How planets form controls elements essential for life

Rice scientists attribute Earth's nitrogen to rapid growth of moon- to Mars-sized bodies

RICE UNIVERSITY

Research News

 

IMAGE: NITROGEN-BEARING, EARTH-LIKE PLANETS CAN BE FORMED IF THEIR FEEDSTOCK MATERIAL GROWS QUICKLY TO AROUND MOON- AND MARS-SIZED PLANETARY EMBRYOS BEFORE SEPARATING INTO CORE-MANTLE-CRUST-ATMOSPHERE, ACCORDING TO RICE UNIVERSITY SCIENTISTS. IF METAL-SILICATE... view more 

CREDIT: ILLUSTRATION BY AMRITA P. VYAS/RICE UNIVERSITY

HOUSTON - (May 10, 2021) - The prospects for life on a given planet depend not only on where it forms but also how, according to Rice University scientists.

Planets like Earth that orbit within a solar system's Goldilocks zone, with conditions supporting liquid water and a rich atmosphere, are more likely to harbor life. As it turns out, how that planet came together also determines whether it captured and retained certain volatile elements and compounds, including nitrogen, carbon and water, that give rise to life.

In a study published in Nature Geoscience, Rice graduate student and lead author Damanveer Grewal and Professor Rajdeep Dasgupta show the competition between the time it takes for material to accrete into a protoplanet and the time the protoplanet takes to separate into its distinct layers -- a metallic core, a shell of silicate mantle and an atmospheric envelope in a process called planetary differentiation -- is critical in determining what volatile elements the rocky planet retains.

Using nitrogen as proxy for volatiles, the researchers showed most of the nitrogen escapes into the atmosphere of protoplanets during differentiation. This nitrogen is subsequently lost to space as the protoplanet either cools down or collides with other protoplanets or cosmic bodies during the next stage of its growth.

This process depletes nitrogen in the atmosphere and mantle of rocky planets, but if the metallic core retains enough, it could still be a significant source of nitrogen during the formation of Earth-like planets.

Dasgupta's high-pressure lab at Rice captured protoplanetary differentiation in action to show the affinity of nitrogen toward metallic cores.

"We simulated high pressure-temperature conditions by subjecting a mixture of nitrogen-bearing metal and silicate powders to nearly 30,000 times the atmospheric pressure and heating them beyond their melting points," Grewal said. "Small metallic blobs embedded in the silicate glasses of the recovered samples were the respective analogs of protoplanetary cores and mantles."

Using this experimental data, the researchers modeled the thermodynamic relationships to show how nitrogen distributes between the atmosphere, molten silicate and core.

"We realized that fractionation of nitrogen between all these reservoirs is very sensitive to the size of the body," Grewal said. "Using this idea, we could calculate how nitrogen would have separated between different reservoirs of protoplanetary bodies through time to finally build a habitable planet like Earth."

Their theory suggests that feedstock materials for Earth grew quickly to around moon- and Mars-sized planetary embryos before they completed the process of differentiating into the familiar metal-silicate-gas vapor arrangement.

In general, they estimate the embryos formed within 1-2 million years of the beginning of the solar system, far sooner than the time it took for them to completely differentiate. If the rate of differentiation was faster than the rate of accretion for these embryos, the rocky planets forming from them could not have accreted enough nitrogen, and likely other volatiles, critical to developing conditions that support life.

"Our calculations show that forming an Earth-size planet via planetary embryos that grew extremely quickly before undergoing metal-silicate differentiation sets a unique pathway to satisfy Earth's nitrogen budget," said Dasgupta, the principal investigator of CLEVER Planets, a NASA-funded collaborative project exploring how life-essential elements might have come together on rocky planets in our solar system or on distant, rocky exoplanets.

"This work shows there's much greater affinity of nitrogen toward core-forming metallic liquid than previously thought," he said.

The study follows earlier works, one showing how the impact by a moon-forming body could have given Earth much of its volatile content, and another suggesting that the planet gained more of its nitrogen from local sources in the solar system than once believed.

In the latter study, Grewal said, "We showed that protoplanets growing in both inner and outer regions of the solar system accreted nitrogen, and Earth sourced its nitrogen by accreting protoplanets from both of these regions. However, it was unknown as to how the nitrogen budget of Earth was established."

"We are making a big claim that will go beyond just the topic of the origin of volatile elements and nitrogen, and will impact a cross-section of the scientific community interested in planet formation and growth," Dasgupta said.

CAPTION

Rice University geochemists analyzed experimental samples of coexisting metals and silicates to learn how they would chemically interact when placed under pressures and temperatures similar to those experienced by differentiating protoplanets. Using nitrogen as a proxy, they theorize that how a planet comes together has implications for whether it captures and retains volatile elements essential to life.

CREDIT

Tommy LaVergne/Rice University

Rice undergraduate intern Taylor Hough and research intern Alexandra Farnell, then a student at St. John's School in Houston and now an undergraduate at Dartmouth College, are co-authors of the study.

NASA grants, including one via the FINESST program, and a Lodieska Stockbridge Vaughn Fellowship at Rice supported the research.

