Semua Kabar

Urea is one of the most important industrial chemicals produced worldwide. It is used as a fertiliser, for the production of synthetic resins and explosives and as a fuel additive for cleaning car exhaust gases. Urea is also believed to be a potential key building block for the formation of biological molecules such as RNA and DNA in connection with the question of the origin of life. Until now, the origin of urea itself on Early Earth has not been conclusively clarified.

A research team led by Ruth Signorell, Professor of Physical Chemistry at ETH Zurich, has discovered a previously unknown reaction pathway for the formation of urea that could provide an answer. The study has just been published in the journalScience.

Either high pressures and temperatures or chemical catalysts are needed for the industrial production of urea from ammonia (NH₃) and carbon dioxide (CO2). Enzymes enable the same reaction to take place in humans and animals, removing toxic ammonia from the breakdown of proteins such as urea. As this simple molecule contains nitrogen as well as carbon and probably existed on the uninhabited Early Earth, many researchers view urea as a possible precursor for complex biomolecules.

"In our study, we show one way in which urea could have formed on the prebiotic Earth," says Signorell – "namely where water molecules interact with atmospheric gases: on the water surface."

Reactor on the edge of a droplet

Signorell's team studied tiny water droplets such as those found in sea spray and fine mist. The researchers observed that urea can form spontaneously from carbon dioxide (CO2) and ammonia (NH₃) in the surface layer of the droplets under ambient conditions. The physical interface between air and liquid creates a special chemical environment at the water surface that makes the spontaneous reaction possible.

As a droplet has a very large surface area in relation to its volume, chemical reactions mainly take place near this surface. Chemical concentration gradients form in this area, which acts like a microscopic reactor. The pH gradient across the interfacial layer of the water droplets creates the required acidic environment, which opens unconventional pathways that would otherwise not take place in liquids.

"The remarkable aspect of this reaction is that it takes place under ambient conditions without any external energy," explains Mercede Mohajer Azizbaig, one of the two first authors. This not only makes the process interesting from a technical perspective but also provides valuable insights into processes that could be significant for evolution.

A window into the early days of the Earth

The origin of life is currently the subject of a great deal of wide-ranging research, with different approaches being explored. First author Pallab Basuri explains: "Given such a controversial field of research, it was important for us to back up our observations." Theoretical calculations by co-authors Evangelos Miliordos and Andrei Evdokimov from Auburn University supported the experimental findings and confirmed that the urea reaction on the droplets takes place without any external energy supply.

The results suggest that this natural reaction could also have been possible in the atmosphere of the Early Earth — an atmosphere that was rich in CO2 and probably contained small traces of ammonia. In such environments, aqueous aerosols or fog droplets could have acted as natural reactors in which precursor molecules such as urea were formed. "Our study shows how seemingly mundane interfaces can become dynamic reaction spaces, suggesting that biological molecules may have a more common origin than was previously thought," says Signorell.

In the long term, the direct reaction of CO2 and ammonia under ambient conditions could also have potential for the climate-friendly production of urea and downstream products.

Materialsprovided byETH Zurich.Note: Content may be edited for style and length.

Many galaxies, including our own Milky Way, are characterized by a flat, extended, rotating stellar disk. These disk galaxies commonly contain two main parts: a thin disk and a thick disk. The thin disk contains younger, metal-rich stars, while the thick disk contains older, metal-poor stars. These distinct components hold fossil records that help astronomers understand how galaxies form stars, build up elements like oxygen and carbon, essential for life, and evolve into their present shapes.

Until now, thin and thick disks have only been identified in the Milky Way and nearby galaxies. It has been impossible with previous telescopes to distinguish the thin edge of a distant galaxy when viewed from the side.

That changed with the launching of the James Webb Space Telescope (JWST) in 2021, which is currently the largest telescope in space.

An international team of researchers has examined 111 JWST images of distant edge-on galaxies, ones where the alignments enabled the researchers to observe the galaxies' vertical disk structures.

Takafumi Tsukui (formerly of the Australian National University and now based at Tohoku University), who led the research team, says that observing distant galaxies is like using a time machine, allowing us to see how galaxies have built their disks over cosmic history.

"Thanks to the JWST's sharp vision, we were able to identify thin and thick disks in galaxies beyond our local universe, some going as far back as 10 billion years ago."

The study revealed a consistent trend: in the earlier universe, more galaxies appear to have had a single thick disk, while in later epochs, more galaxies showed a two-layered structure with an additional thin disk component. This suggests that galaxies first formed a thick disk, followed by the formation of a thin disk within it. In more massive galaxies, this thin disk appears to have formed earlier.

