Scientists with the Double Chooz collaboration have now measured this lingering antineutrino emission for the first time. The research, recently published in Physical Review Letters, was led by Anthony Onillon and Thierry Lassere of the Max-Planck-Institut für Kernphysik (MPIK) in Heidelberg, Germany. The findings show that antineutrino detectors can gather information about nuclear reactors even while they are shut down, potentially creating new opportunities for reactor monitoring, nuclear safety, and safeguards.

Detecting Antineutrinos From a Shutdown Reactor

The measurement took place at the Chooz nuclear power plant in northern France. The Double Chooz detector sits underground about 400 meters from the facility’s two reactor cores. Inside the detector are more than 30 cubic meters of liquid scintillator, a material that produces tiny flashes of light when an antineutrino interacts within it.

“Antineutrinos interact only extremely rarely with matter. However, when one interacts within the Double-Chooz detector, a characteristic double-light signal is produced that can be distinguished from background events,” explains Thierry Lasserre from the independent research group OMINA, also located at MPIK. This distinctive signal enables scientists to identify antineutrinos coming from the reactors.

Researchers examined 17.2 days of observations collected while both reactor units were fully shut down. Over that period, the detector recorded around 100 antineutrino candidate events linked to residual radioactivity in the reactor cores and nearby spent-fuel cooling pools.

Measurements Match Nuclear Fuel Predictions

The detected signal closely matched detailed simulations that accounted for the remaining nuclear fuel inventory and the decay of long-lived fission products. The result provides the first direct experimental confirmation of predictions describing antineutrino emissions from shut down reactors and spent fuel.

“Until now, reactor antineutrino experiments have mainly focused on operating reactors, where the antineutrino flux is much larger. Detecting the tiny residual signal after shutdown required exceptionally low backgrounds and careful analysis techniques developed by the Double Chooz collaboration over many years,” adds Dr. Onillon.

Other experiments are already beginning to explore this new area. Initial results from JUNO-TAO, presented at Neutrino 2026, show that researchers are also using reactor-off data to study the faint antineutrino signal produced by spent nuclear fuel. TAO is working to isolate that weak emission, while the Double Chooz findings now provide the first published benchmark for studying the residual signal from shut-down reactors and spent-fuel pools.

A New Tool for Nuclear Reactor Monitoring

The findings suggest that antineutrino detectors could eventually provide useful information not only while reactors are operating, but also during maintenance and after shutdown. Measurements of this kind could become valuable for independently confirming reactor status and tracking spent-fuel inventories.

Double Chooz was originally built to investigate neutrino oscillations and played a key role in measuring the neutrino mixing angle θ13, a fundamental parameter describing how neutrinos change from one type to another as they travel. That measurement helped pave the way for future research into matter-antimatter asymmetries in the neutrino sector.

Now, Double Chooz has added another first to its scientific record by detecting the faint neutrino glow that continues after a nuclear reactor goes dark.

Scientists are getting a clearer picture of how thermodynamics behaves in the quantum world, and that progress could benefit both quantum technology and our understanding of familiar thermodynamic principles. Researchers at Aalto University have now taken an important step by demonstrating the first cyclic quantum heat engine built inside a superconducting circuit.

The experiment connects two areas of physics that normally describe very different scales. Quantum mechanics explains the behavior of matter at extremely small scales, even below the size of atoms, while thermodynamics describes how heat and energy behave in much larger systems, from collections of molecules to the universe itself. Bringing the two together raises a fundamental question: what happens to familiar thermodynamic processes when quantum effects such as tunneling, entanglement, and superposition enter the picture?

A Heat Engine Built for the Quantum World

Conventional heat engines turn heat into useful work. James Watt’s steam engine is one famous example, but the same basic concept remains central to modern transportation and electricity production, powering cars, ships, planes and many power plants.

The researchers have now created the world’s first superconducting quantum heat engine. The extremely small device combines a transmon qubit, a resonator and a quantum refrigerator.

