A removable and reusable filter attachment system is disclosed. A filter medium is fixed to, and surrounded by, a filter frame having a coaxial, longitudinally extending, annular rim. The rim engages an annular groove which surrounds the opening of a filter housing. The annular groove contains a fusible material and a heating mechanism for melting the fusible material. Upon resolidifying, the fusible material forms a hermetic bond with the rim and groove. Remelting allows detachment and replacement of the filter frame.

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode is described. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure.

An improved downhole steam injector has an angled water orifice to swirl the water through the device for improved heat transfer before it is converted to steam. The injector also has a sloped diameter reduction in the steam chamber to throw water that collects along the side of the chamber during slant drilling into the flame for conversion to steam. In addition, the output of the flame chamber is beveled to reduce hot spots and increase efficiency, and the fuel-oxidant inputs are arranged to minimize coking.

The present invention is directed to a fuel-air control system for a combustor in which coal-derived gas of varying heat content is used. To maintain the temperature in the combustor at an essentially constant value the fuel-to-air ratio is adjusted by using a temperature actuated variable pressure regulator in the gas feed line to compensate for the variability of the heat content of the gas. The velocity of the products of combustion is maintained at an essentially constant flow rate by controlling the mass flow of the air and fuel through linked valves on the gas and air feed lines.

A method is described for the preparation of defined, isomerically pure phospholipid-nucleoside conjugates as a prodrug in which the drug (araC) is attached to the phospholipid by a monophosphate linkage. Key intermediates in the process involve selective blocking and deblocking of the nucleoside derivative. These particular monophosphate-linked derivatives represent a new class of prodrug, which are useful by themselves or in combination with diphosphate linked derivatives. Several new compositions involving diphosphate linked derivatives are described in which the products are isomerically pure and having defined fatty acid chain lengths.

A new composition of matter has been discovered which is an explosive addition compound of ammonium nitrate (AN) and diethylenetriamine trinitrate (DETN) in a 50:50 molar ratio. the compound is stable over extended periods of time only at temperatures higher than 46/sup 0/C, decomposing to a fine-grained eutectic mixture (which is also believed to be new) of AN and DETN at temperatures lower than 46/sup 0/C. The compound of the invention has an x-ray density of 1.61 g/cm/sup 3/, explodes to form essentially only gaseous products, has higher detonation properties (i.e., detonation velocity and pressure) than those of any mechanical mixture having the same density and composition as the compound of the invention, is a quite insensitive explosive material, can be cast at temperatures attainable by high pressure steam, and is prepared from inexpensive ingredients. Methods of preparing the compound and the fine-grained eutectic composition of the invention are given.

This invention is directed to a process of generating silicon tetrafluoride (SiF/sub 4/) from aqueous solutions of hexafluorosilicic acid (H/sub 2/SiF/sub 6/), comprising reacting an aqueous solution of H/sub 2/SiF/sub 6/ with a concentrated aqueous salt solution to produce a precipitate, separating and drying the precipitate, and heating the precipitate in an inert atmosphere to decompose the precipitate producing SiF/sub 4/.

The invention comprises a method for the identification and quantification of sorbed chemical species onto a coating of a device capable of generating and receiving an acoustic wave, by measuring the changes in the velocity of the acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating and by measuring the changes in the attenuation of an acoustic wave resulting from the sorption of the chemical species into the coating as the wave travels through the coating. The inventive method further correlates the magnitudes of the changes of velocity with respect to changes of the attenuation of the acoustic wave to identify the sorbed chemical species. The absolute magnitudes of the velocity changes or the absolute magnitude of the attenuation changes are used to determine the concentration of the identified chemical species.

This invention is comprised of a background-reducing x-ray multilayer mirror. A multiple-layer ``wavetrap`` deposited over the surface of a layered synthetic microstructure soft x-ray mirror optimized for reflectivity at chosen wavelengths is disclosed for reducing the reflectivity of undesired, longer wavelength incident radiation incident thereon. In three separate mirror designs employing an alternating molybdenum and silicon layered mirrored structure overlaid by two layers of a molybdenum/silicon pair anti-reflection coating, reflectivities of near normal incidence 133, 171, and 186 {Angstrom} wavelengths have been optimized, while that at 304 {Angstrom} has been minimized. The optimization process involves the choice of materials, the composition of the layer/pairs as well as the number thereof, and the distance therebetween for the mirror, and the simultaneous choice of materials, the composition of the layer/pairs, their number and distance for the ``wavetrap.``

The present invention is directed to an apparatus for the monitoring of the combustion process within a combustion system. The apparatus comprises; a combustion system, a means for supplying fuel and an oxidizer, a device for igniting the fuel and oxidizer in order to initiate combustion, and a sensor for determining the current conducted by the combustion process. The combustion system comprises a fuel nozzle and an outer shell attached to the combustion nozzle. The outer shell defines a combustion chamber. Preferably the nozzle is a lean premix fuel nozzle (LPN). Fuel and an oxidizer are provided to the fuel nozzle at separate rates. The fuel and oxidizer are ignited. A sensor positioned within the combustion system comprising at least two electrodes in spaced-apart relationship from one another. At least a portion of the combustion process or flame is between the first and second electrodes. A voltage is applied between the first and second electrodes and the magnitude of resulting current between the first and second electrodes is determined.

Rhenium is recovered from an alloy containing that metal and either one or both of the metals molybdenum and tungsten by the following steps: (1) heating the alloy in the presence of O/sub 2/ to remove the Re from the alloy as gaseous Re/sub 2/O/sub 7/; (2) condensing the gaseous Re/sub 2/O/sub 7/; (3) dissolving the obtained solid Re/sub 2/O/sub 7/ in H/sub 2/O; (4) treating the solution of Re/sub 2/O/sub 7/ and H/sub 2/O with KCl to form KReO/sub 4/; and (5) heating the KReO/sub 4/ in the presence of H/sub 2/ to form Re.

The invention relates to an apparatus that acts as a fail save shut off valve. More specifically, the invention relates to a fail save shut off valve that allows fluid flow during normal operational conditions, but prevents the flow of fluids in the event of system failure upstream that causes over-pressurization. The present invention is particularly well suited for use in conjunction with hot gas filtering systems, which utilize ceramic candle filters. Used in such a hot gas system the present invention stops the flow of hot gas and prevents any particulate laden gas from entering the clean side of the system.

An apparatus and method for conducting ultra-sensitive trace element and isotope analysis. The apparatus injects a sample through a fine nozzle to form an atomic beam. A DC discharge is used to elevate select atoms to a metastable energy level. These atoms are then acted on by a laser oriented orthogonally to the beam path to reduce the traverse velocity and to decrease the divergence angle of the beam. The beam then enters a Zeeman slower where a counter-propagating laser beam acts to slow the atoms down. Then select atoms are captured in a magneto-optical trap where they undergo fluorescence. A portion of the scattered photons are imaged onto a photo-detector, and the results analyzed to detect the presence of single atoms of the specific trace elements.