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Brutzer, Hergen, Evgeni Sperling, Katrin Günther, Jasmina Dikic, Friedrich Schwarz, Daniel Klaue, Frank Cichos, Michael Mertig, and Ralf Seidel. "DNA under confinement and the use of DNA as confinement." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198891.
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In living systems DNA is subjected to considerable confinement but the molecule acts itself also as a confinement mechanism for cellular structures. Here we present investigations that study DNA under the confinement of supercoiling and within nanofluidic channels. Furthermore, we use DNA to confine the motion of microscopic and nanoscopic objects. In particular, we show how the motion dynamics of DNA-attached magnetic particles under external tension is affected and how DNA can confine the diffusion of enzymes to one dimension to follow the DNA contour.
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Brutzer, Hergen, Evgeni Sperling, Katrin Günther, Jasmina Dikic, Friedrich Schwarz, Daniel Klaue, Frank Cichos, Michael Mertig, and Ralf Seidel. "DNA under confinement and the use of DNA as confinement." Diffusion fundamentals 23 (2015) 2, S. 1-16, 2015. https://ul.qucosa.de/id/qucosa%3A14581.
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In living systems DNA is subjected to considerable confinement but the molecule acts itself also as a confinement mechanism for cellular structures. Here we present investigations that study DNA under the confinement of supercoiling and within nanofluidic channels. Furthermore, we use DNA to confine the motion of microscopic and nanoscopic objects. In particular, we show how the motion dynamics of DNA-attached magnetic particles under external tension is affected and how DNA can confine the diffusion of enzymes to one dimension to follow the DNA contour.
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Jamie, Elizabeth A. G. "Colloidal interfaces in confinement." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:26b47a79-7198-4983-9109-174ac2d3e01d.
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A fluid-fluid demixing colloid-polymer system provides us with an opportunity to study interfacial phenomena that cannot be observed in molecular systems due to unfavourable length and timescales. We develop such a system compatible with cells of varying dimensions, allowing us to investigate confined interfacial behaviour in real space using Confocal Scanning Laser Microscopy. The degree to which a system is affected by the sedimentation-diffusion gradient is dependent on the ratio of the suspension height to the gravitational length of the colloids. We illustrate that we may control the distance of our interface to the critical point by altering the suspension height, determining the importance of the gravitational field. Furthermore, the timescale on which the sedimentation- diffusion gradient is established is considerably longer than that of initial fluid-fluid demixing. We show that after the formation of the macroscopic interface, the system passes through a series of local mechanical equilibria on the way to achieving full equilibrium. Should the system be of sufficient height, it will pass through the gas-liquid critical point opening up new ways to study critical phenomena. The time and length scales of the fluid-fluid demixing of our system may be manipulated by altering the density and viscosity of our solvent. We exploit a slowed phase separation process to study the interplay between demixing and wetting phenomena of systems in the vicinity of a single wetting surface, and confined between two parallel plates. We demonstrate that the presence of a surface strongly affects the morphology of phase separation. The growth of the wetting layer is determined by the demixing regime of the system, and may be accelerated by hydrodynamics. The additional restriction by a second surface limits the lengthscale of coarsening domains and may further alter the mechanism of wetting layer growth.
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Morgan, Lee W. G. "Inertial confinement fusion neutronics." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/4427/.
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Since fire was first harnessed one million years ago, man's appetite for energy has become ever more insatiable. As we come close to the end of the fossil fuel era, new energy sources must be found as a matter of urgency. The utilisation of renewable energy sources, such as solar and wind, to completely satisfy the world energy demands would be an ideal scenario. However, the low energy density achieved by renewables as well as local opposition to the building of renewable energy infrastructure will ensure that renewable energy sources will continue to play a relatively minor role in the supply of electricity to the grid. Hence, high energy density energy sources must be employed in order to minimize local opposition to building new power stations, while sustaining the growing energy demands. Nuclear fission is a strong candidate for meeting these high energy demands due to its reliability and safety-driven new technologies. However, nuclear waste and accidents, such as Chernobyl and Fukushima, still remains a concern for many people; thus, other high energy density technologies must utilized in conjunction with fission and renewables in order to maintain energy stability without the loss of public approval. A technology which would revolutionise power production is that of nuclear fusion. However, technological complexities and limited funding ensure that commercial fusion power plants are still at least 30 years away. In essence, fusion is a process whereby two light nuclei combine to form a larger nucleus. In order to meet binding energy requirements in the newly formed nucleus, energy is released in the form of gammas or particle kinetic energy. The ejected particles have a large amount of kinetic energy, which can be used to heat water and drive electricity generating turbines as in a conventional fossil fuel power plant. The proposed fuels for all mainstream fusion reactor concepts are deuterium, which can be extracted from sea water, and tritium, which can be manufactured on the power plant site using relatively small amounts of lithium. In order to initiate and maintain fusion reactions, the fusion fuel must be heated to approximately 100 million degrees Celsius, resulting in the fuel being in the plasma state. Until fairly recently, the quest for safe and clean energy in the form of IFE has mainly been driven by areas of research relevant to formation and the ignition of the fuel. The understanding of this physics holds the key to creating a reactor that can efficiently and effectively ignite the fuel and release more energy than is supplied. However, in recent years, as these area of physics have become more understood and the reality of fusion gain actually occurring in the near future has become more apparent, the need to understand the physics and technology issues, which are peripheral to the reactor core, has become more important. An area of research which is gaining popularity is reactor blanket technology. The blanket is a component which surrounds the fusion core whose main functionality includes: Shielding fusion reactor staff from harmful neutron radiation; absorbing the energy of the 14.1MeV neutrons emitted from the D-T reaction and using this energy to convert water into steam and drive turbines; producing tritium, via the ^{\text{6}} Li(n,α)T reaction, in order to maintain reactor tritium self-sufficiency. In order to achieve this functionality, the neutron and materials physics must be understood in greater detail. The extremely high temperatures and neutron fluxes exert forces on the reactor walls which are much higher than experienced by fission reactors. It is vital that fusion energy is to produce energy with significantly less nuclear waste than is produced in the fission industry. To achieve this, blanket materials must be chosen such that they are adequately resilient to transmutation via neutron interactions. Thus, ensuring that the blanket materials, once decommissioned, will be classified as low or medium level nuclear waste and that the amount of such waste is minimal. In addition to environmental concerns, the transmutation of nuclides in the blanket, other than lithium, is not beneficial to the mechanical properties of the material which can reduce the blanket performance. A balance must be found between the addition of impurities, such as molybdenum and niobium in steels, to improve the mechanical properties of materials and the potential nuclear waste associated with the added chemicals. Thus, the study and control of nuclide transmutations within the blanket is crucial in determining the level of success of fusion reactors. The production of tritium is an important function of the blanket, as without this function the reactor core would have no fuel to burn. In order for a fusion reactor to become commercially viable, the blanket must create at least 10% more tritium than the reactor core is burning. This is due to tritium decay, small losses of tritium to the environment and tritium retention within structural materials. The vast majority of tritium produced in the blanket is a result of neutron absorption of lithium-6, which then decays to tritium and releases an alpha particle as a by-product. As the blanket ages, the amount of lithium in blanket decreases and so does the rate of tritium production, hence a solid blanket needs to be replaced every 3-6 years in order to maintain a large enough tritium breeding rate to sustain the reactor core. The concept of utilising the neutron energy, to create electricity, and a lithium blanket, to create tritium, has been studied extensively for magnetic confinement fusion (MCF) devices. Recent advancements in ICF research have lead to the realisation that ICF blanket technology (BT) must now be developed in order to ensure the technology is well understood by the time that commercial scale ignition has been achieved experimentally. However, ICFBT is generally less developed when compared to MCFBT; MCFBT research cannot be assumed to be directly applicable to ICFBT due to the vast difference in temporal distribution of neutron radiation emitted by ICF and MCF confinement regimes which results in different transmutation rates, damage and tritium breeding rates. This thesis includes an introduction to fusion and presents background theory of fusion blanket technology. The main features include the description and benchmarking of a fusion specific depletion code named FATI (Fusion Activation and Transport Interface), the development and evaluation of control theory applied to blanket impurity removal, the study of time-dependent depletion and the development of a fusion specific energy binning format for Monte-Carlo modelling. Both fission and fusion neutronic calculations rely heavily on Monte-carlo neutron transport codes, such as MCNP. The most important and frequently used functions used within these codes is the calculation of reaction rates. Calculating reaction rates can be accomplished via the point-wise estimator approach, which is accurate but very computationally expensive, or the multi-group method, which is fast but can lack accuracy if an inappropriate energy group structure is used to bin the reaction energies. Jean-Christophe Sublet, CCFE, was planning to develop a energy group structure, to be used in conjunction with Monte-carlo calculations of fusion devices. Thus, this work was completed via a collaboration between the author and Jean-Christophe. This study concluded that a 16,000 group structure was required in order to achieve < 5% uncertainty. This study could potentially have a large impact on the group structure used in fusion activation calculations. The most commonly used group structure used for fusion activation analysis is comprised of only 175 groups. Thus, the 175 group calculations could be significantly over estimating activation.
