Almost every particle has an antimatter counterpart: a particle with the same mass but opposite charge, among other qualities.
This seems to be true of neutrinos, tiny particles that are constantly streaming through us. Judging by the particles released when a neutrino interacts with other matter, scientists can tell when they've caught a neutrino versus an antineutrino.
But certain characteristics of neutrinos and antineutrinos make scientists wonder: Are they one and the same? Are neutrinos their own antiparticles?
This isn't unheard of. Gluons and even Higgs bosons are thought to be their own antiparticles. But if scientists discover neutrinos are their own antiparticles, it could be a clue as to where they get their tiny masses -- and whether they played a part in the existence of our matter-dominated universe.
Dirac versus Majorana
The idea of the antiparticle came about in 1928 when British physicist Paul Dirac developed what became known as the Dirac equation. His work sought to explain what happened when electrons moved at close to the speed of light. But his calculations resulted in a strange requirement: that electrons sometimes have negative energy.
"When Dirac wrote down his equation, that's when he learned antiparticles exist," says André de Gouvêa, a theoretical physicist and professor at Northwestern University. "Antiparticles are a consequence of his equation."
Physicist Carl Anderson discovered the antimatter partner of the electron that Dirac foresaw in 1932. He called it the positron -- a particle like an electron but with a positive charge.
Dirac predicted that, in addition to having opposite charges, antimatter partners should have another opposite feature called chirality, which represents one of the inherent quantum properties a particle has. A particle can have either a right-handed or left-handed chirality.
Dirac's equation allowed for neutrinos and antineutrinos to be different particles, and, as a result, four types of neutrino were possible: neutrinos with left- and right-handed chirality and antineutrinos with left- and right-handed chirality.
But if the neutrinos had no mass, as scientists thought at the time, only left-handed neutrinos and right-handed antineutrinos needed to exist.
In 1937, Italian physicist Ettore Majorana debuted another theory: Neutrinos and antineutrinos are actually the same thing. The Majorana equation described neutrinos that, if they happened to have mass after all, could turn into antineutrinos and then back into neutrinos again.
The matter-antimatter imbalance
Whether neutrino masses were zero remained a mystery until 1998, when the Super-Kamiokande and SNO experiments found they do indeed have very small masses -- an achievement recognized with the 2015 Nobel Prize for Physics. Since then, experiments have cropped up across Asia, Europe and North America searching for hints that the neutrino is its own antiparticle.
The key to finding this evidence is something called lepton number conservation. Scientists consider it a fundamental law of nature that lepton number is conserved, meaning that the number of leptons and anti-leptons involved in an interaction should remain the same before and after the interaction occurs.
Scientists think that, just after the big bang, the universe should have contained equal amounts of matter and antimatter. The two types of particles should have interacted, gradually canceling one another until nothing but energy was left behind. Somehow, that's not what happened.
Finding out that lepton number is not conserved would open up a loophole that would allow for the current imbalance between matter and antimatter. And neutrino interactions could be the place to find that loophole.
Neutrinoless double-beta decay
Scientists are looking for lepton number violation in a process called double beta decay, says SLAC theorist Alexander Friedland, who specializes in the study of neutrinos.
In its common form, double beta decay is a process in which a nucleus decays into a different nucleus and emits two electrons and two antineutrinos. This balances leptonic matter and antimatter both before and after the decay process, so it conserves lepton number.
If neutrinos are their own antiparticles, it's possible that the antineutrinos emitted during double beta decay could annihilate one another and disappear, violating lepton number conservation. This is called neutrinoless double beta decay.
Such a process would favor matter over antimatter, creating an imbalance.
"Theoretically it would cause a profound revolution in our understanding of where particles get their mass," Friedland says. "It would also tell us there has to be some new physics at very, very high energy scales -- that there is something new in addition to the Standard Model we know and love."
It's possible that neutrinos and antineutrinos are different, and that there are two neutrino and anti-neutrino states, as called for in Dirac's equation. The two missing states could be so elusive that physicists have yet to spot them.
But spotting evidence of neutrinoless double beta decay would be a sign that Majorana had the right idea instead -- neutrinos and antineutrinos are the same.
Read more at Science Daily
Jan 30, 2016
Super-sharp images through thin optical fibers
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| Electron microscope image of one of the photonic crystal fibres made at MPL for this research. The glass is black, the air is grey and the red dot illustrates the focus. |
Optical imaging via ultrathin fibre probes is extremely useful for taking a look inside the human body in a minimally invasive manner. Unfortunately, the resolution of current fibre endoscopes is one micrometre at best. This is not enough to see interesting and important fine features in biological cells, for example. Some endoscopes use a high number of separate fibres bound together into a fibre bundle. Each fibre then acts like a discrete pixel to form the final pixelated image. However such bundles tend to be quite thick, at least a millimetre in diameter.
An alternative is fibre endoscopes based on 'multimode' fibres. These could offer imaging with a better view and be as thin as a tenth of a millimetre. A multimode fibre uses only a single fibre core that can transmit an entire image. Unfortunately, the image becomes scrambled as it passes through the fibre. However, some tricks for unscrambling these images are available. The main limiting factor for the resolution of these multimode endoscopes is that the fibres only transmit light that propagates along the fibre axis. Light under a small angle can still bounce from the fibre walls. But if this angle gets too large, the light will simply leak out to the side. FOM postdoc Dr Lyubov Amitonova and her colleagues at UT and MPL have now shown that with photonic crystal fibres this limitation can be overcome.
Unique crystal fibre probe
Conventional ('step-index') fibres consist of two zones of different material (an outer cladding and an inner core) with distinct refraction indices, which enable light transmission down the fibre axis by total internal reflection. Photonic crystal fibres are built differently: they are made of one material only and light guiding is realised through the presence of a specific pattern of holes in the cladding, which are filled with air. Tailoring the cladding structure of such a fibre provides a unique tool for engineering specific fibre-optic properties. In this project, the scientists have designed and made such a fibre to focus a laser beam through the fibre down to 0.52 micrometres, using visible red light.
Sharp focus and high resolution
A photonic crystal fibre acts as a multimode fibre in which the image typically gets scrambled due to light bouncing off the possibly irregular wall of the fibre. The technique of complex wavefront shaping, invented at UT, is able to undo such scrambling and make a sharp focus. This is achieved by pre-shaping the light into the precise form needed to make a sharp image behind the fibre before the light actually enters the fibre. Using this approach, Amitonova and her colleagues have succeeded in focusing light at the fibre output facet of different multimode fibres including several unique photonic crystal fibres. They have shown that the complex wavefront shaping technique together with a properly designed multimode photonic crystal fibre allows the creation of a tightly focused spot at the desired position on the fibre output facet with a subwavelength beam waist. This paves the way towards high-resolution endoscopic imaging via fibre probes so thin that they could be inserted, for instance, into tiny blood vessels not much thicker than a human hair.
Read more at Science Daily
Moon-Forming Earth Impact was a Direct Hit
An analysis of seven moon rocks collected by Apollo astronauts, one lunar meteorite and six volcanic rocks from Earth’s mantle shows that the moon and Earth have nearly identical oxygen isotopes, an indication that Earth and second body, known as Theia (“mother of the moon”), ended up quite thoroughly mixed.
