How Lead Gets Into Urban Vegetable Gardens

If you're a vegetable gardener in a lot of older cities, there's a fair chance you have a significant amount of lead in your soil. One common mitigation approach is to build a raised bed and fill it with freshly composted, low-lead soil from elsewhere, right? Maybe not, according to researchers studying the mysterious case of the lead contamination found within raised beds in community gardens in the Boston communities of Roxbury and Dorchester.
"Raised beds are surrounded by a sea of contaminated soil," said Daniel Brabander of Wellesley College. Brabander, his students and colleagues have been studying the lead in 144 backyard gardens in coordination with The Food Project, an organization committed to food security, nutrition and sustainable urban agriculture. Eighty-one percent of the gardens they studied were found to have lead levels above the U.S. EPA limits of 400 micrograms of lead per gram (µg/g) of soil.
To solve that problem, raised wooden beds with freshly composted soil were installed in backyard and community gardens by the Food Project. But the researchers have found that the soil in raised beds that starts with as little as 110 micrograms of lead per gram of soil rose to an average of 336 µg/g of lead in just four years.
Just how this is happening is the focus of a Nov. 1 presentation by Emily Estes at the meeting of the Geological Society of America in Denver.
"We're trying to get a better handle on the mode of transport and the source," said Estes. That means some pretty detailed monitoring and chemical analyses of the minerals in the soils as well as the kind of lead that's in the soil.
Lead contamination in most cities comes from primarily two sources: leaded gasoline and lead paint. Although both sources have been banned, plenty of that lead remains in urban soils all around the raised bed gardens. Roxbury and Dorchester soils have a lot of lead, but they are not unique.
"It's more elevated than similar neighborhoods, but not unlike other cities," said Estes.
"On the East Coast, where cities are a bit older, it's more of a problem," said Brabander. And even within a city the lead contamination can vary significantly, he said, depending on historical traffic patterns and even such very local effects like a house containing lead paint burning down on a lot that is later used for gardening.
The main suspects in transporting lead into raised beds are wind and perhaps rain, which splatters the ground and can potentially throw fine particles of contaminated soil into the raised beds.
The good news in Roxbury and Dorchester is that the kinds of lead being found are not particularly good at being absorbed by the human body, said Estes. There's also a relatively simple and inexpensive way to keep the lead out of raised beds: just scoop away the top inch or two of soil every year from a raised bed and properly dispose of it, according to local regulations.
This research is funded by a Brachman-Hoffman Fellowship that supports new scientific research directions among faculty at Wellesley College.

Unique Duality: 'Exotic' Superconductor With Metallic Surface Discovered

A new material with a split personality -- part superconductor, part metal -- has been observed by a Princeton University-led research team. The discovery may have implications for the development of next-generation electronics that could transform the way information is stored and processed.
The new material -- a crystal called a topological superconductor -- has two electronic identities at once. At very low temperatures, the interior of the crystal behaves like a normal superconductor, able to conduct electricity with zero resistance. At the same time, the surface is metallic, able to carry a current, albeit with some resistance.
This is in direct contrast to most existing materials that are classified as electronic states of matter, including metals, insulators and conventional superconductors, which are consistent in how they do, or don't, conduct electricity. For example, every single atom of every single copper wire is able to carry a current, which dissipates a bit as it travels. Similarly, all the molecules in normal superconductors conduct electricity without resistance when the material is placed at the appropriate temperature.
"The known states of electronic matter are insulators, metals, magnets, semiconductors and superconductors, and each of them has brought us new technology," said M. Zahid Hasan, an associate professor of physics at Princeton who led the research team. "Topological superconductors are superconducting everywhere but on the surface, where they are metallic; this leads to many possibilities for applications."
Hasan and his colleagues published their findings Nov. 1 in the journal Nature Physics.
According to Hasan, one of the most exciting potential uses for the material would be in energy-efficient quantum computers that would have the ability to identify errors in calculation as they occur and resist them during processing. The successful development of such machines is thought to hinge on catching and manipulating elusive particles called Majorana fermions, which were first predicted more than 70 years ago but never before observed, Hasan explained. The split electronic personality of the new superconductors with unusual surface properties, when placed in contact with a special kind of insulator, may enable scientists to coax the electrons whizzing about on the surface to become Majorana fermions, he added.
"These highly unusual superconductors are the most ideal nurseries to create and manipulate Majorana fermions, which could be used to do quantum computing in a fault-resistant way " said L. Andrew Wray, the first author of the paper, who received his doctoral degree from Princeton in 2010. "And because the particles would exist on a superconductor, it could be possible to manipulate them in low power-consumption devices that are not only 'green,' but also immune to the overheating problems that befall current silicon-based electronics."
The significant caveat is that any potential application could be several decades in development.
"Of course, it takes time to go from new physics to new technology -- usually 20 to 30 years, as was the case with semiconductors," Hasan said.
Initial find of insulators begins path to discovery

