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This thesis forms part of a continuing programme of research to investigate the application of NMR to fluid saturated rock. The work falls into four sections; (i) The development of a novel broad line NMR imaging technique for the study of short T2 fluid components in reservoir rock The technique is a repetitive pulse variant of an established gradient echo method which employs oscillating magnetic field gradients. The variant uses low flip angle r.f. pulses to reduce image rounding artefacts and provide naturally T1 weighted data. (ii) The selective imaging of fluids within preserved reservoir rock and the first broad line NMR imaging study of immiscible fluid flow. The selective imaging of reservoir fluids within preserved rock core samples has been achieved using T1 weighted MRI methods. To account for the natural heterogeneity of the rock and the observed mixed wettability, T1 suppression has been enhanced by lowering the temperature of the rock cores, thus exploiting the difference in dominant relaxation mechanisms of the two core fluids. A model has been developed to explain this temperature dependence in terms of pore surface relaxation theory. Fluid flow processes within reservoir rock have been investigated using chemical substitution and T1 weighted imaging. Due to the short transverse relaxation times expected at irreducible saturation, short T2 imaging protocols have been adopted and represent the first such study. This has provided quantitative data from which the individual phase saturations can be directly obtained. (iii) The first broad line NMR imaging study of liquid and vapour phase diffusion processes in partially saturated rock. Excellent agreement is found between the NMR diffusion profiles of partially saturated rock and a model based on a combination of vapour and liquid phase transport. Estimates of the surface water diffusion coefficient and vapour percolation threshold have thus been obtained. (iv) A detailed study of proton relaxation times of water-saturated rock as a function of saturation. The saturation levels range from 0.06%, equivalent to monolayer water coverage, to 100%. The results have been used to test fast diffusion relaxation theory in rock over the full saturation range for the first time. The relaxation measurements at monolayer coverage have led to the first unambiguous estimates of rock plug pore surface relaxivity. Evidence has been obtained for the effect of pore throats on the relaxation times and pore throat size estimates have been made.

The effect of a magnetic field on an electrochemical system, the Leclanche cell, was investigated. Experiments show that there is an increase power output and charge passed when a cell is discharged in an applied magnetic field. Possible explanations for the effect and descriptions of attempts to verify these explanations are presented.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23073号 / 医博第4700号 / 新制||医||1049(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 溝脇 尚志, 教授 黒田 知宏, 教授 増永 慎一郎 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DGAM

Background: Adolescence and young adulthood are particularly vulnerable periods for the development of mental health disorders, including bipolar disorder (BD). Mental health screening at universities could aid in the early identification of particularly at- risk individuals, with the long-term aim of providing early treatment interventions to improve clinical outcomes. However, further research into the identification of appropriate behavioral and biological markers for vulnerability to psychiatric disorders – as well as into the acceptability and efficacy of mental health screening - is warranted. Methods: Young adults were recruited via an already existing Internet-based mental health screening survey of undergraduate students at the University of Oxford. In Study 1, qualitative interviews of young adults with and without previous mental health problems were conducted to assess the acceptability and efficacy of mental health screening within a university setting. In Studies 2-5 we explored the hypotheses of altered emotional decision-making, reward processing and neurostructural integrity as behavioral and neurobiological markers for vulnerability to bipolar disorder via the study of young adults with a common bipolar phenotype (BPP) - some of whom meet diagnostic criteria for bipolar II or not-otherwise-specified disorder (BD II/NOS). To that end, we employed a diverse range of methodologies: alcohol challenge (Study 2); neuropsychological task performance (Study 3); functional magnetic resonance imaging (fMRI; Study 4); diffusion tensor imaging (DTI) and voxel-based morphometry (VBM; Study 5). Results: Findings from Study 1 suggest that young adults are willing to participate in mental health screening within a university setting, and that such screening may be used to offer subsequent treatment interventions. Taken together, findings from Studies 2 and 4 suggest a general blunted reward response among unmedicated young adults at increased risk for BD during euthymia, and additionally suggest pathophysiological similarities between BD and alcohol use disorders (AUDs) that may provide a causal link between the elevated co-occurrence rates of the two disorders. Finally, findings from Study 5 suggest widespread white matter microstructural alterations – which are likely to be neurodevelopmental in origin – among antipsychotic- and mood-stabilizer naïve young adults with BD II/NOS. Conclusions: These data support the hypothesis of neurodevelopmental alterations identifiable prior to significant clinical impairment among young adults at increased risk of – or already meeting DSM-IV criteria for – bipolar disorder. They also suggest that young adults in higher education are willing to participate in mental health screening. Future studies should aim to identify more specific markers for individual disorders such as BD.