The finding, reported in this week’s Science, runs contrary to previous research showing less mixing of the bodies.
“We don’t see any difference between the Earth’s and the moon’s oxygen isotopes. They’re indistinguishable,” geochemist Edward Young, with the University of California Los Angeles, said in a press release.
If Earth and Theia collided in a glancing side blow, as previously hypothesized, most of the moon would be comprised of Theia and it would have a different lineup of oxygen isotopes than Earth.
A head-on crash would cause more mixing, giving Earth and the moon a more similar list of building materials.
“Theia was thoroughly mixed into both the Earth and the moon and (was) evenly dispersed between them,” Young said. “This explains why we don’t see a different signature of Theia in the moon versus the Earth.”
From Discovery News
Jan 29, 2016
500-Pound Bird Was Eaten to Extinction by Humans
The findings, published in the journal Nature Communications, provide the first direct evidence that humans played a substantial role in the extinction of early Australian animals. In this case, the victim was a flightless 7-foot-tall bird known as Genyornis newtoni.
Humans likely enjoyed the bird’s meaty goodness, and there’s also strong evidence that people were cooking its enormous eggs. Each egg was the size of a cantaloupe and weighed about 3.5 pounds, according to co-author Gifford Miller of the University of Colorado Boulder.
Miller and his team unearthed prehistoric burnt Genyornis eggshell fragments in tight clusters less than 10 feet in diameter, with no other eggshell fragments nearby. In a press release, he said that some individual fragments from the same clusters had heat gradient differences of nearly 1,000 degrees Fahrenheit, conditions virtually impossible to reproduce with natural wildfires there.
Miller explained that amino acids, the building blocks of proteins, decompose in a predictable fashion inside eggshells over time. When an egg is burned at one end but not the other, the scorching leaves behind a distinctive “gradient” from total amino acid decomposition to minimal. Such a gradient could only be produced by a localized heat source, likely an ember, he said, and not from the sustained high heat produced regularly by Australian wildfires both in the distant past and today.
“We can’t come up with a scenario that a wildfire could produce those tremendous gradients in heat,” he continued. “We instead argue that the conditions are consistent with early humans harvesting Genyornis eggs, cooking them over fires, and then randomly discarding the eggshell fragments in and around their cooking fires.”
Providing support to that theory is the presence at other Australian sites of nearly identical fire-toasted emu eggshell fragments dating to the same period. Emus still exist today in Australia, where both their eggs and meat are consumed. They are much smaller than Genyornis was, though, weighing about 100 pounds. They also are fairly prodigious egg layers, with each emu producing about 30–50 eggs per breeding season.
In addition to sharing turf with the early emus, Genyornis roamed the Australian outback with an astonishing menagerie of other now-extinct enormous animals. They included a 1,000-pound kangaroo, a 2-ton wombat, a 25-foot-long-lizard, a 300-pound marsupial lion and a Volkswagen-sized tortoise.
While this motley crew had its own set of predators and prey, life really took a turn for the worse after the arrival of the first humans, the researchers indicate. They point out that more than 85 percent of Australia’s mammals, birds and reptiles weighing over 100 pounds went extinct shortly thereafter.
Read more at Discovery News
World's Oldest Tea Found in Chinese Emperor's Tomb
The plant remains were retrieved from burial pits around the tomb of Liu Qi, the fourth emperor of the Han dynasty who lived between 188 and 141 BC, and his wife, a team of researchers from China and Britain wrote in the journal Scientific Reports.
The oldest written reference to tea is from the year 59 BC. And the oldest physical remains ever discovered were hundreds of years younger than the new find — dating from the northern Song Dynasty (960-1,127 AD).
“Our study reveals that tea was drunk by Han Dynasty emperors as early as 2,100 years BP (before present),” wrote the team.
They compared this tea to residues unearthed among burial artifacts at Gurgyam Cemetery in Tibet, and dated to about the second or third century AD.
This revealed that tea was already transported from China to central Asia and the Tibetan Plateau several hundred years earlier than previously recorded — by around 1,800 years ago, said the researchers.
Tea does not grow in Tibet.
“This indicates that one branch of the Silk Road passed through western Tibet at that time,” said the researchers.
The previous oldest record of tea having been carried along the Silk Road into Tibet, central Asia or southern Asia from Chia, was from the Tang Dynasty (618-907 AD).
“These data indicate that tea was part of trade of luxury products, alongside textiles, that moved along the Silk Road around 2,000 years ago and were traded up into Tibet,” the study said.
Read more at Discovery News
Ancient Babylonians Tracked Jupiter With Calculus
An analysis of the tablets, reported in the journal Science, reveals ancient Babylonians were able to calculate the position of Jupiter using geometric techniques previously believed to have been first used some 1,400 years later in 14th century Europe.
“These texts are the earliest evidence we have from antiquity of mathematical astronomy,” said the study’s author Dr Mathieu Ossendrijver, a historian on Babylonian astronomy with the Humboldt University in Berlin.
“It describes Jupiter’s velocity across the sky and how that changes with time.”
The tablets, which are housed at the British Museum, are believed to have been unearthed from an archaeological dig in what is now modern day Iraq sometime in the 1800s.
The almost completely intact tablets are thought to have been written in Babylon between 350 and 50 BCE.
The tablets are part of a larger collection of 450 astronomy tablets from Babylon and Uruk containing celestial data arranged in rows and columns, together with instructions.
Dr Ossendrijver examined five tablets numbered as trapezoid text A to trapezoid text E, four of which deal with geometrical trapezoid shapes, but nobody understood what they were about.
One tablet key to puzzle
However, one of the tablets — trapezoid text A — provided Dr Ossendrijver with the key to understanding the other four tablets.
“I discovered that they describe the motion of Jupiter as a velocity, the number of degrees it moves across the sky in a day,” Dr Ossendrijver said.
“If you plot the velocity of Jupiter against time, you get a creeping curve which looks like a rectangle with a slanted top — that’s the trapezoid.”
The tablets show two intervals from when Jupiter first appears along the horizon at night, to the planet’s position in the sky after 60 and 120 days.
The tablets also computed the time when Jupiter covers half of this 60-day distance by partitioning the trapezoid into two smaller ones of equal area.
“We’re not really sure why the Babylonians were so interested in the motion of the planet Jupiter, but one possible explanation is that Jupiter was associated with Marduk the supreme god of Babylon,” Dr Ossendrijver said.
“These astronomers or priests were employed by Babylon’s main temple where Marduk was venerated. Each god had a star and Marduk’s was Jupiter.”
Babylonian writing is thought to have originally developed as an accounting system for keeping track of property such as sheep, grain, or the size of a field.
Read more at Discovery News
Gigantic Gas Cloud on Collision Course With Our Galaxy
(The dinosaur, not the British rock band.)
And it’s a case of “what goes up must come down” — the cloud is on a ballistic trajectory after being blown out from our own galaxy, 70 million years ago.
