Stop Emitting Carbon Dioxide, Or Geoengineering Could Be Only Hope For Earth's Climate, Experts Warn

Stop Emitting Carbon Dioxide, Or Geoengineering Could Be Only Hope For Earth's Climate, Experts Warn

  10:24:00 AM    Science Lover

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The future of the Earth could rest on potentially dangerous and unproven geoengineering technologies unless emissions of carbon dioxide can be greatly reduced, the latest Royal Society report has found.

A new report finds that unless future efforts to reduce greenhouse gas emissions are much more successful than they have been so far, additional action in the form of geoengineering will be necessary if we are to cool the planet. (Credit: iStockphoto/Andrey Prokhorov)

The report (published September 1, 2009 by the Royal Society, the UK’s national academy of science) found that unless future efforts to reduce greenhouse gas emissions are much more successful than they have been so far, additional action in the form of geoengineering will be necessary if we are to cool the planet. Geoengineering technologies were found to be very likely to be technically possible and some were considered to be potentially useful to augment the continuing efforts to mitigate climate change by reducing emissions. However, the report identified major uncertainties regarding their effectiveness, costs and environmental impacts.

Professor John Shepherd, who chaired the Royal Society’s geoengineering study, said, “It is an unpalatable truth that unless we can succeed in greatly reducing CO₂ emissions we are headed for a very uncomfortable and challenging climate future, and geoengineering will be the only option left to limit further temperature increases. Our research found that some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems - yet we are still failing to take the only action that will prevent us from having to rely on them. Geoengineering and its consequences are the price we may have to pay for failure to act on climate change.”

The report assesses the two main kinds of geoengineering techniques – Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM). CDR techniques address the root of the problem – rising CO₂ – and so have fewer uncertainties and risks, as they work to return the Earth to a more normal state. They are therefore considered preferable to SRM techniques, but none has yet been demonstrated to be effective at an affordable cost, with acceptable environmental impacts, and they only work to reduce temperatures over very long timescales.

SRM techniques act by reflecting the sun’s energy away from Earth, meaning they lower temperatures rapidly, but do not affect CO₂ levels. They therefore fail to address the wider effects of rising CO₂, such as ocean acidification, and would need to be deployed for a very long time. Although they are relatively cheap to deploy, there are considerable uncertainties about their regional consequences, and they only reduce some, but not all, of the effects of climate change, while possibly creating other problems. The report concludes that SRM techniques could be useful if a threshold is reached where action to reduce temperatures must be taken rapidly, but that they are not an alternative to emissions reductions or CDR techniques.

Professor Shepherd added, “None of the geoengineering technologies so far suggested is a magic bullet, and all have risks and uncertainties associated with them. It is essential that we strive to cut emissions now, but we must also face the very real possibility that we will fail. If “Plan B” is to be an option in the future, considerable research and development of the different methods, their environmental impacts and governance issues must be undertaken now. Used irresponsibly or without regard for possible side effects, geoengineering could have catastrophic consequences similar to those of climate change itself. We must ensure that a governance framework is in place to prevent this.”

Of the CDR techniques assessed, the following were considered to have most useful potential:

• CO₂ capture from ambient air – this would be the preferred method of geoengineering, as it effectively reverses the cause of climate change. At this stage no cost-effective methods have yet been demonstrated and much more research and development is needed.
• Enhanced weathering – this technique, which utilises naturally occurring reactions of CO₂ from the air with rocks and minerals, was identified as a prospective longer-term option. However more research is needed to find cost-effective methods and to understand the wider environmental implications.
• Land use and afforestation – the report found that land use management could and should play a small but significant role in reducing the growth of atmospheric CO2 concentrations. However the scope for applying this technique would be limited by land use conflicts, and all the competing demands for land must be considered when assessing the potential for afforestation and reforestation. Should temperatures rise to such a level where more rapid action needs to be taken, the following SRM techniques were considered to have most potential:
• Stratospheric aerosols – these were found to be feasible, and previous volcanic eruptions have effectively provided short-term preliminary case studies of the potential effectiveness of this method. The cost was assessed as likely to be relatively low and the timescale of action short. However, there are some serious questions over adverse effects, particularly depletion of stratospheric ozone.
• Space-based methods – these were considered to be a potential SRM technique for long-term use, if the major problems of implementation and maintenance could be solved. At present the techniques remain prohibitively expensive, complex and would be slow to implement.
• Cloud albedo approaches (eg. cloud ships) – the effects would be localised and the impacts on regional weather patterns and ocean currents are of considerable concern but are not well understood. The feasibility and effectiveness of the technique is uncertain. A great deal more research would be needed before this technique could be seriously considered.

The following techniques were considered to have lower potential:

• Biochar (CDR technique) – the report identified significant doubts relating to the potential scope, effectiveness and safety of this technique and recommended that substantial research would be required before it could be considered for eligibility for UN carbon credits.
• Ocean fertilisation (CDR technique) – the report found that this technique had not been proved to be effective and had high potential for unintended and undesirable ecological side effects.
• Surface albedo approaches (SRM technique, including white roof methods, reflective crops and desert reflectors) – these were found to be ineffective, expensive and, in some cases, likely to have serious impacts on local and regional weather patterns.

