In view of the foreign mariculture is gradually diversified, and even has a trend that the fish cage aquaculture combines with algae culture at the same facility. A submersible single-point-mooring (SPM) cage system was modified and installed in-situ to investigate the feasibility of the cage system. A numercial model was established to simulate the cage dynamic motion as well as the mooring line tension. A detailed cage construction process was described in this study. Tension meter was used to keep track of mooring line tension, while the ADCP( Acoustic Doppler Current Profiler) was utilized to record the sea state during the test period. Those data were used to validate the numerical model. The field experiements were carried out at a location north to Xiaoliuqiu island. Since the testing period was in winter, the wave height was relativly calm and found to be between 0.5 and 1.2 m, wave period 4~7 seconds, and wave current about 0.2~0.6 m/s. The numerical results indicate that the maximum mooring line tension has good agreement with the meauresments of the tension meter. These comparisons verify that this numerical model is sufficient to simulate this kind of alage cage systems.

No description available.

No description available.

No description available.

Doctor of Philosophy / Department of Physics / Bruce M. Law / Three diverse first author surfaces science experiments conducted by Sean P. McBride 1-3 will be discussed in detail and supplemented by secondary co-author projects by Sean P. McBride, 4-7 all of which rely heavily on the use of an atomic force microscope (AFM). First, the slip length parameter, b of liquids is investigated using colloidal probe AFM. The slip length describes how easily a fluid flows over an interface. The slip length, with its exact origin unknown and dependencies not overwhelming decided upon by the scientific community, remains a controversial topic. Colloidal probe AFM uses a spherical probe attached to a standard AFM imaging tip driven through a liquid. With the force on this colloidal AFM probe known, and using the simplest homologous series of test liquids, many of the suspected causes and dependencies of the slip length demonstrated in the literature can be suppressed or eliminated. This leaves the measurable trends in the slip length attributed only to the systematically varying physical properties of the different liquids. When conducting these experiments, it was realized that the spring constant, k, of the system depends upon the cantilever geometry of the experiment and therefore should be measured in-situ. This means that the k calibration needs to be performed in the same viscous liquid in which the slip experiments are performed. Current in-situ calibrations in viscous fluids are very limited, thus a new in-situ k calibration method was developed for use in viscous fluids. This new method is based upon the residuals, namely, the difference between experimental force-distance data and Vinogradova slip theory. Next, the AFM’s ability to acquire accurate sub nanometer height profiles of structures on interfaces was used to develop a novel experimental technique to measure the line tension parameter, τ, of isolated nanoparticles at the three phase interface in a solid-liquid-vapor system. The τ parameter is a result of excess energy caused by the imbalance of the complex intermolecular forces experienced at the three phase contact line. Many differences in the sign and magnitude of the τ parameter exist in the current literature, resulting in τ being a controversial topic.

