Scientists observe “quasiparticles” in classical systems for the first time

Peer-Reviewed Publication

ULSAN NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY(UNIST)

 

IMAGE: DISTINGUISHED PROFESSOR TSVI TLUSTY (FAR RIGHT) AND HIS RESEARCH TEAM AT THE CENTER FOR SOFT AND LIVING MATTER (CSLM) WITHIN THE INSTITUTE FOR BASIC SCIENCE (IBS). view more 

CREDIT: UNIST

Starting with the emergence of quantum mechanics, the world of physics has been divided between classical and quantum physics. Classical physics deals with the motions of objects we typically see every day in the macroscopic world, while quantum physics explains the exotic behaviors of elementary particles in the microscopic world.

Many solids or liquids are composed of particles interacting with one another at close distances, which sometimes results in the rise of “quasiparticles.” Quasiparticles are long-lived excitations that behave effectively as weakly interacting particles. The idea of quasiparticles was introduced by the Soviet physicist Lev Landau in 1941, and ever since has been highly fruitful in quantum matter research. Some examples of quasiparticles include Bogoliubov quasiparticles (i.e. “broken Cooper pairs”) in superconductivity, excitons in semiconductors, and phonons.

Examining emergent collective phenomena in terms of quasiparticles provided insight into a wide variety of physical settings, most notably in superconductivity and superfluidity, and recently in the famous example of Dirac quasiparticles in graphene. But so far, the observation and use of quasiparticles have been limited to quantum physics: in classical condensed matter, the collision rate is typically much too high to allow long-lived particle-like excitations.

However, the standard view that quasiparticles are exclusive to quantum matter has been recently challenged by a group of researchers at the Center for Soft and Living Matter (CSLM) within the Institute for Basic Science (IBS), South Korea. They examined a classical system made of microparticles driven by viscous flow in a thin microfluidic channel. As the particles are dragged by the flow, they perturb the streamlines around them, thereby exerting hydrodynamic forces on each other. This breakthrough has been jointly led by Group Leader Tsvi Tlusty (Department of Physics, UNIST) and Professor Professor Hyuk Kyu Pak (Department of Physics, UNIST) from CSLM.

Remarkably, the researchers found that these long-range forces make the particles organize in pairs (Figure 1 Left). This is because the hydrodynamic interaction breaks Newton’s third law, which states that the forces between two particles must be equal in magnitude and opposite in direction. Instead, the forces are ‘anti-Newtonian’ because they are equal and in the same direction, thus stabilizing the pair.

The large population of particles coupled in pairs hinted that these are the long-lived elementary excitations in the system — its quasiparticles. This hypothesis was proven right when the researchers simulated a large two-dimensional crystal made of thousands of particles and examined its motion (Figure 1 Right). The hydrodynamic forces among the particles make the crystal vibrate, much like the thermal phonons in a vibrating solid body.

These pair quasiparticles propagate through the crystal, stimulating the creation of other pairs through a chain reaction. The quasiparticles travel faster than the speed of phonons, and thus every pair leaves behind an avalanche of newly-formed pairs, just like the Mach cone generated behind a supersonic jet plane (Figure 1 Right). Finally, all those pairs collide with each other, eventually leading to the melting of the crystal (See Movie).

The melting induced by pairs is observed in all crystal symmetries except for one particular case: the hexagonal crystal. Here, the three-fold symmetry of hydrodynamic interaction matches the crystalline symmetry and, as a result, the elementary excitations are extremely slow low-frequency phonons (and not pairs as usual). In the spectrum, one sees a “flat band” where these ultra-slow phonons condense. The interaction among the flat-band phonons is highly collective and correlated, which shows in the much sharper, different class of melting transition.

Notably, when analyzing the spectrum of the phonons, the researchers identified conical structures typical of Dirac quasiparticles, just like the structure found in the electronic spectrum of graphene (Figure 2). In the case of the hydrodynamic crystal, the Dirac quasiparticles are simply particle pairs, which form thanks to the ‘anti-Newtonian’ interaction mediated by the flow. This demonstrates that the system can serve as a classical analog of the particles discovered in graphene.

