Thousands of Invisibility Cloaks Trap a Rainbow

Many people anticipating the creation of an invisibility cloak might be surprised to learn that a group of American researchers has created 25,000 individual cloaks.

But before you rush to buy one from your local shop, the cloaks are just 30 micrometres in diameter and are laid out together on a 25 millimetre gold sheet.

This array of invisibility cloaks is the first of its kind and has been created by researchers from Towson University and University of Maryland who present their study on May 25, in the Institute of Physics and German Physical Society's New Journal of Physics.

Although the well-reported intention to make everyday objects disappear with a Harry Potter-style cloak is beyond this array of cloaks, they could be used to slow down, or even stop, light, creating what is known as a "trapped rainbow."

The trapped rainbow could be utilised in tiny biosensors to identify biological materials based on the amount of light they absorb and then subsequently emit, which is known as fluorescence spectroscopy. Slowed-down light has a stronger interaction with molecules than light travelling at normal speeds, so it enables a more detailed analysis.

Lead author of the study, Dr Vera Smolyaninova, said: "The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once. For example, you could test for multiple genetic conditions in a person's DNA in just one go.

"In our array, light is stopped at the boundary of each of the cloaks, meaning we observe the trapped rainbow at the edge of each cloak. This means we could do 'spectroscopy on-a-chip' and examine fluorescence at thousands of points all in one go."

The 25 000 invisibility cloaks are uniformly laid out on a gold sheet, with each having a microlens that bends light around itself, effectively hiding an area in its middle. As the light squeezes through the gaps between each of the cloaks, the different components of light, or colours, are made to stop at ever narrower points, creating the rainbow.

To construct the array of invisibility cloaks, a commercially available microlens array, containing all of the individual microlenses, was coated with a gold film. This was then placed, gold-side down, onto a glass slide which had also been coated with gold, creating a double layer. A laser beam was directed into the array to test performance of the cloaks at different angles.

Read more at Science Daily

Rare Sumatran Rabbit Photographed

Using camera traps, wildlife researchers including doctoral candidate Jennifer McCarthy and environmental conservation professor Todd Fuller of the University of Massachusetts Amherst recently captured photographs of one of the rarest animals on earth, the Sumatran striped rabbit. They say it may now be found only in two remote national parks on the Indonesian island.

Their pictures and other observations are reported in the current issue of Oryx, The International Journal of Conservation. The rare rabbit was first photographed in Kerinci Seblat National Park in 1998 and has rarely been seen since.

"Whether the rabbit does occur undetected in other parks is not certain, but the importance of protecting these two known strongholds of the species is critical," say McCarthy and colleagues. "As the human population of Sumatra rises, both parks are increasingly threatened by encroachment of villages and development of roads and infrastructure. It is important to focus conservation efforts in these areas to prevent a loss of what could be the final two populations of Sumatran striped rabbits."

Sumatra's Bukit Barisan Mountains, where the rabbits were captured on film, form the rugged backbone of the sixth largest island in the world. Since 2008, McCarthy and Fuller have been conducting an ecological study of the clouded leopard, Asiatic golden cat, marbled cat and leopard cats in Indonesia's Bukit Barisan Seletan National Park.

McCarthy says, "As part of my dissertation research on the four felids, or cats, we also happened to get pictures of this very rare rabbit. There had been a few camera-trap photos seen of it before, but very, very rarely. We wanted to take these observations a step further, so we worked with colleagues from the University of Delaware and the Wildlife Conservation Society's Indonesia Program to contact every researcher we knew throughout Sumatra who was doing camera-trap research, probably 20 or 30 people. This gave us good coverage of the island."

"We asked them about sightings of the Sumatran striped rabbit and report the results in our paper." Overall, the conservation biologist adds, "The biggest news is that we only received recent sighting information from these two parks. For the first time, we can pinpoint that these two areas may be the only ones remaining where this species occurs. We can't say they don't occur elsewhere, but we are saying it's important to preserve those areas in order to save the species."

