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The study found that as people grow older, people are less likely to yawn when others yawn.
Yawning when others yawn, this phenomenon is called infectious yawning. American scientists have said that the link between infectious yawning and age is stronger than people’s energy levels.
In addition, patients with autism and schizophrenia are said to be less likely to be yawned. To help treat these mental illnesses, researchers are currently investigating infectious yawning. In this study, the researchers recruited 328 participants and let them watch the video of people yawning separately and record the number of yawning participants. Overall, 68% yawned. Among them, the proportion of participants under 25 who yawned was about 82%, 60% between 25 and 49, and 41% over 50.
Dr. Elizabeth Cirulli, the leader of the study, said she did not know why contagious yawning would decrease with age, and the overwhelming majority of people's reactions could not be explained.
Professor Robert R Provine of the University of Maryland believes that this study is unique because it shows that there is a certain link between the first ageing and infectious yawning. The results of the study can also help understand why laughter and cough can be transmitted.
He added: "These contagious behaviors remind us that we often blindly congregate rather than rationally control our own behavior."
A type of Grinding Machine that grinds a workpiece plane or a profiled surface.The main types are horizontal axis rectangular table, horizontal axis round table, vertical axis rectangular table, vertical axis round table and various special surface grinders.
â‘ Horizontal axis table surface grinder
The workpiece is held by a rectangular electromagnetic table or clamped on the table and reciprocated longitudinally.
The wheel frame can be used for lateral intermittent feed movement along the dovetail guide of the slide. The sliding seat can be vertically intermittently fed along the guide rail of the column, and the workpiece is ground by the grinding wheel, and the grinding precision is high.
â‘¡ Vertical shaft round table surface grinder
The vertically mounted grinding wheel spindle grinds the workpiece with the grinding wheel end face, and the grinding wheel frame can perform intermittent vertical feeding movement along the guide rail of the column.
The workpiece is mounted on a rotating circular table for continuous grinding and high production efficiency.
In order to facilitate the loading and unloading of the workpiece, the circular table can also be moved longitudinally along the bed rail.
â‘¢ Horizontal axis round table surface grinder
Suitable for grinding round sheet workpieces, and can be used to tilt and grind round workpieces with different thickness.
â‘£ Vertical axis rectangular table surface grinder
Since the diameter of the grinding wheel is larger than the width of the table, the grinding area is large, which is suitable for efficient grinding.
⑤ Double end grinding machine
The two parallel planes of the workpiece are simultaneously ground by the grinding wheel end faces of the two grinding heads, and there are two types which are the horizontal shaft and the vertical shaft.
The workpiece is guided through the grinding wheel by a linear or rotary feeding device.
This type of grinding machine is highly efficient and is suitable for mass production of parts such as bearing rings and piston rings.
In addition, there are guide grinding machines for grinding the guide surface of machine tools, and special grinding machines for grinding turbine blade profiles.
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