A series of lateral load tests were conducted on assemblies of four, 4 foot long U.S. Steel PS32 (regular strength) and PSX32 (high strength) straight web sheet pile sections. The instrumentation adopted in the testing program was geared toward monitoring the assembly displacements, load transfer characteristics, and interlock response. Average effective E-ratios over three different pressure ranges were computed, interlock force versus pressure relationships were derived, the stress states in the pile webs were examined, and interlock force versus interlock displacement trends were obtained from the resulting data. A total of 12 assemblies were tested, 6 each of the PS32 and PSX32 types. Three tests from each lot of 6 incorporated pretensioning of the assembly prior to application of the lateral pressure; whereas, the remaining tests initiated lateral loading of the assemblies while they were in a slacked state. The results from the tests were generally grouped according to assembly designation (PS32 or PSX32) and type of test (pretensioning or no pretensioning). The tabulation of E-ratios and pile web stresses, and interlock force versus pressure plots revealed consistent relationships among tests in a particular grouping over the 0-30 psi loading range. Interlock force versus interlock displacement trends were physically correct, but provided no conclusive information regarding the response at an interlock connection. / M.S.

Models of multiple component, multiple phase adhesives were developed to examine the conflicting demands placed on modern adhesion technology. Styrene and isoprene based block copolymers were investigated 511 order to understand their adhesive properties. The structure of the microphase separated morphology of the materials studied was found to influence the adhesive behavior in applications as hot melt/structural type adhesives and as pressure sensitive adhesives. The thermal and the dynamic mechanical behavior of linear styrene/isoprene/styrene triblock copolymers (40% and 50% by weight styrene) was determined for free films and for films bonding together two rigid adherends. Damping phenomena indicated a broader mechanical relaxation spectrum occurring at higher i temperatures in the bonded assemblies. Microphase separation in the melts of these triblock materials was interpreted as contributing to the formation of residual stresses in both free films and bonded joints under appropriate thermal and pressure histories, illustrating the importance of sample preparation. in the evaluation of multiple phase adhesive systems. / Ph. D. / incomplete_metadata

The theory of soft variable structure control, which produces robustness to parameter variation and fast transient response, is discussed in this thesis. The digital implementation techniques are presented in the aspects of sample rate, prefilter design, hardware selection, and microprocessor arithmetic operation. Simulation and experimental results showed good performance in negative speed range, but this controller created unwanted high armature current fluctuation in positive speed range. The reasons turned out to be the limitation of sample rate, noise from the tachometer, and high gain at positive speed. / Master of Science / incomplete_metadata

Construction of braced excavations in major urban areas has increased over the last few decades. It is a major concern of the designer to limit ground movement around an excavation in order to prevent damage to adjacent structures, utilities and roads. Existing design methods can accurately predict ground and wall movement of a braced excavation, but the calculations become complex when multiple construction stages are considered, or if different design schemes are compared. This thesis presents an interactive personal computer program (called MOVEX) to facilitate braced excavation design. Using input variables for wall stiffness, strut stiffness, and strut spacing, MOVEX includes four design options that allow the designer to adjust the variables in order to develop the optimal bracing design. Details of the design theory, input and output data, and a user's guide are included in this thesis. In addition, the settlement of sand due to pile driving was investigated. A predictive method is presented that relates sand densification to the ground acceleration caused by pile driving. / Master of Science

Ribosomal 5.85 RNA is a component of the large (605) ribosomal subunit in eucaryotes. Studies of 5.85 rRNA in solution have shown that under certain conditions, including standard isolation procedures, the molecule complexes with itself to form dimers and higher multimers. Two models have been proposed in the literature to explain the intermolecular interactions responsible for 5.85 rRNA dimer formation. The terminal interaction model of Sitz et al. (Biochem. 17, 5811-5815, 1978) proposes that the dimer forms through base-pairing of the 5' and 3' terminal sequences of two 5.85 rRNA molecules. Pavlakis et al. (Nucl. Acids Res. 7, 2213-2237, 1978) showed that 5.85 rRNA lacking the 3' terminal region was capable of forming dimer. They proposed an alternative model for 5.85 rRNA dimer formation in which an entirely different part of the molecule interacts to form a double-stranded palindrome. In this study, enzymatic probing techniques and stability measurements (both experimental and theoretical) were used to determine which model most accurately describes the intermolecular interactions of the 5.88 rRNA dimer. The methods used for determining stability were not able to discriminate between the models for 5.88 rRNA dimer formation. Results from the structural probing studies, however, support the terminal interaction model and indicate that the palindrome interaction does not occur in 5.88 rRNA dimer formed from the intact molecule. / Master of Science / incomplete_metadata

