Hubble watches the "flapping" of cosmic bat shadow

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VIDEO: THIS VIDEO SHOWCASES THE "FLAPPING " MOTION OF THE SHADOW OF THE STAR HBC 672 THAT HAS BEEN OBSERVED BY A TEAM OF RESEARCHERS USING THE NASA/ESA HUBBLE SPACE TELESCOPE. THE STAR... view more 

CREDIT: ESA/HUBBLE, K. PONTOPPIDAN, L. CALÇADA, M. KORNMESSER MUSIC: KONSTANTINO POLIZOIS

The young star HBC 672 is known by its nickname of Bat Shadow because of its wing-like shadow feature. The NASA/ESA Hubble Space Telescope has now observed a curious "flapping" motion in the shadow of the star's disc for the first time. The star resides in a stellar nursery called the Serpens Nebula, about 1300 light-years away.

The Hubble Space Telescope captured a striking observation of the fledgling star's unseen, planet-forming disc in 2018. This disc casts a huge shadow across a more distant cloud in a star-forming region -- like a fly wandering into the beam of a flashlight shining on a wall.

Now, astronomers have serendipitously observed the Bat Shadow's "flapping". This may have been caused by a planet pulling on the disc and warping it. "You have a star that is surrounded by a disc, and the disc is not like Saturn's rings -- it's not flat. It's puffed up. And so that means that the light from the star, if it goes straight up, can continue straight up -- it's not blocked by anything. But if it tries to go along the plane of the disc, it doesn't get out, and it casts a shadow," explained lead author Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, USA, whose team have published these results [1].

This "flapping" finding was also a surprise. Pontoppidan and his team observed the shadow in several filters over a period of 13 months. When they combined the old and new images, the shadow appeared to have moved.

The shadow is so large -- about 200 times the diameter of our Solar System -- that light doesn't travel instantaneously across it. In fact, it takes about 45 days for the light to travel from the star out to the best defined edge of the shadow.

Pontoppidan and his team calculate that a planet warping the disc would orbit its star in no fewer than 180 days. They estimate that it would be about the same distance from its star as Earth is from the Sun. Pontoppidan's team also suggest the disc must be flared, with an angle that increases with distance -- like a trumpet. This shape of its two peaks and two dips would explain the "flapping" of the shadow. The team also speculates that a planet is embedded in the disc, inclined to the disc's plane. If it's not a planet, a less likely explanation is a lower-mass stellar companion orbiting HBC 672 outside the plane of the disc. Pontoppidan and his team doubt this is the case, based on the thickness of the disc. There is also no current evidence for a binary companion).

The disc is a circling structure of gas, dust, and rock, and is too small and too distant to be seen, even by Hubble. However, based on the projected shadow, scientists do know that its height-to-radius ratio is 1:5.

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Notes

[1] The team's paper appears in an upcoming edition of the Astrophysical Journal - https://iopscience.iop.org/journal/0004-637X .

More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of K. Pontoppidan, J. Green, T. Pauly, C. Salyk, and J. DePasquale.

These observations were conducted under Hubble observation programmes SNAP 14181 (http://archive.stsci.edu/proposal_search.php?mission=hst&id=14181) (PI: T. Megeath) and GO 15597 (http://archive.stsci.edu/proposal_search.php?mission=hst&id=15597) (M. Mutchler).

Image credit: NASA, ESA, K. Pontoppidan

Links

* Images of Hubble - http://www.spacetelescope.org/images/archive/category/spacecraft/

* Hubble's 2018 observations of the Bat Shadow - https://www.spacetelescope.org/news/heic1819/

* HubbleSite release - https://hubblesite.org/contents/news-releases/2020/news-2020-22

Global pollution estimates reveal surprises, opportunity

Researchers' hybrid dataset includes satellite images, modeling and air samples

WASHINGTON UNIVERSITY IN ST. LOUIS

 

IMAGE: CALCULATED TRENDS IN GEOPHYSICAL PM2.5 VALUES FROM 1998-2018. WARM COLORS INDICATE POSITIVE TRENDS, COOL COLORS INDICATE NEGATIVE TRENDS AND THE OPACITY OF THE COLORS INDICATES THE STATISTICAL SIGNIFICANCE OF THE... view more 

CREDIT: MARTIN LAB

It is not unusual to come across headlines about pollution or global warming and find that they reach different conclusions depending upon the data source.

