Thesis (Ph.D.)--Tennessee Technological University, 2006. / Bibliography: leaves 47-50.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 111-115). Also available in electronic version.

No description available.

Achromobacter w.t. and strain 14 both support phage α3a growth in stationary phase, but unlike the w.t. strain, exponential phase cultures of strain 14 block phage development. A standard method was developed for determining phage growth in stationary phase cultures. Lyophilised cells were used to eliminate variations due to the unstable phenotype of Achromobacter strain 14 cells. Phage α3a growth in stationary phase was characterized by a long and variable latent period of 6 to 9 h and an increased burst size of 709 p.f.u. per cell as compared with 153 p.f.u. per cell in exponential wild type cells. During the latent period the infected cells were very sensitive to changes in growth conditions and in particular, dilution. Pre-conditioning of the bacterial cells by allowing them to stand for 24 h after shaking for 3 days was an important aspect of the stationary phase phage growth system. Cells which had been allowed to stand retained the ability to be infected and to support phage growth for at least 16 days. Shaking cultures gradually lost the ability to support phage growth but the phage could persist in the host cell for 10 days until removal from shaking when the lytic cycle could proceed after allowing the cultures to stand. In comparison the latent period and burst size in Achromobacter w.t. stationary phase cells were reduced to less than 2 h and less than 200 respectively. Stationary phase cultures differed physiologically and morphologically depending on the aeration conditions. In comparison with non-aerated standing cultures, vigorously aerated cultures showed a decrease in viability, RNA synthesis, membrane transport, intracellular ATP levels, UV resistance and heat resistance but had markedly higher protein synthesis levels. Aerated cells were small non-motile rods which did not support phage growth. They developed into large motile rods under conditions of limited aeration and were able to propagate phage. It was proposed that changes in the host control mechanisms for macromolecular synthesis may be instrumental in either blocking or permitting phage development. A spontaneous mutant of Achromobacter strain 14 (14x) which liberated phage and was resistant to superinfection was isolated. The phage-host relationship was unstable and similar to the phage carrier state. The liberated phage were able to grow in exponential strain 14 cells. It was proposed that strain 14 was a defective lysogen and that an immunity phase shift model may account for the differential phage growth in exponential and stationary phase cells. Host transcriptional control appears to be implicated in control of phage development in exponential and stationary phase cells. Achromobacter Lp only supported phage in exponential phase but a rifampicin resistant mutant of this strain was able to propagate phage in stationary phase. In vitro RNA synthesis assays showed that the rifampicin resistance was caused by an alteration in the RNA polymerase. Preliminary experiments to determine intracellular phage macromolecular synthesis were carried out using exponential Achromobacter w.t. cells which had been irradiated with UV prior to infection. In irradiated cells, infection with phage resulted in stimulation of DNA synthesis but no stimulation of protein synthesis. Phage production was drastically reduced in cells which had been treated with very low UV doses. It was proposed that α3a development may rely heavily on host cell functions which are destroyed by UV. Achromobacter mutants with defective leucine transport systems were isolated. Mutants which lost the leucine uptake system completely were totally resistant to phage infection and were unable to adsorb phage α3a. This is the first report to implicate an amino-acid transport system in phage adsorption.

No description available.