“The work is a first-of-its-kind demonstration that fundamental quantum matter concepts – particularly quasiparticles and flat bands – can help us understand the many-body physics of classical dissipative systems,” explains Distinguished Professor Tsvi Tlusty, one of the corresponding authors of the paper.

Moreover, quasiparticles and flat bands are of special interest in condensed matter physics. For example, flat bands were recently observed in double layers of graphene twisted by a specific “magic angle”, and the hydrodynamic system studied at the IBS CSLM happens to exhibit an analogous flat band in a much simpler 2D crystal.

“Altogether, these findings suggest that other emergent collective phenomena that have been so far measured only in quantum systems may be revealed in a variety of classical dissipative settings, such as active and living matter,” says Hyuk Kyu Pak, one of the corresponding authors of the paper.

Their findings have been published in the January 2023 issue of Nature Physics.

Story Source
Materials provided by Institute of Basic Science.

Notes for Editors
The online version of the original article can be found HERE.

Journal Reference
Imran Saeed, Hyuk Kyu Pak, and Tsvi Tlusty, “Quasiparticles, Flat Bands, and the Melting of Hydrodynamic Matter,” Nature Physics, (2023).

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JOURNAL

Nature Physics

ARTICLE TITLE

Quasiparticles, flat bands and the melting of hydrodynamic matter

Electric vehicle batteries could get big boost with new polymer coating

Scientists enhance lithium-ion battery performance at the atomic level

Peer-Reviewed Publication

DOE/LAWRENCE BERKELEY NATIONAL LABORATORY

 

IMAGE: BERKELEY LAB RESEARCHERS DEMONSTRATED THAT THE HOS-PFM COATING SIGNIFICANTLY PREVENTS ALUMINUM-BASED ELECTRODES FROM DEGRADING DURING BATTERY CYCLING WHILE DELIVERING HIGH BATTERY CAPACITY OVER 300 CYCLES. FROM LEFT: SCANNING ELECTRON MICROSCOPE IMAGES OF ALUMINUM ON A COPPER BILAYER DEVICE BEFORE BATTERY CYCLING (FIGURE A) AND AFTER (FIGURE B). FIGURE C SHOWS A COPPER TRI-LAYER DEVICE WITH HOS-PFM COATING AFTER BATTERY CYCLING. view more 

CREDIT: GAO LIU/BERKELEY LAB. COURTESY OF NATURE ENERGY.

Scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a conductive polymer coating – called HOS-PFM – that could enable longer lasting, more powerful lithium-ion batteries for electric vehicles. 

“The advance opens up a new approach to developing EV batteries that are more affordable and easy to manufacture,“ said Gao Liu, a senior scientist in Berkeley Lab’s Energy Technologies Area.

The HOS-PFM coating conducts both electrons and ions at the same time. This ensures battery stability and high charge/discharge rates while enhancing battery life. The coating also shows promise as a battery adhesive that could extend the lifetime of a lithium-ion battery from an average of 10 years to about 15 years, Liu added.

To demonstrate HOS-PFM’s superior conductive and adhesive properties, Liu and his team coated aluminum and silicon electrodes with HOS-PFM, and tested their performance in a lithium-ion battery setup. 

Silicon and aluminum are promising electrode materials for lithium-ion batteries because of their potentially high energy storage capacity and lightweight profiles. But these cheap and abundant materials quickly wear down after multiple charge/discharge cycles.

During experiments at the Advanced Light Source and the Molecular Foundry, the researchers demonstrated that the HOS-PFM coating significantly prevents silicon- and aluminum-based electrodes from degrading during battery cycling while delivering high battery capacity over 300 cycles, a performance rate that’s on par with today’s state-of-the-art electrodes. 

The results are impressive, Liu said, because silicon-based lithium-ion cells typically last for a limited number of charge/discharge cycles and calendar life. The researchers recently described these findings in the journal Nature Energy.

The HOS-PFM coating could allow the use of electrodes containing as much as 80% silicon. Such high silicon content could increase the energy density of lithium-ion batteries by at least 30%, Liu said. And because silicon is cheaper than graphite, the standard material for electrodes today, cheaper batteries could significantly increase the availability of entry-level electric vehicles, he added. 