Habitats critical to many forms of wildlife in the parks face constant pressure from nearby coffee and palm oil plantations and from those who want logging roads built, she adds. Roads would not only destroy habitat but would allow humans, including poachers, access into relatively wild and remote places. In Sumatra between 2000 and 2009, more than 7.6 million acres (3.1 million hectares) of forest were lost to such encroachment, McCarthy says.

Much of her work was done at fairly high altitudes, in dense rainforest and rugged terrain, along volcanic ridges up to 3,900 feet (1,200 meters) high, where human encroachment is low, McCarthy says. The area has a relatively high density of wildlife, including tigers, so the investigators never travel alone and always have a park ranger with them. After walking miles to visit their cameras and snares, they roll out their sleeping bags in local villages as guests of families with no electricity, running water or modern plumbing.

McCarthy says, "It's such a beautiful place. I hope we are able to increase conservation initiatives. At this point we really need to increase the involvement of local people in order to save these areas. There is some appreciation of the value of wildlife, especially for the tiger. But the root of the problem, the loss of habitat, hasn't really slowed down. We feel our presence and the fact that our research supports a park ranger has helped to make a difference."

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Exotic Particles, Chilled and Trapped, Form Giant Matter Wave

Physicists have trapped and cooled exotic particles called excitons so effectively that they condensed and cohered to form a giant matter wave.

This feat will allow scientists to better study the physical properties of excitons, which exist only fleetingly yet offer promising applications as diverse as efficient harvesting of solar energy and ultrafast computing.

"The realization of the exciton condensate in a trap opens the opportunity to study this interesting state. Traps allow control of the condensate, providing a new way to study fundamental properties of light and matter," said Leonid Butov, professor of physics at the University of California, San Diego. A paper reporting his team's success was recently published in the scientific journal Nano Letters.

Excitons are composite particles made up of an electron and a "hole" left by a missing electron in a semiconductor. Created by light, these coupled pairs exist in nature. The formation and dynamics of excitons play a critical role in photosynthesis, for example.

Like other matter, excitons have a dual nature of both particle and wave, in a quantum mechanical view. The waves are usually unsynchronized, but when particles are cooled enough to condense, their waves synchronize and combine to form a giant matter wave, a state that others have observed for atoms.

Scientists can easily create excitons by shining light on a semiconductor, but in order for the excitons to condense they must be chilled before they recombine.

The key to the team's success was to separate the electrons far enough from their holes so that excitons could last long enough for the scientists to cool them into a condensate. They accomplished this by creating structures called "coupled quantum wells" that separate electrons from holes in different layers of alloys made of gallium, arsenic and aluminum.

Then they set an electrostatic trap made by a diamond-shaped electrode and chilled their special semiconducting material in an optical dilution refrigerator to as cold as 50 milli-Kelvin, just a fraction of a degree above absolute zero.

A laser focused on the surface of the material created excitons, which began to accumulate at the bottom of the trap as they cooled. Below 1 Kelvin, the entire cloud of excitons cohered to form a single matter wave, a signature of a state called a Bose-Einstein condensate.

Other scientists have seen whole atoms do this when confined in a trap and cooled, but this is the first time that scientists have seen subatomic particles form coherent matter waves in a trap.

Varying the size and depth of the trap will alter the coherent exciton state, providing this team, and others, the opportunity to study the properties of light and mater in a new way.

Read more at Science Daily

Beam Me Up: 'Tractor Beams' of Light Pull Small Objects Towards Them

'Tractor beams' of light that pull objects towards them are no longer science fiction. Haifeng Wang at the A*STAR Data Storage Institute and co-workers have now demonstrated how a tractor beam can in fact be realized on a small scale.

Tractor beams are a well-known concept in science fiction. These rays of light are often shown pulling objects towards an observer, seemingly violating the laws of physics, and of course, such beams have yet to be realised in the real world. Haifeng Wang at the A*STAR Data Storage Institute and co-workers have now demonstrated how a tractor beam can in fact be realized on a small scale. "Our work demonstrates a tractor beam based only on a single laser to pull or push an object of interest toward the light source," says Wang.

