Researchers may be able to stop the replication of Ebola virus by mutating its most important protein, according to a paper published in the Journal of Biological Chemistry.
Researchers were able to mutate Viral Protein 40 (VP40) in a way that changed the residues of the protein, blocking the budding and replication of Ebola virus in a model system.
VP40 is a peripheral membrane protein that regulates viral budding from the plasma membrane. It interacts with a human plasma-membrane lipid, phosphatidylserine, to facilitate replication of the virus. All animal viruses have to cross membranes for cell entry and exit.
The research team, led by Robert Stahelin of Purdue University, found the specific parts of VP40 that bind with the lipid: a cationic patch on the end of an amino acid chain. This site controls the ability of the protein to form a lipid envelope, the layer that protects the virus from the outside environment.
Water-attracting residues at this site are critical for membrane penetration and budding. Substituting those residues with alanine, which is hydrophobic, reduced lipid binding by 40-fold and stopped localization to the plasma membrane.
VP40 is a transformer protein, capable of rearranging itself into different structures: monomer, dimer and octamer. These various structures interact with the lipid differently, according to the paper. The dimer is best equipped to facilitate replication, performing twice as well as the monomer, and nearly 10 times better than the octamer.
"It's exciting to learn that these different oligomeric structures bind differently with the human lipid cells," Stahelin said. "That might explain why there are different roles for this protein in the viral replication cycle."
There are currently no FDA-approved vaccines or therapeutics available for Ebola virus. Outbreaks are rare but deadly, with fatality rates as high as 90 percent. Knowing how and where the protein interacts with the lipid could allow researchers to better target it with therapeutics.
"This helps us understand how the virus uses human cell membranes to replicate and form new virus particles. The virus needs this one lipid to form the new particle and infect other cells," Stahelin said. "We've been targeting human cells with therapeutics that modulate the way the cell makes lipids, and we like to target the human cell because it isn't likely to mutate and become resistant to the drug.
Cellular and in vitro models were used in this study. In vitro models were used to quantify how well VP40 binds to synthetic membranes. The researchers mutated the DNA code to change the amino acid sequence of VP40, purified those proteins to homogeneity and compared their bindings to that of the original VP40.
In cellular experiments, live cell imaging was used to monitor VP40 localization in human cells. The movement of the mutant VP40 and the original VP40 were compared to see how they bind to the human cell plasma membrane, the site of viral replication.
Read more at Science Daily
Mar 13, 2018
Modern humans flourished through ancient supervolcano eruption 74,000 years ago
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| Students excavating the site at Vleesbaai. |
An eruption a hundred times smaller than Mount Toba -- that of Mount Tambora, also in Indonesia, in 1815 -- is thought to have been responsible for a year without summer in 1816. The impact on the human population was dire -- crop failures in Eurasia and North America, famine and mass migrations. The effect of Mount Toba, a super-volcano that dwarfs even the massive Yellowstone eruptions of the deeper past, would have had a much larger, and longer-felt, impact on people around the globe.
The scale of the ash-fall alone attests to the magnitude of the environmental disaster. Huge quantities of aerosols injected high into the atmosphere would have severely diminished sunlight -- with estimates ranging from a 25 to 90 percent reduction in light. Under these conditions, plant die-off is predictable, and there is evidence of significant drying, wildfires and plant community change in East Africa just after the Toba eruption.
If Mount Tambora created such devastation over a full year -- and Tambora was a hiccup compared to Toba -- we can imagine a worldwide catastrophe with the Toba eruption, an event lasting several years and pushing life to the brink of extinctions.
In Indonesia, the source of the destruction would have been evident to terrified witnesses -- just before they died. However, as a family of hunter-gatherers in Africa 74,000 years ago, you would have had no clue as to the reason for the sudden and devastating change in the weather. Famine sets in and the very young and old die. Your social groups are devastated, and your society is on the brink of collapse.
