# gst: droplets scoot like caterpillars.

<< From swells in an ocean to ripples in a puddle, the shearing effect of wind blowing over a liquid is visible at all scales. This shear determines the interactions between Earth’s atmosphere and its surface water and, researchers now explain, the movement of liquid droplets that crawl up and down the window of a moving car in the rain. In a series of experiments, (AA) show that airflow triggers surface waves that cause such droplets to crawl like caterpillars before they break apart. >>️

<< At first, the airflow across the droplet’s surface caused the droplet to extend into an oval shape. The droplet also began to tilt, with the liquid piling up at the droplet’s downwind edge. When the drag force exerted by the airflow overcame the capillary force between the glycerin and the glass, the droplet began to slide and to stretch out even more. Surface waves then developed on the elongated droplet and traveled toward its leading edge. The waves induced a stable caterpillar-like motion, with the droplet stretching and contracting along its length. Eventually, beyond a threshold length that depended on the droplet’s volume, the caterpillar was no longer able to withstand the shearing force and broke into several droplets. >>️

AA << say that the behavior follows the same pattern as that of an elongated droplet sliding along an incline. >>

️

Rachel Berkowitz. Droplets Scoot Like Caterpillars. Physics 16, s110. Sep 1, 2023.

https://physics.aps.org/articles/v16/s110  

A. Chahine, J. Sebilleau, R. Mathis, D. Legendre. Caterpillar like motion of droplet in a shear flow. Phys. Rev. Fluids 8, 093601. Sep 1, 2023.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.093601

Also: drop, bubble, transition, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, drop, droplet, droploid, bubble, transition

# art: nature as a bizarre artist, the self-sculpted Sphinx.

<< There is evidence that the Great Sphinx was a natural landform before its surface features were chiseled by the ancient Egyptians. Is this controversial theory plausible? >>

AA << carried out experiments on the fluid mechanical erosion of clay. Based on accounts of the nonuniform composition of the Sphinx, we tested the effect of hard inclusions within hillocks of softer clay. The flow of a water tunnel mimics the prevailing winds of Giza, and three-dimensional optical scanning records the history and evolution of the shape as it erodes. >>

<< These results show what ancient peoples may have encountered in the deserts of Egypt and why they envisioned a fantastic creature. >>️

️

Samuel Boury, Scott Weady, Leif Ristroph. Sculpting the Sphinx. Phys. Rev. Fluids 8, 110503. Nov 16, 2023.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.110503

https://gfm.aps.org/meetings/dfd-2022/6323dcaf199e4c2c0873fad7

Also: brain, perception, in https://www.inkgmr.net/kwrds.html 

Keywords: art, sculpt, Sphinx, erosion, fluid mechanical erosion, brain, mind, perceptions.

# gst: collective patterns generated by capillary surfers.

<< Millimeter-sized “surfers” can self-propel across a vibrating liquid surface, interacting with other surfers to create collective patterns. >>

<< Self-propelled objects can move in mesmerizing patterns. The collective movements of groups of such objects typically occur in one of two flow regimes: the inertial regime—think swirling schools of fish in water—or the viscous regime—think swarming colonies of bacteria in mucus. Some self-propelled objects can travel in both flow regimes, a possibility that is less explored. >>️

AA << have studied the motion of a new system of self-propelled objects that move in this intermediate regime, finding that the objects organize into several distinct and tunable motion patterns. >>️️

<< Pairs of self-propelled surfers observed by the team move in one of seven different patterns (the video shows five). These include the “orbit,” where a pair of surfers rotate around a central point; the “tailgate,” where one surfer closely follows another, head to tail in a linear path; and the “jackknife,” where a pair of perpendicular surfers rotate stern to stern around their collision point. >>

<< When only one surfer was present, these mismatched amplitudes propelled the surfer in the direction of its bow. When there were two surfers close to each other, interactions among the waves caused the surfers to either repel each other so that they moved in opposite directions or to come together so that they collectively traced one of seven distinct patterns. >>️

