Does current shellfish anti-predator gear curb ‘crunching’ rays?

Study assesses efficacy of clamming industry anti-predator materials on whitespotted eagle rays

Peer-Reviewed Publication

FLORIDA ATLANTIC UNIVERSITY

 

VIDEO: WHITESPOTTED EAGLE RAYS “CRUNCHING” ON CLAMS IN A LARGE OUTDOOR TANK WITH CLAMS HOUSED WITHIN A VARIETY OF ANTI-PREDATOR MATERIALS. view more 

CREDIT: FAU HARBOR BRANCH OCEANOGRAPHIC INSTITUTE

According to NOAA Fisheries, more than 80 percent of marine aquaculture production in the United States consists of bivalve mollusks such as oysters, clams and mussels. However, it’s not just humans who enjoy eating these shellfish, so do marine rays. They like to “crunch” on clams, which can sometimes take a big bite out of clammers’ profits.

Part of the process of culturing hard clams (Mercenaria mercenaria) involves deploying them in submerged bottom leases in the marine environment where clams can grow to market size. When deployed onto the clam lease, clammers incorporate a variety of anti-predator materials to protect their product, such as woven mesh netting and/or additional mesh, plastic or wire covers.

However, the effectiveness of these materials against highly mobile predators like rays has not been experimentally tested. Some rays, like the whitespotted eagle ray (Aetobatus narinari), are equipped with strong jaws, plate-like teeth and nimble pectoral fins, which make them formidable and highly maneuverable predators of clams.

Inspired by clammer reports of damaged grow-out gear presumably caused by rays, researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute in collaboration with Mote Marine Laboratory, assessed the ability of the whitespotted eagle ray to interact with clams housed within a variety anti-predator materials.

Using aerial and underwater videos, researchers assessed the rays’ responses to anti-predator materials placed within a large outdoor tank. They examined their interactions with a control plot (unprotected clams), clams inside polyester mesh clam bags (dipped in a latex net coating), and with clams under high density polyethylene (HDPE) netting or chicken wire cover netting. After the completion of each trial, researchers assessed the number of crunched clams and frequency of visits to the various randomized patches.

Results, published in the journal Aquaculture Environment Interactions, showed that rays were capable of consuming clams through bags. However, anti-predator treatments reduced clam mortality four- to tenfold compared to control plots. Double-layered (bags with cover netting) treatments had the lowest clam mortality, highlighting the utility of this type of protection in limiting ray impacts.

“Based on our findings, many of the current anti-predator grow-out strategies used in the hard clam shellfish aquaculture industry appear capable of reducing predation by large predators like whitespotted eagle rays,” said Matt Ajemian, Ph.D., senior author, an associate research professor and director of the Fisheries Ecology and Conservation Lab at FAU Harbor Branch. “In par­ticular, bag treatments with cover nettings achieved the highest clam survival rates, although it is important to note that this did not appear to completely deter rays from interacting with the gear.”

Observations from the study suggest that rays appear capable of interacting with aquaculture gear for prolonged periods, potentially diverting them from other natural feeding habitats such as sand and mud flats.

“These habitat associations could expose these sensitive animals to other risks, although we are just beginning to understand them and admittedly have a lot more to learn,” said Brianna Cahill, corresponding author, an FAU Harbor Branch marine science and oceanography graduate, and a research technician at Stony Brook University.

Throughout the course of the study, researchers confirmed that rays are capable of uprooting and manipulating hard clam aquaculture gear, as they moved treat­ments and trays within the tank throughout the course of the experiments.

“Contrary to what we expected, rays did not prefer control plots (mimicking natural conditions) over treatment plots with anti-predator gear,” said Cahill. “This suggests a real possibility that these rays are interacting with shellfish aquaculture gear in the wild, as suggested by our clamming industry partners.”

Among the vari­ety of interactions researchers observed between rays and the treatments included using their lower dental plate to dig through sediment to access clams in the control plots and to move the gear (clam bags, cover netting and trays). In addition, because HDPE netting appeared to snag on the rays’ lower dental plate, it caused them to displace the HDPE cover net­ting more than chicken wire cover netting.

