Chemists Synthesize Artificial Cell Membrane

Neal Devaraj watches as undergraduate student Weilong Li works on a next step in their quest to create an entirely artificial cell. (Credit: Image courtesy of University of California - San Diego)

Chemists have taken an important step in making artificial life forms from scratch. Using a novel chemical reaction, they have created self-assembling cell membranes, the structural envelopes that contain and support the reactions required for life.

Neal Devaraj, assistant professor of chemistry at the University of California, San Diego, and Itay Budin, a graduate student at Harvard University, report their success in theJournal of the American Chemical Society.

"One of our long term, very ambitious goals is to try to make an artificial cell, a synthetic living unit from the bottom up -- to make a living organism from non-living molecules that have never been through or touched a living organism," Devaraj said. "Presumably this occurred at some point in the past. Otherwise life wouldn't exist."

By assembling an essential component of earthly life with no biological precursors, they hope to illuminate life's origins.

"We don't understand this really fundamental step in our existence, which is how non-living matter went to living matter," Devaraj said. "So this is a really ripe area to try to understand what knowledge we lack about how that transition might have occurred. That could teach us a lot -- even the basic chemical, biological principles that are necessary for life."

Molecules that make up cell membranes have heads that mix easily with water and tails that repel it. In water, they form a double layer with heads out and tails in, a barrier that sequesters the contents of the cell.

Devaraj and Budin created similar molecules with a novel reaction that joins two chains of lipids. Nature uses complex enzymes that are themselves embedded in membranes to accomplish this, making it hard to understand how the very first membranes came to be.

"In our system, we use a sort of primitive catalyst, a very simple metal ion," Devaraj said. "The reaction itself is completely artificial. There's no biological equivalent of this chemical reaction. This is how you could have a de novoformation of membranes."

They created the synthetic membranes from a watery emulsion of an oil and a detergent. Alone it's stable. Add copper ions and sturdy vesicles and tubules begin to bud off the oil droplets. After 24 hours, the oil droplets are gone, "consumed" by the self-assembling membranes.

Although other scientists recently announced the creation of a "synthetic cell," only its genome was artificial. The rest was a hijacked bacterial cell. Fully artificial life will require the union of both an information-carrying genome and a three-dimensional structure to house it.

The real value of this discovery might reside in its simplicity. From commercially available precursors, the scientists needed just one preparatory step to create each starting lipid chain.

"It's trivial and can be done in a day," Devaraj said. "New people who join the lab can make membranes from day one."

The National Institute of Biomedical Imaging and Bioengineering supported this work. UC San Diego has filed a patent application on this discovery.

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The above story is reprinted from materials provided byUniversity of California - San Diego. The original article was written by Susan Brown.

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---

Journal Reference:

1. Itay Budin, Neal K. Devaraj. Membrane Assembly Driven by a Biomimetic Coupling Reaction. Journal of the American Chemical Society, 2012; 134 (2): 751 DOI:10.1021/ja2076873

Using math and light to detect misshapen red blood cells

ScienceDaily (Oct. 31, 2011) — Misshapen red blood cells (RBCs) are a sign of serious illnesses, such as malaria and sickle cell anemia. Until recently, the only way to assess whether a person's RBCs were the correct shape was to look at them individually under a microscope -- a time-consuming process for pathologists. Now researchers from the University of Illinois at Urbana-Champaign (UIUC) have pioneered a technique that will allow doctors to ascertain the healthy shape of red blood cells in just a few seconds, by analyzing the light scattered off hundreds of cells at a time.

The team reports its results in the October issue of the Optical Society's (OSA) open-access journal Biomedical Optics Express.

A healthy RBC looks like a disc with a depression -- called a dimple -- in the top and bottom. Stressed RBCs often have deeper dimples than healthy ones, giving the cells a deflated look; others may have shallow dimples or no dimples at all. The UIUC researchers reasoned that if they shone light on a sample of blood and analyzed the light scattering off that sample, they would get a pattern -- a sort of signature produced by the way light interacts with itself in a three-dimensional space -- that would be different from the pattern collected from blood containing mostly misshapen cells. But these light-cell interactions were too complicated to analyze with the usual mathematical tools. So researchers made use of the Born approximation, a mathematical rule that can be used when the object of interest is small and transparent.

By running Fourier Transform Light Scattering (FTLS) -- a method developed by the same group three years ago -- on individual RBCs, the scientists found that the pattern changed significantly with the diameter and dimple width of the cells. Using this information, the UIUC team applied the Born approximation to their findings and calculated what the appropriate scattering signature for healthy cells should be. They then used this new "healthy cell signature" to identify the correct morphology of cells in a blood smear. The new technique may allow for faster, accurate blood tests that could help doctors diagnose various types of anemia, and could be especially useful in resource-poor areas of the world, the researchers say.

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Bartolomeo Della Ventura, Luigi Schiavo, Carlo Altucci, Rosario Esposito, Raffaele Velotta. Light assisted antibody immobilization for bio-sensing. Biomedical Optics Express, 2011; 2 (11): 3223 DOI: 10.1364/BOE.2.003223

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Researchers use carbon nanotubes to make solar cells affordable, flexible

ScienceDaily (Sep. 27, 2011) — Researchers from Northwestern University have developed a carbon-based material that could revolutionize the way solar power is harvested. The new solar cell material -- a transparent conductor made of carbon nanotubes -- provides an alternative to current technology, which is mechanically brittle and reliant on a relatively rare mineral.

Due to Earth's abundance of carbon, carbon nanotubes have the potential to boost the long-term viability of solar power by providing a cost-efficient option as demand for the technology increases. In addition, the material's mechanical flexibility could allow solar cells to be integrated into fabrics and clothing, enabling portable energy supplies that could impact everything from personal electronics to military operations.

