Abstract: An endoscope comprising as an image-transmitting member a multifilament type plastic optical fiber in which 50 to 20,000 islands having a core-sheath structure, a core diameter of 2 to 70 .mu.m and a circular or substantially circular section are arranged in a zigzag-stacked or square-stacked structure in the sea having a circular or substantially circular section, so that the lamination structure of the entire cores has a substantially circular shape in the section of the image-transmitting portion, wherein the same positional relationship of the ends of light-transmitting paths arranged in the section of the optical fiber is maintained on both the ends of the optical fiber, the periphery of the section of the image-transmitting portion of the optical fiber has a circular or substantially circular shape, and an object lens is attached to one end of the image-transmitting member and an image-transmitting light-receiving member is arranged on the other end of the image-transmitting member.

Abstract: An optical fiber photoconductor, comprising at least two multi-filament plastic optical fiber units arranged in parallel and having a substantially rectangular peripheral shape and at least one end fixed in a cap, each optical fiber unit having 50 to 10000 core-sheath light-transmitting islands having a diameter of 5 to 200.mu., which are densely arranged in a sea portion, wherein in each of the multi-filament plastic optical fiber units having a rectangular sectional shape, the end face fixed in the cap is expanded so that the length of one side of the end face is at least 1.01 times the original length of one side of the rectangular peripheral shape of the multi-filament plastic optical fiber unit, whereby a bonding interface between the multi-filament plastic optical fiber units substantially disappears.

Abstract: A multifilament type plastic optical fiber having a substantially rectangular cross-section and an islands-in-the-sea structure in which 100 to 10,000 islands are arranged in the sea, wherein the respective islands have a substantially circular cross-section and a core-sheath structure, the islands are arranged in a zigzag-stacked structure, the core occupaney ratio in the multifilament type optical fiber cores section is at least 50% and the brightness index value I which is defined by the following (1), is at least 4.5.times.10.sup.-2 : ##EQU1## wherein S stands for the core occupancy ratio in the multifilament type optical fiber, .alpha. stands for the transmission loss (dB/m) per meter of the multifilament type optical fiber, NA stands for the numeral apertures, and L stands for the length (m) of the used optical fiber.

Abstract: An endoscope comprising as an image-transmitting member a multifilament type plastic optical fiber, an object lens arranged on one end of the optical fiber and a device for guiding an image of an object transmitted to the other end of the optical fiber to an image-receiving portion, wherein the multifilament type plastic optical fiber has an islands-in-sea structure in which 50 to 10,000 light-transmitting core-sheath structure islands having a diameter of 5 to 200 .mu. are arranged in the sea so that the same positional relationship of the islands is maintained on both ends of the optical fiber, and the core occupancy ratio in the total cross-section of the optical fiber is at least 50%.

Abstract: A multifilament type plastic optical fiber having a substantially rectangular cross-section and an islands-in-the-sea structure in which 100 to 10,000 islands are arranged in the sea, wherein the respective islands have a substantially circular cross-section and a core-sheath structure, the islands are arranged in a sigzag-stacked structure, the core occupancy ratio in the multifilament type optical fiber cores section is at least 50% and the brightness index value I which is defined by the following (1), is at least 4.5.times.10.sup.-2 :I=S.multidot.NA.sup.2 .multidot.10.sup.-(.alpha.L/10) (1)wherein S stands for the core occupancy ratio in the multifilament type optical fiber, .alpha. stands for the transmission loss (db/m) per meter of the multifilament type optical fiber, NA stands for the numeral apertures, and L stands for the length (m) of the used optical fiber.

Abstract: An optical fiber array comprising a great number of multifilament type plastic optical fibers having a substantially rectangular peripheral sectional shape and including 10 to 10000 light-transmitting islands having a diameter of 5 to 200 .mu.m, which are densely arranged in the sea, wherein one ends of the multifilament type plastic optical fibers are arranged in one line or a plurality of lines and the other ends thereof are integrated in a substantially rectangular or substantially circular shape.

Abstract: A multifilament type plastic optical fiber having a substantially uniform cross-section and an islands-in-sea structure, in which 10 to 10,000 islands are arranged in the sea, the respective islands have a substantially uniform cross-section having a diameter of 10 to 200.mu.

Abstract: This invention provides a method and an apparatus for controlling a polymerization reaction. The temperature difference between a target temperature, calculated from the degradation rate of a polymerization initiator, which varies as a function of temperature, and a polymerization reactor temperature is calculated. The difference in polymerization rate between a target polymerization rate previously set and a polymerization rate calculated from a measured heat release value at a certain time in the polymerization process is calculated. The temperature inside the reactor is finely adjusted on the basis of the temperature difference and the difference in polymerization rate.

Abstract: A process for producing a carbon fiber having a tenacity of 450 kg/mm.sup.2 or more, preferably 500 kg/mm.sup.2 or more, and a modulus of elasticity of 25 ton/mm.sup.2 or more which comprises subjecting a polyacrylonitrile-type fiber to a flame-resisting treatment in a flame-resisting treatment furnace provided with a plural number of driving rolls in an oxidizing atmosphere at 200.degree. to 400.degree. C. under application of multistep elongation, during said treatment the respective percentage of elongation in said multistep elongation being set respectively at a value which is equal to or within .+-.3% of the value of the percentage of elongation En indicating an inflection point Pn obtainable from the load and the percentage of elongation determined in advance by experimental measurements, and then subjecting the treated fiber to carbonization.

Abstract: An unsaturated polyester composition for molding compounds, consisting essentially of (1) 20 to 70 parts by weight of an unsaturated polyester obtained by condensing an acid component comprising a major amount of an .alpha.,.beta.-ethylenically unsaturated dicarboxylic acid with a polyol, (2) 25 to 75 parts by weight of a vinyl monomer copolymerizable with said unsaturated polyester, (3) 1 to 25 parts by weight of a thermoplastic polymer, and (4) at least one member selected from the group consisting of hydroxyl-containing vinyl monomers and epoxy-containing vinyl monomers in a ratio of 1 to 40 parts by weight to 100 parts by weight of said unsaturated polyester (to form 100 parts by weight of the composition). The composition may be molded and cured to yield articles which provide good adhesion to surface coatings and are susceptible of decorative finishes.

Abstract: An unsaturated polyester composition for molding compounds, consisting essentially of (1) 20 to 70 parts by weight of an unsaturated polyester obtained by condensing an acid component comprising a major amount of an .alpha.,.beta.-ethylenically unsaturated dicarboxylic acid with a polyol, (2) 25 to 75 parts by weight of a vinyl monomer copolymerizable with said unsaturated polyester, (3) 1 to 25 parts by weight of a thermoplastic polymer, and (4) at least one member selected from the group consisting of hydroxyl-containing vinyl monomers and epoxy-containing vinyl monomers in a ratio of 1 to 40 parts by weight to 100 parts by weight of said unsaturated polyester (to form 100 parts by weight of the composition). The composition may be molded and cured to yield articles which provide good adhesion to surface coatings and are sesceptible of decorative finishes.