3-D-printed biomaterials that degrade on demand

Brown researchers have found a way to 3-D print intricate temporary microstructures that can be degraded on demand using a biocompatible chemical trigger. The technique could be useful could be useful in fabricating microfluidic devices, creating biomaterials that respond dynamically to stimuli and in patterning artificial tissue.

Brown University engineers have demonstrated a technique for making 3-D-printed biomaterials that can degrade on demand, which can be useful in making intricately patterned microfluidic devices or in making cell cultures than can change dynamically during experiments.

"It's a bit like Legos," said Ian Wong, an assistant professor in Brown's School of Engineering and co-author of the research. "We can attach polymers together to build 3-D structures, and then gently detach them again under biocompatible conditions."

The research is published in the journal Lab on a Chip.

The Brown team made their new degradable structures using a type of 3-D printing called stereolithography. The technique uses an ultraviolet laser controlled by a computer-aided design system to trace patterns across the surface of a photoactive polymer solution. The light causes the polymers to link together, forming solid 3-D structures from the solution. The tracing process is repeated until an entire object is built from the bottom up.

Stereolithographic printing usually uses photoactive polymers that link together with covalent bonds, which are strong but irreversible. For this new study, Wong and his colleagues wanted to try creating structures with potentially reversible ionic bonds, which had never been done before using light-based 3-D printing. To do it, the researchers made precursor solutions with sodium alginate, a compound derived from seaweed that is known to be capable of ionic crosslinking.

"The idea is that the attachments between polymers should come apart when the ions are removed, which we can do by adding a chelating agent that grabs all the ions," Wong said. "This way we can pattern transient structures that dissolve away when we want them to."

The researchers showed that alginate could indeed be used in stereolithography. And by using different combinations of ionic salts -- magnesium, barium and calcium -- they could create structures with varying stiffness, which could then be dissolved away at varying rates.

The research also showed several ways in such temporary alginate structures could be useful.

"It's a helpful tool for fabrication," said Thomas M. Valentin, a Ph.D. student in Wong's lab at Brown and the study's lead author. The researchers showed that they could use alginate as a template for making lab-on-a-chip devices with complex microfluidic channels.

"We can print the shape of the channel using alginate, then print a permanent structure around it using a second biomaterial," Valentin said. "Then we simply dissolve away the alginate and we have a hollow channel. We don't have to do any cutting or complex assembly."

The researchers also showed that degradable alginate structures are useful for making dynamic environments for experiments with live cells. They performed a series of experiments with alginate barriers surrounded by human mammary cells, observing how the cells migrate when the barrier is dissolved away. These kinds of experiments can be useful in investigating wound-healing processes or the migration of cells in cancer.

The experiments showed that neither the alginate barrier nor the chelating agent used to dissolve it away had any appreciable toxicity to the cells. That suggests that degradable alginate barriers are a promising option for such experiments.

The biocompatibility of the alginate is promising for additional future applications, including in making scaffolds for artificial tissue and organs, the researchers say.

Read more at Science Daily

Crab nebula in the limelight: Unified model for the entire radiation spectrum

This composite image of the Crab Nebula was assembled with arbitrary colour scaling by combining data from five telescopes spanning nearly the entire electromagnetic spectrum: the radio emission representing the wind of charged particles from the central neutron star in red (from the Karl G. Jansky Very Large Array), the infrared including the glow of dust particles absorbing ultraviolet and visible light in yellow (from the Spitzer Space Telescope), the visible-light image featuring the hot filamentary structures in green (from the Hubble Space Telescope), the ultraviolet image in blue and the X-ray image in purple showing the effect of an energetic cloud of electrons (from the XMM-Newton Observatory and the Chandra X-ray Observatory).

The origin of cosmic rays, high-energy particles from outer space constantly impacting on Earth, is among the most challenging open questions in astrophysics. Now new research published in the journal Monthly Notices of the Royal Astronomical Society sheds new light on the origin of those energetic particles.

Discovered more than a hundred years ago and considered a potential health risk to airplane crews and astronauts, cosmic rays are believed to be produced by shock waves, for example those resulting from supernova explosions. The most energetic cosmic rays streaking across the universe carry 10 to 100 million times the energy generated by particle colliders such as the Large Hadron Collider at CERN.

The Crab nebula, the remnant of a supernova explosion that was observed almost a thousand years ago in AD1054, is one of the best studied objects in the history of astronomy and a known source of cosmic rays. It emits radiation across the entire electromagnetic spectrum, from gamma rays, ultraviolet and visible light, to infrared and radio waves. Most of what we see comes from very energetic particles (electrons), and astrophysicists can construct detailed models to try to reproduce the radiation that these particles emit.

The new study, by Federico Fraschetti at the University of Arizona, USA, and Martin Pohl at the University of Potsdam, Germany, reveals that the electromagnetic radiation streaming from the Crab nebula may originate in a different way than scientists have traditionally thought: the entire zoo of radiation can potentially be unified and arise from a single population of electrons, a hypothesis which was previously deemed impossible.

According to the generally accepted model, once the particles reach a shock boundary, they bounce back and forth many times due to the magnetic turbulence. During this process they gain energy -- in a similar way to a tennis ball being bounced between two rackets that are steadily moving nearer to one other -- and are pushed closer and closer to the speed of light. Such a model follows an idea introduced by the Italian physicist Enrico Fermi in 1949.

"The current models do not include what happens when the particles reach their highest energy," said Federico, a staff scientist at the University of Arizona's Departments of Planetary Sciences, Astronomy and Physics. "Only if we include a different process of acceleration, in which the number of higher energy particles decreases faster than at lower energy, can we explain the entire electromagnetic spectrum we see. This tells us that while the shock wave is the source of the acceleration of the particles, the mechanisms must be different."

Co-author Martin Pohl added: "The new result represents an important advance for our understanding of particle acceleration in cosmic objects, and helps to decipher the origin of the energetic particles that are found almost everywhere in the universe."

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Monkey sees ... monkey knows?

University of Rochester researchers Jessica Cantlon and Stephen Ferrigno determined that non-human primates exhibited metacognitive illusions after they observed primates completing these series of steps on a computer.

Socrates is often quoted as having said, "I know that I know nothing." This ability to know what you know or don't know -- and how confident you are in what you think you know -- is called metacognition.

When asked a question, a human being can decline to answer if he knows that he does not know the answer. Although non-human animals cannot verbally declare any sort of metacognitive judgments, Jessica Cantlon, an assistant professor of brain and cognitive sciences at Rochester, and PhD candidate Stephen Ferrigno, have found that non-human primates exhibit a metacognitive process similar to humans. Their research on metacognition is part of a larger enterprise of figuring out whether non-human animals are "conscious" in the human sense.

In a paper published in Proceedings for the Royal Society B, they report that monkeys, like humans, base their metacognitive confidence level on fluency -- how easy something is to see, hear, or perceive. For example, humans are more confident that something is correct, trustworthy, or memorable -- even if this may not be the case -- if it is written in a larger font.

"Humans have a variety of these metacognitive illusions -- false beliefs about how they learn or remember best," Cantlon says.

Because other primate species exhibit metacognitive illusions like humans do, the researchers believe this cognitive ability could have an evolutionary basis. Cognitive abilities that have an evolutionary basis are likely to emerge early in development.

"Studying metacognition in non-human primates could give us a foothold for how to study metacognition in young children," Cantlon says. "Understanding the most basic and primitive forms of metacognition is important for predicting the circumstances that lead to good versus poor learning in human children."

Cantlon and Ferrigno determined that non-human primates exhibited metacognitive illusions after they observed primates completing a series of steps on a computer.

The monkey touches a start screen.

He sees a picture, which is the sample. The goal is to remember that sample because he will be tested on this later. The monkey touches the sample to move to the next screen.

The next screen shows the sample picture among some distractors. The monkey must touch the image he has seen before.

