Discovered: A Cold, Close Neighbor of the Sun

NASA’s Wide-field Infrared Survey Explorer (WISE) and Spitzer Space Telescope have discovered what appears to be the coldest “brown dwarf” known — a dim, star-like body that  surprisingly is as frosty as Earth’s North Pole. Named “WISE J085510.83-071442.5,” the brown dwarf appears to be 7.2 light-years away, earning it the title for fourth closest system to our sun.

“It’s very exciting to discover a new neighbor of our solar system that is so close,” said Kevin Luhman, an astronomer at Pennsylvania State University’s Center for Exoplanets and Habitable Worlds, University Park.

This animation shows the brown dwarf WISE J085510.83-071442.5 moving across the sky. It was first seen in two infrared images taken six months apart in 2010 by NASA’s Wide-field Infrared Survey Explorer (WISE). Two additional images of the object were taken with NASA’s Spitzer Space Telescope in 2013 and 2014. All four images were used to measure the distance to the object — 7.2 light-years — using the parallax effect.  Movie

Brown dwarfs start their lives like stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight. The newfound coldest brown dwarf is named WISE J085510.83-071442.5. It has a chilly temperature between minus 54 and 9 degrees Fahrenheit (minus 48 to minus 13 degrees Celsius). Previous record holders for coldest brown dwarfs, also found by WISE and Spitzer, were about room temperature.

“It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun’s nearest neighbors,” added Michael Werner, the project scientist for Spitzer at NASA’s Jet Propulsion Laboratory. “This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer.”

WISE was able to spot the rare object because it surveyed the entire sky twice in infrared light, observing some areas up to three times. Cool objects like brown dwarfs can be invisible when viewed by visible-light telescopes, but their thermal glow — even if feeble — stands out in infrared light. In addition, the closer a body, the more it appears to move in images taken months apart. Airplanes are a good example of this effect: a closer, low-flying plane will appear to fly overhead more rapidly than a high-flying one.

“This object appeared to move really fast in the WISE data,” said Luhman. “That told us it was something special.”

After noticing the fast motion of WISE J085510.83-071442.5, Luhman spent time analyzing additional images taken with Spitzer and the Gemini South telescope on Cerro Pachon in Chile. Spitzer’s infrared observations helped determine the frosty temperature of the brown dwarf. Combined detections from WISE and Spitzer, taken from different positions around the sun, revealed the object’s parallax, and thus its distance. The closest system to Earth, a trio of stars, is Alpha Centauri, at about 4 light-years away. WISE J085510.83-071442.5 is only a few light years farther than that.

This diagram pinpoints star systems closest to the sun. The year when the distance to each system was determined is listed after the system’s name.  More

WISE J085510.83-071442.5 appears to be 3 to 10 times the mass of Jupiter. With such a low mass, it could be a gas giant similar to Jupiter that was ejected from its star system. But scientists estimate it is probably a brown dwarf rather than a planet since brown dwarfs are known to be fairly common. If so, it is one of the least massive brown dwarfs known.

In March of 2013, Luhman’s analysis of the images from WISE uncovered a pair of much warmer brown dwarfs at a distance of 6.5 light years, making that system the third closest to the sun. His search for rapidly moving bodies also demonstrated that the outer solar system probably does not contain a large, undiscovered planet, which has been referred to as “Planet X” or “Nemesis.”

Fast and curious: Electrons hurtle into the interior of a new class of quantum materials

As smartphones get smarter and computers compute faster, researchers actively search for ways to speed up the processing of information. Now, scientists at Princeton University have made a step forward in developing a new class of materials that could be used in future technologies.

They have discovered a new quantum effect that enables electrons — the negative-charge-carrying particles that make today’s electronic devices possible — to dash through the interior of these materials with very little resistance.

The discovery is the latest chapter in the story of a curious material known as a “topological insulator,” in which electrons whiz along the surface without penetrating the interior. The newest research indicates that these electrons also can flow through the interior of some of these materials.

“With this discovery, instead of facing the challenge of how to use only the electrons on the surface of a material, now you can just cut the material open and you have light-like electrons flowing in three dimensions inside the materials,” said M. Zahid Hasan, a professor of physics at Princeton, who led the discovery.

