Researchers reveal origin of ultrafast mystery signals in valleytronic materials

 By exciting the transitional metal dichalcogenide monolayers — atomically thin semiconductors — with ultrashort pump pulses, atoms can coherently vibrate and modulate optical responses. The probe pulses can detect ultrafast modulation that shows peculiar high-frequency overtones of K-point acoustic phonons
Credit: Yokohama National University.

Tiny materials hold big mysteries, the solutions to which could bring about next-generation electronics. An international collaboration led by researchers based in Japan has solved the whodunit of cryptic overtone signals in an analysis of molybdenum diselenide, an atomically thin crystal lattice with desirable properties unique from its bulkier three-dimensional form.

They published their results in Nature Communications.

The compound belongs to a family of similarly two-dimensional semiconductors called transitional metal dichalcogenide (TMD) monolayers, all of which have electronic band structures containing so-called valleys. TMD lattices are organized as hexagons, with the corresponding wavevector, known as k-space, along the side. The side center point of the k-space is known as the “M point” and the six corners as “K (-K) points.” The valleys are the dips and rises of the electronic band at the corners of the hexagons, where energy or information-carrying particles can move to tip the material to action. The intervalley activities, especially as related to electron scattering, have remained elusive, though. In this process, phonons, or units of energy manifested as vibrations, cause the electrons to disperse and transition states in the intervalley space at ultrafast speed.

30-million-year-old amphibious beaver fossil is oldest ever found

A comparison of anklebones from the giant beaver and the newly identified species, Microtheriomys articulaquaticus, at the same scale.
Credit: Jonathan Calede / Ohio State University

A new analysis of a beaver anklebone fossil found in Montana suggests the evolution of semi-aquatic beavers may have occurred at least 7 million years earlier than previously thought, and happened in North America rather than Eurasia.

In the study, Ohio State University evolutionary biologist Jonathan Calede describes the find as the oldest known amphibious beaver in the world and the oldest amphibious rodent in North America. He named the newly discovered species Microtheriomys articulaquaticus.

Calede’s findings resulted from comparing measurements of the new species’ anklebone to about 340 other rodent specimens to categorize how it moved around in its environment – which indicated this animal was a swimmer. The Montana-based bone was determined to be 30 million years old – the oldest previously identified semi-aquatic beaver lived in France 23 million years ago.

"Beavers and other rodents can tell us a lot about mammalian evolution," said Calede, an assistant professor of evolution, ecology and organismal biology at Ohio State’s Marion campus.

Study of Ancient Skulls Sheds Light on Human Interbreeding With Neandertals

Homo neanderthalensis adult male. Reconstruction based on Shanidar 1 by John Gurche for the Human Origins Program, NMNH.
Photo Credit: Chip Clark.

Research has established that there are traces of Neandertal DNA in the genome of modern humans. Now an exploratory study that assessed the facial structure of prehistoric skulls is offering new insights, and supports the hypothesis that much of this interbreeding took place in the Near East – the region ranging from North Africa to Iraq.

“Ancient DNA caused a revolution in how we think about human evolution,” says Steven Churchill, co-author of the study and a professor of evolutionary anthropology at Duke University. “We often think of evolution as branches on a tree, and researchers have spent a lot of time trying to trace back the path that led to us, Homo sapiens. But we’re now beginning to understand that it isn’t a tree – it’s more like a series of streams that converge and diverge at multiple points.”

“Our work here gives us a deeper understanding of where those streams came together,” says Ann Ross, corresponding author of the study and a professor of biological sciences at North Carolina State University.

“The picture is really complicated,” Churchill says. “We know there was interbreeding. Modern Asian populations seem to have more Neandertal DNA than modern European populations, which is weird – because Neandertals lived in what is now Europe. That has suggested that Neandertals interbred with what are now modern humans as our prehistoric ancestors left Africa, but before spreading to Asia. Our goal with this study was to see what additional light we could shed on this by assessing the facial structure of prehistoric humans and Neandertals.”

Scientists Calculate What Could Throw El Niño Out of Balance

Abnormal temperature spikes can also lead to unpredictable results during the El Niño period, Dmitry Aleksandrov believes.
Photo credit: Ilya Safarov

Wind, humidity, temperature, ocean currents, and other parameters can lead to unpredictable El Niño results. It is a phenomenon in which the temperature of the upper Pacific Ocean rises and the near-surface waters shift eastward. The onset of El Niño affects precipitation, fisheries in Peru, Chile, Ecuador, and changes in the planet's climate. How external factors determine the behavior of atmospheric-oceanic processes in the Pacific region was calculated by UrFU physicists. They published a description of the features of the unusual phenomenon and its scenarios in the journal Physica D: Nonlinear Phenomena.