Known about since 1963, the “Smith Cloud” — so-called after its discoverer Gail P. Smith — was first detected at the Dwingeloo Radio Observatory in the Netherlands. It’s since been repeatedly observed in radio wavelengths with the NRAO’s Green Bank Observatory in West Virginia and recently with the Hubble Space Telescope, which determined that it does in fact contain heavy elements like sulfur (contrary to some earlier analyses). This, along with its arcing trajectory, strongly indicates an origin from the star-enriched region along the outermost edges of our galaxy.
“The cloud is an example of how the galaxy is changing with time,” said Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland, leader of the research team. “It’s telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another.”
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| Diagram of the 100-million-year “boomerang” trajectory of the Smith Cloud. |
When the high-velocity cloud does impact the disc of the galaxy — in about another 30 million years or so — it will be on a different (albeit neighboring) arm than the one in which our solar system resides.
The collision will likely ignite an explosion of star formation around the impact site, perhaps with enough matter and energy to create two million new solar-mass stars.
Read more at Discovery News
This Toad Isn’t Eating a Bug. The Bug Is Eating It
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| What's the matter, vicious beetle larva got your tongue? |
But like the Mighty Ducks rose up to defeat the seemingly unbeatable Team Iceland, one beetle has evolved to put amphibians in their place. As larvae, beetles of the genus Epomis actually entice frogs and toads and salamanders to attack them, then whip around and sink their huge, hooked jaws into the attackers, slowly draining the life out of them. When the larvae transform into adult beetles, they get right back to it, only now they dispatch amphibians even more brutally. Like, a kind of brutality that involves snipping a frog’s leg muscles so it can’t escape.
Imagine, if you will, that you’re a toad. You’re hopping along when something catches your eye: a beetle larva shifting its jaws and antennae back and forth. Your brain tells you that anything that moves and that’s small enough for you to overpower is probably food.
So it’s decided. As you draw closer to your victim, its movements get more rapid. You draw closer still, and strike.
One of two things is going to happen at this point, neither of which will end—how should I say—well for you. You’ll get the larva in your mouth and it’ll sink its jaws into your tongue, or the larva will get you somewhere on your skin—your lips or throat or flank. The larva is just too fast for you, and may be so smooth that it can repel that famous tongue of yours.
The second outcome, though, is you manage to swallow it. Not that that will do you any good. Scientists once watched a toad nab and successfully swallow a Epomis larva, only to throw it up two hours later. At first the larva lay motionless, but then suddenly it snapped out of it and attacked the toad again.
So … you’re screwed. That larva ain’t about to let go. In fact, it starts digesting your tissue. But strangely, none of your blood is coming out, and indeed “when you slice a larva open you don’t see it full of red blood,” says Gil Wizen, an entomologist at the University of Toronto. What’s probably going on here, Wizen reckons, is the larva is secreting enzymes onto the toad to melt its flesh. “So you can say that the digestion is already beginning before the food enters the mouth,” he says.
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| Those double hooked jaws sink into amphibian flesh and don’t let go. How’s that for attachment issues. |
The larva begins chewing more, says Wizen, “and what we see is that it sort of tears tissues from the amphibian’s body. After a few hours the amphibian is reduced to just a pile of bones and just a little bit of skin.”
But this was no crime of passion. The larva is more like a serial killer. Over the course of its development, it can take down as many as nine toads, frogs, newts, or salamanders. It’s got such an appetite because it goes through three phases, known as instars, in which it needs ever more food. During the first instar, when it’s relatively small, it’ll take down just one victim. In the second instar, though, it’s two or three. In the last, as many as five.
And like a serial killer, its methods grow ever more complex as it matures. The adult beetle ups its game into some seriously sadistic stuff. While it isn’t as picky an eater as the larva, feeding on worms and other insects and even injured rodents and birds, it too loves it an amphibian.
The adult beetle doesn’t lure the victim like the larva, but instead goes full-tilt rodeo with it, jumping on a toad’s rear and sinking its jaws into the flesh. These jaws are different, though. “The jaws of the larva are hooked, modified to lock onto the amphibian’s skin,” says Wizen, “whereas with the [adults], they have serrated jaws.” The adult’s mouthparts aren’t modified to hold on tight, so it has to work fast.
The beetle has jumped onto the rear of the toad for a reason. Once the victim stops bucking, the beetle makes a small incision on the lower back. “We don’t think they damage the spine of the amphibian,” Wizen says. “But what we do think—we still need to confirm this—is that they cut the connecting muscles [of the legs] so the amphibian doesn’t have any way to escape.”
With the bronco incapacitated for good, the beetle can take its time gnawing on the victim alive. When it fills up, it trots off. If the toad isn’t yet dead, something like a bird or mammal will happily finish it off.
The relationship also resists definition. While Epomis is certainly predatory, it’s also in a way parasitic. As a larva, it doesn’t necessarily kill its victims, sometimes filling up enough and just dropping off (indeed, Wizen has collected toads with the tell-tale scars of an attack). And as I mentioned earlier, adults also don’t necessarily kill their victims either. So Epomis seems to be a kind of predator-parasite hybrid.
Read more at Wired Science
Jan 28, 2016
Bed Bugs Show Resistance to Widely Used Chemicals
Virginia Tech and New Mexico State University researchers have found in a new study that a class of insecticide called neonicotinoids, or neonics, are not doing as good a job anymore at killing the nightmarish itch-inducers.
The scientists compared colonies of bed bugs from Cincinnati, Ohio and Michigan that were collected in the wild with a colony that had been kept in isolation in a special lab and had never been exposed to neonics.
The bed bugs that had never been exposed to neonics were killed easily with small amounts of insecticide, whereas the Michigan and Cincinnati bugs showed a whopping resistance, needing multiple times the dose -- 0.3 nanograms of insecticide took care of half the lab bed bugs, while 10,000 nanograms were needed to kill just 50 percent of the resistant bugs.
“Unfortunately, the insecticides we were hoping would help solve some of our bed bug problems are no longer as effective as they used to be, so we need to reevaluate some of our strategies for fighting them,” said Troy Anderson, an assistant professor of entomology at Virginia Tech and study co-author, in a release.
“While we all want a powerful tool to fight bed bug infestations, what we are using as a chemical intervention is not working as effectively as it was designed and, in turn, people are spending a lot of money on products that aren’t working,” Anderson added.
Bed bug infestations have been on the rise coast to coast in the United States, infecting places such as homes, hotels, and shelters. Their bites can wreak havoc with people physically and emotionally, and eradicating them is often costly.
“Companies need to be vigilant for hints of declining performance of products that contain neonicotinoids,” said study co-author Alva Romero, an assistant professor of entomology at New Mexico State University. “For example, bed bugs persisting on previously treated surfaces might be an indication of resistance.”
“If resistance is detected, products with different modes of action need to be considered, along with the use of non-chemical methods,” Romero said.
From Discovery News
Ice-Age Mammoth Bones Found Under Oregon Football Field
A construction crew working on an expansion and renovation of the OSU Beavers’ Valley Football Center uncovered the remains of the beast while digging in the north end of Reser Stadium. They found a large femur bone — likely a mammoth’s — as well as bones from other extinct, ice-age mammals, including a bison and what is either an ancient horse or a camel.
“There are quite a few bones, and dozens of pieces,” Loren Davis, an associate professor of anthropology at OSU, said in a statement. “Some of the bones are not in very good shape, but some are actually quite well preserved.”
