Terbium, one of the rarest of the rare earth elements, produces the green color in cell phone displays and is also used in high-efficiency lighting and solid-state devices. However, there are a variety of chemical, environmental, and political challenges to obtaining terbium and other rare earth elements from the environment. Developing new sources of these metals also requires robust detection methods, which poses another challenge. For example, the gold standard method of detecting rare earth elements in a sample — a type of mass spectrometry called ICP-MS — is expensive and not portable. Portable methods, however, are not as sensitive and do not perform well in complex environmental samples, where acidic conditions and other metals can interfere with detection.

“There is not currently a domestic supply chain of rare earth elements like terbium, but they are actually quite abundant in non-traditional sources in the U.S., including coal byproducts, acid mine drainage, and electronic waste,” said Joseph Cotruvo, Jr., assistant professor and Louis Martarano Career Development Professor of Chemistry at Penn State, a member of Penn State’s Center for Critical Minerals, and senior author of the study. “In this study, we developed a luminescence-based sensor that can be used to detect and even quantify low concentrations of terbium in complex acidic samples.”

The new sensor relies on lanmodulin, a protein that the researchers previously discovered that is almost a billion times better at binding to rare earth elements than to other metals. The protein’s selectivity to bind rare earth elements is ideal for a sensor, as it is most likely to bind to rare earths instead of other metals that are common in environmental samples.

To optimize lanmodulin as a sensor for terbium specifically, the researchers altered the protein by adding the amino acid tryptophan to the protein.

“Tryptophan is what is called a ‘sensitizer’ for terbium, which means that light absorbed by tryptophan can be passed to the terbium, which the terbium then emits at a different wavelength,” said Cotruvo. “The green color of this emission is actually one of the main reasons terbium is used in technologies like smart phone displays. For our purposes, when the tryptophan-lanmodulin compound binds to terbium, we can observe the emitted light, or luminescence, to measure the concentration of terbium in the sample.”

The researchers developed many variants of the tryptophan-lanmodulin sensor, optimizing the location of the tryptophan so that it does not interfere with lanmodulin’s ability to bind to rare earth elements. These variants provided important insights into the key features of the protein that enable it to bind rare earths with such high selectivity. Then, they tested the most promising variant to determine the lowest concentration of terbium the sensor could detect in idealized conditions — with no other metals to interfere. Even under highly acidic conditions, like that found in acid mine drainage, the sensor could detect environmentally relevant levels of terbium.

“One challenge with extracting rare earth elements is that you have to get them out of the rock,” said Cotruvo. “With acid mine drainage, nature has already done that for us, but looking for the rare earths is like finding a needle in a haystack. We have existing infrastructure to treat acid mine drainage sites at both active and inactive mines to mitigate their environmental impact. If we can identify the sites with the most valuable rare earth elements using sensors, we can better focus extraction efforts to turn waste streams into revenue sources.”

Next, the researchers tested the sensor in actual samples from an acid mine drainage treatment facility in Pennsylvania, an acidic sample with many other metals present and very low levels of terbium — 3 parts per billion. The sensor determined a concentration of terbium in the sample that was comparable what they detected with the “gold standard” method, suggesting that the new sensor is a viable way to detect low concentrations of terbium in complex environmental samples.

“We plan to further optimize the sensor so that it is even more sensitive and can be used more easily,” said Cotruvo. “We also hope to target other specific rare earth elements with this approach.”

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Materials provided by Penn State. Original written by Gail McCormick. Note: Content may be edited for style and length.

“We know concussions may have long-term effects on the brain that last beyond getting a doctor’s clearance to return to play,” said study author Tom A. Schweizer, PhD, of St. Michael’s Hospital in Toronto, Canada. “It is unclear, however, to what extent the effects of repeated concussion can be detected among young, otherwise healthy adults. We found even though there was no difference in symptoms or the amount of recovery time, athletes with a history of concussion showed subtle and chronic changes in their brains.”

