Relationships between nontaxonomic aufwuchs community structure and functions were examined over a variety of environmental or physiological conditions in model streams to ascertain any direct relationships or covariance between indices of structure (dry weight, ash free dry weight, adenosine triphosphate and chlorophyll a) and function (primary productivity and assimilatory sulfate reduction). In eleven experiments, individual streams were treated with potential"enrichments" of sucrose, dextrose, ammonium nitrate, potassium dihydrogen phosphate, and toxicants including copper sulfate, potassium dichromate and chlorine, in order to elicit responses by the aufwuchs communities that accumulated on artificial substrates. The carbon-14 method was adapted and refined using a chamber for measurements of primary productivity in lotic systems. Assimilatory (sulfur-35) sulfate reduction was investigated as a method for estimating net microbial production rates. The ability of indices or ratios of structural and functional values to reduce variability and identify perturbed model streams relative to untreated streams was evaluated. In laboratory studies, assimilatory sulfate reduction closely followed growth rates in batch cultures of algae (Stigeoclonium sp., Navicula pelliculosa and Oscillatoria tenuis), bacteria (Pseudomonas flurescens, Enterobacter aerogenes and Bacillus subtilis) and fungi (Penicillium clavigerum, Mucor hiemalis and Coprinus patouillardii). Linear uptake kinetics of sulfur-35 sulfate during a six hour incubation period indicated that the process was active or energy mediated. Patterns of algal sulfate assimilation closely paralleled those for primary productivity. Bacterial and fungal sulfate assimilation rates were generally lower in the light than in the dark although the differences were not statistically significant. Observed rates of assimilatory sulfate reduction by cultures of algae, bacteria and fungi were affected by concentrations of organic carbon (glucose) in the media; at concentrations of glucose greater than 5 mg l⁻¹, dark sulfate uptake by algae was 77-98% of light uptake rates, and at glucose concentrations greater than 50 mg l⁻¹, bacterial and fungal sulfate assimilation rates did not increase proportionately with increasing glucose concentrations. The concentration of organic sulfur as as cysteine and methionine, that caused a decrease in the rates of sulfate assimilation, was between 10 and 100 S l⁻¹ for both the cultures and mixed populations in microcosms. No extracellular sulfur-containing products were found to be excreted by mixed populations in microcosms, and no"luxury" consumption of sulfur was observed. The use of assimilatory sulfate reduction rates to estimate net microbial productivity in aerobic systems was supported by the results from investigations with the cultures and microcosms. A reduction in accumulated matter (as indicated by dry weight, ash-free dry weight and ATP) and chlorophyll a on artificial substrates occurred in toxicant (copper, dichromate and chlorine) treated streams. Photosynthesis (carbon fixation) was most sensitive to the copper treatment and assimilatory sulfate reduction was affected most often by dichromate. The disaccharide, sucrose, significantly increased accumulated matter on substrates, but dextrose did not elicit similar responses. Phosphate and ammonium nitrate additions did not cause significant increases in aufwuchs production and were not considered to be limiting in this system. Net microbial productivity of aufwuchs and primary productivity were estimated by assimilatory sulfate reduction and carbon-14 fixation, respectively, with heterotrophic productivity being the difference. Overall, the reduced carbon compounds (sugar) and the toxicants resulted in stream aufwuchs communities dominated by heterotrophs. Indices used for condensation of information in the model stream experiments were generally unsuccessful in discerning perturbations. From all of the model stream experiments, measurements of functional parameters or indices calculated from functional measurements were significantly less variable than structural measurements or structurally based indices The perturbations or treatments did not reduce variability in the nontaxonomic structural and functional aspects measured. Direct correlations were found between: 1) dry weight and ash-free dry weight, 2) ash-free dry weight and assimilatory sulfate reduction, 3) ash-free dry weight and chlorophyll a, 4) chlorophyll a and assimilatory sulfate reduction, 5) chlorophyll a and primary productivity, 6) primary productivity and assimilatory sulfate reduction, and 7) and primary productivity and net microbial productivity. Field investigations of aufwuchs communities in the vicinity of a fossil-fueled power plant on the New River, Virginia, were inconclusive Variability in measurements overshadowed any differences in nontaxonomic structural and functional aspects that might have been attributed to an intermittently chlorinated thermal effluent. / Ph. D.

