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lunedì 11 aprile 2022

# gst: apropos of instabilities, viscoelastic liquid bridges can be destabilized by torsion.

<< Liquid bridges are formed when liquids are constrained between two (or more) surfaces via the capillary force. They appear in a wide range of contexts including biology, medicine, and engineering. In the context of biology, liquid bridges enable animals like geckos to adhere to vertical walls (..) >>

<< By experiment and simulation, (AA) report that viscoelastic liquid bridges made of constant viscosity elastic liquids, a.k.a. Boger fluids, can be effectively destabilized by torsion. Under torsion, the deformation of the liquid bridge depends on the competition between elastocapillarity and torsion-induced normal stress effects. When the elastocapillary effect dominates, the liquid bridge undergoes elastocapillary instability and thins into a cylindrical thread, whose length increases and whose radius decays exponentially over time. When the torsion-induced normal stress effect dominates, the liquid bridge deforms in a way similar to edge fracture, a flow instability characterized by the sudden indentation of the fluid's free surface when a viscoelastic fluid is sheared at above a critical deformation rate. The vertical component of the normal stress causes the upper and lower portions of the liquid bridge to approach each other, and the radial component of the normal stress results in the liquid bridge thinning more quickly than under elastocapillarity. Whether such quick thinning continues until the bridge breaks depends on both the liquid bridge configuration and the level of torsion applied. >>️

San To Chan, Stylianos Varchanis, et al. Torsional instability of constant viscosity elastic liquid bridges. Soft Matter, 2022,18, 1965-1977. doi: 10.1039/ D1SM01804C. Feb 7, 2022. 



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keyword 'instability' | 'instabilities' in FonT



keyword 'instabile' in Notes (quasi-stochastic poetry)


keyword 'torsione' in Notes (quasi-stochastic poetry)


keywords: instability, torsion, torsional instability, viscoelastic liquid, bridge







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sabato 9 aprile 2022

# phyto: weird, jazzy Nature, the 'transference of sexuality', 'some sexual consequences of being a plant'.

<< Plants have characteristic features that affect the expression of sexual function, notably the existence of a haploid organism in the life cycle, and in their development, which is modular, iterative and environmentally reactive. For instance, primary selection (the first filtering of the products of meiosis) is via gametes in diplontic animals, but via gametophyte organisms in plants. Intragametophytic selfing produces double haploid sporophytes which is in effect a form of clonal reproduction mediated by sexual mechanisms. In homosporous plants, the diploid sporophyte is sexless, sex being only expressed in the haploid gametophyte. However, in seed plants, the timing and location of gamete production is determined by the sporophyte, which therefore has a sexual role, and in dioecious plants has genetic sex, while the seed plant gametophyte has lost genetic sex. This evolutionary transition is one that E.J.H. Corner called ‘the transference of sexuality’. The iterative development characteristic of plants can lead to a wide variety of patterns in the distribution of sexual function, and in dioecious plants poor canalization of reproductive development can lead to intrasexual mating and the production of YY supermales or WW superfemales. Finally, plant modes of asexual reproduction (agamospermy/apogamy) are also distinctive by subverting gametophytic processes. >>

Quentin Cronk. Some sexual consequences of being a plant. Philos Trans R Soc Lond B Biol Sci. doi: 10.1098/ rstb.2021.0213. Mar 21, 2022. 


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keyword 'phyto' | 'plant' in FonT



keywords: evol, evolution, phyto, plant, sex, sexuality

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mercoledì 6 aprile 2022

# astro: going beyond a performance by Frank Zappa (or a speech by – for example – a political entity), two speeds of sound found on Mars

AA << find that atmospheric sounds extend measurements of pressure variations down to 1,000 times smaller scales than ever observed before, revealing a dissipative regime extending over 5 orders of magnitude in energy. Using point sources of sound (Ingenuity rotorcraft, laser-induced sparks), (AA) highlight two distinct values for the speed of sound that are ~10 m/s apart below and above 240 Hz, a unique characteristic of low-pressure CO2-dominated atmosphere. (They) also provide the acoustic attenuation with distance above 2 kHz, allowing to elucidate the large contribution of the CO2 vibrational relaxation in the audible range. >>

Maurice, S., Chide, B., Murdoch, N. et al. In situ recording of Mars soundscape. Nature. doi: 10.1038/ s41586-022-04679-0. Apr 1, 2022. 


<< All of these factors would make it difficult for two people to have a conversation only five meters (16 feet) apart >> Sylvestre Maurice.

Juliette Collen and Daniel Lawler. First audio recorded on Mars reveals two speeds of sound. Phys.org. Apr 1, 2022. 


