Engineer

Bilingual children are strong, creative storytellers, study shows

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Bilingual children use as many words as monolingual children when telling a story, and demonstrate high levels of cognitive flexibility, according to new research by University of Alberta scientists.

“We found that the number of words that bilingual children use in their stories is highly correlated with their cognitive flexibility — the ability to switch between thinking about different concepts,” said Elena Nicoladis, lead author and professor in the Department of Psychology in the Faculty of Science. “This suggests that bilinguals are adept at using the medium of storytelling.”

Vocabulary is a strong predictor of school achievement, and so is storytelling. “These results suggest that parents of bilingual children do not need to be concerned about long-term school achievement, said Nicoladis. “In a storytelling context, bilingual kids are able to use this flexibility to convey stories in creative ways.”

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The research examined a group of French-English bilingual children who have been taught two languages since birth, rather than learning a second language later in life. Results show that bilingual children used just as many words to tell a story in English as monolingual children. Participants also used just as many words in French as they did in English when telling a story.

Previous research has shown that bilingual children score lower than monolingual children on traditional vocabulary tests, meaning this results are changing our understanding of multiple languages and cognition in children.

“The past research is not surprising,” added Nicoladis. “Learning a word is related to how much time you spend in each language. For bilingual children, time is split between languages. So, unsurprisingly, they tend to have lower vocabularies in each of their languages. However, this research shows that as a function of storytelling, bilingual children are equally strong as monolingual children.”

This research used a new, highly sensitive measure for examining cognitive flexibility, examining a participant’s ability to switch between games with different rules, while maintaining accuracy and reaction time. This study builds on previous research examining vocabulary in bilingual children who have learned English as a second language.

New rules illuminate how objects absorb and emit light

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Princeton researchers have uncovered new rules governing how objects absorb and emit light, fine-tuning scientists’ control over light and boosting research into next-generation solar and optical devices.

The discovery solves a longstanding problem of scale, where light’s behavior when interacting with tiny objects violates well-established physical constraints observed at larger scales.

New rules illuminate how objects absorb and emit light
New rules illuminate how objects absorb and emit light

“The kinds of effects you get for very small objects are different from the effects you get from very large objects,” said Sean Molesky, a postdoctoral researcher in electrical engineering and the study’s first author. The difference can be observed in moving from a molecule to a grain of sand. “You can’t simultaneously describe both things,” he said.

The problem stems from light’s famous shapeshifting nature. For ordinary objects, light’s movement can be described by straight lines, or rays. But for microscopic objects, light’s wave properties take over and the neat rules of ray optics break down. The effects are significant. In important modern materials, observations at the micron scale showed infrared light radiating at millions of times more energy per unit area than ray optics predicts.

The new rules, published in Physical Review Letters on Dec. 20, tell scientists how much infrared light an object of any scale can be expected to absorb or emit, resolving a decades-old discrepancy between big and small. The work extends a 19th-century concept, known as a blackbody, into a useful modern context. Blackbodies are idealized objects that absorb and emit light with maximum efficiency.

“There’s been a lot of research done to try to understand in practice, for a given material, how one can approach these blackbody limits,” said Alejandro Rodriguez, an associate professor of electrical engineering and the study’s principal investigator. “How can we make a perfect absorber? A perfect emitter?”

“It’s a very old problem that many physicists — including Planck, Einstein and Boltzmann — tackled early on and laid the foundations for the development of quantum mechanics.”

A large body of previous work has shown that structuring objects with nanoscale features can enhance absorption and emission, effectively trapping photons in a tiny hall of mirrors. But no one had defined the fundamental limits of the possible, leaving open major questions about how to assess a design.

No longer confined to brute-force trial and error, the new level of control will allow engineers to optimize designs mathematically for a wide range of future applications. The work is especially important in technologies like solar panels, optical circuits and quantum computers.

Currently, the team’s findings are specific to thermal sources of light, like the sun or like an incandescent bulb. But the researchers hope to generalize the work further to agree with other light sources, like LEDs, fireflies, or arcing bolts of electricity.

The research was supported in part by the National Science Foundation, the Cornell Center for Materials Research, the Defense Advanced Research Projects Agency and the National Science and Engineering Research Council of Canada.

Unprecedented and worrying rise in sea levels

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A new study led by Simon Fraser University’s Dean of Science, Prof. Paul Kench, has discovered new evidence of sea-level variability in the central Indian Ocean.

The study, which provides new details about sea levels in the past, concludes that sea levels in the central Indian Ocean have risen by close to a meter in the last two centuries.

Prof. Kench says, “We know that certain types of fossil corals act as important recorders of past sea levels. By measuring the ages and the depths of these fossil corals, we are identifying that there have been periods several hundred years ago that the sea level has been much lower than we thought in parts of the Indian Ocean.”

