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Monday, August 29, 2016

Nanoscale Wireless Communication

The pursuit of next-generation technologies places a premium on producing increased speed and efficiency with components built at scales small enough to function on a computer chip.

One of the barriers to advances in "on-chip" communications is the size of the electromagnetic waves at radio and microwave frequencies, which form the backbone of modern wireless technology. The relatively large waves handcuff further miniaturization.

Scientists trying to surpass these limitations are exploring the potential of optical conveyance that exploits the properties of much smaller wavelengths, such as those in the terahertz, infrared and visible frequencies.

A team of researchers at Boston College has developed the first nanoscale wireless communication system that operates at visible wavelengths using antennas that send and receive surface plasmons with an unprecedented degree of control, the team reports in the latest edition of the journal Nature's Scientific Reports.

Furthermore, the device affords an "in-plane" configuration, a prized class of two-way information transmission and recovery in a single path, according to the study, conducted by a team in the lab of Evelyn J. and Robert A. Ferris Professor of Physics Michael J. Naughton.

Surface plasmons possess unique subwavelength capabilities. Researchers trying to exploit those features have developed metallic structures, including plasmonic antennas. But a persistent problem has been the inability to achieve 'in-line' containment of the emission and collection of the electromagnetic radiation.

A Boston College team has developed a device with a three-step conversion process that changes a surface plasmon to a photon on transmission and then converts that elemental electromagnetic particle back to a surface plasmon as the receiver picks it up. The device, illustrated in this video, offers an unprecedented degree of control in this approach to faster, more efficient communications to power computers and optical technologies.

Credit: Michael J. Burns, Juan M. Merlo

The findings mark an important first step toward a nanoscale version - and visible frequency equivalent - of existing wireless communication systems, according to the researchers. Such on-chip systems could be used for high-speed communication, high efficiency plasmonic waveguiding and in-plane circuit switching - a process that is currently used in liquid crystal displays.

The device achieved communication across several wavelengths in tests using near-field scanning optical microscopy, according to lead co-author Juan M. Merlo, a post-doctoral researcher who initiated the project.

"Juan was able to push it beyond the near field - at least to four times the width of a wavelength. That is true far-field transmission and nearly every device we use on a daily basis - from our cell phones to our cars - relies on far-field transmission," said Naughton.

The device could speed the transmission of information by as much as 60 percent compared to earlier plasmonic waveguiding techniques and up to 50 percent faster than plasmonic nanowire waveguides, the team reports.

Surface plasmons are the oscillations of electrons coupled to the interface of an electromagnetic field and a metal. Among their unique abilities, surface plasmons can confine energy on that interface by fitting into spaces smaller than the waves themselves.

Researchers trying to exploit these subwavelength capabilities of surface plasmons have developed metallic structures, including plasmonic antennas. But a persistent problem has been the inability to achieve "in-line" containment of the emission and collection of the electromagnetic radiation.

The BC team developed a device with a three-step conversion process that changes a surface plasmon to a photon on transmission and then converts that elemental electromagnetic particle back to a surface plasmon as the receiver picks it up.

"We have developed a device where plasmonic antennas communicate with each other with photons transmitting between them," said Naughton. "This is done with high efficiency, with energy loss reduced by 50 percent between one antenna and the next, which is a significant enhancement over comparable architectures."

Central to the newfound control of the surface plasmons was the creation of a small gap of air between the waves and the silver surface of the device, said Merlo, who earned his PhD at Mexico's National Institute of Astrophysics, Optics and Electronics. By removing a portion of the glass substrate, the team reduced the disruptive pull of the material on the photons in transmission. Expanding and narrowing that gap proved crucial to tuning the device.

With traditional silicon waveguides, dispersion reduces information transmission speed. Without that impediment, the new device capitalizes on the capability of surface plasmons to travel at 90 to 95 percent of the speed of light on a silver surface and photons traveling between the antennas at their inherent speed of light, Merlo said.

"Silicon-based optical technology has been around for years," said Merlo. "What we are doing is improving it to make it faster. We're developing a tool to make silicon photonics faster and greatly enhance rates of communication."

Contacts and sources
Ed Hayward
Boston College 

In addition to Naughton and Merlo, the paper was co-authored by Professor Krzysztof Kempa, Senior Research Associate Michael J. Burns, and graduate students Nathan T. Nesbitt, Yitzi M. Calm, Aaron H. Rose, Luke D'Imperio, Chaobin Yang and Jeffrey R. Naughton.

The full report can be found at: http://www.nature.com/articles/srep31710

Sunday, August 28, 2016

3-D Printed Structures Remember, Touch and Grip; Can Also Deliver Drugs

Engineers from MIT and Singapore University of Technology and Design (SUTD) are using light to print three-dimensional structures that "remember" their original shapes. Even after being stretched, twisted, and bent at extreme angles, the structures -- from small coils and multimaterial flowers, to an inch-tall replica of the Eiffel tower -- sprang back to their original forms within seconds of being heated to a certain temperature "sweet spot."

Credit: MIT

For some structures, the researchers were able to print micron-scale features as small as the diameter of a human hair -- dimensions that are at least one-tenth as big as what others have been able to achieve with printable shape-memory materials. The team's results were published earlier this month in the online journal Scientific Reports.

In this series, a 3-D printed multimaterial shape-memory minigripper, consisting of shape-memory hinges and adaptive touching tips, grasps a cap screw.

Photo courtesy of Qi (Kevin) Ge

Nicholas X. Fang, associate professor of mechanical engineering at MIT, says shape-memory polymers that can predictably morph in response to temperature can be useful for a number of applications, from soft actuators that turn solar panels toward the sun, to tiny drug capsules that open upon early signs of infection.

"We ultimately want to use body temperature as a trigger," Fang says. "If we can design these polymers properly, we may be able to form a drug delivery device that will only release medicine at the sign of a fever."

Fang's coauthors include former MIT-SUTD research fellow Qi "Kevin" Ge, now an assistant professor at SUTD; former MIT research associate Howon Lee, now an assistant professor at Rutgers University; and others from SUTD and Georgia Institute of Technology.

Ge says the process of 3-D printing shape-memory materials can also be thought of as 4-D printing, as the structures are designed to change over the fourth dimension -- time.

"Our method not only enables 4-D printing at the micron-scale, but also suggests recipes to print shape-memory polymers that can be stretched 10 times larger than those printed by commercial 3-D printers," Ge says. "This will advance 4-D printing into a wide variety of practical applications, including biomedical devices, deployable aerospace structures, and shape-changing photovoltaic solar cells."

Need for speed

Fang and others have been exploring the use of soft, active materials as reliable, pliable tools. These new and emerging materials, which include shape-memory polymers, can stretch and deform dramatically in response to environmental stimuli such as heat, light, and electricity -- properties that researchers have been investigating for use in biomedical devices, soft robotics, wearable sensors, and artificial muscles.

A shape-memory Eiffel tower was 3-D printed using projection microstereolithography. It is shown recovering from being bent, after toughening on a heated Singapore dollar coin.

Photo courtesy of Qi (Kevin) Ge

Shape-memory polymers are particularly intriguing: These materials can switch between two states -- a harder, low-temperature, amorphous state, and a soft, high-temperature, rubbery state. The bent and stretched shapes can be "frozen" at room temperature, and when heated the materials will "remember" and snap back to their original sturdy form.

To fabricate shape-memory structures, some researchers have looked to 3-D printing, as the technology allows them to custom-design structures with relatively fine detail. However, using conventional 3-D printers, researchers have only been able to design structures with details no smaller than a few millimeters. Fang says this size restriction also limits how fast the material can recover its original shape.

"The reality is that, if you're able to make it to much smaller dimensions, these materials can actually respond very quickly, within seconds," Fang says. "For example, a flower can release pollen in milliseconds. It can only do that because its actuation mechanisms are at the micron scale."

