Poland's foreign policy: September 1938 - September 1939

On 31 March 1939, Britain, breaking with hitherto steadfastly pursued policy, declared her commitment to the defence of Poland in the event of a German attack. This gesture was a dramatic change in Britain's foreign policy, not merely in relation to one East European state, but more notably in relation to Europe as a whole. Not surprisingly, the declaration has been the focal point of historical attention, although the events following have received less attention. The crisis days of March 1939 saw a chain of events, not necessarily of the same origin or character but which in sum total caused disquiet in European capitals, most clearly in London. Because of this it is easy to over-look the long-term nature of some of the events which culminated in March 1939 and thus, in consequence, to overestimate the effect of the British guarantee upon Polish foreign policy

Influence of high Al fraction on reactive ion etching of AlGaN/GaN heterostructures

In this study, the results of reactive ion etching (RIE) process of diversified Al content AlxGa1–xN/AlN/GaN/sapphire heterostructures were presented. The Al fractions of 22, 25, 31 and 36% were examined. An impact of Al content in the heterostructures on the etch rates and surface morphology was investigated. The influence of used Cl2/BCl3/Ar gas mixture with varying of BCl3 flow on the etch rate of Al0.2Ga0.8N/GaN/sapphire, surface morphology and angle of mesa slope, was discussed