The literature review was led by Dr. Kristian Goulet of the University of Ottawa’s Faculty of Medicine and Children’s Hospital of Eastern Ontario (CHEO) and calls on provincial and territorial governments to mandate schools — including those involved with school sports — and sports organizations to establish, update, and enforce policies and protocols to prevent concussion, with a keen focus on body contact.

Currently, hockey organizations in Canada allow body contact in competitive and recreational leagues from the age of 13. But studies have shown when body contact is initiated, injuries increase significantly, including concussion rates.

Almost half of hockey injuries are caused by bodychecking, with injury rates four times higher for kids and teens in leagues that allowed bodychecking. Other studies have found concussion rates decrease by over 50% when eliminating body contact. An estimated 200,000 concussions occur annually in Canada, with children and youth affected primarily. Ice hockey is the leading cause of all sports and recreationally related TBI across paediatric age groups, in both boys and girls.

Dr. Goulet is hopeful this review will spur Hockey Canada to lead a new path forward to strengthen our understanding of concussion and guidance for clinical management, especially related to acute care, persistent symptoms, and prevention.

“Sport is incredibly important for the mental physical emotional and social health of our kids. However, it is our duty as healthcare providers, parents, coaches, administrators and decision makers, that we take all reasonable efforts to make sport as safe as possible,” says Dr. Goulet, an Assistant Professor in uOttawa’s Faculty of Medicine and the Medical Director of The CHEO Concussion Clinic, The Eastern Ontario Concussion Clinic, and The Pediatric Sports Medicine Clinic of Ottawa.

Cellular metamaterials — artificial structures composed of units, or cells, that repeat in various patterns — can help achieve these goals. But it is difficult to know which cellular structure will lead to the desired properties. Even if one focuses on structures made of smaller building blocks like interconnected beams or thin plates, there are an infinite number of possible arrangements to consider. So, engineers can manually explore only a small fraction of all the cellular metamaterials that are hypothetically possible.

Researchers from MIT and the Institute of Science and Technology Austria have developed a computational technique that makes it easier for a user to quickly design a metamaterial cell from any of those smaller building blocks, and then evaluate the resulting metamaterial’s properties.

Their approach, like a specialized CAD (computer-aided design) system for metamaterials, allows an engineer to quickly model even very complex metamaterials and experiment with designs that may have otherwise taken days to develop. The user-friendly interface also enables the user to explore the entire space of potential metamaterial shapes, since all building blocks are at their disposal.

“We came up with a representation that can cover all of the different shapes engineers have traditionally shown interest in. Because you can build them all the same way, that means you can switch between them more fluidly,” says MIT electrical engineering and computer science graduate student Liane Makatura, co-lead author of a paper on this technique.

Makatura wrote the paper with co-lead author Bohan Wang, an MIT postdoc; Yi-Lu Chen, a graduate student at the Institute of Science and Technology Austria (ISTA); Bolei Deng, an MIT postdoc; Chris Wojtan and Bernd Bickel, professors at ISTA; and senior author Wojciech Matusik, a professor of electrical engineering and computer science at MIT who leads the Computational Design and Fabrication Group within the MIT Computer Science and Artificial Intelligence Laboratory. The research will be presented at SIGGRAPH.

A unified method

When a scientist develops a cellular metamaterial, she typically begins by choosing a representation that will be used to describe her potential designs. This choice determines the set of shapes that will be available for exploration.

For instance, she may choose a technique that represents metamaterials using many interconnecting beams. However, this prevents her from exploring metamaterials based on other elements, such as thin plates or 3D structures like spheres. Those shapes are given by different representations, but so far, there hasn’t been a unified way to describe all shapes in one method.

“By choosing a specific subspace ahead of time, you limit your exploration and introduce a bias based on your intuition. While this can be useful, intuition can be incorrect, and some of the other shapes may have also been worth exploring for your particular application,” says Makatura.

She and her collaborators took a step back and closely examined different metamaterials. They saw that the shapes that comprise the overall structure could be easily represented by lower-dimensional shapes — a beam could be reduced to a line or a thin-shell could be compressed to a flat surface.

They also noticed that cellular metamaterials often have symmetries, so only a small part of the structure needs to be represented. The rest can be built by rotating and mirroring that initial piece.

“By combining those two observations, we arrived at this idea that cellular metamaterials could be well-represented as a graph structure,” she says.

With their graph-based representation, a user builds a metamaterial skeleton using building blocks that are created by vertices and edges. For instance, to create a beam structure, one places a vertex at each end point of the beam and connects them with a line.

Then the user employs a function over that line to specify the thickness of the beam, which can be varied so one part of the beam is thicker than another.

The process for surfaces is similar — the user marks the most important features with vertices and then chooses a solver that infers the rest of the surface.

These easy-to-use solvers even allow users to quickly construct a highly complex type of metamaterial, called a triply periodic minimal surface (TPMS). These structures are incredibly powerful, but the usual process to develop them is arduous and prone to failure.

“With our representation, you can also start combining these shapes. Perhaps a unit cell containing both a TPMS structure and a beam structure could give you interesting properties. But so far, those combinations really haven’t been explored to any degree,” she says.

At the end of the process, the system outputs the entire graph-based procedure, showing every operation the user took to reach the final structure — all the vertices, edges, solvers, transformations, and thickening operations.

Within the user interface, designers can preview the current structure at any point in the building procedure and directly predict certain properties, such as its stiffness. Then, the user can iteratively tweak some parameters and evaluate it again until a suitable design is reached.

A user-friendly framework

The researchers used their system to recreate structures that spanned many unique classes of metamaterials. Once they had designed the skeletons, each metamaterial structure took only seconds to generate.