Printing with light

To print shape-memory structures with even finer details, Fang and his colleagues used a 3-D printing process they have pioneered, called microstereolithography, in which they use light from a projector to print patterns on successive layers of resin.

The researchers first create a model of a structure using computer-aided design (CAD) software, then divide the model into hundreds of slices, each of which they send through the projector as a bitmap -- an image file format that represents each layer as an arrangement of very fine pixels. The projector then shines light in the pattern of the bitmap, onto a liquid resin, or polymer solution, etching the pattern into the resin, which then solidifies.

"We're printing with light, layer by layer," Fang says. "It's almost like how dentists form replicas of teeth and fill cavities, except that we're doing it with high-resolution lenses that come from the semiconductor industry, which give us intricate parts, with dimensions comparable to the diameter of a human hair."

The researchers then looked through the scientific literature to identify an ideal mix of polymers to create a shape-memory material on which to print their light patterns. They picked two polymers, one composed of long-chain polymers, or spaghetti-like strands, and the other resembling more of a stiff scaffold. When mixed together and cured, the material can be stretched and twisted dramatically without breaking.

What's more, the material can bounce back to its original printed form, within a specific temperature range -- in this case, between 40 and 180 degrees Celsius (104 to 356 degrees Fahrenheit).

The team printed a variety of structures, including coils, flowers, and the miniature Eiffel tower, whose full-size counterpart is known for its intricate steel and beam patterns. Fang found that the structures could be stretched to three times their original length without breaking. When they were exposed to heat within the range of 40 C to 180 C, they snapped back to their original shapes within seconds.

"Because we're using our own printers that offer much smaller pixel size, we're seeing much faster response, on the order of seconds," Fang says. "If we can push to even smaller dimensions, we may also be able to push their response time, to milliseconds."

Soft grip

To demonstrate a simple application for the shape-memory structures, Fang and his colleagues printed a small, rubbery, claw-like gripper. They attached a thin handle to the base of the gripper, then stretched the gripper's claws open. When they cranked the temperature of the surrounding air to at least 40 C, the gripper closed around whatever the engineers placed beneath it.

"The grippers are a nice example of how manipulation can be done with soft materials," Fang says. "We showed that it is possible to pick up a small bolt, and also even fish eggs and soft tofu. That type of soft grip is probably very unique and beneficial."

Going forward, he hopes to find combinations of polymers to make shape-memory materials that react to slightly lower temperatures, approaching the range of human body temperatures, to design soft, active, controllable drug delivery capsules. He says the material may also be printed as soft, responsive hinges to help solar panels track the sun.

"Very often, excessive heat will build up on the back side of the solar cell, so you could use [shape-memory materials] as an actuation mechanism to tune the inclination angle of the solar cell," Fang says. "So we think there will probably be more applications that we can demonstrate."

Contacts and sources:
Abby Abazorius

This research is supported in part by the SUTD Digital Manufacturing and Design Center (DManD) and the SUTD-MIT joint postdoctoral program.

Spherical Tokamaks Could Provide Path to Limitless Fusion Energy

Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility — or “bottle” — that will provide the next steps in the development of fusion reactors. Leading candidates include spherical tokamaks, compact machines that are shaped like cored apples, compared with the doughnut-like shape of conventional tokamaks. The spherical design produces high-pressure plasmas — essential ingredients for fusion reactions — with relatively low and cost-effective magnetic fields.

Creating "a star in a jar" - replicating on Earth the way the sun and stars create energy through fusion - requires a "jar" that can contain superhot plasma and is low-cost enough to be built around the world. Such a device would provide humankind with near limitless energy, ending dependence on fossil fuels for generating electricity.

This image shows a test cell for National Spherical Torus Experiment-Upgrade with tokamak in the center.

Credit: Elle Starkman/PPPL

Physicists at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) say that a model for such a "jar," or fusion device, already exists in experimental form - the compact spherical tokamaks at PPPL and Culham, England. These tokamaks, or fusion reactors, could provide the design for possible next steps in fusion energy - a Fusion Nuclear Science Facility (FNSF) that would develop reactor components and also produce electricity as a pilot plant for a commercial fusion power station.

"New options for future plants"

The detailed proposal for such a "jar" is described in a paper published in August 2016 in the journal Nuclear Fusion. "We are opening up new options for future plants," said lead author Jonathan Menard, program director for the recently completed National Spherical Torus Experiment-Upgrade (NSTX-U) at PPPL. The $94-million upgrade of the NSTX, financed by the U.S. Department of Energy's Office of Science, began operating last year.

Spherical tokamaks are compact devices that are shaped like cored apples, compared with the bulkier doughnut-like shape of conventional tokamaks. The increased power of the upgraded PPPL machine and the soon-to-be completed MAST Upgrade device moves them closer to commercial fusion plants that will create safe, clean and virtually limitless energy without contributing greenhouse gases that warm the Earth and with no long-term radioactive waste.

Credit: Princeton Plasma Physics Laboratory

The NSTX-U and MAST facilities "will push the physics frontier, expand our knowledge of high temperature plasmas, and, if successful, lay the scientific foundation for fusion development paths based on more compact designs," said PPPL Director Stewart Prager.

The devices face a number of physics challenges. For example, they must control the turbulence that arises when superhot plasma particles are subjected to powerful electromagnetic fields. They must also carefully control how the plasma particles interact with the surrounding walls to avoid possible disruptions that can halt fusion reactions if the plasma becomes too dense or impure. Researchers at PPPL, Culham, and elsewhere are looking at ways of solving these challenges for the next generation of fusion devices.

The fourth state of matter

The spherical design produces high-pressure plasmas - the superhot charged gas also known as the fourth state of matter that fuels fusion reactions - with relatively low and inexpensive magnetic fields. This unique capability points the way to a possible next generation of fusion experiments to complement ITER, the international tokamak that 35 nations including the United States are building in France to demonstrate the feasibility of fusion power. ITER is a doughnut-shaped tokamak that will be largest in the world when completed within the next decade.

"The main reason we research spherical tokamaks is to find a way to produce fusion at much less cost than conventional tokamaks require," said Ian Chapman, the newly appointed chief executive of the United Kingdom Atomic Energy Authority and leader of the UK's magnetic confinement fusion research programme at the Culham Science Centre.

Center stack of the NSTX-U.
Photo courtesy of Culham Centre for Fusion Energy.

The 43-page Nuclear Fusion paper describes how the spherical design can provide the next steps in fusion energy. A key issue is the size of the hole in the center of the tokamak that holds and shapes the plasma. In spherical tokamaks, this hole can be half the size of the hole in conventional tokamaks, enabling control of the plasma with relatively low magnetic fields.

The smaller hole could be compatible with a blanket system for the FNSF that would breed tritium, a rare isotope - or form - of hydrogen. Tritium will fuse with deuterium, another isotope of hydrogen, to produce fusion reactions in next-step tokamaks.

Superconducting magnets for pilot plants

For pilot plants, the authors call for superconducting magnets to replace the primary copper magnets in the FNSF. Superconducting magnets can be operated far more efficiently than copper magnets but require thicker shielding. However, recent advances in high-temperature superconductors could lead to much thinner superconducting magnets that would require less space and reduce considerably the size and cost of the machine.

Mega Ampere Spherical Tokamak. 
Photo courtesy of Culham Centre for Fusion Energy.

Included in the paper is a description of a device called a "neutral beam injector" that will start and sustain plasma current without relying on a heating coil in the center of the tokamak. Such a coil is not suitable for continuous long-term operation. The neutral beam injector will pump fast-moving neutral atoms into the plasma and will help optimize the magnetic field that confines and controls the superhot gas.

Taken together, the paper describes concepts that strongly support a spherical facility to develop fusion components and create on Earth "a star in a jar"; the upgraded NSTX and MAST facilities will provide crucial data for determining the best path for ultimately generating electricity from fusion.

