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The chemical synthesis of thymine, cytosine and adenine Peptide Nucleic Acid (PNA) monomers, incorporating a protecting group strategy compatible with solid phase DNA synthesis has been achieved. PNA oligomer synthesis using novel reagents and subsequent PNA/DNA chimeric oligomer synthesis, purification and analysis are described. Ultraviolet melting studies have indicated that PNA/DNA chimeric oligomers form stable hybrids with complementary DNA. The complexes are more stable than the native DNA.DNA duplexes and mismatches involving the PNA segment are extremely destabilising compared to the native DNA.DNA mismatch. Only minor destabilisation of the complex is observed when the mismatch involved the DNA moiety of the chimeric oligomer. The chemical synthesis of 3-deoxyguanosine and 3'-deoxycytidine DNA phosphoramidites and synthesis by solid phase methodology of the corresponding 5'-2' Oligodeoxynucleotides has been successfully achieved. The oligonucleotide was analysed by Capillary Zone Electrophoresis and characterised by electrospray mass spectrometry. U.V. melting analysis indicated that the 5'-2' oligomer hybridised to complementary RNA but not DNA. The 5'-2' DNA/RNA hybrid was found to be thermally and thermodynamically less stable than the native 5'-3' DNA/RNA and RNA/RNA hybrid which could in part explain the preference for the 5'-3' linked isomer in nature.

Thermoacoustic instability which stems from the non-linear interactions between heat release and pressure waves in a confined combustion chamber, can create large amplitude pressure oscillations. These oscillations may cause significant damage to the combustor hardware, and even surroundings. Accurate characterization and prediction of such instability is challenging due to its inherent complexities arising from the non-linear nature of the problem.In this thesis, we design a Rijke tube, a device in which self-excited thermoacoustic instabilities can be studied for relatively simple flame geometries. Subsequently, we used the Rijke tube to investigate dynamics of thermoacoustic instability in premixed laminar flame. We focused on the role of burner design on the ensuing instability and flame dynamics by investigating pressure oscillations observed in four different single- and multi-flame burners. We observed that %a single- and seven-flame burner tip using similar flame conditions were experimentally compared, by recording pressure data. The the single-flame burner did not display transition to an unstable state, when the burner was traversed along the length of the Rijke tube, while a seven-flame burner showed various states of instability and multiple bifurcation points. This observation confirms that the increased degree of freedom, arising from the interaction between individual flames in a multi-fame burner, is responsible for the wider dynamics observed.Subsequently, to quantify the dynamics of individual flames and their roles in the ensuing pressure dynamics, a three flame burner, where the flames are located in-line, were studied in details. The Phase Lock Value, Root Mean Frequency, and Power Spectral Density were analyzed for the heat release rates from individual flames and the acoustic pressure. We observed that the center flame possessed stronger synchronization with the pressure. But, the left and right flames shared a few modes (frequencies) of oscillations with the pressure, that were not present in the center flame. This suggests that the dynamics that effect of the individual flames pose varying degrees of influence on the pressure dynamics.An additional experiment was also conducted using an asymmetric three-flame burner, where the flames are located at the tip of an isosceles triangle, using the same flame conditions. This flame showed stronger pressure oscillations, perhaps due to enhanced degrees of interactions between three flames with the symmetric design, and eventually suffered blow-off. These systematic investigations highlights the strong influence of local flame interactions on the observed pressure dynamics, which is relevant for design of multi-nozzle combustors.

Large amplitude ship motion problems are addressed using a non-linear blended time-domain strip theory. The strip theory utilizes body-exact Froude-Krylov and hydrostatic forces with linear diffraction forces. The radiation forces over the bow region are determined via a fully non-linear two-dimensional potential flow solver, while linear added mass and damping terms are used over the remainder of the hull. The two-dimensional potential flow solver uses a desingularized technique to discretize the domain. A new damping mechanism is introduced that modifies the dynamic free surface boundary condition. The new technique allows the solver to remain stable in large amplitude motions as well as free-surface impacting situations. Results are presented for a ship section oscillating in heave, sway, and roll in two dimensions. Additional results are presented for various two dimensional wedges impacting on a free surface. Finally, motions of a high-speed containership in large seas are presented.