This study focused on changes within two areas in the middle of the brain that are especially vulnerable to concussion. Researchers focused on blood flow in the cingulate cortex and white matter microstructure in the corpus callosum. Changes in blood flow and microstructure that show up on brain scans can indicate underlying brain injury. The cingulate cortex is a layer of gray matter that coordinates sensory and motor skills. Below it is the corpus callosum, a broad band of nerve fibers linking the two hemispheres of the brain.

The study looked at 228 athletes with an average age of 20. This included 61 with a recent concussion and 167 without. Within the first group, 36 had a history of concussion. Within the second group, 73 had a history of concussion.

Researchers took up to five brain scans of each recently concussed athlete, from time of injury to one year after returning to play.

Researchers found that one year after a recent concussion, athletes with a history of concussion had sharper declines in blood flow within one area of the cingulate compared to those without a history of concussions. Those with a history of concussion had an average cerebral blood flow of 40 milliliters (mL) per minute, per 100 grams (g) of brain tissue. Those without a history of concussion had an average cerebral blood flow of 53 mL per minute, per 100g of brain tissue.

In athletes with a history of concussion, in the weeks after a new concussion, researchers also found microstructural changes in a region of the brain called the splenium, which is part of the corpus callosum.

“Our findings suggest that an athlete with a history of concussion should be watched closely, as these subtle brain changes may be worsened by repeated injury,” said Schweizer. “Additionally, our results should raise concern about the cumulative effects of repeated head injuries later in life.”

A limitation of the study is that athletes reported their own histories of concussion and could be inaccurate. Further research is needed that would follow athletes over time.

The study was supported by Canadian Institutes of Health Research, the Canadian Institute for Military and Veterans Health Research and Siemens Healthineers Canada.

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Materials provided by American Academy of Neurology. Note: Content may be edited for style and length.

“Dementia risk scores might be useful to help identify people at higher risk of dementia earlier, so that potential lifestyle factors can be addressed earlier and monitored more closely,” said study author Sebastian Köhler PhD, of Maastricht University, the Netherlands. “Our study found that a substantial proportion of brain changes might be attributable to risk factors that can be modified.”

The study involved 4,164 people with an average age of 59. All participants took a test called the “Lifestyle for Brain Health” (LIBRA). The total score reflects a person’s potential for developing dementia. This study took into account 11 out of 12 lifestyle factors on the test, including high blood pressure, heart disease, smoking, diet and physical activity. Higher scores reflect higher dementia risk, with scores ranging from -2.7 to +12.7. Overall, the study group had an average score of 1.19. Researchers divided the participants into three groups: those with low risk of dementia, with an average score of -1.47, those with medium risk, with an average score of 1.20, and those with high risk, with an average score of 4.6.

Participants in the study took tests of memory and other thinking skills, such as information processing speed, executive function and attention. Researchers also looked at brain scans for signs of cerebral small vessel disease, which are signs of vascular brain damage often seen in patients who have dementia. They also looked for changes in volumes of white matter and gray matter.

Researchers found that people who were in the high-risk group on the LIBRA test, indicating a less brain-healthy lifestyle, had higher volumes of brain lesions, 1.27 ml compared to 0.48 ml for those in the lowest risk group. The high-risk group also had lower scores on two tests of thinking: information processing speed and executive function and attention.

Only in men, however, did researchers find associations between higher scores on the LIBRA test and lower volumes of grey matter, as well as lower scores on tests of memory.

“More research is needed to confirm these findings and determine why there were differences between men and women,” Köhler said. “It’s exciting that a simple test score may indeed be an index of brain health. We need to learn whether people can improve their scores by making changes in their diet, increasing physical activity or limiting alcohol to low-to-moderate use.”

The study does not prove that lifestyle test scores predict dementia, it only shows an association.

