Low Elevations Hold Climate Surprises for Mountain Plants

Ellen Damschen of the University of Wisconsin-Madison (left) makes notes as a research team surveys mountain plants.
Contrary to expectations, climate change has had a significant effect on mountain plants at low elevations, says a new study led by a UC Davis researcher.
The information could guide future conservation efforts at local scales by helping decision makers anticipate biological responses to climate changes, said lead author Susan Harrison, a UC Davis professor of environmental science and policy.
Harrison and scientists from the University of Wisconsin-Madison and the U.S. Geological Survey examined vegetation changes during the past 60 years in the Siskiyou Mountains of Oregon.
They found signs of increased drought stress in the low-elevation forests (1,650 to 4,000 feet), but not at high elevations (4,100 to 6,900 feet). Climate change appeared to affect both logged and unlogged forests at low elevations similarly.
"We were surprised to find such clear signals of climate change in these plant communities, given all the other ecological changes that may be going on in the region, such as logging and fire suppression," Harrison said.
The study was published online Oct. 25 in the Proceedings of the National Academy of Sciences.
It was funded by the National Science Foundation and by the U.S. Geological Survey Global Climate Change Program.

Papyrus Research Provides Insights Into 'Modern Concerns' of Ancient World

UC's Peter Van Minnen, editor of the Bulletin of the American Society of Papyrologists.
A University of Cincinnati-based journal devoted to research on papyri is due out Nov. 1. That research sheds light on an ancient world with surprisingly modern concerns: including hoped-for medical cures, religious confusion and the need for financial safeguards.
What's old is new again. That's the lesson that can be taken from the University of Cincinnati-based journal Bulletin of the American Society of Papyrologists, due out Nov. 1.
The annually produced journal, edited since 2006 by Peter van Minnen, UC associate professor of classics, features the most prestigious global research on papyri, a field of study known as papyrology. (Papyrology is formally known as the study of texts on papyrus and other materials, mainly from ancient Egypt and mainly from the period of Greek and Roman rule.)
It's an area of research that is more difficult than you might think. That's because it was common among antiquities dealers of the early 20th century to tear papyri pages apart in order to increase the number of pieces they could sell.
Below are five topics treated in the upcoming 2010 volume of the Bulletin of the American Society of Papyrologists. The five issues resonate with our own concerns today.
IOU cabbage
Katherine Blouin from the University of Toronto publishes on a papyrus text regarding a Greek loan of money with interest in kind, the interest being paid in cabbages. Such in-kind interest protected the lender from currency inflation, which was rampant after 275 AD -- and no doubt also provided a convenient way to get groceries.
Hippo strapped for cash
Cavan Concannon from Harvard University edits a Greek letter in which a priest of the hippopotamus goddess, Thoeris, asks for a money transfer he is waiting for. Such money transfers were for large amounts and required mutual cooperation between two banks in different places that had sufficient trust between them to accept one another's "checks."
"American Gladiators" ca. 300 AD
Sofie Remijsen of Leuven University in Belgium discusses a Greek letter in which the author details his visit to Alexandria in Egypt, at a time (ca. 300 AD) when the Roman Emperor Diocletian was also visiting the city -- and demanding entertainment. The letter's author, an amateur athlete, was selected to entertain the emperor in "pankration" (Greco-Roman wrestling with very few rules). He did poorly in this event and so challenged five others to do "pammachon," which literally translates to "all-out fight," with even fewer rules. The letter's author fought five "pammachon" rounds, and it appears he won first prize.
Alternative medicine: Don't try this at home
Magali de Haro Sanchez from Liège University in Belgium discusses magical texts from Greco-Roman Egypt that use technical terms for fevers (over 20), wounds, including scorpion bites and epilepsy. The "prescriptions" (magical spells) were as difficult-to-decipher as any written in modern medical scrawl. Here is a translation of an amulet against epilepsy written on gold leaf: "God of Abraham, God of Isaac, God of Jacob, our God, deliver Aurelia from every evil spirit and from every attack of epilepsy, I beg you, Lord Iao Sabaoth Eloai, Ouriel, Michael, Raphael, Gabriel, Sarael, Rasochel, Ablanathanalba, Abrasax, xxxxxx nnnnnn oaa iiiiiiiiii x ouuuuuuu aoooooooo ono e (cross) e (cross) Sesengenbarpharanges, protect, Ippho io Erbeth (magical symbols), protect Aurelia from every attack, from every attack, Iao, Ieou, Ieo, Iammo, Iao, charakoopou, Sesengenbarpharanges, Iao aeeuuai, Ieou, Iao, Sabaoth, Adonai, Eleleth, Iako."
Spelling counts: Orthodoxy and orthography in early Christianity
An essay by William Shandruk from the University of Chicago examines the ways in which Christ and Christian are spelled in Greek papyri. Chrestos, which was pronounced the same way as Christos, was a common slave name meaning "good" or "useful." Confused by this, representatives of the Roman government often misspelled Christ's name "Chrestos" instead of "Christos" meaning "anointed" or "messiah." They also called the early followers of Christ "Chrestianoi" rather than "Christianoi." The early Christians themselves went with the Romans here and often spelled their own name "Chrestianoi," but they stuck to the correct spelling "Christos" for Christ's name.

