Biogeochemical reactions and vadose zone transport, in particular gas phase transport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion. Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbon dioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH4 in the methanogenic zone and oxidation of CH4 in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance.

Brownian dynamics (BD) simulation method has been widely used for studying problems in dispersed systems, such as polymer solutions, colloidal suspensions and more recently, complex (dusty) plasmas. The main problem addressed with this simulation technique is that of time scale separation, which occurs when one form of motion in the system is much faster than the other. This can be a serious problem in Molecular dynamics (MD) simulation where very short time steps are needed to handle the fast motions and thus, requiring very long time runs for the proper evolution of slower modes making the simulation very expensive. More importantly, the fast motions may not be of much interest within themselves, as will be the case in a dusty plasma. The motion of neutral atoms or molecules comprising the plasma occurs at a very fast time scale with respect to the motion of dust particles, and is usually of very little interest, though a large number of such neutrals are present. In such cases, an approximate method is usually adopted, whereby the neutral particles are omitted from the simulation and their effect upon the dynamics of dust particles modeled by a combination of random forces and frictional terms. This leads to a recasting of the Newton's Equation of motion solved in MD, to a Langevin equation, solved in BD. Adopting this approach, we simulate a system of charged dust particles interacting via Yukawa potential in a 2-Dimensional layer, and extract relevant equilibrium statistical features such as the radial distribution function, static structure factor and the low frequency dust wave modes. We then propose the use of a Generalized Hydrodynamical (GH) approach to provide a semi-analytical model for the dust collective modes, which not only provides us with good predictions of the wave dispersion but also provides reasonable estimates for wave-number dependent wave damping, both of which will be compared against the results obtained from BD simulation. Finally, through our simulations, we also observe the equilibrium configuration of dust particles in the presence of cold ions streaming perpendicularly into the 2-Dimensional layer of dust particles. This provides us with novel results in the regime of sub-sonic ion flow speeds.

Brownian dynamics (BD) simulation method has been widely used for studying problems in dispersed systems, such as polymer solutions, colloidal suspensions and more recently, complex (dusty) plasmas. The main problem addressed with this simulation technique is that of time scale separation, which occurs when one form of motion in the system is much faster than the other. This can be a serious problem in Molecular dynamics (MD) simulation where very short time steps are needed to handle the fast motions and thus, requiring very long time runs for the proper evolution of slower modes making the simulation very expensive. More importantly, the fast motions may not be of much interest within themselves, as will be the case in a dusty plasma. The motion of neutral atoms or molecules comprising the plasma occurs at a very fast time scale with respect to the motion of dust particles, and is usually of very little interest, though a large number of such neutrals are present. In such cases, an approximate method is usually adopted, whereby the neutral particles are omitted from the simulation and their effect upon the dynamics of dust particles modeled by a combination of random forces and frictional terms. This leads to a recasting of the Newton's Equation of motion solved in MD, to a Langevin equation, solved in BD. Adopting this approach, we simulate a system of charged dust particles interacting via Yukawa potential in a 2-Dimensional layer, and extract relevant equilibrium statistical features such as the radial distribution function, static structure factor and the low frequency dust wave modes. We then propose the use of a Generalized Hydrodynamical (GH) approach to provide a semi-analytical model for the dust collective modes, which not only provides us with good predictions of the wave dispersion but also provides reasonable estimates for wave-number dependent wave damping, both of which will be compared against the results obtained from BD simulation. Finally, through our simulations, we also observe the equilibrium configuration of dust particles in the presence of cold ions streaming perpendicularly into the 2-Dimensional layer of dust particles. This provides us with novel results in the regime of sub-sonic ion flow speeds.

Though British singer Dusty Springfield had a very prominent and successful career, she is often left out of the history books. Her North American legacy has been reduced to her album Dusty in Memphis, an inaccurate and incomplete representation of Dusty Springfield’s career. Many aspects of her career are largely ignored, for scholars put her sexuality, her ability to “sound black,” and the influence of black musicians at the forefront of Dusty Springfield scholarship. The purpose of this project is to highlight influential musicians, experiences, and talents which have been left out of Dusty Springfield studies. This thesis focuses on Dusty Springfield’s performance experiences, her songwriting abilities, her audience/performer dichotomy, and various people and styles that have influenced her persona. By examining the artists and experiences that influenced her career, this thesis explores the ways in which persona is constructed and how it functions in the pop music industry.

