The objectives of this research were to correlate benzene biodegradation with soil physical, chemical and biological properties, to determine if biodegradation could be predicted based on measured or observed soil properties, and to investigate the role of nutrients on benzene biodegradation in soil. Benzene disappearance over time was measured in aerobic active and control (autoclaved) microcosms prepared with previously-uncontaminated subsurface soils. Soil microcosm experiments were prepared with initial benzene concentrations of 1, 10 and 50 mg/L. For each soil, logistic, zero-, first-, and 3/2- order kinetic models were fit to benzene disappearance versus time data by regression analysis. The logistic and 3/2-order models fit the data better than zero- and first-order models for experiments prepared with initial benzene concentrations of 1 and 10 mg/L. For an initial benzene concentration of 50 mg/L, experimental data were often better fit by zero- or first-order kinetic models. To obtain predictive equations, logistic kinetic model rate constants were related to soil properties using multiple linear regression (MLR). The “best” MLR models and their regression coefficient estimates were statistically significant at p<0.05. For experiments prepared with an initial benzene concentration of 1 mg/L, the resulting predictive equation contained soil phosphorus concentration and cation exchange capacity (CEC). For experiments prepared with an initial benzene concentration of 10 mg/L, the predictive equation contained soil copper, nitrate-N and phosphorus concentrations, CEC, and % sand. A comparison was made between benzene biodegradation in unamended soil microcosms and soil microcosms amended with ammonium and potassium phosphates (11 mM nitrogen, 6 mM phosphorus and 0.6 mM potassium). Benzene disappearance over time in soil microcosms was stimulated by nutrient addition in one (11%), 6 (50%), and 5 (45%) soils at initial benzene concentrations of 1, 10 and 50 mg/L, respectively. In general, nutrient addition had the greatest affect on benzene biodegradation in low pH soils. / Ph. D.

The probabilistic approach to design optimization has received increased attention in the last two decades. It is widely recognized that such an approach should lead to designs that make better use of the resources than designs obtained with the classical deterministic approach by distributing safety onto the different components and/or failure modes of a system in an optimal manner. However, probabilistic models rely on a number of assumptions regarding the magnitude of the uncertainties, their distributions, correlations, etc. In addition, modelling errors and approximate reliability calculations (first order methods for example) introduce uncertainty in the predicted system reliability. Because of these inaccuracies, it is not clear if a design obtained from probabilistic optimization will really be more reliable than a design based on deterministic optimization. The objective of this work is to provide a partial answer to this question through laboratory experiments — such experimental validation is not currently available in the literature. A cantilevered truss structure is used as a test case. First, the uncertainties in stiffness and mass properties of the truss elements are evaluated from a large number of measurements. The transmitted scatter in the natural frequencies of the truss is computed and compared to experimental estimates obtained from measurements on 6 realizations of the structure. The experimental results are in reasonable agreement with the predictions, although the magnitude of the transmitted scatter is extremely small. The truss is then equipped with passive viscoelastic tuned dampers for vibration control. The controlled structure is optimized by selecting locations for the dampers and for tuning masses added to the truss. The objective is to satisfy upper limits on the acceleration at given points on the truss for a specified excitation. The properties of the dampers are the primary sources of uncertainties. Two optimal designs are obtained from deterministic and probabilistic optimizations; the deterministic approach maximizes safety margins while the probability of failure (i.e. exceeding the acceleration limit) is minimized in the probabilistic approach. The optimizations are performed with genetic algorithms. The predicted probability of failure of the optimum probabilistic design is less than half that of the deterministic optimum. Finally, optimal deterministic and probabilistic designs are compared in the laboratory. Because small differences in failure rates between two designs are not measurable with a reasonable number of tests, we use anti-optimization to identify a design problem that maximizes the contrast in probability of failure between the two approaches. The anti-optimization is also performed with a genetic algorithm. For the problem identified by the anti-optimization, the probability of failure of the optimum probabilistic design is 25 times smaller than that of the deterministic design. The rates of failure are then measured by testing 29 realizations of each optimum design. The results agree well with the predictions and confirm the larger reliability of the probabilistic design. However, the probabilistic optimum is shown to be very sensitive to modelling errors. This sensitivity can be reduced by including the modelling errors as additional uncertainties in the probabilistic formulation. / Ph. D.

Sclerotinia crown and stem rot (SCSR) incited by Sclerotinia trifoliorum Eriks. causes severe losses in some fall-seeded, no-tillage plantings of alfalfa (Medicago sativa IL.) in Virginia. A mycelial plug inoculation technique was used to detect differences between cultivar (cv) responses of two alfalfa cvs, Arc and Vertus, under greenhouse conditions. A six dia plug from the margin of a 5-day-old culture of S. trifoliorum was placed near the crown area of a plant and incubated for a pre-determined period in a dew chamber at 18 C and 100% RH. Differences in isolate virulence were detected; cv Vertus was less susceptible than Arc to the less virulent isolates while the more virulent isolate (TAL 4) was equally severe on both. An incubation period of 96 hr produced significantly higher disease severity than 72, 48 or 24 hr, however, cv differentiation was best after 72 hr. Eight-, and nine-week-old plants were found to be most suitable for cv evaluation tests since younger seedlings were severely damaged and more mature plants did not develop sufficient symptom expression. Evaluation of twelve cvs with the virulent isolate (TAL 4) and the less virulent isolate (LAL 3) after 96 hr incubation produced significant differences between the mean disease severity ratings (MDSRs). Disease severity increased up to 20 days and then stabilized. Cultivar Anstar followed by WL 320, Vertus and Saranac AR were less susceptible in a majority of the tests; Endure and Euver performed well in some tests while Pioneer Brand 526 and Raidor performed poorly in all tests. This inoculation technique may act as the primary step in the selection of disease resistant germplasm for propagation, re-evaluation, and mass selection before field testing. / Master of Science

