Physical Sciences and Mathematics Commons^™

Biological Control Of Purple Loosestrife (Lythrum Salicaria): Factors Affecting Galerucella Pusilla And Galerucella Calmariensis Establishment In Tidal Areas, Lynda Kathryn Moore

Dissertations and Theses

Galerucella pusilla and G. calmariensis have provided successful biological control of purple loosestrife (Lythrum salicaria L.) in non-tidal areas but only marginal control in areas of tidal influence. While a previous study identified mechanical scour by tidal waters as the main cause of establishment failure, purple loosestrife stem density explained more than 80% of the variability in presence and absence of Galerucella at my study sites in the Columbia River Estuary. A logistic regression model using purple loosestrife stem density, elevation, and their interaction as predictors accurately predicted 92.5% of Galerucella presence or absence observations of a test data …

Comparison Of The Focal Properties Of Selected Magnetic And Electrostatic Lenses And Tests Of Their Theoretical Models, Luis Thomas Almarez

Dissertations and Theses

The main goal of the present research is to determine whether there is a significant difference between the aberrations of magnetic and electrostatic electron lenses when they are used in the same way. Comparison of the lenses was done in an electron-optical bench, set up to resemble a scanning electron microscope (SEM). Five different lenses, two magnetic and three electrostatic, were compared. Each group included two lenses with different lens-field lengths (pole-face spacing in magnetic lenses and interior length in electrostatic lenses). The lenses were used in turn to focus the electron beam into a demagnified image, or probe. The …

Active Site Chemistry Of The Nadph-Dependent:7-Cyano-7-Deazaguanine (Preq0) Nitrile Oxidoreductase, An Enzyme Involved In Queuosine Biosynthesis, Bobby Wai Keung Lee

Dissertations and Theses

Queuosine (Q) is a modified nucleoside found at the wobble position of bacterial and eukaryotic transfer RNAs (tRNAs) that are specific for the amino acids tyrosine, histidine, aspartate and asparagine. A recently discovered enzyme in the biosynthetic pathway of Q, the NADPH-dependent 7-cyano-7-deazaguanine oxidoreductase (QueF), carries out the two-fold, four-electron reduction of Q precursor preQ0 to preQ1 and represents the first example of the enzymatic conversion of the nitrile functional group to an amine. Presented herein are kinetic, spectroscopic, mutational, biophysical, and isotope labeling studies directed at the elucidation of the chemical and kinetic mechanisms of this new class of …

Prediction Of Persistence Of Fertilizer-Derived Cadmium In Oregon Agricultural Soils Using Equilibrium Modeling And Fertilizer Release Kinetics, Fungai Mukome

Dissertations and Theses

Organic farming has become a multimillion dollar industry and while much emphasis is put on subsequent fertilizer inputs onto these fields, very little consideration is given to the prior fertilization activities of these soils. For a farm to be certified organic it means no harmful chemicals have been applied for at least three years.

The overall hypothesis tested by this research was that equilibrium adsorption models can adequately represent the behavior of fertilizer-derived cadmium in Oregon agricultural soils and that such model results can be easily incorporated into risk assessment models, transport study models and persistence studies for organic or …

Vegetation, Environmental Characteristics, And Their Relationships: Variation Within The Annually Flooded Riparian Zones Of The John Day River Basin, Oregon, Samuel J. Hartsfield

Dissertations and Theses

I hypothesized that vegetation and physical environmental characteristics would differ between the upper and lower extents of the annually flooded riparian zone on the John Day River, and that relationships between species and environmental variables would display differences between these two zones. Vegetation, environmental variables, and relationships between them were assessed for the entire annually flooded riparian zone, and for the proposed upper and lower zones. Data were collected from 60 one-square-meter quadrats: 30 in each the upper and lower zones. Sites were randomly selected and located so that flood duration was roughly equal at all sites within each zone. …

The Role Of Water And Other Resources In The Invasion Of Rubus Armeniacus In Pacific Northwest Ecosystems, Joshua Sundance Caplan

Dissertations and Theses

The factors influencing the invasive success of Rubus armeniacus (Himalayan blackberry) in the Pacific Northwest of North America are only partly understood, but have important implications for its management and for our understanding of the processes driving invasive plant proliferation in regions with seasonally fluctuating resources. I identified patterns of R. armeniacus occurrence and growth under widely ranging soil and light conditions in western Oregon. I found that light availability was a primary determinant of R. armeniacus occurrence and growth. I also found that R. armeniacus was tolerant of a wide range of soil conditions, notably coarse texture, and could …

Studies Of Dna Hybridization Reactions And Applications In Genetic Assays, Fidelis Manyanga

Dissertations and Theses

The intent of this study was to investigate two fundamental aspects of short DNA duplex stability and how that stability differs for duplex molecules consisting of either all perfect match Watson/Crick base pairs or a mixture of perfect match Watson/Crick base pairs and mismatch base pairs. Theoretical and experimental investigations of the origins of the nucleation term in the free energy of DNA duplex formation were revisited. Thermodynamic parameters (ΔG, ΔH, Δ S and Tm) of short DNA/DNA duplexes ranging in length from 6 to 35 base pairs were systematically evaluated by Differential Scanning Calorimetry …