Improved measurements of an electronic transition in helium-4 atoms constrain the size difference between helium-4 and helium-3 nuclei.
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Ultrasound propagation in porous rocks: Theory identifies three distinct wave modes
Ultrasound-based irradiation of rock formations has attracted considerable attention as a technique for enhancing heavy-oil (high-viscosity crude oil) recovery from deep underground reservoirs. However, a unified theoretical framework for wave propagation and energy dissipation in these formations remains lacking because water coexists with heavy oil within rock pores, and gas bubbles in the water respond dynamically to ultrasonic excitation, thereby creating a complex system.
Conventional theories typically treat oil as a purely viscous (Newtonian) fluid or assume frequency ranges markedly below the ultrasonic regime. Consequently, these theories inadequately capture oil viscoelasticity and the influence of bubble oscillations in the ultrasonic regime.
Researchers at University of Tsukuba have developed a theoretical framework to clarify the propagation of ultrasonic waves through complex materials such as rocks containing mixtures of oil, water, and gas bubbles. The work extends previous low-frequency models and constructs a theoretical framework applicable to ultrasonic frequencies by incorporating three notable elements into a unified system of equations: (i) heavy-oil viscoelasticity, (ii) dynamic capillary pressure at fluid-fluid interfaces, and (iii) oscillations of gas bubbles dispersed in water induced by ultrasonic pressure fluctuations.
Brain enzyme caught doing something unexpected—it builds polysialic acid on itself
A chance discovery at Nagoya University in Japan has shown that a well-known brain enzyme has a hidden ability: It builds a sugar chain on itself, becomes secreted from the cell and deactivates, then switches on outside the cell once the chain is removed. The finding, published in the Journal of Biological Chemistry, overturns a decades-old assumption about how polysialic acid, a sugar chain critical for brain development and function, is produced and shows a new way an enzyme can regulate its own activity.
The human brain is covered in sugar chains, or glycans, molecular structures that coat cells and regulate how they communicate. One of the most important is polysialic acid, a long chain found mainly in the brain.
Polysialic acid keeps brain cells from adhering too tightly to each other and binds to growth factors and neurotrophins to regulate the presentation of their receptors. Through this, it plays a key role in learning, memory and neural development. Importantly, these sugar chains change rapidly in response to brain activity. The ability to restore them quickly is thought to be essential for normal brain function.
Hidden electric space waves are quietly cleaning Earth’s ‘killer’ electrons
High above our heads, a silent battle is unfolding within Earth’s magnetic shield. For decades, scientists have tracked “killer electrons”—ultrafast particles capable of piercing satellite armor and endangering astronauts as they zip through the Van Allen radiation belts. While we knew these dangerous particles eventually leak out of the belts and into the atmosphere, the primary mechanism “cleaning” the highest-energy electrons has remained a persistent mystery of space weather.
Now, a study published in Geophysical Research Letters has uncovered the culprit by diving into three years of NASA’s Van Allen Probes data. Led by Lixian Yang and a team of researchers, the study identifies a hidden population of chorus waves that defies standard physics models.
Unlike typical space waves that are mostly magnetic, these highly oblique quasi-electrostatic (HOQE) waves possess an electric field so powerful it dominates their character. This unique electric punch allows them to knock electrons with energies up to 2 MeV out of orbit and into the atmosphere, scattering them with a force far more potent than any previous model predicted.
Trace additive unlocks faster bioplastic biodegradation without losing transparency or strength
Compostable plastics could be part of a solution to the world’s plastic waste problem. But currently these materials need industrial composting facilities to break down. In a step toward making a home-compostable plastic, researchers reporting in ACS Central Science have augmented polylactide (PLA)—a widely used biobased and compostable polymer—with a small amount of an additive. Tests show it helps the material degrade substantially faster without sacrificing critical qualities like strength or transparency.
“PLA can be made to degrade much more effectively under practical composting conditions without compromising the properties that make it useful in everyday applications,” says Marc Hillmyer, a corresponding author of the paper.
PLA is currently found in products such as food packaging, textiles and biomedical devices, and it accounts for roughly two-thirds of total bio-based and biodegradable plastics production worldwide. “Composting is considered one of the most effective end-of-life strategies for PLA products, especially food-contaminated single-use products, because it eliminates the need for additional sorting and washing processes,” says Hillmyer. This process converts organic waste into environmentally innocuous products such as small organic acids.