Organic Solvent System May Improve Catalyst Recycling and Create New Nanomedicine Uses

Rongwei Zhang holds a gold/organic aqua regia solution while Wei Lin holds a silicon substrate coated with 200-nanometer gold. The image on the monitor shows gold recovered from the solution using calcinations.
Noble metals such as platinum and palladium are becoming increasingly important because of growth in environmentally friendly applications such as fuel cells and pollution control catalysts. But the world has limited quantities of these materials, meaning manufacturers will have to rely on efficient recycling processes to help meet the demand.
Existing recycling processes use a combination of two inorganic acids known as "aqua regia" to dissolve noble metals, a class of materials that includes platinum, palladium, gold and silver. But because the metals are often dissolved together, impurities introduced in the recycling process may harm the efficiency of catalysts produced from the recycled materials. Now, researchers at the Georgia Institute of Technology have developed a new organic solvent process that may help address the problem -- and open up new possibilities for using these metals in cancer therapeutics, microelectronics and other applications.
The new Georgia Tech solvent system uses a combination of two chemicals -- thionyl chloride and a variety of organic reagents such as pyridine, N,N-dimethylformamide (DMF), pyrimidine or imidazole. The concentrations can be adjusted to preferentially dissolve gold or palladium, and more importantly, no combination of the organic chemicals dissolves platinum. This ability to preferentially dissolve noble metals creates a customized system that provides a high level of control over the process.
"We need to be able to selectively dissolve these noble metals to ensure their purity in a variety of important applications," said C.P. Wong, a Regents professor in the Georgia Tech School of Materials Science and Engineering. "Though we don't fully understand how it works yet, we believe this system opens a lot of new possibilities for using these metals."
A paper describing the research was published recently in the journal Angewandte Chemie.
Catalyst systems that make use of more than one metal, such as palladium with a gold core, are becoming more widely used in industrial processes. To recycle those, the new solvent system -- dubbed "organic aqua regia" -- could first use a combination of thionyl chloride and DMF to dissolve out the gold, leaving hollow palladium spheres. Then the palladium spheres could be dissolved using a different combination.
So far, the researchers have demonstrated that the solvent system can selectively dissolve gold and palladium from a mixture of gold, palladium and platinum. They have also used it to remove gold from a mixture of gold and palladium.
Beyond recycling, the new solvent system could also provide new ways of producing nanometer-scale cancer chemotherapy agents that involve these metals. And the new solvent approach could have important implications for the electronics industry, which uses noble metals that must often be removed after specific processing steps. Beyond selectivity, the new approach also offers other advantages for electronics manufacturing -- no potentially harmful contamination is left behind and processing is done under mild conditions.
"In semiconductor production, people want to avoid having a metal catalyst remaining in devices, but in many cases, they cannot use existing water-based processes because these can damage the semiconductor oxides and introduce contamination with free ions in the aqueous solution," explained Wei Lin, a graduate research assistant in Wong's laboratory. "Use of this organic system avoids the problem of moisture."
Use of the selective process could also facilitate recycling of noble metals used in electronics manufacturing. Wire-bonding, metallization and interconnect processes currently use noble metals.
Noble metals are also the foundation for widely-used chemotherapy agents, but the chemistry of synthesizing them involves a complex process of surfactants and precursors. Wong believes the new Georgia Tech solvent process may allow creation of novel compounds that could offer improved therapeutic effects.
"We hope this will open up some new ways of making these important pharmaceutical compounds as well as novel gold and palladium catalytic systems," he said.
Lin discovered the new solvent system by accident in 2007 while using thionyl chloride in an unrelated project that involved bonding carbon nanotubes to a gold substrate. "I left my sample in the solution and went to lunch," he recalled. "Then I received a couple of phone calls and the sample stayed in the solution for too long. When I got it out, the gold was gone."
The researchers were intrigued by the discovery and pursued an explanation as they had time over the past three years. They tested other reagents mixed with the thionyl chloride, and learned the proportions necessary for selective dissolution of palladium and gold. They worked with other researchers at Georgia Tech, including nanotechnology pioneer Zhong Lin Wang, to develop a fundamental understanding of the process -- research that is continuing.
The chemicals used by the Georgia Tech research team are well known in organic chemistry, and are used today in polymer synthesis. Beyond their selectivity, the new solvent system is more environmentally friendly than traditional aqua regia -- which is a combination of concentrated nitric and hydrochloric acids -- and can operate at mild conditions. Potential disadvantages compared to traditional aqua regia include higher costs and slower dissolution rates.
"We have opened up a new approach to noble metals using organic chemistry," Wong added. "We don't yet thoroughly understand the mechanism by which this works, but we hope to develop a more complete understanding that may lead to additional applications."
In addition to those already mentioned, the research team included Rong-Wei Zhang, Seung-Soon Jang and Jung-Il Hong, all from the School of Materials Science and Engineering at Georgia Tech.

