Abstract: The invention relates, among other things, to a door sensor device (20) for mounting on a door element (10), more particularly a swing door, which can be rotated about an axis of rotation (D), having at least one transmission device (21) for generating at least one monitoring beam (S) in the direction of the floor, said beam being oriented at an angle to the door leaf plane (E) of the door element (10), at least one receiving device (22) for receiving reflected or back-scattered radiation, and an evaluation device (23) for evaluating the radiation received by the receiving device (22) and generating an object detection signal.

Abstract: The invention relates, among other things, to a door sensor device (20) for mounting on a door element (10), more particularly a swing door, which can be rotated about an axis of rotation (D), having at least one transmission device (21) for generating at least one monitoring beam (S) in the direction of the floor, said beam being oriented at an angle to the door leaf plane (E) of the door element (10), at least one receiving device (22) for receiving reflected or back-scattered radiation, and an evaluation device (23) for evaluating the radiation received by the receiving device (22) and generating an object detection signal.

Abstract: Mixed cyclic acrolein glycerol acetals can be obtained by reacting acrolein with glycerol in the presence of a solid acidic catalyst and by a distillation workup in a higher space-time yield and in very high selectivity in comparison to the state of the art if the reaction is carried out in the presence of the reaction mixture as solvent, which mixture consists essentially of acrolein, glycerol, cyclic acrolein glycerol acetals and water, and in the absence of heterogeneous solvents and, to the extent necessary, the reaction mixture freed of catalyst is compounded prior to being worked up by distillation with such an amount of pH-increasing substance that it exhibits a pH in a range of 4.5 to 7 in tenfold dilution with water. The reaction preferably takes place at 10.degree. to 30.degree. C. using strongly acidic organic or inorganic ion exchangers.