Yak milk consumption among Mongol Empire elites

Peer-Reviewed Publication

UNIVERSITY OF MICHIGAN

Photos

For the first time, researchers have pinpointed a date when elite Mongol Empire people were drinking yak milk, according to a study co-led by a University of Michigan researcher.

By analyzing proteins found within ancient dental calculus, an international team of researchers provides direct evidence for consumption of milk from multiple ruminants, including yak. In addition, they discovered milk and blood proteins associated with both horses and ruminants. The team's results are published in Communication Biology.

The study presents novel protein findings from an elite Mongol Era cemetery with exceptional preservation in the permafrost. This is the first example of yak milk recovered from an archaeological context.

Previous research indicates that milk has been a critical resource in Mongolia for more than 5,000 years. While the consumption of cattle, sheep, goat and even horse milk have securely been dated, until now, when people began drinking milk from yaks has been difficult to determine. Understanding when and where humans domesticated this iconic species has been limited to rarely recovered yak remains and artistic depictions of yaks. However, whether these are wild or domestic is unclear.

The discovery of an elite Mongol era cemetery in northern Mongolia was surprising to the researchers.

"Our most important finding was an elite woman buried with a birchbark hat called a bogtog and silk robes depicting a golden five-clawed dragon. Our proteomic analyses concluded that she drank yak milk during her lifetime," said Alicia Ventresca-Miller, U-M assistant professor of anthropology. "This helped us verify the long-term use of this iconic animal in the region and its ties to elite rulers."

Located along a high-elevation ridgeline covered in mist, the location bears the name 'Khorig,' meaning taboo. It may be that this cemetery was considered elite, as the researchers recovered evidence of connections to the ruling elite, including a five-clawed dragon depicted on a Cizhou vessel and traditional robe, or deel.

"Ceramic vessels were turned into lanterns made of dairy products, which revealed long-standing religious ideas and the daily life of the elites of the Mongol empire," said J. Bayarsaikhan, a researcher at the Max Planck Institute for the Science of Human History and the National Museum of Mongolia.

Archaeologists have spent years collecting and conserving pieces of silk and leather strewn across the surface near the burials. Unfortunately, over the past few decades the permafrost has begun to melt and the sites have been heavily looted.

"The degree of looting that we are seeing is unprecedented. Nearly every burial that we can locate on the surface has recently been destroyed by looting activity," said Julia Clark of Nomad Science.

Archaeologists have long suspected that this area was important, and it remains one of the primary areas of yak herding in the present day. While much was lost to looters, what remained of the burials was still well preserved within the permafrost.

An international team of researchers used proteomic analysis of dental calculus to identify the diets of Mongol era elites. They found proteins associated with milk, blood and other tissues that had been consumed by different individuals.

"What is really exciting is that between cows and yaks, there is only a single difference in the amino acid sequence in the most commonly recovered milk protein, and in this case, we were able to recover the part which is specific to yak, Bos mutus," said study co-lead and palaeoproteomics specialist Shevan Wilkin of the University of Zurich and Max Planck Institute for the Science of Human History.

Due to the incredible preservation made possible through the permafrost environmental conditions, the team was able to identify intriguing proteins recovered for the first time from archaeological samples. These included horse milk curd proteins as well as caprine and equine blood proteins that had not been previously recovered from dental calculus.

Ventresca-Miller is also the director of Ancient Protein and Isotope Laboratory at U-M and a research affiliate at the Max Planck Institute for the Science of Human History.

Study: Permafrost preservation reveals proteomic evidence for yak milk consumption in the 13th century

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JOURNAL

Communications Biology

Can cities make room for woodpeckers?

Researchers say wildlife corridors could help pileated woodpeckers survive forest fragmentation

Reports and Proceedings

UNIVERSITY OF CINCINNATI

 

IMAGE: UNIVERSITY OF CINCINNATI DOCTORAL STUDENT RUIJIA HU, LEFT, AND UC PROFESSOR SUSANNA TONG LOOK FOR PILEATED WOODPECKERS IN BURNET WOODS. view more 

CREDIT: ANDREW HIGLEY/UC

Researchers are deploying the latest mapping techniques to identify the most important suburban habitat for North America’s largest woodpecker.

University of Cincinnati doctoral student Ruijia Hu said wildlife habitat in congested places like southwest Ohio is becoming increasingly fragmented as forests give way to new construction. Eventually, this could spell trouble to an animal with specific habitat needs like Ohio’s pileated woodpecker.