The research, headed by Mark C. Hersam, professor of materials science and engineering and professor of chemistry, and Tobin J. Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and professor of materials science and engineering, is featured on the cover of the October 2011 issue of Advanced Energy Materials, a new journal that specializes in science about materials used in energy applications.

Solar cells are composed of several layers, including a transparent conductor layer that allows light to pass into the cell and electricity to pass out; for both these actions to occur, the conductor must be both electrically conductive and also optically transparent. Few materials concurrently possess both of these properties.

Currently, indium tin oxide is the dominant material used in transparent conductor applications, but the material has two potential limitations. Indium tin oxide is mechanically brittle, which precludes its use in applications that require mechanical flexibility. In addition, Indium tin oxide relies on the relatively rare element indium, so the projected increased demand for solar cells could push the price of indium to problematically high levels.

"If solar technology really becomes widespread, as everyone hopes it will, we will likely have a crisis in the supply of indium," Hersam said. "There's a great desire to identify materials -- especially earth-abundant elements like carbon -- that can take indium's place in solar technology."

Hersam and Marks' team has created an alternative to indium tin oxide using single-walled carbon nanotubes, tiny, hollow cylinders of carbon just one nanometer in diameter.

The researchers have gone further to determine the type of nanotube that is most effective in transparent conductors. Nanotubes' properties vary depending on their diameter and their chiral angle, the angle that describes the arrangement of carbon atoms along the length of the nanotube. These properties determine two types of nanotubes: metallic and semiconducting.

Metallic nanotubes, the researchers found, are 50 times more effective than semiconducting ones when used as transparent conductors in organic solar cells.

"We have now identified precisely the type of carbon nanotube that should be used in this application," Hersam said.

Because carbon nanotubes are flexible, as opposed to the brittle indium tin oxide, the researchers' findings could pave the way for many new applications in solar cells. For example, the military could incorporate the flexible solar cells into tent material to provide solar power directly to soldiers in the field, or the cells could be integrated into clothing, backpacks, or purses for wearable electronics.

"With this mechanically flexible technology, it's much easier to imagine integrating solar technology into everyday life, rather than carrying around a large, inflexible solar cell," Hersam said.

Researchers are now examining other layers of the solar cell to explore also replacing these with carbon-based nanomaterials.

Besides Hersam and Marks, other authors include Timothy P. Tyler, Ryan E. Brock, and Hunter J. Karmel. This work was supported by the Argonne Northwestern-Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Timothy P. Tyler, Ryan E. Brock, Hunter J. Karmel, Tobin J. Marks, Mark C. Hersam. Organic Solar Cell Characterization: Electronically Monodisperse Single-Walled Carbon Nanotube Thin Films as Transparent Conducting Anodes in Organic Photovoltaic Devices (Adv. Energy Mater. 5/2011). Advanced Energy Materials, 2011; 1 (5): 701 DOI: 10.1002/aenm.201190021

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Researchers use carbon nanotubes to make solar cells affordable, flexible

ScienceDaily (Sep. 27, 2011) — Researchers from Northwestern University have developed a carbon-based material that could revolutionize the way solar power is harvested. The new solar cell material -- a transparent conductor made of carbon nanotubes -- provides an alternative to current technology, which is mechanically brittle and reliant on a relatively rare mineral.

Due to Earth's abundance of carbon, carbon nanotubes have the potential to boost the long-term viability of solar power by providing a cost-efficient option as demand for the technology increases. In addition, the material's mechanical flexibility could allow solar cells to be integrated into fabrics and clothing, enabling portable energy supplies that could impact everything from personal electronics to military operations.

The research, headed by Mark C. Hersam, professor of materials science and engineering and professor of chemistry, and Tobin J. Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and professor of materials science and engineering, is featured on the cover of the October 2011 issue of Advanced Energy Materials, a new journal that specializes in science about materials used in energy applications.

Solar cells are composed of several layers, including a transparent conductor layer that allows light to pass into the cell and electricity to pass out; for both these actions to occur, the conductor must be both electrically conductive and also optically transparent. Few materials concurrently possess both of these properties.

Currently, indium tin oxide is the dominant material used in transparent conductor applications, but the material has two potential limitations. Indium tin oxide is mechanically brittle, which precludes its use in applications that require mechanical flexibility. In addition, Indium tin oxide relies on the relatively rare element indium, so the projected increased demand for solar cells could push the price of indium to problematically high levels.

"If solar technology really becomes widespread, as everyone hopes it will, we will likely have a crisis in the supply of indium," Hersam said. "There's a great desire to identify materials -- especially earth-abundant elements like carbon -- that can take indium's place in solar technology."

Hersam and Marks' team has created an alternative to indium tin oxide using single-walled carbon nanotubes, tiny, hollow cylinders of carbon just one nanometer in diameter.

The researchers have gone further to determine the type of nanotube that is most effective in transparent conductors. Nanotubes' properties vary depending on their diameter and their chiral angle, the angle that describes the arrangement of carbon atoms along the length of the nanotube. These properties determine two types of nanotubes: metallic and semiconducting.

Metallic nanotubes, the researchers found, are 50 times more effective than semiconducting ones when used as transparent conductors in organic solar cells.

"We have now identified precisely the type of carbon nanotube that should be used in this application," Hersam said.

Because carbon nanotubes are flexible, as opposed to the brittle indium tin oxide, the researchers' findings could pave the way for many new applications in solar cells. For example, the military could incorporate the flexible solar cells into tent material to provide solar power directly to soldiers in the field, or the cells could be integrated into clothing, backpacks, or purses for wearable electronics.

"With this mechanically flexible technology, it's much easier to imagine integrating solar technology into everyday life, rather than carrying around a large, inflexible solar cell," Hersam said.

Researchers are now examining other layers of the solar cell to explore also replacing these with carbon-based nanomaterials.