Read the paper at https://dx.doi.org/10.1038/s41561-021-00733-0.

This news release can be found online at news.rice.edu.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials:

Much of Earth's nitrogen was locally sourced: http://news.rice.edu/2021/01/21/much-of-earths-nitrogen-was-locally-sourced/

Planetary collision that formed the moon made life possible on Earth: https://news.rice.edu/2019/01/23/planetary-collision-that-formed-the-moon-made-life-possible-on-earth-2/

What recipes produce a habitable planet? http://news.rice.edu/2018/09/17/what-recipes-produce-a-habitable-planet-2/

Breathing? Thank volcanoes, tectonics and bacteria: http://news.rice.edu/2019/12/02/breathing-thank-volcanoes-tectonics-and-bacteria/

ExPeRT: Experimental Petrology Rice Team (Dasgupta group): https://www.dasgupta.rice.edu/expert/people/

CLEVER Planets: http://cleverplanets.org

Rice Earth, Environmental and Planetary Sciences: https://earthscience.rice.edu

Wiess School of Natural Sciences: https://www.rice.edu

Images for download:

https://news-network.rice.edu/news/files/2021/04/0405_NITRO-5-WEB.jpg
Nitrogen-bearing, Earth-like planets can be formed if their feedstock material grows quickly to around moon- and Mars-sized planetary embryos before separating into core-mantle-crust-atmosphere, according to Rice University scientists. If metal-silicate differentiation is faster than the growth of planetary embryo-sized bodies, then solid reservoirs fail to retain much nitrogen and planets growing from such feedstock become extremely nitrogen-poor. (Credit: Illustration by Amrita P. Vyas/Rice University)

CAPTION

Rice University graduate student Damanveer Grewal, left, and geochemist Rajdeep Dasgupta discuss their experiments in the lab, where they compress complex mixtures of elements to simulate conditions deep in protoplanets and planets. In a new study, they determined that how a planet comes together has implications for whether it captures and retains the volatile elements, including nitrogen, carbon and water, essential to life.

CREDIT

Tommy LaVergne/Rice University

https://news-network.rice.edu/news/files/2021/03/0329_NITROGEN-1-WEB.jpg
Rice University geochemists analyzed experimental samples of coexisting metals and silicates to learn how they would chemically interact when placed under pressures and temperatures similar to those experienced by differentiating protoplanets. Using nitrogen as a proxy, they theorize that how a planet comes together has implications for whether it captures and retains volatile elements essential to life. (Credit: Tommy LaVergne/Rice University)

https://news-network.rice.edu/news/files/2021/04/0405_NITRO-4-WEB.jpg
Rice University graduate student Damanveer Grewal, left, and geochemist Rajdeep Dasgupta discuss their experiments in the lab, where they compress complex mixtures of elements to simulate conditions deep in protoplanets and planets. In a new study, they determined that how a planet comes together has implications for whether it captures and retains the volatile elements, including nitrogen, carbon and water, essential to life. (Credit: Tommy LaVergne/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,978 undergraduates and 3,192 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 1 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance.

In soil, high microbial fluctuation leads to more carbon emissions

Modeling shows fluctuating soil microbial populations impact how much carbon is released from soil

SAN DIEGO STATE UNIVERSITY

Research News

 

IMAGE: SAN DIEGO STATE UNIVERSITY ECOLOGISTS FOUND THAT SEASONAL FLUCTUATIONS IN TEMPERATURE LEAD TO A CORRESPONDING FLUCTUATION IN SOIL MICROBIAL POPULATIONS, AND INCREASED CARBON EMISSIONS. view more 

CREDIT: SDSU

As humans, the weather where we live influences our energy consumption. In climates where weather shifts from hot summers to very cold winters, humans consume more energy since the body has to work harder to maintain temperature.

In much the same way, weather influences microbes such as bacteria and fungi in the soil. Seasonal fluctuations in soil temperature and moisture impact microbial activities that in turn impact soil carbon emissions and nutrient cycles.

Microbes consume carbon as the source of energy. As microbes increase in quantity and activities, they consume more carbon which results in more carbon emissions and vice versa.

In a modeling study published in Global Change Biology on May 10, San Diego State University ecologists found that this microbial seasonality has a significant impact on global carbon emissions and acts as a fundamental mechanism that regulates terrestrial-climate interactions and below ground soil biogeochemistry.

"When microbial colonies in the soil are in a productive phase, increasing in numbers and size, they will need more carbon to fuel their growth," said Xiaofeng Xu, global change ecologist and lead author. "When we manipulated the quantities and activities of soil microbes in simulations and observed the reciprocal changes in soil carbon, we found that when seasonal variation was removed, microbial respiratory rates went down."

By keeping the microbial population at a constant average level, carbon emissions can be reduced.

