1
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Nerger BA, Sinha S, Lee NN, Cheriyan M, Bertsch P, Johnson CP, Mahadevan L, Bonventre JV, Mooney DJ. 3D Hydrogel Encapsulation Regulates Nephrogenesis in Kidney Organoids. Adv Mater 2024; 36:e2308325. [PMID: 38180232 PMCID: PMC10994733 DOI: 10.1002/adma.202308325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 12/06/2023] [Indexed: 01/06/2024]
Abstract
Stem cell-derived kidney organoids contain nephron segments that recapitulate morphological and functional aspects of the human kidney. However, directed differentiation protocols for kidney organoids are largely conducted using biochemical signals to control differentiation. Here, the hypothesis that mechanical signals regulate nephrogenesis is investigated in 3D culture by encapsulating kidney organoids within viscoelastic alginate hydrogels with varying rates of stress relaxation. Tubular nephron segments are significantly more convoluted in kidney organoids differentiated in encapsulating hydrogels when compared with those in suspension culture. Hydrogel viscoelasticity regulates the spatial distribution of nephron segments within the differentiating kidney organoids. Consistent with these observations, a particle-based computational model predicts that the extent of deformation of the hydrogel-organoid interface regulates the morphology of nephron segments. Elevated extracellular calcium levels in the culture medium, which can be impacted by the hydrogels, decrease the glomerulus-to-tubule ratio of nephron segments. These findings reveal that hydrogel encapsulation regulates nephron patterning and morphology and suggest that the mechanical microenvironment is an important design variable for kidney regenerative medicine.
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Affiliation(s)
- Bryan A. Nerger
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | - Sumit Sinha
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Data Science, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Nathan N. Lee
- Division of Renal Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Maria Cheriyan
- Harvard College, Harvard University, Cambridge, MA 02138, USA
| | - Pascal Bertsch
- Radboud University Medical Center, Department of Dentistry – Regenerative Biomaterials, Radboud Institute for Molecular Life Sciences, Nijmegen, Netherlands
| | - Christopher P. Johnson
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | - L. Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Physics, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Joseph V. Bonventre
- Division of Renal Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA; Division of Engineering in Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - David J. Mooney
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
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2
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Serra M, Serrano Nájera G, Chuai M, Plum AM, Santhosh S, Spandan V, Weijer CJ, Mahadevan L. A mechanochemical model recapitulates distinct vertebrate gastrulation modes. Sci Adv 2023; 9:eadh8152. [PMID: 38055823 PMCID: PMC10699781 DOI: 10.1126/sciadv.adh8152] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 11/06/2023] [Indexed: 12/08/2023]
Abstract
During vertebrate gastrulation, an embryo transforms from a layer of epithelial cells into a multilayered gastrula. This process requires the coordinated movements of hundreds to tens of thousands of cells, depending on the organism. In the chick embryo, patterns of actomyosin cables spanning several cells drive coordinated tissue flows. Here, we derive a minimal theoretical framework that couples actomyosin activity to global tissue flows. Our model predicts the onset and development of gastrulation flows in normal and experimentally perturbed chick embryos, mimicking different gastrulation modes as an active stress instability. Varying initial conditions and a parameter associated with active cell ingression, our model recapitulates distinct vertebrate gastrulation morphologies, consistent with recently published experiments in the chick embryo. Altogether, our results show how changes in the patterning of critical cell behaviors associated with different force-generating mechanisms contribute to distinct vertebrate gastrulation modes via a self-organizing mechanochemical process.
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Affiliation(s)
- Mattia Serra
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Guillermo Serrano Nájera
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Manli Chuai
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Alex M. Plum
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Sreejith Santhosh
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Vamsi Spandan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Cornelis J. Weijer
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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3
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Chaudhary G, Christ S, Hart AJ, Mahadevan L. Learning to write with the fluid rope trick. Soft Matter 2023; 19:8329-8336. [PMID: 37869971 DOI: 10.1039/d3sm00177f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2023]
Abstract
Direct ink writing, a versatile method of 3D and 4D printing, requires the precise placement of a nozzle just above the print surface to prevent fluid instabilities that cause deviations from the prescribed print path. But what if one could harness the instability associated with the spontaneously folding or coiling of a thin stream of viscous fluid, i.e. use the "fluid rope trick" to write specified patterns on a substrate? Here we use Deep Reinforcement Learning to derive control strategies for the motion of the extruding nozzle and thus the fluid patterns that are deposited on the surface. The method proceeds by having a learner (nozzle) repeatedly interact with the environment (a viscous filament simulator), and improves its strategy using the results of this experience. We demonstrate the outcome of the learned control instructions using experiments to manipulate a falling viscous jet and create cursive writing patterns and Pollockian paintings on substrates.
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Affiliation(s)
- Gaurav Chaudhary
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Stephanie Christ
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
| | - A John Hart
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
- Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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4
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Yin S, Mahadevan L. Contractility-Induced Phase Separation in Active Solids. Phys Rev Lett 2023; 131:148401. [PMID: 37862637 DOI: 10.1103/physrevlett.131.148401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 08/03/2023] [Indexed: 10/22/2023]
Abstract
Experiments over many decades are suggestive that the combination of cellular contractility and active phase separation in cell-matrix composites can enable spatiotemporal patterning in multicellular tissues across scales. To characterize these phenomena, we provide a general theory that incorporates active cellular contractility into the classical Cahn-Hilliard-Larché model for phase separation in passive viscoelastic solids. Within this framework, we show how a homogeneous cell-matrix mixture can be destabilized by activity via either a pitchfork or Hopf bifurcation, resulting in stable phase separation and/or traveling waves. Numerical simulations of the full equations allow us to track the evolution of the resulting self-organized patterns in periodic and mechanically constrained domains, and in different geometries. Altogether, our study underscores the importance of integrating both cellular activity and mechanical phase separation in understanding patterning in soft, active biosolids in both in vivo and in vitro settings.
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Affiliation(s)
- Sifan Yin
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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5
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Mosleh S, Choi GPT, Musser GM, James HF, Abzhanov A, Mahadevan L. Beak morphometry and morphogenesis across avian radiations. Proc Biol Sci 2023; 290:20230420. [PMID: 37752837 PMCID: PMC10523063 DOI: 10.1098/rspb.2023.0420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 08/18/2023] [Indexed: 09/28/2023] Open
Abstract
Adaptive avian radiations associated with the diversification of bird beaks into a multitude of forms enabling different functions are exemplified by Darwin's finches and Hawaiian honeycreepers. To elucidate the nature of these radiations, we quantified beak shape and skull shape using a variety of geometric measures that allowed us to collapse the variability of beak shape into a minimal set of geometric parameters. Furthermore, we find that just two measures of beak shape-the ratio of the width to length and the normalized sharpening rate (increase in the transverse beak curvature near the tip relative to that at the base of the beak)-are strongly correlated with diet. Finally, by considering how transverse sections to the beak centreline evolve with distance from the tip, we show that a simple geometry-driven growth law termed 'modified mean curvature flow' captures the beak shapes of Darwin's finches and Hawaiian honeycreepers. A surprising consequence of the simple growth law is that beak shapes that are not allowed based on the developmental programme of the beak are also not observed in nature, suggesting a link between evolutionary morphology and development in terms of growth-driven developmental constraints.
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Affiliation(s)
- Salem Mosleh
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Gary P. T. Choi
- Department of Mathematics, The Chinese University of Hong Kong, Hong Kong, Hong Kong
| | - Grace M. Musser
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Helen F. James
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Arhat Abzhanov
- Department of Life Sciences, Imperial College London, Ascot SL5 7PY, UK
- Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - L. Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
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6
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Saintyves B, Pic R, Mahadevan L, Bischofberger I. Evaporation-Driven Cellular Patterns in Confined Hyperelastic Hydrogels. Phys Rev Lett 2023; 131:118202. [PMID: 37774285 DOI: 10.1103/physrevlett.131.118202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 08/08/2023] [Indexed: 10/01/2023]
Abstract
When a hyperelastic hydrogel confined between two parallel glass plates begins to dry from a lateral boundary, the volume lost by evaporation is accommodated by an inward displacement of the air-hydrogel interface that induces an elastic deformation of the hydrogel. Once a critical front displacement is reached, we observe intermittent fracture events initiated by a geometric instability resulting in localized bursts at the interface. These bursts relax the stresses and irreversibly form air cavities that lead to cellular networks. We show that the spatial extent of the strain field prior to a burst, influenced by the air-hydrogel interfacial tension and the confinement of the gel, determines the characteristic size of the cavities.
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Affiliation(s)
- Baudouin Saintyves
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Romain Pic
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Irmgard Bischofberger
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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7
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Vafa F, Mahadevan L. Statics and diffusive dynamics of surfaces driven by p-atic topological defects. Soft Matter 2023; 19:6652-6663. [PMID: 37641854 DOI: 10.1039/d3sm00257h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Inspired by epithelial morphogenesis, we consider a minimal model for the shaping of a surface driven by p-atic topological defects. We show that a positive (negative) defect can dynamically generate a (hyperbolic) cone whose shape evolves diffusively, and predict that a defect of charge + 1/p leads to a final semi-cone angle β which satisfies the inequality . By exploiting the fact that for axisymmetric surfaces, the extrinsic geometry is tightly coupled to the intrinsic geometry, we further show that the resulting stationary shape of a membrane with negligible bending modulus and embedded polar order is a deformed lemon with two defects at antipodal points. Finally, we close by pointing out that our results may be relevant beyond epithelial morphogenesis in such contexts as shape transitions in macroscopic closed spheroidal surfaces such as pollen grains.
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Affiliation(s)
- Farzan Vafa
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, MA 02138, USA.
