Plasma flow near sun's surface explains sunspots, other solar phenomena

Sunspots on sun's surface

For 400 years people have tracked sunspots, the dark patches that appear for weeks at a time on the sun's surface. They have observed but been unable to explain why the number of spots peaks every 11 years.

A University of Washington study published this month in the journal Physics of Plasmas proposes a model of plasma motion that would explain the 11-year sunspot cycle and several other previously mysterious properties of the sun.

"Our model is completely different from a normal picture of the sun," said first author Thomas Jarboe, a UW professor of aeronautics and astronautics. "I really think we're the first people that are telling you the nature and source of solar magnetic phenomena -- how the sun works."

The authors created a model based on their previous work with fusion energy research. The model shows that a thin layer beneath the sun's surface is key to many of the features we see from Earth, like sunspots, magnetic reversals and solar flow, and is backed up by comparisons with observations of the sun.

"The observational data are key to confirming our picture of how the sun functions," Jarboe said.

In the new model, a thin layer of magnetic flux and plasma, or free-floating electrons, moves at different speeds on different parts of the sun. The difference in speed between the flows creates twists of magnetism, known as magnetic helicity, that are similar to what happens in some fusion reactor concepts.

"Every 11 years, the sun grows this layer until it's too big to be stable, and then it sloughs off," Jarboe said. Its departure exposes the lower layer of plasma moving in the opposite direction with a flipped magnetic field.

When the circuits in both hemispheres are moving at the same speed, more sunspots appear. When the circuits are different speeds, there is less sunspot activity. That mismatch, Jarboe says, may have happened during the decades of little sunspot activity known as the "Maunder Minimum."

"If the two hemispheres rotate at different speeds, then the sunspots near the equator won't match up, and the whole thing will die," Jarboe said.

"Scientists had thought that a sunspot was generated down at 30 percent of the depth of the sun, and then came up in a twisted rope of plasma that pops out," Jarboe said. Instead, his model shows that the sunspots are in the "supergranules" that form within the thin, subsurface layer of plasma that the study calculates to be roughly 100 to 300 miles (150 to 450 kilometers) thick, or a fraction of the sun's 430,000-mile radius.

"The sunspot is an amazing thing. There's nothing there, and then all of a sudden, you see it in a flash," Jarboe said.

The group's previous research has focused on fusion power reactors, which use very high temperatures similar to those inside the sun to separate hydrogen nuclei from their electrons. In both the sun and in fusion reactors the nuclei of two hydrogen atoms fuse together, releasing huge amounts of energy.

The type of reactor Jarboe has focused on, a spheromak, contains the electron plasma within a sphere that causes it to self-organize into certain patterns. When Jarboe began to consider the sun, he saw similarities, and created a model for what might be happening in the celestial body.

"For 100 years people have been researching this," Jarboe said. "Many of the features we're seeing are below the resolution of the models, so we can only find them in calculations."

Other properties explained by the theory, he said, include flow inside the sun, the twisting action that leads to sunspots and the total magnetic structure of the sun. The paper is likely to provoke intense discussion, Jarboe said.

"My hope is that scientists will look at their data in a new light, and the researchers who worked their whole lives to gather that data will have a new tool to understand what it all means," he said.

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Antimicrobial resistance is drastically rising

Chickens

The world is experiencing unprecedented economic growth in low- and middle-income countries. An increasing number of people in India, China, Latin America and Africa have become wealthier, and this is reflected in their consumption of meat and dairy products. In Africa, meat consumption has risen by more than half; in Asia and Latin America it is up by two-thirds.

To meet this growing demand, animal husbandry has been intensified, with among other things, an increased reliance on the use of antimicrobials. Farmers use antimicrobials to treat and prevent infections for animals raised in crowded conditions but these drugs are also used to increase weight gain, and thus improve profitability.

This excessive and indiscriminate use of antimicrobials has serious consequences: the proportion of bacteria resistant to antimicrobials is rapidly increasing around the world. Drugs are losing their efficacy, with important consequences for the health of animals but also potentially for humans.

Mapping resistance hotspots

Low- and middle income countries have limited surveillance capacities to track antimicrobial use and resistance on farms. Antimicrobial use is typically less regulated and documented there than in wealthy industrialized countries with established surveillance systems.

The team of researchers led by Thomas Van Boeckel, SNF Assistant Professor of Health Geography and Policy at ETH Zurich, has recently published a map of antimicrobial resistance in animals in low- and middle-income countries in the journal Science.

The team assembled a large literature database and found out where, and in which animals species resistance occurred for the common foodborne bacteria Salmonella, E. coli, Campylobacter and Staphylococcus.

According to this study, the regions associated with high rates of antimicrobial resistance in animals are northeast China, northeast India, southern Brazil, Iran and Turkey. In these countries, the bacteria listed above are now resistant to a large number of drug that are used not only in animals but also in human medicine. An important finding of the study is that so far, few resistance hotspots have emerged in Africa with the exception of Nigeria and the surroundings of Johannesburg.

