Motores moleculares são proteínas capazes de transportar objetos tais como vesículas, organelas e macromoléculas ao longo do citoesqueleto. Tratam-se de dispositivos bastante interessantes do ponto de vista físico, pois produzem trabalho em um ambiente extremamente ruidoso. Recentemente, diversos experimentos realizados in vivo têm revelado que objetos transportados por motores moleculares ao longo dos microtúbulos apresentam movimento bidirecional. Embora o movimento unidirecional dos motores envolvidos no transporte destes objetos seja bem caracterizado tanto experimentalmente quanto teoricamente, o movimento bidirecional das partículas transportadas pelos motores ainda não é bem entendido. Contudo, acredita-se que este fenômeno seja causado pela cooperatividade dos motores moleculares. Existem na literatura diversos trabalhos que visam descrever o comportamento coletivo de partículas locomovendo-se sobre uma rede unidimensional com interações de volume excluído e taxas de transição assimétricas. Estes modelos são conhecidos como TASEP (Totally asymmetric simple exclusion processes ) ou ASEP (Asymmetric simple exclusion processes ) e fazem parte de uma classe de modelos denominados sistemas difusivos dirigidos_. Embora alguns autores tenham utilizado modelos do tipo ASEP e TASEP para descrever o movimento dos motores moleculares exclusivamente [37], [38], não há ainda nesta visão microscópica, extensões deste modelo para incorporar as partículas cuja dinâmica depende exclusivamente da presença de motores. No presente trabalho propomos um modelo de exclusão, desenvolvido com o intuito de descrever o movimento conjunto de motores moleculares e das partículas carregadas pelos mesmos, as quais por simplicidade denominamos vesículas. Neste modelo, as vesículas não possuem dinâmica própria, ou seja, dependem da interação com os motores moleculares para se movimentarem. Procuramos soluções analíticas para este modelo para o 1 RESUMO 2 caso em que há apenas uma vesícula locomovendo-se sobre a rede. Utilizando o método das matrizes [32], calculamos a velocidade média da vesícula no estado estacionário e analisamos seu comportamento em situações de interesse. / Molecular motors are proteins that transport objects such as vesicles, organelles and macromolecules along the cytoskeletum of cells. For physics, they are very interesting devices because they are able to generate work in an extremely viscous environment. Recently, many in vivo experiments have revealed that objects transported by molecular motors move bidirectionally along microtubules. Although the unidirectional movement of such molecular motors is experimentally and theoretically well characterized, the movement of particles transported by these motors is not well understood yet. However, this fenomenum is believed to be caused by the cooperativity of molecular motors. A great number of works are found in literature, which were formulated to describe the collective behaviour of many particles moving in a one-dimensional lattice with a preferred hop rate and exclusion. These models are known as TASEP (Totally asymmetric simple exclusion processes) or ASEP (Asymmetric simple exclusion processes) and are part of a class of models named _driven di_usive systems_. Although some authors made use of ASEP and TASEP models to describe the movement of molecular motors [37], [38], there is not yet, in this microscopic point of view, extensions of these models capable of incorporate particles which the dynamics depends exclusivaly from the presence of motors. In this work we propose a exclusion model developed to describe the joint movement of molecular motors and particles, generally called vesicles. In this model, vesicles do not have a proper dynamics, that is, they on the interaction with molecular motors to move. We look after analytical solutions of this model when there is only one vesicle moving on the lattice. We use a matrix formulation [32] to obtain the mean velocity of the vesicle and analyse its behaviour in situations of interest.