In 2007, a Hasan-led research team reported the discovery of three-dimensional topological insulators -- a strange breed of insulator with a metallic surface. While three-dimensional topological insulators may have potential for use in next-generation electronics, their properties alone are not ideal for use in quantum computers, Hasan said.
Quantum computers store and process information using the "quantum" behavior of subatomic particles -- phenomena that occur on the ultrasmall scale and are completely at odds with the world that can be seen by the naked eye, such as the ability of electrons to be in two different places at the same time. Quantum computers could one day enable the manipulation of data at speeds that far exceed today's conventional machines, which are rapidly approaching the fundamental limits of their computing capabilities.
However, efforts to create higher-performing quantum computers have been hampered by the notoriously fickle and unpredictable behavior of particles on the quantum scale.
For the past two years, Hasan and his collaborators have been tweaking the properties of a topological insulator called bismuth selenide to create a material with a metallic surface and a superconducting interior, which would have properties well suited to exploitation in the electronics of the future.
To make a superconductor with topological behavior, or unusual surface properties, Princeton chemistry professor Robert Cava and his research group invented a new kind of crystal by inserting atoms of copper into the atomic lattice structure of a semiconductor made out of the compound bismuth selenide. This process, called intercalation doping, is a method used to change the number of electrons in a material and tweak its electrical properties.
The scientists discovered that, with the right amount of doping, they were able to turn the crystal into a superconductor at very low temperatures -- below 4 degrees Kelvin, or around -452 degrees Fahrenheit. However, initial laboratory-based results suggested that the superconductor cannot retain topological properties indefinitely, though they do persist for months if the material is kept in a vacuum.
To assess the topological characteristics of the material, the researchers used a technique known as X-ray spectroscopy to bombard the crystal with X-rays and "pop" individual electrons out of the material. These electrons were then analyzed, providing a series of clues that allowed the team to determine the true nature of the crystal.
These X-ray tests discovered that the scientists had, indeed, created a topological superconductor. Furthermore, they found that the electrons on the crystal's metallic surface were not normal electrons. Rather, the surface featured rare electrons that act like mass-less, light particles. The scientists recognized the particles because the first direct observation of such electrons, called helical Dirac fermions, in three-dimensional materials was reported last year by a separate Hasan-led research team.
Scientific theory, by physicist Charles Kane of the University of Pennsylvania, predicts that if a topological superconductor were to be placed in contact with a topological insulator, some of the electrons at the interface could become long-sought Majorana fermions if the composite material were placed into a very strong magnetic field.
The particles are desirable in electronic devices because, while normal electrons have a negative charge, Majorana fermions are neutral. This charge-less nature means that they wouldn't interact with each other, nor would they be affected by the other charges on the surrounding atoms that make up the crystal.
Because the fermions would not be attracted or repelled by nearby particles and atoms, they would travel in very predictable, predetermined paths -- and this is where their true potential lies.
If the motion of multiple Majorana fermions could be predicted, then topological quantum computers that stored information in these particles could be fault-tolerant, or resistant to errors, he explained. This could be further extended to design methods that would enable the computer to "know" that it had performed a calculation wrong and correct for the error.
"There are many different types of topological superconductors and the exact identification of the current superconductors will require further experiments," Hasan added.
In addition to Hasan, Cava and Wray, who is now a postdoctoral fellow at the Advanced Light Source facility at the Lawrence Berkeley National Laboratory, Princeton scientists on the team included: graduate student Su-Yang Xu; former postdoctoral researchers Yew San Hor and Dong Qian; and Yuqi Xia, who received his doctoral degree from Princeton in 2010. Additional researchers on the team included Alexei Fedorov of the Advanced Light Source at Berkeley Lab and Hsin Lin and Arun Bansil, both of Northeastern University.
"This is an exciting result by Zahid Hasan and coworkers that builds on his previous experimental discovery of the first three-dimensional topological state of matter, the topological insulator," said Joel Moore, an associate professor of physics at University of California-Berkeley and a member of Princeton's class of 1995.
"Theorists believe that if a topological insulator can be made superconducting, the resulting state would have several remarkable properties," Moore said. "The most exotic might be the existence of a new kind of emergent particle, the Majorana fermion … . We have known for some time that solids made up of ordinary nuclei and electrons can host 'emergent' particles with stranger properties, such as fractional charge, but the Majorana fermion, which has zero mass and zero charge, might be the strangest of all. While no single measurement can confirm the existence of topological superconductivity, the work by Hasan is a considerable step in the right direction."
In future projects, Hasan and his collaborators hope to detect Majorana fermions and invent ways to control their properties. Additionally, the research group will aim to identify other types of topological superconductors and topological insulators. Two important goals will be to find topological materials that exhibit superconductivity at higher temperatures and topological insulators whose interior is highly insulating
The research was funded by the U.S. Department of Energy, a National Science Foundation American Competitiveness and Innovation Fellowship and the Alfred P. Sloan Foundation.

