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Lab News -- June 20, 2008

June 20 , 2008

LabNews 06/20/2008PDF (518 kb)

Sandia scientists spend year developing computer model of Iraq surface water and related systems

By Chris Burroughs

In an effort aimed at building technical capacity, resource sustainability, and regional stability, a team of Sandia scientists spent the past year working with engineers and modelers from Iraq to build a computer model of the country’s surface water and related systems.

The model, aimed at assisting a longer-term national water and land planning effort by the Iraqi government, includes transboundary flows from Turkey, Syria, and Iran, along with agriculture, municipal and industrial uses, salinity, and restoration of the ecologically sensitive and culturally rich Mesopotamian Marshes in the south.

“The Iraqis recognize very clearly that the long-term stability and security of their country depends on the availability of fresh water for agriculture and for municipal and industrial uses,” says Sandia researcher Howard Passell (6313). “We are grateful to have the opportunity to help.”

The project, funded by the US Department of State’s Iraq Transition Assistance Office, included three five-day workshops over the past year. It culminated in early June with a meeting in Istanbul of all the project participants and a pressure-packed demonstration of the model by the Iraqi engineers to three of their directors from the Iraq Ministry of Water Resources (MoWR). The participants included the Sandia team of Howard, Jesse Roach, and Marissa Reno (all 6313), four engineers from the MoWR, a State Department contractor from the US embassy in Baghdad, and a water program manager from UNESCO. Sandia contractor Geoff Klise and Labs researcher Vince Tidwell (both 6313) also helped on the project in Albuquerque.

Jesse says the best part of the project was watching the Iraqi engineers and modelers become engaged in the modeling process, a growing engagement that became apparent as the project unfolded. Jesse was the lead modeler in the project.

“Our approach was to build the computer model in a collaborative fashion with the Iraqis,” he says. “We could have built it for them and then handed it over, but we wanted them to have ownership — to understand how the model went together and how it works. At the end of the third workshop, our Iraqi colleagues presented the model to three high-level Iraqi MoWR officials. They presented it entirely in Arabic, explained how it worked, and answered questions about everything from input data to the scenario runs they were demonstrating. It was a powerful moment in a very successful capacity-building project.”

The model was built in a commercially available system dynamics (SD) modeling platform called Studio Expert, produced by Powersim Inc. It features short run times, user-friendly interfaces, and real-time graphical output. The 6313 staff have used the SD platform for years in collaborative, multistakeholder settings as a way of helping collaborators understand the complexities of their resource systems, identify data and information gaps, and evaluate competing resource management strategies — often in group settings, Howard says.

Over the years the 6313 team has blended this technical/social approach — bridging science and policy — to help decision makers with water, energy, and food resource management problems in New Mexico, the US, and internationally. They have used the approach in one form or another and have engaged scientists and engineers from more than a dozen countries, including Turkey, Syria, Iraq, Libya, Jordan, Japan, and four Central Asian republics.

The first two workshops in the Iraq project took place in Amman, Jordan, in November 2007 and February 2008. The initial workshops focused on helping the Iraqis learn to use the software and think about how the different systems associated with their resource issues were interdependent and interconnected.

By the time of the second workshop, the Sandians — with data and other information from the Iraqis — built a first draft of the model. The Iraqis used their growing skills to also build part of that model.

One of the critical drivers in the model is the flow of water from the headwaters of the Euphrates and Tigris rivers in Turkey through Syria to Iraq. The transboundary nature of the water resource adds a critical wrinkle in Iraqi efforts at water management.

“Surface water in Iraq is affected by infrastructure development and water operations in upstream countries,” says Marissa, who built the transboundary module in the model. “Historically, Turkey and Syria were not major water users, but now both countries have developed the capacity to store and use more, and that is a major concern to Iraq.”

Just as Iraq is at risk as the downstream user in the Tigris-Euphrates system, so are the Mesopotamian Marshes at risk as the downstream user in Iraq. Labeled by some as the original Eden and populated still by the ancient Marsh Arab culture, the southern marshes once covered about 8,000 square kilometers. They are a crucial freshwater wetland ecosystem in the Arabian Gulf region. Water uses upstream have gradually reduced the area of the marshes. Saddam Hussein partially drained them in the 1990s when his enemies hid there, and they are threatened by increasing upstream water use in the future. Now they cover about 5,000 square kilometers.

