Tech

The regular arrangement of atoms in a crystal allows complex interactions that can lead to new states of matter. Some crystals have magnetic interactions in only one dimension, i.e. are they magnetically one-dimensional. If, in addition, successive magnetic moments are pointing in opposite directions , then we are dealing with a one-dimensional antiferromagnet. Hans Bethe first described this system theoretically in 1931, predicting also the presence of excitations of strings of two or more consecutive moments pointing in one direction, so called Bethe strings.

However those string states could not be observed under normal experimental conditions because they are unstable and obscured by the other features of the system. The trick used in this paper is to isolate the strings by applying a magnetic field.

Now an international cooperation around the HZB physicist Bella Lake and her colleague Anup Bera was able to experimentally identify and characterise Bethe strings in a real solid for the first time. The team made crystals of SrCo2V2O8, which is a model system one-dimensional antiferromagnnet. Only the cobalt atoms have magnetic moments, they all are aligned along one direction and adjacent moments cancel each other out.

At the Berlin neutron source BER II it was possible to investigate the sample with neutrons under extremely high magnetic fields up to 25.9 Tesla. From the data, the physicists obtained a phase diagram of the sample as a function of the magnetic field, and also further information about the internal magnetic patterns, which could be compared with the idea of Bethe that were quantified by a theoretical group led by Jianda Wu.

"The experimental data are in excellent agreement with the theory," says Prof. Bella Lake. "We were able to clearly identify two and even three chains of Bethe strings and determine their energy dependence. These results show us once again how fantastically well quantum physics works."

The Arctic polar night remains one of the last undisturbed dark environments on the planet. But as the climate changes and human activities increase in the Arctic, natural light sources -- such as the moon, the stars and the aurora borealis -- are being masked by much stronger illumination from artificial light.

University of Delaware Professor Jonathan Cohen has co-written a new study that looks at how artificial light during the polar night disrupts Arctic fish and zooplankton behavior down to 200 meters in depth. The disruption of species behavior so far down in the water column could introduce biases on stock assessments of commercial and non-commercial fish species.

These findings were recently published in the Communications Biology scientific journal.

Cohen, associate professor in UD's College of Earth, Ocean and Environment, said that research vessels during the Arctic polar night are like Christmas trees illuminated in the middle of the dark ocean.

"You're trying to measure and understand the position of animals in the water column, a process that's very light sensitive, and you're completely changing the light environment around you," said Cohen. "In reality, it's completely impossible to understand the process from a lit-up research vessel because you're swamping the organisms and they're not doing what they would normally do."

To counteract this process, Cohen and other researchers took acoustic surveys of fish and plankton in the water column directly below the lit-up research vessel and then also took surveys using autonomous surface vehicles without lights that were far away from the research vessel.

They found a lot more fish and plankton appearing in the water column underneath the autonomous surface vehicles when they compared the results to the number of fish they saw in the water column directly below the research vessel.

These findings were published in 2018 and for this subsequent study, the researchers wanted to quantify the animal avoidance response and the light field around the vessel in more detail.

"We made a series of measurements of light around the vessel, trying to get a sense of how far away from the vessel this response occurred with the ultimate goal of trying to understand what impact these artificial light fields would have for fisheries surveys conducted during the night time or during the polar night," said Cohen.

It is important to have accurate fish surveys as fishery agencies across the world rely on acoustic surveys to help understand fish populations and then those population estimates ultimately influence catch quotas for fisheries management.

The concern raised in the paper is that artificial light production from fisheries survey vessels could influence the way that those population estimates are made.

"In the paper, we demonstrated that there's a sphere of light around the vessel that causes an influence, and we see it easily through the upper 200 meters of the water column," said Cohen. "So the effect of artificial light isn't just limited to the surface. It goes down quite deep in terms of an avoidance of the organisms. They just go away and so you end up predicting the number of organisms to be a lot lower than you might expect."

The acoustic surveys used in the study show the fish as little dots in the water column. When the researchers measured from the research vessel, the little dots in the water column underneath the boat moved away from the light field. But when the researchers took a surface vehicle or a small boat and went away from the vessel, the natural response came back and more fish appeared in the water column.

The biggest finding in the paper is that the response of fish species occurred so far down in the water column, as the effects of the ship's lights were evident in the fish species all the way down into the Mesopelagic Zone -- or so-called Twilight Zone -- of the ocean.

Cohen and the other researchers are hoping that these findings will help fishery managers think twice about how they are reporting fish populations in the ocean when they are using artificial light in the Arctic polar night, and elsewhere during the nighttime.

"We're basically trying to set the parameters to say if you have a vessel and you're looking at this portion of the water column, the values aren't going to be as useful," said Cohen.

Researchers have designed a machine learning method that can predict battery health with 10x higher accuracy than current industry standard, which could aid in the development of safer and more reliable batteries for electric vehicles and consumer electronics.

The researchers, from Cambridge and Newcastle Universities, have designed a new way to monitor batteries by sending electrical pulses into them and measuring the response. The measurements are then processed by a machine learning algorithm to predict the battery's health and useful lifespan. Their method is non-invasive and is a simple add-on to any existing battery system. The results are reported in the journal Nature Communications.

Predicting the state of health and the remaining useful lifespan of lithium-ion batteries is one of the big problems limiting widespread adoption of electric vehicles: it's also a familiar annoyance to mobile phone users. Over time, battery performance degrades via a complex network of subtle chemical processes. Individually, each of these processes doesn't have much of an effect on battery performance, but collectively they can severely shorten a battery's performance and lifespan.

Current methods for predicting battery health are based on tracking the current and voltage during battery charging and discharging. This misses important features that indicate battery health. Tracking the many processes that are happening within the battery requires new ways of probing batteries in action, as well as new algorithms that can detect subtle signals as they are charged and discharged.