The flotation of sphalerite has been demonstrated without the use of collectors. The effect of redox potential, pH, and copper-activation have been investigated in tests using samples of pure mineral. It has been found that in general, collectorless flotation of sphalerite can be accomplished at potentials greater than -200 mV, SHE, and is more readily carried out in acidic solutions. It has also been shown that although copper-activation was necessary to achieve flotation recoveries above 35%, an excessive addition of cupric ions may result in a decrease in floatability. Batch flotation experiments conducted using Elmwood Mine sphalerite ore have shown that in addition to copper-activation, the addition of sodium sulfide was required to obtain high grades and recoveries. If the ratio of the addition of these reagents is maintained such that the atomic ratio of cupric ions to sulfide ions is 0.31, good flotation is observed over a range of reagent dosages. X-ray photoelectron spectroscopy (XPS) was conducted on pure mineral samples after microflotation testing. Based on the sulfur species identified on highly flotable samples, possible mechanisms for collectorless flotation of sphalerite have been suggested. These include: i) elemental sulfur formed under oxidizing conditions is responsible for collectorless flotation; ii) polysulfides or metal-deficient sulfides formed as a result of mineral oxidation are responsible for collectorless flotation; and iii) removal of HS- ions, which may render the surface hydrophilic, under oxidizing conditions. The third mechanism is based on the assumption that clean, unoxidized sphalerite surfaces are naturally hydrophobic. Evidence has been presented to suggest that the first mechanism may be responsible for collectorless flotation in acidic solutions, while the second mechanism may be of greater importance in nearly neutral or basic solutions where elemental sulfur is thermodynamically less stable. / Master of Science

This study challenges the common assumption that Hemingway's early style is indebted to the work of Sherwood Anderson and Gertrude Stein and finds the evidence less than compelling. Unlike previous examinations, this study considers Hemingway's early journalism and correspondence as well as his first published fiction; additionally, it suggests models of influence other than Anderson and Stein, such as Ring Lardner and Stephen Crane. Because the critical tradition most often identifies "repetition" and "colloquialisms" as bases for attributing influence to Anderson and Stein, I discuss those characteristics individually, concluding that Hemingway's debt to Stein's use of repetition and Anderson's use of colloquial style has been overstated. I also assess the individual style of each author and identify the fundamental differences among them. And, finally, I suggest promising avenues which may lead to new associations between Hemingway and the forces which helped to shape his style. / Master of Arts

The life history of Fusconaia edgariana, the endangered shiny pigtoe pearly mussel, was determined in a two-year study at North Holston Ford, North Fork Holston River (NEHRM 86.9) above Saltville, Virginia. Sixty 0.5m² Quadrats indicated a mean density of 10.6 mussels/m², representing 1 species. Six additional species were collect handpicking or in muskrat middens. The density edgariana was 1 adult/2 m². Distribution of the pigtoe was restricted to shallow areas of mixed gravel, and pebble substrate in low to moderate velocities. Drift nets (130um mesh) indicated glochidia edgariana were released into the water column from 23 June to 18 August, 1981 and 24 June to 28 August, 1982. Of the 4,800 fish examined from June 1981 to June 1982, 1.5% carried shiny pigtoe glochidia. The telescope, common, warpaint, and whitetail shiners were found naturally encysted by 1 to 3 glochidia of F. edgariana. Laboratory induced infestations were conducted on twenty two species of fish, and all but two species sloughed the glochidia within 4 to 14 days. The whitetail and common shiners retained glochidia for 38 days, indicating these two fish species to be probable hosts for the shiny pigtoe. / Master of Science

The Career Development Workshop For Athletes was designed to aid in the comprehensive career development effort at Virginia Tech. The pilot research project involved 40 active freshman varsity football players enrolled during Fall and Winter quarters of the 1984-85 school year. The 40 students were randomly selected from a pool of 65 freshman football players. The experimental design was a two stage stratification. The first stage was selection and the second stage was assignment to control and treatment groups. The independent variables were workshop participation and race. The dependent variables were gain scores from the three intercorrelated scales on the Career Development Inventory. The Workshop was conducted over a six week period, each session lasted approximately two hours and met once each week. The four objectives of the workshop were 1) to assist students in the identification and or selection of career interest and goals; 2) to identify a career support network; 3) to assess and identify skills; and 4) to aid in the perception and procurement of self esteem. / Master of Arts

Geographical variation in taxa must be considered in evolutionary studies. The purpose of the present study is to demonstrate how geographical variation can be measured and documented for a taxon for one slice of time. Future evolutionary studies should document geographical variation for the entire geographical range of the species involved at several points of time throughout its total stratigraphic range. Thus the variation that is present at one time horizon may be separated from the variation that occurs through time. This work consists of a study of geographical variation in the genus Astarte (Phylum Mollusca: Class Bivalvia) from the Yorktown and Jackson Bluff Formations (early Pliocene) of the Atlantic Coastal Plain. Factor analysis, multivariate analysis of variance, and discriminant analysis were performed on measurements of specimens of Astarte from ten localities. There are significant differences in the morphologies of individuals among localities. These differences are due to the presence of different species of Astarte and to variation in size and external ornamentation within the same species. Seven species recognized from literature on Pliocene Astarte were identified among the individuals of the ten localities, but the statistical results indicate that these seven species may be grouped into three "types" that mayor may not represent species. The three types occur together in some localities, suggesting that they are distinct species living in sympatry. Factors influencing geographical variation include larval dispersal strategy and the effect of the environment. / Master of Science