For more information, see: http://www.royalsociety.org/geoengineeringclimate

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Tumors Feel The Deadly Sting Of Nanobees

Tumors Feel The Deadly Sting Of Nanobees

  1:59:00 AM    Science Lover

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When bees sting, they pump poison into their victims. Now the toxin in bee venom has been harnessed to kill tumor cells by researchers at Washington University School of Medicine in St. Louis. The researchers attached the major component of bee venom to nano-sized spheres that they call nanobees.

Bee on a finger. Researchers have recently harnessed the toxin in bee venom
to kill tumor cells. (Credit: iStockphoto/Tatiana Buzuleac)

In mice, nanobees delivered the bee toxin melittin to tumors while protecting other tissues from the toxin's destructive power. The mice's tumors stopped growing or shrank. The nanobees' effectiveness against cancer in the mice is reported in advance online publication Aug. 10 in the Journal of Clinical Investigation.

"The nanobees fly in, land on the surface of cells and deposit their cargo of melittin which rapidly merges with the target cells," says co-author Samuel Wickline, M.D., who heads the Siteman Center of Cancer Nanotechnology Excellence at Washington University. "We've shown that the bee toxin gets taken into the cells where it pokes holes in their internal structures."

Melittin is a small protein, or peptide, that is strongly attracted to cell membranes, where it can form pores that break up cells and kill them.

"Melittin has been of interest to researchers because in high enough concentration it can destroy any cell it comes into contact with, making it an effective antibacterial and antifungal agent and potentially an anticancer agent," says co-author Paul Schlesinger, M.D., Ph.D., associate professor of cell biology and physiology. "Cancer cells can adapt and develop resistance to many anticancer agents that alter gene function or target a cell's DNA, but it's hard for cells to find a way around the mechanism that melittin uses to kill."

The scientists tested nanobees in two kinds of mice with cancerous tumors. One mouse breed was implanted with human breast cancer cells and the other with melanoma tumors. After four to five injections of the melittin-carrying nanoparticles over several days, growth of the mice's breast cancer tumors slowed by nearly 25 percent, and the size of the mice's melanoma tumors decreased by 88 percent compared to untreated tumors.

The researchers indicate that the nanobees gathered in these solid tumors because tumors often have leaky blood vessels and tend to retain material. Scientists call this the enhanced permeability and retention effect of tumors, and it explains how certain drugs concentrate in tumor tissue much more than they do in normal tissues.

But the researchers also developed a more specific method for making sure nanobees go to tumors and not healthy tissue by loading the nanobees with additional components. When they added a targeting agent that was attracted to growing blood vessels around tumors, the nanobees were guided to precancerous skin lesions that were rapidly increasing their blood supply. Injections of targeted nanobees reduced the extent of proliferation of precancerous skin cells in the mice by 80 percent.

Overall, the results suggest that nanobees could not only lessen the growth and size of established cancerous tumors but also act at early stages to prevent cancer from developing.

"Nanobees are an effective way to package the useful, but potentially deadly, melittin, sequestering it so that it neither harms normal cells nor gets degraded before it reaches its target," Schlesinger says.

If a significant amount of melittin were injected directly into the bloodstream, widespread destruction of red blood cells would result. The researchers showed that nanoparticles protected the mice's red cells and other tissues from the toxic effects of melittin. Nanobees injected into the bloodstream did not harm the mice. They had normal blood counts, and tests for the presence of blood-borne enzymes indicative of organ damage were negative.

When secured to the nanobees, melittin is safe from protein-destroying enzymes that the body produces. Although unattached melittin was cleared from the mice's circulation within minutes, half of the melittin on nanobees was still circulating 200 minutes later. Schlesinger indicates that is long enough for the nanobees to circulate through the mice's bloodstream 200 times, giving them ample time to locate tumors.

"Melittin is a workhorse," says Wickline, also professor of medicine in the Cardiovascular Division and professor of physics, of biomedical engineering and of cell biology and physiology. "It's very stable on the nanoparticles, and it's easily and cheaply produced. We are now using a nontoxic part of the melittin molecule to hook other drugs, targeting agents or imaging compounds onto nanoparticles."

The core of the nanobees is composed of perfluorocarbon, an inert compound used in artificial blood. The research group developed perfluorocarbon nanoparticles several years ago and have been studying their use in various medical applications, including diagnosis and treatment of atherosclerosis and cancer. About six millionths of an inch in diameter, the nanoparticles are large enough to carry thousands of active compounds, yet small enough to pass readily through the bloodstream and to attach to cell membranes.

"We can add melittin to our nanoparticles after they are built," Wickline says. "If we've already developed nanoparticles as carriers and given them a targeting agent, we can then add a variety of components using native melittin or melittin-like proteins without needing to rebuild the carrier. Melittin fortunately goes onto the nanoparticles very quickly and completely and remains on the nanobee until cell contact is made."

The flexibility of nanobees and other nanoparticles made by the group suggests they could be readily adapted to fit medical situations as needed. The ability to attach imaging agents to nanoparticles means that the nanoparticles can give a visible indication of how much medication gets to tumors and how tumors respond.