They also created automated exploration algorithms, giving each a set of rules and then turning it loose in their system. In one test, an algorithm returned more than 1,000 potential truss-based structures in about an hour.

In addition, the researchers conducted a user-study with 10 individuals who had little prior experience modeling metamaterials. The users were able to successfully model all six structures they were given, and most agreed that the procedural graph representation made the process easier.

“Our representation makes all sorts of structures more accessible to people. We were especially pleased with users’ ability to generate TPMS. These complex structures are usually difficult even for experts to generate. Still, one TPMS in our study had the lowest average modeling time out of all six structures, which was surprising and exciting,” she says.

In the future, the researchers want to enhance their technique by incorporating more complex skeleton thickening procedures, so the system can model a wider variety of shapes. They also want to continue exploring the use of automatic generation algorithms.

And in the long term, they’d like to use this system for inverse design, where one would specify desired material properties and then use an algorithm to find the optimal metamaterial structure.

This research is funded, in part, by a National Science Foundation Graduate Research Fellowship, the MIT Morningside Academy Design Fellowship, the Defense Advanced Research Projects Agency (DARPA), an ERC Consolidator Grant, and the NewSat project.

El Gordo is a cluster of hundreds of galaxies that existed when the universe was 6.2 billion years old, making it a “cosmic teenager.” It’s the most massive cluster known to exist at that time. (“El Gordo” is Spanish for the “Fat One.”)

The team targeted El Gordo because it acts as a natural, cosmic magnifying glass through a phenomenon known as gravitational lensing. Its powerful gravity bends and distorts the light of objects lying behind it, much like an eyeglass lens.

“Lensing by El Gordo boosts the brightness and magnifies the sizes of distant galaxies. This lensing effect provides a unique window into the distant universe,” said Brenda Frye of the University of Arizona. Frye is co-lead of the PEARLS-Clusters branch of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) team and lead author of one of four papers analyzing the El Gordo observations.

The Fishhook

Within the image of El Gordo, one of the most striking features is a bright arc represented in red at upper right. Nicknamed “El Anzuelo” (The Fishhook) by one of Frye’s students, the light from this galaxy took 10.6 billion years to reach Earth. Its distinctive red color is due to a combination of reddening from dust within the galaxy itself and cosmological redshift due to its extreme distance.

By correcting for the distortions created by lensing, the team was able to determine that the background galaxy is disk-shaped but only 26,000 light-years in diameter — about one-fourth the size of the Milky Way. They also were able to study the galaxy’s star formation history, finding that star formation was already rapidly declining in the galaxy’s center, a process known as quenching.

“We were able to carefully dissect the shroud of dust that envelops the galaxy center where stars are actively forming,” said Patrick Kamieneski of Arizona State University, lead author on a second paper. “Now, with Webb, we can peer through this thick curtain of dust with ease, allowing us to see firsthand the assembly of galaxies from the inside out.”

The Thin One

Another prominent feature in the Webb image is a long, pencil-thin line at left of center. Known as “La Flaca” (the Thin One), it is another lensed background galaxy whose light also took nearly 11 billion years to reach Earth.

Not far from La Flaca is another lensed galaxy. When the researchers examined that galaxy closely, they found a single red giant star that they nicknamed Quyllur, which is the Quechua term for star.

Previously, Hubble has found other lensed stars (such as Earendel), but they were all blue supergiants. Quyllur is the first individual red giant star observed beyond 1 billion light-years from Earth. Such stars at high redshift are only detectable using the infrared filters and sensitivity of Webb.

“It’s almost impossible to see lensed red giant stars unless you go into the infrared. This is the first one we’ve found with Webb, but we expect there will be many more to come,” said Jose Diego of the Instituto de Física de Cantabria in Spain, lead author of a third paper on El Gordo.

Galaxy Group and Smudges

Other objects within the Webb image, while less prominent, are equally interesting scientifically. For example, Frye and her team (which includes nine students from high school to graduate students) identified five multiply lensed galaxies which appear to be a baby galaxy cluster forming about 12.1 billion years ago. There are another dozen candidate galaxies which may also be part of this distant cluster.

“While additional data are required to confirm that there are 17 members of this cluster, we may be witnessing a new galaxy cluster forming right before our eyes, just over a billion years after the big bang,” said Frye.

A final paper examines very faint, smudge-like galaxies known as ultra-diffuse galaxies. As their name suggests, these objects, which are scattered throughout the El Gordo cluster, have their stars widely spread out across space. The team identified some of the most distant ultra-diffuse galaxies ever observed, whose light traveled 7.2 billion years to reach us.

“We examined whether the properties of these galaxies are any different than the ultra-diffuse galaxies we see in the local universe, and we do actually see some differences. In particular, they are bluer, younger, more extended, and more evenly distributed throughout the cluster. This suggests that living in the cluster environment for the past 6 billion years has had a significant effect on these galaxies,” explained Timothy Carleton of Arizona State University, lead author on the fourth paper.

“Gravitational lensing was predicted by Albert Einstein more than 100 years ago. In the El Gordo cluster, we see the power of gravitational lensing in action,” concluded Rogier Windhorst of Arizona State University, principal investigator of the PEARLS program. “The PEARLS images of El Gordo are out-of-this-world beautiful. And, they have shown us how Webb can unlock Einstein’s treasure chest.”

The paper by Frye et al. has been published in the Astrophysical Journal. The paper by Kamieneski et al. has been accepted for publication in the Astrophysical Journal. The paper by Diego et al. has been published in Astronomy & Astrophysics. The paper by Carleton et al. has been accepted for publication in the Astrophysical Journal.