Computers Math

Scientists have taken the clearest picture yet of electronic particles that make up a mysterious magnetic state called quantum spin liquid (QSL).
The achievement could facilitate the development of superfast quantum computers and energy-efficient superconductors.
The scientists are the first to capture an image of how electrons in a QSL decompose into spin-like particles called spinons and charge-like particles called chargons.
“Other studies have seen various footprints of this phenomenon, but we have an actual picture of the state in which the spinon lives. This is something new,” said study leader Mike Crommie, a senior faculty scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) and physics professor at UC.
“Spinons are like ghost particles. They are like the Big Foot of quantum physics — people say that they’ve seen them, but it’s hard to prove that they exist,” said co-author Sung-Kwan Mo, a staff scientist at Berkeley Lab’s Advanced Light Source. “With our method we’ve provided some of the best evidence to date.”
A surprise catch from a quantum wave
In a QSL, spinons freely move about carrying heat and spin — but no electrical charge. To detect them, most researchers have relied on techniques that look for their heat signatures. More

To train robots how to work independently but cooperatively, researchers at the University of Cincinnati gave them a relatable task: move a couch.
If you’ve ever helped someone move furniture, you know it takes coordination — simultaneously pushing or pulling and reacting based on what your helper is doing. That makes it an ideal problem to examine collaboration between robots, said Andrew Barth, a doctoral student in UC’s College of Engineering and Applied Science.
“It’s a good metaphor for cooperation,” Barth said.
In the Intelligent Robotics and Autonomous Systems Lab of UC aerospace engineering professor Ou Ma, student researchers developed artificial intelligence to train robots to work together to move a couch — or in this case a long rod that served as a stand-in — around two obstacles and through a narrow door in computer simulations.
“We made it a little more difficult on ourselves. We want to accomplish the task with as little communication as possible among the robots,” student Barth said.
He was lead author of a study on the project published in the journal Intelligent Service Robotics. Professor Ma, UC doctoral student Yufeng Sun and UC senior research associate Lin Zhang were co-authors. More

