# bot: here you can imagine a scenery where tiny bots jump & wing-flapping

AA << have recently designed two insect-scale microbots, one that jumps and another that flaps its artificial wings. These robot designs, (..) mimic real biological behaviors observed in insects. >>

Ingrid Fadelli. New designs for jumping and wing-flapping microrobots. Phys.org. Aug 28, 2019.    https://m.techxplore.com/news/2019-08-wing-flapping-microrobots.html 

Palak Bhushan, Claire Tomlin. An Insect-scale Untethered Laser-powered Jumping Microrobot.  arXiv:1908.03282v1 [cs.RO]  Aug 8,  2019.    https://arxiv.org/abs/1908.03282  

Palak Bhushan, Claire Tomlin. Design of the first sub-milligram flapping wing aerial vehicle.  arXiv:1908.03203v1 [cs.RO] Aug 9, 2019.   https://arxiv.org/abs/1908.03203  

# gst: apropos of bubbles, the life of a surface bubble.

<< Who has never observed at the surface of a puddle under the rain one bubble that bursts instantly and another one that stays for more than 10 s?  >>️

<< Once a bubble has reached an interface, it adopts a static shape that is governed by the balance between the surface tension and buoyancy effects.  >>

<< To sum-up, (AA) have presented the state of the art concerning the prediction of the lifetime of surface bubbles. In general, the bubble unstability is linked to two facts: (i) the bubble cap is constituted by a thin film, whose thickness decreases along time due to both drainage and evaporation and (ii) this thin film is unstable and eventually bursts. (AA) have shown that the current understanding is that two different behaviors exist depending on whether the film thins until its thickness reaches a few hundreds of nanometers or bursts at higher thicknesses. In the first case, determinist models that describe the thinning of the film down to a rupture thickness of the order of tenth to hundreds of nanometers perform correctely to calculate the bubbles lifetime. In the second case, the presence of a fatal impurity within the film and its propension to break it being a more random process, lifetime distributions are much more spread and only stochastic models may capture the physical mechanism(s) at play. The scenario depends on whether or not surfactants are present to stabilise the thick film. >>

<< In absence of surfactants, the distribution of lifetimes is given by a Weibull distribution. The bursting mechanism available in the literature involves the diffusion of impurities in the film, which cause the film rupture. Film thinning due to evaporation is likely to be rather negligible in such experiments since its impact is small on thick films. >>

<< In presence of surfactants, the film is expected to thin until its thickness reaches a few tens of nanometers. The prediction of the bubble lifetime thus depends on our ability to predict the thinning rate of the film. It is fixed by the evaporation and the drainage. For tiny bubbles, no stable thin film appears and the evaporation is negligible. The lifetime is fixed by the approach velocity of the bubble to the bath. For bigger bubbles, evaporation and drainage must be taken into account. The evaporation is a constant rate, which depends on external conditions such as atmospheric humidity, on the diffusion/convection ratio and on the chemical potential of the solution. It has been shown that an accurate description of the evaporation rates necessitates to take into account the natural convection. >>

<< The drainage mechanism depends on the viscosity of the solution, on the bubble size and on the surfactants used to stabilise the interfaces. (AA) have identified three main mechanisms. For viscous bubbles, the cap is axisymmetric and the thickness decreases continuously from the bottom to the top of the bubble. The drainage is then expected to be exponential with time. In presence of surfactants, a pinch is expected to appear in the vicinity of the meniscus, which slows down the drainage. The destabilization of this pinch may lead to marginal regeneration, that in turn can affect the drainage. >>

<< Several references show that the drainage and evaporation rates are sufficient to predict the average lifetime of the surfaces bubbles in these different cases. >>

<< Many questions remain open and deserve to be addressed in a near future and (AA) try to list some of them below.

The mechanism at the origin of the eventual bursting of the film, whether they are thick (micrometers) or thin (tens of nanometers) is mostly unknown.

The marginal regeneration phenomenon, the dynamics of the pinch, the origin of its destabilisation and its contribution to drainage are under current investigation.

