Computers Math

Think about how many different pieces of technology the average household has purchased in the last decade. Phones, TVs, computers, tablets, and game consoles don’t last forever, and repairing them is difficult and often as expensive as simply buying a replacement.
Electronics are integral to modern society, but electronic waste (e-waste) presents a complex and growing challenge in the path toward a circular economy — a more sustainable economic system that focuses on recycling materials and minimizing waste. Adding to the global waste challenge is the prevalence of dishonest recycling practices by companies who claim to be recycling electronics but actually dispose of them by other means, such as in landfills or shipping the waste to other countries.
New research from the Hypothetical Materials Lab at the University of Pittsburgh Swanson School of Engineering develops a framework to understand the choices a recycler has to make and the role that digital fraud prevention could have in preventing dishonest recycling practices.
“Electronics have huge environmental impacts across their life cycle, from mining rare raw materials to the energy-intensive manufacturing, all the way to the complicated e-waste stream,” said Christopher Wilmer, the William Kepler Whiteford Faculty Fellow and associate professor of chemical and petroleum engineering, who leads the Hypothetical Materials Lab. “A circular economy model is well-suited to mitigating each of these impacts, but less than 40 percent of e-waste is currently estimated to be reused or recycled. If our technology is going to be sustainable, it’s important that we understand the barriers to e-waste recycling.”
Some U.S. firms that have touted safe, ethical and green recycling practices never actually recycle much of what they receive; instead, their e-waste was illegally stockpiled, abandoned or exported. Between 2014 and 2016, the Basel Action Network used GPS trackers in electronics delivered to U.S. recyclers, showing that 30 percent of the products ended up overseas.
The researchers developed a model framework that analyzes dishonest end-of-life electronics management and what leads recyclers to pursue fraudulent activities. They find that the primary way to ensure an e-waste recycler will engage in honest practices with minimum supervision is to make it the more profitable option, either by decreasing the costs of recycling or increasing the penalties for fraudulent practices.
“The main barrier to honest recycling is its cost,” said lead author Daniel Salmon, a graduate student in the Department of Electrical and Computer Engineering. “One of our main findings is that if we find a way to make it more profitable for companies to recycle, we will have less dishonest recycling. Targeted subsidies, higher penalties for fraud and manufacturers ensuring their electronics are more easily recyclable are all things that could potentially solve this problem.”
The researchers also suggest the use of the blockchain as neutral, third-party supervision to avoid fraudulent recycling practices.
“Our model mentions the influence of monitoring and supervision, but self-reporting by companies enables dishonesty. On the other hand, something like the blockchain does not,” said Wilmer, who founded Ledger, the first peer-reviewed scholarly journal dedicated to blockchain and cryptocurrency. “Relying on an immutable record may be one solution to prevent fraud and align behaviors across recyclers toward a circular economy.”
The work is part of a larger NSF-funded convergence research project on the circular economy, which is led by Melissa Bilec, deputy director of the Mascaro Center, associate professor of civil and environmental engineering, and Roberta A. Luxbacher Faculty Fellow at Pitt.
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Materials provided by University of Pittsburgh. Original written by Maggie Pavlick. Note: Content may be edited for style and length. More

A commonly studied perovskite can superfluoresce at temperatures that are practical to achieve and at timescales long enough to make it potentially useful in quantum computing applications. The finding from North Carolina State University researchers also indicates that superfluorescence may be a common characteristic for this entire class of materials.
Superfluorescence is an example of quantum phase transition — when individual atoms within a material all move through the same phases in tandem, becoming a synchronized unit.
For example, when atoms in an optical material such as a perovskite are excited they can individually radiate light, create energy, and fluoresce. Each atom will start moving through these phases randomly, but given the right conditions, they can synchronize in a macroscopic quantum phase transition. That synchronized unit can then interact with external electric fields more strongly than any single atom could, creating a superfluorescent burst.
“Instances of spontaneous synchronization are universal, occurring in everything from planetary orbits to fireflies synchronizing their signals,” says Kenan Gundogdu, professor of physics at NC State and corresponding author of the research. “But in the case of solid materials, these phase transitions were thought to only happen at extremely low temperatures. This is because the atoms move out of phase too quickly for synchronization to occur unless the timing is slowed by cooling.”
Gundogdu and his team observed superfluorescence in the perovskite methyl ammonium lead iodide, or MAPbI3, while exploring its lasing properties. Perovskites are materials with a crystal structure and light-emitting properties useful in creating lasers, among other applications. They are inexpensive, relatively simple to fabricate, and are used in photovoltaics, light sources and scanners.
