Hewlett-packard Company

Biotechnology Research and Development Corporation

Barry G Willis

Paul C Dryden

John A Bridgham

Paul E Stoft

Andrew Stefanski

Arthur Schleifer

Moshe A Fostick

Jacob Y Wong

Norton W Bell

C Nelson Dorny

Robert L Chaney

Charles M Hill

John K Lazier

Richard Lawrence Baer

Paul S Weiss

George W Hopkins, Ii

Lloyd A Bumm

Michael J Farrell

Henry A Schade, Jr

A sample and the tip portion of an alternating current scanning tunneling microscope are electrically enclosed within a cavity with electrically conductive walls. The dimensions of the cavity are smaller than the wavelength of a component of the AC signal applied by the probe to the sample so that the output signal detected by the probe from the sample will not be contaminated by resonant effects of the cavity.

Small cavity analytical instruments

An optical relay having a pair of simple lenses and an opaque barrier defining an aperture. In a spectrometer, the optical relay is positioned between a light source and an opaque barrier defining a slit to focus light of a reference wavelength w.sub.r onto the slit. The location of the aperture and the choice of w.sub.r are selected so that the flux of light through the slit is substantially flat as a function of wavelength.

Flat band optical relay using apertures and simple lenses

An instrument is disclosed which performs measurements and calculates the average and the variance of the measurements. The particular instrument illustrating the invention is a spectrophotometer which measures sets of dark, reference and sample spectra for use in calculating an average absorbance spectrum and its variance. The measurements are performed in an order which enables the cancellation of measurement variation due to variation in instrument response. The order of measurements is determined by measurement subroutines which can be aggregated to produce a series of measurements performed over a user selected period of integration time.

Method of performing measurements and error analysis of the measurements

Apparatus for performing measurements and error analysis of the

A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood. In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an 'inverted cell' being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample. In accordance with another embodiment, the sample cell is isolated from the region surrounding the wheel and positioned so as to be presented in series with the reference cells in the optical detection path. In preferred embodiments, the rotating wheel contains a number of permanent magnets which interact with a number of electromagnets driven in sequence to provide rotation of the wheel.

Medical-analytical gas detector

A transcutaneous pH measuring device is provided in which a known volume of fluid is brought into equilibrium with body fluids through a membrane on a portion of skin whose surface layers have been stripped away. The fluid contains a pH sensitive dye. Optical measurements of the transmission characteristics of the fluid are obtained when the fluid is in the optical path. During portions of each operating cycle, the fluid is driven back into the vicinity of the skin to pH equilibrate with body fluids while standardization measurements are obtained using an optical plug of known transmission characteristics in the optical path.

Transcutaneous pH measuring instrument

Growing community of inventors

Los Altos Hills, CA, United States of America

Barry G Willis