Category Archives: Georgia Institute of Technology


Stretchy sensor keeps watch during brain aneurysm care

Researchers have developed a sensor that could improve the way brain aneurysm treatments are monitored.

Implantation of a stent-like flow diverter offers one option for less invasive treatment of brain aneurysms—bulges in blood vessels—but the procedure requires frequent monitoring while the vessels heal.

“The nanostructured sensor system could provide advantages for patients, including a less invasive aneurysm treatment and an active monitoring capability…”

Now, researchers have demonstrated proof-of-concept for a highly flexible and stretchable sensor that could be integrated with the flow diverter to monitor hemodynamics in a blood vessel without costly diagnostic procedures.

The sensor, which uses capacitance changes to measure blood flow, could reduce the need for testing to monitor the flow through the diverter. Researchers have shown that the sensor accurately measures fluid flow in animal blood vessels in vitro, and are working on the next challenge: wireless operation that could allow in vivo testing.

Tiny and flexible

“The nanostructured sensor system could provide advantages for patients, including a less invasive aneurysm treatment and an active monitoring capability,” says Woon-Hong Yeo, an assistant professor in biomedical engineering department at Georgia Tech and Emory University. “The integrated system could provide active monitoring of hemodynamics after surgery, allowing the doctor to follow up with quantitative measurement of how well the flow diverter is working in the treatment.”

aneurysm sensor (brain aneurysm concept)
With gloved fingers for scale, a proof-of-concept flow sensor is shown here on a stent backbone. (Credit: Woon-Hong Yeo/Georgia Tech)

Cerebral aneurysms occur in up to five percent of the population, with each aneurysm carrying a one percent risk per year of rupturing, notes Youngjae Chun, an associate professor in the Swanson School of Engineering at the University of Pittsburgh. Aneurysm rupture will cause death in up to half of affected patients.

Endovascular therapy using platinum coils to fill the aneurysm sac has become the standard of care for most aneurysms, but recently a new endovascular approach—a flow diverter—has been developed to treat cerebral aneurysms. Flow diversion involves placing a porous stent across the neck of an aneurysm to redirect flow away from the sac, generating local blood clots within the sac.

“We have developed a highly stretchable, hyper-elastic flow diverter using a highly-porous thin film nitinol,” Chun explains. “None of the existing flow diverters, however, provide quantitative, real-time monitoring of hemodynamics within the sac of cerebral aneurysm…. [We] have developed a smart flow-diverter system that can actively monitor the flow alterations during and after surgery.”

Rising to the challenge

Repairing the damaged artery takes months or even years, during which the flow diverter must be monitored using MRI and angiogram technology, which is costly and involves injection of a magnetic dye into the blood stream.

Yeo and his colleagues hope their sensor could provide simpler monitoring in a doctor’s office using a wireless inductive coil to send electromagnetic energy through the sensor. By measuring how the energy’s resonant frequency changes as it passes through the sensor, the system could measure blood flow changes into the sac.

“We are trying to develop a batteryless, wireless device that is extremely stretchable and flexible that can be miniaturized enough to be routed through the tiny and complex blood vessels of the brain and then deployed without damage,” says Yeo. “[It’s] very challenging to insert such [an] electronic system into the brain’s narrow and contoured blood vessels.”

“The sensor has to be completely compressed for placement, so it must be capable of stretching 300 or 400 percent…”

The sensor uses a micro-membrane made of two metal layers surrounding a dielectric material, and wraps around the flow diverter. The device is just a few hundred nanometers thick, and is produced using nanofabrication and material transfer printing techniques, encapsulated in a soft elastomeric material.

“The membrane is deflected by the flow through the diverter, and depending on the strength of the flow, the velocity difference, the amount of deflection changes,” Yeo explains. “We measure the amount of deflection based on the capacitance change, because the capacitance is inversely proportional to the distance between two metal layers.”

Because the brain’s blood vessels are so small, the flow diverters can be no more than five to ten millimeters long and a few millimeters in diameter. That rules out the use of conventional sensors with rigid and bulky electronic circuits.

“Putting functional materials and circuits into something that size is pretty much impossible right now,” Yeo says. “What we are doing is very challenging based on conventional materials and design strategies.”

Blood vessel ‘spaghetti’ makes mini-brain more real

The researchers tested three materials for their sensors: gold, magnesium, and the nickel-titanium alloy known as nitinol. All can be safely used in the body, but magnesium offers the potential to be dissolved into the bloodstream after it is no longer needed.

The proof-of-principle sensor was connected to a guide wire in the in vitro testing, but Yeo and his colleagues are now working on a wireless version that could be implanted in a living animal model. While implantable sensors are being used clinically to monitor abdominal blood vessels, application in the brain creates significant challenges.

“The sensor has to be completely compressed for placement, so it must be capable of stretching 300 or 400 percent,” says Yeo. “The sensor structure has to be able to endure that kind of handling while being conformable and bending to fit inside the blood vessel.”

Supercomputer tests ways to divert blood from aneurysm

The research appears in the journal ACS Nano. Georgia Tech’s Institute for Electronics and Nanotechnology, the University of Pittsburgh, and the Korea Institute of Materials Science supported the research.

Other researchers from Georgia Tech and the University of Pittsburgh, and from Virginia Commonwealth University; the Korea Advanced Institute of Science and Technology; Chonnam National University; and Washington State University  contributed to the work.

Source: Georgia Tech

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Tiny snails suck the life out of stressed corals

A previously overlooked predator—a thumbnail-sized snail—could be increasing the pressure on coral reefs already weakened by the effects of overfishing, rising ocean temperatures, pollution, and other threats, researchers say.