Stewards of the land could look at reducing fluctuation in soil microbial population by reducing tillage and other management practices in order to reduce soil carbon emissions, the researchers said. It can also help agricultural scientists and growers to sustain soil fertility

Using a microbial modeling framework -- CLM-Microbe (Community Land Model) -- developed in the Ecological Modeling and Integration Lab at SDSU where he studies how climate change impacts the terrestrial carbon cycle -- Xu and colleagues deployed the model on an SDSU supercomputer to reach this conclusion.

"We know soil microbes drive carbon flux -- the amount of carbon exchanged between land, ocean and atmosphere -- by producing enzymes that impact carbon flux," Xu said. "Soil carbon completes its cycle with the help of these microbes which have a hand in ultimate control of the carbon."

Different soil microbial groups play distinct roles in the carbon cycle.

"The model's ability to simulate bacterial and fungal dynamics improves our understanding of the soil microbial community's impact on the carbon cycle," said Liyuan He, first author and doctoral student at SDSU.

The finding advances soil microbial ecology and shows the ecological significance of microbial seasonality and our understanding of soil carbon storage under changing climate conditions.

The authors modeled and validated carbon fluxes observed at an individual plot scale in nine natural biomes including tropical/subtropical forest, temperate coniferous forest, temperate broadleaf forest, boreal forest, shrubland, grassland, desert, tundra, and wetland.

"This study demonstrates the need to incorporate microbial seasonality in earth system models so we can better predict climate-carbon interactions," said Chun-Ta Lai, co-author and an ecosystem ecologist at SDSU.

Next, the researchers will explore microbial seasonality and its impact on global carbon balance, given the dynamics of land use change around the world.

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The SDSU researchers also collaborated with senior staff scientist Melanie Mayes at Oak Ridge National Laboratory in Tennessee, and meteorologist Shohei Murayama with the National Institute of Advanced Industrial Science and Technology in Japan.

Funding sources for the study included the U.S Department of Energy Biological and Environmental Research Program and the CSU Program for Education & Research in Biotechnology.

 

Tweet and re-tweet: songbird stuttering allows researchers to pinpoint causes in the brain

Misfiring neurons in specific regions of the bird brain leads to stuttering patterns, and provides a model to explore treatments to restore normal speech

TUFTS UNIVERSITY

Research News

 

AUDIO: BRIEF SEQUENCE OF A NORMAL ZEBRA FINCH SONG view more 

CREDIT: MIMI KAO, TUFTS UNIVERSITY

Speech problems such as stammering or stuttering plague millions of people worldwide, including 3 million Americans. President Biden himself struggled with stuttering as a child and has largely overcome it with speech therapy. The cause of stuttering has long been a mystery, but researchers at Tufts University are beginning to unlock its causes and a strategy to develop potential treatments using a very curious model system - songbirds. In a study published today in Current Biology, the researchers were able to observe that a simple, reversible pharmacological treatment in zebra finches can stimulate rapid firing in a part of the brain that leads to large variations in their song patterns, including the stuttering of short sequences of notes or syllables.

The part of the brain that appears to be linked to birdsong "re-tweeting" of syllables is the lateral magnocellular nucleus of the anterior nidopallium, or LMAN. When the LMAN is stimulated to fire its neurons in short rapid bursts, the birds start to "improvise" by varying the sequence of notes and tweeting a series of repetitions that share many similarities to stuttering in humans, including partial syllable repeats and abnormal pauses mid-sequence, followed by continuation to the next normal syllable after the repetition. Stuttering in syllable transitions can increase from 0.1% before treatment to as much as 13.6%. Typical frequency of stuttering in humans can occur in 4 - 8% of syllables.

The treatment used to induce LMAN to fire its neurons was a simple infusion of a drug, bicuculline methiodide (BMI), that acts on specific neuron receptors and ion channels. The changes in song patterns were observed to accumulate gradually over several days during infusion and can persist for weeks after treatment is stopped. Once the new song patterns are learned in the parts of their brain that control vocal motor activity, LMAN firing is no longer needed to drive them.

"We're excited about the work because it suggests that burst firing may be especially important for driving long-lasting changes in vocal sequences and may be one mechanism that can be targeted to restore normal vocal sequences," said Mimi Kao, assistant professor of biology at Tufts University and corresponding author of the study.

Earlier studies have evoked changes in song patterns not with a drug but by interrupting the auditory feedback by playing back white noise or a different song sequence. Rather than hearing just their own voice, the birds hear something different, and the mismatch causes them to alter the pitch, timing and sequence of syllables in their songs. It's like trying to sing Sinatra's "My Way" while someone is playing heavy metal in the background.

The pharmaceutical disruption of LMAN activity may be causing a similar alteration in auditory feedback to create variations and stuttering in song patterns. In both cases, removal of the disruption allows normal song patterns to return after a few days to weeks. And therein lies the hope for the treatment of speech dysfunction. If sustained aberrant firing patterns in LMAN or other regions of the brain can cause speech dysfunction, correction of those firing patterns could allow the brain to recover normal speech.

"Although the regions of the brain examined in this study have been known to be involved in speech dysfunctions, very little is known about the specific neuronal firing patterns involved," said Sanne Moorman, former postdoctoral fellow at Tufts University, currently at Utrecht University and first author of the study. "This research offers a way to manipulate the firing patterns, so we can learn how they contribute to dysfunctional speech and explore pharmaceutical or other treatments to recover normal function."