Researchers at Washington University in St. Louis used a harmonized approach, incorporating data from multiple satellites and ground monitors with computer modeling to compile a comprehensive, consistent map of pollution across the globe. Their data spans 1998-2018, providing a current picture of the state of the world's air quality that reveals some surprises, both for better and for worse.

The research was led by Melanie Hammer, a postdoctoral research fellow in the lab of Randall Martin, professor of energy, environmental and chemical engineering in the McKelvey School of Engineering.

Results of their study that looked at PM2.5 -- tiny particles that are able to make their way deep into a person's respiratory system -- were published June 3 in Environmental Science & Technology.

"Prior studies that look at long-term PM2.5 haven't used data as recent as we have," Hammer said. Older data can't capture the results of many programs aimed at curbing pollution -- even if they have been in effect for nearly a decade.

That turned out to be the case in China, where a significant drop in pollution in the recent past was the result of strategies begun in earnest around 2011. Other data sets don't capture the drop.

And in India -- another area of concern -- the story was not as positive. "It seems there's a bit of a plateau of PM2.5 levels," Hammer said. Though still, levels are not rising as steeply as other reports may suggest.

PM2.5 refers to the size of particles -- 2.5 microns. These tiny particles are created in nature, but also by human activities, including some manufacturing processes, car exhaust and the use of wood-burning cookstoves.

It's not easy to measure the amount of PM2.5 on the ground because there isn't any kind of comprehensive monitoring network covering the globe. North America and Europe have extensive monitoring systems, as does China. But, Martin said, "There are large gaps in ground-based monitoring. People can be living hundreds of kilometers away from monitors."

To develop a comprehensive pollution map, then, ground-based monitors are simply insufficient.

To capture a global snapshot, Martin's team started with satellite images of columns of atmosphere that spanned the ground to the edge of space. Using the established GEOS-Chem model, which simulates atmospheric composition, they could infer how much PM2.5 should be on the ground, at the bottom of any given column.

When comparing the predictions to actual levels measured by ground monitors, the agreement was striking. In fact, Martin said, "It's the best level of agreement found to date."

But the researchers still went a step further.

The agreement was great, but not perfect. So Hammer added the differences between the observed and predicted amounts of PM2.5 and expanded the ground-based predictions across the globe, filling in the massive gaps between monitors.

This extra step brought the observed and predicted levels of PM2.5 from 81% to 90% agreement.

Once they were able to take a good look at the most recent pollution levels around the world, the researchers saw some stark changes from previous trends. Particularly in China.

"We're used to seeing just large, increasing trends in pollution," Hammer said. But in China, "What we found, from 2011 to 2018, is that there actually is a particularly large negative trend."

Elsewhere in Asia, the picture wasn't as positive.

While pollution levels did not seem to be increasing in India, the country seems to be in a plateau phase. "The broad plateau of very high concentrations, to which a large population is exposed, is quite concerning," Martin said. "It affects the health of a billion people."

However, the takeaway from this research can be, on the balance, a hopeful one: It seems to show one possible way forward.

"The data Melanie's analysis reveals is a real success story for air quality controls," Martin said. "It shows they can be remarkably effective at reducing PM2.5." Although scientists have known these controls contain the potential to make an impact, he said, "The changes in China are very dramatic, larger than we have seen anywhere in the world over the observational record.

"It illustrates a real opportunity to improve air quality through effective controls."

Pollution, health around the world

In people already sick with illness such as asthma, PM2.5 can have immediate health consequences. Long-term, however, breathing in these particles carries consequences for everyone.