Predictive Power of Dairy Cattle Methane Models Insufficient to Provide Sound Environmental Advice, Study Finds

Canadian and Dutch researchers have shown that current equations to predict methane production of cows are inaccurate.
Canadian and Dutch researchers have shown that current equations to predict methane production of cows are inaccurate. Sound mitigation options to reduce greenhouse gas emissions of dairy farms require a significant improvement of current methane equations, according to a study of the Dutch-Canadian team in the journal Global Change Biology.
The researchers, from University of Guelph and University of Manitoba (Canada) and Wageningen University & Research centre (the Netherlands), compared the observed methane production of cows with that predicted by nine different methane equations that are applied in whole farm greenhouse gas models. "The prediction accuracy of these equations is small, and the equations are not suitable to quantify methane production of cows," says Dr Jan Dijkstra, senior researcher worker at Wageningen University and adjunct professor at University of Guelph. "The predictive power of methane equations will have to be markedly improved if such whole farm models are used for sound decisions by governments to reduce environmental impact of dairying."
On a global basis, according to the FAO livestock is responsible for some 18% of all greenhouse gases emitted. Methane is the most important greenhouse gas on a dairy farm.The FAO estimates that about 52% of all greenhouse gases from the dairy sector is in the form of methane. Several whole-farm models are available that predict the total amount of greenhouse gases (the sum of CO₂, CH₄ en N₂O) of dairy farms. Such whole-farm models are applied to make an inventory of total greenhouse gas emission on farm, and to estimate the effect of management changes (changes in breeding, nutrition, etc.) on greenhouse gas emissions. Methane is the single most important element in such estimates. Methane is 25 times more potent than CO₂. Hence, the accuracy of estimation of total greenhouse gas emissions of whole-farm models largely depends on the accuracy of the prediction of methane emitted per cow.
The research team compiled a large dataset of actual observations on methane emissions of dairy cattle. The observations were largely derived from respiration chamber experiments, in which methane produced in the gut of the cow is accurately determined. These observations were used to evaluate the predictive power of equations to predict methane production.
The prediction accuracy of all equations was low. The equations hardly account for the effect of dietary composition on enteric methane production. Most equations do not use any dietary information at all, but estimate methane production based on feed intake or milk production. For example, the widely used IPCC (Intergovernmental Panel on Climate Change) equation that predicts methane production based on energy intake of the cow, cannot distinguish the effect of a higher energy intake on methane due to a rise in feed intake level, from that due to a rise in dietary fat content at the same feed intake level. However, a higher feed intake will increase methane production, whereas a rise in dietary fat content will decrease methane production.
From the analysis, it also appears that the variation in predicted methane production is far smaller that the variation in actually observed methane production. Consequently, the methane equations do not fully represent the range of effects of dietary changes on enteric methane production of cows.
The research team concluded that the low prediction accuracy and poor prediction of variation in observed values may introduce substantial error into inventories of GHG emissions and lead to incorrect mitigation recommendations. For sound inventories and mitigation recommendations, much better methane predictions are required. At present, the researchers are actively developing more detailed and accurate models that predict methane production, based on the fermentation processes in the gastro-intestinal tract of cows.

Electrons Get Confused: Researchers May Have Observed the Fastest Melting of All Time

This is the K1-XV-line-spectrum of beryllium-oxide.
Scientists from Helmholtz-Zentrum Berlin (HZB) have observed exotic behaviour from beryllium oxide (BeO) when they bombarded it with high-speed heavy ions: After being shot in this way, the electrons in the BeO appeared "confused," and seemed to completely forget the material properties of their environment. The researchers' measurements show changes in the electronic structure that can be explained by extremely rapid melting around the firing line of the heavy ions. If this interpretation is correct, then this would have to be the fastest melting ever observed.

The researchers are publishing their results in Physical Review Letters.

In his experiments, Prof. Dr. Gregor Schiwietz and his team irradiated a beryllium oxide film with high-speed heavy ions of such strong charge that they possessed maximum smashing power. Unlike most other methods, the energy of the heavy ions was chosen so that they would interact chiefly with their outer valence electrons. As heavy ions penetrate into a material, there are typically two effects that occur immediately around the fired ions: the electrons in the immediate surroundings heat up and the atoms become strongly charged. At this point, Auger electrons are emitted, whose energy levels are measurable and show up in a so-called line spectrum. The line spectrum is characteristic for each different material, and normally changes only slightly upon bombardment with heavy ions.
As a world's first, the HZB researchers have now bombarded an ion crystal (BeO), which has insulator properties, with very high-speed heavy ions (xenon ions), upon which they demonstrated a hitherto unknown effect: The line spectrum of the Auger electrons changed drastically -- it became "washed out," stretching into higher energies. Together with a team of physicists from Poland, Serbia and Brazil, the researchers observed distinctly metallic signatures from the Auger electrons emitted by the heated BeO material. The Auger electrons appeared to have completely "forgotten" their insulator properties. The researchers see this as clear evidence that the band structure breaks down extremely rapidly when the BeO is bombarded with heavy ions -- in less than about 100 femtoseconds (one femtosecond is a millionth of a millionth of a millisecond). This breakdown is triggered by the high electron temperatures of up to 100000 Kelvin. In the long term, however, the material of the otherwise cold solid remains overall intact.
The HZB researchers' results deliver strong evidence of ultra-fast melting processes around the firing line of the heavy ions. This melting is followed by annealing that deletes all permanent signs of the melting process. Prof. Schiwietz hopes to find other ionic crystals that exhibit the same rapid melting process, but in which the annealing process is suppressed. If any are found, then a conceivable application would be programming at femtosecond speeds.

