Abstract: A narrow band x-ray filter can include: a substrate; and a sheaf of one or more reflection units stacked upon each other on the substrate. Each reflection unit can include: a first set of at least two discrete spacers on a respective underlying structures, a reflector disposed on the first set of spacers so as to form a void between the respective underlying structure and the reflector; and a first set of at least two discrete shims disposed on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector. A first device to produce a narrow band x-ray beam may include such a filter or an x-ray telescope. A second device to make an x-ray image of a subject may include the first device.

Abstract: A portable flood-barrier-system can include a portable block of substantial mass; and a deflatable bladder, a first portion of which is disposed on a substrate; the block being disposed at least partly on the first portion of the bladder so as to releasably compress the first portion between the block and the substrate and so releasably hold the first portion therebetween due to friction.