1
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Wang J, Wang X, Liu W, Hu H. Percolation thresholds of disks with random nonoverlapping patches on four regular two-dimensional lattices. Phys Rev E 2024; 109:064104. [PMID: 39020913 DOI: 10.1103/physreve.109.064104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 05/13/2024] [Indexed: 07/20/2024]
Abstract
In percolation of patchy disks on lattices, each site is occupied by a disk, and neighboring disks are regarded as connected when their patches contact. Clusters of connected disks become larger as the patchy coverage of each disk χ increases. At the percolation threshold χ_{c}, an incipient cluster begins to span the whole lattice. For systems of disks with n symmetric patches on Archimedean lattices, a recent work [Wang et al., Phys. Rev. E 105, 034118 (2022)2470-004510.1103/PhysRevE.105.034118] found symmetric properties of χ_{c}(n), which are due to the coupling of the patches' symmetry and the lattice geometry. How does χ_{c} behave with increasing n if the patches are randomly distributed on the disks? We consider two typical random distributions of the patches, i.e., the equilibrium distribution and a distribution from random sequential adsorption. Combining Monte Carlo simulations and the critical polynomial method, we numerically determine χ_{c} for 106 models of different n on the square, honeycomb, triangular, and kagome lattices. The rules governing χ_{c}(n) are investigated in detail. They are quite different from those for disks with symmetric patches and could be useful for understanding similar systems.
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2
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Gross B, Bonamassa I, Havlin S. Fractal Fluctuations at Mixed-Order Transitions in Interdependent Networks. PHYSICAL REVIEW LETTERS 2022; 129:268301. [PMID: 36608183 DOI: 10.1103/physrevlett.129.268301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 10/24/2022] [Accepted: 11/29/2022] [Indexed: 06/17/2023]
Abstract
We study the critical features of the order parameter's fluctuations near the threshold of mixed-order phase transitions in randomly interdependent spatial networks. Remarkably, we find that although the structure of the order parameter is not scale invariant, its fluctuations are fractal up to a well-defined correlation length ξ^{'} that diverges when approaching the mixed-order transition threshold. We characterize the self-similar nature of these critical fluctuations through their effective fractal dimension d_{f}^{'}=3d/4, and correlation length exponent ν^{'}=2/d, where d is the dimension of the system. By analyzing percolation and magnetization, we demonstrate that d_{f}^{'} and ν^{'} are the same for both, i.e., independent of the symmetry of the process for any d of the underlying networks.
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Affiliation(s)
- Bnaya Gross
- Department of Physics, Bar Ilan University, Ramat Gan, Israel
| | - Ivan Bonamassa
- Department of Physics, Bar Ilan University, Ramat Gan, Israel
- Department of Network and Data Science, CEU, Quellenstrasse 51, A-1100 Vienna, Austria
| | - Shlomo Havlin
- Department of Physics, Bar Ilan University, Ramat Gan, Israel
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3
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Gwak SH, Goh KI. No-exclaves percolation. THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY 2022; 81:680-687. [PMID: 35909500 PMCID: PMC9310376 DOI: 10.1007/s40042-022-00549-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/15/2022] [Accepted: 06/21/2022] [Indexed: 06/15/2023]
Abstract
Network robustness has been a pivotal issue in the study of system failure in network science since its inception. To shed light on this subject, we introduce and study a new percolation process based on a new cluster called an 'exclave' cluster. The entities comprising exclave clusters in a network are the sets of connected unfailed nodes that are completely surrounded by the failed (i.e., nonfunctional) nodes. The exclave clusters are thus detached from other unfailed parts of the network, thereby becoming effectively nonfunctional. This process defines a new class of clusters of nonfunctional nodes. We call it the no-exclave percolation cluster (NExP cluster), formed by the connected union of failed clusters and the exclave clusters they enclose. Here we showcase the effect of NExP cluster, suggesting a wide and disruptive collapse in two empirical infrastructure networks. We also study on two-dimensional Euclidean lattice to analyze the phase transition behavior using finite-size scaling. The NExP model considering the collective failure clusters uncovers new aspects of network collapse as a percolation process, such as quantitative change of transition point and qualitative change of transition type. Our study discloses hidden indirect damage added to the damage directly from attacks, and thus suggests a new useful way for finding nonfunctioning areas in complex systems under external perturbations as well as internal partial closures.
