Abstract: A storage device for storing photographic exposure information employs a closed-loop analog-to-digital (A-D) converter circuit includes a counter and a digital-to-analog (D-A) converter. The influence of erroneous signals which are created at the output of the D-A converter when the exposure information is stored in the counter is eliminated. The D-A converter circuit employs a ladder network of coarse accuracy. The stored exposure value, however, is highly accurate because of the closed-loop nature of the A-D converter circuit. Means responsive to the stored value for operating the exposure system of the camera are disclosed.

Abstract: The target board has an array of discs calorineters spread around the surface to receive the laser energy. The energy striking a disc is sensed by a pair of thermal leads connected to the back side of the disc and the voltage cross the lead is amplified and sent to a recording system.

Abstract: A zone of a subterranean formation penetrated by a well bore is permanently plugged by injecting a liquid resin system containing at least one thermosetting resin and at least one curing agent or catalyst therefor into the formation and injecting into the wellbore following the resin system, a second liquid containing at least one chain stopping compound to react with one component in the resin system to prevent any of the resin system remaining in the well bore from crosslinking to a sufficient crosslink density to form a solid in the wellbore. Preferably, the second liquid also contains a fluid loss additive to minimize loss of the second liquid from the wellbore to the formation. The method permits a zone to be plugged off and abandoned without the need to erect a drilling rig to drill out excess plugging material remaining in the wellbore.

Abstract: A zone of a subterranean formation penetrated by a well bore is permanently plugged by injecting a liquid resin system containing at least one thermosetting resin and at least one curing agent or catalyst therefor into the formation and injecting into the wellbore following the resin system, a second liquid containing at least one chain stopping compound to react with one component in the resin system to prevent any of the resin system remaining in the well bore from crosslinking to a sufficient crosslink density to form a solid in the wellbore. Preferably, the second liquid also contains a fluid loss additive to minimize loss of the second liquid from the wellbore to the formation. The method permits a zone to be plugged off and abandoned without the need to erect a drilling rig to drill out excess plugging material remaining in the wellbore.

Abstract: A cement composition is provided containing portland cement; calcium sulfate hemihydrate; an alkali metal nitrate; one or more retarders selected from the group consisting of a low molecular weight hydroxypolycarboxylic acid and sodium, potassium, and lithium salts thereof, and an alkaline hexametaphosphate; and as optional ingredients, calcium chloride and/or a condensation product of mononaphthalene sulfonic acid and formaldehyde; said ingredients being present in amounts effective to provide a cement which will set within a desired period of time at temperatures below about 80.degree. F down to below freezing, e.g. 32.degree. F, to provide a monolithic mass having adequate strength.

Abstract: A cement composition is provided containing portland cement; calcium sulfate hemihydrate; an alkali metal nitrate; one or more retarders selected from the group consisting of a low molecular weight hydroxypolycarboxylic acid and sodium, potassium, and lithium salts thereof, and an alkaline hexametaphosphate; and as optional ingredients, calcium chloride and/or a condensation product of mononaphthalene sulfonic acid and formaldehyde; said ingredients being present in amounts effective to provide a cement which will set within a desired period of time at temperatures below about 80.degree. F down to below freezing, e.g. 32.degree. F, to provide a monolithic mass having adequate strength.

Abstract: A TTL logic circuit employing single emitter PNP input transistors instead of a multi-emitter input stage, in order to reduce loading on input drive devices. The circuit features a logic swing of 1.6 volts centered on a circuit threshold of 1.6 volts with the logic 0 and logic 1 levels being internally clamped with p-n diode junctions to prevent transistor saturation and improve transistor switching speeds over those normally obtained using Schottky diode clamping techniques. The circuit output incorporates a Darlington stage and provides a logic 1 drive capability permitting the circuit to drive a terminated signal line having a low characteristic impedance, typically 50 ohms while maintaining a logic 1 level above 2.0 volts at 25.degree. C. Use of ion implantation techniques to define the isolation, emitter and base regions as well as the p-n diode junctions permits smaller device geometries and high F.sub.T transistors capable of high speed switching.