I report experimental and numerical studies of microparticle motion in a dusty plasma. These microparticles are negatively charged and are levitated in a plasma consisting of electrons, ions and neutral gas atoms. The microparticles repel each other, and are confined by the electric fields in the plasma. The neutral gas damps the microparticle motion, and also exerts random forces on them. I investigate and characterize microparticle motion. In order to do this, I study velocity distributions of microparticles and correlations of their motion. To perform such a study, I develop new experimental and analysis techniques. My thesis consists of four separate projects. In the first project, the battle between deterministic and random motion of microparticles is investigated. Two particle velocity distributions and correlations have previously studied only in theory. I performed an experiment with a very simple one dimensional (1D) system of two microparticles in a plasma. My study of velocity correlations involves just two microparticles which is the simplest system that allows interactions. A study of such a simple system provides insight into the motions of the microparticles. It allowed for the experimental measurement of two-particle distributions and correlations. For such a system, it is shown that the motion of the microparticles is dominated by deterministic or oscillatory effects. In the second project, two experiments with just two microparticles are performed to isolate the effects of ion wakes. The two experiments differ in the alignment of the two microparticles: they are aligned either perpendicular or parallel to the ion flow. To have different alignments, the sheath is shaped differently in the two experiments. I demonstrate that microparticle motion is more correlated when they are aligned along the ion flow, rather than perpendicular to the ion flow. In the third project, I develop a model with some key assumptions to compare with the experiments in the first two projects. My model includes all significant forces: gravity, electrical forces due to curved sheath and interparticle interaction, and gas forces. The model does not agree with both the experiments. In the last project, I study the non-Gaussian statistics by analyzing data for microparticle motion from an experiment performed under microgranity conditions. Microparticle motion is studied in a very thin region of microparticles in a three dimensional dust cloud. The microparticle velocity distributions exhibit non-Gaussian characteristics.

