Saturday, May 23, 2020

Madagascar copal: New dating for an Antropocene ancient resin

This material is not a semi-fossilized resin

UNIVERSITY OF BARCELONA

IMAGE: THE STUDY STATES THAT THE WELL-KNOWN MADAGASCAR COPAL IS NOT A SEMI-FOSSILIZED RESIN BUT A MATERIAL MADE DURING THE ANTROPOCENE. view more

CREDIT: XAVIER DELCLÒS (UNIVERSITY OF BARCELONA-IRBIO)

The known Madagascar copal is a more recent resin from what was thought -it has about a few hundred years- and trapped pieces in this material are not as palaeontological important as thought traditionally. This is one of the conclusions of the new article in the journal PLOS ONE, whose first author is Xavier Delclòs, professor at the Faculty of Earth Sciences and member of the Biodiversity Research Institute (IRBio) of the University of Barcelona.

The study states that the well-known Madagascar copal is not a semi-fossilized resin but a material made during the Antropocene, historical period in which human impact was extreme globally. The findings would require going over the described taxon during the last hundred and fifty years to avoid taxonomic mistakes and unprecise paleoenvironmental reconstructions, the study notes.

Other participants in this study, the first to describe the oldest age and geographical origin of the Madagascar copal, are Enrique Peñalver, from the Spanish Geological and Mining Institute (IGME), Voajanahary Ranaivosoa, from the University of Antananarivo (Madagascar) and Mónica M. Solórzano Kraemer, from the Senckenberg Research Institute (Frankfurt, Germany).

From Tanzania coasts to Indian markets

Known for hundreds of years, the Madagascar copal crossed the trade routes from Tanzania to China through the Indian Ocean and the Indian markets. Sold as incense at first, it became pricey due to its high value to make varnish. More recently, it was used as disinfectant -burnt in Madagascar houses- and it was sold to scientists and tourists for its high content of arthropods inside.

This ancient resin which was not completely fossilized comes from Hymenaea verrucosa trees, a fabacean that grows in the eastern coast of Madagascar, one of the most threatened and fragile ecosystems in the world.

Wrong dating for an ancient resin

According to the study, the scientific community studied the biological remains inside the copal, named bioinclusions, and dated these findings from a few tens to millions of years. However, the origin of the studied material was never found -it is not cited in any study-, and the exact age of the studied pieces was never proved.

"The correct dating of the copal, as an important factor for a planetological study, can influence all the following paleo-biological studies, such as those related to phylogeny, paleobiogeography, and paleoclimatology", notes Professor Xavier Delclòs, from the Department of Earth and Ocean Dynamics of the UB.

According to the study, some found species in the Madagascar copal -thought to be extinct- could be now in forest habitats that were not considered to be their natural habitats. This can explain the occasional presence of arthropod species inside this old resin and which are currently living in the area.

The study notes that any new described taxon after the Madagascar copal should be attached the dating of Carbon-14 for the studied sample (at least, the sample including the main piece or holotype). Also, museums with Malagasy copal specimen pieces should review the dating with the Carbon-14 system.

An Anthropocene resin to protect Malagasy biodiversity

The loss of biodiversity during the Anthropocene is a threat in different areas of the planet, especially in warm areas of biodiversity such as the island of Madagascar. This study shows the scientific value of the Madagascar copal as a source of biological and paleobiological information to study the loss of biodiversity during the Anthropocene in Malagasy areas which are important areas of threatened biodiversity.

"The Madagascar copal is a file of great scientific interest. It represents a part of the Malagasy biodiversity and ecosystem during historical periods and can contain extinct species due to the high rate of deforestation in the Red Island over the last three hundred years", note the authors. "If this intense deforestation continues at the current rate, it is likely for the preserved species in the resin of Hymenaea trees -together with historical entomological collections- to become the only knowledge reservoirs to do research on a part of the entomofauna of fragile tropical forests of Madagascar lowlands", conclude researchers.

