Abstract: A pacemaker electrode has an axially open, hollow cylinder, a plunger axiy displaceably received in the cylinder and a securing element for attaching the electrode to the heart. The securing element is mounted on the plunger for movement therewith as a unit. The securing element and the plunger have a withdrawn position in which the securing element is in a substantially fully retracted state within the cylinder. Further, the securing element and the plunger have an advanced position in which the securing element projects from the cylinder. The cylinder has a portion which is substantially pervious to X-rays. The plunger substantially blocks the path of X-rays across the cylinder through the X-ray pervious portion when the plunger and the securing element are in the withdrawn position.

Abstract: Grate for cooling or combustion heating of granular materials, fixed or longitudinally reciprocable, comprising a one-piece frame-like base plate and rod-like wear elements individually detachably secured to and over the forward area of the plate to define a material support surface. Attachment of the elements is by means of interengaging, transversely extending, longitudinally spaced guide means integral with the plate and elements. A central recess in the plate enables insertion one by one from above or from below, of the elements, whereupon each may be translated laterally along the guide means into emplaced position leaving only a central space filled by an element distinguished by a rearwardly projecting finger. Means are provided to engage the finger to releasably hold the central wear element in emplaced position. The wear elements conjointly form apertures which, together with those in the plate, enable passage of air through the grate.