Ma thèse développe deux parties. La première considère que la psychologie expérimentale doit clarifier son positionnement épistémologique pour clarifier la validation formelle de sa démarche, sans forcément devoir se référencer au cadre de la Science Physique. A partir d’une réflexion critique, je propose de décaler le cadre épistémologique en psychologie et de poser clairement un cadre pragmatique-réaliste. La thèse essentielle défendue dans ce travail est : 1/ les propriétés mentales doivent être comprises comme des phénomènes émergents, ce qui implique que leurs analyses ne peuvent se faire ni au niveau neuronal, ni au niveau de la dynamique interne de processus cognitifs, mais nécessairement au niveau de ces phénomènes émergents ; 2/ pour analyser les propriétés mentales comme formes émergentes, la psychométrie a besoin d’user de concepts qui sont en tension permanente entre une objectivité et une intersubjectivité ; en conséquence, la psychométrie doit affirmer une démarche pragmatiste-réaliste, en rupture avec l’empirisme-réaliste classique ; 3/ une approche pragmatiste-réaliste, basée entre autre sur l’abduction, permet de dépasser les contradictions pointées dans la littérature académique sur les propriétés mentales et leurs mesures ; 4/ un cadre de mesure de propriétés mentales par des variables latentes devient dès lors possible si ce cadre est compris lui aussi comme pragmatiste-réaliste ; 5/ mais ce recours au pragmatisme-réaliste renvoie en conséquence une critique à la fois des modèles avec variables latentes développés dans la littérature académique et les usages sociaux de ces modèles. La seconde partie de ma thèse porte sur un cadre particulier de formalisation des variables latentes : le cadre formatif. Je développe des simulations Monte Carlo pour vérifier le spectre des paramètres permettant une mesure formative efficiente dans le cadre d’un positionnement réaliste-empirique. / My thesis considers that experimental psychology must clarify its epistemological position to clarify the formal validation of its approach, without necessarily having to refer to the framework of Science Physics. From a critical reflection, I propose to shift the epistemological framework in psychology and clearly pose a pragmatic-realistic framework. The main thesis of this work is: 1 / mental properties must be understood as emerging phenomena, which implies that their analysis can not be done nor at the neuronal level, nor at the internal dynamics of cognitive processes, but necessarily at these emerging phenomena; 2 / to analyze the mental properties as emerging forms, psychometrics need to use concepts that are in permanent tension between objectivity and intersubjectivity; accordingly, psychometrics must assert a pragmatic-realist approach, breaking with classical empiricism-realistic; 3 / a pragmatist-realistic approach, based among other things on the abduction, can overcome the contradictions pointed in the academic literature on mental properties and their measurements; 4 / a framework for measuring mental properties by latent variables becomes possible if the framework is also understood as a pragmatic-realist; 5 / but use realistic-pragmatic returns accordingly critical of both models with latent variables developed in the academic literature and the social uses of these models. The second part of my thesis focuses on a specific part of formalization of latent variables: the formative model. I develop Monte Carlo simulations to check the range of parameters for efficient formative measure as part of a realistic-empirical positioning.

