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Scents and Sensitivity

Scents and SensitivityThe complexity of mammals’ noses plays an important role in helping them distinguish scents, reports a team of Tufts researchers developing high-tech sensory equipment. Medford/Somerville, Mass.

Medford/Somerville, Mass. [05.02.03] A dog's nose always knows, and now scientists think they understand how. Using a plastic replica of a dog's nose built from computer scans, Tufts' David Walt has new test results that indicate the complexity of dogs' noses, like those of other mammals, plays an important role in helping them distinguish scents.

"Tucked into the dark cave beyond the nostrils, dogs and other mammals have a maze of tiny air-filled passages," reported Nature. Scientists suspected the passages played a key role in "sifting out different whiffs in the air."

Using a series of high tech sensors, Walt and his team put the theory to the test.

"To simulate [a dog's nose], Walt built a plastic enlargement of a dog's nasal cavity, based on computed-tomography scans," reported Nature. "Smell sensors distributed through the muzzle-like machine were 10 percent better at recognizing the scents of rums and vodkas, compared with a single sensor."

In addition, the scientists reported that sensors in the nose's twisting passages also picked up the scent up to 15 seconds before sensors at the back of the nose, indicating that the complex air-flow patterns created by the maze of passages also increase the speed of scent detection.

"The noses' rough surfaces create ‘eddies and currents' of air that funnel smaller fragrant molecules through the nose faster than others," reported New Scientist.

Walt's findings support scientists' theory that the construction of a nose is important to its effectiveness.

"We've really validated what people had suspected," Walt, a professor of chemistry at Tufts, told Nature.

And for Walt, who is developing cutting-edge sensory equipment which may one day be used for everything from detecting land mines to medical diagnostics, understanding the science behind the power of a dog's nose could play an important role in improving the sensitivity and efficiency of his equipment.

"[The experiment demonstrates] a novel method to enhance the discriminatory ability of vapor sensors," he wrote in the Journal of the American Chemical Society.

It's not the first time Walt turned to a real nose for help. To develop the design for their sensory equipment, Walt and his team replicated some of the science behind the real thing.

"Inside a dog's snout, an array of cells recognizes a handful of smelly molecules. A particular perfume excites a characteristic combination of cells, creating a fingerprint of signals that the brain learns to recognize," reported Nature. "In place of cells, Walt's [sensory equipment] uses light-transmitting optic fibers, each tipped with a bead. When the beads bind a molecule, they change color in a characteristic way and send light down to the fibers; a computer program distinguishes these patterns."



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