Tracking Evidence of 'The Great Dying'

After massive erosion, runaway microbes depleted oceanic oxygen
More than 251 million years ago, at the end of the Permian period, Earth almost became a lifeless planet. Around 90 percent of all living species disappeared then, in what scientists have called "The Great Dying."
Thomas J. Algeo, has spent much of the past decade investigating the chemical evidence buried in rocks formed during this major extinction. The University of Cincinnati professor of geology has worked with a team of scientific colleagues to understand the ancient catastrophe. Algeo will present his latest findings at the annual meeting of the Geological Society of America, Oct. 31 to Nov. 3, in Denver.
The world revealed by Algeo's research sounds horrific and alien -- a devastated landscape, barren of vegetation, scarred by erosion from showers of acid rain, huge "dead zones" in the oceans and runaway greenhouse gases leading to sizzling temperatures. This was Earth, 251 million years ago.
The more famous "K-T" extinction between the Cretaceous and Tertiary periods -- in which the dinosaurs went extinct -- was triggered by a large meteoroid or bolide striking the Earth. The Great Dying, between the Permian and Triassic periods, has another culprit.
"The Permian-Triassic extinction event is still not fully understood," Algeo said. "It took some time, but it finally dawned on the geologic community that this was not caused by a bolide."
Algeo and his colleagues from around the world are building a better understanding of the events that all but erased life from our planet. The work involves five principal investigators in addition to Algeo. The National Science Foundation has provided several substantial grants to support the research.
The evidence Algeo and his colleagues are looking at points to massive volcanism in Siberia. A large portion of western Siberia reveals volcanic deposits five kilometers (three miles) thick, covering an area equivalent to the continental United States.
"It was a massive outpouring of basaltic lava," Algeo said. And, the lava flowed where it could most endanger life, through a large coal deposit.
Algeo noted that the dinosaur-killing bolide was lethal because it vaporized sulfur-rich sediments, resulting in extremely acidic rainfall. The effects of the Siberian lava eruption were likewise amplified by the coal deposit.
"The eruption released lots of methane when it burned through the coal," he said. "Methane is 30 times more effective as a greenhouse gas than carbon dioxide. We're not sure how long the greenhouse effect lasted, but it seems to be thousands of years, maybe tens of thousands of years."
A lot of the evidence ended up being washed into the ocean, and that is where Algeo and his colleagues look for it. Today, those oceanic deposits are found in Canada, China, Vietnam, Pakistan, India, Spitsbergen and Greenland.
In Denver, Algeo, with Margaret Fraiser of the University of Wisconsin-Milwaukee, will chair a session on "New Developments in Permian-Triassic Paleoceanography" to review some of the newly analyzed evidence. For this session, Algeo contributed to two presentations that suggest the Siberian lava eruption may not have been the only agent of global death during the late Permian.
An analysis of the carbon content of marine sediments at 33 locations around the world shows similar patterns, except for rocks now preserved in southern China. While most rocks deposited during the extinction show increased concentrations of total organic carbon and higher organic carbon accumulation rates, the Chinese samples show the opposite effect.
"It's probable that we're seeing evidence of an explosive regional volcanic eruption," Algeo said. "The sediments there are just sterilized. It may be that the combined effects of this local volcanism and global climate change were especially lethal."
Algeo will also present research on the conditions leading to oxygen depletion in the oceans during the late Permian. Warm global climates certainly played a part as uniformly hot conditions stifled turnover by ocean currents. However, Algeo believes that chemical weathering by acid rain and similar processes also contributed. When erosion seven times the normal rate sent large flows of nutrients into the ocean, it created conditions much like the over-fertilization we see today near the outlets of large rivers. As it does today, this condition led to a microbial feeding frenzy and the removal of oxygen -- and life -- from the late Permian ocean.
"If there is a lesson to all this," Algeo said, "it is a reminder that things can get out of whack pretty quickly and pretty seriously. We are used to a stable world, but it may not always be so stable."