He says understanding where sea levels have been historically, and what happens as they rise, will provide greater insights into how coral reefs systems and islands may be able to respond to the changes in sea levels in the future.

Unprecedented and worrying rise in sea levels
Unprecedented and worrying rise in sea levels

Underscoring the serious threat posed to coastal cities and communities in the region, the ongoing study, which began in 2017, further suggests that if such acceleration continues over the next century, sea levels in the Indian Ocean will have risen to their highest level ever in recorded history.

Nightside barrier gently brakes ‘bursty’ plasma bubbles

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The solar wind that pummels the Earth’s dayside magnetosphere causes turbulence, like air over a wing. Physicists at Rice University have developed new methods to characterize how that influences space weather on the nightside.

It’s rarely quiet up there. The solar wind streams around the Earth and cruises off into the night, but closer to the planet, parcels of plasma get caught in the turbulence and sink back toward Earth. That turbulence causes big ripples in the plasma.

With the help of several spacecraft and computational tools developed over the past decade, Rice scientists led by space plasma physicist Frank Toffoletto can now assess the ripples, called buoyancy waves, caused by the turbulence.

Nightside barrier gently brakes 'bursty' plasma bubbles
Nightside barrier gently brakes ‘bursty’ plasma bubbles

These waves, or oscillations, have been observed in the thin layer of magnetic flux along the base of the plasma sheet that tails away from the planet’s nightside. The Rice theory is the first to quantify their motion.

The theory adds another element to the Rice Convection Model, an established, decades-in-the-making algorithm that helps scientists calculate how the inner and middle magnetosphere will react to events like solar storms that threaten satellites, communications and power grids on Earth.

The new paper in JGR Space Physics by Toffoletto, emeritus professor Richard Wolf and former graduate student Aaron Schutza starts by describing the bubbles — “bursty bulk flows” predicted by Wolf and Rice alumnus Duane Pontius in 1990 — that fall back toward Earth through the plasma tail.

Functionally, they’re the reverse of buoyant air bubbles that bob up and down in the atmosphere because of gravity, but the plasma bubbles respond to magnetic fields instead. The plasma bubbles lose most of their momentum by the time they touch down at the theoretical, filamentlike boundary between the inner plasma sheet and the protective plasmasphere.

Nightside barrier gently brakes 'bursty' plasma bubbles
Nightside barrier gently brakes ‘bursty’ plasma bubbles

That sets the braking boundary into a gentle oscillation, which lasts mere minutes before stabilizing again. Toffoletto compared the motion to a plucked guitar string that quickly returns to equilibrium.

“The fancy name for this is the eigenmode,” he said. “We’re trying to figure out the low-frequency eigenmodes of the magnetosphere. They haven’t been studied very much, though they appear to be associated with dynamic disruptions to the magnetosphere.”

Toffoletto said the Rice team has in recent years discovered through simulations that the magnetosphere doesn’t always respond in a linear fashion to the steady driving force of the solar wind.

“You get all kinds of wave modes in the system,” he said, explaining that bursty bulk flows are one such mode. “Every time one of these things come flying in, when they hit the inner region, they basically reach their equilibrium point and oscillate with a certain frequency. Finding that frequency is what this paper is all about.”

As measured by the THE MIS spacecraft, the periods of these waves are a few minutes and the amplitudes are often bigger than the Earth.

“Understanding the natural frequency of the system and how it behaves can tell us a lot about the physical properties of plasma on the night side, its transport and how it might be related to the aurora,” he said. “A lot of these phenomena show up in the ionosphere as auroral structures, and we don’t understand where these structures come from.”

Toffoletto said the models suggest buoyant waves may play a role in the formation of the ring current that consists of charged particles that flow around Earth as well as magnetospheric substorms, all of which are connected to the aurora.

He said that no more than a decade ago, many magnetosphere simulations “would look very uniform, kind of boring.” The Rice group is collaborating with the Applied Physics Laboratory to include the Rice Convection Model in a newly developed global magnetosphere code called “Gamera,” named after the fictional Japanese monster.

“Now, with such higher-resolution models and much better numerical methods, these structures are starting to show up in the simulations,” Toffoletto said. “This paper is one little piece of the puzzle we’re putting together of how the system behaves. All this plays a big role in understanding how space weather works and how that in turn impacts technology, satellites and ground-based systems.”

The Rice Convection Model itself was refreshed this month in a paper led by recent Rice alumnus Jian Yang, now an associate professor of Earth and space sciences at the Southern University of Science and Technology, Shenzhen, China.

New polymer material may help batteries become self-healing, recyclable

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Lithium-ion batteries are notorious for developing internal electrical shorts that can ignite a battery’s liquid electrolytes, leading to explosions and fires. Engineers at the University of Illinois have developed a solid polymer-based electrolyte that can self-heal after damage — and the material can also be recycled without the use of harsh chemicals or high temperatures.

