Computers Math

Monitoring environmental compliance is a particular challenge for governments in poor countries. A new machine learning approach that uses satellite imagery to pinpoint highly polluting brick kilns in Bangladesh could provide a low-cost solution. Like superheroes capable of seeing through obstacles, environmental regulators may soon wield the power of all-seeing eyes that can identify violators anywhere at any time, according to a new Stanford University-led study. The paper, published the week of April 19 in Proceedings of the National Academy of Sciences (PNAS), demonstrates how artificial intelligence combined with satellite imagery can provide a low-cost, scalable method for locating and monitoring otherwise hard-to-regulate industries.
“Brick kilns have proliferated across Bangladesh to supply the growing economy with construction materials, which makes it really hard for regulators to keep up with new kilns that are constructed,” said co-lead author Nina Brooks, a postdoctoral associate at the University of Minnesota’s Institute for Social Research and Data Innovation who did the research while a PhD student at Stanford.
While previous research has shown the potential to use machine learning and satellite observations for environmental regulation, most studies have focused on wealthy countries with dependable data on industrial locations and activities. To explore the feasibility in developing countries, the Stanford-led research focused on Bangladesh, where government regulators struggle to locate highly pollutive informal brick kilns, let alone enforce rules.
A growing threat
Bricks are key to development across South Asia, especially in regions that lack other construction materials, and the kilns that make them employ millions of people. However, their highly inefficient coal burning presents major health and environmental risks. In Bangladesh, brick kilns are responsible for 17 percent of the country’s total annual carbon dioxide emissions and — in Dhaka, the country’s most populous city — up to half of the small particulate matter considered especially dangerous to human lungs. It’s a significant contributor to the country’s overall air pollution, which is estimated to reduce Bangladeshis’ average life expectancy by almost two years.
“Air pollution kills seven million people every year,” said study senior author Stephen Luby, a professor of infectious diseases at Stanford’s School of Medicine. “We need to identify the sources of this pollution, and reduce these emissions.”
Bangladesh government regulators are attempting to manually map and verify the locations of brick kilns across the country, but the effort is incredibly time and labor intensive. It’s also highly inefficient because of the rapid proliferation of kilns. The work is also likely to suffer from inaccuracy and bias, as government data in low-income countries often does, according to the researchers. More

The fact that the human body is made up of cells is a basic, well-understood concept. Yet amazingly, scientists are still trying to determine the various types of cells that make up our organs and contribute to our health.
A relatively recent technique called single-cell sequencing is enabling researchers to recognize and categorize cell types by characteristics such as which genes they express. But this type of research generates enormous amounts of data, with datasets of hundreds of thousands to millions of cells.
A new algorithm developed by Joshua Welch, Ph.D., of the Department of Computational Medicine and Bioinformatics, Ph.D. candidate Chao Gao and their team uses online learning, greatly speeding up this process and providing a way for researchers world-wide to analyze large data sets using the amount of memory found on a standard laptop computer. The findings are described in the journal Nature Biotechnology.
“Our technique allows anyone with a computer to perform analyses at the scale of an entire organism,” says Welch. “That’s really what the field is moving towards.”
The team demonstrated their proof of principle using data sets from the National Institute of Health’s Brain Initiative, a project aimed at understanding the human brain by mapping every cell, with investigative teams throughout the country, including Welch’s lab.
Typically, explains Welch, for projects like this one, each single-cell data set that is submitted must be re-analyzed with the previous data sets in the order they arrive. Their new approach allows new datasets to the be added to existing ones, without reprocessing the older datasets. It also enables researchers to break up datasets into so-called mini-batches to reduce the amount of memory needed to process them.
“This is crucial for the sets increasingly generated with millions of cells,” Welch says. “This year, there have been five to six papers with two million cells or more and the amount of memory you need just to store the raw data is significantly more than anyone has on their computer.”
Welch likens the online technique to the continuous data processing done by social media platforms like Facebook and Twitter, which must process continuously-generated data from users and serve up relevant posts to people’s feeds. “Here, instead of people writing tweets, we have labs around the world performing experiments and releasing their data.”
The finding has the potential to greatly improve efficiency for other ambitious projects like the Human Body Map and Human Cell Atlas. Says Welch, “Understanding the normal complement of cells in the body is the first step towards understanding how they go wrong in disease.”
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Materials provided by Michigan Medicine – University of Michigan. Original written by Kelly Malcom. Note: Content may be edited for style and length. More