"PM2.5 is a major public health concern globally," said Melanie Hammer, postdoctoral researcher in the lab of Randall Martin in the McKelvey School of Engineering. "It's important to get accurate exposure estimates to estimate health impacts."

That's why organizations, including World Health Organization and Global Burden of Disease, use data from Martin's lab.

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Researchers discover critical new allergy pathway

Mouse study discovery points to potential new drug targets for treating asthma, hay fever, and other inflammatory disorders

JOHNS HOPKINS UNIVERSITY BLOOMBERG SCHOOL OF PUBLIC HEALTH

 

Researchers at Johns Hopkins Bloomberg School of Public Health have identified the sequence of molecular events by which tiny, tick-like creatures called house dust mites trigger asthma and allergic rhinitis.

The researchers, whose study was published online June 22 in Nature Immunology, found that allergy-triggering molecules from dust mites can interact with an immune protein called SAA1, which is better known as a sentinel against bacteria and other infectious agents. The researchers showed step-by-step how this interaction between mite-molecules and SAA1 triggers an allergic-type immune response in mice.

The findings reveal what may be a significant new pathway by which allergic and inflammatory disorders arise. They also suggest that blocking the pathway could potentially work as a preventive or treatment strategy against asthma and other allergic reactions.

"We think that the signaling interactions that occur immediately downstream of the mite-proteins' activation of SAA1 may be good targets for future drugs," says study senior author Marsha Wills-Karp, PhD, the Anna M. Baetjer Professor of Environmental Health and Chair of the Department of Environmental Health and Engineering at the Bloomberg School.

Asthma affects between 8 to 15 percent of people in the U.S., and is typically triggered by dust mites, tree and grass pollens, and other allergens. Researchers suspect that this inappropriate immune triggering happens when the immune system mistakes allergens--which are otherwise harmless--for pieces of bacteria or other infectious agents. However, the molecular mechanisms underlying this misidentification haven't been well understood.

In their study, Wills-Karp and her colleagues zeroed in on SAA1, an immune protein that is found, among other places, in the fluid that lines the airways and other mucosal surfaces. A member of the evolutionarily ancient "innate immune system" of mammals, SAA1 is thought to have evolved as a sentinel or early-responder molecule that, for example, recognizes and helps clear away certain types of bacteria and other infectious agents.

The researchers found that exposure to dust-mite proteins causes an asthma-like sensitization of the airways of the control group mice. In contrast, exposure to dust-mite proteins hardly had any effect in mice in which SAA1 was neutralized by antibodies, or in mice whose genes for SAA1 were knocked out. Further experiments confirmed that SAA1, when it is present, directly binds certain dust-mite allergens called fatty-acid binding proteins, which have structural similarities with proteins found in some bacteria and parasites. This allergen-SAA1 interaction releases SAA1 into its active form, wherein it activates a receptor called FPR2 on airway-lining cells. The airway cells then produce and secrete large quantities of interleukin-33, a protein known for its ability to stimulate allergic-type immune responses.

Confirming the likely relevance to humans, the researchers found evidence of increased production of SAA1 and FPR2 in nasal airway-lining cells from patients with chronic sinusitis--which is often linked to dust-mite allergens--compared to healthy controls.

"We think that different allergens take different routes to the activation of interleukin-33 and related allergic responses, and this SAA1-FPR2 route seems to be one that is taken by some dust-mite allergens," Wills-Karp says.

She and her colleagues now plan to investigate why some people develop allergic disorders in which this pathway is hyperactive, while most don't. They also plan to explore the possibility of blocking this pathway, perhaps at the SAA1-FPR2 interaction, as a way of treating asthma and other allergic disorders.

The researchers suspect that the newly described SAA1-FPR2 allergic pathway may be relevant not only in asthma and hay fever-type disorders but also in atopic dermatitis (eczema) and food allergies--possibly even in chronic inflammatory disorders such as rheumatoid arthritis and atherosclerosis.

