YSM Issue 96.3

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FOCUS Computer Science REPRESENTATION IN ANIMATION Computer Science Captures The Physics of Afro-Textured Hair BY ABIGAIL JOLTEUS PHOTOGRAPH COURTESY OF FAREED SALMON In the past, in computer animation, many Black characters would have poorly animated braids, or more frequently, just have straight hair. For years, computer animations would use these inaccurate representations of tightly coiled hair, also known as afrotextured hair. Recently, as more people of color have been hired and cast for animation roles, the animation industry has moved towards becoming more diverse and inclusive than ever before. However, this increase in diversity did not translate into more accurate animation of afro-textured hair. “The way that hair has been simulated, at least since the ‘90s, has been many line segments chained together, and making them small enough gives a smooth appearance,” said Theodore Kim, an associate professor of computer science at Yale. Animating hair is achieved through various mathematical equations where the twists of each strand must be carefully simulated for accurate hair motion. “Therefore, when a character shakes their head, you can see realistic movement,” Kim said. However, this process only works for the overwhelming majority of animated characters who are white and have straight hair. “The trouble appears with the physics equations selected for simulation,” he said. A team of computer scientists at Yale have created a novel physical model that allows for more accurate animation of tightly coiled hair, more realistically capturing the way it looks and moves. “We were concerned with three different types of elastic energy for hair: stretching, bending, and twisting energies,” said Haomiao Wu, one of the lead researchers on the project. “These energies constrain how the strands behave in an elastic way. We proposed a different set of those three energies for a model so that it is more stable.” In other words, they wanted to capture the true essence of afro-textured hair using sophisticated mathematical modeling. Their isotropic, hyperelastic model was specifically designed for better simulation of tightly coiled hair. “Isotropic means that no matter the direction, the restorative force is the same,” said Alvin Shi, another one of the lead researchers on the study. Restorative force is the force needed for an object to return to its initial size and shape. In this case, it enables a hair strand to return to its initial coiled state, which better captures afro-textured hair. This model is also faster, simpler, and more robust than previous models. The researchers devised this model by discarding the previous assumption for mathematical equations to simulate the curling pattern of each strand and instead consider large bends and torsions, as well as assuming, to a certain extent, that the hair is non-straight. While this model was designed for kinky, curly, or coily hair, the researchers discovered that it is also effective for straight hair. As with all simulations, there are flaws. Some of these limitations include the scaling behavior of tight, coily hair and lack of variation in how the hair can look. Currently, the model can account for only two different appearances of afro-textured hair: a clumped look, well-defined curls, and a more picked-out look, or fluffed-out afro-textured hair. By decreasing the radius of a wisp—a clump of hair strands common in afro-textured hair—but keeping the same total number of hair strands, a more picked-out look is obtained. However, these looks are not incredibly realistic compared to reallife individuals with the same hair type. “We are looking to improve on the realistic aspect of our model,” Shi said. For the next steps, the researchers plan to conduct further experiments with the realism of the simulated hair and possibly test an anisotropic model, meaning the pattern is different in various directions, which could lead to better animations of different hairstyles with afro-textured hair. While no animated content or games are perfect, it is important that Black individuals see themselves adequately represented in the media that they consume. As the creators of one of the first models specifically for tight, coily hair, the team also hopes that other researchers will be inspired to conduct similar research. “We are looking forward to seeing more and more research in this field, not just from us but other researchers as well,” Wu said. Ultimately, they want their model to lead to greater and better racial and ethnic representation in animated games and movies. “It might take longer than we wish for these techniques to be implemented, but we are hoping as soon as possible,” Wu said. ■ 10 Yale Scientific Magazine September 2023 www.yalescientific.org
