The green hairstreak butterfly (Callophrys rubi) gets its blue-green hue from complex nanoscale structures on its wings. The structures, called gyroids, are repeating patterns of spiral-shaped curls. Light waves bouncing off the patterned surface (top inset above) interfere with one another, amplifying green colors while washing out other shades (SN: 6/7/08, p. 26).

Scientists led by Min Gu of the Royal Melbourne Institute of Technology in Australia have now painstakingly re-created the gyroid structure by sculpting the shapes out of a special resin that solidifies when hit with laser light. The technique, called optical two-beam lithography, uses a pair of lasers to set the material in just the right pattern. Afterward, the remaining resin can be washed away, leaving only the gyroid structure. The fabricated version repeats its pattern every 360 nanometers, or billionths of a meter.

The gyroid structures determine more than just color. They also divvy up light that is circularly polarized — its electric fields spiral either clockwise or counterclockwise. In the butterfly, this effect is weak because of irregularities in the structure. But the artificial version sorts the light according to polarization, reflecting one type much more than the other, the researchers report May 13 in Science Advances.

The ability to control circular polarization of light with structures like these could allow scientists to increase the bandwidth of optical communications, the researchers say. The two polarizations of light could each carry different information, which could then be separated and decoded down the line.

Everyone ages. Growing old is a fundamental feature of human existence.

Though we might not always be aware of aging, it looms in all of our futures. As Science News editor in chief Eva Emerson writes, “Aging happens to each of us, everywhere, all the time. It is so ever-present and slow that we tend to take little notice of it. Until we do.”

But, our scientific understanding of aging pales in comparison to its significance in our lives. While new studies reveal exciting prospects for slowing the effects of aging, its causes and extensive effects remain enigmatic.
Scientists are still divided on some fundamentals of aging, and that’s why aging research raises some interesting questions. For example, how does it change the brain? How did different life histories evolve? How old is the oldest blue whale? This special report addresses those questions and more.

In Colorado’s Rocky Mountains, male and female valerian plants have responded differently to hotter, drier conditions, a new study shows. Rapidly changing ratios of the sexes could be a quick sign of climate change, the researchers say.

Valerian (Valeriana edulis) plants range from hot, scrubby lowlands to cold alpine slopes. In each patch of plants, some are male and some are female. The exact proportion of each sex varies with elevation. High on the mountain, females are much more common than males; they can make up 80 percent of some populations.
Four decades ago, in patches of valerian growing in the middle of the plant’s elevation range, 33.4 percent of the plants were males. Those patches grew in the Rockies at elevations around 3,000 meters. Today, you would have to hike considerably higher to find the same proportion of male plants. Males, now 5.5 percent more common on average, are reaching higher elevations than in the past, researchers report in the July 1 Science.

“We think climate is acting almost like a filter on males and females,” says Will Petry of ETH Zurich, who led the study while at the University of California, Irvine. “The settings on this filter are controlling the sex ratio.” Those settings are sweeping up the mountainside like a rising tide at a rate of 175 meters per decade, Petry and colleagues found.
Ecologists already knew that the ratio of male to female plants can vary with altitude or water availability, says ecologist Spencer Barrett of the University of Toronto, who was not involved in this study. But “the idea that a sex ratio is moving upslope — nobody’s ever done that before.”

Those moving sex ratios have kept pace with climate change since the late 1970s. Today, winter snows are melting earlier and summers are hotter, with less rain. As a result, the same amount of precipitation that would have fallen at one elevation in 1978 now falls at higher elevations instead; it has moved upslope by 133 meters per decade. Soil moisture has moved up the mountain, too, by 195 meters per decade.

The parallel shifts mean that changing sex ratios could be a marker of climate change, says population biologist Tom Miller of Rice University in Houston, a coauthor of the study. Today, movements of whole species — often up in latitude or altitude — are a hallmark of climate change. But proportions of males and females are changing “substantially faster than species are moving,” Miller says. They “might be a much more rapid fingerprint of climate change than where species are migrating to.”
Petry’s team found that fingerprint while hiking around the Rocky Mountain Biological Laboratory in Crested Butte, Colo. As the scientists walked through the mountains in Chaffee and Gunnison counties, they counted flowering males and females at 31 sites in 2011, then compared their modern data with historical counts from nine of the same populations, made by coauthor Judy Soule from 1978 to 1980. When Petry saw that the percentage of males and females had changed, “we also started thinking about the consequences,” he says.

