compiled | Feng Weiwei
Science , 19 March 2021 Vol 371, Issue 6535
"scientific" 2021 Nian 3 Yue 19 Ri , Vol. 371 6535 Physics
Physics
Generating arbitrary topological windings of a non-Hermitian band open topology
▲ author: Kai Wang, Avik Dutt, Ki Youl Yang, Casey C. Wojcik, Jelena Vučković, Shanhui Fan
▲ link:
https://science.sciencemag.org/content/371/6535/1240
▲ summary
The topology of the control system provides a route to develop robust devices that are resistant to defects.Although the early development of topological zone theory focused on Hermitian (closed) systems, recent efforts have shifted to non-Hermitian (open) systems.
The author reports the measurement and control of topological non-trivial windings of non-Hermitian bands. By realizing the non-Hermitian lattice Hamiltonian in the frequency synthesis dimension composed of optical frequency modes in the modulated ring resonator, they directly visualized the non-trivial topology with windings and proved that the windings can be controlled. .
This kind of control provides a way for the experimental synthesis, characterization and control of topological non-trivial phases in open physical systems.
▲ Abstract
Controlling the topology of a system provides a route to develop devices that are focused on robust systems, which are focused on recent defects of recent developments of Hermitian band efforts have been toward non-Hermitian (open) systems. K. Wang et al. report on the measurement and control of topologically nontrivial windings of a non-Hermitian energy band. By implementing non-Hermitian lattice Hamiltonians along a frequency synthetic dimension formed by optical frequency modes in a modulated ring-resonator, they directly visualized the nontrivial topological band winding and showed that the winding can be controlled. Such control provides a route for the experimental synthesis, characterization, and control of topologically nontrivial phases in open physical systems.
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Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening
adjusting twisted bilayer graphene electron correlation
▲ author: Xiaoxue Liu, Zhi Wang, K. Watanabe, T. Taniguchi, Oskar Vafek, JIA Li
▲ link:
https: // science. sciencemag.org/content/371/6535/1261
▲ Abstract
superconductivity should be explained in twisted bilayer graphene (span4span) It proved to be tricky.In order to study the role of electron-electron correlation in this state, the author placed another layer of graphene bilayer near the MATBG sample, which uses the traditional arrangement of graphene sheets.
By changing the carrier density in the traditional double-layer membrane, the researchers controlled the interaction strength in MATBG. Weakening the interaction will enhance the superconductivity, which is consistent with the situation where electron-phonon coupling competes with Coulomb interaction to stabilize the superconducting phase.
▲ Abstract
Elucidating the nature of the superconducting state in magic-angle twisted Tolayer study the role of the electron-tricked electron (MATB) proven in the role of proven-angle twisted biGlayer (MATBG). Liu et al. placed another graphene bilayer, this one having a conventional arrangement of the graphene sheets, in the immediate vicinity of a sample of MATBG. By varying the carrier density in the conventional bilayer, the researchers controlled the strength of interactions in MATBG. Weakening the interactions strengthened superconductivity, consistent with scenarios in which the electron-phonon coupling competes against Coulomb interactions to stabilize the superconducting phase.
Chemistry Chemistry Chemistry Chemistry
Detection of identifying two interstellar polycyclic aromatic hydrocarbons via spectral matched filtering
interstellar PAHs of
▲ Author: Brett A. McGuire, Ryan A. Loomis, Anthony J. Remijan, Michael C. McCarthy. Etc.
▲ Link: _span4 strong science span1. /content/371/6535/1265
▲ Abstract
Mid-infrared spectroscopy analysis shows that,Polycyclic aromatic hydrocarbons (PAHs) are abundant in many celestial bodies, but this technology cannot determine the specific polycyclic aromatic hydrocarbon molecules. If the molecules are abundant enough and the dipole moment is large, radio astronomy can provide individual identification, but PAHs are expected to produce a large number of very weak lines.
The author performed a superposition and matching filter analysis on TMC-1 located in the Taurus interstellar molecular cloud, looking for PAHs in radio observations. They identified two isomers of the small polycyclic aromatic hydrocarbon cyanonaphthalene, and two benzene rings connected to the CN group.
▲ Abstract
Midinfrared spectroscopy has shown that this polycyclic aromatic hydrocarbons are abundant in PAHastronomy cannot determine the specific objects, which could provide specific objects, but this polycyclic aromatic hydrocarbons are abundant in PAHs individual identifications if the molecule is sufficiently abundant and has a large dipole moment, but PAHs are expected to produce large numbers of very weak lines. McGuire et al. performed a stacking and matched filter analysis to search for PAHs in radio observations of TMC-1 , located within the interstellar Taurus Molecular Cloud. They identified emission from two isomers of the small PAH cyanonapthalene, two fused benzene rings with a CN group attached.