Someday, scientists believe, tiny DNA-based robots and other nanodevices will deliver medicine inside our bodies, detect the presence of deadly pathogens, and help manufacture increasingly smaller electronics.
Researchers took a big step toward that future by developing a new tool that can design much more complex DNA robots and nanodevices than were ever possible before in a fraction of the time.
In a paper published today (April 19, 2021) in the journal Nature Materials, researchers from The Ohio State University — led by former engineering doctoral student Chao-Min Huang — unveiled new software they call MagicDNA.
The software helps researchers design ways to take tiny strands of DNA and combine them into complex structures with parts like rotors and hinges that can move and complete a variety of tasks, including drug delivery.
Researchers have been doing this for a number of years with slower tools with tedious manual steps, said Carlos Castro, co-author of the study and associate professor of mechanical and aerospace engineering at Ohio State.
“But now, nanodevices that may have taken us several days to design before now take us just a few minutes,” Castro said. More

A new study outlines the need for materials advances in the hardware that goes into making quantum computers if these futuristic devices are to surpass the abilities of the computers we use today.
The study, published in the journal Science by an international team, surveyed the state of research on quantum computing hardware with the goal of illustrating the challenges and opportunities facing scientists and engineers.
While conventional computers encode “bits” of information as ones and zeroes, quantum computers breeze past this binary arrangement by creating “qubits,” which can be complex, continuous quantities. Storing and manipulating information in this exotic form — and ultimately reaching “quantum advantage” where quantum computers do things that conventional computers cannot — requires sophisticated control of the underlying materials.
“There has been an explosion in developing quantum technologies over the last 20 years,” said Nathalie de Leon, assistant professor of electrical and computer engineering at Princeton University and the lead author of the paper, “culminating in current efforts to show quantum advantage for a variety of tasks, from computing and simulation to networking and sensing.”
Until recently, most of this work has aimed to demonstrate proof-of-principle quantum devices and processors, de Leon said, but now the field is poised to address real-world challenges.
“Just as classical computing hardware became an enormous field in materials science and engineering in the last century, I think the quantum technologies field is now ripe for a new approach, where materials scientists, chemists, device engineers and other scientists and engineers can productively bring their expertise to bear on the problem.”
The paper is a call to scientists who study materials to turn to the challenge of developing hardware for quantum computing, said Hanhee Paik, corresponding author and a research staff member at IBM Quantum. More

The internet seems like the place to go to get into fights. Whether they’re with a family member or a complete stranger, these arguments have the potential to destroy important relationships and consume a lot of emotional energy.
Researchers at the University of Washington worked with almost 260 people to understand these disagreements and to develop potential design interventions that could make these discussions more productive and centered around relationship-building. The team published these findings this April in the latest issue of the Proceedings of the ACM in Human Computer Interaction Computer-Supported Cooperative Work.
“Despite the fact that online spaces are often described as toxic and polarizing, what stood out to me is that people, surprisingly, want to have difficult conversations online,” said lead author Amanda Baughan, a UW doctoral student in the Paul G. Allen School of Computer Science & Engineering. “It was really interesting to see that people are not having the conversations they want to have on online platforms. It pointed to a big opportunity to design to support more constructive online conflict.”
In general, the team said, technology has a way of driving users’ behaviors, such as logging onto apps at odd times to avoid people or deleting enjoyable apps to avoid spending too much time on them. The researchers were interested in the opposite: how to make technology respond to people’s behaviors and desires, such as to strengthen relationships or have productive discussions.
“Currently many of the designed features that users leverage during an argument support a no-road-back approach to disagreement — if you don’t like someone’s content, you can unfollow, unfriend or block them. All of those things cut off relationships instead of helping people repair them or find common ground,” said senior author Alexis Hiniker, an assistant professor in the UW Information School. “So we were really driven by the question of how do we help people have hard conversations online without destroying their relationships?”
The researchers did their study in three parts. First, they interviewed 22 adults from the Seattle area about what social media platforms they used and whether they felt like they could talk about challenging topics. The team also asked participants to brainstorm potential ways that these platforms could help people have more productive conversations. More