️

Maggie Hudson. Synchronized Surfing of Self-Propelled Particles. Physics 16, s156. Nov 7, 2023. 

https://physics.aps.org/articles/v16/s156

Ian Ho, Giuseppe Pucci, Anand U. Oza, Daniel M. Harris. Capillary surfers: Wave-driven particles at a vibrating fluid interface. Phys. Rev. Fluids 8, L112001. Nov 7, 2023.

https://link.aps.org/doi/10.1103/PhysRevFluids.8.L112001

Anand U. Oza, Giuseppe Pucci, Ian Ho, Daniel M. Harris. Theoretical modeling of capillary surfer interactions on a vibrating fluid bath. Phys. Rev. Fluids 8, 114001. Nov 7, 2023.

https://link.aps.org/doi/10.1103/PhysRevFluids.8.114001

Also: waves, particle, swarm, in: https://www.inkgmr.net/kwrds.html

Keywords: gst, waves, wave-wave, capillary waves, particles, self-propelled particles, fluid-particle interactions, wave-particle interactions

# gst: reconfiguration and oscillations of sheets subject to vortex

<< The dynamics of a thin low-density polyethylene sheet subject to periodic forcing due to Bénard-Kàrmàn vortices in a long narrow water channel is investigated here. In particular, the time-averaged sheet deflection and its oscillation amplitude are considered. >>

<< The former is first illustrated to be well-approximated by the static equilibrium between the buoyancy force, the elastic restoring force, and the profile drag based on the depth-averaged water speed. >>

AA << observations also indicate that the presence of upstream vortices hinder the overall reconfiguration effect, well-known in an otherwise steady flow. For the sheet-tip oscillations, a simple model based on a torsional-spring-mounted flat plate correctly captures the measured tip amplitude δb over a wide range of sheet physical properties and flow conditions. >>

<< Furthermore, a rich phenomenology of structural dynamics including vortex-forced-vibration, lock-in with the sheet natural frequency, and flow-induced vibration due to the sheet wake, multiple-frequency, and modal response is reported. >>

️

J. John Soundar Jerome, Yohann Bachelier, et al. Reconfiguration and oscillations of a vertical, cantilevered sheet subject to vortex shedding behind a cylinder. Phys. Rev. Fluids 8, 093801. Sep 15, 2023. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.093801

Also: vortex, in https://www.inkgmr.net/kwrds.html

Keywords: gst, sheet, vortex, Benard-Karman vortices

# gst: to find a separation between plunging and spilling wave breakers

<< While understanding breaking waves is crucial for the development of parametrizations used in ocean wave modeling for both deep and shallow water, the complete process of wave breaking is not well understood. Here (AA) present direct numerical simulations of two-dimensional solitary waves that shoal and break on a uniform beach in shallow water, with the presence of storm surge represented by an inshore region. >>️

They << classify wave breaker types and find a separation between plunging and spilling breakers when scaled by breaking amplitude and depth. (AA) compare energy dissipation during the breaking process with results from the literature without storm surge.  >>️

They << conclude that a previously developed shallow-water inertial dissipation model for wave breaking on a uniform slope can be extended to this storm surge environment with good data collapse, and further discuss possibilities for a general parametrization of wave breaking valid across different depth regimes. >>️

Hunter Boswell, Guirong Yan, Wouter Mostert. Characterizing energy dissipation of shallow-water wave breaking in a storm surge. Phys. Rev. Fluids 8, 054801. May 5, 2023. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.8.054801

Also: waves, soliton, drop, in https://www.inkgmr.net/kwrds.html

Keywords: gst, waves, soliton, drop 

# gst: even a single bubble can produce creative musical outcomes

<< Producing original and arranging existing musical outcomes is an art that takes years of learning and practice to master. Yet, despite the constant advances in the field of AI-powered musical creativity, production of quality musical outcomes remains a prerogative of the humans. Here we demonstrate that a single bubble in water can be used to produce creative musical outcomes, when it nonlinearly oscillates under an acoustic pressure signal that encodes a piece of classical music. >>️