Instead of getting a reward right away -- to eliminate decisions based purely on response-reward -- the monkey next sees a betting screen to communicate how certain he is that he's right. If he chooses a high bet and is correct, three tokens are added to a token bank. Once the token bank is full, the monkey gets a treat. If he gets the task incorrect and placed a high bet, he loses three tokens. If he placed a low bet, he gets one token regardless if he is right or wrong.

Researchers manipulated the fluency of the images, first making them easier to see by increasing the contrast (the black image), then making them less fluent by decreasing the contrast (the grey image).

The monkeys were more likely to place a high bet, meaning they were more confident that they knew the answer, when the contrast of the images was increased.

"Fluency doesn't affect actual memory performance," Ferrigno says. "The monkeys are just as likely to get an answer right or wrong. But this does influence how confident they are in their response."

Since metacognition can be incorrect through metacognitive illusion, why then have humans retained this ability?

"Metacognition is a quick way of making a judgment about whether or not you know an answer," Ferrigno says. "We show that you can exploit and manipulate metacognition, but, in the real world, these cues are actually pretty good most of the time."

Take the game of Jeopardy, for example. People press the buzzer more quickly than they could possibly arrive at an answer. Higher fluency cues, such as shorter, more common, and easier-to-pronounce words, allow the mind to make snap judgments about whether or not it thinks it knows the answer, even though it's too quick for it to actually know.

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Nutrition has benefits for brain network organization

An assortment of foods containing omega 3 healthy fats acids.

Nutrition has been linked to cognitive performance, but researchers have not pinpointed what underlies the connection. A new study by University of Illinois researchers found that monounsaturated fatty acids -- a class of nutrients found in olive oils, nuts and avocados -- are linked to general intelligence, and that this relationship is driven by the correlation between MUFAs and the organization of the brain's attention network.

The study of 99 healthy older adults, recruited through Carle Foundation Hospital in Urbana, compared patterns of fatty acid nutrients found in blood samples, functional MRI data that measured the efficiency of brain networks, and results of a general intelligence test. The study was published in the journal NeuroImage.

"Our goal is to understand how nutrition might be used to support cognitive performance and to study the ways in which nutrition may influence the functional organization of the human brain," said study leader Aron Barbey, a professor of psychology. "This is important because if we want to develop nutritional interventions that are effective at enhancing cognitive performance, we need to understand the ways that these nutrients influence brain function."

"In this study, we examined the relationship between groups of fatty acids and brain networks that underlie general intelligence. In doing so, we sought to understand if brain network organization mediated the relationship between fatty acids and general intelligence," said Marta Zamroziewicz, a recent Ph.D. graduate of the neuroscience program at Illinois and lead author of the study.

Studies suggesting cognitive benefits of the Mediterranean diet, which is rich in MUFAs, inspired the researchers to focus on this group of fatty acids. They examined nutrients in participants' blood and found that the fatty acids clustered into two patterns: saturated fatty acids and MUFAs.

"Historically, the approach has been to focus on individual nutrients. But we know that dietary intake doesn't depend on any one specific nutrient; rather, it reflects broader dietary patterns," said Barbey, who also is affiliated with the Beckman Institute for Advanced Science and Technology at Illinois.

The researchers found that general intelligence was associated with the brain's dorsal attention network, which plays a central role in attention-demanding tasks and everyday problem solving. In particular, the researchers found that general intelligence was associated with how efficiently the dorsal attention network is functionally organized used a measure called small-world propensity, which describes how well the neural network is connected within locally clustered regions as well as across globally integrated systems.

In turn, they found that those with higher levels of MUFAs in their blood had greater small-world propensity in their dorsal attention network. Taken together with an observed correlation between higher levels of MUFAs and greater general intelligence, these findings suggest a pathway by which MUFAs affect cognition.

"Our findings provide novel evidence that MUFAs are related to a very specific brain network, the dorsal attentional network, and how optimal this network is functionally organized," Barbey said. "Our results suggest that if we want to understand the relationship between MUFAs and general intelligence, we need to take the dorsal attention network into account. It's part of the underlying mechanism that contributes to their relationship."

Barbey hopes these findings will guide further research into how nutrition affects cognition and intelligence. In particular, the next step is to run an interventional study over time to see whether long-term MUFA intake influences brain network organization and intelligence.

Read more at Science Daily

The Number of Monarch Butterflies in Western North America Is Plummeting

A Monarch butterfly is viewed in a forest of eucalyptus trees at the Goleta Butterfly Preserve on February 10, 2015, in Goleta, California.

Up until the 1980s, around 10 million monarch butterflies spent their winters in coastal California. Their arrival in places like Pacific Grove, aka Butterfly Town USA, was admired by locals and visitors eager to witness these beautiful, delicate insects and their distinctive orange wings.

While Butterfly Town USA still has its renowned monarch butterfly sanctuary, this and other places across western North America have seen numbers of the pollinating insects plummet.

“Today there are barely 300,000,” said Cheryl Schultz, an associate professor of Washington State University, Vancouver.

She and her colleagues arrived at that estimate after combining data from hundreds of volunteers who have participated in the Xerces Society for Invertebrate Conservation’s Western Monarch Thanksgiving Count since 1997, with earlier monarch counts conducted by amateur and professional butterfly enthusiasts in the 1980s and 1990s. The findings are published in the journal Biological Conservation.

Western monarchs form a distinct population segment from eastern monarchs, much like the relationship between different runs of salmon in the Pacific Northwest. Western monarchs intermix with eastern monarchs from time to time, but are not a different species or subspecies.

Like eastern monarchs, which overwinter in Mexico, western monarchs have an impressive and lengthy migration. They spend the winter months in forested groves along coastal California before fanning out in the spring to lay their eggs on milkweed and consume nectar from flowers in Arizona, California, Nevada, Oregon, Washington, Idaho, and Utah. They then return to their coastal overwintering sites in the fall.

A new study finds monarch butterfly populations from western North America have declined far more dramatically than was previously known and face a greater risk of extinction than eastern monarchs.

In a second paper, Sarina Jepsen, endangered species program director at Xerces, and her team list the top 25 highest priority overwintering sites for conservation.

“Among the sites with the most severe population drops are Lighthouse Field and Natural Bridges, which are both in Santa Cruz,” Jepsen said. “However, Santa Cruz is in the core of the overwintering range, and as the population has gotten smaller, many of the peripheral sites in the San Diego area and north of San Francisco no longer host monarchs in the winter.”

Schultz’s colleague Elizabeth Crone, a professor of biology at Tufts University, said some conservation biologists mistakenly assume monarch butterflies are in decline primarily because the insects cannot find enough places to lay their eggs. Instead, research indicates multiple factors could be causing the decline. Drought severity may be one, along with loss of milkweed-rich grasslands throughout the West, and particularly in California’s Central Valley.

“We also know that the use of many insecticides and herbicides have increased dramatically in the past couple of decades in some parts of the West that monarchs use,” Jepsen said. “We have documented the loss of dozens of monarch overwintering sites along coastal California, as housing developments replace forested habitat, and dozens more sites have been degraded.”

Some environmentalists suspect that increased use of glyphosate and neonicotinoid chemicals in crop fields hurt butterflies, along with other pesticides and herbicides. The use of chemicals, however, can actually come back to hurt farmers, since butterflies are pollinators of many plants.

“Monarchs, in particular, are toxic to birds, which allows other, non-toxic butterflies to survive because they look like monarchs and therefore don’t get eaten,” Crone explained.

She added that artists and engineers have observed monarchs for inspiration. Navigation systems, for example, have even been modeled upon butterfly flight.

The insect’s beauty, however, is what tends to captivate us the most.

“So many people spent their childhoods watching monarch caterpillars transform into a chrysalis, then emerge as butterflies,” Jepsen said. “The story of their migration is amazing.”