The impact of the chosen surfactants on bubble drainage and evaporation is crucial but remains an open question.

There is still a lack of data concerning the distributions observed. Additionally, there is no theoretical prediction of the distribution in the presence of surfactants stabilising the interface. >>️

Jonas Miguet, Florence Rouyer,  Emmanuelle Rio. The Life of a Surface Bubble. Molecules. 26(5): 1317.

doi: 10.3390/ molecules26051317. Mar 1,  2021. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7957579/   

Also

keyword "bubble" in FonT

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

# gst: deep, super-resolution vistas through tiny tornadoes of magnetized plasma

<< To get the extremely high-resolution images vital to study new materials, microbes, and more, scientists often build microscopes based on optical vortices. >>

AA << devised a way to make optical vortices with 1000 times more power than previous methods. Their design uses strong, nonuniform magnetic fields to control plasmas, or ionized gases, to create the vortices. >>

US Department of Energy. Magnetized plasmas that twist light can produce powerful microscopes and more. May 7, 2018.

https://m.phys.org/news/2018-05-magnetized-plasmas-powerful-microscopes.html

Kenan Qu, Qing Jia, Nathaniel J. Fisch. Plasma q-plate for generation and manipulation of intense optical vortices. Phys. Rev. E 96, 053207.  doi: 10.1103/PhysRevE.96.053207. Nov 28, 2017.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.96.053207

# zoo; apropos of extreme dwarf entities, the nano-chameleon (Brookesia nana)

<< An international team, (..) has discovered a minuscule new species of chameleon.  (..) They have named the new species Brookesia nana. >>

 << At a body length of just 13.5 mm and a total length of just 22 mm including the tail, the male nano-chameleon is the smallest known male of all 'higher vertebrates' >> Frank Glaw.

<< Unfortunately, the habitat of the Nano-Chameleon is under heavy pressure from deforestation, but the area has recently been designated as a protected area, and hopefully that will enable this tiny new chameleon to survive, >> Oliver Hawlitschek.

Meet the nano-chameleon, a new contender for the title of world's smallest reptile. Staatliche Naturwissenschaftliche Sammlungen Bayerns. Feb 01, 2021. 

https://phys.org/news/2021-02-nano-chameleon-contender-title-world-smallest.html    

Glaw, F., Kohler, J., Hawlitschek, O. et al. Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons. Sci Rep 11, 2522. doi: 10.1038/ s41598-020-80955-1. Jan 28,  2021.

https://www.nature.com/articles/s41598-020-80955-1 

# gst: nano entities that are both twisted and untwisted at the same time

<< Scientists who study the nanoscale-with molecules and materials 10,000 smaller than a pinhead-need to be able to test the way that some molecules twist, known as their chirality, because mirror image molecules with the same structure can have very different properties. >>

<< Recently, a new class of nanoscale materials have been developed to help distinguish the chirality of molecules. These so-called 'nanomaterials' usually consist of tiny twisted metal wires, that are chiral themselves. However, it has become very hard to distinguish the twist of the nanomaterials from the twist of the molecules they are supposed to help study. >>

To solve this problem AA << created a nanomaterial that is both twisted and it is not. This nanomaterial has equal number of opposite twists—meaning they cancel each other out.  >>

<< Using a mathematical analysis of the material's symmetry properties, the team discovered a few special cases, which can bring the 'hidden' twist to light and allow very sensitive detection of chirality in molecules. >>

Chris Melvin. Scientists create a nanomaterial that is both twisted and untwisted at the same time. University of Bath. Sep 13, 2019   https://m.phys.org/news/2019-09-scientists-nanomaterial-untwisted.html  

Christian Kuppe,  Xuezhi Zheng, et al. Measuring optical activity in the far-field from a racemic nanomaterial: diffraction spectroscopy from plasmonic nanogratings. Nanoscale Horizons.  Issue 5, 2019.  doi: 10.1039/C9NH00067D.   https://pubs.rsc.org/en/content/articlelanding/2019/NH/C9NH00067D

