Browsing by Subject "UV"

One of the outstanding goals of neuroscience is to understand how neural circuits are assembled to produce context appropriate behavior. In an ever changing environment, it is critical for animals to be able to flexibly respond to different stimuli to optimize their behavioral responses accordingly. Oviposition, or the process of choosing where to lay eggs, is an important behavior for egg-laying animals, yet the neural mechanisms of this behavior are still not completely understood. Here, we use the genetically tractable organism, Drosophila melanogaster, to investigate how the brain decides which substrates are best for egg deposition. We show that flies prefer to lay eggs away from UV light and that induction egg-laying correlates with increased movement away from UV. Both egg-laying and movement aversion of UV are mediated through R7 photoreceptors, but only movement aversion is mediated through Dm8 amacrine neurons. We then identify octopaminergic neurons as being potential modulators of egg-laying output. Collectively, this work reveals new insights into the neural mechanisms that govern Drosophila egg-laying behavior.

The adenoviruses are nonenveloped double stranded DNA viruses, which cause enteric dysentary and respiratory infection. Adenovirus has become a focus of the water treatment community because of its apparent resistance to ultraviolet disinfection; it is the basis for stringent new EPA regulations regarding all viruses in both surface and ground waters. Most of the work done so far, however, has involved the use of monochromatic (254 nm) low pressure (LP) UV sources and subsequent assay of viral infectivity in cell culture models. LP UV lamps primarily damage DNA, while polychromatic UV sources may damage other parts of the virus as well. Recent research has shown that these newer, polychromatic UV sources--such as medium pressure (MP) UV--are more effective than monochromatic LP UV for disinfection of adenovirus. The objectives of this work were to study adenoviral response to UV using both LP and MP UV as well as using both standard cell culture infectivity assays and more direct methods of assessment based on molecular biology. These include quantitative long PCR for assessment of DNA damage and SDS-PAGE for assessment of protein damage; transmission electron microscopy was used to examine the structure of UV treated viral particles. This work was only the second significant study to show the response of adenoviruses to medium pressure UV and the first to thoroughly examine the response of adenoviruses to both LP and MP UV using cell culture-independent methods. Results confirm that adenovirus is sensitive to MP UV when assayed in cell culture; they show that LP and MP UV are equally effective at inducing damage to the adenoviral genome and that MP UV is more effective than LP UV at damaging the viral proteins. This work helps deepen our understanding of UV disinfection of adenovirus.

In order to meet disinfection guidelines, wastewater utilities must achieve a high level of treatment before discharging treated water for irrigation or industrial use. However, public pressure to reduce disinfection by-products and pharmaceutically-active compounds, recently-promulgated regulations on chlorine-resistant microorganisms such as Cryptosporidium parvum, and growth in population and water demand have driven an interest in alternatives to chlorination. The WateReuse Foundation has funded WRF 02-009 (Innovative Treatment Technologies for Reclaimed Water), which is a survey of current and emerging reuse water treatment technologies. The goal of the project is to evaluate treatment technologies can provide adequate recycled water effluent without the cost of reverse osmosis (RO) or the disinfection by-products (DBPs) formed during chlorination.

The inactivation of indigenous microorganisms (total and fecal coliform bacteria, and total aerobic spores) and spiked surrogate, respiratory, and enteric viruses (MS-2 bacteriophage, adenovirus type 4, reovirus type 3, and coxsackievirus type B5) and chemical degradation by wastewater treatment technologies was evaluated on the bench-scale. These include: low- and medium-pressure UV, LPUV/H₂O₂, ozonation, O₃/H₂O₂, peracetic acid (PAA), LPUV/PAA, chlorination, chloramination, and ultrafiltration. The applicability of the candidate disinfection methods, especially emerging and comparatively untested methods such as PAA and advanced oxidation processes (AOPs), was studied through comparison of their performance and the important water matrix parameters (e.g., alkalinity, BOD, TSS, etc.).

Of the chemical disinfectants, molecular ozone and free chlorine were the most effective, with substantial coliform and virus kill at low doses. Combined chlorine in the form of monochloramine had a reduced disinfectant capacity than free chlorine, and peracetic acid (PAA) performed equally as well as free chlorine with respect to coliform bacteria in some instances but had little to no impact on spiked MS2 bacteriophage. None of the aforementioned disinfectants had an appreciable impact on indigenous aerobic spore-forming bacteria due to their physiology. UV and O₃ rapidly killed human enteric and respiratory viruses, but a consistent benefit by AOPs over their base technologies was not observed for any of their base technologies.

Low and medium-pressure UV inactivated free-floating indigenous coliform bacteria almost immediately, while slower inactivation rates at higher UV fluences illustrated the "tailing" behavior observed when bacteria are embedded in or shielded by particulate matter. Log-linear inactivation of spiked viruses and indigenous aerobic spores by UV was consistent across the utility waters. The UV-based advanced oxidation processes (UV/H₂O₂ and UV/PAA) destroyed spiked organic compounds at much higher rates than direct UV photolysis, while O₃, with or without H₂O₂ , oxidized spiked compounds and reduced estrogenicity (EEQ) at low doses. Recalcitrant chlorinated hydrocarbons such as TCEP were only moderately removed by the tested AOPs, but low doses of O₃ (3 ppm residual O₃) reduced estrogenic activity by 99%. Like other disinfection processes, AOP performance is dependant on pretreatment, especially concerning particulates.