The study estimated the thin disk formation time for Milky Way-sized galaxies to be around 8 billion years ago. This figure aligns with formation timelines for the Milky Way itself, where stellar ages can be measured.

To understand the revealed sequential formation from thick to thin disks and the corresponding formation timelines, the team not only examined the stellar structure but also the motion of gas, direct ingredients of stars obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) and ground-based surveys in the literature. These observations supported a coherent formation scenario:

Tsukui emphasizes that the images provided by JWST help answer one of the biggest questions in astronomy: was our galaxy's formation typical or unique? "The JWST images provided a window into galaxies that resemble the Milky Way's early state, bringing us valuable insights from galaxies far away."

The team hopes that their study will help bridge studies of nearby galaxies with far away ones and refine our understanding of disk formation. The study was published in the journalMonthly Notices of the Royal Astronomical Societyon June 26, 2025.

Materialsprovided byTohoku University.Note: Content may be edited for style and length.

A team of researchers from the Keck School of Medicine of USC's Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) has identified a new brain imaging benchmark that may improve how researchers classify biologically meaningful changes associated with Alzheimer's disease, especially in Hispanic and non-Hispanic White populations. The new study, published inImaging Neuroscience, is part of the Health and Aging Brain Study-Health Disparities (HABS-HD), a multi-university collaboration led by the University of North Texas Health Science Center and supported by the National Institute on Aging.

Using an advanced brain imaging scan called tau PET, the research team studied over 675 older adults from HABS-HD, aiming to identify the optimal brain signal that distinguishes individuals with clinically-relevant biological markers of AD from those who are aging normally.

Tau PET enables researchers to visualize abnormal proteins in the brain which contribute to Alzheimer's disease, known as tau, by using a small amount of a special radioactive tracer that highlights areas where tau has accumulated. With these scans, researchers can establish tau cut-points, a new type of biomarker used to determine whether a scan shows an amount of tau protein in the brain high enough to suggest possible early signs of Alzheimer's disease or related conditions. This new benchmark could eventually inform the way clinicians interpret tau PET scans and better identify who may be at risk for AD.

In this study, researchers compared tau PET scans of study participants who were cognitively impaired with those who were not impaired based on cognitive tests to establish a tau cut-point that would indicate a higher risk for Alzheimer's disease. They found one — but it was only effective in certain circumstances.

"Our tau cut-point was able to distinguish whether study participants had cognitive impairment – but only when another abnormal protein, amyloid, was also present in those with cognitive impairment, and only in Hispanic and non-Hispanic White participants," said senior author Meredith N. Braskie, PhD, assistant professor of neurology. "In non-Hispanic Black participants, the tau cut-point did not perform as expected. This suggests that other pathologies or conditions may be driving cognitive decline in this group. Our study is an important step toward better understanding how tau relates to cognition in diverse populations and has important implications for future clinical trials that aim to target tau."

The team used a new imaging tracer called 18F-PI-2620, to measure tau protein buildup in the brain. They found that when tau levels in the medial temporal lobe­ — a region deep in the brain — exceeded a certain threshold, it strongly indicated cognitive impairment related to AD.

"While our findings support prior research linking medial temporal lobe tau to cognitive impairment, establishing a cut-point in this region using 18F-PI-2620, marks an important step toward defining tau positivity for both research and clinical applications. At the same time, the limited reliability of tau as an indicator of cognitive impairment in non-Hispanic Black participants highlights the need for more diverse populations in research and for future studies to examine both biological and social determinants of Alzheimer's disease," said lead author Victoria R. Tennant, a PhD candidate in USC's Neuroscience Graduate Program.

The findings reflect a growing focus in AD research on making sure diagnostic tools work for everyone — not just in narrow clinical trial populations. Alzheimer's disease is known to affect the brain in stages. While amyloid plaques often build up early, tau tangles are more closely tied to memory loss and other symptoms.

"This type of imaging is critical for understanding who is at risk and how the disease develops," said Stevens INI director Arthur W. Toga, PhD. "These findings are just the latest to come from HABS-HD, which is the most comprehensive study of Alzheimer's disease and related dementias in diverse communities. HABS-HD has already produced key findings related to ethnic variations in AD biomarkers, the influences of social determinants on cognitive health, and vascular contributions to dementia, just to name a few. We hope this work will lead to more personalized care and better outcomes for all communities."

