Richard D. Hiebert

A New Multiparameter Separator for Microscopic Particles and Biological Cells

A new flow‐system instrument for quantitative analysis and sorting of microscopic particles, particularly biological cells, based on multiple measurements of physical and biochemical properties has been developed. Cells stained with fluorescent dyes in liquid suspension enter a unique flow chamber where electrical and optical sensors measure cell volume, single‐ or two‐color fluorescence, and light scatter, and emerge in a liquid jet that is broken into uniform droplets. Sensor signals are electronically processed several ways for optimum cell discrimination and are displayed as pulse‐amplitude distributions using a pulse‐height analyzer. Processed signals trigger cell sorting according to preselected parametric criteria. Sorting is accomplished by electrically charging droplets containing the cells and electrostatically deflecting them into collection vessels. This instrument is described in detail with illustrative examples of experiments using polystyrene fluorescent microspheres, cultured human cells,...

Device Which Separates Minute Particles According to Electronically Sensed Volume

A device has been developed that is able to fractionate a mixture of microscopic particles according to small differences in their volume. A dilute suspension of the particles passes through a sensor within which the volume of each particle is electronically measured. Subsequently the suspension emerges into the air as a liquid jet. This jet is caused to break into a large number of individual droplets, thereby isolating the suspended particles. Droplets containing particles of the desired volume ranges are electronically charged and electrostatically deflected into suitable receptacles. The apparatus is described in considerable detail with illustrative application to polystyrene spheres and to human white blood cells.

Improved multilaser/multiparameter flow cytometer for analysis and sorting of cells and particles

An improved multilaser instrument has been developed for quantitative analysis and separation of biological cells and particles. Argon ion, krypton ion, and dye lasers are employed as excitation sources to sequentially illuminate cells labeled with multiple fluorochromes as they pass through an improved flow chamber that incorporates an electronic cell‐volume sensor and an optical measurement region. Detectors located on the axis of each excitation beam are used to measure axial light loss and forward light scatter. Multicolor fluorescence is measured using a five‐channel detector located orthogonal to the laser beam(s)‐cell stream intersection(s). Sequential measurements are made on a cell‐by‐cell basis to provide pulse height, area, and width signals that are made coincident in time by analog delay modules to increase data throughput. Analog electronics are used to compute real‐time ratios, sums, and differences of signals. Up to eight signals are acquired and displayed as single‐parameter frequency dis...

Gamma insensitive air monitor for radioactive gases

An ionization chamber instrument for measuring the concentration of radioactive gases in air is described. External gamma radiation effects on the instrument are eliminated through use of a compensating chamber mounted next to the measuring chamber with both chambers orbiting about a common axis.

Slit-scan flow cytometer for recording simultaneous waveforms

We have developed a slit‐scan flow cytometer for recording the transient, simultaneous light scattering and fluorescence waveforms from individual metaphase chromosomes flowing through a focused laser beam. The two waveforms are recorded on a single‐memory waveform recorder by delaying one of the waveforms and switching between them. The light scattering and fluorescence waveforms contain complementary information on chromosome structure. The delay and switching electronics developed here may be useful in other contexts.

Photomultiplier tube base for high pulsed anode currents

Abstract The stability of photomultiplier tube (PMT) gain for signal conditions of high pulsed anode currents requires a PMT base circuit capable of maintaining constant voltage to the last few dynodes for the pulse duration. For the experimental conditions at the Los Alamos Meson Physics Facility (LAMPF) with a macropulse duration of 500 μs at 120 Hz, conventional base circuits do not meet stability requirements. The new base circuit uses high voltage transistors to furnish pulse currents to the last four dynodes of the PMT from a single capacitor source which is recharged during the period between macropulses.

High speed single particle sizing by light scattering in a flow system

We present two approaches to rapid, single particle sizing for particles in the I to 20 μm diameter range. One method measures multiangle scattered light over a polar angular range of nearly 360 degrees. A second method is based on the analysis of the pulse shapes from small angle forward scattered light. In both cases the particles in liquid suspension are made to pass one at a time through a focused laser beam for analysis.