Chicken wire has been used in Florida to deter pre­dation from rays because of its strength. Research has suggested that the electric field of the metal can be detected by elasmobranchs such as rays and sharks, potentially acting as an over-stimu­lant and thus, a deterrent.

“Given the frequency of interactions we observed with chicken wire in our experiment, we question whether chicken wire is a deterrent, an attractant or neutral, as it may not have a powerful enough signal to influ­ence the rays,” said Ajemian. “Still, we have more questions than we started with, and look forward to investigating this further with other species and deterrent types.”

Study co-authors are Kayla L. McCulloch, Rosenstiel School of Marine and Atmospheric Science, University of Miami; Breanna C. DeGroot, research coordinator, Fisheries Ecology and Conservation Lab at FAU Harbor Branch; and Kim Bassos-Hull, senior biologist at Mote Marine Laboratory.

Funding for these experiments was provided by the Aquaculture Specialty License Plate Fund (AWD-002112) administered by the Har­bor Branch Oceanographic Institute Foundation.

- FAU -

About Harbor Branch Oceanographic Institute:
Founded in 1971, Harbor Branch Oceanographic Institute at Florida Atlantic University is a research community of marine scientists, engineers, educators and other professionals focused on Ocean Science for a Better World. The institute drives innovation in ocean engineering, at-sea operations, drug discovery and biotechnology from the oceans, coastal ecology and conservation, marine mammal research and conservation, aquaculture, ocean observing systems and marine education. For more information, visit www.fau.edu/hboi.

 

About Florida Atlantic University:
Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 30,000 undergraduate and graduate students across six campuses located along the southeast Florida coast. In recent years, the University has doubled its research expenditures and outpaced its peers in student achievement rates. Through the coexistence of access and excellence, FAU embodies an innovative model where traditional achievement gaps vanish. FAU is designated a Hispanic-serving institution, ranked as a top public university by U.S. News & World Report and a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. For more information, visit www.fau.edu.

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JOURNAL

Aquaculture Environment Interactions

DOI

10.3354/aei00452 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Breaking bags and crunching clams: assessing whitespotted eagle ray interactions with hard clam aquaculture gear

Drinking, drug use and driving increased in West Virginia during COVID-19, WVU study finds

Peer-Reviewed Publication

WEST VIRGINIA UNIVERSITY

 

IMAGE: RESEARCH OUT OF THE WVU SCHOOL OF PUBLIC HEALTH FOUND THAT DRINKING, DRUG USE AND DRIVING INCREASED AMONG PATIENTS BEING TREATED FOR MOTOR VEHICLE COLLISION INJURIES AT A WEST VIRGINIA TRAUMA CENTER DURING THE COVID-19 PANDEMIC. view more 

CREDIT: WVU ILLUSTRATION/AIRA BURKHART

One West Virginia trauma center saw an uptick in alcohol and drug use by patients treated for motor vehicle collision injuries during the COVID-19 pandemic, according to a West Virginia Universitystudy. More specifically, researchers found patients were using a greater number of drugs, including cannabinoids, opioids and stimulants during the pandemic than prior to its onset.

The study was published in Injury Epidemiology, an online peer-reviewed journal focusing on injury prevention and control. Toni Marie Rudisill, assistant professor in the WVU School of Public Health, led the research team that included pre-med student Lucie Steinmetz, of Moon, Pennsylvania, and Dr. James Bardes, assistant professor in the Department of Surgery’s Division of Trauma, Acute Care Surgery and Surgical Critical Care.

The patients were treated at Jon Michael Moore Trauma Center in Morgantown, one of two Level 1 trauma centers in West Virginia.

As stress levels increased at the onset of the COVID-19 pandemic, so did the use of alcohol and drugs among drivers in urban areas, according to several studies. That prompted Rudisill and her team to see if the same held true for rural areas, particularly the Mountain State.