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First author Ursula Smole, PhD, worked on the study while at the Bloomberg School.

"Serum amyloid A is a soluble pattern recognition receptor that drives type 2 immunity" was written by Ursula Smole, Naina Gour, Jordan Phelan, Gerhard Hofer, Cordula Köhler, Bernhard Kratzer, Peter Tauber, Xiao Xiao, Nu Yao, Jan Dvorak, Luis Caraballo, Leonardo Puerta, Sandra Rosskopf, Jamila Chakir, Ernst Malle, Andrew Lane, Winfried Pickl, Stephane Lajoie, and Marsha Wills-Karp.

Funding was provided by the National Institute of Allergy and Infectious Diseases (U19AI070235, R01 AI083315), the National Institutes of Health (R56AI118791, R01AI127644, R01AI132590), and the Austrian Science Fund (DK W1248, SFB F4609).

Common food additive causes adverse health effects in mice

UMass Amherst researchers find TiO2 nanoparticles produce inflammation in colon

UNIVERSITY OF MASSACHUSETTS AMHERST

 

IMAGE: HANG XIAO IS PROFESSOR AND CLYDESDALE SCHOLAR OF FOOD SCIENCE AT UMASS AMHERST. view more 

CREDIT: UMASS AMHERST

A common food additive, recently banned in France but allowed in the U.S. and many other countries, was found to significantly alter gut microbiota in mice, causing inflammation in the colon and changes in protein expression in the liver, according to research led by a University of Massachusetts Amherst food scientist.

"I think our results have a lot of implications in the food industry and on human health and nutrition," says lead author Hang Xiao, professor and Clydesdale Scholar of Food Science. "The study confirmed a strong linkage between foodborne titanium dioxide nanoparticles (TiO2 NPs) and adverse health effects."

Along with colleagues at UMass Amherst and in China, Xiao published the research in Small, a weekly, peer-reviewed, interdisciplinary journal that covers nanotechnology.

Gut microbiota, which refers to the diverse and complex community of microorganisms in the gut, plays a vital role in human health. An imbalance of gut microbiota has been associated with a range of health issues, including inflammatory bowel disease, obesity and cardiovascular disease.

Human exposure to foodborne TiO2 NPs comes primarily from a food additive known as E171, which is made up of different-size particles of TiO2, including one-third or more that are nanoscale. E171, which makes products look whiter and more opaque, is found in such food as desserts, candy, beverages and gum. E171 exposure is two to four times higher in U.S. children than in adults, Xiao points out that one study found.

Smaller than 100 nanometers, foodborne nanoscale particles may have unique physiological properties that cause concern. "The bigger particles won't be absorbed easily, but the smaller ones could get into the tissues and accumulate somewhere," Xiao says.

In their study, Xiao and his team fed either E171 or TiO2 NPs to two populations of mice as part of their daily diet. One population was fed a high-fat diet similar to that of many Americans, two-thirds of whom are obese or overweight; the other group of mice was fed a low-fat diet. The mice fed a high-fat diet eventually became obese, while the mice on the low-fat diet did not.

"In both the non-obese mice and obese mice, the gut microbiota was disturbed by both E171 and TiO2 NPs," Xiao says. "The nanosized particles caused more negative changes in both groups of mice." Moreover, the obese mice were more susceptible to the adverse effects of TiO2 NPs, causing more damage in obese mice than in non-obese ones.

The researchers found TiO2 NPs decreased cecal levels of short-chain fatty acids, which are essential for colon health, and increased pro-inflammatory immune cells and cytokines in the colon, indicating an inflammatory state.

To evaluate the direct health impact of gut microbiota disrupted by TiO2 NP, Xiao and colleagues conducted a fecal transplant study. They gave mice antibiotics to clear out their original gut microbiota and then transplanted fecal bacteria from the TiO2 NP-treated mice to the antibiotic-treated mice. "The results support our hypothesis that including TiO2 NPs in the diet disrupts the homeostasis of the gut microbiota," Xiao says, "which in turn leads to colonic inflammation in the mice."