The team next plans to work with companies to scale up HOS-PFM for mass manufacturing. 

The Advanced Light Source and Molecular Foundry are DOE Office of Science user facilities at Berkeley Lab.

The research was supported by DOE Vehicle Technologies Office. The technology is available for licensing by contacting ipo@lbl.gov.

The HOS-PFM conductive binder is made of a nontoxic polymer that transforms at the atomic level in response to heat. Before heating: At room temperature (20 degrees Celsius), alkyl end-chains (black squiggly lines) on the PFM polymer chain limit the movement of lithium ions (red circles). After heating: When heated to about 450 degrees Celsius (842 degrees Fahrenheit), the alkyl end-chains melt away, creating vacant “sticky” sites (blue squiggly lines) that “grab” onto silicon or aluminum materials at the atomic level. PFM’s polymer chains then self-assemble into spaghetti-like strands called “hierarchically ordered structures” or HOS. Like an atomic expressway, the HOS-PFM strands allow lithium ions to hitch a ride with electrons (blue circles). These lithium ions and electrons move in synchronicity along the aligned conductive polymer chains.

CREDIT

Jenny Nuss/Berkeley Lab

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 16 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy’s Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.

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JOURNAL

Nature Energy

DOI

10.1038/s41560-022-01176-6 

ARTICLE TITLE

Formation of hierarchically ordered structures in conductive polymers to enhance the performances of lithium-ion batteries

A better understanding of gas exchange between the atmosphere and ocean can improve global climate models

Peer-Reviewed Publication

WOODS HOLE OCEANOGRAPHIC INSTITUTION

 

IMAGE: WOODS HOLE OCEANOGRAPHIC INSTITUTION (WHOI) SCIENTIST ALAN SELTZER COLLECTS A WATER SAMPLE IN THE NORTH ATLANTIC OFF THE COAST OF BERMUDA, MAY 2022. BY USING A TECHNIQUE DEVELOPED AT WHOI, SELT-ZER AND COLLEAGUES MADE ULTRA-PRECISE MEASUREMENTS OF DISSOLVED GAS ISOTOPES TO UNRAVEL THE PHYS-ICS OF GAS TRANSFER FROM THE ATMOSPHERE TO DEEP OCEAN. view more 

CREDIT: PHOTO CREDIT: REBECCA TYNE /©WOODS HOLE OCEANOGRAPHIC INSTITUTION.

Woods Hole, Mass. (March 7, 2023) -- The injection of bubbles from waves breaking in turbulent and cold high-latitude regions of the high seas is an underappreciated way in which atmospheric gases are transported into the interior ocean. An improved mechanistic understanding of gas exchange in high latitudes is important for several reasons, including to better constrain climate models that are used to predict changes in the ocean inventory of key gases like oxygen and carbon dioxide.

A new WHOI-led study, “Dissolved gases in the deep North Atlantic track ocean ventilation processes”, published this week in Proceedings of the National Academy of Sciences, combines new geochemical tracers and ocean circulation models to investigate the physics by which atmospheric gases get into the deep ocean. The study uses a new technique to precisely measure noble gas isotopes dissolved in samples of seawater collected from as deep as 4.5 kilometers in the North Atlantic. Noble gases – the elements on the far right-hand side of the periodic table – are unreactive and unused by biology, making them useful tracers of physics.

Noble gases are neither added nor removed from water after the exchange with the atmosphere at the sea-surface. As a result, measuring dissolved noble gases in the deep North Atlantic off the coast of Bermuda tells scientists about the physics of gas exchange that happened in special regions like the Irminger Sea, where the surface ocean becomes dense enough under stormy wintertime conditions to sink and form deep water that slowly flows south.

Alan Seltzer, lead author of the paper, said these new findings suggest that the dissolution of bubbles in the high-latitude ocean “may be the dominant pathway by which all of the noble gases, oxygen, and nitrogen get into the deep ocean.” This study is a step forward toward understanding the basic physics by which gases get into the ocean, said Seltzer, an assistant scientist in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI).