# gst: apropos of bubbles, how simple foams collapse

<< When a bubble breaks, (AA) found that a collapse event propagates via impact with the receding film and tiny scattered droplets breaking other bubbles. >>

<< A key finding was that changing the viscosity of the fluid did not lead to a significant change in the number of bubbles broken. Methods to stabilize foams commonly rely on changing the viscosity, yet the team's findings clearly show how both the number of bubbles collapsed and the velocity of the receding film are unaffected. >>

Two distinct physical mechanisms identified for how simple foams collapse. Tokyo Metropolitan University. June 10, 2019.

https://m.phys.org/news/2019-06-distinct-physical-mechanisms-simple-foams.html

Naoya Yanagisawa, Rei Kurita. In-situ observation of collective bubble collapse dynamics in a quasi-two-dimensional foam. Scientific Reports 9, Article number: 5152. March 26, 2019

https://www.nature.com/articles/s41598-019-41486-6

# gst: apropos of nano vortices: the stabilization of skyrmions by weak higher-order exchange interactions

<< Tiny magnetic whirls that can occur in materials—so-called skyrmions— hold high promises for novel electronic devices or magnetic memory in which they are used as bits to store information. A fundamental prerequisite for any application is the stability of these magnetic whirls. >>

<< Previously, a standard model of the relevant magnetic interactions contributing to the (energy) barrier has been established. >>

<< one type of magnetic interactions has so far been overlooked. In the 1920s Werner Heisenberg could explain the occurrence of ferromagnetism by the quantum mechanical exchange interaction which results from the spin dependent "hopping" of electrons between two atoms. "If one considers the electron hopping between more atoms, higher-order exchange interactions occur," says Dr. Souvik Paul, (..). However, these interactions are much weaker than the pair-wise exchange proposed by Heisenberg and were thus neglected in the research on skyrmions. >>

<< Based on atomistic simulations and quantum mechanical calculations (..)  (AA) have now explained that these weak interactions (at a higher temperature than room temperature) can still provide a surprisingly large contribution to skyrmion stability. Especially the cyclic hopping over four atomic sites (..) influences the energy of the transition state extraordinarily strongly (..), where only a few atomic bar magnets are tilted against each other. Even stable antiskyrmions were found in the simulations which are advantageous for some future data storage concepts but typically decay too fast. >>

Julia Siek­mann. Scientists find a new mechanism for the stabilization of skyrmions. Kiel University. Sep 21, 2020.

https://phys.org/news/2020-09-scientists-mechanism-stabilization-skyrmions.html

Paul, S., Haldar, S., von Malottki, S. et al. Role of higher- order exchange interactions for skyrmion stability. Nat Commun 11, 4756. doi: 10.1038/ s41467-020-18473-x. Sep 21, 2020.

https://www.nature.com/articles/s41467-020-18473-x   

# brain: the hypothesis that a brain organoid (a lab-grown brain) can reach consciousness.

<< In Alysson Muotri’s laboratory, hundreds of miniature human brains, the size of sesame seeds, float in Petri dishes, sparking with electrical activity. 

These tiny structures, known as brain organoids, are grown from human stem cells and have become a familiar fixture in many labs that study the properties of the brain. Muotri, a neuroscientist at the University of California, San Diego (UCSD), has found some unusual ways to deploy his. He has connected organoids to walking robots, modified their genomes with Neanderthal genes, launched them into orbit aboard the International Space Station, and used them as models to develop more human-like artificial-intelligence (AI) systems. (..) But one experiment has drawn more scrutiny than the others. In August 2019, Muotri’s group published a paper in Cell Stem Cell (*) reporting the creation of human brain organoids that produced coordinated waves of activity, resembling those seen in premature babies. The waves continued for months before the team shut the experiment down. This type of brain-wide, coordinated electrical activity is one of the properties of a conscious brain. >> 

Sara Reardon. Can lab-grown brains become conscious? Nature 586, 658-661. doi: 10.1038/ d41586-020-02986-y. Oct 27, 2020. Correction Nov 4, 2020.

