A new version of the periodic table showcases the predicted properties of 2-D metals, an obscure class of synthetic materials.

Arrayed in 1-atom-thick sheets, most of these 2-D metals have yet to be seen in the real world. So Janne Nevalaita and Pekka Koskinen, physicists at the University of Jyväskylä in Finland, simulated 2-D materials of 45 metallic elements, ranging from lithium to bismuth. For each sheet, the researchers measured the average chemical bond length, bond strength and the material’s compressibility, how difficult it is to squeeze the atoms closer together. The team then charted those features in the new periodic table.
The new work, described in the Jan. 15 Physical Review B, could help researchers identify which 2-D metals are most promising for various applications, like spurring chemical reactions or sensing gases.

These metals are similar to previously studied 2-D materials, such as the supermaterial graphene (SN: 10/3/15, p. 7) and its cousin diamondene (SN: 9/2/17, p. 12). But whereas those materials were made up of covalent bonds — in which pairs of atoms share electrons — these 2-D metals are composed of metallic bonds, where electrons flow more freely among atoms. “It’s a whole new type of family of nanostructures,” Koskinen says. “Sky’s the limit, for what the applications could be.”

Like other superflat materials, some potential 2-D metals might exhibit exotic quantum qualities, such as 2-D magnetism or superconductivity, the ability to transmit electricity without resistance. Such properties may make those materials useful for quantum computing, says Joshua Robinson, a materials scientist at Penn State not involved in the work.

Nevalaita and Koskinen created three periodic tables that chart the properties of 2-D metals with atoms in triangular, square or honeycomb configurations. Using their trio of tables, the researchers discovered that the properties of 2-D metals were related to those of their 3-D counterparts. For instance, atoms of any given metal arranged in a triangular lattice typically had about 70 percent the bond strength of atoms in the 3-D version of that metal. Square and honeycomb lattices generally showed about 66 percent and 54 percent the bond strength of 3-D metals, respectively.
The periodic tables revealed similar relationships between 2-D and 3-D metals in bond length and compressibility. These findings could allow researchers to get a quick profile of a 2-D metal that has never been created in the lab or in a computer simulation, just based on the well-known characteristics of its 3-D analog.

Nevalaita and Koskinen also compared the stability of 2-D metals whose atoms were arranged in the three different configurations. The researchers found that many 2-D metals were stable in triangular and honeycomb patterns, but not in squares. Future computer simulations could examine the electric and magnetic properties of these materials, Koskinen says. Knowing the stability and property profiles of 2-D metals could inform which materials scientists fabricate in the lab.

“This is the tip of the iceberg in the area of 2-D metals,” says Mauricio Terrones, a chemical physicist at Penn State not involved in the work.

On July 31, 2012, Maggie de Grauw looked out the window of her flight back to New Zealand after a holiday in Samoa and glimpsed a mysterious mass floating below. That mass turned out to be a raft of lightweight pumice rock, the product of an erupting underwater volcano called Havre. The 2012 eruption turned out to be the largest of its kind in the last 100 years. And now, the pumice raft has become a crucial clue in revealing the eruption’s surprisingly complex nature.
Although underwater eruptions happen all the time, scientists have only recorded such events since the 1990s, and pumice rafts can often float under the radar. Typically, researchers use depth sensors aboard ships to examine the crime scene of an underwater eruption.

But “what we found on the seafloor was almost entirely different from what we expected,” says Rebecca Carey, a volcanologist at the University of Tasmania in Australia. Havre challenges the reliability of the geologic record when it comes to big deep-sea eruptions.

In 2015, Carey and her colleagues set out to get a more detailed view of Havre’s big outburst than what ship-based sensors could reveal. The researchers deployed a robot to measure the depth of the 4-kilometer-wide caldera. Another robot, operated remotely from a ship, allowed the team to get a closer look at specific features in and around the caldera, and to take rock and water samples. A bit of satellite-image detective work revealed the size and path of the pumice raft, which formed no more than 21 1/2 hours after the eruption ended.

