Lasers play essential roles in countless technologies, from medical therapies to metal cutters to electronic gadgets. But to meet modern needs in computation, communications, imaging and sensing, scientists are striving to create ever-smaller laser systems that also consume less energy.

The 91探花nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as the 鈥済ain material鈥� that emits light. The technology is described in a paper published in the .

鈥淭his is a recently discovered, new type of semiconductor which is very thin and emits light efficiently,鈥� said , lead author and a 91探花doctoral candidate in physics. 鈥淩esearchers are making transistors, light-emitting diodes, and solar cells based on this material because of its properties. And now, nanolasers.鈥�

Nanolasers 鈥� which are so small they can鈥檛 be seen with the eye 鈥� have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems. But nanolasers so far haven鈥檛 strayed far from the research lab.

Other nanolaser designs use gain materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electrical circuits and computing technologies.

The 91探花version, instead, uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultrathin nature of the semiconductor 鈥� made from a single layer of a tungsten-based molecule 鈥� yields efficient coordination between the two key components of the laser.

The 91探花nanolaser requires only 27 nanowatts to kickstart its beam, which means it is very energy efficient.

Other advantages of the 91探花team鈥檚 nanolaser are that it can be easily fabricated, and it can potentially work with silicon components common in modern electronics. Using a separate atomic sheet as the gain material offers versatility and the opportunity to more easily manipulate its properties.

鈥淵ou can think of it as the difference between a cell phone where the SIM card is embedded into the phone versus one that鈥檚 removable,” said co-author , 91探花assistant professor of and of .

“When you’re working with other materials, your gain medium is embedded and you can’t change it. In our nanolasers, you can take the monolayer out or put it back, and it鈥檚 much easier to change around,” he said.

The researchers hope this and will enable them to produce an electrically-driven nanolaser that could open the door to using light, rather than electrons, to transfer information between computer chips and boards.

The current process can cause systems to overheat and wastes power, so companies such as Facebook, Oracle, HP, Google and Intel with massive data centers are keenly interested in more energy-efficient solutions.

Using photons rather than electrons to transfer that information would consume less energy and could enable next-generation computing that breaks current bandwidth and power limitations. The recently proven 91探花nanolaser technology is one step toward making optical computing and short distance optical communication a reality.

鈥淲e all want to make devices run faster with less energy consumption, so we need new technologies,鈥� said co-author Xiaodong Xu, 91探花associate professor of and of physics. 鈥淭he real innovation in this new approach of ours, compared to the old nanolasers, is that we鈥檙e able to have scalability and more controls.”

Still, there’s more work to be done in the near future, Xu said. Next steps include investigating photon statistics to establish the coherent properties of the laser’s light.

Co-authors are John Schaibley of the UW, Liefeng Feng of the 91探花and Tianjin University in China, Sonia Buckley and Jelena Vuckovic of Stanford University, Jiaqiang Yan and David G. Mandrus of Oak Ridge National Laboratory and the University of Tennessee, Fariba Hatami of Humboldt University in Berlin and Wang Yao of the University of Hong Kong.

Primary funding came from the Air Force Office of Scientific Research. Other funders include the National Science Foundation, the state of Washington through the Clean Energy Institute, the Presidential Early Award for Scientists and Engineers administered through the Office of Naval Research, the U.S. Department of Energy, and the European Commission.

For more information, contact Xu at xuxd@uw.edu and Majumdar at arka@uw.edu.

Grant numbers: AFOSR (FA9550-14-1-0277), NSF-EFRI-1433496, ECS-9731293, N00014-08-1-0561, FP7-ICT-2013-613024-GRASP

Though many animals can move with more precision and accuracy than our best-engineered aircraft and technologies, gyroscopes are rarely found in nature. Scientists know of just one group of insects, the group including flies, that has something that behaves like a gyroscope 鈥� sensors called , clublike structures that evolved from wings.