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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8
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Al-Mosleh S, Mahadevan L. How to Grow a Flat Leaf. Phys Rev Lett 2023; 131:098401. [PMID: 37721834 DOI: 10.1103/physrevlett.131.098401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 05/08/2023] [Indexed: 09/20/2023]
Abstract
Growing a flat lamina such as a leaf is almost impossible without some feedback to stabilize long wavelength modes that are easy to trigger since they are energetically cheap. Here we combine the physics of thin elastic plates with feedback control theory to explore how a leaf can remain flat while growing. We investigate both in-plane (metric) and out-of-plane (curvature) growth variation and account for both local and nonlocal feedback laws. We show that a linearized feedback theory that accounts for both spatially nonlocal and temporally delayed effects suffices to suppress long wavelength fluctuations effectively and explains recently observed statistical features of growth in tobacco leaves. Our work provides a framework for understanding the regulation of the shape of leaves and other leaflike laminar objects.
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Affiliation(s)
- Salem Al-Mosleh
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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9
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Lawrence C, Jasanoff S, Evans SW, Raffel K, Mahadevan L. Ethics Inside the Black Box: Integrating Science and Technology Studies into Engineering and Public Policy Curricula. Sci Eng Ethics 2023; 29:23. [PMID: 37347323 DOI: 10.1007/s11948-023-00440-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 04/21/2023] [Indexed: 06/23/2023]
Abstract
There is growing need for hybrid curricula that integrate constructivist methods from Science and Technology Studies (STS) into both engineering and policy courses at the undergraduate and graduate levels. However, institutional and disciplinary barriers have made implementing such curricula difficult at many institutions. While several programs have recently been launched that mix technical training with consideration of "societal" or "ethical issues," these programs often lack a constructivist element, leaving newly-minted practitioners entering practical fields ill-equipped to unpack the politics of knowledge and technology or engage with skeptical publics. This paper presents a novel format for designing interdisciplinary coursework that combines conceptual content from STS with training in engineering and policy. Courses following this format would ideally be team taught by instructors with advanced training in diverse fields, and hence co-learning between instructors and disciplines is a key element of the format. Several instruments for facilitating both student and instructor collaborative learning are introduced. The format is also designed for versatility: in addition to being adaptable to both technical and policy training environments, topics are modularized around a conceptual core so that issues ranging from biotech to nuclear security can be incorporated to fit programmatic needs and resources.
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Affiliation(s)
- Christopher Lawrence
- Science, Technology and International Affairs Program, Walsh School of Foreign Service, Geogetown University, Washington, USA.
| | - Sheila Jasanoff
- Program on Science, Technology and Society, Kennedy School of Government, Harvard University, Cambridge, MA, USA
| | - Sam Weiss Evans
- Program on Science, Technology and Society, Kennedy School of Government, Harvard University, Cambridge, MA, USA
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Keith Raffel
- Mather House, Harvard University, Cambridge, MA, USA
| | - L Mahadevan
- Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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10
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Dudte LH, Choi GPT, Becker KP, Mahadevan L. An additive framework for kirigami design. Nat Comput Sci 2023; 3:443-454. [PMID: 38177849 DOI: 10.1038/s43588-023-00448-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 04/10/2023] [Indexed: 01/06/2024]
Abstract
We present an additive approach for the inverse design of kirigami-based mechanical metamaterials by focusing on the empty (negative) spaces instead of the solid tiles. By considering each negative space as a four-bar linkage, we identify a simple recursive relationship between adjacent linkages, yielding an efficient method for creating kirigami patterns. This allows us to solve the kirigami design problem using elementary linear algebra, with compatibility, reconfigurability and rigid-deployability encoded into an iterative procedure involving simple matrix multiplications. The resulting linear design strategy circumvents the solution of a non-convex global optimization problem and allows us to control the degrees of freedom in the deployment angle field, linkage offsets and boundary conditions. We demonstrate this by creating a large variety of rigid-deployable, compact, reconfigurable kirigami patterns. We then realize our kirigami designs physically using two simple but effective fabrication strategies with very different materials. Altogether, our additive approaches present routes for efficient mechanical metamaterial design and fabrication based on ori/kirigami art forms.
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Affiliation(s)
- Levi H Dudte
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Gary P T Choi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kaitlyn P Becker
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
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11
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Chan CU, Xiong F, Michaut A, Vidigueira JMN, Pourquié O, Mahadevan L. Direct force measurement and loading on developing tissues in intact avian embryos. Development 2023; 150:dev201054. [PMID: 37070753 PMCID: PMC10259510 DOI: 10.1242/dev.201054] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 04/06/2023] [Indexed: 04/19/2023]
Abstract
Developmental morphogenesis is driven by tissue stresses acting on tissue rheology. Direct measurements of forces in small tissues (100 µm-1 mm) in situ, such as in early embryos, require high spatial precision and minimal invasiveness. Here, we introduce a control-based approach, tissue force microscopy (TiFM), that integrates a mechanical cantilever probe and live imaging with closed-loop feedback control of mechanical loading in early chicken embryos. By testing previously qualitatively characterized force-producing tissues in the elongating body axis, we show that TiFM quantitatively captures stress dynamics with high sensitivity. TiFM also provides the means to apply stable, minimally invasive and physiologically relevant loads to drive tissue deformation and to follow the resulting morphogenetic progression associated with large-scale cell movements. Together, TiFM allows us to control tissue force measurement and manipulation in small developing embryos, and promises to contribute to the quantitative understanding of complex multi-tissue mechanics during development.
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Affiliation(s)
- Chon U. Chan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Institute of Molecular and Cell Biology, A*STAR, Singapore 138673
| | - Fengzhu Xiong
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Pathology, Brigham Women's Hospital and Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wellcome Trust/CRUK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK
| | - Arthur Michaut
- Department of Pathology, Brigham Women's Hospital and Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | | | - Olivier Pourquié
- Department of Pathology, Brigham Women's Hospital and Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - L. Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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12
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Choi GPT, Liu L, Mahadevan L. Explosive rigidity percolation in kirigami. Proc Math Phys Eng Sci 2023. [DOI: 10.1098/rspa.2022.0798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023] Open
Abstract
Controlling the connectivity and rigidity of kirigami, i.e. the process of cutting paper to deploy it into an articulated system, is critical in the manifestations of kirigami in art, science and technology, as it provides the resulting metamaterial with a range of mechanical and geometric properties. Here, we combine deterministic and stochastic approaches for the control of rigidity in kirigami using the power of
k
choices, an approach borrowed from the statistical mechanics of explosive percolation transitions. We show that several methods for rigidifying a kirigami system by incrementally changing either the connectivity or the rigidity of individual components allow us to control the nature of the explosive transition by a choice of selection rules. Our results suggest simple lessons for the design of mechanical metamaterials.
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13
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Dixit T, Choi GPT, Al-Mosleh S, Lund J, Troscianko J, Moya C, Mahadevan L, Spottiswoode CN. Combined measures of mimetic fidelity explain imperfect mimicry in a brood parasite-host system. Biol Lett 2023; 19:20220538. [PMID: 36789542 PMCID: PMC9929498 DOI: 10.1098/rsbl.2022.0538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
The persistence of imperfect mimicry in nature presents a challenge to mimicry theory. Some hypotheses for the existence of imperfect mimicry make differing predictions depending on how mimetic fidelity is measured. Here, we measure mimetic fidelity in a brood parasite-host system using both trait-based and response-based measures of mimetic fidelity. Cuckoo finches Anomalospiza imberbis lay imperfectly mimetic eggs that lack the fine scribbling characteristic of eggs of the tawny-flanked prinia Prinia subflava, a common host species. A trait-based discriminant analysis based on Minkowski functionals-that use geometric and topological morphometric methods related to egg pattern shape and coverage-reflects this consistent difference between host and parasite eggs. These methods could be applied to quantify other phenotypes including stripes and waved patterns. Furthermore, by painting scribbles onto cuckoo finch eggs and testing their rate of rejection compared to control eggs (i.e. a response-based approach to quantify mimetic fidelity), we show that prinias do not discriminate between eggs based on the absence of scribbles. Overall, our results support relaxed selection on cuckoo finches to mimic scribbles, since prinias do not respond differently to eggs with and without scribbles, despite the existence of this consistent trait difference.
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Affiliation(s)
- Tanmay Dixit
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Gary P T Choi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Salem Al-Mosleh
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Jess Lund
- Department of Zoology, University of Cambridge, Cambridge, UK.,DST-NRF Centre of Excellence at the FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch, Cape Town, South Africa
| | - Jolyon Troscianko
- Centre for Ecology and Conservation, University of Exeter, Penryn, UK
| | | | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.,Department of Physics, Harvard University, Cambridge, MA, USA.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Claire N Spottiswoode
- Department of Zoology, University of Cambridge, Cambridge, UK.,DST-NRF Centre of Excellence at the FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch, Cape Town, South Africa
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14
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Elosegui-Artola A, Gupta A, Najibi AJ, Seo BR, Garry R, Tringides CM, de Lázaro I, Darnell M, Gu W, Zhou Q, Weitz DA, Mahadevan L, Mooney DJ. Matrix viscoelasticity controls spatiotemporal tissue organization. Nat Mater 2023; 22:117-127. [PMID: 36456871 DOI: 10.1038/s41563-022-01400-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 10/07/2022] [Indexed: 06/17/2023]
Abstract
Biomolecular and physical cues of the extracellular matrix environment regulate collective cell dynamics and tissue patterning. Nonetheless, how the viscoelastic properties of the matrix regulate collective cell spatial and temporal organization is not fully understood. Here we show that the passive viscoelastic properties of the matrix encapsulating a spheroidal tissue of breast epithelial cells guide tissue proliferation in space and in time. Matrix viscoelasticity prompts symmetry breaking of the spheroid, leading to the formation of invading finger-like protrusions, YAP nuclear translocation and epithelial-to-mesenchymal transition both in vitro and in vivo in a Arp2/3-complex-dependent manner. Computational modelling of these observations allows us to establish a phase diagram relating morphological stability with matrix viscoelasticity, tissue viscosity, cell motility and cell division rate, which is experimentally validated by biochemical assays and in vitro experiments with an intestinal organoid. Altogether, this work highlights the role of stress relaxation mechanisms in tissue growth dynamics, a fundamental process in morphogenesis and oncogenesis.
