Category: 7. Science

Angular momentum is a fundamental quantity in physics that describes the rotational motion of objects. In quantum physics, it encompasses both the intrinsic spin of particles and their orbital motion around a point. These properties are essential for understanding a wide range of systems, from atoms and molecules to complex materials and high-energy particle interactions.

When a magnetic field is applied to a quantum system, particle spins typically align with or against the field. This well-known effect, known as spin polarization, leads to observable phenomena such as magnetization. Until now, it was widely believed that spin played the dominant role in how particles respond to magnetic fields. However, new research challenges this long-held view.

In this vein, Assistant Professor Kazuya Mameda of Tokyo University of Science, Japan, in collaboration with Professor Kenji Fukushima of School of Science, The University of Tokyo and Dr. Koichi Hattori of Zhejiang University, found that under strong magnetic fields, the orbital motion of magnetovortical matter becomes more significant than spin effects, leading to reversing the overall direction of angular momentum. The study will be published in Physical Review Letters on July 01, 2025.

“It was previously believed that most microscopic phenomena in a magnetic field were governed by spin angular momentum—a physical quantity characterizing the intrinsic rotational motion of microscopic particles,” explains Dr. Mameda. “However, this study found that in a strong magnetic field, orbital motion can overwhelm spin effects, reversing the direction of rotational motion from what was previously believed.”

The researchers studied fermionic systems—specifically Dirac fermions— subjected to both strong magnetic fields and rotation. By ensuring gauge invariance and thermodynamic stability in their theoretical framework, they demonstrated that orbital contributions to bulk properties can exceed spin contributions.

Unlike spin, which aligns with the magnetic field, the orbital angular momentum aligns according to Lenz’s law—opposite to the direction of the magnetic field. As the magnetic field intensifies, the charge density from the orbital-rotation coupling and orbital angular momentum grow twice the magnitude of their spin counterparts, but with opposite sign.

This reversal in total angular momentum reshapes our understanding of magnetovortical matter and links its behavior to a broader class of quantum effects known as anomaly-induced transports. The findings also pave the way for simulations using lattice QCD—a powerful computational tool for studying strongly interacting particles such as quarks and gluons under extreme conditions.

The discovery that a strong magnetic field can reverse angular momentum in quantum systems challenges established theories. It highlights the previously underestimated role of orbital motion, showing it to be more influential than spin in certain regimes. This insight could spark advances in groundbreaking technologies, particularly in orbitronics, a field dedicated to manipulating the orbital motion of electrons.

“Total angular momentum reversal under strong magnetic fields has been overlooked across fields from materials science to astrophysics. Our findings redefine the foundational physics of modern physics and point to new frontiers in orbitronics—where controlling electron orbital motion could lead to innovative device applications,” concludes Dr. Mameda.

There is a growing buzz in the astronomy community about a new object with a hyperbolic trajectory that is moving toward the inner Solar System.

Early on Wednesday, the European Space Agency confirmed that the object, tentatively known as A11pl3Z, did indeed have interstellar origins.

“Astronomers may have just discovered the third interstellar object passing through the Solar System!” the agency’s Operations account shared on Blue Sky. “ESA’s Planetary Defenders are observing the object, provisionally known as #A11pl3Z, right now using telescopes around the world.”

Only recently identified, astronomers have been scrambling to make new observations of the object, which is presently just inside the orbit of Jupiter and will eventually pass inside the orbit of Mars when making its closest approach to the Sun this October. Astronomers are also looking at older data to see if the object showed up in earlier sky surveys.

An engineer at the University of Arizona’s Catalina Sky Survey, David Rankin, said recent estimates of the object’s eccentricity are about 6. A purely circular orbit has an eccentricity value of 0, and anything above 1 is hyperbolic. Essentially, this is a very, very strong indication that A11pl3Z originated outside of the Solar System.

A new technology that uses clinical MRI machines to image metabolic activity in the brain could give researchers and clinicians unique insight into brain function and disease, researchers at the University of Illinois Urbana-Champaign report. The non-invasive, high-resolution metabolic imaging of the whole brain revealed differences in metabolic activity and neurotransmitter levels among brain regions; found metabolic alterations in brain tumors; and mapped and characterized multiple sclerosis lesions – with patients only spending minutes in an MRI scanner.