The purpose of this study was to investigate the relative effectiveness of three categories of variables--sociodemographic, personality, and social support system--in predicting persistence in Adult Basic Education. A particular emphasis was focused upon social support variables and the extent of their capacity to improve the level of prediction success which could be achieved by the other two categories of variables. This study was also concerned with identifying that combination of variables from all three categories which enabled the best possible prediction of persistence. The sample population for this study included 163 adult students enrolled in GED preparatory classes in three urban Virginia school districts. These students all attended classes two nights a week for a total of 5-6 hours. Sociodemographic data pertaining to age, race, sex, employment status, and time since last school attendance, were collected by means of a short questionnaire. Personality measures were acquired relating to self-confidence, achievement need, and affiliation need through use of the appropriate subscales of the Adjective Check List developed by Gough and Heilbrun (1952). Selections of particular sociodemographic and personality variables were based on their frequent inclusion in past studies of Adult Basic Education persistence and participation. This assured meaningful comparisons of the prediction effectiveness of these variables with that of the social support variables emphasized in the present study. Social support data were obtained pertaining to family, work, and church environments through use of selected subscales of the Social Climate Scales designed by Moos (1974). Composite measures were computed, consisting of the average of subscale scores pertaining to each environment area. A series of multiple linear regressions were performed to determine the order of best prediction among various combinations of variables and variable categories. The composite social support (environment average) variables proved poor predictors, a fact which raised doubts about the meaningfulness of the averaging procedure used to derive them. Selected individual subscales of the Social Climate Scales, by contrast, were better predictors of persistence than any of the sociodemographic and personality variables employed in the study. This was particularly true of the group environment subscales used to measure church leader support and member expressiveness. Despite the relative prediction effectiveness of some social support measures as compared to other variables, it should be noted that none of the predictor variables or variable categories employed in this study explained a substantial portion of persistence variance. The results of the study are thus of questionable practical value for Adult Basic Education teachers and administrators. They do, however, suggest some directions for future research. It is recommended that researchers continue to investigate social support systems of Adult Basic Education students. Social support measures are, on the whole, probably as effective predictors of ABE persistence as sociodemographic and personality measures, two categories of variables more frequently focused upon in previous studies. At the same time, many environmental factors can be addressed more directly and effectively by ABE practitioners than relatively fixed sociodemographic and personality characteristics. / Ed. D.

