1
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Smith AM, Inocencio DG, Pardi BM, Gopinath A, Andresen Eguiluz RC. Facile Determination of the Poisson's Ratio and Young's Modulus of Polyacrylamide Gels and Polydimethylsiloxane. ACS Appl Polym Mater 2024; 6:2405-2416. [PMID: 38420286 PMCID: PMC10897882 DOI: 10.1021/acsapm.3c03154] [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] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 01/13/2024] [Accepted: 01/16/2024] [Indexed: 03/02/2024]
Abstract
Polyacrylamide hydrogels (PAH gel) and polydimethylsiloxane (PDMS, an elastomer) are two soft materials often used in cell mechanics and mechanobiology, in manufacturing lab-on-a-chip applications, among others. This is partly due to the ability to tune their elasticity with ease in addition to various chemical modifications. For affine polymeric networks, two (of three) elastic constants, Young's modulus (E), the shear modulus (G), and Poisson's ratio (ν), describe the purely elastic response to external forces. However, the literature addressing the experimental determination of ν for PAH (sometimes called PAA gels in the literature) and the PDMS elastomer is surprisingly limited when compared to the literature that reports values of the elastic moduli, E and G. Here, we present a facile method to obtain the Poisson's ratio and Young's modulus for PAH gel and PDMS elastomer based on static tensile tests. The value of ν obtained from the deformation of the sample is compared to the value determined by comparing E and G via a second independent method that utilizes small amplitude shear rheology. We show that the Poisson's ratio may vary significantly from the value for incompressible materials (ν = 0.5), often assumed in the literature even for soft compressible hydrogels. Surprisingly, we find a high degree of agreement between elastic constants obtained by shear rheology and macroscopic static tension test data for polyacrylamide hydrogels but not for elastomeric PDMS.
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Affiliation(s)
- Ariell Marie Smith
- Department of Materials Science and Engineering, School of Engineering, University of California, Merced, 5200 North Lake Road, Merced, California 95344, United States
| | - Dominique Gabriele Inocencio
- Department of Materials Science and Engineering, School of Engineering, University of California, Merced, 5200 North Lake Road, Merced, California 95344, United States
| | - Brandon Michael Pardi
- Department of Materials Science and Engineering, School of Engineering, University of California, Merced, 5200 North Lake Road, Merced, California 95344, United States
| | - Arvind Gopinath
- Department of Bioengineering, School of Engineering, University of California, Merced, 5200 North Lake Road, Merced, California 95344, United States
- Health Sciences Research Institute, University of California Merced, Merced, 5200 North Lake Road, Merced, California 95344, United States
| | - Roberto Carlos Andresen Eguiluz
- Department of Materials Science and Engineering, School of Engineering, University of California, Merced, 5200 North Lake Road, Merced, California 95344, United States
- Health Sciences Research Institute, University of California Merced, Merced, 5200 North Lake Road, Merced, California 95344, United States
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2
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Fylling C, Tamayo J, Gopinath A, Theillard M. Multi-population dissolution in confined active fluids. Soft Matter 2024; 20:1392-1409. [PMID: 38305767 DOI: 10.1039/d3sm01196h] [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: 02/03/2024]
Abstract
Autonomous out-of-equilibrium agents or cells in suspension are ubiquitous in biology and engineering. Turning chemical energy into mechanical stress, they generate activity in their environment, which may trigger spontaneous large-scale dynamics. Often, these systems are composed of multiple populations that may reflect the coexistence of multiple species, differing phenotypes, or chemically varying agents in engineered settings. Here, we present a new method for modeling such multi-population active fluids subject to confinement. We use a continuum multi-scale mean-field approach to represent each phase by its first three orientational moments and couple their evolution with those of the suspending fluid. The resulting coupled system is solved using a parallel adaptive level-set-based solver for high computational efficiency and maximal flexibility in the confinement geometry. Motivated by recent experimental work, we employ our method to study the spatiotemporal dynamics of confined bacterial suspensions and swarms dominated by fluid hydrodynamic effects. Our in silico explorations reproduce observed emergent collective patterns, including features of active dissolution in two-population active-passive swarms, with results clearly suggesting that hydrodynamic effects dominate dissolution dynamics. Our work lays the foundation for a systematic characterization and study of collective phenomena in natural or synthetic multi-population systems such as bacteria colonies, bird flocks, fish schools, colloid swimmers, or programmable active matter.
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Affiliation(s)
- Cayce Fylling
- Department of Applied Mathematics, University of California Merced, Merced, CA95343, USA.
| | - Joshua Tamayo
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA.
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA.
| | - Maxime Theillard
- Department of Applied Mathematics, University of California Merced, Merced, CA95343, USA.
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3
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Zakharov A, Awan M, Cheng T, Gopinath A, Lee SJJ, Ramasubramanian AK, Dasbiswas K. Clots reveal anomalous elastic behavior of fiber networks. Sci Adv 2024; 10:eadh1265. [PMID: 38198546 PMCID: PMC10780871 DOI: 10.1126/sciadv.adh1265] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 12/06/2023] [Indexed: 01/12/2024]
Abstract
The adaptive mechanical properties of soft and fibrous biological materials are relevant to their functionality. The emergence of the macroscopic response of these materials to external stress and intrinsic cell traction from local deformations of their structural components is not well understood. Here, we investigate the nonlinear elastic behavior of blood clots by combining microscopy, rheology, and an elastic network model that incorporates the stretching, bending, and buckling of constituent fibrin fibers. By inhibiting fibrin cross-linking in blood clots, we observe an anomalous softening regime in the macroscopic shear response as well as a reduction in platelet-induced clot contractility. Our model explains these observations from two independent macroscopic measurements in a unified manner, through a single mechanical parameter, the bending stiffness of individual fibers. Supported by experimental evidence, our mechanics-based model provides a framework for predicting and comprehending the nonlinear elastic behavior of blood clots and other active biopolymer networks in general.
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Affiliation(s)
- Andrei Zakharov
- Department of Physics, University of California, Merced, Merced, CA 95343, USA
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Myra Awan
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Terrence Cheng
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, Merced, CA 95343, USA
| | - Sang-Joon John Lee
- Department of Mechanical Engineering, San José State University, San José, CA 95192, USA
| | - Anand K. Ramasubramanian
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Kinjal Dasbiswas
- Department of Physics, University of California, Merced, Merced, CA 95343, USA
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4
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Gaspar-Morales EA, Waterston A, Sadqi M, Diaz-Parga P, Smith AM, Gopinath A, Andresen Eguiluz RC, de Alba E. Natural and Engineered Isoforms of the Inflammasome Adaptor ASC Form Noncovalent, pH-Responsive Hydrogels. Biomacromolecules 2023; 24:5563-5577. [PMID: 37930828 DOI: 10.1021/acs.biomac.3c00409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
The protein ASC polymerizes into intricate filament networks to assemble the inflammasome, a filamentous multiprotein complex that triggers the inflammatory response. ASC carries two Death Domains integrally involved in protein self-association for filament assembly. We have leveraged this behavior to create noncovalent, pH-responsive hydrogels of full-length, folded ASC by carefully controlling the pH as a critical factor in the polymerization process. We show that natural variants of ASC (ASC isoforms) involved in inflammasome regulation also undergo hydrogelation. To further demonstrate this general capability, we engineered proteins inspired by the ASC structure that also form hydrogels. We analyzed the structural network of the natural and engineered protein hydrogels using transmission and scanning electron microscopy and studied their viscoelastic behavior using shear rheology. Our results reveal one of the very few examples of hydrogels created by the self-assembly of globular proteins and domains in their native conformation and show that Death Domains can be used alone or as building blocks to engineer bioinspired hydrogels.
