Queen's University at Kingston

The United States of America as Represented by the Department of

Stephen Hunt

David B Layzell

Adrian N Dowling

Zhongmin Dong

Roy A Young

Gerry Palmer

R Ford Denison

Lawrence J Winship

A method and apparatus for measuring differential and absolute concentrations of a selected gas, preferably oxygen, in two flowing gas streams is described. A reference gas and a sample gas in separate gas flow paths are passed at selected temperature, pressure and flow rate over a pair of gas sensors, connected in series with their cathodes or anodes connected together, which produce output signals proportional to the differential selected gas concentration between the sensors and the absolute selected gas pressure in each sensor. The output signals may be amplified and recorded by any conventional means.

Differential gas analyzer

A method and apparatus for rapidly measuring nitrogenase activity of a nitrogen fixing plant growing in a medium in a non-porous container, is described. Gas containing hydrogen is sampled at the surface of the medium at a rate approximately equal to the rate of hydrogen diffusion from the medium, and the sample is passed to a hydrogen sensor where it is measured and nitrogenase activity is determined therefrom.

Apparatus for rapid measurement of hydrogen concentration and its use in

An apparatus and method for measuring differential oxygen concentration between two flowing gas streams is described. A reference gas and a sample gas in separate gas flow paths are passed, at selected temperature, pressure and flow rate over a respective one of a pair of electrically connected oxygen sensors which produce an output signal proportional to the differential oxygen concentration between the sensors. The output signal may be amplified and recorded by any conventional means. An internal calibration system is also described.

Method and instrument for measuring differential oxygen concentration

An apparatus for electrolytically generating small volumes of a selected gas such as hydrogen for introduction into a flowing gas stream is described. The gas stream flows through an electrolytic cell wherein the selected gas is generated at an electrode and a portion of the gas stream is diverted through a needle valve and a non-conducting capillary with a small orifice to deliver gas to the electrodes so as to dislodge the selected gas bubbles forming thereon and carry them into the flowing gas stream. To maintain the level of electrolyte in the cell, the cell is connected by a narrow tube to a reservoir of electrolyte. The reservoir has a volume and surface area many times greater than that of the cell and the gas volume above the reservoir is maintained at the pressure and composition of the gas stream entering the electrolytic cell.

Electrolytic apparatus for generating selected concentrations of gas in

A non-invasive method and apparatus are described for measuring the oxygen concentration in the infected cells of the nodules of nitrogen fixing plants in the laboratory or field. In many cases, this information can be used to estimate the nitrogenase activity, and therefore the nitrogen fixation rate, in these nodules since recent studies have shown that the oxygen concentration limits and controls nitrogenase activity under most environmental conditions. Using the same apparatus, a method to measure nodule respiration and nodule oxygen permeability is also described. The nodule oxygen concentration in the infected cells of nodules is maintained at very low levels and has not been measurable previously by non-invasive techniques. The fractional oxygenation of plant hemoglobin is measured spectroscopically using one or more modulated light sources, a number of optical fibres to convey the light to and from the nodules, a photodetector to measure the light passing through the nodule and a detection system such as a photodiode coupled to a microcomputer or a lock-in amplifier to process the output signal.

Growing community of inventors

Kingston, Canada

Stephen Hunt