A new scheme for gravitational-wave detection provides new capabilities to reduce the noise in these high-precision measurements.
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Hippocampal ripples and replay reveal how brain recombines past knowledge for flexible planning
When facing new situations or problems, humans typically rely on knowledge they acquired in the past. Specifically, neuroscience studies suggest that the brain reorganizes past experiences and previously acquired knowledge, creating mental frameworks that can help humans to solve the problems they are facing. The recombination of past knowledge into new mental structures also allows humans to flexibly plan future actions in changing environments. Past studies suggest that two key brain regions contribute to this process, the hippocampus and the medial prefrontal cortex (mPFC).
The hippocampus is a brain structure that plays a key role in the formation of memories and spatial navigation. The mPFC, on the other hand, is known to support decision-making, planning, reasoning and the integration of information.
Researchers at Beijing Normal University, the Chinese Academy of Medical Sciences, University College London (UCL) and other institutes recently set out to investigate how the hippocampus and mPFC work together to combine past knowledge into new configurations. Their findings, published in Nature Neuroscience, suggest that this process is supported by brief bursts of high-frequency neural activity in the hippocampus, called hippocampal ripples, and the replay (i.e., re-activation) of past experiences in the brain.
Physicists create hybrid light-matter particles that interact strongly enough to compute
Eighty years ago, Penn researchers J. Presper Eckert and John Mauchly launched the age of electronic computing by harnessing electrons to solve complex numerical problems with ENIAC, the world’s first general-purpose electronic computer. Today, that same architecture still underlies general computing, but electrons are beginning to show their limits. Because they carry a charge, they lose energy as heat, encounter resistance as they move through materials, and become harder to manage as chips incorporate more transistors and handle larger volumes of data.
With artificial intelligence pushing today’s hardware to process, move, and cool more, Penn physicists led by Bo Zhen in the School of Arts & Sciences are looking to the electron’s massless counterpart, the photon, to shoulder more of the load.
“Because they are charge-neutral and have zero rest mass, photons can carry information quickly over long distances with minimal loss, dominating communications technology,” explains Li He, co-first author of a paper published in Physical Review Letters and a former postdoctoral researcher in the Zhen Lab. “But that neutrality means they barely interact with their environment, making them bad at the sort of signal-switching logic that computers depend on.”
Sustainable chemistry: Iron substitutes noble metals in catalytic reactions
The production of many products used in everyday life and in industry, such as pharmaceuticals, plastics, and coatings, requires chemical catalysts, often expensive noble metals with limited availability. Researchers at the Karlsruhe Institute of Technology (KIT) are now presenting the first air-stable iron compound, which enables the direct use of iron(I) for catalysis and, unlike previous methods, does not require strong reducing agents. A first test yielded active iron catalysts.
The study, “A Simple, Air Stable Single-Ion Source of Iron(I),” is published in the Journal of the American Chemical Society.
Catalysts are required to speed up chemical reactions or even make them possible at all. The catalysts generally used in industry are noble metals, such as rhodium, iridium, or palladium. They are highly effective for many applications, but at the same time expensive and rare.
A hidden threshold enables tunable control of liquid crystal helices for energy-efficient technologies
Liquid crystals are an integral part of modern technology, ranging from displays to advanced sensory systems. In a study published in Scientific Reports, researchers from the Institute of Experimental Physics of the Slovak Academy of Sciences (IEP SAS) in Košice, in collaboration with international partners, have demonstrated how minute changes in material composition can achieve precise control over behavior in electric and magnetic fields.
The research focused on cholesteric liquid crystals, which naturally form spiral (helical) structures. These structures provide unique optical properties used in displays, smart windows, and virtual reality devices.
The team investigated how the addition of a specific substance, a chiral dopant, affects the “unwinding” process of this helix.
