L'objectif de ce travail est d'étudier les évolutions microstructurales des matériaux cimentaires au cours de l'hydratation et d'analyser les dégradations physico-chimiques de ces matériaux lorsqu'ils sont soumis au séchage. Ces évolutions sont caractérisées par les mesures de teneur en eau et de porosité qui sont des paramètres clés pour l'évaluation de la durabilité des matériaux. L'originalité du travail réside en l'utilisation de l'Imagerie par Résonance magnétique IRM. Nous présentons une synthèse bibliographique sur les matériaux cimentaires et sur l'IRM qui permet d'accéder à la densité protonique caractéristique de la teneur en eau et aux temps de relaxation qui donnent une information sur la distribution poreuse. Les résultats sont ensuite identifiés aux données obtenues par des techniques expérimentales du génie civil. Enfin deux problématiques inhérentes aux matériaux cimentaires qui sont l'analyse de l'hydratation et le couplage hydratation/séchage sont étudiées.

<p>Overall aims of the present thesis were to study the prevalence and psychosocial impact of recurrent headache within a school population in comparison with other types of pain and to examine the use and efficacy of various coping strategies. Further aims were to compare the effects of relaxation treatment among adolescents with recurrent headache to a waiting-list control group, and finally to examine the efficacy of relaxation training administered in a school setting.</p><p>From 8 schools, 793 adolescents were recruited to a questionnaire study. The results showed that headache is a very common health complaint particularly among girls. Subjects with frequent headache also reported higher levels of depressive symptoms, anxiety, functional disability and other types of recurrent pain, than those with infrequent headache.</p><p>A Swedish version of the pain coping questionnaire (PCQ) was translated and administered to the same sample of 793 adolescents. Its psychometric properties were replicated and problem solving was regarded to be the most effective coping strategy.</p><p>In a treatment study 36 subjects suffering from migraine and tension-type headache were randomized to either relaxation treatment or a waiting list control group. Results showed that half of the adolescents were clinically improved after treatment. In a final effectiveness study 63 subjects were randomized to one of two types of relaxation training, administered by school nurses. The results showed similar positive outcomes but small differences compared to a non-treated post hoc comparison group. Positive outcomes of relaxation treatment were predicted by one pain coping strategy, positive self-statements but also by higher functional disability before treatment.</p><p>In conclusion, more active strategies such as positive self-statements and problem solving were found to co-vary with a better efficacy or outcome after relaxation training. A further exploration of how to optimize treatment for adolescent headache is warranted in future studies. Generally a broader perspective including social, psychological as well as biological factors could give more information on the complex mechanisms behind headache.</p>

Graduation date: 1998

No description available.

Un excès de fer est observé dans les noyaux du cerveau de patients atteints de maladies neurodégénératives ainsi que dans le foie et la rate de patients souffrant d’hémochromatose et de thalassémie. La ferritine est la protéine qui stocke le fer chez l’Homme. Les tissus contenant du fer apparaissent assombris sur les images IRM pondérées T2 à cause d’une relaxation T2 rapide. Cette caractéristique de la ferritine pourrait donc permettre de déterminer le contenu en fer des organes de façon non invasive. L’IRM pourrait alors être utilisée pour détecter certaines maladies et suivre leur évolution. Dans ce travail, les propriétés de relaxation magnétique nucléaire de tissus contenant du fer sont étudiées. Une corrélation potentielle des taux de relaxation avec le contenu en fer de ces tissus est également recherchée. Les mesures relaxométriques sur des échantillons de noyaux gris du cerveau, de substance blanche, de foie et de rate sont réalisées à différents champs magnétiques (entre 0.00023 T et 14.06 T) et à différents temps inter-écho. Le contenu en fer des tissus est déterminé par ICP (Inductively Coupled Plasma). Pour tous les échantillons, 1/T1 diminue avec le champ magnétique. 1/T2 augmente fortement avec le champ magnétique, soit linéairement, soit quadratiquement suivant les échantillons. Le taux de relaxation transverse dépend également du temps inter-écho, à bas et/ou haut champ selon le type de tissu. Un mélange de contributions (diffusion, déphasage, échange,...), certainement dû à la complexité de ces tissus, est nécessaire pour décrire théoriquement leur relaxation. Une corrélation entre les taux de relaxation et la concentration en fer est observée, principalement, à haut champ et pour les noyaux du cerveau. Les coefficients de corrélation que nous obtenons ne sont pas excellents. La quantification précise du contenu en fer d’un tissu par IRM semble donc complexe. Il n’empêche que l’IRM, à haut champ magnétique, reste un outil de choix pour la détection "qualitative" de ferritine dans un organe.

