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Ultramafic rocks – that are usually located deep below the Earth's surface – are occasionally exhumed by the motion of tectonic plates. The massive chemical disequilibrium that exists between these exposed rocks and the surface waters and atmosphere leads to geologically rapid reactions that consume water and CO₂, binding them to form secondary hydrated/carbonated solid minerals that are found extensively in continental exposures (ophiolites) and at the seafloor near mid-ocean ridges. Pervasive fracturing and faulting in oceanic lithosphere generates pathways for fluids to access and react with rocks that are in some cases located down to depths of tens of kilometers. Over time, the large volumes of fluids and volatiles that are bound up in crustal and upper mantle rocks via such reactions are eventually subducted to extreme depths where subsequent fluid release can trigger melting, arc volcanism and seismic activity. In addition to their geophysical importance, these reactions are also considered to be critical for the survival of organisms in deep sea hydrothermal systems, and a potential source in the origin of life hypothesis. The natural transfer of atmospheric CO₂ to stable, solid carbonate minerals has, in recent years, motivated a large research effort towards investigating its potential as a large-scale carbon sequestration alternative. Understanding the geophysical impact and environmental potential of these reactions and their related processes requires knowledge of their basic physical and chemical behavior. Because of the difficulties of observing these processes in real-time, either experimentally or in the field, there has been a heavy reliance on hypothetical arguments that have been driven by observations in natural rocks. The observations paint a very complex picture – involving an interplay between reaction, fluid flow and fracturing – that is not easily explained by simple model descriptions. Although there has been increasing interest in modeling this class of problems in recent years, to date there remains a considerable gap between the theory and computational framework that is required for a consistent model description. A major theme in said models is their omission of poro-mechanical effects and complications arising from clogging of pore space with precipitating minerals. Both of these are necessary ingredients for a consistent model; however, they require a more complex description that is based on coupled multiphase continuum mechanics, reactive transport, and potentially brittle failure. Each of these components is a technical challenge in its own right, requiring development of novel theory and computation that integrates them in a suitable manner. The overall goals and themes of this thesis are aimed at closing this gap. To this end, I develop a modeling framework and computational tools that are capable of describing reactive flow in brittle media, with a specific focus on fluid-mineral reactions in near-surface ultramafic rock environments. The exposition of this framework is split into 3 separate chapters that build on one other in increments of complexity. Specifically, Chapter 1 presents a poromechanics-based description of coupled fluid flow, mass transfer and solid deformation for a simplified hydration reaction. This model is extended in Chapter 2 to incorporate cracking by adopting modern developments in computational fracture mechanics. Finally, in Chapter 3 I extend the set of reactions to support mixed H₂O-CO₂ fluids by leveraging recently developed tools in computational thermodynamics. Along the way I present a number of numerical model simulations that develop intuition and draw comparisons with natural observations, whilst remaining mindful of its limitations and areas for improvement. Overall, this work represents progress towards better understanding of physical and chemical feedbacks of reactive-brittle processes in the Earth's near-surface and the potential for large-scale carbon sequestration.

One major source of uncertainty in current climate projections is the effect of clouds on the Earth’s climate system due to a direct influence on the radiative energy budget as well as through complex feedback mechanisms. The radiative properties of clouds are governed by their microphysical properties, e.g. the thermodynamic phase. However, the interactions of cloud and aerosol particles leading to complex vertical structures of the thermodynamic phase and their influence on the optical properties of clouds are not yet fully understood. Therefore, measurements with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) are utilized during the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) campaign in the Asian monsoon to detect cloud thermodynamic phase in the terrestrial infrared wavelength range for cloud-side observations. / Der Einfluss von Wolken auf das Klimasystem der Erde bildet einen großen Unsicherheitsfaktor in aktuellen Klimaprojektionen durch einen direkten Effekt auf den Strahlungshaushalt sowie über komplexe Feedbackmechanismen. Die Streueigenschaften von Wolken werden durch deren mikrophysikalische Eigenschaften (z.B. die thermodynamische Phase) bestimmt. Allerdings sind die Wechselwirkungen zwischen Wolken- und Aerosolpartikeln, welche zu komplexen vertikalen Strukturen der thermodynamischen Phase führen und damit die optischen Eigenschaften derWolke beeinflussen, noch nicht endgültig verstanden. Deshalb werden in dieser Studie Messungen mit dem Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) während der Messkampagne StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) in der asiatischen Monsunregion verwendet, um die thermodynamische Phase von Wolken aus Wolkenseitenbeobachtungen im terrestrischen infraroten Wellenlängenbereich abzuleiten.

