A Quantitative Example from Dr. Georgieva's Work
Dr. Georgieva uses computational fluid dynamics to study airflow and gas
uptake in rats' and humans' nasal passages. It is known that formaldehyde
(HCHO) causes nasal cancer in rats at concentrations of 6ppm and higher.
The formaldehyde reacts with the rats' DNA to form DNA-protein crosslinks.
These form lesions. The areas in which the lesions are most likely to
form are the areas which are exposed to the highest concentrations of
formaldehyde as air passes throught the nasal passage.
Intricate models of both rat and human nasal passages were made. First,
computer models were made, like the ones shown above and to the right.
The computer models
enabled mathematical modeling of the concentration of formaldehyde that
would reach each interior point of the nasal passage, given the
concentration of formaldehyde when it entered the nose and where it
entered. Equations such as the ones shown here and the concept
of
conservation of momentum were used to find the concentrations at all of
the locations.
After the computer models and mathematical modeling were used to predict
the airflow in the nasal passages, stereolithography was used to create
physical replica of the human nasal passage. The replica was twice the
size of an actual nasal passage and was made using the computer models and
an ultraviolet laser moving across a liquid photopolymer bath. The model,
shown to the left, was then used to test the theoretical calculations of
the concentrations that reach various areas of the nasal passage. In the
lab, water with red dye was used to represent formaldehyde in air because
the water flowed more slowly and the red dye could be seen easily. In
making the change from air to water, the difference in viscosity had to be
accounted for. This was done by altering the velocity of the fluid.
It was found that the tests done in the lab did agree with the mathmatical
modeling done. It was learned that lesions are most likely to occur in
areas of tissue that are not covered with mucus. The mucus protects the
cells from the formaldehyde.
Teresa.Tetlow@duke.edu
Julia.Whitley@duke.edu