A logit model was employed to determine the relative importance of socioeconomic factors influencing the misuse of pesticides on vegetables in Central Luzon, Philippines. The analysis revealed an increase in pesticide misuse associated with the following factors: a high value placed on advice from a chemical company representative; membership in a cooperative, village or farmers' association; and visits by a Department of Agriculture technician to discuss non-pesticide means of controlling vegetable pests. Those factors which reduced pesticide misuse included: increased age and educational attainment; access to integrated pest management training through the Farmer Field School; receiving credit from a cooperative; and agreement with the perception that killing natural enemies could hasten pest infestation. The effective rate of protection on nine pesticides was calculated to quantify the net effects of pricing and exchange rate policies on the degree of subsidy or tax experienced by pesticide importers. It was found that the effective rate of protection for the nine pesticides was between negative 12 and 25 percent when the exchange rate effects were accounted for. However, the rate of protection became more negative when the equilibrium exchange rate was used indicating that exchange rate overvaluation offset the tax pesticide importers face. In addition, the analysis indicated that pricing and exchange rate policies have created a six to eight percent subsidy on pesticide prices for the years 1989 to 1993. This subsidy on pesticides has increased both consumer and producers welfare and the quantity of pesticides used in the Philippines. / Master of Science

M.S.

Structure-property relationships were investigated for the bis-glycidyl methacrylate deriva-tives of bisphenol-A crosslinked by electron beam irradiation. This material, commonly called bis-GMA, is a viscous liquid at room temperature which crosslinks to form a glassy network when a 3 to 5 mil coating is irradiated with sufficient energy. The major parameters which were systematically varied in this study were radiation dosage, dose rate, aging time after irradiation, and post-cure annealing at higher temperatures. Measurements were conducted first to quantify the crosslinking reaction, then to characterize the physical properties of the resulting networks. Extraction by a solvent was done to deter-mine the degree of network formation through the equilibrium swelling ratio and the gel weight fraction after drying. Another method utilized FTIR to monitor the disappearance of double bonds as the crosslinking reaction proceeded. In order to characterize the physical properties, differential scanning calorimetry (DSC) and dynamic mechanical spectroscopy were done to determine the glass transition temperature. It was found that the network density or amount of cure is proportional to the irradiation dosage, with an upper limit reached above some critical dosage. Dose rate was not found to influence the degree of cure greatly. The crosslinking reaction often became diffusion limited as vitrification occurred. These phenomena were discussed in terms of the well-known Time-Temperature-Transformation diagram. Free radicals trapped in these networks exhibited a finite lifetime. Post-curing can be achieved by annealing at a temperature above the T₉ of the network, as shown by the increase of the glass transition temperature from DSC and dynamic mechanical results. Bis-GMA was mixed with rubbery modifier materials with acrylate and methacrylate functional ends in order to toughen the bis-GMA networks. It was observed that the acrylate end groups were more reactive in EB cured systems than analogous methacrylates probably due to their higher polymerization enthalpy and less steric hindrance. Phase separation, which would provide rubber toughening without depressing the high glass transition temperature, was not achieved by irradiation with the modifying materials at the molecular weights used in this study, but the mixtures were toughened as shown by the dynamic mechanical data. / M.S.

This investigation was conducted to attempt to find an electrolyte that would be suitable for the electrodeposition of boron and to duplicate work performed by previous investigators. Methods for the electrochemical production of boron previously investigated have either yield a product too impure for practical use, or have involved such serious operating difficulties as to be entirely impractical as commercial processes. In the present investigation, the systems 4.5KCl-KBF₄-6B₂O₃ and 8.5KCl-KBF₄ were investigated at 800-850°C in an attempt to duplicate the methods reported in the literature as suitable for use as commercial processes. When the electrolyte 4.5KCl-KBF₄-6B₂O₃ was used, boron, 91.2 per cent pure, was electrodeposited at a cathode current density of 0.83 amperes per square centimeter. When the electrolyte 8.5KCl-KBF₄ was used, boron, 96 per cent pure, was electrodeposited at a cathode current density of 1.41 amperes per square centimeter. The system 5Na₂O-1-LA₂O-6B₂O₃ was investigated at 650 ± 5°C. The deposit obtained proved to contain 68 per cent carbon and only a trace of boron when a cathode current density of 1.04 amperes per square centimeter was employed. The melt attacked the graphite crucible's binder and in no way showed any promise as an electrolyte for commercial use in the production of elemental boron. The systems 3K₂O-KBF₄-B₂O₃ and 2K₂O-2KBF₄-B₂O₃ were also investigated. The melts alkaline in nature and attacked the graphite crucible's binder. The product obtained when the 3K₂O-KBF₄-B₂O₃ system was investigated at 850 ± 5°C proved to contain 78 per cent boron and 13 per cent carbon. The system 2K₂O-2KBF₄-B₂O₃ was studied to determine the effect of decreasing the alkalinity of the bath. The product obtained when this mixture was studied at 850 ± 5°C proved to contain 85 per cent boron and 6 per cent carbon. / Master of Science

