Bacteria Can 'Fertilize' Copper-Polluted Soil

Ramakrishna Wusirika in the greenhouse with PhD student Kefeng Li. Together, they demonstrated that a strain of bacteria can enhance plant growth on soil contaminated by copper.

When miners abandoned Michigan's Copper Country, they left a lot of the red metal behind, and not in a good way. Waste from the mining operations still contains a high fraction of copper, so high that almost nothing can grow on it -- and hasn't for decades, leaving behind moonscape expanses that can stretch for acres.

Now, however, Ramakrishna Wusirika's research team may have discovered how to make plants grow in the mine-waste desert and soak up some copper while they are at it.

Wusirika, a biological sciences professor at Michigan Technological University, began his research using several species of Pseudomonas bacteria from the sediments of Torch Lake. In the region's copper-mining heyday, the lake was used as a dump for mine waste. "We found bacteria that are resistant to high levels of copper," he said. "We thought we might be able to use them to help plants grow better on contaminated soils."
So Wusirika's research team added copper to soil samples and then inoculated them with a copper-resistant strain of Pseudomonas. Finally, they planted the samples with maize and sunflower seeds and waited.
As expected, seeds planted in copper-free soil thrived, and seeds planted in the copper-tainted soil without bacteria were stunted. But seeds planted in the coppery soil enriched with bacteria did much better; some were nearly as vigorous as plants grown without the toxic metal.
"The bacteria seem to help with plant growth, and they also help maize and sunflower uptake copper," said Wusirika. That means some kinds of naturally occurring bacteria could make soil more fertile and, in concert with the plants, remove at least some of the copper, a process known as rhizoremediation.
Their work, coauthored by PhD student Kefeng Li and Wusirika, was published online March 1 in the Journal of Hazardous Materials. For their next project, Wusirika's team has been testing how well their technique might work in a real copper-mining desert. They are in the process of using these bacteria to promote plant growth in stamp sands collected near the small Upper Peninsula village of Gay, where the copper-processing byproduct covers about 500 acres.

Self-Healing, Self-Cooling, Metamaterials: Vascular Composites Enable Dynamic Structural Materials

A vascularized fiber-reinforced composite material. Illinois researchers developed a class of sacrificial fibers that degrade after composite fabrication, leaving hollow vascular tunnels that can transport liquids or gases through the composite.

Taking their cue from biological circulatory systems, University of Illinois researchers have developed vascularized structural composites, creating materials that are lightweight and strong with potential for self-healing, self-cooling, metamaterials and more.

"We can make a material now that's truly multifunctional by simply circulating fluids that do different things within the same material system," said Scott White, the Willet Professor of aerospace engineering who led the group. "We have a vascularized structural material that can do almost anything."

Composite materials are a combination of two or more materials that harness the properties of both. Composites are valued as structural materials because they can be lightweight and strong. Many composites are fiber-reinforced, made of a network of woven fibers embedded in resin -- for example, graphite, fiberglass or Kevlar.
The Illinois team, part of the Autonomous Materials Systems Laboratory in the Beckman Institute for Advanced Science and Technology, developed a method of making fiber-reinforced composites with tiny channels for liquid or gas transport. The channels could wind through the material in one long line or branch out to form a network of capillaries, much like the vascular network in a tree.
"Trees are incredible structural materials, but they're dynamic too," said co-author Jeffrey Moore, the Murchison-Mallory professor of chemistry and a professor of materials science and engineering. "They can pump fluids, transfer mass and energy from the roots to the leaves. This is the first step to making synthetic materials that have that kind of functionality."
The key to the method, published in the journal Advanced Materials, is the use of sacrificial fibers. The team treated commercially available fibers so that they would degrade at high temperatures. The sacrificial fibers are no different from normal fibers during weaving and composite fabrication. But when the temperature is raised further, the treated fibers vaporize -- leaving tiny channels in their place -- without affecting the structural composite material itself.
"There have been vascular materials fabricated previously, including things that we've done, but this paper demonstrated that you can approach the manufacturing with a concept that is vastly superior in terms of scalability and commercial viability," White said.
In the paper, the researchers demonstrate four classes of application by circulating different fluids through a vascular composite: temperature regulation, chemistry, conductivity and electromagnetism. They regulate temperature by circulating coolant or a hot fluid. To demonstrate a chemical reaction, they injected chemicals into different vascular branches that merged, mixing the chemicals to produce a luminescent reaction. They made the structure electrically active by using conductive liquid, and changed its electromagnetic signature with ferrofluids -- a key property for stealth applications.
Next, the researchers hope to develop interconnected networks with membranes between neighboring channels to control transport between channels. Such networks would enable many chemical and energy applications, such as self-healing polymers or fuel cells.
"This is not just another microfluidic device," said co-author Nancy Sottos, the Willett professor of materials science and engineering and a professor of aerospace engineering. "It's not just a widget on a chip. It's a structural material that's capable of many functions that mimic biological systems. That's a big jump."
This work was supported by the Air Force Office of Scientific Research.