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The European viper uses cloak-and-dazzle method to escape predators

by University of Jyväskylä

The European viper uses cloak-and-dazzle to escape predators — The viper's zig-zag pattern helps the snake remain undetected, it also provides a warning of the snake's dangerous defense and it can produce an illusionary effect that may hide the snake's movement as it flees. Credit: The University of Jyväskylä/Janne Valkonen

A study by researchers at the University of Jyväskylä demonstrate that the characteristic zig-zag pattern on a viper's back performs seemingly opposing functions during a predation event. At first, the zig-zag pattern helps the snake remain undetected. But upon exposure, it provides a conspicuous warning of the snake's dangerous defense. Most importantly the zig-zag can also produce an illusionary effect that may hide the snake's movement as it flees. The research, published in Animal Behaviour (2020), reveals how a single color pattern can have multiple effects during a predation event, thereby expanding the discussion on protective coloration and anti-predator adaptations.

Protective coloration is one of the simplest but most effective tools that prey species use to evade predators. Typically, different color patterns are useful at different stages of a predation event. Some color patterns are cryptic, obscuring the prey from being detected—think chameleons. Other patterns are aposematic, which blatantly advertise a warning to predators—think wasps. Finally, some patterns can produce optical illusions to startle or confuse predators and give the prey an escape opportunity—think zebras.

But a recent series of experiments, by a team headed by Janne Valkonen and Johanna Mappes at the University of Jyväskylä (Finland), suggests that European vipers (Vipera sp.) can achieve all three tricks with a single color pattern—their characteristic zig-zag.

At first, the zig-zag pattern helps the viper to hide. The researchers hid plasticine models of snakes with different color patterns along paths and noted how often they were detected by people walking the trail. Models with the zig-zag pattern were detected less often than plainly colored models. This is the first confirmation that the viper's zig-zag pattern provides a cryptic function. But even if the viper is detected, the zig-zag can still work its magic—instead of hiding the snake, the pattern now functions to make it more obvious. Previous research has already established that the pattern warns predators about the snake's dangerous bite.

The rapid flickering from the zigs and zags of a fleeing snake can produce a a 'flicker-fusion effect' to mammalian predators

The most significant contribution from Dr. Janne Valkonen's study deals with a particular class of illusion generated by the zig-zag pattern. Just as a rapid series of still pictures can produce a smooth animation, the rapid flickering from the zigs and zags of a fleeing snake can produce the appearance of a solid shape.

The team measured the speed of fleeing snakes and calculated the flicker rate of the zig-zag. To an observer, a rapidly changing stimulus (such as a moving zig-zag, or spinning helicopter blade) is perceived as continuous if the flicker rate exceeds a threshold in the visual system.

The researchers found that the zig-zag moved quickly enough to produce such a flicker-fusion effect to mammalian predators, although the quicker eyes of a raptor weren't fooled. The effect of this illusion may change the appearance of the moving snake, making it harder to catch. So like a skilled illusionist, the viper hides by revealing.

The viper's zig-zag seems to be a simple pattern, but it is a masterful illusion that can hide, reveal, and paradoxically achieve both at the same time. Similarly, this research resolves theoretical tensions between apparently opposing functions of color patterns—that is, crypsis and aposematism seem mutually exclusive: One is meant to blend an animal into its surroundings, the other to make it stand out.

However, through the magic of movement and optics, both functions can be gained through the same pattern at different stages in the predation sequence. Furthermore, the one-to-many aspect of the zig-zag to its antipredator functions implies a far broader scope for the evolution of color patterns and antipredator adaptations than simple one pattern-to-one function relations.Toad disguises itself as deadly viper to avoid attack

More information: Janne K. Valkonen et al, Protective coloration of European vipers throughout the predation sequence, Animal Behaviour (2020). DOI: 10.1016/j.anbehav.2020.04.005

Journal information: Animal Behaviour

Provided by University of Jyväskylä

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US regulators approve new type of contraceptive gel

by Linda A. Johnson

U.S. regulators on Friday approved a birth control gel that works in a new way to prevent pregnancy.

Phexxi—pronounced FECK'-see—comes in an applicator that women insert before intercourse. The gel made by San Diego-based Evofem Biosciences contains lactic acid, citric acid and potassium bitartrate, all of which are common food additives.

