III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet Incubator Lifescape
2. A Consilience as Physics and Biology Grow Together: Active Matter
Jusup, Marko, et al. Physics Of Metabolic Organization. Physics of Life Reviews. 20/1, 2017. Mathematical biologists from Japan, Portugal, and Croatia scope out the pursuit of a deeper rooting and common cause of life within physical and energetic phenomena. Along with 14 peer comments, the integrative project appears on its way, which hints of universalities such as the von Bertalanffy growth curve.
Karamouzas, Ioannis, et al. Universal Power Law Governing Pedestrian Interactions. Physical Review Letters. 113/238701, 2014. It is worth notice, as this letter by University of Minnesota and Argonne National Laboratory physicists exemplifies, how often statistical mechanics is being applied to a widest range of phenomena and occasions. A result is the discovery of a constant recurrence in kind from physical substrates to social commerce. In this case a deeper mathematics is found to guide even our walk and talk.
Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power-law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory in nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds, and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena. (Abstract)
Katsnelson, Mikhail, et al. Towards Physical Principles of Biological Evolution. Physica Scripta. 93/4, 2018. An entry in a Focus Issue on 21st Century Frontiers (search Lidstrom) by MK, Radboud University along with Yuri Wolf and Eugene Koonin, National Center for Biotechnology Information. While the traditional realms of inorganic and organic have long been apart, seemingly unbreachable, nowadays a robust (re)unification at last seems possible. A first step is to allow the very idea and integration at all. As often, it will involve a clarification of concepts and definitions, such as a thermodynamic basis for population genetic, along with affinities to the major evolutionary transitions scale. Another convergence might be spin-glass complexity theories with life’s emergence from proteins to organisms and the biosphere. The presence of “percolation effects and criticalities,” and natural selection as “measurement” is also suggested. Another version of this paper, Physical Foundations of Biological Complexity, appears in the Proceedings of the National Academy of Sciences (115/E8678, 2018, also at arXiv:1803.0997).
Biological systems reach organizational complexity that far exceeds the complexity of any known inanimate objects. Biological entities undoubtedly obey the laws of quantum physics and statistical mechanics. However, is modern physics sufficient to adequately describe, model and explain the evolution of biological complexity? Detailed parallels have been drawn between statistical thermodynamics and the population-genetic theory of biological evolution. Based on these parallels, we outline new perspectives on biological innovation and major transitions in evolution, and introduce a biological equivalent of thermodynamic potential that reflects the innovation propensity of an evolving population. Deep analogies have been suggested to also exist between the properties of biological entities and processes, and those of frustrated states in physics, such as glasses. Such systems are characterized by frustration whereby local state with minimal free energy conflict with the global minimum, resulting in 'emergent phenomena'. We extend such analogies by examining frustration-type phenomena, such as conflicts between different levels of selection, in biological evolution. These frustration effects appear to drive the evolution of biological complexity. (Abstract excerpt)
Physics of Living Systems.
An editor introduces an Insight collection on this current, vital synthesis of figure and ground as it gains collaborative veracity. The entries include Biophysics Across Time and Space by Ewa Paluch, Ethology as a Physical Science by Andre Brown and Ben de Bivort, Mesoscale Physical Principles of Collective Cell Organization by Joe Chin-Hun Kuo, et al and The Physics of Cooperative Transport in Ants by Ofer Feinerman, et al.
Klotsa, Daphne. As Above, So Below, and also in Between: Mesoscale Active Matter in Fluids. Soft Matter. 15/8946, 2019. After a decade of diverse particle (molecules, colloids, microbes, swimmers) studies, a University of North Carolina biomaterials physicist extends the approach onto macro systems such as bird flocks, insect swarms and whale pods. By so doing, it is found that the same phenomena can be observed at each and every wide scale and instance. Into the 21st century this traditional adage can gain its worldwise quantification. See also The Most Active Matter of All by Nicholas Ouellette in the new Cell Press journal Matter (1/2, 2019, third quote).
Living matter, such as biological tissue, can be viewed as a nonequilibrium hierarchical assembly, where self-driven components come together by consuming energy to form increasingly complex structures. The remarkable properties of such living or “active-matter” systems have prompted these questions: (1) do we understand the biology and biophysics that give rise to these properties? (2) can we achieve similar functionality with synthetic active materials? Here we study active matter in liquids and gases for aquatic and avian movements with finite inertia and expect collective behavior to emerge by way of nonlinearities and many-body interactions. The organisms/particles can become quite complex leading to flocking states and nonequilibrium phase transitions. (Abstract edits)
Krisnanda, Tanjung, et al. Probing Quantum Features of Photosynthetic Organisms. arXiv:1711.06485. We cite this entry by theoretical physicists from Singapore and the UK including Chiara Marletto and Vlatko Vedral to emphasize a current cross-integration and fertilization of macro-classical and micro-quantum phases. Its opening sentence is There is no a priori limit on the complexity, size or mass of objects to which quantum theory is applicable. If to observe, a worldwise sapiensphere is well on her/his way to finally, actually expressing a unified, animate, genesis universe.