Graphene Nanocomposite a Bridge to Better Batteries

Berkeley Lab researchers assembled alternating layers of graphene and tin to create a nanoscale composite. First a thin film of tin is deposited onto graphene. Next, another sheet of graphene is transferred on top of the tin film. This process is repeated and the composite material is then heated to transform a tin film into a series of pillars. The change in height between graphene layers improves the electrode’s performance and allows the battery to be charged quickly and repeatedly without degrading.

Researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have created a graphene and tin nanoscale composite material for high-capacity energy storage in renewable lithium ion batteries. By encapsulating tin between sheets of graphene, the researchers constructed a new, lightweight "sandwich" structure that should bolster battery performance.

"For an electric vehicle, you need a lightweight battery that can be charged quickly and holds its charge capacity after repeated cycling," says Yuegang Zhang, a staff scientist with Berkeley Lab's Molecular Foundry, in the Inorganic Nanostructures Facility, who led this research. "Here, we've shown the rational design of a nanoscale architecture, which doesn't need an additive or binder to operate, to improve battery performance."

Graphene is a single-atom-thick, "chicken-wire" lattice of carbon atoms with stellar electronic and mechanical properties, far beyond silicon and other traditional semiconductor materials. Previous work on graphene by Zhang and his colleagues has emphasized electronic device applications.
In this study, the team assembled alternating layers of graphene and tin to create a nanoscale composite. To create the composite material, a thin film of tin is deposited onto graphene. Next, another sheet of graphene is transferred on top of the tin film. This process is repeated to create a composite material, which is then heated to 300˚ Celsius (572˚ Fahrenheit) in a hydrogen and argon environment. During this heat treatment, the tin film transforms into a series of pillars, increasing the height of the tin layer.
"The formation of these tin nanopillars from a thin film is very particular to this system, and we find the distance between the top and bottom graphene layers also changes to accommodate the height change of the tin layer," says Liwen Ji, a post-doctoral researcher at the Foundry. Ji is the lead author and Zhang the corresponding author of a paper reporting the research in the journal Energy and Environmental Science.
The change in height between the graphene layers in these new nanocomposites helps during electrochemical cycling of the battery, as the volume change of tin improves the electrode's performance. In addition, this accommodating behavior means the battery can be charged quickly and repeatedly without degrading -- crucial for rechargeable batteries in electric vehicles.
"We have a large battery program here at Berkeley Lab, where we are capable of making highly cyclable cells. Through our interactions in the Carbon Cycle 2.0 program, the Materials Science Division researchers benefit from quality battery facilities and personnel, along with our insights in what it takes to make a better electrode," says co-author Battaglia, program manager in the Advanced Energy Technology department of Berkeley Lab's Environmental and Energy Technologies Division. "In return, we have an outlet for getting these requirements out to scientists developing the next generation of materials."