"Safety and reliability are the most important design criteria as we develop batteries that can pack a lot of energy in a small space," said Dr Alpha Lee from Cambridge's Cavendish Laboratory, who co-led the research. "By improving the software that monitors charging and discharging, and using data-driven software to control the charging process, I believe we can power a big improvement in battery performance."

The researchers designed a way to monitor batteries by sending electrical pulses into it and measuring its response. A machine learning model is then used to discover specific features in the electrical response that are the tell-tale sign of battery aging. The researchers performed over 20,000 experimental measurements to train the model, the largest dataset of its kind. Importantly, the model learns how to distinguish important signals from irrelevant noise. Their method is non-invasive and is a simple add-on to any existing battery systems.

The researchers also showed that the machine learning model can be interpreted to give hints about the physical mechanism of degradation. The model can inform which electrical signals are most correlated with aging, which in turn allows them to design specific experiments to probe why and how batteries degrade.

"Machine learning complements and augments physical understanding," said co-first author Dr Yunwei Zhang, also from the Cavendish Laboratory. "The interpretable signals identified by our machine learning model are a starting point for future theoretical and experimental studies."

The researchers are now using their machine learning platform to understand degradation in different battery chemistries. They are also developing optimal battery charging protocols, powering by machine learning, to enable fast charging and minimise degradation.

Researchers have observed directly and for the first time magnetoacoustic waves (sound-driven spin waves), which are considered as potential information carriers for novel computation schemes. These waves have been generated and observed on hybrid magnetic/piezoelectric devices. The experiments were designed by a collaboration between the University of Barcelona (UB), the Institute of Materials Science of Barcelona (ICMAB-CSIC) and the ALBA Synchrotron. The results show that magnetoacoustic waves can travel over long distances -up to centimeters- and have larger amplitudes than expected.

The observation of the magnetization waves was performed in a Nickel ferromagnetic thin film, which was excited by a deformation wave (called surface acoustic wave, SAW) originated in a piezoelectric substrate layer below the Nickel film. Although clear interaction between acoustic waves and magnetization dynamics has been reported in several systems, thus far, no direct observation of the underlying magnetic excitations existed, providing a quantification of both time and space.

Now researchers have published in Physical Review Letters their findings: "We designed an experiment ad hoc to image and quantify the magnetization dynamics generated by surface acoustic waves (SAW). The results clearly show that magnetization waves exist at distinct frequencies and wavelengths and that it is possible to create wave interferences" explains Ferran Macià, leader of the project at the UB and ICMAB.

The experiments show interference patterns of magnetization waves and provides new avenues for manipulation of these waves at room temperature "Our magnetization waves are coupled to the acoustic waves and thus, can travel long distances and have larger amplitudes than spin waves" explains Michael Foerster, beamline scientist of CIRCE-PEEM at ALBA. Such large-amplitude, long-distance waves could be well-suited for carrying information, processing data, or driving small motors.

The generation of magnetization dynamics through acoustic waves has attracted interest because it has some advantages over magnetic field induced excitations, such as more energy efficiency, larger spatial extension, or match of wavelengths.

The experiments were performed using the PEEM (Photoemission Electron Microscopy) at the CIRCE beamline at the ALBA Synchrotron to image the magnetization waves, which were synchronized with the synchrotron light pulses. "As wave are dynamic objects, they were imaged with stroboscopic snapshots thanks to this synchronization. The X-ray magnetic circular dichroism (XMCD) effect was used to obtain magnetic contrast in the images" explains Macià.

By observing electrons that have been accelerated to extremely high energies, scientists are able to unlock clues about the particles that make up our universe.

Accelerating electrons to such high energies in a laboratory setting, however, is challenging: typically, the more energetic the electrons, the bigger the particle accelerator. For instance, to discover the Higgs boson--the recently observed "God particle," responsible for mass in the universe--scientists at the CERN laboratory in Switzerland used a particle accelerator nearly 17 miles long.

But what if there was a way to scale down particle accelerators, producing high-energy electrons in a fraction of the distance?

In a paper published in Physical Review Letters, scientists at the University of Rochester's Laboratory for Laser Energetics (LLE) outlined a method to shape intense laser light in a way that accelerates electrons to record energies in very short distances: the researchers estimate the accelerator would be 10,000 times smaller than a proposed setup recording similar energy, reducing the accelerator from nearly the length of Rhode Island to the length of a dining room table. With such a technology, scientists could perform tabletop experiments to probe the Higgs boson or explore the existence of extra dimensions and new particles that could lead to Albert Einstein's dream of a grand unified theory of the universe.

"The higher energy electrons are required to study fundamental particle physics," says John Palastro, a scientist at the LLE and the paper's lead author. "Electron accelerators provide a looking glass into a sub-atomic world inhabited by the fundamental building blocks of the universe."

While this research is currently theoretical, the LLE is working to make it a reality through plans to construct the highest-powered laser in the world at the LLE. The laser, to be named EP-OPAL, will allow the researchers to create the extremely powerful sculpted light pulses and technology described in this paper.

The electron accelerator outlined by the researchers relies on a revolutionary technique for sculpting the shape of laser pulses so that their peaks can travel faster than the speed of light.

"This technology could allow electrons to be accelerated beyond what is possible with current technologies," says Dustin Froula, a senior scientist at the LLE and one of the paper's authors.

In order to sculpt the laser pulses, the researchers developed a novel optic setup resembling a circular amphitheater with wavelength-sized "steps" used to create a time delay between concentric rings of light delivered from a high-power laser.

A typical lens focuses each ring of light from a laser to a single distance from the lens, forming a single spot of high-intensity light. Instead of using a typical lens, however, the researchers use an exotically shaped lens, which allows them to focus each ring of light to a different distance from the lens, creating a line of high intensity rather than a single spot.

