Abstract: A gas detector and process for detecting a fluorine-containing species in a gas containing same, e.g., an effluent of a semiconductor processing tool undergoing etch cleaning with HF, NF3, etc. The detector in a preferred structural arrangement employs a microelectromechanical system (MEMS)-based device structure and/or a free-standing metal element that functions as a sensing component and optionally as a heat source when elevated temperature sensing is required. The free-standing metal element can be fabricated directly onto a standard chip carrier/device package so that the package becomes a platform of the detector.

Abstract: Methods and apparatus are disclosed for determination of the total concentration of organic carbon compounds in aqueous process streams utilizing a pulsed-flow technique for irradiating a water sample in a chamber (3) with UV or similar wavelength radiation.

Abstract: A vapor sensing device that is sufficiently small and lightweight to be handheld, and also modular so as to allow the device to be conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor.

Abstract: An exhaust gas sensor includes a housing and a sensor element supported by the housing. The sensor element includes a support member having an exhaust side, a reference side, and an aperture extending through the support member between the exhaust side and the reference side. The sensor element further includes an exhaust-side electrode on the exhaust side of the support member. The exhaust-side electrode is electrically connected to a contact on the reference side of the support member via a lead extending through the aperture. The aperture is sealed around the lead such that gas cannot pass through the aperture. The support member is oriented substantially parallel to the flow of exhaust gases when the exhaust gas sensor is installed on a vehicle. The sensor further includes a contact pin in the housing that engages the contact and biases the sensor element against a portion of the housing.

Abstract: Sensor arrays, methods, and systems for detecting the presence of gas phase materials by the formation of films based on the gas phase material are disclosed. The gas phase materials preferentially deposit conductive films on receptor materials that can be detected. The invention may also provide for increased sensitivity to the deposition of conductive materials through the use of closely spaced conductive electrodes interconnected by lines of receptor material. Examples of gas phase materials that may be detected include RuO4, IrO4 and RhO4.

Abstract: An integrated mesopump-sensor suitable for disposition in two- and three-dimensional arrays having small dimensions is disclosed. One mesopump is formed of an electrostatically attractable flexible diaphragm disposed through cavities or pumping chambers formed between two opposing electrostatically chargeable material layers. Fluid is pumped through the chambers by sequentially moving the diaphragm toward the first chargeable layer, then towards the second chargeable layer, which can pull and push the fluid through a series of chambers, and past the sensor. One group of sensors utilizes multiple and varied chemoresistive sensors which can vary in resistance differently in response to the presence of various analytes. Another group of sensors utilizes chemo-fluorescent sensors that fluoresce in the presence of particular analytes.

Abstract: The present invention includes free-standing, shaped ceramic-bearing bodies useful in fluid sensors, filters, and catalyst devices. The invention also includes methods and processes for using such devices. In a preferred embodiment of the invention, shaped metallic foils are converted into free-standing, porous rutile foils having an open pore structure by oxidation at an elevated temperature. The exposure of such foils to increasing concentrations of reducing gases such as carbon monoxide results in an increase in the steady-state electrical resistance. The resultant ceramic-bearing bodies may be used as effective sensors of reducing gas species in such applications as automobile and industrial emissions.

Abstract: A portable instrument for automatic collection and analysis of airborne lead concentrations in ambient air environments. Its improvements to the art of airborne lead detection and analysis permit the apparatus to analyze samples previously collected by personal monitors, for example, worn on the clothing of personnel working in contaminated sites. The apparatus also brings to the art of lead analysis a method of contaminant collection that ensures a greater capture efficiency of airborne contaminants, thereby increasing the accuracy of the instrument and its measurement capabilities while providing near real-time analysis and measurement in a portable self-contained battery-powered device. The apparatus also offers a remarkable improvement in the reduction of wastes incurred in the collection and analysis of airborne lead contaminants which is a novel method of concentrating the samples and recycling the analysis media used to concentrate and solubilize lead contaminants.

