Electronic pathways may enhance collective atomic vibrations’ magnetism

Andrey Baydin (left) and Fuyang Tay
Photo Credit: Gustavo Raskosky/Rice University

Materials with enhanced thermal conductivity are critical for the development of advanced devices to support applications in communications, clean energy and aerospace. But in order to engineer materials with this property, scientists need to understand how phonons, or quantum units of the vibration of atoms, behave in a particular substance.

“Phonons are quite important for studying new materials because they govern several material properties such as thermal conductivity and carrier properties,” said Fuyang Tay, a graduate student in applied physics working with the Rice Advanced Magnet with Broadband Optics (RAMBO), a tabletop spectrometer in Junichiro Kono’s laboratory at Rice University. “For example, it is widely accepted that superconductivity arises from electron–phonon interactions.

“Recently, there has been growing interest in the magnetic moment carried by phonon modes that show circular motion, also known as chiral phonons. But the mechanisms that can lead to a large phonon magnetic moment are not well understood.”

Now an international team of researchers led by Felix Hernandez from Brazil’s Universidade de São Paulo and Rice assistant research professor Andrey Baydin has published a study detailing the intricate connections between the magnetic properties of these quantum whirling dervishes and a material’s underlying topology of the electronic band structure, which determines the range of energy levels that electrons have within it.

Using a fiber optic cable to study Arctic seafloor permafrost

A permafrost-created pingo or “ice pimple” in the North Slope of Alaska. Scientists from Sandia National Laboratories have been using a fiber optic cable to study permafrost in the Arctic seafloor to improve the understanding of global climate change.
Photo Credit: Courtesy of Sandia National Laboratories

The Arctic is remote, with often harsh conditions, and its climate is changing rapidly — warming four times faster than the rest of the Earth. This makes studying the Arctic climate both challenging and vital for understanding global climate change.

Scientists at Sandia National Laboratories are using an existing fiber optic cable off Oliktok Point on the North Slope of Alaska to study the conditions of the Arctic seafloor up to 20 miles from shore. Christian Stanciu, project lead, will present their latest findings on Friday, Dec. 15 at AGU’s Fall Meeting in San Francisco.

Their goal is to determine the seismic structure of miles of Arctic seafloor. Using an emerging technique, they can spot areas of the seafloor where sound travels faster than on the rest of the seafloor, typically because of more ice. They have identified several areas with lots of ice, said Stanciu, a Sandia geophysicist.

The scientists also used the cable to determine temperatures over the stretch of seafloor and monitored temperature changes over seasons. "This data, unlike any collected before, was inserted into a computer model to infer the distribution of submarine permafrost," said Jennifer Frederick, a computational geoscientist.

“One of the innovations of this project is that we can now use a single fiber to get acoustic and temperature data,” Stanciu said. “We developed a new system to remotely collect both types of data using one fiber strand. We’re getting some interesting results.”

The keto diet protects against epileptic seizures. Scientists are uncovering why

Photo Credit: Jenna Hamra

The high-fat, low-carbohydrate ketogenic diet is more than just a trendy weight-loss tactic. It has also been known to help control seizures in children with epilepsy, particularly those who don’t respond to first-line anti-seizure medications.

In a new UCLA study published in the journal Cell Reports, researchers demonstrate that the changes the diet causes in the human gut microbiome — the trillions of bacteria and other microorganisms that live in the digestive tract — can confer protection against seizures in mice.

Understanding how the function of the microbiome is altered by the diet could aid in the development of new therapeutic approaches that incorporate these beneficial changes while avoiding certain drawbacks of the diet, said the study’s lead author, Gregory Lum, a postdoctoral researcher in the laboratory of UCLA professor Elaine Hsiao.

The ketogenic diet is not recommended as a primary anti-seizure option because patients are often averse to drastic changes in their food intake or have trouble staying on the diet due to its strict requirements and potential side effects like, nausea, constipation and fatigue.