Speed Gun for Earth's Insides to Help Measure Mantle Motion

"This study focusses on a mysterious layer where the mantle meets the core, a sphere of iron at the centre of the Earth 7,000 km (4400 miles) across. This part just above the core has curious properties which we can measure using seismic waves that pass through it,"
Researchers at the University of Bristol have reveal in the journal Nature that they have developed a seismological 'speed gun' for the inside of Earth. Using this technique they will be able to measure the way Earth's deep interior slowly moves around. This mantle motion is what controls the location of our continents and oceans, and where the tectonic plates collide to shake the surface we live on.
For 2,900 km (1800 miles) beneath our feet, Earth is made of the rocky mantle. Although solid, it is so hot that it can flow like putty over millions of years. It is heated from below, so that it circulates like water on a stove. While geophysicists know something about how the material moves by the time it reaches the top of the mantle, what goes on at the bottom is still a puzzle. However researchers need to know both to predict how the Earth's surface -- our home -- will behave.
Andy Nowacki, at the School of Earth Sciences at Bristol University, explained: "The only way to measure the inside of the Earth at such huge depths is with seismic waves. When a large earthquake occurs and waves travel through the Earth, they are affected in different ways, and we can examine their properties to work out what is happening thousands of miles beneath our feet, a region where we can never go. This study focusses on a mysterious layer where the mantle meets the core, a sphere of iron at the centre of the Earth 7,000 km (4400 miles) across. This part just above the core has curious properties which we can measure using seismic waves that pass through it."
This enigmatic part of Earth is known as D″ (pronounced 'dee-double-prime'). Dr James Wookey said: "We believe that D″ is made from crystals which line up in a certain orientation when the mantle flows. We can measure how they line up, and in this study we do this for one part of the world -- North and Central America. In the future our method can then be used to see which direction the mantle is moving everywhere."
Professor Mike Kendall added: "This part of the Earth is incredibly important. The lowermost mantle is where two colossal, churning engines -- the mantle and the core -- meet and interact. The core is moving very quickly and creates our magnetic field which protects us from the Sun's rays. The mantle above is sluggish, but drives the motion of the plates on the Earth's surface, which build mountains, feed volcanoes and cause earthquakes. Measuring the flow in the lowermost mantle is vital to understanding the long term evolution of the Earth."

Everything Evaporates, but How?