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Affiliation(s)
- Sang-Hwan Gwak
- Department of Physics, Korea University, Seoul, 02841 Korea
| | - K.-I. Goh
- Department of Physics, Korea University, Seoul, 02841 Korea
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4
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Yadav AC, Quadir A, Jafri HH. Finite-size scaling of critical avalanches. Phys Rev E 2022; 106:014148. [PMID: 35974645 DOI: 10.1103/physreve.106.014148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
We examine probability distribution for avalanche sizes observed in self-organized critical systems. While a power-law distribution with a cutoff because of finite system size is typical behavior, a systematic investigation reveals that it may also decrease with increasing the system size at a fixed avalanche size. We implement the scaling method and identify scaling functions. The data collapse ensures a correct estimation of the critical exponents and distinguishes two exponents related to avalanche size and system size. Our simple analysis provides striking implications. While the exact value for avalanches size exponent remains elusive for the prototype sandpile on a square lattice, we suggest the exponent should be 1. The simulation results represent that the distribution shows a logarithmic system size dependence, consistent with the normalization condition. We also argue that for the train or Oslo sandpile model with bulk drive, the avalanche size exponent is slightly less than 1, which differs significantly from the previous estimate of 1.11.
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Affiliation(s)
- Avinash Chand Yadav
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221 005, India
| | - Abdul Quadir
- Department of Physics, Aligarh Muslim University, Aligarh 202 002, India
| | - Haider Hasan Jafri
- Department of Physics, Aligarh Muslim University, Aligarh 202 002, India
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5
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Lei QL, Hu H, Ni R. Barrier-controlled nonequilibrium criticality in reactive particle systems. Phys Rev E 2021; 103:052607. [PMID: 34134288 DOI: 10.1103/physreve.103.052607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/03/2021] [Indexed: 11/07/2022]
Abstract
Nonequilibrium critical phenomena generally exist in many dynamic systems, like chemical reactions and some driven-dissipative reactive particle systems. Here, by using computer simulation and theoretical analysis, we demonstrate the crucial role of the activation barrier on the criticality of dynamic phase transitions in a minimal reactive hard-sphere model. We find that at zero thermal noise, with increasing the activation barrier, the type of transition changes from a continuous conserved directed percolation into a discontinuous dynamic transition by crossing a tricritical point. A mean-field theory combined with field simulation is proposed to explain this phenomenon. The possibility of Ising-type criticality in the nonequilibrium system at finite thermal noise is also discussed.
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Affiliation(s)
- Qun-Li Lei
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
| | - Hao Hu
- School of Physics and Materials Science, Anhui University, Hefei 230601, China
| | - Ran Ni
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459, Singapore
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6
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Alvarado J, Cipelletti L, Koenderink GH. Uncovering the dynamic precursors to motor-driven contraction of active gels. SOFT MATTER 2019; 15:8552-8565. [PMID: 31637398 DOI: 10.1039/c9sm01172b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cells and tissues have the remarkable ability to actively generate the forces required to change their shape. This active mechanical behavior is largely mediated by the actin cytoskeleton, a crosslinked network of actin filaments that is contracted by myosin motors. Experiments and active gel theories have established that the length scale over which gel contraction occurs is governed by a balance between molecular motor activity and crosslink density. By contrast, the dynamics that govern the contractile activity of the cytoskeleton remain poorly understood. Here we investigate the microscopic dynamics of reconstituted actin-myosin networks using simultaneous real-space video microscopy and Fourier-space dynamic light scattering. Light scattering reveals different regimes of microscopic dynamics as a function of sample age. We uncover two dynamical precursors that precede macroscopic gel contraction. One is characterized by a progressive acceleration of stress-induced rearrangements, while the other consists of sudden, heterogeneous rearrangements. Intriguingly, our findings suggest a qualitative analogy between self-driven rupture and collapse of active gels and the delayed rupture of passive gels observed in earlier studies of colloidal gels under external loads.
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Affiliation(s)
- José Alvarado
- AMOLF, Living Matter Department, 1098 XG Amsterdam, The Netherlands.