The highest resistance rates were associated with the antimicrobials most frequently used in animals: tetracyclines, sulphonamides, penicillins and quinolones. In certain regions, these compounds have almost completely lost their efficacy to treat infections.

Alarming trend in multi-drug resistance

The researchers introduced a new index to track the evolution of resistance to multiple drugs: the proportion of drugs tested in each region with resistance rates higher than 50%. Globally, this index has almost tripled for chicken and pigs over the last 20 years. Currently, one third of drugs fail 50% of the time in chicken and one quarter of drug fail in 50% of the time in pigs.

"This alarming trend shows that the drugs used in animal farming are rapidly losing their efficacy," Van Boeckel says. This will affect the sustainability of the animal industry and potentially the health of consumers.

It is of particular concern that antimicrobial resistance is rising in developing and emerging countries because this is where meat consumption is growing the fastest, while access to veterinary antimicrobials remains largely unregulated. "Antimicrobial resistance is a global problem. There is little point in making considerable efforts to reduce it on one side of the world if it is increasing dramatically on the other side," the ETH researcher says.

Input from thousands of studies

For their current study, the team of researchers from ETH, Princeton University and the Free University of Brussels gathered thousands of publications as well as unpublished veterinary reports from around the world. The researchers used this database to produce the maps of antimicrobial resistance.

However, the maps do not cover the entire research area; there are large gaps in particular in South America, which researchers attribute to a lack of publicly available data. "There are hardly any official figures or data from large parts of South America," says co-author and ETH postdoctoral fellow Joao Pires. He said this surprised him, as much more data is available from some African countries , despite resources for conducting surveys being more limited than in South America.

Open-access web platform

The team has created an open-access web platform resistancebank.org to share their findings and gather additional data on resistance in animals. For example, veterinarians and state-authorities can upload data on resistance in their region to the platform and share it with other people who are interested.

Van Boeckel hopes that scientists from countries with more limited resources for whom publishing cost in academic journal can be a barrier will be able to share their findings and get recognition for their work on the platform. "In this way, we can ensure that the data is not just stuffed away in a drawer" he says, "because there are many relevant findings lying dormant, especially in Africa or India, that would complete the global picture of resistance that we try to draw in this first assessment. The platform could also help donors to identify the regions most affected by resistance in order to be able to finance specific interventions.

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Researchers revolutionize 3D printed products with data-driven design method

Additive manufacturing (AM), also known as three-dimensional printing, is a process that fabricates parts in a layer-by-layer manner by adding and processing materials. Advancements in AM technology have enabled the processing of a wide range of materials to create products in varying scales which span from medical implants to aircraft engine parts. These products, which can be rich in shape, material, hierarchical and functional complexities, offer high potential to revolutionize existing product development processes.

However, it can be a difficult process to fully realize the potential of AM's unique capabilities for product development as it requires product designers to change their design mindsets.

In conventional manufacturing processes, the main task for designers is tailoring their designs to eliminate manufacturing difficulties and minimize costs. On the contrary, AM has fewer manufacturing constraints while offering designers with much more design freedom to explore. Therefore, designers must search for optimal design solutions out of millions of design alternatives that are different in geometry, topology, structure, and material. This can be a tedious task with current design methods and computer-aided design (CAD) tools due to the lack of ability to rapidly explore and exploit such a high dimensional design space.

To address this issue, researchers from Digital Manufacturing and Design (DManD) Centre from the Singapore University of Technology and Design (SUTD) proposed a holistic approach that applies data-driven methods in design search and optimization at successive stages of a design process for AM products.

First, they used simple and computationally inexpensive surrogate models in the design exploration process to approximate and replace complex high-fidelity engineering analysis models for rapidly narrowing down the high-dimensional design space. Next, they conducted design optimization based on refined surrogate models to obtain a single optimal design. These surrogate models are trained based on an updated dataset using the Markov Chain Monte Carlo resampling method.

This design approach was demonstrated in the design of an AM fabricated ankle brace (refer to image) that has a tunable mechanical performance for facilitating the recovery process of joints. In this design, the researchers selected a metamaterial which has a horseshoe-like structure, where its stiffness can be tailored. The proposed design approach was applied to optimize the orientation and dimensions of the horseshoe-like structure's geometry in different areas to achieve desired stiffness distributions.

Such geometry complexities enabled by AM offer the ankle brace design unique and favorable behaviors. The ankle brace is very soft within the allowable range of motions which provides comfort to patients. However, once the movement is out of the permissible range, it becomes stiff enough to protect the users' joints from extreme load conditions due to its geometrical design.

"Previously, it was hard for designers to imagine a design of such complex geometry due to the limitations in conventional manufacturing, but now this design is easily achievable with AM. Our new approach allows designers to embrace the design freedom in AM that comes with the shift in design paradigm and create more optimal products similar to the ankle brace," said first author Dr. Yi Xiong, Research Fellow from SUTD.

With the design space exploration and exploitation capability developed, the research team is working towards a more ambitious goal -- to develop a next-generation CAD system for AM.

