This embodiment could provide a mesh structure as a middle laminate to the inner lumen 16 and the enlarged body 17. [0077] Significantly, if the inner lumen is made of an appropriate material, such as aluminum, there is no need to provide an enlarged part, i.e., the slots can be formed in an inner lumen having no enlarged section. [0078]FIGS. 11A and 11B show a variation of the embodiment of FIGS.