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7
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Min B, San Miguel M. Competing contagion processes: Complex contagion triggered by simple contagion. Sci Rep 2018; 8:10422. [PMID: 29991815 PMCID: PMC6039514 DOI: 10.1038/s41598-018-28615-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 06/26/2018] [Indexed: 11/08/2022] Open
Abstract
Empirical evidence reveals that contagion processes often occur with competition of simple and complex contagion, meaning that while some agents follow simple contagion, others follow complex contagion. Simple contagion refers to spreading processes induced by a single exposure to a contagious entity while complex contagion demands multiple exposures for transmission. Inspired by this observation, we propose a model of contagion dynamics with a transmission probability that initiates a process of complex contagion. With this probability nodes subject to simple contagion get adopted and trigger a process of complex contagion. We obtain a phase diagram in the parameter space of the transmission probability and the fraction of nodes subject to complex contagion. Our contagion model exhibits a rich variety of phase transitions such as continuous, discontinuous, and hybrid phase transitions, criticality, tricriticality, and double transitions. In particular, we find a double phase transition showing a continuous transition and a following discontinuous transition in the density of adopted nodes with respect to the transmission probability. We show that the double transition occurs with an intermediate phase in which nodes following simple contagion become adopted but nodes with complex contagion remain susceptible.
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Affiliation(s)
- Byungjoon Min
- IFISC, Instituto de Física Interdisciplinar y Sistemas Complejos (CSIC-UIB), Campus Universitat Illes Balears, E-07122, Palma de Mallorca, Spain.
- Department of Physics, Chungbuk National University, Cheongju, Chungbuk, 28644, Korea.
| | - Maxi San Miguel
- IFISC, Instituto de Física Interdisciplinar y Sistemas Complejos (CSIC-UIB), Campus Universitat Illes Balears, E-07122, Palma de Mallorca, Spain.
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8
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Lo WC, Madrak C, Kiehart DP, Edwards GS. Unified biophysical mechanism for cell-shape oscillations and cell ingression. Phys Rev E 2018; 97:062414. [PMID: 30011599 PMCID: PMC6440536 DOI: 10.1103/physreve.97.062414] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Indexed: 12/31/2022]
Abstract
We describe a mechanochemical and percolation cascade that augments myosin's regulatory network to tune cytoskeletal forces. Actomyosin forces collectively generate cytoskeletal forces during cell oscillations and ingression, which we quantify by elastic percolation of the internally driven, cross-linked actin network. Contractile units can produce relatively large, oscillatory forces that disrupt crosslinks to reduce cytoskeletal forces. A (reverse) Hopf bifurcation switches contractile units to produce smaller, steady forces that enhance crosslinking and consequently boost cytoskeletal forces to promote ingression. We describe cell-shape changes and cell ingression in terms of intercellular force imbalances along common cell junctions.
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Affiliation(s)
- Wei-Chang Lo
- Physics Department, Duke University, Durham, North Carolina 27708, USA
| | - Craig Madrak
- Physics Department, Duke University, Durham, North Carolina 27708, USA
| | - Daniel P Kiehart
- Biology Department, Duke University, Durham, North Carolina 27708, USA
| | - Glenn S Edwards
- Physics Department, Duke University, Durham, North Carolina 27708, USA
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9
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Nandi SK. Activity-dependent self-regulation of viscous length scales in biological systems. Phys Rev E 2018; 97:052404. [PMID: 29906984 DOI: 10.1103/physreve.97.052404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Indexed: 06/08/2023]
Abstract
The cellular cortex, which is a highly viscous thin cytoplasmic layer just below the cell membrane, controls the cell's mechanical properties, which can be characterized by a hydrodynamic length scale ℓ. Cells actively regulate ℓ via the activity of force-generating molecules, such as myosin II. Here we develop a general theory for such systems through a coarse-grained hydrodynamic approach including activity in the static description of the system providing an experimentally accessible parameter and elucidate the detailed mechanism of how a living system can actively self-regulate its hydrodynamic length scale, controlling the rigidity of the system. Remarkably, we find that ℓ, as a function of activity, behaves universally and roughly inversely proportional to the activity of the system. Our theory rationalizes a number of experimental findings on diverse systems, and comparison of our theory with existing experimental data shows good agreement.
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Affiliation(s)
- Saroj Kumar Nandi
- Max-Planck Institute für Physik Komplexer Systeme, 01187 Dresden, Germany
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10
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Baek Y, Solon AP, Xu X, Nikola N, Kafri Y. Generic Long-Range Interactions Between Passive Bodies in an Active Fluid. PHYSICAL REVIEW LETTERS 2018; 120:058002. [PMID: 29481190 DOI: 10.1103/physrevlett.120.058002] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Indexed: 06/08/2023]
Abstract
A single nonspherical body placed in an active fluid generates currents via breaking of time-reversal symmetry. We show that, when two or more passive bodies are placed in an active fluid, these currents lead to long-range interactions. Using a multipole expansion, we characterize their leading-order behaviors in terms of single-body properties and show that they decay as a power law with the distance between the bodies, are anisotropic, and do not obey an action-reaction principle. The interactions lead to rich dynamics of the bodies, illustrated by the spontaneous synchronized rotation of pinned nonchiral bodies and the formation of traveling bound pairs. The occurrence of these phenomena depends on tunable properties of the bodies, thus opening new possibilities for self-assembly mediated by active fluids.
