Abstract: A parallel plate counter utilizes avalanche event counting over a large area with the ability to locate radioactive sources in two dimensions. One novel embodiment comprises a gas-filled chamber formed by a stretched stainless steel window cathode spaced from a flat semiconductive anode surface between which a high voltage is applied. When a beta ray, for example, enters the chamber, an ionization event occurs and the avalanche effect multiplies the event and results in charge collection on the anode surface for a limited period of time before the charge leaks away. An encoder system, comprising a symmetrical array of planar conductive surfaces separated from the anode by a dielectric material, couples charge currents the amplitude of which define the relative position of the ionization event. A number of preferred encoder system embodiments are disclosed including a novel matrix or grid pattern of electrical paths connected to voltage dividers and charge sensitive integrating amplifiers.

Abstract: A system for mapping radioactive specimens comprises an avalanche counter, an encoder, pre-amplifier circuits, sample and hold circuits and a programmed computer. The parallel plate counter utilizes avalanche event counting over a large area with the ability to locate radioactive sources in two dimensions. When a beta ray, for example, enters a chamber, an ionization event occurs and the avalanche effect multiplies the event and results in charge collection on the anode surface for a limited period of time before the charge leaks away. The encoder comprises a symmetrical array of planar conductive surfaces separated from the anode by a dielectric material. The encoder couples charge currents, the amplitudes of which define the relative position of the ionization event. The amplitude of coupled current, delivered to pre-amplifiers, defines the location of the event.

Abstract: A system for the production and maintenance of genomic libraries of recombinant DNA in a fixed geometric array arranged so that such libraries may be accurately replicated and maintained with the same set of individual DNA inserts occupying reproducible locations and comprising,(a) sets of individual bacterial colonies or plaques of bacteriophage which contain inserts of animal or plant DNA and are present in so large a number that there will be a high probability that the complete library will contain each DNA sequence of all of the sequences present in an animal or plant genome; to be established in subarrays which can individually be replicated,(b) a subsystem for picking up inocula from each of a geometric array simultaneously and transferring them to a second similar geometric array, including carrying and aligning means for maintaining a transfer means in superposed relationship with respect and for raising and lowering the transfer means into and out of proximity to said colonies or plaques, and(c) a s

Abstract: Novel large area spark chamber having a support for carrying a generally planar, radioactive work piece. The spark chamber has a thin window which is either a rigid plastic sheet carrying a thin layer of an electrically conductive material on the surface thereof, or a thin planar piece or film of electrically conductive metal. There is positioned in superposed relationship to the thin window, a layer of semi-conducting glass in spaced-apart relationship from the thin window by a resilient insulating seal to form an enclosed gas retaining chamber. An electrically conducting surface is adhered to the upper surface of the layer of semi-conducting glass. An electrically conductive path is provided between the thin layer of electrically conductive material on the thin window and the electrically conducting surface on said semi-conducting glass. The electrically conductive path includes a high voltage supply and TDCs and ADCs.