Bioremediation in the vadose zone is unpredictable because of poor understanding of factors influencing microbial growth in this environment. A lab-scale experimental system was developed to examine, noninvasively, interactions between microbial growth, water flow, and solute transport in unsaturated porous media. Measurements of microbial colonization, and its impact on hydrology,...
Few studies have directly compared denitrifying community composition and activities in soils by coupling molecular-genetic techniques and traditional measures of denitnfication. I investigated communities of denitrifying bacteria from adjacent meadow and forest soils in the Cascade Mountains, Oregon. A key gene in the denitrification pathway, N₂O reductase (nosZ), served as...
Cometabolic biodegradation processes are potentially useful for the
bioremediation of hazardous waste sites. In this study the potential application of phenol-oxidizing
and nitrifying bacteria as "priming biocatalysts" was examined in the
degradation of polycyclic aromatic hydrocarbons (PAHs), aryl ethers, and aromatic
ethers. We observed that a phenol-oxidizing Pseudomonas strain cometabolically...
It has been held that heuristic training alone is not enough for developing one's mathematical thinking. One missing component is a mathematical point of view. Many educational researchers have proposed problem-based curricula to improve students' views of mathematical thinking. The present study reports findings regarding effects of a problem-based calculus...
My research has focused on understanding N and C cycling in soils at small scales. Isotope dilution methods commonly used to estimate gross rates of soil chemical transformations assume homogeneous distribution of label. I explored the effects of diffusion limitations on isotope dilution experiments in soil aggregates using spherical diffusion-reaction...
There is growing public concern about the high proportion of saturated fatty acids in milk fat; however, feed intake, energy partitioning toward milk synthesis, and milk fat concentrations can decrease when cows are fed high concentrations of unsaturated lipids. The objective of this study was to identify the optimal rate...
Uptake and cycling of nitrogen (N) in mature trees are not well understood.
Fertilizer-N uptake, partitioning, and use-efficiency were studied in standard strain
'Topred Delicious' and spur strain 'Redspur Delicious' mature apple trees {Malus
domestica Borck) on 'Malling 7A' (M.7A) rootstocks. The treatments consisted of a
ground application in spring,...
The black vine weevil (BVW), Otiorhynchus sulcatus (F.) (Coleoptera:
Curculionidae) is a persistent pest of nursery operations in the United States,
feeding on over 140 species of plants. The goals of this research were to 1) assess
the behavioral response of BVW to a commonly employed insecticide bifenthrin
(Talstar 0.2G®)...
This dissertation explores the physiology and gene expression of the ammonia-oxidizing bacterium Nitrosomonas europaea in surface-associated bacterial communities, or biofilms. Biofilms of N. europaea were cultivated in drip flow reactors for several weeks and gene expression microarrays were used to detect 240 genes differentially expressed between the mature biofilms and...
This study examined fish movements and assemblage dynamics in the Wenaha, Grande Ronde, Snake river system of northeast Oregon and southeast Washington. I investigated the role of fish movement in the dynamics of stream fish assemblages and evaluated relationships between species movement, assemblage structure, and the heterogeneity of habitat at...