The study also measured levels of TiO2 in human stool samples, finding a wide range. Xiao says further research is needed to determine the health effects of long-term - such as life-long and multigenerational - exposure to TiO2 NPs.

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Airborne chemicals could become less hazardous, thanks to a missing math formula

Discovery of how to measure surface viscosity of liquids could give machines more precise control over droplets

PURDUE UNIVERSITY

 

IMAGE: PURDUE RESEARCHERS HAVE FIGURED OUT A WAY TO CALCULATE SURFACE VISCOSITY JUST BY LOOKING AT A STRETCHED DROPLET AS IT STARTS TO BREAK. view more 

CREDIT: PURDUE UNIVERSITY IMAGES/BRAYDEN WAGONER AND OSMAN BASARAN

WEST LAFAYETTE, Ind. -- Drones and other aircraft effectively spray pesticides over miles of crops, but the method also can pollute the environment if wind carries the mist off-target.

One of the problems is that tiny droplets are hard for aerial crop sprayers, inkjet printers and a wide range of other machines to control. Purdue University engineers are the first to come up with the math formula that was missing to measure a key property of these droplets.

"There are many properties that affect how a droplet forms. One of those important properties is surface viscosity, which people have had a heck of a time trying to measure because they just didn't have the tools to do it," said Osman Basaran, Purdue's Burton and Kathryn Gedge Professor of Chemical Engineering.

Pesticides and other chemicals contain additives called surfactants. These surfactant molecules resist each other at a liquid's surface, giving rise to a sticky force called surface viscosity that can make the droplet smaller. The higher the surface viscosity, the more compact a droplet's shape.

Basaran and his students have figured out a way to calculate surface viscosity just by looking at how a droplet stretches. A picture taken of the stretched droplet as it starts to break gives the values to put into a simple math formula that provides the surface viscosity measurement.

The formula is described in a paper published in the journal Physical Review Letters. The discovery ends a decades-long race by researchers around the world to make surface viscosity measurable. Other co-authors on this paper include Hansol Wee, Brayden Wagoner and Pritish Kamat.

Not being able to measure exactly how much surface viscosity affects drop formation has put limits on making machines safer and more precise, said Basaran, who directs a center that works to resolve the science behind problems in manufacturing machinery.

Solutions provided by the center, called the Purdue Process Safety and Assurance Center, directly help partners in industries such as agriculture, health care and energy.

A better understanding of droplets and how to control them affects all those industries. Like crop spraying, inkjet printing in a factory produces tiny droplets that can get into the air and cause breathing problems.

More precise control of a liquid-like substance also could enhance a machine's performance, such as giving a 3D printer the ability to produce more reliable or detailed objects.

"A material with too high or too low surface viscosity can lead to bad outcomes in the manufacturing process. Knowing those measurements allows you to use different chemistries to make a material that doesn't lead to a surface viscosity that's going to result in a bad outcome," Basaran said.

Next, Basaran's team plans to incorporate this math formula into experiments for recommending new machine designs. The formula could also become a commercial instrument in the future, such as a smartphone app.

"This discovery opens up a lot of avenues for basic research that just weren't possible before," Basaran said.

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This research received no external funding.

ABSTRACT

Effects of surface viscosity on breakup of viscous threads

Hansol Wee, Brayden W. Wagoner, Pritish M. Kamat, and Osman A. Basaran,

Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, USA

DOI: 10.1103/PhysRevLett.124.204501

In addition to surface tension lowering and Marangoni stresses, surfactants also induce surface rheological effects when they deform against themselves at fluid interfaces. Because surface viscosities are functions of surfactant concentration, surface rheological stresses can compete with capillary, Marangoni, and bulk stresses in surfactant-laden free surface flows with breakup. To elucidate the effects of surface rheology, we examine the breakup of a Stokes thread covered with a monolayer of insoluble surfactant when either surfactants are convected away from the space-time singularity or diffusion is dominant. Surprisingly, in both limits, surface rheological effects always enter the dominant balance of forces and alter the thread's thinning rate. Moreover, if surfactants are convected away from the singularity, we provide an analytical expression for thinning rate that explicitly depends on surface rheological parameters, providing a simple route for measuring surface viscosity.

