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
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