Ivan S. Maksymov. Musical creativity enabled by nonlinear oscillations of a bubble in water. arXiv:2304.00822v1 [cs.SD]. Apr 3, 2023. 

https://arxiv.org/abs/2304.00822

keyword "bubble" in FonT

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

Keywords: gst, ai, fluid dynamics, bubble, sound, music, audio processing

# gst: hidden complexity during the twinkle of a shrinking droplet

<< Captivating patterns found in the light scattered by an evaporating water droplet could be used to infer the properties of the droplet as it shrinks. >>

AA << collected the light that bounced off a spherical water droplet as the droplet shrunk, which happened naturally as it evaporated. The team observed twinkling patterns called Fano combs, which resemble the outlines of hedgehogs. >>

Ryan Wilkinson. Twinkling of a Shrinking Droplet Reveals Hidden Complexity. Physics 16, s9. Jan 24, 2023.

https://physics.aps.org/articles/v16/s9

AA << then fully explain it by expanding the quantum analogy. This turns the droplet into an “optical atom" with angular momentum, tunneling, and excited states. >>

Javier Tello Marmolejo, Adriana Canales, et al. Fano Combs in the Directional Mie Scattering of a Water Droplet. Phys. Rev. Lett. 130, 043804. Jan 24, 2023.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.043804

Also

keyword 'evaporation' in FonT

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

keyword 'drop' | 'droplet' | 'droploids' in FonT

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

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

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

keyword 'goccia' in Notes 

(quasi-stochastic poetry): 

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

Keywords: gst, drop, droplet, shrink, shrinking droplet, evaporation, transition

# gst: when a soliton juggles ('catches' and 'throws') droplets

<< Jugglers normally work with solid objects, but a research team has now demonstrated a system that juggles liquid drops. (AA)  have previously shown that liquid drops can bounce in place above the surface of the same liquid—or bounce while moving across the surface—if the container is continuously vibrated (..) In these past experiments, the surface was nearly flat, except for waves generated by the bouncing drop. In the new work by undergraduate student Camila Sandivari of the University of Chile and her colleagues, the vibrations cause the liquid surface to form a large standing wave that actively “catches” and “throws” the drop during each cycle of its oscillation. The trapping of the drop is similar in principle to other types of wave traps, such as laser-based optical tweezers, and the system could potentially lead to new types of traps for larger objects. >>

AA << placed water mixed with a dye and a surface-tension-reducing agent in a 20-cm-long, 2.6-cm-wide basin that supports an unusual type of surface wave when the basin is vibrated in a specific frequency range. In this wave, rather than a series of oscillating peaks and valleys, there is only a single standing wave peak, called a soliton. However, this peak doesn’t oscillate uniformly across the basin’s short dimension (the width). A peak appears at one of the long walls coincident with a valley at the opposite wall, and then the peak and the valley switch places moments later, keeping a relatively flat “node” line along the central long axis of the basin. >>

AA << used a pipette to place a few-millimeter-wide drop of the same fluid just above the oscillating soliton, close to one of the long walls, and found that drops could be juggled for up to 90 minutes. The team attributes this unusual stability in part to a property of the soliton: if the drop wanders off-center, the oscillating surface wave pulls it back toward its center, similar to the way the laser field in optical tweezers is able to stably hold a small particle at its center. >>

David Ehrenstein. Juggling Water Drops. Physics 16, 21. Feb 10, 2023. 

https://physics.aps.org/articles/v16/21

Also

keyword 'drop' | 'droplet' | 'droploids' in FonT

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

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

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

keyword 'goccia' in Notes 

(quasi-stochastic poetry)

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

keyword 'solitons' in FonT

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

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

Keywords: gst, solitons, drop, droplet, droploids, goccia

# 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. 

https://physics.aps.org/articles/v15/s173

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

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.268001

Also

keyword "bubble" in FonT

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

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

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

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

Keywords: gst, bubble, stability, evaporation, burst

# gst: apropos of transitions, evaporating binary microdroplets with phase segregation

<< Phase segregation triggered by selective evaporation can emerge in multicomponent systems, leading to complex physiochemical hydrodynamics. Recently, Li et al. (2018) and Kim & Stone (2018) reported a segregative behavior (i.e., demixing) in an evaporating binary droplet. In this work, by means of experiments and theoretical analysis, (AA) investigate the flow dynamics after the occurrence of the phase segregation. >>