"Potentially, these could be formulated for a particular patient," Schlesinger says. "We are learning more and more about tumor biology, and that knowledge could soon allow us to create nanoparticles targeted for specific tumors using the nanobee approach."

Funding from the National Institutes of Health and the American Heart Association supported this research.

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World's Smallest Semiconductor Laser Heralds New Era In Optical Science

World's Smallest Semiconductor Laser Heralds New Era In Optical Science

  1:26:00 AM    Science Lover

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Researchers at the University of California, Berkeley, have reached a new milestone in laser physics by creating the world's smallest semiconductor laser, capable of generating visible light in a space smaller than a single protein molecule.

The schematic on the left illustrates light being compressed and sustained in the 5 nanometer gap -- smaller than a protein molecule -- between a nanowire and underlying silver surface. To the right is an electron microscope image of the hybrid design shown in the schematic. (Credit: Courtesy of Xiang Zhang Lab, UC Berkeley)

This breakthrough, described in an advanced online publication of the journal Nature on Aug. 30, breaks new ground in the field of optics. The UC Berkeley team not only successfully squeezed light into such a tight space, but found a novel way to keep that light energy from dissipating as it moved along, thereby achieving laser action.

"This work shatters traditional notions of laser limits, and makes a major advance toward applications in the biomedical, communications and computing fields," said Xiang Zhang, professor of mechanical engineering and director of UC Berkeley's Nanoscale Science and Engineering Center, which is funded by the National Science Foundation (NSF), and head of the research team behind this work.

The achievement helps enable the development of such innovations as nanolasers that can probe, manipulate and characterize DNA molecules; optics-based telecommunications many times faster than current technology; and optical computing in which light replaces electronic circuitry with a corresponding leap in speed and processing power.

While it is traditionally accepted that an electromagnetic wave - including laser light - cannot be focused beyond the size of half its wavelength, research teams around the world have found a way to compress light down to dozens of nanometers by binding it to the electrons that oscillate collectively at the surface of metals. This interaction between light and oscillating electrons is known as surface plasmons.

Scientists have been racing to construct surface plasmon lasers that can sustain and utilize these tiny optical excitations. However, the resistance inherent in metals causes these surface plasmons to dissipate almost immediately after being generated, posing a critical challenge to achieving the buildup of the electromagnetic field necessary for lasing.

Zhang and his research team took a novel approach to stem the loss of light energy by pairing a cadmium sulfide nanowire - 1,000 times thinner than a human hair - with a silver surface separated by an insulating gap of only 5 nanometers, the size of a single protein molecule. In this structure, the gap region stores light within an area 20 times smaller than its wavelength. Because light energy is largely stored in this tiny non-metallic gap, loss is significantly diminished.

With the loss finally under control through this unique "hybrid" design, the researchers could then work on amplifying the light.

"When you are working at such small scales, you do not have much space to play around with," said Rupert Oulton, the research associate in Zhang's lab who first theorized this approach last year and the study's co-lead author. "In our design, the nanowire acts as both a confinement mechanism and an amplifier. It's pulling double duty."

Trapping and sustaining light in radically tight quarters creates such extreme conditions that the very interaction of light and matter is strongly altered, the study authors explained. An increase in the spontaneous emission rate of light is a telltale sign of this altered interaction; in this study, the researchers measured a six-fold increase in the spontaneous emission rate of light in a gap size of 5 nanometers.

Recently, researchers from Norfolk State University reported lasing action of gold spheres in a dye-filled, glasslike shell immersed in a solution. The dye coupled to the gold spheres could generate surface plasmons when exposed to light.

The UC Berkeley researchers used semiconductor materials and fabrication technologies that are commonly employed in modern electronics manufacturing. By engineering hybrid surface plasmons in the tiny gap between semiconductors and metals, they were able to sustain the strongly confined light long enough that its oscillations stabilized into the coherent state that is a key characteristic of a laser.

"What is particularly exciting about the plasmonic lasers we demonstrated here is that they are solid state and fully compatible with semiconductor manufacturing, so they can be electrically pumped and fully integrated at chip-scale," said Volker Sorger, a Ph.D. student in Zhang's lab and study co-lead author.

"Plasmon lasers represent an exciting class of coherent light sources capable of extremely small confinement," said Zhang. "This work can bridge the worlds of electronics and optics at truly molecular length scales."

Scientists hope to eventually shrink light down to the size of an electron's wavelength, which is about a nanometer, or one-billionth of a meter, so that the two can work together on equal footing.

"The advantages of optics over electronics are multifold," added Thomas Zentgraf, a post-doctoral fellow in Zhang's lab and another co-lead author of the Nature paper. "For example, devices will be more power efficient at the same time they offer increased speed or bandwidth."

In addition to the three co-lead authors, other co-authors of the paper are Renmin Ma and Lun Dai from Peking University, and Christopher Gladden and Guy Bartal from Zhang's research group.

This work is supported by the U.S. Air Force Office of Scientific Research and the NSF.