A monarch butterfly on a milkweed plant

Given the new data, all of the researchers now believe that western monarch butterflies should be listed as a threatened species under the Endangered Species Act. Crone explained that the listing would help to motivate agencies and landowners to participate in conservation practices.

“Listing would also substantially raise awareness of the plight of monarchs and similar species,” she continued. “For example, many other butterfly species also seem to be less abundant now than 30 years ago.”

The researchers said homeowners can take part in the butterfly conservation effort too. They are encouraged to plant native, locally sourced milkweed plants. Xerces has a milkweed seed finder to help locate vendors. Homeowners should also include other native plants and monarch-attracting wildflowers in their gardens.

“Some common garden flowers, like petunias and geraniums, don’t produce nectar,” Crone explained. “Others, like pansies, provide nectar and are used by native insects.”

The scientists also urge homeowners to minimize “homogenous” land surfaces, like pavement and grass-only lawns, and to support organic and other wildlife-friendly gardening and farming practices.

At present, Schultz and her team are monitoring where and when monarchs breed across the West. They are working across five states: California, Nevada, Idaho, Oregon, and Washington. They are also involved in a joint five-year project evaluating the importance of species interactions for population viability of rare butterflies, and how these interactions might be impacted by climate change.

The scientists are in talks with scientists in Mexico about collaborating on the larger eastern monarch population that overwinters in Mexico.

The researchers encourage the public to participate in projects in North America, in addition to the Western Monarch Thanksgiving Count, aimed at collecting data about butterfly populations. These projects include the Western Monarch Milkweed Mapper, Project Monarch Health, Journey North, and the Monarch Larva Monitoring Project.

Read more at Seeker

Saturn’s Icy Moons Are a Little Less Mysterious Thanks to Cassini’s Long Mission

An artist rendering of the Cassini spacecraft entering orbit around Saturn.

The Cassini spacecraft will take a death plunge into Saturn next on September 15 after more than a decade observing the planet and its moons. Perhaps its greatest contribution to science is helping us learn about the many icy moons circling Saturn and its elegant rings. Scientists are interested in finding life outside of Earth, to see if it's similar to what we have on our own planet.

Icy moons are likely our best shot at finding microbes. That's because they have a ready source of heat — in this case, tidal interactions with Saturn — as well as abundant water in the form of oceans and lakes. Cassini's observations from orbit showed us geysers, oceans, and other signs of liquid. Future missions on the drawing board might use submarines or little rovers to take a close-up look at the moons.

Here are some of Cassini's key discoveries.

Enceladus

Enceladus is perhaps the most famous icy moon of Saturn, as Cassini has tracked at least 101 geysers spouting water into space from "tiger stripes" or cracks in the ice. Late in Cassini's mission, in April 2017, researchers announced that Cassini detected hydrogen in Enceladus’s plumes, which suggests that there are hydrothermal vents in the ocean below. These vents are warm spots that, on Earth, are places where creatures tend to congregate as it is a ready-made source of energy and food.

Photograph of Enceladus, the sixth-largest moon of Saturn

Perhaps the most notable discovery was in September 2015, when researchers found evidence of a global ocean, based on how the moon wobbles as it orbits Saturn. Other key discoveries included evidence that Enceladus’s spouting water lands in Saturn's atmosphere and that the south polar area changes over time, hinting at evidence of Earth-like plate tectonics. It also recorded multiple observations of the geysers’ composition, structure, and eruption frequency.

This view of Titan, the largest of Saturn's 56 known moons, was taken on 26 December 2005 and reveals structure in the moon's complex atmosphere.

Titan

Scientists knew very little about the surface of Titan because observations showed only an orange blob. Cassini changed that forever, using radar to reveal a world of hydrocarbon-filled lakes that shift with the changing seasons.

Its mission began with the deployment of the European Space Agency’s Huygens lander, which flew to the surface in January 2005. Huygens made the first measurements from the lower atmosphere, finding — to the surprise of investigators — methane, even though the gas is typically broken down by the sun. This means that there is likely a renewable source of methane somewhere on Titan.

Cassini also made several science discoveries of its own, such as finding a disappearing and reappearing island on Titan's surface, watching the evolution of Titan's seasons, and finding evidence of an underground ocean.

Rhea, moon of the planet Saturn, assembled from a composition of multiple photos taken by the Voyager 1 spacecraft, 1980

Rhea

While Rhea is not reported on as much as Titan and Enceladus, it is notable because of its size — it's the second-largest of Saturn’s moon, although at 475 miles (764 kilometers) it is only a third of the radius of Titan. Its surface is likely made of water ice because it is so reflective of light. High reflectivity is also apparent on the small moons Dione and Tethys.

Cassini showed that Rhea likely has a mixture of ice and rock underneath its surface. Cassini also revealed canyons on Rhea — showing that the moon must have had tectonic movement long ago — as well as a wispy atmosphere of oxygen and carbon dioxide. Rings were also found in 2008.

This NASA Cassini Spacecraft image obtained 24 November, 2004 shows Saturn's icy moon Tethys

Tethys

Tethys, a small icy moon of Saturn, has mysterious red arcs on its surface that Cassini first detected in 2004. The scientists are not sure about the source of the arcs, but speculation includes chemical impurities in the ice, or perhaps fractures that are just a little bit smaller than what Cassini's cameras were able to resolve.

Cassini also found a heat signature on Titan that resembles the shape of the 1980s video game character Pac-Man. The approximately V-shaped structure likely happens when electrons, traveling at high speed around Saturn, crash onto the moon. The electron collision turns the soft surface into hard ice, which would not heat up as fast during the day, or cool down as quickly during the night, compared to the surrounding surface. A similar heat signature is present on Mimas.

Read more at Seeker

Pluto features given first official names

Pluto's first official surface-feature names are marked on this map, compiled from images and data gathered by NASA's New Horizons spacecraft during its flight through the Pluto system in 2015.

The IAU has assigned names to fourteen geological features on the surface of Pluto. The names pay homage to the underworld mythology, pioneering space missions, historic pioneers who crossed new horizons in exploration, and scientists and engineers associated with Pluto and the Kuiper Belt. This is the first set of official names of surface features on Pluto to be approved by the IAU, the internationally recognised authority for naming celestial bodies and their surface features.

NASA's New Horizons team proposed the names to the IAU following the first reconnaissance of Pluto and its moons by the New Horizons spacecraft. Some of the names were suggested by members of the public during the Our Pluto campaign, which was launched as a partnership between the IAU, the New Horizons project and the SETI Institute. Other names had been used informally by the New Horizons science team to describe the many regions, mountain ranges, plains, valleys and craters discovered during the first close-up look at the surfaces of Pluto and its largest moon, Charon.

"We're very excited to approve names recognising people of significance to Pluto and the pursuit of exploration as well as the mythology of the underworld. These names highlight the importance of pushing to the frontiers of discovery," said Rita Schulz, chair of the IAU Working Group for Planetary System Nomenclature. "We appreciate the contribution of the general public in the form of their their naming suggestions and the New Horizons team for proposing these names to us."

More names are expected to be proposed to the IAU, both for Pluto and for its moons. "The approved designations honour many people and space missions who paved the way for the historic exploration of Pluto and the Kuiper Belt, the most distant worlds ever explored," said Alan Stern, New Horizons Principal Investigator from the Southwest Research Institute (SwRI) in Boulder, Colorado.

The approved Pluto surface feature names are listed below.

Tombaugh Regio honours Clyde Tombaugh (1906-1997), the U.S. astronomer who discovered Pluto in 1930 from Lowell Observatory in Arizona.

Burney crater honors Venetia Burney (1918-2009), who as an 11-year-old schoolgirl suggested the name "Pluto" for Clyde Tombaugh's newly discovered planet. Later in life she taught mathematics and economics.

Sputnik Planitia is a large plain named after Sputnik 1, the first space satellite, launched by the Soviet Union in 1957.