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5
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Lonner TL, Allred AR, Bonarrigo L, Gopinath A, Smith K, Kravets V, Groen EL, Oman C, DiZio P, Lawson BD, Clark TK. Virtual reality as a countermeasure for astronaut motion sickness during simulated post-flight water landings. Exp Brain Res 2023; 241:2669-2682. [PMID: 37796301 DOI: 10.1007/s00221-023-06715-5] [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: 07/01/2023] [Accepted: 09/24/2023] [Indexed: 10/06/2023]
Abstract
Entry motion sickness (EMS) affects crewmembers upon return to Earth following extended adaptation to microgravity. Anticholinergic pharmaceuticals (e.g., Meclizine) are often taken prior to landing; however, they have operationally adverse side effects (e.g., drowsiness). There is a need to develop non-pharmaceutical countermeasures to EMS. We assessed the efficacy of a technological countermeasure providing external visual cues following splashdown, where otherwise only nauseogenic internal cabin visual references are available. Our countermeasure provided motion-congruent visual cues of an Earth-fixed scene in virtual reality, which was compared to a control condition with a head-fixed fixation point in virtual reality in a between-subject design with 15 subjects in each group. We tested the countermeasure's effectiveness at mitigating motion sickness symptoms at the end of a ground-based reentry analog: approximately 1 h of 2Gx centrifugation followed by up to 1 h of wave-like motion. Secondarily, we explored differences in vestibular-mediated balance performance between the two conditions. While Motion Sickness Questionnaire outcomes did not differ detectably between groups, we found significantly better survival rates (with dropout dictated by reporting moderate nausea consecutively over 2 min) in the visual countermeasure group than the control group (79% survival vs. 33%, t(14) = 2.50, p = 0.027). Following the reentry analogs, subjects demonstrated significantly higher sway prior to recovery (p = 0.0004), which did not differ between control and countermeasure groups. These results imply that providing motion-congruent visual cues may be an effective mean for curbing the development of moderate nausea and increasing comfort following future space missions.
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Affiliation(s)
- T L Lonner
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA.
| | - A R Allred
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
| | - L Bonarrigo
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
| | - A Gopinath
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
| | - K Smith
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
| | - V Kravets
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
| | - E L Groen
- Human Performance Department, TNO, Soesterberg, The Netherlands
| | - C Oman
- Human Systems Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - P DiZio
- Ashton Graybiel Spatial Orientation Laboratory, Brandeis University, Waltham, MA, USA
- Volen Center for Complex Systems, Brandeis University, Waltham, MA, USA
- Psychology Department, Brandeis University, Waltham, MA, USA
| | - B D Lawson
- Naval Submarine Medical Research Laboratory, Groton, CT, USA
| | - T K Clark
- Smead Department of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, CO, USA
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6
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Kumar P, Tamayo J, Shiu RF, Chin WC, Gopinath A. Size-Dependent Diffusion and Dispersion of Particles in Mucin. Polymers (Basel) 2023; 15:3241. [PMID: 37571134 PMCID: PMC10422640 DOI: 10.3390/polym15153241] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Revised: 07/17/2023] [Accepted: 07/17/2023] [Indexed: 08/13/2023] Open
Abstract
Mucus, composed significantly of glycosylated mucins, is a soft and rheologically complex material that lines respiratory, reproductive, and gastrointestinal tracts in mammals. Mucus may present as a gel, as a highly viscous fluid, or as a viscoelastic fluid. Mucus acts as a barrier to the transport of harmful microbes and inhaled atmospheric pollutants to underlying cellular tissue. Studies on mucin gels have provided critical insights into the chemistry of the gels, their swelling kinetics, and the diffusion and permeability of molecular constituents such as water. The transport and dispersion of micron and sub-micron particles in mucin gels and solutions, however, differs from the motion of small molecules since the much larger tracers may interact with microstructure of the mucin network. Here, using brightfield and fluorescence microscopy, high-speed particle tracking, and passive microrheology, we study the thermally driven stochastic movement of 0.5-5.0 μm tracer particles in 10% mucin solutions at neutral pH, and in 10% mucin mixed with industrially relevant dust; specifically, unmodified limestone rock dust, modified limestone, and crystalline silica. Particle trajectories are used to calculate mean square displacements and the displacement probability distributions; these are then used to assess tracer diffusion and transport. Complex moduli are concomitantly extracted using established microrheology techniques. We find that under the conditions analyzed, the reconstituted mucin behaves as a weak viscoelastic fluid rather than as a viscoelastic gel. For small- to moderately sized tracers with a diameter of lessthan 2 μm, we find that effective diffusion coefficients follow the classical Stokes-Einstein relationship. Tracer diffusivity in dust-laden mucin is surprisingly larger than in bare mucin. Probability distributions of mean squared displacements suggest that heterogeneity, transient trapping, and electrostatic interactions impact dispersion and overall transport, especially for larger tracers. Our results motivate further exploration of physiochemical and rheological mechanisms mediating particle transport in mucin solutions and gels.
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Affiliation(s)
- Parveen Kumar
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA; (P.K.); (J.T.)
| | - Joshua Tamayo
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA; (P.K.); (J.T.)
| | - Ruei-Feng Shiu
- Institute of Marine Environment and Ecology, National Taiwan Ocean University, Keelung 202301, Taiwan
| | - Wei-Chun Chin
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA; (P.K.); (J.T.)
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA; (P.K.); (J.T.)
- Health Sciences Research Institute, University of California Merced, Merced, CA 95343, USA
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7
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Gaspar-Morales EA, Waterston A, Diaz-Parga P, Smith AM, Sadqi M, Gopinath A, Andresen Eguiluz RC, de Alba E. Natural and engineered isoforms of the inflammasome adaptor ASC form non-covalent, pH-responsive hydrogels. bioRxiv 2023:2023.05.03.539154. [PMID: 37205378 PMCID: PMC10187214 DOI: 10.1101/2023.05.03.539154] [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] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The protein ASC polymerizes into intricate filament networks to assemble the inflammasome, a filamentous multiprotein complex that triggers the inflammatory response. ASC carries two Death Domains integrally involved in protein self-association for filament assembly. We have leveraged this behavior to create non-covalent, pH-responsive hydrogels of full-length, folded ASC by carefully controlling the pH as a critical factor in the polymerization process. We show that natural variants of ASC (ASC isoforms) involved in inflammasome regulation also undergo hydrogelation. To further demonstrate this general capability, we engineered proteins inspired in the ASC structure that successfully form hydrogels. We analyzed the structural network of the natural and engineered protein hydrogels using transmission and scanning electron microscopy, and studied their viscoelastic behavior by shear rheology. Our results reveal one of the very few examples of hydrogels created by the self-assembly of globular proteins and domains in their native conformation and show that Death Domains can be used alone or as building blocks to engineer bioinspired hydrogels.
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8
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Mohammed I, Baskovich B, Alkhasawneh A, Gopinath A. Adamantinoma-like Ewing sarcoma of thyroid gland-An unfamiliar mimicker of epithelial and mesenchymal neoplasms of the head and neck. Malays J Pathol 2023; 45:129-134. [PMID: 37119253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
INTRODUCTION Adamantinoma-like Ewing Sarcoma (ALES) is a rare variant of the Ewing family of tumours (EFT) harbouring the EWSR1-FLI1 translocation and with complex epithelial differentiation. Very few cases of ALES involving thyroid have been reported in literature. CASE REPORT We report a case of ALES involving the thyroid in a 61-year-old male who presented with an enlarging nodule in the left lobe of the thyroid and underwent hemithyroidectomy. DISCUSSION ALES demonstrates morphologic similarity to a multitude of epithelial and mesenchymal tumours, creating a potential diagnostic pitfall in thyroid and head and neck pathology. Given the rarity of this tumour, there is also a lack of accepted guidelines regarding further surgical management of these cases following hemithyroidectomy.