Davis and his students have yet to determine the mammoth’s species — for instance, it could be a Columbian mammoth (Mammuthus columbi) or a woolly mammoth (M. primigenius), although the latter tended to live farther north.
Davis’ team also plans to use radiocarbon dating to determine how long ago the mammoth lived. Radiocarbon dating can date once-living organisms back to about 50,000 years, although different methods can help date older organic material.
In Siberia, researchers recently found a 45,000-year-old mammoth carcass with injuries indicating that ancient humans had butchered it. But the newfound mammoth in Oregon bears no such injuries, suggesting that it died of natural causes, Davis said.
“They weren’t hunted by people, that’s clear,” he said. “Animals who were sick would often go to a body of water and die there, so it’s not unusual to find a group of bones like this.”
Perhaps when these animals died, at least 10,000 years ago, the area where the stadium now stands was a bog or marsh that served as a watering hole for ice-age animals, Davis said.
Construction workers found the animal bones in a 10-foot-deep (3 meters) plot. They stopped work as soon as they uncovered the femur, said Tim Sissel, the senior project manager of Hunt/Fortis, a joint venture and general contractor on the project.
However, because there were no human artifacts or remains found, the site is not considered an archaeological site, Davis said. So, he and his colleagues removed the dirt containing the bones, and construction on the stadium continued.
Now that he has the bones, Davis said he would soak them in water to thwart further deterioration. The members of the team will also continue to examine the pile of dirt that encased the bones to see whether they can find any more ice-age remains.
Read more at Discovery News
Schizophrenia May Be Linked to Gene Flaw
The findings may allow future treatments to be directed at the root of the affliction rather than at its symptoms, said the authors of a study published in the journal Nature.
Based on genetic analysis of some 700 deceased people and nearly 65,000 living ones, about half of them with schizophrenia, researchers found that sufferers had specific variants of a gene called complement component 4, or C4 for short.
Mouse studies then implicated the gene in a brain process called "synaptic pruning." Synapses are connections between brain cells, or neurons.
Occasional pruning is needed to remove rarely used synapses to increase efficiency of the entire network -- a process that typically begins during adolescence. Excessive pruning, though, can cause problems.
"The findings may help explain the longstanding mystery of why brains from people with schizophrenia tend to have a thinner cerebral cortex with fewer synapses than unaffected individuals do," said a press statement from the Broad Institute of MIT and Harvard, whose experts took part in the study.
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| Google's advanced image detection software has an arty side. |
"The work may also help to explain why the onset of schizophrenia symptoms tends to occur in late adolescence," it said. "The human brain normally undergoes widespread synapse pruning during adolescence, especially in the cerebral cortex."
"Excessive synaptic pruning during adolescence and early adulthood, due to increased complement (C4) activity, could lead to the cognitive symptoms seen in schizophrenia."
The authors said their paper was the first to provide genetic evidence of a long suspected link between schizophrenia and excessive synapse pruning.
The devastating psychological disorder affects more than 20 million people in the world, and is characterized by hallucinations, delusions, paranoia and a breakdown of thought processes.
Symptoms typically start between the ages of 15 and 35. There is no cure, and treatment of the symptoms have limited effect.
"This study marks a crucial turning point in the fight against mental illness," commented Bruce Cuthbert, acting director of the US National Institute of Mental Health.
Read more at Discovery News
NASA Remembers Fallen Astronauts, Pledges Mars Mission
At the Kennedy Space Center in Florida, where the shuttle blasted off on January 28, 1986, singers outfitted in red and blue belted out the Star Spangled Banner for a crowd that included relatives and friends of the seven killed that day.
"The Challenger crew will forever be young, and will never be forgotten," said Bob Cabana, a former astronaut and director of the Kennedy Space Center.
"They continue to motivate us to explore."
A wreath-laying ceremony was planned for Arlington National Cemetery in Virginia as NASA commemorated the 24 US lives lost in space disasters and test flights over the years.
"As we undertake a journey to Mars, they will be with us. They have our eternal respect, love and gratitude," said a statement by NASA administrator Charles Bolden, a former astronaut.
"On this solemn occasion, we pause in our normal routines and remember."
Six NASA astronauts and Christa McAuliffe -- who would have been the first teacher in space -- were killed in the Challenger disaster, when the shuttle exploded 73 seconds after liftoff.
The cause was a failed booster engine, NASA said.
The other major shuttle accident was on February 1, 2003. Seven people died aboard the Columbia shuttle when it broke into pieces while re-entering Earth's atmosphere.
NASA said later that a piece of foam had come loose from the external tank during launch, and formed a hole in one of the shuttle's wings, causing it to break up 16 minutes before it was to have landed.
The US space agency also commemorated the three men who died in the Apollo 1 launch pad fire in 1967, before the nation ever made it to the moon.
"Remembering the crews today that we've lost, especially my best friend Ed White who perished in the Apollo 1 fire," astronaut Buzz Aldrin -- the second person to step foot on the Moon after American astronaut Neil Armstrong -- said on Twitter.
Bolden also recalled the 1967 loss of Mike Adams who died on an X-15 hypersonic rocket-powered aircraft, and others who perished in "test flights and aeronautics research throughout our history."
Read more at Discovery News
No, Earth Isn't Flat: Here's How Ancients Proved It
Earlier this week, rapper B.o.B publicly questioned a spherical Earth, throwing his support behind flat Earth theory in a series of tweets and memes and suggesting a NASA cover-up.
Discounting any photo taken by a NASA spacecraft — an untrustworthy source, according to B.o.B — and setting aside any images captured by other space agencies around the world or photos taken by commercial satellites while we’re at it, how do we know for fact that the Earth is spherical?
The ancient Greeks figured it out 2,500 years ago without having to fly into space and take a snapshot. How hard can it be?
Pythagoras in 500 B.C. provides the earliest arguments for why the Earth is round. The moon, he noted, was also a sphere, so it would follow that the Earth is round as well.
A century and a half later, Aristotle put forward what was likely the physical evidence that the Earth is round, according to the American Physical Society. He noted that ships sailing over the horizon disappear hull first. He also observed that the Earth casts a round shadow on the moon during an eclipse. The stars also change position at different latitudes, which also points to a spherical planet.
“All of which goes to show not only that the Earth is circular in shape, but also that it is a sphere of no great size: for otherwise the effect of so slight a change of place would not be so quickly apparent,” Aristole wrote in “On the Heavens.”
One hundred years after Aristotle, the ancient Greek mathematician Eratosthenes put forward the first scientific estimate of the circumference of the planet using nothing more than shadows and working alongside a team of bematists, professional surveyors in ancient Greece. His estimate of 250,000 stadia (28,738 miles or 46,250 kilometers) is close to Earth’s actual circumference of 24,902 miles (40,075 kilometers) if measured at the equator.
The scientific basis for the Earth being a sphere is often misattributed to the era of Christopher Columbus, whose crew had feared they would sail over the edge of the planet, the myth goes. In reality, Columbus, who would certainly have studied Aristotle, would have known full well that Earth is round. His expedition was initially controversial instead because the scientific advisers to King Ferdinand believed the journey west from Spain to India was too great a distance based on estimates of Earth’s size.
