Determination of Salmonella Species in the Big Sioux River and Development of a Quantitative Most Probable Number Method

In recent years the pollution problems in rivers and lakes have forced the Federal Water Pollution Control Administration to issue requirements for minimum water standards for each State with an interstate stream. Since the Big Sioux River is an interstate river, studies are needed to determine its quality. According to the South Dakota Committee on Water Pollution, water pollution in South Dakota originates from agricultural, municipal, and industrial wastes. For the Big Sioux River, the municipal and meat-processing wastes are the important sources of pollution. Little is known of the sanitary bacteriological quality of rivers and lakes in South Dakota. Standard methods are available for determining the sanitary indicator bacteria in water (coliforms and fecal streptococci), but there is not a standard method available for the determination of pathogens such as the Salmonella spp. Having understood that the Big Sioux River is an interstate stream, Pierce examined the river by bacteriological methods to demonstrate the presence of salmonellae in the river and developed a qualitative method for isolating salmonellae. He showed the presence of salmonellae in the Big Sioux River by isolating Salmonella enteritidis serotypes Anatum, Bredeney, Derby, Infantis, Javiana, Montevideo, and Oranienburg. He also improved the isolation method by using brain heart infusion (BHI) broth as a pre-enrichment medium. Since the Salmonella spp. present in water are likely to have low viability, they need to be made more viable before being placed into highly selective media. Following this line of reasoning, he used BHI broth as a pre-enrichment step and he proved it by the experimental comparison between lactose broth and BHI broth. Although Pierce developed an improved qualitative method using BHI pre-enrichment and membrane filtration for isolations of the salmonellae, he was not able to quantitatively study the distribution of number and kind of the salmonellae in the Big Sioux or James rivers. Thus, there are two objectives in this thesis study: one, the determination of the distribution of Salmonella spp.; two, the development of a method for Salmonella quantitation

Study on Arrangement of Diblock Copolymer Microdomains during Solvent Evaporation and in Hemi-spherically Confined System

Materials Science EngineeringBlock copolymer nanostructures are one of the cutting edge candidates to create long range ordered microstructures. AB block copolymers can be assembled into various nanoscale morphologies such as lamella, cylinder, sphere and gyroid depending on the A block composition f and the interaction strength between segments represented by the Flory-Huggins χ parameter. There have been intense efforts to use the block copolymer morphologies as scaffolds to position nanomaterials into ordered arrays for applications such as high density memory device, metamaterial, and photonic band gap materials. Solvent evaporation and annealing is one of the most common methods to create the block copolymer structure in thin films and enhance its alignment. However, the microdomains usually contain some uncontrolled defects and lack of long-range order due to entropic fluctuation and incomplete annealing. The optimum structural property required in the academic and industrial world can be outlined by the following three keywords: Large area, low defects, and short period. The detailed discussion for these three trendy keywords in this rapidly growing field is included in chapter I. In chapter II, I introduce the main theoretical tool in this research, self-consistent field theory (SCFT), and its application. The most important part in SCFT method is the calculation of partition function which predicts statistical behavior of polymers by solving the modified diffusion equation with potential field w(r). The commonly used numerical methods to solve such equations are real space method, spectral method and pseudospectral method. In this study, I use the real space method to investigate the microstructure evolution of the diblock copolymer thin films in solvent. I also use the pseudospectral method to obtain the morphology of the block copolymers formed in the confined system with two controlled interfaces. In the third chapter, I study the nanostructure evolution of diblock copolymer thin films in solvents. I use SCFT to study the equilibrium block copolymer phases and the quasi-equilibrium dynamic path of the morphology evolution during the slightly selective solvent vaporization process. During the evaporation process, I introduce a small noise field using random function to create the initial block copolymer morphologies. Then, the thickness of block copolymer film h is reduced as the global solvents volume fraction ψ decreases. During this process, I use the previous morphologies as an input for the morphology of the thinner film, which means I model the quasi-static morphology evolution of the thin film. As the solvent evaporates, the film thickness decreases and the number of defects also decrease. This method allows us to track down the detailed mechanism of the defect elimination. The onset of order-disorder transition and the observed morphology matches very well with the theoretical prediction. Confinement of diblock copolymers under certain geometries can offer new methods to develop unique morphologies which have never been known before in bulk or thin film. In chapter IV, I study various block copolymer morphologies in hemispherical and ellipsoidal shape confinements and compare the results with experiments. In the experiment, PS-PMMA block copolymers are physically confined in hemispherical cavities prepared by anodic aluminum oxide template. The cavities have two controlled interfaces, one of them is the top surface of the cavity covered with preferential films and the other is the surface of cavity wall which interacts preferentially or randomly depending on the coating of the cavity wall. Our theoretical modeling uses SCFT which calculates the mean field density distribution of AB block copolymers in this confined geometry. The key parameters for the morphology determination are the size and shape of the container and the surface tension between components. For example, when the container wall is coated with PS polymers and neutral cover film is used, onion-shape lamellar phases with PS at the bottom is observed rather than the parallel lamellar phases. It is also found that preferential cover film promotes the alignment of domains. Our versatile method also allows us to model ellipsoid-shaped confinements, and other interesting morphologies are found depending on the eccentricity of the ellipsoid.ope