The new gel has some similarities to spermicides, which block the entrance to the cervix and slow sperm down. But Phexxi works differently.

The vagina's pH—a measure of acidity—is usually in the range of 3.5 to 4.5, the level needed to maintain healthy bacteria. Sperm typically raise that to a more hospitable level of 7 to 8. Phexxi keeps it in the usual acidic range, killing the sperm.

Unlike some other contraceptives, it only needs to be taken shortly before sex and it doesn't contain hormones, which can cause side effects some women can't tolerate.

The company said Phexxi will have a list price of $250 to $275 for a box of 12 without insurance.

In a study of 1,400 women aged 18 to 35, Phexxi was about 86% effective on average over seven menstrual cycles and a total of more than 34,000 acts of intercourse. That's a bit better than condoms, spermicides and other on-demand contraceptives.

The Food and Drug Administration approved Phexxi only as a contraceptive, but Evofem said its testing indicates the gel also reduces the risk of infection by gonorrhea and chlamydia. The company plans to start a large patient study by year's end, then submit results to the agency for approval as a second product, for preventing those infections.

Evofem would market it under a different name, and likely could tout Phexxi as both birth control and a way of helping to help prevent at least some sexually transmitted diseases.

Supercomputer model simulations reveal cause of Neanderthal extinction

INSTITUTE FOR BASIC SCIENCE

IMAGE: COMPUTER SIMULATIONS OF POPULATION DENSITY OF NEANDERTHALS (LEFT) AND HOMO SAPIENS (RIGHT) 43,000 YEARS AGO (UPPER) AND 38,000 YEARS AGO (LOWER). ORANGE (GREEN) CIRCLES INDICATE ARCHEOLOGICAL SITES OF NEANDERTHALS (HOMO... view more

CREDIT: IBS

Climate scientists from the IBS Center for Climate Physics discover that, contrary to previously held beliefs, Neanderthal extinction was neither caused by abrupt glacial climate shifts, nor by interbreeding with Homo sapiens. According to new supercomputer model simulations, only competition between Neanderthals and Homo sapiens can explain the rapid demise of Neanderthals around 43 to 38 thousand years ago.

Neanderthals lived in Eurasia for at least 300,000 years. Then, around 43 to 38 thousand years ago they quickly disappeared off the face of the earth, leaving only weak genetic traces in present-day Homo sapiens populations. It is well established that their extinction coincided with a period of rapidly fluctuating climatic conditions, as well as with the arrival of Homo sapiens in Europe. However, determining which of these factors was the dominant cause, has remained one of the biggest challenges of evolutionary anthropology.

To quantify which processes played a major role in the collapse of Neanderthal populations one needs to use mathematical models that can realistically simulate the migration of Neanderthals and Homo sapiens, their interactions, competition and interbreeding in a changing climatic environment. Such models did not exist previously.

In a new paper published in the journal Quaternary Science Review, Axel Timmermann, Director of the IBS Center for Climate Physics at Pusan National University, presents the first realistic computer model simulation of the extinction of Neanderthals across Eurasia (Figure 1). The model which is comprised of several thousands of lines of computer code and is run on the IBS supercomputer Aleph, solves a series of mathematical equations that describe how Neanderthals and Homo sapiens moved in a time-varying glacial landscape and under shifting temperature, rainfall and vegetation patterns. In the model both hominin groups compete for the same food resources and a small fraction is allowed to interbreed. The key parameters of the model are obtained from realistic climate computer model simulations, genetic and demographic data.

"This is the first time we can quantify the drivers of Neanderthal extinction," said Timmermann. "In the computer model I can turn on and off different processes, such as abrupt climate change, interbreeding or competition" he said. By comparing the results with existing paleo-anthropological, genetic and archeological data (e.g. Figure 1), Timmermann demonstrated that a realistic extinction in the computer model is only possible, if Homo sapiens had significant advantages over Neanderthals in terms of exploiting existing food resources. Even though the model does not specify the details, possible reasons for the superiority of Homo sapiens could have been associated with better hunting techniques, stronger resistance to pathogens or higher level of fecundity.

