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Open Access Publications from the University of California

Volume 17, Issue 2, 2013


Activity Patterns of Golden Eagles in San Benito County, CA

The golden eagle (Aquila chrysaetos) is a top predator of lagomorphs and ground squirrels in open, mountainous habitats in western North America. It is currently listed as a species of concern by the U.S Fish and Wildlife Service. Understanding the diel and seasonal use of water could enhance conservation of this important species. I quantified the visits (N=402) of golden eagles to 13 water sources using camera trap photo data obtained at the Ventana Ranch, San Benito County, California. Frequency of occurrence was analyzed by the Chi-square test to confirm diel and seasonal activity patterns. Golden eagle activity peaked between 10am and 5pm PST; there were no nocturnal visits to water sources. Bathing and drinking were noted at 32% and 14% of visits, respectively. Visits were rare during the Spring-breeding season and peaked in the hot months of July and August when both adults and juveniles were detected.

Orientation-Dependent Neuronal Degradation Resulting from Axonal Stain Experienced in Football-Realistic Acceleration

Traumatic brain injury (TBI) is a common occurrence that results in neuronal death with hazardous long-term effects. Modeling TBI computationally is necessary in order to gain a better understanding of mechanical effects on neurobiological injury cascades and injury thresholds. A model of a single axon was submitted to accelerations observed in the sport of American Football to test for axonal membrane strains necessary to induce an apoptosis pathway. A neuronal membrane strain of 0.20 [1] has been found to cause a Ca2+ influx necessary to initiate a neuronal degradation pathway. The proposed model sought to identify if accelerations in American Football could cause such detrimental strains. To test this, forces were applied in three directions: parallel to the axon, normal to the axon, and rotational about the axon to account for the multiple orientations forces can act upon to cause neuronal strain. Results from the different orientations with varying force magnitudes made it clear that stresses applied rotationally are the most detrimental and can cause a strain of 0.200 at an acceleration as low as 45g. Accelerations of 45g or greater are found in approximately 10% of the impacts observed in college football [2]. The resulting data from this model can be extrapolated to a larger scale to benefit the design of better head protection to include protection from shear forces.