Applied radiation physics: The use of x-rays for the structural characterization of aqueous emulsions and the development of new insect sterilization protocols

X-rays have great potential of applications in a wide variety of fields. This dissertation presents the use of x-rays for the structural characterization of aqueous emulsions and for insect sterilization. The stabilization of hydrophobic colloids, such as oil droplets, in water has attracted scientist for a variety of scientific, pharmaceutical and industrial applications. Several studies have been done to understand the stability of oil-in-water emulsions. The work of Pashley and his coworkers has demonstrated that the removal of dissolved gasses from water enhances the dispersion of hydrophobic oil in water and these surfactant-free emulsions do not lose their stability when the previously removed gasses are reintroduced. However, very little is known about the structure and stability of these emulsions over time or even to what extent they form. The formation of a stable emulsion in the complete absence of a surfactant could provide an alternative approach to a physiologically safe drug carrier. In this dissertation we demonstrate the formation of stabilized surfactant-free degassed emulsions of hydrocarbons - hexane, heptane and octane and silicone oil in ultra-pure water. The enhancement of dispersion of oil droplets by degassing was large for highly hydrophobic silicone oil. Turbidity measurements and small angle x-ray scattering results show that the uniformly dispersed oil droplets weakly aggregate over a period of several hours. Gentle perturbation re-generates the dispersion to nearly initial conditions.;The control of insect species for the protection of crops, livestock, and prevention of disease, such as dengue fever and malaria, is a high priority in today's global economy. Sterile Insect Technique (SIT), a method of insect extermination without the use of pesticides, has proven very effective in eradicating certain dipteran insect populations. However, when standard sterilization methods developed for dipterans are applied to mosquito populations significant complications arise, such as an inability to compete with non-irradiated males and high mortality rates. To improve mosquito SIT, we have developed new radiation protocols for insect sterilization using long wavelength x-rays. Our results have demonstrated that longer wavelength x-rays have a significant effect on the outcome of the sterile males' longevity as well as on the efficacy of sterilization while employing a substantially lower dose.