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Category: particle physics – Page 3

Flexible Piezoelectric Energy Harvesters with Mechanoluminescence for Mechanical Energy Harvesting and Stress Visualization Sensing

Flexible piezoelectric energy harvesters (FPEHs) have wide applications in mechanical energy harvesting, portable device driving, and piezoelectric sensors. However, the poor output performance of piezoelectric energy harvesters and the intrinsic shortcoming of piezoelectric sensors that can only detect dynamic pressure limit their further applications. BaTiO3 (BT) and PVDF are deposited on the glass fiber electronic cloth (GFEC) by impregnation and spin-coating methods, respectively, to form BT-GFEC/PVDF piezoelectric composite films. A mixed solution of mechanoluminescence (ML) particles ZnS: Cu and PDMS are used as the encapsulation layer to construct a high-performance ML-FPEH with self-powered electrical and optical dual-mode response characteristics. Due to the interconnection structure of the piezoelectric films, the prepared ML-FPEH illustrates a high effective energy harvesting performance (≈58 V, ≈43.56 µW cm−2). It can also effectively harvest mechanical energy from human activities. More importantly, ML-FPEH can sense stress distribution of hand-writing via ML to achieve stress visualization, making up for the shortcomings of piezoelectric sensors. This work provides a new strategy for endowing FPEH with dual-mode sensing and energy harvesting.

Team discovers electrochemical method for highly selective single-carbon insertion in aromatic rings

A research team has discovered an electrochemical method that allows highly selective para-position single-carbon insertion into polysubstituted pyrroles. Their approach has important applications in synthetic organic chemistry, especially in the field of pharmaceuticals.

Their work is published in the Journal of the American Chemical Society on July 14.

“We set out to address the longstanding challenge of achieving single-carbon insertion into aromatic rings with precise positional control,” said Mahito Atobe, Professor, Faculty of Engineering, YOKOHAMA National University. Transformations that modify aromatic rings are central to pharmaceutical and materials synthesis. However, inserting a single carbon atom into a specific position—especially the para-position—has remained extremely rare. Para position describes the location of substituents, those atoms that replace a hydrogen atom on a molecule. In the single carbon insertion approach, researchers add a single carbon atom into a molecule’s carbon framework. This lengthens a carbon chain or expands a ring by one carbon unit.

Method has organic chemistry applications, especially in pharmaceuticals.

New study uncovers surprising physics of ‘marine snow’

The deep ocean can often look like a real-life snow globe. As organic particles from plant and animal matter on the surface sink downward, they combine with dust and other material to create “marine snow,” a beautiful display of ocean weather that plays a crucial role in cycling carbon and other nutrients through the world’s oceans.

Now, researchers from Brown University and the University of North Carolina at Chapel Hill have found surprising new insights into how particles sink in stratified fluids like oceans, where the density of the fluid changes with depth. In a study published in Proceedings of the National Academy of Sciences, they show that the speed at which particles sink is determined not only by resistive drag forces from the fluid, but by the rate at which they can absorb salt relative to their volume.

“It basically means that can sink faster than bigger ones,” said Robert Hunt, a postdoctoral researcher in Brown’s School of Engineering who led the work. “That’s exactly the opposite of what you’d expect in a fluid that has uniform density.”

Heterostructure-Engineered Semiconductor Quantum Dots toward Photocatalyzed-Redox Cooperative Coupling Reaction

Semiconductor quantum dots have been emerging as one of the most ideal materials for artificial photosynthesis. Here, we report the assembled ZnS-CdS hybrid heterostructure for efficient coupling cooperative redox catalysis toward the oxidation of 1-phenylethanol to acetophenone/2,3-diphenyl-2,3-butanediol (pinacol) integrated with the reduction of protons to H2. The strong interaction and typical type-I band-position alignment between CdS quantum dots and ZnS quantum dots result in efficient separation and transfer of electron-hole pairs, thus distinctly enhancing the coupled photocatalyzed-redox activity and stability. The optimal ZnS-CdS hybrid also delivers a superior performance for various aromatic alcohol coupling photoredox reaction, and the ratio of electrons and holes consumed in such redox reaction is close to 1.0, indicating a high atom economy of cooperative coupling catalysis. In addition, by recycling the scattered light in the near field of a SiO2 sphere, the SiO2-supported ZnS-CdS (denoted as ZnS-CdS/SiO2) catalyst can further achieve a 3.5-fold higher yield than ZnS-CdS hybrid. Mechanistic research clarifies that the oxidation of 1-phenylethanol proceeds through the pivotal radical intermediates of • C(CH3)(OH)Ph. This work is expected to promote the rational design of semiconductor quantum dots-based heterostructured catalysts for coupling photoredox catalysis in organic synthesis and clean fuels production.