NASA Perseverance Rover Captures 
Puff, Whir, Zap Sounds from Mars 


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Frank Zappa 


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keywords: astro, mars, acoustics, sound, speed of sound, dissipative regimes, music, jazz, freejazz









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martedì 5 aprile 2022

# gst: the solitary route to chimera states.

AA << show how solitary states in a system of globally coupled FitzHugh-Nagumo oscillators can lead to the emergence of chimera states. By a numerical bifurcation analysis of a suitable reduced system in the thermodynamic limit (they) demonstrate how solitary states, after emerging from the synchronous state, become chaotic in a period-doubling cascade. Subsequently, states with a single chaotic oscillator give rise to states with an increasing number of incoherent chaotic oscillators. In large systems, these chimera states show extensive chaos. (AA) demonstrate the coexistence of many of such chaotic attractors with different Lyapunov dimensions, due to different numbers of incoherent oscillators. >>

<<  While it is well known that self-organized wave patterns typically coexist within an interval of possible different wave numbers (..)(AA) show here the coexistence of coherence-incoherence patterns with different numbers of incoherent oscillators, which are in fact coexisting chaotic attractors with different Lyapunov dimensions. The incoherent oscillators in these coexisting attractors show extensive chaos of different dimensions. The total share of incoherent oscillators in a chimera state is a macroscopic quantity. Hence, within the range of such shares, where stable chimera states exist, (AA) find, for large systems, an increasing number of coexisting attractors with their numbers of incoherent oscillators increasing as well. (They) showed that, varying the coupling parameter, this extensive scenario is linked to the thermodynamic limit of the solitary regime, where the range of admissible numbers of incoherent oscillators shrinks down to one single oscillator in an infinitely large system. For this case, the emergence of the chaotic motion of the single incoherent oscillator could be shown in a period doubling cascade. >>

Leonhard Schulen, Alexander Gerdes, et al. The solitary route to chimera states. arXiv:2204.00385v1 [nlin.CD]. Apr 1, 2022.


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keyword 'FitzHugh-Nagumo oscillators' in APS | PubMed



keyword 'chaos' | 'chaotic' in Font



keyword 'caos' | 'caotico' in Notes (quasi-stochastic poetry)



keywords: gst, solitons, solitary states, period-doubling cascade, chaos, Lyapunov dimension, FitzHugh-Nagumo oscillator, chimera state, dynamical systems.







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venerdì 1 aprile 2022

# life: Chimps distribute their time to groom other individuals in the same manner as humans structure their relationships.

AA << show that the time chimpanzees devote to grooming other individuals is well described by the same model used for human relationships, supporting the existence of similar social signatures for both humans and chimpanzees. Furthermore, the relationship structure depends on group size as predicted by the model, the proportion of high intensity connections being larger for smaller groups. >>

Diego Escribano, Victoria Doldan-Martelli, et al. Chimpanzees organize their social relationships like humans. bioRxiv. doi: 10.1101/ 2022.03.16.484664. March 17, 2022. 


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keywords 'chimp' | 'chimps' in FonT



keyword 'chimps' | 'sileno' in Notes (quasi-stochastic poetry)



keywords 'behav' in FonT


keywords: life, chimps, behav, behavior, behaviour, social relationships





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giovedì 31 marzo 2022

# gst: apropos of transitions, the vortex dynamics from a twisted baker map

<< A natural approach to understanding complicated systems is to analyze a col­lection of simple examples that retain some essential features of the complexity of the original systems. The baker map (..) is one of the simplest models of chaotic dynamical systems. It divides the unit square into p ≥ 2 equal vertical strips, and maps each strip to a horizontal one by squeezing it vertically by the factor p and stretching it horizontally by the same factor. The horizontal strips are laid out covering the square. Due to the squeezing/stretching, small initial errors get amplified under iteration, and results in an unpredictable long-term behavior. The name “baker” is used since the action of the map is reminiscent of the kneading dough (..). In this paper (AA) introduce a piecewise linear model of an interaction of stretching and twisting that produces vortex dynamics. >>

They << show that the set of hyperbolic repelling periodic points with complex conjugate eigenvalues and that without complex conjugate eigenvalues are simultaneously dense in the phase space >>

Yoshitaka Saiki, Hiroki Takahasi, James A. Yorke. The twisted baker map. arXiv: 2202.04304v2 [math.DS]. Feb 9, 2022. 


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keyword 'transition' | 'transitional' in FonT



keyword 'transition' | 'transizion*' in Notes (quasi-stochastic poetry)




keyword 'vortex' in FonT


keyword 'vortice' in Notes
 (quasi-stochastic poetry)


keywords: gst, transition, vortex, baker map









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mercoledì 30 marzo 2022

# gst: solitary wave billiards

<<  In the present work (AA) introduce the concept of solitary wave billiards. I.e., instead of a point particle, (they) consider a solitary wave in an enclosed region and explore its collision with the boundaries and the resulting trajectories in cases which for particle billiards are known to be integrable and for cases that are known to be chaotic. A principal conclusion is that solitary wave billiards are generically found to be chaotic even in cases where the classical particle billiards are integrable. However, the degree of resulting chaoticity depends on the particle speed and on the properties of the potential. >>

J. Cuevas-Maraver, P.G. Kevrekidis, H. Zhang. Solitary wave billiards. arXiv: 2203.09489v1 [nlin.PS]. Mar 17, 2022. 


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keyword 'chaos' | 'chaotic' in Font



keyword 'caos' | 'caotico' in Notes (quasi-stochastic poetry)



keyword | 'soliton' in FonT


keywords: gst, waves, solitons, billiard, chaos 





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