https://www.nature.com/articles/d41586-020-02986-y     

(*)  Trujillo CA, Gao R, et al. Complex Oscillatory Waves Emerging from Cortical Organoids Model Early Human Brain Network Development. Cell Stem Cell. 2019 Oct 3;25(4):558-569.e7. doi: 10.1016/ j.stem.2019.08.002. Aug 29, 2019. 

https://pubmed.ncbi.nlm.nih.gov/31474560/

https://www.cell.com/cell-stem-cell/fulltext/S1934-5909(19)30337-6

# gst: the physics of squeezing; how to squeeze out (quantum) noise

<< 'Squeezing' is used in physics, among other things, to improve the resolution of measuring instruments. It allows disturbing noise to be suppressed in a way that smaller signals can be detected more sensitively. (..) (AA) has now been able to show how such a squeezed state can be measured in a much simpler way than with the existing methods. Moreover, the new method allows examining squeezed states in systems where such measurements were not possible before. >> [1]

<< In the experiment (..) the thermal fluctuations of a vibrating nanomechanical string resonator are squeezed. The nanostring can be thought of as a tiny guitar string, a thousand times thinner and shorter than a human hair. (..)  If the string is deflected far enough, it ceases to behave linearly. This means that the force that deflects the string is no longer proportional to the force that pulls it back to its original position. The strong drive alters the thermal fluctuations as a result of a violation of the time reversal symmetry. In phase space, they no longer look like a circle but like an ellipse: At least in one direction, its diameter, i.e. the noise, becomes significantly smaller—it is squeezed. >> [1]

<< Quantum squeezing was a theory that was first proposed in the 1980s, the general idea being that quantum vacuum noise can be represented as a sphere of uncertainty along two main axes: phase and amplitude. If this sphere were squeezed, like a stress ball, in a way that constricted the sphere along the amplitude axis, this would in effect shrink the uncertainty in the amplitude state of a vacuum (the squeezed part of the stress ball), while increasing the uncertainty in the phase state (stress ball's displaced, distended portion). Since it is predominantly the phase uncertainty that contributes noise to LIGO, shrinking it could make the detector more sensitive to astrophysical signals. (..) The heart of the squeezer is an optical parametric oscillator, or OPO — a bowtie-shaped device that holds a small crystal within a configuration of mirrors. When the researchers direct a laser beam to the crystal, the crystal's atoms facilitate interactions between the laser and the quantum vacuum in a way that rearranges their properties of phase versus amplitude, creating a new, "squeezed" vacuum that then continues down each of the detector's arm as it normally would. This squeezed vacuum has smaller phase fluctuations than an ordinary vacuum, allowing scientists to better detect gravitational waves. >> [2]

[1] - Measure squeezing in a novel way. University of Konstanz. Jun 25, 2020.   https://phys.org/news/2020-06-measure-squeezing-in-a-novel.html ; 

J. S. Huber, G. Rastelli, et al. Spectral Evidence of Squeezing of a Weakly Damped Driven Nanomechanical Mode.  Phys. Rev. X 10, 021066 – Jun 23,  2020.   https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.021066 

[2] - Jennifer Chu. New instrument extends LIGO’s reach. Technology "squeezes" out quantum noise so more gravitational wave signals can be detected. MIT. Dec 5, 2019.   https://news.mit.edu/2019/ligo-reach-quantum-noise-wave-1205

# s-behav: they behave strangely in the darkness caused by a solar eclipse

<< Many accounts of solar eclipses include tales of animals behaving strangely >>

<< There’s a lot of anecdotal evidence for how animals and even plants respond to totality [of solar eclipses] >>

<< Crickets chirped and frogs croaked [..]  Gnats and mosquitoes swarmed [..] Bees returned to hives and chickens to roost >>

<< small, light-sensitive crustaceans and zooplankton swam upward toward the dark during eclipses, similar to how the tiny animals behave at night >>

<< The sun’s disappearance prompted orb weaver spiders to take down their webs >>

