Abstract: Disclosed is a circulating device for cooling and heating superconducting magnet components at controllable rate, including a liquid nitrogen tank and a vacuum container. A container for accommodating the superconducting magnet component is provided at an upper end of an interior of the vacuum container. First and second pipelines join and then connect to a top of the liquid nitrogen tank through a coiled pipe. A third pipeline and a first branch of a fourth pipeline join and then connect to an inlet of an electric heater. A PID closed loop for temperature control is provided at the electric heater. A main pipeline of the outlet pipeline of the electric heater is connected to an inlet of the container. A second branch of the fourth pipeline, an outlet pipeline of the container and a branch pipeline of the outlet pipeline of the electric heater communicate with atmosphere.

Abstract: The present invention provides a novel method for producing the rice haploid, i.e., producing the rice haploid by rice×maize hybridization. In this method, rice is used as the female parent, and the rice panicle is emasculated and then pollinated with fresh maize pollens; the emasculated panicle is sprayed with 2, 4-D solution at 50-200 mg/L 24 h after pollination, and after 15-20 days the rice panicle is cut off to collect caryopses; and the haploid embryos are obtained by dissectting caryopses asepticlly, then inoculated and cultured with ½MS medium, then the haploid embryos directly germinate into rice haploid seedlings. Compared with the existing main methods for producing the rice haploid, such as anther culture and isolated microspore culture, the rice haploid production method of the present invention reduces the dependence on rice genotypes, does not produce mixture of haploid and diploid plants, contains no albino seedling, and is simpler in technical operation.