There have been hints for years that playing football might come at a cost. But a study this year dealt one of the hardest hits yet to the sport, detailing the extensive damage in football players’ brains, and not just those who played professionally.

In a large collection of former NFL players’ postmortem brains, nearly every sample showed signs of chronic traumatic encephalopathy, or CTE, a disorder diagnosed after death that’s associated with memory loss, emotional outbursts, depression and dementia. Damaging clumps of the protein tau were present in 110 of 111 brains, researchers reported in JAMA (SN: 8/19/17, p. 15).
Those startling numbers captured the attention of both the football-loving public and some previously skeptical researchers, says study coauthor Jesse Mez, a behavioral neurologist at Boston University. “This paper did a lot to bring them around.” And that increased awareness and acceptance has already pushed the research further. “The number of brain donors who have donated since the JAMA paper came out has been astronomical,” Mez says.
As the largest and most comprehensive CTE dataset yet, the results described in JAMA are a necessary step on the path to finding ways to treat or prevent CTE, and not just for professional athletes.
Former college and high school football players’ brains were also examined, though in small numbers. Three of 14 high school players and 48 of 53 college players had signs of CTE. Many of the brains were donated by relatives who suspected something was amiss. That skewed sample makes it difficult to draw broad conclusions. Still, the study raised troublesome questions about the safety of youth sports.

Those questions haven’t been answered, though other research this year provided clues. A study of concussed hockey players ages 11 to 14 suggested that young brains may need more time than is usually allotted to heal after a hard knock. Players had troublesome changes in white matter tracts — nerve cell bundles that carry messages across the brain — three months after injury, despite normal thinking and memory abilities, researchers reported in November in Neurology.

To fully understand CTE, scientists need a way to identify and follow the disease as it progresses. A comprehensive study is now under way to look for CTE markers in live people, and has already hit on one clue.

Compared with postmortem brain tissue taken from healthy people and those with Alzheimer’s, tissue from people who had CTE had higher levels of an inflammation protein called CCL11, Mez and other researchers reported in September in PLOS ONE. In people with CTE, the more years that a person played football, the more CCL11. CCL11 levels, or other factors circulating in cerebrospinal fluid or blood, might one day let scientists monitor the brain health of athletes and others exposed to head trauma.

The battle of the sexes, at least among certain ocean mammals, may come down to well-placed skin folds, suggests research by Patricia Brennan, an evolutionary biologist at Mount Holyoke College in South Hadley, Mass., and colleagues.

In some species, enhanced male-female genital fit has evolved over time in ways that make mating easier. This is an example of what scientists call congruent evolution. In other species, genital anatomy reflects a battle, as shape and form change over time to give one sex an edge in control of fertilization. Fittingly, this is called antagonistic evolution.
Brennan’s recent collaboration, examining genitalia of porpoises, dolphins and seals, required extra creativity. In previous studies, her team used saline to inflate preserved penises from birds, snakes, sharks and bats. But the tough, fibroelastic penises of the cetaceans would not inflate with saline alone. So her collaborator, Diane Kelly, a penis biomechanics expert at the University of Massachusetts Amherst, suggested pressurizing the saline with a beer keg.

“We looked at each other and said, ‘This could be the best or worst idea we’ve ever had,’ ” Brennan laughs. But it worked. The scientists then created vaginal endocasts with dental silicone and made 3-D mathematical models to examine male-female fit. The team, led by marine mammalogist Dara Orbach of Dalhousie University in Halifax, Canada, described the work in the Oct. 11 Proceedings of the Royal Society B.

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The results show both antagonistic and congruent coevolution. In the model vaginas of short-beaked common dolphins ( Delphinus delphis) and harbor seals ( Phoca vitulina ), penises encountered no physical barriers to penetration.
But in harbor porpoises (Phocoena phocoena) and bottlenosed dolphins (Tursiops truncatus), the scientists found vaginal folds that may help females physically exert choice over sperm. By subtly changing body position during sex, females may use those folds to decrease penetration depth, reducing the likelihood of fertilization by unwanted males, Brennan says.
Brennan’s work has, understandably, made a splash over the years, attracting media coverage and, in 2013, criticism. Conservative news websites and internet trolls attacked her research, calling it “wasteful government spending.” Surprised by the reaction, Brennan responded publicly with an essay in Slate , arguing that basic science moves society forward and is a valid and valuable use of public funds. The experience convinced her that scientists must defend basic science.
Our ability to innovate is undermined without curiosity-driven science, she says. Brennan has developed an outreach program on basic science and plans to keep expanding knowledge of vertebrate genitalia. “In every species we have looked,” she says, “we have found something weird that nobody else knew.” Reason enough to keep discovering.

NASA’s next mission will go where some spacecraft have gone before. The two finalists in the agency’s selection process will return to either Saturn’s moon Titan or comet 67P/Churyumov-Gerasimenko, NASA announced in a press teleconference on December 20.

The Dragonfly mission would launch a drone-like craft to Saturn’s largest moon in 2025 that would land in 2034. NASA’s Cassini-Huygens mission showed that Titan has lakes and rivers of liquid ethane and methane, and may have chemistry that is conducive to life.
“We can test how far prebiotic chemistry has progressed in an environment that we know has the ingredients for life,” said lead investigator Elizabeth Turtle of the Johns Hopkins Applied Physics Laboratory in Laurel, Md.

The other finalist, the Comet Astrobiology Exploration Sample Return (CAESAR) mission, would launch a spacecraft before the end of 2025 to collect a 100-gram sample from the surface of comet 67P, which was mapped by ESA’s Rosetta spacecraft, and return it to Earth in 2038.

