Twisting a monolayer and a bilayer sheet of graphene into a three-layer structure leads to new quantum mechanical states. — ScienceDaily

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Since the discovery of graphene more than 15 years ago, researchers have been in a global race to unlock its unique properties. Not only is graphene — a one-atom-thick sheet of carbon arranged in a hexagonal lattice — the strongest, thinnest material known to man, it is also an excellent conductor of heat and electricity.

Now, a team of researchers at Columbia University and the University of Washington has discovered that a variety of exotic electronic states, including a rare form of magnetism, can arise in a three-layer graphene structure.

The findings appear in an article published Oct. 12 in Nature Physics.

The work was inspired by recent studies of twisted monolayers or twisted bilayers of graphene, comprising either two or four total sheets. These materials were found to host an array of unusual electronic states driven by strong interactions between electrons.

“We wondered what would happen if we combined graphene monolayers and bilayers into a twisted three-layer system,” said Cory Dean, a professor of physics at Columbia University and one of the paper’s senior authors. “We found that varying the number of graphene layers endows these composite materials with some exciting new properties that had not been seen before.”

In addition to Dean, Assistant Professor Matthew Yankowitz and Professor Xiaodong Xu, both in the departments of physics and materials science and engineering at University of Washington, are senior authors on the work. Columbia graduate student Shaowen Chen, and University of Washington graduate student Minhao He are the paper’s co-lead authors.

To conduct their experiment, the researchers stacked a monolayer sheet of graphene onto a bilayer sheet and twisted them by about 1 degree. At temperatures a few degrees over absolute zero, the team observed an array of insulating states — which do not conduct electricity — driven by

Nano-scientists develop a molecular tool to change the structure of a metal surface — ScienceDaily

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The surface of metals plays a key role in many technologically relevant areas, such as catalysis, sensor technology and battery research. For example, the large-scale production of many chemical compounds takes place on metal surfaces, whose atomic structure determines if and how molecules react with one another. At the same time, the surface structure of a metal influences its electronic properties. This is particularly important for the efficiency of electronic components in batteries. Researchers worldwide are therefore working intensively on developing new kinds of methods to tailor the structure of metal surfaces at the atomic level.

A team of researchers at the University of Münster, consisting of physicists and chemists and led by Dr. Saeed Amirjalayer, has now developed a molecular tool which makes it possible, at the atomic level, to change the structure of a metal surface. Using computer simulations, it was possible to predict that the restructuring of the surface by individual molecules — so-called N-heterocyclic carbenes — takes place similar to a zipper. During the process, at least two carbene molecules cooperate to rearrange the structure of the surface atom by atom. The researchers could experimentally confirm, as part of the study, this “zipper-type” mechanism in which the carbene molecules work together on the gold surface to join two rows of gold atoms into one row. The results of the work have been published in the journal Angewandte Chemie International Edition.

In earlier studies the researchers from Münster had shown the high stability and mobility of carbene molecules at the gold surface. However, no specific change of the surface structure induced by the molecules could previously be demonstrated. In their latest study, the researchers proved for the first time that the structure of a gold surface is modified very precisely as a result of cooperation between

NASA imagery reveals Tropical Storm Chan-hom’s skewed structure

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NASA imagery reveals Tropical Storm Chan-hom's skewed structure
On Oct. 5, 2020, NASA’s Terra satellite provided a visible image of Tropical Storm Chan-hom several hundred miles northwest of Guam (lower right). Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

NASA’s Terra satellite obtained visible imagery of Tropical Storm Chan-hom as it continued moving though the Northwestern Pacific Ocean. The imagery revealed that the center of circulation was exposed and its strongest storms were south of the center.


Tropical Depression 16W formed on Oct. 4 and strengthened into a tropical storm on Oct 5. Once it reached tropical storm strength, it was re-named Chan-hom. Laos submitted the name Chan-hom to the World Meteorological Organization list. The name is a type of tree in Laos.

NASA satellite view: Chan-hom’s organization

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Terra satellite captured a visible image of Tropical Storm Chan-hom on Oct. 5 that showed a couple of things were occurring in the storm. First, bands of thunderstorms were wrapping into a partially exposed low-level circulation center. Second, there was building convection and thunderstorms occurring over the southern quadrant of the storm, giving it an appearance of a backwards letter “C” on satellite imagery. The storm is expected to strengthen over the next three days and when it does, it will likely develop a more circular shape.

