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MIT Researchers Say Their Fusion Reactor Is “Very Likely to Work” – Futurism

A team of researchers at MIT and other institutions say their “SPARC” compact fusion reactor should actually work — at least in theory, as they argue in a series of recently released research papers.

In a total of seven papers penned by 47 researchers from 12 institutions, the team argues that no unexpected impediments or surprises have shown up during the planning stages.

In other words, the research “confirms that the design we’re working on is very likely to work,” Martin Greenwald, deputy director of MIT’s Plasma Science and Fusion Center and project lead, told The New York Times.

Fusion power remains elusive, but the tech promises to one day become a safe and clean way of producing energy by fusing atomic nuclei together like the Sun. Despite almost a century of research, though, nobody has managed to pull it off yet.

SPARC, one of the largest privately funded project of its kind in the field, would be a first of its kind: a “burning plasma” reactor that fuses hydrogen isotopes to form helium, with no other input of energy needed.

Thanks to progress in the field of superconducting magnets, the team hopes to achieve the same performance as far larger reactors, such as the gigantic ITER (International Thermonuclear Experimental Reactor) reactor, which started assembly in July.

The magnets are used to contain the extremely hot and high pressure reactions going on inside the reactor, one of fusion’s greatest challenges.

According to the team’s calculations, SPARC should be able to produce twice as much fusion energy compared to the amount needed to generate the reaction. That would be a massive jump, since no researchers have managed to break even yet.

In fact, in the papers, the researchers note it could be theoretically possible to generate ten times the amount — though there’s plenty of work ahead before they could say that for sure.

The MIT team is hoping to construct its compact reactor over the next three to four years, with the eventual goal of generating electricity starting in 2035, the Times reports.

“What we’re trying to do is put the project on the firmest possible physics basis, so that we’re confident about how it’s going to perform, and then to provide guidance and answer questions for the engineering design as it proceeds,” Greenwald said in an official statement.

READ MORE: Compact Nuclear Fusion Reactor Is ‘Very Likely to Work,’ Studies Suggest [The New York Times]


More on fusion: Scientists Start Construction of World’s Largest Fusion Reactor

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beneath Researchers

Deep beneath the high seas, researchers find rich coral oases – Science Magazine

Corals on the Debussy Seamount, a submerged peak more than 2000 meters below the surface in the North Pacific Ocean

© NOAA Office of Ocean Exploration and Research

By Ian Morse

Aiming to bolster conservation on the high seas, a team of marine researchers today released the first comprehensive survey of coral reefs in the high seas–the roughly two-thirds of the ocean outside of national jurisdictions.

After combing through more than half a million observations of reef-building corals, the team identified 116 reefs located in the high seas. Most of these corals live between 200 and 1200 meters beneath the surface, the researchers found. But a handful are found more than 2 kilometers deep. And there are likely many more high seas corals still to be found, the authors note, as surveys have typically prioritized corals close to shore. 

The study coincides with the launch of the Coral Reefs on the High Seas Coalition, a group of scientists and nonprofits that aims to support research cruises to survey the steep, deep-water slopes where many of the reefs sit. Eventually, the coalition hopes the data will help persuade policymakers to give these poorly understood ecosystems greater protection in global agreements currently under negotiation.

“Some of the first marine protected areas were specifically designed around coral reefs. … So much literature suggests these are the rainforests of the seas,” says co-author Daniel Wagner, the coalition’s coordinator and an ocean technical adviser at Conservation International. The coalition of nonprofits hopes to influence implementation of a United Nations pact, the Intergovernmental Conference on Marine Biodiversity of Areas Beyond National Jurisdiction, which is expected to set rules for establishing marine preserves on the high seas. (A final meeting of the negotiators set for earlier this year was postponed because of the COVID-19 pandemic.)

The deep reefs “are some of the most under surveyed of all ocean ecosystems,” the coalition notes, “and because they are not protected by the laws of any country, they are among the most vulnerable and potentially overexploited reefs on Earth.”

The study suggests scientists have much more to learn about corals beyond the coasts. All records of high seas corals were scleractinian, a common family of hard, reef-building coral, and a few were observed much deeper than where they are typically found. Most reefs were found on seamounts, escarpments, and submarine ridges in the Pacific and Atlantic oceans, with a small minority in the Indian Ocean.

