Led by researchers from NYU Grossman School of Medicine, the study revolves around brain cells called neurons that “fire” — or bring about swings in the balance of their positive and negative charges — to transmit electrical signals that encode memories. Large groups of neurons in a brain region called the hippocampus fire together in rhythmic cycles, creating sequences of signals within milliseconds of each other that can encode complex information.

Called “sharp wave-ripples,” these “shouts” to the rest of the brain represent the near-simultaneous firing of 15 percent of hippocampal neurons, and are named for the shape they take when their activity is captured by electrodes and recorded on a graph.

While past studies had linked ripples with memory formation during sleep, the new study, published online in the journal Science on March 28, found that daytime events followed immediately by five to 20 sharp wave-ripples are replayed more during sleep and so consolidated into permanent memories. Events followed by very few or no sharp wave-ripples failed to form lasting memories.

“Our study finds that sharp wave-ripples are the physiological mechanism used by the brain to ‘decide’ what to keep and what to discard,” said senior study author György Buzsáki, MD, PhD, the Biggs Professor of Neuroscience in the Department of Neuroscience and Physiology at NYU Langone Health.

Walk and Pause

The new study is based on a known pattern: mammals including humans experience the world for a few moments, then pause, then experience a little more, then pause again. After we pay attention to something, say the study authors, brain computation often switches into an “idle” re-assessment mode. Such momentary pauses occur throughout the day, but the longest idling periods occur during sleep.

Buzsaki and colleagues had previously established that no sharp wave-ripples occur as we actively explore sensory information or move, but only during the idle pauses before or after. The current study found that sharp wave-ripples represent the natural tagging mechanism during such pauses after waking experiences, with the tagged neuronal patterns reactivated during post-task sleep.

Importantly, sharp wave-ripples are known to be made up the firing of hippocampal “place cells” in a specific order that encodes every room we enter, and each arm of a maze entered by a mouse. For memories that are remembered, those same cells fire at high speed, as we sleep, “playing back the recorded event thousands times per night.” The process strengthens the connections between the cells involved.

For the current study, successive maze runs by study mice were tracked via electrodes by populations of hippocampal cells that constantly changed over time despite recording very similar experiences. This revealed for the first time the maze runs during which ripples occurred during waking pauses, and then were replayed during sleep.

Sharp wave-ripples were typically recorded when a mouse paused to enjoy a sugary treat after each maze run. The consumption of the reward, say the authors, prepared the brain to switch from an exploratory to an idle pattern so that sharp wave-ripples could occur.

Using dual-sided silicon probes, the research team was able to record up to 500 neurons simultaneously in the hippocampus of animals during maze runs. This in turn created a challenge because data becomes exceedingly complex the more neurons are independently recorded. To gain an intuitive understanding of the data, visualize neuronal activity, and form hypotheses, the team successfully reduced the number of dimensions in the data, in some ways like converting a three-dimensional image into a flat one, and without losing the data’s integrity.

“We worked to take the external world out of the equation, and looked at the mechanisms by which the mammalian brain innately and subconsciously tags some memories to become permanent,” said first author Wannan (Winnie) Yang, PhD, a graduate student in Buzsáki’s lab. “Why such a system evolved is still a mystery, but future research may reveal devices or therapies that can adjust sharp wave-ripples to improve memory, or even lessen recall of traumatic events.”

Along with Drs. Buzsáki and Yang, study authors from the Neuroscience Institute at NYU Langone Health were Roman Huszár and Thomas Hainmueller. Kirill Kiselev of the Center for Neural Science at New York University was also an author, as was Chen Sun of Mila, the Quebec Artificial Intelligence Institute, in Montréal. The work was supported by National Institute of Health grants R01MH122391 and U19NS107616.

The experts addressed setting standards for three key indoor pollutants — carbon dioxide (CO₂), carbon monoxide (CO), PM2.5 which are particles so small they can lodge deep in the lungs and enter the bloodstream — and ventilation rate.

Distinguished Professor Morawska, from the QUT School of Earth and Atmospheric Sciences, internationally known, among others, for leading the appeal to the WHO to recognise the airborne transmission spread of the Covid-19 virus early in the pandemic, has continued to raise the importance of adequate indoor air quality for public spaces.

“Most countries do not have any legislated indoor air quality (IAQ) performance standards for public spaces that address concentration levels of IA pollutants,” Professor Morawska said.