Halteres provide information about the rotation of the body during flight, which helps flies perform aerial acrobatics and maintain stability and direction. But how do other insects without these sensors regulate flight dynamics, biologists have wondered?

91探花 research suggests that insects’ wings may also serve a gyroscopic function 鈥� a discovery that sheds new insight on natural flight and could help with developing new sensory systems in engineering.

Published in January in the , the research was supported by the Air Force Office of Scientific Research. It was a key part of the successful proposal for an , a new 91探花center focused on understanding how elements in nature can inform the development of remotely controlled small aircraft.

“I was surprised at the results,” said Brad Dickerson, a graduate student in biology and co-author of the study. “This idea of wings being gyroscopes has existed for a long time, but this paper is the first to really address how that would be possible.”

and another 91探花graduate student, , conducted the research seeking to determine whether insects could use the bending of their wings to sense rotations of their bodies during flight. This could help explain how these master flyers are able to move with precision and speed.

The pair first developed a computational model of a flapping, flexing, rotating plate. To test their results, they built a robotic model using plastic sheeting mounted on a motor to simulate a flapping wing, then mounted that structure onto a second motor to rotate it.

They discovered that the model wing twisted when flapped and rotated around its base, causing changes in patterns of strain across the wing’s surface. The researchers believe that the strain might stimulate sensors embedded in the wing 鈥� suggesting that the wings of flying insects might, as halteres do, provide them with gyroscopic information.

Eberle, a graduate student in mechanical engineering and the paper’s corresponding author, said the results suggest that additional information about flight dynamics could be gleaned by embedding sensors onto the surface of manufactured wings. In turn, that knowledge could eventually help engineers design more efficient wings for structures such as micro air vehicles, helicopters and turbines.

But first, Eberle said, more research is needed to determine what relationship exists between animals’ wing flexibility and sensing capability.

“We don’t understand yet what those principles might be,” she said. “These are 10-year visions.”

The pair of researchers said they are excited about the opportunities that the new Air Force center offers to uncover biological principles and develop new bio-inspired designs.

Senior authors are , chair of the UW’s mechanical engineering department, and , a 91探花professor of biology and director of the new Air Force center.

In some cases, there’s not much medics can do 鈥� a tourniquet won’t stop bleeding from a chest wound, and clotting treatments that require refrigerated or frozen blood products aren’t always available in the field.

That’s why 91探花 researchers have developed a new injectable polymer that strengthens blood clots, called PolySTAT. Administered in a simple shot, the polymer finds any unseen or internal injuries and starts working immediately.

The new polymer, described featured on the cover of the March 4 issue of could become a first line of defense in everything from battlefield injuries to rural car accidents to search and rescue missions deep in the mountains. It has been tested in rats, and researchers say it could reach human trials in five years.

In the initial study with rats, 100 percent of animals injected with PolySTAT survived a typically-lethal injury to the femoral artery. Only 20 percent of rats treated with a natural protein that helps blood clot survived.

“Most of the patients who die from bleeding die quickly,” said co-author , an assistant professor of who teamed with 91探花 and to develop the macromolecule.

“This is something you could potentially put in a syringe inside a backpack and give right away to reduce blood loss and keep people alive long enough to make it to medical care,” he said.

The 91探花team was inspired by , a natural protein found in the body that helps strengthen blood clots.

Normally after an injury, platelets in the blood begin to congregate at the wound and form an initial barrier. Then a network of specialized fibers 鈥� 鈥� start weaving themselves throughout the clot to reinforce it.

If that scaffolding can’t withstand the pressure of blood pushing against it, the clot breaks apart and the patient keeps bleeding.

Both PolySTAT and factor XIII strengthen clots by binding fibrin strands together and adding “cross-links” that reinforce the latticework of that natural bandage.

“It’s like the difference between twisting two ropes together and weaving a net,” said co-author , the UW’s Robert J. Rushmer Professor of Bioengineering. “The cross-linked net is much stronger.”