The purpose of this study was to investigate the development of the Conference on College Composition and Communication from 1949 through 1975 as a vehicle for the continuing professional education of its members and for the professionalization of the field of college composition teaching. A number of research questions were formulated to guide the investigation. These questions concerned (1) the circumstances under which the organization was founded, (2) its responses to educational movements and social forces, (3) its developing conception of its continuing education function, (4) its conception of and efforts toward professionalization, and (5) its relationship with its parent, the National Council of Teachers of English. The chief sources of information for this study included College Composition and Communication, the official journal of the organization; the programs for the annual conferences; correspondence, minutes, and reports housed in the headquarters of the National Council of Teachers of English in Urbana, Illinois; and a series of interviews with former officers of CCCC conducted in person, by telephone, and through the mail. In addition, some former officers lent materials from their personal files. Using the historical method, the study identified four distinct periods in the history of the organization: 1949-1954, during which the members came together to seek a new professional identity and to found a new organization; 1955-1958, which was characterized primarily by phenomenal growth in membership and expansion of activities; 1959-1967, during which CCCC conducted an inward search for new directions and emerged as a more mature and confident organization; and 1968-1975, a period in which CCCC's activities were marked particularly by a greatly increased concern for social justice. The researcher concluded that CCCC had become the major national forum for the continuing education of college composition teachers. It played a vital role in this process, primarily through its annual conferences and its quarterly journal. The format of the earliest conferences emphasized the workshop/discussion method. However, as the size of the meetings and the body of knowledge about the discipline of writing grew, conference topics evolved from general discussions of problems to the dissemination of more specialized research and theory depending on the leadership of a few persons. The journal evolved from little more than a pamphlet, printing reports of the conference sessions and a few articles on what specific colleges were doing in their freshman writing programs, to a widely recognized professional journal which has provided the major outlet for important research and theory development of many of the outstanding language scholars in the country. In addition, the organization also did much to further the professionalization of college composition teaching, particularly in the areas of developing a knowledge base for the profession, developing skills in applying that knowledge, and strengthening the control of composition teachers over the practice of their own profession. It was also observed, however, that the professionalization process might be speeded if CCCC could encourage more research in the teaching of composition, exert more control over access to the profession, and establish a code of ethics for the practice of the profession. It was further suggested that some of the actions resulting from the organization's overwhelming concern for social justice during the late 1960's and early 1970's might have weakened the effects of its other efforts to professionalize the field of college composition teaching. / Doctor of Education

A numerical investigation of 2n first-order Hamilton's equations, which describe the motion of a dynamical system, has been conducted using Galerkin's approximations and a derivative-free analogue of Newton's iteration method. Furthermore, the motion stability of a dynamical system in the neighborhood of the approximate periodic solutions due to the effect of the extraneous forces, introduced by the process of using the approximate solutions rather than the actual solutions, has been studied by solving the nonlinear nonhomogeneous differential systems of the perturbed motion. The perturbation solutions are obtained to determine the motion stability. An example, using the van der Pol equation, illustrates the accuracy and error bounds between the approximate solutions and the actual solutions. Furthermore, the example also illustrates the motion stability of perturbation solutions. A computer program for numerical computions has been developed for solving the van der Pol equation with a harmonic forcing term. / Ph. D.

The stereochemistry of the energetic ³⁸Cl for Cl substitution was studied in diastereomeric 2,4-dichloropentane and 2,3-dichlorobutane as well as in enantiomeric 2-chloro-1-propanol in solution. It was found that the stereochemical course of the substitution reaction exhibits a strong dependence on the concentration and nature of the solvent added when the diastereomeric compounds were used as substrate. Similar results with a lesser degree of solvent dependence were observed in the 2-chloro-1-propanol system. A conformational analysis of 2,4-dichloropentane was made. It showed that the relative conformer population is not affected to any significant degree by the nature of the solvent. Furthermore, an examination was made of the physical and chemical properties of the solvent which could be responsible for the drastic changes inflicted upon the stereochemistry of the ³⁸Cl for Cl substitution reaction. The experimental results indicate that the stereochemical course of the substitution process is predominantly and directly controlled by the properties of the solvent molecules, most likely by the dielectric constant and molecular size which in turn are responsible for the magnitude of intermolecular interaction between reactants and solvents. Although the experimental results seem to indicate that the radical-radical recombination mechanism is the most likely mechanism as compared to the hot one-step substitution process, they offer no conclusive distinction between these two mechanisms. It appears that strong intermolecular interaction favors substitution via retention of configuration. whereas in solvents having a low dielectric constant or large molecular diameter the retention/inversion ratio decreases. / Ph. D.

Particle orientation in particleboard was characterized by two directional distribution functions, the von Mises and truncated gaussian. This approach has the advantage of characterizing the degree of orientation by specifying only one parameter. A method was developed to measure the orientation of particles in particleboard "in situ", and to express the orientation in terms of the direction distribution functions. Models were developed to compute the tensile and shear modulus of particleboard with various degrees of orientation. The tensile model worked well for several board types. The shear model, however, was only effective for thin plates. Poisson's ratio, the tensile modulus, modulus of elasticity, and modulus of rupture increased in the direction of particle alignment as the degree of orientation increased. The shear modulus decreased as the orientation increased. The results indicate that conventional methods of orienting particles must be greatly refined before the potential benefits of orientation are realized. / Ph. D.