“To have practical value, IAQ standards must be implementable by designing new buildings that are built, operated and maintained to standard or retrofitted to meet the standards.

“While there is a cost in the short term, the social and economic benefits to public health, wellbeing and productivity will likely far outweigh the investment in cost in achieving clean indoor air.”

Professor Morawska said CO₂ sensors were readily available, inexpensive and robust and should be used as a proxy to measure pathogens and CO₂ during human occupancy in a public space.

“CO₂ can serve as a proxy for occupant-emitted contaminants and pathogens and to effectively assess ventilation quality,” she said.

“We propose a CO₂ concentration level of 800ppm with the proviso that outdoor concentration is used as a baseline and recognition of the fact that outdoor concentrations are increasing due to emissions to the atmosphere that outweigh removal.

“Another key indicator of air quality we addressed is the amount of PM2.5 and we propose the WHO air quality guidelines as a basis for indoor air quality standards but with a 1-hour averaging time, as the 24 hours of the WHO AQG is much longer than people usually spend in public places.”

Professor Morawska said mechanical ventilation systems should remove and dilute human-emitted and other indoor-generated pollutants at a higher rate than their production so that they would not accumulate in indoor air.

“The technologies for measuring ventilation already exist in most modern mechanically ventilated buildings but monitoring ventilation rates in terms of clean air delivered to the space requires us to consider the number of people and their activities in the space to ensure adequate IAQ.

“A practical ventilation standard could be air from outside (assumed to be clean), or clean recirculated air to the entire occupied zone and with airflow not directed from one person to another.

“Additional measures in support of ventilation, such as air cleaning and disinfection, could greatly reduce the need to increase the outdoor air supply, which carries a heavy energy demand.

“Filtering recirculated air is an effective way to reduce concentration of, and thus our exposure to, airborne particulate matter, allergens and pathogens.”

The research, led by the University of Cambridge and Penn State University, improves prospects for the elimination and control of bovine tuberculosis (TB), an infectious disease of cattle that results in large economic costs and health impacts across the world.

This is the first study to show that BCG-vaccinated cattle infected with TB are substantially less infectious to other cattle. This remarkable indirect effect of the vaccine beyond its direct protective effect has not been measured before.

The spillover of infection from livestock has been estimated to account for about 10% of human tuberculosis cases. While such zoonotic TB (zTB) infections are most commonly associated with gastro-intestinal infections related to drinking contaminated milk, zTB can also cause chronic lung infections in humans. Lung disease caused by zTB can be indistinguishable from regular tuberculosis, but is more difficult to treat due to natural antibiotic resistance in the cattle bacteria.

TB remains endemic in many countries around the world, including in Europe and the Americas, where its control costs farmers and taxpayers hundreds of millions of dollars each year.

The study is published today in the journal Science.

In the study, carried out in Ethiopia, researchers examined the ability of the vaccine, Bacillus Calmette-Guérin (BCG), to directly protect cattle that receive it, as well as to indirectly protect both vaccinated and unvaccinated cattle by reducing TB transmission. Vaccinated and unvaccinated animals were put into enclosures with naturally infected animals, in a novel crossover design performed over two years.

“Our study found that BCG vaccination reduces TB transmission in cattle by almost 90%. Vaccinated cows also developed significantly fewer visible signs of TB than unvaccinated ones. This suggests that the vaccination not only reduces the progression of the disease, but that if vaccinated animals become infected, they are substantially less infectious to others,” said Andrew Conlan, Associate Professor of Epidemiology at the University of Cambridge’s Department of Veterinary Medicine and a corresponding author of the study.

Using livestock census and movement data from Ethiopia, the team developed a transmission model to explore the potential for routine vaccination to control bovine tuberculosis.

“Results of the model suggest that vaccinating calves within the dairy sector of Ethiopia could reduce the reproduction number of the bacterium — the R₀ — to below 1, arresting the projected increase in the burden of disease and putting herds on a pathway towards elimination of TB,” Conlan said.

The team focused their studies in Ethiopia, a country with the largest cattle herd in Africa and a rapidly growing dairy sector that has a growing burden of bovine tuberculosis and no current control program, as a representative of similarly situated transitional economies.