“The Porites coral is kind of the last man standing, the last hope for some of these reefs coming back…”

The snail damages coral by sucking fluid from coral like a tick, and may have been ignored because it camouflages itself on reefs and doesn’t move around to leave obvious signs of its attack.

In experiments done directly on Fiji Island reefs, scientists quantified the impact of the snails, and found that attacks could reduce the growth of Porites cylindrica coral by as much as 43 percent in less than a month.

“Once the reefs are down and nearly out, these snails are piling on,” says Mark Hay, a professor in the School of Biological Sciences at Georgia Tech.

Porites cylindrica (coral reefs concept)
Porites cylindrica corals were caged to exclude other predators and a Coralliophila snail was attached to feed for 24 days. Although snail feeding is very localized, the negative effects of predation are evident at nearby locations on the coral. (Credit: Cody Clements/Georgia Tech)

“The Porites coral is kind of the last man standing, the last hope for some of these reefs coming back, and they are the ones these snails selectively prey on. As you get fewer and fewer corals, the snails focus on the fewer and fewer of these colonies that remain. This is part of the downward spiral of the reefs.”

As reported in Ecological Applications, in areas protected from fishing, postdoctoral fellow Cody Clements never found more than five of the creatures—whose scientific name is Coralliophila violacea—on a single coral colony.

But on degraded reefs where fishing is permitted, he found hundreds of the snails on some declining coral colonies, as much as 35 times more than colonies in the protected areas. To assess the damage, he devised an experiment to measure how the snails affected coral growth.

coral in cage (coral reefs concept)
Porites cylindrica coral caged. (Credit: Cody Clements, Georgia Tech)

On the reefs near Votoa Village on Fiji’s Coral Coast, Clements isolated coral branches and attached snails to them. After a period of 24 days, he compared the growth of snail-infested coral branches to comparable branches that had no snails. During that three-week period, the predators reduced coral growth by approximately 18 to 43 percent, depending on snail size.

“A single snail can do a considerable amount of damage,” Clements says. “They are sucking the juice out of the coral. If you have a lot of snails feeding on a single coral colony, it can be very hard for the colony to thrive.”

“Overfishing takes a lot of key species out of the communities so that all you have left is the marine equivalent of cockroaches and dandelions.”

In coral ecosystems, fish help keep many predators and seaweeds under control. For that reason, fishing is forbidden in marine protected areas to maintain species diversity. To confirm their suspicions that overfishing was related to the snail problem, Clements tethered individual snails to reefs in a paired protected and unprotected areas.

When they returned to examine the experiment, they found that snails in the protected areas had been eaten, and evidence left behind suggested they had been consumed by triggerfish and other species with teeth able to crack the snail shells. Predation of the snails was 220 percent higher in the marine protected areas compared to unprotected areas with few remaining fish, they found.

“From the predation evidence, it looked like the fish were eating the snails,” Clements says. “It seemed like the main element driving the difference was the protection status of the area where the snails were tethered.”

One unexpected finding was that the shells of larger snails had been taken over by hermit crabs. “The hermit crabs were very direct about getting the shells that they wanted,” Hay says. “This may or may not be ecologically important on a large scale.”

The study began with an accidental discovery while Clements was working on another project in a heavily degraded reef area. “I was fragmenting branches from colonies and noticed these snails,” he says. “I wondered why I had never seen them before, then I started looking around and noticed they were everywhere.”

Want to stop coral bleaching? Get rid of snails

The snail shells are covered with marine growth, so they’re difficult to see—unless you know what to look for, Clements says. During the research, Clements removed more than 2,000 of the snails with needle-nosed pliers.

The Porites coral often provides the foundation for reefs, and is considered one of the most hardy species because it is less susceptible to disease, less attractive to crown-of-thorns sea stars, and more resistant to damage from seaweeds.

For that reason, researchers believe it may provide a way for reefs to recover if conditions improve. Unfortunately, that coral is also a favorite for the small snail.

The findings reinforce a lesson Hay and Clements have been working to explain for years.

“Protecting coral reef areas and keeping food webs intact is really important to maintaining these communities,” Hay says. “Overfishing takes a lot of key species out of the communities so that all you have left is the marine equivalent of cockroaches and dandelions. Taking out the fish takes away the functions the fish have been providing to the community.”

How shark poo keeps coral reefs healthy

The National Science Foundation, the National Institutes of Health, and the Teasley Endowment to the Georgia Institute of Technology funded the work.

Source: Georgia Tech

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How crab shells and trees could keep food fresher

A flexible material made from multiple layers of chitin from crab shells and cellulose from trees could one day replace plastic packaging film.

“The main benchmark that we compare it to is PET, or polyethylene terephthalate, one of the most common petroleum-based materials in the transparent packaging you see in vending machines and soft drink bottles,” says J. Carson Meredith, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.

“Our material showed up to a 67 percent reduction in oxygen permeability over some forms of PET, which means it could in theory keep foods fresher longer.”

Cellulose and chitin

Cellulose, which comes from plants, is the planet’s most common natural biopolymer, followed next by chitin, which comes from shellfish, insects, and fungi.

Researchers devised a method to create a film by suspending cellulose and chitin nanofibers in water and spraying them onto a surface in alternating layers. Once fully dried, the material is flexible, strong, transparent, and compostable.

“We had been looking at cellulose nanocrystals for several years and exploring ways to improve those for use in lightweight composites as well as food packaging, because of the huge market opportunity for renewable and compostable packaging, and how important food packaging overall is going to be as the population continues to grow,” Meredith says.

Alternating layers

The team had been looking into chitin for an unrelated reason when they wondered if it might be useful in food packaging.

“We recognized that because the chitin nanofibers are positively charged, and the cellulose nanocrystals are negatively charged, they might work well as alternating layers in coatings because they would form a nice interface between them,” Meredith says.

