# gst: apropos of transitions among granular entities, the behavior of silicone-coated sand mixtures (the 'magic sand')

<< Sand is a fascinating material. It can flow and be poured like a liquid, but retains many of the properties of solids, clogging pipes or forming sand dunes. (..) Grains interact via simple, Newtonian mechanics, but because so many particles are interacting at once, there is an emergent complexity of flow behavior that cannot yet be explained by simple equations. Scientists are thus not only looking for better theoretical models to explain granular behavior, but convenient "model systems" that can be handled and tuned in the lab to give insights into how the microscopic structure of granular materials gives rise to their macroscopic properties. >>️️

<< A team (..) has studied the properties of mixtures of silicone-coated "magic sand," a popular kids' toy, and normal sand. Silicone-coated sand particles were found to interact only with each other and not with other sand particles. The team discovered that adding silicone-coated sand beyond a certain threshold leads to an abrupt change in clustering and rigidity, a potential way to tune the flow of granular materials for industry.>>️

<< Using three independent methods involving sieving, measuring density and forming stable mounds of sand, they found that the mechanical properties of the mixture changes drastically when the fraction of magic sand to normal sand exceeds 20%. This agreed with findings from percolation theory, which governs how connections between particles span space without any breakages, letting the sand mixture behave in a significantly more solid-like way and bear its own weight. This behavior is known for polymer gels, and helps unify theoretical approaches applied to completely different materials. The team's mixtures also exhibits mechanical properties that can be easily modified. Importantly, the method provides a new, convenient, accurate and informative way to explore granular physics, >>️

️

'Magic sand' might help us understand the physics of granular matter. Tokyo Metropolitan University. Mar 08, 2021.

https://phys.org/news/2021-03-magic-sand-physics-granular.html

️

Marie Tani, Honoka Fujio, Rei Kurita. Transition Behavior in Silicone-coated Sand Mixtures. Journal of the Physical Society of Japan. 90 (3): 033801. doi: 10.7566/ JPSJ.90.033801.

https://journals.jps.jp/doi/10.7566/JPSJ.90.033801

Also

keyword 'grain' in FonT

https://flashontrack.blogspot.com/search?q=grain

keyword 'sand' in FonT

https://flashontrack.blogspot.com/search?q=sand

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

https://inkpi.blogspot.com/search?q=sand

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

https://inkpi.blogspot.com/search?q=sabbia

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

https://inkpi.blogspot.com/search?q=grani

# gst: sand dunes 'communication' via turbulent swirls

<< Even though they are inanimate objects, sand dunes can 'communicate' with each other. A team (..) has found that as they move, sand dunes interact with and repel their downstream neighbours. Using an experimental dune 'racetrack', (they) observed that two identical dunes start out close together, but over time they get further and further apart. This interaction is controlled by turbulent swirls from the upstream dune, which push the downstream dune away.  >>

Sand dunes can 'communicate' with each other. University of Cambridge. 

 Feb 4, 2020.

https://m.phys.org/news/2020-02-sand-dunes.html

Karol A. Bacik, Sean Lovett, et al. Wake Induced Long Range Repulsion of Aqueous Dunes. Phys. Rev. Lett. 124, 054501. Feb 4, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.054501

Also

keyword 'sand' in Notes

https://inkpi.blogspot.com/search?q=sand

# gst: like grains of sand in a sandcastle

<< Cells comprising a tissue can pack into disorderly geometries much as do grains of sand in a sandcastle. In doing so they can freeze into a fixed shape—as in a sandcastle—or flow like sand poured from a beach bucket >>

<< This finding makes a deep connection between the physics of inert granular matter such as sand and the geometry of multicellular living systems >> Lior Atia.

Harvard T.H. Chan School of Public Health. Sandcastles and surprising origins of basic cellular functions. Apr 2, 2018

https://m.phys.org/news/2018-04-sandcastles-basic-cellular-functions.html

Lior Atia, Dapeng Bi, et al. Geometric constraints during epithelial jamming. Nature Physics. doi: 10.1038/s41567-018-0089-9. Apr 2, 2018.

https://www.nature.com/articles/s41567-018-0089-9

# s-astro: the thinning of an atmosphere to flash on track of sand

<< We think Mars had a thicker atmosphere in the past that might have formed smaller wind-drag ripples or even have prevented their formation altogether. Thus, the size of preserved wind-drag ripples, where found in Martian sandstones, may have recorded the thinning of the atmosphere >>

Guy  Webster, Robert  Perkins. NASA Rover's  Sand-Dune  Studies  Yield  Surprise. June 30,  2016.

