Two planets found in nearby solar system
A team of international scientists, including three Livermore researchers, discovered a solar system nearly 5,000 light years away that contains two scaled-down gas giant planets. The two planets are the same distance apart as Jupiter and Saturn are from each other, but they are only half the distance from their parent star as Jupiter and Saturn are from our Sun. “It looks more like our solar system than any other system we’ve seen so far,” says Livermore scientist Bruce Macintosh, “and it has room for a planet like Earth.”
The Optical Gravitational Lensing Experiment detected the first evidence of these planets in 2006 when the star orbited by the planets crossed in front of a star farther from Earth, producing an effect called gravitational microlensing. In a microlensing event, the nearer star’s gravity magnifies the light shining from the farther star. The planets’ orbits of their parent star altered this magnification in a distinctive pattern. After the initial microlensing discovery, astronomers working at ground-based telescopes around the world observed the event and helped analyze the data. Results from the team’s research appeared in the February 15, 2008, issue of Science.
The two new planets have mass and separation ratios and equilibrium temperatures similar to those of Jupiter and Saturn. Their masses are about 71 percent of Jupiter’s mass and 90 percent of Saturn’s. Their parent star is about 50 percent the mass of our Sun. This exoplanetary system, the fifth to be detected via microlensing, indicates that the Milky Way Galaxy is home to many solar systems like ours.
Contact: Kem Cook (925) 423-4634 (email@example.com) or Bruce Macintosh (925) 423-8129 (firstname.lastname@example.org).
Study reveals seismic structure of deep Earth
Livermore scientists and collaborators from the University of Washington, the Carnegie Institution of Washington, and Northwestern University are working to better understand the seismic structure of deep Earth by examining the elastic behavior of iron-containing minerals under extremely high pressures. The researchers have determined for the first time the complete elasticity of ferropericlase, an iron magnesium oxide found in Earth’s lower mantle, through the high-spin to low-spin electronic transition induced by high pressures.
The lower mantle composes more than half of Earth’s volume and is subject to extremely high pressures and temperatures. Pressure directly affects the electronic configuration of iron in mantle minerals, such as ferropericlase. Iron exists in the high-spin state at low pressure but changes dramatically to the low-spin state under extreme pressure. The team found that this transition causes ferropericlase to soften when pressures range from 40 to 60 gigapascals. Research results were published in the January 25, 2008, edition of Science.
According to team lead Jonathan Crowhurst of the Laboratory’s Chemistry, Materials, Earth, and Life Sciences Directorate, the lower mantle profoundly influences many terrestrial phenomena, including some that are directly relevant to Earth’s inhabitants. Characterizing the physical properties of the lower mantle will allow researchers to test and refine geophysical models. “Knowledge of this deep, inaccessible region is derived largely from seismic data,” says Crowhurst. “It is particularly desirable to measure under relevant conditions the acoustic characteristics of candidate materials or mixtures.”
Contact: Jonathan Crowhurst (925) 422-1945 (email@example.com).
Rapid diagnosis of foot-and-mouth disease
In collaboration with the University of California at Davis, Livermore researchers have developed a rapid test to diagnose foot-and-mouth disease and other look-alike animal diseases. The prototype tool combines assays for seven disease-causing viruses into one test that simultaneously analyzes genetic material from RNA and DNA viruses. The team’s results were published in the March 2008 issue of the Journal of Clinical Microbiology.
Researchers at the Institute for Animal Health’s Pirbright Laboratory in the United Kingdom tested the prototype using 287 samples collected from cattle suspected of having foot-and-mouth disease. Assays used in the diagnostic included several previously defined viral signatures as well as new signatures identified by KPATH, Livermore’s bioinformatics software system. In initial tests, the multiplex assay had a diagnostic sensitivity to foot-and-mouth disease of 93.9 percent, which is close to the 98.1 percent achieved when just two single assays are combined. Work is under way to optimize the tool’s performance. Because it tests for multiple viruses in one reaction, the diagnostic will not only reduce the use of reagents and other resources but also increase confidence in test results.
According to Livermore chemist Ben Hindson, who leads the research team, assay development is in the early stages. Extensive validation tests will be required before the technology can be used routinely. The researchers are also developing assays to detect species-specific swine or cattle diseases.
Contact: Ben Hindson (925) 423-8667 (firstname.lastname@example.org).
Nanotweezers save time and energy
A collaboration involving scientists from Lawrence Livermore and Lawrence Berkeley national laboratories and the University of California campuses at Berkeley and Los Angeles used nanometer-scale optoelectronic tweezers to manipulate individual semiconducting and metallic nanowires with diameters less than 20 nanometers. The research showed that in addition to trapping a single wire in a potential well, optoelectronic tweezers can trap arbitrarily large numbers of wires in a given area. The tweezers can also preserve the wires’ position and orientation, which is critical for depositing metallic contacts on a nanoscale material.
Optoelectronic tweezers are already used to move micrometer-size polymer beads and living cells in fluid chambers. When low-intensity light is projected onto a photoconductive layer between two electrodes, it creates a nonuniform electric field, allowing particles to be manipulated by light-actuated virtual electrodes. When used in the nanowire tests, the optical power density of the optoelectronic tweezers was 100,000 times less than that of optical tweezers, and the nanoscale device moved individual wires four times faster.
The tweezers can be used to create vertically aligned nanowire arrays for solar energy conversion, thermoelectric cooling, and transistor applications. The team’s research was featured on the cover of the February 2008 issue of Nature Photonics.
Contact: Peter Pauzauskie (925) 422-7319 (email@example.com).
Simulations predict ground motion of earthquakes
Livermore scientists are working to better understand how the ground will respond to the strong forces of an earthquake. In collaboration with the U.S. Geological Survey (USGS), the University of California at Berkeley, and URS Corporation, the researchers developed high-performance computing models that animate ground motion as waves moving outward, color-coded by intensity. The research appears in three papers published in the April 2008 edition of the Bulletin of the Seismological Society of America on the 102nd anniversary of the 1906 San Francisco earthquake, which ruptured along the San Andreas Fault.
Shawn Larsen, a Livermore geophysicist and computer scientist, worked on two of the papers. In the first study, Larsen’s team used the wave-propagation code E3D to estimate the ground motion that occurred in central and northern California during the 1906 earthquake and that might occur in hypothetical earthquakes along the San Andreas Fault. Team members ran simulations on three Livermore computing systems and the Earth Simulator supercomputer in Japan. The second study used observations of the 1989 Loma Prieta earthquake, which also ruptured along the San Andreas Fault, to validate models of the 1906 quake.
For the third study, a research team led by Livermore seismologist Arthur Rodgers used data from San Francisco Bay Area earthquakes to evaluate a three-dimensional geologic and seismic model created by USGS. Using observations from a network of seismic stations that record broadband data in this region, the team compared computed seismograms with observed recordings for 12 moderate quakes.
The three studies are part of Livermore’s Computing Grand Challenge Program, which allocates computational resources to unclassified science projects that support the Laboratory’s missions. A better understanding of ground motion during earthquakes will help policy makers develop regulations to enhance public safety and emergency response and will lead to improved engineering designs. These studies also support nonproliferation efforts to distinguish the seismic signals from earthquakes and explosions.
Contact: Shawn Larsen (925) 423-9617 (firstname.lastname@example.org) or Arthur Rodgers (925) 423-5018 (email@example.com).