Physics and Physical Sciences

Stitched for Strength: The Physics of Stiff, Knitted Fabrics

admin — Wed, 30 Jul 2025 12:39:36 +0000

Stitched for Strength: The Physics of Stiff, Knitted Fabrics admin Wed, 07/30/2025 - 08:39

School of Physics Associate Professor Elisabetta Matsumoto is unearthing the secrets of the centuries-old practice of knitting through experiments, models, and simulations. Her goal? Leveraging knitting for breakthroughs in advanced manufacturing — including more sustainable textiles, wearable electronics, and soft robotics.

Matsumoto, who is also a principal investigator at the International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2) at Hiroshima University, is the corresponding author on a new study exploring the physics of ‘jamming’ — a phenomenon when soft or stretchy materials become rigid under low stress but soften under higher tension.

The study, "Pulling Apart the Mechanisms That Lead to Jammed Knitted Fabrics," was published this week in Physical Review E, and also includes Georgia Tech Matsumoto Group graduate students Sarah Gonzalez and Alexander Cachine in addition to former postdoctoral fellow Michael Dimitriyev, who is now an assistant professor at Texas A&M University.

The work builds on the group’s previous research demonstrating that knitted materials can be mathematically ‘programmed’ to behave in predictable ways. “These properties are intuitively understood by people who knit by hand,” Matsumoto says, “but in order to manipulate and use these behaviors in an industrial setting, we need to understand the physics behind them. This new research is another step in that direction.”

An Unexpected Twist

Gonzalez, who led the research, first became interested in jamming while conducting adjacent research. “I was using model simulations to characterize how different yarn properties affect the behavior of knitted fabrics and noticed a strange stiff region,” she recalls. “In our previous research, we had also seen this behavior in lab experiments, which suggested that what we were seeing in the simulations was a genuine phenomenon. I wanted to investigate it further.”

After digging into the topic, she realized that what she was seeing was called ‘jamming.’ In knits, Gonzalez explains, jamming occurs when stitches are packed tightly together, and the fabric resists stretching. Although it’s a well-known phenomenon, the physics has mostly been investigated in granular systems, like snow or sand, rather than fabrics.

“In fabrics, when you pull softly, the response is surprisingly stiff, but when you start pulling harder and harder, the stitches rearrange, and the material softens,” Matsumoto says. “In granular systems, this is a little like how avalanches work. At low forces, the snow pack is solid, but when the slope is steep, the force of gravity liquidizes that snow pack into an avalanche.”

“In fabrics, it is a little like having a tangle in a piece of jewelry,” she adds. “If you pull on it, it gets quite stiff, but if you loosen the knot, the chain can reconfigure, and it's not so stiff.”

Unraveling the Physics of Jamming

Using a combination of experiments with industrially knitted fabrics and computer models, the team analyzed what causes jamming in fabrics and how to control it. “We wanted to determine how different yarn properties impacted jamming,” Gonzalez explains. “Our goal was to understand the mechanics of jamming through how yarn interacts at various touchpoints in stitches.”

The team found that both machine tension and yarn thickness played a key role in making a fabric more or less jammed, and that jamming behaves differently depending on which direction the fabric is stretched.

“When you stretch a knit along the rows, the stiffness of the yarn causes fabric jamming. Jamming in the other direction is due to yarn contacts,” says Gonzalez. “We also showed that the impacts of changing machine tension and yarn thickness differ depending on fabric direction.”

“Discovering that fabric jamming works differently in different directions was a key insight,” she adds. “To our knowledge, the physics of this has never been explored before.”

Modern Innovation — With a Centuries-Old Technique

The research dovetails with Matsumoto’s WPI-SKCM2 Center work, which involves investigating fundamental aspects of knots and chirality. The Center is interested in a class of materials called “knotted chiral meta matter” that could lead to more sustainable materials.

For example, knitting — which leverages chiral knots — could be used to create more elastic fabrics from natural materials. “In many cases, manufacturers use yarns that combine, for example, polyester, cotton, and elastane to create a desired elasticity,” Matsumoto says. “Our research suggests that manipulating the topology of the stitches could lead to a similar elasticity, reducing the need for petroleum-based fibers and creating a more sustainable textile.”

“Knitting has the potential to be extremely useful in manufacturing, but knowledge has typically been shared through intuition and word of mouth,” she adds. “By creating these mathematical models, we hope to formalize that knowledge in a way that’s accessible for large-scale manufacturing — so we can leverage this centuries-old intuition for modern innovation.”

Funding: This work was supported by the World Premier International Research Center Initiative (WPI), Ministry of Education, Culture, Sports, Science and Technology of Japan; National Science Foundation (NSF); and Research Corporation for Science Advancement (RCSA).

DOI: https://doi.org/10.1103/g94g-c6tt

Summary sentence

Physicists unravel the secrets of the centuries-old practice of knitting in a new study that explores the physics of ‘jamming’ — a phenomenon when soft or stretchy materials become rigid under low stress but soften under higher tension.

Summary

Researchers in the School of Physics unravel the secrets of the centuries-old practice of knitting in a new study that explores the physics of ‘jamming’ — a phenomenon when soft or stretchy materials become rigid under low stress but soften under higher tension.

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Fri, 07/25/2025 - 12:00

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Wed, 07/30/2025 - 08:38

LIGO Detects Most Massive Binary Black Hole to Date

admin — Wed, 16 Jul 2025 18:35:41 +0000

LIGO Detects Most Massive Binary Black Hole to Date admin Wed, 07/16/2025 - 14:35

The Laser Interferometer Gravitational-Wave Observatory (LIGO)’s LIGO-Virgo-KAGRA (LVK) collaboration has detected an extremely unusual binary black hole merger — a phenomenon that occurs when two black holes are pulled into each other's orbit and combine. Announced yesterday in a California Institute of Technology press release, the binary black hole merger, GW231123, is the largest ever detected with gravitational waves.