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Rosetta’s mapping work “dramatically improves the chances of success for a very difficult activity, which is grabbing a piece of a comet,” said lead investigator Steven Squyres of Cornell University.
Each project will receive funding to further develop the mission concepts. In July 2019, NASA will announce which mission will fly.

Two other missions, one to search for signs of life in the plumes of Saturn’s moon Enceladus and one to land on Venus, will receive funding to tackle specific technology questions to prepare the missions for future competitions.

A new robotic arm made of DNA moves 100,000 times faster than previous DNA machinery.

The DNA nanobot is shaped like a gearshift, with an extendible arm that ranges from 25 to more than 400 nanometers long that’s attached to a 55-by-55-nanometer platform. Researchers remotely control this DNA device, described in the Jan. 19 Science, with electric fields that tug on charged molecules in its arm. Those electric fields help the nanomachine’s arm move much more quickly than previous DNA robots, which relied on chemical interactions between DNA molecules to move (SN: 9/11/10, p. 18).

Friedrich Simmel, a biophysicist at the Technical University of Munich, and his colleagues could swivel their DNA robotic arm 360 degrees in a matter of milliseconds. To lock the arm down in particular positions, the team built latches made of short, single-stranded DNA into the platform.

Such quick, efficient DNA nanobots could someday help move tiny cargo, such as molecules or nanoparticles, in a nanofactory that manufactures new types of materials.

Though they be but little, they are fierce.

Airborne particles smaller than 50 nanometers across can intensify storms, particularly over relatively pristine regions such as the Amazon rainforest or the oceans, new research suggests. In a simulation, a plume of these tiny particles increased a storm’s intensity by as much as 50 percent.

Called ultrafine aerosols, the particles are found in everything from auto emissions to wildfire smoke to printer toner. These aerosols were thought to be too small to affect cloud formation. But the new work suggests they can play a role in the water cycle of the Amazon Basin — which, in turn, has a profound effect on the planet’s hydrologic cycle, researchers report in the Jan. 26 Science.
“I have studied aerosol interactions with storms for a decade,” says Jiwen Fan, an atmospheric scientist at the Pacific Northwest National Laboratory in Richland, Wash., who led the new study. “This is the first time I’ve seen such a huge impact” from these minute aerosols.

Larger aerosol particles greater than 100 nanometers, such as soot or black carbon, are known to help seed clouds. Water vapor in the atmosphere condenses onto these particles, called cloud condensation nuclei, and forms tiny droplets. But water vapor doesn’t condense easily around the tinier particles. For that to be possible, the air must contain even more water vapor than is usually required to form clouds, reaching a very high state of supersaturation.

Such a state is rare — larger aerosols are usually also present to form water droplets, removing that extra water from the atmosphere, Fan says. But in humid places with relatively low background air pollution levels, such as over the Amazon, supersaturation is common, she says.
From 2014 to 2015, Brazilian and U.S. research agencies collaborated on a field experiment to collect data on weather and pollution conditions in the Amazon Basin. As part of the experiment, several observation sites tracked plumes of air pollution traveling from the city of Manaus out across the rainforest. During the warm, wet season, there is little difference day to day in most meteorological conditions over the rainforest, such as temperature, humidity and wind direction, Fan says. So a passing pollution plume represents a distinct, detectable perturbation to the system.

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The international team examined vertical wind motion, or updrafts, and aerosol concentration data from one of these stations from March to May 2014. When a large plume of aerosols with an abundance of ultrafine particles passed by an observation station, the researchers observed a corresponding, more powerful vertical wind motion and heavier rain. Such updrafts intensify storms, helping to drive stronger circulation.

Next, the researchers conducted simulations of an actual storm that occurred on March 17, 2014, matching its temperature, wind and water vapor conditions, as well as a low level of background aerosols in the atmosphere. Then, the team introduced several pollution scenarios to interact with the storm, including no plume and a typical plume from the Manaus metropolis. The results suggested that the ultrafine aerosol particles, in particular, were not only acting as cloud condensation nuclei over the Amazon Basin, but also that the water droplets the aerosols created significantly strengthened the gathering storm.

If the conditions are right, the sheer abundance of the ultrafine particles in such a plume would rapidly create a very large number of cloud droplets. The formation of those droplets would also suddenly release a lot of latent heat — released from a substance as it changes from a vapor to a liquid — into the atmosphere. The heat would rise, creating updrafts and quickly strengthening the storm.

Aside from the Amazon, Fan notes that such pristine, humid conditions can also exist over large swaths of the oceans. One recent study in Geophysical Research Letters that she points to found a link between well-traveled shipping lanes, which would contain abundant exhaust including ultrafine aerosols, and an increase in lightning strikes. “This mechanism may have been at play there,” she says.

Atmospheric scientist Joel Thornton of the University of Washington in Seattle, who led the study on the shipping exhaust, says it’s possible that ultrafine particles play a role in that scenario. “What this paper does is raise the stakes in needing to develop a deeper, more accurate understanding of the sources and fates of atmospheric ultrafine particles,” Thornton says.

Meteorologist Johannes Quaas of the University of Leipzig in Germany, who was not involved in either study, agrees. “It’s a very interesting hypothesis.”

But the observations described in the new study don’t definitively demonstrate that ultrafine aerosols alone drive updrafts, Quaas adds. The weather conditions may appear highly consistent from day to day, but such systems are still highly chaotic. Everything from wind to temperature to how the land surface interacts with incoming solar radiation may be variable, he notes. “In reality, it’s not just the aerosols that change.”