Gas accidents such as toxic gas leakage in factories, carbon monoxide leakage of boilers, or toxic gas suffocation during manhole cleaning continue to claim lives and cause injuries. Developing a sensor that can quickly detect toxic gases or biochemicals is still an important issue in public health, environmental monitoring, and military sectors. Recently, a research team at POSTECH has developed an inexpensive, ultra-compact wearable hologram sensor that immediately notifies the user of volatile gas detection.
A joint research team led by Professor Junsuk Rho of departments of mechanical and chemical engineering and Dr. Inki Kim of Department of Mechanical Engineering with Professor Young-Ki Kim and Ph.D. candidate Won-Sik Kim of Department of Chemical Engineering at POSTECH has integrated metasurface with gas-reactive liquid crystal optical modulator to develop a sensor that provides an immediate visual holographic alarm when harmful gases are detected. The findings from this study were published in Science Advances on April 7, 2021.
For those working in hazardous environments such as petrochemical plants, gas sensors are life. However, conventional gas sensing devices are not widely used due to their high cost of being made with complex machines and electronic devices. In addition, commercial gas sensors have limitations in that they are difficult to use, and have poor portability and reaction speed.
To solve these issues, the research team utilized the metasurface, well known as a future optical device known to have the invisible cloak effect through making visible objects disappear by controlling the refractive index of light. Metasurface is especially used to transmit two-way holograms or 3D video images by freely controlling light.
Using the metasurface, the research team developed a gas sensor that can float a holographic image alarm in space in just a few seconds by using the polarization control of transmitted light that transforms due to the change in orientation of liquid crystal molecules in the liquid crystal layer inside the sensor device when exposed to gas. Moreover, this gas sensor developed by the research team requires no support from external mechanical or electronic devices, unlike other conventional commercial gas sensors. The researchers used isopropyl alcohol as the target hazardous gas, known as a toxic substance that can cause stomach pain, headache, dizziness, and even leukemia.
The newly developed sensor was confirmed to detect even the minute amount of gas of about 200ppm. In an actual experiment using a board marker, a volatile gas source in our daily life, a visual holographic alarm popped up instantaneously the moment the marker was brought to the sensor.
Moreover, the research team developed a one-step nanocomposite printing method to produce this flexible and wearable gas sensor. The metasurface structure, which was previously processed on a hard substrate, was designed to enable rapid production with a single-step nanocasting process on a curved or flexible substrate.
When the flexible sensor fabricated using this method attaches like a sticker on safety glasses, it can detect gas and display a hologram alarm. It is anticipated to be integrable with glass-type AR display systems under development at Apple, Samsung, Google, and Facebook.
Going a step further, the research team is developing a high-performance environmental sensor that can display the type and concentration level of gases or biochemicals in the surroundings with a holographic alarm, and is studying optical design techniques that can encode various holographic images. If these studies are successful, they can be used to reduce accidents caused by biochemical or gas leaks.
“This newly developed ultra-compact wearable gas sensor provides a more intuitive holographic visual alarm than the conventional auditory or simple light alarms,” remarked Prof. Junsuk Rho. “It is anticipated to be especially effective in more extreme work environments where acoustic and visual noise are intense.” More