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Affiliation(s)
- Alberto Elosegui-Artola
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
- Institute for Bioengineering of Catalonia, Barcelona, Spain
- Cell and Tissue Mechanobiology Laboratory, Francis Crick Institute, London, UK
- Department of Physics, King's College London, London, UK
| | - Anupam Gupta
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad, India
| | - Alexander J Najibi
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
| | - Bo Ri Seo
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
| | - Ryan Garry
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Christina M Tringides
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
- Harvard Program in Biophysics, Harvard University, Cambridge, MA, USA
- Harvard-MIT Division in Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Irene de Lázaro
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
| | - Max Darnell
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA
| | - Wei Gu
- Weill Cornell Medicine, Cornell University, New York, NY, USA
| | - Qiao Zhou
- Weill Cornell Medicine, Cornell University, New York, NY, USA
| | - David A Weitz
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - L Mahadevan
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
- Department of Physics, Harvard University, Cambridge, MA, USA.
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
| | - David J Mooney
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
- Wyss Institute for Biologically Inspired Engineering, Cambridge, MA, USA.
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15
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Ganga Prasath S, Mahadevan L. Rheomergy
: collective behaviour mediated by active flow-based recruitment. Proc Math Phys Eng Sci 2023. [DOI: 10.1098/rspa.2022.0470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The physics of signal propagation in a collection of organisms that communicate with each other both enables and limits how active excitations at the individual level reach, recruit and lead to collective patterning. Inspired by the spatio-temporal patterns in a planar swarm of bees that use pheromones and fanning flows to recruit additional bees, we develop a theoretical framework for patterning via active flow-based recruitment. Our model generalizes the well-known Patlak–Keller–Segel model of diffusion dominated aggregation and leads to an enhanced phase space of patterns spanned by two dimensionless parameters that measure the scaled stimulus/activity and the scaled chemotactic response. Together these determine the efficacy of signal communication via fluid flow (which we dub
rheomergy
) that leads to a variety of migration and aggregation patterns, consistent with observations.
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Affiliation(s)
- S. Ganga Prasath
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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16
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Memet E, Farrell B, Mahadevan L. An allometric prior enhances acoustic niche partitioning signal. J R Soc Interface 2022; 19:20220421. [PMID: 36514889 PMCID: PMC9748494 DOI: 10.1098/rsif.2022.0421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The acoustic niche hypothesis suggests that vocal signals of sympatric animal species are structured so as to minimize acoustic interference and facilitate communication. Accordingly, each species attempts to establish its own acoustic bandwidth so that intra-species signals are not masked. Detecting a non-random partitioning of the frequency spectrum among sympatric species could constitute evidence for the existence of acoustic avoidance behaviour. However, results from previous studies have been mixed or inconclusive, possibly as a consequence of overlooking the importance of physiological and ecological constraints. Here we introduce an improved test that incorporates prior information on body mass to account for the allometric correlation between mass (size) and vocalization frequency. By correcting for the bias induced by this correlation, the new test uncovers evidence of acoustic niche partitioning as a function of frequency in several tropical bird communities that would not be detected under a more standard test. Separately, we introduce a spatial version of the acoustic partitioning test which, in theory, could prove effective when data are collected from multiple sites located in close spatial proximity.
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Affiliation(s)
- Edvin Memet
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Brian Farrell
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA,Department of Physics, Harvard University, Cambridge, MA 02138, USA
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17
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Swaminathan K, Tolkova I, Baker L, Arumukhom Revi D, Awad LN, Walsh CJ, Mahadevan L. A continuous statistical-geometric framework for normative and impaired gaits. J R Soc Interface 2022; 19:20220402. [PMID: 36321374 PMCID: PMC9627451 DOI: 10.1098/rsif.2022.0402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023] Open
Abstract
A quantitative analysis of human gait patterns in space-time provides an opportunity to observe variability within and across individuals of varying motor capabilities. Impaired gait significantly affects independence and quality of life, and thus a large part of clinical research is dedicated to improving gait through rehabilitative therapies. Evaluation of these paradigms relies on understanding the characteristic differences in the kinematics and underlying biomechanics of impaired and unimpaired locomotion, which has motivated quantitative measurement and analysis of the gait cycle. Previous analysis has largely been limited to a statistical comparison of manually selected pointwise metrics identified through expert knowledge. Here, we use a recent statistical-geometric framework, elastic functional data analysis (FDA), to decompose kinematic data into continuous 'amplitude' (spatial) and 'phase' (temporal) components, which can then be integrated with established dimensionality reduction techniques. We demonstrate the utility of elastic FDA through two unsupervised applications to post-stroke gait datasets. First, we distinguish between unimpaired, paretic and non-paretic gait presentations. Then, we use FDA to reveal robust, interpretable groups of differential response to exosuit assistance. The proposed methods aim to benefit clinical practice for post-stroke gait rehabilitation, and more broadly, to automate the quantitative analysis of motion.
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Affiliation(s)
- Krithika Swaminathan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Irina Tolkova
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Lauren Baker
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Dheepak Arumukhom Revi
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA, USA
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
| | - Louis N. Awad
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA, USA
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
| | - Conor J. Walsh
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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18
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MacQueen LA, Sheehy SP, Chantre CO, Zimmerman JF, Pasqualini FS, Liu X, Goss JA, Campbell PH, Gonzalez GM, Park SJ, Capulli AK, Ferrier JP, Kosar TF, Mahadevan L, Pu WT, Parker KK. Addendum: A tissue-engineered scale model of the heart ventricle. Nat Biomed Eng 2022; 6:1318. [PMID: 35260798 DOI: 10.1038/s41551-022-00854-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Luke A MacQueen
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Sean P Sheehy
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Christophe O Chantre
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - John F Zimmerman
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Francesco S Pasqualini
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Xujie Liu
- Department of Cardiology, Boston Children's Hospital, Boston, MA, USA
| | - Josue A Goss
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Patrick H Campbell
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Grant M Gonzalez
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Sung-Jin Park
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Andrew K Capulli
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - John P Ferrier
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - T Fettah Kosar
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
| | - L Mahadevan
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - William T Pu
- Department of Cardiology, Boston Children's Hospital, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Kevin Kit Parker
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA.
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19
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Vafa F, Mahadevan L. Active Nematic Defects and Epithelial Morphogenesis. Phys Rev Lett 2022; 129:098102. [PMID: 36083666 DOI: 10.1103/physrevlett.129.098102] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 04/11/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Inspired by recent experiments that highlight the role of nematic defects in the morphogenesis of epithelial tissues, we develop a minimal framework to study the dynamics of an active curved surface driven by its nematic texture. Allowing the surface to evolve via relaxational dynamics leads to a theory linking nematic defect dynamics, cellular division rates, and Gaussian curvature. Regions of large positive (negative) curvature and positive (negative) growth are colocalized with the presence of positive (negative) defects. In an ex-vivo setting of cultured murine neural progenitor cells, we show that our framework is consistent with the observed cell accumulation at positive defects and depletion at negative defects. In an in-vivo setting, we show that the defect configuration consisting of a bound +1 defect state, which is stabilized by activity, surrounded by two -1/2 defects can create a stationary ring configuration of tentacles, consistent with observations of a basal marine invertebrate Hydra.
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Affiliation(s)
- Farzan Vafa
- Department of Physics, University of California Santa Barbara, Santa Barbara, California 93106, USA
- Center of Mathematical Sciences and Applications, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Departments of Physics, and Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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20
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Abstract
Geometric graph models of systems as diverse as proteins, DNA assemblies, architected materials and robot swarms are useful abstract representations of these objects that also unify ways to study their properties and control them in space and time. While much work has been done in the context of characterizing the behaviour of these networks close to critical points associated with bond and rigidity percolation, isostaticity, etc., much less is known about floppy, underconstrained networks that are far more common in nature and technology. Here, we combine geometric rigidity and algebraic sparsity to provide a framework for identifying the zero energy floppy modes via a representation that illuminates the underlying hierarchy and modularity of the network and thence the control of its nestedness and locality. Our framework allows us to demonstrate a range of applications of this approach that include robotic reaching tasks with motion primitives, and predicting the linear and nonlinear response of elastic networks based solely on infinitesimal rigidity and sparsity, which we test using physical experiments. Our approach is thus likely to be of use broadly in dissecting the geometrical properties of floppy networks using algebraic sparsity to optimize their function and performance.
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Affiliation(s)
- Siheng Chen
- School of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138, USA
| | - Fabio Giardina
- School of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138, USA
| | - Gary P. T. Choi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge MA 02139, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge MA 02138, USA
- Department of Physics, Harvard University, Cambridge MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge MA 02138, USA
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21
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Serra M, Al-Mosleh S, Prasath G, Raju V, Mantena S, Chandra J, Iams S, Mahadevan L. Optimal policies for mitigating pandemic costs: a minimal model. Phys Biol 2022; 19. [PMID: 35790172 DOI: 10.1088/1478-3975/ac7e9e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 07/05/2022] [Indexed: 11/11/2022]
Abstract
There have been a number of pharmaceutical and non-pharmaceutical interventions associated with COVID-19 over the past two years. Of the various non-pharmaceutical interventions that were proposed and implemented to control the spread of the COVID-19 pandemic partial and complete lockdowns were used repeatedly in an attempt to minimize the costs associated with mortality, economic losses and social factors, while being subject to constraints such as finite hospital capacity. Here, we use a minimal model to understand the costs and benefits of these strategies that mitigate pandemic costs subject to constraints, we adopt the language of optimal control theory. This allows us to determine top-down policies for the nature and dynamics of social contact rates given an age-structured model for the dynamics of the disease. Depending on the relative weights allocated to mortality and socioeconomic losses, we see that the optimal strategies range from long-term social-distancing only for the most vulnerable, to partial lockdown to ensure not over-running hospitals, to alternating-shifts with significant reduction in mortality and/or socioeconomic losses. Crucially, commonly used strategies that involve long periods of broad lockdown are almost never optimal, as they are highly unstable to reopening {and entail high socioeconomic costs}. Using parameter estimates from data available for Germany and the USA early in the pandemic, we quantify these policies and use sensitivity analysis in the relevant model parameters and initial conditions to determine the range of robustness of our policies. Finally we also discuss how bottom-up behavioral changes affect the dynamics of the pandemic and show they can work in tandem with top-down control policies to mitigate pandemic costs even more effectively.
