#science visualized

A new map of the entire sky, as seen in X-rays, looks deeper into space than any other of its kind.

Butterfly wings are pretty cool, literally. That’s due to special structures that protect them from overheating in the sun.  

Researchers took new thermal images of butterfly wings. These images showed the heat released by each part of a wing, which revealed the living parts of the wing. Those parts include veins that transport insect blood. Those veins also release more heat than surrounding dead scales. And that keeps the living wing parts cooler than the dead ones. The researchers described their findings January 28 in Nature Communications.

Tracking the insect’s heat is important. Small changes in body temperature can affect a butterfly’s ability to fly. The muscles in the insect’s midsection — its thorax — must be warm. That’s so the butterfly can flap its wings fast enough for takeoff. But the butterfly’s wings are thin. So they heat up faster than the thorax and can rapidly overheat.

Creeping tendrils of slime seem to mirror the structure of the universe’s enormous filaments. That superficial similarity, in an organism called a slime mold, helped scientists map out the cosmic web, the vast threads of matter that connect galaxies.

Made up of gas and the unidentified substance called dark matter, the cosmic web began forming early in the universe’s history, as matter clumped together due to gravity. Computer simulations of that formation suggest that a tangled tatting should link galaxies, but the web is so ethereal that scientists struggle to image it directly (SN: 10/3/19).

Enter the slime mold Physarum polycephalum, a single-celled organism that appears as a slimy yellowish lace, often seen bedazzling rotting tree trunks. Normally, a slime mold forms connections between sources of food. Its patterns have striking similarity to human-made networks, such as railroads (SN: 1/21/10).

Scientists produced this map of the universe’s cosmic web based on locations and masses of known galaxies and the lacy patterns of slime mold.

CREDIT: J. BURCHETT ET AL/ASTROPHYSICAL JOURNAL LETTERS 2020

Astronomer Joseph Burchett and computer scientist Oskar Elek, both of the University of California, Santa Cruz, and colleagues adapted a computer method for producing slime mold–like patterns so that, instead of food sources, it could connect more than 37,000 known galaxies sprinkled throughout space. Surprisingly, that technique reproduced the kinds of structures seen in computer simulations of the cosmic web, scientists report March 10 in the Astrophysical Journal Letters.

When liquids containing small particles evaporate, those fluids often leave behind fingerprints like coffee rings or whiskey webs (SN: 10/31/19). But liquids mixed with other liquids leave their own distinct residue patterns.

An evaporating droplet that contains two fluids can sprout fingerlike protrusions or a chain of smaller droplets around its edge, depending on the liquids in the mixture, researchers report February 14 in Physical Review Letters. The researchers caught these phenomena on video using droplets of isopropanol, a component of rubbing alcohol, mixed with either an antifreeze ingredient called ethylene glycol or another chemical called dodecane. Similar patterns appear in other evaporating fluid mixtures, too.

Researchers deposited 1-microliter drops of isopropanol, mixed with either ethylene glycol or dodecane, on a smooth surface. As each drop spread out, the isopropanol evaporated quickly at the edge, where the puddle was thinnest — leaving a higher concentration of either ethylene glycol or dodecane around the puddle’s perimeter.

That distending rim ultimately splintered into a ring of smaller droplets. In pools containing ethylene glycol, those droplets stretched outward to create fingerlike protrusions. In the dodecane-containing pools, the droplets formed a beaded necklace around the puddle.

As a drop of isopropanol mixed with ethylene glycol pools on a surface, the ethylene glycol builds up at the puddle’s edge and splits into a crown of fingerlike protrusions, as seen in the first clip. Thanks to their relatively high surface tension, these ethylene glycol “fingers” can drag fluid out from the puddle’s center, coating the surface in an ethylene glycol film that gets left behind as the evaporating isopropanol recedes. The second clips shows how, in a drop of dodecane-laced isopropanol, dodecane gathers in tiny droplets around the puddle’s edge. Because of their lower surface tension, these beads cannot drag fluid outward like the fingers. So as the isopropanol evaporates and recedes, it leaves behind an array of tiny dodecane islands that eventually merge.  

The difference in puddle edge pattern arose from the liquids’ different surface tensions — how tightly molecules on a fluid’s surface cling to each other (SN: 12/6/18). Liquid tends to flow toward regions with higher surface tension, where molecules exert a stronger pull on each other. “Think tug-of-war,” says coauthor Justin Burton, a physicist at Emory University in Atlanta. “If you have a higher surface tension on one side … one tug-of-war team [is] stronger than the other, and then everything starts to move” in that direction.  