Besides Hersam and Marks, other authors include Timothy P. Tyler, Ryan E. Brock, and Hunter J. Karmel. This work was supported by the Argonne Northwestern-Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Timothy P. Tyler, Ryan E. Brock, Hunter J. Karmel, Tobin J. Marks, Mark C. Hersam. Organic Solar Cell Characterization: Electronically Monodisperse Single-Walled Carbon Nanotube Thin Films as Transparent Conducting Anodes in Organic Photovoltaic Devices (Adv. Energy Mater. 5/2011). Advanced Energy Materials, 2011; 1 (5): 701 DOI: 10.1002/aenm.201190021

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Regenerating nerve cells: Research offers hope in new treatment for spinal cord injuries

ScienceDaily (May 3, 2011) — Rutgers researchers have developed an innovative new treatment that could help minimize nerve damage in spinal cord injuries, promote tissue healing and minimize pain.
After a spinal cord injury there is an increased production of a protein (RhoA) that blocks regeneration of nerve cells that carry signals along the spinal cord and prevents the injured tissue from healing.
Scientists at the W.M. Keck Center for Collaborative Neuroscience and Quark Pharmaceuticals Inc. have developed a chemically synthesized siRNA molecule that decreases the production of the RhoA protein when administered to the spine and allows regeneration of the nerve cells.
"It is exciting because this minimally-invasive treatment can selectively target the injured tissue and thereby promote healing and reduce pain," says Martin Grumet, associate director of the Keck Center and senior author of a recent study published in the Journal of Neurotrauma.
The neuropathic pain, also known as phantom pain that occurs as a result of a spinal cord injury is often associated with an increased production of RhoA. When researchers injected the chemically synthesized molecular substance into the spinal cords of laboratory rats with spinal cord injury using a procedure similar to a spinal tap, there was an overall improvement in tissue healing and recovery.
More than 250,000 people in the United States are living with a spinal cord injury and currently there is no way to reverse the damage. No drugs for early treatment of spinal cord injury have been approved in over a decade. Based on this joint research, Quark Pharmaceuticals, Inc now has a drug development program for the treatment of spinal cord injury and neuropathic pain. This new research is supported by grants from the New Jersey Commission for Spinal Cord Research and Quark.
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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rutgers University.

Journal Reference:
Seiji Otsuka, Crista Adamson, Venkatachalam Sankar, Kurt M Gibbs, Noriko Kane-Goldsmith, Jennifer Jernstedt Ayer, Joanne Babiarz, Hagar Kalinski, Hagit Ashush, Evgenia Alpert, Ron Lahav, Elena Feinstein, Martin Grumet. Delayed intrathecal delivery of RhoA siRNA to the contused spinal cord inhibits allodynia, preserves white matter and increases serotonergic fiber growth. Journal of Neurotrauma, 2011; 110329050021037 DOI: 10.1089/neu.2010.1568
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New method for imaging molecules inside cells

ScienceDaily (June 29, 2011) — Using a new sample holder, researchers at the University of Gothenburg have further developed a new method for imaging individual cells. This makes it possible to produce snapshots that not only show the outline of the cell's contours but also the various molecules inside or on the surface of the cell, and exactly where they are located, something which is impossible with a normal microscope.

Individual human cells are small, just one or two hundredths of a millimeter in diameter. As such, special measuring equipment is needed to distinguish the various parts inside the cell. Researchers generally use a microscope that magnifies the cell and shows its contours outline, but does not provide any information on the molecules inside the cell and on its surface.

"The new sample holder is filled with holds cells in solution," says Ingela Lanekoff, one of the researchers who developed the new method at the University of Gothenburg's Department of Chemistry. "We then rapidly freeze the sample down to -196°C, which enables us to get a snapshot of where the various molecules are at the moment of freezing. Using this technique we can produce images that show not only the outline of the cell's contours, but also the molecules that are there, and where they are located."

Important to measure chemical processes in the body

So why do the researchers want to know which molecules are to be found in a single cell? Because the cell is the smallest living component there is, and the chemical processes that take place here play a major role in how the cell functions in our body. For example, our brain has special cells that can communicate with each other through chemical signals. This vital communication has been shown to be dependent on the molecules in the cell's membrane.

Imaging the molecules in the membrane of single individual cells's membrane enables researchers to measure changes. Together with previous results, Lanekoff's findings show that the rate of communication in the studied cells studied is affected by a change of less than one per cent in the quantities abundance of a specific molecule in the membrane. This would suggest that communication between the cells in the brain is heavily dependent on the chemical composition of the membrane of each individual cell,. This could be an important part of the puzzle which could go some way towards explaining the mechanisms behind learning and memory.

The thesis, Analysis of phospholipids in cellular membranes with LC and imaging mass spectrometry, has been successfully defended at the University of Gothenburg. Supervisors: Andrew Ewing and Roger Karlsson. Download the thesis at: hdl.handle.net/2077/25279

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‘Cling-film’ solar cells could lead to advance in renewable energy

ScienceDaily (July 4, 2011) — A scientific advance in renewable energy which promises a revolution in the ease and cost of using solar cells, has been announced on July 4, 2011. A new study shows that even when using very simple and inexpensive manufacturing methods -- where flexible layers of material are deposited over large areas like cling-film -- efficient solar cell structures can be made.

The study, published in the journal Advanced Energy Materials, paves the way for new solar cell manufacturing techniques and the promise of developments in renewable solar energy. Scientists from the Universities of Sheffield and Cambridge used the ISIS Neutron Source and Diamond Light Source at STFC Rutherford Appleton Laboratory in Oxfordshire to carry out the research.

Plastic (polymer) solar cells are much cheaper to produce than conventional silicon solar cells and have the potential to be produced in large quantities. The study showed that when complex mixtures of molecules in solution are spread onto a surface, like varnishing a table-top, the different molecules separate to the top and bottom of the layer in a way that maximises the efficiency of the resulting solar cell.

