In a recent study published in Nature Communications, a journal of Nature, researchers at the University of Missouri and University of Chicago have developed an artificial material, called a metamaterial, which can respond to its environment, independently make a decision, and perform an action not directed by a human being. For example, a drone making a delivery might evaluate its environment including wind direction, speed or wildlife, and automatically change course in order to complete the delivery safely.

Guoliang Huang, Huber and Helen Croft Chair in Engineering, and co-author on the study, said the mechanical design of their new artificial material incorporates three main functions also displayed by materials found in nature — sensing; information processing; and actuation, or movement.

Some examples of these natural materials include the quick reaction of a Venus fly trap’s leafy jaws to capture an insect, chameleons changing the color of their skin to blend into their surroundings, and pine cones adjusting their shapes in response to changes in air humidity, Huang said.

“Basically, we are controlling how this material responds to changes in external stimuli found in its surroundings,” Huang said. “For example, we can apply this material to stealth technology in the aerospace industry by attaching the material to aerospace structures. It can help control and decrease noises coming from the aircraft, such as engine vibrations, which can increase its multifunctional capabilities.”

The material uses a computer chip to control or manipulate the processing of information that’s needed to perform the requested actions, then uses the electrical power to convert that energy into mechanical energy. The researchers’ next step is to implement their idea in a real-world environment.

“Realization of active metamaterials with odd micropolar elasticity,” was published in Nature Communications. Co-authors include Yangyang Chen and Xiaopeng Li at MU and Colin Scheibner and Vincenzo Vitelli at the University of Chicago.

Funding is provided by grants from the Air Force Office of Scientific Research (AF9550-18-1-0342 and AF 9550-20-0279), the Army Research Office (W911NF-18-1-0031 and W911NF-19-1-0268) and the National Science Foundation Graduate Research Fellowship (1746045). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

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In a study published in the journal Geology, researchers show that samples of the desert glass contain tiny fragments with minerals often found in rocks of extraterrestrial origin. Those minerals closely match the composition of material returned to Earth by NASA’s Stardust mission, which sampled the particles from a comet called Wild 2. The team concludes that those mineral assemblages are likely the remains of an extraterrestrial object — most likely a comet with a composition similar to Wild 2 — that streamed down after the explosion that melted the sandy surface below.

“This is the first time we have clear evidence of glasses on Earth that were created by the thermal radiation and winds from a fireball exploding just above the surface,” said Pete Schultz, a professor emeritus in Brown University’s Department of Earth, Environmental and Planetary Sciences. “To have such a dramatic effect on such a large area, this was a truly massive explosion. Lots of us have seen bolide fireballs streaking across the sky, but those are tiny blips compared to this.”

The glasses are concentrated in patches across the Atacama Desert east of Pampa del Tamarugal, a plateau in northern Chile nestled between the Andes Mountains to the east and the Chilean Coastal Range to the west. Fields of dark green or black glass occur within a corridor stretching about 75 kilometers. There’s no evidence that the glasses could have been created by volcanic activity, Schultz says, so their origin has been a mystery.

Some researchers have posited that the glass resulted from ancient grass fires, as the region wasn’t always desert. During the Pleistocene epoch, there were oases with trees and grassy wetlands created by rivers extending from mountains to the east, and it’s been suggested that widespread fires may have burned hot enough to melt the sandy soil into large glassy slabs.

But the amount of glass present along with several key physical characteristics make simple fires an impossible formation mechanism, the new research found. The glasses show evidence of having been twisted, folded, rolled and even thrown while still in molten form. That’s consistent with a large incoming meteor and airburst explosion, which would have been accompanied by tornado-force winds. The mineralogy of the glass casts further serious doubt on the grassfire idea, Schultz says. Along with researchers from the Fernbank Science Center in Georgia, Chile’s Universidad Santo Tomás and the Chilean Geology and Mining Service, Schultz and colleagues performed a detailed chemical analysis of dozens of samples taken from glass deposits across the region.

The analysis found minerals called zircons that had thermally decomposed to form baddeleyite. That mineral transition typically happens in temperatures in excess of 3,000 degrees Fahrenheit — far hotter than what could be generated by grass fires, Schultz says.

The analysis also turned up assemblages of exotic minerals only found in meteorites and other extraterrestrial rocks, the researchers say. Specific minerals like cubanite, troilite and calcium-aluminum-rich inclusions matched mineral signatures from comet samples retrieved from NASA’s Stardust mission.