Based on pioneering work by Albert Einstein and Max Planck more than a hundred years ago, it is known that light carries momentum that pushes objects away. In addition, the intensity that varies across a laser beam can be used to push objects sideways, and for example can be used to move cells in biotechnology applications. Pulling an object towards an observer, however, has so far proven to be elusive. In 2011, researchers theoretically demonstrated a mechanism where light movement can be controlled using two opposing light beams -- though technically, this differs from the idea behind a tractor beam.

Wang and co-workers have now studied the properties of lasers with a particular type of distribution of light intensity across the beam, or so-called Bessel beams. Usually, if a laser beam hits a small particle in its path, the light is scattered backwards, which in turn pushes the particle forward. What Wang and co-workers have now shown theoretically for Bessel beams is that for particles that are sufficiently small, the light scatters off the particle in a forward direction, meaning that the particle itself is pulled backwards towards the observer. In other words, the behaviour of the particle is the direct opposite of the usual scenario. The size of the tractor beam force depends on parameters such as the electrical and magnetic properties of the particles.

Although the forces are not very large, such tractor beams do have real applications, says Wang. "These beams are not very likely to pull a human or a car, as this would require a huge laser intensity that may damage the object," says Wang. "However, they could manipulate biological cells because the force needed for these doesn't have to be large."

Read more at Science Daily

Were the Cavemen of the Danube Flutists?

Early modern humans could have spent their evenings sitting around the fire, playing bone flutes and singing songs 40,000 years ago, newly discovered ancient musical instruments indicate. The bone flutes push back the date researchers think human creativity evolved.

Researchers were studying a modern human settlement called Geißenklösterle, a part of the Swabian caves system in southern Germany, when they came across the bone flutes. One is made of mammoth ivory, while the other seems to be made of bones from a bird. They also found a collection of perforated teeth, ornaments and stone tools at the site.

"These results are consistent with a hypothesis we made several years ago that the Danube River was a key corridor for the movement of humans and technological innovations into central Europe between 40,000 and 45,000 years ago," study researcher Nick Conard, of Tübingen University, said in a statement.

"Geißenklösterle is one of several caves in the region that has produced important examples of personal ornaments, figurative art, mythical imagery and musical instruments. The new dates prove the great antiquity of the Aurignacian in Swabia." The Aurignacian refers to an ancient culture and the associated tools.

Old bones

The flutes are the earliest record of technological and artistic innovations that are characteristic of the Aurignacian period. This culture also created the oldest known example of art meant to represent a person, found in the same cave system in 2008 (that statue seems to be about 35,000 years old). The musical instruments indicate that these early humans were sharing songs and showing artistic creativity even earlier than previously thought.

The researchers radiocarbon-dated bones found in the same layer of the archaeological dig as the flutes. This carbon dating uses the level of radioactive carbon, which is naturally occurring in the world and decays predictably into nonradioactive carbon, to estimate the age of organic materials.

They found the objects were between 42,000 and 43,000 years old, belonging to the Aurignacian culture dating from the upper Paleolithic period. So far, these dates are the earliest for the Aurignacian and predate equivalent sites from Italy, France, England and other regions.

Read more at Discovery News

Thousand-Year-Old Mummies Found in Peru

Belgian archaeologists have uncovered a spectacular 1,000-year-old tomb in Peru containing more than‭ ‬80‭ ‬skeletons and mummies, many of them infants.

Carved into the earth and covered with a roof of reeds supported by shaped tree trunks, the 60-foot-long, oval chamber was discovered at the site of Pachacamac,‭ ‬about 20 miles south of the capital, Lima.

One of the largest Prehispanic sites in South America, Pachacamac was an important religious, ceremonial, political and economic center, consecrated to the god Pacha Camac.

Pachacamac was ruled by the Ychsma lords from 900 A.D. to 1470 and was rich with temples, plazas and mud-brick pyramids with ramps.

The Inca Empire conquered the religious center less than a century before Spanish Conquistador Francisco Pizarro's brother, Hernando, plundered the site in 1533.

Within a few years of the conquest Pachacamac was completely abandoned.

Today, the impressive ruins make Pachacamac a candidate for inclusion on the list of UNESCO World Heritage sites.