But the synthetic PolySTAT offers greater protection against natural enzymes that dissolve blood clots. Those help during the healing process, but they work against doctors trying to keep patients from bleeding to death.

The enzymes, which cut fibrin strands, don’t target the synthetic PolySTAT bonds that are now integrated into the clot. That helps keep the blood clots intact in the critical hours after an injury.

“We were really testing how robust the clots were that formed,” said lead author , a 91探花doctoral student in bioengineering. “The animals injected with PolySTAT bled much less, and 100 percent of them lived.”

The synthetic polymer offers other advantages over conventional hemorrhaging treatments, said White, who also treats trauma patients at Harborview Medical Center.

Blood products are expensive, need careful storage, and they can grow bacteria or carry infectious diseases, he said. Plus, the hundreds of proteins introduced into a patient’s body during a transfusion can have unintended consequences.

After a traumatic injury, the body also begins to lose a protein that’s critical to forming fibrin. Once those levels drop below a certain threshold, existing treatments stop working and patients are more likely to die.

In the study, researchers found PolySTAT worked to strengthen clots even in cases where those fibrin building blocks were critically low.

The 91探花team also used a highly specific peptide that only binds to fibrin at the wound site. It does not bind to a precursor of fibrin that circulates throughout the body. That means PolySTAT shouldn’t form dangerous clots that can lead to a stroke or embolism.

Though the polymer’s initial safety profile looks promising, researchers said, next steps include testing on larger animals and additional screening to find out if it binds to any other unintended substances. They also plan to investigate its potential for treating hemophilia and for integration into bandages.

Other co-authors are Xu Wang in 91探花emergency medicine, Hua Wei in 91探花bioengineering, and in 91探花chemical engineering.

Funding came from the National Institutes of Health and its National Center for Advancing Translational Science, the 91探花, the Washington Research Foundation, an NIH-supported 91探花Bioengineering Cardiovascular Training Grant and discretionary funds from private donations.

For more information, contact Pun at spun@uw.edu or White at whiten4@uw.edu.

91探花 , published recently in Substance Use & Misuse, found that only 57 percent of Washington parents surveyed knew the legal age for recreational marijuana use and just 63 percent knew that homegrown marijuana is illegal under the law.

And while 71 percent of 10^th-graders correctly identified the legal age, fewer than half (49 percent) knew how much marijuana can legally be possessed.

The findings underscore the need for better educational outreach about the law, said co-author , professor of social work and director of the at the 91探花’s School of Social Work.

“As new states are taking on legalized marijuana, we need to have public information campaigns to make sure people have the information they need,” he said.

The study surveyed 115 low-income families of teens attending Tacoma middle schools, who were part of an ongoing prevention study. Data was initially collected before Washington approved recreational marijuana, and then two years later during the summer of 2013.

The study found that while 70 percent of parents said they talked about marijuana laws with their children, those conversations were infrequent. That is troubling, Haggerty said, since 10^th grade is a critical time for family discussions about drug use.

“We know that parent expectations, even as late as senior year in high school, have an impact on kids’ college-age marijuana use,” he said. “If kids are thinking in 10^th grade that the legal age for marijuana is 18, they could potentially be more likely to use it later.”

The study also found that the Washington law made little difference in the teens’ attitudes about marijuana use or the likelihood of them smoking pot.

鈥淲e were most surprised to see how little parents and teens know about fundamental aspects of the new law, such as the legal age limit,鈥� said corresponding author W. Alex Mason, director of research at the Boys Town National Research Institute.

In 2012, Washington and Colorado became the first U.S. states to legalize recreational marijuana use, and Alaska, Oregon and Washington, D.C. passed marijuana legalization measures last November. The legal age for marijuana use in Washington is 21. Adults can possess up to one ounce, and homegrown pot is prohibited.

The study comes at a time when educators, parents and others are trying to determine what young people need to know about marijuana use and what messages might most effectively steer them away from it.