The effect of the Toba eruption would have certainly impacted some ecosystems more than others, possibly creating areas -- called refugia -- in which some human groups did better than others throughout the event. Whether or not your group lived in such a refuge would have largely depended on the type of resources available. Coastal resources, like shellfish, are highly nutritious and less susceptible to the eruption than the plants and animals of inland areas.
When the column of fire, smoke and debris blasted out the top of Mount Toba, it spewed rock, gas and tiny microscopic pieces (cryptotephra) of glass that, under a microscope, have a characteristic hook shape produced when the glass fractures across a bubble. Pumped into the atmosphere, these invisible fragments spread across the world.
Panagiotis (Takis) Karkanas, director of the Malcolm H. Wiener Laboratory for Archaeological Science, American School of Classical Studies, Greece, saw a single shard of this explosion under a microscope in a slice of archaeological sediment encased in resin.
"It was one shard particle out of millions of other mineral particles that I was investigating. But it was there, and it couldn't be anything else," says Karkanas.
The shard came from an archaeological site in a rockshelter called Pinnacle Point 5-6, on the south coast of South Africa near the town of Mossel Bay. The sediments dated to about 74,000 years ago.
"Takis and I had discussed the potential of finding the Toba shards in the sediments of our archaeological site, and with his eagle eye, he found one," explains Curtis W. Marean, project director of the Pinnacle Point excavations. Marean is the associate director of the Institute of Human Origins at Arizona State University and honorary professor at the Centre for Coastal Palaeoscience at Nelson Mandela University, South Africa.
Marean showed the shard image to Eugene Smith, a volcanologist with the University of Nevada at Las Vegas, and Smith confirmed it was a volcanic shard.
"The Pinnacle Point study brought me back to the study of glass shards from my master's thesis 40 years earlier," says Smith.
Early in the study, the team brought in expert cryptotephra scientist Christine Lane who trained graduate student Amber Ciravolo in the needed techniques. Racheal Johnsen later joined Ciravalo as lab manager and developed new techniques.
From scratch, with National Science Foundation support, they developed the Cryptotephra Laboratory for Archaeological and Geological Research, which is now involved in projects not only in Africa, but in Italy, Nevada and Utah.
Encased in that shard of volcanic glass is a distinct chemical signature, a fingerprint that scientists can use to trace to the killer eruption. In their paper in Nature, the team describes finding these shards in two archaeological sites in coastal South Africa, tracing those shards to Toba through chemical fingerprinting and documenting a continuous human occupation across the volcanic event.
"Many previous studies have tried to test the hypothesis that Toba devastated human populations," Marean notes. "But they have failed because they have been unable to present definitive evidence linking a human occupation to the exact moment of the event."
Most studies have looked at whether or not Toba caused environmental change. It did, but such studies lack the archaeological data needed to show how Toba affected humans.
The Pinnacle Point team has been at the forefront of development and application of highly advanced archaeological techniques. They measure everything on site to millimetric accuracy with a "total station," a laser-measurement device integrated to handheld computers for precise and error-free recording.
Naomi Cleghorn with the University of Texas at Arlington, recorded the Pinnacle Point samples as they were removed.
Cleghorn explains, "We collected a long column of samples -- digging out a small amount of sediment from the wall of our previous excavation. Each time we collected a sample, we shot its position with the total station. We could then precisely compare the position of the sample to our excavated cultural remains -- the trash ancient humans left at the site. We could also compare our cryptotephra sample position with that of samples taken for dating and environmental analyses."
In addition to understanding how Toba affected humans in this region, the study has other important implications for archaeological dating techniques. Archaeological dates at these age ranges are imprecise -- 10 percent (or 1000s of years) error is typical. Toba ash-fall, however, was a very quick event that has been precisely dated. The time of shard deposition was likely about two weeks in duration -- instantaneous in geological terms.
"We found the shards at two sites," explains Marean. "The Pinnacle Point rockshelter (where people lived, ate, worked and slept) and an open air site about 10 kilometers away called Vleesbaai. This latter site is where a group of people, possibly members of the same group as those at Pinnacle Point, sat in a small circle and made stone tools. Finding the shards at both sites allows us to link these two records at almost the same moment in time."
