An international team of researchers, co-led by scientists at the University of York and Yunnan Normal University, has produced the first multi-disciplinary evidence for management of cattle populations in northern China, around the same time cattle domestication took place in the Near East, over 10,000 years ago.
The domestication of cattle is a key achievement in human history. Until now, researchers believed that humans started domesticating cattle around 10,000 years ago in the Near East, which gave rise to humpless (taurine) cattle, while two thousand years later humans began managing humped cattle (zebu) in Southern Asia.
However, the new research, which is published in Nature Communications, reveals morphological and genetic evidence for management of cattle in north-eastern China around 10,000 years ago, around the same time the first domestication of taurine cattle took place in the Near East. This indicates that humans may have started domesticating cows in more regions around the world than was previously believed.
A lower jaw of an ancient cattle specimen was discovered during an excavation in north-east China, and was carbon dated to be 10,660 years old. The jaw displayed a unique pattern of wear on the molars, which, the researchers say, is best explained to be the results of long-term human management of the animal. Ancient DNA from the jaw revealed that the animal did not belong to the same cattle lineages that were domesticated in the Near East and South Asia.
The combination of the age of the jaw, the unique wear and genetic signature suggests that this find represents the earliest evidence for cattle management in north-east China; a time and place not previously considered as potential domestication centre for cattle.
The research was co-led in the Department of Biology at the University of York by Professor Michi Hofreiter and Professor Hucai Zhang of Yunnan Normal University.
Professor Hofreiter said: "The specimen is unique and suggests that, similar to other species such as pigs and dogs, cattle domestication was probably also a complex process rather than a sudden event."
Johanna Paijmans, the PhD student at York who performed the DNA analysis, said: "This is a really exciting example of the power of multi-disciplinary research; the wear pattern on the lower jaw itself is already really interesting, and together with the carbon dating and ancient DNA we have been able to place it in an even bigger picture of early cattle management."
Read more at Science Daily
Nov 9, 2013
'Tiger Stripes' Underneath Antarctic Glaciers Slow the Flow
Just as no-slip strips on flooring prevent people from slipping on a wet floor, these ribs or "tiger stripes" -- named in reference to Princeton's tiger mascot -- provide friction that hinders the glaciers from slipping along the underlying bed of rock and sediment, the researchers report online in the journal Science.
The researchers discovered these tiger stripes, which occur in large, slippery regions under the glaciers, using mathematical modeling based on data from the National Snow and Ice Data Center and the British Antarctic Survey. The work was conducted by Olga Sergienko, an associate research scientist in Princeton's Program in Atmospheric and Oceanic Sciences, and Richard Hindmarsh, a scientist at the British Antarctic Survey.
Researchers would like to understand what factors determine the flow of glaciers, which are massive, moving ice sheets that, when they flow into the ocean, can contribute substantially to sea-level rise. The researchers studied two glaciers, the Pine Island Glacier and the Thwaites Glacier in West Antarctica, which together contribute about 10 percent of the observed sea-level rise over the past 20 years, despite their small areas. The Pine Island Glacier moves at a velocity of about 1.5 miles per year, according to the researchers.
Studying the bottom of these glaciers is next to impossible due to the inability to see through the ice, which is over a mile-and-a-half thick. Instead, the researchers used satellite measurements of the ice velocity and ground-penetrating radar collected from airplane flyovers to detect bedrock and surface topography, as well as field observations. Using the data, Sergienko created a mathematical model that calculated what happens inside the glacier as it flows along the bedrock. The model predicted the formation of the tiger stripes or ribs, which Hindmarsh had theorized some years earlier.
The friction at the interface of the bedrock and glacier ice is a major factor in the speed of a glacier, Sergienko said. When friction is high, the glacier moves slowly. When friction is low, as when melting ice provides a liquid layer that allows the ice to slide over the bedrock, the glacier moves more quickly.
The tiger stripes, which the researchers also call ribs due to their slightly curved structure, lie at roughly 30-degree angles to the direction of the glacier's movement. These ribs arise and decay in response to natural processes over roughly 50 to 100 years, according to the researchers' calculations. The process is strongly affected by how water, which comes from ice melting due to the inherent heat trapped in Earth, infiltrates the space between the ice sheet and the bedrock, the researchers found.
"The ribs may play an important role in buffering the effects of a warming climate, since they slow the movement of ice that reaches the ocean and contributes to sea-level rise," said Sergienko. "These changes can happen independently of climate change, too," she added.
More investigations are needed to verify models of rib formation, according to the researchers. "Our guess is that these ribs are related to typical landforms that exist in the formerly glaciated areas of North America and Europe," said Hindmarsh. "A great example are the drumlins -- raised areas of soil and rock -- that make the hills in Seattle or Glasgow," he said.
The study reveals new patterns of friction that help control the speed of ice flow and determine the effect of Antarctic ice on sea level, according to Douglas MacAyeal, a professor of glaciology at the University of Chicago who was not involved in the work. "This is strongly suggestive of a new style of physical controls over friction, like water flow in the thin zone between the rock of the bed and the ice," he said. "The results of this study will drive new theoretical and observational efforts to understand what causes this pattern."
Read more at Science Daily
Nov 8, 2013
The Anglerfish and the Absolute Worst Sex on Earth
Teen movies are, at their core, veiled studies in evolutionary biology, with young men and women coming to sexual maturity and either giving into or resisting what is arguably an animal’s sole purpose on this planet — to find a mate. Some decide to wait until they’re married, others lack the desirable traits to even get that far, and still others succeed and consequently have to put off college for a while.
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| A female Linophryne polypogon. |
The over 300 extremely varied species of anglerfishes inhabit everything from shallow to super-deep waters, and are so named because they are fish that fish for fish using lures, which are actually highly modified spines of dorsal fins that have migrated to their snouts. But among the 160 deep-sea species, only some 25 engage in the aforementioned biting-fusing-mating, what is known as sexual parasitism. In this group, the diminutive male looks like an entirely different species, lacking the female’s enormous jaws and characteristic lure.
This is because he doesn’t need to hunt. He only exists to attach to a female, and according to evolutionary biologist Theodore W. Pietsch of the University of Washington, mates are so scarce down here that it might be that only 1 percent of males ever find a female. The rest starve to death as virgins — unfortunate guys in a sea that doesn’t have plenty of other fish.
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| Close-up of the head of a male Linophryne sp. showing its greatly enlarged nostril. |
And with two dozen other species of anglerfishes that engage in this manner of reproduction, the male had better be damn sure he chooses the right one. Luckily, the female puts on the red blue light — in the form of glowing bacteria living in her lure. Incredibly, some 90 percent of species in the deep utilize such bioluminescence.
“The bait out there is not only an organ of luminescence, but structurally it’s species-specific,” said Pietsch. “Every species of these 160 forms within this group, they have a pattern of filaments, and pigment patterns, and probably also light flash patterns, like fireflies. And they separate themselves out that way so that males can find females,” distinguishing “the tiny little differences between the structure of the bait.”
