# gst: elastomers fail from the edge.

<< The performance of soft devices is limited by the fracture resistance of elastomers. (..) A key observation is that thicker elastomers can be significantly tougher than thinner ones. (AA) show that this surprising toughness enhancement in thick samples emerges from the 3D geometry of the fracture process. In contrast to the classical picture of a 2D crack, failure is driven by the growth of two separate “edge” cracks that nucleate early on at a sample’s sides. As loading is increased, these cracks propagate in towards the sample midplane. When they merge, samples reach their ultimate failure strength. In thicker samples, edge cracks need to propagate farther before meeting, resulting in increased sample toughness. (AA) demonstrate that edge-crack growth is controlled by the elastomer’s strain-stiffening properties. >>

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Nan Xue, Rong Long, Eric R. Dufresne, Robert W. Style. Elastomers Fail from the Edge. Phys. Rev. X 14, 011054. March 22, 2024. 

https://journals.aps.org/prx/abstract/10.1103/PhysRevX.14.011054

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

Keywords: gst, elastic, crack, elastomers, fracture

# evol: emergence of single vs. multi-state allostery

      FIG. 1. The elastic network model

<< Allostery, the change of activity of a  macromolecule in response to a perturbation at a distance from its active site, is thought to be a ubiquitous feature of proteins. Initially described in the context of multimeric proteins, it is now understood to underlie the regulation of proteins with diverse structural architectures, from receptors to signaling proteins and metabolic enzymes. >>️

<< Here, (AA) analyze a simplified model of protein allostery under a range of physical and evolutionary constraints. (They) find that a continuum of mechanisms between two archetypes emerges through evolution. In one limit, a single-state mechanism exists where ligand binding induces a displacement along a single normal mode, and in the other limit, a multi-state mechanism exists where ligand binding induces a switch across an energy barrier to a different stable state. Importantly, whenever the two mechanisms are possible, the multi-state mechanism confers a stronger allosteric effect and thus a selective advantage. >>

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Eric Rouviere, Rama Ranganathan, Olivier Rivoire. Emergence of Single- versus Multi-State Allostery. PRX Life 1, 023004. Nov 9, 2023.

https://journals.aps.org/prxlife/abstract/10.1103/PRXLife.1.023004

Also: allostery in FonT https://flashontrack.blogspot.com/search?q=allostery

Also: allosterico in Notes 

(quasi-stochastic poetry)

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

Keywords: gst, allostery, elastic, evolution

# brain: the hypothesis of the genetic link between present moment attention and subjective wellbeing.

<< Considerable evidence supports the role of present-moment attention, a central feature of mindfulness, in subjective wellbeing maintenance and enhancement. >>️

<< Consistent with the “generalist genes hypothesis” and prior evidence, (AA) hypothesized that presence and subjective wellbeing would show a substantial genetic correlation and smaller environmental correlation. >>️

<< This study provides the first evidence known to us showing that present-centered attention, a primary component of mindfulness, has both genetic and environmental overlap with subjective wellbeing. >>️

Kirk Warren Brown, Fazil Aliev, et al. A multivariate twin study of the genetic association between present moment attention and subjective wellbeing. Sci Rep 13, 17456 (2023). doi: 10.1038/ s41598-023-42810-x.

https://www.nature.com/articles/s41598-023-42810-x 

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

Keywords: present moment attention, mindfulness, subjective wellbeing, generalist genes hypothesis. 

# astro: black hole portraits will become more frequent

<< This year marks the fifth anniversary of the release of the first-ever image of a black hole, which revealed the glowing doughnut of the supermassive black hole called M87*. The research team that produced the image—the Event Horizon Telescope (EHT) Collaboration—recently released a second image of that same black hole, which lies 55 million light years from Earth (..). This image comes from an updated version of the EHT and confirms key features of the black hole while also revealing changes over time in the pattern of light emanating from the disk surrounding the object. Starting with this release, the collaboration expects to issue increasingly frequent updates in support of the newly developing field of black hole imaging. >>️

<< “Producing the first image of M87* was a herculean effort and involved creating, testing, and verifying many different schemes and approaches to analyzing and interpreting the data,” says Princeton University astrophysicist Andrew Chael, a member of the EHT Collaboration. “Now we are beginning to transition to a point where we understand our instrument and our analysis frameworks really well, so I think we are going to be releasing results a lot more quickly.” >>

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Katherine Wright. Black Hole Portraits Will Become More Frequent. Physics 17, 43. Mar 15, 2024. 

https://physics.aps.org/articles/v17/43

Kazunori Akiyama, Antxon Alberdi, et al. The persistent shadow of the supermassive black hole of M 87. 