“Those minerals are what tell us that this object has all the markings of a comet,” said Scott Harris, a planetary geologist at the Fernbank Science Center and study co-author. “To have the same mineralogy we saw in the Stardust samples entrained in these glasses is really powerful evidence that what we’re seeing is the result of a cometary airburst.”

More work needs to be done to establish the exact ages of the glass, which would determine exactly when the event took place, Schultz says. But the tentative dating puts the impact right around time that large mammals disappeared from the region.

“It’s too soon to say if there was a causal connection or not, but what we can say is that this event did happen around the same time as when we think the megafauna disappeared, which is intriguing,” Schultz said. “There’s also a chance that this was actually witnessed by early inhabitants, who had just arrived in the region. It would have been quite a show.”

Schultz and his team hope that further research may help to constrain the timing and shed light on the size of the impactor. For now, Schultz hopes this study may help researchers identify similar blast sites elsewhere and reveal the potential risk posed by such events.

“There may be lots of these blast scars out there, but until now we haven’t had enough evidence to make us believe they were truly related to airburst events,” Schultz said. “I think this site provides a template to help refine our impact models and will help to identify similar sites elsewhere.”

Other authors of the study were Sebastian Perroud, Nicolas Blanco and Andrew Tomlinson.

Life zones are distinct biogeographic regions characterized by biotemperature, precipitation, and aridity representing broad-scale ecosystem types.

The study revealed that the world’s life zones have already changed from the early 1900s until present day across all biomes, most notably in Boreal Forests, Temperate Coniferous Forests, and Tropical Coniferous Forests. This includes impacts to 27 million square kilometers (10.4 million square miles) or 18.3 percent of earth’s land. Boundaries between life zones have shifted poleward and towards higher elevations, leading to expansions of zones associated with equatorial climates and contractions of zones associated with temperate climates.

Anticipated future changes are expected to accelerate rapidly, particularly if the world does not act on reducing emissions. This includes potential impacts to an additional potential of 62 million square kilometers (24 million square miles) or 42.6 percent of earth’s land under ‘business-as-usual’.

Life zones associated with subpolar rain tundra, wet tundra, and moist tundra are projected to experience the largest decreases while tropical wet forest, tropical rain forest, and cool temperate moist forest are projected to experience the largest increases. Boreal and polar latitudes are projected to experience substantial losses of area, although their vast extent will help compensate for some of these expected losses.

Said Dr. Paul Elsen, WCS Climate Adaptation Scientist and lead author of the study: “The likely future changes in the world’s life zones is likely to have a substantial impact on people livelihoods and biodiversity. Large areas of the world are getting hotter and drier and this is already impacting the earth’s life zones.”

Dr. Hedley Grantham, WCS Director of Conservation Planning and coauthor of the study said: “COP26 is our best chance of countries committing to reducing emissions and putting us on a better future pathway for climate change and its impacts.”

The study is published in Global Change Biology.

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A research letter detailing the study of nearly 2,000 health care workers appears today in the Journal of the American Medical Association.

“This finding adds to our understanding of how immunity against SARS-CoV-2 works, and builds upon an earlier study by our team that showed the mRNA vaccines yielded a robust antibody response, even if a person did not develop significant symptoms following vaccination or did not have a prior SARS-CoV-2 infection,” says study senior author Aaron Milstone, M.D., M.H.S., professor of pediatrics at the Johns Hopkins University School of Medicine and pediatric epidemiologist at Johns Hopkins Children’s Center.

The two mRNA vaccines evaluated in the study introduce the body’s immune system to S1, a protein subunit that’s a component of the spikes found on the surface of SARS-CoV-2. The spikes enable the virus to latch onto healthy cells and infect them. Immunoglobulin G antibodies, elicited by S1 from the vaccines stimulating the immune system, neutralize the virus particles, preventing infection by SARS-CoV-2, or at least, reducing the severity of the disease.

For their latest study, the researchers followed 1,960 Johns Hopkins Medicine health care workers who had received both doses of either the Pfizer/BioNTech or Moderna vaccines, including 73 people who had a positive SARS-CoV-2 polymerase chain reaction (PCR) test result before the first vaccine dose. The 73 were divided into two groups — those who were infected at 90 days or closer to the first vaccine dose, and those whose exposure to the virus was more than 90 days before the initial shot.