Abstract: This invention provides a reduced power consumption gas chromatograph system (10) which includes a capillary gas chromatograph column member (12) which contains a chemical sample to be analyzed. The gas chromatograph system further includes a heating mechanism (16) which extends throughout the length of the capillary gas chromatograph column member (12) and surrounds both the member (12) and a temperature sensing mechanism (14) which is mounted adjacent to the column member (12). The temperature sensing mechanism (14), the heating mechanism (16) and the column member (12) form a chromatograph column assembly (20) which includes a coiled section (28) where the components are tightly packed with respect to each other and allows for a reduced power consumption for temperature programming miniature gas chromatography column assemblies.

Abstract: Circuits include at least one-odor sensitive organic transistor having a conduction channel whose conductivity changes in response to certain odors. The organic transistors are interconnected to increase their response to selected odor signals. The organic transistors may be interconnected to form a ring oscillator whose frequency of oscillation changes in response to an odor signal and in which the alternating signal applied to the gate electrodes of the organic transistors enhances their recovery and reduces their drift.

Abstract: A gas detector for sensing the presence of at least one predetermined gas is operative in conjunction with a electrical power source and includes a detection circuit, a temperature controller, and a electrical current controller, wherein the detection circuit includes a sensing device having first and second electrodes, the first electrode being connected to the power source for heating the first electrode, the temperature controller is operatively connectable to the detection circuit for maintaining a temperature of the first electrode at a predetermined magnitude, and the current controller is operatively connectable to the detection circuit for maintaining a current in the second electrode at a predetermined magnitude.

Abstract: A galvanic measuring device for detecting oxygen content in a gas flow, having a sealed gas flow chamber and a layer of sodium chloride saturated sponge material lining the interior of the gas flow chamber, for providing a constant source of humidity to the chamber.

Abstract: A sample injector valve capable of introducing multiple samples of material into multiple liquid or gas streams is provided. Such a valve is particularly useful for injecting multiple samples under pressure into a combinatorial chemistry system with moving streams of fluid, such as a parallel pressure reactor or a rapid flow analysis system using multi-channel or parallel chromatography and related techniques. The valve is further capable of functioning on a small scale with automatic sampling equipment.

Abstract: An electronic system for selectively detecting and identifying a plurality of chemical species, which comprises an array of nanostructure sensing devices, is disclosed. Within the array, there are at least two different selectivities for sensing among the nanostructure sensing devices. Methods for fabricating the electronic system are also disclosed. The methods involve modifiying nanostructures within the devices to have different selectivity for sensing chemical species. Modification can involve chemical, electrochemical, and self-limiting point defect reactions. Reactants for these reactions can be supplied using a bath method or a chemical jet method. Methods for using the arrays of nanostructure sensing devices to detect and identify a plurality of chemical species are also provided.

Abstract: The present invention involves an artificial nose comprising an array, the array comprising at least a first dye and a second dye deposited directly onto a single support in a predetermined pattern combination, the combination of dyes in the array having a distinct and direct spectral absorbance or reflectance response to distinct analytes comprising one or more parent analytes or their derivatives. In one embodiment, the invention further comprises an oxidizing source to partially oxidize at least one distinct parent analyte to at least one corresponding derivative analyte of said parent analyte, the array at least in part having a stronger distinct and direct absorbance or reflectance response to the derivative analyte than to the corresponding parent analyte.

Abstract: Sensors and methods of monitoring for the presence of gas phase materials by detecting the formation of films based on the gas phase material are disclosed. Advantageously, some gas phase materials preferentially deposit on specific surfaces. As a result, selective detection of those gas phase materials can be obtained by detecting films deposited on those detection surfaces. Examples of gas phase materials that may be detected include RuO4, IrO4 and RhO4.

Abstract: A gas chromatography system having a computer-controlled pressure controller that delivers pressurized pulses to a column junction point of two series-coupled columns having different stationary-phase chemistries and a method of using the same. Each pressurized pulse causes a differential change in the carrier gas velocities in the two columns, which lasts for the duration of the pressurized pulse. Whereby, the pressurized pulse selectively increases the separation of a component pair that exhibits separation at the exit of the first column, but otherwise co-elutes from the column ensemble.

Abstract: The present invention relates to a filtration-detection device for detecting or quantifying an analyte in a test sample including a filtration device having a first binding material immobilized thereto, wherein the first binding material is capable of binding to a portion of the analyte, and a detection assembly positioned relative to the filtration device to detect or quantify analyte bound to the first binding material. The present invention also relates to methods of using the filtration-detection device.