The study also draws attention to a need to coordinate protections from human activities in the ocean. It found that just one-fifth of the known deep-sea reefs are protected from bottom fishing, for example, and none is protected from various impacts of shipping. One known reef already exists in an area protected by the seabed mining regulator International Seabed Authority, and two are near active mining exploration contracts.

Expedition challenges

The coalition has been racing to gather more information on high seas reefs, but pandemic restrictions delayed its first two expeditions until early 2022. The first expedition was scheduled to set sail later this year for seamounts near Rapa Nui, or Easter Island, off the coast of Chile. The seamounts fall within Chile’s national waters, and are already included in a national marine reserve. But expedition leader Richard Pyle, an ichthyologist at the Bishop Museum known for his work on dimly lit mesophotic reefs, expects the conditions to be representative of high seas coral reefs, and the marine reserve may support a legal argument for protection.

A second expedition will explore a number of slopes along the Salas y Gómez, Nazca, and Juan Fernández ridges off Chile. Cruise leader Tina Molodtsova, a senior scientist at the P. P. Shirshov Institute of Oceanology, says the undersea world there is “very particular in terms of biogeography.” Two decades ago, an expedition to the area documented creatures that haven’t been found anywhere else. She expects “to see what they call deep-sea ‘coral gardens,’” which include spindly bamboo corals and glass sponges, which have glasslike structural spicules made of silica.

High seas expeditions don’t come cheap, costing more than $1 million each. So, for the moment, the coalition has set a more modest goal of raising $3 million for pilot surveys of a few targets over the next few years and funding films to screen to policymakers. The immediate goal, Wagner says, is just to gather “kind of a snapshot. We’re trying to get there, and then present that information quickly to policymakers.”

For Pyle, one goal of such expeditions is to document seamount ecosystems before human activities push them “past the point of no recovery, before we even knew what they were, what they meant, and what role they play in the larger picture.”

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Researchers Skeptical Of Russia’s Claim To Have COVID-19 Vaccine | NBC News NOW – NBC News


Researchers Skeptical Of Russia’s Claim To Have COVID-19 Vaccine | NBC News NOW – YouTube
































































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Researchers Study

Duke researchers say mask study wasn’t meant to disparage neck gaiters – WRAL.com

By Adam Owens, WRAL anchor/reporter

Durham, N.C. — Duke University research that showed how poorly some face coverings perform wasn’t exactly the intent of the study, researchers said Wednesday.

The study that WRAL News first reported last week showed neck gaiters do a better job at spreading the coronavirus than containing it, a detail that has since gotten nationwide media attention.

But Martin Fischer, an associate research professor in Duke’s chemistry department who participated in the study, said the research was geared toward demonstrating a way to study the effectiveness of masks and other face coverings.

Researchers used a laser in a box and a camera to record respiratory particles that might escape from different masks.

“It is amazing to see how many particles come out of your mouth when you speak,” Fischer said.

A fitted N95 mask performed the best, but according to the researchers, a neck gaiter used in the test did the worst – appearing to break droplets into smaller particles that then escaped into the air.

“Not all … neck gaiters are bad. There are plenty good ones out there,” Fischer said. “It depends so much on the material, on how many layers you wear.”

The Clark brothers say theirs would have performed better in the Duke tests.

“Not all neck gaiters are the same,” 14-year-old Dylan Clark said. “There are a ton of neck gaiter masks out there, and just because they tested one, it doesn’t apply to all of them.”

He and his 16-year-old brother, Connor, have their own company, CopperSafe, that has sold tens of thousands of gaiters.

“We have seen so many customers reordering masks – individuals and companies,” Dylan Clark said.

Fischer said the study wasn’t meant to rate different coverings, adding that he believes wearing a face covering is an important way to limit the spread of the virus.

“Just because we had one bad mask does not diss all the other masks,” he said. “We don’t have the resources to test all sorts of masks.”

The research team plans to study next how particles escape from masks, whether they’re coming from gaps around the edges or moving through the fabric, he said.

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created Researchers

Researchers created a test to determine which masks are the least effective – CNN

(CNN)Schools are reopening, amusement parks are welcoming back visitors, and outdoor dining is the new way to eat out. But despite the signs that life is returning back to normal, the coronavirus pandemic has gone nowhere.

