Experiments were conducted to study the ontogeny, kinetics, and the influence of aflatoxin B1 on antibody response to sheep erythrocyte (SRBC) antigen in White Leghorn chickens. In the first experiment, chickens from the parental lines and reciprocal crosses between them were fed diets containing graded levels, from 0 to 5697 ppb of aflatoxin B₁. Aflatoxin depressed body weights, feed consumption and feed conversion, with feed conversion being depressed less than either body weight or feed consumption. Although there were no differences among aflatoxin levels for body core temperatures, levels of 1830 ppb and higher caused progressive decreases in surface temperatures. Heterophilia, lymphopenia and reduced liver metabolism were observed at the 5697 ppb level. Although bursa and thymus weights were smaller in the aflatoxin-fed birds, there was no reduction in their SRBC antibody levels. The second experiment was designed to measure primary and secondary antibody response to intravenous immunization of SRBC antigen. Treatments included immunization at the dosage of SRBC antigen under which selection was practiced, and higher and lower concentrations. Although the dosage of primary immunization influenced the magnitude of the secondary response within population-primary dosage correlations between peak primary and secondary antibody response were not different from zero. Differences among populations in antibody levels appeared as early as day 4 and persisted until day 24 post-primary immunization. Yet, the general response patterns were the same for all populations with respective peaks occurring at the same time. The ontogeny of post-hatching production of antibody SRBC antigen and growth of bursa, thymus and spleen were measured in the third experiment. Both parental lines and reciprocal crosses between them reached serological maturity by 14 days of age. By 7 days, there were differences among populations for frequency of responders to SRBC antigen and magnitude of titers, inferring genetic variation for both the event and subsequent levels of antibody production. / Ph. D.

The Variable Temperature Size Exclusion Chromatography (VTSEC) was used to study the dilute solution properties of various homo- and block copolymers as well as polymer blends, focus being primarily on the configuration-dependent properties such as average chain dimensions and hydrodynamic behavior of polymers. The study constituted of three parts. In the first part, the dilute solution properties of a series of poly(alkyl methacrylates) with varying side alkyl(ester) group were investigated as to the effect of the size of the side group on the average chain dimensions at various temperatures. The VTSEC results were found to reveal that the effect of the side group depends on the extent of chain flexibility imparted by the side group. In the second part, VTSEC was employed to investigate the applicability and validity of the various models for block copolymers in solution. For this purpose, several series of samples (all anionically synthesized) with various composition and molecular weight were used: i) poly(alkyl methacrylates), their diblock copolymers and blends and ii) diblock and triblock copolymers of poly(styrene/substituted styrene) and poly(butadiene/isoprene). VTSEC results showed that the applicability of each model to a block copolymer in solution depends on the compatibility among the components, the composition of the samples, the solvating power of the solvent used and the operating temperature. Micellization in the hydrocarbon diblock copolymer solutions was found to occur in selective solvent, its extent depending on the solubility parameter difference between the components, molecular weight, composition and solvent power. In the third part, poly(methyl methacrylate) samples with varying tacticities were studied as to the effect of stereochemical configuration on their dilute solution behavior and found to indicate that both syndiotactic and isotactic stereosequences are required for stereoassociation. Two new VTSEC data reduction procedures were devised in order to correct for the temperature drifts due to instrumentation in the first and to neutralize the effect of molecular weight in the second. In the second, termed as the Molecular Weight-Elution Volume Superposition Procedure, the effect of molecular weight alone was enutralized leaving only the effect of the intrinsic character (such as the size of the side group) of the sample in the elution behavior. Numerical computations, using the Matxrix Generation method based on the Rotational Isomeric State approximation, were carried out for stereoregular chains in order to evaluate their chain dimensions at various temperatures. / Ph. D.

