Novel air-conditioning technology: Artificial muscles deliver sustainable cooling

Reports and Proceedings

SAARLAND UNIVERSITY

 

IMAGE: THE FIRST EVER MACHINE THAT COOLS AIR USING ‘MUSCLES’ MADE OF NICKEL-TITANIUM. FELIX WELSCH AND SUSANNE MARIE KIRSCH HELPED TO DEVELOP THE COOLING SYSTEM AS PART OF THEIR DOCTORAL RESEARCH PROJECTS. THE NEW TYPE OF ENERGY EFFICIENT, ECOLOGICALLY SUSTAINABLE COOLING TECHNOLOGY THAT DOES NOT REQUIRE THE USE OF CLIMATE-DAMAGING REFRIGERANTS IS CURRENTLY BEING DEVELOPED BY PROFESSOR STEFAN SEELECKE AND HIS TEAM AT SAARLAND UNIVERSITY. view more 

CREDIT: CREDIT: OLIVER DIETZE

A new type of energy efficient, ecologically sustainable cooling technology that does not require the use of climate-damaging refrigerants is currently being developed by Professor Stefan Seelecke and his team at Saarland University. The new technology makes use of shape-memory materials that are also known as ‘artificial muscles’. These materials are able to transport heat by loading and unloading nickel-titanium wires. Seelecke’s team is currently developing the technology for use in cooling systems for electric vehicles. The researchers have been presenting their technology at the Hannover Messe, showcasing the world’s first machine that can cool air by flexing artificial muscles.

From the humble fridge and air conditioner to complex cooling systems for use in industrial processes – keeping cool is a significant part of today’s society. Global warming and a growing world population mean that the need for energy-efficient cooling systems will only get larger. But low temperatures typically signify high electricity consumption, which in turn usually means a high carbon footprint and the risk of emissions of refrigerant gases that often have a high global warming potential. A research team of academic and industrial partners led by Professor Stefan Seelecke of Saarland University and the Center for Mechatronics and Automation Technology (ZeMA) is currently developing an environmentally friendly cooling system.

‘Our process is energy efficient and doesn’t require the use of refrigerants that are harmful to the climate. In fact, our technology is up to 15 times more efficient than systems based on conventional refrigerants,’ explained Stefan Seelecke. The EU Commission and the United States Department of Energy have both evaluated the new process and consider it to be the most promising alternative to the vapour-compression refrigeration technology in use today.

Seelecke’s team has developed the world’s first continuously operating prototype that cools air using this new process. The cooling technology that the team is showcasing at this year's Hannover Messe uses artificial muscle fibres composed of bundles of ultrafine shape-memory wires made from the nickel-titanium alloy ‘nitinol’. These wires have the special property that they return to their earlier shape after being stretched or otherwise deformed. They are thus able to tense and relax like human muscles.

The reason for this behaviour is to be found within the structure of the metal alloy. The atoms in the alloy are arranged in a crystal lattice structure. If the nickel-titanium wire is deformed or pulled in tension, the layers of atoms in the lattice crystal move relative to one another creating strain within the material. This strain is released when the wire returns to its original shape. These changes in the material’s crystal structure are known as phase transitions and they cause the wires to absorb or release heat. It is this effect that Seelecke and his team are exploiting in their novel cooling system. ‘The shape-memory material releases heat to its surroundings when it is mechanically loaded in its superelastic state and absorbs heat from its surroundings when it is unloaded. And this effect is particular pronounced in the case of nitinol. When pre-stressed nitinol wires are unloaded at room temperature, they cool down by as much as 20 degrees,’ explained Stefan Seelecke, who holds the Chair of Intelligent Material Systems at Saarland University.

‘We exploit this property to dissipate heat,’ said Susanne-Marie Kirsch, who helped to develop the cooling system as part of her doctoral research project. ‘The basic idea is to allow pre-stressed, superelastic shape-memory wires to relax and thus cool the space by removing heat from it,’ explained Kirsch. The heat taken up by the shape-memory wires is then released externally when the wires are re-stressed in the surroundings.

However, the Saarbrücken cooling system is significantly more complex. The team has designed and developed a cooling circuit in which a patent-pending cam drive rotates in such a way that bundles of 200 micron-thick nitinol wires are alternately stretched and relaxed so that heat is transferred as efficiently as possible. Air is blown through the wire bundles in two separate chambers: in one chamber the air is heated, in the other it is cooled. As a result, the machine can cool and can heat. ‘When the wires are mechanically loaded they heat up by about 20 degrees, so that the process can also be used as a heat pump,’ explained Felix Welsch who also worked on the prototype system as part of his doctorate. Depending on the alloy used, the heating or cooling power of this new technology is up to thirty times greater than the mechanical power required to load and unload the alloy wire bundles. That makes the new system significantly better than currently available heat pumps and conventional refrigerators.