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Affiliation(s)
- Yongjoo Baek
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
- DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, United Kingdom
| | - Alexandre P Solon
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Xinpeng Xu
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
- Department of Physics, Guangdong Technion-Israel Institute of Technology, Shantou, Guangdong 515063, People's Republic of China
| | - Nikolai Nikola
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Yariv Kafri
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
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11
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Wollrab V, Belmonte JM, Baldauf L, Leptin M, Nédeléc F, Koenderink GH. Polarity sorting drives remodeling of actin-myosin networks. J Cell Sci 2018; 132:jcs.219717. [DOI: 10.1242/jcs.219717] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Accepted: 11/01/2018] [Indexed: 12/18/2022] Open
Abstract
Cytoskeletal networks of actin filaments and myosin motors drive many dynamic cell processes. A key characteristic of these networks is their contractility. Despite intense experimental and theoretical efforts, it is not clear what mechanism favors network contraction over expansion. Recent work points to a dominant role for the nonlinear mechanical response of actin filaments, which can withstand stretching but buckle upon compression. Here we present an alternative mechanism. We study how interactions between actin and myosin-2 at the single filament level translate into contraction at the network scale by performing time-lapse imaging on reconstituted quasi-2D-networks mimicking the cell cortex. We observe myosin end-dwelling after it runs processively along actin filaments. This leads to transport and clustering of actin filament ends and the formation of transiently stable bipolar structures. Further we show that myosin-driven polarity sorting produces polar actin asters, which act as contractile nodes that drive contraction in crosslinked networks. Computer simulations comparing the roles of the end-dwelling mechanism and a buckling-dependent mechanism show that the relative contribution of end-dwelling contraction increases as the network mesh-size decreases.
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Affiliation(s)
| | - Julio M. Belmonte
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
| | - Lucia Baldauf
- AMOLF, Science Park 104, 1098 XG Amsterdam, the Netherlands
| | - Maria Leptin
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
| | - François Nédeléc
- EMBL, Cell Biology and Developmental Biology Unit and Director's Research Unit, Meyerhofstraße 1, Heidelberg, Germany
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12
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Abstract
Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field [Formula: see text] At the transition field [Formula: see text], the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length [Formula: see text] Mean-field critical exponents are predicted, since the upper critical dimension of the transition is [Formula: see text] Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.
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13
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Chmiel A, Sienkiewicz J, Sznajd-Weron K. Tricriticality in the q-neighbor Ising model on a partially duplex clique. Phys Rev E 2017; 96:062137. [PMID: 29347453 DOI: 10.1103/physreve.96.062137] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Indexed: 06/07/2023]
Abstract
We analyze a modified kinetic Ising model, a so-called q-neighbor Ising model, with Metropolis dynamics [Phys. Rev. E 92, 052105 (2015)PLEEE81539-375510.1103/PhysRevE.92.052105] on a duplex clique and a partially duplex clique. In the q-neighbor Ising model each spin interacts only with q spins randomly chosen from its whole neighborhood. In the case of a duplex clique the change of a spin is allowed only if both levels simultaneously induce this change. Due to the mean-field-like nature of the model we are able to derive the analytic form of transition probabilities and solve the corresponding master equation. The existence of the second level changes dramatically the character of the phase transition. In the case of the monoplex clique, the q-neighbor Ising model exhibits a continuous phase transition for q=3, discontinuous phase transition for q≥4, and for q=1 and q=2 the phase transition is not observed. On the other hand, in the case of the duplex clique continuous phase transitions are observed for all values of q, even for q=1 and q=2. Subsequently we introduce a partially duplex clique, parametrized by r∈[0,1], which allows us to tune the network from monoplex (r=0) to duplex (r=1). Such a generalized topology, in which a fraction r of all nodes appear on both levels, allows us to obtain the critical value of r=r^{*}(q) at which a tricriticality (switch from continuous to discontinuous phase transition) appears.