“Anything we can do to improve the accuracy of the way models represent our world is helpful, especially when it has to do with gases,” he said. “We care about oxygen for global ecosystems, and we care about CO2 because the ocean is a huge player in taking up our emissions. So if we can improve the way models represent physical processes such as gas exchange, we can have more confidence in future simulations with models as a way of predicting how things will change in a warmer world with more CO2.”

“Understanding how the ocean takes up and releases gases to the atmosphere is a challenging but critically important step toward predicting their response to climate change. Being chemically and biologically inert, noble gases are powerful tools for probing the physical processes involved,” said journal article co-author William Jenkins, an emeritus research scholar in WHOI’s Marine Chemistry and Geochemistry Department. “The Seltzer et al. paper is an important step forward in this journey in that it combines new high-precision noble gas concentration and isotope ratio measurements that are key to unlocking an understanding of these vital processes. Their results also shed light on the oceanic nitrogen cycle, which is both important for climate change issues, but also our fundamental understanding of how ocean food web is supported.”

Measurements for the study come from the Bermuda Atlantic Time Series (BATS) site (31°40 N, 64°10 W), where repeat cruises have surveyed the ocean from top to bottom nearly monthly since 1988. The BATS site is an ideal place to collect samples, because it is located downstream of deep-water formation regions. Deep-ocean noble gas concentrations at the BATS site allow scientists to study gas exchange during wintertime events where the deep ocean  is formed as surface waters cool and become more dense. Under these harsh conditions, direct observations are challenging and scarce, which is why measurements from the deep ocean in warmer, more southern locations are so valuable.

Seltzer said a way to understand why bubbles play such a huge role in transporting noble gases, oxygen, and nitrogen into the deep ocean is to realize that “every time a wave breaks, that massively increases the available surface area for the exchange of gases between the atmosphere and the ocean.”

“The exchange of carbon dioxide and other greenhouse gases between the deep ocean—approximately 75% of the total ocean volume—and the atmosphere occurs at high latitudes during winter, particularly during storm events. Measurements of inert noble gas concentrations in the deep North Atlantic Ocean documented the importance of large bubbles that form during windy storm events, significantly increasing our understanding of the gas exchange rate for the deep water,” said co-author William Smethie, special research scientist and retired research professor at the Lamont-Doherty Earth Observatory of Columbia University. “This improves our ability to quantify the exchange of carbon dioxide and greenhouse gases between the ocean and atmosphere and predict how their atmospheric concentrations will impact the earth’s climate, which is critical for developing policies to mitigate global warming.”

Funding for this research was provided by the U.S. National Science Foundation (NSF) and the UK Natural Environment Research Council. Computing resources were provided by the Climate Simulation Laboratory at the National Center for Atmospheric Research’ Computational and Information Systems Laboratory, sponsored by NSF and other agencies, and by the University of Oxford Advanced Research Computing facility.

Authors: Alan M. Seltzer*1, David P. Nicholson1, William M. Smethie2, Rebecca L. Tyne1, Emilie Le Roy1, Rachel H.R. Stanley1,3, Martin Stute2,4, Peter H. Barry1, Katelyn McPaul1, Perrin W. Davidson1, Bonnie X. Chang5, Patrick A. Rafter6, Paul Lethaby7, Rod J. Johnson7, Samar Khatiwala8, William J. Jenkins1

Affiliations:

1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

2Geochemistry Department, Lamont-Doherty Earth Observatory, Palisades, NY, USA

3Department of Chemistry, Wellesley College, Wellesley, MA, USA

4Environmental Science Department, Barnard College, New York, NY, USA

5Cooperative Institute for Climate, Ocean, & Ecosystem Studies, University of Washington, Seattle, WA, USA

6Department of Earth System Science, University of California Irvine, Irvine, CA, USA

7Bermuda Institute of Ocean Sciences, St George’s, Bermuda, UK

8Department of Earth Sciences, University of Oxford, Oxford, UK

About Woods Hole Oceanographic Institution

The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu

Key takeaways:

•          If scientists can improve the way models represent physical processes such as gas exchange, they can have more confidence in future simulations with models as a way of predicting how things will change in a warmer world with more CO2.