The cooling system is the result of many years of research in different projects, numerous award-winning doctoral thesis and close collaboration with the group led by Professor Andreas Schütze of Saarland University. Funding was provided in part by the German Research Foundation (DFG) through its priority programme ‘Ferroic Cooling’. Through a combination of experimental studies and numerical modelling, the researchers were able to optimize the underlying mechanisms and were able to determine how many nitinol wires need to be included in a bundle or what wire loading level was needed to achieve a specific degree of cooling. Building on these results, the research team is now able to customize the system. They have  developed a software package that allows them to simulate, plan and fine tune cooling systems for specific applications.

The Saarbrücken team is currently working on multiple projects aimed at further optimizing the heat transfer process and thus boosting the efficiency of the new technology even further. The objective is to get to a stage where practically all of the energy from the phase transition is being used for heating or cooling.

The researchers in Seelecke’s team are currently working on developing their elastocaloric technology for use as a cooling system in electric vehicles. Since January 2022 the team has been working with academic and industrial partners in the government-financed collaborative project NEKKA that aims to develop a novel elastomeric cooling system. The project will receive a total of €6 million in funding, of which around €1 million will be provided to the Saarbrücken team for their electric car cooling project. ‘Our aim is to develop, mathematically model and validate an alternative air-con system that can be used in all vehicle classes. The system will be able to provide vehicle heating and cooling while also being more efficient, more environmentally friendly and more sustainable than other previously available systems. Our technology will also be compacter, lighter and more cost-effective,’ explained Paul Motzki, a research engineer and managing director in Seelecke’s team.

To develop this and other smart material systems for commercial and industrial applications, researchers at the Intelligent Material Systems Lab have founded the spin-off company ‘mateligent GmbH’.

Hannover Messe, 30 May to 2 June, Hall 2, Stand B28
Video on the elastocaloric cooling system: https://www.youtube.com/watch?v=_hg--OkUsDs
Intelligent Material Systems Lab: https://imsl.de

The mindful way to manage stress among elite athletes

Peer-Reviewed Publication

UNIVERSITY OF SOUTH AUSTRALIA

 

IMAGE: NORWOOD FOOTBALL PLAYERS ON THE FIELD view more 

CREDIT: HEATHERW

Just like the saying, ‘when the going gets tough, the tough get going’, elite athletes are known for their stamina and determination. But nearly a third of professional athletes struggle with mental health.

Now, a new study from the University of South Australia is exploring the realities of elite sports and stress, finding that dispositional mindfulness – a keen awareness and attention to thoughts and feelings in the present moment – can significantly reduce and protect athletes from stress.

Working with a group of high-performing football athletes, researchers investigated relationships between mindfulness, executive functioning, and psychological distress, finding that athletes who demonstrated greater mindfulness had lower levels of stress.

This relationship was observed at two timepoints: immediately after the initial COVID-19-related shutdown of sport in South Australia and approximately six months later, at the end of the athletes' competitive season.

As the study was conducted during COVID-19, it provided unique insight about the mental skills and resources that shape how athletes respond to significant stress.

Lead researcher and UniSA PhD candidate Ed O’Connor says the findings could help to develop targeted health interventions to combat stress.

“When you’re an elite athlete, staying top of your game also means keeping your stress levels in check, but time and time again we hear about athletes struggling with psychological stress,” O’Connor says.

“Athletes have concerning rates of mental health issues - including depression and anxiety - with the pandemic only adding to their mental health burden.

“Our research explored this with elite footballers, finding that athletes who were able to stay present and calm in the moment reported far lower levels of stress.

“If mindfulness can equip athletes to better cope with unexpected change and uncertainty it could be a very beneficial intervention to minimise potential stress.”

Many high-profile sportspeople have struggled with poor mental health. In the 2022 Olympics, seven-time Olympic champion Simone Biles pulled out of the gymnastics finals due to stress; AFL footballer, Adam Treloar has fought anxiety for many years, saying that he nearly left the game in 2018; and just recently, tennis superstar Nick Kyrgios revealed his battle with depression.

In addition, one in five Australian Institute of Sport athletes have reportedly sought treatment for a mental health condition.

O’Connor says it’s time we look for alternative treatments to manage stress and mental health among sportspeople.

“In recent years we’ve seen Olympians, professional sportspeople, and the next generation of elite athletes succumb to poor mental health,” O’Connor says.

“It’s no surprise that elite athletes deal with a lot of stress. But at the heart of it, we must remember that athletes are people too, and can struggle with the same human conditions as everyone else.

“Right now, we’re only at the start of understanding how stress can manifest and affect athletes. More research is needed, but as this study identified that mindfulness may protect athletes from stress, cognitive training interventions may equip athletes with greater mindfulness and stronger mental resilience, then this is a path absolutely worth investigating.”