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Kärger, Jörg. "Molecular diffusion under confinement." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196367.
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With reference to molecular transport in manifold media of porous structure, a survey is given on the ample spectrum of diffusion phenomena under confinement. The presentation is mainly based on the evidence provided by pulsed field gradient NMR and by interference and IR microscopy. These "microscopic" techniques of diffusion measurement are particularly powerful for exploring the diverse features of
molecular propagation in complex systems. The presented data cover the peculiarities of molecular diffusion under the regime of "intracrystalline" zeolitic diffusion, refer to deviations from normal diffusion and deal with the practically particularly important case where the
overall diffusion process includes molecular propagation in the gas phase. In many cases, the reported experimental studies have been performed in immediate response to theoretical issues including single-file diffusion and sorption hysteresis. Simultaneously, they have given rise to new challenges for basic research correlating equilibrium and non-equilibrium phenomena of molecular propagation.
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Klop, Kira. "Colloidal rods in confinement." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:18e45dff-277f-481b-a7e5-b9aa9a5b7b88.
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We study colloidal rods in confinement and under flow on the single particle level using optical microscopy and laser scanning confocal microscopy. First, we investigate liquid crystals in confinement. A mathematical method for calculating distortion energies is developed and illustrated by applying it to both artificial data and experimental results. Next, we study an isotropic phase in strong confinement, and observe a capillary nematisation transition. This is the first observation of capillary nematisation in a colloidal liquid crystal. The results are compared to the Zwanzig model and a DFT model for semi-flexible rods, and we find good agreement with both. The DFT model, in which rod orientations are unrestricted and rod flexibility is taken into account, was found to have a better quantitative agreement with the experiments. In the second half of this thesis, we study single colloidal rods flowing in a plane Poiseuille flow. For the most simple case of non-magnetic Brownian rods in water, we observe aperiodic kayaking and xy-tumbling behaviour. The results are compared to Jeffery theory for non-Brownian rods in a simple shear flow and to multi-particle collision dynamics simulations. The experimental results were found to undergo the same type of behaviour as predicted by Jeffery's theory, but without periodicity, and particles were seen to switch from one type of behaviour to another. We find qualitative agreement between the experiment and simulations, which indicates that the presence of Brownian motion can explain the differences between theory and experiment. Following on, we investigate further deviations from Jeffery theory by studying the effect of an external magnetic field and of a non-Newtonian fluid on the orientational behaviour of rods. We find that a magnetic field shows somewhat similar behaviour as the kayaking and tumbling found in the non-magnetic system, but suppressed towards a plane perpendicular to the magnetic field. Rods flowing through a non-Newtonian fluid are found to be aligned in the direction of flow, and do not undergo any tumbling behaviour. The absence of tumbling can be explained by the depletion interaction between rods and the wall. It is unclear why the preferred orientation for rods is along the direction of flow.
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Kärger, Jörg. "Molecular diffusion under confinement." Diffusion fundamentals 2 (2005) 78, S. 1-24, 2005. https://ul.qucosa.de/id/qucosa%3A14413.
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With reference to molecular transport in manifold media of porous structure, a survey is given on the ample spectrum of diffusion phenomena under confinement. The presentation is mainly based on the evidence provided by pulsed field gradient NMR and by interference and IR microscopy. These "microscopic" techniques of diffusion measurement are particularly powerful for exploring the diverse features of
molecular propagation in complex systems. The presented data cover the peculiarities of molecular diffusion under the regime of "intracrystalline" zeolitic diffusion, refer to deviations from normal diffusion and deal with the practically particularly important case where the
overall diffusion process includes molecular propagation in the gas phase. In many cases, the reported experimental studies have been performed in immediate response to theoretical issues including single-file diffusion and sorption hysteresis. Simultaneously, they have given rise to new challenges for basic research correlating equilibrium and non-equilibrium phenomena of molecular propagation.
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Hardoüin, Jérôme. "Active Liquid Crystals in Confinement." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/668450.
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Living systems flow. What appears obvious from our daily observation of people, birds or insects remains surprisingly true at the smallest scale of life. Even at the earliest stages of embryonic development, the most elementary units of living systems, cell tissues, exhibit sustained currents. This perpetual movement is a signature of one of the fundamental properties of living systems - their ability to consume energy and transform it into directed motion.
Living systems also cooperate. In the same way as fish swimming collectively form large scale structures to fool their predators, cells self-organize in tissues of increasingly complex shapes. Pattern formation in biology involves many processes from chemical signalling to hydrodynamics. Yet, the striking similarity between the flows and shapes adopted by collective systems at all scales of life motivated the development of a unifying theory, containing the minimal physical processes involved. This framework is called active soft matter. It refers to any system composed of self-driven units that consume and convert energy into directed motion.
In some cases, the particles are so densely packed that they can be described as a continuous phase with long-range orientational order. This particular class has been termed active liquid crystals, of which cell tissues are the flagship illustration. These systems are characterized by a peculiar interplay between order and flows. The constant energy consumption drives them out of thermodynamic equilibrium. As a consequence, they are constantly deforming by sustained - and typically chaotic - flows. Reciprocally, the flow pattern directly depends on the local ordering of the particles.