•          The role of bubbles, which partially dissolve after injection by breaking waves, has been underappreciated as a key mechanism by which gases are transported into the vast ocean interior.

•          The study implements a new technique, developed at WHOI, to precisely measure the isotopes of noble gases in the North Atlantic, which are rare and challenging to measure but offer useful information about physical air-sea gas exchange processes.

•          By pairing new observations of dissolved noble gases in the deep ocean with ocean circulation models, the study is able to estimate the physical signals recorded by other geochemical gas tracers, like nitrogen, in the ocean interior.

•          Using this new understanding of physical gas exchange processes, the authors are able to disentangle biological/chemical signals from physical ones, allowing for the resolution of excess nitrogen in the deep North Atlantic that informs the rate of fixed nitrogen loss, which is crucial for nutrient cycling the global ocean.

 

 

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JOURNAL

Proceedings of the National Academy of Sciences

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Dissolved gases in the deep North Atlantic track ocean ventilation processes

ARTICLE PUBLICATION DATE

6-Mar-2023

Hollow bones that let dinosaurs become giants evolved at least three times independently

The study analyzed fossilized bones from three Brazilian species of the Late Triassic (about 233 million years ago), the period in which the dinosaurs emerged. All the bones were found in recent decades in Rio Grande do Sul, Brazil’s southernmost state

Peer-Reviewed Publication

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO

 

IMAGE: GNATHOVORAX CABREIRAI WAS A HERRERASAURID, A LINEAGE THAT BECAME EXTINCT NOT LONG AFTER THE PERIOD IN WHICH IT LIVED view more 

CREDIT: ILLUSTRATION: MÁRCIO CASTRO

Dinosaurs as big as buses or five-story buildings would not be possible if their bones were dense and heavy like ours. Like present-day birds, dinosaurs had hollow bones with inner structures known as air sacs, which made their skeletons lighter and less dense. These structures were apparently so advantageous that they emerged at least three times during the evolution of dinosaurs and pterosaurs (flying reptiles), according to a study supported by FAPESP and described in an article in Scientific Reports.

“Less dense bones containing more air gave the dinosaurs and pterosaurs [and still give birds] more oxygen circulating in their blood, as well as more agility to hunt, flee and fight, or even to fly. They not only used less energy but also kept their bodies cool more efficiently,” said Tito Aureliano, first author of the article. The study was part of his PhD research at the State University of Campinas’s Institute of Geosciences (IG-UNICAMP).

Aureliano analyzed fossilized bones from three Brazilian species of the Late Triassic (about 233 million years ago), the period in which the dinosaurs emerged. All the bones were found in recent decades in Rio Grande do Sul, Brazil’s southernmost state.

Detailed knowledge of specimens belonging to different groups and dating from an early stage in their evolution provides a basis for understanding when certain traits were developed. In this case, the researchers were looking for signs of the presence of air sacs, which were commonplace in geologically more recent (and more studied) species, such as tyrannosauruses or velociraptors, and are found in present-day birds, as noted earlier. Air sacs are found in bones throughout the body next to the spinal column.

Computerized tomography was used to visualize the fossils’ internal structures. Small spaces in the vertebrae were identified as foramina for veins, arteries and marrow, and attachment points for muscles and tendons could be seen, but none appeared capable of serving as pneumatic chambers through which air might have flowed continuously. 

“The Triassic was very warm and dry. What’s now Rio Grande do Sul was far from the sea in the heart of the supercontinent Pangea. In that context, more oxygen circulating in the blood would cool the body more efficiently and certainly afford a welcome advantage, so much so that it evolved at least three times independently,” said Fresia Ricardi-Branco, penultimate author of the article, a professor at IG-UNICAMP, and principal investigator for the FAPESP-funded project of which the study was part.

Pneumaticity

The fossils analyzed were found between 2011 and 2019 by researchers at the Federal University of Santa Maria (UFSM) in an area known as Quarta Colônia near Santa Maria in Rio Grande do Sul. Some of those researchers are co-authors of the article. 

