A study to determine the effects of a new curriculum model for the biological sciences based on practical application of material, student research, and professional activities, all designed to promote student interest and involvement in course content, was initiated as a supplement to an existing introductory agronomy course during the Fall Quarter, 1973, at Virginia Polytechnic Institute and State University. Based on a pilot program established by the researcher at another institution, the treatment included investigation of research procedures, student utilization of the greenhouse and advanced research equipment, implementation of experimental designs, sampling techniques, and seminars. It was hypothesized that students exposed to the model would have better grades, higher class attendance, and improved attitudes toward the course and toward the agriculture profession than students who were not exposed to the model. Attitudes were determined by answers given on an attitude questionnaire which was developed by the researcher. Differences in attitudes, grades, and attendance between the two groups were analyzed for significance by a multivariate ANOVA. Results of this ANOVA showed that no significant differences existed at the .05 level for grades, attendance, and attitudes between the two groups. A factor analysis of the questionnaire indicated that various attitudes were tested, rather than a single attitude. However, resultant scores for five general attitudes believed to be determined by the questionnaire indicated that no differences in attitudes existed between the two groups. As a result of this study, it was concluded that the model, as implemented, had no effect on grades, class attendance, or attitudes. However, experience gained as a result of this study led to several major recommendations for refinements which would improve the validity and reliability of future, similar studies. / Ed. D.

The purpose of this study was to develop and validate a paper and pencil automotive mechanics achievement test and determine the feasibility of measuring the competence of mechanics using this instrument rather than the traditional performance test. It involved: 1) the selection of a number of accepted performance task items agreed upon by a jury of experts as valid for testing automotive mechanics students; 2) the formulation of each accepted performance task into a paper and pencil test item; and 3) obtaining a correlation between the two like tests of at least .71 corrected for attenuation. Following the construction of the 26 item performance test and construction of the like 26 item paper and pencil test a pilot study was conducted with a total of 25 Automotive Mechanics II students taking the paper and pencil test. These data were collected and subjected to item analysis for the purpose of ranking the test items from those items answered most easily to those answered with most difficulty. Both tests were then arranged in this order. / Ed. D.

The turbulent wakes behind a streamlined drag body, a jet-propelled body, and a propeller-driven body are studied experimentally in a subsonic wind tunnel at a principal nominal free-stream velocity of 206 ft/sec. The wakes produced by the latter two bodies are momentum-less. Mean flow data taken at five axial stations (X/D = 2, 5, 10, 20, and 40) downstream of the sterns of these bodies include velocity and static pressure distributions. The streamwise variation of the maximum values of axial turbulence intensity and radial shear stress are also presented. The mean flow data for the wake behind the drag body compare favorably with previous experiments and establish a rigid reference for the wakes behind slender, self-propelled configurations. The downstream rate of decay of |(U_E-U_c)_max U_E| is essentially the same for the drag and propeller-driven bodies, whereas the decay for the jet-propelled body is substantially faster. A self-similar character is exhibited in the wake of the drag body, but the wake of the propeller- driven body appears to be self-similar in the usual sense only in the inner region. As for the basic turbulence behavior, the magnitude of the axial turbulence intensity is greater for the jet-propelled model than the other models, and the absolute value of the radial shear stress is greater (beyond X/D = 2) for the propeller driven model. The rate of decay of (√u'²)_max is faster for the propeller-driven model than the jet-propelled model; however, the rate of decrease of radial shear stress is faster for the jet-propelled model. A comparison of the axial variation of |(U_E-U_c)_max U_E| with numerical predictions using a turbulent kinetic energy method shows very good agreement for the drag and jet-propelled bodies. The shear stress trends are predicted well in all cases. / Ph. D.