That’s why a group of researchers at Duke University created a simple technique to analyze the effectiveness of various types of masks which have become a critical component in stopping the spread of the virus.
The quest began when a professor at Duke’s School of Medicine was assisting a local group buy masks in bulk to distribute to community members in need. The professor wanted to make sure the group purchased masks that were actually effective.
In the study published Friday, researchers with Duke’s physics department demonstrated the use of a simple method that uses a laser beam and cell phone to evaluate the efficiency of masks by studying the transmission of respiratory droplets during regular speech.
“We use a black box, a laser, and a camera,” Martin Fischer, one of the authors of the study, told CNN. “The laser beam is expanded vertically to form a thin sheet of light, which we shine through slits on the left and right of the box.”
In the front of the box is a hole where a speaker can talk into it. A cell phone camera is placed on the back of the box to record light that is scattered in all directions by the respiratory droplets that cut through the laser beam when they talk.
A simple computer algorithm then counts the droplets seen in the video.

Encouraging the use of effective masks

Public health experts have spent months emphasizing that masks are one of the most effective tools to help fight the pandemic, and many US states have now introduced some kind of mask requirement.
But when testing their effectiveness, researchers discovered that some masks are quite literally useless.
Researchers tested 14 commonly available masks including a professionally fitted N95 mask, usually reserved for health care workers. First the test was performed with a speaker talking without wearing a mask. Then they did it again while a speaker was wearing a mask. Each mask was tested 10 times.
The most effective mask was the fitted N95. Three-layer surgical masks and cotton masks, which many people have been making at home, also performed well.
Neck fleeces, also called gaiter masks and often used by runners, were the least effective. In fact, wearing a fleece mask resulted in a higher number of respiratory droplets because the material seemed to break down larger droplets into smaller particles that are more easily carried away with air.
Folded bandanas and knitted masks also performed poorly and did not offer much protection.
“We were extremely surprised to find that the number of particles measured with the fleece actually exceeded the number of particles measured without wearing any mask,” Fischer said. “We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”
While the setup of the test is quite simple — all that is required is a box, a laser for less than $200, one lens, and a cell phone camera — Fischer does not recommend people to set them up at home.
Unless a person is familiar with laser safety or has optic experience, mishandling powerful lasers can cause permanent eye damage. However, the researchers are hoping companies, museums and community outreach centers will set up the test to show people which masks are the most effective.
“This is a very powerful visual tool to raise awareness that a very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory droplets,” Fischer said. “Companies and manufacturers can set this up and test their mask designs before producing them, which would also be very useful.”

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cannabis Researchers

Researchers look into cannabis as a potential COVID-19 treatment – CBS News

As new daily coronavirus infections continue to break records in the U.S., researchers are considering whether the cannabis plant has the potential to be used in the treatment of COVID-19.

Experts from the University of Nebraska and the Texas Biomedical Research Institute are recommending that scientists study the anti-inflammatory properties in CBD as a potential treatment for lung inflammation caused by the coronavirus.

There is no scientific evidence that cannabis or its compounds can help with COVID-19 specifically, but in a peer-reviewed article in Brain, Behavior, and Immunity, the authors said further research is needed to understand if CBD can help patients infected by the virus.

Emily Earlenbaugh, a Forbes contributor and co-founder of Mindful Cannabis Consulting, joined CBSN to discuss the study. She explained that in severe cases of COVID-19, the body’s immune system overreacts and releases too many cytokines, which is called a “cytokine storm.”

“Cytokines will normally help to create inflammation to fight off infections,” Earlenbaugh said. “But in these extreme cases, you see so much cytokines being released into the system that it creates a cytokine storm. You might see high fever, inflammation, severe fatigue and nausea, and in serious cases, it can lead to death through organ failure.”

Earlenbaugh said CBD is known from previous research as an IL-6 cytokine inhibitor, meaning it helps reduce the production of cytokines.

The authors of the study wrote that one drug, Tocilizumab, resulted in the “clearance of lung consolidation and recovery” in 90% of the 21 treated patients. The drug, however, resulted in adverse side effects like pancreas inflammation and hypertriglyceridemia.

Researchers then turned to cannabis, specifically CBD. The authors said that several cannabinoids in the cannabis plant have anti-inflammatory properties. They said CBD “has shown beneficial anti-inflammatory effects in pre-clinical models of various chronic inflammatory diseases” and noted that the FDA approved one CBD product to treat certain forms of epilepsy.

“CBD has very few side effects, so it’s something that’s being looked at as a much more mild treatment that still has a lot of anti-inflammatory powers,” Earlenbaugh told CBSN. 