“Bovine tuberculosis is largely uncontrolled in low- and middle-income countries, including Ethiopia,” said Abebe Fromsa, associate professor of agriculture and veterinary medicine at Addis Ababa University in Ethiopia and the study’s co-lead author. “Vaccination of cattle has the potential to provide significant benefits in these regions.”

“For over a hundred years, programs to eliminate bovine tuberculosis have relied on intensive testing and slaughtering of infected animals,” said Vivek Kapur, professor of microbiology and infectious diseases and Huck Distinguished Chair in Global Health at Penn State and a corresponding author of the study.

He added: “This approach is unimplementable in many parts of the world for economic and social reasons, resulting in considerable animal suffering and economic losses from lost productivity, alongside an increased risk of spillover of infection to humans. By vaccinating cattle, we hope to be able to protect both cattle and humans from the consequences of this devastating disease.”

Professor James Wood, Alborada Professor of Equine and Farm Animal Science in the University of Cambridge’s Department of Veterinary Medicine, noted that despite TB being more prevalent in lower-income countries, the United Kingdom, Ireland and New Zealand also experience considerable economic pressures from the disease which continues to persist despite intensive and costly control programmes.

Wood said: “For over twenty-years the UK government has pinned hopes on cattle vaccination for bovine tuberculosis as a solution to reduce the disease and the consequent costs of the controls. These results provide important support for the epidemiological benefit that cattle vaccination could have to reduce rates of transmission to and within herds.”

Their report, which will appear in Science, shows that an alternative medication, a viral papain-like protease inhibitor, inhibits disease progression in animals, a necessary step before human drug trials.

“COVID-19 remains the nation’s third leading cause of death, so there’s already a massive need for additional treatment options,” said Jun Wang, senior author of the study and an associate professor who runs a research lab at Rutgers’ Ernest Mario School of Pharmacy. “That need will grow more urgent when, inevitably, COVID-19 mutates in ways that prevent Paxlovid from working.”

The Rutgers team hoped to make a drug that interfered with viral papain-like protease (PLpro), a protein that performs important functions in all known strains of COVID-19.

Creating such a drug required detailed information about PLpro’s structure, which Wang’s team got from the Arnold Lab at Rutgers’ Center for Advanced Biotechnology and Medicine (CABM).

Precise knowledge of PLpro’s structure enabled Wang’s team to design and synthesize 85 drug candidates that would bond to – and interfere with — this vital protein.

“The PLpro crystal structures showed an unexpected arrangement of how the drug candidate molecules bind to its protein target, leading to innovative design ideas implemented by professor Wang’s medicinal chemistry team,” said Eddy Arnold, who is a professor at CABM and the Rutgers Department of Chemistry and Chemical Biology.

Laboratory testing established that the most effective of those drug candidates, a compound dubbed Jun12682, inhibited several strains of the SARS-CoV-2 virus, including strains that resist treatment with Paxlovid.

Subsequent testing on SARS-CoV-2-infected mice by the Deng lab at Oklahoma State University showed that oral treatment with Jun12682 reduced viral lung loads and lesions while improving survival rates.

“Our treatment was about as effective in mice as Paxlovid was in its initial animal tests,” said Wang, who added the experimental drug appears to have at least one major advantage over the older drug.

“Paxlovid interferes with many prescription medications, and most people who face the highest risk of severe COVID-19 take other prescription medicines, so it’s a real problem,” Wang said. “We tested our candidate Jun12682 against major drug-metabolizing enzymes and saw no evidence that it would interfere with other medications.”

Disclosure: Rutgers has submitted patent applications for Jun12682, along with the other 84 drug candidates, and is looking for partners to help move the drug candidate forward through further stages of testing and development.

Indeed, the study finds that many schools that receive relatively low ratings perform better than these ratings would imply. Conventional ratings, the research makes clear, are highly correlated with race. Specifically, many published school ratings are highly positively correlated with the share of the student body that is white.

“A school’s average outcomes reflect, to some extent, the demographic mix of the population it serves,” says MIT economist Josh Angrist, a Nobel Prize winner who has long analyzed education outcomes. Angrist is co-author of a newly published paper detailing the study’s results.

The study, which examines the Denver and New York City school districts, has the potential to significantly improve the way school quality is measured. Instead of raw aggregate measures like test scores, the study uses changes in test scores and a statistical adjustment for racial composition to compute more accurate measures of the causal effects that attending a particular school has on students’ learning gains. This methodologically sophisticated research builds on the fact that Denver and New York City both assign students to schools in ways that allow the researchers to mimic the conditions of a randomized trial.