The intact tomb was unearthed in front of the Temple of Pachacamac and had miraculously survived the pillaging of the colonial period‭.

A dozen newborn babies and infants were buried around the perimeter,‭ with ‬their heads oriented towards the tomb.‭ ‬The main chamber was divided into two sections,‭ ‬separated by a wall of mud bricks which served as a base for yet more burials.

Inside the chambers,‭ the team of ‬ archaeologists‭ ‬from the Université libre de Bruxelles‭ (‬ULB‭) ‬found the remains of more than‭ ‬70‭ ‬skeletons and mummies, all in the characteristic fetal position and many still wrapped.‭

The burials represented both sexes and all ages,‭ ‬and were often accompanied by offerings which included‭ ‬ceramic vessels,‭ ‬dogs,‭ ‬guinea pigs,‭ ‬copper and gold alloy artefacts,‭ and ‬masks‭ of‬ painted wood.‭

Babies and very young infants were particularly common.

"The ratio adult/children is unusually elevated at this burial," archaeologist Peter Eeckhout, who has been carrying out fieldwork at the site for the past‭ ‬20‭ ‬years, told Discovery News.

"We have, at this stage, two hypotheses: human sacrifice or stocking of babies dead from natural causes, kept until their disposal in the tomb because of its special character," Eeckhout said.

‭Several‬ individuals suffered mortal injuries,‭ ‬physical trauma or serious illness.

"One juvenile was killed by a blow on the skull. All over the cemetery we have lots of lethal disease traces, such as cancer and syphillis," Eeckhout said.

‭Indeed, ‬Eeckhout's previous work at the site‭ ‬has revealed many diseases in the skeletal population,‭ ‬leading to the suggestion that Pachacamac was a sort of Prehispanic Lourdes.‭ A‬s testified by Inca sources, the affected individuals had‭ ‬travelled to the site in search of a cure.

Read more at Discovery News

Seal Proves Bethlehem Existed Centuries Before Jesus

Israeli archaeologists have unearthed a 2,700-year-old clay seal with the name of Bethlehem, showing that the town existed centuries before it was revered as Jesus' birthplace.

Discovered during the sifting‭ ‬of‭ debris ‬removed‭ ‬from archaeological excavations near the walls of the Old City of Jerusalem, the coin-sized clay seal, or bulla, was imprinted with three lines in ancient Hebrew script: "in the seventh," "Bethlehem," and "to the king."

"It seems that in the seventh year of the reign of a king ‭(‬it is unclear if the king referred to is Hezekiah,‭ ‬Manasseh or Josiah‭)‬,‭ ‬a shipment was‭ ‬dispatched from Bethlehem to the king in Jerusalem," Eli Shukron, director of the excavation on behalf of the Israel Antiquities Authority, said in a statement on Wednesday.

Belonging to the group of‭ "fiscal‭" ‬bullae‭, ‬ the clay seal was likely placed on a tax shipment of silver or agricultural produce such as wine or wheat which was sent from Bethlehem to the King of Judah in Jerusalem in the 8th or 7th century BC.

"This is the first time the name Bethlehem appears outside the Bible,‭ ‬in an inscription from the First Temple period (1006-586 BC)‭ ‬which proves that Bethlehem was indeed a city in the Kingdom of Judah,‭ ‬and possibly also‭ ‬in earlier periods," Shukron said.

Located just south of Jerusalem, Bethlehem is first mentioned in the Bible in the verse‭ "‬in Ephrath,‭ ‬which is Bethlehem.‭" It was there that‬ Rachel, the matriarch of the Jewish people, died and was buried.

Read more at Discovery News

First Terrestrial Animals Shuffled Onto Land

The transition from swimming to walking involved some awkward first steps, according to a new study that recreated how one of the first animals, which left the sea for land, moved.

The study found that that the fishy four-limbed animal Ichthyostega used its front limbs like crutches, pushing its body up and forward onto land while its legs and tail trailed behind. It lived in water near the shoreline when not on land.