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Affiliation(s)
- I Mohammed
- University of Florida College of Medicine Jacksonville, Department of Pathology, 655 W, 8th street, Jacksonville, Florida, USA 33209.
| | - B Baskovich
- University of Florida College of Medicine Jacksonville, Department of Pathology, 655 W, 8th street, Jacksonville, Florida, USA 33209
| | - A Alkhasawneh
- University of Florida College of Medicine Jacksonville, Department of Pathology, 655 W, 8th street, Jacksonville, Florida, USA 33209
| | - A Gopinath
- University of Florida College of Medicine Jacksonville, Department of Pathology, 655 W, 8th street, Jacksonville, Florida, USA 33209
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9
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Gaspar-Morales EA, Waterston AW, Diaz-Parga P, Smith AM, Eguiluz RCA, Gopinath A, de Alba E. Design and characterization of protein-based, pH-responsive hydrogels with potential biomedical applications. Biophys J 2023; 122:24a. [PMID: 36783229 DOI: 10.1016/j.bpj.2022.11.354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
| | - Anthony W Waterston
- Bioengineering, School of Engineering, University of California, Merced, CA, USA
| | - Pedro Diaz-Parga
- Bioengineering, School of Engineering, University of California, Merced, CA, USA
| | - Ariell M Smith
- Materials Science and Engineering, University of California Merced, Merced, CA, USA
| | | | - Arvind Gopinath
- Bioengineering, School of Engineering, University of California, Merced, CA, USA
| | - Eva de Alba
- Bioengineering, School of Engineering, University of California, Merced, CA, USA
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10
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Mann AS, Smith AM, Saltzherr JO, Gopinath A, Andresen Eguiluz RC. Glycosaminoglycans and glycoproteins influence the elastic response of synovial fluid nanofilms on model oxide surfaces. Colloids Surf B Biointerfaces 2022; 213:112407. [PMID: 35180655 DOI: 10.1016/j.colsurfb.2022.112407] [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: 11/15/2021] [Revised: 01/27/2022] [Accepted: 02/07/2022] [Indexed: 10/19/2022]
Abstract
Synovial fluid (SF) is the natural lubricant found in articulated joints, providing unique cartilage surface protecting films under confinement and relative motion. While it is known that the synergistic interactions of the macromolecular constituents provide its unique load-bearing and tribological performance, it is not fully understood how two of the main constituents, glycosaminoglycans (GAGs) and glycoproteins, regulate the formation and mechanics of robust load-bearing films. Here, we present evidence that the load-bearing capabilities, rather than the tribological performance, of the formed SF films depend strongly on its components' integrity. For this purpose, we used a combination of enzymatic treatments, quartz crystal microbalance with dissipation (QCM-D), and the surface forces apparatus (SFA) to characterize the formation and load-bearing capabilities of SF films on model oxide (i.e., silicates) surfaces. We find that, upon cleavage of proteins, the elasticity of the films is reduced and that cleaving GAGs results in irreversible (plastic) molecular re-arrangements of the film constituents when subjected to confinement. Understanding thin film mechanics of SF can provide insight into the progression of diseases, such as arthritis, but may also be applicable to the development of new implant surface treatments or new biomimetic lubricants.
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Affiliation(s)
- Amar S Mann
- Department of Materials Science and Engineering, University of California, Merced, CA 95344, USA
| | - Ariell M Smith
- Department of Materials Science and Engineering, University of California, Merced, CA 95344, USA
| | - Joyce O Saltzherr
- Department of Materials Science and Engineering, University of California, Merced, CA 95344, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, CA 95344, USA; Health Sciences Research Institute, University of California, Merced, CA 95344, USA
| | - Roberto C Andresen Eguiluz
- Department of Materials Science and Engineering, University of California, Merced, CA 95344, USA; Health Sciences Research Institute, University of California, Merced, CA 95344, USA.
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11
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Asp ME, Ho Thanh MT, Germann DA, Carroll RJ, Franceski A, Welch RD, Gopinath A, Patteson AE. Spreading rates of bacterial colonies depend on substrate stiffness and permeability. PNAS Nexus 2022; 1:pgac025. [PMID: 36712798 PMCID: PMC9802340 DOI: 10.1093/pnasnexus/pgac025] [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] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/25/2022] [Accepted: 03/09/2022] [Indexed: 02/01/2023]
Abstract
The ability of bacteria to colonize and grow on different surfaces is an essential process for biofilm development. Here, we report the use of synthetic hydrogels with tunable stiffness and porosity to assess physical effects of the substrate on biofilm development. Using time-lapse microscopy to track the growth of expanding Serratia marcescens colonies, we find that biofilm colony growth can increase with increasing substrate stiffness, unlike what is found on traditional agar substrates. Using traction force microscopy-based techniques, we find that biofilms exert transient stresses correlated over length scales much larger than a single bacterium, and that the magnitude of these forces also increases with increasing substrate stiffness. Our results are consistent with a model of biofilm development in which the interplay between osmotic pressure arising from the biofilm and the poroelastic response of the underlying substrate controls biofilm growth and morphology.
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Affiliation(s)
- Merrill E Asp
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Minh-Tri Ho Thanh
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Danielle A Germann
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Robert J Carroll
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Alana Franceski
- BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA,Biology Department, Syracuse University, Syracuse, NY 13244, USA
| | - Roy D Welch
- BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA,Biology Department, Syracuse University, Syracuse, NY 13244, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, Merced, CA 95343, USA,Health Sciences Research Institute, University of California, Merced, Merced, CA 95343, USA
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12
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Kirsten F, Marcote B, Nimmo K, Hessels JWT, Bhardwaj M, Tendulkar SP, Keimpema A, Yang J, Snelders MP, Scholz P, Pearlman AB, Law CJ, Peters WM, Giroletti M, Paragi Z, Bassa C, Hewitt DM, Bach U, Bezrukovs V, Burgay M, Buttaccio ST, Conway JE, Corongiu A, Feiler R, Forssén O, Gawroński MP, Karuppusamy R, Kharinov MA, Lindqvist M, Maccaferri G, Melnikov A, Ould-Boukattine OS, Possenti A, Surcis G, Wang N, Yuan J, Aggarwal K, Anna-Thomas R, Bower GC, Blaauw R, Burke-Spolaor S, Cassanelli T, Clarke TE, Fonseca E, Gaensler BM, Gopinath A, Kaspi VM, Kassim N, Lazio TJW, Leung C, Li DZ, Lin HH, Masui KW, Mckinven R, Michilli D, Mikhailov AG, Ng C, Orbidans A, Pen UL, Petroff E, Rahman M, Ransom SM, Shin K, Smith KM, Stairs IH, Vlemmings W. A repeating fast radio burst source in a globular cluster. Nature 2022; 602:585-589. [PMID: 35197615 DOI: 10.1038/s41586-021-04354-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 12/15/2021] [Indexed: 11/09/2022]
Abstract
Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.
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Affiliation(s)
- F Kirsten
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden. .,ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands.