<< First, (AA) experimentally reveal the overall physiochemical hydrodynamics of the evaporation process, including the segregative behavior and the resulting flow structure close to the substrate. By quantifying the evolution of the radial flow, (they) identify three successive life stages of the evaporation process. >>

<< At Stage I, a radially outward flow is observed. It is driven by the Marangoni effect. At the transition to Stage II, the radial flow partially reverses, starting from the contact line. This flow breaks the axial symmetry and remarkably is driven by the segregation itself. Finally at Stage III, the flow decays as the evaporation gradually ceases. At this stage the segregation has grown to the entire droplet, and the flow is again controlled by the Marangoni effect. The resulting Marangoni flow homogenizes the distribution of the entrapped volatile water over the whole droplet. >>️

Yaxing Li, Pengyu Lv, et al. Physiochemical hydrodynamics of the phase segregation in an evaporating binary microdroplet.arXiv:2208.07861v1 [physics.flu-dyn]  Aug 16, 2022.

https://arxiv.org/abs/2208.07861

Marangoni effect. 

https://en.m.wikipedia.org/wiki/Marangoni_effect   

https://youtu.be/vGb6t5Gfq6s   

Also

keyword 'drop' | 'droplet' in FonT

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

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

Keywords: gst, droplet, transition, evaporation, phase transition, phase segregation, Marangoni flow

# life: apropos of transitions, a leap from chemistry to biology, the hypothesis of self-assembling droplets, the 'droplet world'.

AA << identify conditions suitable for concurrent peptide generation and self-assembly, and (..) show how a proliferating peptide-based droplet could be created by using synthesised amino acid thioesters as prebiotic monomers. Oligopeptides generated from the monomers spontaneously formed droplets through liquid–liquid phase separation in water. The droplets underwent a steady growth–division cycle by periodic addition of monomers through autocatalytic self-reproduction. Heterogeneous enrichment of RNA and lipids within droplets enabled RNA to protect the droplet from dissolution by lipids. >>

Matsuo, M., Kurihara, K. Proliferating coacervate droplets as the missing link between chemistry and biology in the origins of life. Nat Commun 12, 5487. doi: 10.1038/ s41467-021-25530-6. Sep 24,  2021.

https://www.nature.com/articles/s41467-021-25530-6

<< By constructing peptide droplets that proliferate with feeding on novel amino acid derivatives, we have experimentally elucidated the long-standing mystery of how prebiotic ancestors were able to proliferate and survive by selectively concentrating prebiotic chemicals, (..) Rather than an RNA world, we found that 'droplet world' may be a more accurate description, as our results suggest that droplets became evolvable molecular aggregates—one of which became our common ancestor. >> Muneyuki Matsuo.

Answering a century-old question on the origins of life. Hiroshima University. Sep 27, 2021. 

https://phys.org/news/2021-09-century-old-life.html

Also

keyword 'drop' | 'droplet' in FonT

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

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

keyword 'transition' in FonT

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

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

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

keywords: life, originsoflife, transitions, drop, droplet

# gst: approaching the dynamics of nanobubble formation and collapse

<< While sequential optical imaging (i.e., recording movies) has contributed significantly to our understanding of cavitation and other complex bubble behavior at the larger (..) scale, the necessary length and temporal resolutions make such a traditional approach infeasible for nanobubbles, >> Garth Egan. ️

<< To take the images at the nanoscale, (AA) shot a 532-nanometer laser pulse (about 12 nanosec) to excite gold nanoparticles inside a 1.2 micron layer of water. The resulting bubbles were observed with a series of nine electron pulses (10 ns) separated by as little as 40 ns peak-to-peak. The researchers found that isolated nanobubbles were observed to collapse in less than 50 ns, while larger (∼2–3 micron) bubbles were observed to grow and collapse in less than 200 ns. >>