What exactly caused the rapid Neanderthal demise has remained elusive for a long time. This new computer modeling approach identifies competitive exclusion as the likely reason for the disappearance of our cousins. "Neanderthals lived in Eurasia for the last 300,000 years and experienced and adapted to abrupt climate shifts, that were even more dramatic than those that occurred during the time of Neanderthal disappearance. It is not a coincidence that Neanderthals vanished just at the time, when Homo sapiens started to spread into Europe" says Timmermann. He adds "The new computer model simulations show clearly that this event was the first major extinction caused by our own species".

A research team at the IBS Center for Climate Physics is now improving the computer model to also include megafauna and implement more realistic climate forcings. "This is a new field of research in which climate scientists can interact with mathematicians, geneticists, archeologists and anthropologists", said Axel Timmermann.

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Bumblebees speed up flowering by piercing plants

by Peter Rüegg, ETH Zurich

When pollen is in short supply, bumblebees damage plant leaves in a way that accelerates flower production, as an ETH research team headed up by Consuelo De Moraes and Mark Mescher has demonstrated.

Spring has sprung earlier than ever before this year, accompanied by temperatures more typical of early summertime. Many plants were already in full bloom by mid-April, about three to four weeks earlier than normal. These types of seasonal anomalies are becoming increasingly frequent due to climate change, and the resulting uncertainty threatens to disrupt the timing of mutualistic relationships between plants and their insect pollinators.

A research team led by ETH Professors Consuelo De Moraes and Mark Mescher has now discovered that one peculiar bumblebee behavior may help to overcome such challenges by facilitating coordination between the bees and the plants they pollinate. The group has found that bumblebee workers use their mouth parts to pinch into the leaves of plants that haven't flowered yet, and that the resulting damage stimulates the production of new flowers that bloom earlier than those on plants that haven't been given this "nudge."

Credit: ETH Zurich

Their study has just been published in the journal Science. "Previous work has shown that various kinds of stress can induce plants to flower, but the role of bee-inflicted damage in accelerating flower production was unexpected," Mescher says.

Surprising behavior from bumblebees

The researchers first noticed the behavior during other experiments being undertaken by one of the authors, Foteini Pashalidou: pollinators were biting the leaves of test plants in the greenhouse. "On further investigation, we found that others had also observed such behaviors, but no one had explored what the bees were doing to the plants or reported an effect on flower production," Mescher explains.

Following up on their observations, the ETH researchers devised several new laboratory experiments, and also conducted outdoor studies using commercially available bumblebee colonies—typically sold for the pollination of agricultural crops—and a variety of plant species.

Based on their lab studies, the researchers were able to show that the bumblebees' propensity to damage leaves has a strong correlation with the amount of pollen they can obtain: Bees damage leaves much more frequently when there is little or no pollen available to them. They also found that damage inflicted on plant leaves had dramatic effects on flowering time in two different plant species. Tomato plants subjected to bumblebee biting flowered up to 30 days earlier than those that hadn't been targeted, while mustard plants flowered about 14 days earlier when damaged by the bees.

"The bee damage had a dramatic influence on the flowering of the plants—one that has never been described before," De Moraes says. She also suggests that the developmental stage of the plant when it is bitten by bumblebees may influence the degree to which flowering is accelerated, a factor the investigators plan to explore in future work.

The researchers tried to manually replicate the damage patterns caused by bees to see if they could reproduce the effect on flowering time. But, while this manipulation did lead to somewhat earlier flowering in both plant species, the effect was not nearly as strong as that caused by the bees themselves. This leads De Moraes to suggest that some chemical or other cue may also be involved. "Either that or our manual imitation of the damage wasn't accurate enough," she says. Her team is currently trying to identify the precise cues responsible for inducing flowering and characterizing the molecular mechanisms involved in the plant response to bee damage.

Phenomenon also observed in the field

The ETH research team was also able to observe the bees' damaging behavior under more natural conditions, with doctoral student Harriet Lambert leading follow-up studies on the rooftops of two ETH buildings in central Zurich. In these experiments, the researchers again observed that hungry bumblebees with insufficient pollen supplies frequently damaged the leaves of non-blooming plants. But the damaging behavior was consistently reduced when the researchers made more flowers available to the bees.

