The present investigation is concerned with determining the role of calcium, phospholipids, and phospholipid metabolites on transepithelial sodium and water transport in response to antidiuretic hormone (ADH). These studies utilize the frog skin for determining sodium transport and amphibian urinary bladder for water flow measurements and scanning electron microscopy of cell surface morphology. The results demonstrate that phospholipids and phospholipid metabolites containing arachidonic acid stimulate transepithelial sodium transport through amiloride sensitive channels and the action of these lipids involves the synthesis of prostaglandins. These lipids also inhibited the increase in water flow induced by ADH, and this effect was prevented with prostaglandin synthesis inhibitors. Prostaglandins alter intracellular calcium concentrations and agents effecting calcium metabolism alter cell surface morphology and the changes in surface substructure induced by ADH. These observations support the hypothesis that alterations in membrane permeability to water and ions may involve metabolism of membrane phospholipids and prostaglandin biosynthesis.

Le futur site de stockage géologique des déchets MAVL français intègre, dans sa conception, des éléments de structure en béton armé (alvéole et conteneurs). Prédire leur durabilité à l'échelle de la phase d'exploitation (environ 100 ans) est décisif. En conditions de service, le système de ventilation assurerait un approvisionnement constant de CO2, soumettant le béton à des phénomènes de séchage et de carbonatation. L'effet de la température (dû à l'exothermie des déchets) et du séchage sur la carbonatation a été évalué par le passé. Les données acquises à ce jour se doivent cependant d'être complétées. Dans ce sens, la prise en compte des transferts hydriques simultanés à la carbonatation est indispensable. D'une part, car la carbonatation est une pathologie courante du béton armé qui mène, à terme, à une corrosion généralisée des armatures. D'autre part, car la durabilité des structures en béton armé est conditionnée par l'évolution de leur état hydrique tout au long de leur période de service. L'évaluation des propriétés de transport d'eau dans les matériaux carbonatés, en milieu insaturé, constitue un enjeu important pour l'Andra chargée de la gestion des déchets radioactifs.Des essais de carbonatation accélérée sont conduits sur quatre pâtes de ciment durci (CEM I, CEM III/A, CEM V/A et un mélange Bas-pH) à une teneur en CO2 de 3%. Les propriétés hydriques des matériaux carbonatés sont évaluées à partir d'une approche simplifiée nécessitant la connaissance de 3 paramètres physiques accessibles par l'expérience : (i) porosité, (ii) isotherme de désorption de la vapeur d'eau et (iii) perméabilité.Les résultats mettent en évidence des modifications minéralogiques et microstructurales majeures engendrées par la carbonatation : décomposition des hydrates et précipitation de carbonate de calcium (CaCO3) selon différents polymorphes. La décalcification forte des C S H et la polymérisation des chaines silicatées, menant à la formation d'un gel de silice enrichi en calcium, sont constatées. La conséquence directe est l'apparition d'un retrait de carbonatation, lui-même à l'origine d'un phénomène de microfissuration. D'autre part, une réduction du volume poreux et de la surface spécifique des matériaux sont observées. Les carbonates formés obturent les pores, réduisant ainsi la porosité totale. Dans ce sens, plus la teneur initiale en portlandite est élevée, plus la quantité de CaCO3 formée est importante et, par conséquent, plus la chute de porosité résultante est marquée. La structure d'un matériau carbonaté n'a alors plus rien à voir avec son état initial. Ces changements se traduisent par une baisse significative de la teneur en eau à l'équilibre et un changement de morphologie des isothermes, en lien direct avec les évolutions microstructurales. Une baisse de la perméabilité est obtenue dans le cas du ciment Portland (CEM I), en raison du large colmatage de la porosité. Par contre, elle augmente dans le cas des ciments avec ajouts (CEM III/A, CEM V/A et Bas-pH), fait directement imputé à l'effet de la microfissuration, qui prédomine devant la chute de porosité. Le cortège minéralogique initial (teneurs en portlandite et C-S-H) joue donc un rôle déterminant vis-à-vis du comportent des matériaux cimentaires face à la carbonatation. La représentativité de la carbonatation accélérée vis-à-vis de la carbonatation naturelle a, par ailleurs, été vérifiée. Le jeu de données récolté au cours de ces