The robotic diving duo provided a high-resolution topographic map of the underwater posteruption landscape. The map shows a massive rupture, lava from 14 different vents ranging from 900 to 1,220 meters below the surface, chunks of pumice, landslide deposits and a blanket of ash. This diversity of volcanic material was unexpected, the researchers write January 10 in Science Advances.
Although the Havre event was larger than the 1980 eruption of Mount St. Helens, a similar type of volcano that shot a huge column of debris into the air, the seafloor data weren’t indicative of such a large eruption. “When you shoot a lot of material up into water, there’s resistance,” Carey says. “So you expect to see a lot of it deposited on the seafloor.” But using an old seafloor map of Havre and satellite data, Carey and her colleagues calculated that more than 75 percent of the material produced by Havre ended up in the 400-square-kilometer pumice raft. That raft eventually broke apart and washed up on Australian and other South Pacific beaches. Volcanic gases might have pushed debris to the surface, Carey speculates, but it’s impossible to pinpoint a cause.

Many submarine eruptions go unnoticed, and few have been mapped in this manner. Frequently, researchers rely only on clues on the seafloor surface to determine an eruption’s size. And, if Carey’s team had just done that, the researchers would have never known the true size and nature of the eruption.

“That is a real eye-opener from this study,” says Bill Chadwick, a volcanologist at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Newport, Ore. “What they found tells us a lot about how submarine eruptions behave differently than those on land.”

And if the Havre data are any guide, previous estimates of underwater eruption size may be off. “Now we know that the geological rock record is unfaithful to these very large magnitude powerful events,” Carey says.

LOS ANGELES — In the search for new superconductors, scientists are leaving no stone — and no meteorite — unturned. A team of physicists has now found the unusual materials, famous for their ability to conduct electricity without resistance, within two space rocks.

The discovery implies that small amounts of superconducting materials might be relatively common in meteorites, James Wampler of the University of California, San Diego, said March 6 at a meeting of the American Physical Society. While the superconducting materials found weren’t new to science, additional interplanetary interlopers might harbor new, more technologically appealing varieties of superconductors, the researchers suggest.
Superconductors could potentially beget new, energy-saving technologies, but they have one fatal flaw: They require very cold temperatures to function, making them impractical for most uses. So scientists are on the hunt for new types of superconductors that work at room temperature (SN: 12/26/15, p. 25). If found, such a substance could lead to dramatic improvements in power transmission, computing and high-speed magnetically levitated trains, among other things.

Space rocks are a good avenue to explore in the search for new, exotic materials, says Wampler. “Meteorites are formed under these really unique, really extreme conditions,” such as high temperatures and pressures.

What makes the meteorite superconductors special, the researchers say, is that they occurred naturally, instead of being fabricated in a lab, as most known superconductors are. In fact, says physicist Ivan Schuller, also of University of California, San Diego, these are the highest temperature naturally occurring superconductors known — although they still have to be superchilled to about 5 kelvins (–268.15° C) to work. They are also the first known to have formed extraterrestrially.

“At this point, it’s a novelty,” says chemist Robert Cava of Princeton University. Although Cava is skeptical that scrutinizing meteorites will lead to new, useful superconductors, he says, it’s “kinda cool” that superconductors show up in meteorites.
Wampler, Schuller and colleagues bombarded bits of powdered meteorite with microwaves and looked for changes in how those waves were absorbed as the temperature changed. The sensitive technique can pick out minute traces of superconducting material within a sample.

Analysis of powdered scrapings from more than a dozen meteorites showed that two meteorites contained superconducting material. However, the superconductors found within the meteorites were run-of-the-mill varieties, made from alloys of metals including indium, tin and lead, which are already known to superconduct.