Pileated woodpeckers are crow-sized birds with colorful red crests and striking white facial stripes. They are found in forests from British Columbia to Florida. They have the nickname carpenter birds for their incessant natural woodworking.

“I think they’re beautiful birds. They were the model for the cartoon character Woody Woodpecker,” Hu said.

They prefer mature woodlands with dead timber that conceals grubs and other preferred food. While they are considered a species of low conservation concern, their particular habitat needs make them potentially vulnerable to human development, Hu said.

Pileated woodpeckers peck out cavities in trees for their nests every year, creating lots of valuable real estate for animals like fox squirrels and screech owls.

“They make new nests every year. They won’t reuse old ones,” Hu said. “Other animals depend on them.”

Pileated woodpeckers are reclusive birds that are more often heard than seen. They make a loud, repetitive chucking call that echoes across the forest canopy. Studying them can be especially tricky. So Hu turned to citizen science for help.

To identify where pileated woodpeckers have been seen in Hamilton County, Ohio, home to Cincinnati and its namesake university, she used eight years of sightings collected by birders and logged into the website eBird, a free online tool and app that anyone can use to record their observations and locations.

She overlaid these sightings with remote sensing data and found that corridors along rivers and creeks with abundant mature trees and deadwood helped the birds adjust to their increasingly fragmented urban landscape. One of the best places for pileated woodpeckers in Hamilton County is found along the Little Miami River.

Then they created a model to identify the most critical habitat corridors, which could help park managers and government planners make better decisions about preserving or restoring the most valuable contiguous forest patches.

Hu presented her findings to the American Association of Geographers’ conference in Denver.

Study co-author and UC Professor Susanna Tong said wildlife corridors are becoming an increasingly important tool to save species in urban spaces.

“With fragmented forests, many habitats that were once suitable for wildlife are broken up,” Tong said. “Wildlife is unable to find habitat big enough to meet their survival needs. And even if there are suitable habitats, the distance between them can be too great.

“Wildlife corridors link up these habitat patches. Since wildlife can travel and migrate from one patch to another, the probability of finding food and shelter is higher and they can still survive in the fragmented landscape.”

While the population of pileated woodpeckers is stable today, that hasn’t always been the case, Hu said.

“This bird’s population saw a huge decline in the late 18th and 19th centuries when a lot of forest was converted to agriculture,” she said. “But when reforestation started, it recovered.”

And the United States has lost similar species in the blink of an eye from sudden habitat loss. Now extinct, the ivory-billed woodpecker was once found from Texas to Florida but disappeared in just a few decades in the early 20th century when timber clear-cutting flattened huge sections of the Southeast.

“There are so many species in urban areas that we don’t pay attention to, especially when they’re not considered vulnerable,” Hu said.

With development chipping away at more forest in this congested county, the tipping point could come quickly and unexpectedly, she said.

“You can’t fix it overnight,” Hu said. “It’s not just about planting more trees. The birds need mature forest, so it could take 30 to 50 years to replace their habitat. At least we can protect these riparian forest corridors and see that existing trees reach maturity.”

Pileated woodpeckers are found from British Columbia south to Florida. They prefer mature forests.

CREDIT

Michael Miller

University of Cincinnati environmental studies Professor Susanna Tong says wildlife corridors could help animals like pileated woodpecker survive habitat fragmentation in cities.

CREDIT: ANDREW HIGLEY/UC

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METHOD OF RESEARCH

Computational simulation/modeling

Hope for salamanders? Illinois study recalibrates climate change effects

Peer-Reviewed Publication

UNIVERSITY OF ILLINOIS COLLEGE OF AGRICULTURAL, CONSUMER AND ENVIRONMENTAL SCIENCES

 

IMAGE: COLLEGE OF ACES RESEARCHERS, INCLUDING SAM STICKLEY (PICTURED), FOUND PLETHODONTID SALAMANDERS MAY NOT DECLINE DUE TO CLIMATE CHANGE AS MUCH AS ORIGINALLY PREDICTED, BASED ON OLDER SPECIES DISTRIBUTION MODELS. RE-RUNNING THOSE MODELS USING MICROCLIMATE DATA MORE RELEVANT TO THE SALAMANDERS' HABITAT, THE RESEARCHERS FOUND LESS DECLINE AND EVEN SOME AREAS WHERE THE AMPHIBIANS MAY GAIN HABITAT BY 2050. view more 

CREDIT: PHOTOS COURTESY OF SAM STICKLEY, UNIVERSITY OF ILLINOIS COLLEGE OF ACES.