Recent experiments have demonstrated strong coupling between living bacteria and light. Here we propose a scheme to infer quantumness of the light-bacteria correlations, as characterised by the presence of quantum discord, without requiring any knowledge of their mutual interactions, and by measuring only the light's degrees of freedom. This is achieved by monitoring the dynamics of the entanglement between few optical modes (probes) that interact independently with the bacteria. When the (light-sensitive part of) bacterium is modelled as a collection of two-level atoms we find that the steady state entanglement between the probes is independent of the initial conditions, is accompanied by entanglement between probes and bacteria, and provides independent evidence of the strong coupling between them. (Abstract)
Le Bihan, Denis. Is the Brain Relativistic?. arXiv:1908.04290. The senior French philosophical neuroscientist is posted at NEUROSPIN: From Physics to the Human Brain, a CEA Parisian research and clinical project, especially for autism studies, by way of novel intense field imaging techniques. In search of a broader natural context of service to cerebral research, the author notes that while cosmic physics has a conceptual basis, a global theory of the working brain to account for cognition, behavior, and consciousness does not exist. A sense of a deep affinity between our human faculty and the extant universe informs the text, as the second and third quotes allude. Neural network theories are engaged, along with genetic (alphabetic) factors in a connectome mode, along with synaptic pruning and visual capacities. As this imaginative rooting goes forward, we visit quantum phenomena, Minkowski diagrams, hyperspace geodesics, and more to show how akin a vital universe and our microcosmic human acumen might actually be. Thus the paper closes with the thought:To paraphrase (physicist) J. A. Wheeler one may conclude that brain spacetime tells activity how to flow while activity tells brain spacetime how to curve. (29)
Due to the large body of knowledge which neuroimaging has achieved over the last three decades, we have gained a fresh view of the brain which could help us make predictions for new imaging instruments to come, such as ultra high field MRI. By doing so, switching back and forth between physics and neurobiology, we come to a sense that time and space in the brain, as in the Universe, are, indeed, tightly mingled, and could be unified through a brain 'spacetime'. Thinking about a speed limit for action potentials flowing along myelinated axons led us to envision a 4-dimensional brain spacetime which holds to a relativistic pseudo-diffusion principle and functional curvature governed by brain activity, in a similar way gravitational masses give our 4-dimensional Universe spacetime its curvature. (Abstract excerpts, edits).
Lee, Chiu Fan and Jean David Wurtz. Novel Physics Arising From Phase Transitions in Biology. Journal of Physics D. 52/2, 2019. In a Special Issue on Collective Behaviour of Living Matter, Imperial College London bioengineers enter another example of the current synthesis of physical phenomena with living systems via a formative agency whence life transitions in kind through serial evolutionary and developmental phases. Thus, universal behaviors previously noted at condensed matter critical points can likewise be seen to occur in biological activities. A further aspect is that many free, contingent entities are yet seen to give rise to an overall coherence. By turns, as worldwide physical and biological sciences cross-inform, a unitary organic procreative ecosmos gains a revolutionary veracity. The work merited notice in Nature Physics (Jan. 2019) as Biological Transitions by Mark Buchanan. Also in this issue, e.g., see Phase Transitions in Huddling Emperor Penguins, Density Distributions and Depth in Flocks, and Emergence of Cooperativity in a Model Biofilm in this collection. See also Physical Principles of Intracellular Organization via Active and Passive Phase Transitions by Joel Berry, et al in Reports on Progress in Physics (81/4, 2018). The third quote is the Issue proposal by Ben Fabry, et al.
Phase transitions, such as the freezing of water and the magnetisation of a ferromagnet due to temperature changes, are familiar physical phenomena. Lately, such collective behaviours at a phase transition are similarly found in effect for living systems. From cytoplasmic organisation inside a cell to the migration of cell tissue during development, phase transitions have emerged as key mechanisms underlying many biological processes. However, a living system is fundamentally different from a thermal system, with metabolism and motility being two hallmarks of its nonequilibrium nature. In this review, we will discuss how such driven chemical reactions can arrest universal coarsening kinetics expected from thermal phase separation, and how motility leads to the emergence of a novel universality class when the rotational symmetry is spontaneously broken. (Abstract edits)
Leng, Biao, et al. Gravitational Scaling in Beijing Subway Network. arXiv:1606.01208. Beihang University (a major public research facility in Beijing) physicists, along with Shlomo Havlin, the veteran Israeli systems theorist, draw upon the physics of Newtonian gravity, self-organized criticality, and network dynamics to discern an independent motive source which serves to organize commuter traffic. The study follows up a similar work as Scaling and Renormalization in the Seoul Bus System by Segun Goh, et al (PLoS One 9/3, 2014), second Abstract. And to reflect, these findings, among many more, infer a double domain of human activities which are actually guided by and exemplify an independent self-organizing mathematics.