“The idea is, try to look for something that is very unusual,” such as a room temperature superconductor, says Schuller, who led the research. So far, that hope hasn’t been realized — but that hasn’t deterred the search for something more exotic. For a previous study, Wampler, Schuller and colleagues scanned 65 tiny micrometeorites, but found no superconductors at all.

Since parts of space are colder than 5 kelvins, some meteorites may even contain materials that were once superconducting in their chilly natural habitat. That’s an interesting idea, Wampler says, although it’s too early to say whether that possibility might have any astronomical implications for how the objects behave out in space.

People have evolved to sleep much less than chimps, baboons or any other primate studied so far.

A large comparison of primate sleep patterns finds that most species get somewhere between nine and 15 hours of shut-eye daily, while humans average just seven. An analysis of several lifestyle and biological factors, however, predicts people should get 9.55 hours, researchers report online February 14 in the American Journal of Physical Anthropology. Most other primates in the study typically sleep as much as the scientists’ statistical models predict they should.
Two long-standing features of human life have contributed to unusually short sleep times, argue evolutionary anthropologists Charles Nunn of Duke University and David Samson of the University of Toronto Mississauga. First, when humans’ ancestors descended from the trees to sleep on the ground, individuals probably had to spend more time awake to guard against predator attacks. Second, humans have faced intense pressure to learn and teach new skills and to make social connections at the expense of sleep.

As sleep declined, rapid-eye movement, or REM — sleep linked to learning and memory (SN: 6/11/16, p. 15) — came to play an outsize role in human slumber, the researchers propose. Non-REM sleep accounts for an unexpectedly small share of human sleep, although it may also aid memory (SN: 7/12/14, p. 8), the scientists contend.

“It’s pretty surprising that non-REM sleep time is so low in humans, but something had to give as we slept less,” Nunn says.

Humans may sleep for a surprisingly short time, but Nunn and Samson’s sample of 30 species is too small to reach any firm conclusions, says evolutionary biologist Isabella Capellini of the University of Hull in England. Estimated numbers of primate species often reach 300 or more.
If the findings hold up, Capellini suspects that sleeping for the most part in one major bout per day, rather than in several episodes of varying durations as some primates do, substantially lessened human sleep time.

Nunn and Samson used two statistical models to calculate expected daily amounts of sleep for each species. For 20 of those species, enough data existed to estimate expected amounts of REM and non-REM sleep.

Estimates of all sleep times relied on databases of previous primate sleep findings, largely involving captive animals wearing electrodes that measure brain activity during slumber. To generate predicted sleep values for each primate, the researchers consulted earlier studies of links between sleep patterns and various aspects of primate biology, behavior and environments. For instance, nocturnal animals tend to sleep more than those awake during the day. Species traveling in small groups or inhabiting open habitats along with predators tend to sleep less.

Based on such factors, the researchers predicted humans should sleep an average of 9.55 hours each day. People today sleep an average of seven hours daily, and even less in some small-scale groups (SN: 2/18/17, p. 13). The 36 percent shortfall between predicted and actual sleep is far greater than for any other primate in the study.

Nunn and Samson estimated that people now spend an average of 1.56 hours of snooze time in REM, about as much as the models predict should be spent in that sleep phase. An apparent rise in the proportion of human sleep devoted to REM resulted mainly from a hefty decline in non-REM sleep, the scientists say. By their calculations, people should spend an average of 8.42 hours in non-REM sleep daily, whereas the actual figure reaches only 5.41 hours.

One other primate, South America’s common marmoset (Callithrix jacchus), sleeps less than predicted. Common marmosets sleep an average of 9.5 hours and also exhibit less non-REM sleep than expected. One species sleeps more than predicted: South America’s nocturnal three-striped night monkey (Aotus trivirgatus) catches nearly 17 hours of shut-eye every day. Why these species’ sleep patterns don’t match up with expectations is unclear, Nunn says. Neither monkey departs from predicted sleep patterns to the extent that humans do.