The Washington State Department of Health launched a $400,000 statewide campaign in June that featured on radio and digital media encouraging parents to talk to their kids about the risks of using marijuana. The UW鈥檚 Alcohol & Drug Abuse Institute has also launched an education which is expected to eventually be supported by marijuana tax revenues.

Washington’s law mandates that a portion of revenues from marijuana sales be used for public education, drug abuse treatment and research, and that the state consult with the 91探花annually to decide which programs to fund. The department of health plans to launch a broader education campaign when marijuana revenues become available later this year.

“This study convincingly points out that people don’t have good information about the new law,” Haggerty said.

Other co-authors are Koren Hanson and Charles Fleming at the 91探花and Jay L. Ringle at Boys Town Research Institute. The work was funded by the National Institute on Drug Abuse.

The , published in The Cryosphere, show a thinning in the central Arctic Ocean of 65 percent between 1975 and 2012. September ice thickness, when the ice cover is at a minimum, is 85 percent thinner for the same 37-year stretch.

“The ice is thinning dramatically,” said lead author , a climatologist at the 91探花. “We knew the ice was thinning, but we now have additional confirmation on how fast, and we can see that it’s not slowing down.”

The study helps gauge how much the climate has changed in recent decades, and helps better predict an Arctic Ocean that may soon be ice-free for parts of the year.

The project is the first to combine all the available observations of Arctic sea ice thickness. The earlier period from 1975 to 1990 relies mostly on under-ice submarines. Those records are less common since 2000, but have been replaced by a host of airborne and satellite measurements, as well as other methods for gathering data directly on or under the ice.

“A number of researchers were lamenting the fact that there were many thickness observations of sea ice, but they were scattered in different databases and were in many different formats,” Lindsay said. The U.S. National Oceanic and Atmospheric Administration funded the effort to compile the various records and match them up for comparison.

The data also includes the NASA that operated from 2003 to 2008, that NASA is conducting until its next satellite launches, long-term under-ice from the Woods Hole Oceanographic Institution, and other measures from aircraft and instruments anchored to the seafloor.

The older submarine records were unearthed for science by former 91探花professor Drew Rothrock, who of ice thickness to first establish the thinning of the ice pack through the 1990s. Vessels carried upward-looking sonar to measure the ice draft so they knew where they could safely surface. of those records found a 36 percent reduction in the average thickness in the quarter century between 1975 and 2000.

“This confirms and extends that study,” Lindsay said. The broader dataset and longer time frame show that what had looked like a leveling off in the late 1990s was only temporary. Instead, adding another 12 years of data almost doubles the amount of ice loss.

The observations included in the paper all have been entered in the that now includes around 50,000 monthly measurements standardized for location and time. The archive is curated by scientists at the 91探花Applied Physics Laboratory and stored at the .

Lindsay also is part of a 91探花group that produces a widely cited that combines weather data, sea-surface temperatures and satellite measurements of sea ice concentration to generate ice thickness maps. Critics have said those estimates of sea ice losses seemed too rapid and questioned their base in a numerical model. But the reality may be changing even faster than the calculations suggest.

“At least for the central Arctic basin, even our most drastic thinning estimate was slower than measured by these observations,” said co-author , a polar scientist at the 91探花Applied Physics Laboratory.

The new study, he said, also helps confirm the methods that use physical processes to calculate the volume of ice each month.

“Using all these different observations that have been collected over time, it pretty much verifies the trend that we have from the model for the past 13 years, though our estimate of thinning compared to previous decades may have been a little slow,” Schweiger said.

The new paper only looks at observations up to the year 2012, when the summer sea ice level reached a record low. The two years since then have had slightly more sea ice in the Arctic Ocean, but the authors say they are not surprised.

“What we see now is a little above the trend, but it’s not inconsistent with it in any way,” Lindsay said. “It’s well within the natural variability around the long-term trend.”

Additional funding for the project was from the National Science Foundation and NASA.

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For more information, contact Lindsay at rlindsay@uw.edu or Schweiger at 206-543-1312 or schweig@uw.edu.