In addition to Tennant and Braskie, the study's other authors are Koral V. Wheeler, Noelle N. Lee, Jamie A. Terner, Maxwell W. Hand, Suchita Ganesan, Patrick Walsh, Aisha Greene, Tyler Berkness, Tiantian Lei, Arthur W. Toga from the Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California; Rema Raman and Robert A. Rissman from the Alzheimer's Therapeutic Research Institute, Keck School of Medicine of USC, University of Southern California; Bradley T. Christian from the Waisman Center, University of Wisconsin-Madison; Melissa Petersen, Ann D. Cohen, Karin L. Meeker, Zhengyang Zhou, Rajesh R. Nandy and Sid E. O'Bryant from the University of North Texas Health Science Center at Fort Worth; Beau M. Ances from the Washington University School of Medicine in St. Louis; and Kristine Yaffe from the Department of Psychiatry, Neurology, and Epidemiology/Biostatistics, University of California, San Francisco.

This research was supported by the National Institute on Aging of the National Institutes of Health [R01AG054073, R01AG058533, R01AG070862, P41EB015922, and U19AG078109], and by the Office of the Director, the National Institutes of Health, [S10OD032285].

Materials provided byKeck School of Medicine of USC.Note: Content may be edited for style and length.

Simon Fraser University researchers are using a new approach to brain imaging that could improve how drugs are prescribed to treat Parkinson's disease.

The new study, published in the journalMovement Disorders, looks at why levodopa – the main drug used in dopamine replacement therapy – is sometimes less effective in patients.

The drug is typically prescribed to help reduce the movement symptoms associated with the neurodegenerative disorder.

While it is effective in improving symptoms for the vast majority of patients, not everyone experiences the same level of benefit.

In order to find out why this is the case, an SFU collaboration with researchers in Sweden has used magnetoencephalography (MEG) technology to determine how the drug affects signals in the brain.

"Parkinson's is the second most prevalent neurodegenerative disease worldwide and it is the most rapidly increasing, in terms of incidence," says Alex Wiesman, assistant professor in biomedical physiology and kinesiology at SFU.

"Treating this disease, both in terms of helping people with their symptoms, but also trying to find ways to reverse the effects, is becoming more and more important.

"If clinicians can see how levodopa activates certain parts of the brain in a patient, it can help to inform a more personalised approach to treatment."

The study was a collaboration with researchers at Karolinska Institute in Sweden, who used MEG to collect data from 17 patients with Parkinson's disease – a relatively small sample size.

Researchers mapped participants' brain signals before and after taking the drug, in order to see how and where the drug impacted brain activity.

MEG is an advanced non-invasive technology that measures the magnetic fields produced by the brain's electrical signals.

It can help clinicians and researchers to study brain disorders and diseases, including brain injuries, tumors, epilepsy, autism, mental illness and more.

Using this rare brain imaging technology, Wiesman and team developed a new analysis that lets them "search" the brain for off-target drug effects.

"With this new way of analyzing brain imaging data, we can track in real time whether or not the drug is affecting the right brain regions and helping patients to manage their symptoms," says Wiesman.

"What we found was that there's sometimes 'off target' effects of the drug. In other words, we could see the drug activating brain regions we don't want to be activating and that's getting in the way of the helpful effects.

"We found that those people who showed 'off target' effects are still being helped by the drug, but not to the same extent as others."

Parkinson's disease is a neurodegenerative disorder, meaning parts of the brain become progressively damaged over time. It affects predominately the dopamine-producing neurons in a specific area of the brain called the substantia nigra.

People with Parkinson's disease may experience a range of movement-related symptoms, such as tremors, slow movement, stiffness and balance problems.

Wiesman hopes that a better understanding of how levodopa affects an individual's brain signals could improve how drugs are prescribed to treat Parkinson's.

"This might be really helpful for tracking individualized responses to these types of drugs and helping with prescribing and therapeutics," he says.

"So maybe we try different medications, maybe we adjust dosages differently. And this helps clinicians get at that question of how we prescribe personalized medicine in a way that really helps the patient.

"The more we can personalize that approach, make it more expedient, make it a bit more specific to that person, the better."

This new type of brain imaging analysis is not only for studying Parkinson's disease; any medications that affect brain signaling can be studied using the method developed by Wiesman and colleagues.

SFU's ImageTech Lab, at the Surrey Memorial Hospital, is home to the only MEG in western Canada.

"We have this really fantastic technology right here at SFU, and combined with the new analysis approaches that we're developing, it gives us a really unprecedented look into what's happening in the brain," says Wiesman.

"We can use this technology moving forward to study Parkinson's disease in ways that no one has ever done before worldwide.

"Our next step is to take our new approach and apply it to a larger patient group. We also need to translate this research to more accessible brain imaging methods, like electroencephalogram (EEG).

"Ultimately, we want to make sure this technology is useful for a diverse population and more widely accessible to patients with Parkinson's disease."

Materialsprovided bySimon Fraser University.Note: Content may be edited for style and length.