When this sculpted light pulse enters a plasma--a hot soup of freely moving electrons and ions--it creates a wake, similar to the wake behind a motorboat. This wake propagates at the speed of light. Much like a water skier riding in a boat's wake, the electrons then accelerate as they ride the wake of the sculpted laser light pulses.

These "laser wakefield accelerators" (LWFA) were first theorized nearly 40 years ago, and were advanced by the invention of chirped-pulse amplification (CPA), a technique developed at the LLE by 2018 Nobel Prize recipients Donna Strickland and Gerard Mourou.

Previous versions of LWFA, however, used traditional, unstructured light pulses that propagated more slowly than the speed of light, which meant the electrons would outrun the wake, limiting their acceleration. The new sculpted light pulses enable faster-than-light speeds so electrons can ride the wake indefinitely and be continually accelerated.

"This work is extremely innovative and would be a game changer for laser-accelerators," says Michael Campbell, director of the LLE. "This research shows the value of theoretical and experimental plasma physics working closely together with outstanding laser scientists and engineers--it represents the best of the culture of LLE."

Extreme rainfall has become increasingly common in metropolitan São Paulo, Brazil. The capital of the state of São Paulo is the largest city in the southern hemisphere. The metropolitan area suffered from flooding due to heavy rain in February. Early in the month, no less than 114 millimeters (mm) fell in a single 24-hour period. This was the second highest 24-hour amount for the month since 1943, according to Brazil's National Meteorological Institute (INMET).

According to a study by researchers at the Natural Disaster Surveillance and Early Warning Center (CEMADEN), an agency of the Brazilian Ministry of Science, Technology, Innovation and Communications (MCTIC), both the total rainfall and the frequency of extreme rainfall events in metropolitan São Paulo have increased significantly in the last seven decades.

While there were practically no days with heavy rain (more than 50 mm) in the 1950s, such days have occurred between twice and five times per year in the last ten years in metropolitan São Paulo, according to the authors.

The study was supported by São Paulo Research Foundation - FAPESP under the aegis of its Research Program on Global Climate Change (RPGCC). The findings are reported in the Annals of the New York Academy of Sciences.

Researchers affiliated with INMET, the National Space Research Institute (INPE) and the University of São Paulo's Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG-USP) also took part in the study.

"Intense rainstorms lasting a few hours with huge amounts of water, as much as 80 mm or 100 mm, are no longer sporadic events. They're happening more and more frequently," José Antonio Marengo, a senior researcher at CEMADEN and principal investigator for the study, told.

The researchers analyzed data collected by INMET's weather stations at IAG-USP and Santana Lookout in the northern part of the city. The analysis showed an increase in the number of days with heavy rain and in the frequency of rainfall extremes, especially during the rainy season (spring-summer).

The dry season used to occur between April and September in most of the state but has lasted until October in recent decades. The number of consecutive days without any rain at all has also gradually increased, suggesting that heavy rainfall events are concentrated in fewer days, interrupted by longer periods of hot dry weather.

With fewer cold nights and more hot days, convective rainfall is more likely to occur, increasing the frequency and intensity of extreme rainfall, the authors note.

In convective rainfall, the ground heats up, boosting evaporation and causing warm moist air to rise (convection). As the air ascends, it cools and forms convective clouds, which precipitate upon reaching saturation.

"We observed a long-term trend in this kind of weather event, with very strong signs that climate change is in progress," Marengo said.

Records from the IAG-USP and Santana Lookout weather stations showed a four-fold increase in the number of days with rainfall exceeding 100 mm between 2000 and 2018 compared with those from the 1940s or 1960s.

Records from IAG-USP also showed an increase in total rainfall, in the frequency and intensity of heavy precipitation, and in the frequency of consecutive dry days in the period 1931-2017.

"This suggests that the increase in total rainfall in São Paulo in recent decades was due to an increase in 'heavy' precipitation, concentrated in fewer days and with longer dry spells in between," Marengo said.

Causes

According to the researchers, the changing rainfall regime in metropolitan São Paulo may be due to natural climate variability but may also be related to global warming and growing urbanization that has occurred especially in the last 40 years, which has exacerbated the occurrence of urban heat islands.

The growth of urbanization has transformed the region's previously exposed soil and Atlantic Rainforest remnants into sealed concrete, cement and asphalt surfaces that absorb heat while retaining no moisture. The temperature rises during the day, and as the sun goes down, the accumulated heat rises into the atmosphere, the relative humidity falls, and water evaporates rapidly from the ground to form towering cumulonimbus clouds, Marengo explained.

In his view, heat islands and similar effects help explain the increase in extreme rainfall events that occurred in metropolitan São Paulo between 1933 and 2010.

In the last 20 years, these changes in the rainfall regime, in conjunction with the high-risk construction of buildings on hillsides and riverbanks, have led to an increase in hydrometeorological hazards, triggering disasters such as flash floods, river flooding and landslides, the authors note.

"An extreme rainfall event isn't itself a natural disaster. So-called natural disasters actually result from a combination of factors ranging from climate and weather to urban, economic and social phenomena. In other words, they're also anthropogenic disasters that result from human action, not just climate," Marengo said.

Most Brazilian states suffer from flooding, but it is worst in São Paulo, which accounts for 33.36% of cases, followed by Santa Catarina (11.25%), Rio Grande do Sul (9.06%), Paraná (8.33%), Rio de Janeiro (7.28%) and Minas Gerais (5.96%).

Some 170 river floods and flash floods occurred in the period 2014-18. Flash floods produced the most deaths and serious injuries, followed by landslides and mudslides.

"The Southeast and South regions of Brazil are the worst affected by hydrometeorological disasters because of their population density," Marengo said.