Statistical physics has been the foundation for much of our understanding about plasma physics. Often, plasma physics phenomena are explained using statistical physics principles and theories. Here, I reverse this paradigm to instead use plasma experiments to test statistical physics principles. In this thesis, I test statistical physics principles with an experimental dusty plasma, which is a four-component mixture of micron-sized ``dust'' particles, electrons, ions, and neutral gas molecules. When immersed in the plasma, the dust particles acquire large negative charges, since they accumulate more electrons than ions. Due to their large electric charges, the dust particles have interparticle potential energies that greatly exceed their kinetic energies, so that the collection of dust particles is considered to be a strongly coupled plasma. Like other strongly coupled plasma, the collection of dust particles can exhibit solid-like or liquid-like behavior. A key advantage offered by dusty plasma experiments is the ability to track the motion of individual dust particles. Dust particles are sufficiently large to allow for direct imaging using a video camera, so that time series data can be obtained for particle positions and velocities. These particle-level data provide a richer description of the dynamics and structure than can be obtained for most other strongly coupled plasmas, simple liquids, or solid materials. In particular, the particle-level data of positions and velocities are often required inputs for testing statistical physics theories or principles. The dusty plasma data I analyze are from the experiment of Haralson~\textit{et al.} [1,2], where dust particles were electrically levitated in a single horizontal layer within a vacuum chamber. The collection of dust particles initially settled into a crystalline lattice with solid-like behavior. To reach a liquid-like state, or to drive a shear flow, dust particles were manipulated using the radiation pressure force of lasers. In this thesis, I test three different statistical physics principles using an experimental dusty plasma. First, I test the fluctuation theorem, which was first was presented in 1993 by Evans, Cohen, and Morriss [3]. The fluctuation theorem, which is one of the most important recent developments in statistical physics, quantifies the probability that the entropy production rate will temporarily fluctuate to negative values in ``violations'' of the second law of thermodynamics. The original formulation of the fluctuation theorem described the entropy production due to viscous heating in a shear flow; this version of the fluctuation theorem had never been experimentally demonstrated in a liquid of any kind. In Chapter 2, I provide the first such demonstration by showing that the entropy production rate in a liquid-like dusty plasma shear flow satisfies the fluctuation theorem. This result also serves as the first demonstration that a strongly coupled plasma obeys the fluctuation theorem. Second, I measure the Einstein frequency $\Omega_E$, which describes the stochastic process of collisions in a strongly coupled plasma, and I compare my measurement to predictions made in the literature that used simulation data. Often, for weakly coupled plasma, a collision frequency is obtained to provide a measure of the strength of particle-particle interactions. However, for strongly coupled plasma (and likewise for liquids and solids), a collision frequency is not well defined since collisions are multibody and occur continuously. Another quantity is needed to describe the strength of particle-particle interactions. I propose that the Einstein frequency $\Omega_E$, a concept more commonly used in solid physics, is better suited for describing particle-particle interactions in a strongly coupled plasma. In Chapter 3, I present and use a new method to obtain the Einstein frequency of a 2D dusty plasma in both a liquid-like state and a crystalline state. My measurement of the Einstein frequency, which serves as a proxy for a collision frequency, is consistent with simulation predictions in the literature. Third, I present particle-coordination survival functions, which provide a richer description of microscopic dynamics in a liquid than the commonly used relaxation time. Relaxation times have been used, for example the Maxwell relaxation time, to describe the characteristic time scale for the crossover between elastic and viscous behavior in viscoelastic liquids. However, relaxation times are single-value measures that cannot fully describe the complexity of a liquid. In Chapter 4, using a survival function that retains temporal information about the local structural in a liquid, I discover that the microscopic arrangements in a liquid-like 2D dusty plasma have multiple time scales. Unexpectedly, non-defects have two time scales, while defects have one. My survival functions are time-series graphs of the probability that a particle's number of nearest neighbors, i.e., its coordination, remains the same. The two time scales for non-defects are revealed by an elbow in their survival-function curve. As a spinoff with a considerable amount of importance, I performed the simplest fluctuation theorem experiment to date, using an aerosol. An aerosol is simply a particle that is immersed in air. In Chapter 5, I show that the fluctuation theorem is applicable for an aerosol particle undergoing free-fall in air due to gravity. While the particle typically fell downwards, it is observed to occasionally fall upwards, against the force of gravity. For such upward displacements, the work done on the particle is negative, which is a temporary violation of the second law. I find that the probability of these temporarily violations obeys the work fluctuation theorem. This result also allowed an application: a novel diagnostic method to measure the mass of aerosol particles.

Thesis advisor: Gabor Kalman / Complex plasma systems have been studied for a long time. In this thesis we focus on a quasi-2D layer system. In fact, most experimental studies of complex plasmas are based on 2D systems, because it is easy to use camera to record the in-plane movement of particles. Unfortunately, due to the finite confining strength, the system is not a strictly 2D layer, it is a quasi-2D layer. We firstly studied the density profile of such a quasi-2D system by density functional theory(DFT). From the density profile research result, we found that the system can form a trilayer structure with proper parameters. Then we studied the dynamical properties of a trilayer system, and for simplicity, we only studied an ideal three layer model, both in liquid and lattice case. In lattice case, we firstly searched the stable lattice structure at different inter-layer distance. Then we used lattice sites summation to construct the dynamical matrix and solve the dispersion relation. For liquid case, we did the theoretical prediction for the collective dispersion by quasi localized charge approximation(QLCA), then we extracted the collective mode information from the molecular dynamics(MD) simulation. The QLCA and MD results were compared and discussed. The reason for the previous gap discrepancy problem is discovered. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