“When trying to figure out the dynamics behind MAPbI3’s lasing properties, we noticed that the dynamics we observed couldn’t be described simply by lasing behavior,” Gundogdu says. “Normally in lasing one excited particle will emit light, stimulate another one, and so on in a geometric amplification. But with this material we saw synchronization and a quantum phase transition, resulting in superfluorescence.”
But the most striking aspects of the superfluorescence were that it occurred at 78 Kelvin and had a phase lifetime of 10 to 30 picoseconds.
“Generally superfluorescence happens at extremely cold temperatures that are difficult and expensive to achieve, and it only lasts for femtoseconds,” Gundogdu says. “But 78 K is about the temperature of dry ice or liquid nitrogen, and the phase lifetime is two to three orders of magnitude longer. This means that we have macroscopic units that last long enough to be manipulated.”
The researchers think that this property may be more widespread in perovskites generally, which could prove useful in quantum applications such as computer processing or storage.
“Observation of superfluorescence in solid state materials is always a big deal because we’ve only seen it in five or six materials thus far,” Gundogdu says. “Being able to observe it at higher temperatures and longer timescales opens the door to many exciting possibilities.”
The work appears in Nature Photonics and is supported by the National Science Foundation (grant 1729383). NC State graduate students Gamze Findik and Melike Biliroglu are co-first authors. Franky So, Walter and Ida Freeman Distinguished Professor of Materials Science and Engineering, is co-author.
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One vision that is currently driving material scientists is to combine organic molecules (and their diverse functionalities) with the technological possibilities offered by extremely sophisticated semiconductor electronics. Thanks to modern methods of micro- and nanotechnology, the latter designs ever more efficient electronic components for a wide variety of applications. However, it is also increasingly reaching its physical limits: Ever smaller structures for functionalizing semiconductor materials such as silicon cannot be produced using the approaches of classical technology. Scientists have now presented a new approach in the journal Nature Chemistry: They show that stable and yet very well-ordered molecular single layers can be produced on silicon surfaces — by self-assembly. To do this, they use N-heterocyclic carbenes. These are small reactive organic ring molecules whose structure and properties vary in many ways and can be tailored by different “functional” groups.
Researchers led by Prof. Dr. Mario Dähne (TU Berlin, Germany), Prof. Dr. Norbert Esser (TU Berlin and Leibniz Institute for Analytical Sciences, Germany), Prof. Dr. Frank Glorius (University of Münster, Germany), Dr. Conor Hogan (Institute of Structure of Matter, National Research Council of Italy, Rome, Italy) and Prof. Dr. Wolf Gero Schmidt (University of Paderborn, Germany) were involved in the study.
Technological miniaturization reaches its limits
“Instead of trying to artificially produce smaller and smaller structures with increasing effort, it is obvious to learn from molecular structures and processes in nature and to merge their functionality with semiconductor technology,” says chemist Frank Glorius. “This would make an interface, so to speak, between molecular function and the electronic user interface for technical applications.” The prerequisite is that the ultra-small molecules with variable structure and functionality would have to be physically incorporated with the semiconductor devices, and they would have to be reproducible, stable and as simple as possible.
Harnessing the self-organization of molecules
The self-organization of molecules on a surface, as an interface to the device, can perform this task very well. Molecules with a defined structure can be adsorbed on surfaces in large numbers and arrange themselves into a desired structure that is predetermined by the molecular properties. “This works quite well on surfaces of metals, for example, but unfortunately not at all satisfactorily for semiconductor materials so far,” explains physicist Norbert Esser. This is because in order to be able to arrange themselves, the molecules must be mobile (diffuse) on the surface. But molecules on semiconductor surfaces do not do that. Rather, they are so strongly bound to the surface that they stick wherever they hit the surface.
N-Heterocyclic carbenes as a solution
Being simultaneously mobile and yet stably bonded to the surface is the crucial problem and at the same time the key to potential applications. And it is precisely here that the researchers now have a possible solution at hand: N-heterocyclic carbenes. Their use for surface functionalization has attracted a lot of interest over the past decade. On surfaces of metals such as gold, silver and copper, for example, they have proven to be very effective surface ligands, often outperforming other molecules. However, their interaction with semiconductor surfaces has remained virtually unexplored.