Before merging, both black holes were spinning exceptionally fast, and their masses fell into a range that should be very rare — or impossible.

“Most models don't predict black holes this big can be made by supernovas, and our data indicates that they were spinning at a rate close to the limit of what’s theoretically possible,” says Margaret Millhouse, a research scientist in the School of Physics who played a key role in the research. “Where could they have come from? It raises interesting questions.”

A binary black hole merger absorbs characteristics from both of the contributors, she adds. “As a result, this is not only the most massive binary black hole ever seen but also the fastest-spinning binary black hole confidently detected with gravitational waves.”

“GW231123 is a record-breaking event,” says School of Physics Professor Laura Cadonati, who has been a member of the LIGO Scientific Collaboration since 2002. “LIGO has been observing the cosmos for 10 years now. This discovery underscores that there is still so much that this instrument can help us learn.”

A Cosmic View

The findings challenge current theories on how smaller black holes form, says School of Physics Assistant Professor and LIGO collaborator Surabhi Sachdev. Smaller black holes are the result of supernovae: dying and collapsing stars. During that collapse, explosions can tear apart or eject part of the star’s mass — limiting the size of the black hole that forms.

“Black holes from supernovae can weigh up to about 60 times the mass of our Sun,” she says. “The black holes in this merger were likely the mass of hundreds of suns.”

Because of its size, GW231123 also allowed the team to study the merger in unprecedented detail. “LIGO has observed scores of black hole mergers,” says Cadonati. “Of these, GW231123 has provided us with the clearest view of the ‘grand finale’ of a merger thus far. This adds a new clue to solve the puzzle that are black holes, including their origins and properties.”

“While we saw that our expectations matched the data, the extreme nature of this event pushed our models to their limits,” Millhouse adds. “A massive, highly spinning system like this will be of interest to researchers who study how binary black holes form.”

Decoding a Split-Second Signal

Millhouse and School of Physics Postdoctoral Fellow Prathamesh Joshi used Einstein’s equations for general relativity to confirm LIGO’s detections.

To find black holes, LIGO measures distortions in spacetime — ripples that are created when two black holes collide. These patterns in gravitational waves can be used to find the signature signal of black hole collisions.

“In this case, the signal lasted for just one-tenth of a second, but it was very clear,” says Joshi. "Previously, we designed a special study to detect these interesting signals, which accounted for all the unusual properties of such massive systems — and it paid off!”

“To ensure it wasn’t noise, the Georgia Tech team first reconstructed the signal in a model-agnostic way,” Millhouse adds. “We then compared those reconstructions to a model that uses Einstein's equations of general relativity, and both reconstructions looked very similar, which helped confirm that this highly unusual phenomenon was a genuine detection.”

Sachdev says that seeing the signal at both LIGO Observatories — placed in Hanford, Washington and Livingston, Louisiana — was also critical. “These short signals are very hard to detect, and this signal is so unlike any of the other binary black holes that we've seen before,” she says. “Without both detectors, we would have missed it.”

A Decade of Discovery

While the team has yet to determine how the original black holes formed, one theory is that they may have resulted from mergers themselves. “This could have been a chain of mergers,” Sachdev explains. “This tells us that they could have existed in a very dense environment like a nuclear star cluster or an active galactic nucleus.” Their spins provide another clue as spinning is a characteristic usually seen in black holes resulting from a merge.

The team adds that GW231123 could provide clues on how larger black holes are formed — including the mysterious supermassive black holes at the center of galaxies.

“Gravitational wave science is almost a decade old, and we're still making fundamental discoveries,” says Millhouse. “It’s exciting that LIGO is continuing to detect new phenomena, and this is at the edge of what we've seen thus far. There's still so much we can learn.”

The team expects to update their catalogue of black holes in August 2025, which will provide another window into how this exceptionally heavy black hole might fit into the universe, and what we can continue to learn from it.

Funding: The LIGO Laboratory is supported by the U.S. National Science Foundation and operated jointly by Caltech and MIT.

Summary sentence

Before merging, both black holes were spinning exceptionally fast, and their masses fell into a range that should be very rare — or impossible.

Summary

Before merging, both black holes were spinning exceptionally fast, and their masses fell into a range that should be very rare — or impossible. The result of the merge, GW231123, is the largest binary black hole merger ever detected with gravitational waves.

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Tue, 07/15/2025 - 12:00

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Wed, 07/16/2025 - 14:35

Georgia Tech to Strengthen Nation’s Faculty Development in Geospace Science

admin — Tue, 20 May 2025 16:30:33 +0000

Georgia Tech to Strengthen Nation’s Faculty Development in Geospace Science admin Tue, 05/20/2025 - 12:30

Georgia Tech’s Colleges of Engineering and Sciences have been chosen by the National Science Foundation (NSF) to hire a new faculty member focused on solar-terrestrial science and space weather research. The NSF is prioritizing a national need in geospace physics and selected Georgia Tech from a pool of national universities.

“Space weather has many societal implications, including dangers to the power grid, the aviation sector, satellite lifetimes, communications, and navigation,” said Morris Cohen, professor in the School of Electrical and Computer Engineering (ECE) and the grant’s co-principal investigator. “However, the number of qualified graduating students interested in this area is not sufficient to meet the future demand. This is especially true as the generation of professionals trained during the space race of the 1960s and ‘70s continues to retire.”