<< captive chimpanzees scaled a climbing structure and faced the blocked sun >>

Lisa Grossman. What do plants and animals do during an eclipse?
A citizen science project aims to gather data to put science behind anecdotal evidence. Aug 12, 2017

https://www.sciencenews.org/article/2017-solar-eclipse-animals

<< The behavior of colonial orb-weaving spiders (Metepeira incrassata) in tropical Veracruz, Mexico was studied during the total solar eclipse on July 11, 1991. Spiders behaved in a manner typical of daily activity until totality, when many began taking down webs. After solar reappearance, most spiders that had begun taking down webs rebuilt them >>

Uetz, G.W., Hieber, C.S., et al.     Behavior of Colonial Orb-weaving Spiders during a Solar Eclipse. Ethology, 96: 24–32. Jan 12, 1994. doi:10.1111/j.1439-0310.1994.tb00878.x

http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0310.1994.tb00878.x/full

<< This year, the California Academy of Sciences is soliciting citizen scientists to record their observations of any animals they see using the academy’s iNaturalist app >>

Solar Eclipse 2017: Life Responds.

http://www.calacademy.org/citizen-science/solar-eclipse-2017

# gst: high entropy can alloy immiscible nanoparticles

<< Making a giant leap in the 'tiny' field of nanoscience, a multi-institutional team of researchers is the first to create nanoscale particles composed of up to eight distinct elements generally known to be  immiscible, or incapable of being mixed or blended together >>

<< To create the high entropy alloy nanoparticles, the researchers employed a two-step method of flash heating followed by flash cooling >>

<< With cross-discipline curiosity, the demonstrated applications of these particles will become even more widespread >> Steven D. Lacey.

University of Maryland. Scientists mix the unmixable to create 'shocking' nanoparticles. Mar 29, 2018.

https://m.phys.org/news/2018-03-scientists-unmixable-nanoparticles.html

Yonggang Yao, Zhennan Huang, et al.
Carbothermal shock synthesis of high-entropy-alloy nanoparticles. Science. 2018; 359 (6383): 1489 - 94. doi: 10.1126/science.aan5412

http://science.sciencemag.org/content/359/6383/1489

# astro: we have to escape with a speed of 550 km/s

<< When a rocket is launched into space, it is thrown out with a speed of 11 km/s to overcome the Earth's gravitational pull [..] Our home galaxy, the Milky Way, is over a trillion times heavier than our tiny planet Earth so to escape its gravitational pull we have to launch with a speed of 550 km/s. >> Prajwal Kafle.

International Centre for Radio Astronomy Research. Milky Way ties with neighbor in galactic arms race. Feb 14, 2018.

https://m.phys.org/news/2018-02-milky-ties-neighbor-galactic-arms.html  

FonT

intrigante il video che simula la collisione- fusione

# gst: apropos of turbulences close to a wall, the repetitive structure of a vortex

<< At the boundary where a fluid flows over a fixed structure, a turbulent boundary layer is created where the fluid interacts with the wall, creating eddies in the current. These eddies may seem to be random on first glance, but they actually create distinct patterns, with countless tiny eddies close to the wall; fewer but larger eddies located a little farther out; and even fewer, but still larger, eddies beyond those. >>

<< "We knew that, underlying these very complicated structures, there had to be a very simple pattern. We just didn't know what that pattern was until now," says McKeon, who next plans to dig deeper into the model to quantify just how many eddies should be included to create an accurate representation of the whole. >>

Engineers exploit the repeating structure of turbulence to create a more complete model of the phenomenon. California Institute of Technology. Nov 6, 2019.

https://m.phys.org/news/2019-11-exploit-turbulence-phenomenon.html

Beverley J. McKeon. Self-similar hierarchies and attached eddies. Phys. Rev. Fluids 4, 082601(R). Aug 26, 2019.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.082601