This study examines interregional monetary trends in the United States, particularly trends involving the income velocity of money. A unique set of state money data are developed in the dissertation and then used to investigate four major topics. First, the analysis determines that interregional changes in velocity generally follow U.S. changes in velocity, indicating that significant interregional economic interdependencies do exist. However, there are significant differences in interregional velocity levels, implying that the factors which determine the demand for money are different. Secondly, the dissertation establishes that in some cases state money supplies are a better predictor of state income than the national monetary supply is, a result which conflicts to some extent with an hypothesis advanced by Milton Friedman. Thirdly, the study focuses attention on preliminary research by Gould and Nelson which indicates that changes in U.S. velocity appear to follow a random walk. Evidence is presented which conflicts with this finding, and methods by which velocity can most accurately be measured are discussed. Finally, the analysis considers some of the possible determinants of velocity, concluding that changes in financial institutions are important in this respect. More specifically, it is found that Savings and Loan Associations have had a strong influence on velocity levels in the post WWII era. / Ph. D.

This dissertation dealt with the problem of devising more relevant chemistry instructional materials for potential medical laboratory technicians. The investigation was designed to determine: 1. competencies needed by medical laboratory technicians in the of their jobs; and 2. the chemistry topics and/or concepts which would aid in the achievement of these needed competencies. A questionnaire consisting of fifty items written in performance terms, was developed and sent to approximately 400 persons located in the following four groups: 1. chemistry teachers at community colleges having medical laboratory technician programs in operation as of 1970; 2. designers of medical laboratory technician programs at community colleges; 3. supervisors of medical laboratory technicians working in hospitals or clinical laboratories; and 4. medical laboratory technicians who graduated from a community college and had worked a minimum of two years on the job. The respondents were asked to indicate the importance and the frequency of application of each skill. From the literature and through interviews and observations, a list of chemistry topics and/or concepts was developed for each item. The were asked to indicate those chemistry topics which they would aid in the achievement of the skill contained in each item. Several conclusions were drawn as a result of the information collected from the questionnaire. First, many professional persons in the area of medical technology were completely ignorant of the relatively new career in medical technology--that of medical laboratory technician. Second, the responses of the chemistry teachers indicated that, as a group, they had a negative attitude about the study. Most indicated that they did not know what skills a medical laboratory technician needed to be able to perform or how often the technician would perform these skills. The medical laboratory technicians who answered the questionnaires were pleased that such an investigation was being conducted. Most agreed that much of the chemistry they had received was irrelevant to their needs. Results of a chi-square statistical test performed on each item indicated that differences of opinions occurred among the four groups. In general, more differences of opinion were found for the frequency of application of skill rather than its importance. The chemistry teachers disagreed significantly more on various items than did the other three groups. This investigation was a successful effort to use questionnaires to determine the competencies needed by medical laboratory technicians and the chemistry content needed to achieve these competencies. The major product of this investigation was an outline of competency-based chemistry instructional materials for the preparation of medical laboratory technicians. / Ed. D.