Once the male closes in, he bites onto the female, usually her belly, and their tissues fuse together to permanently join the pair in incredibly unholy matrimony. The male’s eyes and fins atrophy away, and here he will live out the rest of his life nourished by her blood, still breathing with his own gills and, importantly, still producing sperm.
“This establishes a hormonal connection,” said Pietsch, “so that probably the maturation of eggs and sperm is synchronized by the sharing of hormones. And once the eggs are mature and the male is ready, she extrudes the eggs” in a kind of gelatinous sheath that can be 30 feet long. This acts like a sponge, readily absorbing the water that the male has released his sperm into.
Keep in mind that this is happening several miles down, where there is little plankton for juvenile fish to eat. So the whole gelatinous mess is buoyant, slowly making its way to the surface, where the larvae hatch and feed, ideally growing big and then migrating down to the depths.
The females of these species can live 30 years, according to Pietsch, and over that time might collect several males, who provide sperm season after season after season (there is no “not now, honey, I have a headache” with anglerfishes). But other than the security of maintaining a constant source of sperm, why evolve such a complex ritual of reproduction in the first place?
“The idea is basically that it’s a deep-sea economy measure,” ichthyologist James Maclaine of London’s Natural History Museum wrote in an email to WIRED. “An anglerfish couple requires about half of the amount of food they would if the male was the same size as the female (and presumably living an unattached life). He is stripped down to the absolute bare essentials, she has to remain big due to the relative cost of making large eggs as opposed to tiny sperm.”
Where such a size difference between sexes, known as sexual dimorphism, gets really interesting is its manifestation in the world at large. The famed evolutionary biologist Stephen Jay Gould wrote about this in his essay “Big Fish, Little Fish” — which stars the anglerfishes, of course — arguing that in the majority of animal species, females are larger than males, because the latter often never need to fight for the former.
Read more at Wired Science
Pig-Like Beast Leads Way to Ancient Cave Drawings
On the trail of the pig-like creatures in Brazil, researchers made an unexpected and rare discovery: cave drawings showing armadillos, birds and reptiles, etched into stone thousands of years ago.
Archaeologists who examined the rock art say hunter-gatherers likely created the drawings between 4,000 and 10,000 years ago.
Researchers with the Wildlife Conservation Society (WCS) made the find while surveying white-lipped peccaries in Brazil's Cerrado plateau, a vast savanna region, in 2009. The animals, which travel long distances, are considered environmental indicators of healthy forests.
"Since we often work in remote locations, we sometimes make surprising discoveries, in this case, one that appears to be important for our understanding of human cultural history in the region," Alexine Keuroghlian, a researcher with WCS's Brazil program, said in a statement.
The researchers encountered a series of sandstone formations with caves containing the artwork while tracking the peccaries near the remote city of Corguinho, in the Brazilian state of Mato Grosso do Sul.
Archaeologists say the style of the drawings is more diverse than expected. While some resemble ancient art from the central Brazilian plateau, others, surprisingly, seem etched in the artistic tradition of northeastern Brazil, the researchers said. In addition to human figures and geometric shapes, many different kinds of animals were represented, from big cats and armadillos to birds and reptiles, but alas, no peccaries.
The cave art is described (in Portuguese) in the journal Revista Clio Arqueológica.
"These discoveries of cave drawings emphasize the importance of protecting the Cerrado and Pantanal ecosystems, both for their cultural and natural heritage," Julie Kunen, director of WCS's Latin America and the Caribbean program, said in a statement. "We hope to partner with local landowners to protect these cave sites, as well as the forests that surround them, so that the cultural heritage and wildlife depicted in the drawings are preserved for future generations."
Read more at Discovery News
Indians and Europeans Share 'Light-Skin' Mutation
The study, published today (Nov. 7) in the journal PLOS Genetics, also revealed that the gene, which is responsible for 27 percent of skin color variation in Indians, was positively selected for in North, but not South Indian populations. When something is "selected for," that means it provides some advantage and so gets passed down to offspring, becoming more prevalent in a population over time.
Many shades
The Indian subcontinent has an enormous variation in skin color.
"We have dark brown (tones), yellow tones and whitish-pinkish tones," said study lead author Chandana Basu Mallick, a biologist at the University of Tartu in Estonia. "We have quite a range and diversity in the biological spectrum of skin color."
But because South Asian gene studies are relatively rare, it wasn't clear which genes contributed to this variation. Past research has found at least 126 genes that code for pigmentation in general, Basu Mallick said.
Genetic mosaic
To find out, Basu Mallick and her colleagues took skin color measurements for about 1,228 individuals in Southern India. The researchers then conducted a genetic analysis and found that about 27 percent of the skin color variation was due to a variation in a skin pigmentation gene. Called SLC24A5, this gene code for lighter skin is present in almost 100 percent of Europeans.
The team also examined the gene in 95 people around the subcontinent and found that both South Asian and European populations inherited this particular variant from a common ancestor who lived sometime between 22,000 and 28,000 years ago.
"We don't know the origin of this mutation. We just know that they have a common ancestor," Basu Mallick told LiveScience, referring to both South Asians and Europeans.
The team then looked for the gene in more than 2,000 people from 54 ethnic groups around the subcontinent. Some groups, such as populations in Tibet and Burma, didn't have the gene variant at all, whereas the Northwestern tip of the subcontinent had a nearly 90 percent prevalence of the gene.
Lighter skin has less melanin, a pigment that blocks the sun's UV rays; the body uses these rays to make vitamin D. The SLC24A5 gene is linked to less melanin production, so the gene may have become more common in Europe because it allowed people's skin to make more vitamin D in the continent's low-light conditions.
Read more at Disocvery News
Weird Ancient Black Hole Has Extra Suck
Quasars dominated the early Cosmos, generating vast quantities of radiation that can be observed today right at the edge of our observable Universe. Consisting of an active supermassive black hole and a searing disk of plasma in the cores of young galaxies, the vast majority of quasars eject material from their energetic environments at high speed.
This may sound counter-intuitive; black holes consume matter after all, they don’t eject it. But in a quasar’s hot accretion disk — composed of a superheated soup of blended stars, gas and dust that strayed too close to the supermassive black hole’s gravitational wrath — the intense radiation blasts the surrounding material away from the black hole. Although some material inevitably gets fed from the accretion disk into the black hole, vast quantities are ejected at up to a significant fraction of the speed of light.
However, by taking a Doppler speed check of the motion of gas around known quasars, a team of researchers analyzing data from the Sloan Digital Sky Survey (SDSS-III) have discovered a very rare subset of quasars that don’t fit the norm.