The satellite imagery was created using NASA’s Worldview product at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Chan-hom’s status on Oct. 5

At 11 a.m. EDT (1500 UTC) on Oct. 5, Chan-hom was centered near latitude 23.0 degrees north and longitude 139.2 degrees east. That is about 738 miles south of Yokosuka, Japan. Chan-hom is moving north and has maximum sustained winds of 35 knots (40 mph/64 kph).

Chan-hom’s forecast

The Joint Typhoon Warning Center noted, “Chan-hom

Conserved meaning despite different structure over the years

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Woodpeckers' drumming: Conserved meaning despite different structure over the years
Great spotted woodpecker during the field experiment. Credit: Alain Blanc, ENES team

Animal acoustic signals are amazingly diverse. Researchers from the University of Zurich and the University of Saint-Etienne, together with French, American and Dutch collaborators, explored the function and diversification of animal acoustic signals and the mechanisms underlying the evolution of animal communication systems.


To this end, they used Shannon and Weaver’s “Mathematical Theory of Communication,” originally applied to telecommunications in 1949, which has transformed the scientific understanding of animal communication. This theory allows the amount of information in a signal to be quantified. The researchers were the first to use this framework within an evolutionary perspective to explore the biological information encoded in an animal signal.

How drumming structure evolves over time

In deciding which biological model to choose, the researchers selected the woodpeckers’ drumming as their ideal candidate. This bird family is known for rapidly striking their beaks on tree trunks to communicate. The team combined acoustic analyses of drumming from 92 species of woodpeckers, together with theoretic calculations, evolutionary reconstructions, investigations at the level of ecological communities as well as playback experiments in the field.

“We wanted to test whether drumming has evolved to enhance species-specific biological information, thereby promoting species recognition,” says lead author Maxime Garcia of the UZH Department of Evolutionary Biology and Environmental Studies.

Woodpeckers' drumming: Conserved meaning despite different structure over the years
The researcher performing an acoustic playback experiment on a great spotted woodpecker. The loudspeaker is attached on a branch. Credit: Alain Blanc , ENES team

Constant amount of information for 22 million years

Results demonstrate the emergence of new drumming types during woodpeckers evolution. Yet, despite these changes in drumming structure, the amount of biological information about species identity has remained relatively constant for 22 million years. Selection toward increased biological information thus does not seem to represent a

SEC Issues Agenda for Oct. 5 Meeting of the Fixed Income Market Structure Advisory Committee

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[DATELINE]The Securities and Exchange Commission today released the agenda for the Oct. 5 meeting of the Fixed Income Market Structure Advisory Committee (FIMSAC). The meeting will focus on discussions regarding recent market volatility and the impact of COVID-19 on the corporate bond market, the bond fund and ETF market, the technology and e-trading market, and the municipal securities market. The committee will also consider a recommendation concerning the definition of electronic trading for regulatory purposes, and the meeting will include member observations of the fixed income markets and the Committee’s work. The Commission established the FIMSAC to provide advice and recommendations on fixed income market structure issues.

The meeting will be held by remote means and will be open to the public via webcast on the SEC’s website at www.sec.gov.

Members of the public who wish to provide their views on the matters to be considered by the FIMSAC may submit comments either electronically or on paper, as described below. Please submit comments using one method only. At this time, electronic statements are preferred. Information that is submitted will become part of the public record of the meeting.

Electronic submissions:

Use the SEC’s Internet submission form or send an email to [email protected]

Paper submissions:

Send paper submissions in triplicate to Secretary, Securities and Exchange Commission, 100 F Street, N.E., Washington, D.C. 20549-1090.

All submissions should refer to File Number 265-30, and the file number should be included on the subject line if email is used.

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SEC Fixed Income Market Structure Advisory Committee

Agenda

Oct. 5, 2020

9:30 a.m. Welcome and Opening Remarks

9:45 a.m. Recommendation Regarding Defining Electronic Trading

10:15 a.m. Corporate Bond Market Observations and Lessons Learned

11:30 a.m. Municipal Securities Market Observations and Lessons Learned

12:45 p.m. Lunch Break

1:30 p.m. Bond Fund and ETF Market Observations