Molecular Biology FOCUS SUPER-SIZING LIFE’S SMALLEST SECRETS Pushing The Boundaries of Microscopy BY KARA TAO PHOTOGRAPHY COURTESY OF EMILY POAG Let’s turn the clock way back to when you consisted of only a small clump of cells. How does this tiny clump of cells know to transform into various cell types throughout your body, from hair and eyes to lips and legs? It turns out that these instructions are encoded in our genome. However, our genome is initially “silent.” It needs to be activated and reprogrammed through a process called zygotic genome activation so that our cells can properly differentiate into specific cell types in our body. The Giraldez lab at Yale specifically investigates the cellular mechanisms of this process, which involve a variety of interactions between protein ‘factors’ and DNA that work together to transform the “silent” state of the genome into the activated state. “It’s kind of like erasing the blackboard and writing new instructions,” said Antonio Giraldez, the Fergus F. Wallace Professor of Genetics. “We’re trying to understand the factors that erase the previous instructions and the factors that instruct the genome to employ the first cascade of events that will lead to development.” Traditionally, researchers have relied on indirect biochemical methods to unravel the intricacies of this process, as the existing visualization techniques have presented considerable limitations. “We wondered if we could actually come up with a new way to visualize what happens inside of these clusters,” said Mark Pownall, a member of the Giraldez lab who first looked into this research direction. In collaboration with the Bewersdorf lab at Yale, Pownall adapted their already-established technique of pan-expansion microscopy (pan-ExM), incorporating labeling of protein, RNA, and DNA to create Chromatin Expansion Microscopy (ChromExM). Pan-expansion microscopy involves fixing cells to an expandable gel called a hydrogel that swells via addition of certain functional groups. By layering multiple hydrogels on top of each other, the cells take on a larger size that can be better resolved under a microscope. The cell, and specifically the chromatin that makes up our chromosomes, expands to become four thousand times larger, allowing for a never-before-seen look into the small-scale interactions that thus far, researchers have only been able to theorize about. “This has allowed us to start measuring distances that are ten times higher in www.yalescientific.org resolution than what we have ever captured before,” Giraldez said. “This has revealed how the models and the cartoons we are drawing from biochemical experiments can be visualized for the first time.” One of the main concerns of expansion microscopy was whether the cell’s proportions could be maintained during the expansion process. To ensure that the cell expanded proportionally, the Giraldez lab developed a technique where the initial cell was marked with parallel stripes, and if the stripes remained parallel after expansion, it would have exhibited proportional growth. “This showed us that we preserved these stripes really well after they were cleaved, which was one hint that we actually preserved chromatin structure,” Pownall said. With this novel technique in hand, the Giraldez lab could finally visualize the specific factors involved in activating the genome. Using ChromExM, they were able to study the function of Nanog, a protein that binds to a “gene enhancer” region of DNA that stimulates the activation of genes involved in development. Although Nanog had been shown to interact with RNA polymerase, located at the promoter region of the gene where the polymerase would initially bind to initiate transcription of DNA to mRNA, it was unclear whether these structures actually required transcription to form. By using ChromExM, they found that the Nanog protein was initially in close contact with RNA polymerase, but once transcription was initiated, the protein separated itself from the growing strand of mRNA. The Giraldez lab termed this interaction the “kiss-and-kick model,” where transcription acts as the “kick” to separate the enhancer and promoter regions. The development of the human body is an incredibly complex process directed by genetic codes regulated by countless factors that interact with chromatin and different organelles in our cells. The novel technique of ChromExM not only allows us to visualize these processes, but is also accessible and applicable to other fields of study, as it only requires a confocal microscope that can be found in biological research labs. “I think that this could add a fundamental tool to the global toolbox to really understand how different molecules interact in the nucleus by visualizing these fundamental processes of life,” Giraldez said. “The accessibility is great, and the possibilities to apply ChromExM to other approaches is very large.” ■ September 2023 Yale Scientific Magazine 11
Page 1 and 2: Yale Scientific THE NATION’S OLDE
Page 3 and 4: CONTENTS More articles online at ww
Page 5 and 6: The Editor-in-Chief Speaks PAST, PR
Page 7 and 8: Ecology / Public Health NEWS IT’S
Page 9: Biology FOCUS CANCER: NOT JUST BAD
Page 13 and 14: Electrical Engineering FOCUS Matthi
Page 15 and 16: Planetary Sciences FOCUS be capable
Page 17 and 18: Ophthalmology FOCUS What if you sud
Page 19 and 20: Biomedical Engineering FOCUS COVID-
Page 21 and 22: Biomedical Engineering FOCUS from p
Page 23 and 24: Astronomy FOCUS Beneath the endless
Page 25 and 26: AN EEL-ECTRIFYING INVENTION NEW DRO
Page 27 and 28: Neuroscience FOCUS A Scent-sational
Page 29 and 30: Physics FEATURE associated with the
Page 31 and 32: Geochemistry FEATURE stalked barnac
Page 33 and 34: Astrophysics FEATURE waves give you
Page 35 and 36: ALUMNI PROFILE ILANA YURKIEWICZ YC
Page 37 and 38: " RACISM IN HEALTH BY SAMUEL OBIAMA
Page 39 and 40: INTEGRATION OR INVASION? BY ISAIAH

YSM Issue 96.3

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