Abstract: The present invention is aimed at carrying out high-precision and stable image formation using a gray-level image forming technique. In carrying out image formation by a gray-level electrophotographic process, the relationship between the layer thickness Tp of the photosensitive layer on the photosensitive member and the exposure diameter Db of a light beam emitted onto the photosensitive member is defined as 2Tp <Db, so that the charge diffusion and electric field in the photosensitive layer on the photosensitive member can be small. The maximum exposure within the exposure diameter Db is set at a value that can sufficiently reduce the differential sensitivity of the photosensitive layer, where the exposure diameter Db of the light beam is the minimum diameter at 1/e2 with respect to the peak value of the exposure distribution obtained by integrating the energy distribution of the light beam with the exposure time.

Abstract: In an image forming apparatus for electrophotographically forming an image with an LED (Light Emitting Diode) array having a number of LEDs arranged in an array for controllably emitting light in accordance with image data, dots to be respectively formed by the LEDs have a target dot diameter X satisfying a relation of P<X<2P where P is a pitch P between the LEDs. Despite that the dot diameters of LEDs may slightly differ from each other, an image free from noticeable white stripes or black stripes is achievable although some difference in density may occur, depending on the overlapping degree of or the distance between dots.

Abstract: Disclosed is a structure composed of a ragged base body with a ragged surface and a non-adhesive layer of a non-adhesive high polymer, in which the layer is fixed to at least the depressions of the ragged surface in such a way that the ragged profile of the body appears on the outer surface, reiterated by the layer. The ragged profile has a mean surface roughness Ra of 0.5 to 20 .mu.m and the mean distance Z between the adjacent projections forming the ragged profile is 20 to 1000 .mu.m. The non-adhesive high polymer may be a silicone high polymer having a silicone oil content of 10% or less. It has an effective surface tension of 32 dyn/cm or less. As the structure has improved releasing characteristics, adhesion of an adhesive substance to the structure may be effectively prevented without using any conventional releasing agent.

Abstract: Disclosed is a structure composed of a ragged base body with a ragged surface and a non-adhesive layer of a non-adhesive high polymer, in which the layer is fixed to at least the depressions of the ragged surface in such a way that the ragged profile of the body appears on the outer surface, reiterated by the layer. The ragged profile has a mean surface roughness Ra of 0.5 to 20 .mu.m and the mean distance Z between the adjacent projections forming the ragged profile is 20 to 1000 .mu.m. The non-adhesive high polymer may be a silicone high polymer having a silicone oil content of 10% or less. It has an effective surface tension of 32 dyn/cm or less. As the structure has improved releasing characteristics, adhesion of an adhesive substance to the structure may be effectively prevented without using any conventional releasing agent.

Abstract: Cultivation of phototrophic bacteria such as in the treatment of organic wastes is carried out in a light field substantially free from ultraviolet light having a wavelength of not more than 340 nm. This process promotes growth of the phototrophic bacteria and improves quality of the resulting bacterial cell.

Abstract: A method for cultivating an alga, which comprises growing the alga in a light field substantially free from light of wavelengths of not more than 340 nm; and a covering material for use in the cultivation of algae, said covering material substantially inhibiting the transmission of light of wavelengths of not more than 340 nm.