Tenzing Montes and Hillary Montes are mountain ranges honouring Tenzing Norgay (1914-1986) and Sir Edmund Hillary (1919-2008), the Indian/Nepali Sherpa and New Zealand mountaineer who were the first to reach the summit of Mount Everest and return safely.

Al-Idrisi Montes honours Ash-Sharif al-Idrisi (1100-1165/66), a noted Arab mapmaker and geographer whose landmark work of medieval geography is sometimes translated as "The Pleasure of Him Who Longs to Cross the Horizons."

Djanggawul Fossae defines a network of long, narrow depressions named for the Djanggawuls, three ancestral beings in indigenous Australian mythology who travelled between the island of the dead and Australia, creating the landscape and filling it with vegetation.

Sleipnir Fossa is named for the powerful, eight-legged horse of Norse mythology that carried the god Odin into the underworld.

Virgil Fossae honors Virgil, one of the greatest Roman poets and Dante's fictional guide through hell and purgatory in the Divine Comedy.

Adlivun Cavus is a deep depression named for Adlivun, the underworld in Inuit mythology.

Hayabusa Terra is a large land mass saluting the Japanese spacecraft and mission (2003-2010) that returned the first asteroid sample.

Voyager Terra honours the pair of NASA spacecraft, launched in 1977, that performed the first "grand tour" of all four giant planets. The Voyager spacecraft are now probing the boundary between the Sun and interstellar space.

Tartarus Dorsa is a ridge named for Tartarus, the deepest, darkest pit of the underworld in Greek mythology.

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Direct evidence of sea level 'fingerprints' discovered

"Scientists have a solid understanding of the physics of sea level fingerprints, but we've never had a direct detection of the phenomenon until now," says study co-author Isabella Velicogna, a UCI professor of Earth system science and Jet Propulsion Laboratory research scientist, shown here on an expedition to Greenland.

Researchers from the University of California, Irvine and NASA's Jet Propulsion Laboratory have reported the first observation of sea level "fingerprints," tell-tale differences in sea level rise around the world in response to changes in continental water and ice sheet mass. The team's findings were published in the American Geophysical Union journal Geophysical Research Letters.

"Scientists have a solid understanding of the physics of sea level fingerprints, but we've never had a direct detection of the phenomenon until now," said co-author Isabella Velicogna, UCI professor of Earth system science and JPL research scientist.

As ice sheets and glaciers undergo climate-related melting, they alter Earth's gravity field, which causes nonuniform sea level change. Certain regions, particularly in the middle latitudes, are harder hit. For instance, Antarctica-generated sea level rise in California and Florida is as much as 52 percent greater than what's average in the rest of the world.

The team calculated sea level fingerprints using time-variable gravity data collected by the twin satellites of NASA's Gravity Recovery & Climate Experiment between April 2002 and October 2014. During that time, according to the study, the global mean sea level grew by about 1.8 millimeters per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica, and 30 percent from mountain glaciers. The scientists verified their calculations of sea level fingerprints associated with these mass variations via ocean-bottom pressure readings from stations in the tropics.

"It was very exciting to observe the sea level fingerprints in the tropics, where they were not expected to be detectable," said lead author Chia-Wei Hsu, a graduate student researcher at UCI. "In the tropics, sea level fingerprint values are very close to global average sea level values, making them harder to detect."

Read more at Science Daily

Biologists slow aging, extend lifespan of fruit flies

Fruit flies' mitochondria (in green) at 10 days (top left), 28 days (top right) and 37 days old (both bottom images). At bottom right, the mitochondria have returned to a more youthful state after UCLA biologists increased the fly's level of a protein called Drp1.

UCLA biologists have developed an intervention that serves as a cellular time machine -- turning back the clock on a key component of aging.

In a study on middle-aged fruit flies, the researchers substantially improved the animals' health while significantly slowing their aging. They believe the technique could eventually lead to a way to delay the onset of Parkinson's disease, Alzheimer's disease, cancer, stroke, cardiovascular disease and other age-related diseases in humans.

The approach focuses on mitochondria, the tiny power generators within cells that control the cells' growth and determine when they live and die. Mitochondria often become damaged with age, and as people grow older, those damaged mitochondria tend to accumulate in the brain, muscles and other organs. When cells can't eliminate the damaged mitochondria, those mitochondria can become toxic and contribute to a wide range of age-related diseases, said David Walker, a UCLA professor of integrative biology and physiology, and the study's senior author.

In the new research, Walker and his colleagues found that as fruit flies reach middle age -- about one month into their two-month lifespan -- their mitochondria change from their original small, round shape.

"We think the fact that the mitochondria become larger and elongated impairs the cell's ability to clear the damaged mitochondria," Walker said. "And our research suggests dysfunctional mitochondria accumulate with age, rather than being discarded."

The study, published Sept. 6 in the journal Nature Communications, reports that the UCLA scientists removed the damaged mitochondria by breaking up enlarged mitochondria into smaller pieces -- and that when they did, the flies became more active and more energetic and had more endurance. Following the treatment, female flies lived 20 percent longer than their typical lifespan, while males lived 12 percent longer, on average.

The research highlights the importance of a protein called Drp1 in aging. At least in flies and mice, levels of Drp1 decline with age.

To break apart the flies' mitochondria, Anil Rana, a UCLA project scientist and the study's lead author, increased their levels of Drp1. This enabled the flies to discard the smaller, damaged mitochondria, leaving only healthy mitochondria. Drp1 levels were increased for one week starting when the flies were 30 days old.

At essentially the same time, Rana demonstrated that the flies' Atg1 gene also plays an essential role in turning back the clock on cellular aging. He did this by "turning off" the gene, rendering the flies' cells unable to eliminate the damaged mitochondria. This proved that Atg1 is required to reap the procedure's anti-aging effects: While Drp1 breaks up enlarged mitochondria, the Atg1 gene is needed to dispose of the damaged ones.

"It's like we took middle-aged muscle tissue and rejuvenated it to youthful muscle," said Walker, a member of UCLA's Molecular Biology Institute. "We actually delayed age-related health decline. And seven days of intervention was sufficient to prolong their lives and enhance their health."

One specific health problem the treatment addressed was the onset of leaky intestines, which previous research by Walker's team found commonly occurs about a week before fruit flies die. Subsequent research in other laboratories has determined that an increase in intestines' permeability is a hallmark of aging in worms, mice and monkeys. In the UCLA study, the condition was delayed after flies were given more Drp1.

Fruit flies are often used for studies on aging because their short lifespan enables scientists to track the effects of specific treatments within a manageable period of time, and many of the features of aging at the cellular level are similar to those of humans. In addition, scientists have identified all of the fruit fly's genes and know how to switch individual ones on and off.

Walker hopes that a technique similar to the one his team developed for fruit files could eventually help humans by slowing aging and delaying aging-related diseases. He said the fact that the new approach was effective even after a short time is especially significant because long-term use of nearly any drug can have harmful side effects in humans.

Walker said one of the long-term goals of his research is to develop pharmaceuticals that would mimic the effects of Drp1, in order to extend people's lives and lengthen what he calls people's "health spans," meaning the number of healthy years in their lives.

In another part of the experiment, also involving middle-aged fruit flies, the scientists turned off a protein called Mfn that enables mitochondria to fuse together into larger pieces. Doing so also extended the flies' lives and improved their health.

Read more at Science Daily

Human skin cells transformed directly into motor neurons

Scientists have discovered a new way to convert human skin cells directly into motor neurons (above). The technique, developed at Washington University School of Medicine in St. Louis, could help researchers better understand diseases of motor neurons, such as amyotrophic lateral sclerosis. Human motor neurons are difficult to study since they can't be taken from living patients. The motor neurons pictured were converted from skin cells sampled from a healthy 42-year-old woman.

Scientists working to develop new treatments for neurodegenerative diseases have been stymied by the inability to grow human motor neurons in the lab. Motor neurons drive muscle contractions, and their damage underlies devastating diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy, both of which ultimately lead to paralysis and early death.