Formation of a regular molecular structure
Certain properties of the carbenes are decisive for the fact that it has now been possible for the first time to produce molecular single layers on silicon surfaces: N-heterocyclic carbenes, like other molecules, form very strong covalent bonds with silicon and are thus stably bound. However, side groups of the molecule simultaneously keep them “at a distance” from the surface. Thus, they can still move about on the surface. Although they do not travel very far — only a few atomic distances — this is sufficient to form an almost equally regular molecular structure on the surface of the regularly structured silicon crystal.
Interdisciplinary collaboration
Using a complementary multi-method approach of organic chemical synthesis, scanning probe microscopy, photoelectron spectroscopy and comprehensive material simulations, the researchers clarified the principle of this novel chemical interaction in their interdisciplinary collaboration. They also demonstrated the formation of regular molecular structures in several examples. “This opens a new chapter for the functionalization of semiconductor materials, such as silicon in this case,” emphasizes physicist Dr. Martin Franz, first author of the study.
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Although quantum technology has proven valuable for highly precise timekeeping, making these technologies practical for use in a variety of environments is still a key challenge. In an important step toward portable quantum devices, researchers have developed a new high-flux and compact cold-atom source with low power consumption that can be a key component of many quantum technologies.
“The use of quantum technologies based on laser-cooled atoms has already led to the development of atomic clocks that are used for timekeeping on a national level,” said research team leader Christopher Foot from Oxford University in the U.K. “Precise clocks have many applications in the synchronization of electronic communications and navigation systems such as GPS. Compact atomic clocks that can be deployed more widely, including in space, provide resilience in communications networks because local clocks can maintain accurate timekeeping even if there is a network disruption.”
In The Optical Society (OSA) journal Optics Express, S. Ravenhall, B. Yuen and Foot describe work carried out in Oxford, U.K. to demonstrate a completely new design for a cold atom source. The new device is suitable for a wide range of cold-atom technologies.
“In this project we took a design we made for research purposes and developed it into a compact device,” said Foot. “In addition to timekeeping applications, compact cold-atom devices can also be used for instruments for gravity mapping, inertial navigation and communications and to study physical phenomena in research applications such as dark matter and gravitational waves.”
Cooling atoms with light
Although it may seem counterintuitive, laser light can be used to cool atoms to extremely low temperatures by exerting a force that slows the atoms down. This process can be used to create a cold-atom source that generates a beam of laser-cooled atoms directed toward a region where precision measurements for timekeeping or detecting gravitational waves, for example, are carried out.
Laser cooling usually requires a complicated arrangement of mirrors to shine light onto atoms in a vacuum from all directions. In the new work, the researchers created a completely different design that uses just four mirrors. These mirrors are arranged like a pyramid and placed in a way that allows them to slide past each other like the petals of a flower to create a hole at the top of the pyramid through which the cold atoms are pushed out. The size of this hole can be adjusted to optimize the flow of cold atoms for various applications. The pyramid arrangement reflects the light from a single incoming laser beam that enters the vacuum chamber through a single viewport, thus greatly simplifying the optics.
The mirrors, which are located inside the vacuum region of the cold-atom source, were created by polishing metal and applying a dielectric coating. “The adjustability of this design is an entirely new feature,” said Foot. “Creating a pyramid from four identical polished metal blocks simplifies the assembly, and it can be used without the adjustment mechanism.”
Better measurements with more atoms
To test their new cold-atom source design, the researchers constructed laboratory equipment to fully characterize the flux of atoms emitted through a hole at the apex of the pyramid.
“We demonstrated an exceptionally high flux of rubidium atoms,” said Foot. “Most cold-atom devices take measurements that improve with the number of atoms used. Sources with a higher flux can thus be used to improve measurement accuracy, boost the signal-to-noise ratio or help achieve larger measurement bandwidths.”
The researchers say that the new source is suitable for commercial application. Because it features a small number of components and few assembly steps, scaling up production to produce multiple copies would be straightforward.
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According to the American Burn Association, burn injuries affect approximately 250,000 children in the United States each year. The pain associated with burn injuries extends beyond the injury itself; there is also significant pain from dressing changes, which can be exacerbated by the anxiety of anticipating this additional pain.
Although opioids relieve burn injury-related pain, they have serious adverse side effects. Prior studies have investigated alternative approaches to pain reduction in burn injury patients that focus on distraction, such as music, hypnosis, toys, and virtual reality (VR).