The study was supported by the European Regional Development Fund, the Province of Limburg, the Dutch Ministry of Economic Affairs and Climate Policy, the Weijerhorst Foundation, the Pearl String Diabetes Initiative, Maastricht University, the Annadal Foundation and Health Foundation Limburg, all in the Netherlands.

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Materials provided by American Academy of Neurology. Note: Content may be edited for style and length.

A local ornithological expert conducted regular bird surveys over one year and recorded 126 bird species. Using remote sensing techniques, satellite pictures were processed to produce a map of different land-uses, from which urbanization intensity was measured based on the proportion of sealed surfaces and buildings in the landscape. The researchers analyzed how farmland bird communities changed along a gradient of urbanization using newly developed statistical analyses.

“We found that urban bird communities were impoverished subsets of rural communities, both in terms of species composition and the ecological functions they provide,” says first author Gabriel Marcacci, PhD student in the Functional Agrobiodiversity group at the University of Göttingen. “Birds perform important roles in the environment, for instance controlling pests by eating insects, scavenging and removing carrion, or eating fruits and dispersing the seeds. But only bird species that are well adapted to urban environments such as pigeons or crows can thrive.”

“The homogenization — resulting from losing diversity through the exclusion of certain groups — of farmland bird communities may disrupt important ecosystem functions and services in urban agroecosystems such as pest removal by insect-eating birds,” explains Professor Catrin Westphal, head of the Functional Agrobiodiversity group. Urban communities were found to be more sensitive to species loss, endangering ecosystem resilience.

“Our study underscores urbanization as a serious threat to biological communities and ecosystem functioning that may affect food production systems,” adds Professor Ingo Graß, head of the Department of Ecology of Tropical Agricultural Systems at the University of Hohenheim. Professor Teja Tscharntke concludes, “This concern is especially relevant for countries from the Global South where urban agriculture and ecosystem services play an increasingly important role for food security.”

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“We wanted to establish a way to build scaled wood-frame specimens that would behave, and ultimately fail, under wave loading like their full-scale counterparts have been observed to,” said Sean Duncan, who led the study as a graduate research assistant with the Oregon State College of Engineering. “And we also set out to develop an equation that could predict the distribution of the uplift pressure on elevated structures. We were able to accomplish both of those goals.”

One of the model structures was elevated — built so that the living areas would be off the ground — and the other was “on grade,” or on the ground. As the researchers expected, the on-grade model couldn’t withstand water levels as high as the raised one, and both sustained damage in ways consistent with what was seen in real residential structures during Hurricane Sandy in 2012 and Hurricane Ike in 2008.

The research by Duncan, OSU colleagues Dan Cox, Andre Barbosa and Pedro Lomonaco and collaborators from the University of Hawaii and the University of California, Berkeley, also showed that a remote sensing method known as LiDAR could track the models’ damage progression as the waves and storm surges increased in intensity.

The models were built to one-sixth scale, with strength and stiffness on par with real residences such as those hit by Hurricane Sandy in Ortley Beach, New Jersey, and by Hurricane Ike on Texas’ Bolivar Peninsula. Each of those storms caused extensive damage, which focused greater attention on coastal communities’ vulnerability to waves and storm surges, and on learning more about how to design and construct storm-resistant homes, Duncan said.

“Populations in those types of communities are rising, and so are sea levels,” said Duncan, now a ports and marine engineer with WSP USA in Federal Way, Washington. “That means risk associated with hurricanes is rising too, especially because research indicates hurricanes are increasing in intensity and will continue to do so. That’s why it’s so important to understand the forces these storms generate and how coastal structures respond, so planners and the construction industry can work together to mitigate the potential damage from these very likely, very potent storms.”

Placed on a simulated coastline in the Directional Wave Basin at the O.H. Hinsdale Wave Research Laboratory, the models experienced waves and water depths replicating conditions of Hurricane Sandy. The basin is 48.8 meters long, 26.5 meters wide and just over 2 meters deep, and multiple instruments measured the hydrodynamic loads.