Spin-orbit torque hardware creates random keys and reveals unauthorized access attempts
The information exchanged by modern devices is typically protected by cryptographic techniques, approaches that convert readable data into scrambled, unreadable code that can only be deciphered by authorized parties or devices. To descramble encrypted data, devices or accounts need access to randomly generated cryptographic keys, unique, randomly generated sequences of binary code, letters or numbers that are essential for encrypting or decrypting data.
To detect cyberattacks, most traditional hardware security systems monitor the power consumption, electrical signals or other changes in devices. However, cyberattackers have devised effective techniques that sometimes allow them to bypass these systems’ defenses.
Researchers at Huazhong University of Science and Technology and Hubei University recently introduced a new hardware security system based on spin-orbit torque (SOC) devices, technologies that operate by leveraging both electrical charge and a quantum property known as electron spin.
Before tangles kill neurons, tau-linked transport defects may be reversible
Neurons, specialized cells that transmit information across the nervous system, communicate with each other via projections known as axons. These microscopic, cable-like structures are also used to deliver proteins, signaling molecules and other cargo across different areas of the brain.
Past studies have found that this transfer of cargo, also known as axonal transport, is impaired in models of diseases known as tauopathies. Tauopathies include Alzheimer’s disease (AD), frontotemporal dementia and other neurodegenerative diseases associated with the pathological accumulation of a protein called tau inside neurons, which forms structures known as tau tangles.
Researchers at the UK Dementia Research Institute at University College London (UK DRI, UCL) and the UCL Queen Square Institute of Neurology recently carried out a study in mice aimed at investigating the link between tauopathies and axonal transport. Their findings, published in Nature Neuroscience, show that axonal transport defects prompted by the aggregation of pathological tau could be reversible, identifying a possible strategy for reversing this damage during the early stages of neurodegeneration.
Restless legs syndrome—zebrafish reveal a cerebellar connection
An irresistible urge to move the legs or other areas, often accompanied by unpleasant sensations at night or during rest: Restless Legs Syndrome (RLS) affects millions of people worldwide. Despite being one of the most common sleep-related disorders, its biological causes remain poorly understood.
Researchers led by Professor Alex Schier at the Biozentrum of the University of Basel have discovered new clues about the underlying brain regions and mechanisms. Surprisingly, their findings come from an unlikely model organism: larval zebrafish.
“Studies in humans have implicated many different brain regions, but it remains unclear how they relate to RLS,” says Schier. “Our work highlights possible contributions from the cerebellum, a brain region crucial for coordinating movement.”
Fermi mission uncovers possible sibling supernova remnants
A new study of two supernova remnants, the debris left behind after stars explode, suggests the explosions came from stellar siblings that once orbited each other. The first star’s detonation sent its binary companion hurtling through space, and then, after traveling for thousands of years, the surviving star blew up, too.
“Using 16 years of data from NASA’s Fermi Gamma-ray Space Telescope, our analysis uncovered gamma rays associated with a supernova remnant that was hidden in the glare of its neighbor, the Jellyfish Nebula, one of the brightest gamma-ray-emitting supernova remnants known,” said Miltiadis Michailidis, a postdoctoral fellow in the physics department at Stanford University in California. “There are so many striking connections between the two remnants that we conclude they’re likely related, giving us the first known example of a binary system where both stars have undergone supernova explosions.”
Michailidis presented the findings Wednesday at the 248th meeting of the American Astronomical Society in Pasadena, California. A paper describing the results will appear in a future edition of Nature Communications.
Out-of-equilibrium cesium atoms reveal fractional Fermi seas, exposing new critical quantum phase
In a new study published in Physical Review Letters, a team from the Nägerl group, together with theory collaborator Alvise Bastianello from the CNRS and the Université Paris-Dauphine, demonstrates that highly unusual quantum states known as “fractional Fermi seas” can be quantum engineered.
By driving quantum particles—here, ultracold cesium atoms under one-dimensional confinement—far out of equilibrium through cyclic changes of the particle interaction, a novel critical phase of matter emerges, going beyond what is known from the celebrated Tomonaga-Luttinger liquid theory. The new publication serves as the theoretical companion to, and foundation for, recent experimental work in the group of Hanns-Christoph Nägerl at the Department of Experimental Physics.
Usually, particles in the quantum world follow strict rules about how they organize themselves at low temperatures. As Bastianello explains, “Fermions, for instance, stack neatly into the available energy states to form the so-called ‘Fermi sea.’ But what happens if one forces interacting atoms to continuously cycle through extreme conditions, smoothly shifting them from strongly repelling each other to strongly attracting each other?”