A 91探花 atmospheric scientist is leading a scientific effort to study the evolution of air particles in the eastern U.S. in the winter. The six-week is sampling emissions through mid-March from their source to farther out in the environment, at all times of day and the long winter nights.

“We hope to better understand the fate of pollutants and their impact on the global atmosphere during wintertime,” said lead investigator , a 91探花professor of atmospheric sciences.

The project is measuring pollution from New York City south to Atlanta, over the coal-fired power plants of the Ohio River Valley, and in the more temperate southeastern U.S., and looking at what happens as those pollutants are blown offshore. Measurements are from a C-130 military transport plane owned by the National Science Foundation and operated for research by the National Center for Atmospheric Research.

The team is based out of a hangar at the NASA Langley Research Center in Hampton, Virginia, through March 15.

Observations include the amount and spatial pattern of the winter emissions, the timescale for them to be converted to other molecules such as ozone, or smog, as well as small particulates 鈥� the form of pollution most hazardous to health 鈥� and how those evolve over time.

The findings will be relevant for other densely populated places.

“This is directly applicable to emissions and transport of pollutants in any region that experiences shorter days, longer nights and colder temperatures during the winter,” Thornton said.

Running the flights during winter presents some challenges.

“In winter, pollution over land often stays close to the ground,” Thornton said. To sample these layers the group is conducting “missed approach” maneuvers in which an airport gives permission for the aircraft to come close to landing, about 100 feet from the ground, and then swoop back up while collecting measurements.

Low winter clouds are also an issue.

“If clouds extend too close to the water’s surface they prevent the pilots from flying visually,” Thornton said, “and we don’t have a way to know whether the clouds are too low until we fly out to look.”

The on the plane include a machine developed by Thornton’s group that takes precise chemical measurements several times a second. 91探花graduate student and postdoctoral fellow are operating the instrument during the flights. 91探花graduate student and 91探花meteorologist analyze atmospheric forecasts to determine the best conditions to fly.

Co-principal investigator , a 91探花professor of atmospheric sciences, helped with the flight plans in the first two weeks of February and participated in two of the surveys so far. The winter storms hitting the Northeast have postponed some of the research flights, she said, but the team has planned for some inevitable weather delays.

“The short daylight hours, cold temperatures and ground snow cover lead to different types of chemical reactions in the winter atmosphere compared with summer. In particular, nighttime chemistry plays a much more important role,” Jaegl茅 said.

“We don’t have that much information about what is going on in the winter,” she added. “This will bring a wealth of information in terms of the transformation of pollutants.”

The findings can be used to help regulate emissions and predict air quality during the winter months.

These measurements will complement a recent , in which 91探花and other scientists sampled the air over the same region in June and July of 2013.

The current campaign is funded by the National Science Foundation and the National Oceanic and Atmospheric Administration, and supported by the National Center for Atmospheric Research. Other are from NOAA, the University of Colorado the University of California, Berkeley, and Georgia Institute of Technology. Other partners are the University of New Hampshire, the University of Maryland, Baltimore County and the North Carolina Agricultural and Technical State University.

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聽For more information, contact Thornton at joelt@uw.edu and Jaegl茅 at 206-685-2679 or jaegle@uw.edu.

That humans and the cities we build affect the ecosystem and even drive some evolutionary change in species’ traits is already known. The signs are small but striking: in cities are getting bigger and in rivers are getting smaller; in urban areas are growing tamer and bolder, outcompeting their country cousins.

What’s new is that these evolutionary changes are happening much more quickly than previously thought, and have potential impacts on ecosystem function on a contemporary scale. Not in the distant future, that is 鈥� but now.

A new by of the 91探花 College of Built Environments’ published this month in the journal Trends in Ecology & Evolution suggests that if human-driven evolutionary change affects the functioning of ecosystems 鈥� as evidence is showing 鈥� it “may have significant implications for ecological and human well-being.”