Packaging meant to preserve food needs to prevent oxygen from passing through. Part of the reason the new material improves upon conventional plastic packaging as a gas barrier is because of the crystalline structure of the film.

“It’s difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure,” Meredith says. “Something like PET on the other hand has a significant amount of amorphous or non-crystalline content, so there are more paths easier for a small gas molecule to find its way through.”

Biomaterial made of crabs could cut plastic pollution

Environmentalists have long looked for renewable ways to replace petroleum-based materials in consumer products. With the amount of cellulose already produced and a ready supply of chitin-rich byproducts left over from the shellfish food industry, there’s likely more than enough material available to make the new films a viable flexible-packaging alternative, Meredith says.

Still, there’s more work to be done. To make the new material eventually competitive with flexible packaging film on cost, a manufacturing process that maximizes economy of scale will be necessary.

Plastic bits in barnacles threaten food chain

Additionally, while industrial processes to mass produce cellulose are mature, methods to produce chitin are still in their infancy, Meredith says. And, more research is also needed to improve the material’s ability to block water vapor.

The Georgia Tech Renewable Bioproducts Institute and the Georgia Research Alliance funded the work, which appears in ACS Sustainable Chemistry and Engineering.

Source: Georgia Tech

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What dehydration does to your mind after just 2 hours

Just two hours of vigorous yard work in the summer sun without drinking fluids could be enough to blunt concentration, according to a new study.

After statistically analyzing data from multiple peer-reviewed research papers on dehydration and cognitive ability, researchers found that that cognitive functions often wilt as water departs the body. The data point to functions like attention, coordination, and complex problem solving suffering the most, and activities like reacting quickly when prompted not diminishing much.

“The simplest reaction time tasks were least impacted, even as dehydration got worse, but tasks that require attention were quite impacted,” says Mindy Millard-Stafford, a professor in the School of Biological Sciences at Georgia Tech.

No fluid, no focus

As the bodies of test subjects in various studies lost water, the majority of participants increasingly made errors during attention-related tasks that were mostly repetitive and unexciting, such as punching a button in varying patterns for quite a few minutes. There are situations in life that challenge attentiveness in a similar manner, and when it lapses, snafus can happen.

There’s no hard and fast rule about when exactly such lapses can pop up.

“Maintaining focus in a long meeting, driving a car, a monotonous job in a hot factory that requires you to stay alert are some of them,” says Millard-Stafford, the study’s principal investigator. “Higher-order functions like doing math or applying logic also dropped off.”

The researchers have been concerned that dehydration could raise the risk of an accident, particularly in scenarios that combine heavy sweating and dangerous machinery or military hardware.

Millard-Stafford and first author Matthew Wittbrodt, a former graduate research assistant at Georgia Tech and now a postdoctoral researcher at Emory University, report their work in the journal Medicine & Science in Sports & Exercise.

Sudden onset

There’s no hard and fast rule about when exactly such lapses can pop up, but the researchers examined studies with one to six percent loss of body mass due to dehydration and found more severe impairments started at two percent. That level has been a significant benchmark in related studies.

“If you weigh 200 pounds and you go work out for a few of hours, you drop four pounds, and that’s two percent body mass…”

“There’s already a lot of quantitative documentation that if you lose two percent in water it affects physical abilities like muscle endurance or sports tasks and your ability to regulate your body temperature,” says Millard-Stafford. “We wanted to see if that was similar for cognitive function.”

The researchers looked at 6,591 relevant studies for their comparison, then narrowed them down to 33 papers with scientific criteria and data comparable enough to do metadata analysis. They focused on acute dehydration, which anyone could experience during exertion, heat, and/or not drinking as opposed to chronic dehydration, which can result from a disease or disorder.

How much is too much?

How much fluid loss adds up to two percent body mass loss?

“If you weigh 200 pounds and you go work out for a few of hours, you drop four pounds, and that’s two percent body mass,” Millard-Stafford says. And it can happen fast. “With an hour of moderately intense activity, with a temperature in the mid-80s, and moderate humidity, it’s not uncommon to lose a little over two pounds of water.”

“If you do 12-hour fluid restriction, nothing by mouth, for medical tests, you’ll go down about 1.5 percent,” she says. “Twenty-four hours fluid restriction takes most people about three percent down.”

Scientists say we need a real definition for ‘heat wave’

And that begins to affect more than cognition or athletic abilities and concentration.

“If you drop four or five percent, you’re going to feel really crummy,” Millard-Stafford says. “Water is the most important nutrient.”

She warns that older people can dry out more easily because they often lose their sensation of thirst and also, their kidneys are less able to concentrate urine, which makes them retain less fluid. People with high body fat content also have lower relative water reserves than do lean folks.

A warning about water

Hydration is important, but so is moderation.

“You can have too much water, something called hyponatremia,” Millard-Stafford says. “Some people overly aggressively, out of a fear of dehydration, drink so much water that they dilute their blood and their brain swells.”

Wearable cuffs would detect dehydration in kids

This leads to death in rare, extreme cases, for example, when long-distance runners constantly drink but don’t sweat much and end up massively overhydrating.

“Water needs to be enough, just right,” Millard-Stafford says.

Also, she warns that while salt avoidance may be good for sedentary people or hypertension patients, whoever sweats needs some salt as well, or they won’t retain the water they drink.

Source: Georgia Tech

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Mystery solved: ‘Ghostly’ neutrinos come from a blazar

Scientists have found the first evidence of a source of high-energy cosmic neutrinos, ghostly subatomic particles that can travel unhindered for billions of light years from the most extreme environments in the universe to Earth.