The finding was conducted by a team of scientists from the United States, Taiwan, Singapore, Germany and Sweden and published in two papers in the journal Nature Communications. The first paper, published May 7, demonstrates that fast electrons can flow in the interior of crystals made from cadmium and arsenic, or cadmium arsenide. The second paper, published May 12, explores fast electrons in a material made from the elements bismuth and selenium.

In most materials, including copper and other metals that conduct electricity, electrons navigate an obstacle course of microscopic outcroppings, ledges and other imperfections that obstruct the tiny particles and send them scattering in the wrong directions. This causes resistance and the conversion of electrical current into heat, which is why electronic appliances become warm during use.

Scientists at Princeton University have shown that negatively charged particles known as electrons can flow extremely rapidly due to quantum behaviors in a type of material known as a topological Dirac semi-metal. Previous work by the same group indicated that these electrons can flow on the surface of certain materials, but the new research indicates that they can also flow through the bulk of the material, in this case cadmium arsenide. Using a technique called angle-resolved photoemission spectroscopy (left), the researchers measured the energy and momentum of electrons as they were ejected from the cadmium arsenide. The resulting data revealed each electron as two cones oriented opposite each other that converge at a point, a telltale sign of the quantum behavior that allows electrons to act like light, which has no mass. A 3-D reconstruction (right) shows that the cone-shaped electrons are able to move in all directions in the material. The top-right panel reveals that these electrons are linked, allowing them to move even when deformed by bending or stretching, an attribute that gives them their topological nature. (Image courtesy of M. Zahid Hasan and Suyang Xu)

In topological insulators and the new class of materials the Princeton researchers studied, the unique properties of the atoms combine to create quantum effects that coax electrons into acting similar to a light wave instead of like individual particles. These waves can weave around and dodge — and even move through — barriers that would typically stop most electrons. These properties were theoretically proposed by Charles Kane and a team at the University of Pennsylvania from 2005 to 2007 and first observed experimentally in solid materials by the Hasan group in 2007 and 2008.

In 2011, the Hasan group detected this fast electron-flow in the interior of a material made from combining several elements — bismuth, thallium, sulfur and selenium. The results were published in the journal Science.

In the new study in cadmium arsenide, the electrons have an average velocity that is 10,000 times more than that of the previous bismuth-based materials identified by the group. “This is a big deal,” Hasan said. “It means the electrons can flow quite easily in the material and many more exotic quantum effects can now be studied. That just wasn’t possible in the past.”

The most promising application for these materials may be for a proposed “topological quantum computer” based on novel electronics that would use a property of electrons known as “spin” to do calculations and transmit information.

The quantum behavior in this new class of materials has led them to be called “topological Dirac semi-metals” in reference to English quantum physicist and 1933 Nobel Prize winner Paul Dirac, who noted that electrons could behave like light. Semi-metals that are “topological” are ones that retain their spatial electronic properties — and their speedy electrons — even when deformed by certain types of stretching and twisting.

The speeds achieved by these electrons have led to comparisons to another novel electronic material, graphene. The new class of materials has the potential to be superior to graphene in some aspects, Hasan said, because graphene is a single layer of atoms in which electrons can flow only in two dimensions. Cadmium arsenide permits electrons to flow in three dimensions.
The new study redefines what it means to be a topological material, according to Su-Yang Xu, a graduate student in Hasan’s lab and co-first author of the May 7 paper with postdoctoral research associate Madhab Neupane at Princeton and Raman Sankar of National Taiwan University.

“The term topological insulator is now quite famous, and the yet term ‘insulator’ means that there are no electrons flowing in the bulk of the material,” Xu said. “Our study shows that electrons are flowing in the bulk of the material, so clearly cadmium arsenide is not an insulator, but it is still topological in nature, so this is a totally new type of quantum matter,” he said.

The team made the discovery using a technique called angle-resolved photoemission spectroscopy. The researchers shined a very powerful X-ray beam — using a particle accelerator at the Advanced Light Source at Lawrence Berkeley National Laboratory — onto the surface of the material then monitored the electrons as they were knocked out of the interior.

“When the electron comes out, we measure its energy and velocity, and what we found is that electrons coming out of the cadmium arsenide had measurements that were similar to what is seen in particles that are massless,” Neupane said.