After adjusting for vaccine type, age and sex, antibody levels were compared for those with and without prior SARS-CoV-2 infection at one, three and six months following the second vaccine dose. In addition, antibody levels were compared at one and three months following the second dose between the two groups with prior SARS-CoV-2 infection.

“We found that health care workers with prior SARS-CoV-2 infection followed by two doses of mRNA vaccine — therefore, three independent exposures to the S1 spike protein — developed higher antibody levels than those with vaccination alone,” says study lead author Diana Zhong, M.D., an infectious diseases fellow at the Johns Hopkins University School of Medicine. “The relative differences were 14% higher at 1 month following the second vaccine dose, 19% at three months and 56% at six months.”

Zhong adds that the study participants with a PCR-confirmed SARS-CoV-2 infection more than 90 days before their initial vaccination had adjusted antibody levels 9% (one month following the second vaccine dose) and 13% (three months following the second vaccine dose) higher than those who were exposed to the virus less than or equal to the 90-day mark.

“This suggests that a longer interval between infection and first vaccine dose may enhance the antibody response,” says Milstone.

Milstone says further investigation is needed to determine whether increased post-vaccination durability in previously infected people is attributable to the number of exposures to the virus, the interval between exposures, or the interplay between natural or vaccine-derived immunity.

The study team at Johns Hopkins Medicine was co-led by Zhong and Shaoming Xiao. Along with them and Milstone, the team includes Amanda Debes, Emily Egbert, Patrizio Caturegli and Elizabeth Colantuoni.

This study was supported by National Institute of Allergy and Infectious Diseases/National Institutes of Health grants T32AI007291 and K24AI141580, along with contributions to the COVID-19 research funds of the Johns Hopkins University School of Medicine and the Johns Hopkins Health System.

Silicon’s 3D lattice, however, is too big for next-generation electronics, which include ultra-thin transistors, new devices for optical communication, and flexible bio-sensors that can be worn or implanted in the human body. To slim things down, researchers are experimenting with materials no thicker than a single sheet of atoms, such as graphene. But the tried-and-true method for doping 3D silicon doesn’t work with 2D graphene, which consists of a single layer of carbon atoms that doesn’t normally conduct a current.

Rather than injecting dopants, researchers have tried layering on a “charge-transfer layer” intended to add or pull away electrons from the graphene. However, previous methods used “dirty” materials in their charge-transfer layers; impurities in these would leave the graphene unevenly doped and impede its ability to conduct electricity.

Now, a new study in Nature Electronics proposes a better way. An interdisciplinary team of researchers, led by James Hone and James Teherani at Columbia University, and Won Jong Yoo at Sungkyungkwan University in Korea, describe a clean technique to dope graphene via a charge-transfer layer made of low-impurity tungsten oxyselenide (TOS).

The team generated the new “clean” layer by oxidizing a single atomic layer of another 2D material, tungsten selenide. When TOS was layered on top of graphene, they found that it left the graphene riddled with electricity-conducting holes. Those holes could be fine-tuned to better control the materials’ electricity-conducting properties by adding a few atomic layers of tungsten selenide in between the TOS and the graphene.

The researchers found that graphene’s electrical mobility, or how easily charges move through it, was higher with their new doping method than previous attempts. Adding tungsten selenide spacers further increased the mobility to the point where the effect of the TOS becomes negligible, leaving mobility to be determined by the intrinsic properties of graphene itself. This combination of high doping and high mobility gives graphene greater electrical conductivity than that of highly conductive metals like copper and gold.

As the doped graphene got better at conducting electricity, it also became more transparent, the researchers said. This is due to Pauli blocking, a phenomenon where charges manipulated by doping block the material from absorbing light. At the infrared wavelengths used in telecommunications, the graphene became more than 99 percent transparent. Achieving a high rate of transparency and conductivity is crucial to moving information through light-based photonic devices. If too much light is absorbed, information gets lost. The team found a much smaller loss for TOS-doped graphene than for other conductors, suggesting that this method could hold potential for next-generation ultra-efficient photonic devices.

“This is a new way to tailor the properties of graphene on demand,” Hone said. “We have just begun to explore the possibilities of this new technique.”

One promising direction is to alter graphene’s electronic and optical properties by changing the pattern of the TOS, and to imprint electrical circuits directly on the graphene itself. The team is also working to integrate the doped material into novel photonic devices, with potential applications in transparent electronics, telecommunications systems, and quantum computers.

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Materials provided by Columbia University. Original written by Ellen Neff. Note: Content may be edited for style and length.