If one sex vastly outnumbers the other, populations could die out. “Imagine if it became an Amazonia situation,” says Kailen Mooney, whose lab at UC Irvine led the new study. A 100 percent female population wouldn’t be pollinated, and would disappear once the mature females died, he says.

If those female-only populations grew above a certain altitude and died out because males couldn’t reach them, then male plants would set the upper boundary for the whole species. Sex ratios “add nuance” to the way scientists think about climate-driven migration, Mooney says, because one sex could determine geographic limits for whole species.

A new book on aging starts with what sounds like a promise: “It is a common belief that aging is inevitable and universal. Nothing could be further from the truth.” From this, you might expect the final pages to offer a list of options for fending off the ravages of time. But this is less a how-to guide and more of a dive into why aging happens.
The authors, theoretical biologist Josh Mitteldorf and writer Dorion Sagan, take an extensive stroll through evolutionary theory and aging research in support of an off-center view. After pointing out problems with several theories of why aging evolved, the authors present the controversial premise that aging is a programmed march toward oblivion that evolved as a form of population control. “Aging in animals enforces a common, predictable life span, helping to prevent the dominance of any one individual or one gene type. Diversity is preserved for the health of the community.” Other researchers have been skeptical of that idea.

Aging, however, is unyielding. The authors describe how certain hardships — starvation, exertion, even small amounts of poison — can paradoxically lead to life extension in lab animals. From these findings, Mitteldorf and Sagan make antiaging recommendations that start with familiar medical advice: exercise, lose weight and take a daily aspirin or ibuprofen. But then they jump to suggestions that have not yet been proven, including supplementation with “huge doses of vitamin D” and melatonin, plus metformin (a diabetes drug) and selegiline (a drug used to treat early Parkinson’s and depression). Next comes a list of herbs that could restore telomeres, the protective tips of chromosomes. The book spends much less real estate describing the research behind all of these recommendations, perhaps because the human studies haven’t been done yet.

The crystal ball section of the book is an optimistic look at very preliminary research on the benefits of lengthening telomeres, removing senescent cells from the body and regrowing the shrinking thymus, the organ that produces immune system T cells. The authors may be onto something. But none of these ideas have yet had a chance to mature.

Buy Cracking the Aging Code from Amazon.com. Sales generated through the links to Amazon.com contribute to Society for Science & the Public’s programs.

NASA’s Juno spacecraft has sent back its first picture of Jupiter since arriving at the planet July 4 (SN: 7/23/16, p. 14). The image, taken July 10 when the spacecraft was 4.3 million kilometers from Jupiter, shows off the planet’s clouds, its Great Red Spot (a storm a bit wider than Earth) and three of its moons (Io, Europa and Ganymede).

Juno is on the outbound leg of its first of two 53.5-day orbits of the gas giant (Juno will then settle into 14-day orbits). During orbit insertion, all of Juno’s scientific instruments were turned off while the spacecraft made its first dive through the harsh radiation belts that encircle the planet. This first image indicates that Juno is in good health and ready to study the largest planet in the solar system.

The probe is the ninth to visit Jupiter and the second to stay in orbit (SN: 6/25/2016, p. 32). For the next 20 months, Juno will investigate what lurks beneath the opaque clouds that enshroud the planet (SN: 6/25/2016, p. 16). The spacecraft won’t take its first intimate pictures of Jupiter until August 27, when it flies within 5,000 kilometers of the cloud tops.

Standoffish electrons typically keep one another at arm’s length, repelling their neighbors. But surprisingly, under certain circumstances, this repulsion can cause pairs of electrons to soften their stance toward one another and attract instead, new research shows. The effect may be the key to someday producing a new type of high-temperature superconductor, scientists report in the July 21 Nature.

Though the effect was first predicted over 50 years ago, previous attempts to coerce electrons to behave in this chummy way have failed. Like charges repel, so negatively charged electrons ordinarily rebuff one another. But now researchers have validated the counterintuitive idea that an attraction between electrons can emerge. “Somehow, you have [this] magic that out of all this repulsion you can create attraction,” says study coauthor Shahal Ilani, a physicist at the Weizmann Institute of Science in Rehovot, Israel.
Ilani and colleagues produced the effect in a bare-bones system of electrons in carbon nanotubes. Operating at temperatures just above absolute zero, the system is made up of two perpendicular carbon nanotubes — hollow cylinders of carbon atoms — about 1 nanometer in diameter.