The fossils belonged to three species: Buriolestes schultzi, Pampadromaeus barberenai and Gnathovorax cabreirai. The first two were sauropodomorphs, the group of long-necked dinosaurs that became the largest animals to walk the planet. The third was a herrerasaurid, one of the earliest carnivorous dinosaurs. The lineage became extinct shortly after the period in which this specimen lived.

A study published in 2021 by researchers from South Africa, the United Kingdom, the United States and Canada had already shown that another dinosaur lineage, the ornithischians, also lacked structures that could have housed air sacs. This order of dinosaurs probably emerged later, in the Jurassic (between 201 million and 145 million years ago), and included the popular Triceratops. 

The data collected on ornithischians, herrerasaurids and sauropods showed that air sacs evolved independently in each group. “We discovered that no common ancestor had this trait. All three groups must have developed air sacs independently,” Aureliano said.

The other groups that had air sacs were the pterosaurs (including pterodactyls) and the theropods (including tyrannosaurs and velociraptors, as well as extant birds). Although they descended from B. schultzi and P. barberenai, in the long-necked lineage, hollow bones only evolved later. Exactly when is not yet known.

“The oldest dinosaurs in the world are in South America and have been discovered only in the past two decades,” Ricardi-Branco said. “More of this kind of research needs to be done to show how the dominant organisms of the period coped with a much warmer climate than ours.”

About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-022-25067-8 

ARTICLE TITLE

The absence of an invasive air sac system in the earliest dinosaurs suggests multiple origins of vertebral pneumaticity

Rensselaer researcher breaks through the clouds to advance satellite communication

New method enables effective free-space optical communication regardless of weather

Peer-Reviewed Publication

RENSSELAER POLYTECHNIC INSTITUTE

 

IMAGE: MOUSSA N'GOM view more 

CREDIT: RENSSELAER POLYTECHNIC INSTITUTE

Rensselaer Polytechnic Institute’s Moussa N’Gom, assistant professor of physics, applied physics, and astronomy, has devised a method to make communications between satellites and the ground more effective no matter the weather. In research recently published, N’Gom and his team used ultrafast, femtosecond lasers to cut through the clouds and rain that commonly cause losses in free-space optical communication (FSO).

“The lasers we use are so energetic that they change the environment in which they propagate,” N’Gom said. “The environment starts to change the laser that is changing it, and they have a light-matter interaction. It becomes a cascading effect that creates a long filament of light.”

The filament of light is accompanied by a shockwave, along the lines of a sonic boom. The laser filament propagates through clouds and the accompanying shockwave clears the space around the filament, providing an open pathway for visible light. N’Gom uses structured light, in the form of a spiral with a hole at its center, to propagate through the pathway.

“The Laguerre–Gauss beam travels through this empty space without interacting with the filament and is unobstructed by the clouds,” N’Gom said. “Normally, light travels in one, flat wave, but the light we create travels in a spiral. Imagine it like curling a flat piece of paper with scissors.”

On top of facilitating transmission through clouds, the spiral shape of the light also allows for more information to be transmitted.

The method presents a significant advance for FSO, which already has substantially higher capacity than radio frequency communication. Previous attempts to overcome the persistent obstacle of rain and clouds required substantial energy, large investments, or were less effective.

“Dr. N’Gom’s innovative research shows how to overcome a fundamental barrier in free-space optical communication,” said Curt Breneman, dean of the Rensselaer School of Science. “I expect free-space optical communication technology of this type to enable hyper-speed secure worldwide quantum communications.”

N’Gom was joined in research by doctoral students Tianhong Wang, Saad Bin Ali Reza, Finn Buldt, and postdoctoral associate Pascal Bassène. The work was funded by the National Geospatial Agency.

