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A thermodynamic approach to gravity could explain cosmic acceleration without dark energy

Gravity, the force that attracts objects toward each other, is currently framed by Albert Einstein’s theory of general relativity. This framework describes gravity as the curvature of spacetime, the invisible four-dimensional fabric of the universe.

While general relativity is now the central theory of gravity, it fails to explain some cosmological phenomena and mysteries, such as the so-called cosmological constant problem. This is the unexplained mismatch between the observed energy of empty space and the far greater values predicted by quantum theories.

In a recent paper published in Physical Review Letters, researchers at Imperial College London tried to frame gravity using thermodynamics, the framework that describes how energy and heat transform. Their study builds on a seminal paper by theoretical physicist Ted Jacobson, published more than three decades ago.

The universe should look the same in all directions at large scales, but DESI data suggest otherwise

Earlier this year, the Dark Energy Spectroscopic Instrument (DESI) completed observations that mapped 47 million galaxies across 11 billion light-years, allowing astronomers to better evaluate the large-scale structure of the visible universe. After studying these data, astronomers Francesco Sylos Labini and Marco Galoppo say the universe may not look the same in all directions. Their results, published in Nature, contradict a fundamental assumption in modern cosmology.

At the scale of a single galaxy or local groups of galaxies, the universe clearly appears to be anisotropic, meaning the structure is different depending on which direction you look. In one direction, there may be more void space, while another direction may have a cluster of galaxies.

However, the cosmological principle says that at larger scales, the universe consists of matter that is more or less distributed evenly in all directions. This is based on the Copernican principle, which states that there should be no “special observers” in the universe, meaning that at large scales, the universe should look the same from anywhere else in the universe.

Scientists find molecular-level evidence for two structures in liquid water

A study published in Nature Physics provides new molecular-level evidence from simulations that liquid water is not a single uniform substance, but a constantly shifting mixture of two distinct microscopic structures.

The idea that water might exist in two distinct structural states is not new. For decades, scientists have theorized that liquid water is composed of two interconvertible local structures—one denser and more disordered, the other less dense and more ordered.

This “two-state model” has been invoked to explain water’s many anomalous properties, including why it becomes easier to compress as it cools and why it reaches maximum density at 4°C (39°F) rather than at its freezing point. But the model has remained controversial because direct molecular-level evidence for the two structures has been elusive.

Thirsty desert lizards inspire a new water-harvesting system

When the desert horned lizard (Phrynosoma platyrhinos) is thirsty, it cannot just lap up water or scoop it up like a bird because it lives in environments where water is extremely scarce. Typically, it’s found in damp soil or, even more rarely, in drops of rain.

Instead, its skin contains microscopic channels between overlapping scales that pull in moisture by capillary action. But how it gets that water from these channels into its mouth has remained a mystery until now.

Scientists have discovered how that happens, and it inspired them to design a water-harvesting system that borrows from how the reptiles do it.

It only takes one fake web page to fool AI shopping bots, study finds

AI shopping assistants are popping up all over the internet, changing how we browse, compare and discover products. However, these helpful tools appear to have a serious security flaw. According to a paper published on the arXiv preprint server, a single manipulated web page can trick an AI assistant into promoting a fake product to unsuspecting customers.

Considering that fake goods and fake reviews are everywhere online, researchers Minghao Luo and Liang Chen decided to test how easily search-augmented AI systems can be tricked into promoting bogus brands.

Quantum waves reveal one-sided motion marking elusive critical states

Sound waves, light waves and other types of waves, generally spread freely through space and over time. In 1958, physicist Philip W. Anderson first described a phenomenon via which irregularities or other sources of disorder in materials would prevent waves from propagating freely, which is now known as Anderson localization.

In quantum systems, one can observe quantum states that are spread throughout a system (i.e., extended), confined to a small region (i.e., localized) or somewhere between the two (i.e., critical). Critical quantum states have so far proved to be very difficult to identify and study using Anderson’s localization theory.