In documenting a strong correlation between currently used rating systems and race, the study finds that white and Asian students tend to attend higher-rated schools, while Black and Hispanic students tend to be clustered at lower-rated schools.

“Simple measures of school quality, which are based on the average statistics for the school, are invariably highly correlated with race, and those measures tend to be a misleading guide of what you can expect by sending your child to that school,” Angrist says.

The paper, “Race and the Mismeasure of School Quality,” appears in the latest issue of the American Economic Review: Insights. The authors are Angrist, the Ford Professor of Economics at MIT; Peter Hull, a professor of economics at Brown University; Parag Pathak, the Class of 1922 Professor of Economics at MIT; and Christopher Walters PhD ’13, an associate professor of economics at the University of California at Berkeley. Angrist and Pathak are both professors in the MIT Department of Economics and co-founders of MIT’s Blueprint Labs, a research group that often examines school performance.

The study uses data provided by the Denver and New York City public school districts, where 6th-graders apply for seats at certain middle schools, and the districts use a school-assignment system. In these districts, students can opt for any school in the district, but some schools are oversubscribed. In these circumstances, the district uses a random lottery number to determine who gets a seat where.

By virtue of the lottery inside the seat-assignment algorithm, otherwise-similar sets of students randomly attend an array of different schools. This facilitates comparisons that reveal causal effects of school attendance on learning gains, as in a randomized clinical trial of the sort used in medical research. Using math and English test scores, the researchers evaluated student progress in Denver from the 2012-2013 through the 2018-2019 school years, and in New York City from the 2016-2017 through 2018-2019 school years.

Those school-assignment systems, it happens, are mechanisms some of the researchers have helped construct, allowing them to better grasp and measure the effects of school assignment.

“An unexpected dividend of our work designing Denver and New York City’s centralized choice systems is that we see how students are rationed from [distributed among] schools,” says Pathak. “This leads to a research design that can isolate cause and effect.”

Ultimately, the study shows that much of the school-to-school variation in raw aggregate test scores stems from the types of students at any given school. This is a case of what researchers call “selection bias.” In this case, selection bias arises from the fact that more-advantaged families tend to prefer the same sets of schools.

“The fundamental problem here is selection bias,” Angrist says. “In the case of schools, selection bias is very consequential and a big part of American life. A lot of decision-makers, whether they’re families or policymakers, are being misled by a kind of naïve interpretation of the data.”

Indeed, Pathak notes, the preponderance of more simplistic school ratings today (found on many popular websites) not only creates a deceptive picture of how much value schools add for students, but has a self-reinforcing effect — since well-prepared and better-off families bid up housing costs near highly-rated schools.As the scholars write in the paper, “Biased rating schemes direct households to low-minority rather than high-quality schools, while penalizing schools that improve achievement for disadvantaged groups.”

The research team hopes their study will lead districts to examine and improve the way they measure and report on school quality. To that end, Blueprint Labs is working with the New York City Department of Education to pilot a new ratings system later this year. They also plan additional work examining the way families respond to different sorts of information about school quality.

Given that the researchers are proposing to improve ratings in what they believe is a straightforward way, by accounting for student preparation and improvement, they think more officials and districts may be interested in updating their measurement practices.

“We’re hopeful that the simple regression adjustment we propose makes it relatively easy for school districts to use our measure in practice,” Pathak says.

The research received support from the Walton Foundation and the National Science Foundation.

‘People aren’t purely truth-seekers — many beliefs are influenced by emotions and driven by what is pleasant or comforting. Like belief in an afterlife or optimism about health outcomes,’ says Joël van der Weele, professor of Economic Psychology at the UvA. Working alongside professor of Neuroeconomics Jan Engelmann and an international team, Van der Weele set out to answer whether people become overly optimistic when facing potential hardships. ‘So far studies haven’t provided clear evidence for wishful thinking, with many not backing up the idea,’ explains Engelmann. ‘But these mainly focused on positive outcomes, like winning a lottery. We examined how both positive and negative outcomes influence biased beliefs.’

