Earth's Inner Core: A Mixture of Solid Fe and Liquid-like Light Elements

Earth's interior structure and superionic inner core
Image by IGCAS

Earth's core, the deepest part of our planet, is characterized by extremely high pressure and temperature. It is composed of a liquid outer core and solid inner core.

The inner core is formed and grows due to the solidification of liquid iron at the inner core boundary. The inner core is less dense than pure iron, and some light elements are believed to be present in the inner core.

A joint research team of Prof. LI Heping and Prof. HE Yu from the Institute of Geochemistry of the Chinese Academy of Sciences (IGCAS) and Prof. MAO Ho-kwang and Prof. KIM Duck Young from Center for High Pressure Science & Technology Advanced Research (HPSTAR) has found that the inner core of the Earth is not a normal solid but is composed of a solid iron sublattice and liquid-like light elements, which is also known as a superionic state. The liquid-like light elements are highly diffusive in iron sublattices under inner core conditions.

This study was published in Nature on Feb. 9.

A superionic state, which is an intermediate state between solid and liquid, widely exists in the interior of planets. Using high-pressure and high-temperature computational simulations based on quantum mechanics theory, researchers from IGCAS and the Center for High Pressure Science & Technology Advanced Research (HPSTAR) found that some Fe-H, Fe-C and Fe-O alloys transformed into a superionic state under inner core conditions.

In superionic iron alloys, light elements become disordered and diffuse like a liquid in the lattice, while iron atoms remain ordered and vibrate about their lattice grid, forming the solid iron framework. The diffusion coefficients of C, H and O in superionic iron alloys are the same as those in liquid Fe.

"It is quite abnormal. The solidification of iron at the inner core boundary does not change the mobility of these light elements, and the convection of light elements is continuous in the inner core," said Prof. HE Yu, the first and corresponding author of the study.

A new approach for detecting ultra-low-energy photons

A low energy photon emitted by a qubit can potentially be detected by measuring its energy with two thermometers simultaneously. The two signals are combined into a cross-correlation measurement with superior sensitivity.
Illustration: Bayan Karimi.

Professor Jukka Pekola and Doctoral Candidate Bayan Karimi from Aalto University propose a new approach to measure the energy of single microwave photons. These low energy quanta are emitted by artificial quantum systems such as superconducting qubits. Detecting them continuously has been challenging but would be useful in quantum information processing and other quantum technologies.

A photon is produced when a superconducting qubit transits between states, radiating energy into its environment. The researchers capture the tiny energy of this photon by transferring it into heat. The new technique relies on splitting the energy of a photon across two independent heat baths and making measurements using two uncoupled detectors at once. This would significantly enhance the signal-to-noise ratio, making it easier to detect an absorption event and its energy.

‘In our proposed setup the energy of a qubit is large whereas its typical operating temperature is very low. This contrast opened an opportunity to solve the Schrödinger equation exactly for up to one million external oscillators forming the heat baths in the model describing this measurement,’ Pekola says.

Fossils excavated in the 1960s add missing link to crocodile evolution

Credit: Gabriel Ugueto

A set of Triassic archosaur fossils, excavated in the 1960s in Tanzania, have been formally recognized as a distinct species, representing one of the earliest-known members of the crocodile evolutionary lineage.

Researchers at the University of Birmingham, the Natural History Museum and Virginia Tech University have named the animal Mambawakale ruhuhu. It is among the last to be studied of a collection of fossils dug up nearly 60 years ago from the Manda Beds, a geological formation in southern Tanzania.

The remains, which are the only known example of Mambawakale ruhuhu, include a partial skull, lower jaw, several vertebrae and a hand. From these, the research team were able to identify several distinctive features that set it apart from other archosaurs found in the Manda Beds.

These included a large skull, more than 75 cm in length, and a particularly large nostril, as well as a notably narrow lower jaw and strong variation in the sizes of the teeth at the front of the upper jaws.