In the second paper in Nature Communications, Neupane and co-authors presented a model for controlling the spin direction of the electron particles in a different material, bismuth selenide.

“The Princeton group showed in exquisite details that electrons in certain solids obey the three- dimensional massless Dirac equation,” said Patrick Lee, a professor of physics at the Massachusetts Institute of Technology who was not involved in the work. “While predicted by theoretical calculations, this behavior has never been seen before in real materials until this past year. This work adds greatly to the ongoing excitement of how topology can impact electronic states in real materials.”

The first study, “Observation of a three-dimensional topological Dirac semimetal phase in high-mobility Cd3As2” appeared in the journal Nature Communications on May 7, 2014. The co-first-authors were Madhab Neupane and Su-Yang Xu of Princeton University and Raman Sankar of National Taiwan University. Additional researchers at Princeton who contributed to the work were graduate students Nasser Alidoust and Ilya Belopolski, and postdoctoral research associates Guang Bian and Chang Liu. The team also included Tay-Rong Chang of National Tsing Hua University in Taiwan; Horng-Tay Jeng of National Tsing Hua University and Academia Sinica in Taiwan; Hsin Lin of National University of Singapore; Arun Bansil of Northeastern University; and Fangcheng Chou of National Taiwan University.

The second study, “Observation of a quantum-tunnelling-modulated spin texture in ultrathin topological insulator Bi2Se3 films,” appeared in the journal Nature Communications on May 12, 2014. The first author was Madhab Neupane. Co-authors at Princeton were Su-Yang Xu, Nasser Alidoust, Ilya Belopolski, Chang Liu and Guang Bian. Also on the team were Anthony Richardella, Duming Zhang and Nitin Samarth of Pennsylvania State University; Jaime Sánchez-Barriga, Dmitry Marchenko, Oliver Rader and Andrei Varykhalov of Helmholtz Centre Berlin for Materials and Energy; Mats Leandersson and Thiagarajan Balasubramanian of MAX-lab, Sweden; Tay-Rong Chang of National Tsing Hua University in Taiwan; Horng-Tay Jeng of National Tsing Hua University and Academia Sinica in Taiwan; Hsin Lin of the National University of Singapore; and Susmita Basak and Arun Bansil of Northeastern University.

Primary funding for both studies was provided by the U.S. Department of Energy’s Office of Basic Energy Sciences (grants DE-FG-02-05ER46200, AC03-76SF00098 and DE-FG02-07ER46352).

Counseling Urged for Obese People at Higher Odds for Heart Disease: Experts

The millions of Americans who are overweight with at least one risk factor for heart disease should be offered “lifestyle counseling” by their doctors or other health care workers, an influential government-appointed panel of experts said on Monday.

This counseling should encourage a healthy diet and regular exercise as a means of dropping excess pounds, the U.S. Preventive Services Task Force said in its draft recommendation.

Risk factors for cardiovascular disease — which includes heart disease and stroke — include high blood pressure, high cholesterol and pre-diabetes. It also includes “metabolic syndrome,” a group of symptoms and conditions known to boost the chances of heart trouble.

Timely, intensive counseling on healthy lifestyle changes “can help reduce the risk of cardiovascular disease,” task force member Sue Curry said in a panel news release.

Other experts applauded the recommendation. Katherine Farrell Harris called it “an excellent idea.”

“We’ve learned that the vast majority of adults grappling with obesity have difficulty making changes on their own,” said Harris, a registered dietitian and director of integrated nutrition at Advantage Care Physicians in New York City. “This kind of behavior counseling includes education, goal setting and ongoing monitoring and support in order to help patients make major lifestyle changes and stick to them.”

Dr. Nieca Goldberg, a cardiologist and director of the Tisch Center for Women’s Health at NYU Langone Medical Center, New York City, agreed.

“Lifestyle changes such as diet and exercise can make a big impact in improving these risk factors, but many times people can’t get started because they don’t know where to start,” she said. “There is a big dropout rate, greater than 50 percent, six months into a lifestyle program.”

Heart disease is a leading cause of death in the United States. The panel noted that in 2012, about 35 percent of American adults were obese, which increases their chance of having cardiovascular disease risk factors such as high blood pressure, high cholesterol and diabetes.