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About Rensselaer Polytechnic Institute:

Founded in 1824, Rensselaer Polytechnic Institute is America’s first technological research university. Rensselaer encompasses five schools, over 30 research centers, more than 140 academic programs including 25 new programs, and a dynamic community made up of over 6,800 students and 104,000 living alumni. Rensselaer faculty and alumni include upwards of 155 National Academy members, six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, and a Nobel Prize winner in Physics. With nearly 200 years of experience advancing scientific and technological knowledge, Rensselaer remains focused on addressing global challenges with a spirit of ingenuity and collaboration. To learn more, please visit www.rpi.edu.

Contact: 
Katie Malatino
Sr. Communications Specialist
malatk@rpi.edu
838-240-5691

For general inquiries: newsmedia@rpi.edu

Visit the Rensselaer research and discovery blog: https://everydaymatters.rpi.edu/

Follow us on Twitter: @RPINews

 

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JOURNAL

Journal of Applied Physics

DOI

10.1063/5.0129902 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Structured light signal transmission through clouds

Elegantly modeling earth’s abrupt glacial transitions

Simple and intuitive model illustrates how climate cycles are influenced by our planet’s orbit.

Peer-Reviewed Publication

AMERICAN INSTITUTE OF PHYSICS

WASHINGTON, March 7, 2023 – Proxy data – indirect records of the Earth’s climate found in unlikely places like coral, pollen, trees, and sediments – show interesting oscillations approximately every 100,000 years starting about 1 million years ago. Strong changes in global ice volume, sea level, carbon dioxide concentration, and surface temperature indicate cycles of a long, slow transition to a glacial period and an abrupt switch to a warm and short interglacial period.

Milutin Milankovitch hypothesized that the timing of these cycles was controlled by the orbital parameters of the Earth, including the shape of its path around the sun and the tilt of the planet. A slightly closer orbit or more tilted planet could create a small increase in solar radiation and a feedback loop that leads to massive changes in climate. This idea suggests that there may be some predictability in the climate, a notoriously complex system.

In Chaos, by AIP Publishing, Stefano Pierini of Parthenope University of Naples proposed a new paradigm to simplify the verification of the Milankovitch hypothesis.

“The main motivation behind this study was the wish to characterize and illustrate the Milankovitch hypothesis in a simple, elegant, and intuitive way,” Pierini said.

Many models suggest that Milankovitch is correct; however, such methods are often detailed and study specific. They incorporate climate feedback loops – for example, increased ice cover reflects more radiation back into space, leading to further cooling and more ice cover – as threshold crossing rules. This means that an abrupt jump in climate only occurs once a parameter reaches a given tipping point.  

Pierini’s “deterministic excitation paradigm” combines the physics concepts of relaxation oscillation and excitability to link Earth’s orbital parameters and the glacial cycles in a more generic way. The relaxation oscillation component describes how the climate slowly returns to its original glacier state after it is disturbed. At that point, the excitability piece of the model captures the external orbital changes and triggers the next glacial cycle.

By using his own threshold crossing rules and adopting a classical energy-balance model, Pierini obtained correct and robust timing of the most recent glacial cycles.

“The application of the deterministic excitation paradigm in the present basic formulation can explain the timing of the last four glacial terminations,” he said. “Extending the same analysis to the whole Pleistocene will be the subject of a future investigation.”

Pierini believes similar methods could be used in other fields of nonlinear science and in connection with other climate phenomena.

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The article “The deterministic excitation paradigm and the late Pleistocene glacial terminations” is authored by Stefano Pierini. It will appear in Chaos on March 7, 2023 (DOI: 10.1063/5.0127715). After that date, it can be accessed at https://doi.org/10.1063/5.0127715.

ABOUT THE JOURNAL

Chaos is devoted to increasing the understanding of nonlinear phenomena in all areas of science and engineering and describing their manifestations in a manner comprehensible to researchers from a broad spectrum of disciplines. See https://aip.scitation.org/journal/cha.

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JOURNAL

Chaos An Interdisciplinary Journal of Nonlinear Science

DOI

10.1063/5.0127715 

ARTICLE TITLE

The deterministic excitation paradigm and the late Pleistocene glacial terminations

ARTICLE PUBLICATION DATE

7-Mar-2023

Drunk mice sober up after a hormone shot

Peer-Reviewed Publication

CELL PRESS

 

IMAGE: FGF21 COUNTERACTS ALCOHOL INTOXICATION BY ACTIVATING THE NORADRENERGIC NERVOUS SYSTEM view more 

CREDIT: CELL METABOLISM/CHOI ET AL.