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Affiliation(s)
- Anna Chmiel
- Faculty of Physics, Warsaw University of Technology, 00-662 Warsaw, Poland
- Department of Theoretical Physics, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Julian Sienkiewicz
- Faculty of Physics, Warsaw University of Technology, 00-662 Warsaw, Poland
| | - Katarzyna Sznajd-Weron
- Department of Theoretical Physics, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
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14
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Choi K, Lee D, Cho YS, Thiele JC, Herrmann HJ, Kahng B. Critical phenomena of a hybrid phase transition in cluster merging dynamics. Phys Rev E 2017; 96:042148. [PMID: 29347575 DOI: 10.1103/physreve.96.042148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 11/07/2022]
Abstract
Recently, a hybrid percolation transition (HPT) that exhibits both a discontinuous transition and critical behavior at the same transition point has been observed in diverse complex systems. While the HPT induced by avalanche dynamics has been studied extensively, the HPT induced by cluster merging dynamics (HPT-CMD) has received little attention. Here, we aim to develop a theoretical framework for the HPT-CMD. We find that two correlation-length exponents are necessary for characterizing the giant cluster and finite clusters separately. The conventional formula of the fractal dimension in terms of the critical exponents is not valid. Neither the giant nor finite clusters are fractals, but they have fractal boundaries. A finite-size scaling method for the HPT-CMD is also introduced.
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Affiliation(s)
- K Choi
- CCSS, CTP, and Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Deokjae Lee
- CCSS, CTP, and Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Y S Cho
- Department of Physics, Chonbuk National University, Jeonju 54896, Korea
| | - J C Thiele
- Computational Physics for Engineering Materials, Institute for Building Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - H J Herrmann
- Computational Physics for Engineering Materials, Institute for Building Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - B Kahng
- CCSS, CTP, and Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
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15
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Alvarado J, Sheinman M, Sharma A, MacKintosh FC, Koenderink GH. Force percolation of contractile active gels. SOFT MATTER 2017; 13:5624-5644. [PMID: 28812094 DOI: 10.1039/c7sm00834a] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Living systems provide a paradigmatic example of active soft matter. Cells and tissues comprise viscoelastic materials that exert forces and can actively change shape. This strikingly autonomous behavior is powered by the cytoskeleton, an active gel of semiflexible filaments, crosslinks, and molecular motors inside cells. Although individual motors are only a few nm in size and exert minute forces of a few pN, cells spatially integrate the activity of an ensemble of motors to produce larger contractile forces (∼nN and greater) on cellular, tissue, and organismal length scales. Here we review experimental and theoretical studies on contractile active gels composed of actin filaments and myosin motors. Unlike other active soft matter systems, which tend to form ordered patterns, actin-myosin systems exhibit a generic tendency to contract. Experimental studies of reconstituted actin-myosin model systems have long suggested that a mechanical interplay between motor activity and the network's connectivity governs this contractile behavior. Recent theoretical models indicate that this interplay can be understood in terms of percolation models, extended to include effects of motor activity on the network connectivity. Based on concepts from percolation theory, we propose a state diagram that unites a large body of experimental observations. This framework provides valuable insights into the mechanisms that drive cellular shape changes and also provides design principles for synthetic active materials.
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Affiliation(s)
- José Alvarado
- Systems Biophysics Department, AMOLF, 1098 XG Amsterdam, The Netherlands.
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16
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Roy B, Santra SB. First-order transition in a percolation model with nucleation and preferential growth. Phys Rev E 2017; 95:010101. [PMID: 28208344 DOI: 10.1103/physreve.95.010101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Indexed: 11/07/2022]
Abstract
The spanning cluster properties of a percolation model with nucleation and preferential growth exhibit first-order transitions depending on the values of the growth parameter g_{0} and the initial seed concentration ρ. Except for the preferential growth of smaller clusters with a size-dependent growth probability of amplitude g_{0}, the model preserves all other criteria of the original percolation model. As ρ decreases starting from the percolation threshold p_{c} of the original percolation, a line of continuous transition encounters a coexistence region of percolative and nonpercolative large clusters. At sufficiently small values of ρ (≤0.05), the value of g_{0} exceeds p_{c} and generates compact spanning clusters leading to first-order discontinuous transitions.
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Affiliation(s)
- Bappaditya Roy
- Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India
| | - S B Santra
- Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India
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17
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Juhász R, Iglói F. Mixed-order phase transition of the contact process near multiple junctions. Phys Rev E 2017; 95:022109. [PMID: 28298002 DOI: 10.1103/physreve.95.022109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Indexed: 06/06/2023]
Abstract
We have studied the phase transition of the contact process near a multiple junction of M semi-infinite chains by Monte Carlo simulations. As opposed to the continuous transitions of the translationally invariant (M=2) and semi-infinite (M=1) system, the local order parameter is found to be discontinuous for M>2. Furthermore, the temporal correlation length diverges algebraically as the critical point is approached, but with different exponents on the two sides of the transition. In the active phase, the estimate is compatible with the bulk value, while in the inactive phase it exceeds the bulk value and increases with M. The unusual local critical behavior is explained by a scaling theory with an irrelevant variable, which becomes dangerous in the inactive phase. Quenched spatial disorder is found to make the transition continuous in agreement with earlier renormalization group results.