O processo fermentativo para a obtenção de etanol constitui um sistema complexo. Durante a fermentação se desenvolvem infecções em forma crônica e os surtos de infecção aguda aparecem em condições que; por causa da dinâmica não-linear do processo que envolve uma rede de reações metabólicas dos microrganismos, a alta dependência às condições de contorno e pelas interações sinérgicas e antagônicas envolvidas neste ecossistema; ainda representam um tema relevante de pesquisa em aberto. O presente trabalho propõe contribuir na tarefa de interpretar tais efeitos por intermédio de um modelo que inclua a interferência das bactérias. É proposto um cenário em escala laboratorial e controlado com a linhagem isolada de Saccharomyces cerevisiae PE-2 em co-cultura com bactérias de metabolismo heterofermentativo e homofermentativo. A interferência é explicada por intermédio de um modelo com efeito fixo baseado em um modelo não estruturado proposto por Lee (1983), e modificado a partir dos estudos de Andrietta (2003). São conduzidos ensaios de quatro tratamentos: uma fermentação controle e outras contaminadas com cada um dos diferentes tipos de bactérias e também em conjunto, a fim de fornecer dados experimentais para ajuste do modelo em discussão. Em seguida, são realizadas estimativas dos parâmetros que compõem as equações diferenciais da cinética da fermentação, utilizando um algoritmo genético baseado em evolução diferencial Storn e Price (1997). Completa-se a avaliação dos parâmetros por intermédio da análise de sensibilidade paramétrica dos mesmos. De posse desses resultados, é utilizado o modelo do tratamento controle como base, e são inseridos vetores de variáveis categóricas, correspondentes a efeitos fixos. Tais variáveis permitem modelar a interferência da contaminação no modelo matemático proposto. A estatística descritiva, a análise utilizando inferência bayesiana e a interpretação bioquímica dos resultados complementam as inferências obtidas a respeito do modelo. A análise de sensibilidade e correlação dos parâmetros, mostrou que os modelos para a cinética da fermentação, estudados e bem conhecidos não são adequados para modelar o processo, pela alta correlação dos seus parâmetros. O tratamento controle teve um rendimento de 46,97% na produção de etanol, o tratamento com bactéria heterofermentativa teve uma redução de 2.35% e com a mistura de ambas a redução foi de 1,58%. Uma das principais contribuições deste estudo relacionasse à produção de glicerol, o resultado mostra que no há impacto significativo na presença de bactérias homofermentativas e sim uma clara tendência a inibir a sua produção. Apresentam-se também indícios de sinergia entre as bactérias e de consumo de manitol pela bactéria homofermentativa. / The fermentation process for obtaining ethanol is a complex system. During fermentation develop chronic infections and outbreaks of acute infection in conditions that appear, because of the nonlinear dynamics of the process that involves a network of metabolic reactions of microorganisms, the high dependence on boundary conditions and the synergistic interactions and antagonistic involved in this ecosystem, still represent a relevant topic of research open. This paper proposes to contribute in the interpreting such effects through a model that includes the interference of bacteria. We propose a scenario in laboratory scale and controlled with the strain isolated from Saccharomyces cerevisiae PE-2 in co-culture with bacteria and homofermentativo heterofermentative metabolism. The interference is explained by means of a template with fixed effect based on a non structured proposed by Lee (1983) and modified from studies Andrietta (2003). Tests are conducted four treatments: a control fermentation and other contaminated with each of the different bacteria and also in conjunction in order to provide experimental data to fit the model under discussion. Are then carried estimates of the parameters that make up the differential equations of the kinetics of the fermentation, using a genetic algorithm based on differential evolution Storm and Price (1997). To complete the parameters evaluated through analysis of the same parameter sensitivity. With these results, the model is used as the basis of the control treatment, and are inserted vectors of categorical variables, corresponding to fixed effects. These variables allow modeling the interference of contamination in the mathematical model. Descriptive statistics and Bayesian inference analysis and interpretation of biochemical results obtained complement inferences about the model. Sensitivity analysis and correlation of parameters for the models showed that the kinetics of the fermentation, well studied and known are not suitable for modeling the process, the high correlation between the parameters. The control had a yield of 46.97% in ethanol, treatment with heterofermentative bacteria was reduced by 2.35% and a mixture of both reduction was 1.58%. A major contribution of this study is related to the glycerol, the result shows that no significant impact on the presence of homofermentative bacteria but a clear tendency to inhibit their production. It also presents evidence of synergy between bacteria and consumption of mannitol by homofermentative bacteria.