Alberti, a professor of urban design and planning, said that until recently it was assumed that evolutionary change would take too long to affect ecological processes quite so immediately. Such thinking has prevented evidence from coming together “in a way that can only emerge through a cross-disciplinary lens,” she said, observing the interactions between humans and natural processes.

“We now have evidence that there is rapid evolution. These changes may affect the state of the environment now. This is what’s called eco-evolutionary feedback.

“Cities are not simply affecting biodiversity by reducing the number and variety of species that live in urban habitats,” Alberti said. Humans in cities are causing organisms to undergo accelerated evolutionary changes “that have effects on ecosystem functions such as biodiversity, nutrient cycling, seed dispersal, detoxification, food production and ultimately on human health and well-being.”

In the paper, Alberti systematically reviews evidence of “human signatures,” or documented examples of human-caused trait changes in fish, birds, mammals and plants, and their effects on ecosystem function.

In addition to the shrinking salmon, she cites earthworms with increased tolerance to metals, seeds of some plants dispersing less effectively and a type of urban mouse that is a “critical host” for the ticks that carry Lyme disease, leading to spikes in human exposure to the illness.

Songbirds are becoming tamer and bolder and also are changing their tunes to ensure their acoustic signals are not lost in the noisy urban background. European blackbirds are becoming sedentary and have changed their migratory behavior in response to urbanization.

Humans in cities cause these changes through a variety of ways, Alberti said. Our urbanization alters and breaks up natural vegetation patterns, introduces toxic pollutants and novel disturbances such as noise and light and increases the temperature. Human presence also changes the availability of resources such as food and water, altering the life cycle of many species.

Alberti said the emerging evidence prompts serious questions with implications for the focus and design of future studies:

• Can global rapid urbanization indeed affect the course of Earth’s evolution?
• Is urbanization moving the planet closer to an environmental tipping point on the scale of the that introduced oxygen into the atmosphere more than 2 billion years ago?
• Might different patterns of urbanization alter the effect of human action on eco-evolution?

Still, Alberti said hers is not a “catastrophic” perspective, but one that highlights both the challenges and the unique opportunity that humans have in shaping the evolution of planet Earth.

Ecosystems in urban environments are a sort of hybrid, she said: “It is their hybrid nature that makes them unstable, but also capable of innovating.” She explores the theme further in a book to be published in spring 2016, titled “Cities as Hybrid Ecosystems.”

“We can drive urbanizing ecosystems to collapse 鈥� or we can consciously steer them toward a resilient and sustainable future,” Alberti said. “The question is whether we become aware of the role we are playing.”

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For more information, contact Alberti at 206-295-7985 or malberti@uw.edu. Twitter: @ma003.

The life of a Bangladeshi garment factory worker is not an easy one. But new research from the 91探花 indicates that access to such factory jobs can improve the lives of young Bangladeshi women 鈥� motivating them to stay in school and lowering their likelihood of early marriage and childbirth.

The ready-made garment industry in Bangladesh has grown tremendously in the last 30 years and now accounts for more than three-quarters of the country’s total annual export revenue, according to a 2009 report by the Bangladesh Export Processing Bureau. The Bangladesh Garment Manufacturers and Exporters Association notes there are about 4 million such workers in Bangladesh, 80 percent of whom are women, according to government reports.

The April 2013 collapse of a commercial garment factory building that killed more than 1,100 people thrust the industry into a harsh spotlight and brought attention and concern from human rights groups. But amid the hardships, the new research indicates there is a quiet upside to factory work for many Bangladeshi women.

91探花economist and co-author A. Mushfiq Mobarak of the Yale University School of Management studied data on school enrollment and marriage and childbirth outcomes from 1,395 households in 60 Bangladeshi villages in the year 2009. In a paper accepted for publication in the Journal of Development Economics, they looked at the age at marriage and at the birth of the first child for girls with greater exposure to factory jobs.