Not only that, but the shard location allows the scientists to provide an independent test of the age of the site estimated by other techniques. People lived at the Pinnacle Point 5-6 site from 90,000 to 50,000 years ago. Zenobia Jacobs with the University of Wollongong, Australia, used optically stimulated luminescence (OSL) to date 90 samples and develop a model of the age of all the layers. OSL dates the last time individual sand grains were exposed to light.
"There has been some debate over the accuracy of OSL dating, but Jacobs' age model dated the layers where we found the Toba shards to about 74,000 years ago -- right on the money," says Marean. This lends very strong support to Jacobs' cutting-edge approach to OSL dating, which she has applied to sites across southern Africa and the world.
"OSL dating is the workhorse method for construction of timelines for a large part of our own history. Testing whether the clock ticks at the correct rate is important. So getting this degree of confirmation is pleasing," says Jacobs.
In the 1990s, scientists began arguing that this eruption of Mount Toba, the most powerful in the last two million years, caused a long-lived volcanic winter that may have devastated the ecosystems of the world and caused widespread population crashes, perhaps even a near-extinction event in our own lineage, a so-called bottleneck.
Read more at Science Daily
New insights into the origin of elongated heads in early medieval Germany
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| These are strong, intermediate, and non-deformed skulls (from left to right) from the Early Medieval sites Altenerding and Straubing in Bavaria, Germany. |
In an interdisciplinary study funded by the Volkswagen Foundation, the international research team analyzed the ancient genomes of almost 40 early medieval people from southern Germany. While most of the ancient Bavarians looked genetically like Central and Northern Europeans, one group of individuals had a very different and diverse genetic profile. Members of this group were particularly notable in that they were women whose skulls had been artificially deformed at birth. Such enigmatic deformations give the skull a characteristic tower shape and have been found in past populations from across the world and from different periods of time. "Parents wrapped their children's heads with bandages for a few months after birth in order to achieve the desired head shape," explained Dr. Michaela Harbeck. "It is difficult to answer why they carried out this elaborate process, but it was probably used to emulate a certain ideal of beauty or perhaps to indicate a group affiliation." So far, scholars have only speculated about origins of the practice in medieval Europe. "The presence of these elongated skulls in parts of eastern Europe is most commonly attributed to the nomadic Huns, led by Atilla, during their invasion of the Roman Empire from Asia, but the appearance of these skulls in western Europe is more mysterious, as this was very much the fringes of their territory," said Dr. Krishna Veeramah, first author of the study.
By analyzing DNA obtained from these elongated skulls, Professor Joachim Burger's team revealed that these women likely migrated to early Bavarian settlements from eastern Europe. "Although there is evidence that there was some genetic contribution from Central Asia, the genomic analysis points to the fact that women with deformed skulls in this region are genetically most similar to today's south eastern Europeans, and that the Huns likely played only a minor role in directly transmitting this tradition to Bavaria," Burger noted. Besides their deformed skulls, these women also tended to have darker hair and eye color than the other Bavarians they were buried and probably lived with, who primarily had fair hair and blue eyes.
But the migration of females to Bavaria did not only involve those possessing elongated skulls. Only a little later, two women can be identified who most closely resemble modern Greeks and Turks. In contrast, there was no evidence of men with drastically different genetic profiles. "Most of these foreign women are found with grave goods that look unremarkable compared to the rest of the buried population," added Veeramah. "These cases of female migration would have been invisible from the material culture alone."
"This is an example of long-range female mobility that bridges larger cultural spaces and may have been a way for distant groups to form new strategic alliances during this time of great political upheaval in the absence of a previous Roman hegemony," stated Burger. "We must expect that many more unprecedented population-dynamic phenomena have contributed to the genesis of our early cities and villages."