 

…………………………………………………………………………………………………………………………

 

Contact for interview: Ed O’Connor E: Ed.OConnor@unisa.edu.au 
Media contact: Annabel Mansfield M: +61 417 717 504 E: Annabel.Mansfield@unisa.edu.au

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JOURNAL

Perceptual and Motor Skills

DOI

10.1177/00315125221087523 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Dispositional mindfulness may have protected athletes from psychological distress during COVID-19 in Australia

Major climate benefits when ships “fly” over the surface

Peer-Reviewed Publication

CHALMERS UNIVERSITY OF TECHNOLOGY

 

IMAGE: RESEARCHERS AT CHALMERS UNIVERSITY OF TECHNOLOGY AND SSPA IN SWEDEN PRESENT A UNIQUE MEASUREMENT TECHNIQUE, TESTED ON HYDROFOIL SAILING BOATS, TO ADAPT HYDROFOILS TO LARGER PASSENGER FERRIES, LEADING TO MAJOR CLIMATE BENEFITS. view more 

CREDIT: LLOYD IMAGES

Soon, electric passenger ferries skimming above the surface across the seas may become a reality. At Chalmers University of Technology, Sweden, a research team has created a unique method for further developing hydrofoils that can significantly increase the range of electric vessels and reduce the fuel consumption of fossil-powered ships by 80 per cent.  

While the electrification of cars is well advanced, the world's passenger ferries are still powered almost exclusively by fossil fuels. The limiting factor is battery capacity, which is not enough to power ships and ferries across longer distances. But now researchers at Chalmers and the marine research facility SSPA have succeeded in developing a method that can make the shipping industry significantly greener in the future. The focus is on hydrofoils that, like wings, lift the boat’s hull above the surface of the water and allow the boat to travel with considerably less water resistance. A technology that in recent years has revolutionised sailing, by which hydrofoils make elite sailors' boats fly over the surface of the water at a very high speed.
The researchers at Chalmers and SSPA now want to enable the sailboats' hydrofoil principle to be used on larger passenger ferries as well, resulting in major benefits for the climate.

"The electrification of ferries cannot be done without drastically reducing their water resistance. This method will allow the development of new foil designs that can reduce resistance by up to 80 per cent, which in turn would significantly increase the range of a battery powered ship. In this way, we could also use electric ferries on longer distances in the future," says research leader Arash Eslamdoost, Associate Professor in Applied Hydrodynamics at Chalmers and author of the study Fluid-Structure Interaction of a Foiling Craft published in the Journal of Marine Science and Engineering.

Even for ships that today run on fossil fuels the climate benefit could be  significant, as similar hydrofoil technology could reduce fuel consumption by no less than 80 per cent.

Unique measurement method arouses broad interest
At the centre of the research project is a unique measurement technique that the researchers have put together in order to understand in detail how hydrofoils behave in the water when, for example, the load or speed increases or the positioning of the hydrofoil changes. Using the data collected from the experiments, the team has developed and validated a method to simulate and predict with great precision how the hydrofoil would behave under a variety of conditions. The method is unique of its kind and can now be used to develop the design of hydrofoils for electric powered hydrofoil ferries.

The study was conducted in collaboration with the research facility SSPA – one of only a few of its kind in the world – where Laura Marimon Giovannetti works as a researcher and project manager. She is the lead author of the study and has herself competed at the elite level for both the British and Italian national sailing teams. Today she is a research and development adviser to Sweden's Olympic committee and the Swedish national team with her sights set on helping the team win more medals at the Olympics in 2024. Marimon Giovannetti sees many possibilities for the unique measurement method developed by the team:

"At the Americas Cup in San Francisco Bay in 2013, it was the first time we saw a 72-foot sailing boat learning how to “fly” using hydrofoils during the competition. And since then, we've seen a huge increase in sailing boats with hydrofoils. With this new method and knowledge we are able to bring together a range of different branches of engineering – naval architecture, advanced materials and aeronautics as well as renewable energy."

Paving the way for hydrofoils on electric ferries
Hydrofoil technology is not in itself a novelty, but was developed as early as the 60s and 70s. Back then the focus was on getting boats to travel at as fast as possible and the hydrofoils were made of steel, a heavy material with higher maintenance costs. Today's modern hydrofoils are made of carbon fibre, a much lighter and stiffer material that can maintain its rigidity even under high loads – and can be tailored to the expected loads. Part of the research project was therefore to fully understand how a carbon fibre structure behaves underwater during different operational conditions. The research team's method developed in association with modern technology is now paving the way for the use of carbon fibre hydrofoils on larger passenger ships that can travel in a safe, controlled and climate-friendly way even at low speeds.

"You want the foil to be as efficient as possible, which means carrying as much weight as possible at as low a speed as possible with the least resistance. Our next goal is to use this method when designing more efficient hydrofoils for ferries in the future," says Eslamdoost.

