Science Briefs

July 7, 2013 

Researchers plan for thinnest solar cell

Massachusetts Institute of Technology researchers are working to produce the thinnest and most lightweight solar panels possible.

Such panels, which have the potential to surpass any substance other than reactor-grade uranium in terms of energy produced per pound of material, could be made from stacked sheets of one-molecule-thick materials such as graphene or molybdenum disulfide.

Jeffrey Grossman, an associate professor of power engineering at MIT, is senior author of a new paper describing this approach, published in the journal Nano Letters.

Using two layers of such atom-thick materials, Grossman’s team has predicted solar cells with 1 to 2 percent efficiency in converting sunlight to electricity.

That’s low compared to the 15 to 20 percent efficiency of standard silicon solar cells, he said, but it’s achieved using material that is thousands of times thinner and lighter than tissue paper.

The two-layer solar cell is only 1 nanometer thick, while typical silicon solar cells can be hundreds of thousands of times that. The stacking of several of these two-dimensional layers could boost the efficiency significantly.

For applications where weight is a crucial factor — such as in spacecraft, aviation or for use in remote areas of the developing world where transportation costs are significant — such lightweight cells could have great potential. http://web.mit.edu

Portable X-ray system weighs just 5 pounds

Los Alamos National Laboratory and Tribogenics, a developer of X-ray machines, have created a lightweight, compact, low-cost X-ray system that uses the MiniMAX (Miniature, Mobile, Agile, X-ray) camera to provide real-time inspection of sealed containers and facilities.

Scott Watson of Los Alamos said the new system could be used with security inspection, field medicine, specimen radiography and industrial inspection.

The complete MiniMAX portable radiography system, developed by Los Alamos, weighs less than 5 pounds. www.lanl.gov

Ice-age horse’s genome assembled

When University of Alberta researcher Duane Froese found an unusually large horse fossil in the Yukon permafrost, he knew it was important. Now, in a new study published online in Nature, this fossil is rewriting the story of equine evolution as the ancient horse has its genome sequenced.

Unlike the small ice-age horse fossils that are common across unglaciated areas of the Yukon, Alaska and Siberia, this fossil was at least the size of a modern domestic horse. Froese and his colleagues from the University of Copenhagen, who led the study, dated the permafrost at the site to 700,000 years ago. The team extracted collagen from the fossil and found it had preserved blood proteins, and that short fragments of ancient DNA were present within the bone. After several years, a draft genome of the horse was assembled and is providing new insight into the evolution of horses.

The study showed the horse fell within a line that includes all modern horses and the last remaining truly wild horses, the Przewalski’s horse from the Mongolian steppes. The 700,000-year-old horse genome has allowed the research team to estimate how fast mutations accumulate through time. University of Alberta

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