URBANA, Ill. – For tiny salamanders squirming skin-to-soil, big-picture weather patterns may seem as far away as outer space. But for decades, scientists have mostly relied on free-air temperature data at large spatial scales to predict future salamander distributions under climate change. The outlook was dire for the mini ecosystem engineers, suggesting near elimination of habitat in crucial areas.

Now, University of Illinois researchers are tuning into the microclimates that really matter to the imperiled amphibians and forecasting a somewhat more hopeful future.

“The older estimates were predicting almost 100% of the suitable habitat being wiped out for some of these species. But once we incorporated microclimate data at fine spatial scales for our study area in Great Smoky Mountains National Park (GSMNP), we found it might not be nearly that severe.

“It’s still bad, though; our estimates showed 55-80% reduction in habitat for the three species we studied, but that’s a big difference when we’re talking about a large area,” says study co-author Sam Stickley, assistant professor in the Department of Natural Resources and Environmental Sciences (NRES), part of the College of Agricultural, Consumer and Environmental Sciences at U of I. Jennifer Fraterrigo, also an NRES professor, co-authored the study.

Surprisingly, and for the first time, the team was also able to locate potential gains in highly suitable habitat area for three GSMNP plethodontid salamander species under future climate scenarios. Lacking lungs, plethodontids “breathe” entirely through their skin. They’re currently quite abundant in GSMNP, Stickley says, but when their overall range begins to shrink in the future, the predicted areas of gain could be prioritized for conservation or park management.  

But let’s step back for a moment. Ecologists model species distribution based on what they know about the critter’s environmental requirements and where on the landscape those requirements may be met. The results are displayed like a heat map overlaid on real landscape features, with color gradients indicating low to high habitat suitability. It’s usually an exercise done at large spatial scales: GIS maps showing soil and vegetation types on a kilometer scale or larger, along with climate models developed from regional weather stations.

But salamanders and other small animals don’t operate on those scales. They’re right up next to – or in – the soil, oftentimes carrying out their entire lives within a few square meters. At or near the forest floor, temperature and moisture are much more stable than in open areas, where weather stations tend to be located.

“Using free-air temperature data doesn’t account for the buffering effect of forests,” Stickley says. “The forest is pushing solar energy back out, absorbing it, altering wind patterns, and there are plant-water interactions; just all sorts of microclimate variables near the surface that aren’t accounted for in typical climate layers.”

With the advance of small digital environmental sensors, it’s now easier to gather microclimate data at biologically relevant scales for ground-dwelling animals – for example, 3 square meters vs. multiple kilometers – but species distribution modeling using data at fine spatial scales is still relatively rare.

Stickley obtained a colleague’s data from hundreds of mountaintop locations where the three salamander species, along with many others, make their homes (GSMNP isn’t called the “Salamander Capital of the World” for nothing). He then ran distribution models for each species using standard data inputs (free-air temperatures) or microclimate data from the park, producing distribution maps for three time periods: 2006-2010, 2030, and 2050.

Again, the free-air models predicted much greater habitat loss by mid-century than the microclimate models for all three species. And they underestimated many areas the microclimate models predicted would become highly suitable habitat: a total of 3 square kilometers (km2) for the Ocoee salamander, 9 km2 for the pygmy salamander, and a whopping 39 km2 for the red-cheeked salamander.

“The red-cheeked salamander is endemic to the Smoky Mountains, only found in a small range of high-elevation areas in Great Smoky Mountains National Park and a few little areas nearby,” Stickley says. “To find a relatively large area of potential gain in highly suitable habitat could be important information for park managers and conservationists.”

Stickley is optimistic that fine-resolution, microclimate-based species distribution models will become more common with increased data availability and better modeling techniques. In this case, they offer a glimmer of hope for the Salamander Capital of the World, but even microclimate-based models aren’t perfect. They can’t account for disease, predation, or other biotic interactions snipping the threads of the web of life. But, to Stickley, they’re a worthy exercise if their outcome leads to conservation efforts to protect his favorite amphibians.

