# gst: transitions by coupled instabilities

AA << present an experimental study of quasiperiodic transitions between a highly ordered square-lattice pattern and a disordered, defect-riddled state, in a circular Faraday system. (They)  show that the transition is driven initially by a long-wave amplitude modulation instability, which excites the oscillatory transition phase instability, leading to the formation of dislocations in the Faraday lattice. The appearance of dislocations dampens amplitude modulations, which prevents further defects from being created and allows the system to relax back to its ordered state. The process then repeats itself in a quasiperiodic manner. >>

Valeri Frumkin, Shreyas Gokhale. Coupled instabilities drive quasiperiodic order-disorder transitions in Faraday waves. Phys. Rev. E 108, L012601. July 17, 2023. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.108.L012601

Also: parrondo, tit-for-tat, game, transition, chaos, in https://www.inkgmr.net/kwrds.html

Keywords: parrondo, tit-for-tat, game,  transition, chaos

# gst: inertial particles within co-rotating dusty vortices

 << dispersed particles with moderate inertia cause the vortex pair to push apart to a separation nearly twice as large as the initial separation. >>

 

 << antisymmetric vorticity generated by particles flung out of the rotational cores causes the vortex pair repulsion. Eventually, the two dusty vortices merge into a single vortex with most particles accumulating outside the core similar to the dusty Lamb-Oseen vortex described in Shuai & Kasbaoui (2022) >>

 

 << For weakly inertial particles, (AA) find that the merger dynamics follow the same mechanics as those of a single-phase flow, albeit with a density that must be adjusted to match the mixture density. >>

 

<< Lastly, highly inertial particles tend to fragment the vortex cores leading to murky merger dynamics. >>

Shuai Shuai, Anubhab Roy, M. Houssem Kasbaoui. The merger of co-rotating vortices in dusty flows. arXiv: 2307.05413v1 [physics.flu-dyn]. Jul 11, 2023. 

https://arxiv.org/abs/2307.05413

Also: particle, vortex, in https://www.inkgmr.net/kwrds.html

Keywords: gst, particle, vortex 

# gst: evolution of survivors compared to discrete vs continuous noise

<< Environmental variations can significantly influence how populations compete for resources, and hence shape their evolution. Here, (AA) study population dynamics subject to a fluctuating environment modeled by a varying carrying capacity changing continuously in time according to either binary random switches, or by being driven by a noise of continuous range. >>

<< the slow strain fixation probability can be greatly enhanced for a continuously varying environment compared to binary switches, even when the first two moments of the carrying capacity coincide. >>️

Ami Taitelbaum, Robert West, et al. Evolutionary dynamics in a varying environment: Continuous versus discrete noise. Phys. Rev. Research 5, L022004. April 4, 2023. 

https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.L022004

Also: noise, in https://www.inkgmr.net/kwrds.html

Keywords: gst, evolution, noise, discrete vs continuous noise

# brain: the sense of hearing, the sense of silence.

<< Do we only hear sounds? Or can we also hear silence? These questions are the subject of a centuries-old philosophical debate between two camps: the perceptual view (we literally hear silence), and the cognitive view (we only judge or infer silence). >>

<< In all cases (concerning seven experiments), silences elicited temporal distortions perfectly analogous to their sound-based counterparts, suggesting that auditory processing treats moments of silence the way it treats sounds. Silence is truly perceived, not merely inferred. >>️

️

Rui Zhe Goh, Ian B. Phillips, Chaz Firestone. The perception of silence. 