A group of scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences, headed by Prof. Robert HoByst (above), developed a new theoretical model describing water evaporation.
Evaporation is a common phenomenon in nature. For the last 130 years, it has seemed that its mechanism was understood well. However, computer simulations carried out by scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences proved that the existing theoretical models were based on false assumptions. Thanks to the simulations, it was possible to learn the mechanisms of evaporation of drops into vacuum or into an environment filled with the vapour of a liquid under examination. However, the mechanism that plays a key role in the case of evaporation into a mixture of gases, for instance into air, is still unknown.
Evaporation takes place all the time in our environment. The phenomenon plays an important role in the formation of Earth's ecosystem and the life functions of many organisms -- including humans, who like many other animals use it to stabilise their body temperature.
"The first scientific publication concerning the mechanism of evaporation was written by a famous physicist James Clerk Maxwell. We showed that it contained an error that has been repeated for the last 130 years," says Prof. Robert Hołyst from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw. The computer simulations that have just been completed allowed some of the puzzles connected with the evaporation of a liquid into vacuum or its own vapour to be solved. Currently, in cooperation with the Institute of Physics of the PAS, scientists from the IPC PAS are preparing a series of experiments that will allow them to verify the correctness of the model in the case of the evaporation of drops of water into air.
As much as 71% of Earth is covered by oceans and seas which evaporate continuously. Since the heat of evaporation of water is very high, the evaporation determines Earth's climate. What is more, the content of water vapour -- the main greenhouse gas -- in the atmosphere changes as a result of evaporation. Its concentration in air may reach as much as four per cent, that is the value over one hundred times higher than that of the infamous carbon dioxide. According to various estimates, if there was no water vapour in air, the temperature on Earth would fall by 20-30 degrees.
Although evaporation is so common and it plays a big role in the environment, little attention has been given to the phenomenon. "Our studies also originated accidentally, as it often happens in science," says Prof. Hołyst. "Several years ago, in the Institute of Physical Chemistry of the PAS, it was necessary to test a new program for calculations relating to fluid dynamics. We decided to check the simulator using a popular problem. We chose evaporation because we thought that since the phenomenon was so common and the subject was known for over one hundred years, everybody knew well what happened during the process. However, after we had made calculations using the existing formulas, it turned out that many things simply did not add up."
Polish scientists developed their own theoretical model of the phenomenon and then carried out computer simulations illustrating the process of evaporation of nanodrops into their own vapour or vacuum. The starting point was a drop of liquid closed in a vessel, and in equilibrium with its vapour. In some computer simulations the walls were heated, in some others the vapour was removed, and in the others not only was the vapour removed but the temperature of the system was maintained constant.
During evaporation the most interesting events take place on the border of a liquid and a vapour. The thickness of this interface is more or less equal to the diameter of an atom. The simulation of evaporation in a relatively small cube with faces one meter long would require the calculation of dozens of milliards of points along each of the three dimensional axes. The total number of points would increase to billion of trillions, which exceeds calculation abilities of modern and future computers. In order to deal with this obstacle, scientists from the Institute of Physical Chemistry of the PAS analysed the system of a size of only 1 cm, in which a drop of a diameter of approx. 70 micrometers evaporated. In addition, thanks to the use of symmetry, it was possible to reduce the theoretical description from three-dimensional to one-dimensional. The results of simulation agreed perfectly with the available measurement data.
"Maxwell assumed that evaporation took place at constant temperature. It is so, if we look at the initial state, that is a liquid, and the final state, that is a vapour. It is true that their temperatures are equal. But during the evaporation process itself, the nature acts in a completely different way," explains Ph.D. Marek Litniewski from IPC PAS.
The existing description assumed that the heat transfer in the system was stable and the rate of evaporation was limited by the efficiency of the process during which the particles break away from the surface of drops, i.e. diffusion. However, the simulation carried out in the IPC PAS showed that during the evaporation into vacuum or the liquid's own vapour the system gained mechanical equilibrium very quickly. Particles break away from the surface of a liquid and their mechanical recoil allows the equalisation of the pressure inside the drop. If the rate of evaporation on the surface achieved the maximum value and the system was still unable to equalise the pressures, spaces with new surfaces would open inside the drop and it would start to boil. However, it was observed that the mechanical equilibration of pressure can be insufficient and the temperature on the surface of the liquid decreases: the drop aims at maintaining the pressure equilibrium at the cost of its internal energy. This observation suggests that the factor that is crucial during evaporation is not the diffusion of particles into the environment but the heat transfer and the equality of pressures.
The studies will continue, this time from the point of view of the analysis of evaporation into the mixture of gases, in particular into air. The experimental part will be carried out by scientists from the Institute of Physics of the PAS (IP PAS), headed by Assoc. Prof. Krystyna Kolwas. Physicists from the IP PAS have already observed the evaporation of microdrops of a liquid into the liquid's own vapour or vacuum. Drops of micrometric sizes were used in the experiments. Since their surface was electrically charged, the drops could be caught by the electric field, lighted by a laser and, while recording changes in interference patterns, it could be observed how their size changed during the evaporation.
Currently, thanks to a new measurement chamber with precisely controlled pressure and chemical composition of the atmosphere, a series of experiments on evaporation into air can be conducted, and consequently, it will be possible to determine which factor has a decisive influence on evaporation in the situation where pressures are equalised from the beginning. The results of the experiments along with computer simulations will allow creating a comprehensive picture of the process of evaporation of water drops in the conditions maximally similar to those that exist in nature.
The deeper understanding of physical mechanisms responsible for evaporation will affect many areas of human activity. Better climate models will allow more precise forecast of weather changes in a short and long time perspective, and more efficient devices for cooling processors and lasers will be developed. Since in engines the evaporation of fuel microdrops injected into a combustion chamber must precede the ignition, the knowledge of evaporation will allow increasing car efficiency in future.