In new research, scientists at Washington University School of Medicine in St. Louis have converted skin cells from healthy adults directly into motor neurons without going through a stem cell state.

The technique makes it possible to study motor neurons of the human central nervous system in the lab. Unlike commonly studied mouse motor neurons, human motor neurons growing in the lab would be a new tool since researchers can't take samples of these neurons from living people but can easily take skin samples.

The study is published Sept. 7 in the journal Cell Stem Cell.

Avoiding the stem cell phase eliminates ethical concerns raised when producing what are called pluripotent stem cells, which are similar to embryonic stem cells in their ability to become all adult cell types. And importantly, avoiding a stem cell state allows the resulting motor neurons to retain the age of the original skin cells and, therefore, the age of the patient. Maintaining the chronological age of these cells is vital when studying neurodegenerative diseases that develop in people at different ages and worsen over decades.

"In this study, we only used skin cells from healthy adults ranging in age from early 20s to late 60s," said senior author Andrew S. Yoo, PhD, an assistant professor of developmental biology. "Our research revealed how small RNA molecules can work with other cell signals called transcription factors to generate specific types of neurons, in this case motor neurons. In the future, we would like to study skin cells from patients with disorders of motor neurons. Our conversion process should model late-onset aspects of the disease using neurons derived from patients with the condition."

"Going back through a pluripotent stem cell phase is a bit like demolishing a house and building a new one from the ground up," Yoo said. "What we're doing is more like renovation. We change the interior but leave the original structure, which retains the characteristics of the aging adult neurons that we want to study."

The ability of scientists to convert human skin cells into other cell types, such as neurons, has the potential to enhance understanding of disease and lead to finding new ways to heal damaged tissues and organs, a field called regenerative medicine.

To convert skin cells into motor neurons, the researchers exposed the skin cells to molecular signals that are usually present at high levels in the brain. Past work by Yoo and his colleagues -- then at Stanford University -- showed that exposure to two short snippets of RNA turned human skin cells into neurons. These two microRNAs -- called miR-9 and miR-124 -- are involved with repackaging the genetic instructions of the cell.

In the new study, the researchers extensively characterized this repackaging process, detailing how skin cells reprogrammed into generic neurons then can be guided into specific types of neurons. They found that genes involved in this process become poised for expression but remain inactive until the correct combination of molecules is provided. After much experimentation with multiple combinations, the researchers found that adding two more signals to the mix -- transcription factors called ISL1 and LHX3 -- turned the skin cells into spinal cord motor neurons in about 30 days.

The combination of signals -- microRNAs miR-9 and miR-124 plus transcription factors ISL1 and LHX3 -- tells the cell to fold up the genetic instructions for making skin and unfurl the instructions for making motor neurons, according to Yoo and the study's co-first authors, Daniel G. Abernathy and Matthew J. McCoy, doctoral students in Yoo's lab; and Woo Kyung Kim, PhD, a postdoctoral research associate.

Another past study from Yoo's team showed that exposure to the same two microRNAs, miR-9 and miR-124, plus a different mix of transcription factors could turn skin cells into a different type of neuron. In that case, the skin cells became striatal medium spiny neurons, which are affected in Huntington's disease -- an inherited, eventually fatal genetic disorder that causes involuntary muscle movements and cognitive decline beginning in middle adulthood.

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Discovery of boron on Mars adds to evidence for habitability

A selfie of the NASA Curiosity rover at the Murray Buttes in Gale Crater, Mars, a location where boron was found in light-toned calcium sulfate veins.

The discovery of boron on Mars gives scientists more clues about whether life could have ever existed on the planet, according to a paper published in the journal Geophysical Research Letters.

"Because borates may play an important role in making RNA -- one of the building blocks of life -- finding boron on Mars further opens the possibility that life could have once arisen on the planet," said Patrick Gasda, a postdoctoral researcher at Los Alamos National Laboratory and lead author on the paper. "Borates are one possible bridge from simple organic molecules to RNA. Without RNA, you have no life. The presence of boron tells us that, if organics were present on Mars, these chemical reactions could have occurred."

RNA (ribonucleic acid) is a nucleic acid present in all modern life, but scientists have long hypothesized an "RNA World," where the first proto-life was made of individual RNA strands that both contained genetic information and could copy itself. A key ingredient of RNA is a sugar called ribose. But sugars are notoriously unstable; they decompose quickly in water. The ribose would need another element there to stabilize it. That's where boron comes in. When boron is dissolved in water -- becoming borate -- it will react with the ribose and stabilize it for long enough to make RNA. "We detected borates in a crater on Mars that's 3.8 billion years old, younger than the likely formation of life on Earth," said Gasda. "Essentially, this tells us that the conditions from which life could have potentially grown may have existed on ancient Mars, independent from Earth."

The boron found on Mars was discovered in calcium sulfate mineral veins, meaning the boron was present in Mars groundwater, and provides another indication that some of the groundwater in Gale Cater was habitable, ranging between 0-60 degrees Celsius (32-140 degrees Fahrenheit) and with neutral-to-alkaline pH.

The boron was identified by the rover's laser-shooting ChemCam (Chemistry and Camera) instrument, which was developed at Los Alamos National Laboratory in conjunction with the French space agency. Los Alamos' work on discovery-driven instruments like ChemCam stems from the Laboratory's experience building and operating more than 500 spacecraft instruments for national defense.

The discovery of boron is only one of several recent findings related to the composition of Martian rocks. Curiosity is climbing a layered Martian mountain and finding chemical evidence of how ancient lakes and wet underground environments changed, billions of years ago, in ways that affected their potential favorability for microbial life.

As the rover has progressed uphill, compositions trend toward more clay and more boron. These and other chemical variations can tell us about conditions under which sediments were initially deposited and about how later groundwater moving through the accumulated layers altered and transported dissolved elements, including boron.

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Accretion-powered pulsar reveals unique timing glitch

Composite image of the X-ray pulsar SXP 1062 surrounded by the supernova remnant. The false-color image combines X-ray (blue) and optical data (oxygen: green, hydrogen: red).

The discovery of the largest timing irregularity yet observed in a pulsar is the first confirmation that pulsars in binary systems exhibit the strange phenomenon known as a 'glitch'. The study is published in the journal Monthly Notices of the Royal Astronomical Society.

Pulsars are one possible result of the final stages of evolution of massive stars. Such stars end their lives in huge supernova explosions, ejecting their stellar materials outwards into space and leaving behind an extremely dense and compact object; this could either be a white dwarf, a neutron star or a black hole.

If a neutron star is left, it may have a very strong magnetic field and rotate extremely quickly, emitting a beam of light that can be observed when the beam points towards Earth, in much the same way as a lighthouse beam sweeping past an observer. To the observer on Earth, it looks as though the star is emitting pulses of light, hence the name 'pulsar'.

Now a group of scientists from the Middle East Technical University and Baskent University in Turkey have discovered a sudden change in the rotation speed of the peculiar pulsar SXP 1062. These jumps in frequency, known as 'glitches', are commonly seen in isolated pulsars, but have so far never been observed in binary pulsars (pulsars orbiting with a companion white dwarf or neutron star) such as SXP 1062.

SXP 1062 is located in the Small Magellanic Cloud, a satellite galaxy of our own Milky Way galaxy, and one of our nearest intergalactic neighbours at 200,000 light years away. Lead author of the study, Mr M. Mirac Serim, a senior PhD student working under the supervision of Prof Altan Baykal, said, "This pulsar is particularly interesting, since as well as orbiting its partner star as part of a binary pair, it is also still surrounded by the remnants of the supernova explosion which created it."