"Landslides, for example, only kill people because they're forced to live in high-risk areas where no one should build a home. The streets only fill up with water because the rivers have been channelized and buried, and the city's surfaces are sealed with asphalt and concrete."

Scientists at Caltech and Occidental College have discovered a methane-fueled symbiosis between worms and bacteria at the bottom of the sea, shedding new light on the ecology of deep-sea environments.

They found that bacteria belonging to the Methylococcaceae family have been hitching a ride on the feathery plumes that act as the respiratory organs of Laminatubus and Bispira worms. Methylococcaceae are methanotrophs, meaning that they harvest carbon and energy from methane, a molecule composed of carbon and hydrogen.

The worms, which are a few inches long, have been found in great numbers near deep-sea methane seeps, vents in the ocean floor where hydrocarbon-rich fluids ooze out into the ocean, although it was unclear why the worms favored the vents. As it turns out, the worms slowly digest the hitchhiking bacteria and thus absorb the carbon and energy that the bacteria harvest from the methane.

That is to say, with a little help and some extra steps, the worms have become methanotrophs themselves.

"These worms have long been associated with seeps, but everyone just assumed they were filter-feeding on bacteria. Instead, we find that they are teaming up with a microbe to use chemical energy to feed in a way we hadn't considered," says Victoria Orphan, James Irvine Professor of Environmental Science and Geobiology and co-corresponding author of a paper on the worms that was published by Science Advances on April 3.

Orphan and her colleagues made the discovery during research cruises to study methane vents off the coast of Southern California and Costa Rica.

"We had a colleague on board who was an expert on these worms and noticed that the morphology was unusual. The respiratory plumes were much frillier than anyone had ever seen before, which was the first clue. It was enough to make us say, 'That's interesting. We should investigate,'" says Shana Goffredi, visitor in geobiology at Caltech and lead author of the Science Advances paper. Goffredi is an associate professor of biology at Occidental College in Los Angeles.

To probe the nature of the relationship between the worms and the bacteria, the scientists had to first use robotic submarines to take samples from deep-sea methane vents, which, in this case, lie 1,800 meters below the ocean surface.

Once the worms were brought topside, the scientists analyzed their tissues, cataloging the carbon isotopes that they had consumed. Carbon exists in two stable isotopic forms--different "flavors" of carbon, so to speak. Around 99 percent of all carbon is carbon-12, which has six neutrons and six protons in each atomic nucleus, and about 1 percent is carbon-13 (six protons and seven neutrons). Carbon-14, a radioactive isotope, exists in trace amounts.

All organisms require carbon--in some form--to survive, and they absorb it through metabolic processes. Studying the ratio of carbon-13 to carbon-12 in an organism's tissues can give clues to where that carbon came from and the conditions under which it formed. In the case of the deep-sea worms, their tissues had an unusually low ratio of carbon-13 to carbon-12, meaning that the carbon in the worm's body probably came from methane. Orphan and her collaborators reasoned that because the worms are incapable of processing methane directly, they must be getting their carbon from methanotrophic bacteria.

"The fact that we found this specific isotope of carbon throughout the worms' bodies and not just in their respiratory plumes indicates that they are consuming methane carbon from these bacteria," Orphan says. The research team followed up on this hypothesis by using molecular techniques and microscopy as well as experiments to test the ability of these worms to incorporate a modified, traceable version of methane.

Their research findings change our understanding of seep ecosystems and have implications for deep-sea stewardship, as methane seeps and hydrothermal vents are sure to experience increasing pressure because of human exploitation of energy and minerals.

Particle chasing--it's a game that so many physicists play. Sometimes the hunt takes place inside large supercolliders, where spectacular collisions are necessary to find hidden particles and new physics. For physicists studying solids, the game occurs in a much different environment and the sought-after particles don't come from furious collisions. Instead, particle-like entities, called quasiparticles, emerge from complicated electronic interactions that happen deep within a material. Sometimes the quasiparticles are easy to probe, but others are more difficult to spot, lurking just out of reach.

New measurements show evidence for the presence of exotic Majorana particles on the surface of an unconventional superconductor, Uranium ditelluride. Graphic provided by Dr. E. Edwards, Managing Director of Illinois Quantum Information Science and Technology Center (IQUIST).

New measurements show evidence for the presence of exotic Majorana particles on the surface of an unconventional superconductor, Uranium ditelluride. Graphic provided by Dr. E. Edwards, Managing Director of Illinois Quantum Information Science and Technology Center (IQUIST).

Now a team of researchers at the University of Illinois, led by physicist Vidya Madhavan, in collaboration with researchers from the National Institute of Standards and Technology, the University of Maryland, Boston College, and ETH Zurich, have used high-resolution microscopy tools to peer at the inner-workings of an unusual type of superconductor, uranium ditelluride (UTe2). Their measurements reveal strong evidence that this material may be a natural home to an exotic quasiparticle that's been hiding from physicists for decades. The study is published in the March 26 issue of Nature.

The particles in question were theorized back in 1937 by an Italian physicist named Ettore Majorana, and since then, physicists have been trying to prove that they can exist. Scientists think a particular class of materials called chiral unconventional superconductors may naturally host Majoranas. UTe2 may have all of the right properties to spawn these elusive quasiparticles.

"We know the physics of conventional superconductors and understand how they can conduct electricity or transport electrons from one end of a wire to the other with no resistance," said Madhavan. "Chiral unconventional superconductors are much rarer, and the physics is less well known. Understanding them is important for fundamental physics and has potential applications in quantum computing," she said.

Inside of a normal superconductor, the electrons pair up in a way that enables the lossless, persistent currents. This is in contrast to a normal conductor, like copper wire, which heats up as current passes through it. Part of the theory behind superconductivity was formulated decades ago by three scientists at the U of I who earned a Nobel prize in physics for their work. For this conventional kind of superconductivity, magnetic fields are the enemy and break up the pairs, returning the material back to normal. Over the last year, researchers showed that uranium ditelluride behaves differently.

