M.S. / Applied Physics / A noble gas ion laser with strong transitions in the 196-225 nm wavelength region has been developed for use as an illuminator in a photoelectron microscope. The laser is pulsed, and it can be operated at repetition rates up to 200 Hz to produce average output powers up to 5.0 mW at 219 nm. This is comparable to the output of the brightest available incoherent source, a Hg-Xe-Cd arc lamp that produces 2.6 mW of usable light in the 221-226 nm range. The laser has the advantage that it can be focused to produce much higher intensities than the arc lamp, and less total power is necessary. But the pulsed laser has a low duty cycle (~ 10[superscript minus 5]), and the corresponding peak powers (~ 300 watts) result in a space-charge-limited resolution of approximately 500 Å when the laser illuminates a phthalocyanine target. The magnitude of this aberration is proportional to beam current. Consequently, the resolution o can be improved to about 50 Å by decreasing the input power, or increasing the duty cycle, by a factor of 100-1000. Techniques for achieving such an improvement are suggested.

Ultraviolet radiation (UV-R) is an environmental factor known to increase the risk of developing an irreversible opacification of the lens (cataract). Increased irradiance of UV-R to the earth because of depletion of stratospheric ozone is of current concern considering cataract formation. Detailed metabolic information from the cornea, lens and aqueous humour might give valuable knowledge on the biochcemical processes occurring in the eye after exposure to UV-R, and thereby a better understanding of the mechanisms by which UV-R induces cataractogenesis. The purpose of this thesis was to study metabolic effects of exposure to UV-R on the anterior part of the eye. Effects of UV-B (280-315 nm) and UV-A (315-400 nm) on the aqueous humour, cornea and the lens from animal models were investigated by 1H nuclear magnetic resonance (NMR) spectroscopy. Since the lens is composed of functionally distinct anatomical compartments, with different metabolic activity, biochemical changes in various compartments of the lens were analyzed. Application of NMR-based metabonomics was effective to analyze metabolic changes in the anterior part of the eye after exposure to UV-R. High-resolution (HR) magic angle spinning (MAS) 1H NMR spectroscopy provided high quality spectra from intact tissue of cornea and lens, and provided important information about metabolic alteration occurring in these tissues after exposure to UV-R. The results from this thesis show that in vivo UV-B radiation affects metabolism of the anterior compartments of the eye. Metabolic changes were observed in aqueous humour, cornea, lens and in the different compartments of the lens. The antioxidants, glutathione and ascorbate, several amino acids, high energetic phosphates, and compounds important for membrane building and osmoregulation were substantially altered after exposure to UV-B radiation. Several biochemical effects such as oxidation, membrane disruption, osmoregulatory problems, lipid peroxidation, problems with cellular signalling and impairment of growth and protein synthesis were suggested. After UV-A exposure, no observable metabolic alterations were found in the anterior part of the eye in the present animal models.

No description available.

Microbial Reduction on Eggshell Surfaces by the use of Hydrogen Peroxide and Ultraviolet Light. (August 2011) Steven Michael Gottselig, B.S., Texas A&M University Chair of Advisory Committee: Dr. Craig Coufal The effect of hydrogen peroxide (H2O2) in combination with ultraviolet light (UV) as an egg sanitization process on eggshell surfaces was studied. Preliminary experiments were conducted to develop an optimized methodology for eggshell disinfection that will be an effective and efficient way to reduce microorganisms on hatching eggs. Several experiments were conducted to reduce the natural flora found on the eggshell surface. Hatching eggs were collected from White Leghorn hens housed in floor pens with nest boxes. Eggs had no adhering organic material present. Results from these experiments led to the modification of the prototype equipment as well as the treatment application methodology. Following the experiments to optimize the methodology for H2O2 spraying and UV exposure time, the methodology was applied to eggs inoculated with Salmonella Typhimurium. Eggshell crush and rub methodology was used to enumerate bacteria within the pores and membranes of the egg. The optimized H2O2 and UV combination treatment process was then applied to commercial broiler breeder hatching eggs to evaluate the effects on hatchability. Based on the parameters tested, results indicate that two applications of 3% H2O2 followed by 5 sec of UV exposure after each application produced the most consistent microbial reductions on eggshells. To enhance these effects, the addition of a 180° rotation between the two applications showed to be effective at further reducing the natural flora found on the eggshell surface. Studies using this optimal methodology on eggs inoculated with Salmonella at 9 log10 CFU/egg yielded greater than 5 log10 CFU/egg reductions. However, this methodology had little to no effect on reducing bacteria found within the pores and membranes of the eggs inoculated with Salmonella. These findings indicate that the effects of the disinfection process are largely limited to the eggshell surface. Hatch studies showed significant reductions in eggshell microbial levels under field conditions with eggs having large amounts of organic material present on the shell surface. Hatchability was maintained after treatment when compared to untreated eggs. Additional studies are needed to develop advanced equipment to apply this technology under commercial conditions.

Two experiments were conducted to evaluate the combination of hydrogen peroxide (H2O2) and ultraviolet light (UV) as an alternative eggshell sanitization procedure for shell egg processing. In each experiment, two cases of eggs (720 total) were collected at a commercial inline egg production facility. To assure egg uniformity, only eggs between 57 and 62 g were collected from a single hen house. Half of the eggs (360) were commercially processed (washer and sanitizing rinse) following normal procedures outlined by the U.S. Department of Agriculture (USDA) for shell egg processing (control group). The other half of the eggs (360) were washed as normal but without the sanitizing rinse. These eggs were then treated with 3 percent H2O2 and UV light (treated group). The treatment consisted of spraying the eggs with 3 percent H2O2 over the entire shell surface followed immediately by exposure to UV light for 5 s in an enclosed chamber equipped with germicidal lamps (UV-C). This treatment was performed twice. Eggshell aerobic plate counts (APC), eggshell breaking strength and thickness, albumen height and pH, Haugh units, and yolk color were measured after 1, 15, 30, 45, and 60 days of storage. On d 15 and 45, sensory evaluation of scrambled egg samples was conducted to determine if consumers could detect a difference between treatment groups using a triangle test. Results indicate APC for treated eggs were significantly lower than the control eggs for all sampling days in Experiment 1. However, due to low initial APC in the control eggs on d 1 of Experiment 2, no significant differences were observed for APC between control and treated eggs during storage. No consistent differences were found for eggshell and interior quality measures with the exception of albumen pH. Albumen pH was significantly higher in treated eggs than control on d 45 and 60 and d 1, 15, and 45 of Experiment 1 and 2, respectively, with only an average difference of 0.04 pH. In the sensory evaluation, only 33.5 percent of the participants correctly differentiated between the control and treated eggs. Data from this study suggests that H2O2 and UV light can be used as an alternative eggshell sanitizing procedure without impacting eggshell or internal egg quality.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 88-97).

Reproduction de : Thèse de doctorat : Génie électrique : Toulouse, INPT : 2008. / Titre provenant de l'écran-titre. Bibliogr. 68 réf.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: protein-DNA crosslinking; UV laser. Includes bibliographical references (p. 73-77).

Thesis (Ph. D.)--University of Michigan, 1933. / "Reprinted from the Journal of the Optical society of America, vol. 22, no. 10 ... October, 1932."

Thesis--Auburn University, 2009. / Abstract. Includes bibliographic references (p.46-49).