“It was important to determine what was happening here in West Virginia and if we were following the same trend,” Rudisill said. “Our findings may be generalizable to West Virginia. However, we are unsure if our findings would be generalizable to other rural areas.”

With support from the West Virginia Clinical and Translational Science Institute, housed at WVU, and funding from the National Institute of General Medical Sciences of the National Institutes of Health, the team set out to analyze and compare records of patients ages 18 and older who were treated for motor vehicle-related injuries during two time frames: pre-COVID-19 period — Sept. 1, 2018, to March 15, 2020, and COVID-19 period — March 16, 2020, to Sept. 30, 2021.

Throughout the study period, 1,465 patients received treatment. Patients were given a blood test to determine whether they had been using alcohol, while a urine test was conducted to see if drugs were present in the patients’ systems. Drugs included in the testing panel were cannabinoids, opioids, stimulants and depressants.

Any amount of alcohol was considered a positive test. Patients were considered drug positive if one or more non-alcohol drugs were detected. The discovery of one or more non-alcohol drugs and any amount of alcohol was deemed drug and alcohol positive. Drugs received as part of pre-hospital care were excluded from analyses to avoid misclassification of an individual who may have received the medication as part of post-collision care.

“Given our state’s rurality, it can take quite a bit of time to transport severely injured patients from the scene of a crash to a trauma center,” Rudisill said. “Patients may receive medication from emergency medical services as part of their care during transport. However, drug and alcohol tests are performed on patients when they arrive at the trauma center. It is entirely possible that a patient may have consumed an opioid before the crash, but then received one as part of their care during transport to the trauma center. For that reason, those individuals’ results would be excluded from the analysis as we would not be able to determine if the opioids in their system were taken before the crash or administered by EMS on the way to the trauma center.”

The study found that the number of drugs patients tested positive for was 31% greater during the COVID-19 period. Stimulant and opioid use significantly increased among treated patients and cannabinoid use increased marginally, while depressant use decreased over the study period.

The majority of the patients, 57%, were male and between the ages of 20 and 45. Overall, 84% were drivers of the vehicles and 72% were wearing seatbelts. Most of the crashes occurred during weekdays.

Researchers concluded that, although further studies could investigate whether drug and alcohol use among drivers in West Virginia changed after September 2021, public health interventions may be needed in the state to curb the activity.

“Getting people to stop using drugs and/or alcohol and then driving is a complex issue,” Rudisill said. “Reducing this behavior in a population often requires a combination of educational, environmental, behavioral and policy approaches to be effective.”

WVCTSI Background

WVCTSI is funded by an IDeA Clinical and Translational grant from the National Institute of General Medical Sciences (U54GM104942) to support the mission of building clinical and translational research infrastructure and capacity to impact health disparities in West Virginia.

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JOURNAL

Injury Epidemiology

DOI

10.1186/s40621-023-00415-y 

ARTICLE TITLE

Substance use in rural trauma patients admitted for motor vehicle injuries before and during the COVID-19 pandemic

How does the immune system react to altered gravity?

Parabolic flights: a simulated gravity laboratory

Peer-Reviewed Publication

UNIVERSITY OF BARCELONA

 

IMAGE: MICROGRAVITY CONDITIONS WERE GENERATED DURING A SHORT PARABOLIC FLIGHT —WITH FIFTEEN PARABOLAS— IN AN AEROBATIC FLIGHT CONDUCTED WITH THE MUDRY CAP10 AIRCRAFT. view more 

CREDIT: UNIVERSITY OF BARCELONA

Space travel has always tested the human body by the effects of the new conditions of altered gravity on biological systems. It has long been known that continuous exposure to microgravity conditions human physiology and causes effects that compromise muscular, sensory, endocrine and cardiovascular functions. But is it also risky to be exposed to altered gravity for short periods of time?

Now, a paper published in the journal Acta Astronautica examines the effects on the human immune system of microgravity generated by a parabolic flight. After a short exposure to altered gravity, there were no significant changes in the defensive capacity of blood cells in the volunteers who took part in the study. In addition, the study found no evidence of aggregation processes in erythrocytes —the cells that transport O2 and CO2 to the cardiovascular system— after the parabolic flight.