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Affiliation(s)
- Róbert Juhász
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary
| | - Ferenc Iglói
- Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary
- Institute of Theoretical Physics, Szeged University, H-6720 Szeged, Hungary
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18
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Anglès d'Auriac JC, Iglói F. Phase transitions of the random-bond Potts chain with long-range interactions. Phys Rev E 2017; 94:062126. [PMID: 28085354 DOI: 10.1103/physreve.94.062126] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Indexed: 11/07/2022]
Abstract
We study phase transitions of the ferromagnetic q-state Potts chain with random nearest-neighbor couplings having a variance Δ^{2} and with homogeneous long-range interactions, which decay with distance as a power r^{-(1+σ)}, σ>0. In the large-q limit the free-energy of random samples of length L≤2048 is calculated exactly by a combinatorial optimization algorithm. The phase transition stays first order for σ<σ_{c}(Δ)≤0.5, while the correlation length becomes divergent at the transition point for σ_{c}(Δ)<σ<1. In the latter regime the average magnetization is continuous for small enough Δ, but for larger Δ-according to the numerical results-it becomes discontinuous at the transition point, thus the phase transition is expected of mixed order.
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Affiliation(s)
| | - Ferenc Iglói
- Wigner Research Centre, Institute for Solid State Physics and Optics, H-1525 Budapest, P.O.Box 49, Hungary.,Institute of Theoretical Physics, Szeged University, H-6720 Szeged, Hungary
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19
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Hu H, Ziff RM, Deng Y. No-Enclave Percolation Corresponds to Holes in the Cluster Backbone. PHYSICAL REVIEW LETTERS 2016; 117:185701. [PMID: 27835010 DOI: 10.1103/physrevlett.117.185701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Indexed: 06/06/2023]
Abstract
The no-enclave percolation (NEP) model introduced recently by Sheinman et al. can be mapped to a problem of holes within a standard percolation backbone, and numerical measurements of such holes give the same size-distribution exponent τ=1.82(1) as found for the NEP model. An argument is given that τ=1+d_{B}/2≈1.822 for backbone holes, where d_{B} is the backbone dimension. On the other hand, a model of simple holes within a percolation cluster yields τ=1+d_{f}/2=187/96≈1.948, where d_{f} is the fractal dimension of the cluster, and this value is consistent with the experimental results of gel collapse of Sheinman et al., which give τ=1.91(6). This suggests that the gel clusters are of the universality class of percolation cluster holes. Both models give a discontinuous maximum hole size at p_{c}, signifying explosive percolation behavior.
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Affiliation(s)
- Hao Hu
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China
| | - Robert M Ziff
- Center for the Study of Complex Systems and Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, USA
| | - Youjin Deng
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China
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20
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Abstract
Cells set up contractile actin arrays to drive various shape changes and to exert forces to their environment. To understand their assembly process, we present here a reconstituted contractile system, comprising F-actin and myosin II filaments, where we can control the local activation of myosin by light. By stimulating different symmetries, we show that the force balancing at the boundaries determine the shape changes as well as the dynamics of the global contraction. Spatially anisotropic attachment of initially isotropic networks leads to a self-organization of highly aligned contractile fibres, being reminiscent of the order formation in muscles or stress fibres. The observed shape changes and dynamics are fully recovered by a minimal physical model.
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21
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Bar A, Majumdar SN, Schehr G, Mukamel D. Exact extreme-value statistics at mixed-order transitions. Phys Rev E 2016; 93:052130. [PMID: 27300852 DOI: 10.1103/physreve.93.052130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Indexed: 11/07/2022]
Abstract
We study extreme-value statistics for spatially extended models exhibiting mixed-order phase transitions (MOT). These are phase transitions that exhibit features common to both first-order (discontinuity of the order parameter) and second-order (diverging correlation length) transitions. We consider here the truncated inverse distance squared Ising model, which is a prototypical model exhibiting MOT, and study analytically the extreme-value statistics of the domain lengths The lengths of the domains are identically distributed random variables except for the global constraint that their sum equals the total system size L. In addition, the number of such domains is also a fluctuating variable, and not fixed. In the paramagnetic phase, we show that the distribution of the largest domain length l_{max} converges, in the large L limit, to a Gumbel distribution. However, at the critical point (for a certain range of parameters) and in the ferromagnetic phase, we show that the fluctuations of l_{max} are governed by novel distributions, which we compute exactly. Our main analytical results are verified by numerical simulations.