The pulsar is thought to pull in the leftover material from the supernova explosion, feeding on it in a process known as accretion. The team believe that the size of the glitch is due to the gravitational influence of its companion star and this accretion of the surrounding remnant material, which together exert large forces on the crust of the neutron star. When these forces are no longer sustainable, a rapid change in internal structure transfers momentum to the crust, changing the rotation of the pulsar very suddenly and producing a glitch.

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The Cuckolding Cuckoo Bird's Deceit Is Even Greater Than We Imagined

A cuckoo flies from a perch in a woodland.

The common cuckoo, notorious for evading parental duty by hiding her eggs in the nests of other brooding birds, is even more devious than previously thought, scientists revealed on Monday.

After laying an egg, the female distracts the owner of the nest — a reed warbler, in this case — essentially by frightening the poor bird out of its wits, they said.

The cuckoo gives a “chuckle” that mimics the call of the sparrowhawk -- which loves to snack on warbler flesh -- before abandoning her egg among the warbler’s clutch and flying off to freedom.

“This hawk-like chuckle call increases the success of parasitism by diverting host parents’ attention away from the clutch and towards their own safety,” a duo of Cambridge University researchers wrote in the journal Nature Ecology & Evolution. “As a result, the female cuckoo might have ‘the last laugh’ in this particular battle.”

The bird whose behavior gave us the word “cuckoldry” is an example of a “brood parasite” — birds, insects, or fish that trick others into raising their young.

This is often at the expense of the foster parents’ own offspring.

To avoid getting caught — which will lead to the imposter egg being kicked out of the nest — the cuckoo has developed some nifty tricks, including matching its egg coloring to that of its target, for camouflage.

The bird has also adopted “remarkable secrecy and speed” in depositing its egg, said the team.

For this reason, scientists have battled to understand why the cuckoo would risk exposure by “chuckling” so soon after committing its crime.

‘Kwik-kwik-kwik’

The Cambridge team theorized the purpose was to distract the warbler with fear.

To test this, they played the recorded calls of male and female cuckoos, a sparrowhawk, and a random, non-threatening bird — a collared dove, to reed warblers.

Only the male cuckoo makes the signature sound copied in pendulum clocks. The female utters a laughter-like “kwik-kwik-kwik” not dissimilar in frequency to the sparrowhawk’s “kiii-kiii-kiii.”

The warblers, they observed, reacted with the same vigilance to female cuckoo calls as to hawk calls, and diverted attention away from their clutch.

The warblers ignored male cuckoo and collared dove calls.

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How African Wild Dogs Sneeze at Each Other to Communicate

An African wild dog in a pack.

African wild dogs (Lycaon pictus) once flourished from the mountainous areas of sub-Saharan regions to the deserts of Africa. Now endangered, these pack-living relatives of domesticated dogs still have a population in Botswana, where researchers like Neil Jordan — a research fellow at the University of New South Wales Sydney and Taronga Conservation Society Australia — study them.

While spending immersive hours of observation in the field is less common among researchers these days, Jordan and his colleagues who work with the Botswana Predator Conservation Trust (BPCT) believe this time is well spent. Such efforts often require long hours of watching resting carnivores and waiting for them to become active, such as by leaving their rest site to go hunting.

“It was during these long waits and subsequent high energy rallies that I first noticed a possible relationship between sneezing and leaving,” Jordan said. “I could predict whether or not they were going to move off by listening to the number of sneezes.”

To test the unorthodox theory, he and his team collected data from five packs of African wild dogs in and around the Moremi Game Reserve in the Okavango Delta from June 2014 to May 2015. VHF radio collars affixed to at least one dog in each pack allowed the scientists to track the animals.

Through direct observations and video recordings, the researchers documented 68 “social rallies” that occurred among the five packs. Such rallies are the times in which these dogs interact with each other.

A pack of African wild dogs shares an impala carcass for a meal.

The researchers were amazed that the data confirmed Jordan’s suspicions: the more sneezes that occurred, the more likely it was that a given pack moved off and started hunting.

“The sneeze acts like a type of voting system,” Jordan said.

The findings, published in the journal Proceedings of the Royal Society B, suggest that dogs are not just simply clearing their airways when they sneeze.

Lead author Reena Walker of Brown University said there is evidence supporting that domestic dogs sneeze when they’re excited or anxious. Such “unvoiced” or mechanical sounds turn out to be pervasive in dogs and other canids.

“Panting, huffing, and sneezing are signals observed in domestic dogs, coyotes, and jackals that use the exhalation or inhalation of air as a sound to convey an emotional state — messages that range from ‘let’s play’ to ‘I see an unfamiliar object’ to ‘I’m scared,’” Walker said.

“So, finding that sneezes are a signal utilized by African wild dogs is not out of the realm of already understood means of communication in canids,” she continued, “but it is the first time we have seen a signal like a sneeze used in the context of group decision making.”

African wild dogs play fighting.

Co-author Andrew King of Swansea University added that the sneezes act as a type of quorum, where the sneezes have to reach a certain threshold before the pack changes its activity.

“Quorum-like responses occur in lots of different species,” King said. “For example, ants or bees use quorums when moving to new nest sites. In the case of bees, which dance to direct one another to new sites, once the number of bees at a site reaches a quorum, the bees begin an additional recruitment strategy to dancing, known as piping.”

Meerkats also use quorums to “vote” by emitting moving calls before heading off to a new foraging patch. Prior research has also determined that white-faced capuchin monkeys emit trills and, if the vocalizations reach a certain threshold, the monkeys will collectively depart.

Even bacteria, King said, “use quorums to coordinate gene expression according to the density of their local population,” so the process does not necessarily require substantial, if any, brain power.

For African wild dogs, the sneezing acts like democratic voting, such that each individual in a pack may participate and have a vote count. As for human voting, however, the system does not always seem fair.

The researchers noticed if the dominant male and female within each African wild dog pack sneezed, fewer additional sneezes were needed before the group left the resting site.

“However,” Walker said, “if the dominant pair were not engaged, more sneezes were needed — approximately 10 — before the pack would move off.”

The researchers are not yet certain if the sneezes of dominant and subdominant dogs are acoustically different. How dominance is established in a pack also remains unclear, but age appears to be a factor, with younger dogs tending to be more dominant, Jordan said.

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New Class of Black Hole 100,000 Times Larger Than the Sun Detected in Milky Way

Illustration of a spiral galaxy and black hole.

Black holes are notoriously hard to find, since they don’t emit any light. But there’s one particular size of black hole that has been especially evasive, even though astronomers have theorized that they should be plentiful.

While there is ample evidence for the extra-large, supermassive kind as well as the much smaller, stellar-mass black holes, the in-between size, or so-called "intermediate mass" black holes, have thus far eluded detection.

Astronomers now think they have found one — a black hole 100,000 times more massive than the sun, lurking inside a gas cloud near the middle of the Milky Way. It's located not far from supermassive black hole called Sagittarius A* that lies at the dead center of our galaxy.

Researchers think that intermediate-mass black holes (IMBH) could be a missing link that helps explain how supermassive black holes are formed.

“The observations are rather compelling, and it's going to be exciting as astronomers follow up this source,” astronomer and black hole researcher Kevin Schawinski of the Swiss Federal Institute of Technology in Zurich, who was not involved in the current study, told Seeker.

Last year, a team of researchers led by Tomoharu Oka from Keio University in Japan discovered “a peculiar molecular cloud” named CO–0.40–0.22, which was located 200 light-years away from the Milky Way’s center. The cloud had what the team called “extremely broad velocity width,” meaning it was moving very fast with varying velocities they could not explain. The researchers suspected a massive object was hiding inside, providing the gravitational kick for the variable and speedy gas flows.

Oka and his team followed up their observations using the Atacama Large Millimeter/submillimeter Array (ALMA) Observatory in Chile, and have now reported their findings in a paper published this week in the journal Nature Astronomy. With ALMA’s extremely high-precision data, the researchers were able to confirm the wide distribution of velocities inside the gas cloud, but they also found a telltale clue: a spectrum of radio waves very similar to what Sagittarius A* produces, but about 500 times fainter.