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Cell membrane potential and inorganic ion distributions are currently viewed from a kinetic electric paradigm, which ignores thermodynamics. The resting membrane potential is viewed as a diffusion potential. The 9 major inorganic ions found in blood plasma (Ca2+, Na+, Mg2+, K+, H+, Cl-, HCO3-, H2PO4-, and HPO42-) are distributed unequally across the plasma membrane. This unequal distribution requires the energy of ATP hydrolysis through the action of the Na+-K+ ATPase. The cell resting membrane potential in each of 3 different tissues with widely different resting membrane potentials has been shown to be equal to the Nernst equilibrium potential of the most permeant inorganic ion. The energy of the measured distribution of the 9 major inorganic ions between extra- and intracellular phases was essentially equal to the independently measured energy of ATP hydrolysis, showing that the distribution of these 9 major ions was in near-equilibrium with the ΔG' of ATP. Therefore, thermodynamics does appear to play an essential role in the determination of the cell resting membrane potential and the inorganic ion distribution across the plasma membrane.-Veech, R. L., King, M. T., Pawlosky, R., Bradshaw, P. C., Curtis, W. Relationship between inorganic ion distribution, resting membrane potential, and the ΔG' of ATP hydrolysis: a new paradigm.

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Avec les progrès de la technologie, il est désormais devenu possible de manipuler des faibles quantités d’objets nanométriques, voire des objets uniques. Observer une réaction chimique de quelques centaines de molécules sur des catalyseurs, étudier le travail exercé lors du déploiement d’un brin d’ADN unique ou mesurer la chaleur émise par un unique électron dans un circuit électrique constituent aujourd’hui des actes expérimentaux courants. Cependant, à cette échelle, le caractère aléatoire des processus physiques étudiés se fait plus fortement ressentir. Développer une théorie thermodynamique à ces échelles nécessite d'y inclure de manière exhaustive ces fluctuations.Ces préoccupations et les résultats expérimentaux et théoriques associés ont mené à l’émergence de ce que l’on appelle aujourd’hui la thermodynamique stochastique. Cette thèse se propose de développer une approche originale à la thermodynamique stochastique, basée sur une extension de l'hypothèse d'équilibre local aux variables fluctuantes d'un système. Cette théorie offre de nouvelles définitions des grandeurs thermodynamiques stochastiques, dont l'évolution est donnée par des équations différentielles stochastiques (EDS).Nous avons choisi d'étudier cette théorie à travers des modèles simplifiés de phénomènes physiques variés; transport (diffusif) de chaleur ou de masse, transport couplé (comme la thermodiffusion), ainsi que des modèles de réactions chimiques linéaires et non-linéaires. A travers ces exemples, nous avons proposé des versions stochastiques de plusieurs grandeurs thermodynamiques d'intérêt. Une large part de cette thèse est dévolue à l'entropie et aux différents termes apparaissant dans son bilan (flux d'entropie, production d'entropie ou dissipation). D'autres exemples incluent l'énergie libre d'Helmholtz, la production d'entropie d'excès, ou encore les efficacités thermodynamiques dans le transport couplé.A l'aide de cette théorie, nous avons étudié les propriétés statistiques de ces différentes grandeurs, et plus particulièrement l'effet des contraintes thermodynamiques ainsi que les propriétés cinétiques du modèle sur celles-là. Dans un premier temps, nous montrons comment l'état thermodynamique d'un système (à l' équilibre ou hors d'équilibre) contraint la forme de la distribution de la production d'entropie. Au-delà de la production d'entropie, cette contrainte apparaît également pour d'autres quantités, comme l'énergie libre d'Helmholtz ou la production d'entropie d'excès. Nous montrons ensuite comment des paramètres de contrôle extérieurs peuvent induire des bimodalités dans les distributions d'efficacités stochastiques.Les non-linéarités de la cinétique peuvent également se répercuter sur la thermodynamique stochastique. En utilisant un modèle non-linéaire de réaction chimique, le modèle de Schlögl, nous avons calculé la dissipation moyenne, non-nulle, engendrée par les fluctuations du système. Les non-linéarités offrent aussi la possibilité de produire des bifurcations dans le