Single-molecule RNA mapping may reveal how shape shifts steer health and disease
Researchers from A*STAR Genome Institute of Singapore (A*STAR GIS) have developed a new method to study individual RNA molecules and reveal how their structures influence gene regulation, a fundamental process that affects how cells function in health and disease. Their work was published in Nature Methods.
RNA is best known for carrying genetic instructions from DNA to make proteins. However, RNA does more than act as a messenger. Like a string that can bend, fold and interact with other molecules, RNA can adopt different shapes that affect how it behaves in the cell. These shapes can influence how efficiently proteins are produced, how long RNA molecules last, and how diseases such as viral infections progress.
Until now, studying these structures in detail has been difficult because RNA is highly flexible and dynamic. Most existing methods only provide an average picture across many RNA molecules, making it harder to see how individual RNA molecules may fold differently, even when they come from the same gene.
Exploiting interfacial ionic mobility to make heat-moldable nanoparticle aggregates
If you have ever warped a cheap plastic cup by pouring coffee into it, then you have witnessed thermoplasticity in action. Thermoplasticity is the ability of a material to become pliable under heating. In industry, thermoplasticity is exploited to form materials into complex shapes using heat. However, some materials, such as aggregates of nanoparticles, are not thermoplastic and cannot be easily processed without affecting their particle morphology and properties.
However, researchers at The University of Osaka have been able to use heat to shape nanoparticle aggregates, specifically cellulose nanofibers (CNFs) derived from wood pulp. This exciting advance, showcasing the mechanical and thermal potential of nanoparticles, is published in Science Advances.
Ultra-thin membrane enables high-efficiency hydrogen fuel cells for transport and industry
Engineers have developed a new ultra-thin membrane that allows fuel cells to operate more efficiently at high temperatures by enabling proton transport without water, overcoming a key limitation in clean energy technologies.
The breakthrough, reported in Science Advances, could expand the use of fuel cells in transport, heavy industry, and future clean energy systems.
Fuel cells convert chemical energy directly into electricity, producing water and heat as the main by-products. They are already used in hydrogen-powered vehicles, backup power systems for hospitals and data centers, and space missions where lightweight, reliable energy is essential.
Seeing the invisible: The limits of two-photon vision
Near-infrared light is invisible to humans. And yet, under the right conditions, the human eye can perceive it. Researchers from Poland’s International Center for Translational Eye Research (ICTER) have now shown that the efficiency of this phenomenon depends not only on the laser pulse itself, but also on two highly specific factors: the beam diameter and the precise focusing of light on the retina. The research is published in the journal Optics Letters.
In everyday life, we see visible light—wavelengths detected by the photoreceptors of the retina. Near-infrared light lies outside this range, which is why it normally remains invisible to us. However, for several years, scientists have known of an exception.
This exception is known as two-photon vision. In this phenomenon, a photopigment in the retina absorbs two infrared photons almost simultaneously. Each photon individually carries too little energy to trigger visual perception, but together they can initiate the process of vision. This is why, under certain conditions, humans can “see” radiation that theoretically should remain invisible.
Sunlight-powered generation of correlated photon pairs
Pairs of correlated or entangled photons are a foundational resource in quantum optics. They are most commonly produced through spontaneous parametric down-conversion (SPDC), a nonlinear optical process that typically relies on a stable, coherent laser to pump a nonlinear crystal. Because of this requirement, SPDC has long been viewed as impractical without laboratory-grade laser systems.
Recent studies have shown that fully coherent light is not strictly necessary: Partially coherent sources can also drive SPDC, with their coherence properties transferred to the generated photon pairs. This insight raises a natural and intriguing question—can sunlight, the most abundant natural light source, be used to generate correlated photon pairs?
Using sunlight for SPDC presents clear challenges. Sunlight collected from the ground is inherently unstable, with continuous changes in intensity, angle, and position that interfere with the precise illumination and photon detection required for SPDC experiments. At the same time, sunlight offers a compelling advantage: it removes dependence on lasers and external power sources, opening possibilities for photon-pair generation in remote or extreme environments.