New polymer material may help batteries become self-healing, recyclable
New polymer material may help batteries become self-healing, recyclable

 

The new study, which could help manufacturers produce recyclable, self-healing commercial batteries, is published in the Journal of the American Chemical Society.

As lithium-ion batteries go through multiple cycles of charge and discharge, they develop tiny, branchlike structures of solid lithium called dendrites, the researchers said. These structures reduce battery life, cause hotspots and electrical shorts, and sometimes grow large enough to puncture the internal parts of the battery, causing explosive chemical reactions between the electrodes and electrolyte liquids.

There has been a push by chemists and engineers to replace the liquid electrolytes in lithium-ion batteries with solid materials such as ceramics or polymers, the researchers said. However, many of these materials are rigid and brittle resulting in poor electrolyte-to-electrode contact and reduced conductivity.

“Solid ion-conducting polymers are one option for developing nonliquid electrolytes,” said Brian Jing, a materials science and engineering graduate student and study co-author. “But the high-temperature conditions inside a battery can melt most polymers, again resulting in dendrites and failure.”

Past studies have produced solid electrolytes by using a network of polymer strands that are cross-linked to form a rubbery lithium conductor. This method delays the growth of dendrites; however, these materials are complex and cannot be recovered or healed after damage, Jing said.

To address this issue, the researchers developed a network polymer electrolyte in which the cross-link point can undergo exchange reactions and swap polymer strands. In contrast to linear polymers, these networks actually get stiffer upon heating, which can potentially minimize the dendrite problem, the researchers said. Additionally, they can be easily broken down and resolidified into a networked structure after damage, making them recyclable, and they restore conductivity after being damaged because they are self-healing.

“This new network polymer also shows the remarkable property that both conductivity and stiffness increase with heating, which is not seen in conventional polymer electrolytes,” Jing said.

“Most polymers require strong acids and high temperatures to break down,” said materials science and engineering professor and lead author Christopher Evans. “Our material dissolves in water at room temperature, making it a very energy-efficient and environmentally friendly process.”

The team probed the conductivity of the new material and found its potential as an effective battery electrolyte to be promising, the researchers said, but acknowledge that more work is required before it could be used in batteries that are comparable to what is in use today.

“I think this work presents an interesting platform for others to test,” Evans said. “We used a very specific chemistry and a very specific dynamic bond in our polymer, but we think this platform can be reconfigured to be used with many other chemistries to tweak the conductivity and mechanical properties.”

Grain traits traced to ‘dark matter’ of rice genome

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Domesticated rice has fatter seed grains with higher starch content than its wild rice relatives — the result of many generations of preferential seed sorting and sowing. But even though rice was the first crop to be fully sequenced, scientists have only documented a few of the genetic changes that made rice into a staple food for more than half the world’s population.

New research now finds that a sizeable amount of domestication-related changes in rice reflects selection on traits that are determined by a portion of the genome that does not transcribe proteins.

Grain traits traced to 'dark matter' of rice genome
Grain traits traced to ‘dark matter’ of rice genome

Xiaoming Zheng, a biologist with the Institute of Crop Sciences at the Chinese Academy of Agricultural Sciences, is the first author of newly published paper in Science Advances, “Genome-wide analyses reveal the role of non-coding variation in complex traits during rice domestication.” Qingwen Yang and Jun Liu, also from the Institute of Crop Sciences in the Chinese Academy of Agricultural Sciences, and Kenneth M. Olsen from Washington University in St. Louis are also communicating authors of this paper.

Noncoding RNAs are suspected to play very important roles in regulating growth and development, but they’re only beginning to be characterized.

“Despite almost 20 years of genomics and genome-enabled studies of crop domestication, we still know remarkably little about the genetic basis of most domestication traits in most crop species,” said Olsen, professor of biology in Arts & Sciences at Washington University.

“Early studies tended to go for ‘low-hanging fruit’ — simple traits that were controlled by just one or two genes with easily identifiable mutations,” Olsen said. “Far more difficult is figuring out the more subtle developmental changes that were critical for a lot of the changes during crop domestication.

“This study offers a step in that direction, by examining one regulatory mechanism that has been critical for modulating domestication-associated changes in rice grain development.”

Diversity of traits

A large proportion of the DNA in the chromosomes of many plants and animals comprises genes that do not encode instructions for making proteins — up to 98% of the genome for any given species. But this genetic information is poorly understood. Some scientists have called this stuff the ‘dark matter’ of the genome, or even dismissed it as ‘junk DNA’ — but it appears to have played an out sized role in rice development.

