This work is a collection of three experiments aimed at studyingdifferent facets of non-equilibrium dynamics. Chapter I concernsstrongly compressible turbulence, which turns out to be verydifferent from incompressible turbulence. The focus is on thedispersion of contaminants in such a flow. This type of turbulencecan be studied, at very low mach number, by measuring the velocityfields of particles that float on a turbulently stirred body ofwater. It turns out that in the absence of incompressibility, theturbulence causes particles to cluster rather than to disperse.The implications of the observations are far reaching and includethe transport of pollutants on the oceans surface, phytoplanktongrowth, as well as industrial applications.Chapter II deals with the effects of polymer additives on dragreduction and turbulent suppression, a well-known phenomenon thatis not yet understood. In an attempt to simplify the problem, theeffects of a polymer additive were investigated in a vortex streetformed in a flowing soap film. Measurements suggest that anincrease in elongational viscosity is responsible for asubstantial reduction in periodic velocity fluctuations. Thisstudy also helps to illuminate the mechanism responsible forvortex separation in the wake of a bluff body.Chapter III describes an experiment designed to test a theoreticalapproach aimed at generalizing the classical fluctuationdissipation theorem (FDT). This theorem applies to systems drivenonly slightly away from thermal equilibrium, whereas ours, aliquid crystal undergoing electroconvection, is so stronglydriven, that the FDT does not apply. Both theory and experimentfocus on the flux in global power fluctuations. Physicallimitations did not permit a direct test of the theory, however itwas possible to establish several interesting characteristics ofthe system: the source of the fluctuations is the transient defectstructures that are generated when the system is driven hard. Itis found that the power fluctuations are spatially uncorrelated,but strongly correlated in time and even quasi-periodic.

Molecular Dynamics simulation has been used for the past 20 - 30 years to study interfacial properties of liquids though the foundations for these studies were laid as far back as 1791 when the astronomer Joseph Dalambre used the time reversible algorithm, commonly called the Verlet algorithm, for the integration of Newton's equations. Some of the properties obtained from Molecular Dynamics, commonly called MD, simulation are density profiles, system configurations, as well as stress or pressure tensor profiles. Generally, the surface tension has been calculated by integrating the stress tensor profile over the width of the interfacial region. In an effort to circumvent the stress tensor calculation and the technical difficulties associated with extensions to include many-body interactions, I will study the feasibility of implementing an equality recently developed by C. Jarzynski to determine the equilibrium surface free energy and, subsequently, the surface tension of an immiscible L-J fluid from an ensemble average of a set of non-equilibrium simulations. In addition to exploring suitable systems for this study, we explore relative computational efficiency of the second method. We also compare the equilibrium free energy difference computed by the Jarzynski method to the apparent free energy difference computed by the Irving-Kirkwood (IK1) approach. We conclude first that both the Jarzynski and IK1 approaches can be useful tools in simulating immiscible liquid systems. The Jarzynski relation is quite effective at extracting free energy differences associated with interfacial area changes in systems comprised of closely spaced, interacting interfaces. For isolated interfaces, the IK1 method is still the best approach for obtaining interfacial tension. We also find that a fast switching Jarzynski algorithm is as efficient and much less costly to implement than a slow switching method.

There is a 40-year long history in the search for Bose-Einstein condensation (BEC) of excitons in semiconductors. This thesis presents research directed toward this goal in bulk crystal Cu2O in three dimensions and in GaAs-based coupled quantum wells (CQW) in two dimensions.The Auger recombination process in Cu2O plays a major role in limiting the density of the excitons. We find that the rate for this process increases with applied stress and lattice temperature. We create paraexcitons in Cu2O through a resonant two-photon excitation in a harmonic potential trap with the Auger recombination process as small as possible (at low temperature and low stress), and find that the exciton creation efficiency in the resonant two-photon excitation is greater for one-beam excitation than for two colliding pulses, but the colliding pulse method may be useful for direct creation of a condensate in the ground state. The paraexciton density in this work is about thirty times less than the required density for BEC of paraexcitons. One promising direction for BEC of excitons in Cu2O is that with higher laser power from stronger IR laser sources, or at lower temperature, the critical density can be approached under one-beam two-photon excitation resonant with the paraexciton state.In two dimensions, the CQW structure has been modified with four design strategies: highest possible barriers, introducing into the barriers a superlattice of 60 angstrom GaAs wells, p-i-n doping, and wider quantum wells, which provides indirect excitons low disorder and high mobility. With a cold near-resonant excitation, we conclude that the excitons act as a free gas, travelling distances of hundreds of microns. We also present observations of a narrow beam of emitted light, when the indirect excitons are confined in a two-dimensional harmonic potential trap, in a way quite similar to the first observations of BEC in alkali atoms. A beam-like emission has been suggested as a telltale for BEC of excitons. This opens the door to a whole range of investigations, including attempts to observe coherence of the emitted light, proof of superfludity of the excitons, and other fascinating effects.

This thesis presents the results from the measurement of the lifetimes of charged and neutral B mesons in four final statesin proton-antiproton collisions at a center-of-mass energy of 1.96 TeV using 195 inverse-picobarns of data collected with the CDF detector at the Fermilab Tevatron Collider. The proper decay length is estimated using the J/psi vertex in all cases to reduce the systematics in the ratio.For the Bu meson, the mean life (ctau) is determined to be 499 +- 12 +- 6 microns; for the neutral B meson (Bd), 446+-15+-8 microns. In both measurements, the first error is statistical and the second is systematic. The ratio between Bu and Bd meson lifetimes is found to be 1.119 +- 0.046(stat) +- 0.014(syst).