travaux peut être étendu et, appliqué avec confiance, en condition de carbonatation réelle / The French design of deep geological repository involves the use of cement-based materials (vault cell and containers). The durability assessment over the operational phase (supply 100 years) is decisive. In operating conditions, a ventilation system would maintain the CO2 partial pressure within the disposal, subjecting concrete to drying and carbonation. The temperature (due to the waste thermal output) and drying effects on carbonation have been studied in the past. The data acquired must however be complemented. In this sense, taking into account the water transfers simultaneously to carbonation is essential. On the one hand, because carbonation is a common pathology of reinforced concrete that leads to rebar corrosion. On the other hand, because the durability of reinforced concrete structures is dependent on their water content evolution all along their service life. The assessment of water transport properties in carbonated materials, under unsaturated conditions, is an important issue for Andra in charge of the management of radioactive waste in France.Accelerated carbonation test are performed on four hardened cement pastes (CEM I, CEM III/A, CEM V/A and a Low-pH mix) at 3% CO2 content. The water transport properties of carbonated materials are evaluated using a simplified approach, requiring the knowledge of 3 physical parameters, accessible through experimental way: (i) porosity, (ii) water vapour desorption isotherm and (iii) permeability.The results highlight mineralogical and microstructural changes induced by carbonation: hydrates decomposition and calcium carbonate precipitation (CaCO3) according to various polymorphs. The high decalcification of C-S-H and the polymerisation of silicates chains, leading to the formation of a calcium-enriched silica gel, are found. This results in carbonation shrinkage, responsible of microcracking. On the other hand, the reduction of porosity and specific surface area are observed. The formed carbonates fill the pores, reducing the total porosity. In this sense, the higher the initial portlandite content, the higher the amount of CaCO3 and, consequently, the more the porosity decrease. The structure of the carbonated materials is totally different from the initial state. These changes result into a significant reduction of the water content at the equilibrium and a modification of the isotherms morphology, directly related to the microstructure evolutions. The permeability is found to decrease in the case of Portland cement (CEM I), due to porosity clogging. By contrast, it was found to increase significantly for blended cements (CEM III/A, CEM V/A and Low-pH mix), this is directly attributed to the microcracking effect which is more significant compared to porosity clogging. The initial mineralogy (portlandite and C-S-H contents) therefore plays a determinant role regarding to the carbonation impact on the cementitious materials behaviour. Furthermore, the representativeness of accelerated carbonation compared to natural one was verified. The data set acquired during this work can be extended and, applied confidently under real carbonation conditions

Made available in DSpace on 2015-04-22T22:10:42Z (GMT). No. of bitstreams: 1 rafael.pdf: 2621026 bytes, checksum: 7854419392a09ab6714d0998cdde5fe6 (MD5) Previous issue date: 2013-03-27 / Cabotage is made between ports of the same country, using sea or sea with waterway. In the state of Amazonas cabotage is mainly used to transport general cargo and containers, but cargo in containers handling has the largest growth potential due to the existence of the Polo Industrial de Manaus (PIM), which makes the port city of Manaus the main cargo hub in the Northern Region. This paper proposes the simulation of alternative scenarios for cabotage in the State of Amazonas using techniques of computer simulation to do evaluation of the operational efficiency on implementation service feeder adapted to the regional context. The study characterized the cabotage in the State of Amazonas enabling the modeling of the real system in the state. From the literature concerning the concepts of service feeder and hubs ports was developed alternative scenarios for implementing these approaches in regional transport. Thus it was possible to simulate with software ARENA the models and scenarios constructed in order to verify the performance of the system. The results showed that the operational viability of the use of hubs ports and feeder service depends on the balance