Methods and apparatus, including computer program products, implementing and using techniques for controlling capabilities of a user software application. There is also an electrically conducting carrier substrate with a first surface and a second surface. The gas passing through the external circulation path sucks steam from a steam producing device by using steam suction ejector. The rails depend beyond the magnets, and define a channel for seating securely upon a cylindrical surface. Prior to inserting the sleeve into the corresponding hole of the substrate, the sleeve can be placed onto the mandrel. In this lens, one of these anterior and posterior surfaces includes a first diffractive profile forming at least one first diffractive focal point of order +1 on said optical axis, and a second diffractive profile forming a second diffractive focal point of order +1 on said optical axis which is distinct from the first diffractive focal point of order +1.