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Affiliation(s)
- Mattia Serra
- Harvard University, Pierce Hall, Cambridge, Cambridge, 02138, UNITED STATES
| | - Salem Al-Mosleh
- School of Engineering and Applied Sciences, Harvard University, Pierce Hall, Cambridge, Cambridge, 02138, UNITED STATES
| | - Ganga Prasath
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, Cambridge, Massachusetts, 02138, UNITED STATES
| | - Vidya Raju
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, Cambridge, Massachusetts, 02138, UNITED STATES
| | - Sreekar Mantena
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, Cambridge, 02138, UNITED STATES
| | - Jay Chandra
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, 02138, UNITED STATES
| | - Sarah Iams
- Harvard University, 29 Oxford Street, Cambridge, 02138, UNITED STATES
| | - L Mahadevan
- Harvard University, 29 Oxford Street, Cambridge, Massachusetts, 02138, UNITED STATES
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22
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Cram DL, van der Wal JEM, Uomini N, Cantor M, Afan AI, Attwood MC, Amphaeris J, Balasani F, Blair CJ, Bronstein JL, Buanachique IO, Cuthill RRT, Das J, Daura‐Jorge FG, Deb A, Dixit T, Dlamini GS, Dounias E, Gedi II, Gruber M, Hoffmann LS, Holzlehner T, Isack HA, Laltaika EA, Lloyd‐Jones DJ, Lund J, Machado AMS, Mahadevan L, Moreno IB, Nwaogu CJ, Pierotti R, Rucunua SA, dos Santos WF, Serpa N, Smith BD, Sridhar H, Tolkova I, Tun T, Valle‐Pereira JVS, Wood BM, Wrangham RW, Spottiswoode CN. The ecology and evolution of human‐wildlife cooperation. People and Nature 2022. [DOI: 10.1002/pan3.10369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
| | - Jessica E. M. van der Wal
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Natalie Uomini
- Max Planck Institute for Evolutionary Anthropology Leipzig Germany
| | - Mauricio Cantor
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianópolis Brazil
- Department of Fisheries Wildlife and Conservation Sciences, Marine Mammal Institute, Oregon State University Newport Oregon USA
- Department for the Ecology of Animal Societies Max Planck Institute of Animal Behavior Radolfzell Germany
- Centre of Marine Studies Universidade Federal do Paraná Pontal do Paraná Brazil
| | - Anap I. Afan
- A.P. Leventis Ornithological Research Institute University of Jos Jos Nigeria
| | | | - Jenny Amphaeris
- School of Arts Culture and Language, Bangor University Bangor UK
| | | | - Cameron J. Blair
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Judith L. Bronstein
- Department of Ecology & Evolutionary Biology University of Arizona Tucson Arizona USA
| | | | - Rion R. T. Cuthill
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Jewel Das
- Institute of Marine Sciences University of Chittagong Chittagong Bangladesh
| | - Fábio G. Daura‐Jorge
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianópolis Brazil
| | - Apurba Deb
- Department of Environment, Climate and Parks Government of Manitoba Manitoba Canada
| | - Tanmay Dixit
- Department of Zoology University of Cambridge Cambridge UK
| | | | - Edmond Dounias
- CEFE, Univ Montpellier, CNRS, EPHE, IRD Montpellier France
| | | | - Martin Gruber
- Department of Anthropology and Cultural Research University of Bremen Bremen Germany
| | - Lilian S. Hoffmann
- Cytogenetics and Evolution Lab Instituto de Biociências, Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Tobias Holzlehner
- Seminar für Ethnologie Martin‐Luther‐University Halle‐Wittenberg Halle Germany
| | | | - Eliupendo A. Laltaika
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
- Ngorongoro Conservation Area Authority Ngorongoro Tanzania
| | - David J. Lloyd‐Jones
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Jess Lund
- Department of Zoology University of Cambridge Cambridge UK
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Alexandre M. S. Machado
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianópolis Brazil
| | - L. Mahadevan
- Department of Physics Harvard University Cambridge Massachusetts USA
- School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts USA
- Department of Organismic and Evolutionary Biology Harvard University Cambridge Massachusetts USA
| | - Ignacio B. Moreno
- Centro de Estudos Costeiros Limnológicos e Marinhos, Campus Litoral Norte, Universidade Federal do Rio Grande do Sul Imbé Brazil
- Programa de Pós‐Graduação em Biologia Animal Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Chima J. Nwaogu
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
| | - Raymond Pierotti
- Department of Ecology & Evolutionary Biology University of Kansas Lawrence Kansas USA
| | | | | | - Nathalia Serpa
- Centro de Estudos Costeiros Limnológicos e Marinhos, Campus Litoral Norte, Universidade Federal do Rio Grande do Sul Imbé Brazil
- Programa de Pós‐Graduação em Biologia Animal Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | | | - Hari Sridhar
- Independent Researcher Bengaluru Karnataka India
| | - Irina Tolkova
- School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts USA
| | | | | | - Brian M. Wood
- Department of Anthropology University of California Los Angeles USA
- Department of Human Behavior Ecology, and Culture, Max Planck Institute for Evolutionary Anthropology Leipzig Germany
| | - Richard W. Wrangham
- Department of Human Evolutionary Biology Harvard University Cambridge Massachusetts USA
| | - Claire N. Spottiswoode
- Department of Zoology University of Cambridge Cambridge UK
- FitzPatrick Institute of African Ornithology Department of Science and Innovation‐National Research Foundation Centre of Excellence, University of Cape Town Cape Town South Africa
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23
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van der Wal JEM, Spottiswoode CN, Uomini NT, Cantor M, Daura‐Jorge FG, Afan AI, Attwood MC, Amphaeris J, Balasani F, Begg CM, Blair CJ, Bronstein JL, Buanachique IO, Cuthill RRT, Das J, Deb A, Dixit T, Dlamini GS, Dounias E, Gedi II, Gruber M, Hoffmann LS, Holzlehner T, Isack HA, Laltaika EA, Lloyd‐Jones DJ, Lund J, Machado AMS, Mahadevan L, Moreno IB, Nwaogu CJ, Pereira VL, Pierotti R, Rucunua SA, dos Santos WF, Serpa N, Smith BD, Tolkova I, Tun T, Valle‐Pereira JVS, Wood BM, Wrangham RW, Cram DL. Safeguarding human–wildlife cooperation. Conserv Lett 2022; 15:e12886. [PMID: 36248252 PMCID: PMC9540276 DOI: 10.1111/conl.12886] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 03/19/2022] [Accepted: 04/10/2022] [Indexed: 01/07/2023] Open
Abstract
Human–wildlife cooperation occurs when humans and free‐living wild animals actively coordinate their behavior to achieve a mutually beneficial outcome. These interactions provide important benefits to both the human and wildlife communities involved, have wider impacts on the local ecosystem, and represent a unique intersection of human and animal cultures. The remaining active forms are human–honeyguide and human–dolphin cooperation, but these are at risk of joining several inactive forms (including human–wolf and human–orca cooperation). Human–wildlife cooperation faces a unique set of conservation challenges, as it requires multiple components—a motivated human and wildlife partner, a suitable environment, and compatible interspecies knowledge—which face threats from ecological and cultural changes. To safeguard human–wildlife cooperation, we recommend: (i) establishing ethically sound conservation strategies together with the participating human communities; (ii) conserving opportunities for human and wildlife participation; (iii) protecting suitable environments; (iv) facilitating cultural transmission of traditional knowledge; (v) accessibly archiving Indigenous and scientific knowledge; and (vi) conducting long‐term empirical studies to better understand these interactions and identify threats. Tailored safeguarding plans are therefore necessary to protect these diverse and irreplaceable interactions. Broadly, our review highlights that efforts to conserve biological and cultural diversity should carefully consider interactions between human and animal cultures. Please see AfricanHoneyguides.com/abstract‐translations for Kiswahili and Portuguese translations of the abstract.
