Abstract: A platinum alloy catalyst can be used as a fuel cell catalyst. The platinum alloy is a PtAuX alloy wherein X is one or more metals chosen from the group consisting of transition metals, and wherein the alloy contains 40-97% Pt, 1-40% Au and 2-20% X. Electrodes, catalysed membranes and membrane electrode assemblies comprising the catalyst are also disclosed.

Abstract: A method of making Cu, Zn, and/or Cu/Zn alloy nanoparticles subjects one or more targets to laser energy to form a vapor and condenses the vapor to form nanoparticles having an average particle size of less than 20 nm. The optional application of an electric field results in nanoparticles with aspect ratios greater than 1.0. The target(s) can be a single target or separate targets comprising a mixture of copper, zinc, and/or copper/zinc. When separate targets are used, the laser beam can be split to form two separate beams each of which is made incident upon one of the targets. The nanoparticles can be formed in a chamber having an inert atmosphere or a reactive atmosphere and a convection current is created in the chamber by maintaining the top plate at a lower temperature than the bottom plate.

Abstract: Materials that are useful for absorption enhanced reforming (AER) of a fuel, including absorbent materials and catalyst materials and methods for using the materials. The materials can be fabricated by spray processing. The use of the materials in AER can produce a H2 product gas having a high H2 content and a low level of carbon oxides.

Abstract: A composition is provided that can be used, for example, in a fuel processor for a fuel cell system. The composition includes a first material such as a catalyst, and a second material such as a desiccant. The second material is capable of sorbing and desorbing a heat transfer material such as water, and is present in an amount sufficient to sorb an amount of the heat transfer material sufficient to remove a portion of the heat generated when the first material undergoes an exothermic reaction.

Abstract: A fuel oxidizing catalyst, a method of preparing the same, and a reformer and a fuel cell system including the same. In one embodiment, the fuel oxidizing catalyst for a fuel cell includes CeO2, MO (wherein M is a transition metal), and CuO. In this embodiment, the fuel oxidizing catalyst has a relatively high (or excellent) catalytic activity for a fuel oxidizing catalyst reaction and performs a fuel oxidizing catalyst reaction at a relatively low temperature even though it does not include a noble metal.

Abstract: An object of the present invention is to provide a method for producing a catalyst for treating exhaust gas, enabling a smaller amount of a noble metal to be supported and reducing the production cost thereof. There is provided a method for producing a catalyst for treating an exhaust gas containing carbon monoxide and volatile organic compounds, wherein the method comprises: preparing, as a pH buffer solution, an aqueous metal salt solution in which at least one metal salt is dissolved; reductively-treating the aqueous metal salt solution while keeping the pH constant to prepare a metal colloid solution; and immersing a carrier in the metal colloid solution to support the metal on the carrier. The supported amount of metal may be 0.7 g/L or less per one of the metals.

Abstract: This invention relates to methods for making a stabilized transition alumina of enhanced hydrothermal stability, which include the introduction of at least one structural stabilizer; a steaming step before or after the introduction step, wherein steaming is effective in transforming a transition alumina at least partially to boehmite and/or pseudoboehmite; and a calcining step to create a stabilized transition alumina. The combination of the structural stabilizer and the steaming step is believed to impart high hydrothermal stability to the alumina crystal lattice. Particularly preferred structural stabilizers include boron, cobalt, and zirconium. The stabilized transition alumina is useful as a catalyst support for high water partial pressure environments, and is particularly useful for making a catalyst having improved hydrothermal stability. The invention more specifically discloses Fischer-Tropsch catalysts and processes for the production of hydrocarbons from synthesis gas.

Abstract: The present invention relates to a method of making a catalyst for carbon nanotubes and nanofibers, comprising heating oxygen compound of transition metal in oxidative ambient at a temperature of 800° C. through 1,5000 C to be transformed into an agglomerated transition metal oxide; and powdering the agglomerated transition metal oxide into a minute particle. Thus, the present invention provides a catalyst for carbon nanotubes and carbon nanofibers, and a method of making the same, in which production cost is reduced and it is possible to safekeep for a long time.

