Developed by researchers at RMIT University in Melbourne, Australia, the highly versatile catalysts are cost-effective to make and simple to scale.

The team’s lab demonstrations show the 3D printed catalysts could potentially be used to power hypersonic flight while simultaneously cooling the system.

The research is published in the Royal Society of Chemistry journal, Chemical Communications.

Lead researcher Dr Selvakannan Periasamy said their work tackled one of the biggest challenges in the development of hypersonic aircraft: controlling the incredible heat that builds up when planes fly at more than five times the speed of sound.

“Our lab tests show the 3D printed catalysts we’ve developed have great promise for fuelling the future of hypersonic flight,” Periasamy said.

“Powerful and efficient, they offer an exciting potential solution for thermal management in aviation — and beyond.

“With further development, we hope this new generation of ultra-efficient 3D printed catalysts could be used to transform any industrial process where overheating is an ever-present challenge.”

Need for speed

Only a few experimental planes have reached hypersonic speed (defined as above Mach 5 — over 6,100km an hour or 1.7km per second).

In theory, a hypersonic aircraft could travel fromLondon to New York in less than 90 minutes but many challenges remain in the development of hypersonic air travel, such as the extreme heat levels.

First author and PhD researcher Roxanne Hubesch said using fuel as a coolant was one of the most promising experimental approaches to the overheating problem.

“Fuels that can absorb heat while powering an aircraft are a key focus for scientists, but this idea relies on heat-consuming chemical reactions that need highly efficient catalysts,” Hubesch said.

“Additionally, the heat exchangers where the fuel comes in contact with the catalysts must be as small as possible, because of the tight volume and weight constraints in hypersonic aircraft.”

To make the new catalysts, the team 3D printed tiny heat exchangers made of metal alloys and coated them with synthetic minerals known as zeolites.

The researchers replicated at lab scale the extreme temperatures and pressures experienced by the fuel at hypersonic speeds, to test the functionality of their design.

Miniature chemical reactors

When the 3D printed structures heat up, some of the metal moves into the zeolite framework- a process crucial to the unprecedented efficiency of the new catalysts.

“Our 3D printed catalysts are like miniature chemical reactors and what makes them so incredibly effective is that mix of metal and synthetic minerals,” Hubesch said.

“It’s an exciting new direction for catalysis, but we need more research to fully understand this process and identify the best combination of metal alloys for the greatest impact.”

The next steps for the research team from RMIT’s Centre for Advanced Materials and Industrial Chemistry (CAMIC) include optimising the 3D printed catalysts by studying them with X-ray synchrotron techniques and other in-depth analysis methods.

The researchers also hope to extend the potential applications of the work into air pollution control for vehicles and miniature devices to improve indoor air quality — especially important in managing airborne respiratory viruses like COVID-19.

CAMIC Director, Distinguished Professor Suresh Bhargava, said the trillion-dollar chemical industry was largely based on old catalytic technology.

“This third generation of catalysis can be linked with 3D printing to create new complex designs that were previously not possible,” Bhargava said.

“Our new 3D printed catalysts represent a radical new approach that has real potential to revolutionise the future of catalysis around the world.”

The 3D printed catalysts were produced using Laser Powder Bed Fusion (L-PBF) technology in the Digital Manufacturing Facility, part of RMIT’s Advanced Manufacturing Precinct.

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Materials provided by RMIT University. Original written by Gosia Kaszubska. Note: Content may be edited for style and length.

Postdoctoral fellow Elizabeth Wallace, a paleotempestologist who joined the lab of Rice climate scientist Sylvia Deethis year, is building upon techniques that reveal the frequency of hurricanes in the Atlantic basin over millennia.

Paleoclimate hurricane data (or ‘proxy’ data) is found in archives like tree rings that retain signs of short-term flooding, sediments in blue holes (marine caverns) and coastal ponds that preserve evidence of sand washed inland by storm surges. These natural archives give researchers a rough idea of when and where hurricanes have come ashore.

In a new paper in Geophysical Research Letters, Wallace, Dee and co-author Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology, take hundreds of thousands of “synthetic” storms spun up from global climate model simulations of the past 1,000 years and examine whether or not they are captured by the vast network of Atlantic paleohurricane proxies.

Reconstructing the past will help scientists understand the ebb and flow of Atlantic hurricanes over time. Previous studies by Wallace and others have demonstrated that a single site capturing past storms cannot be used to reconstruct hurricane climate changes; however, a network of proxies might help refine models of how these storms are likely to be affected by climate change going forward.

