Abstract: A read head for perpendicular magnetic recording that reduces side reading. The read head includes a read element and a magnetic shield spaced apart from the read element. The magnetic shield at least partially surrounds the read element at an air-bearing surface of the read element. The ratio of an air-bearing surface area of the magnetic shield to an air-bearing surface area of the read element is from about 1:1 to about 40:1.

Abstract: A read head for perpendicular magnetic recording that reduces side reading. The read head includes a read element and a magnetic shield spaced apart from the read element. The magnetic shield at least partially surrounds the read element at an air-bearing surface of the read element. The ratio of an air-bearing surface area of the magnetic shield to an air-bearing surface area of the read element is from about 1:1 to about 40:1.

Abstract: An AGC system for controlling the gain of an amplifier includes an AGC multiplexer and an AGC circuit. The AGC circuit receives an input signal from the AGC multiplexer and generates, in response thereto a gain control signal. The AGC multiplexer operates in three modes. In a first mode, in which the erased portion of a sector is being detected, the AGC multiplexer couples an input preset signal of a predetermined voltage level to the AGC circuit, enabling it, in turn, to generate a gain control signal to control the gain to a predetermined level. In a second mode, the AGC multiplexer couples a signal related to the output signal from the amplifier to the AGC circuit, enabling the AGC circuit to generate a gain signal related to the output level of the amplifier. In the third mode, the AGC multiplexer maintains its output signal constant, thus enabling the AGC circuit to maintain its gain control constant.

Abstract: Shaped catalyst particles having a polylobal cross-section are utilized in hydrotreating a petroleum residuum to obtain a desulfurized product. The catalyst particles have a surface area greater than 150 m.sup.2 /g and a catalyst pore volume of 0.35-0.85 cc/g resulting from a major portion of pores of diameters in the range 40-90A.

Abstract: There is disclosed a hydrotreating process for petroleum distillate which comprises contacting the distillate with catalyst particles of special shape characteristics in the presence of hydrogen at elevated temperature and pressure.

Abstract: Shaped catalyst particles are described which are particularly useful in hydrocarbon conversion processes and, in particular, in processes which are influenced by mass transfer such as the trickle bed hydrogenation process and hydrotreating of residuum.