“Salamanders are a really integral part of the forest food web. They're eating all these insects and shredding and decomposing that stuff into the soil. They're also cycling nutrients across the forest, within the streams, and all the way up to the highest elevations,” he says. “People don’t realize how many salamanders are under their feet in a forest, performing all these key ecosystem functions. They collectively outweigh the biomass of every other vertebrate in the GSMNP, so the role they play in this ecosystem is extremely important to preserve.”

The study, “Microclimate species distribution models estimate lower levels of climate-related habitat loss for salamanders,” is published in the Journal for Nature Conservation [DOI: 10.1016/j.jnc.2023.126333]. The research was supported by a grant from the National Science Foundation (award #1339944).

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JOURNAL

Journal for Nature Conservation

DOI

10.1016/j.jnc.2023.126333 

New UNC Chapel Hill study quantifies $562M in financial risk from Hurricane Florence using novel modeling approach that evaluates risk of mortgage default and property abandonment

Peer-Reviewed Publication

UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL

When Hurricane Florence made landfall on North Carolina’s coast in 2018, it brought record rainfall causing catastrophic flooding and damages to communities across the eastern portion of the state.

Estimating the financial impacts of household flooding is complex because direct damages often snowball into other financial risks, like a decrease in property value or loss of equity. Generally, post-disaster damage assessments focus on insured and uninsured losses, but these numbers do not account for the secondary impacts to households, lenders, local governments and other stakeholders who may also share in the financial consequences if a property owner defaults on their loan or abandons their property.

A new study published in Earth’s Future by researchers at the University of North Carolina at Chapel Hill estimates $562 million in previously unquantified financial risks arising from property value changes and uninsured flood damages in eastern North Carolina as a result of Hurricane Florence. The research team developed a new modeling framework using data on homes sales, mortgage loans and insurance claims to predict risk of mortgage default and abandonment. These predictions can be used by policy makers and stakeholders to create more effective and equitable strategies for community resilience after a disaster.

“The financial risks imposed in eastern North Carolina by this single hurricane exceed $500 million, compared to roughly $300 million in insured losses, and have not been estimated nor previously considered in flood-related recovery efforts,” said Greg Characklis, W.R. Kenan Jr. Distinguished Professor, as well as a co-author of the study and director of the Center on Financial Risk in Environmental Systems (CoFiRES), a joint center of the UNC Institute for the Environment and Gillings School of Global Public Health. “This work evaluates flood-related financial risk in a new way that extends the analysis beyond just an assessment of the insured and uninsured losses that property owners experience as a result of a flood.”

The team found higher-value homes posed the highest-risk to lenders because of higher unpaid mortgage balances. Lower-value properties, however, posed a disproportionate financial risk to local government because uninsured flood damages more often exceeded the value of a home, leading to higher potential for abandoned properties that require maintenance or demolition.

“This suggests that state-level policies such as targeted incentives for purchasing federal flood insurance at lower-value properties, could keep many more people in their homes following a flood and prevent the cascade of financial risk to other stakeholders, such as local governments,” said Hope Thomson, a former graduate student in CoFiRES, and the paper’s lead author.

The team also suggests stakeholders recognize social equity implications after a flood. Their findings are consistent with other studies that suggest disasters exacerbate existing financial inequities.  For example, those most at risk of defaulting on their mortgage or abandoning their property may be the least able to purchase flood insurance or qualify for loans to repair damaged homes, which can perpetuate negative consequences for those individuals.

“We find that the financial risk varies significantly across eastern NC and within communities,” said UNC faculty member Antonia Sebastian, another co-author. “This type of analysis could assist federal and state efforts to target areas most in need of financial relief in the wake of a hurricane, or to take preemptive steps that make the most vulnerable areas more resilient.”

This research was supported with funding from the North Carolina Collaboratory, as well as the UNC Institute for the Environment and the National Institute of Environmental Health Sciences via its Texas A&M Superfund Research Center.

Jeff Warren, executive director of the North Carolina Collaboratory, noted that the research was funded through a larger $2 million study mandate on flood resiliency by the General Assembly.

“This is a perfect example of harnessing the research capacity of our university faculty to conduct detailed analysis and identify specific solutions that can assist the state’s policymakers and local governments.” Warren said. “The data and conclusions in the report will allow our legislature to better understand the economic impacts of flooding events as well as the fiscal liability to state and local governments associated with buildings not covered by flood insurance.”