A catalyst that can turn carbon dioxide into gasoline 1,000 times more efficiently

Chengshuang Zhou holds vials of ruthenium, left, and the coated catalyst, while Matteo Cargnello holds the pipe used for the reaction experiments.
Image credit: Mark Golden

Captured CO2 can be turned into carbon-neutral fuels, but technological advances are needed. In new research, a new catalyst increased the production of long-chain hydrocarbons in chemical reactions by some 1,000 times over existing methods.

Engineers working to reverse the proliferation of greenhouse gases know that in addition to reducing carbon dioxide emissions we will also need to remove carbon dioxide from power plant fumes or from the skies. But, what do we do with all that captured carbon? Matteo Cargnello, a chemical engineer at Stanford University, is working to turn it into other useful chemicals, such as propane, butane or other hydrocarbon fuels that are made up of long chains of carbon and hydrogen.

“We can create gasoline, basically,” said Cargnello, who is an assistant professor of chemical engineering. “To capture as much carbon as possible, you want the longest chain hydrocarbons. Chains with eight to 12 carbon atoms would be the ideal.”

A new catalyst, invented by Cargnello and colleagues, moves toward this goal by increasing the production of long-chain hydrocarbons in chemical reactions. It produced 1,000 times more butane – the longest hydrocarbon it could produce under its maximum pressure – than the standard catalyst given the same amounts of carbon dioxide, hydrogen, catalyst, pressure, heat and time. The new catalyst is composed of the element ruthenium – a rare transition metal belonging to the platinum group – coated in a thin layer of plastic. Like any catalyst, this invention speeds up chemical reactions without getting used up in the process. Ruthenium also has the advantage of being less expensive than other high-quality catalysts, like palladium and platinum.

'Molecular Velcro' enables tissues to sense, react to mechanical force

University of Illinois professor Deborah Leckband led a study that revealed how Velcro-like cellular proteins called cadherins sense tissue mechanics to regulate cell communication and biological tissue growth. 
Photo courtesy Claire Benjamin

The Velcro-like cellular proteins that hold cells and tissues together also perform critical functions when they experience increased tension. A new University of Illinois Urbana-Champaign study observed that when tugged upon in a controlled manner, these proteins – called cadherins – communicate with growth factors to influence in vitro tumor growth in human carcinoma cells.

The study, led by chemical and biomolecular engineering professor Deborah Leckband, found that cadherins that bond with growth factor receptors can sense mechanical force and respond by altering cell communication and growth.

The findings are published in the Proceedings of the National Academy of Sciences.

When bound to cadherin molecules in normal tissue, growth factor receptors cannot communicate with growth factor proteins – the substance they need to promote tissue growth. However, the study shows that changes in tensional stress on cadherin bonds disrupt the cadherin-growth factor interaction to switch on growth signals in tissues.

Climate drove 7,000 years of dietary changes

A mid-elevation landscape in the Central Andes.
Credit: Kurt Wilson

What a person eats influences a person’s health, longevity and experience in the world. Identifying the factors that determine people’s diets is important to answer bigger questions, such as how changing climates will influence unequal access to preferred foods.

A new study led by University of Utah anthropologists provides a blueprint to systematically untangle and evaluate the power of both climate and population size on the varied diets across a region in the past.

The authors documented that climate had the most influence over diet in the Central Andes between 400 and 7,000 years ago. This makes sense—the climate determines what resources are available for people in the area. The researchers were surprised that population size had little impact on diet variation, despite many complex societies emerging at various points over time that would have brought disparate communities together, fostered trade and increased competition.

The exception was during the Late Horizon (~480-418 yBP), when diets across the region became more similar to one another. This coincides with the Inca Empire that appears to have centralized enough political power to reduce local dietary decisions, and therby dampen influence of climate. The study presents a framework for exploring the relative role of climate and other socio-demographic factors on dietary change through time—including in the future.

This protein can shred our cells. Or it can help us think.

A 3D ultrahigh-resolution image shows how complexin can distort, shred and elongate simulated cellular membranes. Complexin is important for releasing neurotransmitters in the brain, but must be regulated to not damage cells
Credit: The Chapman Lab

A new study reveals that a protein long known to play a role in communication between cells in the brain is also capable of obliterating cells if left unchecked because of its penchant for twisting and puncturing the membranes surrounding cells.

