# gst: an atomic imaging of a (slow) crack

AA << successfully imaged the snapping of individual atomic bonds in a one-atom-thick sheet of rhenium disulfide ( ReS2) using scanning transmission electron microscopy. (STEM) >>

<< Because of its unusual chemistry, Re forms a 2D lattice with "lanes" that guide cracks, allowing the cracks to propagate with ease. The heavy element also efficiently deflects electrons, providing the signal needed to gain clear images. The study is a remarkable example of how a specific material can provide insight into the universal behavior of matter. >>

<< Because of its strong scattering, ReS2 provides an ideal target for STEM. (Interestingly, tungsten, the periodic-table neighbor of Re, has just one fewer proton and is routinely used in electron microscopy to stain viruses and bacterial flagella.)  >>

<< By measuring the deformation of the lattice around the crack, the team showed that the tearing stresses were concentrated around the crack tip. The stresses then decayed as the inverse square root of the distance from the tip, a finding that matches predictions for macroscopic materials. Using these measurements, the team defined a stress intensity threshold for cracks to propagate. >>

<< The images taken by Huang and colleagues used seconds-long exposure times, meaning they could only follow the propagation of the slowest crack (those that moved at a few angstroms per second). There is much interest in how faster cracks behave, as these cracks are subject to instabilities, meaning they can deviate from a straight line or form branches, for example. To observe faster cracks, future experiments could use reduced exposure times. >>

Itamar Kolvin. Atomic Imaging of Cracks. Physics 13, 193. Dec 9, 2020. 

https://physics.aps.org/articles/v13/193

Lingli Huang, Fangyuan Zheng, et al. In Situ Scanning Transmission Electron Microscopy Observations of Fracture at the Atomic Scale. Phys. Rev. Lett. 125, 246102. Dec 9, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.246102

Also

(+)  the intriguing dynamics of a crack. Nov 7, 2017. 

https://flashontrack.blogspot.com/2017/11/gst-intriguing-dynamics-of-crack.html

(+) multiple cracks, simultaneously ... Oct 23, 2016.

https://flashontrack.blogspot.com/2016/10/s-gst-multiple-cracks-simultaneously.html

(+) onda criptica. May 22, 2005 (quasi-stochastic poetry)

https://inkpi.blogspot.com/2005/05/1641b-onda-criptica.html

(+) keyword "fracture" in FonT

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

# life: even a slime mold takes smart decisions about the future (Physarum polycephalum)

<< The slime mold Physarum polycephalum has been puzzling researchers for many decades. Existing at the crossroads between the kingdoms of animals, plants and fungi, this unique organism provides insight into the early evolutionary history of eukaryotes. Its body is a giant single cell made up of interconnected tubes that form intricate networks. This single amoeba-like cell may stretch several centimeters or even meters, featuring as the largest cell on earth in the Guinness Book of World Records. >>

<< The striking abilities of the slime mold to solve complex problems such as finding the shortest path through a maze earned it the attribute "intelligent," intrigued the research community and kindled questions about decision making on the most basic levels of life. >> 

<<  The decision-making ability of Physarum is especially fascinating given that its tubular network constantly undergoes fast reorganization—growing and disintegrating its tubes—while completely lacking an organizing center. The researchers discovered that the organism weaves memories of food encounters directly into the architecture of the network-like body and uses the stored information when making future decisions. >>

Researchers find a single-celled slime mold with no nervous system that remembers food locations. Max Planck Society. Feb 23, 2021.  

https://phys.org/news/2021-02-single-celled-slime-mold-nervous-food.html

Mirna Kramar, Karen Alim. Encoding memory in tube diameter hierarchy of living flow network. PNAS. 118 (10).  e2007815118. doi: 10.1073/ pnas.2007815118

https://www.pnas.org/content/118/10/e2007815118 

# gst: the dynamics of a collective bubble (in a foam) that collapse in a droplet

<< Foams have unique properties that distinguish them from ordinary liquids and gases, and are ubiquitously observed in nature, both in biological systems and industrial products. (..) understanding how bubbles in a foam collapse is an important aspect for product longevity and tailoring physical properties. >>

<< Once a crack appears near the border and a collapse front is formed, (AA) find that the curvature of the front reverses as it migrates, followed by the emergence and emission of droplets. >>

<<  It is particularly interesting to note how the shape of the front changes as it migrates. >>

Naoya Yanagisawa, Marie Tani, Rei Kurita. Dynamics and mechanism of liquid film collapse in a foam. Soft Matter 17, 1738-45. doi: 10.1039/ D0SM02153A. Feb 17, 2021.

https://pubs.rsc.org/en/content/articlelanding/2021/SM/D0SM02153A#!divAbstract   

<< An initial crack in a film creates a RVPB (released vertical plateau border). A second crack event in the film causes a "collapse front" to be formed which sweeps up the RVPB before its shape begins to flatten and invert, finally leaving a droplet. >>

When foams collapse (and when they don't). Tokyo Metropolitan University. Mar 01, 2021. 

https://phys.org/news/2021-03-foams-collapse-dont.html   

Also

keyword 'drop' or 'droplet' in FonT

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

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

# behav: a viral marketing generated by low levels of advertising

<< What they discovered refutes Gladwell's (Malcolm Gladwell) concept that network position is always paramount. They found that in instances where there is even a small amount of advertising—even when it is just a quarter of a percent as strong as word-of-mouth—there's virtually no difference between the influence of the person at the center of a network and those further out on the string. >> 

 << It's not that word-of-mouth doesn't matter—it's that nobody is particularly important for the word-of-mouth process, (..) What we saw is that when advertising doesn't exist, when advertising is exactly zero, it looks like whoever is Mr. Popular, whoever has the most central connections, really matters. And in that scenario, if you start with that person at the center of the network, like the leader of an organization or company, rather than the intern, then whatever you're selling gets an uptick. >> Gabriel Rossman. 