“For years, we’ve had a long list of potential sources for high-energy neutrinos. Now we have a specific source—blazars—that we can look at very carefully.”

The observations, from the IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station in coordination with telescopes around the globe and in Earth’s orbit, help resolve a more than a century-old riddle about what sends subatomic particles such as neutrinos and cosmic rays speeding through the universe.

Since their first detection over one hundred years ago, cosmic rays—highly energetic particles that continuously rain down on Earth from space—have posed an enduring mystery: What creates and launches these particles across such vast distances? Where do they come from?

Because cosmic rays are charged particles, their paths cannot be traced directly back to their sources due to the magnetic fields that fill space and warp their trajectories. But the powerful cosmic accelerators that produce them will also produce neutrinos. Neutrinos are uncharged particles, unaffected by even the most powerful magnetic field. Because they rarely interact with matter and have almost no mass—hence their nickname “ghost particle”—neutrinos travel nearly undisturbed from their accelerators, giving scientists an almost direct pointer to their source.

illustration of IceCube lab and neutrinos under ice
In this composite, based on a real image of the IceCube Lab at the South Pole, a distant source emits neutrinos that are detected below the ice by IceCube sensors, called DOMs. (Credit: IceCube/NSF)

Two new papers (first, second) in the journal Science for the first time provide evidence for a known blazar as a source of high-energy neutrinos detected by the IceCube observatory. This blazar, designated by astronomers as TXS 0506+056, was first singled out following a neutrino alert sent by IceCube on September 22, 2017.

“IceCube-170922A—a high-energy neutrino detected by IceCube on September 22, 2017—had an energy of 300 trillion electron volts and a trajectory pointing back to a small patch of sky in the constellation Orion,” says coauthor Azadeh Keivani, a postdoctoral scholar at Penn State.

“The era of multi-messenger astrophysics is here. Each messenger gives us a more complete understanding of the universe and important new insights into the most powerful objects and events in the sky,” says NSF director France Córdova. “Such breakthroughs are only possible through a long-term commitment to fundamental research and investment in superb research facilities.”

blazar is accelerating protons that produce pions - high-energy neutrinos
In this artistic rendering, a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays. Neutrinos are always the result of a hadronic reaction such as the one visible here. Gamma rays can be produced in both hadronic and electromagnetic interactions. (Credit: via Georgia Tech)

A blazar is a galaxy with a super-massive black hole at its core. A signature feature of blazars is twin jets of light and elementary particles emitted from the poles along the axis of the black hole’s rotation. In this blazar, one of the jets points toward Earth. This blazar is situated in the night sky just off the left shoulder of the constellation Orion and is about four billion light years from Earth.

“Scientifically, this is very good news,” says Ignacio Taboada, an associate professor in Georgia Tech’s School of Physics and member of the Center for Relativistic Astrophysics also at Georgia Tech. As leader of the “Transients Science Working Group” within IceCube, he oversaw all the studies that inquired on the correlation TXS 0506+056’s gamma ray flare and the neutrino alert of September 22, 2017. “For years, we’ve had a long list of potential sources for high-energy neutrinos. Now we have a specific source—blazars—that we can look at very carefully.”

Georgia Tech PhD student Chun Fai (Chris) Tung contributed to the publications by reconstructing archival IceCube data searching for very-high energy neutrinos that might be correlated with blazars other than TXS 0506+056.

“At the highest energies, the universe is essentially opaque to very high energy gamma rays, and the farther away you are, the more opaque the universe is,” Taboada says. “If the blazar had been closer we likely would have seen it with HAWC,” the Higher Altitude Water Cherenkov gamma-ray observatory in central Mexico.

One in a million

Equipped with a nearly real-time alert system—triggered when a very high-energy neutrino collides with an atomic nucleus in the Antarctic ice in or near the IceCube detector—the observatory broadcast coordinates of the September 22 neutrino alert to telescopes worldwide for follow-up observations.

Two gamma-ray observatories, NASA’s orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov Telescope, or MAGIC, in the Canary Islands, detected a flare of high-energy gamma rays associated with TXS 0506+056, a convergence of observations that convincingly implicated the blazar as the most likely source.

Fermi was the first telescope to identify enhanced gamma-ray activity from TXS 0506+056 within 0.06 degrees of the IceCube neutrino direction. In a decade of Fermi observations of this source, this was the strongest flare in gamma rays. A later follow-up by MAGIC detected gamma rays of even higher energies.

colorful spheres on black - signals produced by a high-energy neutrino
This image shows signals produced by a high-energy neutrino detected by IceCube on September 22, 2017. With an estimated energy of 290 TeV, this was the tenth alert of this type sent by IceCube to the international astronomy community and launched a series of multi-messenger observations that allowed the identification of the first source of high-energy neutrinos and cosmic rays. (Credit: via Georgia Tech)

These observations prove that TXS 056+056 is one of the most luminous sources in the known universe and, thus, add support to a multimessenger observation of a cosmic engine powerful enough to accelerate high-energy cosmic rays and produce the associated neutrinos. Because neutrinos interact so weakly with matter, IceCube detected only one out of many millions that sailed through Antarctica’s ice on September 22.

Bolstering these observations are coincident measurements from other instruments, including optical, radio, and X-ray telescopes. “The ability to globally marshal telescopes to make a discovery using a variety of wavelengths in cooperation with a neutrino detector like IceCube marks a milestone in what scientists call multi-messenger astronomy,” says Halzen.

A mystery since 1912

Austrian physicist Victor Hess showed, in 1912, that ionizing particles detected in the atmosphere arrive from space. These cosmic rays are the highest energy particles ever observed, with energies up to a hundred million times the energies of particles in the Large Hadron Collider at CERN in Switzerland, the most powerful human-made particle accelerator.