Led by Zhi-Pei Liang, a professor of electrical and computer engineering and a member of the Beckman Institute for Advanced Science and Technology at the U. of I., the team reported its findings in the journal Nature Biomedical Engineering.

Understanding the brain, how it works and what goes wrong when it is injured or diseased is considered one of the most exciting and challenging scientific endeavors of our time. MRI has played major roles in unlocking the mysteries of the brain over the past four decades. Our new technology adds another dimension to MRI’s capability for brain imaging: visualization of brain metabolism and detection of metabolic alterations associated with brain diseases.”

Zhi-Pei Liang, professor of electrical and computer engineering and member of the Beckman Institute for Advanced Science and Technology at the U. of I.

Conventional MRI provides high-resolution, detailed imaging of brain structures. Functional MRI maps brain activity by detecting changes in blood flow and blood oxygenation level, which are closely linked to neural activity. However, they cannot provide information on the metabolic activity in the brain, which is important for understanding function and disease, said postdoctoral researcher Yibo Zhao, the first author of the paper.

“Metabolic and physiological changes often occur before structural and functional abnormalities are visible on conventional MRI and fMRI images,” Zhao said. “Metabolic imaging, therefore, can lead to early diagnosis and intervention of brain diseases.”

Both MRI and fMRI techniques are based on magnetic resonance signals from water molecules. The new technology measures signals from brain metabolites and neurotransmitters as well as water molecules, a technique known as magnetic resonance spectroscopic imaging. These MRSI images can provide significant new insights into brain function and disease processes, and could improve sensitivity and specificity for the detection and diagnosis of brain diseases, Zhao said.

Other attempts at MRSI have been bogged down by the lengthy times required to capture the images and high levels of noise obscuring the signals from neurotransmitters. The new technique addresses both challenges.

“Our technology overcomes several long-standing technical barriers to fast high-resolution metabolic imaging by synergistically integrating ultrafast data acquisition with physics-based machine learning methods for data processing,” Liang said. With the new MRSI technology, the Illinois team cut the time required for a whole brain scan to 12 and a half minutes.

The researchers tested their MRSI technique on several populations. In healthy subjects, the researchers found and mapped varying metabolic and neurotransmitter activity across different brain regions, indicating that such activity is not universal. In patients with brain tumors, the researchers found metabolic alterations, such as elevated choline and lactate, in tumors of different grades – even when the tumors appeared identical on clinical MRI images. In subjects with multiple sclerosis, the technique detected molecular changes associated with neuroinflammatory response and reduced neuronal activity up to 70 days before changes become visible on clinical MRI images, the researchers report.

The researchers foresee potential for broad clinical use of their technique: By tracking metabolic changes over time, clinicians can assess the effectiveness of treatments for neurological conditions, Liang said. Metabolic information also can be used to tailor treatments to individual patients based on their unique metabolic profiles.

“High-resolution whole-brain metabolic imaging has significant clinical potential,” said Liang, who began his career in the lab of the late Illinois professor Paul Lauterbur, recipient of the Nobel Prize for developing MRI technology. “Paul envisioned this exciting possibility and the general approach, but it has been very difficult to achieve his dream of fast high-resolution metabolic imaging in the clinical setting.

“As healthcare is moving towards personalized, predictive and precision medicine, this high-speed, high-resolution technology can provide a timely and effective tool to address an urgent unmet need for noninvasive metabolic imaging in clinical applications.”

Dust devils on Mars could be crackling with electric currents, according to a new study — and scientists are a little concerned about this because a buildup of such charge could harm rovers rolling along the surface of Mars.

“Electrified dust will adhere to conducting surfaces such as wheels, solar panels and antennas. This may diminish the availability of solar energy, harm communications and complicate the motion of rovers and robots,” Yoav Yair, a professor at Reichman University in Israel who studies planetary lightning and was not part of the new study, told Space.com.

Since 2015, Antarctica has lost sea ice equal to the size of Greenland — the largest environmental shift seen anywhere on Earth in the last decades. The Southern Ocean is also getting saltier, and this unexpected change is making the problem worse.

For decades, the ocean’s surface freshened (becoming less salty), helping sea ice grow. Now, scientists say that trend has sharply reversed.

