Invisibility cloak could hide buildings from quakes

Borrowing from the physics of invisibility cloaks could make it possible to hide buildings from the devastating effects of earthquakes, say physicists in France and the UK.

The “earthquake cloak” idea comes from the team led by Stefan Enoch at the Fresnel Institute in Marseille, France. They were the first to show that the physics of invisibility cloaks could have other applications – designing a cloak that could render objects “invisible” to destructive storm waves or tsunamis. …

The new theoretical cloak comprises a number of large, concentric rings made of plastic fixed to the Earth’s surface. The stiffness and elasticity of the rings must be precisely controlled to ensure that any surface waves pass smoothly into the material, rather than reflecting or scattering at the material’s surface.

When waves travel through the cloak they are compressed into tiny fluctuations in pressure and density that travel along the fastest path available. By tuning the cloak’s properties, that path can be made to be an arc that directs surface waves away from an area inside the cloak. When the waves exit the cloak, they return to their previous, larger size.

Unlike some of the optical invisibility cloaks that have been studied in physics labs in recent years, the new cloak is “broadband”, meaning that it can divert waves across a range of frequencies.

This is made possible by tuning different rings of the cloak to incoming waves of different frequencies. Waves pass largely unaffected through rings not tuned to their frequency.

“The outer rings remain nearly still, but the pair of rings tuned to the frequency of the wave move like crazy, bending up and down and twisting,” says Guenneau. “For each small frequency range, there’s one pair of rings that does most of the work.” The team has simulated cloaks containing as many as 100 rings, says Guenneau, although fewer would be needed to protect against the most common kinds of earthquake surface waves.

via Invisibility cloak could hide buildings from quakes – tech – 26 June 2009 – New Scientist.

New fossil tells how piranhas got their teeth

How did piranhas — the legendary freshwater fish with the razor bite — get their telltale teeth? Researchers from Argentina, the United States and Venezuela have uncovered the jawbone of a striking transitional fossil that sheds light on this question. Named Megapiranha paranensis, this previously unknown fossil fish bridges the evolutionary gap between flesh-eating piranhas and their plant-eating cousins.

Present-day piranhas have a single row of triangular teeth, like the blade on a saw, explained the researchers. But their closest relatives — a group of fishes commonly known as pacus — have two rows of square teeth, presumably for crushing fruits and seeds. “In modern piranhas the teeth are arranged in a single file,” said Wasila Dahdul, a visiting scientist at the National Evolutionary Synthesis Center in North Carolina. “But in the relatives of piranhas — which tend to be herbivorous fishes —the teeth are in two rows,” said Dahdul.

Megapiranha shows an intermediate pattern: it’s teeth are arranged in a zig-zag row. This suggests that the two rows in pacus were compressed to form a single row in piranhas. “It almost looks like the teeth are migrating from the second row into the first row,” said John Lundberg, curator at the Academy of Natural Sciences in Philadelphia and a co-author of the study.

via New fossil tells how piranhas got their teeth.

Reverse-Engineering the Quantum Compass of Birds

Scientists are coming ever closer to understanding the cellular navigation tools that guide birds in their unerring, globe-spanning migrations.

The latest piece of the puzzle is superoxide, an oxygen molecule that may combine with light-sensitive proteins to form an in-eye compass, allowing birds to see Earth’s magnetic field.

“It connects from the subatomic world to a whole bird flying,” said Michael Edidin, an editor of Biphysical Journal, which published the study last week. “That’s exciting!”

The superoxide theory is proposed by Biophysicist Klaus Schulten of the University of Illinois at Urbana-Champaign, lead author of the study and a pioneer in avian magnetoreception. Schulten first hypothesized in 1978 that some sort of biochemical reaction took place in birds’ eyes, most likely producing electrons whose spin was affected by subtle magnetic gradients.

In 2000, Schulten refined this model, suggesting that the compass contained a photoreceptor protein called cryptochrome, which reacted with an as-yet-unidentified molecule to produce pairs of electrons that existed in a state of quantum entanglement — spatially separated, but each still able to affect the other.

According to this model, when a photon hits the compass, entangled electrons are scattered to different parts of the molecule. Variations in Earth’s magnetic field cause them to spin in different ways, each of which leaves the compass in a slightly different chemical state. The state alters the flow of cellular signals through a bird’s visual pathways, ultimately resulting in a perception of magnetism.

Far-fetched as it sounds, subsequent research from multiple groups has found cellular evidence of such a system. Molecular experiments suggest that it’s indeed sensitive to Earth’s geomagnetics, and computational models suggest a level of quantum entanglement only dreamed of by physicists, who hope to use entangled electrons to store information in quantum computers.

