Science360 News Service: Top Story

New way for bridges to withstand earthquakes: Support column design

Wed, 04 Sep 2019 07:00:00 GMT

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Bridges make travel faster and more convenient, but, in an earthquake, these structures are subject to forces that can cause extensive damage and make them unsafe. Now civil and environmental engineer Petros Sideris of Texas A&M University is leading a National Science Foundation (NSF)-funded research project to investigate the performance of hybrid sliding-rocking (HSR) columns. HSR columns provide the same support as conventional bridge infrastructure columns but are more earthquake-resistant. HSR columns are a series of individual concrete segments held together by steel cables that allow for controlled sliding and rocking. This allows the columns to shift without damage, while post-tensioning strands ensure that at the end of an earthquake the columns are pushed back to their original position. Conventional bridges are cast-in-place monolithic concrete elements that are strong but inflexible. Structural damage in these bridge columns, typically caused by a natural disaster, often forces a bridge to close until repairs are completed. But bridges with HSR columns can withstand large earthquakes with minimal damage and require minor repairs, likely without bridge closures. Such infrastructure helps with post-disaster response and recovery and can save thousands in taxpayer dollars. In an earthquake, HSR columns provide "multiple advantages to the public," Sideris said. "By preventing bridge damage, we can maintain access to affected areas immediately after an event for response teams to be easily deployed, and help affected communities recover faster. In mitigating losses related to post-event bridge repairs and bridge closures, more funds can be potentially directed to supporting the recovery of the affected communities." According to Joy Pauschke, NSF program director for natural hazards engineering, "NSF invests in fundamental engineering research so that, in the future, the nation's infrastructure can be more resilient to earthquakes, hurricanes, and other forces of nature."

Image credit: Texas A&M University

Technique uses magnets, light to control and reconfigure soft robots

Tue, 03 Sep 2019 07:00:00 GMT

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National Science Foundation (NSF)-funded researchers from North Carolina State and Elon universities have developed a technique that allows them to remotely control the movement of soft robots, lock them into position for as long as needed and later reconfigure the robots into new shapes. The technique relies on light and magnetic fields. "By engineering the properties of the material, we can control the soft robot's movement remotely; we can get it to hold a given shape; we can then return the robot to its original shape or further modify its movement; and we can do this repeatedly. All of those things are valuable, in terms of this technology's utility in biomedical or aerospace applications," says Joe Tracy, a professor of materials science and engineering at NC State and corresponding author of a paper on the work. In experimental testing, the researchers demonstrated that the soft robots could be used to form "grabbers" for lifting and transporting objects. The soft robots could also be used as cantilevers or folded into "flowers" with petals that bend in different directions. "We are not limited to binary configurations, such as a grabber being either open or closed," says Jessica Liu, first author of the paper and a Ph.D. student at NC State. "We can control the light to ensure that a robot will hold its shape at any point."

Image credit: Jessica A.C. Liu

Astronomers find a golden glow from a distant stellar collision

Fri, 30 Aug 2019 07:00:00 GMT

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On August 17, 2017, scientists made history with the first direct observation of a merger between two neutron stars. It was the first cosmic event detected in both gravitational waves and the entire spectrum of light, from gamma rays to radio emissions. The impact also created a kilonova -- a turbocharged explosion that instantly forged several hundred planets’ worth of gold and platinum. The observations provided the first compelling evidence that kilonovae produce large quantities of heavy metals, a finding long predicted by theory. Astronomers suspect that all of the gold and platinum on Earth formed as a result of ancient kilonovae created during neutron star collisions. Based on data from the 2017 event, first spotted by the Laser Interferometer Gravitational-wave Observatory (LIGO), astronomers began to adjust their assumptions of how a kilonova should appear to Earth-bound observers. A team of scientists reexamined data from a gamma-ray burst spotted in August 2016 and found new evidence for a kilonova that went unnoticed during the initial observations.

Image credit: NASA/ESA/E. Troja

Study finds big increase in ocean carbon dioxide absorption along West Antarctic Peninsula

Thu, 29 Aug 2019 07:00:00 GMT

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A new study shows that the West Antarctic Peninsula is experiencing some of the most rapid climate change on Earth, featuring dramatic increases in temperatures, retreats in glaciers and declines in sea ice. The Southern Ocean absorbs nearly half of the carbon dioxide -- the key greenhouse gas linked to climate change -- that is absorbed by all the world's oceans. The study tapped an unprecedented 25 years of oceanographic measurements in the Southern Ocean and highlights the need for more monitoring in the region. The research revealed that carbon dioxide absorption by surface waters off the West Antarctic Peninsula is linked to the stability of the upper ocean, along with the amount and type of algae present. A stable upper ocean provides algae with ideal growing conditions. During photosynthesis, algae remove carbon dioxide from the surface ocean, which in turn draws carbon dioxide out of the atmosphere. From 1993 to 2017, changes in sea ice dynamics off the West Antarctic Peninsula stabilized the upper ocean, resulting in greater algal concentrations and a shift in the mix of algal species. That's led to a nearly five-fold increase in carbon dioxide absorption during the summertime. The research also found a strong north-south difference in the trend of carbon dioxide absorption. The southern portion of the peninsula, which to date has been less impacted by climate change, experienced the most dramatic increase in carbon dioxide absorption, demonstrating the poleward progression of climate change in the region.