A côté des solides, des liquides et des gaz, le plasma est le quatrième état de la matière. Il est généré en ionisant un gaz. Dans l’univers, 99% de la matière est à l’état de plasma. L’émergence de plusieurs types de plasmas artificiels est due aux multiples et différentes applications, très intéressantes les unes que les autres, des plasmas dans des secteurs aussi variés que l’industrie, l’énergie, le biomédical et la science. Très souvent, des particules solides peuvent se former dans les plasmas. Ceci a tout particulièrement été observé dans ceux utilisés dans l’industrie. La compréhension des mécanismes de leur nucléation et croissance est d’une importance capitale en vue de trouver des solutions pour inhiber leur formation ou d’éviter qu’elles ne se déposent sur les surfaces en cours de traitement. L’objectif du travail de recherche entrant dans le cadre de cette thèse est l’étude de la formation de particules dans un plasma généré par décharge électrique continue. Il a été observé que ce phénomène dépend du flux de gaz neutre injecté dans l’enceinte du réacteur. Nous avons mis en évidence que la fréquence de formation est liée à ce paramètre. Les observations enregistrées à l’aide d’un spectroscope sont complétées et corrélées aux photographies obtenues par microscopie électronique à balayage. L’injection de particules dans le plasma plutôt que de procéder à les faire croitre présente certains avantages. On peut contrôler leur taille y compris du cas de mélanges de particules. On tout particulièrement injecter des particules ayant des tailles beaucoup plus importantes que celles que l’on forme sur des gammes de durées raisonnables des plasmas utilisés. Plusieurs expériences réalisées avec des particules injectées ont mis en exergue le caractère pluridisciplinaire du milieu plasma. Afin de comprendre les interactions mutuelles entre particules il est crucial de déterminer la charge portée par les particules. Plusieurs expériences réalisées au cours de cette thèse et présentées ici ont porté sur la détermination de ce paramètre fondamental. Dans ce cadre une série d’expérience a été réalisée à bord de la Station Spatiale Internationale (ISS) dans le but de déterminer la charge résiduelle des particules dans la phase de post-décharge. Dans la dernière partie, seront présentées et discutées des expériences portant sur l’observation de la rotation de clusters de particules soumis à un confinement supplémentaire. On montre que les particules tendent à former des alignements verticaux dus au faible champ qui se forme en aval de chaque particule. Enfin, les connaissances acquises sur les possibilités de moduler le potentiel d’interaction par l’intermédiaire d’un champ électrique seront discutées. Les résultats sont comparés aux prédictions des simulations. / Plasmas are next to the solid, liquid and gaseous phase the fourth state of matter. It is established by ionizing a gas. About 99% of the visible matter in the universe is in the state of plasma. The industrial, medical and scientific benefits of plasmas led to a variety of artificially produced plasmas. In plasmas dust particles can grow. Especially in industrial plasmas particle formation in the plasma gas phase is very common. The fundamental understanding of the growth is of vital importance in order to suppress undesired particle formation or to deposit particles and films in a certain region. In terms of this thesis the particle growth in a direct current (DC) discharge by using acetylene will be discussed. It has been observed that the particle growth depends on the neutral gas flow fed into the plasma chamber. Depending on the applied flow different growth frequencies and transport phenomena are shown. The observations recorded by a spectrometer will then be complimented by pictures from the particles taken by a scanning electron microscope. Introducing artificial particles into a plasma rather than growing them there yields several advantages. The particle sizes can be controlled, including the possibility of particle mixtures. Furthermore, particles with bigger diameter can be introduced than what can be grown on reasonable time scales in a plasma. Several possible experiments with injected particles underline the interdisciplinary character of the plasma environment. To understand the inter particle interactions the particle charge is a crucial parameter. In this thesis several experiments determining the particle charge will be discussed. In this frame the experiments on board of the International Space Station have been performed to measure the residual charge in the particle afterglow. In the last section experiments on particle cluster rotation as observed in an additional confinement will be discussed. It will be shown that the particles tend to form vertical strings due to the wake field that forms downstream of each particle. Finally the insight gained on the possibilities of tuning of the interaction potential by electric fields will be discussed. The results are then compared to the predictions of earlier simulations.