NSF will fund the position for five years and $1.5 million. The grant is led by Susan Lozier, dean of the College of Sciences and Betsy Middleton and John Clark Sutherland Chair. She and Cohen are joined by Raheem Beyah, dean of the College of Engineering and Southern Company Chair, and Glenn Lightsey, the John W. Young Chair in the Guggenheim School of Aerospace Engineering (AE).

The two Colleges relied heavily on their strength in space research and Georgia Tech’s culture of multidisciplinary collaborations in the NSF application. These traits will allow Georgia Tech to conduct a unique search process. Instead of one unit making the hire as is typical in higher education, leaders from four schools will team up with the Georgia Tech Research Institute (GTRI) for the search process. It’s an approach that addresses a nationwide problem in the field.

“Decades ago, space physics largely fell within electrical engineering,” Beyah said. “These days, it’s highly interdisciplinary and typically has no true home — faculty are often scattered across aerospace engineering, applied physics, and earth sciences.”

Beyah said that a few universities have a large cluster of space physics faculty as a result. Many others have none. He said this limits the pipeline of future space science professionals because a substantial fraction of students has little or no exposure to the field.

Georgia Tech is right in the middle, with a presence in solar-terrestrial science and space weather research but not a large cluster of faculty members. The new hire will allow Tech to reach more students interested in the field. Georgia Tech also pointed to its Vertically Integrated Projects program as a mechanism to get many new students involved in the new hire’s research.

According to Lozier, solar-terrestrial science and space weather encompass at least four buckets: advanced theory and simulations that span the extremes of physics; big data and machine learning; innovative tools to collect new types of measurements; and operational needs in industry and defense, which motivate translation of research into real-world practice.

“This breadth has hampered faculty growth in this area, as it has other interdisciplinary research fields like quantum computing and neuroscience,” Lozier said. “These areas straddle pure science and engineering, which often are separate in university hierarchy. We believe these interdisciplinary aspects of geospace science should be celebrated. More importantly, we believe they can be turned into a strength.”

Representatives from AE, ECE, GTRI, the School of Earth and Atmospheric Sciences, and the School of Physics will form the hiring committee. The hire will complement Georgia Tech’s February announcement of a new Space Research Initiative. Once the NSF-funded position is filled, the Colleges will collectively fund and search for a second faculty member in the field.

Subtitle

With NSF support, Colleges of Sciences and Engineering will collaborate to hire a researcher focused on solar-terrestrial science and space weather.

Summary sentence

With NSF support, Colleges of Sciences and Engineering will collaborate to hire a researcher focused on solar-terrestrial science and space weather.

Summary

With NSF support, Colleges of Sciences and Engineering will collaborate to hire a researcher focused on solar-terrestrial science and space weather.

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Wed, 05/22/2024 - 12:00

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Fri, 05/24/2024 - 15:24

Thesis on Human-Centered AI Earns Honors from International Computing Organization

dgivens8 — Tue, 22 Apr 2025 14:30:41 +0000

Thesis on Human-Centered AI Earns Honors from International Computing Organization dgivens8 Tue, 04/22/2025 - 10:30

A Georgia Tech alum’s dissertation introduced ways to make artificial intelligence (AI) more accessible, interpretable, and accountable. Although it’s been a year since his doctoral defense, Zijie (Jay) Wang’s (Ph.D. ML-CSE 2024) work continues to resonate with researchers.

Wang is a recipient of the 2025 Outstanding Dissertation Award from the Association for Computing Machinery Special Interest Group on Computer-Human Interaction (ACM SIGCHI). The award recognizes Wang for his lifelong work on democratizing human-centered AI.

“Throughout my Ph.D. and industry internships, I observed a gap in existing research: there is a strong need for practical tools for applying human-centered approaches when designing AI systems,” said Wang, now a safety researcher at OpenAI.

“My work not only helps people understand AI and guide its behavior but also provides user-friendly tools that fit into existing workflows.”

Wang’s dissertation presented techniques in visual explanation and interactive guidance to align AI models with user knowledge and values. The work culminated from years of research, fellowship support, and internships.

Wang’s most influential projects formed the core of his dissertation. These included:

CNN Explainer: an open-source tool developed for deep-learning beginners. Since its release in July 2020, more than 436,000 global visitors have used the tool.
DiffusionDB: a first-of-its-kind large-scale dataset that lays a foundation to help people better understand generative AI. This work could lead to new research in detecting deepfakes and designing human-AI interaction tools to help people more easily use these models.
GAM Changer: an interface that empowers users in healthcare, finance, or other domains to edit ML models to include knowledge and values specific to their domain, which improves reliability.
GAM Coach: an interactive ML tool that could help people who have been rejected for a loan by automatically letting an applicant know what is needed for them to receive loan approval.
Farsight: a tool that alerts developers when they write prompts in large language models that could be harmful and misused.

“I feel extremely honored and lucky to receive this award, and I am deeply grateful to many who have supported me along the way, including Polo, mentors, collaborators, and friends,” said Wang, who was advised by School of Computational Science and Engineering (CSE) Professor Polo Chau.

“This recognition also inspired me to continue striving to design and develop easy-to-use tools that help everyone to easily interact with AI systems.”

Like Wang, Chau advised Georgia Tech alumnus Fred Hohman (Ph.D. CSE 2020). Hohman won the ACM SIGCHI Outstanding Dissertation Award in 2022.

Chau’s group synthesizes machine learning (ML) and visualization techniques into scalable, interactive, and trustworthy tools. These tools increase understanding and interaction with large-scale data and ML models.

Chau is the associate director of corporate relations for the Machine Learning Center at Georgia Tech. Wang called the School of CSE his home unit while a student in the ML program under Chau.