Motores moleculares são proteínas capazes de transportar objetos tais como vesículas, organelas e macromoléculas ao longo do citoesqueleto. Tratam-se de dispositivos bastante interessantes do ponto de vista físico, pois produzem trabalho em um ambiente extremamente ruidoso. Recentemente, diversos experimentos realizados in vivo têm revelado que objetos transportados por motores moleculares ao longo dos microtúbulos apresentam movimento bidirecional. Embora o movimento unidirecional dos motores envolvidos no transporte destes objetos seja bem caracterizado tanto experimentalmente quanto teoricamente, o movimento bidirecional das partículas transportadas pelos motores ainda não é bem entendido. Contudo, acredita-se que este fenômeno seja causado pela cooperatividade dos motores moleculares. Existem na literatura diversos trabalhos que visam descrever o comportamento coletivo de partículas locomovendo-se sobre uma rede unidimensional com interações de volume excluído e taxas de transição assimétricas. Estes modelos são conhecidos como TASEP (Totally asymmetric simple exclusion processes ) ou ASEP (Asymmetric simple exclusion processes ) e fazem parte de uma classe de modelos denominados sistemas difusivos dirigidos_. Embora alguns autores tenham utilizado modelos do tipo ASEP e TASEP para descrever o movimento dos motores moleculares exclusivamente [37], [38], não há ainda nesta visão microscópica, extensões deste modelo para incorporar as partículas cuja dinâmica depende exclusivamente da presença de motores. No presente trabalho propomos um modelo de exclusão, desenvolvido com o intuito de descrever o movimento conjunto de motores moleculares e das partículas carregadas pelos mesmos, as quais por simplicidade denominamos vesículas. Neste modelo, as vesículas não possuem dinâmica própria, ou seja, dependem da interação com os motores moleculares para se movimentarem. Procuramos soluções analíticas para este modelo para o 1 RESUMO 2 caso em que há apenas uma vesícula locomovendo-se sobre a rede. Utilizando o método das matrizes [32], calculamos a velocidade média da vesícula no estado estacionário e analisamos seu comportamento em situações de interesse. / Molecular motors are proteins that transport objects such as vesicles, organelles and macromolecules along the cytoskeletum of cells. For physics, they are very interesting devices because they are able to generate work in an extremely viscous environment. Recently, many in vivo experiments have revealed that objects transported by molecular motors move bidirectionally along microtubules. Although the unidirectional movement of such molecular motors is experimentally and theoretically well characterized, the movement of particles transported by these motors is not well understood yet. However, this fenomenum is believed to be caused by the cooperativity of molecular motors. A great number of works are found in literature, which were formulated to describe the collective behaviour of many particles moving in a one-dimensional lattice with a preferred hop rate and exclusion. These models are known as TASEP (Totally asymmetric simple exclusion processes) or ASEP (Asymmetric simple exclusion processes) and are part of a class of models named _driven di_usive systems_. Although some authors made use of ASEP and TASEP models to describe the movement of molecular motors [37], [38], there is not yet, in this microscopic point of view, extensions of these models capable of incorporate particles which the dynamics depends exclusivaly from the presence of motors. In this work we propose a exclusion model developed to describe the joint movement of molecular motors and particles, generally called vesicles. In this model, vesicles do not have a proper dynamics, that is, they on the interaction with molecular motors to move. We look after analytical solutions of this model when there is only one vesicle moving on the lattice. We use a matrix formulation [32] to obtain the mean velocity of the vesicle and analyse its behaviour in situations of interest.

[pt] Estudamos sincronização completa em aneis de mapas logísticos, usando um esquema de acoplamento advectivo-difusivo. O alcance das interações diminui algebricamente com a distância entre mapas, varrendo do caso totalmente conectado ao de primeiros vizinhos, com atualização sincronizada ou com retardo. Estudamos os efeitos do retardo e da advecção separada-mente e combinados. Embora os estudos numéricos tenham sido realizados utilizando o mapa logístico como dinâmica local, alguns resultados analíticos são mais gerais. Na dinâmica síncrona, os estados sincronizados são caóticos, enquanto a presença de atrasos permite a sincronização em órbitas regulares. No entanto, uma forte contribuição de retardos na atualização também pode produzir sincronização caótica. Em todos os casos, as interações de longo alcance favorecem a sincronização, a advecção dificulta a sincronização, e os atrasos podem compensar os efeitos destrutivos da ad-vecção. / [en] We study complete synchronization in rings of logistic maps, using an advection-diffusion coupling scheme. The range of the interactions decays algebraically with distance between maps, sweeping from the totally connected to nearest-neighbor model, with synchronous or delayed lattice update. We studied the effects of delays and advection separately and combined. Although numerical studies were performed using the logistic map as local dynamics, some analytical results are more general. In the synchronous dynamics, synchronized states are chaotic, while the presence of delays allows synchronization in regular orbits. However, a strong contribution of delays in the updating can also produce chaotic synchronization. In all cases, longer interaction range favors synchronization, advection hinders synchronization and delays compensate the destructive effects of advection.