between the demand for container handling and the capacity of the hub port and other ports feeders supported. Therefore, the study shows that it is necessary to equate the volume of container cargo that state of Amazonas is able to generate and attract with the operational characteristics of the hub port to avoid causing unnecessary investments for creation of transport infrastructure that may be underutilized or do not support the demand required. / A cabotagem é a navegação entre portos do mesmo país, utilizando via marítima ou esta em conjunto com navegação interior. No Estado do Amazonas a cabotagem é utilizada principalmente para transportar carga geral e contêineres, sendo que a movimentação de carga conteinizada possui o maior potencial de crescimento devido a existência do Polo Industrial de Manaus (PIM), o que torna o porto da cidade de Manaus o principal concentrador de carga da Região Norte. Este trabalho propõe a simulação de cenários alternativos para o transporte de cabotagem do Estado do Amazonas utilizando técnicas de simulação computacional para avaliar a eficiência operacional da implementação do serviço feeder adaptado ao contexto regional. O estudo caracterizou o transporte de cabotagem no estado do Amazonas permitindo a modelagem do sistema real. A partir do levantamento bibliográfico acerca dos conceitos de serviço feeder e portos concentradores foi elaborado cenários alternativos para implementação dessas abordagens no transporte regional. Desta forma, foi possível simular no ambiente ARENA os modelos e cenários construídos, a fim de verificar o desempenho operacional do sistema. Os resultados apontaram que a viabilidade operacional do uso de portos concentradores e serviço feeder depende do equilíbrio entre a demanda por movimentação de contêineres e a capacidade de movimentação do porto concentrador e demais portos feeders atendidos. Portanto, o estudo revela que é necessário equacionar o volume de cargas conteinizadas que o estado do Amazonas é capaz de gerar e atrair com as características operacionais do porto concentrador, para evitar que ocorra investimentos desnecessários para criação de infraestruturas de transporte que possam ser sub-utilizadas ou não atendam a demanda exigida.

Hemiepiphytes are important components of tropical forests and are attractive to scientists due to their unique epiphytic growth habit during some period of their life cycle. Unique characteristics in plant water relations and carbon economy have been found in hemiepiphytic plants; however, to further understand this group of species on an evolutionary basis it is necessary to carry out comparative studies between hemiepiphytes and their close relatives. In this dissertation I conduced a comparative study in a suite of functional traits related to plant water relations and photosynthesis between hemiepiphytic and non-hemiepiphytic tree species from a single genus-Ficus. Great differentiation in functional traits has been found between species of the two growth forms both during juvenile and adult stages. Seedlings of hemiepiphytic Ficus species (H) had significantly lower xylem hydraulic conductivity, stomatal conductance, net light saturated CO2 assimilation, and higher water use efficiency than congeneric non-hemiepiphytic species (NH), which are adaptive to a drought-prone epiphytic growth conditions under natural conditions. The conservative water use adaptation in H species is likely crucial to the drought tolerance and survival in the forest canopy but is related to much lower growth rates than NH species. Species of the two growth forms both showed relatively large plasticity in responding to variation in light level as in typical light-demanding species. Surprisingly, the NH species showed characteristics related to higher light demand than H species, which is opposite from the prediction that H species are more light-demanding than NH species. Thus, although commonly accepted, it is likely that light was not the selective pressure for the evolution of hemiepiphytism in Ficus. Using adult trees grown in a common garden, I found that H species showed characteristics of more conservative water use even after they established connections to the soil. Moreover, H species showed significantly different traits in photochemistry compared to NH species due to hydraulic-photosynthetic coordination. The evolution of an epiphytic growth habit during the juvenile stage of a life cycle in the hemiepiphytic Ficus species thus involved changes in a suite of functional traits that persist during their terrestrial growth stages.

