. Scientific Frontline

Saturday, April 9, 2022

‘Frustrated’ nanomagnets order themselves through disorder

Source/Credit: Yale University

Extremely small arrays of magnets with strange and unusual properties can order themselves by increasing entropy, or the tendency of physical systems to disorder, a behavior that appears to contradict standard thermodynamics—but doesn’t.

“Paradoxically, the system orders because it wants to be more disordered,” said Cristiano Nisoli, a physicist at Los Alamos and coauthor of a paper about the research published in Nature Physics. “Our research demonstrates entropy-driven order in a structured system of magnets at equilibrium.”

The system examined in this work, known as tetris spin ice, was studied as part of a long-standing collaboration between Nisoli and Peter Schiffer at Yale University, with theoretical analysis and simulations led at Los Alamos and experimental work led at Yale. The research team includes scientists from a number of universities and academic institutions.

Nanomagnet arrays, like tetris spin ice, show promise as circuits of logic gates in neuromorphic computing, a leading-edge computing architecture that closely mimics how the brain works. They also have possible applications in a number of high-frequency devices using “magnonics” that exploit the dynamics of magnetism on the nanoscale.

Newborn cells in the epileptic brain provide a potential target for treatment

Altered cells create an electrical “fire” in patients with epilepsy.
Credit: BioRender illustration by Aswathy Ammothumkandy/Bonaguidi Lab/USC Stem Cell

Over the years, everyone loses a few brain cells. A study led by scientists from USC Stem Cell and the USC Neurorestoration Center presents evidence that adults can replenish at least some of what they’ve lost by generating new brain cells, and that this process is dramatically altered in patients with long-term epilepsy. The findings are published in Nature Neuroscience.

“Our study is the first to detail the presence of newborn neurons and an immature version of a related cell type, known as astroglia, in patients with epilepsy,” said Michael Bonaguidi, an assistant professor of stem cell biology and regenerative medicine, gerontology, and biomedical engineering at USC. “Our findings furnish surprising new insights into how immature astroglia might contribute to epilepsy—opening an unexplored avenue toward the development of new anti-seizure medications for millions of people.”

First author Aswathy Ammothumkandy, who is a postdoctoral fellow in the Bonaguidi Lab, and her colleagues collaborated with USC neurosurgeons Charles Liu and Jonathan Russin, who often treat patients with seizures that can’t be controlled with medication. Drug resistance is particularly common with mesial temporal lobe epilepsy, or MTLE, and affects one-third of all patients with this form of the disease. As a result, some patients need to undergo surgery to remove the section of the brain, the hippocampus, that causes their seizures.

Friday, April 8, 2022

Melting ice caps may not shut down ocean current

Feng He
Credit: Courtesy of 
University of Wisconsin–Madison
Most simulations of our climate’s future may be overly sensitive to Arctic ice melt as a cause of abrupt changes in ocean circulation, according to new research led by scientists at the University of Wisconsin–Madison.

Climate scientists count the Atlantic Meridional Overturning Circulation (or AMOC) among the biggest tipping points on the way to a planetary climate disaster. The Atlantic Ocean current acts like a conveyor belt carrying warm tropical surface water north and cooler, heavier deeper water south.

“We’ve been taught to picture it like a conveyor belt — even in middle school and high school now, it’s taught this way — that shuts down when freshwater comes in from ice melt,” says Feng He, an associate scientist at UW–Madison’s Center for Climatic Research.

However, building upon previous work, He says researchers are revising their understanding of the relationship between AMOC and freshwater from melting polar ice.

In the past, a stalled AMOC has accompanied abrupt climate events like the Bølling-Allerød warming, a 14,500-year-old, sharp global temperature hike. He successfully reproduced that event using a climate model he conducted in 2009 while a UW–Madison graduate student.

“That was a success, reproducing the abrupt warming about 14,700 years ago that is seen in the paleoclimate record,” says He, now. “But our accuracy didn’t continue past that abrupt change period.”