système. Les différentes propriétés statistiques (moments et distributions) de la production d'entropie ont été étudiées à différents points avant, pendant et après la bifurcation dans le modèle de Schlögl.Ces nombreuses propriétés ont été étudiées via des développements analytiques supportés par des simulations numériques des EDS du système. Nous avons ainsi pu montrer la fine connexion existant entre les équations cinétiques du système, les contraintes thermodynamiques et les propriétés statistiques des fluctuations de différentes grandeurs thermodynamiques stochastiques. / Over the last decades, nanotechnology has experienced great steps forwards, opening new ways to manipulate micro- and nanosystems. These advances motivated the development of a thermodynamic theory for such systems, taking fully into account the unavoidable fluctuations appearing at that scale. This ultimately leads to an ensemble of experimental and theoretical results forming the emergent field of stochastic thermodynamics. In this thesis, we propose an original theoretical approach to stochastic thermodynamics, based on the extension of the local equilibrium hypothesis (LEH) to fluctuating variables in small systems. The approach provides new definitions of stochastic thermodynamic quantities, whose evolution is given by stochastic differential equations (SDEs).We applied this new formalism to a diverse range of systems: heat or mass diffusive transport, coupled transport phenomena (thermodiffusion), and linear or non-linear chemical systems. In each model, we used our theory to define key stochastic thermodynamic quantities. A great emphasis has been put on entropy and the different contributions to its evolution (entropy flux and entropy production) throughout this thesis. Other examples include also the stochastic Helmholtz energy, stochastic excess entropy production and stochastic efficiencies in coupled transport. We investigated how the statistical properties of these quantities are affected by external thermodynamic constraints and by the kinetics of the system. We first studied how the thermodynamic state of the system (equilibrium \textit{vs.} non-equilibrium) strongly impacts the distribution of entropy production. We then extended those findings to other related quantities, such as the Helmholtz free energy and excess entropy production. We also analysed how some external control parameters could lead to bimodality in stochastic efficiencies distributions.In addition, non-linearities affect stochastic thermodynamics quantities in different ways. Using the example of the Schlögl chemical model, we computed the average dissipation of the fluctuations in a non-linear system. Such systems can also undergo a bifurcation, and we studied how the moments and the distribution of entropy production change while crossing the critical point.All these properties were investigated with theoretical analyses and supported by numerical simulations of the SDEs describing the system. It allows us to show that properties of the evolution equations and external constraints could strongly reflect in the statistical properties of stochastic thermodynamic quantities. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Zinc is one of the essential elements required for the normal growth plants. The total amount of zinc commonly occurring in soils is usually many times greater than that necessary to supply the needs of actively growing plants. The ability of the soil to "fix" zinc in form unavailable for plant use, however, has made the zinc deficiency disease an important plant nutrition problem in the major fruit and nut growing regions of the West. Fixation mechanisms which have been postulated as contributing to zinc deficiency include organic complexes, precipitation of insoluble inorganic salts, and strong zinc-clay interactions. It may be possible that in certain soils naturally occurring soil minerals, other than the clay minerals, may also exert an influence on the capacity of the soil to retain zinc. The accumulation of lime minerals is a distinguishing profile characteristic of soils in arid and semi-arid region and semi-arid regions. These minerals include: calcite (CaCO3), dolomite (CaMg(CO3)2), and magnesite (MgCO3). Despite the widespread occurrence of these minerals in the soil system, relatively few data exist which specifically isolate the interaction between cations in solution and the solid phase of the above-named lime minerals.