I. Observations, calibration, imaging, and analysis⋆ The Event Horizon Telescope Collaboration. Astron. Astrophys. 681, A79 (2024).

https://www.aanda.org/articles/aa/full_html/2024/01/aa47932-23/aa47932-23.html

Also: astrophysics, black hole, in https://www.inkgmr.net/kwrds.html 

Keywords: astrophysics, black hole

# gst: rearrangements of a jammed 2-D emulsion (during slow compression).

<< As amorphous materials get jammed, both geometric and dynamic heterogeneity are observed. (AA)  investigate the correlation between the local geometric heterogeneity and local rearrangements in a slowly compressed bidisperse quasi-two-dimensional emulsion system. The compression is driven by evaporation of the continuous phase. >>

<< droplets in heterogeneous local regions are more likely to have local rearrangements. These rearrangements are generally T1 events where two droplets converge toward a void, and two droplets move away from the void to make room for the converging droplets. Thus, the presence of the voids tends to orient the T1 events. >>️

<< The presence of a correlation between the structural quantities and the rearrangement dynamics remains qualitatively unchanged over the entire range of packing fractions observed. >>️

Xin Du, Eric R. Weeks. Rearrangements during slow compression of a jammed  two-dimensional emulsion. Phys. Rev. E 109, 034605. Mar 20,  2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.034605

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

Keywords: drops, droplets, droploids 

# brain: apropos of wars ... VR plus tDCS to reduce symptoms of posttraumatic stress disorder (PTSD) (in military veterans).

<< Key Points. Question. Can therapeutic exposure using virtual reality (VR) be augmented with simultaneously applied transcranial direct current stimulation (tDCS) to reduce symptoms of posttraumatic stress disorder (PTSD)? >>

<< Meaning. These findings suggest that the use of combined VR exposure plus tDCS could be a promising treatment for warzone-related PTSD. >>️️

Mascha van’t Wout-Frank, Amanda R. Arulpragasam, et al. Virtual Reality and Transcranial Direct Current Stimulation for Posttraumatic Stress Disorder. A Randomized Clinical Trial. JAMA Psychiatry. doi: 10.1001/jamapsychiatry.2023.5661. Mar 6, 2024.

https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2815835

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

Keywords: life, war, brain, VR, tDCS, PTSD, veterans

# gst: near the Hopf boundary, Intermittency and chimera states.

AA << study collective dynamics of networks of mutually coupled identical Lorenz oscillators near a subcritical Hopf bifurcation. Such systems exhibit induced multistable behavior with interesting spatiotemporal dynamics including synchronization, desynchronization, and chimera states. >>️

<< For analysis, (AA) first consider a ring topology with nearest-neighbor coupling and find that the system may exhibit intermittent behavior due to the complex basin structures and dynamical frustration, where temporal dynamics of the oscillators in the ensemble switches between different attractors. Consequently, different oscillators may show a dynamics that is intermittently synchronized (or desynchronized), giving rise to intermittent chimera states. The behavior of the intermittent laminar phases is characterized by the characteristic time spent in the synchronization manifold, which decays as a power law. >>

<< Such intermittent dynamics is quite general and is also observed in an ensemble of a large number of oscillators arranged in variety of network topologies including nonlocal, scale-free, random, and small-world networks. >>️

Anjuman Ara Khatun, Yusra Ahmed Muthanna, et al. Collective dynamics of coupled Lorenz oscillators near the Hopf boundary: Intermittency and chimera states. Phys. Rev. E 109, 034208. March 15, 2024.

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.109.034208

Also: transition, intermittency, chaos, chimera, network, in https://www.inkgmr.net/kwrds.html

Keywords: gst, transition, intermittency, chaos, chimera, network