Image credit: Drew Spacht/The Ohio State University

When human expertise improves the work of machines

Wed, 28 Aug 2019 07:00:00 GMT

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Machine learning algorithms can sometimes do a great job with a little help from human expertise, at least in the field of materials science. In many specialized areas of science, engineering and medicine, researchers are turning to machine learning algorithms to analyze data sets that have grown too large for humans to understand. In materials science, success with this effort could accelerate the design of next-generation advanced functional materials, where development now usually depends on old-fashioned trial and error. By themselves, however, data analytics techniques borrowed from other research areas often fail to provide the insights needed to help materials scientists and engineers choose which of many variables to adjust -- and the techniques can't account for dramatic changes such as the introduction of a new chemical compound into the process. In a new study, researchers explain a technique known as dimensional stacking, which shows that human experience still has a role to play in the age of machine intelligence. The machines gain an edge at solving a challenge when the data to be analyzed are intelligently organized based on human knowledge of what factors are likely to be important and related. "When your machine accepts strings of data, it really does matter how you are putting those strings together," said Nazanin Bassiri-Gharb, the paper's corresponding author and a scientist at the Georgia Institute of Technology. "We must be mindful that the organization of data before it goes to the algorithm makes a difference. If you don't plug the information in correctly, you will get a result that isn't necessarily correlated with the reality of the physics and chemistry that govern the materials."

Image credit: Rob Felt/Georgia Tech

Genetic diversity couldn't save Darwin's finches

Tue, 27 Aug 2019 07:00:00 GMT

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A National Science Foundation-funded study found that Charles Darwin's famous finches defy what has long been considered a key to evolutionary success: genetic diversity. The research on finches of the Galapagos Islands could change the way conservation biologists think about a species' potential for extinction in naturally fragmented populations. Researchers examined 212 tissue samples from museum specimens and living birds. Some of the museum specimens in the study were collected by Darwin himself in 1835. Only one of the extinct populations, a species called the vegetarian finch, had lower genetic diversity compared to modern survivors. Specifically, researchers believe a biological phenomenon called sink-source dynamics is at play in which larger populations of birds from other islands act as a "source" of immigrants to the island population that is naturally shrinking, the "sink." Without these immigrant individuals, the natural population on the island likely would continue to dwindle to local extinction. The immigrants have diverse genetics because they are coming from a variety of healthier islands, giving this struggling "sink" population inflated genetic diversity.

Image credit: Jose Barreiro

Study identifies main culprit behind lithium metal battery failure

Mon, 26 Aug 2019 07:00:00 GMT

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A National Science Foundation-funded research has discovered the root cause of why lithium metal batteries fail -- bits of lithium metal deposits break off from the surface of the anode during discharging and are trapped as "dead" or inactive lithium that the battery can no longer access. The discovery challenges the conventional belief that lithium metal batteries fail because of the growth of a layer, called the solid electrolyte interphase (SEI), between the lithium anode and the electrolyte. The researchers made their discovery by developing a technique to measure the amounts of inactive lithium species on the anode -- a first in the field of battery research -- and studying their micro- and nanostructures. The findings could pave the way for bringing rechargeable lithium metal batteries from the lab to the market.

Image credit: University of California - San Diego

Shape-shifting sheets

Fri, 23 Aug 2019 07:00:00 GMT

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National Science Foundation-funded engineers have developed a mathematical framework that can turn any sheet of material into any prescribed shape, inspired by the paper craft kirigami (from the Japanese, kiri, meaning to cut and kami, meaning paper). Unlike its better-known cousin origami, which uses folds to shape paper, kirigami relies on a pattern of cuts in a flat paper sheet to change its flexibility and allow it to morph into 3D shapes. Artists have long used this artform to create everything from pop-up cards to castles and dragons. This research follows previous work by the researchers that characterized how origami-based patterns could be used as building blocks to create almost any three-dimensional curved shape. Next the researchers aim to explore how to combine cuts and folds to achieve any shape with a given set of properties, thus linking origami and kirigami.

Image credit: Harvard SEAS

Earth's last magnetic field reversal took far longer than once thought

Thu, 22 Aug 2019 07:00:00 GMT

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Earth's magnetic field seems steady and true -- reliable enough to navigate by. Yet, largely hidden from daily life, the field drifts, waxes and wanes. The magnetic North Pole is currently shifting toward Siberia, forcing the Global Positioning System that underlies modern navigation to update its software sooner than expected. Every several hundred thousand years, the magnetic field dramatically shifts and reverses its polarity. Magnetic north flips to the geographic South Pole and, eventually, back again. This reversal has happened countless times over Earth's history, but scientists' understanding of why and how the field reverses is limited. The researchers find that the most recent field reversal 770,000 years ago took at least 22,000 years to complete, several times longer than previously thought. The results call into question controversial findings that some reversals could occur within a human lifetime.

Image credit: Brad Singer

Wearable sensors detect what's in your sweat

Wed, 21 Aug 2019 07:00:00 GMT

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Needle pricks not your thing? A team of National Science Foundation-funded scientists is developing wearable skin sensors that can detect what's in your sweat. They hope that one day, monitoring perspiration could bypass the need for more invasive procedures like blood draws, and provide real-time updates on health problems such as dehydration or fatigue. In a new paper, the team describes a new sensor design that can be rapidly manufactured using a "roll-to-roll" processing technique that essentially prints the sensors onto a sheet of plastic like words on a newspaper. They used the sensors to monitor the sweat rate, and the electrolytes and metabolites in sweat, from volunteers who were exercising, and others who were experiencing chemically induced perspiration. The new sensors contain a spiraling microscopic tube, or microfluidic, that wicks sweat from the skin. By tracking how fast the sweat moves through the microfluidic, the sensors can report how much a person is sweating, or their sweat rate. The microfluidics are also outfitted with chemical sensors that can detect concentrations of electrolytes like potassium and sodium, and metabolites like glucose.

Image credit: Bizen Maskey/Sunchon National University