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Search Results: 1 - 10 of 653 matches for " Tamas Vicsek "
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Optimal Self-Organization
Dirk Helbing,Tamas Vicsek
Physics , 1999, DOI: 10.1088/1367-2630/1/1/313
Abstract: We present computational and analytical results indicating that systems of driven entities with repulsive interactions tend to reach an optimal state associated with minimal interaction and minimal dissipation. Using concepts from non-equilibrium thermodynamics and game theoretical ideas, we generalize this finding to an even wider class of self-organizing systems which have the ability to reach a state of maximal overall ``success''. This principle is expected to be relevant for driven systems in physics like sheared granular media, but it is also applicable to biological, social, and economic systems, for which only a limited number of quantitative principles are available yet.
Collective behavior of interacting self-propelled particles
Andras Czirok,Tamas Vicsek
Physics , 2006, DOI: 10.1016/S0378-4371(00)00013-3
Abstract: We discuss biologically inspired, inherently non-equilibrium self-propelled particle models, in which the particles interact with their neighbours by choosing at each time step the local average direction of motion. We summarize some of the results of large scale simulations and theoretical approaches to the problem.
Lattice-gas model for collective biological motion
Zoltan Csahok,Tamas Vicsek
Physics , 1998, DOI: 10.1103/PhysRevE.52.5297
Abstract: A simple self-driven lattice-gas model for collective biological motion is introduced. We find weakly first order phase transition from individual random walks to collective migration. A mean-field theory is presented to support the numerical results.
Protein induced morphological transitions in KCl crystal growth
Balint Szabo,Tamas Vicsek
Physics , 2002, DOI: 10.1103/PhysRevE.67.011908
Abstract: We investigated the formation of KCl crystals on glass surface by phase contrast, fluorescent, and atomic force microscopy on the micrometer scale, and observed interesting morphological transitions as a function of the experimental conditions. The presence of proteins in the solution from which the salt crystals grow during the drying up leads to complex microscopic patterns of crystals some of which are analogous to those commonly observed on the macroscopic scale. We tested the effect of tubulin, FITC-labeled albumin and IgG on the morphology of crystals grown either slowly or fast. A rich variety of protein specific and concentration dependent morphologies was found and described by a morphological diagram. We give a phenomenological interpretation, which can explain the growth of complex patterns. Fluorescent images prove that a protein layer covers the surface of the KCl structures. We propose that this layer reduces the anisotropy of the effective surface tension during growth. The tip splitting fractal regime is attributed to the decrease of anisotropy. Other possible mechanisms, which can cause morphological transition, are also discussed. We found elongated saw-toothed crystals induced by proteins, especially IgG and identified their structure.
Cooperative Transport of Brownian Particles
Imre Derenyi,Tamas Vicsek
Physics , 1998, DOI: 10.1103/PhysRevLett.75.374
Abstract: We consider the collective motion of finite-sized, overdamped Brownian particles (e.g., motor proteins) in a periodic potential. Simulations of our model have revealed a number of novel cooperative transport phenomena, including (i) the reversal of direction of the net current as the particle density is increased and (ii) a very strong and complex dependence of the average velocity on both the size and the average distance of the particles.
The kinesin walk: a dynamic model with elastically coupled heads
Imre Derenyi,Tamas Vicsek
Physics , 1998, DOI: 10.1073/pnas.93.13.6775
Abstract: Recently individual two-headed kinesin molecules have been studied in in vitro motility assays revealing a number of their peculiar transport properties. In this paper we propose a simple and robust model for the kinesin stepping process with elastically coupled Brownian heads showing all of these properties. The analytic and numerical treatment of our model results in a very good fit to the experimental data and practically has no free parameters. Changing the values of the parameters in the restricted range allowed by the related experimental estimates has almost no effect on the shape of the curves and results mainly in a variation of the zero load velocity which can be directly fitted to the measured data. In addition, the model is consistent with the measured pathway of the kinesin ATPase.