This was one small step for sea creatures but one big step for animal kind, because those early movements on land around 374-359 million years ago likely later evolved into walking, including human locomotion.

"Ichthyostega's muscular and mobile elbows would have also assisted in station holding (staying in one spot) while in the water and in lifting its head out of the water to breathe and process food," Stephanie Pierce of the Royal Veterinary College's Structure and Motion Laboratory told Discovery News.

"Ichthyostega probably used its paddle-like legs and tail to swim while in the water," she added. "The hind legs probably were not of much use on land, especially compared to the forelimbs."

Pierce and her colleagues Jennifer Clack and John Hutchinson reconstructed the first ever 3-D computer model of the tetrapod's skeleton. Ichthyostega, in addition to having big muscles, possessed huge fang-like teeth and probably ambushed its prey.

The model, which put together the fossils like a jigsaw puzzle in animation software, revealed that most books and museum displays showing Ichthyostega are incorrect. They usually represent this beast marching around like a large salamander with stocky legs.

Instead, the reconstruction determined that the shoulder and hip joint of this species prevented a conventional walking step, since its limbs were incapable of rotating along its long-axis. This motion is critical to locomotion for us and other modern land animals.

Earlier fish relatives of Ichthyostega and other tetrapods, called tetrapodomorphs, had the ability to rotate their fins. This allowed later animals to move well on land. The research was published in this week's issue of Nature.

A separate study, published in the Proceedings of the Royal Society B, looked at a 345-million-year-old eel called Tarrasius problematicus. Lauren Sallan of the University of Chicago discovered that this eel had a spine with multiple segments, similar to that of today's land-dwelling animals.

Read more at Discovery News

Is 'Planet X 2.0' Lurking Beyond Pluto's Orbit?

Before the doomsayers hijacked "Planet X" and used it as a phantom (a.k.a. "Nibiru") to scare people into believing the 2012 doomsday hype, the hunt for Planet X was an exciting astronomical quest to find a hypothetical world in the outermost reaches of the solar system in the early 20th century.

Although dwarf planet Pluto was discovered during the search for Planet X in 1930, apparently ending the quest, there is enduring evidence for the existence of a substantial planet gravitationally shaping the population of minor bodies in the Kuiper belt and beyond. The only problem is, we can't see it.

Earlier this month, at a meeting of the American Astronomical Society in Timberline Lodge, Ore., Rodney Gomes, an astronomer from the National Observatory of Brazil in Rio de Janeiro, announced the results of his simulation of a region beyond Pluto known as the "scattered disk," suggesting the presence of an as yet to be discovered massive world.

The scattered disk is a sparsely populated region that overlaps with the Kuiper belt at around 30 AU (Neptune's orbit), and some scattered disk objects (or SDOs) have extreme orbits that extend to 100 AU.

One such small world is Sedna, a dwarf planet with a highly elongated orbit. "Sedna's orbit is truly peculiar," said Caltech planetary scientist Mike Brown, who led the team that discovered Sedna in 2003.

These extreme orbits, argues Gomes, could be due to the presence of an unknown massive planet. By his reckoning, a planet four times the size of Earth may be out there beyond the orbit of Pluto. In his simulation, he placed the gravitational field of a large planet and watched the effect it had on the SDO's orbits.

"Rodney Gomes is actively seeking further evidence, and I await his findings with interest!" Douglas Hamilton, an astronomer at the University of Maryland, told Life's Little Mysteries. "He has taken on a difficult task, but is taking the right approach. It is definitely a high-risk, high-reward, situation -- a discovery of a new planet would be spectacular!"

Although the presence of a massive planet may explain the extreme orbits, there is little else that suggests Planet X 2.0 really is out there. But the method of seeking out other worlds while looking for their gravitational influence on the orbits of other celestial bodies has been done before, with historic success.

In 1781, British astronomer Sir William Herschel noticed a perturbation in Uranus' orbit. By 1821, French astronomer Alexis Bouvard surmised that Uranus was being slightly "tugged" by the gravity of another, as yet to be discovered, massive planet in the outer solar system. In the 1840s, English and French astronomers John Couch Adams and Urbain Le Verrier independently went on to calculate where this mystery planet should be in the night sky by purely measuring these little deviations in Uranus' path.