In a study published today in JAMA Network Open, Henry Xiang, MD, MPH, PhD, MBA, and his research team reported the use of smartphone-based VR games during dressing changes in pediatric patients with burn injuries. “The smartphone-based VR game was very effective in reducing patient-reported pain,” says Dr. Xiang, a professor of pediatrics and epidemiology at Nationwide Children’s Hospital and director of the Center for Pediatric Trauma Research.
In the pilot study, designed as a randomized clinical trial, the research team divided 90 children, aged 6 to 17 years, into three treatment groups: active VR, passive VR, and standard care (e.g., toys, tablet). These patients, most with second-degree burns, received outpatient care for burn injuries between December 2016 and January 2019.
The VR game, called “Virtual River Cruise,” was designed specifically for the study by Nationwide Children’s Research Information Solutions and Innovation department. “Two factors were considered for the game’s design,” explains Dr. Xiang. “The first factor was a snow, cooling environment within the game. The second factor was cognitive processing to encourage active engagement.”
Patients played the game using a smartphone and a headset. During dressing changes, which lasted approximately 5 to 6 minutes, patients in the active VR group actively engaged with the game; to stay still while playing the game, the patients tilted their head to aim a target, notes Dr. Xiang. Patients in the passive VR group only watched the game.
Along with their caregivers, patients reported their perceived pain and subjective experience with the game in post-intervention surveys. Nurses evaluated the game’s clinical utility.
Among the three treatment groups, patients in the active VR group had the lowest overall pain scores. Most patients and their caregivers reported a positive experience with the game, calling it “fun, engaging, and realistic.”
Nurses considered the game to be clinically useful in the outpatient setting. Previously, computer-based games were used during dressing changes. However, the computers’ bulkiness was not clinically practical. “Smartphones are easy to use, and most families have them,” said Dr. Xiang.
Given the VR games’ ease of use and demonstrated effectiveness at reducing pain during burn dressing changes, Dr. Xiang believes the game can also be played at home to relieve this pain. “Pediatric burn patients still need dressing changes at home after hospital discharge, and these changes could be very painful,” said Dr. Xiang. Currently, Dr. Xiang is leading a research project, funded by the Division of Emergency Medical Service of Ohio Department of Public Safety, to evaluate the feasibility and efficacy of VR games in reducing pain during burn dressing changes at home.
The current opioid crisis underscores the need to continue to explore non-opioid approaches to controlling pain in burn patients. “The future research direction is to evaluate whether smartphone-based VR games have an opioid-sparing effect,” says Dr. Xiang. More

In humans, adenoviruses can infect the cells of the respiratory tract, while herpes viruses can infect those of the skin and nervous system. In most cases, this does not lead to the production of new virus particles, as the viruses are suppressed by the immune system. However, adenoviruses and herpes viruses can cause persistent infections that the immune system is unable to completely suppress and that produce viral particles for years. These same viruses can also cause sudden, violent infections where affected cells release large amounts of viruses, such that the infection spreads rapidly. This can lead to serious acute diseases of the lungs or nervous system.
Automatic detection of virus-infected cells
The research group of Urs Greber, Professor at the Department of Molecular Life Sciences at the University of Zurich (UZH), has now shown for the first time that a machine-learning algorithm can recognize the cells infected with herpes or adenoviruses based solely on the fluorescence of the cell nucleus. “Our method not only reliably identifies virus-infected cells, but also accurately detects virulent infections in advance,” Greber says. The study authors believe that their development has many applications — including predicting how human cells react to other viruses or microorganisms. “The method opens up new ways to better understand infections and to discover new active agents against pathogens such as viruses or bacteria,” Greber adds.
The analysis method is based on combining fluorescence microscopy in living cells with deep-learning processes. The herpes and adenoviruses formed inside an infected cell change the organization of the nucleus, and these changes can be observed under a microscope. The group developed a deep-learning algorithm — an artificial neural network — to automatically detect these changes. The network is trained with a large set of microscopy images through which it learns to identify patterns that are characteristic of infected or uninfected cells. “After training and validation are complete, the neural network automatically detects virus-infected cells,” explains Greber.
Reliably predicting severe acute infections
The research team has also demonstrated that the algorithm is capable of identifying acute and severe infections with 95 percent accuracy and up to 24 hours in advance. Images of living cells from lytic infections, in which the virus particles multiply rapidly and the cells dissolve, as well as images of persistent infections, in which viruses are produced continuously but only in small quantities, served as training material. Despite the great precision of the method, it is not yet clear which features of infected cell nuclei are recognized by the artificial neural network to distinguish the two phases of infection. However, even without this knowledge, the researchers are now able to study the biology of infected cells in greater detail.