Abstract: Chemically sensitive sensors, suitable for detecting analytes in fluids (in gaseous or liquid phase), wherein the chemically sensitive sensors comprise a chemically sensitive probe, which comprises one or a blend of several arylene alkenylene oligomers.

Abstract: A hydrocarbon sensor and collector. An element that is capable of absorbing and releasing hydrocarbons is positioned in the air intake system of a vehicle, upstream from the engine and wholly in the airflow. The element has a plurality of chambers defined in it that allow air to pass through the element. The hydrocarbon sensor and collector also includes a means for detecting the level of hydrocarbons absorbed by the element.

Abstract: A disposable, dry chemistry analytical system is disclosed which is broadly useful for the detection of a variety of analytes present in biological fluids such as whole blood, serum, plasma, urine and cerebral spinal fluid. The invention discloses the use of the reaction interface that forms between two liquids converging from opposite directions within a bibulous material. The discovery comprises a significant improvement over prior art disposable, analytical reagent systems in that the detectable reactant zone is visually distinct and separate from the unreacted reagents allowing for the use of reaction indicators exhibiting only minor changes as well as extremely high concentrations of reactants. In addition, staged, multiple reagents can be incorporated. Whole blood can be used as a sample without the need for separate cell separating materials.

Abstract: The present invention describes novel methods for making a substrate for selective cell patterning, and the substrates themselves, wherein the method comprises contacting reactive hydroxyl groups on the surface of a substrate with a hydroxyl-reactive bifunctional molecule to form a monolayer, and using stencils to deposit cell repulsive or cell adhesive moieties in controlled locations on the cell culture substrate. Methods comprising selective differentiation of stem cells to create tissue specific and organ-specific cell substrates, as well as the cell substrates themselves are also provided.

Abstract: A carbon dioxide sensor including a closed chamber having as a wall substantially water-tight, carbon dioxide-permeable membrane and containing two electrodes. The chamber contains a film of de-ionized water contacting the membrane and both of the electrodes. The change in conductance of the water due to absorption of carbon dioxide is measured.

Abstract: A method and apparatus for detection of a small amount of volatile products from a sample using a transducer which changes voltage as a function of contact of the volatile product with the transducer. The apparatus and method are used to detect spoilage of a biological material, such as a food. The apparatus is also used to detect microorganisms and in particular pathogenic microorganisms.

Abstract: Disclosed is a method for fabricating biosensors, using hydrophilic polyurethane. Bio-active reagents, including enzymes, antibodies, antigens, cells and receptors, are mixed with hydrophilic polyurethane and the mixture is directly coated over a signal transducer to form a sensing film which serves as a signal detector. The method using hydrophilic polyurethane allows the simplification of the fabrication of biosensors without conducting complicated chemical reactions and washing steps, such as crosslinking. The bio-active reagent entrapped within the hydrophilic polyurethane film can retains its high activity for an extended period of time and the intrinsic potentiometric response of the underlying ion-selective polymeric membrane is not affected by the bio-active reagent immobilized polyurethane film coated on its sensing surface. Therefore, the biosensors are superior in specificity, selectivity, and stability.

Abstract: A circuit includes at least one odor-sensitive organic field effect transistor (OFET) having a conduction channel whose conductivity changes in response to certain ambient odors and a feedback loop coupled between an output and an input of the circuit. The feedback loop generates a feedback signal which stabilizes the output signal of the circuit for time drift of the odor-sensitive organic transistor. In one embodiment, the OFET is an integral part of an amplifier and generates input signals to the amplifier in response to certain odors. A selectively enabled switch may be coupled between the output and the input of the amplifier circuit to provide negative feedback that tends to cancel the effect on the amplifier of time drift due to the OFET.

Abstract: RD-2ems and methods are disclosed for evaluation of small amounts of materials of interest for their resistance to exposure to environmental parameters such as chemicals. The invention also enables analysis of multiple samples simultaneously. Embodiments of the invention include the use of acoustic-wave devices for evaluation of chemical resistance of materials to a chemical, where the materials are deposited on the acoustic-wave devices or are resident in a volume of the chemical used for the material evaluation.

