Uncovering how crystals dissolve
Scientists from Lawrence Livermore, Virginia Polytechnic Institute, and State University of New York at Buffalo are discovering how quartz and other silicates erode during geochemical weathering. The team applied methods used in its studies on crystal growth (see Mimicking Nature’s Crystalline Structures) and concluded that mineral dissolution could be understood through the same mechanisms as those in the growth processes.
The team expanded its equations on crystal growth rates to include dissolution rates and created a model that predicts how quartz dissolves as the surrounding fluid becomes less concentrated in silicon dioxide. “The rate at which a crystal dissolves is controlled by the density of layers, or steps, on the surface of the crystal,” says Jim De Yoreo, who leads the Livermore team.
The team used atomic force microscopy to characterize surface changes and document dissolution of the quartz surfaces exposed to four chemical solutions. It then compared the results to those measured for other silicates. In each case, the dissolution processes differed depending on the temperature and solution composition. The findings, which appeared in the October 25, 2005, edition of the Proceedings of the National Academy of Sciences, have broad implications for other families of crystalline materials.
Contact: Jim De Yoreo (925) 423-4240 (email@example.com).
BlueGene/L breaks another record
National Nuclear Security Administration (NNSA) Administrator Linton F. Brooks, Department of Energy Office of Science Director Raymond L. Orbach, and IBM Executive Vice President for Technology and Innovation Nicholas Donofrio were at Livermore on October 27, 2005, to join Laboratory leaders in dedicating IBM BlueGene/L and IBM Purple, which are both part of the Advanced Simulation and Computing (ASC) Program and serve NNSA’s Stockpile Stewardship Program.
Administrator Brooks announced that the BlueGene/L supercomputer at Livermore’s Terascale Simulation Facility reached 280.6 trillion operations per second (teraops) on the LINPACK benchmark, the industry standard to measure computing speed. In a demonstration of its capability, BlueGene/L ran a record-setting materials science application at 101.5 teraops sustained over 7 hours on the machine’s 131,072 processors. It was the largest simulation of its kind ever attempted. The application used in the demonstration is important to NNSA’s effort to ensure the safety, security, and reliability of the nation’s nuclear deterrent.
The Purple and BlueGene/L systems will provide scientists and engineers working at Sandia, Los Alamos, and Lawrence Livermore national laboratories with just under half a petaop (1,000 teraops) of computing power—more than any other scientific computing facility in the world.
Contact: Dona Crawford (925) 422-1985 (firstname.lastname@example.org).
Simulations show global warming dramatically increasing
Laboratory scientists used a coupled climate and carbon-cycle model to look at global climate and carbon-cycle changes that would occur if humans use the entire planet’s available conventional fossil-fuel resources by the year 2300. The simulations showed that the global mean temperature would soar 8°C by 2300. In the polar regions alone, the temperature would spike more than 20°C, forcing the land in this region to change from ice and tundra to boreal forests. The implication is that polar ice caps would be depleted and ocean sea levels would rise by 7 meters over the next three centuries. In addition, the model predicts that the amount of atmospheric carbon dioxide would nearly quadruple to 1,423 parts per million (ppm) from today’s level of 380 ppm.
The simulations showed that about 38 and 17 percent of the carbon dioxide released from the burning of all fossil fuels are taken up by the land and ocean, respectively. The remaining 45 percent remains in the atmosphere. According to lead author Govindasamy Bala of the Energy and Environment Directorate, the models predict large-scale migration of plants and severe disturbances to terrestrial ecosystems. This study revealed a dramatic change not only in the temperature of the oceans but also in their acidity content, which would be especially harmful for marine organisms with shells and skeletal material made of calcium carbonate. The team’s research appeared in the November 1, 2005, issue of the American Meteorological Society’s Journal of Climate.
Contact: Govindasamy Bala (925) 423-0771 (email@example.com).