“The gas in this new type of quasar is moving in two directions: some is moving toward Earth but most of it is moving at high velocities away from us, possibly toward the quasar’s black hole,” said Niel Brandt, study co-author and Distinguished Professor of Astronomy and Astrophysics at Penn State University. “Just as you can use the Doppler shift for sound to tell if an airplane is moving away from you or toward you, we used the Doppler shift for light to tell whether the gas in these quasars is moving away from Earth or toward these distant black holes, which have a mass from millions to billions of times that of the sun.”
“Matter falling into black holes may not sound surprising,” added team leader Patrick Hall of York University in Toronto, “but what we found is, in fact, quite mysterious and was not predicted by current theories.
“The gas in the disc must eventually fall into the black hole to power the quasar, but what is often seen instead is gas blown away from the black hole by the heat and light of the quasar, heading toward us at velocities up to 20 percent of the speed of light,” he said. “If the gas is falling into the black hole, then we don’t understand why it’s so rare to see infalling gas. There’s nothing else unusual about these quasars. If gas can be seen falling into them, why not in other quasars?”
So how rare are these objects? 1-in-10,000 rare. Of the tens of thousands of quasars known, only 17 such objects have been discovered so far.
For now, the researchers are baffled as to why these few distant supermassive black holes, which have masses millions to billions of times of the mass of our sun, appear to have more suck than the rest of their quasar cousins. Their work has been published in the journal Monthly Notices of the Royal Astronomical Society (doi: 10.1093/mnras/stt1012).
Read more at Discovery News
Nov 7, 2013
Big Bang Afterglow Shows Earth Has No Special Place in Expanding Universe
While the findings don't explain the cosmic speed-up, they eliminate one provocative possibility that our planet, solar system and galaxy are at the center of the universe and that there is no dark energy. The findings appear in the journal Physical Review D.
The 2011 Nobel Prize was awarded for the discovery that the expansion of the universe is accelerating. One leading idea to explain the acceleration is a new, mysterious substance called dark energy, which is thought to make up nearly three-fourths of the energy of the universe. But another alternative is that Earth, our solar system and Milky Way galaxy are at the center of the universe. That theory violates the standard assumption that the universe has no center, but if true, then cosmic acceleration could be explained without dark energy or any new laws of physics.
But Dartmouth researchers found that this model can't hold up to other observational tests. The sky glows with light left over from the Big Bang, also known as the Cosmic Microwave Background, so they calculated how that glow would be affected. Their findings show that the model's prediction is completely contrary to the glow that has been measured.
"Essentially, we held a mirror up to the universe and asked if the reflection was special," says Robert Caldwell, a professor of physics and astronomy who co-wrote the article with undergraduate physics major Nina Maksimova. "The reflection shows that we do not appear to live in a special location, and decisively excludes this explanation for the universe's accelerating expansion. It would be a great relief to be able to understand a basic problem of cosmology within the known laws of physics, but our research is an important step in explaining the physics responsible for the cosmic acceleration."
From Science Daily
'Freakish' Asteroid Discovered, Resembles Rotating Lawn Sprinkler
Normal asteroids appear simply as tiny points of light. This bizarre asteroid has six comet-like tails of dust radiating from it like spokes on a wheel.
"It's hard to believe we're looking at an asteroid," said lead investigator David Jewitt, a professor in the UCLA Department of Earth and Space Sciences and the UCLA Department of Physics and Astronomy. "We were dumbfounded when we saw it. Amazingly, its tail structures change dramatically in just 13 days as it belches out dust."
One interpretation is that the asteroid's rotation rate increased to the point where its surface started flying apart, ejecting dust in episodic eruptions, starting last spring. The team has ruled out a recent asteroid impact scenario because a large quantity of dust would have been blasted into space all at once. This object, designated P/2013 P5, has ejected dust for at least five months, Jewitt said.
The asteroid was first seen as an unusually fuzzy-looking object with the Pan-STARRS survey telescope in Hawaii. Its multiple tails were discovered in images taken by NASA's Hubble Space Telescope on Sept. 10, 2013. When Hubble returned to the asteroid on Sept. 23, its appearance had totally changed; it looked as if the entire structure had swung around.
"We were completely knocked out," said Jewitt.
The tails could have been formed by a series of "impulsive dust-ejection events," modeling by team member Jessica Agarwal revealed. Agarwal, of the Max Planck Institute for Solar System Research in Lindau, Germany, calculated that the first ejection event occurred on April 15 and the last one on Sept. 4. The intervening eruptions occurred on July 18, July 24, Aug. 8 and Aug. 26.
Radiation pressure from the sun smears out the dust into streamers. The asteroid could possibly have been spun up if the pressure of sunlight exerted a torque on the body, Jewitt said.
If its spin rate became fast enough, he said, the asteroid's weak gravity would no longer be able to hold it together. Dust might avalanche downslope toward the asteroid's equator and eventually drift into space to make a tail. So far, only a small fraction of the asteroid's main mass -- perhaps 100 to 1,000 tons of dust -- has been lost, Jewitt said. The 700-foot-radius nucleus is thousands of times more massive.
Follow-up observations may reveal whether the dust leaves the asteroid in the equatorial plane; if so, that would indicate a "rotational breakup," Jewitt said.
This must be a common phenomenon in the asteroid belt, Jewitt said, and may even be the main way in which small asteroids die.
"In astronomy, where you find one, you eventually find a whole bunch more," he said. "This is an amazing object and almost certainly the first of many more to come."
Read more at Science Daily
Ants, Like Humans, Can Change Their Priorities
For the first time, Arizona State University researchers have discovered that at least in ants, animals can change their decision-making strategies based on experience. They can also use that experience to weigh different options.
The findings are featured today in the early online edition of the scientific journal Biology Letters, as well as in its Dec. 23 edition.
Co-authors Taka Sasaki and Stephen Pratt, both with ASU's School of Life Sciences, have studied insect collectives, such as ants, for years. Sasaki, a postdoctoral research associate, specializes in adapting psychological theories and experiments that are designed for humans to ants, hoping to understand how the collective decision-making process arises out of individually ignorant ants.
"The interesting thing is we can make decisions and ants can make decisions -- but ants do it collectively," said Sasaki. "So how different are we from ant colonies?"
To answer this question, Sasaki and Pratt gave a number of Temnothorax rugatulus ant colonies a series of choices between two nests with differing qualities. In one treatment, the entrances of the nests had varied sizes, and in the other, the exposure to light was manipulated. Since these ants prefer both a smaller entrance size and a lower level of light exposure, they had to prioritize.
"It's kind of like a humans and buying a house," said Pratt, an associate professor with the school. "There's so many options to consider -- the size, the number of rooms, the neighborhood, the price, if there's a pool. The list goes on and on. And for the ants it's similar, since they live in cavities that can be dark or light, big or small. With all of these things, just like with a human house, it's very unlikely to find a home that has everything you want."
Pratt continued to explain that because it is impossible to find the perfect habitat, ants make various tradeoffs for certain qualities, ordering them in a queue of most important aspects. But, when faced with a decision between two different homes, the ants displayed a previously unseen level of intelligence.