Abstract: A methanol reforming catalyst containing passivated copper and zinc oxide and/or alumina can be prepared by (1) precipitating or spray-drying a mixture of catalyst precursor components dissolved or suspended in a diluent in order to form a solid catalyst precursor in the form of powder or granules, (2) calcining and reducing the solid catalyst precursor obtained in stage (1), (3) passivating the reduced catalyst precursor obtained in stage (2) and (4) shaping the passivated catalyst precursor obtained in stage (3) to form the catalyst. A reduction in the volume shrinkage and an increase in the mechanical hardness during operation of the methanol reforming catalyst are achieved by the preparation process.

Abstract: A catalyst for purifying exhaust gas that provides a superior catalytic performance even at a high temperature by increasing the durability of the promoter. The catalyst for purifying exhaust gas includes a promoter clathrate wherein a promoter component particle is covered with a high heat-resistant oxide. A promoter active species is contained in the promoter clathrate. The catalytic active species are located adjacent to the promoter clathrates. The catalytic active species has a precious metallic particle having a catalyst activity, a metallic oxide particle for bearing the precious metallic particle and a metallic oxide placed around the metallic oxide particle and the precious metallic particle.

Abstract: Supported catalysts are produced with nanometer sized particles comprised of different metals dispersed throughout the catalyst support material. The supported catalysts reduce substantially or completely the amount of platinum that is required without sacrificing catalytic performance. In place of platinum, the supported catalysts employ palladium, silver, or copper, all of which costs significantly less than platinum.

Abstract: The present teachings are directed toward methods of modifying the properties of a composition by providing particles of a first composition having dimensions of less than about 3 nanometers and a substrate of a second composition. The particles of the first composition are placed on the substrate, whereby the particles of the first composition and the substrate interact to modify at least one property of the particles of the first composition relative to the same property of particles of the first composition having dimensions greater than about 10 nanometers placed on a substrate of the second composition.

Abstract: To carry out a heterogeneously catalyzed reaction, a reaction mixture comprising hydrocarbon and water is fed onto a catalyst that is produced by compressing at least one catalyst powder into a highly compressed layer which forms a shaped body. The reaction mixture is pressed through the catalyst layer with a pressure drop.

Abstract: Novel nickel and/or cobalt plated sponge based catalysts are disclosed. The catalyst have an activity and/or selectivity comparable to conventional nickel and/or cobalt sponge catalysts, e.g., Raney® nickel or Raney® cobalt catalysts, but require a reduced content of nickel and/or cobalt. Catalysts in accordance with the invention comprise nickel and/or cobalt coated on at least a portion of the surface of a sponge support. Preferably, the sponge support comprises at least one metal other than or different from the metal(s) contained in the coating. The method of preparing the plated catalysts, and the method of using the catalysts in the preparation of organic compounds are also disclosed.

Abstract: Catalysts, catalyst systems, and methods for removing ammonia and/or carbon monoxide in flue gases are provided where ammonia is used with a selective catalytic reduction catalyst for reducing oxides of nitrogen. A dual oxidation catalyst generally comprises an alkali component, a transition metal, and a metal oxide support. This catalyst is also substantially free from precious metal components and effective for substantially simultaneously oxidizing ammonia (NH3) and carbon monoxide (CO) when placed in an exhaust gas stream. The catalyst is effective to provide low ammonia to nitrogen oxides selectivity.

Abstract: An object of the present invention is to provide a photocatalytic powder containing titanium dioxide fine particles containing an anionically active substance, where the electrokinetic potential of the fine particle is from about ?100 to 0 mV in an aqueous environment at pH 5. Another object of the present invention is to provide a photocatalytic slurry containing the powder, and a polymer composition, a coating agent, a photocatalytic functional molded article and a photocatalytic functional structure using the powder.

Abstract: A precursor to a catalytic structure comprising zinc oxide and copper oxide. The zinc oxide has a sheet-like morphology or a spherical morphology and the copper oxide comprises particles of copper oxide. The copper oxide is reduced to copper, producing the catalytic structure. The catalytic structure is fabricated by a hydrothermal process. A reaction mixture comprising a zinc salt, a copper salt, a hydroxyl ion source, and a structure-directing agent is formed. The reaction mixture is heated under confined volume conditions to produce the precursor. The copper oxide in the precursor is reduced to copper. A method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure.

Abstract: The present invention provides a catalyst that may be used to facilitate the formation of dimethylchlorosilanes. A catalyst in which copper oxide and zinc oxide are in intimate contact and form agglomerated particles allows for the increased selectively of the production of dimethylchlorosilanes.

