Abstract: The invention relates to a system for controlling the positioning of a susceptor (2) rotating in the reaction chamber (3) of an epitaxial reactor. The control is carried out on the basis of the different path of a laser beam transmitted by a source (15) when it is reflected by a pin (8) arranged on the susceptor (2).

Abstract: There is disclosed an improved seat element having a seating surface element that incorporates a plurality of peak portions and a plurality of valley portions. Preferably, the plurality of peak portions and the plurality of valley portions is incorporated in an outermost surface of the seating surface element. The term “outermost surface” is intended to include an area of the seating surface element for contact by and/or support of an occupant of the seat element and does not include, for example, grooves or trenches in which there is disposed a component for attachment of a trim cover. A process and a mold for production of such a seat element are also described.