Researchers at the International Quantum Academy and Southern University of Science and Technology in China recently set out to further explore critical quantum states in a quantum processor based on superconducting qubits.

Microscale hydrogel fibers could enable imaging inside tiny tissue structures

Researchers have developed light-transmitting hydrogel fibers that are just hundreds of micrometers in diameter. With further development, these soft fibers could one day make it possible to use imaging techniques to detect early breast cancer hidden inside very small breast ducts.

“While traditional, relatively rigid fiber probes may cause mechanical damage when entering narrow, curved or soft tissue spaces, our fibers are very soft with mechanical properties more similar to those of human soft tissues,” said research team leader Yu Zhang from Harbin Engineering University in China. “We made these fibers using a draw-spinning method that was inspired by spider-silk spinning.”

In research appearing in Optics Express, the researchers describe how they tested the new hydrogel fibers by incorporating them into an imaging system and using it to analyze standard pathology-stained breast tissue sections. The imaging system successfully reconstructed the microscopic features used by pathologists to evaluate tumors and, when combined with artificial intelligence algorithms, distinguished tumor subtypes with an accuracy of 93.97%.

Tiny water droplets transmutate aniline into pyridine in ambient and catalyst-free conditions

Aniline can now be transformed into pyridine without adding any catalysts, oxidants or toxic reagents. In a recent study published in the Journal of the American Chemical Society, researchers achieved skeletal editing, involving the reorganization of the carbon-nitrogen bonds within an aromatic ring, by turning an aqueous solution of aniline into a mist of microdroplets.

During its millisecond-long airborne lifespan, aniline underwent rapid molecular rearrangement, inserting nitrogen into the aromatic ring and forming pyridine, driven by the uniquely active air-water interface in microdroplets. The green, reagent-free reaction converted up to 80% of the starting material into the product under ambient conditions, eliminating the added energy cost often required to carry out such conversion reactions.

By testing droplets of different sizes, charges and acidity levels, researchers found that the reaction is boosted at the droplet’s interface, a zone that is rich in protons and highly polarized. The smaller the droplet, the larger its reactive surface area relative to its volume, and the better the reaction outcome.

Ultra-fast light-shaping technology could be ‘game-changer’ for future imaging

Scientists have developed a new type of “virtual” metasurface—capable of controlling light in ways traditional lenses and optics can’t—which they say is superior to the current approach, which relies on ultrathin engineered materials. The Nottingham Trent University team says the work will help fully optimize metasurface potential for a range of real-world applications and paves the way for a move from physical to virtual platforms in nanotechnology.

Metasurfaces are many times thinner than a human hair and can bend and focus light, change its color and steer it in different directions, meaning they can replace bulky optical elements in small devices such as lenses, mirrors and filters.

While they are powerful, however, the materials and dimensions of physical metasurfaces are fixed—once built, they can’t change their shape, which can limit how useful they are in real-world technologies.

Ultra-precise technology can count damaged DNA fragments

The Korea Research Institute of Standards and Science has developed an ultrasensitive immunoassay-based analytical platform that can detect and quantify trace amounts of “Small Excised Damaged DNA (sedDNA)” fragments generated during cellular DNA repair. This technology enables highly sensitive detection with quantification down to the level of several thousand molecules, measuring up to 22 times more DNA fragments than conventional methods. It provides a new analytical foundation for comparing DNA repair capacity between individuals and studying cellular responses to anticancer drugs and carcinogenic agents.

Human DNA is continuously exposed to damage from ultraviolet light, chemical agents, smoking and normal metabolic processes. If such damage is not properly repaired, mutations can accumulate and lead to aging and diseases such as cancer. To maintain genomic stability, cells activate the Nucleotide Excision Repair (NER) system, which removes damaged DNA segments and replaces them with newly synthesized DNA. The small excised DNA fragments generated during this process serve as important indicators of DNA repair efficiency and kinetics, providing a valuable tool for studying disease mechanisms and predicting treatment responses.

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