Abstract: Provided are a diamantane compound with which an organic electroluminescent device that can exhibit excellent luminous efficiency characteristics, more preferably excellent drive voltage characteristics and excellent luminous efficiency characteristics, can be produced, and an organic electroluminescent device material containing the diamantane compound. Also provided is an organic electroluminescent device that can achieve luminous efficiency characteristics, more preferably drive voltage characteristics and luminous efficiency characteristics, at high levels. A diamantane compound has a group represented by formula (1) below and a group represented by formula (2) below. (In formula (1), carbon atoms of a diamantane ring are optionally substituted with an aryl group having 6 to 12 carbon atoms. In formula (1), * represents a bond, and a represents an integer of 1 to 6.

Abstract: An optical device includes a first structure, a second structure, one or more optical waveguide regions, and a seal member. The first structure has a first surface. The second structure has a second surface facing the first surface. The one or more optical waveguide regions are located between the first surface of the first structure and the second surface of the second structure and contain a liquid crystal material. The seal member fixes a spacing between the first structure and the second structure, surrounds the one or more optical waveguide regions, and includes an opening through which the liquid crystal material is injected. A width of the opening in a first direction is greater than a width of the one or more optical waveguide regions in the first direction.

Abstract: A hydrogen aircraft includes: an airframe including a fuselage and a wing; at least one propulsion system fixed to the airframe; a pressurized chamber disposed inside the fuselage; a pressure bulkhead that is disposed at a rear part of the pressurized chamber and has strength to withstand pressurization of the pressurized chamber; a hydrogen tank that is disposed in an accommodation section and stores liquid hydrogen, the accommodation section being installed behind the pressure bulkhead, outside the pressurized chamber, and inside the fuselage; and a supply line that supplies the liquid hydrogen stored in the hydrogen tank to the propulsion system.

Abstract: Described are a plant disease control composition with enhanced efficacy and improved rainfastness of D-tagatose, and a plant disease control method using the composition. The plant disease control composition includes D-tagatose as an active ingredient, an oil component and a surfactant, and is effective against plant diseases, especially diseases caused by fungi and bacteria.