Self-Organised Optimality in Driven Systems with Symmetrical Interactions
Dirk Helbing,Tamas Vicsek
Physics , 1999,
Abstract: Extremal principles are fundamental in our interpretation of phenomena in nature. One of the best known examples is the second law of thermodynamics, governing most physical and chemical systems and stating the continuous increase of entropy in closed systems. Biological and social systems, however, are usually open and characterised by self-organised structures. Being results of an evolutionary optimisation process, one may conjecture that such systems use resources like energy very efficiently, but there is no proof for this. Recent results on driven systems indicate that systems composed of competing entities tend to reach a state of self-organised optimality associated with minimal interaction or minimal dissipation, respectively. Using concepts from non-equilibrium thermodynamics and game theoretical ideas, we will show that this is universal to an even wider class of systems which, generally speaking, have the ability to reach a state of maximal overall ``success''. This principle is expected to be relevant for driven systems in physics, but its main significance concerns biological and social systems, for which only a limited number of quantitative principles are available yet.
Group performance is maximized by hierarchical competence distribution
Anna Zafeiris,Tamas Vicsek
Computer Science , 2013, DOI: 10.1038/ncomms3484
Abstract: Groups of people or even robots often face problems they need to solve together. Examples include collectively searching for resources, choosing when and where to invest time and effort, and many more. Although a hierarchical ordering of the relevance of the group members' inputs during collective decision making is abundant, a quantitative demonstration of its origin and advantages using a generic approach has not been described yet. Here we introduce a family of models based on the most general features of group decision making to show that the optimal distribution of competences is a highly skewed function with a structured fat tail. Our results have been obtained by optimizing the groups' compositions through identifying the best performing distributions for both the competences and for the members' flexibilities/pliancies. Potential applications include choosing the best composition for a group intended to solve a given task.
Realistic Models of Biological Motion
Imre Derenyi,Tamas Vicsek
Quantitative Biology , 1998, DOI: 10.1016/S0378-4371(97)00498-6
Abstract: The origin of biological motion can be traced back to the function of molecular motor proteins. Cytoplasmic dynein and kinesin transport organelles within our cells moving along a polymeric filament, the microtubule. The motion of the myosin molecules along the actin filaments is responsible for the contraction of our muscles. Recent experiments have been able to reveal some important features of the motion of individual motor proteins, and a new statistical physical description - often referred to as ``thermal ratchets'' - has been developed for the description of motion of these molecules. In this approach the motors are considered as Brownian particles moving along one-dimensional periodic structures due to the effect of nonequilibrium fluctuations. Assuming specific types of interaction between the particles the models can be made more realistic. We have been able to give analytic solutions for our model of kinesin with elastically coupled Brownian heads and for the motion of the myosin filament where the motors are connected through a rigid backbone. Our theoretical predictions are in a very good agreement with the various experimental results. In addition, we have considered the effects arising as a result of interaction among a large number of molecular motors, leading to a number of novel cooperative transport phenomena.
Collective motion of cells: from experiments to models
Elod Mehes,Tamas Vicsek
Quantitative Biology , 2014,
Abstract: Swarming or collective motion of living entities is one of the most common and spectacular manifestations of living systems having been extensively studied in recent years. A number of general principles have been established. The interactions at the level of cells are quite different from those among individual animals therefore the study of collective motion of cells is likely to reveal some specific important features which are overviewed in this paper. In addition to presenting the most appealing results from the quickly growing related literature we also deliver a critical discussion of the emerging picture and summarize our present understanding of collective motion at the cellular level. Collective motion of cells plays an essential role in a number of experimental and real-life situations. In most cases the coordinated motion is a helpful aspect of the given phenomenon and results in making a related process more efficient (e.g., embryogenesis or wound healing), while in the case of tumor cell invasion it appears to speed up the progression of the disease. In these mechanisms cells both have to be motile and adhere to one another, the adherence feature being the most specific to this sort of collective behavior. One of the central aims of this review is both presenting the related experimental observations and treating them in the light of a few basic computational models so as to make an interpretation of the phenomena at a quantitative level as well.
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