Read more at Science Daily
Arrested development: Hubble finds relic galaxy close to home
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| Upper right: This is a Hubble Space Telescope image of galaxy NGC 1277. Background: The galaxy lives near the center of the Perseus cluster of over 1,000 galaxies, located 240 million light-years away from Earth. |
The very rare and odd assemblage of stars has remained essentially unchanged for the past 10 billion years. This wayward stellar island provides valuable new insights into the origin and evolution of galaxies billions of years ago.
The galaxy, NGC 1277, started its life with a bang long ago, ferociously churning out stars 1,000 times faster than seen in our own Milky Way today. But it abruptly went quiescent as the baby boomer stars aged and grew ever redder.
The findings are being published online in the March 12 issue of the science journal Nature.
Though Hubble has seen such "red and dead" galaxies in the early universe, one has never been conclusively found nearby. Where the early galaxies are so distant, they are just red dots in Hubble deep-sky images. NGC 1277 offers a unique opportunity to see one up close and personal. "We can explore such original galaxies in full detail and probe the conditions of the early universe," said Ignacio Trujillo, of the Instituto de Astrofisica de Canarias at the University of La Laguna, Spain.
The researchers learned that the relic galaxy has twice as many stars as our Milky Way, but physically it is as small as one quarter the size of our galaxy. Essentially, NGC 1277 is in a state of "arrested development." Perhaps like all galaxies it started out as a compact object but failed to accrete more material to grow in size to form a magnificent pinwheel-shaped galaxy.
Approximately one in 1,000 massive galaxies is expected to be a relic (or oddball) galaxy, like NGC 1277, researchers say. They were not surprised to find it, but simply consider that it was in the right place at the right time to evolve -- or rather not evolve -- the way it did.
The telltale sign of the galaxy's state lies in the ancient globular clusters of stars that swarm around it. Massive galaxies tend to have both metal-poor (appearing blue) and metal-rich (appearing red) globular clusters. The red clusters are believed to form as the galaxy forms, while the blue clusters are later brought in as smaller satellites are swallowed by the central galaxy. However, NGC 1277 is almost entirely lacking in blue globular clusters. "I've been studying globular clusters in galaxies for a long time, and this is the first time I've ever seen this," said Michael Beasley, also of the Instituto de Astrofisica de Canarias.
The red clusters are the strongest evidence that the galaxy went out of the star- making business long ago. However, the lack of blue clusters suggests that NGC 1277 never grew further by gobbling up surrounding galaxies.
By contrast, our Milky Way contains approximately 180 blue and red globular clusters. This is due partly to the fact that our Milky Way continues cannibalizing galaxies that swing too close by in our Local Group of a few dozen small galaxies.
It's a markedly different environment for NGC 1277. The galaxy lives near the center of the Perseus cluster of over 1,000 galaxies, located 240 million light-years away. But NGC 1277 is moving so fast through the cluster, at 2 million miles per hour, that it cannot merge with other galaxies to collect stars or pull in gas to fuel star formation. In addition, near the galaxy cluster center, intergalactic gas is so hot it cannot cool to condense and form stars.
The team started looking for "arrested development" galaxies in the Sloan Digital Sky Survey and found 50 candidate massive compact galaxies. Using a similar technique, but out of a different sample, NGC 1277 was identified as unique in that it has a central black hole that is much more massive than it should be for a galaxy of that size. This reinforces the scenario that the supermassive black hole and dense hub of the galaxy grew simultaneously, but the galaxy's stellar population stopped growing and expanding because it was starved of outside material.
"I didn't believe the ancient galaxy hypothesis initially, but finally I was surprised because it's not that common to find what you predict in astronomy," Beasley added. "Typically, the universe always comes up with more surprises that you can think about."
The team has 10 other candidate galaxies to look at with varying degrees of "arrested development."
The upcoming NASA James Webb Space Telescope (scheduled for launch in 2019) will allow astronomers to measure the motions of the globular clusters in NGC 1277. This will provide the first opportunity to measure how much dark matter the primordial galaxy contains.
Read more at Science Daily
Mar 12, 2018
Genetic timeline of early Pacific settlers
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| Anciant skeleton at the Teouma site on Efate. |
The new research, published across two separate research papers, uses a combination of DNA analyses of ancient skeletons and modern samples, as well as archaeological evidence, to put together a complete timeline of migration to the island nation.
