A field emission display is provided. The bladder defines a space devoid of encapsulant and contains a collapsible insert such as an open cell foam material, thereby allowing the unimpeded thermal expansion of the encapsulant. The electrical insulator is hermetically sealed to the inner and outer conductors to prevent water ingress from the signal input to the signal output and vice versa. In particular, the invention relates to the use of the tryptophanyl-esters and their N-acyl derivatives for the treatment andor prophylaxis of Alzheimer’s disease, Parkinson’s disease, apoplectic fit, amyotrophic lateral sclerosis, cancers, arteriosclerosis andor myocardial infarction.