Evidence of supersolids advances

Imagine placing a coin at the center of a turntable and then setting the turntable in motion. The coin rotates with the turntable, right?

Wrong, presuming the coin is made of solid helium-4. That's the implication of a new experiment reported last week in the online journal Science Express by Penn State physicist Moses H.W. Chan and his postdoctoral associate, Eun-Seong Kim.

Chan and Kim have demonstrated additional evidence of a seemingly bizarre new state of matter called a supersolid; that is, a solid that flows without friction, a property that in fluids is known as superfluidity.

It's not something that lends itself to a foreseeable application ---- the helium isotope had to be compressed and cooled to near absolute zero to achieve this new state ---- but the experiment will force theorists to dramatically revise their thinking about the properties of solid helium, said Anthony Leggett, a Nobel laureate physicist at the University of Illinois who wrote an accompanying commentary.

In January, Chan and Kim reported in the journal Nature on an earlier experiment that suggested supersolids were possible. The latest experiment makes an even stronger case, Chan said, though confirmation will have to wait until other groups can replicate the Penn State results.

Let's chat, shall we?

Mix scientific issues with a mug of beer -- or even a cup of joe -- and you've got something called Cafe Scientifique, a form of informal science discussion that's become popular in Europe.

Now the concept is spreading to the States and organizers next week will launch a local version sponsored by the Pittsburgh Technology Council. Cafe Scientifique Pittsburgh will meet at the Penn Brewery, Troy Hill, at 7 p.m. next Monday.

Phil Campbell, a senior research scientist at Carnegie Mellon University's Institute for Complex Engineered Systems, will give a short talk on medical robotics and tissue engineering, which will be followed by an hour of discussion with the audience.

It is free and open to the public. For more information, visit the Web site at www.cafescipgh.org.

Getting rid of CO₂

Serpentine, a common mineral, has the potential for removing carbon dioxide, a greenhouse gas, from all fossil fuel emissions, Penn State researchers say.

The mineral, composed of magnesium, silicon and oxygen, naturally reacts with carbon dioxide, but too slowly for use in treating flue gas. Some researchers have tried to speed it up by grinding it up, but the reaction still requires high temperatures.

A team led by M. Mercedes Maroto-Valer of Penn State's Energy Institute, working with Dan Fauth of the National Energy Technology Laboratory in South Park, found that serpentine could be processed to produce magnesium sulfate and magnesium hydroxide.

When carbon dioxide is passed through a solution of those chemicals, it converts both into magnesium carbonate, a solid that can be used to manufacture construction blocks, or, in hydrated form, to make cosmetics.

The researchers now are developing a reactor to perform laboratory tests of the process.