The present invention relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy, which is distinguished by the fact that it has a value for the ratio \u03b31\u0394n2 in the range 6-45 with a clearing point of >60\xb0 C. Nucleic acids encoding the polypeptides of the invention are also provided. The invention is useful for closing bottles of sparking or non-sparking wine. A new addition in nickel based coating with stabilized gammagamma\u2032 phases at high temperatures lead to a reduction of local stresses. The illumination system comprises only one condenser head that can be switched in or out and that can optimally illuminate the entire range from 1\xd7 to 100\xd7, and a movably arranged focusing lens that ensures optimal adaptation of the illumination to the entrance pupil for all ranges.