Using European satellite data, research led by the University of Southampton has discovered a sudden rise in surface salinity south of 50° latitude.

This has coincided with a dramatic loss of sea ice around Antarctica and the re-emergence of the Maud Rise polynya in the Weddell Sea – a huge hole in the sea ice nearly four times the size of Wales, which hadn’t occurred since the 1970s.

The findings were published on June 30 in the Proceedings of the National Academy of Sciences.

Dr Alessandro Silvano from the University of Southampton who led the research said: “Saltier surface water allows deep ocean heat to rise more easily, melting sea ice from below. It’s a dangerous feedback loop: less ice leads to more heat, which leads to even less ice.

“The return of the Maud Rise polynya signals just how unusual the current conditions are. If this salty, low-ice state continues, it could permanently reshape the Southern Ocean — and with it, the planet. The effects are already global: stronger storms, warmer oceans, and shrinking habitats for penguins and other iconic Antarctic wildlife.”

In these polar waters, cold, fresh surface water overlays warmer, saltier waters from the deep. In the winter, as the surface cools and sea ice forms, the density difference (stratification) between water layers weakens, allowing these layers to mix and heat to be transported upward, melting the sea ice from below and limiting its growth.

Since the early 1980s, the surface of the Southern Ocean had been freshening, and stratification had been strengthening, trapping heat below and sustaining more sea ice coverage.

Now, new satellite technology, combined with information from floating robotic devices which travel up and down the water column, shows this trend has reversed; surface salinity is increasing, stratification is weakening, and sea ice has reached multiple record lows — with large openings of open ocean in the sea ice (polynyas) returning.

It’s the first time scientists have been able to monitor these changes in the Southern Ocean in real-time.

Contrary to the new findings, man-made climate change was generally expected to sustain Antarctic Sea ice cover over the coming years.

Aditya Narayanan, a postdoctoral research fellow at the University of Southampton and co-author on the paper, explains: “While scientists expected that human-driven climate change would eventually lead to Antarctic Sea ice decline, the timing and nature of this shift remained uncertain.

“Previous projections emphasized enhanced surface freshening and stronger ocean stratification, which could have supported sustained sea ice cover. Instead, a rapid reduction in sea ice — an important reflector of solar radiation — has occurred, potentially accelerating global warming.”

Professor Alberto Naveira Garabato, co-author of the study and Regius Professor of Ocean Sciences at the University of Southampton added: “The new findings suggest that our current understanding may be insufficient to accurately predict future changes.”

“It makes the need for continuous satellite and in-situ monitoring all the more pressing, so we can better understand the drivers of recent and future shifts in the ice-ocean system.”

The paper Rising surface salinity and declining sea ice: a new Southern Ocean state revealed by satellites is published in Proceedings of the National Academy of Sciences and is available online.

The project was supported by the European Space Agency.

LUX-INVENTA is a European Research Council-funded project aiming to develop photomagnetic materials – photo-responsive materials that get magnetised by visible light.

The photomagnetic effect is the change of magnetic moment in response to visible light and occurs in compounds called photomagnets. It was coined by the pioneers in the field of molecular magnetism: Hashimoto, Miller, Verdaguer and Dei. Its discovery, however, is a consequence of the seminal work of Hauser et al. on the light-induced excited spin state trapping (LIESST) effect in octahedral iron(II) complexes showing spin crossover (SCO) behaviour.

The photomagnetic effect explained

The term photomagnetic effect applies to all types of magnetic systems responsive to light: diamagnetic, paramagnetic, as well as ferro- and antiferromagnetic. It relies on the observation that absorption of a photon by a specific part of a molecular system (a photomagnetic chromophore) can lead to a series of physical events resulting in a spin state change. This spin state change is directly associated with the change of the magnetisation. In other words, the construction of molecular materials based on photomagnetic chromophores results in compounds that get magnetised when exposed to visible light – the photomagnets.

Currently, photomagnets remain laboratory curiosities due to extremely low temperatures at which they operate, requiring expensive liquid helium cooling. Hence, the major objective of LUX-INVENTA is the design and synthesis of high-temperature photomagnets – paramagnetic compounds that, upon exposure to visible light, become reversibly magnetised at the highest possible temperature – preferably room temperature.

