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The Laboratory
in the News

Lab’s aerogel sets world record
An aerogel developed by researchers in Livermore’s Chemistry and Materials Science (CMS) Directorate has taken the record for the world’s least dense solid. The Laboratory’s aerogel, which is listed in Guinness World Records 2004, has a density of only 1.9 milligrams per cubic centimeter. It replaces the 2003 record holder—an aerogel developed by Jet Propulsion Laboratory having a density of 3 milligrams per cubic centimeter.
Discovered in 1931, aerogel is a translucent solid that looks much heavier than it is. Early scientific application of aerogels was limited by the high densities of the samples and the small amount of materials available for production. Today, less dense samples are used in electronics, acoustics, thermal insulation, and optical devices as well as for physics experiments.
Livermore scientists have been working with aerogels for more than two decades. Not only have they reduced the density of aerogel, but they also have improved material composition and clarity.
According to chemist John Poco, the Laboratory is a leader in aerogel technology. “We use more materials to create it and more innovative procedures than most anyone else.” But he adds, “Setting a world record was never on our radar screen.” When CMS researchers determined that others had claimed the lowest density, they wanted to set the record straight. They contacted Guinness World Records, sent documentation and samples, and received confirmation that they now hold the world record.
Contact: John Poco (925) 423-9976 (poco1@llnl.gov).

Cargo industry briefed on threats
At this summer’s International Cargo Security Summit in Chicago, Livermore’s Executive Officer Ron Cochran described some of the technology solutions being developed at the Laboratory to address the threats that confront the freight transportation industry. He noted that, in addition to the Laboratory’s unique capabilities in assessing nuclear threats, it also has developed breakthrough technologies in radiation and biological detection, information analysis, and infrastructure protection systems.
Topics at the summit included regulatory requirements, how the transportation industry can prepare for and respond to terrorist attacks, and some of the technologies now available to improve security. Participants also discussed the practicality of managing security risks throughout the supply chain and how counterterrorism measures can be implemented by all cargo transporters and related third parties.
“Cargo container security is one of the nation’s most difficult technical and practical challenges in preparing for and countering terrorist threats,” says Cochran. “This [summit] was an opportunity for the top experts in this area to get together to discuss the issues and priorities as well as identify better ways to keep their industry safe.”
Contact: Ron Cochran (925) 422-5153 (cochran5@llnl.gov).

Study confirms human effects on tropopause
A collaborative study including Livermore scientists has shown that human-induced changes in ozone and well-mixed greenhouse gases are the primary drivers of recent changes in the height of the tropopause. The team—which included scientists from Lawrence Livermore and Lawrence Berkeley national laboratories, the National Center for Atmospheric Research, the Institut für Physik der Atmosphäre in Germany, and the University of Birmingham in the United Kingdom—focused its research on understanding how different mechanisms affect atmospheric temperatures and, hence, tropopause height.
The tropopause is the boundary between the lowest layer of the atmosphere—the turbulently mixed troposphere—and the more stable stratosphere. It lies about 16 kilometers above the Earth’s surface at the equator and 8 kilometers above it at the poles. Its altitude is sensitive to changes in vertical profiles of atmospheric temperature.
This collaborative study is the first to show that a model-predicted “fingerprint” of tropopause height changes can be identified in observations. Earlier research showed that increases in the height of the tropopause over the past two decades are directly linked to stratospheric ozone depletion and increased greenhouse gases.
The research team used climate models to provide quantitative estimates of the relative contributions of natural and human influences to overall tropopause height changes. From 1979 to 1999, tropopause height increased about 200 meters, and according to the model calculations,
80 percent of that increase is directly linked to human activities. In the first half of the 20th century, tropopause height increases were smaller and were caused primarily by natural variations in volcanic aerosols and solar irradiance.
A paper describing this work appeared in the July 25, 2003, issue of Science. Output from the climate models is available on the National Energy Research Scientific Computing Center Web site.
Contact: Benjamin Santer (925) 422-7638 (santer1@llnl.gov).

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UCRL-52000-03-10 | October 8, 2003