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Alcohol-producing gut bacteria could cause liver damage even in people who don't drink

Non-alcoholic fatty liver disease (NAFLD) is the build-up of fat in the liver due to factors other than alcohol. It affects about a quarter of the adult population globally, but its cause remains unknown. Now, researchers have linked NAFLD to gut bacteria that produce a large amount of alcohol in the body, finding these bacteria in over 60% of non-alcoholic fatty liver patients. Their findings, publishing September 19 in the journal Cell Metabolism, could help develop a screening method for early diagnosis and treatment of non-alcoholic fatty liver.

"We were surprised that bacteria can produce so much alcohol," says lead author Jing Yuan at Capital Institute of Pediatrics. "When the body is overloaded and can't break down the alcohol produced by these bacteria, you can develop fatty liver disease even if you don't drink."

Yuan and her team discovered the link between gut bacteria and NAFLD when they encountered a patient with severe liver damage and a rare condition called auto-brewery syndrome (ABS). Patients with ABS would become drunk after eating alcohol-free and high-sugar food. The condition has been associated with yeast infection, which can produce alcohol in the gut and lead to intoxication.

"We initially thought it was because of the yeast, but the test result for this patient was negative," Yuan says. "Anti-yeast medicine also didn't work, so we suspected [his disease] might be caused by something else."

By analyzing the patient's feces, the team found he had several strains of the bacteria Klebsiella pneumonia in his gut that produced high levels of alcohol. K. pneumonia is a common type of commensal gut bacteria. Yet, the strains isolated from the patient's gut can generate about four to six times more alcohol than strains found in healthy people.

Moreover, the team sampled the gut microbiota from 43 NAFLD patients and 48 healthy people. They found about 60% of NAFLD patients had high- and medium-alcohol-producing K. pneumonia in their gut, while only 6% of healthy controls carry these strains.

To investigate if K. pneumonia would cause fatty liver, researchers fed germ-free mice with high-alcohol-producing K. pneumonia isolated from the ABS patient for 3 months. These mice started to develop fatty liver after the first month. By 2 months, their livers showed signs of scarring, which means long-term liver damage had been made. The progression of liver disease in these mice was comparable to that of mice fed with alcohol. When the team gave bacteria-fed mice with an antibiotic that killed K. pneumonia, their condition was reversed.

"NAFLD is a heterogenous disease and may have many causes," Yuan says. "Our study shows K. pneumonia is very likely to be one of them. These bacteria damage your liver just like alcohol, except you don't have a choice."

However, it remains unknown why some people have high-alcohol-producing K. pneumonia strain in their gut while others don't.

"It's likely that these particular bacteria enter people's body via some carriers from the environment, like food," says co-author Di Liu at the Chinese Academy of Sciences. "But I don't think the carriers are prevalent -- otherwise we would expect much higher rate of NAFLD. Also, some people may have a gut environment that's more suitable for the growth and colonization of K. pneumonia than others because of their genetics. We don't understand what factors would make someone more susceptible to these particular K. pneumonia, and that's what we want to find out next."

This finding could also help diagnose and treat bacteria-related NAFLD, Yuan says. Because K. pneumonia produce alcohol using sugar, patients who carry these bacteria would have a detectable amount of alcohol in their blood after drinking a simple glucose solution. "In the early stages, fatty liver disease is reversible. If we can identify the cause sooner, we could treat and even prevent liver damage."

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Perception of musical pitch varies across cultures

People who are accustomed to listening to Western music, which is based on a system of notes organized in octaves, can usually perceive the similarity between notes that are same but played in different registers -- say, high C and middle C. However, a longstanding question is whether this a universal phenomenon or one that has been ingrained by musical exposure.

This question has been hard to answer, in part because of the difficulty in finding people who have not been exposed to Western music. Now, a new study led by researchers from MIT and the Max Planck Institute for Empirical Aesthetics has found that unlike residents of the United States, people living in a remote area of the Bolivian rainforest usually do not perceive the similarities between two versions of the same note played at different registers (high or low).

The findings suggest that although there is a natural mathematical relationship between the frequencies of every "C," no matter what octave it's played in, the brain only becomes attuned to those similarities after hearing music based on octaves, says Josh McDermott, an associate professor in MIT's Department of Brain and Cognitive Sciences.

"It may well be that there is a biological predisposition to favor octave relationships, but it doesn't seem to be realized unless you are exposed to music in an octave-based system," says McDermott, who is also a member of MIT's McGovern Institute for Brain Research and Center for Brains, Minds and Machines.

The study also found that members of the Bolivian tribe, known as the Tsimane', and Westerners do have a very similar upper limit on the frequency of notes that they can accurately distinguish, suggesting that that aspect of pitch perception may be independent of musical experience and biologically determined.

McDermott is the senior author of the study, which appears in the journal Current Biology on Sept. 19. Nori Jacoby, a former MIT postdoc who is now a group leader at the Max Planck Institute for Empirical Aesthetics, is the paper's lead author. Other authors are Eduardo Undurraga, an assistant professor at the Pontifical Catholic University of Chile; Malinda McPherson, a graduate student in the Harvard/MIT Program in Speech and Hearing Bioscience and Technology; Joaquin Valdes, a graduate student at the Pontifical Catholic University of Chile; and Tomas Ossandon, an assistant professor at the Pontifical Catholic University of Chile.

