Modal analysis is a tool widely used to describe mathematically the vibratory behavior of structures. In modal analysis, the response of a structure at a given frequency of excitation is represented as the summation of the contributions of a 11 the modes of vibration. Although continuous structures have an infinite number of modes, only a few of them are present to a significant degree in the response at any frequency of excitation. These modes are the dominant modes at the given frequency. A vector fit method was developed to determine the number of dominant modes. This method uses only the transfer function matrix (or some part of it) as input, and it approximates each column vector of the matrix as a linear sum, using as a basis a set of orthogonal unit vectors. The errors resulting from these approximations, defined in a least squares sense, are the plotted versus frequency. The relative magnitudes of the error curves indicate the number of dominant modes in the frequency band in question. The method was tested numerically on three models with known modal parameters. These models were designed to have regions of high modal density. It was found that interpretation of the error curves required a certain amount of qualitative judgement based upon criteria other than simply the relative error magnitudes. With these criteria. identified, it was concluded that the vector fit method reliably predicts the correct number of dominant modes provided only that a sufficiently large transfer function matrix is: employed. Specifically, both the number of rows and the number of columns must be greater than the number of dominant mopes. / Master of Science

Horsenettle is a persistent, native, perennial weed of pastures and cornfields in southwest Virginia. A survey of insects associated with the weed revealed a number of general feeders, several insect pests of economic plants related to horsenettle, and a few lesser known species. The moth, Frumenta nundinella, demonstrated a high degree of host specificity in the tests conducted The larvae attack the plant in two ways: first instars web the terminal leaves together and form a round hollow chamber within which they feed on the growth tip of the plant, or they enter berries and consume all of the seeds. There are two generations per year, each being about 50 days. The insects overwinter as adults. Females oviposit in the spring and mid-summer. Normally first generation larvae occupy leaf chambers and second generation larvae occupy berries. In the absence of berries, leaf chambers will be formed. Predation, desiccation and interspecific competition with first instars appear to be important mortality factors. Four Hymenopterous parasites were reared from the larval or pupal stages. First generation larvae in leaf chambers significantly reduce (P < .05) dry weight of horsenettle regardless of the number of larvae on the plant. The second generation reduces seed production. E· nundinella was found to be present in 9 counties in western and northern Virginia but population levels were low in all the survey areas. / Master of Science

Brassaia actinophylla and Dieffenbachia maculata "Lodd" G.Don were grown in two organic media and treated with five salt solutions to determine the effect of soluble salt concentration on growth and quality. The soluble salt concentration was determined using the saturated paste extract method. Dieffenbachia growth and quality were better when 0.45 g/l 15-30-15 fertilizer was applied than when 0.225 g/l 15-30-15 plus 1.5 g/l NaCl was applied, regardless of medium considered. Dieffenbachia growth and quality were significantly reduced at a conductivity of 4.5 nunho/cm in the peat and sand medium and at 4.1 mmho/cm in the medium containing pine bark. The maximum Dieffenbachia growth and quality occurred at a conductivity of 0.8 to 1.3 mmho/cm. Brassaia growth and quality in medium 1 were poorest with application of 0.225 g/l 15-30-15 plus 1.5 g/l NaCl, and were more favorable with application of 0.225 g/l 15-30-15 plus 0.5 g/l NaCl. The more favorable conductivity range was 2.2 to 2.4 mmho/cm in the peat and sand medium. The growth of Brassaia in the medium containing pine bark was more favorable under application of 1) the low rate of complete fertilizer (0.225 g/l of 15-30-15), 2) the high rate of complete fertilizer (0.45 g/l 15-30-15), and 3) 0.225 g/l 15-30-15 plus 0.5 g/l NaCl than under application of 0.225 g/l 15-30-15 plus 1.5 g/l NaCl. The mean conductivity of the pine bark bearing medium under the three more ' beneficial treatments ranged from 0.7 to 2.4 mmho/cm. Brassaia and Dieffenbachia were shown to be less tolerant of salinity than was determined previously. / Master of Science

An investigation was made of the relationship between the achievement, designated as success or failure; of MSFA participant families and their MMPI scores obtained during basic orienta..tion procedures. Subjects were twenty-eight families enrolled at the MSFA Training Center in vocational and educational classes for an average of 4.9 months. For each family it was determined that both husband and wife had a valid MMPI profile. Husband and wife profiles were paired for each family and the family was considered to have scored high if either spouse scored 70 or above on a given scale. If official MSFA records indicated that the family completed training and at least one spouse remained employed for.three months after placement, the family was defined as a success. A family who dropped ou:t of training before comp~etion or in which neither spouse remained employed for thr~e months was defined as a failure. A chi square analysis revealed no significant relationships between Training Center achievement and scores on any of the ten MMPI clinical scales. Therefore, it cannot be said that there is an association between MMPI scores and Training Center achievement. Another finding of this study was that families classified as migrants are significantly less likely to be successful than are families classified as seasonal farmworkers. A need was perceived for further research investigating the differences between migrants and seasonal farmworkers and for further development and testing of paired spouse MMPI profiles as an approach to measuring family characteristics. / Master of Science