The implications of the research could reach further than speech pathology. Vocal performance is often affected in other basal ganglia movement disorders, such as Parkinson's disease and Huntington's disease, and may serve as a marker to quantify the effectiveness of therapeutic interventions in that region of the brain, according to the study authors.

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In the emptiness of space, Voyager I detects plasma 'hum'

CORNELL UNIVERSITY

Research News

 

ITHACA, N.Y. - Voyager 1 - one of two sibling NASA spacecraft launched 44 years ago and now the most distant human-made object in space - still works and zooms toward infinity.

The craft has long since zipped past the edge of the solar system through the heliopause - the solar system's border with interstellar space - into the interstellar medium. Now, its instruments have detected the constant drone of interstellar gas (plasma waves), according to Cornell University-led research published in Nature Astronomy.

Examining data slowly sent back from more than 14 billion miles away, Stella Koch Ocker, a Cornell doctoral student in astronomy, has uncovered the emission. "It's very faint and monotone, because it is in a narrow frequency bandwidth," Ocker said. "We're detecting the faint, persistent hum of interstellar gas."

This work allows scientists to understand how the interstellar medium interacts with the solar wind, Ocker said, and how the protective bubble of the solar system's heliosphere is shaped and modified by the interstellar environment.

Launched in September 1977, the Voyager 1 spacecraft flew by Jupiter in 1979 and then Saturn in late 1980. Travelling at about 38,000 mph, Voyager 1 crossed the heliopause in August 2012.

After entering interstellar space, the spacecraft's Plasma Wave System detected perturbations in the gas. But, in between those eruptions - caused by our own roiling sun - researchers have uncovered a steady, persistent signature produced by the tenuous near-vacuum of space.

"The interstellar medium is like a quiet or gentle rain," said senior author James Cordes, the George Feldstein Professor of Astronomy. "In the case of a solar outburst, it's like detecting a lightning burst in a thunderstorm and then it's back to a gentle rain."

Ocker believes there is more low-level activity in the interstellar gas than scientists had previously thought, which allows researchers to track the spatial distribution of plasma - that is, when it's not being perturbed by solar flares.

Cornell research scientist Shami Chatterjee explained how continuous tracking of the density of interstellar space is important. "We've never had a chance to evaluate it. Now we know we don't need a fortuitous event related to the sun to measure interstellar plasma," Chatterjee said. "Regardless of what the sun is doing, Voyager is sending back detail. The craft is saying, 'Here's the density I'm swimming through right now. And here it is now. And here it is now. And here it is now.' Voyager is quite distant and will be doing this continuously."

Voyager 1 left Earth carrying a Golden Record created by a committee chaired by the late Cornell professor Carl Sagan, as well as mid-1970s technology. To send a signal to Earth, it took 22 watts, according to NASA's Jet Propulsion Laboratory. The craft has almost 70 kilobytes of computer memory and - at the beginning of the mission - a data rate of 21 kilobits per second.

Due to the 14-billion-mile distance, the communication rate has since slowed to 160-bits-per-second, or about half a 300-baud rate.

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NASA, the Jet Propulsion Laboratory and the National Science Foundation supported the work. Cordes, Chatterjee and Ockler are members of Cornell's Carl Sagan Institute.

Wastewater treatment system recovers electricity, filters water

A dual-function electrode in a microbial fuel cell combines two previously separate functions

WASHINGTON UNIVERSITY IN ST. LOUIS

Research News

 

Whether wastewater is full of "waste" is a matter of perspective.

"Why is it waste?" asked Zhen (Jason) He, professor in the Department of Energy, Environmental & Chemical Engineering in the McKelvey School of Engineering at Washington University in St. Louis.

"It's organic materials," He said, and those can provide energy in a number of ways. Then there's the other valuable resource in wastewater.

Water.

He's lab has developed one system that recovers both, filtering wastewater while creating electricity. Results from bench-scale trials were published May 6 and featured as a front cover article in the journal Environmental Science: Water Research & Technology.

The waste materials in wastewater are full of organic materials which, to bacteria, are food.

"Bacteria love them and can convert them into things we can use," He said. "Biogas is the primary source of energy we can recover from wastewater; the other is bioelectricity."

There already exist ways to capitalize on bacteria to produce energy from wastewater, but such methods often do so at the expense of the water, which could be filtered and otherwise be used -- if not for drinking -- for "grey water" purposes such as irrigation and toilet flushing.

He's lab took the two processes -- filtration and energy production -- and combined them, integrating the filtration system into the anode electrode of a microbial electrochemical system.

The system is set up like a typical microbial fuel cell, a bacterial battery that uses electrochemically active bacteria as a catalyst where a traditional fuel cell would use platinum. In this type of system, the bacteria are attached to the electrode. When wastewater is pumped into the anode, the bacteria "eat" the organic materials and release electrons, creating electricity.

To filter that same water, however, requires a different system.

