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martedì 28 febbraio 2023

# gst: flocking transitions of unfriendly species.

AA consider << two kinds of self-propelled particles, A and B, that tend to align with particles from the same species and to antialign with the other. The model shows a flocking transition (..) it has a liquid-gas phase transition and displays micro-phase-separation in the coexistence region where multiple dense liquid bands propagate in a gaseous background. >>


<< The interesting features (..) are the existence of two kinds of bands, one composed of mainly A particles and one mainly of B particles, the appearance of two dynamical states in the coexistence region: the PF (parallel flocking) state in which all bands of the two species propagate in the same direction, and the APF (antiparallel flocking) state in which the bands of species A and species B move in opposite directions. When PF and APF states exist in the low-density part of the coexistence region they perform stochastic transitions from one to the other. The system size dependence of the transition frequency and dwell times show a pronounced crossover that is determined by the ratio of the band width and the longitudinal system size. >>

AA << work paves the way for studying multispecies flocking models with heterogeneous alignment interactions. >>

Swarnajit Chatterjee, Matthieu Mangeat, et al. Flocking of two unfriendly species: The two-species Vicsek model. Phys. Rev. E 107, 024607. Feb 14, 2023

Also

keyword 'swimmers' in FonT

Keywords: gst, flocking, particles, self-propelled particles, swimmers,  microswimmers


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lunedì 27 febbraio 2023

# life: a proposito di bizzarri scenari, qui una transizione 'a gradino' di ipotetico scenario22


Congo Square, New Orleans (img from web).  https://en.m.wikipedia.org/wiki/Congo_Square

Una senz'altro immaginifica transizione di un sistema anch'esso senz'altro immaginifico "3vs3 palle" 

qui potrebbe verificarsi una improvvisa mutazione "3vs3" verso un sistema auto- riconfigurato in "4vs2" palle.

(-) In prima approx il sistema destrogiro "4palle", sebbene caotico,  quasisticastico, potrebbe dimostrare chance di creativa stabilizzazione, anche a medio-lungo termine, anche grazie a non del tutto improbabili episodi di drammatiche funzionali fagocitosi (e.g. nelle forme predatorie del cannibalismo/ auto- cannibalismo, anche orgiastico estremo) al proprio interno.

(-) Il sistema levogiro "2palle" potrebbe invece lui medesimo risultare vincente sull'altro destrogiro nel caso riuscisse nell'im.probabile stabilizzazione,  ristrutturazione funzionale - dimostrando pubblicamente non banali capacità di risoluzione/ reimpostazione di problemi - perciò animandosi in modalità attrattive, coagulative su una parte significativa del 50% di quelle moltitudini verosimilmente costituite da entità fluttuanti nella solitaria condizione di pulviscoli erratici in emarginata sublimazione.

L'immagini, senz'altro campate in aria purtuttavia intriganti:  'episodi di drammatiche funzionali fagocitosi', 'cannibalismo, auto-cannibalismo anche orgiastico estremo' e 'solitaria condizione di pulviscoli erratici in emarginata sublimazione' meriterebbero una serie di poetiche, quasistocastiche perfino

ma mi astengo.

# life: a proposito di bizzarri scenari, qui un ipotetico scenario22 dipinto dal reale ... FonT.  Oct 17,  2022.

Also

<< Tornando all'analogia con la fisica, il potere, come l'energia, muta continuamente di forma >>. In: Onda anti rumore. Notes (quasi-stochastic poetry). April 21, 2005.

keyword 'dance' | 'dancing' in FonT


keyword 'danza' | 'danzant*' in Notes
(quasi-stochastic poetry)



Keywords: life, gst, Congo Square, danza, dance, jazz, Jelly Roll, transition, three-body




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venerdì 24 febbraio 2023

# gst: apropos of transitions, erratic, bursty growth processes in cellular sprawl

<< A new “bursty growth” model for organelles—internal components of biological cells—helps explain observed size fluctuations. >>

<< Biologists have identified within cells many specialized structures called organelles that carry out crucial tasks, but how cells regulate the size and the number of organelles has remained a puzzle. Now, using simulations backed by experiments, biophysicists have demonstrated that cells appear to produce organelles through a seemingly erratic, or “bursty,” growth process, which enables them to control average organelle sizes and numbers while also constraining organelle size variations within any cell. The work helps to build up a more fundamental understanding of the mechanisms of cellular function. >>️

<< We wondered if organelle growth, far from being an orderly ‘brick-by-brick’ assembly, might occur in more random bursts,  (..) The burst model can thus explain how cells balance organelle sizes and numbers while also keeping size fluctuations within a narrow window, >> Shankar Mukherji.

<< This “universal” behavior suggests that the burst mechanism underlies all organelle growth, despite the fact that each organelle has a unique building process. >>️
️
Mark Buchanan. Organelle Building Codes. Physics 16, 3. Jan 6, 2023. 

Kiandokht Panjtan Amiri, Asa Kalish, Shankar Mukherji. Robustness and Universality in Organelle Size Control. Phys. Rev. Lett. 130, 018401. Jan 6,  2023. 