"We used the classic Vallis model, which describes El Niño. This is a simple model, it takes into account the temperature difference between the east and west coasts, the heat exchange between the Pacific Ocean and the atmosphere, and the speed of air masses movement. We also took into account external noise - parameters that also affect atmospheric and oceanic processes, such as pressure changes, humidity, wind gusts, and ocean currents," says Dmitry Aleksandrov, Head of the Ural Federal University's Laboratory of Multi-Scale Mathematical Modeling.

According to UrFU physicists' calculations, external factors have a serious influence on this phenomenon. For example, the stronger the wind, the greater the temperature amplitude. Moreover, this can throw the system out of balance and cause unpredictable weather conditions.

Sleepless and selfish: Lack of sleep makes us less generous

The new study shows how sleep loss dramatically reduces the desire to help others, triggered by a breakdown in the activity of key prosocial brain networks.
Image credit: Eti Ben Simon and Matthew Walker, UC Berkeley

Humans help each other — it’s one of the foundations of civilized society. But a new study by scientists at the University of California, Berkeley, reveals that a lack of sleep blunts this fundamental human attribute, with real-world consequences.

Lack of sleep is known to be associated with an increased risk of cardiovascular disease, depression, diabetes, hypertension and overall mortality. However, these new discoveries show that a lack of sleep also impairs our basic social conscience, making us withdraw our desire and willingness to help other people.

In one portion of the new study, the scientists showed that charitable giving in the week after the beginning of Daylight-Saving Time, when residents of most states “spring forward” and lose one hour of their day, dropped by 10% — a decrease not seen in states that do not change their clocks or when states return to standard time in the fall.

The study, led by UC Berkeley research scientist Eti Ben Simon and Matthew Walker, a UC Berkeley professor of psychology, adds to a growing body of evidence demonstrating that inadequate sleep not only harms the mental and physical well-being of an individual, but also compromises the bonds between individuals — and even the altruistic sentiment of an entire nation.

Study finds that ocean cooling over millennia led to larger fish

Dahiana Arcila in Reykjavík, Iceland. Arcila is the recipient of a National Science Foundation CAREER award to study the evolutionary history of marine fish.
Source: University of Oklahoma

Earth’s geological history is characterized by many dynamic climate shifts that are often associated with large changes in temperature. These environmental shifts can lead to trait changes, such as body size, that can be directly observed using the fossil record.

To investigate whether temperature shifts that occurred before direct measurements were recorded, called paleoclimatology, are correlated with body size changes, several members of the University of Oklahoma’s Fish Evolution Lab decided to test their hypothesis using tetraodontiform fishes as a model group. Tetradontiform fishes are primarily tropical marine fishes, and include pufferfish, boxfishes and filefish.

The study was led by Dahiana Arcila, assistant professor of biology and assistant curator at the Sam Noble Oklahoma Museum of Natural History, with Ricardo Betancur, assistant professor of biology, along with biology graduate student Emily Troyer, and involved collaborators from the Smithsonian Institution, University of Chicago and George Washington University in the United States, as well as the University of Turin in Italy, University of Lyon in France and CSIRO Australia.

The researchers discovered that the body sizes of these fishes have grown larger over the past hundred million years in conjunction with the gradual cooling of ocean temperatures.

How new motion-sensing technology may help standardize back-pain care

William S. Marras Professor Neurological Surgery, Orthopedics, Physical Medicine and Rehabilitation
 Credit/Source: Ohio State University

Digital health systems can tell clinicians when someone’s heart-disease risk calls for a drug to lower cholesterol or whether insulin shots are warranted for a person with type 2 diabetes.

But for millions of low-back pain sufferers, care decisions rely heavily on subjective measures of patient discomfort – often leading to expensive tests and treatments (back pain is the third-highest U.S. health care expenditure, after diabetes and heart disease) that don’t necessarily offer a permanent solution.

Ohio State University engineering and medical researchers are developing a digital health system approach designed to enhance back-pain clinical decision-making. After completing a series of studies testing precise, objective measurements they’ve perfected in the lab, the team aims to apply the data-driven practices to the assessment and repair of back problems brought on by dysfunction in the spine.

