Apr 26, 2011

Discovery Files: Cleaner water through biodiversity

Diverse Osmosis

New evidence from the University of Michigan that biodiversity promotes water quality suggests that accelerating species losses may compromise future water quality.

Credit: NSF/Karson Productions

Audio Transcript:

It Takes a Village.[1]

I'm Bob Karson with the discovery files -- new advances in science and engineering from the National Science Foundation.

We hear a lot of reports about accelerating losses of species. Does it really matter? Scientists say biodiversity is important in keeping the earth's ecosystem in balance -- from freshening the air to purifying the water. But, some of these benefits have been lacking supporting data.

Now, a groundbreaking or should I say "watershed" study out of the University of Michigan verifies for the first time that biodiversity promotes better water quality.

Streaming: For the study, researchers built 150 miniature model streams with all the riffles, runs and pools you'd find in real streams. They added nitrates, the most common water pollutant and from one to eight species of pollution consuming algae. Each species of algae has evolved to occupy a particular mini-habitat or niche in streams. The more species, the more unique niches are filtered and cleansed.

In the experimental streams with all eight varieties of algae, the water was cleansed about four and a half times faster than streams with just one kind. The scientists say the study adds to the growing evidence that modern mass extinction of species is going to affect humanity in some big, important ways.
We may not need to save the planet as much if we just allow the planet to save itself.

"The Discovery Files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at nsf.gov or on our podcast.

[1] It takes a village.
--The phrase is attributed to the Nigerian Igbo culture and proverb "Ora na azu nwa" which means it takes the community/village to raise a child. For more detail, please visit

Apr 13, 2011

Discovery Files: Catching Rays

Using a common metal most famously found in self-cleaning ovens, Sossina Haile of CalTech University hopes to change our energy future. The metal is cerium[1] oxide -- or ceria -- and it is the centerpiece of a promising new technology developed by Haile and her colleagues that concentrates solar energy and uses it to efficiently convert carbon dioxide and water into fuels.

Credit: NSF/Karson Productions

Audio Transcript:

Capturing Sunbeams in a Jar?

I'm Bob Karson with the discovery files -- new advances in science and engineering from the National Science Foundation.

Solar energy, plentiful and free, but we need to find a practical way to bottle and store it. Scientists at Caltech have taken a unique approach to the challenge. A team has developed a solar reactor technology that uses the sun in a different way.

Their prototype reactor is two feet tall with a quartz window. The quartz acts as a magnifying glass to focus the sun's rays and a chamber that contains a material called ceria, a metal oxide. It has the ability to "inhale" oxygen into its crystalline structure.

When carbon dioxide or water is pumped into the reactor, the ceria strips the oxygen from it leaving behind carbon monoxide and/or hydrogen gas. The hydrogen gas could be used to fuel hydrogen fuel cells or, combined with the carbon monoxide and converted into liquid hydrocarbon fuels and once the ceria has inhaled all the oxygen it can, heating it up using sunlight makes it "exhale" the oxygen it took in starting the process anew.

We could someday have large-scale solar reactors that could actually take the CO2 emissions from coal-fired power plants and use sunlight to convert them to transportation fuels.

Nothing like, "catching some rays."

"The Discovery Files" covers projects funded by the government's National Science Foundation. Federally sponsored research -- brought to you, by you! Learn more at nsf.gov or on our podcast.

[1]cerium /'sɪrɪəm/
--The chemical element of atomic number 58, Ce (鈰). Cerium is a silver-white metal used in the production of glass and ceramics. (See it in Wikipedia.)

Apr 12, 2011

Silver Saver

Nanotechnology keeps the shine on silver

Anyone who's ever polished silver knows that keeping the tarnish at bay[1] is never ending work. But, you may not know that polishing also rubs away some of the precious metal, whether it's your grandmother's silver bowl or a 19th century museum treasure.

"We're always looking for some kind of barrier that will protect the surface so we don't have to keep polishing it," says Terry Drayman-Weisser, director of conservation and technical research at the Walters Art Museum in Baltimore.

Twenty miles from the museum, materials scientist Ray Phaneuf and his team at the University of Maryland are working on a small solution to this big problem. With support from the National Science Foundation (NSF), they're producing and testing a protective coating so thin, you can't see it with the naked eye.

"The method that we use to apply it is called atomic layer deposition. So, literally, we're able to control the thickness of the film at a sub-nanometer level," explains Phaneuf.

Using a special reactor inside a clean room, they apply nanometer thick films of aluminum oxide to a sample silver wafer about the size of a silver dollar. Phaneuf says the films conform to the recesses and protrusions of the silver, creating a protective barrier.

Art conservators say atomic layer deposition, or ALD, will have to pass rigorous testing before they use it to protect irreplaceable treasures.

At the lab, the coating is put through a series of tests. Using a spectrometer the research team measures how light reflects off the surface of a test wafer, and how the ALD coating affects the wafer's color.

Another test measures how quickly sulfur penetrates the coated wafer. Sulfur is what tarnishes silver. The test will help determine how many layers of coating will be needed to keep the silver shiny. In another controlled chamber, the team heats a coated wafer to speed up the tarnishing. Phaneuf says this helps scientists figure out how long a barrier will last.

"Part of the challenge is to determine what the optimal thickness is that keeps sulfur off the silver surface. Eventually, thermodynamics tells us that the sulfur will diffuse through any layer we put down. The denser the layer, the slower the diffusion," explains Phaneuf. "So we'll start with films that may be a few nanometers thick and investigate the efficacy of these films all the way out to maybe a few hundred nanometers. If we can increase the lifetime of these films to a century, you may not need to do this very often."

Art conservators won't give ALD a thumbs-up until they can show that it works better than the lacquers they are using now, which have to be reapplied every decade or two. The conservators also will have to be able to remove the coating without damaging the piece.

"When it comes to art objects, the less treatment the better," says Glenn Gates, a scientist at the Walters Art Museum. "The standard treatments that use lacquers or nitrous cellulose coatings can give off a plastic look. The ALD coating is very, very thin, and orders of magnitude thinner than the wavelength of light; the idea being that it's going to impact the aesthetic presentation of the object much less than a thick organic lacquer coating that we generally apply these days."

If ALD proves a shining success, silver works of art will remain at their best for future generations to enjoy. And for many of us, it may mean never polishing silver again.

From Science Nation


[1] hold/keep somebody/something at bay
--To prevent an enemy from coming close or a problem from having a bad effect