Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Jeffrey K. Bennighof. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Idaho, 2006. / Abstract. "June 2006." "In liquefaction, the movement of particles is generally viewed as random and isotropic. A numerical study has been performed based on the hypothesis that as liquefaction occurs, initially randomly placed particles become organized into a lattice structure. As a result, the initial behavior may be isotropic, but there is a progressive movement to anisotropic behavior as cyclic shearing is applied. The study is performed under ideal conditions considering spherically shaped particles of the same size in pure shear. The results of the study showed that the particles organize to the same lattice structure regardless of friction coefficient or shear plane selection. Consequently, this study provides a tool for calibrating constitutive models related to liquefaction."--p. iii. Includes bibliographical references (leaves 45-51). Also available online in PDF format.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 32-34). Also available via the Internet.

In light of an urgent need for improved antimicrobial diagnostics and therapeutics, understanding bacterial behaviour, and bacterial responses to treatments in particular, is one of the key objectives of modern medical research. While the molecular mode of action of antibiotics is usually well known, their effect on the cell at a "systems" level (on the regulatory networks, metabolism, etc.) is only beginning to be quantitatively understood. We address some of these response phenotypes in Escherichia coli testing different antibiotic classes and growth conditions. We study the short (< 15 s) time-scale fluctuation dynamics of fluorescently-tagged chromosomal loci and cytosolic aggregates, which report for the state of locus ”compaction” and the levels of macromolecular crowding of the cytosol, respectively. We improve the precision of those measurements developing a novel data treatment procedure and discover that sub-lethal doses of ciprofloxacin, rifampicin, and vancomycin as well as hyperosmotic shock conditions cause small but consistent changes (unique to each treatment agent) to the physical organisation of chromosomal Ori2 and Ter3 loci and the cytosol. We reveal, among other findings, strong correlations between the effects in different parts of the chromosome and between the chromosome and cytosol. In addition, we complement the marker dynamics work with single-cell level gene expression measurements during sub-lethal translation inhibition. Specifically, we compare responses to tetracycline and chloramphenicol from constitutive and ribosomal promoters in Ori3 and Ter3 chromosomal positions over long (7 h) treatment times in exponentially growing bacteria. We reveal, for the first time, the kinetics of cellular resource allocation and provide novel insights on globally regulated transcription, relevant to the three-component proteome partitioning model, gene-length dependent effects of the processivity of translation, and ”reversibility” of ribosome-binding antibiotics. In addition, we discover a strong correlation between the timing of responses from promoters in the Ori3 and Ter3 positions, and a small but consistent difference in the response magnitude between the two positions.

No description available.

The evaluation of fluid forces on vibrating framed structures in a fluid environment is of current significance in view of the activity in ocean engineering. Accurate knowledge of the fluid forces under conditions of variable separated flow is lacking. In this study an attempt has been made to find a general method of evaluation of fluid forces on cylinders for variable flow, using published data from tests of constant velocity flow, uniformly accelerated flow and wave motion. The parameters that appear to govern the variable flow forces are discussed and models for relating force magnitudes to these parameters are suggested. The dynamic response of framed structures in an ocean environment has not been investigated except for linear sinusoidal wave motion in deep water conditions. The response of shallow water structures to various types of wave forces, as well as to earthquake excitation, has been analysed numerically here, taking into account the interaction between the structure and fluid motions. The effect of the mass and drag parameters on the structure response has been studied. Governing load cases for the design of framed structures have been related to structural period and water depth. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The spout formed at the free surface of a gas-stirred liquid has received little attention even though it has both theoretical and practical significance. In steelmaking ladles, for example, the spout is the site of strong metal-slag-air mixing which affects: the kinetics of reactions at the slag-metal interface, the absorption of oxygen by the bath and the temperature drop of the bath. Notwithstanding its importance, the spout is usually neglected in flow models of gas-stirred baths because it has not been characterized quantitatively; assumption of a flat top surface, however, reduces the accuracy of the velocity and kinetic energy predictions, particularly close to the spout region. Thus in this study, the spout of upwardly injected gas jets in water was characterized experimentally in terms of gas fraction, bubble frequency and axial velocity distributions. The measurements were made with a two-element electroresistivity probe coupled to a microcomputer. Special hardware and software were developed to analyze the signals generated by contact of the bubbles with the sensor, in real time, for the turbulent flow conditions prevailing in the jet plume and spout. Correlations of the gas fraction with axial and radial position for different gas flow rates have been established from the measurements. The dimensions of the spout were obtained from time-exposure photographs; when compared with the gas fraction measurements, the spout boundary always corresponded to values ranging from 0.82 to 0.86. The radial profiles of bubble frequency at different levels in the spout have a bell shape; the bubble frequency decreases with increasing height. The velocity of the bubbles in the spout drops linearly with increasing axial position. Measurements of bath velocity near the walls of the vessel were also conducted with a laser doppler velocimeter for comparison to model predictions. The gas fraction data obtained for the spout then were incorporated into a mathematical model of turbulent recirculatory flow with which predictions of velocity, kinetic energy and effective viscosity in the bath were made. Predictions of the model were compared with the experimental measurements as well as with predictions assuming a flat bath surface (no spout); and the importance of incorporating the spout thus was demonstrated. The variation of the total kinetic energy in the spout with gas flow rate was determined. The energy increased with flow rate, as expected, but at a critical value, the rate of increase abruptly rose. Based on photographs taken of the gas/liquid dispersion, the increased spout kinetic energy appears to be related to the location of bubble break-up and possibly to gas channeling. At lower flow rates below the critical value, the bubble break-up occurs relatively close to the nozzle, whereas at higher flow rates bubble disintegration is nearer to the surface. At the lower flow rates the gas/liquid interaction was maximum which promoted the gas/liquid momentum transfer. Moreover, at the higher flow rates the gas dispersion was observed intermittently to be a continuous chain of large envelopes which could permit a fraction of the gas to channel through the bath for a considerable distance. The channeling phenomenon could lead to an inefficient gas/liquid energy transfer resulting in a reduced efficiency of bath mixing and enhanced energy release at the surface. These results can explain the observations of previous investigators who found that beyond a critical gas injection rate, the rate of decrease of mixing time with flow rate decreased. The metallurgical consequences of the spout and its influence on the flow field, especially in the near-surface region, have been highlighted, thus unveiling the practical bearing of the spout on the gas injection process. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

It is a theorem of Denker and Urbański that if T:ℂ→ℂ is a rational map of degree at least two and if ϕ:ℂ→ℝ is Hölder continuous and satisfies the “thermodynamic expanding” condition P(T,ϕ) > sup(ϕ), then there exists exactly one equilibrium state μ for T and ϕ, and furthermore (ℂ,T,μ) is metrically exact. We extend these results to the case of a holomorphic random dynamical system on ℂ, using the concepts of relative pressure and relative entropy of such a system, and the variational principle of Bogenschütz. Specifically, if (T,Ω,P,θ) is a holomorphic random dynamical system on ℂ and ϕ:Ω→ ℋα(ℂ) is a Hölder continuous random potential function satisfying one of several sets of technical but reasonable hypotheses, then there exists a unique equilibrium state of (X,P,ϕ) over (Ω,Ρ,θ).