Compounds of general formula, wherein A, Y, R1 and R2 are defined herein are useful in the treatment or prevention of proliferative diseases including cancer or infectious or parasitic diseases. These new steroids nitrooxyderivatives have an improved pharmacological activity and enhanced local tolerability. By assuming a bowed position along the curvature of the seats, the arcuate shaped seats eliminate point pressure exerted by outer ends of conventional horizontal brackets which act as wedges against a crossarm receiving the combined weight of the distal ends of the crossarm. Query metadata can be retrieved from a query repository. The receiving portion includes a bottom surface opposite to the concave section of the vacuum liner when received therein, and defining an exterior liner space therewith.