Transparent Conductive Material Could Lead to Power-Generating Windows

Top: Scanning electron microscopy image and zoom of conjugated polymer (PPV) honeycomb. Bottom (left-to-right): Confocal fluorescence lifetime images of conjugated honeycomb, of polymer/fullerene honeycomb double layer and of polymer/fullerene honeycomb blend. Efficient charge transfer within the whole framework is observed in the case of polymer/fullerene honeycomb blend as a dramatic reduction in the fluorescence lifetime.
Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Los Alamos National Laboratory have fabricated transparent thin films capable of absorbing light and generating electric charge over a relatively large area. The material, described in the journal Chemistry of Materials, could be used to develop transparent solar panels or even windows that absorb solar energy to generate electricity.
The material consists of a semiconducting polymer doped with carbon-rich fullerenes. Under carefully controlled conditions, the material self-assembles to form a reproducible pattern of micron-size hexagon-shaped cells over a relatively large area (up to several millimeters).
"Though such honeycomb-patterned thin films have previously been made using conventional polymers like polystyrene, this is the first report of such a material that blends semiconductors and fullerenes to absorb light and efficiently generate charge and charge separation," said lead scientist Mircea Cotlet, a physical chemist at Brookhaven's Center for Functional Nanomaterials (CFN).
Furthermore, the material remains largely transparent because the polymer chains pack densely only at the edges of the hexagons, while remaining loosely packed and spread very thin across the centers. "The densely packed edges strongly absorb light and may also facilitate conducting electricity," Cotlet explained, "while the centers do not absorb much light and are relatively transparent."
"Combining these traits and achieving large-scale patterning could enable a wide range of practical applications, such as energy-generating solar windows, transparent solar panels, and new kinds of optical displays," said co-author Zhihua Xu, a materials scientist at the CFN.
"Imagine a house with windows made of this kind of material, which, combined with a solar roof, would cut its electricity costs significantly. This is pretty exciting," Cotlet said.
The scientists fabricated the honeycomb thin films by creating a flow of micrometer-size water droplets across a thin layer of the polymer/fullerene blend solution. These water droplets self-assembled into large arrays within the polymer solution. As the solvent completely evaporates, the polymer forms a hexagonal honeycomb pattern over a large area.
"This is a cost-effective method, with potential to be scaled up from the laboratory to industrial-scale production," Xu said.
The scientists verified the uniformity of the honeycomb structure with various scanning probe and electron microscopy techniques, and tested the optical properties and charge generation at various parts of the honeycomb structure (edges, centers, and nodes where individual cells connect) using time-resolved confocal fluorescence microscopy.
The scientists also found that the degree of polymer packing was determined by the rate of solvent evaporation, which in turn determines the rate of charge transport through the material.
"The slower the solvent evaporates, the more tightly packed the polymer, and the better the charge transport," Cotlet said.
"Our work provides a deeper understanding of the optical properties of the honeycomb structure. The next step will be to use these honeycomb thin films to fabricate transparent and flexible organic solar cells and other devices," he said.
The research was supported at Los Alamos by the DOE Office of Science. The work was also carried out in part at the CFN and the Center for Integrated Nanotechnologies Gateway to Los Alamos facility. The Brookhaven team included Mircea Cotlet, Zhihua Xu, and Ranjith Krishna Pai. Collaborators from Los Alamos include Hsing-Lin Wang and Hsinhan Tsai, who are both users of the CFN facilities at Brookhaven, Andrew Dattelbaum from the Center for Integrated Nanotechnologies Gateway to Los Alamos facility, and project leader Andrew Shreve of the Materials Physics and Applications Division.

Corn Starch Solution Can Help Shape Solid Materials

NYU researchers have developed a method to shape solid materials using a corn starch solution. To do this, they submerged a motor-powered, plastic sphere through the cornstarch solution toward a containing wall made of clay, stopping just short of the wall. Using the force of the sphere to harden the cornstarch solution, the researchers were able to make indentations in the wall. In addition, they were able to do so with a degree of precision by taking into account speed, force, and geometry. The process offers a potential technique for material cutting and manufacturing processes.

New York University researchers have developed a method to shape solid materials using a corn starch solution. The process, devised by researchers in NYU's Courant Institute of Mathematical Sciences and Department of Physics, offers a potential technique for material cutting and manufacturing processes.
Their work is described in the journal Physical Review Letters.