New thermal images of butterflies show that living parts of the wing — including veins transporting insect blood, or hemolymph, and scent patches or pads that males use to release pheromones — release more heat than surrounding dead scales, keeping the living areas cooler.

Small changes in body temperature can affect a butterfly’s ability to fly, as muscles in the thorax must be warm so that the insect can flap its wings fast enough for takeoff. But because the wings are so thin, they heat up faster than the thorax and can rapidly overheat.

People might think that scale-covered butterfly wings are “like a fingernail, or a feather of a bird, or human hair — they are lifeless,” says Nanfang Yu, an applied physicist at Columbia University (SN: 5/23/08). But wings are also equipped with living tissues crucial for survival and flight, and high temperatures will make the insect “really feel uncomfortable.”

A thick layer of chitin over butterfly wing veins and scent patches, plus nanostructures in the patches, gives the tissues higher emissivity than the surrounding area (middle), meaning they release more heat and are consequently cooler (right).

CREDIT: NANFANG YU AND CHENG-CHIA TSAI

Butterfly wings’ thin, semitransparent nature has made it difficult for thermal infrared cameras to distinguish heat from the wing versus from background sources. So Yu and colleagues employed an infrared hyperspectral imaging technique to measure wing temperature and heat emissivity at single-scale resolution for more than 50 butterfly species.

Tube-shaped nanostructures and a thicker layer of chitin, a component of an insect’s exoskeleton, radiate excess heat from living wing tissue, the researchers report January 28 in Nature Communications. Wing veins are covered with that thicker chitin layer, and scent pads have those nanostructures, plus the extra chitin. Thicker or hollow materials are better at radiating heat than thin, solid materials, Yu says.

Those structures protect a wing only up to a point, prompting a butterfly to move away from intense light if it gets too warm. When the researchers beamed a laser on the wing’s scales, the temperature went up “but butterflies can’t feel it and they don’t care,” Yu says. But when the light warmed a butterfly’s veins too much, the insect would flap its wings or move away.

Butterfly wings are equipped with living structures such as veins and scent patches that release more heat than surrounding areas, helping to cool the wings down when the insect basks in the sun.

The team also discovered some butterflies have a structure that looks like a beating “heart” in their wings. It pumps hemolymph through the scent pads of male hickory hairstreak (Satyrium caryaevorus) and white M hairstreak (Parrhasius m-album) butterflies, and beats a few dozen times per minute.

Over 100 hours of scanning has yielded a 3-D picture of the whole human brain that’s more detailed than ever before. The new view, enabled by a powerful MRI, has the resolution potentially to spot objects that are smaller than 0.1 millimeters wide.

“We haven’t seen an entire brain like this,” says electrical engineer Priti Balchandani of the Icahn School of Medicine at Mount Sinai in New York City, who was not involved in the study. “It’s definitely unprecedented.”

The scan shows brain structures such as the amygdala in vivid detail, a picture that might lead to a deeper understanding of how subtle changes in anatomy could relate to disorders such as post-traumatic stress disorder.  

To get this new look, researchers at Massachusetts General Hospital in Boston and elsewhere studied a brain from a 58-year-old woman who died of viral pneumonia. Her donated brain, presumed to be healthy, was preserved and stored for nearly three years.

Before the scan began, researchers built a custom spheroid case of urethane that held the brain still and allowed interfering air bubbles to escape. Sturdily encased, the brain then went into a powerful MRI machine called a 7 Tesla, or 7T, and stayed there for almost five days of scanning. The strength of the 7T, the length of the scanning time and the fact that the brain was perfectly still led to the high-resolution images, which are described May 31 at bioRxiv.org. Associated videos of the brain, as well as the underlying dataset, are publicly available.

ZOOM IN This video moves from the outer wrinkles to the inner structures and then back out to the wrinkles of a complete human brain at extremely high resolution. CREDIT: B.L. EDLOW ET AL/BIORXIV.ORG 2019

Researchers can’t get the same kind of resolution on brains of living people. For starters, people couldn’t tolerate a 100-hour scan. And even tiny movements, such as those that come from breathing and blood flow, would blur the images.

But pushing the technology further in postmortem samples “gives us an idea of what’s possible,” Balchandani says. The U.S. Food and Drug Administration approved the first 7T scanner for clinical imaging in 2017, and large medical centers are increasingly using them to diagnose and study illnesses.

Human-driven carbon pollution is wreaking havoc on the global climate, from bleaching tropical corals to melting polar ice caps. But the amount of carbon in Earth’s oceans and atmosphere barely scratches the surface of the planet’s vast carbon reservoirs.