La métrologie des nanoparticules est devenue un enjeu scientifique et industriel capital pour pouvoir contrôler les caractéristiques des nano-objets (taille, densité, etc.) dans les procédés industriels tant pour la qualité des produits fabriqués que pour la protection des personnes et de l’environnement. Il est important, par conséquent, de trouver des méthodes de caractérisation innovantes et simples à mettre en oeuvre. L’objectif de ce travail de recherche fût de développer et d’optimiser des solutions pour caractériser des nanoparticules en voie sèche à l’aide d’un plasma (favorisant la désagglomération de l’échantillon de poudres à étudier). La présence de nanoparticules modifiant sensiblement les caractéristiques électriques du plasma, nous avons, dans un premier temps, développé un diagnostic basé sur la caractérisation électrique de la décharge et du plasma. Cette méthode nous renseignant sur la taille et la densité moyenne des nanoparticules. Puis, dans un second temps, nous avons développé un diagnostic basé sur la diffusion multi-angle de la lumière laser, nous permettant d’obtenir, là aussi, la taille et la densité moyenne des nanoparticules présent dans le plasma mais également leur indice de réfraction. Nous nous sommes, enfin, intéressés à la sédimentation assistée par plasma permettant d’obtenir la distribution en taille des nanoparticules, en l’optimisant. La corrélation de ces trois diagnostics nous donne, donc, un diagnostic efficace et fiable permettant la caractérisation en taille, en densité et en propriétés optiques des nanoparticules piégées dans le plasma. / Dust nanoparticles metrology has become a major scientific and industrial issue in order to control the characteristics of nano-objects (size, density, etc.). For industrial interests it concerns processes control and monitoring, manufactured products quality, human being and environment protection. It is therefore, crucial to find innovative methods of characterization and easy to implement and to handle. The objective of this research program was to develop and optimize solutions for characterizing nanoparticles in dry process and environment using a plasma (promoting disagglomeration of the studied powders). The presence of nanoparticles substantially altering the electrical characteristics of the plasma, we have, at first, developed a diagnostic based on the electrical characteristics of the discharge and the plasma. This method allows the determination the average nanoparticles size and concentration trapped in the plasma gas phase. Then, in a second step, we developed a diagnostic based on multi-angle laser light scattering, allowing us to get the size and the average density of the nanoparticles in the plasma, but also their refractive index. We finally focused our interest on the optimization of the plasma-assisted sedimentation of nanoparticles to obtain their size distribution especially for particles having sizes below 10 nm. The correlation of these three diagnostics gives us, so an efficient and reliable diagnostic for the global characterization in terms of size, density and optical properties of nanoparticles trapped in the plasma.

A dusty plasma is a mixture of electrons, ions, neutral gas atoms, and small particles of solid matter (dust). In a dusty plasma produced in the laboratory, dust particles gain a large electric charge from the other charged species, so that their interparticle interactions can be very strong. Frequently, the average interparticle potential energy is higher than the thermal kinetic energy of the dust particles, and in this case, they constitute a strongly coupled plasma. As with all strongly coupled plasmas, the dust particles can behave like typical solids or liquids. In this thesis, I report the results of dusty plasma experiments that are focused on the behavior of liquids. I use a so-called two-dimensional (2D) dusty plasma that consists of only a single horizontal layer of dust particles. Tracking each particle with video microscopy and image analysis methods allows the calculation of important liquid properties, like the viscosity coefficient. In Chapter 2, I describe an improved laser heating method for producing liquid-like conditions in a 2D dusty plasma. Two laser beams are scanned across the dust layer in a new pattern to increase the kinetic energy of the particles and melt the ground state crystalline lattice. The new scanning pattern improves the randomness of the resulting particle motion so that it more closely resembles that of a liquid in a thermal equilibrium. In Chapter 3, I report a viscosity measurement in a dusty plasma that is unaffected by the complicating effects of temperature nonuniformities and shear thinning. This measurement is enabled by an addition to my experimental apparatus that I also detail here. I find the viscosity to be significantly higher than in previous measurements, which I attribute to the avoidance of shear thinning. In Chapter 4, I present measurements of viscosity using the Green-Kubo method, and compare the results to those of my previous measurement. I find that the two methods yield viscosity values that differ by about 60%, over the entire temperature range attained in the experiment. Possible sources of this difference are evaluated. Finally, in Chapter 5, I report the first experimental confirmation of a theoretical expression describing the decay of time autocorrelation functions. This theoretical expression fits experimentally calculated autocorrelation functions within error bars, especially at short times when a simple exponential decay fails. I also propose an intuitive description wherein an observed transition in the autocorrelation function is due to the onset of collisional scattering.