In 2019, Sheng Ran, Nicholas Butch (both co-authors on this study) and their collaborators announced that UTe2 remains superconducting in the presence of magnetic fields up to 65 Tesla, which is about 10,000 times stronger than a refrigerator magnet. This unconventional behavior, combined with other measurements, led the authors of that paper to surmise that the electrons were pairing up in an unusual way that enabled them to resist break-ups. The pairing is important because superconductors with this property could very likely have Majorana particles on the surface. The new study from Madhavan and collaborators strengthens the case for this.

The team used a high-resolution microscope called a scanning tunneling microscope to look for evidence of the unusual electron pairing and Majorana particles. This microscope can not only map out the surface of uranium ditelluride down to the level of atoms but also probe what's happening with the electrons. The material itself is silvery with steps jutting up from the surface. These step features are where evidence for Majorana quasiparticles is best seen. They provide a clean edge that, if predictions are correct, should show signatures of a continuous current that moves in one direction, even without the application of a voltage. The team scanned opposite sides of the step and saw a signal with a peak. But the peak was different, depending on which side of the step was scanned.

"Looking at both sides of the step, you see a signal that is a mirror image of each other. In a normal superconductor, you cannot find that," said Madhavan. "The best explanation for seeing the mirror images is that we are directly measuring the presence of moving Majorana particles," said Madhavan. The team says that the measurements indicate that free-moving Majorana quasiparticles are circulating together in one direction, giving rise to mirrored, or chiral, signals.

Madhavan says the next step is to make measurements that would confirm that the material has broken time-reversal symmetry. This means that the particles should move differently if the arrow of time were theoretically reversed. Such a study would provide additional evidence for the chiral nature of UTe2.

If confirmed, uranium ditelluride would be the only material, other than superfluid He-3, proven to be a chiral unconventional superconductor. "This is a huge discovery that will allow us to understand this rare kind of superconductivity, and maybe, in time, we could even manipulate Majorana quasiparticles in a useful way for quantum information science."

The use of artificial intelligence (AI), technologies that can interact with the environment and simulate human intelligence, has the potential to significantly change the way we work. Successfully integrating AI into organizations depends on workers' level of trust in the technology. A new review examined two decades of research on how people develop trust in AI. The authors concluded that the way AI is represented, or "embodied," and AI's capabilities contribute to developing trust. They also proposed a framework that addresses the elements that shape users' cognitive and emotional trust in AI, which can help organizations that use it.

The review, by researchers at Carnegie Mellon University and Bar Ilan University, appears in Academy of Management Annals.

"The trust that users develop in AI will be central to determining its role in organizations," explains Anita Williams Woolley, Associate Professor of Organizational Behavior and Theory at Carnegie Mellon University's Tepper School of Business, who coauthored the study. "We addressed the dynamic nature of trust by exploring how trust develops for people interacting with different representations of AI (e.g., robots, virtual agents, or embedded) as well as the features of AI that facilitate the development of trust."

Specifically, the researchers observed the role of tangibility (the capability of being perceived or touched), transparency (the level to which the operating rules and logic of the technology are apparent to users), and reliability (whether the technology exhibits the same expected behavior over time). They also considered task characteristics (how technical versus interpersonal judgments are handled) and immediacy behaviors (socially oriented gestures intended to increase interpersonal closeness, such as active listening and responsiveness). They also looked at anthropomorphism (the perception that technology can have human qualities).

The authors searched Google Scholar for articles on human trust in AI published between 1999 and 2019, identifying about 200 peer-reviewed articles and conference proceedings. Fields represented included organizational behavior, human-computer interactions, robot-human interactions, information systems, information technology, and engineering. They also used three databases to identify an additional 50 articles. In the end, they reviewed approximately 150 articles that presented empirical research on human trust in AI.

The authors found that the representation of AI played an important role in the nature of the cognitive trust people develop. For robotic AI, the trajectory for developing trust resembled that of creating trust in human relationships, starting low and increasing after more experience. But for virtual and embedded AI, the opposite occurred: High initial trust declined following experience.

The authors also found that the level of machine intelligence characterizing AI may moderate the development of cognitive trust, with a high level of intelligence leading to higher trust following use and experience. For robotic AI, a high level of machine intelligence generally led to faster development of a high level of trust. For virtual and embedded AI, high machine intelligence offered the possibility of maintaining the initial high levels of trust. Transparency was also an important factor for establishing cognitive trust in virtual and embedded AI, though the relationship between reliability and the development of trust in AI was complex.

Anthropomorphism was uniquely important for the development of emotional trust, but its effect differed depending on the form of AI. For virtual AI, anthropomorphism had a positive effect. For robotic AI, effects were mixed: People tended to like anthropomorphic robots more than mechanical-looking robots, but these human-like robots could also evoke discomfort and a sense of eeriness.

Factors that influenced emotional trust differed from those that influenced cognitive trust, and some factors may have had different implications for each, the authors concluded.

As a guide to integrating AI into organizations' work, the authors proposed a framework. They considered the form in which AI was used, the level of machine intelligence, behaviors such as responsiveness, and reliability as factors that influenced how people developed trust in AI, both cognitively and emotionally.

"Trust can predict the level of reliance on technology, while the level of correspondence between someone's trust and the capabilities of the technology, known as calibration, can influence how the technology is used," says Ella Glikson, Assistant Professor in the Graduate School of Business Administration at Bar Ilan University, who coauthored the study.

A study conducted by two associate professors of marketing at The University of Texas at Arlington shows that people are more likely to base decisions on anecdotal information instead of facts when they feel anxious and vulnerable.