“The marshes, which are culturally, historically, and economically rich and diverse, have started to dry out — partly by accident and partly by design,” says Geoff, the team member who built the marsh module. “We modeled how they might be restored, looking at flows, reservoir operations, and changes to agriculture, to see how these might affect marshes downstream.”

New funding for phase two of the project is expected in July.

Team members: Howard Passell, Jesse Roach, Marissa Reno, Geoff Klise, Vince Tidwell, Ray Finley (all 6313) -- Chris Burroughs

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Research aids understanding of retrovirus transmission between human cells

By Neal Singer

Under the right conditions, nanotubes may form between human cells with surprising ease, Sandia researchers have found.

The tunnel-like structures have been recognized only in the past few years as tiny but important bodily channels for the good, the bad, and the informational.

“Lipid nanotubes provide a vast array of functions that could greatly impact our approach to treating infection and in understanding how cells respond to pathogens,” says Darryl Sasaki (8331) of Sandia’s Bioscience and Energy Center.

“Our work is the first to show that the formation of nanotubes is not complicated, but can be a general effect of protein-membrane interactions alone.”

Understanding how cellular nanotubes form has become important to medical science over the past few years because of the discovery of what they transport. They seem to serve as routes that protect retroviruses and bacteria as they pass from diseased cells to healthy ones — a fact that may explain why vaccines do poorly against certain invaders. Conversely, the nanotunnels also seem to help trundle bacteria to their doom in the tentacles of microphages. Lastly, the nanotubes may also provide avenues for cells to send and receive information (in the form of chemical molecules) from cell to cell far faster than their random dispersal into the bloodstream would permit.

Given the discovery of this radically different transportation system operating within human tissues, it was natural for researchers to attempt to duplicate the formation of the nanotubes. In their labs, they experimented with giant lipid vesicules that appeared to mimic key aspects of the cellular membrane.

Giant lipid vesicules resemble micron-sized spherical soap bubbles, with the inner side hydrophobic and the outer side hydrophilic.

The object for experimenters was to create conditions in which the spheres would morph into cylinders of nanometer radii.

But researchers had difficulties, says Darryl, perhaps because they used a composite lipid called egg PC that requires unnecessarily high energies to bend into a tubular shape.

Egg PC is inexpensive, readily available, and offers good, stable membrane properties. It is the usual lipid of choice in forming nanocylinders via mechanical stretching techniques.

But Sandia postdoctoral student Haiqing Lui (8331) instead used POPC — a single pure lipid requiring half the bending energy of egg PC.

She was trying to generate nanotubes by a completely different approach that involved the use of motor proteins to stretch naturally occurring membranes into tubes.

Working with George Bachand (8331), she serendipitously found that interaction of the POPC membrane with a high-affinity protein called streptavidin alone was enough to form the nanotubes.

“Perhaps this information — linking membrane-bending energy with nanotube formation — may provide some clue about the membrane structure and the cell’s ability to form such intercellular connections,” Darryl says.

The formation was confirmed by Carl Hayden (8353), who characterized the nanotube formation through a confocal imaging microscope. The custom instrument allows pixel-by-pixel examination of the protein interaction with the membranes comprising the nanotubes by detecting the spectrum and lifetimes of fluorescent labels on the proteins.

Nanotube formation had been noticed previously by cell biologists, but they had dismissed the tiny outgrowths as “junk — an aberration of cells growing in culture,” says Darryl. “The reason they were only noticed recently as trafficking routes is because of labeling studies that marked organelles and proteins. This allowed a focused look at what these nanostructures might be used for.”

It became clear, says Darryl, that the organelles were being transported with “specific directionality” on the backs of motor proteins within the tubes, rather than randomly.

Three-dimensional networks of nanotubes also are found to be created by macrophages — part of the police force of the body — grown in culture, says George. The tubes in appearance and function resemble a kind of spider web, capturing bacteria and transporting them to the macrophages, which eat them.