http://www.jpl.nasa.gov/news/news.php?feature=6551

M. G. A. Lapotre, R. C. Ewing, et al. Large wind ripples on Mars: A record of atmospheric evolution. Science. 01 Jul 2016:Vol. 353, Issue 6294, pp. 55-58DOI: 10.1126/science.aaf3206

http://dx.doi.org/10.1126/science.aaf3206

# s-behav: surprisingly, they (also) show marked social interactions ...

<< sharks [sand tiger sharks Carcharias taurus] prefer to travel in groups of various sizes and spend a surprising amount of time together. Some individuals even spent up to 95 consecutive hours together over the course of the year. >>

Researchers Examine the Social Networks of Sharks. Released: 4-Oct-2016 3:05 PM EDT

http://www.newswise.com/articles/researchers-examine-the-social-networks-of-sharks

Danielle E. Haulsee, Dewayne A. Fox, et al. Network Analysis Reveals Potential Fission-Fusion Behavior in a Shark. Nature. Scientific Reports 6, Article number: 34087 (2016)
doi:10.1038/srep34087  Published online: 30 Sept. 2016

http://www.nature.com/articles/srep34087

# behav: learning walks related to home burrow navigation (among desert grassland scorpions Paruroctonus utahensis)

<< The Navigation by Chemotextural Familiarity Hypothesis (NCFH) suggests that scorpions use their midventral pectines to gather chemical and textural information near their burrows and use this information as they subsequently return home. For NCFH to be viable, animals must somehow acquire home-directed “tastes” of the substrate, such as through path integration (PI) and/or learning walks. >>️

AA << found that once animals established their home burrows, they immediately made one to several short, looping excursions away from and back to their burrows before walking greater distances. We also observed similar excursions when animals made burrows in level sand in the middle of the arena (i.e., no mound provided). These putative learning walks, together with recently reported PI in scorpions, may provide the crucial home-directed information requisite for NCFH. >>️

Douglas D. Gaffin, Maria G. Munoz, Marielle Hoefnagels. Evidence of learning walks related to scorpion home burrow navigation. bioRxiv 2021.12.28.474378; Dec 30, 2021. 

https://www.biorxiv.org/content/10.1101/2021.12.28.474378v1

Also

keyword 'walk' | 'walking' in FonT

https://flashontrack.blogspot.com/search?q=walk

https://flashontrack.blogspot.com/search?q=walking

keyword 'passo lieve' | 'walk' | 'walking' in Notes (quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=passo+lieve

https://inkpi.blogspot.com/search?q=walk

https://inkpi.blogspot.com/search?q=walking

Keywords: behav, walk, walking, learning walk, NCFH

# gst: apropos of slipping, the motion on a deformable ground under fast-moving sheets

<< Backed by experimental data from a laboratory machine that simulates the huge forces involved in glacier flow, glaciologists have written an equation that accounts for the motion of ice that rests on the soft, deformable ground underneath unusually fast-moving parts of ice sheets. >>

<< That equation - or "slip law" - is a tool that scientists can include in computer models of glacier movement over the deformable beds of mud, sand, pebbles, rocks and boulders under glaciers such as the West Antarctic Ice Sheet, >> Neal Iverson

<< Models using the new slip law could better predict how quickly glaciers are sliding, how much ice they're sending to oceans and how that would affect sea-level rise. >>

Neal Iverson. Experiments lead to slip law for better forecasts of glacier speed, sea-level rise. Iowa State University. Apr 2, 2020.

https://m.phys.org/news/2020-04-law-glacier-sea-level.html

<< These observations should help to solve the long-standing problem of constructing a generalized slip law that combines the processes of hard-bedded sliding and bed deformation. >>

Lucas K. Zoet, Neal R. Iverson. A slip law for glaciers on deformable beds.  Science. Vol. 368, Issue 6486, pp. 76-78 doi: 10.1126/science.aaz1183.  Apr 3, 2020.

https://science.sciencemag.org/content/368/6486/76

# gst: movers and shaker, the dynamics of granular matter

 << Granular materials are disordered systems often found in a far-from-equilibrium state. >> 

 << You can think of it like a beaker filled with loose sand, (..) At first there are big holes between the grains. So initially, it's easy for a grain to shift position by falling into an empty space. But as these spaces start to get smaller, it becomes less likely that a grain can fall through one. As the taps continue, it takes increasingly cooperative events to create the space necessary for more compaction. >> Stefan Boettcher. 

<< Previous research has shown a similar statistical pattern for the behavior of amorphous solids that don't form ordered crystals when moving from a liquid to a solid state, such as glass and many polymers. >> 

Carol Clark. Movers and shakers: New evidence for a unifying theory of granular materials. Emory University. Jan 08, 2021. 

https://phys.org/news/2021-01-movers-shakers-evidence-theory-granular.html   

Paula A. Gago, Stefan Boettcher. 

Universal features of annealing and aging in compaction of granular piles. 

PNAS. 117 (52) 33072-33076. doi: 10.1073/ pnas.2012757117. Dec 14, 2020. 

https://www.pnas.org/content/117/52/33072