# 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   

# 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  

# gst: density fluctuations may exist in an amorphous matrix

<< Silicon does not have to be crystalline, but can also be produced as an amorphous thin film. In such amorphous films, the atomic structure is disordered like in a liquid or glass. If additional hydrogen is incorporated during the production of these thin layers, so-called a-Si:H layers are formed. >>

<< With this study, we show that the a-Si:H is by no means a homogeneously amorphous material. The amorphous matrix is interspersed with nanometre-sized areas of varying local density, from cavities to areas of extremely high order, >> Klaus Lips

<< We find a nanoscopic order in the disorder of the a-Si:H layers by X-ray scattering measurements (..) We were then able to determine the distribution of the hydrogen atoms in the amorphous network by neutron scattering (..) We were able to discover nanometer-sized voids, which are created by slightly more than 10 missing atoms. These voids arrange themselves into clusters with a recurrent distance of about 1.6 nanometres to each other, >> Eike Gericke

Density fluctuations in amorphous silicon discovered. Helmholtz Association of German Research Centres. Oct 29, 2020. 

https://phys.org/news/2020-10-density-fluctuations-amorphous-silicon.html

Eike Gericke, Jimmy Melskens, et al. Quantification of Nanoscale Density Fluctuations in Hydrogenated Amorphous Silicon. Phys. Rev. Lett. 125, 185501. Oct 29,  2020. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.185501

# 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    

# gst: stitch together at both ends to selective formation of classes of bicyclic medium-sized ring compounds

AA << have discovered catalyst-controlled divergent reactions to synthesize three different classes of medium-sized bicyclic compounds from the same starting materials  >>

<< Intermolecular higher-order cycloaddition, in which two starting materials are 'stitched' together at both ends, provides great potential to build complex cyclic compounds from simple building blocks. Unfortunately, such transformations to prepare medium-sized rings are often plagued with competitive reaction pathways and low levels of site- and stereo-selectivity >>

<< The most significant aspect of this chemistry was that not one, but three different classes of bicyclic medium-sized ring compounds were obtained with high efficiency and stereo-selectivity from the same set of starting molecules.  >>

Divergent synthesis of bicyclic medium-sized ring structures. National University of Singapore. Oct 26, 2020.

https://phys.org/news/2020-10-divergent-synthesis-bicyclic-medium-sized.html

Li-Cheng Yang, Ya-Nong Wang, et al. Stereoselective access to [5.5.0] and [4.4.1] bicyclic compounds through Pd-catalysed divergent higher-order cycloadditions. Nat. Chem. 12, 860–868. doi: 10.1038/ s41557-020-0503-7. July 27, 2020. 

https://www.nature.com/articles/s41557-020-0503-7

# life: aprops of 1or2 achoo! from Wuhan (SARS-CoV-2), a mask build of 'nanofibers randomly land on a collector to create a sort of non-woven mesh'

<< Recently, students from BYU’s College of Engineering teamed up with Nanos Foundation to develop a nanofiber membrane that can be sandwiched between the cloth pieces in a homemade mask. While today’s typical cloth mask might block fewer than 50% of virus particles, the membrane — which can be made using simple, inexpensive materials — will be able to block 90 to 99% of particles, increasing effectiveness while preserving breathability. The membranes are made through a process called “electrospinning,” which involves dissolving a polymer plastic in a solution and then using an electrical current to move a droplet of the polymer downward through a needle. As the droplet accelerates, it stretches into a very small fiber that retains a static charge. >>

<< Those nanofibers randomly land on a collector to create a sort of non-woven mesh, >> Katie Varela.

Christie Allen. With innovative nanofiber membranes, cloth masks’  efficacy goes up to 99%. Oct 21, 2020.

https://news.byu.edu/intellect/with-new-byu-created-nanofiber-membranes-cloth-masks-efficacy-goes-up-to-99 

https://phys.org/news/2020-10-nanofiber-membranes-masks-efficacy.html   

Also

keyword 'virus' in FonT: 

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

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

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

# astro: the effect of Yarkovsky acceleration to direct the asteroid Apophis (towards us, hypothetically)

<< A University of Hawai Institute for Astronomy (IfA) astronomer has revealed critical new findings linked to a large asteroid expected to pass extremely close to Earth. Dave Tholen and collaborators have announced the detection of Yarkovsky acceleration on the near-Earth asteroid Apophis. This acceleration arises from an extremely weak force on an object due to non-uniform thermal radiation. This force is particularly important for the asteroid Apophis, as it affects the probability of an Earth impact in 2068. >>

Massive asteroid subject of new findings. Oct 26, 2020. 

https://www.hawaii.edu/news/2020/10/26/new-massive-asteroid-findings

"2068" –Massive Asteroid Apophis on Path for Earth Impact. Oct 27, 2020.

https://dailygalaxy.com/2020/10/2068-massive-asteroid-apophis-on-path-for-earth-impact

Also

il ciottolo Apophis. Notes. May 05, 2006 (quasi-stochastic poetry). 

https://inkpi.blogspot.com/2006/05/2001-il-ciottolo-apophis.html

A wicked list in the dino-killing range; waiting for new entries. FonT. Jun 29, 2017. 

https://flashontrack.blogspot.com/2017/06/s-astro-wicked-list-in-dino-killing.html

A few hints of our presence. Notes. Oct 13, 2006 (quasi-stochastic poetry)

https://inkpi.blogspot.com/2006/10/2073-few-hints-of-our-presence.html