Abstract: A metal-supporting photocatalyst includes a metal deposit and nano-particles of a photocatalyst dispersed on the metal deposit. Preferably, the metal deposit is a metal electro-deposit. More preferably, the metal deposit has a dendritic structure. A method for preparing a metal-supporting photocatalyst, including forming a metal deposit of a supporting metal, and forming nano-particles of a photocatalyst on the metal deposit, is also disclosed.

Abstract: The invention relates to a method for the oxidative dehydrogenation of ethane. The inventive method is characterized in that it consists of bringing the ethane into contact with the catalyst containing Mo, Te, V, Nb and at least a fifth element A which is selected from Cu, Ta, Sn, Se, W, Ti, Fe, Co, Ni, Cr, Zr, Sb, Bi, an alkali metal, an alkaline-earth metal and a rare earth, in which at least Mo, Te, V and Nb are present in the form of at least one oxide, said catalyst presenting, in calcined form, an X-ray diffractogram with more than ten intense diffraction lines, typically, the most intense lines corresponding to diffraction angles 2? of 7.7°±0.4, 8.9°±0.4, 22.1°+0.4, 26.6°±0.4, 26.9°±0.4, 27.1°±0.4, 28.1°±0.4, 31.2°±0.4, 35.0°±0.4 and 45.06°±0.

Abstract: Catalysts for the purification of ethylene containing copper and zinc, optionally one or more promoters or supports. These catalysts are produced by precipitation, drying, calcination and compression, optionally with the addition of additives, the compressed catalyst particles are calcinated at a temperature between from 300 to 700° C.

Abstract: Bulk and supported catalysts are prepared from an aqueous slurry containing a catalytically active material and a binder. The slurry is either coated onto a support and dried to form a porous, high surface area phase containing the catalytically active material, or reduced to a paste-like consistency, molded and dried to form a bulk catalyst. The processes and catalysts may be employed in various catalytic chemical processes to achieve high effectiveness factor of the catalytically active material while achieving a lower pressure drop.

Abstract: This invention is directed to an improved process for the preparation of N-(phosphonomethyl)glycine (i.e., “glyphosate”), a salt of N-(phosphonomethyl)glycine, or an ester of N-(phosphonomethyl)glycine. The process comprises combining an N-substituted N-(phosphonomethyl)glycine reactant with oxygen in the presence of a noble metal catalyst. The N-substituted N-(phosphonomethyl)glycine reactant has formula (V): wherein R1 and R2 are independently selected from the group consisting of hydrogen, halogen, —PO3R12R13, —SO3R14, —NO2, hydrocarbyl, and substituted hydrocarbyl other than —CO2R15; and R7, R8, R9, R12, R13, R14 and R15 are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, and an agronomically acceptable cation.

Abstract: The invention provides a method for depositing catalytic clusters on a surface, the method comprising confining the surface to a controlled atmosphere; contacting the surface with catalyst containing vapor for a first period of time; removing the vapor from the controlled atmosphere; and contacting the surface with a reducing agent for a second period of time so as to produce catalyst-containing nucleation sites.

Abstract: The present invention provides a regenerable catalyst composition suitable for entrapping SOx. The composition of the invention comprises a copper oxide having the formula (Cu/(A oxide) where A oxide is SiO2, Zr—SiO2, Al2O3, TiO2—Al2O3, ZrO2 and In2O3 or mixtures thereof. Copper loading may vary from about 10 to 60 mol % and is preferably about 25 mol %. The catalyst composition adsorbs SOx as metal sulfate under lean conditions and desorbs accumulated SOx as SO2 under rich conditions. Such reversible SOx trap are able to operate under conventional NOx trap operating conditions to prevent sulfur poisoning of the NOx trap. Furthermore, these traps may be regenerated under rich conditions at 300-450° C. In another embodiment of the present invention, an irreversible SOx trap capable of collecting SOx under lean conditions is provided. The traps of this embodiment include praseodymia, zirconia-praseodymia and mixed manganese-yttria and mixtures thereof.