<p>A more global analysis of the outcome of heart valve surgery is desirable to reflect the actual benefit for the patient. This thesis focuses on the preoperative assessment of the patient, and the outcome after surgery with regard to operative mortality, long-term survival, valve-related complications, and quality of life. </p><p>Magnetic resonance imaging and echocardiography were comparable in assessing severe mitral regurgitation, but did not agree in measuring regurgitant fraction. Natriuretic peptides correlated well to regurgitant fraction on magnetic resonance imaging and to PISA and vena contracta on echocardiography. </p><p>The risk of death, myocardial injury and postoperative heart failure after valve surgery has decreased over the last decade whereas the proportion older patients has increased. </p><p>Survival is reduced after mitral valve replacement in patients with severe symptoms whereas patients with less symptoms have excellent survival. Older patients are more often severly symptomatic at the time of mitral valve surgery. </p><p>Event-free survival is superior in patients with a mechanical prosthesis, but not influenced by valve type in older patients. A mechanical prosthesis is associated with a higher risk of bleeding < 5 years from surgery, especially in older patients; and a bioprosthesis is associated with a higher risk of thromboembolism > 5 years from surgery. Ageing with a mechanical prosthesis implied an increased risk for an adverse event, this was not true for bioprostheses. </p><p>Quality of life after complicated heart valve surgery resulted in reduced physical health but equal mental health compared to uncomplicated controls.</p>

A more global analysis of the outcome of heart valve surgery is desirable to reflect the actual benefit for the patient. This thesis focuses on the preoperative assessment of the patient, and the outcome after surgery with regard to operative mortality, long-term survival, valve-related complications, and quality of life. Magnetic resonance imaging and echocardiography were comparable in assessing severe mitral regurgitation, but did not agree in measuring regurgitant fraction. Natriuretic peptides correlated well to regurgitant fraction on magnetic resonance imaging and to PISA and vena contracta on echocardiography. The risk of death, myocardial injury and postoperative heart failure after valve surgery has decreased over the last decade whereas the proportion older patients has increased. Survival is reduced after mitral valve replacement in patients with severe symptoms whereas patients with less symptoms have excellent survival. Older patients are more often severly symptomatic at the time of mitral valve surgery. Event-free survival is superior in patients with a mechanical prosthesis, but not influenced by valve type in older patients. A mechanical prosthesis is associated with a higher risk of bleeding &lt; 5 years from surgery, especially in older patients; and a bioprosthesis is associated with a higher risk of thromboembolism &gt; 5 years from surgery. Ageing with a mechanical prosthesis implied an increased risk for an adverse event, this was not true for bioprostheses. Quality of life after complicated heart valve surgery resulted in reduced physical health but equal mental health compared to uncomplicated controls.