A plane frame element based on linear, elastic theory is developed and implemented into the MESS finite element program. Post-processed results include nodal displacements, end reactions, maximum tensile and average shear stress, and a deformed geometry plot. The element is tested for accuracy relative to simple beam theory and by comparison with results generated using another finite element program. In both cases agreement to within 6 significant figures was achieved. Because the intended use is educational, a survey of its benefit as a design aid in undergraduate instruction is included. These benefits are based on test cases from senior design class projects. Results generated using analysis techniques presently available are contrasted with those using the plane frame element. Students' work that was examined contained mistakes resulting from large amounts of hand calculations. Conversely, results generated using the finite element method proved to be easily obtained and to have a higher degree of accuracy. A recommendation for further improvements in program capability is provided at the end of the study. / Master of Science

Investigations into the nitrogen fixing apparatus in cyanobacterium Nostoc commune revealed a gene encoding for a hemoprotein, known as cyanoglobin. The cyanoglobin gene was isolated and subcloned into Escherichia coli previously. The study presented here encompasses the optimization of growth conditions for the transformed F. coli, with subsequent induction of cyanoglobin synthesis. These conditions were applied to large-scale (24-1) fermentor culture, permitting purification of approximately 200 mg cyanoglobin. Structural analyses, including absorption spectroscopy and circular dichroism, are presented. These studies indicate that cyanoglobin is a cytoplasmic hemoglobin with properties quite unlike those of leghemoglobin a and sperm whale myoglobin, which are used as references of comparison. For example, the optical spectral properties of oxycyanoglobin are different from those of leghemoglobin α and sperm whale myoglobin. In addition, the met-form of cyanoglobin has characteristics of a low-spin hemoglobin, in contrast to the high-spin met-forms of sperm whale myoglobin and leghemoglobin α. Unusually, the met- form of cyanoglobin fails to coordinate the strong-field ligands, cyanide and azide, at pH 7 and pH 9. The Soret region circular dichroism (CD) spectrum of cyanoglobin is unlike that of sperm whale myoglobin, yet is very similar to leghemoglobin α, suggesting a similar heme environment in these two hemoproteins. Far-UV CD of cyanoglobin revealed alphahelical character comparable to that of sperm whale myoglobin and leghemoglobin α. Cyanoglobin is the first monomeric hemoglobin detected in a prokaryote, raising questions concerning a possible role of cyanoglobin in early globin gene evolution. / Master of Science

Observed growth in weight of an individual fish is the result of an interaction between the environment and the fish's bioenergetic system. A species-specific model is presented which simulates the bioenergetics and growth of largemouth bass (Micropterus salmoides). The model is used to simulate individual growth with changes in the annual temperature regime and relative levels of prey availability. Interaction among temperature, prey availability, and individual size are examined with the model in terms of their influence on growth. Preliminary tests with the model produced an exponential long term growth pattern which is contrary to the conceptualized trend of individual fish growth. Larger weights are produced by a southern temperature regime because of a longer growing season. Variations in the relative abundance and state of availability suggests an unstable system at limiting levels. Analysis of the interaction between temperature and prey availability indicates a stable maximum growth temperature above limiting levels of prey availability while the temperature range for positive growth narrowed as prey availability declined. At limiting prey levels, the temperature range for positive growth narrowed and maximum growth temperatures declined as individual size increased in the temperature-individual size interaction. The model is tested against observed growth data for the 1975 year class of largemouth bass inhabiting West Point Reservoir, Alabama-Georgia. Simulated weights underestimate the observed weights for the first and second years by 25% and 21%, respectively. An alternative equation for caloric density is developed and employed to improve the model's reality and accuracy. / M.S.

The objective of this study was to determine the association between the student’s general adjustment and his attitudes towards his parents and teachers and his school progress and the degree to which he was accepted by associates in social situations. Seventy high school senior girls and boys living in a small town and the surrounding area furnished the date for this study. The data on these students were secured from five sources. Information on attributes towards parents and teachers, social acceptability, and socio-economic factors was obtained by the questionnaire method. The questionnaires were completed by the students during their homeroom periods. Information on personality adjustments was obtained by the use of the bell adjustment inventory which was completed by the students during their home-room periods and was augmented by the combined ratings of three teachers. Rating of I. Q. was obtained by the Otis Quick-Scoring Gamma test. Information on school progress was obtained from the permanent school records. / Master of Science

This study examines selected variables as they relate to the performance of sixth-grade learning disabled (LD) and behaviorally-emotionally handicapped (BEH) students on minimum competency tests administered by the North Carolina public schools. The sample consisted of 313 LD and 79 BEH subjects who attended the 1988 Basic Education Program Summer School in 38 selected school districts. Data were collected describing the independent variables including students’ race, sex, handicapping condition, parent education level, and school and teacher characteristics including instructional time, class size, teacher training, and teacher certification. The dependent variables for the study included language, reading, and mathematics performance scores on the Minimum Skills Diagnostic Tests (MSDT). Data were analyzed by utilizing a multiple regression model to describe the relationships between selected demographic and school variables and language, math, and reading gain scores on the MSDT and by utilizing dependent t tests for differences between the means for pre- and post-test performances. Although gains were made by LD and BEH students on the MSDT, it was concluded that the student and school variables used in the study were not predictive of achievement. / Ed. D.

Master of Science