More about the scientific article

• The study "Fluid-Structure Interaction of a Foiling Craft" has been published in the Journal of Marine Science and Engineering. The authors are Laura Marimon Giovannetti, Ali Farousi, Fabian Ebbesson, Alois Thollot, Alex Shiri and Arash Eslamdoost. The researchers are active at SSPA (part of RISE Research Institutes of Sweden), Chalmers University of Technology in Sweden and INP-ENSEEITH in France.
• Hugo Hammar’s funding from SSPA and Rolf Sörman’s funding from Chalmers University of Technology provided the financial support to run the experimental tests at SSPA. This study also received funding from the Chalmers University of Technology Foundation for the strategic research project Hydro- and Aerodynamics.

For more information, please contact:

Arash Eslamdoost, Associate Professor in Applied Hydrodynamics at the Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Sweden
 +46 31 772 36 84  arash.eslamdoost@chalmers.se

Laura Marimon Giovannetti, Senior Researcher and Project Manager, SSPA, Sweden
+46 73 072 91 82, laura.marimongiovannetti@sspa.se

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JOURNAL

Journal of Marine Science and Engineering

DOI

10.3390/jmse10030372 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Fluid-Structure Interaction of a Foiling Craft

The possibility of carbon emissions peak in China by 2030 depends on the GDP growth rate

Peer-Reviewed Publication

SCIENCE CHINA PRESS

This research is done by Professor Weidong Liu, Associate Professors Zhipeng Tang and Mengyao Han, and Dr. Wanbei Jiang from the Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences. Extant studies have noticed that China’s ability to peak carbon emissions by 2030 (the Peak hereafter) has something to do with the economic growth rate and suggested a slowdown in economic growth in China to help peak carbon emissions. However, none of them gives a quantitative account for such a relationship.

In a paper published in Science China Earth Sciences, Professor Liu’s team translates the question as to “when China’s carbon emissions peak will occur” into “how can one control the rate of decrease of carbon intensity at a given GDP growth rate”. They use a random forest algorithm method to identify and project the key drivers of changes of carbon intensity in China, and then develop a mathematical model to simulate different scenarios relating to the decreases of carbon intensity. By comparing the decrease rate of carbon intensity and the GDP growth rate, one can easily find a date at which China will peak its carbon emissions.

The research finds that if the GDP growth rate were 5.0% in 2026-2030, and if the share of non-fossil energy in total energy consumption were 23.0% or above, the Peak will occur before 2030. However, if the share of non-fossil fuels were 20.0% or less, there would be uncertainty of realizing the Peak target, which means an acceleration in the pace of restructuring towards non-fossil energy would be required. The projected peak emissions scenarios suggest that the Peak will occur in 2025-2029, with average peak emissions of 11.2 billion tons and a distribution ranging from a minimum of 10.5 billion and a maximum of 11.9 billion tons. If the GDP growth rate were 4.5%, 5.5% or 6.0% in 2026-2030, the share of non-fossil energy must reach 23.0%, 25.0% or 27.0%, respectively, to ensure that the Peak occur by 2030.

The research also shows that unlike the major developed countries where carbon emissions peak was achieved by offshoring of manufacturing and energy restructuring, China must take developing non-fossil energy as the major pathway to achieve its own carbon emission peak as a result of its pursuit of being a “world factory”.

See the article:

Liu W, Jiang W, Tang Z, Han M. 2022. Pathways to peak carbon emissions in China by 2030: An analysis in relation to the economic growth rate. Science China Earth Sciences, https://doi.org/10.1007/s11430-021-9901-y

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JOURNAL

Science China Earth Sciences

DOI

10.1007/s11430-021-9901-y 

A 50% reduction in emissions by 2030 can be achieved. Here’s how

Energy and environmental researchers pooled their knowledge to provide recommendations to fulfill the United States’ climate pledge

Peer-Reviewed Publication

DOE/LAWRENCE BERKELEY NATIONAL LABORATORY

 

IMAGE: REDUCING EMISSIONS WILL REQUIRE MAJOR POLICY CHANGES SUCH AS DOUBLING THE AMOUNT OF ELECTRICITY GENERATED FROM RENEWABLES AND A WIDESPREAD SHIFT TO ELECTRIC VEHICLES. view more 

CREDIT: CHOOCHART CHOOCHAIKUPT/ISTOCK

The United States has set an ambitious goal to reduce greenhouse gas (GHG) emissions by at least 50% by 2030. Are we on track to succeed?  

A new study by a team of scientists and policy analysts from across the nation suggests that there are multiple pathways to achieve this goal – but big commitments will need to be made, immediately. 

“This study should give policy makers and other energy stakeholders some level of comfort, by showing that everybody in the field is pointing in the same direction. The case for clean energy is stronger than ever before and our study shows that the 2030 emission target can be achieved,” said Nikit Abhyankar, one of the study’s authors and a scientist in the Electricity Markets & Policy Department at Lawrence Berkeley National Laboratory (Berkeley Lab). He notes that the most urgent actions will be to double the amount of renewable capacity built each year and transition predominately to electric vehicles within the next decade or so.