Overall aims of the present thesis were to study the prevalence and psychosocial impact of recurrent headache within a school population in comparison with other types of pain and to examine the use and efficacy of various coping strategies. Further aims were to compare the effects of relaxation treatment among adolescents with recurrent headache to a waiting-list control group, and finally to examine the efficacy of relaxation training administered in a school setting. From 8 schools, 793 adolescents were recruited to a questionnaire study. The results showed that headache is a very common health complaint particularly among girls. Subjects with frequent headache also reported higher levels of depressive symptoms, anxiety, functional disability and other types of recurrent pain, than those with infrequent headache. A Swedish version of the pain coping questionnaire (PCQ) was translated and administered to the same sample of 793 adolescents. Its psychometric properties were replicated and problem solving was regarded to be the most effective coping strategy. In a treatment study 36 subjects suffering from migraine and tension-type headache were randomized to either relaxation treatment or a waiting list control group. Results showed that half of the adolescents were clinically improved after treatment. In a final effectiveness study 63 subjects were randomized to one of two types of relaxation training, administered by school nurses. The results showed similar positive outcomes but small differences compared to a non-treated post hoc comparison group. Positive outcomes of relaxation treatment were predicted by one pain coping strategy, positive self-statements but also by higher functional disability before treatment. In conclusion, more active strategies such as positive self-statements and problem solving were found to co-vary with a better efficacy or outcome after relaxation training. A further exploration of how to optimize treatment for adolescent headache is warranted in future studies. Generally a broader perspective including social, psychological as well as biological factors could give more information on the complex mechanisms behind headache.

Dissolution dynamic nuclear polarization (DNP) provides several orders of magnitude of NMR signal enhancement by converting the much larger electron spin polarization to nuclear spin polarization. Polarization occurs at low temperature (1.4K) and is followed by quickly dissolving the sample for room temperature NMR detection. DNP is generally applicable to almost any small molecules and can polarize various nuclei including 1H, 19F and 13C. The large signal from DNP enhancement reduces the limit of detection to micromolar or sub-micromolar concentration in a single scan. Since DNP enhancement often provides the only source for the observable signal, it enables tracking of the polarization flow. Therefore, DNP is ideal for studying chemical processes. Here, quantitative tools are developed to separate kinetics and spin relaxation, as well as to obtain structural information from these measurements. Techniques needed for analyzing DNP polarized sample are different from those used in conventional NMR because a large, yet non-renewable hyperpolarization is available. Using small flip angle pulse excitation, the hyperpolarization can still be divided into multiple scans. Based on this principle, a scheme is presented that allows reconstruction of indirect spectral dimensions similarly to conventional 2D NMR. Additionally, small flip angle pulses can be used to obtain a succession of scans separated in time. A model describing the combined effects of the evolution of a chemical process and of spin-lattice relaxation is shown. Applied to a Diels-Alder reaction, it permitted measuring kinetics along with the effects of auto- and cross-relaxation. DNP polarization of small molecules also shows significant promise for studying protein-ligand interaction. The binding of fluorinated ligands to the protease trypsin was studied through the observation of various NMR parameter changes, such as line width, signal intensity and chemical shift of the ligands. Intermolecular polarization transfer from hyperpolarized ligand to protein can further provide information about the binding pocket of the protein. As an alternative to direct observation of protein signal, a model is presented to describe a two-step intermolecular polarization transfer between competitively binding ligands mediated through the common binding pocket of the protein. The solutions of this model relate the evolution of signal intensities to the intermolecular cross relaxation rates, which depend on individual distances in the binding epitope. In summary, DNP provides incomparable sensitivity, speed and selectivity to NMR. Quantitative models such as those discussed here enable taking full advantage of these benefits for the study of chemical processes.