Researchers have theorized that Transaction Cost Analysis paradigm draws a connection between transaction specific investment and opportunism with guile. This dissertation investigated this relationship during and after the negotiation process with a focus on contractual safeguarding. It was hypothesized that the pattern of the level of anticipated investment in transaction specific investment was related to choice of governance clause (i.e., contractual safeguarding) in the final negotiated contract. Additionally, it was hypothesized that anticipated investment in transaction specific assets would be related to the amount of opportunism (operationalized as falsity) prevalent in the negotiation process. Also, it was hypothesized that after the contract was formed, the resultant investment in transaction specific assets was inversely related to opportunism (operationalized as a reduction in contract performance quality). Anticipated and resultant investment differ in that anticipated investment is proposed and not committed while resultant is not only committed investment but also includes the investment that would result with the enforcement of the negotiated contract clauses. These relationships were tested using a negotiation simulation utilizing working MBA students as subjects. It was found that the pattern of the level of anticipated investment was related to final negotiated contract clause choice. The anticipated investment level patterns and final negotiated contract clauses were related as follows: 1) anticipated symmetric low investment was related to a market forces form of contractual safeguarding, 2) anticipated symmetric high investment was related to a bilateral form of contractual safeguarding, and 3) anticipated asymmetric investment patterns were related to unilateral clauses favoring the high investor. It was concluded that even in a climate of win-win negotiations and emphasis on trust building, that parties to a contract still desire contractually based safeguards appropriate to their anticipated investment in transaction specific investment. No relationship between anticipated investment level and opportunism in the form of falsity in communications was found. Despite the rejection of this hypothesized relationship, it was concluded that one cannot depend on the anticipation of investment to serve as a disincentive to opportunism in the form of falsity in the negotiation process. No relationship between resultant investment level and opportunism in the form of reduction of quality performance was found. Despite the rejection of this hypothesized relationship, it was concluded that one cannot depend on the presence of resultant investment to serve as a disincentive to opportunism in the form of reduction of quality of contract performance. Contributions derived from this research included a disclosure/falsity scale survey items and a content analysis system for rating false communications ranging from bluffing to lying. / Ph. D.

The purpose of the investigation presented in chapter 1 was to determine which of the following artificial stream designs would be most logistically simple yet effective in maintaining riffle insects during a 30-d bioassay: 1) static and no current (S-NC); 2) flow-through and no current (FT-NC); 3) static with current (S-C); or 4) flow-through with current (FT-C). Flow-through and current, when provided, were 12 ml min⁻¹ and 30 cm sec⁻¹, respectively. Streams were covered by emergence traps, and daylight equivalent lights provided a natural photoperiod. The four stream designs were evaluated in triplicate based on changes in insect species-abundances after 30 d. Test organisms were transferred to the artificial streams in rock-filled containers previously colonized for 30 d in a third-order mountain stream riffle. Relative to benthic samples taken directly from the source riffle, the artificial substrates selected for collector-filterers and against collector-gatherers. The FT-C and S-C stream designs maintained most taxa at or above initial densities. Emergent adults comprised a large proportion of mayfly and chironomid densities and must be monitored during bioassays with aquatic insects. The Investigation reported in chapter 2 was conducted to determine if contaminant-induced changes in macroinvertebrate and periphyton communities in laboratory stream microcosms could be used to predict macroinvertebrate and periphyton responses In a natural stream receiving the same contaminant. The microcosms were dosed in quadruplicate with four (0.0, 0.1, 1.0, and 10.0%) concentrations of a complex effluent; these concentrations reflected those in the field. Mayfly densities in the microcosms were significantly (P≤0.05) reduced at 1.0 or 10.0% effluent depending on species. Hydropsychlds were not affected by the effluent, and chironomids and periphyton were stimulated. Overall, the stream microcosms accurately predicted the macroinvertebrate and periphyton response observed in the field. Chapter 3 compared responses to a complex effluent from microcosms of indigenous macroinvertebrates and protozoans to responses observed in acute tests with Daphnia magna, Ceriodaphnia dubia and Pimephales promelas and chronic survival and reproductive tests with C. dubia The predictive utility of these various tests was then evaluated against observed effects in the receiving stream. The LC₅₀_s (% effluent) from the acute tests were 63.09 for Pimephales promelas, 18.8 to 31.3 for Daphnia magna and 54.7 for Ceriodaphnia dubia. Results from 7-day chronic tests indicated that C. dubia survival was significantly (P≤0.05) affected at 30% effluent and reproduction was affected at concentrations ≥3.0% effluent. In the protozoan microcosms, community composition was significantly (P≤0.05) changed at 1.0%; while protozoan species richness was significantly reduced at 3.0% effluent. The microcosms not only were the most sensitive indicators of effluent toxicity, they also correctly predicted which indigenous organisms would be lost and which would be stimulated at various ambient concentrations of the effluent. In the fourth chapter canonical discriminant analysis, 2 diversity indices, and 7 community comparison indices were evaluated to determine their utility in quantifying macroinvertebrate response to a complex effluent in laboratory microcosms. A permutation and randomization procedure was used to test the hypothesis of no treatment effect based on the community comparison indices. The Bray-Curtis index provided the most meaningful condensation of the data. / Ph. D. / incomplete_metadata