Jessica Wolf. Forget what you think you know about viral marketing, study suggests. University of California, Los Angeles. Feb 25, 2021.

https://phys.org/news/2021-02-viral.html  

Gabriel Rossman,  Jacob C. Fisher. Network hubs cease to be influential in the presence of low levels of advertising. PNAS. 118 (7) e2013391118. doi: 10.1073/ pnas.2013391118. Feb 16, 2021. 

https://www.pnas.org/content/118/7/e2013391118

FonT

this could also occur in the generation of fake news ...

keyword "fake" in FonT

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

# gst: labyrinth chaos: revisiting the elegant, chaotic and hyperchaotic walks

<< Labyrinth chaos was discovered by Otto Rossler and Rene' Thomas in their endeavour to identify the necessary mathematical conditions for the appearance of chaotic and hyperchaotic motion in continuous flows. Here, (AA) celebrate their discovery by considering a single labyrinth walks system and an array of coupled labyrinth chaos systems that exhibit complex, chaotic behaviour, reminiscent of chimera-like states, a peculiar synchronisation phenomenon. >>

 << As all Rossler’s pioneering contributions, labyrinth chaos still holds promise for very interesting further developments. Its simplicity and elegance, both in terms of symmetries, topology and feedback-circuit structure, makes it a good candidate to compare it with other nonlinear, cyclically coupled systems, such as the Arabesques, the Lotka-Voltera system and its variants, and the Arnold-Beltrami-Childress  model. >> 

Vasileios Basios, Chris G. Antonopoulos, Anouchah Latifi. Labyrinth chaos: Revisiting the elegant, chaotic and hyperchaotic walks. arXiv: 2011.11009v1. Nov 22, 2020.

https://arxiv.org/abs/2011.11009

# life: even when you play classic (e.g. Montezuma's Revenge), bots win.

<< A team of researchers (..) has developed a set of learning algorithms that proved to be better at playing classic video games than human players or other AI systems. >>

They << explain how their algorithms differ from others and why they believe they have applications in robotics, language processing and even designing new drugs. >>

<< Reinforcement learning algorithms learn how to do things by synthesizing information provided in a large dataset- they recognize patterns and use them to make guesses about new data. (..) But, (..) such algorithms tend to run into trouble when they encounter data that does not fit with other data in the dataset. (AA) have overcome this problem by adding an algorithm that remembers all the paths a previous algorithm has taken as it has tried to solve a problem. When it finds a data point that does not appear to be correct, it goes back to its memory map and tries another route. In terms of playing video games, it retains screen grabs as it plays and when it finds itself losing, goes back to another point in the game and tries another approach. The algorithm also groups together images that look similar to figure out what point in time it should return to if things go awry. >>

<< They then used their system to play 55 Atari games that, over time, have become benchmarks for testing AI systems. The new system beat other AI systems 85.5 percent of the time. It did particularly well at Montezuma's Revenge, scoring higher than any other AI system and beating the record for a human. >>

Bob Yirka. Reinforcement learning algorithms score higher than humans, other AI systems at classic video games. Feb 25, 2021.

https://techxplore.com/news/2021-02-algorithms-score-higher-humans-ai.html

Ecoffet A, Huizinga J, et al. First return, then explore. Nature 590, 580–586. doi: 10.1038/ s41586-020-03157-9. Feb 25, 2021.

https://www.nature.com/articles/s41586-020-03157-9

Also

keyword 'AI' | 'bot' in FonT

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

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

keyword 'ia' | 'ai' | 'robota' in Notes (quasi- stochastic poetry)

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

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

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

# life: apropos of tricks, 'torpor', a survival strategy not as rare as previously thought

<< Life is hard for small animals in the wild, but they have many solutions to the challenges of their environment. One of the most fascinating of these strategies is torpor. Not, to be confused with sleep or Sunday afternoon lethargy, torpor is a complex response to the costs of living. >>

<<  Once thought to occur only in birds and mammals in the Northern Hemisphere where winters are more pronounced, (AA) now know torpor is widespread in small Australian mammals, and has also been observed in many small Australian bird species. >>

<<  The question people often ask about torpor, is "can humans do it?" Interestingly, some small primates have been observed using torpor. While it is technically possible to induce torpor in humans chemically, torpor is a very complex physiological process, and there are many aspects of it scientists still don't fully understand. >>

Chris Wacker. Torpor: a neat survival trick once thought rare in Australian animals is actually widespread. The Conversation. Dec 29, 2020. 

https://theconversation.com/torpor-a-neat-survival-trick-once-thought-rare-in-australian-animals-is-actually-widespread-146409

https://phys.org/news/2020-12-torpor-neat-survival-thought-rare.html    

Also

Hrvatin S., Sun S., Wilcox OF et al. Neurons that regulate mouse torpor. Nature 583, 115–121. doi: 10.1038/ s41586-020-2387-5. Jun 11, 2020.

https://www.nature.com/articles/s41586-020-2387-5

Takahashi TM, Sunagawa GA, et al. A discrete neuronal circuit induces a hibernation-like state in rodents. Nature 583, 109–114. doi: 10.1038/ s41586-020-2163-6. Jun 11, 2020.

https://www.nature.com/articles/s41586-020-2163-6