# 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

# chem: strange transitions: tying a crystal into a knot

<< Single crystals are typically brittle, inelastic materials. Such mechanical responses limit their use in practical applications, particularly in flexible electronics and optical devices >>

AA << describe single crystals of a well-known coordination compound—copper(II) acetylacetonate—that are flexible enough to be reversibly tied into a knot >>

Anna Worthy, Arnaud Grosjean, et al. Atomic resolution of structural changes in elastic crystals of copper(II) acetylacetonate. Nature Chemistry. doi: 10.1038/nchem.2848. Aug 28, 2017

http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2848.html

<< crystals exhibit traditional characteristics of not only hard matter, but soft matter like nylon >> John McMurtrie

<< Under strain the molecules in the crystal reversibly rotate and reorganise to allow the compression and expansion required for elasticity and still maintain the integrity of the crystal structure >> Jack Clegg

Bendable crystals tie current thinking in knots. Aug 29, 2017.

https://m.phys.org/news/2017-08-bendable-crystals-current.html

# 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

# chem: it can stay squishy at the coldest temperatures

<< Normal materials become brittle in deep cryogenic conditions, but a new graphene-based foam (..) stays as flexible as ever. >>

Maria Temming. A new graphene foam stays squishy at the coldest temperatures. Apr 12, 2019.

https://www.sciencenews.org/article/new-graphene-foam-squishy-coldest-temperatures

AA << report wide temperature–invariant large-strain super-elastic behavior in three-dimensionally cross-linked graphene materials that persists even to a liquid helium temperature of 4 K, a property not previously observed for any other material. >>

Kai Zhao, Tengfei Zhang, et al. Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures. Science Advances  12 Apr 2019: Vol. 5, no. 4, eaav2589. doi: 10.1126/sciadv.aav2589

https://advances.sciencemag.org/content/5/4/eaav2589