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A dissertation submitted to the University of the Witwatersrand in ful lment of the requirements for candidacy for the degree of Master of Science. Johannesburg, 2016 / Restricted Schur polynomials can be used to describe large N, non-planar limits of N = 4 super Yang-Mills theory. The R-symmetry generators commute with the dilatation operator. For small deformations of 1 2-BPS operators, the matrix elements of these generators have been computed and a set of recursion relations for the matrix elements of the dilatation operator are obtained from this commutation relation. Together with the knowledge that the smallest eigenvalues of the dilatation operator (corresponding to BPS operators) vanish, these recursion relations can be used to determine the matrix elements of the dilatation operator. Studies up to now have computed the matrix elements of the su(2) generators in the displaced corners approximation. Our first novel result is the computation of the exact su(2) generators. We obtain the matrix elements for the su(3) generators in the displaced corners approximation and exactly, for the first time. This is the first step to computing exact matrix elements of the dilatation operator. / TG2016

Increases in internal dimensions of the chambers of the heart (cardiac dilatation), mediated by right shifts in cardiac chamber diastolic pressure-volume (P-V) relations, predict mortality in patients with established heart failure. However, the mechanisms responsible for the transition from concentric cardiac hypertrophy to cardiac dilatation are unclear. Recent evidence suggests that decreases in the cross-linked properties of myocardial collagen may increase the propensity of collagen to cleavage and hence reduce cardiac myocyte tethering, thus promoting cardiac dilatation. However, decreases in myocardial collagen cross-linking may also reduce myocardial stiffness, thus explaining right shifts in cardiac diastolic P-V relations. In the present dissertation I evaluated whether right shifts in diastolic P-V relations produced by chronic β-adrenoreceptor activation (isoproterenol, a β-adrenoreceptor agonist, 0.02 mg.kg-1.day) in spontaneously hypertensive rats (SHR) with compensated cardiac hypertrophy (12 months of age), can be explained by adverse chamber remodelling or alterations in the myocardial material properties of the heart. After 7 months of daily isoproterenol administration, SHR had marked right shifts in left ventricular (LV) diastolic P-V relations as determined in isolated, perfused hearts, with increases in the volume intercept of these relations, a change that translated into increases in LV cavity diameters (echocardiography). LV dilatation was associated with reductions in LV pump function (decreases in LV endocardial fractional shortening and the slope of the LV systolic P-V relation [LV E]). The reductions in pump function were attributed to the LV dilatation rather than to alterations in intrinsic myocardial contractile properties as LV midwall fractional shortening and myocardial systolic elastance (LV En) were unchanged. Although SHR not receiving isoproterenol had increases in the LV diastolic wall thickness-to-radius ratio, a change commensurate with compensatory concentric LV hypertrophy, LV wall thickness-to-radius ratio in SHR exposed to chronic β-adrenoreceptor activation was reduced to values similar to those noted in normotensive Wistar Kyoto (WKY) control rats, despite further increases in LV weight. SHR not receiving isoproterenol had a marked increase in myocardial stiffness (slope of the linearized LV diastolic stress-strain relationship) as compared to WKY rats, a change that was associated with an increased myocardial collagen of the cross-linked phenotype. Although SHR receiving daily isoproterenol had further increases in myocardial collagen, this did not translate into changes in LV diastolic myocardial stiffness, as the further increase in myocardial collagen was of the non cross-linked phenotype. However, through a susceptibility to digestion, this collagen phenotype could have contributed to LV dilatation. In conclusion, these data suggest that LV dilatation in SHR following chronic β-adrenoreceptor activation is attributed to adverse chamber remodelling rather than to alterations in myocardial material properties as indexed by diastolic stress-strain relations.

Thèse--Méd.--Reims, 1974. N°: N° 13. / Les photogr. manquent. Bibliogr. ff. I-IX.

An instrument for the continuous measurement of cervical dilatation is described. The principle of operation, being that of mutual inductance, utilises two coils, one on the posterior lip of the cervix and the other on the anterior, the axes of these coils being kept parallel by a flexible linkage. A magnetic field, from the primary coil being driven with a lOkHz alternating current of constant amplitude, induces a voltage in the secondary coil. This voltage whose magnitude decreases as the distance between the coils increases, is used by the instrument for the determination of cervical dilatation. A cervical dilatation recording from a multiparous patient is presented and discussed.