Undergrad-led study suggests light environment modifications could maximize productivity

CARL R. WOESE INSTITUTE FOR GENOMIC BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN

 

IMAGE: MAIZE (LEFT) AND MISCANTHUS (RIGHT) view more 

CREDIT: WEST PROJECT/UNIVERSITY OF ILLINOIS

CHAMPAIGN, Ill. -- The crops we grow in the field often form dense canopies with many overlapping leaves, such that young "sun leaves" at the top of the canopy are exposed to full sunlight with older "shade leaves" at the bottom. In order to maximize photosynthesis, resource-use efficiency, and yield, sun leaves typically maximize photosynthetic efficiency at high light, while shade leaves maximize efficiency at low light.

"However, in some of our most important crops, a maladaptation causes a loss of photosynthetic efficiency in leaves at the bottom of the canopy, which limits the plants' ability to photosynthesize and produce yields," said Charles Pignon, a former postdoctoral researcher at the University of Illinois. "In order to address this problem, it's important to know whether this is caused by leaves being older or exposed to a different light environment at the bottom of the canopy."

This question was answered in a recent study published in Frontiers in Plant Science, where researchers from the University of Illinois and the University of Oxford worked with maize and the bioenergy crop Miscanthus to find that the decline in the efficiency of leaves at the bottom of the canopy was not due to their age but to their altered light environment.

This work was conducted through the Illinois Summer Fellows (ISF) program. Launched in 2018, ISF allows undergraduate students to conduct plant science research alongside highly skilled scientists at Illinois. 2018 Fellows Robert Collison and Emma Raven worked with Pignon and Stephen Long, the Stanley O. Ikenberry Chair Professor of Plant Biology and Crop Sciences at Illinois, to confirm and better understand results from previous studies for Water Efficient Sorghum Technologies (WEST), a research project that aimed to develop bioenergy crops that produce more biomass with less water.

Photosynthesis is the natural process that plants use to convert sunlight into energy. Plants usually fall under the two main types of photosynthesis -- C3 and C4. The difference between these types is that C4 plants have a mechanism that concentrates carbon dioxide inside their leaves, allowing them to photosynthesize more efficiently. However, most plants, trees, and crops operate using the less efficient C3 photosynthesis.

Both sun and shade leaves contribute to photosynthetic carbon assimilation, producing the sugars that feed the plant and fuel yield. Therefore, lower canopy photosynthesis is an important process that affects the yield of the whole plant, with an estimated 50 percent of total canopy carbon gain contributed by shade leaves.

Previous studies of C3 plants have shown that shaded leaves are typically more efficient than sun leaves at low light intensities, meaning shaded leaves adapt to their low light environment. However, a previous study by Pignon and Long showed that this is not the case for all plants. The canopies of maize and Miscanthus, C4 crops that usually photosynthesize more efficiently than C3 crops, had shade leaves that were less photosynthetically efficient, suggesting a maladaptation in these important crops.

"Shade leaves receive very little light, so they usually become very efficient with low light use," said Pignon, now a plant physiologist at Benson Hill in St. Louis. "Essentially, they make the most of what little light they do receive. However, in the C4 crops we studied, shade leaves in these crops not only receive very little light, but they also use it less efficiently. It's a very costly maladaptation in crops that are otherwise highly productive -- hence our calling it an Achilles' heel."

With six to eight layers of leaves in our modern maize crop stands, most leaves are shaded and can account for half of the plant's growth during the critical phase of grain filling.