These extremely high-energy cosmic rays can only be created outside our galaxy and their sources have remained a mystery until now. Scientists had speculated that the most violent objects in the cosmos, like the mysterious gamma ray bursts, colliding galaxies, and the energetic black hole cores of galaxies known as active galactic nuclei, such as blazars, could be the sources.

“Fermi has been monitoring some 2,000 blazars for a decade, which is how we were able to identify this blazar as the neutrino source,” says Regina Caputo, the analysis coordinator for the Fermi Large Area Telescope collaboration. “High-energy gamma rays can be produced either by accelerated electrons or protons. The observation of a neutrino, which is a hallmark of proton interactions, is the first definitive evidence of proton acceleration by black holes.”

“Now, we have identified at least one source of cosmic rays because it produces cosmic neutrinos. Neutrinos are the decay products of pions. In order to produce them, you need a proton accelerator,” says Halzen.

Neutrino experiments could rewrite Standard Model of Physics

Cosmic rays are mostly protons and are sent speeding across the universe because the places where they are created act in the same way as particle accelerators on Earth, only they are far more powerful. “Theories predict that the emission of neutrinos will be accompanied by the release of gamma rays,” explains Razmik Mirzoyan, the spokesperson of the MAGIC Collaboration. But there are still a lot of questions on how blazars could accelerate particles to the highest energies. “Gamma rays provide information on how the ‘power plants’ in supermassive black holes work,” adds Mirzoyan.

Neutrinos ‘hardly ever stop to interact’

As the latest astrophysical messenger to enter the game, neutrinos bring crucial new information to uncovering the inner workings of these cosmic ray accelerators. In particular, measurements of neutrinos can reveal the mechanisms for particle acceleration of the proton beam in the densest environments that even high-energy gamma rays may not escape.

“For the most part, neutrinos go through everything and hardly ever stop to interact.”

Following the September 22 detection, the IceCube team quickly scoured the detector’s archival data and discovered a flare of over a dozen astrophysical neutrinos detected in late 2014 and early 2015, coincident with the same blazar, TXS 0506+056. This independent observation greatly strengthens the initial detection of a single high-energy neutrino and adds to a growing body of data that indicates TXS 0506+056 is the first known accelerator of the highest energy neutrinos and cosmic rays.

Detecting high-entry astrophysical neutrinos—particles from outside our galaxy—is no easy task. These particles pass through the Earth as if it were glass and are only detectable when they interact with atomic protons and neutrons that are massive enough to stop them. “For the most part, neutrinos go through everything and hardly ever stop to interact,” says Taboada.

A team at the University of Wisconsin-Madison operates the IceCube Neutrino Observatory, which the National Science Foundation primarily funds.

About 20 observatories on Earth and in space have participated in the identification of what scientists deem to be a source of very high-energy neutrinos and, thus, of cosmic rays. Several follow-up observations are detailed in a few other papers that are also being published.

Source: Georgia Tech (adapted from the original release via IceCube)

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Spin dynamics suggest 2 exoplanets really are Earth-ish

Two exoplanets thought to be similar to Earth apparently are, at least when it comes to climate, research into spin dynamics shows.

Kepler-186f is the first identified Earth-sized planet outside the solar system orbiting a star in the habitable zone. This means it’s the proper distance from its host star for liquid water to pool on the surface.

The study, which appears in the Astronomical Journal, used simulations to analyze and identify the exoplanet’s spin axis dynamics. Those dynamics determine how much a planet tilts on its axis and how that tilt angle evolves over time. Axial tilt contributes to seasons and climate because it affects how sunlight strikes the planet’s surface.

Researchers suggest that Kepler-186f’s axial tilt is very stable, much like the Earth, making it likely that it has regular seasons and a stable climate. Further, they think the same is true for Kepler-62f, a super-Earth-sized planet orbiting around a star about 1,200 light-years away from us.

Unstable Mars

How important is axial tilt for climate? Large variability in axial tilt could be a key reason why Mars transformed from a watery landscape billions of years ago to today’s barren desert, the researchers say.

“Mars is in the habitable zone in our solar system, but its axial tilt has been very unstable—varying from zero to 60 degrees,” says Gongjie Li, assistant professor of physics at Georgia Institute of Technology, who led the study together with graduate student Yutong Shan from the Harvard-Smithsonian Center for Astrophysics. “That instability probably contributed to the decay of the Martian atmosphere and the evaporation of surface water.”

As a comparison, Earth’s axial tilt oscillates more mildly—between 22.1 and 24.5 degrees, going from one extreme to the other every 10,000 or so years.

The orientation angle of a planet’s orbit around its host star can be made to oscillate by gravitational interaction with other planets in the same system. If the orbit were to oscillate at the same speed as the precession of the planet’s spin axis (akin to the circular motion exhibited by the rotation axis of a top or gyroscope), the spin axis would also wobble back and forth, sometimes dramatically.

Mars and Earth interact strongly with each other, as well as with Mercury and Venus. As a result, by themselves, their spin axes would precess with the same rate as the orbital oscillation, which may cause large variations in their axial tilt.

What about moons?

Fortunately, the moon keeps Earth’s variations in check. The moon increases our planet’s spin axis precession rate and makes it differ from the orbital oscillation rate. Mars, on the other hand, doesn’t have a large enough satellite to stabilize its axial tilt.

“It appears that both exoplanets are very different from Mars and the Earth because they have a weaker connection with their sibling planets,” Li says. “We don’t know whether they possess moons, but our calculations show that even without satellites, the spin axes of Kepler-186f and 62f would have remained constant over tens of millions of years.”