Dr Andrew Parnell of the University of Sheffield said, "Our results give important insights into how ultra-cheap solar energy panels for domestic and industrial use can be manufactured on a large scale. Rather than using complex and expensive fabrication methods to create a specific semiconductor nanostructure, high volume printing could be used to produce nano-scale (60 nano-meters) films of solar cells that are over a thousand times thinner than the width of a human hair. These films could then be used to make cost-effective, light and easily transportable plastic solar cell devices such as solar panels."

Dr. Robert Dalgliesh, one of the ISIS scientists involved in the work, said, "This work clearly illustrates the importance of the combined use of neutron and X-ray scattering sources such as ISIS and Diamond in solving modern challenges for society. Using neutron beams at ISIS and Diamond's bright X-rays, we were able to probe the internal structure and properties of the solar cell materials non-destructively. By studying the layers in the materials which convert sunlight into electricity, we are learning how different processing steps change the overall efficiency and affect the overall polymer solar cell performance. "

"Over the next fifty years society is going to need to supply the growing energy demands of the world's population without using fossil fuels, and the only renewable energy source that can do this is the Sun," said Professor Richard Jones of the University of Sheffield. " In a couple of hours enough energy from sunlight falls on the Earth to satisfy the energy needs of the Earth for a whole year, but we need to be able to harness this on a much bigger scale than we can do now. Cheap and efficient polymer solar cells that can cover huge areas could help move us into a new age of renewable energy."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Science and Technology Facilities Council (STFC).

Journal Reference:

Paul A. Staniec, Andrew J. Parnell, Alan D. F. Dunbar, Hunan Yi, Andrew J. Pearson, Tao Wang, Paul E. Hopkinson, Christy Kinane, Robert M. Dalgliesh, Athene M. Donald, Anthony J. Ryan, Ahmed Iraqi, Richard A. L. Jones, David G. Lidzey. The Nanoscale Morphology of a PCDTBT:PCBM Photovoltaic Blend. Advanced Energy Materials, 2011; DOI: 10.1002/aenm.201100144

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New catalyst will allow commercialization of revolutionary fuel cells

ScienceDaily (June 15, 2011) — Cheap, much lighter than before and allowing for continuous operation -- what traditional batteries can not offer -- direct formic acid fuel cells can revolutionize the portable electronics market. A new catalyst developed at the Institute of Physical Chemistry of the Polish Academy of Sciences will enable a widespread use of fuel cells, researchers say.

You can hardly find a consumer electronics user who would not be irritated by problems with power supply. The batteries run out quickly and require continuous replacements or take a long time charging. Fuel cells could significantly improve the comfort of using electronic devices. Their commercialization, however, is hampered by many technological problems. A new catalyst developed at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw represents a substantial milestone on the way to dissemination of cheap, durable, light and environment friendly fuel cells powered by formic acid.

Fuel cell is a device converting chemical energy into electric power. The current is generated directly due to fuel combustion in the presence of catalysts used on the anode and the cathode of the fuel cell. "Theoretical efficiency of conversion of chemical energy into electric power in the cells can reach even one hundred percent. The best present fuel cells, powered by hydrogen, reach up to 60% in real life. For comparison, the efficiency of low-compression engines is as low as 20%," says Dr Andrzej Borodzinski from the IPC PAS.

The biggest obstacle to dissemination of hydrogen fuels is the storage of hydrogen. The issue turned out to be extremely technologically challenging and still is waiting for satisfactory solutions. An alternative to fuel cells powered by pure hydrogen is the methanol fuel cell technology. Methanol, however, is toxic and the methanol powered fuel cells must be produced with expensive platinum based catalysts. Moreover, methanol fuel cells have low power and are operated at a relatively high and so potentially hazardous temperature (approximately 90°C).

An alternative solution is formic acid fuel cells. In this case, the reactions occur at room temperature, and the efficiency and power of these fuel cells are clearly higher than those for methanol ones. In addition, formic acid is easy to store and transport. To have, however, formic acid fuel cell stable in operation you need an efficient and durable catalyst.

"The catalyst developed by us has initially lower activity then the existing catalysts made of pure palladium. The difference disappears, however, already after two hours of operation. And further it is only better. Our catalyst is stable in operation, whereas the activity of a pure palladium-based catalyst decreases in time," says Dr Borodzinski.

An advantage of the catalyst developed in the IPC PAS, particularly important from the economic point of view, is that it preserves its properties while operated in formic acid of low purity. Such formic acid can be easily produced in large quantities, also from biomass, so the fuel for new fuel cells would be very cheap.

Formic acid produced from biomass would be a fully environment friendly fuel. The reactions involving formic acid in fuel cells generate as products water and carbon dioxide. The latter is, as a matter of fact, a greenhouse gas, but the biomass is obtained from plants which use carbon dioxide for their growth. As a result, formic acid produced from biomass and consumed in fuel cells would not change the content of carbon dioxide in atmospheric air. The risk of natural environment contamination by formic acid is also low.

Formic acid fuel cells would find numerous applications. They would be particularly suitable in portable electronic devices -- mobile phones, laptops or GPS-based devices. They could also be installed as power supply sources in vehicles, from wheelchairs through electric bicycles up to yachts.

At the IPC PAS the research is being undertaken on the first batteries based on formic acid fuel cells. The researchers expect that a prototype of a commercial device should be ready within a couple of years.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institute of Physical Chemistry of the Polish Academy of Sciences, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New catalyst will allow commercialization of revolutionary fuel cells

ScienceDaily (June 15, 2011) — Cheap, much lighter than before and allowing for continuous operation -- what traditional batteries can not offer -- direct formic acid fuel cells can revolutionize the portable electronics market. A new catalyst developed at the Institute of Physical Chemistry of the Polish Academy of Sciences will enable a widespread use of fuel cells, researchers say.