The main objective in this work was to learn how the instrument, the Interfacial Shear Rheometer (ISR400), worked and to investigate how the rheological properties, storage modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface pressure at the air-liquid interphase changes. The second objective were to examine the different kind of magnetic needles used in the experiments and to conclude which type of needle is best for its specific field of analysis. It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm was best for systems where the viscous and elastic components are significantly large, where the inertia of the needle is not dominant. It also worked of using the heavier needle for a system of phospholipids. For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51 mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the dynamic modulus therefore had a better agreement with reference literature. A spread layer of class II hydrophobins (HFBII) could be compressed to a surface pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded because the monolayer turned into a very viscous-like liquid, and the oscillating needle, after compression, was kind of stuck in the sub-phase and moved very staggering during a frequency sweep. The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30), at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution with BCC30 added to it. The differences were negligible in terms of surface tension but there was a clear difference between the heavy needle and the light needle, when oscillating at higher frequencies (&gt;≈6 rad/s). With this study, the understanding of ISR400 has increased largely. Several issues have been addressed and the results provide a good basis for further studies within the many areas the instrument can be used for. Despite the project's time limit, and the fact that the instrument was new and untested where the project was carried out, focus areas were prioritized so good results could be achieved within reasonable goals. / Huvudmålet med detta arbete var att lära sig hur instrumentet ytskiktsreometern (ISR400) fungerade och undersöka hur de reologiska egenskaperna, elasticitetsmodulen G' och viskositetsmodulen G'', kommer att förändras när det sker en förändring för yttrycket vid gränsskiktet mellan luft och vätska. Det sekundära målet var att undersöka vilken typ av magnetiska nålar som är bäst att använda för respektive gränsskiktssystem. Av att använda den tyngre nålen med massan 70.6 mg och längden 50 mm kunde man dra slutsatsen att den är bäst att använda för system där de viskösa och elastiska komponenterna är signifikant stora, där nålens tröghet inte är dominant. Den fungerade även att mäta med i ett fosfolipidsystem. I experimentet med 12-hydroxy-stearinsyra (HSA) som utfördes på en subfas av NaCl, syntes en klar förbättring efter att byta från en tyngre nål (massa 41.5 mg; längd 51 mm) till en lättare (massa 6.94 mg; längd 34.7 mm). Värdena för dynamiska modulen stämde därför bättre överens med referenslitteraturen. Det utspridda lagret av klass II hydrophobins (HFBII) kunde komprimeras upp till yttrycket 46 mNm-1. Värdena för G' och G'' förkastades därför att monolagret förvandlades till en väldigt viskösliknande vätska, och den oscillerande nålen, efter kompressionen, satt fast i denna tröga vätska och rörde sig väldigt hackigt och oregelbundet under tiden ett frekvenssvep utfördes. Då en jämförelse av olika typer av nålar genomfördes med kiseldioxidpartiklar (10 % (viktsprocent) Bindzil CC30 med pH 3.5), för att se om det är någon skillnad i känslighet för nålarna vid gränssnittet, som bestod av en ren 10 mM NaCl-lösning eller en 10 mM NaCl-lösning med tillsatt BCC30. Skillnaderna var försumbara gällande ytspänningen, men det var en klar skillnad mellan den tunga nålen och den lätta nålen vid oscillering vid höga frekvenser (&gt;≈6 rad/s). I och med detta arbete så har förståelsen för hur ISR400 fungerar förbättrats mycket sedan starten. Flera frågeställningar har behandlats och resultaten ger en bra grund för fortsatta studier inom de många områden som utrustningen kan användas till. Trots projektets tidsbegränsning, och det faktum att instrumentet var nytt och oprövat på platsen där detta arbete utfördes, så prioriterades fokusområden så att goda resultat kunde uppnås inom rimliga mål.