Changes in nylon 6.6 and polyester filament yarns were determined after heat treatment with dry heat at various temperatures under constant length conditions. An attempt was made to relate structural changes and changes in physical properties due to heat setting. Density, obtained by the density gradient column technique, was used to calculate the degree of crystallinity as a structural parameter. Filament tensile strength and elongation at break were measured on a constant-rate-of-extension machine, and then toughness of the sample was obtained from the load elongation curve. The amount of dye uptake was estimated spectrophotometrically. Degree of crystallinity increased significantly as temperature increased for both nylon 6.6 and polyester fibers. Tenacity decreased substantially for nylon 6.6 and increased marginally for polyester. Elongation and toughness at break decreased for both nylon 6.6 and polyester. Tenacity of nylon 6.6 decreased despite an increase in degree of crystallinity. This suggests degradation of the fibers. Therefore, degree of crystallinity appeared to be of little importance as a contributor to change in tensile strength for degraded nylon 6.6. Tenacity of polyester was well predicted by degree of crystallinity. As crystallinity increased, tenacity of polyester increased. Elongation and toughness of both nylon 6.6 and polyester decreased as degree of crystallinity increased, but the relationship to crystallinity for polyester was not significant. Dyeability of both nylon 6.6 and polyester was well predicted by degree of crystallinity. In both cases, the amount of dye uptake decreased as crystallinity increased. This research suggests that determinations for structural changes such as degradation and orientation might be utilized in addition to crystallinity to predict tenacity of nylon 6.6 and elongation and toughness of polyester. / Ph. D.

Although the Type A behavior pattern (TABP) is firmly established as a risk factor for coronary heart disease, it is neither well understood from a psychological perspective nor is it well understood in women. The present study attempts to describe the TABP in a population of working women. The description is based both on physiological and psychological measures. Ninety-four women were chosen from an original population of 157 women from the Roanoke and Blacksburg, Virginia areas. Each of these women completed the following psychometric instruments: Jenkins Activity Survey (JAS), Framingham Type A Scale, Novaco Anger Inventory, Bem Sex Role Inventory (BSRI), and Perceived Work Environment (PWE). In addition, a blood sample was obtained from each person. The results revealed several personality differences between Type A and Type B women. Type As scored significantly higher on the three descriptive scales of the JAS than did TBs. The Type A women also had significantly higher total anger scores on the Novaco. A priori analysis of the types of items comprising the Novaco revealed that Type As were aroused to situations threatening them personally or their possessions while Type Bs were aroused by situations involving prejudices or injustices to others. Analysis of the BSRI showed Type As to have endorsed significantly more masculine characteristics and fewer feminine characteristics than did Type Bs. Type As also responded in a more socially desirable direction. Three of the PWE factors were found to be significantly different between Type A and Type B women. These factors were task characteristics, co-workers, and pressure to produce. These differences reflect perceptions of the environment. Significant interactions between Type A and the environment were seen in the administrative group indicating that certain environments influence the Type A's perceptions. The physiological assessment was not significant. However, there was a strong trend evident that approached significance. The model was able to correctly classify approximately 78% of the population and there were observable differences between the Type A. Results indicated that Type As displayed characteristics of a stressed population such as increased corticosteroids, ceruloplasmin, and proteins along with decreased levels of glucose, ascorbic acid, and oxidation- reduction protein. / Ph. D.