You can hardly find a consumer electronics user who would not be irritated by problems with power supply. The batteries run out quickly and require continuous replacements or take a long time charging. Fuel cells could significantly improve the comfort of using electronic devices. Their commercialization, however, is hampered by many technological problems. A new catalyst developed at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw represents a substantial milestone on the way to dissemination of cheap, durable, light and environment friendly fuel cells powered by formic acid.

Fuel cell is a device converting chemical energy into electric power. The current is generated directly due to fuel combustion in the presence of catalysts used on the anode and the cathode of the fuel cell. "Theoretical efficiency of conversion of chemical energy into electric power in the cells can reach even one hundred percent. The best present fuel cells, powered by hydrogen, reach up to 60% in real life. For comparison, the efficiency of low-compression engines is as low as 20%," says Dr Andrzej Borodzinski from the IPC PAS.

The biggest obstacle to dissemination of hydrogen fuels is the storage of hydrogen. The issue turned out to be extremely technologically challenging and still is waiting for satisfactory solutions. An alternative to fuel cells powered by pure hydrogen is the methanol fuel cell technology. Methanol, however, is toxic and the methanol powered fuel cells must be produced with expensive platinum based catalysts. Moreover, methanol fuel cells have low power and are operated at a relatively high and so potentially hazardous temperature (approximately 90°C).

An alternative solution is formic acid fuel cells. In this case, the reactions occur at room temperature, and the efficiency and power of these fuel cells are clearly higher than those for methanol ones. In addition, formic acid is easy to store and transport. To have, however, formic acid fuel cell stable in operation you need an efficient and durable catalyst.

"The catalyst developed by us has initially lower activity then the existing catalysts made of pure palladium. The difference disappears, however, already after two hours of operation. And further it is only better. Our catalyst is stable in operation, whereas the activity of a pure palladium-based catalyst decreases in time," says Dr Borodzinski.

An advantage of the catalyst developed in the IPC PAS, particularly important from the economic point of view, is that it preserves its properties while operated in formic acid of low purity. Such formic acid can be easily produced in large quantities, also from biomass, so the fuel for new fuel cells would be very cheap.

Formic acid produced from biomass would be a fully environment friendly fuel. The reactions involving formic acid in fuel cells generate as products water and carbon dioxide. The latter is, as a matter of fact, a greenhouse gas, but the biomass is obtained from plants which use carbon dioxide for their growth. As a result, formic acid produced from biomass and consumed in fuel cells would not change the content of carbon dioxide in atmospheric air. The risk of natural environment contamination by formic acid is also low.

Formic acid fuel cells would find numerous applications. They would be particularly suitable in portable electronic devices -- mobile phones, laptops or GPS-based devices. They could also be installed as power supply sources in vehicles, from wheelchairs through electric bicycles up to yachts.

At the IPC PAS the research is being undertaken on the first batteries based on formic acid fuel cells. The researchers expect that a prototype of a commercial device should be ready within a couple of years.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institute of Physical Chemistry of the Polish Academy of Sciences, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Portable hydrogen reactor for fuel cells

ScienceDaily (May 23, 2011) — Chemical engineering students at Stevens Institute of Technology are transforming the way that American soldiers power their battery-operated devices by making a small change: a really small change. Capitalizing on the unique properties of microscale systems, the students have invented a microreactor that converts everyday fossil fuels like propane and butane into pure hydrogen for fuel cell batteries. These batteries are not only highly efficient, but also can be replenished with hydrogen again and again for years of resilient performance in the field.

With soldiers carrying up to 80% of gear weight in batteries, the Army has a high interest in replacing the current paradigm of single-use batteries with a reliable, reusable power source. The Stevens-made microreactors thus have the potential to not only reduce waste from disposable batteries, but also provide American soldiers with a dependable way to recharge the batteries for the critical devices that keep them safe.

Current methods for generating fuel cell hydrogen are both sophisticated and risky, requiring high temperatures and a vacuum to produce the necessary chemical-reaction-causing plasmas. Once in a container, hydrogen is a highly volatile substance that is dangerous and expensive to transport.

The Stevens microreactor overcomes both of these barriers by using low temperatures and atmospheric pressure, and by producing hydrogen only as needed to avoid creating explosive targets in combat areas. These advanced reactors are created using cutting-edge microfabrication techniques, similar to those used to create plasma television screens, which use microscale physics to produce plasma under normal atmospheres.

The team has already had success producing hydrogen from methanol. After gasifying methanol by suspending it in hot nitrogen gas, the mixture is drawn into a 25µm channel in the microreactor. There, it reacts with plasma to cause thermal decomposition, breaking down the methanol into its elemental components. Now the team is conducting tests to see what kind of yields are realizable from various starter fuels. Eventually, soldiers will be able to convert everyday liquid fuels like propane or butane, commonly found on military bases, into high-potency juice for portable fuel cell batteries.

The team, made up of seniors Ali Acosta, Kyle Lazzaro, Randy Parrilla, and Andrew Robertson, are supporting Ph.D. candidate Peter Lindner in a research project sponsored by the U.S. Army. The project is overseen by Dr. Ronald Besser. The team will be presenting their device prototype at Senior Projects Expo on April 27.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Stevens Institute of Technology.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Portable hydrogen reactor for fuel cells

ScienceDaily (May 23, 2011) — Chemical engineering students at Stevens Institute of Technology are transforming the way that American soldiers power their battery-operated devices by making a small change: a really small change. Capitalizing on the unique properties of microscale systems, the students have invented a microreactor that converts everyday fossil fuels like propane and butane into pure hydrogen for fuel cell batteries. These batteries are not only highly efficient, but also can be replenished with hydrogen again and again for years of resilient performance in the field.

With soldiers carrying up to 80% of gear weight in batteries, the Army has a high interest in replacing the current paradigm of single-use batteries with a reliable, reusable power source. The Stevens-made microreactors thus have the potential to not only reduce waste from disposable batteries, but also provide American soldiers with a dependable way to recharge the batteries for the critical devices that keep them safe.