Just what would be involved in lifestyle counseling? According to panel member Curry, “effective counseling services [typically] include education, goal setting, and ongoing monitoring and feedback … delivered by a trained professional. While there is no magic number of sessions, it is clear that effective counseling is delivered over multiple sessions spread over several months to a year.”

Goldberg said that she will “often refer [obese] patients to the psychologist for cognitive behavioral counseling, to help build confidence, work on stress-reduction techniques for high blood pressure and overeating.

She added that, sometimes, “the only problem with this type of counseling is [a lack of] insurance coverage.”

The draft recommendation, which is open to public comment until June 9, applies only to overweight and obese adults with a risk factor for cardiovascular disease. The task force has a separate recommendation for people who have an average risk for cardiovascular disease.

“All individuals, regardless of their risk of heart disease, can realize the health benefits of improved nutrition, healthy eating behaviors and increased physical activity,” task force member Dr. Mark Ebell said in the news release.

SOURCES: Nieca Goldberg, M.D, clinical associate professor, department of medicine, Leon H. Charney division of cardiology, and director, Joan H. Tisch Center for Women’s Health, NYU Langone Medical Center, New York City; Katherine Farrell Harris, R.D, director of integrated nutrition, Advantage Care Physicians, New York City; U.S. Preventive Services Task Force, news release, May 12, 2014

Car Crash Risk May Go Up During Pregnancy

A woman’s risk of having a serious car accident may increase in her second trimester of pregnancy, a large new Canadian study suggests.

Researchers found that compared with the few years before pregnancy, a woman’s risk of a traffic accident rose by 42 percent during the second trimester. During the third trimester, the odds dropped again.

Experts said they cannot tell why the pattern exists. But the findings do suggest women should be especially mindful about safe driving when they’re pregnant.

“This is not a reason to stop driving,” said Dr. Donald Redelmeier, a researcher with the Institute for Clinical Evaluative Sciences in Toronto, who led the study. “It’s a reason to drive more carefully,” he explained.

“And it doesn’t mean you should give the driving responsibilities to your husband,” Redelmeier added. Even with a 42 percent increase, he noted, pregnant women’s accident rate is lower than that of men their age.

The study, published online May 12 in the journal CMAJ (Canadian Medical Association Journal), is based on records for more than 500,000 Canadian women who gave birth between 2006 and 2011. The researchers looked at the women’s rates of serious car accidents — bad enough for a trip to the ER — during pregnancy and during the three years before pregnancy.

Before pregnancy, the study found, the crash rate was about 4.5 per 1,000 women each year. The rate was similar during the first trimester of pregnancy, but then rose to almost 7.7 crashes per 1,000 women during the first month of the second trimester. During the third trimester, car accidents dipped again.

According to Redelmeier, the second-trimester jump was seen regardless of women’s age or income and education levels. It was also apparent in all seasons of the year.

Still, it’s hard to definitely pin the blame on pregnancy itself, according to an emergency medicine physician who was not involved in the research.

Other factors, that could not be measured in the study, might account for the connection, said Dr. Sampson Davis, of Meadowlands Hospital Medical Center in Secaucus, N.J.

It’s also unclear why the risk would drop again in the third trimester, Davis added.

Despite the questions, though, he agreed that safe driving should be emphasized during pregnancy. “Normally, obstetricians don’t talk to women about driving,” Davis said. “I think adding that to prenatal care is important.”

According to Redelmeier, there could be something about the second trimester, in particular, that makes women more vulnerable to driving errors. He said the “accumulating physiological changes” of pregnancy, plus stress, might leave women fatigued or otherwise off their driving game.

But because their bodies have not yet gone through the outward changes of later pregnancy, they may be going about all their usual activities — without realizing their driving skills are less sharp.

That’s speculation, though. “We can’t get at the mechanisms with this study,” Redelmeier said. “But just because we don’t know the exact causes doesn’t mean we can’t prevent these accidents.”

The bottom line for pregnant women, he added, is to “always obey speed limits, obey stop signs, yield the right of way, minimize distractions and wear a seatbelt.”

Davis agreed, emphasizing the “don’t use your cellphone” rule. “And if you’re tired and not feeling well one day,” he said, “don’t drive.”