Wang is one of five recipients of this year’s award to be presented at the 2025 Conference on Human Factors in Computing Systems (CHI 2025). The conference occurs April 25-May 1 in Yokohama, Japan.

SIGCHI is the world’s largest association of human-computer interaction professionals and practitioners. The group sponsors or co-sponsors 26 conferences, including CHI.

Wang’s outstanding dissertation award is the latest recognition of a career decorated with achievement.

Months after graduating from Georgia Tech, Forbes named Wang to its 30 Under 30 in Science for 2025 for his dissertation. Wang was one of 15 Yellow Jackets included in nine different 30 Under 30 lists and the only Georgia Tech-affiliated individual on the 30 Under 30 in Science list.

While a Georgia Tech student, Wang earned recognition from big names in business and technology. He received the Apple Scholars in AI/ML Ph.D. Fellowship in 2023 and was in the 2022 cohort of the J.P. Morgan AI Ph.D. Fellowships Program.

Along with the CHI award, Wang’s dissertation earned him awards this year at banquets across campus. The Georgia Tech chapter of Sigma Xi presented Wang with the Best Ph.D. Thesis Award. He also received the College of Computing’s Outstanding Dissertation Award.

“Georgia Tech attracts many great minds, and I’m glad that some, like Jay, chose to join our group,” Chau said. “It has been a joy to work alongside them and witness the many wonderful things they have accomplished, and with many more to come in their careers.”

Summary sentence

Zijie (Jay) Wang (Ph.D. ML-CSE 2024) is a recipient of the 2025 Outstanding Dissertation Award from the Association for Computing Machinery Special Interest Group on Computer-Human Interaction (ACM SIGCHI).

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At the Intersection of Climate and AI, Machine Learning is Revolutionizing Climate Science

admin — Fri, 24 Jan 2025 15:47:51 +0000

At the Intersection of Climate and AI, Machine Learning is Revolutionizing Climate Science admin Fri, 01/24/2025 - 10:47

Exponential growth in big data and computing power is transforming climate science, where machine learning is playing a critical role in mapping the physics of our changing climate.

“What is happening within the field is revolutionary,” says School of Earth and Atmospheric Sciences Associate Chair and Professor Annalisa Bracco, adding that because many climate-related processes — from ocean currents to melting glaciers and weather patterns — can be described with physical equations, these advancements have the potential to help us understand and predict climate in critically important ways.

Bracco is the lead author of a new review paper providing a comprehensive look at the intersection of AI and climate physics.

The result of an international collaboration between Georgia Tech’s Bracco, Julien Brajard (Nansen Environmental and Remote Sensing Center), Henk A. Dijkstra (Utrecht University), Pedram Hassanzadeh (University of Chicago), Christian Lessig (European Centre for Medium-Range Weather Forecasts), and Claire Monteleoni (University of Colorado Boulder), the paper, ‘Machine learning for the physics of climate,’ was recently published in Nature Reviews Physics.

“One of our team’s goals was to help people think deeply on how climate science and AI intersect,” Bracco shares. “Machine learning is allowing us to study the physics of climate in a way that was previously impossible. Coupled with increasing amounts of data and observations, we can now investigate climate at scales and resolutions we’ve never been able to before.”

Connecting hidden dots

The team showed that ML is driving change in three key areas: accounting for missing observational data, creating more robust climate models, and enhancing predictions, especially in weather forecasting. However, the research also underscores the limits of AI — and how researchers can work to fill those gaps.

“Machine learning has been fantastic in allowing us to expand the time and the spatial scales for which we have measurements,” says Bracco, explaining that ML could help fill in missing data points — creating a more robust record for researchers to reference. However, like patching a hole in a shirt, this works best when the rest of the material is intact.

“Machine learning can extrapolate from past conditions when observations are abundant, but it can’t yet predict future trends or collect the data we need,” Bracco adds. “To keep advancing, we need scientists who can determine what data we need, collect that data, and solve problems.”

Modeling climate, predicting weather

Machine learning is often used when improving climate models that can simulate changing systems like our atmosphere, oceans, land, biochemistry, and ice. “These models are limited because of our computing power, and are run on a three-dimensional grid,” Bracco explains: below the grid resolution, researchers need to approximate complex physics with simpler equations that computers can solve quickly, a process called ‘parameterization’.

Machine learning is changing that, offering new ways to improve parameterizations, she says. “We can run a model at extremely high resolutions for a short time, so that we don’t need to parameterize as many physical processes — using machine learning to derive the equations that best approximate what is happening at small scales,” she explains. “Then we can use those equations in a coarser model that we can run for hundreds of years.”

While a full climate model based solely on machine learning may remain out of reach, the team found that ML is advancing our ability to accurately predict weather systems and some climate phenomena like El Niño.

Previously, weather prediction was based on knowing the starting conditions — like temperature, humidity, and barometric pressure — and running a model based on physics equations to predict what might happen next. Now, machine learning is giving researchers the opportunity to learn from the past. “We can use information on what has happened when there were similar starting conditions in previous situations to predict the future without solving the underlying governing equations,” Bracco says. “And all while using orders-of-magnitude less computing resources.”

The human connection

Bracco emphasizes that while AI and ML play a critical role in accelerating research, humans are at the core of progress. “I think the in-person collaboration that led to this paper is, in itself, a testament to the importance of human interaction,” she says, recalling that the research was the result of a workshop organized at the Kavli Institute for Theoretical Physics — one of the team’s first in-person discussions after the Covid-19 pandemic.

“Machine learning is a fantastic tool — but it's not the solution to everything,” she adds. “There is also a real need for human researchers collecting high-quality data, and for interdisciplinary collaboration across fields. I see this as a big challenge, but a great opportunity for computer scientists and physicists, mathematicians, biologists, and chemists to work together.”

