Aquaculture of oysters and clams is the device on the left Between 1920 and 1926, Wells pioneered
aquaculture techniques to culture
bivalves. Wells was experimenting with the recently invented
De Laval centrifugal
milk clarifier, and discovered microscopic oyster larvae in the denser portion of clarified seawater. One previous experimenter,
William Keith Brooks, had developed a way to harvest oyster gametes, but the resulting oyster larvae starved to death before they grew large enough to be filtered out of the water. Because the larvae were so small, any attempt to refresh their water supply (which provided their food) would inadvertently remove them. Wells's innovation was to use the clarifier to concentrate the larvae. He used Brooks' method to acquire gametes, and grew them to adulthood in clarified seawater. Wells used the clarifier each day to concentrate the larvae and then replace the separated seawater with fresh water, allowing him to resupply their food without losing them. He and his wife developed the
Wells curve, which describes how the size of respiratory droplets influences their fate and thus their ability to transmit disease. With Richard L. Riley, he also developed the
Wells-Riley equation to model factors for disease transmission. demonstrates that size determines whether respiratory droplets fall to the ground or rapidly dry out and remain airborne after being exhaled. Wells' major contribution was to show that the nuclei of evaporated respiratory droplets can remain in the air long enough for others to breathe them in and become infected. German bacteriologist
Carl Flügge in 1899 was the first to show that microorganisms in droplets expelled from the respiratory tract are a means of disease transmission. The term Flügge droplet was sometimes used for particles that are large enough to not completely dry out. Flügge's concept of droplets as primary source and vector for respiratory transmission of diseases prevailed into the 1930s, when Wells differentiated between large and small droplets, introducing the idea that some infectious droplets could be small enough to remain airborne. In 1935, Wells demonstrated that
ultraviolet germicidal irradiation (UVGI), which had been used to kill microorganisms on surfaces and in liquids, could also be used to kill airborne infectious organisms. This experiment proved that he had been correct that droplet nuclei could be infectious, and also suggested a route for prevention. His next experiment sought to make UVGI more practical by developing upper-room UVGI. This system only sterilized the area above people's heads, allowing the room to be occupied at the time but relying on vertical ventilation to ensure the occupants breathe sterilized air. From 1937 to 1941, Wells implemented a long-term study using upper-room UVGI in suburban Philadelphia schools to prevent the spread of
measles. A misunderstanding led to the widespread assumption—contrary to Wells' original findings—that only particles smaller than 5 microns could transmit disease. == Selected publications ==