Contacts and sources:
John Greenwald
DOE/Princeton Plasma Physics Laboratory

Fusion nuclear science facilities and pilot plants based on the spherical tokamak  http://dx.doi.org/10.1088/0029-5515/56/10/106023

Saturday, August 27, 2016

Fracking Earthquake Risks Can Be Lessened

New research from the U.S. Geological Survey and the University of Colorado shows actions taken by drillers and regulators can lessen risk in the case of earthquakes likely caused by the injection of industrial wastewater deep underground.

While the earthquake that rumbled below Colorado’s eastern plains May 31, 2014, did no major damage, its occurrence surprised both Greeley residents and local seismologists. To some Greeley residents, the magnitude 3.2 earthquake felt like a large truck hitting the house.

The earthquake happened in an area that had seen no seismic activity in at least four decades, according to a new analysis by a team of Colorado researchers. It was likely caused by the injection of industrial wastewater deep underground—and, the team concluded, quick action taken by scientists, regulators and industry may have reduced the risk of larger quakes in the area.

“We were surprised to observe an earthquake right in our backyard, and we knew we needed to know more, so we quickly mobilized seismic monitoring equipment," said Will Yeck, lead author of the study. "As it turned out, our findings were not just scientifically interesting. By sharing our observations with others in real time, we were able to help inform the decisions made to mitigate these earthquakes. It was extremely rewarding to see our scientific observations have a direct and immediate impact.”

Yeck, then finishing up his Ph.D. in geophysics at the University of Colorado Boulder, and now a researcher with the USGS, worked with a team of researchers that included his Ph.D. advisor Anne Sheehan, a professor and CIRES Fellow, two other graduate students and a USGS colleague. Their work appears in the July-August issue of Seismological Research Letters.

A few minutes after 10 p.m. the night of the earthquake, Sheehan also received an email from a neighbor who had felt an earthquake at her home in Boulder. The neighbor quickly looked up the initial details through a USGS website, and relayed them to Sheehan. It looked like the earthquake was centered in the heart of oil and gas country in Weld County, where drillers sometimes disposed of wastewater deep underground—an activity now known to sometimes trigger earthquakes.

In many homes near the earthquake’s epicenter, furniture shifted in rooms. Bricks fell off at least one chimney.

“The next day was very busy,” said Sheehan.

She requested seismometers from a consortium that rapidly supplies equipment for earthquake aftershock monitoring. She began talking with her graduate students, colleagues from the USGS and the oil and gas industry, and regulators about where to deploy the equipment.

The first week of June, Yeck and fellow graduate students Jenny Nakai and Matthew Weingarten deployed six seismometers in an array around the earthquake’s epicenter to monitor further seismic activity. As data flowed in, they analyzed it in detail to pinpoint the locations and the timing of smaller earthquakes following that first one.

The geophysicists communicated their findings with state oil and gas regulators and wastewater disposal company staff, and helped those staff learn to read and understand real-time seismic data themselves.

It quickly became clear that the earthquakes were centered under one specific well: the wastewater disposal well closest to the Greeley earthquake epicenter which happened to be the highest‐rate injection well in northeast Colorado in 2013, according to data compiled by the state. The well had been pumping an average of 250,000 barrels per month since August 2013, more than a mile deep.

“Soon after the magnitude 3.2 earthquake, when the seismic network was in place, we shared earthquake locations and earthquake magnitude frequency with the Colorado Oil and Gas Conservation Commission and local energy companies to better inform them of seismic activity occurring around the wells,” said Jenny Nakai, a co-author of the new study and a graduate student in geophysics at CU Boulder. “We could see fluctuations in seismic activity as the well was shut down and cemented.”

Injection stopped on June 24 for a month, and the company that drilled the disposal well took two actions to reduce seismicity: They reduced injection rates and used cement to plug the bottom of the well, impeding fluid interaction with deeper, subsurface faults.

Injection resumed a month later at reduced rates, starting at just 5,000 barrels a day mid-July. The injection rates were slowly increased over time.

Seismicity dropped, the team found. Following mitigation, between August 13, 2014, and December 29, 2015, no earthquakes larger than magnitude 1.5 occurred near Greeley.

The research team also used data from more distant seismometers, deployed well before the 2014 earthquake, to detect past seismic activity in the area. They found the Greeley earthquake sequence began roughly four months after the initiation of high-rate wastewater injection in 2013. Their analysis suggested that the biggest observed earthquakes in the area were getting bigger over time, an observation made at other injection induced earthquake locations as well.

State regulators with the Colorado Oil and Gas Conservation Commission modified requirements as a result of the seismology team’s findings, Yeck and his colleagues reported in the paper. Regulators began requiring seismic monitoring at recently permitted commercial disposal wells pumping more than 10,000 barrels per day.

Greeley-area seismicity continues to be monitored both by the CU Boulder team and by an independent contractor.

Authors of “Rapid Response, Monitoring, and Mitigation of Induced Seismicity near Greeley, Colorado” in Seismological Research Letters are William Yeck and Harley Benz (U.S. Geological Survey), Anne Sheehan and Jenny Nakai (CIRES and University of Colorado Boulder), and Matthew Weingarten (Stanford University).

Contacts and sources:
Heidi Koontz
United States Geological Survey

Survey Finds Vast Majority of Americans Think USA Is Divided Over Values and Politics

Americans see their country as deeply divided over values and politics -- a gap they do not expect to diminish any time soon, according to a new survey conducted by The Associated Press-NORC Center for Public Affairs Research. But the survey also finds that most Americans report agreement on important values among members of their local communities. Seven in 10 say the news media places too much emphasis on these differences
While few Americans say they have much in common with people of different religions or ethnic backgrounds, most of the public believes the racial, ethnic, and religious diversity of the United States makes the country stronger. Consensus and disagreement over American exceptionalism, the media's role in accentuating the country's divisions, and future levels of conflicts are also explored in the survey.
Credit; Wikimedia
"Political campaigns, especially the presidential campaigns, raise both the extent and intensity of public debate," said Trevor Tompson, director of The AP-NORC Center. "Surveys like the one we have done can reveal important insights that help explain the underlying causes of recent political events."
The survey is part of AP's Divided America series, which explores the issues dividing American voters in this tumultuous presidential election year and what's driving them toward the decision they will make on November 8.
The nationwide poll of 1,008 adults utilized NORC's AmeriSpeak® Omnibus, a monthly multi-client survey using NORC's probability-based panel designed to be representative of the U.S. household population. Interviews were conducted between June 23 and 27, 2016, online and using landlines and cell phones. The AmeriSpeak panel is notable for its representativeness and high rates of participation.
Some of the poll's key findings are:
  • Eighty percent of Americans say the country is greatly divided when it comes to the most important values, and 85 percent say the United States is increasingly divided by politics.
  • While few people think the country as a whole agrees on values, most say their neighbors do share important values. Six in 10 (62 percent) say members of their local community are in agreement about values.
  • Nearly three-quarters (72 percent) say the news media puts too much focus on disagreements, and 63 percent say the same about politicians and elected officials. The entertainment industry is seen by 43 percent as overemphasizing splits within the country.
  • Most Americans regard the country's diverse population as advantageous to the nation. More than half (56 percent) say diversity makes the country stronger, while 16 percent say it weakens the country. Twenty-eight percent say diversity has no effect one way or the other. Democrats, urbanites, and Hispanics are particularly inclined to see the variety of people in the country as a plus for the United States.
  • Is the United States the best country on earth? Only 26 percent of the public agree that the United States "stands above all other countries in the world," while 55 percent of the public say the United States is "one of the greatest countries in the world along with some others." Just 19 percent think there are other countries that are better.
  • The public is closely divided over whether the good times for the country have been left behind or are yet to come. Fifty-two percent say the country's best days are in the past, while 46 percent say they are ahead of us. Blacks and Hispanics tend to have a positive outlook about the future of the country, while most whites say the good times are in the past.
  • While most people say they have a lot in common with other members of their community, few feel they share much in common with wealthier people or those with different political views.
  • Neither the Democratic nor the Republican candidate for President is regarded as particularly capable of uniting the country. However, while 43 percent say Hillary Clinton's election would lead to a more divided nation, many more, 73 percent, say the country will be more separated if Donald Trump prevails in November.