Furthermore, it was not only captive-bred bumblebees from the researchers' experimental colonies that damaged plant leaves. The investigators also observed wild bees from at least two additional bumblebee species biting the leaves of plants in their experimental plots. Other pollinating insects, such as honeybees, did not exhibit such behavior, however: they seemed to ignore the non-flowering plants entirely, despite being frequent visitors to nearby patches of flowering plants.

Delicate balance starting to tip

"Bumblebees may have found an effective method of mitigating local shortages of pollen," De Moraes says. "Our open fields are abuzz with other pollinators, too, which may also benefit from the bumblebees' efforts." But it remains to be seen whether this mechanism is sufficient to overcome the challenges of changing climate. Insects and flowering plants have evolved together, sharing a long history that strikes a delicate balance between efflorescence and pollinator development. However, global warming and other anthropogenic environmental changes have the potential to disrupt the timing of these and other ecologically important interactions among species. Such rapid environmental change could result in insects and plants becoming increasingly out of sync in their development, for example. "And that's something from which both sides stand to lose," Mescher says.'Bee' thankful for the evolution of pollen

More information: Foteini G. Pashalidou et al. Bumble bees damage plant leaves and accelerate flower production when pollen is scarce, Science (2020). DOI: 10.1126/science.aay0496

Journal information: Science

Provided by ETH Zurich

When do plants help or hinder each other?

by Universitaet Tübingen

When plants grow close together, each individual plant has less chance of doing well—at least, that was the accepted wisdom in environmental research. Now Dr. Ruichang Zhang and Professor Katja Tielbörger from the Institute of Evolution and Ecology at the University of Tübingen are challenging that principle. Their investigation of the combined effects of environmental stress and competition on plants has led them to develop a new theoretical model suggesting that plants can 'help' each other out. The researchers were able to confirm their model predictions in detail in an experiment with real plants. Their study has been published in the latest Nature Communications.

Competition leads to fewer resources being available for each individual organism. "If the crowding becomes too much, this can even lead to the death of individual plants," says Katja Tielbörger. Yet there are many empirical studies that show that plants can also facilitate each other. Tielbörger says this is often the case when plants grow under stressful conditions—for instance, when the soil is saline or the temperatures are high. "When it's very hot, for example, large plants can provide shade, which in turn can create better conditions for smaller plants that grow under the canopy of the larger ones," she adds. It seems logical that such positive interactions are most important when environmental stress is high. It has therefore long been postulated that facilitation in bad times may turn into competition when conditions are good.

Experiments with Arabidopsis

The two Tübingen researchers have now combined the density and stress factors in a novel mathematical model. "This showed that under intense stress, it can be advantageous to have many neighbors and that competition only occurs at very high densities," Tielbörger sums up. From the point of view of the individual plant, the relationship between density and thriving is like a hump-shaped curve. The Tübingen researchers simulated the model conditions in an experiment using Arabidopsis thaliana or thale cress—the plant commonly used as a model in molecular biology. "The experiment confirmed all the predictions arising from our model," says Tielbörger. For example, the plants suffered considerably less from salt stress when they had many neighbors. And they suffered from competition by neighbors only when they were not under stress.

Because of the complexity of ecological systems, models are a popular method for better understanding nature. Tielbörger says it is remarkable to find such a close match between theory and reality in ecological research: "This shows how robust and universally valid our actually quite simple model is." The model may help to better predict the response of plants to stress—such as increased heat and drought—which are to be expected as the climate changes.Hormone keys plant growth or stress tolerance, but not both

More information: Ruichang Zhang et al. Density-dependence tips the change of plant–plant interactions under environmental stress, Nature Communications (2020). DOI: 10.1038/s41467-020-16286-6

Journal information: Nature Communications

Provided by Universitaet Tübingen

Researchers create global arsenic-in-groundwater maps to highlight threats

by Bob Yirka , Phys.org

Modeled probability of arsenic concentration in groundwater exceeding 10 µg per liter (red: high probability, blue: low probability). Credit: Joel Podgorski, Michael Berg, Eawag

A pair of researchers at the Swiss Federal Institute of Aquatic Science and Technology has created a global map that highlights areas where there are likely dangerous levels of arsenic in groundwater. In their paper published in the journal Science, Joel Podgorski and Michael Berg describe combining data from a variety of sources to train a machine learning algorithm to highlight possible hot spots on a global map. Yan Zheng, with Southern University of Science and Technology has published a Perspective piece outlining the work by the research pair in the same journal issue.