Simulações acopladas do escoamento reativo e dos processos de transferência de calor para o estudo de chamas são problemas dispendiosos computacionalmente. A transferência de calor por radiação em processos de combustão, devido às elevadas temperaturas, é o processo de troca energética dominante. Ainda, o comportamento altamente irregular do coeficiente de absorção com o comprimento de onda se constitui em uma dificuldade adicional na modelagem da transferência radiativa em meios participantes. Para contornar essa dificuldade modelos espectrais foram desenvolvidos com o objetivo de simular o comportamento de um gás real. Dentre esses modelos destacam-se o gás cinza (GG: Gray Gas), o mais simples, que negligencia o comportamento espectral do coeficiente de absorção, e o modelo da soma-ponderada-de-gases-cinza (WSGG: Weighted-Sum-of-Gray-Gases) onde a integração sobre todo o espectro é substituída por um número finito de gases cinza. Com o avanço de ferramentas computacionais, principalmente códigos CFD (Computational Fluid Dynamics), abordagens computacionais se tornaram atrativas frente ou em complemento às abordagens experimentais. Desse modo, o presente trabalho tem por objetivo a aplicação dos modelos WSGG e GG com novas correlações na simulação detalhada de chamas difusivas laminares de metano diluído com dióxido de carbono e nitrogênio com o código CFD comercial ANSYS/Fluent. Foram desenvolvidas rotinas de usuário (UDF: User-Defined Functions) para o acoplamento dos modelos espectrais ao código CFD. A verificação das rotinas de usuário foi realizada comparando os resultados obtidos via simulação Fluent com dados obtidos pelo modelo WSGG com um código FORTRAN próprio desenvolvido pelo grupo de pesquisa do Laboratório de Radiação Térmica (LRT/UFRGS) para o problema unidimensional de superfícies negras e infinitas preenchidas por um meio não-isotérmico e não-homogêneo. Os erros encontrados para o fluxo de calor radiativo nas superfícies e para o termo fonte radiativo ao longo do meio foram da ordem de 1% indicando o funcionamento correto das rotinas UDF acopladas ao Fluent. Por fim, as rotinas foram aplicadas na simulação numérica para chamas de potência constante com diluição dos reagentes e os dados obtidos com a solução numérica foram comparados com dados experimentais para a fração radiante e fluxo de calor radiativo. Os desvios médios encontrados para o fluxo de calor radiativo ficaram em torno de 10% para todas as chamas, excetuando as chamas com diluição de CO2 de 30%, 40% e 50%, em volume, para as quais os desvios médios ficaram em torno de 15%. O termo fonte para as chamas apontou para a predominância da emissão do meio em relação à absorção. Todas as chamas estudadas se encontram no regime opticamente fino (optically thin) para o qual, segundo apontam estudos da literatura, a escolha do modelo espectral possui impacto pequeno em resultados globais da chama como a temperatura e a concentração das espécies na mistura. Nesse aspecto os resultados encontrados concordaram com a previsão da literatura, entretanto para a transferência radiativa, o modelo GG se mostrou sensivelmente menos preciso em comparação ao modelo WSGG, principalmente para a fração radiante e para o fluxo radiativo na região da pluma aquecida, indicando a dependência do modelo espectral adotado. / Coupled simulations of the reactive flow with the heat transfer processes for flame studying are computationally demanding problems. The radiative transfer in combustion processes is the main heat transfer mechanism due to the high temperatures involved. However, the highly irregular behavior o f the absorption coefficient with the wavenumber composes in an additional difficulty on modeling the radiative transfer in participating media. In order to overcome this issue, spectral models were developed with the objective of simulate the behavior of real gases. Some of the most known models are the gray gas (GG) for which the spectral behavior of the radiative properties of the medium is neglected and the weighted-sum-of-gray-gases (WSGG) for which the integration over the entire spectrum is replaced by a summation over a finite number of gray gases with constant absorption coefficients. With the development of computational tools, mainly Computational Fluid Dynamics (CFD) codes, numerical approaches became attractive instead or in complement of experimental set ups. In this way, the present work aims to couple the WSGG and the GG models with new correlations in a detailed simulation of diffusive laminar flames of methane diluted with carbon dioxide and nitrogen with the commercial CFD code ANSYS/Fluent. User-defined functions (UDF) were developed to the coupling of the spectral models. The verification was carried out through the WSGG model by comparing the Fluent solution with a solution obtained with a FORTRAN code developed by the Thermal Radiation Laboratory (LRT/UFRGS) research group for the one-dimensional system of black surfaces filled with a non-homogeneous and non-isothermal medium. The deviations for the radiative heat flux for the walls and the radiative heat source along the domain were of 1% or less, indicating the correct coupling between the UDF routines and the CFD code. Finally, the UDF were applied in the solution of constant power flames with fuel diluted with carbon dioxide and nitrogen. The obtained data was then compared with experimental measurements for the radiant fraction and the radiative heat flux along the flame axis. The average deviations found were in order of 10% for all flames, except for the flames with 30%, 40% and 50% of CO2 dilution, in volume, for which the deviatioms found were in order of 15%. The radiative heat source was plotted and indicated for the medium emission predominance in comparison with the medium absorption. All flames studied were optically thin flames for which, studies pointed, the spectral model have minor impact over global results as flame temperature and mixture concentration. For this aspect the results found showed agreement with the literature studies predictions, however the GG model showed itself less accurate in comparison with the WSGG model for the radiant fraction and the radiative heat flux computations. So the spectral models have influence on the radiative transfer even if its effect on flame structure can be negligible.

La diffusion chimique est un phénomène clé dans l’élaboration des verres d’intérêt nucléaire. A haute température, dans le liquide, elle permet l’homogénéisation des flux de matière (précurseurs vitreux et déchets) et conduit à la formation d’un verre homogène après refroidissement. A contrario, dans le liquide surfondu, elle peut être à l’origine de processus de séparation de phase ou de cristallisation qui doivent être contrôlés pour le bon fonctionnement du procédé. Dans cette thèse, l’influence de la diffusion chimique sur les processus de cristallisation et d’homogénéisation du liquide est étudiée pour un verre simplifié de type borosilicate de sodium entre sa température de transition vitreuse et sa température d’élaboration. Pour ce type de système, qualifié de multicomposants, la description des phénomènes diffusifs nécessite le calcul d’une matrice de diffusion prenant en compte la diffusion couplée des espèces. Ces couplages sont retranscrits au travers de mécanismes de diffusion ou « échanges diffusifs » qui sont invariants avec la température. Les énergies d’activation associées à ces échanges sont proches de l’énergie d’activation de l’écoulement visqueux ce qui montre que le flux visqueux et la diffusion chimique sont pilotés par un seul et même mécanisme en lien avec la fréquence de rupture des liaisons Si-O et B-O. Nous mettons également en évidence que dans le liquide surfondu, les échanges diffusifs primaire (SiO2-Na2O) et secondaire (SiO2-B2O3) jouent un rôle prépondérant sur la cinétique de cristallisation et la direction de croissance des phases cristallines (cristobalite et tridymite) formées dans nos systèmes. Ces résultats permettent de justifier l’évolution des gradients de compositions à proximité et loin des cristaux. Dans la dernière partie du manuscrit, une complexification des verres a été initiée en ajoutant du lanthane pour simuler un des lanthanides majoritairement présents dans la composition du verre nucléaire de référence R7T7. Les données obtenues ont révélé un couplage diffusif entre le lanthane et le silicium qui entre en compétition avec les autres couplages mis en évidence dans le ternaire SiO2-Na2O-B2O3. Ce couplage, combiné aux autres résultats de la