| | - B Marcote
- Joint Institute for VLBI ERIC, Dwingeloo, The Netherlands
| | - K Nimmo
- ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands.,Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - J W T Hessels
- ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands.,Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - M Bhardwaj
- Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada
| | - S P Tendulkar
- Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai, India.,National Centre for Radio Astrophysics, Pune, India
| | - A Keimpema
- Joint Institute for VLBI ERIC, Dwingeloo, The Netherlands
| | - J Yang
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
| | - M P Snelders
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - P Scholz
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada
| | - A B Pearlman
- Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada.,Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA, USA
| | - C J Law
- Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA.,Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA, USA
| | - W M Peters
- Remote Sensing Division, US Naval Research Laboratory, Washington, DC, USA
| | - M Giroletti
- Istituto Nazionale di Astrofisica, Istituto di Radioastronomia, Bologna, Italy
| | - Z Paragi
- Joint Institute for VLBI ERIC, Dwingeloo, The Netherlands
| | - C Bassa
- ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands
| | - D M Hewitt
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - U Bach
- Max Planck Institute for Radio Astronomy, Bonn, Germany
| | - V Bezrukovs
- Engineering Research Institute Ventspils International Radio Astronomy Centre (ERI VIRAC), Ventspils University of Applied Sciences (VUAS), Ventspils, Latvia
| | - M Burgay
- Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Cagliari, Selargius, Italy
| | - S T Buttaccio
- Istituto Nazionale di Astrofisica, Istituto di Radioastronomia Radiotelescopio di Noto, Noto, Italy
| | - J E Conway
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
| | - A Corongiu
- Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Cagliari, Selargius, Italy
| | - R Feiler
- Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń, Poland
| | - O Forssén
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
| | - M P Gawroński
- Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń, Poland
| | - R Karuppusamy
- Max Planck Institute for Radio Astronomy, Bonn, Germany
| | - M A Kharinov
- Institute of Applied Astronomy of the Russian Academy of Sciences, St. Petersburg, Russia
| | - M Lindqvist
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
| | - G Maccaferri
- Istituto Nazionale di Astrofisica, Istituto di Radioastronomia, Bologna, Italy
| | - A Melnikov
- Institute of Applied Astronomy of the Russian Academy of Sciences, St. Petersburg, Russia
| | - O S Ould-Boukattine
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - A Possenti
- Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Cagliari, Selargius, Italy.,Dipartimento di Fisica, Università di Cagliari, Monserrato, Italy
| | - G Surcis
- Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Cagliari, Selargius, Italy
| | - N Wang
- Xinjiang Astronomical Observatory, Urumqi, China
| | - J Yuan
- Xinjiang Astronomical Observatory, Urumqi, China
| | - K Aggarwal
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA.,Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, WV, USA
| | - R Anna-Thomas
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA.,Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, WV, USA
| | - G C Bower
- Academia Sinica Institute of Astronomy and Astrophysics, Hilo, HI, USA
| | - R Blaauw
- ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands
| | - S Burke-Spolaor
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA.,Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, WV, USA.,Canadian Institute for Advanced Research, CIFAR Azrieli Global Scholar, Toronto, Ontario, Canada
| | - T Cassanelli
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada.,David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada
| | - T E Clarke
- Remote Sensing Division, US Naval Research Laboratory, Washington, DC, USA
| | - E Fonseca
- Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada.,Department of Physics and Astronomy, West Virginia University, Morgantown, WV, USA.,Center for Gravitational Waves and Cosmology, West Virginia University, Morgantown, WV, USA
| | - B M Gaensler
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada.,David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada
| | - A Gopinath
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
| | - V M Kaspi
- Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada
| | - N Kassim
- Remote Sensing Division, US Naval Research Laboratory, Washington, DC, USA
| | - T J W Lazio
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - C Leung
- MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - D Z Li
- Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA
| | - H H Lin
- Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario, Canada.,Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
| | - K W Masui
- MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - R Mckinven
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada
| | - D Michilli
- Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada.,MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - A G Mikhailov
- Institute of Applied Astronomy of the Russian Academy of Sciences, St. Petersburg, Russia
| | - C Ng
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada
| | - A Orbidans
- Engineering Research Institute Ventspils International Radio Astronomy Centre (ERI VIRAC), Ventspils University of Applied Sciences (VUAS), Ventspils, Latvia
| | - U L Pen
- Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada.,Canadian Institute for Advanced Research, CIFAR Azrieli Global Scholar, Toronto, Ontario, Canada.,Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario, Canada.,Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada.,Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
| | - E Petroff
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands.,Department of Physics, McGill University, Montreal, Quebec, Canada.,McGill Space Institute, McGill University, Montreal, Quebec, Canada
| | - M Rahman
- Sidrat Research, Toronto, Ontario, Canada
| | - S M Ransom
- National Radio Astronomy Observatory, Charlottesville, VA, USA
| | - K Shin
- MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - K M Smith
- Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada
| | - I H Stairs
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
| | - W Vlemmings
- Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
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13
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Bose S, Dasbiswas K, Gopinath A. Matrix Stiffness Modulates Mechanical Interactions and Promotes Contact between Motile Cells. Biomedicines 2021; 9:biomedicines9040428. [PMID: 33920918 PMCID: PMC8077938 DOI: 10.3390/biomedicines9040428] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 04/08/2021] [Accepted: 04/10/2021] [Indexed: 02/07/2023] Open
Abstract
The mechanical micro-environment of cells and tissues influences key aspects of cell structure and function, including cell motility. For proper tissue development, cells need to migrate, interact, and form contacts. Cells are known to exert contractile forces on underlying soft substrates and sense deformations in them. Here, we propose and analyze a minimal biophysical model for cell migration and long-range cell–cell interactions through mutual mechanical deformations of the substrate. We compute key metrics of cell motile behavior, such as the number of cell-cell contacts over a given time, the dispersion of cell trajectories, and the probability of permanent cell contact, and analyze how these depend on a cell motility parameter and substrate stiffness. Our results elucidate how cells may sense each other mechanically and generate coordinated movements and provide an extensible framework to further address both mechanical and short-range biophysical interactions.
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Affiliation(s)
- Subhaya Bose
- Department of Physics, University of California Merced, Merced, CA 95343, USA; (S.B.); (K.D.)
| | - Kinjal Dasbiswas
- Department of Physics, University of California Merced, Merced, CA 95343, USA; (S.B.); (K.D.)
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA
- Correspondence:
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14
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Fatehiboroujeni S, Gopinath A, Goyal S. Three-dimensional nonlinear dynamics of prestressed active filaments: Flapping, swirling, and flipping. Phys Rev E 2021; 103:013005. [PMID: 33601644 DOI: 10.1103/physreve.103.013005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 12/24/2020] [Indexed: 11/07/2022]
Abstract
Initially straight slender elastic filaments or rods with constrained ends buckle and form stable two-dimensional shapes when prestressed by bringing the ends together. Beyond a critical value of this prestress, rods can also deform off plane and form twisted three-dimensional equilibrium shapes. Here, we analyze the three-dimensional instabilities and dynamics of such deformed filaments subject to nonconservative active follower forces and fluid drag. We find that softly constrained filaments that are clamped at one end and pinned at the other exhibit stable two-dimensional planar flapping oscillations when active forces are directed toward the clamped end. Reversing the directionality of the forces quenches the instability. For strongly constrained filaments with both ends clamped, computations reveal an instability arising from the twist-bend-activity coupling. Planar oscillations are destabilized by off-planar perturbations resulting in twisted three-dimensional swirling patterns interspersed with periodic flipping or reversal of the swirling direction. These striking swirl-flip transitions are characterized by two distinct timescales: the time period for a swirl (rotation) and the time between flipping events. We interpret these reversals as relaxation oscillation events driven by accumulation of torsional energy. Each cycle is initiated by a fast jump in torsional deformation with a subsequent slow decrease in net torsion until the next cycle. Our work reveals the rich tapestry of spatiotemporal patterns when weakly inertial strongly damped rods are deformed by nonconservative active forces. Taken together, our results suggest avenues by which prestress, elasticity, and activity may be used to design synthetic macroscale pumps or mixers.
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Affiliation(s)
- Soheil Fatehiboroujeni
- Department of Mechanical Engineering, University of California, Merced, California 95343, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, California 95343, USA
| | - Sachin Goyal
- Department of Mechanical Engineering, University of California, Merced, California 95343, USA and Health Sciences Research Institute, University of California, Merced, California 95343, USA
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15
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Chelakkot R, Hagan MF, Gopinath A. Synchronized oscillations, traveling waves, and jammed clusters induced by steric interactions in active filament arrays. Soft Matter 2021; 17:1091-1104. [PMID: 33289748 DOI: 10.1039/d0sm01162b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Autonomous active, elastic filaments that interact with each other to achieve cooperation and synchrony underlie many critical functions in biology. The mechanisms underlying this collective response and the essential ingredients for stable synchronization remain a mystery. Inspired by how these biological entities integrate elasticity with molecular motor activity to generate sustained oscillations, a number of synthetic active filament systems have been developed that mimic oscillations of these biological active filaments. Here, we describe the collective dynamics and stable spatiotemporal patterns that emerge in such biomimetic multi-filament arrays, under conditions where steric interactions may impact or dominate the collective dynamics. To focus on the role of steric interactions, we study the system using Brownian dynamics, without considering long-ranged hydrodynamic interactions. The simulations treat each filament as a connected chain of self-propelling colloids. We demonstrate that short-range steric inter-filament interactions and filament roughness are sufficient - even in the absence of inter-filament hydrodynamic interactions - to generate a rich variety of collective spatiotemporal oscillatory, traveling and static patterns. We first analyze the collective dynamics of two- and three-filament clusters and identify parameter ranges in which steric interactions lead to synchronized oscillations and strongly occluded states. Generalizing these results to large one-dimensional arrays, we find rich emergent behaviors, including traveling metachronal waves, and modulated wavetrains that are controlled by the interplay between the array geometry, filament activity, and filament elasticity. Interestingly, the existence of metachronal waves is non-monotonic with respect to the inter-filament spacing. We also find that the degree of filament roughness significantly affects the dynamics - specifically, filament roughness generates a locking-mechanism that transforms traveling wave patterns into statically stuck and jammed configurations. Taken together, simulations suggest that short-ranged steric inter-filament interactions could combine with complementary hydrodynamic interactions to control the development and regulation of oscillatory collective patterns. Furthermore, roughness and steric interactions may be critical to the development of jammed spatially periodic states; a spatiotemporal feature not observed in purely hydrodynamically interacting systems.