A large number of atomic helium states are excited by inelastic collisions. That excitation may be induced by various methods, including gas discharges, flowing afterglows and electron beams. The first negative nitrogen bands, N₂⁺(B²Σᵤ⁺- X²Σ_g⁺), have been observed with relatively high intensity from small quantities of nitrogen in helium, also induced by such methods. These bands have been studied by passing 26 kev electrons through mixtures. The resolved rotational spectra of the (0,0) and (0,1) bands have been analyzed as functions of pressure and mixture. An observed enhancement of the intensities has been interpreted in terms of selectively enhanced N₂⁺B rotational state populations. The particular helium species responsible for the enhancement are discussed. Experimental results are compared with a general"phase space" approach for calculating the reaction cross sections. / Ph. D.

Statement of the Problem: The central problem of this study was to identify training sponsor perceptions regarding the coordination phase of secondary cooperative-plan distributive education. Specifically, training sponsors from four United States Office of Education codes and classifications for secondary cooperative-plan distributive education programs in Roanoke City and County, Virginia, were interviewed. The purpose of each interview was to identify perceptions regarding objectives, training sponsor roles, training agreements, training plans, training sponsor benefits, and recommendations for improvement of the coordination phase of program operation. Research Procedures: The case study form of descriptive research was used. Twenty training sponsors were randomly selected to participate in the case study. The researcher served as the interviewer for semistructured interviews utilizing open-ended questions on an interview guide. Respondents’ answers, comments, and recommendations were recorded on audio tape during each interview and then transcribed. An interview validation summary which contained a summary of each interview was developed and mailed to each participant. Telephone interviews were conducted to validate the interview summaries. Interview transcripts served as the source material for the content analysis portion of the study. The theme was the unit of analysis selected, and a frequency count of themes was the system of enumeration used to measure the characteristics of the content. Every theme representing a different perception was coded as one category for which a frequency count was indicated. Accuracy of transcripts and content analysis was measured by three experienced teacher-coordinators for cooperative-plan distributive education. Conclusions and Recommendations: 1. Distributive education training sponsors in Roanoke City and County, Virginia, perceived the current use of the training agreement as adequate for quality control in the coordination phase of cooperative-plan distributive education program operation. It was recommended that steps be taken to insure student compliance with the provisions of the training agreement and that the provisions of the training agreement be honored by all parties and enforced by the teacher-coordinator. 2. The majority of distributive education training sponsors in Roanoke City and County, Virginia were not involved in the joint development of training plans, but perceived the training plan as having potential to improve the performance of students, teacher-coordinators, and training sponsors. It was recommended that training sessions be conducted to instruct teacher-coordinators in the use of the training plan concept. Emphasis should be placed on how training plans achieve quality control in the operation of cooperative-plan distributive education programs, how to develop a training plan, and how to promote the use of training plans with training sponsors. Teacher-coordinators should initiate the use of training plans with all cooperative distributive education training sponsors in Roanoke City and County, Virginia. 3. It was recommended that distributive education teacher-coordinators in Roanoke City and County, Virginia, assume the role of career counselor and assist with screening of students who apply for enrollment in distributive education. This would facilitate the enrollment of students with a genuine career interest in cooperative-plan distributive education. 4. It was recommended that distributive education teacher-coordinators in Roanoke City and County, Virginia, schedule appointments, and make more frequent coordination visits. At least twice a month was suggested as most desirable with one visit a month as a minimum of coordination visits. 5. The majority of recommendations for improvement of the coordination phase of program operation in Roanoke City and County, Virginia, were proposals that would be acted on by distributive education teacher-coordinators and would not require additional financial resources. / Ed. D.