LUX-INVENTA: Advancements in photomagnetic materials

Photocrystallographic and photomagnetic studies performed within LUX-INVENTA extend beyond the current state-of-the-art. This enabled the identification of a high-performance photomagnetic chromophore: heptacyanomolybdate(III) complex anion. A complete experimental and theoretical study performed for its potassium salt revealed photoswitching in the solid state, involving an unprecedented change of the coordination sphere of the molybdenum(III) centre from a 7-coordinated capped trigonal prism to a 6-coordinated octahedron. This transformation induces a spin state and magnetisation changes, paving the way for the development of a new class of photo-switchable high-temperature magnets and nanomagnets. The manuscript has been deposited with the ChemRxiv repository.

Tripak

One of the peak achievements of the LUX-INVENTA research team was the rational design and successful isolation of a completely new and yet very simple organic molecule called tripak. The unique redox properties of tripak enabled its isolation in five different valence states, accommodating up to six additional electrons. These states can be reached by applying a small electrical potential, enabling electro-switching between completely different properties: record strong anion-π binding of halides, molecular qubit behaviour, red fluorescence and chemically unique diradicaloid character. The unique combination of vastly different physical properties enclosed within a compact and elegant molecular framework of tripak makes it highly versatile for applications ranging from quantum technologies and energy storage to molecular sensing. These results were published as an open-access research article in the Cell Press journal Chem.

Moreover, the unique physico-chemical character of tripak sparked an in-depth investigation of other derivatives with similar properties and improved potential for further chemical tuning and modifications.

Significant progress: Expanding the limits

While the goal of achieving room-temperature photomagnetism has yet to be reached, the LUX-INVENTA project has already pushed the limits of photomagnets towards an applicable temperature range and demonstrated a completely new photoswitching mechanism based on a reversible photodissociation reaction occurring in the solid state.

Moreover, the search for novel organic molecules suitable for the observation of charge-transfer induced photomagnetic switching has spawned a unique and yet very simple tripak molecule, which seems to be an extremely versatile platform for the construction of completely new magnetic coordination polymers.

Acknowledgments

Publication of this article has been funded under the Strategic Programme Excellence Initiative at the Jagiellonian University.

Please note, this article will also appear in the 23rd edition of our quarterly publication.

Source: Journal of Geophysical Research: Earth Surface

Compared to single-channel meandering rivers, multichannel braided rivers are often found in environments with sparse vegetation and coarse, shifting bars of sediment. Past research has called the way in which the paths of braided rivers shift over time “chaotic” because their migration depends on many factors, including river shape and changing water levels.

However, because the migration of individual channel threads can affect the likelihood of hazards like flooding or erosion, understanding this migration is critical to protect the residents, structures, and ecosystems surrounding these complicated waterways.

Li and Limaye examined a 180-kilometer span of the Brahmaputra-Jamuna River, a river in Bangladesh whose channels have been well resolved through satellite imagery.

Scientists—and many of the 600,000 people living in the islands between the river channels—already know that the river’s water levels are high during the summer months’ monsoon season and low but consistent from January to March. But this research team used a statistical method called dynamic time warping to map long-term changes in the river channels’ sizes, shapes, and routes between 2001 and 2021. This technique allowed them to calculate how much and how quickly the centerlines of channel threads shifted. They then applied an existing model developed for meandering rivers to see whether it could also predict the movement of braided channel threads.

They found that the Brahmaputra-Jamuna River’s movements were more predictable than previously realized. About 43% of its channels moved gradually, rather than abruptly, during the study period. On average, these channel threads migrated more quickly than most meandering rivers, at a rate of about 30% of their width per year. In some cases, the rate of this migration was closely related to the curvature of the channel thread, and across the board, it was weakly related to channel thread width.

These findings have important implications for future research on braided river channels, the authors say. Knowing that at least some channel threads migrate coherently might inform erosion and flooding mitigation efforts for braided river regions, especially those in densely populated areas. (Journal of Geophysical Research: Earth Surface, https://doi.org/10.1029/2024JF008196, 2025)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Coherent, not chaotic, migration in the Brahmaputra-Jamuna River, Eos, 106, https://doi.org/10.1029/2025EO250237. Published on 2 July 2025.

Text © 2025. AGU. CC BY-NC-ND 3.0
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