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JOURNAL

Earth s Future

DOI

10.1029/2022EF003206 

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Systemic Financial Risk Arising From Residential Flood Losses

ARTICLE PUBLICATION DATE

29-Mar-2023

Academic institutions receive lower financial returns from biotechnology licenses than commercial firms

Bentley University study shows disparity between returns from public and private sector investment in biomedical science

Peer-Reviewed Publication

BENTLEY UNIVERSITY

The financial terms of biotechnology licenses from academic institutions are significantly less

favorable than those of comparable licenses between commercial firms according to a new study from Bentley University’s Center for Integration of Science and Industry. The study, published in the journal PLOS ONE, shows that the royalties and payments to academic institutions are significantly lower than those to commercial firms for similar licenses and products at the same stages of development. 

The article, titled “Comparing the economic terms of biotechnology licenses from academic institutions with those between commercial firms,” is the first to make an explicit comparison of academic and commercial licenses. Licenses of biotechnologies from academic institutions provide a mechanism by which scientific discoveries made with government-funded research grants are transferred to companies to develop commercial products. These licenses provide financial returns to the public sector, which universities can use to support research or education, and enable industry to develop innovative products, create jobs, and generate economic growth.

“Our previous work has shown that the U.S. government invests more than a billion dollars for the early-stage basic or applied research underlying each innovative, first-in-class drug. Here, we examined how much of the profit from such products is returned to the public.” said Fred Ledley, Director of the Center for Integration of Science and Industry, and the senior author on this study. “The results suggest that the public sector is not getting the same returns that a company would expect from similar licenses.”

The Bentley University study compared the economic terms of 239 biotechnology licenses from academic institutions to biotechnology companies with 916 comparable licenses between commercial firms. Academic licenses had lower royalty rates (3% versus 8%), lower total payments (deal size) ($900 thousand versus $31 million), and lower payments before product launch (precommercial payments) ($1.1 million versus $25 million). While academic licenses, on average, involved products at less advanced stages of development than corporate licenses, differences in the stage of development accounted for less than half of the disparity between academic and corporate licenses. Considering differences in stage of development together with differences in research payments, co-development, co-commercialization, exclusivity, or grants of stock, academic licenses had royalty rates that were 3-3.6% lower than corporate licenses, deal sizes that were $11.4-$12.2 million lower than corporate licenses, and precommercial payments that were $7.6-$9.4 million lower than corporate licenses.

 

Prateet Shah was the lead author of this work along with Dr. Gregory Vaughan and Dr. Ledley. Mr. Shah conducted this research as an undergraduate researcher at Bentley University.

This analysis used the BioSciDB database provided by Mark Edwards and BioScience Advisors, now part of Evaluate Ltd.

This work was supported by a grant from the National Biomedical Research Foundation.

THE CENTER FOR INTEGRATION OF SCIENCE AND INDUSTRY at Bentley University focuses on advancing the translation of scientific discoveries to create public value. The Center is an environment for interdisciplinary scholarship spanning basic science, data analytics, business and public policy. For more information, visit www.bentley.edu/sciindustry and follow us on Twitter @sciindustry and LinkedIn.

BENTLEY UNIVERSITY is more than just one of the nation's top business schools. It is a lifelong-learning community that creates successful leaders who make business a force for positive change. With a combination of business and the arts and sciences and a flexible, personalized approach to education, Bentley provides students with critical thinking and practical skills that prepare them to lead successful, rewarding careers. Founded in 1917, the university enrolls 4,100 undergraduate and 1,000 graduate and PhD students and is set on 163 acres in Waltham, Massachusetts, 10 miles west of Boston. For more information, visit bentley.edu. For more information, visit bentley.edu. Follow us on Twitter @BentleyU #BentleyUResearch.