Beyond the apparent chaos, this interplay between activity and order also confers to active liquid crystals a fascinating ability to adapt to the environments where they reside. In this work, we investigate the interplay between the geometry, the order and the flows of an active liquid crystal. Using novel micro-printing techniques, we develop versatile experimental setups that allow us to study how geometrical confinement tames the active flows and defect properties. We specifically investigate the effect of lateral confinement, topology, boundary roughness and Gaussian curvature.
We report dramatic transformations of the spatio-temporal dynamics of an in vitro microtuble-based active nematic system. The so-called active turbulence reorganizes into vortex lattices, directed, or defect-free unidirectional flows. Topological defects, which determine the active flow behavior, are created and annihilated on the boundaries rather than in the bulk, and acquire a strong orientational order in narrow channels. Their nucleation is governed by an instability whose wavelength is effectively screened by the lateral confinement. Their density, spatial distribution, orientation, and velocities evade most of the laws derived for unconfined active nematics. The careful description of the co-evolving order and flow patterns away from active turbulence enables us, to some extent, to disentangle the way they interact. In addition, we relate the transition to ordered regimes to generic descriptions of spatio- temporal chaos in out-of-equilibrium fluids, in an effort to understand the physics of these complex systems through universal laws.
Dramatic transitions also occur in the case of closed interfaces i.e surfaces with no boundaries.
In the last part of the manuscript, we report an original example of spinning active nematic droplets. We condense an active nematic layer on the outer surface of oil droplets with an ellipsoidal shape. In this configuration, topology and Gaussian curvature contribute to the emergence of a chiral symmetry breaking in the active deformations. This chirality is transferred to the solid-body dynamics of the ellipsoids, which rotate with a surprisingly constant pulsation. These results demonstrate how the non- equilibrium dynamics of active materials could be converted into macroscopic engines.
Our result not only improve the theoretical understanding of active liquid crystals. We also demonstrate promising strategies to control the spatial organization and the active flows through geometrical confinement, which could contribute to the design of autonomous microfluidic systems performing complex tasks without any external input.Els sistemes vius flueixen. El que sembla evident a partir de la nostra observació diària de persones, aus o insectes segueix sent sorprenentment cert a la menor escala de la vida. Aquest moviment perpetu és una signatura d’una de les propietats fonamentals dels sistemes vius: la seva capacitat de consumir energia i transformar-la en moviment dirigit. Els sistemes de vida també cooperen. La cridanera similitud entre els fluxos i les formes adoptades pels sistemes col·lectius a totes les escales de la vida va motivar el desenvolupament d’una teoria unificadora, que contenia els processos físics mínims implicats. Aquest marc s’anomena matèria tova activa. Es refereix a qualsevol sistema compost per unitats impulsades per si mateixes que consumeixen i converteixen l’energia en moviment dirigit. En aquest treball s’investiga la interacció entre la geometria, l’ordre i els fluxos d’un cristall líquid actiu. Amb noves tècniques de microimpressió, desenvolupem configuracions experimentals versàtils que ens permeten estudiar com la confinament geomètrica doma els fluxos actius i les propietats dels defectes. Investiguem específicament l'efecte del confinament lateral, la topologia, la rugositat del límit i la curvatura gaussiana. Es reporten transformacions dramàtiques de la dinàmica espaciotemporal d’un sistema nemàtic actiu basat en microtubs. Una acurada descripció de l'ordre i dels patrons de flux que evolucionen lluny de les turbulències actives ens permet, fins a cert punt, desvincular la forma en què interactuen. A més, relacionem la transició a règims ordenats a descripcions genèriques del caos espaciotemporal en fluids fora d'equilibri, en un esforç per comprendre la física d'aquests sistemes complexos mitjançant lleis universals. A la darrera part del manuscrit, es presenta un exemple original de gota de gotes nemàtiques actives. Aquests resultats demostren com la dinàmica de no equilibri dels materials actius es podia convertir en motors macroscòpics. El nostre resultat no només millora la comprensió teòrica dels cristalls líquids actius. També demostrem estratègies prometedores per controlar l’organització espacial i els fluxos actius mitjançant confinament geomètric, que podrien contribuir al disseny de sistemes microfluídics autònoms que realitzen tasques complexes sense cap entrada externa.
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Grira, Mongi Ben M. "Innovative approaches to column confinement." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4407.
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Reinforced concrete columns subjected to strong earthquakes may experience inelastic deformations. Inelastic deformability of these columns is of utmost importance for overall strength and stability of structures. Column deformability may be increased through confinement of core concrete. Conventional confinement reinforcement for square mid rectangular columns consist of closely spaced perimeter hoops, overlapping hoops, and crossties. The confinement steel requirements of current building codes often result in high volumetric ratios of transverse reinforcement which may lead to the congestion of column cages, which may result in concrete placement problems. An alternative to conventional transverse reinforcement is to use welded reinforcement steel grids (WRG) prefabricated to the required size and amount of steel, double headed studs (DHS) made of high-strength steel with conventional perimeter hoops, or Fiber Reinforced Plastic (FRP) grids. An experimental investigation was conducted to evaluate physical and mechanical properties of the new confinement reinforcement. Column tests were conducted to investigate structural performance of concrete columns reinforced with WRG, DHS, or FRP grids. Thirty-one large-scale columns with different volumetric ratios, spacings, and arrangements of confinement reinforcement were tested under simulated seismic loading. Test results indicate that the welded reinforcement grids can be used effectively as confinement reinforcement provided that the steel used has sufficient ductility and the welding process employed does not alter the strength and elongation characteristics of steel. The experimental program met these requirements and showed 7% to 10% strains prior to failure. Concrete columns confined with double head snub and conventional perimeter hoops also showed ductile behavior, developing lateral drifts of 4% to 6% prior to a significant loss in moment capacity, depending on the degree of confinement provided. The failure of these columns was characterized by the sudden opening of the 135-degree hooks of perimeter hoops followed by the crushing of core concrete and buckling of longitudinal bars. In addition, test results indicated also that concrete columns properly confined with fiber reinforced plastic grids showed ductile response and behaved as well as the companion columns confined with welded steel grids. The research program also included analysis of columns tested in the experimental phase. A rational analytical model was developed for buckling of longitudinal reinforcement in columns. The model was incorporated in the analytical procedure to compute the ultimate deformation capacity of concrete columns, many of which failed due to bar buckling. (Abstract shortened by UMI.)
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Grira, Mongi. "Innovative approaches to column confinement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0017/NQ45174.pdf.
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Burke, Trina. "Confinement in a Strange Hour." The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-05022008-091642/.
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Williams, Ian. "Colloids in optically defined confinement." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633436.
