# gst: how to create a helix from a straight rod, “twist” or “bend” approaches.

<< There are two independent ways of creating a helix from a straight rod: curl the rod into a circle and then twist the rod all along its length to convert the ring into a helix (“twist” method), or deform the rod into a sine wave and then bend it with a sinusoidal distortion that curls at right angles to the first sine wave (“bend” method). Both procedures produce the same shape, but they generate different internal stresses within the rod, and their implementations require different amounts of energy. >>️

AA << say that their experiments could serve as a model for many physical systems that undergo handedness transitions, including the tendrils of plants, the flagella of microorganisms, and the strands of DNA molecules.  >>

️

David Ehrenstein. Two Experimental Observations of Helix Reversals. Physics 16, s158. Oct 24, 2023.  

https://link.aps.org/doi/10.1103/Physics.16.s158

Paul M. Ryan, Joshua W. Shaevitz,  Charles W. Wolgemuth. Bend or Twist? What Plectonemes Reveal about the Mysterious Motility of Spiroplasma. Phys. Rev. Lett. 131, 178401. Oct 24, 2023. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.178401

Emilien Dilly, Sebastien Neukirch, Julien Derr, Drazen Zanchi. Traveling Perversion as Constant Torque Actuator. Phys. Rev. Lett. 131, 177201. Oct 24, 2023. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.177201

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

Keywords: gst, elastic, elastic deformation, swimming

# gst: multiphase transitions and existence of bistable modes; how morphoelastic donuts get their wrinkles

<< Many biological structures are toroidal, or donut shaped. These structures often contain intricate wrinkling patterns that change as the object grows or contracts. >>

<< The team found that toroidal structures with large holes typically develop surface wrinkles close to the hole, whereas ones with smaller holes tend to form them away from the hole. Additionally, soft structures often have localized dimples, while stiff ones have bidirectional stripes or a mixture of spiral and axisymmetric stripes. Lastly, moderate-stiffness structures are typically adorned with periodic hexagonal patterns or a combination of hexagonal and labyrinth-like patterns. (AA) also found that their theory can predict wrinkling patterns in some nontoroidal structures, suggesting that it could be applied to a diverse range of objects. >>

Ryan Wilkinson. How Nature’s Donuts Get Their Wrinkles. Physics 16, s5. Jan 25, 2023. 

https://physics.aps.org/articles/v16/s5

T. Wang et al. Curvature-regulated multiphase patterns in tori. Phys. Rev. Lett. 130, 048201. Jan 25, 2023.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.048201

Also

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, morphogenesis, transitions, multiphase transitions, bistability, pattern formation, elastic deformation, mechanical deformation

# gst: predict stability in a collapsing ring

<< it is possible to predict the stability of a collapsing ring by counting its kinks. (..) (AA) group describes experiments they conducted that involved placing an elastic ring over a soap film and recording what happens when the ring collapses. >>

Bob Yirka. Counting kinks in a collapsing ring to predict stability. May 20, 2020.

https://phys.org/news/2020-05-kinks-collapsing-stability.html   

Finn Box, Ousmane Kodio, et al. Dynamic Buckling of an Elastic Ring in a Soap Film. Phys. Rev. Lett. 124, 198003. 13 May 13, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.198003   

https://arxiv.org/abs/1812.11009