“These paleo hurricane proxies allow us to reconstruct storms into the past, and we’re using them to figure out how basin-wide storm activity has changed,” said Wallace, a Virginia native who earned her doctorate at MIT and the Woods Hole Oceanographic Institution last year and connected with Dee when the professor spoke there in 2017.

“If I have a sediment core from Florida, it’s only capturing storms that hit Florida,” she said. “I wanted to see if we can use the full collection of records collected from the Bahamas, the East Coast and the Gulf of Mexico over the past few decades to accurately reconstruct basin-wide storm activity over the last few centuries.”

The synthetic storms they built helped illustrate what Wallace already knew: There’s a bias toward the Caribbean and Gulf of Mexico, and a need for more proxies along the east coasts of North and Central America. The Rice team’s quest going forward will be to refine their climate simulations and add more sites to the networks to better reconstruct past hurricane activity.

“In particular, there aren’t really any sites from the Southeast U.S., places like the Carolinas,” she said. “One of the goals of this work is to highlight where scientists should go to core next.”

Wallace has first-hand experience drilling cores. “During a storm event, you get high winds and waves that take the sand from the beach and essentially just throw it back into a coastal pond,” she said. “Only during storm events do these sand layers get deposited in the pond, and in the sediment cores you can see them interspersed with the fine mud that’s typically there. We can date these sand layers and know when a hurricane struck the site.”

She noted there has not yet been an “intensive” effort to compare sediment and tree ring records. “The tree record is still an uncertain proxy,” Wallace said. “We’re looking for tree ring records with rainfall signatures that correspond to storms going over the past 200 or 300 years that match the sediment records for that same interval.”

Dee said the work is fundamentally different from the paleoclimate models she most often studies. “Here we’re taking climate models and generating hundreds of pseudo-tropical storms,” she said. “We’re ‘playing Gaia’ by making a plausible version of reality and combining it with our knowledge of available proxy sites.

“This tells us how many records from how many places we realistically need to capture a climate signal,” Dee said. “It’s really expensive to go out and drill cores, and this helps give us a way to prioritize where to drill.

“This research is crucial as we accelerate into a climate mean state with ever-warmer Atlantic Ocean temperatures,” she said. “Understanding how these storms have evolved over time provides a baseline against which to evaluate tropical cyclones with and without human impacts on the climate system.”

A Pan Postdoctoral Research Fellowship and Rice Academy Fellowship to Wallace and a Gulf Research Program grant to Dee supported the study. Dee is an assistant professor of Earth, environmental and planetary sciences. Emanuel is the Cecil & Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center at MIT.

“We know that there are a range of immune responses to COVID-19, and the biological processes underlying those responses are not well understood,” said co-first author Jihoon Lee, a graduate student at Fred Hutchinson Cancer Research Center. “We analyzed thousands of biological markers linked to metabolic pathways that underlie the immune system and found some clues as to what immune-metabolic changes may be pivotal in severe disease. Our hope is that these observations of immune function will help others piece together the body’s response to COVID-19. The deeper understanding gained here may eventually lead to better therapies that can more precisely target the most problematic immune or metabolic changes.”

The researchers collected 374 blood samples — two draws per patient during the first week after being diagnosed with SARS-CoV-2 infection — and analyzed their plasma and single immune cells. The analysis included 1,387 genes involved in metabolic pathways and 1,050 plasma metabolites.

In plasma samples, the team found that increased COVID-19 severity is associated with metabolite alterations, suggesting increased immune-related activity. Furthermore, through single-cell sequencing, researchers found that each major immune cell type has a distinct metabolic signature.

“We have found metabolic reprogramming that is highly specific to individual immune cell classes (e.g. “killer” CD8+ T cells, “helper” CD4+ T cells, antibody-secreting B cells, etc.) and even cell subtypes, and the complex metabolic reprogramming of the immune system is associated with the plasma global metabolome and are predictive of disease severity and even patient death,” said co-first and co-corresponding author Dr. Yapeng Su, a research scientist at Institute for Systems Biology. “Such deep and clinically relevant insights on sophisticated metabolic reprogramming within our heterogeneous immune systems are otherwise impossible to gain without advanced single-cell multi-omic analysis.”

“This work provides significant insights for developing more effective treatments against COVID-19. It also represents a major technological hurdle,” said Dr. Jim Heath, president and professor of ISB and co-corresponding author on the paper. “Many of the data sets that are collected from these patients tend to measure very different aspects of the disease, and are analyzed in isolation. Of course, one would like these different views to contribute to an overall picture of the patient. The approach described here allows for the sum of the different data sets to be much greater than the parts, and provides for a much richer interpretation of the disease.”

