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How do you study concussions without cracking the skull? Try using an egg scrambler.
In a new study, published Jan. 19 in the journal Fluid physics, scientists were inspired by how Egg jammers mix egg whites and yolks without breaking the shell first. The device simply spins the uncracked egg at very high speeds, and this force is transmitted to the liquid inside, causing the yolk to burst. Likewise, in most concussion head injuries, the skull does not crack, but the brain is still injured, the scientists thought.
Disclaimer: No human brain was interfered with during this study. Instead, the researchers used the egg yolks as a model for the human brain.
Related: From dinosaur brains to thought control – 10 fascinating discoveries about the brain
“I would say it’s a very wild comparison,” said senior author Qianhong Wu, director of the Cellular Biomechanics and Sports Sciences Lab at Villanova University in Pennsylvania. “They are completely different systems, in terms of material properties. On the one hand, egg yolks contain only one substance – the yolk – while the brain contains a variety of cell types arranged in complex structures, he said.
That said, eggs and the human brain have a handful of key similarities, which may provide insight into the fundamentals. physics concussions, he says.
Looking at the brain, we have a squidgy organ surrounded by a fluid called cerebrospinal fluid (CSF) and enclosed in a rigid container, the skull. An egg yolk is also made of soft, viscous matter, surrounded by liquid and enclosed in a hard container, the shell. Wu and his colleagues noticed these similarities and ran with them, designing experiments to see how yellow would warp under different forces. They tested two types of impacts seen in concussions, including rotational impact, which spins the skull, and translational impact, which only moves the skull in space, without rotating it. .
Their lab experiments began with a trip to the grocery store, where they collected fresh chicken eggs. To observe how the force changed the yolk, they threw away the eggshell and placed the whites and yolks in a transparent container; that way, they could directly observe the insides of the eggs while keeping them inside a rigid container. To test the translational impact, the team dropped a 4 pound (1.7 kilogram) hammer on the container 3.2 feet (1 meter) above; for their rotational impact experiments, they spun the container with an electric motor, at up to 64 revolutions per second.
The team recorded these tests using a high-speed camera and found that the rotational impact caused a dramatic transformation of the yellow, while in comparison, the translational impact caused no visible change. . As the container began to rotate, the spherical yellow stretched horizontally, forming an “ellipsoid”. But the most intense change happened when the rotation slowed down. As the speed of rotation decreased, the center of the yolk pinched inward, pulling the horizontal ellipsoid into the vertical plane. In a second, the rounded shape had crashed into a flat disc.
When the rotation came to a complete stop, it took about a minute for the yolk to relax into a sphere. “This large deformation could obviously cause serious damage to the yolk,” noted the authors.
The conclusion? Extreme rotational impacts could also be devastating to the brain. For example, when boxers have a sock on their chin, their head quickly tilts onto their neck, and then quickly slows down when the head can no longer articulate back. This may explain why boxers can easily faint when struck in this manner, Wu noted.
While the spin impact wreaked havoc on the yellow, the hammer fall experience caused no change. “It’s very surprising, it’s counterintuitive,” because you would expect the force to be transmitted through the hard container and the egg whites and into the yolk, Wu said. This surprising result can be explained by the fact that egg whites and yolks share a very similar density, so that under a hammer blow the two can move together as a unit, he said. This would prevent the yolk from changing shape.
Since the brain has a different density than the surrounding CSF, a solid bonk on the head would likely distort the brain a bit. But based on their experiences, the brain may be more sensitive to rotational impacts, Wu said.
In a real concussion, the translational and rotational impacts occur simultaneously. “You really can’t completely separate one from the other… it’s always a combination of the two,” Wu said.
Now that Wu and his colleagues have worked on the physics of concussions in eggs, they plan to check their results in the brain. The lab recently developed an artificial brain, modeled from scans of human brains and surrounded by a transparent skull, which they subjected to impact experiments. The team is also studying brains taken from mice, but Wu said they aim to work with the brains of living animals in the future.
They also teamed up with doctors at Thomas Jefferson University Hospital so that they could compare the results of laboratory experiments with data from patients with traumatic brain injury, he added. This should help connect the dots between the physics seen in eggs and the actual injuries suffered in people.
Originally posted on Live Science.
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