Kepler-186f is less than 10 percent larger in radius than Earth, but its mass, composition, and density remain a mystery. It orbits its host star every 130 days.

According to NASA, the brightness of that star at high noon, while standing on 186f, would appear as bright as the sun just before sunset here on Earth. Kepler-186f is located in the constellation Cygnus as part of a five-planet star system.

Dust and starlight shape future exoplanet exploration

Kepler-62f was the most Earth-like exoplanet until scientists noticed 186f in 2014. It’s about 40 percent larger than our planet and is likely a terrestrial or ocean-covered world. It’s in the constellation Lyra and is the outermost planet among five exoplanets orbiting a single star.

That’s not to say either exoplanet has water, let alone life. But both are relatively good candidates. “Our study is among the first to investigate climate stability of exoplanets and adds to the growing understanding of these potentially habitable nearby worlds,” Li says.

Zippy exoplanet burns hotter than most stars

“I don’t think we understand enough about the origin of life to rule out the possibility of their presence on planets with irregular seasons,” Shan says. “Even on Earth, life is remarkably diverse and has shown incredible resilience in extraordinarily hostile environments.

“But a climatically stable planet might be a more comfortable place to start.”

Source: Georgia Tech

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Sodium-based batteries could be great alternative to lithium

New evidence suggests batteries based on sodium and potassium hold promise as a potential alternative to lithium-based batteries.

The growth in battery technology has led to concerns that the world’s supply of lithium, the metal at the heart of many of the new rechargeable batteries, may eventually be depleted.

“One of the biggest obstacles for sodium- and potassium-ion batteries has been that they tend to decay and degrade faster and hold less energy than alternatives,” says Matthew McDowell, an assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at Georgia Tech.

“But we’ve found that’s not always the case,” he adds.

For the study, which appears in the journal Joule, the research team looked at how three different ions—lithium, sodium, and potassium—reacted with particles of iron sulfide, also called pyrite and fool’s gold.

As batteries charge and discharge, ions are constantly reacting with and penetrating the particles that make up the battery electrode. This reaction process causes large volume changes in the electrode’s particles, often breaking them up into small pieces. Because sodium and potassium ions are larger than lithium, it’s traditionally been thought that they cause more significant degradation when reacting with particles.

In their experiments, the reactions that occur inside a battery were directly observed inside an electron microscope, with the iron sulfide particles playing the role of a battery electrode. The researchers found that iron sulfide was more stable during reaction with sodium and potassium than with lithium, indicating that such a battery based on sodium or potassium could have a much longer life than expected.

The difference between how the different ions reacted was stark visually. When exposed to lithium, iron sulfide particles appeared to almost explode under the electron microscope. On the contrary, the iron sulfide expanded like a balloon when exposed to the sodium and potassium.

“We saw a very robust reaction with no fracture—something that suggests that this material and other materials like it could be used in these novel batteries with greater stability over time,” says graduate student Matthew Boebinger.

The study also casts doubt on the notion that large volume changes that occur during the electrochemical reaction are always a precursor to particle fracture, which causes electrode failure leading to battery degradation.

The researchers suggest that one possible reason for the difference in how the different ions reacted with the iron sulfide is that the lithium was more likely to concentrate its reaction along the particle’s sharp cube-like edges, whereas the reaction with sodium and potassium was more diffuse along all of the surface of the iron sulfide particle.

As a result, the iron sulfide particle when reacting with sodium and potassium developed a more oval shape with rounded edges.

While there’s still more work to be done, the new research findings could help scientists design battery systems that use these types of novel materials.

Sugar cubes solve big problem with lithium metal batteries

“Lithium batteries are still the most attractive right now because they have the most energy density—you can pack a lot of energy in that space,” McDowell says.

“Sodium and potassium batteries at this point don’t have more density, but they are based on elements a thousand times more abundant in the earth’s crust than lithium. So they could be much cheaper in the future, which is important for large scale energy storage—backup power for homes or the energy grid of the future.”

The National Science Foundation and the US Department of Energy funded the research. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.

Source: Georgia Tech

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5 big questions about the science of ‘Star Wars’

As Star Wars: The Force Awakens cleaned up at the box office, researchers from Georgia Tech took a closer look at the science of the films. They answered five big questions about the worlds depicted in the movies and what’s possible in reality. We’re revisiting their responses to celebrate the release of the 2018 installment in the series, Solo: A Star Wars Story.

1. Is light speed even possible?

Han Solo isn’t a bashful hero. So it’s no surprise that it took him only a few moments after we first met him to brag that his Millennium Falcon was the “fastest ship in the galaxy.” But how fast is fast? Solo said his ship can go .5 past light speed.

Deirdre Shoemaker, associate professor in the Georgia Tech School of Physics, explains in this video how fast light speed really is, why it’s not fast enough, and what needs to happen for something to actually travel 186,000 miles per second:

2. Could these new worlds exist in our universe?

The Star Wars universe depicts a diverse set of worlds containing a variety of inhabitants. John Wise, assistant professor in the School of Physics, studies early galaxies and distant objects in the universe. He wonders if there are planets somewhere out there that resemble the ones imagined by George Lucas:

“Until 1991, the only planets known to humans were in our Solar System. In that same year, astronomers discovered the first extrasolar planet, now dubbed as exoplanets, by measuring the Doppler shift of stellar spectral lines, effectively witnessing the planet play gravitational tug-of-war with its parent star as it orbits. Over the next decade or so, astronomers refined their planet hunting skills and found more than 30 exoplanets.

“Imagine how many planets are littered among the 100 billion galaxies in the observable universe. Perhaps planets from a long time ago in a galaxy far, far away?”