Sometimes, Davis noted, pregnant women worry that wearing a seatbelt across the abdomen could be harmful to the baby. But that’s not true, he stressed.

“Wearing a seatbelt protects you if you’re in an accident,” Davis said. “And that protects the baby, too.”

SOURCES: Donald Redelmeier, M.D., researcher, Institute for Clinical Evaluative Sciences, and professor, medicine, University of Toronto, Ontario, Canada; Sampson Davis, M.D., emergency medicine physician, Meadowlands Hospital Medical Center, Secaucus, N.J.; May 12, 2014 CMAJ (Canadian Medical Association Journal), online

The world’s most beautiful birds’ eggs

There’s a dazzling array of colour and pattern in the 600 eggs photographed in Mark Hauber’s The Book of Eggs, plus fascinating insights into their biology

BOILED, coddled, fried, scrambled or poached, our usual interaction with eggs is as a consumer: the inside is to be eaten. Once broken, the shell is lobbed in the bin and forgotten.

Except that this is probably not what you are going to do after reading The Book of Eggs. Newly enlightened on egg biology and physiology, you may find yourself pointing out that the dimple in the broad end of an egg is where the air sac lay. Or perhaps you will be motivated to look at an egg shell through a lens, the better to see the tiny pores that allow air in while keeping water and toxins out – or even pause before eating your fried egg to dissect the yolk in search of its seven layers.

Beyond the brown and white eggs we are used to, there is a dazzling array of colours and patterns. While the occasional speckled egg might elicit a comment at the breakfast table, it pales into insignificance against the rich copper of the eggs of Cetti’s warbler. And the green-blue eggs of the great tinamou are so beautiful that an encounter with the nest of this Amazonian species was the only time I have known one of my long-term field guides to rhapsodise about egg colour rather than edibility.

In terms of pattern, it is hard to beat the eggshell of the guira cuckoo (which looks like a chocolate dessert drizzled with evaporated milk), the scribbled surface of a great bowerbird egg, or the translucent, multi-layered patterning of the eggs of cedar and bohemian waxwings, where the blotching seems to loom through a fog of shell.

Each of the book’s 600 eggs is photographed life size, with magnified views of the smaller ones to allow us to appreciate the detail. For each, a summary of breeding biology links form to function. Oddly, the amazing exercise in biological packaging that is the egg sometimes makes species vulnerable to predators. The Antarctic giant petrel, for example, evolved on rodent-free islands and its white eggs are easy prey for invasive rodents.

The book also wisely includes the egg of the extinct great auk, the last few of which were hunted down to make sure that museums had skins and eggs of this once-abundant seabird.

Altogether, this book achieves a fine synergy between informative text and beautiful photographs. My only trifling criticism is that placing the eggs on a black rather than a white background would have made their lustre and beauty stand out still more.

Adrian Barnett is a rainforest ecologist at Brazil’s National Institute of Amazonian Research in Manaus

Milky Way’s fringe stars show our galaxy’s flare

Our galaxy really has some flare. A rare glimpse of stars on the opposite side of the Milky Way supports the idea that our galaxy fans out at its edges.

The sun sits in one arm of the Milky Way’s relatively flat spiral, orbiting the galactic centre. The stars around us are well mapped, but stars on the other side of the galaxy are largely obscured by dense material at the bulging galactic centre.

“What has been inferred about our galaxy out at these distances has been from radio observations of mostly hydrogen gas,” says Michael Feast at the University of Cape Town in South Africa. Feast and his colleagues have now managed to spot five stars on the far edge.

The team was able to pin down the stars’ locations because they are of a particular type known as “Cepheid variables”. These stars grow and shrink on a regular cycle, and the length of this cycle is related to their true brightness. By measuring the cycle and seeing how bright a Cepheid star appears to be, we can accurately calculate its distance from Earth.

Dark matter sculptor

Using telescopes at the South African Astronomical Observatory in Sutherland, the team identified four Cepheid stars that are about 50,000 light years from the galactic centre. They also found another star further out, at around 70,000 light years.

All five stars are on the far cusp of the galaxy, either far above or below the galactic plane. That tallies with the maps of galactic gas, which suggest the Milky Way is thicker at its edges. Astronomers think this is due to a dark matter halo that surrounds the galaxy.