thèse, permet d’expliquer la formation d’une phase de type borosilicate de lanthane (LaBSiO5). / Chemical diffusion is a key-phenomenon during nuclear glass synthesis. At high temperature, diffusion leads to homogenization of the melt contributing to the transformation of heterogeneous waste and frit precursors to a homogeneous glass after cooling. In contrast, in the supercooled liquid, diffusion is a critical factor affecting phase separation and/or crystallization processes that must be avoided when producing a high quality final product.In this manuscript, the impact of chemical diffusion on crystallization and liquid homogenization is studied for a simplified sodium borosilicate glass between its glass transition temperature and its synthesis temperature. For this kind of system, qualified as multicomponent, the description of diffusive phenomena requires the calculation of a diffusion matrix that takes into account diffusive couplings between species. These couplings can be written in the form of diffusive mechanisms or “diffusive exchanges” that are invariant with temperature. The activation energies associated with these exchanges are close to the activation energy of shear viscosity which suggests that viscous flow and chemical diffusion are driven by a single mechanism related to the frequency of Si-O and B-O bond breaking. It is also highlighted that in the supercooled liquid, the principal diffusive exchange (SiO2-Na2O) and the secondary diffusive exchange (SiO2-B2O3) play a significant role on the kinetics and direction of growth of crystalline phases which are formed in our system. These results are used to rationalise the evolution of compositional gradients in the vicinity and far from crystals. In the last part of this work, a complexification of the glasses was initiated by adding lanthanum to simulate one of the main lanthanides of the R7T7 nuclear glass composition. The data collected reveal diffusive couplings between lanthanum and silicon. These couplings, combined with the other results explain the formation of a lanthanum borosilicate phase (LaBSiO5).

Les objectifs de cette thèse visent le développement d'un traitement inédit dans un repère spatiale tridimensionnel, pour le problème de la dynamique de collisions diffusives d'objets macromoléculaires en solution en écoulement hydrodynamique à l'intérieur des pores de largeur variable, soumis aux forces hydrodynamiques, du mouvement brownien et des collisions diffusifs aux parois des pores, en utilisant la modélisation théorique et les simulations numériques. L'approche par simulation numérique est nécessaire car il est extrêmement complexe d'utiliser des outils analytiques à présent pour traiter le problème de ces collisions diffusives aux parois solides. Les algorithmes que nous avons développés et les simulations correspondantes sont suffisamment généraux et avancés pour être directement appliquée à l'étude de la dynamique d'une grande variété de polymère et des particules biologiques dans des solutions diluées sous diverses conditions physiques et hydrodynamiques à l'intérieur des pores. Par ailleurs, les mécanismes conduisant à l'adhésion de nano particules et de particules macromoléculaires sous conditions de non-équilibre, en raison de l'influence contradictoire des collisions mécaniques diffusifs et les forces attractives de Hamaker aux parois solides, sont d'un intérêt majeur. Nous avons donc développé un modèle théorique pour calculer le coefficient de restitution. L'objectif est de quantifier le bilan énergétique pendant le processus de collision diffusive de ces particules aux parois, sous l'influence des forces de répulsion d'une part et les forces attractives de Hamaker. Cela se fait par l'élaboration d'un modèle, basé sur le JKR et les théories d'Hertz, pour tenir compte des pertes d'énergie lors des collisions et des gains d'énergie en raison des interactions Hamaker. L'adhésion arrive si le bilan énergétique le permet. Notre modèle théorique est développé en proposant une approche particulière basée sur le potentiel Hamaker. Nous démontrons ce bilan par le biais d'une équation caractéristique non linéaire pour le coefficient de restitution, et analysons ses propriétés qui déterminent l'adhésion ou non pour diverses conditions physiques initiales.