Water Could Hold Answer to Graphene Nanoelectronics

Researchers at Rensselaer Polytechnic Institute developed a new method for using water to tune the band gap of the nanomaterial graphene, opening the door to new graphene-based transistors and nanoelectronics. In this optical micrograph image, a graphene film on a silicon dioxide substrate is being electrically tested using a four-point probe.
Researchers at Rensselaer Polytechnic Institute developed a new method for using water to tune the band gap of the nanomaterial graphene, opening the door to new graphene-based transistors and nanoelectronics.
By exposing a graphene film to humidity, Rensselaer Professor Nikhil Koratkar and his research team were able to create a band gap in graphene -- a critical prerequisite to creating graphene transistors. At the heart of modern electronics, transistors are devices that can be switched "on" or "off" to alter an electrical signal. Computer microprocessors are comprised of millions of transistors made from the semiconducting material silicon, for which the industry is actively seeking a successor.
Graphene, an atom-thick sheet of carbon atoms arranged like a nanoscale chain-link fence, has no band gap. Koratkar's team demonstrated how to open a band gap in graphene based on the amount of water they adsorbed to one side of the material, precisely tuning the band gap to any value from 0 to 0.2 electron volts. This effect was fully reversible and the band gap reduced back to zero under vacuum. The technique does not involve any complicated engineering or modification of the graphene, but requires an enclosure where humidity can be precisely controlled.
"Graphene is prized for its unique and attractive mechanical properties. But if you were to build a transistor using graphene, it simply wouldn't work as graphene acts like a semi-metal and has zero band gap," said Koratkar, a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer. "In this study, we demonstrated a relatively easy method for giving graphene a band gap. This could open the door to using graphene for a new generation of transistors, diodes, nanoelectronics, nanophotonics, and other applications."
Results of the study were detailed in an article recently published by the journal Small.
In its natural state, graphene has a peculiar structure but no band gap. It behaves as a metal and is known as a good conductor. This is compared to rubber or most plastics, which are insulators and do not conduct electricity. Insulators have a large band gap -- an energy gap between the valence and conduction bands -- which prevents electrons from conducting freely in the material.
Between the two are semiconductors, which can function as both a conductor and an insulator. Semiconductors have a narrow band gap, and application of an electric field can provoke electrons to jump across the gap. The ability to quickly switch between the two states -- "on" and "off" -- is why semiconductors are so valuable in microelectronics.
"At the heart of any semiconductor device is a material with a band gap," Koratkar said. "If you look at the chips and microprocessors in today's cell phones, mobile devices, and computers, each contains a multitude of transistors made from semiconductors with band gaps. Graphene is a zero band gap material, which limits its utility. So it is critical to develop methods to induce a band gap in graphene to make it a relevant semiconducting material."
The symmetry of graphene's lattice structure has been identified as a reason for the material's lack of band gap. Koratkar explored the idea of breaking this symmetry by binding molecules to only one side of the graphene. To do this, he fabricated graphene on a surface of silicon and silicon dioxide, and then exposed the graphene to an environmental chamber with controlled humidity. In the chamber, water molecules adsorbed to the exposed side of the graphene, but not on the side facing the silicon dioxide. With the symmetry broken, the band gap of graphene did, indeed, open up, Koratkar said. Also contributing to the effect is the moisture interacting with defects in the silicon dioxide substrate.
"Others have shown how to create a band gap in graphene by adsorbing different gasses to its surface, but this is the first time it has been done with water," he said. "The advantage of water adsorption, compared to gasses, is that it is inexpensive, nontoxic, and much easier to control in a chip application. For example, with advances in micro-packaging technologies it is relatively straightforward to construct a small enclosure around certain parts or the entirety of a computer chip in which it would be quite easy to control the level of humidity."
Based on the humidity level in the enclosure, chip makers could reversibly tune the band gap of graphene to any value from 0 to 0.2 electron volts, Korarkar said.
This study was supported by the Advanced Energy Consortium (AEC), National Institute of Standards and Technology (NIST) Nanoelectronics Research Initiative, and the U.S. Department of Energy Office of Basic Energy Sciences (BES).