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Affiliation(s)
- Jessica E. M. van der Wal
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
| | - Claire N. Spottiswoode
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
- Department of Zoology University of Cambridge Cambridge UK
| | | | - Mauricio Cantor
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianopolis Brazil
- Department of Fisheries, Wildlife and Conservation Sciences, Marine Mammal Institute Oregon State University Corvallis Oregon USA
- Department for the Ecology of Animal Societies Max Planck Institute of Animal Behavior Radolfzell Germany
- Centre of Marine Studies Universidade Federal do Paraná Curitiba Brazil
| | - Fábio G. Daura‐Jorge
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianopolis Brazil
| | - Anap I. Afan
- A.P. Leventis Ornithological Research Institute University of Jos Jos Nigeria
| | | | - Jenny Amphaeris
- School of Arts, Culture and Language Bangor University Bangor UK
| | | | - Colleen M. Begg
- Niassa Carnivore Project TRT Conservation Foundation Cape Town South Africa
| | - Cameron J. Blair
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
| | - Judith L. Bronstein
- Department of Ecology & Evolutionary Biology University of Arizona Tucson Arizona USA
| | | | - Rion R. T. Cuthill
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
| | - Jewel Das
- Institute of Marine Sciences University of Chittagong Chittagong Bangladesh
| | - Apurba Deb
- Department of Conservation and Climate Government of Manitoba Winnipeg Manitoba Canada
| | - Tanmay Dixit
- Department of Zoology University of Cambridge Cambridge UK
| | | | - Edmond Dounias
- CEFE Univ Montpellier, CNRS, EPHE, IRD Montpellier France
| | | | - Martin Gruber
- Department of Anthropology and Cultural Research University of Bremen Bremen Germany
| | - Lilian S. Hoffmann
- Cytogenetics and Evolution Lab, Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Tobias Holzlehner
- Seminar für Ethnologie Martin‐Luther‐University Halle‐Wittenberg Halle Germany
| | | | - Eliupendo A. Laltaika
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
- Ngorongoro Conservation Area Authority Ngorongoro Tanzania
| | - David J. Lloyd‐Jones
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
| | - Jess Lund
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
- Department of Zoology University of Cambridge Cambridge UK
| | - Alexandre M. S. Machado
- Department of Ecology and Zoology Universidade Federal de Santa Catarina Florianopolis Brazil
| | - L. Mahadevan
- Department of Physics Harvard University Boston Massachusetts USA
- School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts USA
- Department of Organismic and Evolutionary Biology Harvard University Cambridge Massachusetts USA
| | - Ignacio B. Moreno
- Centro de Estudos Costeiros, Limnológicos e Marinhos Universidade Federal do Rio Grande do Sul Imbé Brazil
- Programa de Pós‐Graduação em Biologia Animal Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Chima J. Nwaogu
- FitzPatrick Institute of African Ornithology, Department of Science and Innovation‐National Research Foundation Centre of Excellence University of Cape Town Cape Town South Africa
| | | | - Raymond Pierotti
- Department of Ecology & Evolutionary Biology University of Kansas Lawrence Kansas USA
| | | | | | - Nathalia Serpa
- Centro de Estudos Costeiros, Limnológicos e Marinhos Universidade Federal do Rio Grande do Sul Imbé Brazil
- Programa de Pós‐Graduação em Biologia Animal Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | | | - Irina Tolkova
- School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts USA
| | | | | | - Brian M. Wood
- Department of Anthropology University of California, Los Angeles Los Angeles California USA
- Department of Human Behavior, Ecology, and Culture Max Planck Institute for Evolutionary Anthropology Leipzig Germany
| | - Richard W. Wrangham
- Department of Human Evolutionary Biology Harvard University Cambridge Massachusetts USA
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24
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Adam I, Bagnoli F, Fanelli D, Mahadevan L, Paoletti P. Prestrain-induced contraction in one-dimensional random elastic chains. Phys Rev E 2022; 105:065002. [PMID: 35854552 DOI: 10.1103/physreve.105.065002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 05/04/2022] [Indexed: 06/15/2023]
Abstract
Prestrained elastic networks arise in a number of biological and technological systems ranging from the cytoskeleton of cells to tensegrity structures. Motivated by this observation, we here consider a minimal model in one dimension to set the stage for understanding the response of such networks as a function of the prestrain. To this end we consider a chain [one-dimensional (1D) network] of elastic springs upon which a random, zero mean, finite variance prestrain is imposed. Numerical simulations and analytical predictions quantify the magnitude of the contraction as a function of the variance of the prestrain, and show that the chain always shrinks. To test these predictions, we vary the topology of the chain, consider more complex connectivity and show that our results are relatively robust to these changes.
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Affiliation(s)
- Ihusan Adam
- Department of Information Engineering, University of Florence, Florence 50019, Italy
- Department of Physics and Astronomy, and CSDC, University of Florence, Sesto Fiorentino 50019, Italy
| | - Franco Bagnoli
- Department of Physics and Astronomy, and CSDC, University of Florence, Sesto Fiorentino 50019, Italy
- INFN, Florence Section, Sesto Fiorentino 50019, Italy
| | - Duccio Fanelli
- Department of Physics and Astronomy, and CSDC, University of Florence, Sesto Fiorentino 50019, Italy
- INFN, Florence Section, Sesto Fiorentino 50019, Italy
| | - L Mahadevan
- School of Engineering and Applied Sciences, Department of Physics, and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Paolo Paoletti
- School of Engineering, University of Liverpool, L69 3GH Liverpool, United Kingdom
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25
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Plumb-Reyes TB, Charles N, Mahadevan L. Combing a double helix. Soft Matter 2022; 18:2767-2775. [PMID: 35315468 DOI: 10.1039/d1sm01533h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Combing hair involves brushing away the topological tangles in a collective curl, defined as a bundle of interacting elastic filaments. Using a combination of experiment and computation, we study this problem that naturally links topology, geometry and mechanics. Observations show that the dominant interactions in hair are those of a two-body nature, corresponding to a braided homochiral double helix. This minimal model allows us to study the detangling of an elastic double helix driven by a single stiff tine that moves along it and leaves two untangled filaments in its wake. Our results quantify how the mechanics of detangling correlates with the dynamics of a topological quantity, the link density, that propagates ahead of the tine and flows out the free end as a link current. This in turn provides a measure of the maximum characteristic length of a single combing stroke in the many-body problem on a head of hair, producing an optimal combing strategy that balances trade-offs between comfort, efficiency and speed of combing in hair curls of varying geometrical and topological complexity.
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Affiliation(s)
- Thomas B Plumb-Reyes
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Nicholas Charles
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Departments of Physics and Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
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26
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Regev I, Guevorkian K, Gupta A, Pourquié O, Mahadevan L. Rectified random cell motility as a mechanism for embryo elongation. Development 2022; 149:274852. [PMID: 35344041 PMCID: PMC9017234 DOI: 10.1242/dev.199423] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 01/25/2022] [Indexed: 12/24/2022]
Abstract
ABSTRACT
The body of vertebrate embryos forms by posterior elongation from a terminal growth zone called the tail bud. The tail bud is a source of highly motile cells that eventually constitute the presomitic mesoderm (PSM), a tissue that plays an important role in elongation movements. PSM cells establish an anterior-posterior cell motility gradient that parallels a gradient associated with the degradation of a specific cellular signal (FGF) known to be implicated in cell motility. Here, we combine the electroporation of fluorescent reporters in the PSM with time-lapse imaging in the chicken embryo to quantify cell diffusive movements along the motility gradient. We show that a simple microscopic model for random cell motility induced by FGF activity along with geometric confinement leads to rectified tissue elongation consistent with our observations. A continuum analog of the microscopic model leads to a macroscopic mechano-chemical model for tissue extension that couples FGF activity-induced cell motility and tissue rheology, and is consistent with the experimentally observed speed and extent of elongation. Together, our experimental observations and theoretical models explain how the continuous addition of cells at the tail bud combined with lateral confinement can be converted into oriented movement and drive body elongation.
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Affiliation(s)
- Ido Regev
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Solar Energy and Environmental Physics, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel
| | - Karine Guevorkian
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Université de Strasbourg, CNRS, Inserm, Illkirch, France
- Harvard Medical School, Department of Genetics, Brigham and Women's Hospital, Department of Pathology, Boston, MA 02115, USA
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - Anupam Gupta
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Physics, Indian Institute of Technology Hyderabad, Telangana 502285, India
| | - Olivier Pourquié
- Harvard Medical School, Department of Genetics, Brigham and Women's Hospital, Department of Pathology, Boston, MA 02115, USA
| | - L. Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Physics and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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27
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Lee WK, Preston DJ, Nemitz MP, Nagarkar A, MacKeith AK, Gorissen B, Vasios N, Sanchez V, Bertoldi K, Mahadevan L, Whitesides GM. A buckling-sheet ring oscillator for electronics-free, multimodal locomotion. Sci Robot 2022; 7:eabg5812. [PMID: 35138883 DOI: 10.1126/scirobotics.abg5812] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Locomotion of soft robots typically relies on control of multiple inflatable actuators by electronic computers and hard valves. Soft pneumatic oscillators can reduce the demand on controllers by generating complex movements required for locomotion from a single, constant input pressure, but either have been constrained to low rates of flow of air or have required complex fabrication processes. Here, we describe a pneumatic oscillator fabricated from flexible, but inextensible, sheets that provides high rates of airflow for practical locomotion by combining three instabilities: out-of-plane buckling of the sheets, kinking of tubing attached to the sheets, and a system-level instability resulting from connection of an odd number of pneumatic inverters made from these sheets in a loop. This device, which we call a "buckling-sheet ring oscillator" (BRO), directly generates movement from its own interaction with its surroundings and consists only of readily available materials assembled in a simple process-specifically, stacking acetate sheets, nylon film, and double-sided tape, and attaching an elastomeric tube. A device incorporating a BRO is capable of both translational and rotational motion over varied terrain (even without a tether) and can climb upward against gravity and downward against the buoyant force encountered under water.
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Affiliation(s)
- Won-Kyu Lee
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Daniel J Preston
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.,Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA
| | - Markus P Nemitz
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.,Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA
| | - Amit Nagarkar
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Arthur K MacKeith
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
| | - Benjamin Gorissen
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
| | - Nikolaos Vasios
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
| | - Vanessa Sanchez
- Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA.,School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
| | - Katia Bertoldi
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA.,Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA.,Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
| | - George M Whitesides
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.,Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA.,Kavli Institute for Bionano Science and Technology, Harvard University, 29 Oxford Street, Cambridge, MA 02138, USA
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28
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Hart Y, Mahadevan L, Dillon MR. Euclid's Random Walk: Developmental Changes in the Use of Simulation for Geometric Reasoning. Cogn Sci 2022; 46:e13070. [PMID: 35085405 DOI: 10.1111/cogs.13070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 09/04/2021] [Accepted: 11/10/2021] [Indexed: 01/29/2023]
Abstract
Euclidean geometry has formed the foundation of architecture, science, and technology for millennia, yet the development of human's intuitive reasoning about Euclidean geometry is not well understood. The present study explores the cognitive processes and representations that support the development of humans' intuitive reasoning about Euclidean geometry. One-hundred-twenty-five 7- to 12-year-old children and 30 adults completed a localization task in which they visually extrapolated missing parts of fragmented planar triangles and a reasoning task in which they answered verbal questions about the general properties of planar triangles. While basic Euclidean principles guided even young children's visual extrapolations, only older children and adults reasoned about triangles in ways that were consistent with Euclidean geometry. Moreover, a relation beteen visual extrapolation and reasoning appeared only in older children and adults. Reasoning consistent with Euclidean geometry may thus emerge when children abandon incorrect, axiomatic-based reasoning strategies and come to reason using mental simulations of visual extrapolations.