Other paper authors include postdoc Hahkjoon Kim (8353) and summer intern Elsa Abate (8331).

The lipid work is supported by Sandia’s Laboratory Directed Research and Development office. Motor protein work is supported by DOE’s Office of Basic Energy Sciences.

Results were published in the American Chemical Society’s Langmuir journal in mid-March.


Neal Singer

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Solution to high-energy costs could lie underground

By Chris Burroughs

Sandia researcher Georgianne Peek (6336) thinks a possible solution to high energy costs lies underground. And it’s not coal or oil.

It’s compressed air energy storage (CAES).

“Until recently energy has been relatively inexpensive. But now prices are rising dramatically, and we need solutions,” Georgianne says. “CAES and other storage technologies are not the only answer to our energy needs, but they can be an important part of the solution.”

CAES facilities function like big batteries. Electric motors drive compressors that compress air into an underground geologic formation during off-peak electric use times like evenings and weekends. Then, when electricity is needed most during high-demand times, the precompressed air is used in modified combustion turbines to generate electricity. Natural gas or other fossil fuels are still required to run the turbines, but the process is more efficient. This method uses up to 50 percent less natural gas than standard electricity production.

While the concept of compressed air energy storage is more than 30 years old, only two such plants exist — a 17-year-old facility in McIntosh, Ala., located about 40 miles north of Mobile, and a 30-year-old plant in Germany, both in caverns in salt domes. A third is being developed near Des Moines, Iowa, in an aquifer. In addition, the Public Service Company of New Mexico (PNM) and several other US utilities are considering CAES to help mitigate potential problems associated with the high proportion of wind generation in their systems.

Iowa project management

Sandia is currently managing DOE money to support the design of the Iowa facility, called the Iowa Stored Energy Park (ISEP). Georgianne is the project manager. Developers include more than 100 municipal utilities in Iowa, Minnesota, and the Dakotas.

ISEP will be a nominal 268 MW/13,400 MWh CAES plant with about 50 hours of storage. It will utilize the abundant wind generation already in Iowa to charge the plant. When ISEP is up and running, it could account for 20 percent of the energy used in a year at a typical municipal Iowa utility and could save cities and their utilities as much as $5 million each year in purchased energy.

Georgianne says the Iowa project is pretty far along and is expected to be operational by 2012.

“One of the most important tasks that has to be done before a CAES facility can be built is to find a geologic formation that will support it,” Georgianne says. “ISEP developers are 95 percent sure that they have the right formation, based on the seismic testing at the site, computer modeling, and data from a sister formation.”

Sandia to study core samples

This summer multiple core samples from the potential Iowa aquifer CAES site will be taken and sent to Sandia for analysis by a team led by Steve Bauer (6315). The analysis will include collection and assessment of the geologic, hydrologic, and rock physics data in the geomechanics laboratory. The data will provide necessary fundamental information used for the design and performance of the underground air storage vessel.

In 2000 Steve did similar analysis of rock mechanics of a limestone mine in Norton, Ohio, that was being studied for a potential CAES facility. That project is still under development.

Georgianne says that PNM is also considering building a CAES plant and is exploring possible locations around the state, including locations near existing wind farms that provide service to PNM.

“Wind often blows at night,” she says. “As electricity is produced at night from the wind farms, it will be stored and eventually make its way into PNM’s transmission lines.”

Several Sandia researchers and the Electric Power Research Institute Initiative are helping PNM plan for a CAES facility.

CAES technology development can trace its roots to the early 1960s when evaluation of gas turbine technology for power production began. The technology gained momentum during the next decade due to its promising fuel efficiency and response capabilities to provide load-following and peaking power support.

Now utilities are starting to tie CAES technology to wind power — first with the Iowa plant and soon with a possible facility in New Mexico, Georgianne says.

“The wind blows in some areas when electricity is not needed or where the transmission system can’t accept all of the energy,” she says. “Storage enables delivery of the off-peak energy that has been saved in storage to be delivered when it is needed most or has the highest value. Thus, more renewable energy can be delivered than might be possible without storage.” -- Chris Burroughs

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