“With the right policies and infrastructure, we can reduce our emissions, while saving American consumers billions of dollars and generating new employment,” he said. 

Reducing GHG emissions by 50% by 2030 would put the United States on a path to limit global warming to 1.5 degrees Celsius, the target scientists say is required to avoid the worst consequences of the climate crisis.

CAPTION

The chart shows how the key economic sectors will contribute to achieve the U.S. goal of reducing greenhouse gas emissions by 50% by 2030. Electric sector (doubling the rate of renewable energy buildout) and Transport sector (selling predominantly EVs by 2030) would be the most critical strategies for achieving this goal.

CREDIT

Nikit Abhyankar/Berkeley Lab

The study, published in Science, consolidates findings from six recently published techno-economic models that simulate the U.S. energy system operations in comprehensive detail. According to the authors, the separate models all agree on four major points:

• The majority of the country’s greenhouse gas emissions come from power generation and transportation, so to reduce overall emissions by 50%, the electricity grid needs to run on 80% clean energy (up from today’s 40%), and the majority of vehicles sold by 2030 need to be electric. Other important sources of GHG emissions reduction include electrification of buildings and industries.
• The primary barrier to increased alternative energy use will not be cost, it will be enacting new policies. A coordinated policy response between states and the federal government will be necessary to succeed.
• Thanks to advances in wind, solar, and energy storage technologies, powering the electric grid with renewables will not be more expensive; and electric vehicles could save every household up to $1,000 per year in net benefits.
• A clean-energy transition would reduce air pollution, prevent up to 200,000 premature deaths, and avoid up to $800 billion in environmental and health costs through 2050. Many of the health benefits will occur in communities of color and frontline communities that are disproportionately exposed to vehicle, power plant, and industrial pollution.

“Our study provides the first detailed roadmap for how the United States can reach its 50% greenhouse gas emissions-reduction target by 2030,” said lead author John Bistline, program manager in the Energy Systems and Climate Analysis Group at the Electric Power Research Institute. “This will require tripling the pace of historic carbon reductions, an ambitious but achievable target if stakeholders collaborate across all sectors. By comparing results across six independent models, we provide greater confidence about the policies and technology deployment needed to achieve near-term climate goals, laying the groundwork for an affordable, reliable, and equitable net-zero future.”

CAPTION

U.S. electricity grid needs to be 80% clean (up from 40% currently) for reaching the U.S. goal of reducing emissions by 50% by 2030. The chart shows the required new electricity generation capacity buildout to achieve this goal (right) and compares with the historical buildout rates (left). The U.S. will need to double its renewable energy buildout rates.

CREDIT

Nikit Abhyankar/Berkeley Lab

According to Abhyankar, who led the development of one of the six models, “By 2030, wind, solar, coupled with energy storage can provide the bulk of the 80% clean electricity. The findings also show that generating the remaining 20% of grid power won’t require the creation of new fossil fuel generators.” He noted that existing gas plants, used infrequently and combined with energy storage, hydropower, and nuclear power are sufficient to meet demand during periods of extraordinarily low renewable energy generation or exceptionally high electricity demand. “And if the right policies are in place, the coal and gas power plants in the country that currently provide the majority of the nation’s electricity would recover their initial investment, thereby avoiding risk of cost under-recovery for investors.”

“Since announcing the nation’s emissions reduction pledge at the 2021 United Nations climate conference, the United States has taken steps in the right direction,” said Abhyankar. “But a lot still needs to happen. What we are hoping is that this study will give some level of a blueprint of how it could be done.”

The other models used for this study were developed by the Electric Power Research Institute, Environmental Defense Fund, National Resources Defense Council, and the MIT Joint Program on the Science and Policy of Global Change.

 

# # #

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 14 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy's Office of Science.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.

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JOURNAL

Science

DOI

10.1126/science.abn0661 

Close encounter more than 10,000 years ago stirred up spirals in accretion disk

Peer-Reviewed Publication

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

 

IMAGE: A SCHEMATIC VIEW OF THE HISTORY OF THE ACCRETION DISK AND THE INTRUDING OBJECT. THE THREE PLOTS STARTING FROM THE BOTTOM LEFT ARE SNAPSHOTS FROM THE NUMERICAL SIMULATION, DEPICTING THE SYSTEM AT THE TIME OF THE FLYBY EVENT, 4000 YEARS LATER, AND 8000 YEARS AFTER THAT, RESPECTIVELY. THE TOP RIGHT IMAGE IS FROM THE ALMA OBSERVATIONS, SHOWING THE DISK WITH SPIRALS AND TWO OBJECTS AROUND IT, CORRESPONDING TO THE SYSTEM 12,000 YEARS AFTER THE FLYBY EVENT. view more 

CREDIT: SHAO

Dr. LU Xing, an associate researcher from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences, along with collaborators from Yunnan University, the Harvard-Smithsonian Center for Astrophysics, and the Max Planck Institute, have used high-resolution observational data from the Atacama Large Millimeter/submillimeter Array (ALMA) to discover a massive protostellar disk in the Galactic Center and determine how its spiral arms were formed.