A hormone called fibroblast growth factor 21 (FGF21) protects mice against ethanol-induced loss of balance and righting reflex, according to a study publishing on March 7 in the journal Cell Metabolism.

“We’ve discovered that the liver is not only involved in metabolizing alcohol but that it also sends a hormonal signal to the brain to protect against the harmful effects of intoxication, including both loss of consciousness and coordination,” says co-senior study author Steven Kliewer of the University of Texas Southwestern Medical Center.

“We’ve further shown that by increasing FGF21 concentrations even higher by injection, we can dramatically accelerate recovery from intoxication. FGF21 does this by activating a very specific part of the brain that controls alertness,” says Kliewer.

The consumption of ethanol produced by the natural fermentation of simple sugars in ripening fruits and nectars can cause intoxication, impairing mobility and judgement. Animals that consume fructose and other simple sugars have evolved liver enzymes to break down ethanol.

FGF21 is a hormone that is induced in the liver by a variety of metabolic stresses, including starvation, protein deficiency, simple sugars, and ethanol. In humans, ethanol is by far the most potent inducer of FGF21 described to date. Previous studies showed that FGF21 suppresses ethanol preference, induces water drinking to prevent dehydration, and protects against alcohol-induced liver injury.

In the new study, Kliewer and co-senior study author David Mangelsdorf of the University of Texas Southwestern Medical Center show that FGF21 plays a broader role in defending against the harmful consequences of ethanol exposure than previously thought. In mice, FGF21 stimulated arousal from intoxication without changing the breakdown of ethanol. Mice lacking FGF21 took longer than their littermates to recover their righting reflex and balance following ethanol exposure. Conversely, pharmacologic FGF21 administration reduced the time needed for mice to recover from ethanol-induced unconsciousness and lack of muscle coordination.

Surprisingly, FGF21 did not counteract sedation caused by ketamine, diazepam, or pentobarbital, indicating specificity for ethanol. FGF21 mediated its anti-intoxicant effects by directly activating noradrenergic neurons in the locus coeruleus region in the brain, which regulates arousal and alertness. Taken together, the results suggest that the FGF21 liver-brain pathway evolved to protect against ethanol-induced intoxication. According to the authors, this pathway may modulate a variety of cognitive and emotional functions to enhance survival under stressful conditions.

Yet it remains to be determined whether activation of the noradrenergic system contributes to FGF21’s other effects, including those on metabolism and ethanol and sweet preference. Although both FGF21 and noradrenergic nervous system activity are induced by ethanol in humans, additional studies will also be required to determine whether FGF21’s anti-intoxicant activity translates to humans.

“Our studies reveal that the brain is the major site of action for FGF21’s effects,” Mangelsdorf says. “We are now exploring in greater depth the neuronal pathways by which FGF21 exerts its sobering effect.”

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This work was supported by the National Institutes of Health, the Robert A. Welch Foundation, and the Howard Hughes Medical Institute. Information about potential conflicts of interest can be found in the paper text.

Cell Metabolism, Choi et al. “FGF21 counteracts alcohol intoxication by activating the noradrenergic nervous system” https://www.cell.com/cell-metabolism/fulltext/S1550-4131(23)00041-4

Cell Metabolism (@Cell_Metabolism), published by Cell Press, is a monthly journal that publishes reports of novel results in metabolic biology, from molecular and cellular biology to translational studies. The journal aims to highlight work addressing the molecular mechanisms underlying physiology and homeostasis in health and disease. Visit http://www.cell.com/cell-metabolism. To receive Cell Press media alerts, contact press@cell.com.

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JOURNAL

Cell Metabolism

DOI

10.1016/j.cmet.2023.02.005 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

FGF21 Counteracts Alcohol Intoxication by Activating the Noradrenergic Nervous System

ARTICLE PUBLICATION DATE

7-Mar-2023