Traci Freling and Ritesh Saini, both in the College of Business, published "When poignant stories outweigh cold hard facts: A meta-analysis of the anecdotal bias" in Organizational Behavior and Human Decision Processes.

"We found that people are more likely to consider personal anecdotes than fact-based information, especially when it deals with medical emergencies," Freling said. "This has a high importance in the current environment, where everyone is concerned about the coronavirus."

Freling said people are more likely to listen to personal stories instead of facts because emotions run high during medical emergencies like the COVID-19 pandemic.

"They are especially dismissive of facts if the incident is something they personally experienced," Freling said. "Specifically, we show that when an issue is health-related, personally relevant or highly threatening, then decision-making is compromised and people tend to rely on anecdotes."

Freling pointed to the run on toilet paper buying during the COVID-19 pandemic as one example of not basing decisions on facts. This example illustrates how consumers who feel vulnerable to a particular problem may rely more heavily on subjective, anecdotal information instead of objective, statistical facts to make decisions.

Former UTA faculty member Zhiyong Yang, now a professor at the University of North Carolina-Greensboro, and two graduate students contributed to the analysis.

The research also revealed that when emotional engagement is low, statistical evidence weighs more heavily.

"Primarily, when there is low-threat severity or it's a non-health issue, people tend to take cold, hard facts into account rather than personal accounts and stories," Freling said.

Additionally, Saini noted that people make "more fact-based decisions when choosing for others, but become surprisingly irrational when choosing for self."

Elten Briggs, chair of the Department of Marketing, said Freling and Saini's analysis could have implications on decision-making processes for business and industry, especially during medical crises.

"Their research provides guidance on how to craft more influential messaging during times like these, when anxiety is heightened for so many people," Briggs said.

Dirac matter is an intriguing class of materials with rather peculiar properties: electrons in these materials behave as if they had no mass. The most prominent Dirac material is graphene, but further members have been discovered during the past 15 years or so. Each one of them serves as a rich playground for exploring 'exotic' electronic behaviours, some of which hold the promise to enable novel components for electronics. However, even if Dirac matter and other so-called topological materials --- in which electrons behave in similarly unexpected ways --- are among the currently most intensively studied condensed-matter systems, there are only very few examples where the topology of the electronic bands is connected in a well-defined manner to the magnetic properties of the materials. One material in which such interplay between topological electronic states and magnetism has been observed is CaMnBi2, but the mechanism connecting the two remained unclear. Writing in Physical Review Letters [1], postdoc Run Yang and PhD student Matteo Corasaniti from the Optical Spectroscopy group of Prof. Leonardo Degiorgi at the Laboratory for Solid State Physics of ETH Zurich, working with colleagues at Brookhaven National Laboratory (US) and the Chinese Academy of Sciences in Beijing, now report a comprehensive study in which they provide clear evidence that it is a slight nudge on the magnetic moments, known as spin canting, that provokes substantial changes in the electronic band structure.

Compass points to the right direction on a bumpy road

CaMnBi2 and the related compound SrMnBi2 have recently attracted attention as they display quantum magnetism -- the manganese ions are antiferromagnetically ordered at around room temperature and below -- and at the same time they host Dirac electrons. That there is interplay between the two properties has been suspected for some while, not least as at ~50 K there appears an unexpected 'bump' in the conduction properties at these materials. But the precise nature of this anomaly was still poorly understood until now.

In earlier work studying optical properties [2], Corasaniti, Yang and co-workers had established already a link to the electronic properties of the material. They used in particular the fact that the bump-like anomaly in the transport properties can be shifted in temperature by replacing some of the calcium atoms with sodium. To get now to the microscopic origins of the observed behaviour, they studied samples with different sodium dopings by torque magnetometry. In this technique, the torque on a magnetic sample is measured when it is exposed to a suitably strong field, similarly as a compass needle aligns with the Earth magnetic field. And this approach proved to point the team to the origins of the anomaly.

A firm link between magnetic and electronic properties

In their magnetic-torque experiments, the researchers found that at temperatures where no anomaly is observed in the electronic transport measurements, the magnetic behaviour is such as one would expect for an antiferromagnet. This was not the case anymore at temperatures at which the anomaly is present. There, a ferromagnetic component appeared, which can be explained by a projection of magnetic moments onto the plane orthogonal to the easy spin c-axis of the original antiferromagnetic order (see the figure). This phenomenon is known as spin-canting, induced by a so-called super-exchange mechanism.

These two sets of experiments -- optical and torque measurements -- were supported by dedicated first-principles calculations. In particular, for the case where spin canting was included in the calculations, a peculiar hybridization between the manganese and bismuth atoms was found to mediate the interlayer magnetic coupling and to govern the electronic properties in the material. Taken together, the study therefore establishes that sought-after direct link between the magnetic properties and changes to the electronic band structure, reflected in the bump anomaly of the transport properties.

With such detailed understanding on board, the door is now open to exploring not only the electronic properties of CaMnBi2 and related compounds, but also the possibilities arising from the connection between magnetic properties and topological states in these intriguing forms of matter.

Scientists know that coronaviruses, including the SARS-CoV-2 virus responsible for the COVID-19 pandemic, can remain infectious for days -- or even longer -- in sewage and drinking water. 

Two researchers, Haizhou Liu, an associate professor of chemical and environmental engineering at the University of California, Riverside; and Professor Vincenzo Naddeo, director of the Sanitary Environmental Engineering Division at the University of Salerno, have called for more testing to determine whether water treatment methods are effective in killing SARS-CoV-2 and coronaviruses in general.

The virus can be transported in microscopic water droplets, or aerosols, which enter the air through evaporation or spray, the researchers wrote in an editorial for Environmental Science: Water Research & Technology, a leading environmental journal of the Royal Society of Chemistry in the United Kingdom.