The thesis of this investigation was that in light of several contemporary pressures (e.g., budget) the utilization of undergraduate student Head Residents may be a feasible alternative to the professionally trained Head Resident staffing approach that colleges and universities should consider. Three medium sized, state supported universities (Institutions A, B, and C) participated in the study. To explore the study's thesis, the effectiveness of undergraduate student Head Residents at Institution A was compared with that of professionally trained (Master's level) Head Residents at Institutions Band C. Effectiveness was measured by the frequency with which Head Residents at each participating institution were perceived by Resident Advisors (RA's) and Student Personnel Administrators (SPA's) as displaying typical Head Resident behaviors. A specially designed instrument containing fifty-eight items of a "person-management" oriented nature was used. All were mailed a copy of the instrument and asked to indicate on a Likert scale the frequency with which they perceived their Head Resident displaying each behavior. Selected SPA's at each institution were mailed two copies of the instrument, one to evaluate male Head Residents as a group and the other to evaluate female Head Residents as a group at their respective institutions. A factor analysis on the RA responses was pursued and five dimensions were identified. These were named the Empathy/Sensitivity, Programming/Activities, Disciplinary, Formal Leadership, and Facilities Management dimensions. ANOVA on mean ratings were used to answer several research questions related to comparative undergraduate student and professionally trained Head Resident effectiveness. The major findings of the study were the following: (a) Undergraduate students were perceived by RA's as being less effective than professionally trained personnel (.01) only in the frequency with which they displayed behaviors related to the Programming/Activities role; (b) Whereas undergraduate student males were perceived by their RA's as performing Disciplinary related behaviors more effectively (.01) than undergraduate student females, when compared with undergraduate student males the undergraduate student females were perceived as being more effective (.01) on the Empathy/Sensitivity and Programming/ Activities dimensions and as displaying person oriented behaviors more frequently (.01); (c) Professionally trained personnel were perceived by SPA's as more frequently displaying person oriented (.01) and management oriented (.01) behaviors than undergraduate student males; (d) SPA's perceived undergraduate student females as displaying person oriented functions more frequently (.01) than undergraduate student males. Among conclusions drawn from the study's findings was that professionally trained personnel are more balanced in effectiveness in the Head Resident role than undergraduate students. As perceived by RA's professionally trained males and females did not differ in effectiveness on the several dimensions analyzed. On the other hand, when the effectiveness of undergraduate student males and undergraduate student females were compared, the males were perceived by RA's as displaying "male type" behaviors (high on the Disciplinary dimension) more frequently and the females were perceived as displaying "female type" behaviors (high on Empathy/Sensitivity dimension) more frequently. Substantial differences ($100,000-$300,000) in annual institutional expenditure for Head Resident staff implied strongly that additional evaluation of the various approaches to Head Resident staffing is crucial. / Ed. D.

Time dependent properties of angle ply laminated Boron/Epoxy and Graphite/Epoxy fiber controlled composites were investigated. The main objective of this study was to develop a technique to establish interconversion of different test results using appropriate viscoelastic theory to formulate an accelerated testing procedure. To achieve this aim, forced vibration, constant strain rate and creep tests were performed at different temperature levels. Due to its practical importance, behavior below the glass transition temperature was studied. Multiple regression techniques were used to generate response surfaces for significant variables. Master curves using the time-temperature superposition principle were established for individual tests. Mechanical model representation, integral equation formulation and numerical integration methods based on linear viscoelasticity were used to predict constant strain rate and long time creep behavior of composites from nondestructive short time dynamic tests. It has been shown that a regression equation and its constants can be conveniently used to obtain horizontal and vertical shift and also to perform viscoelastic analysis. While time-temperature superposition can be applied to each test its validity in general needs further study. Simple mechanical models fail to predict constant strain rate tests. Constant strain rate and creep tests were predicted using measured damping ratios and storage moduli from dynamic tests. Also, relaxation moduli were obtained over eleven decades of time scale from different tests. Thus, applicability of linear viscoelastic theory to predict the gross behavior of these composites is established. / Ph. D.