“We document the likelihood of marriage and childbirth at early ages drops sharply for girls when they gain exposure to the ready-made garment sector,” the authors wrote.

More specifically, the researchers found that:

• Girls 12 to 18 years old who have lived in the proximity of a garment factory for about six years 鈥� the average time studied 鈥� were 28 percent less likely to be married than those living in villages in the same district that were not close to a factory.
• Girls who live near a factory tend to have 1.5 more years of education than their brothers when surveyed. This represents a 50 percent increase in girls’ educational attainment over villages without a garment factory nearby.
• Girls and young women who are exposed to factory jobs when they are 10 to 23 years old are 79 percent more likely to work outside the home before marriage.
• Overall, girls are 7.2 percentage points more likely to be enrolled in school when factories open close to their village. This effect is especially strong among young girls, 5 to 9 years of age.

They also found that in the areas surveyed, the demand for education generated through manufacturing growth in Bangladesh accounts for more of the educational increases among girls than the Female Secondary School Assistance Program, a large-scale government-funded program to encourage female schooling.

“In summary, access to factory jobs significantly lowers the risk of early marriage and childbirth for girls in Bangladesh,” Heath and Mobarak wrote in an accompanying research brief.

A small negative effect to factory job access on education also was found: Unlike the positive effect for those younger girls, those who were 17-18 years old were slightly more likely to leave school for factory employment.

“Of course, to say the industry has had positive effects does not deny that there have been serious tragedies,” Heath said. “We think that increased monitoring of conditions inside the factories can allow Bangladesh to reap the benefits of these jobs while minimizing the safety risks of working in them.”

The results, the researchers write, also provide one explanation, unexplored until now, for accelerated gender equity in education in Bangladesh, “thus generating policy implications for other countries interested in emulating Bangladesh’s success.”

Funding for the research was provided by the National Science Foundation.

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For more information, contact Heath at rmheath@uw.edu or 206-543-5796.
NSF grant number: SES-0527751.

But what happened next? Life can exist without oxygen, but without plentiful nitrogen to build genes 鈥� essential to viruses, bacteria and all other organisms 鈥� life on the early Earth would have been scarce.

The ability to use atmospheric nitrogen to support more widespread life was thought to have appeared roughly 2 billion years ago. Now research from the 91探花 looking at some of the planet’s oldest rocks finds evidence that 3.2 billion years ago, life was already pulling nitrogen out of the air and converting it into a form that could support larger communities.

“People always had the idea that the really ancient biosphere was just tenuously clinging on to this inhospitable planet, and it wasn’t until the emergence of nitrogen fixation that suddenly the biosphere become large and robust and diverse,” said co-author , a 91探花professor of Earth and space sciences. “Our work shows that there was no nitrogen crisis on the early Earth, and therefore it could have supported a fairly large and diverse biosphere.”

The were published Feb. 16 in Nature.

The authors analyzed 52 samples ranging in age from 2.75 to 3.2 billion years old, collected in South Africa and northwestern Australia. These are some of the oldest and best-preserved rocks on the planet. The rocks were formed from sediment deposited on , so are free of chemical irregularities that would occur near a subsea volcano. They also formed before the atmosphere gained oxygen, roughly 2.3 to 2.4 billion years ago, and so preserve chemical clues that have disappeared in modern rocks.

Even the oldest samples, 3.2 billion years old 鈥� three-quarters of the way back to the birth of the planet 鈥� showed chemical evidence that life was pulling nitrogen out of the air. The ratio of heavier to lighter nitrogen atoms fits the pattern of nitrogen-fixing enzymes contained in single-celled organisms, and does not match any chemical reactions that occur in the absence of life.

“Imagining that this really complicated process is so old, and has operated in the same way for 3.2 billion years, I think is fascinating,” said lead author , who did the work as part of her 91探花doctoral research. “It suggests that these really complicated enzymes apparently formed really early, so maybe it’s not so difficult for these enzymes to evolve.”