La tâche de répondre à une demande croissante pour une meilleure qualité de l'expérience utilisateur dans les communications sans fil, est contestée par la quantité d'énergie consommée par les technologies concernées et les méthodes employées. Sans surprise, le problème de la réduction de la consommation d'énergie doit être abordé à diverses couches de l'architecture de réseau et de diverses directions. Cette thèse traite de certains aspects cruciaux de la couche physique de l'architecture de réseau sans fil afin de trouver des solutions efficaces d'énergie. Dans la première partie de cette thèse, nous explorons l'idée de l'efficacité énergétique à un niveau fondamental. A commencer par répondre aux questions telles que: - Qu'est-ce que la forme physique d'information ?, nous construisons un dispositif de communication simple afin d'isoler certaines étapes clés dans le processus physique de la communication et nous dire comment elles affectent l'efficacité énergétique d'une communication système. Dans la deuxième partie, nous utilisons des outils de la géométrie stochastique pour modéliser théoriquement réseaux cellulaires afin d'analyser l'efficacité énergétique du système. L'exploitation de la traçabilité d'une telle modélisation mathématique, nous explorons les conditions dans lesquelles la consommation d'énergie peut être réduite. En outre, dans cette partie, nous introduisons le concept de la mise en cache des données des utilisateurs à la périphérie du réseau (à savoir le final ac BS qui est en contact avec l'utilisateur) et de montrer quantitativement comment la mise en cache peut aider à améliorer l'efficacité énergétique d'un cellulaire réseau. Nous tenons également à ce traitement à un ac Hetnet scénario (à savoir quand il y a plus d'un type de glspl déployé BS) et étudions divers indicateurs de performance clés. Nous explorons également les conditions où l'efficacité énergétique d'un tel système peut être améliorée. Les résultats de thèse fournissent quelques idées clés pour améliorer l'efficacité énergétique dans un réseau cellulaire sans fil contribuant ainsi à l'avancement vers la prochaine génération (5 G) des réseaux cellulaires. / The task of meeting an ever growing demand for better quality of user experience in wireless communications, is challenged by the amount of energy consumed by the technologies involved and the methods employed. Not surprisingly, the problem of reducing energy consumption needs to be addressed at various layers of the network architecture and from various directions. This thesis addresses some crucial aspects of the physical layer of wireless network architecture in order to find energy efficient solutions.In the first part of this thesis, we explore the idea of energy efficiency at a fundamental level. Starting with answering questions such as - emph{What is the physical form of `information'?}, we build a simple communication device in order to isolate certain key steps in the physical process of communication and we comment on how these affect the energy efficiency of a communication system.In the second part, we use tools from stochastic geometry to theoretically model cellular networks so as to analyze the energy efficiency of the system. Exploiting the tractability of such a mathematical modeling, we explore the conditions under which the consumption of energy can be reduced. Further in this part, we introduce the concept of caching users' data at the edge of the network (namely the final ac{BS} that is contact with the user) and show quantitatively how caching can help improve the energy efficiency of a cellular network. We also extend this treatment to a ac{HetNet} scenario (namely when there are more than one type of glspl{BS} deployed) and study various key performance metrics. We also explore the conditions where energy efficiency of such a system can be improved.The results in thesis provide some key ideas to improve energy efficiency in a wireless cellular network thereby contributing to the advancement towards the next generation (5G) cellular networks.

Liquefied natural gas (LNG) cold utilization in small scale regasification stations is a novel topic in the industry, while such systems have been proven feasible in large scale LNG facilities. Cold recovery and utilization in LNG regasification facilities would increase the thermodynamic efficiency and reduce cold pollution. The aim of the study is to analyze the possibility to apply industry-proven thermodynamic cycles in small scale satellite regasification stations for electricity production, taking the characteristics of a real-world regasification station project in Druskininkai, Lithuania for which useful cold utilization is not currently planned. Direct Expansion (DE) and Rankine (ORC) Cycles are analyzed together with cascading using Aspen Hysys software to find the optimal solution considering thermal and exergy efficiency as well as the payback period. Thermoeconomically feasible retrofit solutions of approximately 13% thermal efficiency and approximately 17% exergy efficiency showing payback periods of 5 to 10 years and 3.3 to 6 thousand euro additional capital expenditure (CAPEX) per net kW of power production are found. Increase in complexity of thermodynamic cycles is directly proportional to both increased thermodynamic efficiencies and capital costs and the study proves that there is a limit at which increase in thermodynamic efficiency of a cycle by cascading becomes economically infeasible. Future work is suggested to improve the accuracy of the results by rigorous design to evaluate pressure drops as well as improvements in economic analysis by utilizing the discounted cash flow methodology. Sensitivity analysis of LNG physical and chemical conditions as well as ambient air could be performed whereas changes in working fluid and better engineering of the part related to intial heat exchange could improve thermodynamic efficiencies. Alternative solutions with a higher temperature heat source are also suggested.