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Affiliation(s)
- Raghunath Chelakkot
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India.
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16
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Abstract
Intracellular elastic filaments such as microtubules are subject to thermal Brownian noise and active noise generated by molecular motors that convert chemical energy into mechanical work. Similarly, polymers in living fluids such as bacterial suspensions and swarms suffer bending deformations as they interact with single bacteria or with cell clusters. Often, these filaments perform mechanical functions and interact with their networked environment through cross-links or have other similar constraints placed on them. Here, we examine the mechanical properties-under tension-of such constrained active filaments under canonical boundary conditions motivated by experiments. Fluctuations in the filament shape are a consequence of two types of random forces-thermal Brownian forces and activity derived forces with specified time and space correlation functions. We derive force-extension relationships and expressions for the mean square deflections for tethered filaments under various boundary conditions including hinged and clamped constraints. The expressions for hinged-hinged boundary conditions are reminiscent of the worm-like-chain model and feature effective bending moduli and mode-dependent non-thermodynamic effective temperatures controlled by the imposed force and by the activity. Our results provide methods to estimate the activity by measurements of the force-extension relation of the filaments or their mean square deflections, which can be routinely performed using optical traps, tethered particle experiments, or other single molecule techniques.
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Affiliation(s)
- Xinyu Liao
- Graduate Group in Applied Mathematics and Computational Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Prashant K Purohit
- Graduate Group in Applied Mathematics and Computational Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, California 95343, USA
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17
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Fily Y, Subramanian P, Schneider TM, Chelakkot R, Gopinath A. Buckling instabilities and spatio-temporal dynamics of active elastic filaments. J R Soc Interface 2020; 17:20190794. [PMID: 32316880 DOI: 10.1098/rsif.2019.0794] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Biological filaments driven by molecular motors tend to experience tangential propulsive forces also known as active follower forces. When such a filament encounters an obstacle, it deforms, which reorients its follower forces and alters its entire motion. If the filament pushes a cargo, the friction on the cargo can be enough to deform the filament, thus affecting the transport properties of the cargo. Motivated by cytoskeletal filament motility assays, we study the dynamic buckling instabilities of a two-dimensional slender elastic filament driven through a dissipative medium by tangential propulsive forces in the presence of obstacles or cargo. We observe two distinct instabilities. When the filament's head is pinned or experiences significant translational but little rotational drag from its cargo, it buckles into a steadily rotating coiled state. When it is clamped or experiences both significant translational and rotational drag from its cargo, it buckles into a periodically beating, overall translating state. Using minimal analytically tractable models, linear stability theory and fully nonlinear computations, we study the onset of each buckling instability, characterize each buckled state, and map out the phase diagram of the system. Finally, we use particle-based Brownian dynamics simulations to show our main results are robust to moderate noise and steric repulsion. Overall, our results provide a unified framework to understand the dynamics of tangentially propelled filaments and filament-cargo assemblies.
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Affiliation(s)
- Yaouen Fily
- Wilkes Honors College, Florida Atlantic University, Jupiter, FL, USA
| | | | - Tobias M Schneider
- Emergent Complexity in Physical Systems Laboratory (ECPS), Ecole Polytechnique Federale de Lausanne, CH 1015 Lausanne, Switzerland
| | | | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA, USA
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18
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Rollins K, Gopinath A, Awwad A, Macdonald I, Lobo D. OR37: Psoas Versus Whole L3 Skeletal Muscle Cross-Sectional Area: How Do They Relate? Clin Nutr 2019. [DOI: 10.1016/s0261-5614(19)32509-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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19
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Gopinath A, Sultan Nasar A. Electroactive six arm star poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate): Synthesis and application as cathode material for rechargeable Li-ion batteries. POLYMER 2019. [DOI: 10.1016/j.polymer.2019.121601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Yang J, Arratia PE, Patteson AE, Gopinath A. Quenching active swarms: effects of light exposure on collective motility in swarming Serratia marcescens. J R Soc Interface 2019; 16:20180960. [PMID: 31311436 DOI: 10.1098/rsif.2018.0960] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [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: 01/02/2023] Open
Abstract
Swarming colonies of the light-responsive bacteria Serratia marcescens grown on agar exhibit robust fluctuating large-scale flows that include arrayed vortices, jets and sinuous streamers. We study the immobilization and quenching of these collective flows when the moving swarm is exposed to intense wide-spectrum light with a substantial ultraviolet component. We map the emergent response of the swarm to light in terms of two parameters-light intensity and duration of exposure-and identify the conditions under which collective motility is impacted. For small exposure times and/or low intensities, we find collective motility to be negligibly affected. Increasing exposure times and/or intensity to higher values suppresses collective motility but only temporarily. Terminating exposure allows bacteria to recover and eventually reestablish collective flows similar to that seen in unexposed swarms. For long exposure times or at high intensities, exposed bacteria become paralysed and form aligned, jammed regions where macroscopic speeds reduce to zero. The effective size of the quenched region increases with time and saturates to approximately the extent of the illuminated region. Post-exposure, active bacteria dislodge immotile bacteria; initial dissolution rates are strongly dependent on duration of exposure. Based on our experimental observations, we propose a minimal Brownian dynamics model to examine the escape of exposed bacteria from the region of exposure. Our results complement studies on planktonic bacteria, inform models of patterning in gradated illumination and provide a starting point for the study of specific wavelengths on swarming bacteria.
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Affiliation(s)
- Junyi Yang
- Department of Bioengineering, University of California Merced, Merced, CA, USA
| | - Paulo E Arratia
- Department of Mechanical Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA, USA
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21
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Gopinath A, Manivannan N, Mandal S, Mathivanan N, Nasar AS. Substituent enhanced fluorescence properties of star α-cyanostilbenes and their application in bioimaging. J Mater Chem B 2019; 7:6010-6023. [DOI: 10.1039/c9tb01452g] [Citation(s) in RCA: 15] [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] [Indexed: 12/12/2022]
Abstract
In this paper, we report the fluorescence properties of new star α-cyanostilbene molecules. Fungus cell imaging studies using one of the molecules allowed observing nuclear movement in the live mycelium.
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Affiliation(s)
- A. Gopinath
- Department of Polymer Science
- University of Madras
- Chennai-25
- India
| | - N. Manivannan
- Biocontrol and Microbial Metabolites Lab
- Centre for Advanced Studies in Botany
- University of Madras
- Chennai-600025
- India
| | - Sudip Mandal
- Department of Chemistry
- Indian Institute of Technology Madras
- Chennai-600 036
- India
| | - N. Mathivanan
- Biocontrol and Microbial Metabolites Lab
- Centre for Advanced Studies in Botany
- University of Madras
- Chennai-600025
- India
| | - A. Sultan Nasar
- Department of Polymer Science
- University of Madras
- Chennai-25
- India
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22
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Abstract
Propagating interfaces are ubiquitous in nature, underlying instabilities and pattern formation in biology and material science. Physical principles governing interface growth are well understood in passive settings; however, our understanding of interfaces in active systems is still in its infancy. Here, we study the evolution of an active-passive interface using a model active matter system, bacterial swarms. We use ultra-violet light exposure to create compact domains of passive bacteria within Serratia marcescens swarms, thereby creating interfaces separating motile and immotile cells. Post-exposure, the boundary re-shapes and erodes due to self-emergent collective flows. We demonstrate that the active-passive boundary acts as a diffuse interface with mechanical properties set by the flow. Intriguingly, interfacial velocity couples to local swarm speed and interface curvature, raising the possibility that an active analogue to classic Gibbs-Thomson-Stefan conditions may control this boundary propagation.