There are many more stars at the centre of the Milky Way than at its edges, so at greater distances the gravitational tug of dark matter starts to overcome the force between ordinary matter, pulling it away from the plane to create a flared edge. Exactly how large the flare is depends on the distribution of dark matter in the halo.

“This finding gives us important new data we can input into the models to determine the shape of the Milky Way halo,” says Victor Debattista at the University of Central Lancashire in Preston, UK. These models can be used to understand how other galaxies form as well, he says. “It opens up lots of interesting new science possibilities in terms of galaxy formation.”

Journal reference: Nature, DOI: 10.1038/nature13246

A brief history of space flight – in numbers

Thirty-one astronauts have made a return-trip to Mars. Well, not quite – but they have put in the requisite hours in space. That’s just one of the surprising insights to come out of a recent attempt to chart humanity’s 52-year history in space.

Gilles Clément and Angelia Bukley of the International Space University in Illkirch-Graffenstaden, France, used publicly available information from the US, Russian and Chinese space programmes. Between 12 April 1961, when Yuri Gagarin took a single orbit around the Earth on board the Soviet Vostok-1 craft and December 2013, they counted the humans who have flown to space, how long they collectively spent there and who they were.

We picked out our favourites six insights, then put them in context with data from elsewhere.

1. Astronauts are as common as Nobel prizewinners

As of 31 December 2013, 539 individuals had been to space, defined as reaching an altitude of 100 kilometres or more. That’s a rate of about 10 per year, and roughly equivalent to the 566 people who have ever won a Nobel prize in a science subject (physics, chemistry, or physiology/medicine).

(Note: Clément and Bukley’s analysis does not include the two commercial astronauts who piloted the SpaceShipOne test flights in 2004, who were in space for just a few minutes each.)

2. Space trips last days, months… but rarely years

Gagarin’s single orbit of the Earth lasted just 108 minutes. Clément and Bukley found that of a total of 1211 person-flights, defined as a single crew member flying one mission, most last less than a month. Presumably these short hops were trips to the moon and missions spent inside NASA’s now-retired space shuttle, to build and repair the International Space Station. But a significant minority spent five or six months, representing stays on board the ISS.

3. Many astronauts spend more than a year of their life in space

Though no single trip has been longer than Valeri Polyakov’s 437 days aboard the Soviet space station Mir, if you count total time in space over a lifetime, the figures are quite different.

4. Thirty-one astronauts have been to Mars and back, sort of

One of Clément and Bukley’s most surprising observations is that 31 travellers have spent over a year in total in space, enough to make a trip to Mars and back – though the exact travel time depends on relative positions of Earth and the Red Planet.

5. Like many adventures, space is sexist

Last year, a private foundation announced plans to send a man and woman on a 501-day round-trip to Mars, to “represent all of humanity”. Spaceflight so far has been far from representative when it comes to gender, though it is not the only extreme pursuit with a skew.

6. Space travel is not as dangerous as you might expect

Clément and Bukley also examined the risks of space travel. Counting two lost shuttles and two lost Soyuz capsules, the pair calculated that the chance of dying on a space mission is 1.5 per cent, markedly less than thepercentage of people who die attempting to reach the summit of Mount Everest.

Journal reference: Acta Astronautica, DOI: 10.1016/j.actaastro.2014.04.002

Real-life Inception: Zap your brain to control dreams

If you liked Inception, you’re going to love this. People have been given the ability to control their dreams after a quick zap to their head while they sleep.

Lucid dreaming is an intriguing state of sleep in which a person becomes aware that they are dreaming. As a result, they gain some element of control over what happens in their dream – for example, the dreamer could make athreatening character disappear or decide to fly to an exotic location.

Researchers are interested in lucid dreaming because it can help probe what happens when we switch between conscious states, going from little to full awareness.

In 2010, Ursula Voss at the J.W. Goethe University in Frankfurt, Germany, and her colleagues trained volunteers to move their eyes in a specific pattern during a lucid dream. By scanning their brains while they slept, Voss was able to show that lucid dreams coincided with elevated gamma brainwaves. This kind of brainwave occurs when groups of neurons synchronise their activity, firing together about 40 times a second. The gamma waves occurred mainly in areas situated towards the front of the brain, called the frontal and temporal lobes.