New research published in the journal Clinical Psychological Science reveals that teenagers (ages 13-17) in low socioeconomic settings who spend a moderate amount of time online after a stressful experience deal with adversity far better than those who spend many hours online or avoid digital technology altogether.
“Adolescents are smart, and they make use of technology to their own advantage. Because adolescents in disadvantaged settings tend to have fewer local supports, the study sought to find out whether online engagement helped reduce their stress,” said lead author Kathryn Modecki with Griffith University’s Menzies Health Institute and School of Applied Psychology. “There has been a tendency to assume that technology use by teens is negative and harmful, but such a broad assumption isn’t borne out by what we know about the developmental stage of adolescence.”
To gather firsthand data on teens and technology, the researchers provided iPhones to more than 200 adolescents living in low socioeconomic settings. The teens were instructed to report on their technology use, stressors, and emotions five times a day for a week while using the iPhones exactly as they would use personal smartphones. The data were used to compare the emotional states of adolescents who used technology moderately, excessively, or not at all when coping with stress.
The results revealed that adolescents who engaged with technology in moderation in the hours after a stressful situation bounced back more readily and experienced smaller surges in negative emotions, like sadness and worry, compared to adolescents who didn’t use technology or who routinely used technology as a coping mechanism.
“We found a just-right ‘Goldilocks’ effect in which moderate amounts of online coping helped mitigate surges in negative emotions and dips in happiness,” said Modecki. “In the face of daily stressors, when adolescents engaged in emotional support seeking, they experienced better short-term stress relief.”
According to the researchers, the online space serves not just as a short-term distraction but as a resource for adolescents to find support and information about what is troubling them. By leveling the playing field for accessing that information and support, this coping strategy may be especially pertinent for teens in low-income settings.
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Researchers from the Graduate School of Engineering, Osaka City University have succeeded in storing electricity with the voltage generated from the conversion phenomenon of ferromagnetic resonance (FMR) using an ultra-thin magnetic film of several tens of nanometers.
The research was conducted under the leadership of Prof. Eiji Shikoh. “We are interested in efficiently using the Earth’s natural resources to harvest energy,” states the professor, “and capturing the energy from electromagnetic waves that surround us through the electromotive force (EMF) they generate in magnetic films under FMR shows potential as one such way.” Their research was published in the journal AIP Advances.
Ferromagnetic resonance is a state in which applying electromagnetic waves and an electrostatic magnetic field to a magnetic media causes the electromagnets inside the media to undergo precession at the same frequency as that of the electromagnetic waves. As a technique, it is often used to probe the magnetic properties of a variety of media, from bulk ferromagnetic materials to nano-scale magnetic thin films.
“Research has shown that an EMF is generated in a ferromagnetic metal (FM) that is under FMR,” states Yuta Nogi, first author of the study, “and we explored energy storage possibilities using two FMs that are highly durable, well understood, and thus commonly used in FMR research — an iron-nickel (Ni80Fe20) and iron-cobalt (Co50Fe50) alloy thin film.”
First, the team confirmed the two alloy films generated electricity under ferromagnetic resonance and found that Ni80Fe20 generated about 28 microvolts while Co50Fe50 generated about 6 microvolts of electricity. To store the electricity, they used an electron spin resonance device to pressurize the electromagnetic wave, and the electromagnet of the device for the static magnetic field. Connecting a storage battery directly to the membrane of the sample via a conductor, the team observed that both FM samples successfully stored energy after being in a state of FMR for 30 minutes. However, as the resonance time extended, the amount of energy stored with the iron-nickel alloy film did not change while the iron-cobalt alloy film saw a steady increase.
“This is due to the respective magnetic field ranges for the FMR excitation,” concludes Prof. Shikoh. Upon investigating the different energy storage characteristics of the thin films, the team found when they were in the same thermal states during the experiments, Co50Fe50 could maintain FMR in a detuned condition, while Ni80Fe20 was outside the FMR excitation range. “By appropriately controlling the thermal conditions of the FM film,” continues the professor, “EMF generation under ferromagnetic resonance can be used as an energy harvesting technology.”
Another interesting point about this research is that the team focused on EMF generation itself, independent of its origin. This means that as long as the FMR conditions are met, energy can be stored from electromagnetic waves we interact with daily — for example the Wi-Fi at your favorite café.
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Mathematicians at the Center for Advanced Mathematics for Energy Research Applications (CAMERA) at Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a mathematical algorithm to decipher the rotational dynamics of twisting particles in large complex systems from the X-ray scattering patterns observed in highly sophisticated X-ray photon correlation spectroscopy (XPCS) experiments.
These experiments — designed to study the properties of suspensions and solutions of colloids, macromolecules, and polymers — have been established as key scientific drivers to many of the ongoing coherent light source upgrades occurring within the U.S. Department of Energy (DOE). The new mathematical methods, developed by the CAMERA team of Zixi Hu, Jeffrey Donatelli, and James Sethian, have the potential to reveal far more information about the function and properties of complex materials than was previously possible.
Particles in a suspension undergo Brownian motion, jiggling around as they move (translate) and spin (rotate). The sizes of these random fluctuations depend on the shape and structure of the materials and contain information about dynamics, with applications across molecular biology, drug discovery, and materials science.
XPCS works by focusing a coherent beam of X-rays to capture light scattered off of particles in suspension. A detector picks up the resulting speckle patterns, which contain several tiny fluctuations in the signal that encode detailed information about the dynamics of the observed system. To capitalize on this capability, the upcoming coherent light source upgrades at Berkeley Lab’s Advanced Light Source (ALS), Argonne’s Advanced Photon Source (APS), and SLAC’s Linac Coherent Light Source are all planning some of the world’s most advanced XPCS experiments, taking advantage of the unprecedented coherence and brightness.
But once you collect the data from all these images, how do you get any useful information out of them? A workhorse technique to extract dynamical information from XPCS is to compute what’s known as the temporal autocorrelation, which measures how the pixels in the speckle patterns change after a certain passage of time. The autocorrelation function stitches the still images together, just as an old-time movie comes to life as closely related postcard images fly by.
Current algorithms have mainly been limited to extracting translational motions; think of a Pogo stick jumping from spot to spot. However, no previous algorithms were capable of extracting “rotational diffusion” information about how structures spin and rotate — information that is critical to understanding the function and dynamical properties of a physical system. Getting to this hidden information is a major challenge. More

The COVID-19 pandemic may be the deadliest viral outbreak the world has seen in more than a century. But statistically, such extreme events aren’t as rare as we may think, asserts a new analysis of novel disease outbreaks over the past 400 years.
The study, appearing the week of Aug. 23 in the Proceedings of the National Academy of Sciences, used a newly assembled record of past outbreaks to estimate the intensity of those events and the yearly probability of them recurring.
It found the probability of a pandemic with similar impact to COVID-19 is about 2% in any year, meaning that someone born in the year 2000 would have about a 38% chance of experiencing one by now. And that probability is only growing, which the authors say highlights the need to adjust perceptions of pandemic risks and expectations for preparedness.
“The most important takeaway is that large pandemics like COVID-19 and the Spanish flu are relatively likely,” said William Pan, Ph.D., associate professor of global environmental health at Duke and one of the paper’s co-authors. Understanding that pandemics aren’t so rare should raise the priority of efforts to prevent and control them in the future, he said.
The study, led by Marco Marani, Ph.D., of the University of Padua in Italy, used new statistical methods to measure the scale and frequency of disease outbreaks for which there was no immediate medical intervention over the past four centuries. Their analysis, which covered a murderer’s row of pathogens including plague, smallpox, cholera, typhus and novel influenza viruses, found considerable variability in the rate at which pandemics have occurred in the past. But they also identified patterns that allowed them to describe the probabilities of similar-scale events happening again.
In the case of the deadliest pandemic in modern history — the Spanish flu, which killed more than 30 million people between 1918 and 1920 — the probability of a pandemic of similar magnitude occurring ranged from 0.3% to 1.9% per year over the time period studied. Taken another way, those figures mean it is statistically likely that a pandemic of such extreme scale would occur within the next 400 years. More