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0283887 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Comparing the economic terms of biotechnology licenses from academic institutions with those between commercial firms

ARTICLE PUBLICATION DATE

31-Mar-2023

Harnessing nature to promote planetary sustainability

Special issue of PLOS Biology explores biology-based technologies to keep Earth green

Peer-Reviewed Publication

PLOS

 

IMAGE: A WAX WORM PRODUCING HOLES IN A POLYETHYLENE SHEET FROM A PLASTIC BAG (BLUE). A COCOON PRODUCED BY WAX WORMS IS VISIBLE ON TOP OF A SHEET OF BEEHIVE WAX. SMALL FRAGMENTS OF PLASTICS ARE ATTACHED IN THE THE OUTER PART OF THE COCOON (BLUE DEBRIS). view more 

CREDIT: SIMOAN GADDI (CC-BY 4.0, HTTPS://CREATIVECOMMONS.ORG/LICENSES/BY/4.0/)

As Earth’s population grows, the demands of modern lifestyles place mounting strain on the global environment. Proposed solutions to preserve and promote planetary sustainability can sometimes prove more harmful than helpful. However, technologies that harness natural processes could be more successful.

Such technologies are the focus of the latest issue of the open access journal PLOS Biology, which features a special collection publishing March 31st of papers highlighting biology-based solutions that could be applied to reduce carbon dioxide emissions, eliminate non-degradable plastics, produce food or energy more sustainably, and more.

 

In one of the papers, Federica Bertocchini and Clemente Arias of the Spanish Natural Research Council outline recent research supporting the possibility of using insects to degrade plastic waste, specifically polyethylene. This insect enzyme could serve as a more sustainable alternative to current methods of incineration and mechanical recycling.

Bertocchini adds, “Plastic biodegradation: the technology is not quite there yet, but insect enzymes may represent the tipping point in the field.”

In another plastics-focused article, Sandra Pascoe Ortiz of Universidad del Valle de Atemajac, Mexico, examines ongoing initiatives to develop fully recyclable bioplastics—a broad category of materials that are either made from renewable sources and may or may not be biodegradable, or are made from fossil sources but are biodegradable. Pascoe Ortiz reveals that these initiatives, while promising, are still far from completely solving the problem of plastic pollution.

Pascoe Ortiz adds, “Plastic pollution is a serious problem that needs to be addressed, there are some materials that can help to solve it, but the most important thing is to be aware of the use and disposal we give to different products regardless of the material.”

Turning to the challenge of carbon dioxide pollution, Peter Ralph and Mathieu Pernice of the University of Technology Sydney, Australia describe the potential of using photosynthetic algae to capture carbon dioxide produced as a byproduct of a wide variety of industrial applications, keeping the greenhouse gas out of the atmosphere. The researchers have already put this approach into practice by collaborating with a brewery.

Ralph adds, “Algae-based carbon capture and manufacture (CCM) has great potential to help mitigate climate change by capturing atmospheric carbon and using it to create long-lasting bioproducts to store carbon. Additionally, CCM offers numerous industrial benefits, such as reducing the cost of chemical processes and enabling the use of advanced manufacturing, potentially transforming many industries into climate-positive biomanufacturing.”

Thomas Brück’s research group (Werner Siemens Chair of Synthetic Biotechnology) at the Technical University of Munich, Germany summarizes the current state of available biofuel technologies. Advanced biofuels are sustainable “drop-in” alternatives to fossil equivalents and complement other renewable energy resources, thereby eliminating CO2 emissions. The researchers outline a definitive set of policy recommendations for rapid global deployment of these technologies.

Brück adds, “Advanced biofuels do not compete with agriculture and can be realized via greenhouse gas neutral or even negative processes today. These can contribute to energy security and sustainable mobility but require a stable legislative framework together with financial incentives for broad industrial roll out and applicability.”

Along with the other articles in the collection, these perspectives could help inform and guide policies and further initiatives to keep Earth green.

Pilot plant photobioreactor for oleaginous algae biomass production at the TUM AlgaeTech Center. Extracted lipids from biomass are used for third generation aviation biofuels.

CREDIT

Thomas Brück/TUM (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)

Technology transition from first to fourth generation biofuels.

CREDIT

Dania Awad/TUM (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)

Plastic bottle floating on water. Symbol of environmental pollution

Ivan Radic, Flickr (CC-BY 2.0, https://creativecommons.org/licenses/by/2.0/)

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The full Collection is available in PLOS Biology here: https://collections.plos.org/collection/going-for-green-biology-for-planetary-sustainability/

In your coverage, please use this URL to provide access to the freely available papers in PLOS Biology:

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001979

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002045

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002061

https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002063 

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JOURNAL

PLoS Biology

DOI

10.1371/journal.pbio.3001979 

METHOD OF RESEARCH

Commentary/editorial

SUBJECT OF RESEARCH

Not applicable

COI STATEMENT

see manuscripts

Mathematical model provides bolt of understanding for lightning-produced X-rays

Peer-Reviewed Publication

PENN STATE

 

