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Thu, 20 Oct 2016
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Science & Technology


Samarium hexaboride: The paradoxical crystal that's baffling physicists

© Andrew Testa/Qunata Magazine
Interactions between electrons inside samarium hexaboride appear to be giving rise to an exotic quantum behavior new to researchers.
At super-low temperatures, a crystal called samarium hexaboride behaves in an unexplained, imagination-stretching way.

In a deceptively drab black crystal, physicists have stumbled upon a baffling behavior, one that appears to blur the line between the properties of metals, in which electrons flow freely, and those of insulators, in which electrons are effectively stuck in place. The crystal exhibits hallmarks of both simultaneously.

"This is a big shock," said Suchitra Sebastian, a condensed matter physicist at the University of Cambridge whose findings appeared today in an advance online edition of the journal Science. Insulators and metals are essentially opposites, she said. "But somehow, it's a material that's both. It's contrary to everything that we know.

© Courtesy of Suchitra Sebastian
Suchitra Sebastian, an experimental condensed matter physicist at the University of Cambridge, said the discoveries she and her colleagues have made “mean that something needs to be rewritten completely.”
The material, a much-studied compound called samarium hexaboride or SmB6, is an insulator at very low temperatures, meaning it resists the flow of electricity. Its resistance implies that electrons (the building blocks of electric currents) cannot move through the crystal more than an atom's width in any direction. And yet, Sebastian and her collaborators observed electrons traversing orbits millions of atoms in diameter inside the crystal in response to a magnetic field — a mobility that is only expected in materials that conduct electricity. Calling to mind the famous wave-particle duality of quantum mechanics, the new evidence suggests SmB6 might be neither a textbook metal nor an insulator, Sebastian said, but "something more complicated that we don't know how to imagine."

"It is just a magnificent paradox," said Jan Zaanen, a condensed matter theorist at Leiden University in the Netherlands. "On the basis of established wisdoms this cannot possibly happen, and henceforth completely new physics should be at work."

Bizarro Earth

Oxitec finally admits major risk in technology: GM mosquitoes may increase numbers of disease carrying Asian Tiger mosquito

Genetically modified (GM) mosquito company Oxitec has admitted a major risk of its technology - reducing one mosquito species may increase the numbers of a second disease-carrying species.

The information surfaced Friday when four environment and food safety groups including International Center for Technology Assessment, GeneWatchUK, Food and Water Watch and Friends of the Earth released court documents from the Cayman Islands. Oxitec, a subsidiary of Intrexon, applied for trial releases of its GM mosquito, which, according to the new information, would be inefficient and risky.

Oxitec previously denied that releasing millions of GE Aedes aegypti mosquitoes, with the aim of suppressing wild mosquito numbers, would result in increased numbers of the Aedes albopictus species (known as the Asian Tiger mosquito). The Aedes albopictus also transmits viral tropical diseases such as dengue and zika, and recently has been shown to be a vector of chikungunya, a devastating and sometimes lethal viral disease. The FDA recently approved trial releases of the GE mosquitoes in Florida.

"These court documents show that Oxitec's GM mosquito trials are not worth the risk. The State of Florida and its mosquito control boards have in the past effectively controlled disease from multiple mosquito species using much more benign approaches such as vaccines, screens, repellents, larvicides and removing breeding sites like abandoned tires," said Jaydee Hanson, policy director of the International Center for Technology Assessment.


US and NATO may be preparing unmanned sixth generation fighter jet armed with lasers

© REUTERS/ Northrop Grumman Corp/Handout
The Western defense coalition is already planning on its sixth-generation fleet of fighter jets to counter the aviation advances made by Russia and China in recent years.

The United States and its NATO allies have begun the planning stage for its next generation fighter jets in a bid to ensure lasting air superiority over novel fifth-generation Russian and Chinese fighter jets with a view for producing the next generation combat aircraft in the early 2030s.

While the West has long held the mantle on stealth designed fighter jets starting with the F-22 Raptor and subsequently the F-35 Lightning, both China and Russia's defense aviation industries have caught up to the United States in recent years with the unleashing of the Chengdu J-20 and the Russian T-50 (PAK-FA) which pose a significant threat to NATO's longstanding aerial dominance.

Blue Planet

New research shows bumblebees possess emotional states that influence behavior, just like humans

With all the conveniences of modernity, the human condition has unfortunately lost some of its connection with the natural world. As we separate ourselves ever more from other species, we find it more difficult to think of them beyond something to be used or exterminated.

Science has a way of reconnecting us, though. A study of bumblebees published in the journal Science found that they possess emotional states that influence behavior, just like humans. The research goes against the common presumption that insects are simple creatures carrying out nothing more than pre-programmed sets of actions.

The scientists found that bumblebees took less time to discover ambiguous-colored flowers after drinking a small droplet of very sweet sugar water, and took less time to reinitiate foraging after a simulated spider attack.

Previous experiments have shown the flower color behavior was not due to the bees "getting more excited or searching faster," which "indicates that the sweet sugar water may be causing a positive emotion-like state in bees, similar to humans and other animals."

"The finding that bees exhibit not just surprising levels of intelligence, but also emotion-like states, indicates that we should respect their needs when testing them in experiments, and do more for their conservation," said senior author Professor Lars Chittka.

Comment: Brain scans show insects have a form of consciousness


Scotland's asteroid strike

© Society for Interdisciplinary Studies
This one is geology rather than catastrophism as a geologist is at the heart of the discovery. Channel 4 Had a TV programme about it last week which you can see if you missed it at here ...(and see also here.)