Abstract: The invention describes a new device for the measurement of the partial pressure of carbon dioxide. The device is based on a simple construction and can be manufactured in a cost effective way. The pH dependency of the redox potential of organic substances is used to determine an electrical characteristic that depends on the partial pressure of carbon dioxide. The device for the potentiometric determination of the partial pressure of carbon dioxide consists of a housing with an opening for the entrance for gases, a gas permeable membrane, an electrolyte, at least one redox and one reference electrode with electrode contacts that transmit the electrode potential outwards through the housing. The gas permeable membrane has an electronically conductive layer that works as a redox electrode for a pH dependent redox system.

Abstract: Sensor arrays, methods, and systems for detecting the presence of gas phase materials by the formation of films based on the gas phase material are disclosed. The gas phase materials preferentially deposit conductive films on receptor materials that can be detected. The invention may also provide for increased sensitivity to the deposition of conductive materials through the use of closely spaced conductive electrodes interconnected by lines of receptor material. Examples of gas phase materials that may be detected include RuO4,IrO4 and RhO4.

Abstract: The present invention relates to a device for measuring the concentration of hydrogen in a gaseous mixture and in particular in the air constituting, for example, the atmosphere inside a closed premises. This device comprises a sensor in contact with a gaseous mixture, the sensor being linked to calculating and display function. The sensor comprises a catalyst capable of provoking an exothermic reaction with the hydrogen contained in the gaseous mixture, a conducting function fixed to the catalyst for transferring essentially by conduction the thermal energy release by the reaction from the catalyst to a cold point, a function for measuring the temperature T1 of the catalyst and the temperature T2 of the cold point being linked to the function for calculating the value of the molar concentration of hydrogen in a gaseous mixture from the temperature gradient measured T1-T2.

Abstract: Chemical sensors for detecting the activity of a molecule or analyte of interest is provided. The chemical sensors comprise and array or plurality of sensors that are capable of interacting with a molecule of interest, wherein the interaction provides a response fingerprint. The fingerprint can be associated with a library of similar molecules of interest to determine the molecule's activity and diffusion coefficient.

Abstract: An alcohol sensor having gas-sensitive layers made of polymers or inorganic oxides wherein a signal is read out by means of work function change which is produced in the form of a field-effect transistor.

Abstract: A gas sensor for use in monitoring gases such as H2S, NO2 or SO2 comprises a film or layer of non-protonated polyaniline as the gas sensing material.

Abstract: A robust single-chip hydrogen sensor and a method for fabricating such a sensor. By adding an adhesion-promoting layer between the body of a sensor and an on-chip hydrogen-exposed electrically-resistive hydrogen-sensing element, device yields are improved when compared to directly applying the electrically-resistive hydrogen-sensing elements to the sensor body. The resistance of the sensing element is indicative of the hydrogen in the medium surrounding the sensor. According to a preferred embodiment of the present invention, the adhesion-promoting layer is a chromium (Cr) adhesion layer, and the hydrogen-exposed electrically resistive hydrogen sensing element is a PdNi alloy.

Abstract: A sensor is disclosed that comprises an electrolyte disposed between and in intimate contact with a sensing electrode and a reference electrode. A protective coating is disposed on the protective layer adjacent to the sensing electrode. The protective coating comprises a mixture of a metal oxide, a zeolite, and an alumina. A method for making the sensor is also disclosed.

Abstract: Chemical sensors for detecting the activity of a molecule or analyte of interest is provided. The chemical sensors comprise and array or plurality of sensors that are capable of interacting with a molecule of interest, wherein the interaction provides a response fingerprint. The fingerprint can be associated with a library of similar molecules of interest to determine the molecule's activity and diffusion coefficient.

Abstract: A gas sensor for the detection of gases comprises a housing and an active element disposed within the housing. The active element is surrounded by a porous insulating material having a bulk density no greater than 0.15 g/cc. Another gas sensor comprises an active element surrounded by a porous insulating material having a surface area no greater than approximately 200 m2/cc. Another gas sensor comprises a copper compound positioned so that gas contacts the copper compound before contacting the active element. Another gas sensor comprises an active element surrounded by a porous material having an average pore size of at least approximately 100 Å. Another gas sensor comprises a heating element surrounded by a porous material that supports a catalyst.