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Affiliation(s)
- Alison E Patteson
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA, 19104, USA.
- Physics Department, Syracuse University, Syracuse, NY, 13244, USA.
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, CA, 95340, USA
- Health Sciences Research Institute, University of California, Merced, CA, 95340, USA
| | - Paulo E Arratia
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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23
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Gopinath A, Sultan Nasar A. Fluorescent star ATRP initiators and fluorescent star poly(methyl methacrylate)s: Synthesis and photophysical properties. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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24
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Gopinath A, Ramamurthy K, Subaraja M, Selvaraju C, Nasar AS. A3-Type star stilbene and cyanostilbene molecules: synthesis, fluorescence properties and bio-imaging application. NEW J CHEM 2018. [DOI: 10.1039/c8nj00676h] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this article, we report star-like stilbene and cyanostilbene molecules exhibiting strong fluorescence, ICT and AIE properties. Star cyanostilbene was found to be an excellent fluorophore for bio-imaging application.
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Affiliation(s)
- A. Gopinath
- Department of Polymer Science
- University of Madras
- Chennai-25
- India
| | - K. Ramamurthy
- National Centre for Ultrafast Processes
- University of Madras
- Chennai-600 113
- India
| | | | | | - A. Sultan Nasar
- Department of Polymer Science
- University of Madras
- Chennai-25
- India
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25
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Li C, Qin B, Gopinath A, Arratia PE, Thomases B, Guy RD. Flagellar swimming in viscoelastic fluids: role of fluid elastic stress revealed by simulations based on experimental data. J R Soc Interface 2017; 14:rsif.2017.0289. [PMID: 28978746 DOI: 10.1098/rsif.2017.0289] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [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: 04/18/2017] [Accepted: 09/11/2017] [Indexed: 12/13/2022] Open
Abstract
Many important biological functions depend on microorganisms' ability to move in viscoelastic fluids such as mucus and wet soil. The effects of fluid elasticity on motility remain poorly understood, partly because the swimmer strokes depend on the properties of the fluid medium, which obfuscates the mechanisms responsible for observed behavioural changes. In this study, we use experimental data on the gaits of Chlamydomonas reinhardtii swimming in Newtonian and viscoelastic fluids as inputs to numerical simulations that decouple the swimmer gait and fluid type in order to isolate the effect of fluid elasticity on swimming. In viscoelastic fluids, cells employing the Newtonian gait swim faster but generate larger stresses and use more power, and as a result the viscoelastic gait is more efficient. Furthermore, we show that fundamental principles of swimming based on viscous fluid theory miss important flow dynamics: fluid elasticity provides an elastic memory effect that increases both the forward and backward speeds, and (unlike purely viscous fluids) larger fluid stress accumulates around flagella moving tangent to the swimming direction, compared with the normal direction.
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Affiliation(s)
- Chuanbin Li
- Department of Mathematics, University of California Davis, Davis, CA 95616, USA
| | - Boyang Qin
- Department of Mechanical Engineering and Applied Mechanics, The University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California Merced, Merced, CA 95343, USA
| | - Paulo E Arratia
- Department of Mechanical Engineering and Applied Mechanics, The University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Becca Thomases
- Department of Mathematics, University of California Davis, Davis, CA 95616, USA
| | - Robert D Guy
- Department of Mathematics, University of California Davis, Davis, CA 95616, USA
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26
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Gopinath A, Sathiyaraj S, Sultan Nasar A. Star poly(4-vinylpyridine)s using dendritic ATRP initiators: Synthesis, electrolyte property and performance in dye sensitized solar cell. J Polym Res 2017. [DOI: 10.1007/s10965-017-1274-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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27
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Abstract
We experimentally investigate the effect of particle size on the motion of passive polystyrene spheres in suspensions of Escherichia coli. Using particles covering a range of sizes from 0.6 to 39 microns, we probe particle dynamics at both short and long time scales. In all cases, the particles exhibit super-diffusive ballistic behavior at short times before eventually transitioning to diffusive behavior. Surprisingly, we find a regime in which larger particles can diffuse faster than smaller particles: the particle long-time effective diffusivity exhibits a peak in particle size, which is a deviation from classical thermal diffusion. We also find that the active contribution to particle diffusion is controlled by a dimensionless parameter, the Péclet number. A minimal model qualitatively explains the existence of the effective diffusivity peak and its dependence on bacterial concentration. Our results have broad implications on characterizing active fluids using concepts drawn from classical thermodynamics.
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Affiliation(s)
- Alison E Patteson
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Arvind Gopinath
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA. and School of Engineering, University of California Merced, Merced, CA 95343, USA
| | - Prashant K Purohit
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Paulo E Arratia
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Patteson AE, Gopinath A, Goulian M, Arratia PE. Running and tumbling with E. coli in polymeric solutions. Sci Rep 2015; 5:15761. [PMID: 26507950 PMCID: PMC4938119 DOI: 10.1038/srep15761] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [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: 04/22/2015] [Accepted: 09/29/2015] [Indexed: 12/24/2022] Open
Abstract
Run-and-tumble motility is widely used by swimming microorganisms including numerous prokaryotic and eukaryotic organisms. Here, we experimentally investigate the run-and-tumble dynamics of the bacterium E. coli in polymeric solutions. We find that even small amounts of polymer in solution can drastically change E. coli dynamics: cells tumble less and their velocity increases, leading to an enhancement in cell translational diffusion and a sharp decline in rotational diffusion. We show that suppression of tumbling is due to fluid viscosity while the enhancement in swimming speed is mainly due to fluid elasticity. Visualization of single fluorescently labeled DNA polymers reveals that the flow generated by individual E. coli is sufficiently strong to stretch polymer molecules and induce elastic stresses in the fluid, which in turn can act on the cell in such a way to enhance its transport. Our results show that the transport and spread of chemotactic cells can be independently modified and controlled by the fluid material properties.
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Affiliation(s)
- A E Patteson
- Department of Mechanical Engineering &Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
| | - A Gopinath
- Department of Mechanical Engineering &Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104.,School of Engineering, University of California Merced, Merced, CA 95343
| | - M Goulian
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - P E Arratia
- Department of Mechanical Engineering &Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
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Qin B, Gopinath A, Yang J, Gollub JP, Arratia PE. Flagellar kinematics and swimming of algal cells in viscoelastic fluids. Sci Rep 2015; 5:9190. [PMID: 25778677 PMCID: PMC4361863 DOI: 10.1038/srep09190] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [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: 11/04/2014] [Accepted: 02/23/2015] [Indexed: 12/24/2022] Open
Abstract
The motility of microorganisms is influenced greatly by their hydrodynamic interactions with the fluidic environment they inhabit. We show by direct experimental observation of the bi-flagellated alga Chlamydomonas reinhardtii that fluid elasticity and viscosity strongly influence the beating pattern - the gait - and thereby control the propulsion speed. The beating frequency and the wave speed characterizing the cyclical bending are both enhanced by fluid elasticity. Despite these enhancements, the net swimming speed of the alga is hindered for fluids that are sufficiently elastic. The origin of this complex response lies in the interplay between the elasticity-induced changes in the spatial and temporal aspects of the flagellar cycle and the buildup and subsequent relaxation of elastic stresses during the power and recovery strokes.