In this dissertation, molecular simulation techniques are used for the theoretical prediction of nanoscale properties for peptide-based materials. This work is focused on two particular systems: peptide nanotubes formed by cyclic-D,L peptide units and peptide nanotubes formed by phenylalanine dipeptides [-Phe-Phe-]. Mechanical characterization of cyclic peptide nanotubes is a challenging problem due the anisotropy resulting from the nature of their molecular interactions. To address rigorously the thermo-mechanical stability of cyclic peptide nanotubes (CPNTs), a homogeneous deformation method combined with the generalized elasticity theory and molecular dynamics simulations (MD) were used for the calculation of second order anisotropic elastic constants. The results for anisotropic elastic constants, yield behavior and engineering Young’s modulus show remarkable mechanical stability for these materials supporting experiments for the development of their applications. Furthermore, the heat capacity, thermal expansion coefficient and isothermal compressibility were predicted using numerical difference methods and molecular dynamics. In order to understand the transport properties of confined water in cyclic peptide nanotubes, the influence of nanotube diameter was studied and self-diffusion coefficient, dipole correlation functions and hydrogen bond probabilities were calculated via molecular dynamics and statistical mechanics. Enhanced transport and higher diffusion rates for water were obtained in cyclic peptide nanotubes (CPNTs) compared with commonly used biomedical channels like carbon nanotubes (CNTs). The greater transport efficiency in CPNTs is attributed to the hydrophilic character and high hydrogen bonding presence along their tubular structure, versus the hydrophobic core of CNTs. One of the most important opportunities for cyclic peptide nanotubes is their utilization as artificial ion channels in antibacterial applications. Here, molecular dynamics methods were used to investigate the effect of confinement on the transport properties of Na+ and K+ ions under the influence of electric field; the ion mobility, selectivity, radial distribution function, coordination number and effect of temperature were studied and results from simulations proved their ability to transport ions. Additionally, the molecular organization of phenylalanine dipeptides into ordered peptide nanotubes was investigated, a model for the molecular structure of these nanotubes was proposed and optimized through molecular simulations; a helical pattern was found and characterized. Thermal stability results show that phenylalanine dipeptide nanotubes are stable up to about 400K; above this temperature, a significant decrease in hydrogen bonding was observed and the perfect pattern was altered. Findings from this work open new opportunities for research in the area of peptide based materials and provide tools and methods to study these systems efficiently at nanoscale.

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Rapid and deep transport of solutes in soils can potentially pollute groundwater resources. Field estimates of solute leaching depth based on randomized sampling provide extremely variable field average estimates that confound the treatment effects of the leaching study with the high spatial variation of soil hydraulic properties. The purpose of this study was to investigate the spatial scale of variation of solute (Bromide) leaching depth, and apply this scale of variation to study the leaching depth of Bromide as a function of a sinusoidal application of transport causing factors, i.e., rainfall amount, intensity and application time delay. Solute leaching depth varied over different spatial scales. The deepest leaching was observed on plots where the Br center of mass ranged from 19-30 cm depth. Deep leaching occurred with large quantities of low intensity precipitations (5.5 to 6 cm/day) and short time delays (≤ 17 hours), respectively. The hydraulic gradient presented cyclic variation at 8 m wavelength across the 10-30cm depth compartment. Spectral analysis indicated that spatial variation of the leaching depth was mainly affected by precipitation amount and intensity and only a small portion of the leaching depth variation was caused by time delay. Cross-spectral analysis identified common cyclic variation between the Br leaching depth and precipitation amount, intensity and time delay over 32, 32 and 8 m wavelengths, respectively. Simulated Br concentration over depth and horizontal distance and soil water matric potential ψm were in good agreement with experimental observations, the latter revealing a satisfactory Br and water mass balance.

Liquid water management has a major impact on the performance and durability of the polymer electrolyte membrane fuel cell (PEMFC). The gas diffusion layer (GDL) of a PEMFC provides pathways for mass, heat, and electronic transport to and from the catalyst layers and bipolar plates. When the GDL becomes flooded with liquid water, the PEMFC undergoes mass transport losses that can lead to decreased performance and durability. The work presented in this thesis includes contributions that provide insight into liquid water transport behaviour in and on the surface of the GDL, as well as insight into how future GDLs could be designed to enhance water management. The effects of compression on liquid water transport in the GDL and on the microstructure of the GDL are presented. It was found that compressed regions of the GDL provided preferential locations for water breakthrough, while scanning electron microscopy (SEM) imaging revealed irreversible damage to the GDL due to compression at typical fuel cell assembly pressures. The dynamic behaviour of droplet emergence and detachment in a simulated gas flow channel are also presented. It was found that on an initially dry and hydrophobic GDL, small droplets emerged and detached quickly from the GDL surface. However, over time, this water transport regime transitioned into that of slug formation and channel flooding. It was observed that after being exposed to a saturated environment, the GDL surface became increasingly prone to droplet pinning, which ultimately hindered droplet detachment and encouraged slug formation. A pore network model featuring invasion percolation with trapping was employed to evaluate the breakthrough pattern predictions of designed porous media. These designed pore networks consisted of randomized porous media with applied diagonal and radial gradients. Experimental microfluidic pore networks provided validation for the designed networks. Diagonal biasing provided a means of directing water transport in the pore network, while radially biased networks provided the additional feature of reducing the overall network saturation. Since directed water transport and reduced saturation are both beneficial for the PEMFC GDL, it was proposed that biasing of this nature could be applied to improved GDL designs. Lastly, recommendations for future extensions of this research are proposed at the end of this thesis.