The Gluconobacter phage GW6210, infects the ATCC strain 621 of G. oxydans. This phage possesses a polygonal head and contractile tail; therefore, it can be placed morphologically into Bradley's group A and tentatively placed in the virus family Myoviridae. This intensive electron microscopic study shows phage GW6210 to have a polygonal head, collar, tail sheath, baseplate, and tail pins. This phage is primarily unusual because of its large size. Using Tobacco Mosaic Virus as an internal standard, the head was found to be 170 nm in diameter and the tail was 136 nm long and 34 nm wide. The phage preparation seemed to consist of two plaque types: a small clear plaque having a 0.3 ± 0.1 mm diameter surrounded by a large turbid region that measured 3.5 ± 0.7 mm wide, and a small turbid plaque that varied greatly in size (1.4 ± 0.8 mm). However, subsequent data indicated that these types represented size variation of a single plaque type. In addition to the normal host of GW6210, G. oxydans subspecies suboxydans ATCC 621, the host range of this phage includes: G. suboxydans var. α, IFO 12528; A. melanogenus, ICPB 2096; G. rubiginosis, IFO 3244. Fifty strains of Gluconobacter and 52 strains of Acetobacter were unaffected by the phage as weel as 3 strains of Pseudomonas tested. / Master of Science

The purpose of this study was to investigate the extent to which algal-produced organic matter may react with chlorine in aqueous solution to form trihalogenated methanes. Two species each of green and blue-green algae were cultured in an inorganic medium and harvested on several days throughout the growth cycle. Media filtrates and cell suspensions were analyzed for total organic carbon and chloroform produced after chlorination. Pure solutions of representative algal extracellular metabolites were analyzed in a similar manner. The highest-yielding (chloroform-carbon per total organic carbon) compounds were released during the late exponential growth phase. More organic carbon was accumulated in the external medium through the stationary growth phase by the blue-green species, but higher yields were obtained in the green algae cultures during these later stages of growth. The results indicate that the differences in the total chloroform production potential may be more significant among individual algal strains than between larger taxonomic divisions, such as the green and blue-green algae. None of the model compounds studied produced chloroform yields comparable to those of the. media filtrates or biomass. The chloroform-carbon yields of the culture filtrates were in the same range as those reported for the humic and fulvic acids, and in some cases much higher. Therefore, the algal extracellular products may be important as precursors in the formation of trihalomethanes during water treatment. / Master of Science

The demand for potable water may be culminating in a compromise on what constitutes a "safe" drinking water due to the rapidly approaching need to utilize recycled waters. The elimination of viruses pathogenic to humans from recycled waters will depend on the removal efficiencies of treatment processes and the sensitivity of detection methodologies. Enteric viruses can survive current wastewater treatment practices, and some even persist for long periods of time in natural waters. The objectives of this investigation were threefold: first, to construct a virus concentrator suitable for sampling secondary sewage treatment plant effluents; second, to sample the effluent of trickling filter sewage treatment plants prior to chlorination to determine the remaining amount of enteric viruses; third, to determine the virus removal efficiencies of a final settling and chlorination operation by using bench-scale simulations of the two units. Viruses were not detected in any of the secondary effluents of three trickling filter plants samples. However, these results may have been obtained because the level of viruses was below the minimum detection limits of the virus concentrator that was constructed. Also, if viruses were present, the high pH elution process may have been deleterious, or the BGM host cell was incompatible. Detention times in the model system studies of a final sedimentation basin and chlorine contact chamber were based on Rhodamine WT dye studies of plant-scale units. These studies suggested that 98.5 to 100 percent of the enteric viruses contained in the actual plant effluent would be removed or inactivated by the combination of final settling and chlorination. / Master of Science