He's lab combined the systems, developing a permeable anode that acts as a filter.

The anode is a dynamic membrane, made of conductive, carbon cloth. Together, the bacteria and membrane filter out 80% to 90% of organic materials -- that leaves water clean enough to be released into nature or further treated for non-potable water uses.

He used a mixed culture of bacteria, but they had to share one feature -- the bacteria had to be able to survive in a zero-oxygen environment.

"If there was oxygen, bacteria would just dump electrons to the oxygen not the electrode," He said. "If you cannot respire with the electrode, you'll perish."

To find the correct bacteria, He mostly defers to nature.

"It's not 100 percent natural, but we select those that can survive in this condition," He said. "It's more like 'engineered selection,'" the bacteria that did survive and respire with the electrode were selected for the system.

The amount of electricity created is not enough to, say, power a city, but it is in theory enough to help to offset the substantial amount of energy used in a typical U.S. water treatment plant.

"In the U.S., about 3% to 5% of electricity is used for water and wastewater activity," He said. Considering the usage by a local municipal plant, He believes his system can reduce energy consumption significantly.

"Typically, the process consumes about 0.5 KWH of electricity per cubic meter," He said. Based on bench scale experiments, "We can reduce it by half, or more of that."

But the primary goal of He's system isn't electricity production, it's wastewater treatment and nutrient recovery.

"Bacteria can convert those organic materials into things we can use," He said. "We can also recover nutrients like nitrogen or phosphorus for fertilizer. We can use it to feed plants. It's only when we don't use it, then it becomes waste.

"Wastewater is a resource in the wrong location."

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This system helps robots better navigate emergency rooms

UNIVERSITY OF CALIFORNIA - SAN DIEGO

Research News

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IMAGE: THE TEAM TRAINED THE ALGORITHM ON VIDEOS FROM YOUTUBE, MOSTLY COMING FROM DOCUMENTARIES AND REALITY SHOWS, SUCH AS "TRAUMA: LIFE IN THE ER " AND "BOSTON EMS. " THE SET OF... view more CREDIT: UNIVERSITY OF CALIFORNIA SAN DIEGO

Computer scientists at the University of California San Diego have developed a more accurate navigation system that will allow robots to better negotiate busy clinical environments in general and emergency departments more specifically. The researchers have also developed a dataset of open source videos to help train robotic navigation systems in the future.

The team, led by Professor Laurel Riek and Ph.D. student Angelique Taylor, detail their findings in a paper for the International Conference on Robotics and Automation taking place May 30 to June 5 in Xi'an, China.

The project stemmed from conversations with clinicians over several years. The consensus was that robots would best help physicians, nurses and staff in the emergency department by delivering supplies and materials. But this means robots have to know how to avoid situations where clinicians are busy tending to a patient in critical or serious condition.

"To perform these tasks, robots must understand the context of complex hospital environments and the people working around them," said Riek, who holds appointments both in computer science and emergency medicine at UC San Diego.

Taylor and colleagues built the navigation system, the Safety Critical Deep Q-Network (SafeDQN), around an algorithm that takes into account how many people are clustered together in a space and how quickly and abruptly these people are moving. This is based on observations of clinicians' behavior in the emergency department. When a patient's condition worsens, a team immediately gathers around them to render aid. Clinicians' movements are quick, alert and precise. The navigation system directs the robots to move around these clustered groups of people, staying out of the way.

"Our system was designed to deal with the worst case scenarios that can happen in the ED," said Taylor, who is part of Riek's Healthcare Robotics lab at the UC San Diego Department of Computer Science and Engineering.

The team trained the algorithm on videos from YouTube, mostly coming from documentaries and reality shows, such as "Trauma: Life in the ER" and "Boston EMS." The set of more than 700 videos is available for other research teams to train other algorithms and robots.

Researchers tested their algorithm in a simulation environment, and compared its performance to other state-of-the-art robotic navigation systems. The SafeDQN system generated the most efficient and safest paths in all cases.

Next steps include testing the system on a physical robot in a realistic environment. Riek and colleagues plan to partner with UC San Diego Health researchers who operate the campus' healthcare training and simulation center.

The algorithms could also be used outside of the emergency department, for example during search and rescue missions.

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Ph.D. student Sachiko Matsumoto and undergraduate student Wesley Xiao also contributed to the paper.

Social Navigation for Mobile Robots in the Emergency Department

Angelique M. Taylor, Sachiko Mastumoto, Wesley Xiao and Laurel Riek, University of California San Diego

http://cseweb.ucsd.edu/~lriek/papers/taylor-icra-2021.pdf

Flash flood risk may triple across third pole due to global warming

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

Research News

 

IMAGE: GLACIAL LAKE IN THE HIMALAYAN REGION view more 

CREDIT: LI HENG

An international team led by researchers from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences and the University of Geneva has found that flash floods may triple across the Earth's "Third Pole" in response to ongoing climate change.

Their findings were published in Nature Climate Change on May 6.

The Hindu Kush-Himalaya, Tibetan Plateau and surrounding mountain ranges are widely known as the "Third Pole" of the Earth. It contains the largest number of glaciers outside the polar regions.