The group's research shows that this disk was perturbed by close encounter with a nearby object, thus leading to the formation of the spiral arms. This finding demonstrates that the formation of massive stars may be similar to that of lower-mass stars, through accretion disks and flybys.

The results were published in Nature Astronomy on May 30.

During the formation of stars, accretion disks arise around newborn stars. These accretion disks, also known as "protostellar disks," are an essential component in star formation. Accretion disks continuously feed gas into protostars from the environment. In this sense, they are stellar cradles where stars are born and raised.

For massive protostars, especially early O-type ones of more than 30 solar masses, however, the role of accretion disks in their formation has not been clear.

At a distance of about 26,000 light years from Earth, the Galactic Center is a unique and important star-forming environment. Besides the supermassive black hole Sgr A*, the Galactic Center contains a huge reservoir of dense molecular gas, mostly in the form of molecular hydrogen (H2), which is the raw material for star formation. The gas starts to form stars once gravitational collapse is initiated.

However, the environment in the Galactic Center is unique, with strong turbulence and strong magnetic fields as well as tidal forces from Sgr A*, all of which substantially affect star formation in this region.

Since the distance between the Galactic Center and Earth is huge and complicated foreground contaminations exist, direct observations of star-forming regions around the Galactic Center have been challenging.

The research team led by Dr. LU used ALMA's long baseline observations to achieve a resolution of 40 milliarcseconds. To get an idea how fine that resolution is, it would allow an observer in Shanghai to easily spot a football in Beijing.

With these high-resolution, high-sensitivity ALMA observations, the researchers discovered an accretion disk in the Galactic Center. The disk has a diameter of about 4,000 astronomical units and surrounds a forming, early O-type star with a mass about 32 times that of the Sun. This system is among the most massive protostars with accretion disks and represents the first direct imaging of a protostellar disk in the Galactic Center.

The discovery suggests that massive early-O type stars go through a formation phase involving accretion disks, and this conclusion is valid for the unique environment of the Galactic Center.

What is more interesting is that the disk clearly displays two spiral arms. Such arms are often found in spiral galaxies but are rarely seen in protostellar disks. In general, spiral arms emerge in accretion disks due to fragmentation induced by gravitational instability. However, the disk discovered in this research is hot and turbulent, thus making it able to balance its own gravity.

In trying to explain this phenomenon, the researchers proposed an alternate explanation—that the spirals were induced by external perturbation. The researchers proposed this explanation after detecting an object of about three solar masses—possibly the source of the external perturbation—several thousand astronomical units away from the disk.

To verify this proposition, the researchers calculated several dozen possible orbits of this object. They found that only one of these orbits could perturb the disk to the observed level. They subsequently carried out a numerical simulation on the high-performance supercomputing platform of the Shanghai Astronomical Observatory to trace the trajectory of the intruding object. The scientists were able to successfully reproduce the entire history of the object flying by the disk more than 10,000 years ago, when it would have stirred up spirals in the disk.

"The nice match among analytical calculations, the numerical simulation, and the ALMA observations provides robust evidence that the spiral arms in the disk are relics of the flyby of the intruding object," said Dr. LU.

This finding clearly demonstrates that accretion disks at early evolutionary stages of star formation are subject to frequent dynamic processes such as flybys and these processes can substantially influence the formation of stars and planets.

Interestingly, flybys may have occurred in our own solar system too: A binary stellar system known as Scholz's Star flew by the solar system about 70,000 years ago, probably penetrating through the Oort cloud and sending comets to the inner solar system.

The current study suggests that for more massive stars, especially in the high-stellar-density environment around the Galactic Center, such flybys should also be frequent. "The formation of this massive protostar is similar to its lower-mass cousins like the Sun, with accretion disks and flyby events involved. Although stellar masses are different, certain physical mechanisms in star formation could be the same. This provides important clues to solving the mystery of massive star formation," said Dr. LU.

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JOURNAL

Nature Astronomy

DOI

10.1038/s41550-022-01681-4 

ARTICLE TITLE

A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molecular Zone

Which forces control the elevation of mountains?