The results confirm that Vanuatu's first people were of the Lapita culture and arrived 3,000 years ago from South East Asia, followed by Papuan arrivals from the island of New Britain, in the Bismarck Archipelago just to the east of New Guinea and part of the nation of Papua New Guinea.
Dr Stuart Bedford of the ANU School of Culture History and Language said this was the first time researchers had been able to look at a full sequence of DNA samples from the Vanuatu islands.
"We've been able to track a complete genetic timeline at regular intervals starting with the first inhabitants right through to modern times," Dr Bedford said.
"The very first generation of people into Vanuatu are primarily Asian, then very quickly you see a series of migrations of Papuan people from the Bismarck Archipelago who had been living in the region for around 50,000 years.
"That trend continues over the next 3,000 years right up until today as the genetic ancestry was mostly replaced by that of Papuan migrants. The people of Vanuatu today, like many peoples of the Pacific, can claim a dual heritage."
Co Researcher Professor Matthew Spriggs of the ANU School of Archaeology and Anthropology said for the first time researchers could determine exactly where these Papuan migration groups came from.
"They came from New Britain, a Papuan island just east of New Guinea," Professor Spriggs said.
"This makes sense. New Britain has some of the earliest known Lapita sites.
"So what we think happened is that Lapita people after arriving in New Britain moved fairly directly on to Vanuatu and encouraged some of the local populations already in place on New Britain to move there as well."
Dr Bedford said the strength of the Lapita culture was evident in the continuity of the language.
"The Lapita people who originally came to Vanuatu from South East Asia spoke a form of Austronesian," Dr Bedford said.
"That language persisted and over 120 descendant languages continue to be spoken today, making Vanuatu the most linguistically diverse place on Earth per capita.
"This is a unique case, where a population's genetic ancestry was replaced but its languages continued."
Read more at Science Daily
Digging up the Precambrian: Fossil burrows show early origins of animal behavior
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| Reconstruction of the late Ediacaran (ca. 550 million years ago) sea floor with burrows of a worm-like animal.This was the first discovery of such deeply penetrating burrows. |
In the history of life on Earth, a dramatic and revolutionary change in the nature of the sea floor occurred in the early Cambrian (541–485 million years ago): the “agronomic revolution.” This phenomenon was coupled with the diversification of marine animals that could burrow into seafloor sediments. Previously, the sea floor was covered by hard microbial mats, and animals were limited to standing on, resting on, or moving horizontally along those mats. In the agronomic revolution, part of the so-called Cambrian Explosion of animal diversity and complexity, vertical burrowers began to churn up the underlying sediments, which softened and oxygenated the subsurface, created new ecological niches, and thus radically transformed the marine ecosystem into one more like that observed today.
This event has long been considered to have occurred in the early Cambrian Period. However, new evidence obtained from western Mongolia shows that the agronomic revolution began in the late Ediacaran, the final period of the Precambrian, at least locally.
A team of researchers, primarily based in Japan, surveyed Bayan Gol Valley, western Mongolia, and found late Ediacaran trace fossils in marine carbonate rocks. They identified U-shaped, penetrative trace fossils, called Arenicolites, from 11 beds located more than 130 meters below the lowermost occurrence of Treptichnus pedum, widely recognized as the marker of the Ediacaran–Cambrian boundary. The researchers confirmed the late Ediacaran age of the rocks, estimated to be between 555 and 541 million years old, based on the stable carbon isotope record.
“It is impossible to identify the kind of animal that produced the Arenicolites traces,” lead author Tatsuo Oji says. “However, they were certainly bilaterian animals based on the complexity of the traces, and were probably worm-like in nature. These fossils are the earliest evidence for animals making semi-permanent domiciles in sediment. The evolution of macrophagous predation was probably the selective pressure for these trace makers to build such semi-permanent infaunal structures, as they would have provided safety from many predators.”