Neste trabalho, nós investigamos o comportamento crítico dinâmico de três modelos estatísticos utilizando simulações Monte Carlo em tempos curtos. Inicialmente, estudamos os modelos tridimensionais de dupla-troca e de Heisenberg. O expoente dinâmico de persistência global, bem como o expoente z são estimados através de duas técnicas. Para obter o expoente de persistência global, aplicamos diretamente a lei de potência obtida para a probabilidade de persistência global e em seguida fizemos o colapso de uma função universal para duas redes de tamanhos diferentes. Para estimar o valor de z, nós usamos uma função mista que combina resultados de simulações realizadas com diferentes condições iniciais e o cumulante de Binder de quarta ordem dependente do tempo. O expoente dinâmico que governa o comportamento tipo lei de potência da magnetização inicial, é estimado através da correlação temporal da magnetização (modelos de dupla-troca e Heisenberg) e da aplicação direta de uma lei de potência (modelo de Heisenberg). Os expoentes estáticos da magnetização e comprimento de correlação são estimados seguindo o comportamento de escala do parâmetro de ordem e sua derivada, respectivamente. Os resultados confirmam que esses dois modelos pertencem à mesma classe de universalidade. Em seguida, alguns expoentes críticos dinâmicos e estáticos são estimados no ponto de bifurcação do modelo de spin com simetria Z(5) bidimensional. Neste ponto, o modelo apresenta dois parâmetros de ordem diferentes, cada um possuindo um conjunto diferente de índices críticos. Os valores dos expoentes críticos estáticos estão em boa concordância com os resultados exatos. Até onde sabemos, está é a primeira tentativa de se obter os expoentes críticos dinâmicos para os modelos de dupla troca, Heisenberg e para o modelo Z(5). / In this work, we investigate the dynamic critical behavior of three statistical models by using short-time Monte Carlo simulations. At first, we study the three-dimensional double-exchange and Heisenberg models. The global persistence exponent, as well as the exponent z are estimated through two techniques. The dynamical exponent of global persistence is obtained by using the straight application of the power law obtained for the global persistence probability and by following the scaling collapse of a universal function for two diferent lattice sizes. To estimate the value of z, we use a mixed function which combines results obtained from samples submitted to diferent initial configurations and the time dependent fourth-order Binder cumulant. The dynamical exponent which governs the power law behavior of the initial magnetization, is estimated through the time correlation of the magnetization (double-exchange and Heisenberg models) and through the straight application of a power law(Heisenberg model). The statical exponents of the magnetization and correlation length are estimated through the scaling behavior of the order parameter and its derivative, respectively. The results confirm which those models belong to the same universality class. Following, the dynamical exponents and the statical exponents are estimated at the bifurcation point of the two-dimensional Z(5)-symmetric spin model. In this point, the model presents two diferent order parameters, each one possessing a diferent set of critical indices. The values of the static critical exponents are in good agreement with the exact results. Our study is, to the best of our knowledge, the first attempt to obtain the dynamic critical exponents of the double-exchange, Heisenberg, and Z(5) models.

Depuis le début des années 1980, le Commissariat à l’Énergie Atomique développe et met en oeuvre un système de spectrométrie gamma aéroportée, appelé HELINUCTM. Ce système, composé de détecteurs NaI(Tl) d’un volume de 16 L, est utilisé afin d’établir un état des lieux radiologique des sites survolés. Les principales missions du système HELINUC consistent en la réalisation de contrôles environnementaux, l’intervention en situation de crise et la recherche de sources ponctuelles. La réalisation de ces missions nécessite le développement de méthodes d’analyse adaptées. L’approche considérée dans cette thèse repose sur une rupture conceptuelle de l’analyse des spectres par rapport aux méthodes utilisées jusqu’alors au CEA : l’analyse ne repose plus sur une considération individuelle et séquentielle des mesures aéroportées, mais sur une considération globale et simultanée de celles-ci. L’étude et le développement de méthodes statistiques adaptées à la quantification des radionucléides naturels et du 137Cs (de 600 keV à 3 MeV), à l’estimation de la contamination en 241Am (basse énergie, inférieure à100 keV) en cas de crise radiologique et la détection de sources ponctuelles (moyenne énergie, entre 100 keV et600 keV) permettent d’améliorer la précision sur les activités déterminées en vol et la détection de sources de faibles activités. / Since the beginning of 1980’s, the CEA has been developing an airborne gamma spectrometry (AGS) system called HELINUCTM using large volume (16 L) NaI(Tl) detectors. HELINUC is used to produce radioactivity mapping of the soil. The different missions of HELINUC are environmental control of radioactivity, nuclear emergency response and research of orphan sources. The continuous development of analysis methods is then required.The approach considered in this thesis is based on a conceptual break from the analysis of spectra compared to the methods used at the CEA until now: the analysis does not rely on an individual and sequential consideration of airborne measurements, but on an overall and simultaneous consideration of them. The study and development of statistical methods for the quantification of natural radionuclides and 137Cs (from 600 keV to 3 MeV), for the estimation of 241Am contamination (low energy, inferior to 100 keV) in case of radiological emergency and for the detection of orphan sources (medium energy, between 100 keV and 600 keV) improve the accuracy of activities estimation and detection of low activities sources.