Vertical forces on the elevated specimen were shown to correlate with wave height, air gap and water depth, Duncan said, with the forces peaking in the deepest water at maximum submergence.

“Uplift pressure is also affected by how and where the waves break,” he said. “Waves that broke right on the specimens generally caused bigger vertical forces. And the predictive equation we developed, based on wave height and air gap, is valid for a range of structure length to wavelength ratios, wave heights, air gaps and water depths.”

Air gap refers to the elevation of the bottom of the lowest horizontal member, or LHM, of an elevated structure relative to the still water level.

Findings were published in Coastal Engineering, and the research was supported by Department of Homeland Security and the National Science Foundation.

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Materials provided by Oregon State University. Original written by Steve Lundeberg. Note: Content may be edited for style and length.

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.

Now, as reported in the journal Nature Physics, Crommie, Mo, and their research teams have demonstrated how to characterize spinons in QSLs by directly imaging how they are distributed in a material.

To begin the study, Mo’s group at Berkeley Lab’s Advanced Light Source (ALS) grew single-layer samples of tantalum diselenide (1T-TaSe₂) that are only three-atoms thick. This material is part of a class of materials called transition metal dichalcogenides (TMDCs). The researchers in Mo’s team are experts in molecular beam epitaxy, a technique for synthesizing atomically thin TMDC crystals from their constituent elements.

Mo’s team then characterized the thin films through angle-resolved photoemission spectroscopy, a technique that uses X-rays generated at the ALS.

Using a microscopy technique called scanning tunneling microscopy (STM), researchers in the Crommie lab — including co-first authors Wei Ruan, a postdoctoral fellow at the time, and Yi Chen, then a UC Berkeley graduate student — injected electrons from a metal needle into the tantalum diselenide TMDC sample.

Images gathered by scanning tunneling spectroscopy (STS) — an imaging technique that measures how particles arrange themselves at a particular energy — revealed something quite unexpected: a layer of mysterious waves having wavelengths larger than one nanometer (1 billionth of a meter) blanketing the material’s surface.

“The long wavelengths we saw didn’t correspond to any known behavior of the crystal,” Crommie said. “We scratched our heads for a long time. What could cause such long wavelength modulations in the crystal? We ruled out the conventional explanations one by one. Little did we know that this was the signature of spinon ghost particles.”

How spinons take flight while chargons stand still

With help from a theoretical collaborator at MIT, the researchers realized that when an electron is injected into a QSL from the tip of an STM, it breaks apart into two different particles inside the QSL — spinons (also known as ghost particles) and chargons. This is due to the peculiar way in which spin and charge in a QSL collectively interact with each other. The spinon ghost particles end up separately carrying the spin while the chargons separately bear the electrical charge.

In the current study, STM/STS images show that the chargons freeze in place, forming what scientists call a star-of-David charge-density-wave. Meanwhile, the spinons undergo an “out-of-body experience” as they separate from the immobilized chargons and move freely through the material, Crommie said. “This is unusual since in a conventional material, electrons carry both the spin and charge combined into one particle as they move about,” he explained. “They don’t usually break apart in this funny way.”

Crommie added that QSLs might one day form the basis of robust quantum bits (qubits) used for quantum computing. In conventional computing a bit encodes information either as a zero or a one, but a qubit can hold both zero and one at the same time, thus potentially speeding up certain types of calculations. Understanding how spinons and chargons behave in QSLs could help advance research in this area of next-gen computing.

Another motivation for understanding the inner workings of QSLs is that they have been predicted to be a precursor to exotic superconductivity. Crommie plans to test that prediction with Mo’s help at the ALS.

“Part of the beauty of this topic is that all the complex interactions within a QSL somehow combine to form a simple ghost particle that just bounces around inside the crystal,” he said. “Seeing this behavior was pretty surprising, especially since we weren’t even looking for it.”