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venerdì 3 settembre 2021

# gst: apropos of transitions, when a liquid droplet takes a turn (as a swimming behavior of amoebas)

Masatoshi Ichikawa and coll.  << have analyzed the conditions that cause self-propelling droplets to take linear or curved trajectories. The team studied water droplets between 60 and 800 μm across as they moved through oil that contained a surfactant. The droplets moved as a result of the Marangoni effect, in which an unequal distribution of surfactant molecules on the surface of each droplet creates a surface-tension gradient. (They) found that larger droplets tended to follow more tightly curved paths than smaller droplets. To understand the cause of this difference, Ichikawa and coll.  created a 3D model describing the concentration of surfactant on the surface of the droplets. They also studied the droplets’ internal flow, by observing the paths of small tracer particles. They characterized this flow as the sum of multiple patterns of fluid motion present in each droplet, including radial, dipolar, and quadrupolar motion. These patterns of motion were determined by the surface-tension gradients created by the uneven surfactant distribution on each droplet. In turn, such patterns controlled how the droplets moved. In particular, the team found that the angular difference between the dipolar and quadrupolar flows within droplets was strongly correlated with more curved droplet trajectories. In larger droplets, this angle changed more easily, causing the tightly curved trajectories. The researchers say that this fundamental mechanism may also influence the swimming behavior of amoebas.  >>️

Sophia Chen. When Liquid Droplets Take a Turn. Physics 14, s109. Aug 19, 2021.


Saori Suda, Tomoharu Suda, et al. Straight-to-Curvilinear Motion Transition of a Swimming Droplet Caused by the Susceptibility to Fluctuations. Phys. Rev. Lett. 127, 088005. Aug 19, 2021.








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giovedì 2 settembre 2021

# gst: when randomly-timed external impulses can synchronize

<< Random perturbations applied in tandem to an ensemble of objects can synchronize their motion. (AA) study multiple copies of an object in periodic motion such as a firing neuron, each with an arbitrary phase. Randomly-timed external impulses can synchronize these phases. For impulses slightly too strong to synchronize, (they) find remarkable erratic synchronization, with stochastic fluctuations from near-perfect to more random synchronization. The sampled entropies of these phase distributions themselves form a steady-state ensemble. A stochastic dynamics model for the entropy's evolution accounts for the observed exponential distribution of entropies and the stochastic synchronization. >>

<< One general virtue of noise-induced synchronization is that one may use it to induce synchronization without
specific knowledge about the limit cycle being synchronized, such as the phase map function or the cycle time.(..) As noted in the Introduction, synchronization of a remote oscillator enables transmission of information.
Stochastic synchronization appears to have comparable ability, potentially useable by technology or biology. >>️

<< The stochastic synchronization phenomenon explored above seems to be a distinctive mode of organization. It can be produced via broad classes of driving, and creates striking fluctuations of randomness. This model may aid understanding of other puzzling systems showing erratic fluctuations, such as strong turbulence. >>️
️
Yunxiang Song, Thomas A. Witten. Stochastic synchronization induced by noise. arXiv:2108.13172v1 [cond-mat.stat-mech]. Aug 16, 2021.


Also

<< stabilizzare il volo del fascio di aquiloni  >> in: ️2149 - onda di predazione (to knock seals off the ice).  Notes. Dec 17, 2007. (quasi-stochastic poetry)


keyword 'noise' | 'fuzzy' in FonT




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lunedì 30 agosto 2021

# gst: apropos of 1or2achoos (e.g. from Wuhan), the dynamics of turbulence in a fluid puff

<< Turbulence is everywhere -- in the movement of the wind, the ocean waves and even magnetic fields in space. It can also be seen in more transient phenomena, like smoke billowing from a chimney, or a cough. (..) Understanding this latter type of turbulence -- called puff turbulence -- is important not only for the advancement of fundamental science, but also for practical health and environmental measures, >>️

<< The very nature of turbulence is chaotic, so it's hard to predict, (..) Puff turbulence, which occurs when the ejection of a gas or liquid into the environment is disrupted, rather than continuous, has more complicated characteristics, so it's even more challenging to study. But it's of vital importance -- especially right now for understanding airborne transmission of viruses like SARS-CoV-2. >>️ Marco Edoardo Rosti. 

<< The new model, (..) includes how minute fluctuations within the puff behave, and how both large-scale and small-scale dynamics are impacted by changes in temperature and humidity. (..) at cooler temperatures (15°C or lower), (AA) model deviated from the classical model for turbulence. >>️

<< In the classical model, turbulence reigns supreme -- determining how all the little swirls and eddies within the flow behave. But once temperatures dipped, buoyancy started to have a greater impact. >>

<< The effect of buoyancy was initially very unexpected. It's a completely new addition to the theory of turbulent puffs,>> Marco Edoardo Rosti. ️

Secrets of COVID-19 transmission revealed in turbulent puffs. Okinawa Institute of Science and Technology (OIST). Aug 26, 2021. 


Andrea Mazzino, Marco Edoardo Rosti. Unraveling the Secrets of Turbulence in a Fluid Puff. Phys. Rev. Lett. 127, 094501. Aug 25, 2021. 


Also

keyword 'drop' | 'droplet' in FonT:



keyword 'turbulence' in FonT:


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



keyword 'virus' | 'sars-cov-2' | 'sars' in FonT: 




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



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sabato 21 agosto 2021

# gst: apropos of transitions, randomness can stabilize edge states in short- lifetime regions of disordered periodically-driven systems

<< lifetimes of the edge states exhibit universal behavior when random potentials exist since the edge- and bulk- dominant eigenstates are mixed, leading to that lifetimes are prolonged by random potentials in the region II (short- lifetime region) and shortened in the region I (long- lifetime region). >>

<<  it is an intriguing phenomenon that random potentials tend to stabilize edge states in the region II (short- lifetime regions). >>

Ken Mochizuki, Kaoru Mizuta, Norio Kawakami. Fate of Topological Edge States in Disordered Periodically-driven Nonlinear Systems. arXiv: 2108.00649 (nlin). Aug 2, 2021.


Also

keyword 'random' in FonT


keyword 'disorder' in FonT


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






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martedì 17 agosto 2021

# brain: like a Zazen entity, mice can spontaneously self-modulate cortical dopamine impulses to reward.

AA << recently set out to investigate less understood aspects related to spontaneous impulses of dopamine. Their results, (..) have shown that mice can willfully manipulate (..) random dopamine pulses. >>

<< Rather than only occurring when presented with pleasurable, or reward-based expectations, (..) the neocortex in mice is flooded with unpredictable impulses of dopamine that occur approximately once per minute. >>️

<< mice on a treadmill received a reward if they showed they were able to control the impromptu dopamine signals. Not only were mice aware of these dopamine impulses, the data revealed, but the results confirmed that they learned to anticipate and volitionally act upon a portion of them. >>️️

<< Critically, mice learned to reliably elicit (dopamine) impulses prior to receiving a reward, (..) These effects reversed when the reward was removed. We posit that spontaneous dopamine impulses may serve as a salient cognitive event in behavioral planning. (..) We further conjecture that an animal's sense of spontaneous dopamine impulses may motivate it to search and forage in the absence of known reward-predictive stimuli, >> the researchers noted.️

'Feel good' brain messenger can be willfully controlled, new study reveals. University of California, San Diego. Jul 23, 2021. 


Conrad Foo, Adrian Lozada, et al. Reinforcement learning links spontaneous cortical dopamine impulses to reward. Current Biology. doi: 10.1016/ j.cub.2021.06.069. Jul 23, 2021. 


Also

keywords 'dopamine' and 'meditation' in PUBMED








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sabato 14 agosto 2021

# gst: asymmetric ferroelectric bi-stability with two unequal stable polarization states by broken inversion symmetry

AA << demonstrated this phenomenon for the first time in engineered two-dimensional crystals. (..) These engineered crystals lead to an asymmetric bi-stability with two unequal stable polarization states in contrast to a natural ferroelectric. >>

New electronic phenomenon discovered. University of North Florida. Aug 11, 2021. 


<< In atomic-layer superlattices constructed using three constituent phases, (..) the stacking sequence of the atomic layers is found to control the symmetry of the high-temperature dielectric response. In such a superlattice when a nanostructured asymmetric strain is programmed into the lattice via the stacking order, the natural symmetry at high temperatures is removed and a polarized sample is obtained in which the polarization increases as the temperature is lowered. In contrast to a ferroelectric characterized by a bistable ground state with two equal and opposite electronic polarizations, (they)  experiments show evidence of asymmetric ferroelectric correlations that set in when such a sample becomes hysteretic below a temperature Tx, with two unequal polarization states. >>

Maitri P. Warusawithana, Caitlin S. Kengle, et al. Asymmetric ferroelectricity by design in atomic-layer superlattices with broken inversion symmetry.  Phys. Rev. B 104, 085103. Aug 4,  2021.





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giovedì 12 agosto 2021

# brain: brain images of silence

<< When imagining music, the musicians' brain activity had the opposite electrical polarity to when they listened to it -- indicating different brain activations -- but the same type of activity as for imagery occurred in silent moments of the songs when people would have expected a note but there wasn't one. >>

<< There is no sensory input during silence and imagined music, so the neural activity we discovered is coming purely from the brain's predictions e.g., the brain's internal model of music. Even though the silent time-intervals do not have an input sound, we found consistent patterns of neural activity in those intervals, indicating that the brain reacts to both notes and silences of music. Ultimately, this underlines that music is more than a sensory experience for the brain as it engages the brain in a continuous attempt of predicting upcoming musical events. Our study has isolated the neural activity produced by that prediction process. And our results suggest that such prediction processes are at the foundation of both music listening and imagery. >> Giovanni Di Liberto. 

The music of silence: Imagining a song triggers similar brain activity to moments of mid-music silence. Trinity College Dublin. Aug 3, 2021. 


Guilhem Marion, Giovanni M. Di Liberto,  Shihab A. Shamma. The Music of Silence. Part I: Responses to Musical Imagery Encode Melodic Expectations and Acoustics. Journal of Neuroscience  JN-RM-0183-21. doi: 10.1523/ JNEUROSCI.0183-21.2021. 2 Aug 2, 2021.


Giovanni M. Di Liberto, Guilhem Marion,  Shihab A. Shamma. The music of silence. Part II: Music Listening Induces Imagery Responses. Journal of Neuroscience JN-RM-0184-21. doi: 10.1523/ JNEUROSCI.0184-21.2021. 
Aug 2, 2021.


Also

2123 - le dislocazioni pausali di Theo. 
(quasi-stochastic poetry). Notes. Feb 26, 2007.


A pause (acyclic pauses?)  approach to enhance and manage creativity. Mar 23, 2019.


We pronounce words more slowly compared with verbs and sometimes pause. May 20, 2018.



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