La production d'hydrocarbures de schistes (shales) connait un regain d'intérêt à la fois scientifique et industriel depuis une quinzaine d’années. Cela représente de par le monde d’énormes ressources et risque de modifier durablement le marché énergétique, comme c'est le cas actuellement aux États Unis. Cependant, la récupération des hydrocarbures reste un enjeu majeur impactant au premier ordre la rentabilité de ces ressources. La majorité des hydrocarbures de shales est contenue dans des nodules micrométriques de matière organique : le kérogène, qui est à la fois la roche mère et le réservoir des fluides pétroliers. L’objectif de cette thèse est d’étudier le comportement du kérogène et de ses hydrocarbures grâce à la simulation moléculaire. Pour cela, nous avons effectué des simulations de Dynamique Moléculaire et de Monte Carlo à l’aide de logiciels existants et de développements internes. La première partie de ce travail a consisté à construire des modèles moléculaires visant à reproduire la matière organique contenue dans les shales (le kérogène et ses fluides). À partir de ces modèles, des structures 3D ont été générées en conditions de réservoirs. La représentativité de ces structures a été validée par des mesures expérimentales sur les propriétés volumiques, mécaniques, de stockage et de transport. Puis, nous avons mené une étude approfondie sur l’adsorption et la diffusion d’hydrocarbures dans la matrice kérogène. Les simulations moléculaires ont été effectuées en vue de fournir des données pseudo-expérimentales ainsi que des données de références pour la modélisation. Concernant les propriétés de stockage, un modèle théorique pour l’adsorption de mélanges de fluides sous-critiques (type gaz à condensats ou huiles légères) et super-critique (type gaz sec) a été proposé et validé sur les données de simulation moléculaires. Concernant les propriétés de transport, les mécanismes régissant les transferts de masses ont été identifiés et un modèle a été proposé pour prédire l’évolution des coefficients de diffusion des hydrocarbures avec la température, la pression et la composition des hydrocarbures. / Hydrocarbons production from shales has been of growing industrial and scientific interest for the last fifteen years. The different kinds of shale resources represent huge quantities around the world and may durably change the energy market, as for example in the US. However, the recovery process remains critical and may drastically impact the profitability of these resources. In shales, the majority of the fluids are contained in micrometered nodules of organic matter : the kerogen, which acts as source rock and as reservoir for the oil and gas. The aim of the PhD thesis is to study the kerogen and the petroleum fluids contained in shales, by molecular simulations. For this purpose, Monte Carlo and Molecular Dynamics simulations with existing molecular simulation softwares and in-house codes have been used. The first part of the work has been dedicated to the construction of molecular models mimicking shales organic matter (kerogen and embedded fluids), based on analytical data. From these models, 3D structures have been generated under typical reservoir conditions. Agreements with available experimental results have been found on volumetric, storage, transport and mechanical properties. Then, we have focused our efforts on the adsorption and diffusion of hydrocarbon mixtures in such materials. Molecular simulations have been performed to provide both pseudo-experimental and reference data. On storage properties, a theoretical model which accounts for multicomponent adsorption of super-critical (dry gas) and sub-critical (condensate gas, light oil) mixtures has been developed and validated. On transport properties, the mechanisms governing hydrocarbon mass transfer have been identified and a model has been proposed which describes the dependence of mixture diffusion coefficients with thermodynamic conditions (composition, pressure and temperature).