Octaves apart

Cross-cultural studies of how music is perceived can shed light on the interplay between biological constraints and cultural influences that shape human perception. McDermott's lab has performed several such studies with the participation of Tsimane' tribe members, who live in relative isolation from Western culture and have had little exposure to Western music.

In a study published in 2016, McDermott and his colleagues found that Westerners and Tsimane' had different aesthetic reactions to chords, or combinations of notes. To Western ears, the combination of C and F# is very grating, but Tsimane' listeners rated this chord just as likeable as other chords that Westerners would interpret as more pleasant, such as C and G.

Later, Jacoby and McDermott found that both Westerners and Tsimane' are drawn to musical rhythms composed of simple integer ratios, but the ratios they favor are different, based on which rhythms are more common in the music they listen to.

In their new study, the researchers studied pitch perception using an experimental design in which they play a very simple tune, only two or three notes, and then ask the listener to sing it back. The notes that were played could come from any octave within the range of human hearing, but listeners sang their responses within their vocal range, usually restricted to a single octave.

Western listeners, especially those who were trained musicians, tended to reproduce the tune an exact number of octaves above or below what they heard, though they were not specifically instructed to do so. In Western music, the pitch of the same note doubles with each ascending octave, so tones with frequencies of 27.5 hertz, 55 hertz, 110 hertz, 220 hertz, and so on, are all heard as the note A.

Western listeners in the study, all of whom lived in New York or Boston, accurately reproduced sequences such as A-C-A, but in a different register, as though they hear the similarity of notes separated by octaves. However, the Tsimane' did not.

"The relative pitch was preserved (between notes in the series), but the absolute pitch produced by the Tsimane' didn't have any relationship to the absolute pitch of the stimulus," Jacoby says. "That's consistent with the idea that perceptual similarity is something that we acquire from exposure to Western music, where the octave is structurally very important."

The ability to reproduce the same note in different octaves may be honed by singing along with others whose natural registers are different, or singing along with an instrument being played in a different pitch range, Jacoby says.

Limits of perception

The study findings also shed light on the upper limits of pitch perception for humans. It has been known for a long time that Western listeners cannot accurately distinguish pitches above about 4,000 hertz, although they can still hear frequencies up to nearly 20,000 hertz. In a traditional 88-key piano, the highest note is about 4,100 hertz.

People have speculated that the piano was designed to go only that high because of a fundamental limit on pitch perception, but McDermott thought it could be possible that the opposite was true: That is, the limit was culturally influenced by the fact that few musical instruments produce frequencies higher than 4,000 hertz.

The researchers found that although Tsimane' musical instruments usually have upper limits much lower than 4,000 hertz, Tsimane' listeners could distinguish pitches very well up to about 4,000 hertz, as evidenced by accurate sung reproductions of those pitch intervals. Above that threshold, their perceptions broke down, very similarly to Western listeners.

"It looks almost exactly the same across groups, so we have some evidence for biological constraints on the limits of pitch," Jacoby says.

One possible explanation for this limit is that once frequencies reach about 4,000 hertz, the firing rates of the neurons of our inner ear can't keep up and we lose a critical cue with which to distinguish different frequencies.

Jacoby and McDermott now hope to expand their cross-cultural studies to other groups who have had little exposure to Western music, and to perform more detailed studies of pitch perception among the Tsimane'.

Such studies have already shown the value of including research participants other than the Western-educated, relatively wealthy college undergraduates who are the subjects of most academic studies on perception, McDermott says. These broader studies allow researchers to tease out different elements of perception that cannot be seen when examining only a single, homogenous group.

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Why is the brain disturbed by harsh sounds?

Why do the harsh sounds emitted by alarms or human shrieks grab our attention? What is going on in the brain when it detects these frequencies? Neuroscientists from the University of Geneva (UNIGE) and Geneva University Hospitals (HUG), Switzerland, have been analysing how people react when they listen to a range of different sounds, the aim being to establish the extent to which repetitive sound frequencies are considered unpleasant. The scientists also studied the areas inside the brain that were stimulated when listening to these frequencies. Surprisingly, their results -- which are published in Nature Communications -- showed not only that the conventional sound-processing circuit is activated but also that the cortical and sub-cortical areas involved in the processing of salience and aversion are also solicited. This is a first, and it explains why the brain goes into a state of alert on hearing this type of sound.

Alarm sounds, whether artificial (such as a car horn) or natural (human screams), are characterised by repetitive sound fluctuations, which are usually situated in frequencies of between 40 and 80 Hz. But why were these frequencies selected to signal danger? And what happens in the brain to hold our attention to such an extent? Researchers from UNIGE and HUG played repetitive sounds of between 0 and 250 Hz to 16 participants closer and closer together in order to define the frequencies that the brain finds unbearable. "We then asked participants when they perceived the sounds as being rough (distinct from each other) and when they perceived them as smooth (forming one continuous and single sound)," explains Luc Arnal, a researcher in the Department of Basic Neurosciences in UNIGE's Faculty of Medicine.