It depends, say scientists and propose a novel classification scheme in a new study

Peer-Reviewed Publication

GFZ GEOFORSCHUNGSZENTRUM POTSDAM, HELMHOLTZ CENTRE

 

IMAGE: THE PUNA PLATEAU IS PART OF THE CENTRAL ANDES, A MOUNTAIN BELT IN WHICH THE ELEVATION IS MAINLY DRIVEN BY LITHOSPHERIC STRENGTH AND TECTONIC FORCES. view more 

CREDIT: MITCHELL D'ARCY FOR GFZ

Scientists have come up with a new classification scheme for mountain belts that uses just a single number to describe whether the elevation of the mountain belt is controlled mainly by weathering and erosion or by properties of the Earth’s crust, i.e., the lithospheric strength: the “Beaumont number” (Bm). It’s named after Chris Beaumont, a scientist who, together with his team, developed coupled models of surface processes and tectonic forces. The scientists report about their findings in the current issue of Nature.

A Beaumont number between 0.4 and 0.5 means that the mountains are in a so-called flux steady state in which the controlling factors of mountain growth are tectonic forces and the lithospheric strength, balanced by weathering processes as, for example, in Taiwan. With a Bm value lower than 0.4, mountains are also in a flux steady state but with erosion as controlling factor like the Southern Alps of New Zealand.  A Beaumont number above 0.5 means that the mountains still grow (non-steady state) with lithospheric strength controlling the process. Examples for this type are the Himalaya-Tibet mountains and the Central Andes.

This classification is resolving a long-standing question whether tectonic forces and strength of the Earth’s crust are the controlling factors of mountain elevation or weathering processes. The new study says it can be one or the other – depending on geographic location, climate and underground properties.

The team of scientists led by Sebastian G. Wolf of Bergen University in Norway used a new coupled surface process and mantle-scale tectonic model for their study by combining the thermomechanical tectonic model FANTOM with the landscape evolution model FastScape. Thus, they were able to reconcile high erosion rates in some active orogens with long-term survival of mountain belts for hundreds of millions of years.

Jean Braun of the GFZ German Research Centre for Geosciences, who co-authored the paper, says: “With our Beaumont number we can determine to which proportion tectonics, climate, and crustal strength control the height of mountain belts. And, for most mountain belts, this can be done without complex measurements or assumptions; all that is needed is a knowledge of the rate of convergence obtained from present-day plate velocities or plate reconstructions, the height of the mountain obtained from a topographic map and the widening rate obtained from the geological record. In a nutshell: Whether a mountain is short or tall is the product of slow or fast convergence, wet or dry climate, or strong or weak crust.” The Beaumont number shows which of these three factors is dominating.

Original study: Sebastian G. Wolf, Ritske S. Huismans, Jean Braun & Xiaoping Yuan: “Topography of mountain belts controlled by rheology and surface processes”; in Nature. DOI: 10.1038/s41586-022-04700-6

Link: https://www.nature.com/articles/s41586-022-04700-6

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JOURNAL

Nature

DOI

10.1038/s41586-022-04700-6 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Topography of mountain belts controlled by rheology and surface processes

What oxytocin can tell us about the evolution of human prosociality

Variants unique to modern humans in more than 70% of the population

Peer-Reviewed Publication

UNIVERSITY OF BARCELONA

 

IMAGE: THIS RESEARCH IS PART OF CONSTANTINA THEOFANOPOULOU'S DOCTORAL THESIS CARRIED OUT UNDER THE CO-SUPERVISION OF CEDRIC BOECKX, ICREA RESEARCHER AT THE INSTITUTE OF COMPLEX SYSTEMS AT THE UB (UBICS) AND ERICH D. JARVIS, PROFESSOR AT ROCKEFELLER UNIVERSITY. view more 

CREDIT: UNIVERSITY OF BARCELONA

Modern humans are characterized by their prosociality, a broad term that encompasses intraspecies empathy, social tolerance, cooperation and altruism. These facets of social cognition have been associated with variations in the oxytocin and vasotocin genes (OT and VT) and their receptors (OTR and VTR).To shed light on the genetic basis of this behaviour, scientists from the University of Barcelona (UB) and Rockefeller University carried out a new study comparing the available genomic sequences of these genes between modern humans, non-human primate species (e.g., chimpanzees, bonobos, and macaques) and, for the first time, archaic humans, using all the available genomes of Neanderthals and Denisovans.

In the study, published in the journal Comprehensive Psychoneuroendocrinology, the researchers identified several sites in which modern humans differed from both archaic humans and non-human primates, and others where both modern and archaic humans differed from non-human primates.

“We used an interdisciplinary approach to understand the evolution of hominid prosociality through the lens of the oxytocin and vasotocin receptors, where we combined evidence from modern and archaic genomics, population genetics, transcriptomics, and behavioural and neuroscientific studies, among other methods. These results can shed light on the genetics underlying possible sociality differences identified between modern humans and archaic humans, as well as the similarities between the modern human and bonobo social behaviour”, said first author Constantina Theofanopoulou. This research is part of her doctoral thesis carried out under the co-supervision of Cedric Boeckx, ICREA researcher at the Institute of Complex Systems at the UB (UBICS) and Erich D. Jarvis, professor at Rockefeller University.

