Low cost bandpass filters (less than $100) at microwave frequencies cannot be purchased commercially. However, such filters are essential in the design of RF circuits in communications and radar equipment. Reliable microstrip band pass filters which provide an accurate filter response at microwave frequencies can be easily fabricated with low cost. Equations concerning the design of coupled microstrips and microstrip filters are published in the literature and were implemented in a design procedure for maximally flat microstrip band pass filters. The published equations were theoretical and had not been extensively compared with experimental data. Thus, this work established an enhanced microstrip filter design procedure based on experimental data, for a wide range of frequencies and dielectric substrates. The result of this work is an enhanced design procedure for microstrip band pass filters. The new procedure includes a correction factor for the length of the filter resonators which which controls the center frequency of the filter. This correction factor has been found from the measured responses of over 60 filters, which were designed with two different circuit board materials, three different substrate thicknesses, and frequencies ranging between 0.9 and 6 GHz. The experimentally determined length correction factor decreases the error in center frequency from ±5.9% down to ±L7% of the desired design frequency for a wide range of filter designs. The improved procedure has been implemented in a personal computer (PC) program which calculates all dimensions necessary to fabricate microstrip band pass filters in the low microwave frequency range. The maximally flat response obtained is accurate and requires very little tuning. Low cost microstrip band pass filters can now be designed and fabricated easily and with greater accuracy at microwave frequencies. This thesis describes the development of the enhanced design procedure and the results of the filters designed with the new procedure. / Master of Science

A profit maximizing linear programming model was developed. The model was fitted to a demonstration farm having a forage based livestock feeding system. Restraints where the resources of the McCoy farm in Rockbridge County, Virginia, which included limited pasture, labor, storage availability, and limited financial resources. Row crop production was an option not considered. Only variable costs of production were considered as fixed costs continue in the absence of production. Forage and livestock species used in the model were currently in existence on the farm. Estimated productivity levels were also based on actual farm data and were used to establish the upper limits of forage production. Results of the analysis indicate that alfalfa hay held for sale was the most profitable single enterprise. Grass hay was produced and fed to meet the livestock requirements during February and March. A fall calving cow-calf herd, with calves being marketed, at 634 pounds on September 30 was more profitable than marketing during July at lighter weights even though this system had higher forage requirements. Neither a spring calving cow herd or the purchase of stocker calves for summer grazing ensured the optimal farm plan as forage was better utilized by the fall herd. Seventy three fall calving cows and 152 winter lambing ewes were in the optimal plan. The ratio of fall calving cows to winter lambing ewes was 1 : 2. Stocking ratios between cows and ewes were dependent upon price relationships used and could vary with differing price relationships between feeder calves and slaughter lambs. Stocking rates were limited most by the availability of the improved and unimproved pastures. All available labor was used during November through May. Additional labor had to be hired to offset labor shortages during January through May. Financial resources of the farmer were adequate to meet the variable costs of production without additional use of borrowed capital. / M.S.

A more quantitative understanding of peptide loading and release from polyethylene oxide (PEO) brush layers will provide direction for development of new strategies for drug storage and delivery. The antimicrobial peptide nisin shows potent activity against Gram-positive bacteria including the most prevalent implant-associated pathogens, its mechanism of action minimizes the opportunity for the rise of resistant bacteria and it does not appear to be toxic to humans, suggesting good potential for its use in antibacterial coatings for selected medical devices. In this work, optical waveguide lightmode spectroscopy was used to record changes in adsorbed mass during cyclic adsorption-elution experiments with nisin, at uncoated and PEO-coated surfaces. PEO layers were prepared by radiolytic grafting of Pluronic® surfactant F108 or F68 to silanized silica surfaces, producing long- or short-chain PEO layers, respectively. Kinetic patterns were interpreted with reference to a model accounting for history-dependent adsorption, in order to evaluate rate constants for nisin adsorption and desorption, as well as the effect of pendant PEO on the lateral clustering behavior of nisin. Lateral rearrangement and clustering of adsorbed nisin was apparent on uncoated and F68-coated surfaces, but not on F108-coated surfaces. In addition, nisin showed greater resistance to elution by peptide-free buffer from uncoated and F68-coated surfaces. These results are consistent with shorter PEO chains allowing for peptide adsorption to the base substrate in the case of F68-coated surfaces, while adsorption to the F108-coated surfaces is apparently governed by the presence of a hydrophobic core within the brush layer itself. Further, these results suggest that while peptide location within the hydrophobic core provides stability against lateral rearrangement, the pendant PEO chains themselves provide no steric barrier to nisin rearrangement within the brush layer. / Graduation date: 2012