Manufacturers use a variety of methods for shaping solid materials, ranging from laser cutting to high-speed jets of water. While altering the shape of such materials, such as glass, metal, or stone, is relatively straightforward, doing so with precision often proves challenging.
With this in mind, the NYU researchers sought to create an alternative, but rudimentary, method to shape solid materials in a precise fashion. To do so, they considered a process involving a corn starch solution.
Similar solutions have proved valuable in creating body armor -- but for different reasons. The molecules in these fluids -- also called shear-thickening fluids -- are closely packed, but loosely arranged. Under most conditions, they flow like most liquids. However, when met with pressure from an object or other force, its particles interlock and the fluid acts like a solid. Body armor comprised of shear-thickening fluids, when met with bullets, become hard and deflect incoming projectiles.
The NYU researchers sought to apply these principles in a different manner. Instead of using the solution to deflect objects, they aimed to use it as part of a process to shape solid materials -- in this case, a wall of modeling clay.
To do this, they submerged a motor-powered, plastic sphere through the cornstarch solution toward a containing wall made of modeling clay, stopping just short of the wall. Using the force of the sphere to harden the cornstarch solution, the researchers were able to make indentations in the wall of modeling clay. In addition, they were able to do so with a degree of precision by taking into account speed, force, and geometry. By moving the sphere at fast speeds through the solution, they created large depressions in the clay; by slowing it down, they created smaller depressions.
The study's authors were: Bin Liu, a post-doctoral researcher in NYU's Department of Physics, Michael Shelley, a professor in NYU's Courant Institute of Mathematical Sciences; and Jun Zhang, a professor in NYU's Department of Physics and Courant Institute.

Activated carbon cloth.
Ordinary-looking fabric can be used to filter out and destroy incredibly toxic materials, even when they're only present in tiny amounts, according to new research at the University of Abertay Dundee.
The research team found that activated carbon cloth -- which was originally developed at the Porton Down military research facility -- can be used to create extremely reactive chemicals called hydroxyl radicals. These are so unstable they instantly react with any pollutants, even at tiny concentrations of just a few parts per million.
This inexpensive material could be used on a small-scale in hospitals to filter out waste, or on a massive industrial scale to remove hard-to-detect chemicals that kill essential bacteria in our water system and risk human health.
Professor David Bremner, Chair of Applied Environmental Science at Abertay University, said: "There's been a lot of research into how activated carbon in powder or grain form can be used, but what we found is that using it as a fabric has a number of real advantages.
"There are many applications -- from a hospital to an industrial chemical plant -- where activated carbon cloth could be used to make incredibly sensitive filters, removing dangerous or unpleasant molecules even at very low concentrations.
"We also discovered that using activated carbon cloth in conjunction with the gas ozone (O₃) removes even more potentially dangerous organic content. This really is a step forward for the safety of waste treatment, and we're now working on developing more practical applications for this fascinating fabric."
The initial work was carried out as a knowledge-transfer partnership (KTP) with Carbon Filter Technology, a Kirriemuir-based company which produces different versions of the material which may be used for medical clean rooms, air and water filtration, and highly advanced wound dressings.
Company Director Ian Johnson explained the science behind the research: "Activated carbon cloth can effectively remove contaminants from the air, gas or liquids such as waste water.
"The fabric has countless tiny pores which adsorb the organic molecules onto the surface via weak Van der Waals forces. The pollutants then react with the oxidant (ozone) on the surface of the carbon cloth, converting them into smaller molecules or even carbon dioxide and water. The carbon cloth is really acting as a catalyst, promoting the decomposition of the pollutants."
He added: "The applications we're developing with Abertay University are very exciting, and it's great to be involved with a university that prides itself on working directly with businesses in real-world, applied settings. Hospital patients and industrial companies could both really benefit from this important research."
The original work on activated carbon cloth at Porton Down in the 1980s was focussed on developing a material that could protect soldiers from chemical attacks. Today one of the more recognisable uses for the fabric is the inside of chemical, biological and radiological warfare (CBR) suits for the military.
Some of the other problems that could be solved using this technology include removing drugs like antibiotics from waste before they enter the sewage system, removing unpleasant odours from ostomy bags in hospitals and care homes, or for use as highly absorbent material to protect sensitive equipment.

New Approaches Needed to Gauge Safety of Nanotech-Based Pesticides, Researchers Urge