Perchance to dream

The team wanted to see whether gamma brainwaves caused the lucid dreams, or whether both were side effects of some other change. So Voss and her colleagues began another study in which they stimulated the brain of 27 sleeping volunteers, using a non-invasive technique called transcranial alternating current.

Each volunteer came into the lab on many different nights. As they slept, their neural activity was monitored with EEG to identify when they entered rapid eye movement (REM) sleep. On each night, the subject then received electrical stimulation at a different frequency, ranging between 2 and 100 hertz for 2 minutes, or a sham treatment that had no effect on the brain. The participants were then woken up and asked to rate their dream consciousness on a standard scale.

Previous work has shown that during lucid dreaming, three of eight factors on this scale are substantially increased, including awareness of dreaming, control over plot and third-person perspective.

Sure enough, these three factors all increased after volunteers received stimulation at a frequency of 40 Hz, which caused an increase in gamma brainwave activity. Much higher and lower frequencies of stimulation – outside of the gamma range – had no effect on lucid dreaming.

Split consciousness

Researchers believe that our experience of the world is split into two levels of consciousness. Primary consciousness relates to simple emotions and sensory perceptions – a level which could apply to animals as well as humans. Secondary consciousness involves being aware that we are aware – something many would argue is unique to humans.

The gamma wave oscillations may help different areas of the brain synchronise their activity and thereby talk to one another, “binding” thoughts and feelings to create a cohesive experience. Importantly, the frontal and temporal areas – which are involved in decision making and memory and are most highly evolved in humans – aren’t normally synchronised in REM sleep, but are in waking consciousness. Ramping up the gamma waves may have created a hybrid state with greater synchronisation and awareness in this area, creating some of the characteristics of secondary consciousness, while the rest of the brain sleeps.

The team suggests that brain stimulation might help people with post-traumatic stress disorder who have recurring nightmares. Perhaps by triggering lucid dreaming, people with PTSD can take control of their dreams and make them less frightening. “That’s what we are looking at now,” says Voss, although the results are not yet available.

It is a promising suggestion, says Michael Schredl who works in the sleep laboratory at Heidelberg University, Germany. He says it will be difficult to expand the applications to help treat mental disorders, but “the idea of studying patients with nightmares or PTSD would be very interesting”.

Journal reference: Nature, DOI: 10.1038/nn.3719

Collapse of Antarctic glaciers seems to be unstoppable

Parts of the West Antarctic Ice Sheet are already collapsing and probably can’t be saved. Two independent studies suggest that several glaciers have gone past the point of no return, dooming them to fall into the sea and cause several metres of sea level rise. However the collapse will take centuries.

“A large sector of the West Antarctic Ice Sheet has gone into irreversible retreat,” says Eric Rignot of the University of California at Irvine, who led one of the studies. “We’ve gone beyond the point of no return.”

A study led by Ian Joughin of the University of Washington in Seattle focuses on the Thwaites glacier, a key component of the West Antarctic Ice Sheet(WAIS). It predicts that the glacier will collapse completely within 200 to 1000 years, raising global sea levels by about 60 centimetres.

But because the Thwaites glacier keeps much of the rest of the WAIS in check, its disappearance could destabilise the entire sheet, releasing enough ice to raise sea levels by a further 3 to 4 metres.

Shrinking ice

Joughin and his colleagues used radar images from the air to accurately map the rocks beneath the Thwaites glacier. This enabled them to map the receding “grounding line”, the point at which a glacier rests on open water rather than on rock. The deeper the grounding line penetrates inland, the more ice is supported by water alone, and the likelier it is to collapse and melt.

Using this information, they modelled the glacier’s likely fate over the coming centuries, and projected that a rapid collapse will begin between 200 and 900 years in the future. Once under way, the collapse would cause sea levels to rise by at least 10 centimetres per century.

“The bad news is that such a collapse may be inevitable,” says Joughin. The only uncertainty is over how fast the collapse will happen.

All in retreat

The other study, led by Rignot, tracked the retreats between 1992 and 2011 of the Thwaites glacier, the Pine Island Glacier and the Smith-Kohler glacier system. The results of both studies tally.

Rignot and his colleagues used radar interferometry measurements from satellites to track the retreats of the grounding lines of the glaciers.

