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Himalayan glaciers react, blow cold winds down their slopes

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Himalayan glaciers react, blow cold winds down their slopes


Himalayan Glaciers ‘fight back’ to preserve themselves, but for how long? An international team of researchers, co-led by Professor Francesca Pellicciotti of the Institute of Science and Technology Austria (ISTA), explains a stunning phenomenon: rising global temperatures have led Himalayan glaciers to increasingly cool the air in contact with the ice surface. The ensuing cold winds might help cool the glaciers and preserve the surrounding ecosystems. The results, found across the Himalayan range, were published in Nature Geoscience.

Is global warming causing Himalayan glaciers to melt like ice cream on a hot summer day? Previously, scientists documented an elevation-dependent warming effect: they showed that mountain tops “felt” the effect of global warming stronger and warmed up faster. Yet, a high-altitude climate station at the base of Mount Everest in Nepal showed an unexpected phenomenon: the measured surface air temperature averages remained suspiciously stable instead of increasing. How could this data be interpreted?

The Pyramid International Laboratory/Observatory climate station, located at a glacierized elevation (5050 m) on the southern slopes of Mount Everest, alongside the Khumbu and Lobuche glaciers, has continuously recorded hourly meteorological data for nearly three decades. Now, an international team of researchers led by new ISTA Professor Francesca Pellicciotti and National Research Council of Italy (CNR) researchers Franco Salerno and Nicolas Guyennon cracked the code. The warming climate is triggering a cooling reaction in the glaciers: it is causing cold winds — katabatic winds — to flow down the slopes. But how long can the glaciers locally counterbalance the effects of global warming by cooling themselves? And which characteristics allow the glaciers to do so?

The Devil Is in the Detail

To explain the observed phenomenon, the team had to examine the data thoroughly. “We found that the overall temperature averages seemed stable for a simple reason. While the minimum temperatures have been steadily on the rise, the surface temperature maxima in summer were consistently dropping,” says Salerno. The glaciers are reacting to the warming climate by increasing their temperature exchange with the surface, Pellicciotti explains. Global warming causes an increased temperature difference between the warmer environmental air over the glacier and the air mass in direct contact with the glacier’s surface. “This leads to an increase in turbulent heat exchange at the glacier’s surface and stronger cooling of the surface air mass,” says Pellicciotti. As a result, the cool and dry surface air masses become denser and flow down the slopes into the valleys, cooling the lower parts of the glaciers and the surrounding ecosystems.

What Makes Glaciers ‘Fight Back?’

Going beyond the ground observations uniquely available at Pyramid, the team drew on the latest scientific advances in climate models: the global climate and weather reanalysis called ERA5-Land. ERA5-Land reanalysis combines model data with observations from across the world into a globally complete and consistent dataset using the laws of physics. Interpreting this data allowed the team to demonstrate that the global warming-induced katabatic winds occurred not only on Mount Everest but in the entire Himalayan range. “This phenomenon is the outcome of 30 years of steadily increasing global temperatures. The next step is to find out which key glacier characteristics favor such a reaction,” says Pellicciotti.

Ultimately, the researchers seek to understand which glaciers can react this way to global warming, and for how long. “While other glaciers are experiencing dramatic changes right now, the glaciers in High-Mountain Asia — the Third Pole — are very large, hold more ice masses, and have longer response times. Thus, we might still have a chance to ‘save’ these glaciers.”

Thus, Pellicciotti and her team will soon investigate whether the world’s only stable or growing glaciers in the Pamir and Karakoram mountains, to the north-west of the Himalayas, are also reacting to global warming by blowing cold winds down their slopes. “The slopes of the Pamir and Karakoram glaciers are generally flatter than in the Himalayas. Thus, we hypothesize that the cold winds might act to cool the glaciers themselves rather than reaching lower down into the surrounding environments. We will be able to tell in the next couple of years,” says Pellicciotti.

Glacier Tipping Point?

“We believe that the katabatic winds are the response of healthy glaciers to rising global temperatures and that this phenomenon could help preserve the permafrost and surrounding vegetation,” says Guyennon. Glaciers are indeed essential in maintaining the water security in their ecosystems. But how long can healthy glaciers fight back? The glaciers on the southern Himalayan slopes are classical examples of “accumulation-ablation glaciers”: they accumulate mass at high altitudes from the Indian subcontinent’s summer monsoons and, at the same time, lose mass from the continuous melting. However, the katabatic winds are now shifting this balance: the colder air masses flowing down from the glaciers are lowering the altitude at which precipitation takes place. This leads to the glaciers missing a key mass input while they continue to melt. Thus, perceived cool temperatures flowing down from glaciers are an emergency reaction to global warming rather than an indicator of glacier long-term stability.

Does this mean that the glaciers are approaching their preservation tipping point? “They are in some places, but we do not know where and how,” says Pellicciotti. Yet, she does not lose heart easily: “Even if the glaciers can’t preserve themselves forever, they might still preserve the environment around them for some time. Thus, we call for more multidisciplinary research approaches to converge efforts toward explaining the effects of global warming,” she concludes. These efforts could prove instrumental in changing the course of human-caused climate change.