QC 20100628

The problem of detecting a vector of symbols, drawn from a finite alphabet and transmitted over a multiple-input multiple-output (MIMO) channel with Gaussian noise, is of central importance in digital communications and is encountered in several different applications. Examples include, but are not limited to; detection of symbols spatially multiplexed over a multiple-antenna channel and the multiuser detection problem in a code division multiple access (CDMA) system. Two algorithms previously proposed in the literature are considered and analyzed. Both algorithms have their origin in other fields of science but have gained mainstream recognition as efficient algorithms for the detection problem considered herein. Specifically, we consider the sphere decoder and semidefinite relaxation detector. By incorporating assumptions applicable in the communications context the performance of the two algorithms is addressed. The first algorithm, the sphere decoder, offers optimal performance in terms of its error probability. Further, the algorithm has proved extremely efficient in terms of computational complexity for moderately sized problems at high signal to noise ratio (SNR). Although it is recognized that the algorithm has an exponential worst case complexity, there has been a widespread belief that the algorithm has a polynomial average complexity at high SNR. A contribution made herein is to show that this is incorrect and that the average complexity, as the worst case complexity, is exponential in the number of symbols detected. Instead, another explanation of the observed efficiency of the algorithm is offered by deriving the exponential rate of growth and showing that this rate, although strictly positive for finite SNR, is small in the high SNR regime. The second algorithm, the semidefinite relaxation (SDR) detector, offers polynomial complexity at the expense of suboptimal performance in terms of error probability. Nevertheless, previous numerical observations suggest that error probability of the SDR algorithm is close to that of the optimal detector. Herein, the near optimality is of the SDR algorithm is given a precise meaning by studying the diversity of the SDR algorithm when applied to the (real valued) i.i.d.~Rayleigh fading channel and it is shown that the SDR algorithm achieves the same diversity order as the optimal detector. Further, criteria under which the SDR estimates coincide with the optimal estimates are derived and discussed. / Ett grundläggande problem som påträffats inom digital kommunikation är detektering av en symbolvektor, tillhörande ett ändligt symbolalfabet, som sänts över en MIMO (från engelskans multiple-input multiple-output) kanal med Gausiskt brus. Detta problem påträffas bland annat då symboler sänts över en trådlös kanal med flera antenner hos mottagaren och sändaren samt då flera användare i ett CDMA system simultant skall avkodas. In denna avhandling behandlas två mottagaralgoritmer konstruerade för detta ändamål. Algoritmerna har sin bakgrund i andra forskningsområden men kan i nuläget sägas vara mycket välkända inom kommunikationsområdet. De benämns vanligtvis som sfäravkodaren (eng. sphere decoder) samt den semidefinita relaxeringsdetektorn (eng. semidefinite relaxation detector). Algoritmerna analyseras i denna avhandling matematiskt genom att införa förenklande antaganden som är relevanta och applicerbara för de kommunikationsproblem som är av intesse. Den första algoritmen, sfäravkodaren, löser dessa detektionsproblem på ett optimalt sätt i betydelsen att den minimerar sannolikheten för att detektorn fattar ett felaktigt beslut rörande det sända meddelandet (symbolvektorn). Också vad gäller algoritmens komplexitet har simuleringar visat att den är oväntat låg, åtminstone vid höga signalbrusförhållanden (SNR). Trots att det är allmänt känt att algoritmen i sämsta fall har exponentiell komplexitet så har detta lett till den allmänt spridda uppfattningen att medelkomplexiteten (eller den förväntade komplexiteten) endast är polynomisk vid höga signalbrusförhållanden. Ett av huvudbidragen i denna avhandling är att visa att denna uppfattning är felaktig och att också medelkomplexiteten växer exponentiellt i antalet symboler som simultant detekteras. Ytterligare ett bidrag ligger i att ge en alternativ förklaring till den observerat låga medelkomplexiteten. Det visas att den exponentiella hastighet med vilken komplexiteten växer beror på signalbrusförhållande, och att den är låg för höga SNR. Den andra algoritmen, den semidefinita relaxeringsdetektorn, erbjuder polynomisk komplexitet vid en något högre felsannolikhet. Intressant nog har dock felsannolikheten tidigare, genom simuleringar, visat sig vara endast marginellt högre än felsannolikheten hos den optimala mottagaren. Bidraget som relaterar till den semidefinita relaxeringsmottagaren ligger i att både förklara och i att ge en specifik kvatifierbar mening åt uttalandet att felsannolikheten endast är marginellt högre. I syfte att åstadkomma detta studeras diversitetsordningen för detektorn, och det bevisas att diversitetsordningen för den semidefinita relaxeringsdetektorn är densamma som för den optimala mottagaren. Utöver detta karakteriseras också de krav som måste uppfyllas för att den detektorn skall finna den optimala lösningen. / QC 20100901

Den här rapporten redovisar examensarbetet vars huvudsyfte var att förstå teori och beräkningsgången bakom förspända betongelement samt att jämföra den med teorin för slakarmerade betongelement. Arbetet valdes eftersom inga kurser under studietiden har beaktat denna typ av utformning samt eftersom tillämningen av kunskapen inom området är stor ute i arbetslivet. Arbetet slutfördes genom inläsning av litteratur samt handledning. Det visade sig efter arbetet var slutfört att några delar av teorin och beräkningsgången bakom förspända betongelement var lik den som används vid slakarmerade betongelement, dock existerade även många skillnader. Likheterna erhålls bland annat vid beräkningarna av moment- och tvärkraftskapaciteterna. Skillnaden är att många extra steg måste utföras vid dimensioneringen, steg som till största del bara av olika kontroller, vilka utfördes bland annat vid dimensioneringen av tillverkningsprocessen och i brottgränstillstånd. Slutligen kunde det konstateras att förspända betongelement har många fördelar, vilka bland annat är att större spännvidder, mindre dimensioner på konstruktionerna samt mindre deformationer kan erhållas. Dock så krävs en större mängd beräkningar vid förspända än för slakarmerade betongelement. / The objective of this thesis is to understand the theory and learn the calculation behind prestressed concrete elements and to compare it with the theory of ordinary reinforced concrete elements. This thesis work was chosen in order to promote the study of prestressed concrete and because it´s broad application in civil engineering. The worked was completed by reading literature and guidance. It turned out after the work was completed that some parts of the theory and calculation behind prestressed concrete was similar to that used in the ordinary reinforced concrete. However, there were also many differences that existed. Some of the similarities are obtained when the capacities of moment and shear are calculated. The differences is that many extra steps are required when the design are performed, steps who for the most part due to different controls and are required to be performed to ensure the safety of the design. The controls are to be performed, among other, in the design of the manufacturing process and in the ultimate limit state. Finally, it is found that prestressed concrete elements have many benefits, which includes larger spans, smaller dimensions for structures and that smaller deformations can be obtained. However, it will require a larger amount of calculations as compared to ordinary reinforced concrete.