These titanium dioxide nanoparticles, seen through a scanning electron microscope, are the type of extraordinarily small particles studied in a program at Oregon State University on the safety of nanotechnology.
Nanotechnology is about to emerge in the world of pesticides and pest control, and a range of new approaches are needed to understand the implications for public health, ensure that this is done safely, maximize the potential benefits and prevent possible risks, researchers say in a new report.
In a study published October 4 in the International Journal of Occupational and Environmental Health, scientists from Oregon State University and the European Union outline six regulatory and educational issues that should be considered whenever nanoparticles are going to be used in pesticides.
"If we do it right, it should be possible to design nanoparticles with safety as a primary consideration, so they can help create pesticides that work better or are actually safer," said Stacey Harper, an assistant professor of nanotoxicology at Oregon State University. Harper is a national leader in the safety and environmental impacts of this science that deals with particles so extraordinarily small they can have novel and useful characteristics.
"Unlike some other applications of nanotechnology, which are further along in development, applications for pesticides are in their infancy," Harper said. "There are risks and a lot of uncertainties, however, so we need to understand exactly what's going on, what a particular nanoparticle might do, and work to eliminate use of any that do pose dangers."
A program is already addressing that at OSU, as part of the Oregon Nanoscience and Microtechnologies Institute.
The positive aspect of nanotechnology use with pesticides, researchers say, is that it might allow better control and delivery of active ingredients, less environmental drift, formulations that will most effectively reach the desired pest, and perhaps better protection for agricultural workers.
"If you could use less pesticide and still accomplish the same goal, that's a concept worth pursuing," Harper said.
But researchers need to be equally realistic about the dangers, she said. OSU labs have tested more than 200 nanomaterials, and very few posed any toxic concerns -- but a few did. In one biomedical application, where nanoparticles were being studied as a better way to deliver a cancer drug, six out of 40 evoked a toxic response, most of which was linked to a specific surface chemistry that scientists now know to avoid.
"The emergence of nanotechnology in the pesticide industry has already begun, this isn't just theoretical," said David Stone, an assistant professor in the OSU Department of Environmental and Molecular Toxicology. "But pesticides are already one of the most rigorously tested and regulated class of compounds, so we should be able to modify the existing infrastructure."
One important concern, the researchers said, will be for manufacturers to disclose exactly what nanoparticles are involved in their products and what their characteristics are. Another issue is to ensure that compounds are tested in the same way humans would be exposed in the real world.
"You can't use oral ingestion of a pesticide by a laboratory rat and assume that will tell you what happens when a human inhales the same substance," Stone said. "Exposure of the respiratory tract to nanoparticles is one of our key concerns, and we have to test compounds that way."
Future regulations also need to acknowledge the additional level of uncertainty that will exist for nano-based pesticides with inadequate data, the scientists said in their report. Tests should be done using the commercial form of the pesticides, a health surveillance program should be initiated, and other public educational programs developed.
Special assessments may also need to be developed for nanoparticle exposure to sensitive populations, such as infants, the elderly, or fetal exposure. And new methodologies may be required to understand nanoparticle effects, which are different from most traditional chemical tests.
"These measures will require a coordinated effort between governmental, industry, academic and public entities to effectively deal with a revolutionary class of novel pesticides," the researchers concluded in their report.

New Retinal Implant Enables Blind People to See Shapes and Objects

Functional scheme of subretinal implants.
Research published in Proceedings of the Royal Society B reveals that a group of researchers based in Germany have developed a retinal implant that has allowed three blind people to see shapes and objects within days of the implant being installed.
One blind person was even able to identify and find objects placed on a table in front of him, as well as walking around a room independently and approaching people, reading a clock face and differentiating seven shades of grey. The device, which has been developed by the company Retinal Implant AG together with the Institute for Ophthalmic Research at the University of Tuebingen, represents an unprecedented advance in electronic visual prostheses and could eventually revolutionise the lives of up 200,000 people worldwide who suffer from blindness as a result of retinitis pigmentosa, a degenerative eye disease.
In this disease light receptors in the eye cease to function. Writing in Proceedings of the Royal Society B, Prof. Dr. Eberhart Zrenner (founding Director of Retinal Implant AG and Director and Chairman of the University of Tuebingen Eye Hospital) states that "The results of this pilot study provide strong evidence that the visual functions of patients blinded by a hereditary retinal dystrophy can, in principle, be restored to a degree sufficient for use in daily life."
The device -- known as a subretinal implant -- sits underneath the retina, directly replacing light receptors lost in retinal degeneration. As such, it uses the eyes' natural image processing capabilities beyond the light detection stage to produce a visual perception in the patient that is stable and follows their eye movements. Other types of retinal implants -- known as epiretinal implants -- sit outside the retina and because they bypass the intact light-sensitive structures in the eyes they require the user to wear an external camera and processor unit.
The subretinal implant described in this paper achieves unprecedented clarity because it has a great deal more light receptors than other similar devices. As Prof. Dr. Zrenner states, "The present study...presents proof-of-concept that such devices can restore useful vision in blind human subjects, even though the ultimate goal of broad clinical application will take time to develop."

Drake Passage, South Atlantic Ocean.
Universitat Autònoma de Barcelona scientists have researched how ocean currents in the Atlantic were affected by climate change in the past. The study shows that there was a period when the flow of deep waters in the Atlantic was reversed. The results are relevant for the near future since similar changes are expected to occur in the course of climate warming over the next 100 years.
The Atlantic Ocean circulation (termed meridional overturning circulation, MOC) is an important component of the climate system. Warm currents, such as the Gulf Stream, transport energy from the tropics to the subpolar North Atlantic and influence regional weather and climate patterns. Once they arrive in the North the currents cool, their waters sink and with them they transfer carbon from the atmosphere to the abyss. These processes are important for climate but the way the Atlantic MOC responds to climate change is not well known yet.
An international team of investigators under the leadership of two researchers from the UAB now demonstrates the response of the Atlantic MOC to climate change in the past. The new research results will be published on 4 November 2010 in the journal Nature. The research project was led by Rainer Zahn (ICREA researcher) and Pere Masque, both of the UAB at the Institut de Ciència i Tecnologia Ambientals (ICTA) and Department of Physics. With collaborators at the universities of Seville, Oxford and Cardiff (UK) they investigated the distribution of isotopes in the Atlantic Ocean that are generated from the natural decay of uranium in seawater and are distributed with the flow of deep waters across the Atlantic basin. The young investigator Cesar Negre studied the natural abundance of these isotopes in the seafloor sediments 2.5 km deep in the South Atlantic and achieved a PhD degree in the Environmental Science and Technology doctoral programme at ICTA.
The study shows that the ocean circulation was very different in the past and that there was a period when the flow of deep waters in the Atlantic was reversed. This happened when the climate of the North Atlantic region was substantially colder and deep convection was weakened. At that time the balance of seawater density between the North and South Atlantic was shifted in such a way that deep water convection was stronger in the South Polar Ocean. Recent computer models simulate a reversal of the deep Atlantic circulation under such conditions while it is only now with the new data generated by UAB scientists and their colleagues from Seville and the UK that the details of the circulation reversal become apparent.
This situation occurred during the ice age 20,000 years ago. Although this was far back in time the results are relevant for our climate today and in the near future. The new study shows that the Atlantic MOC in the past was very sensitive to changes in the salt balance of Atlantic Ocean currents. Similar changes in seawater salt concentration are expected to occur in the North Atlantic in the course of climate warming over the next 100 years. Therefore the data to be published in Nature offer the climate modelling community the opportunity to calibrate their models and improve their capacity to predict reliably future ocean and climate changes.