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Materials under spatial confinement are subject to volume exclusion conditions differing from those of a bulk material. On reducing a system to a lengthscale of the order of a few particles onc can observe new structures, modified dynamics and phase behaviour dramatically differing from that of the bulk system. Through understanding and controlling the boundaries confining a system one can alter the energy landscape it experiences. Three colloidal model systems are realised using holographic optical tweezers to investigate confinement phenomena in quasi two dimensions. ~Whereas the bulk of existing rescarch is concerned with confinement by hard boundaries, the systems presented here employ an adaptive, deformable wall or a soft confining potential. The first system, dubbed the colloidal corral consists of a circular boundary of optically trapped colloids confining additional colloids to its interior. Despite the fact that boundary curvature inhibits hexagonal ordering within this geometry, a bistability is observed between locally favoured hexagonal structures and globally preferential configurations mimicking the symmetry of the confinement. Such behaviour is not observed with hard wall confinement and is entirely due to the adaptivity of the boundary. Additionally, a novel technique for the mechanical measurement of pressure is presented, facilitated by the deformable wall. The second system introduces shear to the colloidal corral through rotation of the boundary and is known as the colloidal washing machine. The flow behaviour in this rotating confinement is investigated for a range of rotation rates. Rigid-body- like and shear melted regimes are identified and their structural behaviours characterised. The final system confines colloids within a circularly symmetric optical potential without a boundary. The result is the assembly of two-dimensional clusters, which are characterised for a range of potential widths and depths. The absence of a curved wall allows enhanced hexagonal ordering compared to the colloidal corral.
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Sullivan, Terena Patricia. "Interfacial reactions in nanoscale confinement." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614859.
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Gallagher, Sarah. "Microfluidic confinement of responsive systems." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648567.
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Dammone, Oliver James. "Confinement of colloidal liquid crystals." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:f33c315d-263b-47ad-ace8-1658c532a9c3.
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The behavior of colloidal liquid crystals in confinement is addressed on the single particle level using laser scanning confocal microscopy. We seek to disentangle how equilibrium director fields are controlled by the complex interplay between confinement, elasticity and surface anchoring. First, we study the nematic phase confined to wedge structured channels. Varying the wedge opening angle leads to a splay to bend transition mediated by a defect in the bulk of the wedge. Our results are in quantitative agreement with lattice Boltzmann simulations, and we show that comparison between experiments and simulation yields a new method to obtain the splay-to-bend elasticity ratios of colloidal and biological liquid crystals. Next, we extend our study of the wedge structured channels to the cholesteric phase, and measure a splay to twist transition with increasing wedge angle. We directly visualise the 3D nature of the twisted state, and explain how the transition is intricately determined by the anchoring strength and the splay, bend, and twist elasticities. Next, we investigate the effect of rectangular confinement on the nematic phase. The rectangle aspect ratio is systematically varied and we observe five distinct director fields. Comparison with computations of the Frank-Oseen energies yields the extrapolation length, which we find to be of the order of the rod length. Next, we confine the nematic phase to annular geometries of varying dimensions, and observe the novel director fields that are adopted. We approach a level of confinement which is of the order of the particle size. Interpreting our observations with Monte Carlo simulations, which take into account the finite size of the particles, illuminates the applicability of continuum theories down to microscopic lengthscales. We finish with a study of the isotropic-nematic interface in bulk and confinement. We show that parallel anchoring occurs at the interface, and measure the width of the interface to be of the order of the rod length.
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Calm, Yitzi M. "Optical Confinement in the Nanocoax:." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108652.
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Thesis advisor: Michael J. NaughtonThe nanoscale coaxial cable (nanocoax) has demonstrated sub-diffraction-limited optical confinement in the visible and the near infrared, with the theoretical potential for confinement to scales arbitrarily smaller than the free space wavelength. In the first part of this thesis, I define in clear terms what the diffraction limit is. The conventional resolution formulae used by many are generally only valid in the paraxial limit. I performed a parametric numerical study, employing techniques of Fourier optics, to resolve precisely what that limit should be for nonparaxial (i.e. wide angle) focusing of scalar spherical waves. I also present some novel analytical formulae born out of Debye’s approximation which explain the trends found in the numeric study. These new functional forms remain accurate under wide angle focusing and could materially improve the performance, for example, in high intensity focused ultrasound surgery by further concentrating the power distributed within the point spread function to suppress the side lobes. I also comment of some possible connections to the focusing of electromagnetic waves. In the second part of this thesis I report on a novel fabrication process which yields optically addressable, sub-micron scale, and high aspect ratio metal-insulator-metal nanocoaxes made by atomic layer deposition of Pt and Al2O3. I discuss the observation of optical transmission via the fundamental, TEM-like mode by excitation with a radially polarized optical vortex beam. Also, Laguerre-Gauss beams are shown to overlap well with cylindrical waveguide modes in the nanocoax. My experimental results are based on interrogation with a polarimetric imager and a near-field scanning optical microscope. Various optical apparatus I built during my studies are also reviewed. Numerical simulations were used with uniaxial symmetry to explore 3D adiabatic taper geometries much larger than the wavelength. Finally, I draw some conclusions by assessing the optical performance of the fabricated nanocoaxial structures, and by giving some insights into future directions of investigation
Thesis (PhD) — Boston College, 2019
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Tsegaye, Takele Dessie. "Confinement Mechanisms in Quantum Chromodynamics." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1051373650.
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Takele, Tsegaye. "Confinement mechanisms in quantum cherodynamics." Cincinnati, Ohio : University of Cincinnati, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1051373650.
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Jayaswal, Gaurav. "Spatial confinement of bacterial communities." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3423866.
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The subject of bacterial swimming has intrigued scientists for decades and recently there has been a growing interest in the study of collective swimming behavior of bacteria in a confined geometry. This thesis deals with a systematic experimental investigation of the density distribution of bacterial solutions of different concentration.
Two different types of bacteria, Pseudomonas and E. coli, have been used owing to their diverse propelling mechanism. E. coli behavior has been studied in detail, instead there are no reports in the literature regarding Pseudomonas, to the best of our knowledge.
The experimental set up consisted of two glass plates separated by spacers which define the confinement region. The separation distance ranged from 100 to 250 microns. The two plates were functionalized with bovine serum albumin (BSA) to avoid bacterial adhesion to the glass. The bacterial suspension was subjected to adjustment of buoyancy by addition of a density matching fluid like Percoll.
In agreement with previous studies, we found a significant enhancement of density close to the walls for both bacteria. This effect does not seem to be affected by either the separation distance or the solution concentration. These results were compared with those obtained by numerical simulations of self-propelled rod like particles which do not interact with each other apart from steric interactions. The preliminary data support the experimental outcome suggesting that steric interactions alone are sufficient to produce the observed enhancement effect.Il moto di batteri ha attratto gli scienziati da decenni e, ultimamente, c’è stato un crescente interesse nello studio del moto collettivo di batteri in geometrie confinate. Questa tesi descrive uno studio sperimentale della distribuzione di densità di soluzioni di batteri di concentrazione diversa confinate tra due pareti parallele. Si sono usati due tipi di batteri, Pseudomonas ed E. coli, che presentano diversi meccanismi di propulsione. Il comportamento di E. coli è stato studiato in dettaglio, invece non ci sono lavori in letteratura riguardanti Pseudomonas, per quello che sappiamo. L’apparato sperimentale consisteva di due vetrini separati da spaziatori che definivano la regione confinante. La distanza di separazione variava da 100 a 250 micron. I due vetrini erano funzionalizzati con albumina di serio bovino per evitare l’adesione dei batteri al vetro. Alla sospensione era stato aggiunto del percoll per aggiustare la spinta idrostatica agente sui batteri. In accordo con precedenti studi, abbiamo trovato un significativo aumento di densità in prossimità delle pareti per entrambi i tipi di batteri. Questo effetto non sembra essere influenzato né dalla distanza di separazione, né dalla concentrazione della soluzione. Questi risultati sono stati confrontati con quelli ottenuti da simulazioni numeriche di particelle auto-propellenti c he interagiscono solo mediante interazioni steriche. I dati preliminari supportano l’osservazione sperimentale suggerendo che le sole interazioni steriche sono sufficienti a produrre addensamento dei batteri alle pareti.