<< Isolated bubbles were observed to behave consistently with models derived from data from much larger bubbles. The formation and collapse were observed to be temporally asymmetric, which has implications for how results from alternate methods of experimental analysis are interpreted. More complex interactions between adjacent bubbles also were observed, which led to bubbles living longer than expected and rebounding upon collapse. >>️️

Anne M. Stark. Multiframe imaging of micron and nanoscale bubble dynamics.  Lawrence Livermore National Laboratory. Feb 09, 2022. 

https://phys.org/news/2022-02-multiframe-imaging-micron-nanoscale-dynamics.html

Garth C. Egan, Edmond Y. Lau, Eric Schwegler.  Multiframe Imaging of Micron and Nanoscale Bubble Dynamics. Nano Lett. 2022, 22, 3, 1053–1058. doi: 10.1021/ acs.nanolett.1c04101. Jan 19, 2022.

https://pubs.acs.org/doi/10.1021/acs.nanolett.1c04101

Also

keyword "bubble" in FonT

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

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

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

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

keywords: bubble, nano, nanobubble,  nanobubble dynamics, bubble formation, bubble collapse

# gst: liquid–liquid phase transition, the two forms of liquid water (mixed with the natural antifreeze trehalose)

<< Liquids are structurally disordered, so it’s not immediately obvious how they can support two distinct structures with different densities. But that does seem to be possible for liquids in which some degree of directional bonding, such as hydrogen bonds between adjacent water molecules, makes distinct local structures possible. Liquid–liquid transitions have been reported, for example, in silicon, gallium, phosphorus and silicates. But finding one in supercooled water has proved very challenging. There have been previous claimed observations of a liquid–liquid transition in aqueous solutions at ambient pressure, (..) where the solute, such as the sugar glycerol, sometimes used as a cryoprotectant, lowers the freezing point. But such claims have been disputed.(..) Other researchers have reported liquid-like behaviour as the two well-established high- and low-density forms of amorphous (glass-like) ice interconvert. (..) >>

<< In 2014 Yoshiharu Suzuki (..) working with veteran water researcher Osamu Mishima, reported possible signs of a liquid–liquid transition, ending in a critical point where the two liquid states become indistinguishable, in emulsified, supercooled solutions of glycerol. (..) They saw signs of two distinct disordered states with different densities at a temperature of 150K. But there was no direct evidence that both were liquids, rather than amorphous ice. >>

<< Suzuki has now explored the same approach using trehalose as the solute – a sugar produced as a natural cryoprotectant by some organisms, such as insects, that experience extreme cold, to prevent their blood from freezing. He pressurised dilute emulsified solutions to about 0.6GPa at a range of temperatures below 159K, and then decompressed them again.  >>

<< Such hysteresis – whereby the density jumps at different pressures on compression and decompression – is normal for a first-order transition where a parameter such as density changes discontinuously. It reflects the fact that the transition has to start with the chance formation of a ‘nucleus’ of the new phase, which then grows. >>

<< Suzuki is not yet sure why trehalose stabilises water so well against crystallisation, compared with glycerol – but this might help explain why life uses it as an antifreeze. >>

Philip Ball. Direct evidence emerges for the existence of two forms of liquid water. Feb 1, 2022.

https://www.chemistryworld.com/news/direct-evidence-emerges-for-the-existence-of-two-forms-of-liquid-water/4015144.article  

Also

keyword 'water' in FonT

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

keyword 'transition' | 'transitional' in FonT

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

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

keyword 'transition' | 'transizion*' in Notes (quasi-stochastic poetry)

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

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

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

keywords: gst, transition, liquid-liquid transition, water

# 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.

https://physics.aps.org/articles/v14/s109

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.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.088005

Also

keyword 'drop' | 'droplet' in FonT

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

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

# gst: apropos of transitions, tsunami waves generated by granular collapses.

<< Tsunami waves induced by landslides are a threat to human activities and safety along coastal areas. In this paper, (AA) characterize experimentally the waves generated by the gravity-driven collapse of a dry granular column into water. Three nonlinear wave regimes are identified depending on the Froude number Fr_f based on the ratio of the velocity of the advancing granular front and the velocity of linear gravity waves in shallow water: transient bores for large Fr_f, solitary waves for intermediate values of Fr_f, and nonlinear transition waves at small Fr_f. >>️

Wladimir Sarlin, Cyprien Morize, et al. Nonlinear regimes of tsunami waves generated by a granular collapse.    