IMAGE: ELECTRICAL ENGINEERING POSTDOCTORAL SCHOLAR REZA JANALIZADEH (LEFT) AND VICTOR PASKO, PROFESSOR OF ELECTRICAL ENGINEERING, ARE TWO OF THE RESEARCHERS WHO MATHEMATICALLY MODELED THE PHENOMENON OF TERRESTRIAL GAMMA-RAY FLASHES TO BETTER UNDERSTAND HOW IT CAN OCCUR IN OBSERVED COMPACT SPACE. view more 

CREDIT: JEFF XU/PENN STATE

UNIVERSITY PARK, Pa. — In the early 2000s, scientists observed lightning discharge producing X-rays comprising high energy photons — the same type used for medical imaging. Researchers could recreate this phenomenon in the lab, but they could not fully explain how and why lightning produced X-rays. Now, two decades later, a Penn State-led team has discovered a new physical mechanism explaining naturally occurring X-rays associated with lightning activity in the Earth’s atmosphere. 

They published their results on March 30 in Geophysical Research Letters. 

The team’s finding could also shed light on another phenomenon: the small shock sometimes felt when touching a metal doorknob. Called spark discharge, it occurs when a voltage difference is created between a body and a conductor. In a series of lab experiments in the 1960s, scientists discovered that spark discharges produce X-rays — just as lightning does. More than 60 years later, scientists are still conducting lab experiments to better understand the mechanism underpinning this process.  

Lightning consists in part of relativistic electrons, which emit spectacular high-energy bursts of X-rays with tens of mega electron-volt energies called terrestrial gamma-ray flashes (TGFs). Researchers have created simulations and models to explain the TGF observations, but there is a mismatch between simulated and actual sizes, according to lead author Victor Pasko, Penn State professor of electrical engineering. Pasko and his team mathematically modeled the TGF phenomenon to better understand how it can occur in observed compact space.  

“The simulations are all very big — usually several kilometers across — and the community has difficulty reconciling this right now with actual observations, because when lightning propagates, it's very compact,” Pasko said, explaining that lightning’s space channel is typically several centimeters in scale, with electric discharge activity producing X-rays expanding around tips of these channels up to 100 meters in extreme cases. “Why is that source so compact? It’s been a puzzle until now. Since we’re working with very small volumes, it may also have implications for the lab experiments with spark discharges underway since the 1960s.”

Pasko said that they developed the explanation for how an electric field amplifies the number of electrons, driving the phenomenon. The electrons scatter on individual atoms, which constitute the air, as they experience acceleration. As the electrons move, most of them go forward as they gain energy and multiply, similar to a snow avalanche, allowing them to produce more electrons. As the electrons avalanche, they produce X-rays, which launch the photons backward and produce new electrons.

“From there, the question we wanted to answer mathematically was, ‘What is the electric field you need to apply in order to just replicate this, to launch just enough X-rays backwards to allow amplification of these select electrons?’” Pasko said. 

The mathematical modeling established a threshold for the electric field, according to Pasko, which confirmed the feedback mechanism that amplifies the electron avalanches when X-rays emitted by the electrons travel backward and generate new electrons.

“The model results agree with the observational and experimental evidence indicating that TGFs originate from relatively compact regions of space with spatial extent on the order of 10 to 100 meters,” Pasko said.

In addition to describing high-energy phenomena related to lightning, Pasko said the work may eventually help to design new X-ray sources. The researchers said they plan to examine the mechanism using different materials and gases, as well as different applications of their findings. 

The other authors on the paper are Reza Janalizadeh, a postdoctoral scholar in the Penn State Department of Electrical Engineering; Sebastien Celestin of the University of Orleans in Orleans, France; Anne Bourdon, of Ecole Polytechnique in Palaiseau, France; and Jaroslav Jansky of the University of Defense in Brno, Czechia. 

The National Science Foundation funded this work.  

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JOURNAL

Geophysical Research Letters

DOI

10.1029/2022GL102710 

METHOD OF RESEARCH

Data/statistical analysis

ARTICLE TITLE

Conditions for Inception of Relativistic Runaway Discharges in Air

ARTICLE PUBLICATION DATE

30-Mar-2023