Funding: National Science Foundation, European Research Council, Office of Naval Research, US Department of Energy, European Space Agency, Choose France Chair in AI.

DOI: https://doi.org/10.1038/s42254-024-00776-3

Summary sentence

A Georgia Tech-led review paper recently published in Nature Reviews Physics is exploring the ways machine learning is revolutionizing the field of climate physics — and the role human scientists might play.

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A Georgia Tech-led review paper recently published in Nature Reviews Physics is exploring the ways machine learning is revolutionizing the field of climate physics — and the role human scientists might play.

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Wed, 01/22/2025 - 12:00

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Fri, 01/24/2025 - 10:47

How the Paris Olympic Track Is Designed to Break Records

admin — Fri, 19 Jul 2024 17:45:41 +0000

How the Paris Olympic Track Is Designed to Break Records admin Fri, 07/19/2024 - 13:45

Every millisecond will matter when the world's best athletes gather in Paris for the Summer Olympics, and track and field athletes will compete on a surface designed to produce record-breaking performances.

Mondo athletic tracks have been underneath the feet of Olympians since 1972. In that time, 300 records were broken on surfaces designed and constructed in Alba, Italy, including 15 at the Centennial Olympic Games in Atlanta.

Consistency Is Key

Georgia Tech’s George C. Griffin Track and Field Facility was outfitted with a Mondo track before the 1996 Games to serve as the workout track for the Olympic Village, and the material has been a staple at the facility ever since. Yellow Jacket Track and Field Coach Grover Hinsdale, a coach to three Olympic gold medalists, explains that the consistency in Mondo's construction sets it apart from all other tracks.

"A Mondo track is made in a climate-controlled factory, processed from the raw rubber to the finished product. So, every square inch of Mondo is the same — same durometer, same thickness, everything is the same. All other rubberized track surfaces are poured on-site, so variables like temperature and humidity affect the result, and you may end up with lanes that don't set uniformly,” he said.

Hinsdale likened the installation process to laying carpet. It will take more than 2,800 glue pots to set the 13,000 square meters of track inside Stade de France. Jud Ready, a principal research engineer in the School of Materials Science and Engineering, says the evolution of the company’s technology has also contributed to producing faster tracks.

"They're able to alter the rubber track's energy return mechanism by changing the shape of the particulate and the compressibility of it," Ready said. "Longevity is less of a concern for the Paris track, so they can tune it to emphasize speed."

Maximizing Performance

Each layer of the track surface plays a different role in helping athletes achieve peak performance. Hinsdale describes how those layers come together with each step.

"When your foot strikes down on an asphalt surface or you're running down a sidewalk, there's virtually no give other than what's taking place in the muscles and joints of your body. The surface is giving nothing back. When your foot strikes a Mondo surface, it'll sink in slightly, and the surface gives energy back. This pushes your foot back off that track quicker, putting the foot back into the cycle to complete another stride,” he said.

Because of the energy given back by the thin and firm surface of the Mondo track, Hinsdale says, sprinters and distance runners will run faster with the same effort they normally exert on any other surface.

Athletes look for every edge to get ahead of the competition. Ready's course, Materials Science and Engineering of Sports, examines how that advantage can be found at the scientific level.

"All sports are so heavily driven by material advancements these days,” he said. “Yes, we use the mechanical properties we've used since the Egyptians started racing chariots, but as material scientists, we keep trying to make things better.”

Viewers will notice the unique purple hue of the Paris track when the games begin, but Ready and Hinsdale don't expect the striking color to affect performance.

Subtitle

Like the track laid down at Georgia Tech before the 1996 Olympic Games, the Mondo track in Paris was engineered to produce fast times.

Summary sentence

Like the track laid down at Georgia Tech before the 1996 Olympic Games, the Mondo track in Paris was engineered to produce fast times.

Summary

Like the track laid down at Georgia Tech before the 1996 Olympic Games, the Mondo track in Paris was engineered to produce fast times.

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Fri, 07/19/2024 - 12:00

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Fri, 07/19/2024 - 13:44

The Geometry of Life: Physicists Determine What Controls Biofilm Growth

admin — Fri, 12 Jul 2024 14:25:49 +0000

The Geometry of Life: Physicists Determine What Controls Biofilm Growth admin Fri, 07/12/2024 - 10:25

From plaque sticking to teeth to scum on a pond, biofilms can be found nearly everywhere. These colonies of bacteria grow on implanted medical devices, our skin, contact lenses, and in our guts and lungs. They can be found in sewers and drainage systems, on the surface of plants, and even in the ocean.

“Some research says that 80% of infections in human bodies can be attributed to the bacteria growing in biofilms,” Aawaz Pokhrel says, lead author of a groundbreaking new study that uses physics to investigate how these biofilms grow.

The paper, “The Biophysical Basis of Bacterial Colony Growth,” was published in Nature Physics this week, and it shows that the fitness of a biofilm — its ability to grow, expand, and absorb nutrients from the medium or the substrate — is largely impacted by the contact angle that the biofilm’s edge makes with the substrate. The study also found that this geometry has a bigger influence on fitness than anything else, including the rate at which the cells can reproduce.

“That was the big surprise for us,” says corresponding author Peter Yunker, an associate professor in Georgia Tech’s School of Physics. “We expected that the geometry would play an important role, and we thought that figuring out exactly what the geometry is would be important for understanding why the range expansion rate, for example, [the rate at which the biofilm spreads across the surface over time] is constant. But we didn't start the project thinking that geometry would be the single most important factor.”