In a recent study published in Clinical Biomechanics, researchers combined self-reported pain and disability measures with data from a wearable motion-sensing system to evaluate low-back function in lumbar fusion surgery patients. While post-operative pain relief and lower disability were self-reported within six weeks, the objective metrics didn’t detect actual functional improvement in the spine for at least six months after surgery.

Researchers complete first comprehensive threat assessment of all U.S. trees

 Saplings of Endangered Q. Oglethorpensis at The Morton Arboretum
Credit: The Morton Arboretum

For the first time, researchers have completed threat assessments for all 881 native tree species in the contiguous United States, resulting in a comprehensive checklist and synthesis that will serve as a critical baseline to guide future tree conservation efforts.

The new assessment of U.S. trees reveals that 11-16% of tree species in the contiguous 48 U.S. states are threatened with extinction, with the most common threat being invasive and problematic pests and diseases. According to Abby Meyer, executive director of Botanic Gardens Conservation International-U.S. (BGCI-US), a partner on the project, “These results lay the groundwork for U.S. tree and ecosystem conservation efforts that will contribute to achieving critical international conservation goals, including the United Nations Decade for Ecosystem Restoration and the Global Tree Assessment.”

Murphy Westwood, Ph.D., vice president of science and conservation at The Morton Arboretum and senior author of the report, noted that much of the world’s biodiversity depends on trees, which offer food and habitat for countless plant, animal and fungal species while providing invaluable benefits to humans. “Understanding the current state of trees within the U.S. is imperative to protecting those species, their habitats and the countless communities they support,” she said.

Faster Fish Tracking Through the Cloud

Researchers at Pacific Northwest National Laboratory developed a receiver that can transmit near-real-time information on fish tracking to inform decisions about dam operations that support fish passage. 
 Credit: Composite photo by Cortland Johnson | Pacific Northwest National Laboratory

The fastest way to track a fish is to use the cloud, figuratively speaking. A new acoustic receiver developed by researchers at Pacific Northwest National Laboratory (PNNL) and published in the journal IEEE Internet of Things, sends near-real-time fish tracking data to the digital cloud, providing timely information to dam operators and decision-makers about when, where, and how many fish are expected to pass through dams. Instead of relying on seasonal estimates of fish migration from previous years, these data from tagged fish support more informed decisions about dam operations that affect fish passage.

“This receiver provides up-to-the-hour data to dam operators to assist in making informed day-to-day decisions in support of fish passage, like adjusting water flow when it’s clear that a large group of juvenile fish are approaching the dam,” said Jayson Martinez, a PNNL mechanical engineer who co-developed the receiver.

Hydropower dams are an important source of dependable renewable energy, generating about six percent of total electricity in the United States. Helping fish navigate them safely is a key part of reducing dams’ environmental impact. The new receiver is a critical piece of the puzzle in the ongoing endeavor to improve fish passage.

Unearthing the secrets of plant health, carbon storage with rhizosphere-on-a-chip

Scientists at ORNL have created a rhizosphere-on-a-chip research platform, a miniaturized environment to study the ecosystem around poplar tree roots for insights into plant health and soil carbon sequestration.
Credit: Carlos Jones/ORNL, U.S. Dept. of Energy

Scientists at the Department of Energy’s Oak Ridge National Laboratory have created a miniaturized environment to study the ecosystem around poplar tree roots for insights into plant health and soil carbon sequestration.

The rhizosphere-on-a-chip platform builds on the lab’s history of constructing lab-on-a-chip devices, in which tiny channels and chambers are etched on a microscope slide so that fluids can be introduced and studied for biochemical separations research and testing.

In this case scientists are mimicking soil on the chip, sprouting poplar trees in the fluid and studying the environment around their roots, known as the rhizosphere. Scientists observe how microbes interact with chemicals within the artificial soil to influence plant health and gain a better understanding of the processes governing carbon storage.

The rhizosphere is one of the most complex systems in the world, in which plant roots take up water and nutrients, create a unique physical and biogeochemical environment for microbes, and emit atmospheric carbon into the soil. There may be hundreds of different bacteria that are growing near plant roots or are influenced by the rhizosphere. ORNL researchers are particularly interested in how microbes like bacteria and fungi interact with plant roots to help plants grow faster and survive threats like drought, wildfire, disease and pests.