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Small Fluctuations In Solar Activity, Large Influence On Climate

Small Fluctuations In Solar Activity, Large Influence On Climate

  10:27:00 AM    Science Lover

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Subtle connections between the 11-year solar cycle, the stratosphere, and the tropical Pacific Ocean work in sync to generate periodic weather patterns that affect much of the globe, according to research appearing this week in the journal Science. The study can help scientists get an edge on eventually predicting the intensity of certain climate phenomena, such as the Indian monsoon and tropical Pacific rainfall, years in advance.

Recently published research shows how newly discovered interactions between the Sun and the Earth affect our climate. (Credit: UCAR)

An international team of scientists led by the National Center for Atmospheric Research (NCAR) used more than a century of weather observations and three powerful computer models to tackle one of the more difficult questions in meteorology: if the total energy that reaches Earth from the Sun varies by only 0.1 percent across the approximately 11-year solar cycle, how can such a small variation drive major changes in weather patterns on Earth?

The answer, according to the new study, has to do with the Sun's impact on two seemingly unrelated regions. Chemicals in the stratosphere and sea surface temperatures in the Pacific Ocean respond during solar maximum in a way that amplifies the Sun's influence on some aspects of air movement. This can intensify winds and rainfall, change sea surface temperatures and cloud cover over certain tropical and subtropical regions, and ultimately influence global weather.

"The Sun, the stratosphere, and the oceans are connected in ways that can influence events such as winter rainfall in North America," says NCAR scientist Gerald Meehl, the lead author. "Understanding the role of the solar cycle can provide added insight as scientists work toward predicting regional weather patterns for the next couple of decades."

The study was funded by the National Science Foundation, NCAR's sponsor, and by the Department of Energy. It builds on several recent papers by Meehl and colleagues exploring the link between the peaks in the solar cycle and events on Earth that resemble some aspects of La Nina events, but are distinct from them. The larger amplitude La Nina and El Nino patterns are associated with changes in surface pressure that together are known as the Southern Oscillation.

The connection between peaks in solar energy and cooler water in the equatorial Pacific was first discovered by Harry Van Loon of NCAR and Colorado Research Associates, who is a co-author of the new paper.

Top down and bottom up

The new contribution by Meehl and his colleagues establishes how two mechanisms that physically connect changes in solar output to fluctuations in the Earth's climate can work together to amplify the response in the tropical Pacific.

The team first confirmed a theory that the slight increase in solar energy during the peak production of sunspots is absorbed by stratospheric ozone. The energy warms the air in the stratosphere over the tropics, where sunlight is most intense, while also stimulating the production of additional ozone there that absorbs even more solar energy. Since the stratosphere warms unevenly, with the most pronounced warming occurring at lower latitudes, stratospheric winds are altered and, through a chain of interconnected processes, end up strengthening tropical precipitation.

At the same time, the increased sunlight at solar maximum causes a slight warming of ocean surface waters across the subtropical Pacific, where Sun-blocking clouds are normally scarce. That small amount of extra heat leads to more evaporation, producing additional water vapor. In turn, the moisture is carried by trade winds to the normally rainy areas of the western tropical Pacific, fueling heavier rains and reinforcing the effects of the stratospheric mechanism.

The top-down influence of the stratosphere and the bottom-up influence of the ocean work together to intensify this loop and strengthen the trade winds. As more sunshine hits drier areas, these changes reinforce each other, leading to less clouds in the subtropics, allowing even more sunlight to reach the surface, and producing a positive feedback loop that further magnifies the climate response.

These stratospheric and ocean responses during solar maximum keep the equatorial eastern Pacific even cooler and drier than usual, producing conditions similar to a La Nina event. However, the cooling of about 1-2 degrees Fahrenheit is focused farther east than in a typical La Nina, is only about half as strong, and is associated with different wind patterns in the stratosphere.

Earth's response to the solar cycle continues for a year or two following peak sunspot activity. The La Nina-like pattern triggered by the solar maximum tends to evolve into a pattern similar to El Nino as slow-moving currents replace the cool water over the eastern tropical Pacific with warmer water. The ocean response is only about half as strong as with El Nino and the lagged warmth is not as consistent as the La Nina-like pattern that occurs during peaks in the solar cycle.

Enhancing ocean cooling

Solar maximum could potentially enhance a true La Nina event or dampen a true El Nino event. The La Nina of 1988-89 occurred near the peak of solar maximum. That La Nina became unusually strong and was associated with significant changes in weather patterns, such as an unusually mild and dry winter in the southwestern United States.

The Indian monsoon, Pacific sea surface temperatures and precipitation, and other regional climate patterns are largely driven by rising and sinking air in Earth's tropics and subtropics. Therefore the new study could help scientists use solar-cycle predictions to estimate how that circulation, and the regional climate patterns related to it, might vary over the next decade or two.

Three views, one answer

To tease out the elusive mechanisms that connect the Sun and Earth, the study team needed three computer models that provided overlapping views of the climate system.

One model, which analyzed the interactions between sea surface temperatures and lower atmosphere, produced a small cooling in the equatorial Pacific during solar maximum years. The second model, which simulated the stratospheric ozone response mechanism, produced some increases in tropical precipitation but on a much smaller scale than the observed patterns.