Current methods for generating fuel cell hydrogen are both sophisticated and risky, requiring high temperatures and a vacuum to produce the necessary chemical-reaction-causing plasmas. Once in a container, hydrogen is a highly volatile substance that is dangerous and expensive to transport.

The Stevens microreactor overcomes both of these barriers by using low temperatures and atmospheric pressure, and by producing hydrogen only as needed to avoid creating explosive targets in combat areas. These advanced reactors are created using cutting-edge microfabrication techniques, similar to those used to create plasma television screens, which use microscale physics to produce plasma under normal atmospheres.

The team has already had success producing hydrogen from methanol. After gasifying methanol by suspending it in hot nitrogen gas, the mixture is drawn into a 25µm channel in the microreactor. There, it reacts with plasma to cause thermal decomposition, breaking down the methanol into its elemental components. Now the team is conducting tests to see what kind of yields are realizable from various starter fuels. Eventually, soldiers will be able to convert everyday liquid fuels like propane or butane, commonly found on military bases, into high-potency juice for portable fuel cell batteries.

The team, made up of seniors Ali Acosta, Kyle Lazzaro, Randy Parrilla, and Andrew Robertson, are supporting Ph.D. candidate Peter Lindner in a research project sponsored by the U.S. Army. The project is overseen by Dr. Ronald Besser. The team will be presenting their device prototype at Senior Projects Expo on April 27.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Stevens Institute of Technology.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

'Swiss cheese' design enables thin film silicon solar cells with potential for higher efficiencies

ScienceDaily (May 8, 2011) — A bold new design for thin film solar cells that requires significantly less silicon -- and may boost their efficiency -- is the result of an industry/academia collaboration between Oerlikon Solar in Switzerland and the Institute of Physics' photovoltaic group at the Academy of Sciences of the Czech Republic.

One long-term option for low-cost, high-yield industrial production of solar panels from abundant raw materials can be found in amorphous silicon solar cells and microcrystalline silicon tandem cells (a.k.a. Micromorph) -- providing an energy payback within a year.

A drawback to these cells, however, is that the stable panel efficiency is less than the efficiency of presently dominate crystalline wafer-based silicon, explains Milan Vanecek, who heads the photovoltaic group at the Institute of Physics in Prague.

"To make amorphous and microcrystalline silicon cells more stable they're required to be very thin because of tight spacing between electrical contacts, and the resulting optical absorption isn't sufficient," he notes. "They're basically planar devices. Amorphous silicon has a thickness of 200 to 300 nanometers, while microcrystalline silicon is thicker than 1 micrometer."

The team's new design focuses on optically thick cells that are strongly absorbing, while the distance between the electrodes remains very tight. They describe their design in the American Institute of Physics' journal Applied Physics Letters.

"Our new 3D design of solar cells relies on the mature, robust absorber deposition technology of plasma-enhanced chemical vapor deposition, which is a technology already used for amorphous silicon-based electronics produced for liquid crystal displays. We just added a new nanostructured substrate for the deposition of the solar cell," Vanecek says.

This nanostructured substrate consists of an array of zinc oxide (ZnO) nanocolumns or, alternatively, from a "Swiss cheese" honeycomb array of micro-holes or nano-holes etched into the transparent conductive oxide layer (ZnO).

"This latter approach proved successful for solar cell deposition," Vanecek elaborates. "The potential of these efficiencies is estimated within the range of present multicrystalline wafer solar cells, which dominate solar cell industrial production. And the significantly lower cost of Micromorph panels, with the same panel efficiency as multicrystalline silicon panels (12 to 16 percent), could boost its industrial-scale production."

The next step is a further optimization to continue improving efficiency.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

Milan Vanecek, Oleg Babchenko, Adam Purkrt, Jakub Holovsky, Neda Neykova, Ales Poruba, Zdenek Remes, Johannes Meier, Ulrich Kroll. Nanostructured three-dimensional thin film silicon solar cells with very high efficiency potential. Applied Physics Letters, 2011; 98 (16): 163503 DOI: 10.1063/1.3583377

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

'Swiss cheese' design enables thin film silicon solar cells with potential for higher efficiencies

ScienceDaily (May 8, 2011) — A bold new design for thin film solar cells that requires significantly less silicon -- and may boost their efficiency -- is the result of an industry/academia collaboration between Oerlikon Solar in Switzerland and the Institute of Physics' photovoltaic group at the Academy of Sciences of the Czech Republic.

One long-term option for low-cost, high-yield industrial production of solar panels from abundant raw materials can be found in amorphous silicon solar cells and microcrystalline silicon tandem cells (a.k.a. Micromorph) -- providing an energy payback within a year.

A drawback to these cells, however, is that the stable panel efficiency is less than the efficiency of presently dominate crystalline wafer-based silicon, explains Milan Vanecek, who heads the photovoltaic group at the Institute of Physics in Prague.

"To make amorphous and microcrystalline silicon cells more stable they're required to be very thin because of tight spacing between electrical contacts, and the resulting optical absorption isn't sufficient," he notes. "They're basically planar devices. Amorphous silicon has a thickness of 200 to 300 nanometers, while microcrystalline silicon is thicker than 1 micrometer."

The team's new design focuses on optically thick cells that are strongly absorbing, while the distance between the electrodes remains very tight. They describe their design in the American Institute of Physics' journal Applied Physics Letters.

"Our new 3D design of solar cells relies on the mature, robust absorber deposition technology of plasma-enhanced chemical vapor deposition, which is a technology already used for amorphous silicon-based electronics produced for liquid crystal displays. We just added a new nanostructured substrate for the deposition of the solar cell," Vanecek says.

This nanostructured substrate consists of an array of zinc oxide (ZnO) nanocolumns or, alternatively, from a "Swiss cheese" honeycomb array of micro-holes or nano-holes etched into the transparent conductive oxide layer (ZnO).