La disponibilitat de metalls per part dels organismes no depèn únicament de la concentració total sinó també de l'especiació d'aquestes subtancias. En general, la disponibilitat de les espècies metàl•liques en medis naturals per a organismes està determinada per un conjunt d'esdeveniments encadenats on el equilibri representa només un cas particular de la situació dinàmica general. Espècies poc definides químicament, com ara àcids húmics i fúlvics, actuen com a lligands de metalls i juguen un paper clau en la circulació i la determinació de les propietats ecotoxicològiques de les espècies metàl•liques en medis naturals. La polifuncionalitat dels àcids húmics i fúlvics és descrita en aquest estudi utilitzant mètodes termodinàmics i mecano-estadístics. La tècnica Diffusive Gradients in Thin films (DGT) s'ha utilitzat per mesurar el flux disponible de metall en un sistema sintètic que conté complexos metàl•lics. La principal conclusió d'aquest estudi és que el disc de resina quelant dels sensors juga un paper clau en la determinació del grau de labilitat d'un complex mesurat amb aquesta tècnica. D'altra banda, a un pH baix, o concentració alta de lligand, es pot aconseguir l'equilibri entre la resina del sensor i el metall en el si de la dissolució, pertorbant l'acumulació lineal a temps de contacte relativament curts. Es presenta una anàlisi d'aquests fenòmens, així com la seva justificació mitjançant models teòrics. / La disponibilidad de metales por parte de los organismos no depende únicamente de la concentración total sino también de la especiación de estas subtancias. En general, la disponibilidad de las especies metálicas en medios naturales hacia organismos está determinada por un conjunto de eventos encadenados cuyo equilibrio representa sólo un caso particular de la situación dinámica general. Especies poco definidas químicamente, tales como ácidos húmicos y fúlvicos, actúan como ligandos de metales y juegan un papel clave en la circulación y la determinación de las propiedades ecotoxicológicas de las especies metálicas en los medios naturales. La polifuncionalidad de los ácidos húmicos y fúlvicos es descrita en este estudio usando métodos termodinámicos y mecano-estadísticos. La técnica Diffusive Gradients in Thin films (DGT) se ha utilizado para medir el flujo disponible de metal en un sistema sintético que contiene complejos metálicos. La principal conclusión de este estudio es que el disco de resina quelatante de los sensores juega un papel clave en la determinación del grado de labilidad de un complejo medido esta técnica. Por otra parte, a un pH bajo, o a concentración alta de ligando, puede ser alcanzado el equilibrio entre la resina del sensor y el metal en el seno de la disolución, perturbando la acumulación lineal a tiempos de contacto relativamente cortos. Se presenta un análisis de estos fenómenos, así como su justificación mediante modelos teóricos. / Availability of metals for organisms does not depend only on the total metal concentration but also on speciation of these species. In general, the availability towards organisms is determined by a set of chained events whose equilibrium approach only represents a simplified limiting case of the general dynamic situation. Poorly defined species such as humic and fulvic acids, act as metal ligands and play a key role in the circulation and determination of the ecotoxicological properties of metal species in the natural media. Thermodynamic and statistical mechanics methods are here applied to describe the polyfunctionality of humic and fulvic acids. The Diffusive Gradients in Thin Films (DGT) has been used to measure the available metal flux in a synthetic system that contains metal complexes. A main conclusion of this study is that the chelating resin disc of the sensor plays a key role in determining the lability degree of a complex measured with DGT. Moreover, at relatively low pH, or in presence of high affinity ligands, the equilibrium with the bulk metal concentration can be approached in the sensor, disturbing linear accumulations at relatively short deployment times. Analysis of these phenomena and theoretical explanations are reported.

In this thesis, simple methods to determine sulfide at low levels (µg L-1) in aqueous samples and sediments by water free hydrogen sulfide vapor generation using a commercially available vapor generation accessory have been developed. The hydrogen sulfide is then introduced in the ICP-QMS, equipped with an octopole collision/reaction cell which is vented with hydrogen and helium gases, or in the ICP-AES where the optical path between the plasma and the monochromator is purged with nitrogen. Moreover some studies have been conducted for the determination of arsenic by ICP-MS in natural waters with high sodium and chloride content. Spectral and non spectral interferences on arsenic measurement have been investigated and different experiments have been developed to solve such interferences (optimizations of the cell collision conditions, arithmetic corrections, introduction of small amounts of alcohol). Finally, the use of the DGT technique (diffusive gradients in thin films) has been evaluated in acidic samples and mining wastes for the firs time. / En aquesta tesi, s’han desenvolupat mètodes senzills per a la determinació de sulfur a baixes concentracions (µg L-1) en mostres aquoses i sediments mitjançant la generació de sulfur d’hidrogen, utilitzant un accessori de generació d’hidrurs comercial. Un cop format el sulfur d’hidrogen, aquest es pot introduir a l’ICP-QMS, equipat amb una cel•la de col•lisió/reacció o a l’ICP-AES amb el pas entre el plasma i el monocromador purgat amb nitrogen. També s’han fet alguns estudis per determinar arsènic amb ICP-MS en aigües naturals amb alt contingut de sodi i clor. S’han estudiat les interferències espectrals i no espectrals sobre aquest element i s’han dut a terme diferents experiments per a resoldre-les (optimització de la cel•la de col•lisió, aplicació de correccions matemàtiques, introducció de petites quantitats d’alcohol). Finalment, s’ha avaluat l’ús de la tècnica de DGT (diffusive gradients in thin films) en mostres àcides (pHs de 5 a 10) i residus de mineria per primera vegada.