Flat Earth theory is a modern phenomenon, beginning in the 1800s with the work of Samuel Birley Rowbotham, founder of the Zetetic Society, which would later inspire the Flat Earth Society in the 20th century, according to LiveScience.
Earth looks and feels flat after all from our everyday, ground-level viewpoint. Rowbotham envisioned the planet as a disk with the sun, moon and stars all floating just a few hundred miles away. The Flat Earth Society believes gravity is an illusion, the space program is a hoax, and world governments are conspiring to keep the truth from surfacing for a still-undetermined reason.
Read more at Discovery News
Jan 27, 2016
Elephants Protect Calf from Wild Dogs in Stunning Footage
The clip shows dogs on the Ingwelala preserve advancing cautiously on the calf, heedless of stern warnings and bugle calls from a protective mom elephant that said “Back off!”:
Wild dogs in Africa are fierce, crafty predators that work together, so it’s no surprise they did not take the first warning as the final warning.
Finally, though, the elephant herd makes its way out of the area, calf in tow, and unharmed.
Read more at Discovery News
The Amazing Survival of a Diabolical Fish
But a new genetic analysis confirms that the fish known to science as Cyprinodon diabolis has managed the diabolically impossible: it seems to have arrived at Devil's Hole more recently and somehow mixed with other pupfish species of other desert springs within the last few centuries.
This apparently miraculous feat, while being very mysterious in itself, could actually demystify another inexplicable fact about the Devil's Hole minions that has long bedeviled scientists: how such a small population of fish living in a body of water the length and width of a couple of school buses could have survived for thousands of years without succumbing to inbreeding or the occasional mega drought.
“It's one of the most ridiculous fish habitats in the world,” said Christopher Martin of the University of North Carolina, Chapel Hill, the lead author of the new study which appears online in the Proceedings of the Royal Society B.
Indeed, at 10 feet wide and 70 feet long (3.5 by 22 meters) the steep-sided Devil's Hole is the smallest range of any vertebrate in the world.
That same small range means it would not take much to wipe the species out, which is why Devil's Hole is fenced off from the public and guarded by the National Park Service. But the latest gene sequencing technology is changing the story of these fish, according to Martin.
And while they are still a critically endangered animal, genes have revealed that they aren't exactly the lonely remnants of the ice age they were long thought to be.
“We estimate that Devils Hole was colonized by pupfish between 105 and 830 years ago,” report Martin and his colleagues.
That's based on their genetic sequencing which mapped out more than 13,000 genes and compared them to nearby pupfish species to determine how far the species had diverged from each other.
To estimate the time the species had been separated, they calibrated the rate at which the genes naturally change – the mutation rate – by comparing it to another, similar, pupfish species with a better-known mutation rate.
But how did this impish little fish manage it? Perhaps, Martin offered, a rare duck visited Devil's Hole and inadvertently carried a few sticky pupfish eggs in, and decades or centuries later another carried some away. Or maybe it was humans – Native Americans, in particular – to whom the fish were a precious food source.
It's unlikely we'll ever know. But however they got there, it's now clear the pupfish adapted quickly to their new environment.
“Evolution can happen in decades to a few hundred years,” said Craig Stockwell of North Dakota State University. “So it is possible that pupfish evolved shortly after colonizing Devils Hole.”
Stockwell and his colleagues own research, published in 2015, concluded that there was a 2 percent probability of Devil's Hole pupfish surviving for 10,000 years and a 95 percent probability of them persisting for 133 years. The genetic sequencing would seem to agree.
Read more at Discovery News
Statues of Greek Gods Unearthed in Crete
Found in the archaeological site of Aptera, a city in western Crete destroyed by an earthquake in the 7th century AD, the sculptures date to the first or second century AD and stand at around 21 inches in height.
The one depicting the hunting goddess Artemis is made of copper, while the other, portraying her twin brother Apollo, is carved from marble.
Once standing on an ornate base also made of copper, Artemis is wearing a short chiton, or tunic, and is ready to shoot an arrow.
The statue is described as being in an excellent state of preservation.
“The preservation of the white material used for her eyes is spectacular,” the ministry said.
The marble statuette of Apollo is simpler in style, but nevertheless finely carved. Traces of red paint are still visible on the statue’s pedestal.
According to the team led by archaeologist Vanna Niniou-Kindelis, director of excavations at Aptera, both sculptures were likely imported to the island in order to decorate a shrine in the luxury Roman villa in which they were found.
From Discovery News
Nazi Begged for Life After Helping Kill Millions
Eichmann, who was executed in 1962 for his role in the Holocaust, wrote the letter to then-Israeli President Yitzhak Ben-Zvi following his war crimes trial.
The letter was placed on display Wednesday during a ceremony at the residence of Israeli President Reuven Rivlin marking International Holocaust Remembrance day. Eichmann’s letter forms part of an exhibition commemorating the Eichmann trial.
In the letter Eichmann refused to admit any guilt for his part in the Holocaust, Haaretz reports. “In their evaluation of my personality, the judges have made a significant error, since they cannot put themselves in the time and situation I was in during the war years,” he wrote.
“I never served at a rank so high that it could have been involved in such decisive and independent powers. I never gave any order in my own name, but rather always acted ‘on orders,’” he added.
Eichmann, an SS lieutenant colonel and one of the architects of the Holocaust, argues in the letter that he was “not a responsible leader” but was “forced to serve as a mere instrument in the hands of the leaders.”
Haaretz reports that, although knowledge of Eichmann’s clemency plea was known, the letter, which is written in German and translated into Hebrew, was only recovered recently during a digital archiving process.
Letters from Eichmann’s wife and brothers also are on display as part of the exhibit.
From Discovery News
Milky Way's Neighbor Is a Clean Freak
IC 1613 is a well-known irregular dwarf galaxy in the constellation Cetus (The Sea Monster) and because of its tidy nature, astronomers have been able to observe its stars with striking precision. We now know that the diminutive galaxy is 2.3 million light-years away, placing it within the Local Group, our galactic neighborhood that is made up of over 50 galaxies.
Astronomers have been able to pinpoint IC 1613′s position by studying the Cepheid variable and RR Lyrae variable stars it contains. These variable stars pulse and the timing of these pulsations directly relate to their intrinsic brightness — astronomers can then use these stars as “standard candles”. The further away a star is, the dimmer it becomes (a logical conclusion), but these variables are known to have specific brightnesses depending on their measured pulse rates. Therefore, a relatively simple calculation can take their measured brightness to derive their distance.
Variable stars can be used to measure cosmic distances and in the case of IC 1613, this distance measurement is even more precise thanks to its dust-free nature.
This particular observation of IC 1613 was imaged by the powerful OmegaCAM, 256-million-pixel camera attached to the 2.6-meter VLT Survey Telescope at Paranal Observatory in Chile. The galaxy’s faint glow was first seen in 1906 by German astronomer Max Wolf, but IC 1613′s individual stars weren’t imaged until Walter Baade used the 2.5-meter telescope at the Mount Wilson Observatory in California in 1928.
Now, with the power of modern telescopes and imaging technology, IC 1613′s striking beauty — and freakish cleanliness — can be fully appreciated.