The objectives of this research were to examine factors influencing de novo flowering of Nicotiana on 2-3 x 10mm explants consisting of epidermal and 3-6 layers of subjacent cells (thin cell layers, TCLs) and to compare de novo to in vivo flowers. TCLs from short-day and long-day tobacco plants were compared with TCLs from day-neutral species to examine in vitro floral photoinduction and graft transmissibility of floral promoters and inhibitors. TCLs from photoperiodic species of tobacco did not form flowers de novo , whereas TCLs from day-neutral plants did flower. When TCLs were removed from photoperiodic plants and grafted in vitro to TCLs from day-neutral plants, there was no indication that a floral-promoter or inhibitor was transported through the non-vascular graft union. In vitro photoinduction of TCLs removed from photoperiodic plants was not possible under conditions conducive to in vitro flowering of TCLs from day-neutral species. TCLs taken from intraspecific F₁ and F₂ hybrids between short-day and day-neutral cultivars of N. tabacum were examined to assess the importance of genotype and photoperiod to de novo flowering. Flowering of the F₂ population occurred over a 9 week period under naturally decreasing photoperiod. Photoperiodic response and in vitro flowering were correlated in the F₂ population with fewer flowers produced per TCL with increasing short-day reaction. F₂ segregates whose TCLs did not yield de novo flowers were found among both day-neutral and short-day phenotypes. When de nova flowers were compared to in vivo flowers of diploid (2n=4x=48) N. tabacum 'Samsun' and haploid (2n=2x=24) plants derived from 'Samsun' anther culture, major morphological differences were found. Flower and anther sizes were reduced in de novo flowers and the numbers of anthers and pistils produced per flower were variable. TCLs from haploid plants produced more flowers in a shorter period of time than TCLs from diploid plants. Anthers cultured from de novo haploid plants were embryogenetic resulting in mixoploid plants; anthers from in vivo haploid flowers were not embryogenetic. Anthers from in vivo diploid plants were five times more embryogenetic than anthers from either de novo haploid or diploid flowers. Meiotic analysis revealed similar abnormalities from both in vivo and de novo microsporogenesis of haploids. / Ph. D.

The purpose of this study was to determine what conditions might optimize the implementation and operation of a dual school principalship when it is selected as an alternative administration organization pattern. The population for the study were the principals in the states of Pennsylvania, Virginia and West Virginia who are assigned to administer two separate school organizations. Only those principals whose systems had two or more dual principalships were included in the study. Descriptive survey and case study methodology were combined to gather data to accomplish the purpose of this study. The study consisted of two phases. In the first phase dual principals and their superintendents were surveyed using a seventeen item questionnaire to obtain their perceptions regarding the dual principalship. Qualitative descriptive analysis was utilized, results being presented in tabular form with response sets for both superintendents and principals. The second phase of this study utilized a case study research of four dual principalships to verify and extend data collected through the survey questionnaires. The major conclusions of the study were: 1. While principals and superintendents express dissatisfaction with this administrative arrangement, evidence indicates that this practice will continue to increase. 2. Although principals are required to devote a majority of their time to supervision of educational programs, this is not taking place in dual assignments. 3. Initial savings in this administrative arrangement are eventually offset by hidden expenditures. Some of the recommendations based on the findings of the study were: 1. Experience of the principal and staff should be a factor in utilizing a dual principalship. 2. Numbers and enrollment alone should not be the sole determining factor in making a dual assignment. 3. Support services will add to the flexibility of the principal in scheduling his attendance at both schools. 4. Consideration should be given to the composition and stability of a community prior to making a dual assignment. 5. One principal can accomplish the administrative tasks and meet the demands of a dual assignment; supervision and leadership in educational programs will suffer as a result. / Ed. D.

The accuracy and utility of using Inverse Gas Chromatography (IGC) to characterize the microphase structure of block copolymers, and the strength of the thermodynamic interactions between the components of polymer blends and the unlike segments of block copolymers was examined. There were three parts to the study. First, the Scott ternary solution model, which is used for the study of thermodynamic interactions in polymer blends, was extended to low molecular weight mixtures. From vapor-liquid equilibrium data in the literature, the Gibbs free energy of mixing of binary mixtures (G_M ) calculated with the model were compared to experimental values. Mixtures containing ketones, aromatics hydrocarbons, chlorinated hydrocarbons, alcohols and water were studied. With the exception of mixtures containing water and low molecular weight alcohols, a fair to good correlation between theoretical and experimental values was observed. Second, the Gibbs free energy of mixing of nitrocellulose, polyvinyl chloride and poly(vinylidene fluoride) containing blends were measured with the Scott model from IGC data. For the nitrocellulose containing blend, the calculated Gibbs free energy of mixing values were large in magnitude (-2.0 to -5.0 calories/gram) and in fair agreement with the experimental heats of mixing determined from microcalorimetry measurements. For the remaining blends, the IGC data could not be distinguished from the results normally obtained for immiscible blends. The calculated G_M values were small in magnitude relative to the experimental error of the quantities. Concerning the block copolymers, the relative incompatibility of the constituent blocks of perfectly alternating block copolymers of polydimethylsiloxane and bis-A-polycarbonate and styrene-isoprene-styrene triblock copolymers was reflected in the measured G_M values. Overall, it was concluded that IGC is a good method for characterizing thermodynamic interaction between blend and copolymer constituents, but a severe limitation of the method is that the interactions are often too weak to measure accurately. Finally, the microphase structure of the above copolymers were studied by IGC from the retention behavior of hydrocarbon probes below the upper glass transition temperature of the copolymers. The degree of microphase separation, the size of the hard phases and the continuity of the soft phases in the copolymers characterized, and the results obtained were consistent with small angle x-ray, electron microscopy and differential scanning calorimetry data on the same materials. / Doctor of Philosophy