"This latter approach proved successful for solar cell deposition," Vanecek elaborates. "The potential of these efficiencies is estimated within the range of present multicrystalline wafer solar cells, which dominate solar cell industrial production. And the significantly lower cost of Micromorph panels, with the same panel efficiency as multicrystalline silicon panels (12 to 16 percent), could boost its industrial-scale production."

The next step is a further optimization to continue improving efficiency.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

Milan Vanecek, Oleg Babchenko, Adam Purkrt, Jakub Holovsky, Neda Neykova, Ales Poruba, Zdenek Remes, Johannes Meier, Ulrich Kroll. Nanostructured three-dimensional thin film silicon solar cells with very high efficiency potential. Applied Physics Letters, 2011; 98 (16): 163503 DOI: 10.1063/1.3583377

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New algorithm offers ability to influence systems such as living cells or social networks

ScienceDaily (May 14, 2011) — At first glance, a diagram of the complex network of genes that regulate cellular metabolism might seem hopelessly complex, and efforts to control such a system futile.

However, an MIT researcher has come up with a new computational model that can analyze any type of complex network -- biological, social or electronic -- and reveal the critical points that can be used to control the entire system.

Potential applications of this work, which appears as the cover story in the May 12 issue of Nature, include reprogramming adult cells and identifying new drug targets, says study author Jean-Jacques Slotine, an MIT professor of mechanical engineering and brain and cognitive sciences.

Slotine and his co-authors applied their model to dozens of real-life networks, including cell-phone networks, social networks, the networks that control gene expression in cells and the neuronal network of the C. elegans worm. For each, they calculated the percentage of points that need to be controlled in order to gain control of the entire system.

For sparse networks such as gene regulatory networks, they found the number is high, around 80 percent. For dense networks -- such as neuronal networks -- it's more like 10 percent.

The paper, a collaboration with Albert-Laszlo Barabasi and Yang-Yu Liu of Northeastern University, builds on more than half a century of research in the field of control theory.

Control theory -- the study of how to govern the behavior of dynamic systems -- has guided the development of airplanes, robots, cars and electronics. The principles of control theory allow engineers to design feedback loops that monitor input and output of a system and adjust accordingly. One example is the cruise control system in a car.

However, while commonly used in engineering, control theory has been applied only intermittently to complex, self-assembling networks such as living cells or the Internet, Slotine says. Control research on large networks has been concerned mostly with questions of synchronization, he says.

In the past 10 years, researchers have learned a great deal about the organization of such networks, in particular their topology -- the patterns of connections between different points, or nodes, in the network. Slotine and his colleagues applied traditional control theory to these recent advances, devising a new model for controlling complex, self-assembling networks.

"The area of control of networks is a very important one, and although much work has been done in this area, there are a number of open problems of outstanding practical significance," says Adilson Motter, associate professor of physics at Northwestern University. The biggest contribution of the paper by Slotine and his colleagues is to identify the type of nodes that need to be targeted in order to control complex networks, says Motter, who was not involved with this research.

The researchers started by devising a new computer algorithm to determine how many nodes in a particular network need to be controlled in order to gain control of the entire network. (Examples of nodes include members of a social network, or single neurons in the brain.)

"The obvious answer is to put input to all of the nodes of the network, and you can, but that's a silly answer," Slotine says. "The question is how to find a much smaller set of nodes that allows you to do that."

There are other algorithms that can answer this question, but most of them take far too long -- years, even. The new algorithm quickly tells you both how many points need to be controlled, and where those points -- known as "driver nodes" -- are located.

Next, the researchers figured out what determines the number of driver nodes, which is unique to each network. They found that the number depends on a property called "degree distribution," which describes the number of connections per node.

A higher average degree (meaning the points are densely connected) means fewer nodes are needed to control the entire network. Sparse networks, which have fewer connections, are more difficult to control, as are networks where the node degrees are highly variable.

In future work, Slotine and his collaborators plan to delve further into biological networks, such as those governing metabolism. Figuring out how bacterial metabolic networks are controlled could help biologists identify new targets for antibiotics by determining which points in the network are the most vulnerable.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Massachusetts Institute of Technology. The original article was written by Anne Trafton, MIT News Office.

Journal Reference:

Yang-Yu Liu, Jean-Jacques Slotine, Albert-László Barabási. Controllability of complex networks. Nature, 2011; 473 (7346): 167 DOI: 10.1038/nature10011

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New algorithm offers ability to influence systems such as living cells or social networks

ScienceDaily (May 14, 2011) — At first glance, a diagram of the complex network of genes that regulate cellular metabolism might seem hopelessly complex, and efforts to control such a system futile.

However, an MIT researcher has come up with a new computational model that can analyze any type of complex network -- biological, social or electronic -- and reveal the critical points that can be used to control the entire system.

Potential applications of this work, which appears as the cover story in the May 12 issue of Nature, include reprogramming adult cells and identifying new drug targets, says study author Jean-Jacques Slotine, an MIT professor of mechanical engineering and brain and cognitive sciences.

Slotine and his co-authors applied their model to dozens of real-life networks, including cell-phone networks, social networks, the networks that control gene expression in cells and the neuronal network of the C. elegans worm. For each, they calculated the percentage of points that need to be controlled in order to gain control of the entire system.

For sparse networks such as gene regulatory networks, they found the number is high, around 80 percent. For dense networks -- such as neuronal networks -- it's more like 10 percent.

The paper, a collaboration with Albert-Laszlo Barabasi and Yang-Yu Liu of Northeastern University, builds on more than half a century of research in the field of control theory.

Control theory -- the study of how to govern the behavior of dynamic systems -- has guided the development of airplanes, robots, cars and electronics. The principles of control theory allow engineers to design feedback loops that monitor input and output of a system and adjust accordingly. One example is the cruise control system in a car.