Abstract: A desulfurizing agent comprising a silica-alumina carrier having an Si/Al mole ratio of 10 or less and nickel carried thereon; a desulfurizing agent for hydrocarbons derived from petroleum which comprises a carrier and a metal component carried thereon and has a specific surface area of pores having a pore diameter of 3 nm or less of 100 m2/g or more; an Ni-Cu based desulfurizing agent comprising a carrier and, carried thereon, (A) nickel, (B) copper, and (C) an alkali metal or another metal; a desulfurizing agent for hydrocarbons derived from petroleum which comprises a carrier and a metal component carried thereon and has a hydrogen adsorption capacity of 0.4 mmol/g or more; and methods for producing these nickel-based and nickel-copper-based desulfurizing agents. The above desulfurizing agents are capable of adsorbing and removing with good efficiency the sulfur contained in hydrocarbons derived from petroleum to a content of 0.2 wt. ppm or less and have a long service life.

Abstract: In a fuel cell, a fuel cell system, and a method of preparing the same, a carbon monoxide oxidizing catalyst for a reformer of the fuel cell system includes: a carrier selected from the group consisting of alumina, cordierite, and combinations thereof; and an active material including CeO2, MO, and CuO, where M is a transition element which is supported on the carrier.

Abstract: The alkylhalosilanes are directly synthesized while diminishing the formation of coke by reacting an alkyl halide with silicon in the presence of a catalytically effective amount of (?) a copper metal or a copper-based compound catalyst and (?) a catalyst promoter intermixture therefor which comprises an effective minor amount of an additive ?1 selected from the group consisting of tin, a tin-based compound and mixture thereof, optionally, an effective minor amount of an additive ?2 selected from the group consisting of zinc metal, a zinc-based compound and mixture thereof, an effective minor amount of an additive ?3 selected from the group consisting of cesium, potassium and rubidium, and compound and mixture thereof, and, optionally, an effective minor amount of an additive ?4 selected from the group consisting of the element phosphorus, a phosphorus-based compound and mixture thereof.

Abstract: A method and device for loading a catalyst into a chamber. The catalyst loading is well suited for production of hydrogen producing microreactors. The catalyst is coated onto a strip which is mountable within the chamber.

Abstract: A catalyst for the hydrogenation of C4-dicarboxylic acids and/or their derivatives, preferably maleic anhydride, in the gas phase comprises from 5 to 100% by weight, preferably from 40 to 90% by weight, of copper oxide and from 0 to 95% by weight, preferably from 10 to 60% by weight, of one or more metals or compounds thereof selected from the group consisting of Al, Si, Zn, Pd, La, Ce, the elements of groups III A to VIII A and groups I A and II A as active composition applied in the form of a thin layer to an inert support material.

Abstract: The present invention provides a catalyst that may be used to facilitate the formation of dimethylchlorosilanes. A catalyst in which copper oxide and zinc oxide are in intimate contact and form agglomerated particles allows for the increased selectively of the production of dimethylchlorosilanes.

Abstract: The alkylhalosilanes are directly synthesized by reacting an alkyl halide with silicon in the presence of a catalytically effective amount of (?) a copper metal or a copper-based compound catalyst and (?) a catalyst promoter intermixture therefor which comprises an effective minor amount of an additive ?1 selected from the group consisting of tin, a tin-based compound and mixture thereof, an effective minor amount of an additive ?2 selected from the group consisting of cesium, potassium and rubidium, and compound and mixture thereof, and an effective minor amount of an additive ?3 selected from the group consisting of the element phosphorus, a phosphorus-based compound and mixture thereof.

Abstract: The invention relates to highly active spherical metal support catalysts with a metal content of 10 to 70% by mass, and a process for their production with the use of a mixture of polysaccharides and at least one metal compound which is dropped into a metal salt solution.

Abstract: A fuel or fuel additives is disclosed which includes particles of cerium oxide which have been doped with a divalent or trivalent metal or metalloid which is a rare earth metal, a transition metal or a metal of group IIA, IIIB, VB, or VIB of the Periodic Table.

Abstract: A catalyst for the hydroprocessing of organic compounds, composed of an interstitial metal hydride having a reaction surface at which monatomic hydrogen is available. The activity of the catalyst is maximized by avoiding surface oxide formation. Transition metals and lanthanide metals compose the compound from which the interstitial metal hydride is formed. The catalyst's capabilities can be further enhanced using radio frequency (RF) or microwave energy.