"In the previous study, researchers estimated that this maladaptation was causing a loss of 10 percent in potential canopy photosynthesis gain," said Raven, who recently graduated from Oxford with plans to pursue her doctorate. "There are essentially two potential reasons: the age of the leaves or the light conditions, so we investigated which factor was causing this inefficiency."

Collison and Raven, co-first authors of this newly published paper, collected data and analyzed the maximum quantum yield of photosynthesis -- the maximum efficiency with which light is used to assimilate carbon -- in leaves of the same chronological age but different light environments to discover the crops' Achilles' heel. This was achieved by comparing leaves of the same age in the center of plots of these species versus those on the sunlight southern edge of these plots. From this, they showed that the poor photosynthetic efficiency of these crops' lower leaves is caused by altered light conditions and not age.

"Maize and Miscanthus are both closely related to sugarcane and sorghum, so other C4 crops could potentially have this loss in photosynthetic efficiency caused by the light environment," explained Collison, who has also graduated from Oxford and may pursue graduate studies. "By finding the cause of this loss in efficiency, we can begin to look at potential solutions to this problem, modifying plants to improve their productivity."

Illinois Summer Fellows Program

The ISF program has cultivated an environment where the Fellows have the independence needed to develop as scientists while knowing that they have the support and encouragement of their supervisors. Fellows are paired with a scientist supervisor to assist them with a specific element of a project aimed to increase crops' photosynthetic and/or water-use efficiency. The program aims to provide a rewarding experience that helps students develop as scientists, and ultimately, to consider pursuing careers in plant biology.

"The opportunity to travel to another country and conduct meaningful research in a real-world field environment alongside mentors in their field is invaluable," said Long, who launched and directs the ISF program at the Carl R. Woese Institute for Genomic Biology. "At the end of their time at Illinois, our Fellows have expressed that this experience allowed them to contribute to the world and take back valuable skills they can apply in their future endeavors as innovators in the field of agriculture and beyond."

Collison reflects on his time at Illinois as an experience that not many students, especially so early in their career, get to take part in. "The chance to do any research so early in your career as a scientist is really exciting," he said. "Everyone we met-- including our supervisors and other scientists -- was always willing to help us."

Raven also shared her insights on the value of doing research at Illinois and what differences there may be in other academic or work settings. "When you are attending lectures or practical classes, you never quite get that feeling of true ownership of your own projects because you just follow whatever your professor tells you to do," Raven said. "But having ownership of this paper at Illinois is gratifying. It is also exciting to be a part of something that is bigger than us and will ultimately help farmers in other countries to grow food more sustainably."

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The ISF program is supported by Oxford University in England and the Realizing Increased Photosynthetic Efficiency (RIPE), an international research project led by Illinois that is engineering crops to be more productive by improving photosynthesis. It is supported by the Bill & Melinda Gates Foundation, the U.S. Foundation for Food and Agriculture Research (FFAR), and the U.K. Government's Department for International Development (DFID).

For mor

Bizarre saber-tooth predator from South America was no saber-tooth cat

UNIVERSITY OF BRISTOL

 

IMAGE: SKULLS AND LIFE RECONSTRUCTIONS OF THE MARSUPIAL SABER-TOOTH THYLACOSMILUS ATROX (LEFT) AND THE SABER-TOOTH CAT SMILODON FATALIS (RIGHT). view more 

CREDIT: STEPHAN LAUTENSCHLAGER

A new study led by researchers from the University of Bristol has shown that not all saber-tooths were fearsome predators.

Saber-tooth cats, such as the North American species Smilodon fatalis, are among the most iconic fossil animals with a reputation for being fierce predators. However, saber-tooths came in all shapes and sizes and nearly a hundred different saber-tooths are known to science so far.

Thylacosmilus atrox (which means 'terrible pouched knife') is a well-known animal that lived around five million years ago in Argentina.

A jaguar-sized marsupial, it is popularly known as the 'marsupial saber-tooth', compared with the sabertoothed cats elsewhere in the world, and it is often presented as a classic case of convergent evolution--where animals appear similar in form despite having very different evolutionary relationships (such as marsupial flying possums and placental flying squirrels - both of course being gliders rather than true fliers).