Scientists studying two different configurations of bilayer graphene — the two-dimensional (2-D), atom-thin form of carbon — have detected electronic and optical interlayer resonances. In these resonant states, electrons bounce back and forth between the two atomic planes in the 2-D interface at the same frequency. By characterizing these states, they found that twisting one of the graphene layers by 30 degrees relative to the other, instead of stacking the layers directly on top of each other, shifts the resonance to a lower energy. From this result, just published in Physical Review Letters, they deduced that the distance between the two layers increased significantly in the twisted configuration, compared to the stacked one. When this distance changes, so do the interlayer interactions, influencing how electrons move in the bilayer system. An understanding of this electron motion could inform the design of future quantum technologies for more powerful computing and more secure communication.
“Today’s computer chips are based on our knowledge of how electrons move in semiconductors, specifically silicon,” said first and co-corresponding author Zhongwei Dai, a postdoc in the Interface Science and Catalysis Group at the Center for Functional Nanomaterials (CFN) at the U.S. Department of Energy (DOE)’s Brookhaven National Laboratory. “But the physical properties of silicon are reaching a physical limit in terms of how small transistors can be made and how many can fit on a chip. If we can understand how electrons move at the small scale of a few nanometers in the reduced dimensions of 2-D materials, we may be able to unlock another way to utilize electrons for quantum information science.”
At a few nanometers, or billionths of a meter, the size of a material system is comparable to that of the wavelength of electrons. When electrons are confined in a space with dimensions of their wavelength, the material’s electronic and optical properties change. These quantum confinement effects are the result of quantum mechanical wave-like motion rather than classical mechanical motion, in which electrons move through a material and are scattered by random defects.
For this research, the team selected a simple material model — graphene — to investigate quantum confinement effects, applying two different probes: electrons and photons (particles of light). To probe both electronic and optical resonances, they used a special substrate onto which the graphene could be transferred. Co-corresponding author and CFN Interface Science and Catalysis Group scientist Jurek Sadowski had previously designed this substrate for the Quantum Material Press (QPress). The QPress is an automated tool under development in the CFN Materials Synthesis and Characterization Facility for the synthesis, processing, and characterization of layered 2-D materials. Conventionally, scientists exfoliate 2-D material “flakes” from 3-D parent crystals (e.g., graphene from graphite) on a silicon dioxide substrate several hundred nanometers thick. However, this substrate is insulating, and thus electron-based interrogation techniques don’t work. So, Sadowski and CFN scientist Chang-Yong Nam and Stony Brook University graduate student Ashwanth Subramanian deposited a conductive layer of titanium oxide only three nanometers thick on the silicon dioxide substrate.
“This layer is transparent enough for optical characterization and determination of the thickness of exfoliated flakes and stacked monolayers while conductive enough for electron microscopy or synchrotron-based spectroscopy techniques,” explained Sadowski.
In the Charlie Johnson Group at the University of Pennsylvania — Rebecca W. Bushnell Professor of Physics and Astronomy Charlie Johnson, postdoc Qicheng Zhang, and former postdoc Zhaoli Gao (now an assistant professor at the Chinese University of Hong Kong) — grew the graphene on metal foils and transferred it onto the titanium oxide/silicon dioxide substrate. When graphene is grown in this way, all three domains (single layer, stacked, and twisted) are present. More

Researchers have developed a lightweight optical system for 3D inspection of surfaces with micron-scale precision. The new measurement tool could greatly enhance quality control inspection for high-tech products including semiconductor chips, solar panels and consumer electronics such as flat panel televisions.
Because vibrations make it difficult to capture precision 3D measurements on the production line, samples are periodically taken for analysis in a lab. However, any defective products made while waiting for results must be discarded.
To create a system that could operate in the vibration-prone environment of an industrial manufacturing plant, researchers headed by Georg Schitter from Technische Universität Wien in Austria combined a compact 2D fast steering mirror with a high precision 1D confocal chromatic sensor.
“Robot-based inline inspection and measurement systems such as what we developed can enable 100% quality control in industrial production, replacing current sample-based methods,” said Ernst Csencsics, who co-led the research team with Daniel Wertjanz. “This creates a production process that is more efficient because it saves energy and resources.”
As described in The Optical Society (OSA) journal Applied Optics, the new system is designed to be mounted on tracking platform placed on a robotic arm for contactless 3D measurements of arbitrary shapes and surfaces. It weighs just 300 grams and measures 75 x 63 x 55 millimeters cubed, which is about the size of an espresso cup.
“Our system can measure 3D surface topographies with unprecedented combination of flexibility, precision, and speed,” said Wertjanz, who is pursuing a PhD on this research topic. “This creates less waste because manufacturing problems can be identified in real-time, and processes can be quickly adapted and optimized.”
From lab to fab More