Lab Report

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The Lab Report is a weekly compendium of media reports on science and technology achievements at Lawrence Livermore National Laboratory. Though the Laboratory reviews items for overall accuracy, the reporting organizations are responsible for the content in the links below.

Apr. 03, 2015

A new study answers a long-standing mystery about why Mercury’s surface — shown here in an image from the MESSENGER mission – is darker than the moon’s surface. Photo courtesy of NASA

Paint it black

Mercury may have comet dust to thank for its dark appearance. It's darker than it should be, and scientists aren't sure why. But a new study published this week in Nature Geoscience suggests an answer.

Because Mercury has basically no atmosphere — and is the closest thing to the sun, where solar winds are violent and space debris impacts are most common — it's expected to acquire a lot of tiny iron particles, which are known to absorb light and make planets look darker.

n the new study, Lawrence Livermore researchers calculated how much material passing comets might shed on a defenseless planet close to the sun. It turns out that the answer is lots and lots -- enough to leave Mercury with a surface that's as much as 6 percent carbon after a few billion years of existence, which is about 50 times more than has been left on the moon. It turns out that could account for Mercury's unusual murkiness.

Lawrence Livermore researchers are working with collaborators on brain implants to monitor and control the emotions of mentally ill people.

The ultimate brain fix

The U.S. military continues to develop new technologies for gathering intelligence, attacking enemy positions and defending American lives and interests. Some of the most innovative work focuses on soldiers — amazing breakthroughs to help protect, strengthen and heal them during and after deployment.

One such research project, which involves Lawrence Livermore scientists, is the development of brain implants — not just electrodes, but actual implants — to monitor and control the emotions of mentally ill subjects, including veterans with post-traumatic stress issues and personality disorders such as depression and addiction.

The implants, assembled as an array of mini-electrodes on a tiny plastic host, will intricately monitor parts of the brain — sometimes down to the single neuron level — that are associated with emotion and provide targeted stimulation as the brain changes.

Lawrence Livermore researchers have developed a computer simulation of a beating heart.

Getting to the heart of the matter

At the High Performance Computing Innovation Center at Lawrence Livermore, a new type of simulation has been developed to realistically mimic a beating human heart and provide insight into potentially fatal heartbeats. The simulations were made possible by a highly scalable code called Cardioid that replicates the electrophysiology of the human heart. The code accurately simulates the activation of each heart muscle cell and the cell-to-cell electric coupling.

On every heartbeat, electric signals normally traverse the entire heart in an orderly manner, resulting in a coordinated contraction that efficiently pumps blood throughout the body. However, these signals can become disorganized and cause an arrhythmia, a dysfunctional mechanical response that disrupts the heart’s pumping process and can reduce blood flow throughout the body. Without medical intervention, a serious arrhythmia can lead to sudden death and accounts for about 325,000 deaths every year in the U.S.

The groundbreaking heart simulations were developed and performed on Lawrence Livermore’s Sequoia supercomputer.

This illustration shows a cutaway view of Jupiter, which is believed to contain warm dense matter at its core. Image courtesy of SLAC National Accelerator Laboratory.

Best look yet at warm dense matter

In a recent study, a group of researchers, including scientists from Lawrence Livermore, used the The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory to document the quick transformation of shock-compressed aluminum into warm dense matter. The study provides insight into the formation of planets.

Warm dense matter is a complex state found at pressures of a few million atmospheres and temperatures of tens of thousands of degrees. Materials exposed to these high pressures play important roles in the physics of planetary formation, material science and inertial confinement fusion research.

The new experiment used a tabletop nanosecond-pulsed laser to shock-compress a thin aluminum foil, forcing it to a pressure more than 4,500 times higher than the deepest ocean depths and superheating it to nearly four times hotter than the surface of the sun.

Researchers sample soil at the Pendleton Research Station in Oregon. Photo by Markus Kleber.

Vulnerability in the soil

Organic matter in soil, long thought to be a semi-permanent storehouse for ancient carbon, may be much more vulnerable to climate change than previously thought.

In new research, Lawrence Livermore scientists and collaborators found that the common root secretion, oxalic acid, can promote soil carbon loss by an unconventional mechanism — freeing organic compounds from protective associations with minerals.

Plants direct between 40 percent and 60 percent of photosynthetically fixed carbon to their roots, and much of this carbon is secreted and then taken up by root-associated soil microorganisms. Elevated carbon dioxide (CO2) concentrations in the atmosphere are projected to increase the quantity and alter the composition of root secretions released into the soil.