According to their data, the series of choices the ants faced caused them to re-prioritize their preferences based on the type of decision they faced. Ants that had to choose a nest based on light level prioritized light level over entrance size in the final choice. On the other hand, ants that had to choose a nest based on entrance size ranked light level lower in the later experiment.
This means that, like people, ants take the past into account when weighing options while making a choice. The difference is that ants somehow manage to do this as a colony without any dissent. While this research builds on groundwork previously laid down by Sasaki and Pratt, the newest experiments have already raised more questions.
"You have hundreds of these ants, and somehow they have to reach a consensus," Pratt said. "How do they do it without anyone in charge to tell them what to do?"
Pratt likened individual ants to individual neurons in the human brain. Both play a key role in the decision-making process, but no one understands how every neuron influences a decision.
Read more at Science Daily
Mating Bugs Etched in Stone for 165 Million Years
The fossil, described in the latest PLoS ONE, presents a pair of copulating froghoppers that lived 165 million years ago in what is now northeastern China. The fossil is the earliest record of copulating insects to date.
“We found these two very rare copulating froghoppers, which provide a glimpse of interesting insect behavior and important data to understand their mating position and genitalia orientation during the Middle Jurassic,” co-author Dong Ren of Capital Normal University in China, said in a press release.
Ren and his colleagues point out that our current knowledge of mating positions and genitalia orientation of prehistoric insects and animals is limited, to say the least.
In this fossil, no one doubts what was going on.
Froghoppers are tiny insects that hop from plant to plant in the way that small frogs hop around.
The insects also apparently slept around. The now-fossilized male (in the photo above, at left) inserted his reproductive organ into the female’s copulatory structure.
It’s unclear what happened after that, though. Somehow the two were entombed in this position.
What’s remarkable is that their belly-to-belly mating position, and their genital symmetry, have remained static in froghoppers over the millions of years. We humans are forever “upgrading” this and that gadget but, in nature, if it isn’t broken and the circumstances remain similar, it stays the same.
Read more at Discovery News
Nov 6, 2013
A Shot in the Dark: Detector On the Hunt for Dark Matter
The search will be conducted with a recently retooled, extremely sensitive detector that is currently in a testing and shakeout phase at the University of Washington's Center for Experimental Nuclear Physics and Astrophysics.
The axion was first conjectured by physicists in the late 1970s as a solution to a problem in a theory called quantum chromodynamics. Little is known for sure about the axion. It appears to react gravitationally to matter, but otherwise it seems to have no other interaction.
Since the 1930s, scientists have believed there must be some unseen but massive substance, a sort of gravitational glue, that prevents rotating galaxies from spinning apart. Axions, if they in fact do exist, are candidates for the makeup of cold dark matter that would act as that gravitational glue.
Dark matter is believed to account for about one-quarter of all the mass in the universe. However, because axions react so little -- and the reactions they are likely to produce are so faint -- finding them is tricky.
"We have probably the most sensitive axion detector in operation," Rosenberg said. "It looks for the incredibly feeble interaction between the axion and electromagnetic radiation."
The aim of the Axion Dark Matter Experiment is to search for cold dark matter axions in the halo of the Milky Way galaxy by detecting the very weak conversion of axions into microwave photons.
The detector employs a powerful magnet surrounding a sensitive microwave receiver that is supercooled to 4.2 kelvins, or about minus-452 F. Such low temperature reduces thermal noise and greatly increases the chance that the detector will actually see axions converting to microwave photons.
The microwave receiver can be fine-tuned to the axion mass, which also increases the possibility of detecting an interaction between axions and the detector's magnetic field. A reaction would deposit a minuscule amount of electromagnetic power into the receiver, which could be recorded by computers monitoring the detector.
There have been previous efforts to locate the axion, but there is greater interest in the Axion Dark Matter Experiment because of recent developments in physics research. The most notable is that the Large Hadron Collider near Geneva, Switzerland, lauded for its discovery of the elusive Higgs boson in 2012, did not find evidence to support supersymmetry, a proposed resolution for some inconsistencies among theories of particle physics.
That lack of evidence provided impetus to separate the search for dark matter from work on supersymmetry, Rosenberg said, so the newest version of the Axion Dark Matter Experiment is drawing substantial interest among researchers.
"This is a needle-in-a-haystack experiment. Once we find the needle, we can stop immediately," Rosenberg said.
"We could find it in our first week of data-taking, our last week of data-taking, or never."
Read more at Science Daily
Alga takes first evolutionary leap to multicellularity
This is the second time researchers have coaxed a single-celled organism into becoming multicellular – two years ago, the same was done with brewers yeast. But the alga is an entirely different organism, and comparing the two could explain how the transition to multicellular life happened a billion years ago.
Multicellularity has evolved at least 20 times since life first began, but no organisms have made the leap in the past 200 million years, so the process is difficult to study. To replicate the step in the lab, Will Ratcliff, an evolutionary biologist at the Georgia Institute of Technology in Atlanta, and colleagues grew 10 cultures of a single-celled alga, Chlamydomonas reinhardtii. Every three days, they centrifuged each culture gently and used the bottom tenth to found the next generation. Since clusters of cells settle faster than single ones, this meant that they effectively selected for algal cells that had a tendency to clump together.
Sure enough, after about 50 generations, algal cells in one of the 10 cultures began to form clusters. To the researchers' surprise, these clusters – the first step towards true multicellularity – seemed to pass through a coordinated life cycle. Cells stuck together for hours while they settled, then quickly broke apart into single cells again each of which then divided to form new multicellular colonies (see video, above).
No multicellular ancestor
Ratcliff and his colleagues used a similar technique to evolve multicellularity from a single cell of yeast. However, critics noted that although modern yeasts are single-celled, they have descended from a multicellular ancestor, so the yeast may have merely been exhibiting an ancestral hangover. Chlamydomonas, on the other hand, has always been unicellular.
Another difference between the two organisms is that they become multicellular in different ways. Individual yeast cells remain attached to one another after cell division to form multicellular "snowflakes" that reproduce by breaking off arms. The algal cells, in contrast, divide fully but the cells remain embedded in a jelly-like sheath. This multicellular mass later releases individual cells to reproduce.
"Those differences matter," says Michael Travisano of the University of Minnesota in St Paul, who supervised Ratcliff's work. Further study of the differences could shed light on why multicellularity has developed differently in the various lineages of life, he says.
Read more at New Scientist
Toothy Dino Terrorized Utah Before T. Rex
“King of Gore” (Lythronax argestes) had looks and a lifestyle to match its name. Described in the latest issue of the journal PLoS ONE, it was by far the scariest large predatory dinosaur alive at that time during the Late Cretaceous Period.