PNAS. 120 (29) e2301463120. Jul 10, 2023. 

https://www.pnas.org/doi/10.1073/pnas.2301463120

Roberto Molar Candanosa. The sound of silence? Researchers prove we can  hear it. Johns Hopkins University - HUB. Jul 11, 2023. 

https://hub.jhu.edu/2023/07/11/can-we-hear-silence 

Researchers Prove We Hear the 

Sound of Silence. Jul 10, 2023. 

https://youtu.be/nCRosndUfMc

Also: silence, pause, sound, noise, perception, brain, in https://www.inkgmr.net/kwrds.html 

Keywords:  brain, perception, sound, noise, pause, silence

# gst: complex flows by hairpin vortices behind hills with different scales

 << In the flow around protuberance, separation bubbles occur ahead and behind the protuberance, and a coherent vortex structure exists in the wake. In such a flow field, heat, substance, and momentum are actively transported by the vortex. (..) When multiple protuberances are set in the flow, the wakes of the protuberances interfere with each other, resulting in complicated flows. >> 

 << This study performed a numerical analysis of the hairpin vortex and heat transport generated by the interference of the wakes behind two hills in a laminar boundary layer. In the case of hills with the same scale, the interference between hairpin vortices in the wake is more intensive than in the different-scale hills. When the hills with different scales are installed, hairpin vortices with different scales are periodically shed. >> 

 

  << Regardless of the scale ratio of the hills, when the hill spacing in the spanwise direction is narrowed, the asymmetry of the hairpin vortex in the wake increases due to the interference between the wakes. At this time, the turbulence caused by the leg and the horn-shaped secondary vortex on the spanwise center side in the hairpin vortex increases, and heat transport around the hairpin vortex becomes active. >> 

 

Hideki Yanaoka, Tatsuya Hamada. Hairpin vortices and heat transfer in the wakes behind two hills with different scales. arXiv: 2306.17365v1 [physics.flu-dyn]. Jun 30, 2023. 

https://arxiv.org/abs/2306.17365

Also: vortex, turbulence in https://www.inkgmr.net/kwrds.html

Keywords: gst, vortex, hairpin vortex, turbulence

# life: declining towards turbulence, thus ecstatic (detotuthec)

(1/3) for our birthdays on July 11th (*1th) and July 25th (*9th) ... forever Nomads (*), curious, young.  

https://www.inkgmr.net   https://www.inkgmr.net/tammi

@flashontrack  11:36 11lug21

https://twitter.com/flashontrack/status/1414156586889748482

(2/3) (*) e.g. exotic, maverick, agnostic,  track seeker, meta-mechanic pulsating manipulator, ockhamistic, erratic, chaotic, #detotuthec (declining towards turbulence, thus ecstatic), ab-normal ...

@flashontrack 11:37 11lug21

https://twitter.com/flashontrack/status/1414156987240173569

(3/3) with mindfulness, compassion and tenacity, where also vengeance consists in (try) saving others (whatever 'others' means).

@flashontrack 11:38 11lug21

https://twitter.com/flashontrack/status/1414157124318507008

Keywords: detotutech, detect thou

# gst: myriad of complex dynamics from the atomization of acoustically levitated droplets

AA << report the dynamics of a droplet levitated in a single-axis acoustic levitator. The deformation and atomization behavior of the droplet in the acoustic field exhibits a myriad of complex phenomena, in sequences of steps. These include the primary breakup of the droplet through stable levitation, deformation, sheet formation, and equatorial atomization, followed by secondary breakup which could be umbrella breakup, bag breakup, bubble breakup or multistage breakup depending on the initial size of the droplet. >>

<< Both the primary and the secondary breakup of the droplet admit interfacial instabilities such as Faraday instability, Kelvin Helmholtz (KH) instability, RT instability, and RP instability and are well described with visual evidence. >>️

Sunil K. Saroj, Rochish M. Thaokar. Atomisation of an acoustically levitated droplet: Experimental observations of a myriad of complex phenomenon. arXiv: 2307.00400v1 [physics.flu-dyn]. Jul 1, 2023.

https://arxiv.org/abs/2307.00400

Also:  drop, transition, instability in https://www.inkgmr.net/kwrds.html

Keywords: gst, drop, droplet, transition, instability

# behav: how a microbiota (Curvibacter sp.) could modulate eating behavior in Hydra.

(AA) << studied the eating behavior of Hydra, a host that has a simple nervous system and a low-complexity microbiota. >>