The relationship between dilatation, displacement speed, flame tangential strain rate and flame normal velocity gradient for a premixed turbulent flame in a corrugated/wrinkled flame regime is analyzed. The decomposition of dilatation into the flame tangential and normal strains and their relationship with curvature is studied. Three-dimensional, fully compressible direct numerical simulations (DNS) of premixed flames in a cube have been performed using a uniform 256^3 grid. For the turbulent case, decaying isotropic homogeneous turbulent velocity field is considered with an initial turbulence spectrum imposed. Simple single-step chemistry with an Arrhenius reaction rate is used. This simplification is valid as the flame considered is in the corrugated/wrinkled regime where the flame thickness is smaller than the smallest scales of turbulence. A single laminar flame is initially inserted into the turbulent field. A strongly linear relationship between dilatation and curvature has been seen which is due to the high correlation of displacement speed with curvature. The correlation between tangential strain rate and curvature is shown to be negative with a breakdown due to the curvature reaching the scale of the flame thickness at the cusps. To isolate the effect of heat release and turbulence, cases of a laminar sinusoidal wrinkled flame and a turbulent 𝛕=0 flame have been carried out. For a laminar sinusoidal wrinkled flame, a negative correlation between a^𝛕 and curvature was seen. This contradicts previous hypotheses (Haworth and Poinsot, 1992) (Chakraborty and Cant, 2004) where the negative correlation between a^𝛕 and curvature was explained to be due to different turbulence levels in front and behind the flame. Turbulence and alignment of flame surface with expansive tangential strains is shown to be responsible for the scatter seen in a^n and a^𝛕 relationships with curvature. Changing the peak reaction location towards the front of the flame did not change the trend in the plots of dilatation, tangential and normal strain rates versus curvature, confirming that dilatation relationship with curvature in particular is not due to any curvature distortion of the flame interior. However, it did thicken the flame and reduce the dilatation (and consequently its components, an and at) plot versus curvature and the magnitude of their curvature dependence. / Thesis / Master of Applied Science (MASc)

Thesis (M.A.)--Baylor University, 2007. / Includes bibliographical references (p. 148-154).

Choledochal cysts (CCs) are rare, congenital cystic dilations of the hepatobiliary tree that require surgical resection to avoid complications such as increased risk of malignancy. A 25‑week gestational age male infant developed acholic stools, elevated alkaline phosphatase, and ultrasound findings consistent with CC Todani Type IVA. Surgery was deferred due to the patient’s low weight. The patient’s symptoms and radiographic findings subsequently resolved spontaneously. CCs have not been previously reported in extremely preterm infants. There are rare reported cases of spontaneously resolving hepatic cysts, all containing key differences from our patient. In patients in whom immediate surgery is not feasible, conservative management with close follow‑up and serial ultrasound examinations would appear to be a reasonable course of action.

Un des points clés pour l’utilisation sur le long terme des SOEF et SOFC est l’étanchéité. Les solutions de scellement les plus répandues sont des matériaux rigides de type vitreux. Ils présentent l’inconvénient de se fissurer lorsqu’ils sont soumis à des cycles thermiques. Ceci est dû aux différences de CET entre les composants métalliques ou céramiques et les matériaux vitreux. L’autocicatrisation est une solution prometteuse pour pallier ce problème, deux mécanismes existent : intrinsèque et extrinsèque. L’autocicatrisation intrinsèque de matériaux vitreux est basée sur leur ramollissement. Nous avons développé une formulation de joints vitreux «pâteux» qui présente des propriétés autocicatrisantes, donc moins sensible aux différences de CET. La viscosité de ces verres a été estimée par microscopie de chauffage et leur stabilité a été caractérisée par DRX et microsonde de Castaing. L’autocicatrisation extrinsèque ne nécessite pas d’intervention extérieure. Elle est obtenue par ajout de particules cicatrisantes à la matrice vitreuse. Lors de l’apparition de fissures, les particules s’oxydent au contact de l’atmosphère pour former des oxydes qui donne in situ de nouveaux verres. Ces oxydes, fluides à la température de fonctionnement, s’écoulent dans la fissure, formant localement, par réaction, un nouveau verre. Des tests réalisés in situ par MEBE-HT ont permis de mettre en évidence le processus d’autocicatrisation. La formation de phases cicatrisantes a été caractérisée par microsonde de Castaing et par RMN. Un ensemble de caractérisations a été effectué afin de valider l’applicabilité de l’autocicatrisation extrinsèque aux joints de scellement vitreux. / A key point for using SOEC and SOFC in the long-term is the sealant. The most sealing solutions commonly used are rigid materials, particularly glassy seals. However, they have the disadvantage of cracking in operation when subjected to thermal cycles. This is mainly due to TEC differences between metal and ceramic components and glass materials. The self-healing is a promising solution to overcome this problem. Two mechanisms exist: intrinsic and extrinsic. The intrinsic self-healing of glassy materials is based on their softening at high temperature. We developed a formulation of viscous glass seal that exhibits self-healing properties at the operating temperature systems SOEC/SOFC. They are less sensitive to differences of TEC. The glass viscosity was estimated by hot stage microscopy and their stability under use condition has been characterized by XRD and Castaing microprobe. In contrast, the extrinsic self-healing requires no external intervention. It is obtained by the addition of healing particles in the glassy matrix. When cracks occur, the particles oxidize with atmosphere contact to form oxides and in-situ new glasses. We developed this extrinsic method from particles generating B2O3 and V2O5. These oxides, fluid at operating temperature 700-900°C, flow in the crack and form a new locally glass by reaction with glassy matrix. An in-situ test by HT-ESEM highlights the self-healing process. The formation of glass and crystal phases is characterized by Castaing microprobe and solid state NMR. A set of physico-chemical characterization was performed to validate extrinsic self-healing applicability in the SOEC/SOFC glassy seal.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Includes bibliographical references (p. 29-30).