Dans le cadre de l'augmentation de la densité de stockage des mémoires magnétorésistives à accès direct (MRAM), les matériaux à anisotropie magnétique perpendiculaire sont particulièrement intéressants car ils possèdent une très forte anisotropie. Cependant, cette augmentation d'anisotropie induit également un accroissement de la consommation d'écriture. Un nouveau concept d'écriture assistée thermiquement a été proposé par le laboratoire SPINTEC. Le principe est de concevoir une structure très stable à température ambiante, mais qui perd son anisotropie lorsqu'elle est chauffée, facilitant ainsi l'écriture. Le but de cette thèse est de valider expérimentalement ce concept. Les premiers chapitres sont consacrés à l'optimisation des matériaux à anisotropie perpendiculaire que sont les multicouches (Co/Pt), (Co/Pd) et (Co/Tb). Leur intégration dans une jonction tunnel magnétique est ensuite présentée. L'évolution de l'anisotropie en température, paramètre crucial au bon fonctionnement de l'assistance thermique, a également été étudiée. Enfin, il est démontré que l'écriture thermiquement assistée est particulièrement efficace : les structures développées présentent une consommation d'écriture réduite par rapport aux structures classiques et une forte stabilité à température ambiante. / In order to increase the storage density of magnetoresistive random access memories (MRAM), magnetic materials with perpendicular anisotropy are very appealing thanks to high anisotropy. However, the enhancement of anisotropy induces an increase of writing consumption as well. A new thermally assisted switching concept has been proposed by SPINTEC laboratory. The principle is to design a highly stable structure at stand-by temperature which loses its anisotropy when heated, making thus the switching easier. The aim of this thesis is to validate experimentally this concept. The first chapters describe the optimisation of out-of-plane magnetic materials such as (Co/Pt), (Co/Pd) and (Co/Tb) multilayers. Their integration in magnetic tunnel junctions is then presented. The evolution of anisotropy with temperature is a critical parameter for thermally assisted writing and has been therefore studied. Finally, the efficiency of this thermally assisted writing is demonstrated: the developed structures present a reduced consumption compared to standard structures and high stability at room temperature.

Tunnelmagnetowiderstandselemente (MTJ) mit einer kristallinen MgO Tunnelbarriere zwischen amorphen CoFeB-Elektroden haben Aufgrund ihres hohen Tunnelmagnetowiderstandes (TMR) und der guten Integrationsmöglichkeit in bestehende Prozesse viel Aufmerksamkeit bekommen. Dabei zeigten vorherige Berechnungen, dass die strukturellen und chemischen Eigenschaften der Grenzfläche einen signifikanten Einfluss auf den TMR aufweisen, weshalb diese Grenzfläche im Rahmen dieser Arbeit mittels quantitativer, hochauflösender und analytischer Transmissionselektronenmikroskopie analysiert wurde. Um einen hohen TMR in die diesen Systemen zu erzielen ist ein kristalliner Übergang zwischen der Tunnelbarriere und den Elektroden notwendig. Berechnungen zeigten, dass bereits wenige Monolagen kristallinen Materials an der Grenzfläche ausreichen, um einen hohen TMR in diesen Systemen zu erzielen. Ausgehend von diesen Berechnungen wurde die Mikrostruktur auf der Subnanometer-Skala an der kristallin/amorphen Grenzfläche von MgO-CoFeB in dieser Arbeit untersucht. Die experimentellen Daten wurden hierfür mittels aberrationskorrigierter, hochauflösender Transmissionselektronenmikroskopie (HRTEM) an Modellsystemproben erstellt und die vom MgO induzierte kristalline Ordnung an der Grenzfläche zum CoFeB mittels iterativen Bildserienvergleichs mit simulierten Daten quantifiziert. Zur Simulation der HRTEM-Grenzflächenabbildungen wurde die „Averaged-Projected-Potential“-Näherung genutzt, welche im Rahmen dieser Arbeit um die Berücksichtigung von monoatomaren Stufen entlang der Strahlrichtung des Mikroskops erweitert wurde. Es zeigte sich, dass mit dieser Methode die Ordnung an der MgO-CoFeB-Grenzfläche von nicht ausgelagerten Systemen gut beschrieben werden kann. In ausgelagerten Systemen kommt es dagegen zu einer Bor-diffusion aus dem a-CoFeB heraus um damit eine Kristallisation am MgO zu ermöglichen. Im zweiten Teil dieser Arbeit werden die Bordiffusion und die Kristallisation in Abhängigkeit von der Deckschicht als auch der MgO-Depositionsmethode sowohl an Modellsystemproben als auch an funktionsfähigen MTJs untersucht. Elektronen-Energie-Verlustspektroskopie (EELS) an diesen Proben konnten zeigen, dass sowohl die Deckschicht also auch die MgO-Depositionsmethode einen entscheidenden Einfluss auf die Bor-Diffusion in diesen Systemen ausüben.