Results of drained and undrained triaxial compressions tests on a sensitive clay are presented in this thesis. Contours of water content from both drained and undrained tests are compared, and it appears that for the clay tested, there is not a unique relationship between effective stresses and water content as found by Rendulic and Henkel for remolded soil. The Roscoe concept of a state boundary surface, which is similar to the Rendulic concept is examined, and it also does not hold for the clay tested. The Roscoe energy equation is applied to the results of all tests and it appears to hold quite well. It indicates that for a soil which is yielding there is only one fundamental strength parameter, M, which is independent of both strain and strain rate. Methods of predicting stress-strain relationships are examined. The Roscoe method, which is based on the existence of a state boundary surface is not strictly applicable, but does yield results which are of the same order as the measured relationships. The Landanyi method does not appear to apply to the clay tested. A method for predicting residual pore pressures and or permeability in drained triaxial tests is derived. This enabled allowances to be made for the effect of residual pore pressures in drained tests. However, it is felt that the method may have more application in the examination of soil structure, since a comparison of the permeability of samples at the same void ratio and temperature yields a measure of structural difference. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The effect of a number of variables upon prestress anchorage length was investigated. The end zones of prestressed pretensioned concrete members were simulated by casting against steel bulkheads. 3/8" diameter strands and .276" diameter wires were used. Fifty specimens were tested. The variables investigated were; surface condition of prestressing steel, speed of release of prestress, water/cement ratio of concrete, age of concrete, stress in concrete, and vibration. A relationship between free end pull-in and anchorage length was found and is compared with the results of other investigators. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The use of the photoelastic coating method in determining the stresses in the torispherical head of a pressure vessel was investigated. It was found that the method is valuable to obtain the distribution, direction, and magnitude of stresses on the surface of any structure. The results obtained with the method showed close agreement with the theoretical investigations. The maximum stresses in a torispherical head of a pressure vessel occur in the torus. The same conclusion was drawn from the results obtained with the method. It also revealed, that these stresses were compressive on the outer surface. The mobility of the instruments, the relatively simple way of coating the surface of the structure are other features of the method. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The effect of the mean stress on the endurance limit is a matter of considerable academic and practical importance. So many variable and uncertain factors are involved that it is not surprising that many different formulas and theories have been proposed since the start of investigations into this subject in about 1858. In this thesis, factual data obtained in the course of tests planned primarily for the purpose of determining the effect of the mean stress are presented and discussed. A standard fatigue testing machine vas used for all the tests. Various mean stresses, both for axial-load and torsional tests, were employed. A critical examination of the proposed theories of fatigue failure has been made. The theory which considered that the inception of fatigue resulted from alternating shearing stress and that the resistance to fatigue was influenced by the magnitude and sign of the steady normal stress was found to explain best the damage done to the material structure. It has been the opinion of a number of investigators that the fatigue strength under axial-load is decreased by an increasing tensile mean stress and in torsion the fatigue strength is unaffected by the mean stress. The experiments done here clearly indicate that this conclusion is true. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

An influence line method for the analysis of flexible hingeless arch by the deflection theory is presented in this thesis. To facilitate the work, tables of dimensionless magni fication factors are provided. Prom these tables, influence lines taking into account the flexibility of the arch may be readily drawn and used very much in the ordinary way. The flexibility of the arch was conveniently measured by a dimensionless ratio, [ equation omitted ], and called the stiffness factor of the arch. The tables are for parabolic hingeless arches having rise ratios of 1/8,1/6,1/4,1/3, with constant EI or a prescribed variable EI. Values are given for β = 3 and 5 with some for β = 7. Also the tables contain magnification factors for maximum moments at eleven points in the arch, when the arch is loaded with a uniform load. Although the given tables are good only for parabolic hingeless arches with constant EI or a prescribed variation in EI, the tables may be reasonably extended to other hingeless arches whose shapes are not too different from a parabola and to a wide variety of variation in moment of inertia, provided these variations are not unrealistic. The possibility of using superposition in the deflection theory is based on the fact that calculations showed the horizontal thrust acting on the arch was approximately the same either by the deflection theory or the elastic theory. Because of this, the horizontal thrust becomes independent of deflection and the differential equation for bending of an arch is linear. Thus superposition may be used. The differential equation was hot convenient for calculation. Instead, the solutions in the tables were calculated by a numerical procedure of successive approximations, using the conjugate beam concept. This procedure was conveniently programmed for an electronic computer, the ALWAC III E, at the University of British Columbia. In the first cycle of approximation, the programme assumed the horizontal and vertical deflections were zero. This represented the elastic theory analysis. In subsequent cycles, the deflected shape of the arch from previous analysis was assumed. Successive approximation as such led to a solution based on the deflection theory. Three numerical examples shown in this thesis indicated that the error introduced by the linearized deflection theory was small, and the influence line method may be used for analysis of flexible arches. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate