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martedì 31 gennaio 2023

# gst: analogy between streamers in sinking spheroids, gyrotactic plumes and chemotactic collapse (when a plume structure blows up when a parm is above a threshold)

<< In a dilute suspension where sinking spheroids or motile gyrotactic microorganisms are modelled as orientable and negatively buoyant particles, (AA) have found analytical solutions to their steady distributions for a given parallel flow profile. The coupling between their distribution and the vertical flow is nonlinear, enabling the uniform base state to bifurcate into a structure reminiscent of the streamers in settling spheroid suspension and gyrotactic plume. This bifurcation depends on a single parameter that is proportional to the average number of particles on a horizontal cross section. In a three-dimensional axisymmetric system, the plume structure blows up when the parameter is above a threshold. (AA) discuss how this singularity is analogous to the chemotactic collapse of a Keller-Segel model, and the significance this analogy entails. >>

Lloyd Fung. Analogy between streamers in sinking spheroids, gyrotactic plumes and chemotactic collapse. arXiv: 2301.07164v1 [physics.flu-dyn]. Jan 17, 2023.

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keyword 'collapse' in FonT

keyword 'spheroids' in FonT

Keywords: gst, analogy, spheroids, collapse, chemotactic collapse 


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lunedì 30 gennaio 2023

# gst: towards the characterization of lines, links, writhes and twists in a vortex.


<< Vorticity in turbulent flows is often organized into complex geometries that influence the dynamics. (AA) use a relatively novel approach to describe these geometries: that of obtaining segments of vortex lines embedded in the flow. This enables to quantify the geometric features of these objects. >>

<< Vortex lines differ widely in their behaviour but (AA) find some unifying features. The decay from high levels of vorticity is shown to happen over a short fraction of the vortex length. The local curvature is inversely related with the vorticity magnitude. Strong parts of vortex lines bundle together. >>

Saumav Kapoor, Rama Govindarajan, Siddhartha Mukherjee. Geometric characterization of vortex lines in turbulence. arXiv: 2301.06808v1 [physics.flu-dyn]. Jan 17, 2023.

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keyword 'vortex' in FonT


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


Keywords: gst, vortex, vortices, vortexes, vorticity



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sabato 21 gennaio 2023

# chem: spontaneous reconfiguration of deformable nanoparticles (in response to environmental cues)


<< Deformable nanoparticles (NPs) offer unprecedented opportunities as dynamic building blocks that can spontaneously reconfigure during assembly in response to environmental cues. >>

<< deformable spherical NPs of radius 50 nm whose surface is tailored with octahedrally distributed charged patches and double-cap charged patches adapt their shape differently in response to changes in surface charge coverage and ionic strength. >>

AA << find shape transitions to rounded octahedra, faceted octahedra, faceted bowls, oblate spheroids, spherocylinders, dented beans, and dimpled rounded bowls. >>

AA << demonstrate that similar shape transitions can be achieved in deformable NPs of different sizes. >>️

Fanbo Sun, Nicholas E. Brunk, Vikram Jadhao. Shape control of deformable charge-patterned nanoparticles. Phys. Rev. E 107, 014502. Jan 10, 2023.


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keyword 'self-assembly' in FonT


keyword 'nano' in FonT


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


Keywords: chem, nano, nanoparticles,  NPs, self-assembly, colloids, polymers, vesicle structures.


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giovedì 19 gennaio 2023

# gst: an approach to information content in the music of J. S. Bach

<< Music has a complex structure that expresses emotion and conveys information. Humans process that information through imperfect cognitive instruments that produce a gestalt, smeared version of reality. What is the information that humans see? And how does their perception relate to (and differ from) reality? To address these questions quantitatively, (AA) analyze J. S. Bach's music through the lens of network science and information theory. >>

They << find that Bach's music is structured for efficient communication; that is, it communicates large amounts of information while maintaining small deviations of the inferred network from reality. >>

They << probe the network structures that enable this rapid and efficient communication of information -- namely, high heterogeneity and strong clustering. (..) More generally, (they) gain insight into features that make networks of information effective for communication. >>

Suman Kulkarni, Sophia U. David, et al. Information content of note transitions in the music of J. S. Bach. arXiv: 2301.00783v1 [physics.soc-ph]. Jan 2, 2023. 

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keyword 'music' in FonT


keyword 'jazz' in FonT


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


Keywords: gst, music, jazz, information theory, note transitions, Bach








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lunedì 16 gennaio 2023

# gst: diffusivity of ordered and freely evolving bubbly suspensions.

AA << investigate the dispersion of a passive scalar such as the concentration of a chemical species, or temperature, in homogeneous bubbly suspensions, by determining an effective diffusivity tensor. Defining the longitudinal and transverse components of this tensor with respect to the direction of averaged bubble rise velocity in a zero mixture velocity frame of reference, (AA) focus on the convective contribution thereof, this being expected to be dominant in commonly encountered bubbly flows. >>

<< In the limits of low and of high Péclet number, including inertial effect of the flow does not affect the scaling of the effective diffusivity with respect to the Péclet number. These results are confirmed by direct numerical simulations performed in different flow regimes, for spherical or very deformed bubbles and from vanishingly small to moderate values of the Reynolds number. Scalar transport in arrays of freely rising bubbles is considered by us subsequently, using numerical simulations. In this case, the dispersion is found to be convectively enhanced at low Péclet number, like in ordered arrays. At high Péclet number, the Taylor dispersion scaling obtained for ordered configurations is replaced by the one characterizing a purely mechanical dispersion, like in random media, even if the level of disorder is very low. >>️

Aurore Loisy, Aurore Naso, Peter D. M. Spelt. The effective diffusivity of ordered and freely evolving bubbly suspensions. arXiv:2301.00028v1 [physics.flu-dyn]. Dec 30, 2022. 

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keyword "bubble" in FonT


keyword "bolla" | "bolle" in Notes (quasistochastic-poetry): 



Keywords: gst, bubble, bubbly suspensions, diffusion, fluctuation




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sabato 14 gennaio 2023

# gst: approaching chaotic dynamics to trace the complexity of rough nanostructured surfaces

AA << use the basic ingredients of chaotic dynamics (stretching and folding of phase space points) for the characterization of the complexity of microscopy images of rough surfaces. The key idea is to use an image as the initial condition of a chaotic discrete dynamical system, such as the Arnold cat map, and track its transformations during the first iterations of the map. Since the basic effects of the Arnold map are the stretching and folding of image texture, the application of the map leads to an enhancement of the high frequency content of images along with an increase of discontinuities in pixel intensities. (AA) exploit these effects to quantify the complexity of S type (lying between homogeneity and randomness) of the image texture since the first (enhancement of high frequencies) can be used to quantify the distance of texture from randomness and noise and the second (the proliferation of discontinuities) the distance from order and homogeneity. The method is validated in synthetic images which are generated from computer generated surfaces with controlled correlation length and fractal dimension and it is applied in real images of nanostructured surfaces obtained from a scanning electron microscope with very interesting results. >>️

A. Kondi, V. Constantoudis, P. Sarkiris, K. Ellinas, and E. Gogolides. Using chaotic dynamics to characterize the complexity of rough surfaces. Phys. Rev. E 107, 014206. Jan 11, 2023. 


Also

Able to track changes in noise. 
(quasi-stochastic poetry) 
Notes. Sep 13, 2007. 

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keyword 'chaos' | 'chaotic' in Font



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



Keywords: gst, chaos, chaotic, nano, roughness, wetting, surfaces, etching scanning 


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martedì 10 gennaio 2023

# brain: how the brain says 'Oops!'

AA << have uncovered how signals from a group of neurons in the brain's frontal lobe simultaneously give humans the flexibility to learn new tasks—and the focus to develop highly specific skills. >>

<< The study's key finding is that the brain uses the same group of neurons for performance feedback in many different situations—whether a person is attempting a new task for the first time or working to perfect a specific skill. >>

<< Part of the magic of the human brain is that it is so flexible, (..) We designed our study to decipher how the brain can generalize and specialize at the same time, both of which are critical for helping us pursue a goal. >> Ueli Rutishauser. ️

️
New Study Reveals How the Brain Says 'Oops!'. Cedars-Sinai Medical Center. May 5, 2022. 

AA << recorded the activity of more than 1000 neurons in the medial frontal cortex of human epilepsy patients while they performed complex cognitive tasks. They found that domain-general and domain-specific performance monitoring neurons were intermixed within this brain region. The population activity gave rise to a geometry that allowed domain-general signals to be read out with more than 90% accuracy on single trials while at the same time retaining the ability to separate different conflict conditions. These results show how the human medial frontal cortex resolves the fundamental trade-off between task generalization and specialization, which is critical for cognitive flexibility. >>
️
Zhongzheng Fu, Danielle Beam, et al. The geometry of domain-general performance monitoring in the human medial frontal cortex. Science. Vol 376, Issue 6593. doi: 10.1126/ science.abm9922. May 6, 2022.

Also

keyword 'cervello' | 'brain' in Notes
(quasi-stochastic poetry)



keyword 'brain' in FonT


keyword 'organoids' in FonT


PS: An image of "oops", not completely spanned in the air, could be this:


Keywords: brain, mind, cervello, mente, oops






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lunedì 9 gennaio 2023

# gst: apropos of instability, bubbles may have unexpected chills

<< Bubbles are ubiquitous, existing in everything from the foam on a beer to party toys for children. Despite this pervasiveness, there are open questions on the behavior of bubbles, such as why some bubbles are more resistant to bursting than others. >>️

AA << created a soap bubble from a mixture made of dishwashing liquid, water, and glycerol. They then measured the soap film’s temperature under a variety of environmental conditions. They found that the film could be up to 8 °C colder than the surrounding air. They also found that glycerol content of the soap film impacted this temperature difference, with films containing more glycerol having higher temperatures. Boulogne (Francois Boulogne) says that such a large temperature difference could impact bubble stability.  >>️

Anna Napolitano. Bubbles Have an Unexpected Chill. Physics 15, s173. Dec 19, 2022. 

Francois Boulogne, Frederic Restagno, Emmanuelle Rio. Measurement of the Temperature Decrease in Evaporating Soap Films. Phys. Rev. Lett. 129, 268001. Dec 19, 2022.

Also

keyword "bubble" in FonT


keyword "bolla" | "bolle" in Notes (quasistochastic-poetry): 



Keywords: gst, bubble, stability, evaporation, burst





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