Abstract: An object carrier has a transparent plate with an opaque backing and carries a thin liquid crystal layer which, in turn, is covered with a 2 .mu.m glass plate carrying an object (microorganism, etc.). This carrier is placed in a microscope for photographic observation of the temperature-dependent reflectivity of the crystal layer as heat conductively coupled to the object. The average reflection of light by the crystal layer is used as a representation of its average temperature, to control backlighting of the opaque layer to, thereby, stabilize the average object temperature to at least 10.sup.-3 degrees centigrade.

Abstract: Steel is to be austenitic-ferritic at a 1:1 ratio of austenite to ferrite and contains particular alloy elements. The principal feature is, limiting the sulphure content to below 0.005% in order to obtain a particularly high toughness transversely to the main direction of working.