Two electrons sit at sites inside the first nanotube. Left to their own devices, those two electrons repel one another. A second nanotube, known as the “polarizer,” acts as the “glue” that allows the two electrons to attract. When the scientists brought the two nanotubes close together, says Ilani, “the electrons in the first nanotube changed their nature; they became attractive instead of repulsive.”

This flip is due to the nature of the polarizer. It contains one electron, which is located at one of two sites in the carbon nanotube — either between the first nanotube’s pair of electrons or farther away. The pair of electrons in the first nanotube repels the polarizer’s electron, kicking it from the near to the far site. And the electron’s absence leaves behind a positively charged vacancy, which attracts the pair of electrons toward it — and toward each other.
It’s a “tour de force,” says Takis Kontos, a physicist at the École Normale Supérieure in Paris, who wrote a commentary on the paper in the same issue of Nature. Although the system the scientists created is very simple, he says, “the whole experiment built around it is extremely complex.”
Electrons are known to attract in certain situations. In conventional superconductors, electrons pair up due to their interactions with ions in the material. This buddy system allows superconductors to conduct electricity without resistance. But such superconductors must be cooled to very low temperatures for this effect to occur.

But in 1964, physicist William Little of Stanford University theorized that electron pairs could likewise attract due to their interactions with other electrons, instead of ions. Such pairs should stay linked at higher temperatures. This realization sparked hopes that a material with these attracting electrons could be a room-temperature superconductor, which would open up a wealth of technological possibilities for efficiently transmitting and storing energy.

It’s yet to be seen whether the effect can produce a superconductor, and whether such a superconductor might work at higher temperatures — the new discovery shows only that the attraction can occur due to electrons’ repulsion. It’s “the first important step,” says Ilani. Now, scientists can start thinking of how to build “interesting new materials that are very different than what you can find in nature.”

U.S. drivers love to hit the road. The problem is doing so safely.

In 2013, 32,894 people in the United States died in motor vehicle crashes. Although down since 2000, the overall death rate — 10.3 per 100,000 people — tops 19 other high-income countries, the U.S. Centers for Disease Control and Prevention reported July 8. Belgium is a distant second with 6.5 deaths per 100,000. Researchers reviewed World Health Organization and other data on vehicle crash deaths, seat belt use and alcohol-impaired driving in 2000 and 2013.
Canada had the highest percentage of fatal crashes caused by drunk drivers: 33.6 percent. New Zealand and the United States tied for second at 31 percent. But Canada and 16 other countries outperformed the United States on seat belt use — even though, in 2013, 87 percent of people in the United States reported wearing safety belts while riding in the front seat.

Spain saw the biggest drop — 75 percent — in its crash death rate. That country improved nearly all aspects of road safety, including decreasing alcohol-impaired driving and increasing seat belt use, the researchers say.

The newest and thorniest members of a diverse ant family may have extra help holding their heads high.

Found in the rainforests of Papua New Guinea, Pheidole drogon and Pheidole viserion worker ants have spines protruding from their thoraxes. For many ant species, the spiky growths are a defense against birds and other predators. But Eli Sarnat and colleagues suggest the spines might instead be a muscular support for the ants’ oversized heads, which the insects use to crush seeds. The heads “are so big that it looks like it would be difficult to walk,” says Sarnat, an entomologist at the Okinawa Institute of Science & Technology Graduate University in Japan.
Micro‒CT scans of worker ants with larger heads revealed bundles of thoracic muscle fibers within spines just behind their heads. Worker ants with smaller heads did not have muscles in their spines, the researchers report online July 27 in PLOS One. More research is needed to establish the spines’ function and understand why they evolved, Sarnat says. While buff spines may support big heads, hollow spines probably keep predators at bay, the researchers suspect.
Researchers named the ants after two fearsome dragons, Drogon and Viserion, in the popular book and TV series Game of Thrones.

Thirst drove one of the last populations of woolly mammoths to extinction.