The third model contained ocean-atmosphere interactions as well as ozone. It showed, for the first time, that the two combined to produce a response in the tropical Pacific during peak solar years that was close to actual observations.

"With the help of increased computing power and improved models, as well as observational discoveries, we are uncovering more of how the mechanisms combine to connect solar variability to our weather and climate," Meehl says.

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation.

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'Plasmobot': Scientists To Design First Robot Using Mould

'Plasmobot': Scientists To Design First Robot Using Mould

  10:23:00 PM    Science Lover

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Scientists at the University of the West of England are to design the first ever biological robot using mould.

Plasmodium used in the research.
(Credit: Image courtesy of University of the West of England)

Researchers have received a Leverhulme Trust grant worth £228,000 to develop the amorphous non-silicon biological robot, plasmobot, using plasmodium, the vegetative stage of the slime mould Physarum polycephalum, a commonly occurring mould which lives in forests, gardens and most damp places in the UK. The Leverhulme Trust funded research project aims to design the first every fully biological (no silicon components) amorphous massively-parallel robot.

This project is at the forefront of research into unconventional computing. Professor Andy Adamatzky, who is leading the project, says their previous research has already proved the ability of the mould to have computational abilities.

Professor Adamatzky explains, “Most people’s idea of a computer is a piece of hardware with software designed to carry out specific tasks. This mould, or plasmodium, is a naturally occurring substance with its own embedded intelligence. It propagates and searches for sources of nutrients and when it finds such sources it branches out in a series of veins of protoplasm. The plasmodium is capable of solving complex computational tasks, such as the shortest path between points and other logical calculations. Through previous experiments we have already demonstrated the ability of this mould to transport objects. By feeding it oat flakes, it grows tubes which oscillate and make it move in a certain direction carrying objects with it. We can also use light or chemical stimuli to make it grow in a certain direction.

“This new plasmodium robot, called plasmobot, will sense objects, span them in the shortest and best way possible, and transport tiny objects along pre-programmed directions. The robots will have parallel inputs and outputs, a network of sensors and the number crunching power of super computers. The plasmobot will be controlled by spatial gradients of light, electro-magnetic fields and the characteristics of the substrate on which it is placed. It will be a fully controllable and programmable amorphous intelligent robot with an embedded massively parallel computer.”

This research will lay the groundwork for further investigations into the ways in which this mould can be harnessed for its powerful computational abilities.

Professor Adamatzky says that there are long term potential benefits from harnessing this power, “We are at the very early stages of our understanding of how the potential of the plasmodium can be applied, but in years to come we may be able to use the ability of the mould for example to deliver a small quantity of a chemical substance to a target, using light to help to propel it, or the movement could be used to help assemble micro-components of machines. In the very distant future we may be able to harness the power of plasmodia within the human body, for example to enable drugs to be delivered to certain parts of the human body. It might also be possible for thousands of tiny computers made of plasmodia to live on our skin and carry out routine tasks freeing up our brain for other things. Many scientists see this as a potential development of amorphous computing, but it is purely theoretical at the moment.”

Professor Adamatzky has recently edited and had published by Springer, ‘Artificial Life Models in Hardware’ aimed at students and researchers of robotics. The book focuses on the design and real-world implementation of artificial life robotic devices and covers a range of hopping, climbing, swimming robots, neural networks and slime mould and chemical brains.

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Satellites Unlock Secret To Northern India's Vanishing Water

Satellites Unlock Secret To Northern India's Vanishing Water

  9:50:00 PM    Science Lover

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Using satellite data, UC Irvine and NASA hydrologists have found that groundwater beneath northern India has been receding by as much as 1 foot per year over the past decade – and they believe human consumption is almost entirely to blame.

The map shows groundwater changes in India during 2002-08, with losses in red and gains in blue, based on GRACE satellite observations. The estimated rate of depletion of groundwater in northwestern India is 4.0 centimeters of water per year, equivalent to a water table decline of 33 centimeters per year. Increases in groundwater in southern India are due to recent above-average rainfall, whereas rain in northwestern India was close to normal during the study period. (Credit: I. Velicogna/UC Irvine)

More than 109 cubic kilometers (26 cubic miles) of groundwater disappeared from the region's aquifers between 2002 and 2008 – double the capacity of India's largest surface-water reservoir, the Upper Wainganga, and triple that of Lake Mead, the largest manmade reservoir in the U.S.

People are pumping northern India's underground water, mostly to irrigate cropland, faster than natural processes can replenish it, said Jay Famiglietti and Isabella Velicogna, UCI Earth system scientists, and Matt Rodell of NASA's Goddard Space Flight Center.

"If measures are not soon taken to ensure sustainable groundwater usage, consequences for the 114 million residents of the region may include a collapse of agricultural output, severe shortages of potable water, conflict and suffering," said Rodell, lead author of the study and former doctoral student of Famiglietti's at the University of Texas at Austin.

Study results will be published online Aug. 12 in the journal Nature.