Abstract: An apparatus is disclosed which is capable of detecting a selected gas in a liquid sample to a sensitivity in the range of 10 to 10,000 parts per trillion. Such sensitivity is achieved by concentrating the selected gas in a sample without concentrating sources of ionic interference that are also present in the sample. Selective concentration of the gas is achieved by vaporizing the sample, correcting for non-ideal vaporization, selectively condensing the selected gas from the vapor, and detecting the selected gas. Methods for using the apparatus and detecting the selected gas are also disclosed.

Abstract: A gas concentration measuring apparatus is provided which measures the concentration of two kinds of gas components such as O2 and NOx contained in exhaust gasses of an internal combustion engine of automotive vehicles. The apparatus has a gas sensor which includes a first cell responsive to application of a voltage to discharge O2 in the exhaust gasses to the outside and produce an electric current as a function of concentration of the discharged O2 and a second cell responsive to application of a voltage to produce an electric current as a function of concentration of NOx in the exhaust gasses from which the O2 is discharged by the first cell. The apparatus offsets an error component of the electric current produced by the second cell which depends upon O2 contained in the exhaust gasses, or which in related operations, depends upon any residual oxygen remaining in the second cell without being discharged by the first cell.

Abstract: A filter for reducing the cross-sensitivity of a chlorine dioxide detector to hydrogen sulfide. The filter includes a high surface area substrate impregnated with a silver (I) salt or copper (II) salt which is effective to remove hydrogen sulfide from a gas stream without producing undesirable compounds which might be detected by the sensor. The preferred compounds are copper chloride (CuCl2), copper bromide (CuBr2), silver acetate (AgO2CCH3), silver bromate (AgBrO3), silver bromide (AgBr), silver carbonate (Ag2CO3), silver chloride (AgCl), silver chromate (Ag2CrO4), silver cyanide (AgCN), silver iodate (AgIO3), silver oxide (Ag2O), silver perchlorate (AgClO4), silver permanganate (AgMnO4), silver sulfate (Ag2SO4), silver hexafluorophosphate (AgPF6), silver fluoride (AgF), silver tetrafluoroborate (AgBF4), silver iodide (AgI) and silver trifluoromethane sulfonate (AgO3SCF3).

Abstract: An oxygen sensor for determining the oxygen concentration in the exhaust gas flow of an internal combustion engine. The sensor includes an outer electrode exposed to the exhaust side and a reference electrode exposed to the ambient air. In the sensor, a space adjacent to the reference electrode or surrounding the reference electrode has an adsorbing and/or absorbing agent, which is introduced, for example, in a loose powder packing or a multiple pellet packing. Other versions of the novel oxygen sensor also have an oxygen supplying material, such as, for example, Mn-oxide, Ba-oxide and/or Ce-oxide, to help promote combustion of exhaust gas components/pollutants and any residue chemicals left remaining from the sensor manufacturing process.

Abstract: This invention provides a reduced power consumption gas chromatograph system (10) which includes a capillary gas chromatograph column member (12) which contains a chemical sample to be analyzed. The gas chromatograph system further includes a heating mechanism (16) which extends throughout the length of the capillary gas chromatograph column member (12) and surrounds both the member (12) and a temperature sensing mechanism (14) which is mounted adjacent to the column member (12). The temperature sensing mechanism (14), the heating mechanism (16) and the column member (12) form a chromatograph column assembly (20) which includes a coiled section (28) where the components are tightly packed with respect to each other and allows for a reduced power consumption for temperature programming miniature gas chromatography column assemblies.

Abstract: A gas sensing element having a sample gas chamber into which a sample gas is introduced, and a reference gas chamber into which a reference gas is introduced. A sensor cell detects a specific gas concentration in the sample gas chamber. An oxygen pump cell pump cell pumps oxygen gas from or to the sample gas chamber. An introducing passage includes at least one pinhole provided on a surface of the oxygen pump cell for introducing the measuring gas into the sample gas chamber. The surface of the oxygen pump cell faces an outside of the gas sensing element. And, a porous diffusion resistive layer is provided on the surface of the oxygen pump cell so as to cover a portion corresponding to the introducing passage, thus serving to reduce or eliminate the effects of temperature dependency upon gas sensor output for properly sized and machine pinholes.

