Physicists have identified a new state of matter whose structural order operates by rules more aligned with quantum mechanics than standard thermodynamic theory. In a classical material called artificial spin ice, which in certain phases appears disordered, the material is actually ordered, but in a “topological” form.
Wednesday Apr. 4, 2018 at 7 PM ET
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From the Stone Age to the Silicon Age, nothing has had a more profound influence on the world than our understanding of the materials around us. The Industrial Revolution of the 19th century and the Information Revolution of the 20th were fueled by humankind’s ability to understand, harness, and control materials.
Supernovae produce some of the most powerful explosions in the cosmos, expelling a doomed star’s contents at velocities reaching 10 percent the speed of light. It usually takes a few weeks or months for a supernova to fade into nothingness, but astronomers have now documented a record-setting case in which a star was extinguished in just a few days.
They’re called Fast-Evolving Luminous Transients (FELTs), an exotic type of supernova discovered only a few years ago. As the name implies, these supernovae develop quickly, they’re very bright, and then they disappear. Unlike more “conventional” supernovae, such as Type Ia supernovae, the duration of these explosions can be measured in days rather than weeks or months. These celestial events are rare, and only a handful of FELTs have ever been documented.
The perplexing thing about FELTs, however, isn’t so much that they’re short lived—it’s that they’re also very bright. Scientists have subsequently theorized that they’re the glowing remnant of a gamma-ray burst (a massive explosion produced by a collapsing star that gives birth to a black hole), a supernova fueled by a magnetar (a neutron star with a powerful magnetic field), or a failed Type Ia supernova (in which a white dwarf star sucks up material from a nearby star, eventually causing it to explode). New research published today in Nature Astronomy suggests it’s none of the above.
A full-scale demonstrator of the thrust chamber for an upper-stage rocket engine incorporating the newest propulsion technologies is being prepared for its first hot firing.
The Expander-cycle Technology Integrated Demonstrator, or ETID, has arrived at the DLR German Aerospace Center test facility in Lampoldshausen for tests. It will help to prove new technologies, materials and manufacturing techniques that offer higher performance at lower cost for Europe’s future launchers.
ETID is a precursor of the next generation of 10-tonne rocket engines. Some of the technologies could also be used on upgrades to the existing Vinci, which powers the upper stage of Ariane 6.
Piezoelectric materials, which generate an electric current when compressed or stretched, are familiar and widely used: think of lighters that spark when you press a switch, but also microphones, sensors, motors and all kinds of other devices. Now a group of physicists has found a material with a similar property, but for magnetism. This “piezomagnetic” material changes its magnetic properties when put under mechanical strain.
“Piezomagnetic materials are rarely found in nature, as far as I’m aware,” said Nicholas Curro, professor of physics at UC Davis and senior author of a paper on the discovery published March 13 in the journal Nature Communications.
Curro and colleagues were studying a barium-iron-arsenic compound, BaFe2As2, that can act as a superconductor at temperatures of about 25 Kelvin when doped with small amounts of other elements. This type of iron-based superconductor is interesting because although it has to be kept pretty cold to work, it could be stretched into wires or cables.
Virtual assistants and chatbots don’t have a lot of common sense. It’s because these types of machine learning rely on specific situations they have encountered before, rather than using broader knowledge to answer a question. However, researchers at the Allen Institute for AI (Ai2) have devised a new test, the Arc Reasoning Challenge (ARC) that can test an artificial intelligence on its understanding of the way our world operates.
Humans use common sense to fill in the gaps of any question they are posed, delivering answers within an understood but non-explicit context. Peter Clark, the lead researcher on ARC, explained in a statement, “Machines do not have this common sense, and thus only see what is explicitly written, and miss the many implications and assumptions that underlie a piece of text.”
The test asks basic multiple-choice questions that draw from general knowledge. For example, one ARC question is: “Which item below is not made from a material grown in nature?” The possible answers are a cotton shirt, a wooden chair, a plastic spoon and a grass basket.