Groundwater comes from the percolation of precipitation and other surface waters down through Earth's soil and rock, accumulating in aquifers – cavities and layers of porous rock, gravel, sand or clay. In some subterranean reservoirs, the water may be thousands to millions of years old; in others, water levels decline and rise again naturally each year.

Groundwater levels do not respond to changes in weather as rapidly as lakes, streams and rivers do. So when groundwater is pumped for irrigation or other uses, restoration of original levels can take months or years.

"Groundwater mining – that is when withdrawals exceed replenishment rates – is a rapidly growing problem in many of the world's large aquifers," Famiglietti said. "Since groundwater provides nearly 80 percent of the water required for irrigated agriculture, diminishing groundwater reserves pose a serious threat to global food security."

Data provided by India's Ministry of Water Resources had suggested that groundwater use across the nation was exceeding natural replenishment, but the regional rate of depletion had been unknown.

In the new study, the hydrologists analyzed six years of monthly data for northern India from twin satellites called GRACE – NASA's Gravity Recovery and Climate Experiment – to produce a chronology of underground water storage changes.

GRACE detects differences in gravity brought about by fluctuations in water mass, including water below the Earth's surface. As the satellites orbit 300 miles above Earth, their positions change – relative to each other – in response to variations in the pull of gravity. They fly about 137 miles apart, and microwave ranging systems measure every microscopic variance in the distance between the two.

"With GRACE, we can monitor water storage changes everywhere in the world from our desk," said Velicogna, also with NASA's Jet Propulsion Laboratory. "The satellites allow us to observe how water storage evolves from one month to the next in critical areas of the world."

Groundwater loss in northern India is particularly alarming because there were no unusual trends in rainfall – in fact, it was slightly above normal during the study period. The researchers also examined data on soil moisture, lake and surface reservoir storage, vegetation and glaciers in the nearby Himalayas to confirm that the apparent groundwater trend was real. The only influence they couldn't rule out was human.

"For the first time, we can observe water use on land with no additional ground-based data collection," Famiglietti said. "This is critical because in many developing countries, where hydrological data are both sparse and hard to access, space-based methods provide perhaps the only opportunity to assess changes in freshwater availability across large regions."

About GRACE: The Gravity Recovery and Climate Experiment is a partnership between NASA and the German Aerospace Center. The University of Texas Center for Space Research, Austin, has overall mission responsibility. NASA's Jet Propulsion Laboratory developed the twin satellites. The German Aerospace Center provided the launch, and GeoForschungsZentrum Potsdam, Germany, operates GRACE.

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New Nanolaser Key To Future Optical Computers And Technologies

New Nanolaser Key To Future Optical Computers And Technologies

  7:59:00 PM    Science Lover

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Researchers have created the tiniest laser since its invention nearly 50 years ago, paving the way for a host of innovations, including superfast computers that use light instead of electrons to process information, advanced sensors and imaging.

Researchers have created the tiniest laser since its invention nearly 50 years ago. Because the new device, called a "spaser," is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on "nanophotonic" circuitry. The color diagram (a) shows the nanolaser's design: a gold core surrounded by a glasslike shell filled with green dye. Scanning electron microscope images (b and c) show that the gold core and the thickness of the silica shell were about 14 nanometers and 15 nanometers, respectively. A simulation of the SPASER (d) shows the device emitting visible light with a wavelength of 525 nanometers. (Credit: Birck Nanotechnology Center, Purdue University)

Because the new device, called a "spaser," is the first of its kind to emit visible light, it represents a critical component for possible future technologies based on "nanophotonic" circuitry, said Vladimir Shalaev, the Robert and Anne Burnett Professor of Electrical and Computer Engineering at Purdue University.

Such circuits will require a laser-light source, but current lasers can't be made small enough to integrate them into electronic chips. Now researchers have overcome this obstacle, harnessing clouds of electrons called "surface plasmons," instead of the photons that make up light, to create the tiny spasers.

Findings are detailed in a paper appearing online in the journal Nature, reporting on work conducted by researchers at Purdue, Norfolk State University and Cornell University.

Nanophotonics may usher in a host of radical advances, including powerful "hyperlenses" resulting in sensors and microscopes 10 times more powerful than today's and able to see objects as small as DNA; computers and consumer electronics that use light instead of electronic signals to process information; and more efficient solar collectors.

"Here, we have demonstrated the feasibility of the most critical component - the nanolaser - essential for nanophotonics to become a practical technology," Shalaev said.

The "spaser-based nanolasers" created in the research were spheres 44 nanometers, or billionths of a meter, in diameter - more than 1 million could fit inside a red blood cell. The spheres were fabricated at Cornell, with Norfolk State and Purdue performing the optical characterization needed to determine whether the devices behave as lasers.

The findings confirm work by physicists David Bergman at Tel Aviv University and Mark Stockman at Georgia State University, who first proposed the spaser concept in 2003.

"This work represents an important milestone that may prove to be the start of a revolution in nanophotonics, with applications in imaging and sensing at a scale that is much smaller than the wavelength of visible light," said Timothy D. Sands, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center in Purdue's Discovery Park.