From Discovery News
Jan 26, 2016
Sloth Trapped in Roadway Gets Helping Hand from Police
Police in Quevado, Ecuador, however, came across that very scene after receiving reports of a sloth found clinging to a traffic barrier in the middle of the street.
Officers from the Ecuador Transit Commission were able to successfully rescue the sloth from its dangerous hiding place. Following the rescue, the sloth was examined by a veterinarian, who determined that the animal was in “optimal condition” and could be safely returned to its habitat.
The story doesn’t end there, though, as photos shared by the officers who rescued the sloth instantly went viral on Facebook, garnering nearly 20,000 shares and international media attention.
In a statement, transit officials say that they are “grateful to all who were interested in the health of the animal” and pledge to “continue to support these kinds of cases” and support collaboration with citizens.
From Discovery News
Extremely Rare White Giraffe Spotted in Tanzania
The giraffe calf has a condition called leucism that results in loss of pigmentation. “Her body surface cells are not capable of making pigment, but she is not an albino,” explained the Wild Nature Institute, in a blog post.
A guide named the giraffe Omo after a popular brand of local detergent.
Experts at the Wild Nature Institute first spotted Omo last year. “We were lucky enough to resight her again this January, almost exactly one year later,” the Institute explained, in its blog post. “We are thrilled that she is still alive and well.”
Leucism occurs when some or all pigment cells fail to develop during differentiation, so part or all of the animal’s body surface lacks cells capable of making pigment. “One way to tell the difference between albino and leucistic animals is that albino individuals lack melanin everywhere, including in the eyes, so the resulting eye color is red from the underlying blood vessels,” explained the Institute.
“ is simply a rare genetic condition – drawing four aces in a row from a deck of cards is also a rare occurrence,” noted Derek Lee, quantitative ecologist at the World Nature Institute, in an email to FoxNews.com. “Whether a mutation affecting coloration, such as leucism, is adaptive or not over evolutionary time will require continued observations.”
Omo’s unusual coloration, however, has prompted fears that she could become a target for poachers.
From Discovery News
Stardust Brought Back Comet Pieces 10 Years Ago
Even years later, surprises have emerged. In 2014, Brownlee’s team announced that probable interstellar particle tracks were found in the aerogel and aluminum foil particle detectors. A newer paper (by another team) submitted to the Lunar and Planetary Science Conference in Houston suggests this interplanetary dust is also made up in part of glass, which is a rare element in meteoroids.
“We’re constantly learning new things using better and better techniques,” Brownlee told Discovery News. “The more you look at these, how to deal with them, the more you can refine the techniques.”
Stardust collected samples from Comet Wild-2 in 2004, about two years before a part of the spacecraft came back to Earth with samples on board. The spacecraft was a pioneer in sample collection, with only one spacecraft (Japan’s Hayabusa, in 2010) doing it since on an asteroid. Hayabusa-2 (in flight now) and NASA’s OSIRIS-REx (yet to be launched) plan asteroid sample returns in the coming years.
Another comet mission has been on the mind of the public lately. The European Rosetta mission has been orbiting Comet 67P/Churyumov–Gerasimenko for more than a year, and delivered a lander (Philae) that worked for a few days on the surface. Brownlee said he was sad Philae didn’t function for as long as planned, because that was the best way to do direct comparison with Stardust’s findings. But Rosetta’s gas analysis of 67P is “complementary” to the solids that Stardust brought back to Earth for analysis, he added.
Read more at Discovery News
Hubble Spies on a Beautifully Messed-Up Galaxy
In this recent Hubble Space Telescope observation, one such irregular galaxy, located around 16 million light-years from Earth, has been observed. It looks like a loose collection of stars that have been thrown together and shuffled, like my end-of-semester university dorm room. But this galaxy, called NGC 5408, isn't just a scattering of stars, it's a whole galaxy and it's a galaxy with some interesting astronomical history.
Originally discovered by British astronomer and mathematician John Herschel in June 1834, NGC 5408 was presumed to be a planetary nebula -- a gaseous cloud of gas generated by a dying star. But as astronomical optics improved, its true nature was revealed; NGC 5408 is an entire galaxy living by its own rules, refusing to conform to a regular shape.
According to a NASA news release, NGC 5408 is notable for its ultraluminous X-ray source, known as NGC 5408 X-1. This class of object could be the signature of an intermediate-mass black hole, one of the most sought-after astrophysical objects in the cosmos.
Intermediate-mass black holes (or IMBHs) are the "middleweight" black holes that are thought to be the missing evolutionary link between puny stellar mass black holes and the gargantuan supermassive black holes. They are, however, very hard to find and astronomers are currently keeping tabs on ultraluminous X-ray sources in the hope that they may signal the presence of these mid-sized black holes.
From Discovery News
Orphan Planet May Have Estranged Parent Star
New research shows the planet, a massive world 11 to 15 times bigger than Jupiter, may be orbiting its host star about 7,000 times farther away than Earth circles the sun.
At this distance, light from the star would take a month to reach the planet, research published Monday in the Monthly Notices of the Royal Astronomical Society shows.
“This is the widest planet system found so far,” astronomer Niall Deacon, with England’s University of Hertfordshire, said in a statement.
Both the planet, known as 2MASS J2126 and its prospective parent star, TYC 9486-927-1, were discovered more than eight years ago, but the relationship between the two remained unknown.
Deacon and colleagues found that despite being more than 621 billion miles, or 1 trillion kilometers, apart the two objects are moving together in space.
“Nobody had made the link between the objects before. The planet is not quite as lonely as we first thought,” Deacon said.
Scientists don’t know how a planet could end up so far away from its host star. 2MASS J2126 is almost big enough to be a star itself and may be another type of brown dwarf, or failed star.
"Pinning down the formation of this system is difficult and lends intrigue to this odd pair," co-investigator Josh Schlieder, a post-doctorate researcher at NASA's Ames Research Center in Moffett Field, Calif., wrote in an email to Discovery News.
"It is easier to infer how the system likely did not form. Since the mass ratio is relatively high and the separation so extreme, it is unlikely that 2MASS J2126 formed near its current location from a disk of material orbiting the primary star, similar to the gas giants in our solar system."
Schlieder suggests that 2MASS J2126 may have formed closer to its partner, TYC 9486-927-1, and then migrated outward. This process could have been a result of orbital interactions with currently unseen additional companions, he said.
Read more at Discovery News
Jan 25, 2016
Cats domesticated in China earlier than 3000 BC
Their findings are published on 22 January 2016 in the journal PLOS ONE.
The cat is the most common domestic animal in the world today, with over 500 million individuals. All of today's domestic cats descend from the African and Near Eastern form of the wildcat (Felis silvestris lybica). According to work published in 2004, humans and cats first started to form a close relationship in the Near East from 9000 to 7000 BC, following the birth of agriculture.
In 2001, researchers from the Chinese Academy of Sciences in Beijing discovered cat bones in agricultural settlements in northern China (Shaanxi province) dating from around 3500 BC. Was this evidence of a relationship between small Chinese cats and humans in the fourth millennium BC in China? Or was it the result of the arrival in China of the first domestic cats from the Near East? There was no way of deciding between these two hypotheses without identifying the species to which the bones belonged. Although there are no less than four different forms of small cat in China, the subspecies from which modern cats are descended (Felis silvestris lybica) has never been recorded there.
