A method of fabricating a gallium nitride-based semiconductor structure on a substrate includes the steps of forming a mask having at least one opening therein directly on the substrate, growing a buffer layer through the opening, and growing a layer of gallium nitride upwardly from the buffer layer and laterally across the mask. The intermediate part is fixed in terms of rotation on the first end part and is mounted such that it can be rotated over a limited angle range on the second end part. Movement of the housing to a first orientation causes the flow control assembly to move to a first position to restrict flow of a turbomachine fluid into the housing through the second inlet. The air-to-fuel ratio estimate is generated in dependence of a predetermined fuel deposit factor. In the display device, a first electrode is provided on the surface of the first substrate which faces the second substrate, a second electrode is provided on the surface of the second substrate which faces the first substrate, and a spacer is provided in the space between the periphery of the facing surface of the first substrate and the first electrode. The sizing device may also include an infusion source for delivering the expansion medium and means for measuring the amount and pressure of the expansion medium inside the catheter.