The authors of the study said that CBD can help reduce anxiety in patients and increase the production of interferons, a protein that helps that body fight infections.

But given the very early stages of this research, Earlenbaugh warns that people should “definitely express caution” against using cannabis to fight COVID-19. She said some researchers have warned using the drug early on in the infection stages could cause negative side effects.

“We’re very pretty far away from human research that could really definitively answer those questions for us,” Earlenbaugh says. “The other reason for caution is that cytokines are important in fighting off infections. So, we don’t want to reduce them as a preventative measure or in early stages of the infection.”

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Researchers map SARS-CoV-2 infection in cells of nasal cavity, bronchia, lungs – Medical Xpress

Researchers map SARS-CoV-2 infection in cells of nasal cavity, bronchia, lungs
SARS-CoV-2 (red) infected ciliated cells in the COVID-19 patient’s bronchi. Credit: Takanori Asakura, PhD, UNC School of Medicine

In a major scientific study published in the journal Cell, scientists at the UNC School of Medicine and the UNC Gillings School of Global Public Health have characterized the specific ways in which SARS-CoV-2—the coronavirus that causes COVID-19—infects the nasal cavity to a great degree—replicating specific cell types—and infects and replicates progressively less well in cells lower down the respiratory tract, including the lungs.

The findings suggest the virus tends to become firmly established first in the , but in some cases the virus is aspirated into the lungs, where it may cause more serious disease, including potentially fatal pneumonia.

“If the nose is the dominant initial site from which are seeded, then the widespread use of masks to protect the nasal passages, as well as any therapeutic strategies that reduce virus in the nose, such as nasal irrigation or antiviral nasal sprays, could be beneficial,” said study co-senior author Richard Boucher, MD, the James C. Moeser Eminent Distinguished Professor of Medicine and Director of the Marsico Lung Institute at the UNC School of Medicine.

The other co-senior author of the study was Ralph Baric, Ph.D., the William R. Kenan Distinguished Professor of Epidemiology at the UNC Gillings School of Public Health.

“This is a landmark study that reveals new and unexpected insights into the mechanisms that regulate disease progression and severity following SARS-CoV-2 infection,” said Baric, who also holds a microbiology faculty appointment at the UNC School of Medicine. “In addition, we describe a new reverse genetic platform for SARS-CoV-2 allowing us to produce key indicator viruses that will support national vaccine efforts designed to control the spread and severity of this terrible disease.”

SARS-CoV-2 initially caused outbreaks in late 2019 in China and spread around the world, infecting nearly 6 million people and killing more than 350,000. The United States accounts for almost a third of those infections and deaths.

The UNC-Chapel Hill team in their study sought to understand better a number of things about the virus, including which cells in the airway it infects, and how it gets into the lungs in the patients who develop pneumonia.

In one set of laboratory experiments, the researchers used different isolates of SARS-CoV-2 to see how efficiently they could infect cultured cells from different parts of the human airway. They found a striking pattern of continuous variation, or gradient, from a relatively high infectivity of SARS-CoV-2 in cells lining the nasal passages, to less infectivity in cells lining the throat and bronchia, to relatively low infectivity in cells.

The scientists also found that ACE2—the cell surface receptor that the virus uses to get into cells—was more abundant on nasal-lining cells and less abundant on the surface of lower airway cells. This difference could explain, at least in part, why upper airway nasal-lining cells were more susceptible to infection.

Other experiments focused on TMPRSS2 and furin, two protein-cleaving enzymes found on many human cells. It’s thought that SARS-CoV-2 uses those two enzymes to re-shape key virus proteins and enter human cells. The experiments confirmed that when these human enzymes are more abundant, this particular coronavirus has an increased ability to infect cells and make copies of itself.

The researchers found that the virus can infect airway-lining cells called epithelial cells, and to a limited extent the all-important “pneumocyte” lung cells that help transfer inhaled oxygen into the bloodstream. But SARS-CoV-2 infects almost no other airway cells.

Intriguingly, the virus did not infect airway-lining cells called club cells, despite the fact that these cells express both ACE2 and TMPRSS2. Moreover, the same types of airway epithelial cells from different human donors, especially lower-airway epithelial cells, tended to vary significantly in their susceptibility to infection. Such findings suggest that there are undiscovered factors in airway cells that help determine the course of infection in individuals—a course known to vary widely from mild or no symptoms all the way to respiratory failure and death.