The spasers contain a gold core surrounded by a glasslike shell filled with green dye. When a light was shined on the spheres, plasmons generated by the gold core were amplified by the dye. The plasmons were then converted to photons of visible light, which was emitted as a laser.

Spaser stands for surface plasmon amplification by stimulated emission of radiation. To act like lasers, they require a "feedback system" that causes the surface plasmons to oscillate back and forth so that they gain power and can be emitted as light. Conventional lasers are limited in how small they can be made because this feedback component for photons, called an optical resonator, must be at least half the size of the wavelength of laser light.

The researchers, however, have overcome this hurdle by using not photons but surface plasmons, which enabled them to create a resonator 44 nanometers in diameter, or less than one-tenth the size of the 530-nanometer wavelength emitted by the spaser.

"It's fitting that we have realized a breakthrough in laser technology as we are getting ready to celebrate the 50th anniversary of the invention of the laser," Shalaev said.

The first working laser was demonstrated in 1960.

The research was conducted by Norfolk State researchers Mikhail A. Noginov, Guohua Zhu and Akeisha M. Belgrave; Purdue researchers Reuben M. Bakker, Shalaev and Evgenii E. Narimanov; and Cornell researchers Samantha Stout, Erik Herz, Teeraporn Suteewong and Ulrich B. Wiesner.

Future work may involve creating a spaser-based nanolaser that uses an electrical source instead of a light source, which would make them more practical for computer and electronics applications.

The work was funded by the National Science Foundation and U.S. Army Research Office and is affiliated with the Birck Nanotechnology Center, the Center for Materials Research at Norfolk State, and Cornell's Materials Science and Engineering Department.

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'Hidden Portal' Concept Described: First Tunable Electromagnetic Gateway

'Hidden Portal' Concept Described: First Tunable Electromagnetic Gateway

  5:58:00 PM    Science Lover

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While the researchers can't promise delivery to a parallel universe or a school for wizards, books like Pullman's Dark Materials and JK Rowling's Harry Potter are steps closer to reality now that researchers in China have created the first tunable electromagnetic gateway.

Entrance to platform nine and three-quarters at King's Cross Station, used by Harry Potter on his way to school. New research describes the concept of a gateway that can block electromagnetic waves but that allows the passage of other entities, like a 'hidden portal'. (Credit: iStockphoto/Guy Erwood)

The work is a further advance in the study of metamaterials, published in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society).

In the research paper, the researchers from the Hong Kong University of Science and Technology and Fudan University in Shanghai describe the concept of a "a gateway that can block electromagnetic waves but that allows the passage of other entities" like a "'hidden portal' as mentioned in fictions."

The gateway, which is now much closer to reality, uses transformation optics and an amplified scattering effect from an arrangement of ferrite materials called single-crystal yttrium-iron-garnet that force light and other forms of electromagnetic radiation in complicated directions to create a hidden portal.

Previous attempts at an electromagnetic gateway were hindered by their narrow bandwidth, only capturing a small range of visible light or other forms of electromagnetic radiation. This new configuration of metamaterials however can be manipulated to have optimum permittivity and permeability – able to insulate the electromagnetic field that encounters it with an appropriate magnetic reaction.

Because of the arrangement's response to magnetic fields it also has the added advantage of being tunable and can therefore be switched on and off remotely.

Dr Huanyang Chen from the Physics Department at Hong Kong University of Science and Technology has commented, "In the frequency range in which the metamaterial possesses a negative refraction index, people standing outside the gateway would see something like a mirror. Whether it can block all visible light depends on whether one can make a metamaterial that has a negative refractive index from 300 to 800 nanometres."

Metamaterials, the area of physics research behind the possible creation of a real Harry Potter-style invisibility cloak, are exotic composite materials constructed at the atomic (rather than the usual chemical) level to produce materials with properties beyond those which appear naturally.

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World Record In Packing Puzzle Set In Tetrahedra Jam: Better Understanding Of Matter Itself?

World Record In Packing Puzzle Set In Tetrahedra Jam: Better Understanding Of Matter Itself?

  5:21:00 PM    Science Lover

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Finding the best way to pack the greatest quantity of a specifically shaped object into a confined space may sound simple, yet it consistently has led to deep mathematical concepts and practical applications, such as improved computer security codes.

Princeton researchers have beaten the present world record for packing the most tetrahedra into a volume. Research into these so-called packing problems have produced deep mathematical ideas and led to practical applications as well.
(Credit: Princeton University/Torquato Lab)

When mathematicians solved a famed sphere-packing problem in 2005, one that first had been posed by renowned mathematician and astronomer Johannes Kepler in 1611, it made worldwide headlines.

Now, two Princeton University researchers have made a major advance in addressing a twist in the packing problem, jamming more tetrahedra -- solid figures with four triangular faces -- and other polyhedral solid objects than ever before into a space. The work could result in better ways to store data on compact discs as well as a better understanding of matter itself.

In the cover story of the Aug. 13 issue of Nature, Salvatore Torquato, a professor in the Department of Chemistry and the Princeton Institute for the Science and Technology of Materials, and Yang Jiao, a graduate student in the Department of Mechanical and Aerospace Engineering, report that they have bested the world record, set last year by Elizabeth Chen, a graduate student at the University of Michigan.