These Arenicolites also reached unusually large sizes, greater than one centimeter in diameter. The discovery of these large-sized, penetrative trace fossils contradicts the conclusions of previous studies that small-sized penetrative traces emerged only in the earliest Cambrian.
Read more at Science Daily
15 new planets confirmed around cool dwarf stars
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| Conceptual illustration. A key outcome from the current studies was that planets orbiting red dwarfs may have remarkably similar characteristics to planets orbiting solar-type stars. |
A research team led by Teruyuki Hirano of Tokyo Institute of Technology's Department of Earth and Planetary Sciences has validated 15 exoplanets orbiting red dwarf systems.
One of the brightest red dwarfs, K2-155 that is around 200 light years away from Earth, has three transiting super-Earths, which are slightly bigger than our own planet. Of those three super-Earths, the outermost planet, K2-155d, with a radius 1.6 times that of Earth, could be within the host star's habitable zone.
The findings, published in the form of two papers in The Astronomical Journal, are based on data from NASA Kepler spacecraft's second mission, K2, and follow-up observations using ground-based telescopes, including the Subaru Telescope in Hawaii and the Nordic Optical Telescope (NOT) in Spain.
The researchers found that K2-155d could potentially have liquid water on its surface based on three-dimensional global climate simulations. Hirano expresses both excitement and restraint, as he says: "In our simulations, the atmosphere and the composition of the planet were assumed to be Earth-like, and there's no guarantee that this is the case."
A more precise estimate of the radius and temperature of the K2-155 star would be needed to conclude definitively whether K2-155d is habitable. Achieving such precision would require further studies, for example, using interferometric techniques.
A key outcome from the current studies was that planets orbiting red dwarfs may have remarkably similar characteristics to planets orbiting solar-type stars.
"It's important to note that the number of planets around red dwarfs is much smaller than the number around solar-type stars," says Hirano. "Red dwarf systems, especially coolest red dwarfs, are just beginning to be investigated, so they are very exciting targets for future exoplanet research."
For example, while the so-called radius gap of planets around solar-type stars has been reported previously, this is the first time that researchers have shown a similar gap in planets around red dwarfs. "This is a unique finding, and many theoretical astronomers are now investigating what causes this gap," says Hirano.
He adds that the most likely explanation for the lack of large planets in the proximity of host stars is photoevaporation, which can strip away the envelope of the planetary atmosphere.
The researchers also investigated the relationship between planet radius and metallicity of the host star. "Large planets are only discovered around metal-rich stars," Hirano says, "and what we found was consistent with our predictions. The few planets with a radius about three times that of Earth were found orbiting the most metal-rich red dwarfs."
The studies were conducted as part of the KESPRINT collaboration, a group formed by the merger of KEST (Kepler Exoplanet Science Team) and ESPRINT (Equipo de Seguimiento de Planetas Rocosos Intepretando sus Transitos) in 2016.
Read more at Science Daily
On Twitter, false news travels faster than true stories, study finds
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| Pictured (left to right): Seated, Soroush Vosoughi, a postdoc at the Media Lab's Laboratory for Social Machines; Sinan Aral, the David Austin Professor of Management at MIT Sloan; and Deb Roy, an associate professor of media arts and sciences at the MIT Media Lab, who also served as Twitter's Chief Media Scientist from 2013 to 2017. |
"We found that falsehood diffuses significantly farther, faster, deeper, and more broadly than the truth, in all categories of information, and in many cases by an order of magnitude," says Sinan Aral, a professor at the MIT Sloan School of Management and co-author of a new paper detailing the findings.
"These findings shed new light on fundamental aspects of our online communication ecosystem," says Deb Roy, an associate professor of media arts and sciences at the MIT Media Lab and director of the Media Lab's Laboratory for Social Machines (LSM), who is also a co-author of the study. Roy adds that the researchers were "somewhere between surprised and stunned" at the different trajectories of true and false news on Twitter.
Moreover, the scholars found, the spread of false information is essentially not due to bots that are programmed to disseminate inaccurate stories. Instead, false news speeds faster around Twitter due to people retweeting inaccurate news items.
