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Guillamat Prost Marchetti Toyama Kawaguchi Kageyama Sacks Shani Blanch Kruse Topology 1995 2013 2015 2017 2020 2021
This talk was part of the of the online workshop on "Interdisciplinary Challenges in Nonequilibrium Physics" held April 12 - 16, 2021. Discontinuities within orientational fields configure topological defects [1]. They are often present in materials featuring orientational, nematic, order, and can be found in very diverse areas, which span a vast range of length scales [2]. Interestingly, in active nematic systems, topological defects imply not only strong orientational gradients but also well-defined flow and stress patterns in very localized regions [3]. Recent works have shown the influence of these defects in determining the dynamics of living systems, from cell monolayers [4–6] to simple organisms [7]. Here, we study how nematic monolayers composed of muscle cells self-organize and evolve under circular confinement, which enforces a topological charge S=+1. Under strong confinements, with size competing with the characteristic nematic correlation length, the formation of half-integer defects (s=±1/2) is hampered, resulting in spontaneous cellular arrangements with one single integer defect (s=+1) at the center of the islands, namely, rotating spirals and quasi-static asters [8]. These singularities imply distinct mechanical fields, which lead, eventually, to the localized expression of muscle-specific proteins and the formation of 3D nematic cellular protrusions [9]. [1] P. G. de Gennes and J. Prost, The Physics of Liquid Crystals (Clarendon Press, 1995). [2] M. C. Marchetti, J. F. Joanny, S. Ramaswamy, T. B. Liverpool, J. Prost, M. Rao, and R. A. Simha, Hydrodynamics of Soft Active Matter, Rev. Mod. Phys. 85, 1143 (2013). [3] L. Giomi, Geometry and Topology of Turbulence in Active Nematics, Phys. Rev. X 5, 031003 (2015). [4] G. Duclos, C. Erlenkamper, J.-F. Joanny, and P. Silberzan, Topological Defects in Confined Populations of Spindle-Shaped Cells, Nat Phys 13, 58 (2017). [5] T. B. Saw, A. Doostmohammadi, V. Nier, L. Kocgozlu, S. Thampi, Y. Toyama, P. Marcq, C. T. Lim, J. M. Yeomans, and B. Ladoux, Topological Defects in Epithelia Govern Cell Death and Extrusion, Nature 544, 212 (2017). [6] K. Kawaguchi, R. Kageyama, and M. Sano, Topological Defects Control Collective Dynamics in Neural Progenitor Cell Cultures, Nature 545, 327 (2017). [7] Y. Maroudas-Sacks, L. Garion, L. Shani-Zerbib, A. Livshits, E. Braun, and K. Keren, Topological Defects in the Nematic Order of Actin Fibres as Organization Centres of Hydra Morphogenesis, Nat. Phys. (2020). [8] C. Blanch-Mercader, P. Guillamat, A. Roux, and K. Kruse, Quantifying Material Properties of Cell Monolayers by Analyzing Integer Topological Defects, Phys. Rev. Lett. 126, 028101 (2021). [9] P. Guillamat, C. Blanch-Mercader, K. Kruse, and A. Roux, Integer Topological Defects Organize Stresses Driving Tissue Morphogenesis, BioRxiv 2020.06.02.129262 (2020).
Brenton Broadstock Carneiro Teixeira Webb Cardi Sato Marshall McGuire McGuire Elision Topology 1925 1927 1952 1956 1975 2000 2009 2010 2011
...Only the Living...for piano trio Composed by Brendan Colbert. Performance at the 2011 Resonance Music Series / Melbourne Composers' League 'At First Light' Concert Saturday, 24 September, 2011, Trinity Uniting Church, Brighton, Melbourne, Australia Michael Kieran Harvey (pianoforte), Alister Barker (violoncello) and Tim Veldman (violin). ...Only the living... is dedicated to Brian +••.••(...)), Kathleen +••.••(...)) and Michael +••.••(...)) ...Time may finally prove, only the living move her... Peter Hammill. Originally completed in 2000, ...Only the living... was revised (and finalised) in 2009, and is about eleven minutes long. Brendan Colbert was born in Ballarat, Victoria, in 1956. After moving to Melbourne in 1975 he worked with various progressive-rock bands as keyboard player and songwriter, and in the mid 80s started private composition studies, initially with Brenton Broadstock and then later with Riccardo Formosa. His output includes a large number of works, with many performances and broadcasts around Australia and in Europe and the USA. Performers include the Queensland and West Australian Symphony Orchestras, ensembles such as ELISION, Speak Percussion, Arcko Symphonic Project, Smash Ensemble, Libra, Topology, Duo Contemporain, and soloists Sisco Aparici, Pedro Carneiro, Mario Teixeira, Barrie Webb, Michael Kieran Harvey, Peter Neville, Carl Rosman, Stefano Cardi, Norio Sato, Linda Wetherill, Gisbert Watty, Marshall McGuire, Geoffrey Morris and others. In recent times his percussion works in particular have attracted significant international attention. Other recent performances include premieres of Shades of Futures Past (flute concerto, Arcko Symphonic Project, conducted by Timothy Phillips, featuring Sarah Beggs soloist, Melbourne August 2011), Ebb (percussion quartet, SPEAK Percussion, Sep. 2010), Clash (xylophone and vibes, SPEAK Percussion, Sep. 2010), and ...only the living...
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