Abstract: The oxide materials are of the class of ternary mesoporous mixed oxide materials including lanthanum, a metal M selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu and Zn, and zirconium or cerium such a mesoporous La—Co—Zr mixed oxide material designated as Meso LCZ[x] where x is the atomic ratio (La+Co)/La+Co+Zr. They are useful as catalysts since they show high activities for hydrocarbon oxidation and good resistance against poisoning agents. These highly ordered mesoporous mixed oxides are synthesized by: preparing an amorphous solution of a La-M precursor and adding a salt of zirconium or cerium thereto; acidifying the amorphous solution in the presence of a surfactant under conditions to obtain a clear homogeneous solution; adjusting pH of the solution under conditions to form a solid precipitate; separating the solution and surfactant from the precipitate; and calcinating the precipitate.

Abstract: Methanol steam reforming catalysts, and steam reformers and fuel cell systems incorporating the same. In some embodiments, the methanol steam reforming catalyst includes zinc oxide as an active component. In some embodiments, the methanol steam reforming catalyst further includes at least one of chromium oxide and calcium aluminate. In some embodiments, the methanol steam reforming catalyst is not pyrophoric. Similarly, in some embodiments, steam reformers including a reforming catalyst according to the present disclosure may include an air-permeable or air-accessible reforming catalyst bed. In some embodiments, the methanol steam reforming catalyst is not reduced during use. In some embodiments, the methanol reforming catalysts are not active at temperatures below 275° C. In some embodiments, the methanol steam reforming catalyst includes a sulfur-absorbent material. Steam reformers, reforming systems, fuel cell systems and methods of using the reforming catalysts are also disclosed.

Abstract: A combination comprising a bed of a particulate copper-containing catalyst and, a guard bed of a particulate composition containing a) lead and/or at least one lead compound that reacts with hydrogen chloride and b) a support therefor. The lead compound is preferably lead nitrate. The combination is of particular utility for the low temperature shift reaction wherein carbon monoxide is reacted with steam to produce hydrogen and carbon dioxide.

Abstract: A combination comprising a bed of a particulate copper-containing catalyst bed, a guard bed in the form of shaped units formed from lead carbonate and/or basic lead carbonate particles having an average (by volume) particle size below 100 ?m.

Abstract: This invention provides novel stable metallic mesoporous transition metal oxide molecular sieves and methods for their production. The sieves have high electrical conductivity and may be used as solid electrolyte devices, e.g., in fuel cells, as sorbents, e.g. for hydrogen storage, and as catalysts. The invention also provides room temperature activation of dinitrogen, using the sieves as a catalyst, which permits ammonia production at room temperature.

Abstract: A catalyst system for use with an internal combustion engine to provide emissions reductions under lean and stoichiometric operating conditions. The catalyst system comprises a first catalyst comprised of a newly developed Perovskite-based formulation having an ABO3 crystal structure designed to bring the precious metal and NOx trapping elements close together. The first catalyst acts primarily to maximize the reduction of emissions under lean operating conditions. The catalyst system also comprises a second catalyst comprised of precious metals which acts primarily to maximize the reduction of emissions under stoichiometric conditions.

Abstract: Catalysts and methods useful for the production of olefins from alkanes via oxidative dehydrogenation (ODH) comprise at least one base metal and copper with an optional promoter. The catalyst preferably comprises a base metal and a copper-modified Groups 8, 9, or 10 metal on a support comprising alumina, zirconia, or mixtures thereof. Copper is preferably present in an amount of from about 0.1 to about 1.0 percent by weight of the total catalyst weight. The base metal preferably comprises manganese, chromium, gold, their corresponding oxides, or combinations thereof. The optional promoter preferably comprises platinum, palladium, iridium, rhodium, ruthenium, or any combinations thereof.

Abstract: A process for the preparation of water gas shift catalyst is described. The process includes mixing a copper salt and a zinc salt with an aluminum component in a solution, precipitating a precipitate from the solution, drying an forming the precipitate into the water gas shift catalyst. In an alternate process the aluminum component is prepared separately from the solution of the copper salt and the zinc salt prior to the mixing of the components. After the components are mixed a precipitate is precipitated from the solution, the precipitate is dried and formed into the catalyst.