Genetic analysis of nitrogen-fixing enzymes have placed their origin at between 1.5 and 2.2 billion years ago.

“This is hard evidence that pushes it back a further billion years,” Buick said.

Fixing nitrogen means breaking a tenacious triple bond that holds nitrogen atoms in pairs in the atmosphere and joining a single nitrogen to a molecule that is easier for living things to use. The chemical signature of the rocks suggests that nitrogen was being broken by an enzyme based on , the most common of the three types of nitrogen-fixing enzymes that exist now. Molybdenum is now abundant because oxygen reacts with rocks to wash it into the ocean, but its source on the ancient Earth 鈥� before the atmosphere contained oxygen to weather rocks 鈥� is more mysterious.

The authors hypothesize that this may be further evidence that some early life may have existed in single-celled layers on land, exhaling small amounts of oxygen that reacted with the rock to release molybdenum to the water.

“We’ll never find any direct evidence of land scum one cell thick, but this might be giving us indirect evidence that the land was inhabited,” Buick said. “Microbes could have crawled out of the ocean and lived in a slime layer on the rocks on land, even before 3.2 billion years ago.”

Future work will look at what else could have limited the growth of life on the early Earth. St眉eken has begun a 91探花postdoctoral position funded by NASA to look at trace metals such as zinc, copper and cobalt to see if one of them controlled the growth of ancient life.

Other co-authors are at the University of Johannesburg in South Africa, who provided some samples from gold mines, and 91探花graduate student . The research was funded by NASA, the UW’s , the and the .

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For more information, contact Buick at 206-543-1913 or buick@uw.edu and St眉eken at evast@uw.edu.

“At the UW, this is a marriage that’s been waiting to happen 鈥� 3-D printing from the engineering side, and functional materials from the chemistry side,” said , a 91探花assistant professor of chemistry. He is corresponding author on a recent in the American Chemical Society’s journal of Applied Materials and Interfaces.

Gregory Peterson and Michael Larsen, 91探花doctoral students in chemistry, created a polymer, or plastic made up of many repeated units strung together, and fed the soft plastic into the 91探花chemistry lab’s commercial 3-D printer.

One print head contained , similar to what a 3-D printer company sells as . The other print head contained a plastic that is 99.5 percent identical but the 91探花team made occasional insertions of a molecule, spiropyran, that changes color when it is stretched.

“We wanted to demonstrate that the functional chemistry could be incorporated readily into already printable materials,” Boydston said. “We found that designer chemistry can be incorporated into 3-D printing very rapidly.”

The printed tab is a piece of white plastic with barely visible stripes that turn purple under force. It acts as an inexpensive, mechanical sensor with no electronic parts. The whole device took about 15 minutes to print from materials that cost less than a dollar.

The sensor might be used to record force or strain on a building or other structure. Boydston would like to develop a sensor that also records the speed of the force, or impact, which could allow for a football helmet that changes color when hit with sufficient force.

The project is part of a recent collaboration between Boydston’s group and co-authors and , 91探花mechanical engineers who have developed new 3-D printing and .

Different instructions can program the machine to print the plastics in any configuration 鈥� with the color-changing part in stripes in the middle, completely encased in the other plastic, or in any other desired shape.

Boydston specializes in organic synthesis, or, in his words: “It means making more complex molecules from simpler, more available ones.”

Varying how the plastic is made could yield molecules that respond in different ways.

“Maybe the material isn’t currently under stress, but it had been several times prior to your observing it. And so these types of materials could record that load history,” Boydston said.

Boydston will continue collaborating with Ganter and Storti, to plan and create more 3-D printed objects that incorporate designer molecules. The 3-D printing technology offers new possibilities, he said, for individualized medical implants or other custom shapes that incorporate engineered molecules that respond to their environment.

“This is definitely an area that we want to continue to expand into,” Boydston said.

The research was funded by the 91探花.

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For more information, contact Boydston at 206-616-8195 or boydston@chem.washington.edu.