A number of nanomachines that cooperatively communicate and share information in order to achieve specific tasks is envisioned as a nanonetwork. Due to size and capabilities of nanomachines, the traditional communication paradigms cannot be used for nanonetworks in which network nodes may be composed of just several atoms or molecules and scale on the orders of few nanometers. Instead, the molecular communication is a promising solution approach for nanoscale communication paradigm. However, molecular communication must be thoroughly investigated to realize the nanoscale communication and nanonetworks for many envisioned applications such as nanoscale body area networks, nanoscale molecular computers. In this thesis, a simulation framework (NanoSim) for nanoscale molecular communication networks is presented. The objective of the framework is to provide a simulation experimental tool in order to create a better understanding of nanonetworks and facilitate the development of new communication techniques and validation of theoretical results. The NanoSim framework is built on top of core components of widely used network simulator (ns-2). It incorporates the simulation modules for various nanoscale communication paradigms based on diffusive molecular, motor-based and gap junction-based molecular communication channels. The details of NanoSim are discussed and some functional scenarios are defined to validate NanoSim. In addition to this, the numerical analyses of these functional scenarios and the experimental results for them are presented. The validation of NanoSim is done by comparing these experimental and numerical results.

High density polyethylene (HDPE) geomembranes are normally used as part of a composite liner for waste containment facilities such as municipal solid waste (MSW) landfills and heap leach pads. Field conditions, which include physical stresses on the geomembrane, elevated operating temperatures, and contact with leachate constituents, have the potential to affect the service life of the HDPE geomembranes. This thesis examined the long-term performance of different HDPE geomembranes based on both conventional laboratory accelerated immersion tests and simulated landfill liner tests. A 1.5mm HDPE geomembrane was immersed in different synthetic leachates at different temperatures in order to evaluate the effects of leachate chemical constituents on the depletion of antioxidants. The results showed that a basic leachate with trace metals, surfactant, and a reducing agent was the most appropriate for evaluating the potential degradation of HDPE geomembranes. A similar immersion test was performed to evaluate the effects of thickness on the ageing of HDPE geomembranes. Three commercially available HDPE geomembranes having nominal thicknesses of 1.5, 2.0, and 2.5mm were immersed in a synthetic leachate at four different temperatures in this experiment. The results showed that a thicker geomembrane may have a longer service life if other things are similar. The depletion of antioxidants from a 1.5mm thick HDPE geomembrane was examined by conducting accelerated ageing tests at 55, 70, and 85oC under simulated landfill liner conditions. The results showed that the antioxidant depletion rate was consistently lower for the simulated landfill liner tests compared to the leachate immersion tests. The effectiveness of the aged HDPE geomembrane on the migration of volatile organic compounds (VOCs) was examined by conducting diffusion and partitioning tests using both unaged and aged HDPE geomembranes. The results showed that the ageing of HDPE geomembranes did not increase diffusive migration of organic contaminants, provided that the geomembrane remained intact. A new method was developed to estimate the service life of the HDPE geomembrane based on the landfill liner temperature history. The service lives of the HDPE geomembranes were calculated to be between 20 and 4700 years, depending on the geomembrane type, exposure conditions, and the time-temperature history examined. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2009-01-30 09:30:49.135