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Comparison Of Chlorine And Chlorine Dioxide As Disinfectants For Surface Waters, Kristen S. Tilton

Doctoral Dissertations

Safe supplies of drinking water free of pathogenic agents such as viruses and protozoa are essential for humankind. The evaluation of current treatment practices for the removal of pathogens has become increasingly important with the occurrence of waterborne disease outbreaks. Shortcomings associated with chlorine have prompted the need to assess alternative disinfectants.

The overall objective of this research is to compare chlorine and chlorine dioxide as disinfectants for surface waters using Giardia muris cysts, bacteriophage MS2, total and fecal coliforms, and heterotrophic bacteria. Concentration x time (CT) values for the inactivation of Giardia muris cysts and MS2 bacteriophage as a …

A Comparative Study Of The Ecology Of Smooth Flounder, Pleuronectes Putnami, And Winter Flounder, Pleuronectes Americanus, From Great Bay Estuary, New Hampshire, Michael Patrick Armstrong

Doctoral Dissertations

Smooth flounder, Pleuronectes putnami, and winter flounder, Pleuronectes americanus, co-occur in estuaries along the east coast of North America from Labrador to Massachusetts. Results of a three year sampling program indicated that the two species were partially segregated along salinity and depth gradients in upper Great Bay Estuary, New Hampshire. Along the salinity gradient, smooth flounder were most abundant at the oligo-mesohaline riverine habitat while winter flounder were most abundant at the meso-polyhaline open bay habitat. Both species exhibited a generalized up-river movement with seasonally increasing salinity. Smooth flounder showed ontogenetic changes in distribution along the depth gradient, with the …

Nucleotide And Energy Metabolism During Visual Transduction In Electropermeabilized Rod Outer Segments, Vincent J. Coccia

Doctoral Dissertations

Cyclic GMP and calcium are known to be messengers involved with visual transduction in vertebrate rod photoreceptor outer segments (ROS). However, it has been difficult to study the interrelationship of the calcium and cGMP signaling pathways using biochemical methods. An electropermeabilized rod outer segment (EP-ROS) preparation has been developed to examine these problems.

Square-wave electric field pulses were used to generate permanent disruptions in the plasma membrane of ROS. This treatment also permeabilized the disk membranes within the organelle. EP-ROS retain the characteristic morphology of osmotically intact ROS at the light microscopic level, but are permeable to low molecular weight …

Population Dynamics And Recruitment Ecology Of Some Caribbean Reef Corals, David B. Carlon

Doctoral Dissertations

Processes that limit the distribution arid abundance of marine species may affect larvae, juveniles, or adults. I focus on larval and early benthic phases of reef corals as determinants of spatial pattern. In CHAPTER I examine larval behavior during dispersal and settlement as a mechanism for aggregated spatial pattern in two corals. A short swimming period and non-selective settlement behavior explains the highly aggregated spatial pattern in Favia fragum. Spatial pattern in Agaricia agaricites probably reflects larval behavior at settlement and post-settlement mortality. These larvae had a longer planktonic period and were selective in settlement surfaces.

In CHAPTER II, I …

Chilling Photoinhibition In Zea Mays L And Zea Diploperennis Iltis, Doebely And Guzman: The Role Of Oxygen And Antioxidants, Kajal Bose Ghoshroy

Doctoral Dissertations

Light absorbed by photosynthetic pigments must be distributed either for chemical work, reemitted as fluorescence or safely dissipated as heat. Adverse environmental conditions reduce the dissipation capacity of plants and the excess energy leads to damage to the photosynthetic mechanism, termed photoinhibition. Low, non-freezing temperatures cause such photoinhibition, especially in tropical plants grown in the temperate zone. This damage occurs in the photosystem II and is triggered by highly reactive radicals or reactive forms of dioxygen. Numerous studies point to the involvement of oxygen and antioxidant enzymes and substrates in amelioration of these damages. In C$\sb3$ plants, dioxygen is thought …

A Proposed Acrosomal System For Identifying Stages Of The Cycle Of The Seminiferous Epithelium And A Model For The Kinetics Of Spermatogenesis In The Rabbit, Antonio Carlos S Castro

Doctoral Dissertations

Most quantitative investigations of spermatogenesis requites identification of stages of the cycle of the seminiferous epithelium. The current "tubular morphology" system of staging for the rabbit permits identification of only eight stages and is not applicable to all experimental conditions. A more advantageous staging system, based on changes in the acrosome and morphology of the developing spermatids, had not been developed for the rabbit. Knowledge of spermatogonial kinetics, including the identity of spermatogonial subtypes and the number and timing of spermatogonial divisions, is also important, but had not been fully elucidated in this species. This investigation was undertaken to develop …

Characterization Of The Adherence Mechanisms Of Listeria Monocytogenes To Host Cells And Their Role In The Pathogenesis Of Listeriosis, Marcia M. Pierce

Doctoral Dissertations

Listeria monocytogenes is the facultative intracellular pathogen responsible for causing the foodborne illness known as listeriosis. Disease occurs following invasion of cells of the intestinal tract by the organism following consumption of contaminated foods. In this study, a mechanism of opsonin-independent attachment of L. monocytogenes to host cells was identified. A clinical isolate of L. monocytogenes, together with murine-derived primary peritoneal macrophages were used to study this adherence phenomenon.

Transmission and scanning electron microscopy were used to visualize the attachment and uptake of L. monocytogenes by murine macrophages, while organism enumeration by viable bacterial cell colony counts was used as …

Isolation And Characterization Of The Ccr4 Associated Factors, Haiyan Liu

Doctoral Dissertations

In yeast, Sacchoromyces cerevisiae, transcription of $\underline{ADH2}$ gene (encodes alcohol dehydrogenase II) under glucose derepression conditions requires not only the gene-specific activator, Adr1p, but also the general transcriptional factors like Ccr4p. Ccr4p belongs to the LRR-containing protein superfamily, members of which have often been found to associate with other proteins to form a functional protein complex. This dissertation reports three major conclusions from my research.

1. The CCR4 protein is associated with at least three other proteins by immunoprecipitation using the CCR4 antibody, and more importantly, the LRR in the CCR4 protein is not only essential, but also sufficient to …

Molar And Local Effects Of The Fixed-Ratio Changeover Requirement On Choice, Changeovers, And Visits: A Parametric Examination Of The Fixed-Ratio Changeover Requirement, Michael B. Ehlert

Doctoral Dissertations

The distribution of behavior by organisms in choice situations is of long-standing interest to psychologists. The generalized matching relation accurately predicts choice between concurrent variable-interval schedules of reinforcement. Researchers have assumed, on weak grounds, that the effect of the changeover requirement on sensitivity to reinforcement--the exponent in the generalized matching equation--was consistent. This experiment considered the effects of the changeover requirement by parametrically manipulating the fixed-ratio schedule required to switch alternatives. Pigeons pecked either of two side-response keys in a standard three-key operant chamber for food, delivered according to independent variable-interval schedules. No changeover delay was used, instead completion of …