Choosing the most pleasant outcome

Understanding self-deception and its causes is difficult in real-world situations. The study involved a set of experiments with over 1,700 participants, conducted in a lab and online. Participants were briefly shown various patterns, such as sets of differently oriented stripes or coloured dots, and were asked what kind of pattern they saw. Some of these patterns were linked to a negative outcome to induce anxiety, either a mild and non-dangerous electrical shock (in the lab) or a loss of money (online). ‘We wanted to see if people make more mistakes in recognising patterns associated with a negative outcome, thinking it was actually a harmless pattern. That would indicate wishful thinking,’ explains Van der Weele.

The study consistently found that participants were less likely to correctly identify patterns associated with a shock or loss. ‘The participants tended to see a pattern that aligned with what was more desirable,’ Engelmann says. ‘Previous research looked at wishful thinking related to positive outcomes and found mixed results, with many studies not finding an effect. Our study demonstrates very clearly that the negative emotion of anxiety about an outcome leads to wishful thinking.’

Making people more realistic

The researchers also tested interventions designed to make people more realistic. The first involved making the patterns easier to recognise. ‘Reducing uncertainty did indeed turn out to reduce wishful thinking,’ says Van der Weele. The second intervention was to offer higher potential earnings for correct pattern recognition. This intervention had little effect, except when participants could gather more evidence about the exact pattern they were shown. ‘When people had more time to collect evidence and were better rewarded for a correct answer, they became more realistic,’ explains Engelmann.

Finally, in the experiments where negative outcomes were replaced by positive outcomes, participants showed no wishful thinking. According to the authors this shows that reducing negative emotions can lessen overoptimism.

Wishful thinking in the ‘real world’

The authors recognise that wishful thinking can be useful because it helps us deal with bad feelings and manage uncertainty. Engelmann: ‘Wishful thinking is important for humans in coping with anxiety about possible future events.’ For Van der Weele and Engelmann, the concern is situations in which too much optimism stops people from getting the information they need or from acting in a way that would benefit them. ‘People can get too hopeful when things are uncertain. We observe this happening with climate change, when financial markets fluctuate, and even in personal health situations when people avoid medical help because they think everything will be fine. We need to know more about when wishful thinking helps and when it hurts.’

Crimean-Congo haemorrhagic fever virus (CCHF virus) is spread through tick bites and can cause haemorrhagic fever. The disease is serious and has a mortality rate of up to 40 per cent depending on the health status of the person infected. Common symptoms include fever, muscle pain, abdominal pain, joint pain, vomiting and haemorrhaging that can cause organ failure.

The disease has spread to Europe

The virus is present in around 40 countries, including Central Asia, the Middle East and parts of Africa. In recent years, the disease has spread to new geographical areas as a result of climate change, including Spain and France. The tick species that can spread the disease has also been observed in Germany and Sweden. There are currently no effective treatments for the disease.

In a new study, researchers at Karolinska Institutet in Sweden and others have found that the virus enters our cells via a protein on the cell surface, the so-called LDL receptors that regulate blood cholesterol levels.

To identify the protein, the researchers used human mini-organs grown in test tubes and an advanced stem cell library from JLP Health. The same platform has previously been used to identify how the Ebola virus enters cells.

The results were also confirmed in tests on mice, which showed that mice lacking the LDL receptor did not get as sick as others.

Researchers want to trick the virus

The discovery is an important step towards developing drugs for Crimean-Congo haemorrhagic fever, according to Ali Mirazimi, adjunct professor at the Department of Laboratory Medicine, Karolinska Institutet, and one of the researchers behind the study.

“Once we know which receptor the virus uses, we can produce the receptor in test tubes and administer it as a drug,” he says. “Then we can trick the virus into binding to those receptors instead of to the cells and thus stop the virus from spreading in our bodies.”

This knowledge is essential if the disease were to become more common and spread to new areas. Normally it takes many years to develop a drug, but the COVID-19 pandemic and the development of the SARS-CoV-2 vaccine showed that it can be done much faster if everyone decides it is a priority.

Ticks are spread by migratory birds

“This is an important step in our preparedness for the disease,” says Ali Mirazimi. “Crimean-Congo haemorrhagic fever is a disease we would rather not have. The ticks are spread by migratory birds and have already been found in Sweden. If the disease starts appearing in more places, we may already have a drug that we can take into clinical trials.”