“We thought that Lythron, or gore in Greek, exemplified its presumed lifestyle as a predator with its head covered in the blood of a dead animal,” lead author Mark Loewen, a research associate at the Natural History Museum of Utah, told Discovery News. The dino co-existed with the largest alligator that ever lived, 40-foot-long Deinosuchus, which it probably avoided in favor of easier prey.
“(Lythronax's) forward-facing eyes, powerful limbs and large size would have made it an efficient hunter of both duckbilled dinosaurs and horned dinosaurs like Diabloceratops,” added co-author Joseph Sertich, curator of Vertebrate Paleontology at the Denver Museum of Nature and Science.
“A mouthful of knife-edged teeth set in powerful jaws would have made short work of potential prey, carving out huge chunks of flesh and bone to swallow hole,” Sertich continued.
A Bureau of Land Management employee named Scott Richardson first discovered the dinosaur’s fossilized skeleton. For the study, Loewen and his team excavated the remains and analyzed them. They compared 501 skeletal features of Lythronax with those of 54 different other species of known, carnivorous dinos. The paleontologists found that Lythronax is most closely related to T. rex and another dinosaur known as Tarbosaurus bataar.
In terms of size, Sertich said that Lythronax was smaller than T. rex, reaching around 30 feet in length as opposed to 40 plus feet. Lythronax was no lightweight, though, and would have tipped the scales at about nearly 3 tons.
Both “King of Gore” and “Tyrant Lizard King” had about the same number of teeth set in a wide skull. Their snouts were short and narrow, but widened at the eyes to permit binocular vision.
“Binocular vision requires eyes set slightly apart that have overlapping fields of view, meaning the same eye sees the same thing at the same time from a slightly different perspective,” Loewen explained. “This allows the animal to have depth perception.”
Although T. rex emerged some 10 million years after Lythronax, both lived at a place called Laramidia, which existed along the western shores of a great seaway that separated North America. The tyrannosaurid dinosaurs likely evolved in isolation on the island continent, with incursions of the seaway separating small areas of land from each other. This further allowed different species of dinosaurs to evolve on different parts of the landmass.
Sertich explained that rising mountains and fluctuating sea levels made for a very dynamic landscape, which set the stage for the evolution of unique dinosaurs and their ecosystems.
“Laramidia over its history was a paradise of dinosaur evolution,” Loewen said. “Many groups, including ankylosaurs, ceratopsians, hadrosaurs, ornithomimids and tyrannosaurs underwent radiations on this island continent. In some ways, it was the crucible of evolution during the Late Cretaceous.”
The researchers unearthed the remains of a new specimen of Teratophoneus that is the most complete tyrannosaur from southern Laramidia. Together, all of the fossils suggest that the evolution of T. rex and its relatives was much more complex than previously thought.
Read more at Discovery News
Runner Assigned Number 666 Refuses to Compete
Thacker refused to wear the number because of her religious faith: “I didn’t want to risk my relationship with God and try to take that number,” Thacker told a local television station. Her coach realized the problem and tried to have a different number issued by the race officials but were unsuccessful, so Thacker withdrew from the competition.
While the unlucky number 13 is widely avoided (even in building floors and airplane seats), 666 has an especially sinister tone for many people. According the Book of Revelation a Satanic figure will appear in the End Times and begin to take over the world. Devout Christians are urged to reject anything associated with 666: “And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name” (13:17).
Thacker is of course not the first Christian to take issue with the number. Earlier this year a Tennessee man quit his job as a maintenance worker because the W-2 tax form he received included the number 666. A Colorado / New Mexico road originally numbered 666 was also re-numbered Highway 491; it had been dubbed “The Devil’s Highway” due in part to the Satanic connotation and its high number of traffic fatalities.
Satan, Superstition, and Sports
Thacker’s stand on the issue has divided the community. Some dismiss her as a superstitious sap who threw away a chance at a state championship. Others, however, see her as a hero for standing up to the school and sticking by her Christian convictions.
Regardless of which camp you fall into, Thacker’s decision was almost certainly the wise one: competing under the sinister 666 would definitely have affected her performance. Not because of Satan, but because of its psychological effect.
Competing is difficult enough as it is, and as any athlete knows, the game is as much mental as it is physical. It doesn’t matter how hard you train or how good your equipment is, if you can’t focus you won’t achieve peak performance. Thacker’s belief in the Devil and concern over wearing the Antichrist’s number would have distracted her and kept her from doing her best, turning the situation into a self-fulfilling prophecy.
Read more at Discovery News
Nov 5, 2013
Nests of Big-Clawed Dinosaurs Found in Mongolia
The nesting colony contained at least 17 clutches of eggs.
"Not only is this the largest colony of nonavian theropods, but this is the best documented site," said study co-author Yoshitsugu Kobayashi, a vertebrate paleontologist at Hokkaido University in Japan, who presented the findings here at the 73rd annual Society of Vertebrate Paleontology conference.
The finding suggests the odd little creatures were social animals.
Oddball dinos
Therizinosaurs, which lived about 70 million years ago, sported huge, round guts; stumpy legs; a long neck; and a turtlelike head and beak.
Despite being members of the carnivorous group known as theropods — which includes the deadly king of the predators Tyrannosaurus rex — the waddling dinosaurs were herbivores. They also had enormous Edward Scissorhands-like, three-digit claws that may have been used to grasp branches and scrape up plant material, similar to the way bamboo-eating pandas do today.
Kobayashi and his colleagues discovered the nest while in southeastern Mongolia in 2011. On the last day of their trip, they decided to leave the area they were excavating known for therizinosaur bones to instead examine another bone bed nearby.
"There aren't many bones from this formation, so we didn't expect to find anything good," Kobayashi told LiveScience.
As the sun was setting, a guide pointed out an eggshell, and the team soon found one nest site right next to their car. Further investigation revealed four more nest sites. The following year, they returned and excavated a total of 17 clutches, for a total of about 75 eggs.
Hatched youngsters
The eggs were round, with about a 5-inch (13 centimeters) diameter and rough outer shells. Based on size analysis and the species found in nearby areas, the team concluded that therizinosaurs laid the eggs. The animals would have been about 220 lbs. (99 kilograms) when full-grown.
None of the eggs harbored dinosaur embryos. However, many of them had holes with eggshells inside, as if a baby dinosaur had poked a hole in the top of the egg and the broken shells had fallen back inside. The presence of eggshells inside the eggs suggested that most of the baby dinosaurs had hatched.
That finding, in turn, indicated the adults must have guarded the eggs to protect them from predators, Kobayashi said.
Communal animals
The finding bolsters the notion that therizinosaurs were social animals that hung out together.
"We have some very intriguing evidence of mass congregation in therizinosaurs," said Lindsay Zanno, director of the paleontology and geology research laboratory at the North Carolina Museum of Natural Sciences.