Journal of Fluid Mechanics, 919, R6. doi:10.1017/ jfm.2021.400. May 28, 2021. 

https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/nonlinear-regimes-of-tsunami-waves-generated-by-a-granular-collapse/3F38B26548B891FA9AE8A4018FF992A4#

James Badham. The Science of tsunamis. University of California. Santa Barbara. Jun 21, 2021. 

https://www.sciencedaily.com/releases/2021/06/210621160524.htm

Froude number (Fr_f)

https://en.m.wikipedia.org/wiki/Froude_number

Also

keyword 'grain' in FonT

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

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

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

keyword 'waves' in FonT

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

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

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

# gst: when and how a levitating droplet sings (as a pipe)

<< Sprinkle water onto a very hot pan, and you may notice that the droplets evaporate surprisingly slowly. They stick around because of what’s called the Leidenfrost effect—a thin layer of vapor forms between the droplets and the hot surface, insulating them from the heat, and keeping them from boiling off immediately. (..) droplets of water in this Leidenfrost regime emit periodic sounds, or beats.  >>️

<< While emitting sounds, the droplets oscillated as pulsing stars whose points moved radially in and out. (..) this vapor-layer frequency matched the period of the beats, and (AA) therefore concluded that vapor escaping from beneath the droplet was responsible for producing the periodic sounds. >>️

<< the frequency of the sounds made by a droplet depended on the droplet’s size—following the model of an organ pipe, whose tone depends on the velocity of sound and the length of the pipe. This implies that the sound production mechanism in a Leidenfrost droplet is similar to that of a wind instrument. >>

️

Erika K. Carlson. The Sounds of Levitating Water Droplets. Physics 13, s148. Nov 19, 2020.

https://physics.aps.org/articles/v13/s148

Tanu Singla,  Marco Rivera. Sounds of Leidenfrost drops. Phys. Rev. Fluids 5, 113604. doi: 10.1103/ PhysRevFluids.5.113604. Nov 19, 2020.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.5.113604

img     https://physics.aps.org/assets/73455c27-7d24-443b-a685-de931db74e09/e148_1.png

# evol: ancient photosynthesis could be as old as life itself

<< the earliest bacteria had the tools to perform a crucial step in photosynthesis,  (..) The finding also challenges expectations for how life might have evolved on other planets. >>️

<< Photosystem II show patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve >> Tanai Cardona.️

<< enzymes capable of performing the key process in oxygenic photosynthesis -- splitting water into hydrogen and oxygen -- could actually have been present in some of the earliest bacteria. The earliest evidence for life on Earth is over 3.4 billion years old and some studies have suggested that the earliest life could well be older than 4.0 billion years old.  Like the evolution of the eye, the first version of oxygenic photosynthesis may have been very simple and inefficient; as the earliest eyes sensed only light, the earliest photosynthesis may have been very inefficient and slow. (..) that oxygen production was present at all so early on means in other environments, such as on other planets, the transition to complex life could have taken much less time. >>️

Photosynthesis could be as old as life itself. Imperial College London. Mar 24, 2021. 

https://www.sciencedaily.com/releases/2021/03/210324142839.htm

Thomas Olivera, Patricia Sanchez-Baracaldo, et al. Time-resolved comparative molecular evolution of oxygenic photosynthesis.Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2021; 1862 (6): 148400. doi: 10.1016/ j.bbabio.2021.148400. Jun 1,  2021.

https://www.sciencedirect.com/science/article/pii/S0005272821000335

Also

Lewis M. Ward, Patrick M. Shih. Granick revisited: Synthesizing evolutionary and ecological evidence for the late origin of bacteriochlorophyll via ghost  lineages and horizontal gene transfer. PLoS ONE 16(1): e0239248. doi:10.1371/journal.pone.0239248. 