"The ongoing COVID-19 pandemic highlights the urgent need for a careful evaluation of the fate and control of this contagious virus in the environment," Liu said. "Environmental engineers like us are well positioned to apply our expertise to address these needs with international collaborations to protect public health."

During a 2003 SARS outbreak in Hong Kong, a sewage leak caused a cluster of cases through aerosolization. Though no known cases of COVID-19 have been caused by sewage leaks, the novel coronavirus is closely related to the one that causes SARS, and infection via this route could be possible. 

The novel coronavirus could also colonize biofilms that line drinking water systems, making showerheads a possible source of aerosolized transmission. This transmission pathway is thought to be a major source of exposure to the bacteria that causes Legionnaire's disease, for example.

Fortunately, most water treatment routines are thought to kill or remove coronaviruses effectively in both drinking and wastewater. Oxidation with hypochlorous acid or peracetic acid, and inactivation by ultraviolet irradiation, as well as chlorine, are thought to kill coronaviruses.  In wastewater treatment plants that use membrane bioreactors, the synergistic effects of beneficial microorganisms and the physical separation of suspended solids filter out viruses concentrated in the sewage sludge. 

Liu and Naddeo caution, however, that most of these methods have not been studied for effectiveness specifically on SARS-CoV-2 and other coronaviruses, and they have called for additional research.

They also suggest upgrading existing water and wastewater treatment infrastructure in outbreak hot spots, which possibly receive coronavirus from places such as hospitals, community clinics, and nursing homes. For example, energy-efficient, light-emitting, diode-based, ultraviolet point-of-use systems could disinfect water before it enters the public treatment system.

Potable water-reuse systems, which purify wastewater back into tap water, also need thorough investigation for coronavirus removal, and possibly new regulatory standards for disinfection, the researchers wrote.

The extent to which viruses can colonize biofilms is also not yet known. Biofilms are thin, slimy bacterial growths that line the pipes of many aging drinking water systems. Better monitoring of coronaviruses in biofilms might be necessary to prevent outbreaks.

The surge in household use of bactericides, virucides and disinfectants will probably cause an increase of antibiotic-resistant bacteria in the environment. Treated wastewater discharged into natural waterways demands careful monitoring through the entire water cycle. Liu and Naddeo call on chemists, environmental engineers, microbiologists, and public health specialists to develop multidisciplinary and practical solutions for safe drinking water and healthy aquatic environments.

Lastly, developing countries and some regions within highly developed nations, such as rural and impoverished communities, which lack the basic infrastructure to remove other common contaminants might not be able to remove SARS-CoV-2 either. These places might experience frequent COVID-19 outbreaks that spread easily through globalized trade and travel. Liu and Naddeo suggest governments of developed countries must support and finance water and sanitation systems wherever they are needed.

"It is now clear to all that globalization also introduces new health risks. Where water and sanitation systems are not adequate, the risk of finding novel viruses is very high," Naddeo said. "In a responsible and ideal scenario, the governments of developed countries must support and finance water and sanitation systems in developing countries, in order to also protect the citizens of their own countries."

According to data from the Food and Agriculture Organization of the United Nations (FAO), groundwater supplies half of the world's population with fresh water and makes up 43% of the water used in irrigation. Despite its importance, it is calculated that about a third of the world's greatest aquifers are drying up quickly and that 20% are being overexploited. In Spain, a country where a large number of crops are watered with groundwater, scientific data show that the extraction rate is much higher than the water replenishing rate.

The use of monitoring systems, the use of high added-value crops and governance, as in a way to manage resources using all the sectors, could be some of the main lifesavers for these overexploited aquifers that, in spite of being essential for agriculture, are suffering extreme pressure due to population increase, difficulties in abiding by the laws regulating a resource that usually remains unseen and lack of rainfall and surface water resources.

These are just some of the main conclusions of a research project carried out by the Water, Environmental and Agricultural Resources Economics (WEARE) research group at the Department of Economics, Sociology and Agricultural Policy at the University of Cordoba. The study, performed by researchers María del Mar Delgado and María del Mar Borrego, analyzed the conditions that led an overexploited aquifer in the province of Granada to start showing signs of recovery. The aim was to identify innovation, policies and best practices that guarantee the sustainability of these resources and can be extrapolated to other cases to sustainably manage groundwater.

The case of Fuencaliente: the aquifer that recovered

The Fuencaliente aquifer is an underground water mass located in the town of Huéscar, in the province of Granada. From this aquifer comes a hot spring, with irrigation canals branching off of it. These irrigation ditches have been in use for over seven centuries. This spring dried up due to overexploitation, leaving the water users without access to water. When the EU's Water Framework Directive came into effect, areas that had been at-risk for more than a decade were included in its catalog and upon monitoring the aquifer, data revealed the amount of illegal wells and the existence of uncontrolled irrigation systems.

This research has shown the necessity to analyze interactions between environmental and social aspects of the management and governance of natural resources. Decisions made within the social realm are allowing for the recovery of this natural resource.

"The Guadalquivir Hydrographic Confederation took several exceptional measures in order to regulate the situation, but it was done by negotiating with the irrigation communities using the traditional ditches, as well as with the new water users who use well water to make it possible to accept the new rules", explains researcher Mar Delgado. The number of hectares permitted to irrigate was determined, wells were monitored, flow meters were installed, and the amount of water that could be taken for each authorized plot of land was limited.

At the same time, the Hydrographic Confederation accomplished financial agreements among the old irrigation communities using the traditional irrigation ditches and the new irrigation communities, which were allowed to extract well water. The surface water users were given water from a nearby reservoir, agreeing that the fee for this water would be paid for by the well users who had caused the overexploitation.

Once it was determined which plots of land had the right to irrigate, most of the farmers with this right opted to rent their land to two major producers, specializing in marketing broccoli on the international market. "The production of added value crops partly covered the higher cost of water use but at the same time these producers could rely on yearly water provisions and the possibility of guaranteeing that their crops used water sustainably, an increasing concern for European consumers", explains the lead author of the study.