Read more at Discovery News
New World's Oldest Tomatillo Discovered
The 52.2-million-year-old tomatillo was discovered at the fossil-rich Laguna del Hunco, Argentina, where ancient lakebeds interlayer with volcanic ashes, providing paleontologists with precisely dated discoveries. (Minerals in the ash pin down the rock ages.)
"It's quite amazing," said Peter Wilf, a paleobotanist at Penn State University. "We've collected over 10,000 fossils and there's only one of these."
Though flattened, the ancient fruit (scientific name Physalis) looks remarkably like a modern version of the popular salsa ingredient. The fossil has a dark fruit enclosed by a ribbed calyx (a papery husk) just like modern Physalis, Wilf said. Both the fossil tomatillo and today's plants have husks with five major and five minor ribs, he added. The fossil is nearly an inch (23 millimeters) wide.
Tomatillos are members of the Solanaceae (nightshade) family, which includes tomatoes, potatoes and eggplants. Both fossil and genetic evidence suggests that Solanaceae plants originated and diversified in South America.
But until now, only fossil seeds attributed to Solanaceae plants have been discovered in South America — most of the family's early fossil history comes from Europe. The earliest South American tomato fossil larger than a seed is about 16 million years old.
"This is the first fossil anybody has ever seen of the entire tomato-potato-eggplant family," Wilf said. "It's also pretty old. This actually does match up pretty well with the idea that the Solanaceae family first diversified in South America."
The discovery also pushes back the evolutionary history of the tomato family.
Scientists sequenced the tomato genome in May 2012. The tomato family molecular clock, based on the genetic data and fossil evidence, suggests the tomato genome expanded abruptly about 60 million years ago. A molecular clock estimates when species diverged in the past.
Now, thanks to the tomatillo find, the Solanaceae molecular clock is too young, Wilf said. During his talk, he listed 11 fossils from Laguna del Hunco, such as cycads, trees and the tomatillo, that show their molecular clocks are too young.
"Almost all of the molecular ages are younger than the fossils," Wilf said.
Read more at Discovery News
Oldest Air on Earth Hiding in Antarctic Ice
Geoscientists recently identified regions of the frozen continent that potentially preserved the not-so-fresh air. Getting a whiff of the Earth’s oldest breeze would allow an analysis of chemicals in the air at a crucial point from 1.2 million to 900,000 years ago, known as the Mid-Pleistocene Transition.
During the transition, the Earth went from extreme warmth and cooling cycles alternating approximately every 41,000 years to having the cycles change only about every 100,000 years. Sediment samples drilled from the bottom of the ocean recorded the temperature differences, but scientists don’t know why the global thermostat cycles slowed.
Ice samples from other areas yielded 800,000-year-old air bubbles. Those samples showed a lockstep correlation between higher greenhouse gas levels and increased temperatures over thousands of years, according to research published in Nature.
Greenhouse gases, such as methane and carbon dioxide, may have been the culprits behind the Mid-Pleistocene Transition, as well. However, drills will need to pluck a 2.4 – 3.2 (1.5 – 2 mile)-kilometer-long ice core from the Antarctic ice to give scientists the 1.5 million-year-old sample they need.
Read more at Discovery News
Hubble Gets Personal With Nearest Stellar Neighbor
Red dwarf stars are curious objects. They’re small and dim, but have the habit of erupting in a flaring temper tantrum. In the case of Proxima, the star is not visible by the naked eye despite its relatively close proximity to our solar system. Proxima is known to undergo dramatic changes in brightness and is therefore a known “flare star.”
Exoplanet hunters have shown interest in hunting for small worlds in “habitable” orbits around red dwarfs as current exoplanet-hunting techniques favor the detection of worlds orbiting close to their host stars. As they output less energy than larger mass stars, red dwarfs’ habitable zones — the region surrounding a star where it’s neither too nor or too cold for liquid water to exist on a rocky planet’s surface — are much closer to the stars’ surface than, say, sun-like stars.
So long as any hypothetical extraterrestrial life in a red dwarf system has a high tolerance for the occasional eruption, red dwarfs could be touted as a good target for future exoplanet-hunting telescopes.
Another interesting fact about red dwarfs, that could boost their life-giving potential, is their longevity. According to a NASA/Hubble news release, “astronomers predict that (Proxima) will remain middle-aged — or a “main sequence” star in astronomical terms — for another four trillion years, some 300 times the age of the current Universe.” (Emphasis added.)
Considering our sun will reach the end of its life within approximately 5 billion years (and fry all life on Earth in less than half that time), stars like Proxima Centauri appear to be a better match for the evolution of life, perhaps nurturing lifeforms for tens, hundreds or even thousands of billions of years.
Read more at Discovery News
Nov 4, 2013
Extinct 'Megamouth' Shark Species Identified
The ancient shark likely prowled both deep and shallow waters for plankton and fish, using its massive mouth to filter food.
"It was a species that was known to be a new species for a long time," said study co-author Kenshu Shimada, a paleobiologist at DePaul University in Chicago. "But no one had taken a serious look at it," said Shimada, who described the new species here at the 73rd annual meeting of the Society for Vertebrate Paleontology.
Shark teeth
Scientists first found shark teeth from the species in the 1960s, but at the time, there were no similar living creatures, so scientists didn't quite know what to make of the find. Over time, researchers turned up hundreds of similar teeth along the coast of California and Oregon. All the specimens were tossed in a drawer and forgotten in the collections of the Los Angeles County Museum and a few other California museums.
Then in 1976, scientists discovered the modern megamouth shark, dubbed Megachasma pelagios, which feeds exclusively on shrimplike creatures called plankton. The sharks use their mammoth mouths to engulf plankton-filled water, forcing the water through gills equipped with a filtering apparatus called gill rakers, which direct plankton into the digestive track.
The monster beast is also a vertical migrator, meaning the shark lurks in the deep ocean during the day, but comes up to the shallow surface waters chasing plankton swarms at night, Shimada said.
Revisiting a shark
When Shimada came across the shark teeth at the Los Angeles County Museum, he was told that other scientists were studying them. But it turned out those scientists weren't actively working on the species.
Shimada contacted those scientists, Douglas Long of the California Academy of Sciences and Bruce Welton of the New Mexico Museum of Natural History, and persuaded them to take a second look with him.
The team found the ancient creature was related to M. pelagios. But unlike the modern shark, it had slightly longer, pointier teeth.
"That suggests that they probably had a wider food selection," Shimada told LiveScience. "They could have probably eaten plankton, but they were also probably feeding on fish."
The team determined the ancient creature would've sported a slightly longer, less-wide snout than the modern megamouth shark. The extinct creature also likely grew to an average of 20 feet (6 meters), but the biggest megamouth individuals might have been nearly 27 feet (8 m) long, not much different from their modern relatives.
Because the teeth were found in both deep-ocean and near-shore marine sediments, the extinct monster probably had already begun to migrate between the deep and shallow oceans in search of food.