Jan 28, 2021. 

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0239248

# life: the 'built-in float' of an ancient marine predator

<< About 240 million years ago, when reptiles ruled the ocean, a small lizard-like predator floated near the bottom of the edges in shallow water, picking off prey with fang-like teeth. >>

<< Our analysis of two well-preserved skeletons reveals a reptile with a broad, pachyostotic body (denser boned) and a very short, flattened tail. A long tail can be used to flick through the water, generating thrust, but the new species we've identified was probably better suited to hanging out near the bottom in shallow sea, using its short, flattened tail for balance, like an underwater float, allowing it to preserve energy while searching for prey, >> Qing-Hua Shang.

<< Perhaps this small, slow-swimming marine reptile had to be vigilante for large predators as it floated in the shallows, as well as being a predator itself, >> Xiao-Chun Wu.

Taylor & Francis. Ancient marine predator had a built-in float. Oct 28, 2020. 

https://phys.org/news/2020-10-ancient-marine-predator-built-in.html

Qing-Hua Shang, Xiao-Chun Wu, Chun Li. A New Ladinian Nothosauroid (Sauropterygia) from Fuyuan, Yunnan Province, China. Journal of Vertebrate Paleontology. doi: 10.1080/ 02724634.2020.1789651. Oct 29, 2020.

https://www.tandfonline.com/doi/10.1080/02724634.2020.1789651  

# life: exchange of nomadic music in the sea, male fin whales swap songs

<< Until now, scientists believed the male fin whale sings just one song pattern, which is unique to the males in his particular group—but new research has blown this theory out of the water. This study, (..) suggests that these endangered deep-sea giants actually sing multiple different songs, which may spread to different parts of the ocean through migrating individuals. >>

Male fin whales surprise scientists by swapping songs. Frontiers. Oct 29, 2020. 

https://phys.org/news/2020-10-male-fin-whales-scientists-swapping.html  

Tyler A. Helble, Regina A. Guazzo, et al.  Fin Whale Song Patterns Shift Over Time in the Central North Pacific. Front. Mar. Sci. doi: 10.3389/ fmars.2020.587110. Oct 29, 2020. 

https://www.frontiersin.org/articles/10.3389/fmars.2020.587110/full    

# astro: the turbulent history of Ryugu

<< The asteroid Ryugu may look like a solid piece of rock, but it's more accurate to liken it to an orbiting pile of rubble. >>

<< Ryugu is considered a C-type, or carbonaceous, asteroid, meaning it's primarily composed of rock that contains a lot of carbon and water (..) As expected, most of the surface boulders are also C-type; however, there are a large number of S-type, or siliceous, rocks as well. These are silicate-rich, lack water-rich minerals and are more often found in the inner, rather than outer, solar system. Given the presence of S- as well as C-type rocks on Ryugu, researchers are led to believe the little rubble-pile asteroid likely formed from the collision between a small S-type asteroid and Ryugu's larger C-type parent asteroid.  If the nature of this collision had been the other way around, the ratio of C- to S-type material in Ryugu would also be reversed. >>

Rock types on Ryugu provide clues to the asteroid's turbulent history. University of Tokyo. Sep 21, 2020. 

https://phys.org/news/2020-09-ryugu-clues-asteroid-turbulent-history.html

Tatsumi E., Sugimoto C., et al. Collisional history of Ryugu’s parent body from bright surface boulders. Nat Astron. doi: 10.1038/ s41550-020-1179-z. Sep 21, 2020.

https://www.nature.com/articles/s41550-020-1179-z   

Also

How small particles could reshape an asteroid. FonT. Sep 26, 2020.

https://flashontrack.blogspot.com/2020/09/gst-how-small-particles-could-reshape.html