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sabato 25 maggio 2024
# gst: exotic geometries, a Janus trefoil knot, which rotates as it swims forwards.
mercoledì 20 gennaio 2016
# s-phys: knotted solitary waves: the begin
<< a team of physicists (..) has found a way to create knotted solitary waves, or knot solitons, in a quantum-mechanical field >>
<< Knots are defined mathematically as closed curves in 3D space. A knot soliton consists of an infinite number of rings, each linked with all of the others to generate a toroidal structure >>
<< This is the beginning of the story of quantum knots >>
http://www.sci-news.com/physics/physicists-create-quantum-knots-03569.html
D. S. Hall, M. W. Ray, et al. Tying quantum knots. Nature Physics (2016) doi:10.1038/nphys3624
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3624.html
venerdì 11 maggio 2018
# gst: the dance of complex knots (in DNA), from mobile to jammed states
AA << show for the first time experimentally that knots can go from a mobile to a jammed state by varying an applied strain rate, and that this jamming is reversible >>
Alexander R. Klotz, Beatrice W. Soh, and Patrick S. Doyle. Motion of Knots in DNA Stretched by Elongational Fields. Phys. Rev. Lett. 120, 188003. May 3, 2018.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.188003
Anne Trafton. Chemical engineers discover how to control knots that form in DNA molecules. Massachusetts Institute of Technology. May 3, 2018.
sabato 6 ottobre 2018
# gst: periodic oscillations of flexible knots
AA << study the dynamics of knotted deformable closed chains sedimenting in a viscous fluid. (..) trefoil and other torus knots often attain a remarkably regular horizontal toroidal structure while sedimenting, with a number of intertwined loops, oscillating periodically around each other. (..) this motion (..) is accompanied by a very slow rotation around the vertical symmetry axis. (..) this oscillating mode of the dynamics can spontaneously form even when starting from a qualitatively different initial configuration. (..) the oscillating modes are usually present as transients or final stages of the evolution, depending on chain aspect ratio and flexibility, and the number of loops. >>
Magdalena Gruziel, Krishnan Thyagarajan, et al. Periodic Motion of Sedimenting Flexible Knots. Phys. Rev. Lett. 121, 127801 Sep 18, 2018. doi: 10.1103/PhysRevLett.121.127801.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.127801
The periodic motion of flexible knots, and the connection to DNA. University of Warsaw. Sep 26, 2018.
https://m.phys.org/news/2018-09-periodic-motion-flexible-dna.html
lunedì 21 agosto 2023
# gst: neural networks know their knots.
lunedì 25 gennaio 2021
# gst: apropos of the structure of natural codes, a RNA folding knot (origami-style) dance
sabato 30 luglio 2016
# s-gst: vortex knots in wave systems
<< Waves surround us all the time: sound waves in the noise around us, light waves enabling us to see, and according to quantum mechanics, all matter has a wave nature. Most of these waves, however, do not resemble the regular train of waves at the shore of the ocean—the pattern is much more chaotic. Most significantly, the whirls and eddies form lines in space called vortices. Along these lines, the wave intensity is zero, and natural wave fields - light, sound and quantum matter - are filled with a dense tangle of these null filaments >>
Knots in chaotic waves. July 29, 2016.
http://m.phys.org/news/2016-07-chaotic.html
Alexander J. Taylor & Mark R. Dennis. Vortex knots in tangled quantum eigenfunctions. Nature Communications. Published 29 Jul 2016 DOI: 10.1038/ncomms12346 OPEN
http://www.nature.com/ncomms/2016/160729/ncomms12346/full/ncomms12346.html
martedì 3 maggio 2016
# s-gst: measuring energy levels inside transitional dis-order(s)
<< Vortex filaments in classical and quantum fluids and DNA macromolecules, magnetic flux tubes, phase defects, polymers may interact and recombine through reconnection of neighboring strands. Details of the process depend on specific local mechanisms that may differ from case to case, but certain qualitative features — such as the preservation of the original strand orientation after recombination — are generic and common to all systems. >>
<< The study of these processes is clearly of great importance, because the change of topology is often accompanied by a change in energy, entropy and function. >>
<< (..) HOMFLYPT polynomial recently introduced for fluid knots (..) provides a powerful tool to measure topological complexity of various physical systems. >>
Liu, X., Ricca, R. L. Knots cascade detected by a monotonically decreasing sequence of values. Sci. Rep.6, 24118; doi: 10.1038/srep24118 (2016).
http://www.nature.com/articles/srep24118
Quanta energia è nascosta nel caos? Bicocca, Milano, 2 maggio 2016
http://www.unimib.it/open/news/Quanta-energia-e-nascosta-nel-caos-Ce-lo-dice-il-polinomio-targato-Bicocca-Beijing-UTech/4936093294137195314
sabato 30 maggio 2020
# gst: apropos of unexpected Hopfion tangles
sabato 23 settembre 2017
# chem: strange transitions: tying a crystal into a knot
<< Single crystals are typically brittle, inelastic materials. Such mechanical responses limit their use in practical applications, particularly in flexible electronics and optical devices >>
AA << describe single crystals of a well-known coordination compound—copper(II) acetylacetonate—that are flexible enough to be reversibly tied into a knot >>
Anna Worthy, Arnaud Grosjean, et al. Atomic resolution of structural changes in elastic crystals of copper(II) acetylacetonate. Nature Chemistry. doi: 10.1038/nchem.2848. Aug 28, 2017
http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2848.html
<< crystals exhibit traditional characteristics of not only hard matter, but soft matter like nylon >> John McMurtrie
<< Under strain the molecules in the crystal reversibly rotate and reorganise to allow the compression and expansion required for elasticity and still maintain the integrity of the crystal structure >> Jack Clegg
Bendable crystals tie current thinking in knots. Aug 29, 2017.
https://m.phys.org/news/2017-08-bendable-crystals-current.html
venerdì 4 dicembre 2015
# s-astrophys: a large-scale distribution of matter, with filaments and knots ...
<< Matter known as ordinary, which makes up everything we know, corresponds to only 5% of the Universe. >>
<< (..) the majority of the missing ordinary matter is found in the form of a very hot gas associated with intergalactic filaments >>
http://www.alphagalileo.org/ViewItem.aspx?ItemId=158939&CultureCode=en
Dominique Eckert, Mathilde Jauzac, et al. Warm–hot baryons comprise 5–10 per cent of filaments in the cosmic web. Nature, 2015; 528 (7580): 105 DOI: 10.1038/nature16058
http://www.nature.com/nature/journal/v528/n7580/full/nature16058.html