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Affiliation(s)
- Amir Bar
- Department of Complex Systems, Weizmann Institute, Rehovot, Israel
| | - Satya N Majumdar
- Université Paris-Sud, CNRS, LPTMS, UMR 8626, Orsay F-91405, France
| | - Grégory Schehr
- Université Paris-Sud, CNRS, LPTMS, UMR 8626, Orsay F-91405, France
| | - David Mukamel
- Department of Complex Systems, Weizmann Institute, Rehovot, Israel
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22
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Pruessner G, Lee CF. Comment on "Anomalous Discontinuity at the Percolation Critical Point of Active Gels". PHYSICAL REVIEW LETTERS 2016; 116:189801. [PMID: 27203348 DOI: 10.1103/physrevlett.116.189801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Indexed: 06/05/2023]
Affiliation(s)
- Gunnar Pruessner
- Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Chiu Fan Lee
- Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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23
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Sheinman M, Sharma A, MacKintosh FC. Sheinman, Sharma, and MacKintosh Reply. PHYSICAL REVIEW LETTERS 2016; 116:189802. [PMID: 27203349 DOI: 10.1103/physrevlett.116.189802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Indexed: 06/05/2023]
Affiliation(s)
- M Sheinman
- Department of Physics and Astronomy, VU University, Amsterdam, Netherlands
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
- Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands
| | - A Sharma
- Department of Physics and Astronomy, VU University, Amsterdam, Netherlands
- Drittes Physikalisches Institut, Georg-August-Universitat, 37073 Göttingen, Göttingen, Germany
| | - F C MacKintosh
- Department of Physics and Astronomy, VU University, Amsterdam, Netherlands
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24
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Lee CF, Pruessner G. Percolation mechanism drives actin gels to the critically connected state. Phys Rev E 2016; 93:052414. [PMID: 27300931 DOI: 10.1103/physreve.93.052414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 06/06/2023]
Abstract
Cell motility and tissue morphogenesis depend crucially on the dynamic remodeling of actomyosin networks. An actomyosin network consists of an actin polymer network connected by cross-linker proteins and motor protein myosins that generate internal stresses on the network. A recent discovery shows that for a range of experimental parameters, actomyosin networks contract to clusters with a power-law size distribution [J. Alvarado, Nat. Phys. 9, 591 (2013)1745-247310.1038/nphys2715]. Here, we argue that actomyosin networks can exhibit a robust critical signature without fine-tuning because the dynamics of the system can be mapped onto a modified version of percolation with trapping (PT), which is known to show critical behavior belonging to the static percolation universality class without the need for fine-tuning of a control parameter. We further employ our PT model to generate experimentally testable predictions.
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Affiliation(s)
- Chiu Fan Lee
- Department of Bioengineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Gunnar Pruessner
- Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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25
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Böttcher L, Woolley-Meza O, Goles E, Helbing D, Herrmann HJ. Connectivity disruption sparks explosive epidemic spreading. Phys Rev E 2016; 93:042315. [PMID: 27176320 DOI: 10.1103/physreve.93.042315] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 05/04/2023]
Abstract
We investigate the spread of an infection or other malfunction of cascading nature when a system component can recover only if it remains reachable from a functioning central component. We consider the susceptible-infected-susceptible model, typical of mathematical epidemiology, on a network. Infection spreads from infected to healthy nodes, with the addition that infected nodes can only recover when they remain connected to a predefined central node, through a path that contains only healthy nodes. In this system, clusters of infected nodes will absorb their noninfected interior because no path exists between the central node and encapsulated nodes. This gives rise to the simultaneous infection of multiple nodes. Interestingly, the system converges to only one of two stationary states: either the whole population is healthy or it becomes completely infected. This simultaneous cluster infection can give rise to discontinuous jumps of different sizes in the number of failed nodes. Larger jumps emerge at lower infection rates. The network topology has an important effect on the nature of the transition: we observed hysteresis for networks with dominating local interactions. Our model shows how local spread can abruptly turn uncontrollable when it disrupts connectivity at a larger spatial scale.