The research was conducted by scientists from ISB, Fred Hutchinson Cancer Research Center, Stanford University, Swedish Medical Center St. John’s Cancer Institute at Saint John’s Health Center, the University of Washington, the Howard Hughes Medical Institute.

Funding for this project comes from Merck and the Biomedical Advanced Research and Development Authority (BARDA), the Wilke Family Foundation, the MJ Murdock Charitable Trust, the Swedish Medical Center Foundation, the Parker Institute for Cancer Immunotherapy, Gilead, Amazon Web Services, and the National Institutes of Health.

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“We have found the first observational evidence that white dwarfs can still undergo stable thermonuclear activity,” explained Jianxing Chen of the Alma Mater Studiorum Università di Bologna and the Italian National Institute for Astrophysics, who led this research. “This was quite a surprise, as it is at odds with what is commonly believed.”

White dwarfs are the slowly cooling stars which have cast off their outer layers during the last stages of their lives. They are common objects in the cosmos; roughly 98% of all the stars in the Universe will ultimately end up as white dwarfs, including our own Sun [1]. Studying these cooling stages helps astronomers understand not only white dwarfs, but also their earlier stages as well.

To investigate the physics underpinning white dwarf evolution, astronomers compared cooling white dwarfs in two massive collections of stars: the globular clusters M3 and M13 [2]. These two clusters share many physical properties such as age and metallicity [3] but the populations of stars which will eventually give rise to white dwarfs are different. In particular, the overall colour of stars at an evolutionary stage known as the Horizontal Branch are bluer in M13, indicating a population of hotter stars. This makes M3 and M13 together a perfect natural laboratory in which to test how different populations of white dwarfs cool.

“The superb quality of our Hubble observations provided us with a full view of the stellar populations of the two globular clusters,” continued Chen. “This allowed us to really contrast how stars evolve in M3 and M13.”

Using Hubble’s Wide Field Camera 3 the team observed M3 and M13 at near-ultraviolet wavelengths, allowing them to compare more than 700 white dwarfs in the two clusters. They found that M3 contains standard white dwarfs which are simply cooling stellar cores. M13, on the other hand, contains two populations of white dwarfs: standard white dwarfs and those which have managed to hold on to an outer envelope of hydrogen, allowing them to burn for longer and hence cool more slowly.

Comparing their results with computer simulations of stellar evolution in M13, the researchers were able to show that roughly 70% of the white dwarfs in M13 are burning hydrogen on their surfaces, slowing down the rate at which they are cooling.

This discovery could have consequences for how astronomers measure the ages of stars in the Milky Way. The evolution of white dwarfs has previously been modelled as a predictable cooling process. This relatively straightforward relationship between age and temperature has led astronomers to use the white dwarf cooling rate as a natural clock to determine the ages of star clusters, particularly globular and open clusters. However, white dwarfs burning hydrogen could cause these age estimates to be inaccurate by as much as 1 billion years.

“Our discovery challenges the definition of white dwarfs as we consider a new perspective on the way in which stars get old,” added Francesco Ferraro of the Alma Mater Studiorum Università di Bologna and the Italian National Institute for Astrophysics, who coordinated the study. “We are now investigating other clusters similar to M13 to further constrain the conditions which drive stars to maintain the thin hydrogen envelope which allows them to age slowly”.

Notes

[1] The Sun is only 4.6 billion years through its roughly 10-billion-year lifetime. Once it exhausts hydrogen in its core, the Sun will swell into a red giant, engulfing the inner planets and searing the Earth’s surface. It will then throw off its outer layers, and the exposed core of the Sun will be left as a slowly cooling white dwarf. This stellar ember will be incredibly dense, packing a large fraction of the mass of the Sun into a roughly Earth-sized sphere.

[2] M3 contains roughly half a million stars and lies in the constellation Canes Venatici. M13 — occasionally known as the Great Globular Cluster in Hercules — contains slightly fewer stars, only several hundred thousand. White dwarfs are often used to estimate the ages of globular clusters, and so a significant amount of Hubble time has been dedicated to exploring white dwarfs in old and densely populated globular clusters. Hubble directly observed white dwarfs in globular star clusters for the first time in 2006.

[3] Astronomers use the word “metallicity” to describe the proportion of a star which is composed of elements other than hydrogen and helium. The vast majority of matter in the Universe is either hydrogen or helium — to take the Sun as an example, 74.9% of its mass is hydrogen, 23.8% is helium, and the remaining 1.3% is a mixture of all the other elements, which astronomers refer to as “metals.”

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