Read more at Discovery News
Newly Discovered Giant Platypus Rewrites History
However, a newly discovered extinct 3-foot-long platypus suggests multiple species of the mixed-up mammals swam ancient Australian waters at the same time.
All that remains of the giant platypus, named Obdurodon tharalkooschild, is a single tooth. The tooth dates to between five and 15 million years ago. Like much of the rest of the playtpus, the tooth was unique enough to identify the creature and hint at its lifestyle.
“Like other platypuses, it was probably a mostly aquatic mammal, and would have lived in and around the freshwater pools in the forests that covered the Riversleigh area millions of years ago,” said co-author Suzanne Hand of the University of New South Wales in a press release. “Obdurodon tharalkooschild was a very large platypus with well-developed teeth, and we think it probably fed not only on crayfish and other freshwater crustaceans, but also on small vertebrates including the lungfish, frogs, and small turtles that are preserved with it in the Two Tree Site fossil deposit.”
Platypuses’ bodies feature a bizarre grab-bag of biology. Platypuses eat with rubbery-bills that can sense electromagnetic energy fields. Their body temperature only reaches 90 degrees Fahrenheit. They waddle on land on their knuckles, like gorillas, with their legs splayed like lizards. The animals swim using a hairy, beaver-like tail packed with fat to help them survive starvation. Platypuses’ ear openings lie beneath their jaws. The males sport venomous spikes on their elbows. Females lay eggs, instead of giving birth.
Read more at Discovery News
Weird Forests Once Sprouted in Antarctica
Some 250 million years ago, during the late Permian and early Triassic, the world was a greenhouse, much hotter than it is today. Forests carpeted a non-icy Antarctic. But Antarctica was still at a high latitude, meaning that just as today, the land is bathed in round-the-clock darkness during winter and 24/7 light in the summer.
The question, said Patricia Ryberg, a postdoctoral researcher at the University of Kansas Biodiversity Institute, is how plants coped with photosynthesizing constantly for part of the year and then not at all when the winter sun set.
"The trees are the best way to figure this out, because trees record physiological responses" in their rings, Ryberg told LiveScience.
A forest mystery
Fossilized wood and leaf impressions record a history of the Antarctic forests. The leaf impressions appear to show mats of leaves, as if the trees had all shed at once — a sign of a deciduous forest.
To confirm this, Ryberg and her colleagues gathered samples of fossil wood and examined the tree rings. Wood cells in the rings reveal how the trees grew: Early wood is produced when the tree is growing upward and outward. Late wood is produced when the tree is preparing to go dormant. At that point, the tree stops growing and starts storing carbon in its cells. Late wood is denser than early wood, and has thicker cell walls.
Deciduous and evergreen trees have different patterns of late and early wood. Ryberg and her colleagues examined the Antarctic fossils and found that they looked evergreen.
"Now we have leaves that suggest a deciduous habit and fossil wood that is suggesting an evergreen habit, so we have a bit of a contradiction going on," Ryberg said here Wednesday (Oct. 30) at the annual meeting of the Geological Society of America.
Mixed results
Follow-up studies analyzing carbon molecules in the fossil wood also gives both deciduous and evergreen answers, Ryberg said. The implication is that ancient Antarctic forests may have been a mix of deciduous and evergreen.
"It's not one or the other," she said. "It's actually both."
Much of the ring structure looks tropical, Ryberg added. Tropical trees that are not exposed to seasons experience a sort of short-term dormancy that echoes what is seen in the Antarctic wood.
"But they weren't growing in the tropics, so obviously it's two different environmental characteristics," Ryberg said.
Read more at Discovery News
Galaxy Hosts 10 Billion 'Habitable' Earth-Size Worlds
On Monday, a team of scientists announced an answer: about 10 billion -- enough for one planet for every person in the world, with 3 billion to spare.
“We didn’t know what to expect,” astronomer Geoffrey Marcy, with the University of California at Berkeley, told Discovery News.
“It was only 18 years ago that most of us, myself included, thought we might never discover any planets of any sort around other stars. It was thought to be impossible. To have gone from where we were in the 1990s with nothing, to now finding Earth-sized planets in their habitable zones really boggles my mind,” Marcy said.
Before a positioning system problem sidelined the telescope in May, Kepler focused on a patch of the sky in the constellation Cygnus and dutifully assembled a digital picture every 30 minutes to send back to Earth.
Astronomers analyzed the images to find slight changes in the amount of light coming from about 150,000 target stars.
Some variations were due to star flares and other stellar phenomena, but others provided telltale clues that an orbiting planet had passed across the face of its parent star, relative to Kepler’s point of view, blocking a smidgen of light in the process.
The timing of repeat light dips indicated the planet’s distance from its host star, information scientists could then use to estimate the planet’s surface temperature. Of particular interest are planets suitably positioned for liquid surface water, as water is believed to be necessary for life.
Finally, by measuring how much starlight was blocked during a transit, scientists could calculate a candidate planet’s diameter. Smaller planets like Earth block less light than giant Jupiter-sized worlds.
Accounting for all the other viewing angles not observed by Kepler and extrapolating from the data, the study finds that 22 percent of sun-like stars in the Milky Way have planets one- to two times the size of Earth orbiting in their habitable zones.
With about 50 billion sun-like stars in the galaxy, that means about one out of every five stars, or roughly 10 billion, have an Earth-sized planet in its habitable zone.
“This is the first time that a team has offered such a number for stars like the sun based on a thorough detection analysis,” said Kepler mission science Natalie Batalha, with NASA’s Ames Research Center in Moffett Field, Calif., told reporters on a conference call.
Read more at Discovery News
Nov 3, 2013
Global Warming Led to Dwarfism in Mammals -- Twice
Researchers have known for years that mammals such as primates and the groups that include horses and deer became much smaller during a period of warming, called the Paleocene-Eocene Thermal Maximum (PETM), about 55 million years ago.
Now U-M paleontologist Philip Gingerich and his colleagues have found evidence that mammalian "dwarfing" also occurred during a separate, smaller global warming event that occurred about 2 million years after the PETM, around 53 million years ago.
"The fact that it happened twice significantly increases our confidence that we're seeing cause and effect, that one interesting response to global warming in the past was a substantial decrease in body size in mammalian species," said Gingerich, a professor of earth and environmental sciences.
The research team also includes scientists from the University of New Hampshire, Colorado College and the California Institute of Technology. The researchers are scheduled to present their findings Friday, Nov. 1, in Los Angeles at the annual meeting of the Society of Vertebrate Paleontology.
They concluded that decreased body size "seems to be a common evolutionary response" by mammals to extreme global warming events, known as hyperthermals, "and thus may be a predictable natural response for some lineages to future global warming."
The PETM lasted about 160,000 years, and global temperatures rose an estimated 9 to 14 degrees Fahrenheit at its peak. The smaller, later event analyzed in the latest study, known as ETM2 (Eocene Thermal Maximum 2), lasted 80,000 to 100,000 years and resulted in a peak temperature increase of about 5 degrees Fahrenheit.