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Affiliation(s)
- Yuval Hart
- Department of Psychology, The Hebrew University of Jerusalem.,Paulson School of Engineering and Applied Sciences, Harvard University
| | - L Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University.,Department of Physics, Harvard University.,Center for Brain Science, Harvard University.,Department of Organismic and Evolutionary Biology, Harvard University
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29
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Nadir Kaplan C, Mahadevan L. Geometrical dynamics of edge-driven accretive surface growth. Proc Math Phys Eng Sci 2022. [DOI: 10.1098/rspa.2021.0638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Accretion of mineralized thin wall-like structures via localized growth along their edges is observed in physical and biological systems ranging from molluscan and brachiopod shells to carbonate–silica composite precipitates. To understand the shape of these mineralized structures, we develop a mathematical framework that treats the thin-walled shells as a smooth surface left in the wake of the growth front that can be described as an evolving space curve. Our theory then takes an explicit geometric form for the prescription of the velocity of the growth front curve, along with compatibility relations and a closure equation related to the nature of surface curling. Solutions of these equations capture a range of geometric precipitate patterns seen in abiotic and biotic forms across scales. In addition to providing a framework for the growth and form of these thin-walled morphologies, our theory suggests a new class of dynamical systems involving moving space curves that are compatible with non-Euclidean embeddings of surfaces.
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Affiliation(s)
- C. Nadir Kaplan
- Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
- Center for Soft Matter and Biological Physics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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30
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Prasath SG, Mandal S, Giardina F, Kennedy J, Murthy VN, Mahadevan L. Dynamics of cooperative excavation in ant and robot collectives. eLife 2022; 11:79638. [PMID: 36214457 PMCID: PMC9894586 DOI: 10.7554/elife.79638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 10/07/2022] [Indexed: 02/07/2023] Open
Abstract
The solution of complex problems by the collective action of simple agents in both biologically evolved and synthetically engineered systems involves cooperative action. Understanding the resulting emergent solutions requires integrating across the organismal behavior of many individuals. Here, we investigate an ecologically relevant collective task in black carpenter ants Camponotus pennsylvanicus: excavation of a soft, erodible confining corral. These ants show a transition from individual exploratory excavation at random locations to spatially localized collective exploitative excavation and escape from the corral. Agent-based simulations and a minimal continuum theory that coarse-grains over individual actions and considers their integrated influence on the environment leads to the emergence of an effective phase space of behaviors, characterized in terms of excavation strength and cooperation intensity. To test the theory over the range of both observed and predicted behaviors, we use custom-built robots (RAnts) that respond to stimuli to characterize the phase space of emergence (and failure) of cooperative excavation. Tuning the amount of cooperation between RAnts, allows us to vary the efficiency of excavation and synthetically generate the entire range of macroscopic phases predicted by our theory. Overall, our approach shows how the cooperative completion of tasks can arise from simple rules that involve the interaction of agents with a dynamically changing environment that serves as both an enabler and a modulator of behavior.
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Affiliation(s)
- S Ganga Prasath
- School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
| | - Souvik Mandal
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States,Center for Brain Science, Harvard UniversityCambridgeUnited States
| | - Fabio Giardina
- School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
| | - Jordan Kennedy
- School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States
| | - Venkatesh N Murthy
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States,Center for Brain Science, Harvard UniversityCambridgeUnited States
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard UniversityCambridgeUnited States,Center for Brain Science, Harvard UniversityCambridgeUnited States,Department of Physics, Harvard UniversityCambridgeUnited States,Department of Organismic and Evolutionary Biology, Harvard UniversityCambridgeUnited States
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31
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Peters JM, Peleg O, Mahadevan L. Thermoregulatory morphodynamics of honeybee swarm clusters. J Exp Biol 2021; 225:273815. [PMID: 34931657 DOI: 10.1242/jeb.242234] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 11/29/2021] [Indexed: 11/20/2022]
Abstract
During reproductive swarming, honeybees clusters of more than 10,000 individuals that hang from structures in the environment (e.g., tree branches) are exposed to diurnal variations in ambient temperature for up to a week. Swarm clusters collectively modulate their morphology in response to these variations (i.e., expanding/contracting in response to heating/cooling) to maintain their internal temperature within a tolerable range and to avoid exhausting their honey stores prematurely. To understand the spatiotemporal aspects of thermoregulatory morphing, we measured the change in size, shape and internal temperature profiles of swarm clusters in response to dynamic temperature ramp perturbations. We see that swarm clusters show a two-fold variation in their volume/density when heated from 15°C to 30°C. However, they do not reach an equilibrium size or shape when held at 30°C for 5 hours, long after the core temperature of the cluster has stabilized. Furthermore, the changes in cluster shape and size are hysteretic, contracting in response to cooling faster than expanding in response to heating. Although the base contact diameter of the cluster increased continuously when the swarm is heated, the change in length of the swarm (base totip) over time is non-monotonic. Consequently, the aspect ratio of the swarm fluctuated continuously even when held at a constant temperature. Taken together, our results quantify the hysteretic and anisotropic morphological responses of swarm clusters to ambient temperature variations while suggesting that both mechanical constraints and heat transfer govern their thermoregulatory morphodynamics.
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Affiliation(s)
- Jacob M Peters
- OEB, Harvard University, Cambridge, MA 02138, USA.,SEAS, Harvard University, Cambridge, MA 02138, USA
| | - Orit Peleg
- BioFrontiers Institute, University of Colorado, Boulder, CO 80309, USA.,Santa Fe Institute, Santa Fe, NM 87501, USA
| | - L Mahadevan
- OEB, Harvard University, Cambridge, MA 02138, USA.,SEAS, Harvard University, Cambridge, MA 02138, USA.,Department of Physics, Harvard University, Cambridge, MA 02138, USA
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32
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Chakrabarti A, Al-Mosleh S, Mahadevan L. Instabilities and patterns in a submerged jelling jet. Soft Matter 2021; 17:9745-9754. [PMID: 34647567 DOI: 10.1039/d1sm00517k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
When a thin stream of aqueous sodium alginate is extruded into a reacting calcium chloride bath, it polymerizes into a soft elastic tube that spontaneously forms helical coils due to the ambient fluid drag. We quantify the onset of this drag-induced instability and its nonlinear evolution using experiments, and explain the results using a combination of scaling, theory and simulations. By co-extruding a second (internal) liquid within the aqueous sodium alginate jet and varying the diameter of the jet and the rates of the co-extrusion of the two liquids, we show that we can tune the local composition of the composite filament and the nature of the ensuing instabilities to create soft filaments of variable relative buoyancy, shape and mechanical properties. Altogether, by harnessing the fundamental varicose (jetting) and sinuous (buckling) instabilities associated with the extrusion of a submerged jelling filament, we show that it is possible to print complex three-dimensional filamentous structures in an ambient fluid.
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Affiliation(s)
- Aditi Chakrabarti
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
| | - Salem Al-Mosleh
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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33
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Abstract
The self-assembly of peptides and proteins into amyloid fibrils plays a causative role in a wide range of increasingly common and currently incurable diseases. The molecular mechanisms underlying this process have recently been discovered, prompting the development of drugs that inhibit specific reaction steps as possible treatments for some of these disorders. A crucial part of treatment design is to determine how much drug to give and when to give it, informed by its efficacy and intrinsic toxicity. Since amyloid formation does not proceed at the same pace in different individuals, it is also important that treatment design is informed by local measurements of the extent of protein aggregation. Here, we use stochastic optimal control theory to determine treatment regimens for inhibitory drugs targeting several key reaction steps in protein aggregation, explicitly taking into account variability in the reaction kinetics. We demonstrate how these regimens may be updated "on the fly" as new measurements of the protein aggregate concentration become available, in principle, enabling treatments to be tailored to the individual. We find that treatment timing, duration, and drug dosage all depend strongly on the particular reaction step being targeted. Moreover, for some kinds of inhibitory drugs, the optimal regimen exhibits high sensitivity to stochastic fluctuations. Feedback controls tailored to the individual may therefore substantially increase the effectiveness of future treatments.
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Affiliation(s)
- Alexander J Dear
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Thomas C T Michaels
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Tuomas P J Knowles
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - L Mahadevan
- School of Engineering and Applied Sciences, Department of Physics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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34
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Abstract
Kirigami, the art of paper cutting, has become a paradigm for mechanical metamaterials in recent years. The basic building blocks of any kirigami structures are repetitive deployable patterns that derive inspiration from geometric art forms and simple planar tilings. Here, we complement these approaches by directly linking kirigami patterns to the symmetry associated with the set of 17 repeating patterns that fully characterize the space of periodic tilings of the plane. We start by showing how to construct deployable kirigami patterns using any of the wallpaper groups, and then design symmetry-preserving cut patterns to achieve arbitrary size changes via deployment. We further prove that different symmetry changes can be achieved by controlling the shape and connectivity of the tiles and connect these results to the underlying kirigami-based lattice structures. All together, our work provides a systematic approach for creating a broad range of kirigami-based deployable structures with any prescribed size and symmetry properties.
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Affiliation(s)
- Lucy Liu
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Gary P. T. Choi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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35
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Edwards MB, Choi GPT, Derieg NJ, Min Y, Diana AC, Hodges SA, Mahadevan L, Kramer EM, Ballerini ES. Genetic architecture of floral traits in bee- and hummingbird-pollinated sister species of Aquilegia (columbine). Evolution 2021; 75:2197-2216. [PMID: 34270789 DOI: 10.1111/evo.14313] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/21/2021] [Accepted: 06/25/2021] [Indexed: 01/24/2023]
Abstract
Interactions with animal pollinators have helped shape the stunning diversity of flower morphologies across the angiosperms. A common evolutionary consequence of these interactions is that some flowers have converged on suites of traits, or pollination syndromes, that attract and reward specific pollinator groups. Determining the genetic basis of these floral pollination syndromes can help us understand the processes that contributed to the diversification of the angiosperms. Here, we characterize the genetic architecture of a bee-to-hummingbird pollination shift in Aquilegia (columbine) using QTL mapping of 17 floral traits encompassing color, nectar composition, and organ morphology. In this system, we find that the genetic architectures underlying differences in floral color are quite complex, and we identify several likely candidate genes involved in anthocyanin and carotenoid floral pigmentation. Most morphological and nectar traits also have complex genetic underpinnings; however, one of the key floral morphological phenotypes, nectar spur curvature, is shaped by a single locus of large effect.