Contacts and sources:
Eric Young
NORC at The University of Chicago

Fracking Chemicals Adversely Affecting Fertility, More Than 15 Million Americans within a Mile of Fracking Operations

More than 15 million Americans live within a one-mile radius of unconventional oil and gas (UOG) operations. UOGs combine directional drilling and hydraulic fracturing, or "fracking," to release natural gas from underground rock. Scientific studies, while ongoing, are still inconclusive on the potential long-term effects fracturing has on human development.

Researchers at the University of Missouri released a study that is the first of its kind to link exposure to chemicals released during hydraulic fracturing to adverse reproductive and developmental outcomes in mice. Scientists believe that exposure to these chemicals also could pose a threat to human development.

2011-2014 Hydraulic Fracturing Water Use (square meters/well)
Credit:  USGS  F

“Researchers have previously found that endocrine-disrupting chemicals (EDCs) mimic or block hormones — the chemical messengers that regulate respiration, reproduction, metabolism, growth and other biological functions,” said Susan C. Nagel, Nagel, an associate professor of obstetrics, gynecology and women’s health in the School of Medicine. “Evidence from this study indicates that developmental exposure to fracking and drilling chemicals may pose a threat to fertility in animals and potentially people. Negative outcomes were observed even in mice exposed to the lowest dose of chemicals, which was lower than the concentrations found in groundwater at some locations with past oil and gas wastewater spills.”

Researchers mixed 23 oil and gas chemicals in four different concentrations to reflect concentrations ranging from those found in drinking water and groundwater to concentrations found in industry wastewater. The mixtures were added to drinking water given to pregnant mice in the laboratory until they gave birth. The female offspring of the mice that drank the chemical mixtures were compared to female offspring of mice in a control group that were not exposed. Mice exposed to drilling chemicals had lower levels of key hormones related to reproductive health compared to the control group.

Susan Nagel and her team released a study that is the first of its kind to link exposure to chemicals released during fracking to adverse reproductive and developmental outcomes in mice. Scientists believe that exposure to these chemicals also could pose a threat to human development.

“Female mice that were exposed to commonly used fracking chemicals in utero showed signs of reduced fertility, including alterations in the development of the ovarian follicles and pituitary and reproductive hormone concentrations,” Nagel said, who also serves as an adjunct associate professor of biological sciences in the MU College of Arts and Science. “These findings build on our previous research, which found exposure to the same chemicals was tied to reduced sperm counts in male mice. Our studies suggest adverse developmental and reproductive health outcomes might be expected in humans and animals exposed to chemicals in regions with oil and gas drilling activity.”

The study, “Adverse Reproductive and Developmental Health Outcomes Following Prenatal Exposure to a Hydraulic Fracturing Chemical Mixture in Female C57BI/6 Mice,” was published in the journalEndocrinology. Authors of the study include: Christopher D. Kassotis of Duke University in Durham, N.C.; John J. Bromfield of the University of Florida in Gainesville, FL; Kara C. Klemp, Chun-Xia Meng, Victoria D. Balise and Chiamaka J. Isiguzo of the University of Missouri; Andrew Wolfe of the Johns Hopkins University School of Medicine in Baltimore, MD; R. Thomas Zoeller of the University of Massachusetts Amherst in Amherst, MA; and Donald E. Tillitt of the U.S. Geological Survey’s Columbia Environmental Research Center in Columbia, MO.

The research was funded by the University of Missouri Research Council and Mizzou Advantage, a crowd-funding campaign on Experiment.com, and the U.S. Environmental Protection Agency’s STAR Fellowship Assistance Agreement awarded to Christopher D. Kassotis. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

Contacts and sources:
Jeff Sossamon
University of Missouri - Columbia

The study, "Adverse Reproductive and Developmental Health Outcomes Following Prenatal Exposure to a Hydraulic Fracturing Chemical Mixture in Female C57BI/6 Mice," was published in the journal Endocrinology. Authors of the study include: Christopher D. Kassotis of Duke University in Durham, N.C.; John J. Bromfield of the University of Florida in Gainesville, FL; Kara C. Klemp, Chun-Xia Meng, Victoria D. Balise and Chiamaka J. Isiguzo of the University of Missouri; Andrew Wolfe of the Johns Hopkins University School of Medicine in Baltimore, MD; R. Thomas Zoeller of the University of Massachusetts Amherst in Amherst, MA; and Donald E. Tillitt of the U.S. Geological Survey's Columbia Environmental Research Center in Columbia, MO.

Scientists Solve Puzzle of Converting Gaseous Carbon Dioxide to Fuel with Nanotechnology

Every year, humans advance climate change and global warming - and quite likely our own eventual extinction - by injecting about 30 billion tonnes of carbon dioxide into the atmosphere.

A team of scientists from the University of Toronto (U of T) believes they've found a way to convert all these emissions into energy-rich fuel in a carbon-neutral cycle that uses a very abundant natural resource: silicon. Silicon, readily available in sand, is the seventh most-abundant element in the universe and the second most-abundant element in the earth's crust.

The idea of converting carbon dioxide emissions to energy isn't new: there's been a global race to discover a material that can efficiently convert sunlight, carbon dioxide and water or hydrogen to fuel for decades. However, the chemical stability of carbon dioxide has made it difficult to find a practical solution.

"A chemistry solution to climate change requires a material that is a highly active and selective catalyst to enable the conversion of carbon dioxide to fuel. It also needs to be made of elements that are low cost, non-toxic and readily available," said Geoffrey Ozin, a chemistry professor in U of T's Faculty of Arts & Science, the Canada Research Chair in Materials Chemistry and lead of U of T's Solar Fuels Research Cluster.

Geoffrey Ozin and his colleagues believe they have found a way to convert CO₂ emissions into energy-rich fuel 
Credit: Brian Summers

In an article in Nature Communications published August 23, Ozin and colleagues report silicon nanocrystals that meet all the criteria. The hydride-terminated silicon nanocrystals – nanostructured hydrides for short – have an average diameter of 3.5 nanometres and feature a surface area and optical absorption strength sufficient to efficiently harvest the near-infrared, visible and ultraviolet wavelengths of light from the sun together with a powerful chemical-reducing agent on the surface that efficiently and selectively converts gaseous carbon dioxide to gaseous carbon monoxide.

The potential result: energy without harmful emissions.

"Making use of the reducing power of nanostructured hydrides is a conceptually distinct and commercially interesting strategy for making fuels directly from sunlight," said Ozin.

The U of T Solar Fuels Research Cluster is working to find ways and means to increase the activity, enhance the scale, and boost the rate of production. Their goal is a laboratory demonstration unit and, if successful, a pilot solar refinery.

Contacts and sources:
Sean Bettam
By Kim Luke
University of Toronto 

Hurricanes Are Worse, But Experience, Gender and Politics Determine Who Believes It

Objective measurements of storm intensity show that North Atlantic hurricanes have grown more destructive in recent decades. But coastal residents' views on the matter depend less on scientific fact and more on their gender, belief in climate change and recent experience with hurricanes, according to a new study by researchers at Princeton University, Auburn University-Montgomery, the Louisiana State University and Texas A&M University.

The researchers plumbed data from a survey of Gulf Coast residents and found that the severity of the most recent storm a person weathered tended to play the largest role in determining whether they believed storms were getting worse over time, according to the study published in the International Journal of Climatology. The survey was conducted in 2012 before Hurricane Sandy, the second-most expensive hurricane in history, caused $68 billion in damage.