Teeth and jaw fossils of early hoofed mammals and primates that spanned this later climatic event were collected in Wyoming's Bighorn Basin, and the size of molar teeth was used as a proxy for body size. The researchers found that body size decreased during ETM2, but not as much as the dwarfism seen in PETM fossils.
For example, the study revealed that a lineage of early horses the size of a small dog, called Hyracotherium, experienced a body-size decrease of about 19 percent during ETM2. The same horse lineage showed a body-size decrease of about 30 percent during the PETM. After both events, the animals rebounded to their pre-warming size.
"Interestingly, the extent of mammalian dwarfism may be related to the magnitude of the hyperthermal event," said team member Abigail D'Ambrosia of the University of New Hampshire.
An ancient ungulate called Diacodexis decreased about 20 percent in size during ETM2, and the primate Cantius decreased 8 percent.
The burning of fossil fuels and the resulting release of heat-trapping greenhouse gases -- mainly carbon dioxide -- is blamed for present-day climate warming. The ancient warming events may have been caused by the release of seabed methane clathrates, a kind of methane ice found in ocean sediments, though this topic remains an area of active research, Gingerich said. Methane is a more potent greenhouse gas than carbon dioxide, and atmospheric methane is eventually transformed into carbon dioxide and water.
The parallels between ancient hyperthermals and modern-day warming make studies of the fossil record particularly valuable, said team member Will Clyde of the University of New Hampshire.
"Developing a better understanding of the relationship between mammalian body size change and greenhouse gas-induced global warming during the geological past may help us predict ecological changes that may occur in response to current changes in Earth's climate," Clyde said.
Read more at Science Daily
Important Mechanism Behind Nanoparticle Reactivity Discovered
An international team of researchers has used pioneering electron microscopy techniques to discover an important mechanism behind the reaction of metallic nanoparticles with the environment.
Crucially, the research led by the University of York and reported in Nature Materials, shows that oxidation of metals -- the process that describes, for example, how iron reacts with oxygen, in the presence of water, to form rust -- proceeds much more rapidly in nanoparticles than at the macroscopic scale. This is due to the large amount of strain introduced in the nanoparticles due to their size which is over a thousand times smaller than the width of a human hair.
Improving the understanding of metallic nanoparticles -- particularly those of iron and silver -- is of key importance to scientists because of their many potential applications. For example, iron and iron oxide nanoparticles are considered important in fields ranging from clean fuel technologies, high density data storage and catalysis, to water treatment, soil remediation, targeted drug delivery and cancer therapy.
The research team, which also included scientists from the University of Leicester, the National Institute for Materials Science, Japan and the University of Illinois at Urbana-Champaign, USA, used the unprecedented resolution attainable with aberration-corrected scanning transmission electron microscopy to study the oxidisation of cuboid iron nanoparticles and performed strain analysis at the atomic level.
Lead investigator Dr Roland Kröger, from the University of York's Department of Physics, said: "Using an approach developed at York and Leicester for producing and analysing very well-defined nanoparticles, we were able to study the reaction of metallic nanoparticles with the environment at the atomic level and to obtain information on strain associated with the oxide shell on an iron core.
"We found that the oxide film grows much faster on a nanoparticle than on a bulk single crystal of iron -- in fact many orders of magnitude quicker. Analysis showed there was an astonishing amount of strain and bending in nanoparticles which would lead to defects in bulk material."
The scientists used a method known as Z-contrast imaging to examine the oxide layer that forms around a nanoparticle after exposure to the atmosphere, and found that within two years the particles were completely oxidised.
Corresponding author Dr Andrew Pratt, from York's Department of Physics and Japan's National Institute for Materials Science, said: "Oxidation can drastically alter a nanomaterial's properties -- for better or worse -- and so understanding this process at the nanoscale is of critical importance. This work will therefore help those seeking to use metallic nanoparticles in environmental and technological applications as it provides a deeper insight into the changes that may occur over their desired functional lifetime."
The experimental work was carried out at the York JEOL Nanocentre and the Department of Physics at the University of York, the Department of Physics and Astronomy at the University of Leicester and the Frederick-Seitz Institute for Materials Research at the University of Illinois at Urbana-Champaign.
The scientists obtained images over a period of two years. After this time, the iron nanoparticles, which were originally cube-shaped, had become almost spherical and were completely oxidised.
Read more at Science Daily
Crucially, the research led by the University of York and reported in Nature Materials, shows that oxidation of metals -- the process that describes, for example, how iron reacts with oxygen, in the presence of water, to form rust -- proceeds much more rapidly in nanoparticles than at the macroscopic scale. This is due to the large amount of strain introduced in the nanoparticles due to their size which is over a thousand times smaller than the width of a human hair.
Improving the understanding of metallic nanoparticles -- particularly those of iron and silver -- is of key importance to scientists because of their many potential applications. For example, iron and iron oxide nanoparticles are considered important in fields ranging from clean fuel technologies, high density data storage and catalysis, to water treatment, soil remediation, targeted drug delivery and cancer therapy.
The research team, which also included scientists from the University of Leicester, the National Institute for Materials Science, Japan and the University of Illinois at Urbana-Champaign, USA, used the unprecedented resolution attainable with aberration-corrected scanning transmission electron microscopy to study the oxidisation of cuboid iron nanoparticles and performed strain analysis at the atomic level.
Lead investigator Dr Roland Kröger, from the University of York's Department of Physics, said: "Using an approach developed at York and Leicester for producing and analysing very well-defined nanoparticles, we were able to study the reaction of metallic nanoparticles with the environment at the atomic level and to obtain information on strain associated with the oxide shell on an iron core.
"We found that the oxide film grows much faster on a nanoparticle than on a bulk single crystal of iron -- in fact many orders of magnitude quicker. Analysis showed there was an astonishing amount of strain and bending in nanoparticles which would lead to defects in bulk material."
The scientists used a method known as Z-contrast imaging to examine the oxide layer that forms around a nanoparticle after exposure to the atmosphere, and found that within two years the particles were completely oxidised.
Corresponding author Dr Andrew Pratt, from York's Department of Physics and Japan's National Institute for Materials Science, said: "Oxidation can drastically alter a nanomaterial's properties -- for better or worse -- and so understanding this process at the nanoscale is of critical importance. This work will therefore help those seeking to use metallic nanoparticles in environmental and technological applications as it provides a deeper insight into the changes that may occur over their desired functional lifetime."
The experimental work was carried out at the York JEOL Nanocentre and the Department of Physics at the University of York, the Department of Physics and Astronomy at the University of Leicester and the Frederick-Seitz Institute for Materials Research at the University of Illinois at Urbana-Champaign.
The scientists obtained images over a period of two years. After this time, the iron nanoparticles, which were originally cube-shaped, had become almost spherical and were completely oxidised.
Read more at Science Daily
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