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Researchers create artificial cells that act like living cells

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Researchers create artificial cells that act like living cells


In a new study published in Nature Chemistry, UNC-Chapel Hill researcher Ronit Freeman and her colleagues describe the steps they took to manipulate DNA and proteins — essential building blocks of life — to create cells that look and act like cells from the body. This accomplishment, a first in the field, has implications for efforts in regenerative medicine, drug delivery systems, and diagnostic tools.

“With this discovery, we can think of engineering fabrics or tissues that can be sensitive to changes in their environment and behave in dynamic ways,” says Freeman, whose lab is in the Applied Physical Sciences Department of the UNC College of Arts and Sciences.

Cells and tissues are made of proteins that come together to perform tasks and make structures. Proteins are essential for forming the framework of a cell, called the cytoskeleton. Without it, cells wouldn’t be able to function. The cytoskeleton allows cells to be flexible, both in shape and in response to their environment.

Without using natural proteins, the Freeman Lab built cells with functional cytoskeletons that can change shape and react to their surroundings. To do this, they used a new programmable peptide-DNA technology that directs peptides, the building blocks of proteins, and repurposed genetic material to work together to form a cytoskeleton.

“DNA does not normally appear in a cytoskeleton,” Freeman says. “We reprogrammed sequences of DNA so that it acts as an architectural material, binding the peptides together. Once this programmed material was placed in a droplet of water, the structures took shape.”

The ability to program DNA in this way means scientists can create cells to serve specific functions and even fine-tune a cell’s response to external stressors. While living cells are more complex than the synthetic ones created by the Freeman Lab, they are also more unpredictable and more susceptible to hostile environments, like severe temperatures.

“The synthetic cells were stable even at 122 degrees Fahrenheit, opening up the possibility of manufacturing cells with extraordinary capabilities in environments normally unsuitable to human life,” Freeman says.

Instead of creating materials that are made to last, Freeman says their materials are made to task — perform a specific function and then modify themselves to serve a new function. Their application can be customized by adding different peptide or DNA designs to program cells in materials like fabrics or tissues. These new materials can integrate with other synthetic cell technologies, all with potential applications that could revolutionize fields like biotechnology and medicine.

“This research helps us understand what makes life,” Freeman says. “This synthetic cell technology will not just enable us to reproduce what nature does, but also make materials that surpass biology.”



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This alloy is kinky

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This alloy is kinky


Researchers have uncovered a remarkable metal alloy that won’t crack at extreme temperatures due to kinking, or bending, of crystals in the alloy at the atomic level.  A metal alloy composed of niobium, tantalum, titanium, and hafnium has shocked materials scientists with its impressive strength and toughness at both extremely hot and cold temperatures, a combination of properties that seemed so far to be nearly impossible to achieve. In this context, strength is defined as how much force a material can withstand before it is permanently deformed from its original shape, and toughness is its resistance to fracturing (cracking). The alloy’s resilience to bending and fracture across an enormous range of conditions could open the door for a novel class of materials for next-generation engines that can operate at higher efficiencies.

The team, led by Robert Ritchie at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, in collaboration with the groups led by professors Diran Apelian at UC Irvine and Enrique Lavernia at Texas A&M University, discovered the alloy’s surprising properties and then figured out how they arise from interactions in the atomic structure. Their work is described in a study that was published April 11, 2024 in Science.

“The efficiency of converting heat to electricity or thrust is determined by the temperature at which fuel is burned — the hotter, the better. However, the operating temperature is limited by the structural materials which must withstand it,” said first author David Cook, a Ph.D. student in Ritchie’s lab. “We have exhausted the ability to further optimize the materials we currently use at high temperatures, and there’s a big need for novel metallic materials. That’s what this alloy shows promise in.”

The alloy in this study is from a new class of metals known as refractory high or medium entropy alloys (RHEAs/RMEAs). Most of the metals we see in commercial or industrial applications are alloys made of one main metal mixed with small quantities of other elements, but RHEAs and RMEAs are made by mixing near-equal quantities of metallic elements with very high melting temperatures, which gives them unique properties that scientists are still unraveling. Ritchie’s group has been investigating these alloys for several years because of their potential for high-temperature applications.

“Our team has done previous work on RHEAs and RMEAs and we have found that these materials are very strong, but generally possess extremely low fracture toughness, which is why we were shocked when this alloy displayed exceptionally high toughness,” said co-corresponding author Punit Kumar, a postdoctoral researcher in the group.

According to Cook, most RMEAs have a fracture toughness less than 10 MPa√m, which makes them some of the most brittle metals on record. The best cryogenic steels, specially engineered to resist fracture, are about 20 times tougher than these materials. Yet the niobium, tantalum, titanium, and hafnium (Nb45Ta25Ti15Hf15) RMEA alloy was able to beat even the cryogenic steel, clocking in at over 25 times tougher than typical RMEAs at room temperature.

But engines don’t operate at room temperature. The scientists evaluated strength and toughness at five temperatures total: -196°C (the temperature of liquid nitrogen), 25°C (room temperature), 800°C, 950°C, and 1200°C. The last temperature is about 1/5 the surface temperature of the sun.