Abstract: A silica-rich support and a catalyst containing the silica-rich support and a catalytic component. The support has a specific structure characterized by a set of claimed physicochemical properties: in the 29Si MAS NMR spectrum the state of silicon is characterized by the presence of lines with chemical shifts ?100±3 ppm (line Q3) and ?110±3 ppm (line Q4), with the ratio of the integral intensities of the lines Q3/Q4 of from 0.7 to 1.2 (FIG. 1); in the IR spectrum there is an absorption band of hydroxyl groups with the wave number 3620–3650 cm?1 and half-width 65–75 cm?1 (FIG. 2); the carrier has a specific surface area, as measured by the BET techniques from the thermal desorption of argon, SAR=0.5–30 m2/g and the surface, as measured by alkali titration techniques, SNa=10–250 m2/g, with SNa/SAr=5–30.

Abstract: A composition for controlling NOx emissions during FCC processes comprises (i) an acidic oxide support, (ii) cerium oxide, (iii) a lanthanide oxide other than ceria such as praseodymium oxide, and (iv), optionally, an oxide of a metal from Groups Ib and IIb such as copper, silver and zinc.

Abstract: A high temperature water gas shift catalyst comprising iron and at least one promoter is prepared via a method which comprises the preparation of a high purity iron precursor and which uses a nominal amount of water in the catalyst production. The catalyst prepared according to the inventive method is more efficient in hydrogen production under the high temperature water gas shift reaction conditions in a fixed bed test than prior art catalysts of similar composition.

Abstract: The present invention provides a process for the preparation of an improved copper chromite catalyst for the hydrogenation of diethyl maleate to tetrahydrofuran with very high selectivity. This invention particularly relates to a process for the preparation of an improved copper chromite catalyst with specific composition and physical properties containing copper, chromium, zinc and aluminium as catalyst components in order to achieve selective production of tetrahydrofuran via single step hydrogenation of diethyl maleate. The calcination procedure has also been described to achieve the best activity. The catalyst has a life of more than 630 hours with constant activity. The used catalyst can also be regenerated to match the original hydrogenation activity.

Abstract: Improved Ni catalysts for hydrogenation reactions are disclosed. The catalysts are useful for hydrogenation such as selective hydrogenation of acetylenic impurities in crude olefin and diolefin streams. The catalysts are prepared by depositing nickel on a porous support which has the following specific physical properties; BET surface area of from 30 to about 100 m2/g, total nitrogen pore volume of from 0.4 to about 0.9 cc/g, and an average pore diameter of from about 110 to 450 ? with or without modifiers of one or more elements selected from the group consisting of Cu, Re, Pd, Zn, Mg, Mo, Ca and Bi.

Abstract: The present invention is to provide a metal oxide sintered structure having a homogeneous catalyst supporting ability, and a production method therefor. Hardly reducing oxide powders and reducing oxide powders are mixed, and then kneaded with a binder. By extrusion molding, a structure comprising channels (fluid communicating holes) is formed. Then, after heating reaction and solid solution, it is reduced under an atmosphere containing a hydrogen. Thereby, a metal oxide sintered structure having the fluid communicating holes, with the metal particles precipitated on the surface is produced. The structure is suitable for use as a catalyst for a fuel cell, or the like.

Abstract: A method for uniformly dispersing noble metal particles on a porous carrier by first mixing an alkoxide product of aluminum or silicon and a noble metal precursor together; then mixing a surfactant into the mixture; then mixing ammonia solution into the mixture to form a hydroxide of aluminum or silicon; then mixing a reducing agent into the mixture to convert the noble metal precursor into noble metal nanoparticles dispersed on the hydroxide; then separating the noble metal nanoparticles and the hydroxide from the mixture before calcining the hydroxide into an oxide of aluminum or silicon.

Abstract: A neural network is implemented by discrete-time, continuous voltage state analog device in which neuron, synapse and synaptic strength signals are generated in highly parallel analog circuits in successive states from stored values of the interdependent signals calculated in a previous state. The neuron and synapse signals are refined in a relaxation loop while the synaptic strength signals are held constant. In learning modes, the synaptic strength signals are modified in successive states from stable values of the analog neuron signals. The analog signals are stored for as long as required in master/slaver sample and hold circuits as digitized signals which are periodically refreshed to maintain the stored voltage within a voltage window bracketing the original analog signal.