This baby bird had barely hatched before it died 127 million years ago — and its lack of fully developed bony breastbone, or sternum, suggests it couldn’t yet fly. The tiny fossil, just a few centimeters long, is giving paleontologists a rare window into the early development of a group of extinct birds called Enantiornithes, researchers report March 5 in Nature Communications.

Previous studies of juvenile Enantiornithes have shown that the sternums of these birds ossified in a pattern different from modern and other ancient birds. The sternum’s ossification — a process in which the cartilage is replaced by bone — is a prerequisite to withstand the stresses of flight. But which parts of the sternum fuse first varies widely among modern birds. Those patterns are reflected in modern birds’ life histories, such as how soon birds can fly and how long they rely on their parents after hatching.
Similar diversity existed in how Enantiornithes developed too, the new study suggests. The baby bird’s sternum was still mostly cartilage at death, but some parts were beginning to turn to bone, which fossilized. That ossification pattern differed markedly from patterns in other known juvenile Enantiornithes, the researchers found.
It’s harder to say how these developmental features might have related to behavior. Although the baby bird couldn’t yet fly, it still might have been able to leave the nest. That’s also true of certain modern birds: Some plover chicks can walk and feed themselves shortly after hatching, but take a little longer to fly.

LOS ANGELES — In the search for new superconductors, scientists are leaving no stone — and no meteorite — unturned. A team of physicists has now found the unusual materials, famous for their ability to conduct electricity without resistance, within two space rocks.

The discovery implies that small amounts of superconducting materials might be relatively common in meteorites, James Wampler of the University of California, San Diego, said March 6 at a meeting of the American Physical Society. While the superconducting materials found weren’t new to science, additional interplanetary interlopers might harbor new, more technologically appealing varieties of superconductors, the researchers suggest.
Superconductors could potentially beget new, energy-saving technologies, but they have one fatal flaw: They require very cold temperatures to function, making them impractical for most uses. So scientists are on the hunt for new types of superconductors that work at room temperature (SN: 12/26/15, p. 25). If found, such a substance could lead to dramatic improvements in power transmission, computing and high-speed magnetically levitated trains, among other things.

Space rocks are a good avenue to explore in the search for new, exotic materials, says Wampler. “Meteorites are formed under these really unique, really extreme conditions,” such as high temperatures and pressures.

What makes the meteorite superconductors special, the researchers say, is that they occurred naturally, instead of being fabricated in a lab, as most known superconductors are. In fact, says physicist Ivan Schuller, also of University of California, San Diego, these are the highest temperature naturally occurring superconductors known — although they still have to be superchilled to about 5 kelvins (–268.15° C) to work. They are also the first known to have formed extraterrestrially.

“At this point, it’s a novelty,” says chemist Robert Cava of Princeton University. Although Cava is skeptical that scrutinizing meteorites will lead to new, useful superconductors, he says, it’s “kinda cool” that superconductors show up in meteorites.
Wampler, Schuller and colleagues bombarded bits of powdered meteorite with microwaves and looked for changes in how those waves were absorbed as the temperature changed. The sensitive technique can pick out minute traces of superconducting material within a sample.

Analysis of powdered scrapings from more than a dozen meteorites showed that two meteorites contained superconducting material. However, the superconductors found within the meteorites were run-of-the-mill varieties, made from alloys of metals including indium, tin and lead, which are already known to superconduct.

“The idea is, try to look for something that is very unusual,” such as a room temperature superconductor, says Schuller, who led the research. So far, that hope hasn’t been realized — but that hasn’t deterred the search for something more exotic. For a previous study, Wampler, Schuller and colleagues scanned 65 tiny micrometeorites, but found no superconductors at all.

Since parts of space are colder than 5 kelvins, some meteorites may even contain materials that were once superconducting in their chilly natural habitat. That’s an interesting idea, Wampler says, although it’s too early to say whether that possibility might have any astronomical implications for how the objects behave out in space.