Recently, with the availability of various traffic datasets, human mobility has been studied in different contexts. Researchers attempt to understand the collective behaviors of human movement with respect to the spatio-temporal distribution in traffic dynamics, from which a gravitational scaling law characterizing the relation between the traffic flow, population and distance has been found. However, most studies focus on the integrated properties of gravitational scaling, neglecting its dynamical evolution during different hours of a day. Investigating the hourly traffic flow data of Beijing subway network, based on the hop-count distance of passengers, we find that the scaling exponent of the gravitational law is smaller in Beijing subway system compared to that reported in Seoul subway system. This means that traffic demand in Beijing is much stronger and less sensitive to the travel distance. Furthermore, we analyzed the temporal evolution of the scaling exponents in weekdays and weekends. Our findings may help to understand and improve the traffic congestion control in different subway systems. (Leng abstract)
Lou, Yuting, et al. Homeostasis and Systematic Ageing as Non-equilibrium Phase Transitions in Computational Multicellular Organizations. Royal Society Open Science. Online July 10, 2019. University of Tokyo and Fudan University, Shanghai systems biologists provide another notice of physical principles at work throughout life’s somatic activities and long developmental course.
The breakdown of homeostasis in tissues involves multiscale factors ranging from the accumulation of genetic damages to the deregulation of metabolic processes. Here, we present a multicellular homeostasis model in the form of a two-dimensional stochastic cellular automaton with three cellular states, cell division, cell death and cell cycle arrest. Our model illustrates how organisms can develop into diverse homeostatic patterns with distinct morphologies, turnover rates and lifespans without considering genetic, metabolic or other variations. Those homeostatic states exist in extinctive, proliferative and degenerative phases, which undergo a systematic ageing akin to a transition in non-equilibrium physical systems. (Abstract excerpt)
Love, Alan, et al. Perspectives on Integrating Genetic and Physical Explanations of Evolution and Development. Integrative & Comparative Biology. 57/6, 2017. In this Oxford Academic journal, Love, Thomas Stewart, Gunter Wagner, and Stuart Newman introduce this symposium, notably a century after D’Arcy Thompson’s On Growth and Form, about many intrinsic structural constraints that do in fact affect life’s anatomy and physiology. See, herein for example, The Origin of Novelty through the Evolution of Scaling Relationships, by Fred Nijhout and Ken McKenna.
In the 20th century, genetic explanatory approaches became dominant in both developmental and evolutionary biological research. By contrast, physical approaches, which appeal to properties such as mechanical forces, were largely relegated to the margins, despite important advances in modeling. Recently, there have been renewed attempts to find balanced viewpoints that integrate both biological physics and molecular genetics into explanations of developmental and evolutionary phenomena. Here we introduce the 2017 SICB symposium “Physical and Genetic Mechanisms for Evolutionary Novelty” that was dedicated to exploring empirical cases where both biological physics and developmental genetic considerations are crucial. We conclude by arguing that intentional reflection on conceptual questions about investigation, explanation, and integration is critical to achieving significant empirical and theoretical advances in our understanding of how novel forms originate across the tree of life. (Abstract)
Manning, Lisa and Eva-Maria Schoetz Collins. Focus on Physical Models in Biology: Multicellularity and Active Matter. New Journal of Physics. Circa 2013 –, 2014. Syracuse University and UCSD biophysicists introduce an on-going posting of articles that contribute to this 21st century integration of a conducive cosmos with evolutionary life. A typical paper is “The Origin of Traveling Waves in an Emperor Penguin Huddle” (15/125022). Of interest is how readily scientists have adopted the “active matter” phrase since 2010, and in the quote, a sense of “living materials.” See also Tsimring, et al, herein, for another (re)unification of these premier sciences. Search the March 2014 issue to find.
Living materials, from individual cells to flocks of animals, are a form of 'active matter', i.e. self-propelled entities which exhibit complex behaviors and interactions, and whose understanding is an active area of interdisciplinary research. New imaging techniques such as confocal, multiphoton, SPIM and 3D traction force microscopy have allowed an unprecedented look at the motions and forces that occur in a variety of multicellular systems. To complement the experimental advances on how groups of cells organize and interact at medium to high densities, theories and models are needed which scale up from single-cell behaviors to collective, emergent phenomena at the multi-cell level and allow us to make testable predictions. Much can also be learned by comparing and contrasting groups of cells with other active matter systems. In addition, new and sophisticated image and data analysis techniques are required to pinpoint, in multiple dimensions, features of cell mechanics, interactions and motility in these dense 'living materials'. These active, non-equilibrium systems might also generate new types of physical behavior that simply cannot be observed in inert systems and thus enable us to learn exciting new physics. (Excerpt)