# behav: the oddity about the highly inactive ants (Temnothorax rugatulus)

<< Social insect colonies are highly successful, self-organized complex systems. Surprisingly however, most social insect colonies contain large numbers of highly inactive workers. Although this may seem inefficient, it may be that inactive workers actually contribute to colony function >>

Daniel Charbonneau, Takao Sasaki, Anna Dornhaus. Who needs ‘lazy’ workers? Inactive workers act as a ‘reserve’ labor force replacing active workers, but inactive workers are not replaced when they are removed. PLOS ONE 12(9): e0184074. doi: 10.1371/journal.pone.0184074 Sep 6, 2017

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184074

<< Analyzing the video recordings revealed that a colony breaks down into four main demographics [..]: inactive, lazy ants; so-called walkers that spend most of their time just wandering around the nest; foragers that take care of outside tasks such as foraging and building protective walls from tiny rocks; and nurses in charge of rearing the brood >>

Lazy ants make themselves useful in unexpected ways. Sep 8, 2017

https://m.phys.org/news/2017-09-lazy-ants-unexpected-ways.html

# brain: chaotic scanning and tiny wobbles during (ocular) vision

<< When we read, our eyes don’t scan a page smoothly but perform a series of jumps, darting from one section of text to another. After each jump, known as a saccade, the pupil typically wobbles for a moment. Now researchers have developed a model for this wobble that involves only physical characteristics of the eyeball >>

Why Your Pupils Wobble. Apr 27, 2018

https://physics.aps.org/articles/v11/41

Bouzat S, Freije ML, et al. Inertial Movements of the Iris as the Origin of Postsaccadic Oscillations. Phys Rev  Lett. 120, 178101. doi: 10.1103/PhysRevLett.120.178101 Apr 27, 2018.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.178101

Also

2146 - is not as simple as one might think (chaos in reading). Sep11, 2007.

http://inkpi.blogspot.it/2007/09/2146-is-not-as-simple-as-one-might.html

# ai-bot: use of soft labels with 'less than one'-shot task in AI learning models

<< Deep neural networks require large training sets but suffer from high computational cost and long training times. Training on much smaller training sets while maintaining nearly the same accuracy would be very beneficial. In the few-shot learning setting, a model must learn a new class given only a small number of samples from that class. One-shot learning is an extreme form of few-shot learning where the model must learn a new class from a single example. (AA)  propose the 'less than one'-shot learning task where models must learn N new classes given only M<N examples and (they) show that this is achievable with the help of soft labels. >>

Ilia Sucholutsky, Matthias Schonlau. 'Less Than One'-Shot Learning: Learning N Classes From M<N Samples. arXiv:2009.08449v1. Sep 17, 2020

https://arxiv.org/abs/2009.08449   

Karen Hao. A radical new technique lets AI learn with practically no data. Oct 16, 2020.  

https://www.technologyreview.com/2020/10/16/1010566/ai-machine-learning-with-tiny-data

FonT: sara' verosimilmente intrigante osservare come una 'macchina AI' sapra' esercitare sugli umani il potere di cooptazione ...

# s-phys: squeezing hydrogen ... they're looking at something that's never existed before

<< This is the holy grail of high-pressure physics [..] It's the first-ever sample of metallic hydrogen on Earth, so when you're looking at it, you're looking at something that's never existed before >> Isaac F. Silvera

<< To create it [metallic hydrogen], Silvera and Dias squeezed a tiny hydrogen sample at 495 gigapascal, or more than 71.7 million pounds-per-square inch - greater than the pressure at the center of the Earth >>

<< In addition to helping scientists answer fundamental questions about the nature of matter, the material is theorized to have a wide range of applications, including as a room-temperature superconductor >>

Metallic hydrogen, once theory, becomes reality. Jan. 26, 2017

https://m.phys.org/news/2017-01-metallic-hydrogen-theory-reality.html

Ranga P. Dias, Isaac F. Silvera. Observation of the Wigner-Huntington transition to metallic hydrogen. Science  26 Jan 2017. DOI: 10.1126/science.aal1579

http://science.sciencemag.org/content/early/2017/01/25/science.aal1579