The research was conducted in collaboration with the Medical University of Vienna, Austria, Helmholtz Centre for Infection Research, Germany, the National Institutes of Health, USA, and the company JLP Health. It was financed mainly by the Swedish Research Council and the EU. No conflicts of interest have been reported.

Through DNA sequencing of the animals and their tumors, University of South Florida Assistant Professor of Integrative Biology Mark Margres and doctoral student Dylan Gallinson have tracked the genomic interactions between the devils and the cancer. Their findings are published in a coauthored paper, “Intergenomic signatures of coevolution between Tasmanian devils and an infectious cancer,” in the Proceedings of the National Academy of Sciences.

“A big question in biology is the genetic basis for disease. The classic way to determine this is through genome studies and regression analysis that matches genes with disease risk,” Margres said. “Previously there hadn’t been a technique to study the interactions between both genomes.”

Using a recently developed joint genome-wide association study, Margres and Gallinson assessed 960 genomes and 15 years of data on captured devils to track the co-evolution of the devils and the cancer.

“Our collaborators in Tasmania have been monitoring the spread of the disease and collecting tissue samples,” Gallinson said. “We sequenced the DNA of both the tumors and the devils to find the mutation that contributes to the manifestation of the disease.”

Their findings can inform both epidemiological models that track infectious diseases and devil management strategies that focus on saving the endangered species.

The process of spins lining up, however, does not happen all at once. Rather, when the magnetic field is applied, different regions, or so-called domains, influence others nearby, and the changes spread across the material in a clumpy fashion. Scientists often compare this effect to an avalanche of snow, where one small lump of snow starts falling, pushing on other nearby lumps, until the entire mountainside of snow is tumbling down in the same direction.

This avalanche effect was first demonstrated in magnets by the physicist Heinrich Barkhausen in 1919. By wrapping a coil around a magnetic material and attaching it to a loudspeaker, he showed that these jumps in magnetism can be heard as a crackling sound, known today as Barkhausen noise.

Now, reporting in the journal Proceedings of the National Academy of Sciences (PNAS), Caltech researchers have shown that Barkhausen noise can be produced not only through traditional, or classical means, but through quantum mechanical effects. This is the first time quantum Barkhausen noise has been detected experimentally. The research represents an advance in fundamental physics and could one day have applications in creating quantum sensors and other electronic devices.

“Barkhausen noise is the collection of the little magnets flipping in groups,” says Christopher Simon, lead author of the paper and a postdoctoral scholar in the lab of Thomas F. Rosenbaum, a professor of physics at Caltech, the president of the Institute, and the Sonja and William Davidow Presidential Chair. “We are doing the same experiment that has been done many times, but we are doing it in a quantum material. We are seeing that the quantum effects can lead to macroscopic changes.”

Usually, these magnetic flips occur classically, through thermal activation, where the particles need to temporarily gain enough energy to jump over an energy barrier. However, the new study shows that these flips can also occur quantum mechanically through a process called quantum tunneling.

In tunneling, particles can jump to the other side of an energy barrier without having to actually pass over the barrier. If one could scale up this effect to everyday objects like golf balls, it would be like the golf ball passing straight through a hill rather than having to climb up over it to get to the other side.

“In the quantum world, the ball doesn’t have to go over a hill because the ball, or rather the particle, is actually a wave, and some of it is already on the other side of the hill,” says Simon.

In addition to quantum tunneling, the new research shows a co-tunneling effect, in which groups of tunneling electrons are communicating with each other to drive the electron spins to flip in the same direction.

“Classically, each one of the mini avalanches, where groups of spins flip, would happen on its own,” says co-author Daniel Silevitch, research professor of physics at Caltech. “But we found that through quantum tunneling, two avalanches happen in sync with each other. This is a result of two large ensembles of electrons talking to each other and, through their interactions, they make these changes. This co-tunneling effect was a surprise.”

For their experiments, members of the team used a pink crystalline material called lithium holmium yttrium fluoride cooled to temperatures near absolute zero (equivalent to minus 273.15 degrees Celsius). They wrapped a coil around it, applied a magnetic field, and then measured brief jumps in voltage, not unlike what Barkhausen did in 1919 in his more simplified experiment. The observed voltage spikes indicate when groups of electron spins flip their magnetic orientations. As the groups of spins flip, one after the other, a series of voltage spikes is observed, i.e. the Barkhausen noise.