The study was coordinated by Ginés Viscor, professor at the Department of Cell Biology, Physiology and Immunology of the Faculty of Biology of the University of Barcelona, and it included the participation of experts Jordi Petriz, from the Germans Trias i Pujol Research Institute (IGTP), and Antoni Pérez-Poch, from the Technical University of Catalonia-BarcelonaTech (UPC) and the Institute of Space Studies of Catalonia (IEEC), among other authors. The first author of the study is the researcher Abril Gorgori-González (UB). It counted on the support from the Medical Service of the Safety, Health and Environment Office (OSSMA) of the UB, the Aeroclub Barcelona-Sabadell and the company Thermo Fisher Scientific.

Parabolic flights: a simulated gravity laboratory

Space travel is the ideal scenario to study the effect of microgravity on the human body. These trips make it possible to study the consequences of long-term exposure to microgravity on different astronauts simultaneously, but they require a high cost in terms of time, funding and infrastructure. Without leaving the Earth's atmosphere, it is also possible to simulate simulated gravity conditions on different platforms. For example, through parabolic flights in aircraft, which make it possible to study the effect of altered microgravity in the short term —even for a few seconds— at an affordable cost.

"Artificial platforms such as parabolic flights in aircraft provide valuable but more limited results, as they only allow the effects of altered gravity to be studied in the short term (seconds or minutes). Therefore, the profiles of physiological changes that can be recreated with parabolic flights are immediate and transitory changes that microgravity generates in the human body", says Ginés Viscor, head of the Adaptive Physiology Group: Exercise, Hypoxia and Health at the UB.

As part of the study, a 20-minute parabolic flight was conducted with the Mudry CAP10 aircraft —a 2-seat aerobatic training aircraft— during which fifteen parabolas were performed. "Each parabola allows a period of microgravity to be reached for approximately eight seconds, which is followed and preceded by hypergravity phases of about two seconds", says the researcher Antoni Pérez-Poch, from the Department of Computer Science at the UPC, and lecturer of the School of Engineering of Barcelona East (EEBE) of the UPC and the IEEC.

These parabolic flights with an aerobatic plane —a pioneering method in the world, developed in Catalonia— were operated by the Aeroclub Barcelona-Sabadell and are the result of an aeronautical research carried out in collaboration with the UPC. "This innovative technique has a good ratio of time achieved in microgravity compared to the cost of maintenance, which is very favourable compared to the greater use of aircraft, although it also has some limitations (logistical and space). In the case of parabolic flights with a larger aircraft, a more expensive operation that has been used since the beginning of the space race by agencies such as NASA or ESA (European Space Agency), up to 25 seconds per parabola could be achieved", says Pérez-Poch.

Immune function under pressure

The immediate effects of microgravity on the blood system derive from the redistribution of blood volume, blood flow and body fluids to the upper body. "Cardiovascular adaptations consist of an altered cardiovascular response causing abnormalities in body orientation and balance, poor response to orthostatic stress, decreased cardiac function and inadequate cardiovascular response to exercise", says Ginés Viscor.

One of the most vulnerable physiological systems to any change in environmental conditions is the immune system, and this is explained by its great plasticity and responsiveness to internal and external imbalances. In the scientific literature, there are still no conclusive results on the immune response to short exposure in flights with altered gravity, and in some cases the conclusions are even contradictory.

In this study, the team analysed the response of the immune system to short exposure to microgravity based on several parameters: erythrocyte and leukocyte counts, haemoglobin concentration, phagocytic capacity and oxidative metabolism.

"The results reveal that the human blood samples’ exposure to altered gravity conditions in parabolic flight did not involve negative effects in relation to samples that were left parallelly on the ground during the experimental study. There are also no significant changes in peripheral blood cell counts", says Jordi Petriz (IGTP).