Based on the responses of participants, the scientists were able to establish that the upper limit of sound roughness is around 130 Hz. "Above this limit," continues Arnal, "the frequencies are heard as forming only one continuous sound." But why does the brain judge rough sounds to be unpleasant? In an attempt to answer this question, the neuroscientists asked participants to listen to different frequencies, which they had to classify on a scale of 1 to 5, 1 being bearable and 5 unbearable. "The sounds considered intolerable were mainly between 40 and 80 Hz, i.e. in the range of frequencies used by alarms and human screams, including those of a baby," says Arnal. Since these sounds are perceptible from a distance, unlike a visual stimulus, it is crucial that attention can be captured from a survival perspective. "That's why alarms use these rapid repetitive frequencies to maximise the chances that they are detected and gain our attention," says the researcher. In fact, when the repetitions are spaced less than about 25 milliseconds apart, the brain cannot anticipate them and therefore suppress them. It is constantly on alert and attentive to the stimulus.

Harsh sounds fall outside the conventional auditory system

The researchers then attempted to find out what actually happens in the brain: why are these harsh sounds so unbearable? "We used an intracranial EEG, which records brain activity inside the brain itself in response to sounds," explains Pierre Mégevand, a neurologist and researcher in the Department of Basic Neurosciences in the UNIGE Faculty of Medicine and at HUG.

When the sound is perceived as continuous (above 130 Hz), the auditory cortex in the upper temporal lobe is activated. "This is the conventional circuit for hearing," says Mégevand. But when sounds are perceived as harsh (especially between 40 and 80 Hz), they induce a persistent response that additionally recruits a large number of cortical and sub-cortical regions that are not part of the conventional auditory system. "These sounds solicit the amygdala, hippocampus and insula in particular, all areas related to salience, aversion and pain. This explains why participants experienced them as being unbearable," says Arnal, who was surprised to learn that these regions were involved in processing sounds.

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Long lost human relative unveiled

If you could travel back in time to 100,000 years ago, you'd find yourself living among several different groups of humans, including Modern Humans (those anatomically similar to us), Neanderthals, and Denisovans. We know quite a bit about Neanderthals, thanks to numerous remains found across Europe and Asia. But exactly what our Denisovan relatives might have looked like had been anyone's guess for a simple reason: the entire collection of Denisovan remains includes three teeth, a pinky bone and a lower jaw. Now, as reported in the scientific journal Cell, a team led by Hebrew University of Jerusalem (HUJI) researchers Professor Liran Carmel and Dr. David Gokhman (currently a postdoc at Stanford) has produced reconstructions of these long-lost relatives based on patterns of methylation (chemical changes) in their ancient DNA.

"We provide the first reconstruction of the skeletal anatomy of Denisovans," says lead author Carmel of HUJI's Institute of Life Sciences. "In many ways, Denisovans resembled Neanderthals but in some traits they resembled us and in others they were unique."

Denisovan remains were first discovered in 2008 and have fascinated human evolution researchers ever since. They lived in Siberia and Eastern Asia, and went extinct approximately 50,000 years ago. We don't yet know why. That said, up to 6% of present-day Melanesians and Aboriginal Australians contain Denisovan DNA. Further, Denisovan DNA likely contributed to modern Tibetans' ability to live in high altitudes and to Inuits' ability to withstand freezing temperatures.

Overall, Carmel and his team identified 56 anatomical features in which Denisovans differ from modern humans and/or Neanderthals, 34 of them in the skull. For example, the Denisovan's skull was probably wider than that of modern humans' or Neanderthals'. They likely also had a longer dental arch and no chin.

The researchers came to these conclusions after three years of intense work studying DNA methylation maps. DNA methylation refers to chemical modifications that affect a gene's activity but not its underlying DNA sequence. The researchers first compared DNA methylation patterns among the three human groups to find regions in the genome that were differentially methylated. Next, they looked for evidence about what those differences might mean for anatomical features -- based on what's known about human disorders in which those same genes lose their function.

"In doing so, we got a prediction as to what skeletal parts are affected by differential regulation of each gene and in what direction that skeletal part would change -- for example, a longer or shorter femur bone," Dr. Gokhman explained.

To test this ground-breaking method, the researchers applied it to two species whose anatomy is known: the Neanderthal and the chimpanzee. They found that roughly 85% of their trait reconstructions were accurate in predicting which traits diverged and in which direction they diverged. Then, they applied this method to the Denisovan and were able to produce the first reconstructed anatomical profile of the mysterious Denisovan.

As for the accuracy of their Denisovan profile, Carmel shared, "One of the most exciting moments happened a few weeks after we sent our paper to peer-review. Scientists had discovered a Denisovan jawbone! We quickly compared this bone to our predictions and found that it matched perfectly. Without even planning on it, we received independent confirmation of our ability to reconstruct whole anatomical profiles using DNA that we extracted from a single fingertip."