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Affiliation(s)
- Molly B Edwards
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Gary P T Choi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02142
| | - Nathan J Derieg
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Ya Min
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Angie C Diana
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Scott A Hodges
- Department of Ecology, Evolutionary, and Marine Biology, University of California Santa Barbara, Santa Babara, California, 93106
| | - L Mahadevan
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138.,School of Engineering & Applied Sciences, Harvard University, Cambridge, Massachusetts, 02138.,Department of Physics, Harvard University, Cambridge, Massachusetts, 02138
| | - Elena M Kramer
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Evangeline S Ballerini
- Department of Ecology, Evolutionary, and Marine Biology, University of California Santa Barbara, Santa Babara, California, 93106.,Dept. of Biological Sciences, California State University Sacramento, Sacramento, California, 95819
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36
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Abstract
Pattern formation driven by differential strain in constrained elastic systems is a common motif in many technological and biological systems. Here we introduce a biologically motivated case of elastic patterning that allows us to explore the conditions for the existence of local puckering and global wrinkling patterns: a soft growing composite ring adhered elastically to a constraining rigid ring. We explore how differential growth of the soft ring and the elastic resistance to shear and stretching deformations induced by soft adherence lead to a range of phenomena that include uniform aperture-like modes, localized puckers that are Nambu–Goldstone-like modes and global wrinkles in the system. Our analysis combines computer simulations of a discrete rod model with a nonlinear stability analysis of the differential equations in the continuum limit. We provide phase diagrams and scaling relations that reveal the nature and extent of the deformation patterns. Overall, our study reveals how geometry and mechanics conspire to yield a rich phenomenology that could serve as a guide to the design of programmable localized elastic deformations while being relevant for the mechanical basis of biological morphogenesis.
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Affiliation(s)
- T. C. T. Michaels
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - R. Kusters
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - L. Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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37
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Memet E, Hilitski F, Dogic Z, Mahadevan L. Static adhesion hysteresis in elastic structures. Soft Matter 2021; 17:2704-2710. [PMID: 33586756 DOI: 10.1039/d0sm02192j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Adhesive interactions between elastic structures such as graphene sheets, carbon nanotubes, and microtubules have been shown to exhibit hysteresis due to irrecoverable energy loss associated with bond breakage, even in static (rate-independent) experiments. To understand this phenomenon, we start with a minimal theory for the peeling of a thin sheet from a substrate, coupling the local event of bond breaking to the nonlocal elastic relaxation of the sheet and show that this can drive static adhesion hysteresis over a bonding/debonding cycle. Using this model we quantify hysteresis in terms of the adhesion and elasticity parameters of the system. This allows us to derive a scaling relation that preserves hysteresis at different levels of granularity while resolving a seeming paradox of lattice trapping in the continuum limit of a discrete fracture process. Finally, to verify our theory, we use new experiments to demonstrate and measure adhesion hysteresis in bundled microtubules.
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Affiliation(s)
- Edvin Memet
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Feodor Hilitski
- The Martin Fisher School of Physics, Brandeis University, Waltham, MA 02453, USA
| | - Zvonimir Dogic
- The Martin Fisher School of Physics, Brandeis University, Waltham, MA 02453, USA and Department of Physics, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| | - L Mahadevan
- Department of Physics, Harvard University, Cambridge, MA 02138, USA and School of Engineering and Applied Sciences, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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38
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Abstract
Walking is a common bipedal and quadrupedal gait and is often associated with terrestrial and aquatic organisms. Inspired by recent evidence of the neural underpinnings of primitive aquatic walking in the little skate Leucoraja erinacea, we introduce a theoretical model of aquatic walking that reveals robust and efficient gaits with modest requirements for body morphology and control. The model predicts undulatory behaviour of the system body with a regular foot placement pattern, which is also observed in the animal, and additionally predicts the existence of gait bistability between two states, one with a large energetic cost for locomotion and another associated with almost no energetic cost. We show that these can be discovered using a simple reinforcement learning scheme. To test these theoretical frameworks, we built a bipedal robot and show that its behaviours are similar to those of our minimal model: its gait is also periodic and exhibits bistability, with a low efficiency mode separated from a high efficiency mode by a 'jump' transition. Overall, our study highlights the physical constraints on the evolution of walking and provides a guide for the design of efficient biomimetic robots.
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Affiliation(s)
- F Giardina
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.,Department of Physics, Harvard University, Cambridge, MA, USA.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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39
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Abstract
Understanding the morphology of self-assembled fibrillar bundles and aggregates is relevant to a range of problems in molecular biology, supramolecular chemistry and materials science. Here, we propose a coarse-grained approach that averages over specific molecular details and yields an effective mechanical theory for the spatial complexity of self-assembling fibrillar structures that arises due to the competing effects of (the bending and twisting) elasticity of individual filaments and the adhesive interactions between them. We show that our theoretical framework accounting for this allows us to capture a number of diverse fibril morphologies observed in natural and synthetic systems, ranging from Filopodia to multi-walled carbon nanotubes, and leads to a phase diagram of possible fibril shapes. We also show how the extreme sensitivity of these morphologies can lead to spatially chaotic structures. Together, these results suggest a common mechanical basis for mesoscale fibril morphology as a function of the nanoscale mechanical properties of its filamentous constituents.
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Affiliation(s)
- Thomas C T Michaels
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Edvin Memet
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - L Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA and Department of Physics, Harvard University, Cambridge, MA 02138, USA and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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40
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Derr NJ, Fronk DC, Weber CA, Mahadevan A, Rycroft CH, Mahadevan L. Flow-Driven Branching in a Frangible Porous Medium. Phys Rev Lett 2020; 125:158002. [PMID: 33095596 DOI: 10.1103/physrevlett.125.158002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 08/18/2020] [Indexed: 06/11/2023]
Abstract
Channel formation and branching is widely seen in physical systems where movement of fluid through a porous structure causes the spatiotemporal evolution of the medium. We provide a simple theoretical framework that embodies this feedback mechanism in a multiphase model for flow through a frangible porous medium with a dynamic permeability. Numerical simulations of the model show the emergence of branched networks whose topology is determined by the geometry of external flow forcing. This allows us to delineate the conditions under which splitting and/or coalescing branched network formation is favored, with potential implications for both understanding and controlling branching in soft frangible media.
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Affiliation(s)
- Nicholas J Derr
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - David C Fronk
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Christoph A Weber
- Max Planck Institute for the Physics of Complex Systems, Dresden 01187, Germany
| | - Amala Mahadevan
- Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02450, USA
| | - Chris H Rycroft
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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41
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Abstract
Rectilinear crawling locomotion is a primitive and common mode of locomotion in slender soft-bodied animals. It requires coordinated contractions that propagate along a body that interacts frictionally with its environment. We propose a simple approach to understand how this coordination arises in a neuromechanical model of a segmented, soft-bodied crawler via an iterative process that might have both biological antecedents and technological relevance. Using a simple reinforcement learning algorithm, we show that an initial all-to-all neural coupling converges to a simple nearest-neighbour neural wiring that allows the crawler to move forward using a localized wave of contraction that is qualitatively similar to what is observed in Drosophila melanogaster larvae and used in many biomimetic solutions. The resulting solution is a function of how we weight gait regularization in the reward, with a trade-off between speed and robustness to proprioceptive noise. Overall, our results, which embed the brain-body-environment triad in a learning scheme, have relevance for soft robotics while shedding light on the evolution and development of locomotion.
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Affiliation(s)
- Shruti Mishra
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Wim M. van Rees
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - L. Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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42
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Virot E, Spandan V, Niu L, van Rees WM, Mahadevan L. Elastohydrodynamic Scaling Law for Heart Rates. Phys Rev Lett 2020; 125:058102. [PMID: 32794888 DOI: 10.1103/physrevlett.125.058102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 06/04/2020] [Indexed: 06/11/2023]
Abstract
Animal hearts are soft shells that actively pump blood to oxygenate tissues. Here, we propose an allometric scaling law for the heart rate based on the idea of elastohydrodynamic resonance of a fluid-loaded soft active elastic shell that buckles and contracts axially when twisted periodically. We show that this picture is consistent with numerical simulations of soft cylindrical shells that twist-buckle while pumping a viscous fluid, yielding optimum ejection fractions of 35%-40% when driven resonantly. Our scaling law is consistent with experimental measurements of heart rates over 2 orders of magnitude, and provides a mechanistic basis for how metabolism scales with organism size. In addition to providing a physical rationale for the heart rate and metabolism of an organism, our results suggest a simple design principle for soft fluidic pumps.
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Affiliation(s)
- E Virot
- John A. Paulson School of Engineering and Applied Sciences, Harvard University
| | - V Spandan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University
| | - L Niu
- Department of Physics, Harvard University, Cambridge, Massachusetts 02139, USA
| | - W M van Rees
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University
- Department of Physics, Harvard University, Cambridge, Massachusetts 02139, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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43
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Yodh JS, Spandan V, Mahadevan L. Suspension Jams in a Leaky Microfluidic Channel. Phys Rev Lett 2020; 125:044501. [PMID: 32794808 DOI: 10.1103/physrevlett.125.044501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 02/26/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
Inspired by the jamming in leaky systems that arises in many physiological and industrial settings, we study the propagation of clogs in a leaky microfluidic channel. By driving a colloidal suspension through such a channel with a fluid-permeable wall adjoining a gutter, we follow the formation and propagation of jams and show that they move at a steady speed, in contrast with jams in channels that have impermeable walls. Furthermore, by varying the ratio of the resistance from the leaky wall and that of the gutter, we show that it is possible to control the shape of the propagating jam, which is typically wedge shaped. We complement our experiments with numerical simulations, where we implement an Euler-Lagrangian framework for the simultaneous evolution of both immersed colloidal particles and the carrier fluid. Finally, we show that the particle ordering in the clog can be tuned by adjusting the geometry of the leaky wall. Altogether, the leaky channel serves both as a filter and a shunt with the potential for a range of uses.