The team found that the alloy had the highest strength in the cold and became slightly weaker as the temperature rose, but still boasted impressive figures throughout the wide range. The fracture toughness, which is calculated from how much force it takes to propagate an existing crack in a material, was high at all temperatures.

Unraveling the atomic arrangements

Almost all metallic alloys are crystalline, meaning that the atoms inside the material are arranged in repeating units. However, no crystal is perfect, they all contain defects. The most prominent defect that moves is called the dislocation, which is an unfinished plane of atoms in the crystal. When force is applied to a metal it causes many dislocations to move to accommodate the shape change. For example, when you bend a paper clip which is made of aluminum, the movement of dislocations inside the paper clip accommodates the shape change. However, the movement of dislocations becomes more difficult at lower temperatures and as a result many materials become brittle at low temperatures because dislocations cannot move. This is why the steel hull of the Titanic fractured when it hit an iceberg. Elements with high melting temperatures and their alloys take this to the extreme, with many remaining brittle up to even 800°C. However, this RMEA bucks the trend, withstanding snapping even at temperatures as low as liquid nitrogen (-196°C).

To understand what was happening inside the remarkable metal, co-investigator Andrew Minor and his team analyzed the stressed samples, alongside unbent and uncracked control samples, using four-dimensional scanning transmission electron microscopy (4D-STEM) and scanning transmission electron microscopy (STEM) at the National Center for Electron Microscopy, part of Berkeley Lab’s Molecular Foundry.

The electron microscopy data revealed that the alloy’s unusual toughness comes from an unexpected side effect of a rare defect called a kink band. Kink bands form in a crystal when an applied force causes strips of the crystal to collapse on themselves and abruptly bend. The direction in which the crystal bends in these strips increases the force that dislocations feel, causing them to move more easily. On the bulk level, this phenomenon causes the material to soften (meaning that less force has to be applied to the material as it is deformed). The team knew from past research that kink bands formed easily in RMEAs, but assumed that the softening effect would make the material less tough by making it easier for a crack to spread through the lattice. But in reality, this is not the case.

“We show, for the first time, that in the presence of a sharp crack between atoms, kink bands actually resist the propagation of a crack by distributing damage away from it, preventing fracture and leading to extraordinarily high fracture toughness,” said Cook.

The Nb45Ta25Ti15Hf15 alloy will need to undergo a lot more fundamental research and engineering testing before anything like a jet plane turbine or SpaceX rocket nozzle is made from it, said Ritchie, because mechanical engineers rightfully require a deep understanding of how their materials perform before they use them in the real world. However, this study indicates that the metal has potential to build the engines of the future.

This research was conducted by David H. Cook, Punit Kumar, Madelyn I. Payne, Calvin H. Belcher, Pedro Borges, Wenqing Wang, Flynn Walsh, Zehao Li, Arun Devaraj, Mingwei Zhang, Mark Asta, Andrew M. Minor, Enrique J. Lavernia, Diran Apelian, and Robert O. Ritchie, scientists at Berkeley Lab, UC Berkeley, Pacific Northwest National Laboratory, and UC Irvine, with funding from the Department of Energy (DOE) Office of Science. Experimental and computational analysis was conducted at the Molecular Foundry and the National Energy Research Scientific Computing Center — both are DOE Office of Science user facilities.



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Giant galactic explosion exposes galaxy pollution in action

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Giant galactic explosion exposes galaxy pollution in action


A team of international researchers studied galaxy NGC 4383, in the nearby Virgo cluster, revealing a gas outflow so large that it would take 20,000 years for light to travel from one side to the other.

The discovery was published today in the journal Monthly Notices of the Royal Astronomical Society.

Lead author Dr Adam Watts, from The University of Western Australia node at the International Centre for Radio Astronomy Research (ICRAR), said the outflow was the result of powerful stellar explosions in the central regions of the galaxy that could eject enormous amounts of hydrogen and heavier elements.

The mass of gas ejected is equivalent to more than 50 million Suns.

“Very little is known about the physics of outflows and their properties because outflows are very hard to detect,” Dr Watts said.

“The ejected gas is quite rich in heavy elements giving us a unique view of the complex process of mixing between hydrogen and metals in the outflowing gas.

“In this particular case, we detected oxygen, nitrogen, sulphur and many other chemical elements.”

Gas outflows are crucial to regulate how fast and for how long galaxies can keep forming stars. The gas ejected by these explosions pollutes the space between stars within a galaxy, and even between galaxies, and can float in the intergalactic medium forever.

The high-resolution map was produced with data from the MAUVE survey, co-led by ICRAR researchers Professors Barbara Catinella and Luca Cortese, who were also co-authors of the study.

The survey used the MUSE Integral Field Spectrograph on the European Southern Observatory’s Very Large Telescope, located in northern Chile.

“We designed MAUVE to investigate how physical processes such as gas outflows help stop star formation in galaxies,” Professor Catinella said.

“NGC 4383 was our first target, as we suspected something very interesting was happening, but the data exceeded all our expectations.

“We hope that in the future, MAUVE observations reveal the importance of gas outflows in the local Universe with exquisite detail.”



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