<p>To estimate the propagation of light in tissue-like optical phantoms (fat emulsions), this thesis utilized the diffuse reflectance spectroscopy in combination with Monte Carlo simulations. A method for determining the two-parametric Gegenbauer-kernal phase function was utilized in order to accurately describe the diffuse reflectance from poly-dispersive scattering optical phantoms with small source-detector separations. The method includes the spectral collimated transmission, spatially resolved diffuse reflectance spectra (SRDR) and the inverse technique of matching spectra from Monte Carlo simulations to those measured. An absolute calibration method using polystyrene micro-spheres was utilized to estimate the relation between simulated and measured SRDR intensities. The phase function parameters were comparable with previous studies and were able to model measured spectra with good accuracy. Significant differences between the phase functions for homogenized milk and the nutritive fat emulsions were found.</p><p> </p>

<p>We have studied the critical properties of three-dimensional U(1)-symmetric lattice gauge theories. The models apply to various physical systems such as insulating phases of strongly correlated electron systems as well as superconducting and superfluid states of liquid metallic hydrogen under extreme pressures. This thesis contains an introductory part and a collection of research papers of which seven are published works and one is submitted for publication.</p><p>Paper I: Critical properties of the 2+1-dimensional compact abelian Higgs model with gauge charge q=2 are studied. We introduce a novel method of computing the third moment M₃ of the action which allows us to extract correlation length and specific heat critical exponents ν and α without invoking hyperscaling. Finite-size scaling analysis of M₃ yields the ratio (1+α)/ν and 1/ν separately. We find that α and ν vary along the critical line of the theory, which however exhibits a remarkable resilience of Z₂ criticality. We conclude that the model is a fixed-line theory, which we propose to characterize the zero temperature quantum phase transition from a Mott-Hubbard insulator to a charge fractionalized insulator in two spatial dimensions.</p><p>Paper II: Large scale Monte Carlo simulations are employed to study phase transitions in the three-dimensional compact abelian Higgs model in adjoint representations of the matter field, labeled by an integer q, for q=2,3,4,5. We also study various limiting cases of the model, such as the Z_q lattice gauge theory, dual to the 3DZ_q spin model, and the 3D xy spin model which is dual to the Z_q lattice gauge theory in the limit q → ∞. In addition, for benchmark purposes, we study the 2D square lattice 8-vertex model, which is exactly solvable and features non-universal critical exponents. The critical exponents α and ν are calculated from finite size scaling of the third moment of the action, and the method is tested thoroughly on models with known values for these exponents. We have found that for q=3, the three-dimensional compact abelian Higgs model exhibits a second order phase transition line which joins a first order phase transition line at a tricritical point. The results for q=2 in Paper I are reported with a higher lever of detail.</p><p>Paper III: This paper is based on a talk by F. S. Nogueira in the Aachen HEP 2003 conference where a review of the results for the compact abelian Higgs model from Paper I and Paper II was presented, as well as the results for the q=1 case studied by F. S. Nogueira, H. Kleinert and A. Sudbø.</p><p>Paper IV: We study the effects of a Chern-Simons (CS) term in the phase structure of two different abelian gauge theories in three dimensions. By duality transformations we show how the compact U(1) gauge theory with a CS term for certain values of the CS coupling can be written as a gas of vortex loops interacting through steric repulsion. This theory is known to exhibit a phase transition governed by proliferation of vortex loops. We also employ Monte Carlo simulations to study the non-compact U(1) abelian Higgs model with a CS term. Finite size scaling of the third moment of the action yields critical exponents α and ν that vary continuously with the strength of the CS term, and a comparison with available analytical results is made.</p><p>Paper V: The critical properties of N-component Ginzburg-Landau theory are studied in d=2+1 dimensions. The model is dualized to a theory of N vortex fields interacting through a Coulomb and a screened potential. The model with N=2 shows two anomalies in the specific heat. From Monte Carlo simulations we calculate the critical exponents α and ν and the mass of the gauge field. We conclude that one anomaly corresponds to an inverted 3D xy fixed point, while the other corresponds to a 3D xy fixed point. There are N fixed points, namely one corresponding to an inverted 3D xy fixed point, and N-1corresponding to neutral 3D xy fixed points. Applications are briefly discussed.