Abstract: The invention provides a method for preparing pyrrolidone, and the invention provides a method for catalytically preparing pyrrolidone with ?-aminobutyric acid in the presence of carnitine-CoA ligase CaiC. The carnitine-CoA ligase CaiC has an amino acid sequence as shown in SEQ ID NO:1. The ligase has catalytic activity in the cyclization of ?-aminobutyric acid to produce pyrrolidone. The carnitine-CoA ligase provided in the present invention affords a yield of pyrrolidone of 3.26 g/L and a molar yield of 39.53% in 24 h when ?-aminobutyric acid is used as a substrate, thus reducing the production period, improving the production of pyrrolidone, and accelerating the industrialization process of producing pyrrolidone by enzymatic conversion method.

Abstract: A vortex beam-excited precision grating displacement measurement apparatus, which performs displacement measurement by taking a vortex beam carrying topological charges as an excitation light source of a grating and by using the interference of a ±m-order diffracted vortex beam. In the vortex beam-excited precision grating displacement measurement method and apparatus, the displacement p/m of the measured displacement corresponds to the rotation of a circle 2? rad of an interference petal pattern, and then the rotation of 1° of the interference petal pattern corresponds to the measured displacement amount of p/360m. Compared with a conventional grating measurement method, the present disclosure provides a grating interference sensing signal that realizes a higher optical subdivision rate itself.

Abstract: A vortex beam-excited precision grating displacement measurement apparatus, which performs displacement measurement by taking a vortex beam carrying topological charges as an excitation light source of a grating and by using the interference of a ±m-order diffracted vortex beam. In the vortex beam-excited precision grating displacement measurement method and apparatus, the displacement p/m of the measured displacement corresponds to the rotation of a circle 2? rad of an interference petal pattern, and then the rotation of 1° of the interference petal pattern corresponds to the measured displacement amount of p/360m. Compared with a conventional grating measurement method, the present disclosure provides a grating interference sensing signal that realizes a higher optical subdivision rate itself.