Variants unique to modern humans in more than 70% of the population

Considering the evidence on modern human prosociality and on the involvement of the oxytocin and vasotocin genes in social behaviours, the researchers hypothesized that the evolution of these genes might elucidate the genetic basis of the evolution of hominin prosociality. With this aim in mind, the study explored the differences between modern humans, archaic humans and non-human primates in polymorphic heterozygous sites in the human genome – locations where at least two alternative sequences are found in a population. “Past studies that compared the entire modern human genome with the Neanderthal or the chimpanzee genomes have focused on changes that are fixed or nearly fixed in modern humans. This has led to them identifying sites where, for example, all Neanderthals had Adenine (one of the four nucleotides that with guanine, cytosine and thymine form the DNA) and nearly all modern humans (say, 98%) have Guanine. In this study, we searched for differences on locations where, by definition, not all modern humans share the same nucleotide, namely on polymorphic sites, where for example, 70% of the modern human population has Adenine and 30% Cytosine”, adds Theofanopoulou.

The researchers identified five sites in the oxytocin and vasotocin receptors where modern humans are unique in one of their two (or more) variants compared to archaic humans and non-human primates, and which are at the same time found in more than 70% of the modern human population. Next, they conducted functional and frequency analyses to establish whether the variants are relevant. They performed a range of analyses on the five sites and found that some of the variants are highly functional, indicating that they have an effect on the molecular function of the proteins activated by these genes.

The researchers also found that these sites are encountered in genome regions that are active in the brain, particularly in the cingulate gyrus, a brain region involved in social cognition-relevant pathways. Moreover, all these sites have been associated in other studies with a plethora of social behaviours or social deficits, such as autism, attention deficit hyperactivity disorder (ADHD), aggression, and so on.

These findings may help to explain some of the social differences between modern humans and what we presume to know about the social behaviours of Neanderthals and Denisovans. “For example, they might be relevant to the smaller social groups attributed to Neanderthals and Denisovans or to the decreased modern human androgenization. They might also be relevant to a different social structure, i.e., Neanderthals have been linked to a polygynous social structure and a higher level of male–male competition than most contemporary modern human populations”, says Constantina Theofanopoulou.

Variants present only in modern and archaic humans

The study also found two sites on the oxytocin receptor under a positive selection in modern and archaic humans: that is to say, modern and archaic humans showed a variant that was not present in any other non-human primate. This means that these sites are found in very high percentages in the modern human population (in this case, more than 85%). These same sites have also been associated with a great many social behaviours or deficits, and one of them was predicted to be a highly functional site in their regulation analyses. “The sites that are unique in both us and archaic humans versus non-human primates can elucidate the genetic underpinnings of the progressive social tolerance needed for the intensive cultural transmission of technological innovations (e.g., fire use) in the evolution of humankind, as well as for the reduced aggression indicated by several markers in early hominid evolution, such as the reduction of male canine size and the accelerated demographic success”, adds Theofanopoulou.

Convergent sites with bonobos

Lastly, the researchers found three sites where modern humans and bonobos, a primate species that shows convergence of prosocial behaviours with humans, have the same nucleotide. “The convergent sites in modern humans and bonobos could be insightful for understanding the posited similarities in prosociality, social tolerance and cooperation between us and bonobos, and the differences of both compared to chimpanzees. For example, bonobos outperform chimpanzees on tasks relevant to social causality or theory of mind and are more attentive to the face and eyes, suggestive of higher empathic sensitivity”, notes the researcher.

All the sites identified in this study have also been independently associated with disorders that include social deficits, such as autism spectrum disorders (ASD). “Understanding developmental disorders through evolutionary lenses can aid into us achieving what we call an evo-devo (evolutionary and developmental biology) understanding of these disorders. If indeed “ontogeny recapitulates phylogeny”, then deciphering our evolutionary trajectory may shed light to new genetic spots for clinical research that might, in turn, lead to earlier disorder diagnosis”, highlights Constantina Theofanopoulou.

Future research in larger sample sizes

The next step in this research would be to test these results in larger sample sizes. This objective, as Theofanopoulou says, “is easier” to achieve in non-human primates such as chimpanzees and bonobos, but “is more difficult in the case of Neanderthals or Denisovans”, since obtaining access to more archaic genomes depends on archaeological finds, among other factors. “Another step is to widen the scope of the research and include more genes of the oxytocin pathway, or other genes highlighted in human evolution, such as dopamine”, concludes the researcher.

 

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JOURNAL

Comprehensive Psychoneuroendocrinology

DOI

10.1016/j.cpnec.2022.100139 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Human tissue samples

ARTICLE TITLE

«Oxytocin and vasotocin receptor variation and the evolution of human prosociality