The current pandemic has captured the attention of the world, and for good reason. But other threats continue to put millions of people at risk. One of these, as Zheng notes, is arsenic consumption. Commonly known as a type of poison used to kill rivals, arsenic is a metalloid that, when consumed, can cause serious medical problems and, of course, death. It is also a chemical element that is commonly found in soil and rocks. In some cases, conditions exist that allow arsenic to make its way into groundwater, where it can be pulled up and consumed, putting people at risk.

Scientists have been aware of the problem of arsenic poisoning groundwater in such places as Argentina, Bangladesh and Vietnam. The WHO is also aware of the problem—they have set a concentration of 10 micrograms per liter as a safety limit in consumable water. In this new effort, Podgorski and Berg, an environmental scientist and hydrologist respectively, suspected that there are likely more hotspots than are currently known, so they set themselves the task of revealing likely hotspots around the world by analyzing vast amounts of data.

Play

https://phys.org/news/2020-05-global-arsenic-in-groundwater-highlight-threats.html

Modeled probability of arsenic concentration in groundwater exceeding 10 µg per liter (red: high probability, blue: low probability). Credit: Joel Podgorski, Michael Berg, Eawag

The work involved assembling data from over 80 studies and then using a machine learning algorithm that processed the data and made estimates on the likelihood of arsenic levels in groundwater for 1-km2-patches covering the entire globe. They then used the predictions to create a map showing arsenic threat levels. The map showed that up to 220 million people around the globe may be at risk of drinking water contaminated with dangerous levels of arsenic.

Play

https://phys.org/news/2020-05-global-arsenic-in-groundwater-highlight-threats.html

Modeled probability of arsenic concentration in groundwater exceeding 10 µg per liter (red: high probability, blue: low probability). Credit: Joel Podgorski, Michael Berg, Eawag

River-groundwater hot spot for arsenic

More information: Joel Podgorski et al. Global threat of arsenic in groundwater, Science (2020). DOI: 10.1126/science.aba1510

Environmentalists suggest COVID-19 could represent a new opportunity for a more diverse future

by Bob Yirka , Phys.org

tropical plants — Credit: CC0 Public Domain

A team of environmental researchers at the Australian Rivers Institute–Coast & Estuaries, School of Environment and Science, Griffith University, is suggesting in a Letters piece in the journal Science that the COVID-19 pandemic could represent a new opportunity for a more diverse future—they suggest that with proper planning, we could use what has been learned from the global lockdown to improve global biodiversity.

As the global pandemic has kept millions of people the world over isolating in their homes, nature has reacted. Reports of wild animals roaming city streets and small towns alike have made headlines. Also, the air has become cleaner, and many cities have become quiet. Such changes have served as a reminder that humans are not the sole residents of planet Earth.

In their paper, the team in Australia suggests that the changes we have observed might be presenting the world with a new opportunity to alter the ways that governments and environmentalists approach the issue of diversification as we move into a post-pandemic world. They note that history has shown that dramatic world events can lead to change—the Chernobyl meltdown in Ukraine, for example, led to humans abandoning huge swaths of land, allowing nature to take its course. The result has been the creation of a very large wilderness area now designated as an ecological reserve.

Another example was the Columbian conflict, which, for years, served as a protection zone for plants and animals because humans were afraid to venture into areas occupied by armed rebels. They suggest the lockdown effect could have a similar impact if long-term strategies are put in place to preserve the positive changes that nature has made, and to expand on them to increase biodiversity in other places.