Over the last decade, researchers affiliated with the international Deep Carbon Observatory have taken inventory of where Earth keeps its carbon, and how carbon cycles throughout the planet. Although Earth’s carbon cycle has generally kept all but the tiniest bit of carbon stashed underground, asteroid impacts and massive volcanic eruptions have occasionally released catastrophic amounts of carbon into the atmosphere.

Investigating these historic upsets, outlined in a series of papers published online October 1 in Elements, may lend insight into the consequences of rampant carbon pollution today.

About 43,500 billion metric tons of carbon is found aboveground — peanuts, compared with the 1.845 billion billion tons stockpiled in Earth’s mantle and crust. Estimates for the carbon content of Earth’s core are murky, but “core carbon is pretty locked up,” says Deep Carbon Observatory geologist Celina Suarez of the University of Arkansas in Fayetteville. Mantle carbon, on the other hand, continually escapes through volcanoes and mid-ocean ridges, and sinks back down with subducting tectonic plates.

________________________________________________________________

Where Earth’s carbon is found

The vast majority of Earth’s carbon is stored inside the planet, with a whopping 1.845 billion billion metric tons in the mantle and crust, and a meager 43,500 billion tons above the surface.

CREDIT: E. Otwell; Source:  C.A. Suarez, M. Edmonds and A.P. Jones/Elements 2019

Typically, “what [carbon] comes out goes back in,” Suarez says. But analyses of carbon in rock from different times in Earth’s history have revealed events that severely upended Earth’s balanced carbon budget. Among these cataclysms was the Chicxulub asteroid strike thought to have wiped out the dinosaurs about 66 million years ago. The impact vaporized carbon-rich rock, releasing hundreds of billions of tons of carbon dioxide into the atmosphere (SN: 11/2/17).

________________________________________________________________

Where carbon above Earth’s surface is found

All the carbon found aboveground, including in life-forms (the terrestrial biosphere), oceans and the atmosphere, tallies up to about 43,500 billion metric tons.

CREDIT: E. Otwell; Source:  C.A. Suarez, M. Edmonds and A.P. Jones/Elements 2019

Other disasters include a handful of enormous magma eruptions called large igneous provinces, which each covered up to a million square kilometers. Such widespread lava flows, which could have released a few billion tons of carbon each year as they erupted, may have contributed to mass die-offs like the Permian-Triassic extinction event 252 million years ago (SN: 5/6/11).

Today, people flood the air with carbon at an even higher rate of about 10 billion tons per year. That’s around 100 times the current emissions of all of Earth’s volcanic regions, from volcanic eruptions as well as carbon passively leaking from soil, lakes and other sources, says Tobias Fischer, a Deep Carbon Observatory volcanologist and geochemist at the University of New Mexico in Albuquerque.

We’ve already seen far-reaching consequences of rampant human carbon emissions (SN: 9/25/19). But studying calamitous carbon releases throughout Earth’s history may help us anticipate how runaway carbon pollution plays out in the long run, Suarez says.

________________________________________________________________

Carbon comparison

Earth’s history is punctuated by asteroid impacts, such as the dino-dooming Chicxulub impact, and catastrophic lava outflows that have released enormous amounts of carbon into the atmosphere, throwing the climate out of whack. Human-driven emissions are currently pumping the atmosphere full of carbon faster than past cataclysmic lava outflows called large igneous provinces, and far outpace modern Earth’s natural release of carbon from processes like volcanic activity.

Half of a millennium ago, Portuguese explorer Ferdinand Magellan and his crew embarked on the first voyage to successfully sail around the world. On September 20, 1519, Magellan’s five-ship fleet set sail from Spain and traveled south, crossing the Atlantic to South America. There, the sailors happened upon a channel, later dubbed the Strait of Magellan, to the Pacific Ocean, and the ships continued west.

The journey was anything but smooth sailing. Magellan dealt with shipwrecks, mutiny and conflicts with indigenous people. He was killed during such a conflict in the Philippines in 1521. But his crew carried on, traversing the Indian Ocean and hooking around Africa’s southern tip to sail north back to Spain. A lone ship docked in Seville in 1522.

In the 500 years since Magellan, humankind has found new ways to circle the globe. The goal of many early circumnavigations was to connect the world, says Jeremy Kinney, chair of the aeronautics department at the Smithsonian Air and Space Museum in Washington, D.C. Circumnavigation is the ultimate expression of “humans’ ability to conquer nature and geographic boundaries,” he says.