(They) << demonstrate that different neuronal subpopulations are functioning together to control the eating behavior. The microbiota participates in control of the eating behavior since germ-free or mono-colonized animals have drastic difficulties in mouth opening. This was restored by adding a full complement of the microbiota. >>️

The << findings confirm and expand on the idea that in animals without a central nervous system, a complex behavior is controlled by multiple subpopulations of neurons, forming circuits and modules. (Their)  observations presented here show that this not only requires the coordination of multiple neuronal circuits, but also that signals from the microbial environment play an important role. >>

Christoph Giez, Denis Pinkle, et al.  Microbes as part of ancestral neuronal circuits: Bacterial produced signals affect neurons controlling eating behavior in Hydra. BioRxiv. doi: 10.1101/ 2023.04.28.538719. Apr 29, 2023. 

https://www.biorxiv.org/content/10.1101/2023.04.28.538719v1

Also: How a virus could cause context-dependent manipulation in host social behavior.  Apr 28, 2020.  https://flashontrack.blogspot.com/2020/04/gst-how-virus-could-cause-context.html

Keywords: behav, eating behavior, food, Hydra, microbiota 

# brain: spiral waves at the edge of neural tissue during cognitive processing.

AA << have discovered human brain signals travelling across the outer layer of neural tissue that naturally arrange themselves to resemble swirling spirals. >>️

<< The research (..) indicates these ubiquitous spirals, which are brain signals observed on the cortex during both resting and cognitive states, help organise brain activity and cognitive processing. >>️

<< Our study suggests that gaining insights into how the spirals are related to cognitive processing could significantly enhance our understanding of the dynamics and functions of the brain, (..) These spiral patterns exhibit intricate and complex dynamics, moving across the brain’s surface while rotating around central points known as phase singularities. >> Pulin Gong.

<< One key characteristic of these brain spirals is that they often emerge at the boundaries that separate different functional networks in the brain, >> Yiben Xu. 

Philip Ritchie. Scientists discover spiral-shaped signals that organise brain activity. sydney.edu.au. Jun 16, 2023. 

https://www.sydney.edu.au/news-opinion/news/2023/06/16/scientists-discover-spiral-shaped-signals-that-organise-brain-activity.html

https://youtu.be/YZlqokljqY8️

Yiben Xu, Xian Long, Jianfeng Feng & Pulin Gong. Interacting spiral wave patterns underlie complex brain dynamics and are related to cognitive processing. Nat Hum Behav. doi: 10.1038/ s41562-023-01626-5. Jun 15,  2023.

https://www.nature.com/articles/s41562-023-01626-5

Also: brain, vortex, waves in: https://www.inkgmr.net/kwrds.html

Keywords: brain, vortex, waves,  cognition

# gst: a flapping forward flight (among Papilio polytes and Kallima inachus)

<< The effect of wing shape on a forward-flying butterfly via decoupled factors of the wing-swept angle and the aspect ratio (AR) was investigated numerically. >>️

<< The results show that, through (AA) models, the effects of the wing-swept angle and AR were decoupled; both have distinct flow mechanisms and aerodynamic force trends and are consistent in the two butterfly species (Papilio polytes and Kallima inachus). For a fixed AR, a backward-swept wing increases lift and drag because of the enhanced attachment of the leading-edge vortex with increased strength of the wingtip vortex and the spanwise flow. For a fixed wing-swept angle, a small AR wing increases lift and decreases drag because of the large region of low pressure downstream and the wake-capture effect. Coupling these effects, the largest lift-to-drag ratio occurs for a forward-swept wing with the smallest AR. These results indicate that, in a flapping forward flight, sweeping a forewing forward relative to a hindwing is suitable for cruising. >>

Sheng-Kai Chang, You-Jun Lin, Kuan-Lun Hsu, and Jing-Tang Yang. Decoupling wing-shape effects of wing-swept angle and aspect ratio on a forward-flying butterfly. Phys. Rev. E 107, 065105. Jun 23, 2023. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.107.065105

️

Also: vortex in  https://www.inkgmr.net/kwrds.html

Keywords: gst, butterfly, wing, wing-shape, flight, vortex