The transport of small particles across the aerodynamic boundary layer that developed over a smooth, flat, acrylic plate and their subsequent deposition was investigated. The velocity boundary layer over the flat plate was characterized for a wind tunnel mainstream velocity of 2 m/s. Particle deposition was quantified with respect to location on the experimental plate with a microscope. The deposition of 0.8, 0.9, 1.1, and 2.0 micron diameter unit density, polystyrene latex microspheres on to oil-coated, uncoated, upper, and lower surfaces was investigated. Although experimental deposition velocities exhibited run-to-run variation, they were significantly greater than those reported in the literature. A turbulent flow deposition model which included eddy diffusion, Brownian diffusion, inertial, and gravitational deposition mechanisms underestimated the experimental deposition velocities. The experimental plate was nonconductive and could not be electrically grounded. It appears the electrostatic attraction mechanism was responsible for the increased experimental deposition velocities; this mechanism was not included in the deposition model. There was no significant resuspension of 42 micron diameter microspheres deposited to an initially moist experimental plate after 6 hours in the wind tunnel at a mean air velocity of 2 m/s. / Ph. D.

A unified international method to capture, record, and report the information necessary for documenting the mechanical performance of harvesting machines and systems under specified conditions is presented. It provides a data collection method as a basis for evaluation of systems across international boundaries for better selection of machines, prior to bearing the expense of purchasing the system. An in depth study of a prototype skidder on steep terrain was conducted to test the practicality of the method. The study resulted in some modification of the been received indicating support and suggesting minimal changes. The recommendations of other reviewers will be incorporated in the final Field Manual. A microcomputer program for filing and editing the data collected in the field will be developed. / Doctor of Philosophy

Study one was designed to assess the relationship between television violence viewing and expectations of others physical aggression in conflict situations. Four hundred thirty one children, fourth and fifth graders, completed a television frequency survey and a conflict situations hierarchy. It was found that children who normally view a relatively large amount of television violence expected others to be physically aggressive in conflict situations more than children who normally view a relatively small amount of television violence. Study two was designed to assess the relationships between violence viewing, latency to seek help in the presence of real life violence, and physiological responses to real life violence. Thirty nine children who participated in study one, 19 high violence viewers and 20 low violence viewers, were recruited to serve as subjects. Subjects were led to believe that they alone were responsible for monitoring younger children in another room via a camera and television monitor. Subjects viewed a videotape of two children who initially play quietly, but become increasingly hostile, and the film culminated in a physical fight ending with the apparent destruction of the camera. Latency to seek help and heart rate were measured. High violence viewers took reliably longer to seek help in the presence of real life aggression than low violence viewers. However, when the distribution of latency scores was examined, group differences appeared attributable to the performance of a relatively small number of subjects. This study suggests that increasing levels of television violence viewing may be related to increasing latency to seek help in the presence of real life aggression, that the relationship may be modest, and that replication of the procedures is needed before strong conclusions can be made. High violence viewers and low violence viewers did not differ in their heart rate responses to the scene of real life violence. This study suggests that heavy violence viewing may not be associated with physiological desensitization to real life violence. However, further studies employing different indices of physiological arousal is clearly needed before strong conclusions are warranted. Differential research strategies to address these issues were discussed. / Ph. D.