The development and validation of a video-tutorial approach to the teaching of accounting was the problem of this study. The purpose was to provide an alternate approach which might lead to a more flexible method of instruction that would accommodate varying learning rates of students in accounting. The first phase of the study was the developmental stage. Nine videocassette tapes in color and an instructional manual were prepared by the investigator for the first five weeks of instruction in first year college accounting. The course content for the study was the accounting cycle which was divided into nine major units. A video tape or module was prepared for each unit featuring a brief overview of the concepts leading up to the current topic, specific performance objectives, a visual demonstration and illustration of each new concept, an opportunity to stop the tape and apply new concepts, extensive use of visuals for clarification and emphasis, a summary at the end of each tape, and an introduction of assignments using the related concepts. The objective was to record presentations that would be of such quality that the student would be able to realize comparable benefits of live presentations--but only when the previous objectives had been met. The second phase of the study was the validation stage consisting of the implementation and evaluation of the video-tutorial approach developed by the investigator. The strategy required the teacher to assume the role of manager, motivator, evaluator, and tutor in the classroom. Five 4' by 8' tables were used in the accounting classroom to accommodate six students at a table. A portable stand equipped with a monitor-player unit, a copy of each of the nine tapes, and six headsets was placed at the end of each table. The students worked cooperatively in groups receiving help from the teacher either individually, in small groups, or as a class according to the needs of the students. The study included 113 community college students in five intact class sections registered for Principles of Accounting. Of the three classes assigned to the investigator, two received video-tutorial experimental treatment and one received lecture-demonstration control treatment. Two cooperating teachers were each assigned one class which received the lecture-demonstration control treatment. The experimental group included 40 students taught by the investigator. The control group included 24 students taught by the investigator and 49 taught by the cooperating teachers. The AICPA Orientation Test was administered on the first class meeting and the three subtest scores were used as covariates to adjust the groups for initial differences. An investigator-prepared criterion-achievement test was used as the dependent variable. An analysis of covariance indicated that there was a significant difference in the two treatments in favor of the video-tutorial approach; however, a further analysis of the data revealed that the teacher variable was the major factor contributing to the difference rather than the treatment. The investigator concluded that there is no evidence as a result of the study to believe that the video-tutorial method of instruction is superior to the lecture-demonstration method; however, neither is there any evidence to believe that the video-tutorial is not as effective as the lecture-demonstration method. / Ed. D.

Periodic structures are defined as structures consisting of identical substructures connected to each other in identical manner. In chapter I, the response of periodic structures to harmonic excitation is described by a matrix difference equation. The solution of the matrix difference equation can be obtained by the Z-Transform method and it yields the response to both end conditions and external excitations. The method developed necessitates the eigenvalues of the transfer matrix for a typical substructure, so that the procedure is capable of analyzing a periodic structure with the same computational effort necessary to analyze a single substructure. Added advantage is derived from the fact that the method does not require the eigenvectors of the transfer matrix. In chapter II, infinite periodic structures are considered for different types of loading. Furthermore, it is demonstrated that additional savings are possible when the substructure is symmetric. Chapter III, considers the problem of almost periodic structures. If the system parameters differ slightly from one substructure to another, then the structure becomes almost periodic. An efficient method using a perturbation technique to derive the response of an almost periodic structure is presented. The procedure reduces the solution to a sequential application of the basic algorithm for periodic structures as developed in chapter I. In chapter IV, we consider the undamped response of a periodic structure using a modal analysis technique. The method allows for arbitrary loads and takes full advantage of the periodic properties of the structure. In chapter V, an attempt is made to simulate certain continuous systems by periodic structures. The algorithm as developed in chapter I is now adapted to the treatment of continuous systems. The method is capable of deriving the response of damped and undamped systems subject to harmonic distributed loads. The length of the substructure can be made arbitrarily small without increasing the computational effort. / Ph. D.