Princeton University-led research found that people's view of future storm threat is based on their hurricane experience, gender and political affiliation, despite ample evidence that Atlantic hurricanes are getting stronger. This could affect how policymakers and scientists communicate the increasing deadliness of hurricanes as a result of climate change. The figure shows the wind speed of the latest hurricane landfall (left) on the U.S. Gulf Coast by county up to 2012, with red indicating the strongest winds. The data on the right show for the same area, by county, public agreement with the statement that storms have been strengthening in recent years, which was posed during a 2012 survey. Blue indicates the strongest agreement, while red equals the least agreement.

Image courtesy of Ning Lin, Department of Civil and Environmental Engineering

Respondents' opinions also strongly differed depending on whether they were male or female, whether they believed in climate change and whether they were a Democrat or a Republican. For instance, people who believe in climate change were far more likely to perceive the increasing violence of storms than those who did not. The researchers noted that because climate change has become a politically polarizing issue, party affiliation also was an indicator of belief in strengthening storms.

"Understanding how people in coastal regions perceive the threat is important because it influences whether they will take the necessary actions to address that threat," said Ning Lin, the senior researcher on the study and a Princeton assistant professor of civil and environmental engineering.

"What you see is that there is often a gap between the reality of the storm trends and how people interpret those trends," said Siyuan Xian, a doctoral candidate in Lin's lab and co-lead author of the new paper.

While scientists continue to debate the impact of climate change on the frequency and strength of hurricanes, numerous studies of objective measures -- such as wind speed, storm-surge height and economic damage -- show that hurricanes are stronger than they were even a few decades ago.

For instance, eight of the 10 most economically damaging hurricanes since 1980 have occurred since 2004, according to the National Oceanic and Atmospheric Administration (NOAA). In constant dollars, Hurricanes Katrina (2005) and Sandy caused nearly $154 billion and $68 billion in damage, respectively, according to NOAA.

In comparison, the costliest storms of the 1990s, Hurricanes Andrew (1992) and Floyd (1999), caused $46 billion and $9 billion in damage (adjusted for inflation), respectively. Hurricane Patricia in 2015 was the strongest Western Hemisphere storm in recorded history with maximum sustained winds of 215 miles per hour.

As the intensity of storms has increased, government agencies and coastal residents must grapple with preparing for the next landfall. Residents must decide, for example, whether to invest in storm shutters, roof and wall fortifications, flood-proof flooring and other structural buffers. On a larger scale, coastal planners need voter support to implement land-use policies that take the threat into account and to invest taxpayer dollars into protection measures such as seawalls or sand dunes.

Understanding how people perceive the threat of hurricanes is crucial for predicting whether they will take them seriously, Xian said. Six hurricanes form each year in the North Atlantic on average, although as many as 15 have developed in a single hurricane season.

"If you perceive a higher risk, you will be more likely to support policies and take action to ameliorate the impacts," Xian said. "We wanted to know how people perceive the threat of hurricanes and what influences their perceptions. This information will help guide how agencies communicate the risk, and what policies and actions are proposed to make communities resilient to these storms."

Lin and Xian worked with co-authors Wanyun Shao, assistant professor of geography at Auburn University-Montgomery; Barry Keim, professor of climatology at Louisiana State University; and Kirby Goidel, a Texas A&M professor of communication.

To explore what influences perceptions of hurricane threat, the researchers analyzed data from the 2012 Gulf Coast Climate Change Survey to analyze Gulf Coast residents' beliefs about hurricane trends from 1992 to 2011. Louisiana State University and NOAA conducted the survey.

The survey focused on residents of Texas, Louisiana, Mississippi, Alabama and Florida, who lived in areas of the Gulf Coast that experienced at least one hurricane landfall over the 20-year period from 1992 to 2011.

In addition to probing beliefs about hurricane trends, the survey gathered information on respondents' gender, political affiliations, opinions on climate change and other characteristics that might influence their perspective on hurricane trends.

The researchers' results mirrored a trend seen in other studies of extreme climate events, Lin said.

"The increasing power of Atlantic hurricanes is often connected to climate change, but studies have shown that Republicans and males tend to be more skeptical of climate change," Lin said. "We found a strong link between disbelief in climate change and disbelief that storms are getting worse -- they tend to come as a package."

The researchers were able to tease out what elements of the storms a respondent had experienced left the biggest impression on them. For instance, while storm surges tend to cause the most property damage, gale winds were more likely to convince people that hurricanes are getting stronger.

Behavioral scientists have long hypothesized the most recent landfall of a storm has a stronger influence on people's perceptions of long-term climate trends, said Sander van der Linden, a postdoctoral researcher and lecturer in Princeton's Woodrow Wilson School of Public and International Affairs, and director of the Social and Environmental Decision-Making (SED) Lab. Van der Linden is familiar with the research but had no role in it.

"This study provides strong empirical evidence of this phenomenon," said van der Linden, who studies public policy from a behavioral-science perspective. "This finding is important because it suggests that people may not be thinking about long-term changes in climate patterns but rather are paying attention to more salient variations in and impacts of short-term local weather."

The study's authors said this information could help governments communicate hurricane risk more effectively to the public. Taking into account that people are more likely to respond to the threat of high winds, for instance, could help agencies such as the Federal Emergency Management Agency motivate the public to adequately prepare for storms. The researchers also recommended that public agencies work to further educate the public about the risk posed by storm surge.

"Public opinion can make or break policies intended to address climate change and ameliorate damage from storms," Lin said. "Tapping into the state of current perceptions and what drives them will be critical for governments around the world as the impacts of climate change are increasingly felt."

The researchers are currently conducting other studies related to climate-change perception, including research on flood adaption and insurance-purchasing behavior in the counties along the Gulf Coast, as well as looking at worldwide perceptions of climate change and the willingness to adopt green-energy technologies.

Contacts and sources:
Steven Schultz
Princeton University

The paper, "Understanding perceptions of changing hurricane strength along the US Gulf coast," was published online June 20 by the International Journal of Climatology. Support for the research was provided in part by NOAA's Gulf of Mexico Coastal Storm Program, Texas Sea Grant, Louisiana Sea Grant, Florida Sea Grant and Mississippi-Alabama Sea Grant Consortium.

Friday, August 26, 2016

Acoustic Prism Invented, Can Split a Sound into Its Constituent Frequencies

Ecole Polytechnique Fédérale De Lausanne (EPFL) scientists have invented a new type of “acoustic prism” that can split a sound into its constituent frequencies. Their acoustic prism has applications in sound detection.

Almost 400 years ago, Newton showed that a prism could split white light into the colors of the rainbow, with each colour corresponding to a different wave frequency. Such an “optical prism” relies on a physical phenomenon (refraction) to split light into its constituent frequencies.

Now, a prism exists for sound. Hervé Lissek and his team at EPFL have invented an "acoustic prism" that splits sound into its constituent frequencies using physical properties alone. Its applications in sound detection are published in the Journal of the Acoustical Society of America.

The acoustic prism is entirely man-made, unlike optial prisms, which occur naturally in the form of water droplets. Decomposing sound into its constituent frequencies relies on the physical interaction between a sound wave and the structure of the prism. The acoustic prism modifies the propagation of each individual frequency of the sound wave, without any need of computations or electronic components.

The acoustic prism

The acoustic prism looks like a rectangular tube made of aluminum, complete with ten, perfectly aligned holes along one side. Each hole leads to an air-filled cavity inside the tube, and a membrane is placed between two consecutive cavities.

When sound is directed into the tube at one end, high-frequency components of the sound escape out of the tube through the holes near the source, while low frequencies escape through the holes that are further away, towards the other end of the tube. Like light through an optical prism, the sound is dispersed, with the dispersion angle depending on the wave’s frequency.