Gel delivery enhances cancer treatment

As shown in this demonstration, the hydrogel can be easily injected through a needle and then rapidly self-heals after injection to form a solid-like gel. The needle in this image is a 21-gauge needle, a relevant size for human injection.
Image credit: Abigail K. Grosskopf

One cutting-edge cancer treatment exciting researchers today involves collecting and reprogramming a patient’s T cells – a special set of immune cells – then putting them back into the body ready to detect and destroy cancerous cells. Although effective for widespread blood cancers like leukemia, this method rarely succeeds at treating solid tumors.

Now, Stanford University engineers have developed a delivery method that enhances the “attack power” of the modified immune cells, called chimeric antigen receptor (CAR) T cells. Researchers add CAR-T cells and specialized signaling proteins to a hydrogel – a water-filled gel that has characteristics in common with biological tissues – and inject the substance next to a tumor. This gel provides a temporary environment inside the body where the immune cells multiply and activate in preparation to fight cancerous cells, according to a new study published April 8 in Science Advances. The gel acts like a leaky holding pen that pumps out activated CAR-T cells to continuously attack the tumor over time.

“A lot of the CAR-T cell field is focusing on how to make better cells themselves, but there is much less focus on how to make the cells more effective once in the body,” said Eric Appel, assistant professor of materials science and engineering at Stanford and senior author of the paper. “So, what we’re doing is totally complementary to all of the efforts to engineer better cells.”

Human activity ‘helped fuel’ red tide events, new study reveals

The study is just the beginning of discovering the effects of human activity on red tide blooms.
Credit: File photo/UF

In a new study that is the first to explain what some have long suspected, researchers found that human activity helps sustain and intensify naturally occurring red tide blooms in Southwest Florida.

Conducted by researchers at the University of Florida, Sanibel-Captiva Conservation Foundation and Sarasota Bay Estuary Program, the study found that while a combination of factors contributes to red tide blooms, human activity has played a consistent role in intensifying them during the past decade.

The researchers linked blooms in Charlotte Harbor and surrounding coastal areas to nitrogen inputs from the Caloosahatchee River, Lake Okeechobee and areas upstream of the lake. The study was published in the journal Science of the Total Environment.

“While red tide blooms develop naturally, we took a long view and found evidence that human activity has helped fuel coastal blooms in this estuary to varying extents between 2012 and 2021,” said Miles Medina, lead author of the study and a research scientist at UF’s Center for Coastal Solutions.

Determining what contributes to red tide intensification has been a priority for coastal states, as the harmful toxins these blooms create affect humans and sea and land creatures alike.

In the race to build quantum computing hardware, silicon begins to shine

Silicon-based device in development for use in quantum computers. Gate electrodes shown in blue, red, and green are used to define the quantum dot potentials while the micromagnet on top provides a magnetic field gradient. The image was taken using scanning electron microscopy and the colors were applied for clarity. 
Image credit: Adam Mills, Princeton University

Research conducted by Princeton University physicists is paving the way for the use of silicon-based technologies in quantum computing, especially as quantum bits – the basic units of quantum computers. This research promises to accelerate the use of silicon technology as a viable alternative to other quantum computing technologies, such as superconductors or trapped ions.

In research published in the journal Science Advances, Princeton physicists used a two-qubit silicon quantum device to achieve an unprecedented level of fidelity. At above 99 percent, this is the highest fidelity thus far achieved for a two-qubit gate in a semiconductor and is on par with the best results achieved by competing technologies. Fidelity, which is a measure of a qubit’s ability to perform error-free operations, is a key feature in the quest to develop practical and efficient quantum computing.

Researchers around the world are trying to figure out which technologies — such as superconducting qubits, trapped ions or silicon spin qubits, for example — can best be employed as the basic units of quantum computing. And, equally significant researchers are exploring which technologies will have the ability to scale up most efficiently for commercial use.

“Silicon spin qubits are gaining momentum [in the field],” said Adam Mills, a graduate student in the Department of Physics at Princeton University and the lead author of the recently published study. “It’s looking like a big year for silicon overall.”

A ‘cautionary tale’ about location tracking

New research out of the University of Rochester shows that data collected from your acquaintances and even strangers can predict your location.

Data about our habits and movements are constantly collected via mobile phone apps, fitness trackers, credit card logs, websites visited, and other means.