"Except for the monocytes —a type of leukocyte— no significant differences have been observed in the functionality of immune cells in terms of either their oxidative metabolism or their phagocytic capacity", says researcher Abril Gorgori-González (UB). "Hypothetically, if there were changes in the functionality of leukocytes when exposed to an altered gravity, the immune function and defence against external infections or tumour processes would also be compromised”.

The team has applied the technique of flow cytometry with acoustic focusing with little manipulation of the volunteers' blood samples. According to the authors, the sample limitation typical of acrobatic flight studies —with logistical constraints— does not allow general conclusions to be drawn. Therefore, the goal now is to continue research on the human immune system with other microgravity simulation platforms to study physiological alterations, avoid complications and anticipate risk situations.

Space tourist warning

Space tourism is an activity of great economic interest for some business sectors. However, one of the main differences between space tourists and astronauts is the physical and psychological preparation prior to the trip.

"Altered gravity or the constant lack of gravity is one of several changes in the environment faced by these space travellers. The human body has evolved under the conditions of Earth's gravity and is not adapted to the absence of this attractive force. In space travel, other factors such as ionising radiation, constant noise, isolation, confinement, a total distortion of circadian rhythms and short exposure to extreme temperatures during the return to the atmosphere have to be considered", the experts warn.

"Long-term metabolic, osteoporosis and ophthalmological problems have also been described. Although the effect of space travel on untrained space travellers has not been studied, it is possible that all the stressors of the physical environment could negatively affect the health of space tourists. Therefore, for the time being, 'outer space visits' are designed to be of short duration", the team concludes.

  

The volunteers' blood samples were exposed to altered gravity conditions in parabolic flight.

These parabolic flights with an aerobatic plane —a pioneering method in the world, developed in Catalonia— were operated by the Aeroclub Barcelona-Sabadell.

The study has applied the technique of flow cytometry with acoustic focusing with little manipulation of the volunteers' blood samples.

The human blood samples’ exposure to altered gravity conditions in parabolic flight did not involve negative effects in relation to samples that were left parallelly on the ground during the experimental study.

CREDIT

UNIVERSITY OF BARCELONA

JOURNAL

Acta Astronautica

DOI

10.1016/j.actaastro.2023.02.012 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Effects of rapid gravity load changes on immunophenotyping and leukocyte function of human peripheral blood after parabolic fligh

First visible-light induced simultaneous cleavage of C-C and C-N bonds with silver-modified polyoxometalate photocatalyst, researchers report

Peer-Reviewed Publication

TSINGHUA UNIVERSITY PRESS

 

IMAGE: A CHINESE RESEARCH TEAM SYNTHESIZED SILVER-MODIFIED POLYOXOMETALATES AND ACHIEVED THE FIRST EXAMPLE OF VISIBLE-LIGHT-PROMOTED SIMULTANEOUS CLEAVAGE OF C-C BOND AND C-N BOND CATALYZED BY A POM PHOTOCATALYST. view more 

CREDIT: POLYOXOMETALATES, TSINGHUA UNIVERSITY PRESS

Cracking carbon bonds is a notoriously difficult problem, but it may hold the key to generating greener, more sustainable chemicals. A Chinese research team achieved the first visible-light-promoted simultaneous cleavage of carbon-carbon and carbon-nitrogen bonds via a silver-modified polyoxometalate photocatalyst, unlocking avenues for applications like carbon-neutral alternatives for fossil fuels. The researchers’ findings were published on March 3 in Polyoxometalates.

 

Inexpensive and highly efficient, photocatalytic technology is being used to solve increasingly serious environmental pollution problems. Polyoxometalates (POMs) are a class of metal-oxide clusters with unique physicochemical properties that make them particularly effective in the field of photocatalysis — using light energy to drive a chemical reaction.

 

Thanks to the stability of their molecular structures and reversible redox properties, POMs as photocatalysts can break down organic pollutants in wastewater and reduce carbon dioxide. POMs can also catalyze simple organic transformations, including bond formation reactions of carbon-carbon (C-C) and carbon-nitrogen (C-N).

 

However, most of the POMs can only work using ultraviolet light.