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Affiliation(s)
- B. Qin
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
| | - A. Gopinath
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
- Department of Physics & Astronomy, Haverford College, Haverford, PA 19041
| | - J. Yang
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
- Department of Physics & Astronomy, Haverford College, Haverford, PA 19041
| | - J. P. Gollub
- Department of Physics & Astronomy, Haverford College, Haverford, PA 19041
| | - P. E. Arratia
- Department of Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104
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Abstract
We show that active, self-propelled particles that are connected together to form a single chain that is anchored at one end can produce the graceful beating motions of flagella. Changing the boundary condition from a clamp to a pivot at the anchor leads to steadily rotating tight coils. Strong noise in the system disrupts the regularity of the oscillations. We use a combination of detailed numerical simulations, mean-field scaling analysis and first passage time theory to characterize the phase diagram as a function of the filament length, passive elasticity, propulsion force and noise. Our study suggests minimal experimental tests for the onset of oscillations in an active polar chain.
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Affiliation(s)
- Raghunath Chelakkot
- Martin Fisher School of Physics, Brandeis University, , Waltham, MA 02453, USA
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Admala NR, Gopinath A, Jain S, Reddy J, Raghu D, Patil N. Facial Symmetry: An Illusion? J Indian Orthod Soc 2013. [DOI: 10.1177/0974909820130607s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Naveen Reddy Admala
- Professor and Head, Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
| | - A Gopinath
- Professor, Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
| | - Shrenik Jain
- Postgraduate Student, Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
| | - Jayaprakash Reddy
- Reader Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
| | - D Raghu
- Senior Lecturer Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
| | - Neelakantha Patil
- Senior Lecturer Department of Orthodontics and Dentofacial Orthopedics, AME's Dental College and Hospital, Raichur, Karnataka, India
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Reddy Admala N, Gopinath A. Facial Symmetry: An Illusion? JIOS 2013. [DOI: 10.5005/jp-journals-10021-1182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Mani M, Gopinath A, Mahadevan L. How things get stuck: kinetics, elastohydrodynamics, and soft adhesion. Phys Rev Lett 2012; 108:226104. [PMID: 23003628 DOI: 10.1103/physrevlett.108.226104] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 02/07/2012] [Indexed: 06/01/2023]
Abstract
We consider the sticking of a fluid-immersed colloidal particle with a substrate coated by polymeric tethers, a model for soft, wet adhesion in many natural and artificial systems. Our theory accounts for the kinetics of binding, the elasticity of the tethers, and the hydrodynamics of fluid drainage between the colloid and the substrate, characterized by three dimensionless parameters: the ratio of the viscous drainage time to the kinetics of binding, the ratio of elastic to thermal energies, and the size of the particle relative to the height of the polymer brush. For typical experimental parameters and discrete families of tethers, we find that adhesion proceeds via punctuated steps, where rapid transitions to increasingly bound states are separated by slow aging transients, consistent with recent observations. Our results also suggest that the bound particle is susceptible to fluctuation-driven instabilities parallel to the substrate.
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Affiliation(s)
- Madhav Mani
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
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Gopinath A, Hagan MF, Marchetti MC, Baskaran A. Dynamical self-regulation in self-propelled particle flows. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 85:061903. [PMID: 23005123 DOI: 10.1103/physreve.85.061903] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Indexed: 06/01/2023]
Abstract
We study a continuum model of overdamped self-propelled particles with aligning interactions in two dimensions. Combining analytical theory and computations, we map out the phase diagram for the parameter space covered by the model. We find that the system self-organizes into two robust structures in different regions of parameter space: solitary waves composed of ordered swarms moving through a low density disordered background, and stationary radially symmetric asters. The self-regulating nature of the flow yields phase separation, ubiquitous in this class of systems, and controls the formation of solitary waves. Self-propulsion and the associated active convection play a crucial role in aster formation.
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Affiliation(s)
- Arvind Gopinath
- Martin Fisher School of Physics, Brandeis University, Waltham, Massachusetts, USA
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Sekhar LC, Koganti VP, Shankar BR, Gopinath A. A comparative study of temporary splints: bonded polyethylene fiber reinforcement ribbon and stainless steel wire + composite resin splint in the treatment of chronic periodontitis. J Contemp Dent Pract 2011; 12:343-349. [PMID: 22269194 DOI: 10.5005/jp-journals-10024-1057] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
UNLABELLED The present clinical study was undertaken to determine the effects of splinting overunsplinted mobile teeth following periodontal surgery and compared the efficacy of two splinting materials, i.e. Ribbond ribbon + Composite with Stainless steel wire + Composite. MATERIALS AND METHODS Total of 30 patients (20 experimental and 10 control) formed the study group. Entire study was extended over a period of 12 weeks for each patient and treatment plan was divided into 8 phases. Healing response was monitored and application, durability, biocompatibility of splint material was assessed. RESULTS Splint had a promising and beneficial effects on anterior teeth exhibiting Grade I to Grade II degrees of mobility. Experimental group showed a greater reduction in tooth mobility compared to control group. There was no significant difference in plaque index and Ribbond Ribbon reinforced with composite resin was an excellent material for application, patient comfort, resistance to fracture, biocompatable and esthetic acceptability. CLINICAL SIGNIFICANCE Splinting is recommended as an adjunct to periodontal surgery in the treatment of hypermobile teeth, especially in cases where patient discomfort is a prominent factor.
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Affiliation(s)
- L Chandra Sekhar
- Department of Periodontics, Purvanchal Institute of Dental Sciences, Gorakhpur, Uttar Pradesh, India.
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Abstract
Surfaces covered by bristles, hairs, polymers and other filamentous structures arise in a variety of natural settings in science such as the active lining of many biological organs, e.g. lungs, reproductive tracts, etc., and have increasingly begun to be used in technological applications. We derive an effective field theory for the elastohydrodynamics of ordered brushes and disordered carpets that are made of a large number of elastic filaments grafted on to a substrate and interspersed in a fluid. Our formulation for the elastohydrodynamic response of these materials leads naturally to a set of constitutive equations coupling bed deformation to fluid flow, accounts for the anisotropic properties of the medium, and generalizes the theory of poroelasticity to these systems. We use the effective medium equations to study three canonical problems—the normal settling of a rigid sphere onto a carpet, the squeeze flow in a carpet and the tangential shearing motion of a rigid sphere over the carpet, all problems of relevance in mechanosensation in biology with implications for biomimetic devices.
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Affiliation(s)
- A. Gopinath
- School of Engineering and Applied Sciences, Harvard University, MA 02139, USA
| | - L. Mahadevan
- School of Engineering and Applied Sciences, Harvard University, MA 02139, USA
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Little TJ, Gopinath A, Patel E, McGlone A, Lassman DJ, D'Amato M, McLaughlin JT, Thompson DG. Gastric emptying of hexose sugars: role of osmolality, molecular structure and the CCK₁ receptor. Neurogastroenterol Motil 2010; 22:1183-90, e314. [PMID: 20584263 DOI: 10.1111/j.1365-2982.2010.01552.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND It is widely reported that hexose sugars slow gastric emptying (GE) via osmoreceptor stimulation but this remains uncertain. We evaluated the effects of a panel of hexoses of differing molecular structure, assessing the effects of osmolality, intra-individual reproducibility and the role of the CCK(1) receptor, in the regulation of GE by hexoses. METHODS Thirty one healthy non-obese male and female subjects were studied in a series of protocols, using a (13) C-acetate breath test to evaluate GE of varying concentrations of glucose, galactose, fructose and tagatose, with water, NaCl and lactulose as controls. GE was further evaluated following the administration of a CCK(1) receptor antagonist. Three subjects underwent repeated studies to evaluate intra-individual reproducibility. KEY RESULTS At 250 mOsmol, a hexose-specific effect was apparent: tagatose slowed GE more potently than water, glucose and fructose (P < 0.05). Fructose (P < 0.05) also slowed GE, but with substantial inter-, but not intra-, individual differences. As osmolality increased further the hexose-specific differences were lost. At 500 mOsmol, all hexoses slowed GE compared with water (P < 0.05), whereas lactulose and saline did not. The slowing of GE by hexose sugars appeared to be CCK(1) receptor-dependent. CONCLUSIONS & INFERENCES The effects of hexose sugars on GE appear related to their molecular structure rather than osmolality per se, and are, at least in part, CCK(1) receptor-dependent.