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Malik, Ashima. "Proteins in crowding and confinement." Thesis, IIT Delhi, 2016. http://eprint.iitd.ac.in:80//handle/2074/8190.
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Vettorazzo, Michele. "Topological approach to the confinement problem /." Zürich, 2004. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15755.
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Schäfke, Alexandra. "Yang-Mills-Theorie Confinement und Topologie /." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963198653.
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Boratynska, Susan. "Biological Confinement of Zebrafish Using RNAi." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32775.
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The increasing demand for fish in the food industry has resulted in the extensive overfishing of wild fisheries. In efforts to alleviate the demand from the food industry, genetically modified (GM) fish were developed possessing traits such as larger mass, faster growth, and increased resistance to disease. However, the greater fitness advantage of GM fish presents potential risks for wild type populations in the event of release or escape from a confined fish facility. In addition to physical barriers, it is critical to develop a genetic mechanism in order to ensure that the spread of GM transgene to the natural populations does not occur.
RNA interference (RNAi) is an endogenous mechanism used to regulate gene expression by destroying targeted mRNA molecules. Manipulation of this biological process has been successfully utilized to knockdown specific genes through the introduction of synthetic transgenes in organisms such as C. elegans, M. musculus, and D. melanogaster. Although the use of RNAi as a biological tool is still relatively new in zebrafish, recent work has explored elements of this mechanism allowing for greater knockdown efficiencies.
The deadend (dnd) gene is required for primordial germ cell (PGC) development and survival. Previous studies have shown that zebrafish dnd knockouts develop into sterile adults without disrupting somatic development. In efforts to induce sterility in zebrafish, short hairpin RNA (shRNA) constructs targeting dnd were designed to exploit the endogenous RNAi pathway. Upon qualitative analysis in transient and transgenic zebrafish subjected to the synthetic RNAi construct, a reduction in the germ cell population at early stages of development was observed. However, quantification of dnd mRNA in fish from the same time points did not show significant changes in expression levels compared to their wildtype counterparts. Adult fish subjected to the transgene construct produced viable gametes.
The use of RNAi as a tool for bioconfinement relies on sterility among all individuals subjected to the shRNA bearing transgene. Based on the results obtained, the verdict is still unclear as to whether shRNA is a viable mechanism for large scale bioconfinement.
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Dalnoki-Veress, Kari. "Confinement effects on thin polymer films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0011/NQ33298.pdf.
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Robinson, William Richard. "Spherical Microwave Confinement and Ball Lightning." NCSU, 2010. http://www.lib.ncsu.edu/theses/available/etd-03242010-110137/.
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This dissertation presents the results of research done on unconventional energy technologies from 1995 to 2009. The present civilization depends on an infrastructure that was constructed and is maintained almost entirely using concentrated fuels and ores, both of which will run out. Diffuse renewable energy sources rely on this same infrastructure, and hence face the same limitations. I first examined sonoluminescence directed toward fusion, but demonstrated theoretically that this is impossible. I next studied Low Energy Nuclear Reactions and developed methods for improving results, although these have not been implemented. In 2000 I began Spherical Microwave Confinement (SMC), which confines and heats plasma with microwaves in a spherical chamber. The reactor was designed and built to provide the data needed to investigate the possibility of achieving fusion conditions with microwave confinement. A second objective was to attempt to create ball lightning (BL). The reactor featured 20 magnetrons, which were driven by a capacitor bank and operated in a 0.2 s pulse mode at 2.45 GHz. These provided 20 kW to an icosahedral array of 20 antennas. Video of plasmas led to a redesign of the antennas to provide better coupling of the microwaves to the plasma. A second improvement was a grid at the base of the antennas, which provided corona electrons and an electric field to aid quick formation of plasmas. Although fusion conditions were never achieved and ball lightning not observed, experience gained from operating this basic, affordable system has been incorporated in a more sophisticated reactor design intended for future research. This would use magnets that were originally planned. The cusp geometry of the magnetic fields is suitable for electron cyclotron resonance in the same type of closed surface that in existing reactors has generated high-temperature plasmas. Should ball lightning be created, it could be a practical power source with nearly ideal characteristics that could solve many of our current energy-production problems.
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Santiso, Erik Emilio. "Effect of Confinement on Chemical Reactions." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-08102007-145433/.
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The goal of this project is to gain a fundamental understanding of the different factors that influence chemical reactions in confinement through the systematic study of simple model systems. For this purpose, we consider three different examples: (1) The rotational isomerization of small hydrocarbons in carbon nanopores, showing the impact of the steric hindrance imposed by the confining material on the reacting system; (2) The unimolecular decomposition of formaldehyde on carbon pores, as an example of the effect of physical interactions on a reaction?s mechanism and equilibrium; and (3) The thermal splitting of water over defective graphene and nanotube surfaces, showing how chemical interactions with a catalytic substrate can completely modify the chemical landscape and hence the equilibrium and dynamics of the system. Our main findings from these studies are: (1) In the molecular sieving limit, the steric hindrance imposed by the pore walls can cause dramatic changes in the potential energy surface of a reaction, with the rate varying as the double exponential of the pore dimensions; (2) Physical interactions with a catalytic support can alter both the thermodynamic properties of the confined molecules and the reaction dynamics, the latter being especially important in reactions with relatively low activation barriers; (3) Chemical modification of a carbon substrate can give rise to completely different reaction mechanisms, which could be exploited in the systematic molecular-level design of improved catalytic materials.
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Nduwimana, Alexis. "Confinement effect on semiconductor nanowires properties." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19865.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2008.Committee Chair: Chou, Mei-Yin; Committee Member: First,Phillip; Committee Member: Gao, Jianping; Committee Member: Landman, Uzi; Committee Member: wang, Xiao-Qian.
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Deng, Ying 1972. "Confinement of columns using headed bars." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31047.
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Eight full-scale columns were constructed and tested under monotonic axial compression loading to investigate the influence of headed bars on the confinement of the concrete. One column represented a column with no transverse reinforcement and another column had poor detailing and little confinement. A third column contained seismic hoops and crossties, which represented current detailing practice for significant confinement. A fourth column test investigated the response with the seismic crossties replaced by headed bars. Finally, two column specimens were constructed and tested with all of the transverse reinforcement provided by headed bars. These six specimens enabled an assessment of the effectiveness of headed bars in confining the concrete. It was found that the use of headed bars improved the confinement of the columns.Two additional specimens were constructed without any transverse reinforcement. These columns were later retrofitted, by drilling horizontal holes in the columns, adding special headed bars (one head fixed and one head threaded) and then filling the drilled holes with epoxy. These retrofitted specimens had two different spacings for the added headed bars. The improvement of the response with these added headed bars provided insight into the rehabilitation of older structures containing poorly detailed columns. All of the test specimens were instrumented to determine strain localization during failure and to monitor the strains in the longitudinal and transverse reinforcement.
