An increasing number of professional football players have been diagnosed with a neurodegenerative disease called chronic encephalopathy (CTE), which is likely the result of recurrent concussions or similar repeated brain trauma during their careers. It is also common in other high-contact sports such as boxing, Muay Thai, kickboxing and ice hockey. According to a new paper published in The Physics of Fluids, we can get clues about the underlying physics by studying the deformation of the egg yolk. This in turn may one day lead to better prevention of such trauma.
The egg yolk liquid is submerged in a hard shell in the egg white part of what physicists call “soft matter in a liquid environment”. Other examples include red blood cells that flow through our circulatory systems and our brains, which are surrounded by cerebrospinal fluid (CBR) inside a rigid skull. According to Villanova University physicist Qianhong Wu and his co-authors on this latest study how soft matter is in response to external influences. They indicate red blood cells as an example. It is the ability of red blood cells to change shape under stress (“erythrocyte pathology”)) For example, lets squeeze them through small capillaries, and also moves the spleen to remove red blood cells, whose size, shape, and overall deformity have greatly changed.
In the case of traumatic brain injury, it is associated with brain deformity in response to the effect. The exact cause of CTE is still the subject of ongoing research, but prevailing theories state that repetitive brain trauma can damage the blood vessels in the brain, leading to inflammation and increased clots of proteins called tau. Eventually those clots spread throughout the brain that kill brain cells. People suffering from CTE often experience memory loss, depression, and in severe cases, dementia, among other symptoms.
Prior studies have shown that deformation of soft matter in a fluid environment occurs in response to abrupt changes in the fluid field, such as shear flow or abrupt changes of the flow path. Woo and others. Were interested in the specific case of a soft substance in a liquid environment that is also enclosed in a rigid container – such as an egg yolk, surrounded by liquid egg whites, all enclosed in a shell. He wondered if it is possible to break the yolk without breaking the shell, as this is the case with the most frequent conclusion that brain damage can occur without cracking the skull.
Wu to answer that question and others. Set a simple preliminary experiment with the Golden Goose Egg Scrambler, a novel kitchen tool that enables users to rub eggs right into the shell. Wu’s team applied rotational forces to scrape the eggs and were concerned about how the egg yolk deteriorated and broke while the shell was intact. This prompted him to conduct additional experiments to flow insights into the fundamental flow physics behind the effect.
They bought fresh eggs from a local grocery store, removed yolks and egg whiteness, and then placed them in a transparent rigid container, recording the entire process with high-speed cameras and monitoring distortion better. He made two different instruments. One is called the so-called “translational effect” – a straight guide straightens the container through a small hammer falling from the rail (see fig. 1a in the gallery), with a spring at the bottom to move the container vertically. make capable. They used an accelerometer to measure the acceleration of the container.
For the second setup (see fig. 1B in the gallery), he connected the container to an electric motor to study two types of rotational effects: accelerating the rotational effect and minimizing the rotational effect (that is, when the external contained fast. Getting or slowing down) rotates). They also peeled off the membranes around the fresh yolks and suspended them in petri dishes filled with water, better to study how those membranes also respond to stress.
Woo and others. It was somewhat surprising to find that, in terms of translation effect, there was no distortion of the yolk. Instead, the entire container (and its contents) moved to form a single rigid body. In terms of accelerating the rotational effect, the team found that the yolk would exit in a circular shape and then begin to stretch horizontally to form an ellipse. If the angular velocity was kept constant then the yolk can maintain a stable elliptical shape for several minutes.
The most intriguing results were in terms of reducing the rotational effect. Here, the yolk began to deform almost immediately, expanding horizontally and increasing its radius at the center – a deformation sufficient to severely damage the yolk under constant stress.
“We suspect that rotational, particularly disruptive rotational, effects are more damaging to the brain matter.”
To ensure that this was not primarily the effect of the yolk as a biomaterial, Wu and others. The same experiment was carried out with a soft capsule immersed in a calcium lactate solution surrounded by a thin membrane in a calcium lazonate solution. He said similar results were found, “The major mechanism leading to the deformation of soft matter in a liquid environment is the result of mechanical forces rather than biological reactions,” he wrote.
Based on this, “we suspect that Wünschel stated that rotational, particularly decelerational rotational, effects are more damaging to the brain,” adding that the possibility of centrifugal force plays an important role. “Large deformations of the brain during this process induce stretch of neurons and cause damage.” This may explain why a boxer may exit with a sharp blow to the chin. “Considering the chin is the farthest point from the neck, hitting the chin can lead to the highest rotational acceleration / deceleration of the head,” the author concluded.
Wu said of the implications of his findings, “Simple experiments within the kitchen as well as critical thinking led to a series of systematic studies to investigate the mechanisms that cause egg yolk deformity.” “We hope to implement this by studying brain biomechanics as well as other physiological processes involving soft capsules in a liquid environment, such as red blood cells.”
DOI: Physics of Fluids, 2021. 10.1063 / 5.0035314 (about DOIs).
Image listed by Ji Lang / Qianhong Wu