Fifty-five years after Herschel noticed Uranus' perturbations, the distant planet was officially discovered by German astronomer Johann Galle in the location predicted by Couch Adams and Le Verrier. It was named Neptune.

Following the discovery of Neptune through studying perturbations in the orbit of Uranus, astronomers in the late 19th century still believed there must be another massive planet in the outer solar system causing additional perturbations to Uranus. By 1906, Percival Lowell -- founder of the Lowell Observatory in Flagstaff, Ariz. -- was inspired by these hints of another world and started a search for what he dubbed "Planet X."

It wasn't until 1930 that Clyde Tombaugh, an astronomer at Lowell Observatory, discovered Pluto. At the time, it was thought the search for Planet X had come to an end, but after follow-up observations in the decades after Pluto's discovery, the tiny world was found to have a minuscule gravitational field -- it wasn't the "Planet X" astronomers were looking for.

As it turned out, many of the perturbation measurements were eventually put down to observational error, but that didn't negate the potential for more large planets beyond our observational capabilities existing beyond the Kuiper belt -- the scenario that Gomes is currently investigating.

This new search for a hypothetical world is interesting, and reminiscent of Lowell's hunt for Planet X, but just because extreme SDO orbits hint at the presence of another body doesn't mean there has to be a Planet X 2.0.

"You can go back 100 years to claims of planets in the outer solar system and (their orbital anomalies) have all eventually gone away," said Hal Levison, a planetary scientist at the Southwest Research Institute in Boulder, Colo. "That should give you pause for thought. Just because there's not a good explanation for (the orbits of the scattered disc objects) besides another planet doesn't mean there won't be a good explanation in the future."

Read more at Discovery News

Chile's Vanishing Patagonian Lake

In less than 24 hours Lake Cachet II in Chile's southern Patagonia vanished, leaving behind just some large puddles and chunks of ice in the vast lake bed.

The lake's water comes from ice melting from the Colonia Glacier, located in the Northern Patagonian ice field, some 2,000 kilometers (1,250 miles) south of the capital, Santiago.

The glacier normally acts as a dam containing the water, but rising temperatures have weakened its wall. Twice this year, on January 27 and March 31, water from the lake bore a tunnel between the rocks and the glacier wall.

The result: Lake Cachet II's 200 million cubic liters of water gushed out into the Baker river, tripling its volume in a matter of hours, and emptying the five square kilometer (two square miles) lake bed.

Cachet II has drained 11 times since 2008 -- and with global temperatures climbing, experts believe this will increase in frequency.

"Climate models predict that as temperatures rise, this phenomenon, known as GLOFs (Glacial Lake Outburst Floods), will become more frequent," said glaciologist Gino Casassa from the Center for Scientific Studies (CES).

Casassa, a member of the 2007 Nobel Peace Prize-winning Intergovernmental Panel on Climate Change, told AFP there have been 53 similar cases of lakes draining in Chile between 1896 and January 2010, with increased frequency in the later years.

CES research assistant Daniela Carrion was camped out with a small research team taking measurements of the Colonia Glacier when the lake drained in March.

"When we woke up, we saw a change in the valley," Carrion told AFP. "The paths that we walked on had flooded, and the whole area was filled with large chunks of ice."

The lake dropped 31 meters (90 feet) when the water drained out, according to a report from the General Water Directorate, which monitors lake levels in Chile using satellite data.

When the lake starts draining an alarm system is triggered, giving residents in the sparsely-populated area up to eight hours to move animals and flee to higher ground.

The Tempanos Lake, also in far southern Chile, drained in a similar fashion in May 2007. Forest rangers working to save endangered huemuls -- mid-sized deer native to the region -- were surprised when they came across the empty lake. There were ice floes on the floor of the ten square kilometer lake bed, but no water.

Forestry officials had visited Tempanos in April and it was full, and when a team of scientists and naval officials flew over the area in July they found that the lake, which also is fed by waters from a nearby glacier, was starting to re-fill.

Read more at Discovery News