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Affiliation(s)
- J S Yodh
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - V Spandan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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44
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Chakrabarti A, Choi GPT, Mahadevan L. Self-Excited Motions of Volatile Drops on Swellable Sheets. Phys Rev Lett 2020; 124:258002. [PMID: 32639784 DOI: 10.1103/physrevlett.124.258002] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 02/01/2020] [Accepted: 05/22/2020] [Indexed: 06/11/2023]
Abstract
When a volatile droplet is deposited on a floating swellable sheet, it becomes asymmetric, lobed and mobile. We describe and quantify this phenomena that involves nonequilibrium swelling, evaporation and motion, working together to realize a self-excitable spatially extended oscillator. Solvent penetration causes the film to swell locally and eventually buckle, changing its shape and the drop responds by moving. Simultaneously, solvent evaporation from the swollen film causes it to regain its shape once the droplet has moved away. The process repeats and leads to complex pulsatile spinning and/or sliding movements. We use a one-dimensional experiment to highlight the slow swelling of and evaporation from the film and the fast motion of the drop, a characteristic of excitable systems. Finally, we provide a phase diagram for droplet excitability as a function of drop size and film thickness and scaling laws for the motion of the droplet.
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Affiliation(s)
- Aditi Chakrabarti
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Gary P T Choi
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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45
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Huycke TR, Miller BM, Gill HK, Nerurkar NL, Sprinzak D, Mahadevan L, Tabin CJ. Genetic and Mechanical Regulation of Intestinal Smooth Muscle Development. Cell 2020; 179:90-105.e21. [PMID: 31539501 DOI: 10.1016/j.cell.2019.08.041] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 05/31/2019] [Accepted: 08/22/2019] [Indexed: 11/30/2022]
Abstract
The gastrointestinal tract is enveloped by concentric and orthogonally aligned layers of smooth muscle; however, an understanding of the mechanisms by which these muscles become patterned and aligned in the embryo has been lacking. We find that Hedgehog acts through Bmp to delineate the position of the circumferentially oriented inner muscle layer, whereas localized Bmp inhibition is critical for allowing formation of the later-forming, longitudinally oriented outer layer. Because the layers form at different developmental stages, the muscle cells are exposed to unique mechanical stimuli that direct their alignments. Differential growth within the early gut tube generates residual strains that orient the first layer circumferentially, and when formed, the spontaneous contractions of this layer align the second layer longitudinally. Our data link morphogen-based patterning to mechanically controlled smooth muscle cell alignment and provide a mechanistic context for potentially understanding smooth muscle organization in a wide variety of tubular organs.
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Affiliation(s)
- Tyler R Huycke
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Bess M Miller
- Department of Orthopedic Surgery, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Hasreet K Gill
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Nandan L Nerurkar
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - David Sprinzak
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv, Israel
| | - L Mahadevan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; Department of Physics, Harvard University, Cambridge, MA 02138, USA; Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA 02138, USA
| | - Clifford J Tabin
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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46
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Hart Y, Vaziri-Pashkam M, Mahadevan L. Early warning signals in motion inference. PLoS Comput Biol 2020; 16:e1007821. [PMID: 32469884 PMCID: PMC7259514 DOI: 10.1371/journal.pcbi.1007821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 03/24/2020] [Indexed: 11/19/2022] Open
Abstract
The ability to infer intention lies at the basis of many social interactions played out via motor actions. We consider a simple paradigm of this ability in humans using data from experiments simulating an antagonistic game between an Attacker and a Blocker. Evidence shows early inference of an Attacker move by as much as 100ms but the nature of the informational cues signaling the impending move remains unknown. We show that the transition to action has the hallmark of a critical transition that is accompanied by early warning signals. These early warning signals occur as much as 130 ms before motion ensues-showing a sharp rise in motion autocorrelation at lag-1 and a sharp rise in the autocorrelation decay time. The early warning signals further correlate strongly with Blocker response times. We analyze the variance of the motion near the point of transition and find that it diverges in a manner consistent with the dynamics of a fold-transition. To test if humans can recognize and act upon these early warning signals, we simulate the dynamics of fold-transition events and ask people to recognize the onset of directional motion: participants react faster to fold-transition dynamics than to its uncorrelated counterpart. Together, our findings suggest that people can recognize the intent and onset of motion by inferring its early warning signals.
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Affiliation(s)
- Yuval Hart
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America
- Department of Psychology, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Maryam Vaziri-Pashkam
- Section on Neuro-circuitry, National Institute of Mental Health, Bethesda, Maryland, United States of America
| | - L. Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
- * E-mail:
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47
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Abstract
Tropisms, growth-driven responses to environmental stimuli, cause plant organs to respond in space and time and reorient themselves. Classical experiments from nearly a century ago reveal that plant shoots respond to the integrated history of light and gravity stimuli rather than just responding instantaneously. We introduce a temporally non-local response function for the dynamics of shoot growth formulated as an integro-differential equation whose solution allows us to qualitatively reproduce experimental observations associated with intermittent and unsteady stimuli. Furthermore, an analytic solution for the case of a pulse stimulus expresses the response function as a function of experimentally tractable variables, which we calculate for the case of the phototropic response of Arabidopsis hypocotyls. All together, our model enables us to predict tropic responses to time-varying stimuli, manifested in temporal integration phenomena, and sets the stage for the incorporation of additional effects such as multiple stimuli, gravitational sagging, etc.
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Affiliation(s)
- Yasmine Meroz
- 1 School of Engineering and Applied Sciences, Harvard University , Cambridge, MA 02138 , USA.,2 School of Plant Science and Food Security, Tel Aviv University , Tel Aviv , Israel
| | - Renaud Bastien
- 3 Department of Collective Behaviour, Max Planck Institute for Ornithology, University of Konstanz , Konstanz , Germany.,4 Department of Biology, University of Konstanz , Konstanz , Germany
| | - L Mahadevan
- 1 School of Engineering and Applied Sciences, Harvard University , Cambridge, MA 02138 , USA.,5 Department of Physics, Harvard University , Cambridge, MA , USA.,6 Department of Organismic and Evolutionary Biology, Harvard University , Cambridge, MA , USA.,7 Kavli Institute for NanoBio Science and Technology, Harvard University , Cambridge, MA , USA
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48
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Abstract
During dynamic instability, self-assembling microtubules (MTs) stochastically alternate between phases of growth and shrinkage. This process is driven by the presence of two distinct states of MT subunits, GTP- and GDP-bound tubulin dimers, that have different structural properties. Here, we use a combination of analysis and computer simulations to study the mechanical and kinetic regulation of dynamic instability in three-dimensional (3D) self-assembling MTs. Our model quantifies how the 3D structure and kinetics of the distinct states of tubulin dimers determine the mechanical stability of MTs. We further show that dynamic instability is influenced by the presence of quenched disorder in the state of the tubulin subunit as reflected in the fraction of non-hydrolysed tubulin. Our results connect the 3D geometry, kinetics and statistical mechanics of these tubular assemblies within a single framework, and may be applicable to other self-assembled systems where these same processes are at play.
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Affiliation(s)
- Thomas Ct Michaels
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States
| | - Shuo Feng
- Department of Modern Mechanics, University of Science and Technology of China, Hefei, China.,IAT Chungu Joint Laboratory for Additive Manufacturing, Anhui Chungu 3D Institute of Intelligent Equipment and Industrial Technology, Wuhu, China
| | - Haiyi Liang
- Department of Modern Mechanics, University of Science and Technology of China, Hefei, China.,IAT Chungu Joint Laboratory for Additive Manufacturing, Anhui Chungu 3D Institute of Intelligent Equipment and Industrial Technology, Wuhu, China
| | - L Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States.,Department of Physics, Harvard University, Cambridge, United States.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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49
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Saintyves B, Rallabandi B, Jules T, Ault J, Salez T, Schönecker C, Stone HA, Mahadevan L. Rotation of a submerged finite cylinder moving down a soft incline. Soft Matter 2020; 16:4000-4007. [PMID: 32266883 DOI: 10.1039/c9sm02344e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A submerged finite cylinder moving under its own weight along a soft incline lifts off and slides at a steady velocity while also spinning. Here, we experimentally quantify the steady spinning of the cylinder and show theoretically that it is due to a combination of an elastohydrodynamic torque generated by flow in the variable gap, and the viscous friction on the edges of the finite-length cylinder. The relative influence of the latter depends on the aspect ratio of the cylinder, the angle of the incline, and the deformability of the substrate, which we express in terms of a single scaled compliance parameter. By independently varying these quantities, we show that our experimental results are consistent with a transition from an edge-effect dominated regime for short cylinders to a gap-dominated elastohydrodynamic regime when the cylinder is very long.
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Affiliation(s)
- Baudouin Saintyves
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Bhargav Rallabandi
- Department of Mechanical Engineering, University of California, Riverside, California 92521, USA
| | - Theo Jules
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. and Department de Physique, École Normale Supérieure, Université de Recherche Paris Sciences et Lettres, 75005 Paris, France
| | - Jesse Ault
- School of Engineering, Brown University, Providence, RI 02912, USA
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405, Talence, France and Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Hokkaido 060-0808, Japan
| | - Clarissa Schönecker
- Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany and Max Planck Institute for Polymer Research, 55218 Mainz, Germany
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - L Mahadevan
- School of Engineering and Applied Sciences, Department of Physics, Department of Organismic and Evolutionary Biology, Kavli Institute for Nano-Bio Science and Technology, Harvard University, Cambridge, MA 02138, USA.
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50
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Abstract
Kirigami, the creative art of paper cutting, is a promising paradigm for mechanical metamaterials. However, to make kirigami-inspired structures a reality requires controlling the topology of kirigami to achieve connectivity and rigidity. We address this question by deriving the maximum number of cuts (minimum number of links) that still allow us to preserve global rigidity and connectivity of the kirigami. A deterministic hierarchical construction method yields an efficient topological way to control both the number of connected pieces and the total degrees of freedom. A statistical approach to the control of rigidity and connectivity in kirigami with random cuts complements the deterministic pathway, and shows that both the number of connected pieces and the degrees of freedom show percolation transitions as a function of the density of cuts (links). Together, this provides a general framework for the control of rigidity and connectivity in planar kirigami.
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Affiliation(s)
- Siheng Chen
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
| | - Gary P T Choi
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
| | - L Mahadevan
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138;
- Department of Physics, Harvard University, Cambridge, MA 02138
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
- Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, MA 02138
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