 

“It is of great significance to design and synthesize new visible-light-promoted POMs photocatalysts and explore their potential in new organic reactions,” said Shujun Li, study author from Henan Normal University.

 

With this goal, Li and colleagues explored synthesizing visible-light promoted POMs photocatalysts to wield in selective, simultaneous carbon bond cleaving.

 

“C-C and C-N bonds are the most widespread and fundamental bonds existing in organic compounds,” said Li. “Selectively catalytic cleavage of C–C bonds or C–N bonds for chemical transformations is an important topic in synthetic chemistry and has become one of the most attractive but challenging tasks.”

 

Chemists have pursued this objective over the past few decades because cracking these stubborn bonds might be key to finding valuable new chemicals or more sustainable ways to create known ones. As such, they have developed a variety of catalytic systems to cleave C–C bonds or C–N bonds separately. However, cleavage of both C–C and C–N bonds in a single organic transformation is a challenging objective.

 

“Few examples of simultaneous cleavage of C-C and C-N bonds in one substrate molecule have been reported so far,” said Li.

 

To make things more complicated, rapid, simultaneous cleavage of these types of bonds requires harsh reaction conditions such as high temperatures and strong oxidizing or initiating agents.

 

The research team combined niobium (Nb)/tungsten (W) mixed-addendum POM and silver (Ag) ion to obtain a silver-modified polyniobotungstate (Ag-Nb/W).

 

Ag-Nb/W showed strong absorption in the visible region, which encouraged the researchers to study its catalytic activity under visible light. The researchers’ investigations included analysis of substrate scope and bounds of conditions for best performance, as well as the stability and reusability of Ag-Nb/W.

 

The results indicated that the synthesis and structure of Ag-Nb/W supports efficient catalysis to simultaneously cleave C–C and C–N bonds under visible light in mild conditions. In addition, Ag-Nb/W could be reused up to six times without a reduction in the catalytic activity.

 

“To the best of our knowledge, this is the first example of visible-light-promoted simultaneous cleavage of C-C bond and C-N bond catalyzed by a POM photocatalyst, which coincides with the social demand for green chemistry and sustainable development,” said Li.

 

This work provides a feasible revelation for designing new visible-light-induced polyoxometalates photocatalysts to be used in organic reactions involving the cleavage of C–C and C–N bonds, said Li.

 

In future steps, the researchers plan to combine this compound with other solid carriers to design a dispersed and more stable photocatalytic material suitable for its applications in photocatalysis.

 

This work was supported by the National Natural Science Foundation of China and the Program for Science & Technology Innovation Talents in Universities of Henan Province.

 

Other contributors include Na Li, Gang Li, Yubin Ma, Mengyao Huang, Qingchun Xia, Qianyi Zhao and Xuenian Chen from Henan Normal University. Chen is also affiliated with Zhengzhou University.

 

##

 

About Polyoxometalates  

 

Polyoxometalates is a peer-reviewed, international and interdisciplinary research journal that focuses on all aspects of polyoxometalates, featured in rapid review and fast publishing, sponsored by Tsinghua University and published by Tsinghua University Press. Submissions are solicited in all topical areas, ranging from basic aspects of the science of polyoxometalates to practical applications of such materials. Polyoxometalates offers readers an attractive mix of authoritative and comprehensive Reviews, original cutting-edge research in Communication and Full Paper formats, Comments, and Highlight.

 

About SciOpen 

 

SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.

 

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JOURNAL

Polyoxometalates

DOI

10.26599/POM.2023.9140024 

ARTICLE TITLE

A silver-modified polyniobotungstate for visible-light-induced simultaneous cleavage of C-C and C-N bonds

Flat, pancake-sized metalens images lunar surface in an engineering first

Penn State-led research team creates the first ultrathin, compact metalens telescope capable of imaging far-away objects

Peer-Reviewed Publication

PENN STATE

 

IMAGE: ELECTRICAL ENGINEERING RESEARCHERS CAPTURED IMAGES OF THE LUNAR SURFACE USING THEIR LARGE-APERTURE METALENS TELESCOPE. view more 

CREDIT: XINGJIE NI

UNIVERSITY PARK, Pa. — Astronomers and amateurs alike know the bigger the telescope, the more powerful the imaging capability. To keep the power but streamline one of the bulkier components, a Penn State-led research team created the first ultrathin, compact metalens telescope capable of imaging far-away objects, including the moon. 