Dans cette thèse, nous utilisons des outils de simulation moléculaire pour caractériser les propriétés thermodynamiques de fluides confinés dans des matrices solides nanométriques. Alors qu'à l’échelle macroscopique, les énergies libres de fluides au contact de solides sont décrites par des pressions et des tensions de surface qui sont respectivement des énergies libres volumiques et surfaciques, à l’échelle moléculaire plusieurs paramètres additionnels doivent être considérés. Parmi eux, l'énergie libre de la ligne triple séparant trois phases, la tension de ligne. Les valeurs de la tension de ligne ainsi que les méthodologies permettant de la mesurer sont débattues.Les outils de simulation moléculaire permettent d'étudier théoriquement la thermodynamique des surfaces et des lignes. Plusieurs méthodologies statistiques peuvent être mises en œuvre pour extraire les tensions de surface et de ligne à partir d’une trajectoire moléculaire simulée. Nous nous intéressons en particulier à la méthodologie mécanique, qui consiste à mesurer les contraintes relatives à l’étalement quasi-statique d’un fluide sur un solide.Dans une première partie, nous étudions les expressions microscopiques des contraintes de mouillage à une interface solide-fluide plane. Dans le cas d’un solide latéralement homogène, l'application du théorème du viriel à un film liquide infini sans considération de la région séparant les surfaces mouillées et sèches permet de mesurer les forces relatives à l'extension du film sur un solide sec. Lorsque des hétérogénéités sont présentes à la surface du solide, cette méthodologie néglige des forces concentrées dans la région de la ligne triple. La comparaison de différentes méthodologies de mesure des tensions de surface indique que les termes ainsi négligés sont potentiellement importants dans le cas d'une forte rugosité.Dans une deuxième partie, nous nous concentrons sur des solides sans hétérogénéité tangentielle. Nous développons une méthodologie de mesure de l’énergie libre d’une interface fluide-fluide confinée et de sa tension de ligne qui s’appuie sur la considération des différentes contraintes fluides. Nous simulons des fluides de Van der Waals et de l’eau en équilibre liquide-vapeur, confinés dans des solides de différentes natures. Nous montrons que le concept de tension de ligne est robuste jusqu’à des confinements de quelques diamètres moléculaires. Les valeurs de tension de ligne mesurées sont cohérentes avec différentes approches théoriques, résolvant certains résultats paradoxaux de la littérature.Dans une troisième partie, nous appliquons la méthodologie mécanique à l’étude d’un mélange liquide-gaz confiné. Nous simulons des solvants et des solutés de Van der Waals ainsi que de l’eau avec du dioxyde de carbone. Différentes adsorptions sont observées, relatives aux surfaces mais également à la ligne triple. L’énergie libre de l’interface confinée s’en trouve fortement impactée. L'effet de l’adsorption sur la tension de ligne peut être modélisé par un équivalent linéique de l’équation d’adsorption de Gibbs surfacique. / In this thesis, we use molecular simulation tools to characterize the thermodynamic properties of fluids confined in nanometric solids. While at the macroscopic scale, the free energy of fluids in contact with a solid is described by pressures and surface tensions, respectively free energies per unit volume and per unit area, at the molecular scale, additional parameters are needed. One of them is the free energy per unit length of the triple line, the line tension. Its values and the methodologies used to measure it are controversial.The thermodynamics of interfaces and lines can be theoretically studied with molecular simulation tools. To extract the surface and line tensions from a simulated molecular trajectory, various statistical methodologies are available. In particular, we here use the mechanical methodology, which consists in measuring the stresses related to the quasistatic spreading of a fluid on a solid.In the first part, we study the microscopic expression of wetting stresses at a planar solid-fuid interface. When a laterally homogeneous solid is considered, the virial theorem applied to an infinite fluid film without consideration of the limit between wet and dry surfaces provides the forces related to the film extension on a dry solid. In the case of a laterally heterogeneous solid, this methodology neglects forces that are concentrated at the triple line. By comparing the surface tensions measured with different methodologies, we show that the neglected terms may induce important errors in the case of rough surfaces.In the second part, we focus on laterally homogeneous solids. We develop a methodology to measure the free energy and the line tension of a confined fluid-fluid interface using fluid mechanical stresses. We simulate Van der Waals fluids and water in liquid-vapor equilibrium confined in different solids. The concept of line tension appears robust down to confinements of a few molecular diameters, and its value consistent with various theoretical approaches, thus solving paradoxical results from the literature.In the last part, we apply the mechanical methodology to study the equilibrium of two fluid species in confinement, one liquid and the other gaseous. We simulate Van der Waals solvents and solutes, and water with carbon dioxide. Various adsorptions at the surfaces and the triple line are observed, strongly impacting the free energy of the confined liquid-gas interface. Finally the adsorption-induced variation of the line tension can be modelled by a unidimensional equivalent of the Gibbs isotherm.

