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Category: particle physics

Quantum shell structure reveals new rule for proton-neutron pairing inside nuclei

Nuclear physicists used a little magic in their latest experiment conducted at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, and the result has revealed surprising new information about the behavior of protons and neutrons inside the atom’s nucleus. Specifically, the research revealed another requirement that determines how protons and neutrons pair up.

The result is reported in the journal Nature.

The research involves short-range correlations (SRCs). This phenomenon describes when a proton and a neutron, or two protons or two neutrons, briefly pair up inside the nucleus.

Water-wave tweezers steer tiny ‘surfers’ without touching them

Summer brings with it the sight of surfers moving seamlessly across wave crests, with ocean waters carrying them along coastlines. A team of scientists has now created a similar phenomenon—with small objects rather than surfers—that can be controlled by humans rather than by nature.

Through a series of experiments on a replicated mini-beach, NYU researchers show how water waves can be used to move floating objects or hold them firmly in place—all without direct touch or contact.

“Our study shows how beaming water waves at a floating object can cause it to move sideways or be ‘tweezed’ and held precisely in place,” explains Leif Ristroph, a professor at New York University’s Courant Institute School of Mathematics, Computing, and Data Science and the senior author of the study, which appears in the journal Physical Review Fluids. “These surprising effects could be used to manipulate particles and structures, controlling their motions and positions.”

Cutting a photon in two creates an infinite swarm of particles

By definition, elementary particles can’t be broken into smaller pieces. But in a new theoretical study published in Physical Review Letters, Johannes Skaar and colleagues have revealed what would happen if you tried anyway for a single photon. The answer is deeply strange: attempting to cut a photon in two wouldn’t produce two smaller photons, but instead conjure an infinite number of them out of thin air.

Like any quantum particle, a photon exists simultaneously as a single, localized particle, and an extended wave, spread out across space. For their investigation, Skaar’s team considered what would happen if a single photon passed through an optical shutter—essentially a very fast mirror that can be switched on and off to block part of a pulse of light. If the shutter was fast enough, it could intercept the photon mid-pulse, snipping off part of this extended wave.

To find out what would happen afterward, the researchers applied quantum equations that describe how the photon’s underlying electromagnetic field behaves at the quantum level. Specifically, their analysis tracked precisely how the photon’s quantum state would be transformed by the shutter’s intervention.

Molecular glasses solve long-standing Arrhenius paradox

Glasses are non-crystalline but solid states of matter in which molecules and atoms are not arranged into a regular crystal lattice, but rather in a disordered pattern. Glassy materials are widely used in various settings, for instance, in the synthesis of pharmaceuticals and the development of electronics or optical devices.

When studying movement and changes in various materials and substances, physicists commonly rely on the so-called Arrhenius model. This is a mathematical framework introduced by Svante Arrhenius in 1889, which can be used to calculate how temperature affects the speed of a heat-activated chemical reaction or physical process.

Past studies have shown that when the Arrhenius model is applied to molecular glasses, it yields unrealistically small pre-exponential factors. Pre-exponential factors are values that describe the intrinsic timescale of the movement of molecules without considering temperature effects.

Atomic reshuffle leads to record-breaking catalysts for hydrogen production

Researchers have discovered that atoms can be mixed, separated, and recombined within the same experiment, providing a pathway to a record-breaking catalyst for green hydrogen production. In their study, the team created nanoscale particles containing only a few dozen platinum and nickel atoms and observed unusual dynamic behavior in direct space and in real time. As the two metals separate from one another while maintaining an interface, they become highly active for electrochemical water splitting, leading to efficient hydrogen evolution.

The project was led by the University of Nottingham in collaboration with the University of Birmingham, Diamond Light Source, and Ulm University in Germany. The study appears in Advanced Materials.

Research team leader Dr. Jesum Alves Fernandes, from the School of Chemistry, University of Nottingham, said, “What makes this discovery exciting is that we can reversibly tune the structure of the particle while directly observing the process at the atomic scale. This opens a new strategy for designing adaptive catalysts for a wide range of applications.”

Violent rocket particles could reshape future spacecraft design

When rockets fire into space, the insides of their engines become an extreme environment where temperatures soar and tiny particles are thrown around at hypersonic speeds. These particles behave in ways that break long-held assumptions, according to new research that could help improve the durability, safety and performance of future space and defense technologies.

The study shows that particles traveling at hypersonic speeds do not remain spherical, instead melting and deforming mid-flight in ways that change how heat, drag and energy move through rocket systems. The findings, published in Physics of Fluids, have led researchers to develop a new drag model that more accurately predicts particle behavior under extreme conditions.

The work was led by researchers from the Southeast University–Monash University Joint Research Institute, Monash University and Shanghai University.

Smaller nanoplastics trigger stronger changes in brain neuron activity

Smaller plastic particles have more effects on neurons, the key information processing cells of the brain, new research from the University of Eastern Finland shows. In the study, neuronal cells were exposed to polystyrene nanoplastics at low doses to study subtle changes.

Plastic production continues to rise, despite worldwide concerns. In addition to environmental implications, there is an increasing interest in how exposure to plastics may impact human health, but our understanding is still limited. Only recently it was shown that plastics can accumulate also in the human brain.

Plastic particles smaller than 5,000 nm in diameter are called microplastics, and the smallest plastic particles with a diameter of less than 1,000 nm are called nanoplastics. The small size of nanoplastics enables them to interact with various cell types, and other particles or biological mass, such as bacteria. Compared to microplastics, nanoplastics have larger adsorption capacity and penetrate through biological barriers more easily. This makes them potentially more harmful and a compelling target for research in the field of neurobiology.

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