In their Cell paper, Carmel and his colleagues predict many Denisovan traits that resemble Neanderthals', such as a sloping forehead, long face and large pelvis, and others that are unique among humans, for example, a large dental arch and very wide skull. Do these traits shed light on the Denisovan lifestyle? Could they explain how Denisovans survived the extreme cold of Siberia?

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Study of ancient climate suggests future warming could accelerate

The rate at which the planet warms in response to the ongoing buildup of heat-trapping carbon dioxide gas could increase in the future, according to new simulations of a comparable warm period more than 50 million years ago.

Researchers at the University of Michigan and the University of Arizona used a state-of-the-art climate model to successfully simulate -- for the first time -- the extreme warming of the Early Eocene Period, which is considered an analog for Earth's future climate.

They found that the rate of warming increased dramatically as carbon dioxide levels rose, a finding with far-reaching implications for Earth's future climate, the researchers report in a paper scheduled for publication Sept. 18 in the journal Science Advances.

Another way of stating this result is that the climate of the Early Eocene became increasingly sensitive to additional carbon dioxide as the planet warmed.

"We were surprised that the climate sensitivity increased as much as it did with increasing carbon dioxide levels," said first author Jiang Zhu, a postdoctoral researcher at the U-M Department of Earth and Environmental Sciences.

"It is a scary finding because it indicates that the temperature response to an increase in carbon dioxide in the future might be larger than the response to the same increase in CO2 now. This is not good news for us."

The researchers determined that the large increase in climate sensitivity they observed -- which had not been seen in previous attempts to simulate the Early Eocene using similar amounts of carbon dioxide -- is likely due to an improved representation of cloud processes in the climate model they used, the Community Earth System Model version 1.2, or CESM1.2.

Global warming is expected to change the distribution and types of clouds in the Earth's atmosphere, and clouds can have both warming and cooling effects on the climate. In their simulations of the Early Eocene, Zhu and his colleagues found a reduction in cloud coverage and opacity that amplified CO2-induced warming.

The same cloud processes responsible for increased climate sensitivity in the Eocene simulations are active today, according to the researchers.

"Our findings highlight the role of small-scale cloud processes in determining large-scale climate changes and suggest a potential increase in climate sensitivity with future warming," said U-M paleoclimate researcher Christopher Poulsen, a co-author of the Science Advances paper.

"The sensitivity we're inferring for the Eocene is indeed very high, though it's unlikely that climate sensitivity will reach Eocene levels in our lifetimes," said Jessica Tierney of the University of Arizona, the paper's third author.

The Early Eocene (roughly 48 million to 56 million years ago) was the warmest period of the past 66 million years. It began with the Paleocene-Eocene Thermal Maximum, which is known as the PETM, the most severe of several short, intensely warm events.

The Early Eocene was a time of elevated atmospheric carbon dioxide concentrations and surface temperatures at least 14 degrees Celsius (25 degrees Fahrenheit) warmer, on average, than today. Also, the difference between temperatures at the equator and the poles was much smaller.

Geological evidence suggests that atmospheric carbon dioxide levels reached 1,000 parts per million in the Early Eocene, more than twice the present-day level of 412 ppm. If nothing is done to limit carbon emissions from the burning of fossil fuels, CO2 levels could once again reach 1,000 ppm by the year 2100, according to climate scientists.

Until now, climate models have been unable to simulate the extreme surface warmth of the Early Eocene -- including the sudden and dramatic temperature spikes of the PETM -- by relying solely on atmospheric CO2 levels. Unsubstantiated changes to the models were required to make the numbers work, said Poulsen, a professor in the U-M Department of Earth and Environmental Sciences and associate dean for natural sciences.

"For decades, the models have underestimated these temperatures, and the community has long assumed that the problem was with the geological data, or that there was a warming mechanism that hadn't been recognized," he said.

But the CESM1.2 model was able to simulate both the warm conditions and the low equator-to-pole temperature gradient seen in the geological records.

"For the first time, a climate model matches the geological evidence out of the box -- that is, without deliberate tweaks made to the model. It's a breakthrough for our understanding of past warm climates," Tierney said.

CESM1.2 was one of the climate models used in the authoritative Fifth Assessment Report from the Intergovernmental Panel on Climate Change, finalized in 2014. The model's ability to satisfactorily simulate Early Eocene warming provides strong support for CESM1.2's prediction of future warming, which is expressed through a key climate parameter called equilibrium climate sensitivity.

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Even short-lived solar panels can be economically viable

A new study shows that, contrary to widespread belief within the solar power industry, new kinds of solar cells and panels don't necessarily have to last for 25 to 30 years in order to be economically viable in today's market.

Rather, solar panels with initial lifetimes of as little as 10 years can sometimes make economic sense, even for grid-scale installations -- thus potentially opening the door to promising new solar photovoltaic technologies that have been considered insufficiently durable for widespread use.