Recent reports have appeared on the occurrence of lactose intolerance and low intestinal lactase activity in otherwise apparently healthy populations. In these individuals, administration of an oral lactose load fails to produce a significant increase in blood glucose concentrations and may be associated with moderate to severe gastrointestinal disturbances. Milk and milk products consumed in quantity may also induce these clinical symptoms of lactose intolerance. Since a high incidence of low lactase activity has been found in American Indians, Mestizo children and in Mexican American adult males, the present study was undertaken to determine lactose tolerance in Mexican American children in San Antonio, Texas, and to correlate this data with selected dietary and anthropometric measurements. After an overnight fast, 282 healthy Mexican American and 51 Anglo American children between the ages of 2 and 14 years were given an oral lactose load of 2 g/kg body weight (up to a maximum of 50 g lactose) as a 20% solution in water. Capillary blood was drawn at 0, 15, 30 and 60 min and assayed for true glucose. A blood glucose rise of 25 mg/100 ml was considered a normal lactose tolerance test. A 24-hour dietary recall was obtained for each child, as were height, weight, head circumference, arm circumference and triceps skinfold measurements. Gastrointestinal symptoms were carefully recorded for a 24-hour period following lactase loading. Overall incidence of lactose malabsorption was significantly greater in Mexican American children than in Anglos. Lactose malabsorption increased with age in both groups. Incidence of symptoms occurring after lactose in lactose malabsorbers also increased with age. Most common symptoms reported in order of frequency were abdominal cramps, bloating and diarrhea. Mean protein intake exceeded the RDA at all ages for both ethnic groups. Mexican Americans consumed less protein, riboflavin, vitamin A, calcium and fewer calories than Anglos. There were no differences in caloric and nutrient intakes or in milk consumption between lactose absorbers and malabsorbers, but Anglos drank significantly more milk than Mexican Americans. Mean height and weight for Mexican American males and females were slightly below the 50th percentile of the Stuart-Meredith standards and slightly above the 50th percentile of the Ten-State Nutrition Surveys means for Mexican American children. Triceps skinfold and head circumference measurements were similar to standards. Fifteen percent of the Mexican American lactose absorbers and 23% of the malabsorbers reported having symptoms after milk ingestion. None of the Anglos recognized symptoms after drinking milk. If lactose malabsorption does have a nutritional effect, the effect is not of sufficient magnitude to be revealed in the growth patterns of otherwise healthy children. Most children consumed small to moderate amounts of milk with no adverse gastrointestinal symptoms. Because milk is a source of high quality protein, calcium, riboflavin and vitamin A milk drinking should be encouraged as tolerated. / Ph. D.

If y₁, y₂, ... , y _p represent vectors of independent observations, the generalized multivariate regression model is of the form y_j = X_1j β_1j + X_2j β_2j + ε_j , j = 1, 2, …, p, where X_1j and X_2j are general linear model regression matrices, β_1j and β_2j are vectors of unknown coefficients, and the ε_j are error vectors such that cov(ε_i,ε_j) = σ_ijI. If X_1j = X₁ and X_2j = X₂ , j = 1, 2, …, p, the above is a standard multivariate regression model . Insofar as can be determined, the true relationship between the design variables and a response n_j is n_j = x_1j^’ β_1j + x_2j^’ β_2j where x_1j^’ x_2j^’ are typical row vectors in the matrices X_1j and X_2j. For x_j^* = [x_1j^’, x_2j^’] and β_j^* = [ß_1j^’, β_2j^’], the n_j are to be estimated either by ŷ_j = x_1j^’β̂_1j or ŷ_j* = x_j^*’ β̂_j^* where β̂_1j and β̂_j^* are the least squares estimators of β_1j and β_j^* obtained from the full multivariate regression model. The estimators for the n_j are determined by a test of the hypothesis H_o: J₁ ≤ J₂ where J₁ and J₂ denote the integrated mean squared errors of a linear combination of the ŷ_j and ŷ_j* respectively. Rejection of H_o results in selection of the ŷ_j*; otherwise the ŷ_j are chosen. A test statistic is developed to test H_o with consideration extending to several important special cases. Distinctions are drawn between the preliminary test estimator constructed around H_o, and that based on the usual hypothesis β_2j = 0, j = 1, 2, ..., p. Under the assumption of error normality, an approximation to the distribution of the test statistic is developed in order to determine type I and type II error probabilities. An explicit expression for J_o, the integrated mean squared error of the preliminary test estimator, is obtained, and difficulties in its evaluation are discussed. An estimator of J_o is presented along with a special case in which J_o can be evaluated exactly. Graphical comparisons are made on the relative performance of the estimators based on H_o , and those constructed around the standard hypothesis. An operating range of type I error probabilities is also discussed. / Ph. D.

An extensive investigation of non-uniform material effects on static fracture analyses is undertaken. Included in the study are theoretical, experimental and numerical techniques of focusing attention on the nonsymmetric deformation fields around a crack tip in a non-uniform yield strength varying material. Each analysis independently shows that the material non-uniformities alter stress and strain distributions drastically and that a statically stressed crack can propagate in directions other than the crack axis direction, depending on local conditions at the crack tip. An extremely simple and versatile finite element technique called “Unimod” is developed for use in real material modelling of crack tip material elements. / Ph. D.