Abstract: A gas sensor comprising a pair of electrodes. The gas sensor includes one or more semiconducting organic polymers deposited between the pair of electrodes in such a manner as to effect a semiconducting electrical connection therebetween. The gas sensor also includes a device for applying an electric signal across the electrodes and a detector for detecting a chosen electrical property across the electrodes in the presence of a gas. At least one of the semiconducting organic polymers is polymerized from a monomer comprising a five membered heterocyclic aromatic ring with substituent groups at the 2 and 5 positions.

Abstract: Electrochemiluminescent assay methods for determining an analyte of interest, which methods include forming one or more compositions which include, in the aggregate, (a) a sample to be tested for the analyte of interest, (b) a component capable of specifically binding with the analyte, (c) a label reagent which, when oxidized, is capable of electrochemiluminescence, (d) an amine which, when oxidized, forms a reducing agent, and (e) an electrolyte solution; subjecting such a composition containing the sample to conditions sufficient for specific binding to occur between the analyte of interest, if present, and one or more of the other components in the composition; thereafter, a composition containing the label reagent and amine, and reflecting the outcome of applying the aforementioned binding conditions, is exposed to conditions, such that both the label reagent and the amine are oxidized, the amine forms a reducing agent which interacts with the label reagent, electrochemiluminescence occurs, and the lumine

Abstract: The present invention discloses an integrated ethanol gas sensor and fabrication thereof. The present invention utilities micro electro mechanical system (MEMS) technology and has a main sensing part in the form of a cantilever-bridge structure made of SiC thin film material arranged over a silicon substrate. The present invention integrates an SiC heater of comb or finger electrode shape and an SnO.sub.2 thin film gas sensing element applied over distinct portions on the same Si substrate together with Al2O3 and SnO2 thin films via a VLSI technology.

Abstract: A quartz microbalance detector system for controlling the concentration of a gas component in a gas stream. The quartz microbalance interacts with the gas component, to effect a change in the oscillation frequency of the quartz microbalance detector and produce a signal correlative of concentration of the gas component in the gas stream. A specific embodiment includes a device for sensing concentration of a halogen-containing gas species in a gas stream, comprising a quartz microbalance detector having a quartz crystal with a surface functionalized with --OH functionality that reversibly reacts with the gas component to yield a bound reaction product on the surface that effects a change in the oscillation frequency of the quartz microbalance detector. The quartz microbalance may be utilized to maintain a set-point concentration of a gas compound in a multicomponent stream.

Abstract: A gas sensor includes a substrate preferably made of beryllium oxide which is both an electrical insulator and thermal conductor, the substrate having thereon at least one heating element for the substrate, at lease one gas-sensitive active material deposited on the substrate and a set of at least two space electrodes in contact with the active material. The thermal conductivity of the substrate as arranged together with the heating element cooperate and assists to ensure that the substrate achieves a desired thermal gradient while the sensor establishes a near-uniform temperature throughout substantially the entire sensor, thus enabling the operating temperature of the active material to be maintained substantially constant throughout its entire volume.

Abstract: An apparatus is used to determine whether a container moving along a conveyor is suitable for storing water. The apparatus includes a sampler that obtains a sample from the interior of the container as the container moves along the conveyor. A PID is connected to the sampler to receive the sample and produce a signal corresponding to contents of the sample. A controller is connected to the PID and receives and analyzes the signal to determine whether the container is suitable for storing water. The apparatus may include a vacuum source connected to the PID that produces a reduced pressure for drawing the sample through the PID. A flow restrictor may be positioned between the sampler and PID. The flow restrictor may provide variable resistance to set a desired clearance time through the PID and sensitivity of the PID.

Abstract: A multilayered gas sensor for detecting the presence of gases in air. In particular, sensors are described for sensing hydrocarbons and nitrogen oxides. An additional feature of the invention is to provide a device that is suitable for sensing gases in the harsh environment of an automobile exhaust system. The device features a ceramic substrate and a glass layer to adhere a catalyst support to the substrate. A catalyst layer of either platinum or rhodium is deposited on the catalyst support and a thermally sensitive resistor element detects reactions of hydrocarbons or nitrogen oxides on the corresponding catalyst.