A high data transfer rate is constantly demanded for optical disk drives. One of the solutions is to rotate a disk at a high rotational speed. We need a stable rotation of optical disks and a robust servo control to realize high-rotation-speed optical disk drives. It is difficult to rotate conventional polycarbonate optical disks, whose thickness is 1.2 mm, over 15000 rpm without vibrations. We measured and analyzed disk vibrations at high rotational speeds, and found a condition for suppressing the vibrations of the disks. We confirmed the stable rotation without vibrations up to 20000 rpm under this condition. We also conducted an experiment on tracking servo control at high rotational speeds. We used a double-boosted high-gain servo controller to suppress disturbances at high rotational speeds, and confirmed the robust servo control at 21000 rpm with this controller. #

SummaryWith the intention of examining the effects of dietary protein and oil levels on total cholesterol (T-CHOL) and triacylglycerol (TG) concentrations in the plasma and liver, male Wistar rats, weighing about 170g, were fed diets containing graded levels of casein and corn oil for 2 wk. At the 5, 20, and 30% levels of dietary corn oil, plasma T-CHOL con centrations were generally enhanced in proportion to the rise of dietary casein level, but plasma TG contents were scarcely influenced by the level. At the 8 to 3 5% casein levels, plasma T-CHOL and TG concentrations were the highest at the 5% corn oil level, followed in order by the 20 and 30% levels of oil. At the 5 and 20% oil levels, hepatic T-CHOL contents were hardly changed at the 8 to 30% casein levels, but enhanced at the 35% casein level. At the 30% oil level, the T-CHOL contents tended to be changed proportionally to casein levels. At all levels of casein, hepatic T-CHOL contents tended to be relatively high at the 30% corn oil, middle at the 20% oil, and low at the 5% one. At each corn oil level, TG contents in the liver tended to be elevated at the 8 to 15% casein levels and highly preserved at the 15 to 25% ones. Then, the raised TG contents declined at the 5 and 20% levels of corn oil and re mained constant at the 30% oil. At each casein level, the contents of hepatic TG were gener ally high at the 30% oil level, followed in order by the 20 and 5% oil levels. These results in dicated that plasma and liver T-CHOL concentrations were proportionately enhaaced by the increase in casein level, and plasma TG contents were hardly affected by the level and he patic TG ones were lowered by relatively lower or higher casein level, and the rise in corn oil level generally reduced plasma T-CHOL and TG concentrations, but raised hepatic ones.

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