The key, they claim, is for legislation protecting areas where biodiversity is present and to push for more areas to join them. They also note that the lockdown has coaxed people into rethinking some of their consumer habits—and maybe to changing some as the pandemic ends. They argue that the pandemic could represent a tipping-point in how the human race views the planet. This could be a time for development of new strategies, they suggest, and to implement them—to tip the balance in favor of a more diverse, environmentally friendly planet.Review study shows social interaction a major factor in both morbidity and mortality

More information: Jennifer Sills et al. COVID-19 recovery can benefit biodiversity, Science (2020). DOI: 10.1126/science.abc1430

Journal information: Science

Discovery about the edge of fusion plasma could help realize fusion power

by John Greenwald, Princeton Plasma Physics Laboratory

MAY 22, 2020

PPPL physicist Ammar Hakim, left, and graduate student Noah Mandell with figures from Mandell's paper showing the first computer simulations of kinetic plasma turbulence near the edge of fusion devices that can account for fluctuations of magnetic field lines. Credit: Elle Starkman/PPPL Office of Communications and Krell Institute; composite by Elle Starkman.

A major roadblock to producing safe, clean and abundant fusion energy on Earth is the lack of detailed understanding of how the hot, charged plasma gas that fuels fusion reactions behaves at the edge of fusion facilities called "tokamaks." Recent breakthroughs by researchers at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have advanced understanding of the behavior of the highly complex plasma edge in doughnut-shaped tokamaks on the road to capturing the fusion energy that powers the sun and stars. Understanding this edge region will be particularly important for operating ITER, the international fusion experiment under construction in France to demonstrate the practicality of fusion energy.

First-of-a-kind finding

Among the first-of-a-kind findings has been the discovery that accounting for the turbulent fluctuations in the magnetic fields that confine the plasma that fuels fusion reactions can significantly reduce the turbulent particle flux near the plasma edge. Computer simulations show that the net particle flux can go down by as much as 30 percent, despite the fact that the average magnitude of turbulent particle density fluctuation goes up by 60 percent—indicating that even though the turbulent density fluctuations are more virulent, they are moving particles out of the device less effectively.

Researchers have developed a specialized code called "Gkeyll"—pronounced just like "Jekyll" in Robert Louis Stevenson's "The Strange Case of Dr. Jekyll and Mr. Hyde"—that makes these simulations feasible. The mathematical code, a form of modeling called "gyrokinetics," simulates the orbiting of plasma particles around the magnetic field lines at the edge of a fusion plasma.

"Our recent paper summarizes the Gkeyll group's efforts in the area of gyrokinetic simulation," said PPPL physicist Ammar Hakim, lead author of a Physics of Plasmas paper that provides an overview of the group's achievements, based on an invited talk he gave at the American Physical Society's Division of Plasma Physics (APS-DPP) conference last Fall. The research, coauthored by scientists from six institutions, adapts a state-of-the-art algorithm to the gyrokinetic system to develop the "key numerical breakthroughs needed to provide accurate simulations," Hakim said.

Worldwide effort

Such breakthroughs are part of the worldwide effort to grasp the science behind the production of fusion reactions on Earth. Fusion reactions combine light elements in the form of plasma—the hot, charged state of matter composed of free electrons and atomic nuclei that makes up 99 percent of the visible universe—to generate massive amounts of energy that could provide a virtually inexhaustible supply of power to generate electricity for humanity.

Noah Mandell, a graduate student in the Princeton University Program in Plasma Physics, built on the team's work to develop the first gyrokinetic code able to handle magnetic fluctuations in what is called the plasma scrape-off layer (SOL) at the edge of tokamak plasmas. The British Journal of Plasma Physics has published andhighlighted his report as a featured article .

Mandell explores how blob-like plasma turbulence bends magnetic field lines, leading to the dynamics of "dancing field lines." He finds that field lines usually move smoothly but when dancing can abruptly reconfigure into reconnection events that cause them to converge and violently snap apart.

Mandell's findings are best described as "proof-of-concept" with regard to the magnetic fluctuations, he said. "We know there are more physical effects that need to be added to the code for detailed comparisons with experiments, but already the simulations are showing interesting properties near the plasma edge," he said. "The ability to handle bending of the magnetic field lines will also be essential for future simulations of edge localized modes (ELMs), which we would like to do better to understand the bursts of heat they cause that must be controlled to prevent tokamak damage."