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Affiliation(s)
- T J Little
- Section of Gastrointestinal Sciences, Manchester Academic Health Sciences Centre, Salford Royal NHS Foundation Trust, The University of Manchester, Salford, UK.
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Taxak S, Gopinath A. Insertion of the i-gel airway in prone position. Minerva Anestesiol 2010; 76:381. [PMID: 20395902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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Lockwood CJ, Paidas M, Murk WK, Kayisli UA, Gopinath A, Huang SJ, Krikun G, Schatz F. Involvement of human decidual cell-expressed tissue factor in uterine hemostasis and abruption. Thromb Res 2009; 124:516-20. [PMID: 19720393 DOI: 10.1016/j.thromres.2009.07.017] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 07/06/2009] [Accepted: 07/07/2009] [Indexed: 11/15/2022]
Abstract
Vascular injury increases access and binding of plasma-derived factor VII to perivascular cell membrane-bound tissue factor (TF). The resulting TF/VIIa complex promotes hemostasis by cleaving pro-thrombin to thrombin leading to the fibrin clot. In human pregnancy, decidual cell-expressed TF prevents decidual hemorrhage (abruption). During placentation, trophoblasts remodel decidual spiral arteries into high conductance vessels. Shallow trophoblast invasion impedes decidual vascular conversion, producing an inadequate uteroplacental blood flow that elicits abruption-related placental ischemia. Thrombin induces several biological effects via cell surface protease activated receptors. In first trimester human DCs thrombin increases synthesis of sFlt-1, which elicits placental ischemia by impeding angiogenesis-related decidual vascular remodeling. During pregnacy, the fibrillar collagen-rich amnion and choriodecidua extracellular matrix (ECM) provides greater than additive tensile strength and structural integrity. Thrombin acts as an autocrine/paracrine mediator that degrades these ECMs by augmenting decidual cell expression of: 1) matrix metalloproteinases and 2) interleukin-8, a key mediator of abruption-associated decidual infiltration of neutrophils, which express several ECM degrading proteases. Among the cell types at the maternal fetal interface at term, TF expression is highest in decidual cells indicating that this TF meets the hemostatic demands of labor and delivery. TF expression in cultured term decidual cells is enhanced by progestin and thrombin suggesting that the maintenance of elevated circulating progesterone provides hemostatic protection and that abruption-generated thrombin acts in an autocrine/paracrine fashion on decidual cells to promote hemostasis via enhanced TF expression.
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Affiliation(s)
- C J Lockwood
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
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Yoo H, Delabarre L, Gopinath A, Vaughan JT. RF Magnetic Signal Localization at Very High Magnetic Field Systems. J Med Device 2009. [DOI: 10.1115/1.3147378] [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: 11/08/2022] Open
Abstract
The impetus of this work originated from the advent of high magnetic field magnetic resonance imaging scanners with B0 fields of 4T, 7T, and 9.4T. These ultrahigh magnetic field systems generally improve the signal to noise ratios. However, B1 field non-uniformity also occurs due to the increased RF field frequencies when wavelengths in the head become shorter than its size. As interest in multiple channel transmission line coils increases, the control of the amplitude and phase of individual coil elements is required in order to develop desired B1 field. The choice of the excitation of the coil elements may be determined by convex optimization. Convex optimization is used provides results very fast, when the problem is formulated globally. In addition, convex optimization provides better signal to noise (SNR) ratio when anatomic specific regions are investigated. In this paper, simulation and experimental results are discussed at 9.4T systems based on the number of elements. The primary objective of this study is to increase the signal in a specific target region and decrease the signal and noise in the outside region termed the suppression region. The convex formulations are minimizing the maximum field point in the suppression region while keeping the center of target maximum. Based on this min-max optimization criterion, an iteration method which modifies the selection of suppression fields is also performed to produce better results. The results of the localization on FDTD human data at 9.4T are shown in Fig. 1. In these figures, the axial slices of the center of human head model provided by XFDTD are used after manipulating with MATLAB and the 16 channel head coil is excited. Figure 1 shows an improvement of the homogeneity in the suppression region when the target region is at center. In Fig. 2, received signal localizations are obtained for three different regions of interest (ROI) after using the convex optimization. Note that the selection of ROI is limited by the geometric setting of phantom in the 8-channel TEM head coil. Convex optimization with an iterative method was performed on both the human head and phantom models with operating frequency 400 MHz to design coil channel excitation parameters. By applying the iterative method to the convex optimization, more homogeneous B1 fields are obtained in the suppression region for 9.4T system.
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Affiliation(s)
- H. Yoo
- University of Minnesota, Minneapolis, MN, USA
| | | | - A. Gopinath
- University of Minnesota, Minneapolis, MN, USA
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Gopinath A, Little T, Mcglone A, Patel E, Lassman D, Rhodes S, Mclaughlin J, Thompson D. Gastric emptying of hexose sugars in healthy humans. Effects of osmolality and molecular structure. Appetite 2009. [DOI: 10.1016/j.appet.2009.04.083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Puhan S, Gopinath A, Nagarajan G. Combustion, performance and emission characteristics of a DI CI engine using biodiesel with varied fatty acid composition. ACTA ACUST UNITED AC 2009. [DOI: 10.1504/ijret.2009.024732] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Recent developments in computational cell and biomolecular mechanics have provided valuable insights into the mechanical properties of cells, subcellular components and biomolecules, while simultaneously complementing new experimental techniques used for deciphering the structure-function paradigm in living cells. These computational approaches have direct implications in understanding the state of human health and the progress of disease and can therefore aid immensely in the diagnosis and treatment of diseases. We provide an overview of the computational approaches that are currently used in understanding various aspects of cell and bimolecular mechanics. Our emphasis is on state-of-the-art techniques and the progress made in addressing key challenges in biomechanics.
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Affiliation(s)
- Ashkan Vaziri
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
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Gopinath A, Armstrong RC, Brown RA. Observations on the eigenspectrum of the linearized Doi equation with application to numerical simulations of liquid crystal suspensions. J Chem Phys 2006; 121:6093-4. [PMID: 15367038 DOI: 10.1063/1.1785148] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Abstract
The problem of steady streaming around a rigid isolated sphere in a plane standing acoustic field is considered. Existing results in the literature have been generalized to allow for noncompactness of the sphere, and the influence of fluid compressibility on the streaming behavior has been included. It is found that in the high-frequency limit of interest for which the streaming is strongest, the effective steady slip velocity at the edge of the inner boundary layer region that is responsible for driving the steady streaming in the bulk of the fluid in the outer region, has a complex variation over the surface of the sphere that depends on (i) the sphere position (with respect to the node/antinode of the acoustic field), (ii) the extent of sphere compactness, and (iii) on a well-defined function (representing compressibility effects) of the fluid Prandtl number and its ratio of specific heats. Not surprisingly, the contribution from this function is negligible when the host fluid is a liquid. The steady streaming behavior around the sphere is demonstrated with the help of flow streamlines for various cases in the diffusive limit of weak outer flow for low streaming Reynolds numbers.
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Affiliation(s)
- A Gopinath
- Department of Mechanical Engineering, Naval Postgraduate School, Monterey, California 93943, USA.
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Nikolajeff F, Ballen TA, Leger JR, Gopinath A, Lee TC, Williams RC. Spatial-mode control of vertical-cavity lasers with micromirrors fabricated and replicated in semiconductor materials. Appl Opt 1999; 38:3030-3038. [PMID: 18319888 DOI: 10.1364/ao.38.003030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Micromirrors were fabricated in gallium phosphide by mass transport to provide spatial-mode control of vertical-cavity surface-emitting lasers (VCSEL's). The concave mirrors were used in an external-cavity configuration to provide spatial filtering in the far field. Single-mode cw lasing was demonstrated in 15-microm-diameter VCSEL's with currents as high as 6 times threshold. The fabrication process was extended to micromirrors in gallium arsenide by use of a replication and dry-etch transfer process.
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Affiliation(s)
- F Nikolajeff
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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