7,047 research outputs found
Pelvic Organ Prolapse-Associated Cystitis
This thesis concerns the construction of 2,3-dihydro-4r7-pyran-4-one and 3(2//)-furanone ring systems by mercury(II)-catalysed reactions, or by more conventional cyclisations, and the potential of such reactions for the synthesis of natural products. Chapter one provides a literature survey of reactions permitting the construction of 2,3-dihydro-4/7-pyran-4-one and 3(2//)-furanone ring systems background literature to relevant natural products is also provided, such as polyether antibiotics, carbohydrates and antitumer agents. Chapter two describes the application of mercury(II)-catalysed cyclisations of dihydroxylated ynones to give 3(2//)-furanones this was achieved by the dihydroxylation of enynones using Sharpless's asymmetric dihydroxylation conditions followed by treatment with a mecury(II) catalyst. The scope and limitations of this method were investigated and shown in several cases to give good yields and high enantiomeric excess. In cases where there was an electron-donating group on the alkyne functionality, such as an ethoxy group, the cyclisation occurred spontaneously during the dihydroxylation step. This methodology was applied for the synthesis of a natural product to confirm the selectivity of the cyclisation step. In chapter three the reactions developed in chapter two formed the basis of a proposed route to the natural product (-)-Pestalotin, a gibberellins synergist. Thus, the Sharpless asymmetric dihydroxylation method was applied to (3,y-unsaturated ketones to give a main intermediate for the synthesis. Chapter four details different approaches to NK10958P, a plant growth regulator. The synthesis of two main fragments was achieved and the coupling of these fragments by syn-selective aldol addition is expected to furnish NK10958 P and its methyl analogue, pironetin, which has been reported to have good cytotoxic and immunosuppressive activity. Full experimental details follow chapter 2-4 and reference sections are provided at the end of each chapter
Diabetes mellitus and pulmonary tuberculosis, association or co-incidence?
Objectives: To evaluate the effect of Diabetes Mellitus (DM) on clinical and diagnostic methods and radiological features of pulmonary TB, in comparison to non diabetic pulmonary TB patients, in Golestan province, Northeast of Iran. Methodology: In this retrospective cross-sectional study during 2004-2008, medical records of patients with definite diagnosis of pulmonary TB were reviewed. Demographic data, clinical & diagnostic method and radiological findings were studied. Radiological data and lung High Resolution computed tomographic scan (lung HRCT) were done by two different radiologists. After data entry into SPSS-16, Fischer's exact test and chi-square test were used to compare the two groups (TB with DM & without it). P-value 0.05). Multilobar cavities were significantly more reported in diabetics (p-value = 0.014). No statistical differences were seen between two groups radiologically. Conclusion: Tuberculosis could be more invasive in diabetic patients especially females hence they should be given more attention
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Zero-one IP problems: Polyhedral descriptions & cutting plane procedures
A systematic way for tightening an IP formulation is by employing classes of linear inequalities that define facets of the convex hull of the feasible integer points of the respective problems. Describing as well as identifying these inequalities will help in the efficiency of the LP-based cutting plane methods. In this report, we review classes of inequalities that partially described zero-one poly topes such as the 0-1 knapsack polytope, the set packing polytope and the travelling salesman polytope. Facets or valid inequalities derived from the 0-1 knapsack and the set packing polytopes are algorithmically identifie
Cutting plane methods for general integer programming
Integer programming (IP) problems are difficult to solve due to the integer restrictions imposed on them. A technique for solving these problems is the cutting plane method. In this method, linear constraints are added to the associated linear programming (LP) problem until an integer optimal solution is found. These constraints cut off part of the LP solution space but do not eliminate any feasible integer solution. In this report algorithms for solving IP due to Gomory and to Dantzig are presented. Two other cutting plane approaches and two extensions to Gomory's algorithm are also discussed. Although these methods are mathematically elegant they are known to have slow convergence and an explosive storage requirement. As a result cutting planes are generally not computationally successful
Multiscale turbulence effects in supersonic jets exhausting into still air
A modified version of the multiscale turbulence model of Hanjalic has been applied to the problem of supersonic jets exhausting into still air. In particular, the problem of shock-cell decay through turbulent interaction with the mixing layer has been studied for both mildly interacting and strongly resonant jet conditions. The modified Hanjalic model takes into account the nonequilibrium energy transfer between two different turbulent spectral scales. The turbulence model was incorporated into an existing shock-capturing, parabolized Navier-Stokes computational model in order to perform numerical experiments. The results show that the two-scale turbulence model provides significant improvement over one-scale models in the prediction of plume shock structure for underexpanded supersonic (Mach 2) and sonic (Mach 1) jets. For the supersonic jet, excellent agreement with experiment was obtained for the centerline shock-cell pressure decay up to 40 jet radii. For the sonic jet, the agreement with experiment was not so good, but the two-scale model still showed significant improvement over the one-scale model. It is shown that by relating some of the coefficients in the turbulent-transport equations to the relative time scale for transfer of energy between scales the two-scale model can provide predictions that bound the measured shock-cell decay rate for the sonic jet
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