By analyzing this noise, the researchers were able to show that a magnetic avalanche was taking place even without the presence of classical effects. Specifically, they showed that these effects were insensitive to changes in the temperature of the material. This and other analytical steps led them to conclude that quantum effects were responsible for the sweeping changes.

According to the scientists, these flipping regions can contain up to 1 million billion spins, in comparison to the entire crystal that contains approximately 1 billion trillion spins.

“We are seeing this quantum behavior in materials with up to trillions of spins. Ensembles of microscopic objects are all behaving coherently,” Rosenbaum says. “This work represents the focus of our lab: to isolate quantum mechanical effects where we can quantitively understand what is going on.”

Another recent PNAS paper from Rosenbaum’s lab similarly looks at how tiny quantum effects can lead to larger-scale changes. In this earlier study, the researchers studied the element chromium and showed that two different types of charge modulation (involving the ions in one case and the electrons in the other) operating at different length scales can interfere quantum mechanically. “People have studied chromium for a long time,” says Rosenbaum, “but it took until now to appreciate this aspect of the quantum mechanics. It is another example of engineering simple systems to reveal quantum behavior that we can study on the macroscopic scale.”

The PNAS study titled “Quantum Barkhausen noise induced by domain wall cotunneling” was funded by the U.S. Department of Energy and the National Sciences and Engineering Research Council of Canada. The author list also includes Philip Stamp, a visiting associate in physics at Caltech and a physics professor at University of British Columbia.

Located predominantly in cold regions at high latitude, boreal forests are estimated to store nearly 30 percent of the world’s soil carbon, making them the world’s largest reservoir of land-based carbon. This stored carbon is found mostly in the forests’ humus layer, which contains decomposed leaves and other organic matter.

A global, long-term study led by Duke University researchers has found that higher levels of manganese in this layer stimulated decomposition of soil organic matter, and released more carbon dioxide than did those forest plots with less or no manganese. The work appeared March 19 in the Proceedings of the National Academy of Sciences (PNAS).

“Conventional wisdom is these forests are like a global vault of carbon, where carbon is put into the vault versus taken out,” said William H. Schlesinger, professor emeritus at Duke University’s Nicholas School of the Environment and study co-author. “These findings reveal a crack in the vault, where enough manganese over time stimulates the release of carbon dioxide into the atmosphere, which has implications for climate mitigation efforts and the global carbon cycle,” said Schlesinger.

Certain industrial processes, such as metal smelting or combustion of manganese-containing fuels, can release airborne manganese which is later deposited in soils downwind.

This is one of many human activities, such as the burning of fossil fuels, deforestation, and land-use changes, that have disturbed the natural carbon cycle, leading to an increase in atmospheric carbon dioxide concentrations that contribute to global warming and climate change.

“Carbon inventorying is still an evolving science,” said Yunyu Zhang, lead author and graduate student from the Chinese Academy of Sciences. “It is essential to figure out which factors regulate this huge carbon pool [in boreal forests’ soil], especially given continuous… industrialization.”

Researchers analyzed data from boreal forests worldwide, and fertilized soil with manganese over 14 years (2009-2023) in China’s Daxing’an Mountains. Results showed the level of exchangeable manganese — the part of manganese that plants can use as nutrients — determined how much carbon was stored in boreal forest soil. After four years, carbon storage on plots fertilized with manganese fell by nearly 13 percent, meaning more carbon was released into the atmosphere.

“To develop effective and sustainable strategies, it is critical to understand complex interactions between trace nutrients and carbon storage,” Zhang said. “It is even more important to predict how those interactions work in the long term, considering the impact of human activities.”

Schlesinger emphasized the need for further research and action, noting how the study’s findings highlight the importance of soil nutrient dynamics, such as the level of exchangeable manganese, in climate change mitigation efforts.

He urged further study of the role of manganese not only in soil, but also in the air, on land-based carbon emissions, the boreal forest ecosystem, and climate mitigation.

“There’s no proverbial foolproof vault or absolute forest sink,” Schlesinger said. “We need integrated approaches to land management and climate mitigation. Climate has traditionally been considered a major factor in carbon storage, but we now see how manganese is also a key indicator, something that has long been overlooked and underexamined.”

The National Natural Science Foundation of China and Chinese Academy of Sciences co-funded the study.