"When we removed all of the bots in our dataset, [the] differences between the spread of false and true news stood,"says Soroush Vosoughi, a co-author of the new paper and a postdoc at LSM whose PhD research helped give rise to the current study.
The study provides a variety of ways of quantifying this phenomenon: For instance, false news stories are 70 percent more likely to be retweeted than true stories are. It also takes true stories about six times as long to reach 1,500 people as it does for false stories to reach the same number of people. When it comes to Twitter's "cascades," or unbroken retweet chains, falsehoods reach a cascade depth of 10 about 20 times faster than facts. And falsehoods are retweeted by unique users more broadly than true statements at every depth of cascade.
The paper, "The Spread of True and False News Online," is published today in Science.
Why novelty may drive the spread of falsity
The genesis of the study involves the 2013 Boston Marathon bombings and subsequent casualties, which received massive attention on Twitter.
"Twitter became our main source of news," Vosoughi says. But in the aftermath of the tragic events, he adds, "I realized that … a good chunk of what I was reading on social media was rumors; it was false news." Subsequently, Vosoughi and Roy -- Vosoughi's graduate advisor at the time -- decided to pivot Vosoughi's PhD focus to develop a model that could predict the veracity of rumors on Twitter.
Subsequently, after consultation with Aral -- another of Vosoughi's graduate advisors, who has studied social networks extensively -- the three researchers decided to try the approach used in the new study: objectively identifying news stories as true or false, and charting their Twitter trajectories. Twitter provided support for the research and granted the MIT team full access to its historical archives. Roy served as Twitter's chief media scientist from 2013 to 2017.
To conduct the study, the researchers tracked roughly 126,000 cascades of news stories spreading on Twitter, which were cumulatively tweeted over 4.5 million times by about 3 million people, from the years 2006 to 2017.
To determine whether stories were true or false, the team used the assessments of six fact-checking organizations (factcheck.org, hoax-slayer.com, politifact.com, snopes.org, truthorfiction.com, and urbanlegends.about.com), and found that their judgments overlapped more than 95 percent of the time.
Of the 126,000 cascades, politics comprised the biggest news category, with about 45,000, followed by urban legends, business, terrorism, science, entertainment, and natural disasters. The spread of false stories was more pronounced for political news than for news in the other categories.
The researchers also settled on the term "false news" as their object of study, as distinct from the now-ubiquitous term "fake news," which involves multiple broad meanings.
The bottom-line findings produce a basic question: Why do falsehoods spread more quickly than the truth, on Twitter? Aral, Roy, and Vosoughi suggest the answer may reside in human psychology: We like new things.
"False news is more novel, and people are more likely to share novel information," says Aral, who is the David Austin Professor of Management. And on social networks, people can gain attention by being the first to share previously unknown (but possibly false) information. Thus, as Aral puts it, "people who share novel information are seen as being in the know."
The MIT scholars examined this "novelty hypothesis" in their research by taking a random subsample of Twitter users who propagated false stories, and analyzing the content of the reactions to those stories.
The result? "We saw a different emotional profile for false news and true news," Vosoughi says. "People respond to false news more with surprise and disgust," he notes, whereas true stories produced replies more generally characterized by sadness, anticipation, and trust.
So while the researchers "cannot claim that novelty causes retweets" by itself, as they state in the paper, the surprise people register when they see false news fits with the idea that the novelty of falsehoods may be an important part of their propagation.
Directions for further research
While the three researchers all think the magnitude of the effect they found is highly significant, their views on its civic implications vary slightly. Aral says the result is "very scary" in civic terms, while Roy is a bit more sanguine. But the scholars agree it is important to think about ways to limit the spread of misinformation, and they hope their result will encourage more research on the subject.
On the first count, Aral notes, the recognition that humans, not bots, spread false news more quickly suggests a general approach to the problem.
"Now behavioral interventions become even more important in our fight to stop the spread of false news," Aral says. "Whereas if it were just bots, we would need a technological solution."