The ability of a mixed oak forest in the Ridge and Valley Province of Virginia to provide the seasonal digestible protein and energy requirements of a white-tailed doe following a commercial thinning operation was evaluated. The element of time elapsed since thinning was emphasized and was represented by three contiguous forested parcels thinned over 3 consecutive years and an unthinned parcel. Digestible protein and energy requirements of a doe, whitetailed deer in four different physiological conditions associated with four seasons were obtained directly from the literature or calculated from data in the literature. Availability of dietary digestible energy and protein coincident with the requirement periods were determined by clipping, weighing and analyzing for digestible protein and energy content food items commonly used by white-tailed deer. Calculation of carrying capacity was based on the ability of a white-tailed doe to obtain sufficient energy and protein from the daily diet. When the ratio, energy or protein density of the daily diet: daily energy or protein requirements of the doe was less than 1, the doe was unable to meet her requirements. Thus, carrying capacity was determined to be 0 ha/deer. When this ratio equalled or exceeded 1, carrying capacity was calculated by dividing the daily standing crop of protein or energy by the daily protein or energy requirements of the doe. Summer, winter and mast-supplemented fall diets were deficient in energy. Thus, potential carrying capacity, based on immediately available dietary digestible energy, was estimated as 0 ha/deer during these periods. Spring and mast-supplemental fall diets provided adequate digestible energy for maintenance of the doe. Diets from all parcels and seasons provided sufficient protein for maintenance. For those periods when dietary protein and energy were sufficient, carrying capacity exceeded 0 ha/deer and was greater with increased standing crop of the seasonal diets. Standing crop of seasonal diets tended to be larger with increased time since thinning, although this pattern was confounded by the drier nature of one parcel. The role of seasonal energy and protein excesses and deficiencies in the annual nutrition of white-tailed deer are discussed. The necessity of considering dietary quality as well as quantity and the year-round nutritional plans of deer are emphasized for forage-based evaluations of deer habitat. calculations suggest that dietary energy is a more important limiting factor than protein on the abundance of white-tailed deer in this forest stand. / Master of Science

Materials for and implementation of a course in government nutrition education programs taught by personalized system of instruction (PSI) is described. Twenty-four students learned by progressing through nine units of written objectives, reading assignments and tests at their own pace. Ninety percent mastery was required to pass unit tests and tests were retaken without penalty until the criterion was met. Three course assistants, called proctors, provided immediate individualized scoring of unit tests. Twenty-two students received an A for the course; one student, a B; one student completed only one unit and received an F. Course evaluations reflected positive student and proctor attitudes toward course material and the PSI method. Four factors correlated with final exam performance: quality cumulative average (QCA), the number of unit test retakes, total unit test errors and working rate. High ability students out-performed low ability students on the final exam. Students with fewer test retakes and errors generally did better on the final exam than students who took more tests to achieve the 90 percent mastery criterion or who made more test errors. Those who began taking tests early in the term had higher final exam grades than those who began later in the term. / Master of Science

Temporal production patterns for periphyton have been poorly quantified in small woodland streams. In this study periphyton production on natural substrates was measured in a second order, western Virginia trout stream and two of its tributaries. Measurements were taken about three times monthly from April 1977 through April 1978 excluding 74 days of inaccessibility due to snow. Primary production rates were estimated in situ using ¹⁴C assimilation in light and dark chambers equipped with circulating systems. Allochthonous input and physicochemical parameters were measured concurrently. Annual mean photosynthetic rates at midday were 2.27 ± 0.37 SE, 1.65 ± 0.25 SE, and 1.37 .± 0.19 SE (n = 46) for Guys Run (mainstream), Piney Branch, and Glade Brook, respectively. No relationship between the irradiance and photosynthetic rates was observed. Highest photosynthetic rates occurred in early July following the full emergence of the shading forest canopy. Tests comparing primary production rates between variously shaded and unshaded stream sites suggested periphyton light saturation to be about 20-30% of full sunlight. Mean daily irradiance for each season was calculated from light monitored at stream sites and used to estimate seasonal periphyton production in each stream. Annual autochthonous production, on a flat m² basis, was 6.54, 4.10, and 3.71 g C/y for Guys Run, Piney Branch, and Glade Brook, respectively. Compared to allochthonous input the periphyton contributed 3% of the total energy budget of the main stream and about 2% for the tributaries. Of the total autochthonous production, 90 ± 1% occurred during late spring and summer for all streams. In summer when terrestrially derived detritus was poorest in quantity and quality, periphyton was producing a majority of its annual input. Current concepts, which consider contributions by periphyton to consumer production to be extremely small in low order woodland streams, are based upon annual energy budgets. Because of the seasonal timing and high nutritional quality of periphyton, its true importance in low order streams may be greater than typically indicated in gross annual budgets. The roles of periphyton production and allochthonous input need to be reevaluated and better resolved on a seasonal basis. / Master of Science