To try to settle the question, a collaboration of scientists principally from CNRS, the French Natural History Museum (MNHN), the University of Aberdeen, the Chinese Academy of Social Science and the Shaanxi Provincial Institute of Archaeology undertook a geometric morphometric analysis, which, in the absence of ancient DNA, is the only way of differentiating the bones of such small cats, which have very similar morphologies whose differences are often imperceptible using conventional techniques. The scientists analyzed the mandibles of five cats from Shaanxi and Henan dating from 3500 to 2900 BC. Their work clearly determined that the bones all belonged to the leopard cat (Prionailurus bengalensis). Still very widespread in Eastern Asia today, this wildcat, which is a distant relation of the western wildcat (Felis silvestris lybica), is well-known for its propensity to frequent areas with a strong human presence. Just as in the Near East and Egypt, leopard cats were probably attracted into Chinese settlements by the proliferation of rodents who took advantage of grain stores.
These conclusions show that a process comparable to the one that took place in the Near East and in Egypt developed independently in China following the birth of agriculture in the eighth millennium BC. In China it was the leopard cat (P. bengalensis) and not the western wildcat (F. silvestris) that started to form a relationship with humans. Cat domestication was, at least in three regions of the world, therefore closely connected to the beginnings of agriculture.
Read more at Science Daily
In galaxy clustering, mass may not be the only thing that matters
There is a connection between galaxy clusters and their dark matter halos that holds a great deal of information about the universe's content of dark matter and accelerating expansion due to dark energy. Galaxy clusters are groupings of hundreds to thousands of galaxies bound together by gravity, and are the most massive structures found in the universe. These clusters are embedded in a halo of invisible dark matter. Traditionally, cosmologists have predicted and interpreted clustering by calculating just the masses of the clusters and their halos. However, theoretical studies and cosmological simulations suggested that mass is not the only element at play -- something called assembly bias, which takes into account when and how a galaxy cluster formed, also could impact clustering.
"Simulations have shown us that assembly bias should be part of our picture," said Mandelbaum, a member of Carnegie Mellon's McWilliams Center for Cosmology. "Confirming this observationally is an important piece of understanding galaxy and galaxy cluster formation and evolution."
In the current study, the research team, led by Hironao Miyatake, Surhud More and Masahiro Takada of the Kavli Institute for the Physics and Mathematics of the Universe, analyzed observational data from the Sloan Digital Sky Survey's DR8 galaxy catalog. Using this data, they demonstrated that when and where galaxies group together within a cluster impacts the cluster's relationship with its dark matter environment.
The researchers divided close to 9,000 galaxy clusters into two groups based on the spatial distribution of the galaxies in each cluster. One group consisted of clusters with galaxies aggregated at the center and the other consisted of clusters in which the galaxies were more diffuse. They then used a technique called gravitational lensing to show that, while the two groups of clusters had the same mass, they interacted with their environment much differently. The group of clusters with diffuse galaxies were much more clumpy than the group of clusters that had their galaxies close to the center.
Read more at Science Daily
Metal 'Snow' May Power Earth's Magnetic Field
Magnesium is the fourth most common element in the Earth’s outer layers, but previously, scientists thought there was almost no magnesium in the core. Iron and magnesium don’t easily mix, and researchers thought that the Earth’s core was mostly iron.
However, that thinking has changed because of recent theories proposing that the Earth was born from a series of violent collisions with other protoplanets. During the impacts, temperatures and pressures were so intense that iron and metal could combine in an alloy, according to a study published today (Jan. 20) in the journal Nature. The study authors add that smashing together two planetary bodies likely injected magnesium into the core. About 1 percent of the core (by weight) could be magnesium, the new model shows.
“We think we now understand why the Earth has had a magnetic field for the last 4 billion years, and that the process will keep happening into the foreseeable future,” said lead study author Joseph O’Rourke, a graduate student in planetary science at Caltech in Pasadena, California.
O’Rourke and study co-author Dave Stevenson, a Caltech professor, created a model of Earth’s formation to investigate magnesium’s behavior in the core. As Earth’s core has slowly cooled, magnesium-oxide minerals are “snowing” out from the core’s iron and nickel alloy, the model indicates. This solid magnesium “snow” is lighter than the liquid metal and floats outward through the liquid-metal outer core, churning it and powering the convection that produces the global magnetic field.
The new model could help solve an important question in planetary science: What has powered the Earth’s magnetic field for the past 4 billion years? Many scientists think iron cooling and solidifying in Earth’s core generates the planet’s magnetic field (also called the geodynamo). However, these models can’t explain how the magnetic field was generated before the solid inner core formed about 1 billion years ago. The new magnesium model provides an alternative energy source.
With the new model, “you don’t have to invoke anything crazy in the past to explain the geodynamo,” O’Rourke told Live Science.
The new model needs to be verified with experimental tests, the researchers said. There is little evidence indicating how magnesium behaves at the temperatures and pressures produced during planetary collisions.
“The idea is an interesting one,” said Rebecca Fischer, a postdoctoral fellow at the Smithsonian Museum of Natural History in Washington, D.C., who was not involved in the study. However, “before we can really, conclusively say how much magnesium goes into the core, we need better experimental data,” Fischer told Live Science.
Read more at Discovery News
Mars May Be Too Cold For Life
A group of researchers found negative tests for microbial activity at temperatures below freezing in a region called University Valley, in Antarctica’s McMurdo Dry Valleys. However, in spots just a little above freezing (5 Celsius, or 41 Fahrenheit), the same team found five bacteria and one yeast.
“Detecting activity at this temperature indicates that at least some of the biomass in University Valley soils is viable, and these cells are likely currently dormant and surviving until more favorable conditions come along,” said Jackie Goordial, the principal investigator of the research.
She acknowledged, however, that if only a few cells were active in the permafrost, they could have eluded the detection limits of her instruments. “We also assayed for activity using the same tests we would normally use for other permafrost environments, and which are normally successful,” added Goordial, a postdoctoral fellow in environmental microbiology at McGill University in Montreal, Canada.
McMurdo has been likened to the Phoenix landing site on Mars, which is also at high elevation and at a pole (the north pole, in this case). That said, there have been microbes found in colder temperatures on Earth.
The “champ” is called Planococcus halocryophilus, Goordial said, and it is found in the Ellesmere Island permafrost at the Canadian high Arctic. It reproduces at temperatures down to -15 degrees Celsius (5 Fahrenheit) and can metabolize down to at least -25 Celsius (-13 Fahrenheit). So the new findings come as a bit of a surprise.
We are also hoping to go back to University Valley to obtain more and deeper samples from this site to see if the deeper and older permafrost become truly ‘dead’, which would be our working hypothesis,” said Goordial.
“Our results also indicate that University Valley permafrost soils will be excellent analogues to develop and test life/biosignature detection instruments to be sent if future missions to Mars as well as Europa and Enceladus because of the extremely low biomass present,” she added, referring to icy moons of Jupiter and Saturn (respectively).