Gary Gilligan is more interested in the Torridon sandstone (which subsequently filled the projected crater) as sand is a subject close to his heart (and wherever sand pops up we have to wonder about its origin). For example, sandstones occur on top of chalk geology in southern England (sometimes known as sarsen) and these too were laid down during an upheaval of some kind (during or at the end of the Palaeogene). In the Torridons we have sandstone laid down during or shortly after an asteroid strike. Thank you for the link Gary.

The projected crater site was already classified as an unconformity - it did not fit the usual pattern. There was a gravity anomaly.

This meant a closer look and now it is thought a crater exists beneath sedimentary layers such as sandstone, arkose and shale. For an insight into what these might be, see Torridonian ... Arkose ... and Shale.

Shales are composed of mud and clay particles, Arkose is a sandstone containing 25 per cent feldspar (Arkosian sand is sand rich in feldspar) and the Torridonian formation (from the Torridon Mountains) is a name for a group of sedimentary rocks in NW Scotland, such as red and brown sandstone, shales and arkoses.

The strike site is also associated with shocked quartz and by sandstone flecked with tiny fragments of green glass. The glass represents melted rock - and the heat generated was hot enough to force the glass, or melted rock, to seep into sand grains and become rock in itself, folding them in a dramatic fashion. The shale, in turn, is thought to derive from a volcanic like mud flow - induced by the strike creating a tectonic backlash or simply by the violence of the strike itself creating the mud flow. The inference is that an object hit the ground where sand and mud was a common ingredient (quite unlike the modern landscape of the region). Of course, one could conjecture the sand came out of the bowels of the earth as a result of the strike (along with the mud flow) or arrived with the asteroid (or comet).

It is interesting to see how mainstream takes onboard such catastrophic events but continues to interpret some of the geology in purely uniformitarian terms.


Don't throw out the baby teeth -- they can be harvested for stem cells

© zevendesign.com
A new study has shown that children's baby teeth are a rich source of stem cells. Stem cells, as you may know, are important because they are a kind of "blank" cell that can be grown into multiple kinds of cells as necessary. This comes in handy when cells are lost or damaged due to illness or disease. Though it's not without controversy, doctors are excited about the growing role of stem cells to treat injury, illness, and tissue deterioration due to age.

Most moms and dads store their child's baby teeth as a keepsake, but merely throwing these tiny teeth in a box isn't going to cut it for later medical use. Like the stem cells that can be found in cord blood samples, the cells in baby teeth must be collected and preserved in a particular way.

Solar Flares

Gigantic coronal hole blasts Earth with geomagnetic storm

A massive coronal hole on the sun is currently facing Earth, directing a solar storm at our planet which can potentially wreak havoc on communication and electrical systems.

On the plus side, though, the storm also means an increase in spectacular aurora borealis displays.

The geomagnetic storm was predicted by SpaceWeatherLive after it noted the return of a massive coronal hole that had faced Earth a month ago.

Microscope 1

Researchers use 3D printer to create potential replacement bones

© Phil Noble / Reuters
Bones made out calcium could be going the way of the flip phone! Not really, but researchers at Northwestern University have developed a breakthrough "hyper-elastic bone" that could be used in living tissue to bind bone and tendons together.

If this new composite bone is approved for humans, it could be used to treat several injuries. The hyper-elastic bone can not only function as a custom bone implant but can also promote bone growth.

The current options for bone grafts range from ceramics to mineralized collagen. But the side effects from current bone grafts pretty much result in what can be expected from introducing a foreign object to the body: infections, pain and implant displacement. However, the hyper-elastic bone could be a viable alternative with minimal side effects.

The first test of the hyper-elastic bone was promising. They began with a mouse and surrounded two of its vertebrae with the porous synthetic bone. Eight weeks later, they discovered that bone and tissue had grown into graft material and fused the vertebrae together.


Curtain call: Rosetta spacecraft crashes onto comet for mission finale

© rosettamission / Instagram
The European Space Agency's Rosetta spacecraft has crash landed onto a comet, ending its 12-year mission.

The space probe has been studying the 67P/Churyumov-Gerasimenko comet for two years.

In the end, the Rosetta spacecraft's curtain call was met with a sombre silence and then a brief cheer in the ESA's mission control room after it successfully crash landed onto the comet.


Genetic analysis reveals four species of giraffe, two of which on the most endangered large animals list

© www.zoo.org
Heads above the rest, a tall order!
Up until now, scientists had only recognized a single species of giraffe made up of several subspecies. But, according to the most inclusive genetic analysis of giraffe relationships to date, giraffes actually aren't one species, but four. For comparison, the genetic differences among giraffe species are at least as great as those between polar and brown bears. The unexpected findings reported in the Cell Press journal Current Biology on September 8 highlight the urgent need for further study of the four genetically isolated species and for greater conservation efforts for the world's tallest mammal, the researchers say.

"We were extremely surprised, because the morphological and coat pattern differences between giraffe are limited," says Axel Janke, a geneticist at the Senckenberg Biodiversity and Climate Research Centre and Goethe University in Germany. Giraffes are also assumed to have similar ecological requirements across their range, he added, "but no one really knows, because this megafauna has been largely overlooked by science."

Giraffes are in dramatic decline across their range in Africa. Their numbers have dropped substantially over the last three decades, from more than 150,000 individuals to fewer than 100,000. Despite that, the researchers say that there has been relatively little research done on giraffes in comparison to other large animals, such as elephants, rhinoceroses, gorillas, and lions.