Operating under ultracold quantum conditions, the engine was able to use the tiny amount of available heat to repeatedly produce positive work. Achieving this kind of cyclic operation has been an important objective for researchers working on quantum heat engines. The result provides a proof of concept for superconducting heat engines that could eventually contribute to improved quantum computing technology.

The study, led by Academy Professor Mikko Möttönen, was published in Nature Communications.

Recreating an Otto Cycle Near Absolute Zero

To make the engine operate, the researchers reproduced an Otto cycle inside a superconducting circuit. The Otto cycle is a thermodynamic process also used in car engines and other conventional machines.

“In our experiment, we built a nanofabricated heat engine using superconducting circuits and operated it in a cryostat near absolute zero. At its heart is a transmon qubit, one of the basic building blocks of modern quantum technologies,” says Tuomas Uusnäkki, the study’s first author.

The researchers connected the transmon qubit to a quantum circuit refrigerator, allowing them to control heat flow on the quantum scale and demonstrate that this heat could be transformed into measurable work. A conventional heat engine normally relies on separate hot and cold environments. In this system, however, the same quantum refrigerator can supply both heating and cooling.

“Our quantum-circuit refrigerator can be tuned to both heat and cool the qubit on demand. Using carefully timed control pulses, we drove the engine in an Otto cycle and monitored the qubit state as the engine ran,” explains Uusnäkki.

Measurements showed that heat passing through the qubit during the cycle was producing positive work.

“This is the first experimental demonstration of a cyclic quantum heat engine in superconducting circuits. Using a single controllable quantum refrigerator as both the hot and cold environment of the engine makes it simpler and more versatile,” says Uusnäkki.

Toward Autonomous Quantum Computer Hardware

The researchers are now trying to improve the design and eventually develop a fully autonomous heat engine. One possible use would be reading out qubits without having to carry a microwave pulse from millikelvin temperatures all the way to room temperature.

That capability could become especially valuable as quantum computers grow. Autonomous devices integrated directly into superconducting circuits could reduce both the cost and complexity of machines containing very large numbers of qubits.

“Finland’s Quantum Technology Strategy envisions a quantum computer with one thousand logical qubits by 2035, which probably means hundreds of thousands of physical qubits. Doing that with current technology requires millions of microwave cables costing thousand euros each. The cables also introduce noise into the system. Using autonomous devices instead would mostly eliminate the need for those cables,” Möttönen says.

Reducing the need for those microwave connections could therefore address two challenges at once: the enormous hardware requirements of large quantum computers and the unwanted noise that cables can introduce into quantum systems.

The pioneering experiment was carried out using OtaNano, Finland’s national research infrastructure for nano, micro and quantum technology. Funding came from the Research Council of Finland and the Finnish Cultural Foundation.

The mystery became an ideal research question for a master’s student. Clemens Ries, who had recently joined the Max Planck Institute of Psychiatry for an internship as he approached the end of his biology degree, took on the challenge.

Identifying the Brain’s Repair Cells

Using a mouse model, Ries systematically tested markers for all known cell types. Only one produced a response: the marker for oligodendrocyte progenitor cells (OPCs).

These precursor cells can mature into oligodendrocytes, which produce the myelin sheath surrounding axons. Axons are extensions of nerve cells that allow neurons to communicate with one another. Myelin acts much like the insulating material around an electrical cable. It supports efficient information transmission along axons and also helps supply them with nutrients, making it vital to healthy brain function.

Damage to myelin can have serious consequences. In autoimmune diseases such as multiple sclerosis (MS), the protective coating breaks down. Physical injuries can also harm myelin, and in severe cases, the resulting damage can lead to the death of entire neurons. Restoring myelin around affected axons is therefore an important part of the brain’s response to injury.

A Surprising Stress Hormone Appears After Injury

Ries initially studied the newly identified cells for his master’s thesis. “The topic remained so exciting that it became my doctoral thesis,” says the biologist.