Ultrafast lasers map electrons 'going ballistic' in graphene, with implications for next-gen electronic devices

Ultrafast Laser Lab.
Photo Credit: KU Marketing Communications

Research appearing in ACS Nano, a premier journal on nanoscience and nanotechnology, reveals the ballistic movement of electrons in graphene in real time.

The observations, made at the University of Kansas’ Ultrafast Laser Lab, could lead to breakthroughs in governing electrons in semiconductors, fundamental components in most information and energy technology.

“Generally, electron movement is interrupted by collisions with other particles in solids,” said lead author Ryan Scott, a doctoral student in KU’s Department of Physics & Astronomy. “This is similar to someone running in a ballroom full of dancers. These collisions are rather frequent — about 10 to 100 billion times per second. They slow down the electrons, cause energy loss and generate unwanted heat. Without collisions, an electron would move uninterrupted within a solid, similar to cars on a freeway or ballistic missiles through air. We refer to this as ‘ballistic transport.’”

Scott performed the lab experiments under the mentorship of Hui Zhao, professor of physics & astronomy at KU. They were joined in the work by former KU doctoral student Pavel Valencia-Acuna, now a postdoctoral researcher at the Northwest Pacific National Laboratory.

Zhao said electronic devices utilizing ballistic transport could potentially be faster, more powerful and more energy efficient.

Revealed: Some microbiome species regulate their entire bacterial ecosystem

Image Credit: Scientific Frontline 

A team of mathematicians and biologists led by Carnegie’s Will Ludington and Technische Universität Berlin’s Michael Joswig developed a new approach to reveal key genes and species that regulate biological networks. Their work, published this week in Proceedings of the National Academy of Sciences, identifies genes in cells and species in ecosystems that sit at the top of a regulatory hierarchy and drive evolutionary and ecological trajectories.

Charles Darwin concluded On the Origin of Species with the famous “tangled bank” analogy to explain how organisms in an ecosystem affect one another’s fitness. “It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth,” Darwin wrote. “And to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us.” 

To map these interactions in ecosystems, ecologists use network analysis to study the connections. Keystone species, such as wolves, have a disproportionately large impact on their communities and the other organisms within them.

New Strategy Improves Perovskites' Oxygen Reduction Performance in Hydrogen Fuel Cells

Evidence of calcium leaching during ORR, leading to the high surface area of the LCMO64.
Illustration Credit: ©Hao Li et al.

A research group has reported on a new method to enhance the electrochemical surface area (ECSA) in a calcium-doped perovskite, La0.6Ca0.4MnO3 (LCMO64), thereby overcoming a common bottleneck in the application of perovskite oxides as electrocatalysts in hydrogen fuel cells.

Perovskite oxides exhibit interesting and diverse properties, making them valuable in various technological applications. Their high intrinsic activities also position them as a promising alternative to noble metal catalysts for efficiently catalyzing the oxygen reduction reaction (ORR). However, their application is still hampered by their poor electrical conductivity and low specific surface area.

Acid Sensor and Calcium Store Discovered in Plants

When exposed to blue light, the light-gated H+ channel KCR2 kicks into action, causing a rapid increase in cytosolic H+ concentration. This heightened H+ level is then detected by a H+-sensitive Ca2+ channel (HSCA), prompting the subsequent opening of its gate for Ca2+ release from the endoplasmic reticulum. This chain of events ultimately triggers the opening of SLAC anion channels, leading to stomatal closure.
Image Credit: Huang/Hedrich (JMU)

Using optogenetics, Würzburg researchers have detected a new acid sensor in plant cells that is addressing a cell-internal calcium store, as they report in the journal Science.

When plants are infected by pathogens, suffer from a lack of water or have to react to other external stimuli, the first thing they do is increase the proton and calcium concentration in the affected cells. The protons and calcium ions then act like messenger substances that trigger further reactions in the cell.

The interactions between protons and calcium ions in this process were previously largely unknown. An article in the journal Science by a team led by biophysicist Professor Rainer Hedrich from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, has now shed new light on this subject.

