BIOINSTRUMENTATION
Fernandez-Moran (refs. [ref.163]-[ref.165]), at the University of Chicago, has devised a new multielectrode electrostatic lens which he has incorporated into an electron microscope. This necessitated the development of a novel high-voltage power source and voltage regulator of extreme stability and accuracy. Some promising work has now been done on superconducting lenses. In a series of experiments with a simple electron microscope without pole pieces, using high-field superconducting niobium-zirconium solenoid lenses in an open air core, liquid helium Dewar, electron microscopic images of test specimens have been recorded while operating at 32 200 gauss in a persistent current mode, with regulated accelerating potentials of 4 to 8 kilovolts. These preliminary experiments have demonstrated the exceptional stability of the images (both short term and long term) over a period of 4 to 8 hours and the relatively high quality of the images.
Progress has been made on the viscosimeter for high intrinsic viscosities. This is now working, and the viscosity of DNA preparations has been measured. It is hoped to use the viscosimeter to study the variation in DNA viscosity as a function of the cell cycle.
An instrument is under development by Wald at the University of Pittsburgh to automatically analyze cytogenetic material and, thus, extend cytogenetic methodology both for research and as a biological monitoring procedure, using automatic electronic scanning and computer analysis of chromosomes. Chromosomal aberrations can thus be monitored under unusual and abnormal conditions such as weightlessness and radiation, since chromosomes are very sensitive to stress situations. In this device a sample will be prepared and automatically inserted under a microscope lens. The device will then scan, identify, and photograph on 35-mm film a predetermined number of mitotic cells and process the film. The data will be recorded under the direct control of a digital computer. The computer will perform a detailed quantitative analysis of the pictorial data.
Significant effort has been expended in the development of instrumentation for measuring and recording electrophysiological information. One such instrument, developed by the Franklin Institute, Philadelphia, Pa., is a temperature-sensing microprobe. This microprobe is an implantable and remote broadcasting instrument. These developments are associated, in part, with training programs so that competent individuals may be trained not only in electronics but also in the biological uses of the devices they construct.
A project of interest, conducted at the Stanford Research Institute, is the investigation of the uses of an extremely sensitive method for measuring magnetic susceptibility having the possibility of detecting macroscopic quantum effects in macromolecules of biological interest. Good progress has been made in the first 15 months of a project devoted to the development and initial use of equipment specifically designed for this purpose. A new superconducting circuit, together with superconducting magnetic shields, has been constructed. This apparatus can measure the magnetic susceptibility of small organic samples at temperatures between 1° and 300° K in fields up to 40 000 gauss. It can detect flux changes of 107 gauss-cm2, which is equivalent to detecting a change in specific susceptibility of 1 in 109 in a 100-mg sample under an applied field of 10 000 gauss.
Several hundred preliminary measurements were made on samples of coronene. The most reliable of these were in agreement with published values of the magnetic susceptibility of coronene. Experience during these measurements led to changes which have resulted in an apparatus well suited to the measurements on macromolecules. An improved version of the superconducting circuit now available shows promise of a further improvement in sensitivity by a factor of more than a thousand ([ref.166]).
Living organisms possess many unique processes and systems which are complex and poorly understood. The new theoretical approaches, combined with laboratory studies, are expected to result in advances which will expand both our scientific and technological horizons.
[chapter 6]
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