His subsequent research showed that these precursor cells multiply dramatically around the edges of brain wounds. Most then continue to mature, eventually becoming oligodendrocytes capable of producing new myelin.

But Ries and Deussing also uncovered something that had not been known before. Near the damaged tissue, about one third of the OPCs activate corticotropin-releasing hormone (CRH), a hormone that plays a central role in regulating the body’s stress response. Researchers had not previously known that OPCs could produce neuropeptides such as CRH. The findings have now been published in the renowned journal Cell Reports.

The CRH response begins remarkably quickly. Production can be detected within just a few hours after an injury, but it shuts down again after roughly three days. This short and rapid burst suggests that CRH has an important function during the earliest stages of the healing response.

CRH Helps Control the Timing of Myelin Repair

One of the two known receptors for CRH also appears to be central to this process. CRH receptor 1 is present on a different population of OPCs and allows those cells to respond to the CRH that has been released.

When CRHR1 is absent, OPCs multiply more rapidly after an injury. That initial increase, however, does not translate into better repair. Ultimately, fewer mature oligodendrocytes are produced and remain.

The findings indicate that CRH helps regulate the timing of OPC maturation. That timing appears to be essential for producing enough mature oligodendrocytes to properly restore the damaged myelin sheath.

The Same System Shapes the Developing Brain

OPCs are not only important after injury. They also have a major role in building myelin as the brain matures. Much of this myelination takes place after birth and continues until young adulthood.

Because CRH receptor 1 is found on OPCs even when no injury is present, Ries and Deussing began to wonder whether the receptor might also influence myelination during normal brain development. Working with other researchers, they examined myelin formation in additional mouse models using several different methods.

They found that mice lacking CRH receptor 1 produced more OPCs during the early stages of development. Those changes did not disappear with age. Instead, they had lasting effects on the structure of the brain.

In adult brains, the researchers detected changes in myelination that could be traced to thicker myelin sheaths, particularly around thin axons. The results suggest that CRH receptor 1 on OPCs plays an important role not only in repairing myelin after injury, but also in regulating how myelin develops in the first place.

Where Does CRH Come From During Development?

Following an injury, OPCs themselves respond by producing and releasing CRH. Brain development raises a different question: where does the stress hormone come from when the brain is maturing normally?

The scientists propose that neurons may provide the answer. Their hypothesis is that developing neurons release CRH, which then influences both the multiplication of OPCs and their maturation into oligodendrocytes that produce myelin.

A Possible Connection to Depression and Stress

Neurons are already known to release CRH, particularly during stressful conditions. Stress experienced during early childhood development is also recognized as a risk factor for psychiatric disorders.

The new results therefore raise the possibility that the CRH system operating in OPCs could have broader implications for mental health.

“Our current findings suggest that in stress-associated psychiatric disorders such as depression, the CRH system in OPCs may play a greater role than previously known,” Deussing speculates.

If future research confirms and expands on that connection, understanding how CRH signaling affects OPCs, myelin formation, and brain development could eventually point toward completely new therapeutic approaches.

More than 99 percent of the upper atmosphere consists of electrically neutral gas known as the thermosphere. The term thermospheric density refers to the density of this neutral atmosphere between about 100 and 1000 kilometers above Earth’s surface. By comparison, the ionized gas of the ionosphere accounts for less than 1 percent of the atmosphere. Because ionized gas affects the way radio waves travel, the ionosphere is relatively straightforward to observe. Measuring conditions in the thermosphere is much more difficult.

A New Way to Observe the Thermosphere

Better measurements of thermospheric density could advance research into the upper atmosphere while also providing valuable information for space engineering. Motivated by both needs, researchers at Kyoto University developed a new technique for visualizing this difficult-to-observe region.

“This is a multidisciplinary study between space science and space engineering,” says corresponding author Mamoru Yamamoto. “Reading papers from both research fields, we realized that deeper dialogue between researchers from both fields is necessary.”