Currently, the aquifer is recovering, and some of the methods used "can be replicated in other areas", above all the need to respect natural resources and resources used in closely-linked interconnected systems, the kind in which the systems affect one another as well as the results. This case analysis shows how monitoring and growing high added value crops can be some of the main defense systems for these aquifers. Moreover, as Mar Delgado points out, governance is another fundamental aspect. "The legislation does not always work in the form of a tax. When answers are sought by negotiating with the various stakeholders, sustainable use has more guarantees".

Melatonin controls the body clock - high melatonin levels make us feel tired in the evening. However, the hormone also plays an important role in animals' biological rhythms. Artificial light at night - light pollution - can suppress the production of melatonin in fish, even at very low light intensities, a finding established by researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB).

Melatonin regulates the day-night rhythm in humans and vertebrates. Organs, tissue and cells set their internal clock depending on the level of this hormone. As a result, melatonin also controls processes such as reproduction and growth. Vertebrates and humans detect differences in ambient brightness via photoreceptors, e.g. on the retina of the eye. Bright light perceived by these receptors suppresses the production of melatonin, while the hormone level is elevated during the dark phase. Artificial light at night may disturb melatonin levels.

The team of IGB researchers investigated melatonin production in European perch. During the day, all fish were exposed to daylight. At night, lighting varied depending on the group: the control group spent the night in complete darkness, whereas the other three groups were exposed to light intensities at 0.01, 0.1 and 1 lux. After ten days, the scientists measured melatonin levels at three-hour intervals over a period of 24 hours. The result: even the lowest light intensity of 0.01 lux was enough to suppress melatonin production; higher light intensities led to an increasingly strong gradual reduction of melatonin.

For comparison, illumination intensities to which organisms are exposed at night: on a crystal clear night, illumination intensity is less than 0.001 lux. On a full moon night, it measures a maximum of 0.3 lux. Sky glow over a city can reach illumination intensities of up to 1 lux and more, and street can lighting anything up to 150 lux.

Even nighttime urban sky glow suppresses melatonin formation

"The astonishing thing is that the intensities of urban sky glow are enough to suppress melatonin production in fish," stated lead author Franziska Kupprat from IGB. Large areas throughout the world are affected by this kind of light pollution. This is because light emitted by lighting installations radiates into the sky, and reflects off clouds and particles, creating significant sky glow that extends further than the actual light radius of the light source.

Light intensity had no impact on the rhythm of melatonin production. All specimens experienced an increase in melatonin formation during the course of the afternoon, peaking at night.

"Previous studies have shown that higher intensities of night light, such as 10 and 100 lux, also affect the melatonin rhythm in perch. This is because the melatonin produced at night had declined to such an extent that it no longer differed to low values measured during the day," explained IGB's Dr. Franz Hölker.

Fish spend much of their lives asleep, although this is not apparent because they have no eyelids. Like with all living things, fish need sleep to regenerate. IGB's Professor Werner Kloas, lead investigator of the study, explained the effects of disturbed melatonin levels: "Our previous research methods do not enable us to assess whether urban fish experience a lack of sleep due to light pollution. However, we assume this is the case because melatonin is an important factor influencing sleep in vertebrates, including fish. One thing for sure is that other body functions such as immune defence, growth and reproduction can be disturbed by altered melatonin production."

Researchers at Linköping University, together with colleagues in China, have developed a tiny unit that is both an optical transmitter and a receiver. "This is highly significant for the miniaturisation of optoelectronic systems", says LiU professor Feng Gao.

Chunxiong Bao, postdoc at Linköping University, types in a sentence on a computer screen, and the same sentence immediately appears on the neighbouring screen, optically transferred from one diode to another. The diode is made from perovskite, one of a large family of materials defined by their special crystal structure.

Perovskites consist of metal and halogen and have proved to be versatile semiconductors that are easy and cheap to manufacture. They also have the useful property of both detecting and emitting light. Researchers at Linköping University, together with colleagues in China, have now developed a diode that can be directed in two directions: it can receive optical signals and it can just as easily transmit them. This means that text and photographs can be wirelessly transmitted from one unit to the other and back again, using two identical units. And so rapidly that we experience it as happening in real time.

In the autumn of 2018, Chunxiong Bao discovered the correct perovskite to build a photodetector showing higher performance and longer lifetime, and described this in an article in Advanced Materials. The development of light-emitting diodes from perovskites has also made rapid progress. Weidong Xu, postdoc at Linköping University, developed a perovskite light-emitting diode with an efficiency of 21% last year, which is among the best in the world, and published the results in Nature Photonics. What the scientists have now achieved is to develop a perovskite that comprises a light-emitting diode and that at the same time is an excellent photodetector.

All optical communication requires rapid and reliable photodetectors - devices that capture light and convert it into an electrical signal. Current optical communication systems use photodetectors made from materials such as silicon and indium gallium arsenide. These are, however, expensive and they cannot be used in applications that require low weight, flexibility, or large surfaces.

"In order to demonstrate the potential of our diode with double function, we have built a monolithic sensor that detects heart beats in real time, and an optical, bidirectional communication system", says Chunxiong Bao, researcher in the Division of Biomolecular and Organic Electronics.

This tiny unit that can both receive and transmit optical signals provides a unique opportunity to simplify and shrink the functionality of the current optical systems, in particular given that it can also be integrated with traditional electronic circuits.

"We have managed to integrate optical signal transmission and reception into one circuit, something that makes it possible to transmit optical signals in both directions between two identical circuits. This is valuable in the field of miniaturised and integrated optoelectronics", says Feng Gao, professor and head of research at the Division of Biomolecular and Organic Electronics.