Copyright © 2023 Lin-Xing Zhang et al.

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James Webb Space Telescope Discovers Complex ‘Seeds of Life’ Molecules Beyond the Milky Way For the First Time

In a breakthrough first, University of Maryland scientists using the James Webb Space Telescope have announced the detection of large, complex, organic molecules beyond the Milky Way.

Often called “seeds of life” because these molecules make up the lifeforms found on Earth, the discovery was made within frozen ice particles around a young protostar, ST6, forming in a distant galaxy.

Hydrogen atom

A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral hydrogen atom contains a single positively charged proton in the nucleus, and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. [ 1 ]

In everyday life on Earth, isolated hydrogen atoms (called “atomic hydrogen”) are extremely rare. Instead, a hydrogen atom tends to combine with other atoms in compounds, or with another hydrogen atom to form ordinary (diatomic) hydrogen gas, H2. “Atomic hydrogen” and “hydrogen atom” in ordinary English use have overlapping, yet distinct, meanings. For example, a water molecule contains two hydrogen atoms, but does not contain atomic hydrogen (which would refer to isolated hydrogen atoms).

Atomic spectroscopy shows that there is a discrete infinite set of states in which a hydrogen (or any) atom can exist, contrary to the predictions of classical physics. Attempts to develop a theoretical understanding of the states of the hydrogen atom have been important to the history of quantum mechanics, since all other atoms can be roughly understood by knowing in detail about this simplest atomic structure.

The key to why the universe exists may lie in an 1800s knot idea science once dismissed

In 1867, Lord Kelvin imagined atoms as knots in the aether. The idea was soon disproven. Atoms turned out to be something else entirely. But his discarded vision may yet hold the key to why the universe exists.

Now, for the first time, Japanese physicists have shown that can arise in a realistic particle physics framework, one that also tackles deep puzzles such as neutrino masses, , and the strong CP problem.

Their findings, in Physical Review Letters, suggest these “cosmic knots” could have formed and briefly dominated in the turbulent newborn universe, collapsing in ways that favored matter over antimatter and leaving behind a unique hum in spacetime that future detectors could listen for—a rarity for a physics mystery that’s notoriously hard to probe.

Light particles prefer company: Photons exhibit collective behavior only after reaching certain threshold

As far as particles of light are concerned, the collective is more important than the individual. When they get to decide between two states, they will favor the one that many of their fellow particles have already adopted. However, this collectivist tendency does not kick in until enough photons have assembled in the same place.

A ‘seating chart’ for atoms helps locate their positions in materials

If you think of a single atom as a grain of sand, then a wavelength of visible light—which is a thousand times larger than the atom’s width—is comparable to an ocean wave. The light wave can dwarf an atom, missing it entirely as it passes by. This gulf in size has long made it impossible for scientists to see and resolve individual atoms using optical microscopes alone.

Only recently have scientists found ways to break this “diffraction limit,” to see features that are smaller than the wavelength of light. With new techniques known as , scientists can see down to the scale of a single molecule.

And yet, individual atoms have still been too small for —which are much simpler and less expensive than super-resolution techniques—to distinguish, until now.

US and Japan join forces to present some of the most precise neutrino measurements in the field

Very early on in our universe, when it was a seething hot cauldron of energy, particles made of matter and antimatter bubbled into existence in equal proportions. For example, negatively charged electrons were created in the same numbers as their antimatter siblings, positively charged positrons. When the two particles combined, they canceled each other out.

Billions of years later, our world is dominated by matter. Somehow, matter “won out” over antimatter, but scientists still do not know how. Now, two of the largest experiments attempting to find answers—projects that focus on subatomic particles called —have joined forces.

In a new Nature study, an international collaboration representing the experiments—NOvA in the United States and T2K in Japan—present some of the most precise neutrino measurements in the field. The two teams decided to combine their data to learn more than any one experiment alone could.

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