For the first time, researchers have successfully controlled and observed Kelvin waves in superfluid helium-4, marking a significant step in understanding energy dissipation in quantum systems. The study has provided a controlled method to excite these helical waves, which had previously only been observed in unpredictable conditions. The research opens new possibilities for studying quantised vortices and their role in energy transfer at the quantum level.

Controlled Excitation of Kelvin Waves

According to the study published in Nature Physics, also available on arXiv, Kelvin waves—first described by Lord Kelvin in 1880—are helical disturbances that travel along vortex lines in superfluid systems. These waves play a crucial role in energy dissipation within quantum fluids but have remained difficult to study due to the challenges of controlled excitation.

Associate Professor Yosuke Minowa from Kyoto University, the lead author of the study, told Phys.org that the breakthrough occurred unexpectedly. An electric field was applied to a nanoparticle decorating a quantised vortex with the intention of moving the structure. Instead, the vortex core exhibited a distinct wavy motion, leading researchers to shift their focus toward controlled Kelvin wave excitation.

Superfluid Properties and Quantum Vortex Behaviour

Superfluid helium-4, which exhibits quantum effects at macroscopic scales when cooled below 2.17 Kelvin, has no viscosity, allowing it to flow without friction. This unique state prevents energy from dissipating as heat, leading to the formation of Kelvin waves when disturbances occur in the vortex lines of the fluid. The research team demonstrated that these waves, rather than traditional fluid turbulence, provide an essential mechanism for energy transfer in superfluid systems.

Nanoparticles Used for Wave Visualisation

To track the motion of Kelvin waves, the researchers introduced silicon nanoparticles into superfluid helium-4 at 1.4 Kelvin by directing a laser at a silicon wafer submerged in the fluid. Some nanoparticles became trapped within vortex cores, making them visible under controlled conditions. A time-varying electric field was then applied, forcing oscillations in the trapped particles and generating a helical wave along the vortex.

Experiments were conducted across different excitation frequencies ranging from 0.8 to 3.0 Hertz. A dual-camera system allowed for three-dimensional reconstruction of the wave’s motion, confirming its helical nature.

Experimental Confirmation and Future Research

Prof. Minowa explained to Phys.org that proving the observed phenomenon was indeed a Kelvin wave required an in-depth analysis of dispersion relations, phase velocity, and three-dimensional dynamics. By reconstructing the vortex’s motion in 3D, the researchers provided direct evidence of the wave’s handedness, confirming its left-handed helical structure—something never experimentally demonstrated before.

To validate their findings, the team developed a vortex filament model, which simulated Kelvin wave excitation under similar conditions. These simulations confirmed that forced oscillations of a charged nanoparticle generated helical waves in both directions, aligning with experimental results.

The study introduces a new approach for studying Kelvin waves in superfluid helium, offering insights into the mechanics of quantised vortices. Future research may explore the nonlinearity and decay processes of Kelvin waves, potentially revealing further details about quantum fluid dynamics.

The United States Food and Drug Administration (FDA) has approved suzetrigine, a non-opioid painkiller, for short-term pain management. This approval marks the first time in over two decades that a new pain relief mechanism has been introduced. Suzetrigine, which selectively targets sodium channels on pain-sensing neurons, has been developed as an alternative to opioids, which have been linked to addiction and overdose crises. The drug is expected to provide pain relief similar to opioids but without the associated risks of dependency, sedation, or overdose.

Targeting Sodium Channels for Pain Relief

According to research presented at a major anesthesiology conference last year, suzetrigine, now branded as Journavx, works by blocking the NaV1.8 sodium channel subtype, which plays a key role in transmitting pain signals. Unlike traditional sodium channel-blocking drugs like lidocaine, which act on all nine subtypes indiscriminately, suzetrigine is designed to target pain-sensing neurons specifically. This selectivity reduces side effects and allows the drug to be taken orally rather than requiring local application.

Clinical Trials and Effectiveness

In clinical trials, more than 80% of participants reported effective pain relief after surgery or injury. Trials on individuals undergoing procedures such as bunion removal and tummy tucks showed that suzetrigine provided pain relief comparable to opioid-based regimens, with fewer side effects. Paul White, an anesthesiologist at Cedars-Sinai Medical Center, stated to Nature, that increasing non-opioid options could significantly reduce opioid dependency.

Challenges and Future Prospects

Suzetrigine has been priced at $15.50 per pill, a cost that remains higher than generic opioids but is considered cost-effective given the expenses associated with opioid addiction treatment. While its effectiveness in chronic pain conditions remains uncertain, pharmaceutical companies are advancing similar drugs targeting sodium channels, aiming to expand non-opioid pain relief options.

Polar bears rely on their thick fur and blubber to survive in the Arctic, but recent research has revealed that their fur also plays a crucial role in preventing ice accumulation. Unlike other cold-weather animals, which rely on structural adaptations in feathers or fur, polar bears benefit from a natural oil that stops ice from sticking. The discovery sheds light on how these animals remain stealthy while hunting and could lead to the development of eco-friendly anti-icing materials across various industries.

Study Identifies Oil as Key to Ice Resistance

According to a study published in Science Advances, researchers investigated whether the anti-icing effect of polar bear fur was due to its structure or chemical composition. Bodil Holst, a physicist at the University of Bergen, initially examined the microscopic structure of the fur, finding it similar to human hair. This led to further tests on the role of fur oil in preventing ice formation.

Chemist Julian Carolan from Trinity College Dublin collaborated on experiments that involved freezing blocks of ice onto different materials, including polar bear fur, human hair, and ski skins treated with fluorocarbons. The study found that unwashed polar bear fur was as effective as high-performance ski coatings, while washed fur required significantly more force to remove ice, highlighting the critical role of its natural oils.

Implications for Future Anti-Icing Technologies

Pirouz Kavehpour, a mechanical and aerospace engineer at the University of California, Los Angeles, noted to science.org that polar bears differ from penguins, whose feather structure provides anti-icing benefits. The findings could inspire new coatings for skis, aircraft, and other surfaces, replacing synthetic chemicals with environmentally friendly alternatives. Researchers believe the specific ratio of glycerols and waxes in polar bear fur could be key to developing sustainable solutions.