Thylacosmilus had huge, ever-growing canines, leading people to speculate that it was an even more vicious predator than the placental carnivores it superficially resembled such as Smilodon.

But was it really a fierce predator like the extinct placental saber-toothed cats, which seem to have been much like modern cats but with a different mode of killing their prey?

An international team of researchers, led by Professor Christine Janis from Bristol's School of Earth Sciences, have performed a series of studies on the skull and teeth of this animal and have come to a different conclusion. Their findings are published in the journal PeerJ.

Professor Janis said: "The title of this paper, 'An Eye for a Tooth', sums up how we think this animal has been perceived.

"It has impressive canines, for sure: but if you look at the whole picture of its anatomy, lots of things simply don't add up. For example, it just about lacks incisors, which big cats today use to get meat off the bone, and its lower jaws were not fused together.

"In addition, the canines of Thylacosmilus were different from the teeth of other saber-toothed mammals, being triangular in shape like a claw rather than flat like a blade."

A statistical study, comparing aspects of the skull and teeth of Thylacosmilus with both present-day big cats and a diversity of extinct saber-toothed cats, confirmed suspicions about the differences from its placental supposed counterparts.

Co-author Borja Figueirido of the University of Málaga (Spain) added: "The skull superficially looks rather like that of a saber-toothed placental.

"But if you actually quantify things, it becomes clear that Thylacosmilus' skull was different in many details from any known carnivorous mammal, past or present."

Detailed biomechanical studies comparing the skulls of Thylacosmilus and Smilodon, simulating performance under different conditions, were also revealing.

Stephan Lautenschlager from the University of Birmingham, the contributing author on the paper who performed these analyses, said: "Previous studies by other researchers have shown Thylacosmilus to have had a weaker bite than Smilodon.

"But what we can show is there was probably a difference in behaviour between the two species: Thylacosmilus' skull and canines are weaker in a stabbing action than those of Smilodon, but are stronger in a 'pull-back' type of action. This suggests that Thylacosmilus was not using its canines to kill with, but perhaps instead to open carcasses."

Finally, the other teeth of Thylacosmilus also pose problems for the interpretation of this animal as a cat-like predator, whether saber-toothed or not. Besides the puzzling lack of incisors, the molars are small, and did not wear down along the sides as seen in an animal feeding on meat.

Larisa DeSantis from Vanderbilt University (USA), who conducted a detailed dental study, added: "The molars tend to wear flat from the top, rather like you see in a bone crusher.

"But if you examine the detailed microwear on tooth surfaces, it's clear that it was eating soft food. Its wear is most similar to that of cheetahs which eat from fresh carcasses and suggests an even softer diet than fed to captive lions.

"Thylacosmilus was not a bone-crusher and may have instead specialised on internal organs."

Professor Janis said: "It's a bit of a mystery as to what this animal was actually doing but it's clear that it wasn't just a marsupial version of a saber-toothed cat like Smilodon.

"In addition to the differences in the skull and the teeth, it was also short-legged and stiff-backed, and lacked retractile claws, so it would have had difficulties in pursuing its prey, pouncing on it and holding on to it. I suspect it was some sort of specialised scavenger.

"It may have employed those canines to open carcasses and perhaps also used a big tongue to help extract the innards: other mammals that have lost the incisors, like walruses and anteaters, also have big tongues that they use in feeding."

When Thylacosmilus lived on the plains of Argentina five million years ago, it would have inhabited a very different type of ecosystem to any modern one. Then the big predators were huge flightless birds, the "terror birds" or phorusrachiformes, now all extinct. Life in the past may have been very different to the present day.

Borja Figueirido added: "In Africa today it's the mammals who are the killers and the big birds, like vultures, are the scavengers. But perhaps five million years ago in Argentina it was the other way around, and it was the mammals who were the scavengers."

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