Measured at their centres, the Thwaites glacier had retreated 14 kilometres, the Pine Island glacier by 31 kilometres, and the Smith-Kohler glacier system by 35 kilometres.

“The grounding line has been retreating at record speeds unseen anywhere else in the Antarctic,” says Rignot.

No stopping it

Both studies found that there are no obstacles further inland, such as rocky outcrops, that could halt the retreats. “There’s no barrier to stop it,” says Rignot.

For that reason, Joughin says the Thwaites glacier is probably doomed. “It looks like all the feedbacks tend to point towards it actually accelerating over time, as there’s no stabilising mechanism we can see,” he says.

According to Rignot, the same is true for all the glaciers in the area, except the relatively small Haynes glacier. “Even if the ocean was not warming up, it’s now a chain reaction that’s unstoppable,” he says.

“The only thing that would stop it is a mountain where glaciers would have to climb uphill,” adds Rignot. “We are fairly confident there’s no such hill or mountain.”

Diamond no longer nature’s hardest material

Diamond will always be a girl’s best friend, but it may soon lose favour with industrial drillers.

The gemstone lost its title of the “world’s hardest material” to man-made nanomaterials some time ago. Now a rare natural substance looks likely to leave them all far behind – at 58% harder than diamond.

Zicheng Pan at Shanghai Jiao Tong University in China and colleagues simulated how atoms in two substances believed to have promise as very hard materials would respond to the stress of a finely tipped probe pushing down on them.

Extreme conditions

The first, wurtzite boron nitride has a similar structure to diamond, but is made up of different atoms.

The second, the mineral lonsdaleite, or hexagonal diamond is made from carbon atoms just like diamond, but they are arranged in a different shape.

Only small amounts of wurtzite boron nitride and lonsdaleite exist naturally or have been made in the lab, so until now no one had realised their superior strength. The simulation showed that wurtzide boron nitride would withstand 18 per cent more stress than diamond, and lonsdaleite 58 per cent more. If the results are confirmed with physical experiments, both materials would be far harder than any substance ever measured.

Doing those tests won’t be easy, though. Because both are rare in nature, a way is needed to make enough of either of them to test the prediction.

Rare mineral lonsdaleite is sometimes formed when meteorites containing graphite hit Earth, while wurtzite boron nitride is formed during volcanic eruptions that produce very high temperatures and pressures.

Flexible friend

If confirmed, however, wurtzite boron nitride may turn out most useful of the two, because it is stable in oxygen at higher temperatures than diamond. This makes it ideal to place on the tips of cutting and drilling tools operating at high temperatures, or as corrosion-resistant films on the surface of a space vehicle, for example.

Paradoxically, wurtzite boron nitride’s hardness appears to come from the flexibility of the bonds between the atoms that make it up. When the material is stressed some bonds re-orientate themselves by about 90 degrees to relieve the tension.

Although diamond undergoes a similar process, something about the structure of wurtzite boron nitride makes it nearly 80 per cent stronger after the process takes place, says study co-author Changfeng Chen at the University of Nevada, Las Vegas, an ability diamond does not have.

Single crystals

Natalia Dubrovinskaia from the University of Heidelberg in Germany has carried out similar research.

“This is important because any attempt to give an insight into the mechanism that improves a material’s property, especially hardness, is technologically extremely significant,” she told New Scientist.

The more that is understood about what influences the hardness of materials, the more it will become possible to design hard materials to order, she explains.

However, she points out that in order to prove the theory, single crystals of each material would be needed. So far there are no known ways to isolate or grow such crystals of either material.

The exciting results of the simulations described above remain unconfirmed by experiment, because there’s simply not enough of these exotic materials to test. “There has been no report of synthesis of wurtzite boron nitride or hexagonal diamond in large quantity since our 2009 work,” says Changfeng Chen.

But the search for ultra-hard crystals continues to turn up promising candidates. Last year, Yongjun Tian of Yanshan University in Qinhuangdao, China, and colleagues studied a cubic form of boron nitride – rather than the hexagonal form Chen studied – which they claimed was also harder than diamond.

The experimental details of that study have been criticised, but Chen believes Tian’s material still bears investigating. “The main challenge is to understand the atomistic mechanism underlying this extraordinary result,” says Chen.