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News from the Physical Sciences

Sulfur signals in Antarctic snow reveal clues to climate, past and future

Robina Shaheen
Robina Shaheen measured sulfur isotopes from snow.

Sulfur signals in the Antarctic snow have revealed the importance of overlooked atmospheric chemistry for understanding climate, past and future.

Eruptions of huge volcanoes, the disruptive weather pattern known as El Niño, and a fire season from hell each left distinctive chemical marks in layers of snow excavated near the South Pole, researchers from the University of California, San Diego and France report in the Proceedings of the National Academy of Sciences the week of August 4.

Sorting out the chemical reactions that must have led to those traces revealed a process, known but overlooked, that should be included in models of climate, both forecasts of climate to come and those built to understand Earth’s early history.

“We observed huge signals from ENSO driven changes like extreme dry weather and ensuing biomass burning, which surprised me,” said Robina Shaheen, a project scientist in chemistry at UC San Diego and lead author of the report. “The pattern we saw fits signals that have been observed in pre-Cambrian rocks, which prompted us to take another look at which molecules play a role in this chemistry.” Read more.

A superfluid gas formed in layers of 2D crystals could induce superconductivity at high temperatures

stack of 2D crystalsAn elusive state of matter called superconductivity could be realized in stacks of sheetlike crystals just a few atoms thick, a trio of physicists has determined.

Superconductivity, the flow of electrical current without resistance, is usually found in materials chilled to the most frigid temperatures, which is impractical for most applications. It's been observed at higher temperatures–higher being about 100 kelvin or minus 280 degrees below zero Fahrenheit–in copper oxide materials called cuprate superconductors. But those materials are brittle and unsuitable for fabricating devices like circuits.

In a paper published in Nature Communications, Michael Fogler and Leonid Butov, professors of physics at the University of California, San Diego, and Konstantin Novoselov, Nobel laureate in physics and professor at the University of Manchester, propose a design for an artificially structured material that should support superconductivity at temperatures rivaling those seen for cuprates. Read more.

embryonic stem cells become neural
Image: JACS

Sugar mimic guides stem cells toward neural fate

Long chains of sugars dangle from proteins on the surface of embryonic stem cells and play an important role in how the cells develop into specific cell types. Kamil Godula, an assistant professor of chemistry and biochemistry, and his research group have now synthesized a molecular mimic of these sugar-decorated proteins that helps direct mouse embryonic stem cells down the path toward nerve cells they report in the Journal of the American Chemical Society. The researchers hope others can easily adopt their method to explore how these cell surface sugars influence stem cell differentiation. Read more about these molecular mimics in Chemical and Engineering News.

Silicon sponge improves lithium-ion battery performance

nanoscale silicon spongesThe lithium-ion batteries that power our laptops and electric vehicles could store more energy and run longer on a single charge with the help of a sponge-like silicon material.

The chemistry of lithium-ion batteries limits how much energy they can store. To increase the battery's energy capacity, researchers are looking at new materials such as silicon. Unfortunately, silicon expands as much as three times in size when it charges, creating pressure within the material that causes it to break. 

Jason Zhang and colleagues at the Pacific Northwest National Laboratory wondered if a sponge-like silicon electrode would do the trick. So they approached Michael Sailor, a UC San Diego chemist whose research includes using porous silicon to detect pollutants and deliver drugs, for help. PNNL used Sailor's method to create porous silicon, which they then used to fabricate electrodes. 

These porous silicon electrodes expanded into the empty spaces created by the material's porous structure, they report in Nature Communications. Read more.

Kamen Prize awarded for exceptional work in biochemistry

Miao-ping ChienMiao-Ping Chien and Joseph Lucas have won the 2013-2014 Kamen Prize, given for the outstanding dissertation in biochemistry defended each year at UC San Diego. Chien, who worked with chemistry and biochemistry professor Nathan Gianneschi, was recognized for her work on programming nanoparticles with DNA, peptides and enzymes. Lucas, who worked with molecular biology professor Cornelis Murre, was recognized for his work on the motion of the immunoglobulin heavy chain locus as it relates to recombination.

The prize was established in 1978 by friends and family of Martin D. Kamen, emeritus professor of chemistry, who co-discovered of carbon 14 while at UC Berkeley in the early 1940s. Kamen came to UC San Diego in 1960, where he continued important work on photosynthetic transport proteins until his retirement. He passed away in 2002.

Young professors win support for work toward tenure

Eva-Maria CollinsJelena Bradiing.jpgJelena Bradic, assistant professor of mathematics, and Eva-Maria Schoetz Collins, assistant professor of physics, have been named Hellman Fellows for 2014-2015. The fellowship program provides financial support and encouragement to young faculty in the core disciplines who show capacity for great distinction in their research and creative activities. Funds awarded support activities that will enhance the individual's progress towards tenure.

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