North Sea Oil Recovery Using Carbon Dioxide Is Possible, but Time Is Running Out, Expert Says

There is potential for CO₂ transfer from the industrial centers on the UK's eastern seaboard to the oilfields and saline aquifers of the North Sea.
Oil recovery using carbon dioxide could lead to a North Sea oil bonanza worth £150 billion ($240 billion) -- but only if the current infrastructure is enhanced now, according to a new study published by a world-leading energy expert.
A new calculation by Durham University of the net worth of the UK oil field shows that using carbon dioxide (CO₂) to enhance the recovery from our existing North Sea oil fields could yield an extra three billion barrels of oil over the next 20 years. Three billion barrels of oil could power, heat and transport the UK for two years with every other form of energy switched off.
Importantly, at a time of rising CO₂ emissions, the enhanced oil recovery process is just about carbon neutral with as much carbon being put back in the ground as will be taken out.
The technique could yield an enormous amount of oil revenue at a time of public service cuts and developing the infrastructure would put the UK in the driving seat for developing enhanced recovery off-shore oil production around the world. It would also allow the UK to develop its carbon storage techniques in line with the UK government's commitments on emissions reductions.
The study, funded by DONG Energy (UK) Ltd. and Ikon Science Ltd., will be presented Oct. 14, 2010, at a conference on Carbon Capture and Storage (CCS), at the Institution of Mechanical Engineers, London. The new figures are conservative estimates and extend a previous calculation that predicted a 2.7 billion barrel yield from selected fields in the North Sea.
The UK Government's Energy Statement, published in April 2010, outlines the continued role that fossil fuels will have to play in the UK energy mix. CO₂ enhanced oil recovery in the UK would secure supplies for the next 20 years.
Jon Gluyas, a Professor in CCS & Geo-Energy, Department of Earth Sciences, Durham University, who has calculated the new figures, said: "Time is running out to make best use of our precious remaining oil reserves because we're losing vital infrastructure as the oil fields decline and are abandoned. Once the infrastructure is removed, we will never go back and the opportunity will be wasted.
"We need to act now to develop the capture and transportation infrastructure to take the CO₂ to where it is needed. This would be a world-leading industry using new technology to deliver carbon dioxide to the North Sea oil fields. We must begin to do this as soon as possible before it becomes too expensive to do so.
"My figures are at the low end of expectations but they show that developing this technology could lead to a huge rejuvenation of the North Sea. The industrial CO₂ output from Aberdeen to Hull is all you need to deliver this enhanced oil recovery."
Carbon dioxide is emitted into the atmosphere when fossil fuels are burnt and the UK Government plans to collect it from power stations in the UK. Capturing and storing carbon dioxide is seen as a way to prevent global warming and ocean acidification. Old oil and gas fields, such as those in the North Sea, are considered to be likely stores.
Enhanced oil recovery using carbon dioxide (CO₂ EOR) adds further value to the potential merits of CCS.
Oil is usually recovered by flushing oil wells through with water at pressure. Since the 1970s oil fields in West Texas, USA, have been successfully exploited using carbon dioxide. CO₂ is pumped as a fluid into oil fields at elevated pressure and helps sweep the oil to the production wells by contacting parts of the reservoirs not accessed by water injection; the result is much greater oil production.
Experience from the USA shows that an extra four to twelve per cent of the oil in place can be extracted using CO₂-EOR. Professor Gluyas calculated the total oil in place in the UK fields and the potential UK gain in barrels and revenue from existing reserves using the American model.
David Hanstock, a founding director of Progressive Energy and director of COOTS Ltd, which is developing an offshore CO₂ transport and storage infrastructure in the North Sea, said: "The UK has significant storage capacity potential for captured carbon dioxide in North sea oil and gas fields.
"There is a unique opportunity to develop a new offshore industry using our considerable experience in offshore engineering. This would give us a technical lead on injecting and monitoring CO₂ that we could then export to the wider world to establish the UK as a world leader in carbon capture and storage technology."
Professor Gluyas added: "Enhanced recovery of oil in the North Sea oil fields can secure our energy supplies for the next fifty years. The extra 3 billion barrels of oil that could be produced by enhanced CO₂ recovery would make us self sufficient and would add around £60bn in revenue to the Treasury.
"Priming the system now would mean we have 10-15 years to develop CO₂ recycling and sufficient time to help us bridge to a future serviced by renewable energy."