Wick action is the transport of water through a concrete element from a face in contact with water to a drying face as occurs in basements, tunnels, slabs on grade and hollow offshore structures. Water transport through concrete due to wick action is many times greater due to pressure permeability under typical environmental conditions. Therefore wick action plays an important role in the watertightness and durability of concrete structures. Current models of wick action are based on an equilibrium developing between the rate of water entering concrete by sorptivity and leaving by water vapour diffusion where initial moisture content should not change the steady state rate, only the dominant factor in the early stages. / Wick action tests were conducted on concrete specimens of varying initial moisture condition, thickness, orientation and composition over periods ranging up to 450 days. Some wick action tests were conducted at 50% and 75% relative humidity and using a penetrating solution of reduced surface tension. The rate of wick action was found to be inversely proportional to thickness regardless of the initial moisture content of the specimen. Initial saturation was found to significantly increase wick action and moisture flow in ordinary Portland cement (OPC) and hydrophobic (HI) concretes drying at 75% RH and HI concrete drying at 50% RH. The data are consistent with the well documented hysteresis between sorption/desorption isotherms. Concretes containing silica fume (SF) and ground granulated blast-furnace slag (GGBS) did not exhibit such hysteresis. Reducing the surface tension of the pentrating solution profoundly reduced the sorptivity into dried specimens but not the depth of penetration or the steady state wick action rate. Direct measurements on osmotic flow through vacuum saturated specimens showed that osmotic effects had a limited effect on wick action at salt concentrations expected in most environmental conditions. / The research demonstrates that desorptivity from the drying surface rather than sorptivity into the wetting surface is the dominant factor determining wick action through concrete. The ease with which desorptivity can be measured and the simple empirical model developed provides practicising engineers with a useful tool to estimate water transport due to wick action through concrete in partially immersed conditions.

Enhanced mass transport in carbon-based nanoscale conduits (e.g. carbon nanotubes, graphene nanochannels/capillaries, graphene/graphene oxide membranes) has attracted tremendous interest over the last decade due to its significant implications for water desalination/purification, nanofiltration, electronic cooling, battery/fuel cells, and lab-on-a-chip. Further development of carbon-based nanoscale conduits for practical applications relies on understanding fundamental mechanisms of transport through individual conduits, which have not been well studied due to challenges in fabrication and measurement. In this thesis, the construction of two-dimensional planar graphene nanochannel devices and the studies of enhanced water and ion transport inside the graphene nanochannels are reported for the first time. The graphene nanochannels are fabricated by conformally covering high-quality graphene on the surfaces of silica nanochannels. A new fabrication scheme consisting of graphene wet transfer, graphene patterning and vacuum anodic bonding is developed to create such graphene nanochannels with heights ranging from 24 to 124 nm. Using these nanochannels and a new hybrid nanochannel based capillary flow measurement technique, we successfully measured the hydraulic resistance (water permeability) of single graphene nanochannels. Our results demonstrate that the frictionless surface of graphene induces a boundary slip and enhances water flow inside the graphene nanochannel. The measured slip length of graphene in the graphene nanochannels poses a median value around 16 nm, albeit with a large variation from 0 to 200 nm regardless of the channel height. The small-yet-widely-varying values of the graphene slip length are attributed to the surface charge of graphene and the interaction between graphene and underneath silica substrate, which are in good agreement with the prediction of our molecular dynamics (MD) simulation. In addition, we also investigated enhanced ion transport inside the graphene nanochannels. Higher electroosmotic conductance at low electrolyte concentrations (10-6 M~10-2 M) is observed in graphene nanochannels when compared with silica nanochannels with the same geometry. Our results suggest that the enhanced electroosmotic flow is also due to the boundary slip at the graphene/electrolyte interface. Besides, our analysis shows that the surface charge on the graphene, originating from the dissociation of oxygen-containing functional groups, is crucial to the enhanced electroosmotic flow inside nanochannels.