A small group of holdouts on an isolated Alaskan island managed to last about 8,000 years longer than most of their mainland-dwelling brethren. But by about 5,600 years ago, the island’s lakes — the only source of freshwater — became too small to support the mammoths (Mammuthus primigenius), scientists report online the week of August 1 in the Proceedings of the National Academy of Sciences.
“I don’t think I’ve ever seen something so conclusive about an extinction before,” says Love Dalén, an evolutionary geneticist at the Swedish Museum of Natural History in Stockholm who was not involved in the research. The study highlights “how sensitive small populations are and how easily they can become extinct.”

Surprisingly recent woolly mammoth bones had previously been discovered in a cave on St. Paul Island, which became isolated from the mainland roughly 14,000 years ago. Since there’s no evidence that prehistoric humans lived on St. Paul, the find provided a chance to study extinction in the absence of human influence, says Russell Graham, a paleontologist at Penn State who led the study.

The scientists extracted a core of sediment from a lake bed near the cave to see how environmental conditions had changed over the last 11,000 years. The team found remnants of ancient plants, animals and fungi in the sediment — including traces of mammoth DNA in some layers. By analyzing and dating the different sediment layers, the team could infer when and how the mammoths went extinct.

“We initially thought that vegetation change and habitat would be the major driving factor,” Graham says. Instead, his team found a wealth of evidence — including an increase in salt-tolerant algae and crustaceans 6,000 years ago — suggesting freshwater shortages as the culprit.
A warmer climate after the last Ice Age ended contributed to the St. Paul mammoths’ downfall. Sea level rise shrank the mammoths’ island habitat and cut into their freshwater supplies by raising the water table and making the lake saltier over time, the team concluded. Warmer, drier conditions also caused water to evaporate more quickly from the lake surface.

The study highlights an often-overlooked vulnerability of island and coastal communities. Some islands in the South Pacific are currently experiencing similar freshwater shortages thanks to rising seas, Graham says – and Florida could be next in line. That’s particularly bad news for large island-dwelling and coastal mammals, which tend to need more water to survive than smaller species.

A small device with a heart of crystal can eavesdrop on muscles and nerves, scientists report August 3 in Neuron. Called neural dust, the device is wireless and needs no batteries, appealing attributes for scientists seeking better ways to monitor and influence the body and brain.

“It’s certainly promising,” says electrical engineer Khalil Najafi of the University of Michigan in Ann Arbor. “They have a system that operates, and operates well.”

Michel Maharbiz of the University of California, Berkeley and colleagues presented their neural dust idea in 2013. But the paper in Neuron represents the first time the system has been used in animals. Neural dust detected activity when researchers artificially stimulated rats’ sciatic nerves and muscles.
Unlike other devices that rely on electromagnetic waves, neural dust is powered by ultrasound. When hit with ultrasound generated by a source outside the body, a specialized crystal begins to vibrate. This mechanical motion powers the system, allowing electrodes to pick up electrical activity. This activity can then change ultrasound signals that travel back to the source, offering a readout in a way that’s similar to a sonar measurement.

Neural dust devices may help scientists avoid some of the problems with current implants, such as a limited life span. Implantable devices can falter in the brain’s hostile environment. “It’s like throwing a piece of electronics in the ocean and wanting it to run for 20 years,” Maharbiz says. “Eventually things start to degrade and break down.” But having a simple, small device may increase the life span of such implants — although Maharbiz and colleagues don’t yet know how long their system could last.

What’s more, the brain can mount a defense against the foreign object, which can result in thick tissue surrounding the implant. Smaller systems damage the brain less. At over 2 millimeters long and just under 1 millimeter wide, a particle of the neural dust described in the paper is larger than most actual specks of dust. But the system is still shrinking. “There’s a lot of room here to just really push it, and that’s what excites us,” Maharbiz says. “You can keep getting smaller and smaller and smaller.”

Neural dust could ultimately be used to detect different sorts of data in the body, not just electrical activity, Maharbiz says. The device could be tweaked to sense temperature, pressure, oxygen or pH.

Najafi cautions that it remains to be seen whether the system will prove useful for listening to nerve cell behavior inside the brain. The system would need to include many different pieces of neural dust, and it’s not clear how effective that would be. “It’s a lot harder than the notion of dust implies,” he says.