Abstract: An apparatus for culturing suspended photosynthetic organisms, specifically a flowing thin film photobioreactor, wherein the flowing thin film photobioreactor comprises a light source and a trickle-film insert comprising screen material.

Abstract: A back pressure valve for providing a double barrier to flow for use with a tubing hanger within a well bore, wherein the back pressure valve can have a first body piece threadably engaged and sealed with a second body piece. A first piston can engage a first surface for sealing bottom pressure to provide a first barrier to flow. A second piston can engage a second surface for redundantly sealing bottom pressure to provide a second barrier to flow. The back pressure valve can have one-way and two-way back pressure valve assemblies. The two-way back pressure valve assembly can include a bidirectional piston having a double sealing face for engaging sealing surfaces and sealing bottom pressure from the well bore while allowing testing without stopping a flow of fluid.

Abstract: Techniques for filtering light include, along a central optical axis, an entrance window; a first polarizer, a narrowband polarization-changing material, a second polarizer, and an exit window. The optical paths through the filter are substantively unscattered and pass through unstressed components between the polarizers. The polarization-changing material changes polarization for a narrow wavelength band on the order of about 0.01×10?9 meters and does not condense on optical windows and polarizers during the operational lifetime. An aspect ratio, defined by a distance from the entrance window to the exit window divided by an optical aperture for the entrance window, is less than 4/1. This filter thus transmits light substantively unattenuated in the narrow wavelength band up to a maximum acceptance angle greater than 5 degrees. Combined with optics and imaging detectors, it is suitable for wide area surveillance, including daylight surveillance for combustion like forest fire and missile plume.

Abstract: Techniques for filtering light include, along a central optical axis, an entrance window; a first polarizer, a narrowband polarization-changing material, a second polarizer, and an exit window. The optical paths through the filter are substantively unscattered and pass through unstressed components between the polarizers. The polarization-changing material changes polarization for a narrow wavelength band on the order of about 0.01×10?9 meters and does not condense on optical windows and polarizers during the operational lifetime. An aspect ratio, defined by a distance from the entrance window to the exit window divided by an optical aperture for the entrance window, is less than 4/1. This filter thus transmits light substantively unattenuated in the narrow wavelength band up to a maximum acceptance angle greater than 5 degrees. Combined with optics and imaging detectors, it is suitable for wide area surveillance, including daylight surveillance for combustion like forest fire and missile plume.