“This all changed with the launch of NASA’s Kepler Mission, which continually monitored a patch of sky for brightness variations in 150,000 stars. Any dip in brightness can be caused by a planet passing in front of its star, blocking a small fraction of its light. In its four-year run, Kepler detected and confirmed nearly 2,000 planetary systems, ranging from “Hot Jupiters” to frozen, rocky worlds. Intriguingly, a select few lie within the Goldilocks zone where liquid water could exist because the planet isn’t too hot or too cold.

“This planetary diversity is also seen in Star Wars—Endor, the home of the Ewoks, that orbits a gaseous giant planet; Hoth, where Luke Skywalker almost froze to death; Alderaan, a blue-green orb not unlike our Earth until it was destroyed by the Death Star; and Tatooine, Luke and Anakin Skywalker’s home planet. One of the most vivid scenes of Episode IV happens when Luke gazes toward the horizon at a binary sunset. When the original was released in 1977, such a scene was restricted to the sci-fi realm, but this is no longer the case. Kepler has now discovered 10 planets that orbit binary star systems, whose possible inhabitants see a similar sight every day.

“The Kepler Mission was just the first step in humankind’s discovery of planetary systems in the Milky Way. It only observed 1/400th of the sky. It could only detect planets out to 3,000 light years, which is tiny compared to the Milky Way’s size of 100,000 light years. Using Kepler’s detections, astronomers have estimated that there could be as many as 40 billion planets in our galaxy. But that is only one galaxy! Imagine how many planets are littered among the 100 billion galaxies in the observable universe. Perhaps planets from a long time ago in a galaxy far, far away?”

r2-d2 and c3po watch sunset
(Credit: Michael Li/Flickr)

3. Are C-3PO and R2-D2 coming soon?

Even though C-3PO and R2-D2 lived (in a galaxy) a long time ago, today’s roboticists still haven’t found a way to create their current-day cousins. The College of Computing’s Sonia Chernova is one of many on campus trying to bring robots out of the lab and into the world so that people can have their own droids. She says:

“Robots tend to be on one extreme or the other these days. One kind is found on Mars, battlefields, and in operating rooms. These robots are extensions of humans—they’re rarely autonomous because a human is always in the loop.

“As for R2-D2 and his friends, we’re not that far from personal robots.”

“Others are autonomous. We see this mostly on manufacturing floors, where machines are programmed to do the same repetitive task with extreme precision. Not only are they limited by what they can do, but they’re also often separated from people for safety reasons.

“I’m focused on something in the middle. Full autonomy for personal robots would be great, but it’s not yet practical given today’s technology. Humans are too unpredictable and environments are ever changing. Rather than setting 100 percent autonomy as the goal for getting robots into our lives, we should deploy them when they’re simply “good enough.” Once they’re with us, they can learn the rest.

“Here’s an example: in hospitals, a delivery robot could pass out towels and medication. If it were to get stuck leaving a room, the machine could call a command center where a human technician would figure out the problem and free the robot. Here’s the key: every time a person made a fix, the robot would keep that new information and use it to perform differently the next time it leaves the room. With humans in the mix, this robot could learn from its mistakes and continually push toward 100 percent autonomy.

“As for R2-D2 and his friends, we’re not that far from personal robots. I don’t think we’ll have to clean our houses in 20 years because we’ll have robot helpers. I’m not sure what they’ll cost or if people will psychologically be ready to give up that part of their lives, but we’ll have the software and hardware in place to make it happen.

4. What would it be like to master the Force?

Imagine lifting a spaceship with the tip of your finger like Yoda in The Empire Strikes Back. Nepomuk Otte of the School of Physics says there are a few things you might want to consider: 

“Didn’t we learn from physics classes about Newton’s third law? For every action, there is an equal and opposite reaction. If true, it would mean that when Yoda exerts a force on the X-wing, Luke Skywalker’s spaceship should also exert the same amount of force on Yoda. So why doesn’t the little fella get squished like a mosquito?

“Violating action and reaction would shatter one of the most sacred laws in physics—momentum conservation. But Yoda moves the spacecraft with ease and shuffles away unscathed. The Jedi Master must be surrounded by some sort of shield that absorbs the reaction part of the force. When you attempt to use the Force, make sure you have one of those shields, too, or you might suffer the consequences.”

5. Can the Force be a new interaction that we haven’t discovered yet?

Flavio Fenton of the School of Physics responds—and offers a few questions of his own:

“When the Death Star’s superlaser destroyed Princess Leia’s home planet of Alderaan, Obi-Wan Kenobi delivered one of the saga’s most famous quotes: ‘I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror and were suddenly silenced. I fear something terrible has happened.’

“…if we were to study the Force from a subatomic level, we should consider that, like any other interaction we know in nature, there exist force carriers.”

“The death of the entire planet sent shock waves through the Force, weakening those who were able to feel them. That included Obi-Wan, who briefly became faint. This action at a distance is explained in physics by what is called a field. For example, we are well aware of gravitational and electromagnetic fields. Objects that are affected by a field carry “something” that allows them to interact. For gravity, it is mass. For electricity, it is charge.

“Because there is a Light and a Dark Side of the Force, a field would require that we assume two types of charges, similar to positive and negative charges in the electromagnetic force. Here’s an example: Darth Vader can strangle people by using the Force without physical contact. That means his victims would have to carry both types of charges in equal amounts, and the effects of the two types cancel each other. How does it happen?

“One explanation is that the dark force Vader unleashes attracts the light charge of his victim, leaving the person unbalanced with an excess of dark charge. In this case, all the dark charges then try to come together along the neck, squeezing and nearly choking the person to death. This means that unlike electric charge, particles with equal force charges attract and repel when they have different charges. This could explain why a neutral force charge is common to all objects. It could also explain why the Dark Side has an addictive aspect: when a Jedi turns to the Dark Side, it’s a slippery slope filled with continuous evil.