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Holland, Kieran (Kieran Michael) 1972. "Confinement and deconfinement in gauge theories." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84766.
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Gupta, Malancha 1980. "Polymer and sphere diffusion in confinement." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28849.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2005.Includes bibliographical references (leaf 15).
We use video microscopy and particle tracking to study the diffusion of both colloidal spheres and polymers in slit microchannels. The molecules are allowed to sample the entire height of the microchannel. We find that the sphere data agrees well with a gap-averaged Oseen linear superposition approximation even at very high confinement whereas polymer chains at high confinement can not be modeled by this far field approach. We find that the polymer chain dynamics at high confinement can be explained well by a blob model scaling.
by Malancha Gupta.
S.M.
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Yap, Davin Synn Chi. "Energy confinement in imperfect periodic systems." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627606.
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Levitz, Pierre, Patrick Bonnaud, Pierre-Andre Cazade, Roland J. M. Pellenq, and Benoit Coasne. "Molecular intermittent dynamics in interfacial confinement." Diffusion fundamentals 16 (2011) 16, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13745.
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Ghasemi, Mohsen. "Evaporation of Water in Hydrophobic Confinement." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1503094472074141.
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Théodoly, Olivier. "Polyelectrolytes aux interfaces : adsorption et confinement." Paris 6, 1999. http://www.theses.fr/1999PA066632.
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Cette these traite des proprietes de solutions de polyelectrolytes aux interfaces. La premiere partie s'interesse a l'adsorption de polyelectrolytes (polystyrenes sulfonates statistiques a taux de charge compris entre 30% et 90%) pres de surfaces neutres et hydrophobes. L'etude de l'interface solution/air recoupe des mesures de balance de langmuir, d'ellipsometrie, et de reflectivite des rayons x. L'adsorption est toujours tres lente a cause d'un phenomene de barriere electrostatique. A basse force ionique, l'adsorption presente en outre un maximum avec le taux de charge, ce que nous expliquons par un effet de barriere conformationnelle : les molecules les plus hydrophobes sont effondrees en pelotes isolees et chargees qui sont repoussees par une interface neutre. Enfin, soumises a un rincage par de l'eau pure, les couches ne desorbent pas completement, ce qui montre l'existence de barrieres a la desorption. L'existence de ces differentes barrieres energetiques conduit a des phenomenes d'hysteresis et l'etat d'une surface dans une solution de pss depend fortement de son histoire. Parallelement, l'interface solide/liquide est etudiee par une technique nouvelle de reflectivite de rayons x de haute energie a travers l'eau, qui confirme la minceur systematique des couches adsorbees (20a). La deuxieme partie traite des proprietes des polyelectrolytes en milieu confine dans des films de savon. Avec un melange de tensioactif (c12e6) et de polyelectrolyte (pamps), optimise pour eliminer les interactions polymere/surface, les isothermes de pression de disjonction sont reversibles. Ils presentent des oscillations dont la periode varie avec la concentration en c 1 / 2 et correspond exactement a la distance de correlation en volume (mesuree par saxs). Nous montrons egalement que ce phenomene de structuration presente de fortes analogies avec celui de micelles de sds confinees.
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Ferdeghini, Filippo. "Liquides ioniques sous confinement nanométrique unidimensionnel." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066440/document.
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L'idée à la base de ce projet est de mettre à profit le confinement nanométrique unidimensionnel pour décupler la conduction ionique des électrolytes et donc la puissance des accumulateurs au lithium. Nous avons concentré nos efforts sur une classe particulière d'électrolytes qui, en raison de leurs stabilités physique et électrochimique, ont été identifiés comme prometteurs: les Liquides Ioniques (LI). Nous avons confiné les LI dans deux systèmes poreux présentant une topologie commune (pores cylindriques macroscopiquement orientés) mais aux propriétés physico-chimiques complémentaires: i) des alumines poreuses (AAO, interface hydrophile, diamètre des pores de 25 à 160 nm) et ii) des membranes de NanoTubes de Carbone (NTC, interface hydrophobe, diamètre des pores 4 nm).Nous avons développé un modèle microscopique multi-échelle original, prenant en compte la dynamique complexe des cations des LI: combinaison i) de la dynamique de réorientation rapide des chaînes latérales alkyle, ii) de la diffusion de la molécule au sein des agrégats nanométriques spontanément formés par les LI, puis iii) de la diffusion entre ces agrégats. Ce modèle reproduit de façon remarquablement robuste les données de diffusion quasi-élastique de neutrons sur une gamme étendue de vecteurs de diffusion (0,1 à 2,5 Å-1) et de temps (10-1 à 2.103 ps). A cette échelle locale, nous ne détectons pas d'influence du confinement sur la dynamique du LI confiné au sein des AAO et des CNT. Nous montrons cependant qu'à l'échelle microscopique (PFG-NMR) et macroscopique (spectroscopie d'impédance) le confinement des LI au sein des NTC permet d'obtenir un gain de conductivité d'un facteur 3. Un brevet est déposéThe idea behind this project is to exploit the 1D nanometric confinement in order to increase the electrolytes ionic conductivity and, thus, the power of the lithium accumulators. We have focus on a specific class of electrolytes, which, owing to their physical and electrochemical stabilities, have been identified as very promising: the Ionic Liquids (ILs). We have confined the ILs in porous systems having a common topology (cylindrical pores macroscopically oriented), but with complementary physico-chemical properties: i) the porous alumina (AAO, hydrophilic interface, pores diameter between 25 and 160 nm) and ii) Carbon NanoTubes based membranes (CNT, hydrophobic interface, pores diameter of 4 nm).We have developed an original microscopic multiscale model, taking into account the complex dynamics of ILs cations: combination of i) fast reorientation dynamics of side alkyl-chains, ii) molecule diffusion within nanometric aggregates spontaneously formed in the ILs and iii) diffusion between the aggregates. This model reproduces in a very robust way the quasi-elastic neutrons scattering data on an extent interval of wave vector (0.1 à 2.5 Å-1) and time (10-1 à 2.103 ps). At this local scale, we do not observe any influence due to the confinement on the dynamics of the ILs confined in the AAO and CNTs. We show however that at microscopic (PFG-NMR) and macroscopic (impedance spectroscopy) scale the ILs confinement within the NTCs allows to obtain a conductivity gain of factor 3. A patent is filed
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Levitz, Pierre, Patrick Bonnaud, Pierre-Andre Cazade, Roland J. M. Pellenq, and Benoit Coasne. "Molecular intermittent dynamics in interfacial confinement." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184681.
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Votroubek, George Robert. "Tomographically aided study of field reversed configuration plasma rotation and stability /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/10011.
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Ghiu, Camil-Daniel. "Pool Boiling from Enhanced Structures under Confinement." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16229.