In this study, researchers found that key changes that occurred during rice domestication more than 9,000 years ago could be tied back to molecules called long-noncoding RNAs (lnc RNAs), a class of RNA molecules with a length of more than 200 nucleotides.

About 36 percent of the genetic information recorded in the rice genome can be tracked back to non coding regions, but more than 50 percent of the diversity of traits important to agriculture is linked to these same areas, the researchers found.

“For the first time, the lnc RNAs in noncoding region of cultivated rice and wild rice was deeply annotated and described,” Zheng said.

“Our transgenic experiments and population genetic analysis convincingly demonstrate that selection on lnc RNAs contributed to changes in domesticated rice grain quality by altering the expression of genes that function in starch synthesis and grain pigmentation,” she said.

Working with several hundred rice samples and more than 260 Gbs of sequence, the researchers employed sensitive detection techniques to quantify and robustly track lnc RNA transcription in rice. The new study validates some previously identified lnc RNAs and also provides new information on previously un described molecules.

This new study adds fuel to speculation by some researchers that most adaptive differences between groups of plants or animals are due to changes in gene regulation, and not protein evolution.

“Based on our findings, we propose that selection on lnc RNAs could prove to be a broader mechanism by which genome-wide patterns of gene expression can evolve in many species,” Zheng said.

This rice study also opens eyes and possibly new doors for producing new crops and grains through precision breeding.

Scientists find iron ‘snow’ in Earth’s core

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The Earth’s inner core is hot, under immense pressure and snow-capped, according to new research that could help scientists better understand forces that affect the entire planet.

The snow is made of tiny particles of iron — much heavier than any snowflake on Earth’s surface — that fall from the molten outer core and pile on top of the inner core, creating piles up to 200 miles thick that cover the inner core.

Scientists find iron 'snow' in Earth's core
Scientists find iron ‘snow’ in Earth’s core

The image may sound like an alien winter wonderland. But the scientists who led the research said it is akin to how rocks form inside volcanoes.

“The Earth’s metallic core works like a magma chamber that we know better of in the crust,” said Jung-Fu Lin, a professor in the Jackson School of Geosciences at The University of Texas at Austin and a co-author of the study.

The study is available online and will be published in the print edition of the journal JGR Solid Earth on December 23.

Youjun Zhang, an associate professor at Sichuan University in China, led the study. The other co-authors include Jackson School graduate student Peter Nelson; and Nick Dygert, an assistant professor at the University of Tennessee who conducted the research during a postdoctoral fellowship at the Jackson School.

The Earth’s core can’t be sampled, so scientists study it by recording and analyzing signals from seismic waves (a type of energy wave) as they pass through the Earth.

However, aberrations between recent seismic wave data and the values that would be expected based on the current model of the Earth’s core have raised questions. The waves move more slowly than expected as they passed through the base of the outer core, and they move faster than expected when moving through the eastern hemisphere of the top inner core.

Scientists find iron 'snow' in Earth's core
Scientists find iron ‘snow’ in Earth’s core

The study proposes the iron snow-capped core as an explanation for these aberrations. The scientist S.I. Braginkskii proposed in the early 1960s that a slurry layer exists between the inner and outer core, but prevailing knowledge about heat and pressure conditions in the core environment quashed that theory. However, new data from experiments on core-like materials conducted by Zhang and pulled from more recent scientific literature found that crystallization was possible and that about 15% of the lowermost outer core could be made of iron-based crystals that eventually fall down the liquid outer core and settle on top of the solid inner core.

“It’s sort of a bizarre thing to think about,” Dygert said. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”

The researchers point to the accumulated snow pack as the cause of the seismic aberrations. The slurry-like composition slows the seismic waves. The variation in snow pile size — thinner in the eastern hemisphere and thicker in the western — explains the change in speed.

“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” Zhang said.

The paper compares the snowing of iron particles with a process that happens inside magma chambers closer to the Earth’s surface, which involves minerals crystalizing out of the melt and glomming together. In magma chambers, the compaction of the minerals creates what’s known as “cumulate rock.” In the Earth’s core, the compaction of the iron contributes to the growth of the inner core and shrinking of the outer core.

And given the core’s influence over phenomena that affects the entire planet, from generating its magnetic field to radiating the heat that drives the movement of tectonic plates, understanding more about its composition and behavior could help in understanding how these larger processes work.

Bruce Buffet, a geosciences professor at the University of California, Berkley who studies planet interiors and who was not involved in the study, said that the research confronts longstanding questions about the Earth’s interior and could even help reveal more about how the Earth’s core came to be.

“Relating the model predictions to the anomalous observations allows us to draw inferences about the possible compositions of the liquid core and maybe connect this information to the conditions that prevailed at the time the planet was formed,” he said. “The starting condition is an important factor in Earth becoming the planet we know.”