However, while commonly used in engineering, control theory has been applied only intermittently to complex, self-assembling networks such as living cells or the Internet, Slotine says. Control research on large networks has been concerned mostly with questions of synchronization, he says.

In the past 10 years, researchers have learned a great deal about the organization of such networks, in particular their topology -- the patterns of connections between different points, or nodes, in the network. Slotine and his colleagues applied traditional control theory to these recent advances, devising a new model for controlling complex, self-assembling networks.

"The area of control of networks is a very important one, and although much work has been done in this area, there are a number of open problems of outstanding practical significance," says Adilson Motter, associate professor of physics at Northwestern University. The biggest contribution of the paper by Slotine and his colleagues is to identify the type of nodes that need to be targeted in order to control complex networks, says Motter, who was not involved with this research.

The researchers started by devising a new computer algorithm to determine how many nodes in a particular network need to be controlled in order to gain control of the entire network. (Examples of nodes include members of a social network, or single neurons in the brain.)

"The obvious answer is to put input to all of the nodes of the network, and you can, but that's a silly answer," Slotine says. "The question is how to find a much smaller set of nodes that allows you to do that."

There are other algorithms that can answer this question, but most of them take far too long -- years, even. The new algorithm quickly tells you both how many points need to be controlled, and where those points -- known as "driver nodes" -- are located.

Next, the researchers figured out what determines the number of driver nodes, which is unique to each network. They found that the number depends on a property called "degree distribution," which describes the number of connections per node.

A higher average degree (meaning the points are densely connected) means fewer nodes are needed to control the entire network. Sparse networks, which have fewer connections, are more difficult to control, as are networks where the node degrees are highly variable.

In future work, Slotine and his collaborators plan to delve further into biological networks, such as those governing metabolism. Figuring out how bacterial metabolic networks are controlled could help biologists identify new targets for antibiotics by determining which points in the network are the most vulnerable.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Massachusetts Institute of Technology. The original article was written by Anne Trafton, MIT News Office.

Journal Reference:

Yang-Yu Liu, Jean-Jacques Slotine, Albert-László Barabási. Controllability of complex networks. Nature, 2011; 473 (7346): 167 DOI: 10.1038/nature10011

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Cheaper hydrogen fuel cells: Utility of non-precious-metal catalysts documented

ScienceDaily (Apr. 25, 2011) — Los Alamos National Laboratory scientists have developed a way to avoid the use of expensive platinum in hydrogen fuel cells, the environmentally friendly devices that might replace current power sources in everything from personal data devices to automobiles.

In a paper published April 21 in Science, Los Alamos researchers Gang Wu, Christina Johnston, and Piotr Zelenay, joined by researcher Karren More of Oak Ridge National Laboratory, describe the use of a platinum-free catalyst in the cathode of a hydrogen fuel cell. Eliminating platinum -- a precious metal more expensive than gold -- would solve a significant economic challenge that has thwarted widespread use of large-scale hydrogen fuel cell systems.

Polymer-electrolyte hydrogen fuel cells convert hydrogen and oxygen into electricity. The cells can be enlarged and combined in series for high-power applications, including automobiles. Under optimal conditions, the hydrogen fuel cell produces water as a "waste" product and does not emit greenhouse gasses. However, because the use of platinum in catalysts is necessary to facilitate the reactions that produce electricity within a fuel cell, widespread use of fuel cells in common applications has been cost prohibitive. An increase in the demand for platinum-based catalysts could drive up the cost of platinum even higher than its current value of nearly $1,800 an ounce.

The Los Alamos researchers developed non-precious-metal catalysts for the part of the fuel cell that reacts with oxygen. The catalysts -- which use carbon (partially derived from polyaniline in a high-temperature process), and inexpensive iron and cobalt instead of platinum -- yielded high power output, good efficiency, and promising longevity. The researchers found that fuel cells containing the carbon-iron-cobalt catalyst synthesized by Wu not only generated currents comparable to the output of precious-metal-catalyst fuel cells, but held up favorably when cycled on and off -- a condition that can damage inferior catalysts relatively quickly.

Moreover, the carbon-iron-cobalt catalyst fuel cells effectively completed the conversion of hydrogen and oxygen into water, rather than producing large amounts of undesirable hydrogen peroxide. Inefficient conversion of the fuels, which generates hydrogen peroxide, can reduce power output by up to 50 percent, and also has the potential to destroy fuel cell membranes. Fortunately, the carbon- iron-cobalt catalysts synthesized at Los Alamos create extremely small amounts of hydrogen peroxide, even when compared with state-of-the-art platinum-based oxygen-reduction catalysts.

Because of the successful performance of the new catalyst, the Los Alamos researchers have filed a patent for it.

"The encouraging point is that we have found a catalyst with a good durability and life cycle relative to platinum-based catalysts," said Zelenay, corresponding author for the paper. "For all intents and purposes, this is a zero-cost catalyst in comparison to platinum, so it directly addresses one of the main barriers to hydrogen fuel cells."

The next step in the team's research will be to better understand the mechanism underlying the carbon-iron-cobalt catalyst. Micrographic images of portions of the catalyst by researcher More have provided some insight into how it functions, but further work must be done to confirm theories by the research team. Such an understanding could lead to improvements in non-precious-metal catalysts, further increasing their efficiency and lifespan.

Project funding for the Los Alamos research came from the U.S. Department of Energy's Energy Efficiency and Renewable Energy (EERE) Office as well as from Los Alamos National Laboratory's Laboratory-Directed Research and Development program. Microscopy research was done at Oak Ridge National Laboratory's SHaRE user facility with support from the DOE's Office of Basic Energy Sciences.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Los Alamos National Laboratory.

Journal Reference:

G. Wu, K. L. More, C. M. Johnston, P. Zelenay. High-Performance Electrocatalysts for Oxygen Reduction Derived from Polyaniline, Iron, and Cobalt. Science, 2011; 332 (6028): 443 DOI: 10.1126/science.1200832

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here