Using computer simulations, Torquato and Jiao were able to fill a volume to 78.2 percent of capacity with tetrahedra. Chen, before them, had filled 77.8 percent of the space. The previous world record was set in 2006 by Torquato and John Conway, a Princeton professor of mathematics. They succeeded in filling the space to 72 percent of capacity.

Beyond making a new world record, Torquato and Jiao have devised an approach that involves placing pairs of tetrahedra face-to-face, forming a "kissing" pattern that, viewed from the outside of the container, looks strangely jumbled and irregular.

"We wanted to know this: What's the densest way to pack space?" said Torquato, who is also a senior faculty fellow at the Princeton Center for Theoretical Science. "It's a notoriously difficult problem to solve, and it involves complex objects that, at the time, we simply did not know how to handle."

Henry Cohn, a mathematician with Microsoft Research New England in Cambridge, Mass., said, "What's exciting about Torquato and Jiao's paper is that they give compelling evidence for what happens in more complicated cases than just spheres." The Princeton researchers, he said, employ solid figures as a "wonderful test case for understanding the effects of corners and edges on the packing problem."

Studying shapes and how they fit together is not just an academic exercise. The world is filled with such solids, whether they are spherical oranges or polyhedral grains of sand, and it often matters how they are organized. Real-life specks of matter resembling these solids arise at ultra-low temperatures when materials, especially complex molecular compounds, pass through various chemical phases. How atoms clump can determine their most fundamental properties.

"From a scientific perspective, to know about the packing problem is to know something about the low-temperature phases of matter itself," said Torquato, whose interests are interdisciplinary, spanning physics, applied and computational mathematics, chemistry, chemical engineering, materials science, and mechanical and aerospace engineering.

And the whole topic of the efficient packing of solids is a key part of the mathematics that lies behind the error-detecting and error-correcting codes that are widely used to store information on compact discs and to compress information for efficient transmission around the world.

Beyond solving the practical aspects of the packing problem, the work contributes insight to a field that has fascinated mathematicians and thinkers for thousands of years. The Greek philosopher Plato theorized that the classical elements -- earth, wind, fire and water -- were constructed from polyhedra. Models of them have been found among carved stone balls created by the late Neolithic people of Scotland.

The tetrahedron, which is part of the family of geometric objects known as the Platonic solids, must be packed in the face-to-face fashion for maximum effect. But, for significant mathematical reasons, all other members of the Platonic solids, the researchers found, must be packed as lattices to cram in the largest quantity, much the way a grocer stacks oranges in staggered rows, with successive layers nestled in the dimples formed by lower levels. Lattices have great regularity because they are composed of single units that repeat themselves in exactly the same way.

Mathematicians define the five shapes composing the Platonic solids as being convex polyhedra that are regular. For non-mathematicians, this simply means that these solids have many flat faces, which are plane figures, such as triangles, squares or pentagons. Being regular figures, all angles and faces' sides are equal. The group includes the tetrahedron (with four faces), the cube (six faces), the octahedron (eight faces), the dodecahedron (12 faces) and the icosahedron (20 faces).

There's a good reason why tetrahedra must be packed differently from other Platonic solids, according to the authors. Tetrahedra lack a quality known as central symmetry. To possess this quality, an object must have a center that will bisect any line drawn to connect any two points on separate planes on its surface. The researchers also found this trait absent in 12 out of 13 of an even more complex family of shapes known as the Archimedean solids.

The conclusions of the Princeton scientists are not at all obvious, and it took the development of a complex computer program and theoretical analysis to achieve their groundbreaking results. Previous computer simulations had taken virtual piles of polyhedra and stuffed them in a virtual box and allowed them to "grow."

The algorithm designed by Torquato and Jiao, called "an adaptive shrinking cell optimization technique," did it the other way. It placed virtual polyhedra of a fixed size in a "box" and caused the box to shrink and change shape.

There are tremendous advantages to controlling the size of the box instead of blowing up polyhedra, Torquato said. "When you 'grow' the particles, it's easy for them to get stuck, so you have to wiggle them around to improve the density," he said. "Such programs get bogged down easily; there are all kinds of subtleties. It's much easier and productive, we found, thinking about it in the opposite way."

Cohn, of Microsoft, called the results remarkable. It took four centuries, he noted, for mathematician Tom Hales to prove Kepler's conjecture that the best way to pack spheres is to stack them like cannonballs in a war memorial. Now, the Princeton researchers, he said, have thrown out a new challenge to the math world. "Their results could be considered a 21st Century analogue of Kepler's conjecture about spheres," Cohn said. "And, as with that conjecture, I'm sure their work will inspire many future advances."

Many researchers have pointed to various assemblies of densely packed objects and described them as optimal. The difference with this work, Torquato said, is that the algorithm and analysis developed by the Princeton team most probably shows, in the case of the centrally symmetric Platonic and Archimedean solids, "the best packings, period."

Their simulation results are also supported by theoretical arguments that the densest packings of these objects are likely to be their best lattice arrangements. "This is now a strong conjecture that people can try to prove," Torquato said.

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