Abstract: A rotary optical head apparatus comprises a first rotary member carrying an objective lens and a second rotary member carrying an image rotator. The two rotary members are supported for rotation by means of a single common support shaft so that the axes of rotation of the two rotary members coincide with each other with a high degree of accuracy. Consequently, the linearity of a scanning line of a beam spot which is scanned on an optical magnetic tape is ensured with a high degree of accuracy.

Abstract: A photo-degradable styrene resin composition which comprises a styrene resin and at least one photo-degradable agent selected from the group consisting of benzophenone, anthraquinone, fluorenone, xanthone, phenylalkylketones, phenacyl halides and derivatives of these compounds, and optionally at least one photo-degradable accelerator.

Abstract: A photo-degradable styrene resin composition which comprises a styrene resin and at least one photo-degradable agent selected from the group consisting of benzophenone, anthraquinone, fluorenone, xanthone, phenylalkylketones, phenacyl halides and derivatives of these compounds, and optionally at least one photo-degradable accelerator.

Abstract: A high tensile steel which has a satisfactory yield strength of 60 kg/mm.sup.2 or more and excellent resistances to sulfide corrosive cracking and corrosion, and which comprises, as indispensable components, 0.05 to 0.50 wt % of C, 0.1 to 1.0 wt % of Si, 0.1 to 2.0 wt % of Mn, 0.05 to 1.50 wt % of Co and the balance consisting of Fe, is produced by hot- or cold-rolling it, rapidly heating the rolled steel to austenitize it, quenching the austenitized steel and, finally, tempering the quenched steel at a temperature not higher than the Ac.sub.1 point of the steel.

Abstract: A chlorine-containing resin composition comprising a chlorine-containing resin and at least one calcium compound selected from the group consisting of 2CaO.SiO.sub.2, 3CaO.SiO.sub.2, 3CaO.2SiO.sub.2, the above enumerated compound(s) having coated thereon an organic silicon compound, CaO.TiO.sub.2, 2CaO.TiO.sub.2, 3CaO.TiO.sub.2, CaO.Al.sub.2 O.sub.3, 2CaO.Al.sub.2 O.sub.3, 3CaO.Al.sub.2 O.sub.3, CaAl.sub.2 O.sub.4, CaB.sub.2 O.sub.6, Ca.sub.7 MgAl.sub.10 O.sub.23, CaNb.sub.2 O.sub.6, CaTa.sub.2 O.sub.6, CaTiO.sub.3, CaZrO.sub.3 and CaZrTi.sub.2 O.sub.7. The chlorine-containing resin composition may further comprise an organic acid salt and/or an organic tin compound.

Abstract: A photo-degrading resinous composition which comprises:A. from 50 to 100% by weight of a copolymer composed of i 95.0 - 99.9 % by weight of a monomer selected from the group consisting of styrene and methyl methacrylate, (ii) 5.0 - 0.1% by weight of a diene monomer and (iii) up to 4.9% by weight of an unsaturated ketone having the formula ##EQU1## wherein R.sub.1, R.sub.2 and R.sub.3, which may be the same or different, represent a hydrogen atom or a methyl or phenyl group, andB. up to 50% by weight of a thermoplastic synthetic resin other than said copolymer.