Published Article / Direct feeding damage to head lettuce (Lactuca sativa L.) by varying aphid populations in two differently constructed shadehouse structures (fully- and partially covered) was examined. Fresh lettuce head weight, the number of lettuce leaves formed, and the number of lettuce leaves infested with aphids were compared between the two structures. Warmer months showed a significant lower fresh lettuce head weight in the fully covered structure with more aphid-infested leaves. During June/September, the mean number of aphid-infested leaves and aphid infestation levels were significantly higher in the partially covered structure. Visible feeding damage to the lettuce crop was restricted, but asymptomatic damage in terms of a decrease in head weight did occur under severe infestation levels.

The effect of added head mass during pilot ejection from an aircraft is currently being studied at the Wright Patterson Air Force Base in Ohio. The Articulated Total Body model, a FORTRAN computer program capable of simulating three-dimensional human body motion using rigid body dynamics, has been chosen to simulate the response of the head and neck to an ejection-like acceleration. The present Viscoelastic configuration of the head/neck model, which is capable of head rotation and axial neck deformation, was validated with experimental head acceleration data from live human volunteers subjected to a 10G_Z deceleration in the Vertical Deceleration Tower at Wright Patterson Air Force Base. Experimental head z-direction acceleration data from a first subject, L7, was reproduced accurately using the ATB model. However, Simulated head z-direction acceleration profiles for a second subject, B9, could not match experimental data for this subject, even after numerous variations of parameters controlling the head/neck response of the ATB model. Two of these parameters were determined to be time-varying for subject B9, and regression equations were developed describing the parameters as functions of time. Because the current ATB program does not allow time-varying parameters, the program code was modified to include two new subroutines in which the values of the parameters are calculated with each time increment. Modifications to the ATB model resulted in an improved simulated head z-direction acceleration profile for subject B9 when compared with previous simulations using constant value parameters. / Master of Science