“Going just a bit deeper for my fellow physics fanatics—if we were to study the Force from a subatomic level, we should consider that, like any other interaction we know in nature, there exist force carriers. These are particles that give rise to forces between other particles. For example, the electromagnetic force between two electrons can be explained by the exchange of virtual photons and gravitation by the exchange of virtual gravitons. Therefore the two Force charges should have a carrier. Should we call them Jedi-nos? Should the Large Hadron Collider search for these new particles now that it has found the Higgs particle?”

Source: Georgia Tech (Originally published December 30, 2015)

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Just how gross are airplane cabins really?

The bacterial communities accompanying airline passengers at 30,000 feet have a lot in common with the bacterial communities surrounding people in their homes and offices, according to a new study.

“Airline passengers should not be frightened by sensational stories about germs on a plane…”

Using advanced sequencing technology, researchers studied the bacteria found on three components of an airliner cabin that are commonly touched by passengers: tray tables, seat belt buckles, and the handles of lavatory doors. They swabbed those items before and after ten transcontinental flights and also sampled air in the rear of the cabin during flight.

What they found was surprisingly unexciting.

“Airline passengers should not be frightened by sensational stories about germs on a plane,” says Vicki Stover Hertzberg, a professor in Emory University’s Nell Hodgson Woodruff School of Nursing and a coauthor of the study in Microbial Ecology. “They should recognize that microbes are everywhere and that an airplane is no better and no worse than an office building, a subway car, home, or a classroom. These environments all have microbiomes that look like places occupied by people.”

Given the unusual nature of an aircraft cabin, the researchers hadn’t known what to expect from their microbiome study. On transcontinental flights, passengers spend four or five hours in close proximity breathing a very dry mix of outdoor air and recycled cabin air that passes through special filters, similar to those found in operating rooms.

“There were reasons to believe that the communities of bacteria in an aircraft cabin might be different from those in other parts of the built environment, so it surprised me that what we found was very similar to what other researchers have found in homes and offices,” says Howard Weiss, a professor in Georgia Institute of Technology’s School of Mathematics and the study’s corresponding author. “What we found was bacterial communities that were mostly derived from human skin, the human mouth—and some environmental bacteria.”

The sampling found significant variations from flight to flight, which is consistent with the differences other researchers have found among the cars of passenger trains, Weiss notes. Each aircraft seemed to have its own microbiome, but the researchers did not detect statistically significant differences between preflight and post-flight conditions on the flights they studied.

“I carry a bottle of hand sanitizer in my computer bag whenever I travel…”

“We identified a core airplane microbiome—the genera that were present in every sample we studied,” Weiss adds. The core microbiome included genera Propionibacterium, Burkholderia, Staphylococcus, and Strepococcus (oralis).

Though the study revealed bacteria common to other parts of the built environment, Weiss still suggests travelers exercise reasonable caution.

“I carry a bottle of hand sanitizer in my computer bag whenever I travel,” says Weiss. “It’s a good practice to wash or sanitize your hands, avoid touching your face, and get a flu shot every year.”

This new information on the aircraft microbiome provides a baseline for further study, and could lead to improved techniques for maintaining healthy aircraft.

“The finding that airplanes have their own unique microbiome should not be totally surprising since we have been exploring the unique microbiome of everything from humans to spacecraft to salt ponds in Australia. The study does have important implications for industrial cleaning and sterilization standards for airplanes,” says Christopher Dupont, another coauthor and an associate professor in the microbial and environmental genomics department at the J. Craig Venter Institute, which provided bioinformatics analysis of the study’s data.

The 229 samples researchers obtained from the aircraft cabin testing were subjected to 16S rRNA sequencing, which was done at the HudsonAlpha Institute for Biotechnology in Huntsville, Alabama. The small amount of genetic material captured on the swabs and air sampling limited the level of detail the testing could provide to identifying genera of bacteria, Weiss says.

In March, in the journal Proceedings of the National Academy of Sciences, the researchers reported on the results of another component of the FlyHealthy study that looked at potential transmission of respiratory viruses on aircraft. They found that an infectious passenger with influenza or other droplet-transmitted respiratory infection will most likely not transmit infection to passengers seated farther away than two seats laterally and one row in front or back on an aircraft.

Here’s whose germs can infect you on a plane

That portion of the study was designed to assess rates and routes of possible infectious disease transmission during flights, using a model that combines estimated infectivity and patterns of contact among aircraft passengers and crew members to determine likelihood of infection. FlyHealthy team members monitored specific areas of the passenger cabin, developing information about contacts between passengers as they moved around.

Among next steps, the researchers would like to study the microbiome of airport areas, especially the departure lounges where passengers congregate before boarding. They would also like to study long-haul international flights in which passengers spend more time together—and are more likely to move about the cabin.

Additional coatuhors are from the HudsonAlpha Institute for Biotechnology and the Boeing Company. A contract between the Georgia Institute of Technology and the Boeing Company supported the work.

Source: Georgia Tech

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Why ‘2001: A Space Odyssey’ still matters in 2018

2001: A Space Odyssey (1968) is arguably the world’s most influential science fiction film. Stanley Kubrick’s space epic inspired a generation of filmmakers, including George Lucas, Steven Spielberg, and Christopher Nolan, who likened his film Interstellar (2015) to 2001.

Fifty years after its initial release, the film is getting renewed attention, including the debut of a new 70mm print at the Cannes Film Festival and a limited theatrical release beginning May 18.

Jay Telotte, professor of film studies in the School of Literature, Media, and Communication at Georgia Tech, explains why the legacy of the film endures:

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