Very challenging

What makes this finding unique is that previous gyrokinetic codes have simulated SOL blobs but assumed that the field lines were rigid, Mandell noted. Extending a gyrokinetic code to calculate the movement of magnetic fields lines is computationally very challenging, requiring special algorithms to ensure that two large terms balance each other to an accuracy of better than 1 part in a million.

Moreover, while codes that model turbulence in the core of the tokamak can include magnetic fluctuations, such codes cannot simulate the SOL region. "The SOL requires specialized codes like Gkeyll that can handle much larger plasma fluctuations and interactions with the walls of the reactor," Mandell said.

Future steps for the Gkeyll group will include investigating the precise physical mechanism that affects the dynamics of the plasma edge, an effect likely connected to the bending field lines. "This work provides stepping stones that I think are very important," Hakim said. "Without the algorithms that we made, these findings would be very difficult to apply to ITER and other machines."

New explanation for sudden collapses of heat in plasmas can help create fusion energy on Earth

More information: N. R. Mandell et al, Electromagnetic full- gyrokinetics in the tokamak edge with discontinuous Galerkin methods, Journal of Plasma Physics (2020).

DOI: 10.1017/S0022377820000070

Does MRI have an environmental impact?

Gadolinium found in elevated amounts near water treatment plants in Tokyo rivers

TOKYO METROPOLITAN UNIVERSITY

NEWS RELEASE 23-MAY-2020

IMAGE: SAMPLES WERE TAKEN ALONG RIVERS AROUND TOKYO. MEASUREMENTS OF RARE EARTH ELEMENT QUANTITIES INDICATE A CLEARLY ELEVATED AMOUNT OF GADOLINIUM COMPARED TO THAT IN NATURAL SHALE. view more

CREDIT: TOKYO METROPOLITAN UNIVERSITY

Tokyo, Japan - Researchers from Tokyo Metropolitan University have surveyed the amount of gadolinium found in river water in Tokyo. Gadolinium is contained in contrast agents given to patients undergoing medical magnetic resonance imaging (MRI) scans, and it has been shown in labs to become toxic when exposed to ultraviolet rays. The researchers found significantly elevated levels, particularly near water treatment plants, highlighting the need for new public policy and removal technologies as MRI become even more commonplace.

Modern medicine owes a lot to magnetic resonance imaging (MRI). Doctors can see tumors, inflammation and hemorrhaging deep inside the human body without the need for invasive surgery; unlike CT scans, patients are also not exposed to any ionizing radiation. Its many benefits have meant that MRI machines are now more wide-spread than ever. For example, in 1995, Japan had 6.12 machines per million residents; in 2017, it had 55.21, the highest number per million in the world.

But it might not be all good news. MRI imaging is often carried out after patients are injected with a contrast agent which makes features inside the body clearer in scans. It contains gadolinium, an originally toxic rare earth element that is rendered safe for medical use by binding it to a chelation agent, making it unreactive. After completing its task, 98% of the compound is expelled from a patient's body within 24 hours in the urine and makes its way through the wastewater system. Common wastewater treatment plants cannot remove it, so it passes directly into the environment, albeit in small quantities. On exposure to UV light, lab experiments have shown that it may transform back into a toxic state. This makes it vital to track how much gadolinium finds its way into the environment.

Thus, a team led by Professor Kazumasa Inoue of Tokyo Metropolitan University set out to measure how much gadolinium was being released into rivers in Tokyo. They took samples from a number of locations along the many major rivers of the city. Correcting for the amounts expected in natural shale, they carried out a broad survey of rare earths using mass spectrometry and found a significant elevation in the amount of gadolinium in the water. Importantly, they noticed large spikes in the amounts depending on proximity to water treatment plants. These findings are in agreement with previous work for samples taken inside a treatment plant on the River Weser, Germany.

It should be remembered that the reason why gadolinium is released in the first place is that a patient's kidneys safely pass it from the body. This means that, for the most part, it is also non-reactive in the environment. But as more MRI machines are installed to cater to an ageing population with more healthcare needs, the research team noted that new public policy and the development of new treatment techniques are vital to mitigating the environmental impact of this well-established, lifesaving medical technology.

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