The team mapped the sites of coronavirus infection in the lungs of several people who had died from COVID-19, and found that these sites exhibited a sort of patchiness and other characteristics consistent with the hypothesis that these sites had originated from infection higher in the airway.

The hypothesis that aspiration of oral contents into the lung is a significant contributor to COVID-19 pneumonia is consistent with the observations that people at higher risk for severe lung disease—the elderly, obese, and diabetic—are more prone to aspiration, especially at night.

The team also found that previously described individual antibodies capable of neutralizing the original SARS coronavirus of 2002 and the MERS coronavirus, which has been spreading slowly in the Middle East since 2012, did not neutralize SARS-CoV-2. However, from two of five SARS 2002 patients showed a low level but significant capability to neutralize SARS-CoV-2 infectivity in cultured . These data suggests that people who have been exposed to other coronaviruses may carry some other types of antibodies in their blood that provide at least partial protection against SARS-CoV-2.

“These results, using some novel and innovative methodology, open new directions for future studies on SARS-C0V-2 that may guide therapeutic development and practices for reducing transmission and severity of COVID-19,” said James Kiley, Director of the Division of Lung Diseases at the National Heart, Lung, and Blood Institute, part of the National Institutes of Health.

Boucher, Baric, and colleagues note that their study, apart from its specific findings about SARS-CoV-2 infection in the airway, involved the development of key laboratory tools—including a version of SARS-CoV-2 re-engineered to carry a fluorescent beacon—that should be useful in future investigations of the virus.



More information:
Yixuan J. Hou et al, SARS-CoV-2 Reverse Genetics Reveals a Variable Infection Gradient in the Respiratory Tract, Cell (2020). DOI: 10.1016/j.cell.2020.05.042

Journal information:
Cell



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Researchers Map Green Snow Algae Blooms in Antarctica | Biology – Sci-News.com

Using data from ESA’s Copernicus Sentinel-2 mission and two field campaigns, a team of UK scientists has identified 1,679 blooms of Antarctic green snow algae, seasonally covering 1.95 km2 and equating to 1,300 tons total dry biomass.

A photograph showing a snow algae bloom dominated by green algae on Anchorage Island. Image credit: Gray et al, doi: 1src.1src38/s41467-src2src-16src18-w.

A photograph showing a snow algae bloom dominated by green algae on Anchorage Island. Image credit: Gray et al, doi: 10.1038/s41467-020-16018-w.

Blooms of snow algae in Antarctica were first described by expeditions in the 1950s and 1960s.

They host a diverse range of algal species and are found around the Antarctic coastline, particularly on islands along the west coast of the Antarctic Peninsula. They grow in warmer areas, where average temperatures are just above zero degrees Celsius during the austral summer (November to February).

Dr. Matt Davey, a researcher in the Department of Plant Sciences at the University of Cambridge, and colleagues attempted to estimate the distribution, size and biomass of snow algal blooms across the entire the Antarctic Peninsula.

The scientists used images from ESA’s Sentinel-2 satellite taken between 2017 and 2019, and measurements they made on the ground in Antarctica at Ryder Bay, Adelaide Island, and the Fildes Peninsula, King George Island.

“We identified 1,679 separate blooms of green algae on the snow surface, which together covered an area of 1.95 km2, equating to a carbon sink of around 479 tons per year,” Dr. Davey said.

“Put into context this is the same amount of carbon emitted by about 875,000 average petrol car journeys in the UK.”

Antarctic green snow algae distribution and modeled cell density: (a) overview of the locations of individual blooms of green-dominant snow algae identified across the Antarctic Peninsula using modeled data from satellite imagery and ground data (circles); circle color scale represents the mean cell density of each bloom; red triangles indicate the location of ground validation sites; cyan triangles show the location of our Adelaide Island and King George Island field sites; (b) RGB Sentinel 2A image of green snow algae blooms at one of our validation sites, Anchorage Island (February, 2src2src); (c) output of IB4; pixel values are converted to cell density with the color scale showing the resultant cell density for each pixel identified as containing green snow algae. Image credit: Gray et al, doi: 1src.1src38/s41467-src2src-16src18-w.