A estabilidade de vesículas unilamelares gigantes (GUVs) foi monitorada através de microscopia de contraste de fase e de fluorescência, com o auxílio de gradientes de açúcares, do fluoróforo 1,3,6,8 pireno tetrasulfonato de sódio (PTS), do supressor de fluorescência cloreto de 1,1\'-dimetil-4,4\'-bipiridínio (MV) e do análogo lipídico fluorescente 2-(12-(7-nitrobenz-2-oxa-1,3-diazol-4-il) amino) dodecanoil-1-hexadecanoil-sn-glicero-3-fosfocolina (NBD-PC). Uma grande variabilidade no comportamento individual das GUVs foi obtida no que tange a: (i) manutenção do meio interno; (ii) interações da bicamada lipídica com superfícies e; (iii) estruturas lipídicas conectadas à bicamada. Os resultados experimentais podem ser explicados pelo aparecimento de poros transientes formados pelo aumento da tensão da bicamada lipídica das GUVs. Após o processo de geração de tensão na bicamada, poros são abertos para relaxação desta tensão, com concomitante efluxo da solução internalizada pela GUV, devido a pressão de Laplace. Com a diminuição do volume interno, a tensão da bicamada é relaxada e o fechamento dos poros guiado pela tensão de linha, minimizando o componente energético de curvatura dos lipídios nas bordas do poro. O modelo de poros transientes explica resultados como troca de massa entre meios interno e externo das GUVs, possibilidade da existência de fluxos unilaterais em GUVs, transitoriedade dos poros, diâmetro limite dos poros e manutenção do meio interno em GUVs após abertura e fechamento de poros. / The stability of giant unilamellar vesicles (GUVs) has been monitored by phase contrast and fluorescence microscopy, using sugar gradients, sodium 1,3,6,8 pirene tetrasulfonate (PTS) as fluorescent probe, 1,1\'-dimethyl-4,4\'-bipiridinium chloride (MV) as fluorescence quencher and 2-(12-(7-nitrobenz-2-oxa-1,3-diazol-4-il) amino) dodecanoyl-1-hexadecanoyl-sn-glicero-3-phosphocholine (NBD-PC) as fluorescent lipid analog. An accentuated variability in the individual behaviour of GUVs was observed as far as (i) stability of encapsulation; (ii) lipid bilayer-surface interactions and; (iii) lipid structures connected to GUVs are concerned. Experimental results can be explained by transient pores formation due to an increase in lipid bilayer tension. After processes of bilayer tension generation, pores are opened, while effluxes of GUVs internal solution are promoted by Laplace pressure. With the internal volume decrease, bilayer tension is relaxed and pores closure guided by line tension, minimizing the energetic component of lipid curvature in pore edges. Transient pores model explains experimental results such as mass exchange between internal and external GUVs media, GUVs effluxes, pores\' lifetime, pores diameter\'s limit and stability of GUV encapsulation after opening and closure of pores.

In this thesis the properties of proteins and membranes are studied by molecular dynamics simulations. The subject is decomposed into parts addressing free energy calculations in proteins, mechanical inclusion models for lipid bilayers, phase transitions and structural correlations in lipid bilayers and atomistic lipid bilayer models. The work is based on results from large scale computer simulations, quantum mechanical and continuum models. Efficient statistical sampling and the coarseness of the models needed to describe the ordered and disordered states are of central concern. Classical free energy calculations of zinc binding, in metalloproteins, require a quantum mechanical correction in order to obtain realistic binding energies. Classical electrostatic polarisation will influence the binding energy in a large region surrounding the ion and produce reasonable equilibrium structures in the bound state, when compared to experimental evidence. The free energy for inserting a protein into a membrane is calculated with continuum theory. The free energy is assumed quadratic in the mismatch and depend on two elastic constants of the membrane. Under these circumstances, the free energy can then be written as a line tension multiplied by the circumference of the membrane inclusion. The inclusion model and coarse grained particle simulations of the membranes show that the thickness profile around the protein will be an exponentially damped oscillation. Coarse-grained particle simulations of model membranes containing mixtures of phospholipid and cholesterol molecules at different conditions were performed. The gel-to-liquid crystalline phase transition is successively weakened with increasing amounts of cholesterol without disappearing even at a concentration of cholesterol as high as 60%. A united atom parameterization of diacyl lipids was constructed. The aim was to construct a new force field that retains and improves the good agreement for the fluid phase and at the same time produces a gel phase at low temperatures, with properties coherent with experimental findings. The global bilayer tilt obtains an azimuthal value of 31◦ and is aligned between lattice vectors in the bilayer plane. It is also shown that the model yield a correct heat of melting as well as heat capacities in the fluid and gel phase of DPPC. / <p>QC 20140919</p>