Water Flowing Through Ice Sheets Accelerates Warming, Could Speed Up Ice Flow

Standing melt water in Greenland crevasses can carry warmth to the ice sheet's interior, accelerating the thermal response of the ice sheet to climate change.
Melt water flowing through ice sheets via crevasses, fractures and large drains called moulins can carry warmth into ice sheet interiors, greatly accelerating the thermal response of an ice sheet to climate change, according to a new study involving the University of Colorado at Boulder.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models. Ice flows more readily as it warms, so a warming climate can increase ice flows on ice sheets much faster than previously thought, said the study authors.
"We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years, " said lead author Thomas Phillips, a research scientist with Cooperative Institute for Research in Environmental Sciences. CIRES is a joint institute between CU-Boulder and the National Oceanic and Atmospheric Administration.
Phillips, along with CU-Boulder civil, environmental and architectural engineering Professor Harihar Rajaram and CIRES Director Konrad Steffen described their results in a paper published online in Geophysical Research Letters.
Conventional thermal models of ice sheets do not factor in the presence of water within the ice sheet as a warming agent, but instead use models that primarily consider ice-sheet heating by warmer air on the ice sheet surface. In water's absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
But the Greenland ice sheet is not one solid, smooth mass of ice. As the ice flows towards the coast, grating on bedrock, crevasses and new fractures form in the upper 100 feet of the ice sheet. Melt water flowing through these openings can create "ice caves" and networks of "pipes" that can carry water through the ice and spreading warmth, the authors concluded.
To quantify the influence of melt water, the scientists modeled what would happen to the ice sheet temperature if water flowed through it for eight weeks every summer -- about the length of the active melt season. The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades depending on the spacing of crevasses and other "pipes" that bring warmer water into the ice sheet in summer.
"The key difference between our model and previous models is that we include heat exchange between water flowing through the ice sheet and the ice," said Rajaram.
Several factors contributed to the warming and resulting acceleration of ice flow, including the fact that flowing water into the ice sheets can stay in liquid form even through the winter, slowing seasonal cooling. In addition, warmer ice sheets are more susceptible to increases of water flow, including the basal lubrication of ice that allows ice to flow more readily on bedrock.
A third factor is melt water cascading downward into the ice, which warms the surrounding ice. In this process the water can refreeze, creating additional cracks in the more vulnerable warm ice, according to the study.
Taken together, the interactions between water, temperature, and ice velocity spell even more rapid changes to ice sheets in a changing climate than currently anticipated, the authors concluded. After comparing observed temperature profiles from Greenland with the new model described in the paper, the authors concluded the observations were unexplainable unless they accounted for warming.
"The fact that the ice temperatures warm rather quickly is really the key piece that's been overlooked in models currently being used to determine how Greenland responds to climate warming," Steffen said. "However, this process is not the 'death knell' for the ice sheet. Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
This study was funded by NASA's Cryosphere Science Program.