But if we turn off data tracking on our devices, aren’t we untraceable?

No, according to a new study.

“Switching off your location data is not going to entirely help,” says Gourab Ghoshal, an associate professor of physics, mathematics, and computer science and the Stephen Biggar ’92 and Elizabeth Asaro ’92 Fellow in Data Science at the University of Rochester.

Ghoshal, joined by colleagues at the University of Exeter, the Federal University of Rio de Janeiro, Northeastern University, and the University of Vermont, applied techniques from information theory and network science to find out just how far-reaching a person’s data might be. The researchers discovered that even if individual users turned off data tracking and didn’t share their own information, their mobility patterns could still be predicted with surprising accuracy based on data collected from their acquaintances.

“Worse,” says Ghoshal, “almost as much latent information can be extracted from perfect strangers that the individual tends to co-locate with.”

The researchers published their findings in Nature Communications.

Researchers accurately identify people with PTSD through text data alone

A study participant is interviewed by Ellie, an artificial character, to gather text data.
Credit: Jonathan Gratch, USC Institute for Creative Technologies 

University of Alberta researchers have trained a machine learning model to identify people with post-traumatic stress disorder with 80 per cent accuracy by analyzing text data. The model could one day serve as an accessible and inexpensive screening tool to support health professionals in detecting and diagnosing PTSD or other mental health disorders through telehealth platforms.

Psychiatry PhD candidate Jeff Sawalha, who led the project, performed a sentiment analysis of text from a dataset created by Jonathan Gratch at USC’s Institute for Creative Technologies. Sentiment analysis involves taking a large body of data, such as the contents of a series of tweets, and categorizing them — for example, seeing how many are expressing positive thoughts and how many are expressing negative thoughts.

“We wanted to strictly look at the sentiment analysis from this dataset to see if we could properly identify or distinguish individuals with PTSD just using the emotional content of these interviews,” said Sawalha.

The text in the USC dataset was gathered through 250 semi-structured interviews conducted by an artificial character, Ellie, over video conferencing calls with 188 people without PTSD and 87 with PTSD.

New spin lasers for ultra-fast data transfer

Martin Hofmann receives funding as part of a Reinhart-Koselleck project for the development of spin lasers.
Credit: RUB, Marquard

The conventional type of Internet data transmission soon reaches fundamental physical limits. The process can only become faster if you rely on a different principle. Bochum researchers do that.

The transfer of data today is based on light pulses that are sent through fiber optic cables. The faster the light intensity varies, the faster you can transfer information. However, fundamental physical limits of the lasers that generate the modulated light prevent the process from becoming much faster than it is currently. The team led by Prof. Dr. Martin Hofmann, chair of photonics and terahertz technology at the Ruhr University Bochum. With the help of spin lasers, the researchers want to encode information in the polarization of light instead of in light intensity. The German Research Foundation will support the work in the future as part of a Reinhart-Koselleck project with 1.25 million euros for five years.

Thursday, April 7, 2022

Climate change increases risk of devastating debris flows after wildfires in western U.S.

Part of Interstate 70 in Colorado was washed away by flooding and shut down for six months during 2020 and 2021 for repairs.
Credit: Colorado Department of Transportation

In the early morning hours of January 9, 2018, intense rainfall loosened debris and mud in the Santa Ynez mountains, in Santa Barbara County, that had been torched by the Thomas Fire just months before.

The resulting debris flow killed 23 people, injured another 167 and damaged at least 400 homes. UCLA climate scientist Daniel Swain witnessed the aftermath in person.

“It gives you a sense of the physical forces involved,” he said. “You see cars up in trees and boulders the size of trucks strewn about as if they were pebbles in someone’s garden.”

According to a new research paper co-authored by Swain, events like that one could begin occuring more frequently in the western U.S. because of climate change. In the coming years, hilly or mountainous regions within wildfire burn areas will face a higher risk for debris flows, mudslides and flash floods — all of which are likelier to occur on fire-scorched hillsides without vegetation.

That’s because climate change is projected to increase the conditions — higher temperatures, low humidity and precipitation extremes, both wet and dry — that lead to those disasters, according to the study, which was published in Science Advances.

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