The membranes are key, since they vibrate and transmit the sound to the neighboring cavities with a delay that depends on frequency. The delayed sound then leaks through the holes and towards the exterior, dispersing the sound.

Angular detection by frequency

Credit:  EPFL

To take the concept a step further, the researchers realized that they could use the acoustic prism as an antenna to locate the direction of a distant sound by simply measuring its frequency. Since each dispersion angle corresponds to a particular frequency, it’s enough to measure the main frequency component of an incoming sound to determine where it is coming from, without actually moving the prism.

The principle of the acoustic prism relies on the design of cavities, ducts and membranes, which can be easily fabricated and even miniaturized, possibly leading to cost-effective angular sound detection without resorting to expensive microphone arrays or moving antennas.

Contacts and sources:
by Hillary Sanctuary
Ecole Polytechnique Fédérale De Lausanne

HMS Bounty Mutineers' Pigtails To Undergo Forensic DNA Analysis

Ten pigtails of hair thought to be from seven mutineers of “Mutiny on the Bounty” fame and three of their female Polynesian companions will be analysed in a new collaboration between the Pitcairn Islands Study Centre at Pacific Union College (California, US) and the forensic DNA group at King’s College London (UK).

The forensic DNA group at King’s has been sent hair strands from the ten pigtails, which are currently on display in the California-based centre, to help establish as much information as possible on their origins.

As the pigtails purportedly date back to the pre-1800s, the King’s team will first attempt to extract DNA from the historical hair samples after cleaning the outside and then digesting the hair matrix using a chemical process. Nuclear DNA is not found in hair shafts, only the roots which are not available here; however, mitochondrial DNA may be present. If sufficient mitochondrial DNA can be collected, the first step will be to investigate the ancestral origins of the owners of the pigtails.

Hair from the collection of pigtails donated to the Pitcairn Islands Study Centre will be analyzed by forensics experts at King's College London.
Credit: Pitcairn Islands Study Centre

Unlike nuclear DNA, mitochondrial DNA does not discriminate between all individuals as people sharing a common maternal ancestor will also share a similar profile. However, this type of DNA can provide some indication of maternal geographic origin e.g. whether someone is likely to be of European descent, so the team will aim to establish whether the hair samples do indeed come from seven Europeans and three Polynesian individuals, as the documentation accompanying the samples suggests.

Further, more detailed identification will require genealogical methods to trace the ancestors of the pigtail owners, to be able to link samples to names from historical records and other sources of information. A lot has been written about the possible descendants of the mutineers but this information will not be helpful with regards to the male mutineers; instead, their maternal line will need be traced. The study will therefore try to identify their maternal ancestors, such as their respective mothers and maternal grandmothers, and research other direct female descendants down to individuals living today.

Dr Denise Syndercombe-Court, project lead from the Analytical and Environmental Sciences Division at King’s College London, said: “First, we will have to determine whether we can recover mitochondrial DNA of appropriate quality to be analysed. The hairs, if from the mutineers, are over two hundred years old and we have no idea what environments they might have been exposed to in the intervening time.”

“Potentially as problematic will be the genealogical research as civil registration in the UK did not start until 1837, some 50 years after the mutiny and so, at best, the death of the mother may be listed in these records but other processes would need to be used to gather more information. Because of the patrilineal transmission of surnames we would not even expect to find someone who believes they may be linked to the mutineers and so we will have to depend on this research and hope for the agreed consent from any identified living descendant to act as a modern day reference. We do not anticipate that this will be easy and it will require other interested parties to get involved in this part of the study.”

Credit: Pitcairn Islands Study Centre

Herbert Ford, Director of the Pitcairn Islands Study Centre, said: “This hair is a gift from Joy Allward, wife of the late Maurice Allward of Hatfield, UK, who successfully bid for the hair at a Sotheby’s auction in London in 2000.”

“If the tests and genealogical studies of this hair authenticates that it is of seven of the nine mutineers who hid out from British justice on Pitcairn Island in 1790, it will be the only tangible physical evidence of their having existed. There is only one known mutineer grave on Pitcairn, that of John Adams. Of the whereabouts of the remains of the eight others, we can only speculate.”

The pigtails on display in the US were housed in a nineteenth-century cylindrical tobacco tin. Also with the locks of hair was a handkerchief said to have belonged to Sarah, the daughter of William McCoy, one of the Bounty mutineers.

A worn, faded label with the pigtails notes that it is attached to the hair of William McCoy. The mutineer McCoy died on Pitcairn Island in 1800. Notes written on the label also state that the pigtails are of seven of the mutineers of H.M.S. Bounty and “also that of three of the Tahitian women,” who accompanied the mutineers to Pitcairn in 1789.

Further information on the label notes that “The holders of the hair have been (1) Teio, wife of McCoy. (2) Mrs. Sarah Christian. (3) F. G. Mitchell. Given to F. G. Mitchell, 22nd June 1849 (Jubilee Day) by Mrs. Sarah Nobbs.”

The story of the mutiny that took place on the ship H.M.S. Bounty in the South Pacific Ocean in 1789 was made famous by the publication of a trilogy of books published in the 1930s. Following the publication of the books, a number of Hollywood-type motion pictures about the Bounty mutiny were shown worldwide over the next four decades.

Contacts and sources:
Jenny Gimpel
King’s College London (UK)
Pitcairn Islands Study Centre

Psychosis Associated with Low Levels of Physical Activity

A large international study of more than 200,000 people in nearly 50 countries has revealed that people with psychosis engage in low levels of physical activity, and men with psychosis are over two times more likely to miss global activity targets compared to people without the illness.

People who have a serious mental illness such as schizophrenia, bipolar disorder or schizoaffective disorder have times (called episodes) when they experience some, or all, of the symptom of psychosis – delusions, hallucinations and confused and disturbed thinking.

The research, led by King’s College London and the South London and Maudsley (SLaM) NHS Foundation Trust, also offers important insights into the barriers that prevent people with psychosis from engaging in regular physical activity. This data will inform interventions aimed at helping people with psychosis to be more active and ultimately, to improve their mental and physical health.

People with psychosis die up to 15 years before the general population, largely due to cardiovascular disease. Although pursuing an active lifestyle is thought to be just as effective in preventing cardiovascular disease as medication (e.g. statins), a number of small studies have suggested that people with psychosis tend to engage in low levels of physical activity.

Credit: King's College London

To stay healthy, the World Health Organization (WHO) recommends that adults aged 18-64 should do at least 150 minutes of moderate-intensity physical activity throughout the week, including walking, cycling, household chores or sport. Physical inactivity is the fourth leading cause of avoidable death and is as harmful as smoking, according to the WHO.

The researchers from King’s sought to examine whether people with psychosis are meeting the WHO’s recommended levels of physical activity.

In their study, published today in Schizophrenia Bulletin, the researchers collected data from the World Health Survey, which comprises more than 200,000 people aged 18-64 from nearly 50 low-and-middle-income countries. These individuals, who were living in their local communities at the time of the study, were divided into three groups: people with a diagnosis of psychosis, those with psychotic symptoms but no diagnosis and a control group (of people with no diagnosis of psychosis and no symptoms in the past 12 months). The participants were interviewed to ascertain who had/had not met recommended levels of physical activity.

Overall, people with psychosis were 36 per cent more likely not to meet the recommended physical activity levels compared to controls. When the researchers looked at men only, those with psychosis were over two times more likely not to meet the recommended levels compared to people in the control sample.

When examining potential barriers to physical activity, the researchers found that mobility difficulties, pain, depression and cognitive impairment explained low levels of physical activity in people with psychosis. These insights will be used to guide the ‘Walk this Way’ study at King’s College London, funded and led by the NIHR Collaboration for Leadership in Applied Health Research and Care (CLAHRC) South London.

Dr Brendon Stubbs from King’s College London and the South London and Maudsley NHS Foundation Trust (SLaM), said: ‘Understanding and overcoming these barriers could be an important strategy to help people with psychosis be more active, and potentially to reduce their risk of cardiovascular disease.