Using a sophisticated optogenetic approach, the researchers have discovered a previously unknown endogenous acid sensor in plant cells. And they have discovered in the guard cells of leaves that there is a calcium store that plays an important role in processing proton signals in cellular responses.

Deadly chicken disease: ancient DNA reveals evolution of virulence

With the increase in poultry farming, Marek's disease virus evolved
Photo Credit: Heidi-Ann Fourkiller

Using genetic analyses, an international team led by LMU paleogeneticist Laurent Frantz has revealed the evolutionary history of the pathogen of a fatal disease in chickens.

A notifiable animal disease in Germany, Marek’s disease is caused by the globally distributed Marek’s disease virus (MDV). Over the past century, the virus, which causes tumors in chickens and has a high mortality rate, has become increasingly aggressive. Combating the disease costs the poultry industry over a billion dollars every year. With the help of ancient DNA, an international team of scientists led by LMU paleogenomicist Professor Laurent Frantz and Professor Greger Larson and Professor Adrian Smith from the University of Oxford has now decoded the evolution of MDV and shed light on what is behind the growing virulence.

The international team from the fields of paleogenetics, archeology, and biology isolated viral genomes from chicken bones up to 1,000 years old from 140 archeological sites in Europe and the Near East. “Our data shows that the virus was already widely distributed at least 1,000 years before the first description of the disease in 1907,” says Frantz. When the disease was first described, it was said to produce only mild symptoms in older chickens. With the dramatic increase in poultry farming in the 1950s and 1960s, the virus evolved and has become increasingly virulent despite the development of several vaccines.

How the Immune System Fights to Keep Herpes at Bay

These microscope images show how interferon in the nucleus raises levels of the protective protein IFI16 (stained green) from low background levels (left) to the higher levels needed to resist herpes infection (right).
Image Credit: HMS MicRoN core imaging facility/Nicolas Romero Rata

Herpes simplex virus (HSV) is extremely common, affecting nearly two-thirds of the world’s population, according to the World Health Organization.

Once inside the body, HSV establishes a latent infection that periodically awakens, causing painful blisters on the skin, typically around the nose and mouth. While a mere nuisance for most people, HSV can also lead to dangerous eye infections and brain inflammation in some people and cause life-threatening infections in newborns.

Researchers have long known that the virus and the host immune system are in a perpetual competition, but why does this battle reach a stasis in most people while causing serious infections in others?

More important, precisely how does the battle unfold at the level of cells and molecules? This question has continued to bedevil scientists and hamper the quest for treatments that prevent or cure infections.

A recent study by researchers at Harvard Medical School, conducted using lab-engineered cells and published in PNAS, unveils the precise maneuvers used by host and pathogen in the fight for dominance of the cell.

Long-sought binary star population found! Discovery could answer questions about hydrogen-poor supernova origins

An artist’s conception of the hydrogen being stripped from one half of a binary system, leaving a very hot, helium rich exposed core that will eventually explode as a hydrogen-poor core collapse supernova.
 Illustration Credit: Navid Marvi, courtesy of the Carnegie Institution for Science.

A team of astronomers has found a long- “missing” population of stars that could answer long-standing questions about the origins of a mysterious type of supernova. Their discovery, published in Science, could help researchers understand how hydrogen-poor core-collapse supernovae and neutron star collisions occur—major stellar events that are the source of many of the elements on the periodic table.

The project’s leaders, the University of Toronto’s Maria Drout and the Institute of Science and Technology Austria’s Ylva Götberg, met as junior researchers, and both went on to complete postdoctoral positions at the Carnegie Observatories—where the majority of this work was done—and have since moved onto assistant professor positions at their respective institutions.

Supernovae are violent stellar explosions that spew material into their cosmic surroundings, seeding the next generation of stars. But astronomers are still working to elucidate how they originate and what their various stellar progenitors look like—which differ between types of supernovae.

Drout and Götberg were particularly interested in one type of supernovae that stands out from their celestial peers for being hydrogen poor.