Wave Power Can Drive Sun's Intense Heat

A satellite-derived image, looking down on a layer of the Sun's atmosphere, or corona, at which the temperature is 1 million degrees kelvin (1MK, or 1.8 million degrees Fahrenheit). In this cropped, still image from Movie 1, the curved lines are coronal loops, most likely composed of hot plasma flowing along magnetic field lines. Some coronal loops are so long that their tops extend beyond the field of view. (Visualization by Scott McIntosh, NCAR, of data from the Atmospheric Imaging Assembly, a package of instruments aboard NASA's Solar Dynamics Observatory.

A new study sheds light on why the Sun's outer atmosphere, or corona, is more than 20 times hotter than its surface. The research, led by the National Center for Atmospheric Research (NCAR), may bring scientists a step closer to understanding the solar cycle and the Sun's impacts on Earth.

The study uses satellite observations to reveal that magnetic oscillations carrying energy from the Sun's surface into its corona are far more vigorous than previously thought. These waves are energetic enough to heat the corona and drive the solar wind, a stream of charged particles ejected from the Sun that affects the entire solar system.

"We now understand how hot mass can shoot upward from the solar interior, providing enough energy to maintain the corona at a million degrees and fire off particles into the high-speed solar wind," says Scott McIntosh, the study's lead author and a scientist in NCAR's High Altitude Observatory. "This new research will help us solve essential mysteries about how energy gets out of the Sun and into the solar system."
The study, published this week in the journal Nature, was conducted by a team of scientists from NCAR, Lockheed Martin Solar and Astrophysics Lab, Norway's University of Oslo, and Belgium's Catholic University of Leuven. It was funded by NASA. NCAR is sponsored by the National Science Foundation.
Jets and waves
The flow of mass and energy from the corona influences how much ultraviolet radiation reaches Earth. It also drives upper-atmospheric disturbances known as geomagnetic storms, which can disrupt technologies ranging from telecommunications to electrical transmission.
The new study focuses on the role of oscillations in the corona, known as Alfven waves, in moving energy through the corona.
Alfven waves were directly observed for the first time in 2007. Scientists recognized them as a mechanism for transporting energy upward along the Sun's magnetic field into the corona. But the 2007 observations showed amplitudes on the order of about 1,600 feet (0.5 kilometers) per second, far too small to heat the corona to its high levels or to drive the solar wind.
The new satellite observations used in the current study reveal Alfven waves that are over a hundred times stronger than previously measured, with amplitudes on the order of 12 miles (20 km) per second -- enough to heat the Sun's outer atmosphere to millions of degrees and drive the solar wind. The waves are easily seen in high-resolution images of the outer atmosphere as they cause high-speed jets of hot material, called spicules, to sway.
"The new satellite observations are giving us a close look for the first time at how energy and mass move through the Sun's outer atmosphere," McIntosh says.
The research builds on ongoing efforts to study the connection between spicules and Alfven waves. Scientists have known about spicules for decades but were unable to determine if their mass got hot enough to provide heat for the corona until earlier this year, when McIntosh and colleagues published research in the journal Science that used satellite observations to reveal that a new class of the phenomenon, dubbed "Type II" spicules, moves much faster and reaches coronal temperatures.
The new study reveals the role of Alfven waves. These oscillations play a critical role in transporting heat from the Sun by riding on the spicules and carrying energy into the corona.
Photographing our nearest star
The critical satellite observations described in the study come from the Atmospheric Imaging Assembly, a package of instruments aboard NASA's Solar Dynamics Observatory, which was launched in 2010. The instruments boast high spatial and temporal resolution, enough to detect structures and motions across regions of the Sun as small as 310 miles (500 km) and generate images every 12 seconds at different wavelengths.
"It's like getting a microscope to study the Sun's corona, giving us the spatial and temperature coverage to focus in on the way mass and energy circulate." McIntosh says.
Now that the real power of the waves has been revealed in the corona, the next step in unraveling the mystery of its extreme heat is to study how the waves lose their energy, which is transferred to plasma. To do that, scientists will need to develop computer models that are fine enough in detail to capture how the jets and waves work together to power the atmosphere. By studying the Sun's underlying physics with these tools, scientists could better understand the Sun's 11-year sunspot cycle and its impacts on Earth.