</p><p>Paper VI: The phase diagram and critical properties of the N-component London superconductor are studied both analytically and through large-scale Monte-Carlo simulations in d=2+1 dimensions. The model with different bare phase stiffnesses for each flavor is a model of superconductivity which should arise out of metallic phases of light atoms under extreme pressure. A projected mixture of electronic and protonic condensates in liquid metallic hydrogen under extreme pressure is the simplest example, corresponding to N=2 with individually conserved matter fields. We compute critical exponents α and ν for N=2 and N=3. The results from Paper V are presented at a higher level of detail. For the arbitrary N case, there are N fixed points,namely one charged inverted 3D xy fixed point, and N-1 neutral 3D xy fixed points. We explicitly identify one charged vortex mode and N-1 neutral vortex modes. The model for N=2 and equal bare phase stiffnesses corresponds to a field theoretical description of an easy-plane quantum antiferromagnet. In this case, the critical exponents are computed and found to be non 3D xy values. Furthermore, we study the model in an external magnetic field, and find a novel feature, namely N-1 superfluid phases arising out of N charged condensates. In particular, for N=2 we point out the possibility of two novel types of field-induced phase transitions in ordered quantum fluids: i) A phase transition from a superconductor to a superfluid or vice versa, driven by tuning an external magnetic field. This identifies the superconducting phase of liquid metallic hydrogen as a novel quantum fluid. ii) A phase transition corresponding to a quantum fluid analogue of sublattice melting, where a composite field-induced Abrikosov vortex lattice is decomposed and disorders the phases of the constituent condensate with lowest bare phase stiffness. Both transitions belong to the 3D xy universality class.</p><p>Paper VII: We consider the vortex superconductor with two individually conserved condensates in a finite magnetic field. The ground state is a lattice of cocentered vortices in both order parameters. We find two novel phase transitions when temperature is increased at fixed magnetic field. i) A "vortex sublattice melting" transition where vortices in the field with lowest phase stiffness ("light vortices") loose cocentricity with the vortices with large phase stiffness ("heavy vortices"), entering a liquid state (the structure factor of the light vortex sublattice vanishes continuously.) This transition is in the 3D xy universality class. ii) A first order melting transition of the lattice of heavy vortices in a liquid of light vortices.</p><p>Paper VIII: We report on large-scale Monte Carlo simulations of a novel type of a vortex matter phase transition which should take place in a three dimensional two-component superconductor. We identify the regime where first, at a certain temperature a field-induced lattice of co-centered vortices of both order parameters melts, causing the system to loose superconductivity. In this state the two-gap system retains a broken composite symmetry and we observe that at a higher temperature it undergoes an extra phase transition where the disordered composite one-flux-quantum vortex lines are "ionized" into a "plasma" of constituent fractional flux vortex lines in individual order parameters. This is the hallmark of the superconductor-to-superfluid-to-normal fluid phase transitions projected to occur in e.g. liquid metallic hydrogen.</p>

<p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small;"><span style="font-family: Times New Roman;">This thesis consists of two different parts, related to two different fields in mathematical physics: wave propagation and kinetic theory of gases. Various mathematical and computational problems for equations from these areas are treated.</span></span></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small; font-family: Times New Roman;"> </span></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small;"><span style="font-family: Times New Roman;">The first part is devoted to high order finite difference methods for the Helmholtz equation and the wave equation. Compact schemes with high order accuracy are obtained from an investigation of the function derivatives in the truncation error. With the help of the equation itself, it is possible to transfer high order derivatives to lower order or to transfer time derivatives to space derivatives. For the Helmholtz equation, a compact scheme based on this principle is compared to standard schemes and to deferred correction schemes, and the characteristics of the errors for the different methods are demonstrated and discussed. For the wave equation, a finite difference scheme with fourth order accuracy in both space and time is constructed and applied to a problem in discontinuous media.