“Based on the careful analysis of gas kinematics, we concluded that a compact object with a mass of about [100,000] solar masses is lurking in this cloud,” Oka and his team wrote. They said numerical simulations suggest that CO–0.40–0.22 is one of the most promising candidates for an intermediate-mass black hole.

“If confirmed by others, having such an intermediate mass black hole in our Milky Way is going to open up so many exciting possibilities,” Schawinski said via email. “If there's one, maybe there are others?”

While astronomers understand how stellar-mass black holes form, the origins of supermassive black holes remain unknown. A stellar-mass black hole forms when a massive star goes supernova. This explosion, which can outshine an entire galaxy of stars for a short period of time, leaves behind the small, heavy core of a star. If this core is massive enough, it will collapse on itself and form a black hole. A typical stellar-class of black hole can be between approximately three and 10 solar masses.

Supermassive black holes have masses ranging from millions to billions of solar masses. Why they are so incredibly massive isn't well understood, but astronomers think they may form out of the collapse of gigantic clouds of gas during the early stages of the formation of a galaxy. Since the SMBHs are at the center of galaxies, they have ample stars, gas, and dust to feed on, so they can grow quickly. And since many galaxies collide repeatedly during their long lifetimes, the supermassive black holes collide and coalesce into even heavier supermassive black holes.

How do intermediate-mass black holes form? One idea is that they come from runaway coalescence of stars in young compact star clusters. If these are plentiful, as astronomers theorize, they could merge at the center of a galaxy to form a supermassive black hole. In fact, since CO–0.40–0.22 is so close to the black hole at the center of our galaxy, it very likely could be gobbled up by Sagittarius A*.

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Voyager 1, the Farthest-Reaching Spacecraft Ever, Marks 40 Years in Space

In 1977, NASA's Voyager 1 and 2 spacecraft began their pioneering journey across the solar system to visit the giant outer planets. Now, the Voyagers are hurtling through unexplored territory on their road trip beyond our solar system. Along the way, they are measuring the interstellar medium, the mysterious environment between stars that is filled with the debris from long-dead stars.

NASA's Voyager 1 probe lifted off on Sept. 5, 1977, a few weeks after its twin, Voyager 2. Together, the two Voyager spacecraft performed an epic "Grand Tour" of the solar system's giant planets, flying by Jupiter, Saturn, Uranus, and Neptune.

But their work didn't stop there. Both spacecraft kept flying, pushing farther and farther into the dark, cold, and little-known realms far from the sun.

Then, on Aug. 25, 2012, Voyager 1 popped free into interstellar space, becoming the first human-made object ever to do so. Voyager 2, which took a different route through the solar system, will likely exit the sun's sphere of influence in the next few years as well, mission team members have said.

And both spacecraft still have their eyes and ears open, all these decades later.

"It's amazing that the two spacecraft are still working after 40 years," said Ed Stone, who has been a Voyager project scientist since the mission's inception in 1972.

"When we launched, the Space Age itself was only 20 years old, so this is an unparalleled journey, and we're still in the process of seeing what's out there," Stone, who's based at the California Institute of Technology in Pasadena, told Space.com.

As of Friday (Sept. 1), Voyager 1 was a whopping 12.97 billion miles (20.87 billion kilometers) from Earth — more than 139 times the distance from our planet to the sun. Voyager 2 was about 10.67 billion miles (17.17 billion km) from its home planet.

An artist's concept of one of the NASA's twin Voyager spacecraft in space. Voyager 1 and Voyager 2 are humanity's farthest and longest-lived spacecraft, launching 40 years ago in August and September of 1977.

The Grand Tour

Voyager 1 cruised by Jupiter in March 1979 and Saturn in November 1980. This latter encounter also included a close flyby of Saturn's huge moon Titan.

Voyager 2 pulled off its own Jupiter-Saturn double, flying by those two planets in July 1979 and August 1981, respectively. Then, the spacecraft had encounters with Uranus, in January 1986, and Neptune, in August 1989.

During this Grand Tour, both spacecraft beamed home data that surprised and excited scientists.

For example, before the Voyagers launched, the only known active volcanoes were here on Earth. But Voyager 1 spotted eight erupting volcanoes on the Jupiter moon Io, showing that the little world is far more volcanically active than our own planet.

The mission also determined that Titan has a nitrogen-dominated atmosphere, just as Earth does.

"It may, in some important ways, resemble what the Earth's atmosphere was like before life evolved and created the oxygen that we all breathe," Stone said.

Furthermore, Voyager observations suggested that the Jupiter moon Europa may harbor an ocean of water beneath its icy crust — a notion that subsequent NASA missions have pretty much confirmed.

"I think what Voyager has done is reveal how diverse the planets and the moons and the rings, and the magnetic fields of the planets, are," Stone said. "Our terracentric view was just much narrower than, in fact, reality."

Interstellar ambassadors

Voyager 1 has found that cosmic radiation is incredibly intense beyond the sun's protective bubble, Stone said. The probe is also revealing how the "wind" of charged particles from the sun interact with the winds of other stars.

Meanwhile, Voyager 2 is studying the environment near the solar system's edge. After it enters interstellar space, Voyager 2 will make its own measurements, revealing more about this mysterious region.

But this work cannot go on forever.

The Voyagers are powered by radioisotope thermoelectric generators, which convert the heat produced by the radioactive decay of plutonium-238 into electricity. And that heat is waning.

"We have about 10 years or so of power remaining until we have only enough to power the spacecraft itself, without any of the instruments," Stone said.

But even after the probes power down, they'll continue speeding through the cosmos for eons, making one lap around the Milky Way every 225 million years.

Read more at Seeker

A Low-Fat, High-Carb Diet Is Actually Bad for Your Health

It’s hard to be a healthy eater. For decades, we’ve been told that fat — especially the saturated fat found in butter, meat, and fried foods — is the worst thing for our hearts. Dietary fat raises cholesterol levels, after all, which in turn raises the risk of getting heart disease or suffering a fatal heart attack. But a number of recent studies have called into question the “fat-equals-heart-attack” hypothesis, potentially upending the traditional notion of what constitutes a healthy diet.

This week, a study published in The Lancet further fueled the controversy by strongly challenging the conventional wisdom that the less fat you eat, the better. By closely tracking the eating habits of more than 135,000 people from 18 countries, researchers found that on a global level, diets higher in fat (35 percent of daily calories) are linked to a 23 percent reduction in the overall risk of death compared to diets that are low in fat (11 percent of daily calories). They also found that a higher-fat diet reduced the risk of stroke — also considered a cardiovascular event — by 18 percent.

“Contrary to popular belief, increased consumption of dietary fats was associated with a lower risk of death,” said lead author Mahshid Dehghan, an investigator at McMaster University’s Population Health Research Institute, in an audio interview posted on The Lancet website. “The association with lower mortality was seen with all major types of fat,” she added, even saturated fat.

The real danger, researchers discovered, is when people replaced dietary fats with large amounts of carbohydrates. According to study data, which included middle and low-income individuals living on five continents, more than half of the world gets 60 percent or more of their daily calories from carbohydrates, and a quarter gets more than 70 percent of their calories from carbs.

While high-fat diets failed to predict mortality, high-carb diets proved to be a killer. Diets where 60 percent or more of the daily calories came from carbs were associated with a 28 percent greater risk of death.

Before you run out and buy a “healthy” dinner of fried chicken and ice cream, it’s important to put the new study into perspective. One of the chief motivations for surveying such a large and diverse population was that most current dietary recommendations are based on Western diets. In general, North Americans and Europeans don’t struggle to eat enough fat. But the push to limit fat intake in the West doesn’t apply to places like China and Africa, where fat intake is low, but carbohydrate consumption is sky high.