This thesis is devoted to several aspects of geometry and morphology in wetting problems and hard sphere packings. First, we propose a new method to simulate wetting and slip on nanostructured substrates: a phase field model associated with a dynamical density theory approach. We showed omniphobicity, meaning repellency, no matter the chemical properties of the liquid on monovalued surfaces, i.e. surfaces without overhangs, which is in contradiction with the macroscopic Cassie-Baxter-Wenzel theory, can produce so-called We checked systematically the impact of the surface parameters on omniphobic repellency, and we show that the key ingredient are line tensions, which emerge from needle shaped surface structures. Geometrical effects have also an important influence on glassy or jammed systems, for example amorphous hard sphere systems in infinite pressure limit. Such hard sphere packings got stuck in a so-called jammed phase, and we shall demonstrate that the local structure in such systems is universal, i.e. independent of the protocol of the generation. For this, robust order parameters - so-called Minkowski tensors - are developed, which overcome robustness deficiencies of widely used order parameters. This leads to a unifying picture of local order parameters, based on geometrical principles. Furthermore, we find with the Minkowski tensor analysis crystallization in jammed sphere packs at the random closed packing point

A estabilidade de vesículas unilamelares gigantes (GUVs) foi monitorada através de microscopia de contraste de fase e de fluorescência, com o auxílio de gradientes de açúcares, do fluoróforo 1,3,6,8 pireno tetrasulfonato de sódio (PTS), do supressor de fluorescência cloreto de 1,1\'-dimetil-4,4\'-bipiridínio (MV) e do análogo lipídico fluorescente 2-(12-(7-nitrobenz-2-oxa-1,3-diazol-4-il) amino) dodecanoil-1-hexadecanoil-sn-glicero-3-fosfocolina (NBD-PC). Uma grande variabilidade no comportamento individual das GUVs foi obtida no que tange a: (i) manutenção do meio interno; (ii) interações da bicamada lipídica com superfícies e; (iii) estruturas lipídicas conectadas à bicamada. Os resultados experimentais podem ser explicados pelo aparecimento de poros transientes formados pelo aumento da tensão da bicamada lipídica das GUVs. Após o processo de geração de tensão na bicamada, poros são abertos para relaxação desta tensão, com concomitante efluxo da solução internalizada pela GUV, devido a pressão de Laplace. Com a diminuição do volume interno, a tensão da bicamada é relaxada e o fechamento dos poros guiado pela tensão de linha, minimizando o componente energético de curvatura dos lipídios nas bordas do poro. O modelo de poros transientes explica resultados como troca de massa entre meios interno e externo das GUVs, possibilidade da existência de fluxos unilaterais em GUVs, transitoriedade dos poros, diâmetro limite dos poros e manutenção do meio interno em GUVs após abertura e fechamento de poros. / The stability of giant unilamellar vesicles (GUVs) has been monitored by phase contrast and fluorescence microscopy, using sugar gradients, sodium 1,3,6,8 pirene tetrasulfonate (PTS) as fluorescent probe, 1,1\'-dimethyl-4,4\'-bipiridinium chloride (MV) as fluorescence quencher and 2-(12-(7-nitrobenz-2-oxa-1,3-diazol-4-il) amino) dodecanoyl-1-hexadecanoyl-sn-glicero-3-phosphocholine (NBD-PC) as fluorescent lipid analog. An accentuated variability in the individual behaviour of GUVs was observed as far as (i) stability of encapsulation; (ii) lipid bilayer-surface interactions and; (iii) lipid structures connected to GUVs are concerned. Experimental results can be explained by transient pores formation due to an increase in lipid bilayer tension. After processes of bilayer tension generation, pores are opened, while effluxes of GUVs internal solution are promoted by Laplace pressure. With the internal volume decrease, bilayer tension is relaxed and pores closure guided by line tension, minimizing the energetic component of lipid curvature in pore edges. Transient pores model explains experimental results such as mass exchange between internal and external GUVs media, GUVs effluxes, pores\' lifetime, pores diameter\'s limit and stability of GUV encapsulation after opening and closure of pores.