Also

keyword 'growth' in FonT

keyword 'erratico' | 'erratica' in Notes
(quasi-stochastic poetry)


keyword 'erratic' in FonT

Keywords: gst, cell, cell assembly, growth, erratic growth, transition



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giovedì 23 febbraio 2023

# gst: hidden complexity during the twinkle of a shrinking droplet


<< Captivating patterns found in the light scattered by an evaporating water droplet could be used to infer the properties of the droplet as it shrinks. >>

AA << collected the light that bounced off a spherical water droplet as the droplet shrunk, which happened naturally as it evaporated. The team observed twinkling patterns called Fano combs, which resemble the outlines of hedgehogs. >>

Ryan Wilkinson. Twinkling of a Shrinking Droplet Reveals Hidden Complexity. Physics 16, s9. Jan 24, 2023.

AA << then fully explain it by expanding the quantum analogy. This turns the droplet into an “optical atom" with angular momentum, tunneling, and excited states. >>

Javier Tello Marmolejo, Adriana Canales, et al. Fano Combs in the Directional Mie Scattering of a Water Droplet. Phys. Rev. Lett. 130, 043804. Jan 24, 2023.

Also

keyword 'evaporation' in FonT

keyword 'drop' | 'droplet' | 'droploids' in FonT



keyword 'goccia' in Notes 
(quasi-stochastic poetry): 


Keywords: gst, drop, droplet, shrink, shrinking droplet, evaporation, transition


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martedì 21 febbraio 2023

# gst: towards (insights into) intermittency and inhomogeneity of turbulent mixing

<< Fluid elements deform in turbulence by stretching and folding. In this work, by projecting the material deformation tensor onto the largest stretching direction, the dynamics of folding is depicted through the evolution of the material curvature. Results from direct numerical simulation (DNS) show that the curvature growth exhibits two regimes, first a linear stage dominated by folding fluid elements through a persistent velocity Hessian which then transitions to an exponential growth driven by the stretching of already strongly bent fluid elements. This transition leads to strong curvature intermittency at later stages, which can be explained by a proposed curvature-evolution model. The link between velocity Hessian to folding provides a new way to understand the crucial steps in energy cascade and mixing in turbulence beyond the classical linear description. >>

Yinghe Qi, Charles Meneveau, Greg Voth, Rui Ni. Folding dynamics and its intermittency in turbulence. arXiv: 2301.10341v1 [physics.flu-dyn]. Jan 24, 2023. 

Also

keyword 'intermittency' in FonT

keyword 'turbulence' in FonT

keyword 'turbolento' | 'turbolenza' in Notes (quasi-stochastic poetry)


keyword 'transition' | 'transitional' in FonT


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



Keywords: gst, intermittency, turbulence, transition


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venerdì 17 febbraio 2023

# gst: apropos of bouncing, even balls that undergo rolling are typically found to lift off slipping.

<< A detailed set of experiments are described that capture over a 1000 different instances of the bounce of a golf ball. (..) Data are presented from two different turfs; one artificial and one from a typical tee. >>

<< A better fit to the data is found using a non-physical piecewise-affine landing to lift-off relationship, which distinguishes between cases that bounce in pure slip from those that undergo rolling. Nevertheless, even balls that undergo rolling are typically found to lift off slipping, having undergone spin reversal. >>

Stanisław W. Biber, Kristian M. Jones, et al. Measurements and linearized models for golf ball bounce. arXiv: 2302.02758v1 [physics.class-ph]. Jan 13, 2023. 


Also

keyword 'bouncing' | 'rolling' | 'slipping' in FonT



Keywords: gst, bouncing, rolling,  slipping





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mercoledì 15 febbraio 2023

# gst: when a soliton juggles ('catches' and 'throws') droplets


<< Jugglers normally work with solid objects, but a research team has now demonstrated a system that juggles liquid drops. (AA)  have previously shown that liquid drops can bounce in place above the surface of the same liquid—or bounce while moving across the surface—if the container is continuously vibrated (..) In these past experiments, the surface was nearly flat, except for waves generated by the bouncing drop. In the new work by undergraduate student Camila Sandivari of the University of Chile and her colleagues, the vibrations cause the liquid surface to form a large standing wave that actively “catches” and “throws” the drop during each cycle of its oscillation. The trapping of the drop is similar in principle to other types of wave traps, such as laser-based optical tweezers, and the system could potentially lead to new types of traps for larger objects. >>

AA << placed water mixed with a dye and a surface-tension-reducing agent in a 20-cm-long, 2.6-cm-wide basin that supports an unusual type of surface wave when the basin is vibrated in a specific frequency range. In this wave, rather than a series of oscillating peaks and valleys, there is only a single standing wave peak, called a soliton. However, this peak doesn’t oscillate uniformly across the basin’s short dimension (the width). A peak appears at one of the long walls coincident with a valley at the opposite wall, and then the peak and the valley switch places moments later, keeping a relatively flat “node” line along the central long axis of the basin. >>

AA << used a pipette to place a few-millimeter-wide drop of the same fluid just above the oscillating soliton, close to one of the long walls, and found that drops could be juggled for up to 90 minutes. The team attributes this unusual stability in part to a property of the soliton: if the drop wanders off-center, the oscillating surface wave pulls it back toward its center, similar to the way the laser field in optical tweezers is able to stably hold a small particle at its center. >>

David Ehrenstein. Juggling Water Drops. Physics 16, 21. Feb 10, 2023. 
https://physics.aps.org/articles/v16/21

Also

keyword 'drop' | 'droplet' | 'droploids' in FonT




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


keyword 'solitons' in FonT



Keywords: gst, solitons, drop, droplet, droploids, goccia


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