The researchers used publicly available orbital information from Starlink satellites and applied tomography, a technique commonly associated with medical imaging, to Earth’s upper atmosphere. By examining atmospheric drag through the gradual decay of satellite orbits, the team estimated thermospheric density around approximately 1,200 satellites flying at an altitude of 482 kilometers.

Building a Two-Dimensional Atmospheric Map

Using those measurements, the researchers produced a two-dimensional latitude-longitude snapshot of thermospheric density at an altitude of roughly 500 kilometers. According to the team, this represents the first tomographic analysis of its kind.

The resulting density patterns also showed strong consistency with observations from the European Space Agency’s SWARM satellites, which measure changes in atmospheric density along their orbital paths.

The work expands on an earlier study by the same team. In that research, scientists estimated how thermospheric density changed over time and altitude using general orbital information called Two-Line Element, or TLE, data from Starlink satellites. The new analysis adds another dimension by examining how density varies horizontally across latitude and longitude, revealing more of the thermosphere’s geographic structure.

Making Crowded Orbits Safer

The findings could have practical benefits as the number of objects orbiting Earth continues to grow. More accurate information about atmospheric density can improve predictions of satellite motion, helping reduce the chance of collisions between satellites and between satellites and space debris.

The technique could also eventually support near-real-time measurements of atmospheric density around satellites. Such monitoring could improve space weather forecasting and contribute to safer, more dependable satellite operations in the future.

Glial cells play essential supporting and nourishing roles in the brain. One type, known as astrocytes because of their star-shaped appearance, is especially important for healthy neuron function. Astrocytes provide nerve cells with nutrients, help control blood flow, and support the overall health of brain tissue.

Scientists had long thought that once astrocytes were destroyed, the adult brain could not fully replace them. This loss can occur after brain injuries and in autoimmune diseases such as the rare neuromyelitis optica spectrum disorder, in which the body’s own antibodies attack and destroy astrocytes.

Specialized Astrocytes Rebuild Damaged Brain Tissue

A study led by co-lead authors Marina Herwerth and Matthias Wyss of the Institute of Pharmacology and Toxicology at the University of Zurich (UZH) challenges that long-standing view. The research team, headed by Bruno Weber, identified a specialized population of “regenerative” astrocytes in the brains of living mice.

These cells gather around the edges of damaged brain regions and help rebuild the lost astrocyte network. “The findings of our study reveal a previously unknown ability of the adult brain to repair itself. They point toward new ways of supporting recovery from ailments involving the loss of astrocytes,” Weber says.

New Cell Nuclei Travel Into Damaged Areas

To follow the repair process, the researchers used two-photon microscopy to observe the brains of living mice in real time for several weeks. They also tracked which genes became active in different regions of the brain. Together, these methods allowed the team to identify the astrocytes responsible for restoring injured tissue.

The regenerative cells do more than simply divide. They also carry out an unusual process in which newly created nuclei from daughter cells travel considerable distances through the astrocytes toward the damaged region. As Weber explains, “they send the newly formed nuclei of their daughter cells gliding across long distances to repopulate the damaged area of the brain and knit the astrocyte network back together.”

New Targets for Brain Regeneration

The finding that cell nuclei can move through the long extensions of adult astrocytes into injured tissue adds a new dimension to scientists’ understanding of how the brain organizes its own repair after certain types of damage.

If researchers eventually learn how to selectively activate these repair mechanisms, they may be able to promote more effective restoration of damaged brain tissue, rebuild astrocyte networks, and improve recovery from certain brain disorders.

The team also identified many genes and signaling pathways that become temporarily active while the repair process is underway. These biological signals may provide potential targets for future efforts to influence regeneration after disease or injury.

“We were able to identify numerous genes and signaling pathways that are temporarily activated during repair. They could serve as starting points in the future for influencing post-disease and -injury regeneration processes,” Weber stresses.