Understanding how biofilms grow — and what factors contribute to their growth rate — could lead to critical insights on controlling them, with applications for human health, like slowing the spread of infection or creating cleaner surfaces. “What got me excited was this opportunity to use physics to learn about complex biological systems,” Pokhrel, who is also a Ph.D. student in Yunker’s lab, adds. “Especially on a project that has so many applications. The combination of the importance for human health and exciting research was really intriguing for me.”

A new method

While biofilms are ubiquitous in nature, studying them has proven difficult. Because these “cities of microorganisms” are comprised of tiny individuals, scientists have struggled to image them successfully.

That changed in 2015, when Yunker began wondering if interferometry, a commonly used imaging technique in physics and materials science, could be applied to biofilms. “Given my background in physics, I was familiar with its use in materials applications,” Yunker recalls. “I thought applying this technique more broadly might be interesting, because we know from decades of physics that surface interfaces contain a lot of information about the processes that create them.”

The technique proved to be simple, effective, and time-efficient, providing nanometer-scale resolution of bacterial colonies. “It allows us to essentially get a picture of the topography — the shape of the surface of the bacterial population — with super-resolution,” Yunker adds.

Leveraging interferometry, the team began conducting new biofilm experiments, investigating how colonies’ shapes changed over time. Co-first author Gabi Steinbach, formerly a postdoctoral scholar in Yunker’s lab and now a scientific research coordinator at the University of Maryland, noticed that every colony had a specific shape when it was small: a spherical cap, like a slice from the top of a sphere, or a droplet of water. It’s a shape that shows up often in physics, and that sparked the team’s interest.

“A spherical cap in physics is very interesting, because it is a surface-minimizing shape,” Pokhrel adds. “I was curious why a biological material was growing in this shape, and we started wondering if there was some physics to it – perhaps geometry was involved. And that made us think that maybe we could develop a model. And that got me really excited.”

A mathematical mystery

However, the researchers soon hit a roadblock. “While we could see that the colonies were spherical caps at first, they would deviate from that shape as they grew,” Pokhrel says. “And the shape that they grew into was difficult to describe with existing spherical cap geometry.”

“The middle didn’t grow as quickly as it should to keep the spherical cap shape, and we wanted to connect all of this to the range expansion [the rate at which the colony spread across a surface],” Yunker adds. “But we knew that somehow, geometry was playing a very important role.”

Finally, Thomas Day, a former graduate student in Yunker’s lab, now a postdoctoral fellow at the University of Southern California, and one of the authors of the paper, suggested a quirky problem of geometry called the napkin ring problem.

“As soon as we started to think about the napkin ring problem, we were able to start developing a mathematical toolkit,” Yunker says, though the solution wasn’t effortless. “We couldn't find anyone who had ever looked at a spherical cap napkin ring before, because the application is very rare.”

Pokhrel, alongside two co-authors, was responsible for working out the geometry. He discovered that the cells grew exponentially at the edge of the shape, expanding further onto the medium, while the cells in the middle grew upward, creating a shape not unlike an egg in a frying pan — if the egg white was expanding outwards, while the yolk was only growing taller.

This was the breakthrough discovery: Because the cells at the middle were only contributing to the biofilm’s height, the team only needed to account for how many cells were at the edge of the biofilm, and the shape they needed to be in to grow and spread.

After incorporating their findings into a mathematical model, the team found that the contact angle was the most important factor: the angle that the very edge of the biofilm made when it touched the surface it was growing on. That single geometric quality is even more important to a biofilm’s growth than the rate at which it can reproduce cells.

The physics-biology connection

Overall, the project took more than three years, from conception to publication. “Aawaz really made an incredible effort seeing this work through,” Yunker says. “It was many years and many, many experiments. But the finished product is 100% worth it.”

The team hopes the research will pave the way for future studies, which could lead to applications like controlling biofilm growth to help prevent infections.

“Going forward, there are still a lot of research avenues,” Pokhrel says. “For example, looking at competition experiments between biofilms — do taller colonies change their contact angle so that they can spread faster? What role does this geometry play in competition?”

“Biology is complex,” Yunker adds. In nature, the surface a biofilm grows on may not be as consistent as a laboratory surface, and colonies may have different mutations or may consist of more than one species. And while the model is based on how biofilms behave in a controlled lab environment, it’s a critical first step in understanding how they may behave in nature.

Citation: Pokhrel, A.R., Steinbach, G., Krueger, A. et al. The biophysical basis of bacterial colony growth. Nat. Phys. (2024). https://doi.org/10.1038/s41567-024-02572-3

Funding information: This research was funded by the NIH National Institute of General Medical Sciences and NSF Biomaterials

Summary sentence

Up to 80% of infections in human bodies can be attributed to the bacteria growing in biofilms, and understanding how biofilms grow could lead to critical insights on controlling them.

Summary

A groundbreaking new study published in Nature Physics has revealed that geometry influences biofilm growth more than anything else, including the rate at which cells can reproduce. The research shows that the fitness of a biofilm is largely impacted by the contact angle that the biofilm’s edge makes with the substrate.

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Tue, 07/09/2024 - 12:00

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Fri, 07/12/2024 - 10:24

Physicists Pioneer New Quantum Sensing Platform

admin — Thu, 02 May 2024 20:24:41 +0000

Physicists Pioneer New Quantum Sensing Platform admin Thu, 05/02/2024 - 16:24

Quantum sensors detect the smallest of environmental changes — for example, an atom reacting to a magnetic field. As these sensors “read” the unique behaviors of subatomic particles, they also dramatically improve scientists’ ability to measure and detect changes in our wider environment.