Due to global warming, the widespread and accelerated melting of glaciers over most of the Third Pole is causing rapid expansion and formation of glacial lakes. When water is suddenly released from these lakes through dam failure or overtopping, glacial lake outburst floods occur, posing a severe threat to downstream communities.

Despite the severe threat these extreme events pose for sustainable mountain development across the Third Pole, scientists are uncertain where and when such events are likely to occur.

In this study, the researchers focused on the threat from new lakes forming in front of rapidly retreating glaciers. They used satellite imagery and topographic modeling to establish the risk associated with about 7,000 glacial lakes now located across the Third Pole.

They found that one in six (1,203) of current glacial lakes pose a high to very high risk to downstream communities, most notably in the eastern and central Himalayan regions of China, India, Nepal, and Bhutan.

The researchers also systematically investigated past outburst flood events and hoped to find some patterns from them. Meanwhile, they used these events to validate their approaches. "We found that these approaches allowed us to accurately classify 96% of glacial lakes known to have produced floods in the past as high or very high risk. We can then apply them to future scenarios," said ZHENG Guoxiong from XIEG, one of the co-first authors of the study.

Under the highest emission scenario (sometimes referred to as the "business-as-usual" scenario), the study shows that much of the Third Pole may approach peak risk for glacial lake flooding by the end of the 21st century--or even by the middle of the century in some regions.

In addition to larger potential flood volumes resulting from the expansion of more than 13,000 lakes in the coming years, over time the lakes will grow closer to steep, unstable mountain slopes that may crash into lakes and provoke small tsunamis.

If global warming continues on its current path, the number of lakes classified as high or very high risk will increase from 1,203 to 2,963, with new risk hotspots emerging in the western Himalaya, Karakorum and parts of Central Asia. These regions have experienced glacial lake outburst floods before, but they have tended to be repetitive and linked to advancing glaciers.

The mountain ranges of the Third Pole span 11 nations, giving rise to potential transboundary natural disasters. The study shows that the number of future potential transboundary glacial flood sources could roughly double to a total of 902 lakes, with 402 of these lakes in the high and very high risk categories.

"Such disasters are sudden and highly destructive. Regular monitoring and assessment as well as early warning systems are important to prevent these floods," said Prof. BAO Anming from XIEG, a corresponding author of the study. "We hope this study will motivate relevant nations and the international community to work together to prevent future flood disasters in the Third Pole".

CAPTION

Glacial lake in the Himalayan region

CREDIT

LI Heng

New finding suggests cognitive problems caused by repeat mild head hits could be treated

GEORGETOWN UNIVERSITY MEDICAL CENTER

Research News

 

WASHINGTON - A neurologic pathway by which non-damaging but high frequency brain impact blunts normal brain function and causes long-term problems with learning and memory has been identified. The finding suggests that tailored drug therapy can be designed and developed to reactivate and normalize cognitive function, say neuroscientists at Georgetown University Medical Center.

The investigators, working with collaborators at the National Institutes of Health, had previously found that infrequent mild head impacts did not have an effect on learning and memory, but in their new study, reported May 10 in Nature Communications (DOI: 10.1038/s41467-021-22744-6), the investigators found that when the frequency of these non-damaging head impacts are increased, the brain adapts and changes how it functions. The investigators have found the molecular pathway responsible for this down-tuning of the brain that can prevent this adaptation from occurring.

This study is the first to offer a detailed molecular analysis of what happens in the brain after highly repetitive and very mild blows to the head, using mice as an animal model, says the study's senior investigator, Mark Burns, PhD, an associate professor in Georgetown's Department of Neuroscience and head of the Laboratory for Brain Injury and Dementia.

"Most research in this area has been in mouse models with more severe brain injury, or in human brains with chronic traumatic encephalopathy (CTE)," he says. CTE is a degenerative brain disease found in people with a history of repetitive head impact. "This means that we have been focusing only on how CTE pathology develops. Our goal was to understand how the brain changes in response to the low-level head impacts that many young football players, for example, are regularly experiencing."

Researchers have found that the average high school and college football player receives 21 head impacts per week, while some specialized players, such as defensive ends, experience twice as many. Behavioral issues believed to come from head impact have been reported in athletes with exposure to repeated head impacts. Issues range from mild learning and memory deficits to behavioral changes that include aggression, impulsivity and sleep disorders.

"These findings represent a message of hope to athletes and their families who worry that a change in behavior and memory means that CTE is in their future," says Burns.

In this study with mice, researchers mimicked the mild head impacts experienced by football players. The mice showed slower learning and impaired memory recall at timepoints long after the head impacts had stopped. After the experiment, a detailed analysis of their brains showed that there was no inflammation or tau pathology, as is usually seen in the brains of brain trauma or people with CTE.

To understand the physiology underlying these memory changes, the study's co-first author, Bevan Main, PhD, assistant professor of neuroscience at Georgetown, conducted RNA sequencing of the brain. "There are many things that this type of analysis can point you to, such as issues with energy usage or CTE-like pathways being activated in nerve cells, and so on," Main says. "All of our sequencing studies kept pointing to the same thing - the synapses that provide communication between neurons."