On its own, the protein — known as complexin — is so toxic it can shred cells. Yet, in the brain, a suite of controls makes sure the protein plays nice and helps cells called neurons communicate by aiding in the release of compounds called neurotransmitters.

The findings, published in Nature Structural and Molecular Biology, emphasize how little we still know about how our brains work. Billions of times every second, the brain’s neurons pass information to one another. While many proteins play a role in this crucial task, just how they accomplish it remains stubbornly mysterious.

It all starts inside a neuron when a tiny packet of neurotransmitters fuses with the cell’s outer membrane. That packet then gets released as cargo to make its way to the next neuron.

Big Data Imaging Shows Rock’s Big Role in Channeling Earthquakes in Japan

The aftermath of a 2011 earthquake and tsunami in Japan.
Credit: Direct Relief/Flickr

Thanks to 20 years of seismic data processed through one of the world’s most powerful supercomputers, scientists have created the first complete, 3D visualization of a mountain-size rock called the Kumano Pluton buried miles beneath the coast of southern Japan. They can now see the rock could be acting like a lightning rod for the region’s megaquakes, diverting tectonic energy into points along its sides where several of the region’s largest earthquakes have happened.

Scientists have known about the pluton for years but were aware of only small portions of it. Thanks to new research by an international team of scientists led by The University of Texas at Austin, researchers now have a view of the entire subterranean formation and its effect on the region’s tectonics.

Climate change can worsen impact of invasive plants

Whalen Dillon recording data in the experiment to assess the effects of invasion, drought and their interaction on longleaf pine responses to fire.
Credit: UF/IFAS Camila Guillen

Synergy isn’t always a good thing — take climate change and invasive plants.

Scientists have long hypothesized that climate change, by intensifying stressors like drought or wildfires, would make an ecosystem more vulnerable to invasive plants. Those invasive plants may in turn alter the environment in ways that amplify the impacts of climate change, explained Luke Flory, a professor of ecology in the UF/IFAS agronomy department.

A new long-term field study conducted by Flory’s lab offers the first experimental evidence to support this hypothesis.

The study, published in the journal Ecology Letters, exposed small plots of long-leaf pine to three scenarios: drought conditions, colonization by the invasive plant cogongrass and a combination of these two factors.

To test how the different scenarios influenced the trees’ survival, scientists added another stressor: fire. But before lighting the first fire, the team waited almost six years for the trees to grow under each scenario.

Nasal Spray Booster Keeps COVID-19 at Bay

A nasal spray coronavirus vaccine booster helps protect mice from SARS-CoV-2. In this electron microscopy image, viral particles are shown as blue circles.
Credit: CDC/ Hannah A Bullock; Azaibi Tamin

A new coronavirus vaccine guards one body part especially vulnerable to infection: the nose.

Dosing mice with a nasal spray booster recruited an army of immune defenders to both the nasal cavity, where coronaviruses typically enter the body, and the lungs, scientists report in a preprint posted on bioRxiv.org.

Made only of coronavirus spike protein, the vaccine is part of a one-two punch that could one day protect people from infection. Dubbed “Prime and Spike,” the strategy relies on an mRNA coronavirus vaccine injection that primes the immune system to recognize SARS-CoV-2, followed by a nasal spray vaccine that shores up defenses at the mucus membranes.

Such a strategy might offer a way to counter the waning effectiveness of current mRNA coronavirus vaccines, says study author Akiko Iwasaki, a Howard Hughes Medical Institute Investigator at Yale University.

Until now, scientists had not tested nasal vaccines on animals that already had some pre-existing immunity, says Jacco Boon, a virologist at Washington University School of Medicine in St. Louis who was not involved with the new work. “This paper is telling us that the intranasal booster induces a really good immune response in the nose and the lungs,” he says. “It’s a clever strategy, and I hope they test it in people.”