Monitoring these tiny changes results in a wide range of applications — from improving navigation and natural disaster forecasting, to smarter medical imaging and detection of biomarkers of disease, gravitational wave detection, and even better quantum communication for secure data sharing.

Georgia Tech physicists are pioneering new quantum sensing platforms to aid in these efforts. The research team’s latest study, “Sensing Spin Wave Excitations by Spin Defects in Few-Layer Thick Hexagonal Boron Nitride” was published in Science Advances this week.

The research team includes School of Physics Assistant Professors Chunhui (Rita) Du and Hailong Wang (corresponding authors) alongside fellow Georgia Tech researchers Jingcheng Zhou, Mengqi Huang, Faris Al-matouq, Jiu Chang, Dziga Djugba, and Professor Zhigang Jiang and their collaborators.

An ultra-sensitive platform

The new research investigates quantum sensing by leveraging color centers — small defects within crystals (Du’s team uses diamonds and other 2D layered materials) that allow light to be absorbed and emitted, which also give the crystal unique electronic properties.

By embedding these color centers into a material called hexagonal boron nitride (hBN), the team hoped to create an extremely sensitive quantum sensor — a new resource for developing next-generation, transformative sensing devices.

For its part, hBN is particularly attractive for quantum sensing and computing because it could contain defects that can be manipulated with light — also known as "optically active spin qubits."

The quantum spin defects in hBN are also very magnetically sensitive, and allow scientists to “see” or “sense” in more detail than other conventional techniques. In addition, the sheet-like structure of hBN is compatible with ultra-sensitive tools like nanodevices, making it a particularly intriguing resource for investigation.

The team’s research has resulted in a critical breakthrough in sensing spin waves, Du says, explaining that “in this study, we were able to detect spin excitations that were simply unattainable in previous studies.”

Detecting spin waves is a fundamental component of quantum sensing, because these phenomena can travel for long distances, making them an ideal candidate for energy-efficient information control, communication, and processing.

The future of quantum

“For the first time, we experimentally demonstrated two-dimensional van der Waals quantum sensing — using few-layer thick hBN in a real-world environment,” Du explains, underscoring the potential the material holds for precise quantum sensing. “Further research could make it possible to sense electromagnetic features at the atomic scale using color centers in thin layers of hBN.”

Du also emphasizes the collaborative nature of the research, highlighting the diverse skill sets and resources of researchers within Georgia Tech.

“Within the School of Physics, Professor Zhigang Jiang's research group provided the team with high-quality hBN crystals. Jingcheng Zhou, who is a member of both Professor Hailong Wang’s and my research teams, performed the cutting-edge quantum sensing measurements,” she says. “Many incredible students also helped with this project.”

Du is a leading scientist in the field of quantum sensing — this year, she received a new grant from the U.S. Department of Energy, along with a Sloan Research Fellowship for her pioneering work on developing state-of-the-art quantum sensing techniques for quantum information technology applications. The prestigious Sloan award recognizes researchers whose “creativity, innovation, and research accomplishments make them stand out as the next-generation of leaders in the fields.”

DOI: 10.1126/sciadv.adk8495

This work is supported by the U. S. National Science Foundation (NSF) under award No. DMR-2342569, the Air Force Office of Scientific Research under award No. FA9550-20-1-0319 and its Young Investigator Program under award No. FA9550-21-1-0125, the Office of Naval Research (ONR) under grant No. N00014-23-1-2146, NASA-REVEALS SSERVI (CAN No. NNA17BF68A), and NASA-CLEVER SSERVI (CAN No. 80NSSC23M0229).

Summary sentence

The researchers’ results have created a new resource for developing next-generation, ultra-sensitive quantum electronic devices.

Summary

Georgia Tech physicists are investigating quantum sensing and leveraging cutting-edge techniques — embedding color centers in a 2D layered material called hexagonal boron nitride (hBN). The researchers’ results have created a new resource for developing next-generation, ultra-sensitive quantum electronic devices.

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Thu, 05/02/2024 - 12:00

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Thu, 05/02/2024 - 16:24

Physics Students’ Trip to Totality

admin — Thu, 04 Apr 2024 19:48:41 +0000

Physics Students’ Trip to Totality admin Thu, 04/04/2024 - 15:48

A total solar eclipse is a time of scientific discovery, confirming Albert Einstein's theory of general relativity in 1919, but the astronomical phenomenon can also be a time of personal discovery, just as it was for Dragomir Davidovic.

An associate professor in the School of Physics whose expertise lies outside of astronomy, Davidovic didn't initially understand the hype surrounding the 2017 eclipse. However, he was instantly captivated as the moon passed between the sun and the Earth to reveal the star's corona.

"When I saw my first eclipse, I was surprised by its power. Nature changed around us; the birds became quiet, and all of the animals near the farm were getting ready to go to sleep. It was eerie in a way, and it's a once-in-a-lifetime event that needs to be seen," he said.

Unlike 2017, Georgia will not be in the path of totality for the eclipse occurring on Monday, April 8, so Davidovic and Edwin Greco, associate chair for student success, are leading a trip for 55 School of Physics students, primarily graduate students, to experience totality at the Crab Orchard National Wildlife Refuge in Southwest Illinois following an overnight stay in Nashville, Tennessee.

While the eclipse can be viewed in an urban environment, such as Atlanta, where coverage will reach 85%, Davidovic wanted to give students the opportunity to feel the eclipse's full effect on nature as he experienced it seven years ago.

"A rural setting allows you to have this true connection with nature, and it evokes this feeling of almost being a prehistoric human," he said.

In addition to the reaction of animals, Jim Sowell, director of the Georgia Tech Observatory, explains that as the eclipse reaches its peak, temperatures will drop, and planets may become visible in the darkened sky. To view the eclipse, the group will be bringing safety glasses and a telescope with the appropriate lens for direct sunlight viewing.

