1940's
Pictures show that in World War I and
World War II most stretchers were
poles with canvas strung between them.
1960's
In one 1969 photo, ambulance
stretchers were still two poles with a
pad between them. Stretchers have undergone many improvements in the last several years.
Improvements
Now that they are made out of
aluminum ambulance stretchers are
lighter than they used to be. Pads have become firmer so that CPR is easier to perform than before. To make it easier to move over rough terrain, stretchers now have heavier-duty tires and wheels. Also, modern stretchers are curved so that the patient will stay in the center. |
History
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Stretchers
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Superconducters
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Discovery of Superconductivity
Superconductivity was discovered by a Dutch
scientist, named Heike Kamerlingh Onnes, in
1911 while he was working with the metal mercury. When Onnes cooled the mercury down to the temperature of liquid helium (4.2 degrees Kelvin or -268.9 degrees Celsius) he found that mercury conducted electricity with zero resistance. The temperature needed to make a metal superconducting is called the critical temperature (Tc), in this case 4.2 degrees Kelvin (K). In one experiment Onnes applied electricity to a copper wire that was cooled to Tc; one year later the current was still flowing with no loss of power.
Improvements
Between 1911 and 1986 new alloys were made
that had Tc's of over 50 degrees Kelvin. The
goal was to reach at least 77 degrees K because then liquid nitrogen (which is much cheaper and easier to use than liquid helium) could be used as a cooling agent. Finally, in 1987 Dr. Paul Chu in cooperation with Dr. Maw-Kuen Wu reported finding superconductivity at temperatures over 90 degrees K. |
Click on this picture
of the PCS to return
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