Current-Induced Resonant Motion of a Magnetic Vortex Core: Effect of Nonadiabatic Spin Torque

The current-induced resonant excitation of a magnetic vortex core is investigated by means of analytical and micromagnetic calculations. We find that the radius and the phase shift of the resonant motion are not correctly described by the analytical equations because of the dynamic distortion of a vortex core. In contrast, the initial tilting angle of a vortex core is free from the distortion and determined by the nonadiabaticity of the spin torque. It is insensitive to experimentally uncontrollable current-induced in-plane Oersted field. We propose that a time-resolved imaging of the very initial trajectory of a core is essential to experimentally estimate the nonadiabaticity.Comment: 4 pages, 4 figure

Prediction of the Static/Dynamic Stiffness of Coupling Sections of Rotating Systems

Mechanical EngineeringThe coupling section of rotating systems is a very important factor to determine their static/dynamic stiffness. To ensure the proper performance of the machine tool, the static/dynamic stiffness of the rotating system has to be predicted. Various parameters of the coupling section in rotating systems, such as the spring element, the node number and preload influence the characteristic of rotating system. This study focuses on the prediction of the static and dynamic stiffness of the rotating system with coupling section using the finite element (FE) model. To represent the coupling section of the rotating system, finite element method (FEM) computations on preload effect and the spring element arrangement were performed carried out. MATRIX 27 in ANSYS is the proper spring element to describe the coupling section of the rotating system because the MATRIX 27 can describe the coupling section close to the real object and is applicable to various rotating systems. The preload effect on the coupling section was estimated on the basis of the HERTZIAN contact theory. On the other hand, technical data for the specific ball bearings were obtained from bearing manufacturers. The FE model of the couple section which has the sixteen node using MATRIX 27 was constructed. Comparisons between FEM predictions and experimental results were performed in terms of the static and dynamic stiffness.ope

Egg Yolk Peptide Stimulated Osteogenic Gene Expression

Postmenopausal osteoporosis is characterized by low bone density which leads to increased bone fragility and greater susceptibility to fracture. Current treatments for osteoporosis are dominated by drugs that inhibit bone resorption although they also suppress bone formation that may contribute to pathogenesis of osteonecrosis. To restore the extensive bone loss, there is a great need for anabolic treatments that induce osteoblasts to build new bone. Pre-osteoblastic cells produce proteins of the extra-cellular matrix, including type I collagen at first, and then to successively produce alkaline phosphatase (ALP) and osteocalcin during differentiation to osteoblasts. Finally, osteoblasts deposit calcium. Present study investigated the effects of egg yolk peptide (EYP) on osteogenic activities and bone matrix gene expressions in human osteoblastic MG-63 cells. The effects of EYP on cell proliferation, alkaline phosphatase (ALP) activity, collagen synthesis, and mineralization were measured. The expression of osteogenic genes including COL1A1 (collagen, type I, alpha 1), ALP, BGLAP (osteocalcin), and SPP1 (secreted phosphoprotein 1, osteopontin) were measured by quantitative realtime PCR. EYP dose-dependently increased MG-63 cell proliferation, ALP activity, collagen synthesis, and calcium deposition. Furthermore, COL1A1, ALP, and SPP1 gene expressions were increased by EYP treatment. Present study suggested that EYP treatment enhanced osteogenic activities and increased bone matrix osteogenicgenes. These results could provide a mechanistic explanation for the bone-strengthening effects of EYP