</span></span></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small; font-family: Times New Roman;"> </span></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small;"><span style="font-family: Times New Roman;">The second part addresses some problems related to kinetic equations. A direct simulation Monte-Carlo method is constructed for the Landau-Fokker-Planck equation, and numerical tests are performed to verify the accuracy of the algorithm. A formal derivation of the method from the Boltzmann equation with grazing collisions is performed. The linear and linearized Boltzmann collision operators for the hard sphere molecular model are studied using exact reduction of integral equations to ordinary differential equations. It is demonstrated how the eigenvalues of the operators are found from these equations, and numerical values are computed. A proof of existence of non-zero discrete eigenvalues is given. The ordinary diffential equations are also used for investigation of the Chapman-Enskog distribution function with respect to its asymptotic behavior.</span></span></span></p><p class="MsoNormal" style="margin: 0cm 0cm 0pt;"><span style="mso-ansi-language: EN-US;" lang="EN-US"><span style="font-size: small; font-family: Times New Roman;"> </span></span></p>

<p>Detailed characterization of size and shape of polymers, and development of methods to elucidate the mechanisms behind shape transitions are central issues in this thesis. In particular we characterize grafted polymer chains under confinement in terms of the chain entanglement complexity and mean molecular size. Confinement of polymers into small regions can drastically affect the structural and mechanical properties, and make these systems convenient for a large number of applications, including the design of lubricants, coatings, and various biotechnical applications.</p><p>Using Monte Carlo simulations with a model including both persistence length and intramolecular non-bonded interaction, we find two regimes of polymer behaviour: <i>i) soft mushrooms</i>, where confinement successively flattens the chains with accompanying change in the folding complexity, and <i>ii) hard mushrooms </i>where the compact structures appear to resist confinement and the only way to reorganize the entanglements is by flattening under strong confinement. We also show that a simultaneous use of mean molecular size and chain entanglement complexity renders the possibility to create configurational "phase" diagrams for a wide range of polymers. We have further introduced a new descriptor of folding complexity, <i>the path-space ratio</i>, ζ_α which captures essential features of molecular shape beyond those conveyed by mean size and asphericity.</p><p>This thesis also contains results of light scattering measurements on supramolecular complexes formed when mixing an adamantane end-capped star polymer with a β-cyclodextrin polymer. The specific interactions result in an interplay between the association of the end-caps and a strong inclusion interaction between adamantane and β-cyclodextrin.</p>

<p>Two aspects of applied nuclear physics have been studied in this thesis; Monte Carlo simulations for high-sensitivity monitoring of radioactive xenon and high-accuracy neutron-proton scattering measurements for neutron physics applications and fundamental physics.</p><p>The Monte Carlo simulations have been performed for two systems for detection of radioactive xenon, using the MCNP code. These systems, designed for monitoring of violations of the Comprehensive Nuclear-Test-Ban Treaty, are based on coincident detection of electrons and gamma rays, emitted in beta decay of xenon nuclides produced in nuclear weapons explosions. In general, the simulations describe test data well, and the deviations from experimental data are understood. </p><p>The neutron-proton scattering measurements have been performed by measuring the differential <i>np</i> scattering cross section at 96 MeV in the angular range θ_c.m.= 20° – 76°. Together with an earlier data set at the same energy, covering the angles θ_c.m.= 74° – 180°, a new data set has been formed in the angular range θ_c.m.= 20° – 180°. This extended data set has been normalised to the experimental total <i>np</i> cross section, resulting in a renormalisation of the earlier data of 0.7 %, which is well within the stated normalisation uncertainty for that experiment. The results on forward <i>np</i> scattering are in reasonable agreement with theory models and partial wave analyses and have been compared with data from the literature.</p>