But though cryptochrome is likely part of the compass, the other part is still unknown. In April, another group of magnetoreception researchers showed that oxygen could interact with cryptochrome to produce the necessary electron entanglements. Schulten’s latest proposed role for superoxide, an oxygen anion found in bird eyes, fits with their findings.

Edidin cautioned that “this is still not an experimental demonstration. It’s a possibility.”

As for the perceptual result of the compass, it remains a mystery. Some researchers think birds might see a dot at the edge of their vision, swiveling according to the direction they’re facing. Others think it might produce effects of color or hue. Perhaps migrating birds fly towards the light.

via Reverse-Engineering the Quantum Compass of Birds | Wired Science | Wired.com.

Round-the-world solar plane debut

Swiss adventurer Bertrand Piccard has unveiled a prototype of the solar-powered plane he hopes eventually to fly around the world.

The vehicle, spanning 61m but weighing just 1,500kg, will undergo trials to prove it can fly through the night.

Dr Piccard, who made history in 1999 by circling the globe non-stop in a balloon, says he wants to demonstrate the potential of renewable energies.

The final version of the plane will try first to cross the Atlantic in 2012.

It will be a risky endeavour. Only now is solar and battery technology becoming mature enough to sustain flight through the night – and then only in unmanned planes.

But Dr Piccard’s Solar Impulse team has invested tremendous energy – and no little money – in trying to find what they believe is a breakthrough design.

“I love this type of vision where you set the goal and then you try to find a way to reach it, because this is challenging,” he told BBC News.

The HB-SIA has the look of a glider but is on the scale – in terms of its width – of a modern airliner.

The aeroplane incorporates composite materials to keep it extremely light and uses super-efficient solar cells, batteries, motors and propellers to get it through the dark hours.

It is probable that Dr Piccard will follow a route similar to the one he took in the record-breaking Breitling Orbiter 3 balloon – travelling at a low latitude in the Northern Hemisphere. The flight could go from the United Arab Emirates, to China, to Hawaii, across the southern US, southern Europe, and back to the UAE.

Measuring success

Although the vehicle is expected to be capable of flying non-stop around the globe, Dr Piccard will in fact make five long hops, sharing flying duties with project partner Andre Borschberg.

“The aeroplane could do it theoretically non-stop – but not the pilot,” said Dr Piccard.

“We should fly at roughly 25 knots and that would make it between 20 and 25 days to go around the world, which is too much for a pilot who has to steer the plane.

“In a balloon you can sleep, because it stays in the air even if you sleep. We believe the maximum for one pilot is five days.”

The public unveiling on Friday of the HB-SIA took place at Dubendorf airfield near Zürich.

“The real success for Solar Impulse would be to have enough millions of people following the project, being enthusiastic about it, and saying ‘if they managed to do it around the world with renewable energies and energy savings, then we should be able to do it in our daily life’.”

via BBC NEWS | Science & Environment | Round-the-world solar plane debut.

Rising CO2 Levels Lead To Bigger Fish Ears

For years scientists have observed the deleterious effects of rising levels of carbon dioxide in the oceans on shellfish and corals. Now, a new study by the Scripps Institution of Oceanography has provided evidence that the physiological development of fish ears is also impacted by the gas.

In the June 26 edition of the journal Science, researchers from the San Diego-based institute published a short paper outlining the results of experiments in which young white seabass were continuously exposed to high levels of CO2. The most dramatic change observed was the aberrant enlargement of the fish’s ear bone, or otolith, which plays a critical role in helping the animals to sense their surroundings and swim upright.

The results were particularly surprising to the researchers, whose initial hypothesis had predicted the shrinking of the otolith in response to elevated carbon dioxide levels. In general, there was no increase in the overall size of the fish, only in the relative size of their otolith.

“At this point one doesn’t know what the effects are in terms of anything damaging to the behavior or the survival of the fish with larger otoliths,” explained lead author of the study, David Checkley.

“The assumption is that anything that departs significantly from normality is an abnormality and abnormalities at least have the potential for having deleterious effects.”

As carbon dioxide levels around the planet are on the rise, ostensibly due to human activities, one of the many effects has been an increased acidification of the world’s oceans.

Environmentalists and oceanographers alike have watched with horror as falling pH levels in the oceans have brought on the massive erosion of coral reefs and a dramatic shrinking of plankton populations.

via Rising CO2 Levels Lead To Bigger Fish Ears – Science News – redOrbit.