The present invention relates to a mixture that contains at least one isocyanate and at least one organic andor inorganic acid anhydride. These tissue coated stents provide a barrier against cell migration to the lumen of the vessel. The composition of the powder material is selected so that a desired set of material properties is achieved when the powder material is subjected to the dual-purpose heat cycle. Evaluation based on exponentially weighted moving average and median calculation techniques may result in a new, reset offset for one or more measurement systems. The supernatent ester phase obtained after decantation is then optionally sent to a coalescer, also allowing separation of the glycerin, then to a purification stage by adsorption on solids. A remaining portion of the epitaxial layer is grown.