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A study of pool boiling of a dielectric liquid (PF 5060) from single-layered enhanced structures was conducted. The parameters investigated were the heat flux, the width of the microchannels and the microchannel pitch. The boiling performance of the enhanced structures increases with increase in channel width and decrease in channel pitch. Simple single line curve fits are provided as a practical way of predicting the data over the entire nucleate boiling regime.
The influence of confinement on the thermal performance of the enhanced structures was also assessed. The main parameter investigated was the top space (0 mm { 13 mm). High-speed visualization was used as a tool . For the total confinement ( = 0 mm), the heat transfer performance of the enhanced structures was found to depend weakly on the channel width. For >0 mm, the enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. The maximum heat flux for a prescribed 85 oC surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime.
A semi-analytical predictive model applicable to pool boiling under confinement is developed. The model requires a limited number of empirical constants and is capable of predicting the experimental heat flux within 30%.
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Parrish, Kevin D. "Phonon Scattering and Confinement in Crystalline Films." Thesis, Carnegie Mellon University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10622930.
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The operating temperature of energy conversion and electronic devices affects their efficiency and efficacy. In many devices, however, the reference values of the thermal properties of the materials used are no longer applicable due to processing techniques performed. This leads to challenges in thermal management and thermal engineering that demand accurate predictive tools and high fidelity measurements. The thermal conductivity of strained, nanostructured, and ultra-thin dielectrics are predicted computationally using solutions to the Boltzmann transport equation. Experimental measurements of thermal diffusivity are performed using transient grating spectroscopy.
The thermal conductivities of argon, modeled using the Lennard-Jones potential, and silicon, modeled using density functional theory, are predicted under compressive and tensile strain from lattice dynamics calculations. The thermal conductivity of silicon is found to be invariant with compression, a result that is in disagreement with previous computational efforts. This difference is attributed to the more accurate force constants calculated from density functional theory. The invariance is found to be a result of competing effects of increased phonon group velocities and decreased phonon lifetimes, demonstrating how the anharmonic contribution of the atomic potential can scale differently than the harmonic contribution.
Using three Monte Carlo techniques, the phonon-boundary scattering and the subsequent thermal conductivity reduction are predicted for nanoporous silicon thin films. The Monte Carlo techniques used are free path sampling, isotropic ray-tracing, and a new technique, modal ray-tracing. The thermal conductivity predictions from all three techniques are observed to be comparable to previous experimental measurements on nanoporous silicon films. The phonon mean free paths predicted from isotropic ray-tracing, however, are unphysical as compared to those predicted by free path sampling. Removing the isotropic assumption, leading to the formulation of modal ray-tracing, corrects the mean free path distribution. The effect of phonon line-of-sight is investigated in nanoporous silicon films using free path sampling. When the line-of-sight is cut off there is a distinct change in thermal conductivity versus porosity. By analyzing the free paths of an obstructed phonon mode, it is concluded that the trend change is due to a hard upper limit on the free paths that can exist due to the nanopore geometry in the material.
The transient grating technique is an optical contact-less laser based experiment for measuring the in-plane thermal diffusivity of thin films and membranes. The theory of operation and physical setup of a transient grating experiment is detailed. The procedure for extracting the thermal diffusivity from the raw experimental signal is improved upon by removing arbitrary user choice in the fitting parameters used and constructing a parameterless error minimizing procedure.
The thermal conductivity of ultra-thin argon films modeled with the Lennard-Jones potential is calculated from both the Monte Carlo free path sampling technique and from explicit reduced dimensionality lattice dynamics calculations. In these ultra-thin films, the phonon properties are altered in more than a perturbative manner, referred to as the confinement regime. The free path sampling technique, which is a perturbative method, is compared to a reduced dimensionality lattice dynamics calculation where the entire film thickness is taken as the unit cell. Divergence in thermal conductivity magnitude and trend is found at few unit cell thick argon films. Although the phonon group velocities and lifetimes are affected, it is found that alterations to the phonon density of states are the primary cause of the deviation in thermal conductivity in the confinement regime.
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Kremer, Friedrich, Martin Treß, Emmanuel U. Mapesa, Wycliffe K. Kipnusu, and Wilhelm Kossack. "Glassy dynamics of polymers in geometrical confinement." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-182180.
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Homberger, Margaret Alissa. "Wrongful confinement and Victorian psychiatry, 1840-1880." Thesis, Queen Mary, University of London, 2001. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28851.
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Victorian society witnessed a transformation in the understanding and treatment of psychological disorders. The expansion of nosologies or classifications of lunacy was one measure hailed by psychological physicians as indicative of their mastery over madness. Yet between the 1840s and the 1870s the introduction of moral insanity and monomania to established classificatory systems undercut the medical authority of physicians and challenged their desired cultural stature as benevolent and authoritative agents of cure. Far from consolidating medical authority, these `partial' forms of lunacy (which were detected in the emotions rather than the intellect) paradoxically heightened anxiety about the ease with which eccentric or sane individuals could be wrongfully incarcerated in lunatic asylums. This dissertation examines the themes, motifs and defining issues of wrongful incarceration as they were discussed in Parliament, national and regional newspapers, medical and literary journals, and novels and short stories. Discussing in detail several infamous `cases' of wrongful confinement, it traces the ways in which anxieties were formulated, expressed and negotiated. The public outcry over cultural representations of wrongful confinement generated heated reactions from physicians and lunacy law reformers. The most contentious discussions centred on the manner in which notions of humanity and benevolence, and tyranny and liberty, were marshalled to influence public opinion. These debates represented not solely a legal conflict centring the claim to treatment and authority over the alleged lunatic, but more dramatically a battle for the public's good opinion. As important as medico-legal trials and their consequent rulings was the contested appropriateness of sentiment; this was manifested in words and images utilised to exacerbate or contain anxiety. The wrongful confinement controversy constitutes an important (though largely overlooked) episode in the history of English nineteenth-century psychiatry; formatively altering perceptions of the profession of mental science in the Victorian period.
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Schoch, Stefan. "Multi-phase detonations in elastic-plastic confinement." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608036.
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Otto, Oliver. "Single macromolecules under tension and in confinement." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610166.
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Brock, Elizabeth Martine Gerber. "The lateral confinement of microwave surface waves." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15097.
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Surface waves and their applications have been extensively studied by the photonics and radio engineering communities throughout the whole of the twentieth century. This thesis details briefly the history of both approaches and highlights their signi cance with regard to the subject of this thesis; laterally confining a surface wave in the microwave regime. Detailed within are the experimental, analytical and numerical methods used to ascertain what, if any, effect a change in the dimension of a guiding structure has on the dispersion of a mode supported by a metamaterial. The method of experimentally determining the dispersion of a microwave surface wave is discussed. The insensitivity of a mode supported on a one-dimensional corrugated array to the lateral width of the supporting array, even when the width is much less than the wavelength of radiation incident upon it, is investigated. Spatial dependent reduction of group velocity associated with a microwave surface wave is also detailed. Local electric-field and phase measurements are used to probe this condition. In particular, the measurement of phase associated with the supported microwave surface wave is shown to indicate the trapping location of a surface wave more accurately when compared to local electric-field measurement. The channelling of surface waves via the addition of dielectric overlayers to a metamaterial surface is investigated. By progressively narrowing the width of the channel, the interaction of the electric fields associated with the mode supported in the channel with the bordering dielectric overlayer increases. This investigation leads to a discussion of the electric field overlap between two regions of differing surface impedance.