Slight Change in Wind Turbine Speed Significantly Reduces Bat Mortality

Wind turbines in north eastern US. While wind energy has shown strong potential as a large-scale, emission-free energy source, bat and bird collisions at wind turbines result in thousands of fatalities annually. Migratory bats, such as the hoary bat, are especially at risk for collision with wind turbines as they fly their routes in the forested ridges of the eastern U.S.
While wind energy has shown strong potential as a large-scale, emission-free energy source, bat and bird collisions at wind turbines result in thousands of fatalities annually. Migratory bats, such as the hoary bat, are especially at risk for collision with wind turbines as they fly their routes in the forested ridges of the eastern U.S. This loss not only impacts the immediate area, but is also detrimental to ecosystem health nationwide -- that is, bats help with pest management, pollination and the dispersal of numerous plant seeds.
Since turbine towers and non-spinning turbine blades do not kill bats, some scientists have proposed shutting off or reducing the usage of wind turbines during peak periods of migration in the late summer and early fall months when bat activity and fatalities are highest.
In a study to be published online November 1, 2010 in Frontiers in Ecology and the Environment, a journal of the Ecological Society of America, Edward Arnett from Bat Conservation International in Austin, Texas and colleagues examined the effects of changes in wind turbine speed on bat mortality during the low-wind months of late summer and early fall.
Currently, most wind turbines in the U.S. are programmed to begin rotating and producing power once wind speed has reached approximately 8 to 9 miles per hour (mph) -- the wind speed at which turbines begin generating electricity to the power grid is known as the cut-in speed. Wind turbines with a low cut-in speed run more frequently than those set at higher cut-in speeds since they begin rotating at lower wind speeds.
The researchers found that, by raising the cut-in speed to roughly 11 mph, bat fatalities were reduced by at least 44 percent, and by as much as 93 percent, with an annual power loss of less than one percent. That is, programming the turbines to rotate only when the wind reached approximately 11 mph or higher caused the turbines to rotate less frequently and, therefore, killed significantly fewer bats. Because this was performed during months with seasonably low wind speeds already, the overall energy loss was marginal when the researchers calculated the annual power output.
"This is the only proven mitigation option to reduce bat kills at this time," said Arnett. "If we want to pursue the benefits associated with wind energy, we need to consider the local ecological impacts that the turbines could cause. We have already seen a rise in bat mortality associated with wind energy development, but our study shows that, by marginally limiting the turbines during the summer and fall months, we can save bats as well as promote advances in alternative energy."
Arnett and colleagues monitored 12 of the 23 turbines at the Casselman Wind Project in Somerset County, Pennsylvania in the Appalachian Mountain region and recorded bat fatalities for 25 summer and fall nights in both 2008 and 2009. The researchers analyzed the fatalities following nights when the turbines were fully operational and when the turbines were set to the less sensitive cut-in speeds of roughly 11 mph and 14.5 mph. In both years, the researchers found at least one fresh bat carcass every night that the turbines were fully operational. Specifically, the researchers reported a mortality rate that was, on average, 3.6 to 5.4 times higher at the fully functioning turbines compared with the turbines set to the altered cut-in speeds.
According to John Hayes, co-author of the study from the University of Florida, "the findings are important step forward in building a comprehensive energy strategy with reduced environmental impacts."
"Rarely do you see such a win-win result in a study," said Arnett. "There is a simple, relatively cost-effective solution here that could save thousands of bats. This is good news for conservation and for wind energy development."

Four ways to harvest solar heat from roads

University of Rhode Island graduate student Andrew Correia (left) and Prof. K. Wayne Lee, measuring the solar energy generated by a patch of asphalt

Walk barefoot on an asphalt road and you'll soon realize how good the substance is at storing solar heat – the heat-storing qualities of roadways has even been put forward as an explanation as to why cities tend to be warmer than surrounding rural areas. Not content to see all that heat going to waste, researchers from the University of Rhode Island (URI) want to put it to use in a system that harvests solar heat from the road to melt ice, heat buildings, or to create electricity.
“We have mile after mile of asphalt pavement around the country, and in the summer it absorbs a great deal of heat, warming the roads up to 140 degrees or more,” said Prof. K. Wayne Lee, leader of the URI project. “If we can harvest that heat, we can use it for our daily use, save on fossil fuels, and reduce global warming.”
The research team has four main ideas for how that harvesting could be performed.

Cells on barriers

A relatively simple method of harnessing the sunlight shining on the road, if not the heat stored in it, is to wrap flexible photovoltaic cells around the top of the Jersey barriers on divided highways (Jersey barriers are those long rectangular concrete slabs). These cells could also be embedded in the asphalt between the barriers and the adjacent rumble strips. The electricity generated by the cells could be used to power streetlights and illuminate road signs.

Water pipes in the road

Another approach would be to install water-containing pipes within the asphalt. As the road heated up, so would the water, which could then be piped underneath a bridge deck to reduce icing, used to heat or provide hot water for nearby buildings, or even turned to steam at a power plant. URI grad student Andrew Correia has created a prototype for such a system, which he hopes will demonstrate how it could actually work in the real world.

Thermo-electricity

A small amount of electricity can be created by connecting two semiconductors to form a circuit linking a hot and a cold area. If those semiconductors were embedded in the road at different depths, or in sunny and shady areas, then the difference in temperature between them could conceivably be used to generate electricity. If enough of them were used together, their electrical output could be used for purposes such as defrosting roadways. URI’s Prof. Sze Yang proposes that instead of traditional semiconductors, inexpensive plastic sheet organic polymeric semiconductors could be used.

Electronic block roadways

In what the researchers admit would be the most costly option, asphalt roads could be replaced with roads made from clear-yet-durable electronic blocks. These would contain photovoltaic cells, LED lights and sensors, and could generate electricity, display changeable lane markings, and display illuminated warning messages. Idaho’s Solar Roadways has been working on just such a system, although according to Lee, a driveway made with the blocks cost US$100,000 to create. He believes that such technology may first show up in corporate parking lots, before decreased costs allow it to be used for public roads.