An investigation of shock diffraction through a non-quiescent background medium is presented using both experimental and numerical techniques. Unlike diffracting shocks in quiescent media, a spatial distortion of the shock front occurs, producing a region of constant shock angle. An example of this process arises in the exhaust from a pulse-detonation combustor. As the background velocity is increased, such as through the inclusion of a converging nozzle at the exhaust, the spatial distortion becomes more apparent. Numerical simulations using a compressible Euler solver demonstrate that the distortion is not due to the geometrical influence of the nozzle, but rather is a function of the magnitude of the background flow velocity. The distortion is studied using a modified geometrical shock dynamics formulation which includes the background flow and is validated against experiments. A simple model is presented to predict the shock distortion angle in the weak-shock limit. Finally, the axial decay behaviour of the shock is investigated and it is shown that the advection of the shock by the background flow delays the arrival of the head and tail of the expansion characteristic at the centreline. This leads to an increase in the rate of decay of the shock Mach number as the background flow velocity is increased.

We present an extensive physical characterization of La2/3Ca1/3MnO3 (LCMO) epitaxial films grown on SrTiO3 (STO), LaAlO3 (LAO) and NdGaO3 (NGO) substrates. The main difference among these substrates is that they have a different mismatch (∼ 1.2%, -1.8% and - 0.1%, respectively) with the manganite. The films can be coherently grown up to 180 nm for STO and NGO but partial relaxation is observed for LAO. The magnetotransport data indicate that very thin films (<27nm) display non-conventional magnetoresistive properties: a substantial magnetoresistance develops which can be progressively appreciated for STO and LAO films. 55Mn-Nuclear Magnetic Resonance experiments on all these films reveal the presence of non-homogeneous electronic states. These experiments in fact provide clear evidence of the presence of two distinguishable ferromagnetic Mn states and a non-ferromagnetic phase. The possible role of strain-induced charge localization is discussed. It turns out that electronic phase separation occurs in all films irrespectively of the particular substrate used; thus we conclude that strain is not the unique driving force for charge localization.