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Demontis, Pierfranco, Federico G. Pazzona, and Giuseppe B. Suffritti. "Cellular automata modeling of diffusion under confinement." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193309.
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Zacharoudiou, Ioannis. "Viscous fingering and liquid crystals in confinement." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:09b37fb9-5a93-4ea2-8f4f-4e5e70c5fc07.
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This thesis focuses on two problems lying within the field of soft condensed matter: the viscous fingering or Saffman-Taylor instability and nematic liquid crystals in confinement. Whenever a low viscosity fluid displaces a high viscosity fluid in a porous medium, for example water pushing oil out of oil reservoirs, the interface between the two fluids is rendered unstable. Viscous fingers develop, grow and compete until a single finger spans all the way from inlet to outlet. Here, using a free energy lattice Boltzmann algorithm, we examine the Saffman-Taylor instability for two different wetting situations: (a) when neither of the two fluids wet the walls of the channel and (b) when the displacing fluids completely wets the walls. We demonstrate that curvature effects in the third dimension, which arise because of the wetting boundary conditions, can lead to a novel suppression of the instability. Recent experiments in microchannels using colloid-polymer mixtures support our findings. In the second part of the thesis we examine nematic liquid crystals confined in wedge-structured geometries. In these systems the final stable configuration of the liquid crystal system is controlled by the complex interplay between confinement, elasticity and surface anchoring. Varying the wedge opening angle this competition leads to a splay to bend transition mediated by a defect in the bulk of the wedge. Using a hybrid lattice Boltzmann algorithm we study the splay-bend transition and compare to recent experiments on {em fd} virus particles in microchannels. Our numerical results, in quantitative agreement with the experiments, enable us to predict the position of the defect as a function of opening angle, and elucidate its role in the change of director structure. This has relevance to novel energy saving, liquid crystal devices which rely on defect motion and pinning to create bistable director configurations.
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Petropoulos, Ilias. "Study of high-order vorticity confinement schemes." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0001/document.
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Les tourbillons sont des structures importantes pour une large gamme d'écoulements de fluides, notamment les sillages, l'interaction fluide-structure, les décollements de couche limite et la turbulence. Cependant, les méthodes numériques classiques n'arrivent généralement pas à donner une représentation précise des tourbillons. Ceci est principalement lié à la dissipation numérique des schémas qui, si elle n'est pas spécifiquement calibrée pour le calcul des écoulements tourbillonnaires, conduit à une diffusion artificielle très rapide des tourbillons dans les calculs. Parmi d'autres approches, la méthode "Vorticity Confinement" (VC) de J. Steinhoff permet de compenser la dissipation des schémas au sein des tourbillons en introduisant une anti-dissipation non-linéaire, mais elle n’est précise qu’au premier ordre. D’autre part, des progrès significatifs ont récemment été accomplis dans le développement de méthodes numériques d’ordre élevé. Celles-ci permettent de réduire ce problème de dissipation excessive, mais la diffusion des tourbillons reste importante pour de nombreuses applications. La présente étude vise à développer des extensions d’ordre élevé de la méthode VC pour réduire cette dissipation excessive des tourbillons, tout en préservant la précision d'ordre élevé des schémas. Tout d'abord, les schémas de confinement sont analysés dans le cas de l'équation de transport linéaire, à partir de discrétisations couplées et découplées en espace et en temps. Une analyse spectrale de ces schémas est effectuée analytiquement et numériquement en raison de leur caractère non linéaire. Elle montre des propriétés dispersives et dissipatives améliorées par rapport aux schémas linéaires de base à tous les ordres de précision. Dans un second temps, des schémas VC précis au troisième et cinquième ordre sont développés pour les équations de Navier-Stokes compressibles. Les termes correctifs restent conservatifs, invariants par rotation et indépendants du schéma de base, comme la formulation originale VC2. Les tests numériques valident l'ordre de précision et la capacité des extensions VC d’ordre élevé à réduire la dissipation dans les tourbillons. Enfin, les schémas avec VC sont appliqués au calcul des écoulements turbulents, dans une approche de simulation de grandes échelles implicite (ILES). Les schémas numériques avec VC présentent une résolvabilité améliorée par rapport à leur version linéaire de base, et montrent leur capacité à décrire de façon cohérente ces écoulements tourbillonnaires complexesVortices are flow structures of primary interest in a wide range of fluid dynamics applications including wakes, fluid-structure interaction, flow separation and turbulence. Albeit their importance, standard Computational Fluid Dynamics (CFD) methods very often fail to provide an accurate representation of vortices. This is primarily related to the schemes’ numerical dissipation which, if inadequately tuned for the calculation of vortical flows, results in the artificial spreading and diffusion of vortices in numerical simulations. Among other approaches, the Vorticity Confinement (VC) method of J. Steinhoff allows balancing the baseline dissipation within vortices by introducing non-linear anti-dissipation in the discretization of the flow equations, but remains at most first-order accurate. At the same time, remarkable progress has recently been made on the development of high-order numerical methods. These allow reducing the problem of excess dissipation, but the diffusion of vortices remains important for many applications. The present study aims at developing high-order extensions of the VC method to reduce the excess dissipation of vortices, while preserving the accuracy of high-order methods. First, the schemes are analyzed in the case of the linear transport equation, based on time-space coupled and uncoupled formulations. A spectral analysis of nonlinear schemes with VC is performed analytically and numerically, due to their nonlinear character. These schemes exhibit improved dispersive and dissipative properties compared to their linear counterparts at all orders of accuracy. In a second step, third- and fifth-order accurate VC schemes are developed for the compressible Navier-Stokes equations. These remain conservative, rotationally invariant and independent of the baseline scheme, as the original VC2 formulation. Numerical tests validate the increased order of accuracy and the capability of high-order VC extensions to balance dissipation within vortices. Finally, schemes with VC are applied to the calculation of turbulent flows, in an implicit Large Eddy Simulation (ILES) approach. In these applications, numerical schemes with VC exhibit improved resolvability compared to their baseline linear version, while they are capable of producing consistent results even in complex vortical flows
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Demontis, Pierfranco, Federico G. Pazzona, and Giuseppe B. Suffritti. "Cellular automata modeling of diffusion under confinement." Diffusion fundamentals 6 (2007) 13, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14187.
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Barbaro, Jacques. "Contribution à la fusion par confinement inertiel." Paris 11, 1987. http://www.theses.fr/1987PA112136.
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Un formalisme emprunte à la théorie des plasmas permet de prendre en compte tous les processus et leurs interactions mutuelles afin d'obtenir un modelé auto cohérent de la combustion nucléaire. Dans le cadre d'une description hydrodynamique classique, puis dans le cadre plus général de la théorie cinétique des plasmas des simulations numériques concernant la fusion thermonucléaire sont présentées, toutes ces simulations numériques sont relatives à des combustions thermonucléaires caractérisées par t::(r)
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Makowski, Brian Thomas. "Functionality via Confinement of Photo-Responsive Materials." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1323022488.
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