Vosoughi, for his part, suggests that if some people are deliberately spreading false news while others are doing so unwittingly, then the phenomenon is a two-part problem that may require multiple tactics in response. And Roy says the findings may help create "measurements or indicators that could become benchmarks" for social networks, advertisers, and other parties.
The MIT scholars say it is possible that the same phenomenon occurs on other social media platforms, including Facebook, but they emphasize that careful studies are needed on that and other related questions.
Read more at Science Daily
Mar 11, 2018
Experiment sheds new light on prehistoric ocean conditions
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| This is a graduated cylinder model of the ocean. The green shows cyanobacteria and the brown shows the oxidized iron. |
Swanner, an assistant professor of geological and atmospheric sciences, was part of an international research team including researchers from the University of Tuebingen in Germany and the Chinese Academy of Sciences in Beijing. The team modeled the prehistoric ocean, similar to that of the Archean Era 2.5 billion years ago within a graduated cylinder.
"We really only wanted to simulate it in the vertical dimension, so we used a graduated cylinder and modified it," Swanner said.
In a previous experiment, the researchers had modified the cylinder to simulate an Archean ocean with large amounts of iron and no oxygen except for what was made by cyanobacteria. Ports along the cylinder's side allowed for sampling at various levels.
"We were studying cyanobacteria because these are the organisms which we think put all of the oxygen in the atmosphere originally," she said.
The research, recently published by Scientific Reports, showed that despite the oxygenation by the cyanobacteria, much of the iron did not remain oxidized but was reduced again into its dissolved form.
This unexpected result may be explained by an enzyme on cyanobacteria which reduces iron. In the modern ocean, which contains at least 1,000 times less iron, cyanobacteria reduce a small amount of iron, but the experiment showed a larger amount of iron reduction than the researchers anticipated. Another possible explanation is that the iron is reduced by a photochemical reaction occurring when the iron is hit by light.
The implications of this finding could change the conditions under which iron-rich sedimentary rocks are thought to be formed from the ancient oceans.
"Traditionally if you see iron enriched in sediments from the ocean you tend to think it was deposited under anoxic conditions," Swanner said. "But potentially we have a way to still deposit a lot of iron but have it be deposited under fully oxygenated conditions."
Read more at Science Daily
Unique diamond impurities indicate water deep in Earth's mantle
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| Rough diamond in kimberlite. |
Groundbreaking research by UNLV geoscientist Oliver Tschauner and colleagues found diamonds pushed up from the Earth's interior had traces of unique crystallized water called Ice-VII.
The study, "Ice-VII inclusions in Diamonds: Evidence for aqueous fluid in Earth's deep Mantle," was published Thursday in the journal Science.
In the jewelry business, diamonds with impurities hold less value. But for Tschauner and other scientists, those impurities, known as inclusions have infinite value, as they may hold the key to understanding the inner workings of our planet.
For his study, Tschauner used diamonds found in China, the Republic of South Africa, and Botswana that surged up from inside Earth. "This shows that this is a global phenomenon," the professor said.
Scientists theorize the diamonds used in the study, were born in the mantle under temperatures reaching more than 1,000-degrees Fahrenheit.
The mantle -- which makes up more than 80 percent of the Earth's volume -- is made of silicate minerals containing iron, aluminum, and calcium among others.
And now we can add water to the list.
The discovery of Ice-VII in the diamonds is the first known natural occurrence of the aqueous fluid from the deep mantle. Ice-VII had been found in prior lab testing of materials under intense pressure. Tschauner also found that while under the confines of hardened diamonds found on the surface of the planet, Ice-VII is solid. But in the mantel, it is liquid.
"These discoveries are important in understanding that water-rich regions in the Earth's interior can play a role in the global water budget and the movement of heat-generating radioactive elements," Tschauner said.
This discovery can help scientists create new, more accurate models of what's going on inside the Earth, specifically how and where heat is generated under the Earth's crust.
In other words: "It's another piece of the puzzle in understanding how our planet works," Tschauner said.
Read more at Science Daily
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