Posts Tagged ‘interesting’

Levitation

September 10th, 2009

There has been news of scientists levitating mice to study the effects of bone loss…never mind why they were doing it; how cool is that? A levitating mice!

The news article only says that magnetic fields were used to levitate the mice, but it doesn’t go into any details. Last time I studied biology and physics, living things aren’t very magnetic, so I had to find out if this is a hoax. Turns out it is possible, but it requires a very powerful magnet.

From wikipedia

A substance that is diamagnetic repels a magnetic field. All materials have diamagnetic properties, but the effect is very weak, and is usually overcome by the object’s paramagnetic or ferromagnetic properties, which act in the opposite manner. Any material in which the diamagnetic component is strongest will be repelled by a magnet, though this force is not usually very large.
Diamagnetic levitation can be used to levitate very light pieces of pyrolytic graphite or bismuth above a moderately strong permanent magnet. As water is predominantly diamagnetic, this technique has been used to levitate water droplets and even live animals, such as a grasshopper and a frog. However, the magnetic fields required for this are very high, typically in the range of 16 teslas, and therefore create significant problems if ferromagnetic materials are nearby.

The alleged first living animal to be levitated by this technique was a frog Here’s a short video of one:

I wonder we’ll see this done to humans. The frog is levitated using 10 Tesla magnetic fields, so it would take a much stronger magnet to lift a human being–much stronger than the current strongest man made magnet which is only 45 Tesla.

Aside: Yogis in India claims have been able to levitate as a result of spiritual powers, but they weren’t being completely honest.

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Ambitious Fusion Technology Startup

August 9th, 2009

A new startup called General Fusion is attempting an ambitious project to build a fusion power plant.

It may seem implausible, but some top U.S. fusion experts say General Fusion’s approach, which is a variation on what the industry calls magnetized target fusion, is scientifically sound and could actually work. It’s a long shot, they say, but well worth a try.

[...]

The prototype reactor will be composed of a metal sphere about three meters in diameter containing a liquid mixture of lithium and lead. The liquid is spun to create a vortex inside the sphere that forms a vertical cavity in the middle. At this point, two donut-shaped plasma rings held together by self-generated magnetic fields, called spheromaks, are injected into the cavity from the top and bottom of the sphere and come together to create a target in the center. “Think about it as blowing smoke rings at each other,” says Doug Richardson, chief executive of General Fusion.

original source

Maybe nuclear fusion will be the next big thing that solves our energy problems. Energy from fusion has been the pipe dreams of nuclear physicists for decades, but no one have been able to develop a technique to control the voilent reaction. Looks like technology is catching up.

“I’m rooting for them,” says Ken Fowler, professor emeritus of nuclear engineering and plasma physics at the University of California, Berkeley, and a leading authority on fusion-reactor designs. He’s analyzed the approach and found no technical showstoppers. “Maybe these guys can do it. It’s really luck of the draw.”

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Braess’s Paradox On The Road

August 8th, 2009

Interesting research that finds evidence of Braess’s paradox in greedy traffic route optimization:

Imagine two routes to a destination, a short but narrow bridge and a longer but wider highway. Let’s also imagine that the combined travel times of all the drivers is shortest if half take the bridge and half take the highway. But because each driver is selfishly trying to seek the shortest route for himself, this doesn’t happen. At first, everyone will go for the bridge because it’s shorter. But then, as the bridge becomes backed up, more drivers start taking the highway, until the congestion on the bridge starts to clear up. At that point more drivers go back to the bridge, which then becomes backed up again. Eventually, the traffic flow settles into what’s called the Nash equilibrium (named for the beautifully minded mathematician), in which each route takes the same amount of time. But in this equilibrium the travel time is actually longer than the average time it would take if half of the drivers took each route.

Very counterintuitive!

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