The idea for the trip came from a spontaneous conversation between Davidovic and School Chair Feryal Özel in August, and initially, Davidovic wondered if enough students would share his enthusiasm for such an adventure.

"My biggest worry was that we wouldn't get enough students to sign up, but as it turned out, I was totally wrong," he said. "It goes to show there is a broad interest in this natural phenomenon. You don't have to be an astronomer; we have people signed up across many different fields,” he said.

Among those immediately interested in joining the excursion was Nadia Qutob, a graduating physics major with an emphasis in astrophysics and a member of the Georgia Tech Astronomy Club.

"Everyone in the world at some point in their lives looks up at the sky and wonders what is up there. Space has an incredible ability to unite us in our shared curiosity. It is deeply inspirational to me that so many people, especially young people, are excited about the eclipse. I hope it will lead to more interest in space research in the future," she said.

Student interest in the eclipse is evident, with another trip being led by the Astronomy Club, which will be heading to the Ozarks to witness the event.

Following Monday’s total solar eclipse, the continental U.S. will not see another of its kind until 2044. In the meantime, Davidovic's hobby has also influenced his academic work. He is now conducting research into the effects of merging black holes on quantum computers and continues to study additional astrophysical theories.

Subtitle

Sparked by a professor’s interest, 55 students from the School of Physics will travel to Illinois to enter the path of totality for the April 8 total solar eclipse.

Summary sentence

Sparked by a professor’s interest, 55 students from the School of Physics will travel to Illinois to enter the path of totality for the April 8 total solar eclipse.

Summary

Sparked by a professor’s interest, 55 students from the School of Physics will travel to Illinois to enter the path of totality for the April 8 total solar eclipse.

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Thu, 04/04/2024 - 12:00

Steven.gagliano@gatech.edu

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Thu, 04/04/2024 - 15:46

John Wise Joins Neil deGrasse Tyson at 2024 Asimov Debate

admin — Thu, 04 Apr 2024 14:49:41 +0000

John Wise Joins Neil deGrasse Tyson at 2024 Asimov Debate admin Thu, 04/04/2024 - 10:49

Has the James Webb Space Telescope changed astrophysics? That was the question posed by Neil deGrasse Tyson to a panel of leading experts, including Georgia Tech’s John Wise, at the 25th annual Isaac Asimov Memorial Debate.

The live event was held on March 19 at the American Museum of Natural History in New York City, and while the 800 available tickets sold out within 20 minutes, the discussion is now publicly available on YouTube.

Tyson is the the Frederick P. Rose Director of the Hayden Planetarium. He personally invited Wise, a professor in the School of Physics and director of the Center for Relativistic Astrophysics, who traveled to New York for the event alongside his wife, Emily Alicea-Muñoz, a fellow physicist and academic professional in the School of Physics.

The discussion centered on how the James Webb Space Telescope has indeed changed astrophysics, especially in relation to understanding the first billion years after the Big Bang when galaxies and black holes were rapidly forming — an area where Wise has significant expertise.

Journey to the stars

“My research group and I have been focusing on this topic for several years, so I was ecstatic to participate in the panel,” Wise says. The event was also an opportunity for the astrophysicist to reconnect with fellow experts — the panel also included Mike Boylan-Kolchin of University of Texas at Austin, Wendy Freedman of the University of Chicago, Priya Natarajan of Yale University, and Rachel Somerville of the Flatiron Institute. Wise had previously collaborated on research with several of the panelists, and Tyson is no stranger to Georgia Tech.

“Just after I received my Ph.D., my collaborators and I worked with the Hayden Planetarium at the American National History Museum to produce a planetarium show segment from my simulations of the first stars,” Wise recalls. The show segment, Journey to the Stars, premiered in 2009 and was narrated by Whoopie Goldberg. Georgia Tech also hosted Tyson in 2014 at the Ferst Center, where many members of the Center for Relativistic Astrophysics met with him.

In the spirit of Isaac Asimov’s legacy of science-oriented storytelling, this year’s debate also provided an opportunity for audience members to “eavesdrop” on robust scientific discussion – with Tyson acting as an interpreter and storyteller, explaining the technical language and helping panelists explain advanced topics.

“The conversation was fantastic,” says Wise. “Neil really brought out the best in us and our scientific endeavors in uncovering the mysteries of the early universe with the James Webb Space Telescope.”

About the Isaac Asimov Memorial Debate

The Hayden Planetarium notes that “the late Dr. Isaac Asimov, one of the most prolific and influential authors of our time, was a dear friend and supporter of the American Museum of Natural History. In his memory, the Hayden Planetarium is honored to host the annual Isaac Asimov Memorial Debate — generously endowed by relatives, friends, and admirers of Isaac Asimov and his work — bringing the finest minds in the world to the Museum each year to debate pressing questions on the frontier of scientific discovery. Proceeds from ticket sales of the Isaac Asimov Memorial Debates benefit the scientific and educational programs of the Hayden Planetarium.” Learn more and watch past debates here.

Summary sentence

Wise, a professor in the School of Physics and director of the Center for Relativistic Astrophysics, spoke to how the James Webb Space Telescope has impacted astrophysics and our understanding of the formation of black holes.

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Wed, 04/03/2024 - 12:00

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Thu, 04/04/2024 - 10:49

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The Geometry of Life: Physicists Determine What Controls Biofilm Growth

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Physicists Pioneer New Quantum Sensing Platform

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Physics Students’ Trip to Totality

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John Wise Joins Neil deGrasse Tyson at 2024 Asimov Debate

Journey to the stars

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