‘Our Walk this Way study is the first to specifically target the reduction of a sedentary lifestyle, and an increase in activity levels, in people with psychosis. We will investigate whether health coaching and providing people with pedometers can increase daily activity levels and hope that if successful, this programme will be offered more widely to people with psychosis.’

Dr Fiona Gaughran, also of King’s College London and SLaM, said: ‘People with psychosis have high levels of cardiovascular risk and die earlier as a result. Since physical activity is a key protective factor for cardiovascular disease, our finding that men with psychosis are particularly inactive means that they may benefit most from interventions to increase physical activity and reduce social isolation.

‘It is unclear why men with psychosis showed such low levels of physical activity, although perhaps the earlier onset of illness typically seen in males means that lifestyle habits may have been altered over time by aspects of the illness or its management, such as negative symptoms, sedating medications or hospital admissions. Our data suggests that depression may also be important, which makes sense. Understanding these factors and what we might do about them is an important area for future research.’
Notes to editors

Contacts and sources:
Jack Stonebridge
Institute of Psychiatry, Psychology & Neuroscience

Unexpected Trove of Gas Discovered Around Larger Stars, Findings "Counterintuitive" (Video)

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) surveyed dozens of young stars – some Sun-like and others approximately double that size – and discovered that the larger variety have surprisingly rich reservoirs of carbon monoxide gas in their debris disks. In contrast, the lower-mass, Sun-like stars have debris disks that are virtually gas-free.

This finding runs counter to astronomers’ expectations, which hold that stronger radiation from larger stars should strip away gas from their debris disks faster than the comparatively mild radiation from smaller stars. It may also offer new insights into the timeline for giant planet formation around young stars.

Debris disks are found around stars that have shed their dusty, gas-filled protoplanetary disks and gone on to form planets, asteroids, comets, and other planetesimals. Around younger stars, however, many of these newly formed objects have yet to settle into stately orbits and routinely collide, producing enough rubble to spawn a "second-generation" disk of debris.

ALMA image of the debris disk surrounding a star in the Scorpius-Centaurus Association known as HIP 73145. The green region maps the carbon monoxide gas that suffuses the debris disk. The red is the millimeter-wavelength light emitted by the dust surrounding the central star. The star HIP 73145 is estimated to be approximately twice the mass of the Sun. The disk in this system extends well past what would be the orbit of Neptune in our solar system. 
Credit: J. Lieman-Sifry, et al., ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)

"Previous spectroscopic measurements of debris disks revealed that certain ones had an unexpected chemical signature suggesting they had an overabundance of carbon monoxide gas," said Jesse Lieman-Sifry, lead author on a paper published in Astrophysical Journal. At the time of the observations, Lieman-Sifry was an undergraduate astronomy major at Wesleyan University in Middletown, Connecticut. "This discovery was puzzling since astronomers believe that this gas should be long gone by the time we see evidence of a debris disk," he said. 

In search of clues as to why certain stars harbor gas-rich disks, Lieman-Sifry and his team surveyed 24 star systems in the Scorpius-Centaurus Association. This loose stellar agglomeration, which lies a few hundred light-years from Earth, contains hundreds of low- and intermediate-mass stars. For reference, astronomers consider our Sun to be a low-mass star. 

Podcast on discovery of debris disks surrounding young stars in the Scorpius-Centaurus Association. ALMA discovered that -- contrary to expectations -- the more massive stars in this region retain considerable stores of carbon monoxide gas. This finding could offer new insights into the timeline for giant planet formation around young stars.

Debris Disk Podcast Movie from NRAO Outreach on Vimeo.

The astronomers narrowed their search to stars between five and ten million years old -- old enough to host full-fledged planetary systems and debris disks -- and used ALMA to examine the millimeter-wavelength "glow" from the carbon monoxide in the stars’ debris disks.

The team carried out their survey over a total of six nights between December 2013 and December 2014, observing for a mere ten minutes each night. At the time it was conducted, this study constituted the most extensive millimeter-wavelength interferometric survey of stellar debris disks ever achieved.

Artist impression of a debris disk surrounding a star in the Scorpius-Centaurus Association. ALMA discovered that -- contrary to expectations -- the more massive stars in this region retain considerable stores of carbon monoxide gas. This finding could offer new insights into the timeline for giant planet formation around young stars.
Credit: NRAO/AUI/NSF; D. Berry / SkyWorks

Armed with an incredibly rich set of observations, the astronomers found the most gas-rich disks ever recorded in a single study. Among their sample of two dozen disks, the researchers spotted three that exhibited strong carbon monoxide emission. Much to their surprise, all three gas-rich disks surrounded stars about twice as massive as the Sun. None of the 16 smaller, Sun-like stars in the sample appeared to have disks with large stores of carbon monoxide.

This finding is counterintuitive because higher-mass stars flood their planetary systems with energetic ultraviolet radiation that should destroy the carbon monoxide gas lingering in their debris disks. This new research reveals, however, that the larger stars are somehow able to either preserve or replenish their carbon monoxide stockpiles.

"We’re not sure whether these stars are holding onto reservoirs of gas much longer than expected, or whether there's a sort of 'last gasp' of second-generation gas produced by collisions of comets or evaporation from the icy mantles of dust grains," said Meredith Hughes, an astronomer at Wesleyan University and coauthor of the study.

The existence of this gas may have important implications for planet formation, says Hughes. Carbon monoxide is a major constituent of the atmospheres of giant planets. Its presence in debris disks could mean that other gases, including hydrogen, are present, but perhaps in much lower concentrations. If certain debris disks are able to hold onto appreciable amounts of gas, it might push back astronomers’ expected deadline for giant planet formation around young stars, the astronomers speculate.

Four out of 24 debris disks observed by ALMA in the Scorpius-Centaurus Association. Researchers were surprised to discover that the larger, more energetic stars retained much more gas in their debris disks than smaller, Sun-like stars. 
Credit: Lieman-Sifry et al. ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)

"Future high-resolution observations of these gas-rich systems may allow astronomers to infer the location of the gas within the disk, which may shed light on the origin of the gas," says co-author Antonio Hales, an astronomer with the Joint ALMA Observatory in Santiago, Chile, and the National Radio Astronomy Observatory in Charlottesville, Virginia. "For instance, if the gas was produced by planetesimal collisions, it should be more highly concentrated in regions of the disk where those impacts occurred. ALMA is the only instrument capable of making these kind of high-resolution images."

According to Lieman-Sifry, these dusty disks are just as diverse as the planetary systems they accompany. The discovery that the debris disks around some larger stars retain carbon monoxide longer than their Sun-like counterparts may provide insights into the role this gas plays in the development of planetary systems.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Contacts and sources:
Charles Blue
National Radio Astronomy Observatory

This research is presented in the paper titled “Debris disks in the Scorpius-Centaurus OB association resolved by ALMA,” by J. Lieman-Sifry et al., published in Astrophysical Journal on 25 August 2016.

World Record for Silicon Solar Cells and for Hydrogen Production Without Using Rare Metals

How can we store solar energy for period when the sun doesn't shine? One solution is to convert it into hydrogen through water electrolysis. The idea is to use the electrical current produced by a solar panel to 'split' water molecules into hydrogen and oxygen. Clean hydrogen can then be stored away for future use to produce electricity on demand, or even as a fuel.

But this is where things get complicated. Even though different hydrogen-production technologies have given us promising results in the lab, they are still too unstable or expensive and need to be further developed to use on a commercial and large scale.

The approach taken by the Ecole Polytechnique Fédérale De Lausanne (EPFL) and the Swiss Center for Electronics and Microtechnology (CSEM) researchers is to combine components that have already proven effective in industry in order to develop a robust and effective system.

The device is able to convert solar energy into hydrogen at a rate of 14.2 percent, and has already been run for more than 100 hours straight.