The new findings are described in a paper in the journal Joule, by Joel Jean, a former MIT postdoc and CEO of startup company Swift Solar; Vladimir Bulović, professor of electrical engineering and computer science and director of MIT.nano; and Michael Woodhouse of the National Renewable Energy Laboratory (NREL) in Colorado.

"When you talk to people in the solar field, they say any new solar panel has to last 25 years," Jean says. "If someone comes up with a new technology with a 10-year lifetime, no one is going to look at it. That's considered common knowledge in the field, and it's kind of crippling."

Jean adds that "that's a huge barrier, because you can't prove a 25-year lifetime in a year or two, or even 10." That presumption, he says, has left many promising new technologies stuck on the sidelines, as conventional crystalline silicon technologies overwhelmingly dominate the commercial solar marketplace. But, the researchers found, that does not need to be the case.

"We have to remember that ultimately what people care about is not the cost of the panel; it's the levelized cost of electricity," he says. In other words, it's the actual cost per kilowatt-hour delivered over the system's useful lifetime, including the cost of the panels, inverters, racking, wiring, land, installation labor, permitting, grid interconnection, and other system components, along with ongoing maintenance costs.

Part of the reason that the economics of the solar industry look different today than in the past is that the cost of the panels (also known as modules) has plummeted so far that now, the "balance of system" costs -- that is, everything except the panels themselves -- exceeds that of the panels. That means that, as long as newer solar panels are electrically and physically compatible with the racking and electrical systems, it can make economic sense to replace the panels with newer, better ones as they become available, while reusing the rest of the system.

"Most of the technology is in the panel, but most of the cost is in the system," Jean says. "Instead of having a system where you install it and then replace everything after 30 years, what if you replace the panels earlier and leave everything else the same? One of the reasons that might work economically is if you're replacing them with more efficient panels," which is likely to be the case as a wide variety of more efficient and lower-cost technologies are being explored around the world.

He says that what the team found in their analysis is that "with some caveats about financing, you can, in theory, get to a competitive cost, because your new panels are getting better, with a lifetime as short as 15 or even 10 years."

Although the costs of solar cells have come down year by year, Bulović says, "the expectation that one had to demonstrate a 25-year lifetime for any new solar panel technology has stayed as a tautology. In this study we show that as the solar panels get less expensive and more efficient, the cost balance significantly changes."

He says that one aim of the new paper is to alert the researchers that their new solar inventions can be cost-effective even if relatively short lived, and hence may be adopted and deployed more rapidly than expected. At the same time, he says, investors should know that they stand to make bigger profits by opting for efficient solar technologies that may not have been proven to last as long, knowing that periodically the panels can be replaced by newer, more efficient ones.

"Historical trends show that solar panel technology keeps getting more efficient year after year, and these improvements are bound to continue for years to come," says Bulović. Perovskite-based solar cells, for example, when first developed less than a decade ago, had efficiencies of only a few percent. But recently their record performance exceeded 25 percent efficiency, compared to 27 percent for the record silicon cell and about 20 percent for today's standard silicon modules, according to Bulović. Importantly, in novel device designs, a perovskite solar cell can be stacked on top of another perovskite, silicon, or thin-film cell, to raise the maximum achievable efficiency limit to over 40 percent, which is well above the 30 percent fundamental limit of today's silicon solar technologies. But perovskites have issues with longevity of operation and have not yet been shown to be able to come close to meeting the 25-year standard.

Bulović hopes the study will "shift the paradigm of what has been accepted as a global truth." Up to now, he says, "many promising technologies never even got a start, because the bar is set too high" on the need for durability.

For their analysis, the team looked at three different kinds of solar installations: a typical 6-kilowatt residential system, a 200-kilowatt commercial system, and a large 100-megawatt utility-scale system with solar tracking. They used NREL benchmark parameters for U.S. solar systems and a variety of assumptions about future progress in solar technology development, financing, and the disposal of the initial panels after replacement, including recycling of the used modules. The models were validated using four independent tools for calculating the levelized cost of electricity (LCOE), a standard metric for comparing the economic viability of different sources of electricity.

In all three installation types, they found, depending on the particulars of local conditions, replacement with new modules after 10 to 15 years could in many cases provide economic advantages while maintaining the many environmental and emissions-reduction benefits of solar power. The basic requirement for cost-competitiveness is that any new solar technology that is to be installed in the U.S should start with a module efficiency of at least 20 percent, a cost of no more than 30 cents per watt, and a lifetime of at least 10 years, with the potential to improve on all three.

Jean points out that the solar technologies that are considered standard today, mostly silicon-based but also thin-film variants such as cadmium telluride, "were not very stable in the early years. The reason they last 25 to 30 years today is that they have been developed for many decades." The new analysis may now open the door for some of the promising newer technologies to be deployed at sufficient scale to build up similar levels of experience and improvement over time and to make an impact on climate change earlier than they could without module replacement, he says.