_p1span strong InOspan2 Inspan2 catalyst for coupling of propane dehydrogenation to selective H2 combustion
overcome propylene oxide
▲ Author: Huan Yan, Kun He, Izabela A. Samek, Dian Jing, Macy G. Nanda, Peter C. Stair, Justin M. Notestein
▲ Link:
535/1.
▲ Abstract
The selectivity of propane oxidative dehydrogenation of propylene decreases with the increase of water conversion rate.Because propylene itself is more easily oxidized than propane.
The author created a nanometer by growing a selective hydrogen combustion catalyst indium oxide (a shell of about 2 nanometers) on a propane dehydrogenation catalyst, and supporting platinum nanoparticles on alumina balls. Stage series catalyst. This coating exposes platinum nanoparticles for propane dehydrogenation.
At the indium oxide-platinum interface, the surface hydrogen atoms are oxidized. This method increases the output of propylene to 30%.
▲ Abstract
Catalysts for the oxidative dehydrogenation of propane to propylene and become less oxidized selective with increased conversion of propane to propylene and become less oxidized than the propylene and become less oxidized selective with increasing conversion et al. catalysts by growing an ∼2-nanometer shell of indium oxide, a selective hydrogen combustion catalyst, over a propane dehydrogenation catalyst, platinum nanoparticles supported on alumina spheres. This overcoat exposed the platinum nanoparticles for propane dehydrogenation. Surface hydrogen atoms were oxidized at the indium oxide–platinum interface. This approach boosted yields of propylene to up to 30%.
Earth sciences Earth sciences br1span span span _strong5 span4
Record-breaking aerosol levels explained by span Record-breaking aerosol levels explained by smoke span injection into the stratosphere
span _span 4 author: Eitan Hirsch, Ilan Koren
▲ link:
https://science.sciencemag.org/content/371/6535/1269
▲ Abstract
2020,Australia's large-scale forest fires emitted a large amount of smoke into the stratosphere. Hirsch and Kellen discovered that this smog caused record-breaking levels of suspended particles in the southern hemisphere, comparable to a moderate volcanic eruption.
The reason for this severity is the intensity of the fire and the shallow tropopause and mid-latitude cyclone belt at its latitude. This increase in aerosols has led to a significant cooling in cloudless areas of the ocean.
▲ Abstract
Intense, widespread bushfires in Southern Australia caused huge amounts of smoke into the stratosphere and Kosol found over this recorded over this a huge amount of smoke in Australia. Hemisphere, as much as that from a moderate volcanic eruption. The severity was caused by a combination of the vigor of the fires and their location at a latitude with a shallow tropopause and within the midlatitude cyclones belt. This aerosol increase caused considerable cooling over oceanic cloud-free areas.
Manta-like planktivorous sharks in Late Cretaceous oceans
pelagic shark feeding habits of the age of dinosaurs _p 7p
▲ Author: Romain Vullo, Eberhard Frey, Christina Ifrim, Margarito A. González González, Eva S. Stinnesbeck, Wolfgang Stinnesbeck
▲ link:
https ://science.sciencemag.org/content/371/6535/1253
▲ Abstract
But there is very little morphological diversity, and most of them are streamlined predators. The author describes a new species of shark from the Late Cretaceous, which shows that the current lack of variation is not due to limited morphological "exploration" in the past.
Specifically, this shark (Aquilolamna milarcae) shows many characteristics similar to modern manta rays, especially the elongated fins and the mouth that seems suitable for filter feeding, which indicates that it is based on plankton. food.
This discovery indicates that the plagiobranchians have tried other forms of animals in the evolutionary process. It also shows that the "flyers" that feed on plankton appear more often in this group. What I knew before was at least 30 million years earlier.
▲ Abstract
Modern sharks occupy marine ecosystems across the world but display little morphological diversity from the world but display little morphological predace alarks that mostly describe the new Credace from the world. shows that the lack of current variation is not due to limited morphological “exploration” in the past. Specifically, Aquilolamna milarcae displays many features similar to modern manta rays, notably long, slender fins and a mouth seemingly adapted to filter feeding, suggesting that it was planktivorous. This finding indicates both that elasmobranchs evolutionarily experimented with other forms and that the planktivorous “soarers” emerged in this group at least 30 million years earlier than previously recognized.
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