The next step was to figure out how synaptic function was altered. Stephanie Sloley, PhD, a graduate of Georgetown's Interdisciplinary Program for Neuroscience and the study's other first co-author, conducted electrophysiology studies of different neurons charged with releasing varied neurotransmitters - chemicals passed between neurons, via synapses, that carry functional instructions. "The brain is wired via synaptic communication pathways, and while we found that these wires were intact, the way that they communicated using glutamate was blunted, repressed," says Sloley.

Glutamate is the most abundant neurotransmitter in the brain, and is found in more than 60% of brain synapses. It plays a role in synaptic plasticity, which is the way the brain strengthens or weaken signals between neurons over time to shape learning and memory.

"Glutamate is usually very tightly regulated in the brain, but we know that head impacts cause a burst of glutamate to be released. We believe that brain is adapting to the repeated bursts of glutamate caused by high frequency head impact, and dampens its normal response to glutamate, perhaps as a way to protect the neurons," explains Sloley. She found that there was a shift in the way that neurons detected and responded to glutamate release, which reduced the neurons ability to learn new information.

With a single head hit or infrequent hits, the synapses do not go through this readjustment, Burns says. But after only a week of frequent mild hits, glutamate detection remained blunted for at least a month after the impacts ended. The affected mice showed deficits in learning and memory, compared to a placebo group of animals.

The authors confirmed that the changes in cognition were due to glutamate by giving a group of mice a drug to block glutamate transmission before they experienced the series of head knocks. This drug is FDA-approved for the treatment of Alzheimer's disease. Despite being exposed to the hits, these mice did not develop adaptations in their synapses or neurotransmission, and did not develop cognitive problems.

"This tells us that the cognitive issues we see in our head impact mice are occurring due to a change in the way the brain is working, and not because we have irreparable brain damage or CTE," Main says. "It would be very unlikely that we would use a drug like this in young players as a neuroprotectant before they play sports, because not all players will develop cognitive disorders," he says. "More much likely is that we can use our findings to develop treatments that target the synapses and reverse this condition. That work is already underway"

Burns believes that CTE and this newly discovered mechanism is different. "I believe that CTE is a real concern for athletes exposed to head impact, but I also believe that our newly discovered communication issue is independent of CTE. While it is concerning that head impacts can change the way the brain works, this study reveals that learning and memory deficits after repeated head impacts do not automatically mean a future with an untreatable neurodegenerative disease."

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This work was supported by the National Institutes of Health (NIH) / National Institute of Neurological Disorders and Stroke (R01NS107370 & UG3NS106941), the National Institute of Diabetes and Digestive and Kidney Diseases (R01DK117508 to S.V.), and the National Institute of Aging (R03AG061645). NINDS also supported the Neural Injury and Plasticity Training Grant in the Center for Neural Injury and Recovery at Georgetown (T32NS041218). Funding was also provided by the Advanced Rehabilitation Research and Training Fellowship funded by the Department of Health and Human Services (90AR5005).

The authors report having no personal financial interests related to the study.

About Georgetown University Medical Center

Georgetown University Medical Center (GUMC) is an internationally recognized academic health and science center with a four-part mission of research, teaching, service and patient care (through MedStar Health). GUMC's mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis -- or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing & Health Studies, both nationally ranked; Georgetown Lombardi Comprehensive Cancer Center, designated as a comprehensive cancer center by the National Cancer Institute; and the Biomedical Graduate Research Organization, which accounts for the majority of externally funded research at GUMC including a Clinical and Translational Science Award from the National Institutes of Health. Connect with GUMC on Facebook (Facebook.com/GUMCUpdate), Twitter (@gumedcenter).

How one of the oldest natural insecticides keeps mosquitoes away

Understanding how mosquitoes sniff out certain chemicals could help researchers find new ways to prevent diseases such as malaria, dengue and Zika

DUKE UNIVERSITY

Research News

 

DURHAM, N.C. -- With mosquito season upon us, people are stocking up on repellents to prevent itchy bites. Bug repellents are important because they don't just protect against the buzzing, blood-sucking little pests -- they also safeguard against the diseases they carry, which kill some 700,000 people worldwide each year.

Surprisingly, despite widespread use, no one understood exactly how most mosquito repellents keep the insects away. Now researchers are starting to uncover the first pieces of the puzzle.

A new study has identified a scent receptor in mosquitoes that helps them sniff out and avoid trace amounts of pyrethrum, a plant extract used for centuries to repel biting insects.

One of the oldest insecticides known, pyrethrum comes from the dried, crushed flowers of certain chrysanthemum species. Pyrethrum breaks down quickly in sunlight and isn't readily absorbed through the skin, so the insecticide has long been considered one of the safer options for use around children and pets.

What makes pyrethrum toxic to mosquitoes has been known for some time. It works by binding to tiny pores in the insects' nerve cells and paralyzing them on contact. But it has another property whose mode of action is more of a mystery. At lower concentrations it protects not by killing mosquitoes but by preventing them from getting close enough to land and bite in the first place.