Antarctic green snow algae distribution and modeled cell density: (a) overview of the locations of individual blooms of green-dominant snow algae identified across the Antarctic Peninsula using modeled data from satellite imagery and ground data (circles); circle color scale represents the mean cell density of each bloom; red triangles indicate the location of ground validation sites; cyan triangles show the location of our Adelaide Island and King George Island field sites; (b) RGB Sentinel 2A image of green snow algae blooms at one of our validation sites, Anchorage Island (February, 2020); (c) output of IB4; pixel values are converted to cell density with the color scale showing the resultant cell density for each pixel identified as containing green snow algae. Image credit: Gray et al, doi: 10.1038/s41467-020-16018-w.

Dr. Davey and co-author found that the distribution of green snow algae is strongly influenced by marine birds and mammals, whose excrement acts as a highly nutritious natural fertilizer to accelerate algal growth.

Over 60% of blooms were found within 5 km of a penguin colony. Algae were also observed growing near the nesting sites of other birds, including skuas, and areas where seals come ashore.

Almost two thirds of the green algal blooms were on small, low-lying islands with no high ground.

As the Antarctic Peninsula warms due to rising global temperatures, these islands may lose their summer snow cover and with it their snow algae.

However, in terms of mass, the majority of snow algae is found in a small number of larger blooms in the north of the Peninsula and the South Shetland Islands, in areas where they can spread to higher ground as low-lying snow melts.

“As Antarctica warms, we predict the overall mass of snow algae will increase, as the spread to higher ground will significantly outweigh the loss of small island patches of algae,” said Dr. Andrew Gray, a researcher in the Department of Plant Sciences at the University of Cambridge and NERC Field Spectroscopy Facility.

The team’s paper was published in the journal Nature Communications.

_____

A. Gray et al. 2020. Remote sensing reveals Antarctic green snow algae as important terrestrial carbon sink. Nat Commun 11, 2527; doi: 10.1038/s41467-020-16018-w

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Researchers map tiny twists in magic-angle graphene – Phys.org

Researchers map tiny twists in “magic-angle” graphene
In this illustration, two sheets of graphene are stacked together at a slightly offset “magic” angle, which can become either an insulator or superconductor. “We placed one sheet of graphene on top of another, similar to placing plastic wrap on top of plastic wrap,” MIT professor Pablo Jarillo-Herrero says. “You would expect there would be wrinkles, and regions where the two sheets would be a bit twisted, some less twisted, just as we see in graphene.” Credit: José-Luis Olivares, MIT

Made of a single layer of carbon atoms linked in a hexagonal honeycomb pattern, graphene’s structure is simple and seemingly delicate. Since its discovery in 2004, scientists have found that graphene is in fact exceptionally strong. And although graphene is not a metal, it conducts electricity at ultrahigh speeds, better than most metals.

In 2018, MIT scientists led by Pablo Jarillo-Herrero and Yuan Cao discovered that when two sheets of graphene are stacked together at a slightly offset “magic” angle, the new “twisted” graphene can become either an insulator, completely blocking electricity from flowing through the material, or paradoxically, a superconductor, able to let electrons fly through without resistance. It was a monumental discovery that helped launch a new field known as “twistronics,” the study of electronic behavior in twisted graphene and other materials.

Now the MIT team reports their latest advancements in graphene twistronics, in two papers published this week in the journal Nature.

In the first study, the researchers, along with collaborators at the Weizmann Institute of Science, have imaged and mapped an entire twisted graphene structure for the first time, at a resolution fine enough that they are able to see very slight variations in local twist angle across the entire structure.

The results revealed regions within the structure where the angle between the graphene layers veered slightly away from the average offset of 1.1 degrees.

The team detected these variations at an ultrahigh angular resolution of 0.002 degree. That’s equivalent to being able to see the angle of an apple against the horizon from a mile away.

They found that structures with a narrower range of angle variations had more pronounced exotic properties, such as insulation and superconductivity, versus structures with a wider range of twist angles.

“This is the first time an entire device has been mapped out to see what is the twist angle at a given region in the device,” says Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT. “And we see that you can have a little bit of variation and still show superconductivity and other exotic physics, but it can’t be too much. We now have characterized how much twist variation you can have, and what is the degradation effect of having too much.”

In the second study, the team report creating a new twisted graphene structure with not two, but four layers of graphene. They observed that the new four-layer magic-angle structure is more sensitive to certain electric and magnetic fields compared to its two-layer predecessor. This suggests that researchers may be able to more easily and controllably study the exotic properties of magic-angle graphene in four-layer systems.