When temperatures drop below zero degrees Celsius, water turns to ice. But does everything actually freeze if you just cool it down enough? In the classical picture, matter inherently becomes solid at low temperatures. Quantum mechanics can, however, break this rule. Therefore, helium gas, for example, can become liquid at -270 degrees, but never solid under atmospheric pressure: There is no helium ice.
The same is true for the magnetic properties of materials: at sufficiently low temperatures, the magnetic moments known as ‘spins’, for example, arrange themselves in such a way that they are oriented opposite/antiparallel to their respective neighbors. One can think of this as arrows pointing alternating up and down along a chain or in a checkerboard pattern. It gets frustrating when the pattern is based on triangles: While two spins can align in opposite directions, the third is always parallel to one of them and not to the other — no matter how you turn it.
For this problem, quantum mechanics suggests the solution that the orientation and bond of two spins are not rigid, but the spins fluctuate. The state formed is called a quantum spin liquid in which the spins constitute a quantum mechanically entangled ensemble. This idea was proposed almost fifty years ago by the American Nobel laureate Phil W. Anderson (1923-2020). After decades of research, only a handful of real materials remain in the search for this exotic state of matter. As a particularly promising “candidate” a triangular lattice in a complex organic compound was considered, in which no magnetic order with a regular up-down pattern could be observed, even at extremely low temperatures. Was this the proof that quantum spin liquids really exist?
One problem is that it is extremely challenging to measure electron spins down to such extremely low temperatures, especially along different crystal directions and in variable magnetic fields. All previous experiments have been able to probe quantum spin liquids only more or less indirectly, and their interpretation is based on certain assumptions and models. Therefore, a new method of broadband electron spin resonance spectroscopy has been developed over many years at the Institute of Physics 1 at the University of Stuttgart.
Using on-chip microwave lines, one can directly observe the properties of the spins down to a few hundredths of a degree above absolute zero. In doing so, the researchers found that the magnetic moments do not arrange themselves in the up-down pattern of a typical magnet, nor do they form a dynamic state resembling a liquid. “In fact, we observed the spins in spatially separated pairs. Thus, our experiments have shattered the dream of a quantum spin liquid for now, at least for this compound,” summarizes Prof. Martin Dressel, head of the Institute of Physics 1.
But even though the pairs did not fluctuate as hoped, this exotic ground state of matter has lost none of its fascination for the physicists. “We want to investigate whether quantum spin liquids might be detectable in other triangular lattice compounds or even in completely different systems such as honeycomb structures,” Dressel outlines the next steps. However, it could also be that such a disordered, dynamic state simply does not exist in nature. Perhaps every kind of interaction leads in one way or another to a regular arrangement if the temperature is low enough. Spins just like to pair up.
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Materials provided by Universitaet Stuttgart. Note: Content may be edited for style and length. More

A team of researchers from QuTech in the Netherlands reports realization of the first multi-node quantum network, connecting three quantum processors. In addition, they achieved a proof-of-principle demonstration of key quantum network protocols. Their findings mark an important milestone towards the future quantum internet and have now been published in Science.
The quantum internet
The power of the Internet is that it allows any two computers on Earth to be connected with each other, enabling applications undreamt of at the time of its creation decades ago. Today, researchers in many labs around the world are working towards first versions of a quantum internet — a network that can connect any two quantum devices, such as quantum computers or sensors, over large distances. Whereas today’s Internet distributes information in bits (that can be either 0 or 1), a future quantum internet will make use of quantum bits that can be 0 and 1 at the same time. ‘A quantum internet will open up a range of novel applications, from unhackable communication and cloud computing with complete user privacy to high-precision time-keeping,’ says Matteo Pompili, PhD student and a member of the research team. ‘And like with the Internet 40 years ago, there are probably many applications we cannot foresee right now.’
Towards ubiquitous connectivity
The first steps towards a quantum internet were taken in the past decade by linking two quantum devices that shared a direct physical link. However, being able to pass on quantum information through intermediate nodes (analogous to routers in the classical internet) is essential for creating a scalable quantum network. In addition, many promising quantum internet applications rely on entangled quantum bits, to be distributed between multiple nodes. Entanglement is a phenomenon observed at the quantum scale, fundamentally connecting particles at small and even at large distances. It provides quantum computers their enormous computational power and it is the fundamental resource for sharing quantum information over the future quantum internet. By realizing their quantum network in the lab, a team of researchers at QuTech — a collaboration between Delft University of Technology and TNO — is the first to have connected two quantum processors through an intermediate node and to have established shared entanglement between multiple stand-alone quantum processors.
Operating the quantum network
The rudimentary quantum network consists of three quantum nodes, at some distance within the same building. To make these nodes operate as a true network, the researchers had to invent a novel architecture that enables scaling beyond a single link. The middle node (called Bob) has a physical connection to both outer nodes (called Alice and Charlie), allowing entanglement links with each of these nodes to be established. Bob is equipped with an additional quantum bit that can be used as memory, allowing a previously generated quantum link to be stored while a new link is being established. After establishing the quantum links Alice-Bob and Bob-Charlie, a set of quantum operations at Bob converts these links into a quantum link Alice-Charlie. Alternatively, by performing a different set of quantum operations at Bob, entanglement between all three nodes is established. More