Even the walls of University Valley have cryptoendoliths (microbes hidden within rocks) that are in regions heated by the sun with humidity traps. Inland and elevated areas tend to have more cold, arid and harsh conditions.
Read more at Discovery News
Jan 24, 2016
Cells talk to their neighbors before making a move
"Cells talk to nearby cells and compare notes before they make a move," says Ilya Nemenman, a theoretical biophysicist at Emory University and a co-author of both studies, published by the Proceedings of the National Academy of Sciences (PNAS). The co-authors also include scientists from Johns Hopkins, Yale and Purdue.
The researchers discovered that the cell communication process works similarly to a message relay in the telephone game. "Each cell only talks to its neighbor," Nemenman explains. "A cell in position one only talks to a cell in position two. So position one needs to communicate with position two in order to get information from the cell in position three."
And like the telephone game -- where a line of people whisper a message to the person next to them -- the original message starts to become distorted as it travels down the line.
The researchers found that, for the cells in their experiments, the message begins to get garbled after passing through about four cells, by a factor of about three.
"We built a mathematical model for this linear relay of cellular information and derived a formula for its best possible accuracy," Nemenman says. "Directed cell migration is important in processes from cancer to the development of organs and tissues. Other researchers can apply our model beyond the mouse mammary gland and analyze similar phenomena in a wide variety of healthy and diseased systems."
Since at least the 1970s, and pivotal work by Howard Berg and Ed Purcell, scientists have been trying to understand in detail how cells decide to take an action based on chemical cues.
Every cell in a body has the same genome but they can do different things and go in different directions because they measure different chemical signals in their environment. Those chemical signals are made up of molecules that randomly move around.
"Cells can sense not just the precise concentration of a chemical signal, but concentration differences," Nemenman says. "That's very important because in order to know which direction to move, a cell has to know in which direction the concentration of the chemical signal is higher. Cells sense this gradient and it gives them a reference for the direction in which to move and grow."
Berg and Purcell understood the best possible margin of error -- the detection limit -- for such gradient sensing. During the subsequent 30 years, researchers have established that many different cells, in many different organisms, work at this detection limit. Living cells can sense chemicals better than any humanmade device.
It was not known, however, that cells can sense signals and make movement decisions collectively.
"Previous research has typically focused on cultured cells," Nemenman says. "And when you culture cells, the first thing to go away is cell-to-cell interaction. The cells are no longer a functioning tissue, but a culture of individual cells, so it's difficult to study many collective effects."
The first PNAS paper drew from three-dimensional micro-fluidic techniques from the Yale University lab of Andre Levchenko, a biomedical engineer who studies how cells navigate; research on mouse mammary tissue at the Johns Hopkins lab of Andrew Ewald, a biologist focused on the cellular mechanisms of cancer; and the quantification methods of Nemenman, who studies the physics of biological systems, and Andrew Mugler, a former post-doctoral fellow in Nemenman's lab at Emory who now has his own research group at Purdue.
The 3D micro fluidics allowed the researchers to experiment with functional organoids, or clumps of cells. The method does not disrupt the interaction of the cells.
The results showed that epidermal growth factor, or EGF, is the signal that these cells track, and that the cells were not making decisions about which way to move as individuals, but collectively.
"The clumps of cells, working collectively, could detect insanely small differences in concentration gradients -- such as 498 molecules of EGF versus 502 molecules -- on different sides of one cell," Nemenman says. "That accuracy is way better than the best possible margin of error determined by Berg and Purcell of about plus or minus 20. Even at these small concentration gradients, the organoids start reshaping and moving toward the higher concentration. These cells are not just optimal gradient detectors. They seem super optimal, defying the laws of nature."
Collective cell communication boosts their detection accuracy, turning a line of about four cells into a single, super-accurate measurement unit.
In the second PNAS paper, Nemenman, Mugler and Levchenko looked at the limits to the cells' precision of collective gradient sensing not just spatially, but over time.
Read more at Science Daily
Why are habits so hard to break?
New research by Duke University scientists suggests that a habit leaves a lasting mark on specific circuits in the brain, priming us to feed our cravings.
Published online Jan. 21 in the journal Neuron, the research deepens scientists' understanding of how habits like sugar and other vices manifest in the brain and suggests new strategies for breaking them.
"One day, we may be able to target these circuits in people to help promote habits that we want and kick out those that we don't want," said the study's senior investigator Nicole Calakos, M.D., Ph.D., an associate professor of neurology and neurobiology at the Duke University Medical Center.
Calakos, an expert in the brain's adaptability, teamed up with Henry Yin, an expert in animal models of habit behavior in Duke's department of psychology and neuroscience. Both scientists are also members of the Duke Institute for Brain Sciences.
Their groups trained otherwise healthy mice to form sugar habits of varying severity, a process that entailed pressing a lever to receive tiny sweets. The animals that became hooked kept pressing the lever even after the treats were removed.
The researchers then compared the brains of mice that had formed a habit to the ones that didn't. In particular, the team studied electrical activity in the basal ganglia, a complex network of brain areas that controls motor actions and compulsive behaviors, including drug addiction.
In the basal ganglia, two main types of paths carry opposing messages: One carries a 'go' signal which spurs an action, the other a 'stop' signal.
Experiments by Duke neurobiology graduate student Justin O'Hare found that the stop and go pathways were both more active in the sugar-habit mice. O'Hare said he didn't expect to see the stop signal equally ramped up in the habit brains, because it has been traditionally viewed as the factor that helps prevent a behavior.
The team also discovered a change in the timing of activation in the two pathways. In mice that had formed a habit, the go pathway turned on before the stop pathway. In non-habit brains, the stop signal preceded the go.
These changes in the brain circuitry were so long-lasting and obvious that it was possible for the group to predict which mice had formed a habit just by looking at isolated pieces of their brains in a petri dish.
Scientists have previously noted that these opposing basal ganglia pathways seem to be in a race, though no one has shown that a habit gives the go pathway a head start. O'Hare said that's because the go and stop signals had not been studied in the same brain at the same time. But new labeling strategies used by the Duke scientists allowed researchers to measure activity across dozens of neurons in both pathways simultaneously, in the same animal.
"The go pathway's head start makes sense," said Calakos. "It could prime the animal to be more likely to engage in the behavior." The researchers are testing this idea, as well as investigating how the rearrangements in activity occur in the first place.
Interestingly, the group observed that changes in go and stop activity occurred across the entire region of the basal ganglia they were studying as opposed to specific subsets of brain cells. O'Hare said this may relate to the observation that an addiction to one thing can make a person more likely to engage in other unhealthy habits or addictions as well.
To see if they could break a habit, the researchers encouraged the mice to change their habit by rewarding them only if they stopped pressing the lever. The mice that were the most successful at quitting had weaker go cells. But how this might translate into help for humans with bad habits is still unclear. Because the basal ganglia is involved in a broad array of functions, it may be tricky to target with medicines.
Calakos said some researchers are beginning to explore the possibility of treating drug addiction using transcranial magnetic stimulation or TMS, a noninvasive technique that uses magnetic pulses to stimulate the brain. "TMS is an inroad to access these circuits in more severe diseases," she said, in particular targeting the cortex, a brain area that serves as the main input to the basal ganglia.
Read more at Science Daily
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