Metalenses comprise tiny, antenna-like surface patterns that can focus light to magnify distant objects in the same way as traditional curved glass lenses, but they have the advantage of being flat. Though small, millimeters-wide metalenses have been developed in the past, the researchers scaled the size of the lens to eight centimeters in diameter, or about four inches wide, making it possible to use in large optical systems, such as telescopes. They published their approach in Nano Letters. 

“Traditional camera or telescope lenses have a curved surface of varying thickness, where you have a bump in the middle and thinner edges, which causes the lens to be bulky and heavy,” said corresponding author Xingjie Ni, associate professor of electrical engineering and computer science at Penn State. “Metalenses use nano-structures on the lens instead of curvature to contour light, which allows them to lay flat.” 

That is one of the reasons, Ni said, modern cellphone camera lenses protrude from the body of the phone: the thickness of the lenses take up space, though they appear flat since they are hidden behind a glass window.

Metalenses are typically made using electron beam lithography, which involves scanning a focused beam of electrons onto a piece of glass, or other transparent substrate, to create antenna-like patterns point by point. However, the scanning process of the electron beam limits the size of the lens that can be created, as scanning each point is time-consuming and has low throughput.  

To create a bigger lens, the researchers adapted a fabrication method known as deep ultraviolet (DUV) photolithography, which is commonly used to produce computer chips.  

“DUV photolithography is a high-throughput and high-yield process that can produce many computer chips within seconds,” Ni said. “We found this to be a good fabrication method for metalenses because it allows for much larger pattern sizes while still maintaining small details, which allows the lens to work effectively.”

The researchers modified the method with their own novel procedure, called rotating wafer and stitching. Researchers divided the wafer, on which the metalens was fabricated, into four quadrants, which were further divided into 22 by 22 millimeter regions — smaller than a standard postage stamp. Using a DUV lithography machine at Cornell University, they projected a pattern onto one quadrant through projection lenses, which they then rotated by 90 degrees and projected again. They repeated the rotation until all four quadrants were patterned.

“The process is cost-effective because the masks containing the pattern data for each quadrant can be reused due to the rotation symmetry of the metalens,” Ni said. “This reduces the manufacturing and environmental costs of the method.” 

As the size of the metalens increased, the digital files required to process the patterns became significantly larger, which would take a long time for the DUV lithography machine to process. To overcome this issue, the researchers compressed the files using data approximations and by referencing non-unique data. 

“We utilized every possible method to reduce the file size,” Ni said. “We identified identical data points and referenced existing ones, gradually reducing the data until we had a usable file to send to the machine for creating the metalens.” 

Using the new fabrication method, the researchers developed a single-lens telescope and captured clear images of the lunar surface — achieving greater resolution of objects and much farther imaging distance than previous metalenses. Before the technology can be applied to modern cameras, however, researchers must address the issue of chromatic aberration, which causes image distortion and blurriness when different colors of light, which bend in different directions, enter a lens. 

“We are exploring smaller and more sophisticated designs in the visible range, and will compensate for various optical aberrations, including chromatic aberration,” Ni said.

In addition to Ni, coauthors include Lidan Zhang, Shengyuan Chang, Xi Chen, Yimin Ding, Md Tarek Rahman and Yao Duan, all current or former Penn State graduate students in electrical engineering. Mark Stephen, from the NASA-Goddard Space Flight Center, also contributed. 

The NASA Early Career Faculty Award, the United States Office of Naval Research and the National Science Foundation supported this work.  

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JOURNAL

Nano Letters

DOI

10.1021/acs.nanolett.2c03561 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

High-Efficiency, 80 mm Aperture Metalens Telescope

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