The group has already discovered some differences: The internal pressure of the nucleus is greater during virulent infections than during persistent phases. Furthermore, in a cell with lytic infection, viral proteins accumulate more rapidly in the nucleus. “We suspect that distinct cellular processes determine whether or not a cell disintegrates after it is infected. We can now investigate these and other questions,” says Greber.
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New technology could help cities around the world improve people’s lives while saving billions of dollars. The free, open-source software developed by the Stanford Natural Capital Project creates maps to visualize the links between nature and human wellbeing. City planners and developers can use the software to visualize where investments in nature, such as parks and marshlands, can maximize benefits to people, like protection from flooding and improved health.
“This software helps design cities that are better for both people and nature,” said Anne Guerry, Chief Strategy Officer and Lead Scientist at the Natural Capital Project. “Urban nature is a multitasking benefactor — the trees on your street can lower temperatures so your apartment is cooler on hot summer days. At the same time, they’re soaking up the carbon emissions that cause climate change, creating a free, accessible place to stay healthy through physical activity and just making your city a more pleasant place to be.”
By 2050, experts expect over 70 percent of the world’s people to live in cities — in the United States, more than 80 percent already do. As the global community becomes more urban, developers and city planners are increasingly interested in green infrastructure, such as tree-lined paths and community gardens, that provide a stream of benefits to people. But if planners don’t have detailed information about where a path might encourage the most people to exercise or how a community garden might buffer a neighborhood from flood risk while helping people recharge mentally, they can’t strategically invest in nature.
“We’re answering three crucial questions with this software: where in a city is nature providing what benefits to people, how much of each benefit is it providing and who is receiving those benefits?” said Perrine Hamel, lead author on a new paper about the software published in Urban Sustainability and Livable Cities Program Lead at the Stanford Natural Capital Project at the time of research.
The software, called Urban InVEST, is the first of its kind for cities and allows for the combination of environmental data, like temperature patterns, with social demographics and economic data, like income levels. Users can input their city’s datasets into the software or access a diversity of open global data sources, from NASA satellites to local weather stations. The new software joins the Natural Capital Project’s existing InVEST software suite, a set of tools designed for experts to map and model the benefits that nature provides to people.
To test Urban InVEST, the team applied the software in multiple cities around the world: Paris, France; Lausanne, Switzerland; Shenzhen and Guangzhou, China; and several U.S. cities, including San Francisco and Minneapolis. In many cases, they worked with local partners to understand priority questions — in Paris, candidates in a municipal election were campaigning on the need for urban greenery, while in Minneapolis, planners were deciding how to repurpose underused golf course land. More

Geologic activity on Earth appears to follow a 27.5-million-year cycle, giving the planet a “pulse,” according to a new study published in the journal Geoscience Frontiers.
“Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random,” said Michael Rampino, a geologist and professor in New York University’s Department of Biology, as well as the study’s lead author.
Over the past five decades, researchers have proposed cycles of major geological events — including volcanic activity and mass extinctions on land and sea — ranging from roughly 26 to 36 million years. But early work on these correlations in the geological record was hampered by limitations in the age-dating of geologic events, which prevented scientists from conducting quantitative investigations.
However, there have been significant improvements in radio-isotopic dating techniques and changes in the geologic timescale, leading to new data on the timing of past events. Using the latest age-dating data available, Rampino and his colleagues compiled updated records of major geological events over the last 260 million years and conducted new analyses.
The team analyzed the ages of 89 well-dated major geological events of the last 260 million years. These events include marine and land extinctions, major volcanic outpourings of lava called flood-basalt eruptions, events when oceans were depleted of oxygen, sea-level fluctuations, and changes or reorganization in the Earth’s tectonic plates.
They found that these global geologic events are generally clustered at 10 different timepoints over the 260 million years, grouped in peaks or pulses of roughly 27.5 million years apart. The most recent cluster of geological events was approximately 7 million years ago, suggesting that the next pulse of major geological activity is more than 20 million years in the future.
The researchers posit that these pulses may be a function of cycles of activity in the Earth’s interior — geophysical processes related to the dynamics of plate tectonics and climate. However, similar cycles in the Earth’s orbit in space might also be pacing these events.
“Whatever the origins of these cyclical episodes, our findings support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is a departure from the views held by many geologists,” explained Rampino.
In addition to Rampino, study authors include Yuhong Zhu of NYU’s Center for Data Science and Ken Caldeira of the Carnegie Institution for Science.
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