Led by biology professor Ke Dong, who recently joined the faculty at Duke University, the team did a variety of tests to understand how mosquitoes detect and avoid pyrethrum, and which of the extract's chemical components help them do it.

First, they had people don a special rubber glove and put their hand in a cage holding 50 hungry mosquitoes. The glove had a window screen on the back made of two layers of loose-fitting mesh. The top layer acts as a barrier that mosquitoes are unable to bite through. Normally, mosquitoes find the heat and aroma of human skin wafting through the mesh irresistible, and are quick to land and check it out. But when the bottom layer of mesh closest to the skin was treated with pyrethrum, they lost interest.

These early experiments confirmed that mosquitoes don't have to get close enough to taste or touch pyrethrum-treated skin or clothing to stay away. To find out if smell was involved, the researchers attached tiny wire electrodes to the small hairs covering the mosquitoes' antennae and measured their electrical responses to puffs of air containing chemicals released by pyrethrum and other repellents.

A mosquito's ability to smell comes from special receptors embedded in nerve cells on the insect's antennae and mouth parts. Once odor molecules wafting through the air stimulate these receptors, the nerve cells send a message to the brain, which identifies the smell.

Dong and her colleagues were able to pinpoint a specific ingredient in pyrethrum flower extracts, called EBF, which activates a smell receptor in the mosquito's antenna called Or31.

They found that EBF works together with other components called pyrethrins to make an especially off-putting bouquet. Even tiny doses that mosquitoes barely seem to notice when the compounds occur alone -- fewer than five odor molecules per million molecules of air -- can send the insects flying or crawling away when they occur in combination.

While the researchers focused on the mosquito species Aedes aegypti -- which spreads viruses such as Zika, yellow fever and dengue -- they also found Or31 odor receptors with strikingly similar protein sequences in six other mosquito species.

More than 200 types of mosquitoes live in the United States alone; about a dozen of which spread germs that can make people sick.

With mosquitoes becoming increasingly resistant to our best chemical defenses, researchers are constantly on the lookout for new ways to fight them.

These findings, published May 5 in the journal Nature Communications, could help researchers develop new broad-spectrum repellents to keep a variety of mosquitoes at bay, and by extension stop them from biting people and spreading disease.

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Ke Dong's research program is supported by the U.S. National Institutes of Health (GM115475). The Board of Trustees of Michigan State University have filed a patent for the discovery.

CITATION: "A Dual-Target Molecular Mechanism of Pyrethrum Repellency Against Mosquitoes," Feng Liu, Qiang Wang, Peng Xu, Felipe Andreazza, Wilson R. Valbon, Elizabeth Bandason, Mengli Chen, Ru Yan, Bo Feng, Leticia Smith, Jeffrey G. Scott, Genki Takamatsu, Makoto Ihara, Kazuhiko Matsuda, James Klimavicz, Joel Coats, Eugenio E. Oliveira, Yuzhe Du, Ke Dong. Nature Communications, May 5, 2021. DOI: 10.1038/s41467-021-22847-0

 

Study finds pretty plants hog research and conservation limelight

CURTIN UNIVERSITY

Research News

 

IMAGE: ONE OF THE PLANT SPECIES, GENTINANA NIVALIS, FOUND TO ATTRACT MORE THAN ITS SHARE OF RESEARCH ATTENTION. view more 

CREDIT: N/A

New Curtin University research has found a bias among scientists toward colourful and visually striking plants, means they are more likely to be chosen for scientific study and benefit from subsequent conservation efforts, regardless of their ecological importance.

Co-author John Curtin Distinguished Professor Kingsley Dixon from Curtin's School of Molecular and Life Sciences was part of an international team that looked for evidence of an aesthetic bias among scientists by analysing 113 plant species found in global biodiversity hotspot the Southwestern Alps and mentioned in 280 research papers published between 1975 and 2020.

Professor Dixon said the study tested whether there was a relationship between research focus on plant species and characteristics such as the colour, shape and prominence of species.

"We found flowers that were accessible and conspicuous were among those that were most studied, while colour also played a big role," Professor Dixon said.

"Blue plants, which are relatively rare, received the most research attention and white, red and pink flowers were more likely to feature in research literature than green and brown plants.

"Stem height, which determines a plant's ability to stand out among others, was also a contributing factor, while the rarity of a plant did not significantly influence research attention."

Professor Dixon said plant traits such as colour and prominence were not indicators of their ecological significance, and so the 'attractiveness bias' could divert important research attention away from more deserving species.

"This bias may have the negative consequence of steering conservation efforts away from plants that, while less visually pleasing, are more important to the health of overall ecosystems," Professor Dixon said.

"Our study shows the need to take aesthetic biases more explicitly into consideration in experimental design and choice of species studied, to ensure the best conservation and ecological outcomes."

The full paper, 'Plant scientists research attention is skewed towards colorful, conspicuous, and broadly distributed flowers' was published in Nature Plants.

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