"The current focus on promoting low-fat diets ignores the fact that most people's diets in low and middle-income countries are very high in carbohydrates, which seem to be linked to worse health outcomes,” said Dehghan in a statement, emphasizing that dietary recommendations need to be tailored for specific communities. For much of the world’s populations that means cutting back on carbs and beefing up on fats.

Current global dietary guidelines recommend that 55-65 percent of daily calories come from carbohydrates and less than 10 percent should come from saturated fat, but again, those numbers were based on studies performed in North America and Europe. The new global data showed that very low saturated fat intake (less than three percent) was much worse for people than a diet where 13 percent of calories come from saturated fat.

Dehghan and her team recommended a diet that’s 50-55 percent carbs and 35 percent fat, including both saturated and unsaturated fats. The researchers agreed that trans fats, the “hydrogenated” vegetable fats found in some packaged snacks, should be eliminated completely.

Read more at Seeker

NASA Probe Cassini Enters Last Weeks as Historic Saturn Mission Comes to an End

Saturn and its rings.

It might as well be the mission motto: "Saturn continues to surprise us."

That's what Earl Maize, project manager for the Cassini mission at Saturn, said during a news conference on Aug. 29. He was referring to the fact that the inner ring system where the Cassini probe is spending some of its final weeks doesn't have as much dust as scientists anticipated, and is therefore not as harsh on the spacecraft's instruments. If the mission could last longer — if the probe weren't running out of fuel, that is — Maize said he'd love to have Cassini explore that region longer.

This trend of finding surprising or unexpected physical characteristics — of Saturn and its moons — has characterized Cassini's entire 13-year stint in the Saturnian system, the scientists said, and continues to prove true in the probe's very last weeks. On Sept. 15, Cassini will complete its "Grand Finale" set of maneuvers and crash into Saturn's atmosphere, transmitting data back to Earth right up until the spacecraft breaks apart.

On its current trajectory, Cassini has also taken the first-ever in-situ samples of Saturn's atmosphere, and Linda Spilker, the Cassini project scientist, said those early results suggest that the chemical and dynamic interactions between particles from the planet's rings and the planet's upper atmosphere are "more complex … than we had both anticipated."

That's good news, she said, because "scientists love mysteries, and the Grand Finale is providing mysteries for everyone."

A final tally of some notable numbers from Cassini’s long mission.

Ongoing Mysteries

Cassin began its "Grand Finale" in April, and the first fruits of new science from that curtain call are already sprouting, NASA scientists said during today's news briefing.

For the last few months, Cassini has been looping through Saturn's inner ring system and sampling the top of the planet's atmosphere, which is "like dipping our toe in Saturn's atmosphere, in preparation for the final plunge," Spilker said during the news briefing.

From those initial tastes of Saturn's atmosphere, Cassini scientists are already finding "incredible, intriguing information" about how the material from Saturn's ring system mixes with the upper layers of the planet's atmosphere. On Sept. 15, the probe will plummet to depths of up to 9,300 miles (15,000 kilometers).

"By having in-situ sampling of the atmosphere, we can directly measure things like the hydrogen-to-helium ratio," Spilker said. Both Jupiter and Saturn consist largely of hydrogen and helium, but the ratios of these two elements can help scientists learn about how and when those planets formed, as well as the nature of the solar system at that time.

"We can directly measure composition of… constituents at a very, very low level in the atmosphere — things that would be much harder to see from a distance with remote sensing and spectroscopy," she said.

This image shows Cassini’s last two Grand Finale orbits, followed by a distant flyby of Titan that pushes the spacecraft into Saturn (final half orbit, in orange).

Spilker said scientists also hope that Cassini's plunge will help them understand the nature of Saturn's magnetic field source, the mass of its rings, and the exact length of its day (the time it takes the planet to spin once on its axis).

Getting that data back to Earth before Cassini is destroyed has required a change in the probe's basic data-transmission system, the scientists said. Typically, Cassini stores its data on a hard drive and transmits the information back to Earth much later, but during its final plummet, Cassini will sop up information from the planet and transmit it back to Earth almost immediately. That direct transmission will start about 3 hours before Cassini hits Saturn's atmosphere.

"A 2- to 3-second latency is all we're expecting," Maize said (referring to the time between Cassini collecting data and transmitting it). "So, we will have repurposed Cassini into an atmospheric probe, and we will have it broadcasting data back down to the very last minute."

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The Human Genome May Be Weeding Out Some Unwanted Mutations

A large-scale study of genetic data reveals that harmful genetic mutations are less prevalent in people who live longer, providing evidence that humans continue to evolve.

Evolution is usually associated with long periods of time, such as the millions of years it took for our ancestors to walk on two legs, or for tiny birds to evolve from larger dinosaurs.

A study analyzing the genomes of 210,000 people in the United States and the United Kingdom, however, finds humans are not only still evolving, but also natural selection can occur over just a few decades. The findings were published today in the journal PLOS Biology.

“With the availability of large human data sets, mostly for biomedical purposes, we are now beginning to have the power to look at small changes that happen within a few generations,” said co-author Molly Przeworski, an evolutionary biologist at Columbia University.

Przeworski, lead author Hakhamenesh Mostafavi, and their colleagues made the determinations after analyzing the genomes of 60,000 people of European ancestry genotyped by Kaiser Permanente in California and 150,000 people in Britain genotyped through the UK Biobank.

The researchers tracked the relative rise and fall of specific mutations across the recorded generations to infer which traits are spreading or dwindling. The mutations were associated with 42 common traits, ranging from height to body mass index, which is a weight to height ratio.

To compensate for a lack of elderly individuals genotyped in the Biobank, the researchers used the participants’ parents age at death as a proxy as they looked for the influence of specific mutations on survival.

The scientists found that sets of genetic mutations that predispose people to heart disease, high cholesterol and LDL “bad” cholesterol, obesity, and asthma appeared less often in people who lived longer and whose genes are therefore more likely to be passed down and spread through the population.

In women over 70, the researchers saw a drop in the frequency of the genetic variant ApoE4, which is linked to Alzheimer’s disease. This is consistent with earlier research showing women with one or two copies of the gene tend to die well before those without it.

In middle aged men, the scientists saw a similar drop in the frequency of a mutation in the CHRNA3 gene associated with heavy smoking.

“If no one smokes, this mutation does not have an effect,” Mostafavi explained. “But among smokers, those who carry this mutation tend to smoke more, and consequently are more exposed to the adverse effects of smoking.”

He said the environment in which a person is raised can also influence the impact of genetic variants, which is affecting information on human height trends. In many cultures, people have been gradually growing taller over the decades. Yet, Mostafavi said, “it could be that we are getting taller because of environmental changes, but are getting genetically shorter.”

These changes could be due to factors like better nutrition and improved health care.

Due to the powerful effect of environmental influences, the researchers do not believe people who find out they carry potentially deleterious genetic mutations should avoid having children. Sometimes these individuals and their children are not harmed at all by the genetic variants.

“We have a specific example of this in the CHRNA3 variant, in that in an environment where people don’t smoke, this isn’t an ‘undesirable’ variant at all,” said co-author Joseph Pickrell of Columbia and the New York Genome Center. “It’s basically neutral.”

Natural selection is continuing to weed out these and other genetic mutations. Pickrell said even if men with ApoE4 have just 0.1 percent fewer children on average than men without it, this would be enough for the variant to be removed quickly by natural selection.

On the upside, the researchers found those who are genetically predisposed to delayed puberty and childbearing tend to live longer. A one-year puberty delay lowered the death rate by 3–4 percent in both men and women, while a one-year childbearing delay lowered the death rate by 6 percent in women.

Taken together, the findings on puberty and the timing of first births suggest genetic variants influencing fertility are evolving in at least some US and UK populations and certain beneficial ones are being conserved.

“Our study serves as a proof of concept that it is now becoming possible to directly observe natural selection in contemporary humans with the availability of large data sets,” Mostafavi said.

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