Credit: Infini Lab / EPFL

Their prototype is made up of three interconnected, new-generation, crystalline silicon solar cells attached to an electrolysis system that does not rely on rare metals. The device is able to convert solar energy into hydrogen at a rate of 14.2%, and has already been run for more than 100 hours straight under test conditions. In terms of performance, this is a world record for silicon solar cells and for hydrogen production without using rare metals. It also offers a high level of stability.

Enough to power a fuel cell car over 10,000km every year

The method, which surpasses previous efforts in terms of stability, performance, lifespan and cost efficiency, is published in the Journal of The Electrochemical Society. "A 12-14 m2 system installed in Switzerland would allow the generation and storage of enough hydrogen to power a fuel cell car over 10,000 km every year", says Christophe Ballif, who co-authored the paper.

High voltage cells have an edge

The key here is making the most of existing components, and using a 'hybrid' type of crystalline-silicon solar cell based on heterojunction technology. The researchers' sandwich structure - using layers of crystalline silicon and amorphous silicon - allows for higher voltages. And this means that just three of these cells, interconnected, can already generate an almost ideal voltage for electrolysis to occur. The electrochemical part of the process requires a catalyst made from nickel, which is widely available.

"With conventional crystalline silicon cells, we would have to link up four cells to get the same voltage," says co-author Miguel Modestino at EPFL."So that's the strength of this method."

A stable and economically viable method

The new system is unique when it comes to cost, performance and lifespan. "We wanted to develop a high performance system that can work under current conditions," says Jan-Willem Schüttauf, a researcher at CSEM and co-author of the paper. "The heterojunction cells that we use belong to the family of crystalline silicon cells, which alone account for about 90% of the solar panel market. It is a well-known and robust technology whose lifespan exceeds 25 years. And it also happens to cover the south side of the CSEM building in Neuchâtel."

The researchers used standard heterojunction cells to prove the concept; by using the best cells of that type, they would expect to achieve a performance above 16%.

Contacts and sources:
Miguel Modestino
Ecole Polytechnique Fédérale De Lausanne 

Scientists Unraveling Summer Jet Stream Mystery

Scientists have discovered the cause of the recent run of miserable wet summers as they begin to unravel the mysteries of the Atlantic jet stream,

Rivers of high-speed air in the atmosphere. Jet streams form along the boundaries of global air masses where there is a significant difference in atmospheric temperature. The jet streams may be several hundred miles across and 1-2 miles deep at an altitude of 8-12 miles. They generally move west to east, and are strongest in the winter with core wind speeds as high as 250 mph. Changes in the jet stream indicate changes in the motion of the atmosphere and weather.

Researchers from the University of Sheffield and The Met Office have identified a number of possible factors that may influence the Atlantic jet stream and therefore help to predict summer climate from one year to the next.

Credit: University of Sheffield

The summer weather in the UK and northwest Europe is influenced by the position and strength of the Atlantic jet stream - a ribbon of very strong winds which are caused by the temperature difference between tropical and polar air masses.

A northward shift in the Atlantic jet stream tends to direct low-pressure systems northwards and away from the UK, leading to warm and dry weather during summer.

But, if the summer jet slips southwards it can lead to the jet shifting the low-pressure systems directly over the UK, causing miserable weather like we experienced in the first half of this summer. The big question is: "why does the jet stream shift?"

The report, led by PhD student Richard Hall and Professor Edward Hanna from the University of Sheffield's Department of Geography, discovered that up to 35 per cent of this variability may be predictable - a significant advance which may help in the development of seasonal forecasting models.

High in the sky, 60 to 65 miles above Earth's surface, winds rush through a little understood region of Earth's atmosphere at speeds of 200 to 300 miles per hour.
Credit: NASA

A northward shift in the Atlantic jet stream tends to direct low-pressure systems northwards and away from the UK, leading to warm and dry weather during summer.

Lead author of the study, Richard Hall, said: "There is nothing people in the UK like to discuss more than the weather. This is because it can fluctuate so drastically -- we can be basking in high temperatures and sunshine one week only to be struck by heavy downpours and strong winds the next.

How the jet stream works

"Our study will help forecasters to predict further into the future giving a clearer picture of the weather to come."

Edward Hanna, Professor of Climate Change at the University of Sheffield, said: "Working with The Met Office we were able to look at the different factors which may influence the jet stream, which paves the way for improvements in long-term forecasting."

The findings suggest the latitude of the Atlantic jet stream in summer is influenced by several factors including sea-surface temperatures, solar variability, and the extent of Arctic sea-ice, indicating a potential long-term memory and predictability in the climate system.

Professor Adam Scaife, Head of long range forecasting at the Met Office, said: "We've made big inroads into long-range forecasts for winter, but we are still limited to shorter-range weather forecasts in summer. Studies like this help to identify ways to break into the long-range summer forecast problem."

The study, published in the journal Climate Dynamics was funded by the University of Sheffield's Project Sunshine now the Grantham Centre for Sustainable Futures, and was conducted in collaboration with the University's School of Mathematics and Statistics (SOMAS).

Further research will seek to establish the physical mechanisms behind these links and identify the different influences that jet speed and latitude bring to bear on our summer weather.

The other co-authors on the work were Dr Julie Jones, from the University's Department of Geography, and Professor Robertus von Fay-Siebenburgen, from SOMOS. 

Contacts and sources: 
Amy Pullan
The University of Sheffield


Superabsorbent Polymers Can Store Water and Nutrients and Release Them in Drought Conditions

Soil conditioners called superabsorbent polymers have the potential to reduce irrigation needs for agricultural crops by storing water and nutrients and then releasing them in drought conditions, according to a recent paper published in the Pertanika Journal of Tropical Agricultural Science (JTAS).

Drought is the largest abiotic stress that can reduce crop yields, and its frequency and severity are expected to increase in the face of climate change. Meanwhile, a lack of water supply is an issue for many countries. Adding this to increasing population growth, water demands are predicted to rise even further. Therefore, finding new ways to improve water efficiency in the agricultural sector is necessary. 

Superabsorbent polymers can store water and nutrients and release them in drought conditions, research found.

Copyright : krisckam via 123rf
One way of doing this is to use superabsorbent polymers (SAPs). These are soil conditioners that have the capacity to absorb and retain 1,000 times more water than their size and weight. SAPs are currently used in various sectors including agriculture, horticulture, pharmaceuticals, food packaging, oil drilling and so on. Superabsorbent hydrogels (SAHs) are superior to SAPs due to their unique properties but the extension of their application is limited because of high production costs and their impact on the environment.

In a JTAS review paper, Davoud Khodadadi Dehkordi of Islamic Azad University in Iran looked at the effects of SAPs and SAHs on soils and plants, suitable usage rates and the amount of irrigation water that can be saved by using superabsorbent polymers.

He found that these materials could store water and nutrients and release them in light soils, enabling plants to produce grain and increase their biomass under limited irrigation water and nutrient conditions. What’s more, their water storage capacity lasts for up to five years. They also improve seed germination rates and root growth while decreasing drought or transplanting stresses in plants. Furthermore, superabsorbent materials could reduce soil contamination by preventing pollutants from passing through the soil and thereby improving the quality of drainage water.

However, excessive use of SAPs and SAHs could reduce soil ventilation or expose plants to diseases, some studies suggested. More research is therefore needed in order to determine the most suitable amounts of superabsorbent polymers to be used for each plant in different situations.

Overall, using superabsorbent materials could improve the characteristics of light soils and allow cultivation with less water, the researcher concluded. On the other hand, they are costly in many countries and therefore subsidies may be necessary in order to encourage farmers to use them, he added.

Contacts and sources: 
Universiti Putra Malaysia (UPM)

D. Khodadadi Dehkordi
Department of Water Engineering and Sciences
Ahvaz Branch, Islamic Azad University