experimental finding known as the "risky shift," this essay (1) summarizes the history of the risky shift, (2) presents two different theories which have been proposed to explain the finding, and (3) by employing Roger Brown's "cultural value theory," suggests how members of small groups become more risky/cautions as a function of being in the group context. Furthermore, the essay translates this theory from the context of the small group into the context of the larger collectivity. In the process, several communicative demands and requirements are suggested. The manner in which communication strategies can fulfill these demands is articulated, and potential methods for validating this explanation are offered. (Author)

We study the interaction between gas and dust particles in a protoplanetary disk, comparing analytical and numerical results. We first calculate analytically the trajectories of individual particles undergoing gas drag in the disk, in the asymptotic cases of very small particles (Epstein regime) and very large particles (Stokes regime). Using a Boltzmann averaging method, we then infer their collective behavior. We compare the results of this analytical formulation against numerical computations of a large number of particles. Using successive moments of the Boltzmann equation, we derive the equivalent fluid equations for the average motion of the particles; these are intrinsically different in the Epstein and Stokes regimes. We are also able to study analytically the temporal evolution of a collection of particles with a given initial size-distribution provided collisions are ignored.

We study the interaction between gas and dust particles in a protoplanetary disk, comparing analytical and numerical results. We first calculate analytically the trajectories of individual particles undergoing gas drag in the disk, in the asymptotic cases of very small particles (Epstein regime) and very large particles (Stokes regime). Using a Boltzmann averaging method, we then infer their collective behavior. We compare the results of this analytical formulation against numerical computations of a large number of particles. Using successive moments of the Boltzmann equation, we derive the equivalent fluid equations for the average motion of the particles; these are intrinsically different in the Epstein and Stokes regimes. We are also able to study analytically the temporal evolution of a collection of particles with a given initial size-distribution provided collisions are ignored.

The emergence of nontrivial collective behavior in networks of coupled chaotic maps is investigated by means of a nonlinear mutual prediction method. The resulting prediction error is used to measure the amount of information that a local unit possesses about the collective dynamics. Applications to locally and globally coupled map systems are considered. The prediction error exhibits phase transitions at critical values of the coupling for the onset of ordered collective behavior in these networks. This information measure may be used as an order parameter for the characterization of complex behavior in extended chaotic systems.

The phenomena of synchronization and nontrivial collective behavior are studied in a model of coupled chaotic maps with random global coupling. The mean field of the system is coupled to a fraction of elements randomly chosen at any given time. It is shown that the reinjection of the mean field to a fraction of randomly selected elements can induce synchronization and nontrivial collective behavior in the system. The regions where these collective states emerge on the space of parameters of the system are calculated.

This study is conducted as part of the project EC2 (ec2project.eu). We test the longitudinal relations between visions, collective agency (collective autonomous goals, descriptive norms, injunctive norms, collective efficacy), and participative efficacy on the neighborhood/community level with public/activist behavior.

Iain Couzin studies how animals coordinate behavior. He has discovered that locust plagues don't occur because the insects are cooperating. Rather, it is a forced march: if they stop, they risk being cannibalized. Such insights help communities to track oncoming outbreaks while also challenging scientists' theories of collective animal behavior.

Iain Couzin studies how animals coordinate behavior. He has discovered that locust plagues don't occur because the insects are cooperating. Rather, it is a forced march: if they stop, they risk being cannibalized. Such insights help communities to track oncoming outbreaks while also challenging scientists' theories of collective animal behavior.

We report on experiments of many small motors -- cell phone vibrators -- glued to and interacting through a resonant plate. We find that individual motors interacting with the plate demonstrate hysteresis in their steady-state frequency due to interactions with plate resonances. For multiple motors running simultaneously, the degree of synchronization between motors increases when the motors' frequencies are near a resonance of the plate, and the frequency at which the motors synchronize shows a history dependence.

To uncover underlying mechanism of collective human dynamics, we survey more than 1.8 billion blog entries and observe the statistical properties of word appearances. We focus on words that show dynamic growth and decay with a tendency to diverge on a certain day. After careful pretreatment and fitting method, we found power laws generally approximate the functional forms of growth and decay with various exponents values between -0.1 and -2.5. We also observe news words whose frequency increase suddenly and decay following power laws. In order to explain these dynamics, we propose a simple model of posting blogs involving a keyword, and its validity is checked directly from the data. The model suggests that bloggers are not only responding to the latest number of blogs but also suffering deadline pressure from the divergence day. Our empirical results can be used for predicting the number of blogs in advance and for estimating the period to return to the normal fluctuation level.

Polymer-coated pores play a crucial role in nucleo-cytoplasmic transport and in a number of biomimetic and nanotechnological applications. Here we present Monte Carlo and Density Functional Theory approaches to identify different collective phases of end-grafted polymers in a nanopore and to study their relative stability as a function of intermolecular interactions. Over a range of system parameters that is relevant for nuclear pore complexes, we observe two distinct phases: one with the bulk of the polymers condensed at the wall of the pore, and the other with the polymers condensed along its central axis. The relative stability of these two phases depends on the interpolymer interactions. The existence of the two phases suggests a transport mechanism in which marginal changes in these interactions, possibly induced by nuclear transport receptors, cause the pore to transform between open and closed configurations.

Bibliography: p. 388-427

Bibliography: p. 388-427

Bibliography: p. 388-427

When harvesting collective intelligence, a user wishes to maximize the accuracy and value of the acquired information without spending too much time collecting it. We empirically study how people behave when facing these conflicting objectives using data from Yahoo Answers, a community driven question-and-answer site. We take two complementary approaches. We first study how users behave when trying to maximize the amount of the acquired information, while minimizing the waiting time. We identify and quantify how question authors at Yahoo Answers trade off the number of answers they receive and the cost of waiting. We find that users are willing to wait more to obtain an additional answer when they have only received a small number of answers; this implies decreasing marginal returns in the amount of collected information. We also estimate the user's utility function from the data. Our second approach focuses on how users assess the qualities of the individual answers without explicitly considering the cost of waiting. We assume that users make a sequence of decisions, deciding to wait for an additional answer as long as the quality of the current answer exceeds some threshold. Under this model, the probability distribution for the number of answers that a question gets is an inverse Gaussian, which is a Zipf-like distribution. We use the data to validate this conclusion.