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How people with psychopathic traits control their 'dark impulses'

People with psychopathic traits are predisposed toward antisocial behavior that can result in "unsuccessful" outcomes such as incarceration. However, many individuals with psychopathic traits are able to control their antisocial tendencies and avoid committing the antagonistic acts that can result.

A team of researchers at Virginia Commonwealth University and the University of Kentucky set out to explore what mechanisms might explain why certain people with psychopathic traits are able to successfully control their antisocial tendencies while others are not. Using neuroimaging technology, they investigated the possibility that "successful" psychopathic individuals -- those who control their antisocial tendencies -- have more developed neural structures that promote self-regulation.

Over two structural MRI studies of "successful" psychopathic individuals, the researchers found that participants had greater levels of gray matter density in the ventrolateral prefrontal cortex, one of the brain regions involved in self-regulatory processes, including the down-regulation of more primitive and reactive emotions, such as fear or anger.

"Our findings indicating that this region is denser in people higher on certain psychopathic traits suggests that these individuals may have a greater capacity for self-control," said Emily Lasko, a doctoral student in theDepartment of Psychologyin VCU'sCollege of Humanities and Sciences, who led the study. "This is important because it is some of the first evidence pointing us to a biological mechanism that can potentially explain how some psychopathic people are able to be 'successful' whereas others aren't."

The team's findings will be described in an article, "An Investigation of the Relationship Between Psychopathy and Greater Gray Matter Density in Lateral Prefrontal Cortex," that will be published in a forthcoming edition of the journal Personality Neuroscience.

The first study involved 80 adults in long-term relationships who were placed in an MRI scanner at VCU's Collaborative Advanced Research Imaging center, where researchers took a high-resolution scan of their brain. Afterwards, participants completed a battery of questionnaires, including one that measured the "dark triad" of personality traits, individually assessing psychopathy (e.g., "it's true that I can be mean to others"), narcissism (e.g., "I like to get acquainted with important people"), and Machiavellianism (e.g., "it's not wise to tell your secrets").

The second looked at another "successful" population: undergraduate students. The researchers recruited 64 undergraduate students who were assessed for psychopathic traits and tendencies using an assessment tool designed for use in community and student populations, measuring primary psychopathy (e.g., "I enjoy manipulating other people's feelings") and secondary psychopathy (e.g., "I quickly lose interest in the tasks I start"). The participants were then scanned at the University of Kentucky's Magnetic Resonance Imaging and Spectroscopy Center.

In both studies, the researchers observed that gray matter density in the ventrolateral prefrontal cortex -- which the researchers call "a hub for self-regulation" -- was positively associated with psychopathic traits.

The researchers say their findings support a compensatory model of psychopathy, in which "successful" psychopathic individuals develop inhibitory mechanisms to compensate for their antisocial tendencies.

"Most neuroscientific models of psychopathy emphasize deficits in brain structure and function. These new findings lend preliminary support to the growing notion that psychopathic individuals have some advantages compared to others, not just deficiencies," said study co-authorDavid Chester, Ph.D., an assistant professor in the Department of Psychology who runs theSocial Psychology and Neuroscience Lab, which conducts research on psychopathy, aggression and why people try to harm others.

Across the two samples of individuals who varied widely in their psychopathic tendencies, Chester said, the team found greater structural integrity in brain regions that facilitate impulse control.

"Such neural advantages may allow psychopathic individuals to counteract their selfish and hostile tendencies, allowing them to coexist with others in spite of their antisocial impulses," he said. "To fully understand and effectively treat psychopathic traits in the human population, we need to understand both the shortfalls and the surpluses inherent in psychopathy. These new results are an important, though preliminary, step in that direction."

The compensatory model of psychopathy offers a more optimistic alternative to the traditional view that focuses more on the deficits associated with psychopathy, Lasko said. The finding that the ventrolateral prefrontal cortex is denser in these individuals lends support for the compensatory model because that region is linked to self-regulatory and inhibitory behaviors, she said.

"Psychopathy is a highly nuanced construct and this framework helps to acknowledge those nuances," she said. "People high in psychopathy have 'dark' impulses, but some of these individuals are able to either inhibit them or find a socially acceptable outlet for them. The compensatory model posits that these individuals have enhanced self-regulation abilities, which are able to compensate for their antisocial impulses and facilitate their 'success.'"

Past research has indicated that approximately 1% of the general population, and 15% to 25% of incarcerated people, would meet the clinical criteria for psychopathy. By gaining a deeper understanding of the neurological advantages associated with "successful" psychopathic individuals, researchers may unlock new treatments and rehabilitation strategies for them, Lasko said.

"We believe that it is critical to understand these potential 'advantages' because if we are able to identify biomarkers of psychopathy, and importantly, factors that could be informative in determining an individual's potential for violent behavior and potential for rehabilitation, we will be better equipped to develop effective intervention and treatment strategies," she said.

Lasko emphasized that the researchers' findings are preliminary.

"Although the findings are novel and definitely provide a promising avenue for future research, they still need to be replicated," she said. "They are also correlational so we currently aren't able to make any causal inferences about the [ventrolateral prefrontal cortex]-psychopathy relationship."

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