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Affiliation(s)
- L Böttcher
- ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
| | - O Woolley-Meza
- Computational Social Science, ETH Zurich, Clausiusstrasse 37, CH-8092 Zurich, Switzerland
| | - E Goles
- Universidad Adolfo Ibáñez, Av. Diagonal Las Torres 2640, Peñalolén, Santiago, Chile
| | - D Helbing
- Computational Social Science, ETH Zurich, Clausiusstrasse 50, CH-8092 Zurich, Switzerland
| | - H J Herrmann
- ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland and Departamento de Física, Universidade Federal do Ceará, 60451-970 Fortaleza, Ceará, Brazil
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26
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Jȩdrzejewski A, Chmiel A, Sznajd-Weron K. Oscillating hysteresis in the q-neighbor Ising model. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052105. [PMID: 26651645 DOI: 10.1103/physreve.92.052105] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 06/05/2023]
Abstract
We modify the kinetic Ising model with Metropolis dynamics, allowing each spin to interact only with q spins randomly chosen from the whole system, which corresponds to the topology of a complete graph. We show that the model with q≥3 exhibits a phase transition between ferromagnetic and paramagnetic phases at temperature T*, which linearly increases with q. Moreover, we show that for q=3 the phase transition is continuous and that it is discontinuous for larger values of q. For q>3, the hysteresis exhibits oscillatory behavior-expanding for even values of q and shrinking for odd values of q. Due to the mean-field-like nature of the model, we are able to derive the analytical form of transition probabilities and, therefore, calculate not only the probability density function of the order parameter but also precisely determine the hysteresis and the effective potential showing stable, unstable, and metastable steady states. Our results show that a seemingly small modification of the kinetic Ising model leads not only to the switch from a continuous to a discontinuous phase transition, but also to an unexpected oscillating behavior of the hysteresis and a puzzling phenomenon for q=5, which might be taken as evidence for the so-called mixed-order phase transition.
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Affiliation(s)
| | - Anna Chmiel
- Department of Theoretical Physics, Wroclaw University of Technology, Wroclaw, Poland
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27
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Das T, Lookman T, Bandi MM. A minimal description of morphological hierarchy in two-dimensional aggregates. SOFT MATTER 2015; 11:6740-6746. [PMID: 26107688 DOI: 10.1039/c5sm01222h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A dimensionless parameter Λ is proposed to describe a hierarchy of morphologies in two-dimensional (2D) aggregates formed due to varying competition between short-range attraction and long-range repulsion. Structural transitions from finite non-compact to compact to percolated structures are observed in the configurations simulated by molecular dynamics at a constant temperature and density. Configurational randomness across the transition, measured by the two-body excess entropy S2, exhibits data collapse with the average potential energy [small epsilon, Greek, macron] of the systems. Independent master curves are presented among S2, the reduced second virial coefficient B2* and Λ, justifying this minimal description. This work lays out a coherent basis for the study of 2D aggregate morphologies relevant to diverse nano- and bio-processes.
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Affiliation(s)
- Tamoghna Das
- Collective Interactions Unit, OIST Graduate University, Onna, Okinawa 9040495, Japan.
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28
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Ben-Isaac E, Fodor É, Visco P, van Wijland F, Gov NS. Modeling the dynamics of a tracer particle in an elastic active gel. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012716. [PMID: 26274211 DOI: 10.1103/physreve.92.012716] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Indexed: 06/04/2023]
Abstract
The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies.
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Affiliation(s)
- E Ben-Isaac
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - É Fodor
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - P Visco
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - F van Wijland
- Laboratoire Matière et Systèmes Complexes, UMR 7057 CNRS/P7, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris cedex 13, France
| | - Nir S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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29
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Sheinman M, Sharma A, Alvarado J, Koenderink GH, MacKintosh FC. Inherently unstable networks collapse to a critical point. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012710. [PMID: 26274206 DOI: 10.1103/physreve.92.012710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Indexed: 06/04/2023]
Abstract
Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.
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Affiliation(s)
- M Sheinman
- Department of Physics and Astronomy, VU University, Amsterdam, The Netherlands
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - A Sharma
- Department of Physics and Astronomy, VU University, Amsterdam, The Netherlands
- Drittes Physikalisches Institut, Georg-August-Universitat Göttingen, Göttingen, Germany
| | - J Alvarado
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
- Department of Mechanical Engineering, Hatsopoulos Microfluids Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - G H Koenderink
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - F C MacKintosh
- Department of Physics and Astronomy, VU University, Amsterdam, The Netherlands
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