“These two studies are aiming to better understand the puzzling physical behavior of magic-angle twistronics devices,” says Cao, a graduate student at MIT. “Once understood, physicists believe these devices could help design and engineer a new generation of high-temperature superconductors, topological devices for quantum information processing, and low-energy technologies.”

Like wrinkles in plastic wrap

Since Jarillo-Herrero and his group first discovered magic-angle graphene, others have jumped at the chance to observe and measure its properties. Several groups have imaged magic-angle structures, using scanning tunneling microscopy, or STM, a technique that scans a surface at the atomic level. However, researchers have only been able to scan small patches of magic-angle graphene, spanning at most a few hundred square nanometers, using this approach.

“Going over an entire micron-scale structure to look at millions of atoms is something that STM is not best suited for,” Jarillo-Herrero says. “In principle it could be done, but would take an enormous amount of time.”

So the group consulted with researchers at the Weizmann Institute for Science, who had developed a scanning technique they call “scanning nano-SQUID,” where SQUID stands for Superconducting Quantum Interference Device. Conventional SQUIDs resemble a small bisected ring, the two halves of which are made of superconducting material and joined together by two junctions. Fit around the tip of a device similar to an STM, a SQUID can measure a sample’s magnetic field flowing through the ring at a microscopic scale. The Weizmann Institute researchers scaled down the SQUID design to sense magnetic fields at the nanoscale.

When magic-angle graphene is placed in a small magnetic field, it generates persistent currents across the structure, due to the formation of what are known as “Landau levels.” These Landau levels, and hence the persistent currents, are very sensitive to the local twist angle, for instance, resulting in a magnetic field with a different magnitude, depending on the precise value of the local twist angle. In this way, the nano-SQUID technique can detect regions with tiny offsets from 1.1 degrees.

“It turned out to be an amazing technique that can pick up miniscule angle variations of 0.002 degrees away from 1.1 degrees,” Jarillo-Herrero says. “This was very good for mapping magic-angle graphene.”

The group used the technique to map two magic-angle structures: one with a narrow range of twist variations, and another with a broader range.

“We placed one sheet of graphene on top of another, similar to placing plastic wrap on top of plastic wrap,” Jarillo-Herrero says. “You would expect there would be wrinkles, and regions where the two sheets would be a bit twisted, some less twisted, just as we see in graphene.”

They found that the structure with a narrower range of twist variations had more pronounced properties of exotic physics, such as superconductivity, compared with the structure with more twist variations.

“Now that we can directly see these local twist variations, it might be interesting to study how to engineer variations in twist angles to achieve different quantum phases in a device,” Cao says.

Tunable physics

Over the past two years, researchers have experimented with different configurations of graphene and other materials to see whether twisting them at certain angles would bring out exotic physical behavior. Jarillo-Herrero’s group wondered whether the fascinating physics of magic-angle graphene would hold up if they expanded the structure, to offset not two, but four graphene layers.

Since graphene’s discovery nearly 15 years ago, a huge amount of information has been revealed about its properties, not just as a single sheet, but also stacked and aligned in multiple layers—a configuration that is similar to what you find in graphite, or pencil lead.

“Bilayer graphene—two layers at a 0-degree angle from each-other—is a system whose properties we understand well,” Jarillo-Herrero says. “Theoretical calculations have shown that in a bilayer-on-top-of-bilayer structure, the range of angles over which interesting physics would happen is larger. So this type of structure might be more forgiving in terms of making devices.”

Partly inspired by this theoretical possibility, the researchers fabricated a new magic-angle structure, offsetting one graphene bilayer with another bilayer by 1.1 degrees. They then connected the new “double-layer” twisted structure to a battery, applied a voltage, and measured the current that flowed through the device as they placed the structure under various conditions, such as a , and a perpendicular electric field.

Just like magic-angle structures made from two layers of graphene, the new four-layered structure showed an exotic insulating behavior. But uniquely, the researchers were able to tune this insulating property up and down with an electric field—something that’s not possible with two-layered magic-angle graphene.

“This system is highly tunable, meaning we have a lot of control, which will allow us to study things we cannot understand with monolayer magic-angle ,” Cao says.

“It’s still very early in the field,” Jarillo-Herrero says. “For the moment, the physics community is still fascinated just by the phenomena of it. People fantasize about what type of devices we could make but realize it’s still too early and we have so much yet to learn about these systems.”



More information:
A. Uri et al. Mapping the twist-angle disorder and Landau levels in magic-angle graphene, Nature (2020). DOI: 10.1038/s41586-020-2255-3

Yuan Cao et al. Tunable correlated states and spin-polarized phases in twisted bilayer–bilayer graphene, Nature (2020). DOI: 10.1038/s41586-020-2260-6

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

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Researchers map tiny twists in magic-angle graphene (2020, May 8)
retrieved 8 May 2020
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Researchers establish new timeline for ancient magnetic field on Mars – Phys.org

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Mars had a global magnetic field much earlier—and much later—in the planet’s history than scientists have previously known.

A planet’s global magnetic field arises from what scientists call a dynamo: a flow of molten metal within the planet’s core that produces an electrical current. On Earth, the dynamo is what makes compass needles point north. But Mars’ dynamo has been extinct for billions of years.

New findings from UBC researchers working with colleagues in the U.S. and France, published today in Science Advances, bring us closer to knowing the and duration of Mars’ dynamo.

“We find that the Martian dynamo operated at 4.5 billion and 3.7 billion years ago. Dynamo timing is a big part of a planet’s evolution, and what we find is very different from what we have thought so far,” said Anna Mittelholz, postdoctoral fellow in UBC’s department of earth, ocean and atmospheric sciences, and first author of the study. “The dynamo tells us something about the planet’s thermal history, its evolution, and how it got to where it is today, and it is unique for each of the terrestrial planets—Earth, Mars, Venus and Mercury.”

Clues about a planet’s magnetic history lie in magnetized rocks on and beneath its surface. Rock is like a tape recorder, especially . They begin as lava, but as they cool and solidify in the presence of a magnetic field, minerals within the rocks align themselves with the global magnetic field. By dating these rocks, scientists can estimate if a dynamo was active at the time the was emplaced.

Magnetism in certain rocks on Mars’ surface indicate that the Martian dynamo was active between 4.3 and 4.2 billion years ago, but the absence of magnetism over three large basins that formed 3.9 billion years ago has led most scientists to believe the dynamo was inactive by that time.

The UBC researchers analyzed new satellite data and found clear evidence of a magnetic field coming from the Lucus Planum lava flow that formed less than 3.7 billion years ago—much later than the aforementioned basins.

The researchers also detected low-intensity magnetic fields over the Borealis Basin in the planet’s northern hemisphere, which formed 4.5 billion years ago and is believed to be one of the oldest features on Mars.

“We have these two observations that point to a dynamo at the earliest known time in Mars’ history, and a dynamo that was present half a billion years after many people thought it had already switched off,” said Catherine Johnson, a professor in the department of earth, ocean and atmospheric sciences and senior scientist at the Planetary Science Institute in Tucson, Ariz., who also contributed to the study.

The researchers offer two possible explanations for the absence of magnetic fields over the basins: the may have stopped before the basins formed and then re-started before Lucus Planum formed, or the impacts that created the basins simply displaced the portion of crust containing minerals that can carry strong magnetism.

The new data for this study come from MAVEN, the Mars Atmosphere and Volatile Evolution satellite. Earlier data about magnetism on Mars had been gathered by the Mars Global Surveyor satellite which orbited the planet between 1999 and 2006, mostly at 400 kilometres above the surface. MAVEN, launched in 2013, operates as close as ~135 kilometres from the surface and picks up weaker signals that MGS could not detect.

MAVEN’s ability to pick up signals from smaller features on and near the surface helps researchers distinguish whether the magnetism is coming from those, or from older rocks buried more deeply in the planet’s crust.

These new insights have researchers wondering what could be revealed if they get even closer. Mittelholz noted that this study focused on two particular features, but craters remain all over Mars with stories to tell. In the future, exploration could progress from satellites to drones or balloons, providing even more detailed data.



More information:
“Timing of the martian dynamo: New constraints for a core field at 4.5 and 3.7 Ga” Science Advances (2020). DOI: 10.1